RESUMEN
AIMS: To compare the combination of suture and tissue adhesive with suture alone for closure of enterotomy incisions in an ex vivo caprine jejunal model, by measuring the intraluminal pressure at which leakage occurred and the proportion of closures that leaked at intraluminal pressures <40â mmHg. METHODS: Jejunal tissue was harvested from a goat following euthanasia, and enterotomy incisions (4â mm in length) were made in each of 24 isolated jejunal segments. The enterotomies were randomly assigned to be closed using a single interrupted suture alone (n=12) or in combination with biopolymer tissue adhesive (n=12). The jejunal segments were infused with saline containing fluorescent dye and leakage pressure was defined as the peak pressure attained when visible leakage of saline solution occurred. The number of enterotomies that did or did not exhibit leakage at <40â mmHg intraluminal pressure was also recorded. RESULTS: Enterotomies closed using a combination of suture and tissue adhesive leaked at higher intraluminal pressure (58.2 (SD 4.7) mmHg) than those closed with suture alone (29.8 (SD 4.2) mmHg; p<0.001). The proportion of enterotomy closures in which the intraluminal pressure failed to reach 40â mmHg before leakage occurred was higher in enterotomies closed using suture alone (9/12, 75%) compared to those closed using both suture and tissue adhesive (3/12, 25%; p=0.002). CONCLUSIONS AND CLINICAL RELEVANCE: Use of tissue adhesive in addition to sutures increased the intraluminal pressure achieved before leakage occurred, compared to sutures alone, following enterotomy closure in a caprine cadaver model. In vivo studies are indicated to further assess the value of supplementing intestinal suture lines with tissue adhesive.
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Cabras , Técnicas de Sutura/veterinaria , Suturas/veterinaria , Adhesivos Tisulares/administración & dosificación , Animales , Cadáver , Enterostomía , Modelos Animales , Presión , Técnicas de Sutura/instrumentaciónRESUMEN
Trefoil factor family (TFF) peptides maintain and repair the gastrointestinal mucosa and are aberrantly expressed in human and rodent inflammatory bowel disease and carcinomas, diseases common in dogs and cats. Study objectives were to sequence and translate canine and feline tff cDNAs and define any unique residues that might influence their structure and/or function. After isolation and reverse transcription of canine and feline gastrointestinal mucosal RNA, TFF cDNAs were amplified, sequenced, and cloned. Dogs and cats had unique amino acids in several places that were highly or completely conserved in other mammals, including a hydrophobic area in the TFF1 functional site, loop 2 of each TFF2 trefoil domain, a TFF3 dimerization site, and the TFF2 C-terminus. By identifying conserved and unique characteristics of canine and feline TFFs, this study establishes a foundation for investigation of dog and cat models of TFF-related diseases in both human and veterinary medicine.
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Gatos/genética , Perros/genética , Secuencia de Aminoácidos , Animales , Secuencia de Bases , Colon , Secuencia Conservada , ADN Complementario/genética , Mucosa Gástrica , Mucosa Intestinal , Datos de Secuencia Molecular , Familia de Multigenes , Péptidos , Polimorfismo Genético , ARN , Factor Trefoil-2RESUMEN
RNA and type I collagen were analyzed from cultured skin fibroblasts of a Beagle puppy with fractures consistent with type III osteogenesis imperfecta (OI). In a nonisotopic RNAse cleavage assay (NIRCA), the proband's RNA had a unique cleavage pattern in the region of COL1A2 encoding the C-propeptide. DNA sequence analyses identified a mutation in which nucleotides 3991-3994 ("CTAG") were replaced with "TGTCATTGG." The first seven bases of the inserted sequence were identical to nucleotides 4002-4008 of the normal canine COL1A2 sequence. The resulting frameshift changed 30 amino acids and introduced a premature stop codon. Reverse-transcription polymerase chain reaction (RT-PCR) with primers flanking the mutation site amplified two complementary DNA (cDNA) fragments for the proband and a single product for the control. Restriction enzyme digestions also were consistent with a heterozygous mutation in the proband. Type I procollagen labeled with [3H]proline was analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). Increased density of pC-alpha2(I) suggested comigration with the similarly sized pro-alpha2(I) derived from the mutant allele. Furthermore, a-chains were overhydroxylated and the ratio of alpha1(I):alpha2(I) was 3.2:1, consistent with the presence of alpha1(I) homotrimers. Analyses of COL1A2 and type I collagen were both consistent with the described heterozygous mutation affecting the pro-alpha2(I) C-propeptide and confirmed a diagnosis of OI.
