Your browser doesn't support javascript.
loading
Show: 20 | 50 | 100
Results 1 - 20 de 85
Filter
1.
Article in English | MEDLINE | ID: mdl-38574876

ABSTRACT

BACKGROUND: Palliative care (PC) benefits patients with amyotrophic lateral sclerosis (ALS), however the needs of patients and caregivers and the optimal timing of PC discussions remains unclear. This study reports the analysis of PC consult notes from a larger feasibility trial. The specific aims of this analysis were to i) identify the PC needs of patients with ALS via qualitative analysis and ii) identify characteristics of patients and caregivers that could predict specific PC needs. METHODS: This study was nested within a nonrandomized, prospective study of patients with ALS (and their caregivers) being treated at a multidisciplinary ALS clinic. Exclusion criteria of the main study were age <18 years, inability to complete questionnaires, and prior receipt of PC. All patients were offered a PC consultation (PCC); those who accepted were included in this nested study. Consultation notes were reviewed and thematic and content analyses were conducted. The occurrence of themes across patient and caregiver contextual variables were examined. RESULTS: Thirty-two PCCs were completed between October 2020 and April 2022. Six major themes were identified: PC roles (with subthemes encompassing the spectrum of specialist PC practice including symptom management and advance care planning), engagement with PC, patients' concerns for their caregivers, caregiver-specific concerns, finances, and COVID-19. An average of 12 topics were discussed per PCC (range = 3-22). Discussion of advance care planning, care coordination, and symptom management was common, and these topics were not discussed more frequently in PCCs with patients with lower functional status, more bulbar symptoms, or lower quality of life. Time from diagnosis did not impact topics of discussion. Patients reporting more symptoms of depression more frequently required psychological support, particularly regarding loss of independence, employment, and leisure activities. DISCUSSION: Patients with ALS and their caregivers have a wide range of PC needs. These needs vary irrespective of time from diagnosis, functional status, or quality of life, therefore PCC is recommended for all patients with ALS. PCC should be individualized based on patient and caregiver preferences. TRIAL REGISTRATION INFORMATION: The study was registered with ClinicalTrials.gov (NCT04257760; https://clinicaltrials.gov/ct2/show/NCT04257760) on February 6, 2020. The first enrollment occurred on October 20, 2020.

2.
J Neurol Sci ; 457: 122864, 2024 Feb 15.
Article in English | MEDLINE | ID: mdl-38185014

ABSTRACT

Congenital myopathy with tremor (MYOTREM) is a recently described disorder characterized by mild myopathy and a postural and intention tremor present since early infancy. MYOTREM is associated with pathogenic variants in MYBPC1 which encodes slow myosin-binding protein C, a sarcomere protein with regulatory and structural roles. Here, we describe a family with three generations of variably affected members exhibiting a novel variant in MYBPC1 (c.656 T > C, p.Leu219Pro). Among the unique features of affected family members is the persistence of tremor in sleep. We also present the first muscle magnetic resonance images for this disorder, and report muscle atrophy and fatty infiltration.


Subject(s)
Muscular Diseases , Tremor , Humans , Family , Mutation/genetics , Tremor/diagnostic imaging , Tremor/genetics
3.
Neuromuscul Disord ; 33(11): 824-834, 2023 Nov.
Article in English | MEDLINE | ID: mdl-37926637

ABSTRACT

Oculopharyngeal muscular dystrophy (OPMD) is a rare, primarily autosomal dominant, late onset muscular dystrophy commonly presenting with ptosis, dysphagia, and subsequent weakness of proximal muscles. Although OPMD diagnosis can be confirmed with high confidence by genetic testing, the slow progression of OPMD poses a significant challenge to clinical monitoring and a barrier to assessing the efficacy of treatments during clinical trials. Accordingly, there is a pressing need for more sensitive measures of OPMD progression, particularly those which do not require a muscle biopsy. This review provides an overview of progress in OPMD biomarkers from clinical assessment, quantitative imaging, histological assessments, and genomics, as well as hypothesis-generating "omics" approaches. The ongoing search for biomarkers relevant to OPMD progression needs an integrative, longitudinal approach combining validated and experimental approaches which may include clinical, imaging, demographic, and biochemical assessment methods. A multi-omics approach to biochemical biomarker discovery could help provide context for differences found between individuals with varying levels of disease activity and provide insight into pathomechanisms and prognosis of OPMD.


