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Biomedical subjects

R Kaul

Publications and source records attributed to R Kaul.

At least 73 records · Page 4Linked to original sources
PubMed1996

Selection of an adhesive phenotype of Streptococcus salivarius subsp. thermophilus for use in fixed-bed reactors.

Streptococcus salivarius subsp. thermophilus was cultivated in a chemostat in order to obtain an adhesive phenotype of this strain. When the system was operated at low dilution rates (D < 0.2 h-1) for about 4 weeks, the strain formed a visible film on the surface of the culture vessel. The biofilm cells were not washed out even when dilution rates were increased (D = 6.9 h-1), and this resulted in a high biomass productivity (P = 4.1 g1(-1) h-1). On the other hand, when the culture was grown at dilution rates faster than 0.2 h-1, only the free suspended cells were present in the culture broth, and were washed out at velocities of about 1.0 h-1. The biomass productivity was consequently lower (P = 1.33 g1(-1) h-1) than in the previous case. The selected adhesive phenotype was grown on different glass beads and the possibility of lactate fermentation in a continuous and semicontinuous mode was demonstrated.

Bacterial Adhesion↗
PubMed1996

Investigation of a multiyear multiple critical care unit outbreak due to relatively drug-sensitive Acinetobacter baumannii: risk factors and attributable mortality.

From 1990 to 1993, an outbreak of respiratory Acinetobacter baumannii infection occurred in five intensive care units (ICUs) of a tertiary care center. A. baumannii was subsequently isolated from disinfected temperature probes and ventilator circuits. Pulsed-field gel electrophoresis suggested that a single strain accounted for 93% of patient isolates and 88% of environmental isolates. Univariate risk factors for A. baumannii acquisition were tracheostomy (P < .01), ventilation >3 days (P < .01), dialysis (P = .03), Stenotrophomonas maltophilia respiratory colonization (P = .02), parenteral nutrition (P = .05), and enteric feeding (P < .01). Logistic regression analysis showed duration of ventilation and enteric feeding to be independent risk factors. The outbreak strain was relatively antibiotic-susceptible, but the mortality attributable to respiratory A. baumannii acquisition was 23%. Only the APACHE II score was independently associated with increased mortality. Multifaceted control measures, including gas sterilization of temperature probes, terminated the outbreak.

Acinetobacter Infections↗
PubMed1996

Evidence for the presence of streptococcal-superantigen-neutralizing antibodies in normal polyspecific immunoglobulin G.

Recently we demonstrated that normal polyspecific immunoglobulin given intravenously (IVIG) and plasma samples from patients treated with IVIG neutralize the mitogenic and cytokine-inducing activities of group A streptococcal (GAS) superantigens. Here we investigated whether this neutralizing activity is mediated by antibodies to these superantigens. IVIG and plasma samples collected from a patient with GAS necrotizing fasciitis post-IVIG infusions markedly inhibited the mitogenic activity elicited by the streptococcal pyrogenic exotoxins SpeB and SpeC, as well as by GAS culture supernatant. Immunoblot analysis showed marked increases in the levels of antibodies to SpeC and proteins in the GAS culture supernatant in post-IVIG over those of pre-IVIG plasma samples. Removal of antisuperantigen antibodies in IVIG by adsorption to SpeC- and GAS culture supernatant-coupled Sepharose markedly reduced the neutralizing ability of IVIG against respective stimuli. The neutralizing activity was totally recovered in the eluted antibodies. By contrast, although pre- and post-IVIG plasma samples contained antibodies to SpeA, these antibodies did not block the activity of this superantigen. Nonspecific immunomodulatory activity of IVIG was ruled out because neither the IVIG nor the affinity-purified antibodies significantly inhibited the response to the polyclonal T-cell mitogen phytohemagglutinin A. These data provide direct evidence that the neutralizing activity in IVIG, and in patient plasma samples following IVIG treatment is mediated by antibodies to superantigens and indicate that the quality rather than the quantity of these antibodies may be more clinically relevant.

Adult↗
PubMed1996

Identification and expression of eight novel mutations among non-Jewish patients with Canavan disease.

