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Although corticosteroid therapy is the standard of care for all patients hospitalized with severe coronavirus disease 2019 (COVID-19), the studies demonstrating the mortality–benefit ratio of corticosteroids were limited to fully evaluate their adverse effects. To determine the severity of corticosteroid-induced hyperglycemia in patients with and without diabetes mellitus, we retrospectively collected data from the medical records of patients hospitalized with COVID-19 before and after corticosteroids were the standard of care. Corticosteroid-induced hyperglycemia was more severe in patients hospitalized with COVID-19 with diabetes than those without diabetes. Additionally, patients with diabetes required higher doses of correctional insulin per day when on corticosteroid therapy, suggesting that intensive point-of-care glucose monitoring could be limited in patients without diabetes mellitus and support cautionary use of corticosteroids in patients with COVID-19 discharged with supplemental oxygen.

Objective To examine outcomes of pediatric thyroidectomy in the context of training background, institution, and experience of the surgeon. Study Design Case series with chart review. Setting A tertiary academic medical center and a pediatric hospital. Subjects and Methods Eighty-one thyroidectomy patients younger than 18 years. Outcomes were major complications (recurrent laryngeal nerve injury, permanent hypocalcemia, and wound infection), length of stay (LOS), and need for repeat surgery. Results Eighty-one patients, 39 from the University of Nebraska Medical Center and 42 from the Children’s Hospital and Medical Center–Omaha, were identified over a 12-year time period. No difference was found in surgeon training (otolaryngology/head and neck surgery vs general/pediatric surgery) for complications (1 vs 1, odds ratio [OR] = 0.76, 95% confidence interval [CI] = [0.05, 13.1]), LOS >1 day (5 vs 13, OR = 0.39, 95% CI = [0.13, 1.24]), or need for second surgery (4 vs 7, OR = 1.47, 95% CI = [0.39, 5.49]). Higher surgeon volume (≥12 surgeries) was found to be significant for decreased need for second surgery (3 vs 8, OR = 6.67, 95% CI = [1.57, 27.17]). Patients of higher-volume surgeons were 4.2 times more likely to stay in the hospital 1 day or less compared with those patients operated on by surgeons with less experience (7 vs 11, 95% CI = [1.59, 15.0]). Conclusions Need for second surgery in pediatric thyroidectomy may be predicted by surgical volume.

The viability of near-infrared (NIR) spectroscopy as a technique for the quality control analysis of ingredient concentrations in a rocket propellant fuel liquid pre-mix was investigated. The pre-mix analyzed consisted of a polybutadiene pre-polymer, a plasticizer and two antioxidants. It was determined that NIR spectroscopy offered a fast and convenient method of verifying the percentage level of all four ingredients while requiring no sample preparation. The NIR methodology exhibited a high level of accuracy and precision. There was also a clear indication that the technique allowed monitoring of antioxidant depletion in the pre-mix on ageing.

Double-muscled fetuses develop more muscle fibers than normal-muscled fetuses. To examine whether serum growth factors modulate muscle development in cattle, twin pregnancies were induced in eight Holstein heifers using embryos from Belgian Blue and Holstein genetics representing heavy (HM) and light (LM) muscled cattle, respectively. Twin combinations were 1) two pairs of Belgian Blue fetuses that were designated as HM (HM), 2) two pairs of Holstein fetuses that were designated as LM (LM), and 3) four pairs of mixed fetuses; the four Holstein fetuses were designated as LM (HM) and the four Belgian Blue fetuses were designated as HM (LM). Pregnancies were terminated at 175 +/- 5 d after conception and fetuses, with evidence of vascular anastomosis, were dissected. Carcass weights were greatest (P < .05) for HM fetuses. Total bone and individual femur weights were greatest (P < .05) for LM (LM) fetuses. Total skeletal muscle mass and mass of semitendinosus, quadriceps femoris, infraspinatus, and longissimus muscles were in the order of HM (HM) > HM (LM) > LM (HM) = LM (LM) (P < .05). Estimated apparent muscle fiber number determined from a cross-section of semitendinosus muscle was in the order of HM (LM) > HM (HM) > LM (HM) = LM (LM) (P < .05). These data show that the presence of a co-twinned fetus with a lower genetic propensity for muscle development reduces the capacity of heavily muscled fetuses to develop muscle mass by 175 d after conception and strongly support the idea that blood-borne factors regulate muscle hypertrophy in fetal cattle.

