[Show abstract][Hide abstract] ABSTRACT: Angiotensin II (AII) regulation of renin production by the juxtaglomerular (JG) cells of the kidney is commonly thought to occur through a direct feedback mechanism. However, recent evidence suggests that other cells in the vicinity may indirectly mediate AII's effect on renin production. Therefore we investigated whether an in vitro model of JG cells (As4.1) could have intercellular communication with endothelial or smooth muscle cells, which are in proximity to JG cells in vivo. 6-carboxyfluorescein was introduced to individual bovine aortic endothelial cells in co-culture with As4.1 cells. Coupling was observed 84% of the time at resting membrane potential and was attenuated by membrane depolarization or octanol (1 mM). Calcein green transfer between human aortic smooth muscle and As4.1 cells occurred 82% of the time and was inhibited by octanol. Expression of connexin 37, 40, 43, and 45 were detected in As4.1 cells using RT-PCR. Stimulation of As4.1 cells by AII failed to alter [Ca(2+)](i) or renin mRNA levels. These findings support the existence of gap junctions between renin producing cells and other cell types of the JG region. Moreover the lack of effect by AII suggest that feedback regulation of renin by AII may be due in part to intercellular communication with cells in proximity to JG cells.
[Show abstract][Hide abstract] ABSTRACT: With the advent of HAART, there has been a decline in the incidence of AIDS-defining illnesses. Despite this decline, we increasingly see patients who present with AIDS-defining illnesses similar to those seen during the early days of the HIV epidemic because patients are having difficulty in tolerating or adhering to their HAART regimens. In general, patients today are different: some are receiving prophylaxis to prevent HIV-related infections and many have experienced a more prolonged duration of immunosuppression resulting from intermittent use of HAART. We present 4 patients with neurologic symptoms and focal brain lesions and review and compare the diagnosis and treatment of toxoplasmic encephalitis with that of primary CNS lymphoma.