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Biomedical subjects

G Thériault

Publications and source records attributed to G Thériault.

At least 19 recordsLinked to original sources

Defining and classifying occupational rhinitis.

Three categories of rhinitis may occur in the workplace: occupational rhinitis, work-aggravated rhinitis and rhinitis-like conditions. In the present paper, we propose a new definition and a new classification of occupational rhinitis that takes into account mechanisms of induction as well as clinical presentation. In parallel with occupational asthma, occupational rhinitis is defined as a type of rhinitis characterized by intermittent or sometimes permanent nasal airflow limitation due to causes and conditions attributable to the work environment. Occupational rhinitis is classified according to its mechanism of induction as immunological or irritant-induced (non-immunological) rhinitis. Occupational rhinitis of the immunological type can itself be episodic or persistent, whereas the non-immunological type is subdivided into acute, chronic and corrosive.

Humans↗

Indicator of risk of water contamination by phosphorus from Canadian agricultural land.

The indicator of risk of water contamination by phosphorus (IROWC_P) is designed to estimate where the risk of water P contamination by agriculture is high, and how this risk is changing over time based on the five-year period of data Census frequency. Firstly developed for the province of Quebec (2000), this paper presents an improved version of IROWC_P (intended to be released in 2008), which will be extended to all watersheds and Soil Landscape of Canada (SLC) polygons (scale 1:1, 000, 000) with more than 5% of agriculture. There are three objectives: (i) create a soil phosphorus saturation database for dominant and subdominant soil series of SLC polygons--the soil P saturation values are estimated by the ratio of soil test P to soil P sorption capacity; (ii) calculate an annual P balance considering crop residue P, manure P, and inorganic fertilizer P--agricultural and manure management practices will also be considered; and (iii) develop a transport-hydrology component including P transport estimation by runoff mechanisms (water balance factor, topographic index) and soil erosion, and the area connectivity to water (artificial drainage, soil macropores, and surface water bodies).

Agriculture↗

Mortality and cancer morbidity in a cohort of Canadian petroleum workers.

AIMS: To assess mortality and cancer morbidity in Canadian petroleum workers and explore exposure-response relations for specific petroleum agents. METHODS: A total of 25 292 employees hired between 1964 and 1994 were linked to the Canadian tumour registry and national mortality database. Exposure-response trends were assessed for hydrocarbon solvents/fuels, hydrocarbon lubricants, petroleum coke/spent catalyst, and hydrogen sulphide (H2S). RESULTS: External comparison analyses (mortality and incidence) showed deficits for all causes and all malignant neoplasms combined and were consistent with expectation for most malignant and non-malignant sites analysed. Gall bladder cancer mortality was increased among males based on four deaths, but cases had no common job assignments and the increase was focused in workers employed <10 years. Mesothelioma incidence was increased. Most exposure-specific analyses were compromised by small numbers. Statistically significant increases were observed for H2S exposure and a subgroup of accidental deaths as well as for petroleum coke/spent catalyst exposure and lung cancer. While both findings have a degree of biologic plausibility, the H2S association, which exhibited a clearer exposure-response pattern, could be subject to unmeasured confounders. Additionally, interpretation was complicated by the high correlation between hydrocarbon and H2S exposures. With regard to lung cancer, the analysis could not adequately control for smoking, was based on small numbers, and exhibited a tenuous exposure-response pattern. CONCLUSION: The findings for mesothelioma suggest the need for continued attention to asbestos in the petroleum industry. The relation between accidental deaths and H2S exposure deserves closer scrutiny in similarly exposed populations. Further analyses of lung cancer are underway and will be reported separately.

Adult↗

Cardiac dimensions, physical activity, and submaximal working capacity in youth of the Québec Family Study.

