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P Gupta

Publications and source records attributed to P Gupta.

At least 55 records · Page 3Linked to original sources
PubMed2001

Risk factors for chronic rejection after pediatric liver transplantation.

BACKGROUND: Chronic rejection is a major cause of graft failure and a frequent reason for retransplantation after pediatric liver transplantation. Identification of risk factors for chronic rejection in pediatric transplant recipients is vital to understanding the pathogenesis of chronic rejection and may help prevent further graft loss. METHODS: The study population consisted of 285 children with 385 liver transplants performed at University of Chicago between 1991 and 1999. Logistic regression analysis was used to evaluate risk factors for chronic rejection, including age, sex, race, type of graft (living related vs. cadaveric), native liver disease, acute rejection episodes, cytomegalovirus (CMV) infection, and posttransplant lymphoproliferative disease (PTLD). RESULTS: The chronic rejection rate was significantly lower in recipients of living-related grafts than in recipients of cadaveric grafts (4% vs. 16%, P=0.001). African-American recipients had a significantly higher rate of chronic rejection than did Caucasian recipients (26% vs. 8%, P<0.001). Numbers of acute rejection episodes, transplantation for autoimmune disease, occurrence of PTLD, and CMV infection were also significant risk factors for chronic rejection. However, recipient age, gender, donor-recipient gender mismatch, and donor-recipient ethnicity mismatch were not associated with higher incidence of chronic rejection CONCLUSION: We have identified a number of risk factors for chronic rejection in a large group of pediatric liver allograft recipients. We believe that donor-recipient matching for gender or race is not likely to reduce the incidence of chronic rejection. The elucidation of the mechanisms by which living-related liver transplantation affords protection against chronic rejection may provide insight into the immunogenetics of chronic rejection and help prevent further graft loss.

Black or African American↗
PubMed2001

Enhanced expression of the recombinant lethal factor of Bacillus anthracis by Fed-Batch culture.

High cell density cultivation has been one of the most effective ways to increase cell as well as the product yields. The structural gene for the 90-kDa lethal factor (LF) isolated from Bacillus anthracis was expressed as fusion protein with 6x histidine residues under the transcriptional regulation of the T5 promoter in Escherichia coli. Various strategies were tried to scale up the expression of the recombinant lethal factor by bioprocess optimization using fed batch culture technique in a 14 litre fermentor. The media, a defined mixture of salts, trace elements, vitamins, etc. along with a specified carbon source was used for the growth. The pH of the media was maintained at 6.8 while the temperature was changed from 37 to 28 degrees C during the cultivation. During the growth and induction phases, the DO was maintained above 20% by automatic control of agitation. The specific growth rate was controlled by utilizing an exponential feeding profile determined from mass balance equations. As a result of control of specific growth rate at two different levels, there was about twenty five fold increase in biomass compared to the biomass in the shake flask. E. coli cells yielded a soluble cytosolic protein with an apparent molecular mass of 90 kDa. The protein was purified to homogeneity using metal chelate affinity chromatography, followed by anion exchange on FPLC using Mono-Q column. In solution, trypsin cleaved protective antigen bound to native and recombinant LF with comparable affinity. The recombinant LF resembled the LF purified from B. anthracis in the macrophage lysis assay, using a murine macrophage cell line J774A.1 sensitive to anthrax toxin. It was possible to achieve a yield of 50 mg of the purified protein from 1 litre culture broth.

Antigens, Bacterial↗
PubMed2001

Effect of pH on stability of anthrax lethal factor: correlation between denaturation and activity.

