Tricyclic antidepressant amitriptyline alters sarcoplasmic reticulum calcium handling in ventricular myocytes

Tricyclic antidepressants such as amitriptyline (AMT) have been reported to have adverse side effects on cardiac performance. AMT effects on Ca handling in ventricular myocytes, however, are not well understood. Therefore, we investigated AMT action on sarcoplasmic reticulum (SR) Ca release in ventricular myocytes, ryanodine receptor (RyR) activity, and Ca uptake by SR microsomes. In permeabilized myocytes, AMT transiently increased free luminal Ca concentration ([Ca]) followed by marked depletion. AMT (10 microM) caused a rapid and a transient increase of Ca spark frequency, followed by a significant suppression of spark activity. The latter was associated with a decrease of Ca spark amplitude and SR Ca load to 87 and 60%, respectively. AMT (10 microM) completely abolished propagation of spontaneous Ca waves. Higher concentrations of AMT (0.1-1 mM) evoked SR Ca release reminiscent of the effect of caffeine (20 mM) and caused almost complete depletion of SR Ca content. Studies on single calsequestrin-free RyR channels revealed that AMT increased the mean open time and open probability (Po) in a dose-dependent fashion (dissociation constant = 4.2 microM). High concentrations of AMT (> 25 microM) evoked frequent long openings with Po reaching very high levels (> 0.70). In studies with cardiac SR microsomes, AMT slowed the rate of ATP-dependent Ca uptake. We conclude that AMT affects SR Ca handling in ventricular myocytes by multiple mechanisms, including direct stimulation of RyRs and inhibition of SR Ca uptake. These effects could contribute to AMT cardiotoxicity.

A map of the class III region of the sheep major histocompatibilty complex

Background

The central, or class III, region of the major histocompatibility complex (MHC) is an important gene rich sub-region of the MHC of mammals and contains many loci implicated in disease processes and potential productivity traits. As a prelude to identifying MHC loci associated with productivity traits in sheep, we have used BAC and cosmid libraries of genomic DNA to generate a physical map of the sheep MHC class III region. This map will facilitate association studies and provide insights into the distribution of recombination events in this chromosomal segment.

Results

Twenty eight sheep genes were identified in 10 BAC clones which spanned approximately 700 kbp of a chromosomal region adjacent to the class I region of the sheep MHC and which therefore covers most, if not all, of the class III of the sheep MHC. The relative positions of 17 of these genes was established as well as two additional groups of genes for which the intragroup order was not known. Cosmid mapping permitted a more detailed mapping of the complement genes present in the class III and showed a local inversion (relative to humans) of one pair of the duplicated complement C4 and CYP21 loci. A panel of 26 single nucleotide polymorphisms (SNPs) was identified in 10 loci, covering ≈600 kbp of the mapped region.

Conclusion

This report provides a physical map covering ≈700 kbp of the class III of the sheep MHC together with a SNP panel which will facilitate disease and productivity association studies. The presence of a local inversion (relative to humans) of one pair of the duplicated C4 and CYP21 loci and a previously described dinucleotide tandem repeat locus (BfMs) has been located within an intron of the SK12VL gene.

Luminal Ca2+ regulation of single cardiac ryanodine receptors: insights provided by calsequestrin and its mutants

