Co-overexpression of CD36 and FABPpm increases fatty acid transport additively, not synergistically, within muscle

We aimed to determine the combined effects of over-expressing FABPpm and CD36 on skeletal muscle fatty acid transport to establish if these transport proteins function collaboratively. Electrotransfection with either FABPpm or CD36 increased their protein content at the plasma membrane (+75% and +64%), increased fatty acid transport rates +24% for FABPpm and +62% for CD36, resulting in a calculated transport efficiency of ~0.019 and ~0.053 per unit protein change for FABPpm and CD36, respectively. We subsequently used these data to determine if increasing both proteins additively or synergistically increased fatty acid transport. Co-transfection of FABPpm and CD36 simultaneously increased protein content in whole muscle (FABPpm, +46%; CD36, +45%) and at the sarcolemma (FABPpm, +41% and CD36, +42%), as well as fatty acid transport rates (+50%). Since the relative effects of changing FABPpm and CD36 content had been independently determined, we were able to a predict a change in fatty acid transport based on the overexpression of plasmalemmal transporters in the co-transfection experiments. This prediction yielded an increase in fatty acid transport of +0.984 and +1.722 pmol/mg prot/15sec for FABPpm and CD36, respectively, for a total increase of +2.96 pmol/mg prot/15sec. This calculated determination was remarkably consistent with the measured change in transport, namely +2.89 pmol/mg prot/15sec. Altogether, these data indicate that increasing CD36 and FABPpm alters fatty acid transport rates additively, but not synergistically, suggesting an independent mechanism-of-action within muscle for each transporter. This conclusion was further supported by the observation that plasmalemmal CD36 and FABPpm did not co-immunoprecipitate.

Ablating the protein TBC1D1 impairs contraction-induced sarcolemmal glucose transporter 4 redistribution but not insulin-mediated responses in rats

TBC1 domain family member 1 (TBC1D1), a Rab GTPase-activating protein and paralogue of Akt substrate of 160 kDa (AS160), has been implicated in both insulin- and 5-aminoimidazole-4-carboxamide ribonucleotide formyltransferase/IMP cyclohydrolase-mediated glucose transporter type 4 (GLUT4) translocation. However, the role of TBC1D1 in contracting muscle remains ambiguous. We therefore explored the metabolic consequence of ablating TBC1D1 in both resting and contracting skeletal muscles, utilizing a rat TBC1D1 KO model. Although insulin administration rapidly increased (p < 0.05) plasma membrane GLUT4 content in both red and white gastrocnemius muscles, the TBC1D1 ablation did not alter this response nor did it affect whole-body insulin tolerance, suggesting that TBC1D1 is not required for insulin-induced GLUT4 trafficking events. Consistent with findings in other models of altered TBC1D1 protein levels, whole-animal and ex vivo skeletal muscle fat oxidation was increased in the TBC1D1 KO rats. Although there was no change in mitochondrial content in the KO rats, maximal ADP-stimulated respiration was higher in permeabilized muscle fibers, which may contribute to the increased reliance on fatty acids in resting KO animals. Despite this increase in mitochondrial oxidative capacity, run time to exhaustion at various intensities was impaired in the KO rats. Moreover, contraction-induced increases in sarcolemmal GLUT4 content and glucose uptake were lower in the white gastrocnemius of the KO animals. Altogether, our results highlight a critical role for TBC1D1 in exercise tolerance and contraction-mediated translocation of GLUT4 to the plasma membrane in skeletal muscle.

Extremely rapid increase in fatty acid transport and intramyocellular lipid accumulation but markedly delayed insulin resistance after high fat feeding in rats

AIMS/HYPOTHESIS

The mechanisms for diet-induced intramyocellular lipid accumulation and its association with insulin resistance remain contentious. In a detailed time-course study in rats, we examined whether a high-fat diet increased intramyocellular lipid accumulation via alterations in fatty acid translocase (FAT/CD36)-mediated fatty acid transport, selected enzymes and/or fatty acid oxidation, and whether intramyocellular lipid accretion coincided with the onset of insulin resistance.

METHODS

We measured, daily (on days 1-7) and/or weekly (for 6 weeks), the diet-induced changes in circulating substrates, insulin, sarcolemmal substrate transporters and transport, selected enzymes, intramyocellular lipids, mitochondrial fatty acid oxidation and basal and insulin-stimulated sarcolemmal GLUT4 and glucose transport. We also examined whether upregulating fatty acid oxidation improved glucose transport in insulin-resistant muscles. Finally, in Cd36-knockout mice, we examined the role of FAT/CD36 in intramyocellular lipid accumulation, insulin sensitivity and diet-induced glucose intolerance.

RESULTS

Within 2-3 days, diet-induced increases occurred in insulin, sarcolemmal FAT/CD36 (but not fatty acid binding protein [FABPpm] or fatty acid transporter [FATP]1 or 4), fatty acid transport and intramyocellular triacylglycerol, diacylglycerol and ceramide, independent of enzymatic changes or muscle fatty acid oxidation. Diet-induced increases in mitochondria and mitochondrial fatty acid oxidation and impairments in insulin-stimulated glucose transport and GLUT4 translocation occurred much later (≥21 days). FAT/CD36 ablation impaired insulin-stimulated fatty acid transport and lipid accumulation, improved insulin sensitivity and prevented diet-induced glucose intolerance. Increasing fatty acid oxidation in insulin-resistant muscles improved glucose transport.

CONCLUSIONS/INTERPRETATIONS

High-fat feeding rapidly increases intramyocellular lipids (in 2-3 days) via insulin-mediated upregulation of sarcolemmal FAT/CD36 and fatty acid transport. The 16-19 day delay in the onset of insulin resistance suggests that additional mechanisms besides intramyocellular lipids contribute to this pathology.

Fatty acid transport and transporters in muscle are critically regulated by Akt2

Muscle contains various fatty acid transporters (CD36, FABPpm, FATP1, FATP4). Physiological stimuli (insulin, contraction) induce the translocation of all four transporters to the sarcolemma to enhance fatty acid uptake similarly to glucose uptake stimulation via glucose transporter-4 (GLUT4) translocation. Akt2 mediates insulin-induced, but not contraction-induced, GLUT4 translocation, but its role in muscle fatty acid transporter translocation is unknown. In muscle from Akt2-knockout mice, we observed that Akt2 is critically involved in both insulin-induced and contraction-induced fatty acid transport and translocation of fatty acid translocase/CD36 (CD36) and FATP1, but not of translocation of fatty acid-binding protein (FABPpm) and FATP4. Instead, Akt2 mediates intracellular retention of both latter transporters. Collectively, our observations reveal novel complexities in signaling mechanisms regulating the translocation of fatty acid transporters in muscle.

