Tree species composition and similarity in semideciduous forest fragments of southeastern Brazil

This study investigates the influence of fragment size on tree species composition, species richness and on individual groups of species within 11 semideciduous forest fragments in southeastern Brazil. We compared same-sized samples of 500 trees from 10 fragments <100 ha, allocated to three size categories, with three 500-tree samples collected in different areas within a large forest, used as a reference forest. The variation in species richness, in the proportion of species/individuals in dispersal modes, and in the proportion of rare species was not related to fragment size. Nonetheless, comparisons between the mean values of these variables of each fragment size categories, using 95% confidence intervals, showed a wider range of variation within the category of small-sized fragments than in the other size categories. NMS ordination plot also suggested the absence of a relationship between fragment area and tree species composition. However, multiple regressions using the scores from the NMS ordination as response variables, and area and disturbance intensities as predictor variables, suggested that the interaction of area and disturbance might be a good predictor of species composition. Pre-existing environmental heterogeneity and geographical proximity also appeared to play a role in the variations of forest composition among the fragments studied. Our results demonstrated the high conservation value of small forest fragments.     

Spontaneous granulocytic leukemia in a NOD/Shi-scid IL-2Rγnull mouse

Here, we report a case of spontaneous granulocytic leukemia in a 51-week-old male NOD/Shi-scid IL-2Rγ^null (NOG) mouse. The mouse showed progressive anemia and rough respiratory movement. Macroscopically, the spleen was discolored and enlarged. Histologically, the bone marrow of the sternum and femur was highly cellular and almost exclusively filled with neoplastic cells. The nuclei of neoplastic cells were large, oval to slightly irregular in shape, and a small number of cells had kidney- or ring-shaped nuclei. Neoplastic cells extensively infiltrated the organs, and the spleen and liver were prominently involved. Immunohistochemically, a large population of neoplastic cells in the red pulp of the spleen and sinusoid of the liver was positive for myeloperoxidase. Based on the histological features, this case was diagnosed with granulocytic leukemia. This novel information on spontaneous tumors may be helpful for the appropriate use of this mouse strain in further research.     

Immunohistochemical and histoplanimetrical study on the spatial relationship between the settlement of indigenous bacteria and the secretion of bactericidal peptides in rat alimentary tract

To clarify the regulatory mechanism by bactericidal peptides secretion, the secretion of bactericidal peptides was immunohistochemically and histoplanimetrically compared with the degree of Gram-positive/negative bacterial colonization throughout the rat alimentary tract. In the associated exocrine glands from the oral cavity to the stomach, no comparable differences were observed under the changes of development of indigenous bacterial colonies. In the small intestine, immunopositive granules for lysozyme and secretory phospholipase A2 (sPLA2) were markedly decreased, whereas immunopositive vacuoles in the Paneth cells were more increased at sites with hyper-development of indigenous bacterial colonies in the intervillous spaces than at sites with no or less development. No changes in exocrine glands were observed in the large intestine because of the constant existence of large quantities of bacteria. Gram-positive bacterial colonies on the mucosal surfaces were dominant from the oral cavity to the stomach. Gram-negative bacteria were dominant in the large intestine, and the distributions of both Gram-positive and negative bacteria were intermediate in the small intestine. These findings suggest that lysozyme and sPLA2 secreted from the Paneth cells contribute to the regulation of the proliferation of indigenous bacteria in the intervillous spaces of the small intestine, and that the inversion of distributions of Gram-positive and -negative bacteria in the alimentary tract might be caused by the secretion of lysozyme and sPLA2 in the small intestine.     

Epidemiological survey of Theileria parasite infection of cattle in Northeast China by allele-specific PCR

An epidemiological survey on a Theileria parasite infection of cattle in Northeast China was carried out using allele-specific PCR and DNA sequence analysis of the major piroplasm surface protein (MPSP) gene. The results showed that 14 of 104 blood samples were positive for Theileria by PCR. Among the positive cases, co-infection with various combinations of C- and I-type parasites was detected in 12 samples; no B- and Thai-type parasites were detected by allele-specific PCR. Phylogenetic analysis based on the MPSP gene sequences revealed that Theileria parasites with the MPSP types 1, 2, and 4 were distributed in Northeast China.     

Snapshot of activated G proteins at the membrane: the Galphaq-GRK2-Gbetagamma complex

G protein-coupled receptor kinase 2 (GRK2) plays a key role in the desensitization of G protein-coupled receptor signaling by phosphorylating activated heptahelical receptors and by sequestering heterotrimeric G proteins. We report the atomic structure of GRK2 in complex with Galphaq and Gbetagamma, in which the activated Galpha subunit of Gq is fully dissociated from Gbetagamma and dramatically reoriented from its position in the inactive Galphabetagamma heterotrimer. Galphaq forms an effector-like interaction with the GRK2 regulator of G protein signaling (RGS) homology domain that is distinct from and does not overlap with that used to bind RGS proteins such as RGS4.     

