Chiral recognition in dipeptides containing 1-aminocyclopropane carboxylic acid or alpha-aminoisobutyric acid: NMR studies in solution

Protected dipeptides containing 1-aminocyclopropane carboxylic acid (Ac3c) or alpha-aminoisobutyric acid (Aib) residues at the C-terminus and Phe, Val or Ala residues at the N-terminus displayed different proton NMR spectra for the pure enantiomers and the racemic mixtures in deuterochloroform (CDCl3) solution. An unequal mixture of enantiomers showed two sets of resonances (NMR nonequivalence), one corresponding to major and the other to minor enantiomer. The NMR nonequivalence was originated by the presence of the C-terminal Ac3c or Aib residues, which have been known for their unique spatial preferences in avoiding an extended (C5) conformation. When a C5 conformation favoring residue such as glycine was incorporated in place of Ac3c or Aib, negligible NMR nonequivalence was observed. The magnitude of the NMR nonequivalence depended on the side chain as well as on the protecting groups at N-terminus alpha-amino acid. For the same peptide, the magnitude of nonequivalence increased with increasing solution concentration and/or with decreasing the solution temperature. The NMR nonequivalence disappeared in polar solvent-like deuterated dimethylsulfoxide (DMSO-d6). A preference for hetero-chiral recognition leading to dimeric association under fast exchange conditions had been invoked to explain the observed phenomenon. The dipeptides thus prepared could well serve as 'model peptides' for the evaluation of any preparative methods.

Evaluation of lambdacyhalothrin-impregnated bednets in a malaria endemic area of India. Part 3. Effects on malaria incidence and clinical measures

In Indian villages with high malaria endemicity use of nylon bednets treated at 25 mg/m2 at 6-month intervals for 3 years caused significant reductions in malaria incidence, slide positivity rate, slide falciparum rate, annual parasite index, and parasite rate in the entire population, as well as reductions in rates of splenomegaly and anemia in children. In villages with untreated nets, considerable reduction also occurred in these parameters except for the rate of splenomegaly. In the village without nets, a relatively small drop occurred in the parasite rate and anemia but no change occurred in malaria incidence, and an increase occurred in the rate of splenomegaly. The trial thus showed the efficacy of impregnated bednets against malaria in the forested hills of Orissa State where the existing control strategy based on indoor residual spraying of DDT has remained incapable of interrupting malaria transmission.

The MCM16 gene of the yeast Saccharomyces cerevisiae is required for chromosome segregation

We have cloned and characterized the MCM16 gene required for the maintenance of minichromosomes in the yeast Saccharomyces cerevisiae. This gene corresponds to a 181-amino acid ORF, YPR046W, on chromosome XVI. Mutant cells carrying minichromosomes accumulate them in higher copy numbers than do wild-type cells. Intact dicentric plasmid could be recovered from the mutant, in contrast to the wild-type, in which the plasmid suffered frequent deletions. A wild-type centromere, CEN6, acts as a block to the transcription of a reporter gene, such as beta-galactosidase. This block was less effective in the mutant than in the wild-type strain, suggesting alterations in kinetochore assembly in the former. The mutant also showed increased sensitivity to the antimitotic drugs benomyl and thiabendazole. The mcm16 mutation caused a high rate of loss of chromosome III, without any significant increase in the recombination frequency. A strain carrying a deletion-disruption derivative of the MCM16 gene was viable and, when compared to the wild-type, did not show any significant changes in growth rate or cell morphology at 16, 23 and 37 degrees C. These properties show that MCM16 is required for an important but nonessential role that governs the kinetochore-microtubule mediated process of chromosome segregation.

