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Biomedical subjects

G Weber

Publications and source records attributed to G Weber.

At least 685 records · Page 38Linked to original sources
PubMed1976

The ocellus of the cockroach, Periplaneta americana (Blattariae): receptory area.

The ocelli of Periplaneta americana were studied by light and electron microscopy. The view that the ocellus of the cockroach represents a degenerated structure can no longer be supported. All organelles necessary for function are present. The club-shaped retinular cells lie homogeneously distributed in the cupule of the ocellus. Rhabdoms are seen as sickle-, y-, x- or star-shaped structures with up to six cells in formation. Cells were found which had formed two rhabdomeres. The mass of cell organelles lies in the cytoplasm between the cell nucleus and the rhabdom. Smooth endoplasmic reticulum is wound into a spindle formation of considerable size at the origin of the axon in some cells. A cylindrical body in which 10-40 microtubules are packed, as yet unknown in insect retinular cells, is described. The receptory area of the ocellus terminates in a tapetum which contains granules, soluble in alcohol. The axon bundles of the retinular cells run through the tapetum and immediately thereafter make synaptic contact with dendrites of the ocellar nerve cells, while still within the ocellus.

Animals↗
PubMed1976

Growth and physical training with reference to heredity.

Identical male twins (four sets aged 10 yr, four sets aged 13 yr, and four sets aged 16 yr) were divided so that one twin underwent strenuos endurance training for 10 wk, while his brother served as a control without training. Intrapair comparisons of the training-period changes in aerobic, anaerobic, and cardiorespiratory responses to maximum work on a bicycle ergometer disclosed that 1) 10-yr-old trained twins improved more than untrained twins did in VO2max,2) 16-yr-old trained twins increased their VO2max, O2 pulse, blood lactate, ventilation, and respiratory rate and decreased their maximal heart rates more than their untrained counterparts did, and 3) the trained and the untrained 13-yr-old twins changed commensurately. Further, interage comparisons of the intrapair differences showed that both the 10- and 16-yr olds improved their VO2max more than did the 13-yr olds. In view of this evidence, the old hypothesis that more may be gained by introducing extra exercise at the time when the rate of growth is greatest is not tenable.

Adolescent↗
PubMed1976

Inhibition of glycolytic enzymes of rat liver and hepatomas by free fatty acids.

The action of free fatty acids on glycolytic enzymes was compared in normal and neoplastic tissues. Preincubation of tissue supernatant fractions with octanoate or laurate caused an inhibition of the activities of hexokinase and phosphofructokinase. An inhibition was also observed of lactate production with either glucose or glucose 6-phosphate as substrate. A similar degree of inhibition was observed for actions on normal liver and kidney, on the 7800 and 3924-A hepatomas and on the MK-3 renal cortical tumor. The possible relationship between the inhibition of glycolytic enzymes by fatty acids and anti-tumor activity previously observed with these compounds was noted.

Animals↗
PubMed1976

Perioral dermatitis, an important side-effect of corticosteroids.

Perioral dermatitis has been ascribed to the use of oral contraceptives, cosmetics, toothpastes of to an infection with Candida or Fusobacteria, etc. However, seborrheic diathesis, together with the use of potent topical steroids, appeared to be the main cause of the affection. This was confirmed with the help of a number observations in the clinic and by inference from data regarding the geographical spread of the potent steroids.

Administration, Topical↗
PubMed1976

Behavior of transaldolase (EC 2.2.1.2) and transketolase (EC 2.2.1.1) Activities in normal, neoplastic, differentiating, and regenerating liver.

The objective of this investigation was to throw light on the biological behavior and metabolic regulation of hepatic enzymes of the nonoxidative branch of the pentose phosphate pathway. The activities of transaldolase (EC 2.2.1.2) and trasketolase (EC 2.2.1.1) Were compared in biological conditions that involve modulation of gene expression such as in starvation, in differentiation, after partial hepatectomy, and in a spectrum of hepatomas of different growth rates. The enzyme activities were determined under optimal kinetic conditions by spectrophotometric methods in the 100,000 X g supernatant fluids prepared from tissue homogenates. The kinetic properties of transaldolase and transketolase were similar in normal liver and in rapidly growing hepatoma 3924A. For transaldolase, apparent Km values of 0.13 mM (normal liver) and 0.17 mM (hepatoma) were observed for erythrose 4-phosphate and of 0.30 to 0.35 mM for fructose 6-phosphate. The pH optima in liver and hepatoma were at approximately 6.9 to 7.2. For the transketolase substrates, ribose 5-phosphate and xylulose 5-phosphate, the apparent Km values were 0.3 and 0.5 mM, respectively, in both liver and hepatoma. A broad pH optimum around 7.6 was observed in both tissues. In organ distribution studies, enzyme activities were measured in liver, intestinal mucosa, thymus, kidney, spleen, brain, adipose tissue, lung, heart, and skeletal muscle. Taking the specific activity of liver as 100%, transaldolase activity was the highest in intestinal mucosa (316%) and in thymus (219%); it was the lowest in heart (53%) and in skeletal muscle (21%). Transketolase activity was highest in kidney (155%) and lowest in heart (26%) and skeletal muscle (23%). Starvation decreased transaldolase and transketolase activities in 6 days to 69 and 74%, respectively, of those of the liver of the normal, fed rat. This was in the same range as the decrease in the protein concentration (66%y. In the liver tumors, transaldolase activity was increased 1.5- to 3.4-fold over the activities observed in normal control rat liver. Transketolase activity showed no relationship to tumor proliferation rate. In the regenerating liver at 24 hr after partial hepatectomy, the activity of both pentose phosphate pathway enzymes was in the same range as that of the sham-operated controls. In differentiation at the postnatal age of 5, 12, 23, and 32 days, hepatic transaldolase activities were 33, 44, 55, and 72%, respectively, of the activities observed in the 60-day-old, adult male rat. During the same period, transketolase activ-ties were 18, 21, 26, and 55% of the activities observed in liver of adult rat. The demonstration of increased transaldolase activity in hepatomas, irrespective of the degree of tumor malignancy, differentiation, or growth rate, suggests that the reprogramming of gene expression in malignant transformation is linked with an increase in the expression of this pentose phosphate pathway enzyme...

Animals↗
PubMed1976

Aortic endothelial and sub-endothelial lesions in early stages of experimental atherogenesis and in scurvy.

The endothelial and sub-endothelial lesions during early stages of experimental atherogenesis and scurvy have been studied by means of scanning EM and transmission EM, making use also of the Con-A reaction. The surface coat modifications were accompanied by formation of vacuoles in the endothelial cells and by sub-endothelial 'oedema', not only in rabbits fed a hypercholesterolic diet but also in scorbutic guinea pigs. The endothelial lesions were sometimes found even before clear modifications of the Con-A surface reactive layer were apparent.

Animals↗