Asunto(s)
Analgesia Epidural/métodos , Analgésicos Opioides/administración & dosificación , Morfina/administración & dosificación , Fracturas de las Costillas/complicaciones , Anciano de 80 o más Años , Preparaciones de Acción Retardada , Humanos , Inyecciones Epidurales , Masculino , Persona de Mediana EdadRESUMEN
We report a case of coronary vasculitis with formation of giant coronary artery aneurysms in a child following meningococcal septicemia. We suggest that coronary vasculitis is a rare complication of meningococcal septicemia that should be included in the list of conditions known to elicit a Kawasaki-like inflammatory response.
Asunto(s)
Aneurisma Coronario/etiología , Infecciones Meningocócicas/complicaciones , Neisseria meningitidis , Sepsis/complicaciones , Arteritis/etiología , Preescolar , Aneurisma Coronario/diagnóstico por imagen , Vasos Coronarios/diagnóstico por imagen , Humanos , Masculino , Síndrome Mucocutáneo Linfonodular/diagnóstico , Sepsis/microbiología , UltrasonografíaRESUMEN
Several major histocompatibility complex class II (MHC II) complexes with known minimal immunogenic peptides have now been solved by X-ray crystallography. Specificity pockets within the MHC II binding groove provide distinct peptide contacts that influence peptide conformation and define the binding register within different allelic MHC II molecules. Altering peptide ligands with respect to the residues that contact the T-cell receptor (TCR) can drastically change the nature of the ensuing immune response. Here, we provide an example of how MHC II (I-A) molecules may indirectly effect TCR contacts with a peptide and drive functionally distinct immune responses. We modeled the same immunogenic 12-amino acid peptide into the binding grooves of two allelic MHC II molecules linked to distinct cytokine responses against the peptide. Surprisingly, the favored conformation of the peptide in each molecule was distinct with respect to the exposure of the N- or C-terminus of the peptide above the MHC II binding groove. T-cell clones derived from each allelic MHC II genotype were found to be allele-restricted with respect to the recognition of these N- vs. C-terminal residues on the bound peptide. Taken together, these data suggest that MHC II alleles may influence T-cell functions by restricting TCR access to specific residues of the I-A-bound peptide. Thus, these data are of significance to diseases that display genetic linkage to specific MHC II alleles, e.g. type 1 diabetes and rheumatoid arthritis.
Asunto(s)
Epítopos/química , Antígenos de Histocompatibilidad Clase II/química , Modelos Moleculares , Oligopéptidos/química , Receptores de Antígenos de Linfocitos T/química , Alelos , Secuencia de Aminoácidos , Animales , Enfermedades Autoinmunes/genética , Enfermedades Autoinmunes/inmunología , Sitios de Unión , Linfocitos T CD4-Positivos/inmunología , Células Cultivadas , Epítopos/inmunología , Femenino , Genes MHC Clase II , Antígenos de Histocompatibilidad Clase II/genética , Antígenos de Histocompatibilidad Clase II/inmunología , Células L , Ratones , Datos de Secuencia Molecular , Oligopéptidos/inmunología , Unión Proteica , Conformación Proteica , Receptores de Antígenos de Linfocitos T/inmunología , Subgrupos de Linfocitos T/inmunología , Células TH1/inmunología , Células Th2/inmunología , TransfecciónAsunto(s)
Escarabajos/enzimología , Luciferasas/análisis , Mediciones Luminiscentes , Adenosina Trifosfato/análisis , Adenosina Trifosfato/metabolismo , Animales , Coenzima A/farmacología , Luciferina de Luciérnaga/metabolismo , Concentración de Iones de Hidrógeno , Cinética , Luz , Nucleótidos/farmacología , Fotometría/instrumentación , TemperaturaAsunto(s)
Guanosina Monofosfato/análisis , Mediciones Luminiscentes , Fotometría/métodos , Adenosina Trifosfato/análisis , Adenosina Trifosfato/metabolismo , Animales , Tampones (Química) , Enzimas , Nucleótidos de Guanina/metabolismo , Guanosina Difosfato/metabolismo , Guanosina Monofosfato/metabolismo , Guanosina Monofosfato/normas , Guanosina Trifosfato/metabolismo , Humanos , Indicadores y Reactivos , Luciferasas , Fotometría/instrumentación , Estándares de Referencia , AguaAsunto(s)
Adenosina Monofosfato/análisis , Adenosina Monofosfato/metabolismo , Mediciones Luminiscentes , Nucleótidos de Adenina/análisis , Adenosina Monofosfato/aislamiento & purificación , Adenosina Trifosfato/metabolismo , Animales , Tampones (Química) , Metabolismo Energético , Enzimas , Indicadores y Reactivos , Luciferasas , Fotometría/instrumentación , Soluciones , AguaRESUMEN
