Infection Behavior of Venturia nashicola, the Cause of Scab on Asian Pears

ABSTRACT The infection of Japanese pear by Venturia nashicola, the cause of scab on Asian pears (Japanese pear, Pyrus pylifolia var. culta; Chinese pear, P. ussuriensis), was examined using light and electron microscopy to determine the mechanism of resistance in pears. Early stages of infection were similar on the susceptible cv. Kosui, the resistant cv. Kinchaku, and the nonhost European pear (P. communis) cv. Flemish Beauty. V. nashicola penetrated only the cuticle layer on pear leaves and formed subcuticular hyphae on all three cultivars. Hyphae were localized in the pectin layer of pear leaves and never penetrated into the cytoplasm of epidermal cells. This restriction of fungal growth suggested that pectinases released by infection hyphae or subcuticular hyphae may be important in infection. Subcuticular hyphae were modified ultrastructurally in the pectin layer of resistant pear cultivars accompanied by fungal cell death. In contrast, fungal cells appeared intact in susceptible pear cultivars, suggesting the existence of resistance mechanisms.     

Multiple high-throughput analyses monitor the response of E. coli to perturbations

Analysis of cellular components at multiple levels of biological information can provide valuable functional insights. We performed multiple high-throughput measurements to study the response of Escherichia coli cells to genetic and environmental perturbations. Analysis of metabolic enzyme gene disruptants revealed unexpectedly small changes in messenger RNA and proteins for most disruptants. Overall, metabolite levels were also stable, reflecting the rerouting of fluxes in the metabolic network. In contrast, E. coli actively regulated enzyme levels to maintain a stable metabolic state in response to changes in growth rate. E. coli thus seems to use complementary strategies that result in a metabolic network robust against perturbations.     

Molecular ordering of organic molten salts triggered by single-walled carbon nanotubes

When mixed with imidazolium ion-based room-temperature ionic liquid, pristine single-walled carbon nanotubes formed gels after being ground. The heavily entangled nanotube bundles were found to untangle within the gel to form much finer bundles. Phase transition and rheological properties suggest that the gels are formed by physical cross-linking of the nanotube bundles, mediated by local molecular ordering of the ionic liquids rather than by entanglement of the nanotubes. The gels were thermally stable and did not shrivel, even under reduced pressure resulting from the nonvolatility of the ionic liquids, but they would readily undergo a gel-to-solid transition on absorbent materials. The use of a polymerizable ionic liquid as the gelling medium allows for the fabrication of a highly electroconductive polymer/nanotube composite material, which showed a substantial enhancement in dynamic hardness.     

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.     

Can Shifting Cultivation on Acid Soils in the Southeast Asia Be Sustainable in the Future? A Case Study in Northern Laos

Sustainability of the local shifting cultivation practice in the mountainous region of Northern Laos was investigated. Due to low fertility of the soils derived from shale and its strongly weathered and acidic nature in the eastern side of the Nam Khan River watershed, shortening of the fallow period to produce enough amount of upland rice for the local population would not be sustainable any more. On the other hand, the eroded materials from limestone range were added to the soils in the western side of watershed which made the soil more fertile. Based on the calculated population capacity by Carneiro's equation, a system with 2- or 3-year fallow for 1-year cultivation can be the maximum to afford the current population. To make the shifting cultivation system more sustainable, introduction of fallow system with a tree species, paper mulberry ( Broussonetia papyrifera ) could be a good option to be proposed.