Clinical and Statistical Considerations when Assessing Oxygen Levels in Tumors: Illustrative Results from Clinical EPR Oximetry Studies.

The success of treatment for malignancies, especially those undergoing radiation therapy or chemotherapy, has long been recognized to depend on the degree of hypoxia in the tumor. In addition to the prognostic value of knowing the tumor's initial level of hypoxia, assessing the tumor oxygenation during standard therapy or oxygen-related treatments (such as breathing oxygen-enriched gas mixtures or taking drugs that can increase oxygen supply to tissues) can provide valuable data to improve the efficacy of treatments. A series of early clinical studies of tumors in humans are ongoing at Dartmouth and Emory using electron paramagnetic resonance (EPR) oximetry to assess tumor oxygenation, initially and over time during either natural disease progression or treatment. This approach has the potential for reaching the long-sought goal of enhancing the effectiveness of cancer therapy. In order to effectively reach this goal, we consider the validity of the practical and statistical assumptions when interpreting the measurements made in vivo for patients undergoing treatment for cancer.

'Oxygen Level in a Tissue' - What Do Available Measurements Really Report?

The aim of the paper is to discuss what currently is feasible clinically to measure the level of oxygen and how that measurement can be clinically useful. Because oxygen in tissues is quite heterogeneous and all methods of measurement can only provide an average across heterogeneities at some spatial and temporal resolution, the values that are obtained may have limitations on their clinical utility. However, even if such limitations are significant, if one utilizes repeated measurements and focuses on changes in the measured levels, rather than 'absolute levels', it may be possible to obtain very useful clinical information. While these considerations are especially pertinent in cancer, they also pertain to most other types of pathology.

Skeletal Muscle Oxygenation Measured by EPR Oximetry Using a Highly Sensitive Polymer-Encapsulated Paramagnetic Sensor.

We have incorporated LiNc-BuO, an oxygen-sensing paramagnetic material, in polydimethylsiloxane (PDMS), which is an oxygen-permeable, biocompatible, and stable polymer. We fabricated implantable and retrievable oxygen-sensing chips (40 % LiNc-BuO in PDMS) using a 20-G Teflon tubing to mold the chips into variable shapes and sizes for in vivo studies in rats. In vitro EPR measurements were used to test the chip's oxygen response. Oxygen induced linear and reproducible line broadening with increasing partial pressure (pO2). The oxygen response was similar to that of bare (unencapsulated) crystals and did not change significantly on sterilization by autoclaving. The chips were implanted in rat femoris muscle and EPR oximetry was performed repeatedly (weekly) for 12 weeks post-implantation. The measurements showed good reliability and reproducibility over the period of testing. These results demonstrated that the new formulation of OxyChip with 40 % LiNc-BuO will enable the applicability of EPR oximetry for long-term measurement of oxygen concentration in tissues and has the potential for clinical applications.

Calculation of dose conversion factors for doses in the fingernails to organ doses at external gamma irradiation in air.

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.

Radiation dose reconstruction from L-band in vivo EPR spectroscopy of intact teeth: Comparison of methods.

In vivo EPR tooth dosimetry is a more challenging problem than in vitro EPR dosimetry because of several potential additional sources of variation associated with measurements that are made in the mouth of a living subject. For in vivo measurement a lower RF frequency is used and, unlike in the in vitro studies, the tooth cannot be processed to optimize the amount and configuration of the enamel that is measured. Additional factors involved with in vivo measurements include the reproducibility of positioning the resonator on the surface of the tooth in the mouth, irregular tooth geometry, and the possible influence of environmental noise. Consequently, in addition to using the theoretical and empirical models developed for analyzing data from measurements of teeth in vitro, other unconventional and more robust methods of dose reconstruction may be needed. The experimental parameter of interest is the peak-to-peak amplitude of the spectrum, which is correlated to the radiation dose through a calibration curve to derive the reconstructed dose. In this study we describe and compare the results from seven types of computations to measure the peak-to-peak amplitude for estimation of the radiation induced signal. The data utilized were from three sets of in vivo measurements of irradiated teeth. Six different teeth with different doses were placed in the mouth of a volunteer in situ and measurements of each tooth were carried out on three different days. The standard error of dose prediction (SEP) is used as a figure of merit for quantifying precision of the reconstruction. We found that many of the methods gave fairly similar results, with the best error of prediction resulting from a computation based on a Lorentzian line model whose center field corresponds to the known parameter of the radiation-induced EPR spectra of teeth, with corrections from a standard sample that was measured as part of the data acquisition scheme. When the results from the three days of measurement were pooled, the SEP decreased dramatically, which suggests that one of the principal sources of variation in the data is the ability to precisely standardize the measurements conditions within the mouth. There are very plausible ways to accomplish improvements in the existing procedures.

