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A major problem that usually confronts the breeder is ensuring that there is sufficient genetic variability in a population for the trait being improved because this determines the breeding schemes to use for improvement and whether or not sufficient progress could be made. Three hundred full-sib families from cycle 3 of the early maturing yellow endosperm maize (Zea mays L.) population, TZE-Y Pop DT STR, were evaluated under artificial Striga hermonthica infestation at Mokwa and Abuja, Nigeria in 2003. The objectives of this study were to investigate the type of gene action involved in the inheritance of S. hermonthica resistance in TZE-Y Pop DT STR C3, determine the extent of genetic variability available in the population after three cycles of S1 recurrent selection, and the phenotypic and genetic correlation coefficients among the traits used for selecting for resistance to S. hermonthica. Estimates of dominance variances were larger than additive genetic variances for grain yield, plant height, ear height, number of ears at harvest, and Striga damage rating at 8 weeks after planting (WAP). Even though h² estimates were generally low for most traits (< 0.40), moderate-to-large additive genetic variances, and wide ranges were obtained in TZE-Y Pop DT STR C3 for most traits, suggesting that there was adequate genetic variation for improving Striga resistance and grain yield in the population. Highly significant phenotypic correlation coefficients were obtained between grain yield and ears per plant, plant height, ear height, days to anthesis and silking, anthesis-silking interval, and Striga damage score at 10 WAP. Recurrent selection methods that capitalize on both additive and dominance variances would be effective for improving the population for Striga resistance and grain yield. doi:10.1300/J411v20n01_06 [ABSTRACT FROM AUTHOR]

Idiopathic pulmonary fibrosis is a chronic disease characterized by progressive lung scarring that inhibits gas exchange. Evidence suggests fibroblast-matrix interactions are a prominent driver of disease. However, available preclinical models limit our ability to study these interactions. We present a technique for synthesizing phototunable poly(ethylene glycol) (PEG)-based hybrid-hydrogels comprising healthy or fibrotic decellularized extracellular matrix (dECM) to decouple mechanical properties from composition and elucidate their roles in fibroblast activation. Here, we engineered and characterized phototunable hybrid-hydrogels using molecular techniques such as ninhydrin and Ellman's assays to assess dECM functionalization, and parallel-plate rheology to measure hydrogel mechanical properties. These biomaterials were employed to investigate the activation of fibroblasts from dual-transgenic Col1a1-GFP and αSMA-RFP reporter mice in response to changes in composition and mechanical properties. We show that reacting functionalized dECM from healthy or bleomycin-injured mouse lungs with PEG alpha-methacrylate (αMA) in an off-stoichiometry Michael-addition reaction created soft hydrogels mimicking a healthy lung elastic modulus (4.99 ± 0.98 kPa). Photoinitiated stiffening increased the material modulus to fibrotic values (11.48 ± 1.80 kPa). Percent activation of primary murine fibroblasts expressing Col1a1 and αSMA increased by approximately 40% following dynamic stiffening of both healthy and bleomycin hybrid-hydrogels. There were no significant differences between fibroblast activation on stiffened healthy versus stiffened bleomycin-injured hybrid-hydrogels. Phototunable hybrid-hydrogels provide an important platform for probing cell-matrix interactions and developing a deeper understanding of fibrotic activation in pulmonary fibrosis. Our results suggest that mechanical properties are a more significant contributor to fibroblast activation than biochemical composition within the scope of the hybrid-hydrogel platform evaluated in this study., Supplementary Information: The online version contains supplementary material available at 10.1007/s12195-022-00726-y., Competing Interests: Conflict of interestDr. Magin is an inventor on a pending patent related to the technology described in this manuscript. All remaining authors (KSS, RH, PS, RB, BJS, SEN, BE, and DWHR) have no conflicts of interest to disclose., (© The Author(s) under exclusive licence to Biomedical Engineering Society 2022.)

The muscle-specific glutathione transferase GSTM2-2 modulates the activity of ryanodine receptor (RyR) calcium release channels: it inhibits the activity of cardiac RyR (RyR2) channels with high affinity and activates skeletal RyR (RyR1) channels with low affinity. The C terminal domain of GSTM2-2 (GSTM2C) alone physically binds to RyR2 and inhibits its activity, but it does not bind to RyR1. We have now used yeast two-hybrid analysis, chemical cross-linking, intrinsic tryptophan fluorescence and Ca(2+) release studies to determine that the binding site for GSTM2C is in divergent region 3 (D3) of RyR2. The D3 region encompasses residues 1855-1890 in RyR2. Specific mutagenesis shows the binding primarily involves electrostatic interactions with residues K1875, K1886, R1887 and K1889, all residues that are present in RyR2, but not in RyR1. The significant sequence differences between the D3 regions of RyR2 and RyR1 explain why GSTM2-2 specifically inhibits RyR2. This specific inhibition of RyR2 could modulate Ca cycling and be useful for the treatment of heart failure. RyR2 inhibition during diastole may improve filling of the SR with Ca(2+) and improve contractility., (Copyright © 2012 Elsevier Inc. All rights reserved.)

