RESUMO
Reverse transcription-PCR (RT-PCR) is a sensitive method for detection of RNA virus nucleic acid sequences in clinical respiratory specimens. Previous studies have focused on RT-PCR for a single virus, but this approach is limited by the inability to establish a specific etiology when the RT-PCR result is negative and by the inability to document simultaneous infections involving more than one virus. The purpose of this study was to apply a panel of RT-PCR protocols for respiratory syncytial virus, parainfluenza virus, and picornaviruses to respiratory specimens from 80 children suspected to have acute viral respiratory tract infections and to correlate RT-PCR results with viral culture results and clinical diagnosis. In comparison with viral culture, the RT-PCR panel had a sensitivity of over 94% and showed evidence of simultaneous infections in a significantly greater proportion of specimens (20.0% versus 3.8%; P < 0.002). For specimens in which no viruses were detected by culture, the proportion of specimens with positive picornavirus RT-PCR results was significantly greater than the proportion of specimens with positive respiratory syncytial virus or parainfluenza virus RT-PCR results (P < 0.001). There were no statistically significant associations between RT-PCR results and clinical diagnosis. In summary, the RT-PCR panel provides an improved approach to obtain new insights into acute viral respiratory tract infections in children.
Assuntos
Infecções por Paramyxoviridae/diagnóstico , Infecções por Picornaviridae/diagnóstico , Reação em Cadeia da Polimerase/métodos , Infecções por Vírus Respiratório Sincicial/diagnóstico , Infecções Respiratórias/diagnóstico , Virologia/métodos , Sequência de Bases , Primers do DNA/genética , DNA Viral/genética , Feminino , Humanos , Lactente , Masculino , Dados de Sequência Molecular , Infecções por Paramyxoviridae/virologia , Picornaviridae/genética , Picornaviridae/isolamento & purificação , Infecções por Picornaviridae/virologia , Reação em Cadeia da Polimerase/estatística & dados numéricos , RNA Viral/genética , RNA Viral/isolamento & purificação , Infecções por Vírus Respiratório Sincicial/virologia , Vírus Sinciciais Respiratórios/genética , Vírus Sinciciais Respiratórios/isolamento & purificação , Infecções Respiratórias/virologia , Respirovirus/genética , Respirovirus/isolamento & purificação , Sensibilidade e Especificidade , Virologia/estatística & dados numéricosRESUMO
Cerebral vascular tone is modulated, at least in part, by the vascular endothelium. This probably results from a balance between the release of the endothelium-derived relaxing factor(s) and the endothelium-derived constricting factor(s) (e.g., endothelin). The time course of the induction and the decay of these mutually antagonizing substances differ considerably. Endothelium-derived relaxing factor is probably involved in rapid changes in vascular tone whereas endothelin may be more important in long-term modulation. We have studied the vasoconstrictor properties of endothelin in human cerebral artery strips. Endothelin typically produced an intense, sustained increae in tone over a dose range similar to that seen with other vasoconstrictor substances such as serotonin and prostaglandin F2 alpha (ED50 = 10(-8) M). The response was resistant to selective antagonists of norephinephrine, serotonin, isoproterenol, histamine, acetycholine, and angiotensin II. Only sodium nitroprusside, verapamil, and a disulfide bond reducing agent (dithiothreitol) inhibited the response. The physiological properties of this response are similar to those of a vasoconstrictor protein found in cerebrospinal fluid from patients with cerebral vasospasm after subarachnoid hemorrhage. The time course of the induction of endothelin production is consistent with the temporal sequence of vasospasm, further supporting the hypothesis that endothelin may be involved in this pathological process.
