Composition of free and peptide-bound amino acids in beef chuck, loin, and round cuts.

Meat is a food for humans. However, beef consumption in the United States has steadily declined by >14% over the past decade due to a variety of factors, including insufficient knowledge of animal protein. This study quantified all proteinogenic AA as well as nutritionally and physiologically significant nonproteinogenic AA and small peptides in beef cuts from 3 subprimals (chuck, round, and loin). Beef carcasses ( = 10) were selected at 3 commercial packing plants in the United States. Retail-cut samples were analyzed for the nitrogenous substances after acid, alkaline, or enzymatic hydrolysis and after deproteinization. In these chuck, round, and loin cuts, total amounts of glutamate (free plus peptide bound) were the highest (69-75 mg/g dry weight) followed by lysine, leucine, arginine, and glutamine in descending order. This is the first study to determine aspartate, asparagine, glutamate, and glutamine in meat proteins of any animal species. In all the beef samples evaluated, glutamine was the most abundant free AA (4.0-5.7 mg/g dry weight) followed by taurine, alanine, glutamate, and ß-alanine. Additionally, samples from all beef cuts had high concentrations of anserine, carnosine, and glutathione, which were 2.8 to 3.7, 15.2 to 24.2, and 0.68 to 0.79 mg/g dry weight, respectively. Beef top loin steaks appear to provide higher protein nutrition values than top round steaks and under blade roasts, but all are excellent sources of proteinogenic AA as well as antioxidant AA and peptides to improve human growth, development, and health. Our findings may help guide future decisions regarding human and animal nutrition.

Relationship of brain parenchyma within the caudal cranial fossa and ventricle size to syringomyelia in cavalier King Charles spaniels.

OBJECTIVES: To assess if the volumes of the caudal cranial fossa (CCF), parenchyma within the caudal cranial fossa (CCFP) or ventricles (V) are associated with syringomyelia (SM) in cavalier King Charles spaniels (CKCS) with Chiari-like malformation (CM). To evaluate if volumes are associated with transverse syrinx width. METHODS: Magnetic resonance images of 59 CKCS with CM were retrospectively reviewed and grouped with or without SM. Three-dimensional images were created and volumes of the fossae, brain parenchyma and ventricular system were calculated from which percentages of CCF, CCFP and V were created. If present, syrinx size was measured from its maximal transverse width. The percentages were statistically compared between groups, and correlation between percentages and syrinx dimensions was made. RESULTS: CKCS with SM had significantly higher CCFP (P=0.0001) and V (P=0.0002) to those without but no significant difference in CCF (P=0.925). There was a positive correlation between CCFP and syrinx width (Pearson r=0.437) and ventricle size to syrinx width (Spearman r=0.627). CLINICAL SIGNIFICANCE: A more marked overcrowding of the CCF is associated with SM, which may explain the high incidence of SM in CKCS with CM. The association between ventricle and syrinx dimensions supports the theory that SM development is the result of altered cerebrospinal fluid dynamics.

Comparison of cerebral cranium volumes between cavalier King Charles spaniels with Chiari-like malformation, small breed dogs and Labradors.

OBJECTIVES: To ascertain whether cavalier King Charles spaniels (CKCSs) have a proportionately smaller caudal fossa compared with other small dogs and with Labradors. To evaluate if cerebellar herniation in CKCS correlates with caudal fossa volume. METHODS: In this retrospective study, three-dimensional images were created from magnetic resonance imaging brain series of 117 dogs (split into three groups: CKCS, Labradors and small breeds) from which the volumes of the fossae and brain parenchyma were calculated. These volumes were transformed into percentages of total cranial cavity and parenchyma volumes, respectively. The percentages were statistically compared among the groups. The percentage of herniated cerebellum in the CKCS was compared using linear regression with the caudal fossa and parenchyma percentages. RESULTS: Cavalier King Charles spaniels had a proportionately smaller caudal fossa compared with Labradors (P=0.002) but not to small breeds (P=0.103). Their caudal fossa parenchyma was proportionately the same volume as Labradors (P=0.976) but greater than small breeds (P=0.005). No relationship was found for the per cent of cerebellum herniated. CLINICAL SIGNIFICANCE: The results support mesoderm insufficiency or craniosynostosis as the pathogenesis of Chiari-like malformation (CM) in CKCS. It presents evidence for overcrowding of the caudal fossa due to a mismatch of brain parenchyma and fossa volumes as to why CKCS and not other small dogs are affected.

