Influence of protein nutrition on calpain activity of mouse kidney: Modulation by calpastatin

The effect of protein depletion and refeeding with a normal diet on calpain activity was examined in mouse kidney soluble homogenate. In terms of units per gram of protein, it increased 2.9 times with depletion and decreased upon refeeding. After a DEAE-Sephacel chromatography, the homogenate yielded three enzymatic activities. Their sum, assessed as total calpain activity, was higher than the activity measured before fractionation and did not appreciably change during protein depletion and refeeding. Because the proportion of total activity displayed by the complete homogenate increased with depletion and decreased with refeeding, a low calpastatin content in depleted kidney was envisaged. This was confirmed by direct estimations: depleted kidney had 6 times less calpastatin compared to both normal and 16 h refed tissue. We concluded that a decrease in calpastatin content contributes to an increased calpain activity related to degradable protein in protein depleted kidney. In view of this, it seems not unlikely that the in vivo rate of protein breakdown depicted by kidney during protein depletion and refeeding is in part effected through modulation of the calpain proteolytic system. (Mol Cell Biochem 166: 95-99, 1997)     

EcXyl43 β-xylosidase: molecular modeling,activity on natural and artificial substrates,and synergism with endoxylanases for lignocellulose deconstruction

Applied Microbiology and Biotechnology - Biomass hydrolysis constitutes a bottleneck for the biotransformation of lignocellulosic residues into bioethanol and high-value products. The efficient...     

The edibility of shoots of some bamboos growing in Puerto Rico

In China and Japan bamboo shoots have long served as victuals, but no such use has yet developed in the New World, except for imports of the canned article. Edibility tests on 27 kinds growing in Puerto Rico are here reported, but large plantations and propaganda to create a demand for the shoots would be necessary to establish them as items of diet in America.     

Serotonin Depletion Does not Modify the Short-Term Brain Hypometabolism and Hippocampal Neurodegeneration Induced by the Lithium–Pilocarpine Model of Status Epilepticus in Rats

It has been reported that fluoxetine, a selective serotonin (5-hydroxytryptamine; 5-HT) reuptake inhibitor, has neuroprotective properties in the lithium–pilocarpine model of status epilepticus (SE) in rats. The aim of the present study was to investigate the effect of 5-HT depletion by short-term administration of p-chlorophenylalanine (PCPA), a specific tryptophan hydroxylase inhibitor, on the brain hypometabolism and neurodegeneration induced in the acute phase of this SE model. Our results show that 5-HT depletion did modify neither the brain basal metabolic activity nor the lithium–pilocarpine-induced hypometabolism when evaluated 3 days after the insult. In addition, hippocampal neurodegeneration and astrogliosis triggered by lithium–pilocarpine were not exacerbated by PCPA treatment. These findings point out that in the early latent phase of epileptogenesis, non-5-HT-mediated actions may contribute, at least in some extent, to the neuroprotective effects of fluoxetine in this model of SE.     

Environmental vibrio phage–bacteria interaction networks reflect the genetic structure of host populations

Phages depend on their bacterial hosts to replicate. The habitat, density and genetic diversity of host populations are therefore key factors in phage ecology, but our ability to explore their biology depends on the isolation of a diverse and representative collection of phages from different sources. Here, we compared two populations of marine bacterial hosts and their phages collected during a time series sampling program in an oyster farm. The population of Vibrio crassostreae, a species associated specifically to oysters, was genetically structured into clades of near clonal strains, leading to the isolation of closely related phages forming large modules in phage–bacterial infection networks. For Vibrio chagasii, which blooms in the water column, a lower number of closely related hosts and a higher diversity of isolated phages resulted in small modules in the phage–bacterial infection network. Over time, phage load was correlated with V. chagasii abundance, indicating a role of host blooms in driving phage abundance. Genetic experiments further demonstrated that these phage blooms can generate epigenetic and genetic variability that can counteract host defence systems. These results highlight the importance of considering both the environmental dynamics and the genetic structure of the host when interpreting phage–bacteria networks.     

Relation between Belief and Performance in Perceptual Decision Making

In an uncertain and ambiguous world, effective decision making requires that subjects form and maintain a belief about the correctness of their choices, a process called meta-cognition. Prediction of future outcomes and self-monitoring are only effective if belief closely matches behavioral performance. Equality between belief and performance is also critical for experimentalists to gain insight into the subjects'' belief by simply measuring their performance. Assuming that the decision maker holds the correct model of the world, one might indeed expect that belief and performance should go hand in hand. Unfortunately, we show here that this is rarely the case when performance is defined as the percentage of correct responses for a fixed stimulus, a standard definition in psychophysics. In this case, belief equals performance only for a very narrow family of tasks, whereas in others they will only be very weakly correlated. As we will see it is possible to restore this equality in specific circumstances but this remedy is only effective for a decision-maker, not for an experimenter. We furthermore show that belief and performance do not match when conditioned on task difficulty – as is common practice when plotting the psychometric curve – highlighting common pitfalls in previous neuroscience work. Finally, we demonstrate that miscalibration and the hard-easy effect observed in humans'' and other animals'' certainty judgments could be explained by a mismatch between the experimenter''s and decision maker''s expected distribution of task difficulties. These results have important implications for experimental design and are of relevance for theories that aim to unravel the nature of meta-cognition.     

Allosteric effects of monoclonal antibodies on human growth hormone

We have previously shown that a monoclonal antibody (MAb) recognizing the human growth hormone (hGH) antigenic domain left exposed after binding to lactogenic receptors enhanced hGH binding probably through allosteric effects on the hormone binding site. Since receptors displaying different specificities would not recognize exactly the same hGH region, we explored whether some of our MAb could affect hGH binding to somatogenic receptors from rabbit liver and to human liver hGH-specific receptors.The effect of MAbAE5, AC8 and F11 on hGH binding was measured by determining the formation of¹²⁵I-MAb:hGH:receptor complexes using two different experimental approaches. Results from procedure A, which involved the previous binding of the hormone to microsomes before adding¹²⁵I-MAb, indicated that the hGH domain defined by epitopes AE5, AC8 and F11 is uncovered in the various hormone:receptor complexes.Procedure B was devised to reveal any alteration in the hGH molecule induced by the MAb. In this case preformed¹²⁵I-MAb:hGH complexes were added to microsomes. Data showed that¹²⁵I-MAb AE5:hGH complexes bound better to the various receptors than¹²⁵I-MAb AE5 to hGH:receptor complexes. On the contrary, hGH previously bound to¹²⁵I-MAb AC8 or¹²⁵I-MAb F11 was less recognized by the receptors than the free hormone. Furthermore, binding of MAb AE5 or MAb F11 to hGH 20 K (a natural hGH variant lacking residues 32–46) also enhanced its affinity to the various receptors whereas MAb AC8 did not inhibit hGH 20 K binding.Results indicated that MAb recognizing the hGH antigenic area that remains unmasked after binding to different membrane-bound receptors are able to affect hormone binding site. MAb would induce either positive or negative allosteric changes in the hormone region involved in its binding to lactogenic, somatogenic and hGH-specific receptors.