Subject(s)
Blepharoptosis , Deglutition Disorders , Muscular Dystrophy, Oculopharyngeal , Humans , Muscular Dystrophy, Oculopharyngeal/genetics , Biomarkers , Blepharoptosis/genetics , Genetic Testing
4.
Front Med (Lausanne) ; 10: 1204816, 2023.
Article in English | MEDLINE | ID: mdl-37780560

ABSTRACT

Introduction: Many patients with amyotrophic lateral sclerosis (ALS) receive palliative care (PC) very late or not at all. The impact of PC on patients with ALS and caregivers has not been quantified. Study goals included (1) measuring the impact of early PC on quality of life and mood of patients/caregivers and (2) describing patient/caregiver satisfaction with PC. Methods: The study was a non-randomized, prospective feasibility study of patients with ALS being treated at The Ottawa Hospital ALS Clinic and their caregivers. Exclusion criteria were age < 18 years, inability to complete questionnaires, and prior receipt of PC. The ALS Specific Quality of Life-Revised (ALSSQOL-R) questionnaire (patients only) and Hospital Anxiety and Depression Scale (HADS) were completed at regular intervals for up to 2 years. Patients accepting a PC consultation completed a post-PC satisfaction survey. Primary outcome measures included ALSSQOL-R and HADS scores compared before and after PC consultation, and between groups receiving and not receiving a PC consultation. Secondary outcome measures included responses on the post-PC satisfaction survey (1 = strongly disagree, 5 = strongly agree). Results: 39 patients with ALS (age 66 ± 10 years, median time from diagnosis = 6 months) and 22 caregivers were enrolled. 32 patients had a PC consultation (30 were virtual). Patients and caregivers agreed with statements that the PC consult was helpful (mean ± SD = 4.54 ± 0.60, range = 3-5) and they would recommend PC to others with ALS (4.59 ± 0.59, range = 3-5). Participants disagreed with statements that the consult would have been better later in disease course (1.87 ± 0.80, range = 1-4) and that it took too much time/energy (1.44 ± 0.85, range = 1-4). Average ALSSQOL-R scores worsened significantly over time. HADS and ALSSQOL-R scores did not significantly differ between groups receiving and not receiving PC. Conclusion: Patients with ALS and their caregivers found virtual PC consultations beneficial irrespective of disease duration or severity. Offering routine PC to all patients with ALS is feasible and should be considered as part of standard care. Clinical trial registration: https://clinicaltrials.gov/ct2/show/NCT04257760, identifier NCT04257760.

5.
J Appl Physiol (1985) ; 135(5): 1036-1040, 2023 Nov 01.
Article in English | MEDLINE | ID: mdl-37732377

ABSTRACT

Comparisons of muscle force output are often performed after normalization to muscle physiological cross-sectional area (CSA). Differences in force per CSA (i.e., specific force) suggest the presence of physiological differences in contractile function. Permeabilized mammalian skeletal muscle fibers frequently exhibit substantial declines in specific force with increasing CSA, suggesting that smaller fibers are intrinsically stronger than larger fibers of the same group. However, the potential for CSA assessment error to account for CSA-dependent differences in specific force has not received adequate attention. Assessment of fiber CSA typically involves measurement of fiber width and perhaps also height, and CSA is calculated by assuming the cross sections are either circular or elliptical with major and minor axes aligned with the optical measurement system. Differences between the assumed and real cross-sectional shapes would cause variability in the ratio of assessed CSA (aCSA) to real CSA (rCSA). This variability can insidiously bias aCSA such that large aCSAs typically overstate rCSAs of the fibers they represent, and small aCSAs typically understate the rCSAs of the fibers they represent. As aCSA is the denominator for the specific force calculation, scatterplots of specific force versus aCSA would be expected to show declines in specific force as aCSA increases without a corresponding effect in a scatterplot of specific force versus rCSA. When comparing active and passive muscle forces between data subsets defined by aCSA, the impact of CSA assessment error should be considered before exploring other physiological mechanisms.

