Tyrianthinic acids from Ipomoea tyrianthina and their antimycobacterial activity, cytotoxicity, and effects on the central nervous system

Four new partially acylated tetrasaccharides of 11-hydroxyhexadecanoic acid (1-4) were isolated from a methanolic extract of Ipomoea tyrianthina. The structures of these compounds were elucidated by spectroscopic and chemical methods. The resin glycoside composition of I. tyrianthina varied with the location of growth in Mexico. Compounds 1-4 showed antimycobacterial activity, were cytotoxic against the KB cell line, and, in a mouse model, exhibited potentiation of hypnosis induced by pentobarbital, protected against seizures induced by pentylenetetrazole, and released GABA and glutamic acid.

Therapeutic effect of a novel oxazolidinone, DA-7867, in BALB/c mice infected with Nocardia brasiliensis

Background

Mycetoma is a chronic infectious disease of tropical and subtropical countries. It is produced by true fungi and actinobacteria. In México, Nocardia brasiliensis is the main causative agent of mycetoma, producing about 86% of the cases; the gold standard for the therapy of mycetoma by N. brasiliensis is the use of sulfonamides which give a 70% cure rate. The addition of amikacin to this regime increases to 95% the cure rate; however, the patients have to be monitored for creatinine clearance and audiometry studies because of the potential development of side effects. Because of that it is important to search for new active compounds. In the present work, we evaluated the in vivo effect of DA-7867, an experimental oxazolidinone, on the development of experimental mycetomas by N. brasiliensis in BALB/c mice.

Methodology/Principal Findings

In order to determine the optimal dose utilized to apply to the animals, we first determined by HPLC the plasma levels using several concentrations of the compounds. Based on these results, we used 10 and 25 mg/kg subcutaneously every 24 hr; DA-7867 was also supplied in the drinking water at a calculated dose of 25 mg/kg. As a control we utilized linezolid at 25 mg/kg, a compound active in murine and human infections, three times a day. The mice were infected in the right footpad with a young culture of N. brasiliensis HUJEG-1, and one week later we started the application of the antimicrobials for six more weeks. After that we compared the development of lesions in the groups injected with saline solution or with the antimicrobials; the results were analyzed by the variance ANOVA test. DA-7867 was able to reduce the production of lesions at 25 mg/kg, when given either subcutaneously or in the drinking water.

Conclusions/Significance

The experimental oxazolidinone DA-7867 is active in vivo against N. brasiliensis, which opens the possibility of using this drug once it is accepted for human application. Since oxazolidinones seem to be active against a wide spectrum of actinobacteria, it is possible they could be used in human cases of mycetoma by other actinomycetales, such as Streptomyces somaliensis, highly prevalent in Sudan, or Actinomadura madurae and A. pelletieri, which are commonly observed in Africa and India.

Actinomycetoma is an infectious disease of tropical and subtropical regions produced by actinobacteria of the genera Nocardia, Streptomyces, and Actinomadura. Therapeutic alternatives are scarce and include trimethoprim-sulfamethoxazole, diaminodiphenylsulfone, amoxicillin-clavulanate, imipenem, and amikacin. Oxazolidinones are a new class of antimicrobials with a completely different cellular target; the first compound in the market, linezolid, was introduced in the year 2000. It is active against many species of Nocardia and other aerobic actinomycetes; however, the long-term application in human subjects produces side effects including peripheral neuropathy and mielossupression. Therefore, it is important to screen other oxazolidinones with higher activity and less toxicity. In the present work, we tested DA-7867, a new oxazolidinone, in an experimental mouse model. The drug is active in vivo and decreases the production of lesions using only one dose a day in contrast to linezolid, which needs to be injected three times a day. Although it was tested on N. brasiliensis, it can possibly be active (once it is accepted for its use in humans) against Actinomadura spp and Streptomyces spp, which are frequently found in places of Africa and India where actinomycetoma is also an important consult in dermatology.