Canavan disease is inherited as an autosomal recessive trait that is caused by the deficiency of aspartoacylase (ASPA). The majority of patients with Canavan disease are from an Ashkenazi Jewish background. Mutations in ASPA that lead to loss of enzymatic activity have been identified, and E285A and Y231X are the two predominant mutations that account for 97% of the mutant chromosomes in Ashkenazi Jewish patients. The current study was aimed at finding the molecular basis of Canavan disease in 25 independent patients of non-Jewish background. Eight novel and three previously characterized mutations accounted for 80% (40/50) of mutant chromosomes. The A305E missense mutation accounted for 48% (24/50) of mutant chromosomes in patients of western European descent, while the two predominant Jewish mutations each accounted for a single mutant chromosome. The eight novel mutations identified included 1- and 4-bp deletions (32 deltaT and 876 deltaAGAA, respectively) and I16T, G27R, D114E, G123E, C152Y, and R168C missense mutations. The homozygous 32 deltaT deletion was identified in the only known patient of African-American origin with Canavan disease. The heterozygosity for 876 deltaAGAA mutation was identified in three independent patients from England. Six single-base changes leading to missense mutations were identified in patients from Turkey (D114E, R168C), The Netherlands (I16T), Germany (G27R), Ireland (C152Y), and Canada (G123E). A PCR-based protocol is described that was used to introduce mutations in wild-type cDNA. In vitro expression of mutant cDNA clones demonstrated that all of these mutations led to a deficiency of ASPA and should therefore result in Canavan disease.

Amidohydrolases↗
PubMed1996

Strategies for designing an immunocontraceptive vaccine based on zona pellucida synthetic peptides and recombinant antigen.

Immunization of female bonnet monkeys (Macaca radiata) with pig zona pellucida glycoprotein ZP3 using adjuvants permissible for human use leads to infertility. Fifty per cent of the animals conceived after antibody titres declined. Animals that failed to regain their fertility did not show any obvious ovarian changes. As part of the attempt to design an effective immunocontraceptive vaccine based on synthetic peptides, the epitopes recognized by monoclonal antibodies (mAb) against pig ZP3 alpha and ZP3 beta and possessing contraceptive efficacy in vitro were mapped. These studies identified an N-blocked decapeptide from the N-terminus corresponding to 23-32 amino acids of the precursor protein of pig ZP3 beta. As an alternative approach to using synthetic peptides, DNA encoding bonnet monkey ZP3 was cloned and sequenced. The deduced primary amino acid sequence revealed an overall similarity of 93.9% with human ZP3. Bonnet monkey ZP3 corresponding to an internal 975 nucleotide fragment excluding the N-terminus signal sequence and the C-terminus transmembrane domain has been expressed in Escherichia coli. These results will assist in the design of an immunocontraceptive vaccine based on either synthetic peptides or recombinant glycoproteins or proteins corresponding to ZP.

Adjuvants, Immunologic↗
PubMed1995

TCR gene usage in experimental autoimmune myasthenia gravis pathogenesis. Usage of multiple TCRBV genes in the H-2b strains.

Experimental autoimmune myasthenia gravis (EAMG) is an Ab-mediated autoimmune disease. The pathogenic auto-antibody production depends on the activation of CD4+ cells after their TCR interact with dominant T cell epitopes within acetylcholine receptor (AChR) in the context of the MHC class II molecule. In vitro analysis suggested that the TCRBV6 was the predominant TCR that recognized AChR and one of the dominant epitopes, alpha 146-162, in C57BL6 (B6, H-2b) mice. However, in vivo depletion of TCRBV6 cells in H-2b mice by anti-TCRBV6 mAb neither suppressed the in vitro immune response to AChR nor prevented development of EAMG. Moreover, B10.TCRc (H-2b) strain with a genomic deletion of TCRBV genes including TCRBV6, and B10.V beta 8.2 transgenic mice with a restricted TCRBV8S2 T cell repertoire, responded to AChR, alpha 146-162, and developed EAMG after immunizations with AChR/CFA. These data suggest that more than one TCRBV-bearing cell having the affinity for AChR-dominant peptides is involved in pathogenesis. Therefore, depletion of a single TCRBV (e.g., TCRBV6) with mAb may not be sufficient to completely suppress the response to AChR and development of EAMG. However, if a similar amino acid sequence in the TCR-VDJ (e.g., CDR3) region among different TCRBV gene(s) could be involved in recognizing the dominant AChR epitope(s), then motif-specific mAb reactive to the common motif within the VDJ region of different TCR could be used to eliminate the T cell clones involved in EAMG.

Animals↗
PubMed1995

Human recombinant IL-2 augments immunoglobulin and induces rheumatoid factor production by rheumatoid arthritis lymphocytes engrafted into severe combined immunodeficient mice.

