Comparative proteomics reveals proteins impacted by nitrogen deprivation in wild-type and high lipid-accumulating mutant strains of Tisochrysis lutea

Understanding microalgal lipid accumulation under nitrogen starvation is of major interest for biomass feedstock, food and biofuel production. Using a domesticated oleaginous algae Tisochrysis lutea, we performed the first comparative proteomic analysis on the wild type strain and a selected lipid over-accumulating mutant. 2-DE analysis was made on these strains cultured in two metabolic conditions, with and without nitrogen deprivation, which revealed significant differences in proteomes according to both strain and nitrogen availability. Mass spectrometry allowed us to identify 37 proteins that were differentially expressed between the two strains, and 17 proteins regulated by nitrogen starvation concomitantly with lipid accumulation. The proteins identified are known to be involved in various metabolic pathways including lipid, carbohydrate, amino acid, energy and pigment metabolisms, photosynthesis, protein translation, stress response and cell division. Four candidates were selected for possible implication in the over-accumulation of lipids during nitrogen starvation. These include the plastid beta-ketoacyl-ACP reductase protein, the coccolith scale associated protein and two glycoside hydrolases involved in biosynthesis of fatty acids, carbon homeostasis and carbohydrate catabolism, respectively. This proteomic study confirms the impact of nitrogen starvation on overall metabolism and provides new perspectives to study the lipid over-accumulation in the prymnesiophyte haptophyte T. lutea.

BIOLOGICAL SIGNIFICANCE

This paper study consists of the first proteomic analysis on Tisochrysis lutea, a non-model marine microalga of interest for aquaculture and lipids production. Comparative proteomics revealed proteins putatively involved in the up-accumulation of neutral lipids in a mutant strain during nitrogen starvation. The results are of great importance for future works to improve lipid accumulation in microalgae of biotechnological interest for biofuel production. This article is part of a Special Issue entitled: Proteomics of non-model organisms.

Peripheral muscle endurance and the oxidative profile of the quadriceps in patients with COPD

BACKGROUND

Based on previously reported changes in muscle metabolism that could increase susceptibility to fatigue, we speculated that patients with chronic obstructive pulmonary disease (COPD) have reduced quadriceps endurance and that this will be correlated with the proportion of type I muscle fibres and with the activity of oxidative enzymes.

METHODS

The endurance of the quadriceps was evaluated during an isometric contraction in 29 patients with COPD (mean (SE) age 65 (1) years; forced expiratory volume in 1 second 37 (3)% predicted) and 18 healthy subjects of similar age. The electrical activity of the quadriceps was recorded during muscle contraction as an objective index of fatigue. The time at which the isometric contraction at 60% of maximal voluntary capacity could no longer be sustained was used to define time to fatigue (Tf). Needle biopsies of the quadriceps were performed in 16 subjects in both groups to evaluate possible relationships between Tf and markers of muscle oxidative metabolism (type I fibre proportion and citrate synthase activity).

RESULTS

Tf was lower in patients with COPD than in controls (42 (3) v 80 (7) seconds; mean difference 38 seconds (95% CI 25 to 50), p<0.001). Subjects in both groups had evidence of electrical muscle fatigue at the end of the endurance test. In both groups significant correlations were found between Tf and the proportion of type I fibres and citrate synthase activity.

CONCLUSION

Isometric endurance of the quadriceps muscle is reduced in patients with COPD and the muscle oxidative profile is significantly correlated with muscle endurance.

Effects of peak concentrations on the neurotoxicity of styrene in volunteers

The manufacture of fibreglass reinforced plastic products may give rise to substantial peak exposures to styrene. Such exposure patterns need further consideration in terms of styrene neurotoxicity. The aim of this study was to evaluate the neurotoxic effects of short-term peak exposures in volunteers, at levels respecting the Quebec occupational exposure limits (8 hours time weighed average of 213 mg/m3 and 15 min average of 426 mg/ m3). The volunteers had not been previously exposed to styrene and they had no documented exposure to known neurotoxicants during the study. Twenty-four volunteers were exposed to five exposure scenarios during 6 hours: a, stable exposure to 106 mg/m3; b, variable exposure with a mean concentration of 106 mg/m3 with four 15 min peaks mounting up to 213 mg/m3; c, stable exposure to 213 mg/m3; d, variable exposure with a mean concentration of 213 mg/m3 and four peaks of 426 mg/m3 and e, two stable exposures to 5 mg/m3 (control). Before and after each exposure scenario, volunteers were submitted to a battery of sensory tests (visual and olfactory), neuropsychological tests (reaction time, attention, memory, psychomotor function), and self-evaluation questionnaires (mood and symptoms) in a test-retest design. The results show that the different exposure scenarios involving peak exposures did not influence either the performance to any test or subjective signs and symptoms. However, due caution must be exercised in extrapolation of the current results to occupational exposure since only acute exposures were tested and volunteers were at rest during exposure, which resulted in lower doses than those experienced by physically active workers.

Assessment of bioaccumulation and neurotoxicity in rats with portacaval anastomosis and exposed to manganese phosphate: a pilot study

The use of the additive methylcyclopentadienyl manganese tricarbonyl in unleaded gasoline has resulted in increased attention to the potential toxic effects of manganese (Mn). Hypothetically, people with chronic liver disease may be more sensitive to the adverse neurotoxic effects of Mn. In this work, bioaccumulation of Mn, as well as histopathology and neurobehavioral damage, in end-to-side portacaval anastomosis (PCA) rats exposed to Mn phosphate via inhalation was investigated. During the week before the PCA operation, 4 wk after the PCA operation, and at the end of exposure, the rats were subjected to a locomotor evaluation (day-night activities) using a computerized autotrack system. Then a group of 6 PCA rats (EXP) was exposed to 3050 microg m(-3) (Mn phosphate) for 8 h/day, 5 days/wk for 4 consecutive weeks and compared to a control group (CON), 7 PCA rats exposed to 0.03 microg m(-3). After exposure, the rats were euthanized and Mn content in tissues and organs was determined by neutron activation analysis. The manganese concentrations in blood (0.05 microg/g vs. 0.02 microg/g), lung (1.32 microg/g vs. 0.24 microg/g), cerebellum (0.85 microg/g vs. 0.64 microg/g), frontal cortex (0.87 microg/g vs. 0.61 microg/g), and globus pallidus (3.56 microg/g vs. 1.33 microg/g) were significantly higher in the exposed group compared to the control group (p <.05). No difference was observed in liver, kidney, testes, and caudate putamen between the two groups. Neuronal cell loss was assessed by neuronal cell counts. The loss of cells in globus pallidus and caudate putamen as well as in frontal cortex was significantly higher (p <.05) for the EXP group. Assessment of the locomotor activities did not reveal any significant difference. This study constitutes a first step toward our understanding of the potential adverse effects of Mn in sensitive populations.

