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B Schwab

Publications and source records attributed to B Schwab.

At least 19 recordsLinked to original sources
PubMed2003

Regulation of cell expansion by the DISTORTED genes in Arabidopsis thaliana: actin controls the spatial organization of microtubules.

The control of the directionality of cell expansion was investigated using a class of eight genes, the so-called DISTORTED (DIS) genes, that are required for proper expansion of leaf trichomes in Arabidopsis thaliana. By tracing the separation of latex beads placed on the trichome surface, we demonstrate that trichomes grow by diffuse rather than tip growth, and that in dis mutants deviations from the normal orientation of growth can occur in all possible directions. We could not detect any differences in intracellular organization between wild-type and dis-group mutants by electron microscopy. The analysis of double mutants showed that although the expression of the dis phenotype is generally independent of branching and endoreduplication, dis mutations act synthetically in combination lesions in the ZWI gene, which encodes a kinesin motor protein. Using a MAP4:GFP marker line, we show that the organization of cortical microtubules is affected in dis-group mutants. The finding that most dis-group mutants have actin defects suggested to us that actin is involved in organizing the orientation of microtubules. By analyzing the microtubule organization in plants treated with drugs that bind to actin, we verified that actin is involved in the positioning of cortical microtubules and thereby in plant cell expansion.

Actins↗
PubMed2001

Prenatal diagnosis of congenital heart disease and neonatal outcome--a six years experience.

BACKGROUND: Prenatal diagnosis of congenital heart disease (CHD) is important for proper perinatal and neonatal management, as CHD occurs in approximately eight of 1000 live births. Antenatal detection of cardiac malformations is crucial as altered obstetric and neonatal management may be required and the neonate will benefit from delivery at a tertiary care center. METHODS: A retrospective comparison between pre- and postnatal diagnoses was accomplished. All fetal echocardiographic scans performed and CHD's detected postnatally between January 1994 and December 1999 by the department of obstetrics and gynecology and pediatric cardiology - Grosshadern, Munich University Hospital were reviewed. RESULTS: The incidence of CHD was 1.5% (116/ 7913). CHD was suspected by prenatal ultrasound in 57 fetuses. Postnatally, 116 congenital cardiac anomalies were diagnosed. Overall, the intrauterine detection rate was 38% (44/116). 72% (84) of the diagnosed anomalies were Septal Defects, 16% (19) disorders of the Atrioventricular Valves and 11% (13) Anomalies of the Great Vessels. In 10% (11) of fetuses chromosomal abnormalities were found. 8% (9) newborns suffered from congenital syndromes. In 55% (64) children were delivered preterm (<37 weeks of gestation). 5% (6) of the neonates required surgery within their first year of life. 28% (33) of children with CHD did not survive the first year of life. CONCLUSION: As the prenatal diagnosis is important for pre-, peri- and postnatal management, diagnostic accuracy is essential. Nevertheless, the accuracy of postnatal pediatric echo still exceeds that of the prenatal scan.

Adolescent↗
PubMed2001

Effects of cytochalasin D and latrunculin B on mechanical properties of cells.

Actin microfilaments transmit traction and contraction forces generated within a cell to the extracellular matrix during embryonic development, wound healing and cell motility, and to maintain tissue structure and tone. Therefore, the state of the actin cytoskeleton strongly influences the mechanical properties of cells and tissues. Cytochalasin D and Latrunculin are commonly used reagents that, by different mechanisms, alter the state of actin polymerization or the organization of actin filaments. We have investigated the effect of a wide range of Cytochalasin D and Latrunculin B concentrations (from 40 pM to 10 microM) on the mechanical properties of the cells within fibroblast populated collagen matrices. Contractile force and dynamic stiffness were measured by uniaxial stress-strain testing. The range of effective concentrations of Cytochalasin D (200 pM-2 microM) was broader than that of Latrunculin B (20 nM-200 nM). Activating the cells by serum did not change the effective range of Cytochalasin D concentrations but shifted that of Latrunculin B upward by tenfold. Simple mathematical binding models based on the presumed mechanisms of action of Cytochalasin D and Latrunculin B simulated the concentration-dependent mechanical changes reasonably well. This study shows a strong dependence of the mechanical properties of cells and tissues on the organization and degree of polymerization of actin filaments.

Actins↗
PubMed2001

Image-guided surgery of the anterior skull base.

