Biomedical subjects

J Martinez

Publications and source records attributed to J Martinez.

At least 415 records · Page 23Linked to original sources

PubMed1987

1H and 13C n.m.r. studies of pseudo-peptide analogues of the C-terminal tetrapeptide of gastrin.

1H and 13C n.m.r. study of pseudo-peptide analogues of the C-terminal tetrapeptide of gastrin, obtained by replacing each peptide bond by a "reduced peptide bond", one at a time, e.g. Boc-Trp psi (CH2NH)Leu-Asp-Phe-NH2 2, Boc-Trp-Leu psi (CH2NH) Asp-Phe-NH2 3, Boc-Trp-Leu-Asp psi (CH2NH)Phe-NH2 4, were reported. The CH2NH bond was completely characterized. 1H and 13C spectroscopic data were reported. It appeared from the present work that the modifications produced by the replacement of a peptide bond by a CH2NH bond were localized around the CH2NH.

Carbon Isotopes↗

PubMed1987

Determining [H]Thymidine Incorporation into Bacterioplankton DNA: Improvement of the Method by DNase Treatment.

Determination of [H] thymidine incorporation into bacterial DNA versus other macromolecules is usually achieved by NaOH and hot trichloroacetic acid hydrolysis. This procedure was found not to be specific enough. An alternative method founded on DNase treatment is proposed. Under the new method, the fraction of thymidine incorporated into DNA ranged from 10 to 83%.

Journal Article↗

PubMed1987

Interrupted thymidylate synthase gene of bacteriophages T2 and T6 and other potential self-splicing introns in the T-even bacteriophages.

Southern hybridization analyses of procaryotic DNA from Escherichia coli, lambda bacteriophage, and T1 to T7 phages were carried out. The hybridization probes used consisted of DNA restriction fragments derived from the T4 phage intron-containing thymidylate synthase gene (td) and short synthetic oligodeoxynucleotides defining specific exon and intron regions of the gene. It was shown that intact as well as restricted DNA from the T-even phages hybridized not only to both T4 phage td intron- and exon-specific probes but also to probes defining the td 5' (exon I-intron) and 3' (intron-exon II) presplice junctions. These data strongly suggest that, analogous to the T4 phage, only the T2 and T6 phages among the procaryotes tested contain interrupted td genes. The td intervening sequence in each phage is roughly 1 kilobase pair (kb) in size and interrupts the td gene at a site analogous to that in the T4 phage. This was confirmed by data from Northern (RNA) hybridization analysis of td-specific in vitro transcripts of these phage DNAs. [alpha-32P]GTP in vitro labeling of total RNA from T4 phage-infected cells produced five species of labeled RNAs that were 1, 0.9, 0.83, 0.75, and 0.6 kb in size. Only the 1-, 0.9-, and 0.75-kb species were labeled in RNA from T2- or T6-infected cells. The commonly present 1-kb RNA is the excised td intron, which exists in both linear and circular forms in the respective T-even-phage-infected cells, while the 0.6-kb RNA unique to T4 may be the excised intron derived from the ribonucleotide reductase small subunit gene (nrdB) of the phage. The remaining labeled RNA species are likely candidates for other self-splicing introns.

DNA, Bacterial↗

PubMed1987

CO2 challenge of patients with panic disorder.

In an open trial, five of eight panic disorder patients and none of five control subjects panicked after inhalation of two breaths of 35% CO2 and 65% O2; none panicked after placebo. Using 35% CO2 to induce panic is safe, simple, and well tolerated and may provide a valuable laboratory model of panic.

Administration, Inhalation↗

PubMed1987

The conversion factor between thymidine incorporation and bacterial production in Escherichia coli.

Conversion factors between thymidine incorporation and bacterial production in Escherichia coli have been calculated from bacterial numbers and accumulated thymidine incorporation. The theoretical value calculated from the available bibliographic data is about 20-fold lower than the experimental factor and other conversion factors reported in natural waters. The differences between the observed and the expected conversion factors suggest that the use of thymidine incorporation in aquatic microbiology in order to calculate bacterial production requires estimation of the corresponding conversion factor or the thymidine incorporation into DNA.

DNA, Bacterial↗

PubMed1987

Degradation of a tetragastrin analogue by a membrane fraction from rat gastric mucosa.