The relationships between cardiac dimensions and physical activity and submaximal working capacity were examined in 198 boys and 154 girls, aged 9-18 years, who were participants in the first phase of the Québec Family Study. The sample was divided into three age groups, 9-12 years, 13-15 years, and 16-18 years. Indicators of physical activity included estimated daily energy expenditure (EE) and time spent in moderate-to-vigorous physical activity (median metabolic equivalents of energy expenditure above resting metabolic rate >/=4.8). Submaximal physical working capacity (PWC(150)) was determined using a submaximal exercise test on a Monark cycle ergometer. Echocardiographically determined dimensions included posterior wall thickness, septal wall thickness, and left ventricular mass (LVM). The analyses were based on partial correlation and analysis of covariance, controlling for age and body surface area. Relationships between EE/physical activity variables and cardiac dimensions were low and, at best, moderate (r < 0.45). With subjects grouped into tertiles by indicators of physical activity, LVM was significantly different only among 16- to 18-year-old girls (157 g vs 134 g in the highest and lowest quartiles, respectively; P < 0.05). Correlations between cardiac dimensions and PWC(150) were also low (r < 0.30), with few significant relationships. In general, cardiac dimensions were not related to habitual physical activity and PWC(150) in young subjects aged 9-18 years. However, significant correlations were positive, as expected. LVM may be related to submaximal power output in boys since it accounts for 3% of the variance, after adjusting for age and BSA.

Adolescent↗

Updated mortality among diverse operating segments of a petroleum company.

OBJECTIVES: To update mortality for 34 560 employees from diverse operating segments of a Canadian petroleum company; and to investigate potential relations with occupational factors. METHODS: Employees from 1964-83 were linked to the Canadian mortality data base to provide 11 years additional follow up. There were 6760 deaths and 750 683 person-years of follow up compared with 3909 and 428 190, respectively, in the earlier study. Analyses used standardised mortality ratios (SMRs) to compare worker cause specific mortality with the Canadian general population. Duration of employment and latency analyses were performed for causes previously found to be increased in this and other petroleum cohorts, as well as any findings of interest. RESULTS: For the period 1964-94, employees experienced significantly low overall mortality (SMR=0.86 men, SMR=0.80 women). Kidney cancer, which has been increased in some studies of petroleum workers, was not increased. Acute non-lymphocytic leukaemia in exposed operating segments was consistent with the expected or only slightly, non-significantly increased. The most notable finding was increased deaths from mesothelioma among refinery and petrochemical workers (SMR 8.68; 95% confidence interval (95% CI) 5.51 to 13.03), most of whom were long term employees in jobs with presumed exposure to asbestos (mechanical and pipefitters). Deaths from multiple myeloma among marketing and distribution workers, which were previously increased, remained increased (SMR 2.08; 95% CI 0.95 to 3.95) in the update period 1984-94; however, there was no clear pattern by duration of employment or latency. Aortic aneurysms, which also were previously significantly increased among marketing and distribution workers approached the expected in the update period (SMR 1.18; 95% CI 0. 65-1.98). Analyses by duration of employment showed suggestive trends for aortic aneurysms, but earlier studies of this cohort have not found a relation between aortic aneurysms and exposure to hydrocarbons. CONCLUSION: The additional 2851 deaths and 322 493 person-years of follow up strengthened the assessment of mortality patterns relative to occupational factors. With the exception of mesothelioma, no clear work related increases in disease were identified.

Canada↗

Power-frequency electric and magnetic fields and risk of childhood leukemia in Canada.

In a case-control study of childhood leukemia in relation to exposure to power-frequency electric and magnetic fields (EMF), 399 children resident in five Canadian provinces who were diagnosed at ages 0-14 years between 1990 and 1994 (June 1995 in British Columbia and Quebec) were enrolled, along with 399 controls. Exposure assessment included 48-hour personal EMF measurement, wire coding and magnetic field measurements for subjects' residences from conception to diagnosis/reference date, and a 24-hour magnetic field bedroom measurement. Personal magnetic fields were not related to risk of leukemia (adjusted odds ratio (OR) = 0.95, p for trend = 0.73) or acute lymphatic leukemia (OR = 0.93, p for trend = 0.64). There were no clear associations with predicted magnetic field exposure 2 years before the diagnosis/reference date or over the subject's lifetime or with personal electric field exposure. A statistically nonsignificant elevated risk of acute lymphatic leukemia was observed with very high wiring configurations among residences of subjects 2 years before the diagnosis/reference date (OR = 1.72 compared with underground wiring, 95% confidence interval 0.54-5.45). These results provide little support for a relation between power-frequency EMF exposure and risk of childhood leukemia.

Adolescent↗

Linkage of the Na,K-ATPase alpha 2 and beta 1 genes with resting and exercise heart rate and blood pressure: cross-sectional and longitudinal observations from the Quebec Family Study.

