Protein-Ligand Identification and In Vitro Inhibitory Effects of Cathine on 11 Major Human Drug Metabolizing Cytochrome P450s.

Cathine is the stable form of cathinone, the major active compound found in khat (Catha edulis Forsk) plant. Khat was found to inhibit major phase I drug metabolizing cytochrome P450 (CYP) enzyme activities in vitro and in vivo. With the upsurge of khat consumption and the potential use of cathine to combat obesity, efforts should be channelled into understanding potential cathine-drug interactions, which have been rather limited. The present study aimed to assess CYPs activity and inhibition by cathine in a high-throughput in vitro fluorescence-based enzyme assay and molecular docking analysis to identify how cathine interacts within various CYPs' active sites. The half maximal inhibitory concentration (IC50) values of cathine determined for CYP2A6 and CYP3A4 were 80 and 90 µM, while CYP1A2, CYP2B6, CYP2C8, CYP2C9, CYP2C19, CYP2D6, CYP2E1, CYP2J2 and CYP3A5 showed no significant inhibition. Furthermore, in Ki analysis, the Lineweaver-Burk plots depicted non-competitive mixed inhibition of cathine on both CYP2A6 and CYP3A4 with Ki value of 63 and 100 µM, respectively. Cathine showed negligible time-dependent inhibition on CYPs. Further, molecular docking studies showed that cathine was bound to CYP2A6 via hydrophobic, hydrogen and π-stacking interactions and formed hydrophobic and hydrogen bonds with active site residues in CYP3A4. Both molecular docking prediction and in vitro outcome are in agreement, granting more detailed insights for predicting CYPs metabolism besides the possible cathine-drug interactions. Cathine-drug interactions may occur with concomitant consumption of khat or cathine-containing products with medications metabolized by CYP2A6 and CYP3A4.

A Deep Reinforcement Learning-Based MPPT Control for PV Systems under Partial Shading Condition.

On the issues of global environment protection, the renewable energy systems have been widely considered. The photovoltaic (PV) system converts solar power into electricity and significantly reduces the consumption of fossil fuels from environment pollution. Besides introducing new materials for the solar cells to improve the energy conversion efficiency, the maximum power point tracking (MPPT) algorithms have been developed to ensure the efficient operation of PV systems at the maximum power point (MPP) under various weather conditions. The integration of reinforcement learning and deep learning, named deep reinforcement learning (DRL), is proposed in this paper as a future tool to deal with the optimization control problems. Following the success of deep reinforcement learning (DRL) in several fields, the deep Q network (DQN) and deep deterministic policy gradient (DDPG) are proposed to harvest the MPP in PV systems, especially under a partial shading condition (PSC). Different from the reinforcement learning (RL)-based method, which is only operated with discrete state and action spaces, the methods adopted in this paper are used to deal with continuous state spaces. In this study,DQN solves the problem with discrete action spaces, while DDPG handles the continuous action spaces. The proposed methods are simulated in MATLAB/Simulink for feasibility analysis. Further tests under various input conditions with comparisons to the classical Perturb and observe (P&O) MPPT method are carried out for validation. Based on the simulation results in this study, the performance of the proposed methods is outstanding and efficient, showing its potential for further applications.

Tetraploid/near-tetraploid acute promyelocytic leukaemia with double (15;17) translocation.

A 57-year-old man presented with intermittent fever and bleeding following dental surgery. Peripheral smear and bone marrow aspirate exhibited unusually large and bizarre-looking abnormal cells which were found to be myeloblasts with aberrant CD56 and CD2 expression on immunophenotyping. Fluorescence in situ hybridization analysis revealed an extra RARA gene rearrangement. This finding correlated well with a near-tetraploid karyotype with double t(15;17)(q22;q21). Bcr-3 type PML/ RARA copies were identified in reverse transcriptase-polymerase chain reaction. The diagnosis of near-tetraploid acute promyelocytic leukaemia (APML) was established. The patient was treated with all-trans retinoic acid and idarubicin and six weeks later achieved complete remission. Tetraploid/ near-tetraploid APML is exceedingly rare. It is a distinct cytogenetic subgroup with unique clinical and biological features as highlighted by atypical morphology, frequent CD2 expression and association with the bcr-3 type PML/RARA fusion transcripts. Early recognition of this rare entity is essential for timely and appropriate treatment.

