Acute and persistant effects of smoking on the baroreceptor function.

Recent studies showed that to smoke four cigarettes within one hour impairs baroreflex sensitivity in humans. In the present study, these effects were qualified more precisely from blood pressure and heart rate records by a sequence analysis and by Fourier analysis of Finapres-registrations. The Mayer waves of the heart rate PDS (power density spectrum), partially representing sympathetic activity, increased during smoking (83.7 +/- 1.0 AU to 89.5 +/- 1.1 AU, P < or = 0.05) and decreased after smoking (86 +/- 1.0 AU, P < or = 0.05). They did, however, not reach baseline levels again within 30 min. Probably due to this, mean arterial blood pressure (64.3 +/- 1.3 mmHg vs. 76.9 +/- 1.3 mmHg, P < 0.05) and heart rate (71.8 +/- 1.4 min(-1) vs. 82.9 +/- 1.4 min(-1), P < 0.05) increased unequivocally after smoking. On the other hand, baroreflex sensitivity decreased dramatically from 15.4 +/- 1 to 11.2 +/- 0.6 ms mmHg(-1) (P < 0.05). This finding was associated with an increased heart rate variability after smoking (6 +/- 0.5 min(-1) vs. 9.2 +/- 1 min(-1)) Thus, the present study provides evidence that chronic tobacco (nicotine)-abuse causes pathologic alterations of the baroreflex control. In synergism with other processes like elevated catecholamine blood levels, these alterations may contribute to the higher risk of cardiovascular diseases.

High-signal lesions in the midbrain on T1-weighted MRI in an HIV-infected patient.

In addition to opportunistic infections, neoplasms or cerebrovascular complications, metabolic encephalopathies are a classical cause of diffuse brain dysfunction in HIV infection and are frequent in the terminal stage. We report an HIV-infected patient with symmetrical, focally increased signal in the midbrain on proton density-and T1-weighted MRI without corresponding high signal on T2-weighted images or on CT. While the precise nature and cause of this uncommon finding is not fully understood, the available evidence suggests that these lesions might represent a novel metabolic encephalopathy.