Description of a new species of myxozoan from Notropis hudsonius in the Great Lakes region of Canada

Myxobolus burti n. sp. is described from striated muscle of Notropis hudsonius (Cyprinidae) collected from localities in Lake Superior, Lake Michigan, Lake Huron, Lake St. Claire, Lake Erie, Lake Ontario, and the St. Lawrence River. Myxobolus burti is intracellular, forming thin-walled, cigar-shaped plasmodia within striated muscle cells of the body. It exhibits disporoblastic, oval spores, approximately 10 μm long, 8 μm wide, and 6 μm thick, with a length-to-width ratio of 1.3 ∶ 1. They resemble most closely those of Myxobolus bellus Kudo, 1934, and Myxobolus mutabilis Kudo, 1934, but have polar capsules unequal in length (5.3 vs. 4.7 μm) and oblique filament coils. The new parasite was not encountered in routine examination of other small-bodied fishes at collection locations and thus looks to be specific to N. hudsonius. A comparative plate of similar species encountered during surveys of these fishes in the northeast is presented to contrast the uniqueness of the new species.     

Insights into the evolutionary origins of clostridial neurotoxins from analysis of the <Emphasis Type="Italic">Clostridium botulinum</Emphasis> strain A neurotoxin gene cluster

Background  

Clostridial neurotoxins (CNTs) are the most deadly toxins known and causal agents of botulism and tetanus neuroparalytic diseases. Despite considerable progress in understanding CNT structure and function, the evolutionary origins of CNTs remain a mystery as they are unique to Clostridium and possess a sequence and structural architecture distinct from other protein families. Uncovering the origins of CNTs would be a significant contribution to our understanding of how pathogens evolve and generate novel toxin families.     

Genetic variation in South Indian castes: evidence from Y-chromosome, mitochondrial, and autosomal polymorphisms

Background

Major population movements, social structure, and caste endogamy have influenced the genetic structure of Indian populations. An understanding of these influences is increasingly important as gene mapping and case-control studies are initiated in South Indian populations.

Results

We report new data on 155 individuals from four Tamil caste populations of South India and perform comparative analyses with caste populations from the neighboring state of Andhra Pradesh. Genetic differentiation among Tamil castes is low (R_ST = 0.96% for 45 autosomal short tandem repeat (STR) markers), reflecting a largely common origin. Nonetheless, caste- and continent-specific patterns are evident. For 32 lineage-defining Y-chromosome SNPs, Tamil castes show higher affinity to Europeans than to eastern Asians, and genetic distance estimates to the Europeans are ordered by caste rank. For 32 lineage-defining mitochondrial SNPs and hypervariable sequence (HVS) 1, Tamil castes have higher affinity to eastern Asians than to Europeans. For 45 autosomal STRs, upper and middle rank castes show higher affinity to Europeans than do lower rank castes from either Tamil Nadu or Andhra Pradesh. Local between-caste variation (Tamil Nadu R_ST = 0.96%, Andhra Pradesh R_ST = 0.77%) exceeds the estimate of variation between these geographically separated groups (R_ST = 0.12%). Low, but statistically significant, correlations between caste rank distance and genetic distance are demonstrated for Tamil castes using Y-chromosome, mtDNA, and autosomal data.

Conclusion

Genetic data from Y-chromosome, mtDNA, and autosomal STRs are in accord with historical accounts of northwest to southeast population movements in India. The influence of ancient and historical population movements and caste social structure can be detected and replicated in South Indian caste populations from two different geographic regions.     

A novel autophagy modulator 6-Bio ameliorates SNCA/α-synuclein toxicity

Parkinson disease (PD) is a life-threatening neurodegenerative movement disorder with unmet therapeutic intervention. We have identified a small molecule autophagy modulator, 6-Bio that shows clearance of toxic SNCA/α-synuclein (a protein implicated in synucleopathies) aggregates in yeast and mammalian cell lines. 6-Bio induces autophagy and dramatically enhances autolysosome formation resulting in SNCA degradation. Importantly, neuroprotective function of 6-Bio as envisaged by immunohistology and behavior analyses in a preclinical model of PD where it induces autophagy in dopaminergic (DAergic) neurons of mice midbrain to clear toxic protein aggregates suggesting that it could be a potential therapeutic candidate for protein conformational disorders.     

A case of spontaneous coronary artery disease regression

Coronary angiographic trials have demonstrated that lowering cholesterol can slow the progression of atherosclerosis, limit the formation of new lesions and enhance atherosclerotic regression together with reducing the incidence of clinical events (Waters D, 1996). Spontaneous regression of coronary atherosclerotic lesions is rare. We report the case of a patient with a severe within-stent restenotic lesion whose coronary disease spontaneously regressed 12 months after initial diagnosis, allowing for medical treatment of symptoms rather than repeated intervention. (Int J Cardiovasc Interventions 1999; 2: 121-123)     

Food webs: a plea for parasites

Parasites have the capacity to regulate host populations and may be important determinants of community structure, yet they are usually neglected in studies of food webs. Parasites can provide much of the information on host biology, such as diet and migration, that is necessary to construct accurate webs. Because many parasites have complex life cycles that involve several different hosts, and often depend on trophic interactions for transmission, parasites provide complementary views of web structure and dynamics. Incorporation of parasites in food webs can substantially after baste web properties, Including connectance, chain length and proportions of top and basal species, and can allow the testing of specific hypotheses related to food-web dynamics.     

