Fluorescence and reflectance characteristics of manganese deficient soybean leaves: Effects of leaf age and choice of leaflet

Leaf reflectance and fluorescence characteristics of soybean (Glycine max cv Bragg) are influenced strongly by Mn availability. This report evaluates the effects of leaflet choice, leaf age, and leaf nodal position on several spectral characteristics. Leaves were obtained from soybeans grown hydroponically under controlled environmental conditions with wide differences in Mn supply. The ratio of constant yield fluorescence (F_o) to variable yield fluorescence (F_v), the ratios of reflectance at 750 nm to 550 nm and that at 650 nm to 550 nm, the position of the "red edge" near 700 nm, and an index of leaf "yellowness" were measured periodically. Increasing leaf age caused increases in the "red edge" and in both reflectance ratios. Leaf "yellowness" and the fluorescence ratio F_o/F_v decreased with leaf age and increased with leaf nodal position, primarily in Mn deficient leaves. Effects arising from leaf choice were smaller than those caused by Mn deficiency.     

Risk factors of peripheral arterial disease: a case control study in Sri Lanka

Background

Peripheral artery disease (PAD) is an important global health problem and contributes to notable proportion of morbidity and mortality. This particular manifestation of systemic atherosclerosis is largely under diagnosed and undertreated. For sustainable preventive strategies in a country, it is mandatory to identify country-specific risk factors. We intended to assess the risk factors of PAD among adults aged 40–74 years.

Methods

This case control study was conducted in 2012–2013 in Sri Lanka. Seventy-nine cases and 158 controls in the age group of 40–74 years were selected for the study in order to have case to control ratio 1:2. The criterion for selecting cases and control was based on Ankle brachial pressure index (ABPI). Cases were selected from those who had ABPI 0.85 or less (ABPI ≤0.85) in either lower limb. Controls were selected from those ABPI score between 1.18 and 1.28 in both lower limbs. Only newly identified individuals with PAD were selected as cases. Controls were selected from the same geographical location and within the 5 year age group as cases.

Results

The history of diabetes mellitus more than 10 years (OR 5.8, 95% CI 2.2–14.2), history of dyslipidemia for more than 10 years (OR 4.9, 95% CI 2.1–16.2), history of hypertension for more than 10 years (OR 3.8, 95% CI 1.8–12.7) and smoking (OR 2.9, 95% CI 1.2–6.9), elevated HsCRP (OR 3.7, 95% CI 1.2–12.0) and hyperhomocysteinemia (OR 3.0, 95% CI 1.1–8.1) were revealed as country specific significant risk factor of PAD.

Conclusions

Diabetes mellitus, hypertension, dyslipidemia, smoking as well as elevated homocysteine and HsCRP found as risk factors of PAD. Longer the duration or higher level exposure to these risk factors has increased the risk of PAD. These findings emphasis the need for routine screening of PAD among patients with the identified risk factors.

     

The role of fish-poultry integration on fish growth performance,yields and economic benefits among smallholder farmers in sub-Saharan Africa,Tanzania

Aquaculture practices from sub-Saharan Africa are characterised by low production, owing to improper technology. Production can be increased through integrating fish farming with other existing on-farm activities, particularly livestock husbandry. We assessed the role of fish-poultry integration on all male Nile tilapia, Oreochromis niloticus growth performance, yields and economic benefits among smallholder farmers in sub-Saharan Africa, Tanzania. The study also compared phytoplankton species composition, abundance and biomass between the fish-poultry integration and non-integrated system. After 180 days of the experiment, all male O. niloticus cultured under fish-poultry integration exhibited significantly higher growth rates than those in the non-integrated system (p < 0.05). Gross fish yield (GFY), net fish yield (NFY) and net annual yields (NAY) obtained from fish-poultry integration were significantly higher than those from non-integrated system (p < 0.05). Partial enterprise budget analysis revealed that fish-poultry integration was more profitable than the non-integrated system. Moreover, fish-poultry integrated system produced significantly higher phytoplankton abundance and biomass than those from the non-integrated system. Results demonstrate that rural smallholder farmers can achieve higher growth rate, farm net yields and income by integrating all male O. niloticus with other on-farm activities than practising a stand-alone fish culture system.     

