Lucigenin chemiluminesence. A new approach to study the redox activity of Ehrlich ascetic tumor cells.

OBJECTIVE: To study the mechanism and to measure the oxygenation/reduction activity of Ehrlich ascetic tumor cells in an isotonic solution by means of lucigenin dependent chemiluminescence. METHODS: All the measurements of the chemiluminescence redox activity of Ehrlich ascetic tumor cell samples in suspension medium, were carried out using a photon counting system especially designed to the purpose. The areas under the chemiluminescence kinetic curves were measured at different cell physiological conditions and at different agents concentrations effect. RESULTS: The rates of lucigenin chemiluminescence redox functional activity of Ehrlich ascetic tumor cells were significantly different from normal oxygenation/reduction activity at different physiological environments of Ehrlich ascetic tumor cells suspension conditions (i.e. cell membrane permeability changes, presence and absence of oxidative or reductive agents at different concentrations and oxy/hydroxy free radical protective agents). CONCLUSION: The results explain more fully the mechanism and the value of a lucigenin dependent chemiluminescence probe of the redox functional activity of Ehrlich ascetic tumor cells (at different physiological conditions of suspension).

The Aberdeen Mark II single-photon-emission tomographic scanner: specification and some clinical applications.

The construction, operation and physical characteristics of a single-section multi-detector single-photon-emission scanner are described. The machine has 24 detectors arranged along the sides of a square. Movements and data collection are under the control of a series of distributed microprocessors. Both head and trunk tomograms can be produced. The spatial resolution at the collimator focus is 9 mm in the transverse plane, and the effective slice thickness is 14 mm. The volume sensitivity is 300 counts/s kBq ml with a 20 cm diameter cylindrical phantom filled with 99Tcm solution. The application of this machine to the examination of the brain, liver and heart has been found to be clinically useful.

Lyoluminescence dosimetry part II. State-of-the-art.

This is the second part of a review dealing with the development and current state-of-the-art of lyoluminescence dosimetry. Readout equipment described in the review covers a range of devices from simple manually-operated apparatus to semi-automatic machines suitable for loose powders and for encapsulated dosimeters. The survey of dosimetric properties of mannose and glutamine includes response to X- and gamma-rays, electrons, heavy charged particles and to neutrons. Current applications of lyoluminescence dosimetry include radiotherapy, radiation processing of foods and sterilization of medical products, as well as the use of lyoluminescent phosphors for gamma-ray dose intercomparisons in the high-dose range.

Silicon measurement in a lung phantom by neutron inelastic scattering.

A study was made to assess the feasibility of determining the silicon level in human lungs in vivo by measuring the gamma rays arising from the neutron inelastic scattering reaction 28Si(n, n' gamma)28Si. Neutron energies in the range 5--8 MeV represent the best compromise between the conflicting requirements of high energy for good detection statistics and low energy to minimize the dose to the subject. The sensitivity of measurement was enhanced by pulsing the neutron beam and counting only during the period of bombardment. This effectively reduced the background counts emanating from thermal neutron reactions in the phantom and from the fast neutron reaction 31P(n, alpha)28 A1. In measurements with an anthropomorphic phantom, no interference peaks from other prompt inelastic scattering reactions were observed. With one Ge(Li) detector of 19% relative efficiency, a detection limit of 0.6 g of silicon per 10 mSv was obtained. On this basis, it is estimated that six Ge(Li) detector of 25% efficiency each would be capable of measuring 0.15 g of silicon in the lungs, the average level found in nonoccupationally exposed adults.U

Radiation enhancement with iodinated deoxyuridine.

A technique, Photon Activation Therapy (PAT), is described in which high Linear Energy Transfer (LET) radiations in the form of Auger electron distributions are generated by a photon beam through photoactivation of stable iodine incorporated as an analog of thymidine (Tyd) in DNA. Of the several halogenated deoxyribonucleosides evaluated, iodinated deoxyuridine (IdUrd) was found to be the only viable choice as a Tyd analog for PAT. Calculations show that 5% replacement of Tyd in tumor DNA multiplies the biologic effectiveness of a given photon radiotherapy dose by a factor of approximately 3. If further therapeutic advantages accorded to high LET radiations are taken into account, as well as repair and regeneration of normal tissues during protracted irradiations, an advantage of approximately 6 is realized. Five percent replacement of Tyd has already been reported for human tumor in vivo. Higher replacements of Tyd with IdUrd would provide proportionately greater advantages. The expectation is that previous clinical results with BrdUrd and high-energy X-rays can be significantly improved upon through the use of IdUrd and suitable lower energy activating photons (35-50 keV). In particular, it is suggested that protracted irradiations with implanted sources such as 145Sm or 145Pm may provide unique advantages at selected sites such as brain or head and neck tumors.

Renal osteopenia - an assessment of long-term therapy with vitamin D analogues.

Renal bone disease was assessed for an average of 5.5 years in 9 patients on maintenance haemodialysis. The investigative methods included serial biochemical estimations, radiographic skeletal surveys and quantitative bone histology. Repeated bone mineral analyses and neutron activation analyses of a hand were also performed in order to monitor changes in skeletal calcium content. Before treatment, progressive osteodystrophy was demonstrated by all techniques. Following therapy with the vitamin D analogues, all patients noted symptomatic improvement; serum alkaline phosphatase reverted to normal and serum parathyroid hormone concentrations decreased. Radiographically, subperiosteal erosions healed while the histological features of osteomalacia and osteitis fibrosa were abolished. Both bone mineral and neutron activation analyses indicated that progressive skeletal demineralisation had been halted. However, a sustained increase in the overall mineral content of bone was not demonstrated. Thus, vitamin D therapy although improving the biochemical, radiological, and histological features of renal osteodystrophy may not restore bone mass to osteopenic bone.

Lyoluminescence dosimetry with some saccharides.

Lyoluminescent properties of mannose, glucose monohydrate, sucrose and trehalose dihydrate were investigated from the point of view of suitability as dosimetric materials in a new system of solid state dosimetry. Distilled water was used as a solvent. With a reader equipped with an uncooled PM tube it was possible to measure doses of X- and gamma-rays in the range from a few rad to about 100 krad. Various experimental factors which could affect the dose measurements using lyoluminescence are discussed, including the energy response for X-rays. Some preliminary information on the response of saccharides to fast neutrons is also included.

Transmission detectors for cyclotron in-vivo irradiations with neutrons.

The neutron fluence imparted to the irradiated subjects needs to be measured accurately in order to obtain meaningful results from diagnostic irradiations. A convenient neutron detector for this purpose is in the form of a transmission chamber, which covers the whole beam directed at the subject. In one design the detector is an ionization chamber, filled with propane gas, in another a thin sheet of plastic scintillator is coupled to a pair of photomultipliers.