Inhibition of DNA Synthesis but not of Poly-dAT Synthesis by the Arabinose Analogue of Cytidine <Emphasis Type="Italic">in vitro</Emphasis>

Kimball and Wilson¹ reported that the arabinose analogue of cytidine (ara-C) inhibited DNA polymerase in a crude extract prepared from Ehrlich ascites cells. Furth and Cohen² observed cytosine arabinoside triphosphate (ara-CTP) inhibited DNA polymerase in extracts from either calf thymus or bovine lymphosarcoma tissue, although these investigators³ had already found no effect of ara-CTP on DNA polymerase from Escherichia coli. The inhibition in both of these cases could be substantially reversed by dCTP; but incorporation of the arabinose nucleotide (ara-CMP) into DNA could not be unequivocally demonstrated. Graham and Whitmore⁴ reported the incorporation of ara-C into DNA in vivo and the inhibition of a DNA polymerase from L cells by ara-CTP. They found that ara-CMP was initially incorporated into small DNA strands but subsequently appeared in long strands. Momparler⁵ has presented evidence that, in vitro, ara-C incorporation was limited to the 3′-hydroxyl end of DNA chains. Such incorporation might be expected to block further chain elongation but this expectation was not supported by the evidence presented by Graham and Whitmore.     

Endopeptidase Activity of Phage λ-Endolysin

JACOB and Fuerst^1,2 demonstrated the presence of a bacteriolytic enzyme (λ-endolysin) in the induced cultures of lysogenic Escherichia coli K12 (λ). The enzyme was later identified as the product of gene R; of phage λ³ which is involved in bacterial lysis at the end of a latent period. The enzyme is apt to form spheroplast-like structures in E. coli² and one would therefore expect its substrate to be murein.     

NOR polymorphism in the Iberian species Chondrostoma lusitanicum (Pisces: Cyprinidae)

Chromosomal polymorphism regarding number of NOR sites in the cyprinid fish Chondrostoma lusitanicum was examined using C-banding, silver-staining (Ag), and fluorescent staining with chromomycin A₃ (CMA₃). The analysis of heterochromatic regions allowed a more precise identification of the centromeric regions and the proposal of a revised haploid chromosome formula (7M: 15S: 3A). We describe variability in the number of NOR regions per genome, number of active NOR sites per cell, and relative size of individual NORs. Individuals expressed two or four NOR-bearing chromosomes. Polymorphism was detected in all the populations studied and sex-related differences were not found. The observed chromosomal NOR phenotypes suggest the occurrence of structural rearrangements during the evolutionary process of this diploid leuciscine cyprinid.     

Basement membrane components of bronchial epithelium in humans suffering from chronic nonspecific lung diseases

Collagen IV and laminin are important constituents of the basement membrane (BM). By use of immunocytochemistry we examined the occurrence and distribution of these two components in the BM beneath normal, mucoid and metaplastic epithelium of large bronchi in 22 adults suffering from chronic nonspecific lung diseases. Both collagen IV and laminin were expressed as a thin and continuous layer beneath the epithelium in most tissue specimens with normal epithelium. In a few specimens the layer showed interruptions with a patchy distribution of the immunoreactivity. Three patterns of distribution of BM components were found under the metaplastic epithelium. Total absence of immunoreactive collagen IV and laminin was the most common variant. Weak and scarce staining for both proteins in the BM characterized the second pattern. The third variant showed strong collagen IV immunoreactivity but lack of laminin. The BM beneath the mucoid epithelium was characterized by irregular distribution of collagen IV and laminin. We suggest that the occurrence and distributional pattern of the BM components are related to the type of overlying epithelium and connected with an altered synthesis of these components.     

