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Biomedical subjects

R M Moor

Publications and source records attributed to R M Moor.

At least 127 records · Page 7Linked to original sources
PubMed1979

The fine structure of the cumulus oophorus during follicular development in sheep.

The cumulus and membrana granulosa of non-atretic ovarian follicles from primordial up to a stage shortly before ovulation were studied by electron microscopy. The follicular cells of primordial follicles were undifferentiated and rested on a thick basal lamina. In secondary follicles the endoplasmic reticulum had proliferated forming an anastomosing network. In early antral and antral follicles (0.5--2.0 mm dia.) the ER was composed of short cisternae, the mitochondria had elongated and gap junctions were first observed. In late antral follicles (3.0--5.9 mm dia.) gap junctions were frequent. In the cumulus the glycogen was associated with electron lucent areas whereas in the granulosa it was invariably associated with membranes. In large antral follicles large membrane bound bodies were present in the basal cells of the cumulus. At early oestrus a distinctive mitochondrial morphology was noted in the granulosa but not elsewhere in the follicles. At mid oestrus numerous annular nexuses were present in the granulosa but not in the cumulus. At late oestrus numerous lipid droplets were formed in both cumulus and granulosa, the boundary with theca interna became indistinct and the basal lamina became incomplete.

Animals↗
PubMed1979

Regeneration of atretic sheep ovarian follicles in vitro.

Large (4--6 mm diam.) and small (2--3 mm) atretic follicles were removed from sheep ovaries during the luteal phase of the cycle and maintained in organ culture without hormonal supplementation for up to 5 days. The structure, cell dynamics and steroid-producing capacity of the follicles were compared with those of non-atretic follicles of similar size. The granulosa layer of the atretic follicles invariably regenerated in culture, increasing in thickness more than 2- and 4-fold in large and small follicles respectively. This could not be accounted for by cell division which remained low throughout the culture period. In contrast, non-atretic follicles showed high mitotic activity during the first 24 h in culture: this was not associated with an increase in granulosa thickness in large follicles although there was a 4-fold increase in small ones. An increase in internuclear spacing, a measure of cell size plus intercellular space, partly accounted for the increase in granulosa thickness in atretic follicles. Even when granulosa cells remained in close apposition there was an almost total absence of gap junctions, a prominent feature in the granulosa of non-atretic follicles both in vivo and in vitro. Pyknotic nuclei and atretic bodies rapidly disappeared from the regenerating granulosa layer. The theca interna was restored in culture to a state ultrastructurally closely resembling that of non-atretic follicles in vivo. Total steroid secretion (oestradiol-17beta, testosterone plus progesterone) into the culture medium (pmol.mg tissue-1.24 h-1) was the same for atretic and non-atretic follicles of comparable size. There was, however, a marked difference in the type of steroid produced, largely related to a loss of aromatizing capacity in atretic follicles. The predominant steroid secreted by large non-atretic follicles was oestrogen, with slightly smaller amounts of testosterone, whereas the principal steroid secreted by large atretic follicles was progesterone. In small non-atretic and atretic follicles, the predominant steroid was testosterone, but the non-atretic follicles also secreted appreciable amounts of oestrogen. Addition of FSH to the culture medium did not restore aromatizing capacity to the atretic follicles.

Animals↗
PubMed1979

Effect of exogenous gonadotrophin (PMSG) on the antral follicle population in the sheep.

Follicles were obtained from the ovaries of four groups of 15 ewes. Ewes in the control group were ovariectomized on the 12th day of the oestrous cycle. The other ewes were all given PMSG on the 12th day of the cycle; some were ovariectomized 24 or 40 h later, the others were given prostaglandin followed by hCG and were ovariectomized 6 or 12 h after the hCG injection. All follicles greater than 2 mm in diameter were measured and examined macroscopically for signs of atresia. Some were subjected to detailed morphological examination, the pattern of steroid secretion was determined in others. All the evidence from these three approaches suggested that, in vivo, reversal of the atretic process ('rescue') plays no part in the increase in the number of follicles observed following administration of PMSG.

Animals↗
PubMed1979

Interaction of ovarian tissues in the control of follicular steroidogenesis in culture.

