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Biomedical subjects

P C Patel

Publications and source records attributed to P C Patel.

33 records · Page 2Linked to original sources
PubMed1991

Transvesical vesicovaginal fistula repair: a revival.

Vesicovaginal fistulae are usually traumatic in nature, following obstetric or gynecologic trauma. Here, our experience with vesicovaginal fistula repair in 68 cases, performed transvesically (58 cases) or transperitoneally-transvesically, with pedicled omental interposition in 10 cases over the last 8 years is described. The size of fistulae ranged from 1 to 5 cm, and most were situated near or above the trigone. Two cases required ureteric reimplantation. Recurrent fistulae were found in 4 cases. We attribute our success to the simple access, the construction of a vascularized flap, the tension-free grid-iron closure, and the utilization of Vicryl suture.

Cesarean Section↗
PubMed1990

A novel thymic epithelial adhesion molecule.

Interactions between thymocytes and thymic stromal cells are responsible for positive and negative selection of T cell, their differentiation, maturation and proliferation. The signals required for these events to occur often necessitate close contact, and indeed adhesion, between the cell types involved. The identification of specific adhesion molecules in this context, is, therefore, a vital first step in determining the nature of the signal they mediate or facilitate at a given stage of differentiation. In the present work we identify, isolate and partially characterize a ligand present on thymic medullary epithelial cells which selectively binds CD4+ CD8+ thymocytes found primarily in the thymic cortex. This adhesion molecule is composed of two non-covalently associated glycoproteins of 23 kDa and 45 kDa, respectively, both of which are needed to bind to thymocytes. The importance of the finding is that the ligand, in isolated immobilized form, binds the same thymocyte subset as the original epithelial cell line from which it was isolated. The CD4+ CD8+ thymocyte subset is the precursor of single-positive mature T cells; hence the putative biological activity of the ligand in question takes place at a pivotal stage of T cell differentiation.

Animals↗
PubMed1987

Monoclonal antibodies to TEM-1 plasmid-mediated beta-lactamase.

At least 28 plasmid-mediated beta-lactamases have been described in gram-negative bacteria. To assess the relationship among these enzymes, we produced and characterized 28 murine monoclonal antibodies to the TEM-1 plasmid-mediated beta-lactamase. Radial immunodiffusion identified 3 monoclonal antibodies as immunoglobulin M (IgM), 18 as subclass IgG1, 2 as IgG2a, and 5 as IgG2b. Using a newly described enzyme immunoassay, cross-reactivity of 16 of these monoclonal antibodies was tested against 24 plasmid-determined beta-lactamases. The 16 monoclonal antibodies cross-reacted with TEM-2 and TLE-1 and, to a certain extent, SHV-1. Different levels of cross-reactivity were also observed with OXA-3 (11 of 16), OXA-7 (8 of 16), OXA-1 (2 of 16), OXA-6 (2 of 16), and AER-1 (2 of 16). Six monoclonal antibodies demonstrated partial neutralization of beta-lactamase activity. This study suggests that common epitopes are shared by nine biochemically distinct plasmid-mediated beta-lactamases. On the basis of cross-reactivities with these monoclonal antibodies, we identified four epitopes on TEM-1, TEM-2, TLE-1, and SHV-1 beta-lactamases.

Animals↗
PubMed1986

Use of monoclonal and polyclonal antibodies to detect prostatic acid phosphatase by immunoblotting.

We investigated two techniques of immunoblotting--the Western blot and the dot blot--for use in detecting prostatic acid phosphatase (PAP, EC 3.1.3.2). We used polyclonal antisera to human PAP, produced in rabbits by hyperimmunization with purified PAP, and PAP-specific monoclonal antibodies in the immunoenzymatic protocols. We conclude that PAP can be readily detected by Western blots with use of polyclonal antisera, but not with monoclonal antibodies. On the other hand, using a dot blot assay, we could easily detect PAP with both polyclonal and monoclonal antibodies.

Acid Phosphatase↗
PubMed1984

Effects of certain nucleoside analogues on human cytomegalovirus replication in vitro.

Four nucleoside analogues, 1-(2'-deoxy-2'-fluoro-beta-D-arabinofuranosyl)-5-methyluracil (FMAU), -5-iodouracil (FIAU), -5-methylcytosine (FMAC) and -5-iodocytosine (FIAC), were studied for their effect on human cytomegalovirus (HCMV) replication in vitro. FMAU, FIAU, FMAC and FIAC showed antiviral activities for four strains of HCMV (Major, Clegg, D550 and Towne) in a plaque reduction assay, with a dose required for 50% inhibition (ED50) in the range of 0.1 to 0.65 microM. At a concentration of 1 microM-FMAU or -FIAC, the synthesis of five virus-specific late polypeptides of molecular weights 150 000, 120 000, 67000, 54000 and 27000 was entirely blocked. Quantification of Towne viral DNA synthesis, using complementary RNA-DNA hybridization with a Towne-specific cRNA probe, demonstrated a complete inhibition of HCMV DNA replication at 1 microM of FMAU or FIAC. After the removal of the inhibitors, however, viral DNA synthesis resumed, and infectious virus reappeared, indicating that the inhibition of HCMV replication by these nucleoside analogues was of a virostatic reversible type.

