Search PubMed⌕ Search

Biomedical subjects

G Young

Publications and source records attributed to G Young.

At least 217 records · Page 12Linked to original sources
PubMed1986

Cortisol secretion in vitro by the interrenal of coho salmon (Oncorhynchus kisutch) during smoltification: relationship with plasma thyroxine and plasma cortisol.

An in vitro system for the incubation of interrenal tissue (head kidney fragments) from coho salmon, Oncorhynchus kisutch, was developed in order to examine changes in interrenal sensitivity to ACTH1-24 during smoltification, using cortisol secretion as the endpoint. Time-course studies indicated that maximal cortisol accumulation in incubation media was achieved after 3 hr exposure to ACTH. There was no correlation between head kidney weight, body weight, or sex and the response of the interrenal to ACTH1-24 in vitro. Approximately monthly or bi-weekly experiments were performed during the smoltification period (February-July): tissue was preincubated in hormone-free media for 3 hr, washed twice, and then challenged with 5 X 10(-10)-5 X 10(-7) M (1.5-1500 ng/ml) ACTH1-24 for 3 hr. The pattern of cortisol secretion was similar in February, early March, and late March in the dose range of 5 X 10(-10)-5 X 10(-8) M ACTH1-24. A marked, significant increase in sensitivity to ACTH and in the steroidogenic capacity of the tissue occurred in April, but by May the response was similar to that in the pre-April period. Enhanced sensitivity and steroidogenic capacity were found in interrenal tissue taken from coho salmon in June and July. Maximal in vitro responsiveness of interrenal tissue to ACTH in April was correlated with peak plasma thyroxine titers and enhanced hypoosmoregulatory ability, but not with peak plasma cortisol titers, which occurred in May.

Adrenal Glands↗
PubMed1986

Interactions of medroxyprogesterone acetate with estrogen on the calcium-parathyroid axis in post-menopausal women.

We studied the effect of medroxyprogesterone acetate (MPA) as a single agent and in combination with conjugated equine estrogens (E), on the calcium-parathyroid axis in healthy post-menopausal women. Twenty-six subjects, 2-22 yr post-menopause, were studied under basal conditions, and then following 10 days of MPA (10 mg/day), 30 days of E (0.625 or 1.25 mg/day), and an additional 10 days of E + MPA. As predicted, E decreased urinary excretion of calcium and hydroxyproline. MPA did not alter these excretion variables, either when given alone, or when added to E. Cyclic administration of MPA for 10 days is currently advocated to avoid the adverse endometrial consequences of unopposed estrogen. These data indicate that such a program does not interfere with the beneficial effect of estrogen on the calcium-parathyroid axis.

Adult↗
PubMed1986

Short-term effects of calcium carbonate, lactate, and gluconate on the calcium-parathyroid axis in normal elderly men and women.

We evaluated the impact of three calcium salts on the calcium-parathyroid axis in healthy elderly volunteers. Fasting subjects were administered a standardized 1-g calcium load on three occasions, using calcium carbonate, lactate, and gluconate in random sequence with 8 oz milk or orange juice as carrier. Blood and urine were collected at baseline and for 6 h following the calcium load. Each salt rapidly increased the serum-calcium concentration and urinary-calcium excretion. Response duration was shorter with gluconate than with the other salts, but peak responses were similar for all preparations. Urinary-calcium excretion was slightly lower when orange juice replaced milk, but calcemic responses were not different. Changes in immunoreactive-parathyroid hormone and renal-phosphorus handling did not differ among calcium salts. Except for a shorter duration of effect with gluconate, all three calcium salts provided similar short-term suppression of the parathyroid axis.

Aged↗
PubMed1985

Somatostatin-like immunoreactivity in the pituitary and brain of three teleost fish species: somatostatin as a potential regulator of prolactin cell function.

Somatostatin-like immunofluorescence occurs in the hypothalamus and neurohypophysis of three euryhaline teleosts: tilapia, killifish, and mudsucker. This immunofluorescence was eliminated by incubating the primary antibody with excess somatostatin or somatostatin-28 but not with urotensin II, a partial analogue of somatostatin. In all three fishes, the strongest reaction was seen in the proximal pars distalis and parts of the pars intermedia. Strongly fluorescing processes from cells of the preoptic nucleus extend toward the pituitary. Distinct fluorescence was also associated with the neurohypophysis penetrating into the rostral pars distalis in the tilapia but not in the killifish or mudsucker. In the tilapia, an extensive network of immunofluorescent fibers and small cells were present in the anterior dorsolateral telencephalon, in addition to a moderately fluorescing group of cells anterolateral to the preoptic nucleus. A small area of diffuse fluorescence was also seen in the anterior dorsolateral midbrain tegmentum. Previous physiological studies have implicated somatostatin as a regulator of prolactin cell activity in tilapia. The present study demonstrates the route by which somatostatin may be delivered to the rostral pars distalis to inhibit prolactin secretion.

