Biomedical subjects

H Richter

Publications and source records attributed to H Richter.

At least 55 records · Page 3Linked to original sources

PubMed2000

Hyperpolarization-activated cation currents in stellate and pyramidal neurons of rat entorhinal cortex.

Properties of hyperpolarization-activated cation currents (I(h)) were investigated in neurons of juvenile rat entorhinal cortex using the patch-clamp technique. A rat brain slice preparation containing the entorhinal cortex was used for whole-cell recordings of I(h) in pyramidal cells from layer IV and in stellate cells from layer II of the entorhinal cortex. In both stellate and pyramidal cells, I(h) activated at potentials more negative than -60 mV and did not show any time-dependent inactivation. Half-maximal activation of I(h) was achieved at -95.3 mV in pyramidal cells and at -95.0 mV in stellate cells. The channels were permeable for sodium and potassium ions. I(h) of pyramidal and stellate neurons was reduced by about 50% in the presence of 100 microM ZD7288. Extracellularly applied 1 mM Cs(+) decreased I(h) of pyramidal cells by 92%, whereas I(h) of stellate cells was only reduced by 70%. In both pyramidal and stellate neurons, I(h) was not significantly changed during the application of 1 mM Ba(2+). 8-Bromo-c-AMP increased amplitudes of I(h) in stellate cells, while I(h) of pyramidal cells remained unchanged. It is suggested that different types of hyperpolarization-activated cation channels are expressed in pyramidal and stellate cells of the entorhinal cortex.

8-Bromo Cyclic Adenosine Monophosphate↗

PubMed2000

New approach in the therapy of chronic rejection? ACE- and AT1-blocker reduce the development of chronic rejection after cardiac transplantation in a rat model.

BACKGROUND: Angiotensin II is one of the most potent mitogens of smooth muscle cell proliferation and plays a central role in the development of accelerated coronary artery disease (ACAD), which remains a serious consequence after heart transplantation and limits long-term survival. We investigated the effect of an angiotensin-II blocker, Losartan (angiotensin II Type 1 [AT(1)]-blocker), and an angiotensin-converting enzyme (ACE) inhibitor, Enalapril, on experimental ACAD in a rat cardiac transplant model (Fisher to Lewis). METHODS: After grafting, recipients were treated with 10 mg/kg/day per os Losartan or 40 mg/kg/day per os Enalapril. Two groups of animals received additional pre-treatment with Losartan or Enalapril 7 days before transplantation. All study groups, including the control group, received immunosuppression with cyclosporine (3 mg/kg/day sub-cutaneously). We assessed the extent of ACAD of large and small arteries 80 days after grafting using digitizing morphometry. RESULTS: We observed significant reduction of neointimal proliferation in small arteries in Losartan pre- and post-treated and in Enalapril pre-treated recipients compared with the cyclosporine-treated group (p < 0.05). In epicardial arteries, Enalapril pre- and post-treatment as well as Losartan post-treatment significantly reduced neointimal formation compared with the control group. Reduction of neointima by Enalapril post-treatment in small arteries and Losartan pre-treatment in large arteries trended toward but failed statistical significance. CONCLUSIONS: Our results suggest the important role of the renin-angiotensin system in neointimal proliferation, which can be reduced equally with ACE inhibitors or the angiotensin-II blocker. Therefore AT(1) blockade with Losartan is a useful therapeutic strategy for inhibition of ACAD after cardiac transplantation.

Angiotensin II↗

PubMed2000

Irregular costameres represent nitric oxide synthase-1-positive sarcolemma invaginations enriched in contracted skeletal muscle fibres.

