RESUMEN
A six-month-old, entire female, Irish setter was presented with a two-month history of progressive hindlimb weakness and collapse on exercise. Thoracic auscultation revealed a soft systolic murmur and a split second heart sound. Differential cyanosis and polycythaemia were not observed. Right-to-left shunting patent ductus arteriosus (r-PDA) was confirmed on contrast echocardiography ("bubble study") and selective right ventricular angiography. Comparison of blood gases from the metatarsal and auricular artery confirmed the presence of differential hypoxia. This technique is not known to have been described previously in the diagnostic investigation of r-PDA in dogs.
Asunto(s)
Enfermedades de los Perros/diagnóstico , Conducto Arterioso Permeable/veterinaria , Animales , Enfermedades de los Perros/patología , Perros , Conducto Arterioso Permeable/diagnóstico , Conducto Arterioso Permeable/patología , FemeninoRESUMEN
The aim of this study was to determine whether changes in body position alter feline electrocardiographic parameters. Forty-seven cats referred to the Feline Unit of the University of Bristol had electrocardiograms (ECGs) recorded. Only cats presenting in sinus rhythm were included in the study (n = 41). ECGs were recorded either as part of the investigation for potential cardiac disease (n = 38) or as a preanesthetic screen (n = 3). Standard 6-lead ECGs (leads I, II, III, aVR, aVL, and aVF) were recorded in 3 different recumbent positions in the 41 cats. Recordings were 1st made in right lateral (RL) recumbency, followed by sternal (ST) and then left lateral (LL) recumbency. Measurements were taken of the amplitude and duration of P waves and QRS complexes and duration of PQ and QT intervals from lead II was taken in the 3 different positions. Mean electrical axis (MEA) also was calculated. Repeated measures analysis of variance was performed and identified a significant difference in R wave amplitudes (P = .009) and MEA (P = .037) among the 3 different body positions. Two-tailed paired t-tests demonstrated that the R wave amplitude differed significantly both in ST (P = .025) and LL recumbency (P = .009). The mean R wave amplitude was reduced in both ST and LL recumbency when compared with RL recumbency. The MEA only was significantly different in LL recumbency (P = .037). ST and LL recumbencies should not be used for recording ECGs in cats if amplitudes and MEA are to be compared with standard references.
Asunto(s)
Enfermedades de los Gatos/diagnóstico , Electrocardiografía/veterinaria , Cardiopatías/veterinaria , Animales , Gatos , Electrocardiografía/métodos , Femenino , Cardiopatías/diagnóstico , Masculino , Postura , Sensibilidad y EspecificidadRESUMEN
OBJECTIVES: To assess the ventricular rate response of rate-adaptive (VVIR) pacemakers in dogs using a multi-stage exercise test. METHODS: The rate-responsiveness of VVIR pacemakers was assessed in seven dogs with complete atrioventricular (AV) block and implanted with various models of pulse generators (six motion sensors and one automatic dual-sensor rate-response pacemaker). Response activity was assessed with a multi-stage exercise test on a treadmill. Atrial and ventricular rate were analysed retrospectively at the end of the test and the AV ratio was calculated after each minute of exercise. RESULTS: During exercise, the mean (sd) AV ratio recorded in all paced dogs was 1.7 (0.5) (expected physiological ratio 1.0), although a variety of individual performances was observed. A poor response (AV ratio 2.8 [0.2]) was obtained with the automatic dual-sensor pacemaker, suggesting that this type of rate-responsive device may not be indicated for implantation in dogs with complete AV block. The overall AV ratio for the six dogs implanted with motion sensors was 1.4 (0.2), showing a better performance of these pacemakers during exercise. CLINICAL SIGNIFICANCE: This multi-stage exercise test represents an easy and repeatable method for assessing the accuracy of rate-responsive sensors and offers valuable information for the correct setting of VVIR pacemakers in dogs.
