PubMed Health⌕ Search

Biomedical subjects

Britton Chance

Publications and source records attributed to Britton Chance.

At least 37 records · Page 2Linked to original sources

Diffuse optical tomography of breast cancer during neoadjuvant chemotherapy: a case study with comparison to MRI.

We employ diffuse optical tomography (DOT) to track treatment progress in a female subject presenting with locally advanced invasive carcinoma of the breast during neoadjuvant chemotherapy. Three-dimensional images of total hemoglobin concentration and scattering identified the tumor. Our measurements reveal tumor shrinkage during the course of chemotherapy, in reasonable agreement with magnetic resonance images of the same subject. A decrease in total hemoglobin concentration contrast between tumor and normal tissue was also observed over time. The results demonstrate the potential of DOT for measuring physiological parameters of breast lesions during chemotherapy.

Adult↗

Reduced heterogeneity of muscle deoxygenation during heavy bicycle exercise.

PURPOSE: This study evaluated heterogeneity of muscle O2 dynamics in a single muscle during bicycle exercise using an eight-channel near-infrared continuous wave spectroscopy (NIRcws) mapping system. METHODS: Nine healthy subjects performed bicycle exercise at fixed workloads of 20, 40, 60, 80, and 100% maximal workload for 5 min at each level. Muscle oxygenation in the vastus lateralis (VL) during and after each exercise was monitored using the NIRcws mapping system. Pulmonary O2 uptake and heart rate were monitored continuously during the experiment. Blood samples were taken to measure blood lactate concentration at 30 s after each exercise stage. RESULTS: Half time reoxygenation, the time taken to reach a value of half-maximal recovery, was significantly delayed in distal sites compared with proximal sites of VL. Conversely, muscle deoxygenation for all measurement sites increased incrementally with higher exercise workloads, and no significant difference of deoxygenation level showed within each channel. However, relative dispersion of muscle deoxygenation during exercise significantly decreased when the workload increased. Moreover, relative dispersion of muscle deoxygenation between the subjects also decreased with an increase in the workload. CONCLUSION: Muscle deoxygenation in a single muscle was more heterogeneous at lower exercise workloads, and variations of the muscle deoxygenation heterogeneity between subjects were greater at lower exercise workloads.

Adult↗

Evaluation of physiological responses during recovery following three resistance exercise programs.

The present study was conducted to examine (a) whether there is an association between maximal oxygen uptake (Vo(2)max) and reduction in postexercise heart rate (HR) and blood lactate concentrations ([La]) following resistance exercise and (b) how intensity and Volume of resistance exercise affect postexercise Vo(2). Eleven regularly weight-trained males (20.8 +/- 1.3 years; 96.2 +/- 14.4 kg, 182.4 +/- 7.3 cm) underwent 4 sets of squat exercise on 3 separate occasions that differed in both exercise intensity and volume. During each testing session, subjects performed either 15 repetitions.set(-1) at 60% of 1 repetition maximum (1RM) (L), 10 repetitions.set(-1) at 75% of 1RM (M), or 4 repetitions.set(-1) at 90% of 1RM (H). During each exercise, Vo(2) and HR were measured before (PRE), immediately post (IP), and at 10 (10P), 20 (20P) 30 (30P), and 40 (40P) minutes postexercise. The [La] was measured at PRE, IP, 20P, and 40P. Decrease in HR (DeltaHR) was determined by subtracting HR at 10P from that at IP, whereas decrease in [La] (Delta[La]) was computed by subtracting [La] at 20P from that at IP. A significant correlation (p < 0.05) was found between Vo(2)max and DeltaHR in all exercise conditions. A significant correlation (p < 0.05) was also found between Vo(2)max and Delta[La] in L and M but not in H. The Vo(2) was higher (p < 0.05) during M than H at IP and 10P, while no difference was seen between L and M and between L and H. These results indicate that those with greater aerobic capacity tend to have a greater reduction in HR and [La] during recovery from resistance exercise. In addition, an exercise routine performed at low to moderate intensity coupled with a moderate to high exercise volume is most effective in maximizing caloric expenditure following resistance exercise.

Adaptation, Physiological↗

The effect of a competitive collegiate football season on power performance and muscle oxygen recovery kinetics.

