Search PubMed⌕ Search

Biomedical subjects

A Mehta

Publications and source records attributed to A Mehta.

At least 199 records · Page 11Linked to original sources
PubMed1994

Characterization of sodium-dependent glucose transport in sheep tracheal epithelium.

The nonmetabolizable glucose analogue methyl(alpha-D-[U-14C]gluco)pyranoside ([14C]AMG) was used to study sodium-dependent glucose transport in two preparations: 1) discs punched from strips of sheep tracheal epithelium, and 2) freshly enzyme-isolated sheep tracheal epithelial cells. In discs, cellular accumulation of [14C]AMG was saturable and exhibited a Michaelis-Menten constant (Km) for AMG of 0.63 +/- 0.15 mM. Uptake was linear over 30 min and was inhibited maximally by 100 microM phlorizin [inhibition constant (Ki) approximately 20 nM], by replacement of external sodium with choline or by addition of 10 mM D-glucose (Ki = 0.19 +/- 0.02 mM). Accumulative uptake was activated, in a concentration-dependent manner, by external sodium [affinity constant (Ka) approximately 23 mM] with a Hill coefficient of greater than one but was abolished on depolarizing with high external potassium. In the presence of sodium, D-galactose and AMG both inhibited uptake of [14C]AMG, whereas L-glucose, D-fructose, and D-mannose were ineffective. In isolated cells, [14C]AMG accumulated only in the presence of external sodium and uptake was inhibited by the addition of D-glucose (Ki approximately 0.2 mM), D-galactose, and AMG but not by L-glucose or D-xylose. We conclude that sheep tracheal epithelium exhibits sodium-dependent glucose uptake with a very high affinity for phlorizin, which indicates the presence of a novel isoform of the transporter.

Animals↗
PubMed1994

A novel chloride-dependent GTP-utilizing protein kinase in plasma membranes from human respiratory epithelium.

The protein kinases that stimulate ion flux across airway epithelium are believed to utilize ATP as phosphate donor. Here we show that a chloride-sensitive protein kinase (in an apically enriched plasma membrane fraction from human nasal respiratory epithelium) uses guanosine 5'-triphosphate in preference to ATP as phosphate donor and is not inhibited by the protein kinase inhibitors staurosporine, 1-(5-isoquinolinylsulfonyl)-2-methylpiperazine, and N-(2-guanodinoethyl)-5-isoquinoline sulfonamide. This kinase phosphorylates a 37-kDa membrane protein (p37), which exhibits a 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid (DIDS)-sensitive phosphorylation peak at 40 mM Cl- (DIDS inhibition constant = 8 microM). p37 is additionally phosphorylated by an N-(2-guanodinoethyl)-5-isoquinoline sulfonamide-inhibitable protein kinase that uses ATP and shows a similar chloride sensitivity. The profile of membrane phosphoproteins generated by both kinases is also dependent on the source of Pi, the species of anion, and the concentration of anion. We propose a molecular mechanism for the transduction of Cl- concentration into a guanosine 5'-triphosphate-selective protein kinase signal and show that anion substitution alters the intensity of phosphorylation of membrane proteins in the absence of exogenously added protein kinases.

4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid↗
PubMed1994

E2A/HLF fusion cDNAs and the use of RT-PCR for the detection of minimal residual disease in t(17;19)(q22;p13) acute lymphoblastic leukemia.

Three cases of acute lymphoblastic leukemia (ALL) with the rare t(17;19)(q22;p13) translocation were investigated for E2A/HLF fusion genes using reverse transcription coupled with polymerase chain reaction (RT-PCR). The patients had C-ALL, F/17 years (case 1) or pre-B ALL, M/11 years (case 2) and M/13 years (case 3). Case 1 had an event-free survival (EFS) of 42 months. Case 2 was ultimately refractory to treatment. Case 3 presented following EFS of 16 months in morphological remission (1% blasts), but with immunological and cytogenetic evidence of active disease, then relapsed, remitted and relapsed. Type II E2A/HLF fusion cDNA was found at diagnosis (cases 1, 2), at presentation (case 3) and in all samples tested, whether with active disease or in complete remission (CR). Case 3 showed, in addition, type I fusion E2A/HLF cDNA at presentation, through induction therapy when there was evidence of active disease, but not in CR. Cases 1 and 3 had bone marrow transplantation while in CR but with residual disease detectable by RT-PCR. All patients have died of ALL. Two cases (2 and 3) had hypercalcemia with bone lesions. No case had any evidence of disseminated intravascular coagulation. This is the first demonstration of the value of RT-PCR for the detection of minimal residual disease in t(17;19) ALL.

Adolescent↗
PubMed1993

Effect of statil on kidney structure, function and polyol accumulation in diabetes mellitus.

