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Biomedical subjects

R Wittig

Publications and source records attributed to R Wittig.

At least 19 recordsLinked to original sources
PubMed2003

[Biomechanical properties (compressive strength and compressive pressure at break) of hyaline cartilage under axial load].

INTENTION OF THE STUDY: Explanations concerning the physical properties of hyaline cartilage are different. It was the intention of this study to determine the material parameters of hyaline cartilage under axial load (elasticity, plasticity, elasticity and module pressure stress to break). METHODS: Specimens from the medial femoral condyle (chondro-cortical ships) from adult female domestic pigs (n=28) were used for the experiments. The specimens were completely embedded in plaster to minimize shearing. Axial load was carried out by an universal mechanical testing machine (Zwick Z2.5/TS1S, Ulm, Germany) to determine elastic and plastic deformation and pressure stress to break. RESULTS: Axial load up to 5 MPa produces an almost elastic deformation, an increasing axial load results in a plastic deformation. In the range of 3 to 5 MPa the principle of Hooke is valid. The elasticity module amounted to 39.2 +/- 11.9 N/mm(2), determined under 3.8 MPa axial load. An axial load of 25.8 +/- 5.2 MPa (sigma max ) causes a break of cartilage. A strong correlation between break resistance and thickness of the chondral slice (r=0.71; p < 0.05) was observed. CONCLUSIONS: The low module of chondral elasticity characterizes this tissue as "soft". Moderate axial load causes an ideal elastic, higher axial load a plastic deformation. The medium pressure to break to amounted 25.8 MPa. The medium pressure to break of 25.8 MPa is comparable with the forces produced by an unrestrained limited downfall from a height of 4.3 m. It must be concluded that isolated chondral fractures are rare consequences of a trauma as long as accompanying ligamentous or osseous damages are not found.

Animals↗
PubMed1998

Effectiveness of in-patient rehabilitation for sub-chronic and chronic low back pain by an integrative group treatment program (Swiss Multicentre Study).

In this multicentre intervention study, we compared an integrated group treatment program which combines psychological and education methods into a more active training approach, with the traditional individual approach of physiotherapy and physical procedures for sub-chronic and chronic low back pain. Our 411 patients had a 4-week inpatient treatment: 243 patients in an experimental program and 168 in a traditional program. Outcomes of 283 patients were assessed 3 months and 1 year after entry. The dropout rate was 31.1%. Both conditions demonstrated favourable initial effects on functional and psychological parameters, but the integrated approach showed better long-term results for work rehabilitation than the traditional approach. The most successful patients (n = 58) were younger and had a higher educational level in comparison to the unsuccessful subgroup (n = 71). The main conclusion is that an integrated approach promoting self control and behaviour change through educational measures achieves better long-term results than the traditional individual physiotherapy approach.

Adult↗
PubMed1996

The reliability of the diagnostic features in patients with narcolepsy.

This study determined the test-retest reliability of the polysomnographic findings in narcolepsy. The diagnosis of narcolepsy was based on clinical symptoms and polysomnographic signs. Control subjects were screened before participation and were split based on their screening multiple sleep latency test (MSLT) into high- and low-MSLT groups. Subjects completed two polysomnographic evaluations with at least 5 days between laboratory tests. Narcoleptics had lower sleep efficiencies and high stage 1% when compared to the low MSLT control group. They had more awakenings and less stage 2% than the control groups. Narcoleptics had a shorter latency to 1 when compared to the high-MSLT group but comparable to that of the low-MSLT group. Narcoleptics had a higher number of sleep-onset rapid eye movement periods (SOREMPs) than both control groups. The MSLT scores were stable across the two evaluations and showed a statistically significant correlation. Twenty-eight of the 30 narcoleptic subjects had two or more SOREMPs on reevaluation. None of the controls had multiple SOREMPs. Thus, multiple SOREMPs were shown to be a reliable finding in patients with narcolepsy.

Adolescent↗
PubMed1995

Object-oriented programming for the biosciences.

