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Biomedical subjects

C Werner

Publications and source records attributed to C Werner.

At least 73 records · Page 4Linked to original sources
PubMed2001

Effects of remifentanil/propofol in comparison with isoflurane on dynamic cerebrovascular autoregulation in humans.

BACKGROUND: This study investigates the effects of remifentanil and propofol in comparison to isoflurane on dynamic cerebrovascular autoregulation in humans. METHODS: In 16 awake patients dynamic cerebrovascular autoregulation was measured using transcranial Doppler sonography (TCD). Thereafter patients were intubated, ventilated with O2/air (FiO2=0.33) and randomly assigned to one of the following anesthetic protocols: group 1 (n=8): 0.5 microg x kg(-1) x min(-1) remifentanil combined with a propofol-target plasma concentration of 1.5 microg x ml(-1) group 2 (n=8): 1.8 % isoflurane (1.5 MAC). Following 20 min of equilibration the autoregulatory challenge was repeated. Arterial blood gases and body temperature were maintained constant over time. STATISTICS: Mann-Whitney U-test and Wilcoxon signed-rank test. RESULTS: Dynamic autoregulation was intact in all patients prior to induction of anesthesia expressed by an autoregulatory index (ARI) of 5.4+/-1.21 (mean+/-SD, group 1) and 5.9+/-0.98 (mean+/-SD, group 2). With remifentanil/propofol anesthesia dynamic autoregulation was similar to the awake state (group 1: ARI=4.9+/-0.88). In contrast, autoregulatory response was delayed with 1.5 MAC isoflurane (group 2, ARI=2.1+/-0.92) (P<0.05). CONCLUSION: These data show that dynamic cerebrovascular autoregulation is maintained with remifentanil-based total intravenous anesthesia. This is consistent with the view that narcotics (and hypnotics) do not alter the physiologic cerebrovascular responses to changes in MAP. In contrast, 1.5 MAC isoflurane delays cerebrovascular autoregulation compared to the awake state.

Adult↗
PubMed2001

Influence of walking speed on lower limb muscle activity and energy consumption during treadmill walking of hemiparetic patients.

OBJECTIVE: To identify the relationship between treadmill speed and energy consumption and lower limb muscle activity in ambulatory hemiparetic patients. DESIGN: Experimental cohort. SETTING: Inpatient rehabilitation clinic. PARTICIPANTS: Twenty-four ambulatory hemiparetic subjects. INTERVENTION: Subjects walked harness-secured on the treadmill with no body-weight support at self-reported (V SAS), slow (V SAS - 25%), and fast (V SAS + 25%) speed. MAIN OUTCOME MEASURES: Assessment of basic, limb-dependent cycle parameters, lower limb muscle activity, and energy consumption. RESULTS: Cadence (r = .75), stride length (r = .78), relative double-support duration (r = .31), mean muscle activity of the paretic tibialis anterior (r = .12), gastrocnemius (r = .37), vastus lateralis (r =.19), rectus femoris (r = .31), and biceps femoris (r = .45) muscles, as well as heart rate (r = .54), correlated positively with treadmill speed. Mean maximum heart rate was 131 beats/min. Energy (r = -.67) and cardiac cost (r = -.55) correlated negatively with gait speed (ie, patients walked more efficiently at faster velocities). The qualitative muscle activation pattern analysis revealed earlier (more normal) onset of activation of gastrocnemius, vastus lateralis, biceps femoris, and gluteus medius. CONCLUSIONS: Patients should try to walk fast on the treadmill, thereby facilitating relevant weight-bearing muscles and improving gait efficiency.

Aged↗
PubMed2001

[Effect of intraocular lens design on posterior capsule opacification: an in-vitro model].

