RESUMEN

With the worlds population becoming increasingly focused on coastal locations there is a need to better understand the interactions between anthropogenic emissions and marine atmospheres. Herein an atmospheric chemistry-transport model is used to assess the impacts of sea-spray chemistry on the particle composition in and downwind of a coastal city--Vancouver, British Columbia. It is shown that the model can reasonably represent the average features of the gas phase and particle climate relative to in situ measurements. It is further demonstrated that reactions in/on sea-spray affect the entire particle ensemble and particularly the size distribution of particle nitrate, but that the importance of these heterogeneous reactions is critically dependent on both the initial vertical profile of sea spray and the sea-spray source functions. The results emphasize the need for improved understanding of sea spray production and dispersion and further that model analyses of air quality in coastal cities conducted without inclusion of sea-spray interactions may yield mis-leading results in terms of emission sensitivities of particle composition and concentrations.

Asunto(s)

Contaminantes Atmosféricos/análisis , Modelos Químicos , Agua de Mar , Colombia Británica , Ciudades , Monitoreo del Ambiente , Nitratos/análisis , Ácido Nítrico/análisis , Ozono/análisis , Tamaño de la Partícula , Compuestos de Amonio Cuaternario/análisis , Sulfatos/análisis , Dióxido de Azufre/análisis , Viento

RESUMEN

BACKGROUND: Cell transduction with multiple genes offers opportunities to investigate specific gene interactions on cell function. Detection of multiple transduced genes in hematopoietic cells requires strategies to combine measurements of gene expression with phenotypic cell discriminants. We describe simultaneous flow cytometric detection of two green fluorescent protein (GFP) variants in immunophenotypically defined human hematopoietic subpopulations using only a minor physical adjustment to a standard FACSCalibur. METHODS: The accuracy and sensitivity of enhanced GFP (EGFP) and enhanced yellow fluorescent protein (EYFP) detection in mixtures of transduced and nontransduced PG13 packaging cells were evaluated by flow cytometry. Retroviral vectors encoding EGFP or EYFP were used to transduce CD34(+) hematopoietic cells derived from umbilical cord blood. The transduction efficiency into subpopulations of hematopoietic cells was measured using multivariate flow cytometry. RESULTS: A bicistronic retroviral vector containing the EGFP and puromycin N-acetyltransferase (pac) genes afforded brighter EGFP signals in transduced cells than a retroviral vector encoding a pac-EGFP fusion protein. The sensitivity of detecting EGFP and EYFP-expressing cells among a background of nonexpressing cells was 0.01% and 0.05%, respectively. EGFP or EYFP was expressed in up to 95% of CD34(+) DR(-) or CD34(+) 38(-) subpopulations in cord blood 48 h posttransduction. Simultaneous transduction with EGFP and EYFP viral supernatants (1:1 mixture) led to coexpression of both GFP variants in 15% of CD34(+) DR(-) and 20% of CD34(+) 38(-) cells. CONCLUSIONS: These results demonstrate simultaneous detection of EGFP and EYFP in immunophenotypically discriminated human hematopoietic cells. This technique will be useful to quantify transduction of multiple retroviral constructs in discriminated subpopulations.

Asunto(s)

Citometría de Flujo/métodos , Células Madre Hematopoyéticas/química , Células Madre Hematopoyéticas/citología , Indicadores y Reactivos/análisis , Proteínas Luminiscentes/análisis , Proteínas de la Membrana/análisis , Animales , Proteínas Bacterianas/análisis , Proteínas Bacterianas/genética , Senescencia Celular/fisiología , Sangre Fetal/citología , Regulación del Desarrollo de la Expresión Génica , Regulación Viral de la Expresión Génica , Genes Reporteros , Vectores Genéticos , Proteínas Fluorescentes Verdes , Células Madre Hematopoyéticas/fisiología , Humanos , Indicadores y Reactivos/metabolismo , Proteínas Luminiscentes/genética , Mamíferos , Análisis Multivariante , Fenotipo , Regiones Promotoras Genéticas/fisiología , Retroviridae/genética , Sensibilidad y Especificidad , Activación Transcripcional/fisiología , Transducción Genética

