Tipula iridescent virus infection in the developmental stages of Tipula oleracea

Tipula iridescent virus (TIV) is infective to all four larval instars, pupae, and adults of both sexes of Tipula oleracea, and iridescence has been observed in infected insects at all these stages. Third- and fourth-instar larvae were more resistant to ingested TIV than first and second instars. When TIV was injected into the hemocoel, the results suggested a possible decrease in resistance from the third larval instar to the pupa. Incubation periods (times from injection of TIV to appearance of iridescence) were significantly shorter in older fourth-instar larvae than in younger fourth-instar or thirdinstar larvae, but variability in incubation period was significantly greater in younger fourth-instar larvae than in the other two stages. Many insects which were inoculated with TIV in one stage developed iridescence and died in later stages. The amounts of infective TIV in two infected adults were estimated.     

Analysis of Parvovirus mRNA by Sedimentation and Electrophoresis in Aqueous and Nonaqueous Solution

Adenovirus-associated virus (AAV)-specific RNA present in the cytoplasm of cells coinfected with a helper adenovirus was analyzed by sucrose gradient sedimentation and gel electrophoresis. In aqueous conditions both gels or gradients revealed three AAV RNA components corresponding to 30S, 27S, and 20S and having apparent molecular weights of 2.6 x 10(6), 1.75 x 10(6) to 1.8 x 10(6), and 0.9 x 10(6) to 1.0 x 10(6), respectively. In nonaqueous, denaturing solvents only the 20S AAV RNA species was observed. For this reason, and because they would be apparently significantly larger than a single AAV DNA strand, both the 30S and 27S species are believed to result from conformational or aggregation effects in the aqueous nondenaturing systems. It is concluded that only a single RNA molecule having a molecular weight of approximately 0.9 x 10(6) to 1.0 x 10(6) is synthesized by AAV.     

Improved Hemagglutination Test for Identifying Type A Strains of Pasteurella multocida

A simple, improved, indirect hemagglutination test is described for the recognition of Type A strains of Pasteurella multocida. It involves the treatment of mucoid cultures with testicular hyaluronidase. Hydrolysis of the capsular hyaluronic acid presumably releases the specific antigen for adsorption to erythrocytes.     

Synthesis of two DNA-dependent RNA polymerases in yeast

Specific activities of Saccharomyces cerevisiae RNA polymerases I and II were measured in cells growing under different nutrient conditions and throughout the mitotic cell cycle. The specific activity of RNA polymerase I (possibly the ribosomal polymerase) does not vary during the yeast cell cycle. In contrast the specific activity of RNA polymerase II (messenger polymerase) increases during the first third of the cycle and thereafter declines. The independent regulation of synthesis of these two enzymes is further emphasised by observations on the response to different nutrient conditions. Shifting cells from minimal to rich medium led to enhanced RNA polymerase I activity but very little change in activity of RNA polymerase II. Furthermore the activity of RNA polymerase I varies directly with change in growth rate whereas the activity of RNA polymerase II is approximately constant over a range of growth rates. From this data it is suggested: (i) The synthesis of these two enzymes is independently regulated; (ii) RNA polymerase I is synthesised continuously throughout the cycle whereas RNA polymerase II is synthesised periodically early in the cell cycle.     

Adsorption chromatography of Schardinger dextrins on Sephadex G-15

Both α- and β-Schardinger dextrins and their α-1 → 6-substituted glucosyl derivatives behave anomalously on Sephadex G-15 column chromatography in that they are retarded well beyond their expected elution volumes. It would appear that they are fractionated by adsorption chromatography rather than by molecular sieving. The separations are superior to those on the molecular sieve Bio-Gel P-2, where adsorption does not occur, and offer a useful preparative method for the glucosyl dextrins.     

Use of Yeast Populations Fractionated by Zonal Centrifugation to Study the Cell Cycle

Zonal centrifugation in a sucrose density gradient was used to separate yeast cells primarily by size and thus by age in the cell cycle. This approach provides an alternative to synchronous growth for examining the properties of cells at different stages in the cell cycle.     

Countercurrent distribution of inosol lipids of plant seeds

The inositol lipids of plant seeds consist of phosphatidyl inositol, the phytoglycolipids, and a previously uncharacterized ceramide-phosphate-polysaccharide. These three species have been separated from each other and from the common glycerophosphatides by a series of simple countercurrent distributions, first as the naturally occurring Ca-Mg salts and subsequently in the Na salt form. The new ceramide-phosphate-polysaccharide is present in each of the four plant phosphatides examined (corn, soybean, flax, safflower). It is devoid of glucosamine but contains the other carbohydrate components commonly found in the phytoglycolipids. The basic structural unit of the new glycolipid consists of a ceramide-phosphate-inositol-hexuronic acid moiety to which the other sugars (galactose, mannose, arabinose) are attached. Flax ceramide-phosphate-polysaccharide has fucose in addition to the other sugars.