New alternatives for improving and assessing the color of dark­cutting beef ­ a review

Myoglobin (Mb) is a sarcoplasmic heme protein present in muscle cells, which acts as a short­term oxygen (O2) reserve in the muscle tissue. After slaughtering and exsanguination, Mb is the major pigment that provides the red color in meat. The concentration of Mb together with its redox state are two pivotal factors that determine meat color. The elevated pH of dark­cutting beef can affect both physical and biochemical properties resulting in decreased oxygenation. The darkening observed in high ultimate pH (pHu) beef concerns meat processors as color is the initial attribute that impacts on the purchase. Thus, any atypical meat color (i.e., loss of brightness) reduces consumer interest in the product. Several studies have demonstrated that immunological castration is effective in preventing both aggressive behavior and undesirable dark­cutting of bull meat. However, little information is available on the effects of processing techniques that limit the oxidation of ferrous iron (Fe2+), Mb or promote metmyoglobin (MMb) reduction in dark­cutting beef. Because of the importance of color to fresh beef marketability, this review aimed at overviewing the significance of pHu in beef color and color stability and to discuss new alternatives for improving and assessing the beef color of dark­cutting beef, especially in Nellore bulls and their crossbreds, which are widely used in beef cattle production in Brazil.(AU)

Combined effects of gamma irradiation and aging on tenderness and quality of beef from Nellore cattle.

Combined effects of gamma irradiation (0, 3, 6 and 9 kGy) and aging (1 and 14 days) on quality attributes of vacuum-packaged beef from Nellore cattle were evaluated. The meat water holding capacity was affected by irradiation, increasing (p < 0.05) purge and cooking loss regardless of the dose used. Irradiation negatively affected myofibrillar fragmentation, but samples irradiated at 9 kGy had (p < 0.05) higher soluble collagen and lower shear force values. The meat metmyoglobin reducing activity was reduced (p < 0.05) by the irradiation process, inducing the metmyoglobin accumulation with increasing dose applied. Samples irradiated at 9 kGy presented (p < 0.05) higher lipid oxidation and lower oxymyoglobin proportion and color redness and chroma values. It was concluded that irradiation at 9 kGy combined with aging can be used as an effective tool for improving the tenderness of Nellore beef, but resulted in a discoloration of the beef.

Color attributes and oxidative stability of longissimus lumborum and psoas major muscles from Nellore bulls.

The influence of muscle source on color stability of fresh beef from purebred Bos indicus cattle was investigated. Longissimus lumborum (LL) and psoas major (PM) muscles obtained from twelve (n=12) Nellore bull carcasses (24h post-mortem) were fabricated into 2.54-cm steaks, aerobically packaged, and stored at 4°C for nine days. Steaks were analyzed on day 0 for proximate composition and myoglobin concentration, whereas pH, instrumental color, metmyoglobin reducing activity (MRA), lipid oxidation, and protein oxidation were evaluated on days 0, 3, 6, and 9. LL steaks exhibited greater (P<0.05) redness, color stability, and MRA than PM counterparts. On the other hand, PM steaks demonstrated greater (P<0.05) myoglobin content, lipid oxidation, and protein oxidation than LL steaks. These results indicated the critical influence of muscle source on discoloration of fresh beef from Bos indicus animals and suggested the necessity to engineer muscle-specific strategies to improve color stability and marketability of beef from Bos indicus cattle.

Mechanisms of bee venom-induced acute renal failure.

The spread of Africanized bees in the American continent has increased the number of severe envenomation after swarm attacks. Acute renal failure (ARF) is one of the major hazards in surviving patients. To assess the mechanisms of bee venom-induced ARF, rats were evaluated before, up to 70 min and 24h after 0.5mg/kg of venom injection. Control rats received saline. Bee venom caused an early and significant reduction in glomerular filtration rate (GFR, inulin clearance, 0.84+/-0.05 to 0.40+/-0.08 ml/min/100g, p<0.0001) and renal blood flow (RBF, laser Doppler flowmetry), which was more severe in the cortical (-72%) than in the medullary area (-48%), without systemic blood pressure decrease. Creatine phosphokinase, lactic dehydrogenase (LDH) and serum glutamic oxaloacetic transaminase increased significantly, pointing to rhabdomyolysis, whereas serum glutamic pyruvic transaminase and hematocrit remained stable. Twenty-four hours after venom, RBF recovered but GFR remained significantly impaired. Renal histology showed acute tubular injury and a massive tubular deposition of myoglobin. Venom was added to isolated rat proximal tubules (PT) suspension subjected to normoxia and hypoxia/reoxygenation (H/R) for direct nephrotoxicity evaluation. After 60 min of incubation, 0.1, 2 and 10 microg of venom induced significant increases in LDH release: 47%, 64% and 86%, respectively, vs. 21% in control PT while 2 microg of venom enhanced H/R injury (85% vs. 55%, p<0.01). These results indicate that vasoconstriction, direct nephrotoxicity and rhabdomyolysis are important mechanisms in the installation of bee venom-induced ARF that may occur even without hemolysis or hypotension.