Ten intercollegiate football players were tested within 3 days prior to (T1) and the day following the end (T2) of football preseason training camp and during weeks 7 (T3) and 11 (T4) of the competitive season. During each testing session, subjects performed a 30-second Wingate anaerobic power test. Near-infrared continuous wave spectroscopy was used to measure muscle deoxygenation during exercise. No changes in any power performance measures were seen during the competitive football season. A significant (p < 0.05) decrease in the extent of deoxygenation during exercise was observed between T2 (72.6 +/- 19.4%) and T4 (50.2 +/- 14.2%). A 30 and 29% difference (p < 0.05) in the onset of reoxygenation was observed between T1 and T3 and T4, respectively. A 51% decrease (p < 0.05) in halftime recovery was observed between T2 and T3. Results indicate that the extent of muscle deoxygenation is reduced during high-intensity exercise and that muscle oxygen recovery kinetics improves over the duration of a competitive season of football.

Adult↗

Photobiomodulation directly benefits primary neurons functionally inactivated by toxins: role of cytochrome c oxidase.

Far red and near infrared (NIR) light promotes wound healing, but the mechanism is poorly understood. Our previous studies using 670 nm light-emitting diode (LED) arrays suggest that cytochrome c oxidase, a photoacceptor in the NIR range, plays an important role in therapeutic photobiomodulation. If this is true, then an irreversible inhibitor of cytochrome c oxidase, potassium cyanide (KCN), should compete with LED and reduce its beneficial effects. This hypothesis was tested on primary cultured neurons. LED treatment partially restored enzyme activity blocked by 10-100 microm KCN. It significantly reduced neuronal cell death induced by 300 microm KCN from 83.6 to 43.5%. However, at 1-100 mm KCN, the protective effects of LED decreased, and neuronal deaths increased. LED significantly restored neuronal ATP content only at 10 microm KCN but not at higher concentrations of KCN tested. Pretreatment with LED enhanced efficacy of LED during exposure to 10 or 100 microm KCN but did not restore enzyme activity to control levels. In contrast, LED was able to completely reverse the detrimental effect of tetrodotoxin, which only indirectly down-regulated enzyme levels. Among the wavelengths tested (670, 728, 770, 830, and 880 nm), the most effective ones (830 nm, 670 nm) paralleled the NIR absorption spectrum of oxidized cytochrome c oxidase, whereas the least effective wavelength, 728 nm, did not. The results are consistent with our hypothesis that the mechanism of photobiomodulation involves the up-regulation of cytochrome c oxidase, leading to increased energy metabolism in neurons functionally inactivated by toxins.

Adenosine Triphosphate↗

Metabolic imaging of tumors using intrinsic and extrinsic fluorescent markers.

One of the biochemical "hallmarks" of malignancy is enhanced tumor glycolysis, which is primary due to the overexpression of glucose transporters (GLUTs) and the increased activity of mitochondria-bound hexokinase in tumors. Easy methods for assessing glucose utilization in vitro and in vivo should find widespread application in biological and biomedical studies, as illustrated by the adoption of FDG PET imaging in medicine. We have recently synthesized a new NIR fluorescent pyropheophorbide conjugate of 2-deoxyglucose (2DG), Pyro-2DG, as a GLUT-targeted photosensitizer. In this study, we have evaluated the in vivo uptake of Pyro-2DG and found that Pyro-2DG selectively accumulated in two tumor models, 9L glioma in the rat and c-MYC-induced mammary tumor in the mouse, compared to surrounding normal muscle tissues at a ratio of about 10:1. By simultaneously performing redox ratio and fluorescence imaging, a high degree of correlation between the PN/(Fp+PN) redox ratio, where PN denotes reduced pyridine nucleotides (NADH) and Fp denotes oxidized flavoproteins, and the Pyro-2DG uptake was found in both murine tumor models, indicating that Pyro-2DG could serve as an extrinsic NIR fluorescent metabolic index for the tumors. The fact that only a low level of correlation was observed between the redox ratio and the uptake of Pyro-acid (the free fluorophore without the 2-deoxyglucose moiety) supports the hypothesis that Pyro-2DG is an index of the mitochondrial status (extent of PN reduction) of a tumor.

Animals↗

Protease-triggered photosensitizing beacon based on singlet oxygen quenching and activation.

We report a new concept for type-II photosensitization, based on incorporating the photosensitizer (PS) and a singlet-oxygen (1O2) quenching/scavenging molecule onto a disease-targeting linker, such that the PS becomes activatable by light only when targeting has occurred. In this first proof-of-concept report, a model photosensitizing beacon was synthesized containing a pyropheophorbide as the PS and a carotenoid as the 1O2 quencher. These were kept in close proximity by the self-folding of a caspase-3-specific peptide sequence. Upon caspase-3-induced cleavage, the 1O2 production increased markedly, as measured directly by 1O2 near-infrared luminescence and lifetime measurements.

