Ascaris suum and Onchocerca volvulus: S-adenosylmethionine decarboxylase

Putrescine-dependent S-adenosylmethionine decarboxylase (EC 4.1.1.50) was demonstrated in Ascaris suum and Onchocerca volvulus; activation was found to be about fourfold by putrescine. Mg2+ did not affect the enzyme activity. A. suum was taken as a model nematode and its S-adenosylmethionine decarboxylase was partially purified and characterized. The molecular weight was estimated to be 220,000. The apparent Km-value for adenosylmethionine was determined to be 17 microM. Methylglyoxal bis(guanylhydrazone) and berenil competitively inhibited the enzyme activity; the apparent Ki-values were found to be 0.24 microM and 0.11 microM, respectively. The dependence of filarial worms on uptake and interconversion of putrescine and polyamines as well as properties of the S-adenosylmethionine decarboxylase, different from the host enzyme, points to the polyamine metabolisms as a useful target for chemotherapy.     

Demonstration of correlations between the 8 and 10 kHz atmospherics and the inflammatory reaction of rats after carrageenan injection

Between the mean daily density of 28 kHz atmospherics and the onset of epileptic fits there is a highly significant correlation coefficient (r) of 0.30; there is a negative coefficient of –0.20 between the fits and the mean daily density of 10 kHz atmospherics. The onset of heart infarction is correlated with 28 kHz atmospherics (r=0.15). Furthermore, we have discovered that sudden deafness is also correlated with certain configurations of atmospherics. In this paper we report the following correlation coefficients between the inflammatory reaction of rats to a carrageenan injection (rci) into a hind paw and the mean daily pulse rate of atmospherics of the same day:r=0.49 for the 8 kHz atmospherics (P<0.02) andr=0.44 for the 10 kHz atmospherics (P<0.04). The correlations between rci reaction and other atmospherics (12 and 28 kHz) are smaller and not significant. By the method of multiple linear regression we found a multipleR=0.54 between rci reaction and the 8 and 10 kHz atmospherics (the regression function for the rci reaction is 0.15+0.004×8 kHz+0.002×10 kHz,P<0.05).     

Predictive model of conjugative plasmid transfer in the rhizosphere and phyllosphere.

A computer simulation model was used to predict the dynamics of survival and conjugation of Pseudomonas cepacia (carrying the transmissible recombinant plasmid R388:Tn1721) with a nonrecombinant recipient strain in simple rhizosphere and phyllosphere microcosms. Plasmid transfer rates were derived for a mass action model, and donor and recipient survival were modeled as exponential growth and decay processes or both. Rate parameters were derived from laboratory studies in which donor and recipient strains were incubated in test tubes with a peat-vermiculite solution or on excised radish or bean leaves in petri dishes. The model predicted donor, recipient, and transconjugant populations in hourly time steps. It was tested in a microcosm planted with radish seeds and inoculated with donor and recipient strains and on leaf surfaces of radish and bean plants also growing in microcosms. Bacteria were periodically enumerated on selective media over 7 to 14 days. When donor and recipient populations were 10(6) to 10(8) CFU/g (wet weight) of plant or soil, transconjugant populations of about 10(1) to 10(4) were observed after 1 day. An initial rapid increase and a subsequent decline in numbers of transconjugants in the rhizosphere and on leaf surfaces were correctly predicted.     

Aerial Dispersal and Epiphytic Survival of Pseudomonas syringae during a Pretest for the Release of Genetically Engineered Strains into the Environment

Prospective experimental field evaluation of genetically engineered microorganisms, such as microbial pest control agents, raises issues of how to properly ascertain their fate and survival in the environment. Field trials with recombinant organisms must reflect requirements for sampling and monitoring. Field trials were conducted at Tulelake, Calif., to monitor the numbers of viable cells of a nonrecombinant strain of Pseudomonas syringae that entered the atmosphere and landed on plants and soil during and after an aerosol spray application. An exponential decrease in numbers of viable cells deposited at increasing distances from three sprayed plots was observed. The relative rate of survival of cells sprayed directly on plants was more than 10 times higher than that of cells dispersed through the air to similar adjacent plants. Results are being used to gain experience with the characteristics of a release site that influence containment or dispersal and to develop appropriate sampling methodologies for evaluating survival and dispersal characteristics of genetically engineered bacteria released into the environment. The ability to make predictions about microbial dispersal and survival will reduce the uncertainties associated with environmental releases of recombinant organisms.     