Effect of p38 MAP kinases on contractility and ischemic injury in intact heart.

The p38 MAP kinases are stress-activated MAP kinases whose induction is often associated with the onset of heart failure. This study investigated the role of p38 MAP kinase isoforms in the regulation of myocardial contractility and ischemia/reperfusion injury using mice with cardiac-specific expression of kinase dead (dominant negative) mutants of p38alpha (p38alphadn) or p38beta (p38betadn). Hearts were subjected to 20 min ischemia and 40 min reperfusion. Immunofluorescence staining for p38alphadn and p38betadn protein was performed on neonatal cardiomyocytes infected with adenovirus expressing flag-tagged p38alphadn and p38betadn protein. Basal contractile function was increased in both p38alphadn and p38betadn hearts compared to WT. Ischemic injury was increased in p38betadn vs. WT hearts, as indicated by lower posti-schemic recoveries of contractile function and ATP. However, despite a similar increase in contractility, ischemic injury was not increased in p38alphadn vs. WT hearts. Immunohistological analysis of cardiomyocytes with comparable levels of protein overexpression show that p38alphadn and p38betadn proteins were co-localized with sarcomeric alpha-actinin, however, p38alphadn was detected in the nucleus while p38betadn was exclusively detected in the cytosol. In summary, attenuated p38 activity led to increased myocardial contractility; specific isoforms of p38 and their sub-cellular localization may have different roles in modulating ischemic injury.

Evaluation of fat sources on cholesterol and lipoproteins using pigs selected for high or low serum cholesterol.

At approximately 8 weeks of age, four-way cross (Chester White×Landrace×Large White×Yorkshire) pigs (n=24) were selected based on genetically high (H) or low (L) serum cholesterol levels-12 from each genetic group-to determine the relationship between genetics, fat source, and sex class on plasma cholesterol, growth, carcass characteristics, and cholesterol and lipid content of muscle and adipose tissues. Boars and gilts, six each from the two genetic groups, were assigned randomly to one of three dietary treatments for 46 days. A standard grower diet was modified to include beef tallow (T), corn oil (CR) or coconut oil (CC), and the pigs were given ad libitum access to feed. Cholesterol was added to each diet to ensure the diets contained the same amount of cholesterol. Except for the plasma lipids, there were no differences between boars and gilts at the initial evaluation or at the end of the treatment; therefore, sex means were pooled for statistical analyses. Body weight was unaffected by diet on days 18, 29 or 46. Blood samples were taken on days 1, 29, and 46 via the anterior vena cava. Plasma total cholesterol (TC) and low density lipoprotein cholesterol (LDL) concentrations were greater in the H than L groups (overall TC in H and L pigs=150 and 124 mg/dl, respectively, and LDL in H and L pigs=105 and 76 mg/dl, respectively). Pigs fed diets containing saturated fats had greater TC and LDL than pigs fed unsaturated fats (TC=165, 149, and 126 mg/dl for T, CC, and CR diets, respectively, and LDL=108, 88, and 77 mg/dl for T, CC, and CR diets, respectively). There were significant time×gene×sex interactions for both TC and LDL yielding subtle differences in the response of the sexes from the two genetic groups over time. Pigs were slaughtered on day 46, and carcass data were collected. There were no differences in fat at the first rib, 10th rib, last rib, or last lumbar vertebra, but differences (P <0.05) were found between genetic groups for M. longissimus thoracis et lumborum (LTL) muscle area (H=21.0±0.8 cm(2), L=18.1±1.0 cm(2)) and USDA muscle score (H=2.1±0.1, L=1.7±0.1). There were no genetic or diet effects for cholesterol content of pre-rigor or post-rigor LTL muscle. Neither genetics nor dietary treatment affected the cholesterol content of the adipose tissue. There were no differences in fat percentage between genetic groups for muscle or adipose tissue. There were differences (P <0.05) in total lipid content among the dietary treatments for the pre-rigor (T=6.0±0.6%, CC=4.3±0.3%, CN=3.9±0.5%) and post-rigor (T=6.4±0.9%, CC=4.1±0.3%, CN=5.0±0.4%) LTL. Cholesterol accretion in muscle and adipose tissues of growing pigs was not influenced by source of fat in the diet or by their genetic propensity for high or low plasma cholesterol.