BACKGROUND: The development of posterior capsule opacification (PCO) is one of the commonest complications of modern cataract surgery. The various designs of intraocular lenses (IOL) seem to exert a barrier effect on the proliferation and migration of lens epithelial cells and the following development of PCO. METHODS: We set up a cell culture model (advanced 3D capsular bag model) and investigated six differently designed IOL made of different materials as to their effect on cell proliferation. Proliferation and migration of the cells were analysed and documented over a period of 28 days. A cell viability test using the LIVE/DEAD kit (Molecular Probes) was carried out at the end of the investigation. RESULTS: In all tests, lens epithelial cells adhered to and migrated onto the capsular bag. During the culture period, lens epithelial cells migrated only to the optical rim of two of the implanted IOL. On the other four, lens epithelial cells migrated further and covered the whole optical area of the IOL. CONCLUSIONS: Certain lens designs seem to have a reducing effect on the development of PCO. Our advanced in vitro capsular bag model is a suitable cell culture model for the investigation of the reducing effect of various IOL on the development of PCO.

Cataract↗
PubMed2001

Serial ultrasonography, hormonal profile and antisperm antibody response after testicular sperm aspiration.

BACKGROUND: In many fertility centres, intracytoplasmic sperm injection (ICSI) with epididymal or testicular spermatozoa is a routine treatment for men with azoospermia. In this prospective study, the physiological consequences after testicular sperm aspiration (TESA), using suction and a 19 gauge needle, were evaluated. METHODS AND RESULTS: Thirty-five consecutive men with azoospermia underwent TESA. Testicular ultrasonography with Doppler flow imaging was performed and testicular volumes were evaluated pre-operatively and 3 months after aspiration. If focal testicular lesions were found, further examinations were performed 6 and 9 months after TESA. Serum FSH, testosterone and antisperm antibodies (ASA) were analysed. Focal testicular lesions were seen in four out of 61 testes (6.6%) at the 3 month investigation point. Three lesions were resolved after 6 months and all after 9 months. Testicular echogenicity remained unchanged in 50 cases (82%) 3 months after TESA. Four men (11.4%) reported severe subjective discomfort post-operatively, but only one had a medical consultation where an intratesticular haematoma was diagnosed. There were no significant changes in FSH and testosterone after surgery and testicular volumes were similar after 3 months. There were three borderline cases of ASA in serum, but none was classified as ASA-positive. CONCLUSIONS: The puncture method of testicular sperm aspiration seems to be a safe method for sperm retrieval, with minimal physiological consequences.

Adult↗
PubMed2001

Intraoperative monitoring in neuroanesthesia: a national comparison between two surveys in Germany in 1991 and 1997. Scientific Neuroanesthesia Research Group of the German Society of Anesthesia and Intensive Care Medicine.

UNLABELLED: Two surveys initiated by the Neuroanesthesia Research Group of the German Society of Anesthesia and Intensive Care Medicine examined the practice of intraoperative monitoring during intracranial procedures in Germany in 1991 and 1997. Questionnaires were mailed to departments that were registered members of the German Society of Anesthesia and Intensive Care Medicine and that provided neuroanesthesia service on a routine basis in 1991. In 1997, the survey was repeated in the 1991 respondents. In 1991, 68 departments and in 1997, 44 departments returned completed questionnaires, indicating a response rate of 87% for 1991 and of 65% for 1997. Compared with 1991, the standards for monitoring, such as surveillance of oxygenation, ventilation, circulation, and body temperature, were universally applied in adult and pediatric patients in 1997. Overall, there was a 20% increase in neuromuscular blockade monitoring and in the use of electroencephalography and evoked potentials in 1997 compared with 1991. Further brain-specific monitoring was rarely provided in 1997. Overall, jugular venous oximetry was used in 20% and transcranial Doppler ultrasonography in 15% of responding hospitals. To detect venous air embolism in sitting patients, 75% of all responding hospitals used precordial Doppler ultrasonography in both years, whereas transesophageal echocardiography was more often used in 1997 (38%) as compared with 1991 (17%). IMPLICATIONS: Standards of anesthetic monitoring were surveyed in neuroanesthesia in Germany in 1991 and 1997. Central nervous system monitoring was not the standard of practice.