Influence of chemical modification of cysteine and histidine side chains upon subunit reassembly of alpha crystallin

Alpha crystallin, the important multimeric structural protein of mammalian eye lens, is an assembly composed of 30 alpha-A and 10 alpha-B subunits. The influence of either partial or complete chemical modification of two important amino acid side chains, cysteine and histidine, upon the integrity of native alpha crystallin assembly and also upon the mode of subunit reassembly has been investigated. It has been found that chemical modification of surface-exposed cysteine and histidine side chains does not affect the subunit-subunit interactions stabilizing the native aggregate. Cysteine modifications, either partial or complete, unlike histidine modifications, do not seem to affect the backbone conformation of the subunits refolded after denaturation. Both cysteine and histidine modifications, however, affect the packing of the refolded structural elements forming the tertiary structure of the subunits and also the mode of oligomeric reorganization. The most striking effect of histidine modification is the considerable increase in size of the aggregates upon reassociation of the modified subunits. The chaperone activity, however, has been found to remain almost unaffected in spite of these chemical modifications.

Targets of oxidative stress in cardiovascular system

Although oxidants such as superoxide (O2.) and hydrogen peroxide (H2O2) play a role in host-mediated destruction of foreign pathogens yet excessive generation of oxidants may lead to a variety of pathological complications in the cardiovascular system. An important mechanism by which oxidants cause dysfunction of the cardiovascular system appears to be due to the increase in intracellular free Ca2+ concentration. Oxidants cause cellular Ca2+ mobilization by modulating activities of a variety of regulators such as Na+/H+ and Na+/Ca2+ exchangers, Na+/K+ ATPase and Ca2+ ATPase and Ca2+ channels that are associated with Ca2+ transport in the plasma membrane and the sarco(endo)plasmic reticular membrane of myocardial cells. Recent research have suggested that the increase in Ca2+ level by oxidants plays a pivotal role in inducing several protein kinases such as protein kinase C, tyrosine kinase and mitogen activated protein kinases. Oxidant-mediated alteration of different signal transduction systems and their interations eventually regulate a variety of pathological conditions such as atherosclerosis, apoptosis and necrosis in the myocardium.

Interaction of H(+)-ions with alpha-crystallin: solvent accessibility of ionizable side chains and surface charge

Interaction of H(+)-ions with alpha-crystallin from goat lens has been studied at three different ionic strengths using the potentiometric titration method. Titrations have also been carried out in the presence of 1.5 M and 6 M GuHCl (guanidine hydrochloride). The isoionic pH of the protein in water and the effect of KCl on it have been determined. Titration curves have been found to be reversible between pH 3 to 9.25 at all ionic strengths. To aid in the data analyses, the reactivities of alpha-crystallin lysine residues to trinitrobenzenesulfonic acid have been determined in this work. For alpha-crystallin aggregate, 130 +/- 2 histidine side chains out of a total of 300 and about 134 +/- 4 lysine side chains out of 310 have been found to be inaccessible to the solvent in the native condition. The remaining titratable side chains determine the surface charge of the native protein. In 1.5 M GuHC1, however, the nontitratable histidine side chains are found to be available for titration as are the nontitratable lysine and tyrosine side chains in 6M GuHC1. The theoretical titration curve computed on the basis of Linderstrøm-Lang model is found to fit quite comfortably with the experimental one between pH 4.6 and 9.25. The pKint value for beta gamma-carboxyl side chains has been found to be 5.18 which is somewhat higher than usual indicating that the carboxyl groups in the protein are probably in some constrained condition which is released in the presence of a denaturant. Below pH 4.6, there begins a conformational change in the alpha-crystallin aggregate as is corroborated from the circular dichroism studies. The value of electrostatic interaction factor w which remains more or less constant between pH 4.6 and 9.25 is also found to gradually fall off below pH 4.6.

Characterization of MboI satellites in Cirrhina mrigala and Clarias batrachus (Pisces)

We have cloned and characterized two highly reiterated, tandemly repeated, and A+T rich MboI DNA fragments, one in Cirrhina mrigala (Cyprinidae), with a monomer size of 266 bp, and one in Clarias batrachus (Clariidae), with a monomer size of 227 bp. The MboI fragment in C. mrigala is species-specific and absent in other carps, such as Catla catla and Labeo rohita. The MboI fragment in C. batrachus was also present in two other catfishes tested, namely Clarias gariepinus and Heteropneustes fossilis. In C, mrigala x C. catla and C. mrigala x L. rohita hybrids, the C. mrigala specific MboI fragment is inherited uniparentally. In the reciprocal hybrids of C. batrachus x H. fossilis, the satellite ladder contains the bands of both parental species. The MboI satellite of carp may be useful in genetic introgression analysis and that of catfish in distinguishing between gynogenetic progeny and true hybrids.