Trimetazidine for stable angina pectoris.

Stable angina pectoris, a symptom of coronary heart disease (CHD), manifests as stress-induced ischaemic episodes resulting in severe chest pain. Therapeutic aims are to improve quality of life by decreasing anginal attacks and to prevent myocardial infarction (MI) and death. Current anginal medications include beta-blockers and calcium antagonists, which decrease ischaemic severity by reducing cardiac workload, and nitrates, which increase coronary blood flow. A new therapeutic approach is the use of metabolic agents, such as trimetazidine, which are cytoprotective during ischaemia. Results of several clinical trials demonstrated that trimetazidine, at the standard dose of 20 mg t.i.d., increased exercise capacity, decreased anginal incidence and decreased left-ventricular (LV) dysfunction compared to placebo. Trimetazidine was also as effective as propranolol (120 - 160 mg/day) and nifedipine (40 mg/day) in decreasing anginal episodes and improving exercise parameters. Trimetazidine improved anginal frequency and symptoms in patients in which treatment with diltiazem, nifedipine, propranolol, pindolol, oxprenolol or long-acting nitrates had failed. Trimetazidine was also more effective than isosorbide dinitrate (30 mg/day) as an adjunct to propranolol. Despite efficacy being equivalent to that of beta-blockers and calcium antagonists, trimetazidine does not depress cardiac function and, correspondingly, is not contraindicated in any condition. Adverse effects of trimetazidine are mild and infrequent. In summary, clinical data indicate that trimetazidine is a safe, effective treatment for the symptoms of stable angina pectoris when used either as a monotherapy or an adjunctive therapy. Longer-term trials are necessary to determine whether trimetazidine will be effective in reducing rates of mortality and MI.

Using live estimates and ultrasound measurements to predict beef carcass cutability.

Commercial slaughter steers (n = 329) and heifers (n = 335) were selected to vary in frame size, muscle score, and carcass fat thickness to study the effectiveness of live evaluation and ultrasound as predictors of carcass composition. Three trained personnel evaluated cattle for frame size, muscle score, fat thickness, longissimus muscle area, and USDA quality and yield grade. Live and carcass real-time ultrasound measures for 12th-rib fat thickness and longissimus muscle area were taken on a subset of the cattle. At the time of slaughter, carcass ultrasound measures were taken at "chain speed." After USDA grade data were collected, one side of each carcass was fabricated into boneless primals/subprimals and trimmed to .64 cm of external fat. Simple correlation coefficients showed a moderately high positive relationship between 12th rib fat thickness and fat thickness measures obtained from live estimates (r = .70), live ultrasound (r = .81), and carcass ultrasound (r = .73). The association between estimates of longissimus muscle area and carcass longissimus muscle area were significant (P < .001) and were higher for live evaluation (r = .71) than for the ultrasonic measures (live ultrasound, r = .61; carcass ultrasound, r = .55). Three-variable regression equations, developed from the live ultrasound measures, explained 57% of the variation in percentage yield of boneless subprimals, followed by live estimates (R2 = .49) and carcass ultrasound (R2 = .31). Four-variable equations using frame size, muscle score, and selected fat thickness and weight measures explained from 43% to 66% of the variation for the percentage yield of boneless subprimals trimmed to .64 cm. Live ultrasound and(or) live estimates are viable options for assessing carcass composition before slaughter.

Overexpression of the cardiac beta(2)-adrenergic receptor and expression of a beta-adrenergic receptor kinase-1 (betaARK1) inhibitor both increase myocardial contractility but have differential effects on susceptibility to ischemic injury.

