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Biomedical subjects

R Kunz

Publications and source records attributed to R Kunz.

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

Effect of ethanol on dynamic visual acuity during vertical body oscillation in healthy volunteers.

Visual orientation is the most important sensory input during locomotion (e.g. walking, driving a car, riding a bicycle). We investigated dynamic visual acuity (DVA) during vertical body-oscillations (amplitude 5 cm; frequency 1.5 Hz) in 12 healthy subjects before and twice after ethanol consumption. During oscillation, vertical eye movements were recorded under two test conditions: with eyes closed (EC) and during DVA testing. A significant increase in vertical eye-amplitude after ethanol ingestion occurred only during EC tests, as a possible sign of vestibular hyperreaction. During vestibular stimulation alone (EC), ethanol did not affect the phase shift between stimulus and eye movements. However, when the subjects were given an additional visual stimulus (DVA), the post-alcohol phase shift rose significantly. Surprisingly, the post-alcohol phase shift values for the two test conditions showed no significant differences. After ethanol ingestion we found no changes in static visual acuity but a significant loss of DVA. Volunteers with a change of DVA threshold (DVAT) showed significantly (P = 0.004) higher post-alcoholic changes in the phase shift. In summary, low doses of ethanol disturbed the visually guided oculomotor response during fixation of an earth-fixed target while the observer was subject to linear vertical acceleration. This effect led to an increasing delay between the beginning of body and eye movements. The consequence was an increasing phase shift and thus a decrease in DVA during whole-body oscillation which was comparable to movements during human locomotion.

Acceleration↗
PubMed2000

The localization of an imaginary target under the influence of caloric vestibular stimulation in healthy adults.

It is well known that fixation of an imaginary target (IT) can influence the vestibulo-ocular reflex, but reports on the effect of peripheral vestibular stimulation on the localization of an IT are still lacking. In a prospective study, errors in pointing towards an IT without and after cold caloric vestibular stimulation (VS) were investigated in 24 right-handed volunteers with the head tilted backwards by 60 degrees. After the stationary target had been extinguished for 120 s each subject had to point towards the target position as remembered in darkness. The vestibular response was recorded by electronystagmography. Without VS 73% of the volunteers showed a systematic horizontal pointing error towards the right side. VS led to an increased horizontal pointing error in the direction of the slow phase of the induced nystagmus and the degree of deviation showed a significant (P = 0.001) positive correlation (r = 0.32) with the amplitude of the calorically induced nystagmus. In summary, an IT is not merely a useful visual stimulus for influencing the vestibulo-ocular reflex during linear and angular acceleration. A peripheral vestibular stimulation is itself able to change the position of an IT significantly and the extent of deviation shows a significant correlation with the amplitude of the evoked nystagmus.

Adult↗
PubMed2000

Dynamic visual acuity during linear acceleration along the inter-aural axis.

We investigated visual-vestibular interactions during linear acceleration along the inter-aural axis. Eighteen healthy volunteers and two patients with central neurological diseases were subjected to transaural linear acceleration in the direction of gravity force (frequency: 0.5-1.5 Hz; amplitude: 5 cm). During linear acceleration, eye movements were recorded under three test conditions: eyes closed (EC), while staring at an imaginary target (IT) and during the testing of dynamic visual acuity (DVA). As parameters of evaluation we used the amplitude of horizontal eye movements, phase shift and the decrease of DVA threshold (DVAT). Under all test conditions, eye amplitude increased with rising stimulus frequency and exceeded, especially in the higher frequency range, a hypothetically calculated eye amplitude for smooth pursuit. The combination of a visual and vestibular input (DVA and IT) led to a better compensation (lower phase shift) than under vestibular stimulation alone (EC). Eye movements during low-frequency stimulation depended more on the visual system while responses in the higher frequency range were mainly triggered by the otolith organ. At 1.5 Hz the compensatory function of the visual-vestibular system was limited (rising phase shift) and DVAT decreased even in a significant number of healthy subjects. Patients with diseases of the central nervous system showed a higher phase shift and thus a stronger decrease of DVAT (two levels) already at a stimulus frequency of 1.25 Hz.

Acceleration↗
PubMed2000

Acute vascular rejection is associated with systemic complement activation in a pig-to-primate kidney xenograft model.

