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Biomedical subjects

S Hahn

Publications and source records attributed to S Hahn.

At least 127 records · Page 7Linked to original sources
PubMed1999

Fetal cells in maternal blood. An update from Basel.

OBJECTIVE: The efficiency of two protocols for the enrichment of fetal cells from the blood of pregnant women was compared: a triple density gradient followed by twin magnetic separations (method A) versus a single density gradient and single magnetic separation (method B). STUDY DESIGN: Blood samples were obtained from women prior to undergoing an invasive procedure. The processed samples, 87 by method A and 332 by method B, were examined for the presence of male cells by fluorescence in situ hybridisation. RESULTS: The simpler protocol was found to be superior. The most critical component, however, is the ability of the reader to correctly evaluate the sample, where we observed large variations, with reader B attaining a sensitivity of 82.61% with a corresponding specificity of 86.96%. CONCLUSION: A simpler enrichment protocol can be used from smaller blood samples to attain detection efficiencies which are similar to or superior to current noninvasive methods.

Cell Separation↗
PubMed1999

Influence of attentional capture on oculomotor control.

Previous research has shown that when searching for a color singleton, top-down control cannot prevent attentional capture by an abrupt visual onset. The present research addressed whether a task-irrelevant abrupt onset would affect eye movement behavior when searching for a color singleton. Results show that in many instances the eye moved in the direction of the task-irrelevant abrupt onset. There was evidence that top-down control could neither entirely prevent attentional capture by visual onsets nor prevent the eye from starting to move in the direction of the onset. Results suggest parallel programming of 2 saccades: 1 voluntary goal-directed eye movement toward the color singleton target and 1 stimulus-driven eye movement reflexively elicited by the abrupt onset. A neurophysiologically plausible model that can account for the current findings is discussed.

Adolescent↗
PubMed1999

Attentional capture and aging: implications for visual search performance and oculomotor control.

Two studies examined potential age-related differences in attentional capture. Subjects were instructed to move their eyes as quickly as possible to a color singleton target and to identify a small letter located inside it. On half the trials, a new stimulus (i.e., a sudden onset) appeared simultaneously with the presentation of the color singleton target. The onset was always a task-irrelevant distractor. Response times were lengthened, for both young and old adults, whenever an onset distractor appeared, despite the fact that subjects reported being unaware of the appearance of the abrupt onset. Eye scan strategies were also disrupted by the appearance of the onset distractors. On about 40% of the trials on which an onset appeared, subjects made an eye movement to the task-irrelevant onset before moving their eyes to the target. Fixations close to the onset were brief, suggesting parallel programming of a reflexive eye movement to the onset and goal-directed eye movement to the target. Results are discussed in terms of age-related sparing of the attentional and oculomotor processes that underlie attentional capture.

Adult↗
PubMed1999

Approximately half of the erythroblasts in maternal blood are of fetal origin.

The enrichment of fetal erythroblasts from the peripheral blood of pregnant women is currently actively pursued for the development of a non-invasive means of prenatal diagnosis. Since erythroblasts in maternal blood are not all of fetal origin, and currently no reliable method exists to distinguish between the maternal and fetal erythroblasts, their use for prenatal diagnosis is not without uncertainty. The purpose of this study was to determine the percentage of fetal erythroblasts in maternal blood at the single cell level and to what extent such cells can reproducibly be used for polymerase chain reaction (PCR)-based prenatal diagnostic analyses. Erythroblasts were enriched from the peripheral blood of rhesus negative pregnant women using magnetic cell sorting (MACS). Single erythroblasts identified morphologically were individually micromanipulated and analysed by a multiplex PCR reaction for the fetal SRY and rhesus D genes. As a control for the PCR reaction the beta-globin gene was used. The PCR results were validated by the results obtained by invasive procedures. In all instances where single erythroblasts were examined, the correct fetal genotype for the two fetal specific loci was detected. Furthermore, our results indicate that approximately 50% of the enriched erythroblasts are of fetal origin.

DNA-Binding Proteins↗
PubMed1999

The immunomodulatory role of CD4-positive cytotoxic T-lymphocytes in health and disease.