The development of software systems for the biosciences is always closely connected to experimental practice. Programs must be able to handle the inherent complexity and heterogeneous structure of biological systems in combination with the measuring equipment. Moreover, a high degree of flexibility is required to treat rapidly changing experimental conditions. Object-oriented methodology seems to be well suited for this purpose. It enables an evolutionary approach to software development that still maintains a high degree of modularity. This paper presents experience with object-oriented technology gathered during several years of programming in the fields of bioprocess development and metabolic engineering. It concentrates on the aspects of experimental support, data analysis, interaction and visualization. Several examples are presented and discussed in the general context of the experimental cycle of knowledge acquisition, thus pointing out the benefits and problems of object-oriented technology in the specific application field of the biosciences. Finally, some strategies for future development are described.

Algorithms↗
PubMed1991

Laser midline glossectomy as a treatment for obstructive sleep apnea.

Multiple site specific procedures have been proposed to treat obstructive sleep apnea syndrome (OSAS). Midline glossectomy (MLG) is a procedure that directly enlarges the hypopharyngeal airspace using the carbon dioxide laser. The initial experience of 12 patients is presented. Midline glossectomy as the sole procedure was performed on 11 patients who had failed uvulopalatopharyngoplasty (UPPP) and who were felt to have significant hypopharyngeal collapse on physical examination and Müller's maneuver. One patient with primary hypopharyngeal narrowing underwent MLG. Five (42%) were considered responders with Respiratory Disturbance Index (RDI) decreasing from 60.6 per hour to 14.5 per hour. In seven nonresponders, there was no significant change in the RDI (62.6 events per hour to 48.4 events per hour). Cephalometric analysis showed that responders tended to be more retrognathic (sella-nasion-supramentale (S-N-B = 74.4 degrees)) than nonresponders (S-N-B = 79.3 degrees). Responders were significantly less obese (body mass index (BMI = 30.6)) than nonresponders (BMI = 37.9). There were five minor complications including minor bleeding (n = 3), prolonged odynophagia (n = 1), and minor change in taste (n = 1). There were no major complications, and no persistent difficulties with speech or swallowing. These results demonstrate that direct surgical modification of the tongue base and associated structures can significantly impact obstructive apnea. Midline glossectomy or similar procedures may be useful in a subset of patients with OSAS.

Follow-Up Studies↗
PubMed1991

[4-Tesla 1H MR spectroscopy in patients with temporal lobe epilepsy].

7 patients with drug-resistant temporal lobe epilepsy (TLE) and localized EEG-focus were investigated with a 4 Tesla whole body MR-scanner. Proton (1H) magnetic resonance (MR) spectra were analyzed quantitatively and compared to the healthy side. MRS allowed the differentiation of the following metabolites in 5 patients: N-acetyl-aspartate (NAA), creatine and phosphocreatine, phosphorylcholine and glycerophosphorylcholine, beta- and gamma-glutamate (GLU). To compare the results with those of an already evaluated normal population, these metabolites were measured also in parietal region. The standard deviation was 42-46% in the patients. Unfortunately, in the temporal region, the field homogeneity was worse than parietal and thus the spectral analysis less distinct especially for GLU with a standard deviation of 45% for NAA and 66% for GLU on the healthy side. Thus, no significant findings were seen on focus side. There was only a tendency to an elevation of glutamate and a reduction of N-acetyl-aspartate.

Adolescent↗
PubMed1991

[Mood and body image of women after surgery for breast cancer].

The purpose of the following study is an intensive, longitudinal assessment of psychophysical well-being, stress and stress development after breast cancer diagnosis and surgery. 15 patients were investigated by means of a semistructured diary guiding to systematic daily self-observation during the first ninety days after primary treatment. Although the general trend over time is positive, the results show a considerable variability in the development of mood and body states which cannot exhaustively be explained by medical parameters. The experience of stress is often related to somatic disorders and adjuvant treatment. The results afford an insight in the psychological characteristics of this difficult period and may help to support the patient's rehabilitation more efficiently.

Adaptation, Psychological↗
PubMed1990

In vivo magnetic resonance imaging and spectroscopy of humans with a 4 T whole-body magnet.