[Association of pulmonar tuberculosis with HLA system antigens in Northeastern Mexico]

BACKGROUND

Genetic susceptibility to pulmonary tuberculosis (PTb) has been associated with the HLA (Antigens of the Human Leukocytes) system of the MHC (Major Histocompatibility Complex), mainly with HLA-DR and-DQ antigens. Based on this assumption we carried out a case control study to determine the association of PTb with the HLA-DR and-DQ antigens among a sample of patients attending a medical unit belonging to the Mexican Social Security System (IMSS).

METHODS

HLA system phenotypes from cases (n=50) and controls (n=417), were defined serologically using a complement dependent microlymphocytotoxic assay. B lymphocytes were obtained using immunobeads. The allele and haplotype frequencies were determined using the Arlequin version 3.01 computer software. Relative risk (RR) was calculated with the Epimax Table Calculator.

RESULTS

The alelles HLA-DR11(5), -DR16(2) and -DQ7(3) and haplotypes /DR11(5)-DQ7(3), /DR14(6)-DQS(1) and /DR16(2)-DQ7(3) had a higher frequency in cases than in controls (RR>1, p<0.05). The HLA-DR17(3) and DQ8(3) alelles and /DR17(3)-DQ2 and /DR4-DQ8(3) haplotypes had a higher frequency among controls than among cases (RR<1, p<.05).

CONCLUSIONS

These results indicate an association between PTb with the HLA-DR and -DQ antigens in a Mexican sample. Our results are similar to those found in the international literature.

Activity of intracellular phospholipase A1 and A2 in Giardia lamblia

Neither phospholipase A1 (PLA A1) nor phospholipase A2 (PLA A2), nor their respective genes, have been identified in Giardia lamblia, even though they are essential for lipid metabolism in this parasite. A method to identify, isolate, and characterize these enzymes is needed. The activities of PLA A1 and PLA A2 were analyzed in a total extract (TE) and in vesicular (P30) and soluble (S30) subcellular fractions of G. lamblia trophozoites; the effects of several chemical and physicochemical factors on their activities were investigated. The assays were performed using substrate labeled with 14C, and the mass of the 14C-product was quantified. PLA A1 and PLA A2 activity was present in the TE and the P30 and S30 fractions, and it was dependent on pH and the concentrations of protein and Ca2+. In all trophozoite preparations, PLA A1 and PLA A2 activities were inhibited by ethylenediaminetetraacetic acid and Rosenthal's inhibitor. These results suggest that G. lamblia possesses several PLA A1 and PLA A2 isoforms that may be soluble or associated with membranes. In addition to participating in G. lamblia phospholipid metabolism, PLA A1 and PLA A2 could play important roles in the cytopathogenicity of this parasite.

Use of a colorimetric assay to measure differences in cytotoxicity of Mycobacterium tuberculosis strains

Several techniques have been used to quantify the cytotoxicity produced by Mycobacterium tuberculosis bacilli on cell monolayers; however, they are semi-quantitative or time consuming. Herein, a method based on crystal violet (CV) uptake by THP-1 cell monolayers is described. This colorimetric method quantifies the cytotoxic effect as a function of the number of remaining cells after the infection with M. tuberculosis. Since this micro-organism is not stained by the dye, it does not produce a background that affects absorbance readings. As determined by CV assay (CVA), M. tuberculosis strain H37Rv destroyed 10.5 % of THP-1 cell monolayers at 24 h and 50.52 % at 72 h, while M. tuberculosis strains lacking the complete phospholipase C locus produced a reduced cytotoxic effect. The damage estimated by microscopy corresponded to the effect quantified by CVA. The results show that the use of CVA is a rapid, sensitive and reliable quantitative assay to measure the cytotoxicity of different M. tuberculosis strains.

Antimicrobial activity of Diospyros anisandra

Leaves, root and stem bark of Diospyros anisandra were screened against two strains of Mycobacterium tuberculosis, one resistant and one susceptible to antibiotics, using the microplate Alamar blue assay test. The lypophylic fractions of the root and bark showed significant inhibitory activity against both strains, with the hexane fraction of the bark showing the strongest activity (MIC 6.25 microg/ml) against the resistant strain and a significant antimicrobial activity against Staphylococcus aureus, Bacillus subtilis, Candida albicans, Aspergillus niger, and Colletotrichum gloeosporioides. The bioassay-guided purification of the bioactive hexane fraction resulted in the isolation and identification of the naphthoquinone plumbagin as one of the metabolites responsible for the biological activity.

