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I Johnston

Publications and source records attributed to I Johnston.

At least 37 records · Page 2Linked to original sources
PubMed1998

Latitudinal variation in the abundance and oxidative capacities of muscle mitochondria in perciform fishes

The abundance, distribution and oxidative capacities of mitochondria have been investigated in the red pectoral fin adductor muscles of fish (Order Perciformes) that use a predominantly labriform style of swimming. Mediterranean Sea species from the families Labridae, Serranidae, Sparidae and Antarctic Nototheniidae and non-Antarctic Nototheniidae and Channichthyidae were studied. Sub-Antarctic species from the Beagle Channel, Tierra del Fuego, included the pelagic haemoglobin-less icefish (Champsocephalus esox) and the robalo (Eleginops maclovinus), which occurs as far north as 35 degrees S. In Champsocephalus esox, the mitochondrial volume density of red muscle was 0.51 and mitochondrial cristae surface density (43. 9 microm2 microm-3) was higher than reported for Antarctic icefishes. In the red-blooded, active pelagic or semi-pelagic species, mitochondrial volume density was within the range 0.27-0.33 regardless of habitat temperature. Amongst less active demersal species, mitochondrial volume density ranged from 0.29-0.33 in polar species to 0.08-0.13 in Mediterranean species. In Antarctic species and Champsocephalus esox, myofibrils occurred in ribbons or clusters one fibril thick entirely surrounded by mitochondria. The volume density of intracellular lipid droplets was not correlated with activity patterns or habitat temperature. In a comparison of Eleginops maclovinus caught in summer (approximately 10 degrees C) and winter (approximately 4 degrees C), mitochondrial volume density did not differ, whereas the surface density of mitochondrial clusters was higher in summer fish. The temperature-dependence of the state 3 respiration rate of isolated mitochondria with pyruvate as substrate was described by a single quadratic relationship for all species, indicating no significant up-regulation of the maximum rate of oxygen uptake per milligram mitochondrial protein in Antarctic species. Our results support the conclusion that increasing the volume and surface density of mitochondrial clusters is the primary mechanism for enhancing the aerobic capacity of muscle in cold-water fish.

Journal Article↗
PubMed1998

Embryonic temperature modulates muscle growth characteristics in larval and juvenile herring

The influence of embryonic and larval temperature regime on muscle growth was investigated in Atlantic herring (Clupea harengus L.). Eggs of spring-spawning Clyde herring were incubated at 5 degrees C, 8 degrees C or 12 degrees C until hatching and then reared until after metamorphosis at rising temperatures to simulate a seasonal warming. Metamorphosis to the juvenile stage was complete at 37 mm total length (TL), after an estimated 177 days as a larva at 5 degrees C, 117 days at 8 degrees C and 101 days at 12 degrees C. Growth rate and the development of median fins were retarded in relation to body length at 5 degrees C compared with 8 degrees C and 12 degrees C. Between hatching (at 8-9 mm TL) and 16 mm TL, there was a threefold increase in total muscle cross-sectional area, largely due to the hypertrophy of the embryonic red and white muscle fibres. The recruitment of additional white muscle fibres started at approximately 15 mm TL at all temperatures, and by 37 mm was estimated to be 66 fibres day-1 at 5 degrees C and 103 fibres day-1 at 8 degrees C and 12 degrees C. Peptide mapping studies revealed a change in myosin heavy chain composition in white muscle fibres between 20 and 25 mm TL. Embryonic red muscle fibres expressed fast myosin light chains until 24-28 mm TL at 5 degrees C and 22 mm TL at 12 degrees C, and new red fibres were added at the horizontal septum starting at the same body lengths. Following metamorphosis, the total cross-sectional area of muscle was similar at different temperatures, although the number of red and white fibres per myotome was significantly greater at the warmest than at the coldest regime. For example, the mean number of white muscle fibres per myotome in 50 mm TL juveniles was calculated to be 23.4 % higher at 12 degrees C (12 065) than at 5 degrees C (9775). In other experiments, spring-spawning (Clyde) and autumn-spawning (Manx) herring were reared at different temperatures until first feeding and then transferred to ambient seawater temperature and fed ad libitum for constant periods. These experiments showed that, for both stocks, the temperature of embryonic development influenced the subsequent rate of muscle fibre recruitment and hypertrophy as well as the density of muscle nuclei. Labelling experiments with 5'-bromo-2-deoxyuridine showed that both the hypertrophy and recruitment of muscle fibres involved a rapidly proliferating population of myogenic precursor cells. The cellular mechanisms underlying the environmental modulation of muscle growth phenotype are discussed.