A novel method was developed, utilizing headspace sampling in conjunction with gas chromatography, to quantitatively follow the thermal oxidation in air of a low molecular weight, hydroxy-terminated polybutadiene. This method was found to offer an efficient and simple technique by which to analyze both the rate and the extent of oxidation of the polymer. Rate studies of the oxidation revealed an induction period followed by self-catalyzed oxidation, the rate of which quickly becomes controlled by diffusion of oxygen into the polymer. By determining the rate of oxygen consumption at various temperatures, an Arrhenius-type plot was derived and an activation energy value of 13 kcal/mol was calculated. The relative effects on oxidation of a number of common antioxidants and organometallic cure catalysts were also determined by this technique.

Improvement of USDA Select grade beef is essential for consumer acceptance of leaner beef. Seventy-two large- and medium-framed steer calves of mixed breeding were used in two experiments to evaluate feedlot performance, carcass composition, and beef palatability. Interactions of dietary energy level (corn concentrate or corn silage), breed type (Angus or Simmental), carcass electrical stimulation (ES) voltage (low or high), and chilling rate (normal or delayed) were determined. Grain-fed cattle had similar initial and slaughter weights, heavier carcasses, more marbling, higher quality grades, and higher dressing percentages (Exp. 2) compared with silage-fed cattle, even though all cattle were visually selected for a constant grade end point. Simmental cattle had heavier initial slaughter and warm carcass weights, larger loin eye area, less fat depth, and lower yield grade than Angus cattle. Percentage of lean in the 9-10-11th rib was lower and percentage of fat was higher for grain-fed and Angus steers than for silage-fed and Simmental steers, respectively. Neither diet nor breed influenced chemical composition of the edible portion, except that separable lean in Angus steers was higher in ether extract. No differences in palatability existed between Angus and Simmental steaks. High ES voltage compared with low voltage improved some tenderness characteristics and reduced some juiciness scores. The USDA Select grade beef of accepted palatability can be produced on either corn-grain or corn-silage diets, and only minor differences in beef palatability in such cattle are caused by ES voltage.

Double-muscled (DM) cattle possess more muscle fibers than do normal-muscled (NM) beef or dairy cattle. Serum-borne growth factors have been shown to modulate myogenesis. Media containing serum from 12 DM and 60 NM fetuses grouped by crown-rump lengths (CRL) of < or = 25, 26 to 50, 51 to 75, or > 75 cm were used to test the effect of fetal serum on L6 myoblast proliferation. Because DM and NM fetuses were similar in CRL at ages corresponding to 20- to 60-cm CRL, CRL was used to determine fetal age. Normal-muscled fetal serum-induced thymidine incorporation in L6 myoblasts was greater (P < .05) at CRL > 50- than at < or = 50-cm CRL. Mean incorporation tended to increase with CRL. Thymidine incorporation was 56, 41, and 41% greater (P < .05) with serum from DM fetuses than with that from NM fetuses at CRL of < or = 25, 26 to 50, and 51 to 75 cm, respectively. Morphological examination of cross-sections of the semitendinosus muscle showed that apparent muscle fiber number was greater (P < .05) for DM fetuses than for NM fetuses. These results confirm greater apparent muscle fiber number in DM cattle and show the existence of greater growth factor activity in serum of DM fetuses during early fetal development. This greater growth factor activity may play a role in bovine muscle fiber hyperplasia.

Precooked, uncured meat is not widely available to consumers, partially because of associated palatability problems and lack of published information on heat uptake under different industrial conditions. The objectives of this study were to determine the tenderness, extent of lipid oxidation, and total cooking losses in pre- and posterior beef and pork roasts heated at different rates. The muscles were cooked in stainless-steel, perforated heating chambers at oven temperatures of 150, 200, or 250 degrees C and the temperature rise during and after heating was monitored with a digital temperature recorder. Samples were vacuum-packaged, frozen at -20 degrees C for 45 d, thawed at 4 degrees C for 24 h, and reheated in 60 degrees C water for 1 h. Cooking losses, Warner-Bratzler shear force values, thiobarbituric acid values, and pH were determined. The results provide heating curves for pre- and postrigor beef and pork roasts at three oven temperatures. Prerigor samples of both species were less tender than postrigor samples (P < .05). Cooking losses were generally low in prerigor samples of both species compared with postrigor samples (P < .05). All beef samples had relatively low thiobarbituric acid (TBA) values before and after storage, whereas pork samples had relatively high TBA values before and after storage. Results indicate that prerigor cooked roasts shrink less, are equivalent or better in oxidative stability, and are less tender than postrigor cooked roasts under the conditions of this experiment.

