Biomedical subjects

J Snel

Publications and source records attributed to J Snel.

At least 19 recordsLinked to original sources

PubMed2005

Cross-sectional and longitudinal relationships between alcohol consumption and lipids, blood pressure and body weight indices.

OBJECTIVE: Serum lipids, blood pressure and body mass may mediate the U-shaped relationship of alcohol consumption with type 2 diabetes mellitus and coronary heart disease. This study examines the cross-sectional and long-term longitudinal relationships of (changes in) alcohol consumption with (changes in) serum lipids, blood pressure and body mass indices. METHOD: In this prospective, observational cohort study, two measurements of alcohol consumption, serum total and high-density lipoprotein cholesterol, triglycerides, blood pressure, body weight, the thickness of four skinfolds and waist circumference were performed 4 years apart in healthy volunteers (143 men and 174 women, 32 years old at the first measurement). Alcohol consumption from beer, wine and distilled spirits was assessed using an extensive dietary history interview. Linear regression analyses were performed to study the cross-sectional relationships between the amount of alcohol consumed at the age of 32 years and the levels of the lipids, blood pressure and body weight indices, and to study the longitudinal relationships between the changes in the amount of alcohol consumed over the 4 years of follow-up and the concurrent changes in the lipids, blood pressure and body weight indices. Nonlinearity was investigated for the cross-sectional relationships. RESULTS: A 10-g/day difference in alcohol consumption was positively related with a 0.05 mmol/L (1.9 mg/dl) difference in high-density lipoprotein cholesterol in both cross-sectional (p = .004), and longitudinal (p < .0001) analyses. This relationship did not differ for men and women or for the consumption of beer, wine or distilled spirits. Relationships with changes in total cholesterol, triglycerides, systolic, diastolic, and pulse pressure, body weight and the sum of four skinfolds were not significant. A borderline significant inverse longitudinal relationship was found with waist circumference. The other lifestyle behaviors (tobacco smoking, physical activity and dietary habits) were major confounders of most cross-sectional relationships between alcohol and serum lipids, blood pressure and body mass indices. The longitudinal relationships, however, were not confounded by changes in the other lifestyle behaviors. A significant nonlinear relationship was found for systolic blood pressure, in which drinkers of about 30 g/day had the lowest values. CONCLUSIONS: Moderate alcohol consumption and moderate long-term changes in alcohol consumption are positively related with the levels and changes in high-density lipoprotein cholesterol in healthy adult men and women. A moderate inverse association between alcohol and waist circumference may be expected. No relationships were found with triglycerides, blood pressure, body weight and the sum of the thickness of four skinfolds. Other lifestyle behaviors confound the cross-sectional, but not the longitudinal, relationships between alcohol consumption and serum lipids, blood pressure and body mass indices. Gender and type of beverage do not modify the relationships between alcohol consumption and these indices.

Adult↗

PubMed2002

Comparison of faecal Lactobacillus populations in experimental animals from different breeding facilities and possible consequences for probiotic studies.

AIMS: The effect of probiotic lactobacilli is likely dependent on the indigenous Lactobacillus strains in the intestinal tract. Since a substantial number of probiotic studies is performed in rodents, we compared the Lactobacillus strains of different rat and mouse populations in three animal facilities. METHODS AND RESULTS: SDS-PAGE and 16S rDNA analysis of cultured faecal lactobacilli revealed that different Lactobacillus strains were detected in genetically similar Wistar rats bred at different locations. Further, within the same animal facility host genetics did not affect the types of the predominant lactobacilli strains. CONCLUSIONS: Our results show that the environmental background of laboratory animals rather than host genetics determines the indigenous Lactobacillus strains that are found. SIGNIFICANCE AND IMPACT OF THE STUDY: Our findings underline the importance of microflora analysis in probiotic studies.

Animals↗

PubMed2001

Is calculating pack-years retrospectively a valid method to estimate life-time tobacco smoking? A comparison between prospectively calculated pack-years and retrospectively calculated pack-years.

