Chemoprevention of spontaneous ovarian cancer in the domestic hen

The hen is an attractive animal model for in vivo testing of agents that thwart ovarian carcinogenesis because ovarian cancer in the domestic hen features clinical and molecular alterations that are similar to ovarian cancer in humans, including a high incidence of p53 mutations. The objective of the study was to test the potential ovarian cancer chemopreventive effect of the p53 stabilizing compound CP-31398 on hens that spontaneously present the ovarian cancer phenotype. Beginning at 79 wk of age, 576 egg-laying hens (Gallus domesticus) were randomized to diets containing different amounts of CP-31398 for 94 wk, 5 d, comprising a control group (C) (n = 144), which was fed a diet containing 0 ppm (mg/kg) of CP-31398; a low-dose treatment (LDT) group (n = 144), which was fed a diet containing 100 ppm of CP-31398; a moderate-dose treatment (MDT) group (n = 144) which was fed a diet containing 200 ppm of CP-31398; and a high-dose treatment (HDT) group (n = 144), which was fed a diet containing 300 ppm of CP-31398. Hens were killed at 174 wk of age to determine the incidence of ovarian and oviductal adenocarcinomas. Whereas the incidence of localized and metastatic ovarian cancers in the MDT and HDT groups was significantly lower (up to 77%) compared to levels in the C and LDT groups (P < 0.05), the incidence of oviductal cancer was unaffected by CP-31398. CP-31398 appears to be an effective tool for chemoprevention against ovarian malignancies, but does not appear to affect oviductal malignancies.

The evolution of chicken stem cell culture methods

1. The avian embryo is an excellent model for studying embryology and the production of pharmaceutical proteins in transgenic chickens. Furthermore, chicken stem cells have the potential for proliferation and differentiation and emerged as an attractive tool for various cell-based technologies. 2. The objective of these studies is the derivation and culture of these stem cells is the production of transgenic birds for recombinant biomaterials and vaccine manufacture, drug and cytotoxicity testing, as well as to gain insight into basic science, including cell tracking. 3. Despite similarities among the established chicken stem cell lines, fundamental differences have been reported between their culture conditions and applications. Recent conventional protocols used for expansion and culture of chicken stem cells mostly depend on feeder cells, serum-containing media and static culture. 4. Utilising chicken stem cells for generation of cell-based transgenic birds and a variety of vaccines requires large-scale cell production. However, scaling up the conventional adherent chicken stem cells is challenging and labour intensive. Development of a suspension cell culture process for chicken embryonic stem cells (cESCs), chicken primordial germ cells (PGCs) and chicken induced pluripotent stem cells (ciPSCs) will be an important advance for increasing the growth kinetics of these cells. 6. This review describes various approaches and suggestions to achieve optimal cell growth for defined chicken stem cells cultures and use in future manufacturing applications.

Fiber phenotype and coenzyme Q₁₀ content in Turkey skeletal muscles

Phenotypical differences between muscle fibers are associated with a source of cellular energy. Coenzyme Q(10) (CoQ(10)) is a major component of the mitochondrial oxidative phosphorylation process, and it significantly contributes to the production of cellular energy in the form of ATP. The objective of this study was to determine the relationship between whole-tissue CoQ(10) content, mitochondrial CoQ(10) content, mitochondrial protein, and muscle phenotype in turkeys. Four specialized muscles (anterior latissimus dorsi, ALD; posterior latissimus dorsi, PLD; pectoralis major, PM, and biceps femoris, BF) were evaluated in 9- and 20-week-old turkey toms. The amount of muscle mitochondrial protein was determined using the Bradford assay and CoQ(10) content was measured using HPLC-UV. The amount of mitochondrial protein relative to total protein was significantly lower (p < 0.05) at 9 compared to 20 weeks of age. All ALD fibers stained positive for anti-slow (S35) MyHC antibody. The PLD and PM muscle fibers revealed no staining for slow myosin heavy chain (S35 MyHC), whereas half of BF muscle fibers exhibited staining for S35 MyHC at 9 weeks and 70% at 20 weeks of age. The succinate dehydrogenase (SDH) staining data revealed that SDH significantly increases (p < 0.05) in ALD and BF muscles and significantly decreases (p < 0.05) in PLD and PM muscles with age. The study reveals age-related decreases in mitochondrial CoQ(10) content in muscles with fast/glycolytic profile, and demonstrates that muscles with a slow/oxidative phenotypic profile contain a higher proportion of CoQ(10) than muscles with a fast/glycolytic phenotypic profile.

