Search PubMed⌕ Search

Biomedical subjects

A Richter

Publications and source records attributed to A Richter.

At least 19 recordsLinked to original sources
PubMed2007

"Silent" bone stress injuries in the feet of diabetic patients with polyneuropathy: a report on 12 cases.

BACKGROUND: Bone stress injuries are rarely being diagnosed in patients with sensory neuropathy, most likely because they may be silent in terms of pain. Load-related pain is considered a key feature of any bone stress injury, a symptom, which may be partially or completely absent in subjects with sensory neuropathy (loss of protective sensation). We evaluated the clinical course of bone stress injuries in insensitive feet in diabetic patients with polyneuropathy. METHODS: We investigated 12 consecutive diabetic patients with bone stress injuries of the foot (bone marrow edema, bone bruise and microtrabecular fractures, on magnetic resonance imaging MRI), which were undetectable on plain X-ray. All patients suffered from diabetic polyneuropathy, none of them had an active foot ulcer. RESULTS: The patients presented with a swollen foot, which was only mildly painful and did not prevent them from walking. Complaints were related to the swelling, which increased during load-bearing. In seven cases, a traumatic event preceding the onset of symptoms could be ascertained. MRI disclosed stress injuries in 2.5 (1-8) [median (range)] bones per foot. In 11 patients, treatment was started immediately by off-loading with total contact cast for 17 (8-52) weeks, followed by gradual increase in weight bearing. One patient unfortunately received off-loading treatment only after deforming fractures had developed. All bone injuries healed uneventuelly in eight patients, and with residual mild osteoarthrosis in three patients without gross deformities. However, the untreated patient developed severe Charcot foot deformity. CONCLUSIONS: In diabetic patients with polyneuropathy, symptoms of bone stress injuries of the foot are atypical, in that there is load-related swelling rather than load-related pain. Immediate diagnosis, and treatment with off-loading, leads to a restitutio ad integrum like in non-neuropathic patients. Delayed cessation of overuse, however, may cause irreversible joint and bone damage (Charcot foot).

Aged↗
PubMed2006

Physiological responses of bryophytes Thuidium tamariscinum and Hylocomium splendens to increased nitrogen deposition.

BACKGROUND AND AIMS: Increased levels of nitrogen (N) deposition lead to enhanced N contents and reduced productivity of many bryophyte species. This study aimed at elucidating the mechanisms by which enhanced N uptake may cause growth reduction of bryophytes, focusing on the effects of N addition on carbon (C) metabolism of bryophytes. METHODS: Plantlets of Thuidium tamariscinum and Hylocomium splendens were fertilized with NH(4)NO(3) (N load equalling 30 kg ha(-1) year(-1)) for 80 d, including a pulse labelling experiment with (13)CO(2) to dissect the partitioning of carbon in response to N addition. KEY RESULTS: Growth of T. tamariscinum was not affected by N addition, while H. splendens showed a trend towards growth reduction. Total N concentration was significantly increased by N addition in H. splendens, a significant increase in amino acid-N was found in T. tamariscinum only. In both bryophyte species, a reduction in concentration of lipids, the greatest C storage pool, as well as markedly enhanced turnover rates of C storage pools in fertilized plants were observed. CONCLUSIONS: The results suggest that growth reduction of H. splendens under high levels of N deposition may be caused by enhanced synthesis of N-containing organic compounds, most probably of cell wall proteins. Disturbance of cellular C metabolism, as indicated by enhanced C pool turnover, may further contribute to the decline in productivity of H. splendens.

Bryopsida↗
PubMed2006

Antidystonic effects of Kv7 (KCNQ) channel openers in the dt sz mutant, an animal model of primary paroxysmal dystonia.

BACKGROUND AND PURPOSE: Mutations in neuronal Kv7 (KCNQ) potassium channels can cause episodic neurological disorders. Paroxysmal dyskinesias with dystonia are a group of movement disorders which are regarded as ion channelopathies, but the role of Kv7 channels in the pathogenesis and as targets for the treatment have so far not been examined. EXPERIMENTAL APPROACH: In the present study, we therefore examined the effects of the activators of neuronal Kv7.2/7.3 channels retigabine (5, 7.5, 10 mg kg(-1) i.p. and 10, 20 mg kg(-1) p.o.) and flupirtine (10, 20 mg kg(-1) i.p.) and of the channel blocker 10,10-bis(4-pyridinylmethyl)-9(10H)-anthracenone (XE-991, 3 and 6 mg kg(-1) i.p.) in the dt sz mutant hamster, a model of paroxysmal dyskinesia in which dystonic episodes occur in response to stress. KEY RESULTS: Retigabine (10 mg kg(-1) i.p., 20 mg kg(-1) p.o.) and flupirtine (20 mg kg(-1) i.p.) significantly improved dystonia, while XE-991 caused a significant aggravation in the dt sz mutant. The antidystonic effect of retigabine (10 mg kg(-1) i.p.) was counteracted by XE-991 (3 mg kg(-1) i.p.). CONCLUSIONS AND IMPLICATIONS: These data indicate that dysfunctions of neuronal Kv7 channels deserve attention in dyskinesias. Since retigabine and flupirtine are well tolerated in humans, the present finding of pronounced antidystonic efficacy in the dt sz mutant suggests that neuronal Kv7 channel activators are interesting candidates for the treatment of dystonia-associated dyskinesias and probably of other types of dystonias. The established analgesic effects of Kv7 channel openers might contribute to improvement of these disorders which are often accompanied by painful muscle spasms.