Among the CD4-positive (CD4+) T-lymphocytes a population exists which expresses cytolytic activity. These 'killer' cells belong to the T helper type 1 (Th1) subset and if activated, express Fas-ligand (FasL) which induces apoptosis in Fas-positive target cells. The major targets of these CD4+ cytotoxic T-lymphocytes (CTL) are cells of the immune system, such as T, B cells and macrophages which express Fas upon activation. Thus, CD4+ CTL play a major immunoregulatory part through the elimination of activated myeloid and lymphoid cells during and upon completion of an immune response. In certain diseases, such as in HIV-infection and some autoimmune disorders, the functional activity of CD4+ CTL is disturbed preferentially at the level of FasL-Fas interaction, further emphasizing their important immunoregulatory role. Furthermore, Fas-ligand expressing tumors can evade the attack of Fas-positive CD4+ CTL and other effector cells, thereby giving them an opportunity to expand.

Adjuvants, Immunologic↗
PubMed1999

A comparison of different density gradients and antibodies for enrichment of fetal erythroblasts by MACS.

The enrichment of fetal cells, in particular fetal erythroblasts from the blood of pregnant women offers a promising non-invasive alternative for prenatal diagnosis. The purpose of this study was to compare the retrieval of erythroblasts by different density gradients and different antibodies against erythroid surface antigens, in both a model test system and in blood samples of pregnant women. We enriched erythroblasts from artificial mixtures of cord and adult blood (1:50) and from 16 ml of peripheral blood from pregnant women at a mean gestational age of 14+2 weeks. The yield of erythroblasts was calculated and compared using Wilcoxon's matched-pairs signed-rank test. In the artificial mixture most erythroblasts were retrieved using the heaviest density gradient (specific density of 1119) followed by antibody-labelled magnetic cell sorting (MACS). With anti-GPA the yield of erythroblasts from the artificial mixture was highest (9362.5 erythroblasts) compared with anti-CD36 (5164.3), anti-i (3455.2), anti-CD71 (3055.8) and HAE9 (2364.2). The difference between anti-GPA and anti-CD71, HAE9 and anti-i was significant (p=0.0277). The enrichment of erythroblasts from peripheral blood of pregnant women showed similar results. The yield of erythroblasts using anti-GPA was the highest. These results enable us to simplify our enrichment protocols to a single density gradient of 1119 specific density followed by MACS, with anti-GPA.

Antibodies, Monoclonal↗
PubMed1999

[Not Available].

The Leipzig anatomist Werner Spalteholz (1861-1940) started studies on the anastomoses between the coronary arteries of the heart in 1906. He confirmed the thesis, that "the transparency of tissues depends first of all on the refraction index of permeating liquid", and began to produce transparent organ specimens. The 1st International Hygiene Exposition 1911 in Dresden showed 370 speciments produced by Spalteholz and was a great success. Later Spalteholz worked in the scientific Council of the Hygiene Museum. The exhibition"Transparent man", shown in 1925, testified to the great extent of knowledge that was passed on to the population with the help of these speciments. The "transparent human being" was not only an attractive and instructive collection for exhibition and educational purposes, but also a didactic concept. Fritz Tschackert (1887-1958) created the "transparent man' for the 2nd International Hygiene Exposition in Dresden in 1930. Today the "transparent woman" is the highlight of the museum's permanent exhibition.

Anatomy↗
PubMed1998

[Prenatal diagnosis with fetal cells in maternal blood: report of experiences in Basal].

