[Improvement of the impulsive control in adolescents with attention deficit hyperactivity disorder (ADHD) after a cognitive behavioral therapy]. / Amélioration du contrôle impulsif chez les adolescents avec un trouble de l'attention avec hyperactivité (TDAH) ayant suivi une thérapie cognitive comportementale.

AIM: MPH is the more often prescribed stimulant for Attention Deficit Hyperactivity Disorder (ADHD), but it has been estimated that 30% of patients do not adequately respond or cannot tolerate it. Therefore, some other therapies are needed, such as cognitive behavioral therapy. Cognitive behavioral therapy is an intervention proposed over several sessions and aimed at modifying behavior by teaching different techniques that participants can re-use to control their symptoms. In our Institute, we used a program centered on attentional and metacognitive functions. It consists of a series of workshops performed in group at the rate of one workshop of 90minutes per week for 12 weeks. Positive effects on the behavior of adolescents with ADHD have been reported by parents and educators, but the effects of the program on specific cognitive processes have never been precisely investigated. METHOD: In the present study, we evaluated the impact of the program on impulsive control in adolescents with ADHD who are known to present impaired impulsive control. Impulsive control is required each time there is a conflict between an inappropriate prepotent action and a goal-directed action. At an experimental level, impulsive control can be studied with conflict tasks, such as the Simon reaction time task. Interpreted within the theoretical framework of the so-called « Dual-process activation suppression ¼ (DPAS) model, this task is a powerful conceptual and experimental tool to separately investigate the activation and inhibition of impulsive actions, which is almost never done in studies about impulsive control. Twenty adolescents followed the program and were tested before and at the end of the program by using dynamic analyses of performance associated with DPAS model. RESULTS: The results have shown an improvement of the impulsive control after three months of cognitive behavioral therapy, and this improvement was due to both a decrease of the propensity to trigger impulsive actions and an improvement of inhibitory processes efficiency. CONCLUSION: This program could be a relevant alternative to the stimulant medication, more particularly when parents are reluctant with medication or when the adolescent suffers from important side effects.

[An unexpected discovery of laryngeal neurofibroma during intubation for elective surgery]. / Le cas clinique du mois. Découverte fortuite d'un neurofibrome laryngé lors d'une intubation chez une patiente atteinte de neurofibromatose de type 1.

We report the unexpected discovery of a large laryngeal neurofibroma during a direct laryngoscopy for intubation in a 18-year old female with a medical history of neurofibromatosis type 1. The most striking feature of this case report is the discrepancy between the absence of clinical manifestations and the size and location of the neurofibroma. This case highlights the importance of a careful preoperative assessment, especially in the context of multisystemic disease. Knowledge of the disease, recognition of related complications and adequate preoperative evaluation are crucial to establish the safest anesthesia strategy.

Nous rapportons la découverte fortuite d'un volumineux neurofibrome laryngé lors de la laryngoscopie précédant une intubation endotrachéale chez une patiente de 18 ans atteinte d'une neurofibromatose de type 1, par ailleurs asymptomatique. Ce cas est remarquable par l'absence de toute manifestation clinique rapportée par la patiente malgré le volumineux neurofibrome présent dans le larynx. Il souligne l'importance d'une mise au point préopératoire approfondie, particulièrement dans le cas de maladies multisystémiques. Une bonne connaissance de cette maladie et de ses complications est indispensable pour réaliser un bilan préopératoire adéquat et déterminer la stratégie d'anesthésie la plus adaptée à ces patients.

Palliative surgery for foot drop.

Dysfunction of the common peroneal nerve is the most common mononeuropathy in the lower limb and a source of significant disability for patients. The nerve can be damaged at various levels for various reasons (direct or indirect trauma, extrinsic compression, anatomical variant, endocrine, rheumatological, or neurological disease). Clinical evidence of foot drop with steppage gait is very typical. Conservative treatment should be considered as a first step (avoidance of the contributing factors, functional rehabilitation, foot drop brace ± injection). If properly conducted conservative treatment is not successful, palliative surgery is indicated: either tendon transfer using the posterior tibial tendon or ankle arthrodesis.