RESUMEN

The apparent dissociation constants for 32 phosphodiester and 5 phosphorothioate antisense oligodeoxyribonucleotides (ODN) targeted to murine tumor necrosis factor-alpha (mTNF-alpha) mRNA were determined using a gel-shift binding assay. In this assay, radiolabeled ODN were hybridized in solution to a structured mRNA transcript generated in vitro. Free ODN was resolved from bound ODN on a two-phase discontinuous polyacrylamide gel. Excision of gel slices containing free ODN or bound ODN, followed by Cerenkov counting of the slices, was used to prepare apparent binding isotherms for each ODN. Apparent dissociation constants for the anti-mTNF-alpha ODN varied from > 100 microM to 0.4 nM. Slight differences in RNA target site position resulted in significant differences in apparent affinity, particularly for shorter (12-mer) ODN. This binding assay provides an empirical means for selecting ODN sequences possessing high affinity for a target RNA and lends itself to a high throughput assay in which all possible antisense sequences of a given length can be evaluated to obtain the better binders for use in cell culture or in vivo.

Asunto(s)

Oligonucleótidos Antisentido/química , ARN Mensajero/química , Tionucleótidos/química , Factor de Necrosis Tumoral alfa/genética , Electroforesis en Gel de Poliacrilamida , Hibridación de Ácido Nucleico

RESUMEN

Nucleic acids are increasingly being considered for therapeutic uses, either to interfere with the function of specific nucleic acids or to bind specific proteins. Three types of nucleic acid drugs are discussed in this review: aptamers, compounds which bind specific proteins; triplex forming (antigene) compounds; which bind double stranded DNA; and ribozymes (catalytic RNA), which bind and cleave RNA targets. The binding of aptamers to protein may involve specific sequence recognition, although this is not always the case. The interaction of triplex forming oligonucleotides or ribozymes with their targets always involves specific sequence recognition and hybridization. Early optimism concerning the possibility of designing drugs without a priori knowledge of the structure of the target (except a nucleotide sequence) has been tempered by the finding that target structure has a dramatic effect upon the hybridization potential of the nucleic acid drug. Other obstacles to the creation of effective nucleic acid drugs are their relative high molecular weight (> 3300) and their sensitivity to degradation. The molecular weight of these compounds has created a significant delivery problem which needs to be solved if nucleic acid drugs are to become effective therapies.

Asunto(s)

ADN/metabolismo , Marcación de Gen , Ácidos Nucleicos/metabolismo , ARN Catalítico/metabolismo , Animales , Secuencia de Bases , Sistemas de Liberación de Medicamentos , Humanos , Datos de Secuencia Molecular , Unión Proteica

RESUMEN

STUDY OBJECTIVE: To evaluate two methods of gastrointestinal decontamination, low-volume whole bowel irrigation (WBI) and activated charcoal, for their ability to prevent absorption of salicylate. DESIGN: Randomized, two-phase crossover study. SETTING: A clinical research unit in a university-based teaching hospital. PATIENTS: Six healthy, volunteer men. INTERVENTIONS: Subjects were assigned to receive 3000 ml WBI or syrup of ipecac 30 ml followed by activated charcoal 50 g in sorbitol, and were crossed over to the other treatment phase after 1 week. All treatments began 30 minutes after ingestion of 3.25 g aspirin. Urine was collected over 24 hours for analysis of total urinary excretion of salicylate. Serial blood samples were collected for salicylate determination and were subjected to pharmacokinetic analysis. MEASUREMENTS AND MAIN RESULTS: Mean +/- SD recovery of salicylate were WBI 48.6 +/- 5.4% and ipecac-charcoal 37.0 +/- 2.6% from urine (p < 0.01). CONCLUSION: Ipecac-charcoal produced a significantly lower salicylate absorption (peak concentration, AUC) than WBI (p < 0.01) and thus was superior to low-volume WBI.

