| 1970780 |
Isolation and identification of a novel human metabolite of cyclosporin A: dihydro-CsA M17 |
None |
Drug Metab Dispos |
Isolation and identification of a novel human metabolite of cyclosporin A: dihydro-CsA M17
Abstract
- A novel metabolite of cyclosporin A was observed in human blood and urine. An analytical sample of this metabolite was isolated from human urine and the structure was determined to be (8-hydroxy-6,7-dihydro-MeBMT1) cyclosporin based on the 1H-NMR, 13C-NMR, FAB-MS, and HPLC characteristics of the biological sample as well as by comparison with a synthetically derived authentic sample. The significance of this metabolite in terms of the pathway by which cyclosporin A is metabolized is discussed.
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| 1971578 |
Pharmacokinetics and biotransformation of the cyclosporine metabolite M-17 in the rabbit |
None |
Drug Metab Dispos |
Pharmacokinetics and biotransformation of the cyclosporine metabolite M-17 in the rabbit
Abstract
- The monohydroxylated cyclosporine (CsA) metabolite M-17 was isolated from bile of human liver transplant recipients by preparative HPLC. The structure and purity of the metabolite were confirmed by fast atom bombardment-mass spectroscopy and proton NMR. The isolated metabolite was administered iv to three rabbits at a dose of 1.0 mg/kg with the following mean pharmacokinetic parameters being determined: half-life (t1/2B) 2.22 hr, volume of distribution (Vss) 1.44 liters/kg, and clearance 11.07 ml/min/kg. These are not significantly different from those obtained for CsA. In bile and urine obtained from rabbits administered M-17, the CsA metabolites M-8, M-18, and M-26 were found, indicating that M-17 is further metabolized. The latter data support the proposed biotransformation pathways for M-17.
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| 1974386 |
Pancreatic beta-cell somatostatin receptors |
10.1152/ajpendo.1990.259.2.E216. |
Am J Physiol |
Pancreatic beta-cell somatostatin receptors
Abstract
- The characteristics of somatostatin (SRIF) receptors in rat pancreatic beta-cells were investigated using rat islets and the beta-cell line HIT-T15 (HIT). The biochemical properties of the SRIF receptors were examined with 125I-labeled des-Ala-1,Gly-2-desamino-Cys-3-Tyr-11- dicarba3,14-somatostatin (CGP 23996). 125I-CGP 23996 bound to SRIF receptors in HIT cells with high affinity and in a saturable manner. The binding of 125I-CGP 23996 to SRIF receptors was blocked by SRIF analogues with a rank order of potency of somatostatin 28 (SRIF-28) greater than D-Trp-8-somatostatin greater than somatostatin 14 (SRIF-14). To investigate the physical properties of the HIT cell SRIF receptor, the receptor was covalently labeled with 125I-CGP 23996 using photo-cross-linking techniques. 125I-CGP 23996 specifically labeled a protein of 55 kDa in HIT cell membranes. The size of the SRIF receptor in HIT cells is similar to the size of the SRIF receptor labeled with 125I-CGP 23996 in membranes of freshly isolated islets, suggesting that the physical properties of SRIF receptors in HIT cells and rat islet cells are similar. The binding studies suggest that beta-cells predominantly express a SRIF-28-preferring receptor. In freshly isolated islets, glucose- and arginine-stimulated insulin release was effectively blocked by SRIF-28 but not by SRIF-14. SRIF-14 did inhibit arginine-stimulated glucagon secretion from freshly isolated islets. The dissociation of the inhibitory effects of SRIF-28 and SRIF-14 on insulin and glucagon release from freshly isolated islets suggests that the two peptides act through different receptors in islets to regulate hormone secretion.
