PubMed Health⌕ Search

Biomedical subjects

R Hartmann

Publications and source records attributed to R Hartmann.

16 recordsLinked to original sources
PubMed1992

Glycosphingolipids in cestodes. Chemical structures of ceramide monosaccharide, disaccharide, trisaccharide and tetrasaccharide from metacestodes of the fox tapeworm, Taenia crassiceps (Cestoda: Cyclophyllidea).

The presence of glycosphingolipids in the metacestodes of the fox tapeworm, Taenia crassiceps, has been established. The normal-phase TLC pattern of the neutral-fraction glycolipids revealed groups of bands corresponding to homologous components of increasing sugar chain length. The three simplest glycolipid components have been isolated and their chemical constitution determined as being of the neogala series: Gal beta 1Cer, Gal beta 6Gal beta 1Cer and Gal beta 6Gal beta 6Gal beta 1Cer. The ceramide tetrasaccharide fraction has been found to consist of a mixture of neogalatetraosylceramide, as an elongation of the neogala series, Gal beta 6Gal beta 6Gal beta 6Gal beta 1Cer and the component Gal alpha 4Gal beta 6Gal beta 6Gal beta 1Cer (both occurring in approximately equimolar proportions). The long-chain bases of the ceramide monogalactoside, digalactoside, trigalactoside and tetragalactosides contain, as well as small amounts of sphingosine, predominantly dihydrosphingosine/phytosphingosine in the approximate ratios 1.7:1, 1.4:1, 1:1 and 2.3:1, respectively. The major ceramide fatty acids have particularly long chains, with hexacosanoic and octacosanoic acids predominating. Upon reverse-phase TCL, the glycolipid components ceramide monogalactoside, digalactoside and trigalactoside were each separable into five component bands. Parent glycolipid components therefore show component band distributions comparable to one another in being governed by similar ceramide constitutions.

Animals↗
PubMed1992

The structural elucidation of the two positional isomers of a mono-glucopyranosyl mono-acyl glycerol derivative from Cystobacter fuscus (Myxobacterales).

The structures of two glycolipids produced by Cystobacter fuscus Cb 685 have been determined by 1H-NMR spectroscopy including 2D-techniques, as the positional isomers 1- and 2-isopentadecanoyl-3-beta-D-glucopyranosyl-X-glycerol. The chain length of the fatty acid residue determined by 13C-NMR spectroscopy has been confirmed by negative ion FAB-mass spectrometry.

Glycolipids↗
PubMed1992

O-acetylated gangliosides in bovine buttermilk. Characterization of 7-O-acetyl, 9-O-acetyl, and 7,9-di-O-acetyl GD3.

Three O-acetylated gangliosides, G1, G2, and G3, were purified from bovine buttermilk by using chloroform/methanol extraction, Folch partitioning, chromatography on DEAE-Sephadex A-25, and Iatrobeads columns. The final yields of gangliosides G1, G2, and G3 were 2 mg, 37 mg, and 40 mg per 1.7 kg of the buttermilk powder, respectively. On the basis of immunostaining on high performance thin layer chromatography with specific monoclonal antibodies, mild alkaline treatment, gas-liquid chromatographic analysis, fast atom bombardment mass spectrometry, and proton nuclear magnetic resonance studies, G1 and G2 are characterized as O-acetylated GD3 and G3 as O-acetylated GT3, and the structures of these gangliosides are as follows: [formula: see text] The major fatty acids of these gangliosides were C18:0, C22:0, C23:0, and C24:0, and the long chain base was C18-sphingosine.

Acetylation↗
PubMed1992

Structural characterization of neutral glycosphingolipids from Trypanosoma cruzi.

The major neutral glycosphingolipids from Trypanosoma cruzi ceramide mono- and dihexosides (CMH and CDH, respectively) were analysed after chromatographic purification using 1H 500 MHz nuclear magnetic resonance spectroscopy and fast atom bombardment mass spectrometry. The ceramide monohexoside fraction (CMH) contained both glucosyl- and galactosylceramides. After peracetylation, the CMH fraction was separated into 2 subfractions, CMH-COH and CMH-Cn, containing either hydroxy fatty acids or n-fatty acids. In the CMH-COH fraction glucose and galactose were present in a ratio of 2:1, whereas this ratio was 1:1 in the CMH-Cn fraction. The CDH fraction was identified as lactosylceramide with sphingosine as the long chain base and 16:0, 18:0, and 24:0, 24:4 fatty acids as major components.

Animals↗
PubMed1991

Six-year experience with a comprehensive approach to the treatment of recurrent childhood acute lymphoblastic leukemia (ALL-REZ BFM 85). A relapse study of the BFM group.