Adult↗
PubMed2001

Effects of xenon on cerebral blood flow and cerebral glucose utilization in rats.

BACKGROUND: The effects of xenon inhalation on mean and local cerebral blood flow (CBF) and mean and local cerebral glucose utilization (CGU) were investigated using iodo-[14C]antipyrine and [14C]deoxyglucose autoradiography. METHODS: Rats were randomly assigned to the following groups: conscious controls (n = 12); 30% (n = 12) or 70% xenon (n = 12) for 45 min for the measurement of local CBF and CGU; or 70% xenon for 2 min (n = 6) or 5 min (n = 6) for the measurement of local CBF only. RESULTS: Compared with conscious controls, steady state inhalation of 30 or 70% xenon did not result in changes of either local or mean CBF. However, mean CBF increased by 48 and 37% after 2 and 5 min of 70% xenon short inhalation, which was entirely caused by an increased local CBF in cortical brain regions. Mean CGU determined during steady state 30 or 70% xenon inhalation remained unchanged, although local CGU decreased in 7 (30% xenon) and 18 (70% xenon) of the 40 examined brain regions. The correlation between CBF and CGU in 40 local brain structures was maintained during steady state inhalation of both 30 and 70% xenon inhalation, although at an increased slope at 70% xenon. CONCLUSION: Effects of 70% xenon inhalation on CBF in rats are time-dependent. During steady state xenon inhalation (45 min), mean values of CBF and CGU do not differ from control values, and the relation of regional CBF to CGU is maintained, although reset at a higher level.

Anesthetics, Inhalation↗
PubMed2001

Effects of carbon dioxide pneumoperitoneum on cerebral hemodynamics in pigs.

Previous studies have shown that laparoscopic interventions are associated with increases in intracranial pressure. However, the consequences on cerebral blood flow (CBF) are unknown. This study investigates the effects of carbon dioxide (CO2) pneumoperitoneum on CBF in pigs. Ten pigs (weight, 20-26 kg) were anesthetized with 1.4% isoflurane and fentanyl (1 microg/kg per minute). Mechanical ventilation (fraction of inspired oxygen = 0.4) was set to maintain normocapnia (end-tidal CO2 tension = 35 mm Hg). Arterial and central venous catheters were placed for measurement of mean arterial blood pressure and central venous pressure. Bilateral internal carotid artery blood flow was measured using two transient time flow probes placed around both carotid arteries (with ligated external carotid arteries). Cortical and subcortical cerebral blood flow was measured using laser Doppler flowmetry. Sagittal sinus pressure was measured via a superior sagittal sinus catheter. After baseline measurements, the peritoneal cavity of the animals was insufflated with CO2 to achieve an intraabdominal pressure of 12-mm Hg. After 10 minutes of stable CO2, pneumoperitoneum measurements were repeated. Increases in central venous pressure (6.3 +/- 2.1 to 11.1 +/- 3.0 mm Hg) and sagittal sinus pressure (8.0 +/- 2.8 to 11.9 +/- 3.0 mm Hg) were noted during CO2 pneumoperitoneum (P < .05). Bilateral internal carotid artery blood flow (46.0 +/- 7.4 vs 47.7 +/- 7.1 mL/100g per minute), cortical CBF (263 +/- 115 vs 259 +/- 158 tissue perfusion units), and subcortical CBF (131 +/- 145 vs 133 +/- 149 tissue perfusion units) did not change during CO2 pneumoperitoneum. The current data show that CO2 pneumoperitoneum increases sagittal sinus pressure without changing CBF. Increases in sagittal sinus pressure are likely related to decreases in cerebral venous drainage caused by increases in intraabdominal pressure.

Abdomen↗
PubMed2001

Protein adsorption on preadsorbed polyampholytic monolayers.