6.
Neurol Genet ; 9(1): e200048, 2023 Feb.
Article in English | MEDLINE | ID: mdl-37077559

ABSTRACT

Background and Objectives: Coenzyme Q10 (CoQ10) is an important electron carrier and antioxidant. The COQ7 enzyme catalyzes the hydroxylation of 5-demethoxyubiquinone-10 (DMQ10), the second-to-last step in the CoQ10 biosynthesis pathway. We report a consanguineous family presenting with a hereditary motor neuropathy associated with a homozygous c.1A > G p.? variant of COQ7 with abnormal CoQ10 biosynthesis. Methods: Affected family members underwent clinical assessments that included nerve conduction testing, histologic analysis, and MRI. Pathogenicity of the COQ7 variant was assessed in cultured fibroblasts and skeletal muscle using a combination of immunoblots, respirometry, and quinone analysis. Results: Three affected siblings, ranging from 12 to 24 years of age, presented with a severe length-dependent motor neuropathy with marked symmetric distal weakness and atrophy with normal sensation. Muscle biopsy of the quadriceps revealed chronic denervation pattern. An MRI examination identified moderate to severe fat infiltration in distal muscles. Exome sequencing demonstrated the homozygous COQ7 c.1A > G p.? variant that is expected to bypass the first 38 amino acid residues at the n-terminus, initiating instead with methionine at position 39. This is predicted to cause the loss of the cleavable mitochondrial targeting sequence and 2 additional amino acids, thereby preventing the incorporation and subsequent folding of COQ7 into the inner mitochondrial membrane. Pathogenicity of the COQ7 variant was demonstrated by diminished COQ7 and CoQ10 levels in muscle and fibroblast samples of affected siblings but not in the father, unaffected sibling, or unrelated controls. In addition, fibroblasts from affected siblings had substantial accumulation of DMQ10, and maximal mitochondrial respiration was impaired in both fibroblasts and muscle. Discussion: This report describes a new neurologic phenotype of COQ7-related primary CoQ10 deficiency. Novel aspects of the phenotype presented by this family include pure distal motor neuropathy involvement, as well as the lack of upper motor neuron features, cognitive delay, or sensory involvement in comparison with cases of COQ7-related CoQ10 deficiency previously reported in the literature.

7.
Neuromuscul Disord ; 33(1): 24-31, 2023 01.
Article in English | MEDLINE | ID: mdl-36462961

ABSTRACT

Oculopharyngeal muscular dystrophy (OPMD) is a genetic muscle disease causing ptosis, severe swallowing difficulties and progressive limb weakness, although atypical presentations may be difficult to diagnose. Sensitive biomarkers of disease progression in OPMD are needed to enable more effective clinical trials. This study was designed to test the feasibility of using MRI to aid OPMD diagnosis and monitor OPMD progression. Twenty-five subjects with Dixon whole-body muscle MRI were enrolled: 10 patients with genetically confirmed OPMD, 10 patients with non-OPMD muscular dystrophies, and 5 controls. Using the MRI Dixon technique, muscle fat replacement was evaluated in the tongue, serratus anterior, lumbar paraspinal, adductor magnus, and soleus muscles using quantitative and semi-quantitative rating methods. Changes were compared with muscle strength testing, dysphagia severity, use of gait aids, and presence of dysarthria. Quantitative MRI scores of muscle fat replacement in the tongue could differentiate OPMD from other muscular dystrophies and from controls. Moreover, fat fraction in the tongue correlated with clinical severity of dysphagia. This study provides preliminary support for the use of Dixon-based quantitative MRI images as outcome measures for monitoring disease progression in clinical trials and provides rationale for future prospective studies aimed at methodological refinement and covariate identification.


