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Biomedical subjects

M Riedy

Publications and source records attributed to M Riedy.

13 recordsLinked to original sources
PubMed1991

Introduction of foreign genes into tissues of living mice by DNA-coated microprojectiles.

Foreign genes were expressed in liver and skin cells of live mice by using a new apparatus to accelerate DNA-coated microprojectiles into tissues. After introduction of a plasmid in which the firefly luciferase gene was controlled by the human beta-actin promoter, luciferase activity was detectable for up to 14 days in mouse tissues (skin and liver). In situ hybridization histochemistry revealed that microprojectiles penetrated through multiple cell layers without evidence of tissue injury and that 10-20% of the cells in the bombarded area expressed the foreign gene. An advantage of the new design is that internal organs, such as liver, can be transfected without subjecting the tissue to a vacuum. This procedure potentially is applicable to a wide variety of tissues and cell types for studies of transcriptional control elements and for expression of foreign proteins in intact animals.

Actins↗
PubMed1989

Cardiac adaptations to endurance training in rats with a chronic myocardial infarction.

The hemodynamic response to maximal exercise was determined in sedentary and trained rats with a chronic myocardial infarction (MI) produced by coronary artery ligation and in rats that underwent sham operations (SHAM). Infarct size in the MI groups of rats comprised 28-29% of the total left ventricle and resulted in both metabolic and hemodynamic changes that suggested that these animals had moderate compensated heart failure. The training regimen used in the present study produced significant increases in maximal O2 uptake (VO2max) when expressed in absolute terms (ml/min) or when normalized for body weight (ml.min-1.kg-1) and consisted of treadmill running at work loads that were equivalent to 70-80% of the animal's VO2max for a period of 60 min/day, 5 days/wk over an 8- to 10-wk interval. This training paradigm produced two major cardiocirculatory adaptations in the MI rat that had not been elicited previously when using a training paradigm of a lower intensity. First, the decrement in the maximal heart rate response to exercise (known as "chronotropic incompetence") found in the sedentary MI rat was completely reversed by endurance training. Second, the downregulation of cardiac myosin isozyme composition from the fast ATPase V1 isoform toward the slower ATPase (V2 and V3) isoforms in the MI rat was partially reversed by endurance training. These cardiac adaptations occurred without a significant increase in left ventricular pump function as an increase in maximal cardiac output (Qmax) and maximal stroke volume (SVmax) did not occur in the trained MI rat.(ABSTRACT TRUNCATED AT 250 WORDS)

Adaptation, Physiological↗
PubMed1988

Glycogen concentrations and endurance capacity of rats with chronic heart failure.

The endurance capacities of rats with myocardial infarctions (MI) and of rats having undergone sham operations (SHAM) were tested during a submaximal exercise regimen that consisted of swimming to exhaustion. During this test, a decrement in the endurance capacity of the MI rat was demonstrated as the SHAM rat swam 25% longer than the MI rat (65 +/- 4 vs. 52 +/- 4 min). Glycogen concentrations were measured in the liver and the white gastrocnemius, plantaris, and soleus muscles of SHAM and MI rats that were randomly divided into four subgroups, which consisted of resting control, swim to exhaustion, swim to exhaustion + 24 h recovery, and swim to exhaustion + 24 h recovery + a second swim to exhaustion. The results demonstrated that the glycogen concentrations found in the liver, white gastrocnemius, plantaris, and soleus muscles of the SHAM and MI rats belonging to the resting control groups were similar. After swimming to exhaustion the glycogen concentrations in these tissues were significantly reduced compared with those found in the resting control groups of rats, and after 24 h of recovery the glycogen concentrations in these tissues were again similar to those found in the resting control groups of rats. Since the magnitude of the glycogen depletion in the liver and the white gastrocnemius, plantaris, and soleus muscles was similar in the SHAM and MI rats and because the SHAM rats consistently swam for longer periods of time in each of the experimental groups, it would be logical to assume that the rates of glycogen utilization for the various tissues may have been greater in the MI rat during exercise.(ABSTRACT TRUNCATED AT 250 WORDS)

Analysis of Variance↗
PubMed1985

Adaptive response of hypertrophied skeletal muscle to endurance training.

The response of hypertrophied soleus and plantaris muscle of rats to endurance training was studied. Hypertrophy was produced by bilateral extirpation of the gastrocnemius muscle. A 13-wk training program of treadmill running initiated 30 days after removal of the gastrocnemius muscle accentuated (P less than 0.01) the hypertrophy. Succinate dehydrogenase activities of the enlarged muscles of sedentary rats were similar to those of normal animals, as were the increases associated with training. Phosphorylase and hexokinase activities were unaltered as a result of the experimental perturbations. Rates of glycogen depletion during exercise were lower (P less than 0.01) in the liver and soleus and plantaris muscles of endurance-trained animals. No difference existed in the rate of glycogen depletion of normal and hypertrophied muscle within the sedentary or trained groups. These data demonstrate that extensively hypertrophied muscle responds to training and exercise in a manner similar to that of normal muscle.