A biologically based dynamic model for predicting the disposition of methanol and its metabolites in animals and humans

A multicompartment biologically based dynamic model was developed to describe the time evolution of methanol and its metabolites in the whole body and in accessible biological matrices of rats, monkeys, and humans following different exposure scenarios. The dynamic of intercompartment exchanges was described mathematically by a mass balance differential equation system. The model's conceptual and functional representation was the same for rats, monkeys, and humans, but relevant published data specific to the species of interest served to determine the critical parameters of the kinetics. Simulations provided a close approximation to kinetic data available in the published literature. The average pulmonary absorption fraction of methanol was estimated to be 0.60 in rats, 0.69 in monkeys, and 0.58-0.82 in human volunteers. The corresponding average elimination half-life of absorbed methanol through metabolism to formaldehyde was estimated to be 1.3, 0.7-3.2, and 1.7 h. Saturation of methanol metabolism appeared to occur at a lower exposure in rats than in monkeys and humans. Also, the main species difference in the kinetics was attributed to a metabolism rate constant of whole body formaldehyde to formate estimated to be twice as high in rats as in monkeys. Inversely, in monkeys and in humans, a larger fraction of body burden of formaldehyde is rapidly transferred to a long-term component. The latter represents the formaldehyde that (directly or after oxidation to formate) binds to various endogenous molecules or is taken up by the tetrahydrofolic-acid-dependent one-carbon pathway to become the building block of synthetic pathways. This model can be used to quantitatively relate methanol or its metabolites in biological matrices to the absorbed dose and tissue burden at any point in time in rats, monkeys, and humans for different exposures, thus reducing uncertainties in the dose-response relationship, and animal-to-human and exposure scenario comparisons. The model, adapted to kinetic data in human volunteers exposed acutely to methanol vapors, predicts that 8-h inhalation exposures ranging from 500 to 2000 ppm, without physical activities, are needed to increase concentrations of blood formate and urinary formic acid above mean background values reported by various authors (4.9-10.3 and 6.3-13 mg/liter, respectively). This leaves blood and urinary methanol concentrations as the most sensitive biomarkers of absorbed methanol.

Bioaccumulation and locomotor effect of manganese dust in rats

The primary goal of this study is to determine the effects of Mn exposure via inhalation. The bioaccumulation of Mn in different organs and tissues, the alteration of biochemical parameters, and the locomotor activity were assessed. A group of 26 male Sprague-Dawley rats (E) were exposed to 3750 microg/m(3) of Mn dust for 6 h/day, 5 days/wk for 13 consecutive weeks and compared to a control group of 12 rats (C) exposed to 4 microg/m(3). After exposure, neurological evaluation was carried out for 36 h (a night-day-night cycle) using a computerized autotrack system. Rats were then sacrificed by exsanguination, and Mn content in organs and tissues was determined by neutron activation analysis. Mn concentrations in lung, putamen, and cerebellum were significantly higher in E than in C (0.30 vs. 0.17, 0.89 vs. 0.44, 0.63 vs. 0.48 ppm; p <.01), as well as in the kidney, frontal cortex, and globus pallidus (1.15 vs. 0.96, 0.84 vs. 0.47, 1.28 vs. 0.55 ppm; p <.05). Potassium concentration was significantly lower in E than in C (5.11 vs. 5.79 mmol/L; p <.05), as was alkaline phosphatase (106.9 vs. 129.6 U/L; p <.01). Locomotor activity indicated higher distance covered in the first 12-h period for E (45 383 vs. 36 098 cm; p <.05) and lower resting time in the last 12-h period for E (36 326 vs. 37 393 s; p <.05). This study is the first of several ongoing studies in our laboratory that address health concerns associated with inhalation exposure to different Mn species and to different levels of exposure.

Bioaccumulation and locomotor effect of manganese dust in rats

The primary goal of this study is to determine the effects of Mn exposure via inhalation. The bioaccumulation of Mn in different organs and tissues, the alteration of biochemical parameters, and the locomotor activity were assessed. A group of 26 male Sprague-Dawley rats (E) were exposed to 3750 microg/m(3) of Mn dust for 6 h/day, 5 days/wk for 13 consecutive weeks and compared to a control group of 12 rats (C) exposed to 4 microg/m(3). After exposure, neurological evaluation was carried out for 36 h (a night-day-night cycle) using a computerized autotrack system. Rats were then sacrificed by exsanguination, and Mn content in organs and tissues was determined by neutron activation analysis. Mn concentrations in lung, putamen, and cerebellum were significantly higher in E than in C (0.30 vs. 0.17, 0.89 vs. 0.44, 0.63 vs. 0.48 ppm; p <.01), as well as in the kidney, frontal cortex, and globus pallidus (1.15 vs. 0.96, 0.84 vs. 0.47, 1.28 vs. 0.55 ppm; p <.05). Potassium concentration was significantly lower in E than in C (5.11 vs. 5.79 mmol/L; p <.05), as was alkaline phosphatase (106.9 vs. 129.6 U/L; p <.01). Locomotor activity indicated higher distance covered in the first 12-h period for E (45 383 vs. 36 098 cm; p <.05) and lower resting time in the last 12-h period for E (36 326 vs. 37 393 s; p <.05). This study is the first of several ongoing studies in our laboratory that address health concerns associated with inhalation exposure to different Mn species and to different levels of exposure.

