| 8164258 |
Antineoplastic agents. 278. Isolation and structure of axinastatins 2 and 3 from a western Caroline Island marine sponge |
10.1021/jm00034a014. |
J Med Chem |
Antineoplastic agents. 278. Isolation and structure of axinastatins 2 and 3 from a western Caroline Island marine sponge
Abstract
- The Republic of Palau marine sponge Axinella sp. was found to be an exceptionally productive source of cell growth inhibitory substances. The strongly antineoplastic polyether macrocyclic lactones halichondrin B (1) and homohalichondrin B (2) were isolated in 1.2 x 10(-6)% and 5.4 x 10(-7)% yields, respectively. In addition to axinastatin 1 (3), two new and cytostatic (GI50 values of 0.35 to 0.0072 microgram/mL against six human cancer cell lines) cycloheptapeptides designated axinastatins 2 (4) and 3 (5) were discovered in 1.4 x 10(-6)% and 1.25 x 10(-6)% yields. Structures were elucidated by high-resolution FABMS and tandem MS/MS techniques augmented by high-field (400 and 500 MHz) 2D-NMR spectral analyses. The absolute configurations were established by a combination of hydrolysis, derivatization, and chiral gas chromatographic methods.
|
| 8175045 |
Comparison of in vitro and in vivo properties of rhirudin (HBW 023) and a synthetic analogous peptide |
10.1159/000216883. |
Haemostasis |
Comparison of in vitro and in vivo properties of rhirudin (HBW 023) and a synthetic analogous peptide
Abstract
- Recombinant hirudin and a shortened synthetic analogue, with the amino acid sequence of D-Phe-Pro-Arg-Pro-(Gly)4-Asn-Gly-Asp-Phe-Glu- Glu-Ile-Pro-Glu-Glu-Tyr-Leu, are specific thrombin inhibitors which in a concentration-dependent manner inhibit thrombus formation as well as clot propagation both in vitro and in vivo. In comparison to the analogue, lower molar concentrations of rhirudin affected doubling of aPTT and TT as well as inhibition of thrombin amidolytic activity or thrombin-induced platelet aggregation in vitro. In the rat wire coil-induced thrombosis model, a 50% thromboprotective effect may be brought about with doses of 0.043 mumol/kg of rhirudin and 1.43 mumol/kg of the synthetic peptide. However, doubling of bleeding times is caused, on average, by dosages of between 0.143 and 0.43 mumol/kg rhirudin or approximately 0.143 mumol/kg of the analogue. Treatment groups included animals revealing significant prolongation of bleeding times as well as nonresponders. Despite the 10-fold longer impact on aPTT after application of rhirudin, the extent of mean bleeding time prolongation is identical to that of the analogue.
|
| 8178156 |
Cloning of a Grb2 isoform with apoptotic properties |
10.1126/science.8178156. |
Science |
Cloning of a Grb2 isoform with apoptotic properties
Abstract
- Growth factor receptor-bound protein 2 (Grb2) links tyrosine-phosphorylated proteins to a guanine nucleotide releasing factor of the son of sevenless (Sos) class by attaching to the former by its Src homology 2 (SH2) moiety and to the latter by its SH3 domains. An isoform of grb2 complementary DNA (cDNA) was cloned that has a deletion in the SH2 domain. The protein encoded by this cDNA, Grb3-3, did not bind to phosphorylated epidermal growth factor receptor (EGFR) but retained functional SH3 domains and inhibited EGF-induced transactivation of a Ras-responsive element. The messenger RNA encoding Grb3-3 was expressed in high amounts in the thymus of rats at an age when massive negative selection of thymocytes occurs. Microinjection of Grb3-3 into Swiss 3T3 fibroblasts induced apoptosis. These findings indicate that Grb3-3, by acting as a dominant negative protein over Grb2 and by suppressing proliferative signals, may trigger active programmed cell death.