Lead-vanadate sorbents for iodine trapping and their conversion into an iodoapatite-based conditioning matrix.

New lead-vanadate based sorbents were synthesized with the aim to entrap and confine gaseous iodine in off-gas streams coming from reprocessing facilities of spent nuclear fuel. Their synthesis relies on the shaping of a lead-vanadate, lead sulfide and alginic acid mix as millimetric beads. These beads were calcined between 220°C and 500°C to remove organic alginic compounds template. However, according to the calcination temperature, lead sulfide could be partially oxidized, limiting iodine loading capacity. A compromise temperature between 290°C and 350°C was found to remove most of the alginic acid template and avoiding lead sulfide oxidation. These sorbents were tested for iodine trapping in static conditions at 60°C. They performed well with a sorption capacity up to 155 mg.g-1 by forming PbI2. Furthermore, these iodine-loaded sorbents could be easily converted into an iodine-containing lead-vanadate apatite matrix by spark plasma sintering. A dense sample was produced for a sintering temperature of 500°C under 70 MPa. Such a material could be suitable for radioactive iodine conditioning in deep geological disposal. Finally, lead-vanadate sorbents could provide an easy way to entrap and confine radioactive iodine from off-gas streams into a durable material within a few steps.

Emotional prosody recognition enhances and progressively complexifies from childhood to adolescence.

Emotional prosody results from the dynamic variation of language's acoustic non-verbal aspects that allow people to convey and recognize emotions. The goal of this paper is to understand how this recognition develops from childhood to adolescence. We also aim to investigate how the ability to perceive multiple emotions in the voice matures over time. We tested 133 children and adolescents, aged between 6 and 17 years old, exposed to 4 kinds of linguistically meaningless emotional (anger, fear, happiness, and sadness) and neutral stimuli. Participants were asked to judge the type and intensity of perceived emotion on continuous scales, without a forced choice task. As predicted, a general linear mixed model analysis revealed a significant interaction effect between age and emotion. The ability to recognize emotions significantly increased with age for both emotional and neutral vocalizations. Girls recognized anger better than boys, who instead confused fear with neutral prosody more than girls. Across all ages, only marginally significant differences were found between anger, happiness, and neutral compared to sadness, which was more difficult to recognize. Finally, as age increased, participants were significantly more likely to attribute multiple emotions to emotional prosody, showing that the representation of emotional content becomes increasingly complex. The ability to identify basic emotions in prosody from linguistically meaningless stimuli develops from childhood to adolescence. Interestingly, this maturation was not only evidenced in the accuracy of emotion detection, but also in a complexification of emotion attribution in prosody.

Scapula alata: Diagnosis and treatment by nerve surgery and tendon transfers.

Scapula alata, also known as winged scapula, can lead to severe upper limb impairment. The shoulders' function is altered because the scapula, which supports the upper limb, is no longer stable. Typical scapula alata is described for serratus anterior palsy; however, any scapulothoracic muscle impairment may lead to scapular winging, particularly trapezius palsy, which is easy to miss, thus needed to be considered as a differential diagnosis. The diagnosis is difficult and based on various clinical tests and a thorough examination as well as electroneuromyography and MRI. The treatment ranges from conservative treatments for spontaneous recovery, nerve surgery including neurolysis, nerve transfers and nerve grafts for acute cases, to tendon transfers for more chronic cases and when nerve procedures are no longer feasible. Tendon transfers in serratus anterior palsy produce excellent results with a high rate of patient satisfaction and are described with the sternal or clavicular head of the pectoralis major; we describe our preferred technique in this article. Tendon transfers in trapezius palsy are performed with the levator scapulae, rhomboid minor and major muscles. Our preferred method is the Elhassan triple transfer. Scapula alata is a frequent and often misdiagnosed condition. Appropriate management can yield excellent results. Patients should be referred right away to specialized centers for surgery if recovery is not spontaneous.