A toxicokinetic model for predicting the tissue distribution and elimination of organic and inorganic mercury following exposure to methyl mercury in animals and humans. I. Development and validation of the model using experimental data in rats

The objective of this study was to develop a biologically based dynamic model for predicting the distribution and elimination of methyl mercury and its metabolite, inorganic mercury, under a variety of exposure scenarios in rats. A model is proposed based on a multicompartment approach; each compartment represents an organ or a group of organs or an excreta. The model translates into a set of coupled differential equations taking into account interorgan rates of exchanges and excretion together with the biotransformation process. The free parameters of the model are determined from statistical fits to the experimental data of the Farris et al. (Toxicol. Appl. Pharmacol. 119, 74-90, 1993) study on the time profiles of blood and tissue concentrations and cumulative excretions. The vast range of time scales that govern tissue absorption, distribution, biotransformation, and excretion served to solve the model step by step. This interplay of time scales in the rates explains the buildups and slow attrition of inorganic mercury in certain key organs such as the brain and the kidney, which are also the sites of the more important toxic effects. The model was validated on additional experimental data provided by Norseth and Clarkson (Arch. Environ. Health 21, 717-727, 1970) and Thomas et al. (Environ. Res. 41, 219-234, 1986; Environ. Res. 43, 203-216, 1987). This approach, when adapted to humans, allows the reconstruction of the time course of blood and tissue concentrations, starting from easily accessible data on hair, urine, and feces.

A toxicokinetic model for predicting the tissue distribution and elimination of organic and inorganic mercury following exposure to methyl mercury in animals and humans. II. Application and validation of the model in humans

The objective of this study was to develop a biologically based dynamical model describing the disposition kinetics of methyl mercury and its inorganic mercury metabolites in humans following different methyl mercury exposure scenarios. The model conceptual and functional representation was similar to that used for rats but relevant data on humans served to determine the critical parameters of the kinetic behavior. It was found that the metabolic rate of methyl mercury was on average 3 to 3.5 times slower in humans than in rats. Also, excretion rates of organic mercury from the whole body into feces and hair were 100 and 40 times smaller in humans, respectively, and urinary excretion of organic mercury in humans was found to be negligible. The human transfer rate of inorganic mercury from blood to hair was found to be 5 times lower than that of rats. On the other hand, retention of inorganic mercury in the kidney appeared more important in humans than in rats: the transfer rate of inorganic mercury from blood to kidney was 19 times higher than in rats and that from kidney to blood 19 times smaller. The excretion rate of inorganic mercury from the kidney to urine in humans was found to be twice that of rats. With these model parameters, simulations accurately predicted human kinetic data available in the published literature for different exposure scenarios. The model relates quantitatively mercury species in biological matrices (blood, hair, and urine) to the absorbed dose and tissue burden at any point in time. Thus, accessible measurements on these matrices allow inferences of past, present, and future burdens. This could prove to be a useful tool in assessing the health risks associated with various circumstances of methyl mercury exposure.

The toxicokinetics of pyrene and its metabolites in rats

Five experiments were conducted in male Sprague-Dawley rats regarding the kinetic of urinary excretion of 1-hydroxypyrene (1-OHP) following i.v., oral and dermal exposure to 0.5-50 micromol/kg pyrene either as a single substance or as mixture of various polycyclic aromatic hydrocarbons (PAH). Frequent urine collections over 48 h after exposure and a tissue versus time distribution experiment using [14C]pyrene allowed to define the kinetic profile of both pyrene and 1-OHP. For all exposure routes, there is a linear relationship over two orders of magnitude between the dose of pyrene and the urinary excretion of 1-OHP. Differences in biliary/urinary 1-OHP excretion ratio in canulated rats (3) versus faecal/urinary 1-OHP excretion ratio in non-canulated rats (0.6) indicate major enterohepatic recirculation of the metabolite. Half-lives of both pyrene and 1-OHP in all measured tissues were all comprised between 3.1 and 5.4 h, and 5.2-6.7 h, respectively, so that no long term accumulation would be predicted from these values for any tissue. Binary and ternary mixtures involving naphthalene and benzo(a)pyrene in addition to pyrene has no influence on the urinary excretion profile of 1-OHP. All these observations led to the proposal of a dynamic compartment model of pyrene and metabolite flows indicating that following rapid initial distribution to fatty tissues, pyrene is rapidly biotransformed into various metabolites and undergoes major enterohepatic recycling. Part of the initially formed and part of the recirculated 1-OHP eventually undergoes urinary excretion such that close to 60% of pyrene is eliminated as metabolites in urine by 24 h after injection while 20% is excreted in the faeces over the same period.

Aerobic and strength training in patients with chronic obstructive pulmonary disease

The purpose of this study was to evaluate whether strength training is a useful addition to aerobic training in patients with chronic obstructive pulmonary disease (COPD). Forty-five patients with moderate to severe COPD were randomized to 12 wk of aerobic training alone (AERO) or combined with strength training (AERO + ST). The AERO regimen consisted of three weekly 30-min exercise sessions on a calibrated ergocycle, and the ST regimen included three series of eight to 10 repetitions of four weight lifting exercises. Measurements of peripheral muscle strength, thigh muscle cross-sectional area (MCSA) by computed tomographic scanning, maximal exercise capacity, 6-min walking distance (6MWD), and quality of life with the chronic respiratory questionnaire were obtained at baseline and after training. Thirty-six patients completed the program and constituted the study group. The strength of the quadriceps femoris increased significantly in both groups (p < 0.05), but the improvement was greater in the AERO + ST group (20 +/- 12% versus 8 +/- 10% [mean +/- SD] in the AERO group, p < 0.005). The thigh MCSA and strength of the pectoralis major muscle increased in the AERO + ST group by 8 +/- 13% and 15 +/- 9%, respectively (p < 0.001), but not in the AERO group (3 +/- 6% and 2 +/- 10%, respectively, p > 0.05). These changes were significantly different in the two study groups (p < 0.01). The increase in strength of the latissimus dorsi muscle after training was modest and of similar magnitude for both groups. The changes in peak exercise work rate, 6MWD, and quality of life were comparable in the two groups. In conclusion, the addition of strength training to aerobic training in patients with COPD is associated with significantly greater increases in muscle strength and mass, but does not provide additional improvement in exercise capacity or quality of life.

