Quantification and analysis of reverse mutations at the hgprt locus in Chinese hamster ovary cells

We describe an assay for the quantification of reverse mutations at the hypoxanthine-guanine phosphoribosyltransferase (hgprt) locus in Chinese hamster ovary cells utilizing the selective agent L-azaserine (AS). Conditions are defined in terms of optimal AS concentration, cell density, and phenotypic expression time. After treatment, replicate cultures of 10⁶ cells are allowed a 48-h phenotypic expression time in 100-mm plates. AS (10 μM) is then added directly to the growing culture and AS-resistant (AS^r) cells form visible colonies. This assay is used to quantify ICR-191-, ICR-170-, and N-ethyl-N-nitrosourea-induced reversion of independently isolated HGPRT^? clones. The AS^r phenotype is characterized both physiologically and biochemically. All AS^r clones isolated are stably resistant to AS and aminopterin but sensitive to 6-thioguanine. They also have re-expressed HGPRT enzyme. In addition, several revertants are shown to contain altered HGPRT. The data provide further evidence that ICR-191 and ICR-170 cause structural gene mutations in mammalian cells and also suggest that ICR-191, ICR-170, and N-ethyl-N-nitrosourea induce similar types of mutations in Chinese hamster ovary cells.     

Structure of the central spacer region of extrachromosomal ribosomal DNA in Physarum polycephalum

We have analyzed the sequence organization of the central spacer region of the extrachromosomal ribosomal DNA from two strains of the acellular slime mold Physarum polycephalum. It had been inferred previously from electron microscopy that this region, which comprises about one third of the 60 kb³ palindromic rDNA, contains a complex series of inverted repetitious sequences. By partial digestion of end-labeled fragments isolated from purified rDNA and from rDNA fragments cloned in Escherichia coli, we have constructed a detailed restriction map of this region. The 11 kb of spacer DNA of each half molecule of rDNA contains the following elements: (a) two separate regions, one of 1.1 kb and one of 2.1 kb, composed of many direct repeats of the same 30 base-pair unit; (b) a region of 4.4 kb composed of a complex series of inverted repeats of a 310 base-pair unit; (c) another region of 1.6 kb composed of inverted repeats of the same 310 base-pair unit located directly adjacent to the center of the rDNA; (d) two copies of a unique sequence of 0.85 kb, which probably contains a replication origin. Some of the CpG sequences in the spacer resist cleavage by certain restriction endonucleases and thus appear to be methylated. The lack of perfect symmetry about the central axis and the arrangement of inverted repeated sequences explain the complex pattern of branches and forks of the fold-back molecules previously observed by electron microscopy. Comparison of the rDNA restriction maps from the two strains of Physarum suggests that the repeat units in the spacer are undergoing concerted evolution. We propose a model to explain the evolutionary origin of the several palindromic axes in the Physarum rDNA spacer.     

Identification and characterization of an immunologically conserved adenovirus early region 11,000 Mr protein and its association with the nuclear matrix

Antisera from some hamsters bearing adenovirus-induced tumors contain antibodies to an 11,000 M_r adenovirus-induced protein. In adenovirus-infected HeLa cells, this early viral protein was specifically associated with the nuclear matrix fraction. After two-dimensional gel electrophoresis, two forms of the 11,000 M_r protein at pI 5.6 and pI 5.4 were found. Only the pI 5.4 form of this protein was associated with the nuclear matrix fraction. Adenoviruses from groups A, B, C, D and E all produced an early viral protein (10,000 to 12,000 M_r) that reacted with group C antibody to the 11,000 M_r protein. To date, this is the only known early viral protein that is immunologically conserved in all of the human adenovirus groups.The positions of two methionine and seven leucine residues were determined by sequencing the first 35 amino acids from the N terminus of the adenovirus serotype 2 group C 11,000 M_r protein. The positions of these amino acid residues were compared to the adenovirus serotype 2 nucleotide sequence, which uniquely localized the structural gene of the 11,000 M_r protein to region E4, subregion 3 in type 2 adenovirus. A frameshift mutant, which contained a deletion of one base-pair in the structural gene of the 11,000 M_r protein, was isolated and mapped by marker rescue and nucleotide sequence analysis. This mutant failed to produce immunologically detectable 11,000 M_r protein. The mutant had a viable phenotype, producing normal levels of infectious virus in both HeLa cells and WI38 cells in culture. These experiments identify the first adenovirus early region 4 protein detected in virus-infected cells.     

