785 research outputs found
Evaluation of the hCMEC/D3 cell line, a new "in vitro" model of the human blood-brain barrier for transport and gene regulation studies
No full textBrain endothelial capillary cells form the blood-brain barrier (BBB), a highly selective
membrane between the peripheral blood and the central nervous system. The main
functions of the BBB are to protect the brain tissue by preventing the entry of toxic
compounds and to supply it with nutrients in order to assure proper function. Tight
junctions are the key elements for the establishment of a tight barrier and seal the
intercellular gaps against passive diffusion of hydrophilic compounds. A second important
characteristic of the brain capillary endothelial cells are transport proteins that prevent
brain penetration of their substrates by pumping them back in the blood. These
compounds include a series of clinically used drugs. Important drug efflux transporters
located at the BBB are P-glycoprotein (P-gp), the breast cancer resistance protein
(BCRP) and the family of multidrug resistance proteins (MRP).
During drug development, the question of whether a drug candidate reaches the brain
tissue is of great importance. Therefore, models are needed to predict the BBB
permeability of new compounds. In the past, in vitro models have been developed to
address this question. These models include isolated brain capillaries, isolated primary
brain capillary endothelial cells and BBB cell lines of various origins. A major problem
encountered with these cell lines was an insufficient paracellular resistance.
Recently, the hCMEC/D3 cell line was generated by immortalizing primary human brain
endothelial cells. In culture this cell line shows a morphology that closely resembles to
primary cells, forms tight monolayers and expresses BBB markers such as chemokine
receptors, tight junctional molecules and ATP binding cassette (ABC)-transporters.
The aim of this thesis was to evaluate the hCMEC/D3 cell line as an in vitro model of the
human BBB to study 1) permeability properties including para- and transcellular diffusion
as well as active transport 2) the influence of endo- and exogenous factors on the
paracellular permeability and 3) the regulation of breast cancer resistance protein and Pglycoprotein
by pro-inflammatory cytokines.
The first study describes the characterization of the hCMEC/D3 cells as an in vitro model
of the human BBB for permeability studies (section Error! Reference source not
found.). The ability of the cells to allow discrimination between para- and transcellular
diffusion was investigated by measuring the transport of a series of compounds with
different physicochemical properties. A ratio of 2.8 was observed when comparing the
permeabilities of the compounds with the highest and the lowest diffusion rate. The
passive permeability of sucrose could be reduced significantly by replacing fetal calf
serum with human serum. Furthermore, quantitative mRNA expression of the ABCtransporters
P-gp, BCRP, MRP1, MRP2, MRP3, MRP4, MRP5 as well as the human
transferrin receptor (hTfR) was shown. Protein expression of P-gp, BCRP and the hTfR
was detected and functional activity of P-gp, BCRP and the MRPs was investigated in
efflux experiments. Furthermore, bidirectional P-gp transport activity was observed.
In a second project the impact of endo- and exogenous factors on the paracellular
permeability of hCMEC/D3 monolayers was assessed, since it is know that the molecular
assembly of tight junctions depends on the surrounding milieu (section Error! Reference
source not found.). Based on reports in the literature, the cells were incubated with a
variety of compounds that included anti-inflammatory drugs, growth factors and
antioxidants. The effects on the monolayer tightness of hCMEC/D3 were investigated by
measuring the transport of sucrose, a paracellular permeability marker. N-acetylcystein
(NAC), atorvastatin and sodium nitroprusside (SNP) reduced the sucrose permeability
significantly, and slightly increased zonula occludens protein (ZO-1) expression.
Additionally, NAC and SNP reduced the generation of reactive oxygen species (ROS),
which have been reported to disrupt the assembly of tight junctions.
The effect of the pro-inflammatory cytokines IL-1[beta], IL-6 and TNF-[alpha] on the expression and
activity of the ABC-transporters BCRP and P-gp was investigated in the hCMEC/D3 cell
line (section Error! Reference source not found.). IL-1[beta], IL-6 and TNF-[alpha], which are
know to be elevated during various diseases, suppressed significantly BCRP mRNA
expression. In addition, BCRP activity was reduced under the influence of all tested
cytokines, as shown by efflux experiments. P-gp mRNA levels were slightly reduced by
IL-6 but significantly increased after TNF-[alpha] treatment. TNF-[alpha] also increased the protein
expression of P-gp. This in vitro study indicates that expression levels of BCRP and P-gp
at the BBB might be altered during acute or chronic inflammation, resulting in a changed
brain penetration of their substrates.