Journal Article↗
PubMed1998

Survival in patients with cryptogenic fibrosing alveolitis: a population-based cohort study.

STUDY OBJECTIVES: To determine the median survival of patients with cryptogenic fibrosing alveolitis, in comparison to that expected of individuals of the same age and sex from the general population. To estimate the effect of survival bias incurred by studying both incident and prevalent cases. To identify factors associated with survival. DESIGN: Cohort study. SETTING: Nine hospitals from the Trent Region of England. PATIENTS: Two hundred forty-four cases of cryptogenic fibrosing alveolitis: 168 patients were alive on day 1 of the study (prevalent cases), and 76 patients had newly diagnosed conditions over a prospective 18-month period of patient recruitment (incident cases). MEASUREMENTS: Age, sex, date of diagnosis, lung function at presentation, and details of treatment prescribed were extracted from hospital clinical records. Data on lifetime smoking habits were collected by postal questionnaire. Vital status was established from the general practitioner. The expected survival of each case was extracted from the English life tables. RESULTS: Median survival for incident cases was 2.9 years and for prevalent cases 9 years, compared to expected values of 10 and 13 years, respectively. Incident cases had significantly worse survival than prevalent cases, even after adjustment for the effects of age, sex, smoking history, lung function at presentation, and treatment (hazard ratio, 4.53 [95% confidence interval, 2.71 to 7.56]; p<0.001). Lower FVC at presentation and the use of corticosteroid treatment were both associated with worse survival. CONCLUSIONS: The inclusion of prevalent cases leads to significant overestimation of the median survival for patients with cryptogenic fibrosing alveolitis. In newly diagnosed cases of cryptogenic fibrosing alveolitis, median survival is only 2.9 years, and expected life span is reduced by approximately 7 years.

Adrenal Cortex Hormones↗
PubMed1997

Incidence of serum anti-P/O-type and anti-N-type calcium channel autoantibodies in the Lambert-Eaton myasthenic syndrome.

The Lambert-Eaton myasthenic syndrome (LEMS) is an autoimmune disease in which autoantibodies are directed against voltage-gated calcium channels (VGCCs) at presynaptic nerve terminals. We first demonstrated the presence of P/Q-type and N-type VGCCs in digitonin extracts prepared from human and rabbit cerebellum using the specific ligands 125I-omega-conotoxin MVIIC (125I-omega-CmTx) and 125I-omega-conotoxin GVIA (125I-omega-CgTx), respectively. We then tested sera from 72 LEMS patients' 25 with proven small cell lung cancer (SCLC) and 66 healthy or other neurological, SCLC or autoimmune disease controls in an immunoprecipitation assay using 125I-omega-CmTx-labelled (P/Q-type) VGCCs in human cerebellar extract. Sixty-six of 72 LEMS serum samples (91.7%) were positive for the presence of VGCC antibodies, as defined as a titre greater than 3 standard deviations above the mean for the healthy controls (n = 22). Rabbit cerebellar extract as antigen gave similar results (r = 0.94, P < 0.001, n = 30). By contrast, only 24/72 (33%) LEMS sera were positive in the assay for anti-N-type VGCC antibodies using 125I-omega-CgTx. All these 24 were also positive in the 125I-omega-CmTx assay. All healthy and disease control sera were negative in both assays. The anti-P/Q-type VGCC antibody titres did not correlate with an electrophysiological index of disease severity across individuals; however, longitudinal studies in a LEMS patient with SCLC receiving chemotherapy, and in a non-SCLC LEMS patient receiving immunosuppressive therapy showed an inverse relation between antibody titre and disease severity. These results support the view that anti-P/Q-type VGCC antibodies are implicated in the motor disorder in LEMS, and show that the omega-CmTx radioimmunoassay is a highly specific and sensitive means of detecting them.

Adolescent↗
PubMed1997

Alpha1-antitrypsin phenotypes in patients with cryptogenic fibrosing alveolitis: a case-control study.

