The combination of primaquine with clindamycin is effective in both in vitro and in vivo models of Pneumocystis infection. Primaquine alone at concentrations from 10 to 300 ,ug/ml reduced the numbers of organisms in cultures to less than 7% of control. Significant inhibition was observed down to 0.1 ,ug/ml. Clindamycin at 5 ,ug/ml was ineffective alone. Combinations of clindamycin and primaquine in culture at various concentrations were effective, but there was no evidence of true synergy. In rats with established Pneumocystis pneumonia, clindamycin alone at 5 or 225 mg/kg was ineffective. Primaquine alone at 0.5 or 2 mg/kg did not significantly affect the numbers of organisms remaining. The combination of 0.5 mg of primaquine per kg and 225 mg of clindamycin per kg was effective for therapy, lowering the numbers of organisms in the lungs by about 90%. The combination of 2 mg of primaquine per kg and 225 mg of clindamycin per kg was more effective, lowering the numbers of organisms by almost 98%. In the in vivo prophylaxis model, primaquine at 0.1 or 0.2 mg/kg did not prevent the development of Pneumocystis pneumonia in immune-suppressed rats. Clindamycin at 50 mg/kg had a modest effect alone, but at 5 mg/kg all animals became heavily infected. At 0.5 mg/kg, primaquine alone reduced the severity of infection, but seven of eight rats were still infected. In contrast, the combination of 5 mg of clindamycin per kg and 0.5 mg of primaquine per kg prevented infection in 8 of 10 rats; 2 rats had minimal infection. These studies suggest that the combination of clindamycin and primaquine should be tested in therapy or prophylaxis of Pneumocystis infections in humans.Treatment or prophylaxis of pneumonia caused by Pneumocystis carinii in patients with acquired immune deficiency syndrome (AIDS) has been hampered by the lack of effective, nontoxic agents. Pentamidine causes a variety of side effects which may limit therapy, and relapses are frequent (29,34). Trimethoprim with sulfamethoxazole causes a surprisingly high incidence of side effects in AIDS patients, including severe hypersensitivity reactions that limit use for treatment (29,33,34). Other experimental agents have been tested with variable results. Difluoromethylornithine is effective in some patients, but thrombocytopenia may be a limiting toxicity (9, 34). Pyrimethamine with sulfadoxine (Fansidar) or dapsone with trimethoprim may be effective in individual patients, but significant adverse reactions still occur with both combinations (10, 21, 34). Trimetrexate, a lipid-soluble analog of methotrexate, is being investigated (1).In the course of screening antimicrobial agents for potential effectiveness against P. carinii, we have evaluated combinations as well as individual agents. One of the combinations we chose to test was clindamycin with primaquine. This selection was based on the observation by Schmidt (25) that the curative action of primaquine in malaria was enhanced by mirincamycin. Mirincamycin, like clindamycin, is a lincosamide but has not been exte...

Because Pneumocystis carinii is closely related to fungi, drugs useful for treating mycoses have been considered for use in the treatment ofP. carinii pneumonia. Six antifungal imidazole drugs were tested for their activities against P. carinii in a short-term culture screen and in animals. None of the imidazoles tested was effective in inoculated infected rats, and only miconazole showed slight effects in culture at the high concentration of 10 ,ug/ml. Analysis of cell membranes from culture-grown P. carinii showed that ergosterol, the target for this class of antifungal agents, was absent, so that the lack of effect of these agents is rational.Pneumocystis carinii is an important cause of morbidity and mortality in immunocompromised hosts (8). Although formerly thought to be a protozoan, it is now generally agreed that it is more closely related to fungi, but its exact position among the fungi is not clear. Some studies suggest that P. carinii is closely related to Saccharomyces cerevisiae (5, 10), while others have suggested a relationship to the filamentous fungi in the genera Aspergillus (4, 9) and Rhodotorula (11).Since most fungal infections respond to therapy with imidazoles, a role for these compounds for use in the treatment of P. carinii pneumonia has been discussed. However, successful systemic antifungal agents inhibit the synthesis of ergosterol, the sterol common in most fungal cell membranes, and one report suggests that ergosterol is not present in P. carinii (6). Although the lack of clinical evidence for a response of P. carinii pneumonia to amphotericin B or fluconazole used for the treatment of other fungal infections suggests insensitivity of P. carinii to polyene or imidazole antimicrobial agents, direct evaluations of these compounds have been lacking.Six imidazoles were tested in a short-term culture system with human embryonic lung fibroblast cells (WI-38 or MRC-5) with P. carinii from infected rat lung as described previously (1 278-2018. contained four wells without drug and four wells with drug diluent (1.0 and 0.1% dimethyl sulfoxide) that were inoculated with P. carinii; these wells served as positive growth controls. Experiments were discarded if the numbers of organisms in these wells failed to increase more than threefold over 7 days. Plates were incubated in a gaseous mixture of 5% 02-10% C02-85% N2 at 35°C.The number ofP. carinii organisms was counted as described previously (1). Two individuals counted trophozoites, cysts, and cells in 10 oil immersion fields of each slide. Data are expressed as the percentage of the control counts. The development of infection in rats was by inoculation, as described previously (3). Rats from Harlan Sprague-Dawley (Indianapolis, Ind.) colony 202 were virus-free and P. cariniifree when they were shipped from the supplier. Female rats weighing between 120 and 140 g were given dexamethasone at 0.36 mg/kg of body weight in drinking water for 4 days prior to transtracheal inoculation or until lymphocytes were depleted by 50%. An inoculum from...

