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Biomedical subjects

W R Allen

Publications and source records attributed to W R Allen.

At least 127 records · Page 7Linked to original sources
PubMed1989

Beginning to work together.

Ten people met for the first time as trainees after lunch on Thursday, 4 February, 1988 at an hotel near Ipswich. They were to live and work together until teatime on Saturday. Twelve trainers joined them from late afternoon on Friday, staying on after the trainees left, until lunchtime on the Sunday. The occasion was the start of the 1988 vocational training schemes for East Anglia and North East Thames Regions. In this article, J. K. Horrocks and W. R. Allen given an account of what happened during this time, and how people felt about it.

Dentists↗
PubMed1989

Vasopressin in dehydrated and rehydrated ponies.

Six pony mares deprived of water for 24 hours showed significant increases in plasma vasopressin (2.8 pg/ml) and osmolality (9 mosmol/kg). When water was made available the ponies drank rapidly (5 of 6 drank to satiety within 90 seconds) and corrected their fluid deficits precisely. Vasopressin did not return to predehydration levels until osmolality did after 15 minutes of access to water. The horse differs from rodents and humans, but is similar to pigs in that vasopressin levels do not fall before osmolality returns to normal. Oropharyngeal factors, therefore, may not be as important in vasopressin release in horses as in other species.

Animals↗
PubMed1989

Maternal immunological recognition of pregnancy in equids.

There is little evidence for maternal immunological recognition of pregnancy in most species with the striking exception of the members of the genus Equus. Almost all mares make strong cytotoxic antibody responses to paternally inherited fetal antigens by Day 60 of gestation. Most of these responses are directed against antigens of the Major Histocompatibility Complex (MHC), which constitutes the primary immunogenetic barrier to successful organ transplantation. The source of fetal MHC antigens in the pregnant mare appears to be the specialized trophoblast cells of the chorionic girdle region of the developing placenta. These cells invade the endometrium between Days 36 and 38 after ovulation to form the endometrial cups. The progenitor girdle cells express high levels of paternal MHC antigens, while the non-invasive trophoblast cells of the allantochorion and the differentiated trophoblast cells in the mature endometrial cups do not. This expression of MHC antigens by the chorionic girdle cells is unusual for a trophoblast tissue, and differs from most forms of trophoblast studied in other species. The maternal anti-fetal antibody responses of equine pregnancy do not adversely affect fetal development, nor are they required for successful pregnancy. However, it is possible that fetal loss of an immunological nature could occur in rare cases when the immunoregulatory mechanisms of pregnancy break down.

Animals↗
PubMed1988

A monoclonal antibody recognizes a 39 kDa protein expressed in atretic granulosa cells.

A major problem in ovarian physiology is the lack of conveniently quantifiable markers of atresia. Towards this end, we identified a monoclonal antibody (anti-OA-2) that selectively recognizes granulosa cells in atretic follicles. When cryostat sections of rat ovaries were incubated with anti-OA-2, granulosa cells in atretic follicles showed intense immunofluorescent labeling. In contrast, no anti-OA-2 immunoreactivity was observed in the granulosa of the healthy follicles. The amount of anti-OA-2 binding was significantly enhanced when atresia was stimulated by treatment with human chorionic gonadotropin, testosterone, or estrogen withdrawal. The results of immunoprecipitation and Western blot analyses indicated that the OA-2 antigen is a 39 kDa protein which is actively synthesized by the granulosa during atresia. The 39 kDa protein is localized at or near the inner surface of the plasma membrane. We conclude that the anti-OA-2 monoclonal will prove useful as a convenient analytical tool to study the regulation of granulosa atresia.

Animals↗
PubMed1987

Successful transfer of the embryos of Przewalski's horses (Equus przewalskii) and Grant's zebra (E. burchelli) to domestic mares (E. caballus).

