Biomedical subjects

D L Fletcher

Publications and source records attributed to D L Fletcher.

At least 55 records · Page 3Linked to original sources

PubMed1996

Immunologic basis of transplant-associated arteriosclerosis.

Although immunosuppressive therapy minimizes the risk of graft failure due to acute rejection, transplant-associated arteriosclerosis of the coronary arteries remains a significant obstacle to the long-term survival of heart transplant recipients. The participation of specific inflammatory cell types in the genesis of this lesion was examined in a mouse model in which carotid arteries were transplanted across multiple histocompatibility barriers into seven mutant strains with immunologic defects. An acquired immune response--with the participation of CD4+ (helper) T cells, humoral antibody, and macrophages--was essential to the development of the concentric neointimal proliferation and luminal narrowing characteristic of transplant arteriosclerosis. CD8+ (cytotoxic) T cells and natural killer cells were not involved in the process. Arteries allografted into mice deficient in both T-cell receptors and humoral antibody showed almost no neointimal proliferation, whereas those grafted into mice deficient only in helper T cells, humoral antibody, or macrophages developed small neointimas. These small neointimas and the large neointimas of arteries grafted into control animals contained a similar number of inflammatory cells; however, smooth muscle cell number and collagen deposition were diminished in the small neointimas. Also, the degree of inflammatory reaction in the adventitia did not correlate with the size of the neointima. Thus, the reduction in neointimal size in arteries allografted into mice deficient in helper T cells, humoral antibody, or macrophages may be accounted for by a decrease in smooth muscle cell migration or proliferation.

Animals↗

PubMed1996

Chronic ethanol treatment reduces the responsiveness of the hypothalamic-pituitary-thyroid axis to central stimulation.

The hypothalamic-pituitary-thyroid (HPT) axis functions abnormally in man and animals chronically exposed to ethanol. The most consistent observation in humans is that the thyrotropin response to thyrotropin-releasing hormone (TRH) is blunted. We have tested the hypothesis that chronic ethanol treatment in rats leads to a diminished responsiveness of the hypothalamus to central stimulation. Animals were maintained on 1 of 3 diets for 4 weeks: (1) laboratory chow and water provided ad libitum (chow-fed), (2) Sustacal chocolate liquid diet with vitamin mixture containing 5% (w/v) ethanol provided ad libitum (ethanol), or (3) Sustacal chocolate liquid diet with vitamin mixture containing sucrose substituted isocalorically (35%) for ethanol and provided in amounts matched to a weight-paired, ethanol-treated animal (pair-fed). At the end of 4 weeks, the animals were evaluated for their response to a single injection of ethanol (3 g/kg, ip) and/or exposure to 5 degrees C. Chronic ethanol treatment produced an increase in TRH mRNA in neurons of the paraventricular nucleus and fully blocked the thyrotropic response to cold exposure. However, chronic ethanol-treated animals did not exhibit altered basal levels of triiodothyronine or thyrotropin, nor did they have an altered response to a single injection of ethanol. These data demonstrate that chronic alcohol exposure alters functioning of the hypothalamic-pituitary-thyroid axis at least in part by affecting TRH neurons of the paraventricular nucleus.

Alcoholism↗

PubMed1996

The effect of temperature mishandling at various times during storage on detection of temperature abuse of fresh broiler chicken carcasses.

Experiments were conducted to determine the effect that temperature mishandling at various times during storage has on detection of temperature abuse of fresh broiler chicken carcasses using populations of mesophilic and coliform bacteria as indicators of abuse. Forty-five broiler carcasses were used in each of three independent trials. Five carcasses were analyzed at day of collection (Treatment 0 control). Five carcasses, on each day of the next 7 d (Treatments 1 to 7) were temperature-abused for 12 h at 25 C, stored at 3 C until Day 9, and then sampled. The five remaining carcasses were stored at 3 C and sampled on Day 9 (Treatment 8 control). Carcasses were sampled using a whole carcass rinse procedure and assayed for aerobic plate counts (APC), total coliform counts (TCC), impedance detection times (DT), and impedance coliform detection times (DTCM). Although significant differences were noted using all four microbiological methods, temperature abuse at different times during storage had no consistent effect on populations of mesophilic or coliform bacteria; therefore, temperature abuse determinations may be conducted without regard to the day on which the carcasses were subjected to elevated temperatures.