Adaptation to bed rest or space flight is accompanied by an impaired ability to exercise in an upright position. We hypothesized that a daily, 30-min bout of intense, interval exercise in upright posture or supine against lower body negative pressure (LBNP) would maintain upright exercise heart rate and respiratory responses after bed rest. Twenty-four men (31 +/- 3 yr) underwent 5 d of 6 degree head-down tilt: eight performed no exercise (CON), eight performed upright treadmill exercise (UPex), and eight performed supine treadmill exercise against LBNP at -51.3 +/- 0.4 mm Hg (LBNPex). Submaximal treadmill exercise responses (56, 74, and 85% of VO2peak) were measured pre- and post-bed rest. In CON, submaximal heart rate, respiratory exchange ratio, and ventilation were significantly greater (P < or = 0.05) after bed rest. In UPex and LBNPex, submaximal exercise responses were similar pre- and post-bed rest. Our results indicate that a daily 30-min bout of intense, interval upright exercise training or supine exercise training against LBNP is sufficient to maintain upright exercise responses after 5 d of bed rest. These results may have important implications for the development of exercise countermeasures during space flight.
Asunto(s)
Reposo en Cama , Ejercicio Físico/fisiología , Gravitación , Presión Negativa de la Región Corporal Inferior , Vuelo Espacial , Adulto , Fenómenos Biomecánicos , Prueba de Esfuerzo , Frecuencia Cardíaca , Humanos , Masculino , Postura , Pruebas de Función RespiratoriaRESUMEN
Firefly luciferase utilizes only ATP and a few closely related nucleotides as substrates for the formation of luciferyl adenylate which is an intermediate in the bioluminescent reaction sequence that oxidizes firefly luciferin. The enzyme shows two different time courses of light production depending on ATP concentration used: a flash with high concentrations of ATP (> 8 microM) or a fairly constant production of light with lower concentrations of ATP (< 1 microM). Many nucleotides, nucleotide-containing substances and other compounds, when added either prior to or 1 min after the addition of ATP, change the time course of light production. When added before ATP, these compounds yield a reaction mixture in which light production is fairly constant (at the level characteristic of the flash observed with that ATP concentration). When the compounds are added after ATP addition, light production is markedly stimulated and the higher rate of light production is maintained for several minutes. There is an increase in quanta of light produced per luciferase dimer from 1 to 5/min with the addition of any of several nucleotide analogues. These results are consistent with a stimulated release of the inhibitory product oxyluciferin, allowing turnover of the enzyme. This enzyme turnover permits more light output at high ATP concentrations, thus enhancing the sensitivity of enzyme determination.
Asunto(s)
Nucleótidos de Adenina/farmacología , Adenosina Trifosfato/análisis , Adenosina/farmacología , Luciferasas , Nucleótidos/farmacología , Adenosina/análogos & derivados , Adenosina Trifosfato/análogos & derivados , Adenosina Trifosfato/farmacología , Animales , Escarabajos/enzimología , Cinética , Luciferasas/metabolismo , Mediciones LuminiscentesRESUMEN
The role of self-peptides in shaping the T cell receptor (TCR) repertoire remains to be established. While TCR reactive to certain self-peptides are thought to be depleted in the thymus, the selection of TCR specificity for foreign peptide reactivity appears to require recognition of self-peptide(s) bound to the groove of thymic major histocompatibility complex (MHC) molecules. This dichotomy suggests that different TCR affinities, accessory signals, and/or different sets of self-peptides dictate the eventual fate of any given TCR-bearing clone. Recently, it has been established for several T cell epitopes that derivatives with substitutions in TCR-contact residues can antagonize the proliferation of T cell clones against the wild-type peptide antigen. Moreover, these altered peptide ligands have demonstrated activity in the positive selection of thymocytes with TCR reactive to the wild-type peptide antigen. We have investigated the specificity of T cell antagonism with step-wise substitution of self-amino acids into each nonconserved position of a 12-amino-acid foreign peptide antigen. Our data demonstrate that the ability to antagonize proliferation without competition for MHC binding is unique to the exact self-derivative, where all five of the self-substitutions are inserted. These properties may specifically allow certain self-peptides to downregulate T cell activation to the foreign ligand and/or provide a source of stimulation for immunologic memory.