Synthesis and antimycobacterial activity of 4-(5-substituted-1,3,4-oxadiazol-2-yl)pyridines

4-(5-Substituted-1,3,4-oxadiazol-2-yl)pyridine derivatives 1-12 were synthesized and evaluated for their in vitro antimycobacterial activity. Some compounds showed an interesting activity against Mycobacterium tuberculosis H(37)Rv and five clinical isolates (drug-sensitive and -resistant strains). Compound 4 [4-(5-pentadecyl-1,3,4-oxadiazol-2-yl)pyridine] was 10 times more active than isoniazid, 20 times more active than streptomycin, and 28 times more potent than ethambutol against drug-resistant strain CIBIN 112. Compound 5 [4-(5-heptadecyl-1,3,4-oxadiazol-2-yl)pyridine] showed the same behavior as compound 4. Both of the above structures bear a high lipophilic chain bonded to the 5-position of the oxadiazole moiety. This fact implies that there exists a contribution of lipophilicity, which could facilitate the entrance of these molecules through lipid-enriched bacterial cell membrane.

Evaluation of the flora of northern Mexico for in vitro antimicrobial and antituberculosis activity

The aim of the present study was to evaluate the potential antimicrobial activity of 14 plants used in northeast México for the treatment of respiratory diseases, against drug-sensitive and drug-resistant strains of Streptococcus pneumoniae, Staphylococcus aureus, Haemophilus influenzae type b and Mycobacterium tuberculosis. Forty-eight organic and aqueous extracts were tested against these bacterial strains using a broth microdilution test. No aqueous extracts showed antimicrobial activity, whereas most of the organic extracts presented antimicrobial activity against at least one of the drug-resistant microorganisms tested. Methanol-based extracts from the roots and leaves of Leucophyllum frutescens and ethyl ether extract from the roots of Chrysanctinia mexicana showed the greatest antimicrobial activity against the drug-resistant strain of Mycobacterium tuberculosis; the minimal inhibitory concentration (MIC) were 62.5, 125 and 62.5 microg/mL, respectively; methanol-based extract from the leaves of Cordia boissieri showed the best antimicrobial activity against the drug-resistant strain of Staphylococcus aureus (MIC 250 microg/mL); the hexane-based extract from the fruits of Schinus molle showed considerable antimicrobial activity against the drug-resistant strain of Streptococcus pneumoniae (MIC 62.5 microg/mL). This study supports that selecting plants by ethnobotanical criteria enhances the possibility of finding species with activity against resistant microorganisms.

Two new cassane-type diterpenes from Calliandra californica with antituberculosis and cytotoxic activities

From the root of Calliandra californica two new cassane-type diterpenes were isolated and characterized, escobarine A (1) and B (2), which showed promising activities against two Mycobacterium tuberculosis strains. The microplate alamar blue assay was used to determine the minimum inhibitory concentrations (MIC) of 1 and 2 against M. tuberculosis H37Rv and the resistant CIBIN/UMF15 : 099 strains. The MIC of 1 against the resistant M. tuberculosis strain showed a value 8 times lower than that of rifampin. The structures of the bioactive constituents were established by extensive NMR data analyses (including 1D and 2D NMR). The relative configuration of 2 was confirmed by X-ray analysis and the absolute configurations of 1 and 2 were determined by the circular dichroism method. Additionally, 1 and 2 displayed remarkable cytotoxic activity when evaluated against five human tumor cell lines.

Bactericidal activity of organic extracts from Flourensia cernua DC against strains of Mycobacterium tuberculosis

BACKGROUND

Tuberculosis is a chronic disease caused mainly by Mycobacterium tuberculosis. The emergence of antibiotic-resistant strains of this species underscores the need for novel effective drugs against resistant mycobacteria as first-line antituberculosis medications.