OBJECTIVE: To investigate whether genetic variations in the genes encoding the alpha and beta subunits of the Na,K-ATPase are linked with hemodynamic phenotypes. DESIGN AND PARTICIPANTS: Cross-sectional data based on 533 subjects (no antihypertensive medication) were obtained from 150 families of phase 2 of the Quebec Family Study, together with longitudinal data from 338 subjects (105 families) who had been measured 12 years earlier in phase 1 of the Quebec Family Study. MAIN OUTCOME MEASURES: Restriction fragment length polymorphisms were examined at the alpha 2 (exon 1 and exon 21-22 with BglII) and beta 1 (Msp I and Pvu II) loci of Na,K-ATPase. Hemodynamic phenotypes measured included systolic and diastolic blood pressure, heart rate and rate-pressure product at rest and during low-intensity exercise. RESULTS: Sib-pair analysis revealed relatively strong linkages (P = 0.0003-0.002) between the resting heart rate and rate-pressure product and the alpha 2 exon 21-22 marker and alpha 2 haplotype. Moreover, the alpha 2 exon 21-22 marker showed suggestive linkages (P = 0.01 to 0.043) with resting systolic blood pressure and exercise diastolic blood pressure, heart rate and rate-pressure product, and the alpha 2 haplotype with exercise diastolic blood pressure and rate-pressure product and the 12-year change in resting systolic blood pressure (P = 0.03 to 0.05). Both the beta 1 Msp I marker and the beta 1 haplotype were linked with the resting rate-pressure product (P = 0.007 and 0.003, respectively), and all beta 1 markers showed linkage with the change in resting systolic blood pressure (P = 0.00005 to 0.024). In men, there was a significant (P = 0.01) interaction between the alpha 2 exon 21-22 genotype and the postglucose plasma insulin level with regard to resting systolic blood pressure. CONCLUSIONS: These data suggest that the alpha 2 and beta 1 genes of Na,K-ATPase contribute to the regulation of hemodynamic phenotypes in healthy subjects.

Blood Pressure↗

Comparative analyses of the studies of magnetic fields and cancer in electric utility workers: studies from France, Canada, and the United States.

OBJECTIVES: To summarise and to facilitate comparison of three major studies of electric utility workers that examined the relation between quantitative measurements of occupational exposure to magnetic fields and risk of brain cancer and leukaemia. These studies have been interpreted as providing conflicting evidence. METHODS: A common analytical approach was applied to data from the five cohorts included in the three studies based on original data from four of the cohorts, and published data from one additional cohort. A nested case-control design with conditional logistic regression was used to estimate the relative risk/10 microtesla-years (microT-years) for each of the contributing cohorts and for the combined data. The homogeneity of these estimates among the studies was also evaluated. RESULTS: Apparent inconsistencies in the findings of these studies can be explained by statistical variation. Overall, the studies suggest a small increase in risk of both brain cancer and leukaemia. Different methodological choices had little impact on the results. Based on a combined analysis of data from all five studies, the relative risk/10 microT-years was 1.12 (95% confidence interval (95% CI) 0.98 to 1.28) for brain cancer, and 1.09 (95% CI 0.98 to 1.21) for leukaemia. CONCLUSIONS: The combined estimates seem to provide the best summary measures of the data from all studies. However, fluctuations in risks among studies may reflect real differences, and the exposure measurements in different studies may not be entirely comparable.

Brain Neoplasms↗

Exposures of children in Canada to 60-Hz magnetic and electric fields.

OBJECTIVES: This study sought to characterize personal exposures of Canadian children to 60-Hz magnetic and electric fields and explain the variability. METHODS: Altogether 382 Canadian children up to 15 years of age wore meters recording 60-Hz electric and magnetic fields over 2 days. Meter location was noted. Thereafter, meters measured fields in the center of the children's bedrooms for 24 hours. Personal exposures were calculated for home, school or day care, outside the home, bedroom at night, and all categories combined (total). RESULTS: The arithmetic mean (AM) was 0.121 microT [geometric mean (GM): 0.085 microT), range 0.01-0.8 microT] for total magnetic fields. Fifteen percent of the total exposures exceeded 0.2 microT. The AM of the total electric fields was 14.4 (GM 12.3, range 0.82-64.7) V/m. By location category, the highest and lowest magnetic fields occurred at home during the day (0.142 microT) and during the night (0.112 microT), respectively. Measurements during sleep provided the highest correlation with total magnetic field exposure. Province of measurement explained 14.7% of the variation in the logarithms of total magnetic fields, and season accounted for an additional 1.5%. CONCLUSIONS: This study has identified differences in children's magnetic field exposures between provinces. Measurements at night provided the best surrogate for predicting total magnetic field exposure, followed by at-home exposure and 24-hour bedroom measurements. Electrical heating and air conditioning, wiring type, and type of housing appear to be promising indicators of magnetic field levels.

