UDP-Gal: <Emphasis Type="Italic">N</Emphasis>-acetylglucosamine β 1–4 galactosyltransferase expressing live attenuated parasites as vaccine for visceral leishmaniasis

As compared to cutaneous leishmaniasis, vaccination against visceral leishmaniasis (VL) has received limited attention. In this study, we demonstrate for the first time that an UDP-Galactose: N-acetylglucosamine β 1–4 galactosyltransferase (GenBank Accession No. EF159943) expressing attenuated LD clonal population (A-LD) is able to confer protection against the experimental challenge with the virulent LD AG83 parasite. A-LD was also effective in established leishmania infection. The vaccinated animals showed both cell mediated (in vitro T-cell proliferation, and DTH response) and humoral responses (Th1 type). These results demonstrate the potential of the attenuated clones as an immunotherapeutic and immunoprophylactic agent against visceral leishmaniasis.     

Role of Melanin in Release of Extracellular Enzymes and Selection of Aggressive Isolates of Bipolaris sorokiniana in Barley

Eighteen barley isolates of Bipolaris sorokiniana belonging to wild and clonal type of black, mixed and white subpopulations were quantitatively assayed for their melanin content and aggressiveness with respect to production of some of the extracellular enzymes such as cellulase, pectinase, amylase and protease. Cellulase and pectinase constituted major portion of the enzymes recovered from the black, mixed and white isolates. Enzyme production and aggressiveness were relatively higher in melanin devoid or low melanin isolates. The melanin deficient isolates were also differentiated from black and mixed isolates on the basis of variation in internal transcribed spacer region of the ribosomal DNA. Higher enzyme productions positively correlated with area under disease progress curve (AUDPC) and lesion development. Melanin content was negatively correlated with extracellular enzymes and aggressiveness of the isolates. Based on melanin content, lesion size, AUDPC and extracellular enzymes, the isolates were grouped in two major clusters (I and II) with further division of cluster II into two sub-clusters (II-A and II-B). The results appears to indicate a possible role of melanin in release of extracellular enzymes and hence in evolution and selection of aggressive isolates of B. sorokiniana in barley.     

The renal Na+/Ca2+ exchange system is located exclusively in the distal tubule.

The movement of Ca2+ across the basolateral plasma membrane was determined in purified preparations of this membrane isolated from rabbit proximal and distal convoluted tubules. The ATP-dependent Ca2+ uptake was present in basolateral membranes from both these tubular segments, but the activity was higher in the distal tubules. A very active Na+/Ca2+ exchange system was also demonstrated in the distal-tubular membranes, but in proximal-tubular membranes this exchange system was not demonstrable. The presence of Na+ outside the vesicles gradually inhibited the ATP-dependent Ca2+ uptake in the distal-tubular-membrane preparations, but remained without effect in those from the proximal tubules. The activity of the Na+/Ca2+ exchange system in the distal-tubular membranes was a function of the imposed Na+ gradient. These results suggest that the major differences in the characteristics of Ca2+ transport in the proximal and in the distal tubules are due to the high activity of a Na+/Ca2+ exchange system in the distal tubule and its virtual absence in the proximal tubule.     

Search for chromosomal variations among gas-exposed persons in Bhopal

Summary A chromosomal survey using standard lymphocyte cultures employing different media and G-banding techniques was initiated in 1984. This study became particularly important following the tragic gaseous exposure of the population in Bhopal at midnight on 2 December 1984. We have been able to formulate a chromosomal profile for each person whom we have studied; during 1986–1988, 154 persons were examined twice. Among seemingly normal individuals, as many as 20% might possess some chromosomal abnormality; of these, 50% may develop, at a later date, some kind of pathological complication (such as tumours, recurrent abortion or transmission of defects to their offspring). The people exposed to methyl isocyanate have repeatedly shown Robertsonian translocations, mostly in acrocentric chromosomes 13 and 21. Other types of translocations have been studied among all exposed (53) and normal (101) persons; the involvement of chromosomes 5, 9, 11, 14 and 16 is statistically significant (P= <0.001). One of the major clinical symptoms is dyspnoea; we have estimated that almost all seriously dyspnoeic patients have developed at least two categories of chromosomal aberrations, one of which is Robertsonian translocation, in at least 10% metaphases. Our chromosomal survey will be of significance because we are able to identify people with chromosomal aberrations that might be correlated with future pathological consequences of the accident. The chromosomal load that can be sustained with an apparently normal phenotype can also be measured.     

