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Biomedical subjects

R Schubert

Publications and source records attributed to R Schubert.

At least 73 records · Page 4Linked to original sources
PubMed1999

Type and frequency of chromosome aberrations in 781 couples undergoing intracytoplasmic sperm injection.

Cytogenetic investigations were performed in 781 couples prior to intracytoplasmic sperm injection (ICSI) because of severe male infertility or fertilization failures in previous in-vitro fertilization attempts. Out of these 1562 patients, 1012 had a normal karyotype without any aberrations (64.8%), 204 patients had an abnormal karyotypes (13.1%). These chromosome aberrations included constitutional aberrations (4.4%), fragile sites of autosomes (3.0%), low level mosaicism of sex chromosomes (4.0%) and secondary structural chromosome aberrations (4.2%). Combinations of different types of abnormalities were stated. Another 346 patients (22.1%) showed single cell aberrations; the significance of these is unclear at the moment. Constitutional chromosome aberrations were detected in 69 patients. The following chromosome aberrations were observed: 35 sex chromosomal aberrations (comprising hyperploidies of X or Y chromosomes, mosaicisms and derivative X and Y chromosomes), 34 autosomal aberrations including 14 reciprocal translocations, five Robertsonian translocations, six inversions, one marker chromosome, one trisomy 18 mosaicism and seven other structural aberrations. Three autosomal regions showed fragile sites: 6q13 in 2.9% of the patients, 17p12 and 10q24 in 0.05% each. In conclusion, our data show that a high number of infertile couples in an ICSI programme are affected by chromosome aberrations which occur in both sexes. It is suggested that a chromosomal analysis should be performed on both partners before ICSI treatment is initiated.

Chromosome Aberrations↗
PubMed1999

Protein kinase C reduces the KCa current of rat tail artery smooth muscle cells.

The hypothesis that protein kinase C (PKC) is able to regulate the whole cell Ca-activated K (KCa) current independently of PKC effects on local Ca release events was tested using the patch-clamp technique and freshly isolated rat tail artery smooth muscle cells dialyzed with a strongly buffered low-Ca solution. The active diacylglycerol analog 1,2-dioctanoyl-sn-glycerol (DOG) at 10 microM attenuated the current-voltage (I-V) relationship of the KCa current significantly and reduced the KCa current at +70 mV by 70 +/- 4% (n = 14). In contrast, 10 microM DOG after pretreatment of the cells with 1 microM calphostin C or 1 microM PKC inhibitor peptide, selective PKC inhibitors, and 10 microM 1,3-dioctanoyl-sn-glycerol, an inactive diacylglycerol analog, did not significantly alter the KCa current. Furthermore, the catalytic subunit of PKC (PKCC) at 0.1 U/ml attenuated the I-V relationship of the KCa current significantly, reduced the KCa current at +70 mV by 44 +/- 3% (n = 17), and inhibited the activity of single KCa channels at 0 mV by 79 +/- 9% (n = 6). In contrast, 0.1 U/ml heat-inactivated PKCC did not significantly alter the KCa current or the activity of single KCa channels. Thus these results suggest that PKC is able to considerably attenuate the KCa current of freshly isolated rat tail artery smooth muscle cells independently of effects of PKC on local Ca release events, most likely by a direct effect on the KCa channel.

Animals↗
PubMed1999

cAMP-dependent protein kinase is in an active state in rat small arteries possessing a myogenic tone.

