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Biomedical subjects

M Piontek

Publications and source records attributed to M Piontek.

At least 19 recordsLinked to original sources
PubMed2000

The effect of sewage sludge composting on the quantitative state of some groups of bacteria and fungi.

Analysis of the quantitative state of disease causing bacteria and of other microbic groups were done on the sewage sludge from a sewage treatment plant. The results of the analysis include the ammonifying bacteria, nitrifying and denitrifying bacteria. The general quantity of bacteria and fungi in a secondary dehydrated sludge, fermented secondary dehydrated sludge, and in composted secondary dehydrated sludge was deterinated. Composts were prepared from dehydrated secondary sludge with the addition of sawdust. Microbiological analysis of sewage sludge showed, that the quantities of the fecal coli bacteria were 6500; 220 and 150 cells per cm3 of the secondary dehydrated sludge, fermented secondary dehydrated sludge and composted dehydrated secondary sludge, respectively. The numbers of Salmonella were respectively 67.80; 6.48 and 6.60 cells per cm3. The general numbers of bacteria were 2.98 x 10(7); 2.79 x 10(7); 2.15 x 10(7) cells per cm3 of sludge. The cell numbers of fungi were: 6.20x 10(2); 19.60 x 10(2); 7.80 x 10(2) per cm3 of sludge. In the three types of sludge, the results show great numbers of the ammonifying, nitrifying and denitrifying bacteria. Of the analysed groups of bacteria, the highest numbers of cells were found for general bacteria; ammonifying and nitrifying bacteria were next in abundance; still fewer were the denitrifying bacteria. Fungi and pathogenic bacteria were the least numerous.

Ammonia↗
PubMed1998

Two novel gene expression systems based on the yeasts Schwanniomyces occidentalis and Pichia stipitis.

Two non-Saccharomyces yeasts have been developed as hosts for heterologous gene expression. The celD gene from Clostridium thermocellum, encoding a heat-stable cellulase, served as the test sequence. The first system is based on the amylolytic species Schwanniomyces occidentalis, the second on the xylolytic species Pichia stipitis. The systems comprise auxotrophic host strains (trp5 in the case of S. occidentalis; trp5-10, his3 in the case of P. stipitis) and suitable transformation vectors. Vector components consist of an S. occidentalis-derived autonomously replicating sequence (SwARS) and the Saccharomyces cerevisiae-derived TRP5 sequence for plasmid propagation and selection in the yeast hosts, an ori and an ampicillin-resistance sequence for propagation and selection in a bacterial host. A range of vectors has been engineered employing different promoter elements for heterologous gene expression control in both species. Homologous elements derived from highly expressed genes of the respective hosts appeared to be of superior quality: in the case of S. occidentalis that of the GAM1 gene, in the case of P. stipitis that of the XYL1 gene. Further elements tested are the S. cerevisiae-derived ADH1 and PDC1 promoter sequences.

Cellulase↗
PubMed1996

Recombinant Hansenula polymorpha as a biocatalyst: coexpression of the spinach glycolate oxidase (GO) and the S. cerevisiae catalase T (CTT1) gene.

The methylotrophic yeast Hansenula polymorpha has been developed as an efficient production system for heterologous proteins. The system offers the possibility to cointegrate heterologous genes in anticipated fixed copy numbers into the chromosome. As a consequence co-production of different proteins in stoichiometric ratios can be envisaged. This provides options to design this yeast as an industrial biocatalyst in procedures where several enzymes are required for the efficient conversion of a given inexpensive compound into a valuable product. To this end recombinant strains have been engineered with multiple copies of expression cassettes containing the glycolate oxidase (GO) gene from spinach and the catalase T (CTT1) gene from S. cerevisiae. The newly created strains produce high levels of the peroxisomal glycolate oxidase and the cytosolic catalase T. The strains efficiently convert glycolate into glyoxylic acid, oxidizing the added substrate and decomposing the peroxide formed during this reaction into water and oxygen.

Alcohol Oxidoreductases↗
PubMed1995

High-level secretion of hirudin by Hansenula polymorpha--authentic processing of three different preprohirudins.

