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R Sircar

Publications and source records attributed to R Sircar.

At least 37 records · Page 2Linked to original sources
PubMed1997

Specific activation of resting T cells against CA19-9+ tumor cells by an anti-CD3/CA19-9 bispecific antibody in combination with a costimulatory anti-CD28 antibody.

Specific activation of resting lymphocytes for tumor targeting can be achieved by bispecific monoclonal antibodies (bi-mAb) with specificity for tumor antigens and T-cell-activating antigens, respectively, in combination with a costimulatory anti-CD28 antibody. We describe the generation and function of a bi-mAb with specificity for CD3 and for the tumor antigen CA19-9. The bi-mAb OKT3/NSI19-9 was generated by somatic fusion of two hybridoma lines secreting antibodies against CA19-9 and CD3, respectively. A hybrid/hybridoma was established, and its bi-mAb was characterized. In combination with a costimulatory anti-CD28 mAb resting peripheral lymphocytes could be activated specifically with T-cell proliferation and secretion of high amounts of interferon-gamma. On specific T-cell activation, bi-mAb OKT3/NSI19-9 could also redirect the cytotoxic effects of these T cells toward CA19-9+ tumor cells in vitro. Our results indicate that specific activation of resting T cells with bi-mAb OKT3/NSI19-9 in combination with an anti-CD28 mAb can activate resting T cells specifically and leads to antigen-dependent bi-mAb-mediated cytotoxicity against CA19-9+ target cells. This approach may offer new perspectives for the specific immunotherapy of CA19-9+ tumors.

Antibodies, Bispecific↗
PubMed1996

Postnatal phencyclidine treatment differentially regulates N-methyl-D-aspartate receptor subunit mRNA expression in developing rat cerebral cortex.

The present study was designed to determine the effects of chronic neonatal exposure to the NMDA receptor antagonist phencyclidine (PCP) on [3H]MK-801 binding and on gene expression of NMDA receptor subunits in juvenile male rats. Rat pups were injected daily with PCP from day 5 to 15 and killed on day 21. [3H]MK-801 binding was measured by quantitative autoradiography. A sensitive RNase protection assay was employed to determine simultaneously the mRNA levels of NR1 subunit (comprising all different splice variants) and three NR2 subunits (NR2A-NR2C). The relative distribution profile of NMDA receptor subunits in the cerebral cortex was NR2B > NR1 > NR2A > NR2C and in the cerebellum NR2C = NR1 > NR2A = NR2B. Chronic PCP administration in postnatal rats produced significant reduction in both [3H]MK-801 binding and mRNA level of the NR2B subunit in the cerebral cortex. Expression of the other NMDA receptor subunits in the cerebral cortex did not change following the drug treatment. In the cerebellum, neither [3H]MK-801 binding nor any of the NMDA receptor subunit expression levels showed any alteration. Together, these data provide a molecular correlate for chronic postnatal PCP-induced down-regulation of [3H]MK-801 binding in rat cerebral cortex and suggest that the NR2B subunit plays an important role in developmental plasticity.

Animals↗
PubMed1995

Repeated postnatal phencyclidine administration in female juvenile rat delays onset of puberty but has no effect on pentylenetetrazol-induced seizure-susceptibility.

The effects of chronic phencyclidine (PCP) treatment on sexual maturation and seizure-susceptibility in the developing female rat were studied. Postnatal female rats were injected once daily with 5 mg/kg PCP from Day 5 till Day 15 and were observed for sexual maturation--vaginal opening and estrus cyclicity were used as indices of sexual maturation. PCP-treated rats showed a delay in both vaginal opening and in estrus cyclicity compared to saline-treated pair-fed controls. On postnatal Day 21, PCP-treated rats and saline-treated controls were tested for seizure-susceptibility using the pentylenetetrazol (PTZ)-induced seizure paradigm. PCP-treated female rats did not differ from saline-treated controls in their susceptibility to PTZ-induced seizures. In conclusion, chronic PCP administration during development in female rats disrupts sexual maturation but has no short-term effect on seizure susceptibility.

Animals↗
PubMed1995

Chronic postnatal phencyclidine treatment on [3H](+) pentazocine binding in juvenile rat brain.

