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S Vogt

Publications and source records attributed to S Vogt.

At least 73 records · Page 4Linked to original sources
PubMed1998

[Hemodynamic-kinetic controlled extracorporeal circulation in heart surgery].

Mimicking the physiological characteristics of the circulatory system, pulsatile bloodflow has also been introduced into extracorporeal perfusion to avoid known postoperative complications. In a mathematical consideration of the situation bloodflow is seen as a function of time F(t) for approximately constant vessel diameter over a given time. The kinetic energy of a column of blood produced by the heart-lung machine is transmitted directly to the arterial circulation via the aorta. The nature of the energy release can give rise to both positive (organ perfusion) and negative (damage to endothelium) effects. This study investigates how this energy release can be optimised, using the following experimental approach. A Doppler flow-measuring probe is placed on the ascending aorta to monitor the extracorporeal circulation. At the same time, the blood pressure is measured and converted to a pressure-flow curve via an A/D converter. On the basis of the parameters thus obtained, the energy released by the heart-lung machine is calculated. By regulating the functional parameters of a new generation of heart-lung machines, the bloodflow can then be adapted to the physiological requirements. Within the pulse period (cycle) a 20% rise phase ending in a slightly increasing plateau is established. The energy increase within a cycle should not exceed 150 joules. To optimize the mode of functioning of the heart-lung machine, we introduced the "energy-equivalent pressure" (EEP). Adaptation of the EEP to the physiological conditions required a basic flow of 60% at a pulse rate of 60/min and a pulse duration of 35% within the pulsatile flow interval.

Adult↗
PubMed1997

Comparison of anion-exchange and hydroxyapatite displacement chromatography for the isolation of whey proteins.

In displacement chromatography, several substances may be isolated and concomitantly concentrated, which makes this separation procedure attractive for the processing of diluted product streams containing a number of high value substances. Here, the suitability of anion-exchange and hydroxyapatite displacement chromatography for the processing of technical dairy whey is investigated. The pH and flow-rate of the carrier, the displacer chemistry and, in case of the apatite, the particle diameter of the stationary phase are considered. As a consequence of the pH sensitivity of the beta-lactoglobulin, one major whey component, apatite displacement chromatography is less then successful in whey separation. At a denaturing carrier pH (> 8.5) the beta-lactoglobulin zone is broad and stretches over the entire displacement train. At a lower carrier pH, previously successful polyanionic displacers do not bring about separation, while low-molecular-mass ones do, but they tend to overrun and thus contaminate the protein zones. In the case of anion-exchange displacement chromatography, polyanions, especially polyacrylic acid (PAA, M(r) 6000), constitute suitable displacers. Here too, a carrier pH of 8.0 is most suited to the separation of the whey proteins. The low-molecular mass-displacer iminodiacetic acid (IDA, M(r) 133.4), on the other hand, displaces only alpha-lactalbumin. The beta-lactoglobulin remains on the column. PAA is used as the displacer to process a dairy whey sample.

Animals↗
PubMed1997

Angiotensin-I-converting enzyme DD genotype is a risk factor of coronary artery disease.

Coronary artery disease (CAD) is a polygenic disease whose phenotypic manifestation depends on the interaction of a number of environmental factors. A number of genes, including the angiotensin-I-converting enzyme (ACE) gene, have been implicated in the pathogenesis of CAD. ACE could affect smooth muscle cell and fibroblast migration and proliferation, low-density lipoprotein (LDL) oxidation and endothelial cell function; these are all important factors in atherosclerosis. A polymorphic variant of the ACE gene correlates with higher circulating ACE levels and carries an increased risk of myocardial infarction, and cardiomyopathies. In this study, we sought to determine the distribution of ACE genotypes and the frequency of allele D in patients undergoing coronary angiography at our institution. DNA from 196 patients with angiographically proven CAD and 96 controls without CAD was amplified by polymerase chain reaction (PCR). The primers flanked the region of the ACE gene (intron 16) where the insertion (I) or deletion (D) of a 287-bp fragment results in the I/D polymorphism. PCR amplification of alleles I and D resulted in 490- and 190-bp products, respectively. In the control group, the relative allele frequencies of the polymorphism were similar to those of previously published European studies. The ACE genotype DD was present in 37.3% of patients with CAD as compared to 23.4% in the controls (p < 0.001, odds ratio 1.95, 95% confidence intervals (CI) 1.06-3.57). There was no association with the history of prior myocardial infarction. The genotype distribution in patients with single-vessel involvement was not significantly different from controls (p = 0.14). However, the DD genotype was significantly more common in patients having multivessel CAD when compared to single-vessel disease, indicating an association of this polymorphism with the extent of CAD. ACE genotype DD is more common in patients with multivessel CAD as compared to controls and to patients with single-vessel involvement, indicating that genotype DD is a genetic risk factor for extensive, multivessel CAD.

