Community ecology of helminth parasitism in an insular passerine avifauna.

Three hundred and thirty specimens of 7 species of passerine birds from South Bass Island, Ottawa County, Ohio, were examined for helminth parasites. The total number of helminth specimens collected was 4,333. Forty-one helminth taxa were identified. Ten species of helminths were identified as having foci of infection on the island. An index of association for these 10 species is presented. The low association revealed between helminth species utilizing common species of intermediate hosts indicated that a single intermediate host specimen is likely to harbor infective stages of only one species of parasitic helminth. An index of similarity is presented to express the species importance relationships of the helminth faunas of the 7 species of birds: red-winged blackbirds (Agelaius phoeniceus), blue jays (Cyanocitta cristata), brown-headed cowbirds (Molothrus ater), common grackles (Quiscalus quiscula), house sparrows (Passer domesticus), starlings (Sturnus vulgaris), and robins (Turdus migratorius). The results reveal that competition between these avian species for invertebrate food resources helps to maximize the transmission of those helminth populations which utilize these same invertebrates as intermediate hosts. The aggregation of birds into mixed feeding flocks insures a heavy loading of the feeding grounds with agents infective for the invertebrate populations.     

Renal coccidiosis in interior Canada geese, Branta canadensis interior Todd, of the Mississippi Valley population

Kidneys from 309 Interior Canada geese from three locations in the Mississippi Flyway were examined for renal coccidia. Oocysts and/or young zygotes of Eimeria sp. were found in 6.8% of goose kidneys sampled. Only one type of renal coccidian oocyst was observed. Significantly more immature geese were infected than adults; however, there was no significant difference observed between the prevalences of infection in male and female birds. A host cellular response to zygotes and oocysts was noted in the majority of infected adult geese. Heavily infected kidneys were hypertrophic with minute foci on the surface of the organ. Histological examinations showed large numbers of unsporulated oocysts accumulated in distended collecting tubules, resulting in pressure necrosis to adjacent tissue and urate retention. Zygotes were observed in the cytoplasm of tubule cells and extracellularly in interstitial tissue. Infected tubule cells were characterized by the peripheral location of the nuclei, cytoplasmic basophilia, and cellular hypertrophy. This is the first report of an Eimeria sp. in the kidneys of Canada geese of the Mississippi Valley population.     

Studies on the GABAergic system in astrocytoma and neuroblastoma cells in culture

The GABAergic system was investigated in C-6 astrocytoma cells and C-1300 neuroblastoma cells in culture and compared to that in mouse brain. The activities of glutamate decarboxylase, GABA-transaminase, succinic semialdehyde dehydrogenase and glutamate dehydrogenase were measured. In the cultured cells, only glutamate dehydrogenase activity was equal or greater than that of mouse cerebral cortex. Glutamate decarboxylase in both cell lines was 2%, while GABA-transaminase and succinic semialdehyde dehydrogenase activities were less than 20% of those found in brain. In spite of the disparate enzyme activities, GABA, glutamate, and -ketoglutarate concentrations were similar in the cell lines and cerebral cortex. The anticonvulsant drugs sodium valproate and aminooxyacetic acid increased cortical GABA concentrations but either had no effect or decreased GABA in the cells in a complete medium. The convulsant isoniazid decreased GABA in mouse brain but had no effect in either cell line. In the absence of pyridoxal in the medium, some drug effects could be induced in the cultured cells. It is concluded that the differing responses of the GABAergic system in the mouse brain and cell lines may be attributed in part to the fact that the cells do not represent an integrated system and are of tumor origin.     

Population biology of Camallanus oxycephalus Ward and Magath, 1916 (Nematoda: Camallanidae) in white bass in western Lake Erie.

