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P Ray

Publications and source records attributed to P Ray.

At least 181 records · Page 10Linked to original sources
PubMed1991

Bayesian estimation of doxorubicin pharmacokinetic parameters.

Doxorubicin was given by brief i.v. infusion (doses ranging from 25 to 72 mg/m2) to 28 patients for 2-7 successive courses of chemotherapy (68 courses studied in all). A Bayesian approach was developed to determine the individual pharmacokinetic parameters of doxorubicin. Statistical characteristics of the population pharmacokinetic parameters were first evaluated for 19 patients and a total of 30 courses, which, when combined with 4 individual plasma concentrations of drug, led to a Bayesian estimation of individual pharmacokinetic parameters for the remaining 38 courses. The estimated parameters for the elimination phase (A3/V1 and t1/2 elimination) and the residual plasma level at 48 h as computed by Bayesian estimation on this reduced sub-optimal sampling protocol were compared with a maximal likelihood estimation of these parameters. No statistically significant differences were found. Performance of the developed methodology was evaluated by computing bias and precision. The mean errors were -0.0315 x 10(-4) l-1 for A3/V1, 0.0839 h for t1/2 elimination, and -0.22 ng/ml for c(48 h). The precision of the prediction of these three parameters (0.304 x 10(-5) l-1, 3.34 h, and 0.659 ng/ml, respectively) remained lower than the interindividual standard deviation (1.42 x 10(-4) l-1, 14.9 h, and 4.54 ng/ml, respectively). This procedure enables the estimation of individual pharmacokinetic parameters for doxorubicin at minimal cost and minimal disturbance of the patient.

Bayes Theorem↗
PubMed1991

Cyanide sensitive and insensitive bioenergetics in a clonal neuroblastoma x glioma hybrid cell line.

The primary mechanism of cyanide (CN) intoxication is the inhibition of metabolism in the central nervous system. We determined the effects of CN on several biochemical processes in neuroblastoma x glioma hybrid NG108-15 cells, which possess numerous neuronal properties. These cells were not sensitive to a high concentration (1 mM) of NaCN, but became sensitive in the presence of the anaerobic glycolysis inhibitors sodium iodoacetate (IA) and 2-deoxyglucose (2-DG):cellular metabolic processes (e.g., DNA, RNA and protein synthesis) decreased to about 40% of control due to treatment with 0.5 mM NaCN + 0.05 mM IA and 0.1 mM NaCN + 20 mM 2-DG. ATP in cells exposed to 0.01 or 0.1 mM NaCN + 20 mM 2-DG was reduced 75% and 100% respectively within one min. Pretreatment of cells with the CN antidote cobalt (II) chloride (CoCl2) (0.06-0.18 mM) for 5 min prevented the depression of both [3H]leucine incorporation and ATP synthesis due to 1 mM NaCN + 20 mM 2-DG in a concentration-dependent manner. A proposed CN antidote alpha-ketoglutaric acid (disodium salt) also prevented the depression of cellular metabolism due to NaCN plus 2-DG. These results indicate that blocking anaerobic glycolysis makes NG108-15 cells sensitive to a low concentration of CN. Thus NG108-15 cells should be useful to study the mechanisms of neurotoxicity of CN and to test antidotes.

Adenosine Triphosphate↗
PubMed1991

Measurement of regional cerebrovascular haemoglobin oxygen saturation in cats using optical spectroscopy.

We describe the use of optical spectroscopy in the near infra-red light range to non-invasively measure regional cerebral haemoglobin oxygen saturation (rSHbO2) in cats during progressive cerebral hypoxia. This technique differs from spectroscopic techniques previously described in that the concentration ratio--percentage haemoglobin: oxygen saturation--is quantified. This saturation is the weighted summation of saturation in the cerebrovascular system: arterial, venous, and capillary beds. In a cat model of progressive cerebral hypoxia, a positive linear correlation between this regional measurement of cerebral saturation and actual saturation, calculated from cerebral arterial and mixed venous blood, was noted (n = 20, r = 0.88, p less than 0.01). The spectroscopic measurement rSHbO2 is also used to index cerebral oxygen extraction. During hypoxia spectroscopic indexed oxygen extraction (iOE) and cerebral arterial-venous difference in oxygen content were simultaneously measured. A least-squares positive linear correlation between these two parameters was noted [AVDO2 = iOE (0.05) + 4.4] (n = 40, r = 0.6, s = 1.2). Objective measurement of 'regional cerebrovascular haemoglobin saturation' and an index of cerebral oxygen extraction are possible using optical spectroscopy.

