Biomedical subjects

M Schmid

Publications and source records attributed to M Schmid.

At least 55 records · Page 3Linked to original sources

PubMed2004

Mosaicism for an ectopic NOR at 8pter and a complex rearrangement of chromosome 8 in a patient with severe psychomotor retardation.

We describe a 3-year-old girl with severe delays in mental and motor skills, a history of generalized seizures, and subtle dysmorphic features. Conventional cytogenetics revealed a mosaic karyotype. A de novo ectopic NOR at the telomeric region of the short arm of one chromosome 8 (8ps) was found in 90% of lymphocyte and in 98% of fibroblast metaphases. A small NOR-bearing marker chromosome and a large derivative chromosome 8 without short arm satellites (der(8)) were present in the remaining cells. FISH with a probe specific for centromeres 14 and 22 labeled both the telomeric region of 8ps and the small marker centromere. Der(8) included an inverted duplication of 8p and a rearranged duplication of 8q but lacked a second centromere. A subtelomeric probe for 8p revealed a cryptic deletion in 8ps and der(8). Thus, the karyotype represents a combination of submicroscopic partial monosomy 8pter and mosaic trisomy 8.

Centromere↗

PubMed2004

Distribution and stability of supernumerary microchromosomes in natural populations of the Amazon molly, Poecilia formosa.

In animals, supernumerary chromosomes and their evolution have mostly been studied in sexual reproducing species. In the present study, for the first time, the natural distribution and stability of supernumerary microchromosomes were investigated in the unisexual fish species Poecilia formosa. Natural habitats throughout the range of P. formosa were screened for the presence of microchromosomes over several years. A high frequency of microchromosomes was found in the Río Purificación river system. Evidence points to the presence of the same microchromosome lineage over many generations. No supernumerary chromosomes were found elsewhere than in the Río Purificación representing a significant difference in the distribution of microchromosome-bearing individuals between the Río Purificación and all other collection sites.

Animals↗

PubMed2004

Iodine-123-vascular endothelial growth factor-165 (123I-VEGF165). Biodistribution, safety and radiation dosimetry in patients with pancreatic carcinoma.

AIM: Imaging with radiolabelled vascular endothelial growth factor (VEGF) has been developed for the localisation and diagnosis of a variety of human solid tumors including gastrointestinal tumors. METHODS: In this study we investigated the biodistribution, safety and absorbed dose of iodine-123 radiolabelled VEGF(165) ((123)I-VEGF(165)) in 9 patients with pancreatic carcinoma. Following intravenous administration of (123)I-VEGF(165) (189+/-17 MBq; <130 pmole (<5 microg) VEGF(165) per patient), sequential images were recorded during the initial 30 min PI. Serial whole-body images were acquired in anterior and posterior views at various time points. All patients underwent single-photon emission tomography (SPET) imaging. Dosimetry calculations were performed on the basis of gamma camera data. Estimates of radiation absorbed dose were calculated using the MIRDOSE 3 program. RESULTS: The highest absorbed organ doses were found to be thyroid (0.058+/-0.004 mGy/MBq), spleen (0.046+/- 0.017 mGy/MBq), urinary bladder (0.04+/-0.02 mGy/MBq), lungs (0.034+/-0.009 mGy/MBq) and kidneys (0.033+/-0.005 mGy/MBq). The effective dose was estimated to be 0.017+/-0.002 mSv/MBq. A majority of primary pancreatic tumors and their metastases were visualized by (123)I-VEGF(165) scan. CONCLUSION: In vitro binding results confirmed specific binding of (123)I-VEGF(165) to pancreatic tumor cells and tissues. (123)I-VEGF(165) shows favorable dosimetry and is a safe radiopharmaceutical that may be of potential value for the imaging of VEGF receptor status in vivo.

Adenocarcinoma↗

PubMed2003

Integrated optical Mach-Zehnder modulator based on polycrystalline BaTiO3.

Good-quality polycrystalline BaTiO3 thin films are deposited on MgO substrates by pulsed laserdeposition. The deposition parameters are optimized to achieve optical-quality films with an attenuation coefficient of 4 dB/cm at the 633-nm wavelength. Thin-film electro-optic Mach-Zehnder modulators are fabricated with standard lithography and ion-beam etching. The waveguides patterned by lithography are the ridge type, and they ensure single-mode propagation in the wavelength range of 633-1550 nm. An electro-optic coefficient of 22 pm/V is estimated for the polycrystalline BaTiO3 films.