Subject(s)
Deglutition Disorders , Muscular Dystrophy, Oculopharyngeal , Humans , Muscular Dystrophy, Oculopharyngeal/diagnosis , Deglutition Disorders/diagnostic imaging , Deglutition Disorders/etiology , Prospective Studies , Muscle, Skeletal/diagnostic imaging , Magnetic Resonance Imaging , Biomarkers , Disease Progression
8.
Front Cardiovasc Med ; 9: 899606, 2022.
Article in English | MEDLINE | ID: mdl-35722118

ABSTRACT

Background: Myotonic dystrophy type 1 (DM1) is a hereditary muscular dystrophy affecting ∼2.1-14.3/100,000 adults. Cardiac manifestations of DM1 include conduction disorders and rarely cardiomyopathies. DM1 increases the risk of obstetric complications, however, little is known about the relationship between pregnancy and cardiomyopathy in DM1 due to disease rarity. Case: A 23-year-old with DM1 developed cardiomyopathy during pregnancy. Despite initial medical stabilization, she subsequently developed multiple spontaneous coronary artery dissections postpartum, worsening cardiomyopathy and multiorgan failure. She died 5 months postpartum. Conclusion: Though cardiomyopathy and arterial dissection are both known complications of pregnancy, this case suggests individuals with myotonic dystrophy type 1 may be at heightened risk for cardiac disease during the peripartum period. Physicians caring for women with suspected or proven DM1 should offer counseling and be alerted to the risk of cardiac complications with pregnancy and in the peripartum period. Pregnant and peripartum women with DM1 are likely to benefit from more frequent assessments of cardiac function including echocardiograms and early institution of heart failure management protocols when symptoms of cardiomyopathy present.

9.
Int J Mol Sci ; 22(16)2021 Aug 08.
Article in English | MEDLINE | ID: mdl-34445232

ABSTRACT

Our purpose was to use small-angle X-ray diffraction to investigate the structural changes within sarcomeres at steady-state isometric contraction following active lengthening and shortening, compared to purely isometric contractions performed at the same final lengths. We examined force, stiffness, and the 1,0 and 1,1 equatorial and M3 and M6 meridional reflections in skinned rabbit psoas bundles, at steady-state isometric contraction following active lengthening to a sarcomere length of 3.0 µm (15.4% initial bundle length at 7.7% bundle length/s), and active shortening to a sarcomere length of 2.6 µm (15.4% bundle length at 7.7% bundle length/s), and during purely isometric reference contractions at the corresponding sarcomere lengths. Compared to the reference contraction, the isometric contraction after active lengthening was associated with an increase in force (i.e., residual force enhancement) and M3 spacing, no change in stiffness and the intensity ratio I1,1/I1,0, and decreased lattice spacing and M3 intensity. Compared to the reference contraction, the isometric contraction after active shortening resulted in decreased force, stiffness, I1,1/I1,0, M3 and M6 spacings, and M3 intensity. This suggests that residual force enhancement is achieved without an increase in the proportion of attached cross-bridges, and that force depression is accompanied by a decrease in the proportion of attached cross-bridges. Furthermore, the steady-state isometric contraction following active lengthening and shortening is accompanied by an increase in cross-bridge dispersion and/or a change in the cross-bridge conformation compared to the reference contractions.


Subject(s)
Muscle Contraction , Muscle Fibers, Skeletal/metabolism , Muscle Relaxation , Scattering, Small Angle , X-Ray Diffraction , Animals , Rabbits
10.
Appl Physiol Nutr Metab ; 46(11): 1389-1399, 2021 Nov.
Article in English | MEDLINE | ID: mdl-34139131

