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N Joshi

Publications and source records attributed to N Joshi.

At least 73 records · Page 4Linked to original sources
PubMed1993

The human T-cell receptor beta-chain repertoire: longitudinal fluctuations and assessment in MHC matched populations.

The influence of the environment and of the major histocompatibility complex (MHC) in shaping the human T-cell receptor beta-chain variable region (TCRBV) repertoire has not been systematically studied. Here, expression of TCRBV gene families was estimated by a sensitive polymerase chain reaction (PCR)-based method. Serial studies of peripheral blood, performed at 2-week intervals over a 3-month period, revealed that fluctuation in the expression of many TCRBV genes occurred in healthy individuals and in the absence of clinically evident infections. Fluctuation of TCRBV4, TCRBV5.2, TCRBV9, and TCRBV13.1 genes were present in all subjects. Additional TCRBV genes fluctuated in some but not in other individuals. Comparison of the TCRBV repertoire between these unrelated individuals indicated differences in the mean expression of TCRBV5.1, TCRBV9, TCRBV11, TCRBV15, TCRBV17, and TCRBV20 genes. For any TCRBV gene, intersubject differences were generally of a magnitude of twofold or less. Larger differences characterized the TCRBV repertoire of CD4 compared to CD8 cells. Some differences, for example over-representation of TCRBV2 and TCRBV5.1 on CD4, and TCRBV10, TCRBV14, and TCRBV16 on CD8 cells, were present in most subjects. Individuals homozygous for DR2- or DR3-bearing extended MHC haplotypes displayed similar individual variability of TCRBV expression. These data indicate that the circulating TCRBV repertoire in humans is both dynamic and diverse. Both environment and MHC effects contribute to the diversity of TCRBV expression.

Base Sequence↗
PubMed1993

Hepatic trauma: experience of 110 cases.

A total of 110 patients with hepatic injuries was treated at a major urban trauma centre between June 1988 and December 1991. The mechanism of injury was blunt trauma in 86 patients (78 per cent). Non-operative treatment was given in six patients (5 per cent). Simple hepatorrhaphy, use of topical haemostatic agents or peritoneal drainage alone were performed in 79 (72 per cent) cases. Extensive hepatorrhaphy, hepatotomy with selective vascular ligation, resection and débridement or resection, perihepatic packing and major vascular ligation were undertaken, often in combination, in 25 (23 per cent) cases. Percutaneous arterial embolization was carried out in one case. The mortality rate was 18 per cent. The most frequent postoperative complications related to hepatic injury were intra-abdominal abscess (7 per cent) and coagulopathy (5 per cent); prolonged biliary leak (3 per cent), late haemorrhage (2 per cent) and hepatic necrosis (1 per cent) were also observed.

Adolescent↗
PubMed1992

Haplotypic origin of beta-chain genes expressed by human T-cell clones.

A contribution of allelic variation of T-cell receptor (Tcr) genes to the immune response has not been studied. Here we report that the presence of insertion-deletion-related polymorphisms (IDRP) of the Tcr beta chain (Tcrb) can be utilized to distinguish the parental origin of the gene complex that undergoes rearrangement in individual T-cell clones. Phytohemagglutinin stimulated clones from an individual heterozygous for an IDRP located between the variable (V) and diversity (D)-joining (J) region genes were studied for the presence of V to DJ rearrangements in each of the two parental chromosomes. Results indicate that single rearrangements were present in the majority of clones, in contrast to the double rearrangements of D to J genes that were generally present. In this individual, V to DJ rearrangement also occurred with different frequencies on each of the two germline genes. IDRP clonotyping of the Tcrb complex should prove generally applicable to the study of the influence of allelic variation of Tcrb genes in selection of the expressed T-cell repertoire.

Alleles↗
PubMed1992

A predictive risk index for nosocomial pneumonia in the intensive care unit.