Aged↗
PubMed1996

Muscarinic acetylcholine receptor trafficking in streptolysin O-permeabilized MDCK cells.

We investigated the validity of streptolysin O (SLO)-permeabilized Madin-Darbin canine kidney (MDCK) cells which express muscarinic acetylcholine receptors (mAChRs) coupled to pertussis toxin-sensitive guanine nucleotide-binding proteins (G proteins) for the study of the molecular machinery that regulated mAChR internalization and recycling. Exposure of SLO-permeabilized cells to carbachol-reduced cell surface receptor number by up to 40% without changing total receptor number. The kinetics and maximal extent of receptor internalization as well as the potency of carbachol to induce receptor internalization were almost identical in SLO-permeabilized and non-permeabilized cells. Using this semi-intact cell system, we studied the effect of various agents affecting components potentially involved in receptor trafficking. Internalization was prevented by treatment of the SLO-permeabilized MDCK cells with (i) the stable ATP analogues, adenosine 5'-O-(3-thiotriphosphate) and adenylylimidodiphosphate, to block ATP-dependent processes, and (ii) heparin to block G protein-coupled receptor kinases. Inclusion of the stable GTP analogue, guanosine 5'-O-(3-thiotriphosphate), increased the rate but not the extent of receptor internalization. None of the membrane-impermeant agents affected receptor internalization in intact MDCK cells. This model system also allowed recycling of internalized receptors back to the plasma membrane. After removal of the agonist, cell surface receptor number in SLO-permeabilized cells returned to control values within 90 min with the same kinetics as seen in intact cells. Inclusion of guanosine 5'O-(3-thiotriphosphate) shortened the recovery time. These data suggest that both ATP-dependent kinases including G protein-coupled receptor kinases and G proteins participate in receptor internalization and recycling. In summary, the SLO-permeabilized MDCK cell is a feasible model system for the study of mAChR internalization and recycling and allows manipulation of the intracellular milieu with membrane-impermeable macromolecules.

Adenosine Triphosphate↗
PubMed1996

Imagery and perception-action mediation in imitative actions.

This paper describes two lines of research exploring a hypothetical function of imagery in the context of imitative actions: the mediation between perceptual and motor processes. Both experimental approaches, a sequence learning task and a timing imitation task, demonstrate that engagement into imagery as a temporally distinct activity between observation and performance is not required for accurate imitation. Moreover, evidence is provided that generative processes can take place during event observation itself, thus making a separate recoding stage redundant. Nevertheless, in the absence of a visual display, imagery of a movement sequence exerted similar learning effects as physical and observational practice, and visual and motor imagery were found to be equally effective rehearsal strategies for maintenance of temporal information in short-term memory.

Adult↗
PubMed1996

Intraoperative monitoring of the potassium-activity and pH- value on the myocardial surface during coronary bypass surgery.

INTRODUCTION: Ischemic periods very often occur a dysfunction of the heart. In this series the intraoperative changes of potassium-activity and pH- value on the heart undergoing cardioplegic induced cardiac arrest were studied. Furthermore, the sensitivity of the system in diagnostic fields of ischemic periods and reperfusion damages were investigated. METHODS: In eight patients (7 male and 1 female pts.) undergoing elective cardiosurgical procedures (aortocoronary bypass grafts) the ion activity of potassium and hydrogen ions were monitored on the heart, intraoperatively. By ion-selective electrodes the superficial cardiac ion activities were evaluated on definitive time periods on the left (LV) and right ventricle (RV). RESULTS: Preliminary results suggest: In the reperfusion-period different pH-values result on the ventricles. In the end of reperfusion the pH-values return to the starting points. Though the evaluated parameters are too alcaline in comparison to physiological intervals. The time course of epicardial potassium-concentrations is not different between the RV and LV. Initially, only low concentrations were found during perfusion and reperfusion, in the last interval of reperfusion period an increase of potassium on both ventricles were evaluated. In the end of the operations the superficial ion concentrations approximate to the values evaluated at the starting points. CONCLUSION: These results suggests, that the dynamics of ion-exchange-processes in the myocardium can be monitored with the help of ion-selective probes. This new technique opens new strategies in the qualitative check-up of myocardial protective procedures during cardioplegic cardiac arrest.