ABSTRACT

Obesity is a worldwide health concern associated with impaired physical function. It is not clear if contractile protein dysfunction contributes to the impairment of muscle function observed with obesity. The purpose of this study was to examine if diet-induced obesity affects contractile function of chemically permeabilized vastus intermedius fibres of male Sprague-Dawley rats expressing fast myosin heavy chain (MHC) IIa or slow MHC I. Rats consumed either a high-fat, high sucrose (HFHS) diet or a standard (CHOW) diet beginning as either weanlings (7-week duration: WEAN7 cohort, or 14-week duration: WEAN14 cohort) or young adults (12-week duration: ADULT12 cohort, 24-week duration: ADULT24 cohort). HFHS-fed rats had higher (P < 0.05) whole-body adiposity (derived from dual-energy X-ray absorptiometry) than CHOW-fed rats in all cohorts. Relative to CHOW diet groups, the HFHS diet was associated with impaired force production in (a) MHC I fibres in the ADULT24 cohort; and (b) MHC IIa fibres in the ADULT12 and ADULT24 cohorts combined. However, the HFHS diet did not significantly affect the Ca2+-sensitivity of force production, unloaded shortening velocity, or ratio of active force to active stiffness in any cohort. We conclude that diet-induced obesity can impair force output of permeabilized muscle fibres of adult rats. Novelty: We assessed contractile function of permeabilized skeletal muscle fibres in a rat model of diet-induced obesity. The high-fat, high-sucrose diet was associated with impaired force output of fibres expressing MHC I or MHC IIa in some cohorts of rats. Other measures of contractile function were not significantly affected by diet.


Subject(s)
Diet, High-Fat , Dietary Sucrose/administration & dosage , Muscle Contraction , Obesity/physiopathology , Quadriceps Muscle/physiology , Animals , Biomechanical Phenomena , Body Composition , Disease Models, Animal , Male , Muscle Fibers, Fast-Twitch/physiology , Muscle Fibers, Slow-Twitch/physiology , Myosin Heavy Chains/metabolism , Obesity/metabolism , Rats, Sprague-Dawley
11.
J Appl Res Intellect Disabil ; 34(6): 1442-1451, 2021 Nov.
Article in English | MEDLINE | ID: mdl-33827145

ABSTRACT

BACKGROUND: Health professionals were trained to deliver adapted psychological interventions for depression to people with learning disabilities and depression alongside a supporter. Exploring the delivery of psychological interventions can help increase access to therapy. METHOD: Twenty-seven participants took part in six focus groups, and the data were subject to a Framework Analysis. RESULTS: The structure and focus of the manualised therapies, and the use of specific techniques were perceived as key to service-user engagement. Supporters' involvement was valued by therapists if they had a good relationship and regular contact with the individual they supported. Regular clinical supervision was regarded as vital in understanding their role, assessing progress and delivering the interventions. CONCLUSIONS: The findings highlight that health professionals can embrace a focussed therapeutic role and increase access to psychological therapies for people with intellectual disabilities.


Subject(s)
Intellectual Disability , Learning Disabilities , Adult , Allied Health Personnel , Behavior Therapy , Depression , Humans , Intellectual Disability/therapy
14.
Eur J Appl Physiol ; 121(2): 645-658, 2021 Feb.
Article in English | MEDLINE | ID: mdl-33221935

ABSTRACT

PURPOSE: A period of extra-efficient force production ("boost") followed by a decline in force ("sag") is often observed at the onset of unfused tetanic contractions. We tested the hypothesis that in human muscle boost and sag are diminished in repeated contractions separated by short rest periods and are re-established or enhanced following long rest periods. METHODS: Two sets of 3 unfused tetanic contractions were evoked in the right quadriceps muscle group of 29 participants via percutaneous stimulation of the femoral nerve. Contractions consisted of 20 pulses evoked at inter-pulse intervals of 1.25 × twitch time to peak torque. Contractions were evoked 5 s apart and sets were evoked 5 min apart. RESULTS: The ratio of the angular impulse of pulses 1-10 to the angular impulse of pulses 11-20 was used as the boost indicator. By this metric, boost was higher (P < 0.05) in the first relative to the second and third contractions within a set, but did not differ between sets (Set 1: 1.31 ± 0.15, 1.18 ± 0.12, 1.14 ± 0.12 vs Set 2: 1.34 ± 0.17, 1.17 ± 0.13, 1.14 ± 0.13). Sag (the percent decline in torque within each contraction) was also higher (P < 0.05) in the first relative to the second and third contractions within a set, but did not differ between sets (Set 1: 40.8 ± 7.5%, 35.4 ± 6.8%, 33.2 ± 7.8% vs Set 2: 42.1 ± 8.0%, 35.5 ± 6.8%, 33.9 ± 7.2%). Participants' sex and resistance training background did not influence boost or sag. CONCLUSION: Boost and sag are sensitive to contractile history in whole human quadriceps. Optimizing boost may have application in strength and power sports.


