scholarly journals The cultured rodent follicle as a model for investigations of gonadotrophin surge-attenuating factor (GnSAF) production

Reproduction ◽  
2004 ◽  
Vol 127 (6) ◽  
pp. 679-688 ◽  
Author(s):  
Paul A Fowler ◽  
Norah Spears
Keyword(s):  
Conditioned Medium ◽  
Granulosa Cells ◽  
Cell Types ◽  
Culture Conditions ◽  
Suitable Model ◽  
Molecular Weight Range ◽  
Follicle Culture ◽  
Stage Of Development

Gonadotrophin surge-attenuating factor (GnSAF) bioactivity (the suppression of GnRH-induced but not basal LH and FSH secretion from pituitary gonadotrophs) is produced by granulosa cells in vitro. Previous studies to investigate this bioactivity used dispersed granulosa cells which lack some cell types and the structural components of the follicle in vivo. The aim of this study, therefore, was to investigate whether intact rodent follicle culture was a suitable model for the study of the production of GnSAF bioactivity, allowing GnSAF to be investigated in a more physiologically realistic environment while still retaining culture conditions from which, as with granulosa cell cultures, extraneous factors can be excluded. Follicles from 16-day-old rats and 21-day-old mice were cultured for 3–6 days in the presence or absence of FSH and/or LH. The follicle-conditioned medium, and matching samples of unconditioned culture medium were added to our established rat pituitary monolayer GnSAF bioassay. Both mouse and rat intact follicles produced GnSAF bioactivity, reducing GnRH-induced LH secretion significantly. GnSAF output from the mouse follicles was highest during days 1–3 of culture, when follicles were at an early antral stage of development, and fell on days 4–6 as the follicles grew to the mid antral stage. While the stimulatory effects of FSH on rat follicle GnSAF secretion was dose-dependent, LH alone did not increase GnSAF production. An antibody against human GnSAF blocked GnSAF bioactivity produced by rat follicles, and recognised proteins within the expected pI and molecular weight range for GnSAF in two-dimensional gels of rat follicle-conditioned medium, showing a good homology between rodent and human GnSAF proteins. In conclusion, the release of GnSAF bioactivity is principally from small follicles stimulated by FSH. Therefore, intact rodent follicle culture systems offer an excellent model for the investigation of factors controlling GnSAF production under relatively physiological conditions.

Growth and viability of human blastocysts in vitro

2000 ◽  
Vol 8 (3) ◽  
pp. 241-287 ◽  
Author(s):  
GM Jones
Keyword(s):  
Blastocyst Stage ◽  
Culture Conditions ◽  
Cleavage Stage ◽  
Embryo Viability ◽  
Early Cleavage ◽  
Uterine Endometrium ◽  
Stage Of Development ◽  
Uterine Lavage

The transfer of a blastocyst established the first human clinical pregnancy following in vitro fertilization (IVF). Nine years later Cohen et al. reported pregnancies resulting from the transfer of cryopreserved human blastocysts. However, it was another six years before the first report of births resulting from the transfer of human blastocysts produced in vitro appeared in the medical literature. In the intervening period clinics have opted to transfer embryos at the early cleavage stage to the uterus, despite the fact that in vivo the embryo does not enter the uterus until two to three days later at the morula to blastocyst stage of development. The viability and potential for implantation of blastocysts is high, as indicated by the finding that more than 60% of in-vivo-derived blastocysts, recovered by uterine lavage following artificial insemination of fertile donors, implant and develop into viable fetuses when transferred to recipients. This is in stark contrast to the 10–20% of in-vitro-produced embryos transferred at the early cleavage stage of development that result in a live-birth. This reduction in viability following transfer of in-vitro-derived early cleavage stage embryos may have several possible explanations: (1) a failure of implantation due to poor synchronization between the embryo and the uterine endometrium; (2) a hostile environment in the uterus for early cleavage stage embryos; (3) sub-optimal in vitro culture conditions which result in a reduction in embryo viability; (4) the assumption that all oocytes retrieved in an IVF cycle have an equal ability to develop into viable embryos; and (5) the failure to identify the most viable embryo in a cohort. Certainly, improving culture conditions and laboratory techniques for developing high quality blastocysts routinely in vitro will not only address many of the above questions but will also improve the quality and viability of earlier stages of embryo development.

scholarly journals Modulating the Substrate Stiffness to Manipulate Differentiation of Resident Liver Stem Cells and to Improve the Differentiation State of Hepatocytes

