1Noll Physiological Research Center and 2Department of Chemistry, Pennsylvania State University, University Park, Pennsylvania 16802; 3Department of Cellular and Molecular Physiology, Hershey Medical Center, Pennsylvania State University, Hershey, Pennsylvania 17033; and 4Department of Clinical Neurophysiology, University Hospital, SE-751 85 Uppsala, Sweden
Submitted 29 October 2002 ; accepted in final form 13 April 2003
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ABSTRACT |
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in vitro motility; skeletal muscle fibers; speed of contraction
It is well known that glycation of proteins is an important mechanism underlying aging- and diabetes-related alterations in protein structure, function, and digestibility (4, 25). It is also known that proteins with a slow turnover rate are preferential targets for posttranslational modifications. Myosin, the molecular motor protein in skeletal muscle that converts chemical energy into mechanical work, has been reported to have a half-life as long as 2930 days (17). The aging-related decrease in myosin turnover rate (3) and the lysine-rich regions of the actin-binding site, along with the catalytic domain, make myosin a potential target for modification by glycation. For instance, increased amounts of glycated myosin have been reported in skeletal muscles of aged rodents (31).
In a recent series of experiments, it was demonstrated that glycation of
myosin impairs myosin function by altering the structural properties of the
motor protein (30). A
single-fiber in vitro motility assay was used in which myosin was extracted
from single muscle fiber segments. The effect on actin motility speed of
30-min incubations with 6 mM glucose (with or without -mercaptoethanol)
and with a low-salt buffer or a nonreducing sugar (6 mM sucrose) was measured
for both fast and slow myosin. Thirty minutes of exposure to the reducing
sugar without
-mercaptoethanol had a dramatic effect on both the actin
motility speed and the pattern of filament movement. Motility speed decreased
by
80%, and filaments demonstrated a random motility pattern rather than
the linear motion observed in the control experiments. On the other hand, the
additional incubations had no impact on either motility speed or motility
pattern (30). After 30 min of
glucose exposure, matrix-assisted laser desorption ionization (MALDI) mass
spectra of Lysobacter enzymogenes endoproteinase Lys-C digest of
treated myosin revealed structural modifications in the catalytic domain of
the motor protein. Thus glycation of sarcomeric myosin had a significant
effect on both the structural and functional properties of the motor protein
(30).
The tripeptide GSH is the most abundant nonprotein thiol located in the cytosol and mitochondria of mammalian cells (24). GSH is primarily synthesized in the liver and released into the circulation for transport to peripheral tissues (29). It is a nonenzymic antioxidant that has several antioxidant functions. GSH serves as a substrate for glutathione peroxidase (GPX) and also scavenges singlet oxygen and hydroxyl radicals (16). The GPX system is seen as essential in skeletal muscle, where oxidative stress and lipid peroxidation increase dramatically with increased work, exercise, infection, or disease (29). GSH and glutathione disulfide (GSSG) constitute the most important redox buffer in animal cells both in the cytosol and in the organelles (5). Furthermore, the GSH redox status in human neuroblastoma cells is altered by AGEs because of a decrease in the concentration of the reduced form of GSH (7).
GSH and glucose-6-phosphate dehydrogenase deficiency is reported to increase protein glycation in hemoglobin (13). GSH has also been shown to inhibit glycation of eye lens proteins by dehydroascorbate through a mechanism attributed to reduction of dehydroascorbate to ascorbate (26). A subsequent study showed that GSH inhibits protein glycation by glucosamine (1). However, the influence of GSH on the effect of glycation on skeletal muscle myosin function has not been studied to date. We hypothesize that GSH plays an important role in reversing the effect of early glycation of myosin, namely, formation of Schiff base between myosin and glucose.
To test this hypothesis, we used the single-fiber in vitro motility assay to explore the effects of GSH treatment of myosin that was extracted from single soleus muscle fibers of rats after a 30-min 6 mM glucose incubation.
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MATERIALS AND METHODS |
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Muscle fiber preparation. Small bundles of 2550 fibers
were dissected free from the muscle and tied to glass micro-capillary tubes.
The bundles were then placed in skinning solution at 3°C for 24 h and
treated with a cryoprotectant (sucrose) for long-term storage at -80°C
(8,
19,
21). Before use in the in
vitro motility assay, a sucrose-treated bundle was transferred to a 2.0 M
sucrose solution for 30 min and subsequently incubated in solutions of
decreasing sucrose concentrations (1.50.5 M). The bundle was then
stored in skinning solution at -20°C and was used within 2 wk.
