Search PubMed⌕ Search

Biomedical subjects

T Costa

Publications and source records attributed to T Costa.

At least 127 records · Page 7Linked to original sources
PubMed1985

Desensitization of opioid-stimulated GTPase in neuroblastoma x glioma hybrid cells.

NG108-15 cells were pretreated with the opioid peptide [D-Ala2, D-Leu5]enkephalin and the opioid-dependent low Km GTPase was assayed in membranes. Pretreatment resulted in a small decrease in basal GTPase activity and led to a concentration-dependent reduction in opioid-mediated stimulation of the enzyme. These effects were observed whether the agonist was present or absent throughout all the experimental procedures, but, in the second condition, the desensitization was smaller. The addition of naloxone had no effect on basal GTPase activity, in either control or pretreated cell membranes. Both Na+ and Mg++ were required for the opioid-induced stimulation of the GTPase. Mg++ enhanced basal enzymatic activity in controls, whereas in membranes from pretreated cells, it produced an inhibition. Thus, desensitization of the opioid-dependent low Km GTPase occurs upon chronic opioid treatment and a Mg++ regulatory site might be altered in the course of this process.

Animals↗
PubMed1985

Increased affinity and selectivity of enkephalin tripeptide (Tyr-D-Ala-Gly) dimers.

The binding of alkylendiamide dimers of the three N-terminal residues of [D-Ala2,D-Leu5]enkephalin (DADL) to rat brain and Ng108-15 neuroblastoma-glioma cell membranes was compared with that of DADL, Tyr-D-Ala-Gly-NMe-Phe-Gly-ol (DAGO) and morphiceptin. Tritiated DADL and DAGO were used as labeled ligands for delta- and mu-receptors, respectively. Dimerization of the tripeptides resulted in dramatic increases in both mu and delta binding. The binding to mu-receptors showed two peaks at an alkyl chain length of n = 2 and approximately n = 16. In contrast, delta binding (NG108-15 cells) increased steadily with increasing chain length. The dimers with n less than 18 were mu-preferential, and the one with n = 2 showed the most dramatic increase in mu selectivity with a 400 fold higher affinity to mu- than to delta-receptors. For long-chain alkyl spacers the compounds became delta selective.

Animals↗
PubMed1985

Receptor binding and biological activity of bivalent enkephalins.

Two series of dimeric enkephalin analogues were assayed for opioid activity in two isolated smooth muscle preparations: the guinea pig ileum (GPI) and the mouse vas deferens (MVD). Dimers have the general structure: X-(CH2)n-X, where X is H-Tyr-D-Ala-Gly-Phe-Leu-NH-(n = 0, 2, 4, 6, 8, 10, 12), for the first series of dimeric pentapeptide enkephalins (DPEn), and H-Tyr-D-Ala-Gly-Phe-NH-(n = 2, 4, 6, 8, 12), for the series of dimeric tetrapeptide enkephalins (DTEn). Comparison of biological activities with binding affinities revealed that: (1) the DPE series with n = 2-8 showed increased potency in the MVD assay relative to monomeric [D-Ala2, Leu5]enkephalinamide (DALEA); (2) there was an associated increase affinity for the delta receptor of rat brain or neuroblastoma-glioma hybrid cells. (however, the relative potencies were higher in the MVD assay then predicted on the basis of binding affinities); (3) the DTE series also showed an increase in delta receptor affinities and MVD potencies relative to DALEA, for n = 2-12; (4) for the DTE series, the increase in MVD activities was less than that expected on the basis of delta binding affinity; (5) for both the DPE and DTE series, activities in the GPI assay and mu-receptor affinities were highly correlated: as the length of the methylene bridge increased from 2 to 12, there was a progressive loss of activity in both assays, with a similar pattern for DPE and DTE. Two selected dimers and their corresponding monomers were also assayed for antinociceptive activity in vivo: results were consistent with GPI and mu-binding but not with MVD and delta-binding. Two alkylamide analogs of penta- and tetrapeptide monomers, representing the monomer with the attached spacer of the most active dimers, were also assayed in biological and binding assays. Comparison of these compounds with the corresponding dimers suggest that the changes in activities and selectivities induced by dimerization are not a spurious effect of the presence of an akylamide derivative of the carboxy terminal of enkephalin but rather may represent a specific effect due to the bivalent nature of the ligands.

