Influence of the three RN genotypes on chemical composition, enzyme activities, and myofiber characteristics of porcine skeletal muscle

An experiment was conducted to evaluate the effects of the RN genotype on skeletal muscle characteristics in pigs sharing otherwise the same polygenic background. Animals were genotyped for RN on the basis of RTN (Rendement Technologique Napole) records using segregation analysis methods. Samples of longissimus (L) and semispinalis capitis (S) muscles were taken from 39 rn+/rn+, 38 RN-/rn+ and 37 RN-/RN- pigs slaughtered at 108 +/- 8.6 kg live weight. Activities of lactate dehydrogenase (LDH), citrate synthase (CS), and beta-hydroxy-acyl-coenzyme A dehydrogenase (HAD) were measured on both muscles to assess glycolytic, oxidative, and lipid beta-oxidation capacities, respectively. Histological examinations and chemical analyses were performed on L muscle. The energetic metabolism of the white L muscle was more oxidative in RN-/RN- than in rn+/rn+ pigs, as shown by increased CS and HAD activities (P < .001), decreased LDH activity (P < .001), larger cross-sectional area of IIA (P < .05) and IIB-red (P < .05) fibers, higher relative area of IIA fibers ( P < .05), and lower relative area of IIB-white fibers (P < .001). No significant difference was found between heterozygous and homozygous carriers of the RN- allele, except for CS activity, which was lower in RN-/rn+ than in RN-/RN- pigs. In L muscle, the RN- allele led to a large increase in glycolytic potential (+3.5 phenotypic SD between homozygotes) and lightness (+.7 SD), and a decrease in ultimate pH, dry matter, and protein contents (-1.7 to -2 phenotypic SD for these three traits), with an almost completely dominant effect. No differences were found between genotypes for intramuscular fat and hydroxyproline contents. In the red S muscle, the presence of RN- had no influence on enzyme activities. These results indicate that the RN genotype greatly influences compositional and histochemical traits and metabolic enzyme activities in a muscle type-dependent manner, with a completely or incompletely dominant effect of the RN- allele.

Effects of the halothane genotype and slaughter weight on texture of pork

The objective of this study was to investigate the effects of the halothane (HAL) genotype, slaughter weight (SW), and the HAL x SW interaction on compositional and textural traits of raw and cooked pork. Pigs were bred to exhibit one of the three HAL genotypes (NN, Nn, and nn) with otherwise equivalent genomes. The nn halothane reactors are known to typically produce PSE pork, whereas NN pigs do not typically produce PSE pork. Pietrain x Large White gilts and boars, all with verified Nn genotype (by DNA test), were mated to obtain F2 littermates of the three HAL genotypes. These pigs were slaughtered at either 101 +/- 3 ("light") or 127 +/- 3 ("heavy") kg BW and were evaluated for longissimus muscle traits. The pH at .5 h after death (pH1) was 6.35, 6.13, and 5.68 in NN, Nn, and nn pigs, respectively. Sarcomere length was greater in nn than in NN and Nn pigs (1.94 vs 1.83 and 1.85 microm, respectively). Mechanical resistance was higher in nn than in NN pigs for both raw and cooked meat. Meat from nn pigs was judged by a trained panel to be less rough, more cohesive, harder, more fibrous, less granular, more elastic, and less easy to swallow than meat from NN pigs. For most traits under study, the heterozygotes were intermediate between the homozygotes but closer to NN than to nn pigs. Muscle from heavy pigs had longer sarcomeres and less moisture than muscle from light pigs. The n allele of the HAL gene unfavorably affects pork texture, and this effect is maintained throughout the range of 101 to 127 kg BW.

