In Vitro Excystation of Cryptosporidium baileyi from Chickens1

Release of sporozoites from the oocysts of Cryptosporidium baileyi is described from Nomarski interference-contrast microscopy. Just prior to excystation, the four sporozoites became motile and rearranged themselves within the oocyst. The sporozoites were then rapidly expelled through an opening that formed in the oocyst wall, and the residuum was either released or retained within the oocyst. Excysted sporozoites were crescent shaped and measured 5.0–9.0 μm × 1.0–1.6 μm (x?= 6.8 × 1.1 μm). Excystation occurred when sodium taurocholate or a mixture of trypsin and sodium taurocholate was present in the incubation medium. High levels of excystation occurred at 37° or 40°C, but excystation did not occur at 4°C. The ability of biles from two avian and two mammalian hosts to produce excystation of C. baileyi was also studied. After a 2-h incubation at 40°C, the percentages of excystation were 69.5% in goat bile, 45.0% in pig bile, 33.0% in chicken bile, and 34.5% in turkey bile.     

Neuronal-Glial Interactions in Retina Development

The development of embryonic retinoblasts into phenotypicallymature Müller glial cells has been shown to be dependenton close juxtapositional relationships between heterotypicellsof the retina. In this report, I review experiments in whichwe have attempted to examine the role of actual cell contactin the regulation of biochemical differentiation of retinalglial cells. Probes which bind to cell surface components includingantibodies to the retina cell membrane and plant lectins weretested for their ability to interfere with normal histogenesisand glial maturation in a reaggregation-basedin vitro developmentassay. Data are discussed which show that antibodies to thecell surface and the succinylated derivative of the plant lectinconcanavalin A can markedly impair both histogenesis and glialmaturation potential if introduced into cultures of reaggregatingdissociated embryonic retina cells. Preliminary analyses ofmembrane components which react with the lectin have been performed.The results suggest that certain specific membrane glycopeptidesare expressed by dissociated retina cells in an age-dependentmanner. Also, the results show that decline in the ability ofthe embryonic cells to elaborate these surface components correlateswith the capacity of the cells toreform developmentally regulatoryneuronal-glial communication "linkages"     

Coccidia from the Tiger Salamander, Ambystoma tigrinum, in Northeastern Colorado and in Northern New Mexico

SYNOPSIS. Oocysts of Eimeria ambystomae Saxe, 1955, Eimeria microcapi sp. n., and Eimeria urodela sp. n. are described from the tiger salamander, Ambystoma tigrinum , collected in Colorado and New Mexico. The oocysts of E. ambystomae are ellipsoid, 29.8 × 17.3 (24–38 × 15–25) μm, and the sporocysts lanceolate, 22.6 × 5.4 (16–27 × 5–7) μm. Oocyst and sporocyst residua are present, but not a polar granule and a micropyle. The oocysts and sporocysts of E. microcapi are ellipsoid, measuring respectively 38.1 × 25.3 (35-41 × 23-26) μm and 18.1 × 7.4 (16-19 × 6–8) μm. Oocyst and sporocyst residua, a micropyle (mean 3 μm), and a distinct micropyle cap (2 μm high) are present, but not a polar granule. The oocysts of E. urodela are spheroid, 22.2 (14-26) μm, and the sporocysts lanceolate, 16.3 × 5.8 (12-19 × 4-7) μm. Oocyst and sporocyst residua are present, but a polar granule and a micropyle are absent.     

CONSIDERATIONS OF THE IDIOGNATHOIDES - DECLINOGNATHODUS - NEOGNATHODUS COMPLEX OF MIDDLE CARBONIFEROUS PLATFORM CONODONTS

An earlier proposed hypothesis by Straka & Lane (1970), suggesting 'Idiognathoides' noduliferus and Idiognathoides sulcatus as the progenitors of a closely related group of Lower Pennsylvanian (Morrowan) conodonts, is here considered as unnecessarily complex and based on insufficient data. An alternative and more simple interpretation is offered based on phylogenetic, ontogenetic, and stratigraphic considerations. It is suggested that the Idiognathoides sulcata (and/or I. opimus)-Idiognathoides sinuatus (and/or I. opimus ) group descended from Gnathodus defectus , and that Neognathodus bassleri was descended from Declinognathodus. Declinognathodus noduliferus and Gnathodus defectus are considered as having shared the common ancestor, Gnathodus girtyi simplex.     

Nucleoside diphosphate kinase from lily pollen

Nucleoside diphosphate kinase was a predominantly soluble enzymein lily pollen (Lilium longiflorum, var. Ace), and very littleenzyme activity was associated with the mitochondrial fraction.GTP was the preferred substrate when ADP was the second substrate.The enzyme was purified 18-fold to a specific activity of 7µmoles/min/mg protein. ¹This study was supported by grant GB-8764 from the U.S. NationalScience Foundation. (Received October 5, 1970; )     

Ribosomes,G-factor and Siomycin

G-factor interacts with the 50S ribo-somal subunit at a site which is distinct from the peptidyl transferase centre and which is inactivated by siomycin.     

Antigenic Heterogeneity of Human IgD Immunoglobulins

SUBCLASSES of the three major classes of human immunoglobulins, IgG, IgA and IgM, are recognized: four of IgG are well defined^1,2 and at least two of IgA^3–5 and two of IgM^6,7 have been demonstrated. This communication presents evidence for the existence of an antigenic heterogeneity in the heavy chains of IgD, which may also be indicative of subclasses within this class of immunoglobulin.     

Interactions of Vesicular Stomatitis Virus Structural Proteins with HeLa Plasma Membranes

THE processes whereby nucleoprotein core particles of certain animal viruses become enveloped by and bud off from host cell membranes can be studied by preparing membrane^1,2 or “sedimentable”³ fractions from infected cells and examining them for the presence of virus proteins. We find that similar experiments designed to monitor assembly of vesicular stoma-titus virus (VSV) at sites along the plasma membranes of HeLa cells are best interpreted after first investigating the possibility that virus proteins adsorb to plasma membranes during cell fractionation and membrane isolation. In this report, we show that at 0° C the membrane protein of VSV, among other virus proteins, adsorbs to plasma membranes isolated from uninfected HeLa cells. With appropriate pulse-chase experiments, however, we are able to demonstrate the progressive association, in vivo, of VSV core protein with plasma membranes of infected HeLa cells.