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Biomedical subjects

M Reuter

Publications and source records attributed to M Reuter.

At least 91 records · Page 5Linked to original sources
PubMed2000

The brain of the Nemertodermatida (Platyhelminthes) as revealed by anti-5HT and anti-FMRFamide immunostainings.

The taxa Nemertodermatida and Acoela have traditionally been considered closely related and classified as sister groups within the Acoelomorpha Ehlers 1984 (Platyhelminthes). Recent molecular investigations have questioned their respective position. In this study, the 5-HT and FMRFamide immunoreactivity (IR) in the nervous system of two nemertodermatids, Nemertoderma westbladi and Meara stichopi, is described. The 5-HT immunoreactive pattern differs in the two nemertodermatids studied. In M. stichopi, two loose longitudinal bundles of 5-HT-immunoreactive fibres and an basi-epidermal nerve net were observed. In N. westbladi the 5-HT-IR shows a ring-shaped commissural structure, different from the commissural brain of acoels. In both nemertodermatids, FMRFamide immunoreactive nerve fibres followed the 5-HT-immunoreactive fibres. It is demonstrated that the Nemertodermatida have neither a 'commissural brain' structure similar to that of the Acoela, nor a 'true', ganglionic brain and orthogon, typical for other Platyhelminthes. The question of the plesiomorphic or apomorphic nature of the nervous system in Nemertodermatida cannot yet be answered. The neuroanatomy of the studied worms provides no synapomorphy supporting the taxon Acoelomorpha.

Animals↗
PubMed2000

Energy expenditure, energy intake and prevalence of obesity after therapy for acute lymphoblastic leukemia during childhood.

OBJECTIVES: To investigate the prevalence and potential risk factors of obesity after therapy for childhood acute lymphoblastic leukemia (ALL). STUDY DESIGN: 39 ALL patients (age 10.7-20.5 years) who were in first remission for 3.4-14.6 years after standardized treatment with chemotherapy plus cranial irradiation (n = 25) or with chemotherapy alone (n = 14) were examined. After fasting overnight, the following parameters were investigated: body mass index (BMI) of patients and their parents; patients' BMI before ALL therapy; serum free thyroxin, growth hormone-dependent factors, estradiol, testosterone, cortisol, leptin and c-peptide; fat-free mass (bioelectrical impedance); resting metabolic rate (RMR, indirect calorimetry); caloric intake (24-hour recall); and physical activity (questionnaire). RMR data were applied to the fat-free mass and compared with 83 controls. RESULTS: The prevalence of obesity (criterion: BMI > 2 SDS) was significantly (p < 0.05) higher after ALL therapy (38%; irradiated patients 48%, non-irradiated patients 21%) than before therapy (3%). Compared to non-irradiated patients, irradiated patients had significantly lower RMRs (-1.07 +/- 0.24 vs. -0.32 +/- 0.21 SDS; p < 0.05), reduced physical activity levels (1.41 +/- 0.03 vs. 1.52 +/- 0.03; p < 0.05), and lower concentrations of insulin-like growth factor-binding protein-3 (-0.65 +/- 0.17 vs. 0.25 +/- 0.33 SDS; p < 0.05) and of free thyroxin (1.17 +/- 0.06 vs. 1.38 +/- 0.08 ng/dl; p < 0.05). Caloric intake was adequate. CONCLUSIONS: After ALL during childhood, patients face a higher risk of obesity. In the cranially irradiated patients, the likely causes are low physical activity, RMRs and hormonal insufficiency.

Adolescent↗
PubMed2000

Does diving damage the brain? MR control study of divers' central nervous system.

PURPOSE: To evaluate the prevalence of cerebral white matter changes on MR imaging in healthy elderly compressed air divers with a long diving history in comparison with control subjects who have never dived. MATERIAL AND METHODS: The investigation employed 59 experienced elderly divers and 48 control subjects matched for age, body mass index, alcohol and smoking history. MR studies included a fluid attenuated inversion recovery sequence and T1- and T2-weighted pre- and postcontrast images in axial orientation of the whole brain to localize white matter changes. RESULTS: MR images did not show any morphologic abnormalities in the brains of divers. Both groups - divers and controls - did not differ significantly with respect to white matter changes of the brain. CONCLUSION: No increased prevalence of cerebral white matter changes in compressed air divers compared with a healthy worker sample of similar age were found. Thus, extensive compressed air diving may not necessarily be related to radiological changes on MR.

