Biomedical subjects

A Mor

Publications and source records attributed to A Mor.

At least 19 recordsLinked to original sources

PubMed1992

Interaction of antimicrobial dermaseptin and its fluorescently labeled analogues with phospholipid membranes.

Dermaseptin, a 34 amino-acid residue antimicrobial polypeptide [Mor, A., Nguyen, V. H., Delfour, A., Migliore-Samour, D., & Nicolas, P. (1991) Biochemistry 30, 8824-8830] was synthesized and selectively labeled at its N-terminal amino acid with either 7-nitrobenz-2-oxa-1,3-diazole-4-yl (NBD), rhodamine, or fluorescein. The fluorescent emission spectra of the NBD-labeled dermaseptin displayed a blue-shift upon binding to small unilamellar vesicles (SUV), reflecting the relocation of the fluorescent probe to an environment of increased apolarity. Titrations of solutions containing NBD-labeled dermaseptin with SUV composed of zwitterionic or acidic phospholipids were used to generate binding isotherms, from which were derived surface partition constants of (0.66 +/- 0.06) x 10(4) M-1 and (2.8 +/- 0.3) x 10(4) M-1, respectively. The shape of the binding isotherms, as well as fluorescence energy transfer measurements, suggests that some aggregation of membrane-bound peptide monomers occurs in acidic but not in zwitterionic vesicles. The preferential susceptibility of the peptide to proteolysis when bound to zwitterionic but not to acidic SUV suggests that these aggregates might then penetrate a relatively short distance into the hydrophobic region of the acidic membrane. Furthermore, the results provide good correlation between the peptide's strong binding and its ability to permeate membranes composed of acidic phospholipids, as revealed by a dissipation of diffusion potential and a release of entrapped calcein from SUV.

Amino Acid Sequence↗

PubMed1992

Enter a new post-translational modification: D-amino acids in gene-encoded peptides.

The post-translational processing of peptides plays a key role in conferring biological activity on those peptides. Recently, ribosomally made peptides that contain D-amino acids at specific positions have been discovered in microorganisms as well as in vertebrates and invertebrates. This points to yet another strategy of circumventing stereochemical limitations imposed by the genetic code and conveying biological activity to otherwise inert molecules.

Amino Acid Sequence↗

PubMed1992

Unilateral hydroureteronephrosis caused by abdominoscrotal hydrocele.

Abdominoscrotal hydrocele is extremely rare in children. A case is presented of an unusually large abdominoscrotal hydrocele in a child, with secondary right hydroureteronephrosis due to contiguous pressure and right cryptorchidism. This entity, although unusual, should be considered in the differential diagnosis of a lower abdominal mass in children, as well as a cause of hydroureteronephrosis. Diagnosis is made with ultrasound, computerized tomography and occasionally excretory urography. Complete surgical excision through a groin incision is recommended, but optional inguinoabdominal or abdominal incisions have been reported. After surgical removal, healing is usually complete, including regression of the hydroureteronephrosis.

Abdomen↗

PubMed1992

A 15-year study of the role of Aeromonas spp. in gastroenteritis in hospitalised children.

During a 15-year period, 146 strains of Aeromonas spp. were isolated from 32810 faecal specimens from 13,820 hospitalised patients up to 13 years of age. These isolates constituted 4% of all the pathogenic bacterial strains cultured. For the years 1978-1988, the files of children with gastro-enteritis revealed 81 whose faeces yielded Aeromonas spp. Most of them (94%) were < 3 years of age, 78% < 1 year old. The peak incidence was at 2-6 months, involving severe morbidity including dehydration and vomiting with acidaemia and azotaemia; the mean duration of illness and length of hospitalisation at this age were longer than at other ages. Bloody diarrhoea was found in 7% of the children. Almost all the strains of Aeromonas were resistant to ampicillin. We conclude that Aeromonas spp. are of aetiological significance in gastro-enteritis in small children; culture for this pathogen should be routine in the bacteriological examination of faeces.