NADPH diaphorase histochemistry and NOS-1 immunohistochemistry on 60 microm thick frozen sections of rat extensor digitorum longus muscles led to the detection of prominent rings clearly encompassing the surface of the muscle fibres. These so far unknown costameres were usually found as doublets flanking a space of about 2 microm width. Because these costameric doublets did not appear in regular periods, we designate them irregular costameres to discriminate them from regular ones with a 1 microm periodicity overlying Z-discs and M-lines. Irregular costameres were thicker than the regular ones and free of intercostameres. Immunohistochemistry demonstrated that NOS-1 was co-localized with integral (beta-dystroglycan, alpha-sarcoglycan) and peripheral (caveolin-3, dystrophin) members of the enlarged dystrophin complex in the irregular costameres but not with non-sarcolemmal organized proteins (myosin heavy chain, alpha-actinin, desmin and sarcoplasmic reticulum-located Ca2+-dependent ATPase-1). Invaginations of the sarcolemma to form irregular costameres were observed. In teased myofibres the sarcolemma between two following irregular costameres was ballooned, while the irregular costameres themselves clamped the fibres together. Finally, the number of detectable irregular costameres was significantly increased in maximally contracted extensor digitorum longus muscles generated by electric stimulation but decreased in mechanically stretched ones. Combining these observations, we hypothesize that irregular costameres belong to a reserve zone for the sarcolemma necessary for the contraction/relaxation cycle in myofibres.

Animals↗

PubMed2000

[Recent developments in systematic evaluation of the therapeutic process. Scales for the assessment of adherence and competence].

The assessment of therapists' behaviour an essential part of psychotherapy research, especially for controlling the validity of studies. In the last decade, particularly in English-speaking countries, research has been developed that studied two constructs important in this context: adherence and competence. Adherence refers to the extent to which therapists use the strategies recommended in a therapy manual; competence refers to the quality of the use of these strategies. This article is a review of research associated with adherence and competence scales and its relevance. First of all, definitions and examples of use are presented and discussed. Secondly, some of the most important scales that have been developed in this context are described. Thirdly, aspects of realisation are presented. Finally, the pros and cons of this type of research are discussed. It is argued that despite some problems adherence and competence scales are a significant contribution to the systematic assessment of therapist behaviour.

Germany↗

PubMed2000

Heme oxygenase-2 is present in the sarcolemma region of skeletal muscle fibers and is non-continuously co-localized with nitric oxide synthase-1.

There is increasing evidence that the heme oxygenase-2 (HO-2)/carbon monoxide (CO) pathway and the nitric oxide synthase (NOS)/nitric oxide (NO) pathway functionally cross-talk. Therefore, we investigated the appearance of HO-2 in mammalian skeletal muscles where NOS-1 is known to be expressed in high quantities. Immunoblotting of rat hind limb extensor muscles extracts revealed a single 36 kDa band demonstrating the existence of HO-2 in skeletal muscle and indicating the monospecifity of the antibody that was applied. Immunohistochemistry on healthy rat extensor hind limb muscles showed that HO-2 is present in satellite cells, endothelial cells of the vascular system, fibrocytes/fibroblasts but also fiber type-independently in extrafusal myofibers either in association with the non-junctional sarcolemma region, or in a subsarcolemmal network or, less prominently, in cross-striated stripes connected to longitudinally running lines. Combined HO-2 immunohistochemistry and NOS-1 histochemistry revealed an apparent co-localization of both molecules only in the non-junctional sarcolemma region of extrafusal type II myofibers outside costameres. In diseased muscles of mdx mice, HO-2 expression was not changed. In patients suffering from Duchenne's muscular dystrophy, it was absent in the sarcolemma region. In conclusion, the HO-2/CO system is present in mammalian skeletal muscle where it is non-continuously co-localized with the NOS-1/NO-system. This finding implicates an optionally functional cross-talk between both gaseous signaling pathways.

Animals↗

PubMed2000

Inhaled salbutamol for wheezy infants: a randomised controlled trial.

BACKGROUND: Salbutamol is frequently used as a bronchodilator for infants who wheeze. Many single dose studies have questioned its effectiveness. AIMS: To investigate the response of wheezy infants to salbutamol over an extended time period in order to elucidate either symptomatic relief or a protective effect. METHODS: Eighty infants under 1 year, with persistent or recurrent wheeze and a personal or family history of atopy, were recruited to a randomised, double blind, cross over, placebo controlled trial. Salbutamol (200 microg three times daily) or placebo were administered regularly over two consecutive treatment periods of four weeks via a spacer and mask. Symptoms of wheeze and cough were recorded in a diary. At the end of the study pulmonary function tests were performed before and after salbutamol (400 microg). RESULTS: Forty eight infants completed the diary study; 40 infants underwent pulmonary function testing. No difference in mean daily symptom score was observed between the salbutamol and placebo periods. There was no difference in the number of symptom free days. Compliance and forced expiratory flows remained unchanged and resistance increased following salbutamol. There was no relation between the response measured by symptom score or pulmonary function in individual patients. CONCLUSION: In wheezy infants with an atopic background, there was no significant beneficial effect of salbutamol on either clinical symptoms or pulmonary function. Clinical effects could not be predicted from pulmonary function tests. Salbutamol cannot be recommended as the bronchodilator of choice in this age group.