The luminal Ca2+ regulation of cardiac ryanodine receptor (RyR2) was explored at the single channel level. The luminal Ca2+ and Mg2+ sensitivity of single CSQ2-stripped and CSQ2-associated RyR2 channels was defined. Action of wild-type CSQ2 and of two mutant CSQ2s (R33Q and L167H) was also compared. Two luminal Ca2+ regulatory mechanism(s) were identified. One is a RyR2-resident mechanism that is CSQ2 independent and does not distinguish between luminal Ca2+ and Mg2+. This mechanism modulates the maximal efficacy of cytosolic Ca2+ activation. The second luminal Ca2+ regulatory mechanism is CSQ2 dependent and distinguishes between luminal Ca2+ and Mg2+. It does not depend on CSQ2 oligomerization or CSQ2 monomer Ca2+ binding affinity. The key Ca2+-sensitive step in this mechanism may be the Ca2+-dependent CSQ2 interaction with triadin. The CSQ2-dependent mechanism alters the cytosolic Ca2+ sensitivity of the channel. The R33Q CSQ2 mutant can participate in luminal RyR2 Ca2+ regulation but less effectively than wild-type (WT) CSQ2. CSQ2-L167H does not participate in luminal RyR2 Ca2+ regulation. The disparate actions of these two catecholaminergic polymorphic ventricular tachycardia (CPVT)–linked mutants implies that either alteration or elimination of CSQ2-dependent luminal RyR2 regulation can generate the CPVT phenotype. We propose that the RyR2-resident, CSQ2-independent luminal Ca2+ mechanism may assure that all channels respond robustly to large (>5 μM) local cytosolic Ca2+ stimuli, whereas the CSQ2-dependent mechanism may help close RyR2 channels after luminal Ca2+ falls below ∼0.5 mM.

Effects of pace and stress on upper extremity kinematic responses in sign language interpreters

Sign language interpreters suffer from high levels of upper extremity disorders and burnout due to the physical and cognitive demands of interpreting. The objective of this research was to quantify the wrist kinematics of interpreting and to assess how speaker pace and psychosocial stress influence wrist kinematics. Professional interpreters interpreted a pre-recorded lecture, while the speaking pace of the lecture varied. One group of subjects was exposed to environmental conditions intended to induce stress. Several wrist kinematic variables of interpreting exceeded previously established high risk benchmarks for development of upper extremity disorders in industrial tasks. Wrist velocity and acceleration increased significantly with pace, with increases ranging from 10.7-18.6%. Increased psychosocial stress resulted in significant increase of left hand (non-dominant) wrist velocity and acceleration, with increases ranging from 14.8-19.5%. These results provide an objective assessment of the biomechanical demands of interpreting and support earlier research into different types of work, which found deleterious effects of psychosocial stress on the biomechanical responses of the lower back.

An adaptive transmission protocol for managing dynamic shared states in collaborative surgical simulation

A force prediction algorithm is proposed to facilitate virtual-reality (VR) based collaborative surgical simulation by reducing the effect of network latencies. State regeneration is used to correct the estimated prediction. This algorithm is incorporated into an adaptive transmission protocol in which auxiliary features such as view synchronization and coupling control are equipped to ensure the system consistency. We implemented this protocol using multi-threaded technique on a cluster-based network architecture.

Spatiotemporal patterns of postsynaptic density (PSD)-95 expression after rat spinal cord injury

AIMS

Postsynaptic density (PSD)-95 is a scaffolding protein linking the N-methyl-D-aspartate receptor with neuronal nitric oxide synthase (nNOS), which contributes to many physiological and pathological actions. We here investigated whether PSD-95 was involved in the secondary response following spinal cord injury (SCI).

METHODS

Spinal cord contusion (SCC) and spinal cord transection (SCT) models at thoracic (T) segment 9 (T(9)) were established in adults rats. Real-time polymerase chain reaction, Western blot, immunohistochemistry and immunofluorescence were used to detect the temporal profile and spatial distribution of PSD-95 after SCI. The association between PSD-95 and nNOS in the injured cords was also assessed by coimmmunoprecipation and double immunofluorescent staining.

RESULTS

The mRNA and protein for PSD-95 expression were significantly increased at 2 h or 8 h, and then gradually declined to the baseline level, ultimately up-regulated again from 5 days to 7 days for its mRNA level and at 7 days or 14 days for its protein level after either SCC or SCT. PSD-95 immunoreactivity was found in neurones, oligodendrocytes and synaptic puncta of spinal cord tissues within 5 mm from the lesion site. Importantly, injury-induced expression of PSD-95 was colabelled by active caspase-3 (apoptotic marker), Tau-1 (the marker for pathological oligodendrocytes) and nNOS.

CONCLUSIONS

Accompanied by the spatio-temporal changes for PSD-95 expression, the association between PSD-95 and nNOS undergoes substantial alteration after SCI. These two molecules are likely to form a complex on apoptotic neurones and pathological oligodendrocytes, which may in turn be involved in the secondary response after SCI.

