Detection and Typing of Human Rotavirus in Reference to Repeated Acute Gastroenteritis in Infants

Stool specimens from infants who visited a clinic because of acute gastroenteritis were tested for the presence of human rotavirus. Among the samples obtained were specimens taken from seven patients who had visited the clinic at two different times. In six of these seven children, human rotavirus (HRV) was detected in only one of the specimens taken (i.e. during only one of the two visits). One patient was shown to have excreted HRV twice; in both cases the HRV was serotyped to be type 1. The present results indicate that the symptomatic reinfection of HRV was not a widely occurring phenomenon in the group of infants tested.     

The effect of growth form on the evaporation in some subalpine mosse

In order to evaluate the importance of growth of mosses in controlling evaporative water loss, the evaporation rates of some subalpine moss species of various growth forms were compared with each other. The growth forms of the xerophytic species examined were large cushion and compact mat, while those of the mesophytic species in the coniferous forest floor were smooth mat, weft and tall turf. The evaporation rate per moss dry weight (Ew) was much smaller in the xerophytic species than in the mesophytic species. However, the evaporation rate per basal area of moss colony (Ea) was not necessarily smaller in the xerophytic species. The relation between Ea and dry weight per basal area of the colony (Wa) had a close correlation with the growth form. It was concluded that the difference in the evaporation rate per weight between the exerophytic species and the mesophytic species was largely due to the difference in Wa, and that the growth forms of the xerophytic species were suitable for increasing Wa without increasing surface roughness.     

Possible Involvement of Abscisic Acid in Increases in Activities of Two Vacuolar H+-Pumps in Barley Roots under Aluminum Stress

Levels of abscisic acid (ABA) in barley roots increased upontreatment with AlCl₃. Treatment with AlCl₃ or ABA increasedboth ATP-dependent and PP_i-dependent H⁺-pumping activities intonoplast-enriched membrane vesicles. Increase in the H⁺-pumpingactivities caused by aluminum stress could result from increasedlevels of ABA. ¹Present address: Department of Botany, Faculty of Science,Hirosaki University, Hirosaki, Aomori, 036 Japan     

Field measurements of nitrogen-fixing activity of intact saplings ofAlnus maximowiczii in the subalpine zone of Mt Fuji

Nitrogen-fixing (acetylene-reducing) activity of intact saplings ofAlnus maximowiczii was measured under natural conditions in the subalpine zone of Mt Fuji. The nitrogen-fixing activity was detected from the middle of June when expansion of leaves had just begun to the end of October when the shedding of leaves was almost completed. Diurnal changes in the activity were almost parallel with those of ground temperature. The measured nitrogen-fixing activity was related to ground temperature and total leaf area. Using this relation, annual nitrogen fixation was estimated from the data of ground temperature and leaf area measured in the field. The amount of annual nitrogen fixation was almost the same as that of nitrogen used for annual growth. It was concluded that nitrogen fixation by nodules made a considerable contribution to the nitrogen economy in the saplings ofA. maximowiczii.     

Involvement of Cell Wall-Bound Diferulic Acid in Light-Induced Decrease in Growth Rate and Cell Wall Extensibility of Oryza Coleoptiles

Irradiation of white fluorescent light (5 W m^–2) inhibitedthe growth of Oryza coleoptiles. Light irradiation increasedstress-relaxation parameters of coleoptile cell walls, minimumstressrelaxationtime and relaxation rate, and decreased cellwall extensibility (strain/load). Under light conditions, thecontents of ferulic and diferulic acids ester-linked to thehemicellulosic arabinose residue in cell walls increased andcorrelated with the modification of the cell wall mechanicalproperties. These results suggest that light irradiation enhancesthe formation of diferulic acid bridges in hemicelluloses, makingcell walls mechanically rigid and thus inhibits cell elongationin rice coleoptiles. Also, irrespective of coleoptile age orthe presence of light, the ratio of diferulic acid to ferulicacid was almost constant, suggesting that the rate limitingstep in the formation of diferulic acid bridges in Oryza cellwalls is in the step of feruloylation. (Received September 24, 1991; Accepted December 3, 1991)     

Predation impact of Leptodora kindtii on population dynamics and morphology of Bosmina fatalis and B. longirostris in mesocosms

1. We assessed the impact of predation by the invertebrate predator Leptodora kindtii on Bosmina longirostris and B. fatalis, which show seasonal and reciprocal succession patterns in Lake Suwa, in a mesocosm experiment using 20‐L tanks with or without the predator under different food conditions. We also analysed morphological responses of the two Bosmina species to the predator in the tanks. 2. Bosmina fatalis dominated B. longirostris regardless of predator presence under high food density. However, the presence of Leptodora induced the dominance of B. fatalis more rapidly than its absence. On the contrary, no dominance of B. fatalis was observed in tanks with low food density, irrespective of the presence of the predator. Only B. fatalis showed morphological changes in response to the presence of Leptodora. 3. Mucrone length and antennule shape (angle between body and antennule and angle between antennules) showed marked responses at both high and low food densities, but antennule length responded only at high food density. Mucrone length seems to be a more effective defence against Leptodora. 4. The results suggest that B. fatalis is a superior competitor against B. longirostris and is more resistant to Leptodora predation, especially in good food conditions. The repeatedly observed seasonal succession of the two Bosmina species in the eutrophic Lake Suwa – the replacement of B. longirostris by B. fatalis following the occurrence of abundant Leptodora– seems to be caused by the selective predation of Leptodora on B. longirostris as well as the competitive ability of B. fatalis.     

