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Biomedical subjects

B Hausmann

Publications and source records attributed to B Hausmann.

At least 19 recordsLinked to original sources
PubMed2004

Prognostic value of Doppler transmitral filling patterns in patients with chronic heart failure.

BACKGROUND: Chronic heart failure is a significant cause of cardiovascular morbidity and mortality. This study tested the hypothesis that restrictive filling pattern may provide useful prognostic data for identifying patients with chronic heart failure at high risk of all-cause cardiac death. METHODS: Ninety patients with chronic heart failure [70 men and 20 women, mean age (58.1 +/- 11.6) years] were investigated and followed for (18.8 +/- 7.9) months. During this period, 14 patients died of progressive pump failure, 12 patients underwent heart transplantation, 5 patients died suddenly, and 2 patients died of acute myocardial infarction. A new criterion, the restrictive filling index (RFI), was designed to subgroup patients into a restrictive and a nonrestrictive group. RESULTS: Patients with restrictive filling pattern had a more severe left ventricular dysfunction and a higher cardiac mortality. Analysis by the Kaplan-Meier method revealed that patients in the RFI > or = 1 and RFI < 1 groups had a cardiac events-free survival rate of 52% versus 94% at 1 year, and 27.5% versus 92% at 2 years, respectively. The multivariate Cox proportional hazard model selected RFI as the most powerful prognostic factor (chi(2) = 8.8017, P = 0.0030) for all-cause cardiac death. CONCLUSION: These results indicate that RFI is a simple, noninvasive, and specific clinical predictor for adult chronic heart failure patients who are at a high risk for all-cause cardiac death.

Chronic Disease↗
PubMed2001

A critical role for the T cell receptor alpha-chain connecting peptide domain in positive selection of CD1-independent NKT cells.

Natural killer T (NKT) cells are a subset of mature alpha beta TCR(+) cells that co-express NK lineage markers. Whereas most NKT cells express a canonical Valpha14/Vbeta8.2 TCR and are selected by CD1d, a minority of NKT cells express a diverse TCR repertoire and develop independently of CD1d. Little is known about the selection requirements of CD1d-independent NKT cells. We show here that NKT cells develop in RAG-deficient mice expressing an MHC class II-restricted transgenic TCR (Valpha2/Vbeta8.1) but only under conditions that lead to negative selection of conventional T cells. Moreover development of NKT cells in these mice is absolutely dependent upon an intact TCR alpha-chain connecting peptide domain, which is required for positive selection of conventional T cells via recruitment of the ERK signaling pathway. Collectively our data demonstrate that NKT cells can develop as a result of high avidity TCR/MHC class II interactions and suggest that common signaling pathways are involved in the positive selection of CD1d-independent NKT cells and conventional T cells.

Animals↗
PubMed2000

A motif in the alphabeta T-cell receptor controls positive selection by modulating ERK activity.

Positive selection allows thymocytes that recognize an individual's own major histocompatibility complex (self-MHC) molecules to survive and differentiate, whereas negative selection removes overtly self-reactive thymocytes. Although both forms of thymic selection are mediated by the alphabeta T-cell receptor (TCR) and require self-MHC recognition, an important question is whether they are controlled by distinct signalling cascades. We have shown that mutation of an essential motif within the TCR alpha-chain-connecting peptide domain (alpha-CPM) profoundly affects positive but not negative selection. Using transgenic mice expressing a mutant alpha-CPM TCR we examined the contribution of several mitogen-activated protein kinase (MAPK) cascades to thymic selection. Here we show that in thymocytes expressing a mutant alpha-CPM receptor, a positively selecting peptide failed to activate the extracellular signal-regulated kinase (ERK), although other MAPK cascades were induced normally. The defect in ERK activation was associated with impaired recruitment of the activated tyrosine kinases Lck and ZAP-70, phosphorylated forms of the TCR component CD3zeta and the adaptor protein LAT to detergent-insoluble glycolipid-enriched microdomains (DIGs). Therefore, an intact DIG-associated signalosome is essential for sustained ERK activation, which leads to positive selection.

Amino Acid Motifs↗
PubMed1998

Positive selection through a motif in the alphabeta T cell receptor.

The two lineages of T cells, alphabeta and gammadelta, differ in their developmental requirements: only alphabeta T cells require major histocompatibility complex recognition, a process known as positive selection. The alphabeta T cell receptor (TCR), but not its gammadelta counterpart, contains a motif within the alpha-chain connecting peptide domain (alpha-CPM) that has been conserved over the last 500 million years. In transgenic mice expressing an alphabeta TCR lacking the alpha-CPM, thymocytes were blocked in positive selection but could undergo negative selection. Thus, the alpha-CPM seems to participate in the generation of signals required for positive selection.

