AL Boskey  P Guidon  SB Doty  D Stiner  P Leboy  I Binderman 《Canadian Metallurgical Quarterly》1996,11(11):1694-1702

Differentiating chick limb-bud mesenchymal cells plated in micromass culture form a cartilage matrix that can be mineralized in the presence of 4 mM inorganic phosphate (Pi), and 1 mM calcium. Previous studies showed that when beta-glycerophosphate (beta GP) is used in place of Pi, the mineral crystals formed are larger and differ in distribution. The present study shows that the difference in distribution is not associated with alterations in cell proliferation, protein synthesis, or with collagen, proteoglycan core protein, or alkaline phosphatase gene expression. Cultures with 2.5, 5, and 10 mM beta GP did show different levels of alkaline phosphatase activity, and in the presence of low (0.3 mM) Ca had different Pi contents (4, 6 and 9 mM, respectively), indicating that the increase in CaxP product may in part be responsible for the altered pattern of mineralization. However, cultures with beta GP in which alkaline phosphatase activity was inhibited with levamisole still had an altered mineral distribution as revealed by Fourier transform-infrared (FT-IR) microspectroscopy. The presence of a casein kinase II-like activity in the mineralizing cultures, the ability of specific inhibitors of this enzyme to block mineralization, and the known ability of beta GP to block phosphoprotein phosphatase activity suggests that altered patterns of matrix protein phosphorylation may influence mineral deposition in these cultures.  相似文献   

    

QY He  HQ Zhang  DB Pang  XS Chi  SB Xue 《Canadian Metallurgical Quarterly》1996,31(10):721-726

To further study the relationship between resistance to apoptosis and drug resistance in harringtonine-resistant HL-60 cells (HR20), cyclosporine A (CsA) 20, 10 micrograms.ml-1 was shown to induce the sensitive HL-60 cells to apoptosis, showing a typical DNA \"ladder\" band. But the same concentrations of CsA retarded the HR20 cells in G1 phase and could not induce the cells to apoptosis. The cellular daunorubicin accumulation increased when HR20 cells were treated with low concentration of CsA and the reversal of drug resistance by CsA was unrelated to the retardation of cell cycle progression. High phosphorylation of about 50 kDa protein occured when HR20 cells were treated with CsA 10 micrograms.ml-1. The results domonstrate that cyclosporine A retarded the harringtonine-resistant HL-60 cells in G1 phase but induced HL-60 cells to apoptosis, and the retardation was unrelated to drug resistance.  相似文献   

    

SB Karwacki  JR Bradley 《Canadian Metallurgical Quarterly》1996,26(3):243-255

Associations between coping responses, drinking motivations, expectations of meeting social and academic goals, and family of origin problem drinking and measures of college students' quantity/frequency of alcohol use and social complications of alcohol use were investigated in a sample of 218 college students. Positive associations were found between \"emotion-focused\" forms of coping such as detachment and the criterion measures, whereas \"problem-focused coping\" was not significantly associated with quantity/frequency of alcohol use or drinking complications. Positive correlations were also found between drinking motives, goal attainment expectancies and family models measures and the criterion measures. Regression models constructed for alcohol quantity/frequency and drinking complications implicated the total number of drinking motives, family models of problem drinking and the coping strategy of self-blame as strongly related to criterion measures. Positive social drinking motives and coping by seeking social support were implicated as possible protective factors.  相似文献   

    

GF Makhaeva  IV Filonenko  VL Yankovskaya  SB Fomicheva  VV Malygin 《Canadian Metallurgical Quarterly》1998,19(4-5):623-628

Acetylcholinesterase (AChE) and neuropathy target esterase (neurotoxic esterase, NTE) are two major target enzymes for organophosphorus (OP) esters. The relative potency of an OP ester to react with AChE or with NTE in vitro correlates with its relative potency in vivo to cause acute toxicity (death) or organopohosphate-induced delayed neurotoxicity (OPIDN). On this basis extrapolation from in vitro to in vivo data now seems justifiable to predict risk of OPIDN. The kinetics of NTE and AChE inhibition by experimental pesticides of the general formula (RO)2P(O)ON=CClCH2Cl, where R = methyl, ethyl, isopropyl, propyl, isobutyl, butyl, pentyl, has been studied. Compounds with short R (methyl, ethyl) were shown to be far more potent inhibitors of AChE than NTE. Both anti-NTE activity, selectivity for NTE and, correspondingly, the propensity of compounds to cause OPIDN rise with increasing their hydrophobicity. A high value of ki(NTE)/ki(AChE) for R = pentyl suggests that this compound would have the potential to cause OPIDN at doses lower than the LD50. A quantitative structure-activity relationships (QSAR) analysis indicated that NTE and AChE have different structural and electronic requirements for their respective OP inhibitors.  相似文献   

    

Y Namkung  SM Smith  SB Lee  NV Skrypnyk  HL Kim  H Chin  RH Scheller  RW Tsien  HS Shin 《Canadian Metallurgical Quarterly》1998,95(20):12010-12015

