Time filter

Source Type

Allenstown Elementary School, NH, United States

Khan N.,Center for Viable Systems | Khan N.,Norris Cotton Cancer Center | Hou H.,Center for Viable Systems | Hou H.,Norris Cotton Cancer Center | And 7 more authors.
Advances in Experimental Medicine and Biology | Year: 2014

A lack of strategy to counteract hypoxia (pO2 < 10–15 mmHg) and technique to repeatedly measure tumor pO2 has restricted therapeutic optimization. We report the results obtained with an innovative anti-angiogenic strategy of recurrent low-dose (metronomic) chemotherapy to modulate hypoxia and growth of the Head and Neck tumor xenografts. The FaDu tumors were established in the fl ank of immune defi cient mice and EPR oximetry with lithium phthalocyanine crystals was used to follow the temporal changes in tumor pO2 on treatment with gemcitabine including controls for three weeks. The FaDu tumors were hypoxic with a baseline (pre-treatment) pO2 of 2–8 mmHg. A transient increase in the tumor pO2 was evident on day 3 on treatment with a conventional schedule of gemcitabine (150 mg/kg, d1, d8, d15). No signifi cant change in the tumor pO2 on treatment with metronomic gemcitabine (25 mg/kg on d1, d3, d5 for 3 weeks) was observed. However, tumor pO2 increased signifi cantly on d15–d18 during treatment with a metronomic schedule of 15 mg/kg gemcitabine (d1, d3, d5 for 3 weeks). A modest decrease in the tumor growth was evident on treatment with conventional gemcitabine. Notably, tumor growth was signifi cantly inhibited by metronomic (25 and 15 mg/kg) gemcitabine treatment. The immunohistochemistry (IHC) analyses of the tumor samples indicate a decrease in HIF-1α and TSP-1 on treatment with metronomic gemcitabine. In conclusion, a signifi cant inhibition of tumor growth on treatment with metronomic gemcitabine was observed; however, the increase in pO2 was dose dependent. EPR oximetry can be used to follow the temporal changes in tumor pO2 to identify a therapeutic window on treatment with metronomic chemotherapy for potential combination with radiotherapy. © Springer Science+Business Media, LLC 2014.

Hou H.,Dartmouth Hitchcock Medical Center | Hou H.,Center for Viable Systems | Khan N.,Dartmouth Hitchcock Medical Center | Chen E.Y.,Dartmouth Hitchcock Medical Center | And 5 more authors.
Advances in Experimental Medicine and Biology | Year: 2014

The feasibility of EPR oximetry using a single-probe implantable oxygen sensor (ImOS) was tested for repeated measurement of pO2 in skeletal muscle and ectopic 9L tumors in rats. The ImOS (50 mm length) were constructed using nickel– chromium alloy wires, with lithium phthalocyanine (LiPc, oximetry probe) crystals loaded in the sensor loop and coated with AF 2400 ® Tefl on. These ImOS were implanted into the skeletal muscle in the thigh and subcutaneous 9L tumors. Dynamic changes in tissue pO2 were assessed by EPR oximetry at baseline, during tumor growth, and repeated hyperoxygenation with carbogen breathing. The mean skeletal muscle pO2 of normal rats was stable and signifi cantly increased during carbogen inhalation in experiments repeated for 12 weeks. The 9L tumors were hypoxic with a tissue pO2 of 12.8 ± 6.4 mmHg on day 1; however, the response to carbogen inhalation varied among the animals. A signifi cant increase in the glioma pO2 was observed during carbogen inhalation on day 9 and day 14 only. In summary, EPR oximetry with ImOS allowed direct and longitudinal oxygen measurements in deep muscle tissue and tumors. The heterogeneity of 9L tumors in response to carbogen highlights the need to repeatedly monitor pO2 to confi rm tumor oxygenation so that such changes can be taken into account in planning therapies and interpreting results. © Springer Science+Business Media, LLC 2014.