In vitro motility assay. Actin was purified from rabbit skeletal
muscle as previously described
(27) and was
fluorescent-labeled with rhodamine-phalloidin (Rh-Ph; Molecular Probes, OR). A
fiber segment from the soleus muscle was placed on a glass slide between two
strips of grease, and a coverslip precoated with 0.1% nitrocellulose in amyl
acetate was placed on top, thus creating a flow cell of 2.5-µl volume.
Myosin was extracted from the fiber segment through the addition of high-salt
buffer (0.5 M KCl, 25 mM HEPES pH 7.6, 4 mM MgCl2, 4 mM EGTA, 2 mM
ATP, 1%
-mercaptoethanol). After a 30-min incubation on ice, a low-salt
buffer (25 mM KCl, 25 mM HEPES pH 7.6, 4 mM MgCl2, 1 mM EGTA, 1%
-mercaptoethanol) was applied followed by BSA (1 mg/ml) in low-salt
buffer. To block nonfunctional myosin molecules, unlabeled F-actin filaments
in low-salt buffer (15 µM) were sonicated for 1 min and infused into the
flow cell. To remove F-actin from the functional myosin heads, low-salt buffer
containing 2 mM ATP was applied followed by low-salt buffer. Subsequently,
Rh-Ph-labeled actin filaments in low-salt buffer (20 nM) and low-salt buffer
were added to the flow cell. Filament movement was initiated by adding
motility buffer (2 mM ATP, 0.1 mg/ml glucose oxidase, 23 µg/ml catalase,
2.5 mg/ml glucose in low-salt buffer).
The flow cell was placed on the stage of an inverted epifluorescence microscope (Olympus IX 70, Olympus America), and the fluorescent-labeled actin filaments were visualized through a x60 objective (numerical aperture 0.7) with illumination from a 100-W mercury lamp. The temperature of the flow cell was thermostatically controlled at 25°C (Bionomic Controller, BC-100, 20/20 Technology) by a thermometer probe (HH21, Omega Engineering) placed in contact with the surface of the glass slide next to the flow cell. Actin movement was filmed with an image-intensified SIT camera (SIT 66, DAGE-MIT) and recorded on VCR tape (1012).
As observed in previous experiments, the amount of myosin extracted from a single fiber segment has an impact on the effects of the reducing sugar glucose on motility speed (Ramamurthy et al., unpublished observations). In an attempt to achieve similarity in the amounts of extracted myosin in the 2.5-µl experimental chamber, the length of the fiber segment was kept constant (2 mm) in all experiments.
Motility data analysis. From each single-fiber preparation, 10 actin filaments moving with constant speed in an oriented motion were selected for speed analysis. With the exception of preparations incubated with glucose, in which a larger fraction of the filaments moved randomly, recordings and analyses were performed only on preparations in which >90% of the filaments moved bidirectionally. With an image analysis package (OPTIMAS 6.0, Optimas), a filament was tracked from the center of mass and the speed was calculated from 20 frames at an acquisition rate of 1 frame/s. The average speed and standard deviation of the 10 filaments were calculated. Because the standard deviation in this group of filaments was small (between 10 and 15% of the mean), the average speed was taken as representative of the muscle fiber (1012).
Incubations and motility speed analyses. Preincubation data were
obtained from motility speed measurements on myosin extracted from a single
fiber as described in Motility data analysis. To acquire
postincubation values, the extracted myosin was incubated with 1) 6
mM glucose (Sigma; >99.5%, HPLC grade, without -mercaptoethanol) for
30 min followed by either 10 mM GSH (Sigma; >98.0%) in low-salt buffer
(without
-mercaptoethanol) or low-salt buffer [with 1% (130 mM)
-mercaptoethanol] for 20 min; 2) low-salt buffer (with
-mercaptoethanol) for 50 min; or 3) 10 mM GSH (without
-mercaptoethanol) for 50 min. Furthermore, to obtain postincubation
recordings for a dose-response relationship, 30-min incubations of myosin with
1, 3, and 6 mM glucose (without
-mercaptoethanol) were performed.
Motility speed was analyzed before and after the respective incubations.