Phenotypic and genetic parameters for longissimus muscle fiber characteristics in relation to growth, carcass, and meat quality traits in large white pigs

A total of 383 barrows and gilts from a French Large White experimental herd were slaughtered at 100 kg BW. Samples of longissimus muscle were taken to categorize myofibers according to their contractile (I, IIA, and IIB) and metabolic (oxidative and nonoxidative) properties. Myofiber percentages, cross-sectional areas (CSA), and relative areas were measured. Growth rate, carcass composition, muscle chemical composition, metabolic enzyme activities, and meat quality traits were also measured to estimate phenotypic and genetic correlations between these traits and myofiber characteristics. Genetic parameters were estimated using a REML procedure applied to an individual animal model. Heritabilities of fiber traits were moderate to high (h2 = .20 to .59). Highest heritabilities were found for type I fiber percentage (h2 = .46 +/- .11), type IIBw fiber percentage (h2 = .58 +/- .11), and type I fiber cross-sectional area (h2 = .59 +/- .10). For a given fiber type, the relative area was phenotypically and genetically more closely related to the percentage than to the CSA. Phenotypic correlations between fiber type composition and other traits were low. Genetically, growth rate, carcass leanness, and loin eye area were positively related to fiber CSA. Intramuscular fat content was not related to fiber type composition (r(g) = -.05 to .06), whereas it was positively related to fiber CSA (r(g) = .68). Type IIBw fiber percentage was related to pH at 30 min (r(g) = -.46), pH at 24 h (r(g) = -.62), glycolytic potential (r(g) = .31), and lightness of color (r(g) = .55) of longissimus muscle.

[Comparison of anti-ischemic effect of bepridil and diltiazem evaluated by exercise test in patients with coronary disease. A multicenter study. Groupe d'Investigateurs]

Bepridil (Cordium) is a calcium channel blocker which has been demonstrated to be effective in the preventive treatment of angina. Few controlled trials have compared bepridil to diltiazem (Tildiem), the reference calcium channel blocker. The objective of this study was to evaluate the efficacy and safety of bepridil in stable coronary patients. 148 patients (139 M, 9 F, mean age: 58 +/- 8.6 years), with documented coronary artery disease and positive stress test after 5 days of placebo were included. After double-blind randomization, they received bepridil (300 mg/day ion 3 doses), or diltiazem (180 mg+/day in 3 doses) for 15 days. A stress test was then performed under the same conditions as on inclusion. The anti-ischaemic efficacy of the two drugs was comparable. Total work increased from 4,552.4 +/- 2,179.4 Kpm a 6,103.2 +/- 2,849.2 Kpm with bepridil (p < or = 0.0001) and from 4,524.8 +/- 2,160.5 Kpm a 5,848.3 +/- 2,800.3 Kpm (p < or = 0.0001) with diltiazem, with no intergroup difference. Duration of effort was significantly prolonged: from 10.5 +/- 3.0 min to 12.5 +/- 3.3 min with bepridil (p < or = 0.0001) and from 10.5 +/- 2.9 min to 12.1 +/- 3.4 min with diltiazem (p < or = 0.0001), with no intergroup difference. The time to onset of 1 min of ST depression increased significantly between the two stress tests, from 8.36 +/- 2.7 min to 10.82 +/- 3.4 min with bepridil (p < or = 0.001) and from 8.02 +/- 3.0 min to 10.53 +/- 3.6 min with diltiazem (p < or = 0.001), with no significant difference between the two groups. The clinical safety of the two products was comparable. On the electrocardiogram, the QT interval was significantly prolonged with bepridil, from 368.6 +/- 37.5 msec to 393.6 +/- 38.7 msec (p < or = 0.0001), reflecting cellular impregnation of the drug.

Angina pectoris in patients with a history of myocardial infarction

The existence of a history of myocardial infarction (MI) in patients with angina pectoris is frequently associated with certain patient characteristics, including an established history of coronary artery disease (CAD), depressed left ventricular function in some patients and multivessel coronary disease. Angina is a symptom which reveals the persistence or recurrence of myocardial ischaemia. It is uncertain whether persistent myocardial ischaemia after MI is an adverse prognostic factor. In fact, the most important known prognostic factor is left ventricular function. Before choosing an anti-anginal therapy in patients with a history of MI, coronary angiography should be performed in order to investigate the possibility of left main or multivessel CAD. Angina patients with impaired left ventricular function may benefit from revascularization but the prognostic value of percutaneous transluminal coronary angioplasty in these patients remains to be assessed. Medical anti-anginal therapy for symptoms, added to routine background treatment, is indicated when the results of revascularization are unsatisfactory or if there is an absence of indication, or a contra-indication, for revascularization procedures. Particular attention should be paid to the possible additive negative inotropic or chronotropic effects of beta-blockers and certain calcium antagonists on the myocardium.