Chemical modifications and dissociation characteristics of tyrosine and tryptophan residues in alpha-crystallin

A quantitative estimation of surface accessibility of aromatic residues in alpha-crystallin from goat lens has been accomplished by chemical modifications using different specific reagents having varying sizes. Results of modification of tyrosine residues with N-acetylimidazole and tetranitromethane when combined with those of ionization studies carried out with hydroxyl ions having the smallest size reveal different classes of tyrosine residues in the native protein: 78 +/- 2 residues have been found to be easily available for modification; among the rest, 94 +/- 2 residues appear to be comparatively less exposed to the reagents while 28 +/- 2 residues are found to be completely unavailable for modification in the native protein and are modified only when the protein is denatured. Modification of tryptophan residues with H2O2 also indicates different classes of these residues available for oxidation at different concentrations of the oxidant. 34 +/- 2 residues of tryptophan are found to be easily oxidized at a lower concentration of H2O2 during the first phase of the reaction. The remaining tryptophan residues appear to be less exposed to the reagent. This is also corroborated from the studies of reactivities of these residues towards another specific but bulkier reagent, 2-hydroxy-5-nitrobenzyl bromide. These surface exposed aromatic residues in alpha-crystallin may be considered to be vulnerable to in vivo oxidative modifications forming insoluble aggregates which may finally contribute to the formation of cataract.

Involvement of p21racA, phosphoinositide 3-kinase, and vacuolar ATPase in phagocytosis of bacteria and erythrocytes by Entamoeba histolytica: suggestive evidence for coincidental evolution of amebic invasiveness

Trophozoites of Entamoeba histolytica, the protozoan parasite that causes amebic dysentery, phagocytose bacteria in the colonic lumen and erythrocytes (RBC) in host tissues. Because tissue invasion is an evolutionary dead end, it is likely that amebic pathogenicity is coincidentally selected, i.e., the same methods used to kill bacteria in the colonic lumen are used by parasites to damage host cells and cause disease. In support of this idea, the amebic lectin and pore-forming peptide are involved in binding and killing, respectively, bacteria and host epithelial cells. Here amebic phagocytosis of bacteria, RBC, and mucin-coated beads was disrupted by overexpression of E. histolytica p21(racA-V12), a ras-family protein involved in selection of sites of actin polymerization, which had been mutated to eliminate its GTPase activity. p21(racA-V12) transformants were also defective in capping and cytokinesis, while pinocytosis of fluorescent dextrans was not affected. Wortmannin, a fungal inhibitor of phosphoinositide 3-kinase, markedly inhibited phagocytosis of bacteria, RBC, and mucin-coated beads by wild-type amebae. In contrast to p21(racA-V12) overexpression, wortmannin abolished amebic pinocytosis of dextrans but had no inhibitory effects on capping. Inhibition of amebic vacuolar acidification by bafilomycin also decreased bacterial and RBC uptake. These results, which demonstrate similarities between mechanisms of phagocytosis of bacteria and RBC by amebae and macrophages, support the idea of coincidental selection of amebic genes encoding proteins that mediate destruction of host cells.