Asunto(s)

Carbón Orgánico/farmacología , Absorción Intestinal , Intestinos , Ipeca/farmacología , Salicilatos/farmacocinética , Irrigación Terapéutica/métodos , Adulto , Humanos , Masculino , Intoxicación/terapia

RESUMEN

Antisense oligonucleotides may prove useful tools to elucidate the biological functions of cytokines and to address regulatory control of cytokine expression. The functional activity of cytokines generally is determined by biological assays, and a standard biological assay for TNF activity measures the cytotoxic effect of TNF on actinomycin D-sensitized L929 cells (Matthews and Neale, 1987). We observed that phosphorothioate and phosphodiester oligonucleotides, at concentrations > 100 nM in supernatants tested in this bioassay, prevented TNF-induced lysis of L929 cells. This "protective" effect was due to an interaction of the single-stranded oligonucleotides with actinomycin D as demonstrated by UV spectra of an actinomycin D-oligonucleotide solution. Substitution of cycloheximide for actinomycin D in the L929 assay eliminated the protective effect of the oligonucleotide. Our results reinforce the importance of controlling for nonspecific effects of oligonucleotides, particularly when a functional assay for protein activity is used to screen for antisense-mediated reductions in target protein expression.

Asunto(s)

Supervivencia Celular/efectos de los fármacos , Dactinomicina/metabolismo , Oligonucleótidos Antisentido/metabolismo , Tionucleótidos/metabolismo , Factor de Necrosis Tumoral alfa/farmacología , Animales , Secuencia de Bases , Bioensayo , Línea Celular , Ratones , Datos de Secuencia Molecular , Oligonucleótidos Antisentido/farmacología , Proteínas Recombinantes/toxicidad , Espectrofotometría Ultravioleta , Tionucleótidos/farmacología , Factor de Necrosis Tumoral alfa/análisis

RESUMEN

Antisense oligonucleotides (ASOs) are designed to bind to a specific mRNA and selectively suppress its translation. To facilitate selection of optimal ASO targets, we have developed three thermodynamic indices to evaluate putative structural complexes important in ASO action. These indices are: a secondary structure score (Sscore), which estimates the strength of local mRNA secondary structures at the ASO target site; a duplex score (Dscore), which estimates the delta Gformation for the ASO:mRNA target sequence duplex; and a competition score (Cscore), which is the difference between the Dscore and the Sscore. We also present two histograms to graphically display these indices from different regions of the mRNA. The indices are compared to the inhibition reported in five studies of ASO-mediated suppression of gene expression. The Dscore is the most consistent predictor of ASO efficacy in four of the five studies (r2 from 0.44 to 0.99), while the results of the fifth study could not be predicted by any thermodynamic or physical index. Thus the Dscores and their histogram may prove useful in selection of ASO targets.

Asunto(s)

Conformación de Ácido Nucleico , Oligonucleótidos Antisentido/metabolismo , ARN Mensajero/metabolismo , Algoritmos , Secuencia de Bases , Moléculas de Adhesión Celular/genética , Línea Celular , Genes myc/genética , Globinas/genética , Humanos , Molécula 1 de Adhesión Intercelular , Datos de Secuencia Molecular , Método de Montecarlo , Oligonucleótidos Antisentido/genética , ARN Mensajero/genética , Temperatura , Tetrahidrofolato Deshidrogenasa/genética

RESUMEN

We measured CSF and serum concentrations of monoamines and monoamine metabolites in normal control subjects and in patients with partial epilepsy between and less than 2 h after complex partial seizures (CPS) or secondarily generalized tonic-clonic seizures (SGTCs). After SGTCs, concentrations of norepinephrine in CSF were significantly higher (p less than 0.05) than interictal concentrations, concentrations after PSs, and concentrations in control subjects. Serum epinephrine levels also were significantly higher after SGTCs than interictal and control subjects' levels. CSF HVA levels were significantly higher after PSs than interictal or control subjects' levels. CSF concentrations of norepinephrine and its intraneuronal metabolite, dihydroxyphenylglycol, were highly correlated, both interictally and following SGTCs, whereas correlations between serum and CSF levels of these catechols generally were not statistically significant. The results indicate that seizures are associated with release of catecholamines in the central nervous system.