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| 1975697 |
Permeability of the murine blood-brain barrier to some octapeptide analogs of somatostatin |
10.1073/pnas.87.17.6762. |
Proc Natl Acad Sci U S A |
Permeability of the murine blood-brain barrier to some octapeptide analogs of somatostatin
Abstract
- Analogs of somatostatin are being investigated clinically for the treatment of various malignancies, including brain tumors. We studied the ability of three therapeutically promising radioactively labeled somatostatin octapeptide analogs, RC-160, RC-121, and RC-161, to cross the blood-brain barrier (BBB) after peripheral or central injection. After i.v. injection, intact RC-160 was recovered from the blood and the brain. The entry rates were different from each compound but were generally low. By contrast, entry across the intact BBB increased 220 times when RC-160 was given in a serum-free perfusate. This suggests that some serum-related factor, probably the previously described protein binding or an aggregation-promoting factor, is the main determinant in limiting the blood-to-brain passage of somatostatin analogs. Entry into the brain was not inhibited by the addition of unlabeled analog to the perfusate, showing that passage was probably by diffusion across the membranes that comprise the BBB rather than by saturable transport. By contrast, a saturable system was found to transport peptide out of the central nervous system (CNS). The clearance from the CNS of RC-160 and RC-121, but not RC-161, was faster than could be accounted for by reabsorption of cerebrospinal fluid. Transport of radioactively labeled RC-160 out of the CNS was inhibited by unlabeled RC-160 or somatostatin but was not affected by some other peptide known to cross the BBB by their own transport systems. More than 80% of the radioactivity recovered from the blood after intracerebroventricular injection of RC-160 was eluted by HPLC at the position of the labeled analog, showing that the peptide had crossed the BBB in intact form. Our results indicate the presence of a saturable transport system in one direction across the BBB for some superactive analogs of somatostatin.
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| 1976930 |
Inhibitory effect of sandostatin on secretion of luteinising hormone and ovarian steroids in polycystic ovary syndrome |
10.1016/0140-6736(90)92270-r. |
Lancet |
Inhibitory effect of sandostatin on secretion of luteinising hormone and ovarian steroids in polycystic ovary syndrome
Abstract
- Hyperinsulinism accompanies the raised luteinising hormone (LH) concentrations in women with the polycystic ovary syndrome (PCOS). Somatostatin inhibits insulin and LH secretion in healthy adults, so the effect of treatment with a long-acting somatostatin analogue ('Sandostatin') on gonadotropin and androgen secretion in PCOS was investigated. LH pulsatility, androgen concentrations, and hormonal responses to an oral glucose load and to administration of a GnRH agonist (buserelin) were measured before and after 7 days' treatment with sandostatin 100 micrograms subcutaneously twice a day in 10 amenorrhoeic women with classic features of PCOS. Sandostatin significantly reduced integrated LH concentrations and LH pulse amplitudes, oestradiol, testosterone, and androstenedione concentrations, and LH responses to buserelin; it also suppressed insulin and C-peptide responses to an oral glucose load. Thus sandostatin inhibits pituitary and ovarian hormonal responses in part by a direct influence on pituitary activity, and the possibility of an indirect effect mediated by changes in insulin concentrations requires investigation. These findings have implications for the treatment of infertility in women with PCOS."