Administration, Inhalation↗

PubMed2000

Children's perception of breathlessness in acute asthma.

AIM: To determine whether asthmatic children who present to hospital with hypoxia perceive breathlessness less well than non-hypoxic presenters. METHODS: A total of 27 children aged 5-16 years (mean age 10) admitted with acute asthma had recordings of oxygen saturation (SaO(2)), clinical score, forced expiratory volume in one second (FEV(1)), and breathlessness score (HMP) at admission and at 5, 10, 24, 48, and 72 hours after admission. Those defined as hypoxic (SaO(2) <92%) at admission were compared with a non-hypoxic group. RESULTS: Twelve children were hypoxic at admission. Compared with the non-hypoxic group they were younger (8.6 (SD 2.8) v 11.2 (2. 8) y, p = 0.02), and had greater airway obstruction (FEV(1) 32.5 (10)% v 54.3 (26)%, p = 0.0073, 95% confidence interval (CI) -36.9 to -6.6) yet had a trend towards less breathlessness (median HMP 4 v 3, p = 0.062, CI -0.001 to 2.00) at admission. The hypoxic group had a smaller change in breathlessness from admission to discharge, despite a similar improvement in FEV(1), reflected in a lower ratio of change in HMP to change in FEV(1) (DeltaHMP/DeltaFEV(1)) (median DeltaHMP/DeltaFEV(1) 0.021%(-1) v 0.073%(-1), p = 0.0081, CI -0.075 to -0.016). Linear regression analysis showed a strong relation between DeltaHMP/DeltaFEV(1) and initial SaO(2) (p = 0.004, r = 0. 54). CONCLUSIONS: Asthmatic children who present to hospital hypoxic tend to perceive themselves as less breathless than non-hypoxic children. This may predispose to a future life threatening attack.

Acute Disease↗

PubMed2000

Chemical characterization and bioactivity of polycyclic aromatic hydrocarbons from non-oxidative thermal treatment of pyrene-contaminated soil at 250-1,000 degrees C.

In this paper we report yields, identities, and mutagenicities of products from heating a polycyclic aromatic hydrocarbon (PAH)-contaminated, Superfund-related synthetic soil matrix without exogenous oxygen. We heated batch samples of soil pretreated with 5.08 wt% (by weight) pyrene in a tubular furnace under a constant flow of helium gas at 250, 500, 750, and 1,000 +/- 20 degrees C. Dichloromethane (DCM) extracts of cooled residues of heated soil and of volatiles condensed on a cold finger after 1 sec residence time at furnace temperature were assayed gravimetrically and analyzed for PAH by HPLC, HPLC coupled to mass spectrometry, and gas chromatography coupled to mass spectrometry. All four temperatures volatilized pyrene and generated other PAHs, including alkylated pyrenes. We detected bioactive PAHs in the product volatiles: cyclopenta[cd]pyrene (CPP) at 750 and 1,000 degrees C and benzo[a]pyrene (BaP) at 1,000 degrees C. We found a clean soil residue, i.e., no pyrene or other DCM extracts, only at 750 degrees C. Control experiments with uncontaminated soil, pyrene, and Ottawa sand plus 4.89 wt% pyrene revealed no CPP or BaP production from soil itself, but these experiments imply that pyrene interactions with soil, e.g., soil-bound silica, stimulate CPP and BaP production. We detected mutagenicity to human diploid lymphoblasts (in vitro) in volatiles from 1,000 degrees C heating of soil plus pyrene and sand plus pyrene, and in the residue from 500 degrees C heating of soil plus pyrene. Three plausible pathways for pyrene conversion to other PAHs are a) a reaction with light gas species, e.g., soil- or pyrene-derived acetylene; b) loss of C(2)-units followed by reaction with a PAH; and c) dimerization with further molecular weight growth via cyclodehydrogenation. This study shows that thermal treatment of PAH-polluted soil may generate toxic by-products that require further cleanup by oxidation or other measures.

