An investigation of the association between diet and occurrence of acne: a rational approach from a traditional Chinese medicine perspective.

BACKGROUND: The association between diet and acne vulgaris has long been suggested but remains unproven in western medicine. In contrast, the diet-acne relationship is considered important in traditional Chinese medicine (TCM). Aim. To investigate the association between diet and acne, using a TCM approach. METHODS: Using a cross-sectional study of 322 entrants to a university in Hong Kong, China, we examined the participants' clinical severity of acne using the Global Acne Grading System and the participants' yin and yang scores using a quantitative method. We then divided them into two groups, a yin-predominant group (yin-PG) and a yang-predominant group (yang-PG) before the diet-acne relationship was investigated. RESULTS: In total, 82 (25.2%) participants were in the clinical acne group and 240 (74.5%) were in the reference group. There were 155 (48.1%) participants in the yin-PG and 167 (51.9%) in the yang-PG group. No association of diet and acne was found when the participants were considered as a homogenous group. In yin-PG, intake of foods from street stalls (P = 0.04) was significantly associated with a lower incidence of acne. In yang-PG, the intake of desserts (P = 0.04) and fresh fruit juices (P = 0.02) was significantly associated with a higher incidence of acne, whereas the intake of dairy and soy products (P = 0.04) was significantly associated with a lower incidence of acne. CONCLUSIONS: The application of a TCM approach led to the detection of significant associations between diet and the incidence of acne.

Acne prevalence and beyond: acne disability and its predictive factors among Chinese late adolescents in Hong Kong.

BACKGROUND: Data are lacking on the prevalence of acne, its effects on quality of life (QOL) and the treatment usage among Chinese patients in late adolescence. AIM: To derive data about the prevalence and predictive factors of acne, the disability caused by acne and choice of treatment used by Chinese late adolescents in Hong Kong. METHODS: This was a cross-sectional study of a random sample of 389 entrants in a university in Hong Kong, using the Global Acne Grading System (GAGS) to measure the clinical severity of acne and the Cardiff Acne Disability Index (CADI) to measure QOL. RESULTS: The response rate was 99.3%. The prevalence of acne was of 81.5% (95% CI 77.6-85.4%) and coexisted with a high frequency of acne disability at a rate of 81.8% (95% CI 78.1-85.6%). Assessment of the clinical severity of acne did not correlate strongly with the effect on QOL (gamma(s) = 0.445, P < 0.001). Over the previous 6 months, 30.3% of subjects had used topical treatments, 3.9% had taken systemic conventional western drugs and 3.2% of the subjects had used traditional Chinese medicine. Multivariate logistic regression was used to explore the predictive factors for acne disability. Female gender (P = 0.002), higher GAGS score (P < 0.001), higher perceived stress (P = 0.01) and willingness to pay Hong Kong$15,000 (970 pounds) for a hypothetical permanent cure (P = 0.03) were positive predictors. CONCLUSIONS: Acne is prevalent in Hong Kong and has considerable psychological effects. The association between clinical severity and impaired QOL is not strong.

The nonpeptidyl caspase binding radioligand (S)-1-(4-(2-[18F]Fluoroethoxy)-benzyl)-5-[1-(2-methoxymethylpyrrolidinyl)sulfonyl]isatin ([18F]CbR) as potential positron emission tomography-compatible apoptosis imaging agent.

