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Biomedical subjects

E A Meyer

Publications and source records attributed to E A Meyer.

At least 19 recordsLinked to original sources
PubMed2006

Batch solar disinfection inactivates oocysts of Cryptosporidium parvum and cysts of Giardia muris in drinking water.

AIM: To determine whether batch solar disinfection (SODIS) can be used to inactivate oocysts of Cryptosporidium parvum and cysts of Giardia muris in experimentally contaminated water. METHODS AND RESULTS: Suspensions of oocysts and cysts were exposed to simulated global solar irradiation of 830 W m(-2) for different exposure times at a constant temperature of 40 degrees C. Infectivity tests were carried out using CD-1 suckling mice in the Cryptosporidium experiments and newly weaned CD-1 mice in the Giardia experiments. Exposure times of > or =10 h (total optical dose c. 30 kJ) rendered C. parvum oocysts noninfective. Giardia muris cysts were rendered completely noninfective within 4 h (total optical dose >12 kJ). Scanning electron microscopy and viability (4',6-diamidino-2-phenylindole/propidium iodide fluorogenic dyes and excystation) studies on oocysts of C. parvum suggest that inactivation is caused by damage to the oocyst wall. CONCLUSIONS: Results show that cysts of G. muris and oocysts of C. parvum are rendered completely noninfective after batch SODIS exposures of 4 and 10 h (respectively) and is also likely to be effective against waterborne cysts of Giardia lamblia. SIGNIFICANCE AND IMPACT OF THE STUDY: These results demonstrate that SODIS is an appropriate household water treatment technology for use as an emergency intervention in aftermath of natural or man-made disasters against not only bacterial but also protozoan pathogens.

Animals↗
PubMed1994

Perception of odor mixtures by the spiny lobster Panulirus argus.

We used spiny lobsters (Panulirus argus) in a discrimination learning procedure with aversive conditioning to examine their behavioral discrimination of adenosine-5'-monophosphate (AMP), betaine, L-cysteine and their binary mixtures. Our results show that spiny lobsters can clearly discriminate among binary mixtures and their components. Lobsters aversively conditioned to avoid responding to a binary mixture continued to respond to that mixture's components, and lobsters that were aversively conditioned to avoid responding to a compound tended to continue to respond to binary mixtures containing that compound. Thus, responses of conditioned lobsters to binary mixtures were not usually intermediate between the responses to the mixtures' components, which might be expected for response-matched compounds. This result might arise from any of several factors. First, it might result from mixture interactions in the peripheral olfactory system, if the responses of olfactory receptor neurons to one component of a binary mixture were suppressed by the other component, making the response to the mixture more similar to the suppressing component. Electrophysiological data from a population of 50 singly-recorded olfactory receptor neurons (Daniel and Derby, 1994) do not consistently support this idea. A second possible reason for the behavioral response to a binary mixture not being intermediate between the responses to its components involves higher order processing, such as mixture interactions generated in olfactory interneurons in the CNS (which is known to occur: Derby et al., 1985; Ache, 1989), configural learning or associative processing.

Adenosine Monophosphate↗
PubMed1993

Unique phylogenetic position of Diplomonadida based on the complete small subunit ribosomal RNA sequence of Giardia ardeae, G. muris, G. duodenalis and Hexamita sp.

Complete small-subunit rRNA (SSU-rRNA) coding region sequences were determined for two species of the intestinal parasite Giardia: G. ardeae and G. muris, both belonging to the order Diplomonadida, and a free-living member of this order, Hexamita sp. These sequences were compared to published SSU-rDNA sequences from a third member of the genus Giardia, G. duodenalis (often called G. intestinalis or G. lamblia) and various representative organisms from other taxa. Of the three Giardia sequences analyzed, the SSU-rRNA from G. muris is the smallest (1432 bases as compared to 1435 and 1453 for G. ardeae and G. duodenalis, respectively) and has the lowest G+C content (58.9%). The Hexamita SSU-rRNA is the largest in this group, containing 1550 bases. Because the sizes of the SSU-rRNA are prokaryotic rather than typically eukaryotic, the secondary structures of the SSU-rRNAs were constructed. These structures show a number of typically eukaryotic signature sequences. Sequence alignments based on constraints imposed by secondary structure were used for construction of a phylogenetic tree for these four taxa. The results show that of the four diplomonads represented, the Giardia species form a distinct group. The other diplomonad Hexamita and the microsporidium Vairimorpha necatrix appear to be distinct from Giardia.

