Nonadditive interactive effects of polychlorinated biphenyl congeners in rats: role of the 2,3,7,8-tetrachlorodibenzo-p-dioxin receptor

Administration of 3,3',4,4',5,5'-hexa-,3,3',4,4',5-penta-, and 2,3,3'4,4'5-hexa-chlorobiphenyl to immature male Wistar rats caused a thymic atrophy at high dose levels (1.25, 1.0, and 100 mumol/kg, respectively) and induced the hepatic cytochrome P-448 dependent monooxygenases (benzo[a]pyrene hydroxylase and ethoxyresorufin O-deethylase) at both high and low (0.25, 0.01, and 5 mumol/kg, respectively) doses. In contrast, 2,2',4,4',5,5'-hexachlorobiphenyl (HCBP) (300 mumol/kg) did not elicit any of these effects but elevated hepatic 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) cytosolic receptor protein levels (threefold) as previously reported. The effects of hepatic receptor modulation by 2,2',4,4',5,5'-HCBP (300 mumol/kg) on the enzyme induction activities of 3,3'4,4',5-penta-, 3,3'4,4',5,5'-hexa-, and 2,3,3',4,4',5-hexa-chlorobiphenyl were dose-dependent; no interactive effects were observed at high (toxic) doses of these compounds, whereas apparent synergistically increased hepatic microsomal monooxygenase induction activities were noted at the lower submaximal induction doses. It was concluded that the increased responsiveness of the rats was due to elevated hepatic 2,3,7,8-TCDD receptor levels.     

A note on the use of microwaves in an improved non-radioactive DNA hybridization procedure for the detection of bacteria in foodstuffs

Foodstuffs were artificially contaminated with Escherichia coli carrying plasmid pBR322, dot blotted onto nylon membranes and briefly subjected to microwaves in the presence of 1·5 mol/l NaC1/0·5 mol/l NaOH. Subsequent hybridization with a biotin-labelled probe specific for pBR322 enabled the detection of cell concentrations > 10⁴ cells/dot blot, equivalent to 2 × 10⁷ cells/g food tested. This shortened and simplified method was effective for all ten foods tested, generated low background levels and should be applicable to a wide range of bacteria.     

The structure and evolution of the spider monkey delta-globin gene

We have isolated the delta-globin gene of the New-World spider monkey, Ateles geoffroyi, and compared its nucleotide sequence with those of other primate delta- and beta-globin genes. Among primate delta-globin genes, the rate of nonsynonymous substitutions is much less than the rate of synonymous substitutions. This suggests that primate delta- globin genes may remain under evolutionary conservation, perhaps because hemoglobin A2 has an as yet unknown physiological importance.      

Plasmid transfer and behaviour in Acinetobacter calcoaceticus EBF65/65

At least one plasmid from each of the incompatibility groups B, C, FIV, H2/S, I alpha, I delta, P, W and X was shown to be capable of transfer from Escherichia coli K12 to Acinetobacter calcoaceticus EBF65/65. Transfer was influenced by the presence of pAV2 (thought to encode a restriction-modification system) in the recipient strain; however, not all plasmids belonging to a particular incompatibility group behaved identically. All plasmids were unstable to varying degrees in A. calcoaceticus EBF65/65, but under suitable conditions were capable of transfer to further strains of EBF65/65 and re-transfer to E. coli K12. Of 40 recently isolated trimethoprim R plasmids 31 transferred successfully from E. coli K12 to A. calcoaceticus EBF65/65, but 17 of these 31 required the introduction of a second mobilizing plasmid for re-transfer to occur.     

Biochemical pathways in prokaryotes can be traced backward through evolutionary time

For the first time, a credible prokaryotic phylogenetic tree is being assembled by Woese and others using quantitative sequence analysis of oligonucleotides in the highly conservative rRNA. This provides an evolutionary scale against which the evolutionary steps that led to the arrangement and regulation of contemporary biochemical pathways can be measured. This paper presents an emerging evolutionary picture of aromatic amino acid biosynthesis within a large superfamily assemblage of prokaryotes that is sufficiently developed to illustrate a new perspective that will be applicable to many other biochemical pathways.      

The evolutionary history of the amylase multigene family in Drosophila pseudoobscura

In Drosophila pseudoobscura, the amylase (Amy) multigene family is contained within a series of inversions, or gene arrangements, on the third chromosome. The Standard (ST), Santa Cruz (SC), and Tree Line (TL) inversions are central to the phylogeny of arrangements, and have clusters of other arrangements derived from them. The gene arrangements belonging to each of these three clusters have a characteristic number of Amy genes, ranging from three in ST to two in SC to one in TL. This distribution pattern can reflect a history of either duplications or deletions, although the data available in the past did not permit a decision between these alternatives. We provide unambiguous evidence that three Amy genes were present before the divergence of the ST, SC, and TL arrangements. Thus, the current status of the Amy multigene family is the result of deletions in the TL and SC arrangements, which created three new pseudogenes: TL Amy2-psi, TL Amy3-psi, and SC Amy3- psi. Analysis of pseudogene sequences revealed that, in the SC and ST arrangements, pseudogene evolution has been retarded, most likely due to the homogenization effect of gene conversion. Finally, by determining the original copy number, we have reconstructed the evolutionary history of the Amy multigene family and linked it with the evolution of the central gene arrangements.      

USE OF SENSORY EVALUATION FOR MEASURING DEODORIZING EFFECTS OF AN AIR CONDITIONER

The application of sensory methodology for measuring deodorizing effect of an air conditioner equipped with electric plasma was introduced. Deodorizing effect was measured using chemical and sensory methods at different time (0, 30 and 60 min) and mode (control, blowing and cooling) of an air conditioner. Smoke from a roll of cigarette in a closed room was used as a source of odor and the concentrations of acetic acid and ammonia were measured as odorous chemical components. As one of the sensory methods triangle test was used and as a first step to obtain deodorizing effects by triangle test, the threshold of each panelist was obtained as the log dilution ratio of odor concentration at which the difference from odorless air was detected. The odor concentration at each time and mode was calculated using the threshold of the panel and the deodorizing effect was obtained on the basis of the odor concentration. In addition to a triangle test, scaling methods such as category scaling or magnitude estimation were used to measure deodorizing effect of an air conditioner. Deodorizing effects by scaling methods were calculated based on odor intensity with time at each mode. The regression analysis was done between the efficacy of deodorizing effect by sensory test and those by acetic acid and ammonia, the R² values of the regression equations for triangle test, category scale, and magnitude estimation were 0.84, 0.72 and 0.69, respectively. Deodorizing effect by triangle test explained the decrease of acetic acid and ammonia better than those by category scaling or magnitude estimation while high cost and time consuming labor involved in triangle tests reduced the merit. The results of this study demonstrated that various sensory methods could be used to measure deodorizing effect of air conditioners and further researches on fast and reliable methods are needed to establish the official procedures.     

Replication-competent picornaviruses with complete genomic RNA 3' noncoding region deletions.

The genomic RNA 3' noncoding region is believed to be a major cis-acting molecular genetic determinant for regulating picornavirus negative-strand RNA synthesis by promoting replication complex recognition. We report the replication of two picornavirus RNAs harboring complete deletions of the genomic RNA 3' noncoding regions. Our results suggest that while specific 3'-terminal RNA sequences and/or secondary structures may have evolved to promote or regulate negative-strand RNA synthesis, the basic mechanism of replication initiation is not strictly template specific and may rely primarily upon the proximity of newly translated viral replication proteins to the 3' terminus of template RNAs within tight membranous replication complexes.