1 Department of Food Science and Human Nutrition and 2 Department of Animal Science, Michigan State University, East Lansing, Michigan 48824
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ABSTRACT |
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Age-related changes in satellite cell proliferation and differentiation during rapid growth of porcine skeletal muscle were examined. Satellite cells were isolated from hindlimb muscles of pigs at 1, 7, 14, and 21 wk of age (4 animals/age group). Satellite cells were separated from cellular debris by using Percoll gradient centrifugation and were adsorbed to glass coverslips for fluorescent immunostaining. Positive staining for neural cell adhesion molecule (NCAM) distinguished satellite cells from nonmyogenic cells. The proportion of NCAM-positive cells (satellite cells) in isolates decreased from 1 to 7 wk of age. Greater than 77% of NCAM-positive cells were proliferating cell nuclear antigen positive at all ages studied. Myogenin-positive satellite cells decreased from 30% at 1 wk to 14% at 7 wk of age and remained at constant levels thereafter. These data indicate that a high percentage of satellite cells remain proliferative during rapid postnatal muscle growth. The reduced proportion of myogenin-positive cells during growth may reflect a decrease in the proportion of differentiating satellite cells or accelerated incorporation of myogenin-positive cells into myofibers.
proliferating cell nuclear antigen; myogenin; DNA accretion
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INTRODUCTION |
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POSTNATAL SKELETAL MUSCLE GROWTH in the pig occurs through hypertrophy of existing muscle fibers, because the number of muscle fibers is determined prenatally and remains constant throughout postnatal life (37, 42, 43). Muscle fiber hypertrophy is associated with an increased DNA content, yet myonuclei do not retain the ability to synthesize DNA (38). Satellite cells, first discovered by Alexander Mauro in 1961 (25), are the postnatal source of DNA contributed to growing muscle fibers. DNA accretion occurs through proliferation of satellite cells followed by differentiation and fusion with existing muscle fibers (28).
It is generally accepted that the proportion of myonuclei that are satellite cells declines with age. Campion et al. (8) observed a decrease in the proportion of nuclei classified as satellite cells in histological sections of peroneus longus and sartorius muscles from pigs between 1 and 64 wk of age. However, these authors also suggested that the absolute number of satellite cells in these muscles may increase from 1 to 32 wk of age. Increases in the absolute number of satellite cells throughout postnatal growth also have been reported for semimembranosus muscles of Japanese quail (7) and soleus muscles of the rat (17). Mulvaney et al. (30) observed a decrease in the proportion of nuclei that incorporated [3H]thymidine in the triceps brachii muscle of pigs from 1 to 21 days old and suggested that satellite cell proliferation declined during this period. Similarly, the proportion of muscle nuclei that are satellite cells and the percentage of muscle nuclei that exhibit DNA synthesis decrease with advancing age in mice and rats (1, 9, 36). Age-related changes in satellite cell proliferation throughout the rapid growth phase of porcine skeletal muscle have not been characterized.
Satellite cell differentiation is likely to modulate muscle growth, because it regulates accretion of DNA in muscle fibers as well as the number of satellite cells that remain capable of proliferation. Quinn et al. (32) demonstrated that embryonic myoblasts isolated from fetal calves with the double-muscled phenotype exhibit a delay in differentiation compared with myoblasts isolated from normal fetuses. This delay in differentiation resulted in an enlarged population of myoblasts and an increased production of fused myotubes in vitro. Coutinho et al. (13) observed a similar delay in formation of the brachial somites in quail embryos selected for rapid muscle growth. These data indicate that the timing of differentiation is a critical event in muscle development.
Age-related changes in satellite cell differentiation during postnatal skeletal muscle growth have not been previously examined. We characterized age-related changes in satellite cell proliferation and differentiation to provide insight into the dynamics of these activities during rapid skeletal muscle growth. These data will be useful in elucidating the cellular mechanisms governing skeletal muscle DNA accretion.
