Senescence in cut carnation flowers: Temporal and physiological relationships among water status, ethylene, abscisic acid and membrane permeability

Changes in water status, membrane permeability, ethylene production and levels of abscisic acid (ABA) were measured during senescence of cut carnation flowers ( Dianthus caryophyllus L. cv. White Sim) in order to clarify the temporal sequence of physiological events during this post-harvest period. Ethylene production and ABA content of the petal tissue rose essentially in parallel during natural senescence and after treatment of young flowers with exogenous ethylene, indicating that their syntheses are not widely separated in time. However, solute leakage, reflecting membrane deterioration, was apparent well before the natural rise in ethylene and ABA had begun. In addition, there were marked changes in water status of the tissue, including losses in water potential (ψ_w), and turgor (ψ_p), that preceded the rise in ABA and ethylene. As senescence progressed, ψ_w continued to decline, but ψ_p returned to normal levels. These temporal relationships were less well resolved when senescence of young flowers was induced by treatment with ethylene, presumably because the time-scale had been shortened. Thus changes in membrane permeability and an associated water stress in petal tissue appear to be earlier symptoms of flower senescence than the rises in ABA or ethylene. These observations support the contention that the climacteric-like rise in ethylene production is not the initial or primary event of senescence and that the rise in ABA titre may simply be a response to changes in water status.     

Identification of a UDP-glucosyltransferase conferring deoxynivalenol resistance in Aegilops tauschii and wheat

Aegilops tauschii is the diploid progenitor of the wheat D subgenome and a valuable resource for wheat breeding, yet, genetic analysis of resistance against Fusarium head blight (FHB) and the major Fusarium mycotoxin deoxynivalenol (DON) is lacking. We treated a panel of 147 Ae. tauschii accessions with either Fusarium graminearum spores or DON solution and recorded the associated disease spread or toxin-induced bleaching. A k-mer-based association mapping pipeline dissected the genetic basis of resistance and identified candidate genes. After DON infiltration nine accessions revealed severe bleaching symptoms concomitant with lower conversion rates of DON into the non-toxic DON-3-O-glucoside. We identified the gene AET5Gv20385300 on chromosome 5D encoding a uridine diphosphate (UDP)-glucosyltransferase (UGT) as the causal variant and the mutant allele resulting in a truncated protein was only found in the nine susceptible accessions. This UGT is also polymorphic in hexaploid wheat and when expressed in Saccharomyces cerevisiae only the full-length gene conferred resistance against DON. Analysing the D subgenome helped to elucidate the genetic control of FHB resistance and identified a UGT involved in DON detoxification in Ae. tauschii and hexaploid wheat. This resistance mechanism is highly conserved since the UGT is orthologous to the barley UGT HvUGT13248 indicating descent from a common ancestor of wheat and barley.     

Membrane-associated myo-inositol dehydrogenase activity ofBacillus pumilus strain 5

Summary The influence of the microenvironment on the metabolic behaviour of immobilized cells is discussed in relation to literature data. A model is proposed in which decreased water activity and/or oxygen deficiency result in changed yields and/or new metabolic behaviour of the immobilized cells.     

Comparison of debrisoquine and guanethidine in treatment of hypertension.

A cross-over trail of debrisoquine and guanethidine in 32 patients showed that both drugs were equally effective in lowering both systolic and diastolic blood pressure. The degree to which they were tolerated by the patients, however, differed greatly. After three months on each drug 18 patients preferred debrisoquine, nine preferred guanethidine, and five showed no particular preference. At current prices the cost of daily treatment to the patient was cheaper with debrisoquine than with guanethidine.     

