| 2509009 |
Cyclosporines: correlation of immunosuppressive activity and inhibition of bone resorption |
10.1007/BF02556041. |
Calcif Tissue Int |
Cyclosporines: correlation of immunosuppressive activity and inhibition of bone resorption
Abstract
- Cyclosporine A (CsA) is a potent immunosuppressive agent that inhibits stimulated bone resorption in vitro. To study the mechanism of this effect, we have compared CsA with several cyclosporine analogs that vary in immunosuppressive potency. CsA as well as another potent immunosuppressive analog, CsG, inhibited parathyroid hormone (PTH) and interleukin-1 (IL-1)-stimulated resorption of fetal rat limb bones. The nonimmuno-suppressive analogs CsH and CsF did not inhibit PTH or IL-1-stimulated bone resorption. Likewise, the weakly immunosuppressive analog CsD did not significantly inhibit PTH-stimulated bone resorption. Although other mechanisms cannot be excluded, our data are consistent with the concept that bone resorption may involve an immune cell-derived mediator.
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| 2512589 |
Somatostatin and its analogue (D-Trp8,D-Cys14)-somatostatin do not modify intestinal absorption in vivo of carbohydrates in hamster intestine, but they do modify some disaccharidases |
10.1113/expphysiol.1989.sp003355. |
Q J Exp Physiol |
Somatostatin and its analogue (D-Trp8,D-Cys14)-somatostatin do not modify intestinal absorption in vivo of carbohydrates in hamster intestine, but they do modify some disaccharidases
Abstract
- Somatostatin is a widely distributed hormone localized in the central nervous system, pancreas and gastrointestinal tract. We have investigated the possible influence of somatostatin and a synthetic analogue, (D-Trp8,D-Cys14)-somatostatin, on the intestinal absorption 'in vivo' of D(+)-glucose and D(+)-galactose and also the effect on disaccharidase intestinal activities in hamster. Somatostatin, or its analogue, (12 micrograms/100 g body wt) was administered intraperitoneally 4 or 14 h prior to experiments. The results are compared to control animals. Animals treated with somatostatin and the synthetic analogue showed that there were no significant difference from control animals with respect to intestinal absorption of carbohydrates. Somatostatin produced inhibition of brush-border lactase activity in females only, whereas brush-border sucrase was increased 14 h after treatment in males and females, and brush-border maltase was inhibited in females only 4 h after hormone administration."
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| 2514185 |
Antimicrobial peptides, isolated from horseshoe crab hemocytes, tachyplesin II, and polyphemusins I and II: chemical structures and biological activity |
10.1093/oxfordjournals.jbchem.a122913. |
J Biochem |
Antimicrobial peptides, isolated from horseshoe crab hemocytes, tachyplesin II, and polyphemusins I and II: chemical structures and biological activity
Abstract
- Tachyplesin is an antimicrobial peptide recently found in the acid extract of hemocytes from the Japanese horseshoe crab (Tachypleus tridentatus) Nakamura, T. et al. (1988) J. Biol. Chem. 263, 16709-16713. In our continuing studies on the peptide, we have found an isopeptide, tachyplesin II, and also polyphemusins I and II in hemocytes of the American horseshoe crab (Limulus polyphemus). The complete primary structures of these peptides, which are very similar to that of the previously isolated peptide, now named tachyplesin I, were determined to be as follows: (Table: see text). The isopeptide, tachyplesin II, consists of 17 residues with a COOH-terminal arginine alpha-amide. On the other hand, both polyphemusins I and II were found to contain 18 residues due to an additional Arg residue at the NH2-terminal end as well as a COOH-terminal arginine alpha-amide. The disulfide linkages for polyphemusin I consisted of two bridges between Cys-4 and Cys-17 and between Cys-8 and Cys-13, which was identical to in the case of tachyplesin I. Moreover, all of these peptides inhibited the growth of not only Gram-negative and -positive bacteria but also fungi, such as Candida albicans M9. Furthermore, complex formation between these peptides and bacterial lipopolysaccharides was also observed in a double diffusion test. These results suggest that tachyplesins and polyphemusins are probably located in the hemocyte membrane, where they act on antimicrobial peptides as a self-defense mechanism in the horseshoe crab against invading microorganisms.