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MATERIALS AND METHODS |
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Tissue collection. Duroc × Yorkshire × Landrace pigs at 1, 7, 14, and 21 wk of age (4 animals/age group) were slaughtered at the Michigan State University Meat Laboratory according to procedures outlined in the Code of Federal Regulations for Humane Slaughter of Livestock (sections 313.1-313.9). The right and left semitendinosus (ST) muscles were excised, denuded, and weighed. Satellite cells were isolated from the right ST muscles of 7-, 14-, and 21-wk-old pigs as described by Doumit and Merkel (16). Briefly, muscles were excised, trimmed of visible connective tissue, sectioned, and ground in an aseptically prepared meat grinder. Ground muscle was incubated for 50 min at 37°C in a solution of 0.8 mg/ml protease (EC 3.4.24.31; lot no. 88H1351, Sigma, St. Louis, MO; 3.9 U/mg solid) dissolved in phosphate-buffered saline (PBS; 2 parts muscle:3 parts protease solution, vol/vol). After enzymatic digestion, cells were separated from tissue fragments by repeated centrifugation at 300 g for 5 min, followed by filtration through 500- and 53-µm-mesh nylon cloth. Because of the quantity of muscle mass required for this procedure, the right ST and semimembranosus muscles, which exhibit similar growth patterns (14), were used for satellite cell isolation from 1-wk-old pigs. Primary muscle cell isolates were stored in liquid nitrogen until use.
Samples from the left ST muscle were cut into ~0.5-cm3 sections, frozen in liquid nitrogen, and stored atSatellite cell enrichment and adsorption to coverslips. Porcine satellite cells were separated from tissue debris by using Percoll gradient centrifugation as described by Yablonka-Reuveni (45). Briefly, primary muscle cell suspensions derived from 3.5 g of fresh muscle were loaded onto gradients and centrifuged at 15,000 g for 5 min. The interface between the 20% and 60% Percoll solutions was recovered, diluted, and centrifuged at 300 g for 15 min to pellet cells. Cells were resuspended in 200 µl of minimum essential medium and were allowed to adsorb to 12-mm-diameter glass coverslips (Fisher Scientific, Itasca, IL) for 45 min. For each satellite cell isolate, cells were adsorbed onto separate coverslips for proliferating cell nuclear antigen (PCNA) and myogenin staining, respectively.
Immunostaining for neural cell adhesion molecule.
Cells adsorbed to coverslips were incubated in PBS containing 2% goat
serum (blocking solution) to block nonspecific antibody binding. Cells
were then incubated in undiluted 5.1H11 hybridoma supernatant or 1 µg/ml nonspecific mouse IgG (negative control; Sigma) for 30 min. The
5.1H11 hybridoma, developed by F. S. Walsh, was obtained from the
Developmental Studies Hybridoma Bank developed under the auspices of
the National Institute of Child Health and Human Development (NICHD)
and maintained by the Department of Biological Sciences, University of
Iowa (Iowa City, IA). Monoclonal antibody 5.1H11 has been shown to
specifically recognize a surface antigen [neural cell adhesion
molecule (NCAM)] on human (41) and porcine
(5) myogenic cells. After three washes, cells were incubated for 30 min with 0.4 µg/ml biotinylated goat anti-mouse IgG1 (Caltag Laboratories, Burlingame, CA) and the washing
series was repeated. To detect primary antibody binding, we incubated cells for 30 min with 1:200 ExtrAvidin conjugated to
tetramethylrhodamine isothiocyanate (Sigma). Cells were washed and then
fixed with 1% formalin in PBS for 10 min, followed by a 10-min
exposure to 20°C methanol. The wash series was repeated, and cells
were stained for the presence of either PCNA or myogenin. All washes
and antibody incubations were in blocking solution, unless otherwise
specified. Representative immunostaining for NCAM is depicted in Fig.
1, B and E.
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Immunostaining for PCNA.
Porcine satellite cells were incubated in 1 µg/ml anti-PCNA
monoclonal antibody (PC-10; Boehringer Mannheim, Indianapolis, IN) or 1 µg/ml nonspecific mouse IgG (negative control) for 1-2 h.
Proliferating cell nuclear antigen is expressed in the G1, S, and G2 phases of the cell cycle (6, 27) and
has been used previously as an index of satellite cell proliferation in
vitro (20, 47). Cells were washed and incubated for 30 min
in 0.8 µg/ml goat anti-mouse IgG2a conjugated to
fluorescein isothiocyanate (Caltag Laboratories). The washing
series was repeated, and coverslips were mounted onto microscope
slides with 2.5 µl of VectaShield (Vector Laboratories,
Burlingame, CA) mounting medium containing 4',6-diamidino-2-phenylindole (DAPI) to counterstain DNA. Coverslips were sealed with nail polish, and cells were viewed with a Leica DMLB
fluorescent microscope. Representative immunostaining for PCNA is
depicted in Fig. 1C. At least 600 cells from each animal were evaluated at ×400 magnification in random or sequential fields of
view. For each field of view, total cell number (DAPI+), total proliferating cells (PCNA+), total satellite cells (NCAM+), and proliferating satellite cells (NCAM+/PCNA+) were enumerated by two
independent evaluators blinded to the identity of the sample. The
numbers of nonmyogenic cells (NCAM) and proliferating nonmyogenic cells (NCAM
/PCNA+) were calculated by difference.