Our previous work on the effect of modification of peptide bonds in gastrin-like peptides led us to speculate that cleavage of the bond between the Met and Asp residues occurs in gastric mucosal membranes, and that this cleavage may have functional significance. In agreement with this speculation, we now show that the tetragastrin analogue BOC-Trp-Leu-Asp-Phe-NH2 (1) is degraded by a membrane fraction from rat gastric mucosa, and that the main products are BOC-Trp-Leu and Asp-Phe-NH2. Pseudo-peptide analogues in which the peptide bonds are replaced by CH2NH had differing stabilities; BOC-Trp-Leu-Asp-psi (CH2NH)-Phe NH2 (4) and BOC-Trp-Leu-psi(CH2NH)-Asp-Phe-NH2 (3) were stable under the incubation conditions, whereas BOC-Trp-psi(CH2NH)-Leu-Asp-Phe-NH2 (2) was degraded. The peptide and pseudo-peptide which were degraded (1 and 2) have been shown to stimulate gastric acid secretion in rats, in vivo, whereas 3 and 4 (which were not hydrolyzed) were inactive in stimulating gastric acid secretion and were found to antagonize the action of gastrin.

Animals↗

PubMed1986

Catabolic properties of aglycofibrinogen synthesized by tunicamycin-treated human hepatoma (HepG2) cells and rabbit hepatocytes.

Human hepatoma cell (HepG2) or rabbit hepatocyte monolayers were incubated with [35S]methionine in presence or absence of tunicamycin, a potent inhibitor of asparagine-linked glycosylation. The 35S-labeled nonglycosylated and control fibrinogens purified from the media were used to evaluate the influence of the oligosaccharide on the catabolic properties of this glycoprotein. Plasmin, pronase, cathepsin D or cathepsin B each degraded the nonglycosylated and control fibrinogens similarly, as evidenced by the release of trichloroacetic acid-soluble radioactivity and by SDS-polyacrylamide gel electrophoresis and autoradiography of plasmic digests. Nonglycosylated and control fibrin clots also showed no differences in susceptibility to plasmic digestion. The two forms of fibrinogen demonstrated the same plasma half-life in rabbits. These data indicate that the oligosaccharide does not influence the proteolytic stability or the in vivo plasma survival of fibrinogen, and suggest that other biochemical determinants may influence the catabolic properties of this molecule.

Animals↗

PubMed1986

Solid-phase peptide synthesis of human(Nle-27)-oxyntomodulin. Preliminary evaluation of its biological activities.

Oxyntomodulin is a peptide isolated from porcine intestine which consists of the whole glucagon sequence extended at its C-terminal part by a basic octapeptide. The analogue (Nle-27)-oxyntomodulin of the human sequence has been synthesized by solid-phase peptide synthesis, purified by HPLC and identified. Its biological activities are the same as those of the natural hormone.

Amino Acid Sequence↗

PubMed1986

Monoclonal antibodies to bovine platelet factor 4: species interactions to platelets and megakaryocytes using indirect immunocytofluorescence.

Murine monoclonal antibodies (mAb) were raised to a purified product of bovine PF-4, a 9,500 dalton protein with heparin neutralization activity comparable to that of human PF-4. Using a non-radioactive slide immunoenzymatic assay, four major classes of mAb could be identified when comparisons were made between purified antigens of PF-4 and beta-TG-like protein from both bovine and human species. Type 1 cross-reacted with all four antigens; type 2 reacted with PF-4s; type 3 reacted with only bovine PF-4 and beta-TG-like protein; and type 4 reacted only with bovine PF-4. Differences in immunoreactivities of types 1, 2 and 3 were retained throughout the growth of succeeding clones and in ascitic fluids. Using a modified factor Xa, S-2222 chromogenic substrate-heparin inhibition assay, no mAb was found to block PF-4's ability to neutralize heparin. mAbs representative of types 1, 2 and 3 were successfully raised in stable cell lines from at least second generation clones. These were purified with protein A agarose and found to be IgG1. By indirect immunocytofluorescence a purified type 2 mAb, 2E7, was found to specifically stain granules of human platelets and megakaryocytes, as well as masses (putative platelets within late stage megakaryocytes) without staining other cellular types in either bone marrow or peripheral blood. Species comparisons displayed positive staining for human, rat, and rabbit platelets and megakaryocytes, and negative staining for mouse, guinea pig and dog platelets and megakaryocytes. It seems likely that mAb, 2E7, is directed against an epitope, common to PF-4 of bovine, human, rabbit and rat.

Animals↗

PubMed1986

Evidence for dopaminomimetic effect of intrastriatally injected cholecystokinin octapeptide in mice.

The behavioural effect of intrastriatally injected cholecystokinin sulphated octapeptide (CCK-8S), and its interactions with the antagonists Z-CCK-(27-32)NH2 and proglumide, were investigated in mice. When injected into the right striatum, CCK-8S (0.05-1 ng) induced contralateral rotations, as did the dopamine agonist apomorphine. Non-sulphated CCK-8 was inactive and sulphated desamino-CCK-7 was only weakly active in this respect. CCK-8S-induced turning was antagonized by co-injected Z-CCK-(27-32)NH2 (0.01-10 ng) or proglumide (0.1-1 micrograms), as well as by intraperitoneal injection of the neuroleptic drug haloperidol. These data suggest that CCK-8S may, in these conditions, stimulate dopamine-mediated neurotransmission, and that Z-CCK-(27-32)NH2, in addition to its peripheral effect, is also a very potent CCK antagonist at the striatal level.

