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Biomedical subjects

S Hahn

Publications and source records attributed to S Hahn.

At least 37 records · Page 2Linked to original sources
PubMed2001

Prenatal diagnosis using fetal cells and free fetal DNA in maternal blood.

The presence of fetal cells and free fetal DNA in maternal blood offers an exciting opportunity for the development of safe noninvasive forms of prenatal diagnosis. Research in this field has, however, also indicated that their levels in the maternal circulation are increased in certain pregnancy-related disorders, such as preeclampsia. Their closer examination may shed new light on the underlying etiology of this enigmatic disorder.

Cell Culture Techniques↗
PubMed2001

Severely reduced presence of tissue macrophages in the basal plate of pre-eclamptic placentae.

Pre-eclampsia is a disorder of unknown aetiology peculiar to human pregnancy. A well-described pathological feature being shallow trophoblast invasion into the spiral arteries during placenta development. Epidemiological studies have revealed an increased risk in pregnancies of primipaternity, and an association with the maternal-fetal HLA-DR relationship, both suggesting the involvement of an immunological component. We were therefore interested in the distribution of HLA-DR expressing myeloid cells in the decidua of healthy and pre-eclamptic placentae. We have studied the monocytes in maternal and fetal peripheral blood as well as in the placenta and identified the cluster of differentiation (CD) 14(+)myeloid cells in the basal plate as mannose receptor (ManR) positive tissue macrophages. In a comparison between peripheral blood monocytes from healthy pregnant and pre-eclamptic women we found no significant difference in the subpopulation size of CD14(+)/CD16(+)monocytes. The number and location of macrophages in the placental villi was similar. However, while the basal plate of the normal decidua contained numerous CD14(+), HLA-DR(bright), ManR(+)tissue macrophages, this compartment was virtually void of these phagocytic cells in the pre-eclamptic placenta. This novel finding suggests that in pre-eclampsia not only the migration of endovascular cytotrophoblasts is disturbed, but that also maternal macrophage migration is affected.

Adult↗
PubMed2001

Elevation in erythroblast count in maternal blood before the onset of preeclampsia.

OBJECTIVE: We recently showed that both maternal and fetal erythroblast counts are elevated in the peripheral blood of pregnant women with preeclampsia. The purpose of this study was to examine whether this elevation actually occurs before the clinical onset of the disorder. STUDY DESIGN: Erythroblasts were enriched and enumerated in 97 maternal blood samples obtained in the second trimester, and results were subsequently correlated with pregnancy outcomes. RESULTS: Significantly higher quantities of erythroblasts (mean, 6041.7 vs 928.9; P =.008) were detected in blood samples obtained from women who later acquired preeclampsia (n = 15) than in blood samples from the control cohort (n = 72). Intrauterine growth restriction (n = 10) was not accompanied by a similar rise in erythroblast count. CONCLUSION: Because a large proportion of the erythroblasts in maternal blood are fetal, our data suggest that fetal-maternal cell traffic is affected early in pregnancies that are later complicated by preeclampsia but not in those affected only by intrauterine growth restriction.

Erythroblasts↗
PubMed2001

Elevation of both maternal and fetal extracellular circulating deoxyribonucleic acid concentrations in the plasma of pregnant women with preeclampsia.

OBJECTIVE: Elevated amounts of circulating fetal deoxyribonucleic acid in maternal plasma have recently been detected in pregnancies complicated by preeclampsia. We attempted to confirm this finding and simultaneously examined the quantity of maternal circulating deoxyribonucleic acid. STUDY DESIGN: Circulating deoxyribonucleic acid was measured by realtime quantitative polymerase chain reaction in plasma samples obtained from 44 women with preeclampsia and a matched cohort of 53 normotensive pregnant women. RESULTS: We confirmed that circulating fetal deoxyribonucleic acid levels were significantly elevated in pregnancies complicated by preeclampsia (3194.6 vs 332.8 copies/mL; P < .001). We also showed for the first time that circulating maternal deoxyribonucleic acid levels are also elevated (219,023.9 vs 20,235.8 copies/mL; P < .001). The increases in these deoxyribonucleic acid levels corresponded to the severity of the disorder, and values were correlated with each other in pregnancies complicated by preeclampsia (r = 0.556; P < .001) but not normotensive pregnancies (r = 0.046; P = .747). CONCLUSION: The releases of both free fetal and maternal deoxyribonucleic acid were found to be affected in preeclampsia.

