Variation of actin filament length in dogs.

As the smallest functional unit of force production, the sarcomeres are important in determining muscle function. Actin filament lengths, which are important in determining optimal sarcomere length for a species, have not yet been reported in dogs. This study aims to provide a species-specific value for actin filament length in dogs, while examining intraspecies, intermuscular and intramuscular variations. Muscle samples were taken from the tibialis anterior muscle, the lateral gastrocnemius muscle head and the medial gastrocnemius muscle head in 10 dogs including a Labrador, a Belgian Malinois, a Caucasian Shepherd, German Shepherds and some mixed-breed dogs. Actin filament lengths were determined through transmission electron microscopy. Mean actin filament length across all muscle samples was 0.90 ± 0.01 µm. The low intraspecies variation, combined with a lack of important inter- and intramuscular variation found in this study, affirms the use of a species-specific optimal sarcomere length of 1.89 µm for canine muscles.

Musculotendon excursion potential, tendon slack and muscle fibre length: the interaction of the canine gastrocnemius muscle and tendon.

Although the form-function relation of muscles and tendons has been studied extensively, little in vivo data exist on the musculotendon properties of the gastrocnemius complex in dogs. Using a combination of ultrasound and 3D motion tracking, musculotendon parameters were obtained in vivo from the lateral gastrocnemius muscle and the gastrocnemius tendon in nine healthy Labrador Retrievers. These parameters include musculotendon length and excursion potential, tendon slack length, muscle belly length, muscle fibre length, pennation angle and architectural index. This study also examined the variation of muscle and tendon length contributions to musculotendon length, as well as the relation between musculotendon excursion potential and muscle fibre length or tendon length. To facilitate comparison between dog breeds, the femur length as a potential scaling parameter was examined. In the Labrador gastrocnemius musculotendon complex, the tendon contributes 41% (± 9%) of musculotendon length. In longer musculotendon complexes, the contribution of the muscle belly increases while the tendon contribution decreases. Longer muscle belly and musculotendon complexes were, however, associated with shorter muscle fibres. No significant relations were found between musculotendon excursion potential and muscle fibre length or tendon slack length, and femur length did not prove to be a reliable scale factor for the length-related musculotendon parameters examined in this study. Longer musculotendon complexes exhibit relatively longer muscle bellies, which are in turn associated with shorter muscle fibre lengths. This trade-off between gastrocnemius muscle belly length and muscle fibre length might have the advantage that muscle volume stays constant regardless of the length of the limbs.

FTIR spectra of whey and casein hydrolysates in relation to their functional properties.

Mid-infrared spectra of whey and casein hydrolysates were recorded using Fourier transform infrared (FTIR) spectroscopy. Multivariate data analysis techniques were used to investigate the capacity of FTIR spectra to classify hydrolysates and to study the ability of the spectra to predict bitterness, solubility, emulsifying, and foaming properties of hydrolysates. Principal component analysis revealed that hydrolysates prepared from different protein sources or with different classes of proteolytic enzymes are distinguished effectively on basis of their FTIR spectra. Moreover, multivariate regression analysis showed satisfactory to good prediction of functional parameters; the coefficient of determination (R(2)) varied from 0.60 to 0.92. The accurate prediction of bitterness and emulsion forming ability of hydrolysates by using only one uncomplicated and rapid analytical method has not been reported before. FTIR spectra in combination with multivariate data analysis proved to be valuable in protein hydrolysate fingerprinting and can be used as an alternative for laborious functionality measurements.

Accurate prediction of xanthine oxidase inhibition based on the structure of flavonoids.

The flavonoid family shows a high potential for inhibition of xanthine oxidase. Currently, more than 4,000 flavonoids are known. The data of this study indicate that a planar structure is necessary for high inhibitory activity towards xanthine oxidase. Moreover, the contribution of a hydroxyl conjugate turns out to be a constant factor when the natural logarithm of IC(50) values is taken. This finding allows us to accurately predict the IC(50) value of any given hydroxyl group added to the basic flavone structure towards xanthine oxidase. This new method may provide an important research tool for elucidating the role that flavonoids may have in radical related diseases.

Correlations between biochemical characteristics and foam-forming and -stabilizing ability of whey and casein hydrolysates.

Whey protein and casein were hydrolyzed with 11 commercially available enzymes. Foam properties of 44 samples were measured and were related to biochemical properties of the hydrolysates using statistical data analysis. All casein hydrolysates formed high initial foam levels, whereas whey hydrolysates differed in their foam-forming abilities. Regression analysis using the molecular weight distribution of whey hydrolysates as predictors showed that the hydrolysate fraction containing peptides of 3-5 kDa was most strongly related to foam formation. Foam stability of whey hydrolysates and of most casein hydrolysates was inferior to that of the intact proteins. The foam stability of casein hydrolysate foams was correlated to the molecular weight distribution of the hydrolysates; a high proportion of peptides >7 kDa, composed of both intact casein and high molecular weight peptides, was positively related to foam stability.