Biomedical subjects

O Schmidt

Publications and source records attributed to O Schmidt.

At least 19 recordsLinked to original sources

PubMed2006

Proteomics in neurodegeneration--disease driven approaches.

Proteins as a product from genetic information execute and determine how development, growth, aging and disease factors are orchestrated within the lifetime of an organism. Differential protein expression and/or modification are always context dependent i.e. they happen within a specific context of a tissue, organ, environmental situation and individual fate. Consequently, the function/dysfunction (in a certain disease) of a specific gene cannot be predicted comprehensively by its sequence only. Genetic information can only be understood when genes and proteins are analyzed in the context of the biological system and specific networks they are involved in. In regard to neurodegenerative diseases such as Alzheimer's (AD) and Parkinson's disease (PD) many proteins are known for long years to be the cause or the consequence of the pathomechanism of the respective disease. The treatment of these neurodegenerative diseases represents a major challenge for the pharmaceutical industry, whereas the understanding of their pathogenesis is still in its infancy. With the development of several powerful techniques for proteome analysis it is now possible to investigate the expression of thousands of proteins in single cells, tissues or whole organisms at the same time. These developments opened new doors in medical sciences, and identification of cellular alterations associated with e.g. neurodegeneration will result in the identification of novel diagnostic as well as therapeutic targets. In this review, general considerations and strategies of proteomics technologies, the advantages and challenges as well as the special needs for analyzing brain tissue in the context of AD and AD are described and summarized.

Animals↗

PubMed2005

131 W 220 fs fiber laser system.

We report on an ytterbium-doped photonic-crystal-fiber-based chirped-pulse amplification system delivering 131 W average power 220 fs pulses at 1040 nm center wavelength in a diffraction-limited beam. The pulse repetition rate is 73 MHz, corresponding to a pulse energy of 1.8 microJ and a peak power as high as 8.2 MW.

Journal Article↗

PubMed2005

[Severe intrahepatic cholestasis in a 66-year old male patient with medically treated atrial fibrillation].

A 66-year-old male was admitted to hospital due to painless jaundice. Because of ischemic cardiomyopathy with paroxysmal atrial fibrillation as well as recurrent ventricular tachycardias and fibrillation he was treated with phenprocoumon and amiodarone (200 mg per day) for 2 years. Laboratory tests revealed significant elevation of the parameters of cholestasis and aminotransferase activity. Serological tests excluded infectious, autoimmune or metabolic liver diseases. Abdominal ultrasound and ERCP showed no mechanic cholestasis nor tumor of the pancreas. Cardiac congestive disease was also excluded. Severe intrahepatic cholestasis, consistent with drug-induced hepatotoxic damage, was diagnosed histologically. After discontinuing phenprocoumon the liver enzymes further increased. When amiodarone was stopped, however, laboratory parameters showed a continuous downward tendency. For prevention of malignant cardiac arrhythmia the patient received an atrioventricular defibrillator. Intrahepatic cholestasis is a rare presentation of amiodarone-induced hepatic toxicity. Liver damage can even occur after the drug has been taken for prolonged periods without any problems.

Aged↗

PubMed2003

Possible function of two insect phospholipid-hydroperoxide glutathione peroxidases.

We compared the functional properties of two insect members of the phospholipid hydroperoxide glutathione peroxidases (PHGPx) family, VLP1, a major component of virus-like particles from the hymenopteran endoparasitoid Venturia canescens and its closest Drosophila relative, one of the putative PHGPx-proteins predicted from the Berkeley Drosophila genome sequence project. Recombinant Drosophila PHGPx shows enzymatic activity towards a number of PHGPx substrates, while the recombinant PHGPx-like domain of VLP1 lacks a functionally relevant cysteine and enzyme activity. A possible function of a non-enzymatic extracellular PHGPx-like protein is discussed.

Amino Acid Sequence↗

PubMed2003

Is cell surface calreticulin involved in phagocytosis by insect hemocytes?

The innate immune system of insects consists of humoral and cellular components involved in the recognition of and responses to intruding foreign micro- or macroorganisms. Several molecules have been identified so far that recognize molecular patterns present on microorganisms, such as lipopolysaccharides, peptidoglycans and lipoteichonic acid. These molecules, acting as opsonins, trigger immune responses such as phagocytosis, nodule formation, melanization and encapsulation. Here, we investigated the role of calreticulin (CRT) present on the surface of Pieris rapae hemocytes in phagocytosis. Comparative phagocytosis assays using yeast cells showed that hemocytes from different insects exhibit significant variation in their phagocytosing potential and relative CRT involvement.