Activation of AMPKα2 Is Not Required for Mitochondrial FAT/CD36 Accumulation during Exercise

Exercise has been shown to induce the translocation of fatty acid translocase (FAT/CD36), a fatty acid transport protein, to both plasma and mitochondrial membranes. While previous studies have examined signals involved in the induction of FAT/CD36 translocation to sarcolemmal membranes, to date the signaling events responsible for FAT/CD36 accumulation on mitochondrial membranes have not been investigated. In the current study muscle contraction rapidly increased FAT/CD36 on plasma membranes (7.5 minutes), while in contrast, FAT/CD36 only increased on mitochondrial membranes after 22.5 minutes of muscle contraction, a response that was exercise-intensity dependent. Considering that previous research has shown that AMP activated protein kinase (AMPK) α2 is not required for FAT/CD36 translocation to the plasma membrane, we investigated whether AMPK α2 signaling is necessary for mitochondrial FAT/CD36 accumulation. Administration of 5-Aminoimidazole-4-carboxamide ribonucleotide (AICAR) induced AMPK phosphorylation, and resulted in FAT/CD36 accumulation on SS mitochondria, suggesting AMPK signaling may mediate this response. However, SS mitochondrial FAT/CD36 increased following acute treadmill running in both wild-type (WT) and AMPKα 2 kinase dead (KD) mice. These data suggest that AMPK signaling is not required for SS mitochondrial FAT/CD36 accumulation. The current data also implicates alternative signaling pathways that are exercise-intensity dependent, as IMF mitochondrial FAT/CD36 content only occurred at a higher power output. Taken altogether the current data suggests that activation of AMPK signaling is sufficient but not required for exercise-induced accumulation in mitochondrial FAT/CD36.

Both linoleic and α-linolenic acid prevent insulin resistance but have divergent impacts on skeletal muscle mitochondrial bioenergetics in obese Zucker rats

The therapeutic use of polyunsaturated fatty acids (PUFA) in preserving insulin sensitivity has gained interest in recent decades; however, the roles of linoleic acid (LA) and α-linolenic acid (ALA) remain poorly understood. We investigated the efficacy of diets enriched with either LA or ALA on attenuating the development of insulin resistance (IR) in obesity. Following a 12-wk intervention, LA and ALA both prevented the shift toward an IR phenotype and maintained muscle-specific insulin sensitivity otherwise lost in obese control animals. The beneficial effects of ALA were independent of changes in skeletal muscle mitochondrial content and oxidative capacity, as obese control and ALA-treated rats showed similar increases in these parameters. However, ALA increased the propensity for mitochondrial H2O2 emission and catalase content within whole muscle and reduced markers of oxidative stress (4-HNE and protein carbonylation). In contrast, LA prevented changes in markers of mitochondrial content, respiratory function, H2O2 emission, and oxidative stress in obese animals, thereby resembling levels seen in lean animals. Together, our data suggest that LA and ALA are efficacious in preventing IR but have divergent impacts on skeletal muscle mitochondrial content and function. Moreover, we propose that LA has value in preserving insulin sensitivity in the development of obesity, thereby challenging the classical view that n-6 PUFAs are detrimental.

High-fat diet-induced mitochondrial biogenesis is regulated by mitochondrial-derived reactive oxygen species activation of CaMKII

Calcium/calmodulin-dependent protein kinase (CaMK) activation induces mitochondrial biogenesis in response to increasing cytosolic calcium concentrations. Calcium leak from the ryanodine receptor (RyR) is regulated by reactive oxygen species (ROS), which is increased with high-fat feeding. We examined whether ROS-induced CaMKII-mediated signaling induced skeletal muscle mitochondrial biogenesis in selected models of lipid oversupply. In obese Zucker rats and high-fat-fed rodents, in which muscle mitochondrial content was upregulated, CaMKII phosphorylation was increased independent of changes in calcium uptake because sarco(endo)plasmic reticulum Ca(2+)-ATPase (SERCA) protein expression or activity was not altered, implicating altered sarcoplasmic reticulum (SR) calcium leak in the activation of CaMKII. In support of this, we found that high-fat feeding increased mitochondrial ROS emission and S-nitrosylation of the RyR, whereas hydrogen peroxide induced SR calcium leak from the RyR and activation of CaMKII. Moreover, administration of a mitochondrial-specific antioxidant, SkQ, prevented high-fat diet-induced phosphorylation of CaMKII and the induction of mitochondrial biogenesis. Altogether, these data suggest that increased mitochondrial ROS emission is required for the induction of SR calcium leak, activation of CaMKII, and induction of mitochondrial biogenesis in response to excess lipid availability.

Chronic muscle stimulation improves insulin sensitivity while increasing subcellular lipid droplets and reducing selected diacylglycerol and ceramide species in obese Zucker rats

AIMS/HYPOTHESIS

Although insulin resistance has been associated with accumulations of specific intramuscular fatty acids and altered subcellular localisation of lipid droplets, these concepts remain controversial. Therefore, we aimed to identify specific intramuscular fatty acids and subcellular lipid localisations associated with improved insulin sensitivity following chronic muscle contraction.

METHODS

In lean and insulin-resistant obese Zucker rats the tibialis anterior muscle was stimulated (6 h/day for 6 days). Thereafter, muscles were examined for insulin sensitivity, intramuscular lipid droplet localisation and triacylglycerol (TAG), diacylglycerol (DAG) and ceramide fatty acid composition.

RESULTS

In lean and obese animals, regardless of muscle type, chronic muscle contraction improved muscle insulin sensitivity and increased intramuscular levels of total and most C14-C22 TAG fatty acids (p < 0.05). Therefore, accumulation in subcellular lipid droplet compartments reflected the oversupply of lipids within muscle. In contrast, improvements in insulin sensitivity induced by muscle contraction were associated with reductions in specific DAG and ceramide species that were not uniform in red and white muscle of obese rats. However, these reductions were insufficient to fully normalise insulin sensitivity, indicating that other mechanisms are involved.

