The metabolism of deoxyguanosine in mitochondria. Characterization of the uptake process

Summary The uptake of deoxyguanosine by rat liver mitochondria was characterized. The process required an intact mitochondrial membrane and exhibited a dependence on added phosphate. Deoxyguanosine uptake was minimally influenced by Mg²⁺ or Mn²⁺, but Ca²⁺ at concentrations above 0.5 mM were detrimental. Of the deoxynucleosides tested, only deoxyinosine inhibited the uptake of deoxyguanosine. The ribonucleoside guanosine was not observed to compete with its deoxynucleoside analog. Known inhibitors of nucleoside transport, cytochalasin B and NBMPR, did not block deoxyguanosine uptake, but the sulfhydryl reagents NEM and pCMB were both inhibitory. The uptake of deoxyguanosine was shown to be a saturable process and an apparent Km of 0.64 M was calculated from a Hanes plot.     

Control of a teleost social signal

Territorial male Haplochromis burtoni (Teleostei; Cichlidae) have a dark facial stripe, the 'eyebar', which can appear and disappear within seconds, independently of other coloration patterns. It is used to signal territory ownership and aggressive intent. Some males, called 'barless', have functional melanophores in the eyebar region but never display this pattern, because melanin in eyebar pigment cells is never dispersed. The eyebar melanophores are controlled by a specialized branch of the maxillary nerve. Lesioning the 'eyebar nerve' resulted in immediate melanin dispersion and consequent darkening of the eyebar pattern, and it abolished the normal paling response in all behavioral situations. Nerve lesion produced similar results in both barred and barless males, except that the coloration of the denervated eyebar in barless males was more similar to camouflage markings than to the conspicuous black eyebar used as a social signal. Electrical stimulation of the maxillary nerve produced melanin aggregation. Photoelectric recordings of this paling response revealed no differences between barred and barless males, or between the eyebar and other facial chromatophores that do not function as visual displays. Thus, the difference in the physiological state of eyebar melanophores in intact barred and barless males cannot be explained by differences in peripheral nerve anatomy or physiology.     

Ability ofVibrio vulnificus to obtain iron from transferrin and other iron-binding proteins

The ability of virulent and avirulent strains ofVibrio vulnificus to overcome iron limitations by using iron bound to iron-binding proteins was examined. While no strains were able to obtain iron from lactoferrin or ferritin when these proteins were not fully saturated with iron, growth was enhanced by the iron-saturated form of these proteins. None of the strains was able to scavange iron from 30% saturated transferrin, but there were strain differences in the ability to obtain iron from the saturated form. The virulent strains were able to compete more efficiently with transferrin when it was fully saturated with iron than were the avirulent strains.     

Antibody to myelin constituents: A possible factor in induction of cell-mediated demyelination

Results from this laboratory have demonstrated that¹⁴C-labeled myelin opsonized with antibodies raised to purified CNS myelin in rabbit is phagocytized by cultured macrophages in larger amounts than untreated myelin or myelin opsonized with preimmune serum. The cultured macrophages produced high amounts of radioactive cholesterol ester and triglyceride from the antibody-treated myelin while much less was formed from preimmune serum-treated or untreated myelin. Antiserum to galactocerebroside also greatly enhanced the formation of radioactive cholesterol ester, while that to myelin basic protein as well as to other myelin constituents had little or no effect. Serum from Lewis rats with acute EAE 13–14 days after immunization with whole CNS myelin also stimulated radioactive cholesterol ester formation compared to serum from Freund's adjuvant-injected controls (FAC). Serum from EAE rats as a result of myelin basic protein injection was as active as that from rats with whole myelin injection. No galactocerebroside antibody could be demonstrated in the EAE sera, although a strong immunostaining to myelin basic protein and proteolipid protein was demonstrated. IgG prepared from EAE serum also showed stimulatory effects compared to IgG from FAC serum, but much of the activity was lost, and the possibility that other factors may be involved is discussed. These experiments provide evidence that myelin phagocytosis and digestion by macrophages is enhanced by the presence of antibody to myelin. In EAE this antibody may leak into CNS with the breakdown of the blood-brain barrier. A humoral involvement in demyelination in EAE is implicated, and these findings may be extended eventually to the demyelinative mechanism in multiple sclerosis where IgG is found in large amounts in the CNS.Special Issue Dedicated to Dr. Abel Lajtha.     

Mucosal epithelial cells and Langerhans cells are targets for infection by the immunosuppressive type D retrovirus simian AIDS retrovirus serotype 1

Simian acquired immune deficiency syndrome (SAIDS) caused by the type D retrovirus SRV-1 results in opportunistic infections and a spectrum of oral lesions similar to those seen in humans with AIDS. To better understand the pathogenesis of these oral lesions we have retrospectively examined the oral mucosa from ten rhesus monkeys that died with SAIDS and prospectively examined the oral mucosa of ten additional animals inoculated with SRV-1 to determine at what time, and in what cells SRV-1 infection of the oral mucosa occurs. Using single and double label immunohistologic techniques, and electron microscopy we detected SRV-1 in clusters of oral epithelial cells and rare Langerhans cells as early as 1 month postinoculation.     

