RESUMO
The National Institute of Health R25 Research Education Program was evaluated in the second year of implementation. Twelve mentors and 20 underrepresented minority students (URMs) scholars from partnerships and collaborations among five colleges and universities were added to the program to provide a more diverse research experience. Findings reveal that 100% of research mentors agree that the approachableness and accessibility of the program coordinator were beneficial in achieving mentorship goals and objectives. In addition, 85% of the students strongly agreed that the presentation of their research findings and the weekly reflection on goals, identification of accomplishments, and obstacles through the individual development plan were very effective. Of the 23 successfully tracked students for 2 years, six URMs (26.09%) obtained a bachelor's degree and were admitted into a graduate program; two were directly admitted to a PhD program in biomedical sciences.
RESUMO
Aging alters the skeletal muscle response to overload-induced growth. The onset of functional overload is characterized by increased myoblast proliferation and an altered muscle metabolic profile. The onset of functional overload is associated with increased energy demands that are met through the interconversion of lactate and pyruvate via the activity of lactate dehydrogenase (LDH). Testosterone targets many of the processes activated at the onset of functional overload. However, the effect of aging on this metabolic plasticity at the onset of functional overload and how anabolic steroid administration modulates this response is not well understood. The purpose of this study was to determine if aging would alter overload-induced LDH activity and expression at the onset of functional overload and whether anabolic steroid administration would modulate this response. Five-month and 25-month male Fischer 344xF1 BRN were given nandrolone decanoate (ND) or sham injections for 14days and then the plantaris was functionally overloaded (OV) for 3days by synergist ablation. Aging reduced muscle LDH-A & LDH-B activity 70% (p<0.05). Aging also reduced LDH-A mRNA abundance, however there was no age effect on LDH-B mRNA abundance. In 5-month muscle, both ND and OV decreased LDH-A and LDH-B activity. However, there was no synergistic or additive effect. In 5-month muscle, ND and OV decreased LDH-A mRNA expression with no change in LDH-B expression. In 25-month muscle, ND and OV increased LDH-A and LDH-B activity. LDH-A mRNA expression was not altered by ND or OV in aged muscle. However, there was a main effect of OV to decrease LDH-B mRNA expression. There was also an age-induced LDH isoform shift. ND and OV treatment increased the "fast" LDH isoforms in aged muscle, whereas ND and OV increased the "slow" isoforms in young muscle. Our study provides evidence that aging alters aspects of skeletal muscle metabolic plasticity normally induced by overload and anabolic steroid administration.
Assuntos
Envelhecimento/metabolismo , Anabolizantes/farmacologia , L-Lactato Desidrogenase/metabolismo , Músculo Esquelético/metabolismo , Nandrolona/análogos & derivados , Animais , Composição Corporal , Peso Corporal , Citrato (si)-Sintase/metabolismo , Isoenzimas/metabolismo , Lactato Desidrogenase 5 , Masculino , Músculo Esquelético/efeitos dos fármacos , Nandrolona/farmacologia , Decanoato de Nandrolona , Distribuição Aleatória , Ratos Endogâmicos F344RESUMO
Functionally overloading rat soleus muscle by synergist ablation induces a rapid increase in mass. Muscle remodeling during the first week of overload is critical for the overload-induced growth. Anabolic steroid modulation of this overload-induced remodeling response is not well understood. The purpose of this study was to determine whether pretreatment with nandrolone decanoate, a clinically administered anabolic steroid, alters muscle morphology and gene expression related to muscle growth during the initiation of functional overload in the rat soleus muscle. Adult (5 mo) male Fisher 344 x Brown Norway rats were randomly assigned to control (Sham), 3-day functional overload (OV), nandrolone decanoate administration (ND), or 3-day functional overload with nandrolone decanoate administration (OV+ND) treatment groups. Morphologically, OV increased the percentage of small (361%) and large (150%) fibers and expanded the ECM 50%. ND administration decreased the 3-day OV induction of small fibers 51% and nuclei associated with the ECM 20%. ND administration also attenuated the induction of cell cycle regulator p21 (64%) and myogenin (37%) mRNAs after 3 days of overload. These data demonstrate that nandrolone decanoate pretreatment can alter morphological and cell cycle regulator expression related to muscle growth at the onset of functional overload.
