PubMed Health⌕ Search

Biomedical subjects

B Schröder

Publications and source records attributed to B Schröder.

At least 19 recordsLinked to original sources
PubMed2006

The effects of dietary phosphorus deficiency on surface pH and membrane composition of the mucosa epithelium in caprine jejunum.

In ruminants, the uptake of inorganic phosphate (P(i)) across the intestinal mucosa epithelium by Na-dependent and Na-independent mechanisms is a main regulatory factor in P homeostasis. The aim of the study was to elucidate to which extent Na-independent mechanisms, including pH effects or composition of mucosal brush-border membranes, could be involved in positive stimulation of P(i) absorptive processes seen under the P deficient condition. Therefore, luminal, surface and intracellular pH of the jejunal epithelial cells in control and P depleted goats were compared and biochemical analyses of membrane phospholipids in the apical membrane of the jejunal epithelium were performed. Dietary P depletion resulted in decreased plasma P(i) levels. While pH in jejunal ingesta was not significantly changed, P depletion resulted in a significantly lower surface pH in the crypt region compared to control animals (7.62 +/- 0.02 vs. 7.77 +/- 0.04, n = 4, P < 0.01). Inhibition of apical Na(+)/H(+)-exchange resulted in an increase of the jejunal surface pH in P depleted animals by 0.07 +/- 0.01 (n = 6, P < 0.01) and 0.05 +/- 0.01 (n = 6, P < 0.01) for the villus and the crypt region, respectively. This increase were inversely correlated with the initial surface pH prior to inhibition. In contrast to surface pH, intracellular pH of the jejunal epithelium and the phospholipid composition of the apical jejunal membrane were not affected by P depletion. Although the data suggest the existence of a Na(+)/H(+)-exchange mechanism at the luminal surface of goat jejunum they do not support the hypothesis that adaptational processes of active P(i) absorption from goat jejunum in response to low dietary P could be based on "non P(i) transporter events".

Animals↗
PubMed2006

Effects of defaunation on fermentation characteristics and biotin balance in an artificial rumen-simulation system (RUSITEC) receiving diets with different amounts and types of cereal.

Biotin is required by rumen microbes for efficient fermentation. To evaluate the role of protozoa in ruminal biotin metabolism, five diets composed of grass hay or of grass hay/cereal grain mixtures were supplied to faunated or defaunated RUSITEC fermenters. In the mixed diets, hay was replaced to 33:67 or 67:33 w/w on an air-dried basis by either wheat or maize grain in order to simulate different cellulolytic and amylolytic fermentation conditions. Defaunation increased SCFA production, whereas NH4 concentration and the release of CH4 were reduced. Biotin input declined when cereal grain was used to replace the hay. With the exception of the high-wheat treatment, defaunated fermenters yielded higher biotin outputs than faunated fermenters. The biotin balance, calculated as the difference between the total biotin output (biotin in the solid residue contained in the nylon bags after fermentation plus the biotin in the effluent) and the biotin input with the feed, was negative for all the dietary treatments apart from fermenters supplied with the high-maize diet. It was less negative or, in the case of the high-maize diets, more positive for defaunated compared with faunated fermenters. It was concluded that, under normal faunated conditions, protozoa directly utilise or indirectly affect the bacterial synthesis and/or utilisation of biotin. With diets of a high fermentation potential, as realised with the high-wheat diet, protozoa prevent the development of a bacterial population that would utilise high or synthesise low amounts of biotin.

Acetates↗
PubMed2004

Effects of the probiotic yeast Saccharomyces boulardii on the neurochemistry of myenteric neurones in pig jejunum.