Blastocysts were collected non-surgically from 2 Przewalski's horse and 2 Grant's zebra mares and transferred extra-specifically to domestic horse and donkey recipients. Nine Przewalski's horse embryos were transferred surgically, and 2 non-surgically, to domestic Welsh-type pony mares. After surgical transfer, 7 (77.8%) pregnancies were established and 4 foals were born. Twelve Grant's zebra embryos were transferred surgically to 5 pony and 7 domestic donkey recipients respectively and 1 non-surgically to a donkey; 3 (60%) zebra-in-horse pregnancies were established and 2 went to term. Only 2 (28.6%) zebra-in-donkey pregnancies were established but neither went to term, although one zebra foal was aborted alive at Day 292 but failed to survive. No pregnancies resulted from the non-surgical transfers. Measurement of chorionic gonadotrophin concentrations and parental-specific lymphocytotoxic antibodies in the serum of the recipient animals indicated a pronounced maternal immunological response to the extra-specific embryo, but this could not be correlated with success or failure of pregnancy. The results indicate that extra-specific embryo transfer may be a useful aid to breeding exotic equids in captivity.

Animals↗
PubMed1987

Induction of ovulation in anoestrous mares with a slow-release implant of a GnRH analogue (ICI 118 630).

A total of 18 experimental pony and 136 commercial maiden, barren and foaling Thoroughbred mares in seasonal or lactation-related anoestrus were injected subcutaneously with 1 or 2 slow-release D,L-lactide-glycolide co-polymer implants impregnated with 0.9 or 1.8 mg of the potent GnRH analogue, ICI 118 630, to give a daily release of, respectively, 30 or 60 micrograms analogue for 28 days; 32 of the Thoroughbred mares were also given a daily oral dose of 27.5 mg allyl trenbolone for 5 days after injection of the implant. Thirteen pony (76%) and 120 Thoroughbred (88%) mares ovulated 3-18 days after treatment with ICI 118 630 and the additional treatment with allyl trenbolone did not significantly reduce the considerable variation in the interval between treatment with GnRH analogue and ovulation. Of 100 Thoroughbred mares mated during the GnRH analogue-induced oestrus, (70%) conceived. The results of this trial demonstrated that low-dose, slow-release formulations of GnRH agonists have considerable potential as a practical method of hastening renewed ovarian cyclicity in anoestrous mares.

Anestrus↗
PubMed1987

Extraspecific donkey-in-horse pregnancy as a model of early fetal death.

Transfer of donkey embryos to horse mares provides a useful model of early fetal death. Endometrial cups do not develop in this one type of extraspecific pregnancy and 80% of donkey fetuses are aborted between Days 80 and 100 of gestation in conjunction with abnormal implantation and an intense accumulation of leucocytes in the endometrium of the surrogate mare. Treatment of mares carrying donkey conceptuses with progestagen (allyl trenbolone) or purified horse chorionic gonadotrophin does not prevent abortion. However, passive immunization with serum from mares carrying intraspecific horse fetuses, or active immunization with donkey lymphocytes, causes a marked increase in fetal survival rate and the birth of live foals. Furthermore, both cytotoxic (rejection type) and immunoprotective maternal immune responses to the xenogeneic donkey fetus can be recalled in mares carrying repeated donkey-in-horse pregnancies. We suggest that the endometrial cup reaction in normal equine pregnancy provides a vital and temporally important antigenic stimulus which results in the mare mounting an immunoprotective response towards her allogeneic fetus in utero.

Animals↗
PubMed1987

Differentiation molecules of the equine trophoblast.