Asunto(s)
Autoantígenos/inmunología , Colágeno/inmunología , Antígenos de Histocompatibilidad Clase II/inmunología , Epítopos Inmunodominantes/inmunología , Fragmentos de Péptidos/inmunología , Receptores de Antígenos de Linfocitos T alfa-beta/inmunología , Autotolerancia/inmunología , Linfocitos T Colaboradores-Inductores/inmunología , Secuencia de Aminoácidos , Animales , Presentación de Antígeno , Apoptosis , Células Cultivadas , Supresión Clonal , Colágeno/química , Colágeno/genética , Antígenos H-2/inmunología , Antígenos de Histocompatibilidad Clase II/genética , Humanos , Inmunización , Epítopos Inmunodominantes/química , Ligandos , Activación de Linfocitos , Ratones , Ratones Endogámicos A , Ratones Endogámicos C57BL , Datos de Secuencia Molecular , Fragmentos de Péptidos/química , Especificidad de la EspecieRESUMEN
Light production by firefly luciferase is limited by product release resulting in flash kinetics. Several compounds (CoA, PPi, and nucleotides) transform the flash-form of light production into continuous light production. The sulfhydryl group of CoA is required; however, since nucleotides are also active, at least two mechanisms (sites) must exist.
Asunto(s)
Nucleótidos de Adenina/química , Coenzima A/química , Luciferasas/metabolismo , Compuestos de Sulfhidrilo/química , Animales , Escarabajos/enzimología , Ditiotreitol , Activación Enzimática , Luciferasas/química , Mediciones LuminiscentesRESUMEN
The selection and administration of neuromuscular blocking (NMB) drugs in intensive care unit (ICU) patients remain controversial. We compared the dose-response and recovery pharmacodynamics of a new intermediate-acting NMB drug, cisatracurium besylate, to the intermediate-acting NMB drug, vecuronium (VEC), in a prospective, randomized, double-blind, multicenter study in critically ill adults. After informed consent, 58 mechanically ventilated ICU patients from five medical centers were randomized to receive either cisatracurium or VEC. Fifty-four of the 58 patients received NMB drugs before entering this study but demonstrated at least partial recovery (> or = one twitch) in the train-of-four (TOF) response before initiation of the NMB study drug. NMB drug infusion was titrated by peripheral nerve stimulation to maintain at least one twitch in the TOF response. NMB drugs were infused for 1-5 days. After discontinuation of NMB drug infusion, recovery of neuromuscular transmission was monitored with an accelerometer. NMB drug infusion for 28 cisatracurium patients averaged 2.6 +/- 0.2 (mean +/- SEM) micrograms.kg-1.min-1 with a mean duration of 80 +/- 7 h. After discontinuing cisatracurium administration, recovery to 70% TOF ratio averaged 68 +/- 13 min. The mean infusion rate for 30 VEC patients was 0.9 +/- 0.1 micrograms.kg-1.min-1 with a mean duration of 66 +/- 12 h. Neuromuscular recovery after VEC averaged 387 +/- 163 min, which was significantly longer (P = 0.02) than that after cisatracurium. Prolonged recovery of neuromuscular function after discontinuation of NMB drug infusion (identified by the primary investigator at each medical center) was reported in two cisatracurium patients and 13 VEC patients (P = 0.002), and occurred despite the routine use of neuromuscular twitch monitoring. Seven VEC and one cisatracurium patients died during the infusion of study drug or within 48 h after discontinuation of the NMB drug infusion. In summary, we found recovery of neuromuscular function after discontinuation of NMB drug infusion in ICU patients is significantly faster with cisatracurium than with VEC. In addition, routine neuromuscular monitoring was not sufficient to eliminate prolonged recovery and myopathy in ICU patients.
