Peter J. Bechtel

Changes in the metabolic profile of the equine gluteus medius as a function of sampling depth

1. Cross sections from the middle of the gluteus medius were removed from 10 adult horses and used to evaluate changes in histochemically determined muscle fiber type and biochemically determined metabolic enzyme activities as a function of sample depth. 2. Muscle fiber types determined using histochemical methods for myosin ATPase (pH 9.4) and succinic dehydrogenase (SDH) activity indicated percent fast-twitch glycolytic (FG) muscle fibers decreased and slow-twitch oxidative (SO) fibers increased as a function of increasing sampling depth. 3. Percent histochemically determined fast-twitch oxidative glycolytic (FOG) fibers decreased slightly only in the deepest region of the gluteus medius. 4. Citrate synthase (CS) enzymatic activity, used as a marker for mitochondrial oxidative potential, increased 2.5-fold in activity per g of muscle protein from 1 to 8 cm sampling depth. 5. 3-hydroxyacyl-CoA dehydrogenase (HAD) enzymatic activity, used as a marker for lipid oxidation potential, increased 3-fold in activity per g of muscle protein when the depth increased from 1 to 8 cm. 6. Phosphorylase (PS) enzymatic activity, used as a marker for potential glycogen utilization, decreased 50% in activity per g of muscle protein when going from 1 to 8 cm. 7. Lactate dehydrogenase (LDH) enzymatic activity, used as a marker for anaerobic glycolytic potential, decreased about 50% in activity as the sampling depth increased from 1 to 8 cm. 8. In summary, the superficial portion of the equine gluteus medius was found to be more glycolytic and less aerobic in its metabolic profile than deeper regions. The muscle became progressively more aerobic and less glycolytic with increasing sampling depth.

Hormonal Regulation of the Age‐Associated Decline in Immune Function

The elderly human population has an increased incidence of respiratory, neoplastic, arthritic and cardiovascular disease., I t is generally believed that this increase in disease is related to aberrations that occur in immunoregulation of aged individual^.^ It is well known that thymic size and T-cell function decline with age, but it has not yet been possible to totally reverse this thymic atrophy and completely restore Tdependent immune functions in aged individuals.

Effect of Processing, Packaging and Various Antioxidants on Lipid Oxidation of Restructured Pork

Effects of processing (prerigor vs. postrigor), packaging (vacuum vs. PVC overwrap) and various antioxidants [sodium tripolyphosphate (STP); butylated hydroxyanisole (BHA); butylated hydro xytolulene (BHT) plus citric acid (BBC); α-tocopherol (Toc); and ascorbyl palmitate plus α-tocopherol (APT)] on the oxidation of restructured pork chops after storage at 4°C were evaluated. Three barrows were slaughtered on separate days and were used as replicates in the experiment. One side of each carcass was boned within 1 h postmortem (prerigor) and the remaining side was boned after 24 h at 4°C (postrigor). Restructured chops were formulated to contain 25% fat and six 4.5-kg batches were randomly allotted to the six antioxidant treatments: (a) 0% NaCl (NSC); (b) 0.5% NaCl (SC); (c) 0.5% NaCl + 0.5% STP; (d) 0.5% NaCl + BBC; (e) 0.5% NaCl + Toc; and (f) 0.5% NaCl + APT. Batches were stuffed in a fibrous casing, frozen for 2 h and sliced (19 mm). The sliced chops were randomly allotted to vacuum and PVC overwrap packaging treatments and evaluated for discoloration and TBA value on days 0, 4, 8, 12 and 16. Vacuum packaging reduced discoloration scores and lowered TBA values (P<0.01) on days 8, 12 and 16. TBA values for all antioxidant treatments differed from the SC treatment on days 12 and 16 (P<0.05). These data indicate that antioxidants and/or vacuum packaging are effective methods of controlling discoloration and oxidation of restructured pork during storage; however, processing time postmortem did not affect (P>0.05) the rate of lipid oxidation.

Modulation of IGF mRNA abundance during muscle denervation atrophy.

