British Airways Essay Example | Topics and Well Written Essays - 750 words

British Airways - Essay Example This is according to the chairman of British Airways from 1993 to 2004, lord Marshall of Knightsbridge. While the history of BA in its current structure and name began in 1976, its predecessors can be traced back to the late ‘10s. The first British Airlines, Aircraft Transport and Travel, was established in 1919, with the initial scheduled flight taking off on August the 25th from le Bourget to Honslow, its home. Two other airlines, Handley page and Instone, were established using modified bombers. The three companies underwent a period of great difficulty, especially competition from French airlines, which were cheaper. To solve these problems, they merged to be joined later by British Marine Air Navigation, forming Imperial Airways. Imperial Airways began local and overseas flights immediately, flying as far as Egypt and India with a crew of 250 and a fleet of 18 crafts (Gaskell, 2010). This paper is an essay on British Airways. Later, Imperial Airways was a Brisbane, Austral ia route, whose duration would take grueling 12 days. The new airline added new planes such as the short S.23 C-class model, which signified that the airline was growing, as was a new carrier British Airways limited (Gaskell, 2010). After the start of the 1st World War, these two merged to form British Overseas Airways Corporation, which re-started its transatlantic flights after the war ended. In addition, they created the BEA, a new airline to handle the European flights. At this point, the carriers needed to order new and more efficient aircraft. BOAC consequently ordered the Boeing Strato-cruiser, the Lockheed Constellation, and a Rolls-Royce engine equipped version of the DC-4. It did not take long before they ordered a jet plane, the De Havilland Comet, which dramatically reduced the length of trans-Atlantic flights (Marriott, 2010). The early 60’s saw BOAC order the Rolls-Royce Conway engine driven 707-436 to tide over until the VC-10s were ready. By 1970, with the fir st 747 and rapid growth, BOAC and BAL were ready to merge and work as one, establishing British Airways in 1976. BA’s most crucial year was 1976; it had a partnership with Concorde, coupled with big fleets of Lockheed TriStar and Boeing 747. The early 1980s saw the company face its second major threat, economic trouble, although measures were taken to privatize the company, which duly happened in 1987. Increasing competition from US based carriers also forced BAs hand in the merger with British Caledonian, which saw the A320 among other planes enter the fleet (Marriott, 2010). This merger further enabled BA to begin operations at Gatwick Airport. However, its base remained at Heathrow, where BA operates approximately forty percent of the total flights. In addition, the airline has created service stations in Birmingham, Glasgow and Manchester. British Airways has built its brand around fast travel, which has seen it at the forefront of jet travel. The first jets for short hau l flights were ordered in 1980, with forty four 737-200 planes delivered. New 737s were ordered in the late 80s, most of them being the 400-plane model with increased passenger capacity. Although not a choice of BA, the Airbus A320, entered the British Airways service after it merged with British Caledonian (Marriott, 2010). However, the planes proved quite efficient in their flights and duties. Medium haul flights were performed by the larger Boeing 757 fleet, as well as the 767, which were equipped with engines from Rolls-Royce. A number of Boeing 767-300ER in turn, performs long haul flights, which do not require huge passenger capacity. Most of these carry two hundred and fifty two passengers, with additional Boeing 777-200 and 747-400 complementing this segment. Recently, the company replaced all Boeing

How does globalization affect the environment Essay

How does globalization affect the environment - Essay Example One area of human life that has experienced heavy issues due to globalization is the environment in which human beings live. Policy makers, environmentalist and other stakeholders have attacked globalization for impacting human environment in a negative manner. Body Disadvantages One of the main impacts of globalization is that globalization has led to increase in the spending ability of all individuals and have led to elevation in the consumption levels of human beings and this has impacted the ecological system in a negative manner. Increase in income level have made people demand for more goods and services and this has led to decrease in the natural resources that are offered by the environment. With the increase in demand for goods and services, there has been an increase in the transfer of natural resources from one region to another. Before globalization started spreading, people used to be dependent on their local manufacturers and service providers for goods and services. No w due to decrease in boundaries, people have started demanding for goods and services that are developed in foreign regions. To transfer goods and services, heavy amount of fuel is consumed which has led to degradation of the environment due to increase in pollution. The fuel used in transportation of goods has led to increase in the amount of fossil fuels burned to produce fuel. ... s waste is being dumped in oceans and this dumping process has ruined the underwater life and has led to increase in chemicals being deposited to oceans. For example: during the period of 2010, oil spill from the containers of British Petroleum ended up damaging the ocean in a very negative manner and this happens to be one of the several harmful effects of globalization on the environment (Cook, 2010, p.214). Increase in industrialization along with globalization has led to an increase in the amount of chemicals that are dumped into soil and due to this several plants as well as weeds have been produced. The waste that is toxic in nature and is dumped in soil has severally damaged plant life and had interfered with the natural way of growth of plants. Throughout the world heavy cut down of forests are taking place as wood obtained from forests is used in production of several goods such as furniture and paper. Due to this, carbon dioxide in the environment has increased and release of oxygen by plants has decreased. Similarly, cut down of mountainous regions have even been conducted to create new roads and for real estate purposes and this has long term negative impacts on human health. Plastic is being heavily used throughout that world for several purposes such as packaging and this plastic is not renewable in nature. Plastic is used in then discarded in form of waste which is negatively impacting the environment. Plastic bags tend to enter water lines as well as beaches and as plastic waste is burned, it result in emission of fumes that are toxic in nature and these fumes tend to impact the environment in a negative manner. According to Savedge, more than 100,000 marine animals experience death or are murdered by animals as they dump plastic bags in oceans and

Professional Portfolio Assignment Example | Topics and Well Written Essays - 1500 words

