Search PubMed⌕ Search

Biomedical subjects

P Roy

Publications and source records attributed to P Roy.

At least 19 recordsLinked to original sources
PubMed2000

Role of human liver microsomal CYP3A4 and CYP2B6 in catalyzing N-dechloroethylation of cyclophosphamide and ifosfamide.

The anticancer alkylating agents cyclophosphamide (CPA) and ifosfamide (IFA) are prodrugs that undergo extensive P450-catalyzed metabolism to yield both active (4-hydroxylated) and therapeutically inactive but neurotoxic (N-dechloroethylated) metabolites. Whereas the human liver microsomal P450 catalysts of CPA and IFA 4-hydroxylation are well characterized, the P450 enzyme catalysts of the alternative N-dechloroethylation pathway are poorly defined. Analysis of a panel of fifteen human P450 cDNAs in the baculovirus expression system ('Supersomes') demonstrated that CYP3A4 exhibited the highest N-dechloroethylation activity toward both CPA and IFA, whereas CYP2B6 displayed high N-dechloroethylation activity toward IFA, but not CPA. The contributions of each human P450 to overall liver microsomal N-dechloroethylation were calculated using a recently described relative substrate-activity factor method, and were found to be in excellent agreement with the results of inhibition studies using the CYP3A inhibitor troleandomycin and an inhibitory monoclonal antibody to CYP2B6. With CPA as substrate, CYP3A4 was shown to catalyze >/=95% of liver microsomal N-dechloroethylation, whereas with IFA as substrate, CYP3A4 catalyzed an average of approximately 70% of liver microsomal N-dechloroethylation (range = 40-90%), with the balance of this activity catalyzed by CYP2B6 (range = 10-70%, dependent on the CYP2B6 content of the liver). Because CYP2B6 can make a significant contribution to human liver microsomal IFA N-dechloroethylation, but only a minor contribution to IFA 4-hydroxylation, the selective inhibition of hepatic CYP2B6 activity in individuals with a high hepatic CYP2B6 content may provide a useful approach to minimize the formation of therapeutically inactive but toxic N-dechloroethylated IFA metabolites.

Anti-Bacterial Agents↗
PubMed2000

Aromatic residues mediate the pressure-induced association of digoxigenin and antibody 26-10.

We have previously found that the complex between fluorescently labeled digoxigenin and the monoclonal antibody 26-10 forms with a decrease in volume of approximately 30 ml/mol, leading to increased association of these species under applied hydrostatic pressure. In the present study, we have utilized a panel of mutant antibodies and Fab fragments, previously characterized for their importance in the binding affinity of digoxin:26-10, to probe the molecular basis of pressure sensitivity in this complex, as measured by fluorescence polarization spectroscopy. Several mutations that result in marked decreases in affinity exerted little or no significant effect on the association volume. Mutation at any of several key aromatic residues of the 26-10 Fab heavy chain led to a decrease in the pressure-induced association, and two mutants with Trp-->Arg mutations at heavy chain residue 100 exhibited pressure-induced dissociation. The effect of charged groups was found to depend on their proximity to contacting aromatic groups. The ability to understand and control the pressure sensitivity of antigen-antibody complexes has numerous potential applications in immunoseparations and immunosensors.

Amino Acids↗
PubMed2000

Gonadotropin-releasing hormone stimulates thyroid activity in a freshwater murrel, Channa gachua (ham.), and Carps, Catla catla (ham.) and Cirrhinus mrigala (ham.).

