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Biomedical subjects

S Patel

Publications and source records attributed to S Patel.

At least 397 records · Page 22Linked to original sources
PubMed1997

Phase II study of recombinant interleukin 1alpha and etoposide in patients with relapsed osteosarcoma.

A Phase II trial using interleukin 1alpha (IL-1alpha) and etoposide for patients with relapsed osteosarcoma (OS) was undertaken to assess the feasibility and tolerability of combination therapy with biotherapy and chemotherapy. Nine patients with histologically proven relapsed OS were treated with IL-1alpha immediately followed by etoposide daily for 5 days every 3 weeks. Surgical resection of lung metastasis or peripheral tumor was performed after two or three cycles. We observed three partial responses; disease was stable in another case. One case could not be evaluated. The side effects associated with combination therapy were as predicted from known side effects of the individual agents; however, more profound neutropenia was observed. Four patients exhibited clinical signs of capillary leak syndrome, i.e., hypotension, edema, and weight gain. The etiology of the capillary leak was unclear, because serum IL-1alpha, IL-2, tumor necrosis factor, and nitric oxide levels could not be used to predict which patients would develop capillary leak. Histological analysis of tumor specimens obtained after two or more courses of therapy showed changes consistent with a response to a biological response modifier: peripheral fibrosis surrounded the metastasis with infiltration of chronic and acute inflammatory cells. Because the response of relapsed OS to any type of salvage regimen has been poor, we interpret the clinical response of this therapy as good. However, the significant side effects associated with this therapy must also be taken into consideration before deciding to use this combination therapy. It is unfortunate that the study was stopped early due to halted production of IL-1alpha. If this agent is again manufactured for clinical use, we conclude that additional evaluation in patients with relapsed OS is warranted.

Adolescent↗
PubMed1996

Effects of galanin on 8-OH-DPAT induced decrease in body temperature and brain 5-hydroxytryptamine metabolism in the mouse.

Central administration of galanin dose-dependently (minimum effective dose, M.E.D. = 1 nmol) blocked the hypothermia induced by the 5-HT1A receptor agonist 8-hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT, 0.5 mg/kg s.c.), in mice. This inhibitory effect was reversed by pretreatment with the galanin receptor antagonist galantide (0.3 nmol) and also by pretreatment with the ATP-sensitive potassium channel blockers glibenclamide (10 nmol) and gliquidone (10 nmol). The hypothermic response to 8-OH-DPAT was also blocked by the 5-HT1A receptor antagonist (N-(2,4(2-methoxyphenyl)-1-piperazinyl)ethyl-N-(2-pyridinyl)cyclohexane, (WAY 100,635, M.E.D. = 0.01 mg/kg s.c.), and the centrally acting muscarinic receptor antagonist scopolamine (M.E.D. = 10 mg/kg i.p.) but not the peripheral muscarinic receptor antagonist N-methylscopolamine. 8-OH-DPAT (0.5 mg/kg s.c.) also decreased cortical and hypothalamic 5-HT (5-hydroxytryptamine, serotonin) metabolism, an effect which was not blocked by pretreatment with galanin (0.3-3 nmol intracerebroventricular, i.c.v.). Neither did galanin (0.03-3 nmol/5 microliters i.c.v.) affect basal 5-HT metabolism in these brain regions. Furthermore, pretreatment in vitro of mouse cortical membranes with galanin (10 or 1000 nM) had no effect on 5-HT1A receptor affinity, Bmax or pharmacology determined using [3H]8-OH-DPAT. These results suggest that the inhibition of 8-OH-DPAT induced hypothermia by galanin is probably not mediated by an interaction with 5-HT1A receptors but more likely by blocking the indirect activation by 8-OH-DPAT of central cholinergic pathways involved in temperature regulation.

8-Hydroxy-2-(di-n-propylamino)tetralin↗
PubMed1996

Peptide, disulfide, and glycosylation mapping of recombinant human thrombopoietin from ser1 to Arg246.

