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Biomedical subjects

G Christ

Publications and source records attributed to G Christ.

At least 55 records · Page 3Linked to original sources
PubMed1995

Partial papillary muscle rupture complicating acute myocardial infarction. diagnosis by multiplane transoesophageal echocardiography.

Papillary muscle rupture is a rare but generally fatal mechanical complication of acute myocardial infarction. In contrast to complete papillary muscle rupture, echocardiographic recognition of partial papillary muscle rupture has rarely been reported and seems to be more challenging. We describe a patient with partial papillary muscle rupture that could only be diagnosed by multiplane transoesophageal echocardiography, whereas transthoracic echocardiography and single plane transesophageal echocardiography showed only posterior mitral leaflet prolapse.

Echocardiography, Transesophageal↗
PubMed1995

White polystyrene as a substitute for water in high energy photon dosimetry.

White polystyrene (C8H8 with 2 wt. % to TiO2) has been compared to water using photon beams with nominal accelerating potential of 4 MV, 6 MV, 15 MV and 25 MV. The absolute reading and hence the measured absorbed dose is found to be up to 3% lower in white polystyrene which can be taken into account by using a correction factor. From these data differences in relative measurements (TMR or percentage depth dose) can be calculated showing differences of less than 0.7% normalized to maximum dose. Since the correction factor shows a dependence on photon energy and field size the use of a common scaling factor is not possible. The effect on photon dosimetry is discussed.

Biophysical Phenomena↗
PubMed1995

Social work research in hospital settings: strategies for implementation.

In recent years there has been a growing interest among hospital Social Work departments, especially those associated with major medical research institutions and universities in initiating research which could inform clinical practice. Yet little has been written that describes the process required to develop social work research within health care agencies and institutions. In this paper we discuss some of the challenges social work departments will confront in developing a research program, and alternative solutions that might be considered in different institutional settings. We identify ways to: (1) select an effective model and develop institutional support for social work research; (2) prepare clinical staff for interaction with the research effort; (3) consider relevant factors in selecting topics for study; (4) identify personnel required for specific research functions; and (5) secure outside funding.

Humans↗
PubMed1995

["Teachers' Training Course"--evaluation of continuing studies for faculty in the field of ethics in medicine].

The need for continuing education in the field of ethics in health professions is increasing. A project group of the Academy of Ethics in Medicine, Germany, developed and tested a model for a "Teachers' Training Course" to provide continuing education in this field. Evaluation data of the first two seminars are presented. These data demonstrate that the course matches the demands which participants have requested from such seminars.

Education, Medical, Continuing↗
PubMed1995

[Bicentric stereotaxic convergent-beam irradiation].

PURPOSE: Circular collimated X-ray beams rotated in various non-coplanar planes as commonly used in stereotactic linac-based radiotherapy are generating spherical dose distributions with typically steep dose gradients. In case of irregular, especially elongated lesions, this technique fails to conform the shape of the corresponding planning target volume, and a collimator aperture has to be selected which allows for an acceptable dose distribution only on the expense of an excess dose to a larger amount of normal tissue. Therefore we have investigated a bicentric irradiation technique with sequentially treating an elongated target volume over two separated isocenters. METHODS: For the computer simulation studies we used the planning system of the stereotactic unit SRS-200 by Philips. Selected combinations of different collimator aperture were examined systematically by varying the distance between the two isocenters. Dose distributions for a specially developed head-phantom were calculated and analysed. RESULTS: Optimization tables were generated taking into account the geometric quality criteria as well as the corresponding dose maxima. For a given size of the target volume, the appropriate parameters for the bicentric radiation treatment can be chosen. The calculated dose distributions turned out to be independent of the positioning of the two isocenters within the phantom. CONCLUSION: The optimization tables serve to select a set of starting values for the interactive planning process of an elongated target volume resulting in a significant decrease of the overall time for treatment planning of irregular shaped lesions.

Film Dosimetry↗
PubMed1993

Type 1 plasminogen activator inhibitor synthesis of endothelial cells is downregulated by smooth muscle cells.