Adaptation, Physiological↗
PubMed1985

Differences in metabolic potential of skeletal muscle fibres and their significance for metabolic control.

The role of an increase in oxidative potential of skeletal muscle in the enhanced work capacity and greater use of fat as a fuel after endurance training is discussed. Evidence is presented to illustrate that this adaptive response is probably expressed at the cellular level by a more rapid translocation into the mitochondria of the ADP generated during contractile activity. The consequence of this is a tighter control over the glycolytic process thereby creating more favourable conditions for the entry of acetyl units derived from beta-oxidation of fatty acids into the citric acid cycle.

Animals↗
PubMed1984

Influence of exercise on the fiber composition of skeletal muscle.

Biopsy samples from the vastus lateralis muscle (VLM) of man were examined for fiber composition at rest and at selected intervals during prolonged exercise ranging in intensity from 40% to 75% of the total body maximal oxygen uptake (VO2max) and one-min bouts of exercise at 150% VO2max. Because of the heterogeneity of fibers in human VLM, studies were also completed where the effect of exercise on the fiber composition of the rat soleus muscle (SM) was examined. In some animals the SM from one hindlimb was removed 9 days prior to their being exercised after which the remaining SM was removed. Exercise reduced muscle glycogen in all experiments. In the studies with man, blood lactate exceeded 17 mmoles/l after the heavy exercise but was largely unchanged by endurance exercise. Colonic temperature of the exercised rats exceeded 40 degrees C. In studies where fibers were identified only as type I and type II, type II fibers in the VLM of all samples (16) taken at rest averaged 61.2 +/- 12.5% as compared to 59.0 +/- 12.0% after exercise (54 biopsy samples). In a second series of studies with man where the subtypes of type II fibers were identified, there were also no differences in fiber composition of the VLM after varying periods of exercise. Glycogen content and percent fiber composition were the same in right and left SM obtained from rested rats. Exercise (30 to 40 min) did not alter the fiber composition of the rat SM. These data demonstrate that the histochemically demonstratable myofibrillar actomyosin ATPase of skeletal muscle is not altered by a single exercise bout.

Adenosine Triphosphatases↗
PubMed1983

Fiber number and size in overloaded chicken anterior latissimus dorsi muscle.

The relative contribution of increases in fiber area and number was evaluated in the chicken anterior latissimus dorsi (ALD) muscle in which enlargement was induced by hanging a weight on one wing. ALD muscles from wings to which weights had been attached for periods ranging from 6 to 65 days weighed an average of 105% (range 22-225%) more than control muscles. Total muscle fiber number, determined by direct counts after nitric acid digestion and fiber dissection, and the frequency of branched fibers were unchanged by muscular enlargement. Fiber cross-sectional area was greater (P less than 0.01) in the enlarged muscles. A close relationship existed (r = 0.78) between actual muscle weight and weight calculated as the product of fiber volume, total fiber number, and muscle density for the control and enlarged muscles. Histochemical staining revealed a conversion of type IIa to type I fibers in the stretched muscles. These results support the concept that skeletal muscle enlargement in response to chronic overload is produced by hypertrophy of preexisting fibers and not be a formation of new fibers.

Animals↗
PubMed1982

Effect of training on beta-adrenergic receptor number in rat heart.

Female Sprague-Dawley rats were subjected to endurance-training programs, and the effect of training on myocardial beta-adrenergic receptor number, receptor-binding characteristics, and adenylate cyclase (AC) activities associated with the receptor were examined. Training produced a 45% (P less than 0.01) increase in the succinate dehydrogenase activity of the plantaris muscle. Specific (-)-[3H]dihydroalprenolol (DHA)-binding data were subjected to Scatchard plot analysis to quantify beta-adrenergic receptor number and DHA-binding characteristics of myocardial membranes. The DHA concentrations at which 50% of the total binding sites were occupied were similar for membranes from sedentary (1.95 +/- 0.51) and trained (1.59 +/- 0.34 nM) groups. Total DHA-binding sites of membranes from control (91.6 +/- 13.3) and trained (83.1 +/- 7.6 fmol/mg) groups were also similar. Basal and maximally stimulated AC activities were also unchanged by endurance training. Fluoride-stimulated AC activities of crude homogenate and 10,000 g fractions decreased 47 and 49%, respectively, with training. No differences were observed in a 40,000 g fraction. The specific activities of a ouabain-sensitive Na+-K+-ATPase (a sarcolemmal membrane marker) of crude homogenate, 10,000 g, and 40,000 g membrane fractions were similar. These data indicate that training produces no detectable difference in the potential for adrenergic responses at the receptor level.