|
| 8180837 |
The role of multiple opioid receptors in the maintenance of stimulation-induced feeding |
10.1016/0006-8993(94)91762-0. |
Brain Res |
The role of multiple opioid receptors in the maintenance of stimulation-induced feeding
Abstract
- Feeding induced by lateral hypothalamic electrical stimulation is sensitive to opioid antagonism and has previously been blocked by naloxone and antibodies to dynorphin A fragments. In the present study, high affinity receptor-selective antagonists were used to determine the particular opioid receptor type(s) that mediates stimulation-induced feeding (SIF). Separate groups of rats were used to conduct i.c.v. dose-response studies with TCTAP (mu), naltrindole (delta) and norbinaltorphimine (kappa). TCTAP, at the highest dose tested (i.e. 5.0 nmol) and norbinaltorphimine, at doses of 10.0 and 50.0 nmol, increased the brain stimulation frequency threshold for eliciting SIF. Naltrindole, at doses up to 50.0 nmol, had no effect. Results of another study, recently conducted in this laboratory, indicate that the present doses of TCTAP and norbinaltorphimine have no effect on thresholds for lateral hypothalamic self-stimulation. This suggests that mu and kappa opioid activity are associated with feeding, rather than the eliciting brain stimulation, and excludes non-specific performance deficits as an explanation of elevated SIF thresholds. In the SIF test, where 5 determinations of threshold are obtained in serial order, naloxone characteristically increases thresholds toward the end of a test while conventional appetite suppressants increase thresholds uniformly throughout a test. TCTAP and norbinaltorphimine produced a 'naloxone-like' pattern of threshold elevation, suggesting that mu and kappa receptors are involved in the process whereby endogenous opioid activity sustains feeding once initiated."
|
| 8185180 |
Cholecystokinin receptors in cells of the immune system |
10.1111/j.1749-6632.1994.tb44085.x. |
Ann N Y Acad Sci |
Cholecystokinin receptors in cells of the immune system
Abstract
|
| 8188287 |
Structure and diversity of the murine cryptdin gene family |
10.1006/geno.1994.1093. |
Genomics |
Structure and diversity of the murine cryptdin gene family
Abstract
- Cryptdins are antimicrobial peptides of the defensin family produced by mouse intestinal Paneth cells. Characterization of genomic and cDNA clones of cryptdins 1-3, 5, and 6 revealed that each of these genes has a two-exon structure. The prepro- and mature peptide coding regions are found on different exons separated by an intron of approximately 550 bp. The 5' ends of cryptdin mRNAs are distinguished by a 45-nucleotide untranslated sequence (UTS) encoded completely by the first exon. This feature contrasts with the extended 5' UTS of myeloid defensin mRNAs, which are coded by a third exon that appears to be unique to defensin genes expressed in hematopoietic cells. Sequencing of cryptdin cDNAs from both C3H/HeJ and 129/SVJ mouse small intestine demonstrated the presence of at least 16 different mRNAs, identifying cryptdins as the largest known defensin family. Amplification of these two-exon crypt defensin genes, followed by mutation-induced divergence at a limited number of positions, may have played an important role in the development of a broad-spectrum enteric defense system in the mouse."
|
| 8188715 |
A mutation in the insulin receptor that impairs proreceptor processing but not insulin binding |
None |
J Biol Chem |
A mutation in the insulin receptor that impairs proreceptor processing but not insulin binding
Abstract
- Here we report the identification of a new mutation in the alpha-chain of the insulin receptor, changing Trp412 into Ser using DNA from consanguineous parents who gave birth to a child with leprechaunism. The mutant receptor was expressed stably in CHO and transiently in COS-1 cells. It was found that the Ser412 mutant is not cleaved into alpha- and beta-subunits and remains as a 210-kDa proreceptor at an intracellular site. This property of the mutant receptor is in line with the observed decreased insulin binding to the parental fibroblasts. Cross-linking experiments show that the Ser412 proreceptor is able to bind insulin with an affinity comparable to that of the wild-type alpha-chain. Despite its capacity to bind insulin, the mutant receptor is not autophosphorylated. We postulate that the patient was homozygous for the Trp412-->Ser mutation and that the mutation was responsible for the leprechaun phenotype. This is the first description of a transport-defective receptor with the mutation outside the tetrabasic processing site and a functional insulin binding domain. The ability of the Ser412 mutant to bind insulin in cross-linking experiments suggests that the impaired transport of the proreceptor to the cell surface is the primary cause for the binding defect to intact cells.
