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Biomedical subjects

M Gleissner

Publications and source records attributed to M Gleissner.

15 recordsLinked to original sources
PubMed2000

Risk factors for intraventricular hemorrhage in a birth cohort of 3721 premature infants.

AIMS: In our study we determined possible risk factors for intraventricular hemorrhage grade III to IV (IVH) based on a regional German neonatal data base and tried to build a logistic-regression model to predict the risk of IVH according to gestational age. MATERIALS: We identified 3721 premature infants, 22 to 36 completed weeks of gestational age, born from 1994 through 1997. 136 (3.7%) IVH were diagnosed sonographically. 60 (44%) infants with IVH died. We examined the following variables as risk factors for IVH: gestational age, sex, blood pH of 7.2 or less, body temperature of 35 degrees C or less, multiple birth, small-for-gestational age, intubation after birth, transport to another hospital. RESULTS: In the full logistic regression model sex, blood pH of 7.2 or less, multiple birth, and small-for-gestational age were not associated with a significant risk of IVH. Body temperature of 35 degrees C or less was associated with an increased risk of IVH (adjusted odds ratio, 1.92; 95% confidence interval, 1.09 to 3.40). Intubation after birth increased the risk of IVH in neonates under 28 weeks of gestational age (OR, 3.72; 95% CI, 1.65 to 8.38) only to a moderate extent, but significantly in neonates 32 to 36 weeks of gestational age (OR, 16.51; 95% CI: 7.35 to 36.18). The risk of IVH was mainly related to gestational age. Neonates delivered before 28 weeks of gestation (OR, 75.72; 95% CI, 46.14 to 124.30) faced the highest risk of IVH. Transport to another hospital was connected with an increased risk of IVH regardless of gestational age (adjusted OR, 1.95; 95% CI, 1.07 to 2.56). CONCLUSION: The frequency of IVH could be reduced significantly, if extremely premature infants, the vast majority of patients suffering from IVH, did not have to be transferred postnatally to another hospital.

Birth Weight↗
PubMed1997

The archaeal SoxABCD complex is a proton pump in Sulfolobus acidocaldarius.

The thermoacidophilic archaeon Sulfolobus acidocaldarius expresses a very unusual quinol oxidase, which contains four heme a redox centers and one copper atom. The enzyme was solubilized with dodecyl maltoside and purified to homogeneity by a combination of hydrophobic interaction and anion exchange chromatography. The oxidase complex consists of four polypeptide subunits with apparent molecular masses of 64, 39, 27, and 14 kDa that are encoded by the soxABCD operon (Lübben, M., Kolmerer, B., and Saraste, M. (1992) EMBO J. 11, 805-812). The optical spectra and redox potentials of the SoxABCD complex have been characterized, and the absorption coefficients of the contributing cytochromes a587 and aa3 were determined. The EPR spectra indicate the presence of three low spin and one high spin heme species, the latter associated with the binuclear heme CuB site. Standard midpoint potentials of the cytochrome a587 heme centers were determined as +210 and +270 mV, respectively. The maximum turnover of the complex (1300 s-1 at 65 degrees C) was found to be about three times greater than that of the previously studied isolated cytochrome aa3 subunit alone (Gleissner, M., Elferink, M. G., Driessen, A. J., Konings, W. N., Anemüller, S., and Schäfer, G. (1994) Eur. J. Biochem. 224, 983-990). With N,N,N',N'-tetramethyl-1,4-phenylenediamine as a reductant, the SoxABCD complex reconstituted into liposomes generates a proton motive force. A new method is described by co-reconstitution of SoxABCD with a Sulfolobus Rieske FeS-protein (SoxL), allowing energization by cytochrome c. It is based on the finding that this Rieske protein can equilibrate electrons between cytochrome c and quinones reversibly (Schmidt, C. L., Anemüller, S., Teixeira, M., and Schäfer, G. (1995) FEBS Lett. 359, 239-243). With this system, generating no scalar protons, the stoichiometry of proton translocation could be determined. A net H+/e- ratio >1 was determined, identifying the SoxABCD complex as a proton-pumping quinol oxidase. According to structural analysis, the cytochrome aa3 moiety of the complex does not contain the signature of a H+ pumping channel as identified in Rhodobacter sphaeroides or Paracoccus denitrificans. Therefore, for H+ translocation, a mechanism different from that in typical heme-copper oxidases of the aa3 or bo3 type is discussed.

