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Biomedical subjects

G Evans

Publications and source records attributed to G Evans.

At least 271 records · Page 15Linked to original sources
PubMed1983

Production of prostaglandins by porcine preovulatory follicular tissues and their roles in intrafollicular function.

Prostaglandin production in vitro by theca and granulosa cells isolated from prepubertal pig ovaries was quantified in order to investigate the role of prostaglandins in intrafollicular function. Prepubertal gilts were slaughtered without treatment (O h, control) or treated with 1000 IU pregnant mare's serum gonadotropin (PMSG) and slaughtered at 36 or 72 h, or at 75 h following treatment with 500 IU of hCG at 72 h. Theca and granulosa cells were isolated from preovulatory follicles and cultured for 24 h alone or with follicle-stimulating hormone (FSH) or luteinizing hormone (LH). In vitro accumulation of 6-keto-prostaglandin F1 alpha (6-keto-PGF1 alpha), prostaglandin E2 (PGE2) and prostaglandin F2 alpha (PGF2 alpha) was measured by radioimmunoassay. On a per follicle basis theca produced more of each prostaglandin (approx. 10-fold) than granulosa at each stage of follicular development; production by each tissue type increased with development of the follicle, responding to administration of gonadotropin (PMSG) in vivo. Neither tissue type was generally responsive to further gonadotropin stimulation in vitro. However, production of PGE2 by granulosa cells was increased by addition of gonadotropin, particularly LH, in vitro, with the greatest response observed in tissue obtained at 36 and 72 h after PMSG. There were no functional correlates between prostaglandin production and steroidogenesis by either tissue type and we conclude that prostaglandins do not have an obligatory role in follicular steroidogenesis. However, these data provide additional circumstantial evidence for a role of PGE2 in granulosa cell luteinization, and possibly in ovulation. The data also indicate that prostaglandins derived from thecal tissue in relatively large quantities may play an important role in ovulation.

6-Ketoprostaglandin F1 alpha↗
PubMed1983

Site of androgen inhibition of follicle-stimulating hormone-stimulated progesterone production in porcine granulosa cells.

In granulosa cells derived from medium-sized porcine follicles, certain androgens have been shown to inhibit FSH-stimulated progesterone synthesis. To determine the site at which this inhibition takes place, the effects of androgens on FSH- and (Bu)2cAMP-stimulated pregnenolone and progesterone syntheses were examined. Granulosa cells were isolated from 4- to 6-mm follicles and cultured for 24 h in modified Eagle's Minimum Essential Medium, alone or with FSH (1 microgram/ml) or (Bu)2cAMP (0.5-4 mM) in the presence or absence of androstenedione or testosterone. (Bu)2cAMP stimulated progesterone production in a dose-dependent manner. Testosterone (5 microM) had a slight, but nonsignificant, inhibitory effect on basal progesterone production, but significantly inhibited the synthesis of progesterone in the presence of (Bu)2cAMP, suggesting that testosterone inhibits progesterone synthesis at a step distal to cAMP formation. In the absence of FSH, granulosa cells produced substantial quantities of pregnenolone. FSH caused a 3-fold stimulation of pregnenolone synthesis. The addition of androstenedione or testosterone (5 microM) markedly increased pregnenolone accumulation in FSH-treated cultures. To determine at what step androgens affected FSH-stimulated pregnenolone production, granulosa cells were cultured with (Bu)2cAMP and/or testosterone for 24 h. (Bu)2cAMP stimulated pregnenolone synthesis in a dose-dependent manner. Testosterone (5 microM) significantly increased pregnenolone synthesis in response to (Bu)2cAMP, suggesting that androgens acted at a step distal to cAMP formation. Since these concentrations of androgens markedly inhibited FSH-stimulated progesterone production by these preparations, these results suggest that androgens may affect the conversion of pregnenolone to progesterone.

Animals↗
PubMed1983

Ovulation response and fertilization failure in immature rats induced to superovulate.