Immunostaining for myogenin. Porcine satellite cells were incubated in undiluted F5D hybridoma supernatant or 1 µg/ml nonspecific mouse IgG for 1-2 h. The F5D hybridoma, developed by W. E. Wright, was obtained from the Developmental Studies Hybridoma Bank developed under the auspices of the NICHD and maintained by the Department of Biological Sciences, University of Iowa. The F5D hybridoma cell line produces an antibody against myogenin, a skeletal muscle-specific transcription factor expressed immediately before and throughout differentiation (3, 44). After primary antibody incubation, cells were washed three times in blocking solution and then incubated for 30 min with goat anti-mouse IgG conjugated to fluorescein isothiocyante (Sigma) diluted 1:100 in blocking solution. Cells were washed, mounted onto microscope slides, and viewed as described in Immunostaining for PCNA. Representative immunostaining for myogenin is depicted in Fig. 1F. At least 700 cells were evaluated at ×400 magnification in random or sequential fields of view. Two independent evaluators who were blinded to sample identity enumerated DAPI+, NCAM+, and myogenin-positive (myogenin+) cells.
Statistical analysis. Data were analyzed with Statistical Analysis Software (SAS Institute, Cary, NC). Percentage data were converted to a decimal value and transformed as the inverse sine of the square root. A one-way analysis of variance (ANOVA) and Bonferroni multiple comparisons test were used to compare treatment means with a type I error rate of 5%.
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RESULTS |
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Whole body weight and muscle characteristics.
Live weights for pigs at 1, 7, 14, and 21 wk of age are shown in
Fig. 2. ST muscle weight increased in
proportion to body weight, with the most rapid increase in cumulative
weight gain occurring between 14 and 21 wk of age (Fig. 2). Total DNA
and protein contents of ST muscles (Fig.
3) paralleled increases in ST muscle
weight (Fig. 2).
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Percentage of satellite cells.
The percentage of NCAM+ cells declined (P < 0.05) in
muscle isolates from pigs at 1 to 7 wk of age and then remained
constant thereafter (Fig. 4). This
finding indicates that the proportion of satellite cells to nonmyogenic
cells is highest in isolates from young pigs. Similar percentages of
NCAM+ cells were observed on coverslips stained for the quantification
of PCNA+ or myogenin+ cells (data not shown).
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Percentage of proliferating satellite cells and nonmyogenic cells.
The percentage of NCAM+/PCNA+ cells isolated from muscle of 14-wk-old
pigs was lower (P < 0.05) than that from muscle of
1-wk-old pigs (Fig. 5). However, a high
proportion (>77%) of satellite cells were PCNA+ for all ages
examined. The percentage of NCAM/PCNA+ cells was lower
(P < 0.05) in 1-wk-old pigs than in 7- and 21-wk-old pigs (Fig. 6). No differences in the
percentage of proliferating nonmyogenic cells were detected in isolates
from 7-, 14-, or 21-wk-old pigs.
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Percentage of differentiating satellite cells.
All myogenin+ cells were also NCAM+, as would be expected if both
markers are muscle cell specific. The percentage of myogenin+ satellite
cells was highest (30.7 ± 3.6%, P < 0.05) in
1-wk-old pigs and decreased to 14.4 ± 1.2% in 7-wk-old pigs
(Fig. 7). A slight numerical decline in
the percentage of myogenin+ satellite cells was observed in muscle of
pigs between 7 and 21 wk of age (Fig. 7).
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DISCUSSION |
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Age-related changes in populations of proliferating and differentiating satellite cells were characterized in growing pigs from 1 to 21 wk of age. Satellite cells facilitate skeletal muscle DNA accretion through proliferation, followed by differentiation and fusion with existing muscle fibers. The positive relationship between number of myonuclei and myofiber size is well documented (10, 11, 28). Likewise, Powell and Aberle (31) demonstrated that in lines of swine differing in muscularity, increased muscle mass is associated with an increased DNA content. Quantification of proliferating and differentiating satellite cell populations during growth of large mammals has not been previously reported. Our results indicate that a reduced proportion of differentiating satellite cells and, to a lesser extent, a reduced population of proliferating cells may modulate changes in size of the satellite cell population and myonuclear accretion during muscle growth.
