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B Seifert

Publications and source records attributed to B Seifert.

211 records · Page 12Linked to original sources
PubMedDate not supplied

Development of dendritic trees of rabbit retinal alpha ganglion cells: relation to differential retinal growth.

To provide a quantitative description of the postnatal development of dendritic trees in alpha ganglion cells of the rabbit retina, these cells were stained either by intracellular injection of Lucifer yellow or by application of the lipophilic dye DiI. This was done at three developmental stages: postnatal day (P) 8/9, P 16/17, and in adults. For different retinal locations we quantified the alpha cell dendritic field area, the number of dendritic branch points, and the average dendritic length between branch points. According to the alpha cell location, the data were collected in three groups representing the retinal center, midperiphery, and far periphery, respectively. The data were then correlated with the postnatal retinal expansion which is known to differ among the above topographic regions of the retinae (Reichenbach et al., 1993). Our results show that the growth of alpha ganglion cell dendrites is not proportional to, but significantly exceeds, that of the local retinal tissue. Between P 8/9 and adulthood, the area of central alpha cells increases almost six-fold from 26,000 to 144,000 microns 2 (retinal expansion: 2.2-fold), and that of peripheral cells more than 15-fold from 35,000 to 556,000 microns 2 (retinal expansion: four-fold). During this period, the coverage factor of alpha cell dendritic fields increases about three-fold, and reaches adult levels of about 3 (retinal center) and 2.2 (periphery), respectively. The number of dendritic branch points remains nearly constant, and the distance between them increases by a factor close to the square root of the factor by which the dendritic field area grows. Thus, it appears that, from the second postnatal week on, dendritic trees of rabbit alpha ganglion cells increase by intense "interstitial growth," rather than by outgrowth of (new) dendritic branches. This growth pattern is different from that of some other rabbit retinal ganglion cell types, and of alpha ganglion cells of the cat retina, whose dendritic trees expand at a rate equal to or less than that of the surrounding retinal tissue. The consequences for synaptic contacts with bipolar and amacrine cells are discussed; they suggest a high degree of synaptic plasticity during normal postnatal retinal growth.

Animals↗
PubMedDate not supplied

The German Environmental Survey 1990/1992 (GerES II): a representative population study.

The German Environmental Survey (GerES) is a large-scale population study which has repeatedly been carried out in Germany. GerES I was conducted in 1985/1986 followed by GerES IIa in 1990/1991 (West Germany) and GerES IIb in 1991/1992 (East Germany). GerES III is currently run in both parts of Germany. The main goal of the surveys is to analyse and document the extent, distribution and determinants of the exposure to environmental pollutants of the German general population. Field work is conducted using a combination of several tools, including questionnaires, interviews, human biomonitoring, and indoor and outdoor environmental samplings. This paper describes the design of GerES II, and gives a general outline of the field work and the analytical procedures used. In GerES II, about 4000 adults were representatively selected from the German population with regard to age, gender and community size. Approximately 700 children were also included. Arsenic, cadmium, copper, chromium, lead, and mercury were determined in blood, morning urine and/or scalp hair. In addition, samples were taken and analysed to characterise exposure in the domestic environment (indoor air, house dust, drinking water). The contribution to exposure of food was also studied. Exposure to volatile organic compounds (VOCs) was determined by personal sampling.

Adolescent↗
PubMedDate not supplied

The German Environmental Survey 1990/1992 (GerES II): cadmium in blood, urine and hair of adults and children.

As a follow-up of an earlier population study carried out in West Germany in 1985/1986 (GerES I), a nationwide Environmental Survey was conducted in Germany in 1990-1992 (GerES II). It was the aim of these studies to obtain representative data on the population's body burden and the quality of their indoor environment and immediate surroundings. The present paper reports on cadmium levels in blood, urine and hair of 4021 adults aged 25-69 and 736 children aged 6-14. The statistical analysis included both descriptive and inferential methods. The data were classified according to social factors, lifestyle characteristics, and environmental exposures. Moreover, regression analysis was used to determine the predictors of cadmium concentrations in the types of sample studied. Active cigarette smoking was found to be dominant in affecting blood and urine cadmium levels in adults, but less important for cadmium levels in hair. Age and creatinine level in urine were additional important factors influencing the cadmium concentration in urine, especially in women. Environmental and occupational exposures to cadmium played only a minor role in the exposure models for German adults. The cadmium concentration in blood and urine was generally lower in children than in adults, while no significant difference for cadmium in hair could be detected. The cadmium concentrations in all three samples were significantly higher in East German children than in West German children.

