Acid-soluble nucleotides of pinto bean leaves at different stages of development

Acid-soluble nucleotides of unifoliate leaves of Pinto bean plants (Phaseolus vulgaris L.) were determined at young, mature, and senescent stages of development. At least 25 components could be distinguished on the basis of inorganic phosphorus determinations and 37 or more fractions on the basis of ³²P labeling, with adenosine di- and triphosphates accounting for 60% of the total moles of nucleotide. The total nucleotide P and inorganic P, on a fresh weight basis, decreased about 44% between each stage of leaf development, but decrements in the levels of individual nucleotides varied from this over-all pattern.     

On the ultrastructural localization of catecholamines in the beta lobes (corpora pedunculata) of Periplaneta americana

Summary In the brain of the cockroach Periplaneta americana, the beta lobes of the corpora pedunculata respond with an intense positive reaction to a specific fluorescence histochemical method for catecholamines. The fluorescence reaction disappears completely after prolonged treatment of the cockroaches with reserpine. An ultrastructural examination of the beta lobes in formaldehyde-glutaraldehyde-osmium fixed preparations reveals the presence of two types of fibres: 1) Fibres and nerve endings containing small clear vesicles and sligthly larger vesicles with a semi-dense content. The appearance and size distribution of these vesicles ist not affected by treatment with reserpine. 2) Fibres containing larger and denser vesicles, but practically no clear vesicles. The size distribution of these dense vesicles is only slightly affected by treatment of the cockroaches with reserpine.If brain slices are incubated in a medium containing noradrenaline or -methyl-noradrenaline and fixed in permanganate, small vesicles with electron-dense central cores show up, similar to those which have been described in vertebrate adrenergic nerve fibres (small granular vesicles). They are confined to one of the two types of fibres (a and b) visible in these preparations, namely to type b, whose correspondence with type 2 fibres of formaldehyde-glutaraldehyde-osmium fixed preparations is discussed.The authors wish to thank Mr. E. Chessa and Mr. F. Piccirilli for technical assistance in photography.     

Endotheliochorial Placentation in a Pangolin,Manis tetradactyla

The placenta of a pangolin, Manis tetradactyla, was examined grossly and histologically. The placenta was arranged in longitudinal bands of 2–3 mm width. Microscopically there was a deep labyrinth and an underlying layer of distended endometrial glands. A narrow junctional zone was present containing syncytiotrophoblast. Thoughout the labyrinth cytotrophoblast and syncytiotrophoblast were observed in contact with maternal capillaries. The placentation was considered to be endotheliochorial in type.     

Glucose transport in lysosomal membrane vesicles. Kinetic demonstration of a carrier for neutral hexoses

Lysosomal membrane vesicles isolated from rat liver were exploited to analyze the mechanism of glucose transport across the lysosomal membrane. Uptake kinetics of [14C]D-glucose showed a concentration-dependent saturable process, typical of carrier-mediated facilitated transport, with a Kt of about 75 mM. Uptake was unaffected by Na+ and K+ ions, membrane potentials, and proton gradients but showed an acidic pH optimum. Lowering the pH from 7.4 to 5.5 had no effect on the affinity of the carrier for the substrate but increased the maximum rate of transport about 3-fold. As inferred from the linearity of Scatchard plots, a single transport mechanism could account for the uptake of glucose under all conditions tested. As indicated by the transstimulation properties of the carrier, other neutral monohexoses, including D-galactose, D-mannose, D- and L-fucose were transported by this carrier. The transport rates and affinities of these sugars, measured by the use of their radiolabeled counterparts, were in the same range as those for D-glucose. Pentoses, sialic acid, and other acidic monosaccharides including their lactones, aminosugars, N-acetyl-hexosamines, and most L-stereoisomers, particularly those not present in mammalian tissues, were not transported by this carrier. Glucose uptake and transstimulation were inhibited by cytochalasin B and phloretin. The biochemical properties of this transporter differentiate it from other well-characterized lysosomal sugar carriers, including those for sialic acid and N-acetylhexosamines. The acidic pH optimum of this glucose transporter is a unique feature not shared with any other known glucose carrier and is consistent with its lysosomal origin.     

Reversibility of the reactions catalyzed by cholinephosphotransferase and ethanolaminephosphotransferase solubilized from rat-brain microsomes.

The incorporation of CMP into CDP-ethanolamine and CDP-choline, catalyzed by ethanolaminephosphotransferase (EC 2.7.8.1) and cholinephosphotransferase (EC 2.7.8.2), respectively, has been studied in solubilized preparations of rat-brain microsomes. Mn2+ ions were required for the maximal activity of both enzymes. The CMP concentration needed to reach the half-maximal reaction rate was 1.6 microM for both activities. The rate of incorporation of CMP into CDP-choline and CDP-ethanolamine was increased by increasing the concentration of phosphatidylcholine and phosphatidylethanolamine, respectively, in detergent-phospholipid micellar systems. The rate of the reaction at pH 6.5 was comparable with that measured at pH 8.5, whereas the rate of synthesis of phosphatidylcholine and phosphatidylethanolamine, catalyzed by the same enzymes, increased with pH. Ethanolaminephosphotransferase, which catalyzes the synthesis of phosphatidylethanolamine from CDP-ethanolamine and diacylglycerol, was co-eluted with the enzyme activity catalyzing the reverse reaction, when solubilized microsomes were submitted to anion exchange chromatography on DEAE Bio-Gel A. Cholinephosphotransferase was inactivated during the chromatographic procedure.     