AIM: Radiolabeled Annexin V-derivatives are well characterized phosphatidylserine-targeting biomarkers and considered as state-of-the-art tracers for non-invasive molecular imaging of apoptosis. In contrast to Annexin V-derived imaging agents being surrogate markers of apoptosis, activated cysteinyl aspartate-specific proteases (caspases) represent the common final path of apoptosis being a suitable in vivo target for the exclusive imaging of apoptotic tissues in vivo. METHODS: We suggest 5-pyrrolidinylsulfonyl isatins as a potential nonpeptidyl class of caspase inhibitors for the design of caspase binding radioligands (CbRs), that could be used for in vivo visualization of activated effector caspases. The caspase inhibitor (S)-(+)-5-[1-(2-Methoxy-methylpyrrolidinyl)sulfonyl]isatin 1 (K(i, caspase)-3 (1)=60 nM) was chosen as lead structure for the development of nonpeptidyl CbRs. Its structural expansion at the N-1-position the yields moderate lipophilic p-(2-fluoroethoxy)benzyl variant 2 (log D=2.2), without loss of caspase binding potency (IC(50, caspase)-3 (2)=36.4 nM). RESULTS: Subsequent automated radiosynthesis of the corresponding (18)F-labeled target CbR [(18)F]2 was performed by direct (18)F-labeling of tosylate precursor 4. CONCLUSIONS: As shown by biodistribution studies and small animal positron emission tomography a nonpeptidyl 5-pyrrolidinylsulfonyl isatin-type caspase inhibitor (S)-1-(4-(2-[(18)F]Fluoroetho-xy)benzyl)-5-[1-(2-methoxymethylpyrrolidinyl)sulfonyl]isatin [(18)F]2 with rapid blood clearance characteristics could potentially detect apoptosis in vivo.

Non-invasive molecular imaging of beta-adrenoceptors in vivo: perspectives for PET-radioligands.

Recently, the spectrum of molecular imaging devices such as positron emission tomography (PET) was further expanded by the now clinically available combined imaging modalities such as PET-CT and the preclinically used small animal PET scanners. These are powerful tools that can bridge the gap between preclinical and clinical evaluation studies of new radiotracers for molecular imaging of healthy and diseased states in vivo. The beta-adrenoceptor (beta-AR) radioligands discussed in this review represent a class of molecular probes for the non-invasive in vivo assessment of beta-AR density eg. in the heart with PET. The beta-AR radioligands (S)-[11C]CGP 12177 (1) or (S)-[11C]CGP 12388 (2) are currently investigated in clinical studies with PET. Additionally, subtype-selective beta1-AR radioligands are used in preclinical research which show potential for the diagnostics of the "beta1-AR organ" as such the heart can be defined. Non-invasive quantification of beta-ARs could facilitate the accurate choice and control of therapeutic interventions. Here we summarize the state-of-the-art of the radiochemistry of radioactive beta-AR radioligands.

[High non-specific binding of the beta(1) -selective radioligand 2-(125)I-ICI-H]. / Hohe unspezifische Bindung des beta(1)-selektiven Radioliganden 2-(125)I-ICI-H.

AIM: As results of cardiac biopsies suggest, myocardial beta(1) -adrenoceptor density is reduced in patients with chronic heart failure. However, changes in cardiac beta(2)-adrenoceptors vary. With suitable radiopharmaceuticals single photon emission computed tomography (SPECT) and positron emission tomography (PET) offer the opportunity to assess beta-adrenoceptors non-invasively. Among the novel racemic analogues of the established beta(1)-selective adrenoceptor antagonist ICI 89.406 the iodinated 2-I-ICI-H showed high affinity and selectivity to beta(1)-adrenoceptors in murine ventricular membranes. The aim of this study was its evaluation as a putative sub-type selective beta(1)-adrenergic radioligand in cardiac imaging. METHODS: Competition studies in vitro and in vivo were used to investigate the kinetics of 2-I-ICI-H binding to cardiac beta-adrenoceptors in mice and rats. In addition, the radiosynthesis of 2-(125)I-ICI-H from the silylated precursor 2-SiMe(3)-ICI-H was established. The specific activity was 80 GBq/ micro mol, the radiochemical yield ranged from 70 to 80%. RESULTS: The unlabelled compound 2-I-ICI-H showed high beta(1)-selectivity and -affinity in the in vitro competition studies. In vivo biodistribution studies apparently showed low affinity to cardiac beta-adrenoceptors. The radiolabelled counterpart 2-(125)I-ICI-H showed a high degree of non-specific binding in vitro and no specific binding to cardiac beta(1)-adrenoceptors in vivo. CONCLUSION: Because of its high non-specific binding 2-(125)I-ICI-H is no suitable radiotracer for imaging in vivo.

Radioligands for imaging myocardial alpha- and beta-adrenoceptors.

