RESUMEN
Diabetes is an independent risk factor for development of heart failure and has been associated with poor outcomes in these patients. The prevalence of diabetes continues to rise. Using routine HbA1c measurements on inpatients at a tertiary hospital, we aimed to investigate the prevalence of diabetes amongst patients hospitalised with decompensated heart failure and the association of dysglycaemia with hospital outcomes and mortality. 1191 heart failure admissions were identified and of these, 49% had diabetes (HbA1c ≥ 6.5%) and 34% had pre-diabetes (HbA1c 5.7-6.4%). Using a multivariable analysis adjusting for age, Charlson comorbidity score (excluding diabetes and age) and estimated glomerular filtration rate, diabetes was not associated with length of stay (LOS), Intensive Care Unit (ICU) admission or 28-day readmission. However, diabetes was associated with a lower risk of 6-month mortality. This finding was also supported using HbA1c as a continuous variable. The diabetes group were more likely to have diastolic dysfunction and to be on evidence-based cardiac medications. These observational data are hypothesis generating and possible explanations include that more diabetic patients were on medications that have proven mortality benefit or prevent cardiac remodelling, such as renin-angiotensin system antagonists, which may modulate the severity of heart failure and its consequences.
Asunto(s)
Diabetes Mellitus/epidemiología , Hemoglobina Glucada/análisis , Insuficiencia Cardíaca/sangre , Anciano , Anciano de 80 o más Años , Inhibidores de la Enzima Convertidora de Angiotensina/uso terapéutico , Diabetes Mellitus/sangre , Diabetes Mellitus/diagnóstico , Diabetes Mellitus/tratamiento farmacológico , Femenino , Insuficiencia Cardíaca/diagnóstico , Insuficiencia Cardíaca/mortalidad , Insuficiencia Cardíaca/terapia , Humanos , Pacientes Internos , Tiempo de Internación/estadística & datos numéricos , Masculino , Readmisión del Paciente/estadística & datos numéricos , Prevalencia , Factores de Riesgo , Índice de Severidad de la Enfermedad , Análisis de SupervivenciaRESUMEN
The use of beta-blockers in patients with chronic obstructive pulmonary disease and co-morbid cardiovascular disease is controversial, despite increasing evidence to support their use as safe and efficacious. This study retrospectively assessed the rates of beta-blocker prescription in patients admitted to two Australian tertiary hospitals for acute exacerbation of chronic obstructive pulmonary disease. This revealed that less than half of patients (45%) with known cardiac indications were receiving beta-blocker therapy, evident across all degrees of airways disease severity. Further work is needed to ensure that medical management of this patient group is optimised.
Asunto(s)
Antagonistas Adrenérgicos beta/uso terapéutico , Prescripciones de Medicamentos/estadística & datos numéricos , Insuficiencia Cardíaca/tratamiento farmacológico , Enfermedad Pulmonar Obstructiva Crónica/tratamiento farmacológico , Anciano , Australia , Comorbilidad , Femenino , Hospitalización , Humanos , Masculino , Enfermedad Pulmonar Obstructiva Crónica/fisiopatología , Estudios RetrospectivosRESUMEN
BACKGROUND: The results of two European multi-centre trials on xenon anaesthesia led to the hypothesis that a xenon-based anaesthetic would keep left ventricular (LV) and circulatory function more stable than a propofol-based anaesthetic, in patients with coronary artery disease (CAD). METHODS: In a prospective, randomized design, 40 patients of ASA classes III and IV with known CAD were anaesthetized for elective non-cardiac surgery with either xenon (n=20) or propofol (n=20), each combined with remifentanil. Target criteria were intraoperative LV function as evaluated by transoesophageal echocardiography (TOE: Tei index, circumferential fibre shortening), arterial pressure, and heart rate (HR). RESULTS: Mean arterial pressure was decreased with propofol but was stable at pre-anaesthetic level with xenon (P<0.02) and HR was lower with xenon (P<0.01). The Tei index (also known as myocardial performance index) improved from 0.53 (0.14) to 0.45 (0.10) after 1 h with xenon and changed from 0.50 (0.14) to 0.55 (0.20) with propofol anaesthesia [means (SD); P=0.01 between the groups]. Deviation of circumferential fibre shortening from expected value after 1 h was -2 (14)% with xenon and -14 (18)% with propofol [means (SD); P=0.03]. There were no perioperative signs of acute myocardial ischaemia (TOE, ECG, and troponin T release). CONCLUSIONS: Xenon anaesthesia provided a higher arterial pressure level than propofol, with no signs of cardiovascular compromise, in patients with CAD. Echocardiographic indices showed better LV function with xenon.