PURPOSE: To develop a scoring system for stratifying patients in intensive care units (ICUs) by risk of developing nosocomial pneumonia (NP) and to identify the time period associated with the highest risk. PATIENTS AND METHODS: Two hundred and three patients 18 years of age or older and residing in the ICU for 72 hours or more were followed until development of NP or death or for 48 hours after discharge from the ICU. After the identification of independent risk factors for NP, a scoring system was developed to arrive at a predictive risk index for NP. RESULTS: Twenty-six (12.8%) patients developed NP. The presence of a nasogastric (NG) tube [odds ratio (OR) = 6.48, 95% confidence intervals (CI) = 2.11 to 19.82], upper abdominal/thoracic surgery (OR = 4.34, 95% CI = 1.43 to 13.14), and bronchoscopy (OR = 2.95, 95% CI = 1.02 to 8.52), most commonly performed for respiratory toilet, were identified as independent risk factors on multivariate analysis. The risks associated with endotracheal intubation and altered consciousness, although not independently significant, were highest when these factors were present for 1 to 4 days after the 72 hours required for study entry (endotracheal intubation, OR = 2.2 to 2.5; altered consciousness, OR = 1.4 to 2.0). The risk then declined; ORs of less than 1 were observed at 7 days. The risk associated with the NG tube was highest during the first 6 days (OR = 6.0 to 19.5). Although a subsequent decrease in risk was observed, the OR was still greater than 2 at 7 days. To obtain a predictive risk index for NP, a scoring system was developed using a multivariate model. This system has a sensitivity of 85% and a specificity of 66% in predicting NP in this ICU population. CONCLUSION: ICU patients can be stratified into high- and low-risk groups for NP using a bedside scoring system. Endotracheal intubation, altered mental status, and NG tube are associated with the highest risk of NP during the first 1 to 6 days of their presence after 72 hours of stay in the ICU. After this time period, the risk associated with these factors decreases. Bronchoscopy may be an independent risk factor for NP that has not been previously recognized. This procedure, often done in the ICU for respiratory toilet, may be an avoidable risk in this group of patients.

Adult↗
PubMed1992

Experimental allergic encephalomyelitis in cynomolgus monkeys. Quantitation of T cell responses in peripheral blood.

Chronic relapsing-remitting experimental allergic encephalomyelitis (EAE) was induced in cynomolgus monkeys by a single immunization with a homogenate of human brain white matter (BH) in adjuvant. Proliferative T lymphocyte responses to BH, to myelin basic protein (MBP), but not to proteolipid protein, were detected in peripheral blood mononuclear cells (PBMC) of all animals and persisted until their death or, in surviving animals, for greater than 10 mo postimmunization. Responses of higher magnitude tended to be associated with fatal, compared with nonfatal, episodes of clinical EAE. The frequency of MBP-reactive T cells in PBMC of animals with acute EAE was quantitated with a soft agar colony system; the ratio of T cells that proliferated specifically to MBP was estimated at between 5 and 20 per 10(6) PBMC. A similar frequency of peptide-specific T cells was estimated from PBMC of monkeys immunized with a synthetic 14-mer peptide corresponding to a region near the carboxy terminus of MBP. Thus, autoantigen-reactive T cells can be detected in the circulation throughout the course of chronic EAE, are predictive of disease severity, and occur at a frequency similar to that estimated to be present in humans with multiple sclerosis.

Amino Acid Sequence↗
PubMed1992

T-cell receptors: germline polymorphism and patterns of usage in demyelinating diseases.