A DNA sequence coding for a subtype of the hirudin variant HV1 was expressed in the methylotrophic yeast Hansenula polymorpha from a strongly inducible promoter element derived from a gene of the methanol metabolism pathway. For secretion, the coding sequence was fused to the KEX2 recognition site of three different prepro segments engineered from the MF alpha 1 gene of Saccharomyces cerevisiae, the glucoamylase (GAM1) gene of Schwanniomyces occidentalis and the gene for a crustacean hyperglycemic hormone from the shore crab Carcinus maenas. In all three cases, correct processing of the precursor molecule and efficient secretion of the mature protein were observed. In fermentations on a 10-1 scale of a transformant strain harbouring a MF alpha 1/hirudin-gene fusion yields in the range of grams per litre could be obtained. The majority of the secreted product was identified as the full-length 65-amino-acid hirudin. Only small amounts of a truncated 63-amino- acid product, frequently observed in S. cerevisiae-based expression systems, could be detected.

Amino Acid Sequence↗
PubMed1994

Vascularization of carcinomas of the esophagus and its correlation with tumor proliferation.

Vascularization and tumor cell proliferation were analyzed in 33 resected human squamous cell carcinomas of the esophagus using the endothelium-specific antibody BW 200 and the proliferation-associated antibody Ki-67. Vascular parameters (relative capillary volume, relative total vessel volume, vascular surface area, and vascular length) as well as the percentage of proliferating tumor cells (Ki-67 index) were evaluated on frozen sections by a morphometric method. Vascular parameters of the normal mucosa exceeded those of tumors significantly, by a factor of 1.4-2.3. The mean distance between tumor capillaries and the onset of necrosis was 92 +/- 34 microns. Global vascular density did not correlate with TNM stage, tumor diameter, or overall tumor proliferation (mean Ki-67 index, 35.1%; range, 14.2-64.1%). However, a significant negative correlation existed between the percentage of proliferating tumor cells per tumor cord and the intercapillary distance between capillaries located at the edges of these cords. This observation points to the fact that the esophageal cancers were composed of multiple tumor cords and that each of these cords possessed its own supply capillaries at the base of the cord. The sum of these "supply units" thus constitutes an esophageal cancer. The intercapillary distance may reflect the oxygenation status of tumor cells, which cannot be predicted on the basis of tumor staging or grading.

Aged↗
PubMed1994

Growth inhibition of human gastrointestinal cancer cells by cyclosporin A.

We have studied the ability of cyclosporin A (CsA) to inhibit the growth of human AGS gastric and HT29 colon carcinoma cells in vitro. Using continuous drug exposure in growth assays of cultured tumour cells we found that CsA produced a dose-dependent growth inhibition in gastric and colon cancer cells with a half-maximal effect at 5 microM and 6 microM CsA respectively. The growth inhibition of CsA was reversible in AGS cells, when the tumour cells were incubated in normal growth medium following CsA treatment. Trypan blue dye exclusion in AGS cells indicated a cytostatic rather than a cytotoxic effect in the concentration range used. Coincubation of CsA-treated cells with 10-400 U/ml interleukin-2 (IL-2) could not abrogate this growth inhibition, suggesting an IL-2 independent mechanism of action. Flow-cytometric analysis did not reveal a phase arrest of the gastric cancer cells within the cell cycle. We conclude from our experiments that CsA cytostatically and reversibly inhibits the growth of human gastric cancer cells in a dose-dependent manner. In contrast to its mechanism of action in lymphocytes, this direct antiproliferative effect of CsA seems not to be mediated by an IL-2-dependent pathway or a cell-cycle-phase arrest of the tumour cells.

Adenocarcinoma↗
PubMed1993

Protein kinase C and adenylate cyclase as targets for growth inhibition of human gastric cancer cells.

In the human gastric adenocarcinoma cell line AGS the effects of the protein-kinase-C-activating phorbol ester 12-O-tetradecanoylphorbol 13-acetate (TPA), the protein kinase C inhibitor staurosporine, the adenylate-cyclase activating agent forskolin, and the permeable dibutyryl-adenosine 3',5'-monophosphate (Bt2cAMP) on the proliferation were assessed. Cell counting followed 5 days of incubation. Prolonged activation of protein kinase C by TPA, inhibition of protein kinase C by staurosporine, activation of adenylate cyclase by forskolin or a direct increase of the intracellular cAMP level all result in a dose-dependent growth inhibition of AGS gastric tumour cells. Half-maximal inhibition was achieved at 100 pM for TPA, 1 nM for staurosporine, 20 microM for forskolin, and 600 microM for Bt2cAMP. It is concluded that protein kinase C and adenylate cyclase play a fundamental role in the growth of AGS gastric cancer cells. Interference with these enzymes involved in the signal transduction of growth regulation in tumour cells may represent a target in the development of new antiproliferative principles.