Pigs were in a rapid state of whole body and muscle growth from 1 to 21 wk of age, as indicated by increases in both live weight and ST muscle weight (Fig. 2). The ST muscle was chosen for use in this study because it can be removed quickly and quantitatively, and ST growth parallels changes in total body weight (Dr. R. A. Merkel, personal communication). Accumulation of muscle DNA paralleled increases in ST muscle weight (Figs. 2 and 3). Interestingly, the capacity of skeletal muscle to accumulate DNA appears to increase during growth. The proportions of ST muscle DNA present at 21 wk of age that accumulate before 7 wk, between 7 and 14 wk, and from 14 to 21 wk of age are 20.6, 35.9, and 43.5%, respectively.
In the current study, satellite cells were distinguished from
nonmyogenic cells on the basis of reactivity with monoclonal antibody
5.1H11. This antibody specifically recognizes a cell-surface antigen
(NCAM) on human (41) and porcine (5) myogenic
cells but not on nonmyogenic cells derived from muscle. The proportion of NCAM+ cells in muscle isolates declines in muscle of growing pigs
from 1 to 7 wk of age (Fig. 4). A number of explanations can account
for the observed increase in proportion of nonmyogenic cells to
satellite cells. A relatively high proportion of myogenin+ cells at 1 wk of age (Fig. 7) indicates that a greater proportion of satellite
cells are committed to differentiation and would subsequently fuse with
myofibers and be removed from the extractable mononuclear cell
population. Therefore, as a percentage of total cells isolated from
muscle, the proportion of satellite cells would decrease relative to
nonmyogenic cells at the subsequent ages. It also is possible that
changes in the levels of one or more mitogens in muscle may directly
influence the proportion of satellite cells to nonmyogenic cells.
Vandenburgh et al. (40) demonstrated that a 16- to 22-h
exposure of embryonic chicken muscle cultures to muscle extracts from
86-day-old mice increased the proportion of fibroblastic cells compared
with extracts from younger (28-day-old) mice. It is interesting to note
that the percentage of proliferating nonmyogenic cells (NCAM/PCNA+)
also increased at the later time points examined in this study (Fig. 6). Mitogens released from crushed extracts of rat muscle have been
shown to stimulate the proliferation of satellite cells but not
muscle-derived fibroblasts (4, 12). Expression of an active component of crushed muscle extract, hepatocyte growth factor
(HGF) (39), decreases during development of rat skeletal muscle (19). It is possible that levels of HGF decrease
throughout growth of porcine skeletal muscle or that satellite cells
become unresponsive to HGF, thereby decreasing the proportion of
myogenic to nonmyogenic cells.
It is generally accepted that at birth a high proportion of satellite cells exists in a proliferative state and that as an animal ages, this proportion decreases as satellite cells enter a quiescent state (2). Age-related declines in the proportion of muscle nuclei classified as satellite cells have been reported for the pig (8), mouse (9), and rat (1). Decreased [3H]thymidine and 5-bromo-2'-deoxyuridine (BrdU) labeling of nuclei in muscle during growth has been reported for young pigs (30) and growing turkeys (29), respectively. These studies report labeled nuclei as a percentage of total muscle nuclei, which includes both myofiber nuclei and satellite cell nuclei. Because the number of myonuclei per muscle fiber increases throughout postnatal growth (28), it is difficult to determine whether a decline in DNA labeling index represents an absolute decrease in the proportion of proliferating satellite cells.