Chronic phencyclidine (PCP) administrations in postnatal rats produce long-term behavioral changes. Here we report the effects of repeated postnatal PCP treatment on [3H](+)pentazocine binding in juvenile rats. Saturation analyses of the binding data showed no significant difference in any of the binding characteristics between chronic PCP-related rats and saline-treated controls suggesting that mechanisms other than alterations in sigma1 binding underlie the behavioral effects of repeated postnatal PCP administration in immature rats.

Animals↗
PubMed1995

Antagonist of N-methyl-D-aspartate receptors partially prevent the development of cocaine sensitization.

Behavioral sensitization to cocaine was tested for in rats pretreated with MK-801, a noncompetitive N-methyl-D-aspartate (NMDA) receptor antagonist, or D-3-(2-carboxypiperazin-4-yl)-1-propenyl-1-phosphonic acid (D-CPPene), a competitive NMDA antagonist. A 5-day regimen of once-daily cocaine (15 mg/kg) injections yielded sensitization to cocaine (15 mg/kg)-induced behavioral activation. Cocaine sensitization was partially prevented by MK-801 (0.25 mg/kg) or D-CPPene (20 mg/kg) pretreatment. These results differ from previous reports that NMDA receptor antagonists completely prevented the development of stimulant sensitization. While raising questions about methodological differences among laboratories studying this issue, our findings suggest that sensitization may involve mechanisms dependent on NMDA-receptor function as well as NMDA receptor-independent mechanisms.

Animals↗
PubMed1994

Chronic neonatal phencyclidine treatment produces age-related changes in pentylenetetrazol-induced seizures.

Although excitatory amino acids are known to play a critical role in the plasticity of developing brain, the behavioral effects of blocking the N-methyl-D-aspartate (NMDA) receptor-gated ion channel during development are not clear. Here we report the effects of chronic postnatal administration of 1-phenylcyclohexylpiperidine (phencyclidine or PCP), a NMDA channel blocker, on seizure susceptibility. To study the short-term effects of chronic PCP administration on pentylenetetrazol (PTZ)-induced seizures, rats were treated with PCP (5 mg/kg, i.p.) for 11 days from postnatal days 5-15, 24-34 or 44-54 and tested in the PTZ-induced seizure paradigm on postnatal days 21, 40 and 60, respectively. Administration of PCP in 5-15-day-old rats resulted in increased seizure susceptibility at day 21, while administration of PCP in postweanling rats (days 24-34) markedly attenuated their susceptibility to seizures at day 40. PCP injection had little effect on the seizure susceptibility of older rats. To study the long-term effects of postnatal PCP treatment, rats were injected with PCP (5 mg/kg from postnatal day 5-15, i.p.) and were tested for PTZ-induced seizures on postnatal days 40 and 60; each rat was tested only once. When tested for PTZ-induced seizure on day 40, PCP-treated rats did not differ from saline-treated controls. When tested on day 60, PCP-treated rats had a lower incidence of seizures and in the rats that did have seizures their latencies were significantly prolonged compared to controls. Together, our data suggest that chronic PCP administration alters PTZ-induced seizure susceptibility in an age-dependent manner and chronic PCP administration in postnatal rats produces long-term changes that persist into adulthood.

Aging↗
PubMed1991

Polyamine effects upon N-methyl-D-aspartate receptor functioning: differential alteration by glutamate and glycine site antagonists.

Polyamines such as spermidine potentiate activation of the N-methyl-D-aspartate (NMDA)-type excitatory amino acid receptor. The goal of the present study was to investigate interactions between the putative polyamine binding site and previously described sites for glutamate and glycine. Binding of the high-potency PCP receptor ligand [3H]MK-801 to well-washed rat brain membranes was used as an in vitro probe of NMDA receptor activation. Spermidine concentration-response studies were performed in the absence and presence of both glutamate and glycine, with and without D-(-)-2-amino-5-phosphonovaleric acid (D(-)-AP-5) or 7-chlorokynurenic acid (7Cl-KYN). Incubation in the presence of spermidine alone induced a 20.4-fold increase in [3H]MK-801 binding with an EC50 value of 13.3 microM. The mean concentration of spermidine which induced maximal stimulation of binding was 130 microM (n = 10, S.E.M. = 24.66, range = 25-250 microM). Glutamate (10 microM) decreased the EC50 value for spermidine-induced stimulation of [3H]MK-801 binding to 3.4 microM. Glycine (10 microM) did not significantly alter either maximum spermidine-induced [3H]MK-801 binding or the EC50 value for spermidine-induced stimulation of [3H]MK-801 binding. Incubation in the presence of the specific glutamate antagonist D(-)AP-5 attenuated [3H]MK-801 binding in a glutamate-reversible fashion. The competitive glycine antagonist 7Cl-KYN decreased maximum spermidine-induced [3H]MK-801 binding in a glycine-reversible fashion. In addition, 7Cl-KYN increased the EC50 value for spermidine-induced stimulation of [3H]MK-801 binding while D(-)AP-5 was without effect.(ABSTRACT TRUNCATED AT 250 WORDS)