Gravity resistance, another graviresponse in plants--function of anti-gravitational polysaccharides]

The involvement of anti-gravitational polysaccharides in gravity resistance, one of two major gravity responses in plants, was discussed. In dicotyledons, xyloglucans are the only cell wall polysaccharides, whose level, molecular size, and metabolic turnover were modified under both hypergravity and microgravity conditions, suggesting that xyloglucans act as anti-gravitational polysaccharides. In monocotyledonous Poaceae, (1-->3),(1-->4)-beta glucans, instead of xyloglucans, were shown to play a role as anti-gravitational polysaccharides. These polysaccharides are also involved in plant responses to other environmental factors, such as light and temperature, and to some phytohormones, such as auxin and ethylene. Thus, the type of anti-gravitational polysaccharides is different between dicotyledons and Poaceae, but such polysaccharides are universally involved in plant responses to environmental and hormonal signals. In gravity resistance, the gravity signal may be received by the plasma membrane mechanoreceptors, transformed and transduced within each cell, and then may modify the processes of synthesis and secretion of the anti-gravitational polysaccharides and the cell wall enzymes responsible for their degradation, as well as the apoplastic pH, leading to the cell wall reinforcement. A series of events inducing gravity resistance are quite independent of those leading to gravitropism.     

Concanavalin A Inhibits Auxin-Induced Elongation and Breakdown of (1 -> 3), (1 -> 4)-{beta}-D-Glucans in Segments of Rice Coleoptiles

Concanavalin A (Con A) suppresses auxin-induced elongation ofsurface-abraded segments from both dicotyledonous and poaceousplants. In coleoptile segments of rice (Oryza sativa L.), theauxin-induced decrease in the minimum stress-relaxation timeand increase in the mechanical extensibility of the cell wallswere also inhibited by Con A, indicating that the lectin suppresseselongation by inhibiting the cell wall loosening. Auxin causeda decrease in the level of (1 3), (1 4)-ß-D-glucansin the cell walls of rice coleoptile segments, and this decreasewas also inhibited by the lectin. Con A suppressed the autolytichydrolysis of the glucans, as well as their breakdown in vitroby a protein fraction that had been extracted from the cellwalls of rice coleoptiles with 1 M NaCl. Furthermore, most ofthe glucan-hydrolyzing activity of the wall proteins bound toa Con A-Sepharose column, suggesting that glycoprotein enzymesare involved in the hydrolysis. Although Con A also affectedthe hydrolysis of other wall polysaccharides, the present data,when considered in combination with the inhibitory effects ofglucan-specific or glucanasespecific antibodies, support theview that the breakdown of (1 3),(1 4)-ß-D-glucansis associated with the cell wall loosening that is responsiblefor auxin-induced elongation in Poaceae. (Received August 17, 1994; Accepted February 15, 1995)     

Involvement of plasma membrane potential in the tolerance mechanism of plant roots to aluminium toxicity

H⁺-ATPase activity of a plasma membrane-enriched fraction decreased after the treatment of barley (Hordeum vulgare) seedlings with Al for 5 days. A remarkably high level of Al was found in the membrane fraction of Al-treated roots. A long-term effect of Al was identified as the repression of the H⁺-ATPase of plasma membranes isolated from the roots of barley and wheat (Triticum aestivum) cultivars, Atlas 66 (Al-tolerant) and Scout 66 (Al-sensitive). To monitor short-term effects of Al, the electrical membrane potentials across plasma membranes of both wheat cultivars were compared indirectly by measuring the efflux of K⁺ for 40 min under various conditions. The rate of efflux of K⁺ in Scout was twice that in Atlas at low pH values such as 4.2. Vanadate, an inhibitor of the H⁺-ATPase of the plasma membrane, increased the efflux of K⁺. Al repressed this efflux at low pH, probably through an effect on K⁺ channels, and repression was more pronounced in Scout. Al strongly repressed the efflux of K⁺ irrespective of the presence of vanadate. Ca²⁺ also had a repressive effect on the efflux of K⁺ at low pH. The effect of Ca²⁺, greater in Scout, might be related to the regulation of the net influx of H⁺, since the effect was negated by vanadate. The results suggest that extracellular low pH may cause an increase in the influx of H⁺, which in turn is counteracted by the efflux of K⁺ and H⁺. These results suggest that the ability to maintain the integrity of the plasma membrane and the ability to recover the electrical balance at the plasma membrane through a net influx of H⁺ and the efflux of K⁺ seem to participate in the mechanism of tolerance to Al stress under acidic conditions.