Cooking reduces odor intensity in boar meat but also may induce lipid oxidation unless the meat pH is above approximately 6.0. This research was designed to determine the feasibility of cooking boar meat in the prerigor state to overcome boar odor and lipid oxidation problems. Prerigor and postrigor triceps brachii muscle samples from 40 boars (20 Duroc and 20 Yorkshire) were cooked to 60 degrees C, frozen and stored at -20 degrees C, reheated in a 60 degrees C water bath for 1 h, and then subjected to pH, thiobarbituric acid (TBA), and sensory analyses. Boar odor intensity and skatole concentration in backfat samples were determined by olfactory test and HPLC, respectively. Cooked (initial cooking) prerigor meat was found to have higher (P < .05) pH and lower (P < .05) TBA values than comparable postrigor meat (6.44 vs 6.09 and 2.15 vs 3.23, respectively). Regression analysis indicated an inverse relationship between pH and TBA values (r = -.52; P < .01). No appreciable changes in TBA values were noted after frozen storage for 14 to 98 d, but reheating increased TBA values (P < .05) in both prerigor and postrigor samples (3.45 vs 4.32, respectively). Sensory evaluation scores indicated that prerigor cooked meat was less tender with more pronounced rancid flavor than postrigor cooked meat (P < .05), but panelists may have allowed the toughness of the prerigor samples to adversely affect their flavor scores. No difference in boar odor was detected between rigor states or breeds. Mean skatole concentration in backfat was .12 micrograms/g and no difference was detected between breeds.(ABSTRACT TRUNCATED AT 250 WORDS)

Rapidly heated prerigor beef is tender because of incompletely described myofibrillar disruption and tissue fracture. This study was designed to evaluate the effects of heating rate on heat-induced myofibrillar shortening, ultrastructural changes, and fracture behavior in prerigor triceps brachii muscle. Rapid heating (2°C/2 min) to 53°C caused (P < 0·05) more severe myofibrillar shortening in a shorter time and at higher muscle pH and temperature, less muscle weight loss, and shorter sarcomeres than slow heating (2°C/12 min) to 47 or 53°C. Rapid heating caused more extensive degradation of A and I bands, greater loss of the tridimensional pattern of myofibrils, more fragmentation and melting of myofibrils, widened intermyofibrillar spaces, and maximum separation of fiber bundles as compared to slow heating. Slow heating caused extensive shortening but not extensive degradation and disruption of myofibrils. Muscles slowly heated to 53°C sustained greater loss of structural integrity than those slowly heated to 47°C, but fracture behavior was similar. Separation and fracture occurred near the perimysial/endomysial junction in all heated samples, but the perimysium remained affixed to the endomysium at one side of the interface in many rapidly heated samples. Longitudinal fractures showed a granular endomysium and large numbers of supercontraction nodes alternating with areas of sarcolemmal membrane fragmentation and fiber tearing in rapidly heated samples. Alterations of myofibrillar ultrastructure and fiber structure, and separation of bundles, may account for enhanced tenderness of rapidly heated prerigor muscle., (Copyright © 1992. Published by Elsevier Ltd.)

Five experiments were conducted to evaluate the microbial quality of unrefrigerated cooked prerigor beef after the application of oxygen-permeable packaging. Specific objectives were to combine the beneficial effects of aerobic packaging, meat surface acidification and prerigor rapid cooking rates on meat storage stability at ambient temperature. In the experiments, the triceps brachii muscle was dissected from one side 45 min after exanguination of the animal, and samples of 2 × 3 × 5 cm were prepared. Bags made of a strong barrier, plastic film, and a highly oxygen permeable oriented polypropylene, were used. The cooking of the packaged samples covered a number of treatments ranging from cooking in a 70°C water bath to an internal sample temperature of 65°C to cooking in 100°C water for 40 min. Reheating and multiple heat treatments were also included. The pH values of the cooked samples were determined and aerobic plate counts (log(10)/g) were determined for the cooked samples at various intervals during two weeks of storage at 22°C or at 3°C for the control samples. The results indicate that heat treatment alone did not improve shelf stability at 22°C. However, dipping the samples in 80°C solutions of 0·7% citric acid or 1·25% lactic acid for 1 min and draining for 1 min followed by packaging using oxygen permeable bags and cooking in 100°C water for 40 min consistently resulted in shelf stable products at all 22°C storage intervals. The lactic acid treatment was superior to the citric acid treatment because it completely decontaminated the samples and delayed spoilage, especially at 3°C., (Copyright © 1992. Published by Elsevier Ltd.)

