Biomedical subjects

A Schröder

Publications and source records attributed to A Schröder.

At least 19 recordsLinked to original sources

PubMed2006

What is in a pebble shape?

We propose to characterize the shapes of flat pebbles in terms of the statistical distribution of curvatures measured along the pebble contour. This is demonstrated for the erosion of clay pebbles in a controlled laboratory apparatus. Photographs at various stages of erosion are analyzed, and compared with two models. We find that the curvature distribution complements the usual measurement of aspect ratio, and connects naturally to erosion processes that are typically faster at protruding regions of high curvature.

Journal Article↗

PubMed2006

Quantitative model of electrochemical Ostwald ripening and its application to the time-dependent electrode potential of nanocrystalline metals.

The contact of a metastable nanocrystalline metal ensemble with a metal ion electrolyte leads to an electrochemical Ostwald ripening. The kinetics is modeled on the level of irreversible thermodynamics for the case that the rate is controlled by the electrode/electrolyte transfer resistance. In particular, the kinetic behavior of medium-sized particles and the time dependence of the electromotive force is investigated. Even though it is expressed in electrochemical terms (mixed potential), the modeling is also applicable to chemical Ostwald ripening as long as it is interfacially controlled. Under these conditions, the kinetics exhibits, even though not self-accelerating, strong similarities to selection dynamics, with the competition stemming from the cannibalistic nature of the process.

Journal Article↗

PubMed2006

[Hypospadias].

Explore the source record for details and available documents.

Child↗

PubMed2006

[Chronic fatigue in complementary rehabilitative medicine--predictors of the outcomes].

Chronic exhaustion and fatigue are increasingly important in rehabilitation medicine. Objectives of this study were (a) to describe the effects of in-patient rehabilitation on patients with chronic fatigue syndromes, (b) to identify predictors for treatment outcome, and (c) to analyze the impact of comprehensive diagnosing on these issues. A total of 171 patients with chronic exhaustion or fatigue (90 % female, mean age 55 +/- 10 yrs) from a rehabilitation hospital with a complementary medicine-based treatment concept were included in a prospective observational study. Within the longitudinal study patients were examined three times (on admission to hospital, at discharge as well as six months later). Participation rate of the postal inquiry was 69 %. Besides items constructed ad hoc, Patient questionnaires included the Symptom Checklist and assessment instruments for depression, quality of life, sense of coherence as well as for changes in experience and behaviour. Treatment outcome was defined as sum score of binary-coded response criteria. The pattern of complaints differed clearly between diagnostic subgroups (neurasthenia, affective disorders, adjustment disorders) before treatment. At discharge from hospital patients showed clinically relevant improvements lasting for six months after rehabilitation. Multiple regression analyses revealed a statistically significant relationship (R (mult) = 0.59) between predictors and outcome at discharge from hospital. A better result was associated with higher trust in treatment success, active information seeking on complementary medicine, healthier feeding habits, better somatic health and a decreased mental status, with regard to the status before treatment. The prediction of outcome after six months was comparably poorer (R (mult) = 0.42). Treatment success was higher in the absence of a diagnosis of neurasthenia, in patients accepting the group-oriented treatment concept and in patients not believing that their disease was due to their own way of living. Trust in the success of the treatment was a highly ranked predictor for longer lasting outcome, too. The results underline the importance of motivation aspects for treatment outcome indicating that individual expectations and attitudes should be considered in a more distinct way when allocating patients to rehabilitative programmes.

Complementary Therapies↗

PubMed2006

Effect of dietary methionine on plasma and liver cholesterol concentrations in rats and expression of hepatic genes involved in cholesterol metabolism.