Glutathione transferases (GSTs) are generally recognized for their role in phase II detoxification reactions. However, it is becoming increasingly apparent that members of the GST family also have a diverse range of other functions that are, in general, unrelated to detoxification. One such action is a specific inhibition of the cardiac isoform of the ryanodine receptor (RyR2) intracellular Ca(2+) release channel. In this review, we compare functional and physical interactions between members of the GST family, including GSTO1-1, GSTA1-1, and GSTM2-2, with RyR2 and with the skeletal isoform of the ryanodine receptor (RyR1). The active part of the muscle-specific GSTM2-2 is localized to its nonenzymatic C-terminal α-helical bundle, centered around α-helix 6. The GSTM2-2 binding site is in divergent region 3 (DR3 region) of RyR2. The sequence differences between the DR3 regions of RyR1 and RyR2 explain the specificity of the GSTs for one isoform of the protein. GSTM2-2 is one of the few known endogenous inhibitors of the cardiac RyR and is likely to be important in maintaining low RyR2 activity during diastole. We discuss interactions between a nonenzymatic member of the GST structural family, the CLIC-2 (type 2 chloride intracellular channel) protein, which inhibits both RyR1 and RyR2. The possibility that the GST and CLIC2 proteins bind to different sites on the RyR, and that different structures within the GST and CLIC proteins bind to RyR channels, is discussed. We conclude that the C-terminal part of GSTM2-2 may provide the basis of a therapeutic compound for use in cardiac disorders.

Ca(2+) release from the sarcoplasmic reticulum through cardiac ryanodine receptors (RyR2) is essential for heart function and is inhibited by the carboxy terminal domain of glutathione transferase M2-2 (GSTM2-C) and derivative fragments containing helix 6. Since a peptide encoding helix 6 alone does not fold into a helix and does not inhibit RyR2 Ca(2+) release, the importance of the structure of helix 6 and its role in stabilizing GSTM2-C was tested by inserting potentially destabilizing mutations into this helical segment. GSTM2-C preparations with D156A or L163A mutations were so insoluble that the protein could not be purified. Proteins with F157A and Y260A substitutions were soluble, but had lost their capacity to inhibit both RyR2 Ca(2+) release from vesicles and RyR2 channels in bilayers. Circular dichroism studies indicated that these mutated proteins retained their helical secondary structure, although changes in their endogenous tryptophan fluorescence indicated that the F157A and Y160A mutations caused changes in their folding. The single channel studies were conducted with 2mM ATP and 10microM Ca(2+) in the cytoplasmic solution, mimicking concentrations in the cytosol of cardiac myocytes. Wild type GSTM2-C inhibited RyR2 only at a potential of +40mV, which may develop during Ca(2+) efflux, but not at -40mV. Together, the results indicate that the structure of helix 6 in the C-terminal fold is critical to the inhibitory action of GSTM2-2 and suggest that therapeutics mimicking this structure may reduce excess Ca(2+) release during diastole, which can lead to fatal arrhythmia., (Copyright (c) 2010 Elsevier Inc. All rights reserved.)

The muscle specific glutathione transferase GSTM2-2 inhibits the activity of cardiac ryanodine receptor (RyR2) calcium release channels with high affinity and activates skeletal RyR (RyR1) channels with lower affinity. To determine which overall region of the GSTM2-2 molecule supports binding to RyR2, we examined the effects of truncating GSTM2-2 on its ability to alter Ca(2+) release from sarcoplasmic reticulum (SR) vesicles and RyR channel activity. The C-terminal half of GSTM2-2 which lacks the critical GSH binding site supported the inhibition of RyR2, but did not support activation of RyR1. Smaller fragments of GSTM2-2 indicated that the C-terminal helix 6 was crucial for the action of GSTM2-2 on RyR2. Only fragments containing the helix 6 sequence inhibited Ca(2+) release from cardiac SR. Single RyR2 channels were strongly inhibited by constructs containing the helix 6 sequence in combination with adjacent helices (helices 5-8 or 4-6). Fragments containing helices 5-6 or helix 6 sequences alone had less well-defined effects. Chemical cross-linking indicated that C-terminal helices 5-8 bound to RyR2, but not RyR1. Structural analysis with circular dichroism showed that the helical content was greater in the longer helix 6 containing constructs, while the helix 6 sequence alone had minimal helical structure. Therefore the active centre of GSTM2-2 for inhibition of cardiac RyR2 involves the helix 6 sequence and the helical nature of this region is essential for its efficacy. GSTM2-2 helices 5-8 may provide the basis for RyR2-specific compounds for experimental and therapeutic use.

Background & Objectives: Epaltes divaricata is widely used in Sri Lanka as an Ayurvedic medicine. In the present study the hepatoprotective and antioxidative effects of an aqueous extract of E. divaricata plant (Family-Compositae) were investigated against carbon tetrachloride induced hepatocellular injury in mice., Methods: Healthy male mice (30-35 g body weight, 6-8 wk old) were used. A single dose of carbon tetrachloride (CCl4, 0.5 ml/kg in olive oil) was administered ip to induce hepatotoxicity and the plant extract at a dose of 0.9 g/kg was administered orally by gavage. Animals were sacrificed 24 h and 4 days after the administration of CCl4. Blood and liver tissue were collected for the assessment of serum levels of alanine aminotransferase (ALT), aspartate aminotransferase (AST), alkaline phosphatase (ALP) and liver reduced glutathione level. The liver tissue was used for histopathological assessment of liver damage., Results: Pre-treatment of mice with the plant extract of Epaltes (0.9 g/kg) orally for 7 days significantly reduced serum levels of ALT (P<0.01), AST (P<0.01) and ALP (P<0.001) enzymes by 21.40, 47.36 and 71.12 per cent respectively and significantly increased (P<0.001) the liver reduced glutathione level by 42.32 per cent, 24 h after the administration of carbon tetrachloride. A marked improvement in the enzyme activities and the liver reduced glutathione level was observed in the Epaltes pre-treated mice 4 days after the administration of carbon tetrachloride. Histopathological studies provided supportive evidence for the biochemical analysis., Interpretation & Conclusion: The results of the present study indicated that under the present experimental conditions, aqueous extract of Epaltes divaricata showed hepatoprotective abilities against carbon tetrachloride induced liver damage in mice.