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Biomedical subjects

P Schweizer

Publications and source records attributed to P Schweizer.

At least 37 records · Page 2Linked to original sources
PubMed2000

Constitutive expression of the defense-related Rir1b gene in transgenic rice plants confers enhanced resistance to the rice blast fungus Magnaporthe grisea.

The Rirlb gene of rice (Oryza sativa) is one of a set of putative defense genes whose transcripts accumulate upon inoculation of rice with the non-host pathogen Pseudomonas syringae pv. syringae. It belongs to a family of genes encoding small extracellular proteins so far only identified in cereals. To assess the function of the Rirlb gene in rice blast resistance, it was placed under the control of the CaMV 35S promoter and transferred into rice plants of the japonica variety Taipei 309 by biolistic transformation of immature embryos. Two out of 12 hygromycin-resistant regenerated plants (OE1 and OE3) were fertile. DNA gel blot analysis suggested that these two T0 plants were independent transformants, each of which had stably incorporated one complete copy of the transgene into the genome. In addition, the OE1 plant appeared also a contain a rearranged copy or incomplete copy. T1 plants homozygous for the transgene were identified by DNA gel blot analysis of individual T2 progeny and further propagated. Expression analysis of the transgene showed that the transgene was active both in T1 plants and homozygous decendants. Challenge inoculation of homozygous transgenic plants with Magnaporthe grisea, the causal agent of rice blast disease, revealed that both independent transgenic lines were more resistant than the untransformed wild type, suggesting that over-expression of the Rirlb gene confers partial resistance against this important pathogen.

Gene Expression Regulation, Plant↗
PubMed2000

Technical advance. Double-stranded RNA interferes with gene function at the single-cell level in cereals.

Double-stranded RNA (dsRNA) has been shown to specifically interfere with gene function in several organisms including tobacco and the model plant Arabidopsis. Here, we report on rapid and sequence-specific interference of dsRNA with gene function in cereals. Delivery of cognate dsRNA into single epidermal cells of maize, barley or wheat by particle bombardment interfered with the function of co-bombarded UidA (GUS) and TaGLP2a:GFP reporter genes. Cognate dsRNA was also found to specifically interfere with the function of the endogenous genes A1 and Ant18 encoding dihydroflavonol-4-reductase in maize and barley, respectively. Dihydroflavonol-4-reductase is an essential enzyme of the anthocyanin biosynthetic pathway in maize and barley. This pathway can be induced by transient expression of the C1- and b-Peru genes that encode transcription factors. In the presence of dsRNA corresponding to the dihydroflavonol-4-reductase gene, C1- and b-Peru-dependent, cell-autonomous accumulation of red anthocyanin pigments in bombarded cells of maize and barley was reduced. dsRNA was also demonstrated to negatively interfere with Mlo, which encodes a negative regulator of race non-specific resistance to the powdery mildew fungus in barley. In the presence of Mlo dsRNA, transformed cells became more resistant, thereby phenocopying plants that carry a heritable loss-of function mlo resistance allele. The results suggest that direct delivery of dsRNA to cereals leads to a rapid and sequence-specific interference with gene function at the single-cell level.

Alcohol Oxidoreductases↗
PubMed2000

Neuroblastoma: induction of differentiation (Part I). Basical science in pediatric surgery.

Neuroblastoma is the second-most common solid tumor in childhood. The majority of patients have a very poor outcome due to aggressive growth and metastatic spread. In contrast, in rare cases, spontaneous regression or differentiation towards a benign ganglioneuroma are observed. The mechanism leading to differentiation of neuroblastoma is of particular therapeutic interest. In this paper we report the results of our attempts to induce the expression of genes necessary for differentiation of neuroblastoma cells. TrkA codes for the high affinity receptor of NGF, a neurotrophin known to promote differentiation. Treatment with retinoic acid caused a 3-fold increase of the trkA expression in neuroblastoma cell lines. Neurofibromin, the gene product of the NF-1 gene, is involved in downregulation of the activity of ras-proteins. In contrast to immature neuronal tissues in mature brain, the type II isoform of neurofibromin is predominantly expressed. Retinoic acid was able to raise the proportion of type II NF-1 expressed in neuroblastoma cells.