2016 ◽  
Vol 2016 ◽  
pp. 1-12 ◽  
Author(s):  
Angela Maria Cozzolino ◽  
Valeria Noce ◽  
Cecilia Battistelli ◽  
Alessandra Marchetti ◽  
Germana Grassi ◽  
...  
Keyword(s):  
Stem Cells ◽  
Culture Method ◽  
Cell Types ◽  
Culture Conditions ◽  
Precursor Cells ◽  
Substrate Stiffness ◽  
Growth And Survival ◽  
Liver Stem Cells

In many cell types, several cellular processes, such as differentiation of stem/precursor cells, maintenance of differentiated phenotype, motility, adhesion, growth, and survival, strictly depend on the stiffness of extracellular matrix that,in vivo, characterizes their correspondent organ and tissue. In the liver, the stromal rigidity is essential to obtain the correct organ physiology whereas any alteration causes liver cell dysfunctions. The rigidity of the substrate is an element no longer negligible for the cultivation of several cell types, so that many data so far obtained, where cells have been cultured on plastic, could be revised. Regarding liver cells, standard culture conditions lead to the dedifferentiation of primary hepatocytes, transdifferentiation of stellate cells into myofibroblasts, and loss of fenestration of sinusoidal endothelium. Furthermore, standard cultivation of liver stem/precursor cells impedes an efficient execution of the epithelial/hepatocyte differentiation program, leading to the expansion of a cell population expressing only partially liver functions and products. Overcoming these limitations is mandatory for any approach of liver tissue engineering. Here we propose cell lines asin vitromodels of liver stem cells and hepatocytes and an innovative culture method that takes into account the substrate stiffness to obtain, respectively, a rapid and efficient differentiation process and the maintenance of the fully differentiated phenotype.

scholarly journals Robust and Scalable Angiogenesis Assay of Perfused 3D Human iPSC-Derived Endothelium for Anti-Angiogenic Drug Screening

2020 ◽  
Vol 21 (13) ◽  
pp. 4804
Author(s):  
Vincent van Duinen ◽  
Wendy Stam ◽  
Eva Mulder ◽  
Farbod Famili ◽  
Arie Reijerkerk ◽  
...  
Keyword(s):  
Drug Screening ◽  
Cell Formation ◽  
Cell Types ◽  
Culture Conditions ◽  
In Vitro Assays ◽  
Vegf Receptor ◽  
Screening Assay ◽  
Angiogenesis Assay

To advance pre-clinical vascular drug research, in vitro assays are needed that closely mimic the process of angiogenesis in vivo. Such assays should combine physiological relevant culture conditions with robustness and scalability to enable drug screening. We developed a perfused 3D angiogenesis assay that includes endothelial cells (ECs) from induced pluripotent stem cells (iPSC) and assessed its performance and suitability for anti-angiogenic drug screening. Angiogenic sprouting was compared with primary ECs and showed that the microvessels from iPSC-EC exhibit similar sprouting behavior, including tip cell formation, directional sprouting and lumen formation. Inhibition with sunitinib, a clinically used vascular endothelial growth factor (VEGF) receptor type 2 inhibitor, and 3-(3-pyridinyl)-1-(4-pyridinyl)-2-propen-1-one (3PO), a transient glycolysis inhibitor, both significantly reduced the sprouting of both iPSC-ECs and primary ECs, supporting that both cell types show VEGF gradient-driven angiogenic sprouting. The assay performance was quantified for sunitinib, yielding a minimal signal window of 11 and Z-factor of at least 0.75, both meeting the criteria to be used as screening assay. In conclusion, we have developed a robust and scalable assay that includes physiological relevant culture conditions and is amenable to screening of anti-angiogenic compounds.

Cardiac fibroblasts: friend or foe?

2006 ◽  
Vol 291 (3) ◽  
pp. H1015-H1026 ◽  
Author(s):  
Troy A. Baudino ◽  
Wayne Carver ◽  
Wayne Giles ◽  
Thomas K. Borg
Keyword(s):  
Cardiac Function ◽  
Cardiac Fibroblasts ◽  
Cell Types ◽  
Dynamic Interaction ◽  
Normal Function ◽  
Complex Signals ◽  
Stage Of Development ◽  
Electrical Stimuli

Cardiac function is determined by the dynamic interaction of various cell types and the extracellular matrix that composes the heart. This interaction varies with the stage of development and the degree and duration of mechanical, chemical, and electrical signals between the various cell types and the ECM. Understanding how these complex signals interact at the molecular, cellular, and organ levels is critical to understanding the function of the heart under a variety of physiological and pathophysiological conditions. Quantitative approaches, both in vivo and in vitro, are essential to understand the dynamic interaction of mechanical, chemical, and electrical stimuli that govern cardiac function. The fibroblast can thus be a friend in normal function or a foe in pathophysiological conditions.

