The relation between pituitary gland and thyroid growth during the lifespan of the annual fish Cynolebias whitei and Nothobranchius korthausae: gonadotropic and thyrotropic cells

Summary In the annual cyprinodont Cynolebias whitei the cell types responsible for the increase of pituitary growth at the onset of maturation and for pituitary hyperplasia in old specimens were identified as gonadotropic cells and thyrotropic cells, respectively. The gonadotropic cells showed a high affinity to anti-carp -GTH serum, both at light- and electron-microscopical levels. The allometric relation of total gonadotropic cell volume to body length, determined for fish from six weeks up to six months of age, showed no inflections. Therefore pituitary growth in maturing fish may be partly a result of proliferation of gonadotropes, although gonadotropic cells do not contribute to pituitary hyperplasia in old fish. Thyrotropic cells showed a weak affinity to anti-carp -GTH serum at light-microscopical level. Under the electron microscope thyrotropic cells displayed signs of activation in maturing fish and signs of proliferation in old fish. The allometric relation of thyroid gland volume to body length paralleled that of pituitary volume to body length. Histologically the thyroid gland showed signs of inactivity in adult fish and of hyperplasia in old fish. The possibility, that gonadal maturation, pituitary thyrotropic activity, and growth of the thyroid in maturing fish are related through the inhibitory action of gonadal steroids on thyroid hormone release, is discussed. Pituitary hyperplasia in old fish is the result of proliferation of thyrotropic cells. Similar hyperplasia of pituiary and thyroid glands was observed in old Nothobranchius korthausae.     

Oxidative phosphorylation in membrane vesicles of a gram-positive methylotroph

Membrane preparations, capable of high rates of respiration-linked ATP synthesis, have been obtained from a gram-positive methylotrophic bacterium Bacillus sp. MGA3. NADH, succinate, reduced TMPD and methanol were shown to be suitable substrates for the oxidative phosphorylation. Esterification of orthophosphate was dependent on electron transfer, as evidenced by the requirement for both substrate and oxygen. Phosphorylation was also dependent on ADP and was destroyed by boiling the membrane preparation. The phosphorylation was markedly uncoupled by carbonyl cyanide p-(trichloromethoxy)-phenylhydrazone (CCCP) and was inhibited by N,N-dicyclohexylcarbodiimide (DCCD). KCN caused strong inhibition of substrate oxidation as well as phosphorylation for all substrates tested. Rotenone, amytal and antimycin A caused inhibition when NADH or methanol were used as substrates. Antimycin A inhibited respiration and ATP synthesis with succinate as substrate and had no effect on ascorbate —N,N,N,N-tetramethyl-p-phenylenediimide (TMPD) oxidation by membrane preparations of Bacillus sp. MGA3. P/O ratios determined were 2.4 with NADH, 1.7 with succinate and 0.8 with reduced TMPD. The measured P/O ratio with methanol-oxidizing system was similar to that with NADH (about 2.4).Abbreviations CCCP Carbonyl cyanide p-(trichloromethoxy)-phenylhydrazone - DCCD N,N-dicyclohexylcarbodiimide - TMPD N,N,N,N-tetramethyl-p-phenylenediimide - Q ubiquinone Q     

Ecophysiological aspects of growth and nitrogen fixation inAzospirillum spp.

The nitrogenase activity ofAzospirillum spp. is efficiently regulated by environmental factors. InA. brasilense andA. lipoferum a rapid switch off of nitrogenase activity occurs after the addition of ammonium chloride. As in photosynthetic bacteria, a covalent modification of nitrogenase reductase (Fe-protein) is involved. InA. amazonense, a non-covalent mechanism causes only a partial inhibition of nitrogenase activity after ammonium chloride is added. In anaerobic conditions, nitrogenase reductase is also switched off by a covalent modification inA. brasilense andA. lipoferum. Short-time exposure ofAzospirillum to increased oxygen levels causes a partially reversible inhibition of nitrogenase activity, but no covalent modification is involved.Azospirillum spp. show variations in their oxygen tolerance. High levels of carotenoids confer a slightly improved oxygen tolerance. Certain amino acids (e. g. glutamate, aspartate, histidine and serine) affect growth and nitrogen fixation differently inAzospirillum spp. Amino acids may influence growth and nitrogen fixation ofAzospirillum in the association with plants.Azospirillum brasilense andA. halopraeferens are the more osmotolerant species. They utilize most amino acids poorly and accumulate glycine betaine, which also occurs in osmotically stressed grasses as a compatible solute to counteract osmotic stress. Nitrogen fixation is stimulated by glycine betaine and choline. Efficient iron acquisition is a prerequisite for competitive and aerotoleran growth and for high nitrogenase activity.Azospirillum halopraeferens andA. amazonense assimilate iron reasonably well, whereas growth of someA. brasilense andA. lipoferum strains is severely inhibited by iron limitation and by competition with foreign microbial iron chelators. However, growth of certain iron-limitedA. brasilense strains is stimulated by the phytosiderophore mugineic acid. Thus, various plant-derived substances may stimulate growth and nitrogen fixation ofAzospirillum.     

