Jørgen Bojsen

Evidence for growth inhibition by platinum electrodes at low current levels

Platinum is considered to be a noble metal and is often used for electrodes in biological investigations. However, platinum electrodes can form inhibitory compounds, as pointed out by Rosenberg et al. 1965. The aim of this study was to investigate whether platinum electrodes are inert in the extremely low frequency (ELF) range of currents. Human bone marrow cells cultured in agar were used as target cells and were grown under various electrical conditions. A 50% reduction in growth compared with controls was obtained by average currents of 2300 microA at 8 Hz and 110 microA at 80 Hz, the current being derived from a square bipolar voltage waveform. D.c. currents were also inhibitory, with a value of 50% at the 1.4 microA level. The cells were probably not affected directly by the current, since inhibitory properties could be stored in agar and saline and because titanium electrodes at equal current levels did not produce the same effect.

A portable external two-channel radiotelemetrical GM-detector unit, for measurements of radionuclide-tracers in vivo.

Abstract A two-channel radiotelemetrical measuring device for continuous and simultaneous detection of radionuclide tracers in vivo on humans has been developed. The equipment is suggested for local tracer studies, when continuous long term measurements shall be performed. Two small end-window GM-detectors are used for detection of the tracer. High energy β-emitters, as 32 P, are detected with high efficiency. Low energy γ-emitters like 125 I and 133 Xe can be detected with a sufficiently high efficiency. The range from the equipment to the receiving antenna is 10–15 m. The weight is 260 g.

A radiotelemetrical measuring device, implantable on animals, for long term measurements of radionuclide-tracers

Abstract The construction of a radiotelemetrical measuring device implantable on animals as small as rabbits and designed for continuous long term detection of low γ-energy radionuclide-tracers is presented. The GM-detector and the FM-transmitter are coated in an araldite shield, the total volume is 140 cm 3 and the weight is 135 g. Reliable continuous measurements can be performed on unrestrained animals in periods up to 5 months. It is possible to measure discontinuously by external switching the measuring device on and off. The implication technique is described. The detector seems to have its utility in pharmacological tests and in turnover studies.

Patient-controlled Portable Insulin Infusion Pump in Diabetics

Ten patients with unstable insulin-dependent diabetes mellitus, mean duration 17.5 yr, all treated with highly purified porcine NPH insulin twice daily, were placed on highly purified porcine regular insulin subcutaneously four times daily for 2 days. Thereafter a preplanned intravenous insulin infusion was given for 54 h. Insulin in an amount corresponding to 24-h insulin requirement was infused by a portable infusion pump. Immediately before the main meals the prandial infusion program was released by the patients by pushing a button. Capillary blood glucose was taken every 30 min during the day and every 2 h during the night. Endogenous insulin secretion was calculated by measuring the C-peptide response after 1 mg of glucagon intravenously. Insulin antibodies were measured in all patients. Insulin antibody concentration was low in most cases, and only one patient reacted to glucagon by a significant but low rise of C-peptide. After an equilibration period of 5 h, mean blood glucose (MBG) was in the physiologic range in 6 of 10 patients during the infusion period. MGB in the 10 diabetics averaged 5.5 ±1.0 mmol/L (mean ± SD) compared with 4.4 ± 0.4 mmol/L in nondiabetic controls. The mean amplitude of glycemic excursions (MAGE) was 4.1 ±1.4 mmol/L (mean ± SD) against 1.8 ± 0.6 mmol/L in control subjects. MBG, MAGE, and glucosuria were significantly reduced on the infusion days compared with the days on subcutaneous insulin. It is concluded that near-normal blood glucose fluctuations can be obtained in unstable diabetics by a preplanned prandial insulin infusion program activated by diabetic patients themselves.

Portable cadmium telluride detectors and their applicability for external measurement of 51Cr-EDTA clearance☆

Abstract The combination of portable cadmium telluride detectors and a solid state memory have been examined with reference to point and volume source sensitivities and the equivalent, effective detector thickness. Based on the i.v. injection of 51 Cr-EDTA, the glomerular filtration rate in 23 patients has been measured by external detection of the disappearance rate of the tracer and only one blood sample. Correlation to conventional blood sampling technique is r = 0.992. The glomerular filtration rate determined from the externally measured disappearance rate constant only, is discussed.