A toxicokinetic model to assess the risk of azinphosmethyl exposure in humans through measures of urinary elimination of alkylphosphates

Azinphosmethyl (APM) is one of the most common insecticides used in fruit farming. The object of this paper is to develop a quick and practical test for assessing the risk for humans coming into contact with APM. It has been shown that the principal component of occupational and/or accidental exposure is through the skin (C. A. Franklin et al., 1981, J. Toxicol. Environ. Health 7, 715-731), but our approach is applicable to exposures via any route or a combination of routes. The method proposed in the present paper can accommodate a single-event exposure or repeated exposures over long periods. Urinary alkylphosphate (AP) metabolites are reliable bioindicators of the presence of APM in the body; they are easily accessible and can be used to estimate APM body burden. We developed a simple toxicokinetic model to link the time varying APM body burden to absorbed doses and to rates of elimination in the form of AP urinary metabolites. Using this model and data available in the literature, we are able to propose a "no observed adverse effect level" (NOAEL) for APM body levels and for corresponding absorbed doses. We have established that after a single exposure, the safe limit corresponding to the NOAEL is reached at a cumulative 0.215 mumoles AP/kg bw eliminated in urine in the first 24 hours following the beginning of exposure. For repeated daily exposures at steady state, the corresponding urinary AP metabolite level is equal to a cumulative 0.266 mumoles AP/kg bw eliminated per 24 hours.

Peripheral muscle weakness in patients with chronic obstructive pulmonary disease

Peripheral muscle weakness is commonly found in patients with chronic obstructive pulmonary disease (COPD) and may play a role in reducing exercise capacity. The purposes of this study were to evaluate, in patients with COPD: (1) the relationship between muscle strength and cross-sectional area (CSA), (2) the distribution of peripheral muscle weakness, and (3) the relationship between muscle strength and the severity of lung disease. Thirty-four patients with COPD and 16 normal subjects of similar age and body mass index were evaluated. Compared with normal subjects, the strength of three muscle groups (p < 0.05) and the right thigh muscle CSA, evaluated by computed tomography (83.4 +/- 16.4 versus 109.6 +/- 15.6 cm2, p < 0.0001), were reduced in COPD. The quadriceps strength/thigh muscle CSA ratio was similar for the two groups. The reduction in quadriceps strength was proportionally greater than that of the shoulder girdle muscles (p < 0.05). Similar observations were made whether or not patients had been exposed to systemic corticosteroids in the 6-mo period preceding the study, although there was a tendency for the quadriceps strength/thigh muscle CSA ratio to be lower in patients who had received corticosteroids. In COPD, quadriceps strength and muscle CSA correlated positively with the FEV1 expressed in percentage of predicted value (r = 0.55 and r = 0. 66, respectively, p < 0.0005). In summary, the strength/muscle cross-sectional area ratio was not different between the two groups, suggesting that weakness in COPD is due to muscle atrophy. In COPD, the distribution of peripheral muscle weakness and the correlation between quadriceps strength and the degree of airflow obstruction suggests that chronic inactivity and muscle deconditioning are important factors in the loss in muscle mass and strength.

Clinical, physiological and radiological features of asthma with incomplete reversibility of airflow obstruction compared with those of COPD

OBJECTIVES

To compare clinical features, pulmonary function and high-resolution computed chest tomography (HRCT) findings of asthmatic patients with a component of incomplete reversibility of airflow obstruction (AIRAO) with those of patients with smoking-induced chronic obstructive pulmonary disease (COPD).

METHODS

Thirteen patients with COPD (six males and seven females, mean age 59 years, mean smoking 50.5 pack-years) and 14 patients with AIRAO (six males and eight females, mean age 52 years) despite optimal treatment, with no significant smoking history (mean 1.5 pack-years) and no significant environmental exposure or any other respiratory disease, were studied. Patients had respiratory questionnaires, pulmonary function tests, allergy skin-prick tests and an HRCT to evaluate possible parenchymal or bronchial abnormalities. Eight patients in each group also had exercise tests. All patients were stable at the time of the study.

RESULTS

As expected, atopy was more prevalent in AIRAO (n=13) than in COPD (n=1) patients. Mean forced expiratory volume in 1 s (FEV1) and forced vital capacity (percentage of predicted value) were 39% and 61%, respectively, in COPD patients and 49% and 71%, respectively, in AIRAO patients; FEV1 improved by 18% in COPD patients and and by 22% in AIRAO patients after use of inhaled salbutamol. Mean functional residual capacity was greater in COPD patients than in AIRAO patients (178% versus 144% of the predicted value), while the mean carbon monoxide diffusing capacity of the lungs (DLCO) was lower in COPD patients than in AIRAO patients (62% versus 89% of the predicted value). Exercise tolerance was similar in both groups, as were postexercise changes in arterial oxygen pressure (PaO2). Emphysematous changes were observed in COPD patients and AIRAO patients who had evaluable HRCTs (10 versus two patients, although very mild in asthma), bronchial dilations (zero versus six patients), bronchial wall thickening (two versus eight patients) and an acinar pattern (one versus five patients). Mean thickness of the large airway wall to outer diameter (intermediary bronchus) ratio was 0.176 in COPD and 0.183 in AIRAO (P>0.05).

CONCLUSIONS

Asthma may lead to physiological features similar to COPD but may be distinguished by demonstrating a preserved DLCO and a higher ratio of airway to parenchymal abnormalities on HRCT scan.

Characteristics of bronchial asthma with incomplete reversibility of airflow obstruction

BACKGROUND

Incomplete reversibility of airflow obstruction (IRAO) can be observed in some asthmatic patients without significant smoking history nor evidence of other respiratory condition. The characteristics of this group remain however to be defined.

METHODS

We compared 18 asthmatic patients with persistent airflow obstruction, defined as an FEV1 < or = 75% predicted despite optimal corticosteroid treatment, to others with complete reversibility of airflow obstruction, paired for age and gender (CRAO, FEV1 > 80% of predicted).

