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E Waldman

Publications and source records attributed to E Waldman.

11 recordsLinked to original sources
PubMed1999

Stage-specific activity of pentavalent antimony against Leishmania donovani axenic amastigotes.

The standard treatment of human visceral leishmaniasis involves the use of pentavalent antimony (SbV) compounds. In recent years increasing numbers of clinical failures of treatment with SbV have been reported, probably due to the development of parasite resistance to this compound. The mode of action and mechanisms of resistance to SbV have not been fully elucidated. In the present study an axenic amastigote culture was used to study the in vitro responses of Leishmania donovani to SbV. Susceptibility to both sodium stibogluconate and meglumine antimoniate was found to be stage specific. Amastigotes were 73 to 271 times more susceptible to SbV than were promastigotes. As opposed to SbV, trivalent antimony (SbIII) was similarly toxic to both developmental stages. When promastigotes were transformed to amastigotes, susceptibility to meglumine antimoniate developed after 4 to 5 days, upon the completion of differentiation. In contrast, with transformation from amastigotes to promastigotes, resistance to meglumine antimoniate was acquired rapidly, within 24 h, before the completion of differentiation. The culture of promastigotes at an acidic pH (5.5) or at an elevated temperature (37 degrees C) alone did not lead to the appearance of SbV susceptibility, emphasizing the requirement of both these environmental factors for the development of SbV susceptibility. A previously isolated sodium stibogluconate (Pentostam)-resistant L. donovani mutant (Ld1S.20) is also resistant to meglumine antimoniate, indicating cross-resistance to SbV-containing compounds. In contrast, no cross-resistance was found with SbIII, suggesting a mechanism of SbV resistance different from that described in Leishmania tarentolae. These data show that L. donovani susceptibility to SbV is parasite intrinsic, stage specific, and macrophage independent.

Animals↗
PubMed1998

Characterization of developmentally-regulated activities in axenic amastigotes of Leishmania donovani.

Leishmania donovani is an obligatory intracellular parasite which cycles between the midgut of sand flies (extracellular promastigote) and the phagolysosomes of mammalian macrophages (intracellular amastigote). Promastigotes have been readily cultured, whereas axenic cultures of amastigotes have only recently been developed. A new method for in vitro differentiation of L. donovani promastigotes into amastigotes is presented, in which promastigotes are exposed to environmental changes that mimic the in vivo process. First, promastigotes are subjected to 37 degrees C + 5% CO2 for 24 h, and then are shifted to pH 5.5. Under these conditions, differentiation is completed within 120 h. In the reverse process, amastigotes are induced to differentiate back to promastigotes by transferring them to promastigote growth conditions (medium 199 at pH 7.4 and 26 degrees C). Axenic amastigotes closely resemble animal-derived amastigotes. They manifest all seven proteins of the amastigote-specific A2 gene family. They down-regulate lipophosphoglycan (LPG) synthesis and do not express it on their surface. LPG is up-regulated 2 h after inducing amastigotes to differentiate to promastigotes. Within 6 h, parasites resume the promastigote level of this molecule, although differentiation is completed only after 48 h. Axenic amastigotes also express amastigote-like metabolic activities of proline uptake, as well as thymidine and proline incorporation. In conclusion, the results indicate that the method developed for in vitro differentiation of L. donovani promastigotes to amastigotes is efficient and yields organisms resembling animal-derived amastigotes. Being able to induce in vitro differentiation of L. donovani provides us with an excellent tool to study Leishmania development and differentiation.

Animals↗
PubMed1997

Pentostam induces resistance to antimony and the preservative chlorocresol in Leishmania donovani promastigotes and axenically grown amastigotes.

An axenic amastigote culture system was utilized to directly assess the stage-specific antileishmanial effects of antimony on amastigotes of Leishmania donovani devoid of the macrophage host cell. Pentostam, which contains antimony in the form of sodium stibogluconate and the preservative chlorocresol, was used. Cell density was quantified by measuring the activity of the stable enzyme ornithine decarboxylase. Dose-response curve analyses show that Leishmania promastigotes are susceptible to Pentostam, with the 50% inhibitory concentration (IC50) being 104 microg/ml, while amastigotes are more susceptible, with the IC50 being 24 microg/ml. Promastigotes and amastigotes are also susceptible to chlorocresol, with IC50s being 1.27 and 1.82 microg/ml, respectively. Given that promastigotes are insensitive to antimony, these results suggest that the increased susceptibility of amastigotes to Pentostam is due to the stage-specific activity of sodium stibogluconate. To further study this phenomenon, spontaneous resistance to Pentostam was induced in L. donovani promastigotes by increasing the concentration of Pentostam in the growth medium in a stepwise fashion. Two mutants, Ld1S.04 and Ld1S.20, grew at 0.4 and 2.0 mg of Pentostam per ml, respectively. Promastigotes of these mutants were 11 and 21 times, respectively, more resistant to Pentostam than the wild type. Amastigotes were 40 and 148 times, respectively, more resistant than the wild type. The mutants were also chlorocresol resistant; promastigotes were 6 and 9 times, respectively, more resistant than the wild type, and amastigotes were 14 and 35 times, respectively, more resistant than the wild type. These data show that resistance to Pentostam induced in antimony-insensitive promastigotes is manifested in amastigotes as resistance both to pentavalent antimony and to chlorocresol. The axenic amastigote system is a unique tool which enables direct evaluation of the activity of antileishmanial compounds on the amastigote devoid of its host cell.

Animals↗
PubMed1992

A prospective evaluation of the cumulative illness rating scale.