Yeast functional genomic screens lead to identification of a role for a bacterial effector in innate immunity regulation

Numerous bacterial pathogens manipulate host cell processes to promote infection and ultimately cause disease through the action of proteins that they directly inject into host cells. Identification of the targets and molecular mechanisms of action used by these bacterial effector proteins is critical to understanding pathogenesis. We have developed a systems biological approach using the yeast Saccharomyces cerevisiae that can expedite the identification of cellular processes targeted by bacterial effector proteins. We systematically screened the viable yeast haploid deletion strain collection for mutants hypersensitive to expression of the Shigella type III effector OspF. Statistical data mining of the results identified several cellular processes, including cell wall biogenesis, which when impaired by a deletion caused yeast to be hypersensitive to OspF expression. Microarray experiments revealed that OspF expression resulted in reversed regulation of genes regulated by the yeast cell wall integrity pathway. The yeast cell wall integrity pathway is a highly conserved mitogen-activated protein kinase (MAPK) signaling pathway, normally activated in response to cell wall perturbations. Together these results led us to hypothesize and subsequently demonstrate that OspF inhibited both yeast and mammalian MAPK signaling cascades. Furthermore, inhibition of MAPK signaling by OspF is associated with attenuation of the host innate immune response to Shigella infection in a mouse model. These studies demonstrate how yeast systems biology can facilitate functional characterization of pathogenic bacterial effector proteins.     

Steroids and triterpenoids from Eastern Nigeria mistletoe, Loranthus micranthus Linn. (Loranthaceae) parasitic on Kola acuminata with immunomodulatory potentials

In search of immunomodulatory constituents from the Eastern Nigeria mistletoe, Loranthus micranthus Linn, two new stigmastane steroids: stigmast-7,20 (21)-diene-3β-hydroxy-6-one (1) and 3β-hydroxy-stigmast-23-ene (2); three (two new and one known) lupeol-based triterpenoid esters: 7β,15α-dihydroxyl-lup-20(29)-ene-3β-palmitate (3), 7β,15α-dihydroxyl-lup-20(29)-ene-3β-stearate (4) and 7β,15α-dihydroxyl-lup-20(29)-ene-3β-eicosanoate (5) were isolated and characterized following bioactivity-guided fractionation. The new compounds, 1, 2, 4 and 5 at concentrations of 10, 25 and 100 μg/ml were subjected to cell proliferation and early activation marker (CD69) expression studies in C57Bl/6 mice splenocytes using flow cytometry techniques against Lipopolysaccharide (LPS; 10 μg/ml) and Concanavalin A (ConA; 2 μg/ml) standards. The stigmastane steroids (1 and 2) at the highest concentration of 100 μg/ml showed statistically significantly (p < 0.05) stimulatory activity on the C57B1/6 splenocytes compared to the controls with values of 46 ± 0.76% and 43 ± 0.46% compared to 7.69 ± 0.41% recorded for the negative control. The novel lupeol esters, 4 and 5 at same concentration of 100 μg/ml exhibited lower stimulations of 30 ± 0.41% and 29 ± 0.17% respectively compared to the controls above. The CD69 expression assay at the above doses showed that all the compounds have minimal stimulation. The present study supports the observed immunomodulatory property of the Eastern Nigeria mistletoe and thus confirms the efficacy of this plant in mitigating against wide array of disease conditions orchestrated by immunodeficiency.     

The fatty acid profile of vegetative Azotobacter vinelandii ATCC 12837: growth phase-dependence

Fatty acids of Azotobacter vinelandii ATCC 12837 were determined at various times during aerobic vegetative growth at 30°C to provide baseline data for studying the effects of chemical agents on the organism’s survival and fatty acid biosynthesis. Palmitate (16:0) was the highest at 36.7±4.3 mol% (mean±SD) after the first 5 h in fresh culture, decreasing slightly to 33.4±2.6 mol% at 49 h. The other fatty acids were therefore each normalized as a ratio of 16:0. At 5 h, as a ratio of 16:0, myristate (14:0) was 0.14±0.06, palmitoleate (16:1cΔ^9–10) 0.13±0.06, oleate (18:1cΔ^9–10) 0.21±0.12, cis-vaccenate (18:1cΔ^11–12) 0.30±0.17 and stearate (18:0) 0.68±0.02. As the growth phase advanced to 49 h, 14:0 and 16:1cΔ^9–10 increased, 18:1cΔ^9–10 decreased and cis-vaccenate reciprocally increased, whereas 18:0 decreased. These suggest that the saturated fatty acid biosynthesis pathway yielded 16:0 and 18:0 in the 5-h lag period. By desaturation, 18:0 formed the unsaturated fatty acid (UFA) 18:1cΔ^9–10. As the culture aged, the anaerobic UFA biosynthesis pathway formed 16:1cΔ^9–10, which was elongated to 18:1cΔ^11–12. These fatty acid alterations represent a homeoviscous adaptation, modulating the microbe’s membrane lipid viscosity for optimal cellular function.     