Anxiety and depression in patients with haematological neoplasms in Malaysia.

BACKGROUND: It is not uncommon that anxiety and depression occur in patients with cancers, and past researches have shown that the quality of life of patients is negatively affected. This study aims to determine the prevalence of anxiety and depression of patients with haematological cancers in Malaysia and to investigate the possible association of these psychological symptoms with their quality of life. METHODS: This is a cross-sectional study where patients with haematological cancers attending two major hospitals were recruited. Anxiety and depression symptoms were assessed using the Hospital Anxiety and Depression scale (HADS). Quality of life (QoL) of these patients was measured using the European Organisation for Research and Treatment of Cancer quality of life questionnaire (EORTC QLQ C30). An overall summary QoL score in combination with financial difficulty score and global health score were used for analysis. RESULTS: A total of 319 patients were recruited. Thirty-three percent of patients had anxiety symptoms, 23.5% had depression symptoms. In summary the overall score of QoL is significantly lower in patients with higher scores for depression and anxiety, (p<0.05). Patients who exhibit anxiety symptoms were more frequently female, still undergoing treatment whereas patients who had higher depression scores were older and had acute leukemias or myeloproliferative neoplasms. Patients who have depression are significantly associated with a higher financial difficulty score, p<0.05. CONCLUSION: The poor quality of life in patients who have anxiety and depression should raise awareness amongst the health professions treating them so that additional support can be provided.

A new complex translocation (8;22;21)(q22;q12;q22) in RUNX1/RUNX1T1 acute myeloid leukaemia.

INTRODUCTION: Acute myeloid leukaemia (AML) with t(8;21)(q22;q22) producing RUNX1-RUNX1T1 rearrangement is a distinct sub-type which is usually associated with a favourable clinical outcome. Variant forms of t(8;21) are rare. Herein we describe a novel variant of t(8;21) AML in a 25-year-old pregnant woman who presented with intermittent fever. CASE REPORT: Her peripheral smear and bone marrow aspirate showed many myeloblasts. Chromosomal study revealed t(8;22;21)(q22;q12;q22) and loss of X chromosome. Fluorescence in situ hybridization (FISH) using whole chromosome painting probes confirmed the three-way translocation involving chromosomes 8, 21 and 22. RUNX1-RUNX1T1 rearrangement was identified in FISH and reverse transcriptase polymerase chain reaction confirming the diagnosis of AML with variant t(8;21). The patient was treated with standard chemotherapy. She achieved morphological remission one month after induction chemotherapy. DISCUSSION: Although the clinical significance of variant t(8;21) is not well delineated, the evaluation of 31 such cases suggests patients with variant t(8;21) have similar prognosis to those with classical t(8;21).

Influence of genetic polymorphisms of cytokine genes in the outcome of HLA-matched allogeneic stem cell transplantation in a South East Asian population.

Non-HLA gene polymorphisms have been shown to be associated with the risk of graft-versus-host disease (GVHD) and outcome of allogeneic haematopoietic stem cell transplantation (AHSCT). This study aims to investigate the role of IL6, TNFα, IL10, IL2 and IL12 gene polymorphisms in the outcome of AHSCT in a South East Asian population. A total of 67 patients and 59 donors who underwent HLA-identical matched sibling AHSCT were available for analysis. There was no significant association between the different cytokine genotypes of patients with the incidence and severity of acute GVHD. Patients with IL2 166∗T allele and patients who received donor stem cells who had IL2 166∗G allele appeared to have reduced incidence of cGVHD. Patients who received donor stem cells with IL12 1188∗C allele are found to be associated with better disease free survival. These results suggest a possible role of IL2 and IL12 gene polymorphisms in the outcome of AHSCT in a South East Asian population.