METHODS

Crude aqueous (obtained by decoction, in accordance with the traditional mode of preparation), methanol, acetone, and hexane extracts from aerial parts of Artemisia ludoviciana Nutt., Chenopodium ambrosioides L., Marrubium vulgare L., Mentha spicata L., and Flourensia cernua DC were assessed for their ability to either inhibit the growth of or kill M. tuberculosis strains H37Rv and CIBIN:UMF:15:99, the former being sensitive to, and the latter resistant to, streptomycin, isoniazide, rifampin, ethambutol, and pyrazinamide. These five plant species are used in Mexico to treat respiratory disorders.

RESULTS

Flourensia cernua was the uniquely active plant among those evaluated. Its hexane and acetone extracts not only inhibited the growth of but killed M. tuberculosis. The hexane extract showed a minimal inhibitory concentration (MIC) of 50 and 25 microg/mL against sensitive and resistant strains, respectively; the acetone extract was active against only CIBIN:UMF:15:99 (MIC = 100 microg/mL).

CONCLUSIONS

The hexane extract from F. cernua leaves could be an important source of bactericidal compounds against multidrug-resistant M. tuberculosis.

Association between the stages of cervical cancer and chromosome 1 aneusomy

The high-risk human papillomavirus is known to play a pivotal role in cervical carcinogenesis. Numerical and structural aberrations are known to be related to different behaviors of malignant cervical lesions. The aims of this study were (1) to assess the number of cervical cells with chromosome 1 aneusomy (monosomy, trisomy, and tetrasomy) in 20 women with cervical intraepithelial neoplasia (CIN 1, CIN 2, CIN 3, and invasive cancer) and three women without CIN by fluorescence in situ hybridization (FISH), (2) to determine the heterogeneity of aneusomy among women within each of the five groups studied, (3) to determine the association between the four progressive stages of cervical cancer and the number of cells with and without aneusomy, (4) to determine the association between number of cells with and without aneusomy and human papilloma virus (HPV) infection, and (5) to determine its usefulness as a biomarker of cancer risk. A hospital-based unmatched case-control study in a sample of 23 women grouped by disease stage and selected by histology from the Obstetrics and Gynecology Hospital of the Instituto Mexicano del Seguro Social (IMSS) in Mexico was conducted in 2002. Numerical aberrations of chromosome 1 in cervical smears were detected with FISH. HPV was detected with polymerase chain reaction (PCR) and typing was performed with restriction fragment length polymorphism (RFLPs). Analysis of chromosome 1 aneusomy revealed (1) homogeneity among women within each one of the five groups, (2) a positive linear trend between the aneusomy frequency and grade of lesion, and (3) an association between aneusomy and high-risk HPV infection. These findings suggest the usefulness of the number of cervical cells with chromosome 1 aneusomy as a biomarker. In order to validate this biomarker we suggest a larger prospective study of cytological samples of patients with a longer follow-up.

Morphologic and functional alterations induced by low doses of mercuric chloride in the kidney OK cell line: ultrastructural evidence for an apoptotic mechanism of damage

Mercury produces acute renal failure in experimental animal models, but the mechanism of tubular injury has not completely been clarified. There is an increased interest in the role of apoptosis in the pathogenesis of renal diseases that result primarily from injury to renal tubular epithelial cells. However, detailed studies of morpho-functional alterations induced by mercuric chloride in kidney cell lines are scarce. This work characterizes these alterations in OK cell cultures. Morphological alterations were profiled using light microscopy, transmission electron microscopy, and confocal microscopy, as well as mitochondrial functional assays in the cells exposed to low concentrations of HgCl2. At concentrations of 1 and 10 microM of HgCl2 there were no morphological or ultrastructural alterations, but the mitochondrial function (MTT assay) and intracellular ATP content was increased, especially at longer incubation times (6 and 9 h). At 15 microM HgCl2, both the mitochondrial activity and the endogenous ATP decreased significantly. At this concentration the OK cells rounded up, had increased number of cytoplasmic vacuoles, and detached from the cell monolayer. At 15 microM HgCl2 ultrastructural changes were characterized by dispersion of the ribosomes, dilatation of the cisterns of the rough endoplasmic reticulum, increase of number of cytoplasmic vacuoles, chromatin condensation, invaginations of the nuclear envelope, presence of cytoplasmic inclusion bodies, and alterations in the size and morphology of mitochondria. At 15 microM HgCl2 apoptotic signs included membrane blebbing, chromatin condensation, mitochondrial alterations, apoptotic bodies, and nuclear envelope rupture. Using confocal microscopy and the mitochondrial specific dye MitoTracker Red, it was possible to establish qualitative changes induced by mercury on the mitochondrial membrane potential after incubation of the cells for 6 and 9h with 15 microM HgCl2. This effect was not observed at short times (1 and 3h) with this same concentration, neither with 1 and 10 microM HgCl2 in all the studied times. Taken together, these findings indicate that low concentrations of HgCl2 induce apoptosis by inhibiting mitochondrial function, and the OK cell line may be considered a useful tool for the study of programmed cell death involving mercurial species and other heavy metals.

