Electrical activity in sympathetic fibres to hind limb muscles of the cat produced by hypothalamic stimulation

Electrical stimulation of the "Defence Area" of the hypothalamus in anaesthetized cats was accomplished by stereotaxic placement of bipolar stainless steel electrodes; the spinal cord was sectioned at L4. The muscle blood flow in one hind limb was recorded with an electromagnetic flowmeter. Increases of between 100% and 300% were observed during hypothalamic stimulation. Electroneurographic recordings from small nerve filaments supplying tibialis anterior muscle revealed two populations of neurones whose activity was abolished by lumbar sympathectomy. It appears that the increased blood flow in skeletal muscle during stimulation of the hypothalamic "Defence Area" is brought about by a simultaneous inhibition of vasoconstrictor activity and increase in cholinergic vasodilator discharge.     

Studies on the adenosine 3′,5′-monophosphate-dependent protein kinase of Blastocladiella emersonii

Using a combination of Chromatographic and sucrose density gradient techniques under carefully controlled conditions of pH and protease inhibitors, we demonstrate that there is only one form of adenosine 3′,5′-monophosphate-dependent protein kinase in the cytosol fraction of the Blastocladiella emersonii zoospore. If any of these conditions are omitted during extract preparation, one obtains what are apparently multiple forms of the enzyme, which are in reality artifacts due to extensive endogenous proteolytic activity. This endogenous protease is stimulated by alkaline pH and inhibited by antipain. The zoospore protein kinase is similar to type II protein kinase from mammalian cells in several aspects including Chromatographic behavior on DEAE-cellulose column, conditions for subunit dissociation and reassociation, as well as the molecular weight value of the regulatory subunit.     

Growth and fermentation characteristics of new selected strains of Saccharomyces at high temperatures and high cell densities

Maintenance of high cell viability was the main characteristic of our new strains of thermotolerant Saccharomyces. Total sugar conversion to ethanol was observed for sugarcane juice fermentation at 38-40 degrees C in less than 10 h and without continuous aeration of the culture. Invertase activity differed among the selected strains and increased during fermentation but was not dependent on cell viability. Invertase activity of the cells and optimum temperature for growth, as well as velocity of ethanol formation, were dependent on medium composition and the type of strain used. At high sugarcane syrup concentrations, the best temperature for ethanol formation by strain 781 was 35 degrees C. Distinct differences among the velocities of ethanol production using selected strains were also observed in sugarcane syrup at 35-38 degrees C.     

Presynaptic Mechanism of Action of 4-Aminopyridine: Changes in Intracellular Free Ca2+ Concentration and Its Relationship to B-50 (GAP-43) Phosphorylation

Abstract: Recently we have shown that 4-aminopyridine (4-AP), a drug known to enhance transmitter release, stimulates the phosphorylation of the protein kinase C substrate B-50 (GAP-43) in rat brain synaptosomes and that this effect is dependent on the presence of extracellular Ca²⁺. Hence, we were interested in the relationship between changes induced by 4-AP in the intracellular free Ca²⁺ concentration ([Ca²⁺]_i) and B-50 phosphorylation in synaptosomes. 4-AP (100 μ M ) elevates the [Ca²⁺]_i (as determined with fura-2) to approximately the same extent as depolarization with 30 m M K⁺ (from an initial resting level of 240 n M to ∼480 n M after treatment). However, the underlying mechanisms appear to be different: In the presence of 4-AP, depolarization with K⁺ still evoked an increase in [Ca²⁺]_i, which was additive to the elevation caused by 4-AP. Several Ca²⁺ channel antagonists (CdCl₂, LaCl₃, and diphenylhydantoin) inhibited the increase in B-50 phosphorylation by 4-AP. It is interesting that the increase in [Ca²⁺]_i and the increase in B-50 phosphorylation by 4-AP were attenuated by tetrodotoxin, a finding pointing to a possible involvement of Na⁺ channels in this action. These results suggest that 4-AP (indirectly) stimulates both Ca²⁺ influx and B-50 phosphorylation through voltage-dependent channels by a mechanism dependent on Na⁺ channel activity.     

Enhancement of Endogenous Release of Glutamate and γ-Aminobutyric Acid from Hippocampus CA1 Slices After In Vivo Long-Term Potentiation

The effect of long-term potentiation (LTP) on endogenous amino acid release from rat hippocampus slices was studied. LTP was induced in vivo by application of a tetanus (200 Hz, 200 ms) to the Schaffer collateral fibers in unanesthetized rats. Endogenous release of glutamate and gamma-aminobutyric acid (GABA) was investigated 60 min after tetanization in CA1 subslices of potentiated and control rats. No significant effects of LTP were observed in basal and K(+)-induced Ca(2+)-independent release components of these amino acids. In contrast, K(+)-induced Ca(2+)-dependent release of both glutamate and GABA increased approximately 100% in slices from potentiated rats. No differences were observed in total content of glutamate and GABA between the subslices from control and LTP animals. These results suggest a persistent increase in the recruitment of the presynaptic vesicular pool of glutamate and GABA during LTP.     

Thin-layer separation and quantification of bile acids

A method has been developed for quantification of total free and conjugated bile acids separated on silica gel HR coated thin-layer chromatography plates. Aliquots of bile acid solutions are applied to channeled plates which are developed with either ethyl acetate: isooctane: glacial acetic acid 10:10:2 v/v for free bile acid separation, or chloroform:methanol:glacial acetic acid:water 130:50:4:8 v/v for conjugated bile acid separation. Bile acids are determined directly in serial areas of silica gel by treating gel areas suspended in tris buffer with resazurin reagent. The method is quantitative and as little as 0.1 μg of bile acid is readily determined. Application of the method to determinations of bile acids in crude fecal extracts is described.     

DNA sequences at the sites of three insertions of the transposable element Tn5 in the histidine operon of Salmonella

Summary The DNA sequence has been determined at the sites of three independent occurrences of the transposable element Tn5 in the hisG gene of the histidine operon. All three insertion sites are adjacent to G+C-rich stretches of DNA. In all three cases sequences at the sites of insertion show homology with a region near the ends of Tn5.     

Teratologic evaluation of synthetic delta 9-tetrahydrocannabinol in rabbits.

Synthetic delta 9-tetrahydrocannabinol (THC) was dissolved in undiluted propylene glycol and administered in daily subcutaneous doses of 15.0, 30.0 or 60.0 mg/kg to pregnant New Zealand white rabbits on days 7--19 of gestation. Maternal food consumption and weight gain were markedly reduced at all dose levels. Embryotoxicity and embryocidal effects were observed in the form of reduced litter weight and number of viable fetuses, respectively, in offspring from pregnant mothers treated with THC. However, on the basis of extensive external, visceral and skeletal examination of all fetuses it may be concluded that THC is not teratogenic in the New Zealand white strain rabbit following subcutaneous administration of doses as high as 60.0 mg/kg/day during the critical period of organogenesis (days 7--19 of gestation). On the other hand, an oral dose of thalidomide (200.0 mg/kg/day), the positive control used in this study, was both embryocidal and teratogenic.