PCNA was used to detect proliferating satellite cells in the current study. This antigen is undetectable in quiescent cells via immunofluorescence when methanol is used as a fixative but is upregulated in the G1 phase of the cell cycle, peaks during S phase, and declines during G2 (6, 27). A number of other studies have employed immunostaining against PCNA as an index of proliferation for satellite cells in vitro (20, 46, 47). Nuclei of proliferating, clonally derived porcine satellite cells (15), but not nuclei of porcine satellite cell-derived myotubes, are PCNA immunoreactive (unpublished observations). Expression of PCNA also is correlated to DNA synthesis and is well suited for use as an index of proliferation in vivo, particularly when used in combination with muscle-specific markers (22). In the current study, all cells that exhibited PCNA immunostaining above negative control staining were scored as PCNA+. Although no attempt was made to quantify variation in fluorescent staining intensity, proliferating satellite cells from 14- and 21-wk-old pigs exhibited more heterogeneous PCNA immunostaining (a greater number of weakly immunoreactive nuclei) than PCNA+ satellite cells from younger animals (unpublished observations). Because PCNA expression depends on the phase of the cell cycle, it is tempting to speculate that the heterogeneous staining observed in older pigs may be due to an increased proportion of slowly cycling satellite cells. Although PCNA immunostaining does not allow determination of cell cycle time, it is compatible with detection of other antigens and relatively inexpensive compared with disposal costs incurred following administration of [3H]thymidine or BrdU to large animals.
We observed a relatively modest decline in the proportion of PCNA+ satellite cells during muscle growth of pigs (Fig. 5). Furthermore, >77% of satellite cells isolated from 21-wk-old pigs are PCNA+. These cells were presumed to be in a proliferative state at the time of isolation, although it is conceivable that some PCNA could be synthesized during cell isolation and NCAM staining before fixation (~8 h in a thawed, unfixed state). The high proportion of PCNA+ satellite cells observed is not unexpected because ST muscle weight, DNA content, and protein content increase steadily from 1 to 21 wk of age. Our findings are in agreement with those of Schultz (35), who reported that 80% of satellite cells from 30-day-old growing rats proliferate with a 32-h cell cycle as determined by dual-labeling experiments utilizing [3H]thymidine and BrdU. The remaining 20% proliferate at a much slower rate, possibly entering a quiescent state between divisions (35). The PCNA labeling method utilized in the current study is more likely to positively identify rapidly growing cells than slowly growing cells. The proportion of PCNA+ satellite cells observed from muscle of growing pigs at different ages is similar to the proportion of rapidly cycling satellite cells of growing rat muscle.
Little information exists on the age-related changes in satellite cell differentiation during muscle growth in vivo. Myogenin was used to establish an index of differentiation in the current study because it is upregulated relatively early in the myogenic differentiation program (3). Myogenin expression also precedes irreversible cell cycle withdrawal (3). Cultured porcine satellite cells that have been induced to differentiate, as well as porcine satellite cell-derived myotubes, exhibit positive nuclear myogenin immunofluorescence (unpublished observations). In the current study, myogenin and PCNA are coexpressed, because the percentages of PCNA+ and myogenin+ cells total >100% for 1-wk-old pigs. Approximately 31 ± 3.6% of satellite cells isolated from 1-wk-old pigs are myogenin+, and this percentage declines to ~9 ± 0.3% at 21 wk of age (Fig. 7). Clearly, the proportions of isolated myogenin-positive cells reported herein can be used only as indices of satellite cell differentiation, rather than absolute values, because isolated satellite cells do not include differentiated satellite cells that are undergoing fusion with the sarcolemma. Nonetheless, our findings corroborate the conclusions of Schultz (34), who examined the satellite cell population in mice from 7 to 30 days of age. Schultz (34) demonstrated a high-percentage incorporation of satellite cells in very young mice and suggested that the incorporation of satellite cells decreases with age.
In the current study, the majority of muscle DNA accumulation occurred between 7 and 21 wk of age, a time during which the proportion of myogenin+ satellite cells is relatively low (Fig. 7). A reduced proportion of differentiating satellite cells, combined with a high index of proliferation, may increase the absolute number of satellite cells during muscle growth. Although the absolute number of satellite cells was not quantifiable by using the methods employed in the current study, increases in the absolute number of satellite cells throughout postnatal growth have been suggested for the peroneus longus and sartorius muscles of the pig (8), the semimembranosus muscle of Japanese quail (7), and the soleus muscle of the rat (17). More recently, Yablonka-Reuveni et al. (47) demonstrated that cultured myofibers from old rats support more proliferating MyoD-positive satellite cells than myofibers from young rats, suggesting that the number of myogenic precursors increases with age. Thus it appears that a relatively large population of satellite cells may exist in the muscle of older animals and that the reduced rate of differentiation may facilitate expansion of the satellite cell population. Despite the reduced percentage of myogenin+ satellite cells, the absolute number of satellite cells incorporating into muscle fibers may remain high because of an enlarged satellite cell population.
