Role of moisture evaporation in the taste attributes of dry- and wet-aged beef determined by chemical and electronic tongue analyses

The role of moisture evaporation in the taste attributes of dry- and wet-aged beef was determined in this study. A total of 30 striploins (longissimus lumborum) were dry or wet aged for 28 days and analyzed for moisture content, taste-active compounds [free amino acids (FAAs), inosine 5'-monophophate (IMP), and reducing sugars], and taste attributes by an electronic tongue. After the completion of aging process, higher amounts of FAAs and reducing sugars were found in dry-aged beef (P < .05) in negative correlations with moisture content (r² = -0.9 and - 0.9, respectively), which were not detected in wet-aged beef. However, the different taste attributes of dry- and wet-aged beef were observed by the electronic tongue from day 14, whereas their moisture content was significantly different only at day 28. Consequently, although the moisture evaporation during dry aging process contributed to the increased flavor of dry-aged beef, there are other factors affecting flavor development including microbial activity on the surface crust.

Metabolism of ATP during anoxia in guinea pig seminal vesicle mucosa

The content of adenine nucleotides in guinea pig seminal vesicles was determined enzymatically. Inosine monophosphate (IMP) was isolated from other tissue nucleotides by two-dimensional thin-layer chromatography on cellulose PEI plates, eluted, and quantitated spectrophotometrically. The intracellular concentration of IMP increased 10-fold over control values (aerobic tissue) concomitantly with the strong ATP drain caused by anoxia. This contrasts markedly with other tissues in which ATP depletion is usually associated with an increase in AMP. Tissue inorganic phosphate also accumulated in an amount corresponding to the apparent ATP depletion. Uric acid did not accumulate. Our data suggest the possibility of a special role for IMP in metabolic control in this tissue.

Effects of high frequency electrical stunning and decapitation on early rigor development and meat quality of broiler breast meat

Three independent trials were conducted to determine the effects of high frequency electrical stunning followed by decapitation on broiler breast meat rigor development and meat quality. All birds were stunned and half of the birds were killed using a conventional unilateral neck cut, half were killed by decapitation, and both groups were allowed to bleed for 90 s prior to scalding and picking. New York dressed carcasses were chilled in a static ice-water bath for 90 min and held at 2 degrees C prior to deboning. Breast fillets were removed from the carcasses at 2, 4, and 24 h postmortem. From the right breast fillet, R-values and pH were determined at time of deboning. The left fillet was wrapped in plastic and held for 24 h at 2 degrees C prior to determining lightness (L*), redness (a*), yellowness (b*), cook yield, and Allo-Kramer shear. Deboning time affected raw meat pH, R-value, cook loss, and shear value but had no effect on color. The breast meat from the decapitated birds had significantly higher pH values at 2 and 24 h postmortem than the conventionally killed birds. Other than for the effect on breast meat pH, decapitation had no effect on rigor development, R-value, meat color, or meat quality as measured by cooked-meat yield and Allo-Kramer shear.

Stability of disodium salt of inosine phosphate in aqueous solutions

The HPLC method for the separation of the disodium salt of inosine phosphate (PIN) and the product of its transformation, inosine (IN) and hypoxanthine (HP) were developed and validated. The hydrolysis kinetics of disodium salt of inosine phosphate was studied in aqueous solution at 353 K over a pH range of 0.45-12.13.

[Purine metabolism: determination of adenyl deaminase in human lymphocytes]

Adenylic acid (AMP) deaminase is a "catabolic enzyme" involved in nucleotide degradation, transforming AMP into inosinic acid (IMP). We present a simple method for the determination of the enzyme activity, which combines high sensitivity with requirement of low quantities of lymphocytes. Human lymphocytes were isolated with a Lymphocyte Separation Medium from FLOW and sonicated. After centrifugation at 2,000 rpm x 10 min and treatment with Norit A, the cells were incubated at 37 degrees C with ATP 0.8 mM and 14C-AMP 0.1 mM (specific activity 12 microCi/mumole) in potassium phosphate 100 mM (pH 7.4). 14C-IMP and 14C-AMP were separated through HPLC by an isocratic elution, with 20 mM KH2PO4 (pH 5.5) at a 1.5 ml/min flow rate. Identification of the nucleotides was carried out through retention time, coelution with internal standards: their evaluation by determining the radioactivity of the collected peaks. The enzyme activity is decreased in patients affected by CLL: the decrease is evident only when data are referred to the single cells and not when they are referred to the protein.