Adult↗
PubMed2000

Sublethal hemorrhagic shock reduces tumor necrosis factor-alpha-producing capacity in different cell compartments.

Hemorrhagic shock results in a severe impairment of the immune response. Immunological alterations after hemorrhagic shock thus appear to be responsible for reduced resistance to infectious agents commonly observed after shock and severe injury. In the present study we examined the TNF-alpha-producing capacity of immune cells derived from different organs after sublethal shock in rats. Hemorrhagic shock was established by pressure controlled bleeding to a mean arterial pressure of 35 mm Hg for 35-40 min and consecutive resuscitation in male Sprague-Dawley rats. Twenty four hours after shock, TNF-a production in response to lipopolysaccharide (LPS, Salmonella friedenau) stimulation was measured in isolated spleen, bone marrow and blood cells. TNF-a production could be induced by stimulation with 1 ng/ml, in blood, spleen and bone marrow cells collected from sham-operated animals. A maximal stimulation was observed in all cell types after stimulation with 10 ng/ml LPS and could not be further increased with LPS doses of 100 ng/ml. Hemorrhagic shock of 35 mm Hg for 35-40 min, with consecutive resuscitation did not result in mortality, in contrast to a 4 hours lasting hemorrhagic shock resulting in 80% mortality. Blood, spleen or bone marrow cells, harvested from animals 24 hours after sublethal hemorrhagic shock, showed a significantly reduced TNF-alpha production in all cell populations after LPS stimulation. Serum collected from animals 2 hours after sublethal hemorrhagic shock contained an activity not present either before or 24 hours after shock, that downregulated LPS-induced TNF-alpha production in rat whole blood cultures and the murine macrophage cell line J774. The inhibitory activity present in serum, 2 hours after shock is not IL-10 since this mediator was not detectable in any serum sample. However, in the serum samples with TNF-alpha-inhibitory activity, elevated levels of PGE2 metabolites were found, which suggests the involvement of prostaglandins in trauma-induced immunosuppression. Altered TNF-a expression might be partially explained by an inhibitory activity in the serum already present 2 hours after shock. Since adequate, but not overwhelming TNF-alpha production is essential for host response, the altered cytokine formation might explain local and systemic susceptibility to infections after hemorrhagic shock.

Animals↗
PubMed1999

Regions of endonuclease EcoRII involved in DNA target recognition identified by membrane-bound peptide repertoires.

Target sequence-specific DNA binding regions of the restriction endonuclease EcoRII were identified by screening a membrane-bound EcoRII-derived peptide scan with an EcoRII recognition site (CCWGG) oligonucleotide duplex. Dodecapeptides overlapping by nine amino acids and representing the complete protein were prepared by spot synthesis. Two separate DNA binding regions, amino acids 88-102 and amino acids 256-273, which share the consensus motif KXRXXK, emerged. Screening 570 single substitution analogues obtained by exchanging every residue of both binding sites for all other amino acids demonstrated that replacing basic residues in the consensus motifs significantly reduced DNA binding. EcoRII mutant enzymes generated by substituting alanine or glutamic acid for the consensus lysine residues in DNA binding site I expressed attenuated DNA binding, whereas corresponding substitutions in DNA binding site II caused impaired cleavage, but enzyme secondary structure was unaffected. Furthermore, Glu96, which is part of a potential catalytic motif and also locates to DNA binding site I, was demonstrated to be critical for DNA cleavage and binding. Homology studies of DNA binding site II revealed strong local homology to SsoII (recognition sequence, CCNGG) and patterns of sequence conservation, suggesting the existence of functionally related DNA binding sites in diverse restriction endonucleases with recognition sequences containing terminal C:G or G:C pairs.

Amino Acid Sequence↗
PubMed1999

An experimental, NADPH-diaphorase histochemical and immunocytochemical study of Mesocestoides vogae tetrathyridia.