Injections of mammalian GnRH (mGnRH), salmon GnRH (sGnRH), and a homologous murrel, Channa punctatus, GnRH (cGnRH) to a murrel, Channa gachua, and a carp, Catla catla, at a dose of 1 microg/250 g body wt significantly increased plasma thyroxine (T4) levels above control. Piscine GnRHs (sGnRH and cGnRH) had significantly greater stimulatory effects compared with mGnRH. To observe whether this stimulatory effect by GnRHs is direct or indirect, thyroid follicles were isolated from hypobranchial muscles of freshwater murrel, C. gachua and incubated (1 x 10(6) follicles/well) in vitro at 30 degrees C for 2 h without hormone and for 3 h with hormones. Addition of these three GnRHs separately at a concentration of 1 microg/well stimulated T4 secretion; sGnRH and cGnRH caused greater secretion of T4 into the medium compared with mGnRH. Specificity of GnRH action in vitro was assessed by using anti-GnRH antibody which significantly (P < 0.01) inhibited GnRH-augmented T4 secretion. To gain further insight, 125I uptake by thyroid follicles and formation of [125I]T4 from this radioiodine pool was monitored in the presence or absence of sGnRH. sGnRH greatly augmented 1251 uptake by the follicles which resulted a fourfold increase in [125I]T4 formation out of this pool of 125I compared with the control. The results indicate GnRH stimulation of thyroid hormone formation and release in these teleosts suggesting a possible different mode of regulation of thyroid hormone secretion in teleosts.

Animals↗
PubMed2000

Predicting haloperidol occupancy of central dopamine D2 receptors from plasma levels.

Positron emission tomography (PET) is increasingly being used to study dopamine receptor occupancy and the clinical effects of antipsychotic medication. Dopamine D2 receptor occupancy has been shown to predict several clinical effects of antipsychotic medication including therapeutic response, motor and endocrine side-effects. Plasma levels may be used as a surrogate marker for central occupancy if the relationship between these two measures may be accurately described. This study was designed to test the capacity of a previously derived relationship equation (%D2 occupancy=plasma level/ED50+plasma level, where ED50= 0.40 ng/ml) to predict striatal D2 occupancy from plasma level. Twenty-one patients receiving treatment with low dose haloperidol underwent a 11C-raclopride PET scan to measure D2 occupancy. The D2 occupancy levels were accurately predicted by use of the previously generated equation with only a small degree of error (3.89% CI 0.45-7.33). Predicted and measured D2 occupancy values correlated closely (Pearson's r=0.864, P=0.003). The study indicates that reliable prediction of D2 occupancy from plasma levels is possible. This provides a potentially useful surrogate measure of D2 occupancy for research and possibly clinical practice, as the routine use of PET to measure occupancy levels is not feasible.

Adult↗
PubMed2000

Salicylic acid-independent induction of pathogenesis-related gene expression by fusicoccin.

Treatment of tomato plants (Lycopersicon esculentum Mill.) with fusicoccin (FC), an activator of the plasma-membrane H+-ATPase which maintains an electrochemical gradient across the plasma membrane, resulted in a dose-dependent accumulation of transcripts for intra- and extracellular pathogenesis-related (PR) proteins. The accumulation of PR protein transcripts was paralleled by an increase in leaf salicylic acid (SA) content. Transcripts of PR proteins and SA started to accumulate 3 h after FC treatment. 2-Aminoindan-2-phosphonic acid, an inhibitor of SA synthesis, was used to assess the role of SA in FC-mediated induction of PR gene expression. 2-Aminoindan-2-phosphonic acid was found to suppress the accumulation of SA but not the induction of PR gene expression in response to FC treatment. Furthermore, in transgenic tobacco plants overexpressing a bacterial salicylate hydroxylase gene (nahG-tobacco), PR transcripts accumulated after FC treatment to levels similar to those observed in control tobacco plants. The data indicate a role for the proton gradient across the plasma membrane in the SA-independent induction of PR gene expression.

Glycosides↗
PubMed2000

Nonmalignant obstruction is a common problem with metal stents in the treatment of esophageal cancer.

