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41.
Presynaptic paired-pulse facilitation (PPF) rate decreased in most CA1 pyramidal neurones following the long-term potantiation (LTP) induction. The decrease correlated with the LTP magnitude as well as with the initial (pretetanic) PPF rate. The data obtained suggests an involvement of presynaptic mechanisms in maintaining the early and the delayed LTPs. 相似文献
42.
LL Kontsevich 《Canadian Metallurgical Quarterly》1998,265(1406):1615-1621
This study presents three findings concerning the mechanisms of depth perception. First, the shape of the three-dimensional percept evoked by two-frame motion is defined solely by the rotation component around an axis in the frontoparallel plane; the visual system assigns a default value to this rotation component to arrive at a unique solution. Second, when the visual axes of two eyes are almost parallel, the visual system uses a default vergence value to reconstruct stereoscopic depth. Third, the default vergence and default rotation angles are highly correlated across subjects. This correlation implies that the two modalities share a common scaling default at an internal level. 相似文献
43.
MR Sowers M Jannausch C Wood SK Pope LL Lachance B Peterson 《Canadian Metallurgical Quarterly》1998,147(10):914-920
Little is known about the epidemiology of renal stones, in spite of the relative frequency of this painful condition. This population-based study examined reported renal stone diagnosis in 1,309 women aged 20-92 years to determine whether renal stones are associated with 1) food or water exposures or 2) lower bone mineral density and an increased likelihood of fractures. Results indicated a renal stone prevalence of 3.4%. The average age at diagnosis was 42 years. Renal stone formation was not associated with community of residence, hypertension, bone mineral density, fractures, high-oxalate food consumption, or ascorbic acid from food supplements. Women with renal stones consumed almost 250 mg/day less dietary calcium (p < 0.01) than did women without stones and had a lower energy intake (p < 0.04). The authors' findings do not support the hypothesis that increased dietary calcium is associated with a greater prevalence of renal stones, nor do they identify renal stones as a risk factor for low bone mineral density. Furthermore, lack of other identifiable environmental correlates and the relatively young age at initial diagnosis suggest that genetic components of renal stone formation need further study. 相似文献
44.
The mitochondrial inner membrane anion channel (IMAC) is a transport pathway which is believed to be involved in mitochondrial volume homeostasis. The protein, however, has not been identified. In this paper, we examine the relationship between IMAC and the adenine nucleotide translocator. Many inhibitors of the adenine nucleotide translocase are shown to block IMAC, including Cibacron blue 3GA, bromcresol green, alizarin red S, agaric acid, palmitoyl-CoA, and the fluorescein derivatives erythrosin B, erythrosin isothiocyanate, rose bengal, and eosin Y. The following evidence suggests that Cibacron blue, agaric acid, and palmitoyl-CoA inhibit by binding to a common site. 1) They all only partially block the transport of small anions such as Cl-, NO3-, and HCO3-, but completely block the transport of larger anions such as malonate. 2) They decrease the IC50 values of each other in a manner consistent with competitive binding. 3) N-Ethylmaleimide decreases their IC50 values by a similar extent. 4) Inhibition by all shows no dependence on matrix pH and only a small dependence on medium pH. It is suggested that these agents may selectively bind to an open state of IMAC and inhibit by decreasing its conductance. The physiological nucleotides CoA, NAD+, NADH, NADP+, NADH, and ATP do not inhibit; in fact, IMAC is shown to transport ATP. Despite these similarities between IMAC and the adenine nucleotide translocase, IMAC appears to be a separate entity, since some of the IC50 values differ by up to 8-fold, and carboxyatracyloside, the most selective inhibitor of the adenine nucleotide translocase, has no effect on IMAC. In addition, IMAC is also able to transport AMP, while the adenine nucleotide translocase does not. 相似文献
45.
JP Gagliardi RE Nettles DE McCarty LL Sanders GR Corey DJ Sexton 《Canadian Metallurgical Quarterly》1998,26(5):1165-1168
The effect of age on the presentation and outcome of infective endocarditis (IE) is unclear. Many of the available data are based on analyses of mixed populations of patients including intravenous drug users or those with prosthetic valve endocarditis or native valve IE. We used the Duke criteria to compare the characteristics of 44 episodes of definite native valve IE in elderly patients (> 64 years old) with the characteristics of 64 similarly defined episodes of native valve IE in younger, nonintravenous-drug-using adult patients (> 29 years and < 60 years old). Our data suggest that the clinical presentation, characteristics, and outcome of native valve IE are similar for elderly patients and younger adult patients, although elderly patients were hospitalized an average of 12 days longer. Although we found that the occurrence of renal failure and cerebral embolism during an episode of IE was associated with higher rates of death (odds ratios, 4.8 and 4.0, respectively), age was not a significant contributor to mortality. 相似文献
46.