A research-type 4 T whole-body magnet, built by Siemens AG, Erlangen, FRG, was used to investigate magnetic resonance at high field strengths. Designs for head and body coils operating at 170 MHz are described. Proton images of the human head and body are degraded by dielectric resonances and penetration effects. The nature of the dielectric resonances was demonstrated in phantoms containing distilled and saline doped water. Radiation damping at 170 MHz generates secondary echoes after a spin echo sequence. This effect was observed in phantoms and with reduced amplitude in the human head. Hydrogen spectra of the human head were selected utilizing stimulated and spin echoes. The latter technique allows the volume size to be reduced to 1 cm3. Examples of brain tumors that have been routinely investigated with volumes of 8 cm3 are given. Natural abundance carbon and phosphorus spectra of muscle and liver demonstrate the expected increase in spectral resolution and signal to noise ratio. Carbon spectra from the liver show the glycogen signal. Fluorine spectroscopy was used to study the time course of the absorption and emptying of a fluorinated antibiotic from the human stomach.

Brain↗
PubMed1989

Predictors of objective level of daytime sleepiness in patients with sleep-related breathing disorders.

Excessive daytime sleepiness, the most prevalent symptom associated with the OSAS, is hypothesized to result from either fragmentation of sleep or hypoxemia during sleep. Measures of nocturnal sleep, respiration during sleep, and daytime sleepiness in 466 patients with apnea were collected to evaluate these two hypotheses. The various parameters were submitted to correlation and multiple regression analyses to predict daytime sleepiness as measured by the MSLT. The RAI, which measures the number of arousals from sleep associated with respiratory disturbances (best fragmentation correlation), produced a higher correlation with MSLT scores than did TMES (best hypoxemia correlation); however, the measures were highly intercorrelated, and multiple regression analyses to determine which parameters independently predicted MSLT showed the single best predictor to be the RAI. Additional independent variance in MSLT score was explained by TST and PSG1. Measures of hypoxemia provided little or no independent predictive information. These data support the hypothesis that sleep fragmentation is an important determinant of daytime sleepiness in patients with apnea.

Female↗
PubMed1989

Recovery of alertness after CPAP in apnea.

Excessive daytime sleepiness is the most common symptom in OSAS. Administering CPAP improves breathing during sleep. We evaluated the time course of the recovery of alertness following CPAP therapy in OSAS patients. Thirty-nine patients with OSAS were treated with CPAP and evaluated after one, 14, or 42 nights of treatment, 13 patients being randomly assigned to each group. All received a diagnostic polysomnogram and MSLT before treatment. The three groups had similar baseline values for nocturnal respiratory disturbance, oxygenation during sleep, fragmentation of sleep, and level of EDS. CPAP treatment was associated with a significant improvement in sleep-related respiration, oxygenation, and sleep fragmentation. The EDS showed significant improvement after one night, and further significant improvement after 14 nights, but no further significant improvement after 42 nights. The differential rate of improvement in nocturnal parameters compared with that of primary complaint of EDS suggests that OSAS patients experience a chronic functional sleep loss. As with sleep deprivation, recovery of alertness in OSAS requires several nights of normal sleep.

Adult↗
PubMed1989

[Adjustment, stress and coping with stress in breast cancer. Results of single case studies].

Twelve newly diagnosed breast cancer patients were studied by means of a standardized diary during the first ninety days after diagnosis and surgery in order to obtain a very detailed multivariate description of individual mood states and coping responses in the course of time. The main function of this approach is to identify and evaluate different modes of coping and to propose intervention strategies in consideration of specific conditions of the individual.

Adaptation, Psychological↗
PubMed1988

Narcolepsy in a pediatric population.

Narcolepsy, a sleep-wake disorder of unknown cause, has been reported as occurring in the pediatric population, but only two reports of cases in the literature have included polysomnographic data on children with narcolepsy. We compared the clinical and polysomnographic data on a series of eight patients 15 years of age or younger and an adult comparison group with narcolepsy. All patients presented with excessive daytime sleepiness, and no significant difference was found between groups for the incidence of cataplexy, hypnagogic hallucinations, and sleep paralysis. On polysomnographic evaluation the pediatric group had increased total sleep time, percent-stage 3/4 sleep, percent rapid eye movement sleep, and decreased stage 1 sleep, which all are expected age-related differences. The pediatric group also showed a greater degree of daytime sleepiness and an increased frequency of sleep-onset rapid eye movement periods. While pediatric patients with narcolepsy resemble adults in their mode of presentation and the incidence of accessory symptoms, the increase in severity of sleepiness highlights the importance of diagnosing narcolepsy in children as early as possible so that treatment can be initiated.

Adult↗
PubMed1988

Sleep and memory.