Journal Article↗

PubMed2003

Anaerobic ammonium oxidation by marine and freshwater planctomycete-like bacteria.

Recently, two fresh water species, " Candidatus Brocadia anammoxidans" and " Candidatus Kuenenia stuttgartiensis", and one marine species, " Candidatus Scalindua sorokinii", of planctomycete anammox bacteria have been identified. " Candidatus Scalindua sorokinii" was discovered in the Black Sea, and contributed substantially to the loss of fixed nitrogen. All three species contain a unique organelle--the anammoxosome--in their cytoplasm. The anammoxosome contains the hydrazine/hydroxylamine oxidoreductase enzyme, and is thus the site of anammox catabolism. The anammoxosome is surrounded by a very dense membrane composed almost exclusively of linearly concatenated cyclobutane-containing lipids. These so-called 'ladderanes' are connected to the glycerol moiety via both ester and ether bonds. In natural and man-made ecosystems, anammox bacteria can cooperate with aerobic ammonium-oxidising bacteria, which protect them from harmful oxygen, and provide the necessary nitrite. The cooperation of these two groups of ammonium-oxidising bacteria is the microbial basis for a sustainable one reactor system, CANON (completely autotrophic nitrogen-removal over nitrite) to remove ammonia from high strength wastewater.

Anaerobiosis↗

PubMed2003

Generation and characterization of a transgenic mouse with a functional human TSPY.

To generate an animal model that is suitable for the analysis of regulation and expression of human testis-specific protein, Y-encoded TSPY, a transgenic mouse line, TgTSPY9, harboring a complete structural human TSPY gene was generated. Fluorescence in situ hybridization and Southern analyses show that approximately 50 copies of the human TSPY transgene are integrated at a single chromosomal site that maps to the distal long arm of the Y chromosome. The transgene is correctly transcribed and spliced according to the human pattern and is mainly expressed in testicular tissue, with spermatogonia and early primary spermatocytes (leptotene and zygotene) as expressing germ cells. TSPY transgenic mice are phenotypically normal, and spermatogenesis is neither impaired nor enhanced by the human transgene. The present study shows that a human TSPY gene integrated into the mouse genome follows the human expression pattern although murine tspy had lost its function in rodent evolution millions of years ago.

Animals↗

PubMed2003

Toxoplasma gondii infection, atopy and autoimmune disease.

While for many allergens a dose-response relationship has clearly been established the association between early childhood exposure to cat allergens and risk of sensitisation is still controversial and even inverse relations have been described. At the same time, a negative association between Toxoplasma gondii (T. gondii) infection and atopic diseases has been found in epidemiologic studies. As cats are the major source of T. gondii oocysts, we hypothesize that cat allergen exposure might be a confounder in the association between T. gondii infection and allergic diseases. Furthermore, it is well known that atopic diseases are T helper cell 2 (Th2) driven while autoimmune diseases are dominated by a Th1 response. A counterbalance between Th1 and Th2 cells has been postulated. However, it has been shown recently that subjects with autoimmune disease are more likely to suffer from atopic diseases. Therefore, similar cytokine profiles might underlie these disorders. If this holds true it can be hypothesised that T. gondii infection is associated with a lower prevalence of autoimmune disease.

Allergens↗

PubMed2003

When scanning tunneling microscopy gets the wrong adsorption site: H on Rh(100).

At low tunneling resistance, scanning tunneling microscopy (STM) images of a Rh(100) surface with adsorbed hydrogen reproducibly show protrusions in all bridge sites of the surface, leading to a naive interpretation of all bridge sites being occupied with H atoms. Using quantitative low-energy electron diffraction and temperature programmed desorption we find a much lower H coverage, with most H atoms in fourfold hollow sites. Density functional theory calculations show that the STM result is due to the influence of the tip, attracting the mobile H atoms into bridge sites. This demonstrates that STM images of highly mobile adsorbates can be strongly misleading and underlines the importance of additional analysis techniques.

Journal Article↗

PubMed2003

Neck muscle fatigue affects postural control in man.

