The effect of steroids and their solubilizing agents on mycelial growth ofPhytophthora cactorum

Mycelia ofPhytophthora cactorum, a fungus unable to synthesize sterols, were incubated with a series of sterols and several common sterol solubilizing agents. Cholesterol, campesterol, and sitosterol promoted growth, while carpesterol, saringosterol, 20 α-hydroxy cholesterol, coprostanol, and 5α-cholestane inhibited growth. Cholestanol, epicholestanol, and 5α-cholestan-3-one had no significant effect on growth relative to the sterol-free control. All steroids were solubilized in ethanol for studying structure-activity correlations. The added steroids were reisolated from mycelia and their identity confirmed by gas liquid chromatography (GLC) or combined gas liquid chromatography-mass spectrometry (GLC-MS). Tween 80 promoted growth, Triton X-100 inhibited growth, and ethanol had no effect on growth relative to a control. Scientific Article No. A2441, Contribution No. 5469 of the Maryland Agricultural Experiment Station.     

Function of cryopreserved human effector cells in antibody-dependent, cell-mediated cytotoxicity

Cells active in an ADCC model were studied for their ability to withstand cryopreservation. For this model, we used the [3H]proline microcytotoxicity assay with fibroblast target cells and a serum containing lymphocyte-dependent antibody reactive with the alloantigens on those target cells. Human blood effector cells active in this system can be successfully cryopreserved with minor dimunition in function with standard techniques and concentrations between 9 and 12% DMSO.     

Purification and characterization of a DNA helicase from Saccharomyces cerevisiae

A novel DNA helicase, scHelI, has been purified from whole cell extracts of Saccharomyces cerevisiae using biochemical assays to monitor the fractionation. The enzyme unwinds partial duplex DNA substrates, as long as 343 base pairs in length, in a reaction that is dependent on either ATP or dATP hydrolysis. scHelI also catalyzes a single-stranded DNA-dependent ATP hydrolysis reaction; the apparent Km for ATP is 325 microM. The unwinding reaction on circular partial duplex substrates is biphasic, with a fast component occurring within 5 min of the initiation of the reaction and a slow component continuing to 60 min. This is in contrast to the ATP hydrolysis reaction, which exhibits linear kinetics for 60 min. The direction of the unwinding reaction is 5' to 3' with respect to the strand of DNA on which the enzyme is bound. The unwinding reaction is strongly stimulated by the addition of Escherichia coli single-stranded DNA-binding protein when long partial duplex substrates are used. The enzymatic activity of scHelI copurifies with a polypeptide of 135 kDa as determined by polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate. The polypeptide sediments as a monomer in a glycerol gradient in the presence of 0.2 M NaCl.     

Chronic pancreatitis and neoplasia: correlation or coincidence

Renal biopsy specimens from patients with membranous nephropathy (MN) were studied using immunohistochemical labelling to clarify the aetiological significance of Helicobacter pylori antigen in this disease. Sixteen specimens were examined, from 7 male and 9 female MN patients. Renal specimens from patients with diabetic nephropathy and IgA nephropathy, and from autopsied patients without renal diseases were obtained as controls. Immunohistochemical labelling was performed using one polyclonal antibody and three monoclonal antibodies against H. pylori. Specimens from 11 of the MN patients revealed granular deposits along the glomerular capillary walls, which reacted positively with polyclonal antibody after trypsin pretreatment. None of the control specimens revealed positive labelling. The MN specimens showed no positive reaction with the primary antibody, which had been treated for immunoabsorption testing using sonicated H. pylori. We also determined H. pylori status in these MN patients histologically and/or serologically. Of the 11 patients whose glomeruli were positive for anti-H. pylori antibody, 7 were suitable for analysis, and all were regarded as positive for H. pylori infection. These results suggest that the presence of a specific antigen in the glomeruli of patients with MN and H. pylori infection may be involved in the pathogenesis of MN.     

Neurotransmitter activation of inwardly rectifying potassium current in dissociated hippocampal CA3 neurons: interactions among multiple receptors

We characterized potassium current activated by G-protein-coupled receptors in acutely dissociated hippocampal CA3 neurons. Agonists for serotonin, adenosine, and somatostatin receptors reliably activated a potassium-selective conductance that was inwardly rectifying and that was blocked by 1 mM external Ba2+. The conductance had identical properties to that activated by GABAB receptors in the same cells. In one-half of the CA3 neurons that were tested, the metabotropic glutamate agonist 1S,3R-ACPD also activated inwardly rectifying Ba2+-sensitive potassium current. Activation of the current by serotonin and adenosine agonists occurred with a time constant of 200-700 msec after a lag of 50-100 msec; on removal of agonist the current deactivated with a time constant of 1-2 sec after a lag of 200-400 msec. These kinetics are similar to GABAB-activated current and consistent with a direct action of G-protein on the channels. For somatostatin, both activation and deactivation were approximately fourfold slower, probably limited by agonist binding and unbinding. The half-maximally effective agonist concentrations were approximately 75 nM for somatostatin, approximately 100 nM for serotonin, and approximately 400 nM for 2-chloroadenosine. Dose-response relationships had Hill coefficients of 1.2-1.9, suggesting cooperativity in the receptor-to-channel coupling mechanism. At saturating concentrations of agonists, the combined application of baclofen and either somatostatin, serotonin, or 2-chloroadenosine produced effects that were subadditive and often completely occlusive. However, at subsaturating concentrations the effects of baclofen and 2-chloroadenosine were supra-additive. Thus, low levels of different transmitters can act synergistically in activating inwardly rectifying potassium current.     

Distant entry pneumothorax in a competitive fencer

Glibenclamide or glimepiride pretreatment (5 mg/kg i.p. 30 min prior to coronary ligation) significantly improved the survival rate during reperfusion after 6 min myocardial ischaemia in rats (82% or 67% vs. 17% in controls). Smaller dose of glibenclamide (0.01 mg/kg) did not influence the survival rate (31%), while glimepiride still offered a significant protection (61%). These results suggest that different KATP inhibitors may increase the chance to survive life-threatening arrhythmias during myocardial ischaemia-reperfusion.     

Confluence theory: uniting two houses divided

There has been much progress in automation research, with new important hypotheses, and data supporting those hypotheses, in several domains. Although such progress along a variety of different lines is gratifying, there is a need for a unifying theory to provide an integrative theme that incorporates them under a single large umbrella. In pursuit of this objective, we review several domains in the automation literature that hitherto have been considered to be quite disparate and with little in the way of interconnections. Subsequently, we consider a newly proposed theory in social psychology that ties together several domains within that area. After establishing the capability of this theory to account for much of the social psychology literature, we apply it to account for the various automation issues reviewed in the initial section. Finally, we derive a new prediction from this theory and present an experiment to test it.