Asunto(s)
Anestésicos por Inhalación/farmacología , Anestésicos Intravenosos/farmacología , Enfermedad de la Arteria Coronaria/fisiopatología , Propofol/farmacología , Xenón/farmacología , Anciano , Anciano de 80 o más Años , Presión Sanguínea/efectos de los fármacos , Enfermedad de la Arteria Coronaria/diagnóstico por imagen , Ecocardiografía Transesofágica , Femenino , Frecuencia Cardíaca/efectos de los fármacos , Ventrículos Cardíacos/diagnóstico por imagen , Humanos , Masculino , Persona de Mediana Edad , Estudios Prospectivos , Función Ventricular Izquierda/efectos de los fármacosRESUMEN
Loading of the spine is still not well understood. The most reliable results seemed to come from the intradiscal pressure measurements from studies by Nachemson, 1966. A new similar study by Wilke et al. (1999) complemented the present study and confirmed some of the earlier data, although it contradicted others. The new data did not confirm that the load on the spine is higher in sitting compared with standing and did not find distinct differences between positions in which subjects were lying down. The objective of this paper was to compare results from two independent in vivo studies (applying different methods) to provide information about spinal loading. In one of these studies (Wilke 1999), intradiscal pressure was measured in one volunteer in different postures and exercises, and in the other study (Rohlmann et al. 1994) the loads on an internal spinal fixation device (an implant for stabilising unstable spines) were determined in 10 patients. The absolute values of the results from both studies were normalized and compared for many body positions and dynamic exercises. The relative differences in intradiscal pressure and flexion bending moments in the fixators corresponded in most cases. Both studies showed slightly lower loads for sitting than for standing and comparatively low loads in all lying positions. High loads were measured for jogging, jumping on a trampoline and skipping. Differences between trends for intradiscal pressure and for flexion bending moments in the fixators were found when the load was predominantly carried by the anterior spinal column, as during flexion of the upper part of the body or when lifting and carrying weights. The combination of the results from these two methods may improve the understanding of the biomechanical behaviour of the lumbar spine and may be used to validate models and theories of spinal loading.
Asunto(s)
Ejercicio Físico/fisiología , Fijadores Internos , Disco Intervertebral/fisiología , Postura , Soporte de Peso/fisiología , Anciano , Femenino , Alemania , Humanos , Masculino , Persona de Mediana EdadRESUMEN
OBJECTIVE: To provide a database of intradiscal pressure measurements together with anthropometric data as basis for the validation of models that predict spinal loads. DESIGN: Intradiscal pressure was measured in a non-degenerated L4-5 disc of a volunteer. The anthropometric characteristics of this subject were extensively determined. BACKGROUND: Since it is usually impossible to quantify the load in the spine directly, it is predicted by various biomechanical models. However, they often cannot be validated because of the few in vivo data and missing anthropometric characteristics pertaining to them. METHODS: A pressure transducer (diameter 1.5 mm) was implanted in the nucleus pulposus of a non-degenerated L4-5 disc of a volunteer. Pressure was determined during exercises while standing, lifting activities, sitting unsupported on a stool or an ergonomic sitting ball, sitting in different postures and others. The anthropometric characteristics were determined using different tools. RESULTS: Pressure values: relaxed standing 0.5 MPa; standing flexed forward 1.1 MPa; standing extended backward 0.6 MPa; sitting unsupported 0.46 MPa; maximum values during lateral bending 0.6 MPa, during axial rotation 0.7 MPa, lifting a 20 kg weight with a round flexed back 2.3 MPa, with flexed knees 1.7 MPa, close to the body 1.1 MPa; sitting unsupported relaxed 0.45 MPa, actively straightening the back 0.55 MPa, with flexion 0.9 MPa; non-chalant sitting 0.3 MPa and others. Anthropometric characteristics with emphasis on data for the trunk are provided in tables.Conclusions. Intradiscal pressure depends on the kind of preceding activity, posture, external loads and muscle activity. RELEVANCE: The data set can be used to verify a biomechanical model adjusted to the individual characteristics by a comparison of measured and predicted intradiscal pressures.
Asunto(s)
Disco Intervertebral/fisiología , Postura/fisiología , Antropometría , Electrofisiología/métodos , Humanos , Vértebras Lumbares/fisiología , Imagen por Resonancia Magnética , Masculino , Persona de Mediana Edad , Modelos Anatómicos , Presión , Transductores de Presión , Grabación de Cinta de VideoRESUMEN
Ro 25-1553 is a cyclic VIP derivative with a high affinity for the VPAC(2) receptor subtype. Our goal was to identify the modifications that support its selectivity for VPAC(2) receptors, and to develop a VIP or Ro 25-1553 analog behaving as a high affinity, VPAC(2) selective antagonist. The selectivity of Ro 25-1553 for the human receptor was supported mainly by the acetylation of the amino-terminus, by the introduction of a lysine residue in position 12, and by the carboxyl-terminal extension. The lactam bridge created between positions 21 and 25 contributed to the affinity of the compound for the VIP receptors but participated only marginally to its selectivity. Deletion of the first five aminoacid residues led to a low affinity antagonist with a low selectivity. Introduction of a D-Phe residue in position 2 reduced the affinity, the selectivity and the intrinsic activity, the compound being a partial agonist. Myristoylation of the amino-terminus of [K(12)]VIP(1-26) extended carboxyl-terminally with the -K-K-G-G-T sequence of Ro 25-1553 led to a high affinity, selective VPAC(2) receptor antagonist. This molecule represents the first selective human VPAC(2) receptor antagonist described to date.
