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R Schmidt

Publications and source records attributed to R Schmidt.

At least 217 records · Page 12Linked to original sources
PubMed1999

Human adeno-associated virus type 5 is only distantly related to other known primate helper-dependent parvoviruses.

We have characterized 95% (4,404 nucleotides) of the genome of adeno-associated virus type 5 (AAV5), including part of the terminal repeats and the terminal resolution site. Our results show that AAV5 is different from all other described AAV serotypes at the nucleotide level and at the amino acid level. The sequence homology to AAV2, AAV3B, AAV4, and AAV6 at the nucleotide level is only between 54 and 56%. The positive strand contains two large open reading frames (ORFs). The left ORF encodes the nonstructural (Rep) proteins, and the right ORF encodes the structural (Cap) proteins. At the amino acid level the identities with the capsid proteins of other AAVs range between 51 and 59%, with a high degree of heterogeneity in regions which are considered to be on the exterior surface of the viral capsid. The overall identity for the nonstructural Rep proteins at the amino acid level is 54.4%. It is lowest at the C-terminal 128 amino acids (10%). There are only two instead of the common three putative Zn fingers in the Rep proteins. The Cap protein data suggest differences in capsid surfaces and raise the possibility of a host range distinct from those of other parvoviruses. This may have important implications for AAV vectors used in gene therapy.

Amino Acid Sequence↗
PubMed1999

Surfactant subtype conversion is related to loss of surfactant apoprotein B and surface activity in large surfactant aggregates. Experimental and clinical studies.

Conversion of the highly surface-active subtype of pulmonary surfactant known as large surfactant aggregates (LA) to small aggregates (SA) with poor surface activity has recently been shown to occur upon cyclic changes of the air-liquid interface area in vitro. By subjecting pooled rabbit bronchoalveolar lavage fluid (BALF) to this maneuver, we found that conversion of LA to SA was accompanied by a marked decline in the ability of the remaining LA fraction to reduce surface tension by adsorption and during film compression on a pulsating bubble surfactometer. SA obtained by centrifugation of noncycled rabbit BALF had a similar phospholipid (PL) but different neutral lipid (NL) composition than did the LA. Upon cycling, the increased formation of SA obliterated this difference. No substantial difference in the PL, NL, or fatty acid profile of LA was noted before and after cycling. In contrast, the content of surfactant apoprotein-B (SP-B) in the LA decreased dramatically to nearly undetectable levels during the cycling maneuver, and this decline in SP-B content was closely correlated with the decrease in proportional appearance of LA and loss of surface activity of this fraction. Reconstitution of LA with intact SP-B after cycling virtually fully restored the surface activity of this surfactant subtype. When comparing lavage samples from adults with acute respiratory distress syndrome (ARDS; n = 10) with samples from healthy controls (n = 11), we noted a marked reduction of SP-B in the LA fraction. There was a significant correlation between the SP-B content of the LA fraction and the relative percentage of LA in BALF or the lower surface activity of this surfactant subtype. We conclude that an SP-B-related loss of LA integrity and function may substantially contribute to the decline of this surfactant subtype and the loss of its surface activity during cycling in vitro and in clinical ARDS.

Adult↗
PubMed1999

Inhibition of memory consolidation by antibodies against cell adhesion molecules after active avoidance conditioning in zebrafish.

Cell adhesion molecules are expected to play an important role in long-term storage of information in the central nervous system. Several of these glycoproteins, such as NCAM, L1, and the ependymins, express the HNK-1 carbohydrate structure, which is known to be involved in cell-cell and cell-matrix interactions. To investigate the contribution of the HNK-1 epitope and the secretory glycoproteins ependymins to memory formation in zebrafish (Brachydanio rerio), we developed an active avoidance conditioning paradigm. Zebrafish were trained in a shuttle-box to cross a hurdle, to avoid mild electric shocks following a conditioning light signal. One hour after acquisition of the task, zebrafish were injected intracerebroventricularly with monoclonal antibodies against the HNK-1 epitope or polyclonal antibodies against ependymins. Control fish received immunoglobulins G (IgGs) from nonimmune rat serum or the monoclonal antibody C183 against an unrelated cell-surface protein of the cyprinid brain. Two days later, injected zebrafish were tested for recall, and for quantitative evaluation a retention score (RS), ranging from 1.0 for immediate recall to 0.0, indicating no saving, was calculated. The average RS of anti-HNK-1-injected fish (RS = 0.30) and anti-ependymin-injected fish (0.24) were significantly different from the RS of uninjected fish (0.77), of controls injected with nonimmune serum IgGs (0.68), of C183-injected controls (0.78), and of overtrained fish injected with anti-HNK-1 antibodies (0.81). Anti-HNK-1 and anti-ependymin antibodies were characterized by Western blot analyses of subcellular brain fractions and immunohistochemical staining of the zebrafish optic tectum. Our data suggest that the antibodies influence cell recognition events at synaptic membranes and/or associated intracellular signaling cascades, and thereby block memory consolidation.