Recovery of normal photosynthesis and respiration in common wheat with Agropyron cytoplasms by telocentric Agropyron chromosomes

Summary Alloplasmic common wheat (Triticum aestivum L. cultivais Penjamo 62 and Siete Cerros 66) with cytoplasms of wheatgrass (Agropyron trichophorum and Ag. glaucum) showed two aberrant phenotypes, i.e., gross reduction in plant vigor and male sterility. Plant vigor and male fertility were restored by cytoplasm-specific telocentric chromosomes (telosomes). Studies on carbon assimilation and consumption and on oxygen evolution and uptake showed that maximum rates of apparent photosynthesis were significantly lower in the alloplasmic lines than in their corresponding euplasmic lines and that the telosomes restored a normal level of photosynthesis. The decreased apparent photosynthetic rates in the alloplasmic lines were shown to be not due to decreased rates of true photosynthesis but to increased rates of dark respiration in the green leaves. In contrast, dark respiration in the roots was significantly low in the alloplasmic lines. The alloplasmic lines also showed decreased rates of respiratory consumption of new photosynthates. These results suggest that growth depression and male sterility in the alloplasmic lines are related to aberrant mitochondrial function, which is compensated for by cytoplasm-specific telosomes.     

Short communication: In vitro evaluation of a Bacillus sp. for the biological control of the coffee phytopathogen Mycena citricolor

A cell-free supernatant and an ethanolic extract of a 3-day-old culture of Bacillus UCR-236 inhibited the growth of Mycena citricolor, as determined by the Oxford cylinder method. A 3-day-old culture of the same bacterium also decreased leaf infection by the pathogen in a moisture-chamber test.     

Effect of α(2–6)-linked sialic acid and α(1–3)-linked fucose on the interaction ofN-linked glycopeptides and related oligosaccharides with immobilizedPhaseolus vulgaris leukoagglutinating lectin (L-PHA)

The effects of branching and substitution of branches by sialic acid and fucose on the interaction ofN-linked glycopeptides and related oligosaccharides with immobilizedPhaseolus vulgaris leukoagglutinating lectin (L-PHA) were examined. Asialo bi-, tri-and tetra-antennary glycans were all retarded but to different extents on a long column of L-PHA-agarose. Asialo tri- and tetra-antennary glycans containing the pentasaccharide unit Gal1-4GlcNAc1-2[Gal1-4GlcNAc1-6]Man were strongly retarded, whereas asialo bi- and tri-antennary glycans lacking the Gal1-4GlcNAc1-6 branch were only weakly retarded. In all instances the interaction with the lectin was completely abolished when either (2–6)-linkedN-acetylneuraminic acid or (1–3)-linked fucose was present at the galactose orN-acetylglucosamine residue of the Gal1-4GlcNAc1-6Man1-6 branch, respectively. The same substitutions on the Gal1-4GlcNAc1-6Man1-6 branch decreased but did not abolish the affinity of the lectin for the glycans. The presence of NeuAc2-6 and Fuc1-3 on the other two branches did not interfere with the binding of the glycans to L-PHA. Furthermore, it appeared that the presence of the Man1-4GlcNAc unit is requried for interaction with the lectin. In order to obtain reliable information on the relative occurrence of tri- and tetra-antennary glycopeptides, this study shows that it is essential to desialylate and to defucosylate the glycans prior to application to L-PHA-agarose.Abbreviations L-PHA leukoagglutinating phytohemagglutinin - CMP-NeuAc cytidine-5-monophospho-N-acetylneuraminic acid - GP glycopeptide - OS oligosaccharide - HPLC high-performance liquid chromatography - FNR fraction not retarded - FR fraction retarded suffixes MS, BS and TS indicate mono-, bi- and trisialyl derivatives respectively; suffix MF indicates monofucosyl derivatives.structures of the substratesOS2, OS3, OS3, OS4, GP2, GP3, GP4, GP4-MF, OS2(3) andOS2(-) are presented in Fig. 2     