Asunto(s)
Estimulación Cardíaca Artificial/veterinaria , Enfermedades de los Perros/terapia , Perros/fisiología , Prueba de Esfuerzo/veterinaria , Bloqueo Cardíaco/veterinaria , Marcapaso Artificial/veterinaria , Animales , Estimulación Cardíaca Artificial/métodos , Prueba de Esfuerzo/métodos , Tolerancia al Ejercicio , Femenino , Bloqueo Cardíaco/terapia , Masculino , Marcapaso Artificial/normas , Reproducibilidad de los Resultados , Sensibilidad y EspecificidadRESUMEN
Arrhythmogenic right ventricular cardiomyopathy (ARVC) is a disease characterised by infiltration of the myocardium by adipose and fibrous tissue. The disease is an important cause of sudden death in humans, but has rarely been described in animals. This report describes ARVC in two cats with right-sided congestive heart failure. One cat had also experienced previous episodes of syncope. Standard six-lead and 24-hour (Holter) electrocardiogram recording revealed complete atrioventricular block and multiform ventricular ectopics in both cats, with the addition of ventricular tachycardia, ventricular bigeminy and R-on-T phenomenon in one of them. On echocardiography, the right ventricle and atrium were massively dilated and hypokinetic. The survival times of the cats were three days and 16 days following diagnosis. Histopathology in one case revealed fibro-fatty infiltration of the myocardium, predominantly affecting the right ventricular free wall.
Asunto(s)
Arritmias Cardíacas/veterinaria , Cardiomiopatías/veterinaria , Enfermedades de los Gatos/diagnóstico , Disfunción Ventricular Derecha/veterinaria , Animales , Arritmias Cardíacas/complicaciones , Arritmias Cardíacas/diagnóstico , Cardiomiopatías/complicaciones , Cardiomiopatías/diagnóstico , Gatos , Diagnóstico Diferencial , Ecocardiografía/veterinaria , Electrocardiografía/veterinaria , Resultado Fatal , Insuficiencia Cardíaca/etiología , Insuficiencia Cardíaca/mortalidad , Insuficiencia Cardíaca/veterinaria , Masculino , Pronóstico , Disfunción Ventricular Derecha/complicaciones , Disfunción Ventricular Derecha/diagnósticoRESUMEN
The cellular chaperone, HSP90, is identified here as an essential factor for the activity of NS2/3 protease of hepatitis C virus. The cleavage activity of NS2/3 protease synthesized in reticulocyte lysate is ATP-dependent, as evidenced by ATP depletion experiments and inhibition with nonhydrolyzable ATP analogs. Geldanamycin and radicicol, ATP-competitive inhibitors of the chaperone HSP90, also inhibit the cleavage of in vitro-synthesized NS2/3. Furthermore, these HSP90 inhibitors prevent NS2/3 cleavage when the protease is expressed in mammalian cells. The physical association of NS2/3 with HSP90 is demonstrated by immunoprecipitation. Thus, by way of a chaperone/folding activity, an HSP90-containing complex is required for maturation of the polyprotein that encodes the enzymes essential for hepatitis C virus replication.
Asunto(s)
Cisteína Endopeptidasas/metabolismo , Proteínas HSP90 de Choque Térmico/metabolismo , Hepacivirus/enzimología , Procesamiento Proteico-Postraduccional , Adenosina Trifosfato/metabolismo , Benzoquinonas , Cisteína Endopeptidasas/genética , Proteínas HSP90 de Choque Térmico/antagonistas & inhibidores , Humanos , Células Jurkat , Lactamas Macrocíclicas , Lactonas/farmacología , Macrólidos , Quinonas/metabolismo , Quinonas/farmacologíaRESUMEN
Thirty-five boxers that had been referred to the Royal (Dick) School of Veterinary Studies between 1989 and 1994 with left heart base murmurs and aortic velocities greater than 1.5 m/second on Doppler echocardiography were recalled for clinical examination and Doppler echocardiography between 1995 and 1996. Five dogs (14 per cent) showed an increase in murmur grade on repeat visit. Six dogs (17 per cent) showed an increase in aortic velocity of greater than 20 per cent. Eight dogs (23 per cent) had developed aortic valvular or subvalvular two-dimensional echocardiographic changes that had not been present at the initial visit. Seven dogs (20 per cent) had developed aortic regurgitation, and three dogs (8 per cent) mitral regurgitation.