Birth Weight↗
PubMed2001

Effect of preeclampsia on umbilical cord blood hematopoietic progenitor-stem cells.

OBJECTIVE: The aim of the present study was to determine the influence of preeclampsia on cord blood hematopoietic progenitor-stem cells obtained at delivery because cord blood is increasingly used clinically for stem cell retrieval as an alternative to bone marrow. STUDY DESIGN: Umbilical cord blood was collected from patients fulfilling the criteria for preeclampsia and from gestational age- and birth weight-matched control subjects at delivery (patient/control subjects ratio, 1:2). Cord blood volume and nucleated cell content were measured, and the number of hematopoietic progenitor-stem cells was determined by means of fluorescence-activated cell sorting with the CD34(+) epitope and by means of colony assays with different hematopoietic growth factors. In addition, the expression of adhesion molecules by CD34(+) progenitor-stem cells was examined. RESULTS: In pregnancies affected by preeclampsia, volume and nucleated cell and total CD34(+) cell contents in the collected cord blood were significantly smaller compared with those of control subjects. Furthermore, there was a trend toward a smaller relative number of CD34(+) cells and colony-forming units per nucleated cell in cord blood samples from preeclamptic patients. No difference in the expression of the cell-adhesion molecules leukocyte function-associated antigen 1, very late activation antigen 4, and L-selectin by CD34(+) cells could be found. CONCLUSION: This study shows that preeclampsia affects umbilical cord blood volume and nucleated cell and progenitor-stem cell numbers obtained at birth.

Adult↗
PubMed2001

Circulatory fetal and maternal DNA in pregnancies at risk and those affected by preeclampsia.

Elevations in fetal cell traffic as well as increased release of cell-free fetal DNA into the maternal periphery have previously been shown to occur in pregnancies affected by preeclampsia. Our own investigations have shown that manifestation of preeclampsia is associated with an increased accumulation of circulatory fetal DNA as well as cell-free maternal DNA in maternal plasma. We further established that the increments in these two molecular genetic analytes corresponded to the severity of the disease and to each other. This latter phenomenon was evident in preeclamptic pregnancies, but not in normal ones. As we had recently performed a prospective study to investigate fetal cell traffic prior to onset of preeclamptic symptoms, we examined the levels of cell-free fetal and maternal DNA in these samples. This analysis indicated that circulatory fetal DNA concentrations were significantly elevated prior to onset of the disease symptoms. No similar feature was observed for cell-free maternal DNA levels.

DNA↗
PubMed2001

Both maternal and fetal cell-free DNA in plasma fluctuate.

Elevations in the concentration of cell-free fetal DNA in maternal plasma have recently been determined in various pregnancy-related disorders, including preeclampsia, preterm labor, and polyhydramnios. In addition, almost 2-fold increments in cell-free fetal DNA levels have been recorded in pregnancies with certain aneuploid fetuses, in particular trisomy 21. These findings have led to the speculation that quantitative assessment of circulatory fetal DNA may be useful in the noninvasive prenatal diagnosis of certain fetal genetic constellations or pregnancy-related disorders. A premise for any quantitative analysis is that the quantity of the analyte being assayed does not vary greatly over time. As this aspect has not been examined for circulatory DNA levels, we examined these in normal healthy individuals as well as in pregnant women. Our data indicate that severalfold alterations in circulatory DNA amounts do occur over short periods of time. Of particular note is that we observed almost 2-fold variations in free fetal DNA levels over a period of 3 days, which are in a similar range to the elevations noted in aneuploid pregnancies. Our results, therefore, imply that caution should be used when using small increments in circulatory fetal DNA concentrations for potential diagnostic applications.

Cell-Free System↗
PubMed2001

Rec (formerly Corf) function requires interaction with a complex, folded RNA structure within its responsive element rather than binding to a discrete specific binding site.

