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71.
G. Singh J. F. Hussain A. MacKinnon C. M. Brown D. A. Kendall V. G. Wilson 《Naunyn-Schmiedeberg's archives of pharmacology》1994,351(1):17-26
In the present study we have prepared crude, methanolic extracts of bovine lung and bovine brain and, using radioligand binding assays in conjunction with a number of simple chromatographic techniques, provided evidence for the presence of a non-catecholamine ’clonidine-displacing substance‘ (CDS). The level of CDS in lung extracts (9?units/g wet weight n=11) is approximately 3 times that in the brain extracts. Furthermore, the effect of the crude, methanolic extracts are selective for non-adrenoceptor, imidazoline (labelled by [ 3H]-idazoxan) and a 2-adrenoceptor binding sites (labelled by [ 3H]-clonidine); both extracts are 5–10-fold more potent displacers of ligand binding to a 2-adrenoceptors compared with binding to opiate receptors (labelled by [ 3H]-etorphine) and practically inactive against a 1-adrenoceptor and muscarinic binding sites (labelled by [ 3H]- prazosin and [ 3H]-quinuclidinyl benzilate, respectively). With the exception of the non-adrenoceptor, imidazoline binding assay, which used rat kidney membranes labelled by [ 3H]-idazoxan in the presence of the a 2-adrenoceptor antagonist RS-15385-197, all radioreceptor assays involved bovine cerebral cortex membranes. Although the extracts contain catecholamines (brain only), histamine (lung only) and monovalent cations (both), which have the potential to interfere with the radioligand binding assays, their concentrations were too low to account for the effects observed. Preliminary attempts at purification of the extracts revealed that CDS activities from the two tissues are similar, i.e., practically insoluble in organic solvents at room temperature, not affected by either Sep-Pak C 18 column or anion exchange resins but retained (along with the monovalent cations) by cation exchange resin. However, following chromatographic separation on a Biogel P2 column, the CDS-containing eluates are cation-free and exhibit qualitatively similar elution profiles. Future experiments will involve further purification of ’clonidine-displacing substance‘ to characterize its interaction with a 2-adrenoceptor binding sites in greater detail and establish whether it has biological activity consistent with the properties implied by its effects in radioligand binding assays. 相似文献
72.
Non-invasive tear break-up time (NITBUT) has been proposed as a measure of tear film integrity which is superior to the more commonly used tear break-up time (TBUT), since it does not alter the volume or the physicochemical properties of the tear layer by the addition of fluorescein. We measured NITBUT by measuring the time taken for distortions or discontinuities to appear in the reflected image of a grid pattern which covered about 80 per cent of the corneal surface. NITBUT measures were made 100 times on seven Hong Kong Chinese subjects with up to 20 consecutive measures being made on a single day. We also measured NITBUT on one occasion on an unselected population of 52 Hong Kong Chinese subjects. NITBUT shows a skewed distribution in all subjects, with many shorter values and some extremely long values. There are statistically significant variations in NITBUT from day to day, and from subject to subject. The group of 52 subjects also had a skewed NITBUT distribution with many short values and some very long values. The arithmetic mean does not adequately represent NITBUT data, either for individual subjects or for this group of subjects. As many as five to eight measures may be necessary to gain a stable estimate of the NITBUT and stability of the measure is improved if extreme values are omitted. We recommend the use of nonparametric statistics to compare NITBUT values from day to day in or between subjects. 相似文献
73.
We argue that, for solutions of immobilized protein and for tissue, the dependence of 1/T1 of solvent protons on B(0) at low fields and 1/T1 rho on B1 for all B(0) are both manifestations of the same underlying phenomena: magnetization transfer between mobile water protons and solid-state broadened protein proton levels. Broadening causes rapid mixing of spin orientation within the transverse plane, at all B(0), unless B1 is greater than the protein internal field; this affects 1/T1 rho of solvent protons by magnetization transfer. Similarly, decreasing B(0) below the internal field mixes all orientations of magnetization, which affects the solvent proton low-field 1/T1 and high-field 1/T2. 相似文献
74.