Apoptosis and macrophage infiltration occur simultaneously and present a potential sign of muscle injury in skeletal muscle of nutritionally compromised, early post-hatch turkeys

Physical stress and malnutrition may cause elimination of myonuclei and produce inflammatory response in muscle. The objective of this study was to histochemically determine the association of apoptosis and/or macrophage infiltration with changes in muscle satellite cell mitotic activity in pectoralis thoracicus muscle of early post-hatch turkey toms. Feed-deprived birds and birds provided with three different levels of crude protein and amino acids (0.88 NRC, 1.00 NRC, and 1.12 NRC) were used in this model. The number of apoptotic nuclei was significantly elevated (P<0.05) and presence of macrophage infiltration was readily detectable in feed-deprived and 0.88 NRC treatment groups 72 h and 96 h post-hatch suggesting potential muscle injury and/or muscle remodeling. The number of apoptotic nuclei was the same (P>0.05), and there was no detectable macrophage infiltration present in birds placed on 1.00 NRC and 1.12 NRC diet 72 h, 96 h, and 120 h post-hatch. At 120 h post-hatch, feed-deprived and 0.88 NRC birds were characterized by no detectable levels of macrophage infiltration and a significant drop (P<0.05) in apoptotic nuclei. Understanding mechanisms that correlate early nutrition with skeletal muscle growth and development may present a useful tool in optimizing muscle health and improving meat quality and yield.

The effect of early dietary amino acid levels on muscle satellite cell dynamics in turkeys

Understanding the relationship between nutrition and satellite cell activity will be beneficial in obtaining optimal muscle growth and meat production. The objective of this study was to evaluate the effect of early post-hatch levels of dietary amino acids+/-0.88 NRC, 1.00 NRC, and 1.12 NRC), and feed deprivation on the satellite cell mitotic activity, pectoralis thoracicus muscle weight, and body weight of male turkeys (Meleagris gallopavo). Birds from each treatment were injected with 5-bromo-2'-deoxyuridine (BrdU) to label mitotically active cells. The right pectoralis thoracicus was harvested 1 h after BrdU injection for immunohistochemical and myofiber diameter analysis. On the third day post-hatch, satellite cell mitotic activity was the highest (P<0.05) in the 0.88 NRC amino acid treatment group and the lowest (P<0.05) in the feed-deprived group. On the fourth day post-hatch, feed-deprived birds exhibited the lowest (P<0.05) satellite cell mitotic activity and muscle weight. At 140 days of age, there were no significant differences (P>0.05) between treatments in body weight or pectoralis thoracicus muscle weight. Research evaluating species-related differences in apoptotic events and in genes regulating cell proliferation may be necessary to devise feeding strategies aimed at obtaining optimal pectoralis thoracicus muscle yield at market age.

Production of Chick Germline Chimeras from Fluorescence-Activated Cell-Sorted Gonocytes

Modification of the chicken germline has been difficult, because it has been challenging to fractionate sufficient numbers of primordial germ cells for manipulation and implantation into developing embryos. A technique to enrich cell suspensions for primordial germ cells, using fluorescence-activated cell sorting (FACS), has recently been developed. The objective of the current study was to demonstrate that the FACS-enriched early embryonic gonocytes could fully participate in development of the germline. Therefore, cells were disassociated from stage 27 gonads, incubated with mouse anti-stage-specific embryonic antigen-1, which was detected with goat-antimouse IgM-fluorescein isothiocyanate, and the fluorescently labeled cells were sorted from the unlabeled cells using FACS. The isolated gonocyte population was injected into the blastoderm of unincubated stage X embryos, the germinal crescent of 3-d embryos, and into the circulation of stage 17 embryos that were pretreated with busulfan. Barred Plymouth Rock gonocytes were implanted exclusively into recipient White Leghorn embryos, and White Leghorn gonocytes were implanted exclusively into Barred Plymouth Rock recipient embryos. Embryos were cultured until hatch, and male putative chimeras were reared to sexual maturity. Germline chimerism was evaluated by observing feather color of the progeny. All injection methods resulted in germline chimeras demonstrating that FACS-sorted gonocytes can fully participate in development. Moreover, it was demonstrated that gonocytes isolated from stage 27 embryonic gonads can be introduced into embryos at an earlier stage of development, and the introduced gonocytes can fully participate in germline development.

Early post-hatch fasting induces satellite cell self-renewal

Early post-hatch satellite cell kinetics are an important aspect of muscle development, and understanding the interplay between fasting and muscle development will lead to improvements in muscle mass following an illness, and optimal meat production. The objective of this experiment was to test the influence of immediate post-hatch fasting on satellite cells in the poult. Male Nicholas poults (Meleagris gallopavo) were placed into two treatments: a fed treatment with immediate access to feed and water upon placement and a fasted treatment without access to feed and water for the first three days post-hatch. 5-bromo-2'-deoxyuridine (BrdU) was injected intra-abdominally in all poults to label mitotically active satellite cells. The pectoralis thoracicus muscle was harvested two hours following the BrdU injection. Immunohistochemistry for BrdU, Pax7, Bcl-2, Pax7 with BrdU, and determining myofiber cross-sectional area along with computer-based image analysis was used to study muscle development. Fed poults had higher body masses throughout the experiment (P< or =0.01), and they had higher pectoralis thoracicus muscle mass (P< or =0.01) at ten days of age than the fasted poults. Fed poults had higher satellite cell mitotic activity at three days and four days of age (P< or =0.01) compared to the fasted poults. However, Pax7 labeling index was higher in the fasted poults (P< or =0.01) at three days, four days, and five days post-hatch than the fed group. Similarly Bcl-2 labeling was higher in the fasted than in the fed group at three days post-hatch. Therefore, fasting depleted proliferating satellite cells indicated by the lower BrdU labeling in the fasted poults compared to the fed poults, and conserved the satellite cell proliferative reserve indicated by the higher level of Pax7 labeling for the fasted poults compared to the fed poults.

