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Biomedical subjects

C Hofer

Publications and source records attributed to C Hofer.

At least 19 recordsLinked to original sources
PubMed2001

Total intravenous anaesthesia in a patient with familial hypokalaemic periodic paralysis.

A 35-year-old woman with known familial hypokalaemic periodic paralysis received general anaesthesia for reduction of bilateral breast hyperplasia. Uncomplicated general anaesthesia was performed using a propofol target-controlled infusion, remifentanil infusion and bolus doses of mivacurium with neuromuscular function monitoring. Plasma potassium concentrations were controlled intermittently in the peri-operative period and supplemented to achieve normokalaemia. Despite continuous substitution, an episode of low plasma potassium concentration occurred during the recovery period; this was without any clinical signs of muscle paralysis or respiratory distress.

Adult↗
PubMed2001

Test bed with force-measuring crank for static and dynamic investigations on cycling by means of functional electrical stimulation.

Cycling by means of functional electrical stimulation (FES) is an attractive training method for individuals with paraplegia. The physiological benefits of FES are combined with the psychological incentive of independent locomotion. In addition, cycling has the advantage in that the generated muscle forces are converted into drive power with relatively high efficiency compared to other means of locomotion, e.g., walking. For the design of an appropriate cycling device and the development of optimal stimulation patterns, it has to be investigated how the geometry for FES cycling, influenced by individual parameters of the FES-generated drive torques and the magnitude of variations among subjects with paraplegia, can be optimized. This study shows the design of a freely adjustable test bed with additional motor drive which allows static and dynamic measurements of force components and drive torque at the crank. Furthermore, the influence of geometry and various individual parameters on FES pedaling can be tested for each subject individually. A pedal path realized by a three-bar linkage that was optimized according to preliminary simulations further increases leg cycling efficiency. Safety precautions avoid injuries in case of excessive forces, e.g., spasms. Test results illustrate the application of the test bed and measurement routines. A test series with four paraplegic test persons showed that the presented static and dynamic measurement routines allow to provide optimal stimulation patterns for individual paraplegic subjects. While pedaling with these optimal stimulation patterns only negligible negative active drive torques, due to active muscle forces, were applied to the crank and sufficient drive power was generated to power a cycle independently.

Adult↗
PubMed2001

Diagnosis and monitoring of urological tumors using positron emission tomography.

The purpose of this article was to critically review the diagnostic value of positron emission tomography (PET) in urological oncology. Urinary tract tumor assessment is hampered by the renal elimination of (18)F-fluorodeoxyglucose (FDG), the most commonly used PET radiopharmaceutical. PET imaging offers no significant benefits over conventional imaging modalities for renal cell and bladder carcinomas. As a result of the low metabolic activity of prostate cancer, PET does not differentiate adequately between adenoma and carcinoma, nor detect local recurrence after radical prostatectomy with sufficient sensitivity. However, lymph node staging with FDG-PET, specifically in bladder cancer, has been shown to have a potential clinical benefit. Further studies are required to determine the clinical value of retroperitoneal lymph node staging and recurrent disease detection in germ cell tumors. Finally, encouraging early results exist for the use of serial PET measurements to predict and assess therapy response to chemotherapy which may also be valuable in urological oncology.

Carcinoma, Renal Cell↗
PubMed2000

New ultradeformable drug carriers for potential transdermal application of interleukin-2 and interferon-alpha: theoretic and practical aspects.

