Avian Retroviruses That Cause Carcinoma and Leukemia: Identification of Nucleotide Sequences Associated with Pathogenicity

Avian myelocytomatosis virus (MC29V) is a retrovirus that transforms both fibroblasts and macrophages in culture and induces myelocytomatosis, carcinomas, and sarcomas in birds. Previous work identified a sequence of about 1,500 nucleotides (here denoted onc_MCV) that apparently derived from a normal cellular sequence and that may encode the oncogenic capacity of MC29V. In an effort to further implicate onc_MCV in tumorigenesis, we used molecular hybridization to examine the distribution of nucleotide sequences related to onc_MCV among the genomes of various avian retroviruses. In addition, we characterized further the genetic composition of the remainder of the MC29V genome. Our work exploited the availability of radioactive DNAs (cDNA's) complementary to onc_MCV (cDNA_MCV) or to specific portions of the genome of avian sarcoma virus (ASV). We showed that genomic RNAs of avian erythroblastosis virus (AEV) and avian myeloblastosis virus (AMV) could not hybridize appreciably with cDNA_MCV. By contrast, cDNA_MCV hybridized extensively (about 75%) and with essentially complete fidelity to the genome of Mill Hill 2 virus (MH2V), whose pathogenicity is very similar to that of MC29V, but different from that of AEV or AMV. Hybridization with the ASV cDNA's demonstrated that the MC29V genome includes about half of the ASV envelope protein gene and that the remainder of the MC29V genome is closely related to nucleotide sequences that are shared among the genomes of many avian leukosis and sarcoma viruses. We conclude that onc_MCV probably specifies the unique set of pathogenicities displayed by MC29V and MH2V, whereas the oncogenic potentials of AEV and AMV are presumably encoded by a distinct nucleotide sequence unrelated to onc_MCV. The genomes of ASV, MC29V, and other avian oncoviruses thus share a set of common sequences, but apparently owe their various oncogenic potentials to unrelated transforming genes.     

RNA levels in colchicine-resistant mutants of Chlamydomonas reinhardi

A colchicine-resistant mutant of Chlamydomonas reinhardi (col⁻_{10, 12}) which appears blocked in the final stages of the cell division cycle is shown to have an RNA: protein ratio over four times that which is observed in wild-type cultures. This does not appear to be simply a consequence of reduced overall growth rate, because a comparable reduction in the overall growth rate of wild type by caffeine inhibition did not produce such a large rise in RNA content. The RNA levels in six other colchicine-resistant mutants, which have various abnormalities in colchicine-binding activity, has also been investigated. Two of them have elevated RNA levels.     

A case of D13 ring chromosome

Summary A case of D ring chromosome identified with trypsin banding as a 13 with loss of the bands p12 and q34 is reported. The clinical features characteristically associated with the loss of these specific segments were present.     

Differential scanning calorimetry of dipalmitoyl phosphatidylcholine analogues and of their interaction products with basic polypeptides

The thermotropic behaviour of dipalmitoyl phosphatidylcholine analogues with a varying number (n) of CH₂ groups between the phosphate and the quaternary ammonium has been investigated. The temperature (T_m) and the enthalphy (ΔH) of the phase transition are non-monotonous functions of the number of CH₂ groups. T_m oscillates between 40 and 45°C and ΔH between 7 and 13 kcal/mol for a variation of n between 2 and 11.It is concluded that the hydrocarbon chains in the head groups do not penetrate the hydrocarbon region and do not contribute directly to the melting of the acyl chains. It is suggested that their length may affect the critical ballance between the attractive and the repulsive forces within the bidimensional lattice of the head groups.Copolypeptides of lysine with phenylalanine do not appreciably affect the T_m but have a pronounced effect on ΔH of the lipid phase transition, which depends strongly on the ratio of the two amino acids in the polypeptide. The effect of copolypeptide of any defined composition on ΔH is also a non-monotonous function of the number of CH₂ groups in the phosphatidylcholine head group, but it does not parallel completely the oscilations in the T_m and ΔH of the pure lipids.     

Extinction of differentiated glial functions in somatic cell hybrids is incomplete

Rat glioma cells of clone C₆ were hybridized in vitro with mouse L cells of clone A9 or with freshly isolated mouse macrophages, and the hybrids were assayed for glial cell functions. C₆ cells expressed high levels of 2′,3′-cyclic nucleotide 3′-phosphohydrolase (CNP; EC 3.1.4.37), β-hydroxybutyrate dehydrogenase (HBDH; EC 1.1.1.30), glycerol-3-phosphate dehydrogenase (GPDH; EC 1.1.1.8), and inducibility of GPDH by hydrocortisone (HC). A9 cells and macrophages had very low activities of these functions. Hybrids between C₆ and A9 or between C₆ and macrophages had greatly reduced activities of these functions, but the hybrids expressed significantly higher activities than the non-glial parent. This incomplete extinction was not due to fusion of two glioma cells with one L cell or macrophage. The difference in GPDH activity in the hybrids as compared with the non-glial parent was due to incomplete shut-off of GPDH of the glial parent, and not to an increase in GPDH production by the non-glial genome.     

