Biomedical subjects
Publications and source records attributed to A Riedel.
Of 40 normal volunteers tilted on two separate occasions, seven subjects had vasovagal syncope only during one upright tilt, but showed increased endothelin plasma levels in the supine position and during head-up tilt on both occasions, independent of vasovagal syncope, compared to control subjects.
Two reversed-phase high-performance liquid chromatography (RP-HPLC) methods were developed to investigate the degradation of the acid-labile proton-pump-inhibitor omeprazole in organic polymer solutions and aqueous dispersions of enteric coating polymers (Eudragit L-100, S-100, CAP, HP-55, HPMCAS-HF, -LF, and shellac). The overall goal of the study was to determine the influence of the polymer structure on the degradation of omeprazole, i.e., whether the acid structure of the enteric coating polymers caused an instability of the proton pump inhibitor. Moreover, it was investigated whether a difference in omeprazole degradation could be detected between organic polymer solutions and aqueous dispersions. pKa values of the polymers and pH values of the aqueous dispersions were determined to see whether there was a correlation with the extent of degradation of omeprazole induced by enteric polymers. As the polymers containing phthalate moieties are very susceptible to hydrolysis, the influence of free phthalic acid on omeprazole stability was investigated. Finally, the degradation kinetics of omeprazole in organic polymer solutions were determined. Omeprazole degradation is more pronounced in aqueous polymer dispersions than in organic polymer solutions. The influence of organic polymer solutions on the stability of omeprazole depends on the amount of acidic groups in the polymeric structure, whereas the influence of aqueous polymer dispersions depends on the pH value of the dispersion. The amount of free acids present in some polymers as by-products also cause a degradation of the proton pump inhibitor. Among all investigated polymers, shellac showed the least influence on the stability of omeprazole. The decomposition of omeprazole in organic polymer solutions followed first-order kinetics. The decrease of omeprazole peak area in organic polymer solutions was in the order Eudragit L-100> HPMCAS-HF>shellac.
The aim of this study was to investigate the degradation of the acid-labile proton-pump-inhibitor omeprazole in organic polymer solutions and aqueous dispersions of enteric coating polymers by UV spectroscopy. Furthermore, data were compared with those obtained in a previous HPLC study. For comparative purposes the cationic Eudragit RS 100 and the monomeric acid acetic acid were included in this study. The discolorations of degraded omeprazole solutions were analysed by VIS spectroscopy. UV-VIS spectra were recorded after preparation of the solutions and after 180 min of storage. The change of absorption was calculated as the difference of the absorption values at 305 nm. Degradation of omeprazole depends on the amount of acidic groups in the polymer structure. This decomposition manifests itself in a shifting of the absorption maximum to lower wavelengths and a decrease of absorption intensity. UV-VIS spectroscopy was used to determine the extent of degradation induced by enteric polymers. A good correlation of these results with previous HPLC data was found when excluding UV absorbing polymers. Nevertheless, values obtained by UV-VIS spectroscopy were always lower than those obtained by HPLC. For evaluation of the discoloration of degraded omeprazole solutions, VIS spectroscopy is a simple and fast method.
The Fröhlich interaction is one of the main electron-phonon intrinsic interactions in polar materials originating from the coupling of one itinerant electron with the macroscopic electric field generated by any longitudinal optical (LO) phonon. Infrared magnetoabsorption measurements of doped GaAs quantum well structures have been carried out in order to test the concept of Fröhlich interaction and polaron mass in such systems. These new experimental results lead one to question the validity of this concept in a real system.
A double-blind, 28-day, placebo-controlled study was conducted with three groups of women of child-bearing age (N = 12 in each group) who received standardised antipsychotic medication plus a) 50 microg transdermal estradiol or b) 100 microg transdermal estradiol or c) transdermal placebo. Preliminary analyses show that women receiving 100 microg of estradiol made greater improvements in the symptoms of schizophrenia than either the 50 microg estradiol or placebo groups. The addition of 100 microg adjunctive transdermal oestrogen significantly enhanced treatment responsivity of acute, severe psychotic symptoms in women with schizophrenia. The positive impact of oestrogen treatment on psychotic symptoms via a multiplicity of possible actions (see accompanying articles in this issue) may prove clinically useful in the overall treatment of women with schizophrenia.
