Different precipitin reactions of theAbrus precatorius lectin

Summary Different precipitin reactions of theAbrus precatorius plant lectin with various galactan-polysaccharides are described and compared with a number of other anti-galactose lectins from different sources.     

Role of ascorbic acid on testicular degeneration in alloxan diabetic rats

Résumé On a observé que l'atrophie degénérative des testicules de rats atteints de diabète provoqué par l'alloxane peut être corrigée par un traitement d'acide ascorbique (vitamine C) administré en hautes doses.     

Effect of emetine on certain aspects of protein metabolism

Résumé Le contenu de protéine, de RNA et de DNA dans les tissus de foie, de cur et de rognon a été étudié chez des rats albinos traités à l'émétine. Le traitement a réduit la concentration de la protéine et du DNA dans le foie et dans le rognon. Dans le cur, cette concentration ne fut pas altérée d'une maniére significative. On suggère que l'émétine non settlement empÊche la synthèse de la protéine, mais réduit aussi sa désagrégation.     

1Alpha,25-dihydroxyvitamin D3 inhibits hepatic chromosomal aberrations, DNA strand breaks and specific DNA adducts during rat hepatocarcinogenesis

The possible promoting effect of streptozotocin (STZ; 65 mg/kg body weight, intraperitoneal)-induced diabetes during 2-acetylaminofluorene (2-AAF; 0.04% in basal diet)-initiated hepatocarcinogenesis and modulatory effect of 1α,25-dihydroxyvitamin D₃ (VD₃; 0.3 μg/0.1 ml in propylene glycol, per os) were investigated by monitoring chromosomal aberrations (CAs), DNA strand breaks and specific DNA adducts in rat liver. VD₃ treatment (twice a week) was started 4 weeks before the 2-AAF regimen and continued throughout the study. Aberrant metaphase chromosomes were counted from the regenerating hepatocytes 15, 30 or 45 weeks after STZ injection, while DNA strand break and adduct assays were performed 45 days post-STZ treatment. Dietary exposure to 2-AAF elicited a substantial increase in CAs and elevated the extent of DNA strand breaks and formation of N-(deoxyguanosin-8-yl)-2-aminofluorene. A promoting effect of STZ was evident from CAs coupled with DNA strand break analysis. VD₃ treatment substantially reducted 2-AAF+STZ-induced CAs as well as DNA strand breaks and adducts. Thus, VD₃ appears to be effective in suppressing liver-specific early chromosomal as well as DNA damage during the process of rat hepatocarcinogenesis initiated with 2-AAF and promoted by STZ contributing to its promise as a cancer chemotherapeutic agent. Received 27 April 2001; accepted 22 May 2001     

The surface glycopeptidolipids of mycobacteria: structures and biological properties

One of the most important opportunistic pathogens associated with acquired immunodeficiency syndrome (AIDS) is the M. avium complex. M. avium infections are found in up to 70% of individuals in advanced stages of AIDS. It is apparent that M. avium can replicate in host macrophages and persist for long periods. This group of mycobacteria are distinguished by the presence of unique, highly antigenic, surface-located lipids known as the glycopeptidolipids (GPLs). The GPLs are the chemical basis of the 31 distinct serovars of the M. avium complex, and have also been identified in some other species. The M. avium lipids are immunosuppressive and can induce a variety of cytokines that affect general host responses. Despite extensive chemical characterization of the structures of these GPLs, much work is needed to elucidate the molecular mechanism involved in this complex glycosylation pathway and its genetic basis. The challenges for the future lie in explaining the roles of these copious products in the intracellular life and infectivity of mycobacteria. The intention of our review is to offer a concise account of the structures of the M. avium lipids, their putative roles in the host responses, bacterial physiology and pathogenesis, particularly in immunocompromised patients such as those infected with human immunodeficiency virus (HIV). Advances in chemical synthesis of the various haptenic oligosaccharides are also given to demonstrate how these have helped to define the immunogenic determinants. We believe that future research should involve the creation of conditional mutants defective in these lipids for both functional and biosynthesis studies which will complement biological assays using chemically defined or modified neoglycoconjugates. Received 7 May 2001; received after revision 28 June 2001; accepted 28 June 2001     

Inverse relationship between melanogenesis and endogenous hydroquinone

Summary Inhibition or stimulation of melanogenesis have been found to occur as a result of the alteration of hydroquinone levels in the body. Substances which stimulate melanogenesis are found to lower the level of hydroquinone in amphibia, and evidence for the relationship is also given by mammalian experiments.Acknowledgments. The authors wish to thank Dr S. C. Bhattacharyya and Dr A. K. Barua, Bose Institute, for their interest in the work. The work was partly supported by the Council of Scientific and Industrial Research, New Delhi.     

Gamma-glutamyl-transpeptidase in lymphatic tissues of Mastomys natalensis during an infection with Acanthocheilonema viteae

During Acanthocheilonema viteae infection, the specific activity of gamma-glutamyltranspeptidase (gamma-GT) increased in peritoneal exudate cells and bone marrow and decreased in lymph nodes of Mastomys natalensis throughout the course of infection. However, though there was an increase in specific activity of gamma-GT in thymus and spleen during the prepatent phase of A. viteae infection, the level either returned to normal or decreased during the latent phase of infection. A close correlation was observed between the host's immune status during A. viteae infection and the level of gamma-GT in lymphoid tissues.     

Binding of actinomycin D and divalent cations to lipopolysaccharides ofAgrobacterium tumefaciens as studied by fluorescence spectroscopy

Summary The binding of actinomycin D and divalent cations to lipopolysaccharides ofA. tumefaciens was studied. Fluorimetric titrations revealed 2 binding sites (low and high affinity sites) for divalent cations, and 1 high-affinity site for actinomycin D.Acknowledgment. This project was financed by the Department of Science and Technology, Govt. of India (grant No. D.O. No.11 (19)/77-SERC). To whom reprint requests should be addressed.