The genomic organization of the T-cell receptor (TCR) gene complexes accounts for many central aspects of T-cell immunobiology, including specificity and diversity. Recent data indicate that polymorphism of TCR genes is present within a species and may influence the immune phenotype of an individual. Such polymorphism has been detected by RFLP, by the presence of large regions of insertion or deletion of germline DNA, and by allelic variability of individual gene segments that are expressed. In addition to allelic variation of TCR genes, immune responses may also be influenced by the repertoire of the TCR molecules that are expressed by responding T-cell populations. In some situations, pathogenic T-cell responses may involve expression of limited numbers of TCR gene families. This is true, for example, in experimental allergic encephalomyelitis, an autoimmune nervous system disease mediated by T-cells reactive to myelin basic protein. In the human disease counterpart, multiple sclerosis, a more complex pattern of T-cell recognition to the putative autoantigen is generally present, although in some individuals a restricted response may occur. Specific therapies targeted to certain TCR molecules represents a promising approach to chronic inflammatory diseases in humans. The efficacy of such therapies will be determined in part by the TCR repertoire expressed in individual disease situations and by the potential for plasticity in the pathogenic T-cell response that may exist.

Alleles↗
PubMed1992

Serum adenosine deaminase activity in bacillary or paucibacillary pulmonary tuberculosis.

Serum Adenosine Deaminase (ADA) enzyme levels were estimated in 61 patients with symptoms and signs suggestive of Pulmonary Tuberculosis and correlated with "Gold standards" such as smear positivity of sputum for Acid Fast bacilli, Tuberculin skin testing and Radiological evidence. The mean ADA levels in smear and Tuberculin negative patients was 13.13 +/- 5.97 u/L, while in those with smear and/or strongly positive Tuberculin reaction, the mean levels of ADA were 33.52 +/- 15.22 u/L. The mean serum ADA levels in 25 healthy voluntary donors with no evidence of active or old Tuberculous lesion, were found to be 16.5 +/- 3.18 u/L. The specificity, sensitivity, positive predictive value and negative predictive value of the test was found to be 87%, 71%, 90% and 66.5% respectively. The results conclude that the serum ADA value is sufficiently useful in identifying those patients in whom the diagnosis of Pulmonary Tuberculosis should be actively considered.

Adenosine Deaminase↗
PubMed1991

Anisotropy decays of single tryptophan proteins measured by GHz frequency-domain fluorometry with collisional quenching.

We used harmonic-content frequency-domain fluorometry to determine the anisotropy decays of a variety of single tryptophan peptides and proteins. Resolution of the rapid and complex anisotropy decays was enhanced by global analysis of the data measured in the presence of quenching by either oxygen or acrylamide. For each protein, and for each quencher, data were obtained at four to six quencher concentrations, and the data analyzed globally to recover the anisotropy decay. The decrease in decay times produced by quenching allows measurements to an upper frequency limit of 2 GHz. The chosen proteins provided a range of exposures of the tryptophan residues to the aqueous phase, these being ACTH, monellin, Staphylococcus nuclease and ribonuclease T1, in order of decreasing exposure. Examination of indole and several small peptides demonstrates the resolution limitations of the measurements; a correlation time of 12 ps was measured for indole in methanol at 40 degrees C. Comparison of the anisotropy decays of gly-trp-gly with leu-trp-leu revealed stearic effects of the larger leucine side chains on the indole ring. The anisotropy decay of gly-trp-gly revealed a 40 ps component for the indole side chain, which was resolved from the overall 150 ps correlation time of the tripeptide. Only the longer correlation time was observed for leu-trp-leu. With the exception of ribonuclease T1, each of the proteins displayed a subnanosecond component in the anisotropy decay which we assign to independent motions of the tryptophan residues. For example, Staphylococcus nuclease and monellin displayed segmental tryptophan motions with correlation times of 80 and 275 ps, respectively. The amplitudes of the rapid components increased with increasing exposure to the aqueous phase. These highly resolved anisotropy decays for proteins of known structure are suitable for comparison with molecular dynamic simulations.

Acrylamide↗
PubMed1991

Drug-resistant Nocardia asteroides infection in a patient with acquired immunodeficiency syndrome.

We have reported what we believe to be the first case of disseminated infection due to a multiply drug resistant strain of Nocardia asteroides in a patient with the acquired immunodeficiency syndrome and concomitant disseminated histoplasmosis. This strain of the organism fits a pattern of susceptibility that is rare among N asteroides isolates in general and has been called the type 5 pattern, described as a resistance to broad spectrum cephalosporins, ciprofloxacin, and all aminoglycosides except amikacin. The recognition of disease due to this group of organisms is especially important in patients with AIDS because sulfonamides, considered the drugs of choice for treatment of N asteroides infection, are associated with a high incidence of adverse effects in these patients.