It was recently reported that the human endogenous retrovirus HTDV/HERV-K encodes the regulatory protein Rec (formerly designated Corf), which is functionally equivalent to the nuclear export adapter proteins Rev of human immunodeficiency virus and Rex of human T-cell leukemia virus. We have demonstrated that the Rec protein interacts with a characteristic 429-nucleotide RNA element, the Rec-responsive element (RcRE), present in the 3' long terminal repeat of HTDV/HERV-K transcripts. In analogy to the Rev and Rex proteins, which have distinct RNA binding sites in their responsive elements, we have proposed that Rec may also have a defined binding site in the RcRE. In this report, we demonstrate that not every HTDV/HERV-K copy present in the human genome contains an active RcRE, and we characterize mutations that abrogate Rec function. In addition, we demonstrate that Rec function requires binding to a complex, folded RNA structure rather than binding to a discrete specific binding site, in contrast to Rev and Rex and their homologous responsive elements. We define four stem-loop structures in the RcRE that are essential for Rec function. Finally, we demonstrate that both Rev and Rex can mediate nuclear export through the RcRE but that their binding sites are different from each other and from that of Rec.

Base Sequence↗
PubMed2001

Influence of single and multiple onset distractors on visual search for singleton targets.

In three experiments, we examined attentional and oculomotor capture by single and multiple abrupt onsets in a singleton search paradigm. Subjects were instructed to move their eyes as quickly as possible to a color singleton target and to identify a small letter located inside of it. In Experiment 1, task-irrelevant sudden onsets appeared simultaneously on half the trials with the presentation of the color singleton target. Response times (RTs) were longer when onsets appeared in the display regardless of the number of onsets. Eye-scan strategies were also disrupted by the appearance of the onset distractors, although the proportion of trials on which the eyes were directed to the onsets was the same regardless of the number of onsets. In Experiment 2, we manipulated the time of presentation of two task-irrelevant onsets in order to further examine whether multiple onsets would be attended and fixated prior to attending a color singleton target. Again, subjects made a saccade to a task-irrelevant onset on a substantial proportion of trials prior to fixating the target. However, saccades to the second onset were rare. Experiment 3 served as a replication of Experiment 1 but without the requirement for subjects to move their eyes to detect and identify the singleton target. The RT results were consistent with those in Experiment 1; dual onsets had no larger an effect on response speed than single onset distractors. These data are discussed in terms of the interaction between top-down and bottom-up control of attention and the eyes.

Adult↗
PubMed2001

Photodynamic therapy in the canine prostate using motexafin lutetium.

Our purpose was to determine the feasibility of comprehensive treatment of the canine prostate with photodynamic therapy (PDT) using motexafin lutetium (Lu-Tex) and to evaluate the toxicity and tissue effects associated with this treatment. Twenty-five adult male beagles with normal prostate glands were given an i.v. injection of the second-generation photosensitizer Lu-Tex (2-6 mg/kg). An additional two dogs were used as controls and did not receive any photosensitizing drug. All 27 dogs underwent laparotomy to expose the prostate. Three hours postinjection, a total dose of 75-150 J/cm of 732 nm laser light was delivered interstitially and/or transurethrally to the prostate via cylindrical diffusing fibers. Dogs were euthanized between 2 days and 3 months after PDT. All subjects were monitored for clinical evidence of toxicity. Specimens were examined macroscopically and microscopically to characterize the tissue reaction and assess extent of tissue effect as a result of treatment. Interstitial and/or transurethral PDT were successfully delivered in all dogs with no perioperative complications. No clinical evidence of acute urinary obstruction or rectal bleeding was noted. At all dose levels, macroscopic and microscopic evaluation revealed a prostatic tissue reaction characterized initially (within 48 h) by inflammation and necrosis followed by fibrosis and glandular epithelial atrophy. Comprehensive treatment of the entire prostate could be achieved using the interstitial alone approach or combined transurethral and interstitial approach. The transurethral alone approach did not result in complete coverage of the prostate. Dogs receiving transurethral or combined interstitial and transurethral treatment developed erythema and urethral epithelial disruption at all dose levels. Those receiving combined treatment at the highest dose level (Lu-Tex 6 mg/kg, 150 J/cm light) developed urethral fistulae and peritonitis. Dogs treated with the interstitial alone approach were found to have the least amount of urethral damage. Comprehensive treatment of the canine prostate with Lu-Tex PDT is feasible using an interstitial alone or combined interstitial and transurethral approach. The interstitial alone technique results in the least amount of toxicity. The prostatic tissue reaction to treatment is characterized by initial inflammation and necrosis followed by fibrosis and glandular epithelial atrophy.