Platelet integrin alpha(IIb)beta(3): activation mechanisms

Integrin alpha(IIb)beta(3) plays a critical role in platelet aggregation, a central response in hemostasis and thrombosis. This function of alpha(IIb)beta(3) depends upon a transition from a resting to an activated state such that it acquires the capacity to bind soluble ligands. Diverse platelet agonists alter the cytoplasmic domain of alpha(IIb)beta(3) and initiate a conformational change that traverses the transmembrane region and ultimately triggers rearrangements in the extracellular domain to permit ligand binding. The membrane-proximal regions of alpha(IIb) and beta(3) cytoplasmic tails, together with the transmembrane segments of the subunits, contact each other to form a complex which restrains the integrin in the resting state. It is unclasping of this complex that induces integrin activation. This clasping/unclasping process is influenced by multiple cytoplasmic tail binding partners. Among them, talin appears to be a critical trigger of alpha(IIb)beta(3) activation, but other binding partners, which function as activators or suppressors, are likely to act as co-regulators of integrin activation.

Clinical and molecular survey in 124 Chinese patients with Leigh or Leigh-like syndrome

Leigh syndrome is the most common mitochondrial disorder in children characterized by necrotic lesions in the central nervous system. Both mitochondrial DNA (mtDNA) and nuclear DNA defects in the mitochondrial respiratory chain can lead to this disease. To characterize the clinical and genetic traits of Leigh or Leigh-like syndrome patients in China, 124 unrelated cases were collected between 1992 and 2005. Seventy-seven cases (62.1%) met the typical criteria of Leigh syndrome, including symmetrical bilateral abnormal signals in the basal ganglia, thalamus and brain stem, etc. Other cases (37.9%) belonged to Leigh-like syndrome with atypical clinical or radiological manifestations. Late-onset patients accounted for 20.2%, which is more than previously reported. Movement disorder was the most common symptoms in our patients. Thirty-two patients (25.8%) were confirmed to carry mutant genes. Among them, six cases (4.8%) have been demonstrated to have point mutations in mitochondrial DNA. Two separate patients were detected to have mutations on A8344G and A3243G. The T8993G point mutation was identified in one patient and T8993C in one other patient. SURF1 mutations associated with cytochrome-c oxidase deficiency were identified in 25 patients (20.2%). Four unreported variations have been identified in SURF1 gene from three patients. G604C was found in 22 patients. Only one patient had C214T mutation in the pyruvate dehydrogenase E1alpha subunit gene. In the remaining 92 patients (74.2%), a specific molecular dysfunction or underlying metabolic abnormality could not be identified.

An adaptive framework using cluster-based hybrid architecture for enhancing collaboration in surgical simulation

Research on collaborative virtual surgery opens the opportunity for simulating the cooperative work during surgical operations. It is however a challenging task to design and implement a high performance collaborative surgical simulation system because of the difficulty in maintaining a high level of state consistency under limited network transmission capacity. In this paper, we present an adaptive framework using cluster-based hybrid architecture to support real-time collaboration in surgical simulation. In addition to the TCP communication protocol, the framework is also equipped with UDP for multicasting, allowing for a flexible strategy to reduce network latency. A set of techniques was proposed to assure reliable transmission on top of standard yet unreliable multicast protocols. Experimental results demonstrate that this framework can support collaborative surgical simulation with lower network latencies than traditional client-server architecture.

Oxidized phosphatidylcholine is a marker for neuroinflammation in multiple sclerosis brain