BACKGROUND: The use of metal stents for the treatment of dysphagia due to esophageal malignancy is an important advance because of ease of delivery and their self-expandable property. Obstruction due to tumor overgrowth is a recognized complication, but nonmalignant obstruction in patients with metal stents is rarely reported. METHODS: Database records of patients who had esophageal cancer and underwent metal stent insertion were reviewed. RESULTS: A total of 116 patients were seen between October 1993 and October 1997. Four types of metal stents had been used (Ultraflex, Z Stent, Wallstent, and Esophacoil). Detailed follow-up information was available for 81 patients, who constitute the study sample. Forty-nine (60%) stent obstructions were reported, 26 of the 49 (53%) were due to tumor overgrowth and 23 (47%) were not associated with malignancy. Histologic analysis of the nonmalignant obstructing tissue showed granulation tissue (56%), reactive hyperplasia (22%) and fibrosis (22%). CONCLUSIONS: Nonmalignant obstruction is a common although infrequently reported complication after placement of metal stents for esophageal cancer. The tissue response of the esophageal mucosa occurred with all 4 types of stents used. No specific characteristic of the stent or prior treatment seems to be related to obstruction of the stent in patients with either nonmalignant obstruction or tumor overgrowth.

Adenocarcinoma↗
PubMed2000

Long-term survival in Hodgkin's disease patients. A comparison of relative survival in patients in trials and those recorded in population-based cancer registries.

The prognosis of Hodgkins disease (HD) has improved during the last 30 years. This study was planned to analyse long-term survival of LID patients and to compare survival rates estimated from clinical trials and population-based data. Individual data were analysed on 2,755 adult HD patients entering randomised clinical trials of the British National Lymphoma Investigation BN LI) between 1970 and 1987, and 5,064 patients with HD incident 1978-1984 recorded in the UK population-based cancer registries participating in the EUROCARE study. Relative survival of Hodgkins disease patients allowing for mortality expected from general population rates was analysed by a proportional hazards regression model including covariates. Although relative mortality decreased with longer follow-up, it was still significantly positive at 9-10 years after diagnosis in both the clinical trials and the population-based data sets. Relative mortality was worse for late stage than for early stage patients even at 10-15 years after first treatment (BNLI data). Whereas 10-year relative survival was identical in trials and population-based patients at ages under 45 years (> 69%), it was much higher in BNLI older patients than in the population-based patients. In the older age group (65-74 years) the BNLI patients had 39% relative survival whilst for the population-based patients it was only 27%, Generalisation of clinical trials results to the general population must be done with caution, especially for older patients.

Adolescent↗
PubMed2000

Characterization of Newcastle disease viruses isolated from chickens and ducks in Tamilnadu, India.

During 1993, outbreaks of Newcastle disease occurred on many farms in Tamilnadu, India. Six Newcastle disease virus (NDV) isolates were obtained from the chickens on five different farms and from the birds on one duck farm during outbreaks of the disease. All the isolates were characterized as velogenic, based on the mean death time, intravenous pathogenicity index, intracerebral pathogenicity index (ICPI), stability of haemagglutinin at 56 degrees C, agglutination of equine erythrocytes, haemagglutination elution pattern and adsorption of haemagglutinin by chick brain cells. The isolate obtained from ducks resembled a group D strain, based on its ICPI and its reaction with a panel of monoclonal antibodies. The other five NDV isolates obtained from chickens were placed in groups B(1), C1(2) and D(2) on the basis of their binding patterns with the panel of monoclonal antibodies. In challenge experiments, it was found that LaSota vaccine provided 100% protection against each of these field isolates and against a local NDV strain obtained from the Institute of Veterinary Preventive Medicine, Tamilnadu, India, while unvaccinated chickens succumbed to challenge. The possible origin of epizootic viruses causing outbreaks in vaccinated flocks is discussed.

Animals↗
PubMed2000

Institutional care: risk from family background or pattern of rearing?