An alternative explanation for the reduced percentage of myogenin+ cells is that the rapidly growing satellite cells from younger animals may transition into myogenin-positive states more quickly than those from older animals. Yablonka-Reuveni et al. (47) observed that the increase in number of proliferating satellite cells and transition into the myogenin-positive state was more rapid for cultured satellite cells (in association with muscle fibers) from young rats compared with older rats. It is possible that satellite cells from younger animals become myogenin positive more readily but do not incorporate into muscle fibers as rapidly as satellite cells from older animals. This could explain why a higher proportion of myogenin+ satellite cells exists in 1-wk-old pigs compared with 7- to 21-wk-old pigs, despite the relative increase in muscle DNA accumulation that occurs from 7 to 21 wk of age. It is not clear whether the reduced proportion of myogenin+ cells in 7- to 21-wk-old pigs reflects a decrease in the proportion of differentiating satellite cells, a slower transition of cells into the myogenin-positive state, an accelerated rate of incorporation of myogenin+ cells into myofibers, or a combination of the latter.
Differentiation and incorporation of satellite cells into muscle fibers provides only one mechanism to control the satellite cell population. Another possible satellite cell fate is programmed cell death, or apoptosis. Apoptosis has been observed in satellite cell lines in vitro in response to serum starvation or staurosporine treatment (23, 24, 26). It is unknown whether porcine satellite cells or incorporated myonuclei undergo significant amounts of apoptosis throughout postnatal growth. However, apoptosis may be a mechanism to control the size of a satellite cell population that contains a high proportion of proliferating and a decreasing proportion of differentiating cells as observed in this study.
Our present results suggest that a high proportion of proliferating satellite cells persist in muscle of rapidly growing pigs from 1 to 21 wk of age, whereas an age-related decline in the proportion of myogenin+ satellite cells occurs relatively early in postnatal growth. Decreased satellite cell differentiation may result in an enlarged satellite cell population and increased capacity for myonuclear accretion.
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ACKNOWLEDGEMENTS |
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We thank S. DeBar for technical assistance; J. Heller, M. Ritter, and B. Booren for assistance with sample collection; T. Forton and J. Dominguez for aid in harvesting animals; A. Snedegar for care of animals; Dr. R. A. Merkel for helpful discussions; and J. Grobbel for assistance in preparation of this manuscript.
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FOOTNOTES |
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We are grateful for support from the Michigan Agricultural Experiment Station.
Present address of N. T Mesires: Sackler School of Graduate Biomedical Sciences, Tufts University School of Medicine, Boston, MA 02111.
Address for reprint requests and other correspondence: M. E. Doumit, 3385B Anthony Hall, Michigan State Univ., East Lansing, MI 48824 (E-mail: doumitm{at}msu.edu).
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.
10.1152/ajpcell.00341.2001
Received 24 July 2001; accepted in final form 24 October 2001.
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REFERENCES |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
1.
Allbrook, DB,
Han MF,
and
Hellmuth AE.
Population of muscle satellite cells in relation to age and mitotic activity.
Pathology
3:
233-243,
1971[ISI].
2.
Allen, RE,
Merkel RA,
and
Young RB.
Cellular aspects of muscle growth: myogenic cell proliferation.
J Anim Sci
49:
115-127,
1979[ISI][Medline].
3.
Andres, V,
and
Walsh K.
Myogenin expression, cell cycle withdrawal, and phenotypic differentiation are temporally separable events that precede cell fusion upon myogenesis.
J Cell Biol
132:
657-666,
1996[Abstract].
4.
Bischoff, R.
A satellite cell mitogen from crushed adult muscle.
Dev Biol
115:
140-147,
1986[ISI][Medline].
5.
Blanton, JR,
Grant AL,
McFarland DC,
Robinson JP,
and
Bidwell CA.
Isolation of two populations of myoblasts from porcine skeletal muscle.
Muscle Nerve
22:
43-50,
1999[ISI][Medline].
6.
Bravo, R,
and
Macdonald-Bravo H.
Existence of two populations of cyclin/proliferating cell nuclear antigen during the cell cycle: association with the DNA replication sites.
J Cell Biol
105:
1549-1554,
1987[Abstract].
7.
Campion, DR,
Marks HL,
and
Richardson LR.
An analysis of satellite cell content in the semimembranosus muscle of Japanese quail (Coturnix coturnix japonica) selected for rapid growth.