Animals↗

PubMed1986

Pharmacological profile of a new peptidic gastrin antagonist.

Boc-Trp-Met-Asp-NH2 was described as the smallest peptidic fragment which presented gastric antisecretory activity. Some pharmacological aspects of a peptide analogue, Boc-Trp-Leu-Asp-NH2 (Boc-WLD-NH2), were studied on the main biological functions of gastrin. This compound was found to inhibit the binding of gastrin to isolated gastric fundic mucosal cells (IC50 50 microM). On pentagastrin-induced gastric acid secretion in the rat, a dose-dependent inhibition was observed with an ID50 of 55 mumol/kg when pentagastrin (1 microgram/kg per h) was continuously infused and with an ID50 of 7.8 mumol/kg when pentagastrin (1 microgram/kg) was bolus i.v. injected. Similar inhibition was observed on acid secretion induced by pentagastrin in the isolated rat gastric mucosa (IC50 100 microM), whereas the tripeptide had no effect when acid output was triggered by histamine. A dose-dependent inhibition with the tripeptide was shown on pentagastrin induced guinea-pig ileum contractions (IC50 31 microM). The compound had no activity on histamine-stimulated guinea-pig atria (histamine H2-receptor). These results suggest some evidence for a selective antigastrin activity.

Animals↗

PubMed1986

Oxyntomodulin and its C-terminal octapeptide inhibit liquid meal-stimulated acid secretion.

Oxyntomodulin (OXM), a 37-amino acid glucagon-containing peptide produced mainly in intestine and endocrine pancreas, is present in rat plasma and inhibits pentagastrin-stimulated gastric acid secretion in both the anesthetized and the conscious rat. In order to investigate the modifications in acid and water secretions in a physiological model, we set up a protocol which allowed us to study acid secretion in the conscious rat both under basal conditions (during an 18-hour fast) or after a physiological stimulus (a liquid meal). OXM (110 pmol X kg-1) did not modify the basal acid or water output in an 18-hour fasting state. When injected before the test meal, OXM (225 pmol X kg-1) sharply decreased the acid output stimulated by a liquid meal (milk), which represented 10 times the basal value. Results are compared to those obtained when pentagastrin was the stimulant. Synthetic C-terminal octapeptide of OXM was able to inhibit both basal and meal-stimulated secretions. We can conclude that OXM, or a closely related peptide containing the C-terminal octapeptide, may be a physiological regulator of gastric functions.

Animals↗

PubMed1986

Somatostatin enhances the inhibitory effect of oxyntomodulin and its C-terminal octapeptide on acid secretion.

Somatostatin (SOM) and oxyntomodulin (OXM) are two natural peptides present in the gut which display inhibitory effects on gastric acid secretion in rat. Possible interactions between the effects of these two molecules were tested in the anesthetized rat, using as the stimulant either pentagastrin or histamine at doses that induced 30% of the maximal responses. SOM was tested at sub-threshold doses and OXM at doses inducing an inhibition of less than 50%. SOM induced a highly significant potentiation of the action of OXM both on pentagastrin- and histamine-induced secretion. Similarly, SOM enhanced the inhibitory effects of the C-terminal octapeptide of OXM. Whatever the mechanism involved, this potentiating effect of SOM might be of importance in the in vivo biological effect of OXM.

Animals↗

PubMed1986

Phenethyl ester derivative analogues of the C-terminal tetrapeptide of gastrin as potent gastrin antagonists.

A series of phenethyl ester derivative analogues of the C-terminal tetrapeptide of gastrin, in which the phenylalanyl residue has been replaced by a phenethyl group and the peptide bond between aspartic acid and phenylalanine by an ester bond, were synthesized. None of these derivatives were able to stimulate gastric acid secretion in the anesthetized rat, whereas they inhibited gastrin-induced acid secretion with ED50 values between 0.02 and 1.5 mg/kg. Among these derivatives, Boc-beta Ala-Trp-Leu-Asp phenethyl ester (9) and Boc-beta Ala-Trp-Leu-Asp p-fluorophenethyl ester (16) were very potent in inhibiting gastrin-induced acid secretion. From these studies, the significant role of the C-terminal dipeptide of gastrin was pointed out. More particularly, the functional role of the phenylalanine through the C-terminal carboxamide and its binding role through its aromatic ring were demonstrated.

