Dose distribution in tissues

Biological effects of ionising radiation are dependent on the distribution of doses in tissue. In this article parameters influencing the distribution of dose in tissue are discussed with emphasis on intraoral and rotational panoramic radiography. For both examinations the probability to develop stochastic effects is estimated. For intraoral radiography the probability ranges from 0.1 to 0.3 per million exposures and for rotational panoramic radiography from 0.4 to 0.8 per million. For the whole Dutch population the probability to develop stochastic effects is 0-2 persons per year and 0-1 person per year respectively. Dental radiography is therefore justified if further diagnostic information is to be expected and exposure circumstances are optimal.     

Interhemispheric steal. An experimental study

In 21 cats the pressure in the occluded middle cerebral artery (MCA) was recorded by way of a catheter, introduced in the most proximal portion of this artery by way of the transorbital approach. The effect of temporary occlusion of the ipsilateral and contralateral common carotid artery on the pressure in the occluded MCA was studied. The results seem to prove the existence of the so-called "interhemispheric steal" syndrome.     

Adjuvant immunotherapy with BCG in squamous-cell bronchial carcinoma. Immune-reactivity in relation to immunostimulation (preliminary results in a controlled trial).

Jansen, H M, The, T H, de Gast, G C, Esselink, M T, van der Wal, A M, and Orie, N G M (1978).Thorax, 33, 429-438. Adjuvant immunotherapy with BCG in squamous-cell bronchial carcinoma. Immune-reactivity in relation to immunostimulation (preliminary results in a controlled trial). Twenty-nine patients with, at operation, evidence of locally advanced primary squamous-cell bronchial carcinoma (stage II, UICC, Geneva, 1974) had lung resection to remove all the visible tumour. Postoperatively a randomly chosen group of 16 patients received adjuvant BCG immunostimulation by scarifications, while the control group received no adjuvant treatment. Follow-up studies were done from three to 23 months. Immune-reactivity in vivo with PPD and DNCB skin tests, and in vitro with E-rosetting tests and lymphocyte transformation tests with PHA, Con A, diphtheria toxoid, and PPD was monitored in 10 treated and in seven untreated patients. Recurrence rates decreased appreciably in the BCG-stimulated group after a six to 23 months'' follow-up (p<0·005). A pronounced increase in both in-vivo and in-vitro immune-reactivity went in parallel with a more favourable clinical outcome in the BCG-treated group. In these cases there was a significant increase in skin reactivity to PPD three months after surgery (p<0·025) and a statistically significant rise in lymphocyte reactivity to Con A (p<0·05), diphtheria toxoid (p<0·01), and PPD (p<0·05) but not to PHA 12 months after surgery. DNCB skin reactivity increased as well in the BCG-treated group, but the number of individuals was too small for statistical evaluation. Increase in immune responsiveness did not occur in the control group and appeared to be independent of the initial immune state of the patients. No differences were found in the numbers of E-rosetting lymphocytes in relation to immunotherapy. It is concluded that adjuvant BCG immunotherapy used in patients with minimal residual bronchial carcinoma improves the prognosis and a favourable clinical outcome is mirrored by an increase in cellular immune reactivity.     

Effect of toxic thioureas on resistance of rats to growth in the lungs of intravenously and intratracheally seeded tumour cells.

Clonogenic growth (colony-forming efficiency, CFE) of i.v. injected allogeneic W256 tumour cells in the lungs was markedly enhanced by treatment of rats with alpha-naphthyl thiourea (ANTU) injected i.p. from 2 h before to 2 h after the tumour cells. ANTU specifically increases pulmonary vascular permeability in adult rats and causes acute pulmonary oedema and pleural effusion. Inhibition of drug toxicity to the lungs by tachyphylaxis, specific antimetabolites or iodides did not abolish the effect of ANTU on CFE. CFE was not increased when cells were seeded by i.v. injection the lungs affected by advanced pulmonary oedema at 6 to 24 h after treatment with drug. ANTU did not enhance growth of intratracheally injected cells. Although ANTU has no cytotoxic or immunosuppressive action, treatment of tumour-immunized rats with ANTU caused apparent "breakdown" of tumour immunity in 50% of rats, by causing growth of tumour colonies in the lungs. Possible mechanisms for the ANTU-induced decrease in innate resistance to growth of tumour in the lungs are discussed.     

An increase in intraocular pressure due to clonidine

Summary The rise in intraocular pressure (IOP) observed after the administration of clonidine into the carotid arteries was studied in anesthetized rats and cats. This increase of IOP proved to be blocked by the -sympathicolytic agent piperoxane and by the muscle relaxants d-tubocurarine and gallamine. Our experiments suggest that the elevation of IOP after clonidine injection is due to contraction of the eyelids and extraocular muscles. In these tissues -adrenoceptors seem to play a part.