Medizin - Open Access LMU - Teil 06/22

Recommendations by NCRP and ICRP for a selective increase of the quality factor for neutrons have not been implemented in the practice of radiation protection, but have added urgency to the search for a more consistent new convention on quality factors. In response to this need, a liaison group of ICRP and ICRU has proposed numerical changes, but also a replacement of the reference parameter LET by the microdosimetric variable lineal energy. This would make quality factors and dose equivalents measurable, but would make computations more complicated. To resolve the dilemma, it is proposed to use an equivalence relation between lineal energy and LET which leads to nearly identical definitions whenever one deals with charged particles of sufficiently long range, For photons below 200 keV and for neutrons below 0.5 MeV, the equivalence is imperfect, but it may, even in these cases, be acceptable for the practical purposes of radiation protection.

The use of tumour associated antigens in the diagnosis of serous effusions was studied in 76 patients with benign and 200 patients with malignant disease. Tissue polypeptide antigen (TPA), alpha fetoprotein, and CA 125 were found to be of little value. At cut off points of 3 ng/ml, 10 U/ml, and 30 U/ml, respectively, carcinoembryonic antigen (CEA), biliary glycoprotein I (BGP I), and CA 19-9 discriminated between benign and malignant serous effusions with a sensitivity of between 24% and 67%. The immunocytochemical staining for these markers resulted in malignant cells being detected in 18% to 33% of cases. Various combinations of conventional cytological examination, effusion fluid tumour marker determination, and immunocytochemical analysis identified malignant cells in serous effusions in up to 72% of cases; conventional cytology alone detected tumour cells in only 30%.

Atrial natriuretic factor (ANF) N-terminal (ANF 1–98) and C-terminal (ANF 99–126) fragments were determined by radioimmunoassay in human plasma. Mean basal plasma ANF N-terminal concentrations in 9 healthy subjects were 461 ± 58 fmol/ml,significantly (p<0.0001) higher than ANF C-terminal concentrations ( 4.8 ± 0.5 fmol/ml). Central volume stimulation by one hour head-out water immersion (WI) induced a significant (p<0.01) increase of the C-terminal peptide levels to 11.6 ± 2.3 fmol/ml,paralleled by a significant (p<0.001) increase of the N-terminal fragment levels to 749 ± 96 fmol/ml. Increases of plasma concentrations of both fragments upon WI correlated significantly (r=0.71;p<0.05). These data suggest cosecretion of the N-terminal fragment with the C-terminal fragment of pro ANF 1–126 following a physiological stimulus of ANF release in man.

To study the stimulating effect of adrenaline (ADR) on active Na+/K+ transport we used double-barrelled ion-sensitive micro-electrodes to measure the activities of extracellular K+ (aKe) and intracellular Na+ (aNai) in isolated preparations of rat soleus muscle, normal human intercostal muscle and one case of hyperkalemic periodic paralysis (h.p.p.). In these preparations bath-application of ADR (10−6 M) resulted in a membrane hyperpolarization and transient decreasesaKe andaNai which could be blocked by ouabain (3×10−4 M). In the h.p.p. muslce a continuous rise ofaNai induced by elevation ofaKe to 5.2 mM could be stopped by ADR. In addition, the intracellular K+ activity (aKi), the free intracellular Ca2+ concentration (pCai) and intracellular pH (pHi) were monitored in rat soleus muscle. During ADRaKi increased, pHi remained constant and intracellular Ca2+ apparently decreased. In conclusion, our data show that ADR primarily stimulates the Na+/K+ pump in mammalian skeletal muscle. This stimulating action is not impaired in the h.p.p. muscle.