The hypothesis that cAMP-dependent protein kinase (protein kinase A; PKA) is in an active state in small arteries possessing a myogenic tone was investigated in pressurized rat tail small arteries. At a pressure of 80 mmHg, these vessels constricted to 71.6 +/- 1.0% (n = 32) of the diameter of the fully relaxed state. The PKA inhibitors Rp-8-(4-chlorophenylthio)-adenosine 3',5'-cyclic monophosphothioate (Rp-CPT-cAMPS) and N-(2-([3-(4-bromophenyl)-2-propenyl]amino)-ethyl)-5- isoquinolinesulfonamide HCl (H-89) constricted these vessels dose dependently. For example, 300 microM Rp-CPT-cAMPS and 9 microM H-89 reduced vessel diameter by 11.0 +/- 1.2% (n = 8) and 14.3 +/- 3.6% (n = 5), respectively. The cGMP-dependent protein kinase (protein kinase G; PKG) inhibitor Rp-8-bromo-beta-phenyl-1,N(2)-etheno-guanosine 3', 5'-cyclic monophosphothioate (Rp-8-Br-PET-cGMPS) did not alter vessel diameter up to a concentration of 10 microM. Neither endothelium removal nor inhibition of neural transmission affected the action of Rp-CPT-cAMPS. The effect of 300 microM Rp-CPT-cAMPS was reduced by 82% after pretreatment of the vessel with 100 nM iberiotoxin, a blocker of calcium-activated potassium (K(Ca)) channels. However, the effect of 300 microM Rp-CPT-cAMPS was not altered after pretreatment with 1 mM 4-aminopyridine, a blocker of delayed rectifier potassium channels, or 10 microM ryanodine, a blocker of ryanodine receptor-generated calcium sparks. In inside-out patch-clamp experiments on cells isolated from rat tail small arteries, 10 U/ml of the catalytic subunit of PKA together with 100 microM MgATP increased K(Ca) channel activity 30.1 +/- 9. 8-fold (n = 9). Additionally, neither inhibition of PKA or PKG nor moderate activation of PKA or PKG altered the vessel response to a pressure step from 80 to 120 mmHg. These results suggest that in rat tail small arteries possessing a myogenic tone 1) PKA is in an active state modulating the level of the myogenic tone, and 2) K(Ca) channels mediate, at least partly, this effect of PKA.

Animals↗
PubMed1999

Contrast-enhanced sonography of vesicoureterorenal reflux in children: preliminary results.

OBJECTIVE: The aim of our study was to evaluate contrast-enhanced sonography as an alternative to radiographic voiding cystourethrography in the detection of vesicoureteral reflux. SUBJECTS AND METHODS: A total of 46 children, ranging in age from 3 weeks to 14 years (median: 4 years, 6 months) with 92 ureterorenal units were investigated for reflux using radiographic voiding cystourethrography and contrast-enhanced sonography in one session. After sonography of the urinary tract, the bladder was filled with saline solution via a catheter. Later, a contrast-enhancing agent was instilled and sonography was repeated. Documentation was done using S-VHS video and a laser camera. Reflux was diagnosed when microbubbles were observed in the ureter or in the renal pelvis. In addition, conventional voiding cystourethrography was performed. Patients without micturition during either sonography or radiographic examination were excluded (eight ureterorenal units). RESULTS: The findings obtained by contrast-enhanced sonography and voiding cystourethrography were concordant in 78 ureterorenal units (92.9%). No reflux was detected in 67 units (79.8%) by either method. With voiding cystourethrography as the standard of reference, the sensitivity of contrast-enhanced sonography was 91.7%; the specificity, 93.1%; and the accuracy, 92.9%. The positive predictive value was 68.8%, and the negative predictive value was 98.5%. CONCLUSION: Contrast-enhanced sonography is highly sensitive for the detection of vesicoureteral reflux. Therefore, it may reduce the number of radiographic investigations.

Child, Preschool↗
PubMed1999

The myogenic response: established facts and attractive hypotheses.

