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Biomedical subjects

A Hayek

Publications and source records attributed to A Hayek.

At least 73 records · Page 4Linked to original sources
PubMed1984

Homogeneous magnetic fields influence pancreatic islet function in vitro.

Pancreatic islets were isolated from newborn rats and exposed to homogeneous magnetic fields for 48 hours. Under these conditions insulin release, measured at low (5.6 mM) and high (16.7 mM) glucose concentrations, was significant and dose-dependent only at low glucose concentrations. High glucose and aminophylline (10 mM) inhibited insulin release. Thus, in the absence of stimulatory glucose concentrations, low-intensity magnetic fields (1 to 10 Gauss) significantly influence insulin discharge from rat islets in vitro.

Animals↗
PubMed1984

Treatment of precocious pseudopuberty associated with follicular cysts of the ovary.

Two girls, aged 3 and 6 years, were treated for precocious pseudopuberty associated with a follicular ovarian cyst. Both patients had breast enlargement, areolar pigmentation, and elevated serum estradiol levels. In one girl, a normal displaced uterus was palpated; in the other, an ovarian cyst was identified by ultrasonography. Surgical treatment consisted of limited resection of the follicular cysts. Rapid regression of breast hypertrophy and return of estradiol levels to normal occurred in both children, who were followed for six and 1.5 years. We believe that a conservative operation that preserves normal ovarian tissue bilaterally is the procedure of choice for treating this condition.

Breast↗
PubMed1983

Hypernatremia induces hyperlipemia and a fatty liver.

Hypernatremic states, often the result of hypothalamic osmoreceptor dysfunction in humans, are sometimes accompanied by hyperlipemia. To investigate whether hypernatremia could cause hyperlipemia we induced hypernatremia in three groups of rats with their respective controls: Group A rats received hypertonic saline alone intragastrically; group B animals were pair-fed and tap water was substituted for hypertonic saline in the treated group; in group C the rats were again fed intragastrically with a liquid diet mixed with hypertonic saline. Rats receiving excess salt had mean serum Na+ concentrations exceeding 159 mmoles/l. While the serum triglyceride values were significantly higher in all hypernatremic rats, hepatic triglyceride content was greater only in group C rats (p less than .01). Serum free fatty acids and ketone bodies were also higher in group C rats (p less than .01) as compared to controls. These data suggest that hypernatremia by itself leads to hyperlipemia and a fatty liver.

Animals↗
PubMed1983

Metabolic acidosis in the newborn period.

In this chapter we have described the metabolic diseases which are known to have caused acidosis during the newborn period. We have also provided some diagnostic and treatment guidelines. The occurrence of acidosis in a newborn baby should initiate several actions, aimed simultaneously at treatment and diagnosis. An initial blood gas determination, accompanied by the results of serum electrolytes and glucose, will, in most instances, separate respiratory from metabolic causes. Finding of an increased anion gap and/or presence of hypoglycaemia should direct attention towards errors in intermediary metabolism.

Acidosis↗
PubMed1982

Insulin and glucagon release from cultured neonatal pancreatic islets of lean and preobese Zucker rats.

Pancreatic islets were isolated from individual neonatal (2-5 days of age) lean and preobese Zucker rats to assess insulin and glucagon release were elicited with high glucose (22.2 mM) plus aminophylline (10 mM) and alanine (10 mM), respectively. The similar secretory hormone patterns, both at basal and stimulated conditions, of the islets from rats later identified as lean or obese, suggest that a primary islet defect does not cause the hyperinsulinemia.

Animals↗
PubMed1982

Hypothalamic adipsia without demonstrable structural lesion.

The clinical and laboratory data of a 5-year-old boy with the syndrome of essential hypernatremia are presented. In a four-year follow-up, no demonstrable hypothalamic structural lesion has been identified. Review of the literature has uncovered four similar cases, suggesting a distinct syndrome of altered hypothalamic function. The syndrome is characterized by: adipsia-hypodipsia (5/5 patients), recurrent hypernatremia (5/5), obesity (4/5), inability to excrete a water load (5/5), lack of growth hormone release in response to provocative stimuli (4/4), blunted thyrotropin releasing hormone responses (3/4), hypothyroidism (2/4), and hyperlipemia associated with hypernatremic crisis (1/1). In one of the patients the syndrome has been attributed to a disturbance of the opioid-peptide system.

Child↗
PubMed1981

Growth and somatomedin-C responses to growth hormone in dwarfed children.

