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Biomedical subjects

J C McDermott

Publications and source records attributed to J C McDermott.

At least 19 recordsLinked to original sources
PubMed1992

Epinephrine administration stimulates GLUT4 translocation but reduces glucose transport in muscle.

Epinephrine opposes glucose transport in muscle. Therefore, we investigated the effects of epinephrine administration (25 micrograms/100g body weight) on glucose transport and glucose transporters in rat muscle. Ninety minutes after epinephrine injection 3-O-methyl glucose transport was reduced (approximately 47%) in perfused muscles of the rat hindlimb. Translocation of the insulin-regulatable glucose transporter (GLUT4) in the epinephrine-injected animals was confirmed by the marked increments in the GLUT-4 in the plasma membranes and their concomitant reduction in the intracellular membranes. We speculate a) that it is epinephrine which translocated GLUT4 via a cAMP-linked pathway, and b) that the intrinsic activity reductions are caused either by the glycation of the transporter by the persistent hyperglycemia and/or by epinephrine via the phosphorylation of the GLUT4 transporter protein in muscle.

3-O-Methylglucose↗
PubMed1992

Abdominal abscesses associated with enteric fistulas: percutaneous management.

For many years, surgical dictum stated abdominal fistulas should be treated by means of surgical excision. Recent advances in percutaneous techniques have altered this. The authors reviewed 150 consecutive abdominal abscesses drained percutaneously over a 36-month period. Among these, 24 patients were found to have 26 fistulous communications to bowel, the pancreatic duct, or the biliary system. Initial drainage of their abscesses was performed in the hospital, but 17 of 24 patients were discharged with a tube in place and were followed up as outpatients. The duration of drainage ranged from 4 days to 3 months. Fistulas healed in 21 of 24 patients (88%) without surgical intervention. Complications were few and included inadvertent dislodgment requiring tube replacement (two patients) and inadvertent puncture of the transverse colon (one patient). Treatment of abdominal abscesses with fistulas by means of percutaneous methods is reliable and safe. Hospital stay may be minimized with outpatient management after drainage.

Abdomen↗
PubMed1992

Glyconeogenic and oxidative lactate utilization in skeletal muscle.

In this article we present a synthesis of recent information concerning the fate of lactate in skeletal muscle. This is important since lactate is continuously produced by skeletal muscle at rest and at all levels of exercise. Therefore, the disposal of lactate as an 'intermediary' metabolite is discussed. The two primary fates of lactate in skeletal muscle are (1) oxidation and (2) glycogen synthesis (glyconeogenesis). From recent evidence it seems relatively clear that glycogen formation in muscle is primarily dependent on glucose, although in fast twitch muscles a considerable proportion of lactate can account for muscle glycogen formation, especially immediately after exercise when circulating lactate levels are elevated. Exactly how lactate is converted to glycogen is not known yet, but an extramitochondrial pathway that is divergent from the hepatic gluconeogenic pathway seems likely. Oxidation of lactate is quantitatively the most important means of disposing of lactate, whether in exercising or nonexercising muscle. The lactate gradient between muscle and blood may be an important factor dictating whether lactate is taken up or released by muscle, independent of whether the muscle is active or not. Finally a novel role for epinephrine is considered that may be important for the mitochondrial oxidation of lactate.

Animals↗
PubMed1992

Persistence of glucose metabolism after exercise in trained and untrained soleus muscle.

We tested the hypothesis that increments in glucose metabolism in muscles from trained animals are caused by training adaptations in skeletal muscle and not by the residual effects of the last training session. The effects of a single bout of exercise on glucose metabolism (glycolysis and glycogenesis) were compared, against appropriate controls, in untrained (experiment 1) and trained (experiment 2) rat soleus muscles immediately (t = 0) and 3, 6, 24, 48, and 96 h after a standardized bout of exercise. [3H]Glucose incorporation into glycogen and glycolysis was measured in vitro in the absence and presence of insulin (0.1 and 10 nM). Experiment 1: A single bout of exercise provoked an increase in glycogenesis in the exercised, untrained muscles compared with the nonexercised, untrained muscles (0-96 h; P = 0.006). Glycolysis was not altered (0-96 h; P > 0.05). Experiment 2: In the exercised trained soleus, rates of glycolysis were greater than in the exercised, untrained soleus, at insulin concentrations of 0.1 nM (0-96 h; P = 0.005) and 10 nM (0-96 h; P = 0.01), but not in the absence of insulin (0-96 h; P > 0.05). No differences were observed in the rates of glycogenesis (0-96 h; P > 0.05). Therefore, acute exercise provokes increments in glycogenesis, whereas training increases glycolysis, in the presence of insulin, for some time after exercise. We speculate that insulin-dependent increments in glycolysis in trained muscles are a consequence of increased glucose transport caused by a greater pool of insulin-translocatable, intracellular glucose transporters.