Multiple sclerosis (MS) is a common autoimmune neurodegenerative disease of unknown cause, which results in inflammation and plaques of demyelination in brain and eventual axonal degeneration. We report the novel presence of oxidized phosphatidylcholine [1-palmitoyl-2-(5'-oxo)valeryl-sn-glycero-3-phosphorylcholine (POVPC)], a lipid associated with inflammatory diseases such as atherosclerosis and lung disease, in the brain of MS patients. The OxPC epitope was detected by Western blotting with the E06 monoclonal antibody. E06-positive lipid was present in the highest amounts in MS plaques, which also showed evidence of low-molecular-weight (15-kDa) OxPC-modified protein. E06 reactivity did not change with post-mortem interval, and E06-positive lipids were largely absent from control tissue. We then used a second monoclonal antibody (AB1-2, which recognizes the E06/T15 idiotype and therefore detects the presence of antibody to OxPC) to show that MS brain samples were strongly positive for the 50-kDa antibody heavy chain. We also showed that isoelectric focussing of the oligoclonal IgG characteristic of MS revealed some immunoglobulin bands that Western blotted with the AB1-2 antibody. Spinal cords from mice induced to undergo experimental allergic encephalomyelitis (EAE) also showed strong AB1-2 reactivity by both immunocytochemistry and Western blot analysis. We therefore conclude that we can detect both OxPC and 15-kDa protein modified by OxPC and the antibody to the antibody to OxPC (antiidiotype) in pathological tissue and suggest that this could play a role in the progression of MS.

Unscheduled CDK1 activity in G1 phase of the cell cycle triggers apoptosis in X-irradiated lymphocytic leukemia cells

Cyclin-dependent kinase 1 (CDK1) is a major component of the cell cycle progression engine. Recently, several investigations provided evidence demonstrating that unscheduled CDK1 activation may also be involved in apoptosis in cancerous cells. In this article, we demonstrate that X-ray irradiation induced G1 arrest in MOLT-4 lymphocytic leukemia cells, the arrest being accompanied by reduction in the activity of CDK2, but increased CDK1 activity and cell apoptosis in the G1 phase. Interestingly, this increase in CDK1 and apoptosis by ionizing radiation was prevented by pretreatment with the CDK1 inhibitor, roscovitine, suggesting that CDK1 kinase activity is required for radiation-induced apoptotic cell death in this model system. Furthermore, cyclin B1 and CDK1 were detected co-localizing and associating in G1 phase MOLT-4 cells, with the cellular lysates from these cells revealing a genotoxic stress-induced increase in CDK1 phosphorylation (Thr-161) and dephosphorylation (Tyr-15), as analyzed by postsorting immunoprecipitation and immunoblotting. Finally, X-irradiation was found to increase Bcl-2 phosphorylation in G1 phase cells. Taken together, these novel findings suggest that CDK1 is activated by unscheduled accumulation of cyclin B1 in G1 phase cells exposed to X-ray, and that CDK1 activation, at the wrong time and in the wrong phase, may directly or indirectly trigger a Bcl-2-dependent signaling pathway leading to apoptotic cell death in MOLT-4 cells.

The involvement of chloroplast HSP100/ClpB in the acquired thermotolerance in tomato

The chloroplast HSP100/ClpB is a newly documented member of the ClpB family, but little was known about its role in imparting thermotolerance to cells. A cDNA coding for a HSP100/ClpB homolog has been cloned from Lycopersicon esculentum and termed as Lehsp100/ClpB (the cDNA sequence of Lehsp100/ClpB has been submitted to the GenBank database under accession number: AB219939). The protein encoded by the cDNA was most similar to the putative chloroplast HSP100/ClpBs in higher plants and the ClpB from Cyanobacterium Synechococcus sp. A 97 kDa protein, which matched the predicted size of mature LeHSP100/ClpB, was immunologically detected in chloroplast isolated from heat-treated tomato plants. In addition, the fusion protein, combining the transit sequence of LeHSP100/ClpB and GFP, was found to be located in chloroplast based on the observations of fluorescent microscope images. These results indicated the chloroplast-localization of LeHSP100/ClpB. Both the transcript and the protein of Lehsp100/ClpB were not detected under normal growth conditions, but they were induced by increasingly higher temperatures. An antisense Lehsp100/ClpB cDNA fragment was introduced into the tomato by Agrobacterium-mediated transformation. Antisense lines exhibited an extreme repression of heat-induced expression of Lehsp100/ClpB. The levels of chloroplast HSP60 and small HSP in antisense lines were identical to those of the control plants. After plants preconditioned at 38 degrees C for 2 h were exposed to a lethal heat shock at 46 degrees C for 2 h, the antisense lines were greatly impaired and withered in 21 days of the recovery phase, whereas the untransformed control plants and the vector-transformed plants survived. Furthermore, chlorophyll fluorescence measurements showed that PS II in antisense lines were more susceptible to the thermal irreversible inactivation than the untransformed and vector-transformed control plants. This work provides the first example that induction of chloroplast LeHSP100/ClpB contributes to the acquisition of thermotolerance in higher plants.