Assessment of overall physical health is an important yet little studied problem in geriatric research. The Cumulative Illness Rating Scale (CIRS) was among the first instruments that attempted to summarize the overall severity of illness based on clinical information. This study evaluated the CIRS in a prospective longitudinal study of 181 elderly (mean age +/- SD = 79 +/- 7.4) subjects undergoing comprehensive geriatric assessment in an outpatient unit. The CIRS was found to correlate negatively with activities of daily living (r = -0.49, p = 0.0001), instrumental activities of daily living (r = -0.34, p = 0.0001), patient morale (r = -0.30, p = 0.0001), and positively with days in hospital (r = 0.21, p = 0.0075) and number of medications (r = 0.31, p = 0.0001). Mean CIRS scores for subjects who died during follow-up were significantly higher than the scores for survivors (p less than 0.01). In logistic regression, CIRS was a significant predictor of death, yet it did not improve that prediction over information contained in measures of activities of daily living. In separate logistic analyses, CIRS and age predicted acute care hospital days during follow-up, while ADL or IADL predicted the use of nursing home services. Although the CIRS appears to be a reliable method of summarizing medical information and to have some external validity, in its present form it does not provide additional prognostic information.

Aged↗
PubMed1989

Factor C from rabbit liver. A new poly(dC) and poly[d(G-C)] template-selective stimulatory protein of DNA polymerases.

We have undertaken a search for mammalian DNA-binding proteins that enhance the activity of DNA polymerases in a template sequence-specific fashion. In this paper, we report the extensive purification and characterization of a new DNA-binding protein from rabbit liver that selectively stimulates DNA polymerases to copy synthetic poly[d(G-C)] and the poly(dC) strand of poly(dC).poly(dG) as well as single-stranded natural DNA that contains stretches of oligo(dC). The enhancing protein, a polypeptide of 65 kDa designated factor C, stimulates the copying of the two synthetic templates by Escherichia coli DNA polymerase I, Micrococcus luteus polymerase, and eukaryotic DNA polymerases alpha and beta, but not by avian myeloblastosis virus polymerase. Factor C, however, does not affect utilization by these polymerases of the poly(dG) strand of poly(dC).poly(dG), of poly(dC) primed by oligo(dG), or of poly(dA).poly(dT) and poly[d(A-T)]. With polymerase I, Michaelis constants (Km) of poly[d(G-C)] and of the poly(dC) strand of poly(dC).poly(dG) are decreased by factor C 37- and 4.7-fold, respectively, whereas maximum velocity (Vmax) remains unchanged. By contrast, neither the Km value of the poly(dG) strand of poly(dC).poly(dG) nor the Vmax value with this template is altered by factor C. Rates of copying of activated DNA, denatured DNA, or singly primed M13 DNA are not affected significantly by factor C. However, primer extension analysis of the copying of recombinant M13N4 DNA that contains runs of oligo(dC) within an inserted thymidine kinase gene shows that factor C increases processivity by specifically augmenting the efficiency at which polymerase I traverses the oligo(dC) stretches. Direct binding of factor C to denatured DNA is indicated by retention of the protein-DNA complex on columns of DEAE-cellulose. Binding of factor C to poly[d(G-C)] is demonstrated by the specific adsorption of the enhancing protein to columns of poly[d(G-C)]-Sepharose. We propose that by binding to poly[d(G-C)] and to poly(dC).poly(dG), factor C enables tighter binding of some DNA polymerases to these templates and facilitates enzymatic activity.

Animals↗
PubMed1988

An evaluation of competitive and second generation ELISA screening tests for antibody to HIV.

Two competitive anti-HIV ELISA screening assays (Behring and Wellcozyme) and two second generation assays using antigens generated by recombinant DNA technology (Abbott) and synthetic peptides (Biochrom) were evaluated against common panels of anti-HIV positive sera and sera known or thought likely to give false positive reactions. The assays were also tested on fresh sequential blood donations. Conventional estimates of sensitivity and specificity did not reveal a significant difference between the assays. Statistical analyses using log10 transformed data to determine delta values (the distance of the mean optical density (OD) ratio from the cut-off measured in standard deviation units) showed the Abbott assays to have the highest probability (greater than 99.99%) of detecting anti-HIV positive samples and the Behring assay as having the highest probability (greater than 99.99%) of correctly identifying anti-HIV negative specimens. The combined data from conventional estimates of sensitivity and specificity and delta values suggests that the Abbott assay is the test of choice for screening purposes.

Data Interpretation, Statistical↗
PubMed1988

Gender differences in tobacco use in Africa, Asia, the Pacific, and Latin America.

This paper reviews historical, anthropological and contemporary survey data concerning gender differences in tobacco use in Africa, Asia, the Pacific, and Latin America. In many cultural groups in these regions, tobacco use has been substantially more common among men than among women. In some groups, tobacco use has been about equally common for both sexes. No evidence was found of any group in which tobacco use has been substantially more common among women. The widespread pattern of greater tobacco use by men appears to be linked to general features of sex roles. For example, men have often had greater social power than women, and this has been expressed in greater restrictions on women's behavior, including social prohibitions against women's smoking. These social prohibitions against women's smoking have strongly inhibited women's tobacco use and thus have been a major cause of gender differences in tobacco use. Gender differences in tobacco use have varied in magnitude, depending on the type of tobacco use and the particular cultural group, age group and historical period considered. Causes of the variation in gender differences in tobacco use include variation in women's status and variation in the social significance and benefits attributed to particular types of tobacco use in different cultures. Contact with Western cultures appears to have increased or decreased gender differences in smoking, depending on the specific circumstances. The patterns of gender differences in tobacco use in non-Western societies are similar in many ways to the patterns observed in Western societies, but there are several important differences.(ABSTRACT TRUNCATED AT 250 WORDS)

Africa↗