Fusion of Erythrocytes by Sendai Virus Studied by Immuno-Freeze-Etching

Extensive fusion of human erythrocytes agglutinated by Sendai virus was observed after 30 s of incubation at 37 C. Electron microscopy of thin sections failed to reveal the presence of virions, viral fragments, or discrete viral antigens reactive with ferritin-labeled antibody at the sites of fusion. Immuno-freezeetching of membrane surfaces demonstrated the dispersal of viral envelope antigens from what appeared to be original sites of viral attachment. Virus-induced clustering of membrane glycoproteins was interpreted as resulting from interaction of viral antigens with membrane receptor proteins and forming the structural basis for fusion of membranes with one another.     

Temperature-dependent actinomycin D effect on RNA synthesis during synchronous development in Neurospora crassa

Actinomycin D at a concentration of 5 g/ml of medium inhibited DNA-dependent RNA synthesis by 92% at 35 C, 42% at 30 C, and 28% at 25 C in Neurospora crassa. This concentration also inhibited the development of conidiophores and conidia at 35 C, but not at 30 or 25 C. Mycelia which were induced to synchronous development formed conidiophores in 2.5 hr and conidia in 4.5 hr at 35 C in the absence of drug additives. Addition of actinomycin D to synchronously developing mycelia at zero time and at 0.5-hr intervals thereafter at 35 C indicated that RNA synthesis required for conidiophores occurred before 0.5 hr and for conidia before 2 hr. Addition of cycloheximide at the same times to another synchronous mycelial series at 35 C indicated that protein synthesis required for conidiophores occurred before 2 hr and for conidia before 3.5–4 hr.This work was supported in part by U.S. Public Health Service Training Grant 1 TO1 GM 01968 01.     

Structure and Development of Viruses as Observed in the Electron Microscope IX. Entry of Parainfluenza I (Sendai) Virus

After attachment, the uncoating of Sendai virus, which was accompanied by dissolution of the plasma membrane and fusion of virus to cell, proceeded quickly. Nucleoprotein filaments were found at stages of transit from virus to cytoplasm.     

Properties of influenza C virus grown in cell culture.

Influenza C virus was propagated successfully in primary chicken embryo lung (CEL) and fibroblast cells and in Madin-Darby canine kidney (MDCK) cells. In other cell lines, either no virus or only noninfectious hemagglutinin (HA) was produced. In productively infected cells (CEL), HA and infectious virus appeared by 24 h and reached a maximum by 36 to 48 h, cell-associated virus remaining at a constant low level. Infected Vero cells produced noninfective HA by 24 h which also remained predominantly cell associated until 60 to 72 h, when the cells disintegrated. Viral antigen was demonstrable on membranes of both CEL- and Vero-infected cells at 24 h; Vero cells yielded membrane vesicles containing HA, but none of the spherical or filamentous viral particles synthesized in CEL cells. Influenza C virus produced in cell culture or in eggs differed in several important respects from A and B viruses and from Newcastle diseases virus. All influenza C preparations, regardless of infectivity or source, lacked detectable neuraminidase activity, yet retained the ability specifically to inactivate receptors only for influenza C. Influenza C HA was not inhibited by soluble glycoproteins highly active against HA of A virus. A rat serum glycoprotein uniquely inhibited influenza C by binding to the surface components of virious.     

The Biology of Gregarina fernandoi n. sp. in the Cockroach Pysnoscelus surinamensis with Observations on its Development and Cytochemical Nature

SYNOPSIS. Gregarina fernandoi n. sp. is a eugregarine. Its structure, development and life history in the gut of the cockroach Pycnoscelus surinamensis are described. It is named as a new species on the basis of its size, nuclear structure, structure and form of the gametocyst and oocyst. Observations were made on the different stages of the parasite and related to the pH of the gut. In the ceca, pH 4.5–5, the parasite was in its early stages of development, in the midgut, pH 6.5–7, it was in syzygy and in the rectum, pH 7.5–8, gametocysts were found.     

Distribution of cell lengths in cultures of a lexA mutant of Escherichia coli K-12.

Distributions of cell lengths in lexA+ and lexA mutant cultures during normal growth and under thymidine starvation conditions are presented. During normal growth lexA mutant cells were slightly shorter, on the average, than were lexA+ cells. lexA mutant cells were also shorter in comparison with lexA+ cells after a period of thymidine starvation. These results are consistent with the hypothesis that the lexA gene is involved in the coordination of cell division with DNA repair.     

Fruit production,migrant bird visitation,and seed dispersal of Guarea glabra in Panama

Summary The relationship between bird visitation and the size of the available fruit crop was studied at an understory tree (Guarea glabra Vahl, Meliaceae) in the tropical wet forest of Barro Colorado Island, Panama Canal Zone. Twelve resident species and seven North American migrant species fed on the Bright orange arilloids (seeds with arils), which were not depleted during the normal fruiting period. The number of individual visitors, the number of visiting species, and the number of seeds removed increased linearly with the size of the available fruit crop. The proportion of seeds removed did not increase with the size of the available fruit crop, indicating that dispersal is a function of the number of fruit available and not a disproportionate function of large fruit displays. Four species of North American migrants (Myiarchus crinitus, Catharus ustulatus, Vireo olivaceus, and Vermivora peregrina) accounted for 70% of the visits and 60% of the seeds removed from the trees. No resident species visited Guarea as frequently as any one of these migrants. There was no indication that any single visitor was dependent on this tree for nutrition, nor that the tree was dependent upon any single species for dispersal. We hypothesize that the fruiting season of G. glabra is adaptively synchronized with northward migration of opportunistically frugivorous North American birds.