In the present study, we introduce new views on neuro- and chemoarchitectonics of the rat forebrain subcortex deduced from traditional and current concepts of anatomical organization and from our own results. It is based on double and triple immunofluorescence of markers for transmitter-related enzymes, calcium-binding proteins, receptor proteins, myelin basic protein (MBP) and neuropeptides, and on histological cell/myelin stains. The main findings can be summarized as follows: (i) the dorsal striatum of rat and other myomorph rodents reveals a small caudate equivalent homotopic to the caudate nucleus (C) of other mammals, and a large putamen (Pu). (ii) Shell and core can be distinguished also in the 'rostral pole' of nucleus accumbens (ACC) with the calretinin/calbindin and neuropeptide Y (NPY) immunostaining. The shell reveals characteristics of a genuine striatal but not of an extended amygdala (EA) subunit. (iii) EA and lateral septum show striking similarities in structure and fiber connections and may therefore represent a separate parastriatal complex. (iv) The meandering dense layer (DL) of olfactory tubercle (OT) forms longitudinal gyrus- and sulcus-like structures converging in its rostral pole. (v) The core regions of the islands of Calleja that border the ventral pallidum (VP) sharing some of its features are invaded by myelinated fibers of the medial forebrain bundle (MFB). The island of Calleja magna is also apposed to an inconspicuous, slender dorsal appendage of VP. (vi) The VP is composed of a large dorsal reticulated part traversed by the myelinated GABAergic parvalbumin-immunoreactive axons of the MFB and a slender ventral non-reticulate part close to the islands of Calleja. (vii) Considering their close association to the limbic system, ventral striatum (VS) and VP may represent the oldest part of basal ganglia, whereas dorsal striatopallidal subunits were progressively developed in parallel to the growing neocortical influence on motor behavior.
The potential health risks of radiofrequency electromagnetic fields (EMFs) emitted by mobile phones are of considerable public interest. The present study investigated the hypothesis, based on the results of our previous study, that exposure to EMFs can increase sympathetic vasoconstrictor activity. Forty healthy young males and females underwent a single-blind, placebo-controlled protocol once on each of two different days. Each investigation included successive periods of placebo and EMF exposure, given in a randomized order. The exposure was implemented by a GSM-like signal (900 MHz, pulsed with 217 Hz, 2 W) using a mobile phone mounted on the right-hand side of the head in a typical telephoning position. Each period of placebo exposure and of EMF exposure consisted of 20 min of supine rest, 10 min of 70 degrees upright tilt on a tilt table, and another 20 min of supine rest. Blood pressure, heart rate and cutaneous capillary perfusion were measured continuously. In addition, serum levels of norepinephrine, epinephrine, cortisol and endothelin were analyzed in venous blood samples taken every 10 min. Similar to the previous study, systolic and diastolic blood pressure each showed slow, continuous, statistically significant increases of about 5 mmHg during the course of the protocol. All other parameters either decreased in parallel or remained constant. However, analysis of variance showed that the changes in blood pressure and in all other parameters were independent of the EMF exposure. These findings do not support the assumption of a nonthermal influence of EMFs emitted by mobile phones on the cardiovascular autonomic nervous system in healthy humans.