Amino Acid Sequence↗
PubMed1997

Dynamic on-line quantification of biventricular function with acoustic quantification (AQ). Validation, reproducibility and normal values of a new echocardiographic approach.

OBJECTIVES: Acoustic quantification (AQ), a recently developed ultrasonic integrated backscatter imaging system providing on-line measurements of ventricular cavity areas and their functional indexes, was validated in comparison to angiography and Doppler derived systolic dP/dt. Normal AQ-reference values were established. METHODS AND RESULTS: 1. In 45 patients undergoing heart catheterization, AQ derived areas in end-diastole (EDA), end-systole (ESA) and the resulting fractional area change (FAC) in apical 2- and 4-chamber view were compared to the corresponding biplane angiographic data. All correlations yielded significant values (p < 0.0001; EDA: r = 0.90, SEE = 2.6 cm2; ESA: r = 0.91, SEE = 2.2 cm2; FAC: r = 0.90, SEE = 4.1%). However, AQ-areas were underestimated by about 25%. 2. In 36 patients with mitral regurgitation AQ-FAC and AQ derived systolic dA/dt were compared to the Doppler derived systolic dP/dt, yielding significant correlations with r = 0.91 and r = 0.87; p < 0.0001. 3. In 50 healthy subjects, AQ derived EDA, ESA and FAC averaged 25.7 +/- 4.9, 14.7 +/- 3.3 cm2 and 43.2 +/- 4.8% for the left, and 17.1 +/- 3.8, 9.0 +/- 2.9 cm2 and 47.3 +/- 9.2% for the right ventricle. For EDA normalized peak filling (PFR) and ejection rates (PER) yielded 2.7 +/- 0.28 and -2.4 +/- 0.42 EDA/sec for the left and 3.4 +/- 0.74 and -2.9 +/- 0.62 EDA/sec for the right ventricle. The interobserver and day-to-day variability of AQ in healthy subjects and cardiac patients was low for EDA, ESA and FAC (< 12%) and higher for PFR and PER (< 20%). CONCLUSION: In comparison to angiography AQ reliably quantitates on-line left ventricular fractional area change, although AQ-areas are underestimated. AQ offers reproducible values of systolic and diastolic function and a new approach to cardiac patients.

Coronary Angiography↗
PubMed1997

Detection of diastolic dysfunction: acoustic quantification (AQ) in comparison to Doppler echocardiography.

OBJECTIVES: To evaluate the potential of acoustic quantification (AQ) in detection of diastolic dysfunction in comparison to Doppler analysis, we investigated, as a model of restrictive filling pattern, nonrejecting heart transplant recipients early postoperatively. BACKGROUND: AQ, an ultrasonic backscatter imaging system, enables instantaneous calculation of cavity areas and thus provides a new approach to diastolic function. METHODS: Of 27 pts who have undergone heart transplantation, echocardiography has been performed at the day of biopsy. During a time course of 8 weeks echocardiographic data have been analysed at 3 different time points (early, mid and late) in 16 nonrejecting pts. Indexes of the area-change waveform and its 1. derivative (dA/dt) obtained by AQ were opposed to usual Doppler indexes. RESULTS: In comparing data of the early and late time point of investigation, significant changes of early diastolic filling were detectable by AQ as well as by Doppler: End-diastolic areas have increased (p < 0.001), while peak filling rate (p < 0.0001), slope of area change during rapid filling (p < 0.001) and amount of relative area change during rapid filling (p < 0.001) have decreased. Complementary, Doppler derived pressure half-time (p < 0.0001) and isovolumic relaxation time (p < 0.0001) have increased while the peak early filling velocity (p < 0.0001) and its time velocity integral (p < 0.001) have decreased. CONCLUSION: An initial restrictive filling pattern has improved 8 weeks postoperatively. Since multiple indexes, obtained from the area change waveforms, in particular the for end-diastolic area normalized peak filling rate, seem to be highly sensitive in detecting changes of diastolic function, AQ may play an important complementary role in non-invasive evaluation of restrictive filling pattern.

Adult↗
PubMed1994

Mice transgenic for a soluble form of murine CTLA-4 show enhanced expansion of antigen-specific CD4+ T cells and defective antibody production in vivo.