Animals↗

PubMed1996

The effects of stunning amperage and deboning time on early rigor development and breast meat quality of broilers.

Two trials were conducted to determine the effects of stunning amperage on the early rigor development and quality of broiler breast meat. In each trial, 108 broilers were killed either without stunning or following constant amperage stunning at 50 or 125 mA. The breast muscles (Pectoralis major) were removed from the carcasses at 0.2, 1, 2, 4, 6, 8, 10, 12, or 24 h post-mortem. Breast muscle pH and R-value (inosine to adenosine nucleotide ratio) were determined immediately upon deboning on one side of each carcass. After aging the deboned breast fillets for 48 h, cook loss and Allo-Kramer shear values were determined on the opposite side. Stunning at 50 or 125 mA resulted in significantly higher muscle pH values up to 6 h post-mortem, after which there were no further significant differences. Stunning at 50 and 125 mA resulted in significantly lower R-values up to 6 h post-mortem. Stunning had no effect on cook loss. Stunning at 125 mA resulted in significantly tougher meat up to 10 h post-mortem than meat from unstunned birds or birds stunned at 50 mA. These results indicate that the delayed onset of rigor, as measured by muscle pH and R-value, noted in electrically stunned birds lasts for approximately 4 to 6 h, after which differences due to stunning disappear.

Animals↗

PubMed1996

The influence of temperature on broiler breast muscle shortening and extensibility.

The purpose of this study was to characterize the influence of temperature on muscle shortening and extensibility in broiler breast muscle (Pectoralis major). The extent of prerigor muscle shortening has been shown to affect the ultimate tenderness of meat, whereas a decrease in extensibility has traditionally been used to define rigor mortis in muscle. Muscle shortening over time was determined at three incubation temperatures: 0, 23, and 41 C. Shortening was measured on intact and excised muscles, as well as on muscle strips with and without attached weight (200 g). The time a muscle strip needed to reach loss of extensibility was also determined at each of the three incubation temperatures. The intact and excised muscles showed some evidence of both cold and rigor (hot) shortening. No extreme shortening effects were found in the muscle strips incubated with or without attached weight. The use of muscle strips to predict intact muscle or excised whole muscle shortening in a complex muscle such as poultry Pectoralis may be limited. The time required to loss of extensibility of the muscle strips, i.e., rigor completion, was 5.5, 4.5, and 0.8 h at 0, 23, and 41 C, respectively. The results show that cold-induced shortening may contribute to toughening of early deboned broiler breast muscle, but its impact on commercial processing and subsequent meat tenderness does not appear to be consistent.

Animals↗

PubMed1995

In situ hybridization of mRNA expression for IP3 receptor and IP3-3-kinase in rat brain after transient focal cerebral ischemia.

Loss of intracellular calcium homeostasis has been regarded an important factor underlying neuron cell death after cerebral ischemic insult. In the brain, a major mechanism for regulation of intracellular calcium is through the signal transduction pathway involving hydrolysis of poly-phosphoinositides and release of the second messenger, inositol 1,4,5-trisphosphate (IP3). IP3 mobilizes calcium by interacting with an intracellular receptor. Upon its release after agonist stimulation, this second messenger is catabolized by a 3-kinase and a 5-phosphatase. In this study, in situ hybridization was carried out to examine the mRNA expression of IP3, receptor (IP3R) and IP3 3-kinase (IP3K) in rat brain cortex after transient focal cerebral ischemia induced by temporary occlusion of the middle cerebral artery (MCA) and the common carotid arteries (CCAs). Results indicate a large decrease (52%) in IP3R mRNA levels in the ischemic cortex as compared to that in the contralateral side at 4 h after a 45 min ischemic insult. By 16 h, practically no IP3R mRNA could be detected in the ischemic cortex. On the other hand, IP3K mRNA levels remained unaltered until 16 h after reperfusion, during which time, expression in the infarct core decreased but that surrounding the core area increased instead. Hybridization of adjacent brain sections with probes for neuron specific enolase (NSE) and beta-actin indicated also a time-dependent decrease in mRNA levels after ischemia, but these changes were less dramatic as compared to IP3R. At 16 and 24 h after reperfusion, there was an increase in beta-actin mRNA in cortical areas outside the MCA cortex, suggesting of reactive gliosis.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1995

A comparison of argon, carbon dioxide, and nitrogen in a broiler killing system.