Culture of chicken embryos in surrogate eggshells

The chick embryo is a classical model to study embryonic development. However, most researchers have not studied the effect of embryonic manipulation on chick hatchability. The objective of this study was to determine the effect of egg orientation and type of sealing film on the hatchability of cultured embryos. Windows were made in the small end of recipient surrogate chicken eggshells, and donor embryos were placed into the recipient eggshell for the first 3 d of incubation. Survival over the first 3 d was maximized (P < 0.05) when windowed eggs sealed with Saran Wrap were positioned with the window-end down compared with window-end up. Three-day-old cultured embryos were transferred into recipient turkey eggshells, sealed with cling film, and cultured until hatch. Water weight loss of the surrogate eggshell cultures regardless of cling film type was not significantly different from control intact eggs. The embryos cultured in turkey eggshells and sealed with Handi Wrap exhibited higher hatchability (75% +/- 10.2%) than cultures sealed with Saran Wrap (45.2% +/- 13.8%). Hatchability of control intact eggs (86.4% +/- 5.3%) was not significantly (P > 0.05) different from the hatchability of eggs sealed with Handi Wrap, which suggested that Handi Wrap was an excellent sealant for chick embryos cultured after 3 d of incubation.

The effect of early nutrition on satellite cell dynamics in the young turkey

Early posthatch satellite cell mitotic activity is an important aspect of muscle development. An understanding of the interplay between nutrition and satellite cell mitotic activity will lead to more efficient meat production. The objective of this study was to test the influence of the leucine metabolite, beta-hydroxy beta-methylbutyrate (HMB), and feed deprivation on muscle development in the early posthatch poult. Male Nicholas poults were placed on 1 of 4 treatments: immediately fed a starter diet with 0.1% HMB (IF-HMB), immediately fed a starter diet containing 0.1% Solka-Floc for a control (IF-No HMB), feed and water withheld for 48 h immediately posthatch and then fed the HMB diet (WF-HMB), and feed and water withheld for 48 h immediately posthatch and then fed the control starter diet (WF-No HMB). 5-bromo-2'-deoxyuridine (BrdU) was injected intra-abdominally into all poults to label mitotically active satellite cells. The pectoralis thoracicus was harvested 2 h after the BrdU injection. Immunohistochemistry for BrdU, Pax7, and laminin along with computer-based image analysis was used to study muscle development. IF-HMB poults had higher body weights (P < 0.01) at 48 h and 1 wk of age and had higher satellite cell mitotic activity at 48 h of age (P < 0.01) compared with the IF-No HMB and WF poults. Therefore, dietary supplementation of HMB may have an anabolic effect on early posthatch muscle.

Effects of posthatch feed deprivation on heparan sulfate proteoglycan, syndecan-1, and glypican expression: implications for muscle growth potential in chickens

The heparan sulfate proteoglycans, syndecan-1 and glypican-1 (glypican), are low affinity receptors for fibroblast growth factor 2 (FGF2). Because FGF2 stimulates skeletal muscle cell proliferation but inhibits differentiation, changes in FGF2 signaling due to early posthatch feed deprivation may play a significant role in modulating muscle growth. To study the effect of early posthatch feed deprivation in chickens on heparan sulfate proteoglycan relative protein concentration, syndecan-1 expression, and glypican mRNA expression, pectoralis major muscle tissue was isolated from pretreatment d 0 chicks and chicks fed or feed deprived for 3 d, and after d 3 feeding was resumed in the feed-deprived birds until d 7. Heparan sulfate proteoglycan protein concentration was measured by ELISA analysis and was significantly decreased in the feed-deprived birds beginning at d 2 (P < 0.05). The expression of syndecan-1 and glypican was measured by semi-quantitative reverse transcription PCR. Syndecan-1 expression was unaffected by feed withdrawal and refeeding (P > 0.05). Glypican mRNA expression was decreased in the muscle tissue from feed-deprived birds at d 3 (P < 0.05), but by d 7, after initiating feeding on d 4, it was significantly elevated compared with in muscle tissue from chicks maintained on feed (P < 0.05). The results from the present study demonstrate that the heparan sulfate proteoglycan protein concentration and syndecan-1 and glypican mRNA expressions are differentially affected by early posthatch feed deprivation, which may alter signaling events associated with muscle growth.

