Radioimmunoassay of nicotine.

A sensitive and specific radioimmunoassay of nicotine was developed using antisera raised against 6-(p-aminobenzamido) nicotine coupled to bovine serum albumin. Inhibition studies with various nicotine analogues revealed that the antisera are highly specific for both the N-methylpyrrolidine ring and the pyridine ring of nicotine, and especially for the structural changes of the former. The use of these antisera in an assay of nicotine in biological fluids is desirable, since the pyrrolidine ring of nicotine is first metabolized in vivo and antibodies must, therefore, discriminate nicotine from other nicotine metabolites.     

Intra- and interbreed genetic variations of mitochondrial DNA major non-coding regions in Japanese native dog breeds [Canis familiaris)

Mitochondrial DNA (mtDNA) major non-coding regions were amplified from 73 dogs of eight Japanese native dog breeds and from 21 dogs of 16 non-Japanese dog breeds by the polymerase chain reaction and their DNA sequences were determined. A total of 51 nucleotide positions within the non-coding region (969–972 base pairs) showed nucleotide variations of which 48 were caused by transition. These nucleotide substitutions were abundant in the region proximate to tRNA^Pro. In addition to the nucleotide substitutions, the dog mtDNA D-loop sequences had a heteroplasmic repetitive sequence (TACACGTÀCG) involving size variation. The DNA sequences of the non-coding region were classified into four different groups by phylogenetic analysis and the deepest branchpoints of this dog phylogeny was calculated to about 100 000 years before the present. Phylogenetic analysis showed that Japanese native dog breeds could not be clearly delimited as distinct breeds. Many haplotypes found in members of some clustering groups were seen in each dog breed, and interbreed nucleotide differences between Japanese dog breeds were almost the same as the intrabreed nucleotide diversities.     

Replication slippage may cause parallel evolution in the secondary structures of mitochondrial transfer RNAs

Presence of the dihydrouridine (D) stem in the mitochondrial cysteine tRNA is unusually variable among lepidosaurian reptiles. Phylogenetic and comparative analyses of cysteine tRNA gene sequences identify eight parallel losses of the D-stem, resulting in D-arm replacement loops. Sampling within the monophyletic Acrodonta provides no evidence for reversal. Slipped-strand mispairing of noncontiguous repeated sequences during replication or direct replication slippage can explain repeats observed within cysteine tRNAs that contain a D-arm replacement loop. These two mechanisms involving replication slippage can account for the loss of the cysteine tRNA D-stem in several lepidosaurian lineages, and may represent general mechanisms by which the secondary structures of mitochondrial tRNAs are altered.      

Dimerization of the RelA protein of Escherichia coli.

The RelA protein of Escherichia coli is a ribosome-associated (p)ppGpp synthetase that is activated by amino acid deprivation. It was recently reported that the activity of RelA is regulated by oligomerization mediated by the C-terminal domain of RelA. The oligomerization of RelA is further characterized in this study. The C-terminal domain consisting of amino acids 455-744, designated 'RelA, formed homooligomers as well as heterooligomers with RelA as demonstrated by copurification of RelA and 'RelA and by an affinity blotting assay. Glutaraldehyde-induced cross-linking indicated that the oligomer was a dimer. The functional analysis of 'RelA was based on a combination of yeast two-hybrid analysis, the determination of the effects of overexpression of 'RelA derivatives on the stringent response, and the cellular localization of the overexpressed 'RelA derivatives. These studies indicated that two regions, designated 'RelA-1 (amino acids 455-538) and 'RelA-2 (amino acids 550-682), were involved in dimerization. The involvement of one of these two regions, RelA-2, is consistent with a previous site-directed mutagenesis study. In addition to dimerization, 'RelA-2 apparently contained the main ribosome-binding domain of RelA. The third region, 'RelA-3 (amino acids 682-744), was not involved in either dimerization or ribosome binding. The overexpression of 'RelA-1 and 'RelA-2, but not 'RelA-3, inhibited the stringent response. These results support the previously proposed model which suggests a role for oligomerization in the regulation of (p)ppGpp synthetase.     

Sundasalanx(Sundasalangidae) is a progenetic clupeiform, not a closely‐related group of salangids (Osmeriformes): mitogenomic evidence

Partitioned Bayesian analysis of whole mitochondrial genome sequences from 30 basal teleosts confidently placed Sundasalanx (Sundasalangidae) within the Clupeiformes, not Osmeriformes as originally thought. This study represents the first demonstration of the phylogenetic position of Sundasalanx on a phylogenetic tree.     

Alteration of the kinetics of type I procollagen synthesis in human osteosarcoma cells by 1,25-dihydroxyvitamin D3

The kinetics of type I procollagen synthesis in a human osteosarcoma cell line, MG 63, were investigated after treatment with 1,25-dihydroxyvitamin D₃ (1,25-(OH)₂ D₃), a hormonal inducer of phenotypic differentiation. Pulse label and chase experiments demonstrated greatly enhanced production and more rapid reduction of intracellular procollagen molecules in the 1,25-(OH)₂ D₃–treated cells as compared to the nontreated case. After a chase for 1 h, labeled procollagen was reduced by nine-tenths in 1,25-(OH)₂ D₃–treated cells, while half of the radioactivity still remained in nontreated cells. The expression rate of type I collagen, which was examined by pulse label experiment, was elevated in association with an increase in the mRNA coding for the type I collagen α1 chain by 1,25-(OH)₂ D₃ treatment. However, the amount of intracellular procollagen present after 4 h continuous labeling was almost the same, independent of the 1,25-(OH)₂ D₃ treatment. Thus, we conclude that strage of the molecule was not affected. The results therefore suggest an increase in both the synthesis and secretion of type I collagen. The 1,25-(OH)₂ D₃ treatment was also found to induce the α subunit of prolyl 4-hydroxylase and to be associated with an elevated level of hydroxyproline in the procollagen. Moreover, gelatinase B–resistant procollagen molecules, indicative of intracellular procollagen molecules in the stable triple helical form, were detected only in the 1,25-(OH)₂ D₃–treated cells. These data suggest more efficient proline hydroxylation is involved in rapid secretion of procollagen after hormone administration. The present evidence points to posttranslational control of procollagen synthesis. J. Cell. Biochem. 65:542–549. © 1997 Wiley-Liss Inc.