AIMS: To investigate the relative validity of retrospectively calculated pack-years (py-retro) by comparing py-retro with prospectively calculated pack-years (py-pro). DESIGN: A 23-year ongoing cohort study (1977-2000). PARTICIPANTS: One hundred and fifty-four males and females, 13 years old in 1977 and 36 years old in 2000. SETTING: Amsterdam, the Netherlands. MEASUREMENTS: To calculate py-pro, current smoking and quitting efforts were investigated nine times in a period of 23 years with the help of an interview or a questionnaire. At the age of 36, subjects filled out a comprehensive questionnaire about their smoking history, to calculate py-retro. Individual differences between py-pro and py-retro were calculated. In addition, Cohen's kappa was calculated after categorising py-pro and py-retro into three groups. FINDINGS: (1) Py-retro does not under- or overestimate life-time tobacco smoking. (2) The relative validity of py-retro was moderate due to large individual differences between py-pro and py-retro. (3) The individual differences between py-pro and py-retro became larger, the higher the number of pack-years. (4) Mean difference (and 95% limits of agreement) between py-pro and py-retro was -0.039 (-5.23, 5.32) when average pack-years was < 5.2 and -1.17 (-10.00, 14.65) when pack-years > or = 5.2. 5. Cohen's kappa between categorized py-pro and py-retro was 0.79. CONCLUSIONS: Future researchers in the field of smoking should be aware of the moderate relative validity of py-retro. Categorizing py-retro into smoking groups results in a misclassification error that is smaller than the quantitative error in continuous py-retro, but goes together with a loss of information.

Adolescent↗

PubMed2001

Enhanced antigen-specific delayed-type hypersensitivity and immunoglobulin G2b responses after oral administration of viable Lactobacillus casei YIT9029 in Wistar and Brown Norway rats.

In this study, the effects of orally administered viable Lactobacillus casei Shirota strain YIT9029 on the immunity parameters of Wistar and Brown Norway rats were examined. For this purpose, we used the Trichinella spiralis host resistance model. Two weeks before and during T. spiralis infection, rats were fed 10(9) viable L. casei bacteria 5 days per week. The T. spiralis-specific delayed-type hypersensitivity (DTH) response was significantly enhanced in both Wistar and Brown Norway rats given L. casei. In both rat strains fed L. casei, serum T. spiralis-specific immunoglobulin G2b (IgG2b) concentrations were also significantly increased. In the model, no significant effects of L. casei on larval counts or inflammatory reactions in the tongue musculature, body weights, or lymphoid organ weights were observed. Serum specific antibody responses, other than IgG2b, were not changed by feeding of L. casei. In contrast to L. casei, it was shown that orally administered Bifidobacterium breve or Bifidobacterium bifidum had no influence on the measured infection and immunity indices in the rat infection model. Since the rat DTH response is considered to be a manifestation of Th1 cell-mediated immunity and the IgG2b isotype has been associated with Th1 activity, it was concluded that Th1 cells could play an active role in the immunomodulatory effects of orally administered L. casei. Furthermore, our data do not indicate that the effect of oral supplementation with L. casei is dependent on the genetic background of the host.

Actinomycetales Infections↗

PubMed2001

Personality characteristics and alcohol consumption: longitudinal analyses in men and women followed from ages 13 to 32.

OBJECTIVE: The purpose of the present study was to investigate the relation between personality characteristics and alcohol consumption. Using a general population of young and generally healthy men and women, the focus was not on alcoholism but on the full scope of alcohol consumption, including abstinence and moderate levels of consumption. Modification of the relation between personality and alcohol consumption by gender, age and type of beverage was investigated. METHOD: The population consisted of 483 (259 female) subjects from the Amsterdam Growth and Health Longitudinal Study; they were aged 13 to 32 years over the 20-year course of the study, during which span measurements were taken between two and seven times. The longitudinal relation between five subscales of the Dutch Personality Inventory (DPI) and alcohol consumption were assessed with generalized estimating equations. RESULTS: Low prevalence of heavy alcohol consumption was found in this population. Abstinence from alcohol was more common among subjects who scored higher on Social Inadequacy, Rigidity and Self-sufficiency subscales. The amount of alcohol consumed was higher in drinkers who scored low on Rigidity and Social Inadequacy. Gender, age and type of alcoholic beverage modified some of the found relationships (e.g., adult women who scored high on Dominance were more likely to be the firmer wine drinkers). No significant relationships were found between alcohol consumption and the DPI Inadequacy subscale. CONCLUSIONS: Alcohol consumption was associated with lower scores on Social Inadequacy, Rigidity and Self-sufficiency.