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| 2515402 |
Fatty acid and beta-amino acid syntheses in strains of Bacillus subtilis producing iturinic antibiotics |
10.1007/BF02544538. |
Lipids |
Fatty acid and beta-amino acid syntheses in strains of Bacillus subtilis producing iturinic antibiotics
Abstract
- Iturinic antibiotics, produced by different strains of Bacillus subtilis, contain long-chain beta-amino acids (beta-AA). The regulation of the synthesis of fatty acids (FA) and beta-AA was studied by modifying the culture medium. Addition of possible precursors, branched-chain alpha-amino acids, to the medium affected the FA and beta-AA compositions. According to this, the B. subtilis strains can be divided into two groups. The first contains the producers of mycosubtilin and bacillomycin F which synthesize a high level of iso C16 chains; the second contains the producers of bacillomycin D, bacillomycin L and iturin which synthesize a high level of n carbon chains. The incorporation of radioactive sodium acetate into FA and beta-AA showed rapid FA synthesis followed by a second synthetic step. Although the detailed mechanism has not yet been elucidated, this second step, corresponding to the beta-AA synthesis, seemed to be a key step in determining the alkyl chain of beta-AA.
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| 2535874 |
Design of potent linear alpha-melanotropin 4-10 analogues modified in positions 5 and 10 |
10.1021/jm00121a032. |
J Med Chem |
Design of potent linear alpha-melanotropin 4-10 analogues modified in positions 5 and 10
Abstract
- alpha-Melanocyte stimulating hormone (alpha-MSH) is a linear tridecapeptide (Ac-Ser-Tyr-Ser-Met-Glu-His-Phe-Arg-Trp-Gly-Lys-Pro-Val-NH2) that has diverse physiological functions in addition to its reversible darkening of amphibian skins by stimulating melanosome dispersion within melanophores. On the basis of theoretical and experimental results from our laboratory and others, we have designed a group of 1-13, 4-13, and especially 4-10 analogues related to the superpotent analogue Nle4,D-Phe7alpha-MSH in which the Glu5 has been replaced with Asp5, and the Gly10 has been replaced with Lys10 and other basic amino acid residues in the 4-10 analogues, and in which Gly10 and Lys11 were interchanged in the longer peptide analogues. In the 1-13 and 4-13 series the Lys10, Gly11 analogues generally retained superpotency for the D-Phe7-containing analogues. Most interestingly, synthesis of Ac-Nle4,Xxx5,Yyy7,Zzz10alpha-MSH4-10-NH2 analogues where Xxx = Asp or Glu, Yyy = Phe or D-Phe, and Zzz = basic amino acids (Lys, Orn, alpha,gamma-diaminobutyric acid (Dab), and alpha,beta-diaminopropionic acid (Dpr provided melanotropins with potencies up to 10 times that of the native hormone in stimulating frog (Rana pipiens) skin darkening and 8-50 times more potent than alpha-MSH in stimulating lizard (Anolis carolinensis) skin melanophores in vitro. To our knowledge, Ac-Nle4,Asp5,D-Phe7,Dab10alpha-MSH4-10-NH2, the most potent analogue, is the most potent melanotropin obtained thus far for the Anolis assay system. These results provide new insights into the structural and conformational requirements for biological potency of alpha-MSH and the differential structural and conformational requirements of alpha-MSH and its analogues at two different types of pigment cell receptors.
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| 2538124 |
Alternative splicing of human insulin receptor messenger RNA. |
10.1016/0006-291x(89)92439-x |
Biochem. Biophys. Res. Commun. |
Alternative splicing of human insulin receptor messenger RNA.
Abstract
- The polymerase chain reaction has been used to examine alternative splicing of human insulin receptor (hINSR) mRNA. Alternative splicing of a 36 base pair exon, exon 11, generates hINSR transcripts encoding receptor isoforms which differ in sequence at the C-terminal end of the insulin-binding alpha-subunit. This process appears to be tissue-specific and, in addition, may be developmentally regulated.
