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31.
The biodegradation of different porous β-whitlockite materials are studied by in vivo experiments, radiographie follow-ups and light microscopy observations. The materials were implanted in rabbit tibiae for 16 mnth. Micropores play an important role in the biodegradation rate. The resorbing materials evoke an inflammation with plasma cells. The resorption starts in the medulla, and the phagocytosed particles are removed to the lymph nodes. Normal bone function can be restored after all the implant material is resulted. 相似文献
32.
The right of incarcerated prison and jail inmates to health care is protected by the 8th and the 14th amendments of the Constitution, respectively. Does the right to health care include access to clinical trials? At the time of this writing, clinical trials have become part of the fabric of HIV/AIDS care, allowing patients to participate in studies of new and often lifesaving treatments. Participation in trials can also be dangerous, as illustrated by the recent death of a subject in a gene therapy trial. This danger is compounded by ethical dilemmas that can arise from the large amount of financial support for clinical trials (greater than 75%) that is derived from for-profit corporations. Indeed, clinical trials are the subject of grave concern on the part of the United States Government, which has recently taken steps to shore up human subject safeguards. Following a conference on the conduct of clinical trials in correctional settings, the Office for Human Research Protections suspended prison research conducted by 4 prestigious academic institutions. 相似文献
33.
R. B. Bajnath N. van den Berghe H. R. De Jonge J. A. Groot 《Pflügers Archiv : European journal of physiology》1993,425(1-2):90-99
The differentiated clone 19A of the HT-29 human colon carcinoma cell line was used as a model to study the intracellular electrophysiological effects of interaction of the cAMP, the protein kinase C (PKC) and the Ca2+ pathways, (a) A synergistic effect between ionomycin and forskolin was observed. From intracellular responses it was concluded that the synergistic effect is caused by activation of an apical Cl– conductance by protein kinase A and a basolateral K+ conductance by Ca2+. (b) A transient synergistic effect of ionomycin and the phorbol ester phorbol dibutyrate (PDB) was found. The decrease of the response appeared to be due to PKC-dependent inactivation of the basolateral K+ conductance. The synergism is caused by PKC-dependent increase of the apical Cl– conductance and Ca2+-dependent increase of the basolateral K+ conductance. (c) The effects of carbachol and PDB were not fully additive presumably because of their convergence on PKC activation, (d) Forskolin and PDB, when added in this order, had a less than additive effect. Results of cell-attached patch-clamp studies, presented in the accompanying paper, showed a synergistic effect of forskolin and PDB on non-rectifying small-conductance Cl– channels. Assuming that these channels are involved in the transepithelial responses it is suggested that forskolin and PDB induce a modulatory, synergistic increase of the apical Cl– conductance when both pathways are activated simultaneously. (e) The HT-29cl.19A cells differ from T84 cells in that the latter did not respond with an increase of the short-circuit current to addition of phorbol ester. This may be due to a very low expression of PKC. 相似文献
34.
M. E. Verberne A. C. Gittenberger-de Groot R. E. Poelmann 《Anatomy and embryology》1998,198(3):171-184
We were interested in the contribution of the cardiac neural crest to the complete anterior and posterior nerve plexus of
the chick heart. This includes the pathways by which these cardiac neural crest-derived neuronal precursors enter the heart.