Adolescent↗

PubMed2000

Efficiency of light utilization of Chlamydomonas reinhardtii under medium-duration light/dark cycles.

The light regime inside a photobioreactor is characterized by a light gradient with full (sun)light at the light-exposed surface and darkness in the interior of the bioreactor. Consequently, depending on the mixing characteristics, algae will be exposed to certain light/dark cycles. In this study the green alga Chlamydomonas reinhardtii was cultivated under five different light regimes: (1) continuous illumination; (2) a square-wave light/dark cycle with a light fraction (epsilon) of 0.5 and a duration (t(c)) of 6.1 s; (3) epsilon=0.5, t(c)=14.5 s; (4) epsilon=0.5, t(c)=24.3 s and (5) epsilon=0.8, t(c)=15.2 s. The biomass yield on light energy, protein per photons, decreased under light/dark cycles (epsilon=0. 5) in comparison to continuous light (CL), from 0.207 (CL) to 0.117-0.153 g mol(-1) (epsilon=0.5). Concomitantly, the maximal specific photosynthetic activity, oxygen production per protein, decreased from 0.94 (CL) to 0.64-0.66 g g(-1) h(-1) (epsilon=0.5). Also the quantum yield of photochemistry, yield of the conversion of light energy into chemical energy, decreased from 0.47 (CL) to 0. 23 (epsilon=0.5, t(c)=24.3 s). Apparently, C. reinhardtii is not able to maintain a high photosynthetic capacity under medium-duration light/dark cycles and since specific light absorption did not change, light utilization efficiency decreased in comparison to continuous illumination.

Animals↗

PubMed2000

Positive and negative life events: the relationship with coronary heart disease risk factors in young adults.

OBJECTIVE: to investigate the influence of positive and negative life events (including daily uplifts and daily hassles) on several biological and lifestyle coronary heart disease (CHD) risk factors. METHODS: from the Amsterdam Growth and Health Longitudinal Study (AGHLS), a cross-section sample of 207 males and 231 females aged 32/33 years was used. RESULTS: hardly any associations were found between both positive and negative life events and biological CHD risk factors. On the other hand, daily uplifts and positive life events were positively related to lifestyle. For both positive and negative life events coping behaviour played a role in these relationships. Furthermore, it was shown that the associations of health-related variables with daily uplifts and hassles were comparable to those found for major positive and negative life events. CONCLUSION: This study could not fully determine whether or not different mechanisms play a role in the health benefits of positive life events compared to the health burdens of negative life events.

Adaptation, Psychological↗

PubMed2000

Blood cholesterol levels of 32-year-old alcohol consumers are better than of nonconsumers.

Blood cholesterol levels are expected to be important factors in the causal pathway between alcohol consumption and CHD. The relation between alcohol consumption and blood cholesterol levels is investigated in 130 men and 145 women aged 32.4 years old (+/-1.0), from the Amsterdam Growth and Health Longitudinal Study. When controlled for gender, cholesterol levels at age 13.1 years, and lifestyle at adult age (smoking, physical activity, dietary habits), no significant differences were found for total cholesterol (TC) levels between alcohol consumers and nonconsumers. Serum high-density lipoprotein (HDL) cholesterol levels were 0.12 mmol/l higher in subjects consuming >/=100 grams of alcohol per week than in nonconsumers (p < 0.05). Regression coefficients of subjects consuming 10 to 50, or 50 to 100 g alcohol per week did not differ statistically from those of nonconsumers. The positive relation between alcohol consumption and serum HDL was modified by smoking (found in nonsmokers, but not in smokers). No differences between beer, wine, and spirits were found for their relation with serum HDL. In conclusion, 32.4-year-old nonsmoking subjects who consumed >/=100 g of alcohol per week had improved HDL levels compared with nonconsumers, whereas the protective effect of drinking smaller amounts of alcohol did not reach statistical significance.

