GENETIC VARIATION IN TRAGOPOGON SPECIES: ADDITIONAL ORIGINS OF THE ALLOTETRAPLOIDS T. MIRUS AND T. MISCELLUS (COMPOSITAE)

Genetic diversity in the introduced diploids Tragopogon dubius, T. porrifolius, and T. pratensis and their neoallotetraploid derivatives T. mirus and T. miscellus was estimated to assess the numbers of recurrent, independent origins of the two tetraploid species in the Palouse region of eastern Washington and adjacent Idaho. These tetraploid species arose in this region, probably within the past 50–60 yr, and provide one of the best models for the study of polyploidy in plants. The parental species of both T. mirus and T. miscellus have been well documented, and each tetraploid species has apparently formed multiple times. However, a recent survey of the distributions of these allotetraploids revealed that both tetraploid species have expanded their ranges considerably during the past 50 yr, and several new populations of each species were discovered. Therefore, to evaluate the possibility that these recently discovered populations are of recent independent origin, a broad analysis of genetic diversity in T. mirus, T. miscellus, and their diploid progenitors was conducted. Analyses of allozymic and DNA restriction site variation in all known populations of T. mirus and T. miscellus in the Palouse and several populations of each parental diploid species revealed several distinct genotypes in each tetraploid species. Four isozymic multilocus genotypes were observed in T. mirus, and seven were detected in T. miscellus. Tragopogon mirus possesses a single chloroplast genome, that of T. porrifolius, and two distinct repeat types of the 18S-26S ribosomal RNA genes. Populations of T. miscellus from Pullman, Washington, have the chloroplast genome of T. dubius; all other populations of T. miscellus have the chloroplast DNA of T. pratensis. All populations of T. miscellus combine the ribosomal RNA repeat types of T. dubius and T. pratensis, as demonstrated previously. When all current and previously published data are considered, both T. mirus and T. miscellus appear to have formed numerous times even within the small geographic confines of the Palouse, with estimates of five to nine and two to 21 independent origins, respectively. Such recurrent polyploidization appears to characterize most polyploid plant species investigated to date (although this number is small) and may contribute to the genetic diversity and ultimate success of polyploid species.     

Mapping of the α4 subunit gene (GABRA4) to human chromosome 4 defines an α2—α4—β1—γ1 gene cluster: further evidence that modern GABAA receptor gene clusters are derived from an ancestral cluster

We demonstrated previously that an α₁—β₂—γ₂ gene cluster of the γ-aminobutyric acid (GABA_A) receptor is located on human chromosome 5q34–q35 and that an ancestral α—β—γ gene cluster probably spawned clusters on chromosomes 4, 5, and 15. Here, we report that the α₄ gene (GABRA4) maps to human chromosome 4p14–q12, defining a cluster comprising the α₂, α₄, β₁, and γ₁ genes. The existence of an α₂—α₄—β₁—γ₁ cluster on chromosome 4 and an α₁—α₆—β₂—γ₂ cluster on chromosome 5 provides further evidence that the number of ancestral GABA_A receptor subunit genes has been expanded by duplication within an ancestral gene cluster. Moreover, if duplication of the α gene occurred before duplication of the ancestral gene cluster, then a heretofore undiscovered subtype of α subunit should be located on human chromosome 15q11–q13 within an α₅—α_x—β₃—γ₃ gene cluster at the locus for Angelman and Prader—Willi syndromes.     

N2O Evolution by Green Algae

Evidence is presented here that axenic cultures of Chlorella, Scenedesmus, Coelastrum, and Chlorococcum spp. evolve N₂O when grown on NO₂⁻, showing that the Chlorophyceae are a source of N₂O in aquatic systems.     