Isolation of chicken primordial germ cells using fluorescence-activated cell sorting

Presently, it is difficult to undertake germ line modification of the chicken with primordial germ cells (PGC) because it has been difficult to efficiently fractionate the PGC from the total somatic cell population. The objective of this study was to develop a method that allows isolation of an enriched population of viable PGC from embryonic blood and embryonic gonadal tissue. Blood was harvested from early chick embryos (stages 13 to 15), and cells were liberated from the gonads of stage 27 chick embryos. Subsequently, viable PGC were labeled with anti-stage-specific embryonic antigen-1 (SSEA-1), which was detected with goat-anti-mouse IgM-fluorescein isothiocyanate. Fluorescently labeled cells were sorted from the unlabeled cells using fluorescence-activated cell sorting (FACS), and the identities of the PGC were confirmed using periodic acid-Schiff (PAS) staining or anti-embryonic mouse antigen-1 (EMA-1) staining followed by microscopic evaluation. Finally, PGC were sorted from somatic cells of sex-identified embryos. Less than 0.1% of the blood cell population was collected as SSEA-1-positive cells. Similarly, approximately 2% of the gonadal cell population were collected as SSEA-1-positive cells. Therefore, fewer (-1,000 to 9,000) PGC were recovered from each isolate. Placing the sorted SSEA-1-positive cells on a glass slide from a microcentrifuge tube resulted in a recovery rate of 53 to 73% relative to the number detected by FACS. Furthermore, the proportions of sorted cells that stained with PAS or anti-EMA-1 following sorting were 92+/-4% PAS positive and 94+/-1% anti-EMA-1 positive. Finally, the sorted SSEA-1-positive cells were maintained in vitro to demonstrate their viability after sorting. It was demonstrated that it is possible to label blood and gonadal chicken PGC with SSEA-1 and subsequently to sort viable SSEA-1-positive PGC from somatic cells.

Development of transgenic chickens expressing bacterial beta-galactosidase

Replication-defective retroviral vectors are efficient vehicles for the delivery of exogenous genes, and they may be used in the generation of transgenic animals. The replication-defective retroviral SNTZ vector carrying the lacZ gene with a nuclear localized signal was injected into the subgerminal cavity of freshly laid eggs. Subsequently, the eggs were allowed to hatch, and the chickens were screened for the lacZ gene by using the polymerase chain reaction. Eight of 15 male chickens that survived to sexual maturity contained the lacZ gene in their semen. Subsequently, these males were mated with wild-type female chickens. From one of the eight lacZ-positive G(0) males, two lacZ-positive male chickens were produced from a total of 224 G(1) progeny for a germline transmission rate of 0.89%. Both G(1) male chickens carrying the lacZ gene were mated with wild-type female chickens and 46.5% of the G(2) progeny contained the lacZ gene, which is consistent with the expected Mendelian 50% ratio for a heterozygous dominant allele. The product of the lacZ gene, nuclear localized beta-galactosidase, was expressed in primary myoblast cultures derived from G(2) chickens, and it was also expressed in whole G(2) chicken embryos.

The effect of early posthatch nutrition on satellite cell mitotic activity

Myofiber growth is dependent upon the contribution of new nuclei from the mitotically active satellite cell population. The objective of this study was to examine satellite cell mitotic activity in conjunction with different nutritional paradigms during the early posthatch period. Turkey poults were provided a standard turkey starter diet; the starter diet top-dressed with a hydrated low-fat, highly digestible protein and carbohydrate nutritional hatchling supplement, Oasis; the starter diet top-dressed with Solka-floc dyed green; or no food for the first 3 d posthatch. All birds were fed a standard starter diet during the experimental period. 5-Bromo-2'-deoxyuridine (BrdU) was continuously infused into all treatments (n = 5 all groups) between hatch and 3 d of age. A second group of identically treated poults housed in separate pens (n = 3 to 5) was continuously infused with BrdU between 2 and 9 d of age. Mitotically active satellite cells were identified in the pectoralis thoracicus and quantitated using BrdU immunohistochemistry in combination with computer-based image analysis. Satellite cell mitotic activity was significantly higher (P < or = 0.05) in the birds fed a standard starter diet compared to all other treatments at 3 d posthatch. However, there were no (P > or = 0.05) differences in satellite cell mitotic activity among treatments at 9 d posthatch. The results of the current study suggest that any improvements in meat yield through early nutritional supplementation do not appear to occur through a satellite cell pathway and that there is no compensatory response in the satellite cell population following refeeding after early posthatch starvation.

The effect of early posthatch starvation on calpain mRNA levels

The calpain system is a family of calcium activated proteases that degrade myofibrillar protein. Male broiler chickens (Ross) were provided a standard starter diet top-dressed with Oasis((R)) nutritional supplement (fed; Novus International, St. Louis, MO, USA), or they were not provided any feed (starved) for the first 3 days posthatch. Subsequently, the standard starter diet was provided to all chickens between 3 and 7 days posthatch. RNA was extracted from the Pectoralis thoracicus, and skeletal muscle-specific n-calpain-1 (p94) calpain, mu-calpain, and m-calpain expression was evaluated using quantitative Northern analysis. Early posthatch starvation did not (P>0.05) affect calpain mRNA levels on each day examined. Similarly, there were no (P>0.05) changes in mu-calpain or m-calpain mRNA levels between 0 and 7 days posthatch in fed birds. However, p94 calpain mRNA levels were significantly (P<0.05) lower at 7 days posthatch compared to 0 or 2 days posthatch. Therefore, in the early posthatch chicken, it appears that the calpain system may not be affected by the presence of oral nutrition, and that there is an age-related downregulation of p94 calpain mRNA expression.

