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Biomedical subjects

V Neuhoff

Publications and source records attributed to V Neuhoff.

At least 73 records · Page 4Linked to original sources
PubMed1981

Spot analysis for glycoprotein determination in the nanogram range.

A flexible method for glycoprotein determination with microliter-volumes using spot analysis ("Tüpfelprobe") on cellulose acetate layers is described. With glucose oxidase as an example of a glycoprotein and fluorescein isothiocyanate-labelled Concanavalin A, a sensitivity of 10 ng is reached; in combination with horseradish peroxidase 1 ng of glucose oxidase can be detected. A simultaneous determination of protein and glycoprotein with one single spot of 0.5, 1 or 2 microliters of a glycoprotein solution can be performed. The method is independent of many common external influences, e.g. dodecyl sulfate, Triton X-100, NP 40, mercaptoethanol and desoxycholate. Only pretreatment of the glycoprotein with urea decreases the sensitivity.

Cellulose↗
PubMed1980

Characterization of experimental phenylketonuria. Augmentation of hyperphenylalaninemia with alpha-methylphenylalanine and p-chlorophenylalanine.

Phenylalanine in conjunction with p-chlorophenylalanine or alpha-methylphenylalanine was administered to suckling rats to induce hyperphenylalaninemia reminiscent of untreated phenylketonuria, and developmental parameters were monitored. The experimental model utilizing p-chlorophenylalanine was found to be unsatisfactory, in that the drug had general deleterious effects on growth, numerous side effects including increased mortality, and affected brain levels of biogenic monoamine neurotransmitters. The model utilizing alpha-methylphenylalanine was relatively free from nonspecific effects and thus, changes observed in the animals were attributable to experimental phenylketonuria. The latter animals had slightly decreased body and brain weights, and exhibited grossly elevated serum phenylalanine and urinary excretion of phenylketone metabolites. Hyperphenylalaninemia produced greatly disrupted brain amino acids at 10 days of age (prior to the formalization of the blood-brain barrier and specific transport systems) which was limited by 30 days of age to changes in glycine, gamma-aminobutyric acid and the aliphatic and aromatic amino acids which compete for uptake in the brain by a common carrier. These animals also exhibited a myelin deficit and changes in proteins from isolated nerve cell preparations. Mature animals which had daily treatment up to 60 days of age exhibited a long-term learning impairment. These observations are consistent with many aspects of the clinical picture of untreated phenylketonuric patients, and suggest that this animal model will be beneficial in studying the disease.

Age Factors↗
PubMed1980

Phenylketonuria: clinical and experimental considerations revealed by the use of animal models.

Phenylketonuria is a genetic defect that leads to imbecility, if the diagnosis is not made directly after birth. Since the development of imbecility can be almost totally halted by suitable dietary treatment, phenylketonuria is of more interest to neurochemists than to clinicians. This genetic defect is not known to occur in aminals. It is therefore necessary to develop suitable models for neurochemical analysis. Most successful is the simultaneous application to developing rats of alpha-methyl-phenylalanine (an inhibitor of phenylalanine hydroxylase), together with phenylalanine. With this treatment it is possible to induce changes in the central nervous system which are surprisingly similar to those found in patients with phenylketonuria. This model is therefore of great importance in the analyses of the disturbances of metabolism, which finally causes the severe defects in normal brain function.

Animals↗
PubMed1980

Myelination in rabbit optic nerves is accelerated by artificial eye opening.

Artificial opening of the eyes of young rabbits on the 5th postnatal day led to accelerated myelination: the myelin-specific basic and proteolipid proteins nearly doubled between the 7th and the 10th postnatal days when compared to controls; 2',3'-cyclic nucleotide 3'-phosphodiesterase (CNP) activity also increased by about 60%. Conversely, lowered AChE activities presumably reflected elevated myelin/axolemma ratios. Myelination in treated animals normalized during later ontogenetic stages (greater than 20th postnatal day).