The myogenic response of small arteries and arterioles has been shown to contribute significantly to autoregulation in different vascular beds. It is characterized by a constriction of the vessel after an increase of transmural pressure and a dilation of the vessel after a decrease of transmural pressure. This review examines the evidence for the mechanisms of the myogenic response, with the aim of distinguishing between facts and hypotheses. It appears to be established that the myogenic response is stimulated by an alteration of vessel wall tension, that it does not require the presence of the endothelium and, for pressure increases, that it is accompanied by a membrane depolarization and an increase of the intracellular Ca2+ concentration, which depends largely on an influx of extracellular calcium via voltage-operated calcium channels. Under in vitro conditions, it may further be considered an established fact that the myogenic response can be modulated by transmitters, like noradrenaline, and factors released from the endothelium upon its activation. In contrast, many other aspects of the myogenic response remain hypothetical. Thus, the mechanism of the depolarization, its importance for the development of the myogenic response, the participation of other pathways for calcium influx, and the role of an intracellular calcium release in the myogenic response are still under debate. Furthermore, the participation of a variety of intracellular second messenger systems in the myogenic response, i.e. inositol trisphosphate, diacylglycerol, phospholipase A2, protein kinase C or 20-hydroxyeicosatetraenoic acid, is still unclear. Additionally, the roles of the pulsatility of the blood pressure and of remote signals from neighbouring vessel segments as well as of different metabolites are not clarified. This review suggests that while the primary mechanisms of the myogenic response are well understood, the details of the signalling pathways are still undefined. The clinical significance of the myogenic response remains to be determined.

Animals↗
PubMed1999

Formation of supernumerary euchromatic short arm isochromosomes: parent and cell stage of origin in new cases and review of the literature.

In order to get insight in the formation of isochromosomes we analysed different supernumerary euchromatic short arm isochromosomes for the parent and cell stage of origin. After cytogenetic detection and confirmation by fluorescence-in-situ hybridization we performed short tandem repeat typing in a child with i(9p), three with i(12p) and three with i(18p). The extra chromosomes were monocentric in each case, the i(9p) and i(12p) constitutions were found in mosaic with normal cell lines. Our results and those of other groups indicate a strong role of maternal meiosis in isochromosome formation: in one i(8p), 4 out of 5 i(9p), 7 out of 12 i(12p) and 18 out of 23 i(18p) families a maternal meiotic nondisjunction had occurred prior to the centromere misdivision. For chromosome 18, the majority of isochromosomes originated from a maternal meiosis II error (16/18). For the other tetrasomic constitutions the isochromosomes could be delineated from paternal as well as from maternal origin, the short tandem repeat typing patterns being consistent with meiotic or mitotic cell stages of formation. Thus, independently of the chromosomal origin, in the majority of cases with additional euchromatic isochromosomes maternal meiosis nondisjunction is the initial step followed by centromeric misdivision. Postzygotic nondisjunction as suggested previously due to mosaics observed in tetrasomies 9p and 12p seems to be of minor importance. The observed origin of isochromosomes 18 corresponds to that of trisomy 18, where the majority of cases can be delineated from maternal meiosis II errors.

Child↗
PubMed1999

Interactive volume visualization using "intelligent movies".

High quality visualization of medical volume models as performed by the VOXEL-MAN and similar systems is still too time consuming and the interaction complicated when sophisticated tools like dissection are used. We hence developed a new paradigm allowing to create simpler derivatives of the model, called "intelligent movies". These are in QuickTime or QuickTime VR format which allow interactive exploration with two degrees of freedom. As a decisive novelty, we extended it by a pixelwise link to the knowledge base which may be queried in the image context. Thus scenes emphasizing a selected aspect of the volume model may be created as intelligent movies, which a user (referring physician, student) can explore largely with the functionality of VOXEL-MAN, but in real time--on any standard PC--and also via a JAVA applet within web browsers. This is shown with the example of 3D interactive anatomical atlases and clinical cases.

Anatomy, Cross-Sectional↗
PubMed1999

Analysis of a de novo complex chromosome rearrangement involving chromosomes 4, 11, 12 and 13 and eight breakpoints by conventional cytogenetic, fluorescence in situ hybridization and spectral karyotyping.

A complex chromosome rearrangement (CCR) with eight breakpoints resulting in four derivative chromosomes (4, 11, 12 and 13) was detected prenatally in a male fetus of a twin pregnancy. The karyotype of the female second fetus was normal. The apparently balanced de novo CCR was identified by classical cytogenetic methods and fluorescence in situ hybridization (FISH). We compared these findings with results from spectral karyotyping (SKY).

