Use of Cast Post-and-cores for the Alteration of Crown Position for the Esthetically Compromised Patient

The authors describe the use of cast post-and-cores, which allow a change in position of the clinical crown to permit the fabrication of two fixed partial dentures. The two fixed partial dentures change the clinical appearance of the patient.

Contemporary results for open repair of suprarenal and type IV thoracoabdominal aortic aneurysms

Background

Endovascular and hybrid procedures are not yet widely established in the management of type IV thoracoabdominal aortic aneurysm (TAAA). Open surgery remains the treatment of choice until the long-term outcomes of these novel techniques are known.

Methods

This study reviewed a 10-year experience of open repair of non-ruptured type IV and suprarenal TAAA. All procedures were performed using a totally abdominal approach with supracoeliac clamping of the aorta.

Results

There were 53 patients (31 men; 58 per cent) of median age 69 (range 54–82) years. Forty-four patients had a type IV TAAA and nine a suprarenal aneurysm. Three patients (6 per cent) died within 30 days and the 12-month mortality rate for patients followed for at least 1 year was 6 per cent (three of 49). Ten patients (19 per cent) had a cardiac complication, 20 (38 percent) a respiratory complication, three (6 percent) required early reoperation, and one patient (2 percent) developed permanent paraplegia. There was one late death resulting from an aneurysm-related complication.

Conclusion

Open repair of suprarenal aneurysms and type IV TAAA may be undertaken using a totally abdominal approach with acceptable levels of morbidity and mortality.

A transgenic model to study the pathogenesis of somatic mtDNA mutation accumulation in beta-cells

Low levels of somatic mutations accumulate in mitochondrial DNA (mtDNA) as we age; however, the pathogenic nature of these mutations is unknown. In contrast, mutational loads of >30% of mtDNA are associated with electron transport chain defects that result in mitochondrial diseases such as mitochondrial encephalopathy lactic acidosis and stroke-like episodes. Pancreatic beta-cells may be extremely sensitive to the accumulation of mtDNA mutations, as insulin secretion requires the mitochondrial oxidation of glucose to CO(2). Type 2 diabetes arises when beta-cells fail to compensate for the increased demand for insulin, and many type 2 diabetics progress to insulin dependence because of a loss of beta-cell function or beta-cell death. This loss of beta-cell function/beta-cell death has been attributed to the toxic effects of elevated levels of lipids and glucose resulting in the enhanced production of free radicals in beta-cells. mtDNA, localized in close proximity to one of the major cellular sites of free radical production, comprises more than 95% coding sequences such that mutations result in changes in the coding sequence. It has long been known that mtDNA mutations accumulate with age; however, only recently have studies examined the influence of somatic mtDNA mutation accumulation on disease pathogenesis. This article will focus on the effects of low-level somatic mtDNA mutation accumulation on ageing, cardiovascular disease and diabetes.

Disruption of Sur2-containing K(ATP) channels enhances insulin-stimulated glucose uptake in skeletal muscle

ATP-sensitive potassium channels (K(ATP)) are involved in a diverse array of physiologic functions including protection of tissue against ischemic insult, regulation of vascular tone, and modulation of insulin secretion. To improve our understanding of the role of K(ATP) in these processes, we used a gene-targeting strategy to generate mice with a disruption in the muscle-specific K(ATP) regulatory subunit, SUR2. Insertional mutagenesis of the Sur2 locus generated homozygous null (Sur2(-/-)) mice and heterozygote (Sur2(+/-)) mice that are viable and phenotypically similar to their wild-type littermates to 6 weeks of age despite, respectively, half or no SUR2 mRNA expression or channel activity in skeletal muscle or heart. Sur2(-/-) animals had lower fasting and fed serum glucose, exhibited improved glucose tolerance during a glucose tolerance test, and demonstrated a more rapid and severe hypoglycemia after administration of insulin. Enhanced glucose use was also observed during in vivo hyperinsulinemic euglycemic clamp studies during which Sur2(-/-) mice required a greater glucose infusion rate to maintain a target blood glucose level. Enhanced insulin action was intrinsic to the skeletal muscle, as in vitro insulin-stimulated glucose transport was 1.5-fold greater in Sur2(-/-) muscle than in wild type. Thus, membrane excitability and K(ATP) activity, to our knowledge, seem to be new components of the insulin-stimulated glucose uptake mechanism, suggesting possible future therapeutic approaches for individuals suffering from diabetes mellitus.

Calpains play a role in insulin secretion and action

Studies of the genetic basis of type 2 diabetes suggest that variation in the calpain-10 gene affects susceptibility to this common disorder, raising the possibility that calpain-sensitive pathways may play a role in regulating insulin secretion and/or action. Calpains are ubiquitously expressed cysteine proteases that are thought to regulate a variety of normal cellular functions. Here, we report that short-term (4-h) exposure to the cell-permeable calpain inhibitors calpain inhibitor II and E-64-d increases the insulin secretory response to glucose in mouse pancreatic islets. This dose-dependent effect is observed at glucose concentrations above 8 mmol/l. This effect was also seen with other calpain inhibitors with different mechanisms of action but not with cathepsin inhibitors or other protease inhibitors. Enhancement of insulin secretion with short-term exposure to calpain inhibitors is not mediated by increased responses in intracellular Ca2+ or increased glucose metabolism in islets but by accelerated exocytosis of insulin granules. In muscle strips and adipocytes, exposure to both calpain inhibitor II and E-64-d reduced insulin-mediated glucose transport. Incorporation of glucose into glycogen in muscle also was reduced. These results are consistent with a role for calpains in the regulation of insulin secretion and insulin action.

Predictable success with resin bonded fixed partial dentures

The conservative nature of the resin bonded fixed partial denture is the reason it is used. The ability to replace a missing tooth while avoiding aggressive preparation of the abutment teeth is a desirable concept. The use of conservative preparation forms will aid in the long term predictable success of the resin bonded fixed partial denture.

Dentin bonding agents and resin cements--current status

Contemporary restorative dentistry is a rapidly evolving science which challenges the progressive clinician with a plethora of "new and improved" products. Sound product choices should be couched in the prudent consideration of well conducted in vitro and in vivo product research. This review shall list the most recent product developments in dentin bonding agents (fifth generation agents), resin-containing dental cements and the newest generation of dental cements i.e., resin-ionomer dental cements.

