Crossbridge and non-crossbridge contributions to tension in lengthening rat muscle: force-induced reversal of the power stroke   总被引：5，自引：1，他引：4  

G. J. Pinniger  K. W. Ranatunga  G. W. Offer 《The Journal of physiology》2006,573(3):627-643

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Sarcomere length changes during end-held (isometric) contractions in intact mammalian (rat) fast and slow muscle fibres     

Mutungi G  Ranatunga KW 《Journal of muscle research and cell motility》2000,21(6):565-575

The sarcomere length change, within a 2 mm region, during end-held isometric contractions in intact rat fast and slow muscle fibre bundles was investigated at 20°C and an initial sarcomere length of 2.68 m using He–Ne laser diffraction. In some experiments, the fibre segment displacement was monitored with markers (pieces of human hair) placed at regular intervals on the surface of the muscle fibre bundles. The sarcomere length changes, monitored near the proximal end of the bundle (transducer end), during tetanic contractions were similar to those previously reported in frog muscle fibres. Thus, throughout the tension plateau, sarcomere length remained constant (and shortened) but showed evidence of non-uniform sarcomere behaviour (further shortening) during the rapid tension relaxation phase. Such non-uniform behaviour was not seen during twitch contractions. During a twitch contraction, sarcomeres at the proximal end shortened rapidly at first and continued to shorten – or remained shortened – until the tension had relaxed to between 20–23% of its peak value before lengthening back to the original length. The maximum twitch sarcomere shortening (mean ± SEM) was 5.9 ± 0.2% (n = 16) in fast and 5.4 ± 0.3% (n = 14) in slow fibre bundles at 20°C; sarcomere shortening near body temperature (35°C) was greater, 8.8 ± 0.2% (n = 7) in fast and 8.1 ± 0.2% (n = 5) in slow fibre bundles. Increasing the initial sarcomere length of a preparation decreased the extent of sarcomere shortening and reducing the amount of sarcomere shortening, by sarcomere length clamping, markedly increased the peak twitch tension without significantly altering the twitch time course. When examined at different positions along muscle fibres, a sarcomere shortening was observed along much of the fibre length in most preparations. However, in about a third of the preparations some sarcomere lengthening was recorded in the distal end, but its amplitude was too small to accommodate the fibre shortening elsewhere. Complementary data were obtained using the surface marker technique. The displacement was largest and in opposite – but fibre shortening – direction in the markers placed 0.5–1.0 mm away from the two tendon attachments; the markers placed at or near the centre of the fibre bundle showed the least amount of displacement. The findings suggest that the compliant region, where lengthening occurs, is at fibre ends, i.e. near myotendinous junction.  相似文献   

Pressure-induced changes in the isometric contractions of single intact frog muscle fibres at low temperatures     

F. Vawda  K. W. Ranatunga  M. A. Geeves 《Journal of muscle research and cell motility》1995,16(4):412-419

Summary Effects of increased hydrostatic pressure (range 0.1–10 MPa) on isometric twitch and tetanic contractions of single intact muscle fibres, isolated from frog tibialis anterior muscle, were examined at 4–12° C. The tension changes produced on exposure to steady high pressures are compared with those produced on exposure to low concentrations of caffeine (0.5 mm, subthreshold for contracture) and when pressure is rapidly released during a contraction. The peak twitch tension was potentiated by pressure accompanied by increased rate of tension rise and increased duration; the pressure sensitivity of twitch tension was 8% mPa^-1. The correlation between the rate of tension rise and peak tension in caffeine-induced twitch tension potentiation was quantitatively similar to that in pressure-induced twitch potentiation. Experiments involving the rapid release of pressure (2 ms) during twitch contractions demonstrate that high pressure need only be maintained for a brief period during the early part of tension development to elicit full twitch potentiation. The tetanic tension was depressed by pressure (1% MPa^-1). Results demonstrate that the major effect of increased hydrostatic pressure on intact muscle fibres, which results in tension potentiation, is complete very early during contraction and is similar to that of caffeine.  相似文献   

    

DG Ranatunga  MG Richardson  DM Brooks 《Journal of Medical Imaging and Radiation Oncology》2007,51(2):182-185

Knotting of intravascular catheters is an uncommon but a well‐recognized occurrence. The Swan–Ganz catheter (SGC) is the one that knots most commonly. A case of a knotted SGC is described in a patient with a persistent left‐sided superior vena cava, and we propose that the presence of a left‐sided superior vena cava is a risk factor for knot formation not previously reported. We review the published work on the risk factors for knot formation and on the techniques used to remove knotted SGC. We describe a technique using a gooseneck snare and Omni Flush catheter (Angiodynamics, Queensbury, NY, USA) to loosen and untie a knotted SGC.  相似文献   

Upper-air observation indicators predict outbreaks of asthma exacerbations among elementary school children: integration of daily environmental and school health surveillance systems in Pennsylvania     

Youssefagha AH  Lohrmann DK  Jayawardene WP  El Afandi GS 《The Journal of asthma》2012,49(5):464-473

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Endothermic force generation, temperature-jump experiments and effects of increased [MgADP] in rabbit psoas muscle fibres   总被引：1，自引：1，他引：1  

M. E. Coupland  G. J. Pinniger  K. W. Ranatunga 《The Journal of physiology》2005,567(2):471-492

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TRAPPC9-CDG: A novel congenital disorder of glycosylation with dysmorphic features and intellectual disability     

