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Biomedical subjects

A Lindner

Publications and source records attributed to A Lindner.

At least 37 records · Page 2Linked to original sources
PubMed2000

Viscous fingering in a yield stress fluid

We study the Saffman-Taylor or viscous fingering instability in yield stress fluids. The theory for yield stress fluids shows that the dispersion equation of the instability is similar to that for Newtonian fluids; however, the capillary number governing the instability now contains the yield stress. Experiments using gels and foams reveal very branched fingers in the gel. The results are in excellent agreement with theory for the gel, with, in addition, a crossover from yield stress dominated to viscous behavior. The results for foams are very different due to the existence of wall slip.

Journal Article↗
PubMed2000

[Erythema palmare hereditarium ("red palms")].

We report a woman with erythema palmare hereditarium, an anomaly not documented so far in the German literature. It is characterized by a bright erythema of the palms, usually persistent since birth. It is transmitted in an autosomal-recessive mode and has a benign course. In our patient it was possible to trace the palmar erythema over three generations.

Adult↗
PubMed2000

Initiation of smooth-pursuit eye movements to first-order and second-order motion stimuli.

Since normal human subjects can perform smooth-pursuit eye movements only in the presence of a moving target, the occurrence of these eye movements represents an ideal behavioural probe to monitor the successful processing of visual motion. It has been shown previously that subjects can execute smooth-pursuit eye movements to targets defined by luminance and colour, the first-order stimulus attributes, as well as to targets defined by derived, second-order stimulus attributes such as contrast, flicker or motion. In contrast to these earlier experiments focusing on steady-state pursuit, the present study addressed the course of pre-saccadic pursuit initiation (less than 100 ms), as this early time period is thought to represent open-loop pursuit, i.e. the eye movements are exclusively driven by visual inputs proceeding the onset of the eye movement itself. Eye movements of five human subjects tracking first- and second-order motion stimuli had been measured. The analysis of the obtained eye traces revealed that smooth-pursuit eye movements could be initiated to first-order as well as second-order motion stimuli, even before the execution of the first initial saccade. In contrast to steady-state pursuit, the initiation of pursuit was not exclusively determined by the movement of the target, but rather due to an interaction between dominant first-order and less-weighted second-order motion components. Based on our results, two conclusions may be drawn: first and specific for initiation of smooth-pursuit eye movements, we present evidence supporting the notion that initiation of pursuit reflects integration of all available visual motion information. Second and more general, our results further support the hypothesis that the visual system consists of more than one mechanism for the extraction of first-order and second-order motion.

Adult↗
PubMed2000

Early postoperative transcranial sonography (TCS), CT, and MRI after resection of high grade glioma: evaluation of residual tumour and its influence on prognosis.

PURPOSE: In this prospective study the results of multimodal postoperative neuro-imaging were related to the survival of patients with high grade gliomas. METHODS: All 73 patients included underwent microsurgical tumour resection and had postoperative CT and transcranial sonography (TCS) examinations. In addition, 35 of the 73 patients received an early postoperative MRI. Patients were followed up for at least one year. FINDINGS: At the end of the 7 year study period 56 patients had died. The median survival time was 371 days. Survival rate was significantly higher in patients with anaplastic astrocytomas and inpatients displaying complete tumour resection on MRI (log-rank-test, p < 0.05) or a small postoperative residual tumour bulk on TCS (log-rank-test, p < 0.05). Cox proportional hazards model identified histological tumour grade, postoperative Karnofsky index, complete resection based on MRI and small postoperative residual tumour mass on TCS as independent predictors of survival. INTERPRETATION: This study demonstrates that early postoperative neuro-imaging has prognostic implications for the survival of patients with high grade gliomas. According to our results postoperative imaging with MRI and TCS is a valuable prognostic with regard to patient survival and should therefore be implemented in postoperative follow-up. It also helps to evaluate the efficacy of adjuvant therapy.

Adolescent↗
PubMed2000

Predictive value of S-100beta and neuron-specific enolase serum levels for adverse neurologic outcome after cardiac surgery.