CD4+ T cell responses were analyzed in transgenic mice expressing a soluble form of murine CTLA-4, mCTLA4-H gamma 1, which blocks the interaction of the T cell activation molecules CD28 and CTLA-4 with their costimulatory ligands. Consistent with previous reports (Linsley, P. S., P. M. Wallace, J. Johnson, M. G. Gibson, J. L. Greene, J. A. Ledbetter, C. Singh, and M. A. Tepper. 1992. Science (Wash. DC). 257:792), T cell-dependent antibody production was profoundly inhibited in mCTLA4-H gamma 1 transgenic mice immunized with a protein antigen. Surprisingly, however, transgenic mice could generate quantitatively and qualitatively normal primary T cell responses, as measured by limiting dilution assays and lymphokine production. In addition, in vivo expansion of antigen-specific T cells after secondary or tertiary immunization was enhanced in mCTLA4-H gamma 1 transgenics as compared with normal mice. Although unable to deliver cognate help to B cells in vivo, T cells from mCTLA4-H gamma 1 transgenic mice were not anergic as they could help B cells to produce specific antibodies when adoptively transferred into nude hosts. Taken together, these data suggest that the engagement of CD28 and/or CTLA-4 may not be required for the induction of T cell responses, as is currently understood, but rather for the expression of T cell effector function such as the delivery of T cell help to B cells.

Abatacept↗
PubMed1994

Interferon-gamma- and interleukin-4-producing T cells can be primed on dendritic cells in vivo and do not require the presence of B cells.

The antigen-presenting cell (APC) requirements for the in vivo induction of Th1- and Th2-type responses were investigated using a severe combined immunodeficiency (SCID)mouse chimera model. SCID mice adoptively transferred with either T cells [SCID(T)] or T+B cells [SCID(T+B)] and immunized with antigen in adjuvant were able to generate antigen-specific T cells which could produce both interferon (IFN)-gamma and interleukin (IL)-4 upon in vitro restimulation. This suggests that B cell APC are not necessary for the priming of either IFN-gamma- or IL-4-producing T cells in vivo. The ability of different APC to activate Th2-dependent effector mechanisms was also investigated. SCID(T) and SCID(T + B) mice were infected with the nematode parasite Nippostrongylus brasiliensis and analyzed for the development of IL-5-dependent peripheral blood eosinophilia. Following infection both SCID(T) and SCID(T+B) mice generated similar numbers of peripheral blood eosinophils, suggesting that similar amounts of IL-5 had been produced. Therefore, B cell APC are also not required for the in vivo activation of Th2 cells to lymphokine production. To establish more precisely which APC prime T cells to produce IFN-gamma and IL-4, normal mice were immunized by injection of syngeneic splenic dendritic cells which had been pulsed with antigen in vitro. T cells from these immunized mice were able to produce good IFN-gamma and IL-4 responses upon in vitro restimulation with specific antigen; therefore, dendritic cells appear to be sufficient APC for the in vivo priming of both IFN-gamma- and IL-4-producing T cells.

Animals↗
PubMed1994

[Risk of fat embolism syndrome after intramedullary nailing in femoral fracture and thoracic injury].

Following the insertion of an intramedullary nail, the fat embolism is a frequent complication in patients with long bone fractures. The respiratory function of patients with fractures of the femur and accompanying severe chest injuries was improved. In general these patients have a high risk to develop a respiratory distress syndrome. The average age of the 22 polytrauma patients studied was 40 years. The injury's severity as assessed using the Hannover Polytrauma-Score (PTS) and the average score was 29 points. Using Suter's scoring system the severity of the respiratory distress syndrome was assessed (Table 3). The insertion of an intramedullary nail was performed on 18 patients. Four of them developed an ARDS (adult respiratory distress syndrome) up to grade IV for a period of 5 days. Two patients suffered an ARDS grade I for a period of 2 days. In the study no typical features of fat embolism syndrome were found in any of these patients.

Adult↗
PubMed1994

Functional recognition of in vivo processed self antigen.

C5, the fifth component of complement, is a circulating self protein which induces complete tolerance in MHC class II restricted, CD4+ T cells due to the presentation of C5 taken up from plasma. Functional recognition of in vivo processed C5 was monitored by activation of C5 specific T cell hybrids cultured with antigen presenting cells (APC) from C5 expressing mice. Dendritic cells isolated from various tissues (spleen, thymus, skin) proved to be the most efficient APC, since 10- to 50-fold more macrophages and at least 100- to 500-fold more B cells were needed to achieve similar T cell activation. Stimulatory C5 peptide--class II complexes generated in vivo were retained on the surface of dendritic cells but not on macrophages and B cells upon prolonged culture. Dendritic cells but not macrophages from thymus presented in vivo processed C5. Taken together these findings emphasize the crucial role dendritic cells play for recognition of soluble self proteins by MHC class II restricted T cells.