The distribution and abundance of the nematode Camallanus oxycephalus infecting white bass, Morone chrysops, in western Lake Erie was studied for over 2 years. Infection was generally more frequent and of higher intensity in large fish. The frequency distributions of nematode abundance in all segments of the fish population followed the negative binomial distribution. The data show seasonal cycles in population structure, site selection, intensity of infection, maturation, and reproduction. Infection occurs during July and August with a resulting peak in population density; during late summer and autumn, mortality, probably density-dependent, reduces the population by 30 to 60%; surviving worms are eliminated at 1 year of age. Growth and development of female worms is arrested from November to April, then proceeds at a rapid rate until the worms release their larvae and die. This growth pattern is probably related to temperature but may also involve host hormone cycles. The dispersal period of the nematode coincides with the annual maximum density of the intermediate host, a cyclopoid copepod,and is interpreted as an adaptation which increases the probability of successful transmission. Because the number of larvae produced by each female worm is a function of body volume, natural selection has favored rapid spring growth and attainment of large body size relative to the male worm. Both seasonal timing in the life cycle and the number of larvae produced are important factors in determining the abundance of this and perhaps other parasites. Evidence is presented suggesting that fluctuations of environmental parameters may disrupt the timing of transmission and alter the distribution and abundance of the parasite. It is hypothesized that the magnitude of such changes in parasite abundance may be related to the complexity of the host-parasite system.     

Actin retrograde flow and actomyosin II arc contraction drive receptor cluster dynamics at the immunological synapse in Jurkat T cells

Actin retrograde flow and actomyosin II contraction have both been implicated in the inward movement of T cell receptor (TCR) microclusters and immunological synapse formation, but no study has integrated and quantified their relative contributions. Using Jurkat T cells expressing fluorescent myosin IIA heavy chain and F-tractin-a novel reporter for F-actin-we now provide direct evidence that the distal supramolecular activation cluster (dSMAC) and peripheral supramolecular activation cluster (pSMAC) correspond to lamellipodial (LP) and lamellar (LM) actin networks, respectively, as hypothesized previously. Our images reveal concentric and contracting actomyosin II arcs/rings at the LM/pSMAC. Moreover, the speeds of centripetally moving TCR microclusters correspond very closely to the rates of actin retrograde flow in the LP/dSMAC and actomyosin II arc contraction in the LM/pSMAC. Using cytochalasin D and jasplakinolide to selectively inhibit actin retrograde flow in the LP/dSMAC and blebbistatin to selectively inhibit actomyosin II arc contraction in the LM/pSMAC, we demonstrate that both forces are required for centripetal TCR microcluster transport. Finally, we show that leukocyte function-associated antigen 1 clusters accumulate over time at the inner aspect of the LM/pSMAC and that this accumulation depends on actomyosin II contraction. Thus actin retrograde flow and actomyosin II arc contraction coordinately drive receptor cluster dynamics at the immunological synapse.     

Nutritive value of maygrass,Phalaris caroliniana

Maygrass, Phalaris caroliniana,a native annual grass used as a food resource by prehistoric Indians of the eastern United States, was analyzed for nutritive value. Protein nutrient density of maygrass grains is higher than that for other starchy seeds, oily seeds, and nuts commonly found in paleoethnobotanical samples from the region. Maygrass grains are a good source of several vitamins and minerals, especially thiamin and dietary iron. The amino acid in shortest supply is lysine. Nutritional quality of the grains may have served as an inducement for its protection or cultivation.     

Population biology and behavior of larval Eustrongylides tubifex (Nematoda: Dioctophymatida) in poikilothermous hosts

A total of 178 channel catfish (Ictalurus punctatus), 162 freshwater drum (Aplodinotus grunniens), 60 smallmouth bass (Micropterus dolomieui) and 2,488 yellow perch (Perca flavescens) were examined for larval Eustrongylides tubifex (Nitzsch 1819) J?gerskiold 1909 during 1973 and 1974. Older, large fish exhibited higher prevalence, larger mean numbers of larvae in infected fish, larger mean numbers of larvae in all fish examined, and wider range of intensity of infection. Infections were most extensive in yellow perch. The majority of larvae were removed from mesenteric cysts. Under experimental conditions, larvae migrated from cysts through the body wall when environmental temperatures reached or exceeded 40 C. Fourth-stage larvae removed from yellow perch successfully reinfected a variety of poikilothermous experimental hosts. Both young-of-the-year and I+ age/size class yellow perch exhibited increasing monthly larval worm burdens during portions of the sampling period. Older (II+) age/size class yellow perch did not exhibit significantly increasing worm burdens. No significant differences were noted in numbers of male and female larvae or in worm burdens in male and female yellow perch.