The interaction between developing antral follicles and other ovarian tissues in sheep was examined in vitro. Small follicles (2.0--2.9 mm in diameter) were co-cultured with a single ovarian component for 48 h, then separated and cultured singly for a further 72 h during which time changes in follicular steroidogenesis and structure were measured. Control follicles, cultured together for 48 h before separation, had a mean total daily steroid output during the 72 h test period of 180.4 +/- 12.6 (S.E.M.) pmol mg tissue-1 24 h-1; oestrogen (61.7 +/- 8.2 pmol mg-1 24 h-1) and testosterone (84.4 +/- 9.2 pmol mg-1 24 h-1) accounted for 81% of the steroid secreted by control follicles. The presence of stromal tissue during co-culture depressed (P less than 0.01) the subsequent output of total steroid by 22%, oestrogen by 81% and testosterone by 38%; progesterone output was, however, over twice that of the controls. There was no distinctive structural differences between follicles in the control and stromal groups. Luteal tissue enhanced (P less than 0.01) the output of total steroid by 51%, testosterone by 55% and progesterone by 242%; oestrogen output was similar to that in the controls. Follicles co-cultured with luteal tissue were characterized by extensive hypertrophy of the theca interna. Developing follicles co-cultured with large non-atretic follicles had a similar total steroid output, a slightly higher oestrogen output and more thecal hypertrophy than the controls. Follicles co-cultured with large atretic follicles differed from controls only with respect to their greater capacity to synthesize progesterone.

Animals↗
PubMed1978

Ultrastructure of the theca interna of ovarian follicles in sheep.

The theca interna of non-atretic ovarian follicles from 2.0 mm in diameter up to the stage shortly following ovulation was studied by light and electron microscopy. In follicles less than 3.0 mm in diameter, the theca interna consisted of about 8-12 layers of flattened cells, together with many capillaries and small bundles of collagen. Two main forms of cellular differentiation were seen. These were towards either fibroblast-like cells or presumed steroidogenic cells whose cytoplasm contained large amounts of predominantly smooth tubular endoplasmic reticulum, to which some ribosomes were attached. The majority of cells were of relatively undifferentiated or intermediate structure. In larger follicles up to the early stages of oestrus the theca interna cells became larger and less flattened, and cells rich in tubular endoplasmic reticulum became proportionately more numerous. By 18 h after the onset of oestrus the theca interna was oedematous, and many cells possessed pseudopodia. Many cells also contained numerous lipid droplets, but there were no signs of thecal cell degeneration or death. Shortly after ovulation the basal lamina of the membrana granulosa was incomplete, and it became more difficult to distinguish between theca and granulosa layers. Structural heterogeneity, with two major cell types and cells of intermediate structure, was present at all stages. It was concluded that: (1) the theca interna of 2.0-2.9 mm follicles contained many cells whose structure was compatible with a steroidogenic capacity; (2) changes in the differentiated thecal cells up to the early stages of oestrus were quantitative rather than qualitative, and suggestive of an increased steroidogenic capacity; (3) the accumulation of lipid in many cells of the theca interna by 18 h after the onset of oestrus probably reflected a reduction in steroidogenic activity; and (4) there was no evidence of any structural specialization to facilitate the transport of steroids from the theca interna to the membrana granulosa.

Animals↗
PubMed1978

Sex chromosome chimaerism and the transmission of blood group genes by tetraparental rams.

A previously published study of 4 rams, 3 of them tetraparental chimaeras, has been extended. All were born subsequent to transplantation of separated blastomeres into intact 4--8-cell embryos which were transferred to recipient ewes. All were phenotypically normal males. Study of blood lymphocytes and red cell antigens showed that two were XX/XY chimaeras, one an XY/XY chimaera. Chimaerism was not identified in the 4th animal. The new data show that the previously reported decline in proportions of red cells derived from the one cell line has continued, although the proportions of lymphocytes entering mitosis in culture have remained nearly constant. A decline of potassium concentration in the red cells of one animal and of transferrin type in another also continued. Analysis of blood types in the offspring of the 4 rams revealed that both cell lines of the XY/XY chimaera must have produced functional spermatozoa whereas the genes transmitted by the remaining 3 rams gave evidence of spermatozoa from one cell line only.

Animals↗
PubMed1978

Macroscopic identification and steroidogenic function of atretic follicles in sheep.

