Synthesis by Ribosomes of Viral Coat Protein containing Ester Linkages

Peptidyl transferase, the ribosomal enzyme which synthesizes peptide bonds, can catalyse the formation of ester linkages between α-hydroxyacyl-tRNA and aminoacyl-tRNA when ribosomes carry out a specific translation of phage R17 RNA in vitro.     

Cytidine Analogues and Stomatogenic Recovery in Amicronucleate Paramecium tetraurelia and Paramecium jenningsi

Removal of the micronuclei of Paramecium tetraurelia and Paramecium jenningsi by micropipetting generates amicronucleate cell lines. These cell lines go through a period of growth depression for several dozen fissions, but they gradually recover. Amicronucleate cells in the depression period characteristically exhibit abnormal oral development, particularly reduction in the length of the buccal cavity and an abnormal pattern of the oral membranelles. To test the notion that the macronucleus is involved in the recovery of amicronucleate cell lines, DNA demethylation drugs were administered to amicronucleates in the depression period. After at least 4 fissions, the treated amicronucleates were assessed for their progress in recovery by scoring the proportion of cells with normal oral membranelles. Cvtidine analogues which demethylate cytosine specifically at the 5 position, namely 5-azacytidine, 5-aza-2'- deoxycytidine and 5-fluoro-2'-deoxycytidine. promoted recovery of the amicronucleates. Cytidine, 6-azacytidine, 2'-fluoro-2'-deoxy-cytidine and cytosine-β-D-arabinofuranoside did not. These results suggest that (i) 5-methylcytosine is present in the macronucleus of these Paramecium species, probably in small amounts and (ii) recovery of amicronucleates involves demethylation of macronuclear DNA. This implies that in normal cells the micronuclei are involved in maintaining the macronuclear DNA in a methylated state and hence the inactivation of the macronuclear sequences that are to be employed for stomatogenic recovery. A general mechanism for the control of gene expression may therefore be employed for the regulation of specific sequences.     

Anti-Auxin Activity of Xyloglucan Oligosaccharides: the R?le of Groups other than the Terminal {alpha}-L-Fucose Residue

The quantitatively major nonasaccharide (XG9) derived from xyloglucanby digestion with cellulase exhibits anti-auxin activity inthe pea stem segment straight-growth bioassay; the most effectiveconcentration of XG9 is c. 10^–9 M. Previous work had shownthat XG9 owes its biological activity to the presence of a terminal-L-fucopyranose residue. In order to investigate to what extentthe remainder of the XG9 molecule is essential for activity,several fucose-containing compounds were tested for their abilityto mimic the anti-auxin effect of XG9. A fucose-containing pentasaccharideof xyloglucan (XG5; probable structure FucGalXylGlcGlc) was,at 10^–8 M, about as effective an anti-auxin as 10^–9M XG9; unlike XG9, XG5 did not diminish in effectiveness at10^–7 M. The human milk trisaccharide, 2'-fucosyl-lactose[L-fucopyranosyl--(12)-D-galactopyranosyl-ß-(14)-D-glucose],whose FucGal unit is identical with that of XG9, inhibited auxin-inducedelongation over a wide range of concentrations centred on about10^–8 M. 2'-Fucosyl-lactose at 10^–8 M was about aseffective an anti-auxin as 10^–9 M XG9. Free L-fucose andmethyl--L-fucopyranoside were unable to inhibit auxin-inducedgrowth at any concentration tested (10^–10 M to 10^–6M) and neither compound interfered with the inhibition causedby 10^–9 M XG9 when co-incubated at concentrations up to10^–4 M. The results confirm the essential r?le of an -linkedterminal fucose residue in the anti-auxin activity of XG9 andshow that the sub-terminal galactose residue may also be required.Possible reasons why high concentrations of XG9 fail to antagonizeauxin-induced growth while high concentrations of XG5 and 2'-fucosyl-lactosecontinue to do so are discussed. Key words: Anti-auxin, oligosaccharin, fucose     