Changes in skeletal muscle activity cause dramatic alterations in muscle mass. Increased load on a muscle (synergistic overload) results in muscle hypertrophy. During hypertrophy, skeletal muscle concentrations of insulin-like growth factors (IGF-I and IGF-II) mRNAs increase. To clarify the role of IGFs in regulating muscle mass, this study examined whether IGF-I and -II mRNA levels were altered during decreased muscle activity (denervation). Gastrocnemius weights decreased 4.2%, 7.7%, 18.1%, 27.7%, 35.1%, 45.0%, and 60.3% at 2, 3, 5, 7, 10, 12, and 17 d following denervation, respectively. Muscle DNA content remained constant throughout the first 12 d after surgery, but increased above control levels at day 17. During the first week after surgery, gastrocnemius IGF-II mRNA remained constant. However, IGF-II mRNA abundance was 2.5-fold greater than controls by 10 d of denervation, 3-fold by 12 d, and 6.8-fold by 17 d. On the other hand, IGF-I mRNA levels were not affected by denervation. In conclusion, although increased muscle activity results in a change of IGF-I mRNA expression, decreased muscle activity has no effect on IGF-I mRNA expression. In contrast, IGF-II mRNA levels increase with long-term denervation as well as with increased muscle activity. This study suggests that muscle activity may not be the only factor affecting IGF-I and -II expression.

Properties of Frankfurters Processed with Different Levels of Sodium Bicarbonate

The effect of substituting sodium bicarbonate for sodium chloride in frankfurters was evaluated using chemical and sensory criteria. Frankfurters were formulated and prepared using one of three treatments: (a) 2% sodium chloride control, (b) 1% sodium bicarbonate and 1% sodium chloride or (c) 2% sodium bicarbonate. Substitution of sodium bicarbonate raised the pH from 6.0 to 7.5 and 8.2 (treatments a, b and c, respectively). Percent free water decreased with sodium bicarbonate substitution from 41.3 to 31.7 and 21.6. Sodium bicarbonate substitution did not significantly affect Warner-Bratzler shear force values or sensory determination of moistness or tenderness. However, sensory evaluations of texture and mouthfeel and off-flavor intensity were less desirable with increased sodium bicarbonate content. Visual evaluations indicated that substitution of sodium bicarbonate for sodium chloride resulted in frankfurters having a darker brown color. Scanning electron microscopic evaluation of frankfurters did not show evidence of major structural differences. Frankfurters in vacuum-packaged bags were stored for up to 30 d in a 4°C lighted retail case. Total plate counts were not significantly different between treatments on days 0, 15 or 30 of storage. These results indicate a potential use of sodium bicarbonate to alter pH and percent free water of emulsified meat products; however, some sensory properties are diminished when sodium chloride is replaced with sodium bicarbonate.

Is insulin-like growth factor gene expression modulated during cardiac hypertrophy?

The goal of this study was to examine the relationship between work-induced cardiac hypertrophy and insulin-like growth factor-I and -II (IGF-I and -II) mRNA expression in adult female Sprague-Dawley rats. Increased cardiac work was induced by coarctation, which involved placing a constricting silk ligature around the abdominal aorta to increase peripheral resistance. Cardiac hypertrophy was determined by measuring in vivo left ventricular protein synthesis rates. There was a rapid increase in left ventricular weight (LV) [both absolute and relative to body weight (mg tissue.100 g-1 body weight)] following the coarctation surgery. By the third day following coarctation, LV weight was increased approximately 20% and reached 24% by the 10th day as compared with controls. Protein synthesis rates increased dramatically, reached a peak level at 3 d (133%.d-1) compared with 29% Ks.d-1 in the sham operated group and then began to slowly decrease toward control rates. The fractional synthesis rates of total protein in the LV were unchanged 1 d post-surgery. IGF-I mRNA content in the LV decreased to approximately 38% below the control content at day 1. However, by 3 d post-surgery IGF-I mRNA content increased to 30-50% above controls, were 31% above control by day 7, and remained elevated thereafter. On the other hand, IGF-II mRNA content remained constant throughout the 10 d post-surgery. Work-necessitated increase in cardiac protein mass may be mediated, in part, by a local autocrine/paracrine production of IGF-I.

