Fixed-dose sirolimus with reduced dose calcineurin inhibitor: the University of Colorado experience.
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Calcineurin Inhibitors↗
Biomedical subjects
L Chan
Publications and source records attributed to L Chan.
Upregulation of IL-2 but not IL-15 by allorecognition in human mixed lymphocyte culture.
The redundant and pleiotropic effects of cytokines in transplant models have been shown both in vitro and in vivo. IL-2 is clearly not necessary for allograft rejection, possibly due to upregulated IL-15. We examined IL-15 expression using mixed lymphocyte culture (MLC) as an allorecognition model. IL-2 and IL-15 levels were measured by enzyme-linked immunoassay after 120 hours of culture. Cell proliferation in MLC was examined using [(3)H]thymidine uptake in the presence of either anti-IL-2Ralpha chain antibody or anti-IL-2Rgamma chain antibody. While IL-2 was detectable in cell supernates of MLC, IL-15 was not. Stimulation with an Anti-IL-2 gamma chain antibody which blocks the IL-2 gamma chain, a common unit in IL-2/IL-15 receptors, failed to produce additive antiproliferative effects after maximum inhibition by anti-IL-2alpha chain antibody, which is specific for IL-2. In conclusion, experiments in the MLC model suggest that allorecognition upregulates IL-2 but not IL-15 expression.
Cell Division↗
Meeting National Service Framework goals for patients presenting with acute myocardial infarction.
BACKGROUND: The National Service Framework for coronary heart disease established clear standards for the management of patients with acute myocardial infarction in March 2000. This study evaluates an emergency department's thrombolysis performance in light of these standards. SETTING: Inner city teaching hospital emergency department. METHODS: The data were prospectively collected using a formal clinical pathway for all patients receiving thrombolysis in the emergency department between February 2000 and January 2001. Cases were reviewed at monthly multidisciplinary audit meetings. Regular feedback complemented routine teaching for both nursing and medical staff. RESULTS: 127 patients were thrombolysed, of whom 92 (72%) were immediately eligible. Some 77% of these had a door to needle time of less than 30 minutes and 38% less than 20 minutes. Twenty per cent of patients had a call to door time of less than 30 minutes. Some 84% of patients managed by the emergency department team had a door to needle time of less than 30 minutes compared with 53% of those patients seen by duty physicians. CONCLUSIONS: The thrombolysis target set by the National Service Framework for April 2002 is achievable. The target set for April 2003 remains an ambitious goal. Overall call to needle times are undermined by call to door times. Emergency department teams may be more efficient than duty physicians in processing patients needing thrombolysis.
Cardiology Service, Hospital↗
The use of modified VBM laryngeal tube compared to Laryngeal Mask Airway during spontaneous ventilation.
We have compared the use of the laryngeal mask airway with the new modified laryngeal tube in a prospective randomized controlled study. Sixty ASA 1 or 2 patients, aged 18 to 65 years, scheduled for elective surgery and breathing spontaneously under general anaesthesia, were studied. After preoxygenation, anaesthesia was induced with fentanyl and propofol. The patients were randomized to receive either a laryngeal mask airway or a laryngeal tube. Anaesthesia was maintained with nitrous oxide, oxygen and isoflurane. We recorded the speed and the ease of insertion, the number of attempts needed to successfully secure the airway and intraoperative complications, such as partial airway obstruction needing airway manipulation. The airway devices were removed with the patients fully awake at the end of surgery. Systolic arterial blood pressure, heart rate and end-tidal CO2 were recorded at various time intervals. Postoperative complications were recorded. We found that the incidence of partial airway obstruction needing intraoperative airway manipulation was higher with the laryngeal tube than with the laryngeal mask airway. We conclude that during spontaneous ventilation the modified laryngeal tube is not as reliable in providing a satisfactory airway and we consider it is not a suitable alternative to the laryngeal mask airway.
Adult↗
General anaesthesia in a child with Larsen syndrome.
