NaCl induced morpho-biochemical and anatomical changes in mulberry (<Emphasis Type="Italic">Morus</Emphasis> spp.)

Mulberry is an economically important tree, used for feeding the silkworm Bombyx mori L. Effect of different levels of NaCl on growth and development of mulberry has been studied using five mulberry genotypes selected on the basis of their performance under in vitro salinity. The study while endorsing the efficacy of in vitro screening of axillary buds of mulberry for salt tolerance, showed genotypic variability in its response to salinity. Salinity reduced growth and development of all genotypes. However, the putative tolerant genotypes showed better performance than the putative susceptible genotypes. Under low salinity (<0.5% NaCl) salt tolerant genotypes showed an increase in chlorophyll and protein concentrations, while in susceptible genotypes both were reduced by 3–58% at 0.5% NaCl and 50–64% at 1.00% NaCl. Leaf thickness increased by 16% at 1.00% NaCl in C776 and reduced by 1.0% in Mandalaya. The increase in chlorophyll concentration and leaf thickness under high salinity can be considered as preliminary selection parameters for salt tolerance in mulberry. The study confirmed the efficacy of in vitro method for screening of large number of genotypes for salt tolerance in mulberry.     

Loose shell syndrome of farmed Penaeus monodon in India is caused by a filterable agent

Loose shell syndrome (LSS) of farmed black tiger shrimp Penaeus monodon has been reported from Indian shrimp farms since 1998 and is recognized as a major disease problem causing significant economic loss to the shrimp aquaculture sector. Unlike the rapid mortalities associated with viral pathogens such as white spot syndrome virus and yellow head virus, progression of LSS is gradual, leading to low-level progressive mortalities. The signs of LSS include a flaccid spongy abdomen due to muscular dystrophy, space between the exoskeleton and muscle, and a shrunken hepatopancreas. The feed conversion efficiency is reduced, and shrimp have poor meat quality, caused by impairment of the hepatopancreatic functions such as digestion and absorption as evidenced by the atrophy of the hepatopancreas. Histopathological investigations on LSS-affected shrimp showed shrinkage of extensor and flexor muscles with occasional hemocytic infiltration. The hepatopancreas showed inflammation of hepatopancreatic tubules with enlargement of intertubular spaces, hemocytic infiltration, and low levels of lipid reserves in the R cells. In advanced stages of LSS, many tubules were in highly necrotic condition with a sloughed epithelium, reflecting the dysfunction of the digestive gland. LSS could be induced in healthy tiger shrimp by challenge studies using membrane-filtered LSS-affected shrimp tissues, suggesting involvement of a filterable infectious agent.     

Involvement of Enterobacter cloacae in the mortality of the fish, Mugil cephalus

Aims:  To identify the causative agent of the mortality in the fish, Mugil cephalus , in Muttukadu lagoon.
Methods and Results:  An enteric bacterium from the kidneys of moribund fish M. cephalus , was isolated and identified as Enterobacter cloacae (MK). Mugil cephalus was experimentally infected by this isolate and was re-isolated from the kidneys of the moribund fish. Enterobacter cloacae isolates from the lagoon water (MW1, MW2 and reference strain ATCC 13047) and the reference strain were not able to induce similar pathogenesis. The putative factor imparting pathogenicity to the MK isolate was identified as a cationic molecule, which migrated towards the cathode on agarose gel electrophoresis.
Conclusions:  The Ent. cloacae (MK) isolate harbouring a cationic factor was the causative agent for the mortality of M. cephalus , found in Muttukadu lagoon.
Significance and Impact of the Study:  This study reveals that human enteric bacteria MK which is considered as nonpathogenic to fish, may become pathogenic to fish when it harbours this cationic factor. This cationic factor is found to be pathogenic to the fish M. cephalus leading to mortality. It was also found to be pathogenic to mice. Therefore, the shuttling of Ent. cloacae , harbouring cationic factor, between human and fish may be of human health importance.     

Molecular basis of kainate receptor modulation by sodium

Membrane proteins function in a polarized ionic environment with sodium-rich extracellular and potassium-rich intracellular solutions. Glutamate receptors that mediate excitatory synaptic transmission in the brain show unusual sensitivity to external ions, resulting in an apparent requirement for sodium in order for glutamate to activate kainate receptors. Here, we solve the structure of the Na(+)-binding sites and determine the mechanism by which allosteric anions and cations regulate ligand-binding dimer stability, and hence the rate of desensitization and receptor availability for gating by glutamate. We establish a stoichiometry for binding of 2 Na(+) to 1 Cl(-) and show that allosteric anions and cations bind at physically discrete sites with strong electric fields, that the binding sites are not saturated in CSF, and that the requirement of kainate receptors for Na(+) occurs simply because other cations bind with lower affinity and have lower efficacy compared to Na(+).     