Animals↗

PubMed2003

Genetic analysis of two distinct reproductive strategies in sexual and asexual field populations of an endoparasitic wasp, Venturia canescens.

Asexual (thelytokous) females of the parasitoid Venturia canescens, which develop inside another insect, exhibit evolutionarily stable mixtures of life-history strategies, allowing two genetically distinct wasp lines to coexist sympatrically on the same host resources. Since the two asexual lines differ in a virus-like particle protein-coding gene (VLP1), the question is whether the VLP1 gene is genetically associated with the phenotype. The recent isolation of facultative sexual (arrhenotokous) and asexual V. canescens strains from the same location in Southern France has enabled an investigation of the genetic basis for the observed phenotypic differences, by comparing the two asexual lines with the corresponding homozygous VLP1 genotypes in arrhenotokous strains. This analysis showed similar patterns of morphological and functional differences exist in the ovaries of the two asexual VLP1 lines and in the two homozygous VLP1 genotypes from the field, suggesting that the VLP1 gene alteration either causes the ovarian phenotype or is genetically closely linked to the putative gene. However, the VLP1-gene may not be the only gene contributing to the phenotypic effects observed in the asexual lines. Although the two VLP1-alleles segregate with the relative differences in the ovary distribution of eggs, the absolute egg numbers differ in the corresponding asexual and sexual genotypes. This suggests that an additional unlinked gene may be involved in the transfer of eggs from the ovarioles into the oviduct.

Animals↗

PubMed2003

Differential gene expression in two strains of the endoparasitic wasp Venturia canescens identified by cDNA-amplified fragment length polymorphism analysis.

In the endoparasitic wasp Venturia canescens (Hymenoptera: Ichneumonidae) two genetically distinct lines, which differ at the VLP1 gene locus, appear to coexist sympatrically in thelytokous as well as arrhenotokous field and laboratory strains. Both lines display quite distinct morphological, physiological and behavioural variations, such as different oviposition strategies, egg numbers and growth rates during early embryonic development. To examine whether more than one gene is affected in the two lines, we applied cDNA-amplified fragment length polymorphism analysis to examine patterns of gene expression in ovaries of both wasp lines. We show that a number of ovarian transcripts have an altered expression pattern in either line, which was further confirmed by virtual Northern blot analysis. Sequence analysis of the cDNA-amplified fragment length polymorphism fragments revealed that some of the respective genes are expected to be involved in regulation of protein degradation during stress responses and in signal perception/transduction. The full-length sequence of two transcription factors (a homeodomain containing protein and a zinc finger protein) differentially expressed in both lines was obtained by RACE-polymerase chain reaction and their putative role in regulating key developmental processes during embryogenesis is discussed.

Amino Acid Sequence↗

PubMed2003

Anastomotic leakage after low rectal stapler anastomosis: significance of intraoperative anastomotic testing.

AIMS: One of the most significant surgical complications following rectal resection with primary anastomosis is anastomotic leakage. The aim of this study was to evaluate the benefit of intraoperative anastomotic testing of stapled anastomoses and the impact on leakage rate. METHODS: Between 1987 and 2000, 1360 consecutive rectal resections for carcinoma were performed. In 933 operations rectal resection was completed with either stapled (n=788), handsewn (n=80) or coloanal (n=65) anastomosis. Since 1995 we introduced intraoperative anastomotic testing, routinely. Between 1995 and 2000, 296 patients were treated with stapled anastomosis following rectal resection. Different variables influencing anastomotic leakage were evaluated. RESULTS: Between 1987 and 2000, 68 of 933 patients treated by resection and anastomosis developed a clinically significant anastomotic leak (7.3%) where as between 1995 and 2000 the leakage rate was 9.8% of all patients with stapled anastomosis. There was an increase in resection rate from 62 to 72%. Since 1995 we demonstrated either intraluminal bleeding or leakage in 18.1% of all stapled anastomoses by intraoperative anastomotic testing. The postoperative anastomotic leakage rate was equal in those patients with normal and abnormal findings of anastomotic testing even though 74% of all patients with irregular findings were treated by performing a protective stoma simultaneously. We found no significant risk factor for the development of anastomotic leakage. CONCLUSION: We recommend a protective stoma with any anastomosis within the lower third of the rectum. Anastomoses within the middle and upper third of the rectum demonstrate a lower risk of anastomotic insufficiency and do not need a protective stoma, routinely.

