[Changes in the neuropathological findings created by the advent of new therapeutic measures. Special reference to cases treated by artificial respiration].
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Adolescent↗
Biomedical subjects
H Kubo
Publications and source records attributed to H Kubo.
[On the molecular form and polymerization of glutamic dehydrogenase].
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Oxidoreductases↗
Characteristics of hepatocytes derived from early ES cells and treatment of surgically induced liver failure rats by transplantation.
BACKGROUND: Although liver transplantation has become a standard therapy for diseases such as fulminant hepatitis and cirrhosis, the lack of donor organs remains a major problem. One solution is the development of transplantable hepatocytes. The metabolic characteristics as well as function and adaptation of hepatocytes (R-EES-hep cell) derived from rat early embryonic stem cells were examined after transplantation into rats with surgically induced liver failure. METHODS: Rat hepatocyte cell lines were established from early embryonic stem cells cultured in the presence of embryotrophic factors by colony cloning methods. The cell lines were established from two cell embryos taken from spontaneous dwarf rats using the novel method of Ishiwata et al. Morphologic differentiation as well as albumin and bilirubin production were observed by immunostaining. R-EES-hep cells were transplanted into the spleens of 90% hepatectomized, surgically induced liver failure rats to analyze survival rates. RESULTS: When cultured in type I collagen gel the cells formed cordlike structures resembling the liver. Both albumin and bilirubin production were observed when transplanted; the spleen was converted into a liver-like structure with prolonged survival of the 90% hepatectomized rats for up to 3 months up to the time of killing. CONCLUSIONS: R-EES-hep cells showed many of the distinctive metabolic characteristics of the liver. These cells may be efficient for further research and application for hepatic cell transplantation to treat liver insufficiency patients and as biologic artificial organs.
Animals↗
The effect of theophylline on blood and sputum eosinophils and ECP in patients with bronchial asthma.
It was recently reported that theophylline has an anti-inflammatory and bronchodilating effect on bronchial asthma. Accordingly, to examine the anti-inflammatory effect of theophylline on asthma, especially its effect on eosinophil activation, a sustained-release theophylline preparation (Theolong) was administered (daily dose: 400 mg) to 18 patients with mild to moderate bronchial asthma. This was done in order to study the preparation's effects on lung function, blood and sputum eosinophils and ECP four weeks pre- and post-administration. Lung function was determined by spirometry and sputum by induced sputum. Blood and sputum ECP levels were determined using an ECP RIA kit. In lung function, there were no differences in vital capacity (VC) or in forced expiratory volume 1 s (FEV 1.0) pre- and post-administration. There were also no differences in the number of blood and sputum eosinophils, but serum and sputum ECP levels decreased. Theophylline is thus expected to exert an inhibitory effect on eosinophil activation and it is suggested as an effective therapeutic drug for bronchial asthma.
Asthma↗
Simultaneous determinations of Fe, Cu, Zn, and Br concentrations in human tissue sections.
Proton-induced x-ray fluorescence has been used to determine the concentration of trace elements in human prostate and liver tissue samples. Ca, Fe, Cu, and Zn were observed in all specimens. Small amounts of Br were detected in most of the prostates, and in nearly half of the livers. The data indicate that the Fe content decreases in malignant liver tissues and the quantities of Cu and Zn are also decreased, but to a lesser extent.
Adenoma, Bile Duct↗
Ionization chamber response to a sudden change of ambient temperature in air, water, and polystyrene phantom.
We have studied the time course of current collected with an ionization chamber and electrometer when the chamber was suddenly inserted in an air, water, or polystyrene medium whose temperature was typically 20 degrees C above or below room temperature. The results were analyzed in terms of a temperature time constant tau--the time required for a 63% change of the ionization current. It was found that for a Farmer-type chamber, tau for the in-air measurements ranges from 5-10 min, several times longer than that for the in-water measurements (2-3 min). These tau values were confirmed with in-cavity temperature measurements carried out with a small thermocouple.
Air↗
Determination of the half-life of I-125 encapsulated clinical seeds using a Si(Li) detector.