The interpretation of muscle structure by scanning electron microscopy (SEM) has not been consistent among various studies. Consequently, the literature is confusing with respect to the identity of T-tubules, transverse ridges, Z-disks, and intermyofibrillar connections. The objective of this research was to evaluate the effects of different methods of sample preparation and imaging on ultrastructural details of previously identified transverse structures and intermyofibrillar connections and to verify or disprove the commonality of these structures under different viewing conditions. Scanning electron microscopy coupled with a cold stage, SEM at room temperature, and transmission electron microscopy (TEM) of thin sections were most appropriate for exposing detail of inter- and intracellular structures and for measuring sarcomere length and spacing of intermyofibrillar connections. Scanning electron microscopy of samples mounted on a cold stage, fractured, and sublimed provided excellent images of meat and muscle ultrastructure and may be used in correlative microscopy. Sarcomere length and spacing between intermyofibrillar connections were similar among most specimen preparation techniques and were affected similarly by heat treatments. Results indicate that the regularly spaced transverse structures viewed by conventional SEM and the intermyofibrillar connections viewed by low-temperature SEM are Z-disks.

Forty-eight Yorkshire × Chester White crossbred boars, 28 days of age, were assigned to one of four diets differing in crude protein content. Dietary crude protein content was 23% initially and then adjusted to 14, 17, 20 or 23% at 9 weeks of animal age, and 12, 15, 18 or 21% at 14 weeks of age, respectively. The skatole concentrations in serum of the boars was measured at 24, 32 and 40 weeks of age. Results showed that serum skatole concentrations declined (P < 0·05) with increasing age (0·034, 0·027 and 0·021 μg/ml at 24, 32 and 40 weeks, respectively) and also decreased (P < 0·059) with increasing dietary crude protein concentration (0·033, 0·026, 0·022 and 0·021 μg/ml at 12, 15, 18 and 21% in finishing diets, respectively)., (Copyright © 1992. Published by Elsevier Ltd.)

Semimembranosus muscle samples were obtained from 49 Holstein beef animals representing different USDA maturities. Intramuscular collagen (IMC) was isolated in the frozen state and evaluated for heat-labile collagen solubility (% Sol), thermal shrinkage temperature (Ts), enthalpy (Hs) changes, and mature crosslink (pyridinoline) content. These measures were obtained to elucidate a relationship between pyridinoline content of IMC and beef maturity level and to relate IMC thermal stability (% Sol, Ts, and Hs) to pyridinoline content. With increasing maturity, % Sol decreased (P less than .01) and Ts increased (P less than .01), whereas Hs showed no change (P greater than .05). Thus, IMC melted at increasing temperatures, but the amount of energy required to induce this endothermic change remained constant throughout maturation. The pyridinoline content of IMC increased (P less than .01) linearly with maturity, indicating that this heat-stable, mature crosslink enhances thermal stability of IMC as beef muscle matures. Significant correlations between pyridinoline content and maturity (r = .56; P less than .001) and Ts (r = .34; P less than .05) support this contention.

An HPLC method using 9-fluorenylmethyl chloroformate-1-amino-adamantane (FMOC-ADAM) for the determination of hydroxyproline (HYP) in muscle hydrolyzates is described. The HYP was converted to a stable fluorescent derivative with FMOC after removal of all primary amino acids with ortho-phthaldialdehyde and 2-mercaptoethanol. Excess FMOC was reacted with a hydrophobic amine, ADAM, thus eliminating the need for pentane or diethyl ether extraction. The method was performed without the use of controlled temperature derivatizations or extra equipment (e.g. column switching valves). Analysis of HYP was complete after 3 min, with a total analysis time of 7·5 min. The HYP content of various muscle samples obtained with the HPLC procedure compared very well with values obtained using a colorimetric assay., (Copyright © 1991. Published by Elsevier Ltd.)