Animals↗
PubMed1994

[Dynamic online quantification of left ventricular function by automated boundary detection: validation of a new echocardiography method].

A recently developed ultrasonic integrated backscatter imaging system allows automated border detection (ABD) of the blood-tissue interface in real time and provides instantaneous measurement of left ventricle cavity area in a beat-to-beat fashion. Three validations of this new system have been performed. 1) In 70 subjects (38 normal volunteers and 32 patients) the on-line ABD-derived areas (end-diastole, -systole = EDA, ESA) and the resulting fractional area change (FAC) of the left ventricle (apical four-chamber view) were compared with the off-line areas and FAC traced manually. All correlations were close (EDA r = 0.97, ESA r = 0.98, FAC r = 0.92; p < 0.0001). 2) In 36 patients with mitral regurgitation (MR), ABD-FAC was compared to the Doppler-derived systolic rate of pressure rise (RPR) which corresponds to systolic dP/dt, as simultaneous studies with high-fidelity pressure measurements have shown. Linear regression analysis yielded a significant correlation with r = 0.91; p < 0.0001. 3) In 26 patients undergoing routine heart catheterization, ABD-echo was performed on the same day. ABD-derived areas (end-diastole, -systole) and FAC (apical two- and four-chamber view) were compared to the corresponding angiographic data derived from biplane projection in 30 degrees RAO and 60 degrees LAO. Linear regression analysis yielded significant values for all correlations (EDA r = 0.88, ESA r = 0.95, FAC 0.90; p < 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1994

[Echocardiography online quantification of left and right ventricular function by automatic boundary detection: reference values and reproducibility in healthy probands].

UNLABELLED: Automated border detection (ABD) is a new on-line technique that instantaneously calculates cavity areas from automatic tracking of the endocardial-blood interface with a modified ultrasonic integrated backscatter imaging system. After validation of this new method in comparison with off-line echocardiographic, Doppler- and angiographic analyses, we studied dynamic systolic and diastolic function of the left (LV) and right ventricle (RV) in 50 normal volunteers (31 +/- 9 years) in order to establish ranges of normality for the ABD-parameter. The averaged areas of the LV (apical chamber view) were 25.7 +/- 4.9 sq cm in end-diastole and 14.7 +/- 3.3 sq cm in end-systole, resulting in a fractional area change (FAC) of 43.2 +/- 4.8%. The peak filling (PFR) and peak ejection rate (PER) were 69.3 +/- 11.2 and -61.5 +/- 11.1 sq cm/s. Normalization for end-diastolic area (EDA) yielded 2.7 +/- 0.28 and -2.4 +/- 0.42 EDA/s. The areas of the RV (apical chamber view) were 17.1 +/- 3.8 sq cm in end-diastole and 9.0 +/- 2.0 sq cm in end-systole, resulting in a FAC of 47.3 +/- 9.2%. PFR and PER were 58.2 +/- 13.7 and -51.6 +/- 10.1 sq cm/s. Normalization for EDA yielded 3.4 +/- 0.74 and -2.9 +/- 0.62 EDA/s. The interobserver- and day-to-day-variability for all measured values was less than 10%. CONCLUSION: ABD permits reproducible on-line quantification of systolic and diastolic ventricular function and offers a non-invasive approach for longitudinal monitoring of cardiac patients.

Adult↗
PubMed1993

B lymphocytes in vivo fail to prime naive T cells but can stimulate antigen-experienced T lymphocytes.