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| 2543629 |
Purification and antimicrobial properties of three defensins from rat neutrophils |
10.1128/iai.57.7.2021-2027.1989. |
Infect Immun |
Purification and antimicrobial properties of three defensins from rat neutrophils
Abstract
- Three cysteine-rich cationic peptides, designated RatNP-1, RatNP-3, and RatNP-4, were purified from an acid extract of rat polymorphonuclear neutrophils, sequenced, and tested for antimicrobial activity. The peptides ranged from 29 to 32 amino acids in length (Mr, 3,252 to 3,825), and each contained all eight invariantly conserved "framework" residues that are characteristic of defensins. Each of the peptides killed Escherichia coli ML-35, Acinetobacter calcoaceticus HON-1, Staphylococcus aureus 502A, and Candida albicans 820 in vitro. RatNP-1, the most cationic rat defensin, was also the most potent. With this report, a total of 13 distinct defensins have been characterized in the polymorphonuclear leukocytes of four mammalian species. The existence of the defensin system in rats should facilitate investigations of the in vivo role of defensins in experimental infections.
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| 2543678 |
All autophosphorylation sites of epidermal growth factor (EGF) receptor and HER2/neu are located in their carboxyl-terminal tails. Identification of a novel site in EGF receptor. |
10.1016/s0021-9258(18)81674-x |
J. Biol. Chem. |
All autophosphorylation sites of epidermal growth factor (EGF) receptor and HER2/neu are located in their carboxyl-terminal tails. Identification of a novel site in EGF receptor.
Abstract
- Activation of the epidermal growth factor (EGF) receptor kinase leads to autophosphorylation and to the phosphorylation of various cellular substrates. The three known autophosphorylation sites of EGF receptor are located at the carboxyl-terminal tail where they probably act to compete with and thus modulate substrate phosphorylation. Mutational analysis and microsequencing techniques have been used to localize and identify new autophosphorylation site(s) of the EGF receptor. We have compared the phosphopeptide maps of human EGF receptor, and two deletion mutants lacking 63 and 126 amino acids from the carboxyl-terminal tail with the phosphopeptide maps of HER/neu and a chimeric EGF receptor containing the carboxyl-terminal tail of HER2/neu. HER2/neu is highly homologous to the EGF receptor, and it probably functions as a growth factor receptor for as yet unidentified growth factor. On the basis of this analysis, we have concluded that all autophosphorylation sites of EGF receptor and HER2/neu are located in their carboxyl-terminal tails. Utilizing the EGF receptors with carboxyl-terminal deletions, we were also able to identify tyr1086 as an additional autophosphorylation site of EGF receptor. Direct microsequencing of a phosphorylated tryptic peptide from the human EGF receptor confirmed this assignment.
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| 2544263 |
Characterization of the 3' region of the human DNA topoisomerase I gene. |
10.1111/j.1432-1033.1988.tb14404.x |
Cancer Res. |
Characterization of the 3' region of the human DNA topoisomerase I gene.
Abstract
- Previous studies suggest that topoisomerase I (Topo I) plays a critical role in cell growth. However, the structure of the Topo I gene has not yet been determined. Two complementary DNA (cDNA) clones for the human Topo I 4.1-kilobase mRNA were isolated independently from HeLa and KB cell cDNA libraries. These clones were identical and they contained 679 base pairs of coding and 1138 base pairs of noncoding sequences. The clones had a two-base difference in the 3' noncoding region compared to the Topo I cDNA from human placenta. The structure of the 3' end of the human Topo I gene from six human tumor cell lines was examined. The Topo I cDNA recognized 16.5, 24.2, and 16.0 kilobases of genomic DNA restricted with EcoRI, HindIII and PstI, respectively. The individual genomic fragments were ordered by double digestion and hybridization with cDNA subclones. digestion and hybridization with cDNA subclones. The
Results indicate that the human Topo I gene contains several intervening sequences. The gene arrangement was similar in all six cell lines and no polymorphism was observed. However, each digestion contained genomic fragments that hybridized with all the subclones, suggesting that at least one Topo I pseudogene, or another Topo I gene with a different structure, was present in every cell line. As predicted, double digestions generated at 161 base pair fragment that indicates the presence of an intronless pseudogene. In contrast to the DNA topoisomerase I gene, the presumptive pseudogene(s) appears to be hypomethylated. In addition to the 4.1-kilobase Topo I mRNA, a larger 6-kilobase RNA was identified in human KB and HeLa cells which could be a processed Topo I mRNA intermediate.
