Some factors affecting the in vitro invasion of HeLa cells by Trypanosoma cruzi

The penetration of metacyclic forms of Trypanosoma cruzi into HeLa cells after different treatments was studied. When cell development was synchronized by two different processes, maximum rates of parasitization occurred during the S phase of cell cycle (29.48 and 24.3%). However, when cells were treated with trypsin (0.1%), parasitization rates appeared to be lower than controls, reaching values similar to controls 14 h after the beginning of the treatment. Infection values remained unaltered after treatment with colcemid (0.6 μg ml^?1). Cell treatment either with valinomycin (1 μg ml^?1) or with actinomycin D (250 μg ml^?1) caused a marked decrease in the percentage of parasitization. When cells were treated and infected in the presence of tunicamycin (100 ng ml^?1), parasitization rates were increased (14.7%) compared to control cells (6%). On the other hand, no differences in parasitization rates were observed when cells were treated with cycloheximide (100 μg ml^?1). Infection in a low redox medium (?100 mV) resulted in considerable increase in parasitization.     

Leishmania braziliensis: effects of bacteria (Staphylococcus aureus and Pasteurella multocida) on the developing cutaneous leishmaniasis lesion in the golden hamster

Experimentally induced lesions of cutaneous leishmaniasis and the effect of concurrent bacterial infection on the development of these lesions were studied in the golden hamster. Male outbred golden hamsters received intradermal injections at the base of the tail with approximately 10(7) promastigotes of Leishmania braziliensis panamensis, or promastigotes combined with Staphylococcus aureus or Pasteurella multocida or both, bacteria only, or sterile Eagle's minimal essential medium (MEME). The size of the resulting lesions was measured at least twice each week. Hamsters were killed at postinoculation Days 6, 13, 20, 27, 41, or 48, and each lesion was measured, aseptically excised, and bisected; half was used for bacteriologic culture and the other half was prepared for light microscopic examination. Lesions resulting from L. b. panamensis alone progressed from initial erythema to a granulomatous nodule and finally to a necrotic granuloma, often capped by a crateriform ulcer. Lesions resulting from a suspension of L. b. panamensis with added S. aureus or S. aureus and P. multocida, were initially larger, more erythemic and contained a greater proportion of neutrophils up to postinoculation Days 14-21 than did lesions resulting from L. b. panamensis alone. Concurrent infections with bacteria such as S. aureus and P. multocida had little effect on the development of ulcerating characteristics of lesions, but when S. aureus was present it appeared to enhance the severity of the early lesions. Between postinoculation Days 14-28, lesions produced by L. b. panamensis, with or without added bacteria had similar developmental progression of sufficient size for optimal testing of antileishmanial compounds.     

Taenia solium: cell reactions to the larva (Cysticercus cellulosae) in naturally parasitized, immunized hogs

In hogs naturally infected with Taenia solium larvae (i.e., Cysticercus cellulosae), we studied the host response induced by antigens obtained from the larvae. Histopathological studies of cysticerci removed after 4 and 8 weeks of immunization showed an intense inflammatory reaction surrounding the larvae. The response was greater in the 8-week specimens. A dense layer of eosinophils was in close contact with the external membrane of the bladder wall and, in several cases, the eosinophils had infiltrated this tegument. Many eosinophils were seen in the spiral canal of larvae. This infiltration by eosinophils increased with time. Preparations from the 8-week samples showed many degenerated and disrupted eosinophils whose granules were found in close contact with the outer membrane of the larval tegument and, in some cases, had entered through the broken surface of this structure. More than 90% of the larvae were found in various stages of degeneration; the rest were completely destroyed and surrounded by a mass of eosinophils. After immunization, peripheral blood eosinophilia increased to 17%, whereas the eosinophilia of the control hog was 4% throughout the study. The larval worms removed from control hogs showed intact structures, with a low degree of infiltration by eosinophils and a discrete inflammatory reaction surrounding the bladder wall of the larvae.     

用试管-玻片培养技术研究铵对木麻黄根瘤形成的影响

用植物试管玻片培养技术研究NH_4~ 对细枝木麻黄及Frankia菌株Co01共生体系建立过程的影响。NH_4~ (100,150ppm(NH_4)_2SO_4)通过阻止菌株Cc01与其宿主细枝木麻黄根毛壁的亲和作用来影响结瘤。但NH_4~ 不能阻抑菌株Cc01中结瘤基因pel和cel的表达及纤维素酶和果胶酶活性,且菌丝一旦侵入宿主皮层细胞,并形成根瘤原基及前根瘤,则NH_4~ (250ppm(NH_4)_2SO_4)就不再阻止原基进一步发育为成熟的根瘤。但在这种情况下,NH_4~ 能抑制根瘤的固氮活性。     

Seroprevalence of B virus (Herpesvirus simiae) antibodies in a naturally formed group of rhesus macaques

Eighty-two percent of a group of rhesus monkeys removed from Cayo Santiago were seropositive for B virus (Herpesvirus simiae) antibodies. Similar results were obtained from the Cayo Santiago macaque population two decades ago and from feral Indian rhesus monkeys. Thus it is likely that B virus has been enzootic in the Cayo Santiago population since 1938, when the colony was established with stock imported from India.     

Salmonella typhimurium acrB-like gene: identification and role in resistance to biliary salts and detergents and in murine infection

Abstract Salmonella serotype typhimurium transpositional mutants altered in resistance to biliary salts and detergents were isolated previously. We have characterized further the LX1054 mutant strain, the most sensitive of them. The chromosomal DNA segment flanking transposon insertion was cloned and sequenced. The highest level of identity was found for the acrB (formerly acrE ) gene of Escherichia coli , a gene encoding a drug efflux pump of the Acr family. LX1054 exhibited a reduced capacity to colonize the intestinal tract. After passages in mice, the mutant strain lost the sensitive phenotype. In vitro, a resumption of growth appeared after 17 h of culture in medium with cholate or other tested biological or chemical detergents. Then, the acquired resistant phenotype seemed stable. The data suggested a role of S. typhimurium acrB -like gene in resistance to biliary salts and detergents and in mice intestinal colonization. However, the local and transient sensitivity observed in vivo, and the in vitro adaptations suggest that several detergent-resistance mechanisms operate in S. typhimurium .     

Augmentation of Interferon Production after Cell-Differentiation of U937 Cells by TPA

Persistent infections with mumps virus were established in several human lymphoid cells of T-cell origin (Molt-4, TALL-1, and CCRF-CEM) and human monocyte cells (U937 and THP-1). 2′,5′-Oligoadenylate synthetase (2–5AS) activity was demonstrated to be only slightly induced by interferon (IFN) or TPA (12-O-tetradecanoyl-phorbol-13-acetate) treatment in these cells. Treatment of the persistently infected cells with IFN or TPA did not stimulate an increase in the amount of synthetase mRNA. Induction of cell differentiation and augmentation of IFN production by TPA were demonstrated in U937 cells persistently infected with mumps virus (U937-MP). Similar results for IFN production were obtained from differentiated U937 cells. It is suggested that cell differentiation of U937 cells might be associated with the development of IFN inducibility.