Effects of electrical stimulation on the post-mortem biochemical changes and texture of broiler pectoralis muscle

A study was conducted to determine the influence of electrical stimulation (50,200, or 350 V ac) on biochemical and textural changes in broiler breast muscle. Sixty-four broilers were stunned (50 V ac) prior to kill, and all but a control group were pulse stimulated during bleeding. After processing, carcasses were held in 10-C water for 1 h, then in 2-C ice/water slush for 1 h prior to muscle removal at 2 h post-mortem (PM). Bagged samples were held at 2 C for 24 h, then cooked. The pH, R value (ratio of adenine nucleotides to inosine nucleotides), cook yield, fluids and solids lost (F&S), and objective texture were measured. In addition, 16 broilers processed in the same manner were used in producing a profile of sarcoplasmic protein/enzyme changes in the breast muscle by cation exchange fast protein-liquid chromatography at 10 min, 2, and 24 h PM. The R values and soluble protein were also determined. Stimulation at 200 and 350 V accelerated the onset of rigor noted by lower pH values at 10 min and 1 h PM, and higher R values at 2 h PM. Muscle stimulated at 350 V exhibited the lowest cook yield and highest percentage of F&S lost, suggesting both the loss of functional properties and muscle integrity due to this treatment. All control and stimulated samples exhibited shear values in excess of what would be considered tender. Hardness and chewiness values increased as stimulation voltage levels increased. Only one of the seven principal chromatographic peaks decreased in response to increased electrical stimulation.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenine, guanine, and inosine nucleotides of chick growth cartilage: relationship between energy status and the mineralization process

The major aim of this investigation was to measure the nucleotide content of the developing chick epiphysis and to relate changes in nucleotide levels to chondrocyte maturation and the development of mineralization. Using a cryostat, sections of cartilage were isolated from the proximal head of the tibial growth cartilage, care being taken to preserve the metabolic integrity of the tissue. Sections were identified microscopically, pooled, and the nucleotide and nucleoside content of each sample determined by HPLC. Procedures used for the study were shown to minimize degradation of nucleotides. Their effectiveness was assessed through an evaluation of the rapid freezing technique and by examination of the effects of apatite on the recovery of endogenous and added nucleotides. Analysis of nucleotide levels in the growth cartilage indicated that chondrocytes undergo a profound change in energy metabolism during development and maturation. Thus, in the premineralized resting and proliferative zones, ATP and, to a lesser extent, GTP values were high, suggesting that the chondrocytes obtained metabolic energy through both glycolytic and mitochondrial oxidative processes. In the hypertrophic zone and in calcified cartilage, there was a profound decrease in the ATP concentration and a corresponding fall in the energy charge and the ATP/ADP ratios. The nucleotide levels in this zone indicated that there was increased reliance on nonoxidative metabolism. Measurement of nucleoside levels in premineralized cartilage suggested that there was little resynthesis of nucleotides through the salvage pathway. These observed changes in nucleotide values are consistent with earlier observations concerning chondrocyte redox and the low pO2 tension of the hypertrophic zone.2+off

ATP and IMP in single human muscle fibres after high intensity exercise

Within a muscle there is large variation in the activity of various enzymes among single fibres. It is reasonable, therefore, to expect a corresponding variation in their metabolic response to exercise. This was examined by obtaining muscle biopsies from five men at rest and after intense short-term exercise consisting of three bouts of 30 knee extensions each and intervened by 60 s rest. Freeze-dried dissected single fibres identified as type 1 or type 2 were analysed for ATP and IMP contents by liquid chromatography. Rest. Average ATP tended to be higher in type 2 than in type 1 fibres. The ATP range was 14-30 and 14-32 mmol X kg-1 dry muscle (dm) in type 1 and 2 fibres, respectively. IMP was less than 1 mmol X kg-1 dm in most fibres and similar in types 1 and 2. Exercise. Muscle force decreased 70% during exercise. The average decrease in ATP content was significant for both fibre types with somewhat larger response for type 2 (20%) than type 1 (10%) fibres. The ATP range was 10-28 and 10-30 mmol X kg-1 dm in type 1 and 2 fibres, respectively. Average IMP content increased substantially in both fibre types, more so for type 2, and the range for individual fibres was 0-13 (type 1) and 0-21 (type 2) mmol X kg-1 dm. Conclusion. After exhaustive short-term exercise, a large variation in ATP and IMP contents was evident among single type 1 and type 2 fibres. None of the fibres, however, showed an ATP content lower than 10 mmol X kg-1 dm.(ABSTRACT TRUNCATED AT 250 WORDS)

A clinically useful ion-pairing high-performance liquid chromatographic assay for the monophosphate metabolites of thioguanine and mercaptopurine in human neoplastic cells

A sensitive and rapid assay for the quantitation of thioinosine monophosphate and thioguanosine monophosphate, the major intracellular active metabolites of mercaptopurine and thioguanine, respectively, has been developed. Neoplastic cells are extracted with trichloracetic acid, and the neutralized acid extracts are analyzed by ion-pairing high-performance liquid chromatography with dual-channel uv-wavelength detection. This technique provides a lower limit of sensitivity of 30 pmol of thioinosine monophosphate and 10 pmol of thioguanosine monophosphate. The number of cells assayed per sample was 2 X 10(7). This assay makes it possible to detect and quantitate low levels of thioinosine monophosphate and thioguanosine monophosphate present in neoplastic cells obtained directly from patients receiving mercaptopurine or thioguanine chemotherapy.