The introduction of h-DAF transgenic porcine organs into pre-clinical pig-to-primate discordant xenotransplantation has led to complete and reliable abrogation of hyperacute xenograft rejection (HAR). Despite additional heavy immunosuppression however, most xenografts are still lost due to acute vascular rejection (AVR), with current treatment protocols being of only limited value. In a life-supporting model of pig-to-primate kidney transplantation, unmodified (n=8) or h-DAF-transgenic (n=9) porcine kidneys were transplanted into cynomolgus monkeys under cyclophosphamide (CyP), cyclosporine and low-dose steroid immunosuppression. Longest recipient survival was 11 days in the control group and 68 days in the h-DAF transgenic group. Stable initial graft function with recipient survival >4 days was generated in eight animals (two controls and six transgenics). In these animals, plasma complement levels were analyzed during ongoing AVR. Compared with baseline levels, a two-fold increase in C3a levels and a four-fold increase in sC5b-9 levels were measured. In parallel to systemic complement activation, increased deposition of C3 and C5b-9 along with massive staining for recipient IgM immunoglobulins was detected in the xenografts on immunohistochemistry. We conclude that acute vascular xenograft rejection of porcine kidneys in cynomolgus monkeys is associated with classical pathway complement activation following binding of induced recipient anti-porcine antibodies. This complement activation can be observed despite membrane bound expression of human complement regulators in the porcine xenografts. Therefore, additional short-term fluid phase complement inhibition seems necessary for the future development of protocols designed for treatment of AVR in the pig-to-primate combination.

Acute Disease↗
PubMed2000

[Guidelines Clearing House Statement "Hypertension". Summary and recommendations for a rational hypertension guideline in Germany].

BACKGROUND: In order to promote quality of hypertension management in Germany, a national hypertension guidelines clearing project was initiated in 1999 by the German Guidelines Clearinghouse. OBJECTIVES: To identify and review published German- and English language hypertension guidelines. To establish criteria for future guideline development and implementation. To familiarize stakeholders in Germany with state-of-the-art hypertension guidelines. To identify key topics for a future national evidence-based guideline. METHODS: Search procedure, formal appraisal: Systematic search using literature databases and English-/German-language databases, published between 1990 and 1999. Abstract screening of the search results according to the inclusion criteria (n = 132 of a total of 548 hits). Systematic guideline evaluation using checklist with predefined criteria. APPRAISAL OF GUIDELINES' CONTENTS: Peer review of guidelines with the following inclusion criteria: hypertension--general, German and English language, published later than 1994, original or primary guideline or update, issued for nationwide use. Peer review was performed by a multidisciplinary focus group of EBM experts (primary and secondary care physicians, clinical pharmacologist, clinical epidemiologist). None of these was involved in hypertension guideline development during the review period. DOCUMENTATION OF CRITICAL APPRAISAL RESULTS: Systematic documentation of methodological appraisal and peer review results using a structured abstract form. The focus group wrote a final report (clearing report) including methodological abstracts for each guideline, essential topics for a future German hypertension guideline based on examples from the appraised guidelines, comments and recommendations for health care policy markers in Germany. RESULTS: 11 out of 132 guidelines were in accordance with the formal minimal standard with a wide range range within the following domains: "description of the development process", "declaration of authors' independence", "explicit link between recommendations and the supporting evidence", "management options", "tools for implementation". None of the guidelines identified all the key identified by the focus group, such as: (1) definition of hypertension--epidemiology--health care problems--intended guideline users/goals, (2) blood pressure measurement, (3) medical history and physical examination, (4) case-finding/screening, (5) indications for referral, (6) risk-stratification, (7) diagnostic procedures, (8) therapeutic goals/indications for therapy, (9) nonpharmacological measures, (10), pharmacotherapy, (11) follow-up/patient education/motivation/compliance, (12) comorbidity, hypertension in childhood/elderly, pregnancy, (13) primary prevention, (14) quality assurance/quality management, (15) dissemination/implementation, (16) open questions/challenges for the future. SUMMARY POINTS: To improve the quality of hypertension management in Germany, the expert panel suggested to develop a national evidence-based guideline. This should follow internationally agreed criteria and procedures. The experts identified and reviewed 11 out of 132 hypertension, which might make useful contributions for a future German Hypertension guideline. The expert group identified 16 key topics for a national hypertension guideline.

