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Biomedical subjects

R Bauer

Publications and source records attributed to R Bauer.

At least 199 records · Page 11Linked to original sources
PubMed1997

[Treatment of bullous pemphigoid with low-dose methotrexate].

Three patients with biopsy-proven bullous pemphigoid (BP) and anti-basement-membrane antibodies were treated weekly with low-dose methotrexate (MTX) 12.5-25 mg. To accelerate recovery we initially combined MTX with systemic and/or topical corticosteroids. In combination with MTX, the initial dose of 32 mg corticosteroids/day was sufficient. In all 3 patients the BP disappeared within 4 weeks. To maintain this beneficial effect, very low doses of MTX (25 mg every other week or every four weeks) suffered. Opportunistic infections did not appear. Laboratory tests during MTX-treatment revealed no immunosuppression. The treatment was well tolerated; we could neither observe subjective problems nor other pathologic changes. There are several lines of evidence for immunomodulating effects of MTX and the clinical benefit in BP might be possibly due to these actions of MTX. Our data show, that the treatment of BP with low-dose MTX is an effective alternative with a favorable benefit/side-effect ratio.

Administration, Oral↗
PubMed1997

[Single-image roentgen analysis for the measurement of hip endoprosthesis migration].

A method to determine migration of hip endoprostheses is described. Migration is measured by means of standard AP radiographs and therefore can also be evaluated in retrospective studies. Measurement is conducted in X-ray studies displayed on a computer screen. Enhancement of bony structures by application of filters is available. The developed software can be used with common commercially available computers and X-ray scanners, and does not require special hardware. Several methods to determine accuracy are described. The accuracy of the described method is about 1 mm (95% confidence limit), which compares favourably with other methods, but is less accurate than roentgen stereophotogrammetry. For other methods, accuracy was not determined adequately. Two years after implantation, revision within the first 10 years of follow-up can be predicted with a sensitivity and specificity of more than 80%.

Acetabulum↗
PubMed1997

Fast cortical selection: a principle of neuronal self-organization for perception?

It is commonly accepted that larger visual objects are represented in the cerebral cortex by specific spatial patterns of neuronal activity. Self-organization is a key concept in the different explanations of such neuronal representations. We here propose as a hypothesis that fast cortical selection (FCS) is an intrinsic functional element of cortical self-organization during perception. Selection is a central concept in theoretical biology which has proved its explanatory power in different fields of our natural and cultural world. The central element in the cortical selection process is the pyramidal cell with its two types of excitatory input. In primary cortical areas one of these inputs comes from any of the sensory organs, determining the topological and typological receptive field properties of the cell and also driving it directly. The other type of input connects reciprocally neighbouring pyramidal cells by axon collaterals and only facilitates the driving input. These two functionally different inputs constitute the elementary selection system working by iterative mutual facilitation as a biological algorithm. A short simulation, based entirely on such biological facts, illustrates the dynamic of this selection process: the activity of cells responding better to the external stimulus 'grow and survive' the stimulation, whereas less responsive cells decrease their activity due to competition.

Algorithms↗
PubMed1997

Electrocortical and heart rate response during vibroacoustic stimulation in fetal sheep.

OBJECTIVE: Our purpose was to study effects of vibroacoustic stimuli on electrocortical activity and heart rate changes in fetal sheep in utero. STUDY DESIGN: Seven chronically instrumented near-term fetal sheep were repeatedly stimulated by an electronic artificial larynx for 32 seconds during periods of rapid-eye-movement and non-rapid-eye-movement sleep. Responses to vibroacoustic stimulation were obtained by spectral analysis of the electrocorticogram (fast Fourier transform) and by assessment of changes in fetal heart rate and fetal heart rate variability. RESULTS: During non-rapid-eye-movement sleep vibroacoustic stimulation led to electrocorticogram desynchronization that consisted of a marked reduction of delta and theta band power (p < 0.05). A concomitant fetal heart rate decrease and fetal heart rate variability increase were also noted (p < 0.05). During rapid-eye-movement sleep vibroacoustic stimulation induced a significant increase in alpha and beta band power (p < 0.05) and a slight deviation in basal fetal heart rate and fetal heart rate variability (p < 0.05). CONCLUSION: Vibroacoustic stimulation of fetal sheep provokes reproducible changes in fetal electrocortical activity and heart rate patterns. These changes, which are not easily identifiable in gross polygraphic assessments of the fetal behavioral state, are indicative of fetal arousal.