Enteropathy-associated T-cell lymphoma: An extremely rare cause of chronic diarrhoea.

Chronic diarrhoea in tropical countries may be due to a myriad of causes from infective to non-infective. This case report illustrates the challenges faced in the investigation of a middle-age Chinese gentleman who presented with chronic diarrhoea and weight loss. The diagnosis of type II enteropathy-associated T-cell lymphoma (EATL) was finally made. The diagnosis of EATL was least suspected as the condition is almost unheard of in this part of the world. The epidemiology, presentation, diagnosis, management and prognosis of this rare condition are discussed.

Complementary and alternative medicine use in patients with hematological cancers in Malaysia.

BACKGROUND: Complementary and alternative medicine (CAM) is often used by cancer patients, but not many studies had been published on the prevalence of CAM use in patients with hematological cancers. This study aims to determine the prevalence of CAM and type of CAM used in this group of patients in a multiracial and multicultural country. PATIENTS AND METHODS: This is a cross-sectional survey carried out in two hospitals in Malaysia. Patients with underlying hematological cancers were asked to complete the questionnaires on CAM and the Hospital Anxiety and Depression Scale. RESULTS: A total of 245 patients participated. The prevalence of CAM use was 70.2 %. The most common types of CAM used are biological-based therapies (90.2 %) and mind-body interventions (42 %). Vitamin and diet supplements (68.6 %) and folk/herb remedies (58 %) are the most common biological-based therapies used. There is no significant association of CAM use with age, gender, education level, and household income. Female patients are more likely to use more than one CAM therapies. The most common reason reported for CAM use was to boost immunity (57 %) and cure (24 %). Majority of patients (65 %) felt CAM was effective, and 60 % did not inform their physicians regarding CAM usage. CONCLUSION: In view of the high prevalence of CAM use in patients with hematological cancers, it is important that the physicians play an active role in seeking information from patients and to monitor possible drug-vitamin-herbal interactions.

Safety of elective laparoscopic cholecystectomy in patients on dialysis: an analysis of the ACS NSQIP database.

BACKGROUND: Laparoscopic cholecystectomy (LC) remains one of the most frequently performed surgical procedures. The safety of LC in patients with renal disease is unclear. The postoperative outcomes of elective LC in patients on dialysis were studied and risk factors associated with longer length of stay and mortality were sought. METHODS: Patients who underwent LC between the dates of 1 January 2007 and 31 December 2010 at all hospitals in North America participating in the American College of Surgeons National Surgical Quality Improvement Project were reviewed. Data from 80,995 patients were collected, and the patients on dialysis (N = 512) were separated and compared with those of patients not on dialysis (N = 80,483). RESULTS: Postoperative complications for patients on and not on dialysis, respectively, included mortality (4.1 vs. 0.2%, p < 0.001), myocardial infarction (0.8 vs. 0.1%, p = 0.002), pneumonia (2.3 vs. 0.4%, p < 0.001), sepsis (3.1 vs. 0.4%, p < 0.001), and return to operating room (4.3 vs. 1.0%, p < 0.001). In patients on dialysis, multivariate analysis was used to identify risk factors, including congestive heart failure and prior cardiac surgery as significant independent predictors of longer length of stay and mortality. CONCLUSION: Patients on dialysis who undergo LC should be carefully selected due to the significantly higher complication and mortality rate. Several predictors of longer length of stay and mortality were identified that can determine which patients on dialysis are good candidates for LC.

Resource-Efficient Neural Network Architectures for Classifying Nerve Cuff Recordings on Implantable Devices.

