H.A.S. van den Brenk

Effects of x-radiation on growth and function of the repair blastema (granulation tissue). II. Measurements of angiogenesis in the Selye pouch in the rat.

SummaryThe Selye pouch technique has been used to stimulate growth of the repair blastema and angiogenesis and measure radiosensitivity of capillary blood vessels in the subcutis. Measurements of radiation damage to the tissue were based on (i) weight per unit area and corresponding DNA content of the repair blastema, (ii) the volume of blood produced in the pouch by angiogenesis and (iii) vascular macrocolony counts. Colony counts gave a D0 value of ∼240 rads for single-dose and ∼180 rads recovery for split-dose irradiation. No significant difference was observed for single doses of irradiation given shortly before or after raising the pouches. Increasing the interval between irradiation of intact skin and raising of the pouch, was associated with rapid and marked repair of radiation damage; a delay of 2–3 weeks resulted in a dose-reduction factor of 500–625 rads for single doses of 1500–1800 rads given to intact skin. Local irradiation of an established pouch with a single large dose (2–4 krads) rapidly...

Promotion of Growth of Tumour Cells in Acutely Inflamed Tissues

Acute inflammatory reactions were induced in rats by the intravenous injection of cellulose sulphate (CS) or an extract of normal rat lung homogenate (LH), or by intraperitoneal injections of Compound 48/80. These treatments greatly increased survival and clonogenic growth in the lungs of rats of intravenously injected allogeneic W-256 and Y-P388 tumour cells. Increase in the dose of intravenously injected CS caused a logarithmic increase in colony forming efficiency (CFE) of tumour cells in the lungs. CFE was not stimulated by the intravenous injection of rats with pharmacological mediators of inflammation (histamine, 5-hydroxytryptamine, bradykinin and prostaglandins PGE1 and PGF2α) which are released from tissues by agents which induce inflammation. Stimulation of CFE by CS occurred in adrenalectomized rats but was inhibited by treatment of rats with an anti-inflammatory steroid, dexamethasone. CFE was stimulated by CS in tumour immunized rats; the inflammatory state did not prevent the expression of immunity but “rescued” a proportion (approximately 20%) of the injected tumour cells from immunodestruction in the lungs. A higher proportion of tumours grew in the paws of rats when a small number of W-256 cells were injected interdigitally into the acute inflammatory swellings produced by the local injection of paws with LH or CS.CS is a “synthetic heparin” which causes marked prolongation of blood clotting time and also increases fibrinolytic activity of the blood. Anticoagulant treatment of rats with heparin did not affect CFE. Thus, there was no direct correlation between blood clotting time and CFE of blood borne tumour cells in the rat.The mechanisms which may be responsible for the nonspecific growth promoting effects of inflammatory reactions induced by various types of tissue injury on tumour induction and growth are discussed.

Stimulation of Clonogenic Growth of Tumour Cells and Metastases in the Lungs by Local X-Radiation

Single cell suspensions of two allogeneic tumours (W-256 and Y-P388) injected intravenously produced macrocolonies in the lungs of rats. Colony forming efficiency (CFE, the number of colonies produced by each viable cell injected) was low in 6-week or older rats but was markedly increased by 1000-1500 rad local thoracic irradiation (LTI) given 7-14 days before the tumour cell injection, or by antilymphocytic serum (ALS) but not by sublethal whole body irradiation (WBI). Similarly, LTI increased the incidence of pulmonary metastases produced by a solid tumour growing in the leg muscle. Stimulation of CFE by LTI was a strictly local phenomenon and not due to effects of irradiation on thymus, spleen or other tissues of the rat. LTI failed to increase CFE in immunized rats. It is concluded that (1) LTI stimulates clonogenic growth of tumour cells arrested in the lungs, by causing inflammatory reactions accompanied by regenerative cellular proliferation of lung tissue, which increases the “plating” efficiency of tumour cells, (2) the increase in CFE in lungs is not due to suppression of immunity to tumour growth by LTI.

Effect of Local X-Irradiation of a Primary Sarcoma in the Rat on Dissemination and Growth of Metastases: Dose-Response Characteristics

The effects of local X-irradiation of a solid, rapidly metastasizing sarcoma in the rat on kinetics of dissemination and growth of metastases in lymph nodes and lungs are described. Corresponding dose-effect curves obtained for growth of the primary tumour (Pr) and its metastases in unirradiated tissues showed that local irradiation of Pr caused an exponential decrease in growth of metastases due to any dissemination occurring after irradiation, but was also responsible for stimulating growth of metastases already established before treatment in lymph nodes and in lungs. This stimulating effect was most marked when Pr was larger at the time of treatment and when high doses were given to eradicate Pr. This effect is attributed to the liberation of growth stimulating substances (GSS) from a pool of GSS produced in the irradiated Pr by sterilized, but metabolically active and growing tumour cells (HR cells). This effect of HR cells on tumour growth and metastases was also demonstrated when rats were inoculated with viable tumour cells and subsequently treated by injecting large doses of HR cells prepared in vitro, into tissues remote from the Pr tumour site.The systemic effects of GSS on metastases were most clearly seen after immunosuppression of recipient hosts by sublethal whole body irradiation, since immunosurveillance in unirradiated rats resulting from a rapidly developing allogenic tumour-host incompatibility caused marked reductions in clonogenicity of the tumour which tended to overshadow the GSS effect. The latter was also masked in immunosuppressed hosts when excessively high rates of dissemination were due to growth of large Pr inocula for sufficiently long to “saturate” the capacity for growth of metastatic tumour in lymph nodes and lungs.The relevance of these findings to clinical radiotherapy is discussed.

