Biomedical subjects

S Harvey

Publications and source records attributed to S Harvey.

At least 181 records · Page 10Linked to original sources

PubMed1988

Comparison of the fractionation and assay of domestic duck and fowl pituitary gonadotrophins.

1. Pituitary glycoproteins from domestic ducks and fowls were fractionated to separate luteinising hormone (LH) and follicle stimulating hormone (FSH) activities using the same chromatographic steps. 2. Fractions were bioassayed for LH using the release of progesterone from fowl granulosa cells and for thyroid stimulating hormone (TSH) by measuring the release of thyroxine in 3-d-old chicks. Follicle stimulating hormone activity was measured either in a cockerel-testes radioreceptor assay or by the release of oestrogen from cultured rat Sertoli cells. 3. Fractions containing predominantly FSH or LH activity were isolated from the fowl glycoproteins. Duck gonadotrophin did not occur in fractions corresponding to those containing fowl FSH. 4. Duck gonadotrophin was found in a fraction corresponding with the most highly purified fowl LH fraction. A duck LH fraction was found with little FSH activity for which there was no corresponding fowl LH fraction. 5. It is concluded that domestic fowl and duck gonadotrophins have different chromatographic properties. Further study is required to determine whether the purified duck gonadotrophin preparation comprises proteins with similar physico-chemical properties but with separate FSH and LH biological activities.

Animals↗

PubMed1988

Processing of two protein precursors yields four mature guinea pig seminal vesicle secretory proteins.

The translation of the two most abundant guinea pig seminal vesicle epithelium mRNAs (1800 nucleotides and 950 nucleotides) and the subsequent processing of their protein products were studied in an effort to elucidate the mechanism by which the four mature guinea pig seminal vesicle epithelium (GPSVE) secretory proteins are produced. The primary translation products of the 1800 nt and 950 nt mRNAs are two secretory protein precursors of 45 kDa and 20 kDa, respectively. Removal of signal peptides from these two precursors produces proteins of 43 kDa and 18.5 kDa, which are recognized by polyclonal antisera directed against the four mature secretory proteins. The existence of further processing intermediates in the production of the secretory proteins is suggested by the appearance of other immunoreactive polypeptides following incubation of GPSVE in nutrient medium containing [3H] leucine. Immunological and pulse-chase analysis strongly suggests that the 43-kDa protein gives rise to SVP-1, -3, and -4 and that SVP-2 is derived from the 18.5-kDa protein.

Animals↗

PubMed1988

Loss of the spacer loop sequence from the rrnB operon in the Escherichia coli K-12 subline that bears the relA1 mutation.

A polymorphism affecting the spacer region of the rrnB rRNA operon is described. Strains from a major Escherichia coli K-12 subbranch are missing a 106-nucleotide portion of the rrnB 16S-to-23S spacer, and a 20-nucleotide sequence is found in its place. We have called this mutant operon rrnB2. The rrnB2 spacer was most probably derived from either rrnC or rrnE. This alteration of rrnB may have occurred by a recombinational exchange or by gene conversion. In the genealogy of E. coli K-12 strains, the appearance of rrnB2 is associated with the spontaneous occurrence of the first relaxed mutation, but attempts to show a selective relationship between the two mutational events have had negative results. The sequences of the rrnG and rrnC 16S-to-23S spacers have also been determined and their comparisons to the other rrn operons encoding tRNAGlu2 are presented.

Base Sequence↗

PubMed1988

Parathyroid hormone-like immunoreactivity in brains of tetrapod vertebrates.

Heat-stable nondialyzable immunoreactive (IR) parathyroid hormone (PTH)-like activity, that coelutes with authentic PTH on Sep-Pak C18 columns and reverse-phase high-performance liquid chromatography, was measured in the brain, hypothalamus, and pituitary of amphibian, reptilian, avian, and mammalian species, using two specific antisera raised against the 48-64 region of the intact PTH molecule. In each case the IR PTH concentration was greater than that present in peripheral plasma and in rats was not affected by dietary calcium status. Extracts of muscle, liver, and kidney tissue were without IR PTH activity. These results demonstrate the extraparathyroidal occurrence of PTH-like peptides in nontumorous neuroendocrine tissues of vertebrate species. These findings may have evolutionary significance, since IR PTH was present in the brain and plasma of species that lack encapsulated parathyroid glands.

