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Biomedical subjects

W R Allen

Publications and source records attributed to W R Allen.

At least 145 records · Page 8Linked to original sources
PubMed1985

Deep freezing of horse embryos.

Fourteen horse embryos recovered non-surgically on Days 6-8 after ovulation (Day 0) were cooled slowly to - 35 degrees C (7 embryos) or - 40 degrees C (7 embryos) and stored in liquid nitrogen (- 196 degrees C) for 4-98 days. Surgical transfer of the thawed embryos to unmated recipient mares that had ovulated - 2 to + 1 days with respect to the embryo donors resulted initially in the establishment of 4 conceptuses. However, only one mare maintained her pregnancy to term.

Animals↗
PubMed1985

Hemoperfusion of phencyclidine in the dog.

Experiments were conducted to determine whether charcoal hemoperfusion (HP) would be useful in severe phencyclidine (PCP) overdose. Dogs were given a single 5 mg/kg injection of PCP. In 6 experiments HP for 2.5 hours was done; and in 6 control experiments, the extracorporeal circuit contained no HP cartridge. The number of seizures, symptoms, duration of coma, and PCP concentrations in the tissues of HP dogs were not different from control. PCP clearance by HP was 67 +/- 16.5 ml/min. PCP recovery by HP was 2.25 +/- 0.25 mg (2.0% of the administered dose). Urinary excretion of PCP was 1.33 +/- 0.46 mg (1.2% of the dose). Volume of distribution of PCP was 21.8 +/- 1.7 L/kg. Due to the high volume of distribution, high lipid solubility and low plasma levels of PCP, HP was not effective in managing PCP overdose in the dog.

Animals↗
PubMed1984

Lumen formation and redistribution of inframembranous proteins during differentiation of ducts in the rat mammary gland.

During the development of the rat mammary gland, ducts are formed from end-buds, which contain the stem cells. In this process a lumen is formed in the semisolid mass of the end-bud, and the cells acquire polarity. We have studied this process by following the localization of three inframembranous proteins present in the cells of both end-buds and ducts: microvillin, the microvillar protein p80, and the desmosomal plaque protein p205. We find that the development of ducts is accompanied by a redistribution of these proteins, which in immature parts of the end-buds are found together in the cell. Microvillin and p80 go together to the apical pole of the cells, in contact with the lumen, whereas p205 goes to the basal surface, in contact with cells of the myoepithelial lineage. The acquisition of polarity occurs at the same time as a lumen begins to form by local gaps between cells. It seems likely that the redistribution of the inframembraneous proteins is the consequence of the localization of surface glycoproteins that affect in opposite ways the adhesion between the cells.

Animals↗
PubMed1984

Production of monozygotic (identical) horse twins by embryo micromanipulation.

The blastomeres of 192- to 8-cell embryos recovered surgically 1-3 days after ovulation from 23 Pony mares were mechanically separated and inserted, in various combinations, into evacuated pig zonae pellucidae to make 27 'half' and 17 'quarter' micromanipulated embryos. These were embedded in agar and cultured in vivo in the ligated oviducts of ewes for 3.5-5 days to allow development to the late morula/early blastocyst stage. Subsequent surgical or non-surgical transfer of 13 'half' and 17 'quarter' embryos to mares resulted in 10 established pregnancies, including 2 monozygotic pairs. Surgical transfer to mares that had not been recently used as donors of embryos was more successful (10/20) than surgical or non-surgical transfer to recently operated mares (0/10).

Animals↗
PubMed1983

Biosynthesis of 3 beta-hydroxy-5,7-pregnadien-20-one by the horse fetal gonad.

The production of equilin and the other ring B-unsaturated estrogens by the pregnant mare is anomalous in that they are biosynthesised by a cholesterol-independent pathway. Fetal horse gonads were incubated with tritiated sodium acetate and radiochemically pure 3 beta-hydroxy-5,7-pregnadien-20-one and 3 beta-hydroxy-5,7-androstadien-17-one were isolated. A fetal gonad--placental system is proposed for equilin production, 3 beta-hydroxy-5,7-pregnadien-20-one being a precursor for 3 beta-hydroxy-5,7-androstadien-17-one in the fetal gonad and the latter being the precursor of equilin in the placenta. The nature of the possible precursor of 3 beta-hydroxy-5,7-pregnadien-20-one is discussed.

Animals↗
PubMed1983

Follicle stimulating hormone, luteinising hormone and progesterone concentrations in the blood of thoroughbred mares exhibiting single and twin ovulations.

The concentrations of follicle stimulating hormone, luteinising hormone and progesterone were measured in serial blood samples taken throughout one or more oestrous cycles from 12 Thoroughbred mares, some of which exhibited single and others twin ovulations. The resulting profiles clearly demonstrated that no simple relationship exists between circulating gonadotrophin levels and subsequent ovulation rate in the mare. However, plasma progesterone concentrations during dioestrus are, as expected, higher following twin than single ovulations. The findings suggest that the underlying cause of twin ovulation in some mares may exist at the ovarian end of the pituitary-ovarian axis which controls follicular development and ovulation.