Microbial introductions to apple leaves: Influences of altered immigration on fungal community dynamics

Fungal immigration to apple leaves in the field was altered by the introduction of populations ofChaetomium globosum orAureobasidium pullulans to surface-disinfested leaves either immediately following, or 6 days after, disinfestation. Total numbers of fungal individuals and numbers of filamentous fungal and yeast individuals were estimated and compared over time for 4–7 weeks on control leaves (leaves disinfested but no populations applied), onAureobasidium-treated, and onChaetomium-treated leaves. Fungal communities developing on leaves during three experiments in two different time frames (experiment 1: July 9–August 27; experiments 2 and 3: July 29–August 27), and thus under different immigration regimes, were also compared. Survival of introduced populations was not related to the presence of prior fungal immigrants. Rates of increase in total numbers of fungi and numbers of filamentous fungi and yeasts per leaf varied among experiments, apparently in relation to differences in immigration and environmental history. Differences among leaves in immigration had a short-term (days) influence on community size. However, no long-term effects of altered immigration on phylloplane fungal community size were evident.     

Subcellular distribution,molecular dynamics and catabolism of plasmalogens in myocardium

Recent studies have implicated accelerated sarcolemmal phospholipid catabolism as a mediator of the lethal sequelae of atherosclerotic heart disease. We have demonstrated that plasmalogens are the predominant phospholipid constituents of canine myocardium and that plasmalogens are hydrolyzed by a novel calcium independent plasmalogen selective phospholipase A2. Since the activities of phospholipases are modulated by the molecular dynamics and interfacial characteristics of their phospholipid substrates, we compared the molecular dynamics of plasmenylcholine and phosphatidylcholine vesicles by electron spin resonance spectroscopy and deuterium magnetic resonance spectroscopy. Plasmenylcholine vesicles have separate and distinct molecular dynamics in comparisons to their phosphatidylcholine counterparts as ascertained by substantial decreases in the angular fluctuations and motional velocities of probes attached to their sn-2 aliphatic constituents. Furthermore, since free radical oxidation of myocardial lipid constituents occurs during myocardial ischemia and reperfusion, we demonstrated that ¹O₂ mediated oxidation of plasmenylcholine resulted in the generation of several products which have chromatographic characteristics and molecular masses corresponding to 2-acyl lysophosphatide derivatives. Taken together, these studies underscore the biologic significance of the predominance of sarcolemmal plasmalogens present in mammalian myocardium and suggest that their catabolism by plasmalogen selective phospholipases and/or oxidative processes may contribute to the lethal sequelae of myocardial ischemia.     

Heparin induces changes in the synthesis of porcine aortic endothelial cell heparan sulfate proteoglycans

Heparin is known to bind to cultured endothelial cells. This report documents that addition of heparin to endothelial cells results in an alteration of the heparan sulfate proteoglycan synthetic pattern. Specifically, the addition of saturating amounts of heparin to confluent cultures of porcine aortic endothelial cells results in an increase in the amount of radiolabeled heparan sulfate proteoglycan secreted into the growth medium. The increase is apparent as early as 8 h after heparin administration. Although there is often a decrease in the amount of cell surface heparan sulfate proteoglycan produced, it is not sufficient to account for the increase in the secreted form. Of the other glycosaminoglycans tested, only dextran sulfate and commercial heparan sulfate induce changes in heparan sulfate proteoglycan synthesis and secretion. Chondroitin sulfate glycosaminoglycans do not elicit this synthetic change. These data indicate that endothelial cells can alter the synthesis of heparan sulfate proteoglycans in response to extracellular signals including heparin and related glycosaminoglycans.     

Characterization of Xylose Uptake in the Yeasts Pichia heedii and Pichia stipitis

The kinetics of xylose uptake were investigated in the efficient xylose fermenter Pichia stipitis and in the more readily genetically manipulated, strictly respiratory yeast Pichia heedii. Both yeasts demonstrated more than one xylose uptake system, differing in substrate affinity. The K_m of high-affinity xylose uptake in both organisms was similar to that of the efficient high-affinity glucose uptake system of Saccharomyces cerevisiae. In P. heedii, low-affinity xylose uptake was enhanced with growth on 2% but not 0.05% xylose and high-affinity uptake was reduced. In contrast to glucose uptake, xylose uptake in P. heedii was inhibited by dinitrophenol. Dinitrophenol inhibited both glucose and xylose uptake by P. stipitis. Glucose uptake was not inhibited by a 100-fold molar excess of xylose in P. heedii. It is suggested that xylose uptake in P. heedii is via a carrier system(s) distinct from those for glucose uptake.     

Epizoic and parasitic rotifers

Many rotifer species live in close association with plants or other animals. Most of these associations are of a commensal or synoecious nature, some rotifer species having lost the ability to live independently. Few rotifers are true parasites, actually harming their hosts.The Seisonidae, Monogononta and Bdelloidea include epizoic and parasitic species. The most widely known are probably the parasites of colonial and filamentous algae (e.g. Volvox, Vaucheria). However, rotifers are also found on a wide range of invertebrates: colonial, sessile Protozoa; Porifera; Rotifera; Annelida; Bryozoa; Echinodermata; Mollusca, especially on the shells and egg masses of aquatic gastropods; Crustacea, including the lower forms (e.g. Daphnia, Asellus, Gammarus) and in the gill chambers of Astacus and Chasmagnathus; the aquatic larvae of insects. There appear to be few records of epizoic or parasitic rotifers among vertebrates, apart from Encentrum kozminskii on carp, Limnias ceratophylli on the Amazonian crocodile, Melanosuchus niger, and an unidentified Bdelloid apparently living as a pathogenic rotifer in Man.