Coronary Artery Bypass↗
PubMed1996

[Study of long-term anesthesia in rabbits].

In this study, the possibility of total intravenous anaesthesia with the anaesthetic agents etomidat/fentanyl, ketamine/xylazine and maintenance with halothane, nitrous oxide and oxygen was used in rabbits for long-term experimental surgery with median sternotomy. The clinical course, cardiovascular and respiratory parameters undergoing long-term anaesthesia for experimental cardiac surgery in rabbits were evaluated.

Anesthesia, General↗
PubMed1995

Alteration of temporomandibular joint symptoms after orthognathic surgery: comparison with healthy volunteers.

PURPOSE: The purpose was to investigate alterations in temporomandibular joint (TMJ) dysfunction after orthognathic surgery. PATIENTS AND METHODS: TMJ symptoms of preoperative patients (n = 30) were compared with those of healthy volunteers (n = 30), and changes in the symptoms were evaluated at 3- and 6-month postoperative intervals. RESULTS: There was no significant difference in the incidence of TMJ sounds, deviation of mouth opening, and tenderness of TMJ and masticatory muscles between patients and volunteers. Patients did not report TMJ symptoms significantly more often than the control subjects. At both 3 and 6 months after surgery, half or more of the patients showed no change in TMJ sounds, deviation of mouth opening, or tenderness of TMJ and masticatory muscles. At each evaluation, some patients exhibited improvement of TMJ symptoms or showed changes for the worse. Findings of TMJ sounds were observed to be associated with the postoperative reduction of mandibular mobility. CONCLUSION: These results suggest that alterations of TMJ symptoms after orthognathic surgery do not always result from the correction of malocclusion.

Adolescent↗
PubMed1995

On relations between perceiving, imagining and performing in the learning of cyclical movement sequences.

In three experiments, the effects of observational, mental and physical practice on the performance of cyclical movement sequences were investigated. Experiment 1 revealed that repeated demonstrations of the criterion motion were sufficient for adequate reproductions of the movement form and that mental or physical practice had only small additional effects. Furthermore, consistency of movement tempo and consistency of relative timing, normally seen as dependent on physical practice, were similar in all experimental conditions at the end of practice. Experiment 2 confirmed this counter-intuitive finding by demonstrating equivalent improvements in the consistency of relative timing after physical and mental practice and after practice in a perceptual discrimination task. In Expt 3, discrimination of a nonspatial version of the criterion motion from similar patterns was also found to enhance consistency, indicating that eye movements were not a crucial factor in the observed effects. The findings suggest that performance, observation and imagery of sequential patterns involve a common process, characterized as event generation, which is either coupled to an articulatory system (in the case of physical practice), synchronized with an external event (in the case of observational practice), or 'runs free' without such articulatory or perceptual coupling in the case of imagery.

Adult↗
PubMed1995

[Problems in differential diagnosis and therapy of intracardiac space-occupying lesions--myxoma and thrombus].

The total removal of the myxoma under extracorporeal circulation from the origin maintains the optimal surgical treatment. Differentiation between myxoma and thromboses is a problem of preoperative diagnostics. Both tumors show unspecific symptoms. Therefore echocardiography and angiography are required as diagnostic tools. Between 1984 and 1991, 14 patients were cured from intracardiac tumors in the Clinic for Cardiovascular Surgery of the University of Leipzig. Problems in the sensitivity and security of the preoperative diagnostics and certain aspects of the surgical treatment will be discussed.

Adult↗
PubMed1995

[Ketamine-midazolam combination for anesthesia of rabbits--results of neuroelectrophysiologic studies using evoked potentials].

The study was done in order to investigate the central nervous activities in rabbits (n = 10) during experimental surgery in ketamine and ketamine/midazolam-anaesthesia. The combination of a benzodiazepine with ketamine was thought to be beneficial to reduce the usual excitatory nervous effects after ket amine-anaesthesia. The results of the measured EEG-power spectra and somatosensory-evoked potentials were presented. Additionally, the central effects were correlated with mean arterial blood pressure and the results of blood gas analyzes.

Anesthesia↗
PubMed1994

Sympathetically and nonsympathetically mediated onset of excess fat deposition in Zucker rats.