Antiviral Agents↗
PubMed1982

Effect of 9-(2-hydroxyethoxymethyl)guanine on viral-specific polypeptide synthesis in human cytomegalovirus-infected cells.

Plaque-forming assay resulted in a 50 percent inhibitory dose by 9-(2-hydroxyethoxymethyl)guanine (acyclovir) against Towne strain human cytomegalovirus (HCMV) of approximately 98 mumol. At the drug concentration of 200 mumol, we did not detect any significant inhibition of viral DNA synthesis by cRNA-DNA hybridization. However, at this drug concentration, the synthesis of at least two viral-specific late polypeptides (150K and 67K) was significantly retarded up to 48 hours after infection, but resumed at 72 hours. These data suggest that acyclovir or its in vivo transformed derivative had a transient effect on viral-specific polypeptide synthesis in HCMV-infected human fibroblasts at a high drug concentration.

Acyclovir↗
PubMed1982

Cytotoxic effector cells from infectious mononucleosis patients in the acute phase do not specifically kill Epstein-Barr virus genome-carrying lymphoid cell lines.

We describe a study in which we investigated the cytotoxic activities of thymusderived (T) lymphocytes and natural killer cells against Epstein-Barr virus (EBV) genome-carrying lymphoid cell lines. Purified subpopulations of lymphocytes from eight patients with infectious mononucleosis and six healthy normal EBV-seropositive donors were tested. Enriched T-cells were obtained by passing purified whole blood lymphocyte preparations through human immunoglobulin-anti-immunoglobulin-coated glass bead columns. The cytolytic activity of effector cells was determined by the ability of these cells to lyse human target cells that were internally labeled with (51)Cr. These targets included cells from both EBV genome-carrying and EBV genome-negative lymphoid lines derived from malignant tumors, as well as from lymphocytes transformed in vitro by EBV, and were chosen to represent a wide spectrum of EBV-associated membrane antigens. We found that cytotoxic T-cells from patients with infectious mononucleosis showed no EBV-related specific cell killing per se, although a trend for increased killing of cell lines derived from spontaneous in vivo growing tumors, EBV genome carrying or not, was noted; however, this trend was not observed with cell lines derived from cord blood lymphocytes after EBV infection in vitro. In addition, our data suggest that natural killer cells may play an important role in controlling EBV infection in patients with infectious mononucleosis in the acute phase of the disease, particularly since T-cells (obtained after removal on immunoglobulin-anti-immunoglobulin columns of natural killer cells presumably bearing Fc receptors) were less efficient killers than whole blood lymphocytes; furthermore, lysis by whole blood lymphocytes was also greatest against cell lines derived from malignant tumors (as opposed to in vitro EBV-transformed cord blood lymphoid lines), irrespective of whether these targets were EBV genome positive or negative.

Cell Line↗
PubMed1982

Epstein-Barr virus (EBV)--lymphoid cell interactions. II. The influence of the EBV replication cycle on natural killing and antibody-dependent cellular cytotoxicity against EBV-infected cells.

We investigated the influence of the Epstein-Barr virus (EBV) replication cycle on natural killing (NK) activity and antibody-dependent cellular cytotoxicity (ADCC) against EBV-infected cells. Peripheral blood lymphocytes from healthy EBV-seropositive and -seronegative donors were separated on Ficoll-Hypaque gradients and used as effector cells in the standard 51Cr release assay to measure NK and ADCC. EBV-genome positive RAJI and DAUDI cells superinfected with either the non-transforming P3HR-1 EBV or the transforming B95-8 EBV were used as targets. The results obtained show that most normal individuals have ADCC and NK activity against P3HR-1 EBV-infected RAJI cells. Both the cytotoxic activities increased with the proportional increase in effector/target (E/T) ratios, assay incubation time, dose of the infecting virus and the time of pre-infection with EBV. Moreover, the data obtained indicate that different immune mechanisms are effective at different stages of the virus replication cycle. During the early stages of virus replication, EBV-superinfected cells are more susceptible to ADCC than to NK, whereas in later stages the susceptibility to NK is increased significantly and appears to play a more dominant role. The nature of the target cells or the strain of EBV used to superinfect these targets did not influence their susceptibility to ADCC and NK activity; however some quantitative differences were found. Using metabolic inhibitors such as cytosine arabinoside, phosphonoacetic acid, actinomycin D, cycloheximide and puromycin, it was found that new DNA synthesis is not essential but some RNA and protein synthesis is necessary, late in the viral cycle, for the superinfected cells to become susceptible to NK and ADCC.

Antibodies, Viral↗
PubMed1981

Staphylococcal protein A enhances natural killing activity against lymphoid tumor cell lines.