The half-life of two I-125 encapsulated clinical seeds was measured with a Si(Li) semiconductor detector. Two measurements of each seed yielded an average half-life of 59.56 +/- 0.17 days. The results are discussed in terms of the influence of possible I-126 contamination and leakage of I-125 activity through encapsulation. The present results are compared with a frequently cited value of 60.25 +/- 0.06 days. The difference between the two values was found to be statistically significant at a 95% confidence level.
Brachytherapy↗
On the steady-state drift conditions of a water calorimeter in clinical megavoltage photon and electron beams.
We have investigated the characteristic behavior of a water calorimeter in a clinical environment where the temperature is not strictly controlled. Since the ambient temperature plays a crucial role in the successful operation of a calorimeter, its effects were closely monitored. The results were compared with theoretical predictions based on a simple model of heat transfer by conduction. They were found useful in analyzing the radiation dose measurements. In particular, a relationship between the absorbed dose and the pre- and postirradiation thermal drifts was examined. Finally, some suggestions are made concerning the desirable conditions under which a water calorimeter may be operated.
Calorimetry↗
A thermoregulated enclosure for controlling thermal drift in a radiation calorimeter.
The ability to control thermal drifts is essential in operating a calorimeter. We investigated a thermal enclosure, which envelops the calorimeter with temperature-regulated air, thus thermally isolating the calorimeter from the room. The desired temperature in the enclosure is controlled by a control circuit and a thermoelectric device, which works as a Peltier effect heat pump. In this report, the details of the enclosure design and construction are presented with actual performance evaluations.
Animals↗
Exposure contribution from Ti K x rays produced in the titanium capsule of the clinical I-125 seed.
The iodine-125 radioactive nuclide produces three intrinsic photons, i.e., the 27.4-keV tellurium (Te) K alpha and 31.0-keV K beta x rays, and 35.5-keV gamma rays. In addition, a silver-wire-type seed is known to have silver(Ag) K alpha and K beta x rays as a result of interactions between silver atoms and the intrinsic photons. Since the radioactive iodine-125 is completely sealed with a 0.05-mm-thick titanium capsule, fluorescence x rays from titanium atoms are also expected. This study reports (1) abundance of Ti K x rays at 4.5 keV, (2) contribution to exposure from these photons amounting to approximately 19% of the total exposure at 1-cm source-to-detector distance (SDD), (3) exposure uncertainties of 23% at 1-cm SDD when Ti K x rays are excluded, and (4) negligible dose contribution to tissue from these photons.
Iodine Radioisotopes↗
Comparison of two independent exposure measurement techniques for clinical I-125 seeds.
This investigation contains the results of exposure measurements on two types of clinical I-125 seeds: a model 6702 no-marker seed, and a model 6711 silver wire seed. Measurements were made locally with a parallel-plate mammography chamber, traceable to the National Bureau of Standards (NBS) calibration. The same seeds were also measured at NBS using a reentrant chamber that was developed and calibrated there. The mammography chamber measurements showed an approximately 5% higher exposure rate for the no-marker seed than the reentrant chamber measurements. On the silver wire seed, good agreement was obtained between the two techniques. It was found that exposure rate variations in the plane perpendicular to the long axis of the seed (or seed axis) were substantial, due in part to the nonsymmetric distribution of radioactive material in the seed.
Female↗
Absorbed dose calorimetry: bridge nulling and voltage analysis techniques.
A theoretical analysis is made of the conventional calorimeter approach utilizing a two-thermistor Wheatstone bridge--an approach which requires balancing the bridge by adjusting variable resistances. However, with the current availability of computers and digital precision measuring instruments, the conventional calorimeter approach can now be readily replaced by an automated, nonmechanical, electrical systems approach called differential calorimetry. The analytical theory outlining such an approach is also presented.
Calorimetry↗
Determinations of Ngas and Prepl factors from commercially available parallel-plate chambers: AAPM Task Group 21 protocol.