Asunto(s)
Colágeno/genética , Mutación del Sistema de Lectura , Osteogénesis Imperfecta/genética , Secuencia de Aminoácidos , Animales , Células Cultivadas , Colágeno Tipo I , ADN Complementario/genética , Perros , Femenino , Fibroblastos , Hidroxilación , Técnicas de Diagnóstico Molecular , Datos de Secuencia Molecular , Procolágeno/metabolismo , Subunidades de ProteínaRESUMEN
The sequence of canine COL1A1 cDNA was determined from four overlapping COL1A1 RT-PCR products generated from canine fibroblast RNA. In the translated region, nucleotide identity between canine and human COL1A1 cDNA was 93.2%, although the canine sequence lacked nucleotides 204 to 215 in the region coding for the N-propeptide. Amino acid identity was 97.7%. Total RNA and type I collagen were collected from cultured skin fibroblasts of a 12-week-old male golden retriever with pathologic fractures suggestive of osteogenesis imperfecta (OI) and dentinogenesis imperfecta. Sequential, overlapping approximately 1,000-bp fragments of COL1A1 and COL1A2 cDNA were each amplified by RT-PCR using primers containing 5' T7 polymerase sites. These PCR products were transcribed with T7 RNA polymerase, hybridized into RNA duplexes, and cleaved at mismatch sites with RNase. The proband had an unique cleavage pattern for the fragment of COL1A1 mRNA spanning nucleotides 709 to 1,531. Sequence analysis identified a G to C point mutation for nucleotide 1,276, predicting a codon change from glycine (GGA) to alanine (GCA) for amino acid 208. This change disrupts the normal Gly-X-Y pattern of the collagen triple helix. Restriction enzyme digestion of the RT-PCR product was consistent with a heterozygous COL1A1 mutation. Type I collagen was labeled with 3H-proline, salt precipitated, and analyzed by SDS-PAGE. Pepsin digested alpha chains were over-hydroxylated, and procollagen processing was delayed. Thus, canine and human OI appear homologous in terms of clinical presentation, etiology, and pathogenesis.
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Colágeno Tipo I , Colágeno/genética , Osteogénesis Imperfecta/genética , Alanina/genética , Alanina/metabolismo , Secuencia de Aminoácidos , Animales , Secuencia de Bases , Cadena alfa 1 del Colágeno Tipo I , ADN Complementario/análisis , Modelos Animales de Enfermedad , Perros , Genotipo , Glicina/genética , Glicina/metabolismo , Humanos , Datos de Secuencia Molecular , Fenotipo , Mutación Puntual , Homología de Secuencia de Ácido NucleicoAsunto(s)
Arsénico/toxicidad , Cadmio/toxicidad , Mercurio/toxicidad , Arsénico/metabolismo , Intoxicación por Arsénico , Cadmio/metabolismo , Intoxicación por Cadmio/tratamiento farmacológico , Intoxicación por Cadmio/etiología , Quelantes/uso terapéutico , Técnicas de Laboratorio Clínico , Humanos , Mercurio/metabolismo , Intoxicación por Mercurio/tratamiento farmacológico , Intoxicación por Mercurio/etiologíaAsunto(s)
Cefadroxilo/farmacocinética , Cefalexina/farmacocinética , Cefalosporinas/farmacocinética , Perros/fisiología , Absorción , Animales , Cefadroxilo/administración & dosificación , Cefadroxilo/uso terapéutico , Cefalexina/administración & dosificación , Cefalexina/uso terapéutico , Cefalosporinas/administración & dosificación , Cefalosporinas/uso terapéutico , Enfermedades de los Perros/tratamiento farmacológico , Enfermedades de los Perros/microbiología , Ingestión de Alimentos , Infecciones por Escherichia coli/tratamiento farmacológico , Infecciones por Escherichia coli/veterinaria , Masculino , Infecciones Estafilocócicas/tratamiento farmacológico , Infecciones Estafilocócicas/veterinariaRESUMEN