|
| 8201839 |
Identification of a human delta opioid receptor: cloning and expression |
10.1016/0024-3205(94)90138-4 |
Life Sci |
Identification of a human delta opioid receptor: cloning and expression
Abstract
- The delta opioid receptor is an important target for analgesic drug development. This report describes the identification of delta opioid receptor clones from human cDNA libraries and the preparation of a human delta receptor cDNA in the pcDNA3 expression vector for transfection studies. The cDNA encodes a 372 amino acid protein that has 93% amino acid identity to mouse and rat delta receptors. COS-7 cells transfected with this clone express over 1.0 pmol receptor/mg protein when measured by saturation binding with [3H]naltrindole. The delta receptor selective ligands NTB, BNTX, [4'-Cl-Phe4]DPDPE and [D-Ala2,Glu4]deltorphin all have Ki values under 10 nM while the affinities of the mu and kappa opioid receptor ligands CTAP and U-69593, respectively, are over 4.0 microM. Agonists show binding to multiple affinity states of the receptor consistent with the presence of G-protein coupled and uncoupled forms of the expressed receptor. The 8-fold higher affinity of NTB relative to BNTX suggests that the human delta receptor is of the delta 2 subtype.
|
| 8202364 |
Systematic sequencing of the Escherichia coli genome: analysis of the 2.4- 4.1 min (110,917-193,643 bp) region. |
10.1093/nar/22.9.1637 |
Nucleic Acids Res. |
Systematic sequencing of the Escherichia coli genome: analysis of the 2.4- 4.1 min (110,917-193,643 bp) region.
Abstract
- The complete sequence analysis of the E. coli genome was initiated as a collaborative study in Japan. Following the initial analysis of the 0-2.4 min region (Yura, T. et al. (1992) Nucleic Acids Res. 20, 3305-3308), a contiguous sequence of 82,727 bp corresponding to the 2.4-4.1 min region (110,917-193,643 bp as counted from 0 min) was determined. The resulting sequence was found to contain at least 33 known genes and 24 putative genes predicted from protein sequence homology.
|
| 8211886 |
Leukotriene formation by peripheral monocytes in contact-activated human blood |
10.1016/0049-3848(93)90093-4. |
Thromb Res |
Leukotriene formation by peripheral monocytes in contact-activated human blood
Abstract
- Contact activation of the intrinsic coagulation cascade in whole human blood in vitro has previously been demonstrated to trigger release of leukotrienes (LT) into serum samples. In our present study we intended to identify the cellular origin of the activated 5-lipoxygenase pathway leading to LT formation under these experimental conditions. Therefore, whole human blood samples incubated for 60 min in vitro were supplemented with Percoll-isolated, 5-lipoxygenase-carrying, autologous blood cells. Surprisingly, exogenously added polymorphonuclear neutrophils (PMN, 5 x 10(6) or 15 x 10(6)/ml) capable of producing cysteinyl-LT in response to ionophore A23187 (1 microM) stimulation, had no effect neither on immunoreactive cysteinyl-LT nor on thromboxane (TX) B2 formation. However, exogenously added mononuclear cells (MNC, 5 x 10(6) or 15 x 10(6)/ml) led to a cell number-dependent increase in cysteinyl-LT generation as did supplementation with peripheral monocytes (PM, 5 x 10(5) or 15 x 10(5)/ml). While MNC enhanced the TXB2 production, PM had no such effect. Incubation of PM (5 x 10(5) or 15 x 10(5)/ml) in recalcified platelet-rich plasma (PRP) induced a cysteinyl-LT formation comparable to that in whole human blood. In contrast to the TXB2 generation, the cysteinyl-LT formation appears to be largely independent from thrombin, since recombinant hirudin (HBW 023, 2 microM), a specific thrombin inhibitor, had no significant effect on the cysteinyl-LT production but nearly completely abolished the TXB2 formation. By reverse phase HPLC the immunoreactive cysteinyl-LT were shown to consist of a mixture of LTC4, LTD4 and LTE4, with LTC4 being the predominant metabolite in all samples studied.(ABSTRACT TRUNCATED AT 250 WORDS)