Currently prenatal diagnosis relies on invasive procedures such as chorion villus sampling (CVS) or amniocentesis (AC). Many parents are reluctant to expose themselves and their child to the small, but significant risk posed by these procedures to mother and child. There is, hence, a great need for a risk-free non-invasive alternative. To achieve this goal most research has been focussed on enriching fetal cells from the blood of pregnant women. The erythroblast has emerged as the target cell of choice, since it is abundant in the early fetus, rare in normal adult blood, and since it has a very short half life, there is no risk of obtaining cells from previous pregnancies. Most enrichment protocols rely either on magnetic- or fluorescent activated cell sorting (MACS and FACS) using fetal specific antibodies. These enriched cells can be examined by FISH (fluorescence in-situ hybridisation) for the presence of the most common fetal chromosomal aneuploidies (13, 18, 21, X and Y) or by polymerase chain reaction (PCR) on singly manipulated cells for genetic disorders. The efficacy in detecting fetal aneuploidies is currently being evaluated in a phase II clinical trial under the auspices of the NIH-NICHD, the so-called NIFTY Trial, in which our group is a participant. By modifying our enrichment protocols we have recently been able to obtain detection sensitivities of almost 80%, thereby renewing our optimism that this methodology provides a solid basis for an effective non-invasive prenatal diagnostic test.

Adult↗
PubMed1998

Highly accurate analysis of heterozygous loci bysingle cell PCR.

Single cell PCR is a powerful method for determining the genetic properties of individual cells. In the instance of heterozygous loci, however, preferential amplification of one allele can lead to allele drop out (ADO) of the other allele. Fortunately ADO does not occur in all amplifications, and is usually random when it does occur, with both alleles being equally susceptible to drop out. Therefore pooling of results from multiple independently amplified cells should greatly improve the analysis of diallelic loci, and the misdiagnosis rate of diallelic loci should decrease exponentially with the number of cells analysed. We have shown that this is true and that multiplex PCR allows for the simultaneous identification of a cell in a mixture of cells using microsatellite loci known to be informative, and accurate genotyping at other loci. This approach has practical applications to non-invasive prenatal diagnosis where small numbers of fetal cells in the presence of maternal cells must be both identified and genotyped at loci involved in genetic disease.

Alleles↗
PubMed1998

Laparoscopic-assisted application of interstitial brachytherapy for locally advanced cervical carcinoma: results of a pilot study.

PURPOSE: To assess the efficacy of diagnostic laparoscopy at the time of interstitial brachytherapy in patients with FIGO Stages IIB-IVA cervical carcinoma, who were not candidates for conventional brachytherapy after completion of whole pelvic radiation. MATERIALS AND METHODS: Six patients with FIGO Stages IIB-IVA cervical carcinoma completed whole pelvic radiation (WPR) and were assessed for the placement of conventional intracavitary brachytherapy. Three patients (Stage IIB) received 50.40 Gy WPR and three (Stage IIIA-VA) received 61.20 Gy WPR. Because distorted vaginal anatomy precluded the placement of standard intracavitary brachytherapy equipment, interstitial therapy was selected. To minimize the risk of source misplacement, needles were placed with laparoscopic guidance. 192Iridium was utilized as a source of radiation. RESULTS: A total of 98 needles were placed under direct laparoscopic guidance. The median interstitial brachytherapy tumor dose was 20.00 Gy (range 19.00-41.20 Gy). Eleven perforations in the pelvic peritoneum and/or bladder were identified intraoperatively in 5 of the 6 patients, leading to immediate repositioning of needles. No acute or short-term morbidity related to the procedure was appreciated. CONCLUSION: Interstitial brachytherapy offers an alternative for intracavitary radiation therapy for selected patients, in whom adequate placement of intracavitary afterloading equipment is precluded by abnormal pelvic geometry. Historically, the placement of interstitial sources has been a procedure that was performed without visualization of the pelvic cavity. A major concern is direct injury to pelvic viscera and intestine. The use of diagnostic laparoscopy at the time of placement of interstitial brachytherapy may avert potential complications from misapplication of interstitial sources. Longer follow-up is required to substantiate these results.

Adult↗
PubMed1998

The tumor suppressor gene Smad4/Dpc4 is required for gastrulation and later for anterior development of the mouse embryo.

Mutations in the SMAD4/DPC4 tumor suppressor gene, a key signal transducer in most TGFbeta-related pathways, are involved in 50% of pancreatic cancers. Homozygous Smad4 mutant mice die before day 7.5 of embryogenesis. Mutant embryos have reduced size, fail to gastrulate or express a mesodermal marker, and show abnormal visceral endoderm development. Growth retardation of the Smad4-deficient embryos results from reduced cell proliferation rather than increased apoptosis. Aggregation of mutant Smad4 ES cells with wild-type tetraploid morulae rescues the gastrulation defect. These results indicate that Smad4 is initially required for the differentiation of the visceral endoderm and that the gastrulation defect in the epiblast is secondary and non-cell autonomous. Rescued embryos show severe anterior truncations, indicating a second important role for Smad4 in anterior patterning during embryogenesis.