Muscle regeneration during hindlimb unloading results in a reduction in muscle size after reloading

The hindlimb-unloading model was used to study the ability of muscle injured in a weightless environment to recover after reloading. Satellite cell mitotic activity and DNA unit size were determined in injured and intact soleus muscles from hindlimb-unloaded and age-matched weight-bearing rats at the conclusion of 28 days of hindlimb unloading, 2 wk after reloading, and 9 wk after reloading. The body weights of hindlimb-unloaded rats were significantly (P < 0.05) less than those of weight-bearing rats at the conclusion of hindlimb unloading, but they were the same (P > 0.05) as those of weight-bearing rats 2 and 9 wk after reloading. The soleus muscle weight, soleus muscle weight-to-body weight ratio, myofiber diameter, number of nuclei per millimeter, and DNA unit size were significantly (P < 0.05) smaller for the injured soleus muscles from hindlimb-unloaded rats than for the soleus muscles from weight-bearing rats at each recovery time. Satellite cell mitotic activity was significantly (P < 0.05) higher in the injured soleus muscles from hindlimb-unloaded rats than from weight-bearing rats 2 wk after reloading, but it was the same (P > 0.05) as in the injured soleus muscles from weight-bearing rats 9 wk after reloading. The injured soleus muscles from hindlimb-unloaded rats failed to achieve weight-bearing muscle size 9 wk after reloading, because incomplete compensation for the decrease in myonuclear accretion and DNA unit size expansion occurred during the unloading period.

Hoechst fluorescence intensity can be used to separate viable bromodeoxyuridine-labeled cells from viable non-bromodeoxyuridine-labeled cells

BACKGROUND

5-Bromo-2'-deoxyuridine (BrdU) is a powerful compound to study the mitotic activity of a cell. Most techniques that identify BrdU-labeled cells require conditions that kill the cells. However, the fluorescence intensity of the membrane-permeable Hoechst dyes is reduced by the incorporation of BrdU into DNA, allowing the separation of viable BrdU positive (BrdU+) cells from viable BrdU negative (BrdU-) cells.

METHODS

Cultures of proliferating cells were supplemented with BrdU for 48 h and other cultures of proliferating cells were maintained without BrdU. Mixtures of viable BrdU+ and viable BrdU- cells from the two proliferating cultures were stained with Hoechst 33342. The viable BrdU+ and BrdU- cells were sorted into different fractions from a mixture of BrdU+ and BrdU- cells based on Hoechst fluorescence intensity and the ability to exclude the vital dye, propidium iodide. Subsequently, samples from the original mixture, the sorted BrdU+ cell population, and the sorted BrdU- cell population were immunostained using an anti-BrdU monoclonal antibody and evaluated using flow cytometry.

RESULTS

Two mixtures consisting of approximately 55% and 69% BrdU+ cells were sorted into fractions consisting of greater than 93% BrdU+ cells and 92% BrdU- cells. The separated cell populations were maintained in vitro after sorting to demonstrate their viability.

CONCLUSIONS

Hoechst fluorescence intensity in combination with cell sorting is an effective tool to separate viable BrdU+ from viable BrdU- cells for further study. The separated cell populations were maintained in vitro after sorting to demonstrate their viability.

Telomeric profiles and telomerase activity in turkey satellite cell clones with different in vitro growth characteristics

The satellite cell population in postnatal skeletal muscle is heterogeneous because individual satellite cells isolated from a single muscle have differing abilities to proliferate under the same in vitro conditions. Telomeres are structures found at the ends of all eukaryotic chromosomes that are characterized by repetitive DNA sequences, and they are important in determining cellular proliferation potential. The relationship between satellite cell proliferative heterogeneity and telomeric DNA was examined by digesting genomic DNA from large-colony-forming and small-colony-forming turkey satellite cell clones with HinfI, separating the restriction fragments on an agarose gel, and hybridizing the gels with an oligonucleotide probe specific for telomeric DNA. Turkey satellite cells generated telomeric restriction fragments up to approximately 180 kB. The large-colony-forming satellite cell clones had a larger proportion (P<0.05) of total telomeric restriction fragments below 33 kB than the small-colony-forming satellite cell clones. However, telomerase expression was detected in cultures from large-colony-forming and small-colony-forming turkey satellite cells suggesting that the differences in telomeric restriction fragments may not be related to the differences in in vitro proliferative behavior and that telomerase may contribute to the high in vitro growth capacity of turkey satellite cells.

Unloading of juvenile muscle results in a reduced muscle size 9 wk after reloading

The role of satellite cells and DNA unit size in determining muscle size was examined by inhibiting postnatal skeletal muscle development by using hindlimb suspension. Satellite cell mitotic activity and DNA unit size were determined in the soleus muscles from hindlimb-suspended and age-matched weight-bearing rats before the initiation of hindlimb suspension, at the conclusion of a 28-day hindlimb-suspension period, 2 wk after reloading, and 9 wk after reloading. The body weights of hindlimb-suspended rats were significantly (P < 0.05) less than those of weight-bearing rats at the conclusion of hindlimb suspension, but they were the same (P > 0. 05) as those of weight-bearing rats 9 wk after reloading. The soleus muscle weight, soleus muscle weight-to-body weight ratio, myofiber diameter, nuclei per millimeter, and DNA unit size for the hindlimb-suspended rats were significantly (P < 0.05) smaller than for the weight-bearing rats at all recovery times. Satellite cell mitotic activity was significantly (P < 0.05) higher in the soleus muscles from hindlimb-suspended rats 2 wk after reloading, but it was the same (P > 0.05) as in weight-bearing rats 9 wk after reloading. Juvenile soleus muscles failed to achieve normal muscle size 9 wk after reloading because there was incomplete compensation for the hindlimb-suspension-induced interruptions in myonuclear accretion and DNA unit size expansion.