Permutation distribution estimation applied to the comparison of the profile of the activity of two antianginal drugs

The comparison of the anti-ischemic activity of trimetazidine and propranolol was evaluated by multiple end points (clinical, exercise test, and ambulatory electrocardiogram [ECG] monitoring criteria) in 149 male patients with effort angina who received either trimetazidine 20 mg tid or propranolol 40 mg tid during a period of 3 months. The distribution of the standardized differences between the two treatments for each variable was obtained by a permutation method. The medians (estimation of the actual difference between the two treatments) and the 5, 25, 75 and 95% quantiles were represented on the same diagram for all end points. The pattern of the standardized distribution of the differences showed a similar activity of both drugs on symptoms and nitrates consumption, on exercise tolerance and increase in ischemic threshold at exercise, and on ischemia recorded at ambulatory ECG monitoring. Conversely, only propranolol decreased heart rate and rate pressure product at rest as well as at exercise, underlining the difference in the mode of action of the two drugs. This descriptive technique is an attractive method to evaluate the differences between drugs considering multiple criteria favouring the estimation of these differences together with their variability.

[Return to work following myocardial infarction. Medical and socio-professional factors]

The aim of this study was to assess the influence of medical and socioprofessional factors on return to work after myocardial infarction. The authors studied a continuous series of 174 patients with an average age of 51.3 years, all of whom were active before their illness. The average follow-up period was 33 months. One hundred and thirty of the patients (75%) returned to work. The only clinical factors predictive of not returning to work were older age short exercise time and fall in blood pressure on exercise. On the other hand, nearly all socioprofessional factors, social class, type of occupation, size of company, length of employment in their company, physical stresses related to their occupation, were related to return to work. The average time before returning to work was 5.5 +/- 1 month. Though certain immediate criteria of severity of infarction such as previous myocardial infarction or anterior wall infarction were related to a more delayed return to work. The cardiac status evaluated by complementary investigations (left ventricular ejection fraction, exercise testing and Holter monitoring) was not related to the time before return to work. Of the socioprofessional factors, only difficulties related to the patients' work (modification or change of job) were associated with a more delayed return to work. Forty-four patients (33.8%) returned to work after a change in working hours (28 patients), the tasks involved (20 patients) or position (7 patients). Only the lower socioprofessional classes, independent workers and extremes of age could benefit from these measures.

Accurate mapping of the "acid meat" RN gene on genetic and physical maps of pig chromosome 15

It has been shown that a major gene, called RN, is responsible for the RTN technological yield, a meat quality porcine trait. Experimental families informative for the segregation of RN gene were constituted from animals belonging to the Laconie composite line. We have previously mapped the RN gene to Chromosome (Chr) 15 (Milan et al. Genet. Sel. Evol. 27, 195-199, 1995). A Chr 15 map was established with 16 markers. The RN gene was found to be located between markers Sw120 and Sw936, at 2 cM from Sw936 (LOD = 38.1). In addition, by localizing Sw936 at 15q21-22 using DISC-PCR, we also located RN on the physical map.

Physical activity in the cardiac patient

It is well established that a sedentary lifestyle is a risk factor for coronary heart disease. Regular physical activity has a proven beneficial effect in the general population, reducing, in particular, the risk of myocardial infarction. In patients who have had a myocardial infarction, long-term physical exercise at a sufficiently intense level has a beneficial effect on morbidity and mortality. Although there is no statistical proof, it appears that this effect is accompanied by a slight increase in the risk for nonfatal myocardial infarction. The effects of physical activity on other heart diseases are not well known. The mechanisms by which physical exercise exerts its protective effect are not yet well established. Among the proposed hypotheses are the effect on peripheral muscle of physical training, the reduction of myocardial ischemia, and modifications of the adrenergic response to effort and stress. Moreover, physical training has a favorable effect on certain risk factors for coronary heart disease (e.g., lipids profile, arterial hypertension, smoking). The risks involved with physical training in cardiac patients can be evaluated from the data collected from rehabilitation programs. These risks are very slight, provided that the patients are carefully selected.