Cryptogenic fibrosing alveolitis (CFA) is an interstitial lung disease, which by definition is of unknown aetiology. Recent evidence has suggested that smoking and occupational exposure to dusts may be environmental risk factors for the disease, but there has been little research into potential host risk factors. One previous study has suggested that the prevalence of abnormal alpha1-antitrypsin phenotypes may be increased in patients with CFA. Since alpha1-antitrypsin is important in regulating inflammation within the lung in response to environmental exposures, such abnormalities may be of aetiological importance in this disease. We have compared the alpha1-antitrypsin phenotypes of 189 patients with CFA with 189 age-, sex-, and community-matched controls. This sample size was sufficient to provide more than 95% power to detect an odds ratio (OR) of 2.5. Alpha1-antitrypsin phenotype was established by isoelectric focusing, and the prevalence of abnormal phenotypes in cases and controls was compared by conditional logistic regression. Personal smoking histories were obtained by postal questionnaire. The prevalence of abnormal alpha1-antitrypsin phenotypes was similar in cases and controls (12.7 versus 15.3%; OR 0.88; 95% confidence interval 0.49-1.57; p=0.66). No interaction was found between the presence of abnormal alpha1-antitrypsin phenotypes and a history of smoking. We conclude that cryptogenic fibrosing alveolitis is not associated with abnormal alpha1-antitrypsin phenotypes.

Adult↗
PubMed1997

Muscle power output during escape responses in an Antarctic fish

Escape responses (C-shaped fast-starts) were filmed at 500 frames s-1 in the Antarctic rock cod (Notothenia coriiceps) at 0 &deg;C. The activation and strain patterns of the superficial fast myotomal muscle were measured simultaneously using electromyography and sonomicrometry respectively. In order to bend the body into the initial C-shape, the muscle fibres in the rostral myotomes (at 0.35L, where L is total length) shortened by up to 13 % of their resting length at a maximum velocity of 1.68 fibre lengths s-1. During the contralateral contraction, muscle fibres were stretched (by 5 % and 7 % at 0.35L and 0.65L, respectively) and were activated prior to the end of lengthening, before shortening by up to 12 % of resting fibre length (peak-to-peak strain). Representative strain records were digitised to create cyclical events corresponding to the C-bend and contralateral contraction. Isolated fibres were subjected to the abstracted strain cycles and stimulated at the same point and for the same duration as occurs in vivo. During the early phase of shortening, muscle shortening velocity (V) increased dramatically whilst the load was relatively constant and represented a substantial fraction of the maximum isometric stress. Pre-stretch of active muscle was associated with significant force enhancement. For the contralateral contraction, V exceeded that predicted by the steady-state force&shy;velocity relationship for considerable periods during each tailbeat, contributing to relatively high maximum instantaneous power outputs of up to 290 W kg-1 wet muscle mass. In vitro experiments, involving adjusting strain, cycle duration and stimulation parameters, indicated that in vivo muscle fibres produce close to their maximum power. During escape responses, the maximum velocity and acceleration recorded from the centre of gravity of the fish were 0.71&plusmn;0.03 m s-1 and 17.1&plusmn;1.4 m s-2, respectively (mean &plusmn; s.e.m., N=7 fish). Muscle performance was sufficient to produce maximum velocities and accelerations that were within the lower end of the range reported for temperate-zone fish.

Journal Article↗
PubMed1997

Temperature and developmental plasticity of muscle phenotype in herring larvae

Myogenesis, the expression of myofibrillar protein isoforms and the development of muscle innervation were investigated in Clyde herring (Clupea harengus L.) in two successive spawning seasons at temperatures ranging from 5 &deg;C to 15 &deg;C. Myotube formation occurred in a rostral to caudal progression at similar somite stages at all temperatures. Superficial mononuclear muscle pioneer fibres were present at the horizontal septum. Myofibrillogenesis was retarded with respect to somite stage at low temperatures; for example, by the 50-somite stage, myofibrils were observed in the muscle pioneers of the first 31 somites at 12 &deg;C, but only the first 20 somites at 5 &deg;C. In the electron microscope, the earliest stages of myofibril assembly were observed in the muscle pioneer cells and in a proportion of the multinucleated myotubes within the same somite. By the end of somitogenesis, the density of myofibrils in the rostral myotomes was much higher at 15 &deg;C than at 5 &deg;C. Embryonic isoforms of myosin light chain 2 (LC2), troponin I and troponin T were identified in the presumptive white muscle using two-dimensional gel electrophoresis. Expression of the embryonic isoforms was gradually switched off during the larval stages. The size range over which embryonic isoforms were present was inversely related to rearing temperature. For example, the adult pattern of myosin LC2 expression was established at 11 mm total length (TL) at 15 &deg;C, but not until 15 mm TL at 5 &deg;C. Acetylcholinesterase staining was apparent at the myosepta in 31-somite stage embryos at 15 &deg;C, but not until approximately the 40-somite stage at 5 &deg;C. The red muscle fibres of larvae were initially innervated only at their myoseptal ends. The temperature at which the red muscle fibres became multiply innervated was inversely related to body size, occurring at 12&shy;14 mm at 12 &deg;C, but not until 16&shy;19 mm at 5 &deg;C. We conclude that the temperature during early development determines the relative timing and degree of expression of the myogenic programme, resulting in significant phenotypic variation in the swimming muscles of the larval stages. Our results highlight a potential mechanism whereby early thermal experience could influence survival and hence the strength of particular year classes of fish.

