Measurement of tumor oxygenation: a comparison between polarographic needle electrodes and a time-resolved luminescence-based optical sensor

A novel oxygen sensor which does not rely on electrochemical reduction has been used to measure the oxygenation of the murine sarcoma F in a comparative study with an existing polarographic electrode that is available commercially. The prototype luminescence sensor yielded an oxygen distribution comparable with readings made using a pO2 histograph. The percentage of regions detected that had a pO2 less than 5 mm Hg was 79 and 75 using the Eppendorf pO2 histograph and the luminescence fiber optic sensor, respectively. These values were compatible with a measured radiobiologically hypoxic fraction of 67% in this tumor. The polarographic method detected more regions with a pO2 of 2.5 mm Hg or less (69%) compared with the optical sensor (50%) (P < 0.05). This could reflect differences in the oxygen use of the sensing devices. This initial assessment indicates the potential of a fiber-optic-based oxygen-monitoring system. Such a system should have several advantages including monitoring temporal oxygen changes in a given microregion and use with NMR procedures.

Measurement of oxygen tension in tumours by time-resolved fluorescence

Tumour oxygenation is important in clinical radiotherapy because hypoxic cells are radioresistant. Knowledge of the state of tumour oxygenation would be advantageous for maximising effectiveness of treatment. A prototype fibre optic fluorosensor for measuring low (radiobiologically relevant) levels of oxygen is described. Based on oxygen quenching of the fluorescence of an excited fluorophor immobilised in a polymer at the end of an optical fibre, the sensor shows promise in overcoming some of the limitations of existing oxygen sensor systems. The prototype fibre optic sensor operates most effectively in the 0-2% oxygen range with fast response and settling times. Preliminary results from measurements in tumours are presented.

Maternal death associated with intravenous methylphenidate (Ritalin) and pentazocine (Talwin) abuse

A case of maternal death from pulmonary hypertension secondary to pulmonary granulomatosis is presented. The granulomas are associated with a history of intravenous injection of medications (Ritalin and Talwin) intended for oral use.

Comparative study of the effects of porcine proinsulin and insulin on lipolysis and glucose oxidation in rat adipocytes

Proinsulin blocked lipolysis activation by epinephrine, glucagon or theophylline. The antilipolytic effect of pro-insulin was not blocked by Kunitz pancreatic trypsin inhibitor (KPTI). The-concentrations of proinsulin and insulin required to cause 50 per cent inhibition of epinephrine-stimulated lipolysis were estimated to be approximately 1 × 10−9 M and 3 × 10−11 M respectively. Proinsulin which had been reduced and allowed to reoxidize was found to have approximately the same antilipolytic activity as native proinsulin, indicating that the antilipolytic effect was due to proinsulin and not insulin contamination. The concentrations of proinsulin and insulin required to give 50 per cent of maximal stimulation of glucose oxidation were estimated to be approximately 5 × 10−9 M and 1 × 10−11 M respectively. The effect of proinsulin on glucose oxidation did not appear to be caused by any insulin contamination since reduced-reoxidized proinsulin had approximately the same activity as native proinsulin. KPTI had no effect on proinsulin-stimulated glucose oxidation in isolated fat cells, in contrast to the marked inhibitory effect observed using intact epididymal fat pad. This suggests that the KPTI-sensitive proteolytic activity of the epididymal fat pad is not located in the fat cell but in some other type cell or extracellular space.