Studies of Mechanisms of Chemical Radiation Protection in vivo: II. Effect of High Pressure Oxygen on Radioprotection in vivo and its relationship to ‘oxygen poisoning’

SummaryI. Pure oxygen respired at 45 p.s.i. gauge-pressure by rats during or immediately after whole-body x-irradiation did not significantly alter LD50 (30 days) and LD95 (30 days) survival doses.II. Oxygen respired at 60 p.s.i. gauge-pressure completely abolished the protective effect in vivo of histamine and adrenalin and substantially reduced that of 5-hydroxytryptamine (5HT). The radioprotective actions of cysteamine, cystamine, l-cysteine and AET, were slightly reduced at 60 p.s.i., but cyanide potentiated this reduction for cystamine and 5HT.III. Polarographic measurement of tissue oxygen-tensions for oxygen respired at pressures up to 60 p.s.i. gave a linear relation between the partial pressure of oxygen respired and the subcutaneous tissue oxygen-tension. 5HT and cystamine caused a significant reduction in the slope of this line, but this seemed insufficient to explain radiochemical protection solely in terms of pharmacologically-induced intercellular anoxia. Manometric measurements of arterial ...

Comparison of Oxygen Tensions in Normal Tissues and Yoshida Sarcoma of the Rat Breathing Air or Oxygen at 4 Atmospheres

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EFFECT OF X-RADIATION ON SALIVARY GLAND GROWTH IN THE RAT. II. QUANTITATIVE STUDIES OF SIALADENOTROPHISM INDUCED WITH ISOPROPYLNORADRENALINE AND ITS MODIFICATION BY SINGLE DOSES OF X-RAYS.

SummaryQuantitative and histometric characteristics of sialadenotrophism induced in rats with isopropylnoradrenaline (ISOP) are described, with particular reference to rates of gland growth, rates of cell enlargement and cell proliferation in the submandibular (SM) salivary gland, and effects of ISOP on body-growth and heart weight. Glandular enlargement is principally due to hypertrophy (auxetic growth) and hyperplasia (replicative growth) of serous acinar salivary cells. Local irradiation of salivary tissues of rats before administration of ISOP caused a dose-dependent reduction of sialadenotrophism, 800 rads reducing gland growth by ∼ = 50 per cent. Histometric and autoradiographic studies showed that irradiation reduced growth by inhibiting cell replication, auxetic cell growth being radio-resistant. Cardiomegaly produced by ISOP in rats was also radioresistant. X-radiation inhibits adaptive growth of SM and parotid glands to a similar degree, but dose–effect curves differ, and the reasons for this ar...

Studies of mechanisms of chemical radiation protection in vivo. 3. Changes in fluorescence of intracellular pyridine nucleotides and modification by extracellular hypoxia.

SummaryChanges in the fluorescent signal emitted by the pyridine nucleotide co-enzyme system were recorded from rat tissues in vivo and from ascites tumour cells in vitro. The degree of reduction of this component of the electron transport chain has been shown to be a sensitive index of intracellular oxygen tensions. The effect of selected radioprotective chemicals on the fluorescent emission signal has been studied in rats respiring oxygen at pressures from zero to 760 mm Hg. Similar observations for changes in pO2 have been made for ascites cells treated with protective agents. A quantitative analysis has been made of the redox state of this respiratory co-enzyme system.Results obtained support the view that the radioprotective action of the sulphydryl derivatives, cysteamine and AET (and possibly cystamine and cysteine) is independent of intracellular tissue pO2 levels. That of dimethyl sulphoxide appeared similarly independent of pO2 change. Results with 5-hydroxytryptamine were equivocal. The agents ...

Reactions of the tumour bed to lethally irradiated tumour cells, and the Revesz effect.

Subdermal inoculation of the foot of the rat with lethally irradiated (LI) Walker tumour (W256) cells, mixed with viable (V) W256 cells, decreased the latent period for initiation of allogeneic tumour growth without significantly affecting its rate. This Révész effect decreased with increase in the number of inoculated V cells, and with decrease in age of recipient. LI cells of a different (Y-P388) rat tumour exerted a Révész effect, even in recipients which had been immunized with LI (Y-P388) tumour cells. Local pre-irradiation of the site of inoculation of V cells decreased both the latent period and rate of tumour growth. It acted independently of a Révész effect, and the decrease in tumour growth rate was partly due to emigration of V cells from the inoculum, producing metastases. LI, but not heat-killed cells, induced prolonged swelling of the tumour bed in unimmunized and tumour-immunized rats, which, unlike inflammatory swelling, was inhibited by pre-irradiation of the foot. It is postulated that the Révész effect is due to enhancement of survival of V cells by trophic substances which are principally elaborated by LI (AND V) cells, but also by the tumour bed, due to innate growth and trophic reactions of its tissues to the presence of tumour cells.

Effects of X-radiation on Salivary Gland Growth in the Rat: III. Relative Effects of Local Irradiation on Wet Weight, Protein and Nucleic Acids of the Salivary Gland during Post-natal Growth and Secretion and Resynthesis of Parotid Amylase

SummaryChanges occurring in wet weight, total protein, RNA and DNA of the submandibular salivary gland (SMG) in the rat during post-natal development are described. During gland growth, the ratio DNA/protein increases initially at a less rapid rate than RNA/protein; subsequently, after onset of sexual maturity, both ratios decline, DNA/protein decreasing somewhat earlier. Dose—effect curves for growth of gland after x-irradiation with a single dose, measured in terms of wet weight, total protein, RNA and DNA differed in slope and shape but showed that increase in content of RNA and DNA resulting from gland growth was most radiosensitive and appeared to be largely associated with cell replication. Growth measured in terms of increases in wet weight or total protein was more radioresistant, and protein synthesis appeared to be more closely associated with auxetic cell growth and with cell maturation and differentiation during development. Further evidence that synthesis of acinar protein by salivary tissues...