Effects of vitamin C supplementation on the growth of Heterobranchus longifilis fingerlings

A 12-week growth experiment was conducted to establish the necessity of vitamin C in the nutrition of Heterobranchus longifilis fingerlings. Vitamin C was supplemented at levels of 0 and 50 mg x kg(-1) to a basal diet (42.5% CP), which was fed to triplicate groups of H. longifilis fingerlings. Fish receiving the vitamin C-supplemented diet had significantly improved weight gain (20.7 vs. 16.7 g per fish), feed efficiency ratio (1.03 vs. 1.42), specific growth rate (3.00 vs. 2.74%), protein efficiency ratio (2.26 vs. 1.64), and survival rate (90% vs. 50%). There was a significant decrease in haematocrit and haemoglobin levels in the blood of fish fed no supplemental vitamin C. Furthermore, this group exhibited retarded growth and pathological changes such as vertebral curvature, condensation associated with fragility of the spinal bones. Supplementation of 50 mg vitamin C per kg diet was adequate to prevent the occurrence of vitamin C deficiency in H. longifilis and it was concluded that vitamin C is essential in the nutrition of these fishes.     

Evaluation of Cyanogenic Potentials of Local Cassava Species and Residual Cyanide Contents of Their Locally Processed Food Products in Southeast Nigeria

The cyanogenic potentials and residual cyanide contents of local cassava parenchyma and their locally processed food products in southeastern Nigeria were studied. Seven species of cassava locally grown and four main food products from them were analyzed colorimetrically for their cyanide contents. Results of the analyses indicated that five of the species contain cyanide potentials between 50 and 100 mg HCN/kg fresh weight while only one contains cyanogens level greater than 100 mg HCN/kg fresh weight. Of the cassava products analyzed, two contained cyanide above the level recommended by the WHO/FAO (10 mg HCN/kg). The result raises concern as these cassava products constitute about 80–90% of the diet of the local people and the facts known about cyanide poisoning from intake of high cyanide containing food.     

Detection of lyssavirus antigen and antibody levels among apparently healthy and suspected rabid dogs in South-Eastern Nigeria

Objectives

Domestic dogs are the main reservoir of rabies virus (RABV) infection in Nigeria, thus surveillance of rabies in dog populations is crucial in order to understand the patterns of spread of infection and ultimately devise an appropriate rabies control strategy. This study determined the presence of lyssavirus antigen in brain tissues and anti-rabies antibodies in sera of apparently healthy and suspected-rabid dogs slaughtered for human consumption at local markets in South-Eastern Nigeria.

Results

Our findings demonstrated that 8.3% (n?=?23) of brain tissues were lyssavirus positive and 2.5% (n?=?25) of sera had rabies antibody levels as percentage blocking of 70% and above correlating with a cut-off value?≥?0.5 IU/mL in the fluorescent antibody neutralization test. There was an inverse correlation between lyssavirus positivity and rabies antibody levels confirming that infected individuals most often do not develop virus neutralizing antibodies to the disease. The low percentage of rabies antibodies in this dog population suggests a susceptible population at high risk to RABV infection. These findings highlight a huge challenge to national rabies programs and subsequent elimination of the disease from Nigeria, considering that majority of dogs are confined to rural communal areas, where parenteral dog vaccination is not routinely undertaken.