The phylogenic position of Peptococcus niger based on 16S rRNA sequence studies

A 1330 base-pair fragment of a 16S rRNA gene has been amplified, cloned and sequenced. Comparison to other 16S rRNA sequences of eubacteria showed that P. niger represents a deep branch within the subdivision "Gram-positive with Gram-negative cell walls". It is not related to peptostreptococci, representatives of this genus studied so far are more closely related to clostridia.     

5,6,7,8-Tetrahydromethanopterin-dependent enzymes involved in methanogenesis

Abstract In the process of methanogenesis, 5,6,7,8-tetrahydromethanopterin (H₄MPT) is the carrier of the C₁ unit at the formyl through methyl state of reduction. By the transfer of a formyl group from formylmethanofuran, 5-formyl- and 10-formyl-H₄MPT are formed in hydrogenotrophic and methylotrophic organisms, respectively. Cyclohydrolysis of the 5- and 10-formyl derivatives then yields 5,10-methenyl-H₄MPT, which is reduced in two subsequent coenzyme F₄₂₀-dependent reactions to 5-methyl-H₄MPT. Following the transfer of the methyl group to coenzyme M, the substrate of the terminal step in methanogenesis, methylcoenzyme M, is produced. In this paper properties of the enzymes catalyzing the individual H₄MPT-dependent reactions are discussed.     

Effects of training at simulated altitude on performance and muscle metabolic capacity in competitive road cyclists

Differences between the effects of training at sea level and at simulated altitude on performance and muscle structural and biochemical properties were investigated in 8 competitive cyclists who trained for 3-4 weeks, 4-5 sessions/week, each session consisting of cycling for 60-90 min continuously and 45-60 min intermittently. Four subjects, the altitude group (AG), trained in a hypobaric chamber (574 torr = 2300 m above sea level), and the other four at sea level (SLG). Before and after training work capacity was tested both at simulated altitude (574 torr) and at sea level, by an incremental cycle ergometer test until exhaustion. Work capacity was expressed as total amount of work performed. Venous blood samples were taken during the tests. Leg muscle biopsies were taken at rest before and after the training period. AG exhibited an increase of 33% in both sea level and altitude performance, while SLG increased 22% at sea level and 14% at altitude. Blood lactate concentration at a given submaximal load at altitude was significantly more reduced by training in AG than SLG. Muscle phosphofructokinase (PFK) activity decreased with training in AG but increased in SLG. All AG subjects showed increases in capillary density. In conclusion, work capacity at altitude was increased more by training at altitude than at sea level. Work capacity at sea level was at least as much improved by altitude as by sea level training. The improved work capacity by training at altitude was paralleled by decreased exercise blood lactate concentration, increased capillarization and decreased glycolytic capacity in leg muscle.     

Morphological studies on endocytosis of chondroitin sulphate proteoglycan by rat liver endothelial cells

Summary Endocytosis via the hyaluronic acid/chondroitin sulphate receptor of rat liver endothelial cells was studied ultrastructurally, by use of a probe consisting of chondroitin sulphate proteoglycan attached to 15-nm gold particles. The probe bound to the surface of the cells exclusively in coated regions of the plasma membrane. Internalization at 37° C took place in less than one minute during which time interval the bound probe was transferred to coated vesicles. Further transfer to lysosomes was delayed in association with an accumulation of probes in a prelysosomal compartment consisting of large vacuoles in which probes lined the inner aspect of the membrane. Transport to lysosomes occurred only after a lag phase of at least 40–60 min at 37° C.Abbreviations CS chondroitin sulphate - CSPG chondroitin sulphate proteoglycan - CSPG-Au CSPG-gold complex - EM electronmicroscopical or electron microscopy - HA hyaluronic acid - KC Kuppfer cells - LEC liver endothelial cells - PC parenchymal cells - RES reticuloendothelial system     

Recovery of functional DNA inserts by electroendosmotic elution during gel electrophoresis

In contrast to all previous preparative electrophoresis apparatus which used a pump, electroendosmotic elution uses bound electrical charges at the end of the separating gel to generate a buffer flow. The electroendosmotic flow increased with increasing currents and decreasing buffer concentrations: its exact characteristics for the built apparatus were determined. The electroendosmotic device was able to separate two DNA fragments differing in size by only 5% with a recovery over 95%. As demonstrated in practical examples of recovery and uses of DNA inserts, up to 10 micrograms of DNA per band can be loaded at a time. The recovered DNA can be used directly for nick-translation, ligation... without further treatment. The performances of the method are expected to improve still further if the charge density and pores of the electroendosmotic medium can be "made-to-order" to provide a better flow profile of the eluting buffer.     