We will review the role of magnetic resonance (MR) in assessment of patients with acute neurological abnormalities. The major stumbling block to the use of MR in these patients is the belief that MR is insensitive to hyperacute (<12 h) intracranial hemorrhage and acute subarachnoid hemorrhage (SAH). Hyperacute hemorrhage has characteristic features on MR. Hematomas are iso-to hyperintense on T1-weighted and hyperintense on T2-weighted images. Gradient-echo scans that reveal characteristic peripheral hypointensity are critical to the detection and delineation of hyperacute hematomas. Use of fast fluid-attenuated inversion recovery (FLAIR) sequences has made it possible to detect SAH on MR with a sensitivity that is equal to or greater than computed tomography (CT). SAH produces dramatic hyperintensity in the normally hypointense cerebrospinal fluid on FLAIR. MR has proven useful in the detection of hypertensive encephalopathy and venous thrombosis. These entities can be difficult to diagnose on CT, and in both, early treatment can dramatically improve prognosis. The same is true for acute intracranial infections such as pyogenic abscess, subdural empyema, and herpes simplex encephalitis. MR improves diagnostic accuracy, resulting in more rapid institution of appropriate treatment and improved outcome.
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Encefalopatías/diagnóstico , Encéfalo/patología , Imagen por Resonancia Magnética , Enfermedad Aguda , Adolescente , Adulto , Anciano , Lesiones Encefálicas/diagnóstico , Neoplasias Encefálicas/diagnóstico , Infecciones del Sistema Nervioso Central/diagnóstico , Hemorragia Cerebral/diagnóstico , Infarto Cerebral/diagnóstico , Niño , Urgencias Médicas , Femenino , Humanos , Hipertensión Intracraneal/complicaciones , Masculino , Persona de Mediana Edad , Sensibilidad y Especificidad , Trombosis de los Senos Intracraneales/diagnóstico , Hemorragia Subaracnoidea/diagnósticoRESUMEN
The alpha2 chain of canine type I collagen was characterized with both sequence analysis of COL1A2 cDNA and chemical analysis of alpha2(I) chains. The complete sequence of canine COL1A2 cDNA was determined from reverse-transcribed and polymerase chain reaction-amplified total RNA from cultured skin fibroblasts. Pepsin-digested and cyanogen bromide-digested type I collagen peptides were analyzed with chromatography, gel electrophoresis, and mass spectrometry. Identity between the sequences of canine and human COL1A2 cDNA was 90.9%, predicting conservation of the 3 cysteine residues required for C-propeptide registration and of cleavage sites for signal peptidase, procollagen N-proteinase, vertebrate collagenase, and procollagen C-proteinase. Conservation of all 50 lysine residues was also predicted, including preservation of the 1:2 asymmetry in the X:Y distribution of the 31 lysine residues in the alpha2(I) triple helix. The human and canine sequences differed in the location of Y-position proline residues and the presence of two unique canine cyanogen bromide peptides, alpha2 CB3b and alpha2 CB3c,5. Knowledge of the conserved and unique features of canine COL1A2 will be valuable for analysis of the expression, synthesis, and structure of type I collagen as well as studies of canine osteogenesis imperfecta.
Asunto(s)
Secuencia de Bases , Colágeno/química , Colágeno/genética , Bromuro de Cianógeno/química , ADN Complementario/química , Mapeo Peptídico , Mutación Puntual/genética , Secuencia de Aminoácidos , Animales , Células Cultivadas , Secuencia Conservada , ADN Complementario/genética , Perros , Fibroblastos , Humanos , Lisina/química , Espectrometría de Masas , Datos de Secuencia Molecular , Fragmentos de Péptidos/química , Prolina/químicaRESUMEN
When a young dog is evaluated for multiple fractures with minimal to no accompanying trauma, the primary differential diagnoses are metabolic disease, physical abuse, and osteogenesis imperfecta (OI). Of these, secondary hyperparathyroidism is most common, but if serum concentrations of ionized calcium, phosphorus, vitamin D, and parathormone are within reference ranges, OI must be considered. Osteogenesis imperfecta is a heritable disease characterized by brittle bones. Results of studies using cultured skin fibroblasts indicate that most cases of OI in human beings are caused by a mutation in a type-I collagen gene. Osteogenesis imperfecta was recently identified in 3 dogs. Radiographic findings included multiple fractures in various stages of healing and generalized osteopenia. Cultured fibroblasts from skin biopsy specimens were used to diagnose OI. Structural abnormalities were found in type-I collagen from each dog. This cell culture assay can be used to evaluate dogs with brittle bones.