Abortion, Eugenic↗
PubMed1998

Erosion and controlled release properties of semisolid vesicular phospholipid dispersions.

Phosphatidylcholine, when dispersed in aqueous medium in high concentrations (300 mg/g and above) by high pressure homogenisation, forms semisolid pastes of vesicular morphology. The multivesicular matrix can accommodate hydrophilic compounds in the aqueous compartments. The disintegration and release of hydrophilic marker of these dispersions were studied in vitro by using a flow-through cell. Slow release of the marker over periods of hours up to days took place via two different mechanisms: (1) erosion of the matrix with release of marker-filled liposomes and marker which had been trapped in between the liposomes and (2) diffusion of marker through the membranes. Whereas for lipid concentrations up to 300 mg/g almost spontaneous disintegration occurred, more concentrated pastes (350-400 mg/g) showed zero-order erosion kinetics for 4-6 h. Erosion was rate limiting for overall release. For 450 and 500 mg/g lipid dispersions, the release of free marker followed square root of time kinetics for 13 or 21 h, respectively, which is typical for matrix-controlled diffusion. Underlying the diffusion was a slow zero-order erosion of the matrix. The results are important for the future development of vesicular phospholipid gels as sustained release therapeutic system, e.g. as implantable depot.

Drug Carriers↗
PubMed1998

pH-sensitive liposomes for receptor-mediated delivery to chicken hepatoma (LMH) cells.

pH-sensitive liposomes composed of dioleoylphosphatidylethanolamine and cholesterol hemisuccinate (3:2 mol/mol) bearing the N-acetylglucosamine derivative of bovine serum albumin (N-Ac-BSA) were applied for receptor-mediated delivery in chicken hepatoma (LMH) cells expressing the N-Ac-BSA-binding asialoglycoprotein receptor. Fluorescently labeled dextran was entrapped in liposomes by a modified freeze-thawing method (encapsulation efficiency of 23%). A novel method of coupling proteins onto the surface of preformed liposomes yielded a coupling efficiency of 60-70%. The association of pH-sensitive and lecithin liposomes with LMH cells was monitored by fluorescence-activated cell sorting and confocal microscopy. Prerequisites for receptor-mediated delivery to LMH cells were both the pH sensitivity of liposomes and the presence of N-Ac-BSA on the liposomal surface.

Animals↗
PubMed1998

Genetic counseling in a patient with XXY/XXXY/XY mosaic Klinefelter's syndrome: estimate of sex chromosome aberrations in sperm before intracytoplasmic sperm injection.

OBJECTIVE: To report the sex chromosome aberrations in the sperm of a patient with mosaic Klinefelter's syndrome before ICSI. DESIGN: Case report. SETTING: Institute of Human Genetics, University Hospital PATIENT(S): A patient with an XXY/XXXY/XY mosaic Klinefelter's syndrome and extreme oligozoospermia. INTERVENTION(S): Skin biopsy, buccal smear, hair root sampling, and semen sampling. MAIN OUTCOME MEASURE(S): The karyotypes of three additional somatic cell systems and the ratio of sex chromosome aberrations in sperm. RESULT(S): After two-color fluorescence in situ hybridization of 202 interphase sperm nuclei, both the proportion of hyperhaploid 24, XY and 25, XXY sperm (5.0% and 0.5%, respectively) and of hyperhaploid 24, XX sperm (2.0%) were elevated. In contrast with peripheral lymphocytes, 93.9% of which showed sex chromosome aberrations, in the present patient only 7.5% of sperm proved to be hyperhaploid with an extra sex chromosome. CONCLUSION(S): The determination of sex chromosome aberrations in the sperm of a patient with mosaic Klinefelter's syndrome may provide additional information to estimate the transmission risk to his offspring.

Adult↗
PubMed1998

K+ currents of encephalitogenic memory T cells decrease with encephalitogenicity while interleukin-2 (IL-2) receptor expression remains stable during IL-2 dependent cell expansion.