Collimation of portable cadmium telluride detectors for biotelemetry

Abstract The spatial properties of small, portable γ-sensitive cadmium telluride (CdTe(Cl)) detectors are evaluated for biotelemetry. Various single hole lead collimators are investigated with 99m Tc as point and plane source. Isocount curves of the most efficient collimator are calculated. During local clearance measurements a reduced sensitivity to alterations in geometry is obtained, when all detected photons are counted. The contribution of counts in percent from deep layers of a 99m Tc volume source in increased, when scattered radiation is counted and a single hole lead collimator with parallel sides is used, compared to results obtained with no collimator. γ-Ray energy spectrometers are not required for single tracer biotelemetry investigations with 99m Tc .

Improvement of glucose homeostasis in insulin-dependent diabetics using a miniature insulin infusion pump with a fixed profile

SummaryGlucose homeostasis was studied in nine longstanding insulin-dependent diabetic patients using a portable pump for intravenous insulin infusion. The 24 h infusion dose was calculated from the conventional SC insulin treatment. The range of basal infusion rates was 2.5 to 15 mU/min and peak delivery rates were raised up to 16-fold from start of main meals for 30–60 minutes. Mean blood glucose improved from 12.0±2.4 to 6.4±1.0 mmol/l (SD) during infusion (p<0.01). Glucose excretion decreased from 23 g/24 h (range 1–42) to 4 g/24 h (range 0–14) (p<0.01). Mean amplitude of glycaemic excursions was significantly improved during infusion (from 8.9±4.8 to 4.7±0.9 mmol/l; p< 0.01). No severe hypoglycaemic episodes or other adverse reactions were seen.

HEAT TRANSFER AND BLOOD FLOW IN EXPERIMENTAL TUMORS IN RATS COMPARED WITH THE CIRCADIAN TEMPERATURE RHYTHM OF THE BODY

In the present study, temperatures of two types of experimental rat tumors, the adenocarcinoma induced by 7,12-dimethylbenz(a)anthracene (DMBA) and the Walker 256 carcinosarcoma, were continuously measured in periods up to a maximum of one month. Temperatures were measured telemetrically by implanted radio transmitters, and long-term measurements of the temperatures in the subcutis and the peritoneal cavity were performed as well. To elucidate the significance of long-term temperature measurements and rhythm studies in tumors, some additional experiments were performed: external skin temperature measurements on and around the tumors, blood flow measurements, 32P uptake measurements in tumors and in normal skin, and cell kinetic studies with histological analysis by countings of mitoses and !abeled cells.

Cadmium telluride [CdTe(Cl)] detectors and their geometrical characteristics in local disappearance measurements using radionuclides

Abstract Small cadmium telluride [CdTe(Cl)] detectors are used in a number of clinical investigations with radionuclide tracers. Attached to the skin surface of the body, their portability makes them unique for physiological studies over long periods of time during normal life conditions. Such biotelemetric methods are complementary to the conventional measuring techniques used in nuclear medicine, where stationary equipment limits the investigation periods. Some of the physical characteristics of six practically identical CdTe(Cl) detectors were investigated. The charge collection efficiency, the amplitude frequency distributions and the relative count rates were measured at various γ-photon energies and detector bias voltages. Furthermore the geometrical characteristics of the CdTe(Cl) detectors in local disappearance measurements were investigated with 99m Tc sources disc-shaped in tissue equivalent perspex phantoms. Measurements with a stationary sodium iodide [NaI(Tl)] detector were performed intermittently for comparison. The range of linear proportionality was determined at planes in various depths of the perspex phantom parallel to the phantom surface. For several physiological investigations the energy resolution appeared to be of minor importance and in quantitative absorption measurements the extended tracer depot in the tissue had to be within the linear proportionality range in front of the CdTe(Cl) detector.

Biotelemetry of the glomerular filtration rate (GFR) in man by external detection of DTPA-(Sn)-99mTc with CdTe detectors

Abstract With a small cadmium telluride detector fixed to the skin surface, the kidney function [glomerular filtration rate (GFR)] can be determined in man from the disappearance rate of i.v. injected DTPA-(Sn)- 99m Tc monitored in a three hour period and just one blood sample. The small (2–3 mm 3 ) p-type CdTe-crystals (developed by C.R.N., Strasboug, Frnace) grown by the THM-method, without external chemical compensation have a resistivity of 10 4 –10 6 ω· cm. The combination of CdTe detectors and portable recording media like tape-cassette recorders or semiconductor memory systems (CMOS), constitutes the biotelemetry equipment, which can be used in the clinical routine or in studies of the kidney function in ambulant patients during different physiological conditions. The method and some studies will be presented.