Cell Transformation, Neoplastic↗
PubMed2000

Pathogenesis and symptomatology of cholelithiasis in childhood. A prospective study.

QUESTIONS: How may gallstones develop if there is no hemolytic disorder and no malformation or alteration of the gallbladder and cystic ducts? Was there a change in the incidence of stones and the assignment of the patients to different age groups? The literature gives answers to these questions on the basis of only few cases. Therefore, a relatively large prospective database of collected cases during 30 years shall be used to give additional answers. METHODS: The data are derived from 111 children with symptomatic gallstones without hemolytic diseases. 109 of them required operative therapy. They were examined preoperatively and postoperatively maximum during 30 years of follow-up as well according to a defined program. This program includes taking the patient's history, evaluation of clinical, radiological including sonographical examination, exclusion of hemolytic primary diseases, histological investigation of intraoperatively gained specimens of the gallbladder, and the spectroscopic qualitative as well as semiquantitative analysis of stones and bile. RESULTS: (1) The qualitative and quantitative composition of the stones is different in the four age groups. (2) The causes of lithogenesis are different in the four age groups. (3) Children with long-term TPN, after cardiopulmonary bypass operations, after extended small bowel resection, suffering from obesity, and girls using hormonal contraception are at risk of developing gallstones. We recommend to observe these patients by repeated ultrasound controls for gallstone formation during a minimum of 10 years. (4) Malformations and pathological alterations of the gallbladder are rare causes for increased lithogenity. The gallbladder appeared morphologically normal in 61% of patients with symptomatic gallstones. (5) An increased frequency of gallstones during the last 30 years was only observed in the age group under 1 year.

Adolescent↗
PubMed1999

Epigenetic phenotypes distinguish microsatellite-stable and -unstable colorectal cancers.

Aberrant DNA methylation is a common phenomenon in human cancer, but its patterns, causes, and consequences are poorly defined. Promoter methylation of the DNA mismatch repair gene MutL homologue (MLH1) has been implicated in the subset of colorectal cancers that shows microsatellite instability (MSI). The present analysis of four MspI/HpaII sites at the MLH1 promoter region in a series of 89 sporadic colorectal cancers revealed two main methylation patterns that closely correlated with the MSI status of the tumors. These sites were hypermethylated in tumor tissue relative to normal mucosa in most MSI(+) cases (31/51, 61%). By contrast, in the majority of MSI(-) cases (20/38, 53%) the same sites showed methylation in normal mucosa and hypomethylation in tumor tissue. Hypermethylation displayed a direct correlation with increasing age and proximal location in the bowel and was accompanied by immunohistochemically documented loss of MLH1 protein both in tumors and in normal tissue. Similar patterns of methylation were observed in the promoter region of the calcitonin gene that does not have a known functional role in tumorigenesis. We propose a model of carcinogenesis where different epigenetic phenotypes distinguish the colonic mucosa in individuals who develop MSI(+) and MSI(-) tumors. These phenotypes may underlie the different developmental pathways that are known to occur in these tumors.

Adaptor Proteins, Signal Transducing↗
PubMed1999

SiMa, a new neuroblastoma cell line combining poor prognostic cytogenetic markers with high adrenergic differentiation.

We describe the establishment and characterization of a new neuroblastoma (Nb) cell line, SiMa, carrying the major recurrent chromosome changes associated with poor prognosis Nb, including amplification of N-MYC by formation of double minutes (dmin), der(1)t(1;17)(p35;q12) and der(22)t(17;22)(q22;p13), and loss of chromosome 11, documented at both initiation and late passage. In contrast to these cytogenetic stigmata of poor prognosis, analysis of catecholamine synthesis by high pressure liquid chromatography (HPLC) measurement revealed an advanced degree of adrenergic differentiation with high rates of 3,4-Dihydroxyphenylalanine (DOPA), noradrenaline, homovanillic acid (HVA), and vanillylmandelic acid (VMA) production. Contrastingly advanced differentiation and poor prognostic genetic markers combine to render SiMa a unique instrument for investigating the pathology and therapy of Nb.