Acoustic Stimulation↗
PubMed1997

Morphofunctional effects of moderate forebrain ischemia combined with short-term hypoxia in rats--protective effects of Cerebrolysin.

Morphofunctional effects of combined moderate forebrain ischemia due to permanent bilateral carotid artery ligation and short-term systemic hypoxia in rats were investigated. Moreover, a putative effect of brain protection by Cerebrolysin (Cerebrolysin, EBEWE, Austria), a brain tissue hydrolysate containing a mixture of 85% free amino acids and 15% small peptides (MW < 10,000), was studied. Eighty-seven adult Wistar rats (24 Cerebrolysin treated and 63 controls) were subjected to chronic moderate forebrain ischemia by permanent bilateral carotid artery ligation for 7 days. Twenty-four hours after the onset of ischemia, 56 of them underwent an additional hypoxic hypoxia (FiO2 = 0.08) of 15 min. A first group (19 out of 56 animals) received Cerebrolysin (every dose 2.5 ml/kg body weight s.c.) after ligation, after hypoxia and then daily. A second group (6 out of 56 animals) received an equal volume of physiological saline after ligation and Cerebrolysin the first time after hypoxia and then once a day. An untreated control group (31 out 56 animals) received physiological saline. Changes in behavior were scored and electrophysiological activity was quantified by spectral ECoG analysis before carotid artery ligation, before and after hypoxia, and once a day during the following 7 days. On the 7th day after hypoxia, the animals were sacrificed and the grade of histological damage was quantified by morphometry. After permanent carotid artery ligation, 20 out of 63 (31.7%) untreated control animals died within 24 h but only 4 out of 20 (16.7%) Cerebrolysin treated animals. However, Cerebrolysin had not detectable effect on mortality after the additional acute hypoxia. Within 24 h after hypoxia, ECoG power of the higher frequency ranges remained low (p < 0.05). Surviving animals showed a significantly higher ECoG power during and 15 min after hypoxia than those animals that died within 48 h after hypoxia (p < 0.05). All animals showed reduced behavioral activity (p < 0.01) 20 min after hypoxia, however, basal reflex responses were not altered. The major patterns of neuronal damage were coagulation necrosis and general sponginess of the neuropil which is a sign of brain edema. These changes occurred predominantly within the superolateral convexities of the parietal cortex, in the entorhinal and in the piriform cortex as well as in the CA1 and CA4 region and in the dentate gyrus of the hippocampus. The striatum and the origin nuclei of the brain nerves were also affected. We did not observe a relationship between behavior, ECoG depression and the extent of morphological damage after hypoxia nor did we find any protective effects of Cerebrolysin on these parameters. Rather it is suggested that the degree of ECoG depression immediately after hypoxic hypoxia could be a predictor for prognosis of animal survival. Cerebrolysin reduced the amount of early mortality which was caused by moderate global forebrain ischemia. However, no protective influences of the amount of brain tissue damage could be shown.

Amino Acids↗
PubMed1997

Physiological effects and brain protection by hypothermia and cerebrolysin after moderate forebrain ischemia in rats.