Aeromonas↗

PubMed1992

Brainstem auditory evoked potentials in familial dysautonomia.

The brainstem function of eight children with familial dysautonomia was investigated by brainstem auditory evoked potentials and compared with that of age-matched healthy control children. All median latencies of waves III and V in the study group were significantly higher than those of the control children. Brain transmission times of waves I-III and I-V were significantly prolonged in the study group compared with the control group. These results provide additional objective support for the assumption that the brainstem function of children with familial dysautonomia is affected by this disease.

Adolescent↗

PubMed1992

Fever associated with teething.

A relationship between teething and fever was sought by examining mothers' reports of the 20 days before the eruption of the first tooth in 46 healthy infants. Twenty infants had a fever of greater than 37.5 degrees C on day 0 compared with seven infants (or fewer) from day 19 to day 4. The danger of attributing fever to teething is emphasised.

Fever↗

PubMed1992

Functional and structural damage in Leishmania mexicana exposed to the cationic peptide dermaseptin.

The effect of dermaseptin (DS), a 34 amino acid residue cationic peptide isolated from Phyllomedusa sauvagii skin, has been studied on promastigotes of Leishmania mexicana growing in vitro. Within 5 min of incubation in the presence of DS, the flagellated parasites lost their motility. DS inhibited promastigote growth by 50% at a concentration of 3 microM and by 100% at 10 microM. Immunocytochemical, freeze fracture, label fracture and electron microscopic observations have shown that the amphipathic peptide generates perturbations of the lipid bilayer leading to altered permeability of the surface membrane and death of the parasite.

Amphibian Proteins↗

PubMed1991

Isolation, amino acid sequence, and synthesis of dermaseptin, a novel antimicrobial peptide of amphibian skin.

A 34-residue antimicrobial peptide named dermaseptin was purified to homogeneity from amphibian skin by a 3-step protocol involving molecular sieve filtration, ion-exchange chromatography, and reversed-phase high-performance liquid chromatography. The complete amino acid sequence of dermaseptin, ALWKTMLKKLGTMALHAGKAALGAAADTISQGTQ, was determined by automated Edman degradation of the peptide and of fragments generated by trypsin. Fast atom bombardment mass spectra of dermaseptin gave a protonated molecular ion m/z 3455.4 which matched the theoretical molecular weight predicted from the amino acid sequence. Dermaseptin was synthesized by the solid-phase method. The synthetic replicate was shown to be indistinguishable from natural dermaseptin with respect to chromatographic properties, amino acid sequence determination, and mass spectrometry analysis. Dermaseptin is a water-soluble, thermostable, and nonhemolytic peptide endowed with highly potent antimicrobial activity against pathogenic fungi at micromolar concentration. Circular dichroism spectra of dermaseptin in hydrophobic media indicated 80% alpha-helical conformation, and predictions of secondary structure suggested that dermaseptin can be configured as an amphiphatic alpha-helix spanning over residues 1-27, a structure that perturbs membrane functions regulating water flux.

Amino Acid Sequence↗

PubMed1991

Identification of a D-alanine-containing polypeptide precursor for the peptide opioid, dermorphin.

The naturally occurring amphibian skin peptides dermorphin (Tyr-D-Ala-Phe-Gly-Tyr-Pro-Ser-NH2) and dermenkephalin (Tyr-D-Met-Phe-His-Leu-Met-Asp-NH2) are highly potent and selective agonists at the mu- and the delta-opioid receptors, respectively. For peptides synthesized by animal cells, they have a rather peculiar structural feature of containing a D-amino acid residue in their sequence which imparts biological activity on them. The cloned cDNA encoding the prodermorphin precursor contains the usual alanine and methionine codons at positions where D-alanine and D-methionine are present in the mature products. In this study, dermorphin precursor was characterized in extracts from amphibian skin by antisera recognizing distinct epitopes within the predicted structure of pro-dermorphin. Proteolytic digestion of purified endogenous pro-dermorphin generated a peptide containing a D-alanine in position 2, identified as prepro-dermorphin-(80-89), i.e. Tyr-D-Ala-Phe-Gly-Tyr-Pro-Ser-Gly-Glu-Ala. In addition, analysis of skin extracts by enzyme immunoassays coupled to high performance liquid chromatography separations revealed the presence of, besides dermenkephalin, novel dermenkephalin-related peptides, i.e. [L-Met2]dermenkephalin, dermenkephalin-OH, and [Met(O)6]dermenkephalin. [L-Met2]dermenkephalin was present in frog skin in a concentration of about 100 times that of dermenkephalin. These observations confirm that, despite the presence of D-amino acid residues, dermorphin and dermenkephalin are genuine products of post-translational processing of a ribosomally made precursor. They suggest that D-Ala and D-Met develop from a dehydrogenation/hydrogenation stereoinversion of their corresponding L isomers incorporated into pro-dermorphin, a process that occurs with low efficiency at an early stage of biosynthesis.