Cell Differentiation↗
PubMed1999

Growth inhibition of neuroblastoma cells by lovastatin and L-ascorbic acid is based on different mechanisms.

Hydroxymethyl-glutaryl-CoA-reductase (HMG-CoA-reductase), the key enzyme for cholesterol synthesis and essential for the synthesis of the precursor for p21ras farnesylation, was inhibited in neuroblastoma cells by lovastatin or L-ascorbic acid. Both compounds inhibited clonogenic colony formation of neuroblastoma cells in soft agar. However, while the addition of mevalonate, the product of HMG-CoA-reductase, circumvented the inhibition by lovastatin it had no reversing effect on the inhibition by L-ascorbic acid. The role of reactive oxygen compounds generated by the degradation of catecholamines, and the pro-oxidative effects of L-ascorbic acid are discussed as mechanisms of action of L-ascorbic acid.

Antineoplastic Agents↗
PubMed1999

Transient expression of members of the germin-like gene family in epidermal cells of wheat confers disease resistance.

The wheat genome encodes a family of germin-like proteins that differ with respect to regulation and tissue specificity of expression of the corresponding genes. While germin exhibits oxalate oxidase (E.C. 1.2.3.4.) activity, the germin-like proteins (GLPs) have no known enzymatic activity. A role of oxalate oxidase in plant defence has been proposed, based on the capacity of the enzyme to produce H2O2, a reactive oxygen species. The role in defence of germin and other members of the germin-like gene family was functionally assessed in a transient assay system based on particle bombardment of wheat leaves. Transient expression of the pathogen-induced germin gf-2.8 gene, but not of the constitutively expressed HvGLP1 gene, reduced the penetration efficiency of Blumeria (syn. Erysiphe) graminis f.sp. tritici, the causal agent of wheat powdery mildew, on transformed cells. Two engineered germin-gf-2.8 genes and the TaGLP2a gene, which all encoded proteins without oxalate oxidase activity, also reduced the penetration efficiency of the fungus, demonstrating that oxalate oxidase activity is not required for conferring enhanced resistance. Instead, activity tagging experiments showed that in cells transiently expressing the germin gf-2.8 gene, the transgene product became insolubilized at sites of attempted fungal penetration where localised production of H2O2 was observed. Thus, germin and GLPs may play a structural role in cell-wall re-enforcement during pathogen attack.

Base Sequence↗
PubMed1999

Anatomy of the porta hepatis (PH) as rational basis for the hepatoporto-enterostomy (HPE).

PURPOSE: In a prospective study it was investigated whether and to what degree the morphology of the porta hepatis has a bearing on the early prognosis of children with EHBA. The results will point to consequences of surgery and to the formulation of a rational understanding of the successes and failures of HPE. METHODS: The macroscopy and the microscopy of the liver was studied on native specimen and corrosion preparations of deceased adults, children and embryos. The area potentially draining the bile was determined in excised PH specimen of children with EHBA. The histologically and planimetrically measured areas were correlated to clinical follow-up studies. In order to be able to study exclusively the influence of the PH morphology, the conditions of the intrahepatical structural changes (level of fibrosis, metric and morphic changes of biliary ductules in the Glisson's triads) had to be equal. Under these conditions 61 excised PH specimen were evaluated. The level of fibrosis was determined according to the definition of Schweizer/Müller 1984 (9). RESULTS: 1) Biliary ductules of the PH end in three definable zones according to a regular pattern. 2) Biliary ductules of the PH run in a narrow and immediate relation to the vascular structures. 3) Biliary ductules of the PH are often hidden between the vascular structures of the PH and are not always accessible to preparatory exposure for the anastomosis. 4) The quantity of the bile flow is a significant function of the total area of the biliary ductules secured in the excised PH specimen. 5) Incised biliary ductules at the excision edge may be obstructed again in the scarring of the anastomosis, leading to an early interruption of bile flow. 6) The opening-up of the biliary ductules in the central zone alone is not enough to guarantee a permanent bile flow. Only if intact biliary ductules of the two lateral hepatical lobes are secured, can a positive prognosis be made.