Acquired Immunodeficiency Syndrome↗
PubMed1991

Visual evoked potentials and visual acuity after transurethral resection of the prostate.

Changes in visual evoked potentials, visual acuity, blood ammonia levels and serum electrolytes (Na+ and K+) after transurethral resection of the prostate using glycine as an irrigating fluid performed under subarachnoid block were studied in 12 patients, in the pre-operative and immediate postoperative periods. Visual evoked potentials (p100 latency), recorded by shift of a checkerboard pattern, increased significantly from a pre-operative value of mean (SEM) 101.18 (1.63) msec in the right eye, and 102.5 (1.47) msec in the left eye to 108.91 (1.8) msec (p less than 0.01) and 108.08 (2.53) msec (p less than 0.01) respectively in the postoperative phase. There were no changes in visual acuity as assessed by a Snellen's chart, blood ammonia levels and serum electrolyte concentrations. The amount of glycine used intra-operatively for irrigation ranged from 3 to 31 litres.

Aged↗
PubMed1990

An intracellular pathway is required for ABA-tyrosine presentation to T cells.

Although tyrosine-azobenzenearsonate (ABA-Tyr) is not degraded by proteolytic enzymes, its presentation by accessory cells is inhibited by lysosomotropic agents such as chloroquine. Presentation of ABA-poly-L-glutamic, alanine, tyrosine (ABA-GAT) is similarly inhibited by chloroquine, but in contrast to ABA-Tyr it is also inhibited by leupeptin. Finally formaldehyde fixation of accessory cells after pulsing with ABA-Tyr but not before permits successful stimulation of ABA-specific hybridoma cells. These results suggest that a lysosomal pathway but not digestion is necessary for the association of ABA-Tyr and la molecules for presentation.

Animals↗
PubMed1990

Immunological studies in HBV-related chronic liver diseases.

Humoral immune response in chronic sequelae of HBV infection was assessed in the present study. Serum immunoglobulins (IgG, IgM, IgA) serum complement component C3 and C4 and circulating immune complex (CIC) were estimated in forty cases of HBsAg positive chronic active hepatitis and cirrhosis and sixty cases of age and sex matched healthy control subjects. Hypergammaglobulinemia was observed in chronic liver diseased state. All the three immunoglobulins, IgG, IgA and IgM were elevated significantly. The complement C3 and C4 were significantly decreased in patient group, while the levels of CIC were significantly increased. The increased immunoglobulin levels may be attributed to disorganised Kupffer cell system and also to B cell hyperactivity. The decreased complement levels may be attributed to decreased synthesis and/or increased consumption by increased CIC. A primary or an acquired defect in infected host to generate immune response might result in defective elimination of infected hepatocytes in chronic liver disease.

Adult↗
PubMed1988

Distance distributions in proteins recovered by using frequency-domain fluorometry. Applications to troponin I and its complex with troponin C.

We used resonance energy transfer to examine the distribution of distances between two sites on troponin I (TnI). The donor (D) was the single tryptophan residue at site 158 (Trp 158), and the acceptor (A) was cysteine 133 (Cys 133) which was labeled with N-(iodoacetyl)-N'-(1-sulfo-5-naphthyl)ethylenediamine (IE). A distribution of D-A distances results in a distribution of donor decay times, which were resolved by using frequency-domain fluorometry. In the native state we recovered a relatively narrow distribution of D-A distances. The widths of the distance distributions were found to increase progressively and dramatically with increasing concentrations of guanidine hydrochloride. Binding of calcium-free troponin C (TnC) to troponin I did not alter the distance distribution. Addition of Ca2+ to the TnI.TnC complex resulted in a sharper distance distribution and protected against the guanidine hydrochloride induced increase in the width of the distance distribution. Additionally, the same distance distributions were recovered for native and denatured TnI when the Forster distance for energy transfer was decreased by acrylamide quenching. These results demonstrate that distance distributions can be recovered with good accuracy, to the extent of revealing modest changes due to binding of other components. This technique should have widespread applications in studies of protein folding.