Adenocarcinoma↗
PubMed1992

Heterologous protein production in yeast.

The exploitation of recombinant DNA technology to engineer expression systems for heterologous proteins represented a major task within the field of biotechnology during the last decade. Yeasts attracted the attention of molecular biologists because of properties most favourable for their use as hosts in heterologous protein production. Yeasts follow the general eukaryotic posttranslational modification pattern of expressed polypeptides, exhibit the ability to secrete heterologous proteins and benefit from an established fermentation technology. Aside from the baker's yeast Saccharomyces cerevisiae, an increasing number of alternative non-Saccharomyces yeast species are used as expression systems in basic research and for an industrial application. In the following review a selection from the different yeast systems is described and compared.

Gene Expression↗
PubMed1991

Heterologous gene expression in Hansenula polymorpha: efficient secretion of glucoamylase.

We have introduced the glucoamylase gene (GAM1) from Schwanniomyces occidentalis into the genome of the methylotrophic yeast Hansenula polymorpha to study the potential of this organism as a host for high-level expression of a heterologous gene encoding a secretory protein. Transformants of H. polymorpha containing GAM1 under control of the formate dehydrogenase (FMD) promoter are stable and efficiently secrete an active glucoamylase that is faithfully processed and modified. Yields of up to 1.4g/l of active enzyme were obtained at cell densities of 100-130 grams dry weight per liter.

Amino Acid Sequence↗
PubMed1990

Crohn's disease: what about the pancreas?

Crohn's disease (CD) is now accepted as a systemic illness. The importance of extraintestinal manifestations is underlined by the fact that such "complications" can be more prominent and even more difficult to control than the intestinal disease itself. Lately, evidence for a more than accidental association of pancreatitis and exocrine pancreatic insufficiency with CD is growing. This might have a significant impact on the treatment of abdominal pain and diarrhea in CD, symptoms which have so far been attributed exclusively to the intestinal rather than the extraintestinal manifestations of the disease.

Crohn Disease↗
PubMed1989

[Noncirrhotic liver fibrosis after chronic arsenic poisoning].

A 67-year-old woman with portal hypertension, splenomegaly without portal vein thrombosis, leucopenia and thrombocytopenia of splenic origin had repeated episodes of life-threatening haemorrhage from esophageal varices. Since childhood she had suffered from psoriasis and had been treated over a period of 15 years with Fowler's solution (in all about 25 g of arsenic trioxide). She had the characteristic skin lesions of arsenical poisoning-palmar hyperkeratoses and two basal cell carcinomas on the trunk. Histological examination of a wedge biopsy from the liver showed definite structural changes with fibrosis around the central veins and in the portal tracts. There was no evidence of cirrhotic alteration. The hepatocytes were normal by light microscopy and electron microscopy. This case of noncirrhotic hepatic fibrosis is considered to have been caused by chronic arsenical poisoning.

Aged↗
PubMed1989

[Late initial manifestations of Crohn disease with atypical symptoms].

The case of a 55-year-old patient with Crohn's disease and chronic intermittent diarrhea as well as progressive weight loss of 20 percent of his body weight is reported. The establishment of the diagnosis was difficult at the beginning, since characteristic symptoms were missing and radiological and endoscopical findings were normal. Loam-coloured glossy stools, repeated registration of a reduced chymotrypsin concentration of the stool and the response of the symptoms to a substitution of pancreatic enzymes were initially regarded as signs of an exocrine pancreas insufficiency. Not before multiple biopsies were taken from the macroscopically largely normal small and large intestine during persisting complaints, an extensive infiltration with Crohn's disease could be shown. This case report emphasizes the importance of taking multiple biopsies in etiologically unexplained chronic diarrhea even from macroscopic inconspicuous intestinal mucosa. Because of the rising incidence of Crohn's disease late onset is gaining increasing significance in the differential diagnosis of chronic diarrhea in the elderly patients.

Biopsy↗