Adult↗
PubMed1999

The influence of cholangitis on the prognosis of extrahepatic biliary atresia.

The prognosis of extrahepatic biliary atresia (EHBA) depends first on the progression of the basically existing disease and second on the development of preoperative existing alterations of hepatic structure. In addition there are postoperative complications which have essential influence on the prognosis of the disease. In this context ascending cholangitis poses a very important problem for children who have undergone a portoenterostomy. Both the organism and the frequency of cholangitis may play a part. This study should outline the influence of cholangitis on the prognosis. Since 1972, 146 cases of extrahepatic biliary atresia have been treated and followed up postoperatively. Children with a liver fibrosis degree IV at surgery will develop a cirrhosis in 86% of cases without additional influence of cholangitis. Children with a liver fibrosis degree II/III will develop a cirrhosis in 20% of cases without the influence of cholangitis after 15 years. But children with a fibrosis degree II/III with one or several episodes of cholangitis will develop a liver cirrhosis in 50% of cases after 12.5 years. The difference is statistically significant. In addition the frequency of cholangitis is also an important factor: The more episodes of cholangitis the greater the probability of cirrhosis.

Biliary Atresia↗
PubMed1998

Structure, expression and localization of a germin-like protein in barley (Hordeum vulgare L.) that is insolubilized in stressed leaves.

The primary leaves of young barley seedlings contain two major, extracellular, acid-soluble proteins of ca. 22 and 23 kDa apparent molecular mass. These proteins disappeared from the intercellular washing fluid upon stress treatments that enhanced H2O2 levels and that induced resistance to subsequent challenge by the powdery mildew fungus Erysiphe graminis f. sp. hordei. A partial peptide sequence of the 22 kDa protein was determined, and a cDNA clone was isolated. The 22 kDa protein belongs the the group of germin-like proteins (GLPs) and was designated HvGLP1. Despite its similarity to germin, i.e. oxalate oxidase, no oxalate oxidase activity of HvGLP1 could be detected. The RNA and soluble protein of HvGLP1 was highly abundant in young leaves, less abundant in older leaves and absent in roots. HvGLP1 RNA oscillated with a circadian rhythm, the minimum and maximum of RNA abundance being at the end of the dark and light periods, respectively. Heat and H2O2 treatment as well as pathogen infection caused disappearance of HvGLP1 protein from the fraction of soluble proteins of the intercellular space. HvGLP1 protein could be re-solubilized from cell walls of heat- or H2O2-treated leaves by boiling in SDS suggesting non-covalent cross linking. Although a physiological role of HvGLP1 insolubilization is still open, the protein may serve as marker for oxidative stress in cereals.

Amino Acid Sequence↗
PubMed1998

[Transjugular intrahepatic portosystemic shunt in children. Initial clinical experiences and literature review].

PURPOSE: To present special methodical and clinical findings of transjugular intrahepatic portosystemic shunts (TIPSS) in children and to discuss potential indications. PATIENTS AND METHODS: Between 1993 and 1996, 6 children aged 2-13 years were treated by TIPSS-insertion. In four cases, the underlying disease was extrahepatic biliary atresia (EHBA) and in two cases liver fibrosis secondary to treatment of neoplasms during early childhood. Indications for TIPSS insertion were variceal bleeding resistant to other treatment modalities in three patients, hypersplenism in one patient and both bleeding and hypersplenism in two. Portal vein punctures were performed using 16-gauge needles, because 19-gauge fine-needles showed insufficient stiffness. The mean follow-up was 24.5 months. RESULTS: Shunt insertion succeeded in all children with a mean procedure time of 5.2 hours. Periportal fibrosis associated with EHBA, atypical course of hepatic veins and small diameters and distances of vessels were conditions making the procedure difficult. Bleeding ceased in all patients, peripheral platelet counts rose by a mean value of 58%. Procedure-related complications were minor extrahepatic bleeding in one child and temporary haemolysis in another child. Restenosis resulted in three patients and were treated successfully by means of transjugular interventions. 5 children remain free of symptoms to this day, one child underwent successful orthotopic liver transplantation 8 months after TIPSS. CONCLUSIONS: TIPSS insertion is technically more difficult in children and has to consider child growth and possible subsequent liver transplantation. Potential indications are recurrent variceal bleeding, also of intestinal origin, resistant to standard treatment and clinically significant hypersplenism.