Phytoplankton biomass and production in shelf waters off NW Spain: spatial and seasonal variability in relation to upwelling

Summary Chlorophyll-a and primary production on the euphotic zone of the N-NW Spanish shelf were studied at 125 stations between 1984 and 1992. Three geographic areas (Cantabrian Sea, Rías Altas and Was Baixas), three bathymetric ranges (20 to 60 m, 60 to 150 m and stations deeper than 200 m), and four oceanographic stages (spring and autumn blooms, summer upwelling, summer stratification and winter mixing) were considered. One of the major sources of variability of chlorophyll and production data was season. Bloom and summer upwelling stages have equivalent mean and maximum values. Average chlorophyll-a concentrations approximately doubled in every step of the increasing productivity sequence: winter mixing — summer stratification — high productivity (upwelling and bloom) stages. Average primary production rates increased only 60% in the described sequence. Mean (± sd) values of chlorophyll-a and primary production rates during the high productivity stages were 59.7 ± 39.5 mg Chl-a m^–2 and 86.9 ± 44.0 mg C m^–2 h^–1, respectively. Significant differences in both chlorophyll and primary production resulted between geographic areas in most stages. Only 27 stations showed the effects of the summer upwelling that affected coastal areas in the Cantabrian Sea and Rías Baixas shelf, but also shelf-break stations in the Rías Altas area. The Rías Baixas area had lower chlorophyll than both the Rías Altas and the Cantabrian Sea areas during spring and autumn blooms, but higher during summer upwelling events. On the contrary, primary production rates were higher in the Rías Baixas area during blooms in spring and autumn. Mid-shelf areas showed the highest chlorophyll concentrations during high productivity stages, probably due to the existence of frontal zones in all geographic areas considered. The estimated phytoplankton growth rates were comparable to those of other coastal upwelling systems, with average values lower than the maximum potential growth rates. Doubling rates for upwelling and stratification stages in the northern and Rías Altas shelf areas were equivalent, despite larger biomass accumulations during upwelling events. Low turnover rates of the existing biomass in the Rías Baixas shelf in upwelling stages suggests that the accumulation of phytoplankton was due mainly to the export from the highly productive rías, while the contribution of in situ production to these accumulations was relatively lower.     

Candida albicans stress mannoproteins expression in superficial and systemic candidiasis

The presence of heat shock mannoproteins (HSMPs) reactive with sIgA was demonstrated in several C. albicans strains. The subculture of the C. albicans isolated from mucosal surfaces on Sabouraud's dextrose agar at 25 °C switched off the HSMP expression. A re-expression of the HSMPs was obtained in the same medium by shifting the temperature of incubation to 37 °C. However, expression of HSMPs in two strains isolated from deep infections was maintained during several subcultures on Sabouraud's dextrose agar at 25 °C. A glycoprotein of 200 kDa seemed to be the main HSMP reacting with vaginal sIgA. The data presented in this study suggest that factors other than temperature can influence the expression of C. albicans HSMPs and therefore these antigens should be referred as stress mannoproteins.Abbreviations HSMPs heat shock mannoproteins - MAb monoclonal antibody - sIgA secretory IgA     

Vaccine-induced neutralizing antibodies directed in part to the simian immunodeficiency virus (SIV) V2 domain were unable to protect rhesus monkeys from SIV experimental challenge.

The potential of the simian immunodeficiency virus (SIV) variable 2 (V2) domain as an effective region to boost SIV-neutralizing antibodies and to protect against live SIV challenge was tested in rhesus macaques. In this study, two rhesus macaques were primed with vaccinia virus recombinants expressing the surface glycoprotein gp140 of SIVmac and were given booster injections with the SIVmac V2 domain presented by a highly immunogenic carrier, the hepatitis B surface antigen (HBsAg). The two vaccinated macaques exhibited SIV-neutralizing antibodies after primer injections that were enhanced by the V2/HBsAg injections. Part of these SIV-neutralizing antibodies were directed specifically to the V2 region, as shown by neutralization-blocking experiments. However, despite having consistent SIV-neutralizing antibody titers, animals were not protected against homologous challenge with BK28, the molecular clone of SIVmac251. No SIV envelope-specific cellular cytotoxic response was detected throughout the immunization protocol, suggesting that neutralizing antibodies directed to SIV envelope gp140 and especially to the V2 domain were unable on their own to protect against SIV challenge. Furthermore, the vaccinees seemed to have higher viral loads than control animals after challenge, raising the question of whether neutralizing antibodies induced by vaccination and directed to the SIV envelope selected viral escape mutants, as shown previously in SIV-infected macaques. This mechanism is certainly worthy of intensive investigation and raises some concern for SIV envelope-targeted immunization.