32D TPO, a TPO-Dependent Subclone of the 32d Cell Line, Expresses CXCR4 and Proliferates in Response to SDF-1.

Blood ◽  
2006 ◽  
Vol 108 (11) ◽  
pp. 4216-4216
Author(s):  
Giovanni Amabile ◽  
Rosanna Botta ◽  
Antonella Di Noia ◽  
Elena Alfani ◽  
Anna Rita Migliaccio ◽  
...  
Keyword(s):  
Growth Factors ◽  
Cell Line ◽  
Culture Conditions ◽  
Suitable Model ◽  
Platelet Factor ◽  
Gm Csf ◽  
Dependent Cell ◽  
Von Willebrand

Abstract Both Thrombopoietin (TPO) and Stromal Derived Factor 1 (SDF-1) have been reported to regulate megakaryocyte differentiation in vivo and in vitro. Using growth factors [G-CSF, M-CSF, GM-CSF, erythropoietin (EPO) or thrombopoietin (TPO)], as selective pressure, factor-dependent clones were consistently isolated from the murine multipotential IL-3-dependent cell line 32D. The different clones acquired a phenotype consistent with the growth factor for which they were dependent. In particular, the EPO-dependent clones showed erythroblast morphology and expressed high levels of CD71 and TER119, on the other hand, the TPO-dependent clones were megakaryocytes in morphology and expressed CD41 and CD61 (see Figure). The TPO-dependent subclones retain the capacity to grow in IL-3, but respond to neither EPO, G-CSF or GM-CSF. Here it is shown that the TPO-dependent clone, but not its EPO-dependent sister (see figure) or parental 32D cell lines, express robust level of CXCR4 on their surface. 32D TPO cells are also capable to respond to SDF-1 (the CXCR4 ligand). In fact, these cells die in 3 days in the absence of growth factors but proliferate equally well (from 5x104 to 6–9x105 cells/mL) in the presence of TPO (100 ng/mL) and/or SDF-1 (100 ng/mL), retaining a robust megakaryocytic phenotype in both culture conditions. By expression profile 32D TPO cells growing in TPO express the same level of Gata1 (both ~2−ΔCt = 3.6 ± 0.5x10−2 ) and Platelet Factor-4 (both 2−ΔCt = 3.5±1x10−1) more Gata2 (2−ΔCt = 2.3±0.1x10−1 vs 1.3±0.2x10−1, respectively), and Fog1 (2−ΔCt = 4.5±1x10−2 vs 3.1±0.5x10−2, respectively), and less Acetylcholinesterase (2−ΔCt = 4.96±1x10−5 vs 6.68±2x10−5, respectively), and Von Willebrand Factor (2−ΔCt = 2.7±0.3x10−2 vs 3.4±0.5x10−2, respectively), than those growing in SDF-1. These data indicate that a TPO-dependent cell line acquires the ability to respond to SDF-1, supporting the notion that megakaryocytic differentiation can be sustained equally well by TPO or SDF-1. To our knowledge, the 32D TPO cell line is the first megakaryocytic cell line that is dependent for growth on the presence of SDF-1. As such, it might represent a suitable model to compare TPO and SDF-1 signalling in megakaryocytes. Figure Figure

scholarly journals The Immunomodulatory Properties of Amniotic Cells

2018 ◽  
Vol 27 (1) ◽  
pp. 31-44 ◽  
Author(s):  
Marta Magatti ◽  
Elsa Vertua ◽  
Anna Cargnoni ◽  
Antonietta Silini ◽  
Ornella Parolini
Keyword(s):  
Cell Proliferation ◽  
Cell Types ◽  
Culture Conditions ◽  
Immunostimulatory Activity ◽  
Specific Culture ◽  
The Many ◽  
Regulatory Functions ◽  
Amniotic Cells