|
| 8226313 |
Isolation, structures, and antifungal activities of new aureobasidins |
10.7164/antibiotics.46.1347. |
J Antibiot (Tokyo) |
Isolation, structures, and antifungal activities of new aureobasidins
Abstract
- Aureobasidins are a group of cyclic depsipeptides with antifungal activity and are produced by Aureobasidium pullulans. Aureobasidins are composed of eight amino acids and one hydroxy acid such as 2-hydroxy-3-methylpentanoic acid (Hmp), and highly lipophilic. Five new aureobasidins, S1, S2a, S2b, S3 and S4, which have higher hydrophilicity in reversed phase HPLC than the known aureobasidins A-R, were discovered in a fermentation broth of A. pullulans R106 by means of on-line liquid chromatography/mass spectrometry with electrospray ionization. We identified the structures of the compounds and studied their antifungal activities. Three of the new aureobasidins, S2b, S3 and S4, which have hydroxylated Hmp as the hydroxy acid, were highly active against Candida spp. and Cryptococcus neoformans.
|
| 8226319 |
Biological properties of aureobasidin A, a cyclic depsipeptide antifungal antibiotic |
10.7164/antibiotics.46.1414. |
J Antibiot (Tokyo) |
Biological properties of aureobasidin A, a cyclic depsipeptide antifungal antibiotic
Abstract
- Aureobasidin A (AbA) is a novel cyclic depsipeptide antifungal antibiotic. The antifungal activity of AbA was studied in vitro and in vivo in comparison with clinically effective antifungal agents, amphotericin B and fluconazole. AbA was highly active in vitro against many pathogenic fungi, including Candida albicans, Cryptococcus neoformans, Blastomyces dermatitidis and Histoplasma capsulatum. The activity was superior to amphotericin B in most cases. AbA exhibited fungicidal action toward growing cultures of C. albicans. It was highly tolerated by mice and showed good efficacy in the treatment of murine systemic candidiasis when given orally or subcutaneously. AbA's fungicidal action in mice with candidiasis was more effective than fluconazole and amphotericin B."
|
| 8234901 |
MEN 10,573 and MEN 10,612, novel cyclic pseudopeptides which are potent tachykinin NK-2 receptor antagonists |
10.1016/0167-0115(93)90419-9. |
Regul Pept |
MEN 10,573 and MEN 10,612, novel cyclic pseudopeptides which are potent tachykinin NK-2 receptor antagonists
Abstract
- The activity and selectivity of MEN 10,573 and MEN 10,612, novel cyclic pseudopeptides which are selective tachykinin NK-2 receptor antagonists is described, as compared to that of previously characterized linear and cyclic compounds. For the NK-2 receptor, the activity of test compounds was investigated in the hamster isolated trachea (HT) and the endothelium-deprived rabbit isolated pulmonary artery (RPA), two preparations which are endowed with pharmacologically distinct forms of the NK-2 receptor. The novel cyclic pseudopeptides, MEN 10,573 and MEN 10,612 displayed very high affinity for the NK-2 receptor in the HT (pA2 8.66 and 9.06, respectively) which is higher than that observed in the RPA (pA2 7.31 and 7.41 for MEN 10,573 and MEN 10,612, respectively). The antagonism exerted by MEN 10,573 and MEN 10,612 was of competitive nature in both preparations. MEN 10,573 and MEN 10,612 also displayed competitive antagonism for NK-2 receptor-mediated responses in the rabbit bronchus (RB), rat vas deferens (RVD), circular muscle of the human colon (HUC) and ileum (HUI). In the RB, HUC and HUI, the potency of the novel cyclic pseudopeptides was comparable to that of MDL 29,913 and about 10-fold greater than that of L659,877. In the RVD however, the potency of MEN 10,573 MEN 10,612 or MDL 29,913 was similar to that of L659,877. In anaesthetized rats, i.v. injection of MEN 10,612 produced a selective and long-lasting blockade of the urinary bladder contraction produced by the i.v. injection of the NK-2 receptor selective agonist beta Ala8neurokinin A(4-10), without affecting the response to the NK-1 receptor selective agonist Sar9substance P sulfone.(ABSTRACT TRUNCATED AT 250 WORDS)