As lineage techniques we used the traditional quail-chick chimera in combination with the newly introduced technique of retroviral
reporter gene transfer to premigratory cardiac neural crest cells. Retrovirally infected embryos (n=23) and quail-chick chimeras (n=19) between stages HH27 and 40, were immunohistochemically evaluated, using the lineage markers LacZ (retroviral reporter)
and QCPN (anti-quail nuclear marker), respectively and the neuronal differentiation markers HNK-1, RMO-270 and DO-170. Between
stages HH27 and 33, quail-derived and LacZ positive cells were situated around the arterial cardiac vagal branches at the
arterial pole, and vagal branches along the anterior cardinal veins and the sinal vagal branch at the venous pole. From stage
HH35 onward, QCPN/LacZ-positive cardiac ganglia were observed throughout the anterior and posterior plexus and were mainly
concentrated in the subepicardium near the distal ends of the arterial cardiac vagal branches and the sinal cardiac vagal
branch respectively. From stage HH36 both the anterior and posterior plexus contained a population of large cardiac ganglion
cells and a population of smaller cells along nerve branches as well as in the cardiac ganglia, which means that differentiation
starts in both plexus at the same time. Furthermore only nerve fiber connections between the anterior and posterior plexus
were observed. These results show that the cardiac neural crest contributes to the cardiac ganglion cells from both the entire
anterior and posterior plexus. Furthermore these results suggest that these precursor cells enter the arterial pole via the
arterial cardiac vagal branches and the venous pole via the sinal cardiac vagal branch without intermixing. Finally we show
that in addition to the cardiac ganglia, the cardiac neural crest contributes to small myocardial glia or undifferentiated
cells along nerve fibers, and some myocardial nerve fibers as well as nerve tissue in the adventitia of the large veins at
the venous pole and in the adventitia of the coronary arteries.
Accepted: 30 March 1998 相似文献
35.
A further evaluation of the clinical use of specific IgE antibody testing in allergic diseases 总被引:5,自引:0,他引:5
Söderström L Kober A Ahlstedt S de Groot H Lange CE Paganelli R Roovers MH Sastre J 《Allergy》2003,58(9):921-928
BACKGROUND: The evaluation and interpretation of the results from blood tests measuring specific immunoglobulin E (IgE) antibody concentration is currently made using the dichotomized result from the test despite a quantitative result is obtained. It has been shown that different levels of IgE antibodies, assessed by blood test and skin prick test, may have a relation to presence of symptoms, implying that there is more information in a quantitative result than in the dichotomous--positive or negative. OBJECTIVE: To investigate the clinical utility of quantification of IgE antibodies in the diagnosis of allergic patients and whether such procedure has any advantage to the presently dichotomously used sensitivity and specificity at a fixed cut-off. METHODS: Data from a previously published study (R. Paganelli, I.J. Ansoteugi, J. Sastre, C.-E. Lange, M.H.W.M. Roovers, H. de Groot, N.B. Lindholm, P.W. Ewan, Allergy, 1998; 53) analysing diagnosis of allergic patients in four different clinics were re-evaluated. In the original study consecutive patients with suspected IgE-mediated allergy had been examined and evaluated according to the clinical routine at each clinic, using case history, physical examination, skin tests and laboratory tests, except the test to be evaluated, and given a "doctors' allergen-specific diagnosis" as positive or negative. In the present study the relation between "doctors' allergen-specific diagnosis", expressed as pos/neg, and the quantitative levels of specific IgE antibody concentration was analysed using a logistic regression model. This presentation of results was also compared with the more common characteristics of sensitivity and specificity, and also with Receiver-operator characteristics (ROC) curves. RESULTS: The used logistic model described the relationship between allergen-specific diagnosis in each study and the levels of IgE antibodies. The shape of the curve illustrated the physicians' disposition for a positive diagnose in the study, in relation to the specific IgE antibody level. Differences in the shape of the curve was found both between allergens within clinics and between clinics for the same allergen. No association could be demonstrated between prevalence and shape of the curve. CONCLUSIONS: Conventional sensitivity/specificity figures or ROC concepts only use the qualitative statement of whether IgE is present or not. A risk assessment using the quantitative level of IgE antibody to an allergen increases the utility of the information in clinical context compared with a qualitative statement of whether IgE is present or not. The quantification demonstrated the link between specific IgE antibodies and allergic reactions. The use of objective, well performing quantitative tests should help improve diagnostic accuracy and might provide a way for the patient to understand and manage his or her daily situation and risk for reactions. 相似文献
36.