Adolescent↗
PubMed1998

Extrahepatic bile duct atresia: how efficient is the hepatoporto-enterostomy?

PURPOSE: Prospectively achieved findings of 151 children with EHBA operated between 1972-1997, of 108 patients in particular who were operated five and more years ago, should give evidence of the efficiency of HPE. METHOD: For five and more years the development of the disease was prospectively evaluated according to a cognitively conditioned program. The objective source parameter was the hepatic histology at the time of surgery. Departing from that parameter the structural hepatic changes were followed up for five years and more. They were related to the bile flow achieved and the age of the patient, at the time of surgery as well as to the present time of follow-up. RESULTS: Of 108 patients who were operated five and more years ago, 62 are still alive (57%) 58 children are icterus-free. The following results can be stressed: 1) There is a close correlation between the age of the patient and the fibrosis level of the liver at the time of surgery. 2) There is a close correlation between the age and the fibrosis level at the time of surgery on the one hand and the long-term survival rate, the absence of icterus and the state of the hepatic function on the other. 3) There is a close correlation between the age and the fibrosis level at surgery on the one hand and the operatively feasible (continued) bile flow on the other. 4) With favorable conditions concerning age and fibrosis level at the time of surgery, the size of the bile flow achieved through surgery is influenced positively and negatively by the morphology and bio-physical parameters of the porta hepatis as well as by postoperative cholangitis episodes. CONCLUSION: The efficiency of HPE depends on the age and (in correlation to that) on the level of hepatic fibrosis at the time of surgery, on the morphology and on bio-physical properties of the porta hepatis as well as on cholangitis episodes occurring after surgery. The fibrosis level of the Glisson's triads at the time of surgery, the morphology and bio-physical parameters of the porta hepatis are documented as causes for failing or discontinued bile flow after HPE and for the progression of fibrosis. In the absence of obvious causes it is postulated that the initially obliterating and continuing primary disease has progressed. The performance of the HPE is summarized in the results: of 108 children who were operated five and more years ago 62 are still alive, 58 are icterus-free, 25 show no progression of fibrosis and 46 of 82 patients who were initially cirrhosis-free have no cirrhosis at present.

Bile Ducts, Extrahepatic↗
PubMed1998

Cutin monomers and surface wax constituents elicit H2O2 in conditioned cucumber hypocotyl segments and enhance the activity of other H2O2 elicitors

Hypocotyls from etiolated cucumber (Cucumis sativus L.) seedlings were gently abraded at their epidermal surface and cut segments were conditioned to develop competence for H2O2 elicitation. Alkaline hydrolysates of cutin from cucumber, tomato, and apple elicited H2O2 in such conditioned segments. The most active constituent of cucumber cutin was identified as dodecan-1-ol, a novel cutin monomer capable of forming hydrophobic terminal chains. Additionally, the cutin hydrolysates enhanced the activity of a fungal H2O2 elicitor, similar to cucumber surface wax, which contained newly identified alkan-1,3-diols. The specificity of elicitor and enhancement activity was further elaborated using some pure model compounds. Certain saturated hydroxy fatty acids were potent H2O2 elicitors as well as enhancers. Some unsaturated epoxy and hydroxy fatty acids were also excellent H2O2 elicitors but inhibited the fungal elicitor activity. Short-chain alkanols exhibited good elicitor and enhancer activity, whereas longer-chain alkan-1-ols were barely active. The enhancement effect was also observed for H2O2 elicitation by ergosterol and chitosan. The physiological significance of these observations might be that once the cuticle is degraded by fungal cutinase, the cutin monomers may act as H2O2 elicitors. Corrosion of cutin may also bring surface wax constituents in contact with protoplasts and enhance elicitation.