Asunto(s)
Estenosis de la Válvula Aórtica/veterinaria , Enfermedades de los Perros/patología , Animales , Estenosis de la Válvula Aórtica/diagnóstico por imagen , Estenosis de la Válvula Aórtica/patología , Cruzamiento , Estudios de Cohortes , Progresión de la Enfermedad , Enfermedades de los Perros/diagnóstico por imagen , Perros , Ecocardiografía Doppler/veterinaria , Femenino , Masculino , Registros/veterinaria , Estudios RetrospectivosRESUMEN
Recent results from human clinical trials have established the critical role of HIV protease inhibitors in the treatment of acquired immune-deficiency syndrome (AIDS). However, the emergence of viral resistance, demanding treatment protocols, and adverse side effects have exposed the urgent need for a second generation of HIV protease inhibitors. The continued exploration of our hydroxylaminepentanamide (HAPA) transition-state isostere series of HIV protease inhibitors, which initially resulted in the identification of Crixivan (indinavir sulfate, MK-639, L-735,524), has now yielded MK-944a (L-756,423). This compound is potent, is selective, and competitively inhibits HIV-1 PR with a K(i) value of 0.049 nM. It stops the spread of the HIV(IIIb)-infected MT4 lymphoid cells at 25.0-50.0 nM, even in the presence of alpha(1) acid glycoprotein, human serum albumin, normal human serum, or fetal bovine serum. MK-944a has a longer half-life in several animal models (rats, dogs, and monkeys) than indinavir sulfate and is currently in advanced human clinical trials.
Asunto(s)
Antivirales/síntesis química , Inhibidores de la Proteasa del VIH/síntesis química , VIH-1/efectos de los fármacos , Indanos/síntesis química , Piperazinas/síntesis química , Animales , Antivirales/química , Antivirales/farmacocinética , Antivirales/farmacología , Bovinos , Técnicas de Cultivo de Célula , Perros , Evaluación Preclínica de Medicamentos , Farmacorresistencia Microbiana , Inhibidores de la Proteasa del VIH/química , Inhibidores de la Proteasa del VIH/farmacocinética , Inhibidores de la Proteasa del VIH/farmacología , Haplorrinos , Humanos , Indanos/química , Indanos/farmacocinética , Indanos/farmacología , Masculino , Piperazinas/química , Piperazinas/farmacocinética , Piperazinas/farmacología , Unión Proteica , Ratas , Ratas Sprague-Dawley , Relación Estructura-Actividad , Cálculos Urinarios/inducido químicamente , Cálculos Urinarios/orinaRESUMEN
Viruses of the family Herpesviridae are responsible for a diverse set of human diseases. The available treatments are largely ineffective, with the exception of a few drugs for treatment of herpes simplex virus (HSV) infections. For several members of this DNA virus family, advances have been made recently in the biochemistry and structural biology of the essential viral protease, revealing common features that may be possible to exploit in the development of a new class of anti-herpesvirus agents. The herpesvirus proteases have been identified as belonging to a unique class of serine protease, with a Ser-His-His catalytic triad. A new, single domain protein fold has been determined by X-ray crystallography for the proteases of at least three different herpesviruses. Also unique for serine proteases, dimerization has been shown to be required for activity of the cytomegalovirus and HSV proteases. The dimerization requirement seriously impacts methods needed for productive, functional analysis and inhibitor discovery. The conserved functional and catalytic properties of the herpesvirus proteases lead to common considerations for this group of proteases in the early phases of inhibitor discovery. In general, classical serine protease inhibitors that react with active site residues do not readily inactivate the herpesvirus proteases. There has been progress however, with activated carbonyls that exploit the selective nucleophilicity of the active site serine. In addition, screening of chemical libraries has yielded novel structures as starting points for drug development. Recent crystal structures of the herpesvirus proteases now allow more direct interpretation of ligand structure-activity relationships. This review first describes basic functional aspects of herpesvirus protease biology and enzymology. Then we discuss inhibitors identified to date and the prospects for their future development.