Cardiac beta(2)-adrenergic receptor (beta(2)AR) overexpression is a potential contractile therapy for heart failure. Cardiac contractility was elevated in mice overexpressing beta(2)ARs (TG4s) with no adverse effects under normal conditions. To assess the consequences of beta(2)AR overexpression during ischemia, perfused hearts from TG4 and wild-type mice were subjected to 20-minute ischemia and 40-minute reperfusion. During ischemia, ATP and pH fell lower in TG4 hearts than wild type. Ischemic injury was greater in TG4 hearts, as indicated by lower postischemic recoveries of contractile function, ATP, and phosphocreatine. Because beta(2)ARs, unlike beta(1)ARs, couple to G(i) as well as G(s), we pretreated mice with the G(i) inhibitor pertussis toxin (PTX). PTX treatment increased basal contractility in TG4 hearts and abolished the contractile resistance to isoproterenol. During ischemia, ATP fell lower in TG4+PTX than in TG4 hearts. Recoveries of contractile function and ATP were lower in TG4+PTX than in TG4 hearts. We also studied mice that overexpressed either betaARK1 (TGbetaARK1) or a betaARK1 inhibitor (TGbetaARKct). Recoveries of function, ATP, and phosphocreatine were higher in TGbetaARK1 hearts than in wild-type hearts. Despite basal contractility being elevated in TGbetaARKct hearts to the same level as that of TG4s, ischemic injury was not increased. In summary, beta(2)AR overexpression increased ischemic injury, whereas betaARK1 overexpression was protective. Ischemic injury in the beta(2)AR overexpressors was exacerbated by PTX treatment, implying that it was G(s) not G(i) activity that enhanced injury. Unlike beta(2)AR overexpression, basal contractility was increased by betaARK1 inhibitor expression without increasing ischemic injury, thus implicating a safer potential therapy for heart failure.

Predicting carcass composition of beef cattle using ultrasound technology.

We evaluated 20 slaughtered cattle with ultrasound before hide removal to predict fat thickness and ribeye area at the 12th rib for possible use in carcass composition prediction. Carcasses were fabricated into boneless subprimals that were trimmed progressively from 2.54 to 1.27 to .64 cm maximum fat trim levels. Stepwise regression was used to indicate the relative importance of variables in a model designed to estimate the percentage of boneless subprimals from the carcass at different external fat trim levels. Variables included those obtained on the slaughter floor (ultrasound fat thickness and ribeye area; estimated percentage of kidney, pelvic, and heart [KPH] fat; and warm carcass weight) and those obtained from carcasses following 24 h in the chill cooler (actual fat thickness, actual ribeye area, estimated percentage of KPH fat, warm carcass weight, and marbling score). At all different subprimal trim levels, percentage KPH was the first variable to enter the model. In the models using measures taken on the slaughter floor, ultrasound fat thickness was the only other variable to enter the model. Ultrasound fat thickness increased R2 and decreased residual standard deviation (RSD) in models predicting subprimals at 2.54-cm maximum fat trim; however, at 1.27- and .64-cm trim levels, R2 and RSD increased. Models using the same two variables (except actual fat instead of ultrasound) in the cooler were similar to those using data from the slaughter floor. However, as more cooler measurement variables entered the models, R2 increased and RSD decreased, explaining a greater amount of the variation in the equation. Ultrasonic evaluation on the slaughter floor may be of limited application compared with the greater accuracy found in chilled carcass assessment.

Overexpression of the cardiac Na+/Ca2+ exchanger increases susceptibility to ischemia/reperfusion injury in male, but not female, transgenic mice.

