Sulfide-inhibition of mitochondrial respiration at very low oxygen concentrations.

Our aim was to study the ability of an immortalized cell line (AMJ2-C11) to sustain aerobic cell respiration at decreasing oxygen concentrations under continuous sulfide exposure. We assumed that the rate of elimination of sulfide through the pathway linked to the mitochondrial respiratory chain and therefore operating under aerobic conditions, should decrease with limiting oxygen concentrations. Thus, sulfide's inhibition of cellular respiration would occur faster under continuous sulfide exposure when the oxygen concentration is in the very low range. The experiments were performed with an O2K-oxygraph (Oroboros Instruments) by suspending 0.5-1×10(6) cells in 2 ml of continuously stirred respiration medium at 37 °C and calculating the oxygen flux (JO2) as the negative derivative of the oxygen concentration in the medium. The cells were studied in two different metabolic states, namely under normal physiologic respiration (1) and after uncoupling of mitochondrial respiration (2). Oxygen concentration was controlled by means of a titration-injection pump, resulting in average concentration values of 0.73±0.05 µM, 3.1±0.2 µM, and 6.2±0.2 µM. Simultaneously we injected a 2 mM Na2S solution at a continuous rate of 10 µl/s in order to quantify the titration-time required to reduce the JO2 to 50% of the initial respiratory activity. Under the lowest oxygen concentration this effect was achieved after 3.5 [0.3;3.5] and 11.7 [6.2;21.2]min in the uncoupled and coupled state, respectively. This time was statistically significantly shorter when compared to the intermediate and the highest O2 concentrations tested, which yielded values of 24.6 [15.5;28.1]min (coupled) and 35.9 [27.4;59.2]min (uncoupled), as well as 42.4 [27.5;42.4]min (coupled) and 51.5 [46.4;51.7]min (uncoupled). All data are medians [25%, and 75% percentiles]. Our results confirm that the onset of inhibition of cell respiration by sulfide occurs earlier under a continuous exposure when approaching the anoxic condition. This property may contribute to the physiological role of sulfide as an oxygen sensor.

Correlation of morphologic diagnosis of Pneumocystis carinii with the presence of pneumocystis DNA amplified by the polymerase chain reaction.

We compared the presence of P. carinii in clinical specimens as detected by standard cytomorphologic techniques with amplification of P. carinii-specific DNA by the polymerase chain reaction (PCR). Results correlated in 33 of 37 instances (89%): nine specimens were positive by both PCR and morphology; 24 specimens were negative by both techniques. Two specimens from one patient were obtained 3 days apart. The first specimen was both cytologically and PCR negative, while the second specimen was both cytologically and PCR positive for P. carinii. At least in some instances, therefore, PCR is no more sensitive than morphology, and other factors such as specimen adequacy are more important. Twelve of the 24 negative specimens were from patients with prior histories of P. carinii pneumonia, suggesting that recurrent disease may be from reacquisition of organisms in previously exposed individuals, rather than reactivation of latent organisms. Discrepant results included three morphologically negative specimens that were positive by PCR. It remains to be determined whether the increased sensitivity of PCR in these cases is real or artifactual. One morphologically positive specimen was negative by PCR. Polymerase chain reaction correlates well with cytomorphologic diagnosis of P. carinii pneumonia and may be a valuable diagnostic and epidemiologic tool.

Detection of antibodies to Pneumocystis carinii in bronchoalveolar lavage fluid by immunoreactivity to Pneumocystis carinii within alveoli, granulomas, and disseminated sites.

Although Pneumocystis carinii pneumonia (PCP) is the most common major opportunistic infection in the acquired immunodeficiency syndrome (AIDS), its immunopathogenesis is not fully understood. It is known that anti-pneumocystis antibodies are present in the sera of individuals with and without PCP. In order to determine whether anti-pneumocystis antibodies are also present in bronchoalveolar lavage fluid (BAL), we looked for them, by immunoreactivity with tissue sections of intra-alveolar P. carinii, in the BAL of (a) HIV-seropositive patients with PCP (n = 18); (b) HIV-seropositive patients without PCP (n = 11); and (c) HIV-seronegative patients with nonpneumocystis lung disease (n = 5). BALs from 19 of 29 HIV-seropositive patients were deficient in at least one isotype (13 with PCP, six without PCP), while only one of five HIV-seronegative patients was deficient. Despite the considerable documentation of atypical presentations of disease caused by P. carinii, little is known concerning the mechanisms involved. To determine whether there is any relationship between BAL anti-pneumocystis antibodies and diverse host responses, we studied antibody binding to P. carinii in different settings. IgG antibodies in BAL bound P. carinii within spleen, liver, skin, and muscle, as well as within pulmonary alveoli and granulomas. However, IgA antibodies in BAL bound intraalveolar and disseminated P. carinii but did not bind to P. carinii within pulmonary granulomas.(ABSTRACT TRUNCATED AT 250 WORDS)

In vitro aggregation of macrophages around human-derived Pneumocystis carinii.

Interaction between human monocyte-derived macrophages with human Pneumocystis carinii was examined in this study. Macrophages formed aggregates around P. carinii in the presence of heat-inactivated, but not native serum. This interaction is distinct from phagocytosis and appears to be analogous to granuloma formation.

The role of alpha and beta platelet-derived growth factor receptor in the vascular response to injury in nonhuman primates.

Restenosis remains a significant clinical problem associated with mechanical interventional procedures for arterial revascularization or repair, including coronary angioplasty and stenting. Studies with rodents have established that platelet-derived growth factor (PDGF), a potent chemotactic and mitogenic agent for vascular smooth muscle cells, is a key mediator of lesion formation after vascular injury. To further explore this hypothesis in a more clinically relevant model, neutralizing monoclonal antibodies (mAbs) were used to examine the effect of selective inhibition of alpha or beta PDGF receptor (PDGFR) on neointima formation in nonhuman primates. Carotid arteries were injured by surgical endarterectomy and femoral arteries by balloon catheter dilatation. Immunostaining revealed that both injuries induced cell proliferation and the upregulation of beta PDGFR but not alpha PDGFR. By 7 days after injury, beta PDGFR staining was limited to the luminal region of the media, the small areas of neointima, and the adventitia. Nearly all bromodeoxyuridine-positive cells were found in these regions as well. After 30 days, a concentric neointima that stained strongly for beta PDGFR had formed in the carotid and femoral arteries. Treatment of baboons with anti-beta PDGFR mAb 2A1E2 for 6 days after injury reduced the carotid artery and femoral artery lesion sizes by 37% (P<0.05) and 48% (P<0.005), respectively, when measured at 30 days. Under the same conditions, treatment with anti-alpha PDGFR mAb 2H7C5 had no effect. These findings suggest that PDGF mediates neointima formation through the beta PDGFR, and that antagonism of this pathway may be a promising therapeutic strategy for reducing clinical restenosis.