Estrogen has been shown in animal studies to modulate both the dopamine and serotonin neurotransmitter systems - the main neurotransmitters implicated in the pathogenesis of schizophrenia. A double blind, 28 day, placebo-controlled study was conducted with three groups of women of child-bearing age (N=12 in each group) who received standardized antipsychotic medication plus 50mcg transdermal estradiol or 100mcg transdermal estradiol or transdermal placebo. Analyses show that women receiving 100mcg of estradiol made greater improvements in the symptoms of schizophrenia than both the 50mcg estradiol and placebo groups. Women receiving 50mcg estradiol had more improvement in their symptoms compared with the placebo group. The 100mcg estradiol group had significantly lower mean lutenizing hormone (LH) and higher mean prolactin levels across the study period compared with both the 50mcg and placebo groups. The addition of 100mcg adjunctive transdermal estrogen significantly enhanced the treatment of acute, severe psychotic symptoms in women with schizophrenia. The differential response of adding 50mcg versus 100mcg estradiol on the types of symptom affected may be related to the estrogen effect on LH and prolactin. The positive impact of estrogen treatment on psychotic symptoms by a direct effect on dopamine and serotonin systems or via an indirect prolactin-mediated effect may be very useful in the overall treatment of women with schizophrenia.
Magneto infrared absorption measurements have been performed in a highly doped GaAs quantum well which has been lifted off and bonded to a silicon substrate, in order to study the resonant polaron interaction. It is found that the pinning of the cyclotron energy occurs at an energy close to that of the transverse optical phonon of GaAs. This unexpected result is explained by a model taking into account the full dielectric constant of the quantum well.
OBJECTIVE: To improve the differential diagnosis between patients with multiple system atrophy (MSA) and idiopathic PD (IPD) with autonomic failure. BACKGROUND: Some patients diagnosed with IPD are discovered to have alternative diseases such as MSA, despite the application of stringent diagnostic criteria. This differentiation is particularly difficult if patients with IPD also show symptoms of autonomic failure. In IPD, autonomic failure is caused by damage of the postganglionic part of the autonomic nervous system, whereas in MSA, degeneration of preganglionic and central autonomic neurons is revealed histopathologically. METHODS: Scintigraphy with [123I]metaiodobenzylguanidine (MIBG) enables the quantification of postganglionic sympathetic cardiac innervation. Fifteen patients with IPD and 5 patients with MSA underwent standard autonomic function tests and scintigraphy with MIBG. RESULTS: In all patients, cardiovascular testing showed evidence of autonomic failure of varying severity. In all patients with IPD, the heart-mediastinum (H/M) ratio of MIBG uptake was pathologically impaired, independent of duration and severity of autonomic and parkinsonian symptoms. All patients with MSA had a regular H/M ratio. Each patient could be assigned to the correct diagnostic group based on the results of the MIBG scintigraphy, even if the duration of the disease was only 2 years or less. CONCLUSIONS: This population assessment of the heart-mediastinum ratio of [123I]metaiodobenzylguanidine uptake showed a high sensitivity for the detection of autonomic involvement in patients with idiopathic IPD and also a high specificity for the discrimination between idiopathic PD and MSA.
The interaction of the inhibitor 2,5-dibromo-3-methyl-6-isopropylbenzoquinone (DBMIB) with the Rieske protein of the chloroplast b6f complex has been studied by EPR. All three redox states of DBMIB were found to interact with the iron-sulphur cluster. The presence of the oxidised form of DBMIB altered the equilibrium distribution of the Rieske protein's conformational substates, strongly favouring the proximal position close to heme bL. In addition to this conformational effect, DBMIB shifted the pK-value of the redox-linked proton involved in the iron-sulphur cluster's redox transition by about 1.5 pH units towards more acidic values. The implications of these results with respect to the interaction of the native quinone substrate and the Rieske cluster in cytochrome bc complexes are discussed.
The quantitative sudomotor axon reflex test (QSART) is a useful tool in the evaluation of C-fiber function. Because many neuropathies show a length-dependent loss of nerve function, a new capsule was designed for distal performance of the QSART, allowing measurements on fingers and toes. We investigated 20 healthy volunteers and 15 patients with insulin-dependent diabetes mellitus and normal sensory nerve conduction studies. A QSART was performed on the forearm and on the thumb. The groups showed no differences in the QSARTs on the forearm, but the sweat volume on the thumb was significantly lower in patients. Calculation of the forearm/finger ratio reduced the interindividual variation and showed the highest sensitivity for detecting C-fiber dysfunction in the patient group. We conclude that the distal measuring device and the forearm/finger ratio are more sensitive tools for the early detection of distal-onset neuropathies than are the commonly used proximal testing sites.