Limitations of dual-photopeak window scatter correction for brain imaging.

UNLABELLED: A method for performing scatter corrections that would directly use the photopeak information and would be straightforward for use in clinical practice would be attractive in SPECT imaging. The dual-photopeak window method may be such a method. It relates the scatter fraction to the ratio of the lower to the total parts of a split-photopeak window. We investigated the use of this scatter correction method on a dedicated brain camera. METHODS: Calibration curves for the Ceraspect, a dedicated brain imaging camera, were obtained for four split-window combinations using point sources in air and water. Simulations of the Ceraspect calibration curves at several energy resolution values were obtained using a Monte Carlo simulation of the instrument. RESULTS: The calibration curves, experimental and simulated, revealed an ambiguous and unstable relationship between lower-to-total ratio and scatter fraction. CONCLUSION: The unsatisfactory calibration curves can be attributed to the limited scatter produced in a brain-sized phantom during the calibration process and inherent stability problems in the calibration process. The dual-photopeak window method is not usable for small-field imaging systems and may even be unstable for larger-field systems.

Determination of 3D positions of pacemaker leads from biplane angiographic sequences.

In vitro and in vivo analyses of stress on pacemaker leads and their components during the heart cycle have become especially important because of incidences of failure of some of these mechanical components. For stress analyses, the three-dimensional (3D) position, shape, and motion of the pacemaker leads must be known accurately at each time point during the cardiac cycle. We have developed a method for determination of the in vivo 3D positions of pacemaker leads during the entire heart cycle. Sequences of biplane images of patients with pacemakers were obtained at 30 frames/s for each projection. The sequences usually included at least two heart cycles. After patient imaging, biplane images of a calibration object were obtained from which the biplane imaging geometry was determined. The centerlines of the leads and unique, identifiable points on the attached electrodes were indicated manually for all acquired images. Temporal interpolation of the lead and electrode data was performed so that the temporal nonsynchronicity of the image acquisition was overcome. Epipolar lines, generated from the calculated geometry, were employed to identify corresponding points along the leads in the pairs of biplane images for each time point. The 3D positions of the lead and electrodes were calculated from the known geometry and from the identified corresponding points in the images. Using multiple image sets obtained with the calibration object at various orientations, the precision of the calculated rotation matrix and of the translation vector defining the imaging geometry was found to be approximately 0.7 degree and 1%, respectively. The 3D positions were reproducible to within 2 mm, with the error lying primarily along the axis between the focal spot and the imaging plane. Using data obtained by temporally downsampling to 15 frames/s, the interpolated data were found to lie within approximately 2 mm of the true position for most of the heart cycle. These results indicate that, with this technique, one can reliably determine pacemaker lead positions throughout the heart cycle, and thereby it will provide the basis for stress analysis on pacemaker leads.

Role of 5-hydroxytryptamine in the regulation of brain neuropeptides in normal and diabetic rat.