Canada↗

Golf injuries. An overview.

Over the years, golf has become an increasingly popular sport, attracting new players of almost all ages and socioeconomic groups. Golf is practised by up to 10 to 20% of the overall adult population in many countries. Beyond the enjoyment of the sport itself, the health-related benefits of the exercise involved in walking up to 10 km and of relaxing in a pleasant natural environment are often reported to be the main motives for adhering to this activity by recreational golfers. Golf is considered to be a moderate risk activity for sports injury; however, excessive time spent golfing and technical deficiencies lead to overuse injuries. These are the 2 main causes of injuries among golfers, and each has specific differences in the pattern in which they occur in professional and amateur golfers. Golf injuries originate either from overuse or from a traumatic origin and primarily affect the elbow, wrist, shoulder and the dorsolumbar sites. Professional and weekend golfers, although showing a similar overall anatomical distribution of injuries by body segment, tend to present differences in the ranking of injury occurrence by anatomical site; these differences can be explained by their playing habits and the biomechanical characteristics of their golf swing. Many of these injuries can be prevented by a preseason, and year-round, sport-specific conditioning programme including: (i) muscular strengthening, flexibility and aerobic exercise components; (ii) a short, practical, pre-game warm-up routine; and (iii) the adjustment of an individual's golf swing to meet their physical capacities and limitations through properly supervised golf lessons. Finally, the correct selection of golf equipment and an awareness of the environmental conditions and etiquette of golf can also contribute to making golf a safe and enjoyable lifetime activity.

Adult↗

Regional variation in adipose tissue insulin action and GLUT4 glucose transporter expression in severely obese premenopausal women.

Insulin action and GLUT4 expression were examined in adipose tissue of severely obese premenopausal women undergoing gastrointestinal surgery. Fat samples were taken from three different anatomical regions: the subcutaneous abdominal site, the round ligament (deep abdominal properitoneal fat), and the greater omentum (deep abdominal intraperitoneal fat). The stimulatory effect of insulin on glucose transport and the ability of the hormone to inhibit lipolysis were determined in adipocytes isolated from these three adipose depots. Insulin stimulated glucose transport 2-3 times over basal rates in all adipocytes. However, round ligament adipose cells showed a significantly greater responsiveness to insulin when compared to subcutaneous and omental adipocytes. Round ligament fat cells also displayed the greatest sensitivity and maximal antilipolytic response to insulin. We also investigated whether regional differences in fat cell insulin-stimulated glucose transport were linked to a differential expression of the GLUT4 glucose transporter. GLUT4 protein content in total membranes was 5 and 2.2 times greater in round ligament adipose tissue than in subcutaneous and omental fat depots, respectively. Moreover, GLUT4 mRNA levels were 2.1 and 3 times higher in round ligament than in subcutaneous or omental adipose tissues, respectively. Adipose tissue GLUT4 protein content was strongly and negatively associated (r = -0.79 to -0.89, p < 0.01) with the waist-to-hip ratio but not with total adiposity. In conclusion, these results demonstrate the existence of site differences in adipose tissue insulin action in morbidly obese women. The greater insulin effect on glucose transport in round ligament adipocytes was associated with a higher expression of GLUT4 when compared to subcutaneous abdominal and omental fat cells. Moreover, despite the regional variation in GLUT4 expression, an increased proportion of abdominal fat was found to be associated with lower levels of GLUT4 in all adipose regions investigated.

Adipocytes↗

Residential exposure to 60-Hertz magnetic fields and adult cancers in Taiwan.