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Enfermedades de los Perros/diagnóstico , Osteogénesis Imperfecta/veterinaria , Animales , Enfermedades Óseas Metabólicas/diagnóstico , Enfermedades Óseas Metabólicas/diagnóstico por imagen , Enfermedades Óseas Metabólicas/veterinaria , Células Cultivadas , Colágeno/análisis , Colágeno/genética , Colágeno/metabolismo , Diagnóstico Diferencial , Enfermedades de los Perros/patología , Enfermedades de los Perros/fisiopatología , Perros , Electroforesis en Gel de Poliacrilamida/métodos , Electroforesis en Gel de Poliacrilamida/veterinaria , Femenino , Fémur/diagnóstico por imagen , Fémur/patología , Fibroblastos/química , Fibroblastos/metabolismo , Fibroblastos/patología , Masculino , Mutación , Osteogénesis Imperfecta/diagnóstico , Osteogénesis Imperfecta/fisiopatología , Radiografía , Piel/química , Piel/metabolismo , Piel/patología , Tibia/diagnóstico por imagen , Tibia/patologíaRESUMEN
OBJECTIVE: To determine whether the antibacterial activity of 6 mg of gentamicin/kg of body weight given SC once daily, is equivalent to the standard gentamicin dose of 2 mg/kg given SC every 8 hours. ANIMALS: Guinea pigs with infected thigh wound: 5 in an untreated control group and 12 in 6 and 2 mg/kg gentamicin treatment groups. PROCEDURE: Guinea pigs were inoculated with 10(9) Escherichia coli in the thigh muscle. Gentamicin treatment (2 mg/kg, SC, q 8 h or 6 mg/kg, SC, q 24 h) was begun 4 hours after E coli inoculation and continued for 72 hours. Four hours after the last gentamicin treatment, all guinea pigs were euthanatized and the cranial thigh muscle containing the entire inoculum was removed. Colony-forming units were counted to determine the E coli concentration in each thigh. RESULTS: Mean +/- SD log10 colony-forming units was 9.293 +/- 0.074 in the control group, 8.161 +/- 0.478 in the 2 mg/kg treatment group, and 7.796 +/- 0.182 in the 6 mg/kg treatment group. One-way ANOVA revealed a significant (P < 0.05) difference between the control group and both treatment groups, and between both treatment groups. CONCLUSION: Bacterial killing did not differ between gentamicin given at a dosage of 6 mg/kg once daily, compared with 2 mg/kg every 8 hours in guinea pigs infected with E coli. CLINICAL RELEVANCE: Gentamicin dosage regimens with high peak concentration and long dosing interval are as efficacious as divided dosage regimens. These data support the concept that once daily administration of gentamicin for treatment of E coli infection should be investigated clinically.
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Antibacterianos/uso terapéutico , Infecciones por Escherichia coli/veterinaria , Gentamicinas/uso terapéutico , Cobayas/microbiología , Enfermedades de los Roedores/tratamiento farmacológico , Animales , Antibacterianos/administración & dosificación , Antibacterianos/farmacocinética , Escherichia coli/efectos de los fármacos , Infecciones por Escherichia coli/tratamiento farmacológico , Femenino , Gentamicinas/administración & dosificación , Gentamicinas/farmacocinética , Masculino , Enfermedades de los Roedores/microbiologíaAsunto(s)
Antiinflamatorios/uso terapéutico , Neoplasias Encefálicas/diagnóstico por imagen , Dexametasona/uso terapéutico , Linfoma Relacionado con SIDA/diagnóstico por imagen , Tomografía Computarizada de Emisión de Fotón Único , Adulto , Antiinflamatorios/farmacología , Edema Encefálico/diagnóstico , Edema Encefálico/tratamiento farmacológico , Dexametasona/farmacología , Diagnóstico Diferencial , Reacciones Falso Negativas , Femenino , Humanos , Radioisótopos de Talio , Toxoplasmosis Cerebral/diagnóstico , Toxoplasmosis Cerebral/tratamiento farmacológicoRESUMEN
Microbial ACC deaminase catalyses the conversion of 1-aminocyclopropane-1-carboxylate (ACC), the precursor to the phytohormone ethylene, to ammonia and alpha-ketobutyrate. We screened microorganisms for ACC degrading ability and cloned and sequenced the ACC deaminase genes from two Pseudomonas strains which displayed high enzyme activity. One of the genes was homologous with two previously sequenced ACC deaminase genes, but the other was different.
