Biomedical subjects

W J Bemrick

Publications and source records attributed to W J Bemrick.

At least 19 recordsLinked to original sources

PubMed1990

Prevalence of Giardia spp. in beaver and muskrat populations in northeastern states and Minnesota: detection of intestinal trophozoites at necropsy provides greater sensitivity than detection of cysts in fecal samples.

Surveys of the prevalence of the intestinal protozoan Giardia spp. in animal populations have relied almost exclusively on the detection of cysts in fecal samples. We have determined the prevalence of Giardia spp. in beaver and muskrat populations in four northeastern states and Minnesota by using both the detection of trophozoites in mucosal scrapings from live-trapped animals at necropsy and the detection of cysts in fecal samples collected from kill-trapped animals. In muskrats the prevalence of Giardia infection was 36.6% by cyst detection in fecal samples (n = 790) from kill-trapped animals and 95.9% in live-trapped muskrats when the intestinal contents were analyzed for the presence of trophozoites (n = 219). Similarly, in beavers, Giardia infection was 9.2% by cyst detection in fecal samples (n = 662) from kill-trapped beavers and 13.7% in live-trapped animals examined for the presence of intestinal trophozoites (n = 302). The detection of trophozoites in mucosal scrapings from live-trapped animals consistently yielded a significantly higher prevalence for both muskrats and beavers than did the method based on detection of cysts in the fecal samples. The prevalence of Giardia infection in juvenile and adult live-trapped muskrats was similar (92.5 and 94.4%, respectively), but the prevalence in juvenile live-trapped beavers (23.2%) was significantly greater than that seen in the adult animals (12.6%). No difference in Giardia prevalence on the basis of sex was seen in either animal species. Regional variation, often statistically significant, was seen in the prevalence of Giardia in beavers in the northeastern states and Minnesota, but was not detected for muskrats.

Animals↗

PubMed1990

High-resolution immunogold localization of Giardia cyst wall antigens using field emission SEM with secondary and backscatter electron imaging.

We describe here the ultrastructural localization of Giardia cyst antigens in the filaments associated with the outer portion of intact cysts and on developing cyst wall filaments in encysting trophozoites. Post-embedding immunogold labeling of thin sections of intact Giardia cysts with polyclonal and monoclonal antibodies specific for cyst wall antigens (major protein bands of approximately 29, 75, 88, and 102 KD on Western blots) showed strong labeling of the filamentous cyst wall, whereas no labeling was seen on the membranous portion. High-resolution field emission scanning electron microscopy (FESEM) of Giardia cysts revealed that the cyst wall-specific polyclonal rabbit antisera and monoclonal mouse antibody produced gold labeling of 20-nm filaments in the cyst wall as detected with secondary electron imaging (SEI) and backscatter electron imaging (BEI) at 10 kV, despite coating of the cells with platinum by ion sputtering. FESEM studies of encysting Giardia trophozoites demonstrated that immunostaining with antibodies to cyst wall antigens produced colloidal gold labeling of developing cyst wall filaments on the cell surface; however, the intervening membrane domains were unlabeled. Substitution of normal serum for cyst wall-specific antibodies, or preabsorption of specific antibodies with Giardia cysts, eliminated immunolabeling of the filaments.

Animals↗

PubMed1990

The detection of Giardia muris and Giardia lamblia cysts by immunofluorescence in animal tissues and fecal samples subjected to cycles of freezing and thawing.

The effects of freezing and thawing on the detection of selected Giardia spp. cysts were investigated using immunofluorescence, bright field microscopy, and low voltage scanning electron microscopy (SEM). Giardia muris cysts were obtained from either animal carcasses, fecal pellets, or isolated cyst preparations, whereas Giardia lamblia cysts were isolated from fecal samples. These samples were stained using an immunofluorescence technique after 1-3 freezing (-16 C) and thawing (20 C) cycles. Cysts were detected successfully by immunofluorescence in all samples. However, in those samples subjected to freeze-thawing, the cyst walls often became distorted and then were not detectable by bright field microscopy. Low voltage SEM demonstrated that the filaments in the distorted cyst wall underwent rearrangements of interfilament spacing. Quantitation of cyst recovery after freezing and thawing demonstrated that a substantial loss occurred after 1 cycle of alternating temperature when low concentrations of cysts were used, but not with high concentrations of cysts. Cyst recovery, after 3 freezing and thawing cycles, was dramatically lowered irrespective of the initial cyst concentration. These results demonstrated that immunofluorescence was an effective technique for the detection of Giardia spp. cysts in frozen samples and would suggest that freezing and thawing of fecal samples could prevent the detection of cysts when only bright field microscopy was employed.