Thrombopoietin (TPO) is a hematopoietic factor involved in the regulation of megakaryocytopoiesis. Full length recombinant human TPO (332 residues) has been expressed in BHK cells and purified to homogeneity using conventional means. Peptide, disulfide, and glycosylation mapping of human TPO from residues 1 to 246 has been carried out using liquid chromatography-electrospray mass spectrometry (LC-ESMS). A modification of the ramped orifice method of Carr and co-workers [Carr et al. (1993) Protein Sci. 2, 183-196] is employed, providing additional information for assignment of the LC-ESMS chromatograms. With the modification, b- and y-series peptide ions are produced via front-end CID which confirms the mass-based assignments. The results of our analysis of TPO indicate that the amino acid sequence of TPO 1-246 is as expected from the transfected cDNA with complete cleavage of the signal peptide. Two unique disulfides are formed between the four cysteines in the cytokine domain of TPO: Cys7-Cys151 and Cys29-Cys85. The glycosylation map indicates the position, occupancy, and structures of the N- and O-glycans in TPO 1-246. In addition, site specific structural characterization of the PNGase F-liberated N-glycans has been performed following purification by high-pH anionic exchange chromatography with pulsed amperometric detection (HPAEC-PAD); the results corroborate the LC-ESMS data. The N-glycans are of the complex type with the core-fucosylated disialylated biantennary and trisialylated triantennary structures predominating. The O-glycans are of the mucin type with the monosialylated and disialylated GalGalNAc-S/T structures predominating. Furthermore, we propose that the C-terminal domain of TPO be further divided into two domains on the basis of sequence homology among the cloned sequences and glycosylation/structural features: an N-glycan domain (154-246) and an O-glycan domain (247-332).

Amino Acid Sequence↗
PubMed1996

Lack of development of tolerance to anticonvulsant effects of two excitatory amino acid antagonists, CGP [corrected] 37849 and CGP 39551 in genetically epilepsy-prone rats.

Two selective excitatory amino acid antagonists, DL-(E)-2-amino-4-methyl- 5-phosphono-3-pentenoic acid (CGP 37849) and its carboxyethylester (CGP 39551), were studied against audiogenic seizures in genetically epilepsy-prone rats following oral administration. Acute administration of CGP 37849 attenuated the clonic and tonic phases of the audiogenic seizures (109 dB, 12-16 kHz) 120 min after pretreatment (ED50 19.7 and 11.2 mumol kg-1, respectively). Similarly, CGP 39551 attenuated the clonic and tonic phases of audiogenic seizures 120 min after acute treatment with ED50 values of 17.2 and 8.8 mumol kg-1, respectively. For chronic studies animals were treated orally once daily (at 10 h) for 4 weeks with CGP 37849 (20 or 40 mumol kg-1) or CGP 39551 (15 or 30 mumol kg-1). In order to assess anticonvulsant activity, rats were subjected to auditory stimulation 120 min after drug administration on days 1, 3 and 5 and then every 3 or 4 days. Following 2 and 4 weeks of repeated drug administration with CGP 37849 (20 and 40 mumol kg-1) the ED50 values against clonic and tonic seizures were not significantly different from those observed following an acute administration. Similarly, 2 and 4 weeks after repeated treatment CGP 39551 (15 and 30 mumol kg-1) the ED50 values against clonic and tonic seizures were not significantly different from those observed following an acute administration. There was no significant difference between the ED50 values following either acute or repeated treatment of the two excitatory amino acid antagonists suggesting a lack of development tolerance. The duration of anticonvulsant activity observed between 0.5 and 24 h following administration of CGP 37849- and CGP 39551 was similar in acute and chronic treatment. The effects of CGP 37849 and CGP 39551 on motor behaviour was also evaluated following acute and repeated treatment by a rotarod apparatus 110 min following drug administration. The TD50 values for CGP 37849 and CGP 39551-induced impairment of locomotor performance recorded 2 or 4 weeks of repeated administration were not significantly different from those observed following an acute administration. The TD50 values for CGP 37849- and CGP 39551-induced impairment of locomotor performance were 87.6 and 70.8 mumol kg-1 i.p. respectively following 2 weeks treatment and 92.9 and 76.9 mumol kg-1 i.p. respectively following 4 weeks treatment. The doses of CGP 37849 and CGP 39551 required to elicit motor impairment were at least an order of magnitude above required for anticonvulsant activity. Since these compounds showed anticonvulsant properties after oral administration and lack of development of tolerance after repeated treatment, a potential use for antiepileptic therapy in man is suggested.

2-Amino-5-phosphonovalerate↗
PubMed1996

Are radioligand antagonist/agonist binding ratios in rat pancreas predictive of functional efficacy of cholecystokinin receptor agonists and antagonists?