Subject(s)
Muscle Contraction/physiology , Quadriceps Muscle/physiology , Adult , Electric Stimulation/methods , Female , Femoral Nerve/physiology , Humans , Male , Motor Neurons/physiology , Muscle Fatigue/physiology , Resistance Training , Rest/physiology , Torque
15.
Biochem Biophys Res Commun ; 533(4): 818-823, 2020 12 17.
Article in English | MEDLINE | ID: mdl-32993963

ABSTRACT

Muscle operates across a wide range of sarcomere lengths. Inorganic phosphate (Pi) diminishes force output of striated muscle, with greater influence at short relative to long sarcomere lengths in fast skeletal and cardiac muscle fibres. The purpose of this study was to fill a gap in the literature regarding the length-dependent effects of Pi on contractile function of slow skeletal muscle fibres. Permeabilized slow skeletal muscle fibres from rabbit soleus were assessed at average sarcomere lengths of 2.0, 2.4, or 2.8 µm, with and without 20 mM Pi added to activating solutions (22±1 °C). The magnitude of Pi-induced reductions in peak force (43 ± 7% at 2.0 µm, 38 ± 7% at 2.4 µm, and 31 ± 8% at 2.8 µm) and peak stiffness (41 ± 9% at 2.0 µm, 36 ± 8% at 2.4 µm, and 26 ± 9% at 2.8 µm) were length dependent. Peak stiffness was less affected by Pi than peak force. Pi diminished the Ca2+-sensitivity of the force-pCa and stiffness-pCa relationships to a greater extent at 2.8 µm than 2.0 µm. Comparable results were obtained from a cooperative model of Ca2+ and myosin binding to regulated actin. In conclusion, Pi is more detrimental to the peak force output of slow skeletal muscle fibres held at short relative to long sarcomere lengths, whereas Pi has a greater effect on the Ca2+-sensitivity of force production at long relative to short sarcomere lengths. Stiffness data suggest that Pi-induced reductions in force are primarily due to fewer bound cross-bridges, with a lesser contribution attributable to lower average force per cross-bridge.


Subject(s)
Muscle Contraction , Muscle Fibers, Slow-Twitch/physiology , Phosphates/physiology , Animals , Calcium/metabolism , Muscle Fibers, Slow-Twitch/ultrastructure , Rabbits , Sarcomeres/ultrastructure
16.
J Clin Oncol ; 38(34): 3987-3998, 2020 12 01.
Article in English | MEDLINE | ID: mdl-32954927

ABSTRACT

PURPOSE: Many patients with HR+, HER2- early breast cancer (EBC) will not experience recurrence or have distant recurrence with currently available standard therapies. However, up to 30% of patients with high-risk clinical and/or pathologic features may experience distant recurrence, many in the first few years. Superior treatment options are needed to prevent early recurrence and development of metastases for this group of patients. Abemaciclib is an oral, continuously dosed, CDK4/6 inhibitor approved for HR+, HER2- advanced breast cancer (ABC). Efficacy and safety of abemaciclib in ABC supported evaluation in the adjuvant setting. METHODS: This open-label, phase III study included patients with HR+, HER2-, high-risk EBC, who had surgery and, as indicated, radiotherapy and/or adjuvant/neoadjuvant chemotherapy. Patients with four or more positive nodes, or one to three nodes and either tumor size ≥ 5 cm, histologic grade 3, or central Ki-67 ≥ 20%, were eligible and randomly assigned (1:1) to standard-of-care adjuvant endocrine therapy (ET) with or without abemaciclib (150 mg twice daily for 2 years). The primary end point was invasive disease-free survival (IDFS), and secondary end points included distant relapse-free survival, overall survival, and safety. RESULTS: At a preplanned efficacy interim analysis, among 5,637 randomly assigned patients, 323 IDFS events were observed in the intent-to-treat population. Abemaciclib plus ET demonstrated superior IDFS versus ET alone (P = .01; hazard ratio, 0.75; 95% CI, 0.60 to 0.93), with 2-year IDFS rates of 92.2% versus 88.7%, respectively. Safety data were consistent with the known safety profile of abemaciclib. CONCLUSION: Abemaciclib when combined with ET is the first CDK4/6 inhibitor to demonstrate a significant improvement in IDFS in patients with HR+, HER2- node-positive EBC at high risk of early recurrence.