Animals↗
PubMed1985

NMR imaging and spectroscopy of experimental brain edema.

A canine model of experimental brain edema utilizing the classic cold lesion technique was used to identify the optimal nuclear magnetic resonance (NMR) spin-echo imaging parameters needed to detect cerebral edema with maximum sensitivity. Each animal was studied with four separate spin-echo sequences, utilizing pulse intervals ranging from 0.5 to 2.0 seconds. The echo delays following each pulse interval were 28 and 56 msec. Cerebral edema was best identified with the longest pulse interval (2.0 seconds), and the second echo delay (56 msec). T1 and T2 relaxation values were obtained from in vitro spectroscopy. The relaxation times were prolonged in the edematous white matter; however, absolute T1 and T2 values proved of little use in comparing different animals.

Animals↗
PubMed1985

Plasma cell infiltration of the small bowel: lack of evidence for a non-secretory form of alpha-heavy chain disease.

Eight patients with diffuse plasma cell infiltration of the small bowel who had the clinical features of immunoproliferative small intestinal disease (IPSID), but whose serum was negative for free alpha-heavy chains, were investigated for evidence of a non-secretory form of alpha-chain disease (alpha-CD). Molecular sieving and immunoblotting of serum, immunoperoxidase staining of biopsy specimens, and in vitro protein synthesis studies utilising an immunoprecipitation technique and polyacrylamide gel electrophoresis, failed to detect any new cases of alpha-CD. Four of the eight cases were found to have diffuse intestinal lymphoma. The remaining four patients, who were unsuccessfully investigated for evidence of a significant abnormality in cellular immunity, have not developed detectable alpha-CD protein or lymphoma over a mean of 143 months. Despite continuing exposure to possible environmental stimuli, it is concluded that not all cases of IPSID elaborate detectable alpha-CD protein or evolve to lymphoma.

Adolescent↗
PubMed1984

Long survival in a patient with alpha-chain disease.

A patient with evidence at presentation of alpha-heavy chain disease and an immunoblastic lymphoma is presented, who had remained in clinical, histologic, and immunologic remission for more than 12 years following initial radiotherapy and corticosteroids. The suggested management of this condition and its prognosis is discussed.

Adolescent↗
PubMed1984

Prolactin receptors in tilapia (Sarotherodon mossambicus) tissues: binding studies using 125I-labeled ovine prolactin.

The binding of 125I-labeled ovine prolactin (oPRL) to membrane preparations of tissue from freshwater-adapted tilapia (Sarotherodon mossambicus) was examined. Liver, ovary, and testis showed a relatively high specific binding (5-10%). A lower specific binding occurred consistently in intestine and gill tissue, and inconsistently in urinary bladder and kidney preparations. Desaturation experiments with MgCl2 indicated that a majority of the PRL receptors were already occupied by endogenous PRL. Scatchard analysis of liver binding gave a dissociation constant of 0.6 X 10(-9) M and a capacity of 207 fmol/mg protein.

Animals↗
PubMed1984

In vitro estradiol-17 beta and testosterone production by ovarian follicles of the goldfish, Carassius auratus.

In vitro production of estradiol-17 beta and testosterone by ovarian follicles of goldfish (Carassius auratus) at different developmental stages in response to human chorionic gonadotropin (HCG) was examined using 18-hr incubations. The vitellogenic follicles (primary and secondary yolk stage) produced estradiol-17 beta in response to HCG; follicles at the secondary yolk stage produced about five times more estradiol-17 beta than the primary yolk stage follicles. However, tertiary yolk stage follicles, which could be induced to mature in vitro by HCG treatment, did not produce estradiol-17 beta. HCG also stimulated testosterone production by follicles at all stages of development; maximal production was observed in tertiary yolk stage follicles. An indirect assessment of aromatase activity at each stage was made. Vitellogenic follicles (primary and secondary yolk stage) produced estradiol-17 beta when incubated with testosterone, the larger follicles producing about three times more estradiol-17 beta. Only low levels of estradiol-17 beta were produced by tertiary yolk stage follicles. Addition of HCG to primary yolk stage follicles slightly but significantly enhanced estradiol-17 beta production; however, no enhancement was seen with secondary and tertiary stage follicles. These results suggest that the decrease in estradiol-17 beta production in tertiary yolk stage follicles may be partly due to a decrease of aromatase activity at this stage.

Animals↗
PubMed1984

The effect of amylose content on insulin and glucose responses to ingested rice.