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| 2544402 |
A structurally unique, potent, and selective oxytocin antagonist derived from Streptomyces silvensis |
10.1210/endo-125-1-217. |
Endocrinology |
A structurally unique, potent, and selective oxytocin antagonist derived from Streptomyces silvensis
Abstract
- The in vitro and in vivo oxytocin/arginine vasopressin (OT/AVP) antagonist properties of two cyclic hexapeptides derived from a newly discovered natural product (L-156,373) of Streptomyces silvensis are described. In radioligand binding assays, L-156,373 cyclo(L-Pro-D-Phe-N-OH-L-Ile-D-piperazyl-L-piperazyl-N-Me-D -Phe) exhibited moderate affinity for rat uterine OT receptors (Ki, 150 nM), with some selectivity (approximately 20-fold) vs. liver AVP-V1 and kidney AVP-V2 receptors. Dehydroxylation of N-hydroxyisoleucine and oxidation of the piperazic acid residues of L-156-373 produced an interesting derivative, L-365,209. These structural modifications increased OT receptor affinity and selectivity by 20- and 2.5-5-fold, respectively. In the isolated rat uterus, L-365,209 was a potent (apparent dissociation constant, 1.7 nM) and competitive OT antagonist. L-365,209 also blocked the effects of AVP at both AVP-V1 (phosphatidylinositol turnover in rat hepatocytes) and AVP-V2 (adenylate cyclase in rat kidney medulla) receptors, but only at low micromolar concentrations. L-365,209, given iv to anesthetized rats, antagonized the action of exogenous OT on the uterus (ID50, 460 micrograms/kg) with a relatively long duration of action. L-365,209 represents a unique class of compounds that provides an entirely new approach for the design of antagonists for these neurohypophyseal hormones.
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| 2544997 |
Human diabetes associated with a deletion of the tyrosine kinase domain of the insulin receptor. |
10.1126/science.2544997 |
Science |
Human diabetes associated with a deletion of the tyrosine kinase domain of the insulin receptor.
Abstract
- The insulin receptor has an intrinsic tyrosine kinase activity that is essential for signal transduction. A mutant insulin receptor gene lacking almost the entire kinase domain has been identified in an individual with type A insulin resistance and acanthosis nigricans. Insulin binding to the erythrocytes or cultured fibroblasts from this individual was normal. However receptor autophosphorylation and tyrosine kinase activity toward an exogenous substrate were reduced in partially purified insulin receptors from the proband's lymphocytes that had been transformed by Epstein-Barr virus. The insulin resistance associated with this mutated gene was inherited by the proband from her mother as an apparently autosomal dominant trait. Thus a deletion in one allele of the insulin receptor gene may be at least partly responsible for some instances of insulin-resistant diabetes.
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| 2544998 |
Human diabetes associated with a mutation in the tyrosine kinase domain of the insulin receptor |
10.1126/science.2544998. |
Science |
Human diabetes associated with a mutation in the tyrosine kinase domain of the insulin receptor
Abstract
- Insulin receptor complementary DNA has been cloned from an insulin-resistant individual whose receptors have impaired tyrosine protein kinase activity. One of this individual's alleles has a mutation in which valine is substituted for Gly996, the third glycine in the conserved Gly-X-Gly-X-X-Gly motif in the putative binding site fo adenosine triphosphate. Expression of the mutant receptor by transfection into Chinese hamster ovary cells confirmed that the mutation impairs tyrosine kinase activity.
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| 2558868 |
Isolation and sequence of a cDNA clone for human calcineurin B, the Ca2+- binding subunit of the Ca2+/calmodulin-stimulated protein phosphatase. |
10.1089/dna.1.1989.8.675 |
DNA |
Isolation and sequence of a cDNA clone for human calcineurin B, the Ca2+- binding subunit of the Ca2+/calmodulin-stimulated protein phosphatase.