Acta Anat (Basel)
112:
9-13,
1982[Medline].
8.
Campion, DR,
Richardson RL,
Reagan JO,
and
Kraeling RR.
Changes in the satellite cell population during postnatal growth of pig skeletal muscle.
J Anim Sci
52:
1014-1018,
1981[ISI][Medline].
9.
Cardasis, CA,
and
Cooper GW.
An analysis of nuclear numbers in individual muscle fibers during differentiation and growth: a satellite cell-muscle fiber growth unit.
J Exp Zool
191:
347-358,
1975[ISI][Medline].
10.
Cheek, DB,
and
Hill DE.
Muscle and liver growth: role of hormones and nutritional factors.
Fed Proc
29:
1503-1509,
1970[ISI][Medline].
11.
Cheek, DB,
Holt AB,
Hill DE,
and
Talbert JL.
Skeletal muscle cell mass and growth: the concept of the deoxyribonucleic acid unit.
Pediatr Res
5:
312-328,
1971[ISI].
12.
Chen, GR,
Birnbaum S,
Yablonka-Reuveni Z,
and
Quinn LS.
Separation of mouse crushed muscle extract into distinct mitogenic activities by heparin affinity chromatography.
J Cell Physiol
160:
563-572,
1994[ISI][Medline].
13.
Coutinho, LL,
Morris J,
Marks HL,
Buhr RJ,
and
Ivarie R.
Delayed somite formation in a quail line exhibiting myofiber hyperplasia is accompanied by delayed expression of myogenic regulatory factors and myosin heavy chain.
Development
117:
563-569,
1993
14.
Davies, AS.
A comparison of tissue development in Pietrain and Large White pigs from birth to 64 kg live weight.
Anim Prod
19:
377-387,
1974[ISI].
15.
Doumit, ME,
Cook DR,
and
Merkel RA.
Fibroblast growth factor, epidermal growth factor, insulin-like growth factors, and platelet-derived growth factor-BB stimulate proliferation of clonally derived porcine myogenic satellite cells.
J Cell Physiol
157:
326-332,
1993[ISI][Medline].
16.
Doumit, ME,
and
Merkel RA.
Conditions for isolation and culture of porcine myogenic satellite cells.
Tissue Cell
24:
253-262,
1992[ISI][Medline].
17.
Gibson, MC,
and
Schultz E.
Age-related differences in absolute numbers of skeletal muscle satellite cells.
Muscle Nerve
6:
574-580,
1983[ISI][Medline].
18.
Gornall, AG,
Bardawill CJ,
and
David MM.
Determination of serum proteins by means of the biuret reaction.
J Biol Chem
177:
751-766,
1948[ISI].
19.
Jennische, E,
Ekberg S,
and
Matejka GL.
Expression of hepatocyte growth factor in growing and regenerating rat skeletal muscle.
Am J Physiol Cell Physiol
265:
C122-C128,
1993
20.
Johnson, SE,
and
Allen RE.
Proliferating cell nuclear antigen (PCNA) is expressed in activated rat skeletal muscle satellite cells.
J Cell Physiol
154:
39-43,
1993[ISI][Medline].
21.
Labarca, C,
and
Paigen K.
A simple, rapid and sensitive DNA assay procedure.
Anal Biochem
102:
344-352,
1980[ISI][Medline].
22.
Lawson-Smith, MJ,
and
McGeachie JK.
The identification of myogenic cells in skeletal muscle, with emphasis on the use of tritiated thymidine autoradiography and desmin antibodies.
J Anat
192:
161-171,
1998[ISI][Medline].
23.
Maglara, A,
Jackson MJ,
and
McArdle A.
Programmed cell death in skeletal muscle (Abstract).
Biochem Soc Trans
26:
S259,
1998[ISI][Medline].
24.
Mampuru, LJ,
Chen S,
Kalenik JL,
Bradley ME,
and
Lee T.
Analysis of events associated with serum deprivation-induced apoptosis in C3H/Sol8 muscle satellite cells.
Exp Cell Res
226:
373-380,
1996.
25.
Mauro, A.
Satellite cell of skeletal muscle fibers.
J Biophys Biochem Cytol
9:
493-495,
1961
26.
McArdle, A,
Maglara A,
Appleton P,
Watson AJM,
Grierson I,
and
Jackson MJ.
