Biomedical subjects

P J Bechtel

Publications and source records attributed to P J Bechtel.

At least 19 recordsLinked to original sources

PubMed1998

Elevated growth hormone increases the Ca2+ sensitivity of slow- and fast-twitch skeletal muscle of female rats.

To determine the effect of plasma growth hormone (GH) on skeletal muscle function, we measured the free Ca2+ concentration-tension relationship of slow-twitch (soleus) and fast-twitch (peroneus longus) muscles isolated from rats undergoing acromegaly in response to implanted, GH-secreting tumors. Muscles from adult (9 mo) and aged rats (24 mo) were studied after the tumor-bearing rats weighted over 50% more than their age-matched controls. Ca(2+)-activated isometric tension was recorded from skinned muscle fibers. For soleus muscles, the free Ca2+ concentration producing 50% of maximal tension ([Ca2+]50) was 2.0 microM for rats with tumors and 3.4-3.6 microM for controls. For peroneus longus fibers, [Ca2+]50 shifted from 6.1-6.7 microM in controls to 3.5 microM after tumors were introduced into either adult or aged rats. Soleus muscle fibers from neonatal rats (14 days) were less sensitive to Ca2+ than those isolated from adult rats, having a [Ca2+]50 of 7.3 microM. The Ca2+ sensitivity of peroneus longus fibers did not change with age. We conclude that significant increases in myofibrillar Ca2+ sensitivity occur in skeletal muscles undergoing rapid growth induced by GH-secreting tumors.

Acromegaly↗

PubMed1994

Modulation of IGF mRNA abundance during stretch-induced skeletal muscle hypertrophy and regression.

Increased load on a muscle (synergistic overload or stretch) results in muscle hypertrophy. The expression of insulin-like growth factor I (IGF-I) mRNA in rat skeletal muscle is increased during synergistic overload-induced hypertrophy. Although it has also been established that fasting animals lose muscle protein, it has been shown that compensatory muscle hypertrophy occurs in adult fasting rats that are undergoing a net loss of body weight. The purpose of this investigation was to determine whether a relationship exists between IGF-I mRNA levels and muscle growth and regression. This was accomplished by examining whether IGF-I mRNA levels were altered during muscle hypertrophy after stretch and regression and the effect of fasting on IGF-I mRNA levels during stretch-induced hypertrophy. Patagialis (PAT) muscle weights increased 13 and 44% at 2 and 11 days of stretch, respectively. However, after removal of the stretch stimulus on day 11, PAT weights began to decrease, reaching control weights by 18 days. During the first time point (2 days), PAT muscle IGF-I mRNA remained constant. IGF-I mRNA abundance was threefold greater than contralateral control levels by 11 days of stretch. IGF-I mRNA levels decreased but remained significantly above control levels throughout the regression of hypertrophy (13, 18, and 25 days). Fasting did not alter PAT muscle response to stretch. After 11 days of stretch, PAT muscle weight increased 60% compared with contralateral control muscles and IGF-I mRNA levels increased three-fold. This study supports a role for IGF-I in muscle hypertrophy but not muscle atrophy.

Animals↗

PubMed1993

Regulation of glycogen synthase in human muscle during isometric contraction and recovery.

Six subjects performed isometric contraction (66% maximal force) to fatigue with the knee extensor muscles. Biopsies were taken from the quadriceps femoris muscle at rest, at fatigue and 1 min after termination of contraction. In three of the subjects recovery from contraction occurred in the presence of an intact circulation (non-occluded, NON) to the thigh, whereas in the other three the circulation during recovery was occluded (OCC). Glycogen synthase fractional activity (GSF) decreased in all subjects from (mean +/- SE) 0.53 +/- 0.06 at rest to 0.37 +/- 0.04 at fatigue (P < 0.001). In the OCC group GSF returned to the pre-exercise value within 1 min after termination of contraction (0.59 +/- 0.07 at rest vs. 0.57 +/- 0.04 at 1 min post-exercise), whereas in the NON group GSF increased to a higher extent (0.48 +/- 0.09 at rest vs. 0.70 +/- 0.06 at 1 min post-exercise). The increase in GSF during the 1-min recovery was almost three-fold higher in the NON group (0.15 +/- 0.02 vs. 0.38 +/- 0.03). Cyclic AMP-dependent protein kinase (cAMP-PK) (assayed at 0/100 microM and 0.2/100 microM cAMP) did not change at fatigue or during recovery in either group. Glycogen synthase phosphatase (GSP) increased at fatigue by approximately 30% (P < 0.05 vs. rest). It is concluded that isometric contraction mediated inactivation of GS (i.e. phosphorylation of GS) is due to activation of a protein kinase(s) but not cAMP-PK. The rapid activation of GS in the NON group demonstrates that a humoral factor(s), possibly insulin and/or oxygen, is responsible for this phenomenon.