Radioligand binding assays have been previously used to predict the relative efficacy of novel ligands. In the present study we have investigated whether for the cholecystokinin CCK-A receptors in the rat pancreas, the ratio of binding affinities for compounds for antagonist and agonist radioligands are predictive of functional activity. A number of classical cholecystokinin agonists, such as CCK-8S, caerulein, CCK-8DS, pentagastrin and CCK-4 had antagonist/agonist binding ratios of 4-fold or greater. All compounds behaved as full agonists in the stimulation of phosphatidylinositol (PI) turnover and increase in amylase secretion in rat pancreas. In contrast, compounds such as the benzodiazepine derivatives devazepide and L-365,260 had binding ratios of less than one and lacked agonist activity in either functional assay. Interestingly, the dipeptide derivative CI-988, which has been described as a selective CCK-B antagonist, was found to have an antagonist/agonist binding ratio of 1.5 for the CCK-A receptors in rat pancreas which was sufficiently high for this compound to behave as a full agonist in the amylase assay, although CI-988 did not exhibit agonist activity in the PI assay. These results suggest that the effective receptor reserve in the amylase assay is greater than that required to stimulate PI turnover, and that the selective peptoid CCK-B antagonist CI-988 has weak agonist activity at CCK-A receptors.

Animals↗
PubMed1996

Substitution of fifty four homologue (Ffh) in Escherichia coli with the mammalian 54-kDa protein of signal-recognition particle.

The fifty four homologue (Ffh) of Escherichia coli promotes the translocation of a subset of periplasmic, membrane and secreted proteins across the cytoplasmic membrane. The ffh gene product is essential for cell viability and efficient protein export. Here we show that the mammalian homologue signal-recognition particle (SRP) 54 kDa is not able to suppress the translocation defect in an Ffh conditional mutant Wam 113 [Phillips, G.J. & Silhavy, T.J. (1992) Nature 359, 744-746]. The expression of SRP 54kDa, which is increased when Ffh is suppressed in the Wam 113 strain, causes a pleiotropic defect characterised by cell elongation, and increased accumulation of precursor proteins. The accumulation of precursors of outer membrane protein A (Omp A) and maltose-binding protein (MBP), See-B dependent pre-proteins, was less than the Ffh-dependent proteins ribose-binding protein (RBP) and beta-lactamase. Sec B expression was suppressed by Ffh expression. The recombinant SRP 54 kDa, which forms a ribonucleoprotein complex in E coli, was shown to bind to precursor proteins, but is unable to interact with the filamentous temperature-sensitive Y (Fts Y) membrane receptor of the translocation machinery.

Amino Acid Sequence↗
PubMed1996

Methylation of CpG island transcription factor binding sites is unnecessary for aberrant silencing of the human MGMT gene.

Aberrant transcriptional inactivation of the non-X-linked human O-6-methylguanine DNA methyltransferase (MGMT) gene has been associated with loss of open chromatin structure and increases in cytosine methylation in the Sp1-binding region of the 5'-CpG island of the gene. To examine the necessity of these events for gene silencing, we have isolated and characterized a subline of human MGMT+ T98G glioma cells. The subline, T98Gs, does not express MGMT activity or MGMT mRNA, and exhibits no in vivo DNA-protein interactions at Sp1-like binding sites in the MGMT 5'-CpG island. While the MGMT CpG island is less accessible to exogenously added restriction enzymes in T98Gs nuclei than in T98G nuclei, it is similarly methylated in both T98G and T98Gs cell lines 5' and 3' to the transcription factor binding sites, and similarly unmethylated in the region encompassing the binding sites. Inappropriate transcriptional inactivation of MGMT, therefore, does not require methylation of transcription factor binding sites within the 5'-CpG island. Rather, MGMT gene silencing and transcription factor exclusion from T98Gs MGMT CpG island binding sites is most closely associated with condensed chromatin structure, which is in turn indirectly influenced by distant sites of methylation.

Base Sequence↗
PubMed1996

Kinetic analysis of inositol trisphosphate binding to pure inositol trisphosphate receptors using scintillation proximity assay.