We studied the effects of food supplementation with Saccharomyces boulardii (S. boulardii; synonym S. cerevisiae HANSEN CBS 5926; 1 g per day for 9 days) on the presence and co-localization patterns of neuronal markers in myenteric neurones of the pig jejunum. The pan neuronal marker Hu revealed no change in the number of neuronal cell bodies per ganglion (37 +/- 7 in control vs 34 +/- 9 in the S. boulardii group). Ranked by size the following cell populations were identified: choline acetyltransferase (ChAT), calbindin-28k (CALB), substance P (SP), neurofilament 160 kD (NF-160), vasoactive intestinal polypeptide (VIP), nitric oxide synthase (NOS), calcitonin gene-related peptide (CGRP), calretinin (CALRET). We found a significant decrease in the number of CALB myenteric neurones in animals which received S. boulardii supplemented diet. None of the other neuronal markers revealed any difference between controls and S. boulardii treated animals. The study reports transmitter-localization patterns in the myenteric plexus of the pig jejunum and provides evidence that changes in the neurochemistry of enteric neurones occur with S. boulardii supplemented diet. Although only CALB expression was altered and the functional significance of this finding remains unknown, our study identified a possible new effector level of probiotics in the gut.

Animals↗
PubMed2003

Photoneutron yields from tungsten in the energy range of the giant dipole resonance.

Photoneutron production on the nuclei of high-Z components of medical accelerator heads can lead to a significant secondary dose during a course of bremsstrahlung radiotherapy. However, a quantitative evaluation of secondary neutron dose requires improved data on the photoreaction yields. These have been measured as a function of photon energy, neutron energy and neutron angle for natW, using tagged photons at the MAX-Lab photonuclear facility in Sweden. This work presents neutron yields for natW(gamma, n) and compares these with the predictions of the Monte Carlo code MCNP-GN, developed specifically to simulate photoneutron production at medical accelerators.

Monte Carlo Method↗
PubMed2003

Dietary protein reduction in sheep and goats: different effects on L-alanine and L-leucine transport across the brush-border membrane of jejunal enterocytes.

It was the aim of this study to examine the potential regulatory effects of a long-term low dietary protein supply on the transport capacity of the jejunal brush-border membrane for amino acids. For this purpose, we used the neutral amino acids L-alanine (representative for nonessential amino acids) and L-leucine (representative for essential amino acids) as model substances. Ten sheep lambs, 8 weeks of age and 19-27 kg body weight, were allotted to two dietary regimes with either adequate or reduced protein supply which was achieved by 17.9% and 9.7% of crude protein in the concentrated feed, respectively. The feeding periods were 4-6 weeks in length. Similarly, eight goat kids of 5-7 weeks of age and 8-14 kg body weight were allotted to either adequate (crude protein 20.1%, feeding period 9-12 weeks) or reduced protein supply (10.1%, feeding period 17-18 weeks). Dietary protein reduction in lambs caused a significant body weight loss of 0.6 +/- 0.7 kg, whereas the body weight in control animals increased by 1.9 +/- 0.7 kg (P<0.05). Plasma urea concentrations decreased significantly by 60% (low protein 2.3 +/- 0.1 versus control 5.7 +/- 0.2 mmol l(-1), P<0.001). In kids, reduction of dietary protein intake led to significant decreases of the daily weight gain by 48% from 181 +/- 8 g to 94 +/- 3 g (P<0.001) and daily dry matter intake by 27% from 568 +/- 13 g to 417 +/- 6 g (P<0.01). Respective urea concentrations in plasma were reduced by 77% from 5.2 +/- 0.4 to 1.2 +/- 0.2 mmol l(-1) (P<0.01). Kinetic analyses of the initial rates of alanine uptake into isolated jejunal brush-border membrane vesicles from sheep and goats as affected by low dietary protein supply yielded that the apparent Km was neither significantly different between the species nor significantly affected by the feeding regime thus ranging between 0.12 and 0.16 mmol.l(-1). Reduction of dietary protein, however, resulted in significantly decreased Vmax values of the transport system by 25-30%, irrespective of the species. Kinetic analyses of the initial rates of leucine uptake into jejunal brush-border membrane vesicles from sheep and goats yielded that leucine uptake was mediated by Na+-dependent as well as Na+-independent processes. Similar to alanine, apparent Km values of leucine uptake were neither different between the species nor affected due to low dietary protein and ranged between 0.08 and 0.15 mmol l(-1). In contrast to the alanine transport mechanism, dietary protein reduction resulted in increased Vmax values of Na+-dependent leucine transport by 53% in sheep and 230% in goats. Similarly, Na+-independent leucine uptake was stimulated by 85% and 200% in sheep and in goats, respectively. This study shows adaptation of amino acid absorption at the brush-border membrane level of jejunal enterocytes of small ruminants due to dietary protein reduction. Whereas the transport capacity for the nonessential amino acid alanine was reduced due to low dietary protein, the transport capacity for the essential amino acid leucine was markedly stimulated. From this, the involvement of rather different feedback mechanisms in adaptation of intestinal amino acid transport mechanisms has to be discussed.

