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81.
EL Stowe-Evans RM Harper AV Motchoulski E Liscum 《Canadian Metallurgical Quarterly》1998,118(4):1265-1275
Although sessile in nature, plants are able to use a number of mechanisms to modify their morphology in response to changing environmental conditions. Differential growth is one such mechanism. Despite its importance in plant development, little is known about the molecular events regulating the establishment of differential growth. Here we report analyses of the nph4 (nonphototropic hypocotyl) mutants of Arabidopsis that suggest that the NPH4 protein plays a central role in the modulation of auxin-dependent differential growth. Results from physiological studies demonstrate that NPH4 activity is conditionally required for a number of differential growth responses, including phototropism, gravitropism, phytochrome-dependent hypocotyl curvature, apical hook maintenance, and abaxial/adaxial leaf-blade expansion. The nph4 mutants exhibited auxin resistance and severely impaired auxin-dependent gene expression, indicating that the defects associated with differential growth likely arise because of altered auxin responsiveness. Moreover, the auxin signaling events mediating phototropism are genetically correlated with the abundance of the NPH4 protein. 相似文献
82.
P Xia PM Bungay CC Gibson ON Kovbasnjuk KR Spring 《Canadian Metallurgical Quarterly》1998,74(6):3302-3312
The diffusion coefficients of two caged fluorescent dyes were measured in free solution and in the lateral intercellular spaces (LIS) of cultured Madin-Darby canine kidney (MDCK) cells after photoactivation by illumination with a continuous or pulsed UV laser. Both quantitative video imaging and a new photometric method were utilized to determine the rates of diffusion of the caged fluorescent dyes: 8-((4,5-dimethoxy-2-nitrobenzyl)oxy)pyrene-1,3,6-trisulfonic acid (DMNB-HPTS) and (4,5-dimethoxy-2-nitrobenzyl) fluorescein dextran (10,000 MW) (DMNB-caged fluorescein dextran). The diffusion coefficients at 37 degrees C in free solution were 3.3 x 10(-6) cm2/s (HPTS) and 0.98 x 10(-6) cm2/s (10,000 MW dextran). Diffusion of HPTS within nominally linear stretches of the LIS of MDCK cells grown on glass coverslips was indistinguishable from that in free solution, whereas dextran showed a 1.6 +/- 0.5-fold reduction in diffusivity. Measurements of HPTS diffusion within the LIS of multicellular regions also exhibited a diffusivity comparable to the free solution value. The restriction to diffusion of the dextran within the LIS may be due to molecular hindrance. 相似文献
83.
Y Takahashi CD Bucana Y Akagi W Liu KR Cleary M Mai LM Ellis 《Canadian Metallurgical Quarterly》1998,4(2):429-434
Most patients with primary IgA nephropathy (IgAN) have a significantly higher memory repertoire of IgA1-producing B lymphocytes in their bone marrow together with high plasma levels of IgA1. The connection between the mucosal immune system and the bone marrow compartment is probably based on traffic of either antigen-presenting cells (APC) or antigen-specific lymphocytes. Cytokines play an important role in the proliferation and differentiation of lymphoid cells. In order to mimic the in vivo situation as much as possible, we assessed cytokine production profiles ex vivo in 23 IgAN patients and matched controls, using lipopolysaccharide (LPS)- or phytohaemagglutinin (PHA)-stimulated whole blood (WB) cultures. Interferon-gamma (IFN-gamma), IL-2, IL-6, IL-10 and tumour necrosis factor-alpha (TNF-alpha) production in culture supernatants were determined by cytokine-specific ELISAs. Compared with controls, PHA-stimulated cultures resulted in significantly higher IL-10 (P<0.001), IL-2 (P<0.005) and IFN-gamma (P<0.001) levels in IgAN patients, but no significant differences in TNF-alpha or IL-6 levels were found. In LPS-stimulated cultures, the only significant difference (P<0.001) between the two groups was the increased IL-10 production in IgAN patients. The enhanced cytokine production in stimulated WB cultures suggests altered monocyte-related T cell responses in patients with IgAN. Increased IL-10 production may eventually result in an increased number of IgA-producing B lymphocytes in the bone marrow. In addition, high levels of endogenous IL-10 may down-regulate the effector functions of monocytes, or possibly APC in general, and consequently the IgA response at the mucosal level. 相似文献
84.