Effects of zomepirac and indomethacin on renal blood flow and electrolyte excretion in anesthetized monkeys

Zomepirac sodium is a new inhibitor of prostaglandin cyclooxygenase with an $\text{in vitro}$ potency equivalent to indomethacin. Since inhibitors of prostaglandin synthesis have marked effects on renal hemodynamics, zomepirac may be expected to reduce renal blood flow (RBF) in a manner similar to indomethacin. This study compares the effects of zomepirac and indomethacin on RBF and electrolyte excretion in anesthetized Rhesus monkeys. Each experiment consisted of a control period followed by 3 or 4 drug treatment periods in which increasing doses of zomepirac (0.5 to 20 mg/kg) or indomethacin (0.5 to 10 mg/kg were given. Indomethacin (5 mg/kg) reduced RBF by 22% and the higher dose (10 mg/kg) reduced RBF by an additional 13%. Zomepirac had little effect on RBF in doses as high as 20 mg/kg. At any given dose the mean plasma concentration of zomepirac was equal to or greater than indomethacin. Peak indomethacin concentration was 48 μg/ml after the 10 mg/kg dose while the peak zomepirac, after 20 mg/kg, was 158 μg/ml. Neither drug had a significant effect on either glomerular filtration rate or excretion rate of sodium or potassium. Thus, zomepirac had only minimal effects on RBF while indomethacin decreased RBF of anesthetized monkeys in a manner qualitatively similar to its effect in other species. The minimal renal effects caused by zomepirac relative to indomethacin in this primate may indicate a therapeutic advantage for zomepirac in man.     

Metabolism of propionic acid by golden delicious apples

The headspace of whole Golden Delicious apples treated with propionic acid vapour, was analysed by means of GC, after enrichment on Tenax GC, and its c     

The relationship between coding sequences and function in some heme binding proteins

Summary It is known that globin genes contain three exons with the middle exon coding for a four-helical supersecondary structure responsible for heme binding. Since this portion of the globin peptide chain can be structurally superimposed onto the cytochromec and cytochromeb ₅ chains (Argos and Rossmann 1979), it can be inferred that the cytochromec gene will contain only one coding sequence while the cytochromeb ₅ gene will be composed of three exons as found in the globin gene.     

High-performance liquid chromatographic and gas—liquid chromatographic determination of diazepam and nordiazepam in plasma

A one-step method for extraction of diazepam, nordiazepam, and internal standard into toluene is followed by chromatographic separation and detection with either dual-wavelength high-performance liquid chromatography or electron-capture gas—liquid chromatography. Agreement between the two methods was excellent for diazepam (r = 0.99, n = 38) and good for nordiazepam (r = 0.96, n = 79) over a concentration range that included subtherapeutic, therapeutic, and toxic plasma levels.     

Les Radiolaires d'âge jurassique supérieurà crétacé supérieur dans les Radiolarites du Pinde-Olonos (Presqu'île de Koroni; Péloponnèse méridional,Grèce)

Radiolarians of several radiolarites sections of the Pindos-Olonos zone, southern Peloponnesus, lead to propose direct datations of mesozoic sediments. The acuity of such datations allow to distinguish two periods for depositionof radiolarites s.s. in the tethyan region. The first period would be Upper Jurassic and general in tethyan realm, radiolarites depositing under various latitudes (0–35°N). This would be the result of a strong ocean surface current. The second period would be Upper Cretaceous (Vraconian—Coniacian) and be geographically much more restricted (0–15°N). This could result from a weaker current. The absence of radiolaritic sedimentation is possibly the result of the destruction or insulation of the accurate basins during the obduction of ophiolites on the apulo-african realm. The inventory of Late Cretaceous radiolarian fauna, rarely done on alpine series so far, shows similar result to those obtained in Central American and California.     

Une nouvelle sous-famille,les Poulpinae, et quatre nouvelles espèces de Saitoum radiolaires mésozoiques téthysiens

Studies of skeleton elements of several jurassic species of Saitoum allow to compare them with Poulpus from Trias. The sub-family Poulpinae is introduced, caracterised by three cephalic arcs and the collar position of the cephalic structure. Among the jurassic forms, 4 species are newly described: S. corniculum, S. elegans, S. levium and S. trichylum.