Alanine↗
PubMed2003

Compton scattering from the deuteron and extracted neutron polarizabilities.

Differential cross sections for Compton scattering from the deuteron were measured at MAX-Lab for incident photon energies of 55 and 66 MeV at nominal laboratory angles of 45 degrees, 125 degrees, and 135 degrees. Tagged photons were scattered from liquid deuterium and detected in three NaI spectrometers. By comparing the data with theoretical calculations in the framework of a one-boson-exchange potential model, the sum and the difference of the isospin-averaged nucleon polarizabilities, alpha(N)+beta(N)=17.4+/-3.7 and alpha(N)-beta(N)=6.4+/-2.4 (in units of 10(-4) fm(3)), have been determined. By combining the latter with the global-averaged value for alpha(p)-beta(p) and using the predictions of the Baldin sum rule for the sum of the nucleon polarizabilities, we have obtained values for the neutron electric and magnetic polarizabilities of alpha(n)=8.8+/-2.4(total)+/-3.0(model) and beta(n)=6.5-/+2.4(total)-/+3.0(model), respectively.

Journal Article↗
PubMed2002

Research note: Postnatal development of electrolyte transport in calf rumen as affected by weaning time.

In a previous study we found a positive correlation between early weaning in calves and morphological parameters which were indicative of ruminal development, i.e. the length and width of the papillae. The objective of the present study was to determine to what extent this observation could be reflected by modulations of absorptive and secretory functions of the rumen mucosa. For this purpose the short-circuit currents (Isc) as a measure of electrogenic net ion fluxes and the transepithelial conductances (G(T)) as a measure of the overall tissue permeability were measured in vitro applying the Ussing-chamber technique. Simultaneously, the unidirectional flux rates of sodium and chloride across rumen wall epithelia were determined in the absence of electrochemical gradients. Under these conditions, significant positive net flux rates (Jnet) clearly indicate active mechanisms for electrolyte absorption. For the experiments 12 male Holstein calves 7 d of age were assigned to three groups of 4 animals each: milk group (I, slaughtered after 6 weeks of age), late weaning group (II, slaughtered after 9 weeks of age) and early weaning group (II, weaned after 6 weeks of age and slaughtered after 9 weeks of age). Whereas G(T) values remained unaffected by different age and feeding, Isc values were significantly affected by early weaning but were not influenced by age. Irrespective of weaning time active absorption of Na+ tended to be higher by about 60% in 9 weeks old animals. Active absorption of chloride was significantly increased in milk fed 9 weeke old calves and this effect was further stimulated by early weaning. In conclusion, the data show an increasing active Na+ absorption with age in calf rumen that could not be influenced by early weaning. Similarly, active Cl- absorption was initially increased during postnatal development and this effect could be stimulated further by early weaning.

Absorption↗
PubMed2002

Rho family small GTPases control migration of hematopoietic progenitor cells into multicellular spheroids of bone marrow stroma cells.

Seeding of hematopoietic progenitor cells (HPC) into the bone marrow requires a complex interaction between cell membrane and adhesion systems and cell signaling pathways. We established a multicellular, spheroid coculture model to study HPC migration in a three-dimensional stromal environment. Here, entry of primary CD34(+) cells into stroma cell spheroids was independent of the integrins very late antigen (VLA)-4, VLA-5, lymphocyte function-associated antigen-1, and the chemokine receptor CXCR4. Experiments using a panel of bacterial toxins selectively targeting key regulators of cellular locomotion, the Rho family small GTPases Rho, Rac, and Cdc42, revealed a considerable reduction or even abrogation of TF-1 cell migration without an increase of apoptosis or impairment of proliferation. Pertussis toxin, an inhibitor of Galpha(i) proteins, showed a similar effect. In some in vitro invasion assays, phosphatidylinositol-3 kinase (PI-3K) was shown to mediate Rac- and Cdc42-induced cell motility and invasion. However, inhibition of the PI-3K pathway by LY294002 did not impair TF-1 cell migration in our three-dimensional model system.