Immature female rats (75 g body wt, aged 29 days) were injected with 4 or 40 i.u. PMSG on Day -2 and were killed at intervals between 18:00 h on Day -2 and 09:00 h on Day 1. Control animals (4 i.u.) ovulated between 00:30 and 05:30 h on Day 1 whereas the number of ova recovered from superovulated rats (40 i.u. PMSG) increased slowly between 06:00 h on Day -1 and 24:00 h on Day 0 and markedly between 24:00 on Day 0 and 06:00 on Day 1. Similarly treated rats were caged overnight on Day 0 with males of proven fertility and killed between 14:00 and 16:00 h on Day 1. A significantly lower percentage of normal 1-cell ova was recovered from the superovulated rats compared to control animals (71.6 and 98.5%) and of these 1-cell ova a lower percentage was fertilized (69.7 and 99.1%). In the control group all mated animals had a high proportion of ova fertilized whereas 26% of superovulated rats had none or a very low proportion fertilized. In the control animals there was evidence of sperm penetration and pronucleus formation; in superovulated rats significantly fewer ova had pronuclei than were penetrated. These results suggest that reduced fertility of superovulated immature rats is due to complete or partial failure of fertilization in some animals. The extended period during which ovulation occurs may be a contributory factor.

Animals↗
PubMed1983

Changes in relaxin production by the theca during the preovulatory period of the pig.

Theca and granulosa layers were isolated from the preovulatory follicles of prepubertal gilts which were untreated (Group A), killed 72 h after 1000 i.u. PMSG (Group B), killed 84 h after PMSG (Group C), or killed 84 h after PMSG + 500 i.u. hCG given at 72 h (Group D). The tissues from individual follicles were cultured for 24 h alone (C), with FSH (F) or with LH (L), and the content of immunoreactive relaxin in the culture media was measured by RIA. Concentrations of relaxin-like material were close to the limit of detection of the assay in all granulosa cell cultures, and in the thecal cultures from the untreated gilts. However, thecal cultures from all 19 treated gilts produced relaxin. The mean +/- s.e.m. concentrations (pg/follicle) in Groups AC, BC, CC and DC were 26 X 5 +/- 3 X 04, 93 X 1 +/- 4 X 6, 138 +/- 16 X 4 and 285 X 6 +/- 54 X 1 respectively. Therefore relaxin production was stimulated by PMSG (P less than 0 X 05), with hCG treatment in vivo leading to a further significant increase (P less than 0 X 05). In-vitro treatment with gonadotrophins had no effect in Groups A, C and D, but in Group-B gilts LH produced a significant (P less than 0 X 05) rise in relaxin levels. These studies indicate that the theca is the principal source of relaxin in the porcine preovulatory follicle. The increased production before ovulation suggests that relaxin may be involved in follicular growth or rupture.

Animals↗
PubMed1982

The effect of repeated electroconvulsive shocks on growth hormone secretion and growth hormone responses to clonidine in the intact rat.

The effect of repeated electroconvulsive shocks (ECS) on growth hormone (GH) secretion was studied in rats. Male Sprague-Dawley animals were given one ECS daily for 10 days under halothane anaesthesia. Control animals were anaesthetised only. GH secretion was studied 24 h after the last ECS or sham procedure. Background GH secretion was significantly greater in ECS-treated than in sham-treated animals (P less than 0.001). The GH response to IV clonidine (0.01--0.1 mg/kg) did not differ between the two groups. The size of the GH response was not directly related to the basal GH secretion and could not be explained in terms of it.

Animals↗
PubMed1982

The implications of managing confused and disabled people in non-specialist residential homes for the elderly.

Local Authority residential homes for the elderly are caring for substantial proportions of physically disabled and mentally confused residents in non-specialist settings. The results of an intensive study of six homes caring for varying proportions of disabled and confused residents are summarized. The homes are compared in terms of staff training and attitudes, physical care of residents, social environment, and attitudes of residents. The authors suggest that a "mix" of residents can have advantages over segregation and that most homes can manage around 30% confused residents. If this is to be successful, attention should be given to staffing levels, staff training and the role of health service staff in residential homes.

Aged↗
PubMed1982

Effects of practice on inspection time for mildly mentally retarded and nonretarded adults.

Successive estimates of inspection time (lambda) interspersed with practice were made for 10 mildly retarded adults (mean IQ = 60) and 10 nonretarded adults. Each subject completed approximately 800 trials overall. A significant practice effect was found for both groups, but with average measures of lambda from the retarded group remaining more than twice as long as those from the nonretarded group. Intercorrelations within both groups between measures confirmed that lambda provides a reliable index of discriminative performance. A response requirement involving a keypress was compared with a simplified pointing response, but results indicated that these alternatives did not influence estimates of lambda on the effects of practice.