Dietary creatine monohydrate supplementation increases satellite cell mitotic activity during compensatory hypertrophy

Nutritional status influences muscle growth and athletic performance, but little is known about the effect of nutritional supplements, such as creatine, on satellite cell mitotic activity. The purpose of this study was to examine the effect of oral creatine supplementation on muscle growth, compensatory hypertrophy, and satellite cell mitotic activity. Compensatory hypertrophy was induced in the rat plantaris muscle by removing the soleus and gastrocnemius muscles. Immediately following surgery, a group of six rats was provided with elevated levels of creatine monohydrate in their diet. Another group of six rats was maintained as a non-supplemented control group. Twelve days following surgery, all rats were implanted with mini-osmotic pumps containing the thymidine analog 5-bromo-2'-deoxyuridine (BrdU) to label mitotically active satellite cells. Four weeks after the initial surgery the rats were killed, plantaris muscles were removed and weighed. Subsequently, BrdU-labeled and non-BrdU-labeled nuclei were identified on enzymatically isolated myofiber segments. Muscle mass and myofiber diameters were larger (P < 0.05) in the muscles that underwent compensatory hypertrophy compared to the control muscles, but there were no differences between muscles from creatine-supplemented and non-creatine-supplemented rats. Similarly, compensatory hypertrophy resulted in an increased (P < 0.05) number of BrdU-labeled myofiber nuclei, but creatine supplementation in combination with compensatory hypertrophy resulted in a higher (P < 0.05) number of BrdU-labeled myofiber nuclei compared to compensatory hypertrophy without creatine supplementation. Thus, creatine supplementation in combination with an increased functional load results in increased satellite cell mitotic activity.

Myogenin, MyoD, and myosin heavy chain isoform expression following hindlimb suspension

BACKGROUND

Myogenin expression is associated with a slow myofiber phenotype, and MyoD expression is associated with a fast myofiber phenotype. Hindlimb suspension (HS) will induce muscular atrophy, and a transition from a slow to fast myofiber phenotype in the rat soleus.

HYPOTHESIS

Hindlimb suspension will induce myofiber atrophy, and a slow to fast myofiber type transition with corresponding changes in myogenin and MyoD expression.

METHODS

Myofiber phenotype was evaluated by electrophoretically separating the myosin heavy chain isoforms. Myogenin expression was evaluated by Northern analysis, while MyoD expression was evaluated by Northern analysis and semiquantitative RT-PCR.

RESULT

After 28 d of hindlimb suspension, there was significantly (p < 0.05) less myosin heavy chain Type IIA, and more (p < 0.05) myosin heavy chain Type IIX in the soleus muscles of hindlimb suspended rats compared with soleus muscles from weight-bearing (WB) rats. Although there was a shift to a faster myosin heavy chain phenotype in soleus muscles from hindlimb suspended rats, there was no change in myogenin expression, and MyoD expression was undetectable by Northern analysis. Semi-quantitative RT-PCR revealed an up-regulation of MyoD expression following 14 d of hindlimb suspension.

CONCLUSIONS

Myogenin expression levels do not change during the slow to fast myofiber phenotypic transition that occurs during hindlimb suspension; MyoD expression appears to increase at the same time as the phenotypic transition. Thus, MyoD expression or the Myogenin: MyoD mRNA ratio may be important in the phenotypic transition. Neither myogenin nor MyoD appear to play a critical role in the muscular atrophy that occurs during weightlessness.

Nitric oxide donors, sodium nitroprusside and S-nitroso-N-acetylpencillamine, stimulate myoblast proliferation in vitro

Nitric oxide (NO) is an inter- and intracellular messenger involved in a variety of physiologic and pathophysiologic conditions. The effect of two NO donors, sodium nitroprusside (SNP) and S-nitroso-N-acetylpenicillamine (SNAP) and their effect on myoblast proliferation was examined. Both donors stimulated an increase in myoblast cell number over a range (1-10 microM) of donor concentrations. However, 50 microM SNAP inhibited myoblast proliferation. Cell numbers from cultures treated with degraded 10 microM SNAP were equivalent to the control. Therefore, it appears NO can stimulate as well as inhibit myoblast proliferation.