OBJECTIVES: The aim of this study was to evaluate the time course of S-100beta and neuron-specific enolase serum levels after cardiac surgery and their clinical relevance in predicting postoperative adverse neurologic outcomes; the 2 proteins are only released in peripheral blood in association with nervous system lesions. METHODS: We neurologically assessed 190 consecutive patients undergoing elective cardiac operations for coronary artery bypass (n = 147), valve replacement (n = 29), or both (n = 14), before as well as after the operation. Postoperative outcome was classified as type I (uncomplicated), type II (confusion, agitation, disorientation, or epileptic seizures), or type III (stroke, stupor, or coma). Levels of S-100beta and neuron-specific enolase were evaluated in venous blood samples drawn preoperatively and then daily in the first 5 postoperative days. RESULTS: Levels of S-100beta and neuron-specific enolase differed significantly among the 3 groups (type III > type II > type I) throughout the postoperative period and had a diagnostic specificity and specificity of 89% and 79%, respectively, in identifying patients with type III outcome. S-100beta (but not neuron-specific enolase) levels were identified as significant independent predictors for type II and III outcomes (odds ratio 16.2, P <.0004). The same was true for duration of cardiopulmonary bypass (odds ratio 1.02, P <.006). CONCLUSIONS: Serum levels of S-100beta are reliable markers for adverse neurologic outcomes after cardiac surgery.

Biomarkers↗
PubMed2000

Differentiation between true microembolic signals and artefacts using an arbitrary sample volume.

We evaluated a new discrimination technique between microemboli (MES) and artefact signals. Monitoring was performed over the middle cerebral artery (55 mm) and the brain parenchyma (29 mm). Intensity changes were expressed as percent of change compared to the value measured in the proximal depth. The cut-off value providing the highest sensitivity and specificity in the differentiation was evaluated using 250 MES and 250 artefact signals, and subsequently analysed in the first part of the study. Intensity values derived from the distal depth were subsequently evaluated in 10 patients undergoing cardiac surgery and 45 patients with potential arterial or cardioembolic source. Intensity changes of 87% (84%-90%) and -58% (-71%-(-48%)) were measured in the initial 500 signals for MES and artefact signals, respectively. The best intensity cut-off value was calculated at 27%. This value was subsequently applied to a total of 1858 MES and 1958 artefacts, resulting to sensitivity and specificity of 96% and 98%, respectively. The proposed technique provided adequate results, warranting further evaluation.

Artifacts↗
PubMed2000

Prostate cryoablation without an insertion kit using direct transperineal placement of ultrathin freezing probes.

A modified technique for prostate cryoablation is described. Prostate cryoablation was performed with a gas-based cryomachine using multiple 17-gauge probes. The 17-gauge probes were inserted via a transperineal route directly into the prostate without using an insertion kit. Probe insertion and positioning are simplified, and operative time is reduced. The perineum is less crowded with devices and tubes. Miniaturizing the cryoprobes and their tubing is feasible. The smaller diameter enables direct insertion without an insertion kit. The surgical result does not seem to be inferior to that of conventional ablation, and penetrating trauma to the prostate is minimal. To the best of our knowledge, this is the first report of transperineal prostate cryoablation performed without an insertion kit.

Cryosurgery↗
PubMed2000

Elevated prostate specific antigen serum levels after intravesical instillation of bacillus Calmette-Guerin.

PURPOSE: We determined whether intravesical bacillus Calmette-Guerin (BCG) instillation is associated with elevated prostate specific antigen (PSA). MATERIALS AND METHODS: We treated 36 consecutive patients with bladder cancer with a 6-week course of BCG, followed by cystoscopy at 6 weeks. Blood samples for PSA determination were obtained before each BCG instillation and at cystoscopy with each patient also serving as a control. PSA elevation was defined as 2-fold the baseline level in at least 2 specimens and any PSA level greater than 4 ng./ml. was considered clinically significant. Digital rectal examination was done to identify firm nodules and prostate size. The prostate was examined histologically by transrectal ultrasound guided biopsy or after radical cystectomy. RESULTS: We observed elevated PSA in 27 men (75%) during BCG treatment, of whom 15 (41.6%) had a clinically significant elevation. Overall average PSA increased from 1.3 ng./ml. before BCG instillation to 3.8 during treatment (range 0.1 to 21.5, p <0.0001). In those with a clinically significant elevation average PSA increased from 2.31 ng./ml. at baseline to 6.97 during treatment (p <0.0001) and returned to 3.86 ng./ml. 3 months after treatment. Palpation demonstrated prostatic findings in 10 patients, including firm nodules in 7, while there was significantly elevated PSA in 5 with firm nodules and 2 with diffuse prostatic enlargement. Histological examination of the prostate in 10 patients was diagnostic for granulomatous prostatitis, nonspecific inflammation and benign prostatic hyperplasia in 3, 3 and 4, respectively, of whom none had prostate cancer. CONCLUSIONS: Intravesical BCG therapy is associated with significantly elevated PSA in up to 40% of cases. This effect is self-limited and PSA reverts to normal in 3 months. Therefore, we suggest that prostate biopsy be withheld in such patients and PSA monitored.

Adjuvants, Immunologic↗
PubMed2000

Predicting CAP in patients with intermediate PSA using modified PSA indices.

