Theoretical Basis of Protocols for Seed Storage III. Optimum Moisture Contents for Pea Seeds Stored at Different Temperatures

In previous work, we demonstrated that there was an optimummoisture level for seed storage at a given temperature (Vertucciand Roos, 1990), and suggested, using thermodynamic considerations,that the optimum moisture content increased as the storage temperaturedecreased (Vertucci and Roos, 1993b). In this paper, we presentdata from a two year study of aging rates in pea (Pisum sativum)seeds supporting the hypothesis that the optimum moisture contentfor storage varies with temperature. Seed viability and vigourwere monitored during storage under dark or lighted conditionsat relative humidities between 1 and 90%, and temperatures between-5 and 65°C. The optimum moisture content varied from 0·015g H₂O g^-1 d.wt at 65°C to 0·101 g H₂O g^-1 d.wt at15°C under dark conditions and from 0·057 at 35°Cto 0·092 g H₂O g^-1 d.wt at -5°C under lighted conditions.Our results suggest that optimum moisture contents cannot beconsidered independently of temperature. This conclusion hasimportant implications for 'ultra-dry' and cryopreservationtechnologies.Copyright 1994, 1999 Academic Press Seed storage, seed aging, seed longevity, water content, temperature, glass, desiccation damage, ultradry, Pisum sativum L., pea, cryopreservation     

Evidence that Prostaglandin E2 Can Block Calcium-Activated 86Rb Efflux from Rat Brain Synaptosomes via a Protein Kinase C-Dependent Mechanism

Abstract: The effects of prostaglandin E₂ (PGE₂) on ⁸⁶Rb efflux from rat brain synaptosomes were studied to explore its role in nerve ending potassium (K⁺) channel modulation. A selective dose-dependent inhibition of the calcium-activated charybdotoxin-sensitive component of efflux was found upon application of PGE₂. No significant effect was seen on basal and voltage-dependent components over the concentration range of 10–⁸ to 10–⁵M. The protein kinase C (PKC) inhibitors H-7 (10 μM) and staurosporine (100 nM), as well as prolonged preincubation (90 min) with 40-phorbol 12, 13-dibutyrate, which has been reported to down-regulate PKC, abolished the PGE₂-in- duced inhibition, whereas HA1004 (10 μM) and Rp-3′,5’cyclic phosphorothioate (100 nM), which are relatively more selective for protein kinase A than PKC, did not. 4β-Phorbol 12, 13-dibutyrate (100 nM), an activator of PKC, produced a similar inhibition of the Ca²⁺-dependent component of ⁸⁶Rb efflux but also had no effect on the basal and voltage-dependent components. These data suggest that PGE₂ can inhibit rat brain nerve ending calcium-activated ⁸⁶Rb efflux, and this inhibition may involve PKC activation.     

Gravitropically-stimulated seedlings show autotropism in weightlessness

In a spaceflight experiment, autotropism by oat ( Avena sativa L.) coleoptiles following gravitropic responses was prominent in weightlessness: counter-reactions led to the straightening of the curved coleoptiles. This was not the case during clinorotation on earth. The autotropic reactions appeared to be related to the stimulus received during the stimulus period, i.e. the greater the response the greater the autotropic counter-reaction. Previous models of the gravitropic system which predicted that coleoptiles would not straighten in weightlessness are disproved. A modification to one of the models is proposed which includes the autotropic response observed in spaceflight. The nature of the counter-reactions in the absence of gravitropic stimulation is discussed.     

Ammonium sensing in nitrogen fixing bacteria: Functions of theglnB andglnD gene products

A plentiful supply of fixed nitrogen as ammonium (or other compounds such as nitrate or amino acids) inhibits nitrogen fixation in free-living bacteria by preventing nitrogenase synthesis and/or activity. Ammonium and nitrate have variable effects on the ability ofRhizobiaceae (Rhizobium, Bradyrhizobium andAzorhizobium) species to nodulate legume hosts and on nitrogen fixation capacity in bacteroid cells contained in nodules or in plant-free bacterial cultures. In addition to effects on nitrogen fixation, excess ammonium can inhibit activity or expression of other pathways for utilization of nitrogenous compounds such as nitrate (through nitrate and nitrite reductase), or glutamine synthetase (GS) for assimilation of ammonium. This paper describes the roles of two key genesglnB andglnD, whose gene products sense levels of fixed nitrogen and initiate a cascade of reactions in response to nitrogen status. While work onEscherichia coli and other enteric bacteria provides the model system,glnB and, to a lesser extent,glnD have been studied in several nitrogen fixing bacteria. Such reports will be reviewed here. Recent results on the identity and function of theglnB andglnD gene products inAzotobacter vinelandii (a free-living soil diazotroph) and inRhizobium leguminosarum biovarviciae, hereinafter designatedR.l. viciae will be presented. New data suggests thatAzotobacter vinelandii probably contains aglnB-like gene and this organism may have twoglnD-like genes (one of which was recently identified and namednfrX). In addition, evidence for uridylylation of theglnB gene product (the PII protein) ofR. l. viciae in response to fixed nitrogen deficiency is presented. Also, aglnB mutant ofR. l. viciae has been isolated; its characteristics with respect to expression of nitrogen regulated genes is described.     

