The excretion of 11-hydroxycorticosteroids by rats during exposure to altitude

The effect of exposure to 5,500 m and 7,300 m simulated altitude on rat adrenal glands was assessed by the measurement of urinary 11-hydroxycorticosteroids (11-OHCS). Since rat urine contains large amounts of non-corticosteroid fluorogens, a modification was introduced into the conventional fluorimetric method. At 5,500 m altitude increased excretion of 11-OHCS was confined to the first 24 hr. At 7,300 m the excretion of 11-OHCS continued at elevated levels throughout the exposure period. The excretion of catecholamines was also increased in rats during exposure to altitude. Since changes in the levels of excreted adrenaline and body weight were comparable with changes in 11-OHCS excretion at both altitudes, in the rat urinary 11-OHCS levels appear to constitute an index of the stress imposed by high altitudes.

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Zusammenfassung Die Wirkung von 5.500 m und 7.300 m simulierter Höhe auf die Nebennieren der Ratte wurde überprüft durch Messung der 11-Hydroxykortikosteroide (11-OHCS) im Harn. Da Rattenharn grosse Mengen von Fluorogenen enthält, die keine Kortikosteroide sind, wurde die konventionelle fluorimetrische Methode modifiziert. In 5.500 m Höhe bestand eine erhöhte 11-OHCS Ausscheidung nur in den ersten 24 Stunden. In 7.300 m Höhe wurde eine erhöhte Ausscheidung von 11-OHCS während der gesamten Expositionsperiode von 14 Tagen beobachtet. Die Ausscheidung der Katecholamine war während der Periode in den beiden Höhen ebenfalls erhöht. Da die Veränderungen der Adrenalinausscheidung und des Körpergewichts vergleichbar waren mit den Veränderungen der 11-OHCS Ausscheidung scheint der 11-OHCS Gehalt im Harn als Index für das Ausmass der Höhenbelastung bei Ratten geeignet zu sein.

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Resume On a examiné l'effet de l'exposition à des altitudes simulées de 5,500 m et de 7,300 m sur les surrénales des rats en mesurant le taux de 11-hydroxycorticostéroïde (11-OHCS) dans l'urine. Comme cette dernière contient de grandes quantités de substances fluorogènes qui ne sont pas des corticostéroïdes, on a modifié la méthode conventionelle de mesure fluorimétrique. A 5.500 m d'altitude, on ne constate une sécrétion accrue de 11-OHCS que durant les premières 24 heures d'exposition. A 7.300 m d'altitude par contre, la sécrétion accrue a duré jusqu'à la fin de l'expérience, c'est-à-dire 14 jours. On a constaté en outre une sécrétion accrue de catécholamine dans les deux cas et durant toute la période. Comme les variations de poids et de sécrétion d'adrénaline étaient en relation directe avec celles de 11-OHCS, le taux de ce dernier dans l'urine semble être un bon indice pour déterminer la contrainte d'altitude chez les rats.

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DCIEM Research Paper 821.     

Preliminary X-ray study of crystals of human C-reactive protein

Two different crystal forms of human C-reactive protein have been grown from solutions of 2-methyl-2,4-pentanediol. Both crystal forms are tetragonal, the space group for form I is P4(1)22 (or P4(3)22), and that for form II is P4(2)22. The unit cell parameters for form I are a = b = 103.0(5) A, c = 308.5(7) A and for form II are a = b = 103.1(2) A, c = 312.7(6) A. The crystals of form II diffract to at least 3.0 A resolution, and are suitable for detailed structural studies.     

Direction of carbon flux in starvation and after refeeding: in vitro and in vivo effects of 3-mercaptopicolinate

3-Mercaptopicolinate (3-MPA) is a specific inhibitor of phosphoenolpyruvate carboxykinase (PEP CK). In vivo the hypoglycaemic action of 3-MPA in 24 h-starved rats was abolished on intragastric glucose refeeding. Nonetheless, 3-MPA decreased hepatic glycogen content and rate of synthesis in starved animals re-fed glucose. The inference is that on re-feeding after starvation hepatic glycogen is synthesised mainly de novo via glyconeogenesis involving PEP CK. 3-MPA increased hepatic lipogenesis in water- and glucose-fed normal and diabetic rats. This increase is presumed to result from inhibition of PEP CK and consequent diversion of pyruvate from gluconeogenesis to lipogenesis. In contrast, 3-MPA inhibited brown-fat lipogenesis in water- and glucose-fed rats.     

Contraction of bovine coronary vascular smooth muscle induced by cocaine is not mediated by norepinephrine

This study was designed to assess the effects of cocaine on coronary arterial smooth muscle and to determine whether previously reported cocaine-induced coronary vasospasm is mediated by substances released from the endothelium or by increased adrenergic receptor stimulation. Concentration-response relationships for cocaine (0.1-300 microM) and norepinephrine (0.1-300 microM) were studied in vitro using 2 mm segments of bovine proximal left anterior descending coronary artery. Each segmental ring was mounted in a 70 ml tissue bath for the measurement of isometric tension. Cocaine (3-300 microM) caused significant, concentration-dependent, increases in developed tension (p less than 0.05). Removal of the endothelium or pretreatment with prazosin (0.1 microM) or propranolol (1 microM) did not significantly alter this action of cocaine. In contrast to cocaine, norepinephrine (10-300 microM) caused significant decreases in developed tension (p less than 0.01). These findings suggest that cocaine-induced contraction of bovine coronary vascular smooth muscle is not mediated by endothelium derived contracting substances or norepinephrine.     