Analysis of Variance↗
PubMed1991

Non-exercising muscle metabolism during exercise.

Glycogen decrements have been observed in non-exercising muscles during exercise. We therefore investigated whether the degraded glycogen was retained within the muscle in the form of glycolytic intermediates, or whether it was effluxed from the non-exercising muscles. For these studies a suspension harness was used to unload the hindlimb muscles at rest and during exercise [McDermott et al. (1987) J Appl Physiol 63:1275-1283]. Concentrations of glycogen and glycolytic intermediates glucose 6-phosphate, fructose 6-phosphate, fructose 1,6-bisphosphate, glycerol 3-phosphate, and lactate) were measured in non-exercising and exercising muscles (soleus, plantaris, red and white gastrocnemius) during a 90-min exercise about 15 m/min, 8% grade). On-line electromyographic analysis showed that the contractile activity in the non-exercising muscles was markedly lower than in the exercising muscles. Similar decrements in muscle glycogen levels were observed in both the non-exercising and exercising muscles at the end of the 90-min, exercise bout (P less than 0.05), despite significantly different activity profiles. An increase in tissue lactate concentrations occurred in both non-exercising and exercising muscle (P less than 0.05), although only slight changes in the glycolytic intermediates occurred. The sum total of all the accumulated glycolytic intermediates and lactate (converted to glucosyl units) in the non-exercising muscles only accounted for a small fraction of the glycogen degraded (approximately 15%-28%). We conclude that the metabolism of glycogen is enhanced in non-exercising muscle, and that glycogen utilization is uncoupled from the energetic demands of the muscle. Furthermore, the glycogen mobilized in non-exercising muscle is not retained within the muscle in other metabolite pools.(ABSTRACT TRUNCATED AT 250 WORDS)

Action Potentials↗
PubMed1991

A safe route for deep pelvic biopsy with distention of the iliacus muscle.

To avoid bowel perforation during deep pelvic biopsy, the authors describe a technique in which the iliacus muscle is distended by injecting it with a solution of lidocaine and saline. This muscle distention causes sufficient bowel displacement to allow safe advancement of biopsy needles as large as 14 gauge through the distended muscle belly to the region of interest.

Adult↗
PubMed1991

The regulation of myosin gene transcription in skeletal muscle: effects of altered functional demand.

Perturbations in the activity patterns of skeletal muscle have been used to probe adaptive mechanisms that occur when the function of a muscle is altered. A plethora of information is available concerning the phenotypic changes that occur in the skeletal muscle myosin patterns when the load placed on a muscle is changed. More recently, technological advances in molecular biology have facilitated investigations concerning how these changes at the protein level are mediated via transcription of the genome. The focus of this review will be the recent evidence concerning the regulation of transcription of the myosin isogenes in skeletal muscle. In addition, putative regulatory factors are discussed which may link an alteration in function to altered transcription of the genome.

Adaptation, Physiological↗
PubMed1991

Masked high-frequency bone-conduction audiometry: test reliability.

The present study examines the reliability of masked high-frequency bone-conduction threshold measurements in 95 normal-hearing subjects. High-frequency pure-tone air-and bone-conduction thresholds were measured with a dedicated laboratory high-frequency auditory evaluation system using matched, modified Koss Pro/4X Plus earphones, and the Pracitronic KH 70/5 bone vibrator. A 400-Hz wide band masking noise centered at the frequency of the test tone was used to mask the nontest ear. Monaural masked bone-conduction threshold measurements were obtained at the ipsilateral mastoid of the ear with better high-frequency hearing. Two measurements were performed in each session, and each subject participated in two sessions. In several comparisons for test-retest consistency, high-frequency bone-conduction threshold measurements were as repeatable as air-conduction thresholds of identical frequency, or bone-conduction thresholds for frequencies of 4 kHz and less. High-frequency bone-conduction threshold measurement appears to be a sufficiently reliable tool for diagnosis of auditory disorders.