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| 1980641 |
Synthesis and biological activity of MeTyr1,MeArg7,D-Leu8-dynorphin A(1-9)-NHEt and D-Cys2-Cys5,MeArg7,D-Leu8-dynorphin A(1-9)-NH2 |
10.1248/cpb.38.2274. |
Chem Pharm Bull (Tokyo) |
Synthesis and biological activity of MeTyr1,MeArg7,D-Leu8-dynorphin A(1-9)-NHEt and D-Cys2-Cys5,MeArg7,D-Leu8-dynorphin A(1-9)-NH2
Abstract
- The opioid activities of MeTyr1-Dyn(1-7)-NH2, MeTyr1,D-Leu8-Dyn(1-8)-NH2, MeTyr1,D-Leu8-Dyn(1-9)-NH2, MeTyr1,D-Leu8-Dyn(1-10)-NH2, MeTyr1,D-Leu8-Dyn(1-11)-NH2, and MeTyr1,D-Leu8,12-Dyn(1-13)-NH2 were examined in the bioassays (guinea pig ileum, mouse vas deferens and rabbit vas deferens). Because MeTyr1,D-Leu8-Dyn(1-9)-NH2 showed the most potent opioid activity of the peptides tested, the biological activities of two kinds of Dyn(1-9) analogues, MeTyr1,MeArg7,D-Leu8-Dyn(1-9)-NHEt and D-Cys2-Cys5,MeArg7,D-Leu8-Dyn(1-9)-NH2 were determined and compared with those of MeTyr1,MeArg7,D-Leu8-Dyn(1-8)-NHEt and D-Cys2-Cys5,MeArg7,D-Leu8-Dyn(1-8)-NHEt in the three bioassays, in the receptor binding assays, and in the mouse tail pinch test after subcutaneous administration. The results suggest that the extension of the C-terminal in the peptide chain of MeArg7,D-Leu8-Dyn(1-8)-NH2 analogues by Arg is ineffective for increasing the kappa-opioid activities, kappa-receptor selectivity and/or analgesic effects of the peptides.
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| 1988448 |
Contributory effects of de novo transcription and premature transcript termination in the regulation of human epidermal growth factor receptor proto-oncogene RNA synthesis. |
10.1016/s0021-9258(18)52359-0 |
J. Biol. Chem. |
Contributory effects of de novo transcription and premature transcript termination in the regulation of human epidermal growth factor receptor proto-oncogene RNA synthesis.
Abstract
- Overexpression of the epidermal growth factor (EGF) receptor (c-erbB) proto-oncogene is a frequent occurrence in human carcinoma and appears to accompany autocrine or paracrine transforming growth factor-alpha expression, which in model systems can result in activation of EGF receptor tyrosine kinase activity and phenotypic transformation. Here we have investigated the transcriptional regulation of the EGF receptor gene, by run-on transcription in isolated nuclei derived from epithelioid tumor lines. The level of transcription was measured at various points on the 100-kilobase pair EGF receptor gene locus, on either sense or antisense DNA strands. We find the level of sense strand transcription along exon 1 is 8-fold higher than transcription in exons 2-26. Primary EGF receptor transcripts appear to pause or terminate prematurely between exons 1 and 2. Termination was mapped to a sequenced region approximately 2 kilobase pairs 3' of exon 1, proximal to a previously reported DNase I hypersensitive site and an enhancer-like activity. Transcription in the CpG-rich region surrounding exon 1 is bidirectional, with antisense transcripts initiating in intron 1 and extending through the coding first exon. Activation of protein kinase C
Results in a 5-fold induction of EGF receptor transcription, accompanied by a slow release in the block RNA elongation between exon 2 and exon 26, showing that EGF receptor RNA synthesis may be altered by changes in de novo transcription and by a block to RNA elongation.
|
| 1988661 |
In vitro pharmacological profile of a novel structural class of oxytocin antagonists |
None |
J Pharmacol Exp Ther |
In vitro pharmacological profile of a novel structural class of oxytocin antagonists
Abstract
- A number of structurally novel cyclic hexapeptides have been characterized as potent and selective oxytocin (OT) antagonists in vitro. As a representative of this class of compounds, L-366,948 cyclo(L-prolyl-D-2-naphthylalanyl-L-isoleucyl-D-pipecolyl- L-pipecolyl-D- histidyl) exhibited a high binding affinity (Ki, low nanomolar) for OT receptors in rat (uterus and mammary) and primate (pregnant rhesus and human myometrium) tissue with a several hundred-fold binding selectivity vs. rat arginine vasopressin (AVP)-V1 (liver) and AVP-V2 (kidney medulla) receptors. In functional assays, L-366,948 was a pure OT antagonist, blocking both OT-stimulated contraction of the isolated rat uterus (pA2, 8.5) and phosphatidylinositol turnover in uterine slices (IC50, 40 vs. 3 nM OT), with no evidence of partial agonist activity. L-366,948 was comparatively weak as an antagonist of AVP-induced contraction of the isolated rat tail artery (AVP-V1 receptor) and AVP-stimulated adenylate cyclase (AVP-V2 receptor) activity in rat kidney medulla and did not influence prostaglandin F2 alpha- or bradykinin-induced contractions of the isolated rat uterus. L-366,948 and related compounds described in this report represent new experimental tools for the study of the pharmacology and physiology of OT.