Antigen receptor-induced signal transduction imbalances associated with the negative selection of immature B cells

Signals transduced through the B cell Ag receptor (BCR) drive B cell development. However, BCR-induced responses are developmentally regulated; immature B cells are tolerized following antigenic exposure while mature B cells are triggered to proliferate and differentiate. This differential responsiveness allows for the negative selection of self-reactive immature B cells while simultaneously allowing for clonal expansion of mature B cells in response to foreign Ags. Intrinsic differences in BCR-induced signal transduction at various stages of development may account for this functional dichotomy. We had previously demonstrated that the BCR-induced proliferation of mature B cells is accompanied by an increase in intracellular calcium levels and polyphosphoinositide bis phosphate (PIP2) hydrolysis. In contrast, immature B cells that undergo BCR-induced apoptosis increase intracellular calcium in the relative absence of PIP2 hydrolysis. Since PIP2 hydrolysis leads to the generation of diacylglycerol, a cofactor for protein kinase C (PKC) activation, these data suggested that an "imbalance" in BCR-induced signal transduction resulting from a relative inability to activate PKC may play a role in the susceptibility of immature B cells to BCR-induced apoptosis. In support of this hypothesis, we demonstrate that PKC activation can rescue immature B cells from BCR-induced apoptosis. Furthermore, the susceptibility of immature B cells to BCR-induced apoptosis is recapitulated in mature B cells that are either PKC depleted or are stimulated in the presence of PKC inhibitors, suggesting that an uncoupling of PKC activation from BCR-induced signaling is responsible for the apoptotic response of immature B cells.     

Inhibition of fructose-1,6-bisphosphatase by a new class of allosteric effectors

A highly constrained pseudo-tetrapeptide (OC252-324) further defines a new allosteric binding site located near the center of fructose-1,6-bisphosphatase. In a crystal structure, pairs of inhibitory molecules bind to opposite faces of the enzyme tetramer. Each ligand molecule is in contact with three of four subunits of the tetramer, hydrogen bonding with the side chain of Asp187 and the backbone carbonyl of residue 71, and electrostatically interacting with the backbone carbonyl of residue 51. The ligated complex adopts a quaternary structure between the canonical R- and T-states of fructose-1,6-bisphosphatase, and yet a dynamic loop essential for catalysis (residues 52-72) is in a conformation identical to that of the T-state enzyme. Inhibition by the pseudo-tetrapeptide is cooperative (Hill coefficient of 2), synergistic with both AMP and fructose 2,6-bisphosphate, noncompetitive with respect to Mg2+, and uncompetitive with respect to fructose 1,6-bisphosphate. The ligand dramatically lowers the concentration at which substrate inhibition dominates the kinetics of fructose-1,6-bisphosphatase. Elevated substrate concentrations employed in kinetic screens may have facilitated the discovery of this uncompetitive inhibitor. Moreover, the inhibitor could mimic an unknown natural effector of fructose-1,6-bisphosphatase, as it interacts strongly with a conserved residue of undetermined functional significance.     

Fluid shear stress inhibits TNF-alpha-induced apoptosis in osteoblasts: a role for fluid shear stress-induced activation of PI3-kinase and inhibition of caspase-3

In bone, a large proportion of osteoblasts, the cells responsible for deposition of new bone, normally undergo programmed cell death (apoptosis). Because mechanical loading of bone increases the rate of new bone formation, we hypothesized that mechanical stimulation of osteoblasts might increase their survival. To test this hypothesis, we investigated the effects of fluid shear stress (FSS) on osteoblast apoptosis using three osteoblast cell types: primary rat calvarial osteoblasts (RCOB), MC3T3-E1 osteoblastic cells, and UMR106 osteosarcoma cells. Cells were treated with TNF-alpha in the presence of cyclohexamide (CHX) to rapidly induce apoptosis. Osteoblasts showed significant signs of apoptosis within 4-6 h of exposure to TNF-alpha and CHX, and application of FSS (12 dyne/cm(2)) significantly attenuated this TNF-alpha-induced apoptosis. FSS activated PI3-kinase signaling, induced phosphorylation of Akt, and inhibited TNF-alpha-induced activation of caspase-3. Inhibition of PI3-kinase, using LY294002, blocked the ability of FSS to rescue osteoblasts from TNF-alpha-induced apoptosis and blocked FSS-induced inhibition of caspase-3 activation in osteoblasts treated with TNF-alpha. LY294002 did not, however, prevent FSS-induced phosphorylation of Akt suggesting that activation of Akt alone is not sufficient to rescue cells from apoptosis. This result also suggests that FSS can activate Akt via a PI3-kinase-independent pathway. These studies demonstrate for the first time that application of FSS to osteoblasts in vitro results in inhibition of TNF-alpha-induced apoptosis through a mechanism involving activation of PI3-kinase signaling and inhibition of caspases. FSS-induced activation of PI3-kinase may promote cell survival through a mechanism that is distinct from the Akt-mediated survival pathway.     

