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Biomedical subjects

E P Bauer

Publications and source records attributed to E P Bauer.

At least 37 records · Page 2Linked to original sources
PubMed1999

L-type voltage-gated calcium channels mediate NMDA-independent associative long-term potentiation at thalamic input synapses to the amygdala.

Long-term potentiation (LTP) in the amygdala is a leading candidate mechanism to explain fear conditioning, a prominent model of emotional memory. LTP occurs in the pathway from the auditory thalamus to the lateral amygdala, and during fear conditioning LTP-like changes occur in the synapses of this pathway. Nevertheless, LTP has not been investigated in the thalamoamygdala pathway using in vitro recordings; hence little is known about the underlying mechanisms. We therefore examined thalamoamygdala LTP in vitro using visualized whole-cell patch recording. LTP at these synapses was dependent on postsynaptic calcium entry, similar to synaptic plasticity in other regions of the brain. However, unlike many forms of synaptic plasticity, thalamoamygdala LTP was independent of NMDA receptors, despite their presence at these synapses, and instead was dependent on L-type voltage-gated calcium channels. This was true when LTP was induced by pairing presynaptic activity with either action potentials or constant depolarization in the postsynaptic cell. In addition, the LTP was associative, in that it required concurrent pre- and postsynaptic activity, and it was synapse specific. Thus, although this LTP is different from that described at other synapses in the brain, it is nonetheless well suited to mediate classical fear conditioning.

Afferent Pathways↗
PubMed1999

Spatiotemporal development and distribution of intercellular junctions in adult rat cardiomyocytes in culture.

The mode of development of the intercalated disk (ID) is largely unknown, and the hypothesis was tested that the assembly of cell adhesion junctions may precede the formation of gap junctions (GJ) in developing ID in adult rat cardiomyocyte (ARC) in long-term culture. Immunostaining for connexin 43 (Cx43) and for cell adhesion junction proteins (N-cadherin, catenins, and desmoplakin) in single- and double-label techniques was analyzed and quantified by confocal and electron microscopy. All proteins investigated disappeared 48 hours after ARC isolation and reappeared parallel to redifferentiation of ARC. The newly formed ID, observed after 5 days, showed the presence of N-cadherin, catenins, and desmoplakin, low levels of Cx43, and absence of ultrastructurally discernible gap junctions. A progressive incorporation of Cx43 within ID was observed after 6 days, when cell adhesion junction proteins were already organized as zipper-like structures. Quantitative confocal analysis revealed a progressive augmentation of the fluorescence intensity of Cx43, associated with an increase in both the number and size of GJ, resulting in a substantial increase in the percentage of total GJ length per reassembled ID from 1.67% (day 6) to 15.58% (day 12). In the present study, we show that (1) the formation of the ID can be followed in ARC in culture and (2) the assembly of the adhering type of junction is the prerequisite for subsequent GJ formation within the ID. These findings may have clinical relevance in elaborating strategies for using myocardial grafts and for the potential restoration of GJ communication in cardiac diseases.

Age Factors↗
PubMed1999

Evaluation of reports of periconceptual occupational exposure: maternal-assessed versus industrial hygienist-assessed exposure.

BACKGROUND: While the number of women entering the work force has grown, so has the importance of investigating occupational reproductive hazards. The objective of this study was to examine the concordance between maternal-assessed and industrial hygienist-assessed exposure to four classes of occupational agents - video display terminals, paints, solvents, and agricultural chemicals. METHODS: Case (n=87) and control (n=102) mothers who participated in a population-based study of orofacial clefts provided occupational histories and exposure (yes/no) to selected classes of agents for the one-year period prior to their child's delivery. Two industrial hygienists reviewed the occupational histories and assigned mothers an exposure status for each class of agent. Using industrial hygienist-assessed exposure as the "gold standard", sensitivity and specificity of maternal reports were calculated for each class of agent. Kappa statistics were calculated for the study population to account for chance agreement between the two exposure assessment methods. RESULTS: Sensitivity estimates for cases were the highest for video display terminals (77%) and lowest for agricultural chemicals (14%). Respective estimates for controls were 74% and 14%. Specificity estimates tended to be high for both groups. Kappa values ranged from 0.16-0.45. CONCLUSIONS: With regard to the classes of agents examined, these data suggest screening questions alone may not be the preferred method of obtaining occupational exposure histories, even when the time period of interest is fairly short and recent.

Adult↗
PubMed1999

Repair of an aneurysm of the pulmonary trunk in a 65-year-old patient.

