N.m.r. study on the formation and geometry of inclusion complexes of 6-O-(alpha-maltosyl)cyclomalto-hexaose and -heptaose with p-nitrophenol in aqueous solution.

The formation and molecular geometry of inclusion complexes of some branched cyclomaltaoses with p-nitrophenol in aqueous solution have been investigated by using high-resolution 1H-n.m.r. spectroscopy. 6-O-(alpha-Maltosyl)cyclomalto-hexaose and -heptaose were found to form 1:1 inclusion complexes with p-nitrophenol, and the dissociation constants for their complexes are quite similar to those for corresponding unbranched cyclomaltaose-p-nitrophenol complexes, indicating that formation of these inclusion complexes is not hampered by the maltosyl branch. From measurement of nuclear Overhauser enhancements, it was concluded that the maltosyl branch is not situated over the entrance of the cavity.     

Effect of polymyxin B on liposomal membranes derived from Escherichia coli lipids

The specificity of the action of polymyxin B was studied using liposomes as a model membrane system. Liposomes prepared from total lipids of Gram-negative bacteria Escherichia coli, a mixture of purified E. coli phosphatidylethanolamine and cardiolipin and a mixture of phosphatidylethanolamine and phosphatidylglycerol, were extremely sensitive to polymyxin while those prepared from lipids of Gram-positive bacteria Streptococcus sanguis, lipids of sheep erythrocyte membranes, mixtures of egg lecithin and negatively charged amphiphatic molecules, were less sensitive to the action of the antibiotic. Chlolesterol was shown to suppress the polymyxin-induced response in liposomes.     

Genetic studies of the leptin receptor gene in morbidly obese French Caucasian families

Family studies have shown that in some populations up to 75% of the variation of body mass index can be explained by genetic factors. However, in humans, no major obesity gene has been identified to date. In contrast, there are a number of genetically well defined animal models for obesity. In two of those models (ob/ob and db/db), defects in the same pathway are responsible for obesity. Recently, some evidence has been found for the OB gene also being involved in human obesity. In this study we investigated the potential role of the OB receptor (OBR) in the etiology of massive obesity in humans using familial linkage analyses and case-control association studies. The typing of two microsatellite markers (D1S198 and D1S209), flanking the OBR gene, in 256 sib pairs showed no evidence for linkage with obesity. In order to be able to detect small gene effects, association studies with a 3′-UTR insertion/deletion polymorphism were carried out. The results of these analyses remained non-significant (χ² = 3.442, P = 0.18). However, subjects heterozygous for the insertion/deletion polymorphism showed a slight trend towards lower insulin values 30 min after an oral glucose load compared to homozygous individuals (P = 0.02). In summary, our results do not support a major role of the human OBR gene in the development of morbid obesity in our population. Received: 4 December 1996 / Accepted: 25 June 1997     

Comparison of lethal mutations of Drosophila melanogaster with D. simulans when detected by the attached-X method.

The purpose of this study was to evaluate the attached-X method compared with the standard Basc method, and, using this method, to find out whether the observed differences in genetic polymorphisms are related to differences in lethal mutation rates in D. melanogaster and D. simulans. When EMS-treated Drosophila melanogaster males are mated to untreated attached-X females, a decrease in the progeny sex ratio (male/female + male) is observed due to the induced lethal mutations on the X chromosome. The decrease in the frequency of male progeny were shown as the attached-X index. The expected male number is calculated from the control sex ratio. The difference between the expected and the observed male numbers, expressed as the ratio to the expected male number, defines the attached-X index. The index values for various EMS concentrations were compared to the lethal frequencies obtained by the standard Basc method for the same EMS treatments, and gave a highly positive correlation (gamma = 0.993, p < 0.01, d.f. = 2), thus providing an alternative method for evaluation of possible mutagens. The attached-X method was applied to D. simulans, of which natural populations are known to have relatively low genetic variation, and frequencies of the EMS-induced X chromosome lethal mutations were estimated and compared with those in D. melanogaster. The results indicate that D. melanogaster is slightly more sensitive in the sperm and spermatogonial stages, but less susceptible in the spermatid stage when compared with D. simulans.(ABSTRACT TRUNCATED AT 250 WORDS)     

Mechanism of polymorphonuclear leukocytes accumulation examined using inhibitors of complement and arachidonic acid cascade in rats treated with OK-432

When the streptococcal preparation OK-432 was intraperitoneally injected for the treatment of carcinomatous peritonitis, antitumor polymorphonuclear leukocytes (PMNs) accumulated in the peritoneal cavity. We examined the mechanism of this PMN accumulation using an in vivo system in rats. FUT-175, EDTA and K76 inhibited C5a generation by OK-432 in vitro, but EGTA, prednisolone and inhibitors of arachidonic acid cascade did not. In in vivo experiments, EDTA, FUT-175, antirat C3 serum and K76 reduced the accumulation of PMNs onto filter membranes, when these reagents were reacted with OK-432 for 3 h through filter membranes placed on the turned rat peritoneum. EGTA failed to inhibit PMN accumulation. Prednisolone, indomethacin, OKY046 and AA861 inhibited PMN accumulation in a dose-dependent manner. These inhibitions of PMN accumulation were confirmed by histological examination. It was concluded that complement-derived chemotactic factor C5a generated by OK-432 induced PMN accumulation in association with chemotactic arachidonic acid metabolites.     

The AtXTH28 Gene, a Xyloglucan Endotransglucosylase/Hydrolase, is Involved in Automatic Self-Pollination in Arabidopsis thaliana

Successful automatic self-pollination in flowering plants isdependent on the correct development of reproductive organs.In the stamen, the appropriate growth of the filament, whichlargely depends on the mechanical properties of the cell wall,is required to position the anther correctly close to the stigmaat the pollination stage. Xyloglucan endotransglucosylase/hydrolases(XTHs) are a family of enzymes that mediate the constructionand restructuring of xyloglucan cross-links, thereby controllingthe extensibility or mechanical properties of the cell wallin a wide variety of plant tissues. Our reverse genetic analysishas revealed that a loss-of-function mutation of an ArabidopsisXTH family gene, AtXTH28, led to a decrease in capability forself-pollination, probably due to inhibition of stamen filamentgrowth. Our results also suggest that the role of AtXTH28 inthe development of the stamen is not functionally redundantwith its closest paralog, AtXTH27. Thus, our finding indicatesthat AtXTH28 is specifically involved in the growth of stamenfilaments, and is required for successful automatic self-pollinationin certain flowers in Arabidopsis thaliana.