Previous studies revealed a linkage between increased K+ current and lymphocyte activation upon non-specific stimulation with mitogenic lectins and antibodies. So far no information is available about the behaviour of K+ currents in specifically autoantigen-stimulated lymphocytes. Therefore, we have investigated K+ currents in encephalitogenic T line cells, specifically stimulated with myelin basic protein, using the whole-cell patch-clamp technique. In parallel, the T cell activation marker interleukin-2 (IL-2) receptor was measured quantitatively by flow cytometry. Outward currents were observed in response to depolarizing voltage steps from a holding potential of -80mV. The peak current density increased with more positive membrane potentials, where the current threshold was about -40mV and the maximum conductance was 1.22nS/pF. This current was characterized by a fast activation and a fast inactivation with half maximal inactivation at -67mV. The sensitivity of the peak current to K+ channel blocking agents was as follows: 4-aminopyridine (4-AP) had a half blocking concentration of 0.4mM and a maximal block of 83.7% at 10mM 4-AP, tetraethyl-ammonium caused a block of 6% at 0.1mM, 15% at 1mM and 40% at 10mM, charybdotoxin blocked 90% at 100nM, whereas iberiotoxin had no effect (all values at a clamped membrane potential of +30mV). The encephalitogenic T cells used in our study reach their highest encephalitogenic potency on day 3 to 4 after the onset of restimulation. Furthermore, K+ currents were measured during the whole course of an in vitro restimulation cycle. The peak currents normalized to cell capacitance reached their maximum on day 2 (326+/- 52.8pA/pF, n = 4) and decreased thereafter as follows: day 3: 139.7 +/- 7.87pA/pF (n = 27), day 4: 85.4 +/- 8.95pA/pF (n = 28) and day 5: 40.9 +/- 7.45pA/pF (n = 17). The activation and inactivation characteristics of the current and its responses to selective blockers were similar at all days after restimulation. In contrast to the K+ current, IL-2 receptor expression was maintained on > 95% of cells until day 6 after restimulation. In conclusion, the K+ currents measured in rat encephalitogenic T cells resemble n-type voltage-gated K+ currents described in mice and man. The comparison of K+ current, IL-2 receptor expression and encephalitogenic potency let us suppose that the observed K+ current represents an early event of specific T cell activation and can serve as a parameter of high functional activity of T cells corresponding to their encephalitogenicity.

Animals↗
PubMed1998

Energy-filtered cryotransmission electron microscopy of liposomes prepared from human stratum corneum lipids.

We used cryo-TEM to examine the morphology of vesicles formed from lipids of the human stratum corneum (hSC). Human stratum corneum lipid liposomes (hSCLLs) were prepared in buffer at various pH values, using different preparation methods (film method, extrusion, ultrasonication, detergent dialysis). The morphology of hSCLLs at pH 7.4 differed markedly from that of liposomes formed by phospholipids, showing folds, stacks and membrane thickening. At pH 5.0, corresponding to natural conditions at the skin surface, membrane structures are essentially the same as those prepared at pH 7.4. Sharp edges in hSCLLs, branching membranes and stable membrane stacks were explained by the presence of ceramides, the major components and structural elements of human stratum corneum lipids (hSCLs). Thickened areas in the membranes may be caused by the local accumulation of triacylglycerols and cholesterol esters in the hydrophobic interior of the bilayer.

Journal Article↗
PubMed1998

Energy-filtered cryotransmission electron microscopy of liposomes prepared from human stratum corneum lipids.

We used cryo-TEM to examine the morphology of vesicles formed from lipids of the human stratum corneum (hSC). Human stratum corneum lipid liposomes (hSCLLs) were prepared in buffer at various pH values, using different preparation methods (film method, extrusion, ultrasonication, detergent dialysis). The morphology of hSCLLs at pH 7.4 differed markedly from that of liposomes formed by phospholipids, showing folds, stacks and membrane thickening. At pH 5.0, corresponding to natural conditions at the skin surface, membrane structures are essentially the same as those prepared at pH 7.4. Sharp edges in hSCLLs, branching membranes and stable membrane stacks were explained by the presence of ceramides, the major components and structural elements of human stratum corneum lipids (hSCLs). Thickened areas in the membranes may be caused by the local accumulation of triacylglycerols and cholesterol esters in the hydrophobic interior of the bilayer.