[Breastfeeding counseling and early mother-child contact are associated with exclusive maternal breastfeeding. A hospital-based-case-control study]

BACKGROUND

The aim of this study was to assess the association between exclusive breastfeeding (EBF) and some factors that may influence breastfeeding in a closely related population attending a private hospital sponsored by a major Mexican brewing company.

MATERIALS AND METHODS

We carried out a retrospective hospital-based unmatched case-control study. A sample of 124 mother-newborn couples was interviewed in a private medical unit in Monterrey, Mexico, from January 2001 to January 2002. The association between EBF and 11 explanatory factors was analyzed by logistic regression analysis.

RESULTS

Counseling and early contact between mother-newborn couples were positively associated with EBF.

CONCLUSION

Counseling and early contact improve EBF practice. We believe these two practices would favor better adherence to EBF in other populations.

TRICHOMONAS VAGINALIS: IDENTIFICATION OF SOLUBLE AND MEMBRANE-ASSOCIATED PHOSPHOLIPASE A1AND A2ACTIVITIES WITH DIRECT AND INDIRECT HEMOLYTIC EFFECTS

A direct hemolytic activity, dependent on phospholipase A (PLA) activity, was located in the particulate subcellular fraction (P30) of Trichomonas vaginalis. We identified soluble direct and indirect hemolytic activities in the spent medium and soluble fraction (S30) of T. vaginalis strain GT-13. Spent medium showed the highest specific indirect hemolytic activity (SIHA) at pH 6.0 (91 indirect hemolytic units [HU]/mg/hr). Spent medium and P30, but not S30, showed direct hemolytic activity. PLA activity was protein dose dependent and time dependent. The highest PLA activity was observed at pH 6.0. All trichomonad preparations showed phospholipase A1 (PLA A1) and phospholipase A2 (PLA A2) activities. Indirect and direct hemolytic activity and PLA A1 and PLA A2 diminished at pH 6.0 and 8.0 with increasing concentrations of Rosenthal's inhibitor. The greatest effect was observed with 80 microM at pH 6.0 on the SIHA of S30 (83% reduction) and the lowest at pH 8.0, also on the SIHA of S30 (26% reduction). In conclusion, T. vaginalis contains particulate and soluble acidic, and alkaline direct and indirect hemolytic activities, which are partially dependent on alkaline or acidic PLA A1 and PLA A2 enzymes. These could be responsible for the contact-dependent and -independent hemolytic and cytolytic activities of T. vaginalis.