2-Amino-5-phosphonovalerate↗
PubMed1991

Kinetic mechanisms of glycine requirement for N-methyl-D-aspartate channel activation.

Glycine potentiates N-methyl-D-aspartate (NMDA) receptor-mediated responses via its interaction with a strychnine-insensitive glycine recognition site. We have previously shown that the potent glycine receptor antagonist 7-chlorokynurenic acid (7Cl-KYN) dose-dependently inhibits [3H]MK-801 binding to the PCP receptor and that this effect is reversed by glycine. [3H]MK-801 binding to the PCP receptor within the NMDA receptor-gated ion channel is a measure of channel activation. Association of PCP receptor ligands is biexponential with the fast component of binding serving as a marker of activated NMDA channels. In the present study we utilize 7Cl-KYN as a probe of the kinetic mechanism of the glycine effect upon NMDA receptor functioning. In the presence of L-glutamate, incubation with 7Cl-KYN completely abolished the fast component of [3H]MK-801 association in 4 out of 5 experiments. In the fifth experiment where the fast component was detected, it accounted for less than half of that seen in the presence of L-glutamate alone. 7Cl-KYN-induced inhibition of the fast component of [3H]MK-801 association was reversed by the addition of glycine. Since the fast component represents ligand binding to the PCP receptor via the open NMDA channel, selective reduction of this component by 7Cl-KYN indicates that glycine receptor antagonists reduce the probability of channel opening, and also that the selective reduction in the component of [3H]MK-801 binding that manifests fast kinetics can serve as a marker for glycine antagonists.

Animals↗
PubMed1989

Glycine reverses 7-chlorokynurenic acid-induced inhibition of [3H]MK-801 binding.

7-Chlorokynurenic acid (7-Cl KYNA) has been reported to attenuate N-methyl-D-aspartate (NMDA) receptor functioning by a potent and selective inhibitory action mediated at the strychnine-insensitive glycine recognition site of the NMDA complex. Here we report that 7-Cl KYNA dose-dependently inhibits [3H]MK-801 binding to the PCP receptor, and that this effect is reversed by addition of glycine. Since [3H]MK-801 binding is a measure of channel activation, our results are consistent with the hypotheses that 7-Cl KYNA exerts its NMDA receptor antagonism by acting at the glycine site, and that activation of the glycine site is required for NMDA channel activity to occur.

Animals↗
PubMed1989

Direct method for detecting small quantities of hepatitis B virus DNA in serum and plasma using the polymerase chain reaction.

Serum components inhibit DNA polymerase, thereby obviating direct detection of serum viral DNA sequences by the polymerase chain reaction (PCR). This has necessitated extraction of nucleic acid from sera before performing PCR and has resulted in loss of sensitivity. By adsorbing virus to a solid surface (microcentrifuge tubes or antibody coated microparticles) followed by proteinase K digestion, as little as three viruses per 200 microliters serum may be directly detected by PCR without nucleic acid extraction. The sensitivity is dependent on the surface area of the adsorptive surface and is increased by having antibodies on the adsorptive surface. The nucleic acid sequence of the amplified DNA fragments may be directly determined by the dideoxy method. Of 24 plasma samples from HBsAg+ volunteer blood donors, HBV DNA was detected in 7 by dot blot assay, 7 by liquid hybridization, and 9 by PCR. PCR detected DNA in every sample that was positive by another assay. Analysis of serial samples of two patients with acute self-limited hepatitis B found detectable HBsAg and pre-S2 antigenemia before HBV DNA by the PCR method. These results suggest that surface antigenemia may precede viremia during acute hepatitis.