Postincubation data were obtained by the following method. Two segments (2 mm each) of a fiber were used to obtain the pre- and postincubation values, i.e., myosin isolated from the first fiber segment was assayed to obtain preincubation data and myosin from the second segment was incubated with selected solutions to obtain postincubation data. In previous experiments we showed (11) that there is no significant difference in motility speed when myosin is extracted from two adjacent segments of the same fiber. In addition, we showed (30) the same effects on motility speed in response to glucose exposure when the same segment of the fiber was used for both pre- and postincubation experiments as when two separate segments of the same fiber were used for pre- and postincubation experiments, respectively. However, on occasion, removal of the labeled actin from the preincubation preparation proved difficult and hence interfered with postincubation measurements when the first method (using the same segment for both pre- and postincubation measurements) was employed. Therefore, the second method using two segments of the same fiber was chosen. This method eliminated the ambiguity due to the interference created by the presence of actin filaments remaining from the preincubation preparation (30).
Separation and identification of myofibrillar protein isoforms. Myosin heavy chain (MyHC) isoforms were separated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) from a separate part of the single fiber segments analyzed in the in vitro motility assay. The total acrylamide and bis-acrylamide concentrations were 4% (wt/vol) in the stacking gel and 7% in the running gel, whereas the gel matrix included 30% glycerol. Sample loads were equivalent to 0.1 mm of the fiber segment. The separating gels (160 x 180 x 0.75 mm) were silver stained (see Refs. 9, 20, 21).
Statistics. Means ± SD of data collected were calculated from individual values by standard procedures. A one-way ANOVA and a two-tailed paired t-test were used for comparison. Differences were considered significant at P < 0.05.
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RESULTS |
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Dose-response relationship. To test the effect of increasing glucose concentrations on motility speed, myosin extracted from a 2-mm fiber segment was incubated in 1, 3, and 6 mM glucose for 30 min. A graded and significant reduction in motility speed from preincubation values was observed for all three concentrations, thus confirming a dose-response relationship (Fig. 1). After the 1 mM glucose incubation, motility speed decreased (P < 0.05) 10% from preincubation (1.02 ± 0.07 µm/s, n = 3) to postincubation (0.93 ± 0.05 µm/s, n = 3) values. After the 3 mM glucose incubation, motility speed decreased (P < 0.05) 34% from preincubation (1.22 ± 0.26 µm/s, n = 3) to postincubation (0.81 ± 0.15 µm/s, n = 3) values. Finally, after the 6 mM glucose incubation, motility decreased (P < 0.001) by >90% from preincubation (1.12 ± 0.04 µm/s, n = 3) to postincubation (0.10 ± 0.07 µm/s, n = 3) values.
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Effects of glucose and GSH incubations on actin motility speed. In all preparations, incubations for 30 min with 6 mM glucose reduced motility speed (P < 0.001) by >90%. Subsequent incubation with 10 mM GSH for 20 min restored motility speed (0.98 ± 0.06 µm/s, n = 3) to almost preincubation levels (1.12 ± 0.06 µm/s, n = 3; Fig. 2). Postglucose low-salt buffer incubations did not, on the other hand, increase motility speed (0.03 ± 0.05 µm/s, n = 3) to preincubation values (1.13 ± 0.04 µm/s, n = 3). Furthermore, a 1620% decrease (P < 0.001) in motility speed was observed in response to a 50-min incubation with GSH in low-salt buffer or with low-salt buffer alone (Fig. 2). However, these changes were significantly smaller than the effects of glucose exposure, and it is suggested that they represent a nonspecific degradation of the motor protein.
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There was a greater reduction in motility speed, which was more consistent, in response to glucose incubation in the present study than in our previous report (30). This was because of the more consistent amount of myosin extracted from each fiber (Ramamurthy et al., unpublished observations). In the present study, extraction of similar amounts of myosin was ensured in each experiment by controlling the length of the fiber to 2 mm in each preparation. This control of the amount of myosin extracted enabled us to obtain a consistent postglucose incubation response as well as to test the dose-response relationship of myosin with 1, 3, and 6 mM glucose.
Changes in actin motility pattern in response to glucose and subsequent GSH incubations. Bidirectional movement by at least 90% of the total number of moving actin filaments has been determined to be one of the criteria for acceptance in this single-fiber in vitro motility assay. All recordings fulfilled this criterion except for the postglucose incubation recordings. After the 30-min 6 mM glucose exposure, the large majority of the actin filaments showed no motility, but the few filaments that were moving typically showed a random rather than bidirectional motility pattern. This is in accordance with previous observations after 30 min of incubation with 6 mM glucose (30). Deviations from linearity of postglucose incubation and restoration of linearity of subsequent GSH incubation are depicted in Fig. 3.