Bacterial Proteins↗
PubMed2002

Upstream AUGs modulate prion protein translation in vitro.

The level of expression of the host PrP gene (PRNP) has been shown to affect the progression to a disease, transmissible spongiform encephalopathy (TSE). In order to define sequences that are responsible for translation ofPRNPmRNA we have investigated a region comprising its 5'-leader sequence. Most remarkable, it consists of an almost identical Kozak mRNA sequence and two AUG initiation codons which seem to modulate translation of the prion protein mRNA in vitro. Although transcriptional regulation of the prion protein PRNP gene had been expected to dominate the translational modulation, our observations point to a translational regulation of the mouse prion protein synthesis controlled by ribosomal entry and usage of AUG codons.

5' Untranslated Regions↗
PubMed2001

Murine M2-10B4 and SL/SL cell lines differentially affect the balance between CD34+ cell expansion and maturation.

The ability of bone marrow stroma to modulate hematopoietic progenitor cell expansion is of considerable interest for gene transfer strategies and transplantation of limited stem cell numbers. We compared the capacity of 2 murine stromal cell lines to affect the balance between maturation and proliferation of human CD34+ cells in short-term expansion cultures. In 7-day serum-free cultures, cytokine-induced amplification of granulocyte-macrophage colony-forming cells (CFC-GM), erythroid burst-forming units (BFU-E), and total cells was significantly increased by the presence of genetically engineered Sl/Sl and M2-10B4 stromal cells in a 1:1 ratio (Sl/M2 cells) compared with stroma-free cultures (P < .05). Sl/M2 cultures generated 21-fold more mature CD15+ cells than stroma-free cultures, without further amplifying the number of CD34+ cells. The addition of serum led to a further increase of CFC-GM, total cells, and CD15+ cells, whereas BFU-E were no longer maintained. Pure Sl/Sl stromal layers were likewise superior to stroma-free cultures in expansion of CD34+ cells and total cells when serum was present. However, the differentiation of CD34+ cells was less pronounced in Sl/Sl cultures compared with Sl/M2 layers, as demonstrated by a lower content of CD15+ cells. Neutralization experiments revealed differential contributions of Flt3 ligand and thrombopoietin to the support of total cell and CFC expansion by Sl/M2 and Sl/Sl stromal feeders.

Adjuvants, Immunologic↗
PubMed2001

Polymorphisms within the prion-like protein gene (Prnd) and their implications in human prion diseases, Alzheimer's disease and other neurological disorders.

Only 10% of human transmissible spongiform encephalopathies (TSEs) are associated with mutations of the Prnp region encoding the prion protein (PrP). Recently, the murine PrP-like protein doppel (Dpl) was described and was shown to be overexpressed in certain strains of PrP knockout mice and to cause neurological diseases such as ataxia and Purkinje cell loss. To answer the question of whether there are any polymorphisms within the PrP-like protein gene (Prnd) that might cause or be involved in the development of TSEs, we investigated the complete open reading frame of the human Prnd gene from 58 patients who had died of genetic or sporadic Creutzfeldt-Jakob disease (CJD), Alzheimer's disease or other neurological disorders and from 111 controls. We found five new polymorphisms and one frame shift mutation. One silent polymorphism, which does not lead to an altered amino acid sequence, was also observed. Statistical analysis revealed a significant difference in the distribution of the Prnd genotype at codon 174 between sporadic CJD patients and healthy controls.

Alzheimer Disease↗
PubMed2001

No effect of vitamin D3 treatment on active calcium absorption across ruminal epithelium of sheep.