Bioavailability of zinc derived from beer and the effect of low dietary zinc intake on skeletal muscle zinc concentration

Abstract The bioavailability of zinc from freeze-dried cooked beef was determined using log total tibia zinc and body weight gain as the response criteria. Control diets consisted of different levels of zinc carbonate added to an egg-white protein source. Experimental diets were made by substituting various levels of freeze-dried beef as the zinc source. All diets were isocaloric and isonitrogenous. Zinc in the control diets was utilized as effectively as zinc in the experimental diets. The relative biological value (RBV) of zinc (ZnCO 3 =100) in the experimental diet was 103 for 22-day weight gain, and 102 for total tibia zinc. These results indicate that zinc from cooked beef does not have an increased bioavailability over inorganic zinc added to an egg-white protein diet. Because a, large percentage of the total zinc in an animal is found in skeletal muscle, the content of zinc in two types of skeletal muscle was determined from animals fed different levels of dietary zinc. Animals consuming diets with zinc concentrations below their requirement had depressed growth rates; however, no significant differences were found in the zinc concentrations of either the soleus or plantaris muscle. The average zinc content of the soleus muscle (slow twitch oxidative fiber type) was 69 ppm and the plantaris muscle (fast twitch oxidative fiber type) was 15 ppm. These results indicate that the concentration of zinc in skeletal muscle is not significantly reduced in animals whose growth is restricted by low dietary zinc levels.

Molecular Dynamics of Water in Foods and Related Model Systems: Multinuclear Spin Relaxation Studies and Comparison with Theoretical Calculations

A review of recent studies of molecular dynamics of water in foods and model systems is presented, and the theoretical results are compared with experimental data obtained by several techniques. Both theoretical and experimental approaches are discussed for electrolytes, carbohydrates, and food proteins in solution. Theoretical results from Monte Carlo simulations are compared with experimental NMR relaxation data for quadrupolar nuclei such as those of deuterium and oxygen-17. Hydration studies of wheat, soybean, corn, and myofibrillar proteins by multinuclear spin relaxation techniques are discussed, and several new approaches to the analysis of the experimental data are considered. Correlation times of water motions in hydrated food systems are determined from NMR and dielectric relaxation data. The values of the correlation times for dilute solutions of electrolytes and carbohydrates estimated by NMR are in good agreement with those calculated from dielectric relaxation data, but seem to differ significantly from those proposed from Monte Carlo simulations. Several new and important results concerning the hydration of potato and cereal starches are presented, showing the very different hydration behaviors of these two major groups of starches. The combination of molecular dynamics computations with NMR relaxation techniques will hopefully stimulate novel technological developments in food engineering based on such fundamental studies.

Effects of passive stretch on growth and regression of muscle from chickens of various ages

A non-invasive procedure was used to determine the effect of animal age on the growth response of muscle to passive stretch. Stretch increased patagialis muscle weight 61% in 6-week-old chicks and 34% in 10-month-old chicks, 28-month-old animals had an 18% loss of muscle mass during passive stretch. Removal of the stretch stimulus was followed by a rapid return of patagialis weight to control values in 6-week and 10-month animals, while muscle size of 28-month-old animals had not returned to control levels by 22 days, following removal of the stretch. The stretch-induced changes in muscle wet weight could, in part, be attributed to changes in muscle protein. Total muscle DNA content increased during rapid growth in 6-week- and 10-month-old chickens, and returned to control levels during muscle regression. Muscle hydroxyproline content increased in parallel with increases in muscle mass but did not return to control levels during muscle regression in 6-week-old animals. Results of the present study indicate that there was an effect of animal age on stretch-induced hypertrophy and regression of the patagialis muscle.

Varying amounts of stretch stimulus regulate stretch-induced muscle hypertrophy in the chicken

1. The effects of different amounts of passive stretch per day and number of days of stretch on muscle hypertrophy in the chicken patagialis (PAT) muscle were determined. 2. Stretch for 24 hr per day (h/d) resulted in a more rapid hypertrophy both on a wet and dry tissue basis (P less than 0.001) than stretch for 4 h/d. 3. Stretch increased PAT weight 43% and 25% in 24 h/d and 4 h/d treatments, respectively, after 10 days of stretch, but by day 25 of stretch there was no difference between treatments. 4. In a second experiment, the PAT muscle was hypertrophied and then the effects of intermittent stretch (4 h/d) on regression of hypertrophy (muscle atrophy) were investigated. 5. Intermittent stretch (4 h/d) for 5 and 10 d significantly (P less than 0.001) inhibited regression of hypertrophied muscle. 6. The results of the present study indicate that stretch-induced hypertrophy can be modulated by varying the amount of stretch applied per day. 7. Intermittent stretch can be used to inhibit the regression which occurs when a continuous stretch stimulus is removed. 8. Intermittent stretch is a useful model for investigating mechanisms of muscle hypertrophy and inhibition of muscle atrophy.