Physical locus of the DNA polymerase gene and genetic maps of bacteriophage T5 mutants.

Segments of DNA that contained the DNA polymerase gene of bacteriophage T5 were isolated. The physical locus of the gene was identified by transforming Escherichia coli with purified DNA fragments generated by restriction enzyme digestions, and the transformed cells were used to rescue amber mutants of T5 with mutations in the gene for DNA polymerase. The method is applicable to any other gene that has mutations with low reversion frequencies. We studied the following mutations of the T5 DNA polymerase gene, reading from left to right by the standard convention (D. J. McCorquodale, Crit. Rev. Microbiol. 4:101-159, 1975): D7, D8, aml, ts5E-ts53, am6, and D9. These loci were found to reside within three pieces of DNA with a total length of 3,600 base pairs. Because the structural gene for T5 DNA polymerase is estimated to be 2,600 base pairs long, the whole structural gene may reside in these segments. These are located 58.3 to 61.3% of the distance from the left end of the DNA. The left-end piece of the DNA (1,100 base pairs) containing the polymerase gene has loci D7 and D8, and the right-end piece (1,600 base pairs) has locus D9, according to the results of the transformation assay. These results are consistent with the genetic map.     

Effect of DN-1417, a thyrotropin releasing hormone analog, on dopaminergic neurons in rat brain

Acute and chronic effects of γ-butyrolactone-γ-carbonyl-histidyl-prolinamide (DN-1417) were investigated on motor activity, dopamine (DA) metabolites and DA receptors in various brain regions of rats. The motor activity, as measured with Automex recorder, was enhanced after a single injection with DN-1417 (20 mg/kg, IP), and the motor stimulating action persisted during 21 daily injections. Acute DN-1417 elevated both homovanillic acid (HVA) and 3,4-dihydroxyphenylacetic acid (DOPAC) levels in 7 brain regions, prefrontal cortex polar, medial and lateral fields, nucleus accumbens, olfactory tubercles, amygdala and striatum. After chronic treatment for 7 days, the acute effect of DN-1417 on DA metabolites disappeared in all regions except for the striatum in which DN-1417 still increased HVA and DOPAC. The response of striatal DA metabolites was also observed after chronic treatment for 21 days. Chronic DN-1417 produced no significant change in ³H-spiperone binding in the prefrontal cortex, nucleus accumbens, olfactory tubercles and striatum, while striatal ³H-DA binding displaced by 30 nM spiperone was enhanced after chronic treatment. These results indicate that DN-1417 interacts with mesocortical, mesolimbic and nigrostriatal DA systems in the different modes of action. The lack of tolerance to motor hyperactivity, however, raises the question as to whether DN-1417-induced hyperactivity may be mediated by the activation of mesolimbic DA neurons. The involvement of nigrostriatal neurons in DN-1417-induced motor hyperactivity is suggested.     

Changes of aldolase A and B messenger RNA levels in rat liver during azo-dye-induced hepatocarcinogenesis

The expression of aldolase A and B mRNAs during azo-dye-induced carcinogenesis in rat liver was examined. After feeding the dye for 18 weeks, the level of aldolase A mRNA increased to about 11 times that in a normal liver, with the concomitant decrease of aldolase B mRNA level to about 25% of that in a normal liver. These changes did not occur progressively during the carcinogenesis, but occurred as an additional phase after 4 week-feeding of the azo-dye. At this stage, the levels of aldolase A and B mRNAs were about 7 times and 45% of that in a normal liver, respectively. This biphasic pattern in the aldolase isozyme expression in the azo-dye-fed rat liver is discussed together with the kinetic data of the enzyme activity.     

Multiple catalytic properties of the purified and reconstituted cytochrome P-450 (P-450sccII) system of pig testis microsomes

The catalytic properties of the testis microsomal P-450, termed P-450sccII, have been studied in a refined assay system which consists of P-450sccII (13 nmol of P-450 heme/mg of protein) and its reductase has been purified extensively from pig testis. The results indicated that P-450sccII was highly active in catalyzing hydroxylation of 11 beta-hydroxyprogesterone at the 17 alpha-position to give 21-deoxycortisol and cleavage of 17 alpha-hydroxyprogesterone at the 17-20 bond to give androstenedione with turnover numbers of 25 and 30 mol/min X mol of P-450, respectively. In contrast, many physiologically important corticosteroids we tested were found to be poor substrates for both the hydroxylase and lyase reactions. The possible reason for the importance of these substrate specificity of P-450sccII in production of both corticosteroids and androgens in the endocrine tissues is discussed. P-450sccII also catalyzed conversion of testosterone to androstenedione, but 18O experiments failed to show incorporation of atmospheric oxygen into the androstenedione formed. However, this does not preclude the possibility that the P-450-bound intermediate gem-diol stereoselectively dehydrates to give the nonlabeled ketosteroid. In addition to these steroid-oxidizing activities, P-450sccII revealed considerable specificities toward various xenobiotics, suggesting that P-450sccII and liver microsomal P-450 are basically similar as regards enzymatic functions and activities.     