Animals↗
PubMed2006

Gamow-Teller strengths in the A = 14 multiplet: a challenge to the shell model.

A new experimental approach to the famous problem of the anomalously slow Gamow-Teller (GT) transitions in the beta decay of the A=14 multiplet is presented. The GT strength distributions to excited states in 14C and 14O were studied in high-resolution (d,2He) and (3He,t) charge-exchange reactions on 14N. No-core shell-model calculations capable of reproducing the suppression of the beta decays predict a selective excitation of Jpi=2+ states. The experimental confirmation represents a validation of the assumptions about the underlying structure of the 14N ground state wave function. However, the fragmentation of the GT strength over three 2+ final states remains a fundamental issue not explained by the present no-core shell model using a 6homega model space, suggesting possibly the need to include cluster structure in these light nuclei in a consistent way.

Journal Article↗
PubMed2006

Transgenic peas (Pisum sativum) expressing polygalacturonase inhibiting protein from raspberry (Rubus idaeus) and stilbene synthase from grape (Vitis vinifera).

The pea (Pisum sativum L.) varieties Baroness (United Kingdome) and Baccara (France) were transformed via Agrobacterium tumefaciens-mediated gene transfer with pGPTV binary vectors containing the bar gene in combination with two different antifungal genes coding for polygalacturonase-inhibiting protein (PGIP) from raspberry (Rubus idaeus L.) driven by a double 35S promoter, or the stilbene synthase (Vst1) from grape (Vitis vinifera L.) driven by its own elicitor-inducible promoter. Transgenic lines were established and transgenes combined via conventional crossing. Resveratrol, produced by Vst1 transgenic plants, was detected using HPLC and the PGIP expression was determined in functional inhibition assays against fungal polygalacturonases. Stable inheritance of the antifungal genes in the transgenic plants was demonstrated.

Acyltransferases↗
PubMed2006

Strength distributions and symmetry breaking in coupled microwave billiards.

Flat microwave cavities can be used to experimentally simulate quantum mechanical systems. By coupling two such cavities, we study the equivalent to symmetry breaking in quantum mechanics. As the coupling is tunable, we can measure resonance strength distributions as a function of the symmetry breaking. We analyze the data by employing a qualitative model based on random matrix theory and show that the results derived from the strength distribution are consistent with those previously obtained from spectral statistics.

Journal Article↗
PubMed2006

Retrieval and monitoring of atmospheric trace gas concentrations in nadir and limb geometry using the space-borne SCIAMACHY instrument.

The Scanning Imaging Absorption Spectrometer for Atmospheric Chartography (SCIAMACHY) onboard the European Envisat spacecraft performs continuous spectral observations of reflected, scattered and transmitted sunlight in various observation geometries. A unique feature of SCIAMACHY is the capability of probing the atmosphere in three different observation geometries:The nadir, limb, and occultation measurement modes. In nadir mode, column densities of trace gases are retrieved with a spatial resolution of typically 30 x 60 km using the Differential Optical Absorption Spectroscopy (DOAS) technique (Platt and Perner, 1983). Alternating with the nadir measurement, vertical profiles of absorber concentration in the stratosphere are derived in limb and occultation. In this paper we present an overview over some applications of SCIAMACHY data in space-based monitoring of atmospheric pollution. The DOAS algorithms for the retrieval of total column amounts from nadir spectra are briefly described and case studies of pollution events are presented. We also illustrate the technique used to derive stratospheric concentration profiles from limb observations and show comparisons with other remote sensing systems. Special emphasis will be given to techniques, which take advantage of SCIAMACHY's different viewing geometries. In particular, we will discuss the potential and limits of strategies to infer tropospheric abundances of O3 and NO2.

Air Pollutants↗
PubMed2006

Spectral statistics in an open parametric billiard system.

