[Prevalence of HBs antigen carriers and markers of B virus replication in a population of pregnant women, in France]. / Prévalence du portage de l'antigène HBs et des marqueurs de réplication virale B dans une population de femmes enceintes, en France.

To assess the risk of perinatal B virus transmission in a population of French and immigrant women, 1,923 women were tested for HBs antigen and serological markers of B virus replication, i. e. HBe antigen and HBV DNA, during the last trimester of their pregnancy. The patients included in this study were French (n = 1,295 (67.3 per cent] and immigrant women (n = 628 (32.7 per cent] attending consultation in four public Parisian suburb hospitals. The immigrant population was composed of natives of the Mediterranean area or Portugal (64 per cent), West Africa (23 per cent), and South-East Asia (13 per cent). Serum HBsAg was tested by conventional radioimmunoassay. When present, HBeAg and antiHBe were tested by radioimmunoassay, and HBV DNA by the hybridization procedure. The overall HBsAg prevalence was 1.56 per cent. This high prevalence was in part explained by the large proportion of immigrants in whom it varied from 0.8 to 7.5 per cent according to their origin. Prevalence was 0.85 per cent in French women, higher than that usually admitted in France. Serological markers of viral replication (HBeAg and/or HBV-DNA) were more often present in the immigrants (4 out of 19) than in the French women (1 out of 11). Discrepancies between HBe status and HBV DNA were present in 4 out of the 30 HBs antigen positive women. Due to the possible high prevalence of HBV carriage in pregnant women, routine antenatal HBs antigen screening should be recommended in France. Such screening, associated with immunoprophylaxis of newborns at risk of contamination, can help in the prevention of perinatal transmission of hepatitis B virus.

Approaches to estimating physical activity in the community: calorimetric validation of actometers and heart rate monitoring.

The relationship between actometer measurements, heart rate monitoring and energy expenditure during exercise and resting periods was assessed in a whole-body indirect calorimeter on 12 young male volunteers. Equations derived from these studies were applied to actometer measurements taken during a further 7 d recording in free-living conditions to predict daily energy expenditure over 1 week on an individual basis. Actometers proved to be a satisfactory means of estimating energy expenditure and heart rate monitoring improved the estimates in a few selected subjects. Indirect measures of energy expenditure could be developed by this approach but individual calibration is essential.

Tracking the development of adiposity from one month of age to adulthood.

The development of adiposity was followed in 164 subjects from the age of one month to adulthood. The 25th and 75th centiles of the weight/height2 (W/H2) index were chosen as cut-off points to define the lean, medium and fat subjects at both one and 21 years of age. Only 42% of the children remained in their original category, that is 41% of the lean infants at one year stayed lean, 42% of the medium infants stayed medium and 41% of the fat infants stayed fat. Accordingly, most fat infants did not stay fat, but twice as many fat as non-fat infants became fat adults (41 and 20% respectively). The relative risk of being fat adults was 1 for the lean, 1 for the medium and 2 for the fat infants at one year. Several paths of development emerged: they were related to age at the second rise in adiposity, termed adiposity rebound, which usually occurs at about six years, as observed on skinfold thickness and W/H2 charts. The earlier the rebound, the higher the adiposity at adult age, whether this was measured by W/H2 index or subscapular skinfold. The cohorts of children who left the channel they had been following included fat infants with a late rebound who subsequently returned to normal, and lean infants with an early rebound who grew fatter. Other cohorts remained in their original groups, for example, fat infants with an early rebound who stayed fat and lean infants with a late one who stayed lean. Age at rebound provided two indications: the existence of a regulartory process among the transiently fat or lean infants who returned to average after a late or early rebound respectively, and pathological development among the children who became fat or lean after an early or late rebound. Age at rebound is an indicator of the subsequent development of fatness.

Energy expenditure of young men from obese and non-obese families.

Sixteen young non-obese men, seven of whom had an obese parent, were studied under standardized conditions in a respiration chamber to assess their metabolic rate during sleep, at rest, in response to food and during a variety of exercises. The men from obese families were already fatter than the 'normal' group from non-obese families but reported equivalent intakes of energy, had a normal pattern of energy expenditure and could not be distinguished as a group from the men of normal-weight parents. Only the three men of lighter weight of obese parents had a lower energy expenditure per kg fat-free mass and a lower thermic response to food than the normal group; those who were already overweight did not differ from the normal group in their energy expenditure.

[Markers of the dietary supply of fatty acids. Their use in epidemiologic surveys]. / Marqueurs de l'apport alimentaire en acides gras. Leur utilisation dans les enquêtes épidémiologiques.

The use of tissular markers of dietary fatty acids is based on the potential usefulness of a cellular or membrane witness of usual food intake. Prevalence studies among populations and prospective trials on a change of dietary habits allow a definition of the relationship between dietary fatty acids and adipose ones, according to time, sampling site and the stability of fatty acid pool. The physiological parameters of that relationship are weight changes, age, energy balance, tobacco and probably alcohol consumptions and race. The relationship between dietary fatty acids and fatty acids within serum lipids, erythrocytes, certain epithelial cells and platelets are described and validity of these relationships pointed out. A few examples illustrate potential use of fatty acid markers in investigating risk factors of chronic diseases and in checking adherence to regimen in dietary trials.