Previous research has shown that children receiving substitute parental care tend to have high rates of emotional/behavioural disturbance, but uncertainty remains on the extent to which this derives from genetic risk, adverse experiences before receiving substitute care, or from risks associated with substitute care experiences. In order to examine the effects of institutional rearing (as a specific form of substitute care), two groups of primary school children reared in substitute care from before the age of 12 months were compared: 19 children in residential group (institutional) care and 19 in continuous stable foster family care (matched for age and gender). The two groups were similar in coming from biological families with high rates of psychopathology and social malfunctioning, but differed with respect to pattern of rearing. Both groups were compared with classroom controls, using teacher questionnaires, systematic classroom observations, and standardised cognitive testing. Parental questionnaires were also obtained for the two substitute care groups. As found previously, the combined substitute care groups differed from controls in showing a high level of hyperactivity/inattention. The observational measures showed a similar effect, indicating that the elevated rate was not attributable to rater bias. The teacher questionnaire and observational measures showed, however, that the increased level of hyperactivity/ inattention was substantially higher in the institutional group than the foster family group. Parental questionnaire ratings showed the same contrast between the groups, except that the main difference was on unsociability and emotional disturbance rather than hyperactivity/ inattention. It is concluded that, against a background of genetic and early environmental risk, institutional rearing predisposes to a pattern of hyperactivity/inattention.

Attention Deficit Disorder with Hyperactivity↗
PubMed1999

Bovine leukemia virus Gag particle assembly in insect cells: formation of chimeric particles by domain-switched leukemia/lentivirus Gag polyprotein.

A key stage in the life cycle of C-type retroviruses is the assembly of Gag precursor protein at the plasma membrane of infected cells. Here we report the assembly of bovine leukemia virus (BLV) gag gene product into virus-like particles (VLPs) using the baculovirus expression system. Expression of BLV Pr44(Gag) resulted in the assembly and release of VLPs, thereby confirming the ability of retroviral Gag polyprotein to assemble and bud from insect cells. Efficient particle formation required a myristoylation signal at the N-terminus of BLV Pr44(Gag). Recombinant baculoviruses expressing matrix (MA) or capsid-nucleocapsid (CA-NC) proteins of BLV were generated but neither of these domains was capable of assembling into particulate structures. To assess the compatibility of Gag domains between leukemia and lentivirus groups three different recombinant chimeras each expressing MA of one virus (e.g., simian immunodeficiency or BLV) and CA-NC of another (e.g., BLV or human T-cell leukemia virus type-I) were constructed. Each of the chimeric proteins assembled efficiently and budded as VLPs, suggesting that the MA and CA domains of these two evolutionary divergent retrovirus groups can be functionally exchanged without perturbation of Gag VLP formation. The lenti-leukemia chimeric Gag approach has potential for studying protein-protein interactions in other retroviruses.

Animals↗
PubMed1999

Efficacy of an inactivated oil emulsion vaccine against hydropericardium syndrome in broilers.

Two inactivated vaccines were prepared against hydropericardium syndrome. The vaccine prepared from liver homogenate extracted with chloroform, inactivated with formalin and adjuvanted with liquid paraffin was highly effective against challenge in chickens aged three, five and seven weeks. Seroconversion following vaccination and challenge was assessed by the agar gel immunodiffusion test. The inactivated oil emulsion vaccine was highly effective against the syndrome in both experimental trials and field trials.

Adenoviridae Infections↗
PubMed1999

Efficacy of live adjuvanted mesogenic Newcastle disease vaccine in chickens.

