Biomedical subjects

S Berger

Publications and source records attributed to S Berger.

At least 19 recordsLinked to original sources

PubMed2007

A 1H-NMR thermometer suitable for cryoprobes.

Most established NMR thermometers rely on temperature-dependent chemical shift differences measured from samples that are either neat or concentrated solutions (e.g. ethylene glycol, methanol). These are unsuitable for modern cryoprobes on account of strong radiation damping resulting from the high Q of the probe. Using perdeuterated methanol, we established a relationship between the chemical shift difference and temperature, and we show that this relationship is well fitted by a quadratic equation. The actual temperature within a sample tube in the probe was verified using a Pt-100 resistor.

Journal Article↗

PubMed2006

A simple presurgical necrotizing enterocolitis-mortality scoring system.

OBJECTIVE: To assess the relationship between early laboratory parameters, disease severity, type of management (surgical or conservative) and outcome in necrotizing enterocolitis (NEC). STUDY DESIGN: Retrospective collection and analysis of data from infants treated in a single tertiary care center (1980 to 2002). Data were collected on disease severity (Bell stage), birth weight (BW), gestational age (GA) and pre-intervention laboratory parameters (leukocyte and platelet counts, hemoglobin, lactate, C-reactive protein). RESULTS: Data from 128 infants were sufficient for analysis. Factors significantly associated with survival were Bell stage (P<0.05), lactate (P<0.05), BW and GA (P<0.01, P<0.001, respectively). From receiver operating characteristics curves, the highest predictive value resulted from a score with 0 to 8 points combining BW, Bell stage, lactate and platelet count (P<0.001). At a cutoff level of 4.5 sensitivity and specificity for predicting survival were 0.71 and 0.72, respectively. CONCLUSION: Some single parameters were associated with poor outcome in NEC. Optimal risk stratification was achieved by combining several parameters in a score.

Birth Weight↗

PubMed2006

The virtual crossmatch--a screening tool for sensitized pediatric heart transplant recipients.

Heart transplantation in the setting of human leukocyte antigen (HLA) sensitization is challenging, as a time-consuming prospective crossmatch (XM) may be required, severely limiting the number of potential donors. We evaluated a 'virtual XM', defining a positive virtual XM as the presence of recipient pre-formed anti-HLA antibodies to the prospective donor HLA type, and compared the virtual XM to a standard direct XM. Bead-based flow cytometric analysis was used to identify anti-HLA antibody (Ab) present in a child listed for heart transplantation. Using recipient serum, direct-flow cytometric T- and B-cell XM were run for potential donors against whose HLA type the recipient had specific antibodies (group 1, n = 7) and for potential donors with predicted compatible HLA types by virtual XM (group 2, n = 7). Results were expressed as median channel difference (MCD) between the control and recipient serum. A positive T-cell XM was defined as MCD > 50, whereas MCD > 100 constituted a positive B-cell result. The rate of T-cell reactivity was significantly less in group 2 than in group 1 (29% vs. 100%, p = 0.02); similarly, B-cell reactivity was also less for group 2 (14% vs. 100%, p = 0.005). The virtual XM was 100% sensitive in detecting positive flow cytometric XM results for T and B cells. Although only 72% specific in predicting a negative T-cell XM, and 86% specific for negative B-cell XM, the false negatives were weakly positive and would probably have been clinically acceptable. Currently, potentially suitable donor organs are often declined for lack of a prospective XM; these organs may ultimately be allocated to more distant recipients or perhaps not used at all. While further studies are needed, virtual XM has the potential to improve availability of organs for sensitized patients and improve the overall allocation process.

B-Lymphocytes↗

PubMed2005

A novel liquid crystalline system for partial alignment of polar organic molecules.

A new system for partial alignment of polar organic molecules to measure residual dipolar couplings in NMR consists of a 1:1 or a 2:1 mixture of water and DMSO including 3-13% n-alkylpentaethylene glycol as the surfactant. Temperature and concentration dependence of the alignment system are investigated and, as examples, the 13C,1H residual dipolar couplings for the amino acid methionine 1 and for an alpha-methylene-gamma-butyrolactone 2 have been obtained and are compared with those obtained from the alignment media consisting of n-alkylpentaethylene glycol, n-alkyl alcohol and water.

4-Butyrolactone↗

PubMed2005

Tracheal surgery in children.