Bacterial Outer Membrane Proteins↗
PubMed1997

Immunoisolation of hybrid liver support systems by semipermeable membranes.

Immunoisolation of hybrid liver support systems (LSS) utilizing suitable semipermeable membranes as an immune barrier enables neither immunocompetent cytotoxic factors to cause damage to the hepatocytes in the bioreactor nor xenogenic hepatocyte products to cause immunological side effects in patients. To determine the capability of membranes as an immune barrier, 6 flat membranes were investigated: Cuprophan (C-100), cut-off MW 1000, Cuprophan (C-240), cut-off MW 10,000, Polypropylen hydrophilic and hydrophobic (PPhi, PPho), cut-off MW 500,000-1,000,000, Polysulfon (PS), cut-off MW 1,000,000, Polyamid (PA), cut-off beyond MW 1,000,000. The permeability of the membranes to plasma factors and liver protein fractions (LP) was studied by routine biochemical methods and gel electrophoresis. In a second study, pigs (n=7) were immunised by LP after membrane passage. The results showed PA, PS, and PPhi to be completely permeable for plasma factors and LP C-100 and C-240 for urophanic substances, and C-240 again for LP under MW 14.000. All 7 pig sera studied by Western blot discovered pre-formed xenoreactive natural IgG-antibodies (NAB) against human liver antigen (AG) with MW 26.000. AB de-novo-synthesis was demonstrated for AG with MW 45.000. No AB-synthesis was induced for epitopes under MW 26,000. These results suggest that limiting the cut-off of bioreactor outflow membranes to MW < 26,000 could avoid immunological side effects to patients.

Animals↗
PubMed1996

Resonance Raman spectroscopy of the integral quinol oxidase complex of Sulfolobus acidocaldarius.

The integral quinol oxidase complex of Sulfolobus acidocaldarius (DSM 639) was investigated by resonance Raman spectroscopy. The complex includes four heme a groups which constitute two functional entities, a587 and aa3, containing two low-spin hemes and a low-spin as well as a high-spin heme, respectively. RR spectra were obtained from the fully oxidized and fully reduced states of the complex using different excitation wavelengths in the Soret band region in order to disentangle the contributions from the four heme groups. For the oxidized state, this approach allowed for the identification of two spectrally different types of heme a which were assigned to the bishistidine ligated hemes a of aa3 and a587 (type II) and to the additional heme a of a587 which is ligated by a histidine and methionine (type I). The spectra of both heme a types differ substantially from that of beef heart cytochrome c oxidase. In particular, the formyl stretching modes of types II and I are upshifted by 8 and 15 cm-1, respectively, implying a largely hydrophobic environment of the formyl groups in the quinol oxidase of Sulfolobus. Furthermore, the RR spectra of the oxidized state reveal the characteristic marker bands of a five-coordinated and a six-coordinated high-spin state, indicating that heme a3 exists in a coordination equilibrium, which is in sharp contrast to the purely six-coordinated high-spin configuration of heme a3 in any (quinol or cytochrome) oxidases studied so far. Also the formyl stretching mode of heme a3 appears to be unusual as its frequency is substantially lower than in beef heart oxidase. In the fully reduced state, no heterogeneity of heme a3 is observed and also the spectra of the various hemes a are nearly indistinguishable. Moreover, the formyl stretching vibrations of all hemes a and a3 apparently coincide to one prominent peak at 1658 cm-1 characteristic for a non-hydrogen-bonded carbonyl group. This finding is unique compared to other aa3 oxidases in which the formyl stretchings give rise to widely separated bands at approximately 1610 and approximately 1665 cm-1 for heme a and a3, respectively. In both the oxidized and the reduced states, the spectra of the aa3 entity in the integral complex differ significantly from those of the isolated aa3 entity studied previously [Heibel, G., Anzenbacher, P., Hildebrandt, P., & Schäfer, G. (1993a) Biochemistry 32, 10878-10884], indicating substantial interactions between the various subunits of the integral complex.