Skatole-spiked boar serum was used to evaluate the degradation of skatole during frozen storage and to evaluate gas chromatography (GC) and high performance liquid chromatography (HPLC) for measuring serum skatole. Tubes of serum spiked with 1 ppm skatole which had been stored in a freezer (-15°C) for 4 months and tubes of fresh spiked serum (1 ppm skatole) were utilized. No differences (P > 0·05) between GC and HPLC determination in sensitivity and skatole recovery were observed. Measurements of skatole by GC and HPLC were highly correlated (r = 0·93). Both GC and HPLC revealed no difference (P > 0·05) between fresh spiked serum and stored spiked serum samples., (Copyright © 1991. Published by Elsevier Ltd.)

Three hundred sixty-one market-weight barrow and gilt carcasses were physically dissected into bone, skin, fat and muscle. A three-variable multiple linear regression equation containing the same independent variables (warm carcass weight, 10th rib loin muscle area and 10th rib fat depth) used (U.S.) to determine pork carcass lean weight was found to be the most practical means for predicting weight of muscle standardized to 10% fat. Multiple linear regression equations containing more than three independent variables produced only slight improvements in R2 values; however, the standard deviation about the regression line was not greatly improved by the addition of more independent variables to this three-independent-variable regression model. A single multiple linear regression equation using the three independent variables above may not be adequate to describe variation over the entire live-weight range for all hogs marketed in the U.S. For most accurate muscle weight prediction, different equations should be used for weight subclasses with one equation for carcasses under 100 kg and another for those heavier than 100 kg. A single prediction equation for muscle weight was adequate for carcasses of both barrows and gilts.

Relationships of implanted testosterone, dihydrotestosterone and estradiol-17 beta to collagen degradation and intramuscular collagen concentration and stability were determined. Intramuscular collagen content, solubility and shrinkage temperature and serum hydroxyproline were analyzed in groups of six rams, wethers, and wethers implanted with various levels of testosterone or dihydrotestosterone and groups of 10 rams, wethers and wethers implanted with estradiol-17 beta, dihydrotestosterone or a combination of these two steroids. Intramuscular collagen content in both experiments was higher (P less than .05) in muscles of rams than in muscles of wethers. Administration of the highest level of testosterone to wethers raised (P less than .05) total and insoluble intramuscular collagen to concentrations noted in rams. Administration of the testosterone metabolite, dihydrotestosterone, to wethers had no effect on intramuscular collagen. Administration of estradiol-17 beta to wethers tended to raise concentrations of intramuscular collagen so that they were no longer lower (P less than .05) than those in rams. Collagen stability as measured by solubility and thermal shrinkage temperature did not differ among rams, wethers or implanted wethers (P greater than .05). Increases in collagen accretion due to hormone administration were observed to be the result of increases in the insoluble portion of the intramuscular collagen (P less than .05).

Electrical stimulation-dependent improvement in beef tenderness resulted from mechanisms other than avoidance of cold shortening in excised muscle chilled at a normal rate (10°C at 10h post-stimulation). At normal chilling rate, electrical stimulation enhanced degradation of the myofibrillar proteins, alpha actinin and troponin-T, and increased the amount of a 30 000 dalton protein, as assessed by gel electrophoresis, whereas sarcomere lengths were not different from unstimulated muscle. Under slightly accelerated chilling conditions (10°C at 5 h post stimulation), electrical stimulation prevented cold shortening but the meat was more tender than, and had the same sarcomere length as, unstimulated muscle chilled to 10°C in 10 h. Electrical stimulation did not improve the tenderness of beef chilled at a rapid rate (10°C at 2 h post stimulation), nor did it prevent cold shortening when muscles were chilled rapidly., (Copyright © 1983. Published by Elsevier Ltd.)

Post-mortem changes in physical and thermal stabilities of bovine intramuscular connective tissue were studied during the first 24 h postmortem. Collagen thermal shrinkage temperature (T(s)) decreased (P < 0·01) and collagen solubility increased (P < 0·01) during the first 24 h following slaughter with greatest amount of change occurring in the first 8 h post mortem. The dynamic nature of intramuscular connective tissue during the very early post-mortem (VEP) period is compared to the VEP-tenderness relationships proposed by Marsh and others., (Copyright © 1989. Published by Elsevier Ltd.)

