Isolation and structure determination of two peptides occurring in human seminal plasma

Two previously unknown peptides with a high amount of polar amino acids were isolated from human seminal plasma by a combination of dialysis, gel filtration, ion-exchange chromatography, and RP-HPLC. Their structures were determined by gas-phase sequencing simultaneously considering the different peak intensities.     

The effect of ferricyanide with iodoacetate in calcium-free solution on passive cation permeability in human red blood cells: comparison with the Gardos-effect and with the influence of PCMBS on passive cation permeability

Freshly prepared human red blood cells incubated with 5 mM ferricyanide, 0.2 mM iodoacetate and 2 mM adenosine in the presence of 5 mM EGTA demonstrate comparable increases in Na+ and K+ permeability (ferricyanide effect). This effect is unrelated to the Ca2+-activated K+ channel (Gardos effect) since influx of Ca2+ from outside the cell is excluded. Also this effect is different from the non-specific Na+ and K+ permeability change elicited by PCMBS. These differences become obvious by using various reagents. For example, A23187 and quinidine exert opposite effects in Gardos and ferricyanide experiments, where A23187 and atebrin react oppositely in the latter and in PCMBS experiments. The ferricyanide effect described here does not involve formation of nonspecific channels. The change in Na+ permeability separately from K+ permeability under certain circumstances suggests a more specific effect.     

Expression of interleukin 2 and the interleukin 2 receptor in aging rats

Lymphocytes of aged animals exhibit a marked decrease in proliferative capacity in response to mitogen stimulation when compared to those of younger animals. In humans and mice the decreased proliferation is due at least in part (i) to the inability of lymphocytes to synthesize sufficient interleukin 2 (IL-2) and (ii) to decreased expression of IL-2 receptors (IL-2R) on the surface of aged lymphocytes. We compared proliferative abilities, IL-2 production, and IL-2R expression in splenocyte cultures of 4- to 5- and 22- to 24-month-old Fischer 344 rats stimulated with either concanavalin A (Con A) or A23187 and phorbol myristate acetate (PMA). Proliferation was significantly decreased in aged lymphocytes (30-50%) with both treatment protocols. However, unlike mice and humans we observed no difference in IL-2 activity, IL-2 mRNA levels, or IL-2R cell surface expression of lymphocytes from young and aged rats stimulated with either Con A or A23187 and PMA. These results indicate that factors other than decreased expression of IL-2 and IL-2R are responsible for the diminished proliferative capacity of aged rat lymphocytes following mitogen stimulation.     

Comparison of the NH2-terminal amino acid sequences of the four non-identical subunits of the NAD-linked hydrogenases from Nocardia opaca 1b and Alcaligenes eutrophus H16

The cytoplasmic, NAD-linked hydrogenase of the Gram-positive hydrogen-oxidizing bacterium Nocardia opaca 1b was compared with the analogous enzyme isolated from the Gram-negative bacterium Alcaligenes eutrophus H16. The hydrogenase of N. opaca 1b was purified by a new procedure applying chromatography on phenyl-Sepharose and DEAE-Sephacel with two columns in series. A homogeneous enzyme preparation with a specific activity of 74 mumol H2 oxidized.min-1.mg protein-1 and a yield of 32% was isolated. The A. eutrophus enzyme was purified as previously published. Both enzymes are tetrameric proteins composed of four non-identical subunits (alpha, beta, gamma, delta). The four subunits of both of these enzymes were separated and isolated as single polypeptides by preparative polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate. Immunological comparison of the four subunits of the Nocardia hydrogenase with those of the Alcaligenes enzyme showed that the alpha, beta, gamma, and delta subunits of one organism were serologically related to the analogous subunits of the other organism. Among themselves, the four subunits do not have any serological relationship. The eight individual polypeptides were also compared with respect to the NH2-terminal amino acid sequences determined by automated Edman degradation and to the amino acid compositions. Strong sequence similarities exist between the analogous subunits isolated from the two bacteria. Within the established N-terminal sequences the similarities between both alpha, beta, gamma and delta subunits amount to 63%, 79%, 80% and 65%, respectively. No similarities exist between the different, non-analogous subunits alpha, beta, gamma and delta.     

The superficial cerebral veins

Estimated were the number, the course, and the width of the superficial cerebral veins. The veins on the superolateral surface of the brain are the prefrontal superficial lateral superior, the precentral superficial lateral superior, the central superficial lateral superior, the parietal superficial lateral superior, and the occipital superficial lateral superior veins which drain to the superior sagittal sinus, to bridging veins, and to the falx cerebri. The veins which drain the lateral surface of the brain downwards are the middle superficial cerebral veins, the temporal inferior, occipital inferior, and anastomotic veins. The diameters of these veins were measured at the perforation of the arachnoid membrane and the diameters of the anastomotic veins on their narrowest area. On the medial side of the hemispheres, we divided in precentral superficial superior medial, central superficial medial, parietal superficial medial, occipital superficial medial dorsal veins of the corpus callosum, and internal occipital veins. On the basal surface of the hemispheres, we studied and described the uncal veins and the inferior hemispheric veins. Studied and discussed are also the bridging veins in the course of the inferior cerebral veins, the paracavernous sinuses, and the last course of the veins and their connections with the dura mater or the course inside the dura. Given are besides the numbers of these veins, the area of perforation of the arachnoid membrane, and their width and medical importance.     