Anthrax is caused by Gram positive bacterium Bacillus anthracis. Pathogenesis is result of production of three protein components, protective antigen (PA), lethal factor (LF), and edema factor (EF). PA in combination with LF (lethal toxin) is lethal to animals, while PA in combination with EF (edema toxin), causes edema. PA, LF, and EF are very thermolabile. Differential scanning calorimetry (DSC) was used to unravel the energetics of LF denaturation as a function of pH ranging from 7.8 to 5.5. Transition temperature (T(m)) of LF was found to be approximately equal to 42 degrees C and onset of denaturation occurs at approximately equal to 30 degrees C. The ratio of calorimetric to van't Hoff's enthalpy was nearly equal to unity at pH 7.0, indicative of presence of single structural domain in LF at pH 7.0, unlike PA which has been structurally observed to consist of 4 domains. It was found by cytotoxicity studies using J774A.1 macrophage like cells that LF was most stable at pH approximately 6.5. This paper reports for the first time the denaturation of LF at different pH values at 37 degrees C and tries to establish a correlation between denaturation and loss of LF activity at different pH values.

Animals↗
PubMed2001

A comparison of the effects of lamotrigine on neuroma-induced action potential firing and normal behaviour in rat: implications for establishing a pre-clinical 'therapeutic index'.

The effects of lamotrigine on rat neuroma and behavioural paradigms were evaluated to determine a pre-clinical therapeutic index. Lamotrigine blocked neuroma-induced burst pattern firing at a free plasma concentration of 13.7+/-1.7 microM (n=5). Oral dosing of lamotrigine (50-200 mg/kg) had no significant effects on behaviour but measurements of plasma concentrations of free drug showed non-linear oral absorption and lower than predicted drug levels (5-27 microM). Given intravenously (10-100 mg/kg), lamotrigine did affect behaviour at a free plasma concentration of 42.0 microM (n=2). By comparing free plasma concentrations, a therapeutic index of 3 was calculated, which is lower than published data based on comparing oral doses. We propose that a therapeutic index should only be derived with reference to plasma drug concentrations to prevent non-linear or incomplete drug absorption from confounding accurate estimation.

Action Potentials↗
PubMed2001

De novo hepatitis with autoimmune antibodies and atypical histology: a rare cause of late graft dysfunction after pediatric liver transplantation.

BACKGROUND: Late graft dysfunction after orthotopic liver transplantation is commonly due to chronic rejection, recurrence of primary disease, sepsis, lympho-proliferative disease, or vascular or biliary complications. Herein we describe a subset of pediatric liver transplant patients in whom late graft dysfunction was associated with autoimmune markers, bile ductular proliferation, and portal infiltrates, which progress to fibrosis. This subset of patients has not been previously described. METHODS: Six of the 115 children followed for greater than 5 years after transplantation developed this unusual form of graft dysfunction. All children were on a low-dose single immunosuppressive therapy (mean trough cyclosporine concentration 89 microg/L) and had been tapered off steroids for a median duration of 1.5 year. Liver biopsies were performed in all children to evaluate the graft dysfunction, and the histologic findings were interpreted by an experienced hepato-pathologist. All patients were tested for antibodies to hepatitis C virus, hepatitis B surface antigen, and IgM antibodies to hepatitis A. Smooth muscle antibody, antinuclear antibody, and antibody to liver/kidney microsome type 1 were sought by indirect immunofluorescence. International Autoimmune Hepatitis Group scores were calculated. All patients underwent ultrasonography with doppler studies at the onset of graft dysfunction. Three patients with marked bile duct proliferation on histology had cholangiograms. RESULTS: Histology in all patients showed mononuclear cell infiltrates in the portal area with interface hepatitis, portal fibrosis, and ductular proliferation without duct damage or loss. All six patients had positive antinuclear antibody or smooth muscle antibody titers. Viral studies for hepatitis A, B, and C were negative in all patients. On the International Autoimmune Hepatitis Group scoring system, five patients had probable autoimmune hepatitis (score of 10-15) and one had definite autoimmune hepatitis (score > 15) at the onset of graft dysfunction. All were treated with azathioprine and prednisone similar to treatment for autoimmune hepatitis. However, despite aggressive treatment, four patients developed bridging portal fibrosis resulting in graft loss in two patients. CONCLUSION: This clinical constellation is associated with worse outcome then that previously described for pediatric patients with posttransplantation de novo autoimmune hepatitis. Further studies are needed to find an optimal treatment regimen for these patients.