Postoperative motor deficits following elbow flexion reanimation by nerve transfer.

We aimed to assess the rate and type of postoperative motor deficits that might be encountered following elbow flexion reanimation using ulnar- and/or median-based side-to-end nerve transfers in patients with brachial plexus injuries. All patients who underwent elbow flexion reanimation between November 2015 and October 2017 at our facility by nerve transfer based on partial harvests of the median and/or ulnar nerves were included. Postoperative clinical assessment was conducted the day after surgery to identify motor deficits in the territory of the harvested nerves. If a clinically noticeable deficit was present, the type and extent of the deficit were noted, and postoperative clinical evaluations were conducted monthly to determine its progression. After reviewing the charts of 27 consecutive patients, 4 patients were found to have a postoperative motor deficit (15%). In all four cases, the deficit was limited to the anterior interosseous nerve (AIN) territory in patients who underwent a double transfer (i.e., ulnar-to-biceps and median-to-brachialis). With clinical impairments of the flexor pollicis longus and/or the flexor digitorum profundus of the index and third fingers initially ranging from grade-0 to grade-3 strength, full recovery to preoperative strength levels occurred in all cases after a mean of 7 months' follow-up. Transient motor deficits may be observed in the AIN territory following elbow flexion reanimation when a median-to-brachialis nerve transfer is associated with the original Oberlin procedure.

alpha-Melanocyte-stimulating hormone binding and biological activity in a human melanoma cell line.

Synthetic alpha-melanocyte-stimulating hormone (alpha-MSH) was found to bind to the plasma membrane of the HM6A human melanoma cell line, using an immunocytochemical method. When treated with 10(-7) to 10(-9) M alpha-MSH, melanoma cells exhibited an increase of intracellular cyclic adenosine 3':5'-monophosphate, followed by stimulation of tyrosinase activity. Significant inhibition of DNA synthesis measured by [3H]thymidine uptake and inhibition of cell growth was found. A retrovirus expression was detected in the supernatant of HM6A cells as assayed by the KC cell syncytium-forming test. In he presence of 10(-7) M alpha-MSH, the number of syncytium-forming units was increased 15-fold. These results demonstrate that alpha-MSH modulates human melanoma differentiation and virus expression in vitro.

Distally based sural flap for ankle and foot coverage in children.

BACKGROUND: Coverage of soft-tissue defects of the ankle and foot is often challenging. The distally based sural fascio-cutaneous flap is useful for reconstructing the lower leg, ankle, heel, and foot but has rarely been evaluated in paediatric patients. The objectives of this study were to assess the reliability of this flap in paediatric patients, to describe the complications associated with its use, and to define its indications in paediatric patients with soft-tissue defects of the ankle and foot. HYPOTHESIS: We hypothesised that the sural flap was reliable for covering soft-tissue defects at the ankle and foot in paediatric patients. MATERIAL AND METHODS: A distally based sural fascio-cutaneous flap was used to cover soft-tissue defects of the ankle and foot in 20 paediatric patients between 1997 and 2013. The evaluation at last follow-up included a physical examination and determination of the modified functional Kitaoka score. Mean follow-up was 50.6 months (range, 10-192 months) and mean patient age at surgery was 8.8 years (range, 1.5-17 years). Trauma was the most common cause of soft-tissue defect (n=12); other causes were surgical-site infections (n=2), tumours (n=3), chronic ulcer (n=1), burn injury (n=1), and infusion fluid extravasation (n=1). RESULTS: Of the 20 flaps, 16 (80%) remained fully viable, whereas 4 developed partial necrosis requiring excision and skin grafting, which consistently ensured a good outcome. Other complications consisted of marginal necrosis (n=4), unsightly donor-site scars (n=5), and infection (n=2). Abnormal flap sensation was noted in 11 patients. The mean modified Kitaoka score was 65/80 (range, 0-80), and the score value indicated that function was excellent in 9 (45%) patients, good in 9 (45%) patients, and poor in 2 (10%) patients. DISCUSSION: The distally based sural fascio-cutaneous flap is a method of choice for covering soft-tissue defects of the ankle and foot in paediatric patients. This reliable flap spares the major blood vessels and has a strong blood supply. Its best indication is coverage of an acute traumatic soft-tissue defect with exposure of a vital structure. In patients requiring late reconstruction, caution is in order when considering the use of a distally based sural fascio-cutaneous flap, which can induce delayed complications, most notably at the donor site. LEVEL OF EVIDENCE: IV, retrospective case-series study.