Adolescent↗
PubMedDate not supplied

The German Environmental Survey 1990/92 (GerES II): sources of personal exposure to volatile organic compounds.

In the framework of the second German Environmental Survey carried out in the Western part of Germany in 1990/91 (GerES IIa) 113 adults aged 25-69 years were selected at random from the total study population of about 2500 to investigate personal exposure to about 70 volatile organic compounds (VOCs). Each subject wore a diffusive badge-type sampler for 1 week. The VOCs determined included alkanes, aromatics, aliphatic halocarbons, terpenes, and oxygen-containing compounds. Multivariate regression analysis was carried out to determine and quantify the major sources of personal exposure to various VOCs. In this paper, results are given for benzene, and C8- and C9-aromatics. Being subject to environmental tobacco smoke was found to be the most important determinant of benzene exposure, but automobile-related activities such as driving a car or refuelling, were also associated with significantly increased levels of benzene. The major determinant of C8- and C9-aromatics concentrations was occupational exposure. Emissions from paints, lacquers, newspapers, magazines and print-works were also important contributors to C8-aromatics exposure. Renovation, painting and smoking were associated with a significant increase of the exposure to C9-aromatics.

Adult↗
PubMedDate not supplied

The German Environmental Survey 1990/1992 (GerES II): reference concentrations of selected environmental pollutants in blood, urine, hair, house dust, drinking water and indoor air.

The German Environmental Survey (GerES) is a large-scale, representative population study that has been carried out three times up to now with a time interval of about 7 years. GerES I was performed in 1985/1986, GerES IIa in 1990/1991 in West Germany, and GerES IIb in 1991/1992 in East Germany, the former German Democratic Republic (GDR). In GerES II, blood, urine, and scalp hair samples of 4021 adults aged 25-69 years and of 736 children aged 6-14 years were analysed as well as environmental samples (house dust, drinking water, indoor and personal air, diet). Characteristics of the frequency distributions of the substances analysed in the different media were calculated. The geometric mean (GM) for lead, cadmium, and mercury in the blood of adults amounted to 45.3, 0.36, and 0.51 microg/l, respectively. The corresponding values of arsenic, cadmium, and mercury in urine were 6.3, 0.29, and 0.54 microg/l, respectively. The concentrations of lead in blood, cadmium in blood and urine, and mercury in blood are lower in children than in adults. The GM ofpentachlorophenol (PCP) in urine of adults was 2.67 microg/l and in urine of children, 4.15 microg/l. These results of GerES II were compared with the so-called HBM values which represent health-based exposure guidelines and have been defined by the Human Biomonitoring Commission (HBC) of the Federal Environmental Agency, interalia for lead in blood, cadmium in urine, mercury in blood and urine, and PCP in urine. They also provided asound basis for the setting of reference values to describe the status of the German population. A total of 1.8% and 0.6% of the German females in child-bearing age had a level of lead in blood higher than HBM-I (100 microg/l) and HBM-II ( 150 microg/l), respectively. One percent of the children had a blood lead level above HBM-I. House dust and drinking water were analysed to characterise exposure in the domestic environment. Arsenic, cadmium, and lead deposition in homes amounted to 5.4 ng/(m2 day), 11.7 ng/(m2 day), and 0.29 microg/(m2 day), respectively. In the content of vacuum cleaner bags, concentrations were 2.1,0.9, and 5.9 microg/g. PCP, lindane and permethrin could be detected in the house dust of most German households. The pollutant load of the drinking water is significantly influenced by the corrosion of pipe materials and fittings. The new EC limit value of 10 microg/l for lead was exceeded in 7.7% of the first draw samples. The relatively high percentage (14%) of samples from East Germany that exceeded the current German guideline value for formaldehyde of 0.1 ppm in indoor air may be explained by the widespread use of contaminated particleboard in the former GDR.