The effect of α-tocopherol (0, 100, 200 ppm) on lipid oxidation either in cooked or uncooked ground pork was studied during aerobic storage at 4°C and -20°C. Lipid oxidation was measured using the 2-thiobarbituric acid (TBA) method and rancidity development was scored by a trained sensory panel. Alpha-tocopherol slowed the rate of oxidation in cooked ground pork stored at either 4°C or -20°C and uncooked samples refrigerated for extended periods of time (12 days). In cooked product stored at 4°C where oxidation development was intense and off-flavors were strong, panelists did not detect flavor differences due to treatments. But in cooked product stored at -20°C sensory results were consistent with TBA analysis. Pre-rigor grinding, known to induce a high pH and inhibit lipid oxidation in uncooked fresh pork, had no protective effect on lipid oxidation as measured by TBA values in cooked ground pork, regardless of storage condition. TBA numbers increased during storage of cooked product at 4°C with an increase in internal cooking temperature between 50°C and 80°C. Internal cooking temperatures of 70°C or higher induced a rapid rate of oxidation when stored at 4°C., (Copyright © 1986. Published by Elsevier Ltd.)

Dietary infusion of L-[U-14C]tyrosine was used to estimate the fractional protein synthesis rates (FSR) in broiler and layer chickens. Six 2-wk-old birds of each strain were placed in individual metabolism cages and given a purified diet in agar-gel containing 2 microCi L-[U-14C]tyrosine for 6 h. The birds were sacrificed and the pectoralis major (PM) and two combined leg (LM) muscles (gastrocnemius and peroneous longus) were removed for analysis. Subgroups of chickens were sacrificed 3 d before and 3 d after infusion to observe changes in muscle composition to calculate fractional protein accretion rates (FAR). Fractional protein breakdown rates (FBR) were calculated by difference (FBR = FSR-FAR). Protein, ribonucleic acid (RNA) and deoxyribonucleic acid (DNA) concentrations were determined to observe relationships between these cellular constituents and FSR. Fractional whole body growth rate and FSR in PM was greater (P less than .05) in broiler than layer birds. The FSR in LM of the layer was not different (P greater than .05) from that of broilers, and from the FSR of the PM in each bird-type. The calculated FBR in the layer PM was at least 17% higher than that of the other muscles. Ratios of FSR to FBR indicated that 16% of the protein synthesized in the layer PM was retained, compared with 45% in the broiler PM. The RNA activity of the layer PM was less (P less than .05) than that of the other muscles investigated. Deoxyribonucleic acid activity was lower (P less than .05) in the PM than LM of either bird-type.(ABSTRACT TRUNCATED AT 250 WORDS)

Male rats were run downhill for 90 minutes (nonexhaustive). Following the exercise, muscle protein degradation was increased, as determined by urinary 3-methylhistidine. However, minimal changes were observed in the relative percentage of the minor myofibrillar proteins and in the protease calcium activated factor in the long head of the triceps brachii muscle (eccentrically exercised) following the exercise bout.

This study was conducted to compare the effects of rapid and slow heating rates on muscles from electrically stimulated beef carcasses. Myofibrillar and cooking shortening and related changes were measured with physiograph recordings on pre-rigor M. triceps brachii strips suspended in paraffin oil during heating. Warner-Bratzler shear values were determined on pre-rigor and post-rigor M. triceps brachii samples heated at approximately the same rates at which muscle strips were heated (2°C/2 min and 2°C/12 min), on pre-rigor M. triceps brachii samples heated at 2°C/6 min, 2°C/9 min and 2°C/12 min and on pre-rigor and post-rigor M. triceps brachii and M. longissimus muscle heated similarly at 2°C/12 min. Rapid heating (2°C/2 min) of pre-rigor muscle produced more severe myofibrillar shortening that was complete at higher muscle temperature than slow heating (2°C/12 min). Slow heating, in contrast to rapid heating, resulted in a cooked product of lower shear value in both the pre-rigor and post-rigor states. The slower the heating rate of the pre-rigor M. triceps brachii, the more tender was the product. Heating at a rate of 2°C/12 min produced acceptable tenderness in both the pre-rigor M. longissimus and M. triceps brachii muscles but even greater tenderness when both muscles were heated in the post-rigor state. The tenderizing action of severe muscle shortening could not be induced in electrically stimulated muscle., (Copyright © 1985. Published by Elsevier Ltd.)

Post-mortem changes in the composition and physical stability of bovine intramuscular collagen were evaluated during a 24 h ageing period. The yield of intramuscular connective tissue (IMCT) isolated from the infraspinatus muscle samples and the carbohydrate content of that material did not change significantly (P > 0·05) during the ageing period. The collagen content and total protein content of the isolated IMCT increased (P < 0·05) through 8 h post-mortem. Moisture content of the isolated material decreased numerically but not significantly (P > 0·05). Collagen thermal shrinkage temperature (T(s)) decreased (P < 0·01) and collagen solubility increased (P < 0·05) during the ageing period with most of the changes occurring in the first 8 h., (Copyright © 1989. Published by Elsevier Ltd.)

