On the role of carbonic anhydrase in the anticonvulsant effects of triethyltin (TET)

Summary Triethyltin (TET) and acetazolamide (ACTZ) both produce marked anticonvulsant effects as evaluated by the maximal electroshock seizure test. However, the mechanism responsible for the anticonvulsant effect of TET and ACTZ is probably not the same since TET does not inhibit the activity of carbonic anhydrase isozyme C in vitro.This study was supported by NIEHS Toxicology Training grant No. ES07 090, NIOSH grant No. OH07085 and a University of Texas Biomedical Research grant. We wish to thank Rebecca Crenshaw for her excellent technical assistance.     

Some observations on pigments of the pacific sand dollars,Dendraster excentricus andDentraster laevis

Zusammenfassung Dendraster laevis bildet ein grünes, wasserlösliches Pigment (farblos bei pH unter 5) und kein Echinochrom.Dendraster excentricus dagegen erzeugt zwei purpurrote, wasserlösliche und zwei echinochromähnliche Pigmente.

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Contribution from the Scripps Institution of Oceanography, University of California, New Series No 773.     

Proline isomerism in staphylococcal nuclease characterized by NMR and site-directed mutagenesis

Nuclear magnetic resonance (NMR) studies have shown that two distinct folded conformations of staphylococcal nuclease coexist in solution and that these two states can interconvert directly without passing through an unfolded state. These experiments have also revealed that the two forms have very different folding kinetics, although the possibility that one component is an obligatory intermediate for the folding of the other form could be discounted. Here we report NMR data which show that alternative unfolded states are also distinguishable. These observations led us to hypothesize that cis/trans isomerism at a single peptide bond between a proline and its preceding residue might be the origin of the conformational multiplicity. Proline 117 was identified as a likely candidate for the site concerned and a mutant protein, in which Pro 117 was replaced by Gly, was constructed in order to test this. Alternative conformations are not observed in the spectrum of this mutant, lending powerful support to this hypothesis.     

The sub-energetic gamma-ray burst GRB 031203 as a cosmic analogue to the nearby GRB 980425

Over the six years since the discovery of the gamma-ray burst GRB 980425, which was associated with the nearby (distance approximately 40 Mpc) supernova 1998bw, astronomers have debated fiercely the nature of this event. Relative to bursts located at cosmological distance (redshift z approximately 1), GRB 980425 was under-luminous in gamma-rays by three orders of magnitude. Radio calorimetry showed that the explosion was sub-energetic by a factor of 10. Here we report observations of the radio and X-ray afterglow of the recent GRB 031203 (refs 5-7), which has a redshift of z = 0.105. We demonstrate that it too is sub-energetic which, when taken together with the low gamma-ray luminosity, suggests that GRB 031203 is the first cosmic analogue to GRB 980425. We find no evidence that this event was a highly collimated explosion viewed off-axis. Like GRB 980425, GRB 031203 appears to be an intrinsically sub-energetic gamma-ray burst. Such sub-energetic events have faint afterglows. We expect intensive follow-up of faint bursts with smooth gamma-ray light curves (common to both GRB 031203 and 980425) to reveal a large population of such events.     

The temporal response of the brain after eating revealed by functional MRI

After eating, the human brain senses a biochemical change and then signals satiation, but precisely when this occurs is unknown. Even for well-established physiological systems like glucose-insulin regulation, the timing of interaction between hormonal processes and neural events is inferred mostly from blood sampling. Recently, neuroimaging studies have provided in vivo information about the neuroanatomical correlates of the regulation of energy intake. Temporal orchestration of such systems, however, is crucial to the integration of neuronal and hormonal signals that control eating behaviour. The challenge of this functional magnetic resonance imaging study is to map not only where but also when the brain will respond after food ingestion. Here we use a temporal clustering analysis technique to demonstrate that eating-related neural activity peaks at two different times with distinct localization. Importantly, the differentiated responses are interacting with an internal signal, the plasma insulin. These results support the concept of temporal parcellation of brain activity, which reflects the different natures of stimuli and responses. Moreover, this study provides a neuroimaging basis for detecting dynamic processes without prior knowledge of their timing, such as the acute effects of medication and nutrition in the brain.