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  • 1
    Electronic Resource
    Electronic Resource
    Influence of the Embryo and Uterus on Luteal Function in the Sheep (1964)
    [s.l.] : Nature Publishing Group
    Nature 201 (1964), S. 522-523 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Embryos, ranging from 1 mm to more than 20 cm in length, were recovered from donor ewes in the following manner. The cervix was clamped, and sheep serum was injected into the tip of one uterine horn. The serum and embryos were forced round the body of the uterus to a glass tube positioned in the ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/201522a0
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  • 2
    Electronic Resource
    Electronic Resource
    Regulation of the Meiotic Cycle in Oocytes of Domestic Mammals (1988)
    Oxford, UK : Blackwell Publishing Ltd
    Annals of the New York Academy of Sciences 541 (1988), S. 0 
    Details
    ISSN: 1749-6632
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Natural Sciences in General
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1749-6632.1988.tb22262.x
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  • 3
    Electronic Resource
    Electronic Resource
    Haemoglobin type and superovulation in ewes (1976)
    [s.l.] : Nature Publishing Group
    Nature 262 (1976), S. 329-329 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] PANT and Pandey1 reported that haemoglobin (Hb) type in Binaneri ewes influences the ovulatory response to exogenous gonadotropin (pregnant mare's serum gonadotropin, PMSG). The practical and physiological implications of this finding prompt us to present the results of a study of the relationship ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/262329b0
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  • 4
    Electronic Resource
    Electronic Resource
    Endocrine activity, histochemistry and ultrastructure of ovine corpora lutea (1970)
    Springer
    Cell & tissue research 111 (1970), S. 437-457 
    Details
    ISSN: 1432-0878
    Keywords: Corpora lutea ; Ovine ; Regression ; Oestrous cycle
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The progesterone concentration, histology, histochemistry and ultrastructure of the corpora lutea of 21 Welsh Mountain sheep between day 10 of the cycle and the following oestrus were studied. In two of the animals the corpora lutea had recently regressed to become corpora albicantia. The progesterone concentrations in the luteal tissue were high from day 10–14; on day 15 the progesterone level had dropped to a very low level in 3 out of 4 animals. From day 12 onwards glycogen accumulated in the lutein cells and on day 13 the number of matrical granules in the mitochondria began to increase. The possible significance of these changes is discussed. The first definite structural sign of degeneration of the corpus luteum appeared to be karyorrhexis. Whether or not this occurs before the steroid secretion declines still remains to be determined.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00330923
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  • 5
    Electronic Resource
    Electronic Resource
    Endocrine activity, histochemistry and ultrastructure of ovine corpora lutea (1970)
    Springer
    Cell & tissue research 111 (1970), S. 458-470 
    Details
    ISSN: 1432-0878
    Keywords: Corpora lutea ; Ovine ; Regression ; Hysterectomy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The progesterone concentration, histology, histochemistry and ultrastructure of the corpora lutea of six sheep hysterectomized early in the oestrous cycle were studied 137–146 days after ovulation. In one of these animals the corpus luteum had recently regressed to become a corpus albicans. The progesterone concentrations in the luteal tissue were comparable with the values for active corpora lutea of the cycle. However in the peripheral blood of the hysterectomized sheep the concentration of progesterone was much lower than that in the luteal phase of the cycle. The lutein cells of the hysterectomized sheep differed from those in the cycle in that the nucleoli were smaller, there were fewer free ribosomes and less granular and agranular endoplasmic reticulum; also the lipid droplets were larger, and cytoplasmic granules that stained with azocarmine were seen. Acid phosphatase activity was higher and there were large cytosomes of a type not seen in the cycle; these may be a morphological expression of the impaired hormone release. Karyorrhexis, a distinctive feature of regression at the end of the oestrous cycle, was only observed in the hysterectomized sheep with the corpus albicans. In conclusion, luteal regression following hysterectomy appears to differ from regression at the end of the oestrous cycle in that the initial changes involve impaired hormone release from the gland rather than impaired synthesis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00330924
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  • 6
    Electronic Resource
    Electronic Resource
    Ultrastructure of the theca interna of ovarian follicles in sheep (1978)
    Springer
    Cell & tissue research 187 (1978), S. 457-472 
    Details
    ISSN: 1432-0878
    Keywords: Ovarian follicles (sheep) ; Theca interna ; Oestrogen ; Androgen ; Capillaries ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary 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 〈3.0mm 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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00229610
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  • 7