Seasonality of indoor resting anophelines in stone quarry area of District Allahabad, U.P

Alongitudinal study was conducted in four indicator villages of PHC Shankargarh, District Allahabad, U.P. from July 1991 to June 1992 to have information on seasonality of indoor resting anopheline species in silica sand/hard stone quarry area. Fourteen anopheline species namely, An. aconitus (0.35%), An. annularis (17.03%), An. barbirostris (0.09%), An. culicifacies (36.74%), An. fluviatilis (0.13%), An. nigerrimus (0.01%), An. pallidus (4.40%), An. splendidus (0.02%), An. stephensi (0.01%), An. subpictus (40.84%), An. tessellatus (0.15%), An. turkhudi (0.004%), An. vagus (0.20%) and An. varuna (0.02%) were collected. An. culicifacies, An. subpictus and An. annularis were found throughout the year. An. fluviatilis, An. pallidus, An. vagus and An. aconitus were also observed in all the seasons except extreme summer. However, An. barbirostris and An. splendidus were collected only in monsoon/post-monsoon and winter seasons. An. tessellatus and An. stephensi were recorded in winter and spring seasons. An. nigerrimus and An. varuna were recorded in winter, while An. turkhudi in spring. Prolonged high vector density may be attributed to the extended malaria transmission in this area.

Selective up-regulation of cytokine-induced RANTES gene expression in lung epithelial cells by overexpression of IkappaBR

We previously reported the cloning of a cDNA for IkappaBR (for IkappaB-related) from human lung alveolar epithelial cells. IkappaBR is related to the IkappaB proteins that function as regulators of the NF-kappaB family of transcription factors. Here, we investigated the consequence of IkappaBR overexpression on the expression of NF-kappaB-regulated chemokine genes in lung alveolar epithelial cells. Chemokines play an important role in many inflammatory diseases such as asthma and AIDS. Overexpression of IkappaBR in the lung cells resulted in a rapid 50-100-fold greater production of the RANTES (regulated upon activation, normal T expressed and presumably secreted) protein upon cytokine-induction compared with control cells. IkappaBR overexpression, however, did not enhance interleukin-8 or MIP-1alpha gene expression, despite the fact that the expression of all three chemokine genes are regulated by NF-kappaB. The up-regulation of RANTES gene expression resulting from overexpression of IkappaBR correlated with increased amounts of a unique RANTES-kappaB binding activity and decreased binding of p50 homodimers. Previous studies have shown that p50 homodimers function as repressors of certain kappaB sites. Our studies suggest that IkappaBR can aid activation of select NF-kappaB-regulated genes by sequestering p50 homodimers.

Airborne aflatoxin in the grain processing industries in India

Airborne aflatoxin generated in rice and maize processing plants was assayed by an indirect competitive enzyme-linked immunosorbent assay. In the rice mill, levels of airborne aflatoxin were always higher in the respirable dust samples (< 7 microns) compared with the total dust samples (< 7 microns). The concentrations of total airborne aflatoxin in the respirable dusts were 26 picogram/m3 and 19 pg/m3, respectively, for the workplace and the storage area of the rice mill, while the concentrations of total dust were 12 pg/m3 for the workplace and 11 pg/m3 for the storage area. Airborne aflatoxin was not detected in control sites of either of the grain processing plants or from the total dust samples obtained from the maize plant. Three sites in the maize processing plant-the elevator (18 pg/m3), the loading/unloading area (800 pg/m3), and the oil mill (816 pg/m3)-showed the presence of airborne aflatoxin only in the respirable dust samples.

Interleukin-4 is effective in restoring cytotoxic T cell activity that declines during in vivo progression of a murine B lymphoma

