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971.
    
The metabolic fate of N-ethyl-3-piperidyl benzilate (I) and its potential metabolites 3-piperidyl benzilate (II), N-ethyl-3-hydroxypiperidine (III), and 3-hydroxypiperidine (IV) was studied. Incubation of I with rat liver homogenates resulted in the formation of II and III. Only a trace of unchanged drug appeared in urine after intraperitoneal injection of I. Approximately 9% of the injected dose of I was excreted in urine as III and 2% in the form of metabolites that produced III after acid hydrolysis. After intraperitoneal injection of II in rats, 18% of the dose was excreted in urine as IV. Approximately 26% of the injected dose of III was present in urine as the unchanged drug, and 63% of the dose was excreted in the urine in the form of conjugates that produced III on acid hydrolysis. Urine of rats injected with IV contained approximately 50% of the injected dose as the unchanged drug and 50% of the dose in the form of a conjugate that produced IV on acid hydrolysis. The identity of the metabolites in extracts from urine was established by GLC-mass spectrometry. It is concluded that hydrolysis was one metabolic pathway for I and II. The major routes of elimination of these compounds are not yet known and may include excretion in feces or metabolic transformations resulting in the degradation of the piperidine ring.  相似文献   
972.
G. M. Landau  U. Vishkin 《Algorithmica》1994,12(4-5):375-408
For motivation purpose, imagine the followingcontinuous pattern-matching problem. Two continuous pictures, each consisting of unicolor regions, are given; one picture is called thescene and the other thepattern. The problem is to find all occurrences of the pattern in the scene.As a step toward efficient algorithmic handling of the continuous pattern-matching problem by computers, where discretized representations are involved, we consider pattern-matching problems where the pattern and the text are specified either in terms of the continuous properties, or through other exemplar digitized images—a variety of alternative specifications is considered.From the perspective of areas such as computer vision or image processing, our problem definitions identify an important gap in the fundamental theory of image formation and image processing—how to determine, even in the absence of noise, if a digitized image of a scene could contain an image of a given pattern. This is done using carefulaxiomatization. Such a digitized-based approach may lead toward building on the theory of string-matching algorithms (in one, or higher, dimensions) for the benefit of algorithmic pattern matching in image processing.This paper is the journal version of [LV2].Partially supported by NSF Grants CCR-8908286 and CCR-9305873 and the New York State Science and Technology Foundation, Center for Advanced Technology in Telecommunications, Polytechnic University, Brooklyn, NY, USA.Partially supported by NSF Grants CCR-8906949 and CCR-9111348.  相似文献   
973.
We present an experimental study of the current induced destruction of superconductivity in films of type-1 superconductors. The most interesting aspect of these experiments is the possibility to observe and investigate different mechanisms of the superconductivity destruction depending on the ratio of the sample thickness d to the coherence length (T).If d/(T) < 4.5 we observe, above a critical current value, a resistive state throughout the section of the film, but in the case of d/(T) > 4.5 the destruction of superconductivity starts, as in bulk samples, with the formation of a normal shell along the outer surface of the cylindrical sample together with a layer of the two-dimensional mixed state at the inner surface. Investigations on films allowed for the first time to measure the thickness of the two-dimensional mixed state.On leave from Kapitza Institute for Physical Problems, 117334 Moscow, Russia.  相似文献   
974.
Deep hydrotreating of middle distillates from crude and shale oils   总被引:10,自引:0,他引:10  
The potential scientific and technological solutions to the problems that appear as a result of shifting the hydrotreating of crude oil middle distillates and shale oils from the ‘normal’ to the ‘deep’ mode are considered on the basis of the reactivities and transformation routes of the least-reactive sulfur-, nitrogen-, and oxygen-containing compounds. The efficiency of selecting the optimal feedstock, increasing the process severity, improving the catalysts activity, and using alternative catalytic routes are compared, taking into account the specific issues related to deep hydrodesulfurization/hydrodenitrogenation/ hydrodeoxygenation, i.e., chemical aspects, kinetics and catalysts.  相似文献   
975.