Inositol 1,4,5-triphosphate (InsP3) receptors are regulated by many intracellular signals including proteins and small messengers. By linking purified cerebellar InsP3 receptors to scintillation proximity assay beads, binding of radioligands can be measured without separation of bound from free ligand. InsP3 receptors assayed by scintillation proximity assay bound heparin with high affinity and stereoselectively bound InsP3 with similar affinity to cerebellar membranes. By rapidly freezing scintillation proximity assay reactions and then counting the frozen samples, both fast and slow components of [3H] InsP3 association and dissociation were identified. Our novel freeze-quench method in combination with conventional stopped-quench equipment and scintillation proximity assay allows the rapid kinetics of the interactions of pure receptors with their ligands to be resolved.

Calcium Channels↗
PubMed1996

Controlled modification of acidity in cholecystokinin B receptor antagonists: N-(1,4-benzodiazepin-3-yl)-N'-[3-(tetrazol-5-ylamino) phenyl]ureas.

The design, synthesis, and biological activity of a novel series of CCK-B receptor antagonists (1) which incorporate a tetrazol-5-ylamino functionality attached to the phenyl ring of the arylurea moiety of L-365,260 are described. In these compounds, the acidity of the tetrazole was gradually modified by utilization of simple conformational constraints, and X-ray crystallographic data were obtained to support the conformational depenence of the pK(a) of the aminotetrazoles. Compounds to emerge from the present work such as 1f and 2c,d are among the highest affinity and, in the case of 1f, most selective (CCK-A/CCK-B, 37 000) antagonists so far reported for this receptor. The C(5)-cyclohexyl compound 2c (L-736,380) dose-dependently inhibited gastric acid secretion in anesthetized rats (ID(50), 0.064 mg/kg) and ex vivo binding of [(125)I]CCK-8S in BKTO mice brain membranes (ED(50), 1.7 mg/kg) and is one of the most potent acidic CCK-B receptor antagonists yet described.

Animals↗
PubMed1996

Neuroprotective effect of recombinant neutrophil inhibitory factor in transient focal cerebral ischaemia in the rat.

The neuroprotective effects of recombinant neutrophil inhibitory factor (NIF) have been assessed with temporary (2 h) middle cerebral artery (MCA) occlusion in the rat using the intraluminal suture technique. Administration of NIF (1.5 mg/kg, i.v.) immediately after the onset of reperfusion and at 4 and 6 h post-MCA occlusion significantly reduced both hemispheric infarct volume (P < 0.001) and brain swelling (P < 0.001), and improved neurological outcome (P < 0.02) when assessed at 24 h. These results demonstrated the marked neuroprotective efficacy of NIF in a rat model of transient focal cerebral ischaemia.

Animals↗
PubMed1996

Expression and purification of the canine 54-kDa subunit of signal recognition particle as a his-tagged protein from Escherichia coli.

The 54-kDa subunit of the signal recognition particle (SRP) binds nascent secretory polypeptides, binds the 7SL RNA (SRP RNA) component of SRP, and hydrolyzes GTP. Limited proteolysis of SRP 54-kDa suggests the protein has two domains, termed the G (GTP-binding) and M (methionine-rich) domains. The M domain is predicted to contain a number of amphiphilic helices, which provide a binding cleft for signal sequences. In order to obtain sufficient material for studies of relationships between structure and function, we have expressed the canine cDNA encoding the 54-kDa subunit in Escherichia coli using a T7 expression system. To aid purification, the protein was expressed with an amino-terminal extension encoding an initiating methionine and 10 histidine residues followed by an enterokinase cleavage site; 0.3mg of HIS-SRP 54-kDa was purified to give a single band on SDS-PAGE in 20% yield from 500 ml of cultured E. coli. Purified HIS-SRP 54-kDa was shown to be folded into the G and M domains, to inhibit the translocation of pre-prolactin into canine microsomes, and to bind mammalian SRP RNA only in the presence of the 19-kDa subunit of SRP.

Amino Acid Sequence↗
PubMed1996

Surgical treatment of meningiomas involving the cavernous sinus: evolving ideas based on a ten year experience.

The outcomes of 114 patients with meningiomas operated at the University of Pittsburgh were analyzed. Cerebrospinal fluid leakage was the most frequent complication, observed in 25 patients (21%). Complications were more frequent in patients who had recurrent (previously operated) tumors and patients with extensive tumors. Our current analysis also indicates that patients with prior radio-therapy (usually external beam) have unacceptably high complication rates after microsurgery. Early results indicate that regrowth rates are much higher in patients with incomplete resection (20%) than those with gross total excision (5%). Of the 114 patients, 108 returned to independent living and/or their previous occupation.

Cavernous Sinus↗