Unusual DNA structures at the integration site of an HIV provirus

Supercoiled pHXBc2 DNA (containing the genome of the human immunodeficiency virus type 1 and human sequences) migrated more slowly than linear DNA in native and ethidium bromide agarose gel electrophoresis at 4.5 volts/cm, suggesting the presence of unusual DNA structures. S1 nuclease analysis of pHXBc2 revealed two S1 hypersensitive sites. Site I was located within a 25 bp direct repeat in host DNA 0.6 kB upstream from the 5' LTR. Site II was mapped 0.2 kB upstream from the vif gene start site. Sequence analysis showed that Site I sequences could assume different unusual DNA structures, whereas sequences at Site II could assume either slipped or H-DNA forms. Unusual DNA structures in host DNA may be associated with active chromatin regions and may favor proviral integration.     

The rho gene product expressed in E. coli is a substrate of botulinum ADP-ribosyltransferase C3

The ras-related rho A protein expressed in E. coli, was ADP-ribosylated by botulinum ADP-ribosyltransferase C3. C3 also modified the valine-14 mutant rho protein but not the products of H-ras, R-ras, ral, ypt, and rap 1 genes. A ras-rho chimaera consisting of 60 amino acids from the amino terminus of ras fused to 133 amino acids from the carboxy terminus of rho was not modified by C3. Antibodies raised against the porcine brain cytosolic substrate of C3 cross reacted with the rho, valine-14 rho and ras-rho proteins, but not with the gene products of H-ras, R-ras, ral or rap 1. Polyclonal anti-H-ras antibodies cross reacted with H-ras but not with ral, rho, or the C3 substrate purified from porcine brain.     

The hormonal responses to repetitive brief maximal exercise in humans

The responses of nine men and nine women to brief repetitive maximal exercise have been studied. The exercise involved a 6-s sprint on a non-motorised treadmill repeated 10 times with 30 s recovery between each sprint. The total work done during the ten sprints was 37,693 +/- 3,956 J by the men and 26,555 +/- 4,589 J by the women (M greater than F, P less than 0.01). This difference in performance was not associated with higher blood lactate concentrations in the men (13.96 +/- 1.70 mmol.l-1) than the women (13.09 +/- 3.04 mmol.l-1). An 18-fold increase in plasma adrenaline (AD) occurred with the peak concentration observed after five sprints. The peak AD concentration in the men was larger than that seen in the women (9.2 +/- 7.3 and 3.7 +/- 2.4 nmol.l-1 respectively, P less than 0.05). The maximum noradrenaline (NA) concentration occurred after ten sprints in the men (31.6 +/- 10.9 nmol.l-1) and after five sprints in the women (27.4 +/- 20.8 nmol.l-1). Plasma cardiodilatin (CDN) and atrial natriuretic peptide (ANP) concentrations were elevated in response to the exercise. The peak ANP concentration occurred immediately post-exercise and the response of the women (10.8 +/- 4.5 pmol.l-1) was greater than that of the men (5.1 +/- 2.6 pmol.l-1, P less than 0.05). The peak CDN concentrations were 163 +/- 61 pmol.l-1 for the women and 135 +/- 61 pmol.l-1 for the men. No increases in calcitonin gene related peptide (CGRP) were detected in response to the exercise. These results indicate differences between men and women in performance and hormonal responses. There was no evidence for a role of CGRP in the control of the cardiovascular system after brief intermittent maximal exercise.     

65Zinc uptake from blood into brain and other tissues in the rat

Zinc is essential for normal growth, development and brain function although little is known about brain zinc homeostasis. Therefore, in this investigation we have studied⁶⁵Zn uptake from blood into brain and other tissues and have measured the blood-brain barrier permeability to⁶⁵Zn in the anaesthetized rat in vivo. Adult male Wistar within the weight range 500–600 g were used.⁶⁵ZnCl₂ and [¹²⁵I]albumin, the latter serving as a vascular marker, were injected in a bolus of normal saline I.V. Sequential arterial blood samples were taken during experiments that lasted between 5 min and 5 hr. At termination, samples from the liver, spleen, pancreas, lung, heart, muscle, kidney, bone, testis, ileum, blood cells, csf, and whole brain were taken and analysed for radio-isotope activity. Data have been analysed by Graphical Analysis which suggests⁶⁵Zn uptake from blood by all tissues sampled was unidirectional during this experimental period except brain, where at circulation times<30 min,⁶⁵Zn fluxes were bidirectional. In addition to the blood space, the brain appears to contain a rapidly exchanging compartment(s) for⁶⁵Zn of about 4 ml/100g which is not csf.     

Use of salicylate as a probe for .OH formation in isolated ischemic rat hearts

Salicylic acid was used as a probe for .OH formed during reperfusion of the ischemic myocardium. .OH adds to the phenolic ring of salicylate to yield dihydroxybenzoic acid species. The two principal dihydroxybenzoic acids formed are the 2,3- and 2,5-derivatives and can be isolated and quantitated using HPLC combined with electrochemical detection. In these experiments, dihydroxybenzoic acids were detectable in the f molar range. Rat hearts were perfused in the Langendorff mode with Krebs-Henseleit buffer containing 100 microM salicylate. Following 20 min of global ischemia a 173% increase in tissue content of 2,5-dihydroxybenzoic acid was detected after 2.5 min of reperfusion. The duration of ischemia did not significantly affect tissue content of 2,5-dihydroxybenzoic acid peaked at 250 to 300% of control within 2.5 min of reperfusion. The inclusion of 100 microM salicylate in the perfusion buffer had no effect on myocardial function during the duration of the experiments. The results indicate that salicylate can be used as a very sensitive probe for .OH in the isolated ischemic heart.     

Interspecific comparison of the period gene of Drosophila reveals large blocks of non-conserved coding DNA.

We have cloned and sequenced the coding region of the period (per) gene from Drosophila pseudoobscura and D. virilis. A comparison with that of D. melanogaster reveals that the conceptual translation products consist of interspersed blocks of conserved and non-conserved amino acid sequence. The non-conserved portion, comprising approximately 33% of the protein sequence, includes the perfect Thr-Gly repeat of D. melanogaster, which is absent from the D. pseudoobscura and D. virilis proteins. Based on these observations and cross-species transformation experiments, we suggest that the interspecific variability in the per primary amino acid sequence contributes to the control of species-specific behaviors.