Regulation of folliculogenesis and the determination of ovulation rate in ruminants

2011 ◽  
Vol 23 (3) ◽  
pp. 444 ◽  
Author(s):  
R. J. Scaramuzzi ◽  
D. T. Baird ◽  
B. K. Campbell ◽  
M.-A. Driancourt ◽  
J. Dupont ◽  
...  
Keyword(s):  
Follicular Development ◽  
Oocyte Quality ◽  
Ovulation Rate ◽  
Fetal Life ◽  
Cellular Events ◽  
Sequence Of Events ◽  
Reproductive Cycles ◽  
Ovulatory Follicles ◽  
Original Concept

The paper presents an update of our 1993 model of ovarian follicular development in ruminants, based on knowledge gained from the past 15 years of research. The model addresses the sequence of events from follicular formation in fetal life, through the successive waves of follicular growth and atresia, culminating with the emergence of ovulatory follicles during reproductive cycles. The original concept of five developmental classes of follicles, defined primarily by their responses to gonadotrophins, is retained: primordial, committed, gonadotrophin-responsive, gonadotrophin-dependent and ovulatory follicles. The updated model has more extensive integration of the morphological, molecular and cellular events during folliculogenesis with systemic events in the whole animal. It also incorporates knowledge on factors that influence oocyte quality and the critical roles of the oocyte in regulating follicular development and ovulation rate. The original hypothetical mechanisms determining ovulation rate are retained but with some refinements; the enhanced viability of gonadotrophin-dependent follicles and increases in the number of gonadotrophin-responsive follicles by increases in the throughput of follicles to this stage of growth. Finally, we reexamine how these two mechanisms, which are thought not to be mutually exclusive, appear to account for most of the known genetic and environmental effects on ovulation rate.

Factors affecting folliculogenesis in ruminants

1999 ◽  
Vol 68 (2) ◽  
pp. 257-284 ◽  
Author(s):  
R. Webb ◽  
R. G. Gosden ◽  
E. E. Telfer ◽  
R. M. Moor
Keyword(s):  
New Technologies ◽  
Ovarian Function ◽  
Major Gene ◽  
Follicular Development ◽  
Oocyte Quality ◽  
Ovulation Rate ◽  
Follicular Growth ◽  
Stages Of Development ◽  
Hormone Production ◽  
Factors Affecting

AbstractThis review addresses the reasons for the lack of progress in the control of superovulation and highlights the importance of understanding the mechanisms underlying follicular development. The present inability to provide large numbers of viable embryos from selected females still restricts genetic improvement, whilst variability in ovarian response to hormones limit the present capacity for increasing reproductive efficiency.Females are born with a large store of eggs which rapidly declines as puberty approaches. If these oocytes are normal then there is scope for increasing the reproductive potential of selected females. Oocytes must reach a certain size before they can complete all stages of development and the final changes that occur late in follicular development. It is likely that oocytes that do not produce specific factors at precise stages of development will not be viable. Hence, it is important to characterize oocyte secreted factors since there are potential indicators of oocyte quality.The mechanisms that determine ovulation rate have still not been fully elucidated. Indeed follicular atresia, the process whereby follicles regress, is still not known. A better understanding of these processes should prove pivotal for the synchronization of follicular growth, for more precise oestrous synchronization and improved superovulatory response.Nutrition can influence a whole range of reproductive parameters however, the pathways through which nutrition acts have not been fully elucidated. Metabolic hormones, particularly insulin and IGFs, appear to interact with gonadotrophins at the level of the gonads. Certainly gonadotropins provide the primary drive for the growth of follicles in the later stages of development and both insulin and IGF-1, possibly IGF-2, synergize with gonadotrophins to stimulate cell proliferation and hormone production. More research is required to determine the effects of other growth factors and their interaction with gonadotropins.There is evidence, particularly from studies with rodents, that steroids can also modulate follicular growth and development, although information is very limited for ruminants. There may be a rôle for oestrogens in synchronizing follicular waves, to aid in oestrous synchronization regimes and for removing the dominant follicle to achieve improved superovulatory responses. However more information is required to determine whether these are feasible approaches.Heritability for litter size is higher in sheep than in cattle. Exogenous gonadotropins are a commercially ineffective means of inducing twinning in sheep and cattle. Although there are differences in circulating gonadotropin concentrations, the mechanism(s) responsible for the high ovulation appear to reside essentially within the ovaries. The locus of the Booroola gene, a major gene for ovulation rate, has been established but not specifically identified. However sheep possessing major genes do provide extremely valuable models for investigating the mechanisms controlling ovulation rate, including a direct contrast to mono-ovulatory species such as cattle.In conclusion, the relationship between oocyte quality, in both healthy follicles and those follicles destined for atresia, must be resolved before the future potential for increasing embryo yield can be predicted. In addition, a greater understanding of the factors affecting folliculogenesis in ruminants should ensure that the full benefits ensuing from the precise control of ovarian function are achieved. The improved use of artificial insemination and embryo transfer that would ensue from a greater understanding of the processes of folliculo genesis, coupled with the new technologies of genome and linkage mapping, should ensure a more rapid rate of genetic gain.