Hindlimb suspension reduces muscle regeneration

Exposure of juvenile skeletal muscle to a weightless environment reduces growth and satellite cell mitotic activity. However, the effect of a weightless environment on the satellite cell population during muscle repair remains unknown. Muscle injury was induced in rat soleus muscles using the myotoxic snake venom, notexin. Rats were placed into hindlimb-suspended or weightbearing groups for 10 days following injury. Cellular proliferation during regeneration was evaluated using 5-bromo-2'-deoxyuridine (BrdU) immunohistochemistry and image analysis. Hindlimb suspension reduced (P < 0.05) regenerated muscle mass, regenerated myofiber diameter, uninjured muscle mass, and uninjured myofiber diameter compared to weightbearing rats. Hindlimb suspension reduced (P < 0.05) BrdU labeling in uninjured soleus muscles compared to weight-bearing muscles. However, hindlimb suspension did not abolish muscle regeneration because myofibers formed in the injured soleus muscles of hindlimb-suspended rats, and BrdU labeling was equivalent (P > 0.10) on myofiber segments isolated from the soleus muscles of hindlimb-suspended and weightbearing rats following injury. Thus, hindlimb suspension (weightlessness) does not suppress satellite cell mitotic activity in regenerating muscles before myofiber formation, but reduces growth of the newly formed myofibers.

Superior preservation of the staphylococcal glycocalyx with aldehyde-ruthenium red and select lysine salts using extended fixation times

The utility of lysine-based aldehyde-ruthenium red fixatives for the preservation and/or staining of the fibrous staphylococcal glycocalyx was improved by substitution of alternative forms of lysine for the free amino form. Paraformaldehyde-glutaraldehyde fixatives containing alternative lysines, with or without ruthenium red, were compared at short 20-minute prefixation times and at extended overnight fixation times. Although inclusion of paraformaldehyde made longer fixation times possible, the length of time for "safe" fixation varied per sample and could not be predicted. All alternative lysine forms permitted fixation of at least 24 hours without sample loss. The L-lysine monohydrochloride or L-lysine acetate forms permitted longer fixation times than the L-lysine free amino form, and they had comparable or better preservation of the staphylococcal glycocalyx. Thus, the usefulness of aldehyde-lysine-based fixatives with minor changes has been enhanced.

Myogenin, MyoD, and myosin expression after pharmacologically and surgically induced hypertrophy

The relationship between myogenin or MyoD expression and hypertrophy of the rat soleus produced either by clenbuterol and 3,3', 5-triiodo-L-thyronine (CT) treatment or by surgical overload was examined. Mature female rats were subjected to surgical overload of the right soleus with the left soleus serving as a control. Another group received the same surgical treatment but were administered CT. Soleus muscles were harvested 4 wk after surgical overload and weighed. Myosin heavy chain isoforms were separated by using polyacrylamide gel electrophoresis while myogenin and MyoD expression were evaluated by Northern analysis. CT and functional overload increased soleus muscle weight. CT treatment induced the appearance of the fast type IIX myosin heavy chain isoform, depressed myogenin expression, and induced MyoD expression. However, functional overload did not alter myogenin or MyoD expression in CT-treated or non-CT-treated rats. Thus pharmacologically and surgically induced hypertrophy have differing effects on myogenin and MyoD expression, because their levels were associated with changes in myosin heavy chain composition (especially type IIX) rather than changes in muscle mass.

Paraformaldehyde effect on ruthenium red and lysine preservation and staining of the staphylococcal glycocalyx

The utility of lysine in glutaraldehyde-ruthenium red fixatives for the preservation and/or staining of the fibrous staphylococci glycocalyx was improved by inclusion of paraformaldehyde. Short, 20 min prefixation times for paraformaldehyde-glutaraldehyde fixatives containing lysine, with or without ruthenium red, were compared to an extended overnight fixation. Samples were often lost in fixatives that did not contain paraformaldehyde at extended fixation times hampering the effective use of these fixatives for clinical or environmental applications. Inclusion of paraformaldehyde in the fixation with lysine permitted longer fixation times as well as stabilized the staphylococcal glycocalyx. Thus, the technical usefulness of fixatives employing lysine was significantly improved.

Myonuclear accretion is a major determinant of avian skeletal muscle growth

The role of satellite cells and DNA unit size in determining skeletal muscle growth was studied after mitotic activity was inhibited in the left pectoralis thoracicus of 2-wk-old tom turkeys by means of a 25-Gy dose of irradiation. Toms were killed and muscle weights were obtained 1 (n = 5), 4 (n = 6), 7 (n = 6), and 15 (n = 4) wk after irradiation. Satellite cell mitotic activity and DNA unit size were determined using enzymatically isolated myofiber segments and image analysis. Irradiated and nonirradiated muscle weights increased (P < 0.01) between all ages examined, but irradiated muscle weights were significantly (P < 0.01) lower than nonirradiated muscle weights at 4, 7, and 15 wk after irradiation. Satellite cell mitotic activity was lower (P < 0.01) in irradiated than in nonirradiated muscles at 1 and 4 wk after irradiation and resulted in a significant reduction (P < 0.05) in the number of myofiber nuclei per millimeter at 4 and 7 wk after irradiation. Satellite cell mitotic activity was higher (P < 0.05) in irradiated than in nonirradiated muscles at 7 wk after irradiation, but at 15 wk after irradiation it had fallen to low levels in both muscles. There was no significant (P > 0.10) difference in DNA unit size between muscles at any time, but there was an age-related increase (P < 0.01) for both muscles. Irradiation reduced muscle growth through a transient reduction in myonuclear production at a critical time (3-6 wk of age) in posthatch skeletal muscle development. The age-related increase in DNA unit size was not accelerated to compensate for the reduction in myonuclear accretion. Thus it appears that muscle growth potential is governed mostly by myonuclear accretion and to a lesser extent by DNA unit size.

