Intraspinal Tumors in Children

Thirty cases of intraspinal neoplasms occurring during the first two decades of life are reviewed. Histologic examination showed 13 of these to be astrocytomas, 6 neuroblastomas, 5 sarcomas, 3 ependymomas, 2 neurofibromas and 1 a schwannoma. Orthopedic deformities developed or worsened in 60 percent of patients surviving longer than a year after diagnosis. In five patients some form of endocrine deficiency developed after irradiation. For treatment of radiosensitive extradural malignant lesions, biopsy followed by irradiation is advocated.     

Survival of Vibrio anguillarum and Vibrio salmonicida at different salinities

The fish pathogenic bacteria Vibrio anguillarum and V. salmonicida showed the capacity to survive for more than 50 and 14 months, respectively, in seawater microcosms. A salinity of 5% proved lethal to V. anguillarum harvested in the late-exponential growth phase, whereas a salinity of 9% was lethal to the bacterium after it had been starved at a salinity of 30% for 67 days. The lethal salinity for V. salmonicida harvested in the late-exponential growth phase was probably in the vicinity of 10%. V. anguillarum and V. salmonicida were very sensitive to nalidixic acid. Direct determination of viable cells after incubation with nalidixic acid was not possible, since the cells did not elongate. Samples of V. salmonicida were double stained with fluorescein isothiocyanate-labeled antibodies and 4',6-diamidino-2-phenylindole. After 3 or 4 days of starvation, there was a discrepancy between the total numbers of cells as determined by immunofluorescence versus by staining with 4',6-diamidino-2-phenylindole. The immunofluorescence counts remained high, which indicated the presence of intact cell envelopes but leakage of DNA and other cytoplasm components. After 2 weeks of starvation, for some of the cells, the region stained with 4',6-diamidino-2-phenylindole (i.e., DNA) was markedly smaller than the cell envelope. I attributed this to a shrinkage of the cytoplasm or a confined nucleoid or both. V. anguillarum lost its exoproteolytic activity before 11 days of starvation.     

Protein folding thermodynamics applied to the photocycle of the photoactive yellow protein.

Two complementary aspects of the thermodynamics of the photoactive yellow protein (PYP), a new type of photoreceptor that has been isolated from Ectothiorhodospira halophila, have been investigated. First, the thermal denaturation of PYP at pH 3.4 has been examined by global analysis of the temperature-induced changes in the UV-VIS absorbance spectrum of this chromophoric protein. Subsequently, a thermodynamic model for protein (un)folding processes, incorporating heat capacity changes, has been applied to these data. The second aspect of PYP that has been studied is the temperature dependence of its photocycle kinetics, which have been reported to display an unexplained deviation from normal Arrhenius behavior. We have extended these measurements in two solvents with different hydrophobicities and have analyzed the number of rate constants needed to describe these data. Here we show that the resulting temperature dependence of the rate constants can be quantitatively explained by the application of a thermodynamic model which assumes that heat capacity changes are associated with the two transitions in the photocycle of PYP. This result is the first example of an enzyme catalytic cycle being described by a thermodynamic model including heat capacity changes. It is proposed that a strong link exists between the processes occurring during the photocycle of PYP and protein (un)folding processes. This permits a thermodynamic analysis of the light-induced, physiologically relevant, conformational changes occurring in this photoreceptor protein.     

Oxidation of low density lipoprotein leads to particle aggregation and altered macrophage recognition.

Oxidized (ox-) low density lipoproteins (LDL) is characterized by the formation of lipid peroxides and their decomposition to reactive aldehydes which covalently link to apoB in LDL. These chemical changes are believed to be responsible for the enhanced recognition of ox-LDL by receptors on macrophages in culture. When oxidation is extensive, particle aggregation also occurs. The aim of this study was to characterize aggregation formation and how this influences the interaction of ox-LDL with macrophages in culture. When LDL was oxidized by incubating at 500 micrograms of protein/ml with 10 microM Cu2+ at 20 degrees C for up to 25 h, time-dependent increases in thiobarbituric acid reactive substances, conjugated diene content, electrophoretic mobility, and fluorescence at 360 excitation/430 emission were found. Particle aggregation increased in parallel with several parameters of oxidation and increased with increasing incubation temperatures and LDL concentrations used. When evaluated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, apoB fragments of reproducible sizes and higher molecular weight species appeared after mild oxidation of LDL. The percent of total apoB remaining aggregated in sodium dodecyl sulfate was 50-80% at high degrees of oxidation, whereas it was far less in LDL that had been aggregated without chemical modification. This suggested that intermolecular cross-linking of apoB had occurred during oxidation of LDL at high concentrations. Degradation of ox-LDL in mouse peritoneal macrophages (MPM) increased in parallel with the degree of oxidation and with particle aggregation but reached a plateau after 12 h. Results from cross-competition studies in MPM with soluble and insoluble portions of extensively ox-LDL and with acetyl-LDL were consistent with uptake of soluble ox-LDL via both the scavenger receptor and another receptor on MPM, and uptake of the insoluble ox-LDL by an alternative mechanism.