Asunto(s)
Atracurio/administración & dosificación , Cuidados Críticos , Bromuro de Vecuronio/administración & dosificación , Adulto , Anciano , Anciano de 80 o más Años , Atracurio/farmacología , Enfermedad Crítica , Relación Dosis-Respuesta a Droga , Método Doble Ciego , Estimulación Eléctrica , Femenino , Humanos , Infusiones Intravenosas , Masculino , Persona de Mediana Edad , Monitoreo Fisiológico , Unión Neuromuscular/efectos de los fármacos , Estudios Prospectivos , Respiración Artificial , Estereoisomerismo , Transmisión Sináptica/efectos de los fármacos , Nervio Cubital/efectos de los fármacos , Bromuro de Vecuronio/farmacologíaRESUMEN
Addition of periodate-oxidized ATP (oATP) to firefly luciferase-containing reaction mixtures enhanced light production when the reaction mixture contained > approximately 8 microM ATP. The time course of light production was changed from a flash pattern to a constant light output during incubations of < approximately 10 min. During longer incubation, firefly luciferase was inactivated in a concentration-dependent fashion by oATP. Firefly luciferase has two different time courses of light production that depend on ATP concentration (DeLuca and McElroy, Biochem. Biophys. Res. Commun., 123, 764, 1984). The enhancement of light production occurred only when higher ATP concentrations (> 8 microM) were used. There is little effect of oATP on firefly luciferase activity at low ATP concentrations (< 2 microM) which gave steady production of light. ATP did not antagonize the inactivation of firefly luciferase by oATP. When the oATP was chemically reduced with sodium borohydride (giving or ATP), there was no inactivation of firefly luciferase on incubation. When or ATP was used in a short incubation the enhancement of light production and time course change were the same as those observed with oATP. The corresponding AMP and adenosine compounds (o and or) were slightly inhibitory to firefly luciferase activity. ADP was without effect but both oADP and or ADP enhanced light production. Of these periodate-oxidized ADP, AMP, and adenosine derivatives only oADP inactivated firefly luciferase. The activating effect can be explained by a change in the conformation of the enzyme-product complex so that the product is released faster. In addition there is an inactivation of the enzyme by certain periodate-oxidized nucleotides during longer incubations.
Asunto(s)
Adenosina Trifosfato/análogos & derivados , Luciferasas/metabolismo , Nucleótidos de Adenina/farmacología , Adenosina/análogos & derivados , Adenosina/farmacología , Adenosina Trifosfato/metabolismo , Adenosina Trifosfato/farmacología , Marcadores de Afinidad/farmacología , Animales , Escarabajos/enzimología , Activación Enzimática , Cinética , Luz , Mediciones Luminiscentes , Factores de TiempoRESUMEN
A bioluminescence procedure for the determination of the guanylates has been optimized to allow measurement of 0.1 pmol amounts. Modifications of the Karl procedure include the use of purified firefly luciferase and nucleoside diphosphate kinase instead of a crude extract of firefly tails, the use of Tricine buffer instead of the inhibitory arsenate buffer, and optimization of the amounts of reagents and incubation times for each of the partial reactions. In the determination of GMP, background values varied widely with different lots of bovine guanylate kinase. Careful selection of a suitable lot of bovine brain guanylate kinase was essential for determination of lower amounts of guanylates. This establishes that selection of guanylate kinase must be based on experimental determination and not reported adenylate kinase activity. The wide variation in background was not eliminated by the inclusion of adenylate kinase inhibitors.
Asunto(s)
Adenilato Quinasa/análisis , Nucleótidos de Guanina/análisis , Guanosina Monofosfato/análisis , Nucleósido-Fosfato Quinasa/análisis , Adenilato Quinasa/metabolismo , Animales , Bovinos , Escarabajos/enzimología , Guanilato-Quinasas , Indicadores y Reactivos , Cinética , Luciferasas , Mediciones Luminiscentes , Microquímica , Nucleósido-Difosfato Quinasa , Nucleósido-Fosfato Quinasa/metabolismo , Sensibilidad y Especificidad , Espectrofotometría UltravioletaRESUMEN
Shuttle astronauts currently drink approximately a quart of water with eight salt tablets before reentry to restore lost body fluid and thereby reduce the likelihood of cardiovascular instability and syncope during reentry and after landing. However, the saline loading countermeasure is not entirely effective in restoring orthostatic tolerance to preflight levels. We tested the hypothesis that the effectiveness of this countermeasure could be improved with the use of a vasopressin analog, 1-deamino-8-D-arginine vasopressin (dDAVP). The rationale for this approach is that reducing urine formation with exogenous vasopressin should increase the magnitude and duration of the vascular volume expansion produced by the saline load, and in so doing improve orthostatic tolerance during reentry and postflight.