BACKGROUND: Closed-loop functional electrical stimulation can use recorded nerve signals to create implantable systems that make decisions regarding nerve stimulation in real-time. Previous work demonstrated convolutional neural network (CNN) discrimination of activity from different neural pathways recorded by a high-density multi-contact nerve cuff electrode, achieving state-of-the-art performance but requiring too much data storage and power for a practical implementation on surgically implanted hardware. OBJECTIVE: To reduce resource utilization for an implantable implementation, with minimal performance loss for CNNs that can discriminate between neural pathways in multi-contact cuff electrode recordings. METHODS: Neural networks (NNs) were evaluated using rat sciatic nerve recordings previously collected using 56-channel cuff electrodes to capture spatiotemporal neural activity patterns. NNs were trained to classify individual, natural compound action potentials (nCAPs) elicited by sensory stimuli. Three architectures were explored: the previously reported ESCAPE-NET, a fully convolutional network, and a recurrent neural network. Variations of each architecture were evaluated based on F1-score, number of weights, and floating-point operations (FLOPs). RESULTS: NNs were identified that, when compared to ESCAPE-NET, require 1,132-1,787x fewer weights, 389-995x less memory, and 6-11,073x fewer FLOPs, while maintaining macro F1-scores of 0.70-0.71 compared to a baseline of 0.75. Memory requirements range from 22.69 KB to 58.11 KB, falling within on-chip memory sizes from published deep learning accelerators fabricated in ASIC technology. CONCLUSION: Reduced versions of ESCAPE-NET require significantly fewer resources without significant accuracy loss, thus can be more easily incorporated into a surgically implantable device that performs closed-loop responsive neural stimulation.

Closed-Loop Control of Functional Electrical Stimulation Using a Selectively Recording and Bidirectional Nerve Cuff Interface.

Discriminating recorded afferent neural information can provide sensory feedback for closed-loop control of functional electrical stimulation, which restores movement to paralyzed limbs. Previous work achieved state-of-the-art off-line classification of electrical activity in different neural pathways recorded by a multi-contact nerve cuff electrode, by applying deep learning to spatiotemporal neural patterns. The objective of this study was to demonstrate the feasibility of this approach in the context of closed-loop stimulation. Acute in vivo experiments were conducted on 11 Long Evans rats to demonstrate closed-loop stimulation. A 64-channel ( 8×8 ) nerve cuff electrode was implanted on each rat's sciatic nerve for recording and stimulation. A convolutional neural network (CNN) was trained with spatiotemporal signal recordings associated with 3 different states of the hindpaw (dorsiflexion, plantarflexion, and pricking of the heel). After training, firing rates were reconstructed from the classifier outputs for each of the three target classes. A rule-based closed-loop controller was implemented to produce ankle movement trajectories using neural stimulation, based on the classified nerve recordings. Closed-loop stimulation was successfully demonstrated in 6 subjects. The number of successful movement sequence trials per subject ranged from 1-17 and number of correct state transitions per trial ranged from 3-53. This work demonstrates that a CNN applied to multi-contact nerve cuff recordings can be used for closed-loop control of functional electrical stimulation.

Helicobacter pylori infection in chronic immune thrombocytopenic purpura patients in Malaysia.