Argon, CO2, and N2 gasses were each evaluated in a broiler chicken gas killing system. Birds were killed by individual exposure to one of the three gasses for 2 min in a flow-through system. The gasses were evaluated by determining the time, in seconds, for the following responses: first reaction to the gas, loss of posture, eye closure, initiation of death struggle, and cessation of respiration. Percentage blood loss over a 3-min bleed time was determined by weight loss. Breast muscle pH values were determined at 15 min and 24 h post-mortem on the Pectoralis major muscle. Carbon dioxide resulted in the earliest first reaction, loss of posture, eye closure, and initiation of struggle. Argon and N2 exhibited a delayed first reaction, a less severe early reaction, but a more severe unconscious death struggle. All birds died in approximately 75 s. Results indicate that the flow-through gas system takes longer to kill broilers than the immersion systems previously reported. Gas killing resulted in lower (P < .05) blood loss. Initial breast muscle pH values were significantly highest for the birds killed with CO2, followed by the control treatment, which was significantly higher than the values for broilers killed with either Ar or N2. After 24 h of chilling, there were no differences in broiler breast muscle pH among the four treatments. These results indicated that a flow-through gassing chamber may be a feasible, although slower, method of performing gas killing as compared to an immersion system.

Abattoirs↗

PubMed1995

Effect of stunning amperage on broiler breast muscle rigor development and meat quality.

Two experiments were conducted to determine the effects of constant amperage (as opposed to constant voltage) electrical stunning on broiler blood loss, post-mortem breast muscle (Pectoralis major) rigor development, and breast meat quality. Broilers were individually stunned for 5 s at 0 (unstunned control group), 50, 100, 150, and 200 mA in Experiment 1 and at 0, 50, and 125 mA in Experiment 2. Breast muscle pH and R-value (ratio of adenosine to inosine nucleotides) were determined at 15 min and 24 h post-mortem; breast meat shear value and color were determined at 48 h post-mortem. Stunning amperage had no effect on percentage blood loss in either experiment. The most rapid post-mortem reactions were observed for the unstunned control group as determined by pH and R-value at 15 min post-mortem. Birds stunned with 50 mA were intermediate with regard to rate of rigor development. The slowest post-mortem reactions occurred in broilers stunned from 100 to 200 mA. There were no differences in pH, R-value, or color between stunning treatments after carcasses were aged for 24 h. Stunning amperage did not affect Allo-Kramer shear value for breast muscles deboned at 15 min post-mortem. In Experiment 2, 24 h aged breast meat from broilers stunned with 125 mA required significantly higher shear value (4.5 kg/g) than breast meat from broilers stunned at 0 or 50 mA (3.8 and 3.6 kg/g, respectively). Results indicate that stunning amperages between 0 and 200 mA had effects on the rate of early rigor development but there were no consistent effects on final breast meat quality.

Animals↗

PubMed1995

Effect of electrical stunning amperage and peri-mortem struggle on broiler breast rigor development and meat quality.

Two experiments were conducted to determine the effects of electrical stunning and peri-mortem muscle activity (struggle in and around the time of slaughter) on post-mortem biochemical reactions in broiler breast muscle (Pectoralis major). Broilers were stunned with either 50 or 125 mA or were killed without stunning. In Experiment 1 (n = 273), broilers were either physically restrained to reduce struggling during slaughter or were unrestrained and allowed to struggle freely. Breast mean pH and R-value (ratio of adenosine to inosine nucleotides) were determined at 15 min and 24 h post-mortem, and Allo-Kramer shear was determined on 48 h post-mortem cooked meat samples from muscles excised at 15 min or 24 h. In Experiment 2 (n = 65), the breast muscle was unilaterally denervated by surgically severing the Pectoralis nerve on one side and performing a sham operation on the contralateral side. Results indicated that physical restraint resulted in higher muscle pH and lower R-values at 15 min post-mortem in the unstunned birds and birds stunned at 50 mA, but had no effect on breast meat from birds stunned at 125 mA. There were no treatment effects on meat tenderness or 24-h post-mortem pH or R-values. Stunning amperage had no effect on denervated muscle pH at 15 min post-mortem, but did affect the sham-operated muscle pH and R-values as in Experiment 1. These results indicate that the main effect of electrical stunning on early rigor development may be due primarily to inhibition of peri-mortem struggle.