CONCLUSIONS/INTERPRETATION

Reductions in 18 C length DAG and ceramide species were the most consistent in red and white muscle and therefore may represent therapeutic targets for improving insulin sensitivity.

Exercise- and training-induced upregulation of skeletal muscle fatty acid oxidation are not solely dependent on mitochondrial machinery and biogenesis

  Regulation of skeletal muscle fatty acid oxidation (FAO) and adaptation to exercise training have long been thought to depend on delivery of fatty acids (FAs) to muscle, their diffusion into muscle, and muscle mitochondrial content and biochemical machinery. However, FA entry into muscle occurs via a regulatable, protein-mediated mechanism, involving several transport proteins. Among these CD36 is key. Muscle contraction and pharmacological agents induce CD36 to translocate to the cell surface, a response that regulates FA transport, and hence FAO. In exercising CD36 KO mice, exercise duration (-44%), and FA transport (-41%) and oxidation (-37%) are comparably impaired, while carbohydrate metabolism is augmented. In trained CD36 KO mice, training-induced upregulation of FAO is not observed, despite normal training-induced increases in mitochondrial density and enzymes. Transfecting CD36 into sedentary WT muscle (+41%), comparable to training-induced CD36 increases (+44%) in WT muscle, markedly upregulates FAO to rates observed in trained WT mice, but without any changes in mitochondrial density and enzymes. Evidently, in vivo CD36-mediated FA transport is key for muscle fuel selection and training-induced FAO upregulation, independent of mitochondrial adaptations. This CD36 molecular mechanism challenges the view that skeletal muscle FAO is solely regulated by muscle mitochondrial content and machinery.

Munc18c provides stimulus-selective regulation of GLUT4 but not fatty acid transporter trafficking in skeletal muscle

Insulin-, and contraction-induced GLUT4 and fatty acid (FA) transporter translocation may share common trafficking mechanisms. Our objective was to examine the effects of partial Munc18c ablation on muscle glucose and FA transport, FA oxidation, GLUT4 and FA transporter (FAT/CD36, FABPpm, FATP1, FATP4) trafficking to the sarcolemma, and FAT/CD36 to mitochondria. In Munc18c(-/+) mice, insulin-stimulated glucose transport and GLUT4 sarcolemmal appearance were impaired, but were unaffected by contraction. Insulin- and contraction-stimulated FA transport, sarcolemmal FA transporter appearance, and contraction-mediated mitochondrial FAT/CD36 were increased normally in Munc18c(-/+) mice. Hence, Munc18c provides stimulus-specific regulation of GLUT4 trafficking, but not FA transporter trafficking.

In vivo, fatty acid translocase (CD36) critically regulates skeletal muscle fuel selection, exercise performance, and training-induced adaptation of fatty acid oxidation

For ~40 years it has been widely accepted that (i) the exercise-induced increase in muscle fatty acid oxidation (FAO) is dependent on the increased delivery of circulating fatty acids, and (ii) exercise training-induced FAO up-regulation is largely attributable to muscle mitochondrial biogenesis. These long standing concepts were developed prior to the recent recognition that fatty acid entry into muscle occurs via a regulatable sarcolemmal CD36-mediated mechanism. We examined the role of CD36 in muscle fuel selection under basal conditions, during a metabolic challenge (exercise), and after exercise training. We also investigated whether CD36 overexpression, independent of mitochondrial changes, mimicked exercise training-induced FAO up-regulation. Under basal conditions CD36-KO versus WT mice displayed reduced fatty acid transport (-21%) and oxidation (-25%), intramuscular lipids (less than or equal to -31%), and hepatic glycogen (-20%); but muscle glycogen, VO(2max), and mitochondrial content and enzymes did not differ. In acutely exercised (78% VO(2max)) CD36-KO mice, fatty acid transport (-41%), oxidation (-37%), and exercise duration (-44%) were reduced, whereas muscle and hepatic glycogen depletions were accelerated by 27-55%, revealing 2-fold greater carbohydrate use. Exercise training increased mtDNA and β-hydroxyacyl-CoA dehydrogenase similarly in WT and CD36-KO muscles, but FAO was increased only in WT muscle (+90%). Comparable CD36 increases, induced by exercise training (+44%) or by CD36 overexpression (+41%), increased FAO similarly (84-90%), either when mitochondrial biogenesis and FAO enzymes were up-regulated (exercise training) or when these were unaltered (CD36 overexpression). Thus, sarcolemmal CD36 has a key role in muscle fuel selection, exercise performance, and training-induced muscle FAO adaptation, challenging long held views of mechanisms involved in acute and adaptive regulation of muscle FAO.

Acute endurance exercise increases plasma membrane fatty acid transport proteins in rat and human skeletal muscle

Fatty acid transport proteins are present on the plasma membrane and are involved in the uptake of long-chain fatty acids into skeletal muscle. The present study determined whether acute endurance exercise increased the plasma membrane content of fatty acid transport proteins in rat and human skeletal muscle and whether the increase was accompanied by an increase in long-chain fatty acid transport in rat skeletal muscle. Sixteen subjects cycled for 120 min at ∼60 ± 2% Vo(2) peak. Two skeletal muscle biopsies were taken at rest and again following cycling. In a parallel study, eight Sprague-Dawley rats ran for 120 min at 20 m/min, whereas eight rats acted as nonrunning controls. Giant sarcolemmal vesicles were prepared, and protein content of FAT/CD36 and FABPpm was measured in human and rat vesicles and whole muscle homogenate. Palmitate uptake was measured in the rat vesicles. In human muscle, plasma membrane FAT/CD36 and FABPpm protein contents increased 75 and 20%, respectively, following 120 min of exercise. In rat muscle, plasma membrane FAT/CD36 and FABPpm increased 20 and 30%, respectively, and correlated with a 30% increase in palmitate transport following 120 min of running. These data suggest that the translocation of FAT/CD36 and FABPpm to the plasma membrane in rat skeletal muscle is related to the increase in fatty acid transport and oxidation that occurs with endurance running. This study is also the first to demonstrate that endurance cycling induces an increase in plasma membrane FAT/CD36 and FABPpm content in human skeletal muscle, which is predicted to increase fatty acid transport.