Alpha- and beta-adrenoceptors play an important role in the control of heart function. According to their molecular, biological, and pharmacological characteristics, they are subdivided into alpha(1)-, alpha(2)- and beta(1)-, beta(2)-, beta(3)-, beta(4)-adrenoceptors. In cardiac disease, there is often a selective downregulation of beta(1)-adrenoceptors associated with a relative increase in beta(2)- and alpha(1)-adrenoceptors. Functional imaging techniques like single-photon emission tomography (SPECT) and positron emission tomography (PET) provide the unique capability for non-invasive assessment of cardiac adrenoceptors. Radioligands with high specific binding to cardiac alpha- and beta-adrenoceptors suitable for radiolabelling are required for clinical studies. The non-selective beta-adrenoceptor antagonist [(11)C]CGP-12177 was used to quantify beta-adrenoceptor density using PET in patients with heart disease. New non-selective ligands (e. g. [(11)C]CGP-12388, [(18)F]CGP-12388, [(11)C]carazolol and [(18)F]fluorocarazolol) are currently evaluated; beta(1)-selective radioligands (e. g. [(11)C]CGP-26505, [(11)C]bisoprolol, [(11)C]HX-CH 44) and beta(2)-selective radioligands (e. g. [(11)C]formoterol, [(11)C]ICI-118551) were assessed in animals. None of them turned out as suitable for cardiac PET. Potential radioligands for imaging cardiac alpha(1)-adrenoceptors are based on prazosin. Whereas [(11)C]prazosin shows low specific binding to myocardium, its derivative [(11)C]GB67 looks more promising. The putative alpha(2)-adrenoceptor radioligand [(11)C]MK-912 shows high uptake in rodent myocardium but has not yet been evaluated in man. A number of radioligands were evaluated for assessing cardiac adrenoceptors using PET. New radioligands are needed to provide more insight into cardiac pathophysiology which may influence the therapeutic management of patients with cardiovascular disease.

In vivo imaging of insulin receptors by PET: preclinical evaluation of iodine-125 and iodine-124 labelled human insulin.

[A(14)-*I]iodoinsulin was prepared for studies to assess the suitability of labeled iodoinsulin for positron emission tomography (PET). Iodine-125 was used to establish the methods and for preliminary studies in rats. Further studies and PET scanning in rats were carried out using iodine-124. Tissue and plasma radioactivity was measured as the uptake index (UI = [cpm x (g tissue)(-1)]/[cpm injected x (g body weight)(-1)]) at 1 to 40 min after intravenous injection of either [A(14)-(125)I]iodoinsulin or [A(14)-(124)I]iodoinsulin. For both radiotracers, initial clearance of radioactivity from plasma was rapid (T(1/2) approximately 1 min), reaching a plateau (UI = 2.8) at approximately 5 min which was maintained for 35 min. Tissue biodistributions of the two radiotracers were comparable; at 10 min after injection, UI for myocardium was 2.4, liver, 4.0, pancreas, 5.4, brain, 0.17, kidney, 22, lung, 2.3, muscle, 0.54 and fat, 0.28. Predosing rats with unlabelled insulin reduced the UI for myocardium (0.95), liver (1.8), pancreas (1.2) and brain (0.08), increased that for kidney (61) but had no effect on that for lung (2.5), muscle (0.50) or fat (0.34). Analysis of radioactivity in plasma demonstrated a decrease of [(125)I]iodoinsulin associated with the appearance of labeled metabolites; the percentage of plasma radioactivity due to [(125)I]iodoinsulin was 40% at 5 min and 10% at 10 min. The heart, liver and kidneys were visualized using [(124)I]iodoinsulin with PET.

Selection, design and evaluation of new radioligands for PET studies of cardiac adrenoceptors.

Changes in the numbers of human cardiac adrenoceptors (ARs) are associated with various diseases, such as myocardial ischemia, congestive heart failure, cardiomyopathy and hypertension. There is a clear need for capability to assess human cardiac ARs directly in vivo. Positron emission tomography (PET) is an imaging technique that provides this possibility, if effective radioligands can be developed for the targeted ARs. Here, the status of myocardial AR radioligand development for PET is described. Currently, there exist effective radioligands for imaging beta-ARs in human myocardium. One of these, [11C](S)-CGP 12177, is applied extensively to clinical research with PET, sometimes with other tracers of other aspects of the noradrenalin system. Alternative radioligands are in development for beta-ARs, including beta 1-selective radioligands. A promising radioligand for imaging myocardial alpha 1-ARs, [11C]GB67, is now being evaluated in human PET experiments.

