Syphacia muris: response to environmental stimuli when hatching in vitro.

It is known that several oxyurids have hatched in fluids without extra stimuli except digestive enzymes, whereas the eggs of several other nematodes require for hatching optimal temperature, pH, redox potential, and pCO₂ but no enzymes. Consequently, a study was carried out on the effect of external stimuli on hatching of the eggs of the oxyurid Syphacia muris.Eggs of S. muris, attached to pieces of transparent adhesive tape, proved themselves able to hatch in a PO₄-buffer to which only trypsin and bile had been added. Trypsin acted, like NaOH on other nematode eggs, by dissolving proteins from the surface of the eggshell. The addition of reducing agents, and to some extent CO₂, had a stimulating effect. Hatching began to occur at 19 C and at pH 3, although 41 C and pH 7 gave optimal results.The conclusion is that the eggs of S. muris react in the same way to the environment as those of Ascaris lumbricoides and other nematodes which hatch inside the hosts' intestinal tracts. S. muris eggs distinguish themselves, however, by being dependent on the environment to an appreciably lesser extent.This last characteristic makes it possible to use simple media for routine hatchings of these eggs, for instance, in disinfection tests.     

Serological cross-reactivity between Strongyloides venezuelensis and Syphacia muris in Wistar rats (Rattus norvegicus)

One of the problems frequently faced in laboratory facilities is the possibility of the natural parasitic infection of lab animals, which can interfere with biomedical research results. The present study aimed to evaluate cross-reactivity among serum samples from Wistar rats (Rattus norvegicus) naturally infected with Syphacia muris and experimentally infected with Strongyloides venezuelensis. Forty rats were divided into four groups of ten animals each. Parasite load was evaluated by quantifying the adult worms from both helminthes species recovered from the intestines and the S. venezuelensis eggs eliminated in feces. Serological cross-reactivity by parasite-specific IgG detection was tested via enzyme linked immunosorbent assay (ELISA), immunofluorescence antibody test (IFAT) and immunoblotting. The results demonstrated that the quantity of S. venezuelensis eliminated eggs and parthenogenetic females decreased significantly in cases of co-infection with S. muris. ELISA revealed 100% cross-reactivity of serum samples from both species against the opposing antigen. IgG cross-reactivity was confirmed by IFAT using tissue sections of S. venezuelensis larvae and adult S. muris. Immunoblotting showed that IgG antibodies from the sera of animals infected with S. muris recognized eight antigenic bands from S. venezuelensis saline extract and that IgG antibodies from the sera of animals infected with S. venezuelensis recognized seven bands from S. muris saline extract. These results demonstrate the serological cross-reactivity between S. muris and S. venezuelensis in infected rats.     

The life-cycle of Syphacia muris Yamaguti (Nematoda: Oxyuroidea) in the laboratory rat

The life-cycle of Syphacia muris is described in primary infections of Wistar rats. The life-cycle of S. muris is completed within seven days and no moults were discovered inside the egg. Instead each of two moults were observed outside the egg up to 24 and 40 hours after infection, and TEM studies suggest a third moult occurs up to 64 hours. The development and maturation of the larval stages are described for the first time using both light and electron microscopy. Differences in the size and growth of female S. muris compared with previously published figures could be due to differences in the strains of rats used.     

三种消毒剂对大黄鱼致病性弧菌的体外杀灭作用研究

为了解不同消毒剂对大黄鱼中致病性弧菌的抑菌效果。采用纸片扩散法比较了聚维酮碘(PVP-I)、聚六亚甲基双胍(PHMB)和过氧化氢(H2O2)对溶藻弧菌和副溶血性弧菌的抑菌效果,再以肉汤稀释法测定了三种消毒剂的最低抑菌浓度(MIC)、最低杀菌浓度(MBC)及MBC/MIC比值,在此基础上,获得了抑菌效果相对较优的H2O2、PHMB对溶藻弧菌、副溶血性弧菌及其混菌的杀菌动力学曲线。结果表明,H2O2(3%)对两种弧菌具有最大的抑菌圈直径(19~21mm),PHMB(30mg/mL)次之(约为15mm),PVP-I(10%)的抑菌效果最弱(小于10mm)。3种消毒剂的MIC值由小到大依次为PHMB相似文献   

Syphacia muris: Water permeability of eggs and its effect on hatching

As a result of a previous study, it appeared that hatching of eggs of Syphacia muris is activated by the application of heat (37 °C) or cysteine or trypsin but that these are not the essential stimuli. In the present study it has been established that exposure of eggs prior to hatching for several hours to 37 °C or cysteine or trypsin, or for 3 days to 22 °C, accelerated hatching. Pretreatment with 37 °C or cysteine or trypsin also increased permeability of the eggshell to water; however, it did not induce the operculum to open. The operculum opened only if the eggs, after pretreatment, were immersed in water. The larvae could leave the opened eggs only in water and not in any other medium such as paraffin oil. These data made it possible to distinguish between three stages in the hatching process. During Stage 1, the eggshell becomes permeable to water. This can be induced by dissolving the proteins of the eggshell in a trypsin solution or by stimulating the larvae with temperature or cysteine. The permeability of the eggshell is essential to successful hatching. In Stage 2, which occurs only in the presence of water, the larvae dissolve the chitinous seal between the operculum and the eggshell. In Stage 3 the larvae probably increase their size by water absorption and leave the eggs. In the discussion it has been proposed that all nematodes, both those hatching in the intestine and the species hatching in the open, could well have an identical hatching mechanism to the one observed in Syphacia muris.     