RESULTS

Mean duration of asthma was 31.6 years for IRAO patients and 17.7 for the CRAO group and mean baseline FEV1 was 48.6 +/- 2.6% and 89.3 +/- 3.4%, respectively. Patients with IRAO had more severe airflow obstruction and hyperinflation than those with CRAO, while lung compliance and CO diffusion were similar. Overall healthcare use was similar in the two groups, but those with IRAO had a greater global asthma-related discomfort, increased diurnal variation of airflow obstruction and used higher doses of inhaled corticosteroids than those with CRAO. Patients with IRAO had slightly increased airway wall thickness on high resolution chest tomography compared with CRAO. Baseline FEV1 however, was not correlated with the measured airway wall thickness.

CONCLUSION

We found that asthmatic patients with IRAO have a more severe asthma and asthma of longer duration than asthmatic subjects with CRAO. Our data suggest that in asthma, IRAO may result from long-standing airway inflammation and associated structural changes, although this remains to be further documented.

Health risk assessment for inuit newborns exposed to dioxin-like compounds through breast feeding

Inuit people living in the Arctic receive an unusually high dose of dioxin-like compounds through their traditional diet, which comprises large amounts of fatty tissues from various sea mammal species. During breast feeding, the mother transfers part of their body burden to its newborn. We estimated the impact of breast feeding on the body burden of Inuit from birth to age 75 years. Simulations performed with a toxicokinetic model revealed that breast feeding strongly influences body burden during childhood but not after age 20 years. Liver and adipose tissue concentrations expected in Inuit are well below those which induced severe adverse health effects in laboratory animals, e.g. cancer and reproduction. However, these concentrations approach levels generating subtle effects on reproductive systems.

Weighing contaminant risks and nutrient benefits of country food in Nunavik

In view of the levels of human exposure to priority contaminants assessed in previous surveys in Nunavik, a series of risk reduction scenarios were produced to modelize the effects of different potential health advisories on limiting exposure of women of reproductive age to these contaminants, as well as on maximizing nutritional benefits derived from the consumption of country food. This paper presents part of the results, in particular as regards effects of reducing PCB intake by 46%, 65% and 86%.

Effects of mouth opening on upper airway collapsibility in normal sleeping subjects

We investigated the influence of mouth opening on upper airway (UA) collapsibility in six healthy sleeping volunteers. UA collapsibility was measured during continuous negative airway pressure trials that consisted of the progressive decrease in pressure in a nasal mask, with simultaneous recording of esophageal pressure and instantaneous flow. Measurements were made under two experimental conditions: mouth closed (MC), and mouth open (MO). Cephalometric measurements were obtained with subjects awake in the same position for both experimental conditions. UA critical pressure (Pcrit) was derived from the relationship between the breath-by-breath values of the maximal inspiratory airflow and the corresponding mask pressure. Pcrit was significantly less negative during MO than during MC (MO, -12.7 +/- 4.8 cm H2O; MC, -16.4 +/- 6 cm H2O, mean +/- SD; p = 0.03). Mouth opening was associated with a significant increase in the total respiratory resistance (MO, 3.8 +/- 1.6 cm H2O/ml/s; MC, 3.0 +/- 1.6 cm H2O/ml/s-1, p = 0.03). Besides an increase in the distance between the teeth and a reduction in the distance between the hyoid bone and the mandible, no significant changes in cephalometric parameters were found between MO and MC. We conclude that mouth opening increases UA collapsibility during sleep and that mouth opening may contribute to the occurrence of sleep-related breathing abnormalities.

Airway responsiveness and bronchial-wall thickness in asthma with or without fixed airflow obstruction

To determine whether asthmatic subjects have an increase in airway wall thickness that could enhance airway narrowing during bronchoprovocation, we examined the relationship between airway responsiveness and bronchial wall thickness measured by high-resolution computed tomography (HRCT). We studied 24 nonsmokers with asthma, of whom 13 had a fixed component of airflow obstruction (Group 1) and 11 had an optimal FEV1 of 80% or more of the predicted value (Group 2). These subjects were compared with a control group of 10 nonasthmatic subjects (Group 3). Measurements were taken of each subject's expiratory flows, bronchodilator response, lung volumes, and methacholine responsiveness. All subjects used an inhaled beta 2-agonist on demand, and 19 also used inhaled steroids (13 in a Group 1 and six in Group 2). HRCT sections were obtained at the top and base of the lung and at the level of the intermediary bronchus (IB), although only this last level was found adequate for analysis. The ratio of IB wall thickness to outer diameter (T/D) showed a negative relationship with the outer diameter in Group 1 only. The mean T/D ratio of IB was not significantly different in Groups 1, 2, and 3, with respective values of 0.16 +/- 0.01, 0.15 +/- 0.01, and 0.18 +/- 0.01 at TLC, and 0.16 +/- 0.01, 0.20 +/- 0.01, and 0.19 +/- 0.01 at FRC. In subjects with a fixed component of airflow obstruction, the thicker the airway wall in relation to its diameter, the lower was the PC20 for methacholine. This was not observed in the other study groups. No correlation was found between the T/D ratio and baseline FEV1.(ABSTRACT TRUNCATED AT 250 WORDS)

Increased maximal airway response to methacholine during seasonal allergic rhinitis in nonasthmatic subjects: relationships with airway wall thickness and inflammation

This study was carried out to determine whether the increase in airway responsiveness induced by natural antigenic exposure in nonasthmatic subjects is associated with an increase in maximal bronchoconstrictor response (MBR), and if these changes could be due to an increase in airway wall thickness from allergen-induced increase in airway inflammation. In 11 nonasthmatic subjects with seasonal allergic rhinitis, a methacholine challenge was obtained monthly, during and out of pollen exposure. Each subject had a high-resolution chest tomography in and out of the pollen season, to determine the relative thickness of the right intermediary bronchus over its total diameter (T/D), as well as inflammatory cell counts, apparent basement membrane thickness as an indication of subepithelial fibrosis and epithelial desquamation in bronchial biopsy specimens. In season, the mean provocative concentration of methacholine producing a 20% decrease in forced expiratory volume in one second (PC20) decreased from 51.5 to 25.8 mg.mL-1, and the maximal post-methacholine fall in forced expiratory volume in one second (delta FEV1,max) or forced vital capacity (delta FVC) and the slope of the dose response curve (DRS) increased compared with out of season: delta FEV1,max 44 +/- 5 vs 25 +/- 5%; delta FVC 34 +/- 5 vs 16 +/- 4%; and slope of DRS 14.1 +/- 2.8 vs 6.9 +/- 1.3%/mg.mL-1. No significant change was observed in T/D ratio. The seasonal change in delta FVC was positively correlated with the delta FEV1,max (rs = 0.891) and the change in DRS (rs = 0.909), but not with the change in PC20, nor with changes in bronchial biopsy inflammatory features or T/D ratio.(ABSTRACT TRUNCATED AT 250 WORDS)