Alanine↗

PubMed1990

Evidence for Pro-dermorphin processing products in rat tissues.

Dermorphin (Tyr-D.Ala-Phe-Gly-Tyr-Pro-Ser-NH2) and dermenkephalin (Tyr-D.Met-Phe-His-Leu-Met-Asp-NH2), two powerful opioid peptides issued from a common biosynthetic precursor, were recently isolated from the skin of the frog phyllomedusa sauvagii. Since many amphibian's skin secretory peptides or their homologues are found in the mammalian central nervous system and gastrointestinal tract, dermorphin and dermenkephalin may have counterparts in mammals. We have prepared antibodies directed against dermorphin, dermenkephalin and the spacer sequence lying between them in the progenitor form and developed sensitive enzyme immunoassays that detect under the picogram level to verify the occurrence of these peptides in rat tissues. Immunocytochemical studies of rat brain sections revealed a similar distribution of immunoreactivities both at the regional and the cellular levels when either one of these three anti-sera was used. Characterization of the immunoreactive peptides was achieved with molecular sieve filtration followed with Reverse Phase High Performance Liquid Chromatography of various rat tissues extracts. Identification was achieved by immunological analysis and chromatographic comparison with synthetic peptides. Immunoreactive materials corresponding to dermorphin, dermenkephalin and the spacer peptide were detected in either brain, stomach or intestine, indicating processing of the dermorphin precursor in these tissues. Immunoreactive species of higher Mr were also detected in all three tissues and may represent extended forms or homologous peptides.

Amino Acid Sequence↗

PubMed1990

Characterisation and visualisation of [3H]dermorphin binding to mu opioid receptors in the rat brain. Combined high selectivity and affinity in a natural peptide agonist for the morphine (mu) receptor.

Dermorphin, Tyr-DAla-Phe-Gly-Tyr-Pro-Ser-NH2, a potent opioid peptide isolated from amphibian skin, is endowed with outstanding structural and biological features. It has no common structure with mammalian opioid peptides and is a unique example of a peptide, synthesized by an animal cell, which contains a D-amino acid in its native sequence. We have undertaken a complete evaluation of the receptor selectivity of dermorphin, together with the binding characteristics and receptor distribution of [3H]dermorphin in the rat brain. 1. Dermorphin was tested for its relative affinity to mu-, delta- and chi-opioid receptors by determining its potency in displacing the selective mu-receptor ligand [3H]Tyr-DAla-Gly-MePhe-Gly-ol (where Gly-ol = glycinol), the prototypic delta-receptor ligand [3H]Tyr-DPen-Gly-Phe-DPen (where DPen = beta, beta-dimethylcysteine) and the chi ligand [3H]ethylketocyclazocine from rat brain and/or guinea pig cerebellum membrane preparations. Inhibitory constant (Ki) values of dermorphin were 0.7 nM, 62 nM and greater than 5000 nM respectively for mu, delta and chi sites, indicating a selectivity ratio Ki(delta)/Ki(mu) = 88. Under similar conditions, Tyr-DAla-Gly-MePhe-Gly-ol, which is regarded as one of the most selective high-affinity mu-agonist available, exhibited a selectivity ratio of 84. 2. Specific binding properties of tritium-labeled dermorphin (52 Ci/mmol) were characterized in the rat brain. Equilibrium measurements performed over a large range of concentrations revealed a single homogeneous population of high-affinity binding sites (Kd = 0.46 nM; Bmax = 92 fmol/mg membrane protein). 3. Profound differences were observed in the potencies displayed by various selective opiates and opioids ligands in inhibiting the specific binding of [3H]dermorphin. The rank order of potency was in good agreement with that obtained with other mu-selective radiolabeled ligands. 4. Receptor autoradiography in vitro was used to visualize the distribution of [3H]dermorphin binding sites in rat brain. The labeling pattern paralleled that observed using other mu probes. Binding parameters and selectivity profile of [3H]dermorphin on slide-mounted sections were similar to those obtained with membrane homogenates. 5. Finally, intracerebroventricular administration of synthetic dermorphin into mice showed that this peptide is the most potent analgesic known to date, being up to 5 and 670 times more active than beta-endorphin and morphine, respectively. Higher doses induced catalepsy. The overall data collected demonstrate that dermorphin is the first among the naturally occurring peptides to be highly potent and nearly specific super-agonist towards the morphine (mu) receptor.(ABSTRACT TRUNCATED AT 400 WORDS)