Molecular epidemiology of pneumococcal colonization in response to pneumococcal conjugate vaccination in children with recurrent acute otitis media 下载免费PDF全文
Bogaert D Veenhoven RH Sluijter M Wannet WJ Rijkers GT Mitchell TJ Clarke SC Goessens WH Schilder AG Sanders EA de Groot R Hermans PW 《Journal of clinical microbiology》2005,43(1):74-83
A randomized double-blind trial with a 7-valent pneumococcal conjugate vaccine was conducted in The Netherlands among 383 children, aged 1 to 7 years, with a history of recurrent acute otitis media. No effect of vaccination on the pneumococcal colonization rate was found. However, a shift in serotype distribution was clearly observed (R. Veenhoven et al., Lancet 361:2189-2195, 2003). We investigated the molecular epidemiology of 921 pneumococcal isolates retrieved from both the pneumococcal vaccine (PV) and control vaccine (CV) groups during the vaccination study. Within individuals a high turnover rate of pneumococcal restriction fragment end labeling genotypes, which was unaffected by vaccination, was observed. Comparison of the genetic structures before and after completion of the vaccination scheme revealed that, despite a shift in serotypes, there was clustering of 70% of the pneumococcal populations. The remaining isolates (30%) were equally observed in the PV and CV groups. In addition, the degree of genetic clustering was unaffected by vaccination. However, within the population genetic structure, nonvaccine serotype clusters with the serotypes 11, 15, and 23B became predominant over vaccine-type clusters after vaccination. Finally, overall pneumococcal resistance was low (14%), and, albeit not significant, a reduction in pneumococcal resistance as a result of pneumococcal vaccination was observed. Molecular surveillance of colonization in Dutch children shows no effect of pneumococcal conjugate vaccination on the degree of genetic clustering and the genetic structure of the pneumococcal population. However, within the genetic pneumococcal population structure, a clear shift toward nonvaccine serotype clusters was observed. 相似文献
37.
Reduction of IgM antibodies to DNA with mercaptans such as dithioerythrol or 2-mercaptoethanol completely destroys DNA binding in the Farr assay and in the immunofluorescence technique by Crithidia luciliae. In contrast reduction of IgG antibodies to DNA results in a six-fold increase of DNA binding in the Farr assay while no effect on titres in the immunofluorescence technique can be observed. Our results lead to the following conclusions: 1) The Farr assay is selective for high avidity interactions; only a minor part of IgG antibodies to DNA is measured; 2) 7S IgM antibodies to DNA cannot be demonstrated in the Farr assay or the immunofluorescence technique; obviously only multivalent interactions, as obtained with the intact 19S IgM molecule are stable in these assays; 3) reduction of IgG leads to a greater flexibility of this molecule; this facilitates monogamous bivalent binding to DNA; 4) THE PRESENTATION OF DNA in the kinetoplast of Crithidia luciliae favours a monogamous bivalent binding of antibodies to DNA with high avidity; this accounts for occasionally observed discrepancies between anti-DNA activity in the Farr assay and in the immunofluorescence technique. 相似文献
38.
In vitro solubility tests of hydroxyapatite, tetracalcium phosphate or tricalcium phosphate particles were performed in lactate, citrate, Gomoris or Michaelis buffer with pH 6.2 or 7.2 and in aqua destillata. The results showed that in general the solubility decreased in the order tetracalcium phosphate greater than tricalcium phosphate greater than hydroxyapatite, except for lactate or citrate buffer where the solubility order was tetracalcium phosphate = tricalcium phosphate greater than hydroxyapatite. The influence of the specific buffer used is much larger than either pH or specific calcium phosphate salt tested. The pH stability of lactate buffer and aqua destillata is very low, the other buffer solvents had a rather stable pH value. 相似文献
39.