MJ Telford JW Martin BJ Rock LL Turik JE Hairfield 《Canadian Metallurgical Quarterly》1994,19(3):25-9, 33
Small local chapter groups can present quality cost effective regional seminars. Key components are dedication of members, teamwork, and a sense of direction. The following guidelines and information can provide a framework for planning and coordinating a seminar. 相似文献
47.
48.
Robert A. Moreau David B. Johnston Kevin B. Hicks 《Journal of the American Oil Chemists' Society》2007,84(11):1039-1044
All commercial corn oil is obtained by pressing corn germ and/or extracting the germ with hexane. In the current study, six
types of corn oil were prepared by extracting corn germ, corn fiber and ground corn, each with hexane or with ethanol. The
levels of lutein, zeaxanthin and other carotenoids were quantitatively analyzed in the six corn oils. The levels of lutein + zeaxanthin
in the oil ranged from 2.3 μg/g for hexane-extracted corn germ oil to 220.9 μg/g for ethanol-extracted ground corn oil. These
results indicate that a diet that includes 30 g (~2 tbsp) per day of the unrefined corn oil obtained by extracting ground
corn with ethanol would provide ~6 mg of lutein + zeaxanthin, the daily dosage that is currently considered to be necessary
to slow the progression of age-related macular degeneration.
Mention of trade names or commercial products in this publication is solely for the purpose of providing specific information
and does not imply recommendation or endorsement by the U.S. Department of Agriculture. 相似文献
49.
The synthesis of methanol and other products from CO and H2 was studied over Pd catalysts prepared by adsorption of Pd(π-C3H3)2 on MgO, ZnO, La2O3, γ-Al2O3, SiO2, TiO2, and ZrO2 as well as over a SiO2-supported Pd catalyst prepared from PdCl2 and Pd black. Both the activity and selectivity of Pd were affected strongly by the nature of the support and the composition of the Pd precursor. The specific activity for methanol synthesis decreased in the order ? [derived from PdCl2] > > > PdTiO2 > [derived from Pd(π-C3H5)2] ? Pd black, while the specific activity for hydrocarbon synthesis decreased in the order > > [derived from PdCl2] ? [derived from Pd(π-C33H5)2] ≈ Pd black ? . Dimethyl ether production was observed over four of the catalysts and the activity for formation of this product decreased in the order . The effects of support composition on the catalytic properties of Pd are discussed in the light of current ideas concerning metal-support interactions and the acid-base properties of the support. 相似文献
50.
S Hicks G Frankel JB Kaper G Dougan AD Phillips 《Canadian Metallurgical Quarterly》1998,66(4):1570-1578
Attaching and effacing (A/E) lesion formation is central to enteropathogenic Escherichia coli (EPEC) pathogenesis. In vitro experiments with human epithelial cell lines have implicated virulence plasmid-encoded bundle-forming pili (BFP) in initial binding and intimin in intimate attachment and A/E lesion formation. This study investigated the role of BFP and intimin in EPEC interactions with pediatric small intestinal biopsy tissue in in vitro organ culture. Organ culture infections (2 to 8 h) were performed with E2348/69 (a wild-type EPEC O127:H6 clinical isolate) and E2348/69 derivatives including CVD206 (eae deficient), CVD206(pCVD438) (eae-complemented CVD206), CVD206(pCVD438/01) (expressing intimin, which is nonfunctional due to a single amino acid substitution), JPN15 (spontaneous EPEC adherence factor virulence plasmid-cured E2348/69), and 31-6-1(1) (E2348/69 with a TnphoA insertion inactivation mutation in the virulence plasmid-encoded bfpA gene). Scanning and transmission electron microscopy revealed that after 8 h E2348/69 and CVD206 (pCVD438) (both Int+ BFP+) adhered to all specimens, causing A/E lesions with surrounding microvillous elongation. JPN15 and 31-6-1(1) (both Int+ BFP-) adhered and caused A/E lesions although bacteria adhered in "flat," two-dimensional groups. CVD206 and CVD206(pCVD438/01) (both Int- BFP+) did not adhere to any sample, and no pathological tissue changes were seen. Thus, in human intestinal organ culture, BFP do not appear to be involved in the initial stages of EPEC nonintimate adhesion but are implicated in the formation of complex, three-dimensional colonies via bacterium-bacterium interactions. Intimin appears to play an essential role in establishing colonization of EPEC on pediatric small intestinal tissue. 相似文献