N-nitrosoproline excretion by rural Nebraskans drinking water of varied nitrate content.

The N-nitrosoproline (NPRO) test for in vivo nitrosation was applied in a study of 44 rural Nebraska men drinking high- or low-nitrate water from private wells. The subjects followed diets low in NPRO and nitrate for 5 days. On days 4 and 5 they avoided ascorbate-rich foods. Urine was collected for 24 h on day 4 while the subjects followed normal activities and on day 5 after an overnight fast and taking 500 mg L-proline. We determined NPRO, nitrate, creatinine, and specific gravity in the urines, and nitrite and nitrate in single saliva specimens collected on days 4 and 5. Results for all variables were separated into those above and below the median values and were analyzed by univariate and multivariate consideration of the contingency tables. Nitrate concentration in drinking water (> or = or < 10 ppm nitrate-nitrogen) was significantly associated with both day 4 and day 5 NPRO (> or = or < 1.5 micrograms/day; P < 0.04); and with urine nitrate (> or = or < 1.5 mmol/day), saliva nitrite (> or = or < 5 mg/liter), and saliva nitrate (> or = or < 25 mg/liter) (P < or = 0.002). Urine nitrate was significantly (P < or = 0.03) associated with both day 4 and day 5 NPRO, with odds ratios of 4.2 and 5.4, respectively. Creatinine was positively associated with NPRO on day 4 (P = 0.04). These findings, like those of a recent study in Denmark, showed an association between nitrate intake in water and NPRO formation. Their significance for people drinking high-nitrate water remains to be determined.

The effect of garlic extract on human metabolism of acetaminophen.

Several studies suggest that the constituents of garlic may inhibit experimentally induced carcinogenesis. To evaluate the chemopreventive properties of garlic in humans, the effects of chronic administration of an aged garlic extract on the disposition of acetaminophen and metabolites were studied. This commonly used drug was chosen because it forms a reactive electrophilic metabolite after oxidative metabolism. Sixteen subjects ingested daily doses of garlic extract (approximately equivalent to six to seven cloves of garlic) for 3 months. Before the course of garlic, at the end of each month and 1 month after termination of garlic administration, a 1-g oral dose of acetaminophen was given to each subject. Plasma and urine were measured for acetaminophen and the glucuronide, sulfate, cysteinyl, mercapturate, and methylthio metabolites. It was found that garlic treatment had no discernible effect on oxidative metabolism but was associated with a slight increase in sulfate conjugation of drug. These findings suggest that garlic extract has limited potential as a chemopreventive agent.

Dosing time with ascorbic acid and nitrate, gum and tobacco chewing, fasting, and other factors affecting N-nitrosoproline formation in healthy subjects taking proline with a standard meal.