We hypothesised that, since anomalous neck proprioceptive input can produce perturbing effects on posture, neck muscle fatigue could alter body balance control through a mechanism connected to fatigue-induced afferent inflow. Eighteen normal subjects underwent fatiguing contractions of head extensor muscles. Sway during quiet stance was recorded by a dynamometric platform, both prior to and after fatigue and recovery, with eyes open and eyes closed. After each trial, subjects were asked to rate their postural control. Fatigue was induced by having subjects stand upright and exert a force corresponding to about 35% of maximal voluntary effort against a device exerting a head-flexor torque. The first fatiguing period lasted 5 min (F1). After a 5-min recovery period (R1), a second period of fatiguing contraction (F2) and a second period of recovery (R2) followed. Surface EMG activity from dorsal neck muscles was recorded during the contractions and quiet stance trials. EMG median frequency progressively decreased and EMG amplitude progressively increased during fatiguing contractions, demonstrating that muscle fatigue occurred. After F1, subjects swayed to a larger extent compared with control conditions, recovering after R1. Similar findings were obtained after F2 and after R2. Although such behaviour was detectable under both visual conditions, the effects of fatigue reached significance only without vision. Subjective scores of postural control diminished when sway increased, but diminished more, for equal body sway, after fatigue and recovery. Contractions of the same duration, but not inducing EMG signs of fatigue, had much less influence on body sway or subjective scoring. We argue that neck muscle fatigue affects mechanisms of postural control by producing abnormal sensory input to the CNS and a lasting sense of instability. Vision is able to overcome the disturbing effects connected with neck muscle fatigue.

Adult↗

PubMed2003

The giant B chromosome of the cyprinid fish Alburnus alburnus harbours a retrotransposon-derived repetitive DNA sequence.

The cyprinid fish Alburnus alburnus possesses one of the largest supernumerary chromosomes in all vertebrates. In the present study, amplified fragment length polymorphism analyses (AFLP) and fluorescence in-situ hybridization (FISH) were performed in order to characterize these extraordinary chromosomes in detail. Sequence analysis of the B chromosome-specific DNA revealed a strong homology to a Drosophila Gypsy/Ty3 retrotransposon and also to a medaka (Oryzias latipes) one. The sequence is highly abundant on the B chromosome but undetectable in the normal A chromosome complement. It is also absent from the B chromosome of the closely related species, Rutilus rutilus, suggesting a specific spreading of the mobile element during evolution of the giant supernumerary chromosome within A. alburnus. Meitotic chromosomes were in-situ hybridized with the B chromosome-specific probe, documenting that the additional chromosome behaves as an autopaired ring chromosome in diakineses. Our results suggest that the supernumerary chromosome of A. alburnus is not derived from the normal chromosome complement but has evolved independently.

Animals↗

PubMed2003

In situ identification of intracellular bacteria related to Paenibacillus spp. in the mycelium of the ectomycorrhizal fungus Laccaria bicolor S238N.

Bacterial proliferations have recurrently been observed for the past 15 years in fermentor cultures of the ectomycorrhizal fungus Laccaria bicolor S238N, suggesting the presence of cryptic bacteria in the collection culture of this fungus. In this study, intracellular bacteria were detected by fluorescence in situ hybridization in combination with confocal laser scanning microscopy in several collection subcultures of L. bicolor S238N. They were small (0.5 micro m in diameter), rare, and heterogeneously distributed in the mycelium and were identified as Paenibacillus spp. by using a 16S rRNA-directed oligonucleotide probe initially designed for bacteria isolated from a fermentor culture of L. bicolor S238N.

Agaricales↗

PubMed2003

Child-Pugh versus MELD score in predicting survival in patients undergoing transjugular intrahepatic portosystemic shunt.

BACKGROUND: In patients undergoing transjugular intrahepatic portosystemic shunt (TIPS), prognostic scores may identify those with a poor prognosis or even those with a clear survival benefit. The Child-Pugh score (CPS) is well established but several drawbacks have led to development of the model of end stage liver disease (MELD). AIM: The aim of the study was to compare the predictive power of CPS and MELD, to validate the original MELD formula, and to assess the predictive value of the determinants used in the two prognostic scores outside of a study setting. PATIENTS: A total of 501 patients underwent elective TIPS placement and 475 patients fulfilled the inclusion criteria. METHODS: Data of all patients undergoing elective TIPS in one university hospital and four community hospitals in Vienna, Austria, between 1991 and 2001, were analysed retrospectively. The main statistical tests were Cox proportional hazards regression model, the log rank test, Kaplan-Meier analysis, and concordance c statistics. RESULTS: Median follow up was 5.2 years and median survival was 4.6 years. During follow up, 230 patients died, 75 within three months after TIPS placement. In stepwise proportional hazards analyses, independent predictors of death were creatinine level, bilirubin level, age, and refractory ascites. MELD was better in predicting survival in a stepwise Cox model but both scores were equally predictive in c statistics for one month, three month, and one year survival. Renal function was the strongest independent predictor of survival. CONCLUSIONS: Although MELD was the primary predictor of overall survival in multivariate analysis, c statistics showed that both scores can be used for patients undergoing TIPS with equal accuracy. For assessing prognosis in patients undergoing TIPS implantation, there seems little reason to replace the well established Child-Pugh score.