The ability of B cells or macrophages and dendritic cells (DC) to elicit class II-restricted T cell responses in vivo was compared using a mouse chimera model. Severe combined immunodeficient (SCID) mice (H-2d), reconstituted either with T or T+B lymphocytes from (H-2d x H-2b) donors, were immunized subcutaneously with protein antigen (Ag) to induce a class II-restricted T cell response. The frequency and major histocompatibility complex restriction of the resulting Ag-specific T cells were analyzed to establish whether B cells were necessary for the induction of class II-restricted T cell responses, and to determine the cell type on which priming had occurred. The results indicated that: (a) B cells are not necessary for the induction of a class II-restricted T cell response in vivo, as the frequencies of interleukin 2 (IL-2)- or IL-3-secreting T cells induced in the presence or absence of B cells were comparable. (b) Activation of naive T cells requires presentation of Ag on DC; Ag presented only on B cells is not sufficient to elicit a response. No H-2b-restricted, IL-3-secreting cells could in fact be detected in SCID mice reconstituted with naive (H-2d x H-2b) T cells and nonimmune or antigen-primed (H-2d x H-2b) B cells. (c) Previously primed T cells are able to be stimulated by Ag presented by both B cells and DC. H-2b-restricted, IL-3-secreting cells could in fact be readily demonstrated in SCID mice reconstituted with antigen-primed (H-2d x H-2b) T and B cells. Irrespective of whether the T cells were naive or previously activated, B cells were able to respond with an Ag-specific immunoglobulin G response, indicating that B cells were functional and able to present Ag in order to receive specific T cell help. Therefore, it appears that B cells are not necessary and do not participate in the initial priming of T cells; however, Ag presented by B cells can reactivate previously primed T cells. Taken together, these data indicate that during the course of an immune response Ag is first presented to naive T cells via DC, and only subsequently primed T cells can be stimulated by Ag presented by B cells.

Animals↗
PubMed1993

Localization of self antigen: implications for antigen presentation and induction of tolerance.

The fifth component of complement (C5) is a self antigen expressed in serum of normal mice at a concentration of about 50 micrograms/ml. We have previously shown that C5 is constitutively processed and presented by antigen-presenting cells (APC) in normal mice to induce and maintain complete tolerance in major histocompatibility complex (MHC) class II-restricted T cells. This report addresses the question of whether C5 presentation involves exogenous antigen which has been internalized for processing or whether intracellular, biosynthesized C5 is being presented with MHC class II. Macrophages were found to synthesize, but not secrete C5 in bone marrow chimeras made from irradiated C5-deficient [C5(-)] hosts reconstituted with C5-sufficient [C5(+)] bone marrow [C5(+)-->C5(-)]. In these mice, macrophages are the only source of C5. [C5(+)-->C5(-)] chimeras are not tolerant of C5 and generate C5-specific T and B cell responses upon immunization indistinguishable from those of C5(-) mice. Macrophages from [C5(+)-->C5(-)] chimeras are unable to activate C5-specific T cell hybrids in vitro unlike macrophages from a C5(-) strain that has matured in a C5-expressing environment [C5(-)-->C5(+) chimeras]. This shows that under physiological conditions in vivo intracellular C5 does not get access to the class II presentation pathway and thus, does not induce tolerance in class II-restricted T cells.

Animals↗
PubMed1991

[Flexible aortic valve prostheses: long-term functional results with porcine bioprostheses without mechanical commissure stent and aortic homografts].

The long-term performance of two different types of flexible aortic prostheses was evaluated in 10 patients who received a stentless porcine prosthetic valve (group A) and in 18 patients who underwent aortic valve replacement with an aortic homograft (group B). In group A early postoperative angiography (5-16 days post surgery) revealed a mean gradient across the aortic prosthesis of 8 +/- 6 mmHg. Late postoperative Doppler echocardiography (3.2 +/- 0.9 years post surgery) suggested a mean gradient of 6 +/- 3 mmHg with a Doppler derived valve orifice area of 1.8 +/- 0.6 cm2. Color Doppler visualized mild prosthesis regurgitation in two of the 10 patients and two-dimensional imaging showed no significant leaflet calcification. In group B late postoperative Doppler echography (5.2 +/- 1.6 years post surgery) suggested a mean gradient of 11 +/- 14 mmHg with a mean graft orifice area of 1.8 +/- 0.5 cm2. Color Doppler revealed prosthesis regurgitation in 15 patients (severe 1, moderate 2, mild 12) and two-dimensional imaging visualized significant prosthesis leaflet calcification in two patients. The good hemodynamic function of a stentless porcine bioprosthesis which seems to be preserved for at least several years indicates that the use of the flexible aortic xenograft is worthwhile pursuing. The long-term performance of an aortic homograft is relatively poor and may be due to unsolved problems with regard to sterilizing and storing the valves.

Adult↗
PubMed1989

[Defibrination syndrome after snake bites].

A defibrination syndrome developed in two men (aged 51, and 29 years old) within two hours of having been bitten by vipers Echis carinatus and Agkistrodon halys, respectively. In both the syndrome was characterized by afibrinogenemia with prolongation of the thrombin time, presence of fibrin monomers and split products of fibrinogen. Haemorrhagic signs included oral mucosa bleeding and macrohematuria. Specific serum was administered 9 and 16 hours, respectively, after the bite and achieved normalization of all clotting values within 48 hours.

Adult↗