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Biomedical subjects

S Harvey

Publications and source records attributed to S Harvey.

At least 325 records · Page 18Linked to original sources
PubMed1979

Variations in plasma growth hormone concentrations in laying hens.

1. Variations in plasma concentrations of growth hormone (GH) and luteinising hormone (LH) were measured by radioimmunoassay in blood samples taken during the ovulatory cycle of the domestic hen. 2. A peak in LH concentrationas observed 4 h prior to ovulation. 3. Plasma GH concentrations were quite variable but a significant increase was observed between 2 h before and 2 h after ovulation and the concentration remained elevated for about 4 h thereafter.

Animals↗
PubMed1979

Plasma growth hormone concentrations in growth-retarded, cortisone treated chickens.

1. Weekly variations in body weight, relative body-weight gain and plasma growth hormone (GH) concentrations were determined in control and cortisone-treated (5 mg cortisone acetate/bird d) chickens between 3 and 10 weeks of age. 2. Treatment with cortisone between 3 and 5 weeks of age markedly suppressed growth but did not inhibit GH secretion. 3. After the cortisone injections were stopped these birds grew more rapidly than the controls. However, this period of "catch-up growth" was not accompanied by alterations in plasma GH concentrations.

Animals↗
PubMed1979

Effect of daily injections of ACTH on growth and on the adrenal and lymphoid tissues of two strains of immature fowls.

1. The effects of daily injections of ACTH (30 IU/kg) or physiological saline on growth and on adrenal and lymphoid tissues of Rhode Island Red (RIR) and Light Sussex (LS) chickens were compared at 1, 2 and 3 weeks of age. 2. Saline injections retarded skeletal growth in both strains during the 1st week but only affected weight gain in LS birds. 3. Injections of ACTH depressed growth rate, caused adrenal enlargement and deplenished adrenal cholesterol to the same extent in both strains. 4. ACTH caused a greater reduction in bursal size in RIR than in LS birds. Spleen size was reduced by ACTH only in RIR birds. 5. At 2 and 3 weeks the plasma concentrations of corticosterone of RIR birds were greater than those of LS birds. Plasma corticosterone concentrations were within the normal range 24 h after the last injection of ACTH in both strains. 6. Plasma concentrations of growth hormone was unaffected by ACTH treatment in RIR birds, but it was increased in LS birds after 3 weeks of treatment.

Adrenal Glands↗
PubMed1979

Variations in concentrations of prolactin, luteinizing hormone, growth hormone and progesterone in the plasma of broody bantams (Gallus domesticus).

The concentrations of prolactin, LH, progesterone and GH were measured in the blood of broody bantam hens. The concentration of prolactin was at its highest when the birds began to incubate their eggs and in six out of nine hens it tended to remain raised until the eggs hatched. The increase in the concentration of prolactin was small: in incubating hens it was only 23% higher than in hens caring for their young and 14% higher than in laying hens (P less than 0.05 for both comparisons). The concentration of GH tended to be depressed in hens caring for young but otherwise was not related to reproductive activity. The concentrations of LH and progesterone decreased at the onset of incubation and remained depressed while the hens sat on their eggs (P less than 0.001) for both comparisons). After the chicks hatched, the level of LH began to increase slowly whereas the level of progesterone remained low. The hens stopped showing broody behaviour between 4 and 10 weeks after the chicks had hatched; this corresponded to the time when the concentration of LH had increased to values found in laying hens. These observations provide some evidence that prolactin secretion increases at the onset of incubation and support the view that the hormone is not secreted at an increased rate while hens are caring for their young.

Animals↗
PubMed1979

Effect of chicken hypothalamus on prolactin and growth hormone secretion in male chickens.

The effects of a chicken hypothalamic extract (HE) on the secretion of prolactin and growth hormone (GH) in vivo have been investigated by radioimmunoassay in the domestic fowl. Different i.v. doses of HE (0.25--25 HE equivalents/kg body weight) had no effect on GH secretion in conscious or anaesthetized cockerels. In both groups of birds the concentration of plasma prolactin was significantly increased within 10 min of administration of the extract. Extracts of other brain tissues (cerebral cortex, cerebellum and medulla oblongata) had no stimulatory effect on prolactin or GH secretion. Release of both prolactin and GH by dispersed pituitary cells and by hemipituitary glands in vitro was enhanced following incubation with HE (5 hypothalami equivalents/ml) or with single whole hypothalami respectively. Other brain tissues (cerebellum, optic lobes and medulla oblongata) had no effect on the concentration of prolactin or GH released by incubated hemipituitary glands.

Animals↗
PubMed1979

Plasma growth hormone levels in normal and testosterone implanted growing turkeys.