Influx of Ca2+ into myocytes via Na+/Ca2+ exchange may be stimulated by the high levels of intracellular Na+ and the changes in membrane potential known to occur during ischemia/reperfusion. This increased influx could, in turn, lead to Ca2+ overload and injury. Overexpression of the cardiac Na+/Ca2+ exchanger therefore may increase susceptibility to ischemia/reperfusion injury. To test this hypothesis, the hearts of male and female transgenic mice, overexpressing the Na+/Ca2+ exchange protein, and hearts of their wild-type littermates, were perfused with Krebs-Henseleit buffer and subjected to 20 minutes of ischemia and 40 minutes of reperfusion. Preischemic left ventricular developed pressures and +dP/dtmax, as well as -dP/dtmin, were higher in the male transgenic hearts compared with wild-type, implying a role for Na+/Ca2+ exchange in the contraction, as well as the relaxation, phases of the cardiac beat. Postischemic function was lower in male transgenic than in male wild-type hearts (7+/-2% versus 32+/-6% of preischemic function), but there was no difference between female transgenic and female wild-type hearts, both at approximately 30% of preischemic function. To assess whether this male/female difference was due to female-specific hormones such as estrogen, the hearts of bilaterally ovariectomized and sham-operated transgenic females were subjected to the same protocol. The functional recoveries of ovariectomized female transgenic hearts were lower (17+/-3% of preischemic function) than those of wild-type and sham-operated transgenic females. The lower postischemic functional recovery in the male transgenic and female ovariectomized transgenic hearts correlated with lower recoveries of the energy metabolites, ATP and phosphocreatine, as measured by 31P nuclear magnetic resonance spectroscopy. Alternans were observed during reperfusion in male transgenic and female ovariectomized transgenic hearts only, consistent with intracellular Ca2+ overload. Western analyses showed that alterations in the expression of the Na+/Ca2+ exchange or L-type Ca2+ channel proteins were not responsible for the protection observed in the female transgenic hearts. In conclusion, in males, overexpression of the Na+/Ca2+ exchanger reduced postischemic recovery of both contractile function and energy metabolites, indicating that the Na+/Ca2+ exchanger may play a role in ischemia/reperfusion injury. From the studies of females, however, it appears that this exacerbation of ischemia/reperfusion injury by overexpression of the Na+/Ca2+ exchanger can be overcome partially by female-specific hormones such as estrogen.

Starvation depresses acylglycerol biosynthesis in bovine subcutaneous but not intramuscular adipose tissue homogenates.

The primary objective of this study was to document the effects of starvation on acylglycerol biosynthesis in homogenates of intramuscular and subcutaneous adipose tissues. Adipose tissue samples were obtained from 8th-13th thoracic rib sections from 12 Angus cattle (six steers plus six heifers). Three steers and three heifers were starved for 72 h prior to slaughter while the remainder were slaughtered 4 h after food was withheld. Fat-free 700 x g centrifugal fractions were used to measure the esterification of radiolabeled sn-glycerol 3-phosphate (G-3-P) into acylglycerols at 1.0 mM palmitic or stearic acid, or 0.2 mM oleic, linoleic, or alpha-linolenic acid. There were significant tissue x fatty acid interactions for rates of incorporation into diacylglycerols and triacylglycerols; in subcutaneous, but not intramuscular homogenates, palmitic > stearic = oleic = linoleic = alpha-linolenic acid. Subcutaneous homogenates incorporated a greater percentage of G-3-P into triacylglycerols, and a lesser percentage into phospholipid, than intramuscular homogenates (P < 0.05). In intramuscular homogenates, the primary product of G-3-P esterification to saturated fatty acids was phospholipids. When unsaturated fatty acid served as substrates, triacylglycerols and phospholipids were produced in equal proportions in intramuscular homogenates, and triacylglycerols were the predominant product in subcutaneous homogenates. Intramuscular adipose tissue homogenates exhibited no response to starvation, whereas triacylglycerol and diacylglycerol synthesis was depressed by approximately 50% in subcutaneous adipose tissue homogenates. Similarly, phosphatidic phosphohydrolase activity, initially greater in subcutaneous than in intramuscular adipose tissue, was decreased by approximately 50% by starvation in subcutaneous adipose tissue, but not in intramuscular adipose tissue. We conclude that differences in rates of diacylglycerol and triacylglycerol biosynthesis, and response to starvation, between intramuscular and subcutaneous adipose tissues were due to dissimilarities in the activity of phosphatidic phosphohydrolase.

Determination of sensory, chemical and cooking characteristics of retail beef cuts differing in intramuscular and external fat.