We evaluated the effect of amylose and amylopectin content on the glucose and insulin responses to rice. Thirty-three normal volunteers were given three types of rice containing 0, 14 to 17, or 23 to 25% of carbohydrate in the form of amylose. The glucose and insulin responses were measured over a period of 180 min. Serum glucose response to high amylose rice was significantly lower at 30 min, and dropped more gradually by 180 min than with 0% amylose rice. In addition, the high amylose rice produced significantly lower insulin levels at 30 and 60 min, as well as lower integrated secretion over the 3-h test. Thus, our results suggest the presence of a factor in high-amylose rice which delays digestion and/or absorption of carbohydrate. Since fiber content and surface area of the test rices were identical, other factors must underlie these observed differences. These include differential enzymatic hydrolysis of amylose and amylopectin and the presence of lipid-starch complexes in the amylose-containing rice.

Adult↗
PubMed1984

Age-related changes in parathyroid hormone and parathyroid hormone action in normal humans.

We evaluated parathyroid function in 158 normal subjects, aged 23-85 yr. Calcium, phosphorus, creatinine, and cAMP were measured in blood and urine in the fasting state and after a 1-g oral calcium challenge. Serum immunoreactive PTH (iPTH) was measured with a goat antiserum developed against human PTH, using (43Tyr) human PTH-(44-68) as tracer and standards. With age, a decrease in total serum Ca (r = -0.14; P less than 0.05) was attributable to a fall in serum albumin (r = -0.40; P less than 0.001). Creatinine clearance fell from 124 ml/min at age 20 yr to 61 ml/min at age 80 yr (r = -0.44; P less than 0.001). iPTH rose with age in men (r = 0.21; P less than 0.05) and women (r = 0.31; P less than 0.001) from 29 pg/ml at age 20 yr to 48 pg/ml at 80 yr. iPTH was also correlated with creatinine clearance (r = -0.32; P less than 0.001. When renal function was controlled in the analysis, the regression of iPTH with age was no longer significant. Other significant correlations with age include a decrease in renal phosphorus reabsorption (r = -0.17; P less than 0.05) and an increase in urinary nephrogenous cAMP excretion (r = 0.34; P less than 0.01). The rise in nephrogenous cAMP was not accompanied by a change in total urinary cAMP, since plasma, and therefore filtered, cAMP decreased with age. Basal calcium excretion was stable, but the calciuric response to oral calcium decreased (r = -0.27; P less than 0.01). We conclude that loss of renal function is the major cause of rising iPTH levels with age.

Adult↗
PubMed1984

Assessment of adenosine 3',5'-monophosphate excretion and an oral calcium tolerance test in the diagnosis of mild primary hyperparathyroidism.

An oral calcium tolerance test was administered to 22 hyperparathyroid patients and 162 normal subjects to determine its value in the diagnosis of mild primary hyperparathyroidism. Basal urinary excretion of calcium was higher in patients [0.217 mg/100 ml glomerular filtrate (GF)] than in normal subjects (0.090 mg/100 ml GF), but there was 50% overlap between the two groups. Phosphorus excretion, expressed as the ratio of the maximal tubular reabsorption of phosphorus to the glomerular filtration rate, was lower in patients (2.77) than in normal subjects (3.7), but 38% of the patients fell within the normal range. Urinary excretion of total cAMP also failed to separate hyperparathyroid patients from normal subjects [5.8 +/- 0.32 (+/- SEM) nmol/100 ml GF in patients vs. 3.41 +/- 0.11 in normal subjects]. Determination of nephrogenous cAMP failed to increase the utility of cAMP as a predictor of hyperparathyroidism. In response to oral calcium, the elevation in serum calcium concentration was the same in both groups. The rise in urinary calcium was greater in patients, but showed 77% overlap with that in normal subjects. Conversely, serum immunoreactive PTH, measured with a midregion-specific RIA, was elevated in 90% of the patients. Some normal subjects also had high levels of PTH, but none of these had hypercalcemia. We conclude that the oral calcium tolerance test and measurement of urinary cAMP do not adequately distinguish hyperparathyroid patients from normal subjects. In the absence of renal insufficiency, the combination of hypercalcemia and elevated serum PTH concentration most accurately predicts the diagnosis of primary hyperparathyroidism.

Administration, Oral↗
PubMed1983

Thallium-205 NMR determination of the thermodynamics of the interaction between the thallous ion and gramicidin dimers incorporated into micelles.

A study has been made of the thermodynamics of the interaction between the thallous ion and gramicidin dimers incorporated into micelles using thallium-205 NMR spectroscopy. The chemical shift data obtained are interpreted interms of a model in which the dimer has only one tight binding site. The variation of the binding constant over the temperature range 303-323 K is used to determine the changes in enthalpy and entropy of binding giving values of -11.3 kcal/mole and -16 e.u. at 303 K, respectively.

Colloids↗