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Biomedical subjects

V Neuhoff

Publications and source records attributed to V Neuhoff.

At least 55 records · Page 3Linked to original sources
PubMed1984

A "high-performance" 2D gel scanner.

We describe the design principles of a photometric flatbed scanner with a scan area of 250 X 250 mm2, a dynamic range of 4000 gray levels, a signal/noise ratio of 2000/1, a step size of 0.1 mm, and a step frequency of 2000 steps per second. It is controlled by a microcomputer and used to acquire data for quantitative evaluation of gels or chromatograms. The performance of the instrument is demonstrated by the data obtained by scanning gratings, gray step filters, and high-resolution electropherograms.

Electronic Data Processing↗
PubMed1984

Spot identification in two-dimensional patterns by a least-squares template matching.

The coordinates of the center of measured spots are nonlinearly transformed to get an optimal match between the transformed coordinates and the given coordinates of a reference pattern. The parameters of the transformation are determined by the minimum of a function of squared distances between all spots of the sample and of the reference pattern. The algorithm requires a priori defined correspondences between some pivot points in the sample and the reference and treats their distances differently from the others. The parameters of the transformation are the solutions of a system of nonlinear equations; their numerical values are obtained by iteration.

Amino Acids↗
PubMed1983

Free amino acid concentrations in the gut lumen of developing rats.

Free amino acid concentrations in the lumen and tissue of small intestine of suckling rats were measured by a micromethod. Almost all amino acid concentrations (Lys excepted) in the intestinal juice decrease until 15 days of age whereby the pattern remains constant. Concomitantly, free amino acid concentrations in the intestinal tissue increase between 10 and 15 days p.p. The pool of amino acids in the intestinal juice, reflecting the nutritional input and its utilization, becomes exhausted during the suckling period. At 20 days of age the rats additionally ate the rat chow and free amino acid concentrations in the intestinal tissue increased again. The decline of the amino acid pool in the lumen of small intestine which is both derived by the mother and exhausted by the growing organism may act as a signal for differentiation via (self-) restriction of substrates for protein accretion.

Amino Acids↗
PubMed1983

Artificial release of 3H-taurine after electrical stimulation of retinae.

The 3H-taurine release from rat retina evoked by electrical stimulation was studied. With monophasic pulses, the release could not be reproduced with the same retina preparation unless the stimulation intensity was increased or the electrode was placed in another part of the retina. LDH was released simultaneously with 3H-taurine. When the incubation was carried out at 0 degree C immediately after the stimulation, less 3H-taurine was released as compared to 37 degrees. When the tissue was stimulated at 0 degree release occurred as well. When weak alternating current stimulation was used no release was observed. However, with strong AC current stimulation, 3H-taurine release occurred, but LDH was released as well. From these results it is concluded, that the observed 3H-taurine release was at least partially due to unspecific tissue damage. Possible reasons for artificial release are heat, pH-changes around the electrodes, chlorine generated electrolytically, and silver ions liberated from the electrode. Addition of small amounts of chlorine or silver ions to the incubation medium for 2 min instead of electrical stimulation, caused strong 3H-taurine release from retina.

Animals↗
PubMed1983

Uptake, autoradiography and release of taurine and homotaurine from retinal tissue.

Uptake of 3H-taurine into bovine retina was studied. Kinetic parameters of uptake were Km = 6.3 x 10(-5) mol/l with Vmax = 43 nmol/g wet tissue x min and Km = 5 x 10(-3) mol/l with Vmax = 702 nmol/g wet tissue x min. Unlabeled homotaurine, a close structural analogue of taurine, showed only a single sodium dependent low affinity uptake with mH = 1.5 x 10(-3) mol/l and Vmax = 1322 nmol/g wet tissue x min. Both taurine and homotaurine uptake were highly sensitive to temperature and inhibited equally by addition of taurine or homotaurine. The taurine content of incubated retinae was greatly altered depending on the osmolarity of the incubation medium. Autoradiography showed 3H-taurine mainly in Müller cells and certain photoreceptor cells of rat retinae, whereas 3H-homotaurine was found exclusively in Müller cells. Electrical stimulation as well as elevated external potassium concentration resulted in a substantial release of 3H-taurine and 3H-homotaurine from preloaded retinae. However, unspecific release cannot be excluded.

Animals↗
PubMed1982

The binding of tetanus toxin to retinal cells.

An indirect immunofluorescence assay demonstrated intense binding of tetanus toxin to a minority of cells cultured from neonatal rat retina. These labelled cells were typically spheroid cells bearing long processes. Flat cells and smaller spheroid cells without long processes were essentially unlabelled. A similar assay performed on frozen sections of rat retina showed that tetanus toxin bound intensely to the inner plexiform layer, moderately to the outer plexiform and inner nuclear layers, and only very slightly to the outer nuclear layer. The localization of tetanus toxin bound to frozen sections was confirmed by autoradiography of [125I]tetanus toxin binding. In contrast, the monoclonal antibody A4 bound to all layers of the retina (except that of the outer segments). In cell cultures the monoclonal antibody Ran-2 bound to the flat cells but to neither class of spheroid cells. These data imply that tetanus toxin binds more intensely to retinal neurones than to photoreceptors and other retinal cell types. By assisting identification of cells dissociated from retina, assays of tetanus toxin binding should prove useful in the isolation of specific retinal cell-types.

Animals↗
PubMed1982

Impaired permeability of the blood-cerebrospinal fluid barrier in hyperphenylalaninaemia.

