Biomedical subjects

T Crockford

Publications and source records attributed to T Crockford.

6 recordsLinked to original sources

PubMed1999

Aspects of the epizootiology of pancreas disease in farmed Atlantic salmon Salmo salar in Ireland.

A computerised database containing information on over 17.8 million salmon contained within 49 separate marine populations was used to study the epidemiology of pancreas disease (PD) in Ireland. Of the 43 recorded PD outbreaks, 57% occurred in the 3 mo period August to October inclusive (17 to 32 wk post-transfer). Analysis of variance of mortality rates during PD outbreaks occurring on 6 marine sites over a 5 yr period showed that mortality rates vary significantly between sites (p < 0.001) but not between years over this time period. The mortality rate during PD outbreaks ranged from 0.1 to 63%. Mortality rates were significantly higher when PD outbreaks occurred earlier in the year (y = -1.28x + 59, SE of b 0.33). The mean length of a PD outbreak was 112 d (SE = 7.7, n = 37). There was no correlation between PD mortality rate and smolt input weight, initial stocking density and transfer mortality.

Animals↗

PubMed1995

Isolation of unstable myosins and the analysis of light chains by capillary electrophoresis.

A rapid method for the isolation of unstable fish myosins by Sepharose Q ion-exchange chromatography is described which yields a pure protein essentially free of contamination or breakdown products in less than 6 h. A protocol was developed for determining the molar ratios of myosin light chains (LC) by capillary electrophoresis. The method is quantitative, rapid (<20 min), highly reproducible (<2.1% variation in relative peak migration time), and only uses Femtomole quantities of protein. It was able to separate myosin light chains which could previously only be resolved by 2-D sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). Capillary electrophoresis in the presence of SDS gave similar apparent relative molecular masses (M(r)) for most proteins, but an anomalously high M(r) for myosin light chain 3(LC3), as has been reported previously for SDS-PAGE methods.

Animals↗

PubMed1995

Functionally significant allelic variation in myosin light chain composition in a tropical cichlid

Single fast muscle fibres in the tropical fish Oreochromis andersonii were found to contain two myosin light chains (LC1s; LC1f1* or LC1f2*). Breeding experiments confirmed that the different LC1s were of allelic origin and their inheritance patterns conformed to Mendelian expectations (1:2:1). The LC1s differed in apparent relative molecular mass by 800900. No other differences in myosin subunits were found between the LC1 genotypes. The molar ratios of LC3:LC1(total) in the fast muscle of O. andersonii homozygous for LC1f1* or LC1f2* and heterozygous for both alleles were 2.0:1, 2.1:1 and 2.2:1, respectively, as determined by capillary electrophoresis. The maximum contraction velocity (Vmax) of single skinned muscle fibres was determined at 20 °C by the slack-test method. Vmax values (fibre lengths s-1) for fast muscle fibres from O. andersonii which were homozygous for either LC1f2* or LC1f1* were 5.3 and 3.3, respectively, compared with 3.8 when both alleles were present. Crosses between Oreochromis niloticus and O. andersonii produced F1 hybrids which were heterozygous for either LC1n/LC1f1* or LC1n/LC1f2*, where LC1n is the myosin light chain for O. niloticus. The distribution of myosin light chain genotypes in hybrid offspring was not significantly different from the expected Mendelian 1:1 ratio (47 %: 53 %). The Vmax (fibre lengths s-1) of muscle fibres containing LC1f2* from hybrid Oreochromis was 4.3 compared with 3.1 for the LC1f1* genotype. The results are consistent with a functionally significant allelic variation in myosin LC1 in fast muscle fibres from O. andersonii which is also expressed in hybrid genotypes.

Journal Article↗

PubMed1994

ARE MITOCHONDRIA SUBJECT TO EVOLUTIONARY TEMPERATURE ADAPTATION?

