SUMMARYHuman rotaviruses were capable of efficient multiplication in LLC-MK2 cells when the inoculum was pre-treated with trypsin, centrifuged on to the cell monolayer and the infected cells maintained in a medium containing trypsin. However, not all of the human rotavirus isolates used to infect cells resulted in efficient virus production. The ability of human isolates to multiply in cultured cells was studied by direct observation of virus in the electron microscope, by radioactive labelling with 3H-uridine of the newly synthesized virus and by electron microscopic examination of thin sectioned infected cells. With one of the specimens used (F-6I 7) only 5 to I O % of the cells showed evidence of virus multiplication, with the great majority of the infected cells showing numerous complete (double-capsid) virus particles scattered in the cytoplasm. When cells were inoculated with another human specimen (SIB-I), infected cells were more abundant, reaching a maximum of 6o %; however, a variety of particle types, probably representing different subviral structures or different steps of rotavirus morphogenesis, were commonly observed. The presence of these aberrant or incomplete virus structures may represent a manifestation of the defectiveness of this virus and may explain the difficulties encountered in its serial passage.

The temporal distribution and clinical severity of rotavirus VP7 serotypes 1, 2, 3, and 4 recovered from 427 Venezuelan children with acute gastroenteritis over a period of 11 years were studied. Rotavirus VP7 serotype was established by ELISA serotyping in 298 (69.78%) of the specimens while the serotype of the remaining 129 (30.21%) samples could not be determined. Of the specimens typed, 85 (19.90% of the total) were serotype 1, 43 (10.07%) were serotype 2, 105 (24.59%) were serotype 3, and 65 (15.22%) were serotype 4. Yearly changes in the frequency of individual serotypes were observed. The predominance of a single serotype with minor contribution from others was noted every year. In this study, serotype 1 appears to induce a less severe illness in comparison with serotypes 2, 3, and 4. No apparent association between the proportion of each serotype and the children's age were found.

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We studied gut mucosal perfusion in 24 neonates requiring cardiopulmonary bypass (CPB). Group A patients (n = 12) had obstruction to their aorta such that gut perfusion before operation was dependent on flow through a ductus arteriosus (DA). Group B neonates were of similar age and size and required a similar duration of CPB, but did not have a DA. An orogastric tonometer allowed intermittent calculations of gastric intramucosal pH (pHi), and rectal mucosal perfusion ("flux") was monitored using laser Doppler flowmetry. Measurements of arterial base deficit, and lactate and pyruvate concentrations were made intermittently. Before CPB, mean femoral arterial pressure (MAP) and base deficit in group A were not significantly different from those in group B. However, mean flux before CPB was significantly lower and the lactate/pyruvate (L/P) ratio was significantly higher in group A compared with group B. Mean pHi was below normal (< 7.26) throughout the operative period in group A, although it remained normal (> 7.33) in group B. After corrective surgery, both during warm CPB and after CPB, we found no significant difference in MAP, L/P ratio or base deficit between the groups, but both flux and pHi were significantly lower in group A compared with group B. We conclude that neonates requiring aortic arch surgery may be at particular risk of gut mucosal hypoxia both before and after operation.

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