Asunto(s)
Desamino Arginina Vasopresina/farmacología , Inclinación de Cabeza/fisiología , Hipotensión Ortostática/prevención & control , Presión Negativa de la Región Corporal Inferior , Fármacos Renales/farmacología , Cloruro de Sodio/farmacología , Adulto , Reposo en Cama , Desamino Arginina Vasopresina/uso terapéutico , Fluidoterapia , Humanos , Volumen Plasmático/efectos de los fármacos , Fármacos Renales/uso terapéutico , Cloruro de Sodio/uso terapéutico , Orina/fisiología , Medidas contra la IngravidezRESUMEN
The temporal pattern of light production by firefly luciferase depends on the ATP concentration. With low concentrations of ATP a constant production of light occurred while at high concentrations of ATP (greater than 10 microM) there was a flash of light followed by a decline in light production. This time course of light production with high ATP concentrations was changed from the flash pattern to a pattern with a constant production of light by several cytidine nucleotides. CTP, CDP, dCTP, dCDP, dideoxyCTP, periodate-oxidized CTP and CDP, and the etheno derivatives of CTP and CDP produced that change. CMP, cytidine, CDP-glycerol, CDP-glucose, CDP-ethanolamine, and benzoylbenzoylCTP either were inhibitory to firefly luciferase or were not effective in changing the flash time course. Coenzyme A and related compounds also changed the time course of light production. The changes in time course produced by either cytidine nucleotides or CoA were inhibited by desulfoCoA. These compounds apparently enhanced light production by promoting the dissociation of the inhibitory product, oxidized luciferin, from the enzyme. When the activating compounds were used with high concentrations of ATP, the sensitivity of assay for firefly luciferase was increased. This increased sensitivity is important when using the firefly luciferase gene as a reporter.
Asunto(s)
Nucleótidos de Citosina/metabolismo , Luciferasas/metabolismo , Nucleótidos de Adenina/metabolismo , Adenosina Trifosfato/metabolismo , Animales , Coenzima A/química , Coenzima A/metabolismo , Nucleótidos de Citosina/química , Cinética , Luciferasas/antagonistas & inhibidores , Ortópteros/enzimología , Oxidación-Reducción , Ácido Peryódico/química , Relación Estructura-ActividadRESUMEN
Commercially available crystalline native and recombinant firefly luciferases were compared. The two types of luciferase had indistinguishable responses to variation in ATP and luciferin concentrations and to omission of reaction components. The time courses of light production, the responses to nucleotide analogues, and the stability of the enzymes under several storage conditions were identical. The native enzyme had a slightly greater specific activity and was more sensitive to trypsin degradation. These differences are probably attributable to differences in conformation.
Asunto(s)
Luciferasas/metabolismo , Proteínas Recombinantes/metabolismo , Adenosina Trifosfato/metabolismo , Animales , Escarabajos , Cinética , Luz , Nucleótidos/metabolismo , Especificidad por SustratoRESUMEN
Sixteen ASA class II or III male patients (aged, 52 to 66 years) undergoing elective cardioversion were randomly assigned to receive either thiopental or etomidate according to an observer-blinded, parallel study design. The appropriate drug was administered in 2-mL aliquots every 15 seconds until the patient no longer responded to verbal commands, at which time cardioversion was attempted. The total dose for induction was 0.22 +/- 0.2 mg/kg and 3.2 +/- 0.4 mg/kg for etomidate and thiopental, respectively. The cardiorespiratory data after induction were evaluated for maximal percent change from baseline. The baseline heart rate was 106 +/- 6 beats/min and 98 +/- 8 beats/min for the etomidate and thiopental groups, respectively (mean +/- SEM). The heart rate decreased 5% after induction with etomidate and increased 7% with thiopental (P less than 0.05). The baseline mean arterial pressure (MAP) was 96 +/- 3 mm Hg and 105 +/- 11 mm Hg for the etomidate and thiopental groups, respectively (mean +/- SEM). The MAP decreased 4% with etomidate and 3% with thiopental. Respiratory rate was significantly increased by 22% after etomidate compared with a 22% decrease in respiratory rate with thiopental (P less than 0.05). Seven of eight patients in the thiopental group required only one countershock, whereas four of eight patients in the etomidate group required only one shock. One patient in each group could not be successfully cardioverted. Recovery time and clinical side effects were similar between groups except for mild myoclonus in the etomidate group. Titration to effect of either etomidate or thiopental provided satisfactory anesthesia for elective cardioversion in hemodynamically stable patients.(ABSTRACT TRUNCATED AT 250 WORDS)