Besides the dopaminergic afferent projection system, calbindin (CALB)- and calretinin (CR)-immunoreactive fibres of intrinsic and extrinsic origin represent the most abundant axonal categories in the rat striatal and lateral septal areas. The question arises whether or not they may represent separate populations, or whether they form subgroups which co-express more than one of these antigens. Therefore, the present study is focused on the distribution patterns of the axons single-immunolabelled by the catecholaminergic marker tyrosine hydroxylase (TH), and on TH-immunoreactive axons displaying also CR- and/or CALB-immunoreactivity in double-immunostained sections. Striking differences were found between the patch and matrix compartments of the caudate-putamen (CP). Whereas the vast majority of TH-immunoreactive fibres in the patches and a patch-associated subcallosal layer co-expressed CR but not CALB, fibres mono-labelled by the TH-immunoreactivity were predominant in the matrix. The matrix-like regions of the core of nucleus accumbens (CACC), fundus striati (FS), the striatal cell bridges (CB) and the striatal part of olfactory tubercle (OTU) coincided in this respect with the matrix in CP. The absence of CR-immunoreactivity was also characteristic of the TH-immunoreactive fibres in the patch-like areas of the accumbal core, although a high number of separate CR-immunoreactive axons were present. In the shell of nucleus accumbens (SACC) which receives a rich catecholaminergic innervation, fibres co-expressing either one of the calcium-binding proteins were absent. The islands of Calleja (CJI) displaying a strongly TH-immunoreactive centre and a periphery of lower staining intensity, showed only a low number of TH-immunoreactive fibres co-expressing CR or CALB. The broad shell-like band of TH-immunoreactive axons between medial and lateral part of the septum was single-stained with the TH-immunoreactivity. In contrast, the TH-positive fibres forming basket-like arrangements around some neurons in the dorsal lateral septal nucleus co-expressed also CR, but not CALB. The results are discussed in view of the recent concepts of basal forebrain organization and the cytochemical characteristics of mesencephalic dopaminergic nuclei giving rise to the vast majority of the striatal and septal TH-immunoreactive fibre supply, in order to correlate the known projection patterns with the content of calcium-binding proteins in TH-immunolabelled fibres and presumed cells of origin. The TH-immunoreactive fibres in the striatal patches displaying CR- but not CALB-immunoreactivity may originate mainly from neurons in the ventral tier of pars compacta (SNC) and from the pars reticulata of substantia nigra (SNR) which show identical cytochemical properties. Axons in the matrix of CP and the accumbal core as well as in the islands of Calleja single-labelled by the TH-immunoreactivity or additionally containing CALB and CR may originate from neurons in the dorsal tier of mesencephalic nuclei like SN, pars compacta and ventral tegmental area. CR-containing TH-immunoreactive basket-like axon terminations in the dorsal lateral septal nucleus are likely to originate either from mesencephalic nuclei or from the supramammillary region.
The ventral striatum is more closely related to limbic brain regions than the dorsal striatum in spite of the remarkable similarities in the structural organization between these two brain regions. The present study is focused on the comparison of ventral striatopallidal territories and the dorsal striatopallidal system regarding the GABA(A)-receptor alpha1-subunit and parvalbumin immunoreactivity, as these markers showed specific distribution patterns and coexpression sites in the more intensely studied dorsal regions. Our investigations revealed that: (1) Parvalbumin single-labeled cells and a moderate number of neurons single-labeled with the GABA(A)-receptor alpha1-subunit exist not only in the dorsal but also in the ventral striatum, including the striatal cell bridges. In addition, morphologically similar neurons positive for the alpha1-subunit were also found in the corpus callosum and anterior commissure. (2) A small number of double-labeled neurons was seen not only in dorsal but also in ventral striatal regions. Such cells were mainly located near the border with the globus pallidus and ventral pallidum. They are likely to represent a further type of striatal neuron. (3) The vast majority of neurons in the entopeduncular nucleus, the homologue of the primate internal globus pallidus segment, coexpressed alpha1-subunit and parvalbumin immunoreactivity, as reported previously for the other pallidal compartments. (4) The islands of Calleja adjoining the ventral pallidal extensions in the olfactory tubercle exhibited a strong alpha1-subunit immunoreactivity in the neuropil as well as somata single- or double-labeled for both markers. Our findings indicate that the dorsal and ventral striatopallidal compartments are similarly organized in general with respect to the occurrence and distribution of single- and double-labeled parvalbumin-immunoreactive and GABA(A)-receptor alpha1-subunit-immunoreactive neurons.
