The Gene Encoding the Heat-Stable Enterotoxin of Vibrio cholerae Is Flanked by 123-Base Pair Direct Repeats

The heat-stable enterotoxin (O1-ST) gene (sto) was cloned from chromosome of the strain GP156 of Vibrio cholerae O1 (Inaba, El Tor) in Escherichia coli K-12, and its nucleotide seqence was determined. The nucleotide sequence of sto was very similar to that of NAG-ST gene (stn) of V. cholerae non-O1. Both sto and stn were flanked by 123-base pair direct repeats which had at least 93% homology to one another and included some inverted repeats. All the strains of V. cholerae, V. mimicus, V. metschnikovii, V. hollisae and Yersinia enterocolitica examined by colony hybridization had the direct repeat sequence regardless of ST-gene possession.     

The effects of hemorrhagic shock on thyrotropin-releasing hormone and its receptors in discrete regions of rat brain

The effects of hemorrhagic shock on thyrotropin-releasing hormone (TRH) levels and its receptors were studied in different regions of the rat brain. Rats were bled for 30 min from the left femoral artery, and their mean arterial pressure was kept at 40 mmHg for the following hour. The rats were killed by decapitation. Rat brains were immediately removed and dissected into 7 regions. Hemorrhagic shock decreased TRH significantly in the frontal cortex, septum, hippocampus, and hindbrain but TRH was not changed in the striatum, hypothalamus, and midbrain. Hemorrhagic shock significantly decreased TRH receptor binding in the septum and hindbrain. Scatchard analysis of saturation isotherms of specific TRH binding showed that the decreased specific TRH binding in the hindbrain resulted not from an increase of the dissociation constant (Kd), but from a decrease in the maximum number of binding sites (Bmax). In the septum, the decrease in specific binding was due both to a decrease in Bmax and an increase in Kd. The findings indicate that TRH plays a role in the physiological response to hemorrhagic shock.     

An efficient synthesis of methyl tetra-o-hexyl gentiooctaoside, an octaosyl analogue of ANP receptor antagonist HS-142-1

Methyl

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, a 3-O hexyl analogue of the octaosyl component of fungal lipooligosaccharide HS-142-1, was stereo- and regioselectively synthesized as a potent antagonist for the tetrameric atrial natriuretic peptide (ANP) receptors.     

DIVISION APPARATUS OF THE CHLOROPLAST IN NANNOCHLORIS BACILLARIS (CHLOROPHYTA)1

Chloroplast division in Nannochloris bacillaris Naumann (Chlorophyta) was examined by electron microscopy after preparation of samples by freeze-substitution. A pair of belts appeared on the surface of the outer and inner envelope membranes at the middle of the chloroplast. These belts seemed to be constructed of thin fibrils that run parallel to the longitudinal direction of the belts. The outer fibrillar belt increased in width as the constriction of the chloroplast advanced. It appears that the fibrillar belt is the division apparatus of the chloroplast. It encircles the chloroplast and finally divides the chloroplast in two as the diameter of the belt decreases.     

Influence of hydraulic retention time on anaerobic digestion of pretreated sludge

Continuous anaerobic digestion of waste activated sludge pretreated at low temperatures below 100°C increased methane generation by 30%. pH values of the digestion mixture increased, approximately from 0.3 to 0.55 by pretreatment, although its volatile fatty acids concentration was greater than the control. An abrupt increase in propionate : acetate ratio in digestion stage (e.g. from less than 1:1 to over 3.5 :1), provided a reliable indicator for impending failure.This revised version was published online in October 2005 with corrections to the Cover Date.     

Primary structure and properties of the Na+/glucose symporter (Sg1S) of Vibrio parahaemolyticus.

Previously, we cloned and sequenced a DNA fragment from Vibrio parahaemolyticus and found four open reading frames (ORFs). Here, we clearly demonstrate that one of the ORFs, ORF1, is the gene (sglS) encoding a Na+/glucose symporter (SglS). We characterize the Na+/glucose symporter produced in Escherichia coli mutant (JM1100) cells which lack original glucose transport activity and galactose transport activity. We also show that phlorizin, a potent inhibitor of the SGLT1 Na+/glucose symporter of animal cells, inhibited glucose transport, but not galactose transport, via the SglS system.     

A single amino acid substitution within the mature sequence of ornithine aminotransferase obstructs mitochondrial entry of the precursor.

We describe here evidence of congenital enzyme mistargeting induced not by abnormalities in the signal sequence. We examined the molecular mechanism of hereditary ornithine aminotransferase (OAT) deficiency causing gyrate atrophy of the choroid and retina (GACR). Nucleotide sequencing of OAT cDNA generated from a GACR patient's mRNA revealed a single base change from C to G at position 268, resulting in an amino acid substitution of neutral Gln(CAA) with negatively charged Glu(GAA) at position 90 (Q90E). Immunohistochemical and transient expression analyses suggested expression of a defective labile OAT in the patient's tissues. However, high-level expression and immunocytochemical analyses elucidated that Q90E OAT (the patient's OAT) was localized within the limits of cytoplasmic free ribosomes in precursor form without any mitochondrial entry, indicating that the patient's precursor OAT was synthesized and rapidly degraded because of accumulation in the cytosol. It is interesting that, although the mutation site (Q90E) in this GACR patient's OAT was within the coding sequence of the mature protein, the precursor exhibited loss of mitochondrial targeting function. These findings suggest that not only the signal sequence but a critical part of the mature sequence plays an essential role in mitochondrial entry of the OAT precursor protein.