Mechanisms underlying impaired GLUT-4 translocation in glycogen-supercompensated muscles of exercised rats

Exercise training induces an increase in GLUT-4 in muscle. We previously found that feeding rats a high-carbohydrate diet after exercise, with muscle glycogen supercompensation, results in a decrease in insulin responsiveness so severe that it masks the effect of a training-induced twofold increase in GLUT-4 on insulin-stimulated muscle glucose transport. One purpose of this study was to determine whether insulin signaling is impaired. Maximally insulin-stimulated phosphatidylinositol (PI) 3-kinase activity was not significantly reduced, whereas protein kinase B (PKB) phosphorylation was approximately 50% lower (P < 0.01) in muscles of chow-fed, than in those of fasted, exercise-trained rats. Our second purpose was to determine whether contraction-stimulated glucose transport is also impaired. The stimulation of glucose transport and the increase in cell surface GLUT-4 induced by contractions were both decreased by approximately 65% in glycogen-supercompensated muscles of trained rats. The contraction-stimulated increase in AMP kinase activity, which has been implicated in the activation of glucose transport by contractions, was approximately 80% lower in the muscles of the fed compared with the fasted rats 18 h after exercise. These results show that both the insulin- and contraction-stimulated pathways for muscle glucose transport activation are impaired in glycogen-supercompensated muscles and provide insight regarding possible mechanisms.

High-fat diet-induced muscle insulin resistance: relationship to visceral fat mass

It has been variously hypothesized that the insulin resistance induced in rodents by a high-fat diet is due to increased visceral fat accumulation, to an increase in muscle triglyceride (TG) content, or to an effect of diet composition. In this study we used a number of interventions: fish oil, leptin, caloric restriction, and shorter duration of fat feeding, to try to disassociate an increase in visceral fat from muscle insulin resistance. Substituting fish oil (18% of calories) for corn oil in the high-fat diet partially protected against both the increase in visceral fat and muscle insulin resistance without affecting muscle TG content. Injections of leptin during the last 4 days of a 4-wk period on the high-fat diet partially reversed the increase in visceral fat and the muscle insulin resistance, while completely normalizing muscle TG. Restricting intake of the high-fat diet to 75% of ad libitum completely prevented the increase in visceral fat and muscle insulin resistance. Maximally insulin-stimulated glucose transport was negatively correlated with visceral fat mass (P < 0.001) in both the soleus and epitrochlearis muscles and with muscle TG concentration in the soleus (P < 0.05) but not in the epitrochlearis. Thus we were unable to dissociate the increase in visceral fat from muscle insulin resistance using a variety of approaches. These results support the hypothesis that an increase in visceral fat is associated with development of muscle insulin resistance.

Scholarship in teaching: an imperative for the 21st century

At some medical schools broader definitions of scholarship have emerged along with corresponding changes in their academic reward systems. Such situations are not common, however. The definition of scholarship generally applied by medical schools is unnecessarily narrow and excludes areas of legitimate academic activity and productivity that are vital to the fulfillment of the school's educational mission. The authors maintain that creative teaching with effectiveness that is rigorously substantiated, educational leadership with results that are demonstrable and broadly felt, and educational methods that advance learners' knowledge are consistent with the traditional definition of scholarship. Faculty whose educational activities fulfill the criteria above are scholars and must be recognized by promotion. The authors specifically address scholarship in education, focusing on teaching and other learning-related activities rather than on educational research, which may be assessed and rewarded using the same forms of evidence as basic science or clinical research. They build on Boyer's work, which provides a vocabulary for discussing the assumptions and values that underlie the roles of faculty as academicians. Next, they apply Glassick et al.'s criteria for judging scholarly work to faculty members' educational activities to establish a basis for recognition and reward consistent with those given for other forms of scholarship. Finally, the authors outline the organizational infrastructure needed to support scholars in education.

Transgenic overexpression of hexokinase II in skeletal muscle does not increase glucose disposal in wild-type or Glut1-overexpressing mice

Glut1 transgenic mice were bred with transgenic mice that overexpress hexokinase II in skeletal muscle in order to determine whether whole-body glucose disposal could be further augmented in mice overexpressing glucose transporters. Overexpression of hexokinase alone in skeletal muscle had no effect on glucose transport or metabolism in isolated muscles, nor did it alter blood glucose levels or the rate of whole-body glucose disposal. Expression of the hexokinase transgene in the context of the Glut1 transgenic background did not alter glucose transport in isolated muscles but did cause additional increases in steady-state glucose 6-phosphate (3.2-fold) and glycogen (7.5-fold) levels compared with muscles that overexpress the Glut1 transporter alone. Surprisingly, however, these increases were not accompanied by a change in basal or insulin-stimulated whole-body glucose disposal in the doubly transgenic mice compared with Glut1 transgenic mice, probably due to an inhibition of de novo glycogen synthesis as a result of the high levels of steady-state glycogen in the muscles of doubly transgenic mice (430 micromol/g versus 10 micromol/g in wild-type mice). We conclude that the hexokinase gene may not be a good target for therapies designed to counteract insulin resistance or hyperglycemia.

Current methods of finish-line exposure by practicing prosthodontists

PURPOSE

The purpose of this study was to survey members of The American College of Prosthodontists to evaluate current methods of finish-line exposure. In addition, frequency of use of epinephrine compounds and observed side effects were assessed.

MATERIALS AND METHODS

A questionnaire was mailed to the 2,436 members of The American College of Prosthodontists. Group differences were evaluated using chi 2 analysis.

RESULTS

Completed questionnaires were returned by 1,246 prosthodontists, which is a return rate of 51%. Ninety-eight percent of respondent prosthodontists use retraction cord, and 48% use a double-cord technique. Plain cord is the most commonly used cord (44%), followed by aluminum chloride-impregnated cord (18%), and epinephrine-impregnated cord (14%). Nine hundred one respondents (81%) soak the cord before placing it in the gingival sulcus. The most common medicament for soaking the cords is buffered aluminum chloride (55%). Side effects to epinephrine were reported by 387 respondents (33%), with the most common side effect reported being increased pulse rate, followed by anxiety. Approximately one quarter (24%) of the prosthodontists surveyed had observed side effects to chemical agents other than epinephrine.

CONCLUSIONS

Prosthodontists throughout the country use many different techniques and agents to expose finish lines. No statistically significant differences (p > .05) were found between year of specialty training completion groups with respect to retraction cord use. Copper bands are used significantly more frequently (p < .05) in the northwest region of the United States than elsewhere.

Effects of endurance exercise training on muscle glycogen accumulation in humans

The purpose of this investigation was to determine whether endurance exercise training increases the ability of human skeletal muscle to accumulate glycogen after exercise. Subjects (4 women and 2 men, 31 +/- 8 yr old) performed high-intensity stationary cycling 3 days/wk and continuous running 3 days/wk for 10 wk. Muscle glycogen concentration was measured after a glycogen-depleting exercise bout before and after endurance training. Muscle glycogen accumulation rate from 15 min to 6 h after exercise was twofold higher (P < 0.05) in the trained than in the untrained state: 10.5 +/- 0.2 and 4.5 +/- 1.3 mmol. kg wet wt(-1). h(-1), respectively. Muscle glycogen concentration was higher (P < 0.05) in the trained than in the untrained state at 15 min, 6 h, and 48 h after exercise. Muscle GLUT-4 content after exercise was twofold higher (P < 0.05) in the trained than in the untrained state (10.7 +/- 1.2 and 4.7 +/- 0.7 optical density units, respectively) and was correlated with muscle glycogen concentration 6 h after exercise (r = 0.64, P < 0.05). Total glycogen synthase activity and the percentage of glycogen synthase I were not significantly different before and after training at 15 min, 6 h, and 48 h after exercise. We conclude that endurance exercise training enhances the capacity of human skeletal muscle to accumulate glycogen after glycogen-depleting exercise.