Professional Portfolio - Assignment Example Correspondingly, I would provide a structured portfolio of mine, where I will include a brief description of my educational platform, learning theory along with curriculum map and the use of tools that I have initiated throughout the course of my learning as an educator. Professional Portfolio Educational Platform and Learning Theory Education is one of the most vital aspects of growth for any individual. Understanding the value of learning as the cornerstone of a successful life, individuals from various age groups and demographics have started taking participation in the educational sector. In this regard, the role of an educator has become quite prominent over the years owing to their significance in forming the educational career of an individual. As an educator, I feel esteemed to be rewarded with the opportunity to assist learners in developing their skills and abilities with regard to their competent areas. Correspondingly, in my professional experience, I was able to learn th at an ideal educator is of extreme need to develop the skills and capabilities that might be in need to provide a proper learning experience to the students. In consideration to all these facets, I desire myself to be in a professional career associated with education. ... Additionally, with reference to my desire of becoming an educator will always intend towards maintaining an atmosphere, which will encourage maximum concentration amid the learners and facilitate effective learning in-turn. It would also be vital to mention that I am quite appreciative towards adopting proper learning theories that would allow me to have proper control over the learning capabilities of the students. As per my experience, adoption of effective learning theory is quite important to facilitate learners’ effective performance. Out of the various principles of learning, I prefer Readiness, which depicts that a learner can be able to learn more when he/she is physically, mentally, as well as emotionally deciphers the yearning to learn. Correspondingly, adoption of such theory requires me to create interest among the students by presenting the value of a particular topic or a subject matter. In my professional career, I also emphasize posing continuous mental as well as physical challenges, with the intention to keep the learners’ interests intact for a longer period of time. Curriculum Map and Assessment Strategy Based on my personal and professional experiences, I was able to understand that setting efficient curriculum is among the major needs in the field of education. Educational institutions all over the world have well identified the needs to develop an effective curriculum where learners would be able to perform better. Correspondingly, the role of an educator is also vital in such cases. I, as an educator, understand this particular facet in my role and ensure best possible contribution towards the same. I was mainly engaged with the Master of Education

Substance use and mental health Essay Example | Topics and Well Written Essays - 1000 words

Substance use and mental health - Essay Example The list of substances that are abused is broad and the method and route of administration also vary. The problem with abusing substances however is not present only in young population but is more diffusely distributed in all ages and social groups. Most common substance abuse found in the same statistical analysis in the general population ranging between age of 16 and 74, that was reported by the participants themselves was cannabis (in 24 %), amphetamines were tried or used by 7 % of the cohort group, 5% ever in their life used magic mushrooms, about 4 % of the cohort population ever in their life used or are still using ecstasy, cocaine, LSD, tranquilizers were used by 3% of the population, other volatile substances and gases were used in 1% of the population and other substances like crack, heroin, steroids were also present in about 1%. There are also other substances that were used but are not listed in this text. Also we must have in mind that this study was based on the sel f-report of the participants so there is a possibility for even larger prevalence of these substances if we consider the population that didn’t report abuse of substances. ... iew Schedule CIS-R, where score above 12 is considered a sign of high probability for neurotic disorder in one person and in participants with score above 18 is considered that psychiatric treatment is necessary (Lewis et al, 1992). They also tested for disorders in the personality of the participants using the SCID-II (Semi-structured interview for making DSM-IV Axis II: Personality Disorder diagnoses). It is a set of questions that are completed by the participants in order to assess the personality disorder based on the Diagnostic and Statistical Manual of Mental  Disorders,  Fourth Edition (DSM-IV). They also used Schedules for Clinical Assessment in Neuropsychiatry manual to asses for psychosis or more severe psychiatric disorder in the participants. Based on these examinations it was found that abuse of substances was more common in participants who tested positive in some of the screening tests that were used. It was found that 12 % of the people who scored 12 or above on the CIS-R scale (some type of neurosis) had abused substances in the last month before the survey compared to 5% of the other population. Among the specific neuroses it was found that participants with suspicion for obsessive-compulsive disorder had the higher incidence of substance abuse in the previous month (15%). Most significantly it was found that 32% of the participants that were suspected for presence of anti-social personality disorder was found that were abusing some substance in the previous month before the survey. In the group of participants that were diagnosed with psychosis or other major psychiatric disorder no significance in incidence of abusing substances was found. Based on this study we can conclude that neurosis, antisocial personality disorder, obsessive-compulsive

Baker and McKenzie Law Firm in Worldwide Markets Research Paper - 1

Baker and McKenzie Law Firm in Worldwide Markets - Research Paper Example Baker and McKenzie is an American law firm based in Chicago city. The firm has a total of 3774 attorneys, 1349 partners, and 2425 associates (Baker and McKenzie 1). Baker and McKenzie law firm tops the list of the most successful law firms in the United States. The firm is renowned to have redefined the worldwide law firm of the 20th century in order to meet the global economic challenges of the 21st century. The 3774 lawyers are located in over 70 offices worldwide. The firm has a unique way of working, thinking and behaving. The function across borders and they deal with a wide variety of issues as well as practices (Baker and McKenzie 1). Baker and McKenzie law firm understands the economic challenges facing the globe, and for that reason, it has been of the forefront of matters since the firm’s opening in 1949. Laws that work in Baker and McKenzie law firm include financial litigation, product liability, aviation law, capital markets, bankruptcy, business and industry, com mercial law, insolvency, intellectual property, international law, international trade, and investment law. The firm also deals with consumer law, contracts, copyright, corporate governance, and corporate law among others (Baker and McKenzie 1). The firm has advised leading companies on matters of today’s incorporated world market. Baker and McKenzie law firm has cultivated the tradition, commercial simplicity, and technical, as well as interpersonal skills, vital to offer world-class service tailored to the needs of world-class customers globally.

