Seasonal variation of slipped capital femoral epiphysis

To correlate the season of the year with the prevalence of slipped capital femoral epiphysis, we reviewed the cases of 177 patients who had 243 slips during an eleven-year period. We assessed the month when the patient was seen and the implied time of onset of the slip and found a statistically significant variation for both. The average time of onset was mid-June, with a standard deviation of 2.5 months, and was not significantly different for race, sex, or laterality. We attributed the increased incidence of slipped capital femoral epiphysis during the summer to increased physical activity in that season.     

Evaluation of a new enzyme-linked immunosorbent assay test for rotavirus antigen in faeces

A new commercial test for the diagnosis of rotavirus gastroenteritis was assessed. With some modifications it compared favourably with electron microscopy and immunofluorescence.     

Competitive control of the self-renewing T cell repertoire

We develop a mathematical model for the self-renewing part of the T cell repertoire. Assuming that self-renewing T cells have to be stimulated by immunogenic MHC-peptide complexes presented on the surfaces of antigen-presenting cells, we derive a model of T cell growth in which competition for MHC-peptide complexes limits T cell clone sizes and regulates the total number of self-renewing T cells in the animal. We show that for a sufficient diversity and/or degree of cross-reactivity, the total T cell number hardly depends upon the diversity of the T cell repertoire or the diversity of the set of presented peptides. Conversely, for repertoires of lower diversity and/or cross-reactivity, steady-state total T cell numbers may be limited by the diversity of the T cells. This provides a possible explanation for the limited repertoire expansion in some, but not all, mouse T cell re-constitution experiments. We suggest that the competitive interactions described by our model underlie the normal T cells numbers observed in transgenic mice, germ-free mice and various knockout mice.      

Identifying secondary active solute transport in epithelia

This Editorial Review analyzes the adequacy of the strategies that are commonly used to establish whether the active transport of a solute does or does not occur by secondary active transport. First, the energetics of noncoupled (passive) diffusion, primary active transport, secondary active transport (coupled diffusion), and solvent drag are briefly described. Second, the kinetics of noncoupled and coupled diffusion processes are discussed. Third, the special difficulties of identifying secondary active solute transport in epithelia are outline. Several factors are described that may obscure or mimic true coupled diffusion. Last, the use of transport inhibitors for identifying coupled diffusion processes is briefly illustrated. The adequacy of the strategies that have been employed to evaluate the role of luminal membrane Na+-H+ exchange in mediating proximal tubular acidification is particularly emphasized. It is concluded that many of the findings apparently supporting a major contribution of Na+-independent, primary active H+ secretion to the proximal tubular acidification process are not necessarily inconsistent with secondary active H+ secretion via Na+-H+ exchange.     

Pathological and virological features of arenavirus disease in guinea pigs. Comparison of two Pichinde virus strains.

A guinea pig passage-adapted strain of the arena-virus Pichinde (adPIC) is highly virulent in inbred guinea pigs, whereas the related strain PIC3739 is attenuated. Both viruses were macrophage tropic and infected peritoneal, splenic, liver, and alveolar macrophages during experimental Pichinde virus infection. Infection with the virulent strain was associated with unlimited viral replication in the face of exaggerated delayed-type hypersensitivity response, manifested by the macrophage disappearance reaction. Histopathological lesions unique to adPIC-infected guinea pigs included intestinal villus blunting with mucosal infiltration by pyknotic debris-laden macrophages and apoptosis of crypt epithelial cells. Splenic red pulp necrosis was also significantly associated with adPIC infection but not PIC3739 infection. These findings may provide clues to the pathogenesis of a group of poorly understood human viral hemorrhagic fevers.     

An ultrastructural examination of the interaction between macrophages and Cryptococcus neoformans.

The interaction of mononuclear phagocytes with Cryptococcus neoformans was examined in vitro and in vivo using ultrastructural techniques. Immune serum roughens the surface of the yeast and in the first 2 hr, increases the number of organisms attaching to the macrophage surface, as well as the number of contacts between individual yeasts and the phagocyte. Contact is established by means of thin filopodia and cytoplasmic flaps. During the next few days the macrophages increase in size, and, by intimate apposition of their contiguous cell surfaces, a cellular barrier surrounds the now enclosed yeast. These events are accompanied by thinning of fungal capsule, degradation of the enclosed cryptococcus, and the formation of macrophage polykaryons. Electron cytochemical techniques for peroxidase reveal that these multinucleated cells are formed predominantly by the fusion of stimulated macrophages. Destruction of the enclosed yeast probably results from the secretion of various agents by the surrounding cells.