Monoclonal antibodies raised against horse placenta were tested using an indirect immunoperoxidase-labelling technique for reactivity with a panel of tissues from adult horses and conceptuses of various gestational ages. The pattern of reactivity of 4 of the antibodies (F67.1, F71.3, F71.7, F71.14) on trophoblastic tissues described unique antigenic phenotypes for the non-invasive trophoblast of the allantochorion, the invasive trophoblast of the chorionic girdle, and the mature endometrial cup cells, which are derived from the chorionic girdle. Two of the monoclonal antibodies (F67.1 and F71.3) reacted only with chorionic girdle and the endometrial cups. Antibody F71.7 labelled strongly the non-invasive allantochorion from Day 29 of gestation to term. However, F71.7 failed to label mature endometrial cups and stained chorionic girdle only weakly, suggesting that the ability of the girdle cells to synthesize the molecule identified by F71.7 was gradually lost after development of the girdle. Antibody F71.14 reacted with trophoblastic tissues from all stages of gestation tested, with the exception of chorionic girdle. The other 3 anti-trophoblast monoclonal antibodies (F71.1, F71.2 and F71.8) labelled trophoblast-derived tissues from all stages tested. When the monoclonal antibodies were tested on cultured fetal and placental cells from Day 33 conceptuses recovered non-surgically from pregnant mares, the reactivities of the monoclonal antibodies on cultured cells were mostly identical to their reactivities in situ on tissue samples of similar gestational age; F67.1 and F71.3 were strong, specific markers for chorionic girdle cells, and F71.7 labelled allantochorion weakly in vitro, but failed to label chorionic girdle cells.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1987

Expression of major histocompatibility complex (MHC) antigens on horse trophoblast.

Antibodies to fetal major histocompatibility complex (MHC) antigens are routinely detected in the serum of pregnant mares some 2-4 weeks after formation of the endometrial cups at Day 36-38 after ovulation. Several experimental approaches were taken to determine whether paternal MHC antigens are expressed on horse placental tissues. First, absorption of anti-paternal MHC antisera with a large volume of endometrial cup cells removed antibody activity in only 2 of 4 experiments. Second, repeated immunization of horses with endometrial cup tissue recovered from a mare on Day 47 of pregnancy failed to induce the formation of anti-MHC antibodies. Third, a potent anti-MHC antiserum, raised in a pregnant mare which had previously received skin grafts from the MHC homozygous mating stallion, labelled chorionic girdle, but not normal allantochorion, when tested in an indirect immunoperoxidase labelling assay on tissues bearing the MHC antigens of the stallion. These results indicate that the rapidly dividing cells of the chorionic girdle, the progenitor tissue of the equine endometrial cups, express high levels of paternal MHC antigen, and may serve as the alloantigenic stimulus for cytotoxic antibody production by pregnant mares. Conversely, the mature, CG-secreting endometrial cup cells have a much reduced expression of paternal MHC antigen.

Allantois↗
PubMed1987

Distribution of spermatozoa in the mare's oviduct.

The morphology of the uterotubal junction (UTJ) and caudal isthmus during the peri-ovulatory period, and the distribution of spermatozoa within the region, were studied in 10 Pony mares. The proximal tip of the uterine horn and caudal 1-2 cm of the isthmus were removed during oestrus or shortly after ovulation from animals mated or artificially inseminated within the previous 24 h. The tissues were incised longitudinally and fixed for scanning electron microscopy. Analysis of micrographs showed deep longitudinal and oedematous folds in the preovulatory samples. After ovulation, much of the folding and oedema disappeared. There was a regional arrangement of ciliated and nonciliated cells and the cilia showed evidence of directional orientation. Occasional spermatozoa were seen in some specimens deep in furrows between folds of the UTJ.

Animals↗
PubMed1986

Characteristics of cells derived from the girdle region of the pre-implantation blastocyst of the donkey.

The establishment of a monolayer culture of cells derived from the girdle region of a 34-day-old donkey conceptus is described. These cells have had over 100 repeated passages in culture. Low levels of pregnant mares' serum gonadotrophin (PMSG, eCG) could be detected in the cells by indirect immunofluorescence using some monoclonal anti-eCG antibodies, but the cells did not secrete eCG as measured by radioimmunoassay or inhibition of haemagglutination. There was marked nuclear polymorphism with binucleate and occasional multinucleate cells. The cells were strongly reactive with wheatgerm agglutinin and concanavalin A suggesting the synthesis of many glycosylated products. Some cells were reactive with antisera to prekeratin, others with antisera to vimentin. The cells also contained actin (showing peculiar intercellular communications), alpha-actinin and tubulin. They were able to metabolize certain steroid precursors, but there was no definitive evidence for the presence of aromatase or delta 5-3 beta-hydroxysteroid dehydrogenase in these cells. This cell line appears to resemble trophectodermal girdle epithelium at a stage of development prior to the onset of eCG production, and may be useful in studies on the control of expression of this substance.

