Biomedical subjects

Paul L Greenwood

Publications and source records attributed to Paul L Greenwood.

3 recordsLinked to original sources

PubMed2006

A gene coexpression network for bovine skeletal muscle inferred from microarray data.

We present the application of large-scale multivariate mixed-model equations to the joint analysis of nine gene expression experiments in beef cattle muscle and fat tissues with a total of 147 hybridizations, and we explore 47 experimental conditions or treatments. Using a correlation-based method, we constructed a gene network for 822 genes. Modules of muscle structural proteins and enzymes, extracellular matrix, fat metabolism, and protein synthesis were clearly evident. Detailed analysis of the network identified groupings of proteins on the basis of physical association. For example, expression of three components of the z-disk, MYOZ1, TCAP, and PDLIM3, was significantly correlated. In contrast, expression of these z-disk proteins was not highly correlated with the expression of a cluster of thick (myosins) and thin (actin and tropomyosins) filament proteins or of titin, the third major filament system. However, expression of titin was itself not significantly correlated with the cluster of thick and thin filament proteins and enzymes. Correlation in expression of many fast-twitch muscle structural proteins and enzymes was observed, but slow-twitch-specific proteins were not correlated with the fast-twitch proteins or with each other. In addition, a number of significant associations between genes and transcription factors were also identified. Our results not only recapitulate the known biology of muscle but have also started to reveal some of the underlying associations between and within the structural components of skeletal muscle.

Adipose Tissue↗

PubMed2003

Plasma leptin is regulated predominantly by nutrition in preruminant lambs.

In juvenile and mature animals, the plasma concentration of leptin is regulated by adiposity and nutrition. However, the timing of these influences on plasma leptin, and their relative importance in early postnatal life, are unknown. We investigated these plasma leptin influences in sheep, a species characterized during fetal life by leanness and insensitivity of leptin to variation in maternal nutrition. Small and large neonatal lambs were randomly assigned to either a diet sustaining an average daily weight gain (ADG) of 148 g/d (Low plane) or ate ad libitum a diet sustaining an ADG of 337 g/d (High plane). A subset of animals were slaughtered at 7.5, 10, 15 and 20 kg of body weight. Birth size had no effect on plasma leptin concentrations and adiposity at birth or at later times. Plasma leptin concentrations increased within 6 d of birth in the High plane lambs (P < 0.01) and continued to rise over time. In contrast, plasma leptin concentrations never changed in the Low plane lambs despite increasing adiposity. The positive association between plasma leptin concentration and adiposity was greater in the High plane than in the Low plane lambs, suggesting an independent effect of nutrition. Consistent with this finding, lipid accretion rates, a variable that is mostly independent of adiposity, was a strong predictor of plasma leptin concentrations only in the High plane lambs (R(2) = 0.77, P < 0.01). A positive association between plasma insulin and leptin developed over time in the High plane lambs (R(2) = 0.75, P < 0.01 on d 40), but was not seen in the Low plane lambs. These data indicate that both nutrition and adiposity regulate plasma leptin synthesis in early postnatal life, but in contrast to adulthood, the effects of nutrition appear to be predominant.

Adipose Tissue↗

PubMed2002

Prediction of stage of pregnancy in prolific sheep using ultrasound measurement of fetal bones.

The use of ultrasound to estimate stage of pregnancy was assessed in 32 ewes of a prolific genotype carrying 7 singleton fetuses and 9 twin, 10 triplet and 6 quadruplet litters that were scanned on six occasions from 60 to 120 days of gestation. At least one ultrasound measurement per ewe of fetal metacarpal bone length (MCL), biparietal diameter (BPD), or of both bones was made on over 90% of attempts (n = 152). Measurement of MCL was made on 78% of attempts (n = 371), of BPD on 73% of attempts, and of both bones on 62% of attempts. The equation developed from BPD (mean absolute error (MAE) = 3.2 days) was similar to that developed from measurement of MCL (MAE = 3.3 days) in its capacity to predict stage of pregnancy. Accuracy of prediction was improved using equations that included mean values within litters for BPD (MAE = 2.5 days) and MCL (MAE = 2.6 days). Further improvement in predictive capacity was achieved using multiple regression equations developed from measurement of both bones (individual fetuses: MAE = 2.6 days; equations including mean values within litters: MAE = 2.2 days). The results demonstrate that ultrasound can be used to estimate stage of pregnancy in prolific ewes, and that the use of mean values for bone measurements from different fetuses within litters and/or measurement of bones with different growth allometry can increase the reliability of estimates. The utility of the procedure depends on the number of fetuses measured per ewe, the number of bones measured per fetus and, hence, the time required to measure bones and the degree of accuracy required.

Animals↗