Adolescent↗
PubMed1990

A model for nonexercising hindlimb muscles in exercising animals.

Nonexercising muscles appear to be metabolically active during exercise. Animal models for this purpose have not been established. However, we have been able to teach animals to run on their forelimbs while their hindlimbs are suspended above the treadmill with no visible limb movement. To document that indeed this mode of exercise does not provoke additional muscle activity, we have compared the levels of neural activation of the soleus and plantaris muscles using a computer analysis of the electromyographic interference pattern, recorded from bipolar fine wire electrodes implanted across each muscle. Via computer analyses of the electromyographic interference patterns the frequencies and amplitudes of motor unit action potentials were obtained. The data were sampled during 20 s of every minute of observation. Comparisons were made in four conditions: (i) resting on the treadmill while bearing weight on the hindlimbs (normal rest), (ii) running on the treadmill (15 m/min, 8% grade) on all four limbs (normal exercise), (iii) resting while the hindlimbs were suspended in a harness above the treadmill (suspended rest), and (iv) exercising with the forelimbs (15 m/min, 8% grade) while the hindlimbs were suspended above the treadmill (suspended exercise). All four experimental conditions were carried out for 90 min each and were performed by each animal. The results clearly show that muscle activities (frequencies and amplitudes), when the hindlimbs are suspended above the treadmill, at rest or during exercise, are lower than the activities in these same muscles when the animals are at rest, supporting only their body weight. Activities in the same muscles during exercise were from 300 to 2000% greater than during hindlimb suspension.(ABSTRACT TRUNCATED AT 250 WORDS)

Action Potentials↗
PubMed1990

Glycogenesis and glyconeogenesis in skeletal muscle: effects of pH and hormones.

We examined the effects of selected hormones and pH on the rates of glyconeogenesis (L-[U-14C]-lactate----glycogen) and glycogenesis (D-[U-14C]glucose----glycogen) in mouse fast-twitch (FT) and slow-twitch muscles incubated in vitro (37 degrees C). Glyconeogenesis and glycogenesis increased linearly with increasing concentrations of lactate (5-20 mM) and glucose (2.5-10 mM), respectively, in both muscles. Glyconeogenesis was approximately three- to fourfold greater in the extensor digitorum longus (EDL) than in the soleus, whereas basal glycogenesis was twofold greater in the soleus muscle than in the EDL. Lactate accounted for up to 5% of the glycogen formed in the soleus and up to 32% in the EDL relative to the rates of glycogenesis (i.e., 5 mM glucose + 10 nM insulin) in each muscle. Corticosterone (10(-12)-10(-6) M) failed to alter glyconeogenesis, whereas this hormone reduced glycogenesis. Insulin (10 nM) markedly stimulated glycogenesis but failed to stimulate glyconeogenesis. The rates of both glycogenesis and glyconeogenesis were pH sensitive, with optimal rates at pH 6.5-7.0 in both muscles. Glyconeogenesis increased by 49% in the soleus and by 39% EDL at pH 6.5 compared with pH 7.4. Glycogenesis increased in the soleus (SOL) and EDL in the absence (SOL: +22%; EDL: +52%) and presence of insulin (SOL: +22%; EDL: +51%) at pH 6.5 when compared with pH 7.4. In additional experiments with the perfused rat hindquarter, rates of glyconeogenesis were shown to be highly correlated with proportion of FT muscle fibers in a muscle.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1990

Effects of contralateral masking on high-frequency bone-conduction thresholds.