Plasminogen activator inhibitor type 1 (PAI-1), the physiologic inhibitor of both tissue-type plasminogen activator (tPA) and urokinase-type plasminogen activator (uPA), is a major biosynthetic product of endothelial cells in vitro; endothelial cells in vivo, in contrast, do not appear to produce significant amounts of PAI-1 as made evident by in situ-hybridization studies in normal mice. This suggests that the high rate of PAI-1 synthesis of endothelial cells in vitro might be a result of the culture conditions. When human umbilical vein endothelial cells (HUVEC) were grown on human amniotic membranes, resembling the natural growth support instead of coated plastic, their morphology was changed from the cobblestone-like appearance on plastic to an in vivo like flagstone pattern. However, this morphological change had no significant effect on the synthesis and secretion of PAI-1. When smooth muscle cell (SMC) conditioned media (CM) were added to HUVEC cultures, PAI-1 antigen secretion of HUVEC was reduced by 40% to 60% as measured by enzyme-linked immunosorbent assay (ELISA). Immunoprecipitation experiments using 36S-methionine metabolically labeled HUVEC and Northern blot analysis of HUVEC PAI-1 mRNA indicate that this reduction was attributable to decreased PAI-1 synthesis and reduced steady-state levels of both the 3.2 kb and 2.2 kb form of PAI-1 mRNA. This effect was dose-dependent and observed under serum-containing as well as serum-free conditions, in the absence or presence of endothelial cell growth supplement (ECGS, 0 to 100 micrograms/mL) and attributable to a nondialyzable factor. Our data suggest that the high level of PAI-1 biosynthesis of endothelial cells in vitro may be attributable to the lack of a soluble factor produced by SMC, which controls and suppresses PAI-1 biosynthesis of endothelial cells in vivo.

Cells, Cultured↗
PubMed1993

Gap junctions between human corpus cavernosum smooth muscle cells: gating properties and unitary conductance.

We previously showed that corpus cavernosum smooth muscle cells are connected via gap junctions in situ and in culture and that a major protein component of these gap junctions is connexin43. To characterize the physiological properties of the gap junctions between corpus cavernosum smooth muscle cells, we now demonstrate that the cells are dye and electrically coupled and describe some of the gating properties of these gap junctional channels at macroscopic and single-channel levels. Junctional conductance (gj) between corporal smooth muscle cells was moderately voltage sensitive; was reduced rapidly, reversibly, and completely by halothane; and was increased by treatment with a tumor-promoting phorbol ester [12-O-tetradecanoylphorbol-13-acetate (TPA)] and decreased by isoproterenol. Histograms of unitary junctional currents revealed multiple conductance peaks with events of approximately 90 pS being the most abundant. TPA and phenylephrine produced large increases in relative frequencies of the smaller events, whereas isoproterenol and 8-bromoadenosine 3',5'-cyclic monophosphate (8-BrcAMP) slightly increased the relative frequencies of the larger events. None of the tested drugs substantially affected the steady-state voltage dependence of gj. These second messenger systems also affected expression of connexin43 by corpus cavernosum smooth muscle cells, as judged by immunoblots. At 6 h of treatment, both TPA- and 8-BrcAMP-treated cultures showed markedly elevated levels of connexin43, whereas at 24 h, the level of connexin43 in TPA-treated cultures had returned to control levels. Together, these data indicate that second messenger molecules involved in penile erection produce changes in gap junction expression and function; it is plausible that these changes could be physiologically relevant in altering and propagating changes in vasomotor tone.

Cell Communication↗
PubMed1993

[Dosage specification at the ICRU reference point: the consequences for clinical practice. International Commission on Radiation Units and Measurements].

In the Department of Radiotherapy, University of Tübingen, dose specification is performed according to the new ICRU recommendations since June, 1991. The purpose was to prescribe, record and report photon beam therapy in a consistent way applicable to most clinical situations and to provide uniform criteria for a comparison of treatment results from different radiotherapy centers. For "level 2" plans (including CT planning), the concept of dose specification has been changed to the "ICRU reference point" instead of to form the isodose encompassing the target volume as we did previously. A total of 24 representative treatment plans have been analyzed to assess the consequences of this change on dose prescription, treatment technique, and the size of the irradiated volume. Our results revealed that the prescription of single and total doses have to be individually adjusted according to the specific treatment plans. ICRU recommendations on dose homogeneity may significantly affect treatment technique and field sizes. Small deviations in dose prescription may be of particular influence on late responding normal tissues ("double trouble" due to simultaneous adjustment of single and total doses). Detailed comparisons of individual treatment plans with respect to physical, biological, and clinical data are obviously necessary in order to make sure that the outcome of a radiation treatment is not deviating too much from the clinical experience based on the former dose specification concept.

Germany↗
PubMed1992

Polar secretion of endothelin-1 by cultured endothelial cells.