Adsorption↗
PubMed1987

The novel anticonvulsant MK-801: a potent and specific ligand of the brain phencyclidine/sigma-receptor.

MK-801 (5-methyl-10,11-dihydro-5H-dibenzo[a,d]cyclohepten-5,10-imine maleate) is a novel anticonvulsant agent reported to antagonize certain N-methyl-D-aspartate (NMDA)-mediated effects non-competitively. The question arises of the mechanism underlying the anti-NMDA and anticonvulsant effects of MK-801. In the present study MK-801 is shown to be an extremely potent inhibitor of the binding of N-[3H] (1-[2-thienyl]cyclohexyl)piperidine ([3H]TCP) to brain phencyclidine (PCP)/sigma-receptors. Its IC50 value of 3.8 +/- 0.8 nM in this assay ranks it as the most potent known ligand of brain PCP/sigma-receptors. Addition of MK-801 altered the apparent Kd but not the apparent Bmax values for [3H]TCP binding, indicating a competitive interaction. The specificity of action of MK-801 is supported by the finding that MK-801 strongly inhibited the binding of (+)-N-[3H]allylnormetazocine ((+)-[3H]SKF 10,047) to the PCP/sigma-receptor but its effect on (+)-[3H]SKF 10,047 binding to the non-PCP, haloperidol-sensitive sigma-binding site was weaker by several orders of magnitude. Furthermore, MK-801 exerts PCP-like antagonistic effects upon NMDA-induced [3H]norepinephrine release. These findings support the concept that the anticonvulsant and anti-NMDA effects of MK-801 result from its being the most potent known ligand of PCP/sigma-receptors.

Animals↗
PubMed1987

Non-competitive regulation of phencyclidine/sigma-receptors by the N-methyl-D-aspartate receptor antagonist D-(-)-2-amino-5-phosphonovaleric acid.

D-(-)-2-Amino-5-phosphonovaleric acid (D(-)AP5), a selective, potent competitive antagonist of N-methyl-D-aspartate (NMDA)-type excitatory amino acid receptors was used to investigate the relationship between NMDA receptors and phencyclidine (PCP) binding. Incubation of rat brain membranes with D(-)AP5 decreased the apparent number of PCP/sigma-receptors in dose-dependent fashion without affecting their affinity for [2-thienyl-3H]cyclohexylpiperidine (TCP). These data, taken together with electrophysiological evidence that PCP non-competitively antagonizes NMDA receptor-mediated transmission, are consistent with the hypothesis that the PCP/sigma-receptor may be situated in or near a channel regulated by an NMDA receptor complex.

2-Amino-5-phosphonovalerate↗
PubMed1987

Hepatitis B disease in dialysis and transplant patients. Further epidemiologic and serologic studies.

As hepatitis B virus (HBV) infection in renal transplant recipients is associated with a high incidence of progressive liver disease it may be inadvisable to transplant hemodialysis patients with hepatitis B antigenemia. To determine the natural history of HBV disease in hemodialysis patients, all 49 patients on hemodialysis treatment for at least 1 year, at 3 centers, who developed circulating hepatitis B surface antigen (HBsAG), were studied. A subgroup of these patients (n = 31) aged less than or equal to 50 years, followed for 55 +/- 6 months after detection of HBsAg was compared with 22 previously studied HBsAg-positive transplant patients followed for 81 +/- 9 months. Significantly more transplant patients developed chronic hepatitis defined biochemically (P less than .001) and none of the transplant patients became HBsAg-negative compared with 19% of the hemodialysis group. Taking difference in follow-up into account, mortality was significantly higher in the transplant recipients (P less than .005) following development of HBsAg antigenemia, and the mortality difference was attributable to deaths from liver disease. A total of 36 serum samples from 14 of the 22 HBsAg-positive renal transplant recipients was analyzed for hepatitis B e antigen (HBeAg), antibody to hepatitis D virus (anti-HD), and hepatitis B virus deoxyribonucleic acid (HBVDNA) concentration. No serum sample was anti-HD-positive. Twelve of the 14 patients were HBeAg-positive. Five patients became HBeAg-negative, 3 of whom developed aggressive liver disease. One HBeAg-negative anti-HBe-positive patient had progression of liver disease from asymptomatic carrier status to chronic active hepatitis (CAH). Of 14 patients, 9 developed progressive CAH. HBVDNA concentration was not diagnostic of disease activity on liver biopsy. However only 1 sample of 10 measured in 5 patients with nonprogressive disease had a level greater than 100 pg/L, compared with 9 of 17 in the group who progressed to CAH. During the interval when the liver histology progressed from asymptomatic carriage or chronic persistent hepatitis (CPH) to CAH, the HBVDNA concentration increased by greater than 10 times baseline in 4 of 5 patients who had serial samples, whereas this did not occur in 4 patients with nonprogressive disease. We conclude that the long-term outcome of hepatitis B infection in transplant recipients is significantly worse than in hemodialysis patients. Therefore it may be inadvisable to transplant HBsAg-positive hemodialysis patients.(ABSTRACT TRUNCATED AT 400 WORDS)