In comparison to the well characterized role of the principal subunit of voltage-gated Ca2+ channels, the pore-forming, antagonist-binding alpha1 subunit, considerably less is understood about how beta subunits contribute to neuronal Ca2+ channel function. We studied the role of the Ca2+ channel beta3 subunit, the major Ca2+ channel beta subunit in neurons, by using a gene-targeting strategy. The beta3 deficient (beta3-/-) animals were indistinguishable from the wild type (wt) with no gross morphological or histological differences. However, in sympathetic beta3-/- neurons, the L- and N-type current was significantly reduced relative to wt. Voltage-dependent activation of P/Q-type Ca2+ channels was described by two Boltzmann components with different voltage dependence, analogous to the \"reluctant\" and \"willing\" states reported for N-type channels. The absence of the beta3 subunit was associated with a hyperpolarizing shift of the \"reluctant\" component of activation. Norepinephrine inhibited wt and beta3-/- neurons similarly but the voltage sensitive component was greater for N-type than P/Q-type Ca2+ channels. The reduction in the expression of N-type Ca2+ channels in the beta3-/- mice may be expected to impair Ca2+ entry and therefore synaptic transmission in these animals. This effect may be reversed, at least in part, by the increase in the proportion of P/Q channels activated at less depolarized voltage levels.  相似文献   

    

SB House  A Thomas  K Kusano  H Gainer 《Canadian Metallurgical Quarterly》1998,10(11):849-861

Rat and mouse hypothalami from postnatal animals containing highly differentiated neurones survive very well in long-term (>15 days in vitro, DIV) stationary organotypic cultures. Magnocellular oxytocin (OT) and vasopressin (VP) neurones are present in identifiable paraventricular (PVN), supraoptic (SON) and accessory (ACC) nuclei in these cultures. After 15 DIV in standard medium immunocytochemistry revealed 427 +/- 63 OT cells and 217 +/- 27 VP cells per cultured rat hypothalamus, and 380 +/- 72 OT cells and 622 +/- 91 VP cells per cultured mouse hypothalamus. Following a 7-day adaptation period in standard culture medium containing serum, the rat slice-explants survived very well after subsequent transfer to defined, serum- free media (SFM) for an additional 8 days. The number of OT cells surviving in SFM was 612 +/- 147 OT cells per cultured rat hypothalamus. Only 0.5% of the magnocellular OT and VP neurones in the cultures appeared to express both peptides. Experiments on c-fos gene expression in these cultures showed that while only 12% of the magnocellular OT and VP neurones contained barely detectable Fos protein in their nuclei under control conditions, potassium depolarization of these cultures for 3 h produced intense c-fos expression in 87-91% of these cells. Thus, magnocellular neurones in these cultures are sufficiently stable and responsive to permit long-term physiological and gene expression studies to be done under defined media conditions.  相似文献   

    

JG Jefferys  RM Empson  MA Whittington  SB Prusiner 《Canadian Metallurgical Quarterly》1994,1(1-2):25-30

The human prion encephalopathy Creutzfeldt-Jakob disease often is manifest as rapidly progressing dementia with myoclonus and synchronous, periodic discharges. To investigate the electrophysiology of prion disease we used intra- and extra-cellular recordings from brain slices from Tg(SHaPrP+/+) 81 mice, which express Syrian hamster prion protein and which are susceptible to hamster-passaged scrapie isolates. Forty days after intracerebral inoculation with scrapie isolate Sc237, we recorded prolonged, epileptiform discharges in cortex and hippocampus. Neurological signs were subtle and histopathology was minimal. Central nervous system (CNS) dysfunction progressed; by 57 days the mice were ataxic, had spongiform histopathology and they died in <63 days. During the terminal phase, intrinsic neuronal properties changed dramatically and action potentials broadened from <4 to 20-100 ms in 30% of cortical cells. We conclude that brain dysfunction in experimental scrapie precedes clinical signs and spongiform histopathology, and is preserved in slices maintained in vitro, making it accessible to electrophysiological analysis.  相似文献   

    

Y Zhao  TW Muir  SB Kent  E Tischer  JM Scardina  BT Chait 《Canadian Metallurgical Quarterly》1996,93(9):4020-4024

A precise and rapid method for identifying sites of interaction between proteins was demonstrated; the basis of the method is direct mass spectrometric readout from the complex to determine the specific components of the proteins that interact--a method termed affinity-directed mass spectrometry. The strategy was used to define the region of interaction of a protein growth factor with a monoclonal antibody. A combination of proteolytic digestion and affinity-directed mass spectrometry was used to rapidly determine the approximate location of a continuous binding epitope within the growth factor. The precise boundaries of the binding epitope were determined by affinity-directed mass spectrometric analysis of sets of synthetic peptide ladders that span the approximate binding region. In addition to the mapping of such linear epitopes, affinity-directed mass spectrometry can be applied to the mapping of other types of molecule-molecule contacts, including ligand-receptor and protein-oligonucleotide interactions.  相似文献   

    

M Braun  P Pietsch  A Zepp  K Schr?r  G Baumann  SB Felix 《Canadian Metallurgical Quarterly》1997,17(11):2568-2575

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DY Kuo  S Mallick  HJ Shen  C DeVictoria  J Jones  AL Fields  GL Goldberg  CD Runowicz  SB Horwitz 《Canadian Metallurgical Quarterly》1996,2(12):1981-1992

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