Elevated expression of tumor necrosis factor-alpha signaling molecules in colonic tumors of Zucker obese (fa/fa) rats

Zucker obese rats are highly sensitive to colon cancer and possess a plethora of metabolic abnormalities including elevated levels of cytokine tumor necrosis factor-alpha (TNF-alpha). The main objective of this study was to determine if physiologically elevated TNF-alpha affects colonic tumor phenotype with regard to an altered TNF-alpha signaling pathway. Zucker obese (fa/fa, homozygous recessive for dysfunctional leptin receptors), Zucker lean (Fa/fa, Fa/Fa) and Sprague-Dawley (SD) rats were injected twice with azoxymethane (10 mg/kg) over 2 weeks. After 30 weeks, the animals were terminated and physiological and tumor parameters were assessed. Obese rats had notably higher body and organ weights as well as plasma TNF-alpha, insulin and leptin levels than lean or SD animals. A 100% tumor incidence and significantly higher tumor size, multiplicity and burden were found in obese rats compared to the lean group that had 47.8% tumor incidence. The SD group had the lowest tumor incidence (20.0%). Tumors from obese animals had higher protein levels of TNF-alpha, TNF-alpha-receptor-2 (TNFR2), nuclear transcription factor-kappaB (NF-kappaB) and IkappaB-kinasebeta (IKKbeta) compared to lean animals. In both obese and lean groups, expression levels of these proteins were higher in tumors than in surrounding, normal-appearing colonic mucosae. These findings support an important role for TNF-alpha signaling in tumorigenesis and demonstrate that tumors growing in an obese state had significantly different expression levels of TNFR2 and NF-kappaB, proteins known to play a critical role in growth and survival, than those growing in the lean state. It is concluded that the physiological state of the host intricately affects tumor phenotype.

FAT/CD36-null mice reveal that mitochondrial FAT/CD36 is required to upregulate mitochondrial fatty acid oxidation in contracting muscle

The plasma membrane fatty acid transport protein FAT/CD36 is also present at the mitochondria, where it may contribute to the regulation of fatty acid oxidation, although this has been challenged. Therefore, we have compared enzyme activities and rates of mitochondrial palmitate oxidation in muscles of wild-type (WT) and FAT/CD36 knockout (KO) mice, at rest and after muscle contraction. In WT and KO mice, carnitine palmitoyltransferase-I, citrate synthase, and β-hydroxyacyl-CoA dehydrogenase activities did not differ in subsarcolemmal (SS) and intermyofibrillar (IMF) mitochondria of WT and FAT/CD36 KO mice. Basal palmitate oxidation rates were lower ( P < 0.05) in KO mice (SS −18%; IMF −13%). Muscle contraction increased fatty acid oxidation (+18%) and mitochondrial FAT/CD36 protein (+16%) in WT IMF but not in WT SS, or in either mitochondrial subpopulation in KO mice. This revealed that the difference in IMF mitochondrial fatty acid oxidation between WT and KO mice can be increased ∼2.5-fold from 13% under basal conditions to 35% during muscle contraction. The FAT/CD36 inhibitor sulfo- N-succinimidyl oleate (SSO), inhibited palmitate transport across the plasma membrane in WT, but not in KO mice. In contrast, SSO bound to mitochondrial membranes and reduced palmitate oxidation rates to a similar extent in both WT and KO mitochondria (∼80%; P < 0.05). In addition, SSO reduced state III respiration with succinate as a substrate, without altering mitochondrial coupling (P/O ratios). Thus, while SSO inhibits FAT/CD36-mediated palmitate transport at the plasma membrane, SSO has undefined effects on mitochondria. Nevertheless, the KO animals reveal that FAT/CD36 contributes to the regulation of mitochondrial fatty acid oxidation, which is especially important for meeting the increased metabolic demands during muscle contraction.

Additive effects of insulin and muscle contraction on fatty acid transport and fatty acid transporters, FAT/CD36, FABPpm, FATP1, 4 and 6

Insulin and muscle contraction increase fatty acid transport into muscle by inducing the translocation of FAT/CD36. We examined (a) whether these effects are additive, and (b) whether other fatty acid transporters (FABPpm, FATP1, FATP4, and FATP6) are also induced to translocate. Insulin and muscle contraction increased glucose transport and plasmalemmal GLUT4 independently and additively (positive control). Palmitate transport was also stimulated independently and additively by insulin and by muscle contraction. Insulin and muscle contraction increased plasmalemmal FAT/CD36, FABPpm, FATP1, and FATP4, but not FATP6. Only FAT/CD36 and FATP1 were stimulated in an additive manner by insulin and by muscle contraction.

Greater transport efficiencies of the membrane fatty acid transporters FAT/CD36 and FATP4 compared with FABPpm and FATP1 and differential effects on fatty acid esterification and oxidation in rat skeletal muscle

In selected mammalian tissues, long chain fatty acid transporters (FABPpm, FAT/CD36, FATP1, and FATP4) are co-expressed. There is controversy as to whether they all function as membrane-bound transporters and whether they channel fatty acids to oxidation and/or esterification. Among skeletal muscles, the protein expression of FABPpm, FAT/CD36, and FATP4, but not FATP1, correlated highly with the capacities for oxidative metabolism (r>or=0.94), fatty acid oxidation (r>or=0.88), and triacylglycerol esterification (r>or=0.87). We overexpressed independently FABPpm, FAT/CD36, FATP1, and FATP4, within a normal physiologic range, in rat skeletal muscle, to determine the effects on fatty acid transport and metabolism. Independent overexpression of each fatty acid transporter occurred without altering either the expression or plasmalemmal content of other fatty acid transporters. All transporters increased fatty acid transport, but FAT/CD36 and FATP4 were 2.3- and 1.7-fold more effective than FABPpm and FATP1, respectively. Fatty acid transporters failed to alter the rates of fatty acid esterification into triacylglycerols. In contrast, all transporters increased the rates of long chain fatty acid oxidation, but the effects of FABPpm and FAT/CD36 were 3-fold greater than for FATP1 and FATP4. Thus, fatty acid transporters exhibit different capacities for fatty acid transport and metabolism. In vivo, FAT/CD36 and FATP4 are the most effective fatty acid transporters, whereas FABPpm and FAT/CD36 are key for stimulating fatty acid oxidation.

Outcome of cataract extraction and posterior chamber intraocular lens implantation following glaucoma filtration surgery

PURPOSE

To evaluate the outcome of cataract extraction (CE) after glaucoma filtering surgery (GFS).

