Biomedical subjects
Publications and source records attributed to D Schubert.
5-Bromodeoxyuridine induces the differentiation of mouse neuroblastoma C1300 to cells that morphologically resemble mature neurons. The induced differentiation can take place in the absence of DNA synthesis. This suggests that the halogenated pyrimidine need not be incorporated into DNA to alter the phenotype of the cell.
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Mouse tumor C1300 has been established in tissue culture. The cells have a round cell morphology in both the subcutaneous tumor and in suspension culture. However, when given a surface on which to attach, they send out processes up to 3 mm in length and assume the morphology of mature neurons. The attached cells are stained by the Bodian silver procedure for neurons, whereas the cells grown in suspension are not. Electron microscopy reveals that the attached cells contain neurofilaments, neurotubules, and densecore vesicles indicative of nerve fibers. Both free-floating and attached cells have tyrosine hydroxylase activity characteristic of sympathetic nervous tissue. Apparently cell attachment can induce morphological differentiation from an anaplastic round cell to a cell which has many properties of a mature neuron.
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The multiple species of HSPGs within the nervous system have a variety of functions. These include roles in ECM assembly and a contribution from synaptic vesicles to synaptic cleft matrix. Since the Alzheimer beta-protein precursor is structurally very similar to a HSPG, it is most certainly an ECM-associated protein. An outstanding question then is what role ECM plays in the genesis of Alzheimer's plaques.
In a retrospective study, 34 treated adolescents with phenylketonuria and their relatives were tested with scale 2 of the Culture Fair Intelligence Test (CFT20) and self-developed questionnaire concerning their development in school. The patients also filled in the Anxiety Questionnaire for Children. With an IQ of 93.6, the patients reached a normal mean intellectual performance but this was significantly below the mean IQ of the general population (100, p < 0.01), the IQ of their mothers (98.2, p < 0.05), their fathers (105.4, p < 0.05) and their siblings (110.3, p < 0.05). The patients' IQs correlated significantly with the IQs of their mothers, the socio-economic status of their families, the quality of dietary control since birth and the serum phenylalanine concentration at the moment of testing. With respect to age at which the patients started school, type of school attended and number of school years which had to be repeated, there were no significant differences between the patients and their siblings. The patients did not display a markedly higher degree of general anxiety, nervousness at examination time or a greater reluctance to attend school.
The loosely bound proteins from human erythrocyte membranes induce an up to more than 103-fold increase in the electrical conductivity of black lipid membranes made from oxidized cholesterol. The conductivity increase continues until the membrane breaks. Its magnitude insreases with increasing protein concentration and salt concentration. The results are compared with earlier results obtained with the strongly bound proteins from erythrocyte membranes.
The sedimentation at low speed centrifugation of a lipoprotein recombined from the lipids and the strongly bound proteins of the human erythrocyte membrane depends on pH: between 4.5 and 6.0, most of the liproprotein sediments, whereas at pH 7.0-8.5, up to 90% remains in the supernatant. Precipitation of the lipoprotein can be reversed by increasing the pH, followed by a brief sonication. The mobility of spin-labelled protein groups in the lipoprotein increases with increasing pH. This mobility increase is also reversible and is of equal magnitude in precipitated and nonprecipitated recombinates. It is concluded that, because of these reversibilities, determination of the yield of liproprotein formation in recombination experiments must include analysis of both precipitated and nonprecipitated lipoproteins.
The electrical conductivity of black phosphatidylserine membranes, in solutions of 100 mM NaCl, 10 mM sodium phosphate (pH 7.1), is strongly increased by the intrinsic proteins ("strongly bound" protein fraction) from human erythrocyte membranes. The magnitude of the conductivity increase is highly dependent on the maximum pH-value pH used during the preparation of the protein (8.0 less than or equal to pH less than or equal 11.8). For each pH, membrane conductivity lambdaf and protein concentration c are linked by the equation lambdaf=k-cs, k and s being functions only of pH. The value of s varies between 1.0 (pH 8) and 4.0 (pH 10). It is assumed that the protein-induced conducting sites, at least for protein pretreatment at pH less than or equal to 10, are assembled from four protein subunits. The incorporation of the subunits into the lipid bilayer is supposed to occur either as the final tetramer (pH 8) or as monomers (pH 10) and possibly dimers (pH around 9).