Hydroxyl radical generation during exercise increases mitochondrial protein oxidation and levels of urinary dityrosine

Isolated mitochondria are well-established sources of oxidants in vitro. There is little direct evidence that mitochondria promote oxidative stress in vivo, however. Model system studies demonstrate that ortho-tyrosine, meta-tyrosine, and o,o'-dityrosine increase in proteins oxidized by hydroxyl radical. To determine whether mitochondria generate oxidants in vivo, we used isotope dilution gas chromatography mass spectrometry to quantify levels of these markers in the heart muscle of control and exercised rats. Exercise led to a 50% increase in ortho-tyrosine, metatyrosine, and o,o'-dityrosine in the mitochondrial proteins but not cytosolic proteins of heart muscle. This increase was transient, and levels returned to normal when exercised animals were allowed to rest. There also was a transient increase in the level of o,o'-dityrosine in the urine of exercised rats. This relationship between mitochondrial and urine levels of o,o'-dityrosine suggests that urine assays of this oxidized amino acid may serve as noninvasive measures of oxidative stress. These observations also provide direct evidence that heart muscle mitochondria produce an intermediate resembling the hydroxyl radical that promotes protein oxidation in vivo.

Decreased insulin-stimulated GLUT-4 translocation in glycogen-supercompensated muscles of exercised rats

It was recently found that the effect of an exercise-induced increase in muscle GLUT-4 on insulin-stimulated glucose transport is masked by a decreased responsiveness to insulin in glycogen-supercompensated muscle. We evaluated the role of hexosamines in this decrease in insulin responsiveness and found that UDP-N-acetyl hexosamine concentrations were not higher in glycogen-supercompensated muscles than in control muscles with a low glycogen content. We determined whether the smaller increase in glucose transport is due to translocation of fewer GLUT-4 to the cell surface with the 2-N-4-(1-azi-2,2,2-trifluroethyl)-benzoyl-1, 3-bis(D-mannose-4-yloxy)-2-propylamine (ATB-[2-3H]BMPA) photolabeling technique. The insulin-induced increase in GLUT-4 at the cell surface was no greater in glycogen-supercompensated exercised muscle than in muscles of sedentary controls and only 50% as great as in exercised muscles with a low glycogen content. We conclude that the decreased insulin responsiveness of glucose transport in glycogen-supercompensated muscle is not due to increased accumulation of hexosamine biosynthetic pathway end products and that the smaller increase in glucose transport is mediated by translocation of fewer GLUT-4 to the cell surface.

Insulin resistance of muscle glucose transport in male and female rats fed a high-sucrose diet

It has been reported that, unlike high-fat diets, high-sucrose diets cause insulin resistance in the absence of an increase in visceral fat and that the insulin resistance develops only in male rats. This study was done to 1) determine if isolated muscles of rats fed a high-sucrose diet are resistant to stimulation of glucose transport when studied in vitro and 2) obtain information regarding how the effects of high-sucrose and high-fat diets on muscle insulin resistance differ. We found that, compared with rat chow, semipurified high-sucrose and high-starch diets both caused increased visceral fat accumulation and insulin resistance of skeletal muscle glucose transport. Insulin responsiveness of 2-deoxyglucose (2-DG) transport measured in epitrochlearis and soleus muscles in vitro was decreased approximately 40% (P < 0.01) in both male and female rats fed a high-sucrose compared with a chow diet. The high-sucrose diet also caused resistance of muscle glucose transport to stimulation by contractions. There was a highly significant negative correlation between stimulated muscle 2-DG transport and visceral fat mass. In view of these results, the differences in insulin action in vivo observed by others in rats fed isocaloric high-sucrose and high-starch diets must be due to additional, specific effects of sucrose that do not carry over in muscles studied in vitro. We conclude that, compared with rat chow, semipurified high-sucrose and high-cornstarch diets, like high-fat diets, cause increased visceral fat accumulation and severe resistance of skeletal muscle glucose transport to stimulation by insulin and contractions.

GLUT-1 or GLUT-4 transgenes in obese mice improve glucose tolerance but do not prevent insulin resistance

Insulin-stimulated glucose uptake is defective in patients with type 2 diabetes. To determine whether transgenic glucose transporter overexpression in muscle can prevent diabetes induced by a high-fat, high-sugar diet, singly (GLUT-1, GLUT-4) and doubly (GLUT-1 and -4) transgenic mice were placed on a high-fat, high-sugar diet or a standard chow diet. On the high-fat, high-sugar diet, wild-type but not transgenic mice developed fasting hyperglycemia and glucose intolerance (peak glucose of 337 +/- 19 vs. 185-209 mg/dl in the same groups on the high-fat, high-sugar diet and 293 +/- 13 vs. 166-194 mg/dl on standard chow). Hyperinsulinemic clamps showed that transporter overexpression elevated insulin-stimulated glucose utilization on standard chow (49 +/- 4 mg. kg-1. min-1 in wild-type vs. 61 +/- 4, 67 +/- 5, and 63 +/- 6 mg. kg-1. min-1 in GLUT-1, GLUT-4, and GLUT-1 and -4 transgenic mice given 20 mU. kg-1. min-1 insulin, and 54 +/- 7, 85 +/- 4, and 98 +/- 11 in wild-type, GLUT-1, and GLUT-4 mice given 60-80 mU. kg-1. min-1 insulin). On the high-fat, high-sugar diet, wild-type and GLUT-1 mice developed marked insulin resistance, but GLUT-4 and GLUT-1 and -4 mice were somewhat protected (glucose utilization during hyperinsulinemic clamp of 28.5 +/- 3.4 vs. 42.4 +/- 5.9, 51.2 +/- 8.1, and 55.9 +/- 4. 9 mg. kg-1. min-1 in wild type, GLUT-1, GLUT-4, GLUT-1 and -4 mice). These data demonstrate that overexpression of GLUT-1 and/or GLUT-4 enhances whole body glucose utilization and prevents the development of fasting hyperglycemia and glucose intolerance induced by a high-fat, high-sugar diet. GLUT-4 overexpression improves the insulin resistance induced by the diet. We conclude that upregulation of glucose transporters in skeletal muscle may be an effective therapeutic approach to the treatment of human type 2 diabetes.