120 white leghorn chickens primed with a lentogenic Newcastle disease (ND) live vaccine at 7 days of age were divided into three equal groups of 8 weeks of age and vaccinated with a live mesogenic ND vaccine (NDV). One group received only Newcastle disease mesogenic vaccine (RDVK) in normal saline, the second group received RDVK with groundnut oil as adjuvant and the third group received RDVK with liquid paraffin as adjuvant. Sera were collected at different time points for the assessment of antibody level against ND virus (NDV) by the haemagglutination inhibition (HI) test. The commonly used non-adjuvanted RDVK could not evince 100% protective HI titre beyond 11 weeks of age but in both the adjuvanted groups 100% protective HI titre was evident up to 20 weeks of age. On challenge at 20 weeks of age both the adjuvanted groups withstood challenge but in the non-adjuvanted group 80% of chickens withstood the challenge. A significant difference in immune response between the adjuvanted and non-adjuvanted groups was seen but not between both the adjuvanted groups. The advantage of vegetable oil (groundnut oil) as an adjuvant for live mesogenic ND vaccine has been discussed.

Adjuvants, Immunologic↗
PubMed1999

Exertion of tractional force requires the coordinated up-regulation of cell contractility and adhesion.

Although it is understood that cells exert mechanical forces on the extracellular matrix to promote structural organization, the exact mechanism of force transduction is not clearly understood. Using an in vitro force measurement assay, we evaluated two opposing conditions that inhibit or promote matrix organization by fibroblasts: serum deprivation and lysophosphatidic acid stimulation. Under serum deprivation, in spite of significant cell spreading and pseudopodial motility, rabbit corneal fibroblasts generated little or no force on the matrix within 2 h of observation. Lysophosphatidic acid stimulation of serum-starved cells caused dramatic cell contraction (within 2 min), which correlated temporally with a rapid increase in the tractional force generation on the matrix (0.52 x 10(-7) - 1.9 x 10(-7) N; n = 7 experiments). No cell translocation was observed during the period of force generation in response to lysophosphatidic acid-stimulation. These findings, taken together with a concomitant up-regulation of stress fibers in lysophosphatidic acid stimulated fibroblasts, indicate that contractility of non-motile cells involved in forming stress fibers and strong cell-matrix adhesion is the principal force-generating mechanism involved in matrix organization.

Actins↗
PubMed1999

Dot-enzyme linked immunosorbent assay for demonstration of Newcastle disease virus infection.

Dot-enzyme linked immunosorbent assay (ELISA) was standardised to detect Newcastle disease virus (NDV) specific antigen in chicken tissues, embryos and allantoic fluid samples. Samples positive by virus isolation were also found positive by haemagglutination (HA) and haemagglutination inhibition (HI) tests and by dot-ELISA but negative samples were found negative by all the serological tests used. Dot-ELISA was able to detect 0.25-0.50 HA units of virus. The emerging utility of dot-ELISA for diagnosis of Newcastle disease virus infection has been discussed.

Animals↗
PubMed1999

Effect of pressure on antigen-antibody complexes: modulation by temperature and ionic strength.

Changes in the equilibrium binding affinity of antigen-antibody complexes subjected to hydrostatic pressures of about 2000 bar provide a potential means for the separation and recovery under mild conditions of biological molecules from immunoadsorbents or immunosensors. We have investigated the ability of temperature and ionic strength to modulate the pressure sensitivity of several antigen-antibody complexes in solution. For two different protein:monoclonal antibody complexes (BSA:9.1 and HEWL:HyHEL-10) exhibiting pressure-induced dissociation (positive association volume), we find little temperature dependence to the association volume. For another complex (digoxigenin:26-10) exhibiting pressure-induced association, the association volume increases with temperature, which, via a Maxwell relation, indicates that enthalpic changes drive the pressure effect. An increase in ionic strength decreases the affinity of binding the HEWL:HyHEL-5 complex, which contains several salt bridges. At low ionic strengths (<0.3 M), no pressure dependence of the free energy of association is observed, but at higher ionic strengths, significant pressure-induced association is observed, suggesting that positive contributions to the association volume provided by the salt bridges are counterbalanced by other (e.g., aromatic stacking) interactions that lead to negative association volumes. These results suggest that ionic strength may be used to modulate the pressure sensitivity of antigen antibody complexes, which may be useful in designing processes that exploit this phenomenon for immunoseparations.

Animals↗