The formation of the powerful oxidant peroxynitrite (PN) from the reaction of superoxide anion with nitric oxide has been shown to be a kinetically favored reaction contributing to cellular injury and death at sites of tissue inflammation. The PN molecule is highly reactive causing lipid peroxidation as well as nitration of both free and protein-bound tyrosine. We present evidence for the pharmacological manipulation of PN with decomposition catalysts capable of converting it to nitrate. In target cells challenged with exogenously added synthetic PN, a series of metalloporphyrin catalysts (5,10,15,20-tetrakis(2,4,6-trimethyl-3, 3-disulfonatophenyl)porphyrinato iron (III) (FeTMPS); 5,10,15, 20-tetrakis(4-sulfonatophenyl)porphyrinato iron (III) (FeTPPS); 5,10, 15,20-tetrakis(N-methyl-4'-pyridyl)porphyrinato iron (III) (FeTMPyP)) provided protection against PN-mediated injury with EC50 values for each compound 30-50-fold below the final concentration of PN added. Cytoprotection was correlated with a reduction in the level of measurable nitrotyrosine. In addition, we found our catalysts to be cytoprotective against endogenously generated PN in endotoxin-stimulated RAW 264.7 cells as well as in dissociated cultures of hippocampal neurons and glia that had been exposed to cytokines. Our studies thus provide compelling evidence for the involvement of peroxynitrite in cytokine-mediated cellular injury and suggest the therapeutic potential of PN decomposition catalysts in reducing cellular damage at sites of inflammation.  相似文献   
976.
Cytosolic phenol sulfotransferases (PST) catalyze the sulfation/sulfonation of various phenolic agents, including catecholamines, thyroid hormones, and drugs (e.g., minoxidil and acetaminophen), which usually results in the inactivation and subsequent excretion of the compound. Our recent efforts have focused on the cloning and sequencing of the human gene family encoding the PST isozymes, and the results are summarized in this article. Multiple PST cDNA isolates have been cloned in various laboratories representing alleles of three phenol sulfotransferase gene loci termed as STP1, STP2, and STM. All three genes have been mapped precisely to a small region on human chromosome 16p12.1-p11.2 (homologous to mouse chromosome 7). The two most closely related genes, STP1 and STP2, encode isozymes of phenol-preferring PST (P-PST) and have been mapped to a single genomic cosmid clone, thus in proximity to one another. The STM gene encoding the monoamine neurotransmitter-preferring PST (M-PST) exhibits a lower level of similarity relative to STP1 and STP2. Genomic clones have been sequenced to determine the genomic organization for each of the three highly related genes. All contain seven coding exons, with conserved intron-exon boundaries. Sequencing of individual cDNA isolates from various tissues has revealed heterogeneity in the 5' nontranslated regions, likely due to tissue-specific promoter utilization (or perhaps alternative splicing). DNA and protein polymorphisms have been identified in the population and may be useful for molecular genetic studies of the variability in the metabolism of catecholamines, thyroid hormones, and phenolic drugs, and possibly neuropsychiatric or other metabolic disorders.  相似文献   
977.
978.
This paper presents a model for predicting blood lead levels in adults who are exposed to elevated environmental levels of lead. The model assumes a baseline blood lead level based on average blood lead levels for adults described in two recent U.S. studies. The baseline blood level in adults arises primarily from exposure to lead in diet. Media-specific ingestion and absorption parameters are assessed for the adult population, and a biokinetic slope factor that relates uptake of lead into the body to blood lead levels is estimated. These parameters are applied to predict blood lead levels for adults exposed to a hypothetical site with elevated lead levels in soil, dust and air. Blood lead levels ranging from approximately 3-57 micrograms/dl are predicted, depending on the exposure scenarios and assumptions.  相似文献   
979.