Management, Organisations and People Module Report Essay Example for Free

Management, Organisations and People Module Report Essay Introduction: The aim of this report is to provide an explanation to ‘Mimi Vasquez Hair and Beauty’ managers’ approach to leadership and go on to explore his relationship to his work group and how they have developed over time. It will first outline the methodology used to conduct this report and then go on to introduce the managers and workers and explain how their current work roles have developed over time. Subsequently, the report will provide an explanation to ‘Mimi Vasquez Hair and Beauty’ managers’ approach to leadership and go on to explore his relationship to his work group. To conclude the report, there will be a quick summary of what has already been mentioned and some limitations of the findings, methodology and related theories used in the report. The beauty salon which was named after its manager is privately owned and located in Chiswick in West London. In addition, it has two other branches located in Ealing and Hammersmith, both also within the West London area and owned by the same manager. All three of the beauty salons are relatively small in size making satisfactory profits and located just off the high streets in quieter areas. The first branch was opened in 1999 in Chiswick and the others followed on 5 years later, the Hammersmith branch being the newest. Method This report was conducted using both primary and secondary research. The primary research was collected directly from the manager and team members by interviewing them. By so doing, the research collected was new and wasn’t research that had already existed. Secondary research was collected through the use of books, the internet and articles and hence looking at existing data. Findings and discussion Behavioural theory As the manager, Mimi Vasquez, supervises and manages the overall performance of his staff and the business. His current work role is to analyse and recommend developing strategies on how to improve the quality of their services e.g. more speed and efficiency in cutting hair and accuracy with mixing colours of hair dye. These two examples are some of Mimi’s main targets and he wishes to have met these goals by July 2011. Mimi also examines ways to achieve his business goals of maximising profits and acknowledges that compensations and rewards have worked well in the past as they motivate and encourage staff to work better: Every year he elects 2 people as the most improved and most enthusiastic team members and rewards them in the form of bonuses and HMV vouchers. His work role also involves instructing his team members and allocating them to different parts of the salon when the day gets busy Moreover, this has played a great role in the development of Mimi’s leadership within the business. Yukl (2006, p5) defines leadership as- Leadership is the process wherein an individual member of a group or organization influences the interpretation of events, the choice of objectives and strategies, the organization of work activities, the motivation of people to achieve the objectives, the maintenance of cooperative relationships, the development of skills and confidence by member, and the enlistment of support and cooperation from people outside the group or organisation. Yukl’s definition very closely matches Mimi’s approach to leadership in the sense that it emphasizes the importance of ‘people skills’ and the social influence that leadership can have. One theory to provide evidence for this is the behaviour perspective. This theory claims that people become leaders because of what they do and this can be split into two different categories: task behaviour and relationship behaviour. Task behaviour places the main focus on the degree to which a leader emphasises productivity targets, goal accomplishments and maintaining standards. These behaviours can also be called ‘production-centred’ and it can be seen in Mimi’s leadership style when he uses HMV vouchers to motivate his staff to work harder and faster. Mimi has also said that rewards gave his staff an incentive to work and this played a crucial part in keeping them happy and full of energy, even towards the end of the day. Furthermore, relationship behaviour focuses on manager’s actions that show concern for their staff and their welfare as opposed to behaviours that concentrate on completing tasks. Although this contrasts to task behaviour, this can also be seen in Mimi’s leadership approach in the sense that he aims to improve his staff’s skills and help them gain more confidence in their job role. Trait perspective The controversy in defining leadership has enabled many different theories to be developed in an attempt to explain the meaning of a leader within a business or an organisation. Bratton (2010, p363) cited that ‘individuals who occupy leadership positions possess superior qualities or attributes compared with the traits possessed by non- leaders’. This view is known as the trait perspective and its’ theories such as the ‘great man theories’ focus mostly on positive characteristics such as stamina, intelligence and fluency in speech. Research in 1974 by Stogdill showed that socioeconomic factors also played a great role for example, very few corporate leaders had fathers who held a low class position or who were paid quite poorly. Stogdill also found that intelligence and fluency in speech were very closely related to leadership and used these traits to differentiate leaders from followers. He then concluded that there were ‘specific patterns’ of traits that occurred in some people which gave them an advantage when seeking a leadership position. Shabina and Mario also described their manager to hold very positive characteristics such as friendly, talkative, enthusiastic and organised and wasn’t like the other staff members at ‘Mimi Vasquez hair and beauty’ in the sense that he was much more determined. This therefore justifies why Mimi is a leader. In addition, research into ‘substitute’s for leadership’ claim that there should be a distinct difference between the leader and the followers in a business and there should be inflexible rules and formalized areas of responsibility in order to prevent the followers from being guided by their peers and replacing their existing leader. This would occur if the followers realized that their peers had the skills equivalent to their leader and they decided to follow them instead. Keith Grint (2005) also argues that successful leadership- Is not a list of innate skills and competences, or how much charisma you have, or whether you have a vision or a strategy for achieving that vision, but whether you have a capacity to learn from your followers. This again, provides evidence against the trait perspective stating that this is not what makes an effective leader. The shared/super leadership theory The founding of Mimi’s other branches, helped him gain experience which developed his role even further as he had to identify problems, make choices and provide alternatives actions to his initial plans. His role development throughout the years has been quite significant and his responsibilities have duplicated allowing him to improve his time management and organisation. Mario and Shabina are two team members of the salon who were also interviewed. Mario