Comorbidity↗
PubMed1998

The unpredictability paradox: review of empirical comparisons of randomised and non-randomised clinical trials.

OBJECTIVE: To summarise comparisons of randomised clinical trials and non-randomised clinical trials, trials with adequately concealed random allocation versus inadequately concealed random allocation, and high quality trials versus low quality trials where the effect of randomisation could not be separated from the effects of other methodological manoeuvres. DESIGN: Systematic review. SELECTION CRITERIA: Cohorts or meta-analyses of clinical trials that included an empirical assessment of the relation between randomisation and estimates of effect. DATA SOURCES: Cochrane Review Methodology Database, Medline, SciSearch, bibliographies, hand searching of journals, personal communication with methodologists, and the reference lists of relevant articles. MAIN OUTCOME MEASURES: Relation between randomisation and estimates of effect. RESULTS: Eleven studies that compared randomised controlled trials with non-randomised controlled trials (eight for evaluations of the same intervention and three across different interventions), two studies that compared trials with adequately concealed random allocation and inadequately concealed random allocation, and five studies that assessed the relation between quality scores and estimates of treatment effects, were identified. Failure to use random allocation and concealment of allocation were associated with relative increases in estimates of effects of 150% or more, relative decreases of up to 90%, inversion of the estimated effect and, in some cases, no difference. On average, failure to use randomisation or adequate concealment of allocation resulted in larger estimates of effect due to a poorer prognosis in non-randomly selected control groups compared with randomly selected control groups. CONCLUSIONS: Failure to use adequately concealed random allocation can distort the apparent effects of care in either direction, causing the effects to seem either larger or smaller than they really are. The size of these distortions can be as large as or larger than the size of the effects that are to be detected.

Clinical Trials as Topic↗
PubMed1998

[Sexual dysfunctions with antidepressive drugs--results of a physician survey].

In a survey throughout Switzerland 7.455 general practitioners and psychiatrists were mailed a questionnaire addressing topics in sexual medicine with regard to antidepressant medication, 940 completed questionnaires (response rate 12.5%) were evaluated. 77.6% of the responders agree that knowledge in sexual medicine is important or very important. Only one half of the physicians judge their competence in sexual medicine as fair or good. There are differences in sexual history taking between general practitioners and psychiatrists; the latter addressing more frequently sexual medicine related questions. Sexual dysfunction before and during therapy with antidepressants is observed less frequently than reported in other studies. Only half of the physicians counsel their patients when sexual dysfunction occur during therapy. Treatment strategies of antidepressant induced sexual side effects are rarely seen. The results emphasize the importance of knowledge and competence in sexual medicine for general practitioners and psychiatrists, both showing interest in continuing education on this topic.

Antidepressive Agents↗
PubMed1998

The value of intraoperative laparoscopic examination of the contralateral inguinal ring during hernia repair in children.

Approximately 40% of children with a clinical unilateral inguinal hernia display a patent processus vaginalis on the contralateral side; half of these children subsequently develop an inguinal hernia. The management of this problem is still controversial. Different strategies to identify patients who profit from an open contralateral exploration have been applied (diagnostic pneumoperitoneum, herniography, ultrasound). The purpose of this study was to evaluate the usefulness of intraoperative laparoscopy in a no-puncture technique through the opened hernia sack. In 75 children (age 6 months to 7 years) with clinical unilateral hernia laparoscopy (5-mm Laparoscope, 30 degrees and 70 degrees ), in cases of wide-open contralateral internal inguinal ring (Type III) an open surgical exploration was performed. Twelve patients (17%) fulfilled the laparoscopic criteria of a Type III ring. The diagnose was confirmed during open contralateral exploration. Seven children (8%) showed a patent but small processus vaginalis with a shallow internal ring. These patients were treated conservatively. In the follow-up period (median 6 months) one subsequent hernia developed. There was no technical failure, and no associated complications were seen. The median time for laparoscopy was 6 minutes. Intraoperative laparoscopy during unilateral hernia repair allows the identification of patients who profit from bilateral open surgery during the same operation with little additional operating time, and so far with no resulting complications. Application of this method may avoid a second hospitalization and operation as well as unnecessary routine bilateral open exploration. As an additional source of information through excellent visualization of the abdominal cavity, this method proved helpful to examine the incarcerated bowel after repositioning.