Generally sleep is considered a time of amnesia. It is not uncommon for an individual to experience 8 h of sleep and have no memory for events during that time. Similarly, a substantial proportion of the population has no memory for dreams that occurred during the night, despite the fact that the literature on awakening during rapid eye movement (REM) sleep clearly shows that individuals normally have four to six "dream experiences" a night. Research on this issue seems to indicate that the lack of memory cannot be explained by the organisms' inability to perceive stimuli. The data indicate that although perceptual thresholds are elevated, organisms can clearly perceive stimuli, and, in fact, can discriminate between them during sleep. The amnesia also cannot be explained by a defect in long-term memory, as studies have indicated that stimuli put into the memory during wakefulness are more efficiently retrieved after a sleep period than after a comparable period of wakefulness. The most likely explanation for the amnestic property of sleep seems to be the inability of organisms to transfer information from short-term memory to long-term memory during sleep. There are several sources of evidence to support this hypothesis. First, the probability of remembering a stimulus given during wakefulness is related to the proximity of sleep onset to the stimulus. Generally, information put into the system within 5 min of sleep onset is lost from memory. Secondly, disorders of excessive daytime somnolence which cause individuals to have frequent microsleeps are often associated with complains of memory problems.(ABSTRACT TRUNCATED AT 250 WORDS)

Humans↗
PubMed1987

Amino acid sequences of a-factor mating peptides from Saccharomyces cerevisiae.

The molecular structure of a-factor, the mating hormone produced by mating type a cells of Saccharomyces cerevisiae, has been investigated. In culture filtrates of a cells four oligopeptides (a1 to a4) exhibiting a-factor activity have been found. These peptides have been isolated and their amino acid sequences have been determined. The a-factor peptides comprise two (apparently identical) pairs, a1/a2 and a3/a4, which differ in an interchange at position 6 of a valine in a1/a2 for a leucine in a3/a4. a1 and a4, which can be obtained by oxidation with H2O2 of purified a2 and a3, respectively, obviously represent oxidation artifacts formed under the conditions of culture. The amino acid sequences determined for the a-factor peptides are Tyr-Ile-Ile-Lys-Gly-Val Leu-Phe-Trp-Asp-Pro-Ala-Cys. Several lines of evidence suggest that the carboxyl-terminal cysteine residue is S-alkylated by a hydrophobic moiety.

Amino Acid Sequence↗
PubMed1986

Sleep-wake abnormalities in narcolepsy.

To evaluate the degree to which sleep (REM vs. NREM) intrudes into wake and wake intrudes into sleep in narcolepsy, 103 patients with narcolepsy were compared to 105 patients with other diagnoses of disorders of excessive sleep (DOES). Narcoleptic patients had more frequent REM onsets on the multiple sleep latency test (MSLT) and nocturnal polysomnograms. But the MSLT latencies to REM versus NREM in narcoleptic patients did not differ. Nocturnal measures of REM pressure, percentage of REM, and REM latency excluding the REM onsets, did not differ among patient groups. With respect to the intrusion of wake into sleep, narcoleptic patients had more and longer awakenings compared with other DOES patients, but the distribution of wake into REM and NREM sleep did not differ among groups. These data suggest that narcolepsy is not exclusively a REM-related disorder, but involves an inability to sustain a specific neural state for periods comparable to those in normal subjects or other DOES patients.

Adult↗
PubMed1986

Alerting effects of naps in patients with narcolepsy.

As part of their standard diagnostic evaluation, 45 patients with narcolepsy and 45 patients with other disorders of excessive sleepiness (DOES), primarily obstructive sleep apnea, each underwent one of three nap conditions that involved manipulating time in bed on the 1600 h latency test of the standard multiple sleep latency test (MSLT) and varying the time between the 1600-h latency test and a subsequent fifth latency test. Compared with the mean of tests 1-4, a 15-min nap at 1600 h (condition 1) increased latency to stage 1 sleep on a latency test 15 min later in both groups. However, the increase was greater for patients with narcolepsy than with other DOES. A 30-min nap at 1600 h (condition 2) produced increased latency 15 min later, but the increase was greater for patients with other DOES. While narcoleptic patients showed no change in latency as a function of increased nap duration, the other DOES patients had increased latencies. When tested 30 min after a 15-min nap (condition 3), narcoleptic patients had latencies that did not differ from those of tests 1-4, while the other DOES patients sustained their increased latencies.

Adult↗