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Biomedical subjects

G Engström

Publications and source records attributed to G Engström.

70 records · Page 4Linked to original sources
PubMed1994

Lack of evidence for acute effects of growth hormone-releasing hormone on serum insulin and glucose levels in normal and hypophysectomized rats.

Growth hormone (GH) is diabetogenic but has also been suggested to stimulate insulin release. Our aim was to study whether acute effects of GH on serum insulin and glucose concentrations can be observed when GH release is physiologically induced by GH-releasing hormone (GHRH), which is known to stimulate insulin secretion. We also studied the acute effects of GHRH as such on insulin release in vivo and in vitro. Female Sprague-Dawley rats were hypophysectomized (hypox) at 40 days of age. At day 188, rats received 1 microgram GHRH(1-29)/100 g body weight i.v. In sham-operated rats, GHRH induced a rise in serum GH from 36.5 +/- 1.9 ng/ml (time 0 min) to 560.0 +/- 13.3 ng/ml (5 min;) (n = 6; p < 0.001). In hypox rats, no measurable serum levels of GH were detected either before or after GHRH treatment. Serum insulin was unaffected by GHRH in both groups of animals. Serum glucose was higher in sham operated than in hypox rats (7.3 +/- 0.4 vs. 6.3 +/- 0.1 mM at 0 min; p < 0.01). Serum glucose did not rise following GHRH injection. In isolated rat islets, cultured for 3 days at 11.1 mM glucose, 0.1-10 nM GHRH stimulated basal insulin release at 3 mM glucose. To summarize, GHRH at high concentrations stimulates insulin release in vitro, but neither GHRH, at a concentration where GH secretion is greatly stimulated, nor GHRH-induced GH release, have any acute effects on serum insulin or glucose levels.

Animals↗
PubMed1991

Two and four weeks' treatment for duodenal ulcer. Symptom relief and clinical remission comparing omeprazole and ranitidine. Scandinavian Clinics for United Research.

In a Swedish-Norwegian multicentre study patients with endoscopically verified duodenal ulcers (greater than 5 mm) were randomized to 2 or 4 weeks of treatment with either 20 mg omeprazole once daily or 300 mg ranitidine once daily. The aim was to evaluate 2 and 4 weeks' treatment with regard to symptomatic improvement during treatment, relapse after treatment, and safety of the two drugs. Endoscopy was not performed to check healing at the end of treatment. Instead the patients were instructed to contact the investigator in the event of recurrence of symptoms for renewed endoscopy. Follow-up was ended 10 weeks after stopping active treatment. Altogether 450 patients were evaluated at 17 centres. The symptomatic improvement during treatment was good in all groups, with significantly better reductions of daytime pain and heartburn in omeprazole-treated patients. Symptomatic relapse was commonest in the 2-week ranitidine group (57%), significantly more than in the 2-week omeprazole group (31%) (p less than 0.003). In the 4-week groups relapse rates were 34% (ranitidine) and 39% (omeprazole) (NS). It is suggested that in the short-term treatment of acute duodenal ulcer 20 mg omeprazole once daily is most rationally used in a 2- to 4-week regimen, whereas 300 mg ranitidine once daily should not be used for less than 4 weeks.

Absenteeism↗
PubMed1986

Graded response in the individual thyroid follicle cell to increasing doses of TSH.

The in vivo activation of rat thyroid follicle cells by increasing doses of TSH (1-100 mU) was studied by quantitative light and electron microscopy. The number of pseudopods induced after 20 min by 5, 20, 50 and 100 mU was the same but a dose-dependent increment of the individual pseudopod size (measured as profile area or membrane surface area) was observed, suggesting a graded response in the individual follicle cell. The number of pseudopods induced by 1 mU was only 10% of that in the other group. Another early effect of TSH, besides the induction of psuedopods, is stimulation of exocytosis. The number of exocytotic vesicles in pseudopod-bearing follicle cell profiles (the presence of a pseudopod taken as a sign of activation) decreased in a dose-dependent manner. This indicates that the follicle cell does not respond in an all-or-none mode (in which case a similar decrease in vesicle number in activated cells should be expected irrespective of the level of TSH) and that the response in the individual cell is graded depending on the level of TSH stimulation.