Effect of pyridine compounds on ammonia oxidation by autotrophic nitrifying bacteria andMethylosinus trichosporium OB3b

Ammonia oxidation, as measured by nitrite production, was inhibited by 2-chloro-6-trichloromethyl-pyridine (nitrapyrin, N-serve) in the methane-oxidizing bacterium,Methylosinus trichosporium OB3b, and the autotrophic nitrifying organisms,Nitrosococcus oceanus andNitrosomonas marina. 6-Chloropicolinic acid, a hydrolysis product of nitrapyrin, was ineffective as an inhibitor of ammonia oxidation by either the methanotroph or the autotrophs. Picolinic acid (2-carboxy-pyridine), in contrast, inhibited nitrification by the methane-oxidizing bacterium but not by the autotrophic cultures. Picolinic acid may provide a means for differentiating ammonia oxidation attributable to methanotrophs from that resulting from autotrophs in environmental studies.     

Variations in short term products of inorganic carbon fixation in exponential and stationary phase cultures of Aphanocapsa 6308

Aphanocapsa 6308 metabolizes both NaHCO₃ and Na₂CO₃. The short term incorporation (5-s) metabolic pattern and the patterns of incorporation of bicarbonate for exponential versus stationary phase cultures differ, however. Cells were equilibrated for 10 min in air and distilled water prior to injection of either NaH¹⁴CO₃ at pH 8.0, or Na₂ ¹⁴CO₃ at pH 11.0. Hot ethanol extracts were analyzed via paper chromatography and autoradiography for products of CO₂ fixation. At 5 s, malate (51.5%) predominates slightly as a primary bicarbonate fixation product over 3-phosphoglycerate (40.3%); 3-phosphoglycerate is the primary product of carbonate fixation. At 60 s, the carbonate and bicarbonate labelling patterns are similar. Cells in stationary phase fix in 5 s a greater proportion of bicarbonate into malate (36% vs. 14% for 3-phosphoglycerate) than do cells in exponential growth. Likewise, 60 s incorporations show a large amount of bicarbonate fixed into aspartate (30.9%) in stationary phase cells over that of exponential phase (11.6%). These data suggest an operative C₄ pathway for purposes not related to carbohydrate synthesis but rather as compensation for the incomplete tricarboxylic acid cycle in cyanobacteria. The enhancement of both aspartate fixation and CO₂ fixation into citrulline in stationary phase correlates with an increase in cyanophycin granule production which requires both aspartate and arginine.Nonstandard Abbreviations 3-PGA 3-phosphoglyceric acid - TCA tricarboxylic acid     

Leishmania mexicana: Immunology and histopathology in C3H mice

C3H mice were infected subcutaneously with 10⁵ promastigotes of Leishmania mexicana and subsequent lesions were examined at 3, 5, and 8 months. All animals developed persistent nonulcerating nodules of variable size which did not metastasize. The nodules contained amastigotes with a mononuclear infiltrate of histiocytes, lymphocytes, and plasma cells, but without formation of tuberculoid-type granulomas. Neutrophils and eosinophils were also encountered in some cases. Specific antileishmanial antibodies and delayed-type hypersensitivity to leishmanial antigen were present at 3, 5, and 8 months postinfection. L. mexicana infection in C3H mice differs from classic self-healing cutaneous leishmaniasis by the pesistence of nonhealing, nonulcerating, nonmetastasizing lesions, despite evidence of cellular and humoral immunity.     

Mutation in continuous cultures of Schizosaccharomyces Pombe. I. Dependence of the kinetics of mutation accumulation upon the growth-limiting nutrilite

The rate of spontaneous mutation to resistance to the 12,13-epoxytrichothecene trichodermin has been determined under different growth limiting conditions in continuous cultures of the microbial eukaryote Schizosaccharomyces pombe. In agreement with data obtained in bacterial systems by previous workers the kinetics observed for the accumulation of mutations is found to be dependent upon the nutrient used to limit the growth of the population. Under conditions of glucose-limitation mutation accumulation is directly proportional to the rate of cell division, while under histidine-limitation it is proportional to chronological time. Various possible explanations for these observations are discussed.     