Asunto(s)

Catecolaminas/metabolismo , Dihidroxifenilalanina/metabolismo , Epilepsia/metabolismo , Ácido 3,4-Dihidroxifenilacético/sangre , Ácido 3,4-Dihidroxifenilacético/líquido cefalorraquídeo , Ácido 3,4-Dihidroxifenilacético/metabolismo , Adolescente , Adulto , Catecolaminas/sangre , Catecolaminas/líquido cefalorraquídeo , Niño , Dihidroxifenilalanina/sangre , Dihidroxifenilalanina/líquido cefalorraquídeo , Epilepsias Parciales/sangre , Epilepsias Parciales/líquido cefalorraquídeo , Epilepsias Parciales/metabolismo , Epilepsia/sangre , Epilepsia/líquido cefalorraquídeo , Epilepsia Generalizada/sangre , Epilepsia Generalizada/líquido cefalorraquídeo , Epilepsia Generalizada/metabolismo , Epilepsia Tónico-Clónica/sangre , Epilepsia Tónico-Clónica/líquido cefalorraquídeo , Epilepsia Tónico-Clónica/metabolismo , Femenino , Humanos , Masculino , Metoxihidroxifenilglicol/análogos & derivados , Metoxihidroxifenilglicol/sangre , Metoxihidroxifenilglicol/líquido cefalorraquídeo , Metoxihidroxifenilglicol/metabolismo , Norepinefrina/sangre , Norepinefrina/líquido cefalorraquídeo , Norepinefrina/metabolismo

RESUMEN

The career of Richard J. Stull, II, president and chief executive officer of North Broward Hospital in Fort Lauderdale, FL, reflects the solid grounding he received, literally starting on his father's knee. Dick's career is unusual from another perspective; he moved through the ranks to a distinguished career in one location. A young man still, he speaks of looking back after the next 15 years and saying, "I laid out the vision, plotted the course and stayed to make it happen." We need more leaders with a long vision and the commitment to stay and make things happen.

Asunto(s)

Administradores de Hospital/psicología , Hospitales Públicos/organización & administración , Perfil Laboral , Liderazgo , Sistemas Multiinstitucionales/organización & administración , Florida , Hospitales con más de 500 Camas , Humanos , Objetivos Organizacionales

RESUMEN

The development of computer-aided instructional (CAI) systems suffers from a lack of a cohesive theory of learning--how do students acquire and store knowledge? From studies of computer systems that learn and tutor, we can infer generic activities that appear to be integral parts of the learning process, such as aggregation, clustering, characterization, and storage for later retrieval. Learning is faster and more efficient if the goal of a task is made explicit. Hints should be given with the correct timing in relation to an objective so that students can advance in their own problem-solving strategies with the prerequisites in mind. The general form of a rule should usually be taught first, followed by exceptions and special instances. We review theories of learning associated with CAI that illustrate the classification of different types of knowledge. Rule-based (if-then) knowledge forms are represented in these theories, as are declarative and causal knowledge structures. Extracting the common themes from different classifications of knowledge may help us create better CAI.

Asunto(s)

Instrucción por Computador , Aprendizaje , Modelos Psicológicos , Inteligencia Artificial , Simulación por Computador , Enseñanza/métodos

RESUMEN

Tumor necrosis factor (TNF), a peptide produced by macrophages in response to endotoxin, has been implicated as a mediator of septic shock. This study examined the effects of injections of recombinant (r) human TNF on circulating levels of metabolic substrates and hormones in conscious, unrestrained rats and the effects of TNF on cortisol secretion from human adrenocortical cells in vitro. Sublethal doses of rTNF--doses that did not produce hemodynamic changes in previous work--produced rapid (1 hour), significant increases in blood levels of glucose, lactate, and triglycerides and decreases in plasma levels of branched chain amino acids. Plasma levels of glucagon, corticosterone, ACTH, norepinephrine, and dihydroxyphenylglycol were also increased significantly. Incubation of adrenocortical cells with either 0.15 or 1.5 micrograms of rTNF increased cortisol secretion to the same extent as did 10(-10) mol/L ACTH. Administration of TNF produces a variety of metabolic and neuroendocrine effects including stimulation of anterior pituitary, adrenal cortical, and pancreatic secretion, and sympathoneural activation. These changes, and the in vitro results, are consistent with the view that immune cells can interact with endocrine cells through release of TNF.