Oxidized amino acids in the urine of aging rats: potential markers for assessing oxidative stress in vivo

Oxidative damage of proteins has been implicated in disease and aging. In vitro studies demonstrate that two unnatural amino acids, o,o'-dityrosine and o-tyrosine, are stable markers of protein oxidation. We have investigated the possibility that assaying these compounds in urine could provide a noninvasive way to determine levels of protein oxidation in vivo. Isotope dilution gas chromatography-mass spectrometry was used to quantify levels of o,o'-dityrosine and o-tyrosine in skeletal muscle and urine of aging rats subjected to two interventions: 1) dietary antioxidant supplementation and 2) exercise training. In both sedentary rats and exercise-trained rats, antioxidant therapy reduced levels of protein-bound o,o'-dityrosine in skeletal muscle. In contrast, antioxidant therapy or exercise training minimally affected o-tyrosine levels in this tissue. Levels of the oxidized amino acids in urine samples mirrored those of skeletal muscle proteins. Quantification of the levels of oxidized amino acids in urine may thus serve as a noninvasive measure of oxidative stress in vivo because they change in parallel with levels of protein-bound oxidized amino acids in skeletal muscle.

Effect of brushing with sonic and counterrotational toothbrushes on the bond strength of orthodontic brackets

The purpose of this study was to evaluate the effect of brushing with both a sonic and mechanical counter rotary power toothbrush on the bond strength of orthodontic brackets. Forty-five extracted teeth were divided into three random groups and had orthodontic brackets bonded to them. One group was brushed with a counterrotational toothbrush, the Interplak, one group with a sonic toothbrush, the Sonicare, and a third group was not brushed and was held as a control. After the equivalent of 2 years brushing, the teeth were placed in an Instron machine and the shear force to remove the brackets was recorded. Group 1, the counter rotary power brush, had a mean of 107.5 kg/cm2, the second group, the sonic brush, had a mean of 79.7 kg/cm2, and the control group had a mean of 125. 4 kg/cm2. Single factor analysis of variance followed by the Fisher-Hayter Multiple Comparison Procedure showed a statistically significant difference between the sonic power brush and the control (P <.01), but no significant difference between the counter rotary and the control (P >.05). There was no significant difference between the two power brushes (P >.05).

Removal of adenosine decreases the responsiveness of muscle glucose transport to insulin and contractions

Adenosine in the extracellular space modulates stimulated glucose transport in striated muscle. In the heart and in adipocytes, adenosine potentiates insulin-stimulated glucose transport. There is controversy regarding the effect of adenosine in skeletal muscle, with reports of both an inhibitory effect and no effect, on insulin-stimulated glucose transport. We found that, in rat epitrochlearis and soleus muscles, removing adenosine with adenosine deaminase or blocking its action with the adenosine receptor blocker CPDPX markedly reduces the responsiveness of glucose transport to stimulation by 1) insulin alone, 2) contractions alone, and 3) insulin and contractions in combination. Measurement of the increase in GLUT4 at the cell surface in response to a maximally effective insulin stimulus in the epitrochlearis muscle, using the exofacial label ATB-[3H]BMPA, showed that adenosine deaminase treatment markedly reduces cell-surface GLUT4 labeling. The reduction in cell-surface GLUT4 labeling was similar in magnitude to the decrease in maximally insulin-stimulated glucose transport activity in adenosine deaminase-treated muscles. These results show that adenosine potentiates insulin- and contraction-stimulated glucose transport in skeletal muscle by enhancing the increase in GLUT4 at the cell surface and raise the possibility that decreased adenosine production or action could play a causative role in insulin resistance.

A high fat diet impairs stimulation of glucose transport in muscle. Functional evaluation of potential mechanisms

A high fat diet causes resistance of skeletal muscle glucose transport to insulin and contractions. We tested the hypothesis that fat feeding causes a change in plasma membrane composition that interferes with functioning of glucose transporters and/or insulin receptors. Epitrochlearis muscles of rats fed a high (50% of calories) fat diet for 8 weeks showed approximately 50% decreases in insulin- and contraction-stimulated 3-O-methylglucose transport. Similar decreases in stimulated glucose transport activity occurred in muscles of wild-type mice with 4 weeks of fat feeding. In contrast, GLUT1 overexpressing muscles of transgenic mice fed a high fat diet showed no decreases in their high rates of glucose transport, providing evidence against impaired glucose transporter function. Insulin-stimulated system A amino acid transport, insulin receptor (IR) tyrosine kinase activity, and insulin-stimulated IR and IRS-1 tyrosine phosphorylation were all normal in muscles of rats fed the high fat diet for 8 weeks. However, after 30 weeks on the high fat diet, there was a significant reduction in insulin-stimulated tyrosine phosphorylation in muscle. The increases in GLUT4 at the cell surface induced by insulin or muscle contractions, measured with the 3H-labeled 2-N-4-(1-azi-2,2, 2-trifluoroethyl)-benzoyl-1,3-bis-(D-mannose-4-yloxy)-2-propyla min e photolabel, were 26-36% smaller in muscles of the 8-week high fat-fed rats as compared with control rats. Our findings provide evidence that (a) impairment of muscle glucose transport by 8 weeks of high fat feeding is not due to plasma membrane composition-related reductions in glucose transporter or insulin receptor function, (b) a defect in insulin receptor signaling is a late event, not a primary cause, of the muscle insulin resistance induced by fat feeding, and (c) impaired GLUT4 translocation to the cell surface plays a major role in the decrease in stimulated glucose transport.

Effect of brushing with sonic and counterrotational toothbrushes on the bond strength of full veneer crowns

STATEMENT OF PROBLEM

Earlier studies on orthodontic brackets have shown a loss of bond strength after a sonic toothbrush was used.

PURPOSE

This in vitro study evaluated the difference in bond strength of single complete veneer crowns after being subjected to the equivalent of 2 years of brushing with sonic and counterrotational toothbrushes.

MATERIAL AND METHODS

Complete gold crowns were fabricated with a conventional indirect technique for 30 extracted, intact, prepared human premolar teeth. Castings were then luted to the teeth with glass ionomer cement. Teeth were randomly divided into 3 groups of 10 teeth each, 1 group to be brushed with Sonicare sonic toothbrush, 1 group to be brushed with Interplak counterrotational mechanical toothbrush, and 1 group as the control. Groups 1 and 2 were then brushed for the equivalent of 2 years per tooth. A uniform force of 50 g for the sonic toothbrush and 120 g for the counterrotational toothbrush was used. Control specimens were not brushed. Brush heads and sample teeth in contact with the toothbrush were kept moist at all times. Tensile dislodgment force was determined with an Instron universal testing machine.