Asunto(s)
Diseño de Fármacos , Receptores de Péptido Intestinal Vasoactivo/agonistas , Receptores de Péptido Intestinal Vasoactivo/antagonistas & inhibidores , Péptido Intestinal Vasoactivo/análogos & derivados , Péptido Intestinal Vasoactivo/farmacología , Acilación , Adenilil Ciclasas/metabolismo , Secuencia de Aminoácidos , Animales , Unión Competitiva , Células CHO , Cricetinae , Activación Enzimática/efectos de los fármacos , Humanos , Concentración 50 Inhibidora , Datos de Secuencia Molecular , Ácido Mirístico/metabolismo , Fragmentos de Péptidos/síntesis química , Fragmentos de Péptidos/química , Fragmentos de Péptidos/farmacología , Péptidos Cíclicos/síntesis química , Péptidos Cíclicos/química , Péptidos Cíclicos/farmacología , Receptores de Péptido Intestinal Vasoactivo/genética , Receptores de Péptido Intestinal Vasoactivo/metabolismo , Receptores de Tipo II del Péptido Intestinal Vasoactivo , Receptores de Tipo I del Polipéptido Intestinal Vasoactivo , Proteínas Recombinantes/agonistas , Proteínas Recombinantes/antagonistas & inhibidores , Especificidad por Sustrato , Péptido Intestinal Vasoactivo/síntesis química , Péptido Intestinal Vasoactivo/química , Vasodilatadores/síntesis química , Vasodilatadores/química , Vasodilatadores/farmacologíaRESUMEN
Vasoactive Intestinal Polypeptide (VIP) interacts with a high affinity to two subclasses of G protein coupled receptors named VPAC(1) and VPAC(2), and has a 3 - 10 fold preference for VPAC(1) over VPAC(2) receptors. Selective ligands for each receptor subclass were recently described. [R(16)]-PACAP (1 - 23) and [L(22)]-VIP are two selective VPAC(1) agonists. Chimaeric human VPAC(2)-VPAC(1) recombinant receptors expressed in CHO cells were used to identify the receptor domains implicated in these two selective ligands recognition. The VPAC(2) preference for [R(16)]-PACAP (1 - 27) over [R(16)]-PACAP (1 - 23) did not require the receptor's NH(2)-terminus domain but involved the whole transmembrane domain. In contrast, the selectivity of [L(22)]-VIP depended only on the presence of the NH(2) terminus and EC(2) domains of the VPAC(1) receptor. The present data support the idea that in the GPCR-B family of receptors the different selective ligands require different domains for their selectivity, and that the peptides carboxyl terminal sequence (amino acids 24 - 27) folds back on the transmembrane receptor domain, close to the peptides, aminoterminus.
Asunto(s)
Receptores de Péptido Intestinal Vasoactivo/metabolismo , Secuencia de Aminoácidos , Animales , Sitios de Unión , Unión Competitiva , Células CHO , Cricetinae , ADN Recombinante , Humanos , Datos de Secuencia Molecular , Neuropéptidos/metabolismo , Polipéptido Hipofisario Activador de la Adenilato-Ciclasa , Unión Proteica , Estructura Terciaria de Proteína , Ensayo de Unión Radioligante , Receptores de Péptido Intestinal Vasoactivo/química , Receptores de Péptido Intestinal Vasoactivo/genética , Receptores de Tipo II del Péptido Intestinal Vasoactivo , Receptores de Tipo I del Polipéptido Intestinal Vasoactivo , Homología de Secuencia de Aminoácido , Péptido Intestinal Vasoactivo/metabolismoRESUMEN
A vasoactive intestinal polypeptide (VIP) analog, acylated on the amino-terminal histidine by hexanoic acid (C(6)-VIP), behaved as a VPAC(2) preferring agonist in binding and functional studies on human VIP receptors, and radioiodinated C(6)-VIP was a suitable ligand for binding studies on wild-type and chimeric receptors. We evaluated the properties of C(6)-VIP, its analog AcHis(1)-VIP, and the VPAC(2)-selective agonist Ro 25-1553 on the wild-type VPAC(1) and VPAC(2) receptors and on the chimeric receptors exchanging the different domains between both receptors. VIP had a normal affinity and efficacy on the chimeras starting with the amino-terminal VPAC(2) receptor sequence. The binding and functional profile of these chimeric receptors suggested that the high affinity of Ro 25-1553 for VPAC(2) receptors is supported by the amino-terminal extracellular domain, whereas the ability to prefer C(6)-VIP over VIP is supported by the VPAC(2) fifth transmembrane (TM5)-EC(3) receptor domain. These results further support the hypothesis that the central and carboxyl-terminal regions of the peptide (modified in RO 25-1553) recognize the extracellular amino-terminal region domain, whereas the amino-terminal VIP amino acids bind to the TM receptor core. VIP had a reduced affinity and efficacy on the N-VPAC(1)/VPAC(2) and on the N-->EC(2)-VPAC(1)/VPAC(2) chimeric receptors. C(6)-VIP behaved as a high-affinity agonist on these constructions. The antagonists [AcHis(1),D-Phe(2),Lys(15),Arg(16), Leu(27)]VIP(3-7)/GRF(8-27) and VIP(5-27) had comparable affinities for the wild-type receptors and for the two latter chimeras, supporting the hypothesis that these chimeras were properly folded but unable to reach the high-agonist-affinity, active receptor conformation in response to VIP binding.
