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Similar depressions in growth were observed when rats consumed a 10% casein basal diet containing equal quantities of either methionine or S-methyl-L-cysteine. Supplemental glycine or serine partially alleviated the growth depression caused by the high levels of methionine but were ineffective in alleviating the growth depression caused by high levels of S-methylcysteine. Histological examination of five organs of rats fed the basal, high methionine or high S-methylcysteine diet for 6, 13 or 20 days revealed that only the spleens were affected in that there was erythrocyte engorgement and an accumulation of hemosiderin. The intensity of iron staining in spleens decreased from the second to the third week. The similarity in the depression of growth and splenic damage observed in rats consuming high levels of methionine or S-methylcysteine is consistent with an earlier suggestion that metabolism of the methionine or S-methylcysteine is consistent with an earlier suggestion that metabolism of the methyl group is in some way involved in the toxicity of methionine. 相似文献
64.
Signal Processing for Semiconductor Detectors 总被引:1,自引:0,他引:1
This is a tutorial paper designed to provide a balanced perspective on the processing of signals produced by semiconductor detectors. The general problems of pulse shaping to optimize resolution with constraints imposed by noise, counting rate and rise time fluctuations are discussed. 相似文献
65.
A system for the quantitative assessment of uterine activity during an oxytocin-induced labour has been developed. This has been achieved using relatively simple analogue techniques and can easily be used in the labour ward alongside existing monitoring equipment. Initial results indicate that a plateau of uterine activity can be easily recognised from the display and maintained at oxytocin dosage levels below those that might normally be used. 相似文献
66.
C. M. Trotter J. R. Dymond C. J. Goulding 《International journal of remote sensing》2013,34(10):2209-2223
Optimisation of economic return from forests requires that comprehensive forest inventory data be available to support the design of harvesting strategies. Such inventory data can potentially be obtained by remote sensing. This study investigates the accuracy with which wood volume (m3 ha -1) in a plantation forest can be calculated from Landsat TM data at the pixel and foreststand spatial scales. Wood volumes were estimated from regression analysis, nonparametric line-fitting, and an N-dimensional K-nearest-neighbour classification scheme. At the pixel scale, relations between Landsat data and measured wood volume were found to be significant but weak, with r2 values of 0.3, and with correspondingly poor estimates of wood volume (root-mean-square errors rmses of 100 m3 ha -1). By averaging the pixel-scale estimates, wood volume estimates of acceptable accuracy were obtained for forest-stand areas of about 40 ha (rmses of 46 m3 ha -1). Parametric regression performed slightly better overall than non-parametric line fitting techniques for estimating wood volume. Estimates of similar accuracy to those obtained by regression were also given by NK-classification at the pixel-scale, provided K was large ( 15), although the classifier produced biased results at the forest-stand scale. It is concluded that Landsat TM only provides an acceptable data source for estimating wood volumes in plantation forests for areas of about 40 ha and larger. The very low dynamic range in the Landsat data is probably a significant factor limiting its use for inventory at more detailed scales. 相似文献
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Membrane trafficking intermediates involved in the transport of proteins between the TGN and the lysosome-like vacuole in the yeast Saccharomyces cerevisiae can be accumulated in various vps mutants. Loss of function of Vps45p, an Sec1p-like protein required for the fusion of Golgi-derived transport vesicles with the prevacuolar/endosomal compartment (PVC), results in an accumulation of post-Golgi transport vesicles. Similarly, loss of VPS27 function results in an accumulation of the PVC since this gene is required for traffic out of this compartment. The vacuolar ATPase subunit Vph1p transits to the vacuole in the Golgi-derived transport vesicles, as defined by mutations in VPS45, and through the PVC, as defined by mutations in VPS27. In this study we demonstrate that, whereas VPS45 and VPS27 are required for the vacuolar delivery of several membrane proteins, the vacuolar membrane protein alkaline phosphatase (ALP) reaches its final destination without the function of these two genes. Using a series of ALP derivatives, we find that the information to specify the entry of ALP into this alternative pathway to the vacuole is contained within its cytosolic tail, in the 13 residues adjacent to the transmembrane domain, and loss of this sorting determinant results in a protein that follows the VPS-dependent pathway to the vacuole. Using a combination of immunofluorescence localization and pulse/chase immunoprecipitation analysis, we demonstrate that, in addition to ALP, the vacuolar syntaxin Vam3p also follows this VPS45/27-independent pathway to the vacuole. In addition, the function of Vam3p is required for membrane traffic along the VPS-independent pathway. 相似文献
69.
PD Guinan JP Imperato JS Chmiel NJ Vogelzang J Sylvester 《Canadian Metallurgical Quarterly》1997,5(5):305-308
In a previous study, we showed that overexpression of cyclin D, a G1 cyclin, is frequently associated with keratinocyte carcinogenesis as an early event. Another G1 cyclin, cyclin E, was recently suggested to be a prognostic marker for breast cancer. In order to evaluate the role of cyclin E in human keratinocyte carcinogenesis, we analysed the expression of cyclin E by immunohistochemistry in normal skin, seborrheic keratosis (SK), keratoacanthoma (KA), actinic keratosis (AK), Bowen's disease (BD), basal cell carcinoma (BCC) and squamous cell carcinoma (SCC). Positive cells were seen rarely in normal epidermis, in 9 of 20 cases of SK, in 5 of 6 cases of KA, in 9 of 13 cases of AK and in all 27 cases of BD. Some of the cases of AK and BD had positive cells in the superficial epidermis, where atypicality is less obvious. In contrast, positive cells were seen in 4 of 25 cases of SCC and none of 15 cases of BCC. These results suggest that expression of cyclin E plays a role in the formation of benign and premalignant keratinocytic tumors, whereas down-regulation of cyclin E expression may be involved in carcinogenesis in human keratinocytes. 相似文献
70.
GS Firestein F Echeverri M Yeo NJ Zvaifler DR Green 《Canadian Metallurgical Quarterly》1997,94(20):10895-10900