A significant contribution of the forestomachs in net calcium (Ca2+) absorption from the gastrointestinal tract has been postulated from in vivo and in vitro studies in different ruminant species. However, the potential role of vitamin D3 and its metabolites in controlling these mechanisms is still under discussion. It was therefore the aim of the present study to investigate the effectiveness of treatment with vitamin D3 in stimulating active Ca2+ absorption from sheep rumen. Four mature, non-lactating, non-pregnant sheep that had been treated 7 and 4 days before the Ca2+ flux rate measurements with intramuscular injections of 300000 IU of vitamin D3 each in aqueous solution were used. Two female and three male placebo-treated sheep served as controls. To characterize the effects of vitamin D3 application on plasma parameters the time courses of total calcium, inorganic phosphate, calcitriol and intact parathyroid hormone (iPTH) were recorded. In vitro studies of unidirectional Ca2+ flux rates across isolated, intact rumen wall epithelia were carried out by applying the Ussing-chamber technique. Western blot analysis and reverse transcriptase-polymerase chain reaction analysis (RT-PCR) were applied to identify vitamin D receptors (VDR) in ruminal and jejunal tissues. In addition, Western blot analysis for qualitative examination of epithelial calbindin D9k levels was carried out in these tissues. Total calcium and phosphate levels in plasma were not significantly affected treatment with vitamin whereas calcitriol concentrations significantly increased by about 130 and 63% after the first and second application, respectively. In contrast, iPTH tended to decrease by about 60% indicating regulatory effects of calcitriol on systemic Ca homeostasis. The Ca2+ flux rate measurements in Ussing-chambers revealed significant net Ca2+ absorption indicating the contribution of active mechanisms for Ca2+ transport in rumen epithelia. This, however, was not significantly affected by increased calcitriol concentrations in plasma. Western blot analysis on the basis of a human recombinant VDR protein and RT-PCR clearly indicated the presence of VDR in ruminal and jejunal epithelia, but, in contrast to jejunum, this was not reflected by respective amounts of calbindin-D9k in ruminal tissues. The results suggest the absence of classical calbindin-D9k-mediated mechanisms for active Ca2+ transport in sheep rumen.

Absorption↗
PubMed2001

[Localized argyrosis 58 years after strabismus operation--an ophthalmological rarity].

BACKGROUND: A pigmented episcleral lesion may have several etiologies. We describe the rare occurrence of a localized argyrosis secondary to former strabismus treatment. HISTORY: A 70-year old female patient was referred to our clinic for diagnosis and treatment of a pigmented episcleral process near the insertion of the left lateral rectus muscle which was noticed on a routine control by her ophthalmologist. The patient was free from ocular symptoms. There was a history of strabismus surgery on the left eye at the age of twelve. Due to the suspicious appearance of the lesion the possibility of a conjunctival malignant melanoma was considered. A ultrasound exam could not exclude this suspicion and therefore a biopsy was performed. Silver deposits and rests of a suture could be found. CONCLUSION: Silver deposits are a rare cause of a pigmented localized episcleral lesion. Several possibilities of silver contamination in our patient are discussed. The most likely explanation is the use of silver containing suture material in strabismus surgery performed 58 years ago. A localized argyrosis secondary to past strabismus surgery should therefore be included in the differential diagnosis of a pigmented episcleral lesion.

Aged↗
PubMed2001

Pupillary examination with infrared consumer videocamera.

BACKGROUND: Pupillary observation in the dark is always a problem in a general ophthalmological practice or an outpatient clinic without specialized equipment. We present two methods for observation of the pupils in darkness: 1) illumination of the pupils with the skiascope as a routine examination and 2) infrared observation of the pupils with a consumer digital video camera. METHODS: (1) Pupillary reactions are observed with the skiascope/retinoscope, the observation beam of the device focused to infinity and documented with a video camera. (2) Infrared observation of the pupils was performed with a digital consumer video camera, allowing observation of the pupillary reaction in darkness. After recording, video sequences of interest were transferred to a personal computer and the still images of interest extracted. RESULTS: In everyday clinical routine, observation of the pupillary reaction with the skiascope/retinoscope proves as a reliable tool with a large bandwidth of illumination and a high contrast between pupil and surrounding area. The infrared video camera allows an excellent visualization of the pupillary reflex in darkness. The transfer of the video sequences to a personal computer proved to be simple and single images can easily be chosen. CONCLUSION: Observation of the pupillary reflex with the skiascope proved a useful tool that is available in practically every ophthalmological office. Use of the infrared digital consumer video camera (available at low prices) is a highly sophisticated tool for observation and documentation of pupillary reflex in darkness.