OBJECTIVES: To test a new PSA index: peripheral zone fraction PSA (PSA-PZ) and evaluate its' predictive value in patients with intermediate PSA. METHODS: Fifty seven of 273 patients with serum PSA 4-10 ng/ml had CAP (21%). Total prostate volume and transition zone volume were calculated. Different cut-off points were used to calculate specificity, sensitivity, efficacy, positive and negative predictive values for PSA, PSAD, PSA-TZ and PSA-PZ (PSA-PZ= serum PSA((Total gland volume-TZ volume)/(Total gland volume)) RESULTS: The distribution of PSA-PZ is presented. PSA-PZ is shown to be effective in DRE negative patients with serum PSA 4-10 ng/ml. For patients with PSA-PZ (1.5 ng/ml the biopsy may be spared with no cancer being missed. CONCLUSIONS: The mathematical formula for PSA-PZ is straightforward and easy to use. Its application is convenient in the clinical setting. We suggest the use of PSA-PZ mainly in DRE negative patients having large glands and serum PSA between 4-10.

Aged↗
PubMed1999

Mitochondrial 3243 A-->G mutation (MELAS mutation) associated with painful muscle stiffness.

The mitochondrial mutation A-->G at nucleotide position 3243 is associated with mitochondrial myopathy, encephalopathy, lactic acidosis and stroke-like episodes (MELAS) and other mitochondrial encephalomyopathies. We found this mutation in a 61-year-old patient who developed at the age of 54 a myopathy with painful muscle stiffness as the predominant symptom. Additionally hypacusis, a mild hemisensory syndrome and impaired glucose tolerance were present. Muscle histopathology showed few ragged red fibers. The mutation was detected heteroplasmatically in DNA from muscle and blood. So far painful muscle stiffness has not been a known phenotype of the 3243 mutation.

DNA, Mitochondrial↗
PubMed1999

Long-term follow-up of early treatment of unilateral forced posterior cross-bite. Orofacial status.

Twenty-nine subjects, 20 years old on average and all treated at 4 years of age for unilateral forced posterior dento-alveolar cross-bite by grinding or by expansion of the upper dental arch, were clinically examined to evaluate the long-term effects of their treatment. The frequency of successful treatment-indicated as stable correction of the cross-bite-by means of only 1 treatment sequence was 59%; by grinding, 57%; and by expansion, 60%. The 18 subjects that had only been treated at the age of 4 years formed the 'early group' in our study. Eleven of our subjects had been retreated later in the mixed or permanent dentition because of a relapse of the unilateral forced posterior cross-bite and formed the 'late group'. A significantly higher frequency of mouth breathing, breathing obstacles, and snoring was found in this group. According to our clinical investigation, 2 of the subjects in our cohort still had a unilateral forced posterior cross-bite. Our findings regarding masticatory performance, bite force, and endurance showed no significant differences between the initial cross-bite and the healthy sides or between the early and the late group subjects, which showed that the masticatory function of the treated subjects was symmetrical. Grinding and expansion treatments seem to display similar success rates in the long-term regarding correction of unilateral posterior forced cross-bite.

Adult↗
PubMed1999

Postoperative neuroimaging of high-grade gliomas: comparison of transcranial sonography, magnetic resonance imaging, and computed tomography.

BACKGROUND: A precise and comprehensive knowledge of tumor burden and its extent and growth pattern in the pre- and postsurgical states is required to optimize tumor therapy and to determine treatment success and failure. This prospective study compares the diagnostic potential of computed tomography (CT), magnetic resonance imaging (MRI), and transcranial sonography (TCS) in the postoperative follow-up of brain tumors. METHOD: Twenty-six patients with high-grade gliomas were included in the study. After tumor debulking, a total of 31 biopsy specimens were obtained from the resection margin in 21 patients and histological findings were compared with the findings of early postoperative TCS, CT, and MRI. Findings indicating residual tumor tissue were nonlinear contrast enhancement at the resection site revealed by CT or MRI or hyperechogenic lesions revealed by TCS. Follow-up examinations using all three imaging techniques were performed every 3 months. The end points of the follow-up were tumor recurrence as defined by CT and MRI, death, or severe clinical deterioration. RESULTS: On the basis of the above criteria, TCS identified residual tumor more often than did CT or MRI. In the group of 19 patients with histologically proven tumor remnants, residual tumor tissue was identified by TCS in all patients, whereas MRI and CT failed to show contrast enhancement in three and eight patients, respectively. However, the results of the TCS were false positive for one patient because of hemorrhage into the resection site. The average time to identification of tumor regrowth was 27 weeks using TCS, 29 weeks using CT, and 33 weeks using MRI. Only the differences between TCS and MRI reached statistical significance. For one patient, multicentric tumor recurrence was not detected using TCS. CONCLUSION: TCS may complement CT and MRI in the postoperative follow-up of patients with high-grade gliomas. Because none of these modalities alone is both sensitive and specific, an integrated analysis of imaging findings is recommended.