Animals↗
PubMed1999

Histopathologic analysis of foci of signal loss on gradient-echo T2*-weighted MR images in patients with spontaneous intracerebral hemorrhage: evidence of microangiopathy-related microbleeds.

BACKGROUND AND PURPOSE: Patients with spontaneous intracerebral hemorrhage (ICH) frequently have small areas of signal loss on gradient-echo T2*-weighted MR images, which have been suggested to represent remnants of previous microbleeds. Our aim was to provide histopathologic support for this assumption and to clarify whether the presence and location of microbleeds were associated with microangiopathy. METHODS: We performed MR imaging and correlative histopathologic examination in 11 formalin-fixed brains of patients who had died of an ICH (age range, 45-90 years). RESULTS: Focal areas of signal loss on MR images were noted in seven brains. They were seen in a corticosubcortical location in six brains, in the basal ganglia/thalami in five, and infratentorially in three specimens. Histopathologic examination showed focal hemosiderin deposition in 21 of 34 areas of MR signal loss. No other corresponding abnormalities were found; however, hemosiderin deposits were noted without MR signal changes in two brains. All specimens with MR foci of signal loss showed moderate to severe fibrohyalinosis, and there was additional evidence of amyloid angiopathy in two of those brains. CONCLUSION: Small areas of signal loss on gradient echo T2*-weighted images indicate previous extravasation of blood and are related to bleeding-prone microangiopathy of different origins.

Aged↗
PubMed1999

Simultaneous occurrence of two supernumerary autosomal ring chromosomes r(1) and r(16) in twins.

Ring chromosomes are estimated to occur in 3/10000 newborns and the simultaneous occurrence of two autosomal rings must be a very rare event. Recently, the characterisation of these markers using fluorescence in situ hybridisation (FISH) has greatly enhanced cytogenetic-phenotypic correlations in patients with these marker chromosomes. This kind of analysis enabled us to clarify a unique karyotype containing a r(1) and a r(16) in identical twins born after a 26 week gestation with minimal somatic abnormalities. The origin of the rings was identified using a satellite and whole chromosome painting probes. FISH analysis showed the same abnormal female karyotype in both twins, 48,XX,+r(1)(p13q21),+r(16)(p11q11).ish r(1) (D1Z5+,wcpl+), r(16)(D16Z2+,wcp16+) in about two thirds of the cells. Each also had minor clones with a normal female karyotype or with one or the other supernumerary ring. Half of the r(1) contained CBG band negative material and the r(16) appeared to be totally CBG band positive. These twins represent the second report of the simultaneous occurrence of multiple autosomal rings. Their description may help to delineate a new chromosome disorder and shows the usefulness of FISH analysis.

Chromosomes, Human, Pair 1↗
PubMed1999

Keratinocyte-melanocyte co-cultures and pigmented reconstructed human epidermis: models to study modulation of melanogenesis.

Normal human melanocytes were amplified and cultured in a new defined culture medium without phorbol esters or cholera toxin. The medium decreased considerably the doubling time and increased the possible passage number. Melanocytes were co-seeded with normal human keratinocytes into 24 well culture dishes to screen potentially active modulators of melanogenesis. For the assay, the co-cultures were exposed to the compounds under investigation in the presence of 14C-thiouracil and 3H-leucine. Control cultures contain L-tyrosine or kojic acid, modulators which served as internal calibration standards. Changes in the rate of melanin synthesis were measured on the basis of 14C-thiouracil incorporation into newly synthesized melanin. A reduction or increase in 3H-leucine incorporation was taken as an indication of cytotoxicity or induction of proliferation, respectively. The NHK-NHM co-culture screening assay provides a useful tool to compare the activity of known modulators of melanogenesis and to perform structure-activity studies with newly identified modulators to improve their activity. The efficacy of particularly interesting new compounds was further evaluated on reconstructed pigmented epidermis after repeated topical application. The same model was used to assess the anti-pigmenting effect of sunscreens on UV-induced pigmentation. Integration of melanocytes from different ethnic origin resulted in pigmented epidermis reflecting different skin phenotypes, Caucasian, Asian and African.

1-Methyl-3-isobutylxanthine↗
PubMed1999

Microscope-assisted precision dentistry.

