Coordination mode and reactivity of copper(II) complexes with kasugamycin.

Protonation and Cu(II) coordination of kasugamycin were studied by potentiometry, UV-vis, CD, EPR, 13C NMR, and 1H NMR. Mononuclear complexes with stoichiometries ranging from CuHL to CuH(-1)L were found. The aminoamidine moiety provides the coordination site in the CuHL species. The additional axial coordination of the amino nitrogen of the aminosugar ring is present in CuL. Finally, the CuH(-1)L complex is formed as a result of a deprotonation and coordination of the hydroxyl group of the inositol ring. The non-planar arrangement of the chelate rings results in the relative stabilization of a Cu(I) species. As a consequence, Cu(I) and superoxide radicals are involved in the redox mechanism of H(2)O(2) activation by the Cu(II) complex of kasugamycin.     

Species-specific algal responses to zooplankton: experimental and field observations in three nutrient-limited lakes

A series of 4-day manipulations of zooplankton biomass and nutrientavailability was performed in enclosures in three lakes to determinespecies-specific algal responses to herbivory and nutrient enrichment.Algal performance in enclosures was compared to the relationshipsbetween weekly algal growth rates and the zooplankton in situ.When in situ growth rates were significant functions of zooplanktonbiomass, the responses were generally consistent with responsesin the enclosure experiments. The importance of both nutrientsand zooplankton in mediating algal growth was demonstrated bynumerous observations: strong algal community response to enrichment,unimodal or positive responses of certain algal taxa to zooplanktonbiomass, differences in degree of nutrient limitation amongthe algal response types, lack of nutrient limitation of non-grazedalgal taxa and a preponderance of taxa with no net responseto increasing zooplankton biomass. Variation in the zooplanktoncommunity may be the largest source of variability in nutrientsupply rate during summer in stratified lakes, and causes substationalvariability in the algae. Algae responded more strongly to changesin zooplankton composition than to changes in zooplankton biomass.We conclude that, due to the close coupling of phytoplanktonand zooplankton communities in these nutrient-limited lakes,major compositional changes in the zooplankton have greatereffects on the algae than do changes in biomass of grazers alreadypresent. ¹Present address: Division of Environmental Studies, Universityof California, Davis, CA 95616, USA ²Present address: Division of Biological Sciences, Universityof California, Davis, CA 95616, USA     

Hookworm antigens: the potential for vaccination

Hookworms rank with Ascaris as the most prevalent soil-transmitted helminths of man. Up to 1000 million people may be infected. Not all suffer the life-threatening anaemia that reflects heavy burdens of hookworms, but even mild iron-deficiency anaemia due to hookworms can lead to intellectual and growth retardation - especially among infected children. Health education, mass chemotherapy and the sanitary disposal of faeces have been the traditional mainstays of hookworm control, but more recently chemotherapy targeted only to heavily infected individuals who appear predisposed to hookworm anaemia has emerged as a realistic alternative. Ultimately, however, knowledge of the molecular immunology of hookworm infection may provide the basis for rational vaccine development. Although the evidence for acquired immunity to hookworms in man is not strong, work is now underway to identify and to characterize antigens from third and fourth larval stages and adults of Necator americanus and species of Ancylostoma (Table 1). As this article shows, the work provides real promise for improved immunodiagnosis and possible vaccination.     

Murine monoclonal antibody against aldosterone: production, characterization and use for enzymoimmunoassay

Hybridomas secreting monoclonal antibodies to aldosterone were obtained by fusion of myeloma cells and spleen cells from Balb/c mice immunized with aldosterone-3-carboxylmethyloxime-bovine serum albumin. A monoclonal antibody was purified from ascites fluid and characterized. An affinity constant of 1.61 x 10(9) M-1 has been measured and no cross-reactivity with tetrahydroaldosterone (THA), cortisol, cortisone, corticosterone, deoxycorticosterone (DOC), dehydroepiandrosterone (DHA), progesterone and estrone, could be detected. A peroxidase conjugated-antibody (1.5 mole of enzyme per mole of antibody) was obtained and used for microwell enzyme immunoassay and Immun-Blot assay. The high affinity and specificity of this antibody should make the direct determination of aldosterone in biological fluids possible at concentrations as low as 5 x 10(-10) M.     