Recombinant (r) human IL-2 was administered in vivo to improve homing and engraftment of rheumatoid arthritis (RA) patients' peripheral blood mononuclear cells (PBMC) into severe combined immunodeficient (SCID) mice. Human rIL-2 treatment resulted in augmented human Ig production and induced IgM rheumatoid factor (RF) of human origin in SCID-RA chimeras. The increment of human serum IgG in SCID-RA chimeras after IL-2 treatment ranged between 15 and 43% and for IgM between 50 and 98% during 2-8 weeks postengraftment. Human IgM-RF was detectable after 1 to 2 weeks after engraftment and persisted over a period of 10-13 weeks. No RF was produced in SCID mice engrafted with PBMC from healthy individuals with or without exogenous rIL-2 administration. Thus, human rIL-2 expanded autoreactive clones involved in the production of RF in the SCID-RA chimeras. The present study provides a novel approach to establish an in vivo SCID-RA model to study the cellular and molecular mechanisms involved in the production of RF and development of a RA-like lesion.

Adult↗
PubMed1995

Juvenile circadian core temperature rhythm in Wistar and lean (Fa/-) Zucker rat pups.

We compared the daily rhythms of cold defense in Wistar and lean (Fa/-) Zucker rat pups isolated from maternal care. Pups, born in a colony with lights-on from 7:00 to 19:00, were artificially reared from 10 to 13 days of age in continuous light at moderate cold loads, while we recorded core temperature (Tc) and metabolic rate (MR). Pups of both strains showed daily rhythms distinctly different from those of adult rats: on the first day of artificial rearing Tc steeply decreased shortly before the time of lights-on in the breeding colony and reached a daily minimum of 31.8 +/- 0.4 degree C at 7:17 +/- 17 min in Zucker pups (+/- SE, N = 24) and of 33.4 +/- 0.2 degree C at 8:59 +/- 9 min (N = 25) in Wistar pups. On each day, the average daily minimum Tc was significantly higher in Wistar than in Zucker rats, whereas the daily maximum Tc were close to 36 degrees C in both strains. The daily rhythms of MR resembled those of Tc. We conclude that circadian differences of cold defense, which must be expected to influence a variety of behavioral and physiological parameters, are not a peculiarity of Zucker rat pups but also occur, though with a smaller amplitude, in 10-day-old Wistar pups.

Animals↗
PubMed1995

Canavan disease: from spongy degeneration to molecular analysis.

Establishing the basic defect in Canavan disease has led to reliable biochemical methods for the diagnosis of this disease. The isolation of the gene and identification of mutations causing Canavan disease have led to the possibility of using DNA methods for the diagnosis of Canavan disease and for carrier detection. A surprising finding is the high carrier frequency of this gene defect among Ashkenazi Jewish people. Analysis for two mutations leads to the identification of 97% of Jewish patients with Canavan disease, and screening of Ashkenazi Jews is possible. N-Acetylaspartic acid has been considered to be an inert compound. The pathophysiology of Canavan disease links lack of NAA hydrolysis to a severe, debilitating white matter disease. Currently, NAA is being studied in many other brain disorders, such as Alzheimer disease, Huntington disease, and stroke. However, the only disease with a specific defect in the metabolism of NAA is Canavan disease. An animal model for Canavan disease is needed to study some of the questions regarding the role of NAA in brain tissue, and for the study of therapeutic modalities, including gene therapy.

Age of Onset↗
PubMed1995

Nucleotide sequence of cDNA encoding bonnet monkey (Macaca radiata) zona pellucida glycoprotein-ZP3.

The cDNA encoding bonnet monkey zona pellucida ZP3 from bonnet ovary has been amplified by polymerase chain reaction. The ZP3 gene has an open reading frame of 1272 nucleotides encoding a polypeptide of 424 amino acid residues which shares 93.9% overall identity with human ZP3. Bonnet ZP3 has four potential attachment sites for N-linked sugar chains which are also conserved in human ZP3. Bonnet ZP3 has 14 cysteine residues compared with 15 in human ZP3. The highest disparity between these molecules was restricted to a domain represented by amino acid residues 370-398. These results have important implications for the use of bonnet monkey as an animal model for evaluation and development of contraceptive vaccine based on ZP3 for human use.

Amino Acid Sequence↗
PubMed1995

Chlamydia trachomatis RNA polymerase alpha subunit: sequence and structural analysis.