Subject(s)
Antineoplastic Combined Chemotherapy Protocols/therapeutic use , Breast Neoplasms/drug therapy , Adult , Aged , Aged, 80 and over , Aminopyridines/administration & dosage , Aminopyridines/adverse effects , Antineoplastic Agents, Hormonal/administration & dosage , Antineoplastic Agents, Hormonal/adverse effects , Antineoplastic Combined Chemotherapy Protocols/adverse effects , Benzimidazoles/administration & dosage , Benzimidazoles/adverse effects , Breast Neoplasms/metabolism , Breast Neoplasms/pathology , Chemotherapy, Adjuvant , Disease-Free Survival , Female , Humans , Lymphatic Metastasis , Middle Aged , Neoplasm Recurrence, Local/pathology , Protein Kinase Inhibitors/administration & dosage , Protein Kinase Inhibitors/adverse effects , Receptor, ErbB-2/metabolism , Receptors, Estrogen/metabolism , Receptors, Progesterone/metabolism , Young Adult
17.
J Electromyogr Kinesiol ; 53: 102429, 2020 Aug.
Article in English | MEDLINE | ID: mdl-32505088

ABSTRACT

Unfused tetanic contractions evoked in fast motor units exhibit extra-efficient force production at the onset of contraction, an effect called "boost". Boost is diminished in subsequent contractions if there is a short rest period between contractions, but can be re-established with a longer period of rest. We tested the hypothesis that contractile activity and rest could enhance boost-related metrics. Two sets of 3 unfused tetani were evoked 3 min apart in fast fatigable (FF) and fast fatigue-resistant (FR) motor units of the rat medial gastrocnemius. The greatest changes occurred in the first unfused tetanic contractions. Relative to the first contraction in the first set, the first contraction in the second set exhibited higher peak force during boost in a subset of motor units (76% of FF and 48% of FR). Enhanced force during boost was influenced by interaction of slowing of twitch contraction time (up to 20% and 25%, for FF and FR motor units, respectively), half-relaxation time (up to 37% and 49% for FF and FR motor units, respectively), and potentiation of the first twitch (up to 13% and 5% for FF and FR motor units, respectively). Examination of twitches evoked between sets suggested opportunity for greater enhancement of boost with shorter intervening rest periods. The phenomenon of enhanced boost following motor unit activity may interest sports scientists.


Subject(s)
Muscle Contraction/physiology , Muscle Fatigue/physiology , Muscle, Skeletal/physiology , Recruitment, Neurophysiological/physiology , Rest/physiology , Animals , Electric Stimulation/methods , Female , Motor Neurons/physiology , Rats , Rats, Wistar , Time Factors
18.
Exp Physiol ; 105(4): 676-689, 2020 04.
Article in English | MEDLINE | ID: mdl-32052487