Journal Article↗
PubMed1996

Occupational exposure to metal or wood dust and aetiology of cryptogenic fibrosing alveolitis.

BACKGROUND: We have previously suggested that cryptogenic fibrosing alveolitis (CFA) may be caused by occupational exposures, particularly to metal or wood dust. We have specifically investigated this hypothesis in a case-control study of patients with CFA. METHODS: We obtained lifetime occupational histories by postal questionnaire from 218 patients with CFA and 569 controls matched for age, sex, and community, living in the Trent region of the UK. Information was subsequently verified by telephone interview in 165 cases and 408 controls. Serum IgE, rheumatoid factor, and antinuclear antibodies and skin sensitivity to common allergens were measured in cases and in one matched control for each. FINDINGS: The relative risk of CFA, after adjustment for smoking, was significantly increased in relation to questionnaire-reported exposure to metal dust (odds ratio 1.68 [95% CI 1.07-2.65], p = 0.024) or to wood dust (1.71 [1.01-2.92], p = 0.048). Similar results were obtained with the telephone interview data. Significant exposure-response effects were found for both metal-dust and wood-dust exposure. CFA was also associated with the presence of rheumatoid factor or antinuclear antibodies, but not with positive allergen skin tests or raised IgE concentrations. There was no evidence of interaction between the effects of rheumatoid factor, antinuclear antibodies, positive skin allergen tests, or IgE concentrations and exposure to metal or wood dust. The combined aetiological fraction attributable to exposure to metal or wood dust was of the order of 20%. INTERPRETATION: Occupational exposures to metal or wood dust are independent risk factors for CFA. Avoidance or limitation of these exposures may provide an opportunity to prevent the disease.

Autoantibodies↗
PubMed1996

Mortality rates from cryptogenic fibrosing alveolitis in seven countries.

BACKGROUND: Registered mortality from cryptogenic fibrosing alveolitis (CFA) in England and Wales has increased substantially since the specific International Classification of Diseases code for CFA was introduced in 1979. However, since a significant proportion of deaths from CFA are misclassified as post inflammatory fibrosis (PIF), it is possible that the observed rise in CFA mortality is due to diagnostic transfer from this code. To investigate this, and to assess mortality trends in other countries, annual CFA and PIF mortality data from England and Wales, USA, Australia, Scotland, Canada, New Zealand, and Germany were analysed. METHODS: Crude annual mortality rates were calculated and rates standardised by Poisson regression to allow assessment of changes over time and comparison between countries, sexes, and age groups. The relative trends in mortality from CFA and PIF were assessed by calculating the annual ratio of CFA to PIF deaths. RESULTS: Men were more likely than women to die from both CFA and PIF in all countries. The highest standardised CFA mortality rate occurred in England and Wales, and the lowest in Germany. Since 1979 mortality from CFA has increased in England and Wales, Australia, Scotland and Canada, but there was no trend in CFA mortality in New Zealand or Germany. In the USA mortality from CFA was low and has fallen. Mortality from PIF increased in all countries except New Zealand and Germany, and the highest PIF mortality, together with the greatest increase over time, was seen in the USA. Changes over time in the annual ratio of CFA to PIF deaths in all countries were small, implying that diagnostic transfer is not a major cause of the increasing CFA mortality. CONCLUSIONS: Mortality from CFA continues to increase in England and Wales and in many other countries. Diagnostic transfer from PIF does not appear to be a major cause of this.