Observations on the biology of Leuciscus ‘svallize’ in the Kremasta reservoir (Greece)

The age, growth, feeding habits and reproductive biology of Leuciscus svallize in artificial lake Kremasta (Greece), are described. There is a considerable similarity in the feeding and reproductive characteristics between L. svallize and L. cephalus and also a similarity in the life span, growth patterns and age of maturation between L. svallize and some southern L. cephalus populations, which may suggest similar responses of closely related taxa to similar conditions.     

Modification of competence for in vitro response to Fusarium oxysporum in tomato cells. II. Effect of the integration of Agrobacterium tumefaciens genes for auxin and cytokinin synthesis

We have studied the effect of a change in the endogenous hormone equilibria on the competence of tomato (Lycopersicon esculentum) cells to defend themselves against the fungal pathogen Fusarium oxysporum f. sp. lycopersici. Calluses from cvs Davis and Red River, respectively resistant and susceptible to Fusarium and transgenic for an auxin- or cytokinin-synthesizing gene from Agrobacterium tumefaciens, were used. The integration of Agrobacterium hormone-related genes into susceptible cv Red River can bring the activation of defense processes to a stable competence as assessed by the inhibition of mycelial growth in dual culture and gem-tube elongation of Fusarium conidia, the determination of callose contents, peroxidase induction and ion leakage in the presence of fusaric acid. This is particularly true when the transformation results in a change of phytohormone equilibria towards an higher cytokin in concentration. On the contrary, in resistant cv Davis the inhibition of both fungal growth in dual culture and conidia germination is higher when the hormone balance is modified in favour of the auxins. No significant effect was observed for ion leakage and peroxidase induction, probably because of a constitutive overproduction of cytokinins in Davis cells.     

Die Bedeutung der “feedback”-Hemmung der Threonin-Desaminase für die Synthese von Valin und Leucin

Zusammenfassung In Arthrobacter Stamm 23 führte die durch Mutation verursachte allosterische Unempfindlichkeit der Threonin-Desaminase zur dereprimierten Bildung der Enzyme im Isoleucin-Valin-Leucin-Biosyntheseweg. Derepression erfolgte auch, wenn Wildtypzellen in Gegenwart von -Ketobuttersäure inkubiert wurden. In beiden Fällen wurde Isoleucin überproduziert und ins Kulturmedium ausgeschieden. Wie aus Wachstumsexperimenten hervorging, verursachte der Überschuß an -Ketobuttersäure im Medium primär einen Valin- und Leucin-Mangel, der zu einer vorübergehenden Wachstumshemmung führte. Durch die dereprimierte Bildung der Enzyme im Isoleucin-Valin-Biosyntheseweg konnte die Wachstumshemmung überwunden werden.Der vorübergehende Hemmeffekt der -Ketobuttersäure ließ sich auf eine Konkurrenz der Substrate am ersten gemeinsamen Enzym im Isoleucin-Valin-Biosyntheseweg, der Acetohydroxysäure-Synthase, zurückführen. Wegen des niedrigen K _m-Wertes für -Ketobuttersäure wird dieses Substrat vom Enzym bevorzugt umgesetzt. Durch gaschromatographische Bestimmungen der Acetoin- und Acetyläthylcarbinol-Bildung in Enzymtests mit variierten Substrat-Konzentrationen konnte nachgewiesen werden, daß relativ geringe Konzentrationen an -Ketobuttersäure genügen, um die -Acetolacetat-Bildung vollständig zu unterdrücken. Diese Ergebnisse erklären die durch -Ketobuttersäure verursachte vorübergehende Wachstumshemmung bei Bakterien.