Analgesia↗
PubMed1985

The effect of Mendelian disease on human health: a measurement.

We describe an attempt to measure effects of Mendelian phenotypes on human health (homeostasis) in man. We used the McKusick Catalogs as the source for descriptions of autosomal dominant, recessive, and X-linked phenotypes. Three hundred and fifty one entries (76% of the initial sample) were disadaptive causing an impairment, disability, or handicap. (Terms used are in accordance with World Health Organization (WHO) definitions.) Phenotypic effects were scored to measure impact on life-span, reproductive capability, and psychosocial characteristics. We found 1) 25% of the disadaptive Mendelian phenotypes were apparent at birth and over 90% by the end of puberty; age at onset is unimodal in distribution for autosomal recessive and X-linked diseases, and trimodal for autosomal dominant (with modes during morphogenesis, infancy, and early adult life); 2) 58% of phenotypes involved more than one anatomical or functional system; autosomal dominants were more likely to involve only a single system; 3) life-span was reduced in 57%, particularly in those with onset in pre- or intra-reproductive life, and more often in recessive and X-linked diseases (data corrected for genetic lethals); prognosis varied with system involvement; 4) reproductive capability was impaired in 69% of phenotypes; and 5) most phenotypes compatible with life beyond infancy caused psychosocial handicap and limited the access to schooling and work. These findings have implications for medical care.

Adaptation, Psychological↗
PubMed1985

The effect of Mendelian disease on human health. II: Response to treatment.

We describe an attempt to measure efficacy of treatment in the Mendelian diseases of man. We used the McKusick Catalogs to identify 351 single gene diseases. We scored the impact of each disease in seven phenotypic categories: lifespan, reproductive capability, somatic growth, intellectual development, learning ability, capacity to work, and cosmetic effect. We then scored the success of treatment in ameliorating each of these component manifestations separately and together. The response to treatment was slight in the whole sample (n = 351): lifespan was increased in 15%, reproductive capability in 11%, and social adaptation in 6%. We observed that the mutant gene product was known in only 15% of the conditions comprising our sample. Since the mutant polypeptide is known in most inborn errors of metabolism, the diseases of this type (n = 65) in our sample of Mendelian traits were studied separately. In each of the seven categories of phenotypic impact, only a few of the hereditary metabolic diseases responded in any degree to specific treatment: the treatment gave complete relief in 12%, there was a partial response in 40%, and none in the remaining 48%. These findings have implications for prognosis, genetic counseling, and medical care of patients with Mendelian disease.

Adaptation, Psychological↗
PubMed1985

The Okihiro syndrome of Duane anomaly, radial ray abnormalities, and deafness.

We report on a child with Duane anomaly, deafness, cervical spine, and radial ray abnormalities. A sister of the proposita had hemifacial microsomia, cervical abnormalities, and hypoplasia of the thenar eminence. Four relatives had hypoplasia of the thenar eminence. A fifth had preaxial polydactyly. Duane anomaly was present in two sixth-degree relatives. This appears to be an autosomal dominant trait. Singly or in combination the abnormalities seen in this family have all been described in association with Duane anomaly. Their occurrence in the same family suggests that they are not independent entities but represent pleiotropic effects of the same gene.

Abnormalities, Multiple↗
PubMed1985

Selected opioids and responding for intracranial reinforcement.

Rats fixed with chronically indwelling electrodes for intracranial stimulation (ICS) of the lateral hypothalamus pressed a lever during daily sessions for a fixed intensity of ICS. Before some sessions, they were given placebo, or ethylketocyclazocine (EKC) in racemic or isomeric forms [either (+)EKC or (-)EKC]. Naloxone (NX) was also given with the agents. The racemate facilitated pressing across a narrow range of small doses (centered about 0.02 mg/kg). At no dose did (-)EKC, a potent analgesic, facilitate pressing and typically depressed it. (+)EKC, at doses of 0.04 and 0.08 mg/kg, facilited pressing. These data provide further confirmation that opioid analgesia and ability to enhance pressing are separable. When NX was given with a large dose of the racemate, paradoxically pressing for ICS was facilitated. Apparently, NX selectively blocked the effects of (-)EKC. SKF 10047 was also administered in racemic and isomeric forms. All three forms produced some facilitation of pressing at small doses (e.g., 0.75 mg/kg) and depressed pressing at large doses (e.g., 5.0 mg/kg).