Ceramides↗
PubMed1998

Partonomies for interactive explorable 3D-models of anatomy.

We introduce a concept to model subtle part-whole-semantics for the use with interactive 3d-models of human anatomy. Similar to experiences with modeling partonomies for physical artifacts like machines or buildings we found one unique part-whole-relation to be insufficient to represent anatomical reality. This claim will be illustrated with anatomical examples. According to the requirements these examples demand, a semantic classification of part-whole-relations is introduced. Initial results in modeling anatomical partonomies for a 3d-visualization environment proved this approach to be an promising way to represent anatomy and to enable powerful complex inferences.

Anatomy↗
PubMed1997

Report of two new cases of Pallister-Killian syndrome confirmed by FISH: tissue-specific mosaicism and loss of i(12p) by in vitro selection.

Tissue-specific mosaic distribution of an additional isochromosome 12p is the characteristic chromosomal aberration in Pallister-Killian syndrome. Often it is confined to fibroblasts, whereas lymphocytes show a normal karyotype. Two cases are reported in which the distribution of the additional i(12p) was analysed in various tissues. The isochromosomes were characterised by conventional banding technics and fluorescence in situ hybridization (FISH). In the first case, diagnosed prenatally, 4 different tissues were analysed. A direct preparation of chorionic villi (21 gestational weeks) showed an extra marker chromosome in 19% and two additional copies in 3% of the examined cells. In two cultures of amniocytes (17 and 21 weeks), the i(12p) was observed in 23% and 12%, respectively. It was absent in cultured lymphocytes of fetal blood (21 weeks). The fibroblast long-term culture of umbilical cord showed the i(12p) in 100% of metaphases. In the second case of a term infant the i(12p) was diagnosed in cultured lymphocytes (4%) and fibroblasts (93%). Secondary loss of the isochromosome was evaluated by in vitro selection in case 2 analysing metaphases and interphases of fibroblasts in the 1st, 4th and 5th subculture using FISH. The proportion of cells with i(12p) decreased from 93% to 40% and to 28%, respectively. DNA analysis in case 1 showed a maternal meiotic origin of the i(12p). The prenatally detected clinical findings in both cases showed characteristic abnormalities of the Pallister-Killian syndrome.

Chromosome Aberrations↗
PubMed1997

[Vitamin B1, B2, A and E and beta-carotene content in transitional breast milk and comparative studies in maternal and umbilical cord blood].

The contents of the vitamins B1 (27 ng/ml), B2 (57 ng/ml), A (1.3 micrograms/ml), and E (9.7 micrograms/ml) as well as beta-carotene (0.2 microgram/ml) in transitional human milk were determined for up to 35 women aged between 19 and 31 years. Additionally, the vitamin content in maternal and cord plasma as well as the erythrocytic transketolase- and glutathione-reductase activities of the water soluble vitamins were measured. Dietary recalls were evaluated for the nutritional intake of vitamins. Concerning the fat soluble vitamins, the breast fed newborns received the recommended amounts of the German Society of Nutrition (DGE) for this group. In contrast to this, the supply of the water soluble vitamins (B1: 13.5 micrograms/500 ml; B2: 28.5 micrograms/500 ml) attained only 5 to 10% of the recommendations for newborns during the first two weeks after parturition with breast feeding. Vitamin content of maternal plasma (B1: 6.1 +/- 2.8 ng/ml) and erythrocytic enzyme activities (alpha ETK: 0.86-1.62; alpha EGR: 1.08-1.75) indicated a low or sufficient intake, while the values in cord blood (B1: 19.8 +/- 6.5 ng/ml; alpha ETK: 0.62-1.62; alpha EGR: 1.01-1.47) were in accordance with a satisfactory supply.

Adult↗