The gene for tRNA(Lys) is encoded in the rapeseed (Brassica napus L.) mitochondrial DNA.

The nucleotide sequence of the gene coding for tRNA(Lys) and its flanking regions from the rapeseed mitochondrial genome are presented and compared with other known tRNA(Lys) genes from plant mitochondria. This tRNA sequence can be folded into the standard cloverleaf structure model. Also, this tRNA sequence shows less similarity with its chloroplast counterparts and therefore appears to be 'native' mitochondrial tRNA.     

Elongation and shortening of time required for entry into S phase after release from G 1 and G 0 arrests in temperature-sensitive mutants of rat 3Y1 Cells

Temperature-sensitive (ts) mutants of rat 3Y1 fibroblasts representing four separate complementation groups (3Y1tsD123, 3Y1tsF121, 3Y1tsG125, and 3Y1tsH203) are arrested mainly in the G1 phase when cells of randomly proliferating population at 33.8 degrees C are shifted to 39.8 degrees C (temperature arrest). We examined the time lag of the cellular entry into the S phase after release at 33.8 degrees C, both from the temperature arrest and from the arrest at 33.8 degrees C at a confluent cell density (density arrest). In the temperature-arrested cells, as the duration of temperature arrest increased, the time lag of entry into S phase after shift down to 33.8 degrees C was prolonged, in all four mutants. These observations suggest that the four different functional lesions, each causing arrest in the G1 phase, are also responsible for prolongation of the time lag of entry into the S phase in cells arrested in the G1 phase. The prolongation of the time lag in the temperature-arrested cultures was accelerated at a higher cell density, in medium supplemented with a lower concentration of serum, and at a higher restrictive temperature. In the density-arrested cells, as the duration of pre-exposure to 39.8 degrees C was increased, the time lag of entry into S phase at 33.8 degrees C after release from the arrest was drastically prolonged, in all four mutants. In 3Y1tsF121, 3Y1tsG125, and 3Y1tsH203, when the density-arrested cells were prestimulated by serum at 39.8 degrees C for various periods of time, the time lag of entry into S phase after release from the density arrest at 33.8 degrees C was initially shortened, and then, prolonged progressively as the period of prestimulation increased. These findings, taken together with other data, show that all four ts defects affect cells in states ranging from the deeper resting to mid- or late-G1 phase. It is suggested that events represented by these four mutants are required for entry into the S phase and normally operate in parallel but not in sequence in cells in states ranging from the deeper resting to the mid- or late-G1 phases, though they may affect each other.     

Effect of Ethylene Action Inhibitors upon Wound-Induced Gene Expression in Tomato Pericarp

The contribution of wound-ethylene to wound-induced gene expression was investigated in unripe tomato pericarp using inhibitors of ethylene action. Wounded unripe tomato pericarp was treated with 2,5-norbornadiene or silver thiosulfate to inhibit specifically the induction of ethylene-dependent mRNA species. Poly(A)⁺ RNAs isolated from these tissues after 12 hours of wounding were translated in vitro in a rabbit reticulocyte lysate system and [³⁵S]methionine-labeled polypeptides were compared to unwounded controls after separation by one and two-dimensional polyacrylamide gel electrophoresis. Results show that mechanical wounding induces a dramatic shift in gene expression (over 50 mRNA species) but expression of less than 15% of these genes is affected by the treatment with ethylene action inhibitors. A selective decrease in mRNAs coding for a 37 kilodalton doublet and 75 kilodalton polypeptides is observed in 2,5-norbornadiene and silver thiosulfate treated wounded pericarp. Levels of hydroxyproline-rich glycoprotein mRNAs induced in wounded tissue were not influenced by inhibitors of ethylene action.     

Appearance of retrogradely labeled neurons in the rat superior cervical ganglion after injection of wheat-germ agglutinin-horseradish peroxidase conjugate into the contralateral ganglion

Summary Injection of wheat-germ agglutinin-horseradish peroxidase conjugate (WGA-HRP) into the superior cervical ganglion (SCG) of the rat results in accumulation of WGA-HRP in sympathetic postganglionic neurons in the contralateral SCG. The sympathetic pathways involved and the mechanism underlying the labeling were investigated. The labeling in neurons in the contralateral SCG was apparent 6 h after injection and increased in intensity with longer survival times. The number of labeled neurons reached 1300 at 72 h after the injection. Transection of the external (ECN) or internal carotid nerves (ICN) resulted in considerable reduction in the number of labeled neurons. Combined transection of both ECN and ICN virtually eliminated labeling in the contralateral SCG. This provides strong evidence that these two nerves are the major pathways for WGA-HRP transport out of the SCG. No labeling was observed in the contralateral SCG following injection of horseradish peroxidase (HRP). Therefore, it seems unlikely that a direct nerve connection exists between the bilateral ganglia. Instead, the labeling of contralateral SCG neurons appears to depend on the transneuronal transport capacity of WGA-HRP, which conveys the marker in an anterograde direction along the postganglionic fibers to terminals in sympathetic target organs, and then delivers it transneuronally to contralateral SCG neurons. We suggest that the sympathetic nerve fibers originating in the bilateral SCGs run intermingled and are in close contact in their peripheral target organs.     