INTRODUCTION: Helicobacter Pylori has been implicated with a possible link to immune thrombocytopenia purpura (ITP) and studies have shown contradicting results in platelet recovery after eradication of H pylori infection. OBJECTIVES: To determine the prevalence of H pylori infection in adult ITP patients in Malaysia and to examine the effect of eradication of H pylori infection in these patients. METHOD: 50 ITP adult patients from haematology clinics were recruited. A 13C urea breath test for H. pylori infection was performed in all patients. Those with H. pylori infection were treated with standard eradication regimen. Platelet counts were monitored regularly after eradication therapy to assess response. Complete response (CR) was defined as the achievement of platelet counts of >150x10(9)/L within 3 months after eradication therapy and partial response (PR) was defined as platelet count above 50x10(9)/L and/or at least doubling the baseline count. RESULT: The median age of patients recruited was 50 years. The majority of patients were female (76%). Chinese was the largest ethnic groups (56%) followed by Malays (28%) and Indians (16%). 11 of the 50 patients (22%) were found to have H. pylori infection and all but one had eradication therapy. Overall, some response was observed in 3 patients (30%) with a CR seen in 2 patients and PR in one patient. However, all these patients had a drop in their platelet counts at 6th month follow up. CONCLUSION: The prevalence of H. pylori infection is relatively low in our adult ITP patients (22%) and by eradicating the infection did not have any sustained effect in the platelet recovery.

Antioxidant intake from diet and supplements and elevated serum C-reactive protein and plasma homocysteine concentrations in US adults: a cross-sectional study.

OBJECTIVE: To investigate the association of antioxidant intakes from diet and supplements with elevated blood C-reactive protein (CRP) and homocysteine (Hcy) concentrations. DESIGN: A cross-sectional study. The main exposures were vitamins C and E, carotene, flavonoid and Se intakes from diet and supplements. Elevated blood CRP and Hcy concentrations were the outcome measures. SETTING: The US population and its subgroups. SUBJECTS: We included 8335 US adults aged ≥19 years from the National Health and Nutrition Examination Survey 1999-2002. RESULTS: In this US population, the mean serum CRP concentration was 4·14 (95 % CI 3·91, 4·37) mg/l. Intakes of vitamins C and E and carotene were inversely associated with the probability of having serum CRP concentrations >3 mg/l in multivariate logistic regression models. Flavonoid and Se intakes were not associated with the odds of elevated serum CRP concentrations. The mean plasma Hcy concentration was 8·61 (95 % CI 8·48, 8·74) µmol/l. Intakes of vitamins C, E, carotenes and Se were inversely associated with the odds of plasma Hcy concentrations >13 µmol/l after adjusting for covariates. Flavonoid intake was not associated with the chance of elevated plasma Hcy concentrations. CONCLUSIONS: These results suggest that high antioxidant intake is associated with lower blood concentrations of CRP and Hcy. These inverse associations may be among the potential mechanisms for the beneficial effect of antioxidant intake on CVD risk mediators in observational studies.

Tsukamurella tyrosinosolvens intravascular catheter-related bacteremia in a haematology patient: a case report.

Tsukamurella spp. are a rare but important cause of intravascular catheter-related bacteremia in immunocompromised patients. The organism is an aerobic, Gram-positive, weakly acid-fast bacillus that is difficult to differentiate using standard laboratory methods from other aerobic actinomycetales such as Nocardia spp., Rhododoccus spp., Gordonia spp., and the rapid growing Mycobacterium spp. We report a case of Tsukamurella tyrosinosolvens catheter-related bacteremia in a 51-year-old haematology patient who responded to treatment with imipenem and subsequent line removal. 16srRNA sequencing allowed for the prompt identification of this organism.

Quality of life after haematopoietic stem cell transplantation in a multiracial population.

Haematopoietic stem cell transplantation (HSCT) was started in Malaysia since 1993 and it has improved the survival of patients with otherwise fatal haematological diseases. This study was initiated because quality of life of these survivors is an important tool in assessing the outcome of this treatment modality. The secondary objective was to identify factors that influenced their quality of life. The European Organization of Research and Treatment of Cancer Quality of Life Questionnaire (EORTC-30) was used to assess the quality of life of eligible patients. A total of 62 patents were recruited. The mean global health score (QoL) was 71.2. The major symptoms faced by our patients were fatigue, financial difficulty and appetite loss. Appetite loss was an independent adverse factor for lower QoL.

Reduction of an incarcerated, prolapsed ileostomy with the assistance of sugar as a desiccant.