Apoptosis and multinucleated skeletal muscle myotubes.
Lab Invest
79:
1069-1076,
1999[ISI][Medline].
27.
Morris, GF,
and
Mathews MB.
Regulation of proliferating cell nuclear antigen during the cell cycle.
J Biol Chem
264:
13856-13864,
1989
28.
Moss, FP,
and
LeBlond CP.
Satellite cells as the source of nuclei in muscles of growing rats.
Anat Rec
170:
421-436,
1971[ISI][Medline].
29.
Mozdziak, PE,
Schultz E,
and
Cassens RG.
Satellite cell mitotic activity in posthatch turkey skeletal muscle growth.
Poult Sci
73:
547-555,
1994[ISI][Medline].
30.
Mulvaney, DR,
Marple DN,
and
Merkel RA.
Proliferation of skeletal muscle satellite cells after castration and administration of testosterone propionate.
Proc Soc Exp Biol Med
188:
40-45,
1988[Abstract].
31.
Powell, SE,
and
Aberle ED.
Cellular growth of skeletal muscle in swine differing in muscularity.
J Anim Sci
40:
476-485,
1975[ISI].
32.
Quinn, LS,
Ong LD,
and
Roeder RA.
Paracrine control of myoblast proliferation and differentiation by fibroblasts.
Dev Biol
140:
8-19,
1990[ISI][Medline].
33.
Robson, RM,
Goll DE,
and
Temple MJ.
Determination of proteins in "Tris" buffer by the biuret reaction.
Anal Biochem
24:
339-341,
1968[ISI][Medline].
34.
Schultz, E.
A quantitative study of the satellite cell population in postnatal mouse lumbrical muscle.
Anat Rec
180:
589-596,
1974[ISI][Medline].
35.
Schultz, E.
Satellite cell proliferative compartments in growing skeletal muscle.
Dev Biol
175:
84-94,
1996[ISI][Medline].
36.
Schultz, E,
and
Lipton BH.
Skeletal muscle satellite cells: changes in proliferation potential as a function of age.
Mech Ageing Dev
20:
377-383,
1982[ISI][Medline].
37.
Stickland, NC,
Widdowson EM,
and
Goldspink G.
Effects of severe energy and protein deficiencies on the fibres and nuclei in skeletal muscle of pigs.
Br J Nutr
34:
421-428,
1975[ISI][Medline].
38.
Stockdale, FE,
and
Holtzer H.
DNA synthesis and myogenesis.
Exp Cell Res
24:
508-520,
1961[ISI].
39.
Tatsumi, R,
Anderson JE,
Nevoret CJ,
Halevy O,
and
Allen RE.
HGF/SF is present in normal adult skeletal muscle and is capable of activating satellite cells.
Dev Biol
194:
114-128,
1998[ISI][Medline].
40.
Vandenburgh, HH,
Scheff MF,
and
Zacks SI.
Soluble age-related factors from skeletal muscle which influence muscle development.
Exp Cell Res
153:
389-401,
1984[ISI][Medline].
41.
Walsh, FS,
and
Ritter MA.
Surface antigen differentiation during human myogenesis in culture.
Nature
289:
60-64,
1981[ISI][Medline].
42.
Wigmore, PMC,
and
Stickland NC.
Muscle development in large and small pig fetuses.
J Anat
137:
235-245,
1983[ISI][Medline].
43.
Wigmore, PMC,
and
Stickland NC.
DNA, RNA and protein in skeletal muscle of large and small pig fetuses.
Growth
47:
67-76,
1983[ISI][Medline].
44.
Wright, WE,
Bender M,
and
Funk W.
Cyclic amplification and selection of targets (CASTing) for the myogenin consensus binding site.
Mol Cell Biol
11:
4104-4110,
1991[ISI][Medline].
45.
Yablonka-Reuveni, Z.
Cellular and Molecular Biology of Muscle Development. New York: Liss, 1989, p. 868-879.
46.
Yablonka-Reuveni, Z,
and
Rivera AJ.
Temporal expression of regulatory and structural muscle proteins during myogenesis of satellite cells on isolated adult rat fibers.
Dev Biol
164:
588-603,
1994[ISI][Medline].
47.
Yablonka-Reuveni, Z,
Seger R,
and
Rivera AJ.
Fibroblast growth factor promotes recruitment of skeletal muscle satellite cells in young and old rats.
J Histochem Cytochem
47:
23-42,
1999