Adult↗
PubMed1986

Modulation of brain NMDA receptors: common mechanism of sigma/PCP receptors and their exogenous and endogenous ligands.

Quantitative autoradiographic distribution patterns of sigma/PCP and NMDA receptors show striking similarities but not in all brain areas. We have identified an endogenous ligand of brain PCP receptors which noncompetitively antagonizes NMDA-induced neurotransmitter release from brain slices. These data support the concept that the sigma/PCP receptor ligands may exert their unique behavioral effects by indirect modulation of NMDA-mediated transmission.

Acetylcholine↗
PubMed1986

Characterization and autoradiographic visualization of (+)-[3H]SKF10,047 binding in rat and mouse brain: further evidence for phencyclidine/"sigma opiate" receptor commonality.

The binding specificity of (+)-[3H]N-allylnormetazocine, the dextrorotatory isomer of the prototypical sigma opiate SKF10,047, was determined in rat and mouse brain and the neuroanatomical distribution of its binding sites elucidated by quantitative autoradiography in sections of rat brain. Computer-assisted Scatchard analysis revealed an apparent two-site fit of the binding data in both species and in all rat brain regions examined. In whole rat brain, the Kd values were 3.6 and 153 nM and the maximum binding values were 40 fmol and 1.6 pmol/mg of protein for the apparent high- and low-affinity binding sites, respectively. (+)-SKF10,047, haloperidol and pentazocine were among the most potent inhibitors of 7 nM (+)-[3H]SKF10,047 binding to the higher affinity sites; rank orders of ligand potencies at these sites differ sharply from those that have been reported for the [3H]phencyclidine (PCP) site, or for eliciting PCP-like or SKF10,047-like behaviors. By contrast, rank orders of potency of sigma opiods, PCP derivatives and dioxolanes for displacement of 100 nM (+)-[3H]SKF10,047 from the more numerous lower affinity sites in the presence of 100 nM haloperidol agreed closely with their potencies in the [3H]PCP binding assay as well as their potencies in exerting PCP- or SKF10,047-like behavioral effects. In order to compare directly the anatomical localizations of PCP and (+)-SKF10,047 binding sites, quantitative light microscopy autoradiography utilizing tritium-labeled PCP and (+)-SKF10,047 was carried out in rat brain sections. (+)-[3H]SKF10,047 binding was observed to follow the regional pattern of [3H]PCP binding but also to bind in other regions not associated with PCP receptors.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1985

Quantitative localization of [3H]TCP binding in rat brain by light microscopy autoradiography.

The anatomical localization of phencyclidine (PCP)/sigma-opiate receptors in rat brain was determined by quantitative light microscopy autoradiography using the new ligand N-(1-[2-thienyl]cyclohexyl) [3H]piperidine ([3H]TCP). TCP is a potent analog of PCP which possesses a higher affinity for PCP/sigma-opiate receptor than does PCP itself. The highest level of [3H]TCP binding was detected in the hippocampus. Intermediate levels were found in frontal cortex, striatum, amygdala and cerebellum. Specific [3H]TCP binding was undetectable in anterior commissure and corpus callosum. The distribution pattern of [3H]TCP binding sites is similar to the pattern obtained with [3H]PCP but more sharply defined. On the basis of its greater potency and specificity, [3H]TCP may prove superior to [3H]PCP as a molecular probe for the study of brain sigma opiate/phencyclidine receptors.

Animals↗