Transfersomes (TFs) are highly deformable hydrophilic lipid vesicles that are able to penetrate the skin barrier spontaneously because of their characteristics. Transfersomes are able to transport noninvasively low- and high-molecular-weight molecules into the body. We describe the formulation and several biologic characteristics of interleukin-2 (IL-2)- and interferon-alpha (IFNalpha )-containing TFs. TFs contain natural phosphatidylcholine and sodium cholate. Recombinant human IL-2 and human hybrid IFNalpha were added to TFs and incubated for 24 hours at 4 degrees C. Immunotransfersomes were isolated from free IL-2 and IFNalpha by filtration (Centrisart, Sartorius). The biologic activity of immunotransfersomes was measured by a cytotoxic lymphoid line assay for IL-2 and by an A549-encephalomyocarditis virus assay for IFN; concentrations of proteins were determined by the enzyme-linked immunosorbent assay (ELISA). It was possible to incorporate a large amount of IL-2 and IFN in TFs (75-80%), and the incorporated IL-2, and IFN were biologically active. The increased lipid/protein ratio (90.9/1.0) led to a growing probability of association. We were thus able to show that IL-2 and IFN are trapped by transfersomes in a biologically active form and in sufficient concentrations for immunotherapy. In upcoming experiments these IL-2- and IFN-containing TFs will be used for a transdermal approach in the murine RENCA cell line model.

Administration, Cutaneous↗
PubMed2000

Value of free prostate-specific antigen (Hybritech Tandem-R) in symptomatic patients consulting the urologist.

INTRODUCTION: Prostate-specific antigen (PSA) is a widely used tumor marker in the detection and follow-up of adenocarcinoma of the prostate. Selection of candidates for prostate biopsies is hampered by the lack of specificity resulting in a large number of unnecessary biopsies. The intention of our study was to compare the percent free PSA (f-PSA; Hybritech Tandem-R) with total PSA and age-specific PSA reference values to evaluate the clinical benefit in detecting patients with prostate cancer (PC) in a selected group of patients consulting the urologist. The question was whether cutoff points are influenced by this selection of patients. METHODS: A total of 188 patients, 114 with benign prostate hyperplasia (BPH) and 74 with PC were selected. It is a selected group of patients consulting the urologist. Diagnosis was confirmed in the BPH and PC groups by either ultrasound-guided biopsy or transurethral resection of the prostate or suprapubic adenomectomy or cystoprostatectomy. Total PSA (t-PSA) and f-PSA of all patients were measured before any manipulation by Tandem-R assay for f-PSA and Tandem-E assay for t-PSA (Hybritech). Mean values of age, prostate volume, t-PSA, f-PSA, percent f-PSA were compared in patients with BPH and PC by Mann-Whitney U test. The sensitivity and specificity of t-PSA and age-specific PSA were compared to the sensitivities and specificities of different cutoff points of percent f-PSA. RESULTS: The mean value of t-PSA, f-PSA and percent f-PSA in patients with BPH (n = 114) and PC (n = 74) were statistically significantly different. At PSA levels between 4 and 10 ng/ml 19% of negative biopsies could be avoided by the use of percent f-PSA (cutoff point 25%). There was no additional benefit of age-specific PSA. At a PSA of <4 ng/ml 6 of 7 PCs could be diagnosed by percent f-PSA (cutoff point 25%), whereas only 1 patient would be diagnosed by age-specific PSA. CONCLUSION: Percent f-PSA seems to decrease the biopsy rate at PSA levels from 4 to 10 ng/ml without missing a relevant number of cancers and to increase the detection rate at PSA <4 ng/ml. Our data indicate that it might be necessary to choose high cutoff points (25%; Tandem-E and R assay, Hybritech) in a selected study population consulting the urologist with large glands and a high prevalence of disease. However, this situation is not comparable to testing of screening populations. No benefit of age-specific PSA could be observed in this study.

Aged↗
PubMed1999

Electromyogram-controlled functional electrical stimulation for treatment of the paralyzed upper extremity.

Spinal cord lesions at level C5 to C6 lead to loss of hand functions and lesions at C4 to additional deficits of arm functionality. The presented dual channel surface stimulator with dual channel electromyogram (EMG) measurement was developed to investigate control strategies for an EMG-controlled implantable stimulation system and serves in addition as a therapy device for patients with partial innervation but weak muscle force. Four different control strategies for stimulation amplitude are available. The amplitude can be preset manually or can follow the preprocessed EMG signals proportionally. The shoulder control program allows proportional control of both stimulation channels with one EMG channel while the second EMG channel serves as the channel selector. Finally, a special feedback training program triggers a stimulation burst when EMG activity is detected. During a 2 year patient study, 18 patients from 2 hospitals and 1 rehabilitation center performed the feedback training. Almost all patients obtained an improvement of functionality. Apart from muscle strengthening, the feedback effect led to an improvement of proprioception and supported relearning of motions. For the documentation of the training status, functional muscle test (British Medical Research Council) and measurements of power, angle, torque, muscle fatigue, and EMG were performed. Obviously, EMG triggered stimulation provides several advantages compared to conventional passive electrical stimulation.