RESULTS

The castings brushed with a sonic toothbrush required a mean of 43.22 kg (+/- 11.16) force to remove the crowns from the teeth, whereas the counterrotational group required a mean of 42.87 kg (+/- 10.42) and the control group a mean of 42.12 kg (+/- 6.61). Analysis of variance on the force data indicated no differences among the 3 groups in the force needed to remove the castings (F[2,24] = 0.031, P = .97).

CONCLUSION

This in vitro study demonstrated no significant differences between groups in the amount of tensile dislodgment force required to remove cemented full veneer crowns from prepared teeth after brushing for the equivalent of 2 years time with a sonic toothbrush or a counterrotational toothbrush.

Increased GLUT-4 translocation mediates enhanced insulin sensitivity of muscle glucose transport after exercise

The purpose of this study was to determine whether the increase in insulin sensitivity of skeletal muscle glucose transport induced by a single bout of exercise is mediated by enhanced translocation of the GLUT-4 glucose transporter to the cell surface. The rate of 3-O-[3H]methyl-D-glucose transport stimulated by a submaximally effective concentration of insulin (30 microU/ml) was approximately twofold greater in the muscles studied 3.5 h after exercise than in those of the sedentary controls (0.89 +/- 0.10 vs. 0.43 +/- 0.05 micromol . ml-1 . 10 min-1; means +/- SE for n = 6/group). GLUT-4 translocation was assessed by using the ATB-[2-3H]BMPA exofacial photolabeling technique. Prior exercise resulted in greater cell surface GLUT-4 labeling in response to submaximal insulin treatment (5.36 +/- 0.45 dpm x 10(3)/g in exercised vs. 3.00 +/- 0.38 dpm x 10(3)/g in sedentary group; n = 10/group) that closely mirrored the increase in glucose transport activity. The signal generated by the insulin receptor, as reflected in the extent of insulin receptor substrate-1 tyrosine phosphorylation, was unchanged after the exercise. We conclude that the increase in muscle insulin sensitivity of glucose transport after exercise is due to translocation of more GLUT-4 to the cell surface and that this effect is not due to potentiation of insulin-stimulated tyrosine phosphorylation.

The regulation of carbohydrate and fat metabolism during and after exercise

The rate of carbohydrate utilization during prolonged, strenuous exercise is closely geared to the energy needs of the working muscles. In contrast, fat utilization during exercise is not tightly regulated, as there are no mechanisms for closely matching availability and metabolism of fatty acids to the rate of energy expenditure. As a result, the rate of fat oxidation during exercise is determined by the availability of fatty acids and the rate of carbohydrate utilization. Blood glucose and muscle glycogen are essential for prolonged strenuous exercise, and exhaustion can result either from development of hypoglycemia or depletion of muscle glycogen. Both absolute and relative (i.e. % of maximal O2 uptake) exercise intensities play important roles in the regulation of substrate metabolism. The absolute work rate determines the total quantity of fuel required, while relative exercise intensity plays a major role in determining the proportions of carbohydrate and fat oxidized by the working muscles. As relative exercise intensity is increased, there is a decrease in the proportion of the energy requirement derived from fat oxidation and an increase in that provided by carbohydrate oxidation. During moderately strenuous exercise of an intensity that can be maintained for 90 minutes or longer ( approximately 55-75% of VO2max), there is a progressive decline in the proportion of energy derived from muscle glycogen and a progressive increase in plasma fatty acid oxidation. The adaptations induced by endurance exercise training result in a marked sparing of carbohydrate during exercise, with an increased proportion of the energy being provided by fat oxidation. The mechanisms by which training decreases utilization of blood glucose are not well understood. However, the slower rate of glycogenolysis can be explained on the basis of lower concentrations of inorganic phosphate (Pi) in trained, as compared to untrained, muscles during exercise of the same intensity. The lower Pi level is a consequence of the increase in muscle mitochondria induced by endurance exercise training. A large increase in muscle glycogen concentration, far above the level found in the well-fed sedentary state, occurs in response to carbohydrate feeding following glycogen depleting exercise. It was recently found that this muscle "glycogen supercompensation" is markedly enhanced by endurance exercise training that induces an increase in the GLUT4 isoform of the glucose transporter in skeletal muscle.

Dissociation of GLUT4 translocation and insulin-stimulated glucose transport in transgenic mice overexpressing GLUT1 in skeletal muscle

Overexpression of the human GLUT1 glucose transporter protein in skeletal muscle of transgenic mice results in large increases in basal glucose transport and metabolism, but impaired stimulation of glucose transport by insulin, contractions, or hypoxia (Gulve, E. A., Ren, J.-M., Marshall, B. A., Gao, J., Hansen, P. A., Holloszy, J. O. , and Mueckler, M. (1994) J. Biol. Chem. 269, 18366-18370). This study examined the relationship between glucose transport and cell-surface glucose transporter content in isolated skeletal muscle from wild-type and GLUT1-overexpressing mice using 2-deoxyglucose, 3-O-methylglucose, and the 2-N-[4-(1-azi-2,2, 2-trifluoroethyl)benzoyl]-1,3-bis(D-mannos-4-yloxy)-2-propyl amine exofacial photolabeling technique. Insulin (2 milliunits/ml) stimulated a 3-fold increase in 2-deoxyglucose uptake in extensor digitorum longus muscles of control mice (0.47 +/- 0.07 micromol/ml/20 min in basal muscle versus 1.44 micromol/ml/20 min in insulin-stimulated muscle; mean +/- S.E.). Insulin failed to increase 2-deoxyglucose uptake above basal rates in muscles overexpressing GLUT1 (4.00 +/- 0.40 micromol/ml/20 min in basal muscle versus 3.96 +/- 0.37 micromol/ml/20 min in insulin-stimulated muscle). A similar lack of insulin stimulation in muscles overexpressing GLUT1 was observed using 3-O-methylglucose. However, the magnitude of the insulin-stimulated increase in cell-surface GLUT4 photolabeling was nearly identical (approximately 3-fold) in wild-type and GLUT1-overexpressing muscles. This apparently normal insulin-stimulated translocation of GLUT4 in GLUT1-overexpressing muscle was confirmed by immunoelectron microscopy. Our findings suggest that GLUT4 activity at the plasma membrane can be dissociated from the plasma membrane content of GLUT4 molecules and thus suggest that the intrinsic activity of GLUT4 is subject to regulation.