The case of a 65-year-old patient with asymptomaticaneurysm of the pulmonary trunk associated with severe insufficiency of the pulmonary valve and symptomatic coronary artery disease is presented. The surgical procedure included coronary artery bypass grafting, aneurysmectomy, and pulmonary artery replacement with implantation of a stentless bioprosthesis and lengthening of the root of the bioprosthesis with a reversed vascular Y prosthesis, which was anastomosed to the left and right pulmonary artery.

Aged↗
PubMed1999

Cardioscopy: potential applications and benefit in cardiac surgery.

OBJECTIVE: Cardioscopy in open heart surgery is still not routine in most units. However, since our first report in 1996 we use this device more frequently, because we think that safety and accuracy of different surgical procedures is increased. METHODS: Between 1/96 and 12/97 we performed cardioscopy in 100 patients. Indications (IND) for cardioscopy were as follows: IND (1) resection of hypertrophied septum (N = 15); IND (2) evaluation of aortic valve with low grade stenosis or insufficiency (N = 12); IND (3) removal of intracardiac foreign bodies/tumors (N = 13); IND (4) inspection of VSD prior and after repair (N = 8); IND (5) identification of paravalvular leakage (N = 8); IND (6) diagnostic purposes (N = 4); IND (7) education of surgeons and operating room staff (N = 40). During cardioplegic arrest the 5 mm rigid or flexible cardioscope (Storz, Tuttlingen, Germany) was inserted through ascending aorta, aortic valve or tricuspid valve depending on indication. RESULTS: No complication occurred during cardioscopy. IND (1): there was an excellent view of all intracardiac structures. Thorough resection of hypertrophied septum was possible and there was no injury of adjacent structures or aortic valve. IND (2): all valves were inspected through a 1 cm aortic incision and the pathology of the valves was documented. In case of severe calcification, the valve was replaced although transvalvular gradient was less than 50 mm Hg. IND (3): intraventricular foreign bodies, such as felt pledges (N = 2), debris (N = 5), thrombi (N = 4) and tumors (N = 2) were entirely removed through the aortic valve with a special forceps. IND (4): anatomy of VSD was documented in all cases. It was possible to test accuracy of all patch-sutures. IND (5): all paravalvular leakages were identified even though there was heavy immobility of the mechanical valve. IND (6): a papillary muscle (N = 2) and a thrombus formation (N = 2) were diagnosed. IND (7): the surgeons and operating room staff could follow the entire procedure in all cases. CONCLUSIONS: Cardioscopy is a supporting technique to clearly identify intracardiac structures, to control several surgical procedures, to document valve pathology, and to educate surgeons and operating room staff. Handling is easy and does not increase operative risk. Some procedures will be performed with minimal invasivity in future.

Aortic Valve Stenosis↗
PubMed1999

Transmyocardial laser revascularisation has no beneficial effect on high energy phosphates and lactate content during acute myocardial ischaemia in pigs.

OBJECTIVE: Transmyocardial laser revascularisation (TMLR) is used to treat endstage coronary heart disease. There is evidence that angina is significantly reduced after TMLR. However, the precise mechanism by which symptoms disappear remains unknown. The objective of the present study was to examine the potential effects of TMLR on high-energy phosphates and myocardial perfusion in an acute ischaemic model. METHOD: Five male landrace pigs (42 +/- 1.8 kg) had TMLR of the anterolateral wall of the left ventricle using a 1000 W CO2 laser (PLC, USA). Thereafter the anterior descending coronary artery was occluded with a tourniquet. After 90 min of ischaemia, drill-biopsies were taken from ischaemic and non-ischaemic areas as well as from laser channels. The specimens were snap-frozen in liquid nitrogen. Subsequently, methylene blue was injected into the left atrium to study tissue distribution. The hearts were excised and the patency of channels was examined visually. RESULTS: Coronary artery occlusion resulted in immediate blue discoloration in both TMLR and control areas. There was no subendocardial methylene blue staining around laser channels. Inspection of hearts showed occlusion of laser channels due to thrombus formation at both endo- and epicardial levels. ATP-metabolites significantly increased in ischaemic areas compared to non-ischaemic areas. Furthermore there was significant upregulation of purine-content in ischaemic regions even in areas with laser channels. CONCLUSIONS: In our acute model there was early occlusion of the channels after TMLR. We suggest that clinical improvement after this procedure is not due to increased myocardial oxygen delivery, since high energy phosphate levels and lactate content remained unchanged.

Acute Disease↗
PubMed1999

Midterm results after the Mini-Maze procedure.