METHODS

A total of 77 eyes (77 patients) who underwent CE with posterior chamber intraocular lens (PCIOL) implantation following GFS by a single surgeon were reviewed. Main outcome measures were preoperative and postoperative intraocular pressures (IOPs), visual acuities, medications, astigmatism, bleb survival, time of surgical failure, complications, and success rate.

RESULTS

Mean time interval between GFS and CE was 46.8+/-50.9 months (range, 2-348 months). The mean preoperative IOP was 13.9+/-4.7 mmHg (range 3-27 mmHg) and mean postoperative IOP at 3 weeks was 13.6+/-5.5 mmHg (range, 6-44 mmHg). The mean follow-up was 19.5+/-20.1 months (range, 1.4-73 months; median 10.6 months). Complete success was achieved in 59 eyes (76.7%). The cumulative probability of complete success was 91.3+/-3.7, 82.0+/-5.6 and 78.1+/-6.5% at the end of 6 months, 1, and 2 years, respectively. Visual acuity before CE was < or =20/50 in all eyes (100%). Visual acuity at last visit was > or =20/40 in 33 eyes (42.8 %), 20/50-20/80 in 30 eyes (39.0%), < or =20/100 in 14 eyes (18.2%). Risk factors identified for qualified success included age at CE>60 years, interval of < or =5 months between GFS and CE, use of preoperative glaucoma medications, and postoperative IOP >19 mmHg within 2 weeks.

CONCLUSIONS

IOP and bleb function was maintained after CE with PCIOL implantation following successful GFS with good visual recovery.

Anterior capsular staining with trypan blue for capsulorhexis in mature and hypermature cataracts. A preliminary study

PURPOSE

To study the efficacy and safety of 0.1% Trypan Blue dye to stain the anterior capsule for capsulorhexis in mature and hypermature cataracts.

METHODS

This preliminary study included 25 eyes of 25 patients with a unilateral mature or hypermature cataract, including one case of traumatic mature cataract. In all these cases 0.2 ml of 0.1% trypan blue dye was used to stain the anterior capsule. The efficacy and safety of the dye was evaluated on the basis of intraoperative and postoperative observations.

RESULTS

In all 25 eyes the capsulorhexis was completed. There was peripheral extension of the capsulorhexis in the eye with traumatic cataract and the stained edge of the anterior capsule helped identification and redirection of the capsulorhexis. Successful phacoemulsification with intraocular lens implantation was performed in all eyes. Adverse reactions related to the dye such as raised intraocular pressure, anterior chamber inflammation and endothelial damage were not observed in the immediate postoperative period or at the end of mean follow-up of 3 months.

CONCLUSION

Trypan blue dye staining of the anterior capsule appears to be a very useful and safe technique that simplifies capsulorhexis in mature and hypermature cataracts.

Measuring professionalism in a physiatry residency training program

A 12-item questionnaire modeled after the one prepared by the American Board of Internal Medicine dealing with professionalism was distributed to 122 physiatry residents representing six training programs, of whom 59% (72) responded. The mean item score on the survey was 7.7 (SD = 1.0) on a scale from 1 to 10, where 10 represents the highest level of professionalism. The internal reliability of the questionnaire was found to be satisfactory (Cronbach's alpha = 0.75). A factor analysis of the questionnaire items resulted in three factors explaining 64% of the variance. These factors were: excellence, honor/integrity, and altruism/respect; Eigen values were 3.35, 2.37, and 1.31, respectively. These factors are similar to those obtained in the American Board of Internal Medicine survey. This similarity is a positive feature in ongoing efforts to develop a reliable tool for measuring professionalism in physiatry residency training.

One program's experience of OSCE vs. written board certification results: a pilot study

The objective structured clinical examination (OSCE) has been the focus of a lot debate with respect to reliability and validity. Much of the controversy surrounding these components lies in a lack of comparison with a "gold standard." Further work is needed to improve the evaluation of clinical skills to the point that a gold standard can truly be said to exist.

Malignant melanoma of ciliary body: a case report

Ocular malignant melanomas are infrequently seen in Indian patents and most them involve the choroid. Ciliary body malignant melanoma is rather rare. This case report illustrates an occurrence in an Indian patient.

Lipaemia retinalis in a case of juvenile diabetic ketoacidosis

A rare case of diabetic retinal lipaemia is described in a 5-year-old child.

Evidence-based medicine in physiatry: the experience of one department's faculty and trainees

Evidence-based medicine is regarded by many as the new paradigm in medical practice. Sixty-seven medical school faculty and trainees in a physical medicine and rehabilitation department were surveyed with regard to training and competence in the use of evidence-based medicine techniques. The majority of subjects in the present study supported the use of evidence-based medicine techniques, although a number of the respondents indicated that they lacked adequate training or competence in their use. It is suggested that medical schools and physiatry residency programs provide a greater emphasis on training in evidence-based medicine. Recommendations are provided that individuals can use to develop a systematic strategy to keep up with the rapidly expanding medical literature.

Physiatric research fellows' perceptions of the quality of their training

A survey was conducted to evaluate the physiatric research fellowship training. A 22-item questionnaire was sent to the 42 identified physiatrists who had completed at least a 1-yr research fellowship. Twenty-nine of these individuals (69%) responded. The physiatrists, all of whom have completed their research fellowships, uniformly cited competent faculty research mentors as being critical, even if they were not in the same department. Having protected research time as well as a research didactic program and journal club were highly rated issues. The trainees preferred a 2-yr fellowship that also stressed initiation of their own research, grant writing and management experience, and first authorship on research papers. We conclude that the majority of the research fellows agree on what are important issues with respect to their training.

Further experience in development of an objective structured clinical examination for physical medicine and rehabilitation residents

Since the last report, two additional objective structured clinical examinations (PGY-2, PGY-3, and PGY-4, as well as incoming PGY-2) have been administered. As a result, our curriculum has been modified to strengthen physical examination skills, including specific workshops. Interrater reliability of evaluators has been tested for the first time to verify reliability, and refinements have been made in the standardized checklist grading system. The interrater grading of history-taking had good reliability (0.73-0.96), as did neurological and spine physical examination (0.84-0.88). The interrater grading reliability of small and large joint examination was more problematic (0.46-0.62) because of examiners' inability to have full visibility, evaluator's fatigue, and confusing evaluation scoring descriptions. We now use a two-point grading scale (correct or incorrect) for history but continue a three-point scale (correct, partially correct, or incorrect) for physical examination. The examination schedule is being modified to add more encounters, give time for trainee feedback, and further refinement of grading expectations for a more efficient and reliable scoring system.