Animals↗
PubMed1986

Changes in serum muscle enzyme levels associated with training schedules and stage of the oestrous cycle in Thoroughbred racehorses.

Blood samples were collected twice weekly over a nine month period from 24 Thoroughbred racehorses in training at Newmarket to study the effects of daily training schedules and stage of oestrous cycle on serum enzyme levels and clinical signs of equine exertional myopathy. The sampling period extended from November to July and was performed between 16:00 h and 18:00 h so as to be at least 6 h after exercise. Serum creatine kinase, aspartate aminotransferase and plasma progestogen concentrations were measured. All horses were subjected to a similar traditional training programme. The study demonstrated marked fluctuations in serum muscle enzyme concentrations which were more pronounced in two-year-old fillies than three-year-old fillies and colts. There was no correlation, however, with the stage of oestrous cycle. It was concluded that some degree of muscle cell damage, which results in a variable increase in serum creatine kinase levels, occurs in all horses following light exercise after a rest day. Traditional flat race training may not be ideal in this respect and it is suggested that, for horses with an observed tendency towards exertional myopathy, more consistent and longer periods of less strenuous exercise may be advantageous.

Animals↗
PubMed1986

The shifting social and economic tides of black America, 1950-1980.

"This article examines significant demographic trends that illustrate the advances of many black Americans from 1954 to 1984. We also examine trends which indicate deterioration in the socioeconomic circumstances and life chances of a significant portion of the black population. The two competing trends in the status of black Americans (at one extreme an emerging black elite, at the other a growing black underclass) have been central in provocative debates about economics and race over the past decade. This article locates the debate in historical context, summarizing the work of early theorists on this issue." The authors use U.S. census data "to document changes from 1950-1980 in occupational distribution, labor force participation, educational attainment, income and earnings, fertility and mortality rates, and family organizational patterns for blacks and whites. Using the political economy perspective, we argue that race and economic status are inexorably linked in this society. Shifts in the society's economic base coupled with historical (and contemporary) patterns of racial oppression explain the disproportionate concentration of blacks in the underclass."

Black or African American↗
PubMed1986

Marker evolution during the development of the rat mammary gland: stem cells identified by markers and the role of myoepithelial cells.

Using monoclonal antibodies and other immunological reagents we have identified characteristic markers for various epithelial cell types within the rat mammary gland. We have followed the evolution of cell types from the emergence of mammary ducts from the epidermis in the fetus to adulthood. Throughout mammary development some cells retain a group of markers which characterize the early stages of development. We have previously suggested that these cells are the stem cells for mammary development. In the adult, these cells are present in end buds and in the myoepithelial layer of ducts. We suggest that the myoepithelial layer, which we propose should be called the "basal" layer, contains several cell types, of which two are pluripotent. It contains the stem cells for mammary development, which also are present in end buds, and a precursor of ductules and alveoli. In the ducts, basal cells are probably also the precursor of luminal cells. We propose a scheme of mammary development.

Age Factors↗
PubMed1986

Distribution of developmental markers in rat mammary tumors induced by N-nitrosomethylurea.

