A flexible and fast Monte Carlo-based model of diffuse reflectance has been developed for the extraction of the absorption and scattering properties of turbid media, such as human tissues. This method is valid for a wide range of optical properties and is easily adaptable to existing probe geometries, provided a single phantom calibration measurement is made. A condensed Monte Carlo method was used to speed up the forward simulations. This model was validated by use of two sets of liquid-tissue phantoms containing Nigrosin or hemoglobin as absorbers and polystyrene spheres as scatterers. The phantoms had a wide range of absorption $\left(0–20{\text{cm}}^{-1}\right)$ and reduced scattering coefficients $\left(7–33{\text{cm}}^{-1}\right)$. Mie theory and a spectrophotometer were used to determine the absorption and reduced scattering coefficients of the phantoms. The diffuse reflectance spectra of the phantoms were measured over a wavelength range of $350–850\text{\hspace{0.17em} nm}$. It was found that optical properties could be extracted from the experimentally measured diffuse reflectance spectra with an average error of $3\%$ or less for phantoms containing hemoglobin and $12\%$ or less for phantoms containing Nigrosin.

Exercise has been shown to improve postischemia perfusion of normal tissues; we investigated whether these effects extend to solid tumors. Estrogen receptor–negative (ER-, 4T1) and ER+ (E0771) tumor cells were implanted orthotopically into syngeneic mice (BALB/c, N = 11–12 per group) randomly assigned to exercise or sedentary control. Tumor growth, perfusion, hypoxia, and components of the angiogenic and apoptotic cascades were assessed by MRI, immunohistochemistry, western blotting, and quantitative polymerase chain reaction and analyzed with one-way and repeated measures analysis of variance and linear regression. All statistical tests were two-sided. Exercise statistically significantly reduced tumor growth and was associated with a 1.4-fold increase in apoptosis (sedentary vs exercise: 1544 cells/mm², 95% CI = 1223 to 1865 vs 2168 cells/mm², 95% CI = 1620 to 2717; P = .048), increased microvessel density (P = .004), vessel maturity (P = .006) and perfusion, and reduced intratumoral hypoxia (P = .012), compared with sedentary controls. We also tested whether exercise could improve chemotherapy (cyclophosphamide) efficacy. Exercise plus chemotherapy prolonged growth delay compared with chemotherapy alone (P < .001) in the orthotopic 4T1 model (n = 17 per group). Exercise is a potential novel adjuvant treatment of breast cancer.

Significance: Engineering of highly functional skeletal muscle tissues can provide accurate models of muscle physiology and disease and aid treatment of various muscle disorders. Previous tissue-engineering efforts have fallen short of recreating structural and contractile properties of native muscle in vitro. Here, we describe the creation of biomimetic skeletal muscle tissues with structural, functional, and myogenic properties characteristic of native muscle and contractile stress values that surpass those of neonatal rat muscle. When implanted and real-time imaged in live animals, engineered muscle grafts undergo robust vascularization and perfusion, exhibit continued myogenesis, and show further improvements in intracellular calcium handling and contractile function. This process is significantly enhanced by myogenic predifferentiation and formation of aligned muscle architecture in vitro.