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DISCUSSION |
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Glycation of myosin has an impact on both structure and function of the
motor protein. as shown in a recent study
(30). Structural analyses
using MALDI mass spectrometry demonstrated the disappearance of a Lys-C
digestion product corresponding to the ATPase site of myosin after 30-min
incubation with a reducing sugar, with concomitant appearance of
higher-molecular-mass peptides. This change was paralleled by a significant
impairment in myosin function, i.e., motility speed and bidirectional movement
of actin filaments were affected by the glucose incubation. After 30 min of
incubation of myosin with glucose, motility speed dropped significantly by
80% in both fast (type IIxb and IIb) and slow (type I) myosin isoforms
and bidirectionality of the actin filaments was lost. These dramatic changes
in myosin function were confirmed in the present study, i.e., motility speed
was reduced by >90% after 30 min of 6 mM glucose exposure. However,
incubation with 10 mM GSH for 20 min restored motility to almost preincubation
values, whereas postglucose buffer incubation had no effect on motility. This
would therefore confirm that we are dealing with a GSH-specific effect.
GSH is primarily synthesized in the liver and released into the circulation
for transport to peripheral tissues
(6). The membrane-bound enzyme
-glutamyltransferase cleaves GSH into its amino acids for transport
into the cell. These amino acids are utilized for intracellular synthesis of
GSH (24). GSH and GSSG play a
very important role as redox buffers in the cytosol as well as in the
organelles. Tissue levels of GSH vary widely between different tissues, with
the highest concentrations in the eye lens (
10 mM) and the lowest
concentrations in fast-twitch skeletal muscles (
0.5 mM). However, there
are muscle type-specific differences in GSH and total glutathione content (GSH
and GSSG) related to the oxidative capacity of the muscle. GSH contents in the
slow-twitch oxidative rat soleus (
3 mM) is higher than that found in
erythrocytes as well as in lung and brain tissue
(15).
GSH has several antioxidant functions. First, it readily interacts with a variety of radicals, including hydroxyl and carbon radicals, by donating a proton (36). A second important antioxidant function of GSH is to act as a cosubstrate of GPX in the elimination of both H2O2 and other organic peroxides. In this reaction, GSH donates a pair of protons and two GSH molecules are oxidized to form GSSG. GSSG is converted back to GSH through the catalytic action of glutathione reductase, with NADPH providing the reducing power (15). The reducing power for the glutathione reductase system in skeletal muscle is mainly provided by NADP-specific isocitrate dehydrogenase (22).
In skeletal muscle, unlike many tissues, antioxidant enzyme activities including GPX appear to increase with age (14, 16). This can be attributed to an increase in the insults of oxidative stress and other oxidative stress-mediated modifications in the cells, such as glycation, during the aging process. However, there are to our knowledge no studies focusing on the role of GSH in relation to glycation of intracellular proteins. The only study published so far has demonstrated an increased glycation of extracellular proteins in response to a GSH deficiency (13). Furthermore, AGEs have been known to alter the GSH redox state in human neuroblastoma cells, generally toward more oxidizing conditions (7).
It is well known that GSH is an important antioxidant. In addition to its
antioxidant functions, GSH is also a reactive nucleophile that plays an
important role in the breakdown of exogenous and endogenous electrophilic
toxins. The present results demonstrate that GSH reverses the formation of
early glycation products. The restoration of motility by GSH after incubation
with a reducing sugar implies a reversal of Schiff base formation. Strong
nucleophiles such as hydroxylamine can displace carbonyl groups from protein
side chains. GSH is capable of reacting with reactive carbonyl groups, forming
hemithioacetals, as is the case with -oxoaldehydes
(33,
34). We propose that GSH
degrades early glycation products as a strong nucleophile that displaces
glucose, and potentially other carbonyl compounds, from the Schiff base
adducts at the lysine residues of myosin.
