Breathing at high altitude

Acclimatization to long-term hypoxia takes place at high altitude and allows gradual improvement of the ability to tolerate the hypoxic environment. An important component of this process is the hypoxic ventilatory acclimatization (HVA) that develops over several days. HVA reveals profound cellular and neurochemical re-organization occurring both in the peripheral chemoreceptors and in the central nervous system (in brainstem respiratory groups). These changes lead to an enhanced activity of peripheral chemoreceptor and re-inforce the central translation of peripheral inputs to efficient respiratory motor activity under the steady low O₂ pressure. We will review the cellular processes underlying these changes with a particular emphasis on changes of neurotransmitter function and ion channel properties in peripheral chemoreceptors, and present evidence that low O₂ level acts directly on brainstem nuclei to induce cellular changes contributing to maintain a high tonic respiratory drive under chronic hypoxia. (This study is part of a multi-author review.)     

Influence of high magnetic fields on meiosis

Summary In a homogeneous, high magnetic field, the number of chromosomal aberrations during meiotic division in the sporogenic tissue of lily is increased.     

Radioresistance in cells with high content of metallothionein

Summary An endogenous cytoplasmic protein, metallothionein (MT) apparently gave rise to radioresistance in 2 different cell lines. A dose reduction factor of 1.9 was achieved in MT-containing cells. MT accounted for a 3–4-fold increase of total sulfhydryl groups in the resistant cell strains, compared to the non-resistant lines from which they were derived. The protein is rich in cysteine (30%), an amino acid known to give radioprotection when administered exogeneously. Glutathione levels and cell-cycle phase distribution showed no marked difference between resistant and corresponding non-resistant cells.We thank Dr F. Devik, Dr L. Eldjarn and Dr E. Jellum for stimulating discussions, and Miss A. K. Syversen and Mrs T. Nysted for skillful technical assistance. This work was partly supported by the Norgwegian Council for Science and the Humanitites. LE is a fellow of the Norwegian Society for Fighting Cancer.     

Anomalous stability of insulin at very high pressure

Insulin is unaffected by pressures of 48,000 b in the solid state at room temperature, as elucidated both by spectroscopic measurements and bioassay. Its compression curve is reversible. The presence of water does not alter this property. Of a number of other proteins investigated insulin appears to be unique with regard to its pressure stability. The relative rigidity of the molecule combined with its small size may account for some of these properties.     

The neurogenic activity of high potency substance P

Zusammenfassung Gereinigte Präparate von Substanz P mit Aktivitäten von 10, 1000 und 10 000 E/mg verstärken das vierte Potential der dorsalen Nervenwurzel im Rückenmark der Katze (Verabreichung nach LSD). Unsere Befunde bestätigen frühere Beobachtungen und legen die Vermutung nahe, dass bei fortschreitender Reinigung ein Teil der neurotropen Aktivität zusammen mit der leiotropen angereichert wird.     

Uptake of noradrenaline in high altitude native's heart

Summary Uptake of³H-noradrenaline by the heart was studied with sections of isolated atria obtained from high or lowlanders. In native highlanders, affinity for³H-noradrenaline by human atria is more significant than in lowlanders. Furthermore, the Michaelis Menten constant is lower in high altitude native's heart.     

Anomalous stability of insulin at very high pressure

Summary Insulin is unaffected by pressures of 48,000 b in the solid state at room temperature, as elucidated both by spectroscopic measurements and bioassay. Its compression curve is reversible. The presence of water does not alter this property. Of a number of other proteins investigated insulin appears to be unique with regard to its pressure stability. The relative rigidity of the molecule combined with its small size may account for some of these properties.Acknowlegments. I should like to thank Prof. Willard F. Libby of the Department of Chemistry and Institute of Geophysics of the University of California, Los Angeles, for his interest and support of this study.     

Chromatin ofh regions of human chromosomes at high resolution

Summary Segmentation of the secondary constriction region (h) of human chromosomes 1, 9 and 16 is demonstrated by a high resolution banding technique. Based on these staining properties, it is suggested that the composition of theh region in human chromosomes is heterochromatic as well as euchromatic.     