To enhance their vision for both clinical and laboratory procedures, an increasing number of dental practitioners are introducing magnification into their practices. Most are using either simple or compound loupes mounted on glasses frames. And although magnification is not new to dentistry, it is a trend that is gaining a broader acceptance among both seasoned practitioners and recent graduates. Many dental schools are allowing their students to use loupes on a discretionary basis, so the notion that magnification is reserved only to compensate for deteriorating vision is rapidly disappearing. Dental professionals have also begun to recognize that the quantity and quality of light in the working field is just as important as magnification. Headlamps with focused, color-correct light sources in combination with loupes are becoming popular. It is highly unlikely that a practitioner using loupes would relinquish them and return to practicing without magnification. The newest addition to the vision enhancement arena in dentistry is the operating microscope. In some medical subspecialties--such as otolaryngology, ophthalmology, plastic surgery, and neurosurgery--extensive microsurgical training is required to perform procedures at acceptable standards of precision. In 1998, the American Association of Endodontists (AAE) elected to mandate that all endodontic postgraduate students demonstrate proficiency using an operating microscope before they receive their certificates. Microscope use has also been reported in periodontics. For several decades, many dental laboratory technicians have used stereomicroscopes for trimming dies, refining castings, and performing other procedures that require a high degree of precision. However, according to microscope manufacturers, most current instrument sales are to general practitioners, who are not limiting the use of their microscopes to endodontic therapy--they are using them for a wide variety of procedures. Microscopes have the potential to enhance a dental practitioner's vision to unprecedented levels, but there are some practical questions that need to be addressed. What kind of visual acuity do dentists really need to perform high-quality dentistry? If a dentist wants to improve his or her vision, do loupes provide an adequate level of magnification? Is using a microscope too complicated for restorative and prosthodontic procedures, and how long does it take to become proficient with a microscope? These are some of the questions I posed to two outstanding dentists who have had extensive clinical experience using surgical microscopes. I also share my own experience with a microscope.

Dental Equipment↗
PubMed1998

Cloning and evaluation of the role of rat GALR-2, a novel subtype of galanin receptor, in the control of pain perception.

We have identified a novel subtype of galanin receptor (GALR-2) in rat dorsal root ganglia and spinal cord. The open reading frame of GALR-2 is 1116 nucleotides long, encoding a protein of 372 amino acids with a theoretical molecular mass of 40.7 kD. Membranes prepared from stable pools of 293 cells expressing GALR-2, but not wild-type 293 cells, demonstrated high affinity galanin binding sites. Rat galanin and galanin-related peptides M40, C7, M15, and galanin effectively competed for binding; peptide C7 demonstrated a lower affinity for rGALR-2, and all these peptides were agonists at rGALR-2 when assessed on a microphysiometer. Studies on the expression of GALR-2 in various tissues by Northern and in situ hybridization analyses suggest a low abundance but wide distribution of GALR-2 mRNA, including several discrete areas in brain and spinal cord and a high abundance in the dorsal root ganglia.

Amino Acid Sequence↗
PubMed1998

Two distinct phospholipases C of Listeria monocytogenes induce ceramide generation, nuclear factor-kappa B activation, and E-selectin expression in human endothelial cells.

Infection of endothelial cells by Listeria monocytogenes is an essential step in the pathogenesis of listeriosis. We recently reported that L. monocytogenes induces up-regulation of E-selectin and other endothelial adhesion molecules and subsequent polymorphonuclear leukocyte (PMN) adhesion into cultured human endothelial cells. In the present study, we characterized the mechanisms of enhanced E-selectin expression using L. monocytogenes wild type (EGD), the isogenic in-frame deletion mutants for phosphatidylcholine (PC)- and phosphatidylinositol (PI)-specific phospholipases EGD delta plcA and EGD delta plcB, as well as the nonvirulent control strain Listeria innocua. Infection of endothelial cells with EGD delta plcA or EGD delta plcB for 6 h induced, as compared with EGD wild type, intermediate levels of E-selectin mRNA and protein as well as PMN rolling and adhesion at a shear rate of 1 dyne/cm2, indicating that both bacterial phospholipases are required for a maximal effect. Similarly, ceramide content and NF-kappa B activity were increased in L. monocytogenes-exposed endothelial cells, but only to intermediate levels for PC- or PI-phospholipase C (PLC)-deficient listerial mutants. Phospholipase effects could be mimicked by exogenously added ceramides or bacterial sphingomyelinase. The data presented indicate that PI-PLC and PC-PLC are important virulence factors for L. monocytogenes infections that induce accumulation of ceramides that in turn may act as second messengers to control host cell signal-transduction pathways leading to persistent NF-kappa B activation, increased E-selectin expression, and enhanced PMN rolling/adhesion. The ability of L. monocytogenes to stimulate PMN adhesion to endothelial cells may be an important mechanism in the pathogenesis of severe listeriosis.