Evaluation of [11C]GB67, a novel radioligand for imaging myocardial alpha 1-adrenoceptors with positron emission tomography.

Dysfunction of the sympathetic nervous system underlies a number of myocardial disorders. Positron emission tomography (PET) offers a way of assessing receptor function non-invasively in humans, but there are no PET radioligands for assessing myocardial alpha-adrenoceptors. GB67, a structural and pharmacological analogue of the alpha 1-adrenoceptor antagonist prazosin, was labelled with positron-emitting carbon-11 (t1/2 = 20.4 min) by 11C-methylation of N-desmethylamido-GB67 (GB99). [11C]GB67 was injected intravenously into conscious rats. Serial arterial blood samples were taken. Rats were killed and tissues removed to determine radioactivity. The percentages of unchanged [11C]GB67 and its radioactive metabolites in plasma and tissues were assessed by HPLC. Plasma clearance of radioactivity was rapid. Myocardial uptake was maximal at 1-2 min and decreased slowly during 60 min. Predosing with adrenoceptor antagonists demonstrated selectivity for myocardial alpha 1-adrenoceptors. GB67 and prazosin blocked uptake of radioactivity; the non-selective antagonist, phentolamine, partially blocked uptake; the alpha 2-adrenoceptor antagonist, RX 821002, only blocked uptake at high dose and the beta-adrenoceptor antagonist, CGP 12177, had no effect. Additionally, injection of prazosin at 20 min after radioligand displaced radioactivity. In vivo competition curves obtained by injecting [11C]GB67 with varying amounts of either unlabelled GB67 or its precursor GB99 were fitted to a competitive binding model to provide estimates of the maximum number of binding sites (Bmax) and half saturation doses (K) for myocardium. Assuming a tissue protein content of 10%, the values of Bmax [approximately 13 pmol.(g tissue)-1[ were similar to those ]50-170 fmol.(mg protein)-1] reported for myocardial alpha 1-adrenoceptors assessed in vitro. Both GB67 and its precursor GB99 had high affinity for alpha 1-adrenoceptors [KGB67 = 1.5 nmol.(kg body weight)-1, KGB99 = 4.8 nmol.(kg body weight)-1]. HPLC demonstrated four radioactive metabolites in plasma. [11C]GB67 was 80% of the radioactivity at 5 min and 50% at 45 min. No radioactive metabolites were detected in myocardium up to 60 min after injection. [11C]GB67 was assessed in two male human volunteers. PET demonstrated high myocardial uptake. The profile of radioactive metabolites in plasma was comparable to that in the rat, although metabolism was slower in humans. Thus, [11C]GB67 is a promising radioligand for assessing alpha 1-adrenoceptors in human myocardium with PET.

Biodistribution and metabolism of [N-methyl-11C]m-hydroxyephedrine in the rat.

Biodistribution and metabolism of [N-methyl-11C]m-hydroxyephedrine ([11C]mHED), an analogue of noradrenaline, were assessed in rats. Pretreatment with desipramine, an uptake blocker, reduced uptake of radioactivity in myocardium but not in lung, liver, kidney, and muscle. Brain uptake was negligible. HPLC showed six radioactive metabolites in plasma and liver but none in myocardium. Co-injection of unlabelled mHED or metaraminol with [11C]mHED demonstrated no difference between the in vivo binding potentials for mHED and metaraminol in myocardium.

Evaluation in rat of RS-79948-197 as a potential PET ligand for central alpha 2-adrenoceptors.