Adult↗

PubMed2000

The influence of caffeine on sustained attention: an ERP study.

The present study investigated the effects of caffeine on sustained attention by measuring concentration and fatigue. Event-related potentials (ERPs) and behavioral measures were recorded from 12 participants who worked continuously for approximately 10 min in a self-paced reaction task under conditions of both caffeine (250 mg) and placebo. The ERP data revealed more positive frontal P2 and parietal P3 components in the caffeine condition. However, a combination of different indices of the behavioral data did not reveal any effects of caffeine intake. These results suggest that caffeine increases arousal, thereby reducing fatigue, as was observed in the ERP results. A probable explanation for the absence of any effects of caffeine in the behavioral data can be found in the demanding properties of the task that was used, thereby supporting evidence for more pronounced effects of caffeine in suboptimal conditions. In addition, these results appeal for an increase in the use of ERPs in drug research, in order to discover possible effects on the brain which do not necessarily result in behavioral changes.

Adult↗

PubMed2000

The influence of caffeine on spatial-selective attention: an event-related potential study.

OBJECTIVES: Following the indications of previous studies that caffeine might have a specific effect on the processing of spatial information compared with other types of information, the present study investigated the influence of caffeine on an often used spatial-selective attention task. METHODS: Event-related potentials (ERPs) were recorded from 11 participants under conditions of caffeine (250 mg) and placebo. RESULTS: Spatial-selective attention effects were reflected in the ERPs as more positive going occipital P1 and broadly distributed P2 components, and more negative going occipital-temporal N1 and broadly distributed N2 components. A treatment effect was found as a more positive going frontal P2 component in the caffeine condition, whereas interactions between treatment and attention were observed for P2 and N2 components, but not for P1 and N1 components. CONCLUSIONS: This pattern of results suggests that caffeine has no specific influence on spatial-selective attention, but rather, has a more general facilitating effect on perceptual processing, as well as a possible effect on the frontal control mechanisms, i.e. focusing attention and increasing selectivity.

Adult↗

PubMed2000

Physical activity of young people: the Amsterdam Longitudinal Growth and Health Study.

PURPOSE: To describe the natural development of habitual physical activity behavior (HPA) of young Dutch male and female subjects between the ages of 13 and 27, using data from the Amsterdam Longitudinal Growth and Health Study. METHODS: HPA was measured by means of a structured interview at ages 13, 14, 15, 16, 21, and 27 and concerned all activities (at work, school, during leisure, organized and nonorganized sports, and active transportation) exceeding a level of intensity of 4 METs. Complete longitudinal data concern 98 female and 83 male subjects. MANOVA for repeated measurements were done for total HPA (expressed in min x wk(-1) and in METs x wk(-1)). Similar analyses were done for organized sports activities, leisure time activities, and all "other" activities separately (also min x wk(-1) and METs x wk(-1)), as well as for weekly time at three different levels of intensity of HPA, i.e. 4-7 MET (moderate), 7-10 MET (vigorous), and >10 MET (very vigorous). RESULTS: Our data showed regarding total HPA (min x wk(-1)) in male, but not in female, subjects a significant decrease in weekly time spent on HPA between the ages of 13 and 27. Regarding the three different levels of intensity in male and female subjects, a significant increase was found in time spent on moderate activities, where female subjects were spending significantly more time on moderate activities than male subjects; both in male and female subjects, a significant decrease was found in time spent on vigorous activities: in male subjects a significant decrease was found in time spent on very vigorous activities, whereas in female subjects time spent at this level of activity remained more or less stable. For the total weighted activity score (METs x wk(-1)), a significant decrease was found for both male (42%) and female subjects (17%). This decrease was significantly greater for male than for female subjects. Regarding more specific activities, it was found that in the course of time organized sports activities became relatively more important contributors to both weekly HPA time and energy expenditure, both in male and female subjects. CONCLUSIONS: Our data show a considerable decrease in HPA over a 15-yr period of time, both in male and female subjects. Differences between male and female subjects are predominantly caused by differences in time spent in moderate and very vigorous activities. In the course of time, organized sports activities became a relatively more important contributor of weekly HPA.