Adolescent↗
PubMed2001

Trp 346 and Leu 352 residues in protective antigen are required for the expression of anthrax lethal toxin activity.

The three separate proteins that make up anthrax toxin-protective antigen (PA), edema factor (EF) and lethal factor (LF) act in binary combinations to produce two distinct reactions in experimental animals: edema (PA+EF) and death (PA+LF). PA is believed to interact with a membrane receptor and, after proteolytic processing, to mediate endocytosis and subsequent translocation of EF or LF into the cytosol. Residues W346, M350, and L352 in loop 3 of domain 2 have been implicated to induce a conformational change when the pH is lowered from 7.4 to 6.5. Modification of the residues Trp (346), Met (350), and Leu (352) to alanine individually and all the three residues together to alanine residues resulted in the loss of cytotoxic activity in combination with LF. The mutant proteins were able to bind to the cell surface receptor, become cleaved by trypsin, bind LF, and oligomerize. These residues might play an important role in the membrane insertion of PA and/or translocation of LF/EF into the cytosol.

Alanine↗
PubMed2001

Involvement of residues 147VYYEIGK153 in binding of lethal factor to protective antigen of Bacillus anthracis.

Anthrax toxin is a complex of protective antigen (PA, 735 aa), lethal factor (LF, 776 aa), and edema factor (EF, 767 aa). PA binds to cell surface receptors and is cleaved by cell surface proteases into PA63, while LF and EF compete for binding to PA63. The PA63-LF/EF complex is internalized into the cytosol and causes different pathogenic responses in animals and cultured cells. 1-300 amino acid residues of LF have been viewed as the region responsible for the high affinity binding of LF to PA. Amino acid analysis of LF and EF revealed a common stretch of 7 amino acids (147VYYEIGK153). In the present study, each amino acid of this stretch was replaced by alanine at a time. Y148A, Y149A, I151A, and K153A mutants were found to be deficient in their ability to lyse J774A.1 cells and their binding ability to PA63 was drastically reduced. We propose that these four amino acids play a crucial role in the process of binding of LF to PA63.

Amino Acid Sequence↗
PubMed2001

Probing chromosome structure with dynamic force relaxation.

We report measurements of the dynamics of force relaxation in single mitotic chromosomes, following step strains applied with micropipettes of force constant approximately 1 nN/microm. The force relaxes exponentially after an elongation (l/l(0)) to less than 3x native length, with a relaxation time approximately 2 sec. This relaxation time corresponds to an effective viscosity approximately 10(5) times that of water. We experimentally rule out solvent flow into the chromosome as the mechanism for the relaxation time. Instead, the relaxation can be explained in terms of the disentanglement dynamics of approximately 80 kb chromatin loop domains.

Animals↗
PubMed2001

Preoperative sonography in presumed thyroglossal duct cysts.

OBJECTIVE: To determine the utility of ultrasonography as a sole diagnostic study in the preoperative preparation of patients with presumed thyroglossal duct cysts. DESIGN: Retrospective chart review. SETTINGS: Children's Memorial Hospital, Chicago, Ill. PATIENTS: Forty-five pediatric patients with midline masses. MAIN OUTCOME MEASURE: Accuracy in the determination of a normally positioned thyroid gland excluding the presence of a solitary ectopic thyroid gland. RESULTS: A retrospective chart review was performed at our institution for the period February 1990 to January 1996. A total of 45 patients with midline masses were identified, 39 of whom had undergone preoperative ultrasonography as their sole diagnostic imaging study. In all 39 patients, both a cyst and a normal thyroid gland were identified. All 39 patients underwent the standard Sistrunk procedure. Thirty-seven patients had pathologically confirmed thyroglossal duct cysts. The remaining 2 had dermoid cysts. There were no cases of postoperative hypothyroidism. CONCLUSIONS: The incidence of ectopic thyroid in the diagnosis of thyroglossal duct cysts has been reported to be as high as 1% to 2%. In our surgical and clinical experience, the actual incidence of solitary ectopic thyroid tissue is substantially lower. Nevertheless, to prevent the inadvertent removal of the only functioning thyroid tissue, with resultant postoperative hypothyroidism and possible medicolegal consequences, we advocate the routine preoperative identification of normal thyroid gland. We recommend ultrasound as an accurate, cost-effective, noninvasive imaging modality in the preoperative evaluation of all patients with neck masses suspicious for thyroglossal duct cyst. Also, it does not require sedation.