The aim of this study was to determine the permeability of endothelial monolayers for endothelin-1 and a possible directionality of the endothelin-1 secretion process. Human umbilical vein endothelial cells were cultured on acellular amniotic membranes, dividing the tissue culture wells into an apical (luminal) and a basolateral (abluminal) compartment. Whereas in the absence of endothelial monolayers 44.9 +/- 2.3 and 43.5 +/- 2.0% of the unilaterally added endothelin-1 permeated from the apical to the basolateral side and from the basolateral to the apical side, respectively, only 6.5 +/- 0.6 and 6.6 +/- 0.4% diffused in the presence of endothelial cells. Analyzing endothelin-1 secretion, approximately 80% of the total amount of synthesized endothelin-1 was found in the basolateral compartment; thrombin (10 units/ml) stimulated the production of endothelin-1 approximately 2-fold, but did not change the relative distribution of endothelin-1 between the apical and basolateral compartments. In the presence of dexamethasone (10(-7) M), a decrease in the level of endothelin-1 was found in the apical compartment, whereas the total amount of endothelin-1 produced was not affected. Dexamethasone did not influence the permeability of human umbilical vein endothelial cell monolayers for endothelin-1. These results strongly support the hypothesis that endothelin-1 is a local paracrine regulator of vasotone.

Amnion↗
PubMed1992

Reducing the prevalence of unmet needs for concrete services of patients with cancer. Evaluation of a computerized telephone outreach system.

A two-stage study was undertaken of outpatients with advanced cancer who were receiving chemotherapy. In Stage 1 of the study, their needs for practical services and the barriers to those needs being met were assessed. Based on these results, an intervention was designed to reduce the prevalence of patients' unmet needs. The intervention was an automated telephone needs assessment coupled with social worker follow-up. The efficacy of this intervention was evaluated using an independent sample in Stage 2 in an experimental trial. Patients in the experimental group (n = 109), who received three automated surveys, reported fewer unmet needs in a subsequent comprehensive assessment than those in the control group (n = 130). The computerized telephone outreach system proved to be a cost-effective and reliable method for the early identification of unmet patient needs soon after they emerge and efficient deployment of limited professional staff.

Aged↗
PubMed1992

Psychosocial adjustment of children with a terminally ill parent.

Although a substantial number of children experience serious parental illness and death, the adjustment problems attendant to the stress of having a fatally ill parent have not been examined systematically. This paper compares the psychosocial adjustment of 62 school-aged children with a terminally ill parent (study sample) with that of children in a community sample, using several standard rating scales. Study children had significantly higher levels of self-reported depression (Children's Depression Inventory) and anxiety (State-Trait Anxiety Inventory) and lower self-esteem (Self-Esteem Inventory). Parents also reported study children's significantly higher behavior problems and lower social competence (Child Behavior Checklist). Increased professional attention to this vulnerable population is encouraged.

Adaptation, Psychological↗
PubMed1991

Fibrinolytic parameters in spermatozoas and seminal plasma.

Urokinase-type (u-PA) and tissue-type plasminogen activator antigen (t-PA) as well as plasminogen activator-inhibitor activity were determined in seminal plasma and lysates of the respective spermatozoas in 67 ejaculate of males in infertile marriage without genito urinary pathology. U-PA was determined by a competition RIA, t-PA by an ELISA and PAI by a spectrophotometric assay. 15 patients showed normozoospermia, 11 azoospermia and 41 oligoasthenoteratozoospermia (OAT-syndrome). In lysates of spermatozoas, significantly higher levels of both plasminogenactivators and PAI were found in patients with OAT syndrome as compared to those exhibiting normozoospermia. Whereas PAI was absent in the seminal plasma of normozoospermic ejaculate, patients with azoospermia (180 +/- 13 mU/ml.) and OAT-syndrome (60 +/- 5 mU/ml.) showed high PAI levels. The similarly high values of t-PA (190.8-227.8 ng./ml.) and u-PA (19.4-32 ng./ml.) in the same compartment confirm their predominantly prostatic origin and seem to have no influence on the quality of the ejaculate.

Enzyme-Linked Immunosorbent Assay↗
PubMed1991

Hyperthermia stimulates plasminogen activator inhibitor type 1 expression in human umbilical vein endothelial cells in vitro.

The effect of exposure to hyperthermia on the fibrinolytic potential of human umbilical vein endothelial cells (HUVEC) in culture was studied. HUVEC responded to exposure to 42 degrees C with a time-dependent increase in plasminogen activator inhibitor type 1 (PAI-1) activity and antigen accompanied by a four- to fivefold increase in PAI-1 specific m-RNA and a decrease in tissue-type plasminogen activator (t-PA) antigen. The effect of 8 hours exposure to hyperthermia on PAI-1 activity and antigen could not be reversed by reexposure of the cells to 37 degrees C for 24 hours as evidenced by continuously increased amounts of PAI-1 released into the conditioned media. t-PA release, however, decreased during the 24-hour period at 37 degrees C after exposure to hyperthermia. No difference in PAI-1 antigen present in the extracellular matrix of heat treated HUVEC as compared to HUVEC kept at 37 degrees C could be found. Our data supports the idea that hyperthermia is one stress factor that influences the fibrinolytic potential of endothelial cells.