Among the many cell types useful in developing therapeutic treatments, human amniotic cells from placenta have been proposed as valid candidates. Both human amniotic epithelial and mesenchymal stromal cells, and the conditioned medium generated from their culture, exert multiple immunosuppressive activities. Indeed, they inhibit T and B cell proliferation, suppress inflammatory properties of monocytes, macrophages, dendritic cells, neutrophils, and natural killer cells, while promoting induction of cells with regulatory functions such as regulatory T cells and anti-inflammatory M2 macrophages. These properties have laid the foundation for their use for the treatment of inflammatory-based diseases, and encouraging results have been obtained in different preclinical disease models where exacerbated inflammation is present. Moreover, an immune-privileged status of amniotic cells has been often highlighted. However, even if long-term engraftment of amniotic cells has been reported into immunocompetent animals, only few cells survive after infusion. Furthermore, amniotic cells have been shown to be able to induce immune responses in vivo and, under specific culture conditions, they can stimulate T cell proliferation in vitro. Although immunosuppressive properties are a widely recognized characteristic of amniotic cells, immunogenic and stimulatory activities appear to be less reported, sporadic events. In order to improve therapeutic outcome, the mechanisms responsible for the suppressive versus stimulatory activity need to be carefully addressed. In this review, both the immunosuppressive and immunostimulatory activity of amniotic cells will be discussed.

Either exogenous or endogenous fibronectin can promote adherence of human endothelial cells

1986 ◽  
Vol 82 (1) ◽  
pp. 263-280
Author(s):  
R.A. Clark ◽  
J.M. Folkvord ◽  
L.D. Nielsen
Keyword(s):  
Endothelial Cells ◽  
Wound Repair ◽  
Cell Types ◽  
Culture Conditions ◽  
Collagen Type Iv ◽  
Human Endothelial Cells ◽  
Small Vessels ◽  
Microvascular Cells

Recently, we have presented evidence that proliferating blood vessels produce and deposit fibronectin in situ during the angiogenesis of wound repair. This report extends these observations by demonstrating that human endothelial cells from both large and small vessels depend on fibronectin for their adherence in vitro. Endothelial cells were grown from human umbilical veins (HUVEC) by the method of Gimbrone and from the microvasculature of human omentum by the method of Kern, Knedler and Eckel. Second-passage cells were plated into microtitre wells that had been coated with 100 micrograms ml-1 of fibronectin, types I and III collagen, type IV collagen or laminin. After a 3-h incubation, adherent cells were solubilized with Zap-Isoton and quantified on a Coulter Counter. Under normal culture conditions HUVEC showed no preference for fibronectin substrates while microvascular cells always demonstrated a striking preference for fibronectin substrates. However, when HUVEC were exposed to 2.5 or 25 micrograms ml-1 of cycloheximide for 4 h before and during the adherence assays, the adherence to fibronectin was 50–200% greater than to types I and III collagen. Immunofluorescence studies showed that while HUVEC expressed a large quantity of surface fibronectin, microvascular cells expressed very little. Metabolic labelling studies confirmed that HUVEC cultures had substantial quantities of fibronectin in their cell layer while microvascular cells did not. In antibody blocking experiments, preincubation of fibronectin-coated surfaces with anti-fibronectin antibodies totally blocked microvascular cell adhesion but only abrogated HUVEC adherence by 50%, presumably since these latter cells were able to deposit additional fibronectin onto the surface during the 3 h assay period. In the presence of cycloheximide anti-fibronectin antibodies totally blocked HUVEC adherence. These results demonstrate that both endothelial cell types rely, at least in part, on fibronectin for adherence in vitro. HUVEC can synthesize, secrete and deposit enough fibronectin for their adherence in vitro, while microvascular cells rely on an exogenous source of fibronectin under these culture conditions. Thus, the increased blood vessel fibronectin observed during angiogenesis in vivo may mediate adherence of the proliferating and migrating endothelial cells.