The N-nitrosoproline (NPRO) test measures the potential for intragastric formation of carcinogenic nitrosamines in humans. Nitrate and L-proline are administered to volunteers. Noncarcinogenic NPRO is produced by an acid-catalyzed reaction of proline (a model for ingested amines) with nitrate-derived nitrite in the stomach. It is then absorbed and excreted in the urine, which is analyzed for NPRO. We studied the effect of certain dietary and other factors on the levels of urinary NPRO. For (generally) 5 days, healthy adult subjects (mostly men) followed a diet low in preformed NPRO, nitrate, proline, and (on days 4 and 5) ascorbic acid. The tests were conducted on days 4 and 5. In the standard test, the subjects took 400 mg nitrate at 11 a.m., and at noon they ate a standard 700-calorie meal containing 500 mg proline. (In previous tests, proline was given 1 h after or between meals.) Urines were collected for 24 h, and samples were analyzed for NPRO by published methods. This standard test yielded 26 +/- 2 (mean +/- SE) nmol NPRO compared with 5 +/- 1 nmol NPRO when proline alone was taken. In variations of the standard test, NPRO yield was not significantly affected by the subjects' gender, the time at which the standard meal was eaten, the size of the meal, or the drinking of extra water after the meal. Doses of 100 and 200 mg nitrate had lesser effects on NPRO yield than did the dose of 400 mg nitrate. Nitrate (400 mg) produced the most NPRO when it was given 1 h before the meal. Fasting increased NPRO yield by 3-4 times compared to giving proline with a meal. One g of ASC given 5 or 2 h before, with, or 1 or 2 h after the meal with proline inhibited NPRO formation by mean values of 0, 71, 71, 67, and 19%, respectively. Chewing gum or tobacco for 2-3 h after the test meal did not increase NPRO formation or salivary nitrate levels, but salivary nitrite was not taken, chewing tobacco appeared to increase salivary nitrite and nitrate levels. The weak carcinogen N-nitrososarcosine (NSAR) was also detected in some tests, and the standard group showed 21 +/- 3 nmol NSAR. A high NSAR result (44 +/- 7 nmol) for women undergoing the standard test should be reexamined. We discuss applying these results to the conduct of future NPRO tests, as well as their implications for reducing the potential production of carcinogenic nitrosamines in the stomach.

Nitrate and nitrite concentrations in human saliva for men and women at different ages and times of the day and their consistency over time.

Salivary nitrite arises from nitrate and is the main source of gastric nitrite, a precursor of carcinogenic N-nitroso compounds. We examined nitrate and nitrite levels in unstimulated saliva from subjects consuming low-nitrate low-vitamin C diets. When saliva was collected from six men at nine times of the day (Experiment 1), night time nitrite levels were significantly higher than day time values and nitrite varied more than nitrate. When saliva was collected from 29 subjects aged 19-37 or 60-84 years at four times of the day during 1991-1993 (Experiment 2), all older subjects and older men had significantly higher nitrite levels than the corresponding younger subjects, night time nitrite levels in men were significantly raised, and nitrate and nitrite levels in the same samples were closely correlated. Saliva was collected at 6.00 a.m. on two successive days in 1997 from 16 subjects who had collected saliva in 1991-1993 (Experiment 3). Nitrate and nitrite levels on day 1 of experiment 3 were closely correlated with those on day 2. Nitrate and nitrite levels on days 1 and 2 of Experiment 3 were correlated with the corresponding parameters in Experiment 2 with P = 0.04 and 0.08 for day 1, and 0.10 and 0.28 for day 2, respectively. Hence, saliva nitrite levels rose at night and were higher in older people, especially older men, and saliva nitrate and nitrite levels varied little from day to day, but varied more after 4-6 years.

Effects of 5-fluorouracil on various melanoma cell metabolisms. Its use for assessing the cold thymidine pool.

5-Fluorouracil (5FU) increases the rate of incorporation of tritiated thymidine (3HTdR) and iododeoxyuridine (125 IUdR) into the cell and its DNA. 5FU has differential effect on metabolism of DNA through its specific action on thymidylate synthetase. Effects of 5FU on the incorporation of other metabolic precursors were studied, as well as the sensitivity of different cells to 5FU. This multiparametric approach enables us to predict the effect of 5FU on a cell type depending on its cold thymidine (TdR) pool size and the permeation of the cell to the drug. Furthermore, 5FU was used as a tool to recognize the difference between the effects of TdR on the 3HTdR and 125IUdR incorporation. Three parameters are superimposed: isotope dilution, inhibition of metabolic activity of the pyrimidine synthesis and metabolic competition between TdR and UdR. The measurement of the TdR pool size of the cell can be obtained using a specific equation, which is a function of the slope of the inhibition curve of the labelled precursors (3HTdR and 125IUdR) incorporation.