Trophozoites grown in vitro were shown to undergo binary fission by transmission electron microscopy (TEM). Standard fixation with subsequent embedding in Spurr was employed using 3% glutaraldehyde and 1% osmium tetroxide with 5% sucrose added to both fixatives and 0.1 M cacodylate buffer washes. Trophozoites were grown on WI-38 cells in vitro. Trophozoites were found in various stages of fission. The dividing trophozoite has daughter cells that are rounder than the pleomorphic, non-dividing trophozoites. Tubular forms external to the dividing trophozoites were decreased in number; tubular forms when present were concentrated around the forming septa. Nuclear material was sometimes, but not always, well defined in both daughter cells. There was no concentration of nuclear material at the poles. Vacuoles without membrane were present in the dividing forms. Separate nuclear regions were sometimes found in the dividing trophozoites. These observations suggest that binary fission does occur in culture; however, the significance of binary fission to the life cycle of Pneumocystis carinii (Pc) is not yet clear.

.Trophozoites grown in vitro were shown to undergo binary fission by transmission electron microscopy (TEM). Standard fixation with subsequent embedding in Spun‐ was employed using 3% glularaldehyde and 1% osmium tetroxide with 5% sucrose added to both fixatives and 0.1 M cacodylate buffer washes. Trophozoites were grown on WI‐38 cells in vitro. Trophozoites were found in various stages of fission. The dividing trophozoite has daughter cells that arc rounder than the pleomorphic, non‐dividing trophozoites. Tubular forms external to the dividing trophozoites were decreased in number, tubular forms when present were concentrated around the forming sepia. Nuclear material was sometimes, but not always, well defined in both daughter cells. There was no concentration of nuclear material at the poles. Vacuoles without membrane were present in the dividing forms. Separate nuclear regions were sometimes found in the dividing trophozoites. These observations suggest that binary fission does occur in culture; however, the significance of binary fission to the life cycle of Pneumocystis carinii (Pc) is not yet clear.

This work analyzes Voyager 2 observations on November 2018 and compares them with Voyager 1 data at the vicinity of the heliopause in July-August 2012. We describe the plasma and cosmic-ray variations at the radial distance of $\approx$ 1 astronomical unit (AU) from the heliopause. We use a simple convection-diffusion cosmic-ray modulation model to qualitatively explain the particle observations. We found a thin layer, with a thickness of $\approx$ 0.04 AU where the radial component of the solar wind speed vanished, the galactic cosmic ray intensity rapidly increased to reach its heliosphere boundary level, and low-energy heliospheric ion intensity drooped. We called this layer the "skin of the heliosphere". Plasma data suggest that Voyager 2 crossed the heliopause on November 5, 2018, at the radial distance of 119.03 AU. We apply our analysis to Voyager 1 observations and conclude that similar behavior in solar wind speed could qualitatively explain the GCR counting rate and that the "skin of the heliosphere" maybe a global characteristic along the heliopause.