The T cell receptor V alpha 3 gene segment is associated with reactivity to p-azobenzenearsonate

The murine T cell receptor V alpha 3 gene segment is associated with reactivity to p-azobenzenearsonate, as indicated by several independent lines of evidence. First, three out of four arsonate-reactive T cell clones tested (two I-Ad-and one I-Ak-restricted) utilized V alpha 3. Second, bulk splenic cultures enriched for arsonate/H-2d and arsonate/H-2k responsive T cells showed increased expression of V alpha 3 mRNA. Third, a V alpha 3-containing alpha chain (Ar-5: arsonate/I-Ad) transferred arsonate responsiveness to an appropriate recipient T cell (O3: ovalbumin/I-Ad). Fourth, an independently derived V alpha 3-expressing T cell clone (2C: alloreactive to Ld) showed a response to arsonate/Ld. Thus, a V alpha 3 gene segment, in conjunction with at least two different J alpha segments (J alpha 20'(Ar-5) and J alpha pHDS58(2C)) and at least three different beta chains (V beta 2(Ar-5), V beta 6(O3), and V beta 8(2C], confers reactivity to arsonate in association with at least three different MHC proteins (I-Ad, I-Ak, and Ld). We suggest that V alpha 3 encodes a protein sequence with a binding site for the arsonate hapten.     

Selective solubilization of xylan in pulp using a purified xylanase fromTrichoderma harzianum

Summary The specificity of action of a cellulase-free xylanase preparation on pulp fibers was revealed by the composition of the solubilized products after enzyme treatment. The neutral carbohydrates released by the treatment of two hardwood kraft pulps were composed exclusively of xylooligomers. A similar treatment of Solka Floc showed no detrimental effect on the degree of polymerization of the cellulose fibers, as determined by size exclusion chromatographic analysis.     

The photosynthetic apparatus of C3 and CAM-induced Mesembryanthemum crystallinum L.

Accompanying the CAM induction of Mesembryanthemum crystallinum L. grown in high salinity there are changes in the enzymes of carbon metabolism. However, there are no changes in the electron transport activities, Chla/b ratios or in the distribution of chlorophyll amongst the various pigment-protein complexes of isolated thylakoids. Hence with CAM induction there are no changes in the photochemical apparatus of M. crystallinum thylakoids. Despite comparable amounts of chlorophylla/b-proteins of photosystem II to those found in typical C₃ sun plants, both the C₃ and CAM M. crystallinum chloroplasts have relatively more photosystem II, and, concommitantly, less photosystem I complex. This is consistent with greater fluorescence emission at 685 and 695 nm, and lower emission at 735 nm (measured at 77 K) than typically found for C₃ plants, whether sun or shade species. Photoinhibition of isolated C₃ and CAM thylakoids by white light led to comparable decreases in electron transport capacities and fluorescence emission at 77 K with photosystem II being more affected than PSI. We suggest however, that the presence of more core PSII complexes relative to PSI complexes in this CAM-inducible plant, may provide an additional strategy to mitigate photoinhibition in the short-term.     

Pigment organization and energy transfer in the green photosynthetic bacterium Chloroflexus aurantiacus. III. Energy transfer in whole cells

The transfer of excitation energy in intact cells of the thermophilic green photosynthetic bacterium Chloroflexus aurantiacus was studied both at low temperature and under more physiological conditions. Analysis of excitation spectra measured at 4K indicates that the minor fraction of bacteriochlorophyll a present in the chlorosome functions as an intermediate in energy transfer between the main light-harvesting pigment BChl c and the membrane-bound B808-866 antenna complex. This supports the hypothesis that BChl a is associated with the base plate which connects the chlorosome with the membrane. The overall efficiency for energy transfer from the chlorosome to the membrane is only 15% at 4K. High efficiencies of close to 100% are observed above 40°C near the temperature where the cultures are grown. Cooling to 20°C resulted in a sudden drop of the transfer efficiency which appeared to originate in the chlorosome. This decrease may be related to a lipid phase transition. Further cooling mainly affected the efficiency of transfer between the chlorosome and the membrane. This effect can only partially be explained by a decreased Förster overlap between the chlorosomal BChl a and BChl a 808 associated with the membrane-bound antenna system. The temperature dependence of the fluorescence yield of BChl a 866 also appeared to be affected by lipid phase transitions, suggesting that this fluorescence can be used as a native probe of the physical state of the membrane.