Animals↗
PubMed1983

Sodium reabsorption during intrarenal diazoxide infusion in the dog.

Infusion of diazoxide, a potent benzothiazide antihypertensive, into the renal artery results in diuresis and natriuresis. The site within the nephron of decreased reabsorption has been controversial. Thus free flow recollection micropuncture studies of the superficial proximal tubule of the dog were undertaken to determine if diazoxide decreased sodium reabsorption from this part of the nephron. Renal blood flow, monitored by an electromagnetic flow meter, was increased by about 15% with the diazoxide infusion. Systemic blood pressure and hematocrit remained unchanged. Glomerular filtration rate increased significantly from 26 +/- 2 to 34 +/- 3 ml/min, urine flow and sodium excretion also increased (0.13 +/- 0.01 to 0.33 +/- 0.06 ml/min and 5.5 +/- 0.90 to 35.5 +/- 11.0 microEq/min, respectively). Decreased sodium reabsorption from the proximal tubule was demonstrated by a decrease in the tubular fluid to plasma inulin ratio (1.62 +/- 0.1 1.47 +/- 0.1) thus giving a reduction in fractional sodium reabsorption to the site of micropuncture (36.1 +/- 4.3 to 29.5 +/- 5.1%, p less than 0.05). To examine peritubular effects of diazoxide infusion, capillary protein concentration and pressure were measured; the former increasing significantly (9.17 +/- 0.32 to 9.80 +/- 0.35, p less than 0.05) and the latter did not change (13.1 +/- 1.0 vs. 15.2 +/- 1.4 mm Hg). Thus intrarenal diazoxide causes whole kidney vasodilatation with diuresis, natriuresis and decreased sodium reabsorption from the superficial proximal tubule. Additional studies provided no data to indicate that changes in peritubular physical factors account for the changes in sodium handling.(ABSTRACT TRUNCATED AT 250 WORDS)

Absorption↗
PubMed1983

Identification of 3 beta-hydroxy-5,7-pregnadien-20-one and 3 beta-hydroxy-5,7-androstadien-17-one as endogenous steroids in the fetal horse gonad.

The 5,7-dienes, 3 beta-hydroxy-5,7-pregnadien-20-one and 3 beta-hydroxy-5,7-androstadien-17-one were extracted from fetal horse gonads and purified by solvent partition, thin-layer chromatography and high performance liquid chromatography. The isolated steroids were identified by comparison with the synthetic steroids using ultraviolet and mass spectroscopy and by gas chromatography-mass spectroscopy. The identification of these compounds as endogenous steroids, together with the data on their biosynthesis reported previously, support the proposal that in the fetal horse gonad there is a 5,7-diene pathway biosynthesizing 3 beta-hydroxy-5,7-androstadien-17-one, which is the proposed precursor for equilin in the placenta.

Androstadienes↗
PubMed1982

Synergistic stimulation of S6 ribosomal protein phosphorylation and DNA synthesis by epidermal growth factor and insulin in quiescent 3T3 cells.

Using an improved method to quantify the level of phosphorylation of the S6 ribosomal protein, we have analyzed the effect of growth stimuli on S6 phosphorylation in quiescent murine Swiss/3T3 cells to see if it can be dissociated from the later increase in DNA synthesis. Saturating concentrations of epidermal growth factor (EGF), insulin and serum each stimulate phosphorylation of the S6 ribosomal protein to the same maximal level; this is not so for DNA synthesis. Subsaturating concentrations of EGF and insulin act synergistically to stimulate both S6 phosphorylation and DNA synthesis, but qualitatively the two synergistic interactions are expressed differently. Insulin increases the maximal response of DNA synthesis to EGF, whereas it decreases the concentration of EGF required for half-maximal stimulation of S6 phosphorylation. We conclude that S6 phosphorylation is not a principal regulator of DNA synthesis, and that insulin and EGF regulate both S6 phosphorylation and DNA synthesis through different, but interacting, pathways of action.

Animals↗
PubMed1982

Immune deposits and mesangial hypercellularity in minimal change nephrotic syndrome: clinical relevance.

Occasional patients with nephrotic syndrome and minimal histologic change demonstrate glomerular deposition of small amounts of immunoglobulin and complement. Some consider this a disease distinct from MCNS. To investigate the clinical importance of immune deposits and mesangial hypercellularity in the initial biopsy, the clinical records, follow-up data, and renal biopsies of 68 patients (ages 6 months to 16 years) with MCNS by light microscopy were reviewed. Among 68 patients followed a mean of 6.2 years, eight of 25 patients with immune deposits on initial renal biopsy were steroid nonresponsive. Only one of 43 patients without immune deposits was steroid nonresponsive (P = 0.00005). Of 44 patients with normal mesangial cellularity, 31 experienced fewer than three relapses a year, whereas of 15 patients with mesangial hypercellularity, only six experienced fewer than three relapses a year (P = 0.035). The data suggest that immune deposits and increased mesangial cellularity in children with NS and minimal light microscopic change may predict the clinical course.