BACKGROUND: The aim of this study is to show that five distinct types of tracheal anomalies should be differentiated with respect to therapy and prognosis. METHODS: The records of 12 infants and children seen over a period of 20 years for different tracheal anomalies such as laryngotracheal stenosis (n = 3), long or short-segment stenosis of the upper (n = 2), middle (n = 6), and lower (n = 1) trachea were reviewed. In addition to these 12 patients with congenital stenosis, 3 other patients needed tracheal resections because of oncologic or traumatic disease: in 2, the trachea was infiltrated by a papillary carcinoma of the thyroid gland and in one, the upper part of the trachea was injured by an oral explosion accident. 25 patients presenting during the same period for other tracheal pathologies including esophagotracheal cleft syndrome (n = 7), tracheomalacia (n = 4), total tracheal agenesis (n = 3), or for placement of a tracheostomy (n = 11) due to other diseases were excluded from this study. RESULTS: There was 1 early death after repair of a laryngotracheal stenosis by cricoid-split and cricoid-splint due to both cerebral hemorrhage and cardiac insufficiency secondary to Fallot's tetralogy. Another child died four weeks after slide tracheoplasty as a result of hypoxic cerebral lesions induced by severe central catheter-related septicemia. One child with therapy-resistant obstructing granulation tissue which developed after a slide tracheoplasty required a tracheostomy. The patient with the tracheal injury died after another accident one year after discharge. All other patients (n = 11) are doing well. CONCLUSIONS: With respect to therapy of congenital and post-intubation tracheal stenosis, four types should be distinguished. Each of these types requires an adequate surgical procedure. The most important postoperative problem in tracheal surgery is the development of granulation tissue. However, the pathogenesis of granulation is still unknown.

Bronchoscopy↗

PubMed2005

Design of oligolactone-based scaffolds for bone tissue engineering.

Novel difunctional oligolactone macromers have been synthesized by ring-opening oligomerization of various lactones (L-lactide, glycolide, p-dioxanone) in the presence of suitable diols (propane-1,2-diol, dianhydro-D-glucitol) and subsequent endcapping of the formed oligolactones with methacrylate moieties. Based on these macromers, two fabrication procedures were developed to fabricate highly porous scaffolds and the material properties including in vitro biodegradation behaviour of the resulting polymeric scaffolds were investigated. Preliminary in vitro studies on the cytocompatibility of the fabricated scaffolds and on osteoblast cultivation on the optimized polymeric materials demonstrated that the oligolactide based polymer networks possess an excellent biocompatibility and that they are promising candidates as scaffolds in bone tissue engineering.

3T3 Cells↗

PubMed2004

Right esophageal lung in a preterm child with VACTERL association and Mayer-Rokitansky-Kuster-Hauser syndrome.

We report on a preterm girl (birth weight 1,200 g) with a right esophageal lung in esophageal atresia type VIag (according to the extended classification of Kluth). Additionally, the child suffered from an atrioseptal defect, a dextrocardia with a left descending aorta, a duodenal atresia, a high type of anal atresia (VACTERL association), agenesis of the left kidney, and agenesis of the vagina, uterus, and ovarian tubes (Mayer-Rokitansky-Kuster-Hauser syndrome or incomplete MURCS association). The child was treated with an emergency gastrostomy because of increasing abdominal dilatation. Thereafter, the parents refused further surgical treatment, and the child was maintained on basic therapy. After an uneventful period of 4 weeks, the child died of an acute massive aspiration. This case shows that sufficient spontaneous ventilation is possible in esophageal lung as long as a gastrostomy is kept on suction to prevent overinflation of the affected lung and the stomach. Ethical aspects have to be considered when treatment is planned in cases of prematurity and associated malformations when a chance of good survival is rather limited. The stepwise approach as proposed in the present case appears to be the only possible therapeutic regimen that can be offered in this complicated condition.

Abnormalities, Multiple↗

PubMed2004

Zebrafish beta tubulin 1 expression is limited to the nervous system throughout development, and in the adult brain is restricted to a subset of proliferative regions.

Tubulin, the building block of microtubules, consists of an alpha and beta subunit, each in itself a family of several highly homologous isotypes. Abundance, tissue specificity, developmental regulation, and possibly function vary between isotypes. Six isotypes of beta tubulin (class I to class VI) have been cloned from several vertebrate species. Class I beta tubulin is believed to be widely expressed, but has not been studied by in situ hybridization in any vertebrate species so far. We have cloned a beta tubulin from zebrafish that appears most similar to other vertebrate class I tubulins and name it zbeta1 tubulin, accordingly. We report a distinct expression pattern of zbeta1 tubulin in the zebrafish embryo in restricted regions of the peripheral and central nervous system that comprise early-differentiating neurons. The expression pattern changes during development and in the adult zebrafish expression mostly is confined to a subset of proliferative zones that include the subependymal zone around the telencephalic ventricle, zones in the preoptic and hypothalamic area and in the olfactory epithelium. Thus, zbeta1 tubulin is expressed with remarkable selectivity during neuronal differentiation and neurogenesis in the embryonic and adult nervous system, respectively.

