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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
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↗
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↗
PubMed1981

Effect of chlorine on Giardia lamblia cyst viability.

The effect of chlorine concentration on Giardia lamblia cyst viability was tested under a variety of conditions. The ability of Giardia cysts to undergo excystation was used as the criterion of viability. The experimental variables employed included temperature (25, 15, and 5 degrees C), pH (6, 7, and 8), chlorine-cyst contact time (10, 30, and 60 min), and chlorine concentration (1 to 8 mg/liter). In the pH range studied, cyst survival generally was observed to increase as buffer pH increased. Water temperature coupled with chlorination proved to be important in cyst survival. Results of these experiments at the three temperatures studied can be summarized as follows: at 25 degrees C, exposure to 1.5 mg/liter for 10 min killed all cysts at pH 6, 7, and 8. At 15 degrees C, 2.5 mg of chlorine per liter for 10 min killed all cysts at pH 6, but at pH 7 and 8 small numbers of cysts remained viable after 30 min but not after 60 min. At 5 degrees C, 1 mg of chlorine per liter for 60 min failed to kill all the cysts at any pH tested. At this temperature, 2 mg of chlorine per liter killed all cysts after 60 min at pH 6 and 7, but not at pH 8. A chlorine concentration of 4 mg/liter killed all the cysts at all three pH values after 60 min, but not after 30 min. A chlorine concentration of 8 mg/liter killed all Giardia cysts at pH 6 and 7 after contact for 10 min, and at pH 8 after 30 min. This study points up the role of temperature, pH, and chlorine demand in the halogen treatment of drinking water to destroy cysts. It also raises an epidemiological problem, namely: low water temperatures, where killing of Giardia requires relatively high chlorine concentrations and long contact times, are (i) to be expected in many areas where epidemic waterborne giardiasis has been reported and (ii) particularly conducive to the long-term survival of Giardia cysts.

Animals↗
PubMed1981

Opsonization in vitro of Giardia lamblia trophozoites.

The ability of peritoneal rabbit macrophages from immunized and nonimmunized animals to phagocytose Giardia lamblia trophozoites in the presence of serum was studied and compared in an in vitro system. The rabbits which served as the source of immune serum and macrophages were injected repeatedly at multiple sites (intramuscularly, subcutaneously, and intradermally) with a mixture of G. lamblia trophozoites and Freund complete adjuvant. In the presence of normal rabbit serum, a low level of phagocytosis of Giardia trophozoites by normal and immune macrophages was observed. In the presence of hyperimmune rabbit serum, an increased phagocytic activity of both types of macrophages occurred. The opsonic activity was similar whether whole serum or purified immunoglobulin G was used and whether or not these were heat inactivated. G. lamblia trophozoites in suspension were shown to be agglutinated in the presence of hyperimmune serum. Tests employing serial dilutions of hyperimmune serum resulted in a parallel loss of opsonifying and agglutinating activities. It is suggested that opsonization in vivo may play a role in the ability of the host to limit infection by these organisms.

Animals↗
PubMed1980

Giardiasis.

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Adult↗
PubMed1980

Dipetalonema from the eye of a man in Oregon, U.S.A. A case report.

A 21-mm filarial worm appeared suddenly in the anterior chamber of the right eye of a 32-year-old man in western Oregon. By a simultaneous irrigation-aspiration procedure, it was removed alive and only slightly damaged and was identified as a female Dipetalonema in the fourth stage of development. It was the third such case to be reported from western Oregon. In this and one other case the worms were morphologically similar to adult worms identified as Dipetalonema arbuta Highby 1943 from the body cavity of the porcupine (Erethizon dorsatum) and a similar species, Dipetalonema sprenti Anderson 1953, from the body cavity of the beaver (Castor canadensis).

Adult↗