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Biomedical subjects

S Vogt

Publications and source records attributed to S Vogt.

At least 19 recordsLinked to original sources
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↗
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

[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↗
PubMed1992

[Immunologic studies in patients with dilated cardiomyopathy].

In 10 cases of dilated cardiomyopathy the HLA-loci (A, B, C, DR) and marker expression on lymphocytes were studied. In this group the T4/T8-ratio was decreased and interleukin-2-expression was increased in relation to normals or patients with chronic coronary heart disease, respectively. 9 patients had the HLA-A1 or HLA-A2-locus in their siblings. In correlation analysis between immunological and hemodynamic parameters a good correlation of the number of NK-cells to the ejection fraction (r = 0.79) and negative correlation of helpercells (CD4) to the cardiac output were found (r = -0.80). The results of this attempt suggest an immunological pathogenesis of the dilated cardiomyopathy.

Adult↗
PubMed1990

Heart valve replacement with the Björk-Shiley and St Jude Medical prostheses: a randomized comparison in 178 patients.

In 178 patients, a randomized prospective comparison between the 60 degrees spherical disc Björk-Shiley (BS) and the St Jude Medical (SJM) heart valve prostheses was performed. Four-week perioperative mortality was zero in the BS (n = 84) and 4.3% in the SJM group (n = 94). During a mean (+/- SD) follow-up of 52 +/- 20 months or 778 patient-years, late cardiac mortality per year was 2.4% in the BS and 2.2% in the SJM group. The yearly thromboembolic rates were 1.4% in the BS and 2.0% in the SJM group. There was no mechanical valve failure or haemolytic anaemia. Paravalvular leaks and major bleeding complications occurred at low rates in both groups (1.1% and 2.2% per year in BS; 0.7% and 1.7% per year in SJM). Functional results were similarly good with 96% of patients with BS valves and 95% of patients with SJM prostheses being in NYHA classes I and II, respectively. We conclude that heart valve replacement with mechanical prostheses can be performed with equally good results using either the Björk-Shiley spherical disc valve or the St Jude Medical bileaflet prosthesis.

Aged↗
PubMed1990

[Sonographic diagnosis of gastroesophageal reflux in infancy].

The gastroesophageal reflux is a common problem in the pediatric clinical practice in the 1st year of life. Its diagnosis is mainly based on the x-ray and the measurement of the esophageal pH. Our investigation shows the possibility of the ultrasonographical diagnosis of this disturbance. We could demonstrate a good correlation between the x-ray and the ultrasonographical findings. A continuous lasting gastroesophageal reflux which takes more than 5 minutes points to a pathologic reflux pattern with the well known complications. Thus, ultrasonographical investigation should perform before an extensive diagnostic is taken into consideration.

Esophagus↗