Increased maximal airway response to methacholine during seasonal allergic rhinitis in nonasthmatic subjects: relationships with airway wall thickness and inflammation

This study was carried out to determine whether the increase in airway responsiveness induced by natural antigenic exposure in nonasthmatic subjects is associated with an increase in maximal bronchoconstrictor response (MBR), and if these changes could be due to an increase in airway wall thickness from allergen-induced increase in airway inflammation. In 11 nonasthmatic subjects with seasonal allergic rhinitis, a methacholine challenge was obtained monthly, during and out of pollen exposure. Each subject had a high-resolution chest tomography in and out of the pollen season, to determine the relative thickness of the right intermediary bronchus over its total diameter (T/D), as well as inflammatory cell counts, apparent basement membrane thickness as an indication of subepithelial fibrosis and epithelial desquamation in bronchial biopsy specimens. In season, the mean provocative concentration of methacholine producing a 20% decrease in forced expiratory volume in one second (PC20) decreased from 51.5 to 25.8 mg.mL-1, and the maximal post-methacholine fall in forced expiratory volume in one second (delta FEV1,max) or forced vital capacity (delta FVC) and the slope of the dose response curve (DRS) increased compared with out of season: delta FEV1,max 44 +/- 5 vs 25 +/- 5%; delta FVC 34 +/- 5 vs 16 +/- 4%; and slope of DRS 14.1 +/- 2.8 vs 6.9 +/- 1.3%/mg.mL-1. No significant change was observed in T/D ratio. The seasonal change in delta FVC was positively correlated with the delta FEV1,max (rs = 0.891) and the change in DRS (rs = 0.909), but not with the change in PC20, nor with changes in bronchial biopsy inflammatory features or T/D ratio.(ABSTRACT TRUNCATED AT 250 WORDS)

Modeling of the toxicokinetics of polychlorinated dibenzo-p-dioxins and dibenzofurans in mammalians, including humans. II. Kinetics of absorption and disposition of PCDDs/PCDFs

In the present study, a physiologically based model which describes the absorption and disposition kinetics of PCDDs/PCDFs (globally called PCDXs) in mammalian species, including humans, is developed. The model integrates the distribution model developed in the first article of this series, which described the fractional distribution of total PCDXs between liver and adipose tissues as a function of overall body concentration (G. Carrier, R. C. Brunet, and J. Brodeur, 1995, Toxicol. Appl. Pharmacol. 131, 253-266). In particular it is shown that the liver fraction of the total body burden decreases as overall body concentration decreases. Since elimination is principally through the liver, this leads to lower global elimination rates and longer half-lives of PCDXs. Absorption and disposition kinetics of PCDXs are captured using nonlinear differential equations with anatomically and biochemically relevant input parameters which are readily available. These are solved to predict the fate of PCDXs in liver, adipose tissues, and the body as a whole, as a function of time. Model simulations are in agreement with published data on absorption and disposition kinetics of these substances in rats and in humans. The kinetic profiles are similar for rats and humans, but the varying half-lives differ considerably in both species: weeks with rats, years with humans. For a given body burden, the adipose tissue concentrations vary in an inversely proportional manner to the mass of the adipose tissues; this observation has considerable relevance for interpretation of clinical data for humans. The interest of the proposed model rests upon the fact that it is generalized and broadly applicable: it allows the study of the kinetics of PCDXs for any pattern of exposure from background to highly toxic levels, taking into account variations in time of anatomical and biochemical parameters.

Modeling of the toxicokinetics of polychlorinated dibenzo-p-dioxins and dibenzofurans in mammalians, including humans. I. Nonlinear distribution of PCDD/PCDF body burden between liver and adipose tissues

Mixtures of polychlorinated dibenzo-p-dioxins and dibenzofurans, globally called PCDXs, are ubiquitously present in the environment. They accumulate in the human organism, especially through uptake from food. In view of their long residence time in the body and their potential adverse health effects for humans, it is therefore important to develop toxicokinetic models capable of predicting their distribution in human tissues. In the present study a physiologically based model which describes the distribution kinetics of PCDXs in various mammalian species is proposed. The approach is both theoretical and empirical. First, a plausible and general dynamical model that takes into account intercellular diffusion, PCDX-receptor and PCDX-protein binding, and PCDX-dependent enzyme induction in the liver is developed. Simplified formulas are proposed to predict the functional dependencies fh(Cb) and f(at)(Cb), which establish the fractions of the total PCDX body burden contained in liver and adipose tissues as a function of overall body concentration at any one moment. These formulas have fewer free parameters that can be determined for various species with the use of already available data. Model simulations are in agreement with published data on the distribution kinetics of PCDXs in rodents and monkeys and clinical data in humans. In rodents and monkeys as well as in humans, the respective relations fh(Cb) and f(at)(Cb) follow a similar nonlinear pattern. These varying distribution functions constitute the basis for a generalized toxicokinetic model of absorption and disposition described in a companion article (G. Carrier, R. C. Brunet, and J. Brodeur, 1995, Toxicol. Appl. Pharmacol. 131, 267-276).