Silvia Radenkovic  Diego Martinelli  Yuebo Zhang  Graeme J. Preston  Arianna Maiorana  Alessandra Terracciano  Maria Lisa Dentici  Elisa Pisaneschi  Antonio Novelli  Wasantha Ranatunga  Anna N. Ligezka  Bart Ghesquière  David R. Deyle  Tamas Kozicz  Filippo Pinto e Vairo  Peter Witters  Eva Morava 《Genetics in medicine》2022,24(4):894-904

PurposeTRAPPC9 deficiency is an autosomal recessive disorder mainly associated with intellectual disability (ID), microcephaly, and obesity. Previously, TRAPPC9 deficiency has not been associated with biochemical abnormalities.MethodsExome sequencing was performed in 3 individuals with ID and dysmorphic features. N-Glycosylation analyses were performed in the patients’ blood samples to test for possible congenital disorder of glycosylation (CDG). TRAPPC9 gene, TRAPPC9 protein expression, and N-glycosylation markers were assessed in patient fibroblasts. Complementation with wild-type TRAPPC9 and immunofluorescence studies to assess TRAPPC9 expression and localization were performed. The metabolic consequences of TRAPPC9 deficiency were evaluated using tracer metabolomics.ResultsAll 3 patients carried biallelic missense variants in TRAPPC9 and presented with an N-glycosylation defect in blood, consistent with CDG type I. Extensive investigations in patient fibroblasts corroborated TRAPPC9 deficiency and an N-glycosylation defect. Tracer metabolomics revealed global metabolic changes with several affected glycosylation-related metabolites.ConclusionWe identified 3 TRAPPC9 deficient patients presenting with ID, dysmorphic features, and abnormal glycosylation. On the basis of our findings, we propose that TRAPPC9 deficiency could lead to a CDG (TRAPPC9-CDG). The finding of abnormal glycosylation in these patients is highly relevant for diagnosis, further elucidation of the pathophysiology, and management of the disease.  相似文献   

Osteoporosis and Cardiovascular Risk Among Premenopausal Women in Sri Lanka     

Sarath Lekamwasam  Thilak Weerarathna  Mahinda Rodrigo  Wasantha Kodikara Arachchi  Duminda Munidasa 《Journal of clinical densitometry》2009,12(2):245-250

We examined the association between bone mineral density (BMD) and cardiovascular risk in a group of premenopausal women selected from the Southern province of Sri Lanka. One hundred six previously healthy premenopausal volunteers (aged 30–54 yr) were recruited by open invitations. Subjects with previous history of diabetes, hypertension, epilepsy, chronic renal or liver disease, hyperlipidemia, ischemic heart disease, endocrine diseases, or prolonged inflammatory conditions were excluded. Subjects who were taking medications that can affect bone density, blood sugar, serum lipids, or blood pressure (BP) were also excluded. Women with the history of previous fractures were not excluded. BMDs in the spine, hip, and total body (TB) were measured using a Hologic Discovery scanner (Hologic Inc, Bedford, MA). BP, fasting glucose, and fasting lipids were also measured. Independent of body mass index (BMI) and age, TB bone mineral content (BMC) and spine BMD showed inverse and significant correlations with total cholesterol (TC), low density cholesterol, and the ratio between TC and high density lipoprotein cholesterol (r ranged from ?0.24 to ?0.27, p < 0.05 for all). The highest mean lipid levels were seen among the women in the lowest third of spine BMD, whereas women in the upper third of spine BMD had the lowest lipid levels. The number of women with metabolic syndrome in the 3 tirtiles of spine BMD was not significantly different. Fasting glucose or BP had no association with either BMD or BMC. In conclusion, our data demonstrates an association, independent of age and BMI, between BMD and BMC or lipid levels among previously healthy, premenopausal women. This may explain the high cardiovascular risk seen in women with osteoporosis in old age.  相似文献   

Dietary intake of vitamin E and folic acid in a defined population in Sri Lanka     

Mendis S  Bulugahapitiya DU  Ranatunga PK  Gunawardene PR  Kandegedera PG 《The Ceylon medical journal》1999,44(1):25-27

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Patterns of disease in Sri Lankan dengue patients     

Malavige GN  Ranatunga PK  Velathanthiri VG  Fernando S  Karunatilaka DH  Aaskov J  Seneviratne SL 《Archives of disease in childhood》2006,91(5):396-400

Background

Dengue is the most important mosquito borne viral infection in the world. Nearly 90% of infections occur in children. At present, prospective information on clinical and laboratory findings in South Asian children with dengue is generally lacking.

Aim

To describe patterns of clinical disease in a cohort of children hospitalised with dengue during a major dengue epidemic in Sri Lanka.

Results

A total of 104 children were studied during a three month period. Eighteen had dengue fever (DF) and 86 had dengue haemorrhagic fever (DHF). Of those with DHF, 34, 23, 27, and 2 had DHF grade I, II, III, and IV respectively. Based on dengue serology testing, 13 of the DF patients had a primary infection and 5 had secondary dengue infections. In contrast, 68 of the children with DHF had secondary and 18 had primary dengue infections. Oral candidiasis was seen in 19 children. The odds ratio for children with secondary dengue infection to develop DHF was 9.8 (95% CI 3.1 to 31.2).

Conclusion

Studies on patterns of paediatric dengue disease in different regions should help clinicians and health administrators make more informed and evidence based health planning decisions. It should also help towards mapping out dengue trends on a global scale. Oral candidiasis has not been previously documented in children suffering with acute dengue in Sri Lanka or elsewhere. Studying underlying reasons for this manifestation during future dengue epidemics may provide useful leads in understanding overall dengue pathogenesis.  相似文献