Adolescent↗
PubMed1996

Plasticity of fish muscle mitochondria with thermal acclimation

Short-horned sculpin Myoxocephalus scorpius were acclimated to 5 and 15 &deg;C to evaluate the impact of thermal acclimation upon maximal rates of substrate oxidation by mitochondria and upon the thermal sensitivity of their ADP affinity. Cold acclimation virtually doubled maximal rates of pyruvate oxidation at all experimental temperatures (2.5, 7.5, 12.5 and 20 &deg;C). Rates of palmitoyl carnitine oxidation were also enhanced by cold acclimation, but to a lesser degree. At their respective acclimation temperatures, the mitochondria attained similar rates of pyruvate oxidation. For warm-acclimated sculpin, the Q10 values for mitochondrial pyruvate and palmitoyl carnitine oxidation were higher between 2.5 and 7.5 &deg;C than between 7.5 and 12.5 &deg;C or between 12.5 and 20 &deg;C. In contrast, for cold-acclimated fish, the Q10 values did not differ over these thermal ranges. The Arrhenius activation energy for pyruvate oxidation was reduced by cold acclimation (from 70 to 55 kJ mol-1), whereas that for palmitoyl carnitine oxidation was unchanged (approximately 75 kJ mol-1). Cold acclimation did not alter the ADP affinity of mitochondria at low temperatures but markedly increased the apparent Km for ADP (Km,app) at 12.5 and 20 &deg;C. At the acclimation temperatures, mitochondrial ADP Km,app values did not differ. The loss of ADP affinity at higher temperatures may represent a cost of the enhanced maximal oxidative capacity achieved during cold acclimation.

Journal Article↗
PubMed1996

Molecular mechanisms underlying the plasticity of muscle contractile properties with temperature acclimation in the marine fish Myoxocephalus scorpius

Single fibres were isolated from the fast myotomal muscle of the short-horned sculpin (Myoxocephalus scorpius L.). Fish were acclimated to either 5 &deg;C (10 h:14 h light:dark) or 15 &deg;C (12 h:12 h light:dark) for 1&shy;2 months. Isometric tension (Fmax) and unloaded contraction velocity (Vslack) were determined in maximally activated skinned fibres over the range 0 to 20 &deg;C. Fibres isolated from 5 &deg;C-acclimated and 15 &deg;C-acclimated fish failed to relax completely following activations at 15 &deg;C and 20 &deg;C respectively. In 5 &deg;C-acclimated fish, Fmax increased from 75 kN m-2 at 0 &deg;C to 123 kN m-2 at 10 &deg;C and was not significantly higher at 15 or 20 &deg;C. The relationship between Fmax and temperature was not significantly different for cold- and warm-acclimated fish. Vslack was around 2.8 fibre lengths s-1 in both acclimation groups at 0 &deg;C, but it increased at a significantly faster rate with temperature in 15 &deg;C- than in 5 &deg;C-acclimated fish. At 20 &deg;C, Vmax was significantly higher in 15 &deg;C-acclimated (8.7 fibre lengths s-1) than in 5 &deg;C-acclimated fish (5.3 fibre lengths s-1). In order to investigate the molecular mechanism(s) underlying changes in Vmax, myosin was purified by ion-exchange chromatography. No difference in myosin heavy chain composition could be detected on the basis of peptide mapping with four different proteolytic enzymes. Two-dimensional polyacrylamide gel electrophoresis revealed no myofibrillar protein isoforms unique to either acclimation temperature. However, the ratio of myosin alkali light chain contents (LC3f:LC1f), as determined by capillary electrophoresis, was significantly lower in muscle from 15 &deg;C-acclimated (0.73) than from 5 &deg;C-acclimated fish (1.66). The results suggest that changes in Vmax are achieved via altered expression of myosin light chains independently of myosin heavy chain composition. In support of this hypothesis, the myofibrillar ATPase activity of fast muscle was not altered by temperature acclimation.

Journal Article↗
PubMed1995

High fertilization rate with intracytoplasmic sperm injection in mosaic Klinefelter's syndrome.