Animals↗
PubMed1985

Effects of shape and size on red blood cell deformability: a static bending analysis.

When flowing down a tapered tube, such as a narrow capillary, red blood cells (RBCs) are subject to deformation, the first event of which is folding in a pancake manner. The RBC deformability is reduced during cell ageing, a phenomenon that may reflect alterations in intracellular viscosity, membrane rigidity or RBC shape. Age related shape changes and their importance for increased RBC rigidity were theoretically analysed. The average empirically observed RBC profile is shown to offer little resistance to bending as compared to other, theoretically possible profiles of the same membrane area and RBC volume. Because of a decrease in projected area (diameter size), and therefore in pressure load, the pressure needed to initiate folding of an old RBC is between 20 and 55% higher than that required to fold a young one if, during RBC ageing, membrane area to cell volume ratio is constant as empirically observed. This difference exists whether the RBC is mathematically treated as a solid body or as a membrane shell.

Age Factors↗
PubMed1982

Absorption of gas in dental gold alloys during melting.

The absorption of gas during heating and melting of pure gold and of two dental gold alloys was studied by gas chromatography. The metals were melted by two methods, i.e. gas-torch and electric heating. The specimens were analysed regarding the content of hydrogen, oxygen and nitrogen. The amount of nitrogen was not measurable in all specimens. Oxygen gas occurred with rather high values in the two dental gold alloys. The hydrogen content was often larger than the solubility limit. It is proposed that hydrogen often gives pore precipitation. It is also proposed that special caution must be taken during melting to reduce the hydrogen content in the melt before casting. D-alloy (palladium) demonstrated high H and O values on gas-torch heating.

Absorption↗
PubMed1981

Effect of graded doses of thyrotropin on exocytosis and early phase of endocytosis in the rat thyroid.

Our previous studies on the follicle cell have shown that exocytosis and endocytosis induced by a large dose of TSH (500 mU) are functionally related elements of a redistribution of membrane in the apical cell region. To explore the significance of exocytosis at submaximal levels of stimulation, T4-treated rats were injected iv with 5 or 50 mU TSH 5, 10, or 20 min before perfusion fixation of the thyroid. Additional groups were given 20 or 100 mU TSH or saline 20 min before fixation. Electron microscopic stereology showed that TSH induced exocytosis and endocytosis and a redistribution of membrane in the apical part of the follicle cell. Exocytosis preceded endocytosis. The redistribution of membrane was quantitatively different but qualitatively similar to that previously observed after a large dose of TSH. The rate of exocytosis was linearly correlated with the logarithm of the TSH dose. The size, but not the number (counted in the light microscope), of pseudopods was related to the TSH dose; at 20 min, the membrane surface area of a pseudopod induced by 100 mU was about twice that of a pseudopod induced by 5 mU. The total membrane surface area of endocytotic structures (pseudopods, colloid droplets, and micropinocytotic vesicles) was related to the surface area of the membrane added to the apical plasma membrane by exocytosis. The findings indicate that exocytosis is part of the normal response of the follicle cell to stimulation and represents the first step in the redistribution of membranes in the apical part of the follicle cell induced by TSH. At all levels of stimulation, the membrane of the exocytotis vesicles, rather than the apical plasma membrane, is the membrane reserve used to make endocytotic structures. (Endocrinology 108: 399, 1981)

Animals↗
PubMed1978

Effect of thyroxine treatment on carnitine levels in mice.