is a professional hair stylist whose work role involves restyling and cutting clients’ hair, dying, permanent hair straightening, Brazilian hair blow drying etc. His work role is crucial to the business as he has qualities and skills that require a lot of training and experience in order to gain. Mario’s work role has developed over the years as his experience has allowed him to move up the ladder in regards to the styles and haircuts he can confidently perform. The number of clients he reserves on a daily basis has also increased over the past 6 years of working at the salon showing an improvement in his abilities. He is now responsible for his own clients as before he would only deal with Mimi’s clients and help around. However, he is still in a lower position to Mimi and is usually responsible for making sure that Mimi’s clients are booked in for the dates and times they requested, making sure none of the time slots clash with one another. The Shared/super leadership theory suggests that excellent leaders are those who help their followers develop by acting as their teacher rather than keeping all of their knowledge to themselves. To add, Peter Senge(1990) also stated that ‘leaders are designers, stewards and teachers’ which supports the view. Mimi has constantly trained his team members, in particularly Mario and this also adds towards the statement that Mimi is an effective leadership. Fiedler’s leadership contingency theory Shabina is the only beautician at ‘Mimi Vasquez Hair and Beauty’ and her role involves taking care of her own customers and making her own bookings as well as offering all of the services; waxing, laser hair removal, threading, massages etc. Her role doesn’t involve anything to do with hair, and she works in her own room downstairs. However, Mimi is her manager also and so it is her responsibility to follow all of his guidelines and instructions. Her role has developed over the past 3 years as she first started out as an assistant, cleaning around and helping the beautician. She then worked her way up by gaining experience and qualifications and developed her role into a full-time professional beautician. Fiedler’s leadership contingency theory proposes that the effectiveness of the leader depends on whether the leadership style is matched with the followers and the environment. It is based on 3 main assumptions: 1) leader-member relations, which relate to whether the leader receives support, respect and trust of the followers; 2) task structure, which relates to how structured the tasks performed by followers are; 3) position power, which relates to the formal authority that the leader can exert through the use of punishment and rewards. This theory can explain Mimi’s leadership style as it explains why Mimi’s leadership is effective and hence how he has been able to successfully run the business for so many years. In relation to this theory, Mimi is placed to be known as a relationship-orientated leader and so it explains that his team members have been able to develop throughout the years because of his concern for them. The situational leadership theory Mimi’s relationship to his group is fairly hierarchical where he would force influence upon others to do something that they otherwise wouldn’t. This hair and beauty business is a good example as it shows how Mario takes responsibility for making bookings for both, his and Mimi’s clients. The group itself had developed over the years as they have slowly started to work as a team, helping each other and finishing each other’s jobs off when the salon gets busy. In 1999, manager Mimi’s Vasquez’s main roles were to simply open and close the salon, receive payments for the service provided and order raw materials such as; hair dye, scissors, wax etc. Now, with the growth of the business, all of the team members in the salon have developed their roles as they have had to cover for each other and enhance coordination skills. The situational leadership model is where the leaders’ leadership style depends on the maturity of the followers; it can explain that why Mimi trusts his staff to look after his salon whilst he is in a different branch. The friendly nature of the business also allows Mimi to be less formal and more flexible with rules and procedures. Bratton (2010, p.370) states that ‘Follower maturity is determined by the ability and willingness of the followers to accept responsibility for completing their work’. The fact that each team member has their own set of responsibilities proves that their levels of maturity are very high and hence can explain why Mimi’s rules are quite flexible, according to Mario and Shabina. Conclusion The report has explored Mimi’s approach to leadership using the behavioural, trait, shared/super leadership, contingency and situational theories and it can clearly be seen that leadership is not easily defined and its effectiveness isn’t easily measured. It has also outlined the work roles of the manager as well as the team members and explained how their roles have developed. To conclude, although the report gives a sense of idea of what Mimi’s leadership approach may be, in reality it is very hard to accurately describe using only one theory. Appendix Bratton, J. (2010) Work and organisational behaviour. 2nd edn, Hampshire: Palgrave Macmillan Grint,K.(2005) Leadership: limits and possibilities, Basingstoke: Palgrave Senge, P.M.(1990) The Fifth Discipline. New York: Currency/Doubleday Yukl, G.(2006) Leadership in organizations.6th edn, Englewood Cliffs, NJ: Prentice Hall

Effects of Physiological Reproductive Events on Ovary

Effects of Physiological Reproductive Events on Ovary Chapter one Introduction Background The two majors function of the ovary is the differentiation and release of female gametes (oocyte), which can then be successfully fertilised and ensure the survival of species. The ovary is also an endocrine organ that produces steroid hormones that allow the development of female secondary sexual characteristics and supports pregnancy. The mammalian ovary is covered by a single layer of epithelial cells (surface epithelium), which vary in type from simple squamous to cuboidal to low pseudostratified columnar (Anderson et al. 1976). Directly underneath the surface epithelium there is a layer of dense connective tissue known as the tunica albuginea. The mammalian ovary is a heterogeneous organ containing follicles and corpora lutea at various stages of development. The ovarian follicle is the fundamental unit of the ovary, each follicle consists of an oocyte, surrounded by granulosa cells and outer layer of theca cells ( 1.2 Folliculogenesis During embryogenesis, primordial germ cells (PGCS) migrate from the yolk sac through the dorsal mesentery of the hindgut, to the genital ridge. The germ cells then undergo extensive proliferation, and lose their motile characteristics, in addition, somatic cells derived from the mesenchyme of the genital ridge, proliferate as well (Hirshfield 1991). The germ cells cease mitotic division and form association with small numbers of pre-granulosa cells to form primordial follicle (Telfer et al. 1988). The germ cells undergo the first meiotic division and are now called primary oocytes. The oocytes then become arrested in the diplotene stage of prophase I of meiosis until the primordial follicles start to grow