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Liasas de Carbono-Carbono , Genes Bacterianos , Liasas/genética , Pseudomonas/enzimología , Pseudomonas/genética , Secuencia de Aminoácidos , Secuencia de Bases , Clonación Molecular , Secuencia de Consenso , ADN Bacteriano/genética , Datos de Secuencia Molecular , Homología de Secuencia de Aminoácido , Especificidad de la EspecieRESUMEN
An analog of 1,3-di-o-tolylguanidine (DTG), [125I]-labeled 1-(p-iodophenyl)-3-(1-adamantyl)guanidine (PIPAG), was synthesized as a potential ligand for cerebral sigma binding sites. Data from in vitro binding experiments and in vivo experiments on brain distribution suggested that PIPAG binds to sigma binding sites with high affinity (Kd in low nanomolar range) as determined by Scatchard analysis and relative potencies of sigma-specific drugs. Haloperidol had the highest potency to inhibit [125I]PIPAG binding. It was followed by DTG, BMY 14802, and (+)-N-allylnormetazocine. Compounds with high affinities for dopamine receptors (but low affinity for sigma binding sites), for opioid receptors, for nicotinic acetylcholine receptors, and for phencyclidine receptors were ineffective inhibitors of [125I]PIPAG binding.
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Encéfalo/metabolismo , Guanidinas/metabolismo , Yodobencenos/metabolismo , Receptores sigma/metabolismo , Animales , Autorradiografía , Sitios de Unión , Unión Competitiva , Guanidinas/síntesis química , Guanidinas/farmacocinética , Cobayas , Yodobencenos/síntesis química , Yodobencenos/farmacocinética , Masculino , Ratones , Distribución TisularRESUMEN
A large subconjunctival cyst of 4 weeks' duration was surgically excised from the left eye of a 7-month-old Simmental calf. Two white, partially mineralized, approximately 1-cm-long, fertile female nematodes subsequently identified as Thelazia gulosa were found embedded in the cyst wall. Thelazia spp are generally regarded as nonpathogenic or mildly pathogenic in cattle in North America, despite reported infection rates ranging from 12.2 to 34.2%. Additionally, parasitic subconjunctival nodules associated with Thelazia spp rarely have been reported in the past, and cyst formation has not been described. It was postulated that in this calf, immature or adult worms may have penetrated normal tissue barriers, or entered via an earlier conjunctival wound, and created an inflammatory response with subsequent cyst formation.
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Enfermedades de los Bovinos/parasitología , Conjuntiva/parasitología , Infecciones Parasitarias del Ojo/veterinaria , Infecciones por Spirurida/veterinaria , Thelazioidea/aislamiento & purificación , Animales , Bovinos , Infecciones Parasitarias del Ojo/parasitología , Femenino , Infecciones por Spirurida/parasitologíaRESUMEN
Glutamate evoked contractions of the longitudinal muscle/myenteric plexus (LMMP) preparation by an action at N-methyl-D-aspartate (NMDA) receptors. Other agonists at the NMDA recognition site, but not quisquilate or kainate, also contracted the LMMP, and glutamate-evoked contractions were competitively inhibited by selective NMDA receptor antagonists. Glutamate-evoked contractions were noncompetitively inhibited by MK-801 [(+)-5-methyl-10,11-dihydro-5H-dibenzo-[a,d]cyclohepten-5,10-imine moleate], phencyclidine (PCP) and other compounds that bind to the PCP receptor, which is a binding site on the NMDA channel complex. Their potencies for this effect were highly correlated with their affinities for the PCP receptor. Glycine significantly shifted the glutamate concentration-response curve to the left. Glycine site antagonists caused a glycine-sensitive, noncompetitive inhibition of glutamate-evoked contractions, and their potencies for this effect were highly correlated with their affinities for the glycine binding site of the NMDA channel complex. Mg++ and Zn++ also noncompetitively inhibited glutamate-evoked contractions. The modulatory effects of glycine, Mg++, Zn++ and PCP receptor ligands were specific to glutamate-evoked contractions. MK-801 was highly selective for inhibition of glutamate-evoked contractions; MK-801 also inhibited nicotinic responses at a 500-fold lower potency. Two novel compounds are described that bind to the PCP receptor with high affinity and selectively inhibit glutamate-evoked contractions in the LMMP.
