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Biomedical subjects

G Samuelson

Publications and source records attributed to G Samuelson.

At least 19 recordsLinked to original sources
PubMed2005

Iron status influences trace element levels in human blood and serum.

Food is the main source of trace elements for the general population. The gastrointestinal absorption of certain trace elements, e.g., cadmium, is strongly influenced by iron (Fe) status. This factor may also be relevant for the bioavailability of other trace elements. Therefore, we investigated relationships between Fe status indicators and trace element concentrations in blood and serum of 234 boys and girls at ages 15 and 17 years. Fe status was measured using serum ferritin (S-Ft), soluble transferrin receptor in serum (sTfR), and the ratio sTfR/S-Ft. The trace elements we investigated were, in blood, cadmium, cobalt, copper, zinc, selenium, rubidium, mercury, and lead, and, in serum, cobalt, copper, zinc, selenium, rubidium, tungsten, mercury, and lead. We found inverse correlations between Fe status and blood cadmium, blood or serum cobalt, or blood copper. There were positive correlations between Fe status and mercury concentrations. Selenium was positively correlated with sTfR. The relationships between Fe status and lead were equivocal. There were fewer correlations for serum than for blood, but the inverse relationships between Fe status and cobalt were equally strong in serum and blood. We found only occasional, and perhaps spurious, correlations with zinc, rubidium, and tungsten. In conclusion, previous indications that cadmium, cobalt, and copper are absorbed by transport mechanisms similar to that of Fe are supported by this study. Strong positive correlations between Fe status and mercury concentrations remain to be explained.

Adolescent↗
PubMed2005

Physical activity, energy expenditure and their correlates in two cohorts of Swedish subjects between adolescence and early adulthood.

OBJECTIVE: To assess physical activity and energy expenditure and to identify their correlates during adolescence and early adulthood. DESIGN: In a cohort study, total energy expenditure (TEE) and physical activity level (PAL) were assessed at 15 and 21 y from a 7-day activity diary and predicted BMR. The influences on TEE and PAL of body size, gender, sexual maturity, physical activity habits, sitting time, region, social conditions, employment, food habits, smoking and alcohol intake were examined in multivariate analyses. SUBJECTS: 71 male and 89 female subjects, living in two socioeconomically different regions of Sweden, a university region and an industrial region. SETTING: The university city of Uppsala and the industrial town of Trollhättan. RESULTS: At both 15 and 21 y, PAL and TEE were high, with gender, sitting time and physical activity habits as main correlates. At age 21 y, employment and the mother's educational level also appeared as significant correlates. The relations between the main variables and their correlates were more complex than at age 15 y, and the sitting time was reduced and the activity habits were changed. CONCLUSIONS: A reduction of daily sitting appears to be a major reason why high levels of physical activity and energy expenditure were maintained from 15 to 21 y of age in spite of changed and less frequent activity habits during this interval.

Adolescent↗
PubMed2004

Muscle strength correlates with total body bone mineral density in young women but not in men.

BACKGROUND: Osteoporosis is a growing health problem. One of the proposed reasons for this is a more sedentary lifestyle. The aim of this study was to investigate the associations between muscle strength and total body bone mineral density (TBMD) in young adults at expected peak bone mass. METHODS: Sixty-four women and 61 men (total 125) 21 years of age were included. Handgrip strength, isokinetic knee-flexion and -extension muscle strength, TBMD, and body composition were measured. RESULTS: Univariate regression analyses showed that knee flexion and extension explained almost 30% of the variation in TBMD in women, whereas handgrip strength was not associated with TBMD. In men, no correlation between any measures of muscle strength and TBMD was evident. Stepwise regression analysis showed that knee-flexion and -extension muscle strength in women were associated with TBMD, R2=0.27. In men, lean body mass, fat mass, weight, and height were predictors for TBMD, R2=0.43, whereas muscle strength did not affect the prediction of TBMD. CONCLUSIONS: Muscle strength at weight-bearing sites is related to TBMD in women, whereas body composition is related to TBMD in men. The association of lower limb strength on TBMD only in young women indicates a gender difference.