Inactivation of Bacillus piliformis spores by heat and certain chemical disinfectants

The inactivation of Tyzzer's organism (Bacillus piliformis) spore isolated from rats by heat and various chemical disinfectants was studied. The spores were from B. piliformis-infected rat liver tissues. The spore suspension (10(4) 50% of rat liver lesion producing dose with prednisolone treatment/ml) was treated with heart or disinfectants. Inactivation of the spores was examined in experimentally infected rats. Rats were inoculated perorally with a treated spore suspension and injected subcutaneously with prednisolone. On the sixth day after inoculation, rats were examined grossly for liver lesions. Spores were inactivated at 80 degrees C for 15 min but not at 60 degrees C for 30 min. Spores were inactivated by 0.4% peracetic acid, 0.015% sodium hypochrolite, 1% iodophol, 5% phenol. Alcide and 0.37% formaldehyde solution, but not by 0.037% formaldehyde solution, 70% ethanol, 0.3% benzethonium chloride solution, 3% cresol and soap solution, or 4% chlorhexidine digluconate. These findings suggest that B. piliformis spores are relatively sensitive to heat and certain chemical disinfectants.     

The effects of heat on Sporothrix schenckii in vitro and in vivo

In order to clarify the mechanism of action of topical thermotherapy on sporotrichosis, the effects of heat on Sporothrix schenckii in vitro and in vivo were investigated by observing the percentage germination and the ultrastructure. When the spores were heated to 42 degrees C, it took 10 hr with the conidia, 2 hr with the yeast-like cells and 1 hr with the spores in vivo to reduce the germination rates to 10%. The percentage germination curves were reduced slowly at first but later exponentially. Changes in the ultrastructure became evident in 2 hr with the yeast-like cells and in 8 hr with the conidia. The ribosome count declined and amorphous dense materials appeared in the cytoplasm and mitochondria. In vivo, the outstanding feature of the heated spores was the diversity of internal ultrastructural changes encountered and morphological changes. These were observed at 1 hr post treatment.     

Giardia muris: ultrastructural analysis of in vitro excystation

Giardia muris cysts were examined by transmission electron microscopy before treatment, after induction, and at timed intervals during the incubation phase of in vitro excystation. Untreated G. muris cysts had a thick cyst wall composed of a fibrous outer wall and a thin, electron-dense inner membrane which extended from the trophozoite plasma membrane. The cytoplasm was devoid of endoplasmic reticulum, Golgi bodies,and mitochondria. Numerous large vacuoles were present within the ectoplasm just beneath the plasma membrane in untreated cysts. Following induction these cysts lacked ectoplasmic vacuoles. Concurrently, numerous membrane bound vesicles were seen in the peritrophic space closely adhering to the surface of the trophozoite. These vesicles appear to be of cytoplasmic origin. The cytoplasm of fully excysted trophozoites lacked ectoplasmic vacuoles but displayed well-developed ribbons of microtubular bodies, probably precursors of ventral disk, lateral flange, and median bodies and also contained extensive granular endoplasmic reticulum. No more than two nuclei were observed within each organism. The earliest excysted organisms were observed 0-5 min after incubation had begun and most organisms had excysted within 10 min. Cytokinesis occurred only after excystation was complete.     

Fungicidal effects of chemical disinfectants, UV light, desiccation and heat on the amphibian chytrid Batrachochytrium dendrobatidis

The efficacy of a number of disinfection treatments was tested on in vitro cultures of the fungus Batrachochytrium dendrobatidis, the causative agent of chytridiomycosis in amphibians. The aim was to evaluate the fungicidal effects of chemical disinfectants, sterilising ultraviolet (UV) light, heat and desiccation, using methods that were feasible for either disinfection in the field, in amphibian husbandry or in the laboratory. The chemical disinfectants tested were: sodium chloride, household bleach (active ingredient: sodium hypochlorite), potassium permanganate, formaldehyde solution, Path-X agricultural disinfectant (active ingredient: didecyl dimethyl ammonium chloride, DDAC), quaternary ammonium compound 128 (DDAC), Dithane, Virkon, ethanol and benzalkonium chloride. In 2 series of experiments using separate isolates of B. dendrobatidis, the fungicidal effect was evaluated for various time periods and at a range of chemical concentrations. The end point measured was death of 100% of zoospores and zoosporangia. Nearly all chemical disinfectants resulted in 100%, mortality for at least one of the concentrations tested. However, concentration and time of exposure was critical for most chemicals. Exposure to 70% ethanol, 1 mg Virkon ml(-1) or 1 mg benzalkonium chloride ml(-1) resulted in death of all zoosporangia after 20 s. The most effective products for field use were Path-X and the quaternary ammonium compound 128, which can be used at dilutions containing low levels (e.g. 0.012 or 0.008%, respectively) of the active compound didecyl dimethyl ammonium chloride. Bleach, containing the active ingredient sodium hypochlorite, was effective at concentrations of 1% sodium hypochlorite and above. Cultures did not survive complete drying, which occurred after <3 h at room temperature. B. dendrobatidis was sensitive to heating, and within 4 h at 37 degrees C, 30 min at 47 degrees C and 5 min at 60 degrees C, 100% mortality occurred. UV light (at 1000 mW m(-2) with a wavelength of 254 nm) was ineffective at killing B. dendrobatidis in culture.     