We examined the effects of an aldose-reductase inhibitor, statil, which blocks the conversion of glucose to sorbitol, in rats rendered diabetic with streptozotocin in order to determine whether the anticipated changes in sorbitol content was associated with beneficial lack of changes in renal morphology and function. Groups of diabetic, insulin-treated and untreated rats were fed statil daily for a period of five months; each group was paired with a non-drug-treatment control group. At the conclusion of the study period, statil was not found to affect renal sorbitol concentrations nor did it effect functional or structural changes seen in the kidney. We conclude that further study, using other doses of statil and longer duration over which data is collected, must be undertaken in order to implicate the polyol pathway in the renal complications of diabetes mellitus.

Aldehyde Reductase↗
PubMed1993

sICAM-1 enhances cytokine production stimulated by alloantigen.

The leucocyte adhesion molecules lymphocyte functional antigen-1 (LFA-1; CD11a/CD18) and intercellular adhesion molecule-1 (ICAM-1; CD54) facilitate the cell-to-cell interactions which are required for the initiation of immune responses. The role of this interaction in the response to alloantigen was assessed by comparing the effects of monoclonal antibodies against these molecules to the effects of a soluble form of the ICAM-1 molecule in the mixed lymphocyte response (MLR). In contrast to the well-documented inhibitory effects of anti-ICAM-1 or anti-LFA-1 antibodies on mixed lymphocyte responses, we were unable to block these responses with the soluble form of ICAM-1 (sICAM-1). In contrast, the addition of sICAM-1 to these cultures resulted in a two- to sixfold enhancement in the T-cell proliferative response to alloantigen over the normal response. Unlike previous reports, the biological activity of sICAM-1 was not dependent on generation of a solid-phase form of the molecule. The enhanced proliferative response correlated with an increase in the level of TNF-alpha detected in the MLR supernatants and could be blocked by antibodies to TNF-alpha. sICAM-1 had no effect on proliferation or cytokine production in the absence of alloantigen. These results suggest that antibodies which block ICAM-1/LFA-1 not only block the adhesion which is required to stabilize cell-to-cell contact, but also block the costimulatory signal which is required for T-cell activation.

Cell Adhesion Molecules↗
PubMed1993

Antibiotic inhibition of pectolytic and cellulolytic enzyme activity in two Fusarium species.

Among all antibiotics tested, amoxycillin (500 ppm) completely inhibited the polygalacturonase and pectinmethylgalacturonase enzyme activity in F. oxysporum; none of the antibiotics did so in F. moniliforme. No antibiotic completely inhibited the cellulase activity in both test organisms, however, amoxycillin was better than other antibiotics in inhibiting the cellulase activity in both the organisms.

Amoxicillin↗
PubMed1993

MK 886, an antagonist of leukotriene generation, inhibits DNA synthesis in a subset of acute myeloid leukaemia cells.

We have studied the actions of inhibitors of leukotriene generation on DNA synthesis (measured by 3H-thymidine incorporation) in blast cells from patients with acute myeloid leukaemia (AML). Cells from a subset only of these patients were sensitive to MK 886, a potent selective inhibitor of leukotriene synthesis. By contrast, DNA replication in cells from all of the patients was inhibited by nordihydroguiaretic acid (NDGA), a leukotriene synthesis inhibitor of lower selectivity. DNA synthesis in normal bone marrow cells and phytohaemagglutinin-stimulated lymphocytes was sensitive to NDGA but not to MK 886. The data suggest that NDGA inhibits DNA replication by a mechanism other than the abolition of leukotriene biosynthesis, but that DNA synthesis in a subset of AML cells may be dependent on the generation of lipoxygenase products, as indicated by sensitivity to MK 886.

Adult↗
PubMed1993

Partial denervation of the medial gastrocnemius muscle results in growth-associated protein-43 immunoreactivity in sprouting axons and Schwann cells.

Regeneration in the mammalian peripheral nervous system following nerve injury is associated with the upregulation of a developmentally regulated phosphoprotein, growth-associated protein-43 (GAP-43), in the injured neurons. We have examined whether uninjured adult neurons also express GAP-43 when they sprout. The model system investigated has been the sprouting induced in the terminal axons of intact motor neurons by a partial muscle denervation. Partial denervation of the medial gastrocnemius muscle in adult rats was produced by resecting the terminal nerve supply to the anterolateral quadrant of the muscle. Three zones could be identified in the motor endplate region of the muscle after such a denervation using protein gene product (PGP) 9.5, calcitonin gene-related peptide and silver staining as axonal markers and S-100 to identify Schwann cells: a normally innervated zone, a totally denervated zone and a border or intermediate zone between the two which contained axons at the endplates with nodal and terminal sprouts. The endplates in the normally innervated zone were GAP-43 negative. In the denervated zone, Schwann cells were GAP-43 positive and had a distinctive appearance with a lack of any normal endplate organization. Endplates in the intermediate zone were GAP-43 immunoreactive. In approximately half, the GAP-43 immunoreactivity was axonal-like, identical to PGP 9.5 in an adjacent section; in the remainder it was Schwann cell-like, identical to S-100 staining. Partial muscle denervation results, therefore, in the appearance of GAP-43 both in axons and Schwann cells in the endplates bordering the denervated zone. The presence of GAP-43 in these cells may contribute to their capacity to sprout.