Animals↗

PubMed1986

Synthesis of analogues of the Des-Phe-NH2 C-terminal hexapeptide of cholecystokinin showing gastrin antagonist activity.

Four analogues of Z-CCK-27-32-NH2, Z-Tyr(SO3-)-Met-Gly-Trp-Met-Asp-NH2, a cholecystokinin receptor antagonist have been synthesized by solution methodology. In these analogues, Z-Tyr(SO3-)-Nle-Gly-Trp-Met-Asp-NH2 16, Z-Tyr(SO3-)-Nle-Gly-Trp-Nle-Asp-NH2 17, BOC-Tyr(SO3-)-Met-Gly-Trp-Met-Asp-NH2 24 and Boc-Tyr(SO3-)-Met-Gly-Trp-Nle-Asp-NH2 25 methionyl residues were replaced by norleucyl residues. Preliminary biological activity on gastrin-induced acid secretion, in rat, are reported. These derivatives proved to antagonize the action of gastrin, with ED 50 of between 0.5 and 3 mg/kg.

Animals↗

PubMed1986

Synthesis of pseudo-peptide analogues of the C-terminal tetrapeptide of gastrin and evaluation of their biological activity on acid secretion.

The syntheses of pseudo-tetrapeptides Boc-Trp-psi (CH2-NH)-Met-Asp-Phe-NH2 21 and Boc-Trp-Met-psi (CH2-NH)-Asp-Phe-NH2 20, representing the C-terminal tetrapeptide sequence of gastrin, in which amide bonds were replaced by CH2-NH bond, are described, as well as the syntheses of pseudo-peptide analogues Boc-Trp-psi (CH2-NH)-Nle-Asp-Phe-NH2 16, Boc-Trp-Nle-psi (CH2-NH)-Asp-Phe-NH2 11, and Boc-Trp-Nle-Asp-psi (CH2-NH)-Phe-NH2 5, in which the methionyl residue was replaced by a norleucyl residue. Pseudo-peptides 16 and 21, in which the amide bond between Trp and Met (or Nle) was substituted by a CH2-NH bond, stimulated gastric acid secretion in the rat in vivo. Pseudo-peptides 11 and 20, where the amide bond between Met (or Nle) and Asp was replaced by a CH2-NH bond, did not exhibit any activity on acid secretion in the rat in vivo but were potent inhibitors of pentagastrin-induced acid secretion. Peptides 11, 16, 20 and 21 all recognize the gastrin receptor on a mucosal cell preparation. Pseudo-peptide 5, in which the amide bond between Asp and Phe was replaced by a CH2-NH bond, was a less potent inhibitor of pentagastin-induced acid secretion and had a weaker affinity than the other pseudo-peptides.

Amino Acid Sequence↗

PubMed1986

Phenylethylamide derivatives of the C-terminal tetrapeptide of gastrin. Potent inhibitors of gastrin-stimulated acid secretion.

Peptide analogues of the C-terminal tetrapeptide of gastrin in which the phenylalanine had been replaced were synthesized and their biological activity on acid secretion evaluated. Compounds Boc-Trp-Leu-Asp phenylethylamide 6, Boc-beta-Ala-Trp-Leu-Asp phenylethylamide 9, Boc-Trp-Leu-Asp p-fluorophenylethylamide 19, Boc-Trp-psi(CH2NH)-Leu-Asp phenylethylamide 23, Boc-Trp-Leu-Asp 2,2-diphenylethylamide 15, and Boc-D Trp-Leu-Asp 2,2-diphenylethylamide 21, in which the phenylalanine had been replaced by phenylethylamine, p-fluorophenylethylamine or 2,2-diphenylethylamine were synthesized. None of these derivatives showed activity on acid secretion in the anaesthetized rat at doses as high as 5 mg/kg. However, they were potent inhibitors of gastrin-induced acid secretion, with ED50 varying from 0.1 to 0.6 mg/kg.

Animals↗

PubMed1986

Molecular cloning and analysis of three cDNA clones homologous to human cytomegalovirus RNAs present during late infection.

Three virus-specific clones were isolated from a cDNA library synthesized from human cytomegalovirus (AD169)-infected cell RNA and cloned into the expression vector lambda gt11. These clones, designated C3, D10, and H10 were each found to express a human cytomegalovirus/beta-galactosidase fusion protein that was reactive with antibody prepared against purified virions. By using the cloned cDNA, we were able to identify the transcripts that code for each gene product and study the kinetics of expression during permissive infection. Our results suggest that at least two of the RNAs undergo posttranscriptional processing and appear in infected cells at immediate-early times. The authentic C3 gene product was identified by probing Western blots with antibody prepared against fusion protein fpC3.

Cell Line↗