We describe the cloning and sequence analysis of the region surrounding the gene for the alpha subunit of RNA polymerase from Chlamydia trachomatis. This region contains genes for proteins in the order SecY, S13, S11, alpha, and L17, which are equivalent to Escherichia coli and Bacillus subtilis r proteins. The incorporation of chlamydial alpha subunit protein into the E. coli RNA polymerase holoenzyme rather than its truncated variant lacking the amino terminus suggests the existence of structural conservation among alpha subunits from distantly related genera.

Amino Acid Sequence↗
PubMed1994

Effect of MHC class I and CD8 cell deficiency on experimental autoimmune myasthenia gravis pathogenesis.

MHC class I and CD8+ cell deficiency have either prevented systemic lupus erythematosus-like disease in mice or enhanced type I diabetes in nonobese diabetic mice. To study the involvement of MHC class I and class I-restricted CD8+ T cells in the induction of a classical Ab-mediated disease, experimental autoimmune myasthenia gravis (EAMG), we immunized beta 2 microglobulin (beta 2-m) gene-disrupted (beta 2 m-/-) C57BL10 (B10) mice, deficient in class I gene expression and CD8+ cells, and heterozygous (beta 2-m+/-) B10 mice with normal expression of class I molecules and sufficient CD8+ cells with Torpedo acetylcholine receptor in CFA, and assessed them for clinical and immunopathologic manifestations of EAMG. Despite MHC class I and CD8+ cell deficiency, beta 2-m-/- mice developed EAMG. Moreover, the incidence of EAMG in the beta 2-m-/- mice was higher than that of beta 2-m+/- heterozygous mice with normal class I expression and frequency of CD8+ cells. The finding provided direct genetic evidence against a pathogenic effector role in C57BL10 mice for MHC class I molecule and class I-restricted CD8+ T cells in EAMG pathogenesis.

Animals↗
PubMed1994

Cloning and characterization of a secY homolog from Chlamydia trachomatis.

Characterization of the genes involved in the process of protein translocation is important in understanding their structure-function relationships. However, little is known about the signals that govern chlamydial gene expression and translocation. We have cloned a 1.7 kb HindIII-PstI fragment containing the secY gene of Chlamydia trachomatis. The complete nucleotide sequence reveals three open reading frames. The amino acid sequence shows highest homology with Escherichia coli proteins L15, SecY and S13, corresponding to the spc-alpha ribosomal protein operons. The product of the C. trachomatis secY gene is composed of 457 amino acids with a calculated molecular mass of 50,195 Daltons. Its amino acid sequence shows 27.4% and 35.7% identity to E. coli and Bacillus subtilis SecY proteins, respectively. The distribution of hydrophobic amino acids in the C. trachomatis secY gene product is suggestive of it being an integral membrane protein with ten transmembrane segments, the second, third and seventh membrane segments sharing > 45% identity with E. coli SecY. Our results suggest that despite evolutionary differences, eubacteria share a similar protein export apparatus.

Amino Acid Sequence↗
PubMed1994

Canavan disease: genomic organization and localization of human ASPA to 17p13-ter and conservation of the ASPA gene during evolution.

Canavan disease, or spongy degeneration of the brain, is a severe leukodystrophy caused by the deficiency of aspartoacylase (ASPA). Recently, a missense mutation was identified in human ASPA coding sequence from patients with Canavan disease. The human ASPA gene has been cloned and found to span 29 kb of the genome. Human aspartoacylase is coded by six exons intervened by five introns. The exons vary from 94 (exon III) to 514 (exon VI) bases. The exon/intron splice junction sites follow the gt/ag consensus sequence rule. Southern blot analysis of genomic DNA from human/mouse somatic cell hybrid cell lines localized ASPA to human chromosome 17. The human ASPA locus was further mapped in the 17p13-ter region by fluorescence in situ hybridization. The bovine aspa gene has also been cloned, and its exon/intron organization is identical to that of the human gene. The 500-base sequence upstream of the initiator ATG codon in the human gene and that in the bovine gene are 77% identical. Human ASPA coding sequences cross-hybridize with genomic DNA from yeast, chicken, rabbit, cow, dog, mouse, rat, and monkey. The specificity of cross-species hybridization of coding sequences suggests that aspartoacylase has been conserved during evolution. It should now be possible to identify mutations in the noncoding genomic sequences that lead to Canavan disease and to study the regulation of ASPA.

Amidohydrolases↗