Poder pronóstico precoz de la mioglobina en los síndromes coronarios agudos sin elevación del segmento ST / Prognostic value of myoglobin in non-ST elevation acute coronary syndromes

Antecedentes: La mioglobina es un marcador precoz de necrosis miocárdica. Sin embargo, su valor pronóstico aún no se ha aclarado en forma prospectiva en las primeras horas de evolución de pacientes con síndromes coronarios agudos (SCA) sin supradesnivel del segmento ST. Objetivos: Determinar la relación entre los valores de mioglobina al ingreso y la ocurrencia de muerte o infarto a los 30 días en pacientes con SCA sin supradesnivel del ST. Material y métodos: Se realizó un estudio de cohortes prospectivo y multicéntrico que incluyó 366 pacientes para evaluar el valor pronóstico de la mioglobina en el momento de la admisión. Se determinó también la concentración de troponina T, la proteína C reactiva (PCR) y la CK-MB masa a las 12 horas del comienzo de los síntomas. Las determinaciones fueron realizadas a doble ciego por un laboratorio central e independiente. El punto final primario fue muerte y/o reinfarto no fatal a los 30 días. Se realizó un análisis multivariado para determinar la asociación entre los niveles de mioglobina y el punto final clínico. Resultados: La mediana de tiempo síntomas-admisión fue de 4 horas. La tasa de eventos a los 30 días fue del 10,1 por ciento. De acuerdo con la regresión logística, se observó una asociación entre los niveles elevados de mioglobina al ingreso y los eventos clínicos (OR 3,5 [IC 95 por ciento 1,6-7,6]), independiente de marcadores clínicos y bioquímicos convencionales. Conclusiones: La elevación precoz de la mioglobina agrega información pronóstica independiente a marcadores clínicos y bioquímicos convencionales y además se asocia con mala evolución clínica a los 30 días en pacientes con SCA sin supradesnivel del ST.

Rhabdomyolysis, acute renal failure, and death after monensin ingestion.

We report a case of human monensin intoxication; to our knowledge, this is the first reported case in the medical literature. The patient took a dose of monensin three times higher than a dose considered lethal for cattle and developed a clinical picture similar to that reported in veterinary medicine. There was an early and extremely severe rhabdomyolysis followed by acute renal failure, heart failure, and death. The main changes observed at autopsy were extensive skeletal muscle necrosis, complement deposition at the myocardial level, pulmonary edema, and acute tubular damage.

Valor diagnóstico da CK-MB assa, à mioglobina e à troponina I nas síndromes isquêmicas agudas / Diagnostic Value of CK-MB Activity Compared to Mecglobin, CK-MB Mass, Traponin 1 in Acute Coronary Syndrome

A síndrome isquêmica aguda varia de angina instável a infarto agudo do miocárdio, e seu manuseio atual requer rapidez e eficácia. O diagnóstico do infarto agudo do miocárdio foi estabelecido pela Organização Mundial da Saúde, e a CK-MB atividade foi considerada a enzima padrão. O objetivo deste estudo foi comparar o valor diagnóstico e o desempenho da CK-MB atividade à CK-MB massa, à troponina I e à mioglobina em portadores de dor precordial prolongada, atendidos no pronto-socorro. A casuística incluiu 217 pacientes, com dor precordial de duração igual ou superior a 20 minutos, distribuídos em três grupos: grupo I, 29 pacientes com infarto agudo do miocárdio, diagnosticado por supradesnivelamento do segmento ST e dor; grupo II, 24 pacientes com infarto agudo do miocárdio, diagnosticado por elevação da CK-MB atividade e dor, e grupo III, 164 pacientes, com dor, sem alteração da CK-MB atividade e do eletrocardiograma compatível com infarto agudo. As dosagens dos marcadores bioquímicos foram realizadas na ocasião da inclusão do paciente no estudo, duas, quatro, seis, oito, dez, 12 e 24 horas após, e as análises foram realizadas em relação à hora do início da dor. As características demográficas dos grupos foram semelhantes, exceto o tabagismo, que foi menor no grupo III. Quanto às alterações eletrocardiográficas, todos os pacientes com eletrocardiograma normal situaram-se no grupo III, e os níveis dos marcadores bioquímicos foram mais elevados nos pacientes com alterações eletrocardiográficas compatíveis com isquemia aguda. A sensibilidade e a especificidade da CK-MB massa (5,6 ng/ml), da cTnI (1,5 ng/ml), da CK-MB massa (9,4 ng/ml) e da mioglobina (110 ng/ml), em relação à CK-MB atividade, foram 98% e 78,6%, 98% e 74,4%, 98% e 84,5%, 85,7% e 85,1% respectivamente. O valor preditivo positivo variou de 52,7% a 64,8% e o valor preditivo negativo variou de 95,3% a 99,3%. A CK-MB atividade não se elevou em níveis compatíveis com IAM em 13,8% dos pacientes do grupo I, tendo ocorrido um resultado falso positivo no grupo II...