Carotenoids↗

Diffuse optical tomography with physiological and spatial a priori constraints.

Diffuse optical tomography is a typical inverse problem plagued by ill-condition. To overcome this drawback, regularization or constraining techniques are incorporated in the inverse formulation. In this work, we investigate the enhancement in recovering functional parameters by using physiological and spatial a priori constraints. More accurate recovery of the two main functional parameters that are the blood volume and the relative saturation is demonstrated through simulations by using our method compared to actual techniques.

Algorithms↗

Carbocyanine labeled LDL for optical imaging of tumors.

RATIONALE AND OBJECTIVES: The purpose of this study was to define and characterize carbocyanine labeled low-density lipoprotein (LDL) to be used in the optical imaging of LDL receptor (LDLr)-overexpressing tumor models. MATERIALS AND METHODS: 1,1'-dioctadecyl-3,3,3',3'-tetramethylindocarbocyanine perchlorate (DiI) was used to label LDL (DiI-LDL). Scatchard plots were generated to determine the maximum binding capacity B(max) and dissociation constants K(D) of DiI-LDL in B16 melanoma (B16) and hepatoblastoma G(2) (HepG(2)) cell lines. Selective uptake of DiI-LDL into both tumor cells and corresponding subcutaneous tumors in mice were demonstrated by confocal microscopy and three-dimensional Cryo-imaging, respectively. RESULTS: The labeling efficiency of DiI-LDL was 61 ng DiI/microg LDL protein (34 mol DiI/mol LDL protein). B(max) and K(D) for B16 cells were 6.311 ng LDL/mg cell protein and 60.38 microg protein/mL (117 nM), respectively. B(max) and K(D) were 7.573 ng LDL/mg cell protein and 26.79 microg protein/mL (52 nM) for HepG(2) cells, respectively. Confocal microscopic images showed specific uptake of DiI-LDL throughout the cytoplasm in the B16/HepG(2) cells. Cryo-imaging demonstrated preferential accumulations of DiI-LDL in the viable tumor regions of both B16 and HepG(2) tumors compared with their adjacent normal tissues and corresponding necrotic tumor regions. In addition, uptake of DiI-LDL by the HepG(2) tumor was much higher than that of the B16 tumor, consistent with the fact that the probe binding affinity for LDLrs of HepG(2) cells is 2.3 times that of B16 cells. CONCLUSION: This study suggested that carbocyanine labeled LDL could be used for optical imaging of tumors overexpressing LDLr.

Animals↗

The Stopped-flow Method and Chemical Intermediates in Enzyme Reactions - A Personal Essay.

My perspective does not deal directly with photosynthesis research. However, the methods evolved have played an important role in several areas of biochemistry and biophysics including photosynthesis. Improvements of rapid reaction methods, based upon the pioneering studies of Hamilton Hartridge and F.J.W. Roughton, and Glenn Millikan, required a detailed study of the hydraulics of small-bore tubes and jet mixers, taking into account, that economy of reactants was demanded by the sparcity of enzyme preparations in the 1930s. This Personal perspective recites the steps taken to minimize the volumes expended in rapid flow studies, together with the improvements in electronic technology of rapid and sensitive spectrophotometry of labile intermediates in enzyme reactions. Of the methods studied, continuous, accelerated and stopped flow, the latter was designed for the highest fluid economy and subsequently proved to be of wide use for studying biochemical kinetics. Advances in fast spectrophotometry of dilute solutions led to great improvements in Millikan's dual-wavelength system, both in speed of recording and decreases of background noise level, largely due to electronic stabilization of light sources and sensitive amplifiers. The application of these technologies to studies of hemoglobin, myoglobin and heme enzymes was, more recently, followed by studies of suspensions of organelles, cells, and tissues not only in vivo but also at low temperatures with cryoprotectants, leading to the use of flash activation in carbon monoxide inhibited heme enzymes. Laser technology allowed photosynthetic systems to be studied at cryotemperatures, leading to the development of electron tunneling theories for biological reactions (not discussed in this paper). All in all, the many fundamental developments of electronics, optics and hydraulics indicate how technology can respond effectively to the needs of biology in general, and photobiology in particular.

Journal Article↗

Inhibition of tumor necrosis factor-induced apoptosis in transgenic mouse liver expressing creatine kinase.

