Case report: left bundle branch block--a rare complication of citalopram overdose.
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Adult↗
Biomedical subjects
R D Snider
Publications and source records attributed to R D Snider.
Catheter breakage: an unusual complication of nasoenteric feeding tubes.
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Aged↗
Differences in glucose transport rates between perfused and in vitro incubated muscles.
In vitro incubated muscles are a convenient preparation for glucose transport studies, but it is not known how closely they reflect the in vivo condition. Perfused muscle preparations more closely resemble the in vivo condition, and thus to validate the use of in vitro incubated muscles, we have compared glucose transport rates in the two preparations. 3-O-Methylglucose transport rates in incubated soleus (SOL) and extensor digitorum longus (EDL) muscle strips were compared to transport rates obtained in SOL and EDL muscles removed from perfused hindquarters. Male Sprague-Dawley rats (250 g) were used for both procedures. SOL muscles showed an average 25% higher transport rate than EDL muscles at all insulin concentrations examined (0-100 nM) in the perfused system. This difference was diminished in the incubated muscles, SOL being 15% greater than EDL, but the relationship between the two muscles was maintained. Basal transport was lower and maximal transport was higher in the perfused muscles compared to the incubated muscles. This resulted in significantly higher fold stimulation in the perfused vs. incubated muscles (15 vs. 2.5 in the SOL, and 9.8 vs. 2.3 in the EDL). We conclude that in vitro muscle preparations may be convenient for showing relative differences between experimental treatments, but absolute transport rates and insulin stimulation must be interpreted with caution.
Animals↗
Total and myofibrillar protein degradation in isolated soleus muscles after exercise.
The effect of exercise on the rate of total and myofibrillar protein degradation was determined by measuring the rate of release of tyrosine and 3-methylhistidine, respectively, from isolated rat soleus muscle strips after exercise. The rate of tyrosine release was 30-50% greater from the muscles of the exercised rats, whereas the rate of 3-methylhistidine release was unchanged. Thus the exercise-induced increase in the rate of protein degradation is due to increased breakdown of nonmyofibrillar proteins. The rate of protein degradation increases as a function of exercise duration and rapidly returns to the preexercise level during recovery. The exercise-induced increase in the rate of protein degradation is not inhibited by chloroquine. Together these observations suggest that the increase in the rate of protein degradation observed immediately after exercise is due to the breakdown of nonmyofibrillar proteins and occurs via the nonlysosomal pathway of protein degradation.
Animals↗
Effect of exercise intensity and starvation on activation of branched-chain keto acid dehydrogenase by exercise.
Branched-chain keto acid (BCKA) dehydrogenase activity was examined in rat skeletal muscle as a function of exercise intensity and nutritional status. The activity of BCKA dehydrogenase increased with increasing exercise intensity, showing increases over resting values of 76, 172, and 245% at 10, 20, and 30 m X min-1. The exercise-induced increase in BCKA dehydrogenase activity was the same in the gastrocnemius and in the quadriceps muscles. Rapid removal of the muscle after death is essential because the activity of BCKA dehydrogenase decreased rapidly after death. Thus the likely reasons Wagenmakers et al. (Biochem. J. 223: 815-821, 1984) found exercise caused a much smaller increase in BCKA dehydrogenase activity than Kasperek et al. [Am. J. Physiol. 248 (Regulatory Integrative Comp. Physiol. 17): R166-R171, 1985] are differences in muscle removal time and the duration of exercise. Starvation for 24 h before exercise increased the exercise-induced activation of BCKA dehydrogenase by 160%, which suggests that the increased BCKA dehydrogenase activity is in response to an increased requirement for citric acid cycle intermediates.
3-Methyl-2-Oxobutanoate Dehydrogenase (Lipoamide)↗
The effect of exercise on protein turnover in isolated soleus and extensor digitorum longus muscles.
The rate of protein degradation was found to be increased in isolated soleus and extensor digitorum muscles of 60-80 g rats after exercise consisting of running for 120 min. These findings support the hypothesis that exercise causes an increase in skeletal muscle protein degradation, and that both red and white muscles are affected similarly.
Animals↗
The susceptibility to exercise-induced muscle damage increases as rats grow larger.
Glucose-6-phosphate dehydrogenase and N-acetyl-beta-glucosaminidase activities were both elevated after eccentric exercise indicating that this type of exercise causes muscle damage. Muscle damage as measured by glucose-6-phosphate dehydrogenase activity in the vastus intermedius was greater and occurred later in larger rats indicating that the susceptibility to muscle damage is increased and the repair process delayed in older and larger animals.
Acetylglucosaminidase↗
Increased protein degradation after eccentric exercise.
The purposes of these experiments were to compare the activities of glucose 6-phosphate dehydrogenase (G6PDH) and the lysosomal enzyme N-acetyl-beta-glucosaminidase (NAG) in rat muscles and to assess protein degradation after eccentric exercise (running down a 18 degrees grade). The following results were obtained: (1) Muscles in which the G6PDH activity was increased also showed an increase in NAG activity that was smaller and occurred later and/or was more prolonged than the increase in G6PDH activity. (2) The urinary 3-methylhistidine/creatinine ratio was statistically elevated for 3 days after eccentric exercise and this increase was much larger and more prolonged than previously observed in rats run on the level. Taken together our results suggest that increased protein degradation after exercise is due to increased proteolysis of muscle tissue damaged during the exercise bout and that lysosomal enzymes may be involved in this degradation.