Relations between grapevine replant disease and root colonization of grapevine (Vitis sp.) by fluorescent pseudomonads and endomycorrhizal fungi

In pot experiments cuttings of grapevine rootstock cultivar 5C were grown on a soil from a grapevine nursery affected with replant disease (replant soil) and on a similar soil that had not been planted with grapevines before (non-replant soil). Plants were also inoculated with the vesicular-arbuscular (VA) mycorrhizal fungus,Glomus mosseae, or left without mycorrhizal fungus inoculation. Shoot and root growth, mycorrhization of roots and numbers of total aerobic bacteria and fluorescent pseudomonads on the rhizoplane of grapevines were determined at several sampling dates. On replant soil, numbers of fluorescent pseudomonads on the rhizoplane were higher compared to non-replant soil, before differences in shoot and root weight between replant and non-replant soil occurred. Without inoculation withG. mosseae, the mycorrhization of roots was much lower on replant soil (13%) than on non-replant soil (51%). On replant soil, inoculation withG. mosseae increased mycorrhization to 39% and increased shoot length, leaf area and shoot weight. The beneficial effect of VA-fungus inoculation on replant soil was not due to increased nutrient concentrations in leaves. On replant soil, the inoculation withG. mosseae reduced the number of fluorescent pseudomonads on rhizoplane of grapevine, while the numbers of total aerobic bacteria were not influenced by inoculation withG. mosseae. These results suggest a direct or indirect role of fluorescent pseudomonads in replant disease of grapevine.     

Comparison of prevalence of schizophrenia among residents of hostels for homeless people in 1966 and 1992.

OBJECTIVE--To determine whether the prevalence of schizophrenia among the homeless population of Edinburgh resident in hostels has changed between 1966 and 1992. DESIGN--Comparison of two cross sectional surveys. SETTINGS--Hostels for homeless people in Edinburgh. SUBJECTS--In 1966 a random sample of 98 residents of three common lodging houses. In 1992 a random sample of 198 residents of nine hostels. MAIN OUTCOME MEASURE--Prevalence of schizophrenia. RESULTS--The prevalence of schizophrenia in 1992 was 12/136 (9%) compared with 20/79 (25%) in 1966 (odds ratio 0.29; 95% confidence interval 0.13 to 0.62; P = 0.001). Adjustment for confounding by age, current hostel, and duration of unemployment by means of logistic regression produced an adjusted odds ratio of 0.22 (0.08 to 0.58). CONCLUSIONS--The prevalence of schizophrenia was lower in 1992 even after other changes in the population resident in hostels occurring between 1966 and 1992 were taken into account. The findings are not consistent with an increase in the prevalence of schizophrenia among homeless people despite a 66% reduction in adult psychiatric beds in the region during 1966-92.     

1α,25-dihydroxyvitamin D3 hybrid analogs with structural changes at both the A-ring and the C,D-ring side-chain

Calcitrol analogs 5, designed to combine two remote structural changes each of which separately produces a sharply different biological profile, have biological activities that are a blending of the effects of each structural change.     

Mapping of two new markers within the smallest interval harboring the spinal muscular atrophy locus by family and radiation hybrid analysis

The locus responsible for the childhood-onset proximal spinal muscular atrophies (SMA) has recently been mapped to an area of 2–3 Mb in the region q12–13.3 of chromosome 5. We have used a series of radiation hybrids (RHs) containing distinct parts of the SMA region as defined by reference markers. A cosmid library was constructed from one RH. Thirteen clones were isolated and five of these were mapped within the SMA region. Both RH mapping and fluorescence in situ hybridization analysis showed that two clones map in the region between loci D5S125 and D5S351. One of the cosmids contains expressed sequences. Polymorphic dinucleotide repeats were identified in both clones and used for segregation analysis of key recombinant SMA families. One recombination between the SMA locus and the new marker 9Ic (D5S685) indicates that 9Ic is probably the closest distal marker. The absence of recombination between the SMA locus and marker Fc (D5S684) suggests that Fc is located close to the disease gene. These new loci should refine linkage analysis in SMA family studies and may facilitate the isolation of the disease gene.     

Thermotolerant varieties of Bacillus licheniformis isolated from desert environments

One hundred and nineteen thermotolerant and thermophilic Bacillus strains isolated from solar-heated and non-heated environments in Jordan were classified by numerical techniques. Some strains were classified into thermophilic taxa which did not equate with established species. However, most of the isolates were identified phenotypically as Bacillus licheniformis, a conclusion supported by the high DNA hybridization which was detected between these strains and a reference strain of this species (gt64% at optimal renaturation temperature). Several of the B. licheniformis isolates had a higher ratio of iso-C₁₅ and iso-C₁₇ fatty acids to the anteiso equivalents in their membranes than the reference strain of B. licheniformis and they grew more strongly at high temperature than the reference strain. This suggests that the B. licheniformis isolates represent thermotolerant variants of this species.