Methylene blue plus light mediates 8-hydroxyguanine formation in DNA

Exposure to methylene blue (MB) plus light mediates formation of large levels of 8-hydroxyguanine in DNA. The amount of 8-hydroxy-2'-deoxyguanosine (8-OHdG) present in DNA increased as the amount of MB concentration increased throughout the 2 to 200 microM range studied and was dependent on light exposure. As the time of light exposure increased so did the 8-OHdG content to levels of about 750 8-OHdG/10(5) deoxyguanosine after 15 min of light exposure when MB was at 20 microM. Even though previous research has demonstrated that hydroxyl free radicals formed from a variety of sources mediate 8-OHdG formation in DNA, inclusion of mannitol, superoxide dismutase, catalase, and desferal in the MB plus light experiments demonstrated that these scavengers of oxygen free radical intermediates or precursors caused either no change or an increase in the 8-OHdG content of DNA exposed to MB plus light. These results appear to rule out the direct role of oxygen free radical intermediates in the primary events involved in the MB plus light mediated formation of 8-OHdG in DNA. Oxygen was essential to cause MB plus light mediated 8-OHdG formation in DNA. It was noted that when the reaction was carried out where the deuterium oxide content had been increased to 100%, the amount of 8-OHdG formed in DNA increased about threefold over that observed when comparable reactions were carried out in pure H2O. Use of the singlet oxygen scavenger 2,5-dimethylfuran has yielded variable results on the MB plus light mediated formation of 8-OHdG in DNA. The data taken collectively clearly indicate that MB plus light mediates 8-OHdG formation in DNA. The D2O data and the requirement for oxygen suggest that singlet oxygen may be an intermediate.     

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.     

Physiological and biomechanical differences between wheelchair-dependent and able-bodied subjects during wheelchair ergometry

The purpose of this study was to compare the physiological and biomechanical responses of wheelchair-dependent persons (WCD) to able-bodied persons (AB) during manual wheelchair ergometry. Five WCD and five AB performed a discontinuous wheelchair ergometer test starting at 12.8 W at 30 rev.min-1 (57 m.min-1) with increments of 7.0 W at 6-min intervals. Biomechanical data were collected 3.5 min into each stage followed by the collection of physiological data. After the fifth stage, peak oxygen consumption was determined by having the subject work against a resistance of 14.7-19.6 N at 30 rev.min-1. The WCD had significantly higher net mechanical efficiency at 26.7, 33.6 and 40.6 W in comparison to the AB. The WCD had significantly greater shoulder extension at the point of initial wheel contact as measured by the shoulder angle, while the AB had significantly greater shoulder range of motion at all work rates in comparison to the WCD. The results demonstrate that a significant physiological difference exists in the manner by which WCD and AB accomplish wheelchair ergometry. The biomechanical differences between AB and WCD were found to be a prominent factor contributing to the higher mechanical efficiency of WCD over AB. It was concluded that basic physiological and biomechanical differences exist between WCD and AB in manual wheelchair locomotion and that these differences are important considerations to the interpretation of data in wheelchair ergometry studies.     

The endogenous lectins of the chick blastoderm are present in association with an apolipoprotein in distinct organelles and in the extracellular matrix

Summary Affinity purified preparations of the galactose-binding lectin from gastrulating chick blastoderms consist of three main polypeptides. Two of these have been identified as the 14 kD and 16 kD galactose-binding lectins. A third one migrates in SDS-PAGE gels with a relative molecular weight of 6,500±500 and has been identified as an apolipoprotein (Apo) of plasma very low density lipoproteins, Apo-VLDL-II. We have studied the localization of these polypeptides using immunofluorescence and ultrastructural immunocytochemistry with peroxidase and protein-A gold. The 14 kD lectin occurs in the intracellular yolk where it is mainly present within the electron lucent component. The 16 kD is also present in the intracellular yolk platelets, but tends to predominate in the electron-dense component. In addition, the 16 kD lectin is also present in pleiomorphic yolk-associated organelles and in the extracellular matrix. Apo-VLDL-II is also localized in the electron-lucent component of the yolk platelet and in the extracellular matrix. Our results suggest that the lectin(s) are associated with Apo-VLDL-II in the yolk platelet, and may subsequently become externalized.