Asunto(s)

Aminoácidos/sangre , Hormonas/sangre , Factor de Necrosis Tumoral alfa/farmacología , Hormona Adrenocorticotrópica/sangre , Animales , Glucemia/metabolismo , Corticosterona/sangre , Epinefrina/sangre , Glucagón/sangre , Insulina/sangre , Lactatos/sangre , Masculino , Norepinefrina/sangre , Ratas , Ratas Endogámicas F344 , Proteínas Recombinantes/farmacología , Valores de Referencia , Triglicéridos/sangre

RESUMEN

L-659,066 is a new alpha 2-adrenoceptor antagonist which does not enter the central nervous system after systemic administration and therefore can be used to examine effects of blockade of peripheral alpha 2-receptors on hemodynamics and plasma levels of catechols. After i.v. administration to conscious rats, L-659,066 produced dose-related, small decreases in mean arterial pressure (MAP) and large increases in heart rate (HR), arterial plasma levels of norepinephrine (NE), and levels of the intraneuronal NE metabolite, dihydroxyphenylglycol (DHPG). After administration of L-659,066, HR, but not MAP, was strongly correlated with NE levels (r = 0.93, P less than 0.001). Levels of DHPG and dihydroxyphenylalanine (DOPA) also were strongly correlated with NE levels (r = 098 and r = 0.71). After comparison with responses during hypotension induced by the vasodilator, nitroprusside, the results indicated that L-659,066 increases sympathetically mediated NE release and catecholamine turnover due to inhibition of presynaptic alpha 2-receptors as well as due to reflexive sympathetic activation related to blockade of alpha 2-receptors on arterial smooth muscle cells.

Asunto(s)

Agonistas alfa-Adrenérgicos/farmacología , Catecoles/sangre , Hemodinámica/efectos de los fármacos , Quinolizinas/farmacología , Ácido 3,4-Dihidroxifenilacético/sangre , Animales , Presión Sanguínea/efectos de los fármacos , Dihidroxifenilalanina/sangre , Frecuencia Cardíaca/efectos de los fármacos , Masculino , Metoxihidroxifenilglicol/análogos & derivados , Metoxihidroxifenilglicol/sangre , Nitroprusiato/farmacología , Norepinefrina/sangre , Ratas , Ratas Endogámicas

RESUMEN

Patients with neurogenic orthostatic hypotension can have deficits in sympathetic neural function at any of several levels of the sympathetic neuraxis. We determined whether patterns of plasma levels of dopa, norepinephrine, dihydroxyphenylglycol, and dihydroxyphenylacetic acid would distinguish patients with orthostatic hypotension associated with multiple system atrophy, pure autonomic failure, or deficiency of dopamine-beta-hydroxylase. Plasma levels of catechols were normal in most patients with multiple system atrophy, consistent with relatively intact peripheral sympathetic neurons; in contrast, most patients with pure autonomic failure had decreased levels of all four catechols, consistent with degenerative loss of sympathetic nerve endings. Patients with deficiency of dopamine-beta-hydroxylase had increased levels of dopa and dihydroxyphenylacetic acid and markedly decreased levels of norepinephrine and dihydroxyphenylglycol, suggesting compensatory increases in sympathetic nerve activity in the absence of norepinephrine biosynthesis. Subgroups of patients with pure autonomic failure or multiple system atrophy had low levels of norepinephrine with normal levels of dopa, dihydroxyphenylglycol, and dihydroxyphenylacetic acid, consistent with normal catecholamine biosynthesis and decreased postganglionic sympathetic nerve traffic or decreased exocytotic release from sympathetic nerve endings. The results demonstrate the value of examining patterns of plasma levels of catechols to elucidate mechanisms of neurogenic orthostatic hypotension.