We previously reported [Chakrabarti et al. (1992) Cell Immunol 142:54; 144:455] that, in a murine B lymphoma model 2C3, idiotype (Id)-specific CD8+ cytotoxic T lymphocytes (CTL) are generated in mice following hyperimmunization with irradiated tumor cells, and that they are effective in tumor rejection. The present study reveals that 2C3-specific CTL are also induced in spleens during tumor progression, but are not sustained. At the early stage of tumor growth, the splenic T cells following a 5-day incubation in vitro with killed 2C3 tumor targets, produce high levels of cytokines, namely interleukin-4 (IL-4), IL-10 and interferon gamma (IFN gamma). Their cytotoxic T lymphocyte (CTL) activity and cytokine levels, except IL-2, sharply decline at the late stage when the mice are increasingly moribund. Although the decline in cytokine level is also evident with CD4+ T cells, a precipitous and concurrent decrease occurs primarily in the IL-4 level with both CD4+ and CD8+ T cells of late-tumor-bearing animals (TBA). Study with the unseparated splenocytes also reveals that sevenfold less IL-4 is produced at the late stage. Furthermore, the cytotoxicity of CTL from late TBA can be effectively restored by addition of supernatants from the splenocyte culture of early TBA, or by IL-4, but not by IFN gamma and IL-10. In addition, only IL-4-activated CD8+ T cells from the late TBA are found, by Winn assay, to be protective in vivo. Thus it appears that IL-4, required to sustain antitumor CTL activity, is consumed by T and possibly other cells at the late stage of tumor growth, thereby compromising host immunity against the tumor. We contend that induction or maintenance of protective immunity depends not only on the tumor antigen but also on the specific cytokine milieu in a tumor-bearing host.

Effects of mutating specific residues present near the amino terminus of 2'-5'-oligoadenylate synthetase

In this study, we investigated the role of specific amino acid residues present near the amino terminus of the 9-2 isozyme of 2'-5'-oligoadenylate synthetase. In vitro expression of deletion mutants showed that residues 1-9 are required for enzyme activity. Within this region, residues 3, 7, and 8 were found to be conserved among all known isozymes of 2'-5'-oligoadenylate synthetase. Mutation of these residues singly or in combination resulted in partial or total loss of enzyme activity. Substitution of the proline residue at position 7 by different residues caused a partial or complete loss of activity. The properties of the inactive P7Q mutant were further explored by expressing the protein in bacteria. The bacterially expressed protein was also enzymatically inactive. The mutant protein could bind the substrate ATP and the activator double-stranded RNA normally. Oligomerization properties of the protein were examined by an affinity-based interaction assay and by glycerol gradient centrifugation; there was no detectable difference between the wild type and the P7Q mutant. These results demonstrated the importance of the proline residue at position 7 in conferring enzyme activity to the protein without affecting its other properties.

Repression of interleukin-6 gene expression by 17 beta-estradiol: inhibition of the DNA-binding activity of the transcription factors NF-IL6 and NF-kappa B by the estrogen receptor

The cytokine interleukin-6 (IL-6), a key mediator of immune and acute phase responses of the liver, has also been implicated in uterine functions. Estrogens are potent repressors of IL-6 production by uterine stromal cells. In the endometrial adenocarcinoma cell line Ishikawa, phorbol ester-induced activation of the IL-6 promoter was inhibited to basal levels by 17 beta-estradiol (E2) in a wild-type receptor-dependent fashion. Although tamoxifen has been shown to have estrogenic effects on the endometrium, it did not inhibit induction of the IL-6 promoter. We previously showed that inhibition of IL-6 gene expression by E2 does not involve high-affinity binding of the estrogen receptor (ER) to IL-6 DNA. We now report that the ER can directly interact with the transcription factors NF-IL6 and NF-kappa B and can inhibit their ability to bind DNA which might be the molecular basis for repression of IL-6 gene expression by estrogens.

Pseudohypophosphatasia

Two rare cases of pseudohypophosphatasia in two siblings which so far, to best of our knowledge have not been reported.

Genetic structure of Plasmodium vivax isolates in India

Variations in the allelic composition of glucose phosphate isomerase (GPI), NADP-dependent glutamate dehydrogenase (GDH) and adenosine deaminase (ADA) enzyme systems of Plasmodium vivax were observed in isolates of Indian origin in 1985-1993. No significant difference was observed in allelic frequencies in different years. The data indicated random distribution of GPI, GDH and ADA alleles among the isolates, suggesting that loci for these enzymes were not linked. A high proportion of the isolates comprised at least 2 genetically distinct clones, the mean number of clones per isolate being 1.4. There was no significant difference in the number of oocysts in Anopheles stephensi fed on uniclonal and multiclonal isolates. No difference was observed in the proportions of uniclonal and multiclonal isolates during low and high transmission periods.