We present experimental results on the eigenfrequency statistics of a superconducting, chaotic microwave billiard containing a rotatable obstacle. Deviations of the spectral fluctuations from predictions based on Gaussian orthogonal ensembles of random matrices are found. They are explained by treating the billiard as an open scattering system in which microwave power is coupled in and out via antennas. To study the interaction of the quantum (or wave) system with its environment, a highly sensitive parametric correlator is used.

Journal Article↗
PubMed2006

Fine structure of the Gamow-Teller resonance in 90Nb and level density of 1+ states.

The fine structure of the Gamow-Teller resonance in a medium-heavy nucleus is observed for the first time in a high-resolution 90Zr(3He,t)90Nb experiment at the Research Center for Nuclear Physics, Osaka. Using a novel wavelet analysis technique, it is possible to extract characteristic energy scales and to quantify their relative importance for the generation of the fine structure. This method combined with the selectivity of the reaction permits an extraction of the level density of 1+ states in 90Nb.

Journal Article↗
PubMed2006

[Acute colonic pseudoobstruction following fixation of a pertrochanteric fracture].

Acute colonic pseudoobstruction, following traumatic injuries, is a rare diagnosis. Nevertheless it is life threatening, if it is not recognized and treated promptly. We report one case of this so-called Ogilvie's syndrome, which followed fixation of a trochanteric fracture by intramedullary nailing within 2 days. Due to massive acute colonic distension, the patient suffered from respiratory failure. We excluded other intestinal diseases by CT scanning. After conservative colonic decompression, he recovered after 2 days in the intensive care unit. We describe a variable treatment depending on the severity of the colonic atony. Knowledge of Ogilvie's syndrome, or acute colonic pseudoobstruction, is a must for trauma surgeons, since it can occur within a few hours and can lead to dramatic situations.

Acute Disease↗
PubMed2006

Surgery of cavernous malformations with and without navigational support--a comparative study.

BACKGROUND: The aim of this descriptive study was the comparison of the clinical and surgical data of patients who suffered from cavernoma and were treated surgically with and without intraoperative navigation (ultrasound, neuronavigation). METHOD: Between 1995 and 2002, 40 patients were treated for cavernous malformations microsurgically: 24 patients (group I) using a neuronavigation system (STP 4.0, SNN, Germany), 7 patients (group II) using ultrasound (Siemens Omnia with 5.0 MHz Probe) and 9 patients (group III) without any image guidance using anatomic landmarks. FINDINGS: With the use of neuronavigation the mean sizes of cavernous malformations, which were resected, were reduced from 25.6 mm (group III) and 24.4 mm (group II) to 16.3 mm (group I) (p > or = 0.05). Corresponding to the reduction of the cavernoma size, the mean distances of the vascular lesion to the cortical surface increased from 13.9 mm (group III) and 17.8 mm (group II) to 24.4 mm under neuronavigational support (p > or = 0.05). All cavernomas were resected completely in all 40 patients. Postoperative neuroradiological control (MRI) confirmed complete resection in all cases. No significant differences in the clinical outcome could be evaluated in all three groups up to three months postoperatively. CONCLUSIONS: Use of neuronavigation was associated with a more comfortable and safer surgery of smaller and more deeper-seated cavernomas. In spite of the lack of significance between all groups, the advantages of neuronavigation in planning and realising surgery could be documented, which justify the additional costs and time-consuming acquisition of planning image data and postprocessing as well as intraoperative navigation.

Adolescent↗
PubMed2006

The diabetic charcot foot: MRI discloses bone stress injury as trigger mechanism of neuroarthropathy.

It is generally accepted that traumatic bone injury contributes to the clinical picture of neuroarthropathy of the foot in diabetes, i.e., of the diabetic Charcot foot. While radiology is capable of visualizing only advanced bone injuries, like complete fractures, magnetic resonance imaging (MRI) discloses bone injuries that precede complete fractures (stress bone injuries). In diabetic polyneuropathy, stress bone injuries are silent in terms of pain, due to the lack of pain sensation. At the foot, their clinical appearance is characterized by inflammatory swelling with little or no pain. The present paper reviews the contribution of MRI to the detection of bone injuries in what is called stage 0 Charcot foot, with emphasis on the bearings for the treatment strategy.

Bone Marrow Diseases↗
PubMed2006

Age-related changes in striatal nitric oxide synthase-immunoreactive interneurones in the dystonic dtsz mutant hamster.