Abstract
- We have identified and cloned human cDNA for the Ca2+-binding subunit of calcineurin, the brain isozyme of the Ca2+/calmodulin-stimulated protein phosphatase. The 2.5-kb cDNA has an open reading frame of 510 bp, a leader sequence of at least 500 bp, and a 1,277-bp 3'-noncoding sequence. The deduced sequence of the human protein differs from bovine brain calcineurin B by an additional valine at the carboxyl terminus and substitution of Met-11 and Ser-153 by cysteine. A partial clone of the mouse protein corresponding to amino acids 75-150 was also isolated. This portion of the human and mouse protein sequence is identical, with the DNA sequences showing 94% identity. The respective mRNAs in human and mouse are also of similar size. As was observed with protein levels, mRNA abundance in brain is 20-60 times that found in other tissues with the exception of HeLa cells which, like brain, contain abundant calcineurin B mRNA.
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| 2563334 |
Localization and characterization of somatostatin binding sites in the mouse retina |
10.1016/0006-8993(89)91538-2. |
Brain Res |
Localization and characterization of somatostatin binding sites in the mouse retina
Abstract
- We studied the binding of 125ITyr11-somatostatin-14 and 125ILeu8,D-Trp22,Tyr25-somatostatin-28 to frozen, unfixed sections of C57BL/6J mouse eyes with autoradiography. Specific binding of both ligands occurred in 3 maxima, a broad band extending from the retinal ganglion cell to the inner nuclear layers, a narrow and inconstant band over the outer plexiform layer, and a band over the retinal pigment epithelium and choroid. We quantified the label over the inner plexiform layer and found evidence for a single, saturable binding site after Scatchard analysis of saturation binding data. With 125ITyr11-somatostatin-14 the dissociation constant (Kd) was 1.48 nM and the total number of binding sites (Bmax) was 68 fmol/mg protein; in competition experiments the inhibitory binding constant (Ki) was 900 pM for somatostatin-14 and 350 pM for somatostatin-28. With 125ILeu8,D-Trp22,Tyr25-somatostatin-28, Kd was 625 pM and Bmax was 69 fmol/mg protein; in competition experiments Ki was 4.58 nM for somatostatin-14 and 710 pM for somatostatin-28. These results demonstrate the existence of somatostatin receptors in the inner plexiform layer of the retina that appear to have greater specificity for somatostatin-28 than for somatostatin-14.
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| 2564678 |
Somatostatin analogues inhibit growth of pancreatic cancer by stimulating tyrosine phosphatase |
10.1073/pnas.86.6.2003. |
Proc Natl Acad Sci U S A |
Somatostatin analogues inhibit growth of pancreatic cancer by stimulating tyrosine phosphatase
Abstract
- Several analogues of somatostatin were examined in the Mia PaCa-2 human pancreatic cancer cell line for their ability to promote tyrosine phosphatase activity affecting the receptors for the epidermal growth factor. The inhibition of growth of the Mia PaCa-2 cells in culture was also evaluated to determine the mechanism of action of somatostatin analogues and their relative effectiveness in inhibiting cancer growth. Of the analogues tested D-Phe-Cys-Tyr-D-Trp-Lys-Val-Cys-Trp-NH2 (RC-160) caused the greatest stimulation of tyrosine phosphatase activity. Analogue D-Phe-Cys-Tyr-D-Trp-Lys-Val-Cys-Thr-NH2 (RC-121) had less effect but was more potent than somatostatin-14. Analogue D-Phe-Cys-Phe-D-Trp-Lys-Thr-Cys-Thr(ol) (SMS 201-995) produced no significant dephosphorylation. The analogues displayed the same order of activity in assays on growth inhibition of Mia PaCa-2 cells in cultures. Analogue (SMS-201-995) caused virtually no tyrosine phosphatase stimulation or growth inhibition in this cancer cell line, although it possesses a much higher antisecretory activity than somatostatin-14 in normal tissues. These observations indicate that somatostatin and some of its analogues can act as growth inhibitors in cancer cells through the activation of tyrosine phosphatase. These data reinforce the view that somatostatin analogue RC-160 and related compounds could be used for treatment of pancreatic cancer.
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