Animals↗

PubMed2004

Genetic dissection of corticosteroid receptor function in mice.

Functional genomic technologies, including artificial chromosome-based transgenesis and conditional gene targeting, allowed us to generate mouse models harboring genes with loss-of-function mutations, gain-of-function mutations, spatially and/or temporally restricted mutations, tissue-specific mutations, and function-selective mutations. This kind of "allelic series" for corticosteroid receptors in mouse models provides a very useful resource for the molecular understanding of corticosteroid function in vivo. These models will also support the identification of steroid receptor target genes in order to define a steroid signaling cascade in molecular terms. They provide opportunities for the identification of compounds that regulate steroid receptors in a tissue-specific and function-selective manner. For example, selective glucocorticoid receptor modulators preventing receptor dimerization and DNA binding can be expected to reduce osteoporotic and/or diabetogenic side effects, but to display partial or full anti-inflammatory potential. Thus, these mouse models will help to evaluate distinct steroid receptor functions for therapeutic intervention.

Animals↗

PubMed2004

Cell cycle arrest and aberration yield in normal human fibroblasts. I. Effects of X-rays and 195 MeV u(-1) C ions.

PURPOSE: To examine the relationship between cell proliferation and the expression of chromosomal damage in normal human skin fibroblasts after X-ray and particle irradiation. MATERIALS AND METHODS: Confluent G0/G1 AG1522B cells were exposed to X-rays or 195MeV u(-1) C ions with a linear energy transfer of 16.6 keV microm(-1) in the dose range 1-4 Gy. Directly after irradiation, cells were reseeded at a low density in medium containing 5-bromo-2'-deoxyuridine. At multiple time points post-irradiation, the cumulative BrdU-labelling index, mitotic index and aberration frequency were measured. Based on these data, the total amount of damage induced within the entire cell population was estimated by means of mathematical analysis. RESULTS: Both types of radiation exposure exert a pronounced effect on the cell cycle progression of fibroblasts. They result in delayed entry of cells into S-phase and into the first mitosis, and cause a dramatic reduction in mitotic activity. Measurement of chromosomal damage in first-cycle cells at multiple time points post-irradiation shows that the frequencies of aberrant cells and aberrations increase with time up to twofold for the lower doses. However, for the higher doses, this effect is less pronounced or even disappears. When the data for the whole cell population are analysed, it becomes evident that only a few damaged fibroblasts can progress to the first mitosis, a response attributable at least in part to a long-term arrest of injured cells in the initial G0/G1-phase. As observed in other investigations, the effectiveness of 195 MeV u(-1) C ions was similar or slightly higher than X-rays for all endpoints studied leading to a relative biological effectiveness in the range 1.0-1.4. CONCLUSIONS: Cell cycle arrests affect the aberration yield observable in normal human fibroblasts at mitosis. The data obtained for the cell population as a whole reveal that injured cells are rapidly removed from the mitotically active population through a chronic cell cycle arrest, which is consistent with other studies that indicate that this response is a specific strategy of fibroblasts to minimize the fixation and propagation of genetic alterations.

Apoptosis↗

PubMed2004

Ultrasonic wave propagation in human cancellous bone: application of Biot theory.

Ultrasonic wave propagation in human cancellous bone is considered. Reflection and transmission coefficients are derived for a slab of cancellous bone having an elastic frame using Biot's theory modified by the model of Johnson et al. [J. Fluid Mech. 176, 379-402 (1987)] for viscous exchange between fluid and structure. Numerical simulations of transmitted waves in the time domain are worked out by varying the modified Biot parameters. The variation is applied to the governing parameters and is about 20%. From this study, we can gain an insight into the sensitivity of each physical parameter used in this theory. Some parameters play an important role in slow-wave wave form, such as the viscous characteristic length lambda and pore fluid bulk modulus Kf. However, other parameters play an important role in the fast-wave wave form, such as solid density rhos and shear modulus N. We also note from these simulations that some parameters such as porosity phi, tortuosity alpha(infinty), thickness, solid bulk modulus Ks, and skeletal compressibility frame Kb, play an important role simultaneously in both fast and slow wave forms compared to other parameters which act on the wave form of just one of the two waves. The sensitivity of the modified Biot parameters with respect to the transmitted wave depends strongly on the coupling between the solid and fluid phases of the cancellous bone. Experimental results for slow and fast waves transmitted through human cancellous bone samples are given and compared with theoretical predictions.