Animals↗

PubMed1995

Spoilage bacteria of fresh broiler chicken carcasses.

Studies were conducted to identify the bacteria responsible for spoilage of fresh broiler chicken carcasses and to characterize the off-odors these bacteria produce. Broiler carcasses were collected from processing plants in the northeast Georgia area, the southeastern U.S., Arkansas, California, and North Carolina. The carcasses were allowed to spoil under controlled conditions at 3 C and spoilage bacteria were isolated. Each spoilage bacterium was separately inoculated into a sterile chicken skin medium, incubated at 25 C for 48 h, and subjectively evaluated for odor. The bacteria isolated from spoiled carcasses that consistently produced off-odors in the chicken skin medium, regardless of the geographical location from which the chickens were obtained, were Shewanella putrefaciens A, B, and D, Pseudomonas fluorescens A, B, and D, and Pseudomonas fragi. These bacteria produced off-odors that resembled "sulfur", "dishrag", "ammonia", "wet dog", "skunk", "dirty socks", "rancid fish", "unspecified bad odor", or a sweet smell resembling "canned corn". Odors produced by the spoilage bacteria were varied; however, odors most associated with spoiled poultry, such as "dishraggy" odors, were produced by the bacteria that were most consistently isolated, such as S. putrefaciens and the pseudomonads.

Acinetobacter↗

PubMed1994

A single administration of ethanol simultaneously increases c-fos mRNA and reduces c-jun mRNA in the hypothalamus and hippocampus.

We have previously demonstrated that a single administration of ethanol induces the expression of c-fos mRNA in the hypothalamic paraventricular nucleus (PVN). However, Fos protein must interact with a member of the Jun family to form functional heterodimers. To determine whether ethanol may have differential effects on c-fos and c-jun expression, we injected male rats acclimated to a 25 degrees C environment with ethanol (3 g/kg b.wt.) or saline. Using in situ hybridization histochemistry with oligonucleotide probes, we found that ethanol increased c-fos mRNA in the PVN, but decreased c-jun mRNA both in the PVN and in hippocampus. Considering that ethanol produces hypothermia and that the PVN contains neurons activated during hypothermia, we evaluated the effect of cold on c-fos and c-jun mRNA. Both cold and ethanol increased c-fos mRNA, and the effects were additive. However, c-jun mRNA levels in both PVN and hippocampus were unaffected by temperature. Finally, c-jun mRNA levels in the hippocampus were significantly reduced by chronic ethanol exposure, and this trend was also observed in the PVN. These findings demonstrate that a single injection of ethanol has opposite effects on the expression of nuclear transcription factors which interact to regulate gene expression in the nervous system.

Alcoholism↗

PubMed1994

Limited postnatal ethanol exposure permanently alters the expression of mRNAS encoding myelin basic protein and myelin-associated glycoprotein in cerebellum.

Experiments were designed to test the hypothesis that ethanol exposure during development can selectively affect the expression of specific isoforms of myelin protein gene expression in the rat cerebellum. We focused on myelin basic protein (MBP) and myelin-associated glycoprotein (MAG) gene expression. Both of these genes are alternatively spliced to yield 4 (MBP) or 2 (MAG) mRNA isoforms. Prenatal ethanol exposure, delivered to the dams in a liquid diet, did not significantly alter the expression of MBP or MAG gene expression in the cerebellums of 15-day-old pups, as measured by quantitative in situ hybridization using specific oligodeoxynucleotide probes. In contrast, postnatal ethanol exposure delivered directly to the pups over a 6-day period by gastrostomy tube (PN days 4-10) reduced the expression of specific MBP and MAG isoforms in the cerebellum of animals in adulthood. These data demonstrate that ethanol exposure, especially during the period of rapid myelination, has selective effects on mRNA isoforms encoding specific MBPs and MAG.

Animals↗

PubMed1994

Effect of freezing on the recovery of mesophilic bacteria from temperature-abused broiler chicken carcasses.