Arm↗
PubMed1999

Personal computer supported eight channel surface stimulator for paraplegic walking: first results.

Today functional electrical stimulation (FES) is used among other treatments to restore hand and arm function, to restore mobility of the lower extremities, for phrenic pacing, and in cardiomyoplasty. Common to all FES applications is that they require careful setup of stimulation parameters. To improve these tasks, personal computer (PC) based software for stimulation parameter evaluation and data acquisition was written. First, the described software was used to mobilize paraplegic patients in conjunction with an 12C bus controlled 8 channel surface stimulator. Electrodes were placed on each leg on the m. quadriceps and m. gluteus for hip and knee extension and the peroneal nerve to elicit flexion reflex. The fourth channel was used to correspond to subjects' individual needs. The stimulation patterns for standing up, walking, and sitting down easily could be set up and optimized by adjusting up to 128 stimulation parameters in a task-specific way.

Electric Stimulation Therapy↗
PubMed1999

MYOSTIM-FES to prevent muscle atrophy in microgravity and bed rest: preliminary report.

Long-term flights in microgravity cause atrophy and morphological changes of skeletal muscles. Training with mechanical devices is insufficient regarding the required time to exercise and space for devices. The objective of this project is to develop a passive training method based on functional electrostimulation (FES) to preserve muscle mass and fiber composition with minimal impairment to the cosmonaut. For a pilot experiment on the MIR space station, a suitable 8 channel FES device was developed. It consists of electrode trousers that carry surface electrodes and cables, 2 interconnected 4 channel stimulators, and a laptop personal computer (PC) for stimulator programming and processing compliance data. An automatic extensive training of 4 muscle groups of the lower extremities is performed for 6 h/day, with 1 s on and 2 s off tetanic contractions at 20-30% of maximum tetanic muscle force. The synchronous activation of antagonists of the thigh and lower leg prevents uncoordinated movements.

Bed Rest↗
PubMed1999

Standing up with denervated muscles in humans using functional electrical stimulation.

The use of electrical stimulation for denervated muscles is still considered to be a controversial issue by many rehabilitation facilities and medical professionals because prior clinical experience has shown that treating denervated muscle tissue using exponential current over a long time period constitutes an impossible task. Despite this fact, we managed to evoke tetanic contractions in denervated muscle using a long duration stimulation with anatomically shaped electrodes and sufficiently high amplitudes. The pulse amplitudes, which were being used for this purpose, exceeded by far the MED-GV and EC regulations (300 mJ/impulse). For this reason, an application has recently been submitted to have the EC regulations changed accordingly. It takes a tetanic contraction to achieve the desired muscle fiber tension, constituting a hypertrophic stimulus. It is also an appropriate means of exercise, which is capable of creating the metabolic and structural conditions needed (e.g, increased mitochondrial volume and capillary density) to obtain satisfactory muscle performance. With patients suffering from a complete spinal cord injury at level D12/L1, having motor and sensory loss in both lower extremities, we were able to train denervated muscle using long-duration stimulation, evoking single muscle contractions at first, soon followed by tetanic contractions against gravity. To increase the efficacy of this functional electrical stimulation (FES) strengthening program, we used ankle weights. With daily FES training over a period of 1-2 years, denervated muscle was exercised until it produced torques between 16 and 38 Nm in the m. quadriceps. With that muscle force, it is possible to stand up from a sitting position in parallel bars. Our results show that denervated muscle in humans is indeed trainable and can perform functional activities with FES. Furthermore, this method of stimulation can assist in decubitus prevention and significantly improve the mobility of paraplegics.