Urinary excretion kinetics of 1-hydroxypyrene in volunteers exposed to pyrene by the oral and dermal route

Two well-informed human volunteers were exposed to 500 micrograms pyrene by ingestion and by dermal application, in two separate experiments. Urinary measurements of 1-hydroxypyrene (1-OHP) were performed on all micturitions taken at intervals of 0.5-4 h for a total period of 48 h after dosing. Following the absorption phase, 1-OHP is excreted with a first order apparent half-life of approximately 12 h for both volunteers and both exposure routes. These results compare well with other previously published studies. A more refined analysis of the data was performed using a two-compartment toxicokinetic model for 'pyrene' (its fraction eventually excreted as 1-OHP). As it was found that a classical first-order system did not adequately fit the data, a non-linear term was introduced in the model for the elimination of urinary 1-OHP. Computer iteration performed on the oral absorption data allowed an estimation of various toxicokinetic parameter values. The mean intercompartmental exchange (k12 and k21) and elimination coefficients were 0.010, 0.006 and 0.012 min-1, respectively. The first two values compare well with those previously published for the rat, whereas the latter is smaller in humans. These values were used to satisfactorily simulate the experimental data for both routes of exposure, adjusting only for kabs which was estimated at 0.014 and 0.0029 min-1 for the oral and dermal exposure, respectively. The proposed model generates new hypotheses on the metabolism of pyrene. The information collected will contribute to the validation of the utilisation of 1-OHP as a biological indicator of exposure to pyrene.

Interobserver variation in the computed tomographic evaluation of mediastinal lymph node size in patients with potentially resectable lung cancer. Canadian Lung Oncology Group

OBJECTIVE

To measure the reliability of the assessment of mediastinal lymph node size in computed tomographic (CT) scans of the thorax.

DESIGN

Observer agreement study in which radiologists, blinded to one anothers' interpretation, were randomized to read 30 scans each.

POPULATION

Sixty scans from patients with apparently operable non-small cell carcinoma of the lung were read by radiologists responsible for clinical interpretation (clinical radiologists) and four radiologists with a special interest in thoracic CT (study radiologists).

MEASUREMENTS

Radiologists measured the size of left and right superior mediastinal nodes, aortic nodes, and the subcarinal nodes and, on the basis of whether any nodes accessible to mediastinoscopy were greater than 1 cm, recommended whether mediastinoscopy be undertaken. Agreement was quantified using kappa, a measure of chance-corrected agreement.

RESULTS

Among all radiologists, agreement on whether there were any nodes larger than 1 cm for right superior mediastinal nodes was 0.68; for left superior mediastinal nodes it was 0.28; for aortic pulmonary nodes it was 0.62; for subcarinal nodes it was 0.58; and for any node greater than 1 cm and accessible to mediastinoscopy it was 0.61. The agreement was very similar when the analysis was restricted to the study radiologists.

CONCLUSION

Although the good level of overall agreement suggests that CT provides useful information in the evaluation of mediastinal lymph node size, the disagreement was sufficient that it likely contributes to suboptimal sensitivity and specificity of CT in detecting tumor spread reported in previous studies.

Kinetics of hemoglobin and albumin adducts in rabbits subchronically exposed to benzo[a]pyrene

Benzo[a]pyrene (BaP) can form adducts with proteins after activation to a diolepoxide. Benzo[a]pyrene-hemoglobin and BaP-albumin adducts were measured in rabbits exposed to 0.5 or 5 mumol.kg-1.week-1 for a total of 11 weeks (last injection on Day 75). Each dose group of nine rabbits was divided into three equal subgroups. For each dose, one subgroup received a single weekly injection (Mondays), the second had two equal weekly injections (Mondays and Thursdays), and the third had five weekly injections (Mondays through Fridays). Blood was collected prior to injection on Days 0, 7, 14, 21, 28, 35, 42, 49, 56, 77, 78, 80, 84, 92, 108, and 140 for adducts determinations, with Day 0 being a Monday. The measured concentration of hemoglobin adducts was independent of the frequency of administration for a given total weekly dose giving support to its value as a "biointegrator." In addition, animals injected with 0.5 and 5 mumol BaP.kg-1.week-1 had respective mean adduct concentrations of 0.3 and 3 pmol/g hemoglobin. The blood concentration of albumin adducts was related to the frequency of injection with the animals receiving one, two and five injections/week having the lowest, intermediate, and highest adduct concentrations, respectively. Animals injected with 0.5 and 5 mumol BaP.kg-1.week-1 had respective mean adduct concentrations of 5 and 20 pmol/g which are 17 and 7 times higher than their corresponding hemoglobin adducts' values. The corresponding albumin adducts' half-lives calculated from the day of cessation of exposure were 5.8 and 9.6 days, compared with a reported 5.7 days for the half-life of the intact protein.(ABSTRACT TRUNCATED AT 250 WORDS)

Exposure of remote maritime populations to coplanar PCBs

Two remote maritime populations were evaluated for their biological exposure to organochlorines in 1989-1990. Because of their high intake of seafood, these two populations have high biological levels. One hundred nine breast milk samples from Inuit women from Arctic Québec were analyzed to determine levels of polychlorodibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs), and coplanar polychlorinated biphenyls (PCBs) including non-ortho, mono-ortho, and di-ortho congeners. Total 2,3,7,8-tetrachlorodibenzo-p-dioxin equivalents (TEqs) for PCBs were 3.5 times higher in Inuit milk samples than in 96 Caucasian milk samples. Among the 185 fishermen from the Lower North Shore of the Gulf of the St. Lawrence River, we evaluated 10 highly exposed fishermen for their coplanar PCB blood levels. Total TEqs were 900 ng/kg for highly exposed individuals with 36 ng/kg for controls. In these two nonoccupationally exposed populations, coplanar PCBs make a larger contribution to the TEq than PCDDs and PCDFs. However, the mono-ortho penta CB No. 118 is the major contributor for the total toxicity.

Farmer's lung. Long-term outcome and lack of predictive value of bronchoalveolar lavage fibrosing factors

This study evaluates the long-term outcome of farmer's lung (FL), adding high-resolution computed tomograms (HRCT) to previously reported procedures and verifying whether bronchoalveolar lavage (BAL) fluid markers or substrates of fibrosis (hyaluronic acid, Type III procollagen, fibronectin, and fibroblast growth factors) (FF) predict outcome. A total of 33 subjects with a history of FL dating back at least 6 yr were evaluated with pulmonary function tests, chest x-ray (CXR), and HRCT. All subjects had an initial evaluation, which included a BAL, 6 yr before the current study. Subjects were then either in acute FL (n = 19) or in clinical remission despite continued contact (n = 14). In the current study, pulmonary function tests revealed an obstructive profile in 13 subjects, restrictive changes in 1, an isolated decrease in lung diffusion capacity in 3, and normal values in 16. Chest radiographs (CXR) were normal in 22 subjects, abnormal with interstitial or reticulonodular changes in 6, and suggestive of emphysema in 5. HRCT revealed emphysema in 9 subjects; 3 had localized fibrotic changes, 2 a ground-glass pattern, and 19 were normal. There was a good correlation between the findings on pulmonary function tests and HRCT; however, CXR alone did not suggest the existence of emphysema in 4 subjects who had such findings on HRCT. No correlations were found between most outcome parameters and the level of the BAL FF measured 6 yr previously. We conclude that airflow obstruction with or without emphysema is an important long-term sequela of FL and that BAL FF do not predict outcome in this disease.