|
| 1989352 |
Assessment of the biological activity of cyclosporine metabolites using the human JURKAT cell line |
None |
Transplant Proc |
Assessment of the biological activity of cyclosporine metabolites using the human JURKAT cell line
Abstract
|
| 2001252 |
Assignment of disulphide bonds in human platelet GPIIIa. A disulphide pattern for the beta-subunits of the integrin family. |
10.1042/bj2740063 |
Biochem. J. |
Assignment of disulphide bonds in human platelet GPIIIa. A disulphide pattern for the beta-subunits of the integrin family.
Abstract
- Integrins are cell-surface heterodimers formed by the association of one alpha- and one beta-subunit. Glycoprotein IIIa (GPIIIa or beta 3 subunit) is the common beta-subunit of the beta 3 subfamily of integrins, which, when associated with glycoprotein IIb (GPIIb), constitutes the receptor for fibrinogen and other adhesive proteins at the platelet surface (the GPIIb-IIIa complex) and, when associated with the alpha v-subunit, constitutes the vitronectin receptor present in several cell types. Protein chemical analysis of GPIIIa allows us to define the following structural domains: the cysteine-rich and proteinase-resistant N-terminal domain (GPIIIa 1-62); the adhesive-protein-binding domain (GPIIIa 101-422); the cysteine-rich and proteinase-resistant core (GPIIIa 423-622); and the C-terminal domain comprising an extracellular subdomain (GPIIIa 623-692), a transmembrane subdomain (GPIIIa 693-721), and a cytoplasmic subdomain (GPIIIa 722-762). We also assign unambiguously the disulphide bonds within the N-terminal, the fibrinogen-binding and the C-terminal domains, and the two long-range disulphide bonds which join the N-terminus to the proteinase-resistant core (Cys5-Cys435) and the fibrinogen-binding domain to the extracellular side of the C-terminal domain (Cys406-Cys655). In addition, we propose three alternative models for the arrangement of the disulphide bonds within the core and of the disulphide bonds joining the core to the extracellular side of the C-terminal domain, consistent with our experimental findings, favouring temporarily that which imposes less steric hindrance for the formation of these disulphide bonds. On the basis of this information and on the highly conserved overall structure observed in the beta-subunits of the integrin family known so far, except in beta 4, we propose to extend the cysteine-pairing pattern and the structural domains outlined here for GPIIIa to all the beta-subunits of the integrin family.