Capillaries↗
PubMed1999

Fluorine-18-fluorodeoxyglucose positron emission tomography is useless for the detection of local recurrence after radical prostatectomy.

OBJECTIVE: After radical retropubic prostatectomy a rise of the prostate-specific antigen (PSA) indicates a local recurrent or metastatic disease. If the bone scan shows no apparent bone metastasis, morphological imaging methods like x-ray computed tomography, magnetic resonance imaging or transrectal ultrasound often cannot distinguish between postoperative scar and local recurrence. Therefore we investigated the feasibility of fluorine-18-fluorodeoxyglucose positron emission tomography (F-18 FDG PET) for metabolic characterization of prostatic cancer, especially for differentiation of scar or recurrent prostate cancer after radical prostatectomy. METHODS: Dynamic PET with 370 MBq F-18 deoxyglucose (F-18 FDG) up to 60 min p.i. was performed in 2 patients with biopsy-proven benign prostatic hyperplasia, in 11 patients with a histologically proven prostate cancer prior to radical retropubic prostatectomy (RRP) and 7 patients with suspected local recurrence (with negative bone scan) after RRP prior to biopsy of anastomosis (3 local recurrence, 4 postoperative scar). RESULTS: Prostate cancer showed a very low F-18 FDG uptake. The placement of regions of interest was only possible by the use of other imaging methods. There was not difference between the F-18 FDG uptake of benign prostate hyperplasia, prostate carcinoma, postoperative scar or local recurrence after radical prostatectomy. CONCLUSION: F-18 FDG seems not to be useful to distinguish between postoperative scar and local recurrence after radical prostatectomy.

Adenocarcinoma↗
PubMed1998

Gender and survival after AIDS in Rio de Janeiro, Brazil.

The relation between gender and survival after a diagnosis of AIDS was studied in a cohort of patients with HIV infection in Rio de Janeiro, Brazil. During the study period, 124 of 617 patients (20%) developed AIDS. Of this group, 91 patients were men and 33 were women. There were no gender related differences regarding the access to antiretroviral therapy or to prophylaxis for Pneumocystis carinii pneumonia. Survival was shorter among women (hazard ratio [HR] = 4.43; p < .001) after adjustment for age and AIDS-defining condition. Adjusting for CD4+ and CD8+ counts reduced the difference between genders (HR = 3.33; p = .017). These results suggest that survival after an AIDS diagnosis may be shorter among women than men in Brazil. Further studies are needed to determine the factors that may be negatively influencing the prognosis of women with AIDS in Brazil.

AIDS-Related Opportunistic Infections↗
PubMed1997

Strategies for managing group A streptococcal pharyngitis. A survey of board-certified pediatricians.

OBJECTIVE: To assess the management strategies and knowledge of board-certified pediatricians regarding group A beta-hemolytic streptococcal (GABHS) pharyngitis. DESIGN: Survey of 1000 US pediatricians in 1991, chosen randomly from the membership of the American Academy of Pediatrics. The survey included questions related to 2 clinical scenarios, respondent demographics, and knowledge of streptococcal pharyngitis. SUBJECTS: Pediatricians who treated patients with pharyngitis. Of the 690 surveys that were returned, 510 pediatricians treated patients with pharyngitis and were included in the data analysis. DATA ANALYSIS: Data were analyzed using Chi 2 statistics for categorical data and the Student t test for continuous variables. RESULTS: Antigen detection tests (ADTs) were used by 64% of the pediatricians; 85% used throat cultures. Strategies for diagnosing streptococcal pharyngitis were throat culture alone (38%), consider positive ADTs definitive and use throat culture when ADTs are negative (42%), ADT alone (13%), ADT and throat culture for all patients with pharyngitis (5%), and no tests for GABHS performed (2%). Thirty-one percent usually or always treated with antibiotics before test results were available. Only 29% of these "early treaters" always discontinued antibiotics when tests did not confirm the presence of group A streptococci. The drug of choice for treatment was penicillin (73%); another 26% preferred a derivative of penicillin, particularly amoxicillin. Many pediatricians altered their management when a patient had recurrent streptococcal pharyngitis. Nearly half of the respondents would use a different antibiotic than they used for routine acute streptococcal pharyngitis. They most often changed to erythromycin (25%), cefadroxil (23%), or amoxicillin-clavulanate (20%). Follow-up throat culture was obtained by 51% of pediatricians after treatment of recurrent streptococcal pharyngitis. A patient with chronic carriage of GABHS and symptoms of pharyngitis would be treated with an antibiotic by 84%; most (62%) would use a penicillin. Other choices were cephalosporins (19%), erythromycin (12%), clindamycin (3%), or rifampin plus penicillin (3%). Tonsillectomy was recommended for symptomatic carriers by 31% of respondents. Carriers without symptoms were less likely to be treated with antibiotics (23%) or referred for tonsillectomy (21%). CONCLUSIONS: Most surveyed board-certified pediatricians managed acute GABHS pharyngitis appropriately, but 15% to 20% used diagnostic or treatment strategies that are not recommended. There was lack of a consensus about the management of recurrent GABHS pharyngitis and chronic carriage of GABHS.