In order to test the role of nitric oxide in flatworms, Mesocestoides vogae tetrathyridia were incubated together with L-arginine, which is the substrate for nitric oxide synthesis, or with NG-nitro-L-arginine, which is an irreversible inhibitor of nitric oxide synthase. Normally, tetrathyridia attach to each other with the aid of their suckers, forming clusters. The rate of cluster formation was followed during the incubations. L-Arginine stimulated, and NG-nitro-L-arginine clearly inhibited, the cluster formation. This is the first time that an effect of nitric oxide has been observed in a flatworm. In addition, the pattern of the NADPH-diaphorase histochemical reaction in the nervous system and the pattern of F-actin filaments in the musculature stained with TRITC-labelled phalloidin were studied. NADPH-d staining occurred in the brain and the main nerve cords but also followed the muscle fibres stained with phalloidin. The pattern of the NADPH-d reaction was compared with that of 5-HT immunoreactivity. The implications of the results are discussed in relation to the background of data on neuronal signal substances in M. vogae.

Animals↗
PubMed1999

Bronchoalveolar lavage cell profiles in Wegener's granulomatosis.

Pulmonary involvement due to Wegener's granulomatosis (WG) can present radiologically either as diffuse infiltrates or as nodular and linear opacities. Clinical experience suggest that these radiological patterns are associated with different bronchoalveolar lavage (BAL) cell profiles, but this has not been examined formally. We compared the BAL cell profile in eight WG patients with diffuse infiltrates on chest X-ray, indicative of highly active pneumonitis, with corresponding findings in 37 patients with nodular, linear and focal low-attenuation infiltrates on high-resolution computed tomography (HRCT) which reflected low-grade, mainly interstitial disease. A control group was composed of 11 patients with pulmonary sarcoidosis. Diffuse infiltrates occurred in association with high systemic disease activity and featured a neutrophilic BAL profile in the presence of generally normal BAL lymphocytes. HRCT findings suggestive mainly of interstitial disease were associated with either a lymphocytic BAL cell profile or a normal cell pattern. Patients with a lymphocytic cell profile generally had a preferential elevation of CD4+ cells in the BAL in the presence of a normal CD4/CD8 ratio in the blood. This was a common feature of WG and pulmonary sarcoidosis. In conclusion, highly active pneumonitis and pulmonary disease of low or moderate activity in WG are associated with disparate BAL cell profiles. It remains to be examined whether the preferential elevation of CD4+ cells in the latter condition reflects a common pathogenetic role of this subset of cells in WG and pulmonary sarcoidosis.

Aged↗
PubMed1999

Subclinical alveolar bleeding in pulmonary vasculitides: correlation with indices of disease activity.

Haemosiderin-laden alveolar macrophages are a common finding in patients with alveolar bleeding. Iron-positive macrophages, suggestive of subclinical alveolar bleeding, were found to be fairly common in bronchoalveolar lavage (BAL) fluid in primary systemic vasculitis but uncommon in collagen vascular diseases (CVDs) and rheumatoid arthritis (RA). To substantiate the impression that subclinical alveolar bleeding may be a feature distinguishing between these disorders, fibreoptic bronchoscopy and BAL were performed in 49 patients with active Wegener's granulomatosis or Churg-Strauss syndrome and 44 patients with CVDs or RA, all of them without clinically manifest alveolar bleeding. The percentage of iron-positive cells was compared with clinical and radiological findings. Only a minority of the CVD and RA patients had iron-positive alveolar macrophages; the 95th percentile of the median number of such cells was 5%. Fifty-three per cent of the patients in the vasculitis group had >5% iron-positive cells, with individual counts ranging up to 95%. Patients with iron-positive macrophages had more extensive disease, more frequent microhaematuria, a higher antineutrophil cytoplasmic antibody titre, a higher myeloperoxidase concentration in the BAL fluid and somewhat more frequent low-attenuation opacities in pulmonary high-resolution computed tomography than the patients with a low iron-positive cell count. In conclusion, subclinical alveolar bleeding was, indeed, a common finding in antineutrophil cytoplasmic antibody-associated vasculitis, which distinguished these disorders from lung disease due to collagen vascular diseases or rheumatoid arthritis. Its association with indices of disease activity, although weak in this cross-sectional study, merits a longitudinal study of its value for the long-term monitoring of vasculitis patients.

Aged↗
PubMed1999

Magnetic resonance signal abnormalities and neuropsychological deficits in elderly compressed-air divers.