Tritium-labelled RS-79948-197 {(8aR,12aS,13aS)-5, 8,8a,9,10,11,12,12a,13,13a-decahydro-3-methoxy-12-(ethylsulphon yl)-6H-iso- quino[2,1-g][1,6]naphthyridine} was evaluated in rat brain as an in vivo ligand for central alpha 2-adrenoceptors, as a preliminary step in the development of a radioligand for positron-emission tomography (PET) studies. The maximal receptor-specific signal was achieved within 90-120 min after i.v. injection of [ethyl-3H]RS-79948-197 and was selective for the alpha 2- compared with the alpha 1-adrenoceptor, with no detectable binding to the imidazoline-I2 site. Estimates for binding potential (approximating to Bmax/Kd) ranged between 3.4 in entorhinal cortex and 0.5 in medulla oblongata. The results, which indicate a similarly localised but 2-fold increase in specific binding compared with that previously demonstrated using [3H]RX 821002 (2-methoxy-idazoxan), are sufficiently encouraging as to support further investment in the development of 11C-labelled RS-79948-197, or a close structural analogue, as a ligand for clinical PET.

Propionyl-L-carnitine: labelling in the N-methyl position with carbon-11 and pharmacokinetic studies in rats.

The prospective therapeutic, propionyl-L-carnitine, was labelled in the N-methyl position with the positron-emitter, carbon-11 (t1/2 = 20.4 min), with a view to studying its pharmacokinetics in humans using PET. Labelling was achieved by methylating nor-propionyl-L-carnitine hydrochloride with no-carrier-added [11C]iodomethane (produced from cyclotron-produced [11C]carbon dioxide) in ethanol in the presence of 1,2,2,6,6-pentamethylpiperidine. HPLC of the reaction mixture on a strong cation exchange column provided high purity [N-methyl-11C]propionyl-L-carnitine in 62% radiochemical yield (decay-corrected from [11C]iodomethane), ready for intravenous administration within 35 min from the end of radionuclide production. [N-methyl-11C]Propionyl-L-carnitine, given intravenously to rats, cleared rapidly from plasma. A slow uptake of radioactivity into myocardium and striated muscle was observed. In plasma, unchanged tracer represented 84% of the radioactivity at 2.5 min and 2.5% of the radioactivity at 60 min. In heart, unchanged tracer represented 18% of radioactivity at 2.5 min and 2.4% at 15 min. The remainder of radioactivity detected in plasma and heart was identified as [N-methyl-11C]L-carnitine and [N-methyl-11C]acetyl-L-carnitine.

Demonstration of the suitability of CGP 12177 for in vivo studies of beta-adrenoceptors.

1. Positron emission tomography (PET) with appropriate radioligands offers the possibility of studying receptors non-invasively in man. The suitability of CGP 12177, a hydrophilic non-selective beta-adrenoceptor antagonist which can be labelled with the positron emitter 11C, as a ligand for in vivo studies of beta-adrenoceptors was assessed in rats. 2. [3H]-CGP 12177 was injected into the tail veins of restrained conscious rats. Serial blood samples were taken from tail arteries to determine clearance from plasma. Rats were killed and tissues removed to determine tissue uptake. Radioactivity was assessed by liquid scintillation counting. 3. The uptake of (-)-[3H]-CGP 12177 in various tissues was compared to that of (+/-)-[3H]-CGP 12177. Maximum tissue:plasma ratios obtained for the (-)-enantiomer in lung, heart and liver were 170, 42 and 13 compared with 60, 15 and 12 for the racemate. Prior injection of excess unlabelled (+/-)-CGP 12177 blocked the uptake of both (-)- and (+/-)-[3H]-CGP 12177 in lung and heart but not liver, tissue:plasma ratios for both tracers being reduced to 7, 3 and 7 respectively. 4. Clearance of (-)-[3H]-CGP 12177 from plasma was rapid during the first 5 min but showed only small changes during 5 to 90 min. Uptake in lung and heart reached a maximum at 1 to 5 min and showed a slow decrease during 5-90 min. Prior injection of unlabelled (+/-)-CGP 12177 reduced uptake in lung and heart to 10% and 20% respectively. Injection of unlabelled ( +/-)-CGP 12177 at 15 mind is placed ~75% of the radioactivity by 90 min.5. ( +/- )-Propranolol had a similar effect to that of unlabelled ( +/-)-CGP 12177. Prior injection reduced uptake of radioactivity in lung and heart to 15% and 20% respectively. Injection of ( +/- )-propranolol at 15 min displaced ~ 60% of the radioactivity by 90 min indicating that the tracer binds to beta-adrenoceptor sites in vivo.6. In vivo saturation curves, obtained by injection of (-)-[3H]-CGP 12177 with increasing amounts of unlabelled (- )-CGP 12177, gave values of Bmax for lung of ~45 pmol per g wet weight of tissue and for heart of ~6 pmol per g wet weight of tissue. KD could only be expressed as nmol injected per kg bodyweight, that for lung (2.5 nmol kg-1) being greater than that for heart (1.3 nmol kg-1).7. Competition studies carried out by co-injecting (-)-[3H]-CGP 12177 with unlabelled (+/- )-CGP12177 or (-)-propranolol gave similar values for Bmax (lung 44 pmol g-1, heart 6 pmol g-1,). Values of KD for (+/-)-CGP 12177 (lung 4.7 pmol kg-1, heart 2.6 pmol kg-1) were approximately twice those for(-)-CGP 12177. Values of KD for (-)-propranolol (lung 38 nmol kg-1, heart 104 nmol kg-1) were greater.8. The results show that (-)-[3H]-CGP 12177 is a suitable ligand for assessing beta-adrenoceptors in vivo.