The "therapeutic window" of neuroprotective intervention due to hypoxic-ischemic brain injuries are initial disturbances of the neuronal function in regions of only moderate decrease of local cerebral blood flow (ICBF). Because of limited effects of single therapeutic principles therapeutic combinations should be tested. Neuroprotective effects of mild hypothermia and the nootropic drug Cerebrolysin (Cerebrolysin, EBEWE, Austria) on ICBF and development of brain edema were used. Four groups of adult Wistar rats (untreated and Cerebrolysin treated animals with 35 degrees C and 37 degrees C rectal temperature) were subjected to moderate forebrain ischemia by permanent bilateral carotid artery ligation for 6 h. The ICBF was measured continuously in the frontal and the occipital cortex by a 2-channel Laser Doppler flowmeter. The ECoG was derived from 4 ECoG leads above the frontal and occipital cortex and quantified by spectral analysis. Six hours after the onset of ischemia, the function of the blood-brain barrier to proteins was determined by staining with Evans Blue, the animals were sacrificed and the brain water content was estimated by gravimetry. Permanent bilateral carotid artery ligation led to an abrupt ICBF reduction to between 40-50% of baseline levels. Within a few minutes, however, the ICBF increased again to 50-80% of the baseline. The reduced spectral band power of the ECoG was correlated with the decreased ICBF values (p < 0.05) that indirectly indicated changes in the energy state of the neurons (p < 0.05). Changes in the ECoG appeared only with a delay of approximately 4 sec after the onset of ICBF reduction. Six hours after the onset of ischemia, a cytotoxic brain edema was shown in the frontoparietal cortex and hippocampus. Reducing the temperature by 2 degrees C diminished the decrease in ICBF between 10 min and 2 h after the onset of ischemia (p < 0.05). This effect was noted in the frontal but not in the occipital cortex. Furthermore, mild hypothermia prevented the loss of ECoG spectral power in the beta, alpha and theta bands (p < 0.05) as well as the development of cytotoxic brain edema. Cerebrolysin prevented the development of brain edema, too, both under normo- and hypothermic conditions. The ICBF was restored to higher levels in the occipital cortex in comparison both to the normothermic Cerebrolysin treated and hypothermic untreated rats (p < 0.05). This effect of Cerebrolysin was associated with only slight changes in ECoG, indicating that the neuronal activity state and the energy supply was obviously not decisively influenced. In conclusion, moderate ICBF reduction in rats to about 50-80% of baseline values was detectable in the ECoG by using spectral analysis. This reduction led to the development of cytotoxic brain edema in rats within 6 h. Thus, hypothermia prevents the development of cytotoxic brain edema. Cerebrolysin enhanced the effects of hypothermia on ICBF reduction and on the development of brain edema.

Amino Acids↗
PubMed1997

Changed systemic and cerebral hemodynamics and oxygen supply due to gradual hemorrhagic hypotension induced by an external PID-controller in newborn swine.