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The effect of the feedback inhibition of threonine deaminase on valine-leucine biosynthesis

In Arthrobacter strain 23 the allosteric insensitivity of threonin deaminase caused by mutation resulted in derepressed formation of the enzymes of the isoleucine-valine-leucine pathway. Derepression was also observed, when wild type cells were incubated in the presence of -oxobutyrate. In both cases isoleucine was overproduced and excreted. As growth experiments indicated the excess of -oxobutyrate in the medium caused endogenous valine and leucine deficiency and a transient inhibition of growth. Derepressed formation of the isoleucinevaline biosynthetic enzymes resulted in relief of growth inhibition.The transient inhibitory effect of -oxobutyrate has been traced back to substrate competition at the first enzyme common to the isoleucine and valine pathway, acetohydroxy acid synthase. Due to the low K _m of the enzyme for -oxobutyrate this substrate is preferentially converted. As proven by gaschromatographical measurements of acetoin and acetylethyl carbinol produced in enzyme (acetohydroxy acid synthase) assays with varied substrate concentrations, relatively low concentrations of -oxobutyrate are able to suppress the formation of -acetolactate completely. These results explain the transient inhibitory effect of -oxobutyrate on the growth of bacteria.

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Abkürzungen -KBS -Ketobuttersäure - FAD Flavin-adenin-dinucleotid - AHS Acetohydroxysäure - IPM Isopropylmalat - TPP Thiaminpyrophosphat     

Reconstitution of cytoplasmic streaming inCharaceae

Summary The active sites of actin of oneCharaceae species were found to interact with the endoplasmic factor from a different species. Protoplasm was suqueezed out of cells ofChara australis with vacuoles that had been perfused beforehand with a medium containing EGTA and Mg · ATP. Centrifugation of this protoplasmic mixture divided it into the supernatant composed of endoplasmic granules and the precipitate composed of chloroplasts and nuclei. When the endoplasmic granular aggregates were introduced into a tonoplast-freeNitella axilliformis cell treated with NEM to inactivate the endoplasmic factor, they became attached to theNitella gel and streamed longitudinally with the polarity. Treatment of the endoplasmic granules with the strong Mg²⁺chelator CyDTA (1,2-cyclohexane diamineN, N-tetraacetic acid) irreversibly inhibited reconstitution of the cytoplasmic streaming.Abbreviations APW artificial pond water - ATP adenosine-5-triphosphoric acid - CyDTA cyclohexanediamine-N,N-tetraacetic acid - DTT dithiothreitol - EGTA ethyleneglycol-bis-(-aminoethylether)-N,N-tetraacetic acid - HMM heavy meromyosin - NEM N-ethylmaleimide - PEP phosphoenolypyruvate - PIPES piperazine-N,N-bis-(2-ethane-sulfonic acid) - PK pyruvate kinase - PMSF phenylmethylsulfonylfluoride     

Inheritance of resistance to the bean-pod weevil (Apion godmani Wagner) in common beans from Mexico

The bean-pod weevil (BPW), Apion godmani Wagner, often causes heavy losses in crops of common bean (Phaseolus vulgaris L.). Farmers need resistant bean cultivars to minimize losses, cut production costs, stabilize seed yield, and reduce pesticide use and consequent health hazards. To design effective breeding methods, breeders need new and better sources of resistance and increased knowledge of their modes of inheritance. We therefore: (1) compared sources of resistance to BPW, (2) studied the inheritance of resistance, and (3) determined whether the sources possess similar or different genes for BPW resistance. The following sources of resistance, originating from the Mexican highlands, were evaluated for 3 years at INIFAP-Santa Lucía de Prias, Texcoco, Mexico: Amarillo 153, Amarillo 169, Hidalgo 58, J 117, Pinto Texcoco, Pinto 168, and Puebla 36. All except Puebla 36 were crossed with the susceptible cultivar Jamapa. Amarillo 153 and Puebla 36 were crossed with another susceptible cultivar, Bayo Mex. The parents, F₁ hybrids, and F₂ populations were evaluated for BPW damage in 1992. Backcrosses of the F₁ of Jamapa/Pinto 168 to the respective susceptible and resistant parents were also evaluated in 1992. All seven resistant accessions were crossed in all possible combinations, excluding reciprocals. The resulting 21 F₁ hybrids and 21 F₂ populations were evaluated for BPW damage in 1994. J 117 had the highest level of resistance to BPW. Pinto Texcoco and Puebla 36 had the highest mean damage score of all seven sources of resistance. The F₁ hybrids between susceptible parents and resistant sources were generally intermediate. Two genes segregating independently controlled the BPW resistance in each accession. One gene, Agm, has no effect when present alone, whereas the other gene, Agr, alone conferred intermediate resistance. When both genes were present, resistance to BPW was higher. Based on mean BPW damage scores, all 21 F₁ hybrids and their F₂ populations, derived from crosses among seven resistant accessions, were resistant. However, data from individual plant damage scores in F₂ populations of Amarillo 169/Pinto 168 and Pinto Texcoco/Pinto 168 suggested that at least one gene in each of the three accessions was non-allelic. Data also indicated that Amarillo 169 had a dominant gene that conferred high levels of BPW resistance, irrespective of the alleles at the other locus; and that Pinto Texcoco and Pinto 168 possessed two different genes for intermediate resistance.     