|
| 2002058 |
Insulin resistance and diabetes due to different mutations in the tyrosine kinase domain of both insulin receptor gene alleles |
None |
J Biol Chem |
Insulin resistance and diabetes due to different mutations in the tyrosine kinase domain of both insulin receptor gene alleles
Abstract
- Mutations in the insulin receptor gene can lead to in vivo and in vitro insulin resistance and can be the cause of diabetes mellitus in selected patients. We have studied a 22-year-old diabetic woman with Type A insulin resistance and acanthosis nigricans. Insulin binding to the patient's erythrocytes, monocytes, adipocytes, fibroblasts, and transformed lymphocytes was decreased. Receptor autophosphorylation and tyrosine kinase activity toward an exogenous substrate were reduced in partially purified insulin receptors from the proband's transformed lymphocytes. Determination of the nucleotide sequence of the patient's insulin receptor cDNA revealed that the subject was a compound heterozygote who inherited two different mutant insulin receptor gene alleles. The paternal allele contains a missense mutation encoding the substitution of glutamine for arginine at position 981 in the tyrosine kinase domain of the receptor. The maternal allele contains a nonsense mutation causing premature termination after amino acid 988 in the beta-subunit, thereby deleting most of the kinase domain. The mRNA encoded by the allele with the premature stop codon is likely to be unstable, since mRNA transcripts from this allele were decreased markedly compared with the other allele. The mother, who is heterozygous for the nonsense mutation, exhibited only mild insulin resistance, whereas the proband was severely insulin-resistant; this indicates that the missense mutation is biologically significant. In summary, (1) we have identified a patient and her family with a genetic form of insulin resistance and diabetes due to a defect at the level of the insulin receptor; (2) the proband is a compound heterozygote displaying a missense mutation (position 981) in one allele and a nonsense mutation (position 988) in the other insulin receptor gene allele; (3) the missense mutation is in the kinase domain and encodes a receptor with impaired in vitro kinase activity; and (4) based on the in vitro and in vivo phenotype, the kinase domain mutation at position 981 is biologically significant leading to insulin resistance.
|
| 2004391 |
Pleural exudates in patients with lung cancer. Comparative study |
None |
Cas Lek Cesk |
Pleural exudates in patients with lung cancer. Comparative study
Abstract
- A group of 228 patients with cancer of the lungs admitted in the course of 15 months to the Second Clinic for TB and Respiratory Diseases was classified according to the complicating pleural exudate. At the onset or in the course of the disease the exudate developed in 24 patients (11%)--group A, in the remaining 204--group B--there is no information on an exudate. The mean age of the two groups did not differ, smoking habits were similar. Significant differences were recorded as regards the incidence of subjective complaints, in group A the patients complained significantly more frequently of dyspnoea grade III to IV, chest pain, loss of weight and oedema of the neck. As to the number with haemoptysis and exposure to cancerogens the two groups did not differ. As to subsidiary diseases, only CHOPN was more frequent in group B. Differences were recorded also in the ratio of morphological types, in group A the small-cell type was most frequent, in group B the spinocellular type. The two groups differed also as to the incidence of peripheral and central forms, which were significantly more frequent in group A. The TNM stages differed: in group A stage IV predominated, in group B there were 40% of the patients in stage I and II. Significant differences between the groups were found also as to treatment: 17.6% in group B were operated and in group A. In group A all patients died, in group B to the day of evaluation 25 subjects survive, this difference, is, however, not significant.
|
| 2005582 |
Antagonism of oxytocin in rats and pregnant rhesus monkeys by the novel cyclic hexapeptides, L-366,682 and L-366,948 |
None |
J Pharmacol Exp Ther |
Antagonism of oxytocin in rats and pregnant rhesus monkeys by the novel cyclic hexapeptides, L-366,682 and L-366,948
Abstract
- Two cyclic hexapeptides unrelated in chemical structure to oxytocin (OT) were shown in vivo to be antagonists of the contractile action of OT on the uterus. In anesthetized rats challenged with OT (1 micrograms/kg) administered as an i.v. bolus, L-366,682 cyclo-(L-Pro-D-Trp-L-Ile-D-pipecolic acid-L-pipecolic acid-D-His) and L-366,948 (D-2-naphthyl-alanine in place of D-Trp) were equipotent with AD50 values of about 100 micrograms/kg i.v. At doses of L-366,682 or L-366,948 causing approximately 90 to 95% block (approximately the AD95 dose) of OT, the duration of action of the antagonists exceeded 145 min. Both compounds exhibited selectivity in the rat, as a dose of either at 300 micrograms/kg i.v. shifted the dose-response for OT-induced uterine contraction to the right by approximately 5-fold but did not affect the dose-response to prostaglandin F2 alpha. Furthermore, neither compound, at a dose of 3 mg/kg i.v., antagonized the action of arginine vasopressin acting at V-1 (pressor effect in pithed rats) or V-2 (antidiuretic) receptors. In conscious, freely moving, pregnant rhesus monkeys, L-366,948 or L-366,682 given i.v. or s.c. were effective antagonists of uterine contractions elicited by an infusion of OT. OT- or arginine vasopressin-like agonist activity was not observed in any of the in vivo models. It is concluded that L-366,682 and L-366,948 act in vivo as reasonably potent, long-acting and selective antagonists at OT receptors in the rat and rhesus uterus.