In vivo biocompatibility of dextran-based hydrogels 总被引:4,自引:0,他引:4
Cadée JA van Luyn MJ Brouwer LA Plantinga JA van Wachem PB de Groot CJ den Otter W Hennink WE 《Journal of biomedical materials research》2000,50(3):397-404
Dextran-based hydrogels were obtained by polymerization of aqueous solutions of methacrylated dextran (dex-MA) or lactate-hydroxyethyl methacrylate-derivatized dextran (dex-lactate-HEMA). Both nondegradable dex-MA and degradable dex-lactate-HEMA disk-shaped hydrogels, varying in initial water content and degree of substitution (DS, the number of methacrylate groups per 100 glucose units), were implanted subcutaneously in rats. The tissue reaction was evaluated over a period of 6 weeks. The initial foreign-body reaction to the dex-MA hydrogels was characterized by infiltration of granulocytes and macrophages and the formation of fibrin, and exudate, as well as new blood vessels. This reaction depended on the initial water content as well as on the DS of the hydrogel and decreased within 10 days. The mildest tissue response was observed for the gel with the highest water content and intermediate DS. At day 21 all dex-MA hydrogels were surrounded by a fibrous capsule and no toxic effects on the surrounding tissue were found. No signs of degradation were observed. The initial foreign-body reaction to the degradable dex-lactate-HEMA hydrogels was less severe compared with the dex-MA gels. In general, the size of the dex-lactate-HEMA hydrogels increased progressively with time and finally the gels completely dissolved. Degradation of the dex-lactate-HEMA hydrogels was associated with infiltration of macrophages and the formation of giant cells, both of which phagocytosed pieces of the hydrogel. A good correlation between the in vitro and the in vivo degradation time was found. This suggests that extra-cellular degradation is not caused by enzymes but depends only on hydrolysis of the ester and/or carbonate bonds present in the crosslinks of the hydrogels. After 21 days, the degradable hydrogels, as such, could not be retrieved, but accumulation of macrophages and giant cells was observed, both of which contained particles of the gels intracellularly. As for the dex-MA hydrogels, no toxic effects on the surrounding tissue were found. The results presented in this study demonstrate that dextran-based hydrogels can be considered as biocompatible materials, making these hydrogels attractive systems for drug delivery purposes. 相似文献
40.
L M Groot 《Effective health care》1984,2(2):69-81
In the last years endeavours have been made in several health systems to get a firm grip on the explosive cost development in hospitals which amounts to nearly half of all health care expenditures. The fee-for-service system for doctors coupled with the professional autonomy leads to expansion of quality and quantity of services provided. In many systems hospitals are financed on basis of output items as patient days, examinations and therapies. As hospital costs are in the short run preponderantly constant prices fixed at average costs are higher than marginal costs. This situation favours expansion of services as in that case marginal revenue exceeds marginal cost. Inversely the decrease of services provided generates losses for the hospital. In systems, where financing takes place in the way of budgets like the U.K., Denmark and Italy, the authorities have more influence on the cost development in the system. In systems where the hospitals are financed by social security on basis of output, arrangements are now made to bring budgetary elements in the financing of these institutions. In France the "Budget Global" will be applied to services financed by the Sécurité sociale. In Belgium arrangements have been made to contain the amount of patient days allowed for reimbursement and in the Netherlands in 1983 budget-financing has been introduced for all general and teaching hospitals. In 1984 this system also applies to all other intramural institutions. If a way has been found to focus the financing mechanism of these institutions on budgeted costs, the way is open for budgeting these institutions. A very important problem in this context is the budget formula, which will be used to determine the budgets. In this respect a distinction can be made between internal and external budgeting. Internal budgeting is understood here as a process whereby the hospital itself puts a limit to the use of resources or adapts its resources to budget constraints coming from the outside. External budgeting can be defined as the budgetary constraint given from the outside by third parties to the hospitals. Of course, both internal and external budgeting are narrowly interrelated. The distinction between these two ways of budgeting should be sought in the character of the budget formula. External budgeting should be based on global indications whilst internal budgeting should be more differentiated than the external budget formula.(ABSTRACT TRUNCATED AT 400 WORDS) 相似文献