ABSTRACT

NEW FINDINGS: What is the central question of this study? How do contraction-induced reductions in twitch duration, without changes in twitch force, affect summation of twitch pairs into higher force contractions in skeletal muscle? What is the main finding and its importance? Abbreviating twitch duration with a brief contraction resulted in enhanced summation of fully fused twitch pairs, but impaired summation in partially fused twitch pairs even after accounting for the differences in relaxation of the first twitch. An inherent mechanism which enhances relaxation without sacrificing force generation in forceful contractions would benefit cyclic muscle activities, such as locomotion. ABSTRACT: During electrically evoked contractions of skeletal muscle, the interplay between twitch duration and the time between electrical stimuli (inter-pulse interval, IPI) determines how effectively twitch forces summate into high force contractions. A brief muscle contraction can impair summation by abbreviating twitch duration, though it is not clear if these impairments occur at all physiologically relevant IPI. This study was designed to test how a brief contraction affects summation of nominally isometric twitch pairs with IPIs lasting 10-5000 ms. Left adductor pollicis muscles of human participants (n = 9) were electrically activated using stimulus pairs applied both before (Pre) and after (Post) a 10 Hz, 1.0 s contraction. Force-time records were mathematically separated into Pulse 1 (single twitch) and Pulse 2 (summated twitch) components. The ratio of Pulse 2 peak force to Pulse 1 peak force was used as our measure of summation effectiveness. Consistent with the observed decline of Pulse 1 duration at Post relative to Pre (4.7 ± 0.6%; P < 0.001; duration was defined as the time from stimulation to the time required for active force to decline by 50%), summation effectiveness was higher at Pre than at Post at IPIs of 100-333 ms. Summation effectiveness was not different between Pre and Post at IPIs of 50-83 ms or 500-5000 ms. Intriguingly, summation effectiveness was higher at Post than at Pre at IPIs of 10-25 ms. In summary, a brief contraction has complex effects on the relationship between inter-pulse interval and summation effectiveness. Future experiments are needed to reveal the mechanisms behind this novel observation.


Subject(s)
Muscle Contraction/physiology , Adult , Electric Stimulation/methods , Female , Humans , Male , Muscle, Skeletal/physiology
19.
J Appl Res Intellect Disabil ; 32(5): 1203-1215, 2019 Sep.
Article in English | MEDLINE | ID: mdl-31066173

ABSTRACT

BACKGROUND: This study explored understandings that service-users with intellectual disabilities and challenging behaviour held around their behaviour, what shaped these understandings, and the relationship between how behaviours are managed and well-being. METHODS: Eight participants (three female, five male) partook in individual semi-structured qualitative interviews. Interviews were transcribed and analysed using interpretative phenomenological analysis. RESULTS: Three master themes emerged from this analysis: (a) challenging behaviour can be explained via an internal or external frame of reference, with each framework having different implications for how participants attempted to manage behaviour. (b) Positive relationships provide a long-term buffer to challenging behaviour, with positive relationships with family, staff and peers operating through different mechanisms to achieve this. (c) A greater ability to exert power and control in day-to-day life was perceived to reduce challenging behaviour in the long term. CONCLUSIONS: Implications for practice are discussed.


Subject(s)
Intellectual Disability/psychology , Persons with Mental Disabilities/psychology , Problem Behavior/psychology , Adult , Female , Humans , Male , Qualitative Research , Young Adult
20.
Magn Reson Med ; 82(2): 527-550, 2019 08.
Article in English | MEDLINE | ID: mdl-30919510

ABSTRACT

Proton MRS (1 H MRS) provides noninvasive, quantitative metabolite profiles of tissue and has been shown to aid the clinical management of several brain diseases. Although most modern clinical MR scanners support MRS capabilities, routine use is largely restricted to specialized centers with good access to MR research support. Widespread adoption has been slow for several reasons, and technical challenges toward obtaining reliable good-quality results have been identified as a contributing factor. Considerable progress has been made by the research community to address many of these challenges, and in this paper a consensus is presented on deficiencies in widely available MRS methodology and validated improvements that are currently in routine use at several clinical research institutions. In particular, the localization error for the PRESS localization sequence was found to be unacceptably high at 3 T, and use of the semi-adiabatic localization by adiabatic selective refocusing sequence is a recommended solution. Incorporation of simulated metabolite basis sets into analysis routines is recommended for reliably capturing the full spectral detail available from short TE acquisitions. In addition, the importance of achieving a highly homogenous static magnetic field (B0 ) in the acquisition region is emphasized, and the limitations of current methods and hardware are discussed. Most recommendations require only software improvements, greatly enhancing the capabilities of clinical MRS on existing hardware. Implementation of these recommendations should strengthen current clinical applications and advance progress toward developing and validating new MRS biomarkers for clinical use.


Subject(s)
Brain/diagnostic imaging , Magnetic Resonance Imaging/methods , Brain/metabolism , Consensus , Humans , Protons
SELECTION OF CITATIONS
SEARCH DETAIL
...