Heterochromatin integrity affects chromosome reorganization after centromere dysfunction

The centromere is essential for the inheritance of genetic information on eukaryotic chromosomes. Epigenetic regulation of centromere identity has been implicated in genome stability, karyotype evolution, and speciation. However, little is known regarding the manner in which centromere dysfunction affects the chromosomal architectures. Here we show that in the fission yeast Schizosaccharomyces pombe, the conditional deletion of the centromere produces survivors that carry either a neocentromere-acquired chromosome at the subtelomeric region or an acentric chromosome rescued by intertelomere fusion with either of the remaining chromosomes. The ratio of neocentromere formation to telomere fusion is considerably decreased by the inactivation of genes involved in RNA interference-dependent heterochromatin formation. By affecting the modes of chromosomal reorganization, the genomic distribution of heterochromatin may influence the fate of karyotype evolution.     

Coronary artery spasm induced in atherosclerotic miniature swine

Angiographically demonstrable coronary artery spasm could be provoked repeatedly by giving intracoronary or intravenous injections of histamine to miniature swine with experimentally induced atherosclerotic lesions of the coronary artery. The spasm induced in this way subsided either spontaneously or after the administration of nitroglycerin and was prevented by a calcium antagonist or an agent that blocks histamine H1 receptors. This model, which suggests that atherosclerotic changes may be one of the primary factors in the occurrence of coronary artery spasm, should facilitate studies on the pathogenesis of this condition.     

Tumor promoters inhibit morphological differentiation in cultured mouse neuroblastoma cells

When added to mouse neuroblastoma cultures, the potent tumor promoter 12-O-tetradecanoyl-phorbol-13-acetate (TPA) inhibits spontaneous neurite formation as well as that induced in response to serum deprivation, prostaglandin E1, 5-bromo-2'-deoxyuridine, and papaverine. Other tumor-promoting macrocyclic plant diterpenes also inhibit neurite formation, whereas nonpromoting diterpenes do not. Inhibition by TPA was reversible and was unrelated to toxicity.     

An astronomical 2175 angstrom feature in interplanetary dust particles

The 2175 angstrom extinction feature is the strongest (visible-ultraviolet) spectral signature of dust in the interstellar medium. Forty years after its discovery, the origin of the feature and the nature of the carrier(s) remain controversial. Using a transmission electron microscope, we detected a 5.7-electron volt (2175 angstrom) feature in interstellar grains embedded within interplanetary dust particles (IDPs). The carriers are organic carbon and amorphous silicates that are abundant in IDPs and in the interstellar medium. These multiple carriers may explain the enigmatic invariant central wavelength and variable bandwidth of the astronomical 2175 angstrom feature.     

The physicochemical property of shark type I collagen gel and membrane

The physicochemical properties of shark type I collagen gel and membrane were not same as those of pig type I collagen. The denaturation temperature of shark collagen gel was about 15 degrees C lower. According to scanning electronic micrography, the diameter of shark collagen fibril was relatively thin and more homogeneous. The breaking strength of shark collagen gel was greater, and shark collagen membrane had a greater mechanical strength and a higher water vapor sorption.     

Effectiveness of some management procedures for seed regeneration of plant genetic resources accessions

Procedures for seed regeneration of plant genetic resource accessions were investigated in terms of their effect on the variance effective population size and the probability that the initial allelic diversity is maintained after 10 and 20 cycles of regeneration. Four regeneration systems were compared: a bulk system (BL) where seeds are collected and treated in bulk, a partial sampling system (PS) where seeds are collected from not all, but some plants in the population with an equal number of offspring being raised from each sampled plant, a single seed system (SS) where accessions are regenerated so that each plant leaves one progeny, and the biparental mating system (BP) of Gale & Lawrence (1984) where plants are pollinated in pairs with one offspring being raised from each of the paired plants, or two offspring from one of the paired plants. It was shown that the relative efficiency of the four systems largely depends on the rate of selfing and that differences in the effective population size of the systems increase with increasing rates of selfing. The SS system gave by far the largest effective population size in regenerating the seed of moderately or highly selfing species. Although the BP system gave the largest effective size for outcrossing species, the SS system, when combined with selfing, gave a much larger effective size. The BL and PS systems were in no case the most effective. Of these two, PS system with a sampling fraction of 50% was as effective as BL, but less effective with a sampling fraction smaller than 50%. Calculations of the maintenance of the allelic diversity, however, revealed that differences between the systems are not appreciably large unless the accessions are regenerated over 10 or more cycles with 50 or fewer plants.     

Low molecular weight compounds responsible for savory taste of Indonesian soy sauce

Indonesian soy sauce is made using only soybeans as the nitrogenous source. Moromi obtained from fermentation of yellow soybeans using Aspergillus sojae as the starter was investigated. The fraction with molecular weights of less than 500 Da obtained by stepwise ultrafiltration was then fractionated by several chromatographic procedures, including gel filtration chromatography and RP-HPLC. Several chemical analyses, CE profiles, and taste profiles were performed to obtain the most intense umami fraction. The main components eliciting or enhancing the umami taste present in the fraction were purified and identified by protein sequencing, ESI-MS, and (1)H NMR at 400 MHz. Besides free l-glutamic acid and aspartic acid, free aromatic amino acids such as l-phenylalanine and l-tyrosine may also play an important role in impressing savory or umami taste of Indonesian soy sauce at their subthreshold concentrations and in the presence of salt and free acidic amino acids. This is reported as a new phenomenon of the so-called bitter amino acids.     

Transgenic rice plants expressing human CYP1A1 remediate the triazine herbicides atrazine and simazine

The human cytochrome P450 CYP1A1 gene was introduced into rice plants (Oryza sativa cv. Nipponbare). One-month-old CYP1A1 plants grown in soil clearly showed a healthy growth and tolerance to 8.8 microM atrazine and 50 microM simazine, but nontransgenic plants were completely killed by the herbicides. Although transgenic and nontransgenic plants metabolized the two herbicides into the same sets of compounds, CYP1A1 plants metabolized atrazine and simazine more rapidly than did control plants. In small-scale experiments, residual amounts of atrazine and simazine in the culture medium of CYP1A1 plants were 43.4 and 12.3% of those in control medium; those of nontransgenic Nipponbare were 68.3 and 57.2%, respectively. When cultivated in soil with 2.95 microM atrazine and 3.15 microM simazine for 25 days, CYP1A1 plants eliminated 1.3 times more atrazine and 1.4 times more simazine from the soil than did control plants. Thus, CYP1A1 rice plants make it possible to remove atrazine and simazine more rapidly from the culture medium and soil than can nontransgenic Nipponbare.     

Phytoremediation of metolachlor by transgenic rice plants expressing human CYP2B6

We introduced the human cytochrome P450 gene CYP2B6 into rice plants (Oryza sativa L. cv. Nipponbare), and the CYP2B6-expressing rice plants became more tolerant to various herbicides than nontransgenic Nipponbare rice plants. In particular, CYP2B6 rice plants grown in soil showed tolerance to the chloroacetanilide herbicides alachlor and metolachlor. We evaluated the degradation of metolachlor by CYP2B6 rice plants to confirm the metabolic activity of the introduced CYP2B6. Although both CYP2B6 and nontransgenic Nipponbare rice plants could decrease the amount of metolachlor in plant tissue and culture medium, CYP2B6 rice plants could remove much greater amounts. In a greenhouse, the ability of CYP2B6 rice plants to remove metolachlor was confirmed in large-scale experiments, in which these plants appeared able to decrease residual quantities of metolachlor in water and soil.