Adolescent↗
PubMedDate not supplied

The German Environmental Survey 1990/92 (GerES II): primary predictors of blood cadmium levels in adults.

As part of the representative Environmental Survey in Germany in 1990-1992, investigators determined cadmium levels in blood provided by 3,965 subjects aged 25-69 yr. The investigators considered approximately 150 variables (i.e., demographics, household and occupational characteristics, environmental exposures, smoking habits, frequency of food consumption, and additional life-style features) as potential predictors in multivariate regression analysis. On the basis of the results of multivariate regression analysis, the authors derived 2 slightly different models for the prediction of blood cadmium levels in populations from West and East Germany. Both models included 3 primary predictors of blood cadmium levels. The 2 models explained 51.3% and 61.2% of the observed variance in blood cadmium levels in West and East Germany, respectively. The most important predictor was a specific indicator for smoking habits, which was determined from a separate mathematical model. In this model, the effect of smoking was considered, and the model accounted for the biological half-life of cadmium in blood.

Adult↗
PubMedDate not supplied

Measures of body mass and of obesity from infancy to adulthood and their appropriate transformation.

In this paper we investigate first the choice of an appropriate index of body mass. The traditional indices weight/height (W/H), W/H2 and W/H3 are compared, as well as an approach due to Cole (1986) making the index W/Hp age-dependent, i.e. by allowing the power p to depend on age. While there may be no perfect index reflecting over- and underweight--irrespective of height and width--the Quetelet index W/H2 turned out to be a reasonable index from childhood to adulthood. Second, we study the development of the body mass index W/H2 longitudinally from birth onwards, based on structural average distance, velocity and acceleration curves. As a third topic, transformations for obtaining an approximate normal distribution for W/H2, weight and skinfolds are compared. The usual log-transformation turned out to be unsatisfactory. While for height and arm skinfolds a transformation -1/square root of x performs rather well across age and sex, a transformation -1/x is more appropriate for trunk skinfolds and W/H2.

Age Factors↗
PubMedDate not supplied

Prediction of adult skinfolds and body mass from infancy through adolescence.

In this paper age-to-age correlations for the body mass index and for skinfolds are evaluated for a sample of normal children studied from birth to adulthood. While correlations over larger age spans are modest, they become appreciable from childhood to adolescence and from adolescence to adulthood. Correlations are consistently higher for boys compared to girls, and only for the former does the body mass index correlate better than skinfolds. Significant correlations between weight increase in the first year and the adult body mass index were found, as well as between the age of 'adiposity rebound' and the adult body mass index. However, the small size of the correlations forbids any predictive applications. As it turns out, the individual prediction of the adult size of the body mass index or of skinfolds is a thorny problem, whatever variables and methods are chosen. The precision of such a prediction is very low up to late childhood and becomes somewhat better in adolescence. From a positive side, this leaves much room for overweight children to improve their state. On the other hand, the relative risk for becoming a heavy adult is much increased for those who are already heavy as children and adolescents. This underlines the dangers of early overweight from an epidemiological viewpoint.

Adolescent↗
PubMedDate not supplied

Extended follow-up after atrial repair for transposition of the great arteries: a younger age at surgery improves late survival.

BACKGROUND: Surgical treatment for transposition of the great arteries (TGA) usually involves anatomic repair, although atrial repair is used in cases with special coronary artery patterns. METHODS: Records of all 239 patients surviving at least 30 days after atrial correction of TGA between 1962 and 1987 at the University Hospital in Zurich were reviewed. The mean length of follow-up time was 13.7 years (median 14.9 years; range from 0.05 to 30.1 years). The average age at surgery was 45.7 months (range from 7 days to 24.4 years). One hundred twenty-one patients had a simple TGA, whereas the remaining 118 had a complex TGA. RESULTS: The surviving patients were in NYHA class I at time of follow-up. The most common reasons for death were systemic right ventricular dysfunction and sudden rhythm disturbances. There was a major risk for late cardiac event in patients over 3 years old at operation (p = 0.02) and also in patients with complex TGA (p = 0.03). However, date of surgery, previous surgery, or the postoperative requirement for a pacemaker did not greatly affect late cardiac mortality. CONCLUSIONS: Although the procedure of choice for TGA is the arterial switch operation, the promising findings of the current long-term study, which reports the longest follow-up to date, indicate that the atrial switch operation is a good alternative procedure for the rare cases where the use of arterial switch procedures is limited.

