Aminoglycoside suppression at UAG, UAA and UGA codons in Escherichia coli and human tissue culture cells

Summary We have compared the suppression of nonsense mutations by aminoglycoside antibiotics inEscherichia coli and in human 293 cells. Six nonsense alleles of the chloramphenicol acetyl transferase (cat) gene, in the vector pRSVcat, were suppressed by growth in G418 and paromomycin. Readthrough at UAG, UAA and UGA codons was monitored with enzyme assays for chloramphenicol acetyl transferase (CAT), in stably transformed bacteria and during transient expression from the same plasmid in human 293 tissue culture cells. We have found significant differences in the degree of suppression amongst three UAG codons and two UAA codons in different mRNA contexts. However, the pattern of these effects are not the same in the two organisms. Our data suggest that context effects of nonsense suppression may operate under different rules inE. coli and human cells.     

Book Review

International Journal of Primatology -     

Investigation into the critical equilibrium humidity,active atmospheric water absorption and water content ofRhipicephalus evertsi mimeticus

The critical equilibrium humidity for fully engorged nymphs ofRhipicephalus evertsi mimeticus was shown to be between 91% and 93.5% r.h., and for adult male and female ticks to be between 82% and 84.5% r.h. Studies on gnathosoma and idiosoma by selective exposure to differing relative humidities have shown that dehydrated adult male and female ticks are capable of active uptake of atmospheric water vapor only through their mouthparts. The percentage of water content of unfed adult male and female ticks previously dehydrated was not influenced by subsequent exposure to different relative humidities, varying similarly in both sexes, male imagines between 59.6% and 63.7%, female imagines between 59.6% and 64.4%. Analogous values (62.3% and 61.1%) were obtained for the water content of male and female imagines not previously dehydrated, which were incubated at 30°C and 100% r.h. for 7 days.     

Effects of various alcoholic supplements on the growth rate of Clostridium acetobutylicum ATCC 824

Summary The inhibitory effect of various alkanols, benzyl alcohol and phenethyl alcohol on the growth rate of Clostridium acetobutylicum ATCC 824 was investigated. Inhibition of cell growth was studied by treating cultures with varied concentrations of alcohols. There was a threshold concentration above which growth inhibition occurred. The degree of inhibition was a linear function of the alcohol concentration used. The natural logarithm of the inhibition constant was shown to be: (1) a linear function of the chain length of the alkanols, (2) a linear function of the natural logarithm of the octanol/water partition coefficient for both aliphatic and cyclic alcohols.     

Transport of CMP-N-glycoloylneuraminic acid into mouse liver Golgi vesicles

CMP-Neu5Gc has been shown to be transported into mouse liver Golgi vesicles by a specific carrier the characteristics of which were investigated in detail. In the system employed, CMP-Neu5Gc enters the Golgi vesicles within 2 min; transport was saturable with high concentrations of the sugar-nucleotide and was dependent on temperature. A kinetic analysis gave an apparent K_m of 1.3 μM and a maximal transport velocity of 335 pmol/mg protein per min. Almost identical values were obtained with CMP-Neu5Ac, under the same incubation conditions. Furthermore, the uptake of CMP-Neu5Gc was inhibited by CMP-Neu5Ac, a substrate analogue. Conversely, the uptake of CMP-Neu5Ac was inhibited by CMP-Neu5Gc to the same extent, leading to the conclusion that the transport of CMP-Neu5Ac and CMP-Neu5Gc is mediated by the same carrier molecule. This transport system for CMP-Neu5Gc involves both CMP and CMP-Neu5Gc since intravesicular CMP induced the entry of external CMP-Neu5Gc.     

Physiological, chemical, morphological, and plant infectivity characteristics of Frankia isolates from Myrica pennsylvanica: correlation to DNA restriction patterns.

The filter exclusion method was used to isolate Frankia strains from Myrica pennsylvanica (bayberry) root nodules collected at diverse sites in New Jersey. A total of 16 isolates from five locations were cultured. The isolates were characterized by morphological, chemical, physiological, and plant infectivity criteria and compared with genomic DNA restriction pattern data, which were used to assign the isolates into gel groups (see accompanying paper). The isolates from M. pennsylvanica evaluated in this study were characteristic of Frankia physiological group B strains and were indistinguishable on the basis of whole-cell wall chemistry and diaminopimelic acid isomer analysis. Distinct differences in the spectrum of utilized organic acids and carbohydrates were observed among the isolates and were the only phenotypic criteria by which the isolates could be separated and assigned into separate groups. In general, isolates within a restriction pattern gel group had identical utilization patterns, whereas intragroup isolates had different utilization patterns. Correlation of these phenotypic characteristics with the results of molecular analysis revealed an exclusive carbohydrate and organic acid utilization pattern for each gel group as established by restriction pattern analysis.     

Pregnancy-associated changes in oligomannose oligosaccharides of human and bovine uromodulin (Tamm-Horsfall glycoprotein)

The urinary glycoprotein uromodulin (Tamm-Horsfall glycoprotein) exhibits a pregnancy-associated ability to inhibit antigen-specific T cell proliferation, and the activity is associated with a carbohydrate moiety [Muchmore and Decker (1985) Science 229:479–81; Hessionet al., (1987) Science 237:1479–84; Muchmore, Shifrin and Decker (1987) J Immunol 138:2547–53]. We report here that the Man₆₍₇₎GlcNAc₂-R glycopeptides derived from uromodulin inhibit antigen-specific T cell proliferation by 50% at 0.2–2 M, and further studies, reported elsewhere, confirm that oligomannose glycopeptides from other sources are also inhibitory, with Man₉GlcNAc₂-R the most inhibitory of those tested [Muchmoreet al., J Leukocyte Biol (in press)]. In this work, we have extended the observation of pregnancy-associated inhibitory activity to a second species, and have compared the oligomannose profile of Tamm-Horsfall glycoprotein (nonpregnant) with that of uromodulin (pregnant) derived from both human and bovine sources. Surprisingly, there was a pregnancy-associated decrease in the total content of oligomannose chains due predominantly to a reduction in Man₅GlcNAc₂-R and Man₆GlcNAc₂-R. Man₇GlcNAc₂-R, which did not decrease with pregnancy, comprised a significantly greater proportion of the total oligomannose chains in pregnant vs. nonpregnant samples from both species (human; 34.6% vs. 25.9%: bovine; 14.4% vs. 7.2%).