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71.
Blood serum melatonin concentrations were measured in male Wistar rats exposed to acute water-immersion emotional stress (ES) during intraperitoneal injections of physiological saline or different doses of melatonin. ES increased blood melatonin levels in rats receiving physiological saline 1 hour before or just after ES. When physiological saline was administered just ES, blood melatonin concentrations remained unchanged. The blood levels of melatonin both in control and stressed animals injected with exogenous melatonin were higher than those in rats given physiological saline alone. Immersion ES decreased blood melatonin concentrations in rats receiving different exogenous melatonin doses just before ES. However, in rats given melatonin, 1.0 mg/kg, after ES, its blood levels after ES was higher than those in the animals unexposed to stress. The findings suggest that it is just exogenous rather than endogenous melatonin that is consumed in rats injected with its different doses just prior to immersion ES.  相似文献   
72.
Concentrations of unconjugated testosterone, 17-hydroxyprogesterone (170HP) and progesterone were measured by radioimmunoassay in amniotic fluid (AF) specimens from normal pregnancies of 9-40 weeks gestation. In two-thirds of samples from pregnancies with male fetuses. AF testosterone exceeded the upper limit found in female samples, with minimal overlap in the 12-18 week period of gestation. Although AF testosterone levels associated with male and female fetuses were both significantly lower toward term, the sex-difference persisted. Between 9-19 weeks gestation, fetal sex was also found to influence AF 170HP, a steroid thought to be predominantly of placental and fetal adrenal origin; in this case, female levels exceeded male. Awareness of the influence of sex and gestation upon AF concentrations of these steroids is an important prerequisite for their application to the prenatal diagnosis of endocrine disease (e.g., congenital adrenal hyperplasia). There was no sex difference in AF progesterone concentrations at 12-18 weeks gestation. The median progesterone concentration at 34-40 weeks was higher with female fetuses, but this difference may be related to a difference in gestational age between AF samples obtained from male and female fetuses.  相似文献   
73.
The cocaine analogue RTI-121 (3 beta-(4-iodophenyl)tropane-2 beta-carboxylic acid isopropyl ester), when labeled with carbon-11, was evaluated in rats as a potential PET ligand for the dopamine transporter. The compound gave in vivo striatum:cerebellum ratios that were similar to those obtained with the related ligand [11C]RTI-55 (2 beta-(4-iodophenyl)tropane-2 beta-carboxylic acid methyl ester) but showed a much greater selectivity for the dopamine compared with the 5-HT uptake site. The results indicate that [11C]RTI-121 could be used in preference to [11C]RTI-55 in man. Experimentally, [11C]RTI-121 has potential in the quantification of dopamine terminal function in rat models of disease, using a combination of autoradiography, postmortem sampling, and in vivo tomography.  相似文献   
74.
Despite a tradition in cognitive psychology that views encoding and retrieval processes in human memory as being similar, F. I. M. Craik, R. Govoni, M. Naveh-Benjamin and N. D. Anderson (1996) have recently shown that notable differences exist between the 2 when divided-attention manipulations are used. In this article, the authors further examined this asymmetry by using several manipulations that changed task demands at encoding and retrieval. The authors also used a secondary-task methodology that allowed a microlevel analysis of the secondary-task costs associated with encoding and retrieval. The results illustrated the resiliency of retrieval processes to manipulations involving different task demands. They also indicated different loci of attention demands at encoding and retrieval. The authors contend that whereas encoding processes are controlled, retrieval processes are obligatory but do require attentional resources for their execution.  相似文献   
75.