Net-shape forming of composite packages with high thermal conductivity

The continuing miniaturization of electronic devices in microelectronics and semiconductors drives the development of new packaging materials with enhanced thermal conductivity to dissipate the heat generated in electronic packages.In recent years,several promising composite materials with high thermal conductivity have been developed successfully for high performance electronic equipment to replace the traditional Kovar and Cu/W or Cu/Mo alloys,such as SiCp/Al,SICp/Cu,diamond/Al and diamond/Cu.However,thes...     

The high activity of fluorohydroxybenzylbenzimidazoles against some small RNA-viruses

Zusammenfassung Fluorierte Derivate des 2-(-Oxybenzyl)-benzimidazol hemmen die Vermehrung des Poliovirus, 1, 2 und 3, sowie diejenige des Coxsackievirus A9 und A21.     

Hypertriglyceridemia in rats at simulated high altitudes

Zusammenfassung Ratten, die 3–12 Tage in einer Luftverdünnung entsprechend einer Höhe von 3000, 5000 und 7000 m gehalten wurden, hatten eine signifikante Hypertriglyceridämie und eine leichte Tendenz zu erhöhten Lebertriglyceridkonzentrationen. Die freien Fettsäuren des Serums waren nicht erhöht.     

Biomolecular stability and life at high temperatures

It is not clear what the upper temperature limit for life is, or what specific factors will set this limit, but it is generally assumed that the limit will be dictated by molecular instability. In this review, we examine the thermal stability of two key groups of biological molecules: the intracellular small molecules/metabolites and the major classes of macromolecules. Certain small molecules/metabolites are unstable in vitro at the growth temperatures of the hyperthermophiles in which they are found. This instability appears to be dealt with in vivo by a range of mechanisms including rapid turnover, metabolic channelling and local stabilisation. Evidence to date suggests that proteins have the potential to be stable at substantially higher temperatures than those known to support life, but evidence concerning degradative reactions above 100 degrees C is slight. DNA duplex stability is apparently achieved at high temperature by elevated salt concentrations, polyamines, cationic proteins, and supercoiling rather than manipulation of C-G ratios. RNA stability seems dependent upon covalent modification, although secondary structure is probably also critical. The diether-linked lipids, which make up the monolayer membrane of most organisms growing above 85 degrees C are chemically very stable and seem potentially capable of maintaining membrane integrity at much higher temperatures. However, the in vivo implications of the in vitro instability of biomolecules are difficult to assess, and in vivo data are rare.     

Carboxylesterases of high molecular weight in the hemolymph ofLocusta migratoria

Summary The main carboxylesterase in the hemolymph of the migratory locust,Locusta migratoria, is a protein of high molecular weight; about 700–750 kDa. This esterase hydrolyzes juvenile hormone III, -naphthylacetate and -naphthylacetate. The carboxylesterase dissociates to give an esterase of molecular weight 148 kDa after treatment of the hemolymph with mercaptoethanol.     

Separation of canavanine and canaline by high performance liquid chromatography

Summary The plant amino acid canavanine and its hydrolytic product canaline were successfully separated and identified by Reverse Phase High Performance Liquid Chromatograph (RP-HPLC). This procedure was used to demonstrate the arginasemediated cleavage of canavanine to yield canaline and urea, and the subsequent formation of a Schiff's base complex between canaline and pyridoxal phosphate. Both aforementioned reactions were demonstrated by RP-HPLC.     

Separation of canavanine and canaline by high performance liquid chromatography

The plant amino acid canavanine and its hydrolytic product canaline were successfully separated and identified by Reverse Phase High Performance Liquid Chromatograph (RP-HPLC). This procedure was used to demonstrate the arginase-mediated cleavage of canavanine to yield canaline and urea, and the subsequent formation of a Schiff's base complex between canaline and pyridoxal phosphate. Both aforementioned reactions were demonstrated by RP-HPLC.