BACKGROUND: The mitochondrion acts as a pivotal decision center in many types of apoptotic responses. To clarify the effects of the enhanced mitochondrial function on tumor necrosis factoralpha (TNFalpha)-induced apoptosis, we studied hepatic injuries in transgenic mice whose livers express creatine kinase (CK). METHODS: Mice fed a diet containing 10% creatine, came to accumulate phosphocreatine and to enhance hepatic ATP levels and mitochondrial oxidative phosphorylation activities. TNFalpha-mediated hepatic apoptosis in normally fed and Cr-feeding CK transgenic mice were assessed. RESULTS: TNFalpha and actinomycin D cause severe liver failure in normally fed transgenic mice, and in the wild-type mice. In contrast, no significant elevations in transaminase levels after injection were observed in Cr feeding transgenic mice. The disruption of the mitochondrial transmembrane potential at 2 h after TNFalpha injection, prior to ATP depletion, activation of caspase 3 like protease, and DNA fragmentation at 4-6 h after injection, were observed in normally fed transgenic mice. These were fully suppressed in Cr feeding transgenic mice. However, anti-Fas antibody-induced apoptosis was not inhibited in both groups. CONCLUSIONS: The results indicate that TNFalpha-induced apoptosis was inhibited in CK transgenic mice livers by maintaining mitochondrial function.

Adenine↗

Cyclophosphamide treatment modifies tumor oxygenation and glycolytic rates of RIF-1 tumors: 13C magnetic resonance spectroscopy, Eppendorf electrode, and redox scanning.

The effect of cyclophosphamide (Cp) on the glycolytic rate of radiation-induced fibrosarcomas (RIF-1) was measured in vivo in C3H mice by following the production of [3-(13)C]lactate after tail vein infusion of labeled [1-(13)C]glucose. Cp administered i.p. at a dose of 300 mg/kg caused a significant drop in glycolytic rate 24 h after treatment (P < 0.01). This drop was accompanied by an increase in [C-3]/[C-4] glutamate ratio in perchloric acid extracts of the tumors, indicating an increase in the Kreb's cycle activity. Treatment with Cp led to a significant decrease (P < 0.01) in tissue pO(2), measured in vivo with an oxygen Eppendorf electrode. Increases in NADH levels were also observed in rapidly frozen excised tumors examined by three-dimensional optical redox scanning. A significant decrease in tumor pO(2) and an increase in the NADH levels are suggestive of an increase in oxygen consumption by these tumors after Cp treatment. Overall, these data indicate that the reduction in glycolytic rate of Cp-treated RIF-1 tumors is due to an increase in aerobic metabolism.

Animals↗

Relationship between muscle architectural features and oxygenation status determined by near infrared device.

This study tested whether regional differences in oxygenation status could result from differences in muscle fiber architecture. Architectural properties, oxygen supply, and consumption in the medial head of the gastrocnemius muscle (GM) were determined in vivo in six men using B-mode ultrasound and functional near infrared (NIR) imaging devices. Fascicle length, fascicle angle, NIR-O(2) saturation (deoxygenated Hb or oxygenated Hb), and NIR-blood volume (sum of deoxygenated and oxygenated Hb) were obtained in the distal and proximal portions of the GM at rest and during contraction. Exercise consisted of 2 min of standing plantar flexion at 1 Hz with an additional load of 50% of each subject's weight. Plantar flexion produced larger decreases (Delta: difference between rest and exercise values) in NIR-O(2) saturation [mean saturation (SD) of 0.14 (0.05) vs 0.07 (0.04) optical density units] and NIR-blood volume [mean saturation (SD) of -0.23 (0.08) vs -0.13 (0.04) optical density units] in the distal compared with the proximal portion ( P<0.05 for all comparisons). It also produced larger changes (Delta) in fascicle length [mean length (SD) of -16.5 (4.7) vs -8.2 (4.2) mm] and fascicle angle (mean angle (SD) of 10.8 (1.4) degrees vs 3.9 (2.1) degrees ] in the distal compared with the proximal portion ( P<0.05 for all comparisons). There were significant correlations between DeltaNIR-O(2 )saturation and Deltafascicle length ( r=-0.84, P<0.05), and between DeltaNIR-O(2) saturation and Deltafascicle angle ( r=-0.90, P<0.05), between DeltaNIR-blood volume and Deltafascicle length ( r=0.91, P<0.05), between DeltaNIR-blood volume and Deltafascicle angle ( r=-0.85, P<0.05). In conclusion, the plantar flexion exercise produced regional differences in oxygenation status consistent with regional differences in muscle architecture.