Thermal tolerance and the respiratory properties of isolated red muscle mitochondria were investigated in Oreochromis alcalicus grahami from the alkaline hot-springs, Lake Magadi, Kenya. Populations of O. a. grahami were resident in pools at 42.8 °C and migrated into water reaching temperatures of 44.8 °C for short periods. The maximum respiration rates of mitochondria with pyruvate as substrate were 217 and 284 natom O mg-1 mitochondrial protein min-1 at 37 °C and 42 °C, respectively (Q10=1.71). Fatty acyl carnitines (chain lengths C8, C12 and C16), malate and glutamate were oxidised at 7080 % of the rate for pyruvate. In order to assess evolutionary temperature adaptation of maximum mitochondrial oxidative capacities, the rates of pyruvate and palmitoyl carnitine utilisation in red muscle mitochondria were measured from species living at other temperatures: Notothenia coriiceps from Antarctica (-1.5 to +1 °C); summer-caught Myoxocephalus scorpius from the North Sea (1015 °C); and Oreochromis andersoni from African lakes and rivers (2230 °C). State 3 respiration rates had Q10 values in the range 1.82.7. At the lower lethal temperature of O. andersoni (12.5 °C), isolated mitochondria utilised pyruvate at a similar rate to mitochondria from N. coriiceps at 2.5 °C (30 natom O mg-1 mitochondrial protein min-1). Rates of pyruvate oxidation by mitochondria from M. scorpius and N. coriiceps were similar and were higher at a given temperature than for O. andersoni. At their normal body temperature (-1.2 °C), mitochondria from the Antarctic fish oxidised pyruvate at 5.5 % and palmitoyl-dl-carnitine at 8.8 % of the rates of mitochondria from the hot-spring species at 42 °C. The results indicate only modest evolutionary adjustments in the maximal rates of mitochondrial respiration in fish living at different temperatures.

Journal Article↗

PubMed1991

Inter- and intra-specific variation in myosin light chain and troponin I composition in fast muscle fibres from two species of fish (genus Oreochromis) which have different temperature-dependent contractile properties.

The contractile properties and myofibrillar protein composition of fast muscle have been characterized in pure strains of two tropical fish Oreochromis niloticus and O. andersoni. Single fast muscle fibres were isolated from the abdominal myotomes and chemically skinned. The maximum tension-temperature relationships of fibres were similar at 25-30 degrees C, but diverged below 17 degrees C. At 10 degrees C, maximum tension was around 60% higher in O. andersoni (160 +/- 15 kN m-2) than O. niloticus (105 +/- 13 kN m-2) (mean +/- SD). The myofibrillar protein composition of fast fibres was investigated using one-dimensional and two-dimensional gel electrophoresis and peptide mapping. The two Oreochromis species differed with respect to the composition of myosin light chains, troponin I and myosin heavy chains (V8 protease and chymotrypsin peptide maps). An unexpected finding was the presence of two isoforms of myosin light chain 1 in O. andersoni, with apparent molecular masses of 27.5 kDa (LC1f1) and 26.9 kDa (LC1f2). Individuals with LC1f1 (n = 20) and LC1f1 + LC1f2 (n = 12) were represented in the population studied. The myosin light chain 3 (LC3f) content of fibres was similar in both cases. Breeding experiments established that these intra-specific variations in isoform composition were heritable. Fast muscle from O. niloticus and O. andersoni contain two isoforms of troponin I (TNIfl + TNIf2) which were both expressed in single fibres. The identity of TNI was confirmed using a stationary phase troponin-C affinity column. Of the 20 O. niloticus studied seven contained only TNIf1.(ABSTRACT TRUNCATED AT 250 WORDS)

Adaptation, Physiological↗

PubMed1990

Thermal acclimation and muscle contractile properties in cyprinid fish.

After several weeks of cold acclimation, the swimming performance of some fish is increased at low temperatures and decreased at high temperatures. The temperature compensation of locomotory activity involves changes in central patterns of muscle fiber recruitment and in the properties of the peripheral nervous system and muscle tissues. In some freshwater fish belonging to the family Cyprinidae, including the goldfish (Carassius auratus), the common carp (Cyprinus carpio), and the roach (Rutilus rutilus), the intrinsic contractile properties of muscles are modified by thermal acclimation. Parameters that can be altered by temperature acclimation in both fast and slow muscle fibers include isometric twitch contraction time, maximum force production, and unloaded shortening speed. The molecular mechanisms responsible for these changes in contractility are discussed.

Acclimatization↗