Child↗
PubMed2001

The different behaviors of skeletal muscle cells and chondrocytes on PEGT/PBT block copolymers are related to the surface properties of the substrate.

The attachment, proliferation, morphology, and differentiation of two cell types-skeletal muscle cells and chondrocytes-were investigated on different compositions of poly(ethylene glycol) and poly(butylene terephthalate) segmented block copolymers. Four weight percentages (40, 55, 60, and 70%) and two different molecular weights (300 and 1000 Da) of poly(ethylene glycol) were tested. Varying the weight percentage and molecular weight of poly(ethylene glycol) resulted in different behaviors for skeletal muscle cells and chondrocytes. The attachment of skeletal muscle was the highest (similar to tissue culture polystyrene) when copolymers containing 55 wt % of poly(ethylene glycol) were used, regardless of the poly(ethylene glycol) molecular weight. Maximum proliferation and differentiation of skeletal muscle cells was achieved when copolymers containing 55 wt % and 300 Da molecular weight of poly(ethylene glycol) were used. In contrast, the weight percentage and molecular weight of poly(ethylene glycol) had no significant effect on chondrocyte attachment and proliferation; the attached chondrocytes retained a differentiated phenotype only when a 70 wt % of poly(ethylene glycol) was used. Cell behavior was correlated with the surface properties of the copolymer films, as indicated by contact-angle measurements. These results suggest that an optimized wt % and molecular weight of poly(ethylene glycol) will be useful depending on the specific cell type.

Animals↗
PubMed2001

Histamine--can it cause an acute coronary event?

Myocardial infarction (MI) occurring during the course of an allergic urticarial reaction in the absence of systemic hypotension has been rarely reported. This paper reports the case of a 28-year-old woman with no significant risk factors for coronary artery disease who presented with generalized urticaria associated with chest pain and had electrocardiographic and enzymatic evidence of an acute MI. Review of the literature suggests that local histamine release may induce spasm of the coronary vasculature, thus leading to myocardial ischemia and infarction.

Adult↗
PubMed2001

Do you still need a biopsy to diagnose celiac disease?

Celiac disease is a common and permanent condition caused by an abnormal immune response to ingested gluten in genetically susceptible individuals. Its proper diagnosis is very important even in patients presenting with mild symptoms because severe and debilitating complications may occur in celiac patients not following a strict gluten-free diet. In the past several years, important progress has been made not only in our understanding of the pathogenesis of this condition but also in the availability of tools to screen it. Antigliadin antibodies, once largely used for this purpose, have been basically replaced by the more costly but far more accurate antiendomysium antibodies. More recently, the enzyme-linked immunosorbent assay (ELISA), which measures the antibodies directed against the autoantigen responsible for the disease (tissue transglutaminase), has also been developed and tested as a screening tool. Currently, however, the poor positive predictive value of this test does not allow practitioners to diagnose celiac disease without the duodenal biopsy showing the typical morphologic changes.

Algorithms↗
PubMed2001

Infantile neuronal ceroid lipofuscinosis: no longer just a 'Finnish' disease.