Factors influencing the release of proteins by cultured schwann cells

Cultured rat schwann cells grown in association with sensory neurons when labeled with [(3)H]leucinem, [(3)H]glucosamine, or [(35)S]methionine release labeled polypeptides into the culture medium. Analysis by SDS-polyacrylamide gel electrophoresis (SDS-PAGE) of the culture medium reveals a reproducible pattern of more than 20 polypeptides with molecular weights ranging from 15,000 to more than 250,000. Five major polypeptides (apparent molecular weights 225,000, 210,000, 90,000, 66,000, 50,000, and 40,000) account for approximately 40 percent of the leucine or methionine radioactivity in medium polypeptide. Schwann cells grown in a serum-free defined medium, in which schwann cells do not relate normally to axons, release approximately four times less labeled medium polypeptides tha cultures grown in medium supplemented with serum and chick embryo extract. In addition, there is a qualitative difference in the pattern of medium polypeptides resolved by SDS-PAGE, so that a single polypeptide (mol wt 40,000) accounts for nearly all of the label in medium polypeptides. Switching of cultures grown in defined medium to supplemented medium for 2 d results in a fourfold increase in the amount of labeled polypeptides appearing in the culture medium, and a return to the normal pattern of medium polypeptides appearing in the culture medium, and a return to the normal pattern of medium polypeptides as resolved by SDS-PAGE. This change in the pattern of polypeptides release by schwann cells is accompanied by changes in the association between schwann cells and axons. An early step in the establishment of normal axon-schwann cell relations appears to be an inward migration of schwann cells into axonal bundles and spreading of schwann cells along neurites. These changes are evident within 48 h after medium shift. Our results thus suggest that the release of proteins by schwann cells may be important for the development of normal axonal ensheathment.     

Seasonal occurrence of Lernaea cyprinacea on fishes in Belews Lake, North Carolina

Prevalence, abundance, and mean intensity of Lernaea cyprinacea were monitored on 3 species of fishes from June 1984 through August 1986 in Belews Lake, North Carolina. Copepods were observed parasitizing fishes only during summer, when water temperatures exceeded 25 C. Infection levels in mosquitofish (Gambusia affinis) and red shiners (Notropis lutrensis) were very low, but they were much higher in fathead minnows (Pimephales promelas). Infection levels do not appear to be related to the size of the host. Host differences in parasite prevalence may be due to the host habitats.     

The relationship between codon boundaries and multiple reading-frame preferences: coding organization of bacterial insertion sequences

Theoretical considerations have shown that the five possible overlapping reading-frame configurations differ significantly in their coding flexibility and thus in their information content (Siegel and Fitch 1980; Smith and Waterman 1980). Contrary to expectation, the overlapping frame configuration allowing the greatest coding flexibility is rarely seen, whereas one of the most constraining is common. We point out here that this overlapping reading-frame paradox and an observed but unexplained preference in coding regions for a pyrimidine-purine at codon boundaries (Shepherd 1981; Jones and Kafatos 1982; Smith et al. 1983) are intimately linked. The codon boundary preference, which may be related to translation efficiency or accuracy, places constraints on the evolution of overlapping coding regions. These considerations may help identify actual coding regions in DNA sequences. We have analyzed five sequenced (enteric) bacterial insertion sequences for codon boundary incidences and reading-frame configurations and find that they are consistent with these proposed constraints.      

Effects of waterborne zinc on reproduction, survival and morphometrics of Gyrodactylus turnbulli (Monogenea) on guppies (Poecilia reticulata)

Recent reviews indicate that pollutants in the surrounding macroenvironment directly influence the population dynamics, distribution and dispersal of fish ectoparasites, often leading to increased parasitism. The aim of the current study was to explore the effects of sublethal concentrations of waterborne zinc (up to 240 microg Zn/L) on survival, reproduction and morphometrics of Gyrodactylus turnbulli, a viviparous monogenean infecting the skin and fins of the guppy, Poecilia reticulata. Parasite survival and reproduction on the fish were recorded daily for individual parasites maintained in isolated containers. Both survival and reproduction were reduced in 30 and 120 microg Zn/L, compared with 0, 15, and 60 microg Zn/L indicating direct toxic effects of Zn on the parasite. However, as generation time was unaffected by Zn, we attribute the reduced reproduction to the shorter lifespan. Parasite survival off the fish was monitored hourly. Average lifespan of the detached parasites decreased linearly from 19.5 h in 0 microg Zn/L to 17.3h in 240 microg Zn/L, further supporting the direct toxic effect of Zn to the parasite. In addition, temporal dynamics of parasite morphometrics were monitored from mini-epidemics sampled after 1, 5, 10, and 15 days exposure to various Zn concentrations. All morphological parameters decreased significantly in response both to concentration and duration of exposure to waterborne Zn. Together these data clearly indicate that concentrations as low as 120 microg Zn/L are directly toxic to G. turnbulli.