Presynaptic control of dopamine metabolism in the nucleus accumbens. Lack of effect of buspirone as demonstrated using in vivo voltammetry

Buspirone is a non-benzodiazepine drug with anxiolytic properties. It has been reported to induce a marked increase in the metabolism of dopamine in the striatum and the nucleus accumbens which is similar to that induced by neuroleptics. It has been suggested that the effect observed in the striatum reflects an action of buspirone on dopaminergic autoreceptors in both terminals and cell bodies. In the present study, presynaptic effects of buspirone on dopaminergic metabolism in the nucleus accumbens were investigated, and they were compared to the effects of the classical neuroleptic, haloperidol. Dopaminergic terminals were isolated by infusion of tetrodotoxin into the median forebrain bundle in order to evaluate the effects of buspirone and haloperidol on presynaptic receptors. Changes in dopamine metabolism were determined by in vivo voltammetry. Buspirone administered after interruption of the impulse flow did not affect dopamine metabolism. In contrast haloperidol treatment led to an increase in metabolism of dopamine. It is concluded that buspirone did not act at the presynaptic level and furthermore on dopaminergic autoreceptors.     

Effects of electrical stimulation upon post-hatching development of fibre types in normally innervated fast and slow latissimus dorsii muscles of the chicken

In chicken, the main characteristic properties of muscle fibre types in slow anterior (ALD) and fast posterior (PLD) latissimus dorsii are acquired during post-hatching development. At day 4 it becomes possible to distinguish between alpha' and beta' fibre types in ALD muscle. At the same time, mATPase staining and NADH-TR activity permit recognition of alpha w and alpha R fibres within PLD muscle. During further development, muscle fibre typology progressively changes towards the adult slow and fast type. Chronic stimulation at a slow rhythm (5 Hz) of PLD prevents the change in relative proportions of alpha R and alpha W fibres within the muscle that occurs in normal post-hatching development and increases the number of beta R fibres. Moreover, oxidative activity is increased in all muscle fibre types following stimulation. In ALD muscle, chronic stimulation at a fast rhythm (40 Hz) results in a decrease in oxidative activity and inhibits the differentiation of alpha' and beta' muscle fibre types. This study demonstrates that in young chicken, the pattern of activity influences the differenciation of fibre types in slow and fast muscles.     

Comparative EPR studies on the nitrite reductases from Escherichia coli and Wolinella succinogenes

Hexaheme nitrite reductases purified to homogeneity from Escherichia coli K-12 and Wolinella succinogenes were studied by low-temperature EPR spectroscopy. In their isolated states, the two enzymes revealed nearly identical EPR spectra when measured at 12 K. Both high-spin and low-spin ferric heme EPR resonances with g values of 9.7, 3.7, 2.9, 2.3 and 1.5 were observed. These signals disappeared upon reduction by dithionite. Reaction of reduced enzyme with nitrite resulted in the formation of ferrous heme-NO complexes with distinct EPR spectral characteristics. The heme-NO complexes formed with the two enzymes differed, however, in g values and line-shapes. When reacted with hydroxylamine, reduced enzymes also showed the formation of ferrous heme-NO complexes. These results suggested the involvement of an enzyme-bound NO intermediate during the six-electron reduction of nitrite to ammonia catalyzed by these two hexaheme nitrite reductases. Heme proteins that can either expose bound NO to reduction or release it are significant components of both assimilatory and dissimilatory metabolisms of nitrate. The different ferrous heme-NO complexes detected for the two enzymes indicated, nevertheless, their subtle variation in heme reactivity during the reduction reaction.     