Asunto(s)

Catecolaminas/sangre , Hipotensión Ortostática/metabolismo , Enfermedades del Sistema Nervioso/complicaciones , Sistema Nervioso Simpático/fisiopatología , Ácido 3,4-Dihidroxifenilacético/sangre , Adulto , Dihidroxifenilalanina/sangre , Humanos , Hipotensión Ortostática/etiología , Metoxihidroxifenilglicol/sangre , Persona de Mediana Edad , Enfermedades del Sistema Nervioso/metabolismo , Norepinefrina/sangre , Sistema Nervioso Simpático/metabolismo

RESUMEN

The present study evaluated the hypothesis that increased plasma levels of epinephrine (EPI) stimulate immunoreactive beta-endorphin (i beta END) secretion in humans experiencing a mild stress. The stressor consisted of intraoral injections of a local anesthetic solution (with or without EPI) just before the surgical extraction of impacted third molars in 26 awake unsedated patients. The EPI group experienced a 30-fold increase in plasma EPI levels by 2 min after injection; these concentrations were physiologically active, as evidenced by increased pulse rate and systolic blood pressure. However, compared to a no EPI control group the EPI group had a significantly reduced i beta END response to the stressor, as evaluated by comparison of plasma levels at individual time points, maximal increases in plasma i beta END levels, and areas under the time-response curve. Whereas there was no association between plasma levels of EPI and i beta END in the EPI group (r = 0.119; P = NS), EPI and i beta END levels were strongly related in the no EPI group (r = 0.82; P less than 0.001). These results do not support the hypothesis of a stimulatory effect for EPI on i beta END release and, instead, suggest that an inhibitory relationship may exist in humans experiencing stress. The association between EPI and i beta END responses observed in the control group during this form of stress appears to be due to activation of a common central neural element.

Asunto(s)

Epinefrina/farmacología , Estrés Psicológico/fisiopatología , betaendorfina/metabolismo , Anestésicos Locales , Presión Sanguínea/efectos de los fármacos , Ensayos Clínicos como Asunto , Método Doble Ciego , Epinefrina/sangre , Femenino , Frecuencia Cardíaca/efectos de los fármacos , Humanos , Cinética , Masculino , Norepinefrina/sangre , Pulso Arterial/efectos de los fármacos , Extracción Dental , betaendorfina/sangre

RESUMEN

Many authors of software providing computer-aided instruction (CAI) have no background in educational theories. This paper reviews teaching theories and ways in which instructional principles can be applied to CAI. While the lecture form of teaching has often been maligned, there are techniques for enhancing lectures that can also apply to CAI. Effective communication methods, both verbal and audiovisual, are as important in computer modules as they are in face-to-face teaching. The quality of interactive questioning and the nature and timing of feedback are critical to the success of instruction by computer. Appropriate feedback can improve retention, as can the use of proper distractors in multiple-choice questions. We present steps for developing a CAI learning module based on established principles of teaching and learning, as well as proper identification of educational goals.

Asunto(s)

Instrucción por Computador/métodos , Enseñanza/métodos , Programas Informáticos

RESUMEN

Levels of homovanillic acid (HVA), dihydroxyphenylacetic acid (DOPAC) and dihydroxyphenylglycol (DHPG) in plasma and the striatium were measured after inhibition of monoamine oxidase type A (MAO-A) by clorgyline (4 mg/kg i.p.), MAO-B by (-)deprenyl (1 mg/kg i.p.), both MAO-A and MAO-B by nialamide (75 mg/kg i.p.) or peripheral neuronal MAO by debrisoquin (40 mg/kg i.p.). Levels of HVA in plasma decreased by about 60% after single doses of nialamide or clorgyline, by about 80% after repeated doses of nialamide, by about 40% after a single dose of debrisoquin and by about 50% after repeated doses of debrisoquin. The administration of clorgyline, nialamide or debrisoquin significantly decreased concentrations of DOPAC and DHPG in plasma, whereas (-)deprenyl did not affect levels of DHPG or HVA. None of the MAO inhibitors produced more than about 80% depression of levels of any of the deaminated metabolites. The results suggest that most of the HVA in plasma is derived from deamination of DA by MAO-A in peripheral neurons; that DOPAC in plasma is derived from cells outside the central nervous system; that DHPG in plasma is derived virtually exclusively from the metabolism of norepinephrine in sympathetic nerve endings and that residual levels of HVA after treatment with debrisoquin provide an improved but limited indication of central dopaminergic activity.