In an isolated project, the pharmacokinetics and pharmacodynamics of increasing oral
doses of the satiety peptides GLP-1 and PYY3-36 were assessed in healthy male
volunteers. Oral administration of either peptide induced a rapid and dose-dependent
increase in plasma drug concentrations. Oral administration of GLP-1 induced a potent
effect on insulin release and both peptides suppressed ghrelin secretion. In conclusion,
this study showed, for the first time, that satiety peptides such as GLP-1 and PYY3-36
can be orally delivered safely and effectively in humans
Goffman, E. Sacks, H. Cicourel, A. Poller, M. y Díaz, F. Sociologías de la Situación
No full textE. GOFFMAN ; H. SACKS ; A. CICOUREL ; M. POLLER ; D. DÍAZ, Sociologías de la Situació
Goffman, E. Sacks, H. Cicourel, A. Poller, M. y Díaz, F. Sociologías de la Situación
No full textE. GOFFMAN ; H. SACKS ; A. CICOUREL ; M. POLLER ; D. DÍAZ, Sociologías de la Situació
Use of Poller Screws in Proximal and Distal Metaphyseal Fractures of Tibia: A Prospective study
No full textINTRODUCTION: Treatment of metaphyseal fractures of tibia remains a challenge. The
goals of surgical management include correction and maintenance of sagittal
and coronal alignment, establishment of length and rotation and early
functional range of movements of knee and ankle.
Treatment options include medullary implants, half pin, thin wire or
hybrid external fixation, plate fixation or combination techniques.
Interlocking nailing of tibial fractures are desirable because this
technique allows some load sharing, spares extraosseous blood supply, avoids
extensive soft tissue dissection and is familiar to most surgeons1.
Nailing of metaphyseal fractures with short proximal or distal fragment
is associated with an increase in malalignment particularly in coronal plane,
non union and need for secondary procedures to achieve union. The cause has
been attributed both to displacing muscular forces and residual instability.
Various techniques have been recommended to improve nailing the
metaphyseal fractures including blocking screws (poller screw), temporary
unicortical plating, different nail designs with different proximal bends
(proximal third fractures) and fibular plating (distal third fractures).
AIM: To evaluate the clinical use of poller screws as a supplement to stability
in metaphyseal fractures of tibia treated with statically locked intramedullary nail.
MATERIALS AND METHODS: This was a prospective study of 20 cases of tibial metaphyseal fractures treated with statically locked intra medullary nailing with supplementary poller
screws between August 2006 and September 2007 at Kilpauk Medical College.
Inclusion Criteria -
Displaced tibial metaphyseal fractures of proximal or distal third in adults treated with intramedullary nailing were included in the study. The fractures included were acute fractures and delayed union. Both open and closed fractures were included in the study.
Exclusion Criteria - Tibial diaphyseal fractures were excluded from the study. Metaphyseal fractures treated with statically locked intramedullary nails but with additional procedures like fibular plating were excluded from the study.
RESULTS: All the relevant data were analysed. All the fractures eventually united in a mean period of 11.5 weeks (95% LCL 10.11weeks and 95%UCL 12.88 weeks). Karlstrom-Olerud score was excellent in 13 fractures (65%), good in 6 patients (25%) and fair in 2 patients (10%). The mean ratio of fracture segment to the nail length (i.e the length of tibia) was 15%.
The poller screw related complication was encountered in one case where we had new fracture lines while introducing the nail after placement of poller screw. But the alignment was achieved and maintained and the fracture united within 12 weeks.
Complications which were not related to poller screw were encountered
in three cases. Two patients had deep infection and both of them went in for
delayed union of which one required dynamisation to achieve union. In one
patient tibialis anterior tendon was found cut at the time of open reduction of
the fracture and was repaired. He was given cast support for four weeks.
No complications of nerve injury or compartment syndrome were
encountered. There were no incidences of breakage of nail, locking screw or
blocking screw.