We conducted a case-control study, using matching on date of birth, sex, and date of diagnosis, in northern Taiwan to evaluate the risks of adult leukemia, brain tumors, and female breast cancers in relation to residential exposure to 60-Hertz (Hz) magnetic fields. Cases were persons with newly diagnosed cancers reported to the cancer registry between 1987 and 1992, and controls were persons with cancers sites other than those previously suspected of being associated with magnetic fields. Magnetic fields in the residences occupied by the study subjects at the time of diagnosis were estimated from high-voltage transmission lines. The results were based on the separate analysis of 870 cases of leukemia, 577 brain tumors, and 1,980 female breast cancers. We estimated the risk of leukemia among those exposed to magnetic fields of > 0.2 microtesla (microT), relative to the risk among those exposed to fields of < 0.1 microT; the odds ratio was 1.4 [95% confidence interval (CI) = 1.0-1.9]. For distance < 50 meters relative to > or = 100 meters, the relative risk was 2.0 (95% CI = 1.4-2.9). For brain tumors and female breast cancers, the odds ratios were close to unity.

Adult↗

Lung cancer in relation to employment in the electrical utility industry and exposure to magnetic fields.

OBJECTIVES: A recent study found that lung cancer may be associated with exposures encountered in the electrical utility industry. To further evaluate this possibility, data were collected and analysed from five large electrical utility companies in the United States. METHODS: A cohort of 138905 male workers employed between 1950 and 1986 was followed up for mortality to the end of 1988, with 20733 deaths identified of which 1692 were due to lung cancer. Mortality from lung cancer was examined in relation to the duration of employment in specific jobs thought to have high exposure to 60 Hz magnetic fields and to an index of cumulative exposure to magnetic fields based on personal measurements. Exposure to pulsed electromagnetic fields (PEMFs) as estimated from another study was also considered. Poisson regression generated rate ratios for categories of exposure based on comparisons within the cohort adjusted for age, calendar year, race, socioeconomic status, work status, and estimated exposure to asbestos. RESULTS: Mortality rose modestly with duration of work as an electrician or power plant operator reaching rate ratios of 1.4 with > or = 20 years in those jobs but not with duration of work as a lineman or a combination of jobs thought to have high exposures to 60 Hz magnetic fields or PEMFs. Cumulative indices of exposure to 60 Hz magnetic fields and PEMFs were both associated with rate ratios of 1.2-1.3 in the highest intervals. CONCLUSIONS: These data suggest that lung cancer is not strongly associated with duration of employment in specific jobs associated with high potential exposure to 60 Hz magnetic fields or to PEMFs. Small associations of lung cancer with indices of both 60 Hz magnetic fields and PEMFs leave open the possibility that larger associations have been diluted through exposure misclassification. Refined exposure assessment, especially to PEMFs, would be required to evaluate that possibility.

Cohort Studies↗

Risks of leukaemia among residents close to high voltage transmission electric lines.

OBJECTIVES: To reassess the risk of leukaemia associated with residential exposure near high voltage transmission electric lines of 49 kV and above in view of the recent publications. METHODS: Through a review of papers considering the risk of leukaemia among people living near high voltage transmission lines, the combined risks of leukaemia were calculated for distances < or = 50 m and < or = 25 m and for exposures at 2 mG, 3 mG, 4 mG, and 10 mG. RESULTS: The combined analysis of the contributive studies indicated an estimate of risk (odds ratio (OR)) for exposure > or = 2 mG of 1.3, 95% confidence interval (95%CI) 1.0 to 1.7. The ORs increased with exposures at 3 mG, 4 mG, and 10 mG. The risks were also increased for distances of 50 and 25 m from the lines. CONCLUSIONS: This meta-analysis tends to confirm the presence of an association between exposure to magnetic fields and leukaemia among people who reside in the vicinity of high voltage transmission electric lines of > or = 49 kV. There is consistency across studies. Measures of exposure used in the studies were either distance from the lines or calculated fields estimated from pertinent line features. The results apply to adults as well as to children.

Adult↗

Negative energy balance with exercise in identical twins: plasma glucose and insulin responses.