Amphibians↗

PubMed1988

Immunocytochemical distribution of PTH immunoreactivity in vertebrate brains.

Immunoreactive (IR) cell bodies, reacting with an antiserum specific for the 48-64 region of bovine parathyroid hormone (PTH), were detected in the brains of primitive vertebrates (hagfish), bullfrogs, and higher vertebrates (mice). In each species the IR perikarya were located in the preoptic region, although the precise location and abundance of IR perikarya differed among species. Fiber tracts from these IR perikarya were traced to the neurohypophysis in the hagfish but only to the median eminence in the bullfrog and mouse, where the axonal terminals were in close proximity to hypophyseal portal blood vessels. These results suggest that a novel PTH-like peptidergic system, similar to those secreting hypophysiotropic-releasing factors, is present in the vertebrate brain.

Animals↗

PubMed1988

Growth hormone secretion induced by thyrotropin-releasing hormone in adult chickens: evidence of dose-dependent induction of either refractoriness or sensitization.

Thyrotropin-releasing hormone (TRH) has been previously demonstrated to both stimulate growth hormone (GH) secretion and induce refractoriness to subsequent TRH provocation in vivo in chickens. Challenges with TRH at intervals of 1 h evoked different patterns of GH release in anesthetized adult chickens dependent upon TRH dosage. Initially, the administration of TRH at 10 micrograms/kg increased the plasma concentration of GH. However, the second and subsequent, through to the sixth challenges with TRH did not affect GH release. Plasma concentrations of GH were elevated by repeated injections of TRH (1.0 micrograms/kg). The magnitude of the response was reduced for the second and third challenges with full recovery of the GH response to the fifth challenge and an enhanced response to the sixth challenge. Similar GH secretory responses to TRH (at 0.1 micrograms/kg) were observed with the first through fourth challenge but the magnitude of response was again increased for the fifth and sixth challenge. At a lower dose (0.01 microgram/kg), TRH did not initially affect plasma concentrations of GH. However, GH release was increased by the third challenge, and subsequent TRH administration evoked progressively larger increases in plasma concentration of GH. It would appear that only high doses of TRH induce refractoriness to subsequent challenge, while lower doses presensitize the pituitary to TRH. If TRH challenges at a dose which provokes the complete refractoriness (10 micrograms/kg) are administered at intervals of 2, 3 or 4 h, the GH secretory response is consistent for each challenge. The refractoriness to TRH is thus overcome within a period of 2 h.

Animals↗

PubMed1988

Effects of passive immunization with antisomatostatin serum on plasma corticosterone concentrations in young domestic cockerels.

Young cockerels (6-8 weeks old) were injected with serum from sheep immunized against somatostatin-14 (anti-SRIF) or normal sheep serum (NSS). Blood samples were withdrawn periodically for the determination of plasma corticosterone concentration by radioimmunoassay. With frequent (every 10 min) sampling, NSS-treated control animals exhibited increased plasma corticosterone levels, presumably as a stress response to the experimental manipulation. Anti-SRIF stimulated a much greater increase in plasma corticosterone concentrations and a peak response was observed within 10 to 20 min, when the plasma corticosterone level reached more than twice that of the corresponding control value. With less frequent sampling, plasma corticosterone increased with anti-SRIF administration to as much as nine times the corresponding control value, and the peak response occurred much later. Under pentobarbitone anaesthesia, which itself increased basal corticosterone concentrations, anti-SRIF treatment promoted further increases in plasma corticosterone levels although to a smaller magnitude compared with conscious birds. The results suggest that endogenous somatostatin may play a role in the regulation of adrenocortical function in the domestic fowl. The mechanism of response may involve a central component.

Animals↗

PubMed1988

In-vitro control of growth hormone secretion by synthetic releasing factors in young and adult ducks (Anas platyrhynchos).