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Maleato de Dizocilpina/farmacología , Glutamatos/farmacología , Músculo Liso/efectos de los fármacos , Receptores de N-Metil-D-Aspartato/efectos de los fármacos , Receptores de Neurotransmisores/efectos de los fármacos , Animales , Encéfalo/metabolismo , Antagonistas de Aminoácidos Excitadores , Femenino , Ácido Glutámico , Glicina/metabolismo , Cobayas , Íleon , Masculino , Contracción Muscular/efectos de los fármacos , Receptores de Glicina , Receptores de FenciclidinaRESUMEN
A new nematode species, Huffmanela schouteni sp. n., has been established on the basis of its egg morphology and biological characters (adult nematodes are unknown). The dark-shelled eggs of this histozoic parasite occur in masses in the abdominal cavity, serose covers of internal organs and in the liver of the flying fishes Hirundichthys affinis Günther (type host) and Cypselurus cyanopterus Cuvier et Valenciennes in Curaçao. The eggs of H. schouteni sp. n. differ from those in other congeneric species mainly in the absence of small spines on the surface of the transparent envelope enclosing the egg proper, measurements (size of eggs 0.069-0.075 x 0.027-0.030 mm) and their localization in the host. A key to Huffmanela species based on egg morphology has been provided.
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Enfermedades de los Peces/parasitología , Nematodos/ultraestructura , Infecciones por Nematodos/veterinaria , Animales , Peces , Humanos , Microscopía Electrónica , Infecciones por Nematodos/parasitología , Antillas Holandesas , Óvulo/ultraestructuraRESUMEN
This report describes the diagnostic problem caused by an atypical immunoglobulin-bound creatine kinase isoenzyme in a patient who had a myocardial infarction. In the presence of this atypical isoenzyme, creatine kinase isoenzyme electrophoresis was of no help in determining whether myocardial infarction had occurred. A diagnosis of myocardial infarction was confirmed by carrying out lactate dehydrogenase isoenzyme electrophoresis and finding the characteristic increase in LD1/LD2 ratio and by following the total creatine kinase, aspartate aminotransferase and lactate dehydrogenase activities over a 5-day period. Further investigations were carried out which characterized the atypical isoenzyme as an uncommon type: creatine kinase-BB bound to immunoglobulin A lambda.