Asunto(s)
Antivirales/uso terapéutico , Endopeptidasas/metabolismo , Infecciones por Herpesviridae/tratamiento farmacológico , Herpesviridae/enzimología , Inhibidores de Proteasas/uso terapéutico , Secuencia de Aminoácidos , Dominio Catalítico , Endopeptidasas/química , Herpesviridae/fisiología , Humanos , Cinética , Especificidad por Sustrato , Replicación ViralRESUMEN
The NS2/3 protease of hepatitis C virus is responsible for a single cleavage in the viral polyprotein between the nonstructural proteins NS2 and NS3. The minimal protein region necessary to catalyze this cleavage includes most of NS2 and the N-terminal one-third of NS3. Autocleavage reactions using NS2/3 protein translated in vitro are used here to investigate the inhibitory potential of peptides likely to affect the reaction. Peptides representing the cleaved sequence have no effect upon reaction rates, and the reaction rate is insensitive to dilution. Both results are consistent with prior suggestions that the NS2/3 cleavage is an intramolecular reaction. Surprisingly, peptides containing the 12-amino acid region of NS4A responsible for binding to NS3 inhibit the NS2/3 reaction with K(i) values as low as 3 microM. Unrelated peptide sequences of similar composition are not inhibitory, and neither are peptides containing incomplete segments of the NS4A region that binds to NS3. Inhibition of NS2/3 by NS4A peptides can be rationalized from the organizing effect of NS4A on the N terminus of NS3 (the NS2/3 cleavage point) as suggested by the known three-dimensional structure of the NS3 protease domain (Yan, Y., Li, Y., Munshi, S., Sardana, V., Cole, J. L., Sardana, M., Steinkuhler, C., Tomei, L., De Francesco, R., Kuo, L. C., and Chen, Z. (1998) Protein Sci. 7, 837-847). These findings may imply a sequential order to proteolytic maturation events in hepatitis C virus.
Asunto(s)
Péptidos/farmacología , Proteínas no Estructurales Virales/antagonistas & inhibidores , Proteínas no Estructurales Virales/farmacología , Secuencia de Aminoácidos , Electroforesis en Gel de Poliacrilamida , Concentración 50 Inhibidora , Cinética , Datos de Secuencia MolecularRESUMEN
Doppler echocardiography is a specialized processing of cardiac ultrasound that is characterized by a continuously updated display of blood velocity during the cardiac cycle. Doppler examinations, which include color-coded Doppler echocardiography, pulsed-wave examination, and continuous-wave studies, are readily applicable to veterinary patients.
Asunto(s)
Enfermedades de los Gatos/diagnóstico por imagen , Enfermedades de los Perros/diagnóstico por imagen , Ecocardiografía Doppler de Pulso/veterinaria , Ecocardiografía Doppler/veterinaria , Cardiopatías/veterinaria , Animales , Gatos , Perros , Cardiopatías/diagnóstico por imagenAsunto(s)
Antivirales/química , Inhibidores de la Proteasa del VIH/química , Proteasa del VIH/metabolismo , Pirroles/química , Administración Oral , Antivirales/administración & dosificación , Antivirales/farmacocinética , Disponibilidad Biológica , Cristalografía por Rayos X , Dipéptidos/administración & dosificación , Dipéptidos/química , Dipéptidos/farmacocinética , Diseño de Fármacos , Inhibidores de la Proteasa del VIH/administración & dosificación , Inhibidores de la Proteasa del VIH/farmacocinética , Enlace de Hidrógeno , Indinavir/química , Indoles/administración & dosificación , Indoles/química , Indoles/farmacocinética , Modelos Moleculares , Peso Molecular , Conformación Proteica , Pirroles/administración & dosificación , Pirroles/farmacocinéticaRESUMEN
The quaternary state of the herpes simplex virus type 1 (HSV-1) protease has been analyzed in relation to its catalytic activity. The dependence of specific activity upon enzyme concentration indicated that association of the 27-kDa subunits strongly increased activity. Size-exclusion chromatography identified the association as a monomer-dimer equilibrium. Isolation of monomeric and dimeric species from a size-exclusion column followed by immediate assay identified the dimer as the active form of the enzyme. Activation of the protease by antichaotropic cosolvents correlated with changes in the monomer-dimer equilibrium. Thus, dimerization of the enzyme was enhanced in solvents containing glycerol or the anions citrate or phosphate. These are substances previously identified as activators of HSV-1 protease (Hall, D. L., and Darke, P. L. (1995) J. Biol. Chem. 270, 22697-22700). The relative potencies of these cosolvents as enzyme activators correlated with their efficiency in promoting dimerization. Under all solvent conditions examined, the dependence of specific activity upon enzyme concentration was consistent with a kinetic model in which only the dimer is active. Dissociation constants for the HSV-1 protease dimer determined with this model at 15 degrees C, pH 7.5, were 964 and 225 nM in 20% glycerol with 0.2 and 0.5 M citrate present, respectively. The activation of the HSV-1 protease by antichaotropic cosolvents was hereby shown to be similar in nature to the activation of the other well characterized herpesvirus protease, that from human cytomegalovirus.
Asunto(s)
Cápside/metabolismo , Serina Endopeptidasas/metabolismo , Proteínas Virales , Secuencia de Aminoácidos , Biopolímeros , Cromatografía en Gel , Activación Enzimática , Cinética , Datos de Secuencia Molecular , Conformación ProteicaRESUMEN
Measurement of cardiac output by Doppler echocardiography were compared to simultaneous measurements by thermodilution in 9 conscious horses. In the Doppler technique, mean blood flow velocities for estimation of cardiac output were recorded from the aorta and pulmonary artery. The flow area of each vessel was calculated from the vessel diameter, measured from a 2-dimensional ultrasound image. Differences in the site and method of measuring the vessel diameter altered the estimation of cardiac output by the Doppler method. Cardiac output was modified by the i.v. infusion of 4 micrograms/kg bwt/min dopamine and 4 micrograms/kg bwt/min dobutamine and by the i.v. administration of 10 micrograms/kg bwt detomidine and 20 micrograms/kg bwt butorphanol. Doppler measurements of cardiac output correlated closely with measurement by thermodilution. Measurements from the aortic outflow correlated more closely with thermodilution, than those from the pulmonary artery (r = 0.89 and r = 0.77, respectively). Doppler measurements when the mean flow velocity was recorded from the aorta and the flow area was measured from the ascending aorta using the leading edge method. There was no significant bias between the 2 techniques when Doppler flow velocities were recorded by this method and the limits of agreement were narrow (+/- 12.26 l/min). The differences between the 2 methods increased with increasing cardiac output. Doppler echocardiography is a safe noninvasive method of measuring cardiac output in horses. The agreement between Doppler echocardiography and thermodilution in this study is similar to that reported in man and is similar to that reported between thermodilution and other techniques in man.
Asunto(s)
Gasto Cardíaco/fisiología , Ecocardiografía Doppler/veterinaria , Caballos/fisiología , Termodilución/veterinaria , Analgésicos/farmacología , Animales , Butorfanol/farmacología , Gasto Cardíaco/efectos de los fármacos , Cardiotónicos/farmacología , Dobutamina/farmacología , Dopamina/farmacología , Ecocardiografía Doppler/métodos , Femenino , Imidazoles/farmacología , Masculino , Narcóticos/farmacología , Neurotransmisores/farmacología , Arteria Pulmonar/diagnóstico por imagen , Arteria Pulmonar/efectos de los fármacos , Arteria Pulmonar/fisiología , Valores de Referencia , Flujo Sanguíneo Regional/efectos de los fármacos , Reproducibilidad de los Resultados , Termodilución/métodosRESUMEN
Design and synthesis of nonpeptidal bis-tetrahydrofuran ligands based upon the X-ray crystal structure of the HIV-1 protease-inhibitor complex 1 led to replacement of two amide bonds and a 10 pi-aromatic system of Ro 31-8959 class of HIV protease inhibitors. Detailed structure-activity studies have now established that the position of ring oxygens, ring size, and stereochemistry are all crucial to potency. Of particular interest, compound 49 with (3S,3aS,6aS)-bis-Thf is the most potent inhibitor (IC50 value 1.8 +/- 0.2 nM; CIC95 value 46 +/- 4 nM) in this series. The X-ray structure of protein-inhibitor complex 49 has provided insight into the ligand-binding site interactions. As it turned out, both oxygens in the bis-Thf ligands are involved in hydrogen-bonding interactions with Asp 29 and Asp 30 NH present in the S2 subsite of HIV-1 protease. Stereoselective routes have been developed to obtain these novel ligands in optically pure form.