Glycogen supercompensation masks the effect of a traininginduced increase in GLUT-4 on muscle glucose transport

Endurance exercise training induces a rapid increase in the GLUT-4 isoform of the glucose transporter in muscle. In fasted rats, insulin-stimulated muscle glucose transport is increased in proportion to the increase in GLUT-4. There is evidence that high muscle glycogen may decrease insulin-stimulated glucose transport. This study was undertaken to determine whether glycogen supercompensation interferes with the increase in glucose transport associated with an exercise-induced increase in GLUT-4. Rats were trained by means of swimming for 6 h/day for 2 days. Rats fasted overnight after the last exercise bout had an approximately twofold increase in epitrochlearis muscle GLUT-4 and an associated approximately twofold increase in maximally insulin-stimulated glucose transport activity. Epitrochlearis muscles of rats fed rodent chow after exercise were glycogen supercompensated (86.4 +/- 4.8 micromol/g wet wt) and showed no significant increase in maximally insulin-stimulated glucose transport above the sedentary control value despite an approximately twofold increase in GLUT-4. Fasting resulted in higher basal muscle glucose transport rates in both sedentary and trained rats but did not significantly increase maximally insulin-stimulated transport in the sedentary group. We conclude that carbohydrate feeding that results in muscle glycogen supercompensation prevents the increase in maximally insulin-stimulated glucose transport associated with an exercise training-induced increase in muscle GLUT-4.

Short-term exposure to tumor necrosis factor-alpha does not affect insulin-stimulated glucose uptake in skeletal muscle

It has been hypothesized that increased production of tumor necrosis factor-alpha (TNF-alpha) plays a role in causing the insulin resistance associated with obesity. Obesity with insulin resistance is associated with increased production of TNF-alpha by fat cells. Exposure of 3T3-L1 adipocytes to TNF-alpha for 3-4 days makes them insulin resistant. TNF-alpha has also been reported to rapidly (15-60 min) cause insulin resistance, with a decrease in insulin-stimulated tyrosine phosphorylation, in a number of cultured cell lines. Because skeletal muscle is the major tissue responsible for insulin-stimulated glucose disposal, we performed the present study to determine if acute exposure to TNF-alpha causes insulin resistance in muscle. We found that exposure of soleus muscles to 6 nmol/l TNF-alpha for 45 min in vitro had no inhibitory effect on insulin-stimulated tyrosine phosphorylation of the insulin receptor or insulin receptor substrate 1 (IRS-1) or on phosphatidylinositol 3-kinase association with IRS-1. Incubation of epitrochlearis and soleus muscles with 6 nmol/l TNF-alpha for 45 min or 4 h had no effect on insulin-stimulated 2-deoxyglucose (2-DG) uptake. Treatment of epitrochlearis muscles with 2 nmol/l TNF-alpha for 8 h also had no effect on insulin-stimulated 2-DG uptake. We conclude that in contrast to Fao hepatoma cells and 3T3-L1 fibroblasts, skeletal muscle does not become insulin resistant in response to short-term exposure to TNF-alpha.

Rapid reversal of adaptive increases in muscle GLUT-4 and glucose transport capacity after training cessation

Previous studies have shown that when exercise is stopped there is a rapid reversal of the training-induced adaptive increase in muscle glucose transport capacity. Endurance exercise training brings about an increase in GLUT-4 in skeletal muscle. The primary purpose of this study was to determine whether the rapid reversal of the increase in maximally insulin-stimulated glucose transport after cessation of training can be explained by a similarly rapid decrease in GLUT-4. A second purpose was to evaluate the possibility, suggested by previous studies, that the magnitude of the adaptive increase in muscle GLUT-4 decreases when exercise training is extended beyond a few days. We found that both GLUT-4 and maximally insulin-stimulated glucose transport were increased approximately twofold in epitrochlearis muscles of rats trained by swimming for 6 h/day for 5 days or 5 wk. GLUT-4 was 90% higher, citrate synthase activity was 23% higher, and hexokinase activity was 28% higher in triceps muscle of the 5-day trained animals compared with the controls. The increases in GLUT-4 protein and in insulin-stimulated glucose transport were completely reversed within 40 h after the last exercise bout, after both 5 days and 5 wk of training. In contrast, the increases in citrate synthase and hexokinase activities were unchanged 40 h after 5 days of exercise. These results support the conclusion that the rapid reversal of the increase in the insulin responsiveness of muscle glucose transport after cessation of training is explained by the short half-life of the GLUT-4 protein.

DHEA treatment reduces fat accumulation and protects against insulin resistance in male rats

The purpose of this study was to determine whether administration of dehydroepiandrosterone (DHEA) protects male rats against the accumulation of body fat the development of insulin resistance with advancing age. We found that supplementation of the diet with 0.3% DHEA between the ages of 5 months and approximately 25 months resulted in a significantly lower final body weight (DHEA, 593 +/- 18 g vs control, 668 +/- 12 g, p < 0.02), despite no decrease in food intake. Lean body mass was unaffected by the DHEA, and the lower body weight was due to a approximately 25% reduction in body fat. The rate of glucose disposal during a euglycemic, hyperinsulinemic clamp was 30% higher in the DHEA group than in the sedentary controls due to a greater insulin responsiveness. The DHEA administration was as effective in reducing body fat content and maintaining insulin responsiveness as exercise in the form of voluntary wheel running. The DHEA had no significant effect on muscle GLUT4 content. A preliminary experiment provided evidence suggesting that muscle insulin signaling, as reflected in binding of phosphatidylinositol 3-kinase to the insulin receptor substrate-1, was enhanced in the DHEA-treated and wheel running groups as compared to controls. These results provide evidence that DHEA, like exercise, protects against excess fat accumulation and development of insulin resistance in rats.

Insulin resistance of muscle glucose transport in rats fed a high-fat diet: a reevaluation

Rats fed a high-fat diet develop skeletal muscle insulin resistance. There is disagreement regarding whether a decrease in the GLUT4 isoform of the glucose transporter is responsible. We found that feeding rats a high-fat diet that reduced the responsiveness of glucose transport to insulin in skeletal muscles by approximately 25-45% in 4 weeks, had no significant effect on muscle GLUT4 content. There is also controversy regarding whether the contraction/anoxia activated pathway of glucose transport stimulation is affected by fat feeding. We found that stimulation of muscle glucose transport by either swimming, in situ contractions, or anoxia was depressed to a similar extent as insulin responsiveness in high-fat-fed rats. It has been suggested that the muscle insulin resistance caused by a high-fat diet is due to increased fat oxidation and glucose-fatty acid cycle activity. However, we found that insulin-stimulated glucose transport was reduced by approximately 40% when muscles of fat-fed rats were incubated under anoxic conditions under which fatty acid oxidation should not occur. Rats maintained on the high-fat diet up to 32 weeks developed the characteristics of the abdominal obesity syndrome, including insulin resistance, hyperinsulinemia, hyperglycemia, elevated LDL cholesterol and VLDL triglycerides, and marked visceral obesity. We conclude that 1) in rats fed a high-fat diet the muscle insulin resistance is not due to a decrease in total GLUT4 content or to increased fat oxidation, 2) fat feeding also results in resistance of muscle glucose transport to stimulation via the contraction/anoxia pathway, and 3) rats fed a high-fat diet may be a useful model of the abdominal obesity syndrome.