Surgical correction of nasal obstruction in the treatment of mild sleep apnoea: importance of cephalometry in predicting outcome

BACKGROUND

A study was undertaken to determine if cephalometric radiographs could identify those who will benefit from nasal surgery in patients with a sleep apnoea hypopnoea syndrome (SAHS) and chronic nasal obstruction.

METHODS

Fourteen patients with SAHS were enrolled. Those with normal posterior airway space and mandibular plane to hyoid bone distances on preoperative cephalometric radiographs were matched with those with abnormal cephalometry for the frequency of sleep disordered breathing and body mass index. Polysomnographic studies (all subjects) and nasal resistance measurements (n = 10) were performed one to three months before and two to three months after surgery (septoplasty, turbinectomy, and polypectomy).

RESULTS

There was no difference in the baseline results of the polysomnographic studies between the two groups of patients. Nasal resistance decreased from a mean (SE) value of 2.9 (0.3) cm H2O/l/s before surgery to 1.4 (0.1) cm H2O/l/s after surgery in the normal cephalometry group and from 2.7 (0.3) cm H2O/l/s to 1.3 (0.3) cm H2O/l/s in the other group. The apnoea + hypopnoea index returned to normal (< 10 breathing abnormalities/hour) in all but one subject with normal cephalometric measurements, and sleep fragmentation improved with a decrease in the arousal index from 23.9 (3.3)/hour at baseline to 10.6 (2.5)/hour after surgery. Both of these parameters remained unchanged after surgery in the patients with abnormal cephalometry.

CONCLUSIONS

Normal cephalometry is helpful in identifying patients with mild SAHS and nasal obstruction who will benefit from nasal surgery. The presence of craniomandibular abnormalities makes it unlikely that nasal surgery will improve sleep related breathing abnormalities.

Effects of surgical correction of nasal obstruction in the treatment of obstructive sleep apnea

Negative upper airway pressure is thought to play a key role in the pathophysiology of obstructive sleep apnea. Because nasal resistance contributes to the increase of the transpharyngeal pressure gradient, we evaluated the effects of nasal surgery on sleep-related breathing abnormalities in 20 adults with obstructive sleep apnea. Polysomnographic studies were done before (baseline), and 2 to 3 mo after surgery (septoplasty, turbinectomy, and/or polypectomy). Nasal resistances were measured at these visits in 14 patients. Cephalometric measurements were obtained before surgery. Cephalometric abnormalities consisted in an increase in the distance from the mandibular plane to the hyoid bone (MP-H), a decrease in the space between the base of the tongue and the posterior soft tissues (PAS), a retroposition of the mandibule, and an increase in the length of the soft palate. Body weight did not change between the two studies. Nasal resistance decreased significantly after nasal surgery. The composition of the total sleep time spent in the rapid eye movement stage increased from 11.5 +/- 1.3% (mean +/- SEM) to 14 +/- 1.2% after surgery. For the group as the whole, there was no difference between baseline and postsurgical values in the frequency of respiratory disturbances (39.8 +/- 6.1, 36.8 +/- 5.9 n/h), the total apnea time (17.8 +/- 4.2, 15.4 +/- 2.8), the distribution of the apnea time within the different apnea types (obstructive and nonobstructive), and the severity of the nocturnal desaturations. Interestingly, apnea and apnea plus hypopnea indices returned to normal values (< 5 and 10, respectively) in four subjects with normal posterior soft tissues and mandibular plane to the hyoid bone distances.(ABSTRACT TRUNCATED AT 250 WORDS)

Cephalometric measurements in snorers, non-snorers, and patients with sleep apnoea

Cephalometry is often used to assess patients with sleep apnoea but whether these measurements differ from those in non-apnoeic snorers and how they are influenced by age is not clear. Cephalometric radiographs of patients with sleep apnoea were compared with those of snorers without sleep apnoea and those of non-snorers. Fifty two snorers with suspected sleep apnoea had a conventional sleep study and were divided into two groups: those with an apnoea-hypopnoea index greater than 10/h (n = 40, sleep apnoea group) and those whose apnoea-hypopnoea index was 10/h or less (n = 12, snorer group). The cephalometric measurements in these patients were compared with those of 34 non-snoring control subjects. Controls were subdivided into two groups: control group 1 included 17 subjects similar in age to the sleep apnoea and snorer groups (mean (SD) age 50.0 (10.9), 50.7 (9.4), and 50.6 (9.7) years); control group 2 included 15 young men (25.4 (2.6) years). The distance from the mandibular plane to the hyoid bone (MP-H) and the length of the soft palate were greater in the patients with sleep apnoea (28.7 (7.8) and 43.6 (5.0) mm) than in the snorers (23.7 (4.2) and 40.3 (4.9 mm). The MP-H was similar in snorers and age matched control subjects, but was significantly greater in the older than in the younger control subjects (22.1 (6.1) vs 17.0 (6.8]. The soft palate was longer in subjects who snored (both sleep apnoea patients and snorers) than in control subjects. The MP-H distance significantly correlated with age for all subjects (snorers and controls) and for the control subjects alone. This study shows that non-apnoeic snorers have cephalometric abnormalities that differ from those of patients with sleep apnoea and that cephalometric values are influenced by the subject's age.

Fibrovascular polyp of the esophagus with computed tomographic and pathological correlation

The authors report a patient with a fibrovascular polyp of the esophagus. Radiologic and pathological features of this rare tumor include computed tomographic findings of a lesion of low density, situated intraluminally so that the findings may be relatively specific.