CONCLUSION: We conclude that Poller screws, when supplemented the
intramedullary nailing of metaphyseal fractures of tibia,
1. Were effective in achieving the fracture alignment, acting as a
reduction tool.
2. Improved the stability of the bone – implant construct, by
functionally reducing the medullary width.
3. Maintained the fracture alignment till union, preventing loss of initial
reduction
Definition of the INR and its consequences for the calibration procedure of thromboplastin preparations : a rebuttal
No full textA multicentre randomised clinical end-point study of PARMA 5 computer-assisted oral anticoagulant dosage
No full textThe use of Poller screws as blocking screws in stabilising tibial fractures treated with small diameter intramedullary nails
No full text Intramedullary nailing of metaphyseal fractures may be associated with deformity as a result of instability after fixation. Our aim was to evaluate the clinical use of Poller screws (blocking screws) as a supplement to stability after fixation with statically locked intramedullary nails of small diameter. We studied, prospectively, 21 tibial fractures, 10 in the proximal third and 11 in the distal third in 20 patients after the insertion of Poller screws over a mean period of 18.5 months (12 to 29). All fractures had united. Healing was evident radiologically at a mean of 5.4 ± 2.1 months (3 to 12) with a mean varus-valgus alignment of −1.0° (−5 to 3) and mean antecurvatum-recurvatum alignment of 1.6° (−6 to 11). The mean loss of reduction between placement of the initial Poller screw and follow-up was 0.5° in the frontal plane and 0.4° in the sagittal plane. There were no complications related to the Poller screw. The clinical outcome, according to the Karström-Olerud score, was not influenced by previous or concomitant injuries in 18 patients and was judged as excellent in three (17%), good in seven (39%), satisfactory in six (33%), fair in one (6%), and poor in one (6%). </jats:p
Cerclajes o tornillos tipo poller como ayuda a la reducción y estabilización del enclavado retrógrado en fracturas del fémur distal. Técnica y comparación sobre una breve serie de casos
No full textRetrograde nailing is widely accepted in the management of fractures of the distal femur. The mechanical characteristics of the nail and the distal femur make it difficult to achieve proper alignment, so there are several methods to improve reduction and stability. In this retrospective, single-center study, the use of cerclages or poller screws defined two groups of patients, with one-year follow-up. We included 33 patients, predominating elderly women. Cerclages were used in 22 and poller screws in 11. Cerclages predominated in spiroid fractures (16/22) and yielded better sagittal alignments (malalignment 0.6º vs. 2.6º for poller; p<0.01). We found no differences in bone healing times, bleeding or complications. Cerclages and poller are useful in combination with femoral retrograde nails. Cerclages are especially helpful in spiroid fractures, which are frequent in fragile populatio
European Concerted Action on Anticoagulation (ECAA): An assessment of a method for ISI calibration of two whole blood point-of-care PT monitor systems based on lyophilized plasmas using whole blood equivalent PT
No full textPreviously, the attempt to simplify the International Sensitivity Index (ISI) calibration of the CoaguChek Mini whole blood point-of-care test prothrombin time (PT) monitor system was successful using lyophilized plasmas from coumar-in-treated patients but not with lyophilized artificially depleted plasmas. With the TAS PT-NC monitor system, both types of plasma failed to provide reliable calibrations. The present study assesses a procedure for the ISI calibration of a TAS PT-NC and CoaguChek Mini whole blood point-of-care test PT monitor systems using lyophilized plasmas. Using lyophilized artificially depleted and coumarin plasma calibrations, we have evaluated a correction for the monitor displayed PT. This was based on a 'line of equivalence' derived from the relationship between whole blood and fresh plasma PT with both types of monitor system. With the TAS PT-NC, the use of this 'line of equivalence' resulted in reliable ISI with both lyophilized coumarin and artificially depleted plasmas. There was no significant difference between mean monitor and mean reference International Normalized Ratio (INR) with the artificially depleted plasmas. With the lyophilized coumarin plasma calibrations there was only a small INR difference. Correction with the 'line of equivalence' therefore facilitates calibration of the TAS PT-NC with lyophilized plasmas. With the CoaguChek Mini, the correction based on the 'line of equivalence' did not improve results but was not required with this system. © 2003 International Society on Thrombosis and Haemostasis
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