Specificity of tyrosine protein kinases of the structurally related receptors for insulin and insulin-like growth factor I: Tyr-containing synthetic polymers as specific inhibitors or substrates

The receptors for insulin and insulin-like growth factor (IGF) I are structurally similar transmembrane proteins. Ligand binding to the extracellular domain of the receptor stimulates its cytoplasmic tyrosine protein kinase which phosphorylates its own beta subunit as well as exogenous substrates. It is believed, from several lines of evidence, that tyrosine-specific protein kinases are mediating some or all of the actions of insulin (or IGF-I). In order to gain insights into the substrate specificity of the structurally related insulin and IGF-I receptor kinases, we have studied the action of highly purified receptors isolated from human placental membranes. Present studies using selected tyrosine-containing polymers have revealed: (i) Polymers such as (Y,A,E)n and (Y-A-E)n inhibit beta subunit autophosphorylation and exogenous substrate phosphorylation by autophosphorylated receptors. (ii) Insulin receptor kinase is at least 10 times more sensitive to these inhibitors than IGF-I receptor kinase. (iii) (Y-A-E)n is approximately 8 times more potent an inhibitor than (Y,A,E)n toward both receptors. (iv) While (E4,Y1)n and (E6,A3,Y1)n are good substrates for both receptor kinases, the ratio of phosphate incorporation into the former to the latter is characteristically high (approximately 4) for the IGF-I receptor and low (approximately 1) for the insulin receptor. These results imply that the substrate specificity and enzymatic action of these two receptor kinases are distinct.     

Cloning of a cDNA encoding the smallest neurofilament protein from the rat

We have cloned a cDNA coding for the smallest rat neurofilament protein. The cDNA is 861 nucleotides long coding for 287 amino acids from the internal alpha-helical region and the carboxy-terminal tail domain of the neurofilament protein. Comparison of the porcine, mouse and rat neurofilament protein sequences shows that the protein is highly conserved (greater than 93% identity). Blot analysis indicates that the cDNA is derived from a single neurofilament gene that codes for two different poly(A)+ mRNA species.     

Spatial phase and frequency in motion capture of random-dot patterns

A square matrix of spots (A) was presented in rapid alternation with an uncorrelated matrix (B). If the square arrays are superimposed spatially one sees random incoherent motion. However, incoherent motion was seen only if the outer edges were exactly aligned. If the outline of matrix A is shifted horizontally by 1 degree in relation to B, then the edges are seen to oscillate to and fro. Surprisingly, all the dots in the matrix were seen to 'adhere' to the edges and to move horizontally (Ramachandran, 1981). We then aligned the edges again to produce incoherent motion and superimposed a sine-wave grating on the pattern. If the grating was moved horizontally then all the spots 'adhered' to it and moved horizontally as well. This illusion ('motion capture') was optimal (a) at a 90 degrees spatial phase shift of the grating; (b) at low spatial frequencies (less than 0.5 cycles); and (c) when the grating was alternated in step with the dot patterns. Density modulated gratings were just as effective. We conclude that the unambiguous motion signal derived from the grating is applied spontaneously to the dots as well.     

Amino acid sequence of retinal transducin at the site ADP-ribosylated by cholera toxin

Transducin was [32P]ADP-ribosylated by cholera toxin in bovine retinal rod outer segments and then partially purified on omega-amino octyl agarose to remove other ADP-ribosylated proteins. Trypsin digestion of the ADP-ribosylated transducin and further purification using boronate-polyacrylamide beads and high performance liquid chromatography yielded a single radiolabeled tetrapeptide, Ser-Arg-Val-Lys. The ADP-ribose is linked to the guanidinium group of arginine.