A Ser315Thr substitution in KatG is predominant in genetically heterogeneous multidrug-resistant Mycobacterium tuberculosis isolates originating from the St. Petersburg area in Russia

Parts of katG and rpoB from 27 Russian Mycobacterium tuberculosis isolates were sequenced to detect mutations causing resistance to isoniazid (INH) and rifampin (RMP), respectively. All 24 INH-resistant isolates had a mutated katG, and 22 of them (91.7%) carried a mutation coding for a Ser315Thr shift. An rpoB mutation was noted for each of the 21 RMP-resistant isolates, with Ser531Leu being the most prevalent change encoded. Only two isolates had identical IS6110 fingerprints.     

Tachykinin NK1 receptor antagonists enhance stress-induced c-fos in rat locus coeruleus

These experiments tested the hypothesis that substance P neurotransmission at tachykinin NK1 receptors in the locus coeruleus is involved in stress-induced activation of the locus coeruleus, using c-fos as an index of activation. Selective tachykinin NK1 receptor antagonists administered systemically did not result in substantial locus coeruleus c-fos expression. Restraint stress resulted in a large number of locus coeruleus c-fos expressing cells. Administration of two selective tachykinin NK1 receptor antagonists prior to restraint resulted in an increase in the number of locus coeruleus c-fos expressing cells, compared to restraint alone. These results suggest that the enhanced c-fos expression observed in response to tachykinin NK1 receptor antagonists combined with stress, could be due to the blockade of tachykinin NK1 receptor-mediated activity at sites other than the locus coeruleus, resulting in an overall activation of the locus coeruleus.     

A novel peptide-grafted liposomal delivery system targeted to macrophages

Insulin-like growth factor II (IGF-II) is highly expressed during hepatocarcinogenesis (P. Schirmacher et al., Cancer Res., 52: 2549-2556, 1992; B. C. Park et al., J. Hepatol., 22: 286-294, 1995). However, the mechanism of its enhanced expression is largely unknown. In this study, we show that IGF-II mRNA levels are increased within six h of exposing human hepatoma cell cultures to hypoxia, suggesting that hypoxia may be a strong stimulus for the induction of IGF-II expression in the process of hepatocarcinogenesis. This finding and the fact that hepatocellular carcinoma (HCC) is a typical hypervascular tumor (M. Mise et al., Hepatology, 23: 455-464, 1996) imply that IGF-II may play an important role in the development of neovascularization of HCC. Here we demonstrate that IGF-II substantially increases vascular endothelial growth factor (VEGF) mRNA and protein levels in a time-dependent manner in human hepatoma cells. The induction of VEGF by IGF-II was additively increased by hypoxia. Moreover, the direct angiogenic activity of IGF-II was observed in the quantitative chick chorioallantoic membrane assay (M. Nguyen et al., Microvasc. Res., 47: 31-40, 1994). These data suggest that IGF-II may be a hypoxia-inducible angiogenic factor in HCC.     

Schistosoma mansoni: an enkephalinergic system that may participate in internal and host-parasite signaling

The present study is concerned with an opioid system in the human trematode Schistosoma mansoni, both as part of the endogenous chemical messenger system and as a tool in the parasite reaction to the host(s). A high-affinity opioid binding site was characterized in membrane suspensions prepared from adult worms. Scatchard analysis revealed a single class of receptors with a dissociation constant of 1.8 nM and a Bmax of 24.9 pmol/g protein for (D-Ala2, Met5)-enkephalin (DAME). The displacement experiments demonstrated that the most potent ligands were beta-endorphin, DAME, and met-enkephalin. These characteristics and the effects of various ions on DAME affinity suggest that S. mansoni has a delta-like opioid receptor, as previously described in other invertebrates. A met-enkephalin-like peptide was also characterized in a miracidial extract. Radioimmunoassay, reverse-phase HPLC, and bioassay by induction of cell conformational changes of human polymorphonuclear leukocytes revealed that the parasite peptide is very similar to authentic met-enkephalin. A met-enkephalin-like peptide was also shown to be present in adult worms and in their incubation medium. Taken together, these observations demonstrate the existence of a complete opiate system in S. mansoni. We discuss its role in molecular signaling within the parasite and in host-parasite interactions.     

High resolution slab gel electrophoresis of 8-amino-1,3, 6-pyrenetrisulfonic acid (APTS) tagged oligosaccharides using a DNA sequencer

A novel electrophoretic method for the analysis of oligosaccharides using DNA sequencer technology is illustrated using malto-oligosaccharide distributions obtained following isoamylase digestion of glycogen, wheat starch and potato starch. The debranched starches were derivatized at the reducing and with the charged fluorophore 8-amino-1,3,6-pyrenetrisulfonic acid (APTS). This highly reproducible method provides baseline resolution of oligomers from chain lengths of 3 to more than 80 glucose units, and exhibits high sensitivity with detection thresholds of one femtomole per resolved band. In addition, the reductive amination procedure attaches a single fluorophore per oligosaccharide, allowing calculation of the results on either a mass or a molar basis. The efficacy of the method is illustrated through the determination of the profile of individual oligosaccharides of chain length with a degree of polymerization (DP) < 80, derived from loading less than 15 ng per analysis of glycogen, wheat and potato starches. While the results obtained were superior in resolution and sensitivity to previously reported observations using a range of techniques, they were nonetheless consistent with the overall differences between these polysaccharides. The resolution, sensitivity, reproducibility and high throughput of the method provides substantial advantages over existing methods for the analysis of linear oligosaccharide chain length distributions.