An enzymatic method for inosine 5'-monophosphate in the femtomole range

A method for measuring inosine 5'-monophosphate (IMP) by enzymatic generation of NADPH is described. Procedures are given for direct fluorometric assay in the nanomole range and indirect measurement with amplification by enzymatic cycling in the pico- and femtomole ranges. The most sensitive procedure represents a nearly 50,000-fold increase in sensitivity over enzymatic methods now available. Specificity of the assay was greatly enhanced by the use of the antibiotic coformycin, a potent inhibitor of adenosine deaminase (EC 3.5.4.4). This enzyme was found to be a major contaminant of one of the necessary enzymes, phosphoglucomutase (EC 2.7.5.1). The use of the method is illustrated by measurements of IMP in single stimulated and control rat muscle fibers.

Ion-pair high performance liquid chromatographic determination of inosinic acid in meat

An ion-pair high performance liquid chromatographic (HPLC) technique is described for the determination of inosinic acid (IMP) in meat. The compound was extracted with perchloric acid and analyzed without cleanup. IMP is effectively separated, identified, and quantitated by using a reverse phase column, with ultraviolet detection. A C8 stationary phase and tetrabutyl ammonium as counter ion are used. Recovery of IMP added to meat at 500 or 2500 ppm levels was more than 95%; the limit of detection for IMP is 50 ppm.

Assay of thioinosinic acid, an active metabolite of azathioprine, in human lymphocytes

1 A specific assay for the measurement of thioinosinic acid, in human lymphocytes, has been developed with a sensitivity of 50 ng of thioinosinic acid per 5 x 10(6) lymphocytes. 2 Thioinosinic acid is precipitated from purified lymphocytes as the lanthanum salt. Acid hydrolysis results in the formation of 6-mercaptopurine which, when converted into its phenyl mercury derivative, can be easily extracted into toluene. Back-extraction of the toluene layer with 0.1N HCl regenerates 6-mercaptopurine which is then assayed fluorometrically. 3 Blood samples were taken from renal transplant recipients 3 h after an oral dose of 50 mg azathioprine. The results from 5 patients gave a range of 54 to 173 ng of thioinosinic acid per 5 x 10(6) lymphocytes, with a mean of 110 ng. 4 In an in vitro incubation of azathioprine, 1mM with fresh human blood, 160 and 180 ng of thioinosinic acid per 5 x 10(6) lymphocytes was formed after 0.5 h and 5 h respectively. 5 The assay is suitable for the study of the kinetics of thioinosinic acid formation in lymphocytes of patients with kidney transplants. It could also prove useful in the study of thioinosinic acid formation in leukaemia patients undergoing 6-mercaptopurine treatment.

Structure-independent nucleotide sequence analysis

Substitution of inosine for granosine in the nucleic acid fragments synthesized for the sequencing of RNA effectively prevents the formation of secondary structures during electrophoretic analysis. Consequently, the mobility of each fragment in the sequencing gel is a strict function of its molecular weight. Inosine substitution should markedly improve the resolution that can be obtained in the sequencing of DNA as well as RNA.

[Nucleotide pool of the brains of rats during different stages of dying]

Composition of acid-extractable fraction of nucleotides was studied in brain of dying rats after acute hemorrhage. Within the first 5 min content of ATP, GTP, UTP, GDP, UDP and NAD was distinctly decreased; content of AMP, GMP, IMP, CMP, nucleosides and nitrogen bases was markedly increased. Within the following 30 min of the dying rpocess concentration of CMP and nitrogen bases was increased but content of the other substances studied was decreased as compared with the previous experimental period. Possible effect of the alterations found on reanimation of an organism is discussed.

Conformations of purine ribosyl 5'-nucleotides bound to glycogen phosphorylase b. A proton T2 relaxation time investigation

The conformation of 5'-nucleotides in the active site of glycogen phosphorylase b has been deduced from linewidth measurements of protons H-1', H-8 and H-2. It is shown by selective deuteration of the purine ring in position 8 that the orientation of the base is anti in the case of strong activators like AMP and syn in that of weak activators like IMP. The orientation correlation time of the nucleotides in the active site is nearly that of the enzyme, i.e. 160 ns at 21 degrees C.