DHEA protects against visceral obesity and muscle insulin resistance in rats fed a high-fat diet

Visceral obesity is frequently associated with muscle insulin resistance. Rats fed a high-fat diet rapidly develop obesity and insulin resistance. Dehydroepiandrosterone (DHEA) has been reported to protect against the development of obesity. This study tested the hypothesis that DHEA protects against the increase in visceral fat and the development of muscle insulin resistance induced by a high-fat diet in rats. Feeding rats a diet providing 50% of the energy as fat for 4 wk resulted in a twofold greater visceral fat mass and a 50% lower rate of maximally insulin-stimulated muscle 2-deoxyglucose (2-DG) uptake compared with controls. Rats fed the high-fat diet plus 0.3% DHEA were largely protected against the increase in visceral fat (+ 11.3 g in high fat vs. + 2.9 g in high fat plus DHEA, compared with controls) and against the decrease in insulin-stimulated muscle 2-DG uptake (0.94 +/- 0.15 mumol.ml-1.20 min-1, controls; 0.46 +/- 0.06 mumol.ml-1.20 min-1, high-fat diet; 0.78 +/- 0.07 mumol.ml-1.20 min-1, high fat + DHEA). DHEA did not affect food intake. These results show that DHEA has a protective effect against accumulation of visceral fat and development of muscle insulin resistance in rats fed a high-fat diet.

Effects of epinephrine on insulin-stimulated glucose uptake and GLUT-4 phosphorylation in muscle

beta-Adrenergic stimulation has been reported to inhibit insulin-stimulated glucose transport in adipocytes. This effect has been attributed to a decrease in the intrinsic activity of the GLUT-4 isoform of the glucose transporter that is mediated by phosphorylation of GLUT-4. Early studies showed no inhibition of insulin-stimulated glucose transport by epinephrine in skeletal muscle. The purpose of this study was to determine the effect of epinephrine on GLUT-4 phosphorylation, and reevaluate the effect of beta-adrenergic stimulation on insulin-activated glucose transport, in skeletal muscle. We found that 1 microM epinephrine, which raised adenosine 3',5'-cyclic monophosphate approximately ninefold, resulted in GLUT-4 phosphorylation in rat skeletal muscle but had no inhibitory effect on insulin-stimulated 3-O-methyl-D-glucose (3-MG) transport. In contrast to 3-MG transport, the uptakes of 2-deoxyglucose and glucose were markedly inhibited by epinephrine treatment. This inhibitory effect was presumably mediated by stimulation of glycogenolysis, which resulted in an increase in glucose 6-phosphate concentration to levels known to severely inhibit hexokinase. We conclude that 1) beta-adrenergic stimulation decreases glucose uptake by raising glucose 6-phosphate concentration, thus inhibiting hexokinase, but does not inhibit insulin-stimulated glucose transport and 2) phosphorylation of GLUT-4 has no effect on glucose transport in skeletal muscle.

Muscle glycogen accumulation after endurance exercise in trained and untrained individuals

Muscle glycogen accumulation was determined in six trained cyclists (Trn) and six untrained subjects (UT) at 6 and either 48 or 72 h after 2 h of cycling exercise at approximately 75% peak O2 uptake (VO2 peak), which terminated with five 1-min sprints. Subjects ate 10 g carbohydrate . kg-1 . day-1 for 48-72 h postexercise. Muscle glycogen accumulation averaged 71 +/- 9 (SE) mmol/kg (Trn) and 31 +/- 9 mmol/kg (UT) during the first 6 h postexercise (P < 0.01) and 79 +/- 22 mmol/kg (Trn) and 60 +/- 9 mmol/kg (UT) between 6 and 48 or 72 h postexercise (not significant). Muscle glycogen concentration was 164 +/- 21 mmol/kg (Trn) and 99 +/- 16 mmol/kg (UT) 48-72 h postexercise (P < 0.05). Muscle GLUT-4 content immediately postexercise was threefold higher in Trn than in UT (P < 0.05) and correlated with glycogen accumulation rates (r = 0.66, P < 0.05). Glycogen synthase in the active I form was 2.5 +/- 0.5, 3.3 +/- 0.5, and 1.0 +/- 0.3 micromol . g-1 . min-1 in Trn at 0, 6, and 48 or 72 h postexercise, respectively; corresponding values were 1.2 +/- 0.3, 2.7 +/- 0.5, and 1.6 +/- 0.3 micromol . g-1 . min-1 in UT (P < 0.05 at 0 h). Plasma insulin and plasma C-peptide area under the curve were lower in Trn than in UT over the first 6 h postexercise (P < 0.05). Plasma creatine kinase concentrations were 125 +/- 25 IU/l (Trn) and 91 +/- 9 IU/l (UT) preexercise and 112 +/- 14 IU/l (Trn) and 144 +/- 22 IU/l (UT; P < 0.05 vs. preexercise) at 48-72 h postexercise (normal: 30-200 IU/l). We conclude that endurance exercise training results in an increased ability to accumulate muscle glycogen after exercise.

Phorbol esters stimulate muscle glucose transport by a mechanism distinct from the insulin and hypoxia pathways

Glucose transport in skeletal muscle can be stimulated by insulin and also by contractions and hypoxia. Activation of protein kinase C (PKC) stimulates glucose transport in muscle and other insulin-responsive cells. This study was performed to determine if the diacylglycerol (DAG)/phorbol ester-sensitive PKC isoforms participate in insulin and/or hypoxia-stimulated glucose transport in skeletal muscle. The phorbol ester 12-deoxyphorbol 13-phenylacetate 20-acetate (dPPA) induced a three- to fourfold increase in glucose transport in rat epitrochlearis muscle. The effects of dPPA on glucose transport and on cell surface GLUT-4 were completely additive to the maximal effects of insulin or hypoxia. Phorbol ester treatment induced 5- to 10-fold increases in phosphorylation of the myristoylated alanine-rich C kinase substrate protein in muscle, whereas insulin and hypoxia had negligible effects. Calphostin C, an inhibitor of DAG-sensitive PKC isoforms, decreased glucose transport stimulation by dPPA but not by insulin or hypoxia. These results provide evidence that activation of DAG/phorbol ester-sensitive PKCs is not involved in the pathways by which either insulin or hypoxia stimulates muscle glucose transport. They also show that activation of this group of PKCs increases glucose transport by a mechanism that is independent of and additive to the effects of insulin or hypoxia.