Assuntos
Anabolizantes/farmacologia , Ciclo Celular/efeitos dos fármacos , Músculo Esquelético/citologia , Músculo Esquelético/fisiologia , Nandrolona/análogos & derivados , Nandrolona/farmacologia , Esforço Físico/fisiologia , Animais , Northern Blotting , Proliferação de Células , Ciclina D1/metabolismo , Regulação da Expressão Gênica , Fator de Crescimento Insulin-Like I/metabolismo , Masculino , Fibras Musculares Esqueléticas/fisiologia , Fibras Musculares Esqueléticas/ultraestrutura , Fatores de Regulação Miogênica/metabolismo , Decanoato de Nandrolona , Proteína Oncogênica p21(ras)/metabolismo , Tamanho do Órgão , Fosforilação , RNA/biossíntese , Ratos , Ratos Endogâmicos F344 , Reação em Cadeia da Polimerase Via Transcriptase Reversa , Proteínas Quinases S6 Ribossômicas 70-kDa/metabolismoRESUMO
Both functional overload and hindlimb disuse induce significant energy-dependent remodeling of skeletal muscle. Lactate dehydrogenase (LDH), an important enzyme involved in anaerobic glycolysis, catalyzes the interconversion of lactate and pyruvate critical for meeting rapid high-energy demands. The purpose of this study was to determine rat soleus LDH-A and -B isoform expression, mRNA abundance, and enzymatic activity at the onset of increased or decreased loading in the rat soleus muscle. The soleus muscles from male Sprague-Dawley rats were functionally overloaded for up to 3 days by a modified synergist ablation or subjected to disuse by hindlimb suspension for 3 days. LDH mRNA concentration was determined by Northern blotting, LDH protein isoenzyme composition was determined by zymogram analysis, and LDH enzymatic activity was determined spectrophotometrically. LDH-A mRNA abundance increased by 372%, and LDH-B mRNA abundance decreased by 43 and 31% after 24 h and 3 days of functional overload, respectively, compared with that in control rats. LDH protein expression demonstrated a shift by decreasing LDH-B isoforms and increasing LDH-A isoforms. LDH-B activity decreased 80% after 3 days of functional overload. Additionally, LDH-A activity increased by 234% following 3 days of hindlimb suspension. However, neither LDH-A or LDH-B mRNA abundance was affected following 3 days of hindlimb suspension. In summary, the onset of altered loading induced a differential expression of LDH-A and -B in the rat soleus muscle, favoring rapid energy production. Long-term altered loading is associated with myofiber conversion; however, the rapid changes in LDH at the onset of altered loading may be involved in other physiological processes.
Assuntos
Transtornos Traumáticos Cumulativos/fisiopatologia , Elevação dos Membros Posteriores/efeitos adversos , Elevação dos Membros Posteriores/métodos , L-Lactato Desidrogenase/metabolismo , Músculo Esquelético/fisiopatologia , Atrofia Muscular/etiologia , Atrofia Muscular/fisiopatologia , Esforço Físico , Adaptação Fisiológica/fisiologia , Animais , Masculino , Ratos , Ratos Sprague-DawleyRESUMO
The introduction of flow cytometric bead-based technology has added a new approach for investigators to simultaneously measure multiple analytes in biological and environmental samples. This new technology allows for (1) evaluation of multiple analytes in a single sample; (2) utilization of minimal sample volumes to glean data; (3) reproducibility and results comparative with previous experiments; (4) direct comparison with existing assays; and (5) a more rapid evaluation of multiple samples in a single platform. The cytometric bead array (CBA) system enables simultaneous measurement of multiple analytes in sample volumes too small for traditional immunoassays. Results have been presented for the analysis of a variety of human cytokines. In addition, the technology allows for the design and creation of assays to measure a variety of analytes including inflammatory mediators, chemokines, immunoglobulin isotypes, intracellular signaling molecules, apoptotic mediators, adhesion molecules, and antibodies. New initiatives put forward by the Human Genome Project and the FDA require the development and use of assays for the rapid simultaneous quantitation of multiple analytes. The CBA technology provides the ability to quantify multiple proteins within a given sample, with precision and consistency.
Assuntos
Citometria de Fluxo/métodos , Imunoensaio/métodos , Anafilatoxinas/análise , Anafilatoxinas/imunologia , Animais , Anticorpos/análise , Anticorpos/imunologia , Apoptose/imunologia , Caspases/análise , Caspases/imunologia , Citocinas/análise , Citocinas/imunologia , Ensaio de Imunoadsorção Enzimática , Humanos , Microesferas , Fosfotransferases/análise , Fosfotransferases/imunologia , Reprodutibilidade dos Testes , Sensibilidade e EspecificidadeRESUMO
The regulation of skeletal muscle regeneration and growth in response to functional overload is a coordinated interaction of mechanical and endocrine signaling pathways. This study's purpose was to determine if RhoA expression and activity in rat plantaris muscle was induced by functional overload with or without anabolic steroid administration. Male Sprague Dawley (125 g) rats were subjected to bilateral ablation of the gastrocnemius muscle for 3 and 21 days and treated with nandrolone decanoate (ND, 6 mg/kg b.w.) or sesame seed oil injections. Western blot analysis revealed that RhoA protein expression was induced 2.1-fold by overload and 1.9-fold by ND at 3 days. RhoA protein remained elevated by overload after 21 days (3.8-fold). In addition, RhoA protein expression in C2C12 myotubes was induced after 18 h of 1% (1.8-fold) or 2% (2.2-fold) chronic radial stretch. Competitive RT PCR revealed that RhoA mRNA concentration increased 1.9-fold with ND, 2.9-fold with overload, and 11.8-fold with overload and ND administration when compared to sham at 3 days, indicating pre-translational control of RhoA by ND and a synergism between ND and overload to up-regulate RhoA mRNA. The ratio of RhoA protein associated with the muscle membrane fraction, an indicator of RhoA activity, increased 3.7-fold after 3 days of overload compared to controls. Although ND with overload (3.8-fold) produced a larger induction of RhoA protein than overload alone, the ratio of RhoA protein associated with the membrane fraction was not altered by ND treatment at 3 days. In conclusion, RhoA is an integrator of both mechanical and growth factor signaling whose expression and activity are increased by the combination of anabolic steroid and functional overload treatments in rat plantaris muscle.