2',3'-Cyclic-Nucleotide Phosphodiesterases↗
PubMed1980

The lipid composition of light and heavy myelin subfractions isolated from rabbit sciatic nerve.

Centrifugation of adult rabbit sciatic nerve homogenates on continuous sucrose density gradients yields three distinct maxima at 0.12, 0.33 and 0.57 M sucrose (labeled A, B and C), respectively. Fraction A is absent in homogenates of immature rabbit sciatic nerve and the material isolated from adult animals is found to contain large amounts of triglycerides. It is proposed that fraction A results from the presence of adipose tissue adhering to the adult nerve preparations and should not be regarded as a true myelin subfraction. The concentration of the major membrane lipid classes (phospholipid, cholesterol and galactosyl ceramide) decreases from the light to the heavy side of the gradient. The ethanolamine phosphatide to sphingomyelin ratio increases from 1.06 to 1.42 between fractions B and C, due to an increase in the phosphatidal ethanolamine content at the expense of sphingomyelin.

Animals↗
PubMed1979

Neurochemical and morphological studies of bulk isolated rat brain cells. II. Preparation of viable cerebral neurons which retain synaptic complexes.

The bulk isolation from rat cerebral cortex of viable neurons retaining synaptic complexes is described. The basis of this procedure is to dissociate the neurons in situ from the surrounding glial cells. The glial structures that are normally adjacent to the neuronal cell body and to the proximal parts of the neuronal processes are largely destroyed by perfusion of the brain under special conditions. The most important of these conditions was found to be a hyperosmolar concentration of hexoses in the perfusion medium. In addition, the presence of collagenase and hyaluronidase in the perfusion medium and specific perfusate flow characteristics were required to produce the structural changes throughout the brain tissue. When the perfused brain was further dissociated into a cell suspension by mincing and sieving, isolated neurons were obtained, the majority of which retained the proximal parts of their processes. A novel feature of these neurons was the retention of synaptic boutons on the plasma membrane. Presynaptic terminals with mitochondria and vesicles as well as pre- and postsynaptic membranes and densities were observed on the isolated neurons. The neurons were fractionated to 90--95% purity using discontinuous Ficoll density gradient centrifugation with a liquid fluorocarbon as cushion. Highly purified, viable cerebral neurons retaining synaptic complexes are thus available in bulk for neurobiological studies.

Animals↗
PubMed1979

Myelin protein composition in the rat spinal cord in culture and in vivo: a developmental comparison.

Biochemical characterization of the development of myelin in vitro was extended to an analysis of myelin protein composition in cultures of explanted foetal rat spinal cord. Myelin fractions were isolated from pooled explants after 12-30 days in vitro and, for comparison, from the spinal cords of rats of equivalent developmental ages. Electron microscopic examination of the culture myelin fractions revealed the presence of multilamellar myelin fragments and some single membranes. All fractions were analyzed using a micro-polyacrylamide gel electrophoresis technique. Qualitatively similar protein profiles were observed for myelin isolated from either cultures or from spinal cords. Fractions from cultures contained a greater proportion of high molecular weight proteins than those from spinal cords, although with respect to the 'major' myelin proteins, a quantitatively similar developmental pattern was observed both in vivo and in vitro.

Age Factors↗
PubMed1979

Carbonic anhydrase activity in myelin fractions from rat optic nerves.

The carbonic anhydrase activity of myelin fractions isolated from the optic nerves of adult and immature (20-day-old) rats was examined. The specific activity in both total homogenate and myelin fractions was about 2-fold higher in adult than in immature animals and at both ages, the activity in the homogenate was higher than in myelin. After subfractionation by zonal gradient centrifugation, it was shown that carbonic anhydrase activity was greatest in the heaviest myelin particles at both ages. These data are consistent with the hypothesis that a small proportion of the total enzyme activity is localised in myelin.

Aging↗