Residency training in physiatry during a time of change: funding of graduate medical education and other issues

Decision makers at the federal and state level are considering, and some states have enacted, a reduction in total United States residency positions, a shift in emphasis from specialist to generalist training, a need for programs to join together in training consortia to determine local residency position allocation strategy, a reduction in funding of international medical graduates, and a reduction in funding beyond the first certificate or a total of five years. A 5-page, 24-item questionnaire was sent to all physiatry residency training directors. The objective was to discern a descriptive database of physiatry training programs and how their institutions might respond to cuts in graduate medical education funding. Fifty-eight (73%) of the questionnaires were returned. Most training directors believe that their primary mission is to train general physiatrists and, to a much lesser extent, to train subspecialty or research fellows. Directors were asked how they might handle reductions in house staff such as using physician extenders, shifting clinical workload to faculty, hiring additional faculty, and funding physiatry residents from practice plans and endowments. Physiatry has had little experience (29%; 17/58) with voluntary graduate medical education consortiums, but most (67%; 34/58) seem to feel that if a consortium system is mandated, they would favor a local or regional over a national body because they do not believe the specialty has a strong enough national stature. The major barriers to a consortium for graduate medical education allocation were governance, academic, fiscal, bureaucratic, and competition.

Chronic fatigue syndrome: a literature review from a physiatric perspective

To examine the literature on chronic fatigue syndrome (CFS), especially as it relates to cognitive deficits and exercise, more than 200 articles related to CFS were selected from computer-based research as well as pertinent articles noted in the references of individual articles. All were relevant articles on CFS, although articles in a foreign language were excluded. CFS is a controversial diagnosis of exclusion, but certain subgroups do appear to exist. It may represent multiple diseases or multiple stages of the same disease. Although cognitive deficits are commonly reported, the measured impairments are relatively subtle and are in the area of complex information processing speed, or efficiency. Magnetic resonance imaging, single-photon emission computer tomography, and neuroendocrine studies present preliminary evidence suggestive of the cerebral involvement primarily in the white matter. The weakness and fatigue may be the result of alterations in the central nervous system, not in the peripheral muscles. However, it is hard to separate the documented weakness and endurance deficits from deconditioning. Autonomic symptoms such as orthostatic intolerance and a predisposition to neurally mediated syncope may be explained by cardiovascular deconditioning, a postviral idiopathic autonomic neuropathy, or both. The review points out the need for more carefully designed studies of CFS that focus on the relationship between neuropathology, psychopathology and neuropsychologic functioning. The role of exercise as a stimulus for exacerbation or in treatment needs to be further studied using clear diagnostic criteria as well as control groups that carefully match the activity level.

Clinical dysautonomia in diabetes mellitus--a study with seven autonomic reflex function tests

Thirty-eight patients of NIDDM, 12 of IDDM and 10 healthy age matched controls were subjected to seven standardised autonomic reflex function tests. A scoring criteria was utilised for diagnosing and grading the severity of dysautonomia. Eight patients of IDDM and 24 of NIDDM had dysautonomia. One-third of the patients in each group had grade IV autonomic dysfunction. Severity of autonomic dysfunction was directly related to the duration of disease in NIDDM whereas in IDDM this relation was not seen. Peripheral neuropathy was almost always associated with dysautonomia in NIDDM. On the contrary, in IDDM dysautonomia was independent of peripheral neuropathy. Charcot's arthopathy, dysphagia, constipation and nocturnal diarrhea were always associated with evidence of dysautonomia. Other symptoms viz. gustatory sweating, postural dizziness and impotence did not necessarily indicate dysautonomia.

Practice and career satisfaction among physiatrists. A national survey

To evaluate physiatrist career satisfaction and current practice patterns, a 15-page survey was mailed randomly to 400 fellow members of the American Academy of Physical Medicine and Rehabilitation. The 208 questionnaires (52%) returned revealed respondents' level of satisfaction with career choice, current practice, relationships with other physicians, their own residency training, and problems experienced that impede their practice. Factor analysis identified six areas of satisfaction: time demands, organizational support, current practice, current specialty, profession, and training. Problems with work consisted of four factors: external intrusions into practice, having to deal with non-rehabilitation problems, dealing with PM&R problems, and insufficient time for patients. Results showed that 75% of physiatrists were satisfied with their practice/profession. Satisfaction with current practice was greater with fewer external intrusions into practice, a larger percentage of income from traditional non-managed payment sources (including Medicaid), and less competition. Changes in health care, such as managed care, competition, and increased external regulations, appear to interfere with current practice. Variation in satisfaction was not significantly correlated with size of community, variation in rates of payment denials, workloads of greater than 50 hours per week, and a number of other factors that one might expect to affect satisfaction. Physiatrists had made many changes in their practice in response to the changes in the health care environment but had not cut care for indigent patients. Needs for greater residency training in outpatient clinics, physicians' offices, managed care, and long-term care settings were expressed. This is the first comprehensive published report on physiatric satisfaction in a changing health care environment. Further research in some of the areas will be required.

Development of an objective structured clinical examination (OSCE) for physical medicine and rehabilitation residents

Clinical competency is poorly measured by knowledge-based written examinations. A five-station, four-interstation objective structured clinical examination (OSCE) has been developed in consultation with the National Board of Medical Examiners as a pilot study to standardize assessment methods that serve to evaluate the clinical competency of senior physical medicine and rehabilitation residents. Various stations demonstrating musculoskeletal and neurologic conditions commonly encountered in physiatric practice were included, incorporating the use of standardized patients into the OSCE format. This is a descriptive study of individual stations-evaluated history-taking, physical examination, and communication skills, whereas the interstations measured the residents' ability to write therapy and prosthetic/orthotic prescriptions, as well as interpret x-ray and electrodiagnostic data. The OSCE program development including case background, principal tasks, time allotment, evaluation objectives, performance criteria, therapeutic plan, standardized patients case descriptions, and assessment checklists as well as the training procedure is discussed. Additionally, cost analysis and scheduling issues are reviewed. This information should aid other training programs or consortiums in developing similar clinical evaluation tools.