Animals↗

PubMed1990

Axenic culture and characterization of Giardia ardeae from the great blue heron (Ardea herodias).

Trophozoites of Giardia ardeae were obtained from the great blue heron (Ardea herodias) and established in axenic culture using the TYI-S-33 medium. The generation time in culture for G. ardeae was 22-25 hr, which was 3-fold longer than for Giardia duodenalis (WB strain). A morphological comparison of trophozoites in the original intestinal isolate to those grown in culture revealed that they were identical for the following characteristics: a pyriform-shaped body, a ventral adhesive disc with a deep notch in the posterior border, teardrop-shaped nuclei, pleomorphism in median body structure ranging from a round-oval appearance (Giardia muris type) to that of a clawhammer (G. duodenalis type), and a single caudal flagellum on the right side (as viewed dorsally) with the left one being rudimentary. Analysis of the chromosomal migration patterns was performed by orthogonal-field-alternation gel electrophoresis and demonstrated that the pattern for G. ardeae was distinctly different from that for G. duodenalis (Portland 1-CCW strain). Bacterial symbionts were seen attached to trophozoites in the original isolate but could not be detected in cultured trophozoites using scanning electron microscopy, fluorescence light microscopy using the Hoechst 33258 dye for DNA localization, or by standard microbiological techniques using nonselective media for growing aerobic or anaerobic bacteria. This study demonstrated that avian-derived Giardia could be grown in axenic culture; based on morphological criteria and chromosomal migration patterns, that G. ardeae should be considered a distinct species; and that rationale for determining Giardia spp., based on median body structure alone, should no longer be considered adequate for classification at the species level.

Animals↗

PubMed1989

High-resolution electron microscopic evidence for the filamentous structure of the cyst wall in Giardia muris and Giardia duodenalis.

High-resolution morphological studies of the cyst wall of Giardia spp. were performed using low-voltage scanning electron microscopy (LVSEM) and transmission electron microscopy (TEM). The cyst wall was composed of membranous and filamentous layers. The membranous layer consisted of an inner and an outer cyst membrane separated by a thin layer of cytoplasm. The filamentous layer contained individual filaments that ranged from 7 to 20 nm in diameter when measured by LVSEM, formed a dense meshwork with branches or interconnections, and were occasionally arranged on the surface in whorled patterns. Cysts of Giardia muris from mice, Giardia duodenalis from dogs, pigs, voles, beavers, muskrats, and humans, and Giardia psittaci from a bird (parakeet), possessed an essentially identical wall composed of filaments. Inducement of excystation in viable Giardia cysts produced a dramatic increase in the interfilament spacing over an entire cyst, but none was observed in heat-killed or chemically fixed control cysts. These results demonstrated that the cyst wall of Giardia spp. was composed of a complex arrangement of filaments, presumably formed during the process of encystment.

Animals↗

PubMed1988

Production of viable Giardia cysts in vitro: determination by fluorogenic dye staining, excystation, and animal infectivity in the mouse and Mongolian gerbil.

The purpose of this research was to document the formation of viable Giardia cysts in vitro. Viability staining, using fluorogenic dyes that required metabolic conversion for detection, and immunocytochemistry at the light microscopic level provided information on viability and for the identification of formed in vitro. Analysis of cysts formed in vivo and in vitro showed similar morphologic appearances by both light and electron microscopy. Cysts formed in vitro were capable of establishing infections in both mouse and gerbil models for giardiasis. Trophozoites obtained from mice experimentally infected with in vitro-formed cysts could be maintained in culture and induced a second time to form cysts in vitro. This model for the production of viable Giardia cysts in vitro should facilitate research on controlling the complete life cycle of Giardia outside an animal host.

Animals↗

PubMed1988

Cross-species transmission of Giardia spp.: inoculation of beavers and muskrats with cysts of human, beaver, mouse, and muskrat origin.