Release of GH from perifused duckling hemipituitaries was stimulated, in a biphasic manner, by synthetic TRH and human pancreatic GH-releasing factor (GRF). At all effective concentrations, the level of GH release was increased within 5 min of TRH or GRF perifusion and was maximal after 10 min of TRH perifusion and after 20 min of GRF perifusion. Although TRH was perifused for 20 min the level of GH release declined during the last 10 min. The most effective dose of TRH (1.0 micrograms/ml; 2.7 mumol/l) and GRF (0.5 micrograms/ml; 110 nmol/l) provoked similar (250-300%) increases in the level of GH release. However, since the effect of TRH was only of short duration, the total release of GH induced by GRF was higher than that elicited by TRH, especially with the low dose. The increase in release of GH induced by TRH or GRF was blunted when pituitaries from adult ducks were used. As in young ducks, the GH response to GRF was higher, whereas the response to TRH was very low. The GH response of perifused adult pituitaries to GRF was, however, potentiated when TRH was perifused simultaneously. The basal release of GH from both young and adult pituitary glands was unaffected by perifusion with somatostatin-14 (SRIF-14) at doses of 1 and 2 micrograms/ml. The perifusion of hemipituitary glands with similar doses of SRIF-14 was also unable to suppress the stimulation of GH release induced by prior perifusion with GRF, although when SRIF-14 and TRH were simultaneously perifused TRH-induced GH release was markedly suppressed.(ABSTRACT TRUNCATED AT 250 WORDS)

Age Factors↗

PubMed1987

Parathyroid hormone in sodium-dependent hypertension.

Plasma parathyroid hormone (pPTH) levels have been assessed in three separate radioimmunoassay systems in samples from Wistar-Kyoto rats. The animals were subjected to one of three dietary regimens throughout the study period: Group 1 animals consumed normal rat chow and drank tap water; Group 2 animals consumed normal rat chow and tap water was replaced with 0.5% saline solution; Group 3 animals consumed normal rat chow to which 2.5% CaCO3 (by weight) had been added and also drank 0.5% saline solution. Animals had consumed these diets for approximately 7 months prior to sacrifice for blood collection. Blood pressure was measured by tail cuff plethysmography in these animals and, as previously reported, saline consuming animals showed a moderate hypertension (Gp 2) only when diets did not contain added calcium (Gp 3). In the week prior to sacrifice, mean blood pressures were: Gp 1: 128.0 +/- 3.46 mmHg; Gp 2: 140.2 +/- 3.15 mmHg; and Gp 3: 133.5 +/- 2.90 mmHg. Three assay systems were used to measure pPTH levels from trunk blood samples obtained by guillotine decapitation. One assay used an antiserum directed toward the vasoactive N terminal fragment 1-34 and produced pPTH measurements of 0.74 +/- 0.05 ng/ml in Gp 1 animals, 1.04 +/- 0.07 ng/ml in Gp 2 animals and 1.12 +/- 0.08 ng/ml in Gp 3 animals. This pattern was consistent with that obtained by another antiserum which had been raised against the intact 1-84 PTH molecule and produced values of 0.25 +/- 0.03 ng/ml in Gp 1 animals, 0.55 +/- 0.07 ng/ml in Gp 2 animals and 0.74 +/- 0.04 ng/ml in Gp 3 animals. Antiserum raised against the C-terminal did not show any difference in pPTH across groups. We conclude that saline consumption may increase some portions of circulating PTH. Such elevation of pPTH may not be a pathophysiological component in the sodium dependent elevation of blood pressure since animals concurrently consuming both saline and calcium supplemented diets retained elevated pPTH levels even though blood pressures did not differ from controls. Rather, elevation of circulating PTH levels may be a response to prolonged increases in sodium consumption.

Animals↗

PubMed1987

Somatostatin immunoneutralization overcomes the inhibitory effects of quipazine and pargyline on growth hormone secretion in domestic fowl.

The inhibitory effects of pargyline and quipazine on chicken growth hormone secretion were overcome by passive immunoneutralization of endogenous somatostatin (SRIF)-14 or SRIF-28(1-14)-like immunoreactivity. Administration of the specific antisera to control birds pretreated with 0.9% NaCl elevated the basal plasma GH concentrations. These results suggest that peptides with SRIF-14 or SRIF-28(1-14)-like immunoreactivity tonically inhibit GH secretion and are at least partially responsible for the inhibitory effects of pargyline and quipazine on GH release in immature domestic fowl.

