On the dynamics of the mass mortality of Diadema antillarum in Barbados

Widespread mortality of the black sea urchin Diadema antillarum occurred in the Caribbean in 1983; beginning in Panama in January, and having its major impact at Barbados in September. Mortality on ten reefs surveyed in Barbados was 93.2%, with the highest being 99.9% and the lowest 86.9%. Mortality on each reef was independent of the pre-mortality density on the reef. Urchins with test diameters between 20 and 40 mm were more severely affected than smaller or larger urchins. Populations on reefs exposed to incoming oceanic water suffered heavier mortality than those on protected reefs. Mean size of urchins was smallest on high density reefs. This may indicate a negative effect of density on urchin growth. At post-mortality densities, urchins may grow faster and reach sexual maturity sooner.     

Alpha-melanotropin in the frog brain: regional distribution, quantification and subcellular distribution

The distribution of alpha-MSH containing neurons was studied by immunofluorescence in the brain of the frog Rana ridibunda. Most immunoreactive cell bodies were found in the ventral hypothalamic area. A rich network of fluorescent fibers was observed in the ventral infundibular region, coursing towards the preoptic area and the ventral telencephalon. Some fibers, directed backwards, project into median eminence. By means of a specific radioimmunoassay, the concentrations of alpha-MSH immunoreactive material has been determined in 10 different regions of the brain. The highest concentrations were observed in the infundibular and the preoptic regions. Using the immunogold technique, electron microscopy showed that immunostaining was restricted to 70-100 nm dense core vesicles in positive cell bodies and fibers. These results suggest that, in addition to well known hormonal (melanotropic) activity, alpha-MSH could play the role of a neurotransmitter in the frog brain.     

Cytoarchitectonic localization of foci of electrocortical activity accompanying focused attention in cats

Beta electrocorticographic rhythms (30-45 Hz) develop during focused immobile attention within two distinct foci in cats. A multiple electrode exploration was performed, followed by post-mortem histological analysis, to determine the precise localization of these foci. Electrode tips recording beta rhythms in the waking attentive cat were located: in motor areas (Brodmann's areas 4 and 6), in a band extending from the postcruciate cortex to the walls of the presylvian sulcus, crossing the frontal pole (anterior beta focus); in the posterior parietal associative area 5a, along the divisions of the ansate sulcus (posterior beta focus). The two foci are separated by somatic areas 3, 2 and 1, where beta rhythms were never recorded. The location of the posterior focus may suggest that area 5 is, in the cat as it is in the monkey, involved in motor control.     

Comparative study of the edema-forming activity of Costa Rican snake venoms and its neutralization by a polyvalent antivenom

The edema-forming activity of eight Costa Rican crotaline snake venoms and its neutralization by a polyvalent antivenom were studied using the mouse footpad test. All of the venoms induced edema, the highest activity being present in the venoms of Bothrops lateralis and Bothrops picadoi. When experiments were performed with preincubation of venom and antivenom, neutralization of edema was poor. Moreover, it was observed that, with some venoms, edema increased when large doses of antivenom were used. This effect was also observed when some venoms were incubated with coral snake antivenom, suggesting that venoms may release some pharmacologically active component(s) from antivenom, since the latter contains traces of alpha-2 and beta globulins. Based on these findings, an alternative approach to the study of the neutralization of edema was used; in this new method, antivenom was injected i.v. before venom administration, thereby avoiding preincubation. With this technique, a much better neutralization of edema was observed, although with some venoms it was still poor. Venoms contain low molecular weight factors which induce edema, suggesting that lack of immunogenicity of some components may cause a poor neutralization. However, such components are responsible for only a minor portion of the edema induced by crude venoms. It is suggested that experiments in which venom and antivenom are preincubated preincubated in testing the neutralization of edema should be avoided, and that a more adequate approach may be an independent inoculation of venom and antivenom.     

Looking for probes of gated channels: studies of the inhibition of glucose and choline transport in erythrocytes

Two seemingly contradictory sets of observations have been made in studies of biological transport, which are essential for our understanding of the transport mechanism: carriers are integral membrane proteins, which span the membrane and are not free to rotate across the membrane; carriers appear to function like a ferryboat, with a substrate binding site moving back and forth from one side of the membrane to the other. To reconcile these facts, it is necessary to postulated gated channels connecting the substrate site with the two membrane surfaces: the channels are arranged so that as one opens the other closes, with the result that the substrate site is alternately accessible from opposite sides of the membrane. Based on these properties, the following distinguishing features of molecules specifically bound in the channels may be predicted: if sufficiently bulky, they inhibit transport; they bind outside the substrate site (though adjacent to it), they bind asymmetrically either to the outward-facing carrier and on the outer surface of the membrane, or to the inward-facing carrier and on the inner surface of the membrane. The asymmetrical inhibition of the glucose and choline transport systems of erythrocytes by various inhibitors is examined, and the behavior in every case is found to conform with these criteria. From the results it may be concluded that the glucose carrier binds cytochalasin B in the inner gated channel and phloretin and tetrathionate in the outer gated channel.(ABSTRACT TRUNCATED AT 250 WORDS)     

Poly(ADP-ribose) accessibility to poly(ADP-ribose) glycohydrolase activity on poly(ADP-ribosyl)ated nucleosomal proteins

Hydrolysis of protein-bound 32P-labelled poly(ADP-ribose) by poly(ADP-ribose) glycohydrolase shows that there is differential accessibility of poly(ADP-ribosyl)ated proteins in chromatin to poly(ADP-ribose) glycohydrolase. The rapid hydrolysis of hyper(ADP-ribosyl)ated forms of histone H1 indicates the absence of an H1 dimer complex of histone molecules. When the pattern of hydrolysis of poly(ADP-ribosyl)ated histones was analyzed it was found that poly(ADP-ribose) attached to histone H2B is more resistant than the polymer attached to histone H1 or H2A or protein A24. Polymer hydrolysis of the acceptors, which had been labelled at high substrate concentrations (greater than or equal to 10 microM), indicate that the only high molecular weight acceptor protein is poly(ADP-ribose) polymerase and that little processing of the enzyme occurs. Finally, electron microscopic evidence shows that hyper(ADP-ribosyl)ated poly(ADP-ribose) polymerase, which is dissociated from its DNA-enzyme complex, binds again to DNA after poly(ADP-ribose) glycohydrolase action.     