Algorithms↗
PubMed1991

Ectopic expression of a c-kitW42 minigene in transgenic mice: recapitulation of W phenotypes and evidence for c-kit function in melanoblast progenitors.

The proto-oncogene c-kit encodes a transmembrane tyrosine kinase receptor that is allelic with the murine white-spotting locus (W). W mutations affect melanogenesis, gametogenesis, and hematopoiesis during development and adult life, and they result from the partial or complete loss of c-kit function. The W42 allele is a W mutation with severe effects in both the homozygous and the heterozygous states. Previous analysis of the W42 allele identified a missense mutation in an essential amino acid of the c-kitW42 kinase domain that abolishes the in vitro kinase activity of the c-kitW42 protein but does not affect its normal expression. These results suggested that the c-kitW42 allele was a dominant negative mutation within the context of c-kit-mediated signal transduction. To further explore the dominant negative characteristics of the W42 mutation, we have generated transgenic mice in which ectopic expression is driven by the human beta-actin promoter (hAP). Two mouse lines carrying the hAP-c-kitW42 transgene show an effect on pigmentation and the number of tissue mast cells. The patchy coat color pattern of the line 695 mice may reflect variable expression of the transgene in melanoblast progenitors and their descendants and, consequently, is indicative of a function for c-kit in early melanoblasts. Germ cell development and erythropoiesis, however, do not appear to be affected by the transgene. Mice expressing the c-kitW42 transgene therefore recapitulate some of the phenotypes of mice with W mutations. These results are therefore in agreement with the molecular basis of the W42 mutation and the dominant-negative characteristics of the c-kitW42 protein product.

Alleles↗
PubMed1991

Influence of Growth Conditions on the Production of a Bacteriocin, Pediocin AcH, by Pediococcus acidilactici H.

The influence of growth parameters on the production of pediocin AcH by Pediococcus acidilactici H was studied. This strain produced large quantities of pediocin AcH in TGE broth (Trypticase [1%], glucose [1%], yeast extract [1%], Tween 80 [0.2%], Mn [0.033 mM], Mg [0.02 mM] [pH 6.5]) within 16 to 18 h at 30 to 37 degrees C (final pH, 3.6 to 3.7). Pediocin AcH production was negligible when the pH of the medium was maintained at 5.0 or above, even in the presence of high cell mass.

Journal Article↗
PubMed1991

Isolation and serological characterization of a Plasmodium vivax recombinant antigen.

A genomic library for Plasmodium vivax was constructed in lambda gt11 and immunologically screened with pooled serum samples from vivax patients. Six seroreactive clones were isolated, and one clone, denoted PV9, was studied further. This clone has an unusual base composition (65% G + C), does not share any homology with P. falciparum, and codes for an entirely new antigenic determinant. Antibodies (immunoglobulin G type) against the PV9-encoded polypeptide were produced in all vivax patients older than 15 years. This seroreactivity was lower among patients younger than 15 years (53%). The antigenic epitope(s) of the PV9-encoded polypeptide was recognized at a similar rate by serum samples from P. vivax patients who were living 350 to 973 km apart. Fifty percent of uninfected Indian adults were also seropositive, whereas all European and American (United States) sera tested were negative, suggesting that anti-PV9 antibodies persist after infection. The seroreactivity pattern of this antigen is similar to that of the immunity developed in malaria after repeated infections.

Adolescent↗
PubMed1990

Presence of pancreatic trypsin inhibitor in adrenal medullary chromaffin cells.

A bovine pancreatic trypsin inhibitor was isolated from bovine adrenal medullary chromaffin granules. Its N-terminal sequence is: arg-pro-asp-phe-cys-leu-glu-pro-pro-tyr-thr-gly-pro-cys-lys-ala-arg-ile- arg-tyr- phe-tyr-asn-ala-lys-ala-gly-leu-cys-gln-thr-phe-val-tyr-gly-gly-cys-arg- ala-lys-arg-asn-asn-phe-lys- which corresponds precisely with the N-terminus of Bovine Pancreatic Trypsin inhibitor. The presence of this inhibitor in these granules suggests another method of regulating the prohormone proteases present there.

Adrenal Medulla↗
PubMed1990

The dominant W42 spotting phenotype results from a missense mutation in the c-kit receptor kinase.