Characterization of Chitin Synthases from Entamoeba

A major component of the Entamoeba cyst wall is chitin, a homopolymer of beta-(1,4)-linked N-acetyl-D-glucosamine. Polymerization of chitin requires the presence of active chitin synthases (CHS), a group of enzymes belonging to the family of beta-glycosyl transferases. CHS have been described for fungi, insects, and nematodes; however, information is lacking about the structure and expression of this class of enzymes in protozoons such as Entamoeba. In this study, the primary structures of two putative E. histolytica CHS (EhCHS-1 and EhCHS-2) were determined by gene cloning and homologous proteins were identified in databases from E. dispar and the reptilian parasite E. invadens. The latter constitutes the widely used model organism for the study of Entamoeba cyst development. The two ameba enzymes revealed between 23% and 33% sequence similarity to CHS from other organisms with full conservation of all residues critically important for CHS activity. Interestingly, EhCHS-1 and EhCHS-2 differed substantially in their predicted molecular weights (73 kD vs. 114 kD) as well as in their isoelectric points (5.04 vs. 8.05), and homology was restricted to a central stretch of about 400 amino acid residues containing the catalytic domain. Outside the catalytic domain, EhCHS-1 was predicted to have seven transmembrane helices (TMH) of which the majority is located within the C-terminal part, resembling the situation found in yeast; whereas, EhCHS-2 is structurally related to nematode or insect chitin synthases, as it contained 17 predicted TMHs of which the majority is located within the N-terminal part of the molecule. Northern blot analysis revealed that genes corresponding to CHS-1 and CHS-2 are not expressed in Entamoeba trophozoites, but substantial amounts of CHS-1 and CHS-2 RNA were present 4 to 8 hours after induction of cyst formation by glucose deprivation of E. invadens. The time-courses of expression differed slightly between the two ameba CHS genes, as in contrast to CHS-1 RNA, expression of CHS-2 RNA was more transient and no plateau was observed between 8 and 16 hours of encystation. However, both CHS RNAs were no longer detectable after 48 hours when most of the cells had been transformed into mature cysts.

In vitro and in vivo activities of antimicrobials against Nocardia brasiliensis

In Mexico mycetomas are mostly produced by Nocardia brasiliensis, which can be isolated from about 86% of cases. In the present work, we determined the sensitivities of 30 N. brasiliensis strains isolated from patients with mycetoma to several groups of antimicrobials. As a first screening step we carried out disk diffusion assays with 44 antimicrobials, including aminoglycosides, cephalosporins, penicillins, quinolones, macrolides, and some others. In these assays we observed that some antimicrobials have an effect on more than 66% of the strains: linezolid, amikacin, gentamicin, isepamicin, netilmicin, tobramycin, minocycline, amoxicillin-clavulanic acid, piperacillin-tazobactam, nitroxolin, and spiramycin. Drug activity was confirmed quantitatively by the broth microdilution method. Amoxicillin-clavulanic acid, linezolid, and amikacin, which have been used to treat patients, were tested in an experimental model of mycetoma in BALB/c mice in order to validate the in vitro results. Linezolid showed the highest activity in vivo, followed by the combination amoxicillin-clavulanic acid and amikacin.

Identification of acidic, alkaline, and neutral sphingomyelinase activities in Mycobacterium tuberculosis

BACKGROUND

Sphingomyelinase enzymes are pathogenic factors of several intracellular bacteria species, which have been little studied in Mycobacterium tuberculosis.

MATERIAL/METHODS

Cell free extracts from H37Rv and CDC-1551 M. tuberculosis strains were assayed for sphingomyelinase activity by using [N-methyl-14C]-sphingomyelin as substrate. Double-directional thin-layer chromatography was used to separate the substrate and hydrolysis product. Sphingomyelinase activity was analyzed as a function of incubation time, dose, pH and the presence of MgCl2, CaCl2, ZnSO4, HgCl2, MnCl2, CoCl2 and EDTA (1 or 10 mM).

RESULTS

Mycobacterial preparations hydrolyzed [14C]-sphingomyelin, in time- and dose-dependent manners, producing [14C]-phosphorylcholine as a unique product. The activity of H37Rv neutral sphingomyelinase at pH 7.5 was 2.15 times higher than that of CDC-1551. This activity was inhibited 21-82% by Ca2+, Hg2+ or Zn2+ and EDTA, and stimulated 40-117% by Mn2+ and Mg2+. In addition, preparations from both strains showed two peaks of sphingomyelinase, one at pH 5.5 and the other at pH 3.0. However, these activities were 4-22 times lower than that observed at pH 7.5 for strain H37Rv. Preparations from H37Rv, but not those of CDC-1551, hydrolyzed sphingomyelin at pH 8-9, with a specific activity similar to that of the neutral CDC-1551 enzyme.

CONCLUSIONS

Both strains H37Rv and CDC-1551 of M. tuberculosis have cation-dependent acidic and neutral sphingomyelinase-C enzymes, showing the neutral as the major activity. In addition, H37Rv has an alkaline sphingomyelinase-C. The importance of SMases in M. tuberculosis pathogenesis remains to be elucidated.