TR Mahalingam S Vijayalakshmi RK Prabhu A Thiruvengadasami CK Mathews KR Shanmugasundaram 《Canadian Metallurgical Quarterly》1997,57(3):191-206
Blood is one of the widely used specimens for biological trace element research because of its biological significance and ease of sampling. We have conducted a study of the blood of the Kalpakkam township population for trace and minor elements. For this purpose, analytical methods have been developed and standardized in our laboratory for the elemental analysis of blood plasma and red cells. Inductively coupled plasma-mass spectrometry (ICP-MS), a relatively new technique, has been applied for the analysis of trace elements. Details regarding spectral interference and matrix interference encountered in the analysis of blood and the methods of correcting them have been discussed. Flame atomic absorption spectrometry (AAS)/atomic emission spectrometry (AES) has been applied for the determination of minor elements. Precision and accuracy of these methods have also been discussed. 相似文献
85.
86.
Aluminum (Al) transport across yeast cells was studied using Dy(NO3)3 as a shift reagent by 27Al-NMR spectroscopy. The results showed that (a) Al enters the yeast cells at 15 min and over a period of time, within 4 h, an equilibrium sets in between outside and inside Al; (b) citrate does not favor Al going into the yeast cells at pH 5.0; and (c) EDTA brings out all the Al that has entered the yeast cells. 相似文献
87.
PB Kruger S Mathews M Katz KR Aggarwala S Nowbotsing 《Canadian Metallurgical Quarterly》1997,37(18):2511-2526
Accommodation was monitored continuously under open-loop conditions while subjects viewed a sinusoidally oscillating sine-wave grating (0.2 Hz; +/- 1 D; 2.7 c/d; 0.56 contrast) in a Badal optometer. The target was illuminated by monochromatic light (590 nm) or white light (3000 K) with longitudinal chromatic aberration (LCA) normal, doubled, neutralized and reversed. Subjects (12) accommodated well in white light with LCA normal and doubled (mean gains = 0.85 and 0.94), gain was reduced in the neutralized condition (0.54), in monochromatic light (0.43), and especially when LCA was reversed (0.30). The results suggest that accommodation responds to changes in the relative contrast of spectral components of the retinal image and perhaps to the vergence of light. 相似文献
88.
89.
OBJECTIVE: Our purpose was to evaluate flow-induced responses, myogenic tone, and norepinephrine-induced constriction in myometrial resistance arteries from normal term pregnant women and the role that nitric oxide and prostanoids may play in these responses. STUDY DESIGN: Arteries (approximately 200 microns, n = 14, at 40 mm Hg) were dissected from myometrial biopsy specimens from women undergoing cesarean section and then were mounted in a pressure arteriograph. Responses to intraluminal flow, pressure, and a constrictor agonist (norepinephrine 10(-6) mol/L) were studied in the absence and presence of N omega-nitro-L-arginine methyl ester (n = 7) or indomethacin (n = 5). Myogenic and norepinephrine-induced tone were calculated after the determination of artery diameter in the absence of extracellular calcium. RESULTS: Arteries developed myogenic tone (80 mm Hg) that was not modulated by nitric oxide or prostanoid release, whereas norepinephrine-induced tone was significantly enhanced by the nitric oxide inhibitor. An increase in intraluminal flow led to dilatation in physiologic salt solution and indomethacin, but to constriction in the presence of N omega-nitro-L-arginine methyl ester (percent increase in diameter at flow rate of 184.6 microliters/min, 24% +/- 8% in physiologic salt solution and 20% +/- 4% in the presence of indomethacin versus -27% +/- 12% in N omega-nitro-L-arginine methyl ester alone and -21% +/- 10% in indomethacin and N omega-nitro-L-arginine methyl ester, respectively, analysis of variance, p < 0.05). CONCLUSIONS: Flow-induced shear stress is a physiologic modulator of vascular tone in myometrial arteries from pregnant women. Nitric oxide, but not prostanoids, mediates this response and also blunts norepinephrine constriction. Nitric oxide may play a fundamental role in the maintenance of adequate blood supply to the fetus during human pregnancy. 相似文献
90.