Synthesis of an H type 2 and a Y (Ley) glycoside from thioglycoside intermediates

The trisaccharide 2-(p-trifluoroacetamidophenyl)ethyl 2-acetamido-2-deoxy-4-O-[2-O-(-l-fucopyranosyl)--d-galactopyranosyl]--d-glucopyranoside 1 and the tetrasaccharide 2-(p-trifluoroacetamidophenyl)ethyl 2-acetamido-2-deoxy-3-O-(-l-fucopyranosyl)-4-O-[2-O-(-l-fucopyranosyl)--d-galactopyranosyl]--d-glucopyranoside 2 were synthesized. Thioglycosides, suitably protected, activated directly with methyl trifluoromethanesulfonate or dimethyl(methylthio)sulfonium tetrafluoroborate or activated after bromine treatment with halophilic reagents, were used as glycosyl donors in the construction of the glycosidic linkages.Abbreviations DMTSB dimethyl(methylthio)sulfonium tetrafluoroborate - Phth phthaloyl - MBn p-methoxybenzyl - ClBn p-chlorobenzyl     

Binary oscillations in the Kok model of oxygen evolution in oxygenic photosynthesis

The flash-induced kinetics of various characteristics of Photosystem II (PS II) in the thylakoids of oxygenic plants are modulated by a period of two, due to the function of a two-electron gate in the electron acceptor side, and by a period of four, due to the changes in the state of the oxygen-evolving complex. In the absence of inhibitors of PS II, the assignment of measured signal to the oxygen-evolving complex or to quinone acceptor side has frequently been done on the basis of the periodicity of its flash-induced oscillations, i.e. four or two. However, in some circumstances, the period four oscillatory processes of the donor side of PS II can generate period two oscillations. It is shown here that in the Kok model of oxygen evolution (equal misses and equal double hits), the sum of the concentrations of the S ₀ and S ₂ states (as well as the sum of concentrations of S ₁ and S ₃ states) oscillates with period of two: S ₀+S ₂S ₁+S ₃S ₀+S ₂S ₁+S ₃. Moreover, in the generalized Kok model (with specific miss factors and double hits for each S-state) there always exist such ₀, ₁, ₂, ₃ that the sum ₀[S₀] + ₁[S₁] + ₂[S₂] + ₃[S₃] oscillates with period of two as a function of flash number. Any other coefficients which are linearly connected with these coefficients, % MathType!MTEF!2!1!+-% feaafiart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr% 4rNCHbGeaGak0dh9WrFfpC0xh9vqqj-hEeeu0xXdbba9frFj0-OqFf% ea0dXdd9vqaq-JfrVkFHe9pgea0dXdar-Jb9hs0dXdbPYxe9vr0-vr% 0-vqpWqaaeaabiGaciaacaqabeaadaqaaqaaaOqaaiqbew7aLzaaja% aaaa!3917!\[\hat \varepsilon \]_i = c_1i + c₂, also generate binary oscillations of this sum. Therefore, the decomposition of the flash-induced oscillations of some measured parameters into binary oscillations, depending only on the acceptor side of PS II, and quaternary oscillations, depending only on the donor side of PS II, becomes practically impossible when measured with techniques (such as fluorescence of chlorophyll a, delayed fluorescence, electrochromic shift, transmembrane electrical potential, changes of pH and others) that could not spectrally distinguish the donor and acceptor sides. This property of the Kok cycle puts limits on the simultaneous analysis of the donor and acceptor sides of the RC of PS II in vivo and suggests that binary oscillations are no longer a certain indicator of the origin of a signal in the acceptor side of PS II.Abbreviations PS II Photosystem II - P680 primary electron donor of reaction center of PS II - Q_A one electron acceptor plastoquinone - Q_B two electron acceptor plastoquinone - S _n redox state of the oxygen evolving complex, where n=0,1,2,3 and 4 - Chl a chlorophyll a This paper is dedicated to the memory of Alexander Kononenko.     