Benzopyrenes↗

PubMed2000

Characterization of dimethyldiacyloxysilanes by differential scanning calorimetry, Raman scattering and X-ray diffraction.

The phase behaviour of diacyloxydimethylsilanes (DMS Cn; n = 10, 12, 14, 16, 18, 20, 22) was investigated by differential scanning calorimetry, X-ray diffraction and Raman spectroscopy. All DMS Cn melt from a crystalline phase to an isotropic liquid with a single sharp transition. On cooling, the homologous DMS C16 up to DMS C22 show a characteristic monotropic phase (L beta'H). In contrast to the calorimetrical investigations, it was not possible to analyse the monotropic phase of DMS C16 by X-ray diffraction. This behaviour is due to a two-phase region (gel phase--crystalline phase). The Raman spectra of all DMS are very similar. Only in the low frequency range we find different bands of the longitudinal acoustic modes. The Raman measurements demonstrate undoubtedly that in the solid state the alkyl chains are in all-trans conformation. The factor group splitting of the CH2 scissoring Raman mode show that the DMS Cn are arranged in a subcell packing with two molecules per unit cell. The highly ordered all-trans structure of the alkyl chains is present up to the melting transition. On melting there are changes in different regions of the Raman spectra: C-H stretching, CH2 scissoring mode, C-C skeletal stretching, CH3 rocking and longitudinal acoustic modes. On cooling DMS C18 and DMS C20 from the melt to the crystalline state, the gel phase is also proved by Raman scattering. Based on the results of the Raman and X-ray data the gel phase is characterized by a hexagonal subcell packing and by an ordered structure of the alkyl chain residues.

Calorimetry, Differential Scanning↗

PubMed2000

[Synthesis of long-chain 2-(dimethylalkylsilyl)ethylsaccharides].

Research has shown that acetyl protected sugars bond over silicon-oxygen are quiet hard to handle in order to remove the protected group with methods described in literature. However free OH-groups are essential for instance for the processes of biochemical identification. Through the fitting of an ethylen-spacer-group between the silicon atom and the oxygen atom, it is possible to get sugar compounds without the protected acetyl group. The target compounds 14, 16, 18 and 20 were received through reaction of 11 or 12 with 5 or 7 with a mixture of HgO and HgBr2 as a catalyst and following reaction with KOCH3. Compounds 21 and 22, prepared analogeously to 10 and 5 or 7, were isolated as a product mixture, which contained the target compounds relatively in low yield. All synthesized compounds were identified by 1H-, 13C- and 29Si-NMR spectroscopy.

Glucosides↗

PubMed2000

Massive pelvic hemangioma in a patient with blue rubber bleb nevus syndrome.

Blue rubber bleb nevus syndrome (BRBNS) is a rare disorder characterized by gastrointestinal and cutaneous hemangiomas. Patients typically present with gastrointestinal bleeding and anemia. Management of gastrointestinal bleeding may be challenging, since these lesions may be diffusely distributed throughout the gastrointestinal tract. The most common location is the small bowel, and recurrence is common. We describe a patient with BRBNS and lower gastrointestinal bleeding resulting from a large pelvic hemangioma eroding into the rectal wall.

Adult↗

PubMed1999

When are children diagnosed as having severe haemophilia and when do they start to bleed? A 10-year single-centre PUP study.

UNLABELLED: The aim of this single-centre study was to obtain data prospectively on when children are diagnosed as having severe haemophilia and when they start to bleed. Results of this 10-year PUP study suggest that severe haemophilia is nowadays diagnosed much earlier than in the Sixties. Patients with severe haemophilia (n = 37: FV III <0.01 U/ml) start to bleed at very different ages. While 44% of patients have their first bleeding episode within the first year of life, others do not bleed before the age of four. The onset of joint bleedings generally occurs about half a year later than other types of bleeding. While half our patients developed their first bleeding by the age of 1.22 years, the mean age for the first joint bleeding was 1.91 years. CONCLUSION: Early-onset prophylactic therapy can prevent damage to the joints, but for rational therapy the age at onset of bleeding must also be taken into account. A non-bleeding child does not benefit from prophylactic treatment.

Age of Onset↗

PubMed1999

Drawing under visuomotor incongruence.