Adult↗

Transabdominal near infrared oximetry of hypoxic stress in fetal sheep brain in utero.

The feasibility of transabdominal near-infrared (NIR) spectroscopy for detecting and quantifying fetal hypoxia in utero is demonstrated in a pregnant ewe model. A frequency domain NIR spectroscopy probe, consisting of two detectors and six sources operating at three wavelengths (675, 786, and 830 nm), was placed on the maternal abdomen directly above the fetal head. Fetal hypoxia was indirectly induced through occlusion of uterine blood flow for approximately 3 min. NIR photon diffusion measurements were made during a baseline period, during hypoxia of the fetus, and during recovery. Fetal blood samples were drawn from the fetal brachial artery and jugular veins at several time points during the cycle. Seven hypoxic cycles were induced in a total of five pregnant ewes. The NIR measurements were analyzed by using a two-layer diffusion model to deconvolve the fetal blood saturation from that of the pregnant ewe. Fetal hypoxia was detected. Good agreement was found between fetal blood saturation determined by the transabdominal NIR method and arterial and venous fetal blood saturation quantified from fetal blood samples by using a hemoximeter.

Abdomen↗

Discrepancy between cardiorespiratory system and skeletal muscle in elite cyclists after hypoxic training.

BACKGROUND: The purpose of this study was to determine the effects of hypoxic training on the cardiorespiratory system and skeletal muscle among well-trained endurance athletes in a randomized cross-over design. METHODS: Eight junior national level competitive cyclists were separated into two groups; Group A trained under normoxic condition (21% O2) for 2 hours/day, 3 days/week for 3 weeks while Group B used the same training protocol under hypoxic condition (15% O2). After 3 weeks of each initial training condition, five weeks of self-training under usual field conditions intervened before the training condition was switched from NT to HT in Group A, from HT to NT in Group B. The subjects were tested at sea level before and after each training period. O2 uptake (O2), blood samples, and muscle deoxygenation were measured during bicycle exercise test. RESULTS AND DISCUSSION: No changes in maximal workload, arterial O2 content, O2 at lactate threshold and O2max were observed before or after each training period. In contrast, deoxygenation change during submaximal exercise in the vastus lateralis was significantly higher at HT than NT (p < 0.01). In addition, half time of oxygenation recovery was significantly faster after HT (13.2 PlusMinus; 2.6 sec) than NT (18.8 PlusMinus; 2.7 sec) (p < 0.001). CONCLUSIONS: Three weeks of HT may not give an additional performance benefit at sea level for elite competitive cyclists, even though HT may induce some physiological adaptations on muscle tissue level.

Journal Article↗

Correlation between near-infrared spectroscopy and magnetic resonance imaging of rat brain oxygenation modulation.

We measure the tissue oxygen and haemoglobin concentrations in the rat brain during modulation of inhaled oxygen concentration (FiO2), using non-invasive frequency domain near-infrared oximetry. The rise in oxygenated haemoglobin concentration and the decline in deoxygenated haemoglobin concentration are demonstrated in correspondence with the modulation of FiO2, which is changed from 20% to 100% in increments of 20%. Furthermore, the tissue oxygenation saturation also shows the corresponding trend and changes ranging from approximately 70% to 90%. The relative changes in deoxygenated haemoglobin concentration are compared to the blood-oxygenation-level-dependent (BOLD) MRI signal recorded during a similar FiO2 protocol. A linear relationship with high correlation coefficient between the relative changes in the BOLD MRI signal and the NIRS signal is observed.

Administration, Inhalation↗

Quantitative brain tissue oximetry, phase spectroscopy and imaging the range of homeostasis in piglet brain.

The quantification of tissue oxygen by frequency or time domain methods has been discussed in a number of prior publications where the meaning of the tissue hemoglobin oxygen saturation was unclear and where the CW instruments were unsuitable for proper quantitative measurements [1, 2]. The development of the IQ Phase Meter has greatly simplified and made reliable the difficult determination of precise phase and amplitude signals from brain. This contribution reports on the calibration of the instrument in model systems and the use of the instrument to measure tissue saturation (StO2) in a small animal model. In addition, a global interpretation of the meaning of tissue oxygen has been formulated based on the idea that autoregulation will maintain tissue oxygen at a fixed value over a range of arterial and venous oxygen values over the range of autoregulation. Beyond that range, the tissue oxygen is still correctly measured but, as expected, approaches the arterial saturation at low metabolic rates and the venous saturation at high metabolic rates of mitochondria.

Animals↗