The effect of 5-hydroxytryptamine (5-HT) alteration on brain dopamine (DA), norepinephrine (NE), beta-endorphin (beta E) and immunoreactive insulin (IRI) was studied in Sprague-Dawley diabetic and control rats. Diabetes was induced using alloxan (45 mg/kg), 15 days prior to sacrificing. Both control and diabetic animals were treated with either p-chlorophenylalanine (PCPA, 300 mg/kg) 3 days prior to sacrificing or fluoxetine (10 mg/kg) twice daily for 3 days. PCPA treatment significantly decreased brain content of 5-HT and 5-hydroxyindole acetic acid (5-HIAA) while it caused significant increase and decrease in brain beta E and insulin levels, respectively, in both normal and diabetic rat. Meanwhile, the administration of fluoxetine resulted in significant increase in brain content of 5-HT, DA, NE and insulin but significant decline of beta E in diabetic and saline control rats. The results of this experiment indicate that 5-HT may be regulating both beta E and insulin regardless of the availability of pancreatic insulin.

Periodic alternating nystagmus clearing after cataract surgery.

A 60-year-old man developed periodic alternating nystagmus in association with decreased vision due to cataracts. Prior to surgery, vision was limited to hand motion only in both eyes. An extracapsular cataract extraction with insertion of a posterior chamber intraocular lens was performed in the patient's left eye. On the first postoperative day, vision was 20/60 in the left eye and the nystagmus was absent with both eyes open. Periodic alternating nystagmus that occurs with poor vision is related to a loss of fixation. Surgery aimed at improving the visual status may be effective in extinguishing the nystagmus.

Effect of hyperglycemia on biogenic amines, beta-endorphin and insulin of the rat brain.

Three experiments were designed to study the changes in brain biogenic amines, beta-endorphin and insulin in response to hyperglycemia in adult male rats. In all three experiments, animals were decapitated 10 minutes post injection (IP) of either 2.5 ml of 40% glucose or 0.9% saline. In the first experiment brain DA, NE, 5-HT and 5-HIAA were measured using fluorometric method. Plasma glucose, insulin (RIA) and corticosterone (CPB) were also determined. In addition to these measurements, brain beta-endorphin was determined (RIA) in the second experiment and brain insulin (RIA) in the third experiment. In all three experiments the hyperglycemic groups showed a significant increase in plasma insulin, brain NE and 5-HT and a significant decrease in brain 5-HIAA and no significant change in plasma corticosterone, brain DA, beta-endorphin and insulin. The results obtained in these experiments suggest that high levels of glucose may have an inhibitory effect on the metabolism of NE and 5-HT resulting in increases in the level of both amines. They also suggest that brain insulin is independent of the pancreatic one since high blood glucose did not influence the central level.

Antiviral activity in sera of patients with Crohn's disease.

Sera from patients with Crohn's disease were tested for antiviral activity using a microtiter assay with end points showing 50% reduction of cytopathic effects. Patients were significantly more likely to have serum antiviral activity equivalent to interferon levels of 20 or more units/ml than were control subjects. The mean antiviral activity in the patients' sera (34 +/- 20 (s.d.) units/ml) was significantly greater than that in the control subjects' sera (0.6 +/- 1.7 (s.d.) units/ml). Following acidification the mean antiviral activity of the patients' sera (28 +/- 17 (s.d.) units/ml) had not changed significantly while heat inactivation resulted in significant loss of activity (7.5 +/- 2.7 (s.d.) units/ml). These findings are suggestive of the presence of circulating leucocyte interferon in the sera of patients with Crohn's disease.

Pharmacokinetics of interferon in blood, cerebrospinal fluid, and brain after administration of modified polyriboinosinic-polyribocytidylic acid and amphotericin B.

Polyriboinosinic-polyribocytidylic acid (with a sedimentation coefficient of 9S) prepared in a complex with poly-L-lysine and carboxymethylcellulose (poly ICLC) was given intravenously to rabbits in a priming technique with two infusions 4 hr apart; and with low-dose amphotericin B (AmB, 0.5 mg) to trace the transfer of interferon (IFN) in serum to cerebrospinal fluid (CSF) and brain. Peak titers of IFN in serum were at 4 hr, but peak titers of IFN in CSF and brain occurred at 8 hr. At 4 hr, CSF IFN was 0.6%-2.7% of serum titers but at 8 hr had increased to 11.7%-51.1%. IFN was uniformly distributed to all areas of the brain and spinal cord at 8 hr. Titers of IFN in the brain were independent of CSF values, and varied from 5.9%-44.1% of the serum titers. When two injections of poly ICLC were given 4 hr apart, IFN titers in serum, CSF, and brain were significantly raised. Poly ICLC together with AmB increased serum IFN.