Animals↗
PubMed1989

Compatibility of ADSOL-stored red cells with intravenous solutions.

Five percent dextrose in water (D5W) and lactated Ringer's (RL) are two intravenous solutions that are incompatible with citrate phosphate dextrose (CPD) anticoagulated RBCs. Hemolysis, agglutination, and clotting can occur when RBCs are mixed with, infused together with, or transfused in the same line following administration of these fluids. Although minimal plasma remains in units of RBCs containing adenine-saline-dextrose solution (ADSOL; Fenwal Laboratories, Deerfield, IL), clots are seen immediately after contact is made with RL. Clumping and hemolysis are seen when ADSOL-stored RBCs or saline-washed RBCs are mixed with D5W. This study reinforces the unsafe practice of mixing RBCs with certain intravenous solutions.

Adenine↗
PubMed1989

The sensitivity and specificity of the immediate-spin crossmatch.

The immediate-spin (IS) crossmatch is used to detect ABO incompatibility between donor red cells (RBCs) and the serum of the intended recipient. However, this test may be positive in the absence of ABO incompatibility (false positive) or it may be negative when ABO incompatibility exists (false negative). During a 25-month study, the rates of both false-positive and false-negative IS crossmatch results were evaluated, and the sensitivity and specificity of the IS crossmatch were determined. During the study period, 53,656 IS crossmatches were performed for patients without significant RBC antibodies. Fifty-five patients had positive IS crossmatches, and no false-negative reactions were found. In tests of 55 patients with positive IS crossmatches, 77 false-positive and 5 true-positive reactions were noted. The causes of the false-positive reactions were rouleaux (36 patients), cold-reactive antibodies (8 patients), a combination of rouleaux and cold-reactive antibodies (2 patients), fibrin clot (1 patient), and undetermined (3 patients). The sensitivity and specificity of the IS crossmatch were 100 and 99.86 percent, respectively. Laboratory personnel should be aware that the IS crossmatch may have false-positive or false-negative results, and they should develop written protocols to distinguish quickly between true-positive and false-positive reactions.

ABO Blood-Group System↗
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↗
PubMed1985

The epidemiology of Giardiasis.

Giardiasis is now known to occur not only endemically, but also as an epidemic disease spread primarily via drinking water. Giardia from different animals, although morphologically indistinguishable, vary in host specificity. This raises the possibility that lower animals may harbour representatives of this genus which are transmissible to humans. In this article, Ernest Meyer discusses our present understanding of the epidemiology of Giardia, related to problems of speciation in this genus.

Journal Article↗
PubMed1984

Giardia lamblia: autoradiographic analysis of nuclear replication.

Giardia lamblia trophozoites, grown in axenic culture, were labeled for various periods of time with [3H]thymidine. After autoradiography, grains were counted over each of the two nuclei in each trophozoite. Analysis of the fraction of trophozoites labeled for each time period resulted in an estimate of a generation time of 15 hr. The DNA synthetic or S phase for a trophozoite in culture was calculated to be 1.8 hr. G1 and G2 periods were determined to be 8.5 and 3 hr, respectively. A comparison of the labeling density between the two nuclei indicated that replication takes place simultaneously in both nuclei for at least 70% of S period. The fraction of asymmetrically labeled trophozoites is consistent with a model in which the nuclei replicate out of phase by 15-30 min, but, due to the small diameter of the nuclei relative to the grain size, the possibility that replication takes place simultaneously in both nuclei of a trophozoite throughout the S phase cannot be ruled out.

Animals↗
PubMed1984

Occurrence of specific secretory immunoglobulin A in bile after inoculation of Giardia lamblia trophozoites into rat duodenum.