Adult↗

PubMed2002

The coagulation of insect hemolymph.

In contrast to both vertebrates and non-insect arthropods, little is known about the coagulation of hemolymph (hemostasis) in insects. We discuss the integration of the hemostatic response with other branches of the insect immune system. We also describe the present stage in the characterization of both soluble and cellular factors that contribute to hemostasis in insects. The factors of the well-characterized clotting cascades of vertebrates, primitive chelicerates and crustaceans are used to assess the implications of sequencing the whole Drosophila genome for searching candidate genes involved in hemostasis. Some striking similarities between blood clotting in vertebrates and the reaction of insect cells involved in hemolymph coagulation have implications for a phylogenetic comparison of hemostasis between divergent animal classes.

Animals↗

PubMed2002

Insect hemolymph clotting: evidence for interaction between the coagulation system and the prophenoloxidase activating cascade.

Here we describe a novel approach to isolate proteins involved in insect hemolymph coagulation. In order to avoid problems in purifying clot proteins after they had been crosslinked, we performed an in vitro coagulation reaction with cell-free hemolymph from the lepidopteran Galleria mellonella and used the resulting complexes to produce a specific antiserum. The antiserum reacted with a subset of hemolymph proteins as well as with granular cells, but not with other hemocyte types of Galleria. Screening expression libraries identified some positive clones, which turned out to code for some previously characterized components of immune cascades, as well as some novel candidates for clotting factors. Known components include members of both the coagulation system and the prophenol-activating cascade, lending support to the idea that both systems work together during the formation of a hemolymph clot. Novel candidates for insect clotting factors include a mucin-like protein, a glutathione-S-transferase, and a distant member of the alpha-crystallin/small heat shock protein family. Using assays measuring the activity of transglutaminase, a key enzyme in clotting reactions in both vertebrates and invertebrates, we found a partial overlap between transglutaminase substrates and proteins recognized by the antiserum against the in vitro-induced clot.

Amino Acid Sequence↗

PubMed2002

Sequence analysis and expression of a virus-like particle protein, VLP2, from the parasitic wasp Venturia canescens.

Endoparasitoid wasps produce maternal protein secretions, which are transported into the body of insect hosts at oviposition to regulate host physiology for successful development of their offspring. Venturia canescens calyx fluid contains so-called virus-like particles (VLPs) that are essential for immune evasion of the developing parasitoid inside the host. VLPs consist of four major proteins. In this paper, we describe the isolation and molecular cloning of a gene (vlp2) that is a constituent of VLPs and discuss its possible role in VLP structure and function.

Amino Acid Sequence↗

PubMed2001

Innate immunity and its evasion and suppression by hymenopteran endoparasitoids.

Recent studies suggest that insects use pattern recognition molecules to distinguish prokaryotic pathogens and fungi from "self" structures. Less understood is how the innate immune system of insects recognizes endoparasitic Hymenoptera and other eukaryotic invaders as foreign. Here we discuss candidate recognition factors and the strategies used by parasitoids to overcome host defense responses. We suggest that host-parasitoid systems are important experimental models for studying how the innate immune system of insects recognizes foreign invaders that are phylogenetically more closely related to their hosts. The strategies used by parasitoids suggest that insects may employ "hidden-self" recognition molecules for attacking foreign objects intruding the open circulatory system. BioEssays 23:344-351, 2001.

Animals↗

PubMed2001

Promoter studies of a polydnavirus gene from Cotesia rubecula (Hym: Braconidae).

The Cotesia rubecula polydnavirus gene, CrV1, is expressed in a highly transient fashion. Within four hours after egg deposition and virus infection, tissues of the host caterpillar, Pieris rapae, express high levels of the transcript. Twelve hours after infection no transcripts are visible. We have previously shown that the CrV1 secreted protein is mainly produced in host haemocytes. In haemocytes, immune functions such as phagocytosis and cell spreading are abolished by destabilization of the cell cytoskeleton. To test whether the observed down-regulation of CrV1 transcripts is mediated by transcriptional control or by other factors, such as the disruption of cytoskeleton in CrV1-inactivated cells, we cloned the promoter and the 3' untranslated region of the CrV1 gene to study CrV1 expression. The promoter region of the CrV1 gene was cloned into baculovirus expression systems along with the CAT reporter gene. Molecular analyses showed that the CAT gene under the control of CrV1 promoter is expressed as early as 2 h post infection and continues until late phase of infection suggesting that down-regulation of CrV1 expression in host haemocytes is perhaps mediated by post-transcriptional mechanisms.