Differences in ischemia-reperfusion-induced endothelial changes in hearts perfused at constant flow and constant pressure

Isolated hearts subjected to ischemia-reperfusion (I/R) exhibit depressed cardiac performance and alterations in subcellular function. Since hearts perfused at constant flow (CF) and constant pressure (CP) show differences in their contractile response to I/R, this study was undertaken to examine mechanisms responsible for these I/R-induced alterations in CF-perfused and CP-perfused hearts. Rat hearts, perfused at CF (10 ml/min) or CP (80 mmHg), were subjected to I/R (30 min global ischemia followed by 60 min reperfusion), and changes in cardiac function as well as sarcolemmal (SL) Na(+)-K(+)-ATPase activity, sarcoplasmic reticulum (SR) Ca(2+) uptake, and endothelial function were monitored. The I/R-induced depressions in cardiac function, SL Na(+)-K(+)-ATPase, and SR Ca(2+)-uptake activities were greater in hearts perfused at CF than in hearts perfused at CP. In hearts perfused at CF, I/R-induced increase in calpain activity and decrease in nitric oxide (NO) synthase (endothelial NO synthase) protein content in the heart as well as decrease in NO concentration of the perfusate were greater than in hearts perfused at CP. These changes in contractile activity and biochemical parameters due to I/R in hearts perfused at CF were attenuated by treatment with l-arginine, a substrate for NO synthase, while those in hearts perfused at CP were augmented by treatment with N(G)-nitro-l-arginine methyl ester, an inhibitor of NO synthase. The results indicate that the I/R-induced differences in contractile responses and alterations in subcellular organelles between hearts perfused at CF and CP may partly be attributed to greater endothelial dysfunction in CF-perfused hearts than that in CP-perfused hearts.     

Fiber-type susceptibility to eccentric contraction-induced damage of hindlimb-unloaded rat AL muscles.

Slow oxidative (SO) fibers of the adductor longus (AL) were predominantly damaged during voluntary reloading of hindlimb unloaded (HU) rats and appeared explainable by preferential SO fiber recruitment. The present study assessed damage after eliminating the variable of voluntary recruitment by tetanically activating all fibers in situ through the motor nerve while applying eccentric (lengthening) or isometric contractions. Muscles were aldehyde fixed and resin embedded, and semithin sections were cut. Sarcomere lesions were quantified in toluidine blue-stained sections. Fibers were typed in serial sections immunostained with antifast myosin and antitotal myosin (which highlights slow fibers). Both isometric and eccentric paradigms caused fatigue. Lesions occurred only in eccentrically contracted control and HU muscles. Fatigue did not cause lesions. HU increased damage because lesioned- fiber percentages within fiber types and lesion sizes were greater than control. Fast oxidative glycolytic (FOG) fibers were predominantly damaged. In no case did damaged SO fibers predominate. Thus, when FOG, SO, and hybrid fibers are actively lengthened in chronically unloaded muscle, FOG fibers are intrinsically more susceptible to damage than SO fibers. Damaged hybrid-fiber proportions ranged between these extremes.     

AT1 Receptor blockade limits myocardial injury and upregulates AT2 receptors during reperfused myocardial infarction

Persistent left ventricular (LV) dysfunction after reperfused myocardial infarction (RMI) is a significant problem and angiotensin II (AngII) type 1 receptor (AT₁R) blockers (ARBs) may limit reperfusion injury involving upregulation of AngII type 2 receptors (AT₂R). To determine whether ARBs valsartan and irbesartan limit reperfusion injury and upregulate AT₂R protein during RMI, we randomized dogs with anterior RMI (90 min ischemia; 120 min reperfusion) to 4 groups [valsartan (n = 6); irbesartan (n = 9); vehicle controls (n = 8); and sham (n = 6)] and measured serial in vivo hemodynamics, LV systolic and diastolic function, and inhibition of AngII pressor responses to the ARBs, and ex vivo infarct size, and regional AT₁R and AT₂R protein expression at the end of the reperfusion. Compared to the control group, both ARBs significantly limited the increase in left atrial pressure, promptly limited the deterioration of LV dP/dt_max, dP/dt_min, ejection fraction and diastolic function, limited infarct expansion and thinning, and limited infarct size. Importantly, both ARBs increased AT₂R protein in the postischemic reperfused zone, with no change in AT₁R protein. There were no changes in the sham group. The results suggest that limitation of myocardial injury associated with AT₁R blockade combined with upregulation of AT₂R protein expression contributes to the cardioprotective effects of ARBs during RMI. This beneficial effect of ARBs on persistent LV dysfunction after RMI should be evaluated in the clinical setting to determine the relative benefit of ARBs in patients who undergo reperfusion therapy for acute coronary syndromes.     