Asunto(s)
Receptores de Péptido Intestinal Vasoactivo/metabolismo , Péptido Intestinal Vasoactivo/farmacología , Animales , Unión Competitiva , Células CHO , Cricetinae , Humanos , Ligandos , Datos de Secuencia Molecular , Péptidos Cíclicos/farmacología , Conformación Proteica , Receptores de Péptido Intestinal Vasoactivo/química , Receptores de Péptido Intestinal Vasoactivo/efectos de los fármacos , Receptores de Tipo II del Péptido Intestinal Vasoactivo , Receptores de Tipo I del Polipéptido Intestinal Vasoactivo , Proteínas Recombinantes/química , Proteínas Recombinantes/metabolismo , Péptido Intestinal Vasoactivo/análogos & derivados , Péptido Intestinal Vasoactivo/químicaRESUMEN
In order to identify the receptor domains responsible for the VPAC1 selectivity of the VIP1 agonist, [Lys15, Arg16, Leu27] VIP (1-7)/GRF (8-27) and VIP1 antagonist, Ac His1 [D-Phe2, Lys15, Arg16, Leu27] VIP (3-7)/GRF (8-27), we evaluated their binding and functional properties on chimeric VPAC1/VPAC2 receptors. Our results suggest that the N-terminal extracellular domain is responsible for the selectivity of the VIP1 antagonist. Selective recognition of the VIP1 agonist was supported by a larger receptor area: in addition to the N-terminal domain, the first extracellular loop, as well as additional determinants in the distal part of the VPAC1 receptor were involved. Furthermore, these additional domains were critical for an efficient receptor activation, as replacement of EC1 in VPAC1 by its counter part in the VPAC2 receptor markedly reduced the maximal response.
Asunto(s)
Receptores de Péptido Intestinal Vasoactivo/metabolismo , Proteínas Recombinantes de Fusión/metabolismo , Péptido Intestinal Vasoactivo/análogos & derivados , Adenilil Ciclasas , Sitios de Unión , Relación Dosis-Respuesta a Droga , Activación Enzimática , Ligandos , Fragmentos de Péptidos/metabolismo , Receptores de Péptido Intestinal Vasoactivo/agonistas , Receptores de Péptido Intestinal Vasoactivo/antagonistas & inhibidores , Receptores de Péptido Intestinal Vasoactivo/genética , Receptores de Tipo II del Péptido Intestinal Vasoactivo , Receptores de Tipo I del Polipéptido Intestinal Vasoactivo , Proteínas Recombinantes de Fusión/agonistas , Proteínas Recombinantes de Fusión/antagonistas & inhibidores , Péptido Intestinal Vasoactivo/metabolismoRESUMEN
BACKGROUND: The 28-amino-acid neuropeptide vasoactive intestinal peptide (VIP) might play an important role in the physiology of the prostate, since it stimulates glandular secretion, inhibits muscle contraction, stimulates proliferation of epithelial cells, and increases the secretion of prostate-specific antigen (PSA). This neuropeptide may act through interaction with two types of high-affinity receptors, named VPAC(1) and VPAC(2) receptors. Recently, selective agonists and antagonists for each receptor subtype were synthesized. We used them to identify the VIP receptor subclass expressed in rat prostatic tissue. METHODS: We tested the capacity of selective labeled and unlabeled agonists and antagonists of VPAC(1) and VPAC(2) receptors to bind to rat prostatic membranes and to stimulate or prevent the stimulation of adenylate cyclase activity. RESULTS: The following selective peptides were used: VPAC(1) agonist ([K(15), R(16), L(27)] VIP (1-7)/GRF (8-27)); VPAC(1) antagonist (PG 97-269); and VPAC(2) agonist (RO 25-1553). The IC(50) values of [(125)I]-VIP binding inhibition for the different peptides in rat prostatic membranes were: VIP (1.7 nM) < VPAC(1) agonist (20 nM) < VPAC(1) antagonist (40 nM) < VPAC(2) agonist (329 nM). The EC(50) values of adenylate cyclase stimulation were similar to the IC(50) values for each peptide, and the Ki values for the VPAC(1) antagonist, inhibiting the adenylate cyclase activity stimulated by VIP and the VPAC(1) agonist, were 22 and 35 nM, respectively. Comparison of binding of [(125)I]-VIP and of [(125)I]-RO 25-1553 indicates the presence of 80% of VPAC(1) and 20% VPAC(2) receptors. CONCLUSIONS: In rat prostate membranes, VPAC(1) receptors are largely predominant. Binding studies were compatible with a ratio of 80/20 of VPAC(1)/VPAC(2) receptors, whereas functionally only VPAC(1) receptors were detected.