and finally reach the ovulatory stage. In the diplotene stage, the oocyte may prepare itself for rapid mitosis and implantation, by producing large amounts of mRNA and ribosomes (Picton et al. 1998). Primordial follicles may be observed from week 22 in the human (Faddy and Gosden 19 95) and week 13 in the cow (van den Hurk and Zhao 2005). The pool of primordial follicles develops during fetal life in some species (e.g primates, ruminants), but in others it develops during the early neonatal period (e.g rodents, rabbits) (Marion et al. 1971). The number of primordial follicles present at birth represents the total population of germ cells available to mammalian females during their entire reproductive life (Kezele et al. 2002), and is believed to serve as the source of developing follicles and oocytes (Eppig 2001). Although recent studies have suggested that postnatal oogenesis may also occur in female mammals (Johnson et al. 2004), they suggested that germline stem cells can repopulate the postnatal ovary and renew the primordial follicle pool. This group subsequently went on to suggest that these cells were derived from bone marrow (Johnson et al. 2005). This has attracted a great deal of attention as well as criticism (Gosden 2004; Byskov et al. 2005; Telfer et al. 2005). This is an ongoing debate but the balance of evidence suggests that renewal is not a major factor in ovarian development (Eggan et al. 2006). In mammals, the number of primordial follicles in the ovaries at birth varies enormously between species, ranging from tens of thousands in mice to millions in humans and domestic species (Gosden and Telfer 1987). These follicles must develop through primordial, primary and secondary stages before reaching the preovulatory stage, and subsequent ovulation (Figure 1.1). Proper follicle development involves maturation of the oocyte, which is surrounded by variable layers of granulosa cells, enveloped by theca cells (Drummond 2005). Granulosa cells provide physical support of the oocyte and mediate signals between the oocyte, outer theca cells and endocrine hormones. Once the pool of primordial follicles has been established, follicles gradually and continually leave the resting pool to begin growth. However, less than 1% of primordi al follicles present at the time of birth of an animal will ever proceed to ovulation (Erickson 1966), with the majority of follicles degenerating by atresia. 1.3 Regulation of early folliculogenesis A critical process in ovarian biology is the transition of the developmentally arrested primordial follicle to the developing primary follicle. Follicular growth may begin at any time during the females life. The primordial follicle contains an oocyte arrested in meiosis I surrounded by flattened somatic cells termed the pregranulosa (Kezele et al. 2002). During onset of primordial follicle growth, flattened pregranulosa cells become cuboidal and begin to proliferate. The enclosed oocyte begins to grow at the same time (Anderson et al. 2000; Clark and Eddy 1975). The growths of both the primordial follicles with oocytes characterize the initiation of the growing phase. The oocytes within the primordial follicles remain quiescent for months to years until they receive the appropriate signals to initiate folliculogenesis and primordial to primary follicle transition. So far, little is known about the molecular mechanisms and extracellular signalling factors that regulate this process. These processes directly affect the number of oocytes available to a female throughout her reproductive life. Once the pool of primordial follicles is depleted, ovarian steroidogenesis ends and the series of physiological changes called menopause begins (Richardson et al. 1987). It is unclear whether the signals originate from the oocyte, or/and from surrounding somatic cells, or from outside the ovary. It is also unknown if it is an inhibitory factor preventing resting primordial follicles from leaving the stock or a stimulus acting on the resting primordial follicles store that stimulates some follicle to leave it (Gougeon and Busso 2000). A multitude of factors may act locally to regulate early folliculogenesis by promoting growth (Bennett et al. 1996) or by inhibiting growth (Bukovsky et al. 1995). The initial growth signal appears to be independent of the pitui tary gonadotropins (Peters et al. 1975) (Figure 1.3). Primordial follicles do not possess receptors for FSH hormone (Oktay et al. 1997). Despite some studies suggesting that gonadotropins are involved in the initiation of follicular growth in immature rodents (Lintern-Moore 1977; Neal and Baker 1973), nevertheless, during natural hypopituitary conditions in both animal species and humans, the initiation process is not completely abolished (Howe et al. 1978; Halpin et al. 1986). Although follicles at early stages of development have been shown to express follicle stimulating hormone receptors (FSH-R) (Bao et al. 1998), in the absence of gonadotropins during the early stages of follicle growth, follicles can still develop to the early antral stage (Awotwi et al. 1984; Gong et al. 1996). Knockout mice who are null mutants for either FSH receptor or LH receptor are able to undergo the primordial to primary follicle transition (Zhang et al. 2001; Abel et al. 2000). Several local factors have been found that can regulate the primordial to primary follicle transition. Bone morphogenetic protein-7 (BMP-7) has been shown to promote the primordial to primary follicle transition and to increase granulosa cell proliferation (Lee et al. 2001). Leukemia inhibitory factor (LIF) has also been shown to promote the primordial to primary follicle transition and to up-regulate granulosa cell expression of kit ligand (KL) (Nilsson et al. 2002). Bone morphogenic protein-15 (BMP-15) is a growth factor expressed in the oocytes of developing follicles that plays a role in early follicle progression (Dube et al. 1998) and stimulates granulosa cell proliferation (Otsuka et al. 2000). Growth differentiation factor-9 (GDF-9) has been localized inthe oocytes of mouse (Dong et al. 1996) rat (Jaatinen et al. 1999) and human (Aaltonen et al. 1999) primary follicles. Nilsson and Skinner (2002) have shown that GDF-9 promotesthe development of primary follicles in neonatal r at ovaries,but it has no effect on the growth of primordial follicles (Nilsson and Skinner 2002).Studies by Wang and Roy (2004) have provided the first evidence that GDF-9 can promote the formation of primordialfollicles and their subsequent growth in neonatal hamster ovaries (Wang and Roy 2004) . Anti-Mullerian hormone (AMH) is a member of the transforming growth factor- ÃŽ ² (TGF-ÃŽ ²) is considered as a negative regulator of the early stages of follicular development. AMH is produced by the granulosa cells of developing preantral and small antral follicles which inhibits the primordial to primary follicle transition (Durlinger et al. 1999). AMH is never found in primordial follicles, theca cells or oocytes (Ueno et al. 1989; Hirobe et al. 1994; Baarends et al. 1995). Examination of ovarian follicles in AMH-deficient female mice revealed lower numbers of primordial follicles and more growing follicles compared with wild-type mice, these findings revealed that, in the absence of AMH, ovaries are depleted of their primordial follicles earlier than they are in