Promoter/leader deletion analysis and plant expression vectors with the figwort mosaic virus (FMV) full length transcript (FLt) promoter containing single or double enhancer domains

The boundaries required for maximal expression from the promoter/leader region of the full length transcript of figwort mosaic virus (FLt promoter) coupled to reporter genes were defined by 5' and 3' deletion analyses. In transient expression assays using protoplasts of Nicotiana edwardsonii, a 314 bp FLt promoter fragment sequence (-249 to +65 from the transcription start site) was sufficient for strong expression activity. Plant expression vectors developed with modified FLt promoters were tested with GUS or CAT as reporter genes in transgenic plants. The FLt promoter is a strong constitutive promoter, with strength comparable to or greater than that of the CaMV 35S promoter. The FLt promoter with its double enhancer domain linked to GUS or CAT reporter genes provides an average 4-fold greater activity than the FLt promoter with a single enhancer domain (-55 to -249 bp upstream fragment) in tests with transgenic plants and in protoplast transient expression assays.

Kinetic analysis of the cis-diamminedichloroplatinum(II)--cysteine reaction: implications to the extent of platinum--DNA binding

The reaction between cis-diamminedichloroplatinum(II) (cis-DDP) and L-cysteine was examined at neutral pH at 37 degrees C. The reaction proceeds through a Pt(NH3)2 (cys)Cl intermediate which undergoes parallel reactions with a second molecule of cysteine to form a bis(cysteine) complex, Pt(NH3)2(cys)2 and with the starting platinum complex to form a cysteine-bridged dinuclear complex. In the presence of excess cysteine, the product is predominantly the bis(cysteine) complex. The intermediate is formed by the direct reaction of the platinum complex with cysteine with a bimolecular rate constant 2.2 +/- 0.2 x 10(-2) M-1.s-1 at 37 degrees C as well as through a rapid reaction with the mono aqua-platinum complex. The rate constant for the formation of the dimer was evaluated to be 0.24 +/- 0.4 M-1.s-1, an order of magnitude higher than that for the mononuclear complex formation. The intermediate reacts with a second cysteine molecule with a bimolecular rate constant, 5.6 +/- 0.4 x 10(-2) M-1.s-1. The rate constant for the equation of Pt(NH3)2(cys)Cl was evaluated to be 1.8 +/- 0.2 10(-4) s-1. The Pt-195 chemical shifts for the mono(cysteine), bis(cysteine), and cysteine bridged dimer were found to be -3308, -3705, and -3104 ppm. The bis(cysteine) complex at neutral pH undergoes slow reaction (t1/2 approximately equal to four days) to form a secondary product, presumably Pt(NH3)(cys)2, in which one cysteine acts a bidentate chelating agent. In acidic solution, with equimolar concentrations of cysteine and diaqua-platinum complex, the reaction predominantly yielded a cysteine bridged dimeric complex. When cysteine concentration was increased fourfold over the platinum complex, the bis(cysteine) chelate with complete removal of coordinated ammonia appeared as the dominant product. The platinum-195 chemical shift for this chelate was found to be -3290 ppm. Considering the abundance of thiols in amino acids/peptides and replication enzymes in the cellular milieu, it remains to be seen how platinum complexes react with DNA. Direct platination to replication enzymes as a possible mechanism for antineoplactic activity is yet to be ruled out.

Lupus erythematosus panniculitis

Lupus erythematosus panniculitis is a quite rare clinical entity characterised by one or several firm, asymptomatic, often fairly large subcutaneous nodules, as a manifestation of SLE or DLE. Two cases of lupus panniculitis, both female, are described here. Both of them had absence of typical lesions of SLE or DLE elsewhere in the body. Systemic symptoms were not present, antinuclear factor was positive in one case. Both showed typical lobular panniculitis on biospy and responded favourably to systemic chloroquine therapy.