Adaptation to chronic hypobaric hypoxia and sexual hormones

The role of the gonads and their hormones on body weight was studied in rats of both sexes submitted to chronic hypoxia and their controls at sea level atmospheric pressure. Intact rats were exposed to either 4 700 or 6 000 m simulated altitude in a hypopressure chamber. Castrated rats and castrated rats daily injected with either 0.5 mg of testosterone or 20 microgram of estradiol or the vehicle, were exposed to the higher altitude. The rat weight was recorded for a period of at least eight weeks. All groups of hypoxic male animals increased their weight significantly less than the controls at sea level. Also in castrated females and in castrated injected with testosterone or the vehicle the same pattern of weight curves was observed. On the contrary, groups of intact females and castrated females injected with estradiol did not show significant differences between hypoxic and control animals. Only in a group of smaller intact females (50-80 g) the body weight increase was significantly diminished by exposure to either 4 700 or 6 000 m simulated altitude.     

Action of alkyl cations and the natural ATPase inhibitor from mitochondria on soluble mitochondrial ATPase

The effect of the natural ATPase inhibitor and octylguanidine on the ATPase activity of soluble oligomycin-insensitive mitochondrial F₁ were compared. Both compounds induced a maximal inhibition of 60–80% in various preparations of F₁ studied. The inhibition was of the uncompetitive type with respect to MgATP, and the action of the compounds was partially additive. The data suggest that octylguanidine reproduces the action of the natural ATPase inhibitor. Alkylammonium salts also affect the ATPase activity in a similar form. F₁ bound to Sepharose-hexylammonium is largely inactive, whilst free hexylammonium at higher concentrations induces only a partial inhibition of the activity. This suggests that the degree of immobilization of F₁ is related to the magnitude of inhibition of ATPase activity induced by alkyl cations. The binding of F₁ to Sepharose-hexylammonium is prevented by high concentrations of Na⁺ or K⁺.     

Inactivation of penicillin by purulent exudates.

Four of 22 specimens of human pus inactivated up to 90% of added penicillin within one hour in vitro. Ampicillin and cephaloridine were also inactivated, but streptomycin and fusidic acid were not. The effect was not related to the protein content of the pus, nor to its pH value. Microbes that may produce beta-lactamase in small quantities were isolated from three of the four specimens, but the enzyme was not detected in the pus by physical methods nor by microbiological inhibition assay. The inactivating effect was shown to be a property of the solid portion of the pus, and was absent from the filtrate. We suggest that the effect may be an intrinsic property of the host, which should be investigated further as it has important implications for clinical practice.     

Aggregative properties of different cell types of the fresh-water spongeEphydatia fluviatilis isolated on ficoll gradients

Summary Cell suspensions of the fresh-watersponge Ephydatia fluviatilis have been fractionated by means ofFicoll gradient centrifugation. Three fractions were isolated. The densest contains archeocyte-like cells only; the intermediate fraction is very rich in choanocytes, and the lightest is a mixture of cell types. Earch fraction shows specificaggregative properties and potentialities to reconstitute functional sponges.It appears that the sequence of reconstitution events can be selectively altered by certain disequilibria in the cell populationThese preliminary results constitute a first approach to the analysis ofcell type specificity in sponges.     

Effect of culture filtrates of black-pigmented Bacteroides species on the matrix production of chick embryo chondrocytes in vitro

Antonie van Leeuwenhoek -     

Modified oscillation behavior and decreased D-3-hydroxybutyrate dehydrogenase activity in diabetic rat liver mitochondria

One month after induction of diabetes in adult white rats with streptozotocin or 4–10 months after its induction by pancreatectomy (in every case glycemia was over 3 g/liter), the following alterations were observed in liver mitochondria: (a) a decrease of amplitude and an increase of the damping factor of volume oscillations induced by potassium ions and valinomycin; (b) a 50% decrease of d-3-hydroxybutyrate dehydrogenase (HBD) activity in mitochondria disrupted by repeated freeze-thawing; (c) a similar decrease in the rate of d-3-hydroxybutyrate oxidation by intact mitochondria; (d) a significant increase of cytochrome oxidase activity and cytochrome aa₃ content. Measurement of succinate dehydrogenase and NADH dehydrogenase activity, the cytochrome b, c₁, and c content, and the P:O ratio for mitochondria oxidizing d-3-hydroxybutyrate did not reveal significant differences between control and diabetic rat mitochondria. In the streptozotocin-injected rats, the variation of HBD activity and the modification of the mitochondrial oscillation pattern were time-dependent phenomena, both effects reaching their maximal expression about 1 month after the onset of diabetes. The variation of HBD activity followed a biphasic course, since it rose to above the control level during the first 2 weeks of diabetes, then fell progressively to about half the control value after the third week. Treatment of diabetic rats with NPH insulin (5 IU twice daily, for 3 days, reinforced by the same dose 45 min before sacrifice) restored the mitochondrial oscillation pattern, HBD activity, and rate of d-3-hydroxybutyrate oxidation by intact mitochondria to their normal values.     

Gramicidin induces the formation of non-bilayer structures in phosphatidylcholine dispersions in a fatty acid chain length dependent way

The hydrophobic peptide gramicidin is shown by ³¹P-NMR, freeze-fracture electron microscopy and small-angle X-ray diffraction, to induce a hexogonal H_II-phase lipid organization when incorporated in liquid crystalline saturated and unsaturated synthetic and natural phosphatidylcholines if the length of the fatty acids exceeds a 16 carbon atoms chain. The amount of hexagonally organized lipid increases with increasing fatty acid chain length. With phosphatidylcholines possessing shorter fatty acid chains, as well as with the longer phosphatidylcholines in the gel state, a lamellar organization results. Of the various possible models to explain the induction of the hexagonal H_II phase by gramicidin, one in which gramicidin dimers span adjacent cylinders of the hexagonal H_II phase seems most plausible. In phosphatidylcholines with intermediary chain lengths gramicidin induces intermediary structures, such as lipidic particles and possibly cubic phases. These experiments suggest that the balance between the length of the hydrophobic domain of a peptide and the membrane thickness is of critical importance for the structure of the membrane. In relation to this observation, the possible involvement of non-bilayer lipid structures in insertion and anchoring of membrane proteins is discussed.