To evaluate whether a low sympathetic activity is essential for the onset of Zucker rat obesity, we artificially reared fa/fa and Fa/fa littermates from 4 days of age with identical amounts of milk containing norepinephrine (NE). The NE concentration was adjusted to keep the mass-specific metabolic rate (MR) roughly either 100 or 50% above its thermoneutral level. At both doses, no genotype difference in total MR occurred before day 16, but between 16 and 21 days of age, total MR of fa/fa pups was 10% less than that of their Fa/fa littermates. The 21-day-old fa/fa pups had approximately 1 g more body fat than their lean littermates, and this was energetically accounted for to 50-80% by their lower MR and to 10-25% by the reduced growth of their fat-free dry mass. We conclude that factors not dependent on decreased sympathetic outflow trigger the onset of excess fat deposition in the 3rd postnatal wk, even if sympathetic activity was high throughout the previous weeks during which excessive fat deposition is mainly dependent on decreased thermoregulatory thermogenesis.

Animals↗
PubMed1994

Synovial tissue implants from patients with rheumatoid arthritis cause cartilage destruction in knee joints of SCID.bg mice.

OBJECTIVE: To establish in SCID.bg mice a model in which joint destruction is initiated by human inflammatory cells from patients with rheumatoid arthritis (RA). METHODS: Development of a surgical technique and immunohistologic analysis. RESULTS: Initial experiments with single cell suspensions failed because more than 70% of the cells injected intraarticularly left the mouse knee joint within 16 h without causing destruction. This was observed with peripheral blood mononuclear cells, T cell lines reactive to mouse or rat collagen type II, and synovial mononuclear cells. Cell immigration was reduced but not prevented by preactivation with mitogens. In contrast, small tissue implants from human synovial membrane which were transferred by surgical intervention into mouse knee joints remained at the site of injection and could be easily localized within the mouse joint (observation period up to 8 weeks). The human synovial membrane implants induced pannus formation and erosion of cartilage and bone while only a mild and transient synovitis was observed with normal synovial membrane and control tissues like human thymus. The predominant cells at the site of destruction were human (CD68+) and murine (Mac-2+) monocytes/macrophages. CONCLUSION: The human/murine SCID arthritis is a useful model for studying pathogenetic aspects of joint destruction as well as effects of new drugs or novel treatment strategies.

Animals↗
PubMed1993

[Follow-up and prognosis of pyelonephritis in infancy].

128 infants between 1 and 18 months, 80 girls and 48 boys suffering from their first pyelonephritis (PN), were investigated and followed up over 2.9 +/- 2.2 years (mean +/- SD). 20 children showed urinary tract obstructions. In 49 of 108 cases (45%) with nonobstructive PN a vesico-uretero-renal reflux (VUR) was found and surgically corrected in 13 cases. In 36 patients (52 renal units) the VUR disappeared in most cases under medical management within 3 years. Recurrences of urinary tract infections (UTI) were found in the same frequency in children with and without reflux (28%), but those with VUR showed significantly more PN. 22 of 108 patients with nonobstructive PN (20%) developed renal scars, 39% of children with reflux (mostly VUR III. or IV. degree), 5% of those without reflux. In more than half of these cases renal scars were found already after the first PN. We conclude that a reduction of the risk of renal damage and an improvement of the prognosis can achieved by the following measures: 1. early detection of obstruction by pre- or postnatal sonographic screening, 2. early and exact diagnosis of PN and antibiotic therapy without delay. PN has to be excluded in all infants with unclear fever. 3. In all infants with PN a voiding cystography should be performed. In children with VUR, long-term chemoprophylaxis is necessary to avoid recurrence of PN.

Diagnosis, Differential↗
PubMed1992

[Heart valve substitution: the effect of preoperative findings on long-term outcome].

BACKGROUND: In a retrospective analysis of 653 consecutive patients who underwent heart valve replacement by one single type of mechanical prosthesis (St. Jude Medical) at three Swiss university medical centers (Basel, Bern, Lausanne), the outcome was judged on the basis of preoperative variables. These variables should facilitate the timing of heart valve replacement. METHODS: Preoperative evaluation includes NYHA classification of symptoms, chest X-ray, ECG, and LVEF on angiography. Postoperative outcome was assessed clinically at yearly intervals by NYHA classification, documentation of complications and mortality. RESULTS: Five-year-survival rates were 96 and 88%, and complication-free rates were 82 and 76% respectively in patients after isolated aortic and mitral valve replacement. An unsatisfactory outcome with death or persistent severe symptoms was more frequent when preoperative symptoms at rest and atrial fibrillation were present. CONCLUSION: Heart valve replacement should not be postponed until severe symptoms and functional impairment occur. Clinical criteria are at least as important for the timing of operation as the findings of more complex investigations.

Adolescent↗