Inhibition of phosphorylation of p38 MAPK involved in the protection of nephropathy by emodin in diabetic rats

To explore the protection of emodin on renal dysfunction in the streptozotocin-induced diabetic rats with nephropathy and the role of p38 mitogen-activated protein kinase (p38 MAPK) signal transduction pathway in this protection. 30 male Spraque-Dawley rats were randomly divided into control group, model group and emodin group. The rats in the model group and emodin group were administered with streptozotocin (60 mg/kg) to induce diabetes. 40 mg/kg/day of emodin were orally given to the rats in emodin group. The rats in other groups were only given solvent. Biochemical index were analysed by oxidase and oxidase dynamical enzyme method. Glomerular area and volume were determined quantitatively by using Image Analysis System. Western blotting and immunohistochemical staining was used to detect the total p38 MAPK, phosphorylated p38 MAPK, phosphorylated cAMP response element binding protein (CREB) and fibronectin. The average kidney weight/body weight, glomerular area, glomerular volume and all biochemical indexes significantly increased in model group as compared to the control group (P<0.05), while the average body weight decreased. The expressions of phosphorylaed p38 MAPK, phosphorylated CREB and fibronectin increased by 1.98-fold, 1.94-fold and 1.96-fold respectively in model group compared with those in the control group (P<0.05). Emodin markedly decreased the average kidney weight/body weight, glomerular area, glomerular volume and all biochemical indexes (P<0.05), having a weak action on the level of blood glucose. The expressions of phosphorylated p38 MAPK, phosphorylated CREB and fibronectin also significantly downregulated in emodin group compared with those in model group (P<0.05). Emodin was efficient to ameliorate renal dysfunction in diabetic nephropathy rats probably by its inhibition of the activation of p38 MAPK pathway and downregulation of the expression of fibronectin.

On Methods for Gene Function Scoring as a Means of Facilitating the Interpretation of Microarray Results

As gene annotation databases continue to evolve and improve, it has become feasible to incorporate the functional and pathway information about genes, available in these databases into the analysis of gene expression data, for a better understanding of the underlying mechanisms. A few methods have been proposed in the literature to formally convert individual gene results into gene function results. In this paper, we will compare the various methods, propose and examine some new ones, and offer a structured approach to incorporating gene function or pathway information into the analysis of expression data. We study the performance of the various methods and also compare them on real data, using a case study from the toxicogenomics area. Our results show that the approaches based on gene function scores yield a different, and functionally more interpretable, array of genes than methods that rely solely on individual gene scores. They also suggest that functional class scoring methods appear to perform better and more consistently than overrepresentation analysis and distributional score methods.

Regulator of G-protein signaling 2 (RGS2) inhibits androgen-independent activation of androgen receptor in prostate cancer cells

Hormones acting through G protein-coupled receptors (GPCRs) can cause androgen-independent activation of androgen receptor (AR) in prostate cancer cells. Regulators of G-protein signaling (RGS) proteins, through their GTPase activating protein (GAP) activities, inhibit GPCR-mediated signaling by inactivating G proteins. Here, we identified RGS2 as a gene specifically downregulated in androgen-independent prostate cancer cells. Expression of RGS2, but not other RGS proteins, abolished androgen-independent AR activity in androgen-independent LNCaP cells and CWR22Rv1 cells. In LNCaP cells, RGS2 inhibited G(q)-coupled GPCR signaling. Expression of exogenous wild-type RGS2, but not its GAP-deficient mutant, significantly reduced AR activation by constitutively activated G(q)Q209L mutant whereas silencing endogenous RGS2 by siRNA enhanced G(q)Q209L-stimulated AR activity. RGS2 had no effect on RGS-insensitive G(q)Q209L/G188S-induced AR activation. Furthermore, extracellular signal-regulated kinase 1/2 (ERK1/2) was found to be involved in RGS2-mediated regulation of androgen-independent AR activity. In addition, RGS2 functioned as a growth suppressor for androgen-independent LNCaP cells whereas androgen-sensitive LNCaP cells with RGS2 silencing had a growth advantage under steroid-reduced conditions. Finally, RGS2 expression level was significantly decreased in human prostate tumor specimens. Taken together, our results suggest RGS2 as a novel regulator of AR signaling and its repression may be an important step during prostate tumorigenesis and progression.