The murine white spotting locus (W) is allelic with the proto-oncogene c-kit, which encodes a transmembrane tyrosine protein kinase receptor for an unknown ligand. Mutations at the W locus affect various aspects of hematopoiesis and the proliferation and migration of primordial germ cells and melanoblasts during development to varying degrees of severity. The W42 mutation has a particularly severe effect in both the homozygous and the heterozygous states. The molecular basis of the W42 mutation was determined. The c-kit protein products in homozygous mutant mast cells were expressed normally but displayed a defective tyrosine kinase activity in vitro. Nucleotide sequence analysis of mutant complementary DNAs revealed a missense mutation that replaces aspartic acid with asparagine at position 790 in the c-kit protein product. Aspartic acid-790 is a conserved residue in all protein kinases. These results provide an explanation for the dominant nature of the W42 mutation and provide insight into the mechanism of c-kit-mediated signal transduction.

Amino Acid Sequence↗
PubMed1990

Molecular bases of dominant negative and loss of function mutations at the murine c-kit/white spotting locus: W37, Wv, W41 and W.

The proto-oncogene c-kit encodes a transmembrane tyrosine protein kinase receptor for an unknown ligand and is allelic with the murine white-spotting locus (W). Mutations at the W locus affect various aspects of hematopoiesis, the proliferation and migration of primordial germ cells and melanoblasts during development. The original W mutation and W37 are severe lethal mutations when homozygous. In the heterozygous state the W mutation has a weak phenotype while W37 has dominant characteristics. Wv and W41 are weak W mutations with dominant characteristics. We have characterized the molecular basis of these four W mutations and determined their effects on mast cell differentiation by using a fibroblast/mast cell co-culture assay. We show that W37, Wv and W41 are the result of missense mutations in the kinase domain of the c-kit coding sequence (W37 E----K at position 582; Wv T----M position 660 and W41 V----M position 831), which affect the c-kit associated tyrosine kinase to varying degrees. The c-kit protein products in homozygous mutant mast cells are expressed normally, although the 160 kd cell membrane form of the c-kitW37 protein displays accelerated turnover characteristics. The W mutation is the result of a 78 amino acid deletion which includes the transmembrane domain of the c-kit protein. A 125 kd c-kit protein was detected in homozygous W/W mast cells which lacks kinase activity and is not expressed on the cell surface.(ABSTRACT TRUNCATED AT 250 WORDS)

Alleles↗
PubMed1990

Entry and replication of Japanese encephalitis virus in cultured neurogenic cells.

The entry mode and growth pattern of Japanese encephalitis (JE) virus in mouse neuroblastoma N18TG2 cells and mouse neuroblastoma x rat glioma NG108-15 hybrid cells were studied by electron microscopy. At two minutes after inoculation, JE virions adsorbed onto and directly penetrated through the plasma membrane of the hybrid cells, whereas virions did not adsorb nor entered the neuroblastoma cells. Correspondingly, the hybrid cells showed assembling progeny JE virions in the cisternae of rough endoplasmic reticulum (RER) 1 day postinoculation (p.i.) although virions were rarely found on the following days during the experiment. On the other hand, progeny virions did not assemble in the RER cisternae of the neuroblastoma cells throughout the experiment. The morphologic observations, therefore, suggest that (a) the hybrid cells express JE-virus receptors which facilitate the viral attachment onto and entry into the cells, while the neuroblastoma cells do not and (b) JE virus replicates very poorly after the entry into the hybrid cells while it does not replicate at all in the neuroblastoma cells. The virus titrations of the media of the neuroblastoma and hybrid cell cultures showed only titers indicative of residual virus of the inoculum that progressively decreased during the experiment. The present results show therefore that of the two neurogenic cell culture lines studied only the hybrid cell line can be used for the study of viral entry and replication, although it is not suited for virus production. Possible reasons for the poor replication of JE virus in the hybrid cells are discussed.

Animals↗
PubMed1990

The mouse W/c-kit locus.

The mature cells in the haemopoietic system arise as the result of the extensive developmental and proliferative capacity of pluripotential stem cells. In order to understand the molecular basis for these developmental processes, it will be necessary to identify and characterize the cellular genes that control early steps in haemopoiesis. Mutations at the mouse W locus on chromosome 5 lead to pleiotropic developmental defects, including sterility, coat colour abnormalities, severe macrocytic anaemia and mast cell deficiency. The defects in all these lineages are cell autonomous and intrinsic, suggesting that the W locus encodes a gene product required directly for cellular differentiation. In an attempt to understand this classical mouse developmental mutation, we have demonstrated that the c-kit proto-oncogene, which encodes a transmembrane receptor tyrosine kinase, is very closely linked to W. Several further observations are consistent with the idea that W and c-kit are allelic: first, c-kit is expressed in those cell populations affected by W mutations; second, the expression of c-kit transcripts can be affected by mutations at the W locus; third, the tyrosine kinase activity associated with the protein encoded by c-kit is functionally impaired in mast cells derived from mutant W/Wv mice; and fourth, rearrangements within the c-kit gene have been reported in two W mutant alleles. These observations suggest that the dominant phenotype associated with W mutations results from loss-of-function alterations that affect the receptor tyrosine kinase encoded by c-kit. The demonstration that the W locus encodes a transmembrane growth factor receptor provides a molecular basis for understanding the intrinsic haemopoietic defect in W mutant mice and the role that this cellular proto-oncogene plays in haemopoiesis and other developmental processes.