Functional morphology of synostosial articulations in the crinoid column

The rarest articulation found in the crinoid column is the synostosis, in which adjacent articular facets are essentially planar. 'Synostoses' in the columns of post-Palaeozoic isocrinids are more correctly termed cryptosymplexies. comprising symplectial articulations which have become infilled by secondary calcite. Cryptosymplexial joints are totally inflexible and are the preferred sites of stem autotomy. Synostoses sensu stricto appear to have been limited to early Palaeozoic taxa, but this form of articulation was soon succeeded by the symplexy. Synostoses were probably commonest in meric columns which evolved from hohlwurzels and in which the main flexibility was along meric sutures, rather than between columnals. With the evolution of the holomeric columnal. a more flexible articulation between columnals was a functional necessity in order that the stem did not develop into a stiffened rod. The solution was the evolution of the symplexy. *** Crinoids, columnals. synostosis, functional morphology evolution.     

CHARACTERIZATION OF A BOTTLENOSE DOLPHIN (TURSIOPS TRUNCATUS) KIDNEY EPITHELIAL CELL LINE

Abstract: An epithelial cell line, Carvan dolphin kidney (CDK), isolated from a prematurely born female bottlenose dolphin, Tursiops truncatus , exhibited growth characteristics not previously reported for cetacean cells in culture. CDK cells were cytokeratin positive and demonstrated a maximum doubling time of 1.31 days, with plating and colony forming efficiencies approaching 100% for the early population doublings. Despite an unusually efficient colony-forming ability and rapid growth, these cells were neither transformed nor immortal, displaying normal contact inhibition, anchorage dependence, and the requirement for high concentrations of fetal bovine serum in the growth medium. CDK cells exhibited age-dependent changes in growth rate, colony-forming efficiency, and cytoplasmic profile, and showed a finite lifespan of about 50 population doublings and a stable 2N = 44 karyotype which correlates with previously reported cytogenetic analyses. Velocity sedimentation analysis showed that CDK cells contained nuclear aryl hydrocarbon receptor (Ah), indicating their potential to be induced for cytochrome P450. These data suggest that CDK cells may have utility as an in vitro toxicological model for evaluating hydrocarbon contaminant effects on Tursiops truncatus , a protected marine mammal.     

Discrimination Amongst Leishmania by Polymerase Chain Reaction and Hybridization with Small Subunit Ribosomal DNA Derived Oligonucleotides

ABSTRACT. A method for discriminating among Leishmania is described, based upon small subunit ribosomal DNA sequence differences. The method was to amplify the entire 2.2 kb small subunit rDNA by polymerase chain reaction using conserved primers specific for the 5' and 3' termini of the small subunit ribosomal RNA, and then hybridize the product dotted onto nylon membranes with labeled oligonucleotides. The design of the hybridization probes was based upon complete small subunit rDNA sequences from L. amazonensis, L. major and L. guyanensis and partial sequences of L. mexicana, L. braziliensis, L. tropica and L. chagasi. A high degree of sequence similarity (> 99%) among species was found. However, sufficient sequence divergence occurred to permit the design of internal oligonucleotide probes specific for species complexes. This procedure successfully discriminated amongst a wide range of Leishmania isolates. The method detected as few as 10 cultured organisms and detected parasites in tissue samples from experimentally infected animals. Non-radioactive labeling showed the same specificity and sensitivity as radioactive probes.     

Trypanosoma Manulis N. Sp. From the Russian Pallas Cat Felis Manul

ABSTRACT. The morphology of Trypanosoma manulis n. sp. is described from living and stained specimens obtained from the blood of a Pallas cat, Felis manul , from Kazakhstan. the cat was also infected with a Hepatozoon sp. and feline immunodeficiency virus. the morphology of the trypanosome most closely resembles that of Trypanosoma mpapuense Reichenow and Trypanosoma heybergi Rodhain found in bats. Trypanosoma manulis does not grow well in conventional media, but co-culture with African green monkey kidney cells in Eagle's Minimum Essential Medium supplemented with 10% fetal calf serum at approximately 27° C resulted in luxuriant growth of trypanosomes. Under these growth conditions, epimastigotes adhered to the surface of the culture flask and to African green monkey kidney cells, as well as forming large rosettes. At 37° C, although growth was poor, transformation of the epimastigotes into the bloodstream forms occurred. This represents the first report of a trypanosome of the subgenus Megatrypanum in a felid.