Asunto(s)
Membrana Celular/metabolismo , Próstata/metabolismo , Receptores de Péptido Intestinal Vasoactivo/metabolismo , Adenilil Ciclasas/metabolismo , Animales , Unión Competitiva , Células CHO , Membrana Celular/efectos de los fármacos , Membrana Celular/enzimología , Cricetinae , Activación Enzimática/efectos de los fármacos , Concentración 50 Inhibidora , Cinética , Masculino , Fragmentos de Péptidos/metabolismo , Fragmentos de Péptidos/farmacología , Péptidos Cíclicos/metabolismo , Péptidos Cíclicos/farmacología , Próstata/enzimología , Ratas , Ratas Wistar , Receptores de Péptido Intestinal Vasoactivo/agonistas , Receptores de Péptido Intestinal Vasoactivo/antagonistas & inhibidores , Receptores de Tipo II del Péptido Intestinal Vasoactivo , Receptores de Tipo I del Polipéptido Intestinal Vasoactivo , Péptido Intestinal Vasoactivo/agonistas , Péptido Intestinal Vasoactivo/análogos & derivados , Péptido Intestinal Vasoactivo/antagonistas & inhibidores , Péptido Intestinal Vasoactivo/metabolismo , Péptido Intestinal Vasoactivo/farmacologíaRESUMEN
A secretin receptor was cloned from a commercial human pancreatic complementary DNA (cDNA) bank. The amino acid sequence deduced from the nucleotide sequence differed slightly from the three different sequences previously published, suggesting a genetic polymorphism of the human receptor. The binding properties of the receptor were evaluated by testing natural secretin, related peptides, and synthetic analogs or fragments on membranes of Chinese hamster ovary (CHO) cells expressing the receptor after transfection. The second-messenger coupling was evaluated by adenylate cyclase measurement. The human secretin receptor was compared with the rat and the rabbit receptors. In the three animals species, rat and human secretin were equipotent; rabbit secretin was equipotent on human and rabbit secretin receptors and less potent on the rat receptor. Similar data were obtained for the [Arg16]-secretin analog. Deletion of histidine 1 and replacement of aspartate 3 reduced the affinity of the peptides for the three receptors; however, the reduction was more pronounced on rat than on human and rabbit secretin receptors. Finally, the low affinity of the rat and human receptors for vasoactive intestinal peptide (VIP) was identical; the rabbit receptor, however, had a 20-fold higher affinity. Thus the human secretin receptor shows properties of both rat and rabbit receptors. Evaluation of the properties of chimeric receptors will be useful to fit the ligand on the receptors.
Asunto(s)
Receptores de la Hormona Gastrointestinal/genética , Secretina/genética , Adenilil Ciclasas/metabolismo , Secuencia de Aminoácidos , Animales , Células CHO/metabolismo , Clonación Molecular , Cricetinae , ADN Complementario/análisis , Biblioteca de Genes , Humanos , Datos de Secuencia Molecular , Páncreas , Conejos , Ratas , Receptores Acoplados a Proteínas G , Receptores de la Hormona Gastrointestinal/metabolismo , Proteínas Recombinantes , Secretina/metabolismo , Especificidad de la Especie , Transfección , Péptido Intestinal Vasoactivo/metabolismoRESUMEN
The secretin amino terminal residues are essential for high affinity binding to the cognate receptor and for the subsequent activation of adenylate cyclase. It has been already established that two basic residues of the receptor TM 2 are involved in the interaction with aspartate 3 of the ligand. The present work investigated the hypothesis that two conserved tyrosine residues of the TM 1 (Tyrosines 124 and 128) could also participate to the positioning of the amino terminus of the ligand. Tyrosines 124 and 128 were mutated into alanine and histidine residues, and the properties of the mutant receptors, expressed in CHO cells, were compared with those of the wild-type receptor. Mutation of tyrosine 124 to Ala or His decreased the affinity of the receptor for secretin, [Glu3]secretin, [Asn3]secretin and the secretin fragment 2-27, and reduced the intrinsic activity of [Asn3]secretin. Mutation of tyrosine 128 to Ala, but not to His reduced 50-fold secretin and [Asn3]secretin affinity but only 3-fold that of [Glu3]secretin. Secretin and [Glu3]Sn were equipotent in that mutant receptor. These results suggested that tyrosine 128 of the secretin receptor interacted directly with the [Asp3] residue of secretin and thus that the amino terminal domain of secretin interacts with amino acids buried in both the TM 1 and TM 2 helices.