|
| 8240717 |
Identification and characterization of microcystin-LY from Microcystis aeruginosa (strain 298) |
10.1515/bchm3.1993.374.7-12.635. |
Biol Chem Hoppe Seyler |
Identification and characterization of microcystin-LY from Microcystis aeruginosa (strain 298)
Abstract
- Two toxins, a main component A and a minor component B, were isolated from the freshwater cyanobacterium Microcystis aeruginosa (strain 298) and characterized in their chemical structure by amino-acid analysis, configurational analysis, by FAB-MS and 1H-NMR spectroscopy. The acid hydrolysate yielded for toxin A as constituent amino acids D-Ala, L-Leu, D-Glu, erythro-D-beta-Me-Asp and L-Arg, and for toxin B the amino acids D-Ala, L-Leu, D-Glu, erythro-D-beta-Me-Asp and L-Tyr. 1D and 2D 1H-NMR spectroscopy of the toxins A and B in DMSO-d6 allowed to characterize them as cyclic heptapeptides containing both the unusual beta-amino acid Adda (3-amino-9-methoxy-2,6,8-trimethyl-10-phenyldeca-4,6-dienoic acid) and N-methyldehydroalanine (Mdha) as additional constituent residues. Toxin A was found to correspond to the known and structurally well characterized microcystin-LR and toxin B to microsystin-LY. The presence of this variant has already been proposed, but its primary structure could be confirmed in this study.
|
| 8242067 |
Substitution of Leu for Pro-193 in the insulin receptor in a patient with a genetic form of severe insulin resistance |
10.1093/hmg/2.9.1437. |
Hum Mol Genet |
Substitution of Leu for Pro-193 in the insulin receptor in a patient with a genetic form of severe insulin resistance
Abstract
- Mutations have been identified in the insulin receptor (IR) gene in patients who are insensitive to insulin action. We studied an extremely insulin resistant patient whose insulin binding to Epstein-Barr virus (EBV) transformed lymphocytes was severely reduced. Transmembrane signalling, evaluated as insulin receptor autophosphorylation, was normal. The patient's IR was immunoprecipitated normally by AbP6, a polyclonal antibody directed to the beta subunit. However, there was an approximately 50% decrease in the affinity of IR immunoprecipitation by a monoclonal antibody (MA-10) directed against the alpha subunit. These observations suggested that there were likely to be a mutation in the patient's insulin receptor that caused misfolding of the IR alpha subunit. Analysis of gene structure by Southern blotting experiments did not reveal any major deletion in the IR gene of the proband. Northern blot analysis showed a normal level of expression of IR gene. We applied denaturing gradient gel electrophoresis (DGGE) as well as direct sequence analysis to study the 22 exons of IR gene amplified by polymerase chain reaction (PCR) using the proband's genomic DNA as a template. We identified a new missense mutation substituting leucine (CTG) for proline (CCG) in homozygous state at codon 193 in exon 3. Both parents are heterozygous for the Leu193 mutation. The Leu193 mutation was not detected in any of 75 normal subjects (150 chromosomes), indicating that it is not a common sequence variant of the insulin receptor. In addition, during the course of screening the patient's DNA with perpendicular DGGE, we identified two previously unreported silent substitutions in exon 9.(ABSTRACT TRUNCATED AT 250 WORDS)
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