The infective stages of Leishmania braziliensis, amastigotes and promastigotes subcultured a limited number of times, were agglutinated by Ricinus communis agglutinin and Concanavalin A. These results suggest that terminal ligands similar or identical with alpha-D mannose, alpha-D glucose (specific receptors for Con A), and alpha-D galactose (specific receptor for RCA) are present in the surface membrane of L. braziliensis. Noninfective promastigotes from the same stock, but subcultured approximately 500 times, were not agglutinated by RCA suggesting either the absence of the alpha-D galactose groups in the surface membrane or their presence in a very reduced number. Agglutination with soybean agglutinin, wheat germ agglutinin, or phytohemagglutinin P was not observed in any of the L. braziliensis forms tested. The difference in polysaccharide residues on the surface membrane of L. braziliensis may be related to the different pathogenic properties of the cell.

Leishmania braziliensis (isolate 2903) was naturally resistant to ketoconazole or the bis-triazole D0870, inhibitors of sterol C-14 demethylase, which produced only moderate effects on the proliferation of promastigotes at 10 microM. In contrast, Leishmania mexicana (isolate NR) was extremely susceptible to the azoles, as complete growth arrest and cell lysis were induced by incubation of the parasites with 0.05 microM concentrations of the drugs for 72 h. The opposite response was observed with terbinafine, an inhibitor of squalene epoxidase: L. braziliensis 2903 was three times more susceptible to the drug than L. mexicana NR (MICs of 5 and 15 microM, respectively). However, when the L. braziliensis stock was grown in the presence of 1 microM terbinafine, which by itself produced only marginal (< 10%) effects on growth, it became highly susceptible to the azoles, with an MIC of 0.03 microM. Analysis of cellular free sterols by high-resolution capillary gas chromatography coupled to mass spectrometry showed that 14-methyl sterols can support normal growth of L. braziliensis 2903 but not of L. mexicana NR. On the other hand, the higher susceptibility of the L. braziliensis isolate to terbinafine was correlated with a massive accumulation of squalene in the presence of the allylamine while no significant effects on L. mexicana sterol composition were observed at drug concentrations up to 1 microM. Thus, the > 300-fold increase in the susceptibility of L. braziliensis promastigotes to azoles in the presence of terbinafine was attributed to the combined effect of squalene and the methylated sterol precursors on the physical properties of the cell's membranes, leading to the loss of cell viability. Combination therapy with azoles and terbinafine in the treatment of human L. braziliensis infections deserves further study.

A simple procedure that allowed the extraction and partial purification of a component of 65,000 mol.wt. from the surface of Leishmania braziliensis promastigotes is described. Iodinated cell surface membrane fractions were solubilized using Triton X-100 followed by Nonidet P-40. The macromolecular components were then freed of the detergents by passage of the extracts through a column of DE52 cellulose. The component of 65,000 mol.wt. was eluted from the column with 1 m NaCl. This component in whole parasites was immunoprecipitated by sera from patients with cutaneous, mucocutaneous, and diffuse cutaneous leishmaniasis and kala-azar. None of the major surface determinants reacted with sera from normal individuals with antibovine rabbit serum. The relevance and the possible applications on the immunoprophylaxis of the disease are briefly discussed.

A correlation between the ratio of the cell surface protease activity to phosphatase activity and the complexity of the pattern of cell surface exposed polypeptides of Leishmania promastigotes was demonstrated for various strains grown under similar conditions. The ratio of the cell surface protease activity to acid phosphatase activity was high for L. major and L.b. panamensis and it correlates with the expression of a single polypeptide of 63 KDa on their cell surface. Intermediate and lower ratios of these enzymatic activities relate with more complex radio-iodinated patterns: two main bands in L.b. guyanensis (70 and 58 KDa) and L.b. braziliensis (72 and 60 KDa) and three main bands 65, 50, 27 KDa in all L.m. mexicana strains tested. Evidence is presented that the acid phosphatase located on the L.m. mexicana cell surface is not an artifact due to a secondary absorption of the secreted acid phosphatase from the culture medium. These results confirm the Leishmania antigen cell surface heterogeneity. The implications on the biology of Leishmania and the clinical manifestation of leishmaniasis are discussed.

The effect of tunicamycin (TM) on Leishmania braziliensis promastigotes in culture has been studied. TM at different concentrations (2, 4, 6 micrograms/ml) inhibits promastigote growth as the mean generation time of control cells, 36 hr, is changed to 41, 46 and 55 hr, respectively. Cells remain viable after long exposure to 2 micrograms/ml of TM and can be cultured in the presence of the drug for several generations. Under these conditions cells tend to round up and many "ruffle"-like structures appear at the parasite cell surface. At the ultrastructural level, cell coat disappears and the rough endoplasmic reticulum appears distended. Other structures remain unaltered by the drug treatment. The changes in cell morphology are discussed in relation to changes in cell surface morphology. The possible use of these TM-transformed cells as experimental systems for host-parasite studies is also considered.

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Homogenates of rat brain cortex were fractionated by conventional methods of velocity sedimentation and separated into a microsomal and a washed mitochondrial fraction. By electron microscopy the mitochondrial fraction was shown to be rich in synaptosomes. The mitochondria-synaptosome fraction synthesized protein in vitro by a route that was partially inhibited by cycloheximide and partly by chloramphenicol. The relative effectiveness of the two inhibitors varied greatly with the medium uised. In the mitochondria-synaptosome fraction active 80 S cytoplasmic ribosomes and active 55 S mitochondrial ribosomes were detected; these were also seen in the electron microscope. Mild osmotic shock of the mitochondriasynaptosome fraction followed by velocity sedimentation in sucrose-EDTA allowed isolation ofa mitochondrial fraction free ofsynaptosomes. Protein synthesis in this fraction was entirely inhibited by chloramphenicol, but was completely resistant to cycloheximide both in a medium promoting oxidative phosphorylation and in ATP-generating medium. Ouabain had no inhibitory effect on protein synthesis in a purified mitochondrial preparation. It is concluded that brain-cortex mitochondria synthesize protein entirely on 55 S mitochondrial ribosomes.