Monoclonal antibodies to human melanoma associated antigens: study of their specificity and visualization at the cellular level of the antigenic distribution.

Six monoclonal antibodies(Mabs) including 4 anti-melanoma, one anti-glioma, and one anti-HLA-DR have been tested in a 125I-protein A antibody binding assay using a panel of 34 different cell lines. This panel included 19 melanomas from different clinical and geographical origins, 10 fibroblast lines out of which 9 were established from melanoma patients, 2 glial cell lines, 1 osteosarcoma, 1 teratocarcinoma, and 1 murine melanoma. The reactivity pattern of the 4 anti-melanoma Mabs showed that they were not directed against antigens strictly restricted to melanoma, but rather against antigenic structures preferentially expressed on melanoma cells. These Mabs were found to crossreact with gliomas, thus they seem to recognize neuroectoderm associated differentiation antigens. The high crossreactivity of the anti-glioma Mab for melanoma was confirmed in this study. As expected from the literature, HLA-DR antigens were found to be expressed on more than 50% of the melanoma lines tested. The cellular distribution of the antigens recognized by two anti-melanoma Mabs on melanoma cells could be visualized by an autoradiographic procedure. From the labeling pattern it was concluded that only a proportion of the cells, varying from 13 to 38%, expressed the relevant antigen.

A new test for phagocytosis of human alveolar macrophages in suspension, using 99mTc labelled human serum albumin particles.

Current studies on human alveolar macrophages (HAM phi) indicate that two subpopulations may exist: adherent and nonadherent HAM phi. Most works in the literature were done exclusively on adherent HAM phi. In order to obviate to the loss of nonadherent HAM phi, we elaborated a new test for measuring endocytosis in HAM phi suspensions. According to this method, HAM phi in suspension were allowed to phagocytize millimicrospheres of human serum albumin labelled with 99m Tc (0.2 less than 0 less than 0.5 m; TcK9R - Cis Sorin Biomedica). Bound activity was separated from free activity by centrifugation on PercollR. The resulting internatant ring was found to contain activity bound to HAM phi which had phagocytized human serum albumin millimicrospheres. HAM phi were characterized by morphology and cytochemistry. The method here presented allows the functional study of both adherent and non-adherent HAM phi populations.

Production of interleukin 1 by activated blood monocytes and alveolar macrophages from melanoma patients.

The production of Interleukin 1 (Il1) by circulating blood monocytes and alveolar macrophages was studied in melanoma patients. There were 144 patients in the monocytes study and 5 patients in the alveolar macrophages study. The Il1 activity was tested by a bioassay and reported in units based on the integration of the area under the curve. This was shown to be preferable to the standard method, i.e. probit analysis. Results showed that there was no depression of Il1 activity in melanoma patients as compared to control (98 + 32 units, versus 100 units). There was no difference when the values were compared according to sex, age and stage of the disease. However, a significant difference was found between phototype I and phototype IV. Alveolar macrophages, in all experiments (n = 5), had a significantly lower Il1 activity than the autologous monocytes. It is concluded that we can question the relevance of Il1 production by peripheral blood monocytes to the state of the immunity of melanoma patients.

Studies on factors influencing human plasma alpha-MSH.