The neuronal ceroid lipofuscinoses (NCLs) are a group of enigmatic neurodegenerative disorders of children that have in common the storage of autofluorescent lipofuscin, or aging pigment, in the brain. With the identification of the three major genes involved in the disorder, the NCLs are now appreciated to represent true lysosomal storage disorders. The most severe (infantile) form of NCL is caused by mutations in a lysosomal thioesterase that removes fatty acids from modified cysteine residues in proteins. Although the disorder was first described in Finland (and the identification of the underlying gene (CLN1) made in this population) defects in CLN1 and the underlying deficiency have been widely reported outside of Scandinavia. In this report, we summarize the relationship of genotype to phenotype in the disorder and evaluate known mutations in light of the recently solved crystal structure of defective enzyme, palmitoyl-protein thioesterase (PPT). We also discuss progress in identifying the fatty acyl cysteine thioesters that accumulate in PPT deficiency and in working toward animal models of NCL. Recent progress in these areas holds promise for the eventual treatment of the disorder.

Animals↗
PubMed2001

Localized oxygen use of healthy and low back pain individuals during controlled trunk movements.

Individuals who have low back pain (LBP) have significantly different motion characteristics than healthy individuals. However, the cause of these differences is unknown. Oxygen use of the erector spinae muscle was examined while simultaneously monitoring motion characteristics to determine whether oxygen use differed between healthy and LBP individuals. Thirty volunteers were classified as healthy, structural, or muscular-based LBP. A near-infrared spectrometer monitored oxygen use and blood volume in the lumbar region. Results showed significant differences in oxygen use but not blood volume between healthy and LBP subjects with muscular-based disorders. Inability of the muscular group to use oxygen in a manner similar to the healthy group indicates different processes at the tissue level, indicating that differences in oxygen use may provide insight into why motion patterns differ between healthy and LBP groups.

Adult↗
PubMed2001

6-mercaptopurine metabolite levels in children with inflammatory bowel disease.

OBJECTIVES: Some authors suggest that efficacy of 6-mercaptopurine (6-MP) in patients with inflammatory bowel disease correlates with circulating 6-thioguanine (6-TG) levels more than 235 pmol/8 x 10(8) red blood cells. The authors evaluated the relation between 6-MP metabolite levels and disease activity in children and adolescents with inflammatory bowel disease. METHODS: Clinical status and hematologic and hepatic parameters were determined in 101 children with inflammatory bowel disease from a single center and compared with 6-MP metabolite levels. RESULTS: There was a trend for higher 6-TG levels among patients in remission than among those with active disease (217 vs. 173); however the difference was not statistically significant ( P = 0.09). The likelihood of therapeutic response did not increase significantly at 6-TG levels greater than 235 pmol/8 x 10(8) red blood cells (odds ratio 1.7; P = 0.1). In the current study, 58% of patients in remission had 6-TG levels less than 235. However, serial measurements of 6-MP metabolite levels in 50 patients with active disease showed that increasing 6-TG levels correlated significantly with disease remission in patients followed up longitudinally ( P = 0.04). Leukopenia was significantly associated with high 6-TG levels ( P = 0.03) but not with clinical response ( P = 0.2). CONCLUSIONS: These data suggest that the target range of 6-TG levels previously described by others did not apply to 58% of the pediatric patients with IBD in remission. However, serial monitoring of 6-MP metabolite levels in individual patients with active disease should allow dose escalation and induction of remission while minimizing the risk of toxicity.

Adolescent↗
PubMed2001

Complications associated with the Sistrunk procedure.

OBJECTIVE: To assess the type and rate of complications in the postoperative period of pediatric patients undergoing the Sistrunk procedure. STUDY DESIGN: A retrospective review of patients with a diagnosis of thyroglossal duct cyst who had not had corrective surgery previously. An attempt to standardize the study was made as follows: all patients had surgery under the direction of one surgeon, using the Sistrunk procedure with minor modifications from its original description. Complications were divided into major and minor categories. METHODS: Charts were reviewed for age, sex, preoperative assessment, and postoperative follow-up. Complications were recorded. A postoperative telephone survey was conducted. RESULTS: A minor complication rate of 29% was observed. There were no recurrences or major complications. CONCLUSIONS: The Sistrunk procedure remains the operation of choice for removal of the thyroglossal duct cyst. When the surgery is properly performed, with attention to key surgical landmarks, the risk of major complication is minimal. Complications that do occur are minor and wound related.

Bandages↗