Methyl dynamics for understanding hydrophobic core packing of dynamically different motifs of double-stranded RNA binding domain of protein kinase R

Double-stranded RNA binding domains of human protein kinase R (dsRBD-PKR) regulate distinct cellular functions and the fate of an RNA molecule in the cell. This highly homologous domains present in multiple copies in a number of species, exhibit individual and specific functional specificity. Number of NMR and X-ray crystallographic structural studies reveals that such domains take a common alpha-beta-beta-beta-alpha tertiary fold. However, the functional specificities of these domains could be due to the dynamics of the individual amino acid residues, as has been shown earlier in the case of backbone dynamics of 15N-1H of dsRNA binding motifs (dsRBMs) of human protein kinase R (PKR) (Nanduri S, Rahman F, Williams BRG, Qin J. EMBO J 2000;19:5567-5574). To further investigate if the differences in dynamics of the two dsRBMs are restricted to only backbone, or if the side-chain motions are also different to the extent of influencing their packing of the two hydrophobic cores, we have investigated the methyl group dynamics using 13C-methyl relaxation measurements. The results show that the hydrophobic core of dsRBM1 is more tightly packed than dsRBM2, and it seems to undergo less fast scale motions in the subnanosecond regime.

Microarray analysis of gene expression following the formalin test in the infant rat☆

Injury and pain experienced by the infant results in immediate changes in pain sensitivity that last into adulthood. These long-term changes are likely initiated by altered gene expression. Here we measured how injury alters gene expression in the lumbar spinal cord early and late in the preweaning period of the rat. The expression of large numbers of genes was altered significantly at 3 days of age, when injury has long-term consequences. The functional classes of altered genes included transcription factors, cell death related and metal ion genes. The intensity of the stimulus in the 3-day-old pups induced changes in different classes of genes. Fewer changes were noted at 21 days of age. The increased expression of transcription factors and decreased expression of genes whose products are protective against cell death are hypothesized to underlie the long-term changes that are seen after injury in the neonate.

Hematopoietic stem cell mobilization with intravenous melphalan and G-CSF in patients with chemoresponsive multiple myeloma: report of a phase II trial

Multiple myeloma (MM) is an incurable hematologic malignancy for which autologous hematopoietic stem cell transplantation (HCT) is a standard therapy. The optimal method of stem cell mobilization is not defined. We evaluated intravenous melphalan (60 mg/m2), the most effective agent for MM, and G-CSF (10 microg/kg/day) for mobilization. End points were safety, adequacy of CD34+ collections, MM response, and contamination of stem cell components (SCC). In total, 32 patients were mobilized. There were no deaths or significant bleeding episodes; 14 patients (44%) required hospitalization for neutropenic fever. Median days of grade 3 or 4 neutropenia or thrombocytopenia were 7 (2-20) and 8 (3-17). Median mobilization days, CD34+ cells/kg and total leukaphereses were 16 (12-30), 12.1 million (2.6-52.8), and 2 (1-5) respectively. Four patients (12.5 %) failed to achieve the target of 4 million CD34+ cells/kg in five leukaphereses. Reduction in myeloma was seen in 11 patients (34%) with 3 (9%) achieving complete response; 15 (47%) maintained prior responses. Estimated MM contamination per SCC (N=48) was 0.0009% (range 0-0.1) and 0.21 x 10(4) cells per kg (range 0-41.2). Increased contamination was associated with increased patient age. This strategy for mobilization is feasible, frequently requires hospitalization and transfusion, and controls disease in most patients.