An experimental design including an external closed-loop PID-(proportional-integral-differential-)controller is presented which enables the induction of gradual hemorrhagic hypotension at different stages of blood flow reduction up to stages of critically disturbed systemic and regional hemodynamics and oxygen supply. For this purpose nine newborn piglets (12-26 hours old, body weight 1626+/-160 g) were anesthetized and artificially ventilated. Gradual hemorrhagic hypotension was induced at four different steady state stages (stage 1 = 60 mmHg; stage 2 = 50 mmHg; stage 3 = 40 mmHg; stage 4 = 35 mmHg) every 30 minutes by gradual blood withdrawal using external PID controller equipment. Cardiac output and brain regional blood flows were measured by the colored microsphere technique. Systemic and brain regional hemodynamics and O2 supply, metabolic parameters and blood catecholamine concentrations were obtained under baseline conditions and at every 25th minute of the four different steady state stages. About 35 percent of the calculated total blood volume (cTBV) was withdrawn in order to reach the first stage of hemorrhagic hypotension. Further blood withdrawal of about 10 percent of the cTBV, about 5 percent of the cTBV, and about 3 percent of the cTBV were necessary to reach the other respective hypotensive stages. Gradual hemorrhagic hypotension led to an increasing reduction of the cardiac output at every hypotensive stage up to about 20 percent of the baseline value (p<0.05). This was accompanied by a concomitant increase of the total peripheral resistance to about 2.5 fold (p<0.05) and a huge increase in the blood catecholamine concentrations (epinephrine: about 64 fold; norepinephrine: about 35 fold). The induced redistribution of the circulating blood volume was shunted to the vital organs. Therefore, brain cortical blood flow was slightly increased at stage 1 and stage 2. A significant reduction of rCBF did not occur until stage 4 (p<0.05). Regional cerebrovascular resistance was concomitantly reduced at stage 1 and stage 2 (p<0.05) and thereafter again slightly elevated. Brain cortical oxygen consumption was maintained up to stage 2, reduced by about 20% at the next stage of hemorrhagic hypotension (p<0.05) and reached the lowest level of about 50% from baseline at stage 4 (p<0.05). Excellent accuracy and stability was shown at each stage for the external PID controller equipment, so that each given setpoint of the instantaneous mean arterial blood pressure was reached and stabilized even at the lowest hypotensive stage (stage 1: 59.53+/-0.23; stage 2: 50.03+/-0.56; stage 3: 39.18+/-1.75; stage 4: 35.28+/-0.45 mmHg (mean+/-SD)). We conclude that the experimental design presented, with an external PID controller to induce gradual hemorrhagic hypotension in newborn piglets is sufficient for producing functional states with changed systemic and cerebral features with high stability and accuracy, enabling a systematic study of disturbed regional hemodynamics and energy metabolism under steady state conditions even under critically changed states of the systemic cardiovascular regulation.

Animals↗
PubMed1997

5-Lipoxygenase and cyclooxygenase inhibitory active constituents from Qianghuo (Notopterygium incisum).

The n-hexane extract of Qianghuo (underground parts of Notopterygium incisum Ting x H.T. Chang, Umbelliferae) showed inhibitory activity in vitro in 5-lipoxygenase (5-LO) and cyclooxygenase (COS) assays. Two major constituents, phenethyl ferulate and falcarindiol, and one minor compound (-)-bornyl ferulate, were identified as the main active principles. The correlation between the content of active constituents and the inhibitory activity of the extracts was examined with seven commercial drug samples from different sources. It was obvious that the content of phenethyl ferulate was mainly responsible for the COX inhibitory activity of the extracts and falcarindiol for 5-LO inhibitory activity. Since the main active constituents phenethyl ferulate and falcarindiol can easily be quantified by HPLC, this is a suitable method for standardization and characterization of the drug.

Animals↗
PubMed1997

Comparison of personal history with patch test results in metal allergy.

In order to compare the validity of patient personal history of contact sensitivity to metal alloys with patch test results, 160 patients with hand eczema were patch tested with a standard series according to the ICDRG after a special questionnaire. In 65%, history and patch test results were identical. Seventy-eight (48.8%) patients thought they would be allergic to metal ions, whereas the patch test revealed a positive result in only 21.3% cases. Positive history but negative test was more frequent in women; in the male group, negative history and positive patch test was the most common finding. Although 82 patients had a negative history, the patch test was positive for contact sensitivity to metal allergens in 12 of them. Both false positive patch tests and false negative histories are possible. Since many factors influence a positive patch test, not only the patient's history but also a synopsis of the anamnesis and patch testing will help to achieve the correct diagnosis of metal contact hypersensitivity.

Dermatitis, Allergic Contact↗
PubMed1997

Episodic secretion of parathyroid hormone in postmenopausal women: assessment by deconvolution analysis and approximate entropy.