Adolescent↗
PubMed1981

The effect of 6-aminonicotinamide on the levels of brain amino acids and glucose, and their labeling with 14C after injection of [U-14C] glucose.

The brains of rats paralysed at 4 hr after the administration of 6-aminonicotinamide were found to contain decreased levels of glutamate and gamma-aminobutyrate. The glucose content of the brain of the treated rats was several fold higher than in controls. The incorporation of 14C into brain amino acids at 30 min after the injection of [U-14C]glucose was decreased by 16%: this was attributed to mainly decreased labeling of glutamate and associated amino acids. The results are discussed in the light of previous findings that the administration of 6-aminonicotinamide resulted in the blockade of the direct oxidation of glucose by the pentose phosphate pathway.

6-Aminonicotinamide↗
PubMed1981

In vitro oestrogen synthesis by bovine placenta during pregnancy and induced parturition.

Foetal (cotyledon) placental tissue was collected from 7 pregnant cows and from 8 cows immediately after delivery of the foetus during parturition induced by luteal removal at 250 or 270 days of gestation. These tissues were incubated with [3H]androstenedione (A), [3H]17 alpha-hydroxyprogesterone (17 alpha HP), or [3H]pregnenolone (P5) to examine potential oestrogen precursors in the mid to late pregnant cow. Percentage conversion to unconjugated and conjugated oestrone (Oe1) and oestradiol (Oe2) was measured for each tissue with the various substrates. Unconjugated oestrogens predominated over conjugated (P less than 0.001), and Oe1 over Oe2 (P less than 0.001) in all incubations. There was no difference in conversion of A between pre- and post-partum foetal tissues. There was a significant elevation in conversion of P5 in post-partum foetal tissue (P less than 0.05). These data demonstrate a) placental aromatase activity does not appear to increase as pregnancy progresses towards parturition, b) the bovine placenta is able to convert C21 steroids to oestrogens, and c) induction of enzymes for converting pregnenolone or related substrates to oestrogens may be involved in the pre-partum rise in oestrogen levels.

Androstenedione↗
PubMed1981

Hypersensitivity to tobacco glycoprotein in human peripheral vascular disease.

One hundred and sixty-four patients with peripheral vascular disease (PVD) were skin tested with a purified tobacco glycoprotein (TGP). A basophil degranulation test (BDT) was also performed to assess in vitro reactivity to TGP. Immediate skin test hypersensitivity to TGP was found in 18 of 164 (11%) patients with radiologically demonstrable PVD. BDT was positive in 25/42 (60%) smokers as opposed to 6/23 (24%) nonsmokers (p less than 0.01). Twenty-one of 49 (43%) skin test-negative and 10/11 (91%) skin test-positive patients wih PVD had a positive BDT (p less than 0.02). Only 1/34 (3%) patients with negative BDT had a positive skin test. Skin test-positive patients had significantly higher BDT at 0.01 and 0.001 microgram/ml TGP in vitro compared to skin test-negative patients (p less than 0.01). When PVD was graded by arteriography, one of 11 patients with "mild," 11/87 with "moderate" and 4/20 with "severe" PVD were skin test-positive to TGP (p less than 0.01 "mild" vs "moderate"; p less than 0.05 "mild" vs. "severe"). These differences could not be attributed to age, sex, atopy or smoking status. Reactivity to TGP exists in a proportion of patients with PVD and may be causally related in such cases to the development of atherosclerotic vascular disease.

Adult↗
PubMed1981

Effects of complete or partial occlusion of a coronary artery.

We investigated the effects of a partial compared to a complete thrombotic occlusion of the left anterior descending coronary artery in dogs. A completely occlusive thrombus was associated with a full thickness myocardial infarction. Mural thrombus was associated with focal areas of myocardial injury, mainly subendocardial in location. The findings are compatible with the concept that mural thrombus can give rise to platelet or platelet-fibrin emboli in the microcirculation which cause focal areas of ischemic damage. This pathogenesis was further explored using a thrombogenic wire placed in the left anterior descending coronary artery by indirect technique. Five of 10 dogs had developed a completely occlusive thrombus, whereas five had a mural thrombus at death, which occurred within 2 days. Three of the five dogs with mural thrombus had focal ischemic myocardial damage and platelet-fibrin thrombi; the other two that died early showed only platelet fibrin masses in the microcirculation. When platelets were labeled with 111Indium, there was increased radioactivity in the territory of the myocardium served by the artery containing a developing thrombus.

Animals↗