Asunto(s)

Catecoles/metabolismo , Cuerpo Estriado/metabolismo , Ácido Homovanílico/metabolismo , Inhibidores de la Monoaminooxidasa/farmacología , Ácido 3,4-Dihidroxifenilacético/sangre , Ácido 3,4-Dihidroxifenilacético/metabolismo , Animales , Catecoles/sangre , Clorgilina/farmacología , Cuerpo Estriado/efectos de los fármacos , Debrisoquina/farmacología , Ácido Homovanílico/sangre , Masculino , Metoxihidroxifenilglicol/análogos & derivados , Metoxihidroxifenilglicol/sangre , Nialamida/farmacología , Norepinefrina/metabolismo , Ratas , Ratas Endogámicas , Selegilina/farmacología

RESUMEN

Relationships between changes in levels of catechols and directly recorded sympathetic nerve activity were examined using simultaneous measurements of renal sympathetic nerve activity and arterial and renal venous concentrations of norepinephrine (NE), dihydroxyphenylalanine (dopa), and dihyroxyphenylglycol (DHPG) during reflexive alterations in renal sympathetic nerve activity in anesthetized, adrenal-demedullated rats. Nitroprusside infusion increased renal sympathetic nerve activity by 90%, arterial levels of dopa by 96%, NE by 326%, and DHPG by 141%. Phenylephrine infusion increased arterial DHPG levels by 81% and decreased renal sympathetic nerve activity by 37% and NE levels by 26%; arterial dopa levels were unchanged. Ganglionic blockade by chlorisondamine (with concomitant phenylephrine infusion to maintain MAP) decreased renal sympathetic nerve activity by 65% and NE concentrations by 37%; arterial dopa concentrations were unchanged, and DHPG concentrations increased by 60%. Proportionate responses of arterial levels of NE were strongly related to proportionate changes in renal sympathetic nerve activity. Clearance of DHPG from arterial plasma was prolonged by phenylephrine-induced hypertension and by nitroprusside-induced hypotension. The results suggest that changes in arterial NE levels reflect changes in sympathetic activity; changes in dopa levels reflect changes in catecholamine biosynthesis; and changes in DHPG levels depend on reuptake of released NE and on hemodynamic factors affecting DHPG clearance.

Asunto(s)

Catecoles/sangre , Reflejo/fisiología , Sistema Nervioso Simpático/fisiología , Animales , Clorisondamina/farmacología , Dihidroxifenilalanina/sangre , Hemodinámica , Riñón/inervación , Metoxihidroxifenilglicol/análogos & derivados , Metoxihidroxifenilglicol/sangre , Nitroprusiato/farmacología , Norepinefrina/sangre , Fenilefrina/farmacología , Ratas , Ratas Endogámicas

RESUMEN

1. Urinary excretion of dopamine (DA) increases during dietary salt loading. The majority of urinary DA is derived from circulating dihydroxyphenylalanine (dopa). Whether the increase in urinary DA excretion during salt loading results from increased efficiency of uptake of dopa by proximal tubular cells of the kidney, facilitation of intracellular conversion of dopa to DA, or increased delivery of dopa to tubular uptake sites, has been unknown. 2. In 10 inpatient normal volunteers on a constant diet, daily excretion of dopa and DA was assessed during normal sodium intake (109 mmol/day) for 1 week, low sodium intake (9 mmol/day) for 1 week and high sodium intake (249 mmol/day) for 1 week. 3. Urinary DA excretion exceeded urinary dopa excretion by about tenfold, and the excretion of both DA and dopa increased by about twofold between the low and high salt diets, with similar proportionate changes. Plasma dopa was unchanged by dietary salt manipulation. 4. The results indicate that increases in urinary DA excretion during dietary salt loading can be accounted for by increased delivery of dopa to sites of uptake by proximal tubular cells. Since dopa is released into the bloodstream by sympathetic nerve endings and by the brain, and since interference with decarboxylation of dopa attenuates natriuretic responses, dopa may function indirectly as a neurohormone involved in homoeostatic regulation of sodium balance.