The present study reports effects of contralateral masking on high-frequency threshold force levels in 28 normal-hearing subjects. High-frequency air- and bone-conduction thresholds were measured with a high-frequency auditory evaluation system using matched Koss HV/1A earphones and the Pracitronic KH 70/5 bone vibrator. Measurements were made for both unmasked and masked bone-conduction thresholds at the ipsilateral mastoid of the better ear. The contralateral masked condition was performed using 30-dB-SL 400-Hz narrow-band masking noise centered at frequency of test tone. The results demonstrated that masked high-frequency bone-conduction thresholds were 1.5 to 3.4 dB poorer than the unmasked thresholds and that these differences were statistically significant at 0.01 level of confidence except at 12 kHz. ANSI and ISO standards for bone-conduction threshold force levels for frequencies below 8.0 kHz have been established with contralateral masking stimuli. This study supports the need to use effective contralateral masking to eliminate cross hearing in investigations of high-frequency bone-conduction threshold measurements.

Adult↗
PubMed1989

The effect of phosphate, sodium chloride, sodium nitrite, storage temperature and pH on the growth of enteropathogenic Escherichia coli in a laboratory medium.

The effect of eight phosphates in combination with sodium chloride/nitrite mixtures on growth of mixed strains of enteropathogenic Escherichia coli over a period of 10 weeks at three pH values (5.6, 6.2, 6.8) and at seven temperatures ranging from 10 degrees C to 35 degrees C is reported. All eight phosphates inhibited growth to varying degrees in at least some of the conditions investigated. Instances of inhibition increased with concentration of sodium chloride/nitrite and were more frequent at lower temperatures and pH values.

Culture Media↗
PubMed1989

Carbohydrate metabolism in skeletal muscle: an update of current concepts.

We have reviewed carbohydrate metabolism in skeletal muscle with an emphasis on recent information. In this review a significant number of points have been made. These are summarized below. 1. CP and glycogen are concomitantly metabolized during short-term (less than or equal to 10 s) intense exercise. 2. Both epinephrine and contractile activity regulate glycogen use in muscle. 3. Glycogen sparing during exercise is promoted by fatty acids and probably glucose. 4. Glycogenesis increases during exercise in exercising muscle. 5. Ingested glucose is easily metabolized during exercise. 6. The heterogeneity in glucose uptake among muscles at rest and during exercise is likely not caused by blood flow differences per se. 7. Insulin binding, glucose transporters, glucose uptake, and glycogenesis are greater in ST than in FT muscles. 8. Acute changes in glucose metabolism are not always attributable to concomitant changes in insulin binding to its receptor. 9. Contractile activity alone will increase glucose uptake in muscle, and insulin is not required. 10. Insulin and contractile effects on glucose uptake are additive, suggesting that these stimuli mobilize different pools of glucose transporters. 11. Glycogen loss occurs in exercising and non-exercising muscle; therefore this substrate is not an appropriate index of muscle contractile activity. 12. Carbohydrate mobilization does not appear to be strictly determined by need for this substrate nor by the rate of muscle metabolism. 13. Glyconeogenesis from lactate occurs in ST and FT muscles and is regulated by pH.

Animals↗
PubMed1989

The use of a cell-free perfusate in the perfused rat hindquarter: methodological concerns.

The viability of using a cell-free perfusate in a rat hindlimb preparation to assess skeletal muscle glycogenesis was investigated. A perfusate containing 10 mM glucose and 10 microCi (1 Ci = 37 GBq) of D-[5-3H]glucose was recycled for a 60-min period. In agreement with other studies using more complex media, oxygen uptake of the preparation indicated adequate tissue oxygenation (8 mumol.min-1.g-1). Skeletal muscle fiber type heterogeneity in basal glycogen synthesis from glucose was shown (slow oxidative greater than fast oxidative glycolytic greater than fast glycolytic fibres). Insulin (4.2 mU/mL) markedly stimulated glycogenesis from D-[5-3H]glucose in the soleus (slow oxidative fiber), red gastrocnemius (fast oxidative glycolytic fiber), and white gastrocnemius muscles (p less than 0.05). A recent report indicates that tissue edema in this preparation did not affect insulin responsiveness of the tissue. In contrast, our observations indicate that glucos uptake was enhanced by insulin when edema was absent (p less than 0.05), but not when edema was present (p less than 0.05). In addition, the presence of tissue edema negated insulin-mediated glycogenesis in slow oxidative and fast oxidative glycolytic muscle (p less than 0.05 compared with control) but not in fast glycolytic muscle (p less than 0.05). These data warrant caution when using a cell-free media in the perfused rat hindquarter; however, in the absence of edema, normal responses of glucose metabolism are observed.

Animals↗