Adult↗

PubMed2003

HHV-8 DNA sequences in the peripheral blood and skin lesions of an HIV-negative patient with multiple eruptive dermatofibromas: implications for the detection of HHV-8 as a diagnostic marker for Kaposi's sarcoma.

BACKGROUND: Multiple eruptive dermatofibroma (MEDF) is a rare disorder seen in immunocompromised patients, simulating Kaposi's sarcoma (KS). Whereas KS is strongly associated with human herpesvirus 8 (HHV-8), the virus has never been detected in MEDF until now. OBJECTIVE: To present a patient with MEDF who showed no signs of immunodeficiency but was seropositive for HHV-8 antibodies and demonstrated HHV-8 DNA both in the peripheral blood and lesional skin of MEDF. METHODS: Clinical, histological and serological investigations were performed as well as polymerase chain reaction (PCR) studies and in situ hybridization (ISH). RESULTS: A 35-year-old white man with suspected KS was referred for evaluation of multiple pigmented nodules and patches. Biopsies revealed features of dermatofibroma, superficial fibrosing dermatitis and scar. One of the nodular lesions harbored HHV-8 DNA sequences. A faint amplification product was detected in the superficial fibrosing dermatitis lesion, while no HHV-8 sequences were found in normal skin and scar. Whole-blood samples and serum were positive for HHV-8. None of the skin lesions shown to harbor HHV-8 DNA sequences by nested PCR displayed a signal for HHV-8 RNA by ISH. Repetitive peripheral blood examinations did not reveal any serum antibodies against or antigens of HIV. Serum antibodies against the HHV-8 capsid antigen orf 65.2 were detected. CONCLUSION: Results of PCR studies and ISH indicate that the presence of HHV-8 in the lesional tissue was probably blood-borne due to viremia and not due to viral replication in tumor cells. The presence of HHV-8 is not fully restricted to KS. The differential diagnosis of KS and its simulators should be based on an integrative analysis of all available clinicopathological and molecular data and should not rely exclusively or predominantly on the presence or absence of HHV-8.

Adult↗

PubMed2003

The rare human fragile site 16B.

The rare human fragile site 16B (FRA16B) has been found to occur spontaneously. Its expression in lymphocyte cultures can also be induced or greatly enhanced by addition of chemicals which are known to bind to AT-rich DNA regions. Following optimal treatment with 150 microg/ml berenil 24 h prior to fixation, the heterozygote frequency of FRA16B is found to be about 5% in populations of European descent. Thus, FRA16B represents the most common of the rare fragile sites. Consistent with cytogenetic observations, the molecular characterization of FRA16B revealed that it is an amplified 33-base pair AT-rich minisatellite repeat. These interindividually variable, extremely large repeat expansions of 15-70 kb in size do not seem to interfere with the expression of genes essential for human development since heterozygotes and homozygotes for FRA16B are normal.

Chromosome Aberrations↗

PubMed2003

Chromosome banding in Amphibia. XXVII. DNA replication banding patterns in three anuran species with greatly differing genome sizes.

The mitotic chromosomes of three anuran species, Scaphiopus holbrooki, Litoria infrafrenata and Odontophrynus americanus, were analyzed by means of the 5-bromodeoxyuridine/deoxythymidine (BrdU/dT) replication banding technique. These species exhibit large differences in their genome sizes: S. holbrooki possesses one of the smallest genomes among vertebrates, L. infrafrenata has a genome size near the modal DNA value of most Amphibia, whereas O. americanus is a tetraploid species. BrdU/dT labeling induces reproducible and reliable R- and G-replication bands along the metaphase chromosomes of all three species. Irrespective of the genome size of the species considered, the number of early (R-) and late (G-) replicating bands per haploid karyotype is nearly the same. The chromosomes of the autotetraploid O. americanus can be arranged into sets of four homologous chromosomes (quartets). C-bands and BrdU/dT replication bands reveal heterogeneity within the quartets 1, 3 and 4 that are interpreted as the initiation of a diploidization process.