Allergic reaction following insertion of a Pd-Cu-Au fixed partial denture: a clinical report

A severe allergic reaction to a porcelain-fused-to-metal fixed partial denture containing 79% palladium, 2% gold, and 19% copper, resulting in a variety of symptoms and hospitalization of the patient, is reported. The reaction occurred 4 hours after cementation of the fixed partial denture. Suggestions for use of nongold metal alloys are discussed.

Effect of endurance exercise training on muscle glycogen supercompensation in rats

The purpose of this study was to test the hypothesis that the rate and extent of glycogen supercompensation in skeletal muscle are increased by endurance exercise training. Rats were trained by using a 5-wk-long swimming program in which the duration of swimming was gradually increased to 6 h/day over 3 wk and then maintained at 6 h/day for an additional 2 wk. Glycogen repletion was measured in trained and untrained rats after a glycogen-depleting bout of exercise. The rats were given a rodent chow diet plus 5% sucrose in their drinking water and libitum during the recovery period. There were remarkable differences in both the rates of glycogen accumulation and the glycogen concentrations attained in the two groups. The concentration of glycogen in epitrochlearis muscle averaged 13.1 +/- 0.9 mg/g wet wt in the untrained group and 31.7 +/- 2.7 mg/g in the trained group (P < 0.001) 24 h after the exercise. This difference could not be explained by a training effect on glycogen synthase. The training induced approximately 50% increases in muscle GLUT-4 glucose transporter protein and in hexokinase activity in epitrochlearis muscles. We conclude that endurance exercise training results in increases in both the rate and magnitude of muscle glycogen supercompensation in rats.

Insulin unmasks a COOH-terminal Glut4 epitope and increases glucose transport across T-tubules in skeletal muscle

An improved immunogold labeling procedure was used to examine the subcellular distribution of glucose transporters in Lowricryl HM20-embedded skeletal muscle from transgenic mice overexpressing either Glut1 or Glut4. In basal muscle, Glut4 was highly enriched in membranes of the transverse tubules and the terminal cisternae of the triadic junctions. Less than 10% of total muscle Glut4 was present in the vicinity of the sarcolemmal membrane. Insulin treatment increased the number of gold particles associated with the transverse tubules and the sarcolemma by three-fold. However, insulin also increased the total Glut4 immunogold reactivity in muscle ultrathin sections by up to 1.8-fold and dramatically increased the amount of Glut4 in muscle sections as observed by laser confocal immunofluorescence microscopy. The average diameter of transverse tubules observed in longitudinal sections increased by 50% after insulin treatment. Glut1 was highly enriched in the sarcolemma, both in the basal state and after insulin treatment. Disruption of transverse tubule morphology by in vitro glycerol shock completely abolished insulin-stimulated glucose transport in isolated rat epitrochlearis muscles. These data indicate that: (a) Glut1 and Glut4 are targeted to distinct plasma membrane domains in skeletal muscle; (b) Glut1 contributes to basal transport at the sarcolemma and the bulk of insulin-stimulated transport is mediated by Glut4 localized in the transverse tubules; (c) insulin increases the apparent surface area of transverse tubules in skeletal muscle; and (d) insulin causes the unmasking of a COOH-terminal antigenic epitope in skeletal muscle in much the same fashion as it does in rat adipocytes.

Effects of ovariectomy and exercise training on muscle GLUT-4 content and glucose metabolism in rats

The present study examined the effects of 6 wk of ovarian endocrine deficiency on skeletal muscle GLUT-4 glucose transporter protein and glucose transport activity in sedentary and endurance-trained rats. Female Wistar rats (10 wk old) underwent bilateral ovariectomy (OVX) or sham surgery followed by a 5-wk swim-training protocol. OVX resulted in no significant changes in glycogen or GLUT-4 glucose transporter concentration in the soleus, epitrochlearis, or flexor digitorum brevis (FDB) muscles or in basal and maximally insulin-stimulated 2-deoxy-D-[1,2-3H]glucose (2-[3H]DG) transport in the soleus or epitrochlearis, suggesting that moderate-duration ovarian hormone deficiency does not significantly impair insulin action in skeletal muscle. In contrast, OVX decreased the maximal activation of 2-[3H]DG transport in the FDB by in vitro electrical stimulation. OVX had no significant effect on the training-induced changes in oxidative enzyme activities, GLUT-4 protein expression, glycogen content, or insulin-stimulated 2-[3H]DG transport in the soleus or epitrochlearis. These findings provide the first evidence that ovarian hormone deficiency decreases contraction-stimulated glucose transport in skeletal muscle.

Changes in insulin action and GLUT-4 with 6 days of inactivity in endurance runners

The purpose of this investigation was to determine whether decreased insulin action after 6 days of inactivity in endurance-trained runners was associated with a decrease in skeletal muscle glucose transporter protein levels (GLUT-4) in the gastrocnemius muscle. Seven endurance runners (5 men and 2 women) volunteered to participate in this investigation. All subjects had normal glucose tolerance as determined by the National Diabetes Data Group guidelines. Each individual completed two hyperinsulinemic euglycemic clamps at insulin infusion rates of 15 (LO) and 40 (HI) mU.m-2.min-1, one approximately 18 h after a training bout and the second after 6 days of inactivity (IA). Muscle biopsies for the measurement of GLUT-4 were obtained from the gastrocnemius before each clamp. Glucose disposal rates during the last 30 min of each insulin infusion were significantly reduced after 6 days of IA, averaging 6.45 +/- 1.04 mg.kg fat-free mass (FFM)-1.min-1 before and 4.55 +/- 0.56 mg.kg FFM-1.min-1 after detraining for the LO insulin infusion rate and 13.77 +/- 0.88 mg.kg FFM-1.min-1 before and 11.81 +/- 0.60 mg.kg FFM-1.min-1 after detraining for the HI insulin infusion rate (both P < 0.05), despite the fact that plasma insulin was higher in the inactive state (LO, 19.2 +/- 0.9 microU/ml before and 23.4 +/- 1.5 microU/ml after detraining; HI, 56.0 +/- 2.0 microU/ml before and 61.6 +/- 1.6 microU/ml after detraining; P < 0.05)). Calculated insulin clearance was greater in the trained than in the inactive state (P < 0.03). Muscle GLUT-4 transporter protein after 6 days of IA was reduced by 17.5 +/- 5.4% (P < 0.02). These results demonstrate that 6 days of IA reduces insulin action in endurance-trained runners and suggest that a reduction in muscle GLUT-4 transporter level plays a role in the decrease in glucose disposal rates.

Indomethacin in controlling "normal perfusion pressure breakthrough" in a case of large cerebral arteriovenous malformation

Control of "normal perfusion pressure breakthrough" is difficult and controversial. We describe a case in which indomethacin was used with success. We recommend extensive cerebral monitoring including regional cerebral oximetry when using indomethacin to detect impending cerebral ischemia.