Swartz H.M.,Center for the Study of Viable Systems | Hou H.,Dartmouth College | Khan N.,Dartmouth College | Jarvis L.A.,Dartmouth College | And 3 more authors.
Advances in Experimental Medicine and Biology | Year: 2014

EPR oximetry, which enables reliable, accurate, and repeated measurements of the partial pressure of oxygen in tissues, provides a unique opportunity to investigate the role of oxygen in the pathogenesis and treatment of several diseases including cancer, stroke, and heart failure. Building on signifi cant advances in the in vivo application of EPR oximetry for small animal models of disease, we are developing suitable probes and instrumentation required for use in human subjects. Our laboratory has established the feasibility of clinical EPR oximetry in cancer patients using India ink, the only material presently approved for clinical use. We now are developing the next generation of probes, which are both superior in terms of oxygen sensitivity and biocompatibility including an excellent safety profi le for use in humans. Further advances include the development of implantable oxygen sensors linked to an external coupling loop for measurements of deep-tissue oxygenations at any depth, overcoming the current limitation of 10 mm. This paper presents an overview of recent developments in our ability to make meaningful measurements of oxygen partial pressures in human subjects under clinical settings. © Springer Science+Business Media, LLC 2014.

Das S.,Johns Hopkins University | Sysa-Shah P.,Johns Hopkins Medical Institutions | Sivakumaran V.,Johns Hopkins Medical Institutions | Stanley B.,Johns Hopkins Medical Institutions | And 8 more authors.
American Journal of Physiology - Heart and Circulatory Physiology | Year: 2015

Levels of the HER2/ErbB2 protein in the heart are upregulated in some women during breast cancer therapy, and these women are at high risk for developing heart dysfunction after sequential treatment with anti-ErbB2/trastuzumab or doxorubicin. Doxorubicin is known to increase oxidative stress in the heart, and thus we considered the possibility that ErbB2 protein influences the status of cardiac antioxidant defenses in cardiomyocytes. In this study, we measured reactive oxygen species (ROS) in cardiac mitochondria and whole hearts from mice with cardiacspecific overexpression of ErbB2 (ErbB2tg) and found that, compared with control mice, high levels of ErbB2 in myocardium result in lower levels of ROS in mitochondria (P = 0.0075) and whole hearts (P = 0.0381). Neonatal cardiomyocytes isolated from ErbB2tg hearts have lower ROS levels and less cellular death (P < 0.0001) following doxorubicin treatment. Analyzing antioxidant enzyme levels and activities, we found that ErbB2tg hearts have increased levels of glutathione peroxidase 1 (GPx1) protein (P < 0.0001) and GPx activity (P < 0.0031) in addition to increased levels of two known GPx activators, c-Abl (P < 0.0284) and Arg (P < 0.0001). Interestingly, although mitochondrial ROS emission is reduced in the ErbB2tg hearts, oxygen consumption rates and complex I activity are similar to control littermates. Compared with these in vivo studies, H9c2 cells transfected with ErbB2 showed less cellular toxicity and produced less ROS (P < 0.0001) after doxorubicin treatment but upregulated GR activity (P < 0.0237) instead of GPx. Our study shows that ErbB2-dependent signaling contributes to antioxidant defenses and suggests a novel mechanism by which anticancer therapies involving ErbB2 antagonists can harm myocardial structure and function. © 2015 the American Physiological Society.

Khailov A.M.,Medical Radiological Research Center Named By yb | Ivannikov A.I.,Medical Radiological Research Center Named By yb | Skvortsov V.G.,Medical Radiological Research Center Named By yb | Stepanenko V.F.,Medical Radiological Research Center Named By yb | And 4 more authors.
Radiation Measurements | Year: 2015

Absorbed doses to fingernails and organs were calculated for a set of homogenous external gamma-ray irradiation geometries in air. The doses were obtained by stochastic modeling of the ionizing particle transport (Monte Carlo method) for a mathematical human phantom with arms and hands placed loosely along the sides of the body. The resulting dose conversion factors for absorbed doses in fingernails can be used to assess the dose distribution and magnitude in practical dose reconstruction problems. For purposes of estimating dose in a large population exposed to radiation in order to triage people for treatment of acute radiation syndrome, the calculated data for a range of energies having a width of from 0.05 to 3.5 MeV were used to convert absorbed doses in fingernails to corresponding doses in organs and the whole body as well as the effective dose. Doses were assessed based on assumed rates of radioactive fallout at different time periods following a nuclear explosion. © 2015 Elsevier Ltd. All rights reserved.

Discover hidden collaborations