OBJECTIVE: Atrial fibrillation (AF) is the most common arrhythmia. However, its precise electrophysiologic mechanism is still not well understood. Chronic symptomatic AF resistant to medical therapy, can successfully be treated by the Maze III procedure (M III). However, there are several publications dealing with alternative surgical techniques. This study describes technique and midterm results of a Mini-variant of the M III procedure. METHODS: During a 38-month period we performed either an M III (seven patients) (group I) or a MINI-operation (45 patients) (group II) with chronic symptomatic AF and additional cardiac pathology. Patients were controlled 3.6 +/- 0.9 and 14.9 +/- 2.2 months after operation by means of thorough electrophysiological assessment, right heart catheterization, magnetic resonance imaging (MRI), echocardiography, stress-EGG and 24-h-ECG. RESULTS: There was no significant differences between the two groups with regard to sex, age and duration of AF. Echocardiographic left atrial diameter (LAD) was 75 +/- 11 mm in group I and 67 +/- 8 mm in group II (P = 0.01). Whereas right atrial diameter was 62 +/- 8 mm in group I and 56 +/- 7 mm in group II (NS). Perioperative data (n = 52): aortic cross clamp time was 127 +/- 40 mm in group I and 87 +/- 21 mm in group II, (P = 0.0002). Cardiopulmonary bypass time was 185 +/- 71 mm in group I and 137 +/- 46 mm in group II, (P = 0.02). Postoperative data: there was no difference between the two groups with regard to sinus rhythm, prolonged sinus node recovery time, pacemaker (PM) in AAI-mode, inducible atrial fibrillation, reduction of left and right atrial size after a follow-up interval of 3.6 months and 1 year, respectively. CONCLUSION: Midterm results are identical after M III and MINI. MINI is less complex compared to the M III procedure and there is a significant reduction of crossclamp- and ECC-time. We recommend the MINI especially for polymorbid patients, and for those with poor left ventricular function.

Adult↗
PubMed1998

Upregulated and downregulated transcription of myocardial genes after pulmonary artery banding in pigs.

BACKGROUND: Acute or chronic pressure overload may occur during or after cardiac surgical procedures. Typical examples are aortic cross-clamping and pulmonary artery banding. It is well known that mechanical stress induces transcription of different myocardial genes. However, these results were mainly obtained from in vitro studies and experiments with rodents. This experiment was carried out to investigate molecular alterations after pressure overload in porcine hearts. METHODS: The study was performed with 35 Landrace pigs with a mean weight of 32+/-1.2 kg. The five groups consisted of 7 pigs each, 3 sham-operated pigs and 4 banded pigs. The hearts were exised after different time intervals. We investigated messenger RNA expression of sarcoplasmic reticulum adenosine triphosphatase, phospholamban, alpha-/beta-myosin heavy chain, and atrial natriuretic factor by Northern blot analysis. RESULTS: The ratio of right ventricular weight to body weight increased significantly after 7 and 24 days in banded pigs (p < 0.05). Atrial natriuretic factor messenger RNA was significantly upregulated in banded pigs versus sham-operated pigs after 1 day (240%+/-7% versus 100%+/-6%; p < 0.01) and 3 days (520%+/-8% versus 100%+/-8%; p < 0.01). There was insignificant downregulation of sarcoplasmic reticulum adenosine triphosphatase and phospholamban after 1, 3, and 7 days. Myosin heavy chain messenger RNA expression remained unchanged. CONCLUSIONS: Pulmonary artery banding results in hypertrophic response of the porcine right ventricle; however, the weight increase is not the result of myosin heavy chain messenger RNA upregulation. Atrial natriuretic factor messenger RNA is locally expressed in mechanically stressed myocytes. Furthermore, pressure overload downregulates transcription of calcium-binding proteins that can influence ventricular contractility. These results may have an impact on cardiac surgical procedures.

Adenosine Triphosphate↗
PubMed1997

Video-assisted resection of hypertrophied and fibrous intraventricular tissue.

There is increasing interest in endoscopic techniques in cardiac surgery. However, use of the endoscope during open heart operations is still not routine. Cardioscopy has been used in patients with hypertrophied obstructive cardiomyopathy, asymmetric septal hypertrophy, or membranous subaortic stenosis. We demonstrate the resection of this pathologic tissue under direct visualization. With this technique we could increase the safety and accuracy of this surgical procedure. Beside this advantage, the entire operating room staff could follow the surgical intervention, which increases its educational side-effect.

Cardiomyopathy, Hypertrophic↗
PubMed1997

Reoperations after dacron patch aortoplasty with heparinized femoro-femoral bypass.