Amlodipine reduces transient myocardial ischemia in patients with coronary artery disease: double-blind Circadian Anti-Ischemia Program in Europe (CAPE Trial)

OBJECTIVES

This study was carried out to determine the effect of the once-daily calcium channel blocking agent amlodipine (half-life 35 to 50 h) on the circadian pattern of myocardial ischemia in patients with chronic stable angina.

BACKGROUND

Myocardial ischemia during normal daily life, both symptomatic and asymptomatic, has been associated with increased risk of cardiovascular morbidity and mortality, and the circadian pattern parallels that for myocardial infarction and sudden death.

METHODS

The Circadian Anti-Ischemia Program in Europe (CAPE) was a large, 10-week international (63 sites), double-blind, parallel study. After a 2-week, single-blind placebo phase, during which stable doses of antianginal treatment were maintained (beta-adrenergic blocking agents in 65% of patients), patients with chronic stable angina with at least three attacks of angina per week, with at least four ischemic episodes or > or = 20 min of ST segment depression in 48 h of Holter monitoring, were randomized to receive treatment with either 5 mg/day of amlodipine or placebo (2:1 randomization). The dose was increased to 10 mg/day after 4 weeks. During week 7 of treatment, 48-h ambulatory ECG monitoring was repeated.

RESULTS

Three hundred fifteen of 1,160 patients screened were eligible, and 250 had complete evaluable data. Compared with placebo, amlodipine significantly reduced both the frequency of ST segment depression episodes (60% for amlodipine vs. 44% for placebo, p = 0.025) and total integrated ST ischemic area (62% mm-min vs. 50% mm-min, p = 0.042). Amlodipine reduced ischemia over the 24 h with the intrinsic circadian pattern maintained. In addition, diary data showed a significant reduction in angina (70% for amlodipine vs. 44% for placebo, p = 0.0001) and in nitroglycerin consumption (67% vs. 22%, respectively, p = 0.0006). Amlodipine and placebo demonstrated similar safety profiles (adverse events 17.3% for amlodipine and 13.3% for placebo; discontinuation rates due to adverse events were 2% vs. 4.4%, respectively).

CONCLUSIONS

Once-daily amlodipine, when added to background treatment, significantly reduced both symptomatic and asymptomatic ischemic events over 24 h in patients with chronic stable angina.

Lack of effects of trimetazidine on systemic hemodynamics in patients with coronary artery disease: a placebo-controlled study

Trimetazidine has been shown to improve anginal symptoms and exercise tolerance in patients with coronary artery disease (CAD). To determine the hemodynamic effects of trimetazidine, systemic hemodynamics were studied in 15 patients suffering from CAD (12 male, 3 female, mean age +/- SEM = 58.6 +/- 1.8 years). Cardiac index was determined by thermodilution method. Left ventricular and aortic pressures were measured using micromanometers (Miller Instruments). After basal measurements, patients were randomly given either placebo (n = 5) or one of two therapeutic doses of trimetazidine 1 mg.kg-1 (n = 5) or trimetazidine 1.5 mg.kg-1 (n = 5) in a double-blind procedure. Data were recorded 5, 10 and 20 min after intravenous drug bolus. Throughout the procedure, the evolution of systemic hemodynamic parameters was not statistically different between the three groups, in particular heart rate, cardiac index, systolic, diastolic and mean aortic pressures, end-diastolic ventricular pressure, mean capillary wedge pressure, pulmonary artery pressures or systemic vascular resistances. We conclude that, unlike other antianginal drugs (particularly beta-blockers, nitrates and calcium-channel inhibitors), trimetazidine does not modify systemic hemodynamics in patients with CAD. These results are consistent with a direct effect of trimetazidine on the ischemic myocardial cell previously reported.