Asunto(s)
Pruebas Enzimáticas Clínicas , Creatina Quinasa/sangre , Infarto del Miocardio/diagnóstico , Anciano , Anciano de 80 o más Años , Femenino , Humanos , Inmunoglobulinas/metabolismo , IsoenzimasRESUMEN
Sigma receptors are specific, highly localized binding sites in limbic and sensorimotor structures of the brain that interact with many psychotropic drugs. These agents include the psychotomimetic benzomorphan opiates, the psychotomimetic drug phencyclidine and its analogs, as well as numerous typical and atypical antipsychotics such as haloperidol, chlorpromazine, and the novel drugs BMY 14802 and rimcazole. So far, no physiological function has been assigned to these binding sites. We have synthesized a number of novel sigma receptor-active drugs derived from the selective sigma ligand N,N'-di(o-tolyl)guanidine (DTG). DTG and its congeners were found to inhibit contractions of the guinea pig ileal longitudinal muscle/myenteric plexus (LMMP) preparation evoked by electrical stimulation. In addition, the sigma ligands noncompetitively antagonized contractions of the LMMP preparation evoked by serotonin (5-HT). The 5-HT-evoked contractions were found to be largely due to 5-HT's activation of 5-HT3 receptors to release ACh. The activity of DTG congeners in inhibiting electrically or 5-HT-evoked contractions of the LMMP highly correlated with their potency to inhibit binding of both 3H-DTG and (+)3H-3-PPP [3(3-OH-phenyl)-N-(1-propyl)piperidine] to sigma receptors in guinea pig brain homogenates. Two DTG congeners that did not bind to sigma receptors also showed no activity in the bioassay. Many other (but not all) sigma receptor ligands showed a high correlation between their potency to inhibit electrically evoked contractions of the LMMP and their sigma receptor binding affinity. The benzomorphans (+)SKF 10,047 and (+)cyclazocine potentiated electrically evoked contractions of the LMMP. Sigma ligands also inhibited the contractions of the LMMP in the presence of the opiate antagonist naloxone and in preparations in which opioid receptors had been inactivated by treatment with the irreversible opiate antagonist beta-chlornaltrexamine. Control experiments suggested that the sigma ligands act via a neuronal mechanism to inhibit ACh release evoked by electrical stimulation or by stimulation with 5-HT. These results suggest that there are functional sigma receptors on cholinergic nerve terminals or within the myenteric plexus and that these receptors can inhibit stimulated ACh release through an opioid receptor-independent mechanism. However, sigma receptor activation in the ileum has the same effect on ACh release as activation of naloxone-sensitive opioid receptors. The LMMP may be an in vitro bioassay system for characterizing the mechanism of action of sigma receptors and for determining the biological efficacy of drugs known to bind to sigma receptors in radioligand binding assays.
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Íleon/fisiología , Contracción Muscular , Músculo Liso/fisiología , Plexo Mientérico/fisiología , Receptores Opioides/fisiología , Serotonina/farmacología , Animales , Benzomorfanos/metabolismo , Benzomorfanos/farmacología , Estimulación Eléctrica , Guanidinas/metabolismo , Cobayas , Técnicas In Vitro , Isomerismo , Ligandos , Contracción Muscular/efectos de los fármacos , Músculo Liso/efectos de los fármacos , Parasimpaticomiméticos/farmacología , Receptores Opioides/metabolismo , Receptores sigmaRESUMEN
Ditolylguanidine (DTG) is a ligand which binds with high affinity to neuronal sigma receptors. Activation of sigma receptors inhibits the release of acetylcholine (ACh) from guinea pig ileum myenteric plexus preparations. A study was therefore undertaken to investigate the action of sigma receptor ligands on single neurons. Nicotinic responses to locally applied ACh onto single neurons of the guinea pig ileum myenteric plexus were studied using intracellular recording techniques. DTG and (+)-SKF10047 (N-allylnormetazocine) produced a concentration-dependent suppression of the depolarization of enteric neurons evoked by ionophoresis of ACh. The EC50 values for DTG and (+)-SKF10047 were 4.7 and 3.8 microM, respectively, and were similar to that for hexamethonium (3.2 microM). The inhibition of the ACh-depolarization was not mediated at sigma receptors because (-)SKF10047 and Bridge-DPG (2-imino-1,3H-dibenzo[d,f]-[1,3]-diazepine), which are inactive at sigma receptors, were as potent as DTG and (+)-SKF10047. DTG and hexamethonium (each at 1 microM) were more effective blockers of ACh-induced inward currents at a holding potential of -100 mV than at -40 mV. This voltage dependence is consistent with a channel blocking mechanism. DTG (10 microM) did not affect the depolarization (mediated by 5-HT3 receptors) induced by pressure application of 5-HT onto single neurons. DTG and Bridge-DPG inhibited contractures of the longitudinal muscle-myenteric plexus preparation elicited by dimethylphenylpiperazinium noncompetitively (EC50 values were 8.0 and 12.3 microM, respectively) whereas DTG but not Bridge-DPG inhibited 5-HT-induced contractions of the longitudinal muscle-myenteric plexus noncompetitively.(ABSTRACT TRUNCATED AT 250 WORDS)