In skeletal muscle, increased amounts of glycated myosin and a glycation-induced decline in myosin ATP-ase activity have been reported in aging rodent skeletal muscle (31, 32). During aging, GSH and total glutathione content is known to increase in skeletal muscles of rats (23). A concomitant increase in the oxidative stress in skeletal muscles during aging (see Ref. 28) as measured by malondialdehyde levels is also observed in healthy, active elderly women. In light of these observations, it can be surmised that the increase in GSH content could primarily be targeted toward combating the increased oxidative stress, and it could potentially also play a role in the reversal of early glycation products in skeletal muscle. However, despite the increase in GSH content during the aging process, glycation of myofibrillar proteins is found to increase with age. Deuther-Conrad et al. (7) report that AGEs cause a dose-dependent and long-term increase in GSSG in vitro. This could, in part, explain the decrease in efficacy of GSH in controlling the formation of AGEs in aged tissue.
Nonenzymatic glycation has been implicated in the pathophysiology of diabetes and aging (31, 35, 37). The present results suggest that GSH, in addition to its antioxidant function, could play an important role in preventing the progress of glycation of intracellular proteins. This is, to our knowledge, the first report documenting the direct effects of GSH in reversing early glycation effects on myosin.
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DISCLOSURES |
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ACKNOWLEDGMENTS |
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FOOTNOTES |
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The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
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REFERENCES |
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![]() ![]() ![]() ![]() ![]() ![]() |
---|
2. Avigad G, Kniep A, and Bailin G. Reaction of rabbit skeletal myosin with D-glucose 6-phosphate. Biochem Mol Biol Int 40: 273284, 1996.[ISI][Medline]
3. Balagopal P,
Rooyackers OE, Adey DB, Ades PA, and Nair KS. Effects of aging on in vivo
synthesis of skeletal muscle myosin heavy-chain and sarcoplasmic protein in
humans. Am J Physiol Endocrinol Metab
273: E790E800,
1997.
4. Brownlee M. Advanced protein glycosylation in diabetes and aging. Annu Rev Med 46: 223234, 1995.[ISI][Medline]
5. Csala M, Fulceri R, Mandl J, Benedetti A, and Banhegyi G. Ryanodine receptor channel-dependent glutathione transport in the sarcoplasmic reticulum of skeletal muscle. Biochem Biophys Res Commun 287: 696700, 2001.[ISI][Medline]
6. Deneke SM and
Fanburg BL. Regulation of cellular glutathione. Am J Physiol
Lung Cell Mol Physiol 257:
L163L173, 1989.
7. Deuther-Conrad W, Loske C, Schinzel R, Dringen R, Riederer P, and Munch G. Advanced glycation endproducts change glutathione redox status in SH-SY5Y human neuroblastoma cells by a hydrogen peroxide dependent mechanism. Neurosci Lett 312: 2932, 2001.[ISI][Medline]
8. Frontera WR and Larsson L. A methodological study on three different techniques for membrane permeabilization of human single muscle cells obtained by percutaneous biopsy. Muscle Nerve 20: 948952, 1997.[ISI][Medline]
9. Giulian GG, Moss RL, and Greaser M. Improved methodology for analysis and quantitation of proteins on one-dimensional silver-stained slab gels. Anal Biochem 129: 277287, 1983.[ISI][Medline]
10. Hook P and Larsson L. Actomyosin interactions in a novel single muscle fiber in vitro motility assay. J Muscle Res Cell Motil 21: 357365, 2000.[ISI][Medline]
11. Hook P, Li X,
Sleep J, Hughes S, and Larsson L. In vitro motility speed of slow myosin
extracted from single soleus fibers from young and old rats. J
Physiol 520:
463471, 1999.
12. Höök P, Sriramoju V, and Larsson L. Effects of aging
on actin sliding speed on myosin from single skeletal muscle cells of mice,
rats, and humans. Am J Physiol Cell Physiol
280: C782C788,
2001.
13. Jain SK. Glutathione and glucose-6-phosphate dehydrogenase deficiency can increase protein glycosylation. Free Radic Biol Med 24: 197201, 1998.[ISI][Medline]
14. Ji LL, Dillon
D, and Wu E. Alteration of antioxidant enzymes with aging in rat skeletal
muscle and liver. Am J Physiol Regul Integr Comp
Physiol 258:
R918R923, 1990.
15. Ji LL, Fu R,
and Mitchell EW. Glutathione and antioxidant enzymes in skeletal muscle:
effects of fiber type and exercise intensity. J Appl
Physiol 73:
18541859, 1992.
16. Ji LL,
Leeuwenburgh C, Leichtweis S, Gore M, Fiebig R, Hollander J, and Bejma J.