A photoaffinity label for the thromboxane A2/prostaglandin H2 receptor in human blood platelets

A photoactive iodoarylazide derivative (I-APA-PhN3) of the competitive thromboxane A2/prostaglandin H2 (TXA2/PGH2) antagonist 13-azaprostanoic acid is evaluated. Upon photoactivation, the compound was found to inhibit specifically and irreversibly human platelet aggregation induced by the TXA2/PGH2 mimetic U46619. In receptor-binding studies using [3H]U46619, I-APA-PhN3 exhibited an IC50 of 300 nM for inhibition of U46619 binding. Photoactivation of I-APA-PhN3 resulted in an irreversible 58% reduction in specific binding of U46619. This compound and its corresponding ratio-iodinated form will prove to be useful tools for the isolation and purification of the TXA2/PGH2-binding protein in human platelets.     

Impact d'une pollution urbaine sur la partie zooplanctonique d'un systeme neitique (Marseille - Cortiou)

Sewage of Marseilles' main outfall permanently pollutes a large coastal area centered around Cortiou, south of the city. In order to study the impact of that urban pollution on the zooplankton, more than 200 samples were collected between 1977 and 1981, according to several sampling strategies.Quantitatively, the study area showed a rather poor zooplankton. The more important populations were encountered near Cortiou, the non-perturbated reference point with lowest abundance of organisms. Sampling sites located near the outfall are sometimes azoic. Qualitatively, the observed communities are not characteristic of a heavily polluted environment, but correspond to an impoverished neritic community. In the more polluted area, the community is organized around the copepods Clausocalanus sp., Paracalanus sp. and Oithona helgolandica, and a group of less important species (Oithona nana and the cladoceran Evadne spinifera). Centropagidae, Coryceidae, Onceidae, but also Chaetognathians, Fritilliarins and the meroplanktonic larvae are more frequently encountered in clean water. Community structure is higher during the cold months than summer. The latter period frequently shows a disorganized zooplankton. In most situations, the copepod Acartia clausi plays a minor role in the structural definition of the communities.The variations observed seem largely independent of the parameters reflecting pollution intensity. Stress integration, in relation with the anterior community history (intensity of contact with polluted water, trophic potential of the area) seem to be the main regulator factors.

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Impact d'une pollution urbaine sur la partie zooplanctonique d'un systeme neitique (Marseille - Cortiou)

Resumé Le rejet permanent du grand émissaire de Marseille (5 m³, sec^–1) perturbe considérablement, par son importance, le système néritique du secteur de Cortiou. Afin d'approcher l'impact de cette pollution sur la partie zooplanctonique du système, plus de 200 prélèvements, concernant l'hydrologie et le plancton, ont of é\'t é réalises entre 1977 et 1981, selon différentes strategiés d'échantillonnage (suivi de masse d'eau, radiales, réseaux).Quantitativement on observe, sur l'ensemble de la zone étudiée, une abondance générale en zooplancton moyenne, voire faible. Les effectifs les plus importants se rencontrent cependant dans la cuvette de Cortiou, alors que le point de référence considéré comme non perturbé présente les effectifs les plus faibles. Les stations situées face à l'égout sont parfois azoïques.Qualitativement les peuplements ne paraissent pas trés caractéristiques d'un secteur pollué mais correspondent plutôt à un appauvrissement du peuplement néritique. Dans le secteur le plus pollué, la composition spécifique varie au cours du temps autour d'une communauté composée d'un groupe important avec Clausocalanus sp., Paracalanus sp., Oithona helgolandica et d'un groups de taxons moins fréquents représentés par des larves méroplanctoniques, Oithona nana et Evadne spinifera, tandis que les coryceidés, onceidés, Centropages typicus, chaetognathes et fritillaires se retrouvent plus fréquemment en eaux propres. La structure des populations est plus importante en période froide qu'en période chaude, période durant laquelle la communauté planctonique est fortement désorganisée. Paradoxalement Acartia clausi joue un rôle assez secondaire dans la définition structurelle de la communauté.Les fluctuations observées paraissent cependant peu liées à des paramètres reflétant l'intensité de la pollution. L'intégration du stress, en relation avec l'histoire antérieure de la communauté (intensité et durée du contact avec la nappe de dilution, potentialités trophiques) semblent ainsi prépondérantes.