Search PubMed⌕ Search

Biomedical subjects

K F Becker

Publications and source records attributed to K F Becker.

32 records · Page 2Linked to original sources
PubMed1997

Efficiency of single-cell polymerase chain reaction from stained histologic slides and integrity of DNA in archival tissue.

Molecular analysis of isolated single cells is a powerful tool for studying heterogeneity within a population of cells and for clarifying issues of cell origin and clonality. Here, we investigate the applicability of molecular techniques at a single-cell level by using routinely processed archival tissue. An ultraviolet laser in conjunction with a computer-controlled micromanipulator and a microscope were used for the contamination-free isolation of single tumor cells from stained sections of diffuse-type gastric cancer. A total of 1,328 single cells and 654 clusters of 10-30 cells each, taken from specimens of 14 patients, were analyzed for parts of the E-cadherin gene by the polymerase chain reaction (PCR). With increasing length in base pairs (bp) of the amplified fragments, the efficiency of single-cell PCR as measured by the rate of detectable amplification products declined from approximately 25% (156, 213, and 228 bp) to 14% (246 bp) and 11% (264 and 296 bp). For groups of 10-30 cells, a similar effect was seen at a higher level at 33% (246 bp), 31% (264 bp), and 26% (296 bp), respectively. To our knowledge, this is the first report that has studied the outcome of single-cell PCR on a large systematic scale. The average degree of DNA disintegration in paraffin-embedded, stained tissues was estimated to be approximately 100 bp when the aforementioned data were used in a mathematical model. This study provides evidence that in order to obtain reasonable sensitivity with single-cell PCR, short fragments, preferably < 200 bp long, should be used. Furthermore, whenever applicable, pooling of cells of interest may be another favorable option.

DNA↗
PubMed1996

No evidence for mutations in the alpha- and beta-catenin genes in human gastric and breast carcinomas.

Disturbed function of E-cadherin and/or of one of its anchoring proteins, the catenins, is thought to destabilize E-cadherin-mediated cell-cell adhesion, which may enhance the invasiveness of epithelial cells and thus favor carcinoma progression. Reduced expression of E-cadherin and alpha-catenin, as well as mutations in the E-cadherin gene, have been found in various carcinomas, whereas mutations in the alpha- and beta-catenin genes have been described only in carcinoma cell lines. Using reverse transcription-PCR, followed by agarose gel electrophoresis and single-strand conformational polymorphism, we examined 16 diffuse- and 5 intestinal-type gastric carcinomas, as well as 9 lobular and 2 ductal breast carcinomas, for mutations of alpha- and beta-catenin cDNA. All of the investigated tumors were analyzed previously for E-cadherin mutations. Comparing tumorous and nontumorous samples, we detected neither deletions nor aberrant single-strand conformational polymorphism patterns. At nucleotide 2220 of the alpha-catenin gene, we identified one frequent polymorphism. Our findings suggest that, in contrast to E-cadherin, mutations of alpha- and beta-catenin do not contribute to the pathogenesis or the diffuse growth patterns of gastric or breast carcinomas.

Breast Neoplasms↗
PubMed1996

Single-cell mutation analysis of tumors from stained histologic slides.

Formalin-fixed and paraffin-embedded tissues are a valuable resource for diagnosis and research. PCR is one of the most powerful methods of retrospective analysis of the DNA present in fixed tissues. One major problem with the molecular analysis of tissue samples, however, is cellular heterogeneity, ie, the large variety of cell types usually present in these specimens can mask cell-specific genetic alterations associated with disease. Herein we describe a procedure for obtaining and analyzing single cells recovered from stained histologic tissue sections without risking contamination from neighboring cells. An ultraviolet laser microbeam was used to physically destroy the tissue surrounding the single cells of interest. These cells, now freed from adjacent cells, were then easily retrieved with a motorized, computer-controlled micromanipulator and molecularly characterized through the use of PCR-based microanalysis. This accurate microdissection technique, followed by DNA amplification and direct sequencing, revealed a novel mutation in the gene coding for the cell adhesion molecule E-cadherin in single tumor cells that was absent in the adjacent single epithelial cells of a patient with early gastric cancer of the diffuse type. In this form of malignancy, tumor cells lose homophilic cell-to-cell interactions and invade the connective tissue as single cells. E-cadherin gene mutations have previously been detected in advanced diffuse-type gastric cancer and gastric carcinoma cell lines. The present study suggests that E-cadherin gene mutations may be an early event in gastric tumorigenesis. The laser-based isolation and subsequent molecular characterization of individual cells, as described herein, allows for micrometer-sized precision and should prove useful in detecting the nucleic acid abnormalities that underlie cancer, infection, and genetic disease.