Adolescent↗
PubMed2004

Glycerol kinase deficiency: follow-up during 20 years, genetics, biochemistry and prognosis.

AIM: To follow two children with isolated glycerol kinase deficiency (GKD) with severe symptoms into adulthood. METHODS: The patients were followed during approximately 20 y and interviewed about symptoms, diet and physical activity. Fasting provocations, bicycle ergometer tests, dietary registrations, enzyme and mutation analysis were performed by standard protocols. RESULTS: The activity of glycerol kinase (GK) in fibroblasts was <10% of reference. One case had a deletion of exon 17, the other a mutation in exon 7 of the GK gene (601 A-->G). Both mothers were heterozygotes. Two maternal male cousins in one of the families were hemizygotes without symptoms. Tests performed in childhood documented pronounced sensitivity to fasting and physical exercise, whereas such tests at 23 and 31 y of age were essentially normal but with pronounced ketonaemia. After puberty, the boys had no hypoglycaemic symptoms and now report no problems with their condition; thus, their phenotype has changed over time. CONCLUSION: The greater importance of glycerol as a gluconeogenetic substrate in children than in adults may explain the episodes in young patients with GKD, often elicited by catabolic stress. With meals at frequent intervals, access to glucose and avoidance of strenuous sports, the prognosis is good for a normal adult life of a young child with isolated GKD and symptoms of hypoglycaemia.

Acetoacetates↗
PubMed2003

Serum ferritin and transferrin receptor concentrations during the transition from adolescence to adulthood in a healthy Swedish population.

AIM: As part of a longitudinal nutrition study of adolescents, changes in serum ferritin (s-Ft), serum transferrin receptors (s-TfR) and the TfR/Ft ratio from 15 to 21 y of age were studied in randomly selected Swedish adolescents. METHODS: Blood samples from 60 males and 66 females were drawn at 15, 17 and 21 y of age. RESULTS: In males, median s-Ft increased significantly from 33 microg l(-1) at 15 y to 96 microg l(-1) at 21 y, and in females, after a non-significant decrease at 17 y, from 27 at 15 y to 34 microg l(-1) at 21 y. Between 15 and 17 y, s-TfR increased significantly, in males from 5.9 to 7.7 microg l(-1), and in females from 5.2 to 7.6 microg l(-1), whereas s-TfR decreased significantly in both genders between 17 and 21 y. The log (TfR/Ft) ratio did not change in males between 15 and 17 y, but decreased significantly from 2.2 +/- 0.3 to 1.8 +/- 0.3 by the age of 21 y. In females, the TfR/Ft ratio increased significantly between 15 and 17 y, whereas a significant decrease was found by the age of 21 y. S-Ft <12 microg l(-1) at 15, 17 and 21 y was 3, 2 and 2% in males, and in females 18, 26 and 21%, respectively. CONCLUSION: This study shows an increase in s-Ft and a decline in s-TfR in males, indicating increased iron stores. In females, s-Ft did not increase significantly, whereas s-TfR and the TfR/Ft ratio decreased between 17 and 21 y, indicating that cellular iron needs were met.

Adolescent↗
PubMed2002

Changes in food habits in healthy Swedish adolescents during the transition from adolescence to adulthood.