The adsorption behaviour of five different globular proteins on pure silicon substrates and on preadsorbed polyampholytic monolayers has been investigated as a function of protein concentration. The prelayers were prepared by adsorption of the ampholytic diblock copolymerpoly(methacrylic acid)-block-poly((dimethylamino)ethyl methacrylate) (PMAA-b-PDMAEMA). This polyampholyte adsorbs in densely packed micelles directly from aqueous solution. Ellipsometry was used to determine the amount of adsorbed polyampholyte and protein. While ATR-IR spectroscopy gives information about the adsorption and desorption behaviour of the preadsorbed polyampholytic layer, the lateral structures of the dried films were investigated by scanning force microscopy (SFM). The amount of protein adsorbed was found to be strongly influenced by the preadsorbed polyampholyte compared to the adsorption on the pure silicon substrates. No displacement of the polyampholyte by the proteins was detected. In most cases the protein adsorption was reduced by the preadsorbed polyampholytic layer. The observed trends are explained by the change in electrostatic and hydrophilic characteristics of the substrates. Furthermore, the entropy of adsorption has to be taken into account.

Adsorption↗
PubMed2001

An electromechanical gait trainer for restoration of gait in hemiparetic stroke patients: preliminary results.

Modern concepts of gait rehabilitation after stroke favor a task-specific repetitive approach. In practice, the required physical effort of the therapists limits the realization of this approach. Therefore, a mechanized gait trainer enabling nonambulatory patients to have the repetitive practice of a gait-like movement without overstraining therapists was constructed. This preliminary study investigated whether an additional 4-week daily therapy on the gait trainer could improve gait ability in 14 chronic wheelchair-bound hemiparetic subjects. The 4 weeks of physiotherapy and gait-trainer therapy resulted in a relevant improvement of gait ability in all subjects. Velocity, cadence, and stride length improved significantly (p < 0.01). The kinesiologic electromyogram of selected lower-limb muscles revealed a more physiologic pattern. The confounding influence of spontaneous recovery, the lack of a control group, and the double amount of therapy limit the clinical relevance of this study. Nevertheless, the gait trainer seems feasible as an adjunctive tool in gait rehabilitation after stroke; further studies are needed.

Adult↗
PubMed2001

Botulinum toxin A treatment of adult upper and lower limb spasticity.

This article discusses the treatment of spasticity with botulinum toxin A as a new approach in the neurological rehabilitation of patients after stroke. Clinical studies have been reviewed to provide information about target groups, technical aspects and the advantages and disadvantages of treating spasticity with botulinum toxin A. Open and controlled studies showed that the intramuscular injection of Dysport 500 to 1,500U or Botox 100 to 300U could reversibly relieve upper limb flexor and lower limb extensor spasticity. A reduced muscle tone, pain relief, better hand hygiene and improved walking function were the main benefits. Patients tolerated the treatment well. Activity or, if not possible, electrical stimulation of the injected muscles may enhance the effectiveness of the costly toxin. Serial casting is another option. With respect to the action of botulinum toxin A, it is suggested that the effect of the toxin could be mediated by paresis of both the extrafusal and intrafusal muscle fibres, thereby altering the afferent discharge in the muscle.

Adult↗
PubMed2000

An Improved Method of Determining the zeta-Potential and Surface Conductance.