Amino Acid Sequence↗

PubMed1990

Reaction of thrombin and proteinases of the fibrinolytic system with a mechanism-based inhibitor, 3,4-dihydro-3-benzyl-6-chloromethylcoumarin.

Thrombin, plasmin and tissue plasminogen activator (one- and two-chain forms) were examined with respect to their reaction with the suicide substrate, 3,4-dihydro-3-benzyl-6-chloromethylcoumarin, at 4 degrees C. The enzymes were irreversibly inhibited and the apparent second-order rate constants ki/Ki were 31,000, 316, 187 and 250 M-1.s-1, respectively. The extent of fibrin clot lysis induced by urokinase and two-chain tissue plasminogen activator was considerably decreased after treatment of these enzymes with the dihydrocoumarin derivative (molar excess of inhibitor over enzyme ranging from 6 to 21 for urokinase and 50 to 1500 for tissue plasminogen activator). This inhibitor has been tested as anticoagulant in human plasma and was effective at prolonging the prothrombin time from 12 to 40 s.

Blood Coagulation↗

PubMed1990

Role of AMP on the activation of glycogen synthase and phosphorylase by adenosine, fructose, and glutamine in rat hepatocytes.

The mechanism for glycogen synthesis stimulation produced by adenosine, fructose, and glutamine has been investigated. We have analyzed the relationship between adenine nucleotides and glycogen metabolism rate-limiting enzymes upon hepatocyte incubation with these three compounds. In isolated hepatocytes, inhibition of AMP deaminase with erythro-9-(2-hydroxyl-3nonyl)adenine further increases the accumulation of AMP and the activation of glycogen synthase and phosphorylase by fructose. This ketose does not increase cyclic AMP or the activity of cyclic AMP-dependent protein kinase. Adenosine raises AMP and ATP concentration. This nucleotide also activates glycogen synthase and phosphorylase by covalent modification. The correlation coefficient between AMP and glycogen synthase activity is 0.974. Nitrobenzylthioinosine, a transport inhibitor of adenosine, blocks (by 50%) the effect of the nucleoside on AMP formation and glycogen synthase but not on phosphorylase. 2-Chloroadenosine and N6-phenylisopropyladenosine, nonmetabolizable analogues of adenosine, activate phosphorylase (6-fold) without increasing the concentration of adenine nucleotides or the activity of glycogen synthase. Cyclic AMP is not increased by adenosine in hepatocytes from starved rats but is in cells from fed animals. [Ethylenebis (oxyethylenenitrilo)]tetraacetic acid (EGTA) blocks by 60% the activation of phosphorylase by adenosine but not that of glycogen synthase. Glutamine also increases AMP concentration and glycogen synthase and phosphorylase activities, and these effects are blocked by 6-mercaptopurine, a purine synthesis inhibitor. Neither adenosine nor glutamine increases glucose 6-phosphate. It is proposed that the observed efficient glycogen synthesis from fructose, adenosine, and glutamine is due to the generation of AMP that activates glycogen synthase probably through increases in synthase phosphatase activity. It is also concluded that the activation of phosphorylase by the above-mentioned compounds can be triggered by metabolic changes.

