RESUMEN
A worker provided a routine faecal sample for plutonium and americium analysis. In the course of this analysis 500 mBq of (228)Th was discovered. There seemed no credible occupational route for intake of thorium. Further investigation revealed that the worker consumed approximately 25 g d(-1) of nuts, including Brazil nuts. A sample of these nuts was analysed and found to contain activities of (228)Th in sufficient quantity to account for the faecal activity. However, follow-up urine samples taken from the worker showed 0.6-0.7 mBq of (228)Th. The intake of (228)Th via nuts is insufficient to account for this activity in urine. However, it is likely that the intake of (228)Th was accompanied by similar activity of the parent (228)Ra, and biokinetic calculations show that decay of (228)Ra in vivo would produce sufficient (228)Th to account for the observed urine activity.
Asunto(s)
Bertholletia/química , Ingestión de Alimentos , Heces/química , Contaminación Radiactiva de Alimentos/análisis , Torio/orina , Adulto , Carga Corporal (Radioterapia) , Humanos , Masculino , Tasa de Depuración Metabólica , Efectividad Biológica Relativa , Torio/análisisRESUMEN
The family Picornaviridae includes several viruses of great economic and medical importance. Poliovirus replicates in the human digestive tract, causing disease that may range in severity from a mild infection to a fatal paralysis. The human rhinovirus is the most important etiologic agent of the common cold in adults and children. Foot-and-mouth disease virus (FMDV) causes one of the most economically important diseases in cattle. These viruses have in common a capsid structure composed of 60 copies of four different proteins, VP1 to VP4, and their 3D structures show similar general features. In this study we describe the differences in stability against high pressure and cold denaturation of these viruses. Both poliovirus and rhinovirus are stable to high pressure at room temperature, because pressures up to 2.4 kbar are not enough to promote viral disassembly and inactivation. Within the same pressure range, FMDV particles are dramatically affected by pressure, with a loss of infectivity of more than 4 log units observed. The dissociation of polio and rhino viruses can be observed only under pressure (2.4 kbar) at low temperatures in the presence of subdenaturing concentrations of urea (1-2 M). The pressure and low temperature data reveal clear differences in stability among the three picornaviruses, FMDV being the most sensitive, polio being the most resistant, and rhino having intermediate stability. Whereas rhino and poliovirus differ little in stability (less than 10 kcal/mol at 0 degrees C), the difference in free energy between these two viruses and FMDV was remarkable (more than 200 kcal/mol of particle). These differences are crucial to understanding the different factors that control the assembly and disassembly of the virus particles during their life cycle. The inactivation of these viruses by pressure (combined or not with low temperature) has potential as a method for producing vaccines.
Asunto(s)
Cápside/química , Picornaviridae/química , Adulto , Animales , Aphthovirus/química , Fenómenos Biofísicos , Biofisica , Bovinos , Línea Celular , Niño , Frío , Células HeLa , Humanos , Modelos Moleculares , Picornaviridae/patogenicidad , Picornaviridae/fisiología , Poliovirus/química , Presión , Conformación Proteica , Desnaturalización Proteica , Rhinovirus/química , Termodinámica , Vacunas Virales/aislamiento & purificaciónRESUMEN
Following the introduction of A2/Hong Kong/68 influenza virus into 2 different susceptible populations residing in Thailand and the Panama Canal Zone, epidemic disease occurred within approximately 1 month. The establishment and transmission of the virus, and the disease it caused, were studied in detail. The rates of progression and extent of overt epidemic disease and the proportions of overt to subclinical infection in the 2 areas were different. In Korat Royal Thai Air Force Base, only 8% of US servicemen became ill, although 13% of them were infected. The epidemic progressed slowly, so that no more than 1.5% of the population were ill at any one time during the 3 months of its recognized presence. In contrast, in the Canal Zone the clinical attack rate approached 50%, and subclinical infection occurred in 5% or less of the population during a 6-week period when absenteeism from schools and work was quite obvious. Factors such as immunization status of the populations and virulence of virus seemed not to be primarily responsible for the differences. Rather, the latter appear to be related to differences in environmental circumstances, with crowding contributing to the higher disease incidence in the Canal Zone.The data show that this variant A2 virus may produce different epidemiological patterns of disease in tropical areas, similar to those observed in temperate zones.