This paper describes the use of a neonatal sphygmomanometer cuff as a simple, inexpensive pinch meter. Normal values for key pinch, pulp pinch and side pinch in the dominant hand of healthy Nepali people are provided. The pinch meter was also used to test pinch strength in hands affected by leprosy and normal hands. Some patients with leprosy who have no objective weakness on voluntary muscle testing (VMT) have less pinch strength than people without leprosy. The pinch meter is a useful tool for the early detection of motor function loss.
The light-induced electron transfer in a crosslinked complex between plastocyanin and photosystem I from spinach was studied by EPR at low temperature. Electron donation from reduced plastocyanin to P700+ was observed under illumination above a temperature of about 160 K, resulting in a second charge separation and an electron transfer from rereduced P700 to the terminal electron acceptors FA/FB. The charge-separated state Pc oxP700+ [FA/FB](2-) was found to be stable at 15 K. Implications of these results for the kinetic constants of the donation reaction and the backtransfer of electrons from reduced acceptors as well as for the structural models of the terminal acceptors are discussed.
Cerebral metastases occur in 25% to 35% of all cancer patients. The advances in systemic and topical treatment as well as the rising incidence of lung cancer and melanomas are associated with an increasing incidence of cerebral metastases. More than 20,000 patients die every year in the Federal Republic of Germany of this disease. This retrospective analysis covers 145 patients who underwent surgery. Survival analysis of different subgroups was performed. The patients were grouped according to their clinical status and the different therapeutical procedures which were performed. Group A, consisting of all those patients where a gross total resection could be performed and where no systemic disease was apparent at the time of craniotomy showed the best results, having the highest portion of long term survivors. Group B, consisting of those patients who underwent a subtotal resection and who had no systemic disease at the time of craniotomy, had a worse outcome. Group C patients (gross total resection and systemic disease) as well as Group D (subtotal resection and systemic disease) presented the poorest results with respect to survival. A benefit was mediated by adjuvant radiation as well as multiple resections. Surgery is the method of choice for the treatment of a single metastasis. Advances in microsurgery nowadays sometimes justify even the removal of multiple metastases, depending on their location, on the general condition of the patient and on prognosis.
Advances in chemotherapy significantly prolong survival of patients with acute myeloid leukemia (AML) and may cure a significant percentage of patients. Therefore, the assessment of quality of life (QL) of patients undergoing chemotherapy is of growing interest. This study was designed to evaluate QL in patients with AML treated according to the protocol of the German AML-Cooperative Group (Münster, FRG). Based on conceptual, methodological and practical criteria, the EORTC-QLQ C 30 questionnaire was used. In addition, patients' coping strategies were assessed by the FQCI. Patients' individual perception of their disease and therapy was evaluated by a semi-structured interview. Currently, 61 patients are enrolled in the protocol. For those patients having completed the course of inpatient treatment, individual assessment of Global Health Status and Subjective QL improves significantly. The content analysis of the interviews shows to what extent aspects of the inpatient setting influence patients' QL. Although only a minority of patients with AML remain in continuous complete remission, the evaluation of QL in patients undergoing treatment shows that subjective benefit outweighs the effects of antileukemic therapy.