P–439 Carbohydrate metabolism profile during oocyte final maturation reveals culture induced aberrations in in vitro grown and matured mouse antral follicles

2021 ◽  
Vol 36 (Supplement_1) ◽  
Author(s):  
A C Herta ◽  
L Vo. Mengden ◽  
N Akin ◽  
K Billooye ◽  
J Va. Leersum ◽  
...  
Keyword(s):  
Antioxidant Capacity ◽  
Tca Cycle ◽  
Cell Types ◽  
Follicle Culture ◽  
Antral Follicles ◽  
Culture Systems ◽  
Final Maturation ◽  
Quality Markers

Abstract Study question Are there significant differences in carbohydrate metabolism trends between in vivo and in vitro grown mouse antral follicles during oocyte final maturation? Summary answer Glucose metabolism characterization during GV to MII transition revealed altered metabolic patterns mainly in cumulus cells of in vitro grown and matured mouse antral follicles. What is known already For some cancer patients fertility restoration is dependent on using efficient in vitro follicle culture systems. As human donor ovarian tissue available for research is limited, establishing such culture systems relies on data generated from animal models. The culture system previously developed in our laboratory supports in vitro growth of mouse preantral follicles with good oocyte maturation rates but lower developmental competence compared to in vivo grown oocytes. Tracking and comparing the metabolic changes after meiotic maturation in in vitro and in vivo follicles could serve as a screening tool for improving culture conditions and identifying metabolic quality markers. Study design, size, duration Mouse secondary follicle culture was performed. In vitro grown oocytes, their corresponding cumulus (CC) and granulosa cells (GC) were collected from antral follicles, at germinal vesicle stage (GV) on day 9, and at metaphase 2 (MII) on day 10, after hCG/EGF stimulation. In vivo age-matched controls were obtained after intraperitoneal injections with eCG for GV, or with eCG and hCG for MII. In vivo GC after ovulation were not included. Participants/materials, setting, methods Glucose metabolism trends were compared during final maturation between in vitro grown antral follicles and their in vivo controls. Follicles that failed to resume meiosis in vitro were also included. Enzymatic spectrophotometric assays were used to measure glycolysis, pentose phosphate pathway (PPP), tricarboxylic acid (TCA) cycle, and the antioxidant capacity in individual cell types. Pools of 5 oocytes and corresponding somatic cells were collected, from 3 independent experiments. Unpaired t-test was performed with significance when p < 0.05. Main results and the role of chance Important differences were detected between in vivo and in vitro conditions. GV to MII transition in in vivo follicles leads to a metabolic boost in CC as indicated by: i. significant increase in glycolysis, PPP and TCA cycle activity; ii. higher total antioxidant capacity (TAC) (p < 0.05) and small molecule antioxidant capacity (SMAC) (p < 0.01). After ovulation, the only significant change in oocytes was an increase in nicotinamide adenine dinucleotide phosphate (NADP+) level (p < 0.01), possibly due to increased reduced-NADP recycling. Meiotic maturation triggered no significant differences in any of the metabolic pathways for in vitro grown oocytes. Contrary to their in vivo controls, in vitro CC showed significant upregulations limited to aconitase, lactate dehydrogenase (LDH) and glutathione-s-transferase (GST) activity (p < 0.05). In vitro GC showed increased G6PDH activity (p < 0.05), suggesting PPP upregulation. Significant differences were detected between in vivo GV follicles and the in vitro failed-to-mature ones. Oocytes from impaired follicles have higher NADP+ levels (p < 0.0001) than their in vivo immature counterparts. CC showed higher phosphofructokinase (PFK), LDH, catalase activity and increased NADP + (p < 0.01), TAC and SMAC (p < 0.05) compared to in vivo GV CCs. GCs from failed-to-mature follicles have significantly higher LDH and superoxide dismutase (SOD) activity than in vivo GV GC (p < 0.05). Limitations, reasons for caution The altered metabolic patterns described here in in vitro follicles during oocyte GV to MII transition are probably the cumulative effects of both growth and maturation in vitro. Wider implications of the findings: We explored extensively and directly, for the first time, several enzymes and metabolites involved in follicle glucose and redox metabolism in different cell types separately. Understanding of the follicle metabolic requirements is essential for the optimization of follicle culture systems and could lead to development of oocyte quality markers. Trial registration number Not applicable

Meat and Livestock Association Plenary Lecture 2005. Oocyte signalling molecules and their effects on reproduction in ruminants

2006 ◽  
Vol 18 (4) ◽  
pp. 403 ◽  
Author(s):  
Kenneth P. McNatty ◽  
Stephen Lawrence ◽  
Nigel P. Groome ◽  
Mohammed F. Meerasahib ◽  
Norma L. Hudson ◽  
...  
Keyword(s):  
Granulosa Cells ◽  
Point Mutations ◽  
Follicular Development ◽  
Ovis Aries ◽  
Ovulation Rate ◽  
Active Immunisation ◽  
Signalling Molecules ◽  
Stage Of Development