Rapid analysis for metabolites of 11C-labelled drugs: fate of [11C]-S-4-(tert.-butylamino-2-hydroxypropoxy)-benzimidazol-2-one in the dog.

Positron emission tomography (PET) requires the use of compounds labelled with short-lived, positron-emitting isotopes (e.g., t1/2 of 11C approximately 120 min). As the concentration of unbound, non-metabolised drug is required as the input function for modeling, this presents particular problems for the study of the kinetics and metabolism of such compounds. We have now developed a rapid extraction procedure, followed by high-performance liquid chromatography using a short analytical column coupled to an on-line gamma-detector to determine the metabolism and kinetics of a non-selective beta-adrenergic antagonist of high affinity, S-4-(tert.-butylamino-2-hydroxypropoxy)benzimidazol-2-one. This antagonist is potentially well suited to the non-invasive localisation of beta-receptors in vivo. The ligand was rapidly taken up into the beta-receptor pool or excreted in urine, with less than 5% of the drug converted to metabolites. Plasma protein binding was only 16%. No significant metabolism of the ligand was observed in the anaesthetised dog, and, therefore, no correction for blood metabolite concentration is required for kinetic analysis of the 11C-labelled ligand during PET studies in this species. The analytical method reported here should be widely applicable: quantification of metabolites enables accurate estimation of the input function and is critical to the interpretation of PET data.

Vascular and epithelial damage in the lung of the mouse after X rays or neutrons.

The response of the lung was studied in CFLP mice after exposure of the whole thorax to X rays (250 kVp) or cyclotron neutrons (16 MeV deuterons on Be, mean energy 7.5 MeV). To measure blood volume and leakage of plasma proteins, 51Cr-labeled red blood cells and 125I-albumin were injected intravenously and 24 h later lungs were lavaged via the trachea. Radioactivities in lung tissue and lavage fluid were determined to estimate the accumulation of albumin in the interstitial and alveolar spaces indicating damage to blood vessels and alveolar epithelium respectively. Function of type II pneumonocytes was assessed by the amounts of surfactant (assayed as lipid phosphorous) released into the lavage fluid. During the first 6 weeks, lavage protein and surfactant were increased, the neutron relative biological effectiveness (RBE) being unity. During pneumonitis at 12-24 weeks, surfactant levels were normal, blood volume was decreased, and both interstitial and alveolar albumin were increased. Albumin levels then decreased. At late times after exposure (42-64 weeks) alveolar albumin returned to normal but interstitial albumin was still slightly elevated. Values of RBE for changes in blood volume and interstitial and alveolar albumin at 15 weeks and for changes in blood volume and interstitial albumin at 46 weeks were 1.4, comparable with that for animal survival at 180 days. The results indicate that surfactant production is not critical for animal survival. They suggest that changes in blood vessels and alveolar epithelium occur during acute pneumonitis; epithelial repair follows but some vascular damage may persist. The time course of the changes in albumin levels did not correlate with increases in collagen biosynthesis which have been observed as early as 1 month after exposure and persist for up to 1 year. Furthermore, a dose which had no effect on leakage caused a marked increase in collagen biosynthesis. Thus the present results do not support a causal relationship between exudation of vascular protein during pneumonitis and the later development of fibrosis.