The present paper describes the total chemical synthesis of the precursor molecule of the Aequorea green fluorescent protein (GFP). The molecule is made up of 238 amino acid residues in a single polypeptide chain and is nonfluorescent. To carry out the synthesis, a procedure, first described in 1981 for the synthesis of complex peptides, was used. The procedure is based on performing segment condensation reactions in solution while providing maximum protection to the segment. The effectiveness of the procedure has been demonstrated by the synthesis of various biologically active peptides and small proteins, such as human angiogenin, a 123-residue protein analogue of ribonuclease A, human midkine, a 121-residue protein, and pleiotrophin, a 136-residue protein analogue of midkine. The GFP precursor molecule was synthesized from 26 fully protected segments in solution, and the final 238-residue peptide was treated with anhydrous hydrogen fluoride to obtain the precursor molecule of GFP containing two Cys(acetamidomethyl) residues. After removal of the acetamidomethyl groups, the product was dissolved in 0.1 M Tris. HCl buffer (pH 8.0) in the presence of DTT. After several hours at room temperature, the solution began to emit a green fluorescence (lambdamax = 509 nm) under near-UV light. Both fluorescence excitation and fluorescence emission spectra were measured and were found to have the same shape and maxima as those reported for native GFP. The present results demonstrate the utility of the segment condensation procedure in synthesizing large protein molecules such as GFP. The result also provides evidence that the formation of the chromophore in GFP is not dependent on any external cofactor.  相似文献   
76.
Interactions of human immunodeficiency virus type 1 (HIV-1) with hematopoietic stem cells may define restrictions on immune reconstitution following effective antiretroviral therapy and affect stem cell gene therapy strategies for AIDS. In the present study, we demonstrated mRNA and cell surface expression of HIV-1 receptors CD4 and the chemokine receptors CCR-5 and CXCR-4 in fractionated cells representing multiple stages of hematopoietic development. Chemokine receptor function was documented in subsets of cells by calcium flux in response to a cognate ligand. Productive infection by HIV-1 via these receptors was observed with the notable exception of stem cells, in which case the presence of CD4, CXCR-4, and CCR-5, as documented by single-cell analysis for expression and function, was insufficient for infection. Neither productive infection, transgene expression, nor virus entry was detectable following exposure of stem cells to either wild-type HIV-1 or lentivirus constructs pseudotyped in HIV-1 envelopes of macrophage-tropic, T-cell-tropic, or dualtropic specificity. Successful entry into stem cells of a vesicular stomatitis virus G protein-pseudotyped HIV-1 construct demonstrated that the resistance to HIV-1 was mediated at the level of virus-cell membrane fusion and entry. These data define the hematopoietic stem cell as a sanctuary cell which is resistant to HIV-1 infection by a mechanism independent of receptor and coreceptor expression that suggests a novel means of cellular protection from HIV-1.  相似文献   
77.
The prevalence and clinical significance of antibodies against beta2-glycoprotein I (anti-beta2GPI) and antibodies against oxidized low-density lipoprotein (anti-ox-LDL) were evaluated as potential indicators of arterial disease in patients with systemic lupus erythematosus (SLE) and SLE with secondary antiphospholipid syndrome (APS). IgG anti-beta2GPI and IgG anti-ox-LDL were measured by enzyme-linked immunosorbent assay (ELISA) in serum samples from 118 patients with SLE, including 40 with secondary APS. IgG anti-beta2GPI were positive in 17% (20/118) of SLE patients. The presence and titres of IgG anti-beta2GPI were strongly associated with a history of arterial thrombosis. Haemolytic anaemia was also significantly associated with the presence of IgG anti-beta2GPI. The prevalence of IgG anti-ox-LDL was 53% (63/118), but there was no association with arterial thrombosis. No correlation between the values of anti-ox-LDL and those of anti-beta2GPI was found. These results suggest that IgG anti-beta2GPI could be a marker for arterial thrombosis in SLE patients, while IgG anti-ox-LDL were not associated with arterial disease in this group of lupus patients.  相似文献   
78.