Asunto(s)
Receptores de la Hormona Gastrointestinal/genética , Transducción de Señal/genética , Adenilil Ciclasas/metabolismo , Secuencia de Aminoácidos , Sustitución de Aminoácidos , Animales , Activación Enzimática , Datos de Secuencia Molecular , Mutagénesis Sitio-Dirigida , Unión Proteica , Ratas , Receptores Acoplados a Proteínas G , Receptores de la Hormona Gastrointestinal/química , Receptores de la Hormona Gastrointestinal/fisiología , Proteínas Recombinantes/química , Relación Estructura-Actividad , Tirosina/químicaRESUMEN
STUDY DESIGN: We conducted intradiscal pressure measurements with one volunteer performing various activities normally found in daily life, sports, and spinal therapy. OBJECTIVES: The goal of this study was to measure intradiscal pressure to complement earlier data from Nachemson with dynamic and long-term measurements over a broad range of activities. SUMMARY OF BACKGROUND DATA: Loading of the spine still is not well understood. The most important in vivo data are from pioneering intradiscal pressure measurements recorded by Nachemson during the 1960s. Since that time, there have been few data to corroborate or dispute those findings. METHODS: Under sterile surgical conditions, a pressure transducer with a diameter of 1.5 mm was implanted in the nucleus pulposus of a nondegenerated L4-L5 disc of a male volunteer 45-years-old and weighing 70 kg. Pressure was recorded with a telemetry system during a period of approximately 24 hours for various lying positions; sitting positions in a chair, in an armchair, and on a pezziball (ergonomic sitting ball); during sneezing, laughing, walking, jogging, stair climbing, load lifting during hydration over 7 hours of sleeping, and others. RESULTS: The following values and more were measured: lying prone, 0.1 MPa; lying laterally, 0.12 MPa; relaxed standing, 0.5 MPa; standing flexed forward, 1.1 MPa; sitting unsupported, 0.46 MPa; sitting with maximum flexion, 0.83 MPa; nonchalant sitting, 0.3 MPa; and lifting a 20-kg weight with round flexed back, 2.3 MPa; with flexed knees, 1.7 MPa; and close to the body, 1.1 MPa. During the night, pressure increased from 0.1 to 0.24 MPa. CONCLUSIONS: Good correlation was found with Nachemson's data during many exercises, with the exception of the comparison of standing and sitting or of the various lying positions. Notwithstanding the limitations related to the single-subject design of this study, these differences may be explained by the different transducers used. It can be cautiously concluded that the intradiscal pressure during sitting may in fact be less than that in erect standing, that muscle activity increases pressure, that constantly changing position is important to promote flow of fluid (nutrition) to the disc, and that many of the physiotherapy methods studied are valid, but a number of them should be re-evaluated.
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Ritmo Circadiano/fisiología , Disco Intervertebral/fisiología , Vértebras Lumbares , Soporte de Peso/fisiología , Electrofisiología/métodos , Ejercicio Físico/fisiología , Humanos , Masculino , Persona de Mediana Edad , Presión , Valores de ReferenciaRESUMEN
The receptor subtypes involved in the relaxant effect of vasoactive intestinal polypeptide (VIP) in the rat gastric fundus were investigated in vitro. The selective VIP2 receptor agonist [Ac-H1,E8,K12,Nle17,A19,D25,L26,K27,28,G29,30,++ +T31]VIP(cyclo21-25) (RO25-1553) induced a concentration-dependent relaxation (EC50 2.8 nM), while the selective VIP1 receptor agonist derived from growth hormone-releasing factor (GRF) [K15,R16,L27]VIP-(1-7)/GRF-(8-27) had no effect up to 1 microM. [R16] chicken secretin, a selective VIP1 receptor agonist, induced relaxation with a potency of 4.8 nM but its maximal effect was clearly lower than that of VIP, pituitary adenylate cyclase-activating peptide [PACAP-(1-27)] and RO25-1553. This effect was reproduced by porcine secretin (EC50 2.1 nM). It is concluded that the rat gastric fundus contains functional VIP2 receptors but not VIP1 receptors, and that specific secretin receptors are also present.
