Patterns of disjunction frequencies in heterozygous reciprocal translocations from the German cockroach

Metaphase I cells from heterozygotes in eight reciprocal chromosome translocation stocks of Blattella germanica (L.) have been examined and counted. The data show that three stocks have random disjunction (adjacent and alternate orientations are equally frequent), but the cell types adjacent-1, alternate-1, adjacent-2, and alternate-2 are present in a ratio of 2112. Four stocks with directed disjunction have similar patterns, except for a heavy preponderance of alternate-2 cells. This difference is reflected in the finding that 60–65% of all cells in these interchanges are type II cells (alternate-2 plus adjacent-2), and the individual percentages agree closely with the percent directed disjunction in each case. One inter-change with directed disjunction is distinctly different in that the frequencies of both alternate-1 and alternate-2 cells are elevated and contribute to directed disjunction. It has also been demonstrated with two stocks that changes in disjunction frequencies can be brought about by genetic manipulation. These observations provide a better understanding of the differences between random and directed disjunction.     

Partial sequence analysis of Xenopus alpha- and beta-globin mRNA as determined from recombinant DNA plasmids

Recombinant plasmids containing Xenopus globin mRNA sequences have been constructed using the mRNA:cDNA hybrid conditions of Zain et al. (1979, Cell16, 851–861). The partial nucleotide sequence of two of these recombinants has been determined. They have been identified as containing α- and β-globin-like sequences by homology to other amphibian globin proteins. The nucleotide sequence of these recombinants permits the comparison of conserved regions in both the coding and 3′ nontranslated regions of Xenopus globin mRNAs with the known sequences of other eukaryotic globin proteins and mRNAs. Among the features which have been conserved though evolution is the sequence AAUAAA close to the 3′ terminus of the nontranslated region. Extensive regions of homology occur between the 3′ nontranslated regions of Xenopus α- and β-globin mRNA.     

Myelin Gangliosides in Vertebrates

Abstract: A phylogenetic survey of brain myelin ganglioside patterns and concentrations has been carried out on 16 vertebrate species. Gangliosides were isolated from purified myelin and found to vary in concentration from 25 μg of sialic acid per 100 mg of myeh for goldfish to a value of 395 for turkey. The latter species had approximately equivalent amounts of G_M1 and G_M4 as the two major gangliosides. The 11 mammals studied all had G_M1 as the major ganglioside, with variable amounts of G_M4; rhesus monkey and human had 20-25% G_M4, whereas the others had less than 10%. Amphibia and fish myelin contained the least total ganglioside, with patterns that showed relatively little G_M1 and no detectable G_M4. Alligator myelin was unique in having a total concentration as high as the avian species, but a pattern with predominantly diand trisialo gangliosides.     

Molecular Cloning and Physical Mapping of Restriction Endonuclease Fragments of Autographa californica Nuclear Polyhedrosis Virus DNA

A restriction fragment library containing Autographa californica nuclear polyhedrosis virus (AcNPV) DNA was constructed by using the pBR322 plasmid as a vector. The library, which is representative of more than 95% of the viral genome, consists of 2 of the 7 BamHI fragments, 12 of the 24 HindIII fragments, and 23 of the 24 EcoRI fragments. The cloned fragments were characterized and used to generate physical maps of the genome by hybridizing nick-translated recombinant plasmid to Southern blots of AcNPV DNA digested with SmaI, BamHI, XhoI, PstI, HindIII, and EcoRI restriction endonucleases. This information was used to define our strain of AcNPV (HR3) with respect to other strains for which physical maps have been previously published. The hybridization data also indicate that reiteration of DNA sequences occurs at the HindIII-L and -Q regions of the genome.     

Post-transcriptional control of protein synthesis in Balb/c-3T3 cells by platelet-derived growth factor and platelet-poor plasma

Platelet-derived growth factor (PDGF) and platelet-poor plasma, which lacks PDGF, both induce a rapid increase in the rate of total protein synthesis within quiescent, density-arrested Balb/c-3T3 cells. This stimulation of protein synthesis is associated with an increased aggregation of ribosomes into polyribosomes. Nuclear functions are not required for this response, as demonstrated by the observation that this stimulation of protein synthesis occurs in cells pretreated with actinomycin D and in enucleated cells (cytoplasts). The response to PDGF persists even after PDGF has been removed from the culture medium, but in contrast, when plasma is removed from the medium, polysomes disaggregate and protein synthesis declines. PDGF and plasma do not function synergistically to increase protein synthesis, whereas they do to induce optimum DNA synthesis. Thus stimulation of the translational apparatus may be necessary for the mitogenic response of Balb/c-3T3 cells to growth factors, but it is not by itself sufficient.     

Sedimentation characteristics of the scrapie agent from murine spleen and brain.

Sedimentation profiles of the scrapie agent in extracts of murine spleen and brain were determined by analytical differential centrifugation. Infectivity profiles of the agent from the two tissues were similar. Sedimentation of the agent was not substantially altered by detergent treatment with sodium deoxycholate. In the presence of detergent, centrifugation at an omega2t value of 3.0 x 1010 rad2/s in a fixed-angle rotor sedimented 90% of the agent. Comparative studies with radioisotopically labeled Simian virus 40 showed that centrifugation at an omega2t value of 1.6 x 10(10) rad2/s removed 90% of the virions. The sedimentation profile of the scrapie agent was similar to that observed for cellular ribosomal RNA. Heating infectious extracts of spleen to 80 degrees C for 30 min resulted in the destruction of 95% of the RNA while sedimentation of the scrapie agent was unchanged. These studies establish a limited range of particle sizes for the scrapie agent.     

Effect of heparin on vascular smooth muscle cells. II. Specific protein synthesis

Heparin suppresses the proliferation of vascular smooth muscle cells both in vivo and in vitro. The mechanism of action of the antiproliferative activity of heparin is not known. We have detected differences in the synthesis of specific proteins when vascular smooth muscle cells are exposed to heparin and report here that many characteristics of these protein alterations parallel the properties of the antiproliferative activity. The induction into the culture medium of a pair of proteins of approximately 35,000 dalton mw in heparin-treated smooth muscle cell cultures and the antiproliferative effect of heparin share the following characteristics: 1) the effect is reversible, 2) the effect is specific for smooth muscle cells, 3) anticoagulant and non-anticoagulant heparin are equally effective, 4) the effect is lost with time in culture and, 5) heparin is the most potent glycosaminoglycan in producing the effect. Furthermore, heparin causes a transient suppression of a 48,000 dalton substrate-attached protein, whereas chondroitin sulfate A and C and dermatan sulfate had much less effect. Dextran sulfate was almost as effective as heparin in suppressing the synthesis of the substrate-attached protein. These proteins appear to be noncollagenous and the induced synthesis of the 35,000 dalton proteins is inhibited by actinomycin D. Although a direct relationship between these specific protein changes and the antiproliferative effect of heparin has not been proven, these protein alterations may play a crucial role in the effect of heparin on smooth muscle cell growth.