Reduced ovarian follicular development as a consequence of low body condition in ewes

1987 ◽  
Vol 115 (1) ◽  
pp. 75-83 ◽  
Author(s):  
A. S. McNeilly ◽  
J. A. Jonassen ◽  
S. M. Rhind
Keyword(s):  
Body Condition ◽  
Follicular Fluid ◽  
Follicular Development ◽  
Lower Proportion ◽  
Ovulation Rate ◽  
Luteal Regression ◽  
Ovarian Follicular Development ◽  
Ovulatory Follicles ◽  
Fluid Levels ◽  
Oestradiol Production

Abstract. The effect of body condition on ovarian follicular development was investigated in Scottish Blackface ewes in high and low body condition. Follicles were dissected from ovaries on days 11 and 12 of the luteal phase and 24 h after prostaglandin-induced luteal regression. Ewes in low body condition had a lower ovulation rate (low: 0.9; high: 1.8 P < 0.05) and lower mean plasma levels of FSH during both the luteal (low: 54; high: 72 μg/l) and follicular (low: 34; high: 43 μg/l) phases of the cycle. Low body condition was associated with a reduced number of large (⩾ 4 mm) follicles in both the luteal and follicular phases, and in low condition a lower proportion of these follicles was oestrogenic and potentially ovulatory as assessed by follicular fluid levels of oestradiol. However, within the different oestrogenic classifications of these large follicles there were no significant differences in the steroidogenic capacity as assessed by the concentrations of either oestradiol or testosterone in follicular fluid, basal and hCG-stimulated testosterone production, thecal 125I hCG binding or basal and testosterone-stimulated oestradiol production by granulosa cells in relation to body condition. These results suggest that body condition influences ovulation rate by altering the concentration of FSH in blood, which in turn affects the number of potentially ovulatory follicles growing beyond 4 mm.

Evaluation of Follicular Development and Oocyte Quality in Pre-pubertal Cats

2010 ◽  
Vol 45 (6) ◽  
pp. e405-e411 ◽  
Author(s):  
K Uchikura ◽  
M Nagano ◽  
M Hishinuma
Keyword(s):  
Follicular Development ◽  
Oocyte Quality

scholarly journals Large-Scale Metadata Analysis of Ovary Based Multi-Omics Datasets for Understanding the Genes Regulating Litter Size

2020 ◽  
Author(s):  
Ayyappa Kumar Sista Kameshwar ◽  
Julang Li
Keyword(s):  
Gene Expression ◽  
Differentially Expressed Genes ◽  
Litter Size ◽  
Large Scale ◽  
Expression Patterns ◽  
Genetic Selection ◽  
Follicular Development ◽  
Oocyte Quality ◽  
Differentially Expressed ◽  
Metadata Analysis