Alleles↗
PubMed1998

Biliary glycoprotein (CD66a), a cell adhesion molecule of the immunoglobulin superfamily, on human lymphocytes: structure, expression and involvement in T cell activation.

The biliary glycoproteins (BGP or CD66a), a group of different splice variants of a single gene, are members of the carcinoembryonic antigen family and the immunoglobulin superfamily. Recently, we detected CD66a on IL-2 activated lymphocytes. In this study we characterized the structure and the expression pattern of BGP on human lymphocytes and investigated its role in T cell activation. Lymphocytes express 2 of the 13 known splice variants, i.e. BGPa and BGPb, which are glycosylated in a lymphocyte-specific manner. Both BGPa and BGPb have the long cytoplasmic tail, which contains two immunoreceptor tyrosine-based inhibitory motif (ITIM)-like motifs, but differ in their extracellular region containing 4 and 3 immunoglobulin-like domains, respectively. On PBL BGP is expressed in small amounts only on B cells and Th cells. Stimulation with IL-2 leads to a strong up-regulation of BGP by these cells, and induces de novo BGP expression on gammabeta T cells, CD8+ and CD56+ cells, but not on CD16+ lymphocytes. This up-regulation of BGP seems to be part of the physiological process of T cell activation, since stimulation with anti-CD3 mAb is sufficient to induce BGP up-regulation. Based on the presence of the two ITIM-like motifs, one may expect that BGP inhibits T cell activation, but surprisingly, engagement of BGP enhances the proliferation of anti-CD3-stimulated T cells.

Antigens, CD↗
PubMed1998

Disturbed feto-maternal cell traffic in preeclampsia.

OBJECTIVE: To investigate whether the transfer of fetal blood cells to the maternal circulation is perturbed in pregnancies affected by preeclampsia. METHODS: Fetal erythroblasts were isolated from eight women with clinically diagnosed preeclampsia (blood pressure values of at least 140/90 mmHg and associated proteinuria) and an equal number of matched corresponding controls. All patients in both groups were pregnant with male singleton fetuses. The presence of fetal cells was evaluated histologically and by fluorescence in situ hybridization for X and Y chromosomes. RESULTS: The number of fetal cells was higher in preeclamptic patients than in controls, with respect to both nucleated red blood cells (median per 200 cells 38 versus 7; P < .001) and the proportion of these cells that were of fetal origin (median per 2000 cells 9 versus 2; P = .001). CONCLUSION: These results suggest that the trafficking of fetal cells into the maternal periphery is disturbed in patients with preeclampsia. Because it is unlikely that such an altered flow of cells is restricted to the erythroblasts examined in this study, these findings also may lead to interesting new concepts regarding the development of preeclampsia and possibly the associated syndrome of hemolysis, elevated liver enzymes, and low platelets.

Erythroblasts↗
PubMed1998

Allele drop-out can occur in alleles differing by a single nucleotide and is not alleviated by preamplification or minor template increments.

The ability to analyze the genetic material of single cells by the PCR opens up new prospects for diagnostics. Because only two copies of the genetic template are available for amplification, a problem that frequently arises when examining heterozygous loci in single cells is allele drop-out (ADO). ADO results from the preferential amplification of one of a pair of heterozygous alleles, in which the other allele is totally under-represented. In examining single cells from carriers heterozygous for beta-thalassemia mutations, we have found ADO to occur in alleles differing by a single nucleotide, where either the normal or the mutant genotype was absent. We have found that ADO is not overcome by either increasing the amount of DNA template to 20 pg or by primer extension preamplification (PEP), but rather that the best diagnostic accuracy is obtained by examining multiple single cells and basing a diagnosis on the combined results of such an examination.

Alleles↗