The dt(sz) mutant hamster represents a model of paroxysmal dyskinesia in which dystonic episodes can be age-dependently induced by stress. GABAergic interneurones which co-express calcium binding proteins were found to be reduced in the striatum of the dt(sz) mutant. Other types of striatal interneurones have so far not been examined. In the present study, we therefore determined the density of nitric oxide synthase (NOS)-immunoreactive interneurones in the striatum of the dt(sz) mutant in comparison with nondystonic control hamsters. At the age of most marked expression of dystonia (30-40 days of life), the density of NOS-positive interneurones was decreased in the striatum of dt(sz) hamsters (-21%) in comparison with age-matched nondystonic control hamsters. Spontaneous remission of dystonia (age >90 days) coincided with a normalization of the density of NOS-reactive interneurones within the whole striatum of dt(sz) hamsters, but there remained a reduced density in distinct subregions. Together with previous findings the present data indicate that the development of striatal interneurones is retarded in mutant hamsters. The age-related deficit of NOS-reactive interneurones may at least in part contribute to an abnormal activity of striatal GABAergic projection neurones and thereby to the age-dependent dystonic syndrome in the dt(sz) mutant.

Age Factors↗
PubMed2006

Monitoring of plasmin and plasminogen activator activity in blood of patients under fibrinolytic treatment by reteplase.

There are no reliable data on plasmin or plasminogen activator (PA) activities in blood of patients receiving fibrinolytic treatment. This is due to continuing in vitro action of PA after blood withdrawal. These artefactual changes of PA or plasmin activities have been prevented by arginine stabilization of blood samples of myocardial infarction patients treated with plasminogen activators. Twelve patients with myocardial infarction were treated with reteplase 2 x 10,000,000 units in bolus application; one patient was treated with 100 mg t-PA in continuous infusion. Blood was immediately stabilized with EDTA and arginine. The plasma was analyzed with newly developed assays for plasmin and PA. Maximal plasmin activities in blood were obtained at 40 to 60 minutes reteplase treatment time (0.1-0.6 U/mL = approximately 0.05-0.3 micromol/L plasmin). The 50% clearance rate for plasmatic Pli was greater than 30 minutes. The plasmatic reteplase concentration peaked at approximately 2,000 U/mL after the first bolus infusion and at approximately 1,500-3,500 U/mL after the second bolus infusion. Reteplase was cleared to 50% within less than 30 minutes, also with great inter-individual variation. Arginine stabilization of blood allows reliable determinations of activities of plasmin and PA in blood of patients under fibrinolytic treatment: substantial plasmin activities occur in patients treated by reteplase. Therapeutic thrombolysis might be improved, imitating the physiologic cellular thrombolysis; i.e., polymorphonuclear phagocytes (PMN) that can be activated by singlet oxygen ((1)O(2)). PMN might be superior to PA in selective lysis of pathologic thrombi.

Arginine↗
PubMed2006

Targeting dsRNA-specific single-chain Fv antibody fragments to different cellular locations in Nicotiana tabacum L.

Expression of antibodies or antibody fragments in plants is a useful tool for producing active antibody derivatives for diagnostic or pharmaceutical purposes as well as for immunomodulation. We investigated the effect of cellular expression site on the stability and yield of double-stranded RNA (dsRNA)-specific single-chain Fv-fragments (scFv) in transgenic tobacco. Two antibodies (J2 and P6) belonging to the V23(J558) heavy chain variable gene family but differing in the light chain variable domain were used. scFvs were targeted to the cytoplasm - with or without anchoring them in the plasma membrane -, into the endoplasmic reticulum (ER) and to the apoplast. Although high mRNA concentrations were detected in all cases, scFv proteins accumulated only when scFvs were made ER-resident by appropriate signal sequences. When the ER retention signal was removed to allow scFv-secretion to the apoplast, no scFv-proteins were detected. Despite the strong homology of the VH-sequences of J2 and P6 antibodies, only P6 provided a stable scFv scaffold for intracytoplasmic expression. J2-scFv could not be stabilised either by adding a C-terminal stabilisation signal or by anchoring the protein on the cytoplasmic side of the plasma membrane (PM). It was found that dsRNA-specific J2-scFvs are active in vivo and enhance Potato Virus Y induced symptoms in infected tobacco. This is the first report describing the expression and biological effect of RNA-specific antibodies in plants.

Antibodies↗
PubMed2006

[Investigations on the influence of selected compulsory measures on clinically relevant haematological and blood-chemical parameters of racing pigeons (Columba livia f. dom.)].

In the presented study the influence of stress and environmental factors on selected haematological and blood-chemical parameters in racing pigeons was examined. Blood was taken at three defined days and haematological as well as blood-chemical parameters of clinical relevance were determined. In comparison to reference values published for pigeons, the majority of the values obtained in this study were within physiological borders. The daily handling of the pigeons did not have any significant effect on the examined parameters. Also the heterophile/lymphocyte ratio did not show any changes characteristic of a stress reaction. In contrast, after change of the housing dies with pigeons originating normally from a flock, the first blood sampling should be performed after a 4 or 5-day lasting period of acclimatisation to the the individual housing conditions.

Animals↗