Six human subjects were asked to draw ellipses presented on a screen by moving a manipulandum that controlled the position of a cursor. Six visual templates were used, which comprised three different ellipses displayed either horizontally or vertically; the ratio between the major and minor axes was 2, 4, or 5. For each visual template, the gains were set such that the movement trajectories required to trace the template with the cursor corresponded to one of six ellipses. Thus these movement ellipses were horizontal or vertical with a ratio between major and minor axes of 2, 4, or 5. All 36 combinations of six visual ellipses and six required movement ellipses were used. Therefore, in some conditions the required movement ellipse had a different orientation (with respect to the major axis) than the visual template. These conditions were called orientation incongruent, whereas, when the orientation of the required movement ellipse matched the orientation of the visual template, the conditions were called orientation congruent. Similarly, eccentricity incongruent referred to conditions where the eccentricities of the visual ellipse and the required movement ellipse were different, as opposed to eccentricity congruent. The main results were as follows: (a) The perimeter of the traced ellipse always tended to be larger than that of the visual template. In addition, it was significantly larger in the orientation incongruent conditions than in the orientation congruent conditions. Nevertheless, the perimeter of the traced figure increased with the template in both orientation congruent and incongruent conditions. (b) The shape of the traced figure varied appropriately with the visual template, but differed significantly between the orientation congruent and incongruent conditions. It was closer to the one of the template in the orientation congruent than in the incongruent conditions. Finally, (c) the instantaneous speed was significantly correlated with curvature but more tightly so in the orientation congruent than in the orientation incongruent conditions. The parameters defining the relation between speed and curvature were affected by the required movement ellipse, but not by the particular visuomotor condition. These results showed that although spatial motor performance was affected by changes in the correspondence between visual and movement coordinates, the relation between the speed and curvature of the movement trajectory was stable despite drastic changes in this correspondence.

Adult↗

PubMed1999

Successful long-term implantation of electrically inactive epiretinal microelectrode arrays in rabbits.

BACKGROUND: In the ongoing discussion concerning the realization of an epiretinal prosthesis for electric stimulation of retinal ganglion cells, long-term fixation of such a device is a crucial question. We evaluated surgical techniques for implantation and fixation of electrically inactive microelectrode arrays (MA) into the retinas of rabbits and secondary tissue reactions to the implant. METHODS: Vitrectomy and laser coagulation of the prospective fixation area were performed in rabbits. Implantation of MAs was performed 3 weeks later in 10 animals. The MA was fixated using retinal tacks. The follow-up included ophthalmoscopy and electrophysiology. At the end of the follow-up, the enucleated eyes were processed for light microscopy using standard procedures and grinding techniques. RESULTS: Nine of 10 rabbits were implanted without serious complications. Clinical and electrophysiologic data through 6 months of follow-up did not indicate any adverse effect of the surgery, the implant, or the tack itself. No change in retinal architecture underneath the implant was found by light microscopy. In these cases, the implant was stable at its original fixation area. In three cases, mild cataract formation was observed, and in one case, a total retinal detachment was found. CONCLUSION: Tack fixation of electrode arrays for electric stimulation of the inner retinal surface seems to be a useful approach in long-term implantation of an epiretinal prosthesis.

Animals↗

PubMed1998

S-(1,2-dichlorovinyl)-L-cysteine-induced dedifferentiation and p53 gene mutations in LLC-PK1 cells: a comparative investigation with S-(2-chloroethyl)cysteine, potassium bromate, cis-platinum and styrene oxide.