The various physiological effects of alpha-MSH, mainly on the CNS and on pigmentation in animal models, are well documented in the literature. Only a few investigators have confirmed similar properties in the human. However, the possible physiopathological role played by this hormone in human melanoma is still poorly defined. In order to approach this subject in a manner as complete as possible, we have performed, during the past four years, three different series of experiments: 1) alpha-MSH measurements in plasma samples from: a. melanoma and other cancer patients, b. whole body UVA irradiated healthy adults, c. circadian rhythm determinations in melanoma patients and in healthy male adults; 2) alpha-MSH measurements in human melanoma tumours; 3) alpha-MSH receptor expression on human melanoma cells in culture involving: a. alpha-MSH radio-binding assays and b. tyrosinase assay. Our results so far show 1) increased alpha-MSH levels in melanoma patients' plasma, alpha-MSH responsiveness to UVA stimulated skin, large immunoreactive alpha-MSH content in melanoma metastases and an alpha-MSH circadian rhythm in some individuals different from cortisol; 2) alpha-MSH receptor expression in melanoma cells could be increased by various effectors able to stimulate melanogenesis.

Nutritional status of elderly participants in a congregate meals program.

This study was conducted to determine the nutritional status of elderly subjects participating in a congregate meals program. Twenty-four-hour recalls, anthropometric measurements, and biochemical determinations were the criteria used to determine nutritional status of the 30 volunteers. Information regarding use of dietary supplements was also obtained. Ninety-three percent of the participants consumed diets providing at least 70 percent of the RDA for the 13 nutrients calculated. Seven percent consumed diets rated as "poor," but none of the participants consumed diets supplying less than 54 percent of the RDA. Twenty-seven percent of the sample reported daily use of dietary supplements. Height, weight, mid-arm circumference, triceps skinfold, and abdominal circumference were measured. The incidence of obesity was high, with 42 percent of the women and 78 percent of the men being over 119 percent of ideal body weight. Mid-arm circumference, triceps skinfold, and abdominal circumference data agreed with the weight-for-height data. The incidence of obesity was greater in this study than in other studies cited, and, as was not the case in other studies, the incidence of obesity was greater in men. Biochemical determinations included hemoglobin, hematocrit, serum albumin, serum folate, ascorbic acid, and vitamins A, B6, and B12. Comparison of biochemical data with accepted standards indicated that the nutritional status of the participants was adequate.

Effects of ozone on the yield of spring wheat (Triticum aestivum L., cv. Albis) grown in open-top field chambers.

Spring wheat (Triticum aestivum L., cv. Albis) was grown in the field at a site located in central Switzerland, and exposed to chronic doses of ozone (O(3)) in open-top chambers to study impacts on yield. The experiment was carried out in 1986, 1987 and 1988. The treatments used included charcoal-filtered air (CF), non-filtered air (NF) and non-filtered air to which constant amounts of O(3) (two levels, O(3)-1 and O(3)-2) were added daily from 09.00 until 17.00 local time. Mean solar radiation-weighted O(3) concentrations during the fumigation period were in the range 0.016-0.022 microl litre(-1) (CF), 0.036-0.039 microl litre(-1) (NF), 0.057-0.058 microl litre(-1) (O(3)-1, used in 1987 and 1988 only) and 0.078-0.090 microl litre(-1) (O(3)-2). Fumigation was maintained from the three-leaf stage until harvest. Ambient plots were used as a reference. Plant characteristics examined included straw yield, grain yield, number of grains per head, number of heads per surface area, weight of individual grains and harvest index (ratio of grain weight to total dry weight). Pollutant concentrations and other environmental parameters were monitored continuously inside and outside the chambers. In 1986 and 1987, enclosure mostly increased the values of different parameters, while in 1988, they were decreased. The negative enclosure effect was due to extremely turbulent winds, which caused lodging inside the chambers. In all 3 years, increasing O(3) concentrations negatively affected the parameters studied, except for the number of heads per surface area, which showed no treatment response. Grain yield showed a very sensitive response to O(3). The effect of O(3) on grain yield was due to an effect primarily on grain size and secondarily on grain number. The relative response of grain yield to O(3) was similar in all 3 years, despite year-to-year differences in climatic conditions and enclosure effects. The analysis of the data for combined years revealed an increase of about 10% in grain yield due to air filtration. The corresponding increase in straw yield was only about 3.5%. Exposure-response models were developed for individual years and combined years. It is concluded that, in the study area, ambient O(3) may affect grain yield in spring wheat.