Adolescent↗

PubMed2000

Transmission electron microscopic demonstration of phagocytosis and intracellular processing of segmented filamentous bacteria by intestinal epithelial cells of the chick ileum.

Segmented filamentous bacteria (SFB) are autochthonous bacteria colonizing the ileum of many young animals by attaching to intestinal epithelial cells. These nonpathogenic bacteria strongly stimulate the mucosal immune system and induce intestinal epithelial cells to express major histocompatibility complex class II molecules. We tried to discover whether SFB are phagocytized and intracellularly processed by the host cells, which is indicative of antigen processing. The middle part of the ileum was extracted from 10- and 20-day-old broiler chicks (Gallus gallus domesticus). Samples were processed and examined by scanning and transmission electron microscopy (SEM and TEM, respectively). In SEM, no, few, medium, and dense SFB colonization levels were classified. In TEM of cells from animals with medium or dense SFB colonization levels, we could observe extracellular particles ranging from those only indenting the cell membrane to particles found in the cytoplasmatic area beyond the terminal web. These particles had a structural similarity with SFB that were floating freely in the intestinal lumen. Furthermore, we observed unlacing of the membrane and septum surrounding the extracellular particles and their incorporation into host cytoplasmatic components, which strongly suggests that these particles are phagocytized and intracellularly processed SFB. This conclusion is supported by TEM analysis of samples with no or few SFB, in which we failed to find these characteristic morphologies. The phagocytosis process described here could be an important trigger for the stimulating effect of SFB on the mucosal immune system.

Animals↗

PubMed2000

Development and stability of alcohol consumption from adolescence into adulthood: the Amsterdam Growth and Health Longitudinal Study.

When studying long-term effects of alcohol consumption on health, the stability of alcohol consumption should be known. In this paper the development and stability of alcohol consumption were investigated. Seven measurements of alcohol consumption were carried out over a period of 20 years, starting at age 13 years, in a cohort of 65 men and 85 women. Effects of age, gender, and type of beverage on the stability of drinking as a dichotomous variable (drink or abstain) and on the stability of relative amounts of alcohol consumption were analyzed. The stability of the drink/abstain dichotomy was high (odds ratios>4) and increased with age. The stability of relative amounts of alcohol consumption was moderate (rS<0.6), and no effect of age was found. No sex effects were found, while the consumption of beer often showed higher stability than that of wine and spirits.

Adolescent↗

PubMed2000

The effects of caffeine on visual selective attention to color: an ERP study.

Event-related potentials were recorded from 11 subjects after ingesting caffeine (250 mg) or placebo. Subjects were instructed to attend selectively to stimuli with a specified color (red or blue) in order to react to the occurrence of a target within the attended category. Reaction times revealed faster responses for the caffeine condition, whereas no differences in strategy were observed. Color attention effects were identified as frontal selection positivity, occipital selection negativity, and N2b, whereas target detection was reflected in P3b. Effects of treatment were found as a more positive-going frontal P2 component in the caffeine condition. In addition, an interaction between attention and treatment could be observed on the N2b component. This pattern of results suggests that caffeine yields a higher overall arousal level, more profound processing of both attended and unattended information, and an acceleration of motor processes.

Adult↗

PubMed1999

Changes in daily hassles and life events and the relationship with coronary heart disease risk factors: a 2-year longitudinal study in 27-29-year-old males and females.