Cells, Cultured↗
PubMed1998

De novo expression of the alpha5beta1-fibronectin receptor in HT29 colon-cancer cells reduces activity of C-SRC. Increase of C-SRC activity by attachment on fibronectin.

Changes in integrin expression during malignant transformation have been observed in many tumors. Colon-carcinoma cells show reduced expression or even loss of the alpha5beta1 integrin compared to normal or adenoma cells. To determine the significance of absent alpha5beta1 integrin signaling, we transfected the cDNA coding for the alpha5 integrin sub-unit into the human colon-carcinoma cell line HT29, which constitutively lacks this subunit but does express the beta1 subunit. We show here that the newly expressed fibronectin receptor alpha5beta1 generates multiple signals, causing marked changes in cytoskeletal arrangements within a few minutes of adhesion to fibronectin. Cells expressing the alpha5beta1 integrin exhibit the formation of actin stress fibers and focal adhesions, as well as the induction of tyrosine phosphorylation of several proteins, within 10 min. We identified the focal adhesion kinase pp125FAK and the cytoskeletal protein paxillin as major phosphorylation substrates in these cells. These proteins remained hypophosphorylated when alpha5-negative control cells were plated on fibronectin. The tyrosine kinase pp60c-src, regarded as central in the regulation of cellular proliferation and constitutively over-expressed in HT29 and in colon-carcinoma cells, showed reduced intrinsic kinase activity in unstimulated HT29alpha5 cells. In contrast, fibronectin-induced signaling through alpha5beta1 increased pp60c-src activity. Moreover, immunoprecipitation of pp60c-src from extracts of HT29alpha5 cells cultivated on fibronectin for 20 min revealed complex formation of pp60c-src and tyrosine-phosphorylated pp125FAK. Our data suggest that de novo expression of the alpha5beta1 integrin in HT29 colon-cancer cells restores signaling via pp125FAK and pp60c-src. Thus, loss of this receptor during malignant transformation may contribute to tumor-cell autonomy, while reduced activity of pp60c-src in HT29alpha5-cells may participate directly in growth control.

Cell Adhesion↗
PubMed1998

Mood disorders and dysfunction of the hypothalamic-pituitary-adrenal axis in multiple sclerosis: association with cerebral inflammation.

OBJECTIVE: To investigate the association between affective and neuroendocrine abnormalities, commonly observed in multiple sclerosis, with inflammatory disease activity. DESIGN: Cross-sectional design. Twenty-three patients with definite relapsing-remitting multiple sclerosis and age- and sex-matched control subjects were investigated. Depression and anxiety were assessed using structured interviews, self-report measures, and Diagnostic and Statistical Manual of Mental Disorders, Third Edition, Revised criteria. Neurologic impairment was assessed by the Kurtzke Expanded Disability Status Scale and function of hypothalamic-adrenal-pituitary axis was analyzed using a corticotropin-releasing hormone stimulation test after dexamethasone suppression. Inflammatory disease activity was evaluated first by routine and experimental laboratory tests, and second by magnetic resonance assessment of gadolinium uptake of multiple sclerotic plaques. SETTING: University hospital, a major provider of acute neurologic care. RESULTS: Compared with controls, patients with multiple sclerosis had higher scores on depression and anxiety scales and exhibited a failure of suppression of cortisol release after dexamethasone pretreatment. Both affective symptoms and neuroendocrine abnormalities were correlated with cerebrospinal fluid white blood cell counts and presence of gadolinium-enhancing lesions on magnetic resonance images; however, no association with the degree of neurologic impairment was observed. CONCLUSION: Affective and neuroendocrine disorders were related to inflammatory disease activity but not to degree of disability, supporting the hypothesis that these symptoms are causally associated with brain injury.

Adult↗
PubMed1998

The physical basis for radiotherapy with neutrons.

Radiotherapy with neutrons requires a large quantity of physical information about neutrons and their interaction with matter. Primarily the absorbed dose at a reference point needs to be determined. For treatment planning the dose distribution in a phantom must be measured and algorithms for the simulation of the dose distribution in a patient must be available. As neutrons interact with matter in a more complicated way as high-energy photons and electrons commonly used in radiotherapy, biological effects based on microdosimetric data are used for treatment planning. This paper presents a brief summary of the neutron sources used in radiotherapy. The dosimetry of the clinical neutron beams is described. Special aspects of the treatment planning with fast neutrons are discussed. For further radiobiological interpretation the fundamentals of microdosimetry are described. Finally recent and future developments in the field of physics for neutron therapy are mentioned.