Acetylglucosaminidase↗
Activation of branched-chain keto acid dehydrogenase by exercise.
The present study was conducted to investigate the metabolic regulation of leucine oxidation during exercise. Ten rats per group were run at 27 m/min (0% grade) on a treadmill for 30 and 120 min or until exhausted, and the total and basal activity of branched-chain keto acid dehydrogenase was examined in the muscle, liver, and heart. The total activity of the dehydrogenase in the heart, liver, or skeletal muscle was unchanged by exercise. However, exercise increased the basal activity levels of the dehydrogenase about 10-fold in muscle and 5-fold in heart. The basal dehydrogenase activity in the liver was unchanged by exercise. Activation of the dehydrogenase in both muscle and heart was statistically elevated after 30 min exercise and continued to increase during the remainder of the exercise bout. The basal activity of the dehydrogenase returned to resting levels by 10 min postexercise. The activation of the dehydrogenase in muscle and heart during exercise likely is due to dephosphorylation because activity of the enzyme in mitochondria isolated from exercised muscles reverts to control values when the mitochondria are incubated in the presence of ATP. Thus the increased leucine oxidation observed during exercise is due to activation of the branched-chain keto acid dehydrogenase by dephosphorylation. This is the first example of a large increase in branched-chain keto acid dehydrogenase activity caused by a physiological process. This demonstrates that the muscle's latent capacity of oxidize branched-chain amino acids is much larger than previously thought and that this capacity is used in exercising muscle.
3-Methyl-2-Oxobutanoate Dehydrogenase (Lipoamide)↗
Effect of eccentric exercise on muscle protein degradation.
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Animals↗
Fatty acid oxidation by liver and muscle preparations of exhaustively exercised rats.
The influence of exhaustive exercise on the capacity of liver and muscle of rats to oxidize fatty acids was investigated in vitro. The rate of oxidation of fatty acids by liver preparations was significantly elevated as a result of exhaustion. Concurrently, the concentrations of beta-hydroxybutyrate were elevated in the plasma of the exhausted rats, suggesting that oxidation of fatty acids was also elevated in vivo. These findings are analogous to the findings of increased oxidation of fatty acids that results from training. In muscle, oxidation of palmitate, palmitoylcarnitine and beta-hydroxybutyrate by homogenates and isolated mitochondria was depressed with exercise. Despite the decrease in the oxidative capacity of the muscle preparations, the activities of several enzymes of beta-oxidation were either increased or unchanged as a result of exercise, suggesting that the depression in fatty acid oxidation may not be related to alterations in the process of beta-oxidation. Further studies showed that oxidation of [2-(14)C]pyruvate by muscle was depressed, whereas oxidation of [1-(14)C]pyruvate was not changed as a result of exercise. These results suggest that the decrease in fatty acid oxidation may be related to aberrations in the oxidation of acetyl-CoA. The changes in fatty acid oxidation that were observed, which are at variance with what is reported to occur with training, may have resulted from increased fragility of muscle mitochondria as a result of exercise. This increased fragility may render the mitochondria more susceptible to experimental manipulations in vitro and a subsequent loss of normal function.
Animals↗
The role of lysosomes in exercise-induced hepatic protein loss.
Previous reports have shown that exercise causes a loss of liver protein. The purpose of the present study was to elucidate the mechanism of this exercise-induced protein loss. Exercise caused: (1) an increase in mechanical and osmotic lysosomal fragility; (2) a significant loss of hepatic water, glycogen, protein, phospholipid and RNA; (3) loss of protein from the soluble, mitochondrial and microsomal fractions: (4) loss of mitochondrial, microsomal and cytosolic, but not lysosomal, enzyme activity; (5) an increase in the number of autophagic vacuoles; (6) an increase in the lysosomal size. Taken together, these results suggest that the autophagolysosomal system is responsible for the exercise-induced hepatic protein loss.
Animals↗
Accuracy of estimated creatinine clearance in obese patients with stable renal function in the intensive care unit.
We compared agreement between creatinine clearance values in obese, critically ill patients calculated using three common empirically derived formulas and modifications thereof, with creatinine clearance obtained by conventional 24-hour urine collection. We selected the charts of 22 patients in intensive care units (86% medical, 14% surgical) according to the following criteria: actual body weight greater than 150% of ideal body weight; serum creatinine variation of less than 15% from the day of starting 24-hour urine collection to the day before or after the collection; presence of a urinary bladder catheter; no history of renal dialysis; and clinical indication for renal function assessment. Mean measured 24-hour urinary creatinine clearance for all patients was 72 +/- 64 ml/minute (range 8-248 ml/min). The method of estimating creatinine clearance that showed the least mean bias was the equation of Salazar and Corcoran using a corrected serum creatinine concentration (mean bias -2 ml/min); however, the corresponding 95% confidence intervals were wide (-133-129 ml/min). The narrowest range of 95% confidence intervals were seen with Jelliffe's equation (mean bias 25 ml/min, 95% confidence intervals -41-90 ml/min). In this sample, estimated creatinine clearances did not agree acceptably with measured values. Despite low mean bias values, none of the empirically derived equations that we studied had clinically acceptable 95% confidence intervals. We recommend using the 24-hour urine collection method when assessing creatinine clearance in obese, critically ill patients.
Adult↗