Animals↗
PubMed1996

Respiratory chains of archaea and extremophiles.

Extremophilic organisms are adapted to harsh environmental conditions like high temperature, extremely acidic or alkaline pH, high salt, or a combination of those. With a few exceptions extremophilic bacteria are colonizing only moderately hot biotopes, whereas hyperthermophiles are found specifically among archaea (formerly 'archaebacteria') which can thrive at temperatures close to or even above the boiling point of water. It has been a challenging question whether the special properties of their proteins and membranes have been acquired by adaptation, or whether they might reflect early evolutionary states as suggested by their phylogenetic position at the lowest branches of the universal tree of life.

Amino Acid Sequence↗
PubMed1994

Sulfolobus acidocaldarius terminal oxidase. A kinetic investigation and its structural interpretation.

The thermoacidophilic archaebacterium Sulfolobus acidocaldarius possesses a very unusual terminal oxidase. We report original kinetic experiments on membranes of this microorganism carried out by stopped flow, using time-resolved optical spectroscopy combined with singular value decomposition analysis. The reduced-oxidized kinetic difference spectrum of the Sulfolobus membranes is characterized by three significant peaks in the visible region at 605, 586, and 560 nm. The 605-nm peak and part of the 586-nm peak (cytochrome aa3-type quinol oxidase) are reduced synchronously by both ascorbate plus N,N,N',N'-tetramethyl-p-phenylendiamine (TMPD) and dithionite, and they are very rapidly oxidized by molecular oxygen. A second pool of cytochromes seems to contribute to the 586-nm peak which is not reduced by ascorbate plus TMPD and reacts very slowly with dithionite. The b-type cytochromes (560 nm peak) are reduced by both reductants and are essentially "non-autoxidizable" at room temperature. Only one CO binding site with spectral features, kinetic properties, and ligand affinity not very dissimilar from those of mammalian cytochrome oxidase can be detected in the ascorbate-reduced membranes. On the contrary, a second CO binding site having unusual properties for aa3 terminal oxidases can be detected in the dithionite-reduced membranes.

Ascorbic Acid↗
PubMed1994

Generation of proton-motive force by an archaeal terminal quinol oxidase from Sulfolobus acidocaldarius.

The terminal quinol oxidase of the cytochrome aa3 type was isolated from the extreme thermoacidophilic archaeon Sulfolobus acidocaldarius. In micellar solution, the enzyme oxidized various quinols and exerted the highest activity with the physiological substrate caldariella quinol. The enzyme was functionally reconstituted into monolayer liposomes composed of archaeal tetraether lipids also derived from S. acidocaldarius. With the electron donor system ascorbate and N,N,N',N'-tetramethyl-p-phenylenediamine, the reconstituted enzyme was more active in the archaeal lipids as compared to lipids derived from Escherichia coli at temperatures above 50 degrees C. Due to the low proton permeability of the tetraether lipids, it was possible to generate a steady-state transmembrane electrical potential (delta psi, interior negative), and transmembrane pH gradient (delta pH, interior alkaline) at temperatures up to 70 degrees C. The successful functional reconstitution of the cytochrome aa3-type quinol oxidase from Sulfolobus identifies it as the key energy converter in the respiratory system of this hyperthermophilic archaeon.

Catalysis↗
PubMed1992

Flicker perimetry resists retinal image degradation.

