Viability of Giardia cysts suspended in lake, river, and tap water

Numerous waterborne outbreaks of giardiasis have occurred since 1965, yet little or no information has been reported on the viability of Giardia cysts in different aquatic environments. We have studied the viability of Giardia muris cysts suspended in lake, river, and tap water, while also monitoring water temperature, dissolved oxygen, pH, and other water quality parameters. Fecal pellets containing G. muris cysts were placed in glass vials covered with filter paper and exposed to (i) lake water at 15 ft (ca. 4.6 m) and 30 ft (ca. 9.2 m), (ii) river water, (iii) tap water, and (iv) distilled water stored under laboratory conditions. At 3, 7, 14, 28, 56, and 84 days, two vials from each environment were removed, and cyst viability was determined by (i) fluorogenic dye exclusion, (ii) production of giardiasis in an animal, and (iii) cyst morphology by Nomarski microscopy. In the fall, the cysts suspended at 30 ft in lake water remained viable for up to 56 days whereas cysts stored at 15 ft were nonviable after day 28. The G. muris cysts exposed to river water remained viable up to 28 days as determined by the production of giardiasis in mice. G. muris cysts suspended in tap water showed no signs of viability after 14 days, while cysts serving as controls (exposed to refrigerated distilled water) remained viable for up to 56 days. In the winter, Giardia cysts suspended in either lake or river water were viable for 56 to 84 days whereas cysts exposed to tap water were nonviable by day 14.(ABSTRACT TRUNCATED AT 250 WORDS)     

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.     

Esterase-16 (Es-16): Characterization,polymorphism, and linkage to chromosome 3 of a kidney esterase locus of the house mouse

A polymorphism for an isozyme of a presumed arylesterase, esterase-16 (EC 3.1.1.2), has been detected in kidney, heart, and spleen of the house mouse, Mus musculus, by means of isoelectric focusing and by disc electrophoresis. Three phenotypes can be distinguished: the ES-16A phenotype (IEP 5.9) was found in C57BL/10Sn and many other laboratory inbred strains; the ES-16B phenotype (IEP 6.1) was found in M. m. molossinus; and the ES-16C phenotype (IEP 5.9; very weak activity) was found in Peru-Coppock. Esterase-16 is strongly inhibited by 10^?3 m p-chloromercuribenzoate, but not by 2·10^?4 m bis-p-nitrophenyl phosphate or by 10^?3 m Diamox. It stains well with indoxyl acetate and other indigogenic substrates but only weakly with α-naphthyl acetate. Esterase-16 is completely insoluble in water. It is apparently governed by a structural gene locus, Es-16, with three alleles, Es-16 ^a , Es-16^b, and Es-16 ^c, respectively. Es-16 is closely linked to Car-1 and Car-2 on chromosome 3. Typing of 94 animals of the backcross (C57BL/10Sn × M. m. mol.) F₁ × M. m. mol. revealed a recombination frequency of 8.51±2.9%.     

Spatial patterns of acorn dispersal by rodents: do acorn crop size and ungulate presence matter?

Seed dispersal is qualitatively effective when it increases recruitment probability. A poorly studied factor likely affecting recruitment is the spatial distribution of dispersed seeds. Seed-caching animals are thought to disperse seeds in a way that reduces clumping and density to impede cache pilfering. Furthermore, dispersal might differ depending on whether the seed is immediately consumed versus cached for later consumption, and might differ depending on the ecological context. The main objectives of this study were to determine: 1) the spatial pattern of seed dispersal by rodents in a heterogeneous environment; 2) whether the patterns differ among years and among acorn competitor exclosure treatments, and 3) whether rodents create different spatial patterns of dispersal for acorns that are cached versus consumed immediately following dispersal. We studied the degree of spatial aggregation of acorn dispersal by rodents using two different estimators derived from the Ripley K and the Diggle G functions. We also analyzed various metrics of dispersal distances. For both analyses we used observed acorn dispersal patterns in two years differing in crop size and inside versus outside exclosures restricting access to acorn-consuming ungulates. During 2003, a year with a larger crop size, maximum seed dispersal distances were less, and the pattern of dispersed seeds was more clumped, than in 2004, a year with a smaller crop size. Median dispersal distances did not differ between years. In the presence of ungulates, seed dispersal was marginally sparser than in their absence. Cached acorns were dispersed more sparsely than acorns eaten immediately. These results have important implications for the quality of seed dispersal for oak recruitment that are likely relevant to other systems as well.     

Evidence for acyl homoserine lactone signal production in bacteria associated with marine sponges

We report for the first time the production of acyl homoserine lactones (AHLs) by bacteria associated with marine sponges. Given the involvement of AHLs in bacterial colonization of many higher organisms, we speculate that such quorum sensing signals could play a part in interactions between sponges and the dense bacterial communities living within them.     

A point mutation in the IL-12R beta 2 gene underlies the IL-12 unresponsiveness of Lps-defective C57BL/10ScCr mice

Lps-defective C57BL/10ScCr (Cr) mice are homozygous for a deletion encompassing Toll-like receptor 4 that makes them refractory to the biological activity of LPS. In addition, these mice exhibit an inherited IL-12 unresponsiveness resulting in impaired IFN-gamma responses to different microorganisms. By positional cloning methods, we show here that this second defect of Cr mice is due to a mutation in a single gene located on mouse chromosome 6, in close proximity to the Igkappa locus. The gene is IL-12Rbeta2. Cr mice carry a point mutation creating a stop codon that is predicted to cause premature termination of the translated IL-12Rbeta2 after a lysine residue at position 777. The truncated beta2 chain can still form a heterodimeric IL-12R that allows phosphorylation of Janus kinase 2, but, unlike the wild-type IL-12R, can no longer mediate phosphorylation of STAT4. Because the phosphorylation of STAT4 is a prerequisite for the IL-12-mediated induction of IFN-gamma, its absence in Cr mice is responsible for their defective IFN-gamma response to microorganisms.     

Glutamatergic plasticity by synaptic delivery of GluR-B(long)-containing AMPA receptors

Activity-driven delivery of AMPA receptors is proposed to mediate glutamatergic synaptic plasticity, both during development and learning. In hippocampal CA1 principal neurons, such trafficking is primarily mediated by the abundant GluR-A subunit. We now report a study of GluR-B(long), a C-terminal splice variant of the GluR-B subunit. GluR-B(long) synaptic delivery is regulated by two forms of activity. Spontaneous synaptic activity-driven GluR-B(long) transport maintains one-third of the steady-state AMPA receptor-mediated responses, while GluR-B(long) delivery following the induction of LTP is responsible for approximately 50% of the resulting potentiation at the hippocampal CA3 to CA1 synapses at the time of GluR-B(long) peak expression-the second postnatal week. Trafficking of GluR-B(long)-containing receptors thus mediates a GluR-A-independent form of glutamatergic synaptic plasticity in the juvenile hippocampus.