In the classical "slope-intercept" method of determining the zeta potential and the surface conductance, the relationship between DeltaP and E(s) is measured experimentally at a number of different channel sizes (e.g., the height of a slit channel, h). The parameter (epsilon(r)epsilon(0)DeltaP/µE(s)lambda(b)) is then plotted as a function of 1/h and linear regression is performed. The y-intercept of the regressed line is then related to the zeta-potential and its slope to the surface conductance. However, in this classical method, the electrical double layer effect or the electrokinetic effects on the liquid flow are not considered. Consequently, this technique is valid or accurate only when the following conditions are met: (1) relatively large channels are used; (2) the electrical double layer is sufficiently thin; and (3) the streaming potential is sufficiently small that the electroosmotic body force on the mobile ions in the double layer region can be ignored. In this paper a more general or improved slope-intercept method is developed to account for cases where the above three conditions are not met. Additionally a general least-squares analysis is described which accounts for uncertainty in the measured channel height as well as unequal variance in the streaming potential measurements. In this paper, both the classical and the improved slope-intercept techniques have been applied to streaming potential data measured with slit glass channels, ranging in height from 3 µm to 66 µm, for several aqueous electrolyte solutions. The comparison shows that the classical method will always overestimate both the zeta-potential and the surface conductance. Significant errors will occur when the classical method is applied to systems with small channel heights and low ionic concentrations. Furthermore, it is demonstrated that traditional regression techniques where the uncertainty is confined only to the dependent variable and each measurement is given equal weight may produce physically inconsistent results. Copyright 2000 Academic Press.

Journal Article↗
PubMed2000

Immobilization of PEO-PPO-PEO triblock copolymers on PTFE-like fluorocarbon surfaces.

Poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) (PEO-PPO-PEO) triblock copolymers were immobilized on thin fluorocarbon films with a structure very similar to poly(tetrafluoroethylene) (PTFE) using a microwave argon plasma. Fourier transform infrared attenuated total reflection and spectroscopic ellipsometry were used to study this process. After investigating the decomposition behavior of PEO-PPO-PEO triblock copolymers, we found that under appropriate plasma conditions, this material can be immobilized on a PTFE-like surface, while its general structure is preserved.

Biocompatible Materials↗
PubMed2000

Antimicrobial activities of secondary metabolites produced by endophytic fungi from Spondias mombin.

We performed a search for bioactive compounds produced by fungal endophytes from Spondias mombin (Anacardiaceae). Culture broth extracts of Guignardia sp., Phomopsis sp. and Pestalotiopsis guepinii were separated by chromatographic methods and tested for biological activities. The crude extracts of these endophytes were tested against fourteen organisms, including actinomycetes, Gram-negative and Gram-positive bacteria, yeast, and filamentous fungi. All fungal extracts inhibited actinomycete growth. Guignardia sp. was also active against Escherichia coli, Staphylococcus aureus, Saccharomyces cerevisiae, Geotrichum sp., and Penicillium canadensis. Culture extracts of P. guepinii were active against S. cerevisae, while strains of Phomopsis sp. showed a pronounced antifungal effect against Cladosporium elatum, Mycotypha sp. and S. cerevisae.

Anti-Bacterial Agents↗
PubMed2000

High-dose S(+)-ketamine improves neurological outcome following incomplete cerebral ischemia in rats.

PURPOSE: To determine the effects of the non-competitive NMDA-receptor antagonist S(+)-ketamine on neurological outcome in a rat model of incomplete cerebral ischemia. METHODS: Thirty rats were anesthetized, intubated and mechanically ventilated with isoflurane, O2 30% and nitrous oxide 70%. Following surgery animals were randomly assigned to one of the following treatment groups: Rats in group 1 (n = 10,OFF control) received fentanyl (bolus: 10 microg x kg(-1) i.v.; infusion 25 microg x kg(-1) x h(-1)) and N2O 70% / O2. Rats in group 2 (n = 10) received O2 30% in air and low-dose S(+)-ketamine (infusion: 0.25 mg x kg(-1) x min(-1)). Rats in group 3 (n = 10) received O2 30% in air and high-dose S(+)-ketamine (infusion: 1.0 mg x kg(-1) min(-1)). Following 30 min equilibration period ischemia was induced by combined unilateral common carotid artery ligation and hemorrhagic hypotension to 35 mm Hg for 30 min. Plasma catecholamines were assayed before and at the end of ischemia. Neurological deficit was evaluated for three postischemic days. RESULTS: Neurological outcome was improved with high-dose S(+)-ketamine when compared to fentanyl / N2O -anesthetized controls (9 vs. 1 stroke related deaths, P<0.05). Increases in plasma catecholamine concentrations were higher in fentanyl / N2O -anesthetized (adrenaline baseline 105.5+/-92.1 pg x ml(-1), during ischemia 948+/-602.8 pg x ml(-1), P<0.05; noradrenaline baseline 407+/-120.2 pg x ml(-1), ischemia 1267+/-422.2 pg x ml(-1), P <0.05) than in high-dose S(+)-ketamine-treated animals (adrenaline baseline 71+/-79.5 pg x ml(-1), ischemia 237 +/-131.9; noradrenaline baseline 317.9+/-310.5 pg x ml(-1), ischemia 310.5+/-85.7 pg x ml(-1)). CONCLUSION: Neurological outcome is improved following incomplete cerebral ischemia with S(+)-ketamine. Decreases in neuronal injury may be related to suppression of sympathetic discharge.