Child↗
PubMed1998

Association between the angiotensin-converting enzyme-insertion/deletion polymorphism and diabetic nephropathy: a methodologic appraisal and systematic review.

Recent studies have implicated a variant of the angiotensin-converting enzyme gene (ACE), associated with increased activity of this enzyme, in the development and progression of diabetic nephropathy. This study provides a systematic review of all cross-sectional, case-control, and cohort studies in patients with insulin-dependent (IDDM) or non-insulin-dependent (NIDDM) diabetes mellitus of any race, examining the relationship between the ACE-insertion/deletion polymorphism and nephropathy. Nineteen studies in 21 populations published between 1994 and 1997 presenting data on 5336 patients were reviewed. Two investigators independently assessed the studies on methodologic quality, performance of study, and association between the ACE-insertion/deletion polymorphism and nephropathy. Separate analyses of the relationship between genotype and allele frequencies were performed for patients with IDDM and NIDDM by race, using Peto's odds ratio. In Caucasians with IDDM, pooling was not performed due to heterogeneity of the studies, but among the homogeneous studies, no association was detected. Likewise, no association was observed in Caucasian patients with NIDDM (odds ratio [OR], 1.10; 95% confidence interval [95% CI], 0.83 to 1.45). In Asian patients with NIDDM, the risk of nephropathy was increased in the presence of the DD or ID genotype (OR, 1.88; 95% CI, 1.42 to 2.85). Although this analysis fails to confirm an association between the ACE-insertion/deletion genotype and nephropathy in Caucasians with NIDDM or IDDM, a role for this genetic marker in Asian patients cannot be ruled out. However, due to methodologic limitations of individual studies, no definite conclusions can be drawn from this analysis. Clearly, more rigorous methodology needs to be applied in future studies.

Adult↗
PubMed1997

[Differences between evidence based-medicine and best conventional medicine].

The practical application of rational concepts will be possible in the health care system if two conditions will be met. The legal framework has to fit these goals and new strategies are to establish. The new strategies will be needed to identify from the huge amount of data "evidence" which will support the medical progress. Evidence-Based Medicine (EBM) offers these strategies. Modifications of our conventional procedures are necessary to establish EBM: the conditions of clinical actions, the definitions of goals of medical training, the rational of clinical decisions and the continued medical education.

Cost-Benefit Analysis↗
PubMed1997

Maintenance therapy with triple versus double immunosuppressive regimen in renal transplantation: a meta-analysis.

BACKGROUND: The purpose of this study was to compare the effect of triple immunosuppressive maintenance therapy (cyclosporine, azathioprine, and prednisolone) with that of double therapy (cyclosporine and prednisolone) in renal transplant patients using graft failure, mortality, and acute rejection episodes as outcome measures. METHODS: A systematic overview of articles published between 1984 and 1995 was done. MEDLINE, Science Citation Index, reference lists, and expert files were searched. Of 449 originally identified studies, five controlled trials were finally selected. Information was retrieved on the topics of methodological quality, baseline characteristics, interventions, and outcomes. The Mantel-Haenszel fixed effect method was used to combine results from different studies. RESULTS: Pooled analysis did not show a statistically significant difference between triple-drug therapy and double-drug therapy in the main outcome of graft failure (odds ratio [OR], 0.82; 95% confidence interval [CI], 0.61-1.16), survival (OR, 0.83; 95% CI, 0.57-1.21), or the occurrence of acute graft rejection (OR, 1.02; 95% CI, 0.76-1.36). There was a nonsignificant trend for better graft survival under triple therapy. A lower withdrawal rate suggests a more stable immunosuppressive effect on triple therapy. CONCLUSIONS: There is no statistically significant difference in the long-term management of renal transplant recipients between the two treatment regimens.

Acute Disease↗
PubMed1997

[Evidence-based medicine].

New instruments are required to allocate the available resources to services which are not only effective but also beneficial to the patients. These instruments are needed to manage the huge amount of new information in medicine and to appraise its quality. Evidence-based medicine (EBM) provides these instruments to find the relevant literature, to appraise its quality and to merge it with the user's clinical experience. EBM is different from "conventionally best medicine (CMB)" of four levels; conditions of clinical action, teaching goals, medicine at the patient, and goals of continued medical education. We can increase our chances to benefit from medical progress if we use these new instruments.

Cost-Benefit Analysis↗