Adult↗
PubMed1999

Effects of conditioning horses with lactate-guided exercise on muscle glycogen content.

The effects of 3 different conditioning programmes on muscle glycogen concentration in horses were examined. Speed of exercise was selected according to the blood lactate values for each horse derived from a standardised exercise test before beginning a conditioning programme. Six 2-year-old Haflinger stallions were assigned randomly to one of 3 conditioning programmes according to a 6 x 3 latin square design: 45 min at their individual v1.5 or v2.5 and 25 min at v4. Each conditioning programme lasted 6 weeks (21 exercise sessions), followed by 5 weeks without conditioning (resting period). All exercise was carried out on a treadmill inclined at 17%. Muscle biopsies were taken 5 times from the gluteus medius muscle at 2 cm and 6 cm depth: before the start and in the middle of the conditioning period, then at Days 2, 9 and 35 after the last exercise session. It was found that glycogen concentration was not affected by conditioning until 9 days after finishing conditioning at v1.5 and v2.5 for 45 min (P < 0.05). By this time glycogen concentration in the muscle samples taken at 6 cm depth increased by 47 and 48%, respectively, and remained elevated until the end of the resting period. It was concluded that conditioning at lower intensity and for longer duration seemed to increase glycogen stores in the muscle while faster intensity but shorter duration exercise did not. To increase the likelihood of measuring effects of conditioning programmes on muscle variables, sampling should be done at different depths of a muscle and at several days after finishing a conditioning programme.

Animals↗
PubMed1999

Diagnostic yield of a 1-MHz transducer in evaluation of the basal cerebral arteries.

The authors examined the efficacy of a 1-MHz transducer in routine ultrasound monitoring. Fifty outpatients (34 women, 16 men; mean age, 65 +/- 2) with inadequate temporal bone window for examination with 2-MHz transducers were re-examined with a 1-MHz transducer. Additionally, 50 controls (34 men, 16 women; mean age 49 +/- 2) with adequate temporal bone window were examined with both the 1- and 2-MHz transducers. Signal quality was classified as good (GQ), adequate (AQ), or poor (PQ). Finally, 30 normal controls were examined with both transducers under standardized conditions, to evaluate potential differences in velocity measurements. A total of 90 temporal windows were lacking in the 50 patients. Use of the 1-MHz transducer resulted in identification of the middle cerebral artery in 68 cases (76%; PQ, n = 13; AQ, n = 29; GQ, n = 26), the anterior cerebral artery in 51 cases (57%; PQ, n = 23; AQ, n = 17; GQ, n = 11) and the posterior cerebral artery in 46 cases (51%; PQ, n = 12; AQ, n = 21; GQ, n = 13). Examination was feasible with both transducers in the 50 controls, with minimal differences in signal quality between the two transducers. Correlation between velocity values acquired with the 1- and 2-MHz transducers was significant for all vessels examined. Best values were measured for the middle cerebral artery, followed by the anterior cerebral artery and posterior cerebral artery. The authors conclude that the use of the 1-MHz transducer increases the yield of transcranial Doppler sonography.

Aged↗
PubMed1999

Ureteral catheterization and patient mobilization: is bed restriction mandatory?

OBJECTIVES: We determined whether patient mobilization influences ureteral catheter position in the collecting system. METHODS: 26 consecutive patients (28 renal units) who underwent ureteral catheterization for the purpose of retrograde pyelography or the relief of ureteral obstruction, were included. The position of the catheter's tip within the collecting system and versus the vertebrae was determined for each patient in the baseline supine position; standing upright, and supine again after walking a distance of 5 m. Catheteral displacement was determined by comparing its position in the upright and supine post-walking postures to its original position with the patient supine before any maneuver was undertaken. RESULTS: Assuming the upright position caused an average downward displacement of ureteral catheters by 7.8 mm (ranges 36 mm downward to 14 mm upward displacements, p = 0.0014). In the supine posture following a 5-meter walk, the catheters were downward displaced by 0. 36 mm on average (ranges 12 mm downward and 30 mm upward displacements p = 0.8). None of the ureteral catheters migrated below the uretero-pelvic junction during any phase of the above maneuvers. CONCLUSION: The position of ureteral catheters remains unchanged within the collecting system when patients stand or walk for 5 m. Therefore, mandatory bed restriction is not justified in patients with ureteral catheters.

Adolescent↗