The effect of beef carcass electrical stimulation on the thermal stability of intramuscular collagen was determined. Differential scanning calorimetric determinations of thermal shrinkage temperature revealed that electrical stimulation lowered the shrinkage temperature of collagen by an average of .6 C in the population of cattle studied. No difference between Hereford x Angus crossbreds and Charolais crossbreds were found, but the extent of the reduction of collagen shrinkage temperature caused by electrical stimulation was greater in animals that did not receive high grain diets or received grain for only a short period than in those fed grain for up to 210 days. Furthermore, panel tenderness and Warner-Bratzler shear tests showed that stimulation-induced tenderization was also greater in animals fed no grain or fed grain for a short time. No evidence of stimulation effects on myofibrillar proteins was observed from data on sarcomere length or myofibrillar fragmentation index. The reduction of thermal stability of bovine intramuscular collagen by electrical stimulation may result from a decrease in the number or strength of the collagen cross-links.

Pre-rigor cooked beef is tender if the cooking produces severe shortening. This study was conducted to compare the effects of different heating rates on shortening and tenderness. Myofibrillar and cooking shortening and related changes were measured with physiograph recordings on pre-rigor M. triceps brachii strips suspended in paraffin oil during heating. Warner-Bratzler shear values were determined on M. triceps brachii samples heated at approximately the same rates at which the muscle strips were heated. Rapid heating (2°C/2min) produced more (p < 0·01) severe myofibrillar shortening that was complete at higher (p < 0·01) muscle temperatures than slow heating (2°C/12 min). Regardless of animal age, rapid heating resulted in a cooked product that was more (p < 0·01) tender than that produced by slow heating in the pre-rigor state and slow heating resulted in a more (p < 0·01) tender product than that achieved by rapid heating in the post-rigor state. Data on muscle shortening and from differential scanning calorimetry suggest that the tenderness produced from pre-rigor rapid heating results from a heat-induced active contraction., (Copyright © 1985. Published by Elsevier Ltd.)

Dietary infusion of L-[U-14C]tyrosine was used to estimate the fractional protein synthesis rates (FSR) in normal and dwarf female broiler chicks. Five 2-week-old and five 3-week-old birds of each genotype were placed in individual metabolism cages and given a purified diet in agar-gel containing 2 mu Ci L-[U-14C]tyrosine for 6 hr. Birds were killed and the pectoralis major (PM) and combined gastrocnemius and peroneous longus muscles (LM) were removed for analyses. Additional groups of 4 to 5 chickens were killed 3 days before and 3 days after each infusion to determine fractional protein accretion rate (FAR) over the 6-day period. Fractional degradation rate (FDR) was obtained by difference (FDR = FSR - FAR). Protein, ribonucleic acid (RNA), and deoxyribonucleic acid (DNA) concentrations were determined to observe possible relationships between these cellular constituents and FSR. Activities of RNA and DNA were determined as units of protein synthesized per unit RNA or DNA per day. Two-week-old chicks, dwarf chicks, and the PM muscles had higher (P less than .05) FSR than 3-week-old chicks, normal chicks, and the LM, respectively. Two-week-old chicks and dwarf chicks had higher FDR than 3-week-old chicks, respectively. There was a significant decrease in RNA concentration and RNA activity from 2 to 3 weeks. The RNA activity tended to be higher in dwarf than normal birds. Concentration of RNA was higher (P less than .05) in the PM than LM. However, DNA concentration was higher (P less than .05) in the LM than PM.(ABSTRACT TRUNCATED AT 250 WORDS)

The objective of this study was to estimate the fractional breakdown rate (FBR) of muscle protein in the chicken from measurements of 3-methylhistidine (3-Mehis) excretion and the amount of 3-Mehis bound in the skeletal muscle pool. Excreta were collected for a 24-hr period from six 2-week-old broiler chicks that were fed a purified diet, and 3-Mehis was quantified. The concentration of 3-Mehis was determined in the dissected tissues of skeletal muscle, heart, gizzard, intestine, crop, stomach, brain, lung, kidney, liver, skin, feathers, and skeleton. Detectable amounts of 3-Mehis were not found within serum either before or after acid hydrolysis. Heart, gizzard, intestine, crop, and stomach contained considerable amounts of 3-Mehis, but because of their small contribution to body weight, they contributed only 11% of the total body 3-Mehis. Muscle contributed 84% of the 3-Mehis in the body. Muscle protein FBR determined from 3-Mehis excretion was 5.3%/day, about half that estimated using continuous infusion methods. The difference between the two quantification methods was attributed to the slow turnover rate of actin, which contains most of the 3-Mehis.

