Differential pulse polarographic determination of plasma menadione

A differential pulse polarographic assay for plasma vitamin K₃ (menadione) has been developed. Details of the assay are (i) lipid-soluble material is extracted from plasma into ether by the method of Bjornsson et al. [(1978) Thromb. Haemostas.2, 466–473]; (ii) ether is evaporated under nitrogen and the residue is dissolved in the supporting electrolyte, methanol: 0.2 m borate buffer (9:1), pH 6.8; (iii) current height is measured at ?0.32 V vs SCE on the differential pulse polarogram. The lower sensitivity limit of this technique after addition of standard vitamin K₃ to plasma is 0.3 μm; the calibration curve is linear from 0.6 through 10 μm. Two patients treated with a single dose of menadiol sodium diphosphate, 20 mg/M² i.m., achieved measurable plasma vitamin K₃ levels at 0.5 to 1.0 h ranging between 0.5 (0.08 μg/ml) and 2 μm (0.3 μg/ml).     

The regulatory effects of clomiphene and tamoxifen on mTOR and LC3-II expressions in relation to autophagy in experimental polycystic ovary syndrome (PCOS)

Molecular Biology Reports - Polycystic ovary syndrome (PCOS) is a metabolic disease that causes infertility due to anovulation in women in reproductive age. It is known that clomiphene citrate (CC)...     

Nonmyeloablative bone marrow transplantation of BXSB lupus mice using fully matched allogeneic donor cells from green fluorescent protein transgenic mice

Male BXSB mice, a mouse model of systemic lupus erythematosus, were given bone marrow transplants (BMT) at 20 wk of age using MHC-matched donor cells and nonmyeloablative conditioning (550 cGy irradiation). Transplanted mice and irradiation controls were followed for a period of 20 wk. Mice transgenic for green fluorescent protein were used as donors to allow tracking of donor cells and a determination of chimerism. Radiation controls had reduced renal pathology at 10 wk posttransplant, but not at 20 wk compared with untreated mice, while nonmyeloablative BMT mice had significantly reduced pathology at both time intervals. The monocytosis characteristic of older BXSB mice was also reduced by BMT, but the treatment did not prevent production of Ab to dsDNA. A stable chimerism of 24-40% donor CD45-positive cells was achieved in spleen and bone marrow, and there was no evidence of clinical graft vs host disease. Donor cells were detected in most recipient organs, notably the thymus and renal glomeruli. The results suggest that complete depletion of mature lymphocytes or of progenitor stem cells is not required to control lupus nephritis in BXSB mice.     

Nonlinear time series analysis of jerk congenital nystagmus

Nonlinear dynamics provides a complementary framework to control theory for the quantitative analysis of the oculomotor control system. This paper presents a number of findings relating to the aetiology and mechanics of the pathological ocular oscillation jerk congenital nystagmus (jerk CN). A range of time series analysis techniques were applied to recorded jerk CN waveforms, and also to simulated jerk waveforms produced by an established model in which the oscillations are a consequence of an unstable neural integrator. The results of the analysis were then interpreted within the framework of a generalised model of the unforced oculomotor system. This work suggests that for jerk oscillations, the origin of the instability lies in one of the five oculomotor subsystems, rather than in the final common pathway (the neural integrator and muscle plant). Additionally, experimental estimates of the linearised foveation dynamics imply that a refixating fast phase induced by a near-homoclinic trajectory will result in periodic oscillations. Local dimension calculations show that the dimension of the experimental jerk CN data increases during the fast phase, indicating that the oscillations are not periodic, and hence that the refixation mechanism is of greater complexity than a homoclinic reinjection. The dimension increase is hypothesised to result either from a signal-dependent noise process in the saccadic system, or the activation of additional oculomotor components at the beginning of the fast phase. The modification of a recent saccadic system model to incorporate biologically realistic signal-dependent noise is suggested, in order to test the first of these hypotheses. Action Editor: Peter Latham     

Nickel resistance in fission yeast associated with the magnesium transport system

We isolated and characterized a nickel (Ni²⁺)-resistant mutant (GA1) of Schizosaccharomyces pombe. This mutant strain displayed resistance to both Ni²⁺ and Zn²⁺, but not to Cd²⁺, Co²⁺, and Cu²⁺. The growth rate of GA1 increased proportionally with increasing Mg²⁺ concentrations until 50 mM Mg²⁺. The GA1 mutation phenotype suggests a defect in Mg²⁺ uptake. Sequence analysis of the GA1 open reading frame (ORF) O13779, which is homologous to the prokaryotic and eukaryotic CorA Mg²⁺ transport systems, revealed a point mutation at codon 153 (ccc to acc) resulting in a Pro 153Thr substitution in the N-terminus of the CorA domain. Our results provide novel genetic information about Ni²⁺ resistance in fission yeast. Specifically, that reducing Mg²⁺ influx through the CorA Mg²⁺ transport membrane protein confers Ni²⁺ resistance in S. pombe. We also report that Ni²⁺ ion detoxification of the fission yeast is related to histidine metabolism and pH.     

DNA base modifications induced in isolated human chromatin by NADH dehydrogenase-catalyzed reduction of doxorubicin.

The antineoplastic benzanthroquinone drug doxorubicin can undergo flavoenzyme-catalyzed one-electron reduction which, in an aerobic environment, leads to the generation of oxygen-derived species. We therefore sought to determine whether doxorubicin in the presence of NADH dehydrogenase and the transition metal ions Fe(III) or Cu(II) induces DNA base modifications in isolated human chromatin. NADH dehydrogenase-catalyzed reduction of doxorubicin (25-100 microM) caused hydroxyl radical production detected as methane generated from dimethyl sulfoxide; addition of isolated human chromatin to the system produced a concentration-dependent quenching of detectable hydroxyl radical formation. Doxorubicin (5-50 microM)-stimulated enzyme-catalyzed oxidation of NADH was also diminished, but still detectable, in the presence of chromatin. Doxorubicin-induced DNA base modifications in chromatin were measured by gas chromatography/mass spectrometry with selected-ion monitoring. Production of modified bases required the addition of transition metal ion and was enhanced by the addition of active flavoenzyme. The non-redox cycling analogue 5-iminodaunorubicin induced significantly less base modification than did doxorubicin. In the presence of Fe(III), NADH dehydrogenase-catalyzed reduction of doxorubicin caused enhancement in the content of all modified bases over control levels. Substitution of Cu(II) for Fe(III) altered both the degree and the pattern of doxorubicin/NADH dehydrogenase-induced base modifications. The scavengers of hydroxyl radical mannitol and dimethyl sulfoxide or catalase did not significantly affect doxorubicin/NADH/NADH dehydrogenase/transition metal ion-induced base modifications. Superoxide dismutase further enhanced production of all base modifications. The data demonstrate that flavoenzyme-catalyzed redox cycling of doxorubicin generates typical hydroxyl radical-induced base modifications in the DNA of isolated human chromatin, suggesting a possible mechanism for the mutagenicity of doxorubicin in vivo.