A double fluorescence staining protocol to determine the cross-sectional area of myofibers using image analysis

A double fluorescence staining protocol was developed to facilitate computer based image analysis. Myofibers from experimentally treated (irradiated) and control growing turkey skeletal muscle were labeled with the anti-myosin antibody MF-20 and detected using fluorescein-5-isothiocyanate (FITC). Extracellular material was stained with concanavalin A (ConA)-Texas red. The cross-sectional area of the myofibers was determined by calculating the number of pixels (0.83 mu m(2)) overlying each myofiber after subtracting the ConA-Texas red image from the MF-20-FITC image for each region of interest. As expected, myofibers in the irradiated muscle were smaller (P < 0.05) than those in the non-irradiated muscle. This double fluorescence staining protocol combined with image analysis is accurate and less labor-intensive than classical procedures for determining the cross-sectional area of myofibers.

The effect of in vivo and in vitro irradiation (25 Gy) on the subsequent in vitro growth of satellite cells

The effect of in vivo and in vitro irradiation on subsequent satellite cell growth, in vitro, was investigated to ascertain the ability of a 25 Gy dose to inhibit satellite cell proliferation. Satellite cells were isolated from the left (irradiated) and right (non-irradiated) Pectoralis thoracicus of two-week-old tom turkeys 16 h (n=3) and seven weeks (n=2) after the left Pectoralis thoracicus had been irradiated (25 Gy). Satellite cells isolated from the irradiated and non-irradiated muscles exhibited similar (P>0.10) in vitro proliferation indicating that a population of satellite cells survived an in vivo dose of 25 Gy. In additional experiments, satellite cell cultures derived from tom turkey Pectoralis thoracicus were irradiated (25 Gy) in vitro. The number of satellite cells did not (P>0.05) increase in irradiated cultures for 134 h following irradiation, while satellite cells in non-irradiated cultures proliferated (P<0.05) over this time. At later time periods, satellite cell number increased (P<0.05) in irradiated cultures indicating that a population of satellite cells survived irradiation. The results of these in vitro experiments suggest that a 25 Gy dose of irradiation does not abolish satellite cell divisions in the turkey Pectoralis thoracicus.

Quantitation of satellite cell proliferation in vivo using image analysis

A nonisotopic, double fluorescence technique was developed to study myogenic satellite cell proliferation in posthatch turkey skeletal muscle. Labeled satellite cell nuclei were identified on enzymatically isolated myofiber segments using a mouse monoclonal antibody (anti-BrdU) followed by fluorescein-5-isothiocyanate (FITC) conjugated goat anti-mouse IgG secondary antibody. Myofiber nuclei (myonuclei+satellite cell nuclei) were counterstained with propidium iodide (PI). The myofiber segment length, myofiber segment diameter, and the number of PI and FITC labeled nuclei contained in each segment was determined using a Nikon fluorescence microscope, a SIT video camera and Image-1 software. Data collected by three different operators of the image analysis system revealed 5.0 +/- 1.4 satellite cell nuclei per 1000 myofiber nuclei and 5284 +/- 462 microns3 of cytoplasm surrounding each myofiber nucleus in the pectoralis thoracicus of 9-week-old tom turkeys. BrdU immunohistochemistry coupled with the new approach of PI staining of whole myofiber mounts is an effective combination to allow the use of an efficient semi-automated image analysis protocol.

Satellite cell mitotic activity in posthatch turkey skeletal muscle growth

The relationship between satellite cell mitotic activity and skeletal myofiber growth was examined in Pectoralis thoracicus and Biceps femoris muscles of Large White tom turkeys (Nicholas strain) at 3, 6, 9, 18, and 26 wk of age. Mitotically active satellite cells were labeled with 5-bromo-2'-deoxyuridine (BrdU). Labeled satellite cells were identified on enzymatically isolated myofiber segments using mouse anti-BrdU followed by fluorescein-5-isothiocyanate (FITC) conjugated goat anti-mouse IgG secondary antibodies. Myofiber nuclei (satellite cell nuclei + myonuclei) were counterstained with propidium iodide (PI). Myofiber segment diameter, myofiber segment length, and number of FITC- and PI-labeled nuclei were determined for each segment. At each age interval there was an increase in myofiber diameter, suggesting that the myofibers were growing during the entire experimental period. There was an age-related (P < .001) decrease in satellite cell mitotic activity and an age-related increase (P < .001) in the cytoplasmic volume to nucleus ratio (CNR) from 3 to 26 wk of age. An early phase of myofiber growth, between 3 and 6 wk of age, was characterized by a high level of satellite cell mitotic activity and increased CNR. Between 6 and 9 wk of age, satellite cell mitotic activity decreased, but the CNR showed no change (P > .05). During a late phase of myofiber growth, beyond 9 wk of age, satellite cell mitotic activity continued to decrease and myofiber growth occurred by an increased CNR. This study demonstrated that both Pectoralis thoracicus and Biceps femoris undergo a significant late phase of growth without appreciable production of myonuclei by satellite cell proliferation.