Fluorometry↗
PubMed1987

Correction for contaminant fluorescence in frequency-domain fluorometry.

We describe a general method to correct for contaminant fluorescence when using the technique of frequency-domain fluorometry. The method can be applied regardless of the origin of the background signal, from scattered light, impurity fluorescence, or both. The procedure requires measurement of the frequency-dependent phase and modulation of the background at enough frequencies to approximate the decay law of the background. We also describe a general method to propagate the uncertainties in the measured phase and modulation values into the corrected values. This propagation is necessary to ensure proper weighting of the frequency-dependent data in the least-squares fitting algorithms. The practical usefulness of this correction method is demonstrated using frequency-domain data for one and two component mixtures which were deliberately contaminated with scattered light and/or other fluorophores.

Anthracenes↗
PubMed1987

Analysis of fluorescence decay kinetics measured in the frequency domain using distributions of decay times.

We describe the theoretical and practical aspects of analyzing complex fluorescence decay kinetics using continuous distributions of decay times. Our analysis uses frequency-domain data, provides for global analysis of multiple data sets and includes the possibility of excited-state processes. Simulated data were used to estimate the types of distributions which can be reasonably recovered from the measurements. Additionally, we describe a variety of distributions recovered from experimental data. For mixtures of one, two or three exponentially decaying fluorophores we recovered narrow lifetime distributions, which are essentially identical to a multiexponential decay. Similarly, a two-state excited-state reaction also yielded a narrow distribution with negative preexponential factors. The presence of time-dependent spectral relaxation of labeled lipids results in a wide distribution of decay times, which becomes narrower for faster relaxation rates at higher temperatures. Hence, the decay-time distributions appear to be sensitive to the dynamics of the environment surrounding the fluorophore. Additionally, distributions of decay times were observed to result from transient effects in collisional quenching, from energy transfer in the presence of a range of donor-to-acceptor distances, and for several single-tryptophan proteins.

Energy Transfer↗
PubMed1987

Enhanced resolution of fluorescence anisotropy decays by simultaneous analysis of progressively quenched samples. Applications to anisotropic rotations and to protein dynamics.

Enhanced resolution of rapid and complex anisotropy decays was obtained by measurement and analysis of data from progressively quenched samples. Collisional quenching by acrylamide was used to vary the mean decay time of indole or of the tryptophan fluorescence from melittin. Anisotropy decays were obtained from the frequency-response of the polarized emission at frequencies from 4 to 2,000 MHz. Quenching increases the fraction of the total emission, which occurs on the subnanosecond timescale, and thereby provides increased information on picosecond rotational motions or local motions in proteins. For monoexponential subnanosecond anisotropy decays, enhanced resolution is obtained by measurement of the most highly quenched samples. For complex anisotropy decays, such as those due to both local motions and overall protein rotational diffusion, superior resolution is obtained by simultaneous analysis of data from quenched and unquenched samples. We demonstrate that measurement of quenched samples greatly reduces the uncertainty of the 50-ps correlation time of indole in water at 20 degrees C, and allows resolution of the anisotropic rotation of indole with correlation times of 140 and 720 ps. The method was applied to melittin in the monomeric and tetrameric forms. With increased quenching, the anisotropy data showed decreasing contributions from overall protein rotation and increased contribution from picosecond tryptophan motions. The tryptophan residues in both the monomeric and the tetrameric forms of melittin displayed substantial local motions with correlation times near 0.16 and 0.06 ns, respectively. The amplitude of the local motion is twofold less in the tetramer. These highly resolved anisotropy decays should be valuable for comparison with molecular dynamics simulations of melittin.

Acrylamide↗