Transforming growth factor-β inhibition of interleukin-1 activity involves down-regulation of interleukin-1 receptors on chondrocytes

Interleukin-1 (IL-1) plays an important role in cartilage destruction associated with inflammatory and degenerative arthritis because of its ability to induce matrix degrading enzymes. Previously, we have shown that the IL-1-induced chondrocyte protease activity was inhibited by transforming growth factor-β (TGF-β). In this paper, we show that TGF-β inhibits the IL-1-induced synthesis of collagenase and stromelysin by reducing the steady-state mRNA levels in rabbit articular chondrocytes. We further demonstrate that TGF-β-treated chondrocytes show reduced ¹²⁵I-IL-1 binding that returns to a normal level when TGF-β is removed from the culture medium. The inhibitory effect of TGF-β is observed for both naturally occurring as well as fibroblast growth factor (FGF)-inducible binding sites (receptors). Scatchard analysis of receptor—ligand interactions demonstrate that the reduced binding is due to a reduction in the number of receptors for IL-1 and is not due to changes in affinity. Affinity cross-linking studies suggest that control chondrocytes contain two major cross-linked bands of M_r =116 and 80 kDa and a minor band of M_r =100 kDa. FGF-treated cells show enhanced levels of all the bands, plus an additional 200-kDa band. TGF-β treatment of chondrocytes results in the reduction of all of these bands in both control as well as FGF-induced cells. These observations suggest that the ability of TGF-β to down-regulate the IL-1 receptor may be a mechanism by which it exerts its effects in antagonizing the IL-1 activity on chondrocytes.     

Seasonal commitment of HMGCoA reductase activity to vitellogenin production

In female frogs (Rana Esculenta) during gametogenesis the cholesterol synthesized in the liver by 3-hydroxy-3-methylglutaryl coenzyme A reductase is mostly exported into the blood and taken up by the oocytes.In order to understand the fate of the neosynthesized cholesterol, female and male frogs and estrogenized male controls were injected with the labelled precursor¹⁴C mevalonate.In females and in estrogenized controls, mevalonate-derived radioactivity is found in a plasmatic lipoprotein that has been identified as vitellogenin by immunological detection.The increased 3-hydroxy-3-methylglutaryl coenzyme A reductase activity present in females in Fall is likely to be committed to provide cholesterol for the lipidation of this cholesterol-rich protein.     

Purine nucleosides and nucleotides stimulate proliferation of a wide range of cell types

Summary Presumptive astrocytes isolated from 10-day white Leghorn chick embryos, Factor VIII-positive human brain capillary endothelial cells, meningeal fibroblasts from 10-day chick embryos, Swiss mouse 3T3 cells, and human astrocytoma cell lines, SKMG-1 and U373, were rendered quiescent when placed in culture medium that contained 0 or 0.2% serum for 48 h; their proliferation was markedly reduced and they incorporated [³H]thymidine at a low rate. [³H]Thymidine incorporation and cell proliferation were induced in all types of cells by addition of guanosine, GMP, GDP, GTP, and to a lesser extent, adenosine, AMP, ADP or ATP to the culture medium. The stimulation of proliferation by adenosine and guanosine was abolished by 1,3-dipropyl-7-methylxanthine (DPMX), an adenosine A₂ receptor antagonist, but not by 1,3,-dipropyl-8-(2-amino-4-chorophenyl)xanthine (PACPX), an A₁ antagonist. Stimulation of proliferation by the nucleotides was not abolished by either DPMX or PACPX. The P₂ receptor agonists,α,β-methyleneATP and 2-methylthioATP, also stimulated [³H]thymidine incorporation into the cells with peak activity at approximately 3.5 and 0.03 nM, respectively. These data imply that adenosine and guanosine stimulate proliferation of these cell types through activation of an adenosine A₂ receptor, and the stimulation of cell proliferation by the nucleotides may be due to the activation of purinergic P_2y receptors. As the primary cultures grew older their growth rate slowed. The capacity of the purine nucleosides and nucleotides to stimulate their growth diminished concomitantly. The 3T3 cells showed neither decreased growth with increased passages nor reduced response to the purines. In contrast, although the doubling time of the immortalized human astrocytoma cell lines SKMG-1 and U373 remained constant, the responsiveness to purinergic stimulation of the U373 cells decreased but that of the SKMG-1 did not. These data are compatible with a decrease in the number, or the ligand-binding affinity of the purinergic receptors, or a decreased coupling of purinergic receptors to intracellular mediators in primary cells aged in tissue culture.