Dark Adaptation↗
PubMed2001

Colonic fermentation as affected by antibiotics and acidic pH: Application of an in vitro model.

Antimicrobial substances such as vancomycin or metronidazole suppress normal gut flora, thereby preventing physiological fermentation of colonic substrates that may promote mucosal inflammation. This study was designed to establish an in vitro model of microbial metabolism in the colon under control and disturbed conditions (acidic pH) to investigate specific effects of vancomycin and metronidazole on the production of short chain fatty acids (SCFA), which play a pivotal role in maintaining homeostasis in the colon. The experiments were carried out with the colon simulation technique (Cositec) representing an in vitro model for the semi-continuous incubation of defined colon contents. Inocula and fermentable substrates were sampled from cecal contents of fistulated pigs. Disturbed microbial metabolism was generated by reduction of pH in the fermentation vessels from 6.7 to 5.8 and 5.1. In general, application of either vancomycin or metronidazole resulted in a significant decrease of SCFA production rates indicating substantial disturbance of the homeostasis of microbial metabolism. With low doses of vancomycin acetate and butyrate production rates were reduced and with high doses of the antibiotic propionate production was inhibited to a greater extent. Treatment with metronidazole inhibited butyrate production almost completely. Similarly, low pH caused a reduction in total SCFA production, which was mainly due to respective decrease of acetate synthesis. Metronidazole effects were not consistently changed at low pH. The Cositec system provides an excellent facility to test the effects of different antibiotics under defined conditions. In this study, both vancomycin and metronidazole affected microbial metabolism to a considerable extent. Both substances may thus be responsible for disturbances of colon function in vivo.

Acid-Base Equilibrium↗
PubMed2001

Interleukin 3 improves the ex vivo expansion of primitive human cord blood progenitor cells and maintains the engraftment potential of scid repopulating cells.

In umbilical cord blood (UCB) transplantation, the number of nucleated cells per kilogram is a major predictive and critical factor of hematopoietic recovery. Thus, ex vivo expansion of hematopoietic UCB progenitors could potentially accelerate engraftment. Whereas Flt-3 ligand (FL), stem cell factor (SCF), and thrombopoietin (TPO) are considered indispensable, the role of interleukin 3 (IL-3) is still controversial: it has been reported either to support or abrogate the reconstituting ability of stem cells. By adding IL-3 we aimed to enhance the amplification of early and committed progenitor cells without impairing the long-term engraftment of stem cells. Demonstrating a positive impact of IL-3 on the proliferation of all progenitor subsets, the amplification of CD34+ UCB cells was increased 20.9-fold +/- 5.4 (mean +/- standard error) in serum-free culture with FL, SCF, TPO, and IL-3 as opposed to 9.3-fold +/- 3.2 without IL-3 after 7 days. If IL-3 was included, primitive long-term culture-initiating cells and committed colony-forming cells were expanded 16.3-fold +/- 5.5 and 18.1-fold +/- 2.4, respectively, compared to 12.6-fold +/- 5.6 and 9.1-fold +/- 2.0 without IL-3. Analysis of cultured CD34+ UCB cells in sublethally irradiated nonobese diabetic/severe combined immunodeficient mice confirmed that cultured cells had preserved their repopulating potential. After 6 weeks, all mice showed multilineage engraftment with their bone marrow containing an average of 45% human CD45+ cells of the unmanipulated sample, 43% of cells after culture in the presence of IL-3, and 27% of cells after culture without IL-3. In combination with early acting cytokines, IL-3 therefore improves the ex vivo expansion of UCB stem and progenitor cells without impairing their engraftment potential.

Animals↗