Protein A (pA), was found to augment the natural killing (NK) activity of peripheral blood lymphocytes against Burkitt's lymphoma-derived Raji and Daudi cells. This pA-enhanced NK activity was determined using the 51Chromium release microcytotoxicity assay. It was found that the increased NK activity was dependent on the concentration of pA used. In addition, the pA-enhanced NK activity was dependent on the time of incubation of pA with the effector and target cell mixture. Pretreatment of effectors for 16 h or more dramatically increased the NK activity against a wide range of tumor targets of different origin and possessing either B, T or null cell surface characteristics. The presence of the Epstein-Barr virus (EBV)-genome in the target cells did not influence the pA-enhanced NK activity. Nylon-wool column-fractionated, non-adherent lymphocytes (enriched in NK cells) showed an increased NK activity in the presence of pA than unfractionated lymphocytes. Pretreatment of certain targets with pA rendered them more sensitive to NK lysis. Interferon production was readily detected in supernatants from cultures of pA-treated effectors or effector-target mixtures, but not in supernatants from pA-treated target cultures tested. Results of different physicochemical treatments indicate that the pA-induced interferon is of gamma type (type II). Thus, the data presented suggest that the pA-induced enhancement of NK activity is most likely mediated by the pA-induced interferon.

Burkitt Lymphoma↗
PubMed1981

Human cytomegalovirus-associated DNA polymerase and protein kinase activities.

Human cytomegalovirus (HCMV), purified exclusively from the extracellular media, contained a DNA polymerase activity in addition to a protein kinase activity. The DNA polymerase expressed its maximum activity in the presence of 5 to 10 mM-MgCl2. The enzyme was able to use effectively activated calf thymus DNA, poly(dA).oligo(dT)12--18 and poly(dC).oligo(dG)12--18 as the template primers. The DNA polymerizing activity was eluted with 0.18 to 0.2 M-KCl from a phosphocellulose column. It was relatively resistant to phosphonoacetic acid inhibition even at a high concentration of 100 micrograms/ml with activated calf thymus DNA as the template primer, but the DNA polymerase activity was totally suppressed at this concentration when poly(dA).oligo(dT)12--18 was used as the template primer. The enzyme activity was inhibited by ammonium sulphate at 0.01 to 0.3 M with either activated calf thymus DNA or poly(dA).oligo(dT)12--18 as the template primer. The protein kinase has maximum activity in the presence of 10 to 20 mM-MgCl2, and preferred virion proteins as phospho-acceptor to protamine sulphate. Histone, caesin and bovine serum albumin (BSA) were found to be poor substrates. The phosphorylated protein pattern of the in vivo [32P]orthophosphate-labelled virions was not identical to that of the in vitro phosphorylated Nonidet P40-dissociated virions, although seven phosphorylated polypeptides did co-migrate in SDS--polyacrylamide gel electrophoresis (SDS--PAGE). Procedures known to solubilize virions showed that the DNA polymerase and protein kinase were internal components of the virion.

Ammonium Sulfate↗
PubMed1978

Isolation and identification of the cytoplasmic membrane from Saccharomyces carlsbergensis by radioactive labeling.

The cytoplasmic membrane of Saccharomyces carlsbergensis was isolated by enzymatic digestion of the yeast cell wall, followed by lysis of the protoplasts and fractionation by ultracentrifugation in a discontinuous sucrose density gradient. Location of the cytoplasmic membrane fraction on the sucrose gradient was made by labeling intact protoplasts with [G-3H]dansyl chloride, and was settled at the 50% (wt/vol) sucrose gradient (d = 1.186 g/cm3). Approximately 80% of the radioactivity was found in the membrane fraction prepared in the presence of Mg2+ ions. However, when protease inhibitors were used in the preparation step, the membrane fraction contained over 90% of the total radioactivity. The presence of Mg2+ ions during membrane isolation and purification enhanced the aggregation of membrane components but, at higher concentrations, as well as in the prolonged presence of Mg2+ ions in the membrane suspension, it caused the breakdown of membrane components. The membrane preparation contained Mg2+-adenosine triphosphatase, which was insensitive to oligomycin and ouabain. The distribution of Mg2+-adenosine triphosphatase in different fractions during sucrose gradient is reported.

Adenosine Triphosphatases↗
PubMedDate not supplied

Rosette formation by human lymphoid cells with monkey red blood cells.

The present paper describes a study on rosette formation by human lymphoid cells with monkey erythrocytes (MRBC) obtained from two species: African green monkey (Cercopithecus aethiops) and rhesus monkey (Macaca mulata). All the lymphocyte preparations obtained from peripheral blood, tonsils, thymocytes, bone-marrow and spleen biopsies formed rosettes in variable proportions with erythrocytes obtained from these two monkey species tested. Cells of established lymphoblastoid cell lines characterized as being of either B- or T-cell origin also formed rosettes with MRBC. Taken together, the data obtained suggest that the MRBC-rosette assay cannot be reliably used for identifying lymphocyte subpopulations presently known to us, thus largely contradicting the observations previously reported by others on the use of this assay. In addition, we found that the binding sites for MRBC on the above lymphoid cells are highly sensitive to trypsin treatment and can fully be regenerated within 14-15 h when these treated cells are cultured at 37 degrees.

Animals↗