Animals↗
PubMed1985

Increased affinity of dimeric enkephalins is not dependent on receptor density.

The equilibrium binding and dissociation kinetics of the enkephalin dimer bis-(D-Ala2-D-Leu5-enkephalin)-ethylenediamide (designated DPE2) to neuroblastoma glioma NG108-15 cells were investigated and compared with the monomers D-Ala2-D-Leu5-enkephalin (DADL) and D-Ala2-Leu5-enkephalinamide (DALEA). Binding was studied after exposure of the membrane to increasing concentrations of the irreversible delta receptor selective ligand FIT in order to decrease the density of binding sites on the cell membrane. The increased affinity of DPE2 did not revert to that of the monomer DADL by this reduction of binding sites. Similarly, the dissociation of DPE2 did not approach that of the monomer DALEA in the presence of 1 microM DALEA. These data strongly suggest that crosslinking does not occur, and fail to confirm the hypothesis that dimers with short spanning chain length aid the clustering of receptors. We postulate: 1) If the dimer binds to a bivalent binding site, the monovalent binding state of our bivalent ligand may not exist to an appreciable extent, and 2) the bivalent ligand cannot bind when the binding site is irreversibly blocked by a monovalent ligand.

Animals↗
PubMed1985

Serotoninergic system in scrapie-infected hamsters.

Hamsters inoculated with scrapie virus show a dramatic hypersensitivity to serotoninergic drugs, developing a behavioral syndrome not unlike that obtained with pharmacologically induced lesions of the raphe nuclei. In an attempt to explain the state of hypersensitivity and to determine whether or not serotoninergic neurons were targets of the scrapie virus, pre- and postsynaptic serotoninergic sites were studied in the cerebral cortices of scrapie-infected and sham-inoculated hamsters. [3H]Imipramine binding and the uptake of endogenous 5-hydroxytryptamine (5-HT, serotonin) in synaptosomes prepared from scrapie-inoculated animals were not different from those of controls. This suggests integrity of the serotoninergic neurons in scrapie-infected hamsters. In contrast, affinity for the 5-HT1 receptor (which modulates inhibitory response) was diminished whereas that for the 5-HT2 receptor (which modulates excitatory response) was increased. This "imbalance" between the two receptors which is amplified in in vivo responses may account for the 5-HT hypersensitivity. The alteration in the affinity of the two postsynaptic 5-HT receptors supports the observation that scrapie virus alters cell plasma membranes.

Animals↗
PubMed1985

Multiple states of opioid receptors may modulate adenylate cyclase in intact neuroblastoma X glioma hybrid cells.

Opioid receptor binding and opioid-mediated inhibition of cAMP accumulation were studied simultaneously in intact NG108-15 cells. The dose-response curves for the biological response were suggestive of positive cooperativity and systematically occurred at lower ligand concentrations than those for the binding of [3H] [D-Ala2, D-Leu5]enkephalin (DADLE), which were instead shallow and suggestive of a site heterogeneity or of a cooperative phenomenon. Computer modeling of the binding isotherms revealed that the data are best described assuming two binding sites with different affinities for the agonist; the mean ratio between the DADLE concentrations yielding half-maximal occupancy of the high affinity site and half-maximal response was 1.5, but it was 36 when the fractional occupancy of the sum of the two sites was considered. On examining several opioids, no direct correlation was found between high affinity site and biological response; however, several agonists displayed different affinities for the two sites, while the antagonist naloxone and the partial agonist diprenorphine bound to them with identical affinities. Furthermore, naloxone exhibited a good agreement between half-maximal receptor occupancy and Ki in blocking the agonist response. Thus, the binding heterogeneity detectable in intact cells is agonist-specific, and suggests rather that the sites are states of an identical receptor population. When [3H]diprenorphine was used to label the opioid receptors, the competition curves for DADLE were consistent with the existence of an additional, very low affinity state undetectable by direct binding with labeled agonist and, again, not discriminated by naloxone. Multiple affinity states of the opioid receptor in intact cells may reflect its interaction with the effector system in the plasma membrane.