The effect in mice of 8 subcutaneous injections of 20 microgram of L-thyroxine at 12 hr-intervals on the carnitine concentration in the heart and skeletal muscle tissue was studied. In skeletal muscle tissue, the thyroxine treatment resulted in a depressed carnitine concentration. The mean values were 1.59 +/- 0.034 (S.E.M.) and 2.03 +/- 0.045 mumol/g noncollagen protein and 1.11 +/- 0.035 and 1.45 +/- 0.037 mumol/g dry weight for the thyroxine treated and the control animals, respectively. Thyroxine produced myocardial hypertrophy. The thyroxine treated animals had lower cardiac values when dry weight was used as reference base 4.17 +/- 0.10 mumol/g dry weight than the control group, 4.69 +/- 0.18 mumol/g dry weight. No statistically significant difference was found between the two groups when the cardiac carnitine concentration was expressed per g noncollagen protein or as carnitine in the entire hearts. Thus, thyroxine has been showed to influence the metabolism of carnitine in mice.

Animals↗
PubMed1978

Quantitative electron microscopic studies on exocytosis and endocytosis in the thyroid follicle cell.

The effect of TSH (0.5 U), given iv to T4-treated rats, on the distribution of membranes in the apical part of the thyroid follicle cell was investigated by electron microscopic morphometry. In unstimulated cells, the membrane surface area of exocytotic vesicles (Ev) was slightly larger than that of the apical plasma membrane; the latter had an estimated surface area of 180-190 micron2/follicle cell. Three phases in the action of TSH could be discerned. A first phase (up to 5 min) was dominated by exocytosis; the membrane surface area of Ev decreased by about 40% and the apical plasma membrane showed a corresponding increase; pseudopods were rare. A second phase (5-20 min) was characterized by an increase in the membrane surface area of pseudopods while the area of Ev and apical plasma membrane decreased. A third phase (20-30 min) was characterized by a decrease in the membrane surface area of the pseudopods and an equivalent increase in the membrane surface area of colloid droplets. The total membrane surface area measured was about the same in all groups of rats. The membrane surface area of endocytotic structures (pseudopods and colloid droplets) at 20 and 30 min was about the same as that of the apical plasma membrane in unstimulated cells. The present results are consistent with the hypothesis that after stimulation of the thyroid follicle cell, membrane is first transferred from Ev to the apical plasma membrane. From the enlarged apical plasma membrane, pseudopods are formed. Membrane from pseudopods is then internalized in the form of colloid droplets.

Animals↗
PubMed1975

Exocytosis of protein into the thyroid follicle lumen: an early effect of TSH.

As shown in a preceding paper, only exocytotic vesicles conveying newly synthesized protein to the follicle lumen remain in the apical part of rat thyroid follicle cells following elimination of TSH secretion. In the present paper the effect of TSH on these exocytotic vesicles was investigated. TSH secretion was suppressed by administration of thyroxine for 2 days. In the electron microscope administration of TSH was seen to induce well-known signs of endocytosis, such as formation of pseudopods and colloid droplets. In addition, a previously unrecognized change was noted, namely a progressive decrease in the number of exocytotic vesicles. At 5 min after TSH the number was obviously reduced and at 20 min less than 10% of the original number of vesicles remained. Quantitative electron microscopic autoradiography after administration of [3H]leucine showed that TSH caused, concomitant with the disappearance of vesicles, a transfer of radioactivity from the apical region of the follicle cell to the periphery of the follicle lumen. The distribution of labeled protein in thyroid subcellular fractions was studied 1.5 h after administration of [14C]leucine. At 5 min after administration of TSH there was an increase of protein-bound label in the supernatant fraction, containing the luminal colloid, and a corresponding decrease of label in the particle fraction which contained most of the cell organelles, including the exocytotic vesicles. This TSH-induced redistribution of labeled proteins was more pronounced at 10 min and still more at 20 min and appeared to be dose-dependent. These observations taken together are considered to justify the conclusion that TSH induces transfer of newly synthesized protein from the follicle cells to the follicle lumen by exocytosis (i.e., emptying of specific apical vesicles). It is suggested that a causal and functional interrelation may exist between the exocytotic and endocytotic processes.

Animals↗