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991.
A field study of work and sleep patterns among commercial merchant marine personnel is reported. Data collected over a 10-30-d period from 141 subjects aboard eight ships included information concerning work-rest schedules, sleep timing, alertness on the job and critical fatigue. The data indicate that watchstanders on the 4-on, 8-off schedule show considerable disruption in their sleep. The average sleep duration for all mariners is 6.6 h; watchstanders obtain their sleep in fragmented periods that are frequently less than 5 h in duration. Analysis of critical fatigue shows an incidence of 1-24% across personnel and measures. Of particular concern are the watchstanders on the 04.00-08.00 schedule, who sleep less than 4 h per 24-h period 22% of the time. Potential countermeasures, including changes in scheduling and staffing are proposed. 相似文献
992.
993.
EJ Murphy AP Slivka TA Rosenberger LA Horrocks 《Canadian Metallurgical Quarterly》1993,209(2):339-342
A sensitive, reliable method for the extraction, separation, and quantitation of methylprednisolone from rat brain is reported. The method can accurately quantitate methylprednisolone levels between 9.8 and 2500 ng/injection using a two-step HPLC separation and monitoring absorbance at 254 nm. A 90% extraction recovery of methylprednisolone (interday variation of 9.0% and an intraday variation of 0.0 to 7.7%) from rat cortex was obtained with a double extraction method using low toxicity solvents. These solvents are known to quantitatively extract the neutral lipids and phospholipids from brain. Combined with the ability to separate the neutral lipid and methylprednisolone fractions for further separation, and the ability to separate all phospholipid classes in the first run, this method offers great utility combined with the reliable, high extraction recovery and sensitive quantitation of methylprednisolone. 相似文献
994.
995.
SE Theocharis AP Margeli C Spiliopoulou SD Skaltsas A Koutselinis 《Canadian Metallurgical Quarterly》1998,43(8):1732-1736
The liver is of central importance in the metabolism of essential and toxic metals such as cadmium. Cadmium pretreatment suppressed the liver regenerative response to partial hepatectomy, due to the inhibition of the enzymatic activity of thymidine kinase. Exogenous putrescine administration has been reported to stimulate liver regeneration in animal models of acute liver failure. The purpose of this study was to document whether the administration of this polyamine enhances the impaired regenerative capacity of hepatocytes in cadmium-pretreated partially hepatectomized rats. The intraperitoneal administration of putrescine (1 or 10 mg/kg body weight), at the time of surgery and at 4 and 8 hr postoperatively partly restored the suppressed hepatocyte deoxyribonucleic acid (DNA) biosynthesis and thymidine kinase activity in cadmium-pretreated partially hepatectomized rats. Mitotic activity and the percentage of hepatocytes positive for proliferating cell nuclear antigen nuclei were in accordance with the liver proliferative status. Our results showed that exogenous putrescine administration is able to improve diminished liver regeneration after partial hepatectomy in this animal model of acute hepatic injury. 相似文献
996.
The frequency of schistosomiasis mansoni, of its clinicopathological forms, and of the distribution of Schistosoma mansoni eggs in ectopic locations in each clinicopathological form were studied in 1863 complete consecutive autopsies performed in Belo Horizonte, Brazil, in the period from 1971 to 1990. Three hundred and thirteen cases of S. mansoni infection (16.8%) were found. The intestinal form was the most frequent (67.4%), followed by the hepatosplenic form without pulmonary hypertension (24.9%). The intestinal form showed a smaller number of ectopic sites and a lower percentage of involvement of these sites compared to the more severe forms, particularly the hepatosplenic form with pulmonary hypertension. The distribution of the frequency of schistosomiasis mansoni cases, of the clinicopathological forms of the disease, and of the ectopic sites of S. mansoni eggs over the decades considered showed a marked reduction in all of these parameters, particularly in the more severe forms. These findings can be explained only by earlier diagnosis of the disease and the greater efficacy of the specific chemotherapy used today, preventing progression to the more severe forms of the parasitosis. 相似文献
997.
998.
999.
pulE, one of 14 genes specifically required for pullulanase secretion in Klebsiella oxytoca, codes for a putative nucleotide-binding protein. Subcellular fractionation indicated that the majority of PulE in Escherichia coli cells expressing all 14 secretion genes is mainly associated with the cytoplasmic membrane through both hydrophobic and non-hydrophobic interactions. Mutational analysis revealed that one of the two regions of PulE that are conserved in many nucleotide-binding proteins (Walker box A) is essential for pullulanase secretion. Likewise, mutations that removed aspartate residues from each of two regions immediately downstream from the Walker box A also reduced secretion. These aspartate-rich regions are highly conserved in all 16 known PulE homologues but not in any other nucleotide-binding proteins. Altogether, these results indicate that PulE might belong to a new family of nucleotide-binding proteins. The protein could not be cross-linked to the photoactivatable ATP analogue azido-ATP, however. Most pulE point or deletion mutations which prevented pullulanase secretion exhibited transdominance when expressed at high levels in cells producing wild-type PulE protein. Evidence presented suggests that PulE might be a homodimer. 相似文献
1000.
Twelve cases of optic nerve glioma seen over a 28 year period are analysed herein in this autopsy study. 相似文献