To investigate the relationship between changes in daily hassles and life events and biological (lipoproteins, blood pressure, body fat, and body fat distribution) and lifestyle (physical activity, smoking and alcohol consumption) risk factors for coronary heart disease (CHD) 166 subjects were measured twice, at 27 and 29 years of age. The results showed that changes in daily hassles were positively related to changes in lipoprotein levels, daily physical activity, and to smoking behavior. These relationships were more pronounced for subjects with a "rigid" coping style and subjects with type A behavior. Changes in life events were also positively related to lipoprotein levels, but only for subjects with a "rigid" coping style and only when the subjective appraisal of life events was taken into account. It was concluded that the relationships seemed to be mediated by different coping styles and type A behavior, that daily hassles were more important in these relationships than life events, and that the relationships with biological CHD risk factors were not influenced by lifestyle.

Adaptation, Psychological↗

PubMed1999

Longitudinal relationships between lifestyle and cardiovascular and bone health status indicators in males and females between 13 and 27 years of age; a review of findings from the Amsterdam Growth and Health Longitudinal Study.

UNLABELLED: The Amsterdam Growth and Health Longitudinal Study is longitudinal co-hort study on 181 males and females initially aged 13 years, with follow-up measurements at ages 14, 15, 16, 21 and 27 years. METHODS: Anthropometrical, biological and lifestyle parameters, and age 27 also bone mineral density (BMD) of the lumbar spine (L2-L4), were measured repeatedly. Adolescent dietary intake and physical activity was related to adult cardiovascular and bone health status indicators by MLR; longitudinal relationships between physical activity and dietary intake, and cardiovascular health status indicators were assessed hy GEE-analysis. RESULTS: Adolescent physical activity was not related to most of the indicators of adult cardiovascular health status, with the exception of a positive relationship with the waist-to-hip in females; in males 'energetic' adolescent physical activity contributed significantly to adult BMD; both in males and females, when taking the entire longitudinal period into account, peak strain physical activity was a relatively more important predictor of adult BMD than 'energetic' physical activity; calcium intake during adolescence was not a significant predictor of bone health status measured at age 27, both in males and females; a consistent significant positive longitudinal relationship was found between physical activity and serum HDL-cholesterol and significant negative longitudinal relationships were found with the subscapular skinfold and with body fat mass; a positive longitudinal relationship was found between serum total cholesterol (TC) and cholesterol intake, saturated fat (SFA) intake and the Keys-score; a negative longitudinal relationship was found between TC and polyunsaturated fit and total energy intake; for HDL a positive longitudinal relationship was found with SFA intake; low tracking was found for physical (in-) activity and dietary intake variables.

Adolescent↗

PubMed1998

Overview of gut flora and probiotics.

Scientific developments in recent years have opened new frontiers and enable a better understanding of the gastrointestinal tract (GIT) as a complex and delicately balanced ecosystem. This paper focuses on more recent information related to the microbial population of the GIT and its functional role in human physiology and health. Special attention is also given to modern approaches for improving or stabilising the intestinal system and its functioning by the deliberate application of viable microbial cultures, so-called 'probiotics', selected for special functional properties.

Bacterial Physiological Phenomena↗

PubMed1998

P3 scalp topography to target and novel visual stimuli in children of alcoholics.

The P3 event-related potential (ERP) component was recorded from 7- to 18-year-old children of alcoholics (COAs, n = 50) and age- and sex-matched control children (n = 50) using a visual oddball paradigm, involving nontarget (76%), target (12%), and novel (12%) stimuli. Topographic maps of P3 and associated scalp current density were obtained to supplement a topographic profile analysis. COAs manifested a smaller amplitude P3 to target stimuli over the centroparietal, parietal, and occipital scalp locations than controls. Also, COAs exhibited a smaller amplitude P3 to novel stimuli over the occipital scalp than controls. There were no significant differences between COAs and controls in the P3 scalp topography, indicating that differences in intracranial source strength rather than in source configuration were responsible for the between-group amplitude differences. Also, no significant group differences were observed in the P3 peak latency or in behavioral performance. These results support the notion that the visual P3 may provide a vulnerability marker of alcoholism.

Adolescent↗