The first case of the human immunodeficiency virus (HIV) infection was detected in Singapore in 1985 and the first case of the acquired immunodeficiency syndrome (AIDS) in 1986. Since then, the number of infections had increased. By the end of 1993, there were 222 residents with HIV infection, including 75 cases of AIDS. In view of the rapidly increasing magnitude of HIV infection, a microcomputer-based surveillance system was designed and developed in 1992 to better monitor epidemiological trends of HIV infection in Singapore. OBJECTIVE--The objective was to define a composite model of a successful HIV and AIDS registry that included: (a) patient data forms, (b) patient's contact data forms, (c) data analysis, and (d) report generation. METHODOLOGY--An IBM-compatible desk-top microcomputer was used for the project. The main software used for computer programming and data analysis were DBase IV (Version 1.5) and Epi Info (Version 5.0), respectively. Security features were incorporated into the programme to ensure confidentiality of information and that only authorized personnel could gain access to the programme. MAIN FINDINGS--The system functioned as the National HIV Notification Registry and was able to track notifications, analyse data and enabled prompt dissemination of information. The system was also linked to another database system for tuberculosis to enhance surveillance of both HIV infection and tuberculosis. CONCLUSION--The authors believe that this system would enhance surveillance and provide timely information for national AIDS control programmes. However, the effectiveness of this computer-based surveillance system is dependent on an established notification structure with notifications of sufficient completeness for both HIV infection and AIDS.  相似文献   
79.
Background and Aims: A 3‐year study was carried out in order to evaluate the ecophysiology, yield and quality characteristics of Vitis vinifera L. cv. Kékfrankos (syn. Limberger) at Eger‐Nagyeged hill (steep slope) and at Eger‐K?lyuktet? (flat) vineyard sites located in the Eger wine region, Hungary. The aim of this paper was to analyse the effect of ‘vintage’ and ‘terroir’ on the seasonal changes of Kékfrankos ecophysiology and its possible relationship with yield and wine composition. Methods and Results: Grapevine physiological responses (midday‐ and pre‐dawn water potential, pressure–volume analysis and gas‐exchange), growing stages, yield and wine composition of each vineyard were studied. Lower grapevine water supply was detected at Eger‐Nagyeged hill in each season due to its steep slope and soil characteristics. Pressure‐volume curves indicated that there was no osmotic adjustment in the leaves of this variety. Higher osmotic concentration was measured at turgor loss and full turgor in the leaves of the unstressed vineyard (Eger‐K?lyuktet?) presumably due to higher photosynthetic activity. Differences in soil water content of the vineyards resulted in a slightly altered cell wall elasticity. Stomatal conductance, transpiration rate and photosynthetic production per unit leaf area were affected by water availability. Lower yield in Eger‐Nagyeged hill was partly associated with decreased photosynthetic production of the canopy. Improved wine quality of Eger‐Nagyeged hill was due to moderate water stress which induced higher concentration of anthocyanins and phenolics in the berries. The duration of the phenological stages was dependent on vintage temperature characteristics rather than on vineyard site. Conclusion: There was a close relationship between environmental conditions, Kékfrankos gas‐exchange, water relations, yield and wine composition. Water deficit plays an important role in creating a terroir effect, resulting in decreased yield, better sun exposure of leaves and clusters and thus higher concentration of phenolics and anthocyanins. Although quality is mainly influenced by vintage differences, vineyard characteristics are able to buffer unfavourable vintage effects even within a small wine region. Significance of the Study: Stomatal conductance, pre‐dawn water potential and climatic data may be reliable parameters for terroir classification, although variety–terroir interactions must always be considered.  相似文献   
80.
The electrochemical behaviour of two alkaline iron(III) oxides, LiFeO2 and NaFeO2, was studied by means of carbon paste electrodes with conducting binder. The differences between the behaviours of the two oxides, ratio of the amplitudes of the two peaks, potential of the peak corresponding to the reduction of the solid, and the changes in the voltammograms correlated to modifications of the experimental procedure (pH, nature of the binder and of the electrolyte) indicate clearly that the electrochemical reduction of the two iron mixed oxides involves a previously slow chemical dissolution of the solid followed by a quick reduction of solvated Fe3+ ions in solvated Fe2+ ions. Some morphological considerations are defined by the shape of the peaks on the voltammograms.  相似文献   
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