The effects of freezing on the recovery of mesophilic bacteria from broiler chicken carcasses were determined. Fifty fresh broiler carcasses were used in each of three independent trials. Ten carcasses were sampled at time of collection (Treatment 1: Day 0 control). The other 40 carcasses were sampled at Day 7 following one of four additional treatments with 10 carcasses each: held at 3 C (Treatment 2: 7-d control), frozen and then held at 3 C (Treatment 3: frozen control), temperature abused at 25 C for 12 h and held at 3 C (Treatment 4: temperature abused), and temperature abused at 25 C for 12 h, frozen, and held at 3 C (Treatment 5: temperature abused and frozen). Carcasses were sampled by rinsing, and total plate counts (TPC) expressed as log10 colony-forming units per milliliter and impedance detection times (DT) in hours were determined using incubation temperatures of 42 and 43 C, respectively. Results for TPC for Treatments 1 to 5 were 3.89, 3.52, 2.86, 6.53, and 5.57 log10 cfu/mL, respectively. Results for DT for Treatments 1 to 5 were 5.41, 6.50, 7.10, 2.55, and 3.42 log10 cfu/mL, respectively. Freezing reduced the ability to detect temperature abuse because of a significant reduction in the number of mesophiles recovered using either microbiological technique. Freezing appears to decrease, but may not completely eliminate, the ability of selective incubation to detect temperature abuse.

Animals↗

PubMed1994

The effect of incubation temperature on recovery of mesophilic bacteria from broiler chicken carcasses subjected to temperature abuse.

The optimum temperature to recover mesophilic organisms from temperature-abused broiler chicken carcasses was determined. Twenty broiler carcasses were collected from a commercial processing plant in each of three trials. Ten carcasses were sampled immediately (Day 0 control); 8 carcasses were sampled after holding at 3 C for 3 d, temperature abusing at 25 C for 12 h, and holding them at 3 C for an additional 3 d (temperature abused); and the remaining 2 carcasses were sampled after holding at 3 C for 7 d (Day 7 control). Whole carcass rinses were analyzed using total aerobic plate counts (TPC) and impedimetric detection times (DT) at incubation temperatures of 41, 42, 43, and 44 C. Total plate counts decreased (P < .05) and DT increased (P < .05), at all incubation temperatures tested, for carcasses held under refrigeration (Day 7 control). This demonstrates that mesophilic bacteria, rather than psychrotrophic bacteria, are being enumerated, because psychrotrophs increase on chicken skin upon cold storage. Total plate count was greater (P < .05) and DT was significantly lower for temperature-abused vs Day 7 control birds (5.7 vs 3.6 log10 cfu/mL and 3.7 vs 6.5 h), respectively. These results indicate that temperature-abused carcasses can be microbiologically distinguished from nonabused controls at all incubation temperatures tested. Recovery of mesophiles was optimal at 41 and 42 C for TPC and 41, 42, and 43 C for DT. Because there were no differences between DT at 41, 42, and 43 C, and because 42 C has been successfully used in the past, either 42 C or 43 C can be used when determining DT.

Animals↗

PubMed1993

Effect of lactic acid fermentation on bacterial pathogens and indicator organisms in broiler processing waste.

Broiler processing offal (heads, viscera, and feet) was collected on 3 separate days from a commercial processing plant. Each sample was separately ground, supplemented with sucrose (6% initial concentration), inoculated with actively growing lactic acid bacteria (10(6) cfu/g of offal) from a commercial silage culture, and fermented at 37 C. Replicate samples were taken for standard microbiological analysis after 0, 48, and 120 h of fermentation. In fresh offal, heterotrophic plate count, total and fecal coliforms, fecal streptococci, and Aeromonas hydrophila concentrations were 7.4, 5.9, 5.9, 5.4, and 3.9 log10 cfu/g wet weight, respectively. After 48 h of fermentation, the bacterial concentrations were 7.6, 2.2, < 1.3, 5.5, and < 2.3 log10 cfu/g wet weight, respectively. After 120 h of fermentation, the bacterial concentrations were 6.9, < 1.1, < 1.1, < 1.1, and < 1.1 log10 cfu/g wet weight, respectively. Salmonella concentrations in fresh, 48-h fermented, and 120-h fermented offal samples were 3.7, < 1.5, and < 1.5 log10 most-probable-number/100 g wet weight, respectively. Lactic acid fermentation appears to be effective in reducing the number of bacterial pathogens and indicator organisms in poultry processing offal.

Animal Feed↗

PubMed1993

An evaluation of a rinse procedure using sodium bicarbonate and hydrogen peroxide on the recovery of bacteria from broiler carcasses.