control mice and these observations led to the propsal that AMH inhibits primordial follicle recruitment (Durlinger et al. 1999). Results were obtained from another in vitro experiments on the bovine ovarian cortex sugges ted that, at least in nonhuman species, the presence of AMH acts as a brake on the activation of primordial follicles and the growth of preantral follicles (Gigli et al. 2005). It has been demonstrated that oocytes from early preantral, late preantral and preovulatory follicles up-regulate AMH mRNA levels in granulosa cells, in a fashion that is dependent upon the developmental stage of the oocyte (Salmon et al. 2004). These findings suggest that oocyte regulation of AMH expression may play a role in intra- and interfollicular coordination of follicle development. ; kit ligand (KL) and basic fibroblast growth factor (bFGF) secreted by pre-granulosa cells and oocyte respectively, have mutual stimulatory effects on oocytes and granulosa cells; they also promote recruitment of theca cells from the surrounding stromal/interstitial cell population. Stromal/interstitial cells and theca cells secrete BMP-4 and BMP-7, which promote follicle activation and survival. GDF-9 and/or BMP-15 secreted by the oocyte of the activated follicle promote granulosa cell proliferation, KL expression and theca formation. Granulosa cells of growing follicles secrete AMH that appears to act as a ‘brake on primordial follicle recruitment (Knight and Glister 2006). Foxo3a (FKHRL1), a member of the FOXO subfamily of forkhead transcription factors, has been implicated in the regulation of follicle activation. It has been indicated that Foxo3a functions at the earliest stages of follicular growth as a suppressor of follicular activation (Castrillon et al. 2003). It was suggested that Foxo3a serves an essential role by suppressing the growth of primordial follicles, thereby preserving them until later in life (John et al. 2007). It was shown that Foxo3a -/-ovaries contained markedly elevated numbers of early growing follicles, and this extensive of follicular growth in Foxo3a -/- females resulted in the progression of increased numbers of follicles to more advanced stages of follicular development and this misregulation of this process can lead to premature ovarian failure (Castrillon et al. 2003). Kit ligand (KL) is produced by the granulosa cells of developing ovaries (Manova et al. 1993; Ismail et al. 1996) and KL receptors (c-kit) are present on oocytes and theca cells (Manova et al. 1990). C-kit is expressed at the surface of mammalian oocytes at all stages of follicular development in postnatal ovaries of the mouse, the rat and humans (Driancourt et al. 2000; Horie et al. 1991; Manova et al. 1990; Orr-Urtreger et al. 1990) and its only known ligand, Kit-ligand (KL), which is also referred to as stem cell factor (SCF). KL acts to recruit theca cells from surrounding ovarian stroma during folliculogenesis (Parrott and Skinner 2000). Therfore, KL is thought to act as a signal from the granulosa cells around primordial follicles to the oocyte and surrounding stroma to promote the events of the primordial to primary follicle transition (Parrott and Skinner 1999). In this study (Parrott and Skinner 1999), treatment of in vitro cultured follicles from postnatal ovaries from 4 da y old rats, with KL dramatically induced the development of primordial follicles, but was completely blocked by the Kit antibody ACK2. 1.4 Follicle development Follicular development is regulated by both endocrine and intraovarin mechanisms which co-ordinate the processes of somatic cell proliferation and differentiation (Moley and Schreiber 1995). The basic functional unit in the ovary is the ovarian follicle that is composed of somatic cells and developing oocyte. The two primary somatic cell types are the theca cells and granulosa cells. These two somatic cell types are the site of action and synthesis of a number of hormone that promote a complex regulation of follicular development. The prolifetation of these two cell types is in part responsible for the development of the antral ovarian follicle. At the same time, the oocyte is undergoing developmental changes necessary to allow the resumption of meiosis after the preovulatory surge of gonadotrophins (Montgomery et al. 2001). This regulation occurs according to endocrine principles, involving hormones such as pituitary gonadotropins , ovarian steroids and locally produced factors that act either on the cell that produces them (autocrine) or on neighbouring cells (paracrine) (Salha et al. 1998). Ovarian follicular development is a long process which can take around 6 months from the initiation of growth of primordial follicles until development of a preovulatory follicle in humans, cattle and sheep (Lussier et al. 1987; Cahill and Mauleon 1980) and around 4 months in pigs (Morbeck et al. 1992). The majority of this time is spent in the pre-antral stages of development. Already at this stage, a considerable proportion of growing follicles fail to survive and they degenerate through a process termed follicular atresia. Observations in humans and in animals suggest that apoptosis is the mechanism of follicular atresia (Tilly 1996; Kaipia and Hsueh 1997). In women, the dominant follicle orginates from primordial follicle that was recruited to grow almost 1 year earlier Folliculogenesis can be divided into two stages: the gonadotropin-independent (preantral) and gonadotropin-dependent (antral or Graafian) periods (Erickson and Shimasaki 2000). Locally produced growth factors are critically involved in controlling preantral follicle development during the gonadotropin-independent period. After antraum formation, the follicle becomes dependent on FSH stimulation for continued growth and development. Interestingly, it was discovered that the process of folliculogenesis is controled by growth factors secreted by the oocyte (Matzuk 2000). Five growth factors have been identified in mamalian oocytes: growth differentiation factor-9 (GDF-9) (McGrath et al. 1995), bone morphogenetic protein -15 (BMP-15) (Dube et al. 1998; Laitinen et al. 1998), bone morphogenetic protein -6 (BMP-6) (Knight and Glister 2006), transforming growth factor -ÃŽ ²2 ( TGF-ÃŽ ²2) (Schmid et al. 1994), and fibroblast growth factor-8 (FGF-8) (Valve et al. 1997). Experiments with knockout mice have demonstrated that in the absence of GDF-9, folliculogenesis is blocked at the primary to preantral stage (Dong et al. 1996). Consequently, there are no Graafian follicles, no ovulations, and no pregnancies. 1.4.1 Follicular cell types and follicle classification The two primary somatic cell types in the ovarian follicle are the theca cells and granulosa cells. These two somatic cell types are the site of action and synthesis of a number of hormones that are involved in the complete regulation of follicular development. 