Between April 1985 and March 1987 130 children and adolescents up to 18 years of age with first relapse of acute lymphoblastic leukemia (ALL) were registered on the stratified and randomized multicentric trial ALL-REZ BFM 85 designed for patients pretreated with intensive front-line therapies. Stratification criteria were time and site of relapse: bone marrow (BM) relapse on or up to 6 months after stopping front-line therapy (group A), BM relapse beyond 6 months after therapy (group B), and isolated extramedullary relapse at any time (group C). Treatment consisted of alternating courses of polychemotherapy including randomly administered high- or intermediate-dose methotrexate (HDMTX:12 g/m2 as 4-hour infusion; IDMTX: 1 g/m2 as 36-hour infusion). During maintenance therapy the patients received daily oral thioguanine and biweekly intravenous (IV) MTX. The overall second complete remission (CR) rate was 92% (groups A, B, and C: 88%, 92%, and 100%), and the probability of event-free survival (EFS) at 6 years is 0.31 +/- 0.04 (groups A, B, and C: 0.18 +/- 0.05, 0.30 +/- 0.07, and 0.72 +/- 0.11). HDMTX did not prove to be superior to IDMTX, which led to premature stopping of randomization. Risk factor analyses showed early relapse, particularly BM relapse within 18 months, and T-cell phenotype to be independent predictors of poor outcome. The incidence of central nervous system (CNS) relapses following BM relapse was 19%, indicating that reprophylaxis to the CNS with IV/intrathecal (IT) MTX was insufficient. For 17 children who received bone marrow transplantation in second CR from HLA-compatible siblings the EFS was 0.53 +/- 0.12 at 5 years. Their outcome was not influenced by the above-mentioned risk factors. With the proposed treatment regimen long-lasting second remissions can be achieved in about one third of patients even after intensive front-line treatment.

Adolescent↗
PubMed1979

[Physiological basis for a cochlear prosthesis (author's transl)].

For the attempt to develop a cochlear prosthesis, which allows some understanding of speech, it seems--at least for the first attempts--to be appropriate to mimic natural conditions as far as possible. The auditory nerve contains about 30,000 afferent fibres. Qualitatively, their behavior is similar but quantitative measures show considerably differences (2.3). Nothing certain can be said at present however about the spiral fibres originating from the outer hair cells. The quantitative differences between single afferents concern tuning, frequency selectivity, thresholds, intensity functions and--of particular interest for electrical stimulation--differences in timing of the activity pattern, brought about by differences in travelling time along the cochlear duct (2.3). The time differences seen in the activity pattern of different fibres are in the order of several ms (2.3.6;2.3.7). Actionpotentials elicited by natural acoustic stimuli show probabilistic behavior, that is they are not strictly determined. It is obvious that with artificial electrical stimulation not every surviving single fibre can be selectively stimulated. An electrode will always stimulate a group of fibres simultaneously. With any conceivable electrical stimulation all fibres in the suprathreshold region of the electrode will be synchronously activated (3.2); a fundamental difference to the natural situation. To estimate the number of channels, necessary to stimulate the auditory nerve with sufficient accuracy to allow speech perception we consider some psychoacoustic data. These have shown that the auditory system possesses the ability to differentiate a great number of different pitches, but on the other hand it is capable of integrating different frequency areas to a so called critical bandwidth. Sound energy falling into one critical bandwidth is integrated to a uniform auditory sensation. If one is to integrate various fibres of the auditory nerve to one channel of stimulation it seems to be adequate to use the critical bandwidth as a measure (3.1). According to this criterion 15 channels would have to be introduced into the speech region of the cochlea. This would allow 1.2 mm of cochlear length for each channel. Perfect electrical separation of the channels is required. Considering the severe distortions in neuronal activity pattern, introduced by electrical stimulation in comparison to the natural conditions it is not clear even whether the number given would be sufficient. On the other hand, current spreading would appear to prohibit any higher electrode density. As far as coding of sound parameters within one channel is concerned it is proposed that full use should be made of frequency analysis according to the place principle. In respect to coding of periodicity and loudness it is proposed to approach natural conditions as far as possible (3.3). Here delay times between the individual channels and a probabilistic character of the stimuli should be introduced to avoid dominance of periodicity pitch...

Action Potentials↗
PubMed1978

Potassium uniport and ATP synthesis in Halobacterium halobium.

Light-driven potassium ion uptake in Halobacterium halobium is mediated by bacteriorhodopsin. This uptake is charge-balanced by sodium ions and not by proton release. Light-induced shifts in concentrations of divalent cations were found to be negligible. The transient changes in extracellular pH (alkaline overshoot) can be understood by the concomitant processes of ATP synthesis, proton/sodium exchange and potassium uptake. The driving force of potassium ion uptake is the membrane potential, no ATP-dependent potassium transport process is found. Fluorescence measurements indicate a high permeability of the membrane to potassium ions compared to sodium ions. Therefore the potassium ion diffusion potential contributes to the membrane potential (about 30 mV/decade) and thereby influences the ATP level. Sudden enhancement of the diffusion potential by the potassium ionophore monactin leads to the expected transient increase in cellular ATP level. Due to the large size (up to 100-fold) of the potassium ion gradient and its high capacity (intracellular concentration up to 3 M) the potassium ion gradient can well serve the cell as a long term storage form of energy.