    Electronic Resource
    Electronic Resource
    Structural changes occurring during atresia in sheep ovarian follicles (1976)
    Springer
    Cell & tissue research 169 (1976), S. 515-529 
    Details
    ISSN: 1432-0878
    Keywords: Graafian follicle (sheep) ; Atresia ; Ovum ; Capillaries ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary 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 μm but occasionally reached as much as 400 μm. 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 play 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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00218150
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  • 8
    Electronic Resource
    Electronic Resource
    The fine structure of the cumulus oophorus during follicular development in sheep (1979)
    Springer
    Cell & tissue research 202 (1979), S. 439-451 
    Details
    ISSN: 1432-0878
    Keywords: Ovarian follicles (sheep) ; Cumulus ; Membrana granulosa ; Glycogen ; Oestrogen
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary 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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00220436
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  • 9
    Electronic Resource
    Electronic Resource
    Effect of follicle cells on the maturation and developmental competence of ovine oocytes matured outside the follicle (1984)
    New York, NY : Wiley-Blackwell
    Gamete Research 9 (1984), S. 221-229 
    Details
    ISSN: 0148-7280
    Keywords: oocyte ; in vitro maturation ; blastocysts ; sheep ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: The hypothesis that follicle cells play a central role in endowing the oocyte with developmental competence during maturation has been tested in coculture studies. Oocytes and follicle cells in various combinations were cultured for 24 h with gonadotrophins and estrogen in a nonstatic culture system. Developmental competence was assessed by transfer of oocytes to inseminated receipient ewes followed by embryonic examination 12 days later or at parturition.Denuded and corona-enclosed oocytes resume meiosis in culture but remain immature and developmentally incompetent. By contrast, oocytes supported by the cumulus and underlying granulosa (cumulus-oocyte complexes) undergo full maturation and normal subsequent embryonic development (42.6% to embryos). Addition of supplementary follicle cells during culture (5 × 106 cells/ml medium) is without beneficial effect on denuded oocytes. However, supplementary cells confer competence on corona-enclosed oocytes (37% to embryos).A dual cellular requirement for full maturation involving both cell numbers and some direct cell-oocyte contact is highlighted by our experiments. The results demonstrate further that the nonstatic system provides a simple but reliable method of producing large numbers of fully matured oocytes for both research and clinical purposes.
    Additional Material: 2 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrd.1120090211
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  • 10
    Electronic Resource
    Electronic Resource
    Protein and nuclear changes in pig eggs at fertilization (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Molecular Reproduction and Development 31 (1992), S. 287-296 
    Details
    ISSN: 1040-452X
    Keywords: Phosphorylation ; Protein synthesis ; Pronuclei ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: The nuclear restructuring that occurs between insemination and full pronuclear formation in pig eggs is accompanied by posttranslational changes to specific egg proteins. Sperm penetration begins in vitro at 3 hr postinsemination (hpi). By 5 hr, decondensing sperm heads and anaphase II plates are observed in 50% of eggs, and, by 8 hpi, both male and female pronuclei have formed. Three consistent changes to the pattern of newly synthesised proteins are triggered in this period; they affect the 46K, 25K, and 22K polypeptides. Changes are also triggered in the 180-200K polypeptides and in the 14K polypeptides, but these are highly variable. The same changes in the prefertilization pattern were observed when prelabelled eggs were used and new protein synthesis was suppressed. The first and most abrupt change involves the apparent catabolic elimination of a group of 46K unphosphorylated polypeptides (pl 7.3-6.4), whose synthesis was greatest before germinal vesicle breakdown but declined slowly in the final phase of maturation, then declined precipitously after activation. Ageing (beyond maturation) also leads to the disappearance of these polypeptides. The progressive disappearance of a set of 25K polypeptides and the concomitant appearance of a dominant 22K polypeptide is the most characteristic fertilization-induced modification to porcine egg proteins. These modifications begin within 1 hr of sperm penetration or activation, are specific to the pig, and involve heavily phosphorylated polypeptides (25K, pl 6.7-6.0) whose synthesis is begun in the early metaphase I stage. Dual ([35S] and [32P]) labelling, protein blocking experiments, and use of alkaline phosphatase suggest that dephosphorylation selectively affects these 25K polypeptides and is mainly or wholly responsible for converting them (completely within 6 hr) to a single, new (22K, pl 7.6) species that is positively charged. The 25K/22K polypeptide modification has a close temporal relationship with the formation of the male and female pronuclei.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrd.1080310410
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