Biphasic mode of epithelial regeneration in murine pulmonary alveoli

After administration to mice of butylated hydroxytoluene, the pulmonary alveolar epithelium adopts a biphasic pattern of regenerative proliferation. This hitherto-unnoticed pattern of epithelial repair in the lung was revealed by the investigation of stereologic parameters. The earliest evidence of epithelial injury involved the type I pneumocytes, whose necrosis and disappearance from the septal surface was shown by a lowered surface density (SV). Proliferation of the type II pneumocytes ensued: the volume density (VV) rose above normal soon after the onset of necrosis, only to decrease as the cells slowly differentiated into intermediate and then type I pneumocytes. A second peak of type II pneumocytes appeared as the denuding of septa persisted. This twofold proliferation was also shown by the numerical density count (NV). Differentiation into an intermediate pneumocyte was itself documented by the raised VV and SV values. These observations of a biphasic mode of proliferation of type II pneumocytes raise the question of an unsuspected, persistent action of the toxic agent within pulmonary alveoli and serve to document the homeostasis of epithelial regeneration.     

Isolement et sélection de souches d'actinomycètes productrices de substances antifongiques de structure non-polyénique

Résumé Dans le but d'étudier des souches d'actinomycètes productrices de substances antifongiques de structure non-polyénique, 13, échantillons de sol prélevés dans le sud de la France ont été examinés. L'utilisation de milieux sélectifs a permis d'isoler 486 souches d'actinomycètes qui ont été testées vis-à-vis de quatre espèces de champignons et de levures: 18% des souches isolées sont actives sur au moins l'une des espèces utilisées. Parmi celles-ci 14 souches, productrices de substances de structure non-polyénique, ont été sélectionnées après étude des spectres d'absorption en UV des surnageants de culture, des extraits butanoliques de ces surnageants ou des extraits méthanoliques de mycélium. L'utilisation d'un test bactérien de toxicité à court terme (SOS Chromotest) a permis de montrer que 10 souches sur 14 présentent aussi une activité génotoxique.

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Summary In order to study actinomycete strains producing non-polyenic antifungal substances 13 soil samples were collected in S. France. By using selective media 486 strains of actinomycetes were isolated and tested on four species of moulds and yeasts: 18% of the isolated strains were active against one or more of the test organisms. From these isolates 14 producers of non-polyenic antifungal substances were selected by means of u.v. absorption spectra of culture supernatant fractions, butanol extracts of these fractions, or methanol extracts of mycelium. A rapid bacterial toxicity assay (SOS Chromotest) demonstrated that 10 of the 14 selected strains had genotoxic activity.

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Resumen Para el estudio de cepas de actinomicetes productores de sustancias antifúngicas no poliénicas, se recogieron 13 muestras de suelo en el S. de Francia. Utilizando medios selectivos se aislaron 486 cepas de actinomicetes que se ensayaron frente a cuatro especies de mohos y levaduras: 18% de las cepas aisladas mostraron actividad frente a uno o más de los organismos utilizados en el test. De estas cepas se seleccionaron 14 que eran productoras de sustancias antifúngicas no poliénicas mediante el espectro de absorción al U.V. de las fracciones sobrenadantes del cultivo, de extractos butanólicos de dichas fracciones o de extractos metanólicos del micelio. Un ensayo rápido de toxicidad bacteriana (SOS Chromotest) mostró que de las 14 cepas seleccionadas lo tenían actividad genotóxica.

     

Angina pectoris-like pain provoked by intravenous adenosine in healthy volunteers.

In a study to characterise the chest pain induced by adenosine this agent was given as a bolus into a peripheral vein to six healthy volunteers (five men) aged 30-44. On the first day the maximum tolerable dose was determined in each case. On the second day three doses of adenosine (one third, two thirds, and the full maximum tolerable dose) and three doses of saline were given single blind in randomised order. Thereafter aminophylline 5 mg/kg was given and the procedure repeated in a different randomised order. On the third day between two thirds and the full maximum tolerable dose was given followed by 10 mg dipyridamole intravenously and a second injection of the same dose of adenosine. Heart rate and atrioventricular blocks were recorded by electrocardiography. One minute after each dose of adenosine the chest pain was scored. The maximum tolerable dose of adenosine ranged from 10.6 to 37.1 mg. All subjects experienced uneasy central chest pain provoking anxiety. The pain radiated to the shoulders, ulnar aspect of the arms, epigastric area, back, and into the throat. The pain began about 20 seconds after the injection and lasted 10-15 seconds. Increasing the dose of adenosine increased the intensity of the pain. Administration of aminophylline reduced the pain significantly. Second degree heart block was recorded in five of the six subjects during the time that the pain was experienced. After aminophylline no block was observed. Dipyridamole increased the intensity of pain. The duration of second degree heart block increased in four of the subjects, and in two of these third degree heart block occurred. These findings suggest that adenosine released from the myocardium during ischaemia induces angina pectoris by stimulating theophylline sensitive receptors.