Prolapse is a well-described complication after ileostomy or colostomy, and is typically asymptomatic and easily reduced. Acute incarceration of a prolapsed stoma is a rare event, however. A patient presented with an incarcerated, prolapsed ileostomy causing small bowel obstruction and stomal ischemia. Successful reduction was performed with the assistance of sugar as a desiccant. Incarceration of a prolapsed ileostomy is highly atypical, but can be approached in a similar manner to an incarcerated rectal prolapse. Successful reduction can prevent an emergent operation, allowing for medical optimization and elective surgical treatment if necessary.

Matching of calcineurin activity to upstream effectors is critical for skeletal muscle fiber growth.

Calcineurin-dependent pathways have been implicated in the hypertrophic response of skeletal muscle to functional overload (OV) (Dunn, S.E., J.L. Burns, and R.N. Michel. 1999. J. Biol. Chem. 274:21908-21912). Here we show that skeletal muscles overexpressing an activated form of calcineurin (CnA*) exhibit a phenotype indistinguishable from wild-type counterparts under normal weightbearing conditions and respond to OV with a similar doubling in cell size and slow fiber number. These adaptations occurred despite the fact that CnA* muscles displayed threefold higher calcineurin activity and enhanced dephosphorylation of the calcineurin targets NFATc1, MEF2A, and MEF2D. Moreover, when calcineurin signaling is compromised with cyclosporin A, muscles from OV wild-type mice display a lower molecular weight form of CnA, originally detected in failing hearts, whereas CnA* muscles are spared this manifestation. We also show that OV-induced growth and type transformations are prevented in muscle fibers of transgenic mice overexpressing a peptide that inhibits calmodulin from signaling to target enzymes. Taken together, these findings provide evidence that both calcineurin and its activity-linked upstream signaling elements are crucial for muscle adaptations to OV and that, unless significantly compromised, endogenous levels of this enzyme can accommodate large fluctuations in upstream calcium-dependent signaling events.

Microtubule dynamics from mating through the first zygotic division in the budding yeast Saccharomyces cerevisiae.

We have used time-lapse digital imaging microscopy to examine cytoplasmic astral microtubules (Mts) and spindle dynamics during the mating pathway in budding yeast Saccharomyces cerevisiae. Mating begins when two cells of opposite mating type come into proximity. The cells arrest in the G1 phase of the cell cycle and grow a projection towards one another forming a shmoo projection. Imaging of microtubule dynamics with green fluorescent protein (GFP) fusions to dynein or tubulin revealed that the nucleus and spindle pole body (SPB) became oriented and tethered to the shmoo tip by a Mt-dependent search and capture mechanism. Dynamically unstable astral Mts were captured at the shmoo tip forming a bundle of three or four astral Mts. This bundle changed length as the tethered nucleus and SPB oscillated toward and away from the shmoo tip at growth and shortening velocities typical of free plus end astral Mts (approximately 0.5 micrometer/min). Fluorescent fiduciary marks in Mt bundles showed that Mt growth and shortening occurred primarily at the shmoo tip, not the SPB. This indicates that Mt plus end assembly/disassembly was coupled to pushing and pulling of the nucleus. Upon cell fusion, a fluorescent bar of Mts was formed between the two shmoo tip bundles, which slowly shortened (0.23 +/- 0.07 micrometer/min) as the two nuclei and their SPBs came together and fused (karyogamy). Bud emergence occurred adjacent to the fused SPB approximately 30 min after SPB fusion. During the first mitosis, the SPBs separated as the spindle elongated at a constant velocity (0.75 micrometer/min) into the zygotic bud. There was no indication of a temporal delay at the 2-micrometer stage of spindle morphogenesis or a lag in Mt nucleation by replicated SPBs as occurs in vegetative mitosis implying a lack of normal checkpoints. Thus, the shmoo tip appears to be a new model system for studying Mt plus end dynamic attachments and much like higher eukaryotes, the first mitosis after haploid cell fusion in budding yeast may forgo cell cycle checkpoints present in vegetative mitosis.