Blotting, Northern↗
PubMed1991

[Computer-assisted irradiation planning in whole-body irradiation].

Using a commercial system designed for external beam radiation treatment planning a simple method is described for calculating dose distribution in total body irradiation. Scaling factors are applied to keep the range of all distances within the limits preset for the routine use of the planning system. As an example the validity of the method is tested in the lung region which due to dose inhomogeneities is especially critical to an accurate dose determination. Comparing dose calculation and phantom measurements reasonable agreement is obtained.

Humans↗
PubMed1990

Monitoring quality-of-life needs of cancer patients.

The advent of prepayment systems in hospitals has greatly shortened the length of stay of patients who are therefore increasingly treated and cared for in outpatient settings while living at home with family or other caretakers. This shift in the locus of treatment has created a critical need for the development of organized systems of follow-up that monitor a patient's needs while he or she is undergoing active treatment but living at home. Over time, failure to develop such systems of care is likely to result in major gaps in the continuity of care, a decrease in the quality of patients' lives while on treatment, tremendous stress on caretakers, and a general decrease in the quality of services provided to patients. This article reports on a study of one such system of monitoring i.e., a computer-automated telephone outreach system that would routinely assess the concrete needs of chemotherapy outpatients (e.g., transportation to the hospital and need for assistance with activities of daily living). This automated intervention was designed in response to previous findings that 62% of chemotherapy outpatients had at least one unmet need within the month before assessment and 39% had two or more; clinical knowledge that cancer patients' needs vary considerably over time as a consequence of both the disease and its treatment; and that, because of limited professional staff, patients' needs cannot be routinely assessed without the aid of automation, particularly as the proportion of cancer patients treated as outpatients continues to increase. These conditions suggested the need to develop a cost-efficient strategy for the universal assessment of patients' need on a periodic basis, so that emerging needs could be identified in a timely way. For the feasibility study, 97 chemotherapy outpatients were surveyed at least once over the telephone by a computer in a high quality digitally-stored voice asking 12 questions regarding the patients' concrete needs. The data suggested that our computer-automated telephone outreach system is reliable and valid and has the potential for relatively broad-based acceptance. In addition, the intervention frequently allows for timely social work assistance for identified needs. It further serves as a form of outreach that can compensate for patients' reluctance to identify themselves as needing help and for passivity that may be associated with depression or physical illness. This intervention appears to have the potential to be a time- and labor-efficient strategy for ongoing assessment of the changing needs of large numbers of cancer or other chronic diseased outpatients, insuring timely professional intervention as needs arise.

Activities of Daily Living↗
PubMed1990

TBI technique and clinical results of leukemia patients at the University of Tübingen.

Since 1976, more than 180 patients suffering from leukemia or aplastic anemia have been treated with BMT and TBI. The improvement of TBI-technique starting from single fraction irradiation without any shielding to different types of fractionation schemes with lung, head and neck shielding and an electron boost to the thoracal wall is shown. A more detailed description of the actual TBI-technique is given; this has been applied to 64 patients to-date. Some clinical results are summarised into four subgroups. Life table analyses are shown for single fraction irradiation as well as for fractionated irradiation separated for high and for low risk patient groups.

Anemia, Aplastic↗
PubMed1990

Plasminogen activators, plasminogen activator inhibitor, and fibronectin in human granulosa cells and follicular fluid related to oocyte maturation and intrafollicular gonadotropin levels.

We determined the relative distribution of tissue plasminogen activator (TPA) antigen, urokinase-type PA antigen, PA inhibitor activity, and fibronectin levels in lysates of human granulosa cells (GC) and the respective follicular fluid (FF) in relationship to oocyte-corona-cumulus complex morphology. In addition, FF gonadotropins were measured to investigate a possible relationship of gonadotropins to PA activity. A significant increase of TPA antigen in GC lysates of intermediate and mature oocyte-corona-cumulus complex was found when compared with immature oocyte-corona-cumulus complex. Urokinase-type plasminogen activator levels and PA inhibitor levels did not reveal any significant differences between the different groups. In FF the concentrations of PA and PA inhibitor were significantly lower than in GC lysates and showed no significant difference between the oocyte-corona-cumulus complex groups. The concentration of fibronectin was significantly elevated in GC lysates of mature follicles. The marked increase of TPA in human GC during oocyte maturation showed a positive correlation with the increase of FF follicle-stimulating hormone and beta-human chorionic gonadotropin in the group of mature oocyte-corona-cumulus complex. The data obtained suggest that in man TPA is the predominant PA involved in the process leading to follicular rupture.

Adult↗