Sequence diversity of TT virus in geographically dispersed human populations.

TT virus (TTV) is a newly discovered DNA virus originally classified as a member of the Parvoviridae. TTV is transmitted by blood transfusion where it has been reported to be associated with mild post-transfusion hepatitis. TTV can cause persistent infection, and is widely distributed geographically; we recently reported extremely high prevalences of viraemia in individuals living in tropical countries (e.g. 74% in Papua New Guinea, 83% in Gambia; Prescott & Simmonds, New England Journal of Medicine 339, 776, 1998). In the current study we have compared nucleotide sequences from the N22 region of TTV (222 bases) detected in eight widely dispersed human populations. Some variants of TTV, previously classified as genotypes 1a, 1b and 2, were widely distributed throughout the world, while others, such as a novel subtype of type 1 in Papua New Guinea, were confined to a single geographical area. Five of the 122 sequences obtained in this study (from Gambia, Nigeria, Papua New Guinea, Brazil and Ecuador) could not be classified as types 1, 2 or 3, with the variant from Brazil displaying only 46-50% nucleotide (32-35% amino acid) sequence similarity to other variants. This study provides an indication of the extreme sequence diversity of TTV, a characteristic which is untypical of parvoviruses.

EEG and autonomic responding to verbal, spatial and emotionally arousing tasks: differences among adults, adolescents and inhalant abusers.

The present study investigated the physiological responses of an adolescent inhalant abuse group, an adolescent non-abuse group, and an adult non-abuse group elicited by three types of tasks: verbal, spatial, and emotionally arousing. Each group consisted of 10 male Mexican-American subjects. Bilateral EEG and electrodermal activity, as well as heart rate, were monitored. While exploring for possible heart rate and hemispheric alpha wave differences in response to predominantly verbal and spatial tasks, an attempt was also made to discover if electrodermal responses could be bilaterally differentiated. Another purpose of the study was to explore possible psychophysiological differences between a younger and older group, and between an inhalant abusing group and a non-abuse group, in response to the three types of tasks. Results indicated that attempts to produce task-related EEG hemispheric asymmetry were largely nonsuccessful. Bilateral electrodermal responses were also not greatly differentiated. It was suggested that stronger task manipulations were needed. Significant group differences were found for initial physiological response levels (adults demonstrated higher levels than the two adolescent groups) and for heart rate response to the emotionally arousing task (non-abusing subjects demonstrated greater heart rate acceleration than inhalant abusing subjects). It was suggested that group differences in initial levels occurred due to the adult groups's greater involvement in the experimental situation. Heart rate differences to the emotionally arousing situation were discussed in terms of Zuckerman's sensation seeking hypothesis.