The growth of normal and testosterone implanted female turkeys was followed between 2 and 16 weeks of age and the concentration of immunoreactive growth hormone (GH) in the peripheral plasma measured. The testosterone treated birds were larger than the controls between 3 and 11 weeks of age. In both groups the plasma GH levels were inversely correlated with the bird's age and body weight and directly correlated with the percentage weekly weight gain Plasma GH concentrations in the testosterone treated birds were higher than in the controls at 4 weeks of age and lower at 3, 6, 7, 8, and 9 weeks of age. Significant differences between the groups in percentage weekly weight gain were not consistently associated with corresponding differences in plasma GH level.

Animals↗
PubMed1979

The effect of rapeseed meal and methimazole on levels of plasma hormones in growing broiler cockerels.

The effects of feeding a heat treated rapeseed meal, which has goitrogenic properties, on the concentrations of plasma pituitary and thyroid gland hormones was investigated in broiler cockerels of between 3 and 10 weeks of age. For purposes of comparison, two other groups were included in the study; one was fed the goitrogen, methimazole, and the other a normal control diet. The hormones measured were thyroxine (T4), triiodothyronine (T3), growth hormone (GH), prolactin, and luteinizing hormone (LH). In birds fed methimazole the thyroid glands were greatly enlarged, the concentrations of plasma T4 and T3 were depressed and the concentrations of growth hormone, prolactin, and LH were elevated. The high level of plasma LH in the birds fed methimazole was not due to the absence of sufficient concentrations of plasma testosterone to exert a negative feedback effect. Although the inclusion of rapeseed meal in the diet caused the thyroid glands to enlarge, the concentrations of all the hormones studied, with the exception of T3, were similar to those in the control birds. However, there was a tendency, which was more pronounced in birds of between 3 and 5 weeks of age, for rapeseed meal to depress the concentrations of plasma T4, GH, and LH and to increase the concentration of plasma prolactin. The most significant observation was that between 3 and 5 weeks of age the inclusion of rapeseed meal in the diet significantly (P less than .001) depressed the concentration of plasma T3.

Age Factors↗
PubMed1978

The effect of thyrotropin-releasing hormone (TRH) and somatostatin (GHRIH) on growth hormone and prolactin secretion in vitro and in vivo in the domestic fowl (Gallus domesticus).

The effects of thyrotropin-releasing hormone (TRH) on growth hormone (GH) and prolactin (Prl) secretion have been investigated in vitro and in vivo in domestic fowl. In both conscious and anaesthetized immature chickens the administration (i.v.) of TRH (2.5 and 25 microgram/kg) significantly increased the concentration of plasma GH. The simultaneous administration of somatostatin (GHRIH), 2.5 microgram/kg, to conscious birds significantly reduced the magnitude of the GH response to TRH treatment, but had no effect on the basal levels of plasma GH. The repeated injection of TRH (10 microgram/kg) every 20 min over a 100-min period failed to maintain the concentration of plasma GH at a high level. Prl secretion was not stimulated in any of these experiments, and in anaesthetized birds TRH (2.5 and 25 microgram/kg) treatment was followed by a depression in the level of plasma Prl. The effects of TRH and GHRIH on GH secretion by an in vitro dispersed pituitary cell suspension system were very similar to the in vivo studies. TRH stimulated Prl release in vitro, in contrast to the in vivo studies, and the response was dose related. GHRIH had no effect on the basal release of Prl in vitro but significantly inhibited the response to TRH treatment.

Anesthesia, General↗
PubMed1978

Influence of fasting, glucose and insulin on the levels of growth hormone and prolactin in the plasma of the domestic fowl (Gallus domesticus).

The concentrations of both GH and prolactin in the circulation of the domestic fowl have been determined after various treatments known to affect carbohydrate metabolism. Fasting decreased the level of glucose, stimulated the secretion of GH and inhibited the secretion of prolactin. Administration of insulin significantly depressed the level of GH in the plasma of normal or fasted birds and also in chickens which had received simultaneous injections of glucose or 2-deoxy-D-glucose. No consistent effect of insulin on the secretion of prolactin was observed. Hyperglycaemia subsequent to administration of glucose had no effect on the levels of either GH or prolactin. Glucagon-induced hyperglycaemia suppressed the level of GH in the plasma and stimulated that of prolactin.

Animals↗
PubMed1978

Developmental priority of identity conservation: acceleration of identity and equivalence in normal and moderately retarded children.

In an attempt to clarify the chronological relationship between identity and equivalence conservation, normal preschool-aged children (experiment 1) were exposed to brief videotape demonstrations of a model conserving identity and equivalence, identity only, equivalence only, or neither. Subsequent performances indicate that identity was easier to accelerate than equivalence, and training in both identity and equivalence appeared to be most effective in accelerating conservation. Trainable mentally retarded (TMR) children were then exposed to either the identity-equivalence-conserving or control model (experiment 2). This population, which some have argued remains at a preoperational level of functioning, was more likely to conserve identity than equivalence. In addition, conservation in the training group increased following training, though these gains were not maintained over a 3-week retention interval.

Child Development↗