Methionine has been shown to increase plasma cholesterol in animals. In the present study, mechanisms were investigated by which methionine could alter cholesterol metabolism. In the first experiment, forty growing rats were fed four casein-based diets differing in methionine content (2.6, 3.5, 4.5 or 6.0 g/kg) for 14 d. In the second experiment, isolated rat hepatocytes were incubated in media supplemented with 50, 100 or 200 micromol/l methionine. Dietary methionine tended to increase plasma homocysteine concentrations in the rats (P=0.058). A weak positive correlation between circulating homocysteine and plasma cholesterol was observed (R2 0.27, P<0.01). Rats fed 3.5 g/kg or more of methionine had higher concentrations of cholesterol in their plasma, in lipoprotein fractions of density (rho; kg/l) 1.006 1.063, and in liver than rats fed 2.6 g/kg methionine. Rats fed 6 g/kg methionine had a higher hepatic expression of 3-hydroxy-3-methylglutaryl coenzyme A reductase and cholesterol-7alpha-hydroxylase than rats fed less methionine. The phosphatidylcholine:phosphatidylethanolamine ratio in rat liver increased with rising dietary methionine concentration; the relative mRNA concentrations of phosphatidylethanolamine N-methyltransferase and cystathionine beta-synthase remained unaffected. Hepatocytes incubated in media supplemented with 100 or 200 micromol/l methionine had a higher cholesterol synthesis than hepatocytes incubated in a medium supplemented with 50 micromol/l methionine; the LDL uptake in hepatocytes was independent of the methionine concentration of the medium. In conclusion, the present study suggests that dietary methionine induces hypercholesterolaemia at least in part via an enhanced hepatic cholesterol synthesis.

Amino Acids↗

PubMed2006

Effects of amount of intake and stage of forage maturity on urinary allantoin excretion and estimated microbial crude protein synthesis in the rumen of steers.

Using ruminally cannulated steers, we investigated how urinary allantoin excretion was related to variations in feed intake and stage of forage maturity. Further, different approaches were compared for predicting ruminal microbial crude protein (MCP) synthesis and its efficiency. Experimental diets were arranged in a replicated 3 x 3 Latin square design (experiment 1) and a 4 x 4 Latin square design (experiment 2). In experiment 1, a mixed diet [forage to concentrate, 68:32 on a dry matter (DM) basis] was fed at three intake levels corresponding to 1, 1.5 and 2 times maintenance energy requirements. In experiment 2, four silage-based diets were fed based on perennial ryegrass (Lolium perenneL.), which was harvested at four maturity stages. Both experiments demonstrated the influence of diet on microbial growth rate and by this on efficiency of MCP synthesis, although the magnitude of the effects differed between approaches used for estimating MCP. Linear functions satisfactorily characterised the relationship between urinary allantoin excretion (y) and digestible organic matter (OM) intake (x, kg/day; experiment 1: y = 7.94 + 17.34 x; R(2) = 0.785) or intake of OM effectively degraded in the rumen (x, kg/day; experiment 2; y = 22.32 + 5.93 x; R(2) = 0.695). Urinary excretion of allantoin permitted a semi-quantitative prediction of MCP synthesis: ranking of diets and magnitude of changes in MCP synthesis were reflected.

Allantoin↗

PubMed2005

[Central and peripheral corneal pachymetry--standard evaluation with the Pentacam system].

BACKGROUND: Corneal thickness measurements are important in refractive surgery, for interpretation of IOP and in corneal diseases. The purpose of this study was to generate specific standard values for the Pentacam system and to investigate the influence of body size, body mass index, body weight, gender and refraction on central and peripheral corneal thickness for a more detailed characterization of the corneal anatomy. MATERIALS AND METHODS: The Pentacam system is based on a 180 degrees rotating computer-aided Scheimpflug camera, which generates reconstructions of the anterior segment from 12 to 50 single captures. The central corneal thickness was calculated from 25 single captures in both eyes of 182 normal Caucasian subjects (age: 18 - 83 years). The peripheral corneal thickness was measured within 3 mm distances at 0 degrees , 90 degrees , 180 degrees and 270 degrees . All subjects underwent an ophthalmological examination. Correlations between corneal thickness and body size, body mass index, body weight, gender and refraction were analyzed statistically by non-parametric tests. RESULTS: The mean central corneal thickness of all 364 eyes was 534 +/- 36 microm. Divided into sides it was the same, 534 +/- 36 microm, in the right and in the left eyes. The mean central corneal thickness for female subjects was 533 +/- 40 microm, for males it was 534 +/- 35 microm. Statistically there was no proof of any dependence of the central corneal thickness values on the sides, gender, age, height, body mass index (BMI) or refraction. However, there was a positive significant correlation between central corneal thickness and body weight. The peripheral corneal thickness values were lowest in the temporal and inferior areas and greatest in the superior and in the nasal areas. In the superior and in the nasal areas there was a statistically significant negative correlation between age and peripheral corneal thickness. CONCLUSIONS: The corneal thickness can be measured touchless with the Pentacam system. The central corneal thickness seems to be correlated with the body weight. Anatomical features lead to lower peripheral corneal thickness values in the temporal and inferior areas than in the nasal and superior areas. In the nasal and in the superior areas the corneal thickness seems to decrease with age. Further trials are necessary to confirm these findings and to evaluate the precision, reproducibilitiy and independence of investigators of the corneal pachymetry with the Pentacam system.