Transport interactions between cadmium and zinc in roots of bread and durum wheat seedlings

Field studies have shown that the addition of Zn to Cd-containing soils can help reduce accumulation of Cd in crop plants. To understand the mechanisms involved, this study used ¹⁰⁹Cd and ⁶⁵Zn to examine the transport interactions of Zn and Cd at the root cell plasma membrane of bread wheat ( Triticum aestivum L.) and durum wheat ( Triticum turgidum L. var. durum ). Results showed that Cd²⁺ uptake was inhibited by Zn²⁺ and Zn²⁺ uptake was inhibited by Cd²⁺. Concentration-dependent uptake of both Cd²⁺ and Zn²⁺ consisted of a combination of linear binding by cell walls and saturable, Michaelis-Menten influx across the plasma membrane. Saturable influx data from experiments with and without 10 µm concentrations of the corresponding inhibiting ion were converted to double reciprocal plots. The results revealed a competitive interaction between Cd²⁺ and Zn²⁺, confirming that Cd²⁺ and Zn²⁺ share a common transport system at the root cell plasma membrane in both bread and durum wheat. The study suggests that breeding or agronomic strategies that aim to decrease Cd uptake or increase Zn uptake must take into account the potential accompanying change in transport of the competing ion.     

Regulation of PGE(2) and PGI(2) release from human umbilical vein endothelial cells by actin cytoskeleton

Disruption of microfilaments in human umbilical vein endothelialcells (HUVEC) with cytochalasin D (cytD) or latrunculin A (latA)resulted in a 3.3- to 5.7-fold increase in total synthesis ofprostaglandin E₂ (PGE₂) and a 3.4- to 6.5-foldincrease in prostacyclin (PGI₂) compared with controlcells. Disruption of the microtubule network with nocodazole orcolchicine increased synthesis of PGE₂ 1.7- to 1.9-fold andPGI₂ 1.9- to 2.0-fold compared with control cells.Interestingly, however, increased release of PGE₂ andPGI₂ from HUVEC into the media occurred only when microfilaments were disrupted. CytD treatment resulted in 6.7-fold morePGE₂ and 3.8-fold more PGI₂ released from HUVECcompared with control cells; latA treatment resulted in 17.7-fold more PGE₂ and 11.2-fold more PGI₂ released comparedwith control cells. Both increased synthesis and release ofprostaglandins in response to all drug treatments were completelyinhibited by NS-398, a specific inhibitor of cyclooxygenase-2 (COX-2).Disruption of either microfilaments using cytD or latA or ofmicrotubules using nocodazole or colchicine resulted in a significantincrease in COX-2 protein levels, suggesting that the increasedsynthesis of prostaglandins in response to drug treatments may resultfrom increased activity of COX-2. These results, together with studies demonstrating a vasoprotective role for prostaglandins, suggest thatthe cytoskeleton plays an important role in maintenance of endothelialbarrier function by regulating prostaglandin synthesis and release from HUVEC.

     

Influence of varied zinc supply on re-translocation of cadmium (109Cd) and rubidium (86Rb) applied on mature leaf of durum wheat seedlings

Effect of varied zinc (Zn) supply (0, 0.1, 1, 5 M) on re-translocation of radio-labeled cadmium (¹⁰⁹Cd) and rubidium (⁸⁶Rb) from mature leaf to root and other parts of shoot was studied in 11-day-old durum wheat (Triticum durum cv. C-1252) plants grown in nutrient solution under controlled environmental conditions. Application of ¹⁰⁹Cd and ⁸⁶Rb was carried out by immersing the tips (3 cm) of mature leaf in radio-labeled solutions for 10 s at three different times over a 42 h period. Differences in Zn supply for 11 days did not affect plant growth nor did it cause visual leaf symptoms, such as necrosis and chlorosis, at either the lowest or the highest Zn supply. Only at the nil Zn supply (0 M), shoot and root dry weights tended to decrease and increase, respectively, causing a lower shoot/root dry weight ratio. Partitioning of more dry matter to roots rather than shoots, a typical phenomena for Zn-deficient plants in nutrient solution experiments, indicated existence of a mild Zn deficiency stress at the nil-Zn treatment. Irrespective of Zn supply, plants could, on average, retranslocate 3.8% and 38% of the total absorbed ¹⁰⁹Cd and ⁸⁶Rb from the treated leaf to roots and other parts of shoots within 42 h, respectively. At nil-Zn treatment, 2.8% of the total absorbed ¹⁰⁹Cd was re-translocated from the treated leaf, particularly into roots. The highest re-translocation of ¹⁰⁹Cd (6.5%) was found in plants supplied with 0.1 M Zn. Increases in Zn supply from 0.1 M reduced ¹⁰⁹Cd re-translocation from 6.5% to 4.3% at 1 M Zn and 1.3% at 5 M Zn. With the exception of the nil-Zn treatment, the proportion of re-translocated ¹⁰⁹Cd was greater in the remainder of the shoot than in the roots. Contrary to the ¹⁰⁹Cd results, re-translocation of ⁸⁶Rb was not (at 0, 0.1 and 1 M Zn), or only slightly (at 5 M), affected by changing Zn supply. The results indicate an inhibitory action of increased concentrations of Zn in shoot tissues on phloem-mediated Cd transport. This effect is discussed in relation to competitive inhibition of Cd loading into phloem sap by Zn.