Role of guanosine tetraphosphate in gene expression and the survival of glucose or seryl-tRNA starved cells of Escherichia coli K12

The concentration of guanosine 3,5-bispyrophosphate (ppGpp) increases in bacteria in response to amino acid or carbon/energy source starvation. An Escherichia coli K12 relAspoT mutant lacking the ability to synthesize ppGpp lost viability at an increased rate during both glucose and seryl-tRNA starvation. Also, the deleterious effect of chloramphenicol on starved wild-type cells could be overcome by inducing expression of RelA from a plasmid carrying the relA gene transcribed from a tac promoter, prior to starvation and chloramphenicol treatment. As demonstrated by two dimensional gel electrophoresis, this induction of the RelA protein resulted in global alterations in gene expression including increased synthesis of some rpoS-dependent proteins. The relAspoT mutant maintained high expression of several ribosomal proteins during starvation and appeared to exhibit significantly decreased translational fidelity, as demonstrated by an unusual heterogeneity in the isoelectric point of several proteins and the failure to express higher molecular weight proteins during starvation. Moreover, both rpoS-dependent and independent genes failed to exhibit increased expression in the mutant. It is suggested that the deleterious effects on the cells of the relA, spoT deletions are not due solely to the inability of these cells to induce the sigma factor ^s, but also to deficiencies in translational fidelity and failure to exert classical stringent regulation.     

Occurrence,structure and function of intracellular polyglucose in the obligate chemolithotroph Thiobacillus neapolitanus

Nitrogen-limited cells of the obligate chemolithotroph Thiobacillus neapolitanus formed an intracellular polymer during growth in the chemostat. This polymer was isolated and characterized as a branched polyglucose composed of units joined by -14 and -16 linkages. Polyglucose in T. neapolitanus can be considered a storage compound since formation of this compound took place during excess of energy and CO₂ whilst shortage of CO₂ resulted in rapid breakdown of polyglucose. Moreover the breakdown of polyglucose generated metabolically useful energy as could be demonstrated by polyglucose-dependent protein synthesis. Possession of polyglucose did not influence the viability of T. neapolitanus during prolonged periods of energy starvation. Activities of key enzymes of the oxidative pentose phosphate cycle, glucose-6-phosphatedehydrogenase and 6-phospho-gluconate-dehydrogenase, were demonstrated in cell free extracts of T. neapolitanus and appeared to increase 5- and 3-fold, respectively, during growth on NO ₃ ^- instead of NH ₄ ⁺ as a nitrogen source.     

RFLP markers to identify the alleles on the Mla locus conferring powdery mildew resistance in barley

Summary To identify the mildew resistance locus Mla in barley with molecular markers, closely linked genomic RFLP clones were selected with the help of near-isogenic lines having the Pallas and Siri background. Out of 22 polymorphic clones 3 were located around the Mla locus on chromosome 5 with a distance of 5.1 + 2.9 cM (MWG 1H068), 4.2±1.7 cM (MWG 1H060) and 0.7 ± 0.7 cM (MWG 1H036), respectively. The polymorphic clone MWG 1H036 displayed the same RFLP pattern in both Pallas and Siri near-isogenic lines and in different varieties digested with six restriction enzymes possessing the same mildew resistance gene. The alleles of the Mla locus were grouped in 11 classes according to their specific RFLP patterns; 3 of these groups contain the majority of Mla alleles already used in barley breeding programs in Europe.     

O-Glycosidically linked oligosaccharides from peptidorhamnomannans ofSporothrix schenckii

-Elimination of peptidorhamnomannans purified from yeast-like and mycelial phases ofSporothrix schenckii released neutral and acidic reduced oligosaccharides that were O linked to serine and/or threonine. Man-(1–2)Man-ol, Rha(1–3)Man(1–2)Man-ol, Rha(1–4)GlcA(1–2)Man(1–2)Man-ol, and Rha(1–4)[Rha(1–2)] GlcA(1–2)Man(1–2)Man-ol were characterized based on methylation analysis, proton magnetic resonance and fast atom bombardment mass spectrometry.Abbreviations FAB fast atom bombardment - GLC gas liquid chromatography - GlcA d-glucopyranosyluronic acid - Man d-mannopyranose - Man-ol d-mannitol - MS mass spectrometry - NMR nuclear magnetic resonance - Rha l-rhamnopyranose     