Adenine↗

PubMed1990

Acute gastroenteritis due to double infection with enteropathogenic Escherichia coli or Salmonella and another bacterial pathogen.

Two enteric bacterial pathogens were concomitantly isolated from the feces of 18 infants less than 6 months of age admitted to the Assaf Harofeh Medical Center over a 7-year period. In all but two patients stool cultures grew enteropathogenic Escherichia coli, six of serogroup 0119. The other organisms cultured were Shigella, Salmonella, Campylobacter jejuni and Aeromonas hydrophila. The usual clinical presentation was diarrhea, dehydration and vomiting of acute onset, and low grade fever. Patients with gastroenteritis due to a single agent compared with multiple pathogens had a milder course of disease, a milder degree of dehydration and acidosis, a lesser need for i.v. fluid treatment and shorter hospitalization.

Academic Medical Centers↗

PubMed1989

Molecular determinants of receptor affinity and selectivity of the natural delta-opioid agonist, dermenkephalin.

Processing of the polyprotein precursor pro-dermorphin generates two distantly related D-amino acid-containing peptides, dermorphin and dermenkephalin, which are among the most selective high affinity agonists described, respectively, for the mu- and delta-opioid receptors. Dermenkephalin, Tyr-D-Met-Phe-His-Leu-Met-Asp-NH2, is a linear, potentially flexible peptide devoid of structural homology with either enkephalins, endorphins, or dynorphins and, as such, represents a useful tool for identifying determinants of high affinity and selective binding of opioids to the delta-receptor. A series of selected dermenkephalin analogs and homologs was investigated for affinity at the mu- and delta-sites in the brain. Whereas dermenkephalin has high affinity and specificity for the delta-opioid receptors, its tetrapeptide amino end, dermenkephalin-[1-4]-NH2 binds almost exclusively at the mu-receptors. Dermorphin, Tyr-D-Ala-Phe-Gly-Tyr-Pro-Ser-NH2, is only marginally more selective for the u-sites than is dermenkephalin-[1-4]-NH2. Using dermorphin-dermenkephalin peptide hybrids and C-terminal deletion analogs of dermenkephalin, we showed the critical role that the C-terminal residues Met6 and Asp7 play in specifying correct addressing of dermenkephalin toward delta-receptors. The potent mu-deteminant located within the amino end of dermenkephalin is over-whelmed by the powerful delta-directing ability of the carboxy end. The negatively charged side chain of Asp7 makes a significant contribution to the delta-addressing ability of the C-terminal region, a finding consistent with Schwyzer's membrane selection model (Schwyzer, R. (1986) Biochemistry 25, 6335-6342). The Leu residue in position 5 and D-configuration about the alpha-carbon of Met2 were found to be of crucial importance for high affinity binding to delta-receptors. Whereas the Met residue in position 6 in dermenkephalin could safely be oxidized or replaced with D-Met, oxidation of Met2 led to deleterious effects, this analog being 1/100 as potent as dermenkephalin at delta-sites. Overall, the data collected demonstrate that highest levels of selectivity and affinity for the delta-opioid receptors can be achieved with small-sized, potentially flexible, linear peptides and further support the model according to which, in addition to optimum accommodation at the receptor, selection for delta-receptors is reduced by the effective positive charge of the molecule. Dermenkephalin may provide a starting point for the design of agonists and antagonists with nearly total specificity for the delta-sites. Such pharmacological agents could be used to explore the ill-defined physiological role and behavioral actions conveyed by delta-opioid receptors.