Base Sequence↗
PubMed1995

Microsatellite instability in adenocarcinomas of the upper gastrointestinal tract. Relation to clinicopathological data and family history.

We analyzed 66 adenocarcinomas arising in the upper gastrointestinal tract for microsatellite instability at eight microsatellite loci to investigate the role of these genetic alterations in the etiology of these tumors. We identified alterations in at least one locus in 11/46 adenocarcinomas of the stomach, in 2/15 adenocarcinomas arising in Barrett's esophagus, and in 1/5 adenocarcinomas of the duodenum and jejunum. Microsatellite instability in gastric tumors was found in 5/22 of intestinal, 1/3 of mixed, and 5/21 of diffuse type tumors. No relationship to the tumor stage (TNM), age, and survival time of the patients was observed. One patient had two synchronous gastric tumors both exhibiting microsatellite instability at multiple loci. His family history revealed four individuals in the maternal line afflicted with gastric carcinoma in three generations. Our data show that microsatellite instability is a genetic event in 11 to 24% of tumors of the upper gastrointestinal tract. The observation of microsatellite instability and a familial clustering of gastric tumors may suggest a genetic predisposition for a subset of gastric tumors, which may be identified by microsatellite analysis.

Adenocarcinoma↗
PubMed1994

E-cadherin gene mutations provide clues to diffuse type gastric carcinomas.

The calcium-dependent homophilic cell adhesion molecule and candidate suppressor gene, E (epithelial)-cadherin, plays a major role in the organization and integrity of most epithelial tissues. Diffusely growing gastric carcinomas show markedly reduced homophilic cell-to-cell interactions. We speculated that mutations in the E-cadherin gene may be responsible for the scattered phenotype of this type of carcinoma. For that reason we have examined E-cadherin in 26 diffuse type, 20 intestinal type and 7 mixed gastric carcinomas (Laurén's classification) at the DNA, RNA, and protein levels. Reverse transcription polymerase chain reaction and direct sequencing of amplified E-cadherin complementary DNA fragments revealed inframe skipping of either exon 8 or exon 9 in 10 patients with diffuse tumors and an exon 9 deletion in one patient with a mixed carcinoma; both exons encode putative calcium binding domains. These alterations were not seen in nontumorous gastric tissues. Splice site mutations responsible for the exon deletions were identified in six of these patients, eliminating the possibility of alternative splicing mechanisms. Five of these splice site alterations were confirmed as somatic mutations. Non-splice site mutations were observed in three diffuse type tumors, namely a 69-base pair deletion of exon 10 and two point mutations, one of which destroys a putative calcium binding region. Immunohistochemical evaluation showed E-cadherin immunoreactivity in tumors and lymph node metastases of patients expressing abnormal mRNA. The allelic status of the E-cadherin gene was analyzed in one patient, revealing loss of heterozygosity with retention of a mutated E-cadherin allele. Overall, E-cadherin mutations were identified in 50% (13 of 26) of the diffuse type and in 14% (1 of 7) of the mixed carcinomas. In contrast, two silent E-cadherin mutations (not changing the amino acid sequence) were detected in two tumors of the intestinal type. Our study provides strong in vivo evidence that E-cadherin gene mutations may contribute to the development of diffusely growing gastric carcinomas and support a tumor/metastasis suppressor gene hypothesis.

Base Sequence↗
PubMed1992

New mechanisms of hormone secretion: MDR-like gene products as extrusion pumps for hormones?