We investigated the association between MR signal abnormalities of the central nervous system, neuropsychologic performance and exposure indices in 20 experienced elderly compressed-air divers who had no history of neurological decompression illness (DCI). Results of MRI of the brain and psychometric testing were compared with 20 matched healthy commercial employees who never dived: 60% of the divers and 45% of the controls had hyperintense MR abnormalities. Among divers, both the number and the size of abnormalities correlated with hours diving in the deep air-diving range of 40-60 m (p < 0.05). Divers' mental flexibility and visual tracking performance were decreased in comparison with controls (p < 0.05 and p < 0.01). Divers thus are at risk of detrimental long-term effects of compressed-air diving on the central nervous system even in the absence of a history of neurological DCI.

Barotrauma↗
PubMed1999

Functional and high-resolution computed tomographic studies of divers' lungs.

OBJECTIVES: Several cross-sectional studies have described a decrease in the expiratory flow rates of divers. The objective of this study was to determine whether the combined application of high-resolution computed tomography (HRCT) and lung function testing supports the reported development of small airway obstruction in divers. METHODS: Thirty-two navy divers, 27 commercial divers, and 48 referents matched for age and smoking history underwent pulmonary function testing and HRCT of the lungs supplemented by a limited number of expiratory scans. The commercial divers were older and dived longer than the navy divers. Multivariate regression analysis was used to assess the relevant correlations of age, height, pack-years of cigarette smoking, and indices of diving exposure with lung function parameters. RESULTS: The inspiratory vital capacity and forced vital capacity (FVC) were greater, while the FEV% [(100 x FEV10)FVC] and maximum expiratory flow (MEF) at 25% (MEF25) of the FVC were lower for the navy divers than for the referents. The lung volumes and expiratory airflow pattern did not differ between the commercial divers and the corresponding referents. The forced expiratory volume in 1 second (FEV10), FEV%, MEF75, and MEF25 correlated negatively with the years of diving experience. This association was independent of age, height, and pack-years of cigarette smoking. For the majority of the divers and referents the expiratory HRCT revealed minor lobular air trapping without any difference between the groups. The HRCT did not show relevant morphologic abnormalities of small or large airways. CONCLUSIONS: The data confirm that diving may affect pulmonary function. However, there is no radiologic evidence for the development of small airway disease in these 2 subgroups of divers.

Adult↗
PubMed1999

Hyperbaric chamber-related decompression illness in a patient with asymptomatic pulmonary sarcoidosis.

An asymptomatic 46-yr-old male sustained an acute neurologic insult, appearing during the decompression phase of a 50-m dry hyperbaric chamber dive. The right hemisyndrome was most probably related to diving, since symptoms responded rapidly to the early commenced recompression therapy. Further diagnostics revealed a previously unknown pulmonary sarcoidosis with bilateral pulmonary opacities and pleural adhesions that might have predisposed to arterial gas embolism secondary to pulmonary barotrauma. This case may illustrate a potential risk of decompression illness even during dry chamber dives in patients suffering from asymptomatic pleuro-parenchymal pulmonary disease. The value of chest X-ray in the medical assessment of fitness to dive is therefore emphasized.

Biopsy↗
PubMed1998

An ESS treatment of the pattern of female arrival at the mating site in the yellow dung fly scathophaga stercoraria (L.)

In most previous work on the yellow dung fly Scathophaga stercoraria (L.), as on other species, adaptive explanations have been sought for male behaviour whereas female behaviour has not been examined in similar detail. Here, the arrival of females at the mating site, fresh cattle droppings, is investigated. While almost all males are present shortly after pat deposition females arrive at a low, decreasing rate over an interval of about 5 hours. We propose that the distribution of female arrival times represents a mixed Evolutionarily Stable Strategy (ESS), formed by different trade-offs between costs and benefits of early and late arrival. Early arrival could be favoured by advantages due to better conditions for oviposition, faster egg development of reduced larval competition. Late arrival could be favoured by negative effects on females of male-male competition being weaker later after deposition. Computer simulations with distributions of arrival times deviating from the natural one were performed to "measure" the costs for females arriving at different times. These costs were compared with estimated benefits corresponding to the females' arrival times. This procedure revealed that females coming to the pat later in a population of females arriving shortly after deposition would be favoured. In a population arriving according to a uniform distribution, early females would have fitness advantages. Thus, evolution should lead to an intermediate distribution of arrival times, as in nature, i.e. female arrival behaviour is probably adaptive. The simulations also revealed that the intensity of sexual selection though male-male competition is highest with the natural pattern of female arrival. Therefore, natural selection generating this pattern amplifies the intensity of male-male interaction as a by-product. Copyright 1998 Academic Press

Journal Article↗
PubMed1998

In situ transmission electron microscopy observations of the formation of self-assembled Ge islands on Si.