Asunto(s)
Fundus Gástrico/efectos de los fármacos , Receptores de Péptido Intestinal Vasoactivo/agonistas , Péptido Intestinal Vasoactivo/farmacología , Animales , Dinoprost/metabolismo , Relación Dosis-Respuesta a Droga , Fundus Gástrico/metabolismo , Masculino , Neuropéptidos/farmacología , Fragmentos de Péptidos/farmacología , Péptidos Cíclicos/farmacología , Polipéptido Hipofisario Activador de la Adenilato-Ciclasa , Ratas , Ratas Wistar , Péptido Intestinal Vasoactivo/análogos & derivados , Vasodilatadores/farmacologíaRESUMEN
Stearyl vasoactive intestinal polypeptide has been reported to be a VIP (vasoactive intestinal polypeptide) receptor agonist of high potency with an original bioavailability and action. We synthesized three fatty acyl derivatives, myristyl-, palmityl- and stearyl-[Nle17]VIP, and tested their capacity to recognize recombinant rat- and human VIP1- and VIP2/PACAP (pituitary adenylate cyclase-activating polypeptide) receptors and to stimulate adenylate cyclase activity. The three lipophilic analogues bound with high affinity (from 0.5 to 20 nM) to both receptor subtypes but did not distinguish between them. In preparations expressing a high density of human VIP1/PACAP receptors, the three lipophilic analogues had the same efficacy as VIP and [Nle17]VIP. In preparations expressing the rat receptors, stearyl-[Nle17]VIP had a lower efficacy than the other peptides tested. In preparations expressing a low level of VIP1/PACAP receptors and in those expressing VIP2/PACAP receptors, all analogues behaved like partial agonists. The lowest efficacy was observed for stearyl-[Nle17]VIP on the VIP2/PACAP receptor subclass. Based on our results, a complex pattern of in vivo biological effects of the lipophilic VIP derivatives should be expected: these compounds might behave as full agonists, partial agonists, or antagonists of the VIP response, depending on the number and the subtype of receptor expressed.
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Neuropéptidos/metabolismo , Receptores de la Hormona Hipofisaria/metabolismo , Receptores de Péptido Intestinal Vasoactivo/metabolismo , Péptido Intestinal Vasoactivo/análogos & derivados , Adenilil Ciclasas/efectos de los fármacos , Adenilil Ciclasas/metabolismo , Animales , Unión Competitiva , Células CHO/metabolismo , Células CHO/ultraestructura , Cricetinae , Activación Enzimática/efectos de los fármacos , Humanos , Cinética , Neuropéptidos/efectos de los fármacos , Polipéptido Hipofisario Activador de la Adenilato-Ciclasa , Ratas , Receptores del Polipéptido Activador de la Adenilato-Ciclasa Hipofisaria , Receptores de la Hormona Hipofisaria/efectos de los fármacos , Receptores de Péptido Intestinal Vasoactivo/efectos de los fármacos , Estimulación Química , Relación Estructura-Actividad , Péptido Intestinal Vasoactivo/síntesis química , Péptido Intestinal Vasoactivo/farmacologíaRESUMEN
The rabbit secretion receptor cDNA was cloned from rabbit pancreas using combined polymerase chain reaction (PCR)/rapid amplification of cDNA ends (PCR/RACE) approaches. The rabbit cDNA encoded 445 amino acids and had 80 and 85% homology with rat- and human receptor, respectively, in terms of nucleic and amino acid sequences. Several regions where the rabbit receptor sequence diverged from the rat/human receptor sequences were observed in the putative extracellular domains of the receptor. A cDNA coding for a similar sequence with a 76 bp deletion after the 5th transmembrane domain was also found; it probably encoded an inactive protein. The whole rabbit secretin receptor cDNA was subcloned in expression vector pCR3.1, then stably and transiently transfected in Chinese hamster ovary (CHO) cells. The pharmacological properties of the rat and rabbit secretin receptor studies were compared by radiolabeled secretin binding, binding inhibition, and adenylate cyclase activation (using secretin analogs and fragments). Porcine secretin was equipotent with rabbit secretin on the rabbit secretin receptor, but fivefold more potent than rabbit secretin on the rat receptor. This was due to the serine-->arginine residue replacement, in position 16 of rabbit secretin. Amino terminal modified secretin analogs (secretin (2-27), [E3]secretin, [N3]secretin) and VIP were less potent than secretin on both secretin receptors, but more potent on the rabbit than on the rat receptor. The carboxy-terminally truncated fragment (1-26) had the same reduced potency on rat and rabbit receptors. Thus, the rabbit secretin receptor had original properties, different from those of the rat receptor.
