Search Results
You are looking at 1 - 4 of 4 items for
- Author: S. Harris x
- Refine by access: All content x
Search for other papers by F. G. L. Hartley in
Google Scholar
PubMed
Search for other papers by B. K. Follett in
Google Scholar
PubMed
Search for other papers by S. Harris in
Google Scholar
PubMed
Search for other papers by D. Hirst in
Google Scholar
PubMed
Search for other papers by A. S. McNeilly in
Google Scholar
PubMed
The endocrine basis of reproductive failure in red fox vixens was examined over two breeding seasons in a total of 11 animals. Weekly blood samples were assayed for progesterone, prolactin, LH and cortisol. Vaginal smears taken every 2 days over the oestrous period indicated that all vixens had mated. Vixens that successfully gave birth to a litter of cubs demonstrated significantly higher plasma progesterone and prolactin concentrations but significantly lower cortisol concentrations than did females that had ovulated, but then failed to whelp. There were no significant differences in plasma LH concentrations. These data suggest that reproductive losses could result from lowered plasma progesterone concentrations, possibly resulting from inadequate luteotrophic support by prolactin. A stress-induced mechanism of reproductive failure is implicated and is discussed in relation to social suppression of reproduction.
Search for other papers by S. Harris in
Google Scholar
PubMed
Search for other papers by M. McClenaghan in
Google Scholar
PubMed
Search for other papers by J. P. Simons in
Google Scholar
PubMed
Search for other papers by S. Ali in
Google Scholar
PubMed
Search for other papers by A. J. Clark in
Google Scholar
PubMed
AFRC Institute of Animal Physiology and Genetics Research, Edinburgh Research Station, Roslin, Midlothian EH25 9PS, UK
Keywords: Mammary gland; β-lactoglobulin; transgenic; gene expression
Introduction
The mammary gland is the specialized secretory organ that provides essential nourishment to mammalian young in the form of milk. Milk is primarily composed of water, fats, lactose and proteins; the major protein components are the various caseins and the whey proteins α-lactalbumin, β-lactoglobulin (ruminants) and whey acidic protein (rodents).
Mammary development and milk protein gene expression are regulated by a number of peptide and steroid hormones, as well as cell-cell and cell-substratum interactions within the gland (Topper & Freeman, 1980; Levine & Stockdale, 1985; Li et al., 1987). During gestation the secretory capacity of the mammary gland increases due to cellular proliferation and differentiation; concomitantly milk protein gene expression is initiated in preparation for sustained milk production after parturition. In late lactation milk production
Search for other papers by H M Picton in
Google Scholar
PubMed
Search for other papers by S E Harris in
Google Scholar
PubMed
Search for other papers by W Muruvi in
Google Scholar
PubMed
Search for other papers by E L Chambers in
Google Scholar
PubMed
The development of technologies to grow oocytes from the most abundant primordial follicles to maturity in vitro holds many attractions for clinical practice, animal production technology and research. The production of fertile oocytes and live offspring has been achieved in mice following the long-term culture of oocytes in primordial follicles from both fresh and cryopreserved ovarian tissue. In contrast, in non-rodent species advances in follicle culture are centred on the growth of isolated preantral follicles. As a functional unit, mammalian preantral follicles are well-suited to culture but primordial and primary follicles do not grow well after isolation from the ovarian stroma. The current challenges for follicle culture are numerous and include: optimisation of culture media and the tailoring of culture environments to match the physiological needs of the cell in vivo; the maintenance of cell–cell communication and signalling during culture; and the evaluation of the epigenetic status, genetic health and fertility of in vitro derived mature oocytes. In large animals and humans, the complete in vitro growth and maturation of oocytes is only likely to be achieved following the development of a multistage strategy that closely mimics the ovary in vivo. In this approach, primordial follicle growth will be initiated in situ by the culture of ovarian cortex. Isolated preantral follicles will then be grown to antral stages before steroidogenic function is induced in the somatic cells. Finally, cytoplasmic and nuclear maturation will be induced in the in vitro derived oocytes with the production of fertile metaphase II gametes.
Search for other papers by N A Czarny in
Google Scholar
PubMed
Search for other papers by J I Garnham in
Google Scholar
PubMed
Search for other papers by M S Harris in
Google Scholar
PubMed
Search for other papers by J C Rodger in
Google Scholar
PubMed
This study describes ovarian changes during the natural and stimulated reproductive cycle of breeding (≤12 month) and retired (>12 month) fat-tailed dunnarts, Sminthopsis crassicaudata. Increased urinary cornified epithelial cells and the influx of leukocytes defined day 0, at which time the naturally cycling females had already ovulated; at day 16 females had no antral follicles, but by day 20 antral follicles had begun to develop. There was no difference between naturally cycling breeding and retired females. Females were stimulated with 1 IU equine serum gonadotropin (eSG) during the intermediate phase on day 16 and killed 3, 4, or 5 days later. Stimulation resulted in a significant increase in the number of growing antral follicles but retired females demonstrated a reduced response. Upon collection from breeding females 4 days following eSG stimulation, 100% of oocytes were at the first polar body (PB1) stage, those collected from retired females were immature upon collection but within 48 h 98.2±1.9% were cultured to the PB1 stage. The rate of ovulation was high in breeding females 5 days following stimulation but retired females were less reliable, and in both groups all oocytes were degraded. This is the first study to describe a reliable technique, involving ovarian stimulation during the intermediate phase and segregation of age groups, allowing the collection of a large number of healthy PB1 stage oocytes from S. crassicaudata. This is important for the development of further assisted reproductive techniques for this species and threatened dasyurids.