Acetylcholinesterase↗
PubMed1993

Impact of aprotinin on blood transfusion requirements in liver transplantation.

A retrospective study was carried out to ascertain the blood bank provision required to support a liver transplant programme and to assess the effect of intraoperative aprotinin on blood product requirements in liver transplant recipients with cirrhosis. Sixty patients with end-stage liver disease underwent 62 consecutive orthotopic liver transplants between October 1988 and January 1991. The total and intraoperative requirements of red cells, platelets and fresh frozen plasma (FFP) were analysed for three groups of liver transplant recipients, those without cirrhosis (n = 15), those with cirrhosis (n = 25) and those with cirrhosis who received intraoperative aprotinin (n = 20). Fifteen without cirrhosis had mean total requirements of 15 units of red cells, 18 units of platelets and 16 units of FFP. Twenty patients with cirrhosis who received intraoperative aprotinin had broadly similar requirements. However, blood product requirements for 25 patients with cirrhosis were significantly greater (46 units of red cells, 41 units of platelets, 43 units of FFP, excluding the seven patients with primary biliary cirrhosis). We conclude that a liver transplant programme can be supported by a teaching hospital blood bank. The use of intraoperative aprotinin significantly reduces blood product requirements.

Adult↗
PubMed1993

H-ras-1 restriction fragment length polymorphism in normal individuals and oral cancer patients in India.

Restriction fragment length polymorphism (RFLP) of the human H-ras-1 gene has been indicated as a marker for detection of individuals at high risk of cancer. We have investigated the association of RFLP at the H-ras-1 locus and susceptibility to oral cancer by Southern hybridization analysis in 77 primary oral tumors and 99 healthy donors. The frequency distribution of the BamHI fragments of H-ras-1 revealed homozygous or heterozygous alleles in the two subpopulations. The heterozygous genotype occurred more frequently in the normal subjects (53%) as compared to the cancer patients (36%). Four common alleles-C1 to C4, were noted predominantly in both groups, with rare alleles detected at a lower frequency. The common allele with 7.6 kb BamHI fragment was significantly higher in normals (10%) than in the tumor population (4%) (P < 0.05). However, a similar distribution of rare alleles in both groups indicated that the presence of rare alleles is not indicative of predisposition to oral cancer.

Alleles↗
PubMed1993

Unilateral auto-PEEP in the recipient of a single lung transplant.

We report a patient who received a right single lung transplant (SLT) for progressive lymphangioleiomyomatosis and required reintubation for postoperative respiratory distress. She developed hemodynamic instability due to mediastinal shift from unilateral auto-PEEP with hyperinflation of the native lung. Placement of a double lumen endotracheal tube (DLET) and institution of differential lung ventilation restored equal lung inflation and hemodynamic stability.

Adult↗
PubMed1993

Minimal residual disease in acute lymphoblastic leukaemia--PCR analysis of immunoglobulin gene rearrangements.

Rearrangement of the immunoglobulin heavy chain (IgH) gene can be utilized as a marker of clonality in a number of B-lineage lymphoproliferative disorders including acute lymphoblastic leukaemia (ALL). We have used a PCR technique involving a panel of amplimers for the 6 different Variable (VH) region families and for a consensus sequence of the Joining (JH) segment to detect clonal IgH rearrangements in the peripheral blood (PB) and/or bone marrow (BM) of 28 patients (17 children and 11 adults) with B-lineage ALL at presentation (20 patients) or with overt relapse (8 patients). The age range of the patients was 2-65 years (mean 15.7 years). Follow up remission BM samples were analysed in 22 patients during and after therapy (2-7 samples per patient), 1-50 months after presentation or relapse. In 1 relapsed case, previously stored complete remission (CR) samples were analysed retrospectively. Clonal IgH chain rearrangements were detected by PCR in 90% of patients studied initially. The 2 VH region families most commonly used were the large VH3 family (65%) and the smaller more JH-proximal VH4 family (22%). More than one VH clone was detectable in 25% of the cases. A gene "fingerprinting" modification of a previously described method was applied to the detection of minimal residual disease (MRD) in follow up BM samples with a sensitivity of 10(-3) to 10(-4). In 8 of 14 patients remaining in complete remission (CR) during the time of study, all PCR analyses on BM samples in the first 6 months were negative, in some cases as early as 2 weeks post-induction therapy, and a further patient reverted from being PCR positive in the first month after the commencement of therapy to sustained PCR negativity. One adult remains in CR at 50 months after presentation and has been PCR negative at 2 time points after cessation of maintenance therapy (30 and 50 months). Eight patients relapsed in the study period comprising 6 BM and 2 isolated CNS relapses. In 4 cases of BM relapse occurring within 7 months of the start of therapy, all BM remission samples tested in this period were PCR positive. In 2 other patients BM samples tested 7 and 2 months respectively prior to relapse were PCR negative. In the 2 patients with isolated CNS relapse, PCR of BM samples from 2 and 10 months before the relapse were negative.(ABSTRACT TRUNCATED AT 400 WORDS)

Adolescent↗