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Biomedical subjects

J Bischof

Publications and source records attributed to J Bischof.

17 recordsLinked to original sources
PubMed2002

[Reliability, trainability and stability of auditory discrimination performance in 2 computer-assisted assessment and training methods].

OBJECTIVES: The present study focuses on the possibilities and effects of training dyslexic children in tone and phoneme discrimination tasks. METHODS: A computer program was developed to train dyslexic children to discriminate between tone and speech stimuli. The correlation between auditory discrimination and reading and orthography performance was then tested in a preliminary study of n = 63 children. In a prospective study 44 children were assigned to one of three paralyzed groups: tone training, phoneme training or a control group. Upon completion of the initial diagnostics for all groups, the two training groups received four weeks of discrimination training, after which all three groups were immediately re-tested for the first time. Parallel thereto all children underwent specific training in reading and orthography at their school. Six months later all were re-tested a second time. RESULTS: Both test methods showed a high reliability (rn = .94; .95). Significant correlations between auditory discrimination and reading and orthography performance were confirmed. Auditory discrimination was significantly trainable. Specific training effects, as well as independent developmental effects were found. While the training effects of phoneme discrimination were stable over six months, those of tone discrimination were not. CONCLUSION: The central auditory discrimination between tone and phoneme stimuli can be trained successfully in dyslexic children and might also affect their reading and orthography performance.

Child↗
PubMed2001

A parametric study of freezing injury in ELT-3 uterine leiomyoma tumour cells.

Cellular level freeze injury was investigated after controlled freezing of an Eker rat uterine fibroid cell line in both the presence and absence of oestradiol. The connection between thermal history and cell injury in single ELT-3 cells in suspension (without oestradiol) was studied through a two-level, four-parameter (2(4)) experiment with membrane dye exclusion as the end-point. The four parameters considered were cooling rate (CR), end temperature (ET), hold time (HT) and thawing rate (TR). A high and low value of each parameter was selected as follows: CR, 5-25 degrees C/min; ET, -20 to -30 degrees C; HT, 0-5 min; TR 20-200 degrees C/min. The greatest parameter effect on freeze injury in this range was ET followed by HT, then TR and finally CR. In addition, significant parameter interactions and curvature were found. Additional CR results outside the original parameter range showed a reduction in survival at both 1 and 50 degrees C/min suggestive of an inverted U-shaped survival curve. These results show that this tumour system is susceptible to cryoinjury, particularly at temperatures below -30 degrees C with HT of >5 min and slow thawing. In addition, the presence of oestradiol was found to increase the susceptibility of these cells to cryoinjury.

Animals↗
PubMed2000

DNA-Based diagnostic approaches for identification of Burkholderia cepacia complex, Burkholderia vietnamiensis, Burkholderia multivorans, Burkholderia stabilis, and Burkholderia cepacia genomovars I and III.

Bacteria of the Burkholderia cepacia complex consist of five discrete genomic species, including genomovars I and III and three new species: Burkholderia multivorans (formerly genomovar II), Burkholderia stabilis (formerly genomovar IV), and Burkholderia vietnamiensis (formerly genomovar V). Strains of all five genomovars are capable of causing opportunistic human infection, and microbiological identification of these closely related species is difficult. The 16S rRNA gene (16S rDNA) and recA gene of these bacteria were examined in order to develop rapid tests for genomovar identification. Restriction fragment length polymorphism (RFLP) analysis of PCR-amplified 16S rDNA revealed sequence polymorphisms capable of identifying B. multivorans and B. vietnamiensis but insufficient to discriminate strains of B. cepacia genomovars I and III and B. stabilis. RFLP analysis of PCR-amplified recA demonstrated sufficient nucleotide sequence variation to enable separation of strains of all five B. cepacia complex genomovars. Complete recA nucleotide sequences were obtained for 20 strains representative of the diversity of the B. cepacia complex. Construction of a recA phylogenetic tree identified six distinct clusters (recA groups): B. multivorans, B. vietnamiensis, B. stabilis, genomovar I, and the subdivision of genomovar III isolates into two recA groups, III-A and III-B. Alignment of recA sequences enabled the design of PCR primers for the specific detection of each of the six latter recA groups. The recA gene was found on the largest chromosome within the genome of B. cepacia complex strains and, in contrast to the findings of a previous study, only a single copy of the gene was present. In conclusion, analysis of the recA gene of the B. cepacia complex provides a rapid and robust nucleotide sequence-based approach to identify and classify this taxonomically complex group of opportunistic pathogens.

Burkholderia Infections↗
PubMed1999

Transient transfection of mammary epithelial cells with a PEI/DNA/adenovirus system.

Studies on epithelial cells often require the transient expression of exogenous proteins in polarized epithelial cells. However, the major limitation of this approach has been the difficulty of obtaining transient gene expression in polarized epithelial cell cultures. We report here on the application of a polyethylenimine (PEI)/DNA/adenovirus system for efficient transient gene expression in mammary epithelial cells. Based on luciferase assay and FACScan analysis the PEI/DNA/adenovirus system is shown to be an effective and simple method for transfecting epithelial cells.

