Denitrifying bacteria of genus Alcaligenes isolated from soil]

The organism isolated is a small non-sporulating Gram-negative rod, motile by means of peritrichous flagellae. It is an oxidase-positive chemo-organotroph utilizing O2,NO-3,NO-2 and N2O as resiratory substrates. Primary alcohols as well as numerous organic and amino acids are utilized as carbon and energy sources. Carbohydrates are not assimilated. Poly-beta-hydroxybutyrate is accumulated intracellularly. The bacterium is assigned to the genus Alcaligenes and its phenotype characteristics are compared with those of A. faecalis.     

Effect of enkephalins in the presence of the antibiotic bacitracin in the longitudinal muscle strip preparation from guinea-pig ileum

Summary The antibiotic bacitracin (5×10^–5–4×10^–4 M) increases the inhibition of the contractile response caused by both enkephalin release and direct application of Met-enkephalin 5×10^–7 M in the longitudinal muscle strip preparation from guinea-pig ileum. This effect is attributed to an inhibition of enkephalin degrading peptidases by bacitracin.     

Two-step binding mechanism for T-cell receptor recognition of peptide MHC

T cells probe a diverse milieu of peptides presented by molecules of the major histocompatibility complex (MHC) by using the T-cell receptor (TCR) to scan these ligands with high sensitivity and specificity. Here we describe a physical basis for this scanning process by studying the residues involved in both the initial association and the stable binding of TCR to peptide-MHC, using the well-characterized TCR and peptide-MHC pair of 2B4 and MCC-IE(k) (moth cytochrome c, residues 88 103). We show that MHC contacts dictate the initial association, guiding TCR docking in a way that is mainly independent of the peptide. Subsequently, MCC-IE(k) peptide contacts dominate stabilization, imparting specificity and influencing T-cell activation by modulating the duration of binding. This functional subdivision of the peptide-MHC ligand suggests that a two-step process for TCR recognition facilitates the efficient scanning of diverse peptide-MHC complexes on the surface of cells and also makes TCRs inherently crossreactive towards different peptides bound by the same MHC.     

Proteolytic enzymes in theRhodnius prolixus midgut

Summary Sequential chromatographic fractionation ofRhodnius prolixus midgut homogenate yielded only one endopeptidase, but revealed the presence of carboxypeptidase-A and B-like enzymes, di- and tripeptidases, as well as aminopeptidase activities.Work subsidized by FINEP and CNPq, Rio and FAPESP, São paulo.     

Isolation of bacteria that use that use nitric oxide as a respiratory electron acceptor under anaerobiosis]

Ten bacteria of the genus Bacillus were isolated from pasteurized soils, in anaerobiosis and at 32 degrees C, on peptone broth containing 0.5% KNO2. They are Gram variable rods producing oval spores. They are oxidase positive and have catalase. They grow, in anaerobiosis, on NO-3, NO-2, N2O, and NO as respiratory electron acceptors. These compounds are reduced to N2.     

Slow inward calcium currents have no obvious role in muscle excitation-contraction coupling

It has been proposed that an influx of calcium ions into twitch muscle fibres during an action potential might initiate contraction. However, when external Ca2+ is lowered to 10(-8) M with EGTA, the fibres can produce normal twitches for many minutes. Nevertheless, a clear Ca2+ influx during contraction has been demonstrated, and it has been found that phasic skeletal muscle has an inward calcium current (ICa) which can give rise to calcium spikes. In certain conditions, a reduction in external Ca2+ with 80-90 mM EGTA results in reversible blockade of excitation-contraction (e-c) coupling, leading some authors to suggest that extracellular Ca2+ moved into the myoplasm due to ICa may be involved in the e-c coupling mechanism that triggers contraction. This proposition was further supported by the localization of ICa in the T-system, which circumvented the problem of the delay due to calcium diffusion from the surface membrane. We have now investigated whether ICa has a clear role in initiating or sustaining contractions in twitch muscle fibres. Our approach was to decrease or eliminate ICa with the calcium-blocking agent diltiazem (Herbesser) and to see how the twitch, tetanic and potassium-contracture tensions were affected. We found that ICa could be decreased or cancelled with the calcium-blocking agent, but that the same concentration of the drug potentiated the twitch, tetanus and contractures. We conclude, therefore, that ICa has no role in e-c coupling. A preliminary report of these results has been presented elsewhere.     

Iproniazid interaction with the H3 norepinephrine uptake and retention,on isolated left atrium of guinea-pig

Resumen La incorporación de H³NE a la auricula aislada de cobayo reserpinizado, tratado con Iproniazida (IPN) y atmosfera de Nitrogeno, es superior a la de sus controles sin IPN. En auriculas no reserpinizadas, la IPN aparece como agente bloquenate de la incorporación. Se sugiere que este bloqueo ocurre a nivel de las vesiculas especificas de almacenamiento presentes en las terminaciones nerviosas adrenergicas.     

Agreement in endpoints from circadian rhythmometry on healthy human beings living on different continents

Zusammenfassung Circadiane Akrophasen — Gipfel der ungefähren 24-h-Periodik — von Blut- und Harnkortikosteroiden, Kalium im Harn, Körpertemperatur, Pulsrate und 2-min-Schätzung wurden mittels elektronischer Anpassung einer Kosinusfunktion vermöge der Methode der kleinsten Quadrate bestimmt. Solche Charakteristika circadianer Rhythmen empfehlen sich als Referenzstandarde dem Mediziner und Biologen durch ihre zufriedenstellende übereinstimmung in Daten von Untersuchungen auf verschiedenen Kontinenten mit zum Teil unterschiedlichen Methoden.