Top loin (TLS), top sirloin (TSS), and eye of round (EYS) steaks, and loin end (LRR) and blade end (BRR) rib, and eye of round (EYR) roasts were used to determine the effect of USDA quality grade, Choice or Select, external fat trim level, and internal temperature endpoint on sensory, chemical and cooking characteristics. Cuts cooked with external fat required slightly greater cooking times and had higher fat content in the lean than cuts cooked without external fat (p < 0.05). Regardless of quality grade or external fat trim, increasing internal temperature endpoint resulted in tougher, drier cuts with longer cooking times and greater cooking loss (p < 0.05). Choice TLS, TSS and LRR were higher (p < 0.05) in palatability than Select, but quality grade did not affect palatability of BRR, EYS or EYR.

Decreased intracellular pH is not due to increased H+ extrusion in preconditioned rat hearts.

Ischemic preconditioning reduces intracellular acidification during a subsequent, prolonged period of ischemia. This may reflect decreased anaerobic glycolysis or increased H+ efflux. To distinguish between these hypotheses, we monitored intracellular and extracellular pH during a sustained period of ischemia to determine whether the preconditioned hearts had increased H+ efflux compared with nonpreconditioned hearts. At the end of 20 min of ischemia, intracellular pH in nonpreconditioned hearts was 5.90 +/- 0.08 and extracellular pH was 5.51 +/- 0.21, whereas in preconditioned hearts, intracellular pH was 6.50 +/- 0.06 and extracellular pH was 6.62 +/- 0.06. To investigate whether an Na+/H+ exchange inhibitor would alter the reduced acidification during ischemia, we preconditioned hearts with and without dimethylamiloride (DMA). Intracellular pH during ischemia was similar in preconditioned hearts with and without DMA treatment (pH 6.42 +/- 0.02 vs. 6.45 +/- 0.03, respectively). These data do not support the hypothesis that enhanced proton efflux is responsible for the more alkaline intracellular pH during sustained ischemia in preconditioned hearts.

Consumer evaluation of beef of known categories of tenderness.

A study was conducted to determine consumer perceptions of beef top loin steaks of known shear force and to evaluate how buying trends were modified by the tenderness and price variations of these steaks. Strip loins were cut into a 2.54-cm-thick steaks, and the center steak from each strip loin was used to determine Warner-Bratzler shear force. The remaining steaks were placed into one of the following shear force categories based on that shear force and color-coded accordingly: 1) 2.27 to 3.58 kg (Red); 2) 4.08 to 5.40 kg (White); and 3) 5.90 to 7.21 kg (Blue). Randomly recruited consumers were allowed to evaluate steaks and then purchase steaks based on their findings. A $1.10/kg price difference was placed between each category. Results of the analysis indicated that consumers were able to differentiate between the three categories of tenderness (P < .05). In addition, consumers gave higher (P < .05) juiciness and flavor ratings to Red steaks than to Blue steaks. Overall satisfaction was higher (P < .05) for Red steaks than for the other two categories of steaks. The following percentages of steaks were purchased: 1) Red, 94.6%; 2) White, 3.6%; and 3) Blue, 1.8%. These results suggest that consumers could discern between categories of tenderness and were willing to pay a premium for improved tenderness.

Influence of realimentation of mature cows on maturity, color, collagen solubility, and sensory characteristics.

Cull beef cows (n = 80) that had consumed similar grassland diets were assigned to one of four feeding periods (0, 28, 56, and 84 d) and subdivided into two groups fed either a high-energy, high-protein diet or a high-energy, low-protein diet. Treatments were designed to examine the effect of time on feed, dietary protein, and electrical stimulation on carcass traits, composition, shear force, sensory profile, collagen characteristics, and myoglobin state. Within 1 h of slaughter, the right side of each carcass was electrically stimulated, and the left side served as the control. The only trait influenced by protein level was longissimus muscle area, for which a high-protein diet resulted in larger (P < .05) longissimus muscle areas. Increased time on a high-energy diet increased USDA yield grade and sensory ratings; however, metmyoglobin and reduced myoglobin values decreased between 0 and 28 d on feed. Electrical stimulation improved lean color, shear force values, and sensory attributes. Electrical stimulation decreased shear force by 2.8 kg for 0-d carcasses. With subsequent days on feed, shear force values continued to decrease, but this effect was minimal in electrically stimulated carcasses. However, protein level did not significantly influence palatability and quality attributes. The greatest (P < .05) improvement in marbling score was observed in electrically stimulated carcasses from cows fed for 84 d. Additionally, feeding a high-protein diet for 84 d resulted in a slightly lower maturity score. Even though values for palatability and quality traits were improved by antemortem and postmortem treatments, the magnitude of improvement may not be great enough for steaks from mature fed cows to be considered as acceptable as steaks from young fed beef.