[The utility of rapid qualitative determination of troponin T, the MB fraction of creatine phosphokinase and myoglobin in acute ischemic coronary syndromes]. / Utilidad de la determinación cualitativa rápida de troponina-T, fracción MB de creatina fosfocinasa y mioglobina en los síndromes isquémicos coronarios agudos.

The objective of our study was to validate the diagnostic utility of cardiac troponine T in acute ischemic syndromes, and also in cases of difficult diagnosis. We analyzed its concordance and compare them with conventional enzymatic quantitative methods. We determined sensitivity, specificity, positive and negative predictive values and likelihood ratio. Kappa index was used to know the concordance grade between T troponin and the positive or negative results of the quantitative enzymatic curve. Stochastic significance was valued by Chi square of Mcnemar test. In seventy patients who arrived to the hospital with chest pain who were assigned to five different groups. The sensitivity in quantitative markers was higher than qualitative methods, however the specificity, likelihood ratio was lower. In the total group the concordance analysis between qualitative and quantitative markers was adequate, (kappa index 0.65 p < 0.05). This study suggest that the rapid bedside qualitative test by cardiac Troponin T is a good diagnostic marker compared with conventional quantitative markers to evaluate chest pain in acute ischemic syndromes.

Hypertonic-hyperosmotic solution modifies myoglobin levels in early reperfusion after ischemic cardiac arrest. Experimental model

To evaluate the effect of reperfusison with hypertonic-hyperosmotic solution, cardiectomy was performed in 25 New Zealand white rabbits. Seven isolated hearts were submitted to 30 min of global ischemia and reperfused with oxygenated uffer for 60 min. Myoglobin and isoensyme MB of creatine kinase concnetrations were each measured in the effluent 15 min, and values were correlated (r=0.5011, p=0.015). After this procedure, 18 isolated hearts were radomized in two groups. Hearts of group I were reperfused with hypertonic-hyperosmotic solution (NaCl 7.5 percent dextran 60,000 MW) diluted in oxygenated buffer, and group II with oxygenated buffer. Myoglobin and coronary flow were measured in both groups, group I showed lower levels of myoglobin (p=0.0069) and higher coronary flow (p = 0.028) than group II. In conclusion, changes in myoglobin concentration in the heart effluent are more sensitive than changes in isoenxyme MB of creatine kinase; thus, evaluation of this parameter may be useful in the detection of ishcemia reperfusion injury. Additionally, hypertonic-hyperosmotic solution improves the coronary flow and has a protective effect against ichemia-reperfusion injury

Determinación de la mioglobina por radioinmunoenzayo en pacientes con coronariografía / Myoblobin determination by radioimmunoassay in patients with coronarography

Se estudiaron 15 pacientes adultos en forma consecutiva, ingresados en el Instituto de Cardiológia Cardiovascular con el diagnóstico de cardiopatía isquémica , entre los meses de septiembre y noviembre de 1988 para ventricolografía y coronorariografía selectiva bilateral, con el objetivo de determinar si se presentaban variaciones en los niveles de la mioglobina en los pacientes a los cuales se les realizó coronariografía. A todos se les cuantificó la mioglobina por radioinmunoensayo 1 hora antes, al finalizar y 4 horas después de haber concluido la coronariografía y el valor promedio para cada tiempo fue de 34, 40 y 42ng/ml, respectivamente. En nuestra investigación los valores obtenidos de la mioglobina oscilaron dentro del rango normal(8 a 80 ng x mL). No se presentaron complicaciones en el estudio. No se encontró diferencias estadísticamente significativas entre los diferentes horarios(p> 0,05).

The complete amino acid sequence of the major component myoglobin of Amazon river dolphin (Inia geoffrensis).

The complete amino acid sequence of the major component myoglobin from Amazon River dolphin, Inia geoffrensis, was determined by specific cleavage of the protein to obtain large peptides which are readily degraded by the automatic sequencer. Three easily separable peptides were obtained by cleaving the protein with cyanogen bromide at the methionine residues and four peptides were obtained by cleaving the methyl-acetimidated protein with trypsin at the arginine residues. From these peptides over 85% of the sequence was completed. The remainder of the sequence was obtained by fragmentation of the large cyanogen bromide peptide with trypsin. This protein differs from that of the common porpoise, Phocoena phocoena, at seven positions, from that of the common dolphin, Delphinus delphis, at 11 positions, and from that of the sperm whale, Physeter catodon, at 15 positions. By comparison of this sequence with the three-dimensional structure of sperm whale myoglobin it appears that those residues close to the heme group are most conserved followed by those in nonhelical regions and lastly by those in the helical segments. All of the substitutions observed in this sequence fit easily into the three-dimensional structure of the sperm whale myoglobin.