Animals↗
PubMed2001

Cell-free DNA in urine: a marker for kidney graft rejection, but not for prenatal diagnosis?

Intrigued by the rapid clearance of free fetal DNA from the maternal circulation, we have investigated whether this fetal genetic material could be cleared via the kidney. For this purpose, we examined for the presence of Y chromosome-specific DNA sequences in urine samples obtained from 8 women pregnant with male fetuses. No male-specific sequences could be detected, despite the use of a very sensitive nested PCR assay nor a highly reproducible real-time PCR assay. We did, however, detect maternal DNA sequences. To determine if this cell-free DNA was derived from the kidney or another source, we next examined urine from female kidney transplant patients who had received male kidneys. Y chromosome-specific sequences were indeed detectable by both nested and real-time PCR in these samples, thereby confirming a recent report describing urinary DNA microchimerism. Quantitative analysis of serially obtained samples furthermore suggests that transplant-derived sequences are elevated during periods of graft rejection. These results imply that the measurement of graft-derived urinary DNA may serve as a new marker for kidney graft tolerance.

Biomarkers↗
PubMed2001

Enrichment of fetal cells and free fetal DNA from maternal blood: An insight into the Basel experience.

Our laboratory is a leading pioneer in the enrichment of fetal cells from maternal blood with the aim of developing a non-invasive risk free form of prenatal diagnosis. By using the then novel Magnetic Activated Cell Sorting (MACS) we were among the first to detect fetal aneuploidies. The efficacy of this methodology is currently being explored in the large scale so-called, NIFTY study conducted under the auspices of the NIH, in which our group is participating. We have extended the scope of these investigations by analysing single micromanipulated erythroblasts by single cell PCR. These studies have shown that fetal genetic loci such as sex and rhesus D status can be identified with great reliability non-invasively. This analysis also irrevocably demonstrated that a large proportion of the erythroblasts in maternal circulation are of fetal origin. This aspect has now been incorporated into the next phase of the NIH study. Recent research from our laboratory has indicated that the traffic of fetal cells into the maternal periphery is significantly enhanced in preeclamptic pregnancies. We have now investigated whether this perturbation takes place early in pregnancy prior to the onset of disease symptoms, by performing a prospective study in which close to 100 pregnant women were recruited at around 20 weeks of gestation. By correlating the number of enriched erythroblasts with subsequent pregnancy outcome, we were able to show that the traffic of fetal cells was indeed significantly elevated in those pregnancies which developed preeclampsia, but not those which were affected by fetal growth retardation. We have also explored the new finding of free fetal DNA in maternal plasma. By the use of sensitive quantitative PCR we were recently able to show that the levels of this circulatory fetal DNA are elevated in pregnancies with certain aneuploidies, thereby opening the prospect of a new additional screening tool.

DNA↗
PubMed2000

Assessing the potential for bias in meta-analysis due to selective reporting of subgroup analyses within studies.

Subgroup analysis is frequently used to investigate heterogeneity in meta-analysis. Subgroup data are not always available, and researchers should record what data were available for each trial. If data were not available, and it is known that the subgroup data were collected, the potential for selective reporting should be considered. Bias due to selective publishing of reports is widely recognized in meta-analysis. In contrast, selective reporting within studies is little discussed but potentially important. We explored this problem by evaluating the effect of potential bias in subgroup analysis due to within-study selective reporting with an existing meta-analysis. The review addressed malaria chemoprophylaxis in pregnancy. The conclusion in the original review, that benefit is limited to primigravidae, was based on subgroup analysis using the three trials out of five which reported on subgroups. We developed a method of sensitivity analysis that imputes data for the missing subgroups to assess the robustness of the results and the conclusions drawn. In this particular example, our analysis indicates that the estimate of effect reported in the review is most likely to overestimate the true effect and the conclusion that benefit is limited to primigravidae may be false.

Bias↗