OBJECTIVE: To investigate the change in food habits in Swedish adolescents between 15 and 21 y of age with reference to age, sex, region and socioeconomic background. DESIGN: A longitudinal study from 1993 to 1999. SETTING: Two different regions in Sweden, the university city of Uppsala and the industrial town of Trollhättan. SUBJECTS: On three different occasions, 1993, 1995 and 1999, 208 adolescents, 96 males and 112 females, were studied. METHODS: A food frequency questionnaire containing 29 different food groups was used. The questionnaire also contained questions about food habits and amounts of some food items and socioeconomic conditions of the participants and their families. RESULTS: At 17 and 21 y of age, the adolescents consumed significantly more often pasta, vegetables, coffee and tea compared to age 15, while the frequency consumption of fat spread, milk, bread, potatoes, carrots and buns and biscuits decreased. The changes between 15 and 17 were smaller than between age 17 and 21. At age 21, the males decreased their intake of fruit, while the females decreased their intake of meat. No-meat consumers among females increased from 2 to 13%. Higher educational level of the mothers of the adolescents was associated with more frequent consumption of vegetables and pasta between ages 17 and 21. Milk consumption decreased significantly in both sexes. Breakfast habits did not change: 90% had breakfast five times/week or more. CONCLUSIONS: Food habits change significantly during adolescence along with lifestyle changes. Therefore, health promotion during adolescence ought to be more supported by the society.

Adolescent↗
PubMed2002

Whole-body mineral measurements in Swedish adolescents at 17 years compared to 15 years of age.

AIM: To provide reference data for bone mineral variables in 15- and 17-y-old adolescents and to analyse the relationships between these variables and measures of bone and body size, gender, puberty, growth, various lifestyle and environmental factors and socioeconomic background. METHODS: In the same 321 randomly selected adolescents (147 boys and 174 girls) living in two different regions of Sweden, the total bone mineral content (TBMC), bone area (BA) and total bone mineral density (TBMD) were assessed by dual-energy X-ray absorptiometry at ages 15 and 17 y. The effects of bone and body size, gender, growth, sexual maturity, physical activity, region of domicile, social conditions, food habits, smoking and alcohol intake on TBMC and TBMD were examined in multivariate analyses. RESULTS: In the 15-y-old adolescents, BA, height, gender, physical activity, maturity and weight explained 91% and 48%, of the variance in TBMC and TBMD, respectively. In similar analyses in the 17-y-olds, the corresponding figures were 92% and 62%, respectively, when BA, height, growth, physical activity, gender and region emerged as significant in the model. In all these analyses, BA explained most of the variance in TBMC and TBMD. No significant reduction of variance was found when different measures of social conditions, smoking, food habits, alcohol or dietary intakes of energy, calcium or vitamin D were included in the models. The reason why region of domicile had a significant impact on TBMC in the 17-y-olds is not known. The fact that the normal fluoride concentration in drinking water (1.1 mg/L) is 10 times higher in the region where TBMC was higher than in the other region is an interesting observation. CONCLUSION: Almost 90% of the variance in TBMC and 50% of that in TBMD was explained by measures of bone and body size and only a few percent by gender, physical activity, Tanner stage, growth and region of domicile.

Adolescent↗
PubMed2001

Dietary fat intake in healthy adolescents: inverse relationships between the estimated intake of saturated fatty acids and serum cholesterol.

The objective of the present study was to describe the intake of dietary fatty acids among healthy 15-year-old boys and girls and to relate the intake of specific fatty acids and the fatty acid composition of the serum cholesterol esters to serum lipid, apolipoprotein (Apo) and insulin concentrations respectively. Fifty-two girls and forty-two boys were randomly selected from the official population register. Unexpectedly, significant inverse associations were found between the dietary content of saturated fatty acids with a chain length of four to fifteen C atoms, mainly derived from milk fat, as well as the corresponding fatty acids in the serum cholesterol esters, on the one hand and the serum concentrations of cholesterol and ApoB on the other. The estimated dietary intake of 4:0-10:0, 12:0 and 14:0 respectively, were all significantly inversely related to the serum cholesterol (r -0.32, r -0.31, r -0.30, all and ApoB (r -0.42, r -0.42, and r -0.40, all concentrations in girls and 12:0 to the ApoB concentration (r -0.55, in boys. The proportions of 12:0 and 15:0 in the serum cholesterol esters were negatively correlated with the serum cholesterol concentrations in both girls (r -0.34, r -0.32, and boys (r -0.53, r -0.32, and with the ApoB concentrations among boys (r -0.61, r -0.43, It is conceivable that milk fat contains or is associated with some component in the diet, or some other characteristics of the food intake, which counterbalances the expected positive relationships between saturated fat intake and lipid levels.