Adenylyl Cyclases↗
PubMed1982

Acute fasting and fiber number in rat soleus muscle.

The influence of fasting on fiber number in the soleus muscle (SM) of weanling male and female rats was investigated. For female rats, comparisons were made among groups of animals fed normally, rats fasted and then fed until prefast body weight was regained, and animals that grew to maturity. For male rats, comparisons were made only between control and fasted groups. Prior to the experimental treatments the SM was surgically removed from one leg. There was a 40% loss in body weight after fasting. Although major weight losses occurred in most muscles and organs, there was no change in the SM. Over the same period SM weight increased 31% in normal animals. Total fiber number (direct counts after nitric acid digestion) was unaltered by the treatments. Although wide variation existed between animals, total fiber number between legs for the same animal was closely correlated (r = 0.98). SM weight for male rats calculated from fiber length, cross-sectional area, and total fiber number could account for from 91 to 99% of the total muscle weight. There was no change in fiber number from weaning to maturity. It is concluded that fiber number is unchanged by fasting or during normal maturation.

Animals↗
PubMed1981

Muscular enlargement and number of fibers in skeletal muscles of rats.

The effect of muscular enlargement produced by surgical ablation of a synergist and the combination of synergist ablation and exercise on the number of fibers in the soleus (S), plantaris (P), and extensor digitorum longus (EDL) muscles of the rat was studied. The number of fibers per muscle was determined by direct counts of individual fibers dissected from HNO3-treated muscles. Ablation of a synergist produced average enlargements of about 25, 45, and 29% for the S, P, and EDL muscles, respectively. Exercise and synergist ablation produced increases in wet weight to about 44 and 88% for the S and P muscles, respectively, whereas no further increases were observed in the EDL muscles. Intra-animal comparisons revealed that no differences existed for total fiber number or the incidence of fibers with bifurcations between the enlarged and contralateral control muscles. The difference in dry weight of fibers from the enlarged as compared with control muscles was closely correlated to differences in total muscle wet weight. These data demonstrate that hypertrophy rather than hyperplasia was responsible for increases from 10 to over 100% in the weight of skeletal muscles.

Animals↗
PubMed1979

Radiochemical plasma salicylamide assay using ring-labeled tritiated salicylamide.

A rat plasma salicylamide assay was developed using ring-labeled tritiated salicylamide, synthesized by reacting salicylamide with tritium oxide in the presence of heptafluorobutyric acid. The reaction yielded 3H-salicylamide of specific activity up to 8.41 mCi/mmole, 60% yield. Plasma containing 3H-salicylamide and its metabolites was extracted with a toluene-based scintillation fluid, which was subsequently counted. Specificity for free salicylamide was demonstrated by radio chemical and standard fluorescence plasma salicylamide level-time curves. Specificity resulted from nonextraction of the salicylamide sulfate and glucuronide metabolites. Sulfatase and beta-glucuronidase treatment allowed the analysis of plasma sulfate and glucuronide conjugates as free salicylamide. This procedure should be effective for the analysis of salicylamide and its metabolites in the presence of similar phenolic compounds.

Animals↗
PubMedDate not supplied

Elevated plasma hydroxyproline. A possible risk factor associated with connective tissue injuries during overuse.

Basal plasma hydroxyproline was measured in 104 male Navy Seal candidates 1 week into their intense physical training program, which lasted 7 weeks, and correlated to the incidence of connective tissue injuries incurred later in the training program. Eleven subjects (10.6%) were diagnosed as having connective tissue injuries. Those subjects with connective tissue injuries had a significantly higher (P less than 0.05) mean plasma hydroxyproline value (4.02 micrograms/ml) than subjects without injury (3.10 micrograms/ml). The majority of graduates (75%) had plasma hydroxyproline values less than 3.3 micrograms/ml. These graduates represented the strongest and most enduring injury-free subjects. Of the subject pool who incurred connective tissue injuries, only 27% had plasma hydroxyproline values less than 3.3 micrograms/ml. The majority of the injured subjects (73%) had plasma hydroxyproline values greater than or equal to 3.3 micrograms/ml. In conclusion, there is a relationship between initial training basal plasma hydroxyproline levels and connective tissue injuries later incurred in an intense physical training program. These data suggest that elevated plasma hydroxyproline levels may represent a risk factor associated with connective tissue injuries.

Adolescent↗