Animals↗

PubMed1987

Parathyroid hormone-like immunoreactivity in fish plasma and tissues.

Although fish lack parathyroid glands, parathyroid hormone (PTH)-like substances, reacting with guinea pig antibodies raised against bovine PTH1(-84), were detected in the circulation of trout (Salmo gairdneri) and goldfish (Carassius auratus). The immunoreactive (IR) PTH concentration in plasma (0.5-1.5 ng/ml) was less than that measured in heat-treated and dialyzed 0.6% NaCl extracts of brain tissue (4.0-5.0 ng/g wet wt brain) and much less than that present in pituitary extracts (20-40 ng/g pituitary gland). Heat-treated saline extracts of hake (Urophycis tenuis) and coho salmon (Oncorhynchus kisutch) pituitary glands also had PTH-like immunoreactivity in radioimmunoassays for C-terminal and N-terminal PTH, in which serial dilutions of the extracts were parallel to the respective standards. The IR PTH material present in the pituitary glands was absorbed on Sep Pak columns and was eluted in the same buffer (90% methanol, 4% acetic acid) and same volume as authentic bovine PTH1(-84). IR PTH was not detected in extracts of muscle, liver, or kidney tissue, but was present in the corpuscles of Stannius (CS), at levels comparable to those in the pituitary glands. While heating the CS extracts had no effect on the IR C-terminal PTH content, it completely destroyed that of the N-terminal PTH. These results suggest that the brain, pituitary, and CS all produce a peptide which shows immunoreactive cross-reactivity with mammalian PTH but that the peptide produced by the CS is not identical to that produced by the brain or pituitary. The brain, pituitary, and CS may be the source of plasma IR PTH in fish.

Animals↗

PubMed1987

Inhibition of growth hormone secretion in anaesthetized fowl: hypothalamic participation.

Sodium pentobarbitone anaesthesia lowered the circulating growth hormone (GH) concentration in immature chickens and reduced basal and stimulated pituitary GH release in vitro. The immunoneutralization of endogenous somatostatin (SRIF), by passive SRIF immunization, overcame the inhibitory effect of anaesthesia on basal GH secretion in vivo, but had no direct effects on GH release in vitro. However, while SRIF immunization restored the resting GH concentration in the anaesthetized birds, it increased greatly the GH level in conscious birds. These results therefore suggest that the inhibition of GH secretion in anaesthetized birds may be partly SRIF-mediated, although a suppression of hypothalamic stimulation may also be involved.

Anesthesia↗

PubMed1987

Opiate inhibition of growth hormone secretion in young chickens.

Plasma concentrations of growth hormone (GH) were decreased following the intravenous administration of morphine sulfate. Maximum inhibition of GH secretion was observed 40 min after morphine sulfate challenge. At this time, doses of morphine sulfate (at 5 mg and 50 mg/kg) reduced the GH concentrations by 86 and 90%, respectively, in comparison with those in the vehicle-injected controls. An opiate antagonist, naloxone, had no stimulatory effect on basal GH concentrations, but attenuated the GH response to morphine. Neither morphine nor naloxone had any significant effect on circulating luteinizing hormone (LH) levels. These results indicate an inhibitory opiate pathway in the control of GH release and demonstrate effects on GH and LH secretion contrary to those observed in mammalian species.

Animals↗

PubMed1987

Calcium participation in thyroid function in fowl (Gallus domesticus).

The effects of the calcium antagonists ethyleneglycol-bis-(beta-aminoethylether)-N,N,N',N'-tetraace tic acid (EGTA), cobalt chloride (CoCl2), and magnesium chloride (MgCl2) on the concentrations of plasma thyroxine (T4) and triiodothyronine (T3) and on the basal and stimulated release of T4 from incubated thyroid glands have been determined in the domestic fowl. Plasma T4 levels were consistently reduced 2 hr after the administration of each calcium antagonist, although only EGTA and CoCl2 lowered the concentration of plasma total calcium. Concentrations of plasma T3 were increased following MgCl2 treatment but reduced after CoCl2 administration. The basal release of T4 by incubated thyroid glands was reduced following in vivo EGTA and CoCl2 treatment, but increased after MgCl2 injection. The addition of bovine thyroid stimulating hormone (TSH, 200 mU) to the incubation consistently stimulated in vitro T4 release, although the magnitude of the stimulation was increased following in vivo EGTA or CoCl2 treatment and reduced after MgCl2 administration. These results demonstrate the involvement of calcium dependent mechanisms in the control of T4 release in fowl.