New ganglioside analogs that inhibit influenze virus sialidase

Synthetic thioglycoside-analogs of gangliosides such as Neu5Ac)2-S-6)Glc-(1-1)Ceramide (1) and the GM3 analog Neu5Ac(2-S-6)Gal-(1–4)Glc(1-1)Ceramide (2), competitively inhibited GM3 hydrolysis by the sialidase of different subtypes of human and animal influenza viruses with an apparent K_i value of 2.8×10^–6 and 1.5×10^–5 M, respectively. The inhibitory activity of the ganglioside GM4 analog [Neu5Ac-(2-S-6)Gal-(1-1)Ceramide (3)], in which the glucose of 1 was substituted by galactose, was lower than that of 1 (K_i =1.0×10^–4 M). The thioglycoside-analogs (1, 2, 3) of the gangliosides were nonhydrolyzable substrates for influenza virus sialidase. The inhibitory activity of 1 to bacterial sialidases fromClostridium perfringens andArthrobacter ureafaciens was considerably lower than that to influenza virus sialidase, indicating that the structure of the active site in bacterial and influenza virus sialidase may be different and the analogs may be useful to determine the orientation of the substrate to the active site of sialidases, especially of influenza viruses.Abbreviations Cer ceramide - GM3 Neu5Ac(2–3)Gal(1–4)Glc(1-1)Cer - GM4 Neu5Ac(2–3)Gal(1-1)Cer Gangliosides were abbreviated according to Svennerholm [1] and the recommendation of the IUPAC-IUB Commission on Biochemical Nomenclature [2].     

Mutations that are synthetically lethal with a<Emphasis Type="Italic"> gas1Δ</Emphasis> allele cause defects in the cell wall of<Emphasis Type="Italic"> Saccharomyces cerevisiae</Emphasis>

The GAS1 -related genes of fungi encode GPI-anchored proteins with -1,3-glucanosyltransferase activity. Loss of this activity results in defects in the assembly of the cell wall. We isolated mutants that show a synthetic defect when combined with a gas1 allele in Saccharomyces cerevisiae, and identified nine wild-type genes that rescue this defect. The indispensability of BIG1 and KRE6 for the viability of gas1 cells confirmed the important role of -1,6-glucan in cells that are defective in the processing of -1,3-glucan. The identification of the Wsc1p hypo-osmotic stress sensor and components of the PKC signal transduction pathway in our screen also confirmed that the cell wall integrity response attenuates the otherwise lethal gas1 defect. Unexpectedly, we found that the KEX2 gene is also required for the viability of the gas1 mutant. Kex2p is a Golgi/endosome-membrane-anchored protease that processes secretory preproteins. A cell wall defect was also found in the kex2 mutant, which was suppressible by multiple copies of the MKC7 or YAP3 gene, both of which encode other GPI-anchored proteases. Therefore, normal cell wall assembly requires proteolytic processing of secretory preproteins. Furthermore, the genes CSG2 and IPT1 were found to be required for normal growth of gas1 cells in the presence of 1 M sorbitol. This finding suggests that complex sphingolipids play a role in the hyper-osmotic response.Communicated by C. P. Hollenberg     

The Influence of Leaf Windows on the Utilization and Absorption of Radiant Energy in Seven Desert Succulents

Four fluorescence parameters [F_v/F_m = the intrinsic efficiency of energy conversion via photosystem 2 (PS2); F_v/F_m= the efficiency of energy conversion via PS2 in the light; P = fraction of absorbed radiant energy utilized for photosynthesis; and D = fraction of absorbed radiant energy dissipated as heat] were measured on leaves of seven species of succulents having epidermal windows. While the function of leaf windows has reportedly been to increase absorption of radiant energy and, hence, the rate of photosynthesis in these species, recent evidence indicates that this translucent portion of epidermal tissue, lacking chlorophyll, may also result in photoinhibition in these species, especially for those with growth habits aboveground. Species with aboveground and belowground growth habits were compared with their leaf windows covered with reflective tape and with windows unobstructed. Results showed no increase in photoinhibition for these species resulting from the radiant energy penetrating the window tissue. Although the efficiency of the photosynthetic mechanism was not significantly influenced by the additional radiant energy provided by the window for individual species, there were significant differences in the efficiencies of radiant energy capture (F_v/F_m) and utilization (P) between the two growth habits. Species with an aboveground growth habit were less efficient in radiant energy utilization compared with the species having a belowground growth habit.