Using a Farmer chamber as a reference dosimeter, we have measured the Ngas (cavity-gas calibration factor) and Prepl (replacement correction factor) values for four parallel-plate chambers: a Holt chamber, a Capintec chamber, a Markus chamber, and an SHM chamber. Ngas determinations were done primarily using 60Co photons and nominal 18-MeV electrons for Ngas determinations. For Prepl determinations, we used nominal 18-, 15-, 12-, 9-, 6-, and 4-MeV electrons.
Calibration↗
Unexpectedly large dose rate dependent output from a linear accelerator.
During our routine calibration of a Varian Clinac-20 linear accelerator, the absorbed dose for a fixed monitor unit (mu) was found to decrease with increasing dose rate. Between dose rates of 100 and 500 mu/min, there was up to 20% difference in absorbed dose for a 20-MeV electron beam. The cause of this problem was a failure in the electronics circuit of an integrating board. This paper presents our analysis of the problem and suggests a possible means of isolating such a failure to warn technologists, physicists, and engineers.
Biophysical Phenomena↗
Absorbed dose comparison among commercial ionization chambers in polystyrene and acrylic phantoms.
Using the AAPM Task Group 21 protocol, photon and electron doses were compared in polystyrene and acrylic phantoms. The ionization chambers used were a Farmer graphite chamber, a PTW acrylic chamber, a homemade polystyrene chamber, and an Exradin air-equivalent chamber, all being of cylindrical type. A Memorial parallel-plate polystyrene chamber was also included. 60Co, 4-, 6-, and 18-MV x rays as well as 9- and 20-MeV electron beams were investigated.
Acrylates↗
Measurements of backscattered radiation from Therac-20 collimator and trimmer jaws into beam monitor chamber.
The field size dependent photon output is known to be influenced by the existence of backscattered radiation (BSR) generated in the collimator or trimmer jaws of a linear accelerator. This paper describes the results of measurements made to study the existence of such backscatter by simulating the geometry of the treatment head of a Therac-20 linear accelerator. The machine's monitor chamber, flattening filter, and collimator jaws were simulated by another real monitor chamber, a 1-cm thick lead sheet and 2.5-cm thick low-melting-point alloy divergent blocks, respectively. BSR from the simulated collimator jaws (SCJ) was measured with the simulated monitor chamber (SMC) as a function of the openings of the SCJ and as a function of distance between SMC and SCJ. The present results demonstrate the presence of BSR in an 18-MV photon beam from a Therac-20 linear accelerator.
Humans↗
Telescopic measurements of backscattered radiation from secondary collimator jaws to a beam monitor chamber using a pair of slits.
A contribution to field-size dependent output by backscattered radiation (BSR) from secondary collimator jaws to a beam monitor chamber of a linear accelerator was measured with a Farmer ionization chamber, positioned 200 cm from the source behind a low-melting-point alloy slab with a 10-cm wide slit. Another slit was positioned against the collimator jaws. Both slits were in the form of a 6.3-mm-diam hole in the middle and were aligned to the source. The use of a pair of slits was intended to eliminate any influence on the ion chamber readings due to field-size dependent charge contribution from the flattening filter and collimator jaw forward scattering. In addition, the setup permits to observe the degree of field-size dependence on BSR. Charge measurements from the Therac-20 18-MV x rays showed a 7.5% field-size dependence on BSR whereas 6- and 18-MV x rays from Varian Clinac-1800 showed less than 2% dependence on BSR. The telescopic method was found to be easy to use and permitted direct determination of BSR contributions.
Humans↗
Radiation leakage through electron applicators on Clinac-1800 accelerators.
Radiation leakage through electron applicators by 6-, 9-, 12-, 16-, and 20-MeV electron beams from Varian Clinac-1800 has been measured with films. High levels of leakage were found under the corners of applicators and the touch-plate mounting port holes. The radiation leakage, relative to the central-axis dose at dmax, was found to be up to 13% on the patient plane [100-cm source-to-film distance (SFD)] and up to 35% beneath the corners of applicators (96-cm SFD). Up to 18% radiation leakage was measured beneath the touch plate near the mounting port holes (96-cm SFD). The extent of radiation leakage in all electron beams was investigated and some simple shielding solutions to reduce the leakage are suggested.
Electrons↗