Interrelationships among concentrations and maturation of intramuscular collagen, serum concentration of hydroxyproline and testosterone and meat tenderness were determined in growing bulls and steers. Sixty-four Charolais X Angus bulls were assigned to sex treatment groups (intact or castrate) and slaughter groups (9, 12, 15 or 18 mo of age). Animals were bled at 30-min intervals via intrajugular catheters between 0600 and 1400 beginning 48 h before slaughter. Serum concentrations of testosterone were determined in each sample from bulls and from four samples from steers; serum hydroxyproline was determined in the last sample from both sexes. Testosterone mean values for the collection period were calculated. Samples of the longissimus, semitendinosus and infraspinatus muscles secured within 45 min postmortem were analyzed for intramuscular collagen concentration, percent soluble collagen and collagen thermal shrinkage temperature. Tenderness of loin steaks was determined by Warner-Bratzler shear test. Serum concentrations of hydroxyproline and testosterone were higher (P less than .01) in bulls than steers. Age effects were noted for both hydroxyproline (P less than .01) and testosterone (P less than .06). Total intramuscular collagen was greater (P less than .01) in bulls than steers and was different (P less than .01) among muscles, but the muscle differences were not uniform over all ages (P less than .05). Percent soluble collagen declined (P less than .01) with age and was different (P less than .01) among muscles. Interaction of age and muscle (P less than .01) and age and sex (P less than .05) also were noted for percent soluble collagen.(ABSTRACT TRUNCATED AT 250 WORDS)

Frozen sections of equine musculus semitendinosus were examined for myosin adenosine triphosphatase (ATPase) and reduced nicotinamide adenine dinucleotide-tetrazolium reductase (NADH-TR), using standard histochemical procedures, and the proportions of the various fiber types and average fiber sectional size were determined. With ATPase staining, approximately 70% of the fibers were classified as alpha fibers (ATPase positive), and 30%, as beta fibers (ATPase negative). In addition, 2 populations of alpha fibers could be readily distinguished on the basis of the intensity of the ATPase reaction, and these were designated alpha positive and alpha intermediate. The relationship of this difference in ATPase reaction to contraction speed of the fibers is not known. With NADH-TR staining, fibers were classified as either red fibers (positive) having aerobic metabolism or white fibers (negative) having primarily anaerobic metabolism. All beta fibers were red by NADH-TR; thus, they conformed to the criteria for beta R fibers. All alpha positive fibers were white by NADH-TR, as were most of the alpha intermediate fibers, and would be classified alpha W. Some of the alpha intermediate fibers gave an intermediate reaction with NADH-TR and could be classified as alpha R fibers which have not transformed to alpha W fibers. The alpha positive fibers were 7 to 10 mum larger in diameter than either beta or alpha intermediate fibers.

Concentration and maturation of collagen and serum concentrations of hydroxyproline and testosterone were determined in growing rams and wethers to characterize developmental changes in collagen associated with a representative testicular steroid. Groups of eight rams and eight wethers were slaughtered at 12, 18, 24 and 30 wk of age. Concentrations of collagen in longissimus, supraspinatus and infraspinatus muscles and serum hydroxyproline were greater (P less than .05) in rams than in wethers at all ages. Collagen stability, as measured by collagen solubility and thermal shrinkage temperature, was greater (P less than .05) in wethers than in rams. Differences in collagen stability and serum hydroxyproline concentration indicated that collagen synthesis and turnover were more rapid in rams than in wethers. Serum hydroxyproline decreased (P less than .05) and collagen solubility decreased (P less than .05) with age, indicating that collagen turnover was occurring most rapidly in 12-wk-old lambs and that collagen maturation was predominant in 24- to 30-wk old lambs. Testosterone parameters measured in rams were unrelated within groups to collagen characteristics, possibly reflecting the high variability in testosterone secretion and the slow development of collagen. However, rams as young as 12 wk of age were under the influence of testosterone, and differences in collagen between rams and wethers were apparent at that time.