The degree of translucency, vascularization of the follicle wall and the integrity of the membrana granulosa, as seen under a stereoscopic microscope, were used to distinguish between non-atretic and atretic isolated follicles. Subsequent histological evaluation showed that both non-atretic and severely atretic follicles could be correctly identified with over 95% accuracy. The concentrations of steroids were measured in both follicular tissue and fluid. The total steroid content of large (3.1-6.0 mm diameter) non-atretic follicles in vivo (115 pmol/follicle) exceeded that of large atretic follicles (54 pmol) and also that of small (2.0-3.0 mm diameter) non-atretic and atretic follicles (6 pmol). Oestrogen accounted for 80%, testosterone 13% and progesterone 7% of the total steroid content in large non-atretic follicles, whereas testosterone accounted for 75% of the steroid content in the other three categories of follicles. A similar pattern is observed when the concentrations of steroids are expressed on the basis of follicular weight. Total oestrogen secretion, as measured by the output of steroid into the culture medium in 24 h, was 937 pmol for large non-atretic, 31 pmol for large atretic, 65 pmol for small non-atretic and 4 pmol for small atretic follicles. In terms of steroid production (pmol/mg tissue), the four follicular categories were equally efficient. However, the type of steroid produced depended on the category of follicle and corresponded to its steroid content.

Animals↗
PubMed1977

Reproductive function in prepubertal lambs: ovulation, embryo development and ovarian steroidogenesis.

When 23 10-16 week-old Welsh Mountain lambs were treated with PMSG 19 ovulated, the number of eggs ovulated being directly correlated with the duration of progesterone pretreatment (0-5 +/- 0-29 (S.E.M.) after 3 days; 7-8 +/- 3-47 after 18 days). Injection of HCG at the time of the induced oestrus had no effect on ovulation. The eggs shed from immature ovaries became fertilized and developed normally when tested in the ligated rabbit oviduct for development to the morula stage and by transfer to adult ewes (1 live lamb). Luteal function in lambs with a single CL was similar to that in nonpregnant ewes; progesterone levels in entire lambs with multiple CL and in hysterectomized lambs remained elevated for at least 60 days. The capacity of ovarian follicles from PMSG-primed lambs to secrete oestrogen, testosterone and progesterone in vitro was similar to that of follicles from adult ewes. However, oestrogen production by lamb follicles immediately after explantation was higher than that of adult follicles and the administration of progesterone to lambs before PMSG treatment decreased subsequent follicular testosterone production.

Animals↗
PubMed1977

Hormonal and follicular factors affecting maturation of sheep oocytes in vitro and their subsequent developmental capacity.

Oocytes removed from, or retained within, non-atretic and atretic follicles of different sizes were cultured for 24 h in the presence of a variety of hormones in an attempt to identify the factors affecting oocyte maturation in vitro. Resumption of meiosis was assessed morphologically; the developmental capacity of oocytes after culture was determined by transfer to the oviducts of inseminated ewes. About 70% of oocytes cultured after removal from follicles of different sizes resumed meiosis in vitro, but they did not undergo normal development after transplantation. Oocytes cultured within the follicle in hormone-free medium remained at the germinal vesicle stage. In the presence of FSH and LH some oocytes reached the second meiotic metaphase: 19% in small (2-3 mm diam.) and 73% in larger (3-5 mm diam.) non-atretic follicles, and 54% in small and 45% in larger atretic follicles. Less than 5% of oocytes cultured in follicles developed into normal blastocysts after transplantation when either no hormone or only FSH and LH were added to the culture medium. The addition of oestradiol-17beta to medium containing FSH (2 mug/ml) and LH (1 mug/ml) resulted in the development to blastocysts of 26% of oocytes from small non-atretic follicles, 46% from large non-atretic follicles and 50% from atretic follicles. Blastocyst formation was greatly depressed and fragmentation rate signinificantly increased with concentrations of 10 mugFSH/ml and 2 mug LH/ml. Developmental capacity after culture was further demonstrated by the birth of lambs from 63% of blastocysts derived from oocytes matured in vitro; 52% of control blastocysts developed to lambs after transfer.

Animals↗
PubMed1977

Changes in protein synthesis during maturation of sheep oocytes in vivo and in vitro.

The qualitative profiles of the proteins synthesized by sheep oocytes at various stages of maturation were determined by electrophoretic separation in one dimension on polyacrylamide SDS gels. No change in protein synthetic pattern was observed in ooce changes had taken place in at least 12 separate protein bands. Marked alterations in the synthesis of some proteins were apparent 15 h after LH; formation of proteins in 5 of the original bands was either reduced or not detectable, while new synthesis was evident from the appearance of 7 additional bands. The pattern of proteins produced by oocytes cultured within the follicle corresponded closely with that observed in vivo: changes in synthesis were initiated about 9 h after addition of gonadotrophin and were completed by 15 h. Oocytes cultured outside the follicle in a gonadotrophin-containing medium did not exhibit a change in protein synthesis and at 15 h only those proteins produced during the early stages of maturation were being synthesized.