The in situ transmission electron microscope allows us to visualise processes occurring at surfaces and interfaces in real time and is therefore capable of providing detailed, quantitative information about reaction mechanisms. We have used a UHV TEM equipped with in situ growth capabilities to study the process of chemical vapour deposition of Ge on Si(100), with particular emphasis on the formation of self-assembled, nanosize Ge islands. Video-rate image acquisition enables us to track the development of individual islands from nucleation onwards and to observe the introduction of dislocations as the strained islands relax. For islands less than 80 nm in diameter, which are coherently strained, we observe an interesting coarsening process during growth. This coarsening results in a bimodal distribution of island sizes at certain times and a narrow size distribution at later times. We explain the phenomenon by a model in which coarsening occurs among a population of islands for which the equilibrium island shape depends on the size. Numerical simulations of coarsening in the presence of a shape transition are in good agreement with experiment. As the islands grow larger, dislocations form and we observe rapid shape changes associated with dislocation introduction. These changes can also be understood by considering a strain-dependent island shape. The insight that these results provide into the understanding of island growth and evolution can be used to develop arrays of uniformly sized islands ("quantum dots") for a variety of potential applications.

Crystallization↗
PubMed1998

Cooperative binding properties of restriction endonuclease EcoRII with DNA recognition sites.

EcoRII is a member of the expanding group of type IIe restriction endonucleases that share the distinguishing feature of requiring cooperativity between two recognition sites in their substrate DNA. To determine the stoichiometry of the active DNA-enzyme complex and the mode of cooperative interaction, we have investigated the dependence of EcoRII cleavage on the concentration of EcoRII dimers. Maximal restriction was observed at dimer/site ratios of 0.25 and 0. 5. The molecular weight of the DNA-enzyme complex eluted from a gel filtration column also corresponds to a dimeric enzyme structure bound to two substrate sites. We conclude that one EcoRII dimer is sufficient to interact cooperatively with two DNA recognition sites. A Lac repressor "barrier" bound between two normally reactive EcoRII sites did not inhibit restriction endonuclease activity, indicating that cooperativity between EcoRII sites is achieved by bending or looping of the intervening DNA stretch. Comparative cleavage of linear substrates with differently spaced interacting sites revealed an inverse correlation between cleavage rate and site distance. At the optimal distance of one helical turn, EcoRII cleavage is independent of the orientation of the recognition sequence in the DNA double strand.

Bacterial Proteins↗
PubMed1998

Intravenous pulse cyclophosphamide in the treatment of interstitial lung disease due to collagen vascular diseases.

OBJECTIVE: Substantial toxicity limits the use of daily oral cyclophosphamide (CYC) for the treatment of interstitial lung disease (ILD) due to collagen vascular diseases. We examined whether intravenous (i.v.) pulse CYC can be substituted for daily oral therapy. METHODS: Six patients with rapidly progressive ILD due to polymyositis, systemic sclerosis, systemic lupus erythematosus, or primary Sjögren's syndrome received 6-9 cycles of i.v. pulse CYC (0.5 gm/m2 of body surface area), together with an initial course of 50 mg of prednisolone, which was tapered to a maintenance dosage of 5-7.5 mg/day, and their response was measured clinically, by high-resolution computed tomography (HRCT) and by assessment of the bronchoalveolar lavage (BAL) cell profile. RESULTS: All patients showed significant improvement in exercise tolerance and lung function. Elevated BAL neutrophils dropped substantially, whereas the response of BAL lymphocytes was inconsistent. Low-attenuation opacities in the HRCT regressed in 4 patients and remained unchanged in 2, but reticular infiltrates remained largely unaffected. Remission was maintained with hydroxychloroquine, azathioprine, or cyclosporin A. CONCLUSION: I.v. pulse CYC proved to be an effective and well-tolerated treatment in these patients. Since it appears to target mainly the inflammatory component of the disease, it should be reserved for progressive ILD featuring indices of high inflammatory activity.

Adult↗