With the introduction of intracytoplasmic sperm injection (ICSI) as a practical successful treatment for male infertility, we are able to offer the procedure to a group of patients who probably could never father a child of their own. From a patient with mosaic Klinefelter's syndrome, sufficient motile sperm for intracytoplasmic sperm injection were obtained from a fresh ejaculate estimated to contain < 100 motile sperm. In the first IVF-ICSI attempt, out of seven oocytes that were collected from the wife, four were mature and were injected by ICSI. Fertilization occurred in all four oocytes but only one cleaved and was transferred to the uterus. Pregnancy test was negative 16 days after ET. In the second treatment cycle four out of eight oocytes were selected for ICSI. All four fertilized, three cleaved at the right time, and two were transferred into the wife's uterus. One embryo was frozen. Pregnancy test 16 days after ET was negative. The high fertilization rate achieved in this case indicates the potential of ICSI to treat extreme male infertility. Its use offers hope to those patients with conditions previously considered to be untreatable.

Adult↗
PubMed1995

Life-span development of odor identification, learning, and olfactory sensitivity.

In the first of three studies, children (aged 8 to 14 years) were found to perform worse than young and middle-aged adults in unprompted identification of doors, with average performance much like that of elderly adults. Comparisons on other tasks, specifically odor threshold, prompted odor identification, and object naming (Boston Naming Test), across the life span (five groups) revealed that children have the same excellent olfactory sensitivity as young adults and merely lack odor-specific knowledge that accumulates slowly through life. Such knowledge apparently accumulates so slowly that age-associated discriminative losses, measurable by early middle age, begin to wear away gains obtained through experience before odors can become overlearned. In the second study, a novel adaptive psychophysical method, the step procedure, confirmed the equivalent sensitivity of children and young adults. In the third study, a paired-associate task illustrated the sluggish course of odor learning. Young adults outperformed children, though the youngest group, first graders, made up ground relatively fast. For children and adults, common odors facilitated performance relative to novel odors. The outcome highlighted the relevance of semantic factors in odor learning irrespective of age.

Adolescent↗
PubMed1995

An improved diagnostic assay for Lambert-Eaton myasthenic syndrome.

A new immunoprecipitation assay has been established for detecting antibodies to voltage-gated calcium channels (VGCCs) in Lambert-Eaton myasthenic syndrome (LEMS), using 125I-omega-conotoxin MVIIC, which binds to P-type VGCCs, to label extracts of human cerebellum. Fifty six of 66 serum samples (85%) from patients with clinically and electrophysiologically definite LEMS were positive for the presence of VGCC antibodies, defined as a titre > 3 SD above the mean for the healthy controls (n = 10). All disease controls (n = 40) were negative. This sensitive immunoassay should prove valuable in the diagnosis of LEMS.

Aged↗
PubMed1995

Plasticity of muscle contractile properties following temperature acclimation in the marine fish Myoxocephalus scorpius

Live fibre bundles were isolated from the fast myotomal muscle of short-horned sculpin (Myoxocephalus scorpius L.) and isometric contractile properties and the force&shy;velocity (P&shy;V) relationship determined at 5, 10 and 15 &deg;C. Experiments were carried out on winter- and summer-caught sculpins and on individuals acclimated for 6&shy;8 weeks to either 5 or 15 &deg;C (12 h:12 h light:dark). Maximum tetanic tension (P0) in fibres from 15 &deg;C-acclimated fish increased from 125 kN m-2 at 5 &deg;C to 282 kN m-2 at 15 &deg;C (R10=2.3). For 5 &deg;C-acclimated fish, P0 was 139 kN m-2 at 5 &deg;C, but fell to 78 kN m-2 at 15 &deg;C, consistent with a partial failure of excitation&shy;contraction coupling at high temperatures. Peak force at 15 &deg;C was increased 2.2 times following depolarisation with a high-K+ solution, but was unaffected by the addition of caffeine and/or eserine to the Ringer's solution. The results from winter- and summer-caught fish were similar to those from 5 &deg;C- and 15 &deg;C-acclimated sculpins respectively. In 15 &deg;C-acclimated fish, the power output of muscle fibres calculated from the P&shy;V relationship was 55 W kg-1 at 5 &deg;C and 206 W kg-1 at 15 &deg;C. The P&shy;V relationship at 5 &deg;C was significantly less curved in muscle fibres from 5 &deg;C- than from 15 &deg;C-acclimated fish. After normalizing the curves for P0 and Vmax, it was found that the change in curvature was sufficient to produce a 40 % increase in relative power output at 5 &deg;C in cold-acclimated fish. The maximum contraction speed of muscle fibres at 15 &deg;C was 2.4 times higher in 15 &deg;C- than in 5 &deg;C-acclimated fish. It was concluded that acclimation modifies the contractile properties of fast muscle fibres at both low and high temperatures.

Journal Article↗