Adolescent↗

PubMed2004

[Changes in muscarinic receptors of the aging bladder].

The prevalence of the overactive bladder syndrome (OAB) increases with age. Unfortunately, treatment of the condition is still unsatisfactory. Since muscarinic receptor antagonists are the only effective drug treatment to date, it is logical to assume that muscarinic receptors play an important role in the pathogenesis of OAB. Muscarinic receptors are involved in both the normal and overactive detrusor contraction, and age-dependent changes in muscarinic receptor functions have been found in both animals and human detrusors. In animals as well as humans, two components of detrusor contraction have been demonstrated, the dominating one mediated by muscarinic receptors and the other by ATP (atropine-resistant component). The muscarinic receptor-mediated component decreases with age, and the ATP (purinergic) part increases. However, the clinical consequence of this is unclear, since no major age-dependent changes in the efficacy of antimuscarinic agents in the treatment of OAB have been demonstrated.

Aged↗

PubMed2004

Synergistic interaction of two independent genetic loci causes extreme elevation of serum IgA in mice.

Understanding the molecular regulation of immunoglobulin A (IgA) expression is important as it plays an essential role in the first-line defence through mucosal secretions. Using inbred mouse strains, we identified two independent and dominant acting genetic loci that synergistically cause a 40-fold upregulation in serum IgA levels when introduced into the murine strain C57Bl/6J (B6). The first locus on chromosome 12 appears to be mainly responsible for the natural four-fold higher IgA levels in C3HeB/FeJ (C3H) compared to B6 mice. A second independent, chemically induced mutation on chromosome 5 caused a two-fold elevation when transferred from C3H into B6 mice. Both loci in concert effect a 40-fold elevation against the B6 genetic background. We determined the chromosomal localization of the two loci simultaneously by a one-step mapping process. The chemically induced mutation was identified within the immunoglobulin joining chain (IgJ) gene on chromosome 5. The major serum IgA modifier between the C3H and B6 was located on chromosome 12. This modifier region was mapped to a 350 kb region containing several immunoglobulin heavy-chain genes and the Ig alpha germline switch gene. We speculate that by interfering with both IgA expression and distribution, synergistic regulation of IgA is achieved.

Amino Acid Transport Systems, Neutral↗

PubMed2003

[Analysis of risk factors and comparison of heparin and hemodilution therapies for retinal artery occlusion].

No standards are available for the treatment of central retinal artery occlusion (CRAO). The aim of this study was to compare data about visual acuity development under heparin treatment with those from hemodilution. Data on 139 patients suffering from CRAO between 1991 and 2000 were examined retrospectively. Risk factors were listed. Therapies were compared in 38 of these patients, 23 of whom received full heparinization and 15 of whom received hemodilution. Many risk factors were shown. Neither therapy showed serious complications. Visual acuity improved significantly, by three or more lines, in five of 23 patients (21.7%) under full heparinization and six of 15 patients (40%) receiving hemodilution. Differences were not significant. For ethical reasons, the normal cause of disease in these patients cannot be studied and is still unknown. Because of many vascular risk factors, we recommend adapted therapies. Treatments should be examined in controlled studies.

Adolescent↗

PubMed2003

The nutrition of the chinchilla as a companion animal--basic data, influences and dependences.

This contribution is meant to obtain basic data for feeding chinchillas (ingestion behaviour, feed and water intake) kept as companion animals. The chinchillas ingested more than 70% of their total feed intake during the dark phase (highest level of activity between 9:00 pm and 7:00 am). Daily amounts of feed intake varied between 2.5 (fresh grass) or 2.6 (hay) and 5.5 (pelleted complete diet) g of dry matter per 100 g of body weight. An offered mixed feed based on native components led to a selection of individual ingredients (high palatability: carob, beet pulp, sunflower seeds). The chinchillas' daily water intake varied between 30 (mixed feed in briquette form) and 40 ml (alfalfa cubes) and amounted on average between 1.5 and 3 ml/g of dry matter. Compared with rabbits or guinea-pigs, the chinchillas generally showed noticeable differences (rhythm of feed intake, palatability of individual ingredients, capacity for digestion, etc.) which must be considered in order to optimize the nutrition of this species.

