Synthesis and Assembly of Simian Virus 40 I. Differential Synthesis of Intact Virions and Empty Shells

Intact virions and empty shells of simian virus 40 may be rapidly separated from each other and from cell contaminants by a procedure employing a CsCl cushion. This approach permits quantitation of their respective syntheses in infected cells labeled with radioactive amino acids. As much as 5 to 10% of the total acid-precipitable radioactive lysine in infected cell extracts was incorporated into viral particles in a two-hour pulse late in infection. Evidence for multiple origins of empty shells is presented. Some of the empty shells result from breakdown of intact virions. However, empty shells can also form independently of intact virions. First, labeling for periods of 15 min to 2 hr late in the course of infection results in preferential incorporation of (3)H-lysine into empty shells. Secondly, treatment with the deoxyribonucleic acid inhibitor cytosine-beta-d-arabinofuranoside late in infection results in a 50% inhibition in the rate of formation of intact virions with minimal reduction in the rate of appearance of empty shells.     

A competitive labelling method for determining the ionization constants and reactivity of individual histidine residues in proteins. The histidines of α-chymotrypsin

A competitive labelling method (Kaplan et al., 1971), using tritiated 1-fluoro-2,4-dinitrobenzene as the labelling reagent, is described for determining the ionization constants and reactivities of individual histidine residues in proteins. When this method was applied to the two histidines of alpha-chymotrypsin, histidine-57 was found to have pK(a) 6.8 and a reactivity ten times that of alpha-N-acetyl-l-histidine. Histidine-40 had pK(a) 6.7 and a reactivity approximately six times that of alpha-N-acetyl-l-histidine. Between pH7.5 and 8 the reactivities of both histidines decrease simultaneously to approximately that of alpha-N-acetyl-l-histidine. The high reactivities of the histidines are attributed to hydrogen bonding, which increases the nucleophilicity of the imidazole ring. The sharp decrease in reactivity between pH7.5 and 8 is attributed to a conformational change that disrupts the hydrogen bonding by these residues. The reactivity data support the proposal of a charge-relay mechanism involving histidine-57 (Blow et al., 1969), which makes serine-195 more nucleophilic but indicates that this system is fully operative only in the enzyme-substate complex.     

The salt-extractable fraction of dynein from sea urchin sperm flagella: An analysis by gel electrophoresis and by adenosine triphosphatase activity

Previous work has shown that the dynein from axonemes of sea urchin sperm consists of two distinct fractions which differ substantially in their extractability by salt. Upon gel electrophoresis of whole demembranated axonemes solubilized with sodium dodecyl sulfate, the dynein fraction shows two closely spaced bands with apparent molecular weights of 520,000 and 460,000; the proteins in these bands are termed the A and B components of the dynein. Similar electrophoresis of the soluble fraction obtained by extracting the axonemes with 0.5 M NaCl shows a single prominent band containing approximately half of the A component of the dynein (A₁ component). The residue of extracted axonemes contain the other half of the A component of the dynein (A₂ component) and all the B component. Densitometry of the bands indicates that the A₁, A₂ and B components of the dynein are present in approximately equal molar quantity. Electron microscopic studies show that the A₁ component of the dynein constitutes the outer arms on the doublet tubules. Assay of ATPase activity in 0.05 M KCl and l mM ATP indicates about 65% of the total ATPase activity becomes soluble when the A₁ component of the dynein is extracted with salt.     

Suppressive effect of streptomycin on the phagocytic activity of mouse peritoneal macrophages for Histoplasma capsulatum

Streptomycin inhibited the phagocytic activity of mouse peritoneal macrophages forHistoplasma capsulatum. The inhibitory effect was demonstrable following both in vitro and in vivo administration of drug. The observations from examination by direct smear were confirmed by culturing for viable phagocytized organisms. A simple and reproducible technique for the counting of viable phagocytized organisms was developed. Forty-eight hours in vitro treatment of macrophage cultures with 10 to 200 µg/ml of streptomycin produced a graded inhibition of phagocytic activity, minimal at 10 µg/ml and maximal at 200 µg/ml of streptomycin. The parenteral administration of streptomycin significantly reduced phagocytic activity of mouse peritoneal macrophages forH. capsulatum. Mice were treated daily with the subcutaneous injections of 5, 2.5 or 1 mg streptomycin or saline. At 7, 14, 21 and 28 days post-treatment phagocytic activity of macrophages obtained from these mice was tested. There was a progressive, dose-dependent decrease in the phagocytic activity of macrophages derived from streptomycin-treated mice.     

Partial XYY syndrome

Summary A 13-year-old boy with 47 chromosomes, an extra small metacentric chromosome and karyotype 47,XY,?Yq- is presented. He has psychiatric symptoms typical of boys with karyotype 47,XYY as seen in the tabulated results of a psychiatric study of 22 boys with the XYY syndrome, examined at the Cytogenetic Laboratory, Århus State Hospital, Risskov.

---

Zusammenfassung Es wird über einen 13 Jahre alten Jungen berichtet mit 47 Chromosomen, einem zusätzlichen kleinen metazentrischen Chromosom und der Karyotype 47,XY, ?Yq-. Er weist die typischen psychischen Symptome für Jungen mit der Karyotype 47,XYY auf, wie man aus den tabellarisch dargestellten Ergebnissen der psychiatrischen Untersuchung von insgesamt 22 Jungen mit XYY-Syndrom, die am cytogenetischen Labor, Århus State Hospital, Risskov, untersucht wurden, ersehen kann.

     

MITOSIS,CYTOKINESIS, AND COLONY FORMATION IN THE GREEN ALGA SORASTRUM1

Synchronous mitotic divisions produce multi-nucleate cells of Sorastrum. Perinuclear envelopes of endoplasmic reticulum and a virtually intact nuclear envelope enclose mitotic nuclei. Cytoplasmic cleavage, which shirts before the last round of Synchronous mitoses, gives rise to uninucleate fragments which differentiate to form zoospores. These zoospores are released into a spherical vesicle, presumably derived from the inner layer of the parental cell wall, in which they swarm actively before aggregating as a spherical colony. The roughly conical shaped zoospores apparently adhere laterally before withdrawing their flagella and extending horns and a stipe, which, following wall deposition, interconnects the cells at the center of the colony. The probable role of the microtubules, which underlie the plasmalemma of aggregating cells, in determining the shape of both the cells and the colony itself is discussed.     

Translation of mRNA from Simian Virus 40-Infected Cells into Simian Virus 40 Capsid Protein by Cell-Free Extracts

Messenger RNA was isolated from simian virus 40 (SV40)-infected and mock-infected cells by chromatography on poly(U) sepharose. When added to cell-free extracts from Chinese hamster ovary cells or rabbit reticulocytes, RNA from the infected cells, but not from mock-infected cells, stimulated synthesis of the major SV40 capsid protein. Identification of this species was done by sodium dodecyl sulfate gel electrophoresis, peptide mapping, and immunoprecipitation. The in vitro synthesized capsid protein was slightly different from virion assembled capsid protein, as shown by separation upon chromatography on hydroxylapatite and by minor differences in the peptide map.