Animals↗
PubMed1990

Tyrosine protein kinase activity of the HZ4-feline sarcoma virus P80gag-kit-transforming protein.

The Hardy-Zuckerman 4 feline sarcoma virus (HZ4-FeSV), isolated from a feline fibrosarcoma, is a replication defective acute transforming feline retrovirus that originated by transduction of feline c-kit sequences with feline leukemia virus (FeLV). The v-kit sequences of the HZ4-FeSV, a segment of 1106 nucleotides, correspond to sequences of the cytoplasmic domain of the c-kit receptor kinase. The HZ4-FeSV is known to encode an 80-kilodalton protein with FeLV gag and kit determinants. The P80gag-kit protein and its associated activities from HZ4-FeSV-transformed mink cells were characterized. The P80gag-kit protein was found to be myristoylated, suggesting a membrane association for this protein. In agreement with the predicted relationship with tyrosine kinases, by using the in vitro immune complex-kinase procedure, the P80gag-kit protein was shown to display a tyrosine-specific autophosphorylation activity. In vivo, the P80 protein was found to be phosphorylated on serine and threonine and to a lesser degree on tyrosine. In addition, potential in vivo protein substrates for tyrosine-specific phosphorylation mediated by the P80gag-kit kinase were identified in HZ4-FeSV-transformed cells.

Animals↗
PubMed1990

Evaluation of different methods for detection of Helicobacter pylori in patients with gastric disease.

Endoscopic gastric antral biopsy specimens (133) from 92 dyspeptic patients with endoscopically evident gastritis (34; including one patient with dual pathology) gastric ulcer (13), duodenitis (17; including one patient with dual pathology) duodenal ulcer (29) and 41 subjects of non ulcer dyspepsia (NUD) with endoscopically normal upper gastrointestinal tract were examined for H. pylori by stained smear, various urease tests, culture and histopathology. Crushed tissue smear stained by Gram's method using carbol fuchsin counterstain proved to be the simplest and a reliable technique. Up to 4 h urease broth + ve test correlated well with smear and culture. Positive association of H. pylori with disease was considered when at least two of the above methods were suggestive. Significantly higher positivities were observed in gastritis (61.7%), gastric ulcer (84.6%), duodenitis (58.8%) and duodenal ulcer (82.8%) patients, as compared to NUD subjects (46.3%). Severe histopathological lesions were frequently associated with multiple bacteriological test positives.

Adult↗
PubMed1989

Prevention of muscarinic acetylcholine receptor down-regulation by chloroquine: antilysosomal or antimuscarinic mechanisms.

The effect of the antimalarial drug chloroquine on the carbachol-induced down-regulation of muscarinic acetylcholine receptors (mAChRs) was studied in the neuroblastoma-glioma hybrid NG108-15 cells. Chloroquine, which is proposed to have both antilysosomal and antimuscarinic effects (4,11), blocked the loss of both cell surface and total mAChRs as monitored by [3H]N-methyl-scopolamine (NMS) and [3H] quinuclidinyl benzilate (QNB) bindings respectively. To the contrary, NH4Cl, only an antilysosomal agent, had no effect on the loss of surface receptors, but blocked degradation of internalized receptors following the effect of carbachol. These findings demonstrate that chloroquine prevents the agonist-induced mAChR down-regulation in NG108-15 cells by both its antilysosomal and antimuscarinic effects.

Ammonium Chloride↗
PubMed1989

Expression of c-kit gene products in known cellular targets of W mutations in normal and W mutant mice--evidence for an impaired c-kit kinase in mutant mice.

The proto-oncogene c-kit, a transmembrane tyrosine protein kinase receptor for an unknown ligand, was shown recently to map to the dominant white spotting locus (W) of the mouse. Mutations at the W locus affect various aspects of hematopoiesis, as well as the proliferation and/or migration of primordial germ cells and melanoblasts during development. Here, we show that c-kit is expressed in tissues known to be affected by W mutations in fetal and adult erythropoietic tissues, mast cells, and neural-crest-derived melanocytes. We demonstrate that the c-kit associated tyrosine-specific protein kinase is functionally impaired in W/WV mast cells, thus providing a molecular basis for understanding the developmental defects that result from these mutations.

Alleles↗