Adenosine Diphosphate↗
PubMed1978

[The effect of glucagon on serum electrolyte concentrations in man].

Intravenous application of 1 mg glucagon causes a significant decrease of the magnesium, calcium, and phosphate concentrations in the serum. Concerning the potassium level there is a biphasic change of concentration. Initially a significant increase of the potassium concentration is to be measured which transgresses into a longer phase of decrease of concentration. The possible causes of these changes of electrolytes after application of glucagon are discussed and it is referred to the possible clinical importance. In longer therapeutic application of glucagon a control of the serum parameters of the electrolytes metabolism appears indicated.

Adult↗
PubMed1977

Bacteriorhodopsin-mediated photophosphorylation in Halobacterium halobium.

The rate of halobacterial photophosphorylation was found to be a linear function of light intensity over a wide range (between 1 and 20 mW/cm2). At higher light intensities (above 25 mW/cm2) the ATP-synthesizing system itself limits the maximal rate of photophosphorylation. The optimal external pH range for this type of photophosphorylation is between pH 6.2 and 7.2 external. The photophosphorylation rate is directly proportional to the bacteriorhodopsin content of the cells. The quantum requirement for photophosphorylation was found to be 22 +/- 5 photons per ATP molecule synthesized. According to Mitchell's chemiosmotic hypothesis of energy coupling phosphorylation can be driven by a membrane potential or a pH gradient or a combination of both. From the results of experiments with drugs which abolish or reduce either one of the two components we conclude that the major driving force for photophosphorylation above an external pH value of 6.5 is the membrane potential, while at more acidic pH value the pH gradient becomes dominating. We did not observe a correlation between a transient alkalinization of the medium and ATP-synthesis upon illumination under certain conditions.

Adenosine Triphosphate↗
PubMed1976

[The effects of lithium ions on circadian rhythms (author's transl)].

Lithium ions lengthen the critical dark period in short-day plants, increase the period length of circadian rhythms in Kalanchoe plants, in the rodent Meriones and influence the activity rhythm of birds. In the case of the Kalanchoe rhythm, mainly the process of the petal opening is affected.

Animals↗
PubMed1975

Separation protest in day-care and home-reared infants.

Separation protest was measured by the onset and duration of fretting or crying in 24 day-care and 28 home-reared infants during a two-minute period of isolated separation from their mothers in an unfamiliar room. Separation episodes were repeated under similarly controlled circumstances at two-month intervals from 3 1/2 through 13 1/2 months and at 20 months of age. The composition of the day-care and home-reared groups was similar for sex, ordinal position, and family background. Day-care and home-reared infants showed similar patterns in the manifestation of separation protest over age, with sharp reductions in latency to crying and marked increases in the occurrence of crying at 9 1/2 and 13 1/2 months. These results suggest that the psychological processes underlying separation protest are not materially altered by the continuing presence of the young infant in a day-care program designed to meet both his physical and psychological requirements.

Age Factors↗
PubMedDate not supplied

[Long-term study of anthracycline-induced cardiomyopathy in children and adolescents].

In order to detect changes in cardiac function, electrocardiographic, echocardiographic and radiologic studies were performed in 71 patients (age 1-26 yrs) who had been treated at the University Children's Hospital Berlin because of malignant diseases according to protocols of the DAL/GPO and had received anthracyclines (doxorubicin or daunorubicin) at cumulative doses up to 480 mg/m2 (median 280 mg/m2). Clinically overt cardiomyopathy was observed in one girl and required transient administration of digoxin. In 2 patients echocardiographic changes led to a reduction of the scheduled anthracycline doses. No patient died from congestive heart failure. During treatment, an increase in the cardiothoracic index was observed in 14 children, and in 16 the ECG showed pathological findings. A decrease in contractility to 25% or less as detected by ultrasound was seen in 15 patients. More than 50% of patients developed echocardiographical signs indicating an impairment of myocardial function. However, persistent changes were only found in 1 patient after discontinuation of treatment. Long-term echocardiographic follow-up studies for 4-48 months (median 14 months) after completion of anthracycline therapy were performed in 18 patients and the findings compared to matched-pair controls. The observed M-mode parameters were completely normal, and the ejection fractions calculated from the two-dimensional ultrasound investigations were in the normal range but slightly diminished compared to controls. Cardiac ultrasound is a non-invasive, reproducible and tolerable procedure for early detection of an anthracycline cardiomyopathy. In our patients, time of occurrence and the extent of pathological changes were not associated with the cumulative applied anthracycline doses.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