P-glycoprotein, the product of the multidrug resistance (MDR1) gene, is an ATP-driven transmembrane pump that increases the resistance of cells by actively exporting toxic chemicals. In addition to transporting anticancer drugs, P-glycoprotein has been reported to extrude a variety of lipophilic drugs, such as calcium channel blockers, phenothiazines, cyclosporines etc. Interestingly, recent experiments suggest that steroid hormones may be physiologic substrates for P-glycoprotein. In addition, there exists a family of transporter genes with high structural homology to P-glycoprotein, the so-called ABC (ATP-binding casette) family. Although the physiological ligands for most of these transporters are unknown, there is increasing evidence that peptides may be transported by some of these proteins. Thus, the a-factor, a farnesylated pheromone with 13 amino acids, is exported from yeast cells by the product of the STE6 gene, a transporter protein with high homology to P-glycoprotein. Recently, we have cloned a novel member of the ABC-transporter gene family from neuroblastoma x glioma hybrid (NG-108-15) cells. This putative transporter gene ("NG-TRA") is expressed in the adrenal gland, kidney and in the brain. High amounts of NG-TRA mRNA are found in a variety of human brain tumors. Whether NG-TRA and/or other MDR-related transporters are involved in the transport of steroids, peptide hormones or growth factors remains to be established. If so, the cellular export of hormones by active pumps may represent a new mechanism of hormone secretion.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1991

The multidrug-resistance gene MDR1 is expressed in human glial tumors.

The most consistantly reported alteration of multidrug-resistant carcinoma cells is the overexpression of a membrane glycoprotein, termed P-glycoprotein. In this study we examined whether the strong intrinsic chemotherapy resistance of glial tumors might be related to the expression of the MDR1 gene which codes for P-glycoprotein. Fourteen glial tumors were examined immunohistochemically using the monoclonal antibody C219. In addition, RNA samples of 11 of these tumors were analysed using a sensitive Northern blot assay. P-glycoprotein is expressed in all 14 glial tumors; the number of stained tumor cells, however, varied considerably ranging from 0.3% to 15%. There was no correlation between the number of MDR1-positive cells and the histological malignancy. Varying amounts of MDR1 mRNA were detectable in 7 from 11 examined tumors. The results of our study show that the MDR1 gene is expressed in human glial tumors and suggest that the multidrug transporter may contribute to the clinical non-responsiveness of these tumors to chemotherapy.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMedDate not supplied

Laser-assisted preparation of single cells from stained histological slides for gene analysis.

Individual cells are prepared from histological tissue sections of routinely formalin-fixed and paraffin-embedded tissues using an ultraviolet laser micromanipulator. This technology, in combination with polymerase chain reaction (PCR)-based gene analysis, will enable researchers to routinely detect a variety of nucleic acid abnormalities underlying cancer, infection, and genetic disease with previously unknown sensitivity: at the single cell level. The utility of this technique is demonstrated by PCR amplification and sequencing of the E-cadherin gene, which codes for a homophilic cell-to-cell adhesion molecule, in early gastric carcinomas of the diffuse type of Lauren's classification. The main characteristics of the laser-assisted microdissection technique are high precision without contamination and easy application. The assignment of individual gene sequences to single cells will now provide a direct link between molecular biology on the one hand and histology and pathology on the other.

Cadherins↗
PubMedDate not supplied

[The elderly man--historical aspects. Several sketches from Bible and church history].

Using biblical and biblical-apocryphal sources, the characteristics of Jewish-Christian patriarchism are shown which as a system, especially embodied by elderly men, was very efficient up to the beginning of the 19th century. Following industrialization a decline set in which still continues, and by far exceeds the mere loss of masculine predominance. Particularly elderly men are affected by this. It is remarkable that the general decline of the Protestant Church (in Germany) is connected with the dwindling of responsible paternity. It is presumed that female emancipation and the recovery of masculine responsibility are not contrary but complementary qualities.

Aged↗
PubMedDate not supplied

[The church and old age in history and in the present].

Firstly, the considerable cultural-historical efficiency of the biblical belief is shown in its influence upon the status and the self-comprehension of elderly people. The Old Testamental monotheism leads to the disenchantment of man and a sober judgement of age, free of superstition. The theology of grace in the New Testament teaches the old to look upon the Lord hopefully, despite all deficits of life, instead of ending in a desperate balance of life. In the course of ecclesiastical history the basic biblical positions have mainly been kept till the 19th century with social efficiency, despite a certain narrowness by patriarchalism. Industrialisation however, was accompanied by a theological development, which did rather follow philosophical fashions of that time than social requirement. In connection with empirical Gerontology some Protestant theologians have tried a new concretisation of the fourth commandment for our time and conditions of life for more than one decade.

Aged↗