In health young subjects, parathyroid hormone (PTH) is secreted presumptively in a dual fashion, with low amplitude pulses apparently superimposed on tonic secretion. In contrast, PTH secretion has not been as well characterized in postmenopausal women, and relationships among bone density, estrogen status, and PTH release have not been explored. It is possible that a pulsatile pattern of PTH secretion is important for bone remodeling, since exogenous PTH administered in a pulsatile manner stimulates bone formation. To assess the importance of pulsatile PTH secretion as a determinant of bone mass, we measured PTH in blood sampled every 2 minutes for 6 h in four groups of older women: (1) high bone density receiving estrogen (n = 6), (2) high bone density not receiving estrogen (n = 5), (3) low bone density receiving estrogen (n = 6), and (4) low bone density not receiving estrogen (n = 8). The plasma PTH release profiles were subjected to deconvolution analysis, which resolves measured hormone concentrations into secretion and clearance components, and to an approximate entropy (ApEn) estimate, which provides an ensemble measure of the serial regularity or orderliness of the release process. In postmenopausal subjects, PTH was secreted in a fashion similar to that observed in young adults, with significant tonic secretion and PTH pulse occurrences averaging every 18-19 minutes. Pulsatile PTH secretion accounted for approximately 25% of the total secreted PTH. There were no differences in the amplitude or frequency of pulsatile PTH secretory parameters or in ApEn values among the four groups or compared with young controls. We conclude that in postmenopausal women, PTH secretory patterns and temporal organization are similar to those in healthy young subjects and are not altered in states of low bone density or estrogen deficiency. This suggests that abnormalities in orderly pulsatile PTH secretion are unlikely to play a major role in established postmenopausal osteoporosis.

Adult↗
PubMed1997

Adjustment of reduced arterial blood pressure--a tool for investigations into gradually reduced brain function.

Hypoxic-ischemic disorders of the neonatal brain function depend in particular on critical decrease of arterial blood pressure (ABP) below the limited range of cerebral autoregulation. An experimental design including an extracorporal ABP controller is presented which enables the induction of gradual hemorrhagic hypotension at different stages of blood flow reduction up to stages of critically disturbed systemic and regional hemodynamics and oxygen supply. In nine newborn piglets several levels of critically reduced ABP (60, 50, 40, 35 mmHg, normal about 75 mmHg) were stabilized over 30 min, and heart rate, breathing, blood gases, systemic and cerebral hemodynamics, and electrocorticogram were recorded. It was found that the reduced circulating blood volume was redistributed in favour of the vital organs. Therefore, brain cortical blood flow was slightly increased at ABP = 60 and ABP = 50 mmHg. A significant reduction of cortical blood flow occurred only at ABP = 35 mmHg. The experimental design which was based on an extracorporal ABP controller is necessary and sufficient for producing functional states of gradual hemorrhagic hypotension with high stability and accuracy, enabling a systematic study of disturbed regional hemodynamics and disturbed energy metabolism under steady state conditions, even under critically changed states of the systemic cardiovascular regulation.

Animals↗
PubMed1997

[Radioiodine therapy of small, solitary autonomous adenomas].

AIM: In most cases of unifocal autonomous adenomas the indication of radioiodine therapy has so far been given only if the volume of the adenomas is > 8 ml, or if the Tc-Uptake is > 2% in combination with suppressed TSH incretion. We have investigated the question how far the indication of radioiodine therapy should be extended to other cases. METHODS: Between March 1993 and April 1994 we treated 11 patients who did not fulfil these criteria but suffered from thyreogenic complaints. RESULTS: After the radioiodine therapy, all the 11 patients improved evidently. CONCLUSION: We suggest extending the indication of radioiodine therapy in order also to treat small unifocal adenomas.

Adenoma↗
PubMed1997

[Deterministic-chaotic and spectral-functional analysis of heart rate and respiratory movements].

After an introduction into the analysis of periodical-linear and deterministic- chaotic characteristics of heart rate fluctuations and respiratory movements their physiological background and clinical aspects are debated. Using the example of own results at the mature rabbit and new-born pig different relations of periodical-linear and deterministic-chaotic characteristics in dependence on the experimental status and neurovegetative blockades are demonstrated. From the data assignments of these characteristics are derived.

Animals↗