1.4.1.1 Granulosa cells Granulosa cells are the primary somatic cell type in the ovary that provides a physical support of the oocyte and mediated signals between the oocyte, outer theca cells and endocrine hormone. Regulation of granulosa cell differentiation during folliculogenesis requires the actions of a number of hormones and growth factors. Specific receptors have been demonstrated on granulosa cells for gonadotropins follicle stimulating hormone (FSH) and luteinizing hormone (LH) (Richards and Midgley, Jr. 1976). In addition, receptors have been found for factors such as insulin-like growth factor (IGF) (Adashi 1998) epidermal growth factor (EGF) (Vlodavsky et al. 1978) and anti-Mullerian hormone (AMH) (Josso et al. 2001). Actions of these hormones and growth factors on granulosa cells vary with the stage of differentiation. Follicular growth and steroidogenesis are dependent on the coordinated actions of FSH and LH with their receptors on granulosa cells and thecal cells of ovarian follicles. Both granulosal and thecal cells are involved in production of estradiol-17ÃŽ ² (two cell/two gonadotropin model which is well accepted for many species). 1.4.1.2 Theca cells Another important cell type in the ovary is the ovarian theca cell. These are differentiated stromal cells that surround the follicle and have also been termed theca interstitial cells (Erickson and Case 1983). The thecal cells can be distinguished as two distinct layers, the inner layer of cells, the theca interna has a basement membrane separating it from the outmost layer of granulosa cells. The theca interna is a highly vascular layer. One of the major functions of theca cells in species such as the cow, human and rodent is the secretion of androgens (Fortune and Armstrong 1977). At the primordial stage, no theca cells are present; however during the transition to the primary stage, theca cells at this stage of development are gonadotropin and steroid independent and non-steroidogenic (Braw-Tal and Roth 2005). Theca externa which is less vascularized layer and merges into the stromal tissue without clear boundaries. The ‘two-gonadotrophin, two-cell model of follicular estradiol biosynthesis According to the two-cell-two-gonadotrophin theory, the ovary has two cellular compartments that are driven independently by LH and FSH to produce ovarian steroids. Androgen production by theca cells is a function of LH, whereas aromatization of these androgens to oestradiol by granulosa cells is controlled by FSH (Gougeon 1996) (Figure 1.5). Androgen synthesis occurs in the theca interna regulated by LH, by expressing P450c17, the rate-limiting steroidogenic enzyme in androgen synthesis (Sasano et al. 1989). Theca interna are capable of synthesizing all the steroids from cholesterol to testosterone and are the major source of follicular androstenedione. In contrast, granulosa cells are the major source of follicular estradiol. Granulosa cells are intrafollicular sites of androgen metabolism (Ghersevich et al. 1994) and express aromatase P450arom (Whitelaw et al. 1992) this enzyme converts androgens to estrogens. FSH also induces granulosa cell LH receptors that are functionally coup led to aromatase. Thus, uniquely in the preovulatory follicle, both the synthesis of androgen (in theca cells) and its aromatization to estradiol (in granulosa cells) are directly regulated by LH (Fortune and Armstrong 1977). . In the theca, under the influence of LH, cholesterol is converted to pregnenolone and metabolised through a series of substrates ending in androgen production. The two-cell, two-gonadotrophin model comes into play with androgens produced by the theca cells transported to the granulosa cells where they are aromatised to oestrogens (Drummond 2006). 1.4.2 Classification of follicle stages In sheep, the stages of follicular development have been classified on the basis of the number of granulosa cells in the largest cross-section of follicles (McNatty et al. 1999), 1.4.3 Follicular development in primates 1.4.3.1 Oocyte growth and maturation Once follicles have been initiated to grow, the granulosa cells proliferate to form the different stages of follicular development (Telfer et al. 2000). During follicular activation and early development in mice, for example, the oocyte growth occurs rapidly with an approximatly 300-fold increase in volume during the 2-3 week growth phase (Wassarman and Albertini 1994), which is also accompanied by a 300-fold increase in RNA content (Sternlicht and Schultz 1981) and a 38-fold increase in absolute rate of protein synthesis (Schultz et al. 1979). These events are indicative of a period of cell growth with high metabolic activity (Wassarman and Albertini 1994). Oocytes complete most of their growth phase before the formation of a follicular antrum (Wassarman and Albertini 1994), and the increase in oocyte diameter and volume during antral follicular growth is relatively small (Eppig 2001; Wassarman and Albertini 1994). If the oocyte is to be capable of fertilization and subsequent embry onic development, it must acquire the ability to resume meiosis. Oocytes from immature follicles are unable to resume meiosis (Iwamatsu and Yanagimachi 1975) however, by the time the follicles have reached the antral stages the oocytes of most species have acquired the ability to resume meiosis (Mattioli and Barboni 2000; Telfer 1998). 1.4.3.2 Follicular growth Early in oocyte growth, a homogenous glycoprotein layer called the zona pellucida (ZP) is secreted shortly after initiation of follicular growth (Epifano and Dean 1994). It forms a translucent acellular layer separating the oocyte from the surrounding granulosa cells. However, contact between granulosa cells and the oocyte is maintained via cytoplasmic processes, which penetrate the zona and form gap junction at the oocyte surface. Progressively, follicles become secondary follicles. In addition to oocyte growth and granulosa cell proliferation, the preantral follicle also increases in size through formation and growth of ovarian stromal cells on the outer membrane of the follicle forming the theca layers of the follicle. The thecal cells can be distinguished as two distinct layers: highly vascular theca interna, surrounded by a fibrous capsule, the theca externa. The granulosa cells continue to proliferate, resulting in a further increase in follicular size. The formation of the follicular antrum marks the beginning of the antral phase of development. The appearance of an antral cavity starts with the development of small fluid-filled cavities that aggregate to form the antrum. As the follicular antrum grows, the oocyte, surrounded by a dense mass of granulosa cells called the cumulus oophorus which become suspended in fluid. It is connected to the rim of peripheral granulosa cells only by a thin stalk of cells. Attached to the zona pellucida, which surrounds the oocyte, is a small ring of granulosa cells called the corona radiata, these cells will be expelled with the oocyte during ovulation. In humans and monkeys, follicles pass from the preantral to the early antral stage at a follicular diameter between 180 and 250 ÃŽ ¼m (Koering 1983; Bomsel-Helmreich et al. 1979). Further, growth of the follicle is under the influence of follicle stimulating hormone (Gougeon 1996). The follicle is then termed a Graafian follicle. When the proper ho rmonal balance is present, normally one Graafian follicle in mono-ovulatory mammals (e.g. primates, ruminants, equine) and several ones in poly-ovulatory animals (e.g. rodent, porcine) fully develop and the oocyte matures and ovulate (Hafez 1993). 