Adolescent↗
PubMed2001

Cosmic radiation measurements on-board aircraft with the variance method.

The microdosimetric variance-covariance method has been used for cosmic radiation measurements on-board aircraft. Two independent methods of data analysis are presented; the first based on a high energy neutron calibration and the second on identification of single high LET events in the measured multiple event spectrum. Reduced dose levels at high geomagnetic latitudes are observed on one flight in a period of enhanced solar activity as indicated by a reduced ground-level neutron fluence rate. It is shown that with a reduced 137Cs-calibration factor, a Geiger-Mueller tube can be used as a low LET monitor, and that the wall thickness of a tissue-equivalent proportional counter is not crucial for flight measurements. No covariance is observed on any flight indicating it is sufficient to base dose determinations on variance measurements with only one detector. The uncertainties involved are also discussed in some detail.

Aircraft↗
PubMed2001

The response of the sievert instrument in neutron beams up to 180 MeV.

Measurements with a tissue-equivalent proportional counter (TEPC) using the variance-covariance method have been performed in neutron beams between 71 keV and 180 MeV and in the cosmic radiation reference field (CERF) at CERN. The results show that with appropriate linear QD(yD) relations, the ambient dose equivalent can be determined within about 55% in these beams. Build-up measurements show that wall thickness is not crucial for H* determinations at 60 and 180 MeV.

Brachytherapy↗
PubMed2000

Dietary habits and nutritional status in adolescents over Europe. An overview of current studies in the Nordic countries.

OBJECTIVE: To give an overview of the dietary habits among adolescents in the Nordic countries and to present results from studies showing the relationship between dietary habits and other lifestyle factors, nutritional status and socio-economic conditions. DESIGN: A number of nutritional studies among adolescents performed during recent decades using recalls, dietary records and food frequency questionnaire. SETTING: Denmark, Finland, Norway and Sweden. SUBJECTS: Adolescents aged 13-18 y. RESULTS: Food habits are characterized by an irregular meal pattern; many adolescents skip breakfast and also the school lunch, whereas most of them have dinner. However, snacking and light meals are very common, contributing 25-35% of the daily energy intake. Smoking is linked to their dietary habits as well as socio-economic conditions. Dietary intakes of vitamins and minerals are adequate for normal health and growth. Dietary calcium intake is high, whereas the intake of fibre, vitamin D, zinc and selenium and, in girls, iron is below the Nordic recommendations. Relatively low prevalence figures of iron deficiency were found. Many studies show a decrease over time in physical activity. The time spent in sedentary activities, such as television and video watching and computer games has increased during recent decades. CONCLUSION: Overweight and obesity are becoming more prevalent in all the Nordic countries, even though the prevalence figures are far below those in the USA. On the other hand, dieting girls are common, which might be a factor behind their irregular meal pattern and food choice. In a perspective, overweight and diseases attributable to obesity will be an immense challenge in the coming decades for both the individuals and the society as well.

Adolescent↗
PubMed2000

A follow-up study of serum ferritin and transferrin receptor concentrations in Swedish adolescents at age 17 age 15.