|
| 2016704 |
Conformationally constrained renin inhibitory peptides: cyclic (3-1)-1-(carboxymethyl)-L-prolyl-L-phenylalanyl-L-histidinamide as a conformational restriction at the P2-P4 tripeptide portion of the angiotensinogen template |
10.1021/jm00108a006. |
J Med Chem |
Conformationally constrained renin inhibitory peptides: cyclic (3-1)-1-(carboxymethyl)-L-prolyl-L-phenylalanyl-L-histidinamide as a conformational restriction at the P2-P4 tripeptide portion of the angiotensinogen template
Abstract
- Interest in conformationally constrained peptides as potential inhibitors of renin led us to examine an N-terminal cycle of linear renin inhibitory peptides. A cyclic structure was prepared by joining the N-terminal proline at the P4 site to the imidazole ring of histidine at the P2 site via a carboxymethylene fragment. An efficient synthetic route to this 14-membered macrocycle was developed and this N-terminal cyclic tripeptide could be readily incorporated into renin inhibitory peptides. Monte Carlo molecular modeling methods were used to generate bound conformations of a representative inhibitor in a model of the renin active site, suggesting possible modes of binding of these inhibitors to renin. Two representative compounds that contain this 14-membered macrocycle were evaluated for their inhibitory activities against human plasma renin and they were found to exhibit very high binding affinity with IC50 values in the nanomolar and subnanomolar range.
|
| 2033005 |
Attenuation of IL-2-induced multisystem organ edema by phalloidin and antamanide |
10.1152/jappl.1991.70.3.1364. |
J Appl Physiol (1985) |
Attenuation of IL-2-induced multisystem organ edema by phalloidin and antamanide
Abstract
- Interleukin 2 (IL-2) is a potent cytokine with diverse effects, including the ability to stimulate lymphocyte differentiation into cells capable of lysing tumor. Its therapeutic efficacy is limited because of side effects such as breakdown of the microvascular barrier and edema. Control of the microvascular barrier is in part regulated by endothelial cell cytoskeletal contractile proteins. This study tests whether the cyclopeptides that maintain actin filament organization and distribution and reduce macromolecular flux across the endothelial cell junction in vitro would similarly maintain barrier tightness and prevent early edema produced by IL-2 in vivo. Anesthetized rats were treated at 30-min periods with intravenous saline (0.5 ml, n = 41), phalloidin (20 micrograms in 0.5 ml, n = 21), or antamanide, (20 micrograms in 0.5 ml, n = 21), starting 30 min before the 1-h infusion of 10(6) U of recombinant human IL-2 or saline. Six hours after the start of IL-2, there was edema in the saline/IL-2 group, as measured by increased wet-to-dry ratios (W/D) in the lungs, heart, and kidney. With saline/IL-2, bronchoalveolar lavage (BAL) fluid contained an elevated protein concentration and higher plasma thromboxane levels compared with controls. The number of neutrophils sequestered in the lungs was more than twice that of saline controls. Phalloidin significantly attenuated edema in lung and reduced BAL protein leak. Antamanide treatment was as effective in limiting lung and heart edema, but, in contrast to phalloidin, antamanide prevented kidney edema and did not lead to an alteration in the liver W/D. Antamanide also prevented BAL fluid protein leak.(ABSTRACT TRUNCATED AT 250 WORDS)
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