Leaf characters relating to nitrogen response in the rice plant

In a previous paper (1) it was pointed out that in rice heavy mutual shading produced by a large leaf area at high nitrogen levels results in an inefficient utilization of light for dry matter production. Because of mutual shading, tall, leafy varieties do not show yeild responses to nitrogen, especially under the limited sunshine conditions which prevail during the rainy season in the tropics.     

Some regulative properties of glutamine synthetase in cucumber leaves

Glutamine synthetase (L-glutamate: ammonia ligase (ADP) EC 6. 3. t 2) was prepared from cucumber leaves grown on ammonium medium and some regulative properties were investigated. The apparent Michaelis constant (Km) values of the various substrates and cofactors were determined. Lineweaver-Burk plots gave a Km of 4.5mM with L-glutamate, 0.74mM with ATP and 3.1 mM with NH₂OH. Metals, including Cu²⁺, Hg²⁺, Zn²⁺, Ni²⁺, Fe²⁺, and Fe³⁺, strongly inhibited the enzyme activity, Cd²⁺ did not inhibit the enzyme activity markedly, in contrast with its effect on the rice enzyme. Ca²⁺ was quite inhibitive to enzyme reaction and more than 50% of the activity was lost at 3 mM. The amino acids tested generally had no effect on the enzyme activity except alanine, which showed little but clear inhibition. Isocitrate and α-ketoglutarate were slightly promotive to enzyme activity while pyruvate and glyoxylate (24 mM) significantly inhibited the enzyme activity. Glucose-l- or -6-phosphate and fructose-6-phosphate were inhibitive to similar degrees, about 20% at 22.5 mM, and 3-phosphoglycerate (22.5 mM) markedly inhibited the enzyme activity up to 56%. Among the nucleotides tested, UTP, CTP, and GTP inhibited slightly, and marked inhibitions of H and 78% were observed after the addition of AMP (5 mM) and ADP (5 mM) respectively. Pyridoxal-5′-phosphate, which is a characteristic incompetitive inhibitor of L-glutamate and NH₂-OH, here inhibited enzyme activity significantly. On the other hand, pyridoxamine-5′-phosphate had almost no effect. The inhibition caused by the former was not recovered by the latter. This response of glutamine synthetase to both compounds was in agreement with the idea that the nitrogen status of the plant could be reflected by the ratio pyridoxamine phosphate/pyridoxal phosphate. Also this suggested that the regulative properties of glutamine synthetase with respect to pyridoxal or pyridoxamine phosphate could be understood from the point of view of the economical use of nitrogen.     

Comparison of adaptability to flash flood between rice cultivars differing in flash flood tolerance

The mechanism of flash flood tolerance was investigated by using a flash flood-intolerant rice cultivar (Oryza sativa), IR42 and a tolerant one, FR13A. The photosynthetic rate of the rice seedlings from both types of cultivars decreased during submergence, whereas the photosynthetic rate of FR13A remained higher than that of IR42. The decrease in photosynthesis in IR42 was partially due to a higher inhibition of the activities of ribulose-1,5-bisphosphate carboxylase, fructose-1,6-bisphosphatase, and glyceraldehyde-3-phosphate dehydrogenase, than in FR13A. After submergence receded (hereafter referred as “desubmergence”), both types of submerged rice cultivars experienced oxidative damage. However the oxidation of the lipids and proteins in FR13A was maintained at a lower level than that in IR42 after desubmergence. On the other hand, the superoxide dismutase activity in FR13A increased more than that in IR42 after desubmergence. Moreover, the content of total ascorbate (reduced and oxidized ascorbates), a main antioxidant increased in FR13A, while in IR42 the content remained low after desubmergence. It is assumed that the photosynthetic activity during submergence may be related to flash flood tolerance. Moreover, flash flood tolerance requires a rapid stimulation of antioxidant systems after desubmergence.     

<Emphasis Type="Italic">Ageratum</Emphasis><Emphasis Type="Italic">yellow vein virus</Emphasis> isolated from tomato plants with leaf curl on Ishigaki Island,Okinawa, Japan

In 2005, severe leaf curling and yellowing were observed on tomato plants on Ishigaki Island. Because the symptoms were consistent with infection by a begomovirus, we used a polymerase chain reaction (PCR) with specific primers for begomovirus DNA-A and DNA satellite component (DNA-β) and detected products of the expected sizes from symptomatic tomato plant samples. DNA sequence analyses of the PCR products revealed that the symptomatic tomato plants were associated with Ageratum yellow vein virus (AYVV) infection. We confirmed AYVV transmission from the naturally infected weed host, Ageratum conyzoides, to healthy tomato plants by the insect vector Bemisia tabaci B biotype. This report is the first of AYVV occurrence in Japan.