Amino Acid Sequence↗

PubMed1989

Isolation of dermenkephalin from amphibian skin, a high-affinity delta-selective opioid heptapeptide containing a D-amino acid residue.

The predicted amino acid sequence of the biosynthetic precursor of dermorphin, a highly potent and nearly specific mu-opioid peptide from amphibian skin, contains four repeats of the dermorphin progenitor sequence and one single copy of a different heptapeptide sequence. We have developed a specific enzyme immunoassay and used synthetic peptides to detect and purify the new predicted heptapeptide (2.4 micrograms/g dry skin) from the skin of the Phyllomedusa sauvagei frog from which dermorphin was originally isolated. The identity of the novel pro-dermorphin related peptide, Tyr-D-Met-Phe-His-Leu-Met-Asp-NH2, was established by co-chromatography with synthetic peptides on reverse-phase HPLC, immunological analysis, gas-phase sequencing, mass spectrometry and by pharmacological assays. Opioid-binding assays in vitro demonstrated that both the natural and synthetic heptapeptides displayed exceptionally high selectivity and affinity towards the delta-opioid receptors. Because of its origin and its delta-opioid (enkephalin) activity and specificity, this novel D-amino acid containing peptide is named dermenkephalin.

Acetylcholinesterase↗

PubMed1989

Differential contribution of C-terminal regions of dermorphin and dermenkephalin to opioid-sites selection and binding potency.

Dermorphin and dermenkephalin are D-aminoacid containing peptides generated from processing of the plurifonctional biosynthetic precursor pro-dermorphin. Dermorphin, Tyr-D-Ala-Phe-Gly-Tyr-Pro-Ser-NH2 (DRM) and dermenkephalin, Tyr-D-Met-Phe-His-Leu-Met-Asp-NH2 (DREK), are among the most selective and potent agonists described respectively for the mu- and delta-opioid receptors. In order to identify determinants of selectivity and high-affinity receptor binding of dermorphin and dermenkephalin, a series of analogs was investigated for their affinity at the mu- and delta-receptors in the brain. The tetrapeptide amino end of both DRM and DREK were found to display high affinity and selectivity towards mu-receptors. Substitution of the C-terminal tripeptide of DREK with that of DRM reversed the receptor selectivity of DREK from delta to mu. Replacement of the C-terminal tripeptide of DRM with the C-terminal counterpart of DREK shifted the selectivity of DRM from mu to delta. These data emphasize the critical contribution of the carboxy end of DREK to delta-selectivity. They further suggest that the potent mu-address lying in the N terminus of DREK is overwhelmed by the powerful delta-directing ability of the carboxy end. Unlike DREK, the C-terminus of DRM is not involved in opioid receptor sites selection but is important insofar as it serves to stabilize interactions of DRM with the mu-receptor binding site.

Animals↗

PubMed1989

Dermorphin and related peptides in rat tissues.

Dermorphin (Tyr-D-Ala-Phe-Gly-Tyr-Pro-Ser-NH2), a naturally occurring peptide isolated from arboreal frog skin, is endowed with outstanding structural and biological features. It has no structural community with the sequence of mammalian opioid peptides and is a unique example of a D-aminoacid containing peptide which is synthesized via ribosomal route. Dermorphin is the most potent of the opioid peptides or opiates in producing long lasting analgesia and catalepsy. Since most amphibians' secretory peptides have counterparts in the mammalian central nervous system and gastrointestinal tract, we have developed a sensitive enzyme immunoassay that can detect 1 pg dermorphin to verify the possibility of dermorphin or dermorphin-related peptides occurrence in mammalian tissues. Dermorphin-related peptides were purified by fast protein liquid chromatography followed by reverse phase high pressure liquid chromatography. Identification was achieved by chromatographic comparison with synthetic standards and immunological analysis. A peptide behaving like authentic dermorphin was detected (2 ng/g) in rat small intestine. Immunoreactive species of higher Mr were also detected in the brain, adrenal glands and gastrointestinal tract, they may represent extended forms of dermorphin or homologous peptides.

Animals↗