Animals↗

PubMed1987

Plasma immunoreactive-growth hormone in domestic fowl: measurement by homologous and heterologous radioimmunoassays.

Concentrations of immunoreactive (IR) growth hormone (GH) in the plasma of domestic fowl have been measured by homologous and heterologous radioimmunoassays and the estimates compared. Both assays detected an age-related decline in the circulating IR-GH concentration, an increase in IR-GH secretion following TRH-stimulation or fasting, and a fall in the IR-GH concentration following adrenocorticotropin administration. However, while the overall estimates of IR-GH concentration were significantly correlated, the magnitude of the changes in IR-GH concentration determined by the homologous assay were far greater than those detected by the heterologous system, which failed to show any inhibitory effect of anesthesia or exogenous thyroid hormones on basal or stimulated IR-GH release. These results suggest that the heterologous GH radioimmunoassay lacks the sensitivity of the homologous chicken GH assay and that circulating GH in birds is probably composed of heterogeneous moieties with differing immunoreactivities with rat GH antibodies.

Adrenocorticotropic Hormone↗

PubMed1987

Somatostatin-28(1-14) immunoneutralization stimulates growth hormone secretion in fowl.

Immunoneutralization of endogenous somatostatin (SRIF)-28(1-14) by the intravenous or intramuscular administration of a specific antiserum promptly enhanced the growth hormone (GH) concentration in the plasma of 4 to 8-week-old cockerels. The magnitude of the GH response was related to the volume of antiserum administered. The release of GH from chicken pituitary glands incubated with intact hypothalami was increased in the presence of anti-SRIF-28(1-14). These results suggest that SRIF-28(1-14)-like peptides are physiologically involved in the control of GH secretion in chickens, in which they may tonically inhibit GH release.

Animals↗

PubMed1987

Adrenocortical responses of pigeons (Columba livia) to treadwheel exercise.

Voluntary flight has previously been observed to stimulate adrenocortical activity in pigeons and in the present study increased circulating corticosterone levels were observed in adult feral pigeons forced to exercise in a treadwheel. The magnitude of the corticosterone response to treadwheel exercise was related to the speed of the moving drum, and hence to the work rate involved. Rapidly increasing the ambient temperature also stimulated corticosterone secretion in pigeons and masked the stimulatory effect of exercise. Treadwheel locomotion may serve as a laboratory model for the endocrine physiology of exercise and complements studies on flight.

Adrenal Cortex↗

PubMed1987

Somatostatin inhibition of growth hormone secretion in an adult bird: the domestic fowl.

1. The intravenous (i.v.) infusion of somatostatin (SRIF, 1.0 microgram/kg per min) promptly (within 5 min) reduced the growth hormone (GH) concentration in the plasma of conscious adult chickens. 2. The GH concentration progressively declined throughout a 60-min period of SRIF infusion, but was dramatically increased above pre-infusion levels within 5 min of SRIF withdrawal and maintained at an elevated level for at least 30 min afterwards. 3. Sodium pentobarbitone-anaesthesia lowered the basal GH concentration to levels comparable with those in conscious birds infused with SRIF. When administered to anaesthetized birds, exogenous SRIF was unable to further reduce the GH concentration and unable to induce 'rebound' GH release. 4. While thyrotropin releasing hormone (TRH, 10 micrograms/kg) increased the GH concentration in both conscious and anaesthetized birds, only the GH response in the anaesthetized birds was diminished by SRIF infusion. 5. Rebound GH secretion following the termination of SRIF infusion was observed in both conscious and anaesthetized birds injected with TRH. 6. These results demonstrate that SRIF can inhibit basal and TRH-stimulated GH secretion in adult domestic fowl and indicate that anaesthesia disrupts the normal control of GH releases.

Animals↗