Abstract Background : Litter size is a very important production index in the livestock industry, which is controlled by various complex physiological processes. To understand and reveal the common gene expression patterns involved in controlling prolificacy, we have performed a large-scale metadata analysis of five genome-wide transcriptome datasets of pig and sheep ovary samples obtained from high and low litter groups, respectively. We analyzed separately each transcriptome dataset using GeneSpring v14.8 software by implementing standard, generic analysis pipelines and further compared the list of most significant and differentially expressed genes obtained from each dataset to identify genes that are found to be common and significant across all the studies. Results : We have observed a total of 62 differentially expressed genes common among more than two gene expression datasets. The KEGG pathway analysis of most significant genes has shown that they are involved in metabolism, the biosynthesis of lipids, cholesterol and steroid hormones, immune system, cell growth and death, cancer-related pathways and signal transduction pathways. Of these 62 genes, we further narrowed the list to the 25 most significant genes by focusing on the ones with fold change >1.5 and p<0.05. These genes are CYP11A1, HSD17B2, STAR, SCARB1, IGSF8, MSMB, SERPINA1 , FAM46C, HEXA, PTTG1, TIMP1, FAM167B, CCNG1, FAXDC2, HMGCS1, L2HGDH, Lipin1, MME, MSMO1, PARM1, PTGFR, SLC22A4, SLC35F5, CCNA2, CENPU, CEP55, RASSF2, and SLC16A3 . Conclusions : Interestingly, comparing the list of genes with the list of genes obtained from our literature search analysis, we found only three genes in common. These genes are HEXA, PTTG1, and TIMP1. Our finding points to the potential of a few genes that may be important for ovarian follicular development and oocyte quality. Future studies revealing the function of these genes will further our understanding of how litter size is controlled in the ovary while also providing insight on genetic selection of high litter gilts.

scholarly journals Role of Melatonin as a Survival Factor for In vitro Development of Sheep Preantral Follicles

2021 ◽  
Author(s):  
C. Chetan Kumar ◽  
B. Rambabu Naik ◽  
A.V.N. Siva Kumar ◽  
A. Ravi ◽  
L.S.S. Varaprasad Reddy ◽  
...  
Keyword(s):  
Growth Factors ◽  
Ovarian Function ◽  
Follicular Development ◽  
Oocyte Quality ◽  
Free Radical Scavenger ◽  
Radical Scavenger ◽  
Optimum Level ◽  
Preantral Follicles ◽  
Positive Effects

Background: Melatonin, a powerful free radical scavenger and broad-spectrum antioxidant may directly affect ovarian function by regulating folliculogenesis, maintenance of follicular integrity, oocyte quality and maturation capacity. Therefore, we aimed to study effects of melatonin and its interaction with growth factors in sheep preantral follicles. Methods: The influence of different concentrations of Melatonin (5-500 pM) on in vitro culture of preantral follicles (PFs’) isolated from sheep ovaries was studied. Experiments I and II were conducted to standardize the optimum concentration of Melatonin that supports better development of preantral follicles. Experiment III was conducted with the optimum level of Melatonin derived in the Experiments I and II to evaluate the effect of melatonin at 100pM in combination with various growth factors. Result: Overall follicular development was found to be the best in the PFs’ cultured in medium supplemented with 100pM of Melatonin. Melatonin supplementation showed positive effects on the preantral follicular development in combination with different growth factors.

Ovarian follicular development during the follicular phase of oestrous cycle in manchega ewes with different ovulation rate

1996 ◽  
Vol 45 (1) ◽  
pp. 299 ◽  
Author(s):  
A.Gómez Brunet ◽  
A.López Sebastián ◽  
A.González de Bulnes ◽  
J.Santiago Moreno ◽  
M.García López
Keyword(s):  
Follicular Development ◽  
Follicular Phase ◽  
Oestrous Cycle ◽  
Ovulation Rate ◽  
Ovarian Follicular Development