Animals↗
PubMed1977

Sites of steroid production in ovine graafian follicles in culture.

The follicular components responsible for the synthesis of oestrogen, testosterone, and progesterone have been localized by studying in vitro the steroidogenic capacity of (1) intact follicles, (2) opened but undisturbed follicle walls, (3) isolated thecal shells, (4) granulosa cells and (5) co-cultures of thecal shells and granulosa monolayers. Oestrogen was secreted throughout the five-day culture period by intact follicles and explants of follicle wall. Neither the isolated thecal shell nor the membrana granulosa alone secreted oestrogen in vitro, but granulosa cells converted exogenous testosterone to oestrogen during the first few hours after explantation. A limited and transient production of oestrogen occurred in co-cultures of theca and granulosa. Testosterone was secreted in the presence of FSH in approximately equal amounts by intact follicle, follicle wall and thecal shells. No testosterone was secreted by the isolated granulosa cells. Progesterone was secreted by each cellular component but the highest output occurred where granulosa cells were grown in monolayer culture. The results indicate that the theca is the source of follicular androgen synthesis but that an interaction between theca and granulosa is required for the production of oestrogen. It is postulated that direct contact between two cell components is important in the modulation of steroidogenic function within the follicle.

Animals↗
PubMed1977

Influence of foetal genotype on the follicle-stimulating hormone:luteinizing hormone ratio of pregnant mare serum gonadotrophin.

Rat testicular radioreceptor assays specific for FSH and LH were used to determine the FSH:LH ratio of PMSG produced by horse, donkey, mule and hinny conceptuses. Measurements of FSH and LH activities in PMSG produced both in vivo and in vitro by the four types of conceptuses showed that the genotype of the foetus markedly influences the FSH:LH ratio of PMSG. The FSH:LH ratio of PMSG produced by the horse conceptus was around unity whereas the ratio of PMSG produced by the donkey conceptus was as low as 0-2. Furthermore, the hybrid mule and hinny conceptuses both produced PMSG with an FSH:LH ratio which was approximately midway between those of the horse and donkey.

Animals↗
PubMed1977

The influence of anaesthesia on the concentrations of progesterone and cortisol in peripheral blood plasma of sheep.

Levels of progesterone and cortisol were measured in the peripheral plasma of sheep subjected to barbiturate (sodium pentobarbitone) and gaseous (halothane) anaesthesia both alone and in combination. Significant increases were recorded inthe level of cortisol in all experiments and in the levels of progesterone in all experiments except that involving halothane alone. It was also found that the cortisol levels remained elevated for a greater period of time than those of progesterone.

Anesthesia↗
PubMed1976

Structural changes occurring during atresia in sheep ovarian follicles.

The structural changes that characterize primary, secondary and tertiary atresia in sheep Graafian follicles have been studied by means of histological, histochemical and ultrastructural techniques. In primary atresia vacuoles representing swollen endoplasmic reticulum are prominent along the antral border together with disorganized granulosa cells containing pyknotic nuclei. Phagocytic cells, which increase in number as atresia progresses, were seen within the membrana granulosa and are considered to be transformed granulosa cells. Even in follicles classified as nonatretic, a few antral vacuoles and occasional pyknotic nuclei are present. During secondary atresia there is a large increase in the number of cells with pyknotic nuclei; many of these nuclei had been extruded and had fused to form the characteristic Feulgen-positive atretic bodies found along the edge of the antral cavity. These bodies usually have a diameter of up to 15 mum but occasionally reached as much as 400 mum. A second area of degeneration is frequently present in the membrana granulosa, two or three cell layers from the basal lamina, and it is at this level that exfoliation of granulosa cells occurs in tertiary atresia. In contrast to the membrana granulosa, there are during secondary atresia, only slight indications of degeneration in the cumulus. In tertiary atresia the membrana granulosa is highly disorganized; the atretic bodies are often fewer in number than at earlier stages. The basal lamina remains essentially intact. It is at this stage that the first clear signs of degeneration occur in the theca interna. Despite some disintegration of the cumulus, the integrity of the oocyte is maintained and its nucleus remains vesicular. Changes in the thecal microcirculation may plan a key role in atresia: adjacent to the basal lamina of non-atretic follicles, there is a well-developed capillary network which is significantly reduced as atresia progresses.

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