Asunto(s)
Furanos , Furanos/síntesis química , Furanos/farmacología , Inhibidores de la Proteasa del VIH/síntesis química , Proteasa del VIH/metabolismo , Secuencia de Aminoácidos , Ácido Aspártico , Sitios de Unión , Cristalografía por Rayos X , Diseño de Fármacos , Furanos/química , Proteasa del VIH/química , Inhibidores de la Proteasa del VIH/química , Inhibidores de la Proteasa del VIH/farmacología , VIH-1/enzimología , Enlace de Hidrógeno , Ligandos , Espectroscopía de Resonancia Magnética , Modelos Moleculares , Estructura Molecular , Rotación Óptica , Estereoisomerismo , Relación Estructura-ActividadRESUMEN
Influenza virus utilizes a unique mechanism for initiating the transcription of viral mRNA. The viral transcriptase ribonucleoprotein complex hydrolyzes host cell transcripts containing the cap 1 structure (m7GpppG(2'-OMe)-) to generate a capped primer for viral mRNA transcription. Basic aspects of this viral endonuclease reaction are elucidated in this study through the use of synthetic, radiolabeled RNA substrates and substrate analogs containing the cap 1 structure. Unlike most ribonucleases, this viral endonuclease is shown to catalyze the hydrolysis of the scissile phosphodiester, resulting in 5'-phosphate- and 3'-hydroxyl-containing fragments. Nevertheless, the 2'-OH adjacent to the released ribosyl 3'-OH is shown to be important for catalysis. In addition, while the endonuclease steady-state turnover rate is measured to be 2 h(-1), phosphodiester bond hydrolysis is not rate-limiting. The direct generation of a free 3'-OH and the subsequent slow release of this product are consistent with the viral need for efficient use of the capped primer in subsequent reactions of the influenza transcriptase complex.
Asunto(s)
Endorribonucleasas/metabolismo , Oligorribonucleótidos/síntesis química , Oligorribonucleótidos/metabolismo , Orthomyxoviridae/enzimología , ARN Mensajero/biosíntesis , ARN Viral/biosíntesis , ARN/metabolismo , Autorradiografía , Secuencia de Bases , Cartilla de ADN , Cinética , Datos de Secuencia Molecular , Oligorribonucleótidos/química , Radioisótopos de Fósforo , ARN/síntesis química , Caperuzas de ARN/metabolismo , Especificidad por Sustrato , Transcripción GenéticaRESUMEN
The quaternary state of the human cytomegalovirus (hCMV) protease has been analyzed in relation to its catalysis of peptide hydrolysis. Based on results obtained from steady state kinetics, size exclusion chromatography, and velocity sedimentation, the hCMV protease exists in a monomer-dimer equilibrium. Dimerization of the protease is enhanced by the presence of glycerol and high concentrations of enzyme. Isolation of monomeric and dimeric species eluted from a size exclusion column, followed by immediate assay, identifies the dimer as the active species. Activity measurements conducted with a range of enzyme concentrations are also consistent with a kinetic model in which only the dimeric hCMV protease is active. Using this model, the dissociation constant of the protease is 6.6 microM in 10% glycerol and 0.55 microM in 20% glycerol at 30 degrees C and pH 7.5.