Minimally invasive surgical procedures have revolutionized surgery of the paranasal sinuses. The endonasal procedure has become standard practice due to a better understanding of pathological physiology. However, malformations, previous operations and bleeding can interfere greatly with intraoperative orientation. Together with microscopy and endoscopy, image-guided surgery has the potential to be of significant assistance to the surgeon. We evaluated the electromagnetic navigation system InstaTrak 2000 (Visualization Technologies Inc., Lawrence, MA) in 168 patients with various disorders of the paranasal sinuses who underwent endonasal surgery. The system consists of a headset attached to an electronic transmitter which is fitted on the dorsum of the nose and in the external auditory canal. With the aid of low-frequency magnetic fields the position of the instrument equipped with an electromagnetic receiver is calculated on the basis of the reaction of ferromagnetic components in the magnetic field; the location is displayed in orthogonal sections on a high resolution screen. The intraoperative accuracy of the system was estimated to be 1.2-2.8 mm. The preparation time amounted to < 10 min. No system failures were observed. The InstaTrak 2000 navigation system is only suitable for endonasal surgery. The placement of the electromagnetic transmitter and receiver allows flexible head positioning through the use of a headset. This system is a valuable aid for the surgeon under anatomically complex conditions. The technology also lends itself well to training purposes, as visualization in different sectional planes augments the understanding of anatomy and pathological anatomy.

Adult↗
PubMed2000

Trichome morphogenesis in Arabidopsis.

Trichomes (plant hairs) in Arabidopsis thaliana are large non-secreting epidermal cells with a characteristic three-dimensional architecture. Because trichomes are easily accessible to a combination of genetic, cell biological and molecular methods they have become an ideal model system to study various aspects of plant cell morphogenesis. In this review we will summarize recent progress in the understanding of trichome morphogenesis.

Arabidopsis↗
PubMed2000

Magnesium sulfate potentiates morphine antinociception at the spinal level.

UNLABELLED: Intrathecal magnesium sulfate coinfusion with morphine increases antinociception in normal rats; however, because magnesium also delays the onset of tolerance, it is not clear whether this additional antinociception is a result of potentiated analgesia or tolerance abatement. We examined the antinociceptive interaction of intrathecal (IT) bolus magnesium sulfate and morphine in morphine naive rats and those with mechanical allodynia after a surgical incision. After intrathecal catheter implantation, rats were given preinjections of magnesium or saline, followed by injections of morphine or saline. In morphine naïve rats, IT bolus magnesium sulfate 281 and 375 microg followed by IT morphine 0.25 or 0.5 nmol enhanced peak antinociception and area under the response versus time curve two-to-three-fold in the tail-flick test as compared with morphine alone. Likewise, in rats with incisional pain, IT bolus magnesium sulfate 188 and 375 microg followed by morphine 0.5 nmol reduced mechanical allodynia, whereas morphine 0.5 nmol alone did not. This study suggests that IT magnesium sulfate potentiates morphine at a spinal site of action. IMPLICATIONS: Magnesium sulfate potentiates morphine analgesia when coadministered intrathecally in normal rats, and in an animal model of mechanical allodynia after a surgical incision. These results suggest that intrathecal administration of magnesium sulfate may be a useful adjunct to spinal morphine analgesia.

Analgesics, Opioid↗
PubMed1999

Isolation of ethyl methanesulfonate-induced gametophytic mutants in Arabidopsis thaliana by a segregation distortion assay using the multimarker chromosome 1.

The life cycle of plants comprises two alternating generations, the diploid sporophyte (spore-bearing plant) and the haploid gametophyte (gamete-bearing plant). In contrast to animals, the postmeiotic cells give rise to haploid organisms whose function is to produce the gametes and to mediate fertilization. Analysis of gametophyte development and function has been hampered by the difficulty of identifying haplo-phase-specific mutants in conventional mutagenesis screens. Here we use a genetic strategy that is based on segregation distortion of nearby visible markers to screen for EMS-induced gametophytic mutants in Arabidopsis thaliana. Using the multiple marker chromosome mm1 we have isolated seven lines that displayed an altered segregation of markers. Reciprocal backcrosses of these lines showed a marked reduction of the transmission of the male and/or female gametes. Phenotypic analysis revealed that different aspects of either gametophytic development or function were affected. Three male gametophytic lines showed specific arrests during pollen development. One male gametophytic line was specifically defective in pollen tube elongation. Three gametophytic lines showed variable defects in both male and female gametophytic development.

Arabidopsis↗
PubMed1999

Generation of a spacing pattern: the role of triptychon in trichome patterning in Arabidopsis.

Trichomes in Arabidopsis are single-celled hairs that exhibit a regular spacing pattern. Here, the role of TRIPTYCHON (TRY) in the generation of this spacing pattern is studied. By using genetic mosaics, we demonstrate that the formation of trichome clusters in try mutants is not correlated with cell lineage, indicating that TRY is required to single out trichome cells in a process involving cellular interactions. The genetic interactions of TRY, GLABRA1 (GL1), and TRANSPARENT TESTA GLABRA (T TG) in trichome patterning are assessed by determining the cluster frequency in various genetic combinations. It is shown that TRY acts as a negative regulator of GL1- and TTG-dependent pathways. Furthermore, it is demonstrated that trichome initiation in ttg-1, a strong ttg allele, is rescued almost to wild-type levels in a try background in which GL1 is expressed under the control of the cauliflower mosaic virus 35S promoter, indicating that T TG acts upstream of GL1 and TRY. These findings are incorporated into a model to explain the generation of a trichome spacing pattern from a homogeneous population of epidermal cells.

Arabidopsis↗