Giardia cysts isolated from humans, beavers, mice, and muskrats were tested in cross-species transmission experiments for their ability to infect either beavers or muskrats. Giardia cysts, derived from multiple symptomatic human donors and used for inoculation of beavers or muskrats, were shown to be viable by incorporation of fluorogenic dyes, excystation, and their ability to produce infections in the Mongolian gerbil model. Inoculation of beavers with 5 x 10(5) Giardia lamblia cysts resulted in the infection of 75% of the animals (n = 8), as judged by the presence of fecal cysts or intestinal trophozoites at necropsy. The mean prepatent period was 13.1 days. An infective dose experiment, using 5 x 10(1) to 5 x 10(5) viable G. lamblia cysts collected by fluorescence-activated cell sorting, demonstrated that doses of between, less than 50, and less than 500 viable cysts were required to produce infection in beavers. Scanning electron microscopy of beaver small intestine revealed that attachment of G. lamblia trophozoites produced lesions in the microvillous border. Inoculation of muskrats with G. lamblia cysts produced infections when the dose of cysts was equal to or greater than 1.25 x 10(5). The inoculation of beavers with Giardia ondatrae or Giardia muris cysts did not produce any infection; however, the administration to muskrats of Giardia cysts of beaver origin resulted in the infection of 62% of the animals (n = 8), with a prepatent period of 5 days. Our results demonstrated that beavers and muskrats could be infected with Giardia cysts derived from humans, but only by using large numbers of cysts.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1988

A comparison of Giardia microti and Spironucleus muris cysts in the vole: an immunocytochemical, light, and electron microscopic study.

We have shown that cysts of the genus Spironucleus share many common morphological features with Giardia cysts including: 2-4 nuclei, flagellar axonemes, a distinct cyst wall, and they even display the same immunostaining as Giardia cysts when labeled with antibodies specific for Giardia cyst wall. A direct comparison of Spironucleus muris and Giardia microti cysts have revealed that cysts of S. muris are significantly smaller than cysts of G. miroti. At the ultrastructural level, the cyst walls are similar in fibrillar appearance, but the width of the S. muris cyst wall is significantly less than that of G. microti. The cysts of S. muris also differ from G. microti in that they contain a striated rootlet fiber, flagellar sheath, and numerous glycogen rosettes. Characteristic features of Giardia include the adhesive disc and median body. Although the cysts of Spironucleus and Giardia are similar in appearance, these unique morphological features can be used to distinguish between the 2 protozoa and should be employed in the detection of Giardia cysts in water samples.

Animals↗

PubMed1987

SEM evidence for a new species, Giardia psittaci.

The genus Giardia has been subdivided by Filice (1952) into 3 species, G. agilis, G. muris, and G. duodenalis, based on the morphology of the median body and subtle variations in the dimensions of trophozoites. Giardia trophozoites were isolated from the small intestine of budgerigars (parakeets) and examined morphologically with light and scanning electron microscopy. These trophozoites, like other Giardia spp., possessed a flattened dorso-ventral shape, 8 flagella, and an adhesive disc on the ventral surface. The presence of a claw hammer-shaped median body suggested classification of these trophozoites as G. duodenalis. However, unlike any known members of G. duodenalis, the Giardia trophozoites from budgerigars were morphologically distinct in that they lacked the ventrolateral flange and therefore did not have a marginal groove bordering the anterior and lateral border of the adhesive disc. This distinct morphology clearly indicated that trophozoites from budgerigars should be considered as a separate species, G. psittaci. Our evidence has demonstrated that median body shape cannot serve as a sole criterion for speciation of Giardia. In addition, if other avian species of Giardia also resemble G. psittaci, then this would suggest that evolutionary divergence has occurred in the genus Giardia.

Adhesiveness↗

PubMed1986

Experimental bovine coccidiosis: control with monensin.

Young Holstein-Friesian bull calves were used in a controlled experiment to evaluate the efficacy of monensin against coccidiosis. The calves were given oocysts of Eimeria bovis and/or E. zurnii. Medication was started 3 days prior to inoculation and continued during the 30-day experimental period. Oocyst shedding was quantified prior to and throughout the experiment and demonstrated that monensin at the rate of 20 or 30 g ton-1 of feed significantly reduced oocyst shedding and clinical coccidiosis. Clinical infection with E. zurnii was very difficult to establish, even when calves were treated with 20 mg dexamethasone IM on Days 12, 15, and 16 post-inoculation.

Animals↗

PubMed1986