Adolescent↗

PubMed1993

Bioavailability of zinc in ground beef.

Based on zinc uptake in chick tibia, Zn bioavailability in cooked ground beef was equal to that of Zn in an inorganic standard (ZnSO4), whether Zn supplements were added to a soy-concentrate diet containing phytate or to a phytate-free egg-white diet. With both diet types, total tibia Zn was a linear (P < .01) function of supplemental Zn intake from ZnSO4, but the slope of the linear regression line was twice as great for the egg-white diet as for the soy-concentrate diet that contained phytate. At 10 mg/kg of supplemental Zn, freeze-dried ground beef produced the same tibia Zn concentration (and total Zn content) as that obtained with ZnSO4. The results suggest that the relative bioavailability of Zn in cooked ground beef is as great as that in ZnSO4, whether consumed in diets with or in those without phytate.

Animals↗

PubMed1993

Effect of hyperalimentation on body composition in swine.

Fifty growing pigs were used in two experiments to evaluate the effects of cannulation and hyperalimentation on performance and body composition responses. Surgical implantation of a cannula into the greater curvature of the stomach and subsequent management associated with maintenance of the cannula did not result in a reduction (P > .05) of voluntary feed intake. Cannulation did not negatively affect gain (P > .05). Over the entire trial, feed efficiency was not changed by cannulation (P > .05). Cannulation itself did not affect protein or fat deposition (P > .05) in the carcass. Hyperalimentation to approximately 120% of control intake resulted in increased daily gain (P < .05) and similar feed efficiency (P > .05) compared with that of control animals. Hyperalimentation decreased protein deposition (P < .05) and tended to increase fat deposition.

Adipose Tissue↗

PubMed1993

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.

Animals↗

PubMed1993

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.

Animals↗

PubMed1992

Effects of diet containing extruded full-fat soybeans or butter on the growth, composition, and sensory characteristics of pork.

Ninety-six crossbred barrows were randomly allotted to five replications of four treatments to determine the effects of diets containing 20% extruded full-fat soybeans (FFS) or 4% butter (B) on the growth, composition, and sensory characteristics of finishing pigs. Pigs were housed five per pen, except for one replication that had four pigs per pen, in environmentally regulated barns. Pigs were given ad libitum access to a corn-soybean meal diet for 11 wk (control); a corn-extruded soybeans and soft wheat midds diet for 11 wk (FFS-11); a corn-soybean meal diet for 6 wk, changed to a corn-extruded soybeans and soft wheat midds diet for 5 wk (FFS-5); or a corn-soybean meal diet for 6 wk, changed to a corn-soybean meal, soft wheat midds, and 4% butter diet for 5 wk (B). Feed intake and weight gain were measured once every 2 wk. Pigs were slaughtered and carcass data were collected. Sensory characteristics (tenderness, juiciness, pork flavor intensity, off-flavor intensity, and overall acceptability), shear force, moisture, and fat content were determined for the longissimus muscle. Sensory characteristics (pork flavor, off-flavor, rubbery, cohesiveness, and juiciness) and 2- thiobarbituric acid values were determined for ground pork (30% fat) after 1, 4, and 7 d for control, FFS-11, and B treatments. No differences (P > .05) in ADG were observed between diets. Feed efficiency of the FFS-11 group was better (P < .05) than that of the control or B groups. No consistent differences were observed for carcass, sensory, or shear-force characteristics of the longissimus muscle or ground pork.(ABSTRACT TRUNCATED AT 250 WORDS)

Adipose Tissue↗

PubMed1992

Effect of feeding finishing pigs extruded full-fat soybeans on performance and pork quality.

This experiment was designed to test whether changing the type and amount of added dietary fat would affect performance or meat quality. Dietary fat was added as tallow or extruded full-fat soybeans (FFS). Isoenergetic diets containing 10% FFS, 20% FFS, or 4% tallow were fed for 3 or 6 wk before slaughther. A conventional corn-soybean meal diet served as a no-added-fat control. Each of the seven dietary groups contained 20 pigs, equally distributed among four pens, with barrows and gilts segregated. Significance of treatment, sex, and interaction effects were evaluated for 34 meat quality, composition, and sensory evaluation traits. Treatment x sex interactions were not detected (P greater than .05). Treatment main effects were detected for percentage of fat and water in the bacon and for lipid oxidation in bacon and the longissimus muscle. The 6 df for treatment were partitioned into six contrasts to test for the trends within and between diets. A trend toward reduced fat and increased moisture in bacon was detected in the 10% FFS diet over time (P less than .05). In general, lipid oxidation of bacon and longissimus muscle increased with level of FFS in the diet, length of time on the diet, and storage time of the meat. Although statistically significant, the magnitude of these effects was small and did not affect the sensory characteristics of longissimus muscle samples. It was concluded that short-term feeding of FFS before slaughter did not adversely affect animal growth or meat quality.