UNLABELLED: Serum ferritin and serum transferrin receptor concentrations, growth and food habits were studied in healthy Swedish boys (n = 103) and girls (n = 124) at the age of 17 y and compared with those in the same adolescents at age 15. Between these ages, serum transferrin receptor increased significantly in both boys and girls. Serum ferritin increased significantly in boys but not in girls. The transferrin receptor/ferritin ratio increased significantly in girls but not in boys, indicating insufficient iron stores in the 17-y-old girls in relation to erythropoiesis and iron needs. Between 15 and 17 y the boys' frequency of consumption of milk and bread decreased, while they more often consumed pasta, cheese and coffee. The girls decreased their frequency intake of fat products, milk and meat. The frequency of meat consumption emerged as the single significant predictor for serum ferritin <12 microg/L in girls, but not in boys. The median daily iron intake, determined in a subsample, decreased in boys from 18.7 to 13.6 mg and in girls from 14.1 to 8.8 mg, and the decrease was to a large extent due to cessation of iron fortification of flour. CONCLUSIONS: The results indicate insufficient iron stores in the 17-y-old girls in relation to erythropoiesis and iron needs, but more favourable iron stores in the boys. The absence of a significant decrease in mean serum ferritin despite rapid growth suggests that the earlier iron fortification of flour only marginally contributed to the iron status of Swedish adolescents of this age group.

Adolescent↗
PubMed1999

[The AD-drops can be replaced by D-drops].

Since 1932, when vitamin A and D supplementation, in the form of cod liver oil, was introduced in Sweden, rickets has been a rare diagnosis among Swedish infants. In 1978, the National Board of Health and Welfare issued recommendations of daily supplementation with 300 micrograms (1000 IU) of vitamin A and 10 micrograms (400 IU) of vitamin D. This has recently been under review by the Paediatric Committee on Nutrition and Health, of the Swedish Paediatric Association and the National Food Administration, who concluded that there is no reason to retain vitamin A supplementation, but that vitamin D supplementation should continue to be recommended at the same daily dose (400 IU).

Child, Preschool↗
PubMed1999

[Recommendations for prevention of iron deficiency. Delay cow's milk intake as a beverage to infants until 10-12 months of age!].

Breast-feeding is to be encouraged during the first six months of life. Iron deficiency is extremely rare in exclusively breast-fed infants during this period. Any cow-milk based formula used should be iron-fortified. During the second half of infancy, the iron content of weaning foods is important in preventing iron deficiency. Indeed, owing to the low iron content of dairy products, it is hard to compose a weaning diet sufficiently rich in iron to meet the demands of rapidly growing infants, if it is to include substantial amounts of cow milk, sour milk or yoghurt. Accordingly, the Paediatric Committee on Nutrition and Health, of the Swedish Paediatric Association and the National Food Administration, recommend delaying the introduction of cow's milk and cow-milk products until the infant is 10-12 months of age. Until then, breast-feeding, and the use of iron-fortified formula or gruel with modified protein and sodium content are encouraged; iron-fortified porridges of softer consistency can be prepared to circumvent the need of extra fluids, or porridge can be served with breast milk or iron-fortified formula; small amounts of milk may be used for cooking purposes.

Animals↗
PubMed1999

Whole-body bone mineral measurements in 15-year-old Swedish adolescents.

Bone mineral area (BA), total bone mineral content (TBMC) and total bone mineral density (TBMD) were assessed by dual-energy X-ray absorptiometry (DXA) in 396 randomly selected, healthy 15-year-old Swedish boys and girls. The influence of body size, pubertal development, physical activity level (PAL), total energy expenditure (TEE), dietary intake of energy, calcium and vitamin D, and alcohol and smoking habits on TBMC and TBMD were examined in bi- and multivariate analyses. In bivariate analyses BA, TBMC and TBMD showed strong correlations with weight, height and TEE in both sexes. In boys but not in girls these bone variables were significantly correlated with dietary intakes of energy, calcium and vitamin D. No significant correlations were found between PAL and the three bone variables. In multivariate analyses with TBMC as dependent variable BA, height, weight and Tanner stages explained 88% and 87% of the variance in boys and girls respectively. In similar analyses with TBMD as dependent variable the corresponding figures were 50% and 54%. The major part of the variance in all these models was explained by BA, and only a few percent by all the other independent variables. No significant reduction was found when TEE or daily intakes of calcium or vitamin D were introduced into the models. These results illustrate the importance of including BA, weight and height as independent variables in regression models of TBMC to avoid spurious associations with other variables in the analyses. The results may also indicate that in normal Swedish adolescents environmental factors such as dietary intake of nutrients play a minor role as determinants of bone mineralization. High levels of physical activity and bone mineral measures possibly explain the lack of significant correlations between these variables and do not imply a lack of association.