A patent entitled "Reduction of Bacteria Count on Poultry Being Processed into Food at a Poultry Processing Plant" (U.S. Patent No. 4,683,618) claimed that a three-step rinse process using sodium bicarbonate and hydrogen peroxide solutions would remove bacteria from the surface of broiler carcasses. In three replicate trials, 40 broilers were obtained postchill from a commercial processing plant. Broilers (n = 20) were treated according to the patent by spraying the inside and outside surfaces of each carcass with a 2% NaHCO3 solution for 5 s and rinsing with water, repeating, spraying with a 3% H2O2 solution for 5 s, and rinsing a final time with water. Controls (n = 20) were treated identically except that in each of the rinse steps tap water was used in place of the test solutions. Whole carcass rinses were conducted and total aerobic plate counts (TPC) and impedance detection times (DT) were determined after 1 h and 7 days at 4 C. The NaHCO3 + H2O2 treatment resulted in no significant difference in TPC at 1 h post-treatment but did result in lower TPC after 7 days and greater DT at both 1 h and 7 days. The procedure was effective in reducing the recovery of bacteria at 7 days post-treatment by .3 log10 but was not effective in removing the bacteria to the extent implied in the patient. Based on previous studies using H2O2, these results are not unexpected, but commercial applicability remains questionable based on actual reduction levels.

Analysis of Variance↗

PubMed1993

Utilization of crude and refined palm and palm kernel oils in broiler diets.

Four experiments were conducted to evaluate the use of crude and refined palm (PAO) and palm kernel oil (PKO) in diets for broiler chickens. In Experiment 1, refined PAO and PKO were compared with corn oil (CO) and poultry oil (PO) at levels up to 10%. In Experiment 2, refined PAO and PKO were compared with PO at levels up to 8%. In Experiments 3 and 4, crude PAO and PKO were compared with PO at levels up to 8%. Diets were formulated based on the energy level assigned to PAO; other oils were added in amounts calculated to be isocaloric with an inert filler as required. Live production variables were measured. Samples of birds were processed to determine carcass characteristics, and fatty acid composition of adipose tissue was determined. In all studies, broilers fed crude or refined sources of PAO and PKO grew as well and utilized their feed as efficiently as those fed diets with isocaloric amounts of CO or PO. There were minimal interactions of source and dietary level of oil in any of the studies. Dressing percentage and quantity of abdominal fat were not influenced by source of supplemental oil; however, the fatty acid profile of adipose tissue was altered by the source of supplemental oil. There were only minor differences in fatty acid content of adipose tissue of broilers fed PAO (either crude or refined) versus those fed PO. However, increasing levels of PKO resulted in increased deposition of saturated fatty acids, especially lauric and myristic acid, and decreased concentrations of both monoenoic and polyunsaturated fatty acids. The resulting change in hardness of adipose tissue may prove to be advantageous in marketing.

Adipose Tissue↗

PubMed1992

Effect of genetic background on the developmental expression of c-fos and c-myc in chicken.

The developmental expression of the protooncogenes, c-fos and c-myc, in muscle and liver of 14- and 19-day embryos and 1-, 6-, 8- and 28-day-old chicks of Athens Canadian Random Bred (ACRB) Single Comb White Leghorn (SCWL) and Peterson X Arbor Acres commercial broiler (PXAA) was determined. For the three stocks of chicken, significant differences were found in c-fos and c-myc expression. For both muscle and liver, averaged across ages, abundance of c-fos RNA was highest in PXAA and lowest in ACRB with differences significant at the P less than 0.01 level. c-myc RNA levels were significantly higher (P less than 0.01) in PXAA than in ACRB or SCWL liver. Taken over the developmental period, expression of c-fos RNA in muscle increased at different rates between breeds from 14-day embryo levels to peak levels in 6- to 8-day-old chicks and declined in 28-day-old chicks. Levels of c-fos were much lower in liver and showed no consistent differences related to developmental stage. A steady decline in c-myc from 14-day embryo levels to 28-day-old chicks was found in both muscle and liver. This decline in c-myc levels generally parallels the decline in relative growth rates which occurs in all breeds over the developmental period. In liver, the fast growing PXAA had the highest levels of c-myc, c-fos, on the other hand, showed elevated levels in PXAA for both muscle and liver and distinctly different patterns between these two tissues over the developmental period, suggesting tissue-specific involvement in growth.

Animals↗