Animals↗

PubMed2001

Prophylactic antibiotics and pancreatic necrosis.

Recent controlled clinical studies suggest a positive effect of early antibiotic treatment on late morbidity and mortality in severe acute pancreatitis. In contrast, widespread use of antibiotics may lead to an increased number of fungal infections and multiresistant bacteria. Optimal choice, duration, and route of administration of the antibiotic agent(s) are far from being established. The additional administration of an antifungal agent with prophylactic intention cannot be supported by the currently available data.

Animals↗

PubMed2001

Two distinct reproductive strategies are correlated with an ovarian phenotype in co-existing parthenogenetic strains of a parasitic wasp.

The question whether different organisms are able to compete for the same resource is of fundamental importance to evolutionary biology. Sympatric co-existence of similar species on a single resource has long been claimed to be unstable. However, indirect evidence suggests that parasitic wasps exhibit evolutionarily stable mixtures of life-history strategies. Here we describe genetically distinct strains of a parthenogenetic wasp Venturia canescens, with different ovarian phenotypes that affect egg numbers in oviducts. Wasp females with large egg load search for caterpillars and deposit eggs immediately after host encounter, whereas females with fewer eggs delay parasitism. Since the outcome of interlarval competition within super-parasitized caterpillars depends on the age distribution of competing larvae, the two egg deposition strategies may co-exist under conditions that favor super-parasitism.

Journal Article↗

PubMed2001

Changes in glycosylation during Drosophila development. The influence of ecdysone on hemomucin isoforms.

To explore a possible signal function of glycodeterminants and the tissue specificity of glycosylation in Drosophila melanogaster, hemomucin, a surface mucin previously isolated from cell lines was studied. It was shown to exist in two glycoforms with molecular masses of 100 and 105 kDa, respectively. The two forms differ by the presence of O-linked galactose, which was only detected in the larger glycoform using the beta-galactose specific peanut agglutinin (PNA). The 105 form was found in cell lines after addition of the cell cycle inhibitor taxol and after induction with ecdysone. When whole animal tissues were analyzed using PNA, dramatic changes were observed during development. We were able to identify a number of proteins, which showed strong PNA-staining in stages with a high ecdysone titer, while virtually no staining was detected in adults. This pattern was specific for PNA and was not observed with any of the other lectins employed in this study. Surprisingly, in contrast to our observation in cell lines, PNA staining of hemomucin was not observed in late third larval and pupal stages, which are known to produce high ecdysone titers. The only organ, in which significant amounts of the 105 form were detected, were the ovaries, where hemomucin is produced in follicle cells during the late phase of oogenesis and subsequently incorporated into the chorion.

Animals↗

PubMed2001

Acute occlusion of the left iliac artery after long-distance-running.

We report a case of spontaneous iliac occlusion in a 44-year-old male patient after long-distance running. Atherogenic risk factors like hypertension, diabetes, hypercholesterolemia and smoking were missing. Spontaneous iliac occlusion is extremely rare and only a few cases have been documented. Angiography showed occlusion of the left iliac artery with collateral flow via the obturator artery to the common femoral artery. Thrombectomy was performed but reocclusion occurred. An iliacofemoral bypass, arterial lysis and bypass thrombectomy was necessary within a few months. At the last follow-up visit two years afterwards the patient was symptom-free. This case indicates that exercise-dependent blood flow disturbances in long-distance-runners could produce changes of the intima.

Adult↗

PubMed2001

Imaging of three-dimensional objects in emission electron microscopy.

Under investigation by emission electron microscopy, the shape and size of three-dimensional objects are distorted because of the appearance of a characteristic potential relief and a possible contact potential difference between the particles and the substrate. An estimation of these effects for spherical particles is made. It is shown that the apparent size of particles observed in an emission electron microscope (EEM) could be increased as well as decreased depending on the relation between the work functions of the particle and the substrate. The corresponding formulae are given and several possibilities are shown which permit us to determine from the EEM image the real size of particles and their work function relative to the substrate.

Journal Article↗