Asunto(s)
Citomegalovirus/enzimología , Endopeptidasas/química , Endopeptidasas/metabolismo , Conformación Proteica , Serina Endopeptidasas , Secuencia de Aminoácidos , Cromatografía en Gel , Endopeptidasas/biosíntesis , Endopeptidasas/aislamiento & purificación , Glicerol/farmacología , Humanos , Cinética , Sustancias Macromoleculares , Datos de Secuencia Molecular , Peso Molecular , Oligopéptidos/síntesis química , Oligopéptidos/metabolismo , Proteínas Recombinantes/química , Proteínas Recombinantes/aislamiento & purificación , Proteínas Recombinantes/metabolismo , Especificidad por SustratoRESUMEN
The catalytic efficiency of the mature HSV-1 protease has been examined as a function of solvent composition. With the peptide substrate HTYLQASEKFKMWG-amide, the specificity constant (kcat/Km) at pH 7.5 for cleavage is 5.2 M-1 s-1. This value increases to 38 M-1 s-1 when 25% glycerol is present in the reaction mixture. It was found that glycerol activation is but one case of the general phenomenon of HSV-1 protease activation by kosmotropes, or water structure-forming cosolvents. For example, an 860-fold increase in the protease activity (kcat/Km = 4500 M-1 s-1) occurs in the presence of 0.8 M sodium citrate. Similarly, the presence of 0.8 M sodium phosphate activates the catalytic efficiency by 420-fold (kcat/Km = 2200 M-1 s-1). The extent of HSV-1 protease activation by various anions correlates with the Hofmeister series. Both the susceptibility to proteolysis by trypsin and the protein fluorescence spectra of the HSV-1 protease change in the presence of activating solvents, suggesting a conformational change accompanying activation.
Asunto(s)
Endopeptidasas/metabolismo , Herpesvirus Humano 1/enzimología , Serina Endopeptidasas/metabolismo , Proteínas Virales , Secuencia de Aminoácidos , Aniones/farmacología , Endopeptidasas/aislamiento & purificación , Activación Enzimática , Inhibidores Enzimáticos/farmacología , Cinética , Datos de Secuencia Molecular , Nucleótidos/farmacología , Péptidos/química , Proteínas Recombinantes/aislamiento & purificación , Proteínas Recombinantes/metabolismo , Serina Endopeptidasas/aislamiento & purificación , Solventes/farmacología , Espectrometría de Fluorescencia , Especificidad por SustratoRESUMEN
Transoesophageal Doppler echocardiography was performed in 7 Thoroughbred horses anaesthetised with halothane. The procedure was performed on 4 occasions under standard conditions. On one occasion dobutamine hydrochloride was infused at 4 micrograms/kg/min for 20 min. Recordings of aortic blood velocity, obtained using high pulsed repetition frequency Doppler echocardiography (HPRF), were used to derive maximum acceleration (dv/dtmax), maximum velocity (Vmax), left ventricular ejection time (ET), pre-ejection period (PEP), velocity time integral (VTI) and cardiac output (CO). The coefficient of variation and 95% confidence intervals were narrower for the Doppler variables than for those obtained from cardiac catheterisation. For each horse the anaesthetic to anaesthetic repeatability of the Doppler indices of left ventricular function, exceeded that of maximum rate of rise of left ventricular pressure (LVdp/dtmax). The horse to horse variability was significant for heart rates Vmax, dv/dtmax, and VTI. After dobutamine infusion there were significant changes in all measured variables except heart rate, VTI and CO. The % change that occurred exceeded the predicted 95% confidence intervals for single measurements in all significantly affected variables. This suggests Doppler indices of cardiac performance may be useful to assess changes in haemodynamic function. Passage of the probe into the oesophagus was not associated with serious adverse effects. Mild serous nasal discharge was visible for up to 24 h after the horses recovered from anaesthesia. Mild nasal haemorrhage occurred on 5 occasions during probe insertion. It is concluded that transoesophageal Doppler echocardiography provides a minimally invasive, continuous method for monitoring left ventricular systolic performance in anaesthetised horses.