Bone Density↗

PubMed2003

Scanning-force techniques to monitor time-dependent changes in topography and adhesion force of proteins on surfaces.

Scanning-force microscopy (SFM) investigations were conducted to probe the influences of the interactions of proteins with surfaces relevant in medicine. These interactions are an important feature in the area of biofilm formation. The adsorption of proteins leads to changes in topography, which was monitored for the build up of protein layers of hen egg-white lysozyme and bovine serum albumin (BSA) on mica in real time in phosphate-buffered aqueous solution over a time period of 10 min. Phase imaging was additionally applied to compare material contrasts and to evaluate this method for further application in this field. The adhesion forces that develop on a time scale below 20 s between a protein-modified SFM tip and titanium surfaces (TiO(2), TiAl6V4 and TiAl6Nb7) were investigated. The influences of the parameters loading force and interaction time between the protein and the surface were monitored as well as the influence of protein structure. The interaction time dependency of the adhesion force could be described with a kinetic model of two consecutive first-order reactions. For the maximal adhesion force a correlation to the ratio of the amino acids cysteine, proline and glycine has been proposed.

Adhesiveness↗

PubMed2003

Multiparameter single-molecule fluorescence spectroscopy reveals heterogeneity of HIV-1 reverse transcriptase:primer/template complexes.

By using single-molecule multiparameter fluorescence detection, fluorescence resonance energy transfer experiments, and newly developed data analysis methods, this study demonstrates directly the existence of three structurally distinct forms of reverse transcriptase (RT):nucleic acid complexes in solution. Single-molecule multiparameter fluorescence detection also provides first information on the structure of a complex not observed by x-ray crystallography. This species did not incorporate nucleotides and is structurally distinct from the other two observed species. We determined that the nucleic acid substrate is bound at a site far removed from the nucleic acid-binding tract observed by crystallography. In contrast, the other two states are identified as being similar to the x-ray crystal structure and represent distinct enzymatically productive stages in DNA polymerization. These species differ by only a 5-A shift in the position of the nucleic acid. Addition of nucleoside triphosphate or of inorganic pyrophosphate allowed us to assign them as the educt and product state in the polymerization reaction cycle; i.e., the educt state is a complex in which the nucleic acid is positioned to allow nucleotide incorporation. The second RT:nucleic acid complex is the product state, which is formed immediately after nucleotide incorporation, but before RT translates to the next nucleotide.

Crystallography, X-Ray↗

PubMed2003

Cytoskeletal 10 nm filaments in cells of the algal phyla Chlorophyta, Charophyta, and Chrysophyta and their developmentally regulated and species-specific association with prosomes.

10 nm diameter filaments were observed in whole-mount preparations of algae of diverse phyla: Acetabularia acetabulum and A. major (Chlorophyta), Chara australis and Nitella flexilis (Charophyta), and Poterioochromonas malhamensis (Chrysophyta). A polyclonal antibody raised against a basic, 50 kDa DNA-binding protein of A. acetabulum stains the filaments of A. acetabulumand and A. major as well as of C. australis and N. flexilis. While in the perinuclear region of A. acetabulumand and A. major and throughout the cytoplasm of P. malhamensis the 10 nm filaments have a smooth appearance, in the stalk of A. acetabulumand and A. major they are densely covered by globular structures; in C. australis and N. flexilis they are less frequently associated with such material. The morphology of a part of the globular particles is quite reminiscent of prosomes. A monoclonal antibody elicited against prosomes isolated from A. acetabulum indeed decorates the globular particles on the A. acetabulum and A. major filaments. The possible role of these filament-particle associations is discussed.

Characeae↗

PubMed2003

Novel mode of hormone induction of tandem tomato invertase genes in floral tissues.

The genomic organization of two extracellular invertase genes from tomato (Lin5 and Lin7), which are linked in a direct tandem repeat, and their tissue-specific and hormone-inducible expression are shown. Transient expression analysis of Lin5 promoter sequences fused to the beta-glucuronidase (GUS) reporter gene (uidA) demonstrates a specific expression of Lin5 during tomato fruit development. A Lin5 promoter fragment was fused to the truncated nos promoter to analyse hormone induction via GUS reporter gene activity in transiently transformed tobacco leaves. A specific up-regulation of GUS activity conferred by this Lin5 promoter fragment in response to gibberellic acid (GA), auxin and abscisic acid (ABA) treatment was observed, indicating a critical role of the regulation of Lin5 by phytohormones in tomato flower and fruit development. In situ hybridization analysis of Lin7 shows a high tissue-specific expression in tapetum and pollen. These results support an important role for Lin5 and Lin7 extracellular invertases in the development of reproductive organs in tomato and contribute to unravel the underlying regulatory mechanisms.