Trimetazidine: a new concept in the treatment of angina. Comparison with propranolol in patients with stable angina. Trimetazidine European Multicenter Study Group

1. Trimetazidine has a direct anti-ischaemic effect on the myocardium without altering the rate x pressure product or coronary blood flow. 2. The effects of trimetazidine (20 mg three times daily) were compared with those of propranolol (40 mg three times daily) in a double-blind parallel group multicentre study in 149 men with stable angina. 3. Reproducibility of exercise performance was verified during a 3 week run-in placebo washout period. All patients had > 1 mm ST-depression on exercise test. 4. After 3 months, similar anti-anginal efficacy was observed between the trimetazidine (n = 71) and propranolol (n = 78) groups. No significant differences were observed between trimetazidine and propranolol as regards anginal attack rate per week (mean difference P-TMZ: 2; 95% CI: -4.4, 0.5) and exercise duration (mean difference P-TMZ: 0 s; 95% CI: -33, 34) or time to 1 mm ST segment depression (mean difference P-TMZ: 13 s; 95% CI: -24, 51). Heart rate and rate x pressure product at rest and at peak exercise remained unchanged in the trimetazidine group but significantly decreased with propranolol (P < 0.001 in all cases). With both drugs there was a trend to decreased ischaemic episodes in the 46% patients who experienced ambulatory ischaemia on Holter monitoring. Six patients stopped trimetazidine and 12 propranolol. Of these, five in each group were withdrawn because of deterioration in cardiovascular status. 5. The results suggest that trimetazidine and propranolol at the doses studied have similar efficacy in patients with stable angina pectoris.(ABSTRACT TRUNCATED AT 250 WORDS)

[Detection and prognostic value of silent myocardial ischemia]

Silent myocardial ischaemia (SMI) is a common manifestation of coronary artery disease. Continuous electrocardiographic recordings have shown that 75% of ischemic episodes are asymptomatic. In addition, SMI has the same consequences as symptomatic ischaemia on myocardial perfusion and ventricular function. There are many means of detecting SMI, continuous electrocardiographic monitoring, exercise stress testing with or without methods of analysis of myocardial perfusion or wall motion using radioactive tracers or echocardiography. The latter techniques seem to improve the sensitivity of exercise stress testing. More recently, pharmacological stress testing coupled with myocardial scintigraphy or echocardiography has been introduced. In coronary patients, the prevalence of SMI on Holter monitoring is about 50% in angina and 25% after myocardial infarction. The prognostic value of SMI has been the object of much research. In asymptomatic patients with documented coronary artery disease, SMI is associated with a relative risk of a cardiac event 2 to 3 times greater than that of subjects without ischaemia. In angina pectoris, the relative risk of future cardiac events is 5.3 times greater, and that of death is 2.3 times greater. These results reported with the Holter method have been confirmed by those of exercise stress testing with and without coupled imaging techniques. In unstable angina, the results are the same: the relative risk of cardiac events in patients with SMI on Holter monitoring is increased by a factor of 4.5, and that of death by a factor of 4. This increased risk is also observed after myocardial infarction whether SMI is recorded by Holter monitoring or exercise stress testing. However, these observations are not confirmed in all reports.(ABSTRACT TRUNCATED AT 250 WORDS)

[Tuberculosis in human immunodeficiency virus infection. 22 cases]

A retrospective study of 22 bacteriologically documented cases of tuberculosis associated with HIV1 positivity was carried out in the department of infectious diseases of Marseille, south of France, a high prevalence area for HIV infection. Sixty-seven percent of the patients were intravenous drug abusers. Thirty-two percent were classified as having AIDS prior to the diagnosis of tuberculosis. All but one had M. tuberculosis isolated from bronchopulmonary samples; 5 had no parenchymatous radiological abnormalities, 5 had excavated lesions. Four patients had cervical adenopathies, 4 other patients had asymptomatic extra-pulmonary sites of infection. All patients responded well to chemotherapy; no relapse was observed during or after treatment. Eight died, two of them before treatment (cause of death unknown), 6 from other complications of AIDS within the 2 years following the diagnosis of tuberculosis. The low incidence of extra-thoracic involvement and the high frequency of excavated pulmonary lesions are discordant with most US studies, as is the relatively late onset of tuberculosis in the course of HIV infection. We suggest that different local epidemiological factors and maybe the practice of systematic BCG vaccination during childhood in France could contribute to these differences.