Variance Component Analysis of Allozyme Frequency Data from Eastern Populations of DROSOPHILA MELANOGASTER

Gene frequency variation at eight polymorphic allozyme loci in Drosophila melanogaster populations in North Carollina and the east coast of the United States were analyzed utilizing the variance component estimation procedures suggested by Cockerham (1969, 1973). These variance components were used to estimate correlations of genes within small geographic regions. The average (over loci) correlation between genes in the same individual within subpopulations was estimated to be 0.033. That between genes in the same subpopulation in different individuals was estimated to be very small, although significantly different from zero. The macrogeographic variation measured by the correlation of genes sampled from the same local region was large for some loci and smaller for others. this variation was also analyzed by correlation with latitude and longitude. Several previously recognized clines were identified as were several new clines.--These results were interpreted as indicating either some degree of nonrandom mating and local breeding unit isolation or a low frequency of null alleles. The geographic and temporal variation has no simple interpretation.     

Chromosome constitution of in vitro segregated haploid and diploid cells of the mouse

The composition in segregated haploid sets of paternal and maternal chromosomes has been studied in order to verify whether their composition is uniparental of mixed, fixed or variable. Primary cultures where prepared using kidneys from hybrids of strains of Mus musculus in which the parental chromosomes are distinguishable; the maternal set consists of 20 teleocentric chromosomes, the paternal set of 9 metacentric chromosomes, derived by Robertsonian fusion and 2 telocentrics. Applying Seabright's banding technique, an analysis of segregated haploid and diploid cells, which have originated spontaneously through polyploidisation-segregation processes was carried out. It was concluded that the haploid sets have a variable composition of paternal and maternal chromosomes.     

Optimal conditions for studies of amino acid incorporation in vitro by isolated skeletal muscle mitochondria

Optimal conditions for amino acid incorporation into protein in vitro by isolated skeletal muscle mitochondria were established. Maximum incorporation rates were obtained when atractylate and glutamate were added to the incubation medium in the absence of any exogenous adenine nucleotides. Under these conditions, the rate of amino acid incorporation was more than 5-fold greater than that observed with glutamate and ADP and nearly 12-fold greater than that observed with ATP and an ATP-regenerating system consisting of phosphoenolpyruvate and pyruvate kinase. The optimal concentrations of adenine nucleotides, glutamate, cofactors and the substrate leucine were determined for all three energy-providing systems. The inhibitors of protein synthesis, puromycin and chloramphenicol, completely blocked amino acid incorporation by isolated skeletal muscle in mitochondria, while cycloheximide had no effect. Analysis of the labeled mitochondrial proteins by sodium dodecylsulfate polyacrylamide gel electrophoresis revealed five labeled bands of molecular weights ranging from 38,000 to 10,000.Amino acid incorporation by skeletal muscle mitochondria isolated from diabetic rats was decreased over 60% as compared to mitochondria from controls when measured in the presence of glutamate and atractylate, ADP and glutamate or the ATP regenerating system. By contrast, amino acid incorporation by liver mitochondria isolated from diabetic rats did not differ significantly from control values when measured with four different energy sources.     

The antagonism by anti-inflammatory analgesics of prostaglandin F2α-induced contractions of human and rabbit myometrium

The anti-inflammatory analgesic drugs, aspirin, indomethacin, phenylbutazone, mefenamic acid, ibuprofen and flurbiprofen are shown to inhibit in a dose-dependent manner the force of contraction of isolated human pregnant myometrial strips which have been stimulated to contract by adding prostaglandin (PG) F_2α to the tissue bath. These drugs and also flufenamic acid and salicin show a similar antagonism of the action of PGF_2α with isolated rabbit non-pregnant myometrium. The ratio of the inhibitory concentration to the maximum plasma level after a normal dose suggests that phenylbutazone and possibly ibuprofen may be capable of inhibiting human uterine contractions . Patients who were treated with aspirin during induction of abortion using PGF_2α during the second trimester of pregnancy showed no significant change in the induction-abortion interval compared with patients not taking aspirin.     

Frequent Unanticipated Alleles of lethal giant larvae in Drosophila Second Chromosome Stocks

Forty years ago, a high frequency of lethal giant larvae (lgl) alleles in wild populations of Drosophila melanogaster was reported. This locus has been intensively studied for its roles in epithelial polarity, asymmetric neural divisions, and restriction of tissue proliferation. Here, we identify a high frequency of lgl alleles in the Bloomington second chromosome deficiency kit and the University of California at Los Angeles Bruinfly FRT40A-lethal P collection. These unrecognized aberrations confound the use of these workhorse collections for phenotypic screening or genetic mapping. In addition, we determined that independent alleles of insensitive, reported to affect asymmetric cell divisions during sensory organ development, carry lgl deletions that are responsible for the observed phenotypes. Taken together, these results encourage the routine testing of second chromosome stocks for second-site alleles of lgl.