We have examined the distribution of immunological markers in 55 intraductal carcinomas induced in rats by N-nitrosomethylurea using several different regimens of carcinogen treatment. The goal was to determine the possible relationship of the marker distribution to those existing at various stages of development of the mammary gland. We have also examined two passage lines in syngeneic rats derived from two of the tumors. The distribution of markers was not affected by the regimen of administration. The primary tumors were found to maintain the general topography of mammary ducts but with infoldings of the basal layer without accompanying stroma. We attribute this to an abnormal expression of the tendency of basal cells to migrate towards the lumen to generate luminal cells. The distribution of markers in the tumors was evaluated by identifying 13 special features of distribution that are common in tumors, using all-or-none criteria. The distribution of these features bears out the high heterogeneity of tumors in which the various features vary in a seemingly independent way. There is also heterogeneity within tumors, adjacent nodes often having different marker distributions. The distribution of the markers is related to that found in the early stages of mammary development. Because of this characteristic and of the fact that the tumors contain both basal and luminal cells, they must originate from multipotent cells, probably the stem cells present in end buds and ducts as already proposed by other work. As they develop, the tumors can both differentiate towards the adult type and dedifferentiate towards a fetal type. Of the two transplanted lines one retained the same general features of primary tumors in several passages, whereas the other evolved into a fusiform cell type with a marker distribution not seen at any stage of mammary development. Foci of similar cells were already present in the primary tumor, suggesting that the tendency to progress was already determined at an early stage. The fusiform cells are similar and probably equivalent to the fusiform cells that arise in vitro in cultures of rat mammary cancers.

Animals↗
PubMed1985

The biosynthesis of 3 beta-hydroxy-5,7-androstadien-17-one by the horse fetal gonad.

Horse fetal gonadal tissue was incubated with 3 beta-hydroxy-5,7-pregnadien-20-one and 5,7-cholestadien-3 beta-ol and it was shown that both substrates were converted to 3 beta-hydroxy-5,7-androstadien-17-one. These findings support the proposal that in this tissue there is a 5,7-diene pathway producing 3 beta-hydroxy-5,7-androstadien-17-one, the putative precursor of equilin in the placenta.

Androstadienes↗
PubMed1985

A monoclonal antibody to a mammary cell line recognizes two distinct subtypes of ovarian granulosa cells.

When screening supernatant fluids from hybridoma clones, Dulbecco and co-workers found that a mouse monoclonal antibody generated against a mammary tumor cell line showed rather striking high binding to rat oocytes and granulosa cells. In this study we have specifically investigated the reactivity of the monoclonal antibody (designated anti-OA-1) with granulosa cells during the differentiation process. This was accomplished using the two-step indirect immunocytochemical technique. When a primordial follicle is recruited to initiate growth, intense immunoreactivity appears in the surface membrane of the granulosa cells. As a follicle proceeds through the preantral stages, the plasma membrane of the granulosa cells is strongly positive for anti-OA-1 reactivity, and the granulosa appear as a homogeneous population. However, once Graafian follicle development is initiated, a major shift in anti-OA-1 immunoreactivity occurs among the granulosa cells. As the antrum expands, 75% of the granulosa in the mural region (those nearest the basal lamina) elongate and become negative for anti-OA-1. This is in contrast to the periantral and cumulus granulosa, which remain rounded and show strong anti-OA-1 reactivity up to the preovulatory stage. The disappearance of anti-OA-1 reactivity in the subpopulation of mural cells is specifically initiated by FSH and occurs very rapidly after a 12-h lag phase. After the loss of anti-OA-1 reactivity, the elongated mural granulosa cells express their terminal differentiated state by acquiring LH/hCG receptor, 3 beta-hydroxysteroid dehydrogenase activity and cytoplasmic lipid inclusions. By contrast, the periantral and cumulus granulosa, which remain positive for anti-OA-1, do not express these differentiated functions; however, they do differentiate ultrastructurally, indicating that they respond to the FSH signal. These results strongly suggest that a monoclonal antibody recognizes a major surface differentiation antigen in the granulosa cell. This antigen is under hormonal control and is inversely linked to expression of the terminal differentiation program in the granulosa cells. We anticipate that the monoclonal antibody will be a valuable probe to aide in the analysis of structure/function relationships in subpopulations of granulosa cells.

Animals↗