Efficient integrative transformation of the phytopathogenic fungus Alternaria alternata mediated by the repetitive rDNA sequences

An attempt was made to transform Alternaria alternata protoplasts using a plasmid vector, pDH25, bearing the Escherichia coli hygromycin B (Hy) phosphotransferase gene (hph) under the control of the Aspergillus nidulans trpC promoter. Transformants arose on a selective medium containing 100 μg Hy/ml. There were two types of transformants, forming large and small colonies on the selective medium. Transformation with one μg of the vector produced an average of 4.5 large colonies and 600 small ones. In large-colony transformants, the vector often integrated into the recipient chromosome in the form of highly rearranged tandem arrays. To increase transformation efficiency, fragments of the highly repetitive ribosomal RNA gene cluster (rDNA) of A. alternata were used to construct four new vectors for homologous recombination system. Use of these vectors gave higher transformation efficiency than the original plasmid. The best vector, pDH25r1a, gave rise to large-colony transformants at a frequency 20 times higher than pDH25. Transformation events in A. alternata with pDH25r1a occured by homologous recombination as a single crossover between the plasmid-borne rDNA segment and its homologue in the chromosome, often giving rise to tandemly repeated vector DNA.     

Day-night changes in production of carbohydrate and protein by natural phytoplankton population from Lake Biwa, Japan

The ¹³C and gas chromatography-mass spectrometry (¹³C-GC-MS)method was applied to determine the day-night changes in thecomposition of photosynthetic products of the natural phytoplanktonpopulation from Lake Biwa, Japan. Glucose is the most abundantmonosaccharide in acid-hydrolyzable carbohydrate. The contributionof glucose was high in incubatesd samples in daytime and decreasedduring the night. Other monosaccharides (rhamnose, fucose, ribose,arabinose, xylose, mannose and galactose) and amino acids tendedto be produced throughout both day- and night-time. These resultssuggested that the carbon flows from glucose, which might constitutereserve glucan, to other monosaccharides and amino acids duringnight-time. The disproportionate production of glucose (reservedglucan) during daytime was thus partly cancelled out at night.     

Blood pressure profile in two adult male populations.

Causal blood pressure measurements were recorded in two groups of men aged 40 to 64 years; of the 7024 men in metropolitan Saint John, NB, and the 4044 men in seven suburbs of Quebec who were asked, 5840 (83.1%) and 3097 (76.6%) respectively agreed to participate. Of the Saint John group 9.0% were taking antihypertensive drugs, as compared with only 3.3% of the Quebec group (p less than 0.0001). Among the treated subjects 33% in Saint John and 53% in Quebec still had a diastolic pressure greater than 95 mm Hg (p less than 0.01). Among the participants not taking antihypertensive drugs the systolic blood pressure increased with age, but the diastolic blood pressure increased only slightly up to 55 years of age and then decreased. On average the subjects in Saint John who were not being treated had a systolic pressure 6.2 mm Hg lower and a diastolic blood pressure 3.6 mm Hg lower than their Quebec counterparts (p less than 0.0001). This difference was observed in all the age groups and was not the result of the treatment of a greater proportion of the Saint John cohort. Despite the higher blood pressures and the smaller number receiving adequate treatment in the Quebec group, the rate of death due to coronary artery disease was 10% lower than that in the Saint John group. A bias in the data from Quebec may have influenced the magnitude of the differences between the two samples, but if present it should have underestimated the blood pressures in the Quebec group and therefore not have changed the outcome.     

Vasorelaxant effect of C16-PAF and C18-PAF on renal blood flow and systemic blood pressure in the anesthetized rat

The renal vasoactive and systemic hypotensive effects of platelet activating factor (C16:0-PAF and C18:1-PAF) were examined in anesthetized male Wistar rats. Bolus injections of C16-PAF (0.5-25 ng/kg) and C18-PAF (2.5-200 ng/kg) into the arterial circulation of the kidney produced increases in renal blood flow (6-15%) before causing dose-dependent systemic hypotension (2-64 mmHg). The dose-response curves for renal blood flow and systemic blood pressure generated by intrarenal C18-PAF administration were approximately 7 fold to the right of the dose-response curves generated by C16-DPAF. Intrarenal injections of vehicle or the biologically inactive enantiomer C16-DPAF (25-200 ng/kg) did not affect renal blood flow or systemic blood pressure. These results suggest that C16:0-PAF is a more potent renal vasodilator and hypotensive lipid than C18:1-PAF.