Isocratic separation of some purine nucleotide, nucleoside, and base metabolites from biological extracts by high-performance liquid chromatography

Separation of ATP, ADP, AMP, adenine, adenosine, cAMP, ITP, IDP, IMP, hypoxanthine, inosine, cIMP, the guanine series, NAD, NADPH, xanthine, 3-methylxanthine, theobromine, theophylline, and caffeine was accomplished using high-performance liquid chromatography with a microparticulate reversed-phase column. Under isocratic conditions all compounds could be eluted with reasonable resolution and retention time. Quantitation by peak height for several of the compounds was used to the 10-ng level.

Effects of antimycin and 2-deoxyglucose on adenine nucleotides in human platelets. Role of metabolic adenosine triphosphate in primary aggregation, secondary aggregation and shape change of platetets

1. Human platelet-rich plasma prelabelled with [(3)H]adenine was incubated at 37 degrees C with antimycin A and 2-deoxy-d-glucose. Variations in the amounts of ATP, ADP and P(i), and in the radioactivity of ATP, ADP, AMP, IMP, hypoxanthine+inosine and adenine were determined during incubation. Adrenaline- and ADP-induced platelet aggregation and the ADP-induced shape change of the platelets were determined concurrently. 2. 2-Deoxyglucose caused conversion of [(3)H]ATP to [(3)H]hypoxanthine+inosine. The rate of this conversion increased with increasing 2-deoxyglucose concentration and was markedly stimulated by addition of antimycin, which had no effect alone. At maximal ATP-hypoxanthine conversion rates, the IMP radioactivity remained at values tenfold higher than control, whereas [(3)H]ADP and [(3)H]AMP radioactivity gave variations typical for product/substrates in consecutive reactions. The specific radioactivityof ethanol-soluble platelet ATP decreased during incubation to less than one-tenth of its original value. The amounts and radioactivity of ethanol-insoluble ADP did not vary during incubation with the metabolic inhibitors. 3. The rate of ADP- and adrenaline-induced primary aggregation decreased as the amount of radioactive ATP declined, and complete inhibition of aggregation was obtained at a certain ATP concentration (metabolic ATP threshold). This threshold decreased with increasing concentration of inducer ADP. 4. Secondary platelet aggregation (release reaction) had a metabolic ATP threshold markedly higher than that of primary aggregation. 5. Shape change was gradually inhibited as the ATP radioactivity decreased, and had a metabolic ATP threshold distinctly lower than that of primary aggregation, and which decreased with increasing concentration of ADP. 6. A small but distinct fraction of [(3)H]ATP disappeared rapidly during the combined shape change-aggregation process induced by ADP in platelets incubated with metabolic inhibitors, whereas no ATP disappearance occurred during aggregation in their absence.

Equilibrium of nucleotides in frog sartorius muscle during an isometric tetanus at 20 degrees C

1. The concentrations of creatine, phosphorylcreatine (PC), ATP, ADP, AMP and IMP have been measured in frog sartorius muscles at 20 degrees C during isometric tetani lasting from 0.5 to 12 sec. Each muscle was tetanized once only for the chosen duration. The muscles were poisoned with iodoacetic acid and nitrogen to prevent oxidative and glycolytic activity.2. The rate of PC splitting decreased exponentially with the duration of the tetanus (alpha = 0.16 sec(-1)). Net ATP splitting began after 2 sec, accompanied by an increase in AMP and ADP; inosine monophosphate (IMP) also appeared both earlier and faster than adenosine monophosphate (AMP).3. On the basis of two equilibrium reactions, the Lohmann and myokinase reactions, the concentration of adenosine nucleotides should be a function of the ratio creatine/phosphorylcreatine.4. The agreement between nucleotide concentrations predicted by this equilibrium hypothesis and those observed experimentally was good provided it was assumed that 90% of the acid-labile ADP found in resting muscle was bound in vivo and remained so throughout the tetanus. The validity of this assumption is discussed.5. The IMP concentration was an exponential function of the ratio creatine/phosphorylcreatine.

Relative importance of liver and kidney in synthesis of uric acid in chickens

Broiler chickens of 1, 2, and 7 months of age were used for enzymatic spectrophotometric determination of uric acid and its precursors, xanthine, hypoxanthine, and inosinic acid, in the liver and kidney in an attempt to show the relative importance of the two organs in the synthesis of uric acid, the major nitrogenous compound excreted by birds.Uric acid concentration of the kidney was two to three times as high as the liver, probably attributable in part to preformed uric acid trapped in the urinary passages in the kidney. Significantly higher concentrations of xanthine, hypoxanthine, and inosinic acid were found in the kidney than in the liver. The calculations based on organ weight and the concentrations of uric acid precursors suggest that the kidney synthesizes 96, 60, and 73% as much uric acid as does the liver for the 1-, 2-, and 7-month-old chickens, respectively.