Miconia zanonii (Melastomataceae: Miconieae), a new species from Hispaniola

Miconia zanonii, which occurs in broad-leaved cloud forests at four localities in the Cordillera Central of the Dominican Republic, is described and illustrated. It is compared withM. krugii andM. samanensis, two probably close relatives withinMiconia sect.Chaenopleura.     

Three-dimensional architecture of chromosome fibres in the crane fly: co-oriented autosomal bivalents and amphitelic sex univalents during prometaphase

A technique for the fixation of cells during live observation (Nicklas et al. 1979) was used to investigate chromosomes which were moving at the time of fixation. Chromosome fibres were reconstructed by tracking their microtubules in longitudinal serial sections. A considerable proportion of non-kinetochoric microtubules (free microtubules, fMTs) is skewed with respect to the fibre axis. These skew fMTs contribute to the degree of disorder. It was found that the difference in the relative proportion of skew fMTs between active fibres (oriented in the direction of movement) and passive fibres (oriented backwards) is significantly correlated with the chromosome velocity (correlation coefficient r=0.796, P=0.01). It can be concluded that the pulling force generated in the chromosome fibre is a function of skew fMTs.     

Transposon mutagenesis in Azospirillum brasilense: isolation of auxotrophic and Nif- mutants and molecular cloning of the mutagenized nifDNA

Summary We report the successful mutagenesis of Azospirillum brasilense 29710 Rif Sm with transposon Tn5. The narrow host-range plasmid pGS9 (p15A replicon), which possesses broad host-range N-type transfer genes, was used as the suicide vehicle to deliver Tn5 in Azospirillum. Out of 900 colonies tested, 0.8% proved to be auxotrophic. One mutant altered in indoleacetic acid (auxin) biosynthesis was isolated and, in addition, three mutants completely defective in nitrogen fixation (nif) were obtained. All the mutants tested contained a single copy of Tn5 integrated randomly in the genome. The Tn5-mutagenized EcoRI fragments were cloned from the three Nif^- mutants. Physical analysis of cloned DNA showed that Tn5 was present on a different EcoRI fragment in each case, ranging in size from 15–17 kb. The nitrogenase structural genes (nifHDK) in A. brasilense 29710 Rif Sm were localized on a 6.7 kb EcoRI fragment. We found that Tn5 is not inserted in the nifHDK genes in the Nif^- mutants reported here. Site-directed mutagenesis using the cloned, Tn5-containing DNA from mutant Nif27(pMS188), produced a large number of Nif^- transconjugants of the A. brasilense 29710 Rif wild-type strain, showing the linkage between Tn5 insertion and the Nif^- phenotype. This is the first time that transposon-mutagenized auxotrophic, Nif^- and other mutants have been available for genetic analysis in Azospirillum. This should greatly facilitate the cloning and mapping of genes involved in nitrogen fixation as well as in many other phenotypic characteristics of Azospirillum.     

Effect of glycerol on plasmid transfer in genetically competent Haemophilus influenzae

Summary The small plasmid pAT4 transformed at characteristically low frequencies those competent Haemophilus influenzae Rd strains that had no DNA homology with this plasmid. Transformation was increased up to 100 times, however, when the recipient cells were exposed to 30% glycerol before plating for transformants. Expression of plasmid resistance markers was then immediate. Ultraviolet irradiation experiments indicated that this large increase was due to release by the glycerol of double-stranded plasmid molecules, presumably from transformasomes. Several other plasmids exhibited the same phenomenon. Dimethylsulfoxide also stimulated plasmid transformation but lysolecithin and high concentrations of NaCl or glucose were ineffective. Glycerol did not increase the efficiency of transformation by either chromosomal DNA or linearized plasmid DNA.