Clinical assessment of autonomic functions in anemics

Sixty five anemics and 20 healthy control subjects carefully age and sex matched were subjected to seven standardised tests to evaluate autonomic status. Due care was taken to remove factors which could interfare with the results. Tests concerned with the basal parasympalhetec tone viz heart rate response to standing (p < 0.001) and intravenous atropine test (p < 0.05) showed significant difference which persisted with severity and type of anemia. Test requiring stimulation of the parasympathatic system i.e. deep breathing test, valsalva maneuver and carotid sinus massage did show not significant difference. No difference of significance was found with postural fall of blood pressure and sustained hand grip test, chiefly concerned with the sympathatic system. These results suggest that anemics have low basal parasympathatic outflow to increase the heart rate as compensatory mechanism. Stimulation of parasympathatic and sympathetic system arouse normal response.

Factors influencing the specialty choice of the physical medicine and rehabilitation graduating class of 1994 and the entering class of 1995

To understand better how career choices are made by physiatrists, a 16-item, 7-page questionnaire was sent to all 1994 graduating physical medicine and rehabilitation (PM&R) resident physicians in the United States. Of the 343 senior residents, 202 completed the questionnaire for a response rate of 59%. The questionnaire focused on the following areas: timing of the decision to enter PM&R; and how the medical school curriculum, certain groups of people, and certain specific factors influenced their choices. There were 130 factors modeled after the American Association of Medical Colleges (AAMC) annual medical student questionnaire that the recipients were asked to grade on a numerical scale: 1 = unimportant to 5 = very important. Of the graduating residents, 60.1% (119/198) made the decision to enter PM&R in their 3rd or 4th yr of medical school, 13.1% (26/198) in the first 2 yr, and 11.1% (22/198) after starting another residency. The five factors ranked most important in the decision were (mean rank score): sufficient time/flexibility for family obligations (4.60); opportunity to make a difference in peoples lives (4.57); interest in helping people (4.55); types of patient problems encountered (4.50); and consistency with personality (4.49). We also obtained the AAMC's 1993 annual data on medical students choosing PM&R. Their top five factors were the same as those listed by the graduating residents, but in a slightly different rank order. Profiles have also been derived on those graduating PM&R residents who chose an academic career (n = 68) v nonacademic (n = 133) and fellowship (n = 34) v nonfellowship (n = 163).

Postoperative transcutaneous oxygen measurement in the prediction of delayed wound healing and prosthetic fitting among amputees during rehabilitation. A pilot study

Postoperative assessment of amputation wound healing remains largely subjective in nature, being based on the physician's clinical judgement. These considerations significantly impact on the rehabilitation course, as premature prosthetic fitting may result in wound breakdown. Alternatively, delayed healing may result in prolonged hospital length of stay. Few attempts have been made to correlate objective parameters of limb perfusion with amputation wound healing or prosthetic fitting outcome during the rehabilitation phase of treatment. A pilot study was conducted, in which the transcutaneous oxygen monitor, a noninvasive device measuring transcutaneous partial pressure of oxygen (tcpO2), was applied to the stumps of 11 consecutive above-or below-knee amputees admitted for rehabilitation after amputation. All patients were tested within 1 wk of admission and 45 days of amputation. The treatment team was blinded as to the test results. A direct correlation was observed between wound healing outcome and tcpO2 results (Fisher's exact test [FET], P = 0.03), and no patient with a tcpO2 of < or 15 mm Hg healed during their rehabilitation stay (FET, P = 0.006). TcpO2 of < or = 15 mm Hg was significantly correlated with prolonged length of stay (Point Biserial Correlation Coefficient [rpbi], = -0.835; P = 0.01), delayed prosthetic fitting (rpbi = 0.742; p = 0.01), and poorer wound healing at admission (rpbi = 0.932; P = 0.001). Postoperative tcpO2 measurement may have use in objectively identifying patients at greater risk of delayed wound healing and prosthetic fitting, although further study is warranted.

Methods used in the evaluation of clinical competency of physical medicine and rehabilitation residents

A 17-item questionnaire was designed to determine how physical medicine and rehabilitation (PM&R) training directors assess their residents' clinical competency. A response rate of 83% (62/75) was obtained. Seventy-nine percent (49/62) have a written resident supervision policy, and 73% (45/62) have a written resident probation policy. Ninety-four percent (58/62) believe that their system of evaluating residents' clinical competency is effective, although many commented that it could be improved. 76% (47/62) of the residency training directors made the final decision regarding residents' clinical competency. Fifty-two percent (32/62) have a departmental written examination, and 23% (14/62) have formal oral examinations. Eighteen percent (11/62) use an objective structured clinical examination (OSCE), 8% (5/62) use standardized patients and 3% (2/62) use videotaped patient encounters. Forty percent (25/62) use medical record audits. Fifty percent of the programs have rated at least one resident unsatisfactory during a clinical rotation in the past 3 yr, and 11% (7/62) have reported to the American Board of Physical Medicine and Rehabilitation that the overall clinical evaluation of one resident was unsatisfactory in the past 3 yr. Forty-seven percent (29/62) of the programs have asked at least one resident to leave their program in the past 3 yr. The OSCE is emerging as the state-of-the-art method for assessing clinical skills, although it is expensive. The measurement of clinical competency is important in the certification and recertification process, and our specialty needs better methods to assess these performance skills.

Factors used by physical medicine and rehabilitation residency training directors to select their residents

A 17-item questionnaire was designed to assess the relative importance of various factors to physical medicine and rehabilitation (PM&R) training directors when ranking PM&R resident applicants during the National Resident Match. The questionnaire was sent to all PM&R residency training directors. The recipients were asked to grade most selection factors based on a numerical scale: 1, unimportant; 2, some importance; 3, important; 4, very important; 5, critical. The specific factors addressed in the questionnaire were: academic criteria, letters of recommendation, individual applicant characteristics and aspects of the interview process. Twelve yes-or-no questions were also designed to determine the weight that residency training directors place on certain academic criteria. A response rate of 88% (66/75) was obtained. The most important academic criteria were grades in a PM&R clerkship in their facility (4.1 +/- 0.8), followed by grades in a PM&R clerkship in another facility (3.6 +/- 0.9). The most important letters of recommendation were from a PM&R faculty member in the respondent's department (4.0 +/- 0.8), followed by the dean's letter (3.7 +/- 1.0) and the PM&R chairman's letter (3.7 +/- 1.0). The three most important applicant characteristics evaluated during the interview were compatibility with the program (4.4 +/- 0.8), the ability to articulate thoughts (4.2 +/- 0.8) and the ability to work with the team (4.2 +/- 0.8). Most program directors used multiple criteria to complete their rank list, but the most important were based upon the interview (4.5 +/- 0.9), letters of recommendation (3.7 +/- 0.9), medical school transcript (3.6 +/- 0.8) and the dean's letter (3.6 +/- 1.1).(ABSTRACT TRUNCATED AT 250 WORDS)