Abscisic Acid↗

PubMed2003

Measuring the porosity and the tortuosity of porous materials via reflected waves at oblique incidence.

An ultrasonic reflectivity method is proposed for measuring porosity and tortuosity of porous materials having a rigid frame. Porosity is the relative fraction by volume of the air contained within a material. Tortuosity is a geometrical parameter which intervenes in the description of the inertial effects between the fluid filled the porous material and its structure at high frequency range. It is generally easy to evaluate the tortuosity from transmitted waves, this is not the case for porosity because of its weak sensitivity in transmitted mode. The proposed method is based on measurement of reflected wave by the first interface of a slab of rigid porous material. This method is obtained from a temporal model of the direct and inverse scattering problems for the propagation of transient ultrasonic waves in a homogeneous isotropic slab of porous material having a rigid frame [Z. E. A. Fellah, M. Fellah, W. Lauriks, and C. Depollier, J. Acoust. Soc. Am. 113, 61 (2003)]. Reflection and transmission scattering operators for a slab of porous material are derived from the responses of the medium to an incident acoustic pulse at oblique incidence. The porosity and tortuosity are determined simultaneously from the measurements of reflected waves at two oblique incidence angles. Experimental and numerical validation results of this method are presented.

Journal Article↗

PubMed2003

Determination of transport parameters in air-saturated porous materials via reflected ultrasonic waves.

An ultrasonic reflectivity method of evaluating the acoustic parameters of porous materials saturated by air (or any other gas) is discussed. The method is based on experimental detection of waves reflected at normal incidence by the first and second interface of the material. This method is based on a temporal model of direct and inverse scattering problems for the propagation of transient ultrasonic waves in a homogeneous isotropic slab of porous material with a rigid frame [Fellah et al., J. Acoust. Soc. Am. 113, 61-73 (2003)]. Generally, the conventional ultrasonic approach can be used to determine tortuosity, and viscous and thermal characteristic lengths via transmitted waves. Porosity cannot be estimated in transmitted mode because of its very weak sensitivity. First interface use of the reflected wave at oblique incidence leads to the determination of porosity and tortuosity [Fellah et al., J. Acoust. Soc. Am. 113, 2424-2433 (2003)] but this is not possible at normal incidence. Using experimental data of reflected waves by the first and second interface at normal incidence simultaneously leads to the determination of porosity, tortuosity, viscous and thermal characteristic lengths. As with the classic ultrasonic approach for characterizing porous material saturated with one gas, both characteristic lengths are estimated individually by assuming a given ratio between them. Tests are performed using weakly resistive industrial plastic foams. Experimental and numerical results, and prospects are discussed.

Journal Article↗

PubMed2003

A glutamate mutase is involved in the biosynthesis of the lipopeptide antibiotic friulimicin in Actinoplanes friuliensis.

Actinoplanes friuliensis produces the lipopeptide antibiotic friulimicin. This antibiotic is active against gram-positive bacteria such as multiresistant Enterococcus and Staphylococcus strains. It consists of 10 amino acids that form a ring structure and 1 exocyclic amino acid to which an acyl residue is attached. By a reverse genetic approach, biosynthetic genes were identified that are required for the nonribosomal synthesis of the antibiotic. In close proximity two genes (glmA and glmB) were found which are involved in the production of methylaspartate, one of the amino acids of the peptide core. Methylaspartate is synthesized by a glutamate mutase mechanism, which was up to now only described for glutamate fermentation in Clostridium sp. or members of the family ENTEROBACTERIACEAE: The active enzyme consists of two subunits, and the corresponding genes overlap each other. To demonstrate enzyme activity in a heterologous host, it was necessary to genetically fuse glmA and glmB. The resulting gene was overexpressed in Streptomyces lividans, and the fusion protein was purified in an active form. For gene disruption mutagenesis, a host-vector system was established which enables genetic manipulation of Actinoplanes spp. for the first time. Thus, targeted inactivation of biosynthetic genes was possible, and their involvement in friulimicin biosynthesis was demonstrated.

Amino Acid Sequence↗