Animals↗
PubMed2000

[The neuroprotective effect of the glutamate antagonist acamprosate following experimental cerebral ischemia. A study with the lipid peroxidase inhibitor u-101033e].

INTRODUCTION: This study investigates the effects of acamprosate, a glutamatergic modulator, and the lipid peroxidation inhibitor U-101033E on neurological outcome following incomplete cerebral ischemia and reperfusion in rats. MATERIAL AND METHODS: Twenty-seven male Sprague-Dawley rats were randomly assigned to one of the following treatment groups: 1 (n = 9, control, no drug treatment), 2 (n = 9, 2 x 200 mg/kg acamprosate i.p.), and 3 (n = 9, 2 x 0.3 mg/kg U-101033E i.v.). Background anesthesia was maintained using a combination of fentanyl and O2/N2O (FiO2 = 0.3). Ischemia was produced by combined unilateral common carotid artery ligation and hemorrhagic hypotension to a mean arterial blood pressure (MAP) of 35 mm Hg for 30 minutes. Functional neurological deficit was evaluated for the following 3 days after cerebral ischemia. RESULTS: At the third postischemic day, five control animals and five animals treated with U-101033E were dead for stroke-related reasons. Surviving animals presented severe neurological deficits. In contrast, acamprosate improved neurological outcome, with stroke-related death occurring in one animal only and a minor neurological deficit in the surviving rats. DISCUSSION: The present study demonstrates that acamprosate, in contrast to U-101033E, significantly reduces neurological deficits following transient hemispheric ischemia. The neuroprotective mechanisms of acamprosate may be related to its antiglutamatergic effect with consecutive reduction of transmembraneous Ca++ flux through NMDA-activated ion channels.

Acamprosate↗
PubMed2000

Bioluminescent most-probable-number monitoring of a genetically engineered bacterium during a long-term contained field release.

Pseudomonas fluorescens HK44 is a lux-based bioluminescent bioreporter capable of emitting light upon exposure to naphthalene, salicylate, and other substituted analogs. The bacterium was inoculated into intermediate-scale field lysimeters and population dynamics were monitored with time. Two methods were used to enumerate cell numbers in soil: a standard selective plating technique with colony hybridization verification and a modified lux-based most-probable-number (lux-MPN) assay based on the detection of bioluminescence. The lux-MPN assay was developed and evaluated as a possible supplement or replacement for the labor-intensive and time-consuming selective plating assay. Comparisons between selective plate counts and lux-MPN population estimates showed similar trends over the 2-year study, except that lux-MPN estimates were consistently less than selective plate counts. Verification of P. fluorescens HK44 genotype through colony hybridization techniques revealed that selective plating was actually overestimating HK44 populations and that lux-MPN values were more closely approximating true HK44 cell densities, except within the first few weeks after inoculation, when lux-MPN estimates underrepresented population densities. Thus, utilizing bioluminescence as a population monitoring tool for lux-based microorganisms was shown to be more effective and precise than standard selective plating techniques, and provided an accurate ecological analysis of P. fluorescens HK44 population dynamics over an extended period.

Colony Count, Microbial↗