Chief residents in physiatry. Expectations v training

A large majority of physical medicine and rehabilitation residencies have chief resident positions, but little has been written about the expectations of the program directors and the training of the chief resident to fulfill those expectations. A 20-item questionnaire was mailed to 73 program directors in physical medicine and rehabilitation in May 1992. The participants were asked about selection methods, their perception of the duties of the chief resident(s), their concerns about the chief resident(s) position, the training and the evaluation of the chief resident(s). An 85% (62/73) response rate was achieved. There was a chief resident position(s) in 98% of the programs responding. Chief resident selection was made mostly by appointment of the chairman and/or program director and/or the vote of the faculty. The program directors perceived the most important duties of the chief resident to be: act as a liaison between faculty and the residents, act as a role model, do scheduling, build teamwork and give constructive feedback. The most important skills were considered to be leadership and stress management. Causes of concern were time pressure, abuse of power, stress and work overload. Opportunities to develop leadership and administrative/management skills were considered the most exciting aspects of the position. It was surprising, however, that only 15 of 61 (25%) provided some formal training. Only 28 of 61 (46%) had a position description.

A method to assess the trainee profiles of medical students attracted to our physical medicine and rehabilitation residency training program

A 35-item questionnaire was designed to assess the relative importance of various factors to medical students when ranking physical medicine and rehabilitation (PM&R) residency training programs. The questionnaire was used to assess the relative importance of the various factors to three groups of medical students: those who interviewed, those who matched and those who were listed on the match list of the UMDNJ-New Jersey Medical School (NJMS) Department of PM&R, as well as our current residents. Recipients were asked to grade selection factors based on a numerical scale: 1, extremely important; 2, very important; 3, important; 4, minimally important; 5, not important. A response rate of 100% (n = 72 medical students + 25 residents) was attained. The analysis indicates that, overall, there is no significant difference in ranking of the factors by each of the four groups. However, the medical students who recently matched with the UMDNJ-NJMS PM&R program rated the opportunity to conduct research significantly higher than the current house staff or the medical students on the entire match list. This is a desirable result, as the program strives to provide an environment that is conducive to the growth of research and academic physiatrists. This questionnaire could also be used by other residency training directors to guide the development of their program and to gain valuable information regarding the perception of their program among in-coming residents and the importance of various factors to the students interested in their program.

Current status of chairpersons in physical medicine and rehabilitation

There are currently 77 academic departments, divisions or units of physical medicine and rehabilitation (PM&R) in the United States. The authors conducted a survey to develop a profile of the current chairpersons of PM&R, as well as to assess the short- and long-term needs of the field. The survey addressed basic demographic information as well as the level of formal training and/or experience in various management, patient care and academic areas. The level of satisfaction with various aspects of the position such as workload, relationship with the university and role as a researcher were also measured. The chairpersons were asked when they plan to vacate their position and if they felt there were any members of their faculty who are qualified and ready to assume a chairperson position. Those that identified a qualified individual were then asked whether the person had formal training and/or experience in the various management, patient care and academic areas. The results indicate that, although the chairpersons have a high level of job satisfaction with respect to the challenge of the position and their administrative and supervisory roles, they are least satisfied with their role as a researcher. The field must be concerned with this finding, because academic PM&R units in the United States will experience a substantial change in leadership by the end of the 20th century. Approximately 39% of the current chairpersons who returned the questionnaire are planning to step down by 1999, with an additional 37% unsure when they will vacate the position.(ABSTRACT TRUNCATED AT 250 WORDS)

Selecting a physical medicine and rehabilitation residency

A 35-item questionnaire, designed to assess the relative importance of various factors to medical students when ranking physical medicine and rehabilitation (PM&R) residency training programs during the Match, was sent to all members of the 1991 senior class after Match Day. This mailing was coordinated with the National Resident Matching Program. The questionnaire was also sent to all PM&R residency training program directors and all physiatrist faculty members at the University of Medicine and Dentistry of New Jersey--New Jersey Medical School (UMDNJ-NJMS). Recipients were asked to grade selection factors based on a numerical scale: 1, extremely important; 2, very important; 3, important; 4, minimally important; 5, not important. A response rate of 41% (73/179) for medical students, 87% (62/71) for residency training directors and 71% (22/31) for UMDNJ-NJMS faculty members was attained. Analysis of the results indicates that, overall, there is no significant difference in ranking of the factors by each of the three groups surveyed. The intergroup responses for one-third of the factors were significantly different. Diversity of the training experience, current house officer satisfaction, it "feels" right and house officer quality were the four most important selection factors to the medical students.

Resident interest in physical medicine and rehabilitation fellowships. Results of a survey

Physiatry, one of the six medical specialties that does not currently offer added or special qualification certification examinations, does not have accredited fellowships in potential subspecialty areas. These issues are currently being debated by the leadership organizations within physical medicine and rehabilitation such as the Association of Academic Physiatrists, the American Academy of Physical Medicine and Rehabilitation, the Physical Medicine and Rehabilitation Residency Review Committee and the American Board of Physical Medicine and Rehabilitation. Recent events, such as the establishment of funding agencies with an interest in medical rehabilitation research training, suggest that physiatric fellowships may become more available. A survey was conducted to determine whether physiatric residents desire postresidency training and, if interested, what type of additional training they would seek. This information could be used in formulating policies regarding the establishment, accreditation and certification of subspecialty fellowships within physical medicine and rehabilitation. Of 968 physiatric residents currently in training, 525 (54%) responded to a 22-question survey assessing resident interest regarding fellowship training, the different subspecialty areas, salary expectations, fellowship duration, preferred amount of time devoted to clinical v research work, mentorship, double boarding, accreditation, certification and a section for general comments. The results of the survey indicate considerable interest in fellowship training, which diminishes as residents approach graduation. Residents favored clinically oriented fellowships of 1-yr duration, which should be accredited and certified. Sports medicine was identified as the area of greatest subspecialty interest.