Expression of A mating type genes of Coprinus cinereus in a heterologous basidiomycete host

The A mating factor of Coprinus cinereus determines compatibility in mating by regulating part of a developmental sequence that leads to dikaryon formation. The A genes that trigger development encode two different classes of homeodomain proteins, and for a successful mating, a protein of one class, HD 1, must interact with a protein of the other class, HD 2. In this report we show that C. cinereus A genes that encode HD 2 proteins, a2-1 and b2-1, can elicit A-regulated development in the heterologous host C. bilanatus. Transformation rates were very low, suggesting that the genes were poorly transcribed. The fact that the HD 2 genes are functionally expressed implies successful heteromultimeric association of putative DNA-binding proteins coded by the two Coprinus species. This interaction was sufficient to satisfy the need for different A factors in the formation of a fertile C. bilanatus dikaryon, but fertile dikaryons were more readily produced in matings with the a2-1 gene transformants. The C. cinereus A genes, b1-1 and d1-1, which encode HD1 proteins, were either not expressed or their proteins were non-functional in C. bilanatus. These experiments raise some interesting questions regarding HD1–HD2 protein interactions.     

Enhanced transformation of tomato co-cultivated with Agrobacterium tumefaciens C58C1Rifr::pGSFR1161 in the presence of acetosyringone

Summary Explants of tomato (Lycopersicon esculentum Mill cv. Ailsa Craig) were co-cultivated with Agrobacterium tumefaciens C58C1Rif^r::pGSFR1161 in the presence of 20 (M acetosyringone). Transformed root clones were selected on kanamycin medium and the presence of the nptII gene in the plant DNA confirmed by the polymerase chain reaction. Root clones derived from acetosyringone treatment grew more vigorously in the presence of kanamycin and synthesized a greater amount of NPT-II enzyme. The conclusion is that acetosyringone treatment enhances the transformation process, possibly by stimulating multiple insertions of the T-DNA into the host genome.Abbreviations AS acetosyringone - CTAB hexadecyltrimethylammonium bromide - EDTA ethylenediaminetetraacetic acid - ELISA enzyme-linked immunosorbant assay - MS Murashige and Skoog (1962) medium - PCR polymerase chain reaction     

Vegetative growth and productivity ofEichhornia azurea with special emphasis on leaf dynamics

The lifeform and the biological production of pure stands ofEichhornia azurea Kunth in three lakes in tropical Brazil were studied. The lifeform ofE. azurea is termed ‘semi-emergent’, because the plant has well developed trailing stems just under the water, and the aerial lamina emerges with the thick petiole. The density of shoot apices was 9.9, 17.2 and 17.1 m⁻² in Lake Dom Helvecio, Lake Jacaré and Lake Carioca, respectively. The mean daily increment of the apical shoot biomass was between 1.8 and 4.8 g m⁻² day⁻¹. The mean leaf life-span in Lake Dom Helvecio, Lake Jacaré and Lake Carioca was estimated to be 78, 49 and 64 days in the wet season and 73, 70 and 73 days in the dry season, respectively. The stem life-span was estimated to be about 28 months. Starch content in the current years' stem ranged from 24 to 118 mg g⁻¹ dry matter with fluctuations, the amplitude of which decreased with age. The differences for most of the growth parameters, such as density of shoot apices, daily increment of biomass and leaf life-span, between dry and wet season are smaller than those among the three lakes. Both the decrease in daily dry matter production and the increase in leaf life-span occurred in order from Lake Dom Helvecio to Lake Jacaré and Lake Carioca. The low productivity ofE. azurea is considered to be related to a low leaf area index, a long time interval for the emergence of new leaves, long leaf life-span and a low capacity for branching.     

Occurrence of subcutaneous zygomycosis (Entomophthoromycosis Basidiobolae) caused by Basidiobolus haptosporus with pulmonary involvement

A case of a two-year-old boy with multiple subcutaneous lesions caused by Basidiobolus haptosporus is presented.The child had also a non-toxic familial goiter and clinical and radiological features of a pulmonary illness. The pulmonary manifestations only disappeared with the treatment with potassium iodide. The authors think that the pulmonary lesions must have arisen by direct spread of the fungus from the subcutaneous lesions of the chest.