Neurotensin stimulates pancreatic exocrine secretion in rats

Neurotensin (NT) stimulates pancreatic exocrine secretion in dogs and humans. The purpose of this study was to examine the effect of exogenous neurotensin on pancreatic exocrine secretion in rats. Five Sprague-Dawley male rats were prepared with pancreatic, gastric and duodenal fistulas. Bile was shunted into the duodenum in order to collect pure pancreatic juice. 24 h later, neurotensin (0.05, 0.1, 0.2, 0.3, 1.0 nmol/kg) was infused intravenously in a random fashion. Pancreatic juice was collected every 10 min, and the volume was recorded and protein and bicarbonate were measured. Neurotensin stimulated, in a dose-related manner, the pancreatic secretion of water, protein and bicarbonate. Neurotensin may be involved in the physiologic control of pancreatic secretion in rats.     

Nuclear activity from F9 embryonal carcinoma cells binding specifically to the enhancers of wild-type polyoma virus and PyEC mutant DNAs.

Although wild-type polyoma virus does not productively infect murine embryonal carcinoma (EC) cells, a number of mutants (PyEC mutants) that do infect undifferentiated EC cells have been isolated. All PyEC mutants have DNA sequence alterations within the enhancer region of the viral genome. This report describes an activity present in nuclear extracts of F9 EC cells which, by "footprint" analyses, binds specifically to a small region of about 20 base pairs (nucleotides 5180-5200) within the subregion of the polyoma enhancer designated as the B or beta element. While no difference in binding of factor was detected between wild-type polyoma enhancer and the enhancers of the PyEC mutants, PyF111 and PyF441, which had been selected for productive infection of F9 cells, definite differences between wild-type and mutants were observed in the digestion patterns of their naked DNAs with either DNAase I or exonuclease III. This difference was restricted to the region around the point mutation (nucleotide 5258) common to these mutant DNAs.     

Conversion of 4-aminobutyraldehyde to γ-aminobutyric acid in striatum treated with semicarbazide and kainic acid

4-Aminobutyraldehyde (ABAL) has been shown to cross the blood-brain barrier and to be converted rapidly to -aminobutyric acid (GABA) in various regions of the brain. In this paper, the formation of GABA from ABAL was studied with striatum that had suffered a lesion to GABA synthesis via glutamic acid decarboxylase (GAD). The GABA formation from ABAL was invariably observed in striatum in which GAD was severely inhibited by semicarbazide or kainic acid. Thus, this is another pathway for GABA formation.     

Cycling of soil carbon in a Japanese red pine forest II. Changes occurring in the first year after a clear-felling

Cycling of soil carbon in the first year after a clear-felling was compared with that before the felling in a Japanese red pine forest in Hiroshima Prefecture, west Japan. The daily mean temperature at the soil surface in summer was increased after the felling in comparison to that before felling, and the water content of both the A₀ layer and the surface mineral soil was decreased due to the loss of the forest canopy. The rate of weight loss of the A₀ layer was reduced after felling. However, accumulation of the A₀ layer rapidly decreased because of the lack of litter supply to the forest floor. Low soil respiration after felling was mainly caused by the cessation of root respiration. Analysis of annual soil carbon cycling was then conducted using a compartment model. The relative decomposition rate of the A₀ layer decreased whereas that of humus and dead roots in mineral soil increased to some extent after felling. The accumulation of carbon in mineral soil, however, increased slightly due to the supply of humus from roots killed by the felling.     

Structure and affinities of the petrified plants from the cretaceous of Northern Japan and Saghalien III petrified plants from the upper cretaceous of Saghalien

Five species including two new species,Araucarioxylon kiiense Ogura,Taxodioxylon albertense (Penhal.) Shimakura,Cupressinoxylon cryptomerioides Stopes,Xenoxylon watarianum sp. nov. andCedroxylon shimakurae sp. nov., were described from the Upper Cretaceous (Late Turonian-Santonian) of southern Saghalien. Consecutive number from the previous paper (Nishida and Nishida, 1985). Contributions from the Laboratory of Phylogenetic Botany, Chiba University No. 100. Supported by a Grant-in-Aid for Scientific Research from the Ministry of Education, Science and Culture No. 59540441.