Adolescent↗
PubMedDate not supplied

Inhibition of sodium-dependent transport systems in LLC-PK1 cells by metabolites of ifosfamide.

Ifosfamide (IF) is an alkylating cytostatic derived from nitrogen mustard. In addition to its well-known urotoxic effects (hemorrhagic cystitis), several cases of Fanconi syndrome following IF therapy have been reported. No information is available concerning the pathomechanisms of this tubulotoxicity. We used the permanent renal epithelial cell line LLC-PK1 in order to investigate whether major metabolites of IF (i.e. 4-OH-IF, acrolein and chloracetyldehyde) induced the transport defects most frequently detected after IF therapy in vivo. LLC-PK1 cells of passages 162-177, grown in plastic culture dishes, were used in a confluent state. Sodium-dependent and independent fluxes of l-[3H]alanine and of D-[3H]glucose were determined by standard techniques. Activities of marker enzymes of apical and basolateral membranes, of mitochondria and of endoplasmic reticulum were determined in cell homogenates. IF itself has no detectable effect on fluxes of l-alanine and D-glucose in LLC-PK1 cells. The IF metabolite 4-OOH-IF induces a clear inhibition of sodium-dependent fluxes of both substrates after a 24-hour exposure of cells to 100 mumol/l of 4-OOH-IF. Chloracetaldehyde induces a biphasic response of sodium-dependent fluxes of l-alanine with increased uptake rates at low concentrations (< 200 mumol/l) and with a short incubation time, while higher concentrations and long exposure of the cells leads to a reduction in sodium coupled transport. Glucose transport is affected in a comparable way, however, in contrast to alanine transport, chloracetaldehyde also stimulates sodium-independent fluxes of glucose. Acrolein is the most toxic substance tested. It severely damages cell monolayers at concentrations beyond 75 mumol/l. Sodium-coupled glucose and alanine transport is inhibited by acrolein at concentrations higher than 50 mumol/l. Sodium-coupled glucose transport is more sensitive to all metabolites tested than alanine transport. While acrolein strongly affects both transport systems, marker enzymes of the apical plasma membrane, i.e. alkaline phosphatase and leucine amino-peptidase, are not significantly inhibited, suggesting a specificity of the toxic effect for the transport proteins. We conclude that LLC-PK1 cells represent a good model for further investigation of the pathogenesis of Fanconi syndrome after IF therapy. Sodium-dependent transport systems are more sensitive to acrolein than other cell surface proteins.

Acetaldehyde↗
PubMedDate not supplied

[Forensic entomology exemplified by a homicide. A combined stain and postmortem time analysis].

The combined analysis of both ant and blow fly evidence recovered from a corpse, and from the boot of a suspect, suggested that an assumed scenario in a high profile murder case was likely to be true. The ants (Lasius fuliginous) were used as classical crime scene stains that linked the suspect to the scene. Blow fly maggots (Calliphora spec.) helped to determine the post mortem interval (PMI) with the calculated PMI overlapping with the assumed time of the killing. In the trial, the results of the medico-legal analysis of the insects was understood to be crucial scientific evidence, and the suspect was sentenced to 8 years in prison.

Animals↗
PubMedDate not supplied

[The sick building syndrome].

The term "sick building syndrome" (SBS) has been used for several years to describe a number of mostly unspecific complaints of some occupants of air-conditioned buildings. Based on the literature, a definition of the SBS is given and some results of larger SBS studies carried out in Germany, Denmark and the United Kingdom are described. These studies show that SBS is a multifactorial event which may include physical, chemical, biological as well as psychological factors. In many cases, the occurrence of SBS in a building is due to insufficient maintenance of the HVAC system. SBS-induced investigations in a building should be carried out stepwise, the measurement of indoor air pollutants not being the first step. Strategies to avoid SBS must take into account factors specific to the building, the HVAC system and the equipment as well as psychological factors.

Air Microbiology↗