Adolescent↗
PubMed1982

Epidermoid carcinoma of the penis.

One hundred and twenty-two cases of penile carcinoma at the Medical University of South Carolina from 1945 to 1979 have been analysed. The age and race distribution of these patients, initial clinical staging and surgical treatment have been recorded. In addition, clinical inguinal involvement, results of inguinal lymphadenectomy and survival data based on retrospective staging are listed. The role of adjunctive lymphadenectomy is discussed and the importance of pelvic lymphadenectomy in addition to inguinal node dissection is emphasised. A treatment plan is outlined for the management of penile carcinoma in order to increase survival without increasing patient morbidity.

Adult↗
PubMed1982

Alterations of lipid metabolism in response to nerve growth factor.

In response to nerve growth factor (NGF), clonal pheochromocytoma cells flatten and extend neurites capable of making functional synapses. Although no significant changes in overall phospholipid composition occur in the presence of NGF, there is increased incorporation of 32PO4 into phosphatidylinositol and phosphatidic acid within 10 min after the addition of NGF. NGF stimulates the incorporation of 32PO4 into other lipids, such as phosphatidylcholine, to a lesser extent. The kinetics of the NGF-induced phosphatidylinositol responses are different when the cells are in suspension from when they are attached to culture dishes. These changes in phospholipid metabolism are discussed with respect to their role in NGF-induced nerve differentiation.

Adrenal Gland Neoplasms↗
PubMed1982

Dehydroepiandrosterone synthesis by the fetal foal and its importance as an oestrogen precursor.

The gonads of the fetal horse were found to be relatively devoid of 3 beta-hydroxysteroid dehydrogenase and other enzymes which metabolize dehydroepiandrosterone (DHA). In short-term in-vitro incubation experiments fetal liver converted DHA to the potential equilin precursor, 7 alpha-hydroxy DHA. DHA was converted to oestrone when incubated with extracts of horse placenta but 7 alpha-hydroxy DHA was not converted to equilin. Levels of DHA measured in peripheral blood of mares throughout pregnancy paralleled those of equilin and oestrone, and DHA concentrations fell rapidly after fetal gonadectomy, as did those of equilin and oestrone. Administration of [4-(14)C]-DHA and [7-3H]DHA to the fetus resulted in the incorporation of both 14C and 3H into maternal urinary oestrone but neither isotope was present in urinary equilin. These findings confirm the role of fetal DHA as a precursor of oestrone, but do not support the previously suggested role of the fetal liver in the synthesis of equilin. They are, however, compatible with the hypothesis that equilin is formed via a pathway which diverges from the terpenoid steroid synthetic route before DHA.

Animals↗
PubMed1982

Pituitary and chorionic gonadotrophic control of ovarian function during early pregnancy in equids.

Concentrations of FSH, LH, chorionic gonadotrophin (CG) and progesterone were measured during early pregnancy in mares and donkeys carrying normal intraspecies and transferred extraspecies conceptuses. A secondary rise in progesterone concentrations occurred in normal intraspecies horse and donkey pregnancy soon after the appearance of CG but FSH concentrations continued to fluctuate and were not influenced by CG production. In donkeys carrying transferred horse conceptuses FSH concentrations fell sharply and progesterone concentrations rose steeply, coincidental with the appearance of abnormally high levels of CG. In horses carrying donkey conceptuses, on the other hand, there was a complete absence of CG production and in 7 of the 8 mares studied there was no secondary progesterone rise; FSH levels fluctuated as in the intraspecies pregnancies. Pregnancy continued to term in only 1 of 8 mares carrying a donkey conceptus despite attempts to maintain it in 4 animals by exogenous progestagen therapy. Our findings indicate that pituitary FSH, not CG, stimulates secondary follicular growth during normal equine pregnancy and the LH-like activity of CG induces ovulation of these follicles to form secondary corpora lutea.

Animals↗
PubMed1982

Studies on oestrogen synthesis by the preimplantation equine conceptus.

Aromatase activity measured by the incorporation of [3H]androstenedione into unconjugated and conjugated oestrogens was detectable in the equine conceptus during early pregnancy. Activity was substantially higher in yolk sac compared to allantochorion between Days 20 and 52 after ovulation. Oestrone sulphate concentrations in yolk-sac fluid measured by radioimmunoassay increased markedly to reach values of about 3 micrograms/ml at Day 36, approximately 10-fold higher than those in allantoic fluid. Extra-embryonic membranes in a 28-day conceptus all contained aromatase (chorionic girdle greater than trilaminar omphalopleure greater than bilaminar omphalopleure greater than allantochorion), implying that the enzyme complex was present in trophoblast and/or endoderm rather than mesoderm. Aromatase activity in chorionic girdle cells was low before their migration into the endometrium. Endometrial tissue contained substantial sulphotransferase and glucuronidase activity. The ability of the preimplantation equine conceptus to synthesize oestrogens was strikingly similar to that found previously in the pig; in both species the allantochorionic placenta is non-invasive.

Allantoin↗