Pulsatile activity and hatching of in vitro produced cow blastocysts: effects of serum supplementation.

The effect of serum added to a modified SOF medium on pulsatile activity and hatching of in vitro produced cow blastocysts was investigated by time-lapse cinematography. Embryos were generated from abattoir material and cultured in mSOF without serum or with 10% FCS added at 42h pi. Addition of serum significantly increases pulsatile activity before zona rupture and reduces the time of hatching. Pulsatile activity does not seem to be involved in the hatching process.     

In vitro potential genotoxic effects of surface drinking water treated with chlorine and alternative disinfectants

A battery of in vitro short-term tests revealing different genetic end-points was set up in order to study surface-water genotoxicity after disinfection with different biocides: sodium hypochlorite (NaClO), chlorine dioxide (ClO(2)) and peracetic acid (PAA). The surface water both before and after disinfection was concentrated by adsorption on C(18) silica cartridges and the concentrates containing non-volatile organics were divided into different portions for chemical analyses and biological assays. The following in vitro tests were conducted on the water concentrates dissolved in DMSO: the Salmonella mutagenicity assay with S. typhimurium strains TA98 and TA100; the SOS Chromotest with Escherichia coli, the Microtox and Mutatox assays with Vibrio fischeri; and gene conversion, point mutation and mitochondrial DNA mutability assays with D7 diploid Saccharomices cerevisiae strain. The results show that the SOS Chromotest and the yeast assays are highly sensitive in detecting genotoxicity. The surface-water extracts were very often toxic to most of the test organisms considered, partially masking their potential mutagenic activity. Therefore, the assays with E. coli and with S. cerevisiae are more likely to show a mutagenic effect because these organisms are generally less sensitive to most toxic compounds. Among the tested disinfectants, NaClO and ClO(2) increased water genotoxicity, whereas PAA was able to slightly reduce raw water activity. However, because the organic compounds in the lake water varied with the season of the year, the disinfection processes, at times, both increased and decreased the raw water activity.     

Giardia muris: scanning electron microscopy of in vitro excystation

A recently developed in vitro excystation procedure results in almost total excystation of Giardia muris, an intestinal parasite of mice. The present experiment examines the G. muris cyst morphology by scanning electron microscopy and the efficacy of the excystation procedure. Untreated cysts of G. muris were elliptical and displayed a distinctive surface structure. Excystation began almost immediately after incubation had begun and most trophozoites emerged within 30 min. Excystation appears to involve flagellar action of the encysted trophozoite. A tear of the wall occurred at one pole. This opening was subsequently enlarged, presumably by flagellar action. Trophozoites emerged, posterior end first, and an associated mucoid-like material was extruded. Newly emerged trophozoites were nearly oval in shape. Trophozoites quickly became flattened, elongate, and underwent cytokinesis resulting in two daughter trophozoites. Few organisms not excysted were seen after 30 min incubation.     

Modulating effects of humic acids on genotoxicity induced by water disinfectants in Cyprinus carpio

The use of chlorinated disinfectants during drinking-water production has been shown to generate halogenated compounds as a result of interactions of humic acids with chlorine. Such chlorinated by-products have been shown to induce genotoxic effects and consumption of chlorinated drinking-water has been correlated with increased risk for cancer induction in human populations. The aim of this work was to test the potential genotoxic effects on circulating erythrocytes of the fish Cyprinus carpio exposed in vivo to well-waters disinfected with sodium hypochlorite (NaClO), chlorine dioxide (ClO2) or peracetic acid (CH3COO2H, PAA), in the absence or presence of standard humic acids (HA). The effects were measured by use of the micronucleus (MN) and the single-cell gel electrophoresis (Comet) assays at different sampling times after a 3-day exposure period. The exposure to chlorine disinfectants without the addition of HA produced a clear toxic effect. Significant cytogenetic damage (i.e. MN induction) was detected in fish populations exposed to both NaClO and ClO2 with humic acids. In the Comet assay, a significant decrease of DNA migration was observed in erythrocytes of specimens after exposure to NaClO-disinfected water without HA. No effects were observed in any other experimental condition.