Adenoviridae↗
PubMed1998

Spinodal dewetting in liquid crystal and liquid metal films

Theory predicts that dewetting of a homogeneous liquid film from a solid surface may proceed via unstable surface waves on the liquid. This phenomenon, usually termed spinodal dewetting, has been sought after in many systems. Observations in liquid crystal and liquid metal films showed that, as expected, the emerging structures were similar to those found for spinodal decomposition in mixtures. Certain differences, however, could be attributed to peculiarities of the wetting forces in these two dissimilar systems, thereby demonstrating the role of nonlinearities inherent in the wetting forces.

Journal Article↗
PubMed1993

A morphological study of cooling rate response in normal and neoplastic human liver tissue: cryosurgical implications.

The process of freezing in normal human livers and in human liver tumors was studied by freezing samples of these tissues with constant cooling rates and then examining the morphology of the frozen tissue, after freeze substitution, with the light microscope. Cooling rates varied from 2 degrees C/min up to approximately 2000 degrees C/min. It was observed that high cooling rates produce extensive intracellular ice in both normal and neoplastic liver. At slow rates of cooling, normal and neoplastic liver cells dehydrated and large extracellular ice crystals formed. Comparison of the frozen normal liver and the frozen malignant tumors shows that for the same rates of freezing, the tumor cells retain more cellular water and therefore show less susceptibility to dehydration at low rates of cooling. At slow cooling rates, the amount of cellular dehydration and consequent vascular and interstitial space engorgement changed with the type of tissue frozen. The greatest amount of dehydration occurred in normal human liver, followed by metastatic colon carcinoma and finally primary hepatocellular carcinoma. These results are important for cryosurgery since they suggest that malignant tissues have a different response to freezing than normal tissues.

Adenocarcinoma↗
PubMed1992

Cryomicroscopic analysis of freezing in liver of the freeze-tolerant wood frog.

The technique of directional solidification coupled with low-temperature scanning electron microscopy was applied to analyze the freezing of liver slices from the freeze-tolerant frog Rana sylvatica. Micrographs of liver slices from 5 degrees C-acclimated frogs frozen on the directional stage to -7 degrees C showed continuous ice formed along an expanded vasculature with hepatocytes that were shrunken and virtually dehydrated. However, when frogs were given a survivable freezing exposure at -4 degrees C for 24 h, liver slices subsequently frozen in vitro at -7 degrees C were much less shrunken and the presence of intracellular ice crystals (formed when samples were plunged into liquid N2 before microscopy) demonstrated that ample free water remained in these hepatocytes at -7 degrees C. This reduced level of cell dehydration was correlated with the buildup of 280 +/- 61 mumol/g wet wt glucose as a cryoprotectant in liver during the -4 degrees C exposure in vivo. The study provides the first direct cytological analysis of the freezing process in an organ of a freeze-tolerant vertebrate and the first confirmation of the relationship between maintenance of a critical minimum cell volume and freezing survival by these animals.

Acclimatization↗
PubMed1990

Effects of cooling rate and glycerol concentration on the structure of the frozen kidney: assessment by cryo-scanning electron microscopy.

An experimental technique, employing a directional solidification stage for controlled freezing of tissue samples and low-temperature scanning electron microscopy for observation of the structure of the frozen-hydrated samples, was used to study freezing processes in the kidney. Parametric studies in which the cooling rate during freezing and the concentration of glycerol in the tissue were varied confirmed the results of earlier freeze-substitution studies. The results suggest a mechanism for ice propagation in the kidney similar to that already proposed for the liver, in which ice originates in, and is subsequently propagated through, the peritubular vasculature. The ice front dehydrates the cells and tubular structures encountered in its path, thus preventing intraluminal freezing. At higher rates of cooling and increased concentrations of glycerol there is less dehydration of cortical structure and intraluminal freezing occurs.

Animals↗
PubMed1988

[The knowledge of cancer patients about their disease].

160 patients suffering from malignant tumors were interviewed by means of a questionnaire. Most of them had been treated by radiotherapy in a curative intent. The treatment had been finished about one year before, all patients submitted to curative therapy were free from recurrences. 80% out of them knew about their diseases, benignity or malignancy, sites of the primary tumors, and extent of lymph node metastases. Only 5% of the patients had to be informed about their disease at the Radio-oncology Hospital, 88% had been informed already by the physicians before. About 90% of the patients were of the opinion that a complete information was suitable and desired by them. As our patients got older, their desire for information diminished considerably. Even one year after the end of their disease, 34% did not speak frankly with other persons about their disease. The study showed furthermore that the hope of being cured is not affected by information. In this context, 90% of the patients were of the opinion that information should not exceed a certain degree.

Adolescent↗