Journal Article↗
PubMed1997

Theory and practice of predictive assays in radiation therapy.

PURPOSE: An overview of the field of predictive assays is presented. It has been written with the many clinicians and scientists in mind who would like to become better acquainted with the general scope, principles and themes in the field. RESULTS: Predictive assays have yielded much valuable information about the radiobiology of tumors e.g. the overall treatment time for rapidly proliferating tumors should be kept to a minimum. However, alteration of current treatment protocols based on results from predictive assays is still a matter of debate. What justification do we have to change established treatment protocols? A necessary and sufficient justification would be when the test value indicated an alternative treatment producing a better outcome, i.e. higher survival, improved local control, etc. Necessary but not always sufficient justification is correlation between the parameter measured and clinical outcome, if insufficient clinical benefit can be derived even when this is known. It is not sufficient that a test be demonstrated to be discriminatory. It must discriminate a sufficient number of patients, and its use must provide the patient with useful therapeutic alternatives. These parameters measured by predictive assays may well interact radiobiologically, and restricting observations to just one assay is probably insufficient for reliable indications. In the future, it is more likely that a panel of tests will be performed, and clinical decisions based on multi-parametric analysis of biopsy material. CONCLUSION: In the following overview general predictive assay theory is presented followed by a brief introduction to some of the more established assays and finally some guidelines are suggested for the development of new assays.

Humans↗
PubMed1997

Regulation of expression of two different transcripts of the NF-1 gene in neuroblastoma.

Neurofibromin, the gene product of the NF-1 gene is expressed in two isoforms. The m-RNA of NF-1 type II contains an insertion of 63 bases in the so called GAP-related domain, that distinguishes it from the type I transcript. By sequence homology neurofibromin is supposed to have a similar function in regulating activity of ras in intracellular signal transduction as the GTPase activating protein (GAP). Both transcripts of NF-1 are simultaneously expressed in different molar ratio in neuroblastoma tumors. 1) We examined 9 different neuroblastoma cell lines for the ratio of expression of NF-1 type I and type II. For quantification of the two transcripts we performed RT-PCR of the m-RNA of the neuroblastoma cells using primers designed to cover the GAP-related domain. We found values ranging from a more than 3-fold excess of type I transcript in the cell line Kelly to a slight excess of the type II transcript (I/II = 0.6) in the cell line IMR 5. 2) As there are indications that expression of NF-1 type II is related to the state of differentiation, we tried to shift expression of NF-1 from type I to type II by treatment of the neuroblastoma cells with retinoic acid. Treatment of Kelly cells with 5 microM retinoic acid for 24 h already lowered the excess of the type I transcript from 3-fold to an only 1.6-fold excess. An inversion of the molar ratio from an excess of the type I transcript to an excess of type II transcript would enable to investigate the different role of the two transcripts in the regulation of ras-activity and differentiation.

Antineoplastic Agents↗
PubMed1997

Three-dimensional endosonography of the pelvic floor: an additional diagnostic tool in surgery for continence problems in children.

Three-dimensional endorectal sonography with a specially developed system is able to produce an image of the entire pelvic floor including the sphincter muscles and the rectal wall even in small children. This special system is based on conventional endorectal ultrasound and allows recording of a controlled withdrawal of the axially rotating transducer, creating an image sequence resembling that of a spiral CT-scan; this sequence is digitized off-line and evaluated in a three-dimensional form by a workstation computer. This evaluation has several advantages compared with conventional examination, for example, the complete recording of organs with the possibility of volumetry, construction of arbitrary sections, volume-rendering procedures and the interactive segmentation of organ borders and their three-dimensional visualization. Based on images from this 3D endorectal sonography, the normal anatomy of the pelvic floor that is visible using ultrasound is described, followed by some pathological findings concerning continence surgery. Finally we discuss the advantages and restrictions compared to other examination procedures and the possibilities of technical development.

Child↗