Role of glucose and insulin in regulating glycogen synthase and phosphorylase activities in rainbow trout hepatocytes

This study, using ¹³C nuclear magnetic resonance spectroscopy showed enrichment of glycogen carbon (C1) from ¹³C-labelled (C1) glucose indicating a direct pathway for glycogen synthesis from glucose in rainbow trout (Oncorhynchus mykiss) hepatocytes. There was a direct relationship between hepatocyte glycogen content and total glycogen synthase, total glycogen phosphorylase and glycogen phosphorylase a activities, whereas the relationship was inverse between glycogen content and % glycogen synthase a and glycogen synthase a/glycogen phosphorylase a ratio. Incubation of hepatocytes with glucose (3 or 10 mmol·1^-1) did not modify either glycogen synthase or glycogen phosphorylase activities. Insulin (porcine, 10^-8 mol·1^-1) in the medium significantly decreased total glycogen phosphorylase and glycogen phosphorylase a activities, but had no significant effect on glycogen synthase activities when compared to the controls (absence of insulin). In the presence of 10 mmol·1^-1 glucose, insulin increased % glycogen synthase a and decreased % glycogen phosphorylase a activities in trout hepatocytes. Also, the effect of insulin on the activities of % glycogen synthase a and glycogen synthase a/glycogen phosphorylase a ratio were more pronounced at low than at high hepatocyte glycogen content. The results indicate that in trout hepatocytes both the glycogen synthetic and breakdown pathways are active concurrently in vitro and any subtle alterations in the phosphorylase to synthase ratio may determine the hepatic glycogen content. Insulin plays an important role in the regulation of glycogen metabolism in rainbow trout hepatocytes. The effect of insulin on hepatocyte glycogen content may be under the control of several factors, including plasma glucose concentration and hepatocyte glycogen content.     

A partial reduction of VDAC1 enhances mitophagy,autophagy, synaptic activities in a transgenic Tau mouse model

Alzheimer''s disease (AD) is the most common cause of mental dementia in the aged population. AD is characterized by the progressive decline of memory and multiple cognitive functions, and changes in behavior and personality. Recent research has revealed age‐dependent increased levels of VDAC1 in postmortem AD brains and cerebral cortices of APP, APPxPS1, and 3xAD.Tg mice. Further, we found abnormal interaction between VDAC1 and P‐Tau in the AD brains, leading to mitochondrial structural and functional defects. Our current study aimed to understand the impact of a partial reduction of voltage‐dependent anion channel 1 (VDAC1) protein on mitophagy/autophagy, mitochondrial and synaptic activities, and behavior changes in transgenic TAU mice in Alzheimer''s disease. To determine if a partial reduction of VDAC1 reduces mitochondrial and synaptic toxicities in transgenic Tau (P301L) mice, we crossed heterozygote VDAC1 knockout (VDAC1^+/−) mice with TAU mice and generated double mutant (VDAC1^+/−/TAU) mice. We assessed phenotypic behavior, protein levels of mitophagy, autophagy, synaptic, other key proteins, mitochondrial morphology, and dendritic spines in TAU mice relative to double mutant mice. Partial reduction of VDAC1 rescued the TAU‐induced behavioral impairments such as motor coordination and exploratory behavioral changes, and learning and spatial memory impairments in VDAC1^+/−/TAU mice. Protein levels of mitophagy, autophagy, and synaptic proteins were significantly increased in double mutant mice compared with TAU mice. In addition, dendritic spines were significantly increased; the mitochondrial number was significantly reduced, and mitochondrial length was increased in double mutant mice. Based on these observations, we conclude that reduced VDAC1 is beneficial in symptomatic‐transgenic TAU mice.     

Sequence Determinants of Circadian Gene Expression Phase in Cyanobacteria

The cyanobacterium Synechococcus elongatus PCC 7942 exhibits global biphasic circadian oscillations in gene expression under constant-light conditions. Class I genes are maximally expressed in the subjective dusk, whereas class II genes are maximally expressed in the subjective dawn. Here, we identify sequence features that encode the phase of circadian gene expression. We find that, for multiple genes, an ∼70-nucleotide promoter fragment is sufficient to specify class I or II phase. We demonstrate that the gene expression phase can be changed by random mutagenesis and that a single-nucleotide substitution is sufficient to change the phase. Our study provides insight into how the gene expression phase is encoded in the cyanobacterial genome.