Adipose Tissue↗

PubMed1992

Characterization of lipid in loin and bacon from finishing pigs fed full-fat soybeans or tallow.

This experiment tested whether the lipid composition of pork could be altered by changes in dietary lipid, that what effects these changes would have on production and meat characteristics. Pigs were fed diets containing 10 or 20%+ extruded full-fat soybeans (FFS) or 4% tallow for a 3- or 6-wk finishing period, with a corn-soybean meal diet fed as a control. Seventy barrows and 70 gilts were allotted into seven treatment groups with four pens per group. Analysis was on 28 experimental units, which were composite samples from pens. The significance of treatment, sex, and treatment x sex interaction F-statistics was evaluated on chloroform-methanol extractable total lipid, triacylglycerol, phospholipids, cholesterol, individually fatty acids (FA), and the major classes of FA obtained from longissimus muscle and bacon. Treatment effects (P less than .05) were detected for cholesterol content of longissimus and for total lipid and phospholipid content of bacon. Treatment effects (P less than .01) were detected for monoenoic, dienoic, and polyenoic (P) FA in both tissues, and for saturated (S) FA in bacon (P less than .05). Treatment effects (P less than .001) were detected in both tissues for the P:S ratio. The P:S ratio increased 54% for longissimus and 100% for bacon in the pigs fed FFS for 6 wk compared with pigs consuming a corn-soybean meal diet.

Adipose Tissue↗

PubMed1991

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.

Carbohydrates↗

PubMed1991

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.

Animals↗

PubMed1991

Expression of embryonic myosin heavy chain mRNA in stretched adult chicken skeletal muscle.

Chronic stretch of the chicken fast-twitch patagialis muscle increases the rate of growth and percentage of fast-twitch oxidative fibers. We have analyzed the effects of stretch on the expression of two previously identified "embryonic" myosin heavy chain (MHC) mRNAs (p251 and p110). Both MHC mRNAs were expressed in the patagialis at their highest levels in the embryo and 1 wk after hatching. During posthatch development (7-52 wk), the p110 mRNA was expressed in only trace quantities while the p251 mRNA was not detectable. After 2 wk of stretch of the patagialis in 7- or 38-wk-old birds, the p110 mRNA was increased to levels similar to that found in patagialis of newly hatched chicks, whereas expression of the p251 transcript was not affected. The existence of two other MHC mRNAs homologous to the p110 mRNA was suggested by the S1 mapping analysis, one of which was expressed at dramatically reduced levels in the stretched patagialis. It is concluded that stretch can cause selective alterations in the expression of developmentally regulated MHC isoforms in chicken fast-twitch muscle.

Aging↗

PubMed1991

The effect of ractopamine hydrochloride on the carcass cutting yields of finishing swine.

This study was designed to evaluate growth performance, carcass cutting yield, and processing characteristics of boneless hams and bellies from finishing pigs fed diets containing 0, 5, 10, or 20 ppm of the phenethanolamine ractopamine hydrochloride (RAC). Sixty pigs were blocked by starting weight and randomly assigned to pens (four pigs/pen) within each of three blocks. Treatments were then randomly assigned to the pens to total six pens of the 0-ppm level and three pens each at the 5-, 10-, and 20-ppm RAC levels. Weight gain and feed consumption were monitored and animals were slaughtered by weight block after approximately 48 d on trial. Slaughter weight, ADG, and feed/gain were improved (P less than .05) for RAC treatments. Dressing percentage was higher and increased linearly (P less than .05) for RAC treatments. Carcass weight, length, leaf fat weight, backfat thickness, loin eye area, and color, marbling, and firmness of the longissimus were evaluated. The RAC-treated carcasses were heavier (P less than .05) and loin eye area increased linearly (P less than .05). One side of each carcass was fabricated using National Association of Meat Purveyors specifications. Trimmed hams and loins from the RAC treatments were heavier (P less than .05) than those from control animals. No differences (P greater than .05) in carcass cutting yield (percentage of trimmed primal cuts) were observed between treatments. However, trimmed hams and loins from the 20-ppm RAC treatment represented a greater (P less than .05) percentage of carcass weight than did those from control animals. Ractopamine did not affect raw belly or bacon characteristics (P less than .05).(ABSTRACT TRUNCATED AT 250 WORDS)

Adipose Tissue↗

PubMed1990

Multinuclear spin relaxation and high-resolution nuclear magnetic resonance studies of food proteins, agriculturally important materials and related systems.

