Purpose To measure the solubility of four drugs in human gastric aspirates, canine gastric aspirates (CGF) and simulated gastric fluids
in order to propose a medium for estimating intragastric drug solubility relevant to a bioavailability study in the fasted
state.
Materials and Methods Intragastric environment after administration of water to healthy fasted adults and to healthy fasted dogs (this study) was
initially characterized. Solubilities were then measured with the shake-flask method in gastric fluid aspirated after the
administration of water to healthy fasted adults and to healthy fasted dogs, in various simulated gastric fluids, i.e. SGFSLS, SGFTriton, FaSSGF, FaSSGFNaCl, and in various HCl solutions with pH values ranging from 1.2 to 2.9.
Results In all cases, FaSSGF performed better than canine aspirates, SGFSLS, SGFTriton, or FaSSGFNaCl in predicting solubility in HGF. However, its superiority over HCl pH 1.6 was not clear. For ketoconazole, dipyridamole,
miconazole, and felodipine deviations of solubility data in FaSSGF from solubility data in HGF were non-significant, 34, −39
and 252%, respectively, whereas the corresponding deviations of data in HCl pH 1.6 from data in HGF were non-significant,
24, 70, and 130%, respectively.
Conclusions Combining data in FaSSGF and HCl pH 1.6 is comparatively the most efficient way to get an estimate of drug solubility in the
fasting gastric contents during a bioavailability study. However, accurate estimation of intragastric solubility is limited
by the changing environment during intragastric residence of solid particles and the degree of simulation of intragastric
composition. 相似文献
Previously,the choice of prosthetic implant-retained overdentures has depended on data from previous studies about the retention-fatigue strength of the attachment system selected.Little or no data have been available on the correlation between the attachment system selected and the overdenture support configuration.The purpose of the present study was to evaluate the retention force and fatigue resistance of three attachment systems and four support designs of overdenture prosthesis.Four lower edentulous acrylic models were prepared and eight combinations of attachments groups were investi-gated in the study.These included:O-Rings with mini-dental implants (MDIs),Dalbo elliptic with Dalbo Rotex and fabricated flexible acrylic attachments with both MDI and Dalbo Rotex.The study was divided into four test groups:groups A and B,controls,and groups C and D,experimental groups.Con-trol group A contained three overdenture supports:two free standing MDIs in the canine region and at the midline,and one simulated tooth root with Dalbo Rotex screwed in.Control group B contained four overdenture support foundations:two free standing MDIs in the right canine region and the first premo-lar region,and two simulated tooth roots with Dalbo Rotex screwed in at the same MDI position,but on the left side of the model.Experimental group C contained three overdenture support foundations:two free standing MDIs in the canine region and at the midline,and one simulated tooth root with MDI screwed in.Experimental group D contained four overdenture support foundations:two free standing MDIs in the right canine region and the first premolar region,and two simulated tooth roots with MDIs screwed in at the same MDI position,but on the left side of the model.Each group was further divided into two subgroups according to attachment type used.Five samples were prepared for each group.Re-tention force (N) values were recorded initially (0 cycles) and after 360,720,1440 and 2880 insertion and removal cycles.During the tensile test a cross-head speed of 10 mm/min was applied.Values of ab-solute force (AF) and relative force (RF) were statistically analyzed by two-way ANOVA and multiple comparison Tukey’s tests between groups and cycles periods.The results of fatigue tests showed a 50% reduction in retention force in the subgroups with flexible attachments.A triangular design of overden-ture support foundations with O-Ring attachments revealed the lowest value of AF and a relatively high reduction in RF.The four overdenture support designs with flexible acrylic attachments improved the retention force and reduced the fatigue retention.Furthermore,the results of the investigation demon-strate that flexible acrylic attachments for both teeth and implant-supported overdentures offer a wide range of retention forces. 相似文献
An innovative light-curable calcium-silicate cement containing a HEMA-TEGDMA-based resin (lc-MTA) was designed to obtain a bioactive fast setting root-end filling and root repair material.
Methods
lc-MTA was tested for setting time, solubility, water absorption, calcium release, alkalinizing activity (pH of soaking water), bioactivity (apatite-forming ability) and cell growth-proliferation. The apatite-forming ability was investigated by micro-Raman, ATR-FTIR and ESEM/EDX after immersion at 37 °C for 1-28 days in DPBS or DMEM + FBS. The marginal adaptation of cement in root-end cavities of extracted teeth was assessed by ESEM/EDX, and the viability of Saos-2 cell on cements was evaluated.
Results
lc-MTA demonstrated a rapid setting time (2 min), low solubility, high calcium release (150-200 ppm) and alkalinizing power (pH 10-12). lc-MTA proved the formation of bone-like apatite spherulites just after 1 day. Apatite precipitates completely filled the interface porosities and created a perfect marginal adaptation. lc-MTA allowed Saos-2 cell viability and growth and no compromising toxicity was exerted.
Significance
HEMA-TEGDMA creates a polymeric network able to stabilize the outer surface of the cement and a hydrophilic matrix permeable enough to allow water absorption. SiO−/Si-OH groups from the mineral particles induce heterogeneous nucleation of apatite by sorption of calcium and phosphate ions. Oxygen-containing groups from poly-HEMA-TEGDMA provide additional apatite nucleating sites through the formation of calcium chelates. The strong novelty was that the combination of a hydraulic calcium-silicate powder and a poly-HEMA-TEGDMA hydrophilic resin creates the conditions (calcium release and functional groups able to chelate Ca ions) for a bioactive fast setting light-curable material for clinical applications in dental and maxillofacial surgery. The first and unique/exclusive light-curable calcium-silicate MTA cement for endodontics and root-end application was created, with a potential strong impact on surgical procedures. 相似文献
As man embarks on space exploration and contemplates space habitation, there is a critical need for basic understanding of
the impact of the environmental factors of space, and in particular gravity, on human survival, health, reproduction and development.
This review summarizes our present knowledge on the effect of altered gravity on the developing CNS with respect to the response
of the developing CNS to altered gravity (gravireaction), the physiological changes associated with altered gravity that could
contribute to this effect (gravitransduction), and the possible mechanisms involved in the detection of altered gravity (graviperception).
Some of these findings transcend gravitational research and are relevant to our understanding of the impact of environmental
factors on CNS development on Earth. 相似文献
Objectives: To formally assess the strength of evidence for the efficacy of simulated presence therapy for challenging behaviours in dementia (playing an audio or videotape to an individual, personalized by a carer and containing positive experiences from the client's life and shared memories involving family and friends) using meta-analytic techniques.
Method: Systematic review and meta-analysis of k = 4 studies of simulated presence therapy for challenging behaviours in dementia.
Results: Meta-analysis indicated a significance effect (d = 0.70, 95% CI = 0.38–1.02), although this was reduced when the first published study was removed from the analysis.
Conclusion: These findings provide limited support for the use of simulated presence therapy with this population and stress the importance of assessing participants’ suitability for such an approach and monitoring their responses closely. Future adequately powered studies are necessary to confirm the efficacy of simulated presence therapy. 相似文献