Animal Feed↗

PubMed2002

[Expression analysis of protein tyrosine kinases of the FAK (focal adhesion kinase) family in osteosarcoma].

AIMS: Expression analysis of the protein tyrosine kinases, focal adhesion kinase (FAK) and proline-rich tyrosine kinase2 (Pyk2) in high grade osteosarcomas. MATERIALS AND METHODS: Expression of the kinases was evaluated qualitatively by immunohistochemical staining and quantitatively by real-time PCR. RESULTS: Osteoblastic cells of high grade osteosarcomas show a distinct FAK expression but an overexpression at the transcriptional level could not be detected. The Pyk2-mRNA expression was decreased in osteosarcomas. CONCLUSION: An altered relationship of FAK and Pyk2 was observed for different tumors and could also be important for osteosarcoma development.

Adolescent↗

PubMed2002

[Color vision defects in patients with arterial hypertension].

PURPOSE: In view of the generally impaired vascular condition in patients with arterial hypertension, we were interested in their colour perception. METHODS: Patients (n = 35, f:m = 14:21, mean age 52 +/- 11 years) with arterial hypertension without damage in end-organs and normal subjects (n = 62, :m = 28:34, mean age 49 +/- 9 years) as a control group were included in this study. Exclusion criteria were other systemic or ophthalmological diseases. In addition to the ophthalmological examinations (visual acuity, refraction, intraocular pressure, slit lamp and fundus examination) the colour vision was tested by the colour arrangement test Roth 28-hue (E) desaturated under standard conditions: The background used was black cardboard, illuminated by two Osram fluorescent lamps (L36 W/12LDL Daylight) providing 2000 lux at the test table. RESULTS: The ophthalmological examinations in the patients and in the control group were normal. The patients with arterial hypertension had a significantly higher mean error score (median +/- mean absolute deviation 150 +/- 56, Mann-Witney U-test: p < 0.001) in the colour arrangement test than the control group (median +/- mean absolute deviation 72 +/- 53.4). A particular colour axis (blue-yellow or red-green) was not found. CONCLUSION: Although the ophthalmological examinations were normal we found a disturbed colour vision in patients with arterial hypertension. This has to be taken into account in colour vision testing to avoid diagnostic interferences between specifically ocular diseases (e.g. glaucoma) and arterial hypertension.

Adult↗

PubMed2001

Inhibition of inflammatory endothelial responses by a pathway involving caspase activation and p65 cleavage.

Suppression of NF kappa B activation has been involved in the elimination of survival programs during endothelial cell (EC) apoptosis. We used alpha-tocopheryl succinate (alpha-TOS) to trigger apoptosome formation and the subsequent activation of executioner caspases. The level of bcl-2 was reduced by alpha-TOS, and its downregulation potentiated and its overexpression suppressed pro-apoptotic effects of alpha-TOS, indicating a mitochondrial role in alpha-TOS-induced apoptosis in EC. alpha-TOS treatment was associated with induction of TUNEL-positive apoptosis in EC with a high but not with a low proliferation index. The use of the pan-caspase inhibitor z-VAD.fmk suggested the involvement of caspases in cleavage of p65, and in inhibition of nuclear translocation of p65 and NF kappa B-dependent transactivation of a gene construct encoding the green fluorescence protein elicited by TNF alpha in contact-arrested EC. The suppression by alpha-TOS of inflammatory EC responses induced by TNF alpha such as VCAM-1 mRNA and surface protein expression and shear-resistant arrest of monocytic cells were also reversed by z-VAD.fmk. NF kappa B-dependent transactivation was preserved in alpha-TOS-treated EC stably transfected with a caspase-noncleavable p65 mutant but not with its truncated form, thus establishing a direct link between alpha-TOS-induced effects and p65 cleavage. Our data infer a pathway by which caspase activation in EC inhibits NF kappa B-dependent inflammatory activation and monocyte recruitment, and provide evidence for a relationship between pro-apoptotic and anti-inflammatory pathways.

Apoptosis↗

PubMed2001

Spins in the vortices of a high-temperature superconductor.

Neutron scattering is used to characterize the magnetism of the vortices for the optimally doped high-temperature superconductor La(2-x)Sr(x)CuO4 (x = 0.163) in an applied magnetic field. As temperature is reduced, low-frequency spin fluctuations first disappear with the loss of vortex mobility, but then reappear. We find that the vortex state can be regarded as an inhomogeneous mixture of a superconducting spin fluid and a material containing a nearly ordered antiferromagnet. These experiments show that as for many other properties of cuprate superconductors, the important underlying microscopic forces are magnetic.