An overview of the applications of Nuclear Magnetic Resonance (NMR) techniques in Agriculture and Food Chemistry, covering high-resolution, solid-state, pulsed gradient and two-dimensional techniques is presented. The systems investigated by such techniques range from purified proteins to mixtures, starch granules and wheat grains. Both hydration and structural/composition approaches that employ NMR techniques are discussed from the point of view of applications rather than technique development. Hydration models derived from multinuclear studies are discussed for food proteins and enzymes. The role of protein-protein interactions in the analysis of the NMR results on hydration is also discussed. Amongst the food proteins considered are: wheat gliadins, glutenins, corn zeins, soy glycinins and conglycinins, as well as muscle proteins. Several new applications and new directions of development of NMR in Agriculture and Food Chemistry are suggested, and potential practical applications are pointed out.

Agriculture↗

PubMed1990

Effects of food restriction on stretch induced muscle hypertrophy in chickens of various ages.

1. The patagialis muscle of three groups of different aged chickens was subjected to passive stretch by placing an inflexible sleeve over the left wing, and the right wing served as the control. 2. Food was removed from the animals 2 days prior to applying passive stretch. After 6 days of passive stretch on young 7-week-old animals, the stretched muscle was 200% larger than the control. 3. During the restriction, control muscle lost 69% of its weight and the stretched muscle maintained its original weight. 4. Changes in muscle DNA and hydroxyproline content were similar to changes in muscle weight but hydroxyproline content lagged changes in muscle weight. 5. Restricted 10-month-old chickens responded to passive stretch with an absolute increase in muscle mass which was accompanied by increases in protein, DNA and hydroxyproline content. 6. Muscle from the 28-month-old chickens did not respond to either 11 days of restriction or passive stretch. 7. The results of the present study indicate that as the chicken grows older, the ability of the muscle to respond to stimuli, stretch and/or starvation, is reduced.

Aging↗

PubMed1990

Dibutyryl cAMP-induced increases in triacylglycerol lipase activity in developing L8 myotube cultures.

Triacylglycerol (TG) lipase activity, with an alkaline pH optimum, has been identified in the cellular fraction of L8 myotube cultures. This TG lipase activity was stimulated by serum and inhibited by NaCl and protamine sulfate. These characteristics have been classically described for lipoprotein lipase. It was possible to increase the activity of this TG lipase three- to five-fold by incubating the cells with dibutyryl cAMP. Maximal enzyme activity was observed 16 h following the addition of 10-100 microM dibutyryl cAMP to the cultured cells. Enzyme activity returned to control levels 24 h after removal of the nucleotide from the culture medium. Serum-sensitive alkaline TG lipase activity was also identified in five other myotube preparations of cultured muscle cells. The highest levels of activity were found in rat skeletal muscle primary, H9, and L6 cell types. The finding that dibutyryl cAMP is an effective inducer of alkaline TG lipase activity provides us with a valuable model to investigate mechanisms regulating synthesis, compartmentalization, and transport of lipoprotein lipase in muscle.

Animals↗

PubMed1990

Activation of insulin-like growth factor gene expression during work-induced skeletal muscle growth.

We have investigated the hypothesis that there is local regulation of insulin-like growth factor (IGF) gene expression during skeletal muscle growth. Compensatory hypertrophy was induced in the soleus, a predominantly slow-twitch muscle, and plantaris, a fast-twitch muscle, in 11- to 12-wk-old female Wistar rats by unilateral cutting of the distal gastrocnemius tendon. Animals were killed 2, 4, or 8 days later, and muscles of the nonoperated leg served as controls. Muscle weight increased throughout the experimental period, reaching 127% (soleus) or 122% (plantaris) of control values by day 8. In both growing muscles, IGF-I mRNA, quantitated by a solution-hybridization nuclease-protection assay, rose by nearly threefold on day 2 and remained elevated throughout the experimental period. IGF-II mRNA levels also increased over controls. A more dramatic response was seen in hypophysectomized rats, where IGF-I mRNA levels rose by 8- to 13-fold, IGF-II values by 3- to 7-fold, and muscle mass increased on day 8 to 149% (soleus) or 133% (plantaris) of the control contralateral limb. These results indicate that signals propagated during muscle hypertrophy enhance the expression of both IGF genes, that modulation of IGF-I mRNA levels can occur in the absence of growth hormone, and that locally produced IGF-I and IGF-II may play a role in skeletal muscle growth.

Animals↗