1.4.4 Regulation of follicular development 1.4.4.1 Oocytes somatic cell communication Oocyte growth is dependent on signals, growth factors and nutrients from granulosa cells; at the same time oocytes play an important role in the proliferation and differentiation of granulosa cells. Communication between oocytes and somatic cells have a crucial role in ovarian follicular development (Albertini and Barrett 2003; Eppig 2001). Several studies have shown the importance of oocyte-derived factors such as growth and differentiation factor-9 (GDF-9) and bone morphogenetic protein-15 (BMP-15) in female reproduction. GDF-9 and BMP-15 promote the proliferation of granulosa cells from small antral follicles (Hayashi et al. 1999; Vitt et al. 2000; Otsuka et al. 2000). Mutation of the GDF-9 gene in mice prevented the development of somatic cells beyond the primary follicle stages (Dong et al. 1996). C-kit receptor or (Kit) is expressed at the surface of mammalian oocytes at all stages of follicular development in postnatal ovaries of the mouse, the rat and humans (Driancourt et al . 2000b; Horie et al. 1991; Manova et al. 1993). An in vivo study by (Yoshida et al. 1997) has indicated the requirement for C-kit in development of the ovarian follicle in mice. In this study, postnatal mice were injected with Kit-blocking antibody ACK2, and the first wave of follicular development was studied. The blockade of Kit signalling was found to disturb the onset of primordial follicle development, primary follicle growth and follicular fluid formation of preantral follicles (Yoshida et al. 1997). On the other hand, primordial follicle formation, ovulation and luteinization of the ovulated follicle were not affected by ACK2 (Yoshida et al. 1997). 1.4.4.2 Gonadotropins Before the onset of puberty, the normal fate of growing follicles is atresia. After puberty, stimulation by cyclic gonadotropins allows the survival and continued growth with only a limited number of antral follicles that will reach the preovulatory stage. Activation and maintenance of normal follicular function is dependent on gonadotropins secreted by the pituitary. Follicle stimulating hormone (FSH) and Luteinizing hormone (LH) are glycoprotein, secreted by gonadotrophs in the anterior pituitary under the influence of hypothalamic GnRH (Gonadotrophin releasing hormone) neurones, which regulate the synthesis and secretion of those hormones). Gonadotropins are probably not involved in the initiation of follicle growth (Wandji et al. 1992; Fortune et al. 2000; McNatty et al. 1999). Whilst there may not be an absolute requirement for FSH at these early stages the presence of FSH receptor (FSHr) in granulosa cells of immature follicles in cow (Wandji et al. 1992), human (Zheng et al. 1 996) and sheep (Eckery et al. 1997) suggests an involvement. A role for LH in the early stages of development has not been described, although expression of LH receptor (LHr) mRNA is first detected when the theca interna forms around the granulosa cells (Bao et al. 1998; Bao and Garverick 1998). FSH and LH are involved in endocrine control of follicle development, FSH stimulates granulosa cell division and the formation of glycosaminoglycans that are essential components of antral fluid (Hillier 1991). FSH is vital for the formation of the antral cavity (Nayudu and Osborn 1992) in mouse ovarian follicles cultured in vitro. Granulosa cells are the only cells in the female body possess FSH receptors, and binding of FSH to its receptor on the cell surface altered expression of multiple genes crucial to cytoproliferation and differentiation (Richards 1994). Granulosa cell genes that are responsive to FSH include: aromatase (P450arom) the steroidogenic cytochrome P450 crucial to estrogen synthesis (Simpson et al. 1994); cholesterol side-chain cleavage (P450scc) (Richards 1994) and LH receptors (Segaloff and Ascoli 1993). FSH and LH are important factors for the proliferation and survival of follicular somatic cells and the cyclic recruitment of antral follicles. Suppression of serum gonadotropins after hypophysectomy leads to atresia and apoptosis of developing follicles (Nahum et al. 1996). Whereas FSH treatment of cultured early antral follicles prevents the spontaneous onset of follicular apoptosis (Chun et al. 1996). Although FSH is the central regulator of dominant follicle survival and development, LH signalling pathways play fundamental physiological roles. LH-dependent signal pathways in the theca interstitial cells induce changes in gene expression that are critical for estrogen production (Erickson et al. 1985). Activation of the LH receptors in theca cells leads directly to the stimulation of high levels of androstenedione production. The major physiolog ical significance of this LH response is to provide aromatase substrate to the granulosa cells where it is metabolized by P450 aromatase to E2. Additionally, the preovulatory surge of LH is responsible for ovulation and corpus luteum formation. Also, LH is essential for P4 and E2 production by the CL during the early and midluteal phase of the menstrual cycle. The hypothalamus produces and secretes luteinizing hormone-releasing hormone (LHRH) into a system of blood vessels that link the hypothalamus and the pituitary gland. LHRH stimulates the pituitary gland by attaching to specific molecules (i.e., receptors). After the coupling of LHRH with these receptors, a cascade of biochemical events causes the pituitary gland to produce and secrete two hormones, luteinizing hormone (LH) and follicle-stimulating hormone (FSH). LH and FSH are two of a class of hormones commonly known as gonadotropins. They are secreted into the general circulation and attach to receptors on the ovary, where they trigger ovulation and stimulate ovarian production of the hormones estrogen and progesterone. Adapted from (Kanis 1994) 1.4.4.3 Growth factors A number of locally produced growth factors are known to be important for follicle development, they exert paracrine communication within follicles. During preantral follicle development, growth factors such as epidermal growth factor (EGF), transforming growth factors (TGF) may influence folliculogenesis (van den and Zhao 2005). Vascular endothelial growth factor (VEGF) (Danforth et al. 2003) and mullerian inhibitory substance (MIS) (McGee et al. 2001) have been reported to stimulate preantral follicle growth. It has been demonstrated that bone morphogenetic proteins (BMP) can alter bovine granulosa cell steroidogenesis and proliferation in vitro (Glister et al. 2004). Transforming growth factor-ÃŽ ² (TGF-ÃŽ ²) superfamily contains a range of proteins, including inhibins and activins. The precise roles of these factors are not known, but it is likely that they are involved in follicular differentiation by enhancing the action of gonadotropins (Campbell and Baird 2001; Knight and Gli ster 2001; Montgomery et al. 2001). Insulin growth factors (IGF) and their receptors play important role in follicle growth and development (Poretsky et al. 1999). The IGF family comprises of IGF peptides, IGF receptors which are family of proteins called insulin-like growth factor binding proteins (IGFBP) that regulate the availability of the IGF to their target cells, and IGFBP proteases (Giudice 1992). The IGFs affect biosynthetic processes in granulosa and theca cells and have an influence on mitotic activity in the granulosa cells (Giudice 1992; Poretsky et al. 1999). Additionally, a functional link between the IGF system and FSH action has been demonstrated by the finding that IGFBP-4 is a potent inhibitor of FSH