In hyperphenylalaninaemic rats the accumulation of 5-hydroxytryptophan (5-HTP) in the cerebrospinal fluid (CSF) could be shown in spite of the fact, that the 5-HTP levels of serum and brain remain constant. In vitro studies of the influx and efflux of 5-HTP and phenylalanine on isolated beef choroid plexus suggested that both aminoacids use the same carrier system. It is concluded that a high concentration of phenylalanine inhibits the re-uptake of 5-HTP by the endothelial cells of the choroid plexus. Additionally, an increased efflux of 5-HTP from choroid plexus leads to the accumulation of 5-HTP in the cerebrospinal fluid.

5-Hydroxytryptophan↗
PubMed1982

Brain development in experimental hyperphenylalaninaemia: myelination.

The influence of hyperphenylalaninaemia on the formation and composition of myelin has been investigated in forebrain and spinal cord of young rats (10-60 days p.p.). The injection of alpha-methylphenylalanine plus phenylalanine in 12 hour intervals (from 3rd day post partum) resulted in decreased wet weights of brain and spinal cord and reduced myelin yields; both were more pronounced in the forebrain. Myelination was initially delayed in the forebrain but thereafter the rate of myelination was the same in both control and hyperphenylalaninaemic rats. Transient alterations of several parameters of myelination were observed during early stages of development. Myelin isolated from the CNS of hyperphenylalaninaemic rats at 10 and 20 days p.p. was slightly more mature with respect to sedimentation characteristics, protein pattern, fatty acid composition of certain myelin lipids, and electron microscopical structure of myelin preparations. No significant changes in the myelin composition of the preparations of both forebrain and spinal cord were found at later developmental stages (30 and 60 days p.p.). The findings are discussed in relation to alterations in the axonal outgrowth rather than to a specific effect of hyperphenylalaninaemia on myelin formation.

Animals↗
PubMed1982

Demonstration of alpha 1-acid glycoprotein (orosomucoid) by double one-dimensional slab gel electrophoresis: evidence for intra- and interindividual variability of the microheterogeneity pattern in health and disease.

This double one-dimensional slab gel electrophoresis technique, in the sequence polyacrylamide gel electrophoresis followed by isoelectric focusing in polyacrylamide gels, permits the selective demonstration and comparison of the micro-heterogeneity pattern of alpha 1-acid glycoprotein (orosomucoid) in as many as 96 human plasma or serum samples on one gel. The electrophoretic analysis is performed on 8 microL of serum or plasma without prior purification. Several hundred samples can be analyzed by one investigator during a working day. Densitometric evaluation of the patterns revealed two new findings: 1) The microheterogeneity pattern can be described by a parameter that is independent of the concentration of orosomucoid in plasma: the center of density of the pattern, with the peak number as coordinate. 2) There is a considerable average shift of the center of density towards more basic components among the patterns obtained for samples from hospital patients. The results suggest that followup of the intra-individual variation of the orosomucoid pattern in health and disease might help in studying the still-uncertain function of this protein as well as the diseases affecting the pattern.

Adult↗
PubMed1981

Central nervous system myelin proteins and glycoproteins in vertebrates: a phylogenetic study.

CNS myelin was isolated by a conventional method from a wide range of vertebrate classes and analyzed by SDS-PAGE for proteins (Coomassie blue) and glycoproteins (concanavalin A (Con-A)-peroxidase). Mammalian, avian and reptilian myelin shared similar protein patterns (basic protein, BP; intermediate protein, DM-20; proteolipid protein, PLP; Wolfgram protein, W). Amphibians lacked DM-20 but were characterized by specific activities of 2',3'-cyclic nucleotide 3'-phosphodiesterase (CNP) higher than those of the other classes examined. The Con A-binding profiles were similar in the high molecular weight (HMW) regions of the classes listed above, while the typical myelin proteins in the low molecular weight (LMW) regions were devoid of Con A-binding properties. In teleost myelin a putative BP band ran well ahead of rat small basic protein (SBP), whereas the region corresponding to rat PLP was covered by several closely spaced bands, most of which bound Con A. In elasmobranch myelin, apart from bands corresponding to BP, Con A-binding glycoproteins were detected migrating in the region of rat DM-20 and PLP as well as with mammalian PNS P0 protein. Cyclostomates yielded only very small amounts of material in the myelin preparation and displayed undifferentiated Coomassie blue- and Con A-binding in the HMW region, while typical LMW myelin proteins were absent. These results demonstrate that CNS myelin from bony and cartilaginous fishes is characterized by containing several major Con A-binding proteins of low molecular weight. This is in striking contrast to myelin from phylogenetically higher classes.

2',3'-Cyclic-Nucleotide Phosphodiesterases↗
PubMed1981

[Digital image analysis as an optical tool in biochemistry].

Digital image analysis can be used to assist of complement visual perception. In quantifying light intensities it is superior to the human visual system and therefore is an appropriate and useful tool for research. Using microphotometry as an example the physical bases of digital image analysis are explained and the applications of this measuring technique to biochemical analysis are demonstrated.

Computers↗
PubMed1981

Oligodendrocytes from postnatal cat brain in cell culture. I. Regeneration and maintenance.

Oligodendrocytes isolated in bulk from white matter of cat brain (8-12 weeks of age) employing a Percoll gradient as the final purification step, were cultured and maintained for more than 10 weeks. Different parameters, e.g. coating material and the age of the animals appeared to have some influence on attachment rate and survival of the cells. Oligodendrocytes from older animals, or oligodendrocytes seeded into poly-L-lysine coated culture dishes revealed a marked tendency to form aggregates. Of the dispersed cells, 80-99% can be classified as oligodendrocytes by transmission electron microscopy (TEM) and immunocytochemical markers. Aggregates which were re-seeded consisted of more than 90% oligodendrocytes. About one day after attachment to the supporting layer the cells start to regenerate their processes which sometimes broaden at their ends into shovel-like, membranous extensions.

Animals↗