Publications

Although adolescents account for only 0.4% of reported cases of the acquired immunodeficiency syndrome (AIDS) in the United States, they are sexually active and, therefore, at risk of acquiring human immunodeficiency virus (HIV) infection. To address issues of HIV control in adolescents, we developed guidelines that emphasize education and medical care and deemphasize antibody testing. For adolescents known to be infected with HIV, we recommend no restrictions on access to educational or treatment programs except when their health providers recommend such restrictions to protect them from exposure to opportunistic infections. For adolescents of unknown antibody status with a possible previous exposure to HIV, we recommend that as long as the incidence of HIV infection and clinical AIDS remains low, there should be no restrictions on residential placements and no routine antibody testing.

Arachidonic acid metabolites have previously been demonstrated to mediate the airway hyperresponsiveness observed in guinea pigs and dogs after exposure to ozone. Guinea pigs were treated with indomethacin (a cyclooxygenase inhibitor), U-60,257 (piriprost, a 5-lipoxygenase inhibitor), or BW775c (a lipoxygenase and cyclooxygenase inhibitor) and exposed to air or 3 ppm TDI. Airway responsiveness to acetylcholine aerosol was examined 2 h after exposure. In control animals, the provocative concentration of acetylcholine which caused a 200% increase in pulmonary resistance over baseline (PC200) was significantly less (p less than 0.05) after exposure to TDI (8.6 +/- 2.0 mg/ml, geometric mean + geometric SE, n = 10) than after exposure to air (23.9 + 2.5 mg/ml, n = 14). The airway responsiveness to acetylcholine in animals treated with indomethacin or piriprost and exposed to TDI was not different from that of control animals exposed to TDI. Treatment with BW755c enhanced the airway hyperresponsiveness observed in animals exposed to TDI without altering the PC200 of animals exposed to air. The PC200 of animals treated with BW755c and exposed to TDI (2.3 + 0.8 mg/ml, n = 8) was significantly lower than the PC200 of control animals exposed to TDI (p less than 0.025). These results suggest that products of arachidonic acid metabolism are not responsible for TDI-induced airway hyperresponsiveness in guinea pigs. BW755c, however, appears to potentiate the TDI-induced airway hyperresponsiveness to acetylcholine by an as yet unidentified mechanism.

A neutral proteinase, capable of degrading gelatin, has been found in both an active and a latent form in the medium from the culture of rat mesangial cells. The latent form had an Mr of 80,000-100,000 and could be activated with either 4-aminophenylmercuric acetate or prolonged incubation at neutral pH. The active form of the enzyme was extensively purified. The estimated Mr of the purified enzyme on gel filtration was approximately 200,000, indicating that the active enzyme formed aggregates. However, analysis by SDS/polyacrylamide-gel electrophoresis under reducing conditions showed two protein bands, with Mr 68,000 and 66,000. Both proteins were found to contain proteolytic activity when run on SDS/substrate gels. The enzyme was inhibited by EDTA and 1,10-phenanthroline, but not by inhibitors for cysteine, serine or aspartic proteinases. The enzyme did not digest fibronectin, bovine serum albumin, proteoglycan or interstitial collagen. The enzyme degraded pepsin-solubilized placental type V collagen at 31 degrees C, whereas similarly solubilized type IV collagen was only degraded at higher temperatures. In addition, the neutral proteinase degraded native soluble type IV collagen. It also had activity on insoluble type IV collagen of glomerular basement membrane. The above properties suggest that the mesangial neutral proteinase belongs to the gelatinase group of metalloproteinases and that it may play a role in the normal turnover of extracellular glomerular matrix.

Discrete peptide domains within the primary sequence of cell-surface receptor glycoproteins are believed to regulate not only their function but also their targeting to the cell membrane. To identify sequence elements required for intracellular transport and ligand binding by the human Tac interleukin-2 (IL-2) receptor, we prepared expression plasmids encoding a series of artificially mutated or naturally occurring variants of the Tac cDNA. In particular, we sought to further delineate the functional role of the sequences contributed by each of the eight exons that together encode the Tac protein. Deletion of exons 5 through 8 of the receptor had no detectable effect on IL-2 binding or intracellular transport of the Tac protein, and resulted in secreted forms of this IL-2-binding protein. Removal of sequences corresponding to all of exon 4 ablated IL-2 binding activity yet still permitted transport to the cell surface. In contrast, partial deletion of exon 4 sequences resulted in proteins that not only lacked IL-2 binding activity but also were sequestered within the endoplasmic reticulum. Removal of one or both of the N-linked glycosylation sites present in the Tac protein did not impair receptor transport or ligand binding. These results demonstrate that exon 4 of the Tac gene encodes amino acid residues that play an important role in regulating both the intracellular transport and function of this IL-2 receptor.