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Receptores de la Hormona Gastrointestinal/química , Adenilil Ciclasas/metabolismo , Secuencia de Aminoácidos , Animales , Secuencia de Bases , Células CHO , Clonación Molecular , Cricetinae , Humanos , Datos de Secuencia Molecular , Unión Proteica , Conejos , Ratas , Receptores Acoplados a Proteínas G , Receptores de la Hormona Gastrointestinal/genética , Receptores de la Hormona Gastrointestinal/metabolismo , Proteínas Recombinantes/química , Proteínas Recombinantes/genética , Proteínas Recombinantes/metabolismo , Secretina/análogos & derivados , Secretina/metabolismoRESUMEN
Secretin and growth hormone releasing factor (GRF) have a weak affinity for VIP (vasoactive intestinal peptide)/PACAP (pituitary adenylate cyclase activating polypeptide) receptors, but discriminate between VIP1/PACAP and VIP2/PACAP receptors. This previously allowed us to develop modified secretin and GRF derivatives as high affinity and highly selective VIP1/PACAP receptor ligands. We tested the hypothesis that the presence of a Gln residue at position 24 and a Leu residue at position 22 was responsible for their VIP1/PACAP receptor selectivity. [Gln24]VIP was not different from VIP but [Leu22]VIP had a 100-fold lower affinity for VIP2/PACAP receptors as compared to VIP1/PACAP receptors. The substitution of Tyr22 by Phe22 in VIP had no significant effect on the recognition of both receptors but [Ala22]VIP had a reduced affinity for the VIP2/PACAP receptor. This indicated that an aromatic residue at position 22 of VIP was required for a high affinity for the VIP2/PACAP receptor but not for the VIP1/PACAP receptor.
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Receptores de Péptido Intestinal Vasoactivo/química , Receptores de Péptido Intestinal Vasoactivo/metabolismo , Péptido Intestinal Vasoactivo/química , Péptido Intestinal Vasoactivo/metabolismo , Secuencia de Aminoácidos , Animales , Células CHO , Cricetinae , Membranas/metabolismo , Datos de Secuencia Molecular , Neuropéptidos/metabolismo , Péptidos/síntesis química , Péptidos/química , Polipéptido Hipofisario Activador de la Adenilato-Ciclasa , Receptores del Polipéptido Activador de la Adenilato-Ciclasa Hipofisaria , Receptores de la Hormona Hipofisaria/metabolismo , Péptido Intestinal Vasoactivo/análogos & derivadosRESUMEN
The secretin amino-terminal residues are essential for high affinity binding to its cognate receptor and for its biological activity. Mutation of the [Asp3] residue of secretin to [Asn3] decreased the ligand's affinity for the rat wild-type receptor 100-300-fold. Receptor mutations in the transmembrane 2 domain and the beginning of the first extracellular loop allowed the identification of three residues involved in recognition of the [Asp3] residue: D174, K173 and R166. Mutation of K173 and D174 not only reduced the secretin and [Asn3]secretin affinities, but also changed the receptor's selectivity as judged by a decreased secretin and [Asn3]secretin potency ratio. The most striking effect was observed when R166 was mutated to Q, D or L. This led to receptors with a very low affinity for secretin but an up to 10-fold higher affinity than the wild-type receptor for [Asn3]secretin. This suggested that R166, highly conserved in that subgroup of receptor, is a major determinant for the recognition of the [Asp3] of the ligand.
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Receptores de la Hormona Gastrointestinal/química , Receptores de la Hormona Gastrointestinal/metabolismo , Secretina/metabolismo , Adenilil Ciclasas/metabolismo , Animales , Arginina , Sitios de Unión , Activación Enzimática , Mutación , Conformación Proteica , Ratas , Receptores Acoplados a Proteínas G , Receptores de la Hormona Gastrointestinal/genéticaRESUMEN
Vasoactive intestinal polypeptide (VIP) acts through interaction with two subclasses of seven transmembrane G protein-coupled receptors named VIP1 and VIP2 receptors. These receptors have been cloned in different species, such as rat and human. Considering the different distribution of both receptor subclasses, there is considerable interest in the development of selective agonists and antagonists. The present study compares the binding properties of VIP, PACAP, GRF, secretin, and helodermin analogues on recombinant rat and human VIP1 and VIP2 receptors. On both rat and human receptors, secretin and GRF had a higher affinity for the VIP1 receptor subtypes. The amino-shortened VIP, and the carboxy terminal-shortened VIP and PACAP analogues also presented a higher affinity for the VIP1 receptor. PHI, PHV, helodermin, and helospectin were selective for the human VIP2 receptor subtypes. These results suggest that the helical structure of the carboxy terminal end is necessary for VIP2 recognition. The differences between species were the following: PHI, PHV, helodermin, and helospectin had a higher affinity for the rat VIP1 receptor than for the human VIP1 receptor. On both rat and human receptors, D-Ala4 VIP and D-Phe4 VIP had a high affinity for the VIP1 receptor and a low affinity for the VIP2 receptor. Thus, three domains of the ligand involved in VIP1/VIP2 receptor discrimination were identified: the amino acid residue in position 4 ([D-Ala4], [D-Phe4]VIP), in positions 8 and 9 (the effects of helodermin and helospectin), and the carboxy terminal end (the effects of the shortened VIP and pituitary adenylate cyclase activating polypeptide analogues).