Dacron patch aortoplasty used to be a standard therapy in some surgical units. Occurrence of aneurysm formation after this procedure is well known. The incidence of aneurysms is reported to be 0-35% with a high risk of lethal rupture. We report three cases of aneurysm repair of the descending thoracic aorta after dacron patch aortoplasty using femoro-femoral extracorporeal system. Heparin-coated system was used primarily to prevent ischemic spinal cord injury through hypotension of the distal aorta and secondarily to reduce the risk of intraoperative hemorrhage.

Adult↗
PubMed1997

Increased growth factor transcription after pulmonary artery banding.

OBJECTIVE: Several mechanisms are known to produce mechanical stress during and after cardiac surgery, e.g. aortic cross-clamping and pulmonary artery banding (PAB). However, little is known about the transcription of myocardial genes which are changed during mechanical overload. This study was performed to investigate growth factor mRNA expression after PAB in porcine hearts. METHODS: The experiment was performed in 35 pigs (five groups). Each group consisted of three sham-pigs (S-pigs) and four banding-pigs (B-pigs). The mean transbanding gradient in B-pigs was 29 +/- 2.5 mm Hg. The hearts were excised after different time intervals. The probes were snap-frozen in liquid nitrogen and stored at -80 degrees C. Analysis was performed by Northern blot. RESULTS: Right ventricular weight increased significantly after 7 and 24 days (P < 0.05). There was an upregulation of transcriptional and growth factors in B-pigs: c-jun mRNA: 412 +/- 12.1% after 2 h (P < 0.001); c-fos mRNA: 303 +/- 18.5% after 2 h (P < 0.001); vascular endothelial growth factor (VEGF) mRNA: 203 +/- 18.2% after 2 h (P < 0.001); Flk-1 mRNA: 156 +/- 16% after 2 h (P < 0.05), 253 +/- 5% after 24 h (P < 0.01) and 184 +/- 12% after 3 days (P < 0.01); transforming growth factor-beta1 (TGF-beta1) mRNA: 255 +/- 21.5% after 24 h (P < 0.002). Fibroblast growth factors 1 and 2 (FGF-1 and FGF-2) were constitutively expressed in B- and S-pigs and did not change their expression. CONCLUSIONS: Pulmonary artery banding results in significant right ventricular hypertrophy and upregulation of different growth factors. However, growth factors known to induce hypertrophy in vitro, like the FGFs, showed unchanged expression. We think that myocardial growth factors may have trophic functions in the heart which may be useful for cardiac surgery in future.

Animals↗
PubMed1996

Diagnostic transaortic cardioscopy of the left ventricle.

Preoperative diagnosis of pathologic intracardiac structures by noninvasive techniques is sometimes difficult or even impossible. In these cases a heart operation is required with opening of one or more cardiac chambers. We demonstrate direct visualization of the left ventricular cavity by transaortic cardioscopy in a patient with a pathologic intraventricular structure. With this technique we could avoid ventriculotomy.

Cardiac Surgical Procedures↗
PubMed1996

Valve surgery combined with coronary artery operation: is the use of internal mammary artery a predictor for early complications?

The internal mammary artery (IMA) provides better early and long-term patency than venous grafts do. Although IMA is the conduit of choice in isolated coronary artery bypass grafting (CABG), its use in combined procedures is not routine in some cardiovascular units. During a 16-month period, 188 patients underwent valve surgery combined with CABG. Internal mammary grafts were used in 68/188 (36%) patients (group 1) and vein grafts without arterial grafts (group 2) in 120/188 (64%). Left IMA was implanted in 67/68 (99%) and right IMA in 1/68 1%) cases. Surgeon A used IMA in 28/44 (64%), surgeon B in 20/32 (63%), surgeon C in 18/44 (41%), surgeon D in 1/4 (25%) and surgeon E in 1/63 (2%) patients. The final decision to use IMA in a combined procedure was left up to the surgeon. Statistically, the preoperative- and perioperative data were identical in the two groups, although the frequency of IMA grafting in patients with double valve replacement and reoperation was lower (1/68 vs 11/120, ns, and 3/68 vs 9/120, ns). Ten of 188 (5.3%) patients died within 30 days after operation. Longer cross-clamp time (P = 0.008) and mitral valve replacement (P = 0.05) were independent risk factors for early death. The use of IMA did not increase the risk of early mortality. The postoperative variables were similar in the IMA and vein groups, in particular data suggesting perioperative myocardial infarction (CK-MB, catecholamine support). Postoperative mechanical ventilation was longer in the IMA group, although not significantly (P = 0.06). Early mortality and morbidity were identical in the two groups in combined procedures. We did not find any hints for an increased risk of using IMA in this type of surgery. Internal mammary artery implantation is safe in selected patients undergoing combined valve and CABG surgery. Beside the better long-term patency of IMA, its use may have several technical advantages.

Aged↗