The effects of long-term (93 days) negative energy balance on plasma glucose and insulin were investigated by means of exercise with constant energy intake in seven pairs of young sedentary male identical twins. Results showed a significant decrease in fasting (-24%, P < 0.02) and postprandial insulin (-16%, P < 0.05). Fasting and postprandial plasma glucose and glucagon were not modified. Mean glucose disposal rate measured during a euglycemic-hyperinsulinemic clamp performed in five twin pairs was increased by 34% (P = 0.13). No significant intrapair similarity was found for the responses of fasting and postprandial insulin levels and of glucose disposal rate. Changes in glucose disposal rate were significantly greater in high compared with low losers for computerized tomography-measured abdominal visceral fat (3.0 +/- 1.1 vs. 0.3 +/- 0.5 mg x kg(-1) x min(-1), P < 0.05) despite similar losses in total body fat. We conclude that 1) a long-term negative energy balance generated by exercise training significantly reduces plasma insulin levels, whereas insulin sensitivity tends to be improved; 2) training-induced changes in insulin sensitivity are associated with changes in abdominal visceral fat; and 3) data from this experiment conducted with a small number of twin pairs suggest that the genotype does not seem to be a major determinant of the changes in insulin levels and sensitivity brought about by negative energy balance with exercise.

Abdomen↗

Task-based estimation of past exposures to 60-hertz magnetic and electric fields at an electrical utility.

OBJECTIVES: Past exposures of electric utility workers to extremely low-frequency (ELF) magnetic (B) and electric fields (E) in Quebec were estimated. METHODS: The current intensities were measured and durations of exposures determined for tasks or work locations in 14 job categories. Past task or location intensities were extrapolated from the present on the basis of interviews with long-term workers and utility personnel. Past task or location durations were estimated for the long-term workers. Time-weighted average (TWA) exposures for past periods were reconstructed for jobs from the intensity and duration estimates. RESULTS: Magnetic fields were estimated to have increased the most over time for substation and distribution-line jobs. Magnetic field exposures for jobs in the generation and transmission of electricity were estimated to have increased very little. For substation jobs, the ratios of magnetic fields in 1945 to those in 1990 ranged from 0.42 to 0.69; the corresponding figures for distribution-line jobs ranged from 0.36 to 0.94. For electric fields in substations, the estimated increase over time was less than for magnetic fields, the 1945:1990 ratios ranging from 0.59 to 0.88. For the distribution line jobs, the 1945:1990 ratios for electric fields were less than 1.0 in 4 cases (0.6 to 0.89), more than 1.0 in 3 others (1.13 to 2.01) and unchanged in 1. CONCLUSIONS: Reconstruction of TWA exposures allowed changes in the intensity and the duration of exposures to be considered separately. Documentation of the intensity and duration of exposures for different tasks allows exposure reconstruction for jobs that have ceased to exist. The method is applicable elsewhere if exposure-monitoring records allow the level and duration of exposures for tasks or locations to be calculated and if estimates of past durations and intensities of exposures can be reliably obtained.

Electromagnetic Fields↗

Electrical stimulation-induced changes in performance and fiber type proportion of human knee extensor muscles.

The purpose of the present study was to look at the changes in the performance of human knee extensor muscles (KEM) induced by 6 weeks of low-frequency (8 Hz) electrical stimulation (LFES). KEM performance of 20 sedentary (before and after stimulation), ten active, and five endurance-trained subjects was evaluated during 25 consecutive 10-s isometric contractions, each separated by a rest period of 5 s. The mean force maintained during six consecutive 10-s contractions was expressed as a relative percentage of that of the first contraction. The mean performance of the first series of six contractions was not altered in response to stimulation, whereas that of the other four series was significantly increased. No significant difference was noted among the three groups in terms of KEM performance during the first series of six contractions. However, after the first series of six contractions, KEM performance of endurance-trained subjects was better in comparison to the other groups. Citrate synthase (CS) activity, capillary number per type IIA and IIB fibers, and the percentage of type IIA muscle fibers determined from vastus lateralis samples were significantly increased in response to the stimulation protocol. No significant change was observed in the proportion or capillary number of type I fibers, or in the areas of type I, IIA, and IIB fibers. The present study provides evidence that resistance to fatigue of human skeletal muscle can be significantly altered in response to 6 weeks of transcutaneous low-frequency electrical stimulation. The improvement in KEM resistance to fatigue of the sedentary subjects was such that, at the end of the stimulation protocol, resistance to fatigue was similar to that of active subjects. However, the ability of endurance-trained subjects to withstand fatigue was still superior compared to that of the other untrained or active subjects.

Adult↗