Journal Article↗

PubMed2001

The effect of urine volume and nitric oxide on basal bladder blood flow: response to catheterization and drainage.

Preliminary studies demonstrated that catheterization and drainage of the urinary bladder resulted in a significant increase in blood flow to the bladder. The objectives of this study were to determine 1) the relationship between urine volume and basal blood flow to the bladder smooth muscle and mucosa, 2) the effect of acute catheterization and drainage on bladder mucosal and smooth muscle blood flow, and 3) whether nitric oxide was involved in regulation of basal blood flow or the increase in blood flow observed after catheterization and bladder drainage. Twenty-four rabbits were separated into two groups: group 1 (14 rabbits) and group 2 (10 rabbits) treated with L-NAME (NOS inhibitor) 30 minutes before blood flow measurement. Blood flow was measured in all animals using a fluorescent microsphere technique before and immediately after catheterization and drainage of the bladder. The results demonstrated that 1) blood flow to the muscle and mucosa were independent of urine volume at the time of catheterization and drainage; 2) catheterization and drainage significantly increased blood flow to both the bladder smooth muscle and bladder mucosa, but not to the kidney; 3) L-NAME significantly reduced basal blood flow to the kidney, but not to the bladder smooth muscle or mucosa; and 4) L-NAME completely prevented the catheterization- and drainage-induced increases in blood flow to the bladder body mucosa and muscle. This study demonstrates that basal blood flow to the bladder smooth muscle and mucosa during filling is independent of NO control; although bladder blood flow may be increased significantly by NO synthesis and release during bladder emptying, and thus may be an important regulator of blood flow during and immediately following micturition.

Animals↗

PubMed2001

Synthesis and spectral characterization of a new class of heterocyclic analogues of crystal violet dyes.

Deep purple: By the transformation of readily available N,N-disubstituted 2-aminothiophenes and 2-aminothiazoles into heterocyclic analogues of Crystal Violet, such as, tris(2-dimethylamino-5-thienyl)methinium prechlorate (cation shown), the series of dyes derived from these heterocyclic structural units as the important chromophoric component is significantly extended and a gap in the class of heteroanalogous triphenylmethane dyes has been closed.

Crystal Violet↗

PubMed2001

Increased blood flow after catheterization and drainage in the chronically obstructed rabbit urinary bladder.

OBJECTIVES: To determine the effect of drainage on rabbit bladder blood flow after 4 weeks of partial outlet obstruction. Previous studies have shown that catheterization and drainage of the urinary bladder in control rabbits resulted in a significant nitric oxide-induced increase of blood flow to the bladder. It was also shown that 4 weeks' partial outlet obstruction caused a significant decrease in blood flow to the bladder. METHODS: Male New Zealand White rabbits underwent partial outlet obstruction by standard methods. After 4 weeks, the blood flow to the bladder muscle and mucosa was determined by a microsphere technique. Within 1 to 2 minutes after transurethral catheterization and complete drainage of the bladder, the blood flow was again determined. Unobstructed animals served as controls. Four other control animals underwent a repetitive blood flow study during 10 minutes to determine the time frame of blood flow changes after drainage. Blood flow was also measured in 2 control rabbits after transurethral catheterization without drainage and in 2 control rabbits after drainage by suprapubic puncture. To exclude the possibility that increased intravesical pressure alters the blood flow measurements, the relationship between the intravesical volume and the bladder pressure was examined in the obstructed rabbits. RESULTS: After drainage of the bladder, the blood flow to the bladder muscle increased 4.5-fold in the decompensated obstructed group (bladder weights greater than 15 g) and 2.5-fold in the compensated animals (bladder weights less than 5 g) and control animals. Blood flow to the mucosa followed the same pattern but without reaching significance. Blood flow returned to near baseline values within 5 minutes. Catheterization without drainage did not alter the blood flow. In contrast, drainage by puncture increased the blood flow significantly. Higher intravesical volumes increased the intravesical pressure slightly, but after opening the abdominal fascia, the intravesical pressure did not change with increasing volumes. CONCLUSIONS: Although the previously shown decreased blood flow to the bladder smooth muscle may be an etiologic factor in bladder contractile dysfunction secondary to partial outlet obstruction, the bladder does have the ability to increase the blood flow after drainage. This ability could be a compensatory and possibly protective mechanism after outlet obstruction.

Animals↗