Immobilized α-amylase from Bacillus licheniformis: a potential enzymic time—temperature integrator for thermal processing

Biphasic and nth-order models were tested as to their usefulness to fit experimental inactivation data of Bacillus licheniformis α-amylase, immobilized on glass beads, and were discussed with respect to their suitability to characterize the considered enzymic system as a time—temperature integrator (TTI) to evaluate heat processes. Both isothermal and non-isothermal inactivation experiments were carried out. Model (kinetic) parameters (rate constant k, activation energy E_A and reaction order n) were estimated using a non-linear regression procedure. The results obtained, especially the activation energy of about 293 kJ mole^–1, indicated a potential use of this system as a TTI for heating processes in the temperature range of 96–108°C.     

Characterization of the intracellular GLUT-4 compartment

Learned behaviors and tolerance to ethanol can be maintained by peripheral injection of arginine8-vasopressin (vasopressin) under conditions in which they would otherwise be lost. However, the sites of this action in the brain have not been clearly identified. Using a polyclonal antibody raised against Fos and Fos-like proteins, we have demonstrated increases in immunoreactive Fos and Fos-like proteins in the suprachiasmatic, supraoptic and paraventricular nuclei of the hypothalamus, and lesser increases in piriform cortex and amygdala, of the rat 2 h after a s.c. injection of vasopressin. Our results suggest that the exogenous vasopressin may exert its central action by activating a cellular immediate early gene in specific brain regions.     

A novel miniature multilayer MMIC CPW single side band CPW mixer for up conversion at 44.5 GHz

This letter presents the results of a novel miniature single sideband (SSB) subharmonic direct upconverter GaAs MMIC developed in multilayer coplanar waveguide. The mixer uses 50 MHz I and Q signals to directly modulate the second harmonic of a 22.25 GHz carrier, producing the required 44.55 GHz RF output. Two pairs of antiparallel diodes reduce feedthrough of the fundamental 22.25 GHz signal to the RF output while novel coplanar waveguide/asymmetric coplanar stripline, centre conductor based structures provide matching. This 1.7/spl times/1.7 mm/sup 2/ chip also uses a previously developed, reduced size Wilkinson divider based on asymmetric coplanar stripline and a reduced size three-dimensional 90/spl deg/ coupler.     

Palatability of prerigor cooked boar meat

Cooking reduces odor intensity in boar meat but also may induce lipid oxidation unless the meat pH is above approximately 6.0. This research was designed to determine the feasibility of cooking boar meat in the prerigor state to overcome boar odor and lipid oxidation problems. Prerigor and postrigor triceps brachii muscle samples from 40 boars (20 Duroc and 20 Yorkshire) were cooked to 60 degrees C, frozen and stored at -20 degrees C, reheated in a 60 degrees C water bath for 1 h, and then subjected to pH, thiobarbituric acid (TBA), and sensory analyses. Boar odor intensity and skatole concentration in backfat samples were determined by olfactory test and HPLC, respectively. Cooked (initial cooking) prerigor meat was found to have higher (P < .05) pH and lower (P < .05) TBA values than comparable postrigor meat (6.44 vs 6.09 and 2.15 vs 3.23, respectively). Regression analysis indicated an inverse relationship between pH and TBA values (r = -.52; P < .01). No appreciable changes in TBA values were noted after frozen storage for 14 to 98 d, but reheating increased TBA values (P < .05) in both prerigor and postrigor samples (3.45 vs 4.32, respectively). Sensory evaluation scores indicated that prerigor cooked meat was less tender with more pronounced rancid flavor than postrigor cooked meat (P < .05), but panelists may have allowed the toughness of the prerigor samples to adversely affect their flavor scores. No difference in boar odor was detected between rigor states or breeds. Mean skatole concentration in backfat was .12 micrograms/g and no difference was detected between breeds.(ABSTRACT TRUNCATED AT 250 WORDS)     

The complex pathology of trinucleotide repeats

The expansion of trinucleotide repeat sequences has now been shown to be the underlying cause of at least ten human disorders. Unifying features among these diseases include the unstable behavior of the triplet repeat during germline transmission when the length of the repeat exceeds a critical value. However, the trinucleotide repeat disorders can be divided into two distinct groups. Type I disorders involve the expansion of CAG repeats, which encode an expanded polyglutamine, inserted into the open-reading frame of a gene that is usually quite broadly expressed. Recently, mouse models for type I disorders have been developed and the basis of pathology is under study, both in these models and through biochemical and cell biological approaches. The type II disorders involve repeat expansions in noncoding regions of genes. The mechanisms by which these repeat expansions lead to pathology may be quite diverse.     

Calcium-sensitive calcium influx in photoreceptor inner segments

The effect of external calcium concentration ([Ca2+]o) on membrane potential-dependent calcium signals in isolated tiger salamander rod and cone photoreceptor inner segments was investigated with patch-clamp and calcium imaging techniques. Mild depolarizations led to increases in intracellular Ca2+ levels ([Ca2+]i) that were smaller when [Ca2+]o was elevated to 10 mM than when it was 3 mM, even though maximum Ca2+ conductance increased 30% with the increase in [Ca2+]o. When external calcium was lowered to 1 mM [Ca2+]o, maximum Ca2+ conductance was reduced, as expected, but the mild depolarization-induced increase in [Ca2+]i was larger than in 3 mM [Ca2+]o. In contrast, when photoreceptors were strongly depolarized, the increase in [Ca2+]i was less when [Ca2+]o was reduced. An explanation for these observations comes from an assessment of Ca2+ channel gating in voltage-clamped photoreceptors under changing conditions of [Ca2+]o. Although Ca2+ conductance increased with increasing [Ca2+]o, surface charge effects dictated large shifts in the voltage dependence of Ca2+ channel gating. Relative to the control condition (3 mM [Ca2+]o), 10 mM [Ca2+]o shifted Ca2+ channel activation 8 mV positive, reducing channel open probability over a broad range of potentials. Reducing [Ca2+]o to 1 mM reduced Ca2+ conductance but shifted Ca2+ channel activation negative by 6 mV. Thus the intracellular calcium signals reflect a balance between competing changes in gating and permeation of Ca2+ channels mediated by [Ca2+]o. In mildly depolarized cells, the [Ca2+]o-induced changes in Ca2+ channel activation proved stronger than the [Ca2+]o-induced changes in conductance. In response to the larger depolarizations caused by 80 mM [K+]o, the opposite is true, with conductance changes dominating the effects on channel activation.     

Synthesis of (R,S)-10-methyloctadecanoic acid (tuberculostearic acid) and key chiral 2-methyl branched intermediates

Tuberculostearic acid, (R)-10-methyloctadecanoic acid, is a characteristic component of pathogenic mycobacteria and related organisms. Sensitive detection of this acid in infected material allows rapid detection of mycobacterial disease. A novel, convergent synthesis of tuberculostearic acid and key chiral intermediates is described in this communication, to provide a reference compound. Racemic and (R)- and (S)-1-iodo-2-methyldecanes were synthesised from 1-octanal and 1-carboethoxyethylidenetriphenylphosphorane as initial starting materials. 1-Hydroxyoct-7-yne was made from 1,6-hexanediol by two alternative methods and coupled with the above racemic iodide. Hydrogenation and oxidation of the resulting (R,S)-10-methyloctadec-7-yn-1-ol gave racemic tuberculostearic acid.