BACKGROUND: Functional iron deficiency may develop and cause erythropoietin resistance in haemodialysis patients with iron overload. Controversy remains as to whether intravenous iron medication can improve this hyporesponsiveness due to decreased iron availability, or whether iron therapy will aggravate haemosiderosis. Intravenous administration of ascorbic acid has been shown to effectively circumvent resistant anaemia associated with iron overload in a small preliminary study. To elucidate further the possible mechanisms of this resistance, a parallel, comparative study was conducted to compare the effects of intravenous iron and ascorbate therapies in iron-overloaded haemodialysis patients. METHODS: Fifty haemodialysis patients with serum ferritin of > 500 microg/l were randomly divided into two protocols. They were further stratified into controls (Control I, n = 11) and intravenous iron group (IVFE, n = 15) in protocol I; and into controls (Control II, n = 12) and intravenous ascorbic acid group (IVAA, n = 12) in protocol II. Controls had a haematocrit of > 30% and did not receive any adjuvant therapy. IVFE and IVAA patients were hyporesponsive to erythropoietin and functionally iron deficient. Ferric saccharate (100 mg dose) was administered intravenously postdialysis on five consecutive dialysis sessions in the first 2 weeks; and ascorbic acid (300 mg dose) thrice a week for 8 weeks. Red cell and iron metabolism indices were examined before and following therapy. RESULTS: Mean values of haematocrit and transferrin saturation were significantly lower, and erythropoietin dose was higher in IVFE and IVAA patients compared to controls. Intravenous iron therapy neither improved erythropoiesis nor reduced erythropoietin dose during 12 weeks. Iron metabolism indices significantly increased at 2 and 6 weeks, but decreased at 12 weeks returning to the baselines. In contrast, mean haematocrit significantly increased from 25.8+/-0.5 to 30.6+/-0.6% with a concomitant reduction of 20% in erythropoietin dose after 8 weeks of ascorbate therapy. Serum ferritin modestly fell but with no statistical significance. The enhanced erythropoiesis paralleled a rise in transferrin saturation from 27+/-3 to 48+/-6% and serum iron from 70+/-11 to 107+/-19 microg/dl (P<0.05). CONCLUSIONS: Short term intravenous iron therapy cannot resolve the issue of functional iron deficiency in haemodialysis patients with iron overload. Intravenous administration of ascorbic acid not only facilitates iron release from storage sites, but also increases iron utilization in the erythron. Our study draws attention to a potential adjuvant therapy, intravenous ascorbic acid, to treat erythropoietin-hyporesponsive anaemia in iron-overloaded patients.  相似文献   
980.
OBJECTIVE: To determine the distribution and prevalence of sarcoptic mange in wombats, particularly the common wombat (Vombatus ursinus). DESIGN: Questionnaire survey in two parts. PROCEDURE: Questionnaires were distributed to biologists, rangers, animal carers and naturalists. Part 1 of the questionnaire aimed to determine the present distribution of sarcoptic mange in wombats (103 responses). Part 2 invited respondents to assess the prevalence of sarcoptic mange in wombats over a 3 month period (four responses). Information on wombats from 66 localities was received. Each locality represented an area of about 2500 km2. RESULTS: Mange was observed at 93% of localities surveyed and Sarcoptes scabiei was present in common wombats at 52% of localities. Sarcoptic mange was highly prevalent (22%) in two common wombat populations in Victoria. Anecdotal evidence suggested that mange epizootics are sporadic, cause significant morbidity and mortality and have a substantial effect on local abundance. The respondents did not report sarcoptic mange in either northern hairy-nosed wombats (Lasiorhinus krefftii) or southern hairy-nosed wombats (Lasiorhinus latifrons). CONCLUSIONS: Sarcoptic mange occurs in common wombat populations throughout the range of the common wombat including Tasmania and Flinders Island. While mange epizootics are sporadic, they have the potential to threaten the long-term survival of small, remnant populations.  相似文献   
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