Stimulation of flux through hepatic pyruvate dehydrogenase by 3-mercaptopicolinate

Isolated hepatocytes from 24-h-starved rats were used to assess the possible effect of Ahe hypoglycaemic agent 3-mercaptopicolinate on flux through the hepatic pyruvate dehydrogenase complex. Increasing the extraceIIular pyruvate concentration from 1 mM to 2 mM or 5 mM resulted in an increase in flux through pyruvate dehydrogenase and the tricarboxylic acid cycle as measured by¹⁴CO₂ evolution from [1-¹⁴C]pyruvate and [3-¹⁴C]pyruvate. Gluconeogenesis was inhibited by 3-mercaptopicolinate from both 1 mM and 2 mM pyruvate, but significant increases in malate and citrate concentrations only occurred in cells incubated with 1 mM pyruvate. Flux through pyruvate dehydrogenase was stimulated by 3-mercaptopicolinate with 1 mM pyruvate but was unaltered with 2 mM pyruvate. Dichloroacetate stimulated flux through pyruvate dehydrogenase with no effect on gluconeogenesis in the presence of I mM pyruvate. There was no effect of 3-mercaptopicolinate, administered in vivo, to 24-h-starved rats on the activity of pyruvate dehydrogenase in freeze-clamped heart or liver tissue, although the drug did decrease blood glucose concentration and increase the blood concentrations of lactate and alanine. Dichloroacetate, administered in vivo to 24-h-starved rats, increased the activity of pyruvate dehydrogenase in freeze-clamped heart and liver, and caused decreases in the blood concentrations of glucose, lactate , and alanine. The results suggest that 3-mercaptopicolinate increases flux through hepatocyte pyruvate dehydrogenase by an indirect mechanism.     

Utilization of DNA photolyase, pyrimidine dimer endonucleases, and alkali hydrolysis in the analysis of aberrant ABC excinuclease incisions adjacent to UV-induced DNA photoproducts.

ABC excinuclease of Escherichia coli removes 6-4 photoproducts and pyrimidine dimers from DNA by making two single strand incisions, one 8 phosphodiester bonds 5' and another 4 or 5 phosphodiester bonds 3' to the lesion. We describe in this communication a method, which utilizes DNA photolyase from E. coli, pyrimidine dimer endonucleases from M. luteus and bacteriophage T4, and alkali hydrolysis, for analyzing the ABC excinuclease incision pattern corresponding to each of these photoproducts in a DNA fragment. On occasion, ABC excinuclease does not incise DNA exclusively 8 phosphodiester bonds 5' or 4 or 5 phosphodiester bonds 3' to the photoproduct. Both the nature of the adduct (6-4 photoproduct or pyrimidine dimer) and the sequence of neighboring nucleotides influence the incision pattern of ABC excinuclease. We show directly that photolyase stimulates the removal of pyrimidine dimers (but not 6-4 photoproducts) by the excinuclease. Also, photolyase does not repair CC pyrimidine dimers efficiently while it does repair TT or TC pyrimidine dimers.     

Recent positive selection of a human androgen receptor/ectodysplasin A2 receptor haplotype and its relationship to male pattern baldness

Genetic variants in the human androgen receptor gene (AR) are associated with male pattern baldness (androgenetic alopecia, AGA) in Europeans. Previous observations of long-range linkage disequilibrium at the AR locus are consistent with the hypothesis of recent positive selection. Here, we further investigate this signature and its relationship to the AGA risk haplotype. The haplotype homozygosity suggests that the AGA risk haplotype was driven to high frequency by positive selection in Europeans although a low meiotic recombination rate contributed to the high haplotype homozygosity. Further, we find high levels of population differentiation as measured by F _ST and a series of fixed derived alleles along an extended region centromeric to AR in the Asian HapMap sample. The predominant AGA risk haplotype also carries the putatively functional variant 57K in the flanking ectodysplasin A2 receptor gene (EDA2R). It is therefore probable that the AGA risk haplotype rose to high frequency in combination with this EDA2R variant, possibly by hitchhiking on a positively selected 57K haplotype. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Cell surface topography duringMarsilea spermiogenesis: Flagellar reorientation and membrane particle arrays

Summary Changes in the cell surface during spermiogenesis in the fern,Marsilea, have been investigated by freeze-fracture. Early in development 150 or more flagella appear on the surface of the spermatid cell. As they grow in length, they change orientation in relation to the spermatid cell surface and to each other. While the flagella are growing, a band of membrane particles surrounds each flagellum at the transition zone. These particles disappear near the end of development and are not seen in mature sperm. Other particles are associated with the plasma membrane during development. One set of particles is found early in spermiogenesis in hexagonal arrays. At the end of spermiogenesis, these are no longer observed, but clusters of particles, with no particular order, appear around the flagellar bases, following the line of the flagellar band.