Exposure of cultured renal (LLC-PK1) cells for 7 weeks to non-cytotoxic concentrations of S-(1,2-dichlorovinyl)-L-cysteine had resulted in the induction of morphologically and biochemically dedifferentiated clones, which retained their altered properties after removal of the chemical. In this study we investigated by polymerase chain reaction-single strand conformational polymorphism (PCR-SSCP) analysis and direct sequencing if S-(1,2-dichlorovinyl)-L-cysteine-induced LLC-PK1 clones display mutations in the p53 gene in comparison with wild-type clones. In addition, the characteristics of S-(1,2-dichlorovinyl)-L-cysteine-induced clones were compared with clones induced by carcinogens/metabolites of carcinogens with different mechanisms of action: (i) The potent alkylating agent and bacterial mutagen chloroethylcysteine, the key metabolite of the carcinogen dichloroethane; (ii) potassium bromate, a nephrocarcinogen inducing reactive oxygen species, which give rise to the formation of 8OHdG and DNA strand-breaks; (iii) cis-platinum, a bifunctional cross-linking agent and strand-break inducer and (iv) styrene oxide, the main intermediate metabolite of styrene, an epoxide whose carcinogenicity is thought to be based on cytotoxicity. Three essential markers of the physiological integrity and renal tubule origin of the wild-type LLC-PK1 cells were disrupted in all chemical-derived clones: (i) the polarisation of the plasma membrane into a luminal and basolateral part; (ii) the sodium-dependent glucose uptake and (iii) the pH-dependent ammonia production. Compared with the wild-type clones, poly(ADP-ribosyl)ation, a posttranslational modification of nuclear proteins, was clearly increased in clones induced by S-(1,2-dichlorovinyl)-L-cysteine, potassium bromate and cis-platinum. These clones displayed also band shifts of p53 exon 7, indicating mutations, which were confirmed by sequencing: a double mutation consisting of a base substitution followed by one base insertion in the case of S-(1,2-dichlorovinyl)-L-cysteine and potassium bromate and a base substitution in the case of cis-platinum. The base insertions both lead to the formation of the stop codon UGA resulting in loss of protein function.

Ammonia↗

PubMed1998

[Compartment syndrome and Volkmann contracture--can they be prevented in supracondylar humerus fracture?].

The arterial blood supply of the arm is unique, as the collateral circulation is especially good. Because of this anatomic perculiarity it is possible to deal with lack of peripheral pulse without critical ischemia occurring in fractures in the elbow region. We present two children with supracondylar fractures of the humerus with damage to the brachial artery and the different management results. It is necessary to carry out the immediate diagnostic and therapeutic procedures in order to prevent late complications. We conclude that Volkmann's ischemic contracture can always be prevented.

Adolescent↗

PubMed1998

Early nebulized budesonide in the treatment of bronchiolitis and the prevention of postbronchiolitic wheezing.

OBJECTIVE: To determine the effectiveness of nebulized budesonide in the treatment of acute bronchiolitis and in the prevention of postbronchiolitic wheezing. STUDY DESIGN: A randomized, double-blind, placebo-controlled trial was performed. PATIENTS: Forty infants with bronchiolitis (83% RSV), mean age 13.5 weeks (range 4 to 41 weeks), were admitted to the Royal Alexandra Children's Hospital, Brighton, UK. METHODS: Twenty-one infants received nebulized budesonide 1 mg every 12 hours for 5 days, then 500 micrograms every 12 hours continuing to a total of 6 weeks. Nineteen received nebulized placebo (0.9% saline) for 6 weeks. A clinical scoring system was used to rate acute symptoms, and diary cards were used to assess persistent respiratory symptoms over a 6-month follow-up period. RESULTS: No significant differences were found between the budesonide and placebo groups in change in clinical score 48 hours after trial entry, mean oxygen requirements, or length of hospital stay during the acute illness. At 6-month follow-up, the two groups did not differ significantly in prevalence of wheeze, respiratory symptom scores, or proportion requiring bronchodilators or steroids. CONCLUSION: This study did not demonstrate that a 6-week course of nebulized budesonide reduced the symptoms of acute bronchiolitis or prevented postbronchiolitic wheezing.

Acute Disease↗

PubMed1998

[The treatment history of patients with borderline personality disorder in the Republic of Germany].

The present study was undertaken to explore the treatment history of women with borderline personality disorder and to provide an estimation of the treatment costs. Using a semi-structured interview, forty-five carefully diagnosed patients were interrogated about their lifetime treatment history with respect to every inpatient and outpatient treatment received for any psychical symptoms, including physical treatment after self-injurious behaviour. Results demonstrate an extensive and protracted use of psychiatric, psychotherapeutic and physical help, and a chaotic course of treatment with discontinuance of treatments as a characteristic feature. Treatment costs were estimated at a minimum of 24,000 DM per year and patient; 22,000 DM due to hospitalisations. The unsatisfactory treatment situation for these patients in the public health system and the socioeconomic advantages of a specified treatment programme are discussed.

Adolescent↗