The influence of refractive defocus and artificial media opacities on perimetric thresholds in automated light-sense and flicker perimetry was investigated in 20 eyes of 20 normal subjects. Thresholds were determined at 13 locations in the central visual field up to 25 degrees. Refractive defocus was induced by blurring with glasses of +1, +2, +3, +6 and +9 diopters spherical. Three diffusers were used as artificial media opacities, causing a mean reduction of visual acuity to 0.46, 0.08, and 0.02. Blurring of the retinal image by a small defocus or by slight artificial media opacities causes a measurable reduction of light-difference sensitivity. Mean sensitivity (MS) and defocus are related logarithmically (log(MS)/defocus, r = -0.9297; P < 0.0001). The correlation between MS and the luminance factor l15, characterizing the artificial media opacities, is linear (MS/l15, r = -0.9736; P < 0.0001). Flicker fusion frequency resists retinal image degradation much better. Mean flicker frequency (MF) and defocus are related logarithmically (log(MF)/defocus, r = -0.4960; P < 0.0001). The correlation between mean flicker frequency (MF) and the luminance factor l15 is nonlinear (MF/[l15]2, r = 0.8693; P < 0.0001). The results of the present study show that perimetric methods that use temporal threshold criteria, such as flicker fusion frequency, should be more suitable than methods that use static criteria for detecting neuronal damage in the presence of factors that disturb retinal image quality.

Adult↗
PubMed1992

[Light perception and flicker perimetry. Effect of refractive error, artificial media opacities and pupillary size].

The influence of defocus, artificial media opacities and pupil size on perimetric thresholds in automated light sense and flicker perimetry was investigated in 20 eyes of 20 normal subjects. Thresholds were determined at 13 locations in the central visual field. Blurring the retinal image by a small defocus or by slight artificial media opacities causes a measurable reduction in light-difference sensitivity. Flicker fusion frequency, however, is much more resistant to degradation of the retinal image. Artificial pupil size has a similar effect on both light-difference sensitivity and flicker fusion frequency. The present study shows that perimetric methods using temporal threshold criteria should be more suitable for the detection of neuronal damage in the presence of factors disturbing the quality of the retinal image than methods using static criteria.

Adult↗
PubMed1990

The good old days are now!

This article discusses the advantages of automating an agency and the criteria an administrator should consider before purchasing a computer system. Specific attention is given to nursing documentation software, as this area of home health care is of utmost importance.

Commerce↗
PubMed1990

[Measuring temporal transmission properties of the visual system. Diagnostic value in suspected optic nerve neuritis].

The temporal transfer properties of the visual system were examined in 157 patients with suspected acute optic neuritis or papillitis. Foveal modulation sensitivity was measured as a function of temporal frequency (DeLange curve) both for the affected eye and the unaffected fellow eye. Patients with acute optic neuritis typically show a reduction of foveal modulation sensitivity at all temporal frequencies, high temporal frequencies above 10 cps being more markedly affected. The aim of the present study was to determine the sensitivity and specificity of this simple psychophysical procedure for the diagnosis of neuritis or papillitis in a reasonably large population of patients with suspected acute optic neuritis or papillitis. In each case the final diagnosis was confirmed by evaluation of the clinical signs and symptoms, the course of disease and additional diagnostic procedures, e.g. electrophysiology, perimetry, neurological examination including CT, lumbal puncture and examination of cerebrospinal fluid. In 136 cases (86.6%) the result read from the DeLange curve was correctly positive or negative. In 17 cases (10.8%) the DeLange curve indicated a false-positive and in 4 cases (2.6%), a false-negative result.

Flicker Fusion↗
PubMed1989

[Automated flicker perimetry].

Flicker fusion frequency (FFF), the threshold criterion of flicker perimetry, is a functional parameter of the temporal transfer properties of the visual system. An automated flicker perimeter suitable for clinical routine purposes is presented that allows perimetric examination of the central visual field with high spatial resolution. The intent of the present study was to investigate the outcome of flicker perimetry in comparison to static light-sense perimetry. In the majority of cases of ocular hypertension and suspected glaucoma (n = 31), chronic open-angle glaucoma (n = 36) and acute neuritis/papillitis (n = 10) defects are indicated by flicker perimetry in areas of the visual field with normal light sensitivity according to static light-sense perimetry (Octopus 201, program G 1). In many cases of preproliferative diabetic retinopathy (n = 10), however, flicker perimetry indicates fewer defects than static perimetry (Octopus 201, program 32). The results collected up to now suggest that automated flicker perimetry might represent a specific functional test of the retinal Y-ganglion cells.

Diabetic Retinopathy↗