Analysis of dose perturbation factors of a NACP-02 ionization chamber in clinical electron beams.

For well-guarded plane-parallel ionization chambers, international dosimetry protocols recommend a value of unity for electron perturbation factors in water. However, recent data published by various groups have challenged this. Specifically for the NACP-02 chamber, non-unity electron perturbation factors have already been published by Verhaegen et al (2006 Phys. Med. Biol. 51 1221-35) and Buckley and Rogers (2006 Med. Phys. 33 1788-96). Recently it was found that the mass thickness of the front chamber window can be 35% greater than is listed in the IAEA's TRS-398 absorbed dose protocol (Chin et al 2008 Phys. Med. Biol. 53 N119-26). This study therefore recalculated NACP-02 electron perturbation correction factors for energies 4-18 MeV at depths z(ref) and R(50) to determine the effect of the chamber model change. Results showed that perturbation factors at z(ref) are fairly stable for similar chamber models but become highly sensitive to small changes at deeper depths. The results also showed some dependence on using 1 keV versus 10 keV for the transport cut-off. Additional investigations revealed that the wall perturbation factor, p(wall), is strongly influenced by the chamber back wall at z(ref) and at larger depths small changes in the positioning of the effective point of measurement cause large fluctuations in the final value. Finally, the cavity perturbation factor, p(cav), was found to be primarily influenced by electron backscatter.

Defects in sarcolemma repair and skeletal muscle function after injury in a mouse model of Niemann-Pick type A/B disease.

BACKGROUND: Niemann-Pick disease type A (NPDA), a disease caused by mutations in acid sphingomyelinase (ASM), involves severe neurodegeneration and early death. Intracellular lipid accumulation and plasma membrane alterations are implicated in the pathology. ASM is also linked to the mechanism of plasma membrane repair, so we investigated the impact of ASM deficiency in skeletal muscle, a tissue that undergoes frequent cycles of injury and repair in vivo. METHODS: Utilizing the NPDA/B mouse model ASM-/- and wild type (WT) littermates, we performed excitation-contraction coupling/Ca2+ mobilization and sarcolemma injury/repair assays with isolated flexor digitorum brevis fibers, proteomic analyses with quadriceps femoris, flexor digitorum brevis, and tibialis posterior muscle and in vivo tests of the contractile force (maximal isometric torque) of the quadriceps femoris muscle before and after eccentric contraction-induced muscle injury. RESULTS: ASM-/- flexor digitorum brevis fibers showed impaired excitation-contraction coupling compared to WT, a defect expressed as reduced tetanic [Ca2+]i in response to electrical stimulation and early failure in sustaining [Ca2+]i during repeated tetanic contractions. When injured mechanically by needle passage, ASM-/- flexor digitorum brevis fibers showed susceptibility to injury similar to WT, but a reduced ability to reseal the sarcolemma. Proteomic analyses revealed changes in a small group of skeletal muscle proteins as a consequence of ASM deficiency, with downregulation of calsequestrin occurring in the three different muscles analyzed. In vivo, the loss in maximal isometric torque of WT quadriceps femoris was similar immediately after and 2 min after injury. The loss in ASM-/- mice immediately after injury was similar to WT, but was markedly larger at 2 min after injury. CONCLUSIONS: Skeletal muscle fibers from ASM-/- mice have an impairment in intracellular Ca2+ handling that results in reduced Ca2+ mobilization and a more rapid decline in peak Ca2+ transients during repeated contraction-relaxation cycles. Isolated fibers show reduced ability to repair damage to the sarcolemma, and this is associated with an exaggerated deficit in force during recovery from an in vivo eccentric contraction-induced muscle injury. Our findings uncover the possibility that skeletal muscle functional defects may play a role in the pathology of NPDA/B disease.