Humans↗
PubMed1998

European results of neutron therapy in soft tissue sarcomas.

The purpose of this publication is to review the data of European neutron therapy facilities in the treatment of soft tissue sarcoma. In the past locally advanced soft tissue sarcoma was a common indication for neutron therapy in several European centers. Data from 1171 patients treated at 11 centers were analysed on the basis of published data or personal communication. Neutron therapy was of benefit especially for patients with primary radiotherapy of inoperable tumors, and with macroscopic disease after surgery. Local control was about 50% in these patients. These results are superior to those from photon therapy from the literature. Results for postoperative neutron therapy after R0- and R1-resection are similar to those from photon therapy. The incidence of late side effects was considerably high in some neutron series. This is influenced by the treatment of most patients with first-generation machines of limited technical standard, and that in most cases large treatment volumes were irradiated.

Humans↗
PubMed1998

The spectrum of age-associated brain abnormalities: their measurement and histopathological correlates.

Magnetic resonance imaging (MRI) has dramatically increased our ability to detect morphological abnormalities in relation to aging of the brain. Among those changes are alterations of the white matter which display high signal intensity on both proton density and T2-weighted images. They may be seen in the deep and subcortical white matter or in a periventricular location. In clinically asymptomatic individuals the reported prevalence ranges from 20% to 60% for deep and subcortical white matter hyperintensities and from 15% to 94% for periventricular changes. Besides different characteristics of the populations examined these wide ranges are a consequence of quite diverse rating schemes and measurement approaches. Inadequate grading of MRI hyperintensities may also explain some of the inconsistencies in the reported associations of white matter damage with cerebrovascular risk factors or cognitive functions. Therefore development of a commonly accepted rating scheme would be desirable. Histopathologic observations could lay the basis. Hyperintense periventricular capping of the frontal horns and a smooth halo of periventricular hyperintensity have been linked to disruption of the ependymal lining, subependymal gliosis and concomitant loss of myelin. Punctate lesions in the deep and subcortical white matter corresponded to minor perivascular reduction in myelin content possibly because of a lower permeability of thickened arteriolar walls. Larger patchy and confluent hyperintensities, however, appear to indicate more extensive ischemic damage consistent with advanced microangiopathy. In parallel, newer MRI techniques may also contribute to the delineation and separation of these various types of tissue alteration.

Aging↗
PubMed1998

Concepts on the prognostic significance of white matter changes.

Magnetic resonance imaging white matter changes are a common observation in the elderly. The prognostic significance of such abnormalities is incompletely understood. Correlative studies which are reviewed here, suggested a predictive potential of white matter abnormalities for ischemic stroke, intracerebral hemorrhage, cognitive decline or even dementia. According to current review of literature the most compelling evidence for such a relationship exists for intellectual dysfunction. So far, there exist only preliminary data on the rate of WMH progression, but these demonstrate, at least some increase in number or extent within relatively short observational periods.

Aging↗
PubMed1998

Reconstructed human epidermis composed of keratinocytes, melanocytes and Langerhans cells.

In addition to their basic biological interest, models of reconstructed epidermis provide useful tools for in vitro assessment of the toxicology and efficacy of new chemicals and drugs. The fact that the majority of these in vitro models are composed only of keratinocytes has excluded their use in the fields of skin pigmentation and immunology. After the successful introduction of functional melanocytes into the epidermal reconstruct, the integration of Langerhans cells remains an important challenge, particularly since after isolation of Langerhans cells from human epidermis, these cells cannot be subcultured and do not integrate into the reconstructing epidermis. The authors show that cord blood derived and CD34+ progenitors isolated from the peripheral blood give rise to residential Langerhans cells when co-seeded with normal human keratinocytes.

Cell Culture Techniques↗
PubMed1998

[Finite element modeling and simulation of the human tympanic membrane].

Besides a knowledge of material properties geometric properties are needed to investigate the mechanical behavior of the human eardrum. Although the geometry of the eardrum has been examined methodically, its composition has been described in the literature. The true surface geometry of a cadaver specimen of the human eardrum was examined under a laser-scanning microscope. Forty points (85 parameters) depicted the surface of this cadaver specimen and formed the basis for a finite shell model. Furthermore, the coupling with the malleus and its suspension was simulated. Additional geometric and material parameters were chosen from the available literature. Both static behavior and the influence of a parameter variation to modal behavior of the finite element model were tested. ANSYS 5.1 software was used for this study.

Biomechanical Phenomena↗