Adenylyl Cyclases↗
PubMed1984

Sodium regulation of opioid agonist binding is potentiated by pertussis toxin.

Pretreatment of intact NG108-15 cells with pertussis toxin suppresses opioid inhibition of cyclic AMP accumulation mediated by the inhibitory guanine nucleotide-binding regulatory protein, Ni, which apparently also mediates the inhibitory nucleotide effects on opioid against binding. The toxin treatment had no effect on opioid agonist binding measured in NG108-15 cell membranes without sodium present. However, the toxin potentiated the inhibitory effect of sodium on agonist binding, leading to an agonist-specific reduction of opioid receptor affinity in the presence of sodium in the binding reaction. The potency of the stable GTP analog, GTP gamma S, to reduce agonist binding in the presence of sodium was little changed in membranes prepared from pertussis toxin-treated cells compared to control membranes, whereas the potency of the stable GDP analog, GDP beta S, was magnified. The data indicate that ADP-ribosylation of Ni by pertussis toxin potentiates sodium regulation of opioid agonist binding and that the communication between Ni and opioid receptors is not lost by the covalent modification of Ni.

Animals↗
PubMed1984

A very high affinity opioid binding site in rat brain: demonstration by computer modeling.

We present substantial new evidence for at least four distinct types of opioid receptors in rat brain, using quantitative ligand binding studies and mathematical modeling. Three of these binding sites are consistent with the well established "mu", "delta" and "kappa" receptors. The fourth has two distinctive features: 1) extremely high affinity (dissociation constant less than 1 nM); 2) almost complete lack of specificity for the classical "delta" or "mu" selective ligands. These properties are consistent with the putative "mu1" receptor described by Pasternak and coworkers.

Animals↗
PubMed1984

Importance of the stereo-orientation of aromatic groups in enkephalins to opiate receptor recognition.

PO +Dehydrophenylalanine (delta Phe) having the E-configuration (delta EPhe ; phenyl and C = O cis) was incorporated into [Leu5]-enkephalin in order to restrict its conformation. Compared with the Z-isomer, in the radio-ligand receptor binding assays, [D-Ala2, delta EPhe4 , Leu5] enkephalin showed drastically decreased potency for the delta and mu opiate receptors, i.e., 260- and 150-fold loss of affinity, respectively. The results strongly indicate that the opiate receptors require the Z-configuration (phenyl and C = O, trans) of the delta Phe4 residue and may require a specific interrelationship between the aromatic rings of the Tyr1 and Phe4 residues in the molecule for binding. The conformation of [Leu5]-enkephalin specific for the delta receptors was analyzed and a comparison made with its crystal structure recently elucidated.

Animals↗
PubMed1983

Opioid antinociception and positive reinforcement are mediated by different types of opioid receptors.

Fentanyl (FEN) and diprenorphine's (DIPR) potentials for analgesia and reinforcement were assayed using rats. Analgesia was measured by the classic tail-flick test. The test germane to opioid reinforcement involved measuring pressing rates for direct electrical stimulation of the lateral hypothalamus and ventral tegmental area. FEN, as does morphine and heroin, produced strong analgesia and enhanced pressing rates for brain stimulation. DIPR produced no analgesia and antagonized FEN's analgesia. DIPR, at doses antagonizing FEN's analgesia, enhanced pressing for brain stimulation. DIPR's enhancement of pressing was antagonized by naloxone (100 micrograms/kg). When FEN and DIPR were given concurrently, pressing for brain stimulation was not reduced and was greater than after FEN alone was given. These data support a conclusion that different types of receptors are associated with opioid analgesia and reinforcement.

Analgesics↗
PubMed1983

Opiate receptor binding sites in human spinal cord.

Opiate receptor binding sites were analyzed in various regions of human spinal cord and compared to results obtained in spinal cord and brain of certain animals. mu-, delta- and kappa binding sites were individually monitored by the overall labeling of opiate binding sites with [3H]diprenorphine followed by the sequential elimination of binding to particular sites by the use of selective ligands. kappa-Receptors were the predominant type (approximately 50%), followed by mu-receptors (approximately 40%), and, in rather small amounts, delta-receptors. A similar proportion of receptor types was found in the spinal cord of guinea pigs.

Aged↗