Absorptiometry, Photon↗
PubMed1999

Differences in whole body measurements by DXA-scanning using two Lunar DPX-L machines.

OBJECTIVE: To compare bone mineral and body composition results of two dual-energy X-ray absorptiometry (DXA) instruments from the same manufacturer. SETTINGS: The Medical departments of Sahlgrenska University Hospital, Göteborg and University Hospital, Uppsala, Sweden. DESIGN: Unique aluminium spine phantoms (Phant A and B) delivered with each DXA machine (DXA-A and DXA-B) were cross-checked on the other machine by using the 'AP spine mode'. Eight adolescents were examined on both instruments within 5 h to ascertain total body variables by using standard, as well as extended, modes of analysis. All these double-examinations were undertaken on two occasions, before and after exchange of a detector on the DXA-B. SUBJECTS: Four males and four females aged 15.4-19.2 y with normal body weights, were examined on both occasions. On each occasion, the first examination was performed in Göteborg on four individuals and in Uppsala on four individuals. RESULTS: On the first occasion the phantom measurements resulted in much lower bone mineral density (BMD) values on the DXA-B than on the DXA-A. Later it was detected that a so-called R-value and the corresponding '%-fat' value were out of range on the DXA-B. After exchange of detector, the difference in phantom BMD-values between the two machines had diminished. On the first occasion in vivo BMD values were lowest on the DXA-B (P < 0.01), while on the second occasion they were significantly lower on the DXA-A (P < 0.05). Soft tissue differences were greater after detector exchange and as compared to DXA-A, DXA-B underestimated body fat by 3.5 kg (13.2 vs 9.7 kg, P < 0.001) and overestimated lean tissue mass by 3.8 kg (47.1 vs 50.9 kg, P < 0.001) on the second occasion. CONCLUSIONS: The differences in results between two apparently identical Lunar DPX-L machines were not acceptable. In multicenter studies, it may be necessary to standardise results of participating machines into results of one machine by means of regression equations obtained by examining subsamples of individuals on one master machine and other participating instruments.

Absorptiometry, Photon↗
PubMed1998

Ultrastructural, physiological, and molecular defects in the inner ear of a gene-knockout mouse model for autosomal Alport syndrome.

The cochleae from a COL4A3-deficient mouse line were examined for defects that might shed light on the molecular mechanism of otopathology observed in humans with Alport syndrome. At the light microscopic level no obvious defects were observed. Immunohistochemical analysis using antibodies specific for the basement membrane collagen chains revealed the absence of the COL4A3 and COL4A4 chains throughout the membranous labyrinth. The COL4A5 chain was absent from all cochlear basement membranes except those in the vessels of the stria vascularis. Expression of the COL4A1 and COL4A2 chains was unchanged in the mutant. Electron microscopic examination of the cochlear basement membranes revealed significant thinning of the basement membrane running from the spiral limbus, down the inner sulcus, across the basilar membrane and up to the spiral prominence. Basement membranes that normally ensheathe the root cells were not detectable. In contrast, the basement membranes surrounding the vessels of the stria vascularis were significantly thickened in the mutant. This was associated with endothelial cell swelling and a marked decrease in internal capillary diameter. In severe cases, pathology was observed in the marginal cells with a loss of basolateral infoldings. Immunohistochemical analysis of the strial vessels revealed an increase in entactin and collagen COL4A1 and COL4A2 chains. Auditory-evoked brainstem response measurements suggest a small increase in thresholds across all frequencies when successive measurements on individual mutant mice were examined between 6 and 8 postnatal weeks. Combined, these results illustrate changes in the basement membranes of the strial vessels that bear resemblance to Alport glomerular basement membrane pathology. A closer look at this compartment in human Alport biopsy specimen may be warranted.

Animals↗