Pattern formation in the Blue-Green Alga, Anabaena

1973 ◽  
Vol 12 (3) ◽  
pp. 707-723 ◽  
Author(s):  
MICHAEL WILCOX ◽  
G. J. MITCHISON ◽  
R. J. SMITH
Keyword(s):  
Pattern Formation ◽  
Green Alga ◽  
Normal Growth ◽  
Growth Conditions ◽  
Inhibitory Effect ◽  
Blue Green Alga ◽  
Interactive Model ◽  
Differentiated Cells ◽  
Sequence Of Events

Filaments of Anabaena have a spaced pattern of differentiated cells called heterocysts, which is maintained as a filament grows by the regular determination of new heterocysts. By following the growth of every cell in a filament, we have identified proheterocysts (prospective heterocysts) at their earliest appearance, and described the sequence of events in the formation of the pattern. The determination of proheterocysts obeys 2 rules: (1) that there are inhibitory zones around pre-existing heterocysts, and (2) that only the smaller daughter of a division can become a heterocyst (all divisions are asymmetrical). There are, however, certain conditions in which these rules are over-ridden, where a pattern consisting of groups of consecutive proheterocysts is seen which resolves into a normal discrete pattern. This process is highly suggestive of interaction between developing cells. We have tested this hypothesis in normal growth conditions by breaking filaments near to early proheterocysts, on the assumption that this will cause a build-up of inhibitory effect of the cell upon itself. It is found that these cells regress, losing their differentiated character and dividing. We therefore propose an interactive model for pattern formation in Anabaena.

The lack of a compensatory ovulation rate effect following hemi-ovariectomy in sheep superovulated with oFSH

1998 ◽  
Vol 1998 ◽  
pp. 185-185
Author(s):  
I.M. Joyce ◽  
M. Khalid ◽  
W. Haresign
Keyword(s):  
Embryo Transfer ◽  
Rate Effect ◽  
Treatment Regime ◽  
Ovulation Rate ◽  
Sheep Breed ◽  
Size Category ◽  
Chemical Products ◽  
Breed Improvement ◽  
Major Factors ◽  
Ovulatory Follicles

Variability in superovulatory responses remains one of the major factors preventing the more widespread utilisation of embryo transfer in sheep breed improvement. Previous work in our group has suggested that in sheep receiving a standard superovulatory treatment regime using oFSH (Ovagen, Immuno-chemical Products Ltd., Auckland, NZ) there is an identifiable pool of follicles at the start of oFSH treatment that eventually ovulate following treatment. If this is the case then research efforts to increase the consistency of superovulatory responses should be focused on increasing the supply of follicles in this category. This experiment therefore had two aims, i) to test the theory that variability in superovulatory responses is a function of variability in the number of potentially ovulatory follicles at the time of the first FSH injection, and ii) to identify the size category of follicles at the start of superovulatory treatment that forms this ovulatory pool.

scholarly journals Design and kinematics of a 3-D printed walking robot “Big Foot”, overcoming obstacles

2019 ◽  
Vol 16 (6) ◽  
pp. 172988141989132
Author(s):  
Ivan Chavdarov ◽  
Bozhidar Naydenov
Keyword(s):  
Control System ◽  
Walking Robots ◽  
Energy Losses ◽  
Simple Design ◽  
Walking Robot ◽  
Minimum Number ◽  
And Control ◽  
Original Concept ◽  
Dimensional Optimization

The proposed study presents an original concept for the design of a walking robot with a minimum number of motors. The robot has a simple design and control system, successfully moves by walking, avoids or overcomes obstacles using only two independently controlled motors. Described are basic geometric and kinematic dependencies related to its movement. It is proposed optimization of basic dimensions of the robot in order to reduce energy losses when moving on flat terrain. Developed and produced is a 3-D printed prototype of the robot. Simulation and experiments for overcoming an obstacle are presented. Trajectories and instantaneous velocities centers of links from the robot are experimentally determined. The phases of walking and the stages of overcoming an obstacle are described. The theoretical and experimental results are compared. The suggested dimensional optimization approaches to reduce energy loss and experimental determination of the instant center of rotation are also applicable to other walking robots.

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