Sheep (Ovis aries) are a highly diverse species, with more than 900 different breeds that vary significantly in their physiological characteristics, including ovulation rate and fecundity. From examination of inherited patterns of ovulation rate, several breeds have been identified with point mutations in two growth factor genes that are expressed in oocytes. Currently, five different point mutations have been identified in the BMP15 (GDF9b) gene and one in GDF9. Animals heterozygous for the GDF9 and/or the BMP15 mutations have higher ovulation rates than their wild-type counterparts. In contrast, those homozygous for any of the aforementioned BMP15 or GDF9 mutations are sterile owing to arrested follicular development. In bovine and ovine ovaries, GDF9 was expressed exclusively in oocytes throughout follicular growth from the primordial stage of development, whereas in sheep BMP15 was expressed exclusively in oocytes from the primary stage: no data for the ontogeny of BMP15 expression are currently available for cattle. In vitro, ovine growth differentiation factor 9 (oGDF9) has no effect on 3H-thymidine incorporation by either bovine or ovine granulosa cells, whereas ovine bone morphogenetic protein 15 (oBMP15) has modest (1.2- to 1.6-fold; P < 0.05) stimulatory effects. Ovine GDF9 or oBMP15 alone inhibited progesterone production by bovine granulosa cells, whereas in ovine cells only oGDF9 was inhibitory. The effects of oGDF9 and oBMP15 together were often cooperative and not always the same as those observed for each factor alone. Active immunisation of ewes with BMP15 and/or GDF9 peptides affected ovarian follicular development and ovulation rate. Depending on the GDF9 and/or BMP15 vaccine formulation, ovulation rate was either increased or suppressed. A primary and single booster immunisation of ewes with a BMP15 peptide in a water-based adjuvant has led to 19–40% increases in lambs born per ewe lambing. Collectively, the evidence suggests that oocyte signalling molecules have profound effects on reproduction in mammals, including rodents, humans and ruminants. Moreover, in vivo manipulation of these oocyte signalling molecules provides new opportunities for the management of the fertility of ruminants.

STUDIES ON TISSUE CULTURE OF EQUINE OVARIAN CELL TYPES: EFFECT OF GONADOTROPHINS AND STAGE OF CYCLE ON STEROIDOGENESIS

1969 ◽  
Vol 43 (3) ◽  
pp. 415-425 ◽  
Author(s):  
CORNELIA P. CHANNING
Keyword(s):  
Tissue Culture ◽  
Cell Cultures ◽  
Granulosa Cells ◽  
Horse Serum ◽  
Cell Types ◽  
Phase Cell ◽  
Medium Change ◽  
Midluteal Phase

SUMMARY Granulosa cells were harvested from follicles of mares at various stages of the oestrous cycle and maintained in a tissue culture medium containing 15% horse serum, 30% medium '199' and 55% Hanks's solution. Between days 4 and 10 of culture the granulosa cells harvested from small follicles (1–2 cm. diam.) of mares in the midluteal phase of the cycle secreted an average of 0·36 pg. progesterone/cell/day. Cells harvested from large follicles of mares in the late and/or early oestrous stage of the cycle secreted an average of 29·5 pg. progesterone cell/day; the cells harvested from the large vascular follicles found at oestrus secreted an average of 173 pg./cell/day. The small, poorly vascularized follicles found adjacent to the large vascular follicles of mares in oestrus yielded cells which secreted less progesterone than those from the larger follicles. Addition of 5 to 10 i.u. human chorionic gonadotrophin (HCG)/ml. at each medium change (every 2–3 days) or for the first 4 days of culture brought about a marked stimulation of progesterone secretion in cultures of ' mid-luteal phase' cells which was maximal after 4 to 7 days. Pregnenolone was converted primarily to progesterone, 20α-hydroxypregn-4-en-3-one and 17-hydroxyprogesterone; the metabolism was not significantly altered by the addition of a mixture of 10 i.u. HCG plus 10 i.u. pregnant mare serum gonadotrophin (PMSG). Cells harvested from mares in oestrus converted pregnenolone to progesterone in a higher yield compared with cells harvested from mares in the midluteal phase of the cycle. Addition of 10 i.u. HCG/ml. or PMSG plus HCG (10 i.u. each/ml.) stimulated aromatization of testosterone by 'midluteal phase' cultures but not by 'oestrous phase' cell cultures. These results demonstrate that the in vivo environment as well as the in vitro conditions influence the steroidogenic activity of equine granulosa cell cultures.

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