Animals↗

PubMed2003

Chromosome banding in Amphibia. XXVIII. Homomorphic XY sex chromosomes and a derived Y-autosome translocation in Eleutherodactylus riveroi (Anura, Leptodactylidae).

Extensive cytogenetic analyses on a population of the leptodactylid frog Eleutherodactylus riveroi in northern Venezuela revealed the existence of multiple XXAA male/XYAA female/XAA(Y) female sex chromosomes. The XAA(Y) karyotype originated by a centric (Robertsonian) fusion between the original, free Y chromosome and an autosome. 46.2% of the male individuals in this population are carriers of this Y-autosome fusion. In male meiosis the XAA(Y) sex chromosomes pair in the expected trivalent configuration. In the same population 53.8% of the male animals still possess the original, free XY sex chromosomes. E. riveroi is only the second vertebrate species discovered in which a derived Y-autosome fusion coexists with the ancestral free XY sex chromosomes. The free XY sex chromosomes, as well as the multiple XA(Y) sex chromosomes are still in a very primitive (homomorphic) stage of differentiation. With no banding technique applied it is possible to distinguish the Y from the X. Various banding techniques and in situ hybridizations have been carried out to characterize the karyotypes. DNA flow cytometric measurements show that the genome size of E. riveroi resembles that of other Eleutherodactylus species. The cytogenetic data obtained in E. riveroi are compared with those of the sole other vertebrate known to possess the extremely rare, multiple XXAA male/XYAA female/XAA(Y) female sex chromosomes. Surprisingly enough, this vertebrate again is a frog belonging to the genus Eleutherodactylus [E. ((maussi) biporcatus] which lives exactly in the same habitat in northern Venezuela as does E. riveroi.

Animals↗

PubMed2003

Chromosome banding in Amphibia. XXIX. The primitive XY/XX sex chromosomes of Hyla femoralis (Anura, Hylidae).

The karyotype of the pine woods treefrog, Hyla femoralis, is characterized by primitive XY female/XX male sex chromosomes. The sole difference between the X and the Y is the presence of a nucleolus organizer region (NOR) in the X. Due to a deletion of the NOR in the Y, this chromosome is distinctly smaller than the X. Since no autosomal NORs exist in the karyotype of this species, the NOR deletion in the Y results in a sex-specific difference in the number of ribosomal RNA genes, with a female:male ratio of about 2:1. Interphase nuclei of male animals contain always one silver-stained nucleolus, whereas most nuclei of female specimens exhibit two nucleoli. This is in agreement with the absence of dosage compensation for sex-linked genes in amphibian cells. The consequences of the loss of about 50% of ribosomal RNA genes for the viability of male individuals and spermatogenesis are discussed.

Animals↗

PubMed2003

Multicolor spectral karyotyping of rat chromosomes.

Rat and mouse have become important animal models to study various human diseases such as cancer. Cytogenetic analysis of the respective karyotypes is frequently required to investigate the causative genetic defects and especially neoplastic cells often show complex chromosome aberrations and many different marker chromosomes. However, structural homogeneity of the chromosomes in these species as well as less pronounced differences in banding patterns make it difficult to assign genetic abnormalities to certain chromosomes by conventional banding techniques. Here we report for the first time the successful application of multicolor spectral karyotyping (SKY) to rat chromosomes, which allows unequivocal identification of all rat chromosomes with the exception of chromosomes 13 and 14 in different colors, thus enabling the elucidation of even complex rearrangements in the rat karyotype. Flow-sorted chromosome specific painting probes for all 22 rat chromosomes (20 autosomes, X, and Y) were combinatorially labeled by a set of five different fluorochromes and hybridized in situ to metaphase spreads of a healthy rat, to diakineses from testicular material, and to cells from a rat FAO hepatoma cell line. Measuring the complete spectrum at each image point by using the SpectraCube((R)) spectral imaging system and respective computer software allowed identification of the individual rat chromosomes by their specific emission spectra. Classification algorithms in the analysis software can then display the rat chromosomes in specific pseudo-colors and automatically order them in a karyotype table. After its successful application to human and mouse chromosomes, spectral karyotyping of rat chromosomes now also allows cytogenetic screening of the complete rat genome by a single hybridization.

Animals↗