Asunto(s)

Dihidroxifenilalanina/orina , Dopamina/orina , Sodio en la Dieta/administración & dosificación , Adulto , Dihidroxifenilalanina/sangre , Dopamina/sangre , Humanos , Metoxihidroxifenilglicol/análogos & derivados , Metoxihidroxifenilglicol/sangre

RESUMEN

We examined the uptake and release of norepinephrine in the cardiac circulation and other regional vascular beds in 11 patients with hypertrophic cardiomyopathy (HCM) and in 10 control subjects during simultaneous infusion of tracer-labeled norepinephrine and isoproterenol. Cardiac neuronal uptake of norepinephrine was assessed by comparing regional removal of tracer-labeled norepinephrine with that of tracer-labeled isoproterenol (which is not a substrate for neuronal uptake) and by the relation between production of dihydroxyphenylglycol (DHPG), an exclusively intraneuronal metabolite of norepinephrine, and regional spillover of norepinephrine. Cardiac extraction of norepinephrine averaged 59 +/- 17% in the patients with HCM, significantly less than in the control subjects (79 +/- 13%, p less than 0.05), whereas cardiac extraction of isoproterenol was similar in the two groups (13 +/- 23% versus 13 +/- 14%), indicating that neuronal uptake of norepinephrine was decreased in the patients with HCM. The cardiac arteriovenous difference in norepinephrine was significantly larger in the patients with HCM than in the control subjects (73 +/- 77 versus 13 +/- 50 pg/ml, p less than 0.05), as was the product of the arteriovenous difference in norepinephrine and coronary blood flow (7.3 +/- 7.3 versus 0.8 +/- 3.0 ng/min, p less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Asunto(s)

Cardiomiopatía Hipertrófica/metabolismo , Glicoles/biosíntesis , Metoxihidroxifenilglicol/biosíntesis , Miocardio/metabolismo , Norepinefrina/farmacocinética , Adulto , Cardiomiopatía Hipertrófica/etiología , Femenino , Humanos , Isoproterenol/farmacocinética , Masculino , Metoxihidroxifenilglicol/análogos & derivados , Persona de Mediana Edad , Neuronas/metabolismo , Sistema Nervioso Simpático/fisiopatología , Tritio

RESUMEN

Although plasma levels of L-dopa are derived substantially from catecholamine-synthesizing tissues, melanocytes--which produce L-dopa as part of the melanin synthetic cascade--also may be a source of circulating L-dopa. We compared plasma L-dopa levels in albino subjects and in Caucasian and Black normal volunteers and patients with essential hypertension. DOPA levels were similar among the subject groups. Among Caucasian normal volunteers, L-dopa levels were negatively correlated with subject age (r = -0.30, P less than 0.05), whereas norepinephrine levels tended to increase with subject age (r = 0.25, 0.05 less than P less than 0.10), so that the L-dopa:norepinephrine ratio was highly negatively correlated with subject age (r = -0.50, P less than 0.01). Skin pigmentation does not contribute importantly to plasma L-dopa levels in humans. In contrast with levels of norepinephrine, L-dopa levels appear to decrease during normal aging.

Asunto(s)

Envejecimiento/metabolismo , Levodopa/sangre , Pigmentación de la Piel , Adolescente , Adulto , Anciano , Envejecimiento/etnología , Población Negra , Humanos , Persona de Mediana Edad , Norepinefrina/fisiología , Población Blanca