Trichomonas vaginalis: identification of a phospholipase A-dependent hemolytic activity in a vesicular subcellular fraction

Trichomonad total extracts (TTE), or vesicular (P30) and soluble (530) subcellular fractions from 3 pathogenic Trichomonas vaginalis strains (GT-3. GT-13. and GT-15), lysed both human and Sprague-Dawley rat erythrocytes in a time- and dose-dependent manner. The entire hemolytic activity of TTE was located in P30, showing 2 peaks of maximum activity, one at pH 6.0 and another at pH 8.0. in the presence of 1 mM Ca2+. Hemolytic activity on rat erythrocytes was greater at pH 6.0 16.71 +/- 0.33 hemolytic units IHU]/mg/hr to 11.60 +/- 0.24 HU/mg/hr) than at pH 8.0 (3.81 +/- 0.30 HU/mg/hr to 5.75 +/- 0.65 HU/mg/hr). and it was greater than that on human red blood cells at pH 6.0 (2.67 +/- 0.19 HU/mg/hr to 4.08 +/- 0.15 HU/mg/hr) or pH 8.0 (2.24 +/- 0.0 9 HU/mg/hr to 2.81 +/- 0.06 HU/mg/hr). The alkaline and acidic hemolytic activity diminished (60-93% at pH 6.0 and 78-93% at pH 8.0) by the effect of 80 microM Rosenthal's inhibitor, which also inhibited 27-45% and 29-54% trichomonad alkaline and acidic phospholipase A activities, respectively. Vesicles, vacuoles, and hydrogenosomes were rich in P30. Trichomonas vaginalis has a hemolytic PLA, which could be involved in its cytopathogenic mechanism.

Mg2+, Mn2+, and Co2+ stimulate Entamoeba histolytica to produce chitin-like material

The mechanism of Entamoeba histolytica cyst cell wall synthesis is not well understood. Previous research has shown that cyst-like structures formed in the presence of chitin synthase cofactors (Mg2+, Mn2+, and Co2+) resist 1% sodium dodecyl sulfate lysis (RCLS), whereas those formed in the absence of cofactors (CLS) do not, and trophozoites are immediately destroyed. This suggests that E. histolytica is able to synthesize chitin, initiating a differentiation process under axenic conditions. To test this hypothesis, polysaccharide hydrolysates from E. histolytica trophozoites, CLS, or RCLS were analyzed with high-performance liquid chromatography. The major components found in all 3 preparations were N-acetylglucosamine (NAG) and glucose (GLC), with RCLS possessing 129 and 180 times more NAG and 2.4 and 2.0 more GLC than trophozoites and CLS, respectively. After 36 hr of incubation with chitinase (16 U/ml) in a hypotonic medium (50 mOsm/kg), 68% of RCLS was lysed, and 100% lost affinity for calcofluor white M2R. The RCLS polysaccharides bound wheat germ agglutinin and appeared as long and thin or short and thick fibers. Accordingly, Mg2+, Mn2+, and Co2+ stimulated E. histolytica to synthesize a chitin-like material.

Auxotrophy to lipoproteins of Entamoeba histolytica cultivated under axenic conditions

Entamoeba histolytica grows in media without serum but with a mixture of aminoacids, vitamins, lipoproteins, free cholesterol, phospholipids and fatty acids called PACSR. The ability of lipoproteins and free lipids to support growth of three E. histolytica strains (HK9, HMI:IMSS and HM3:IMSS) was analysed. Tubes containing 5 ml culture medium, amino acids, vitamins and either 120-1,200 microg lipoproteins/ml or 0.017-0.10 mg free lipids/ml (predissolved in absolute ethanol) were inoculated with 1x10(4) trophozoites/ml and incubated at 37 degrees C for 72 h. Amoebae died within 12 h in the presence of any free lipid combination, while those having 240-480 mg lipoproteins/ml reached densities similar to or higher than those of controls (depending on strain). The addition of ethanol (0.1%) to the media produced stable lipid solutions and did not show significant adverse effects. Accordingly, E. histolytica is auxotrophic to lipoproteins and unable to use free cholesterol, phospholipids or fatty acids.