R. J. Rona A. V. Swan R. Beech D. M. Wilson F. B. Kavanagh C. Brown C. Axtell S. Mandalia 《Clinical genetics》1992,42(4):186-195
For certain genetic conditions DNA testing identifies carriers and determines the risk status of foetuses, thus helping parents to make more informed prenatal decisions. Data, collected from three genetic centres in England and Wales from August 1986 to July 1990, are used to describe trends in demand for DNA testing, the impact of DNA tests on carrier risk assessment, and the use of DNA tests in relation to pregnancy outcome. Altogether the data include 23,388 subjects and 681 pregnancies in 8738 families divided into five cohorts by year of entry and referral. The most frequent gene disorders referred to the genetic centres are currently being tested or will soon be tested. For these disorders the initial high level of activity has declined and may have reached steady state. Demand for DNA services is high for cystic fibrosis and Duchenne muscular dystrophy, intermediate for Huntington's disease, and low for adult polycystic kidney disease, phenylketonuria and tuberous sclerosis. Based on these findings we suggest that demand for DNA tests will be high in serious, untreatable and slow progressing conditions with early onset; intermediate for conditions affecting intellect and neurological integrity with later onset; and low for treatable, late-onset conditions, or those for which there is evidence of heterogeneity, and variable penetrance. It would be helpful to assess the extent to which this view of demand is confirmed when the new disorders being DNA tested are considered and for the pattern of activity of DNA testing for some types of cancer. Since no DNA centre could offer a fully comprehensive testing service, it is recommended that a structure is created to audit overall activity, assist in policy formulation, and influence supraregional service organisation, in order that the spread of DNA services be planned as effectively as possible. This structure would facilitate monitoring of the evolution of contract specifications agreed by commissioners and providers on a regional basis. 相似文献
75.
76.
77.
The risk of cytomegalovirus infection in seronegative transfusion recipients not receiving exogenous immunosuppression 总被引:3,自引:0,他引:3
We studied 637 transfusion recipients seronegative for cytomegalovirus (CMV) in the following categories: neonates; pregnant women; and patients experiencing trauma, burns, cardiovascular surgery (adult or pediatric), major surgery, or gastrointestinal hemorrhages. Cultures and serological tests were used to follow up subjects for evidence of CMV infection for a period of three months after their last transfusion. Six (0.9%) developed CMV infection. No significant differences in risk among patient categories were observed. Infected patients received a significantly larger mean number of units of cellular blood products (CBP; 50.0 +/- 38.9 vs. 6.2 +/- 8.5; P less than .001) and plasma (23.7 +/- 15.3 vs. 2.6 +/- 4.6, P less than .001) than did uninfected patients. This result represents a risk per unit of CBP transfused of 0.14%, or approximately 0.38% per unit of seropositive CBP transfused. We observed, however, that patients exposed to CBP from greater than 30 donors had a higher risk of acquiring CMV infection than would be predicted if infectious units were randomly distributed among all donors (P less than .01). 相似文献
78.
1. Six volunteers ingested 74As-labelled arsenobetaine with a fish meal. The retention and distribution of the tracer were studied by body radioactivity measurements. 2. The tracer became rapidly dispersed in soft tissues, with no major concentration in any localized organ or region. 3. In all subjects less than 1% of the ingested activity remained in the body after 24 days. 4. Any losses from the skin were minor in relation to those by other routes of excretion. 相似文献
79.
80.
F D McCool R Brown R J Mayewski R W Hyde 《The American review of respiratory disease》1988,138(1):101-105
Quadriplegics are able to compensate for alterations of operational length of the diaphragm by reflexly increasing neural drive to the diaphragm. This increase in neural drive is adequate to maintain required tidal volume and minute ventilation during quiet breathing in these patients with limited inspiratory muscle function. It is not known, however, if this neural compensation is sufficient to preserve ventilation when the diaphragm is stressed by simultaneously changing its operational length and increasing ventilatory demands. This issue was explored in 7 quadriplegics whose vital capacity was reduced to 15 to 53% of predicted. The diaphragm was stressed by shortening its length from the supine to a 60 degree tilted position, and also by inducing hyperventilation by having the subjects rebreathe 7% CO2. Response to this stress was recorded by monitoring the ventilatory response to rebreathing CO2 (delta VE/delta PCO2), and also by measuring mouth pressure 0.1 s after occluding the airway at the start of inspiration during CO2 rebreathing (delta P0.1/delta PCO2). A change from the supine to the tilted position caused an increase in resting end-expiratory volume of 0.8 +/- 0.2 L (SD) and therefore shortened the diaphragm. Despite this shortening of diaphragm length and the stress of CO2 rebreathing, there was no significant change in delta VE/delta PCO2 and delta P0.1/delta PCO2 with changes in posture. The delta VE/delta PCO2 was 0.82 +/- 0.42 L/min/mm Hg supine versus 0.95 +/- 0.65 L/min/mm Hg when tilted. The delta P0.1/delta PCO2 was 0.18 +/- 0.08 cm H2O/mm Hg supine versus 0.20 +/- 0.10 cm H2O/mm Hg tilted.(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献