Biologic interaction of gamma radiation with phenylbutazone, phenytoin, or hydralazine.

Combination of repeated administration of phenylbutazone (7 mg/kg for two weeks) or phenytoin (20 mg/kg for four weeks) and acute exposure to gamma radiation (696 REM) induced increased lethality in mice much greater than that observed fro use of either drug or radiation alone. Lethality in chronic hydralazine (10 mg/kg for four weeks) treated mice subjected also to gamma radiation was not different than that observed after either drug or radiation alone. Decrease in liver glutathione was observed in mice receiving combined drug-radiation treatment as also were leucocyte counts, but neither of these parameters supported as assumption of site of common lethal mechanism.

Some previously unrecognized features of herpes simplex virus encephalitis.

The courses of 15 brain biopsy-proven cases of herpes simplex virus encephalitis (HSVE) were followed for 6 to 67 months. Convulsive disorders were often temporary, but paralysis was permanent. Patients usually entered the hospital free of paralysis or coma, in a potentially reversible febrile confusional state. Later, paralysis and coma fixed subsequent courses. Mortality was 53.3 percent but, at follow-up, 93.3 percent (14 patients) were dead or living a vegetative existence at home or in institutions. If a definitive diagnosis of HSVE could be made at the time of hospital admission, the prognosis might be remarkably changed.

Tetrazole analogs of phenylalanine derivatives as tyrosine hydroxylase inhibitors.

Eight new tetrazole analogs of phenylalanine derivatives in which the carboxyl group was replaced by a tetrazole ring were synthesized. At a concentration of 2.5 time 10(-5) M, each compound exhibited greater than 50% inhibition of tyrosine hydroxylase activity.

Inhibitory and lethal concentrations of 9-beta-D-arabinofuranosyladenine and its hypoxanthine-derivative versus herpes simplex virus, type 1.

Minimum inhibitory concentrations of 9-beta-D-arabinofuranosyladenine (ara-A, adenine arabinoside, vidarabine) and a purified preparation of 9-beta-D-arabinofuranosylhypoxanthine (arabinoslhypoxanthine, ara-Hx) at end points of 50% MIC50) and 100% (MIC100) reduction to challenges of approximately 50 p.f.u. of herpes simplex virus, type 1 (HSV-1) were determined in vero renal tissue cultures. Adenosine deaminase is universally present in tissue cultures and serum. These same tests were repeated in the presence of a potent inhibitor of adenosine deaminase, R-3-(2-deoxy-beta-D-erythro-pentofuranosyl)-3,6,7,8-tetrahydroimidazo-4,5-d)-(1,3)-diazepin-8-ol (co-vidarabine, co-ara-A). Addition of co-ara-A to assays of MIC50 or MIC100 for ara-A ensures standard reproducible results which can be compared in different laboratories. After incubations of HSV-1 in infected cultures for 96 hours, 35 degrees C., with concentrations of ara-A or ara-Hx at the MIC100 and over, cells were scraped and sonicated. Supernates were then reinoculated into vero flasks free of antiviral agents to determine minimum lethal concentrations (MLC's). Standard values (microng/ml.) for ara-A with co-ara-A are 11.3 (MIC50), 17.0 (MIC100), and 34.0 (MLC) but are 68.1 (MIC50), 170.4 (MIC100) and 375 (MLC) for ara-Hx. These data confirm that as a virustatic agent (MIC100) ara-A is 10 times more active than ara-Hx. Ara-A and ara-Hx have virucidal potentials which require approximately two times the respective MIC100.