Acute Disease↗
PubMed1996

The ceramic cup type Lindenhof. Results 10-14 years after implantation.

We followed up 10-14 years postoperatively the 106 ceramic cups type 'Lindenhof' that were implanted in the years 1978-1982. In that time, only 7 (6.6%) cups had to be changed due to aseptic loosening. Examination of 73 (68.9%) cups showed that only 4% of the patients were dissatisfied. Using the score of Merle d'Aubigne, we found 89% good and very good results. The high number of cup migrations reported by other authors could not be verified: we saw 35% in all. Most of them appeared in the early postoperative period, stabilized themselves and were not accompanied by pain. Our 10-year survival rate for this ceramic cup is 92%, including the septic changing of arthroplasties.

Acetabulum↗
PubMed1994

[Report of experience in reconstruction of the lower urinary tract in the man and woman].

For some decades uretero(ileo) cutaneostomy and ureterosigmoidostomy were the methods of choice for urinary diversion in cystectomized patients. In recent years, lower urinary tract reconstruction with an anastomosis from an intestinal urinary reservoir to the urethra has established itself as an alternative for male patients undergoing cystectomy. We present the results obtained in 35 patients (32 men, 3 women) who chose to have a ureteroileal urethrostomy to the residual urethra after radical cystectomy for bladder cancer. These patients were followed up by clinical, serologic, radiographic, and urodynamic evaluation conducted at short intervals according to a strict protocol. There was no perioperative mortality, and the early postoperative complication rate was 17% (6/35 patients). For all patients, including those followed only for 3 months so far, the diurnal continence rate was 87% and the nocturnal continence rate was 78%. In every patient, male and female, the maximum urethral pressure (average value in the urethra pressure profile 50.8 cm H2O) was higher than the average resting intraluminal pressure in the pouch (average 12 cm H2O) with physiologic capacity (250-550 ml) of the urinary bladder. Patient acceptance, measured on a numerical self-rating scale, was high (average value 8.75 out of 10).

Adult↗
PubMed1989

[Tumor markers and immunomodulator substances in ascites--their value as screening and diagnosis parameters].

The object of this study was to determine the known laboratory parameters, tumor markers and immunomodulatory substances in 69 ascites of various etiology, and to test their diagnostic significance. The usual parameters such as protein content, LDH ratio, albumin quotient and albumin gradient, fibronectin, cholesterol and cell count did not reliably differentiate the etiology in each particular case, although the mean values of the various groups differed significantly. Even cytological investigation was negative in 6 out of 29 malignant ascites. Neither were the immunomodulatory substances such as neopterin, beta 2-microglobulin and interleukin-2 receptors suitable for differentiation. In patients with carcinoma of the prostate the values of prostate-specific antigen were significantly increased in ascites. The best separation between benign hepatic or cardiac ascites and malignant ascites was provided by ferritin (sensitivity 97%, specificity 100%). The values in benign hepatic or cardiac ascites were lower than 150 ng/ml and those in malignant ascites higher than 170 ng/ml.

Adjuvants, Immunologic↗