Oxidative stress and aging. Role of exercise and its influences on antioxidant
systems. Ann NY Acad Sci 854:
102117, 1998.
17. Kay J. Intracellular protein degradation. Biochem Soc Trans 6: 789797, 1978.[Medline]
18. Lal S, Chithra P, and Chandrakasan G. The possible relevance of autoxidative glycosylation in glucose mediated alterations of proteins: an in vitro study on myofibrillar proteins. Mol Cell Biochem 154: 95100, 1996.[ISI][Medline]
19. Larsson L, Höök P, and Pircher P. Regulation of human muscle contraction at the cellular and molecular levels. Ital J Neurol Sci 20: 413422, 1999.[ISI][Medline]
20. Larsson L, Li X, Teresi A, and Salviati G. Effects of thyroid hormone on fast- and slow-twitch skeletal muscles in young and old rats. J Physiol 481: 149161, 1994.[Abstract]
21. Larsson L and Moss RL. Maximum velocity of shortening in relation to myosin isoform composition in single fibers from human skeletal muscles. J Physiol 472: 595614, 1993.[Abstract]
22. Lawler JM and Demaree SR. Relationship between NADP-specific isocitrate dehydrogenase and glutathione peroxidase in aging rat skeletal muscle. Mech Ageing Dev 122: 291304, 2001.[ISI][Medline]
23. Leeuwenburgh C,
Fiebig R, Chandwaney R, and Ji LL. Aging and exercise training in skeletal
muscle: responses of glutathione and antioxidant enzyme systems. Am
J Physiol Regul Integr Comp Physiol 267:
R439R445, 1994.
24. Meister A and Anderson ME. Glutathione. Annu Rev Biochem 52: 711760, 1983.[ISI][Medline]
25. Mooradian AD and Wong NC. Molecular biology of aging. Part II: A synopsis of current research. J Am Geriatr Soc 39: 717723, 1991.[ISI][Medline]
26. Ortwerth BJ and Olesen PR. Glutathione inhibits the glycation and crosslinking of lens proteins by ascorbic acid. Exp Eye Res 47: 737750, 1988.[ISI][Medline]
27. Pardee JD and Spudich JA. Purification of muscle actin. Methods Cell Biol 24: 271289, 1982.[ISI][Medline]
28. Polidori MC, Mecocci P, Cherubini A, and Senin U. Physical activity and oxidative stress during aging. Int J Sports Med 21: 154157, 2000.[ISI][Medline]
29. Powers SK and Lennon SL. Analysis of cellular responses to free radicals: focus on exercise and skeletal muscle. Proc Nutr Soc 58: 10251033, 1999.[ISI][Medline]
30. Ramamurthy B,
Höök P, Jones AD, and Larsson L. Changes in myosin structure and
function in response to glycation. FASEB J
15: 24152422,
2001.
31. Syrovy I and Hodny Z. Non-enzymatic glycosylation of myosin: effects of diabetes and aging. Gen Physiol Biophys 11: 301307, 1992.[ISI][Medline]
32. Syrovy I and Hodny Z. In vitro non-enzymatic glycosylation of myofibrillar proteins. Int J Biochem 25: 941946, 1993.[ISI][Medline]
33. Thornalley PJ. Glutathione-dependent detoxification of alpha-oxoaldehydes by the glyoxalase system: involvement in disease mechanisms and antiproliferative activity of glyoxalase I inhibitors. Chem Biol Interact 111112: 137151, 1998.
34. Vander Jagt DL, Hassebrook RK, Hunsaker LA, Brown WM, and Royer RE. Metabolism of the 2-oxoaldehyde methylglyoxal by aldose reductase and by glyoxalase-I: roles for glutathione in both enzymes and implications for diabetic complications. Chem Biol Interact 130132: 549562, 2001.[ISI]
35. Watanabe H, Ogasawara M, Suzuki N, Nishizawa N, and Ambo K. Glycation of myofibrillar protein in aged rats and mice. Biosci Biotechnol Biochem 56: 11091112, 1992.[ISI]
36. Yu BP.
Cellular defenses against damage from reactive oxygen species.
Physiol Rev 74:
139162, 1994.
37. Yudkin JS, Cooper MB, Gould BJ, and Oughton J. Glycosylation and cross-linkage of cardiac myosin in diabetic subjects: a post-mortem study. Diabet Med 5: 338342, 1988.[ISI][Medline]