We studied the appearance of specific secretory immunoglobulin A (IgA) antibody in bile after inoculation of live Giardia lamblia trophozoites into rat intestine. Serial bile specimens collected before and after inoculation of trophozoites were assayed for IgA antibodies by indirect immunofluorescence. Secretory IgA antibodies to Giardia lamblia were first detected in bile at 3 days after inoculation, remained elevated through 12 days, and then returned to control levels. Positive immunofluorescence of trophozoites for IgA was observed at bile titers of 1:80 to 1:160, whereas control biles were usually negative at dilutions of 1:10 or less. Scanning electron microscopic examination of Giardia in conjunction with immunocytochemistry revealed IgA antibodies bound to the flagella and surfaces of the trophozoites including the adhesive disk. These data demonstrate the occurrence of a secretory IgA immune response directed against surface antigens of Giardia lamblia trophozoites in the rat.

Animals↗
PubMed1984

A morphometric comparison of five axenic Giardia isolates.

The length and width of trophozoites from axenic cultures of 5 Giardia isolates were measured both live and after fixation and Giemsa staining. These isolates, as named on the basis of host source, are classified as G. lamblia (3 isolates), G. felis (1 isolate), and G. caviae (1 isolate). The size of live, unstained trophozoites from the 5 isolates, measured without regard to the presence or absence of median bodies, showed only occasional significant differences in length. Statistically significant differences in length and/or width were observed for all comparisons when stained preparations of the isolates were compared. These size differences occurred between isolates assigned to different species as well as among the 3 G. lamblia isolates. These data and previously reported isozyme studies of these isolates most appropriately led to a re-examination of the presently utilized criteria for Giardia speciation.

Animals↗
PubMed1983

A comparison of isozymes of five axenic Giardia isolates.

The relative mobilities of six enzymes from the trophozoites of five axenically-cultured isolates of Giardia from human, cat, and guinea pig hosts were compared by starch and polyacrylamide gel electrophoresis. The six enzymes compared were malate dehydrogenase (NAD+) (MDH) (EC 1.1.1.37), malate dehydrogenase (decarboxylating) (ME) (EC 1.1.1.40), hexokinase (EC 2.7.1.1), 6-phosphogluconate dehydrogenase (EC 1.1.1.44), glucose-6-phosphate dehydrogenase (G6P) (EC 1.1.1.49), and alpha-glycerophosphate dehydrogenase (EC 1.1.1.8). The latter three enzymes have not been previously reported in Giardia. On the basis of zymogram patterns, the five Giardia isolates were divided into three zymodemes. Zymodeme I comprised human-1/England, human-1/Bethesda, and cat-1/Portland, Zymodeme II the guinea pig-1/Portland isolate, and Zymodeme III the human-1/Portland isolate. These zymodemes were further substantiated when several physical and kinetic properties of three of the enzymes, MDH, ME, and G6P, were examined. Our results, in which Giardia isolated from different mammalian hosts share multiple isoenzymes, question the validity of the practice of assigning Giardia species names on the basis of the animal host from which the protozoan was obtained.

Animals↗
PubMed1981

Lipid and carbohydrate metabolism of Giardia lamblia.

The lipid and carbohydrate metabolism of Giardia lamblia was studied using trophozoites isolated from a human and axenically grown in vitro in medium containing fetal bovine serum. The phospholipid, fatty acid and neutral lipid composition of the G. lamblia trophozoites was similar to that of the medium. Phosphatidylethanolamine, phosphatidylcholine and sphingomyelin were the major phospholipids detected; monoacyl-, diacyl-, triacylglycerides, sterols, and sterol esters were the major neutral lipids found. Several unidentified glycolipids were also detected. Glucose and threonine were readily incorporated by the trophozoites, but not into cellular phospholipids or sterols. However, approximately 86% of the glucose incorporated into the trophozoites was found in the nucleic acids, and 38% of the threonine incorporated was detected in the cellular proteins. Small amounts of the glucose and threonine were incorporated into glycolipid-containing fractions. Glycerol and acetate were not appreciably incorporated into trophozoites while glycerol 3-phosphate incorporation was not detected. Cholesterol was readily assimilated by the trophozoites; 98% of the incorporated was found in the sterol fraction. Radiorespirometric data suggest that the major routes of glucose metabolism in G. lamblia are via Embden- Meyerhof-Parnas and pentose phosphate pathways. However, endogenous acetate (as acetyl-CoA) formed during the metabolism of glucose is not used for lipid biosynthesis. These findings suggest that G. lamblia trophozoites are incapable of synthesizing cellular phospholipids or sterols de novo, but rather, utilize lipids already present in the medium.

Animals↗