Biosynthesis and degradation of collagen in X-irradiated mouse lung.

Fibrosis, characterized by accumulation of collagen, is a delayed result of radiation injury in many tissues, including lung. To investigate its development, synthesis and degradation of collagen were measured in lungs of mice after X irradiation of the whole thorax. The ratio of type I (coarse fibered) to type III (meshwork) collagen was also determined. Synthesis of procollagen, measured as the activities of prolyl-4-hydroxylase and protein disulfide isomerase in lung tissue, was increased at 2 months after X-ray doses of 5, 7.5, and 9 Gy. Maximal increases were observed 6 to 7 months after doses of 9 Gy and persisted up to 15 months after exposure. Increases after 5 and 7.5 Gy were more gradual, but by 1 year after irradiation they had reached levels similar to those after 9 Gy. X irradiation had no effect on the degradation of collagen as assessed by collagenase activity in lung. The ratio of type I to type III collagen, analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis of collagen-derived cyanogen bromide peptides, was the same in irradiated lungs as in age-matched controls. Therefore, increased synthesis of procollagen, rather than decreased degradation of collagen or changes in collagen type, is an important factor in the accumulation of collagen in irradiated lung.

Thermotolerance induced by fractionated hyperthermia: dependence of the interval between fractions.

The induction of thermotolerance by fractionated hyperthermia was investigated in the mouse ear. Ears were heated at 43.5 degrees C by immersion in water. One to ten treatments of 20 min were followed by test treatments. Thermotolerance was assessed as the increase in the duration of the test treatment required for a thermal response in 50 per cent of the ears (NT50). A single treatment induced thermotolerance which reached a maximum at 24 h when the NT50 was increased by a factor of 2.4. The same maximum was observed after each fractionated treatment used in the present study. The time course of development, however, depended on the interval between fractions. (1) When the interval was too short to allow development of thermotolerance after a single fraction (4 h), thermotolerance was not induced during fractionated treatment but it developed during the first 24 h after treatment. (2) When the interval between fractions allowed the maximal development of thermotolerance (24 h), this maximum was maintained during fractionated treatment and persisted for 24 h after treatment. (3) When the interval allowed some decay of thermotolerance (72 or 168 h) there was a further increase to maximal thermotolerance after each fraction. The decay of thermotolerance from the maximum did not depend on the interval between fractions. These results indicate that the degree of thermotolerance may fluctuate during fractionated hyperthermia.

A long-term effect of prior irradiation on the thermal enhancement of radiation damage in the mouse ear.

The responses of the mouse ear to heat alone, X-rays alone or X-rays combined with heat were measured at 10 months after initial X-ray treatments (19 Gy or 10 X 3.8 Gy), which caused similar acute reactions. Fractionating the initial dose had little effect on the response to retreatment. Prior irradiation increased thermal sensitivity so that the heating time at 43.5 degrees C required to cause necrosis was about 65 per cent that in age-matched controls. Prior irradiation also increased the response to X-rays alone, but had different effects on the susceptibilities to develop acute radiodermatitis and late deformity. For acute radiodermatitis, the second X-ray dose required to cause a given response in previously irradiated ears was 80-90 per cent that in age-matched controls and for late deformity it was 60-65 per cent. Prior irradiation had the same effects on the responses to X-rays given 6 min before mild hyperthermia (43.5 degrees C, 12 min) as on those to X-rays alone but had little effect on the responses to X-rays given 6 min after hyperthermia. Consequently, the thermal enhancement ratios for heat given after X-rays did not depend on prior irradiation whereas those for heat given before X-rays were reduced. This reduction may be due to a reduced ability of irradiated blood vessels to elicit an hyperaemic response to heat.