The beta/alpha peak height ratio of ATP. A measure of free [Mg2+] using 31P NMR.

From 31P NMR measurements made in vitro at 38 degrees C, I = 0.25, pH 5. 75-8.5, and calculated free [Mg2+] from 0 to 5 mM, we show that, within the physiological range of cytosolic free [Mg2+] from 0.25 to 1.5 mM, the chemical shift difference between the alpha- and beta-ATP resonances, deltaalphabeta, changes by only 0.6 ppm. Consequently, we developed new formalisms from known acid and Mg2+ dissociation constants by which the observed chemical shift of Pi, deltaPi, and the peak height ratio of the beta- and alpha-ATP resonances, hbeta/alpha, could be related to free [Mg2+] by simultaneous solution of: [equation: see text] We found that hbeta/alpha changed 2.5-fold as free [Mg2+] varied from 0.25 to 1.5 mM, providing a more sensitive and accurate measure of free cytosolic [Mg2+]. In working rat heart perfused with glucose, free [Mg2+] was 1.0 +/- 0.1 from hbeta/alpha and 1.2 +/- 0.03 from measured [citrate]/[isocitrate] but 0.51 +/- 0.1 from deltaalphabeta. Addition of ketone bodies to the perfusate decreased free [Mg2+] estimated from hbeta/alpha to 0.61 +/- 0.02 and 0.74 +/- 0.11 by [citrate]/[isocitrate] but the estimate from deltaalphabeta was unchanged at 0.46 +/- 0.04 mM. Such differences in estimated free [Mg2+] alter the apparent Keq of the creatine kinase reaction and hence the estimated cytosolic free [SigmaADP].

A diet containing myristoleic plus palmitoleic acids elevates plasma cholesterol in young growing swine.

The objective of this study was to test the effect of a novel fatty acid mixture, enriched with myristoleic and palmitoleic acids, on plasma lipoprotein cholesterol concentrations. Weanling pigs were assigned to one of six groups and each group received a diet differing in fatty acid composition. Diets were fed for 35 days and contained 10 g added cornstarch/100 g (to provide baseline data) or 10 g added fatty acids/100 g. For those diets containing added fatty acids, extracted lipids contained 36% myristoleic plus palmitoleic acid combined (14:1/16:1 diet), 52% palmitic acid (16:0 diet), 51% stearic acid (18:0 diet), 47% oleic acid (18:1 diet), or 38% linoleic acid (18:2 diet). With the exception of the cornstarch diet, all diets contained approximately 30% myristic acid. There were no significant differences in weight gain across treatment groups (P = 0.22). All diets caused a significant increase in triglycerides and in total, low density lipoprotein, high density lipoprotein, and very low density lipoprotein cholesterol. The increase in total plasma cholesterol from pretreatment values was greatest in pigs fed the 14:1/16:1 and 18:1 diets. However, the increase in low density lipoprotein cholesterol from the pretreatment concentration was greatest in the 14:1/16:1-fed pigs. Increases in very low density lipoprotein cholesterol above pretreatment concentrations were lowest in 16:0-fed pigs and greatest in 18:1-fed pigs. Dietary fatty acids elicited changes in plasma fatty acids which generally were reflective of the diets, although the 18:0 diet did not alter plasma fatty acid concentrations and the 16:0 diet increased plasma 16:0 only at the end of the study. These results demonstrated that the combination of myristoleic plus palmitoleic acids increased plasma cholesterol in young pigs, suggesting that fatty acid chain length, rather than degree of unsaturation, is primarily responsible for the effects of fatty acids on circulating lipoprotein cholesterol concentrations.