Nineteen children were studied because of short stature. They had in common abnormally low Sm-C values for age, and each received a ten-day course of exogenous GH therapy. Based on their endogenous GH concentrations and the response to GH therapy, in terms of Sm-C and height increments, they were classified into three groups. Group I included patients with GH insufficiency who had blunted GH responses to stimulation, but responded to therapy by normalizing the Sm-C concentration and velocity of growth. Group II patients all had normal GH responses to stimulation, but their responses to exogenous GH were similar to those observed in the GH deficient subjects. In the two children in Group III who had normal release of endogenous GH, Sm-C values and growth rate did not increase in response to GH. Group II patients may represent children with biologically inactive but immunoreactive GH, whereas the children in Group III are examples of the Laron type of dwarfism. Thus, rather than the plasma GH response to provocative stimuli, the Sm-C and growth increment responses to short-term exogenous GH therapy may more precisely identify children that will benefit from long-term GH therapy.

Adolescent↗
PubMed1981

Insulin release at physiologic potassium concentrations.

While high concentrations of potassium directly stimulate pancreatic insulin release, it has not been shown whether potassium ions within the physiologic range produce the same effect. Rats fed a low potassium diet were given KCl intraperitoneally. Insulin levels measured in the portal vein were significantly elevated (172.9 +/- 17 vs 76.5 +/- 14.9 microunits/ml, p less than .05) at 30 minutes, compared to peripheral insulin levels in which the increase did not reach significance. Thus insulin, when measured in portal vein blood samples, is significantly released by potassium increments within the normal range in the absence of exogenous glucose loads.

Animals↗
PubMed1980

Short-term influences of dichloroacetate on genetically hyperlipemic rats.

The effects of short-term (7 days) administration of dichloroacetate (DCA) on carbohydrate and lipid metabolism in the Zucker obese and lean rat were investigated. Metabolic effects of the drug were more pronounced in the obese than in the lean rat. DCA decreased fasting blood glucose concentrations in both lean and obese rats, but more so in the fat animals, probably because of higher initial levels. The hypoglycemic action of DCA is likely attributable to a direct effect on liver and peripheral tissues and not to an indirect action caused by a decrease in the glucagon-to-insulin ratio because the drug induced just the opposite effect. DCA decreased plasma triglycerides (TG) and free fatty acids (FFA) in the hyperlipemic rats but not in lean rats. Intrahepatic triglyceride content diminished after drug treatment in fat rats, suggesting decreased hepatic TG synthesis. Hyperketonemia, induced in both lean and fat rats by DCA treatment, was also greater in the obese animal. This response was probably caused by accelerated hepatic ketone body production due to increased beta-oxidation, and not to enhance FFA substrate supply. These data demonstrate that DCA is capable of correcting many of the underlying abnormalities in carbohydrate and fat metabolism in the obese Zucker rat.

Acetates↗
PubMed1979

Reverse tri-iodothyronine to tri-iodothyronine ratio and gestational age.

The biologic significance of reverse tri-iodothyronine is not yet identified. Cord blood values reflect the fetal thyroid state, with rT3 excess and tri-iodothyronine deficiency. In an attempt to correlate thyroid function and gestational age, T3 and rT3 concentrations were measured by radioimmunoassay on 64 cord blood samples. Infant gestational ages ranged from 29 to 42 weeks; birth weights from 650 to 3,870 gm. The results show a significant positive correlation between gestational age and T3 and a significant negative correlation between gestational age and rT3. The rT3/T3 offers the best correlation.

Female↗
PubMed1979

Correlation between morphology and function in isolated islets of the Zucker rat.

Obesity in the Zucker rat is accompanied by hyperlipemia, hyperinsulinism, insulin resistance, pancreatic hyperplasia, and islet hypertrophy. This study correlates the morphologic heterogeneity of isolated pancreatic islets with secretion of insulin and glucagon in the perifusion system. Islet size was arbitrarily defined as large (greater than 0.45 mm) or small (smaller than 0.12 mm). Protein content and volume (V = 4/3pir3) were calculated for groups and individual islets, respectively. Islets from obese rats secreted more insulin in response to glucose and aminophylline than islets from lean rats (peak 7.8 +/- 2.4 vs. 1.5 +/- 0.37 microU/islet/min, P less than 0.005). Insulin release was related directly to islet size and protein content. Small islets from lean and obese animals produced less insulin per islet than large islets (P less than 0.005). In terms of islet volume, however, large islets were inefficient insulin releasers as compared to small islets (P less than 0.005). Stimulation with Br-cAMP released glucagon from islets of lean but not from large islets of obese animals (peak 11 +/- 3.3 vs. 4.1 +/- 0.3 pg/microgram protein per minute, P less than 0.05). Arginine produced the same effect on glucagon release (P less than 0.05) as stimulation with Br-cAMP. The observed increased insulin release rates and the blunted glucagon response are related to islet size in the pancreas of the Zucker rat.

Aminophylline↗