Larsen syndrome is a rare congenital connective tissue disorder which is characterized by multiple dislocations of major joints, typical facial appearance, cervical spine narrowing and instability and respiratory difficulties secondary to laryngotracheomalacia. A case of general anaesthesia for laparoscopic hernia repair in a male child aged 16 months with this syndrome is presented. Anaesthesia was well tolerated though intubation proved difficult. Cervical spine instability and postoperative respiratory complications are potential problems.
Anesthesia, General↗
Drug release properties of pectinate microspheres prepared by emulsification method.
This study explored the potential of pectin for use in making microspheres for sustained-release of drugs. The pectin microspheres were prepared by external gelation using an emulsification technique with calcium chloride as the crosslinking agent. The influences of drug core (sulphanilamide, sulphaguanidine and sulphathiazole) and dissolution media (distilled water, USP HCl and phosphate buffers) on the drug release properties of the pectinate microspheres were examined. The morphology and drug content of the microspheres, and the solubility and solution pH of the drugs were also determined. Pectinate microspheres were successfully prepared by the emulsification technique. The rate of drug released from microspheres was highest in USP HCl buffer, followed by USP phosphate buffer and distilled water. Interestingly, the lowest percentage of drug released was produced by microspheres which were smallest in size and therefore largest in specific surface area, and consisting of sulphanilamide, the most water soluble drug. Further investigation showed that the microspheres consisted of both bound and unbound drugs. The percentage of drug released was predominantly determined by the relative contents of bound and unbound drugs embedded in the pectinate matrix.
Anti-Infective Agents↗
Cross-linking mechanisms of calcium and zinc in production of alginate microspheres.
Calcium chloride and zinc sulphate were used to cross-link alginate microspheres prepared by an emulsification method. The microspheres cross-linked by a combination of these two salts showed different morphology and slower drug release compared with those cross-linked by the calcium salt alone. From viscosity study, it was found that zinc cations interacted with the alginate molecules to a greater extent than calcium cations. The varying effects of the salts on the properties of the microspheres were largely attributed to their ability to interact with the alginate molecules.
Alginates↗
Production of alginate microspheres by internal gelation using an emulsification method.
Alginate is a natural polysaccharide found in brown algae. Alginates are widely used in the food and pharmaceutical industries and have been employed as a matrix for the entrapment of drugs, macromolecules and biological cells. Alginate microspheres can be produced by the external or internal gelation method using calcium salts. The addition of calcium chloride solution in the final phase of production of microspheres by external gelation method using an emulsification technique causes the disruption of the equilibrium of the system being stirred, resulting in a significant degree of clumping of microspheres. Therefore, in this study, production of alginate microspheres by the internal gelation method using a modified emulsification technique was explored. The influence of calcium salt, added in varying amounts and at different stages, on the morphology of the microspheres was investigated. The effects of other hardening agents and different drying methods were also studied.
Alginates↗
Influence of polyvinylpyrrolidone on aggregation propensity of coated spheroids.
The influence of polyvinylpyrrolidone (PVP), a commonly used binder and adhesive, on the aggregation of spheroids coated with hydroxypropylmethylcellulose (HPMC) was studied. The aggregation propensities of spheroids coated by HPMC alone and by HPMC with polyethylene glycol (PEG) were compared with those coated by HPMC with PVP and the viscosity of the coating solutions determined. The coating was conducted at a maximum spray rate of 11 g/min to avoid premature termination of the coating process at higher spray rates due to uncontrollable aggregation of spheroids. PVP was able to reduce the extent of aggregation of spheroids. It was more effective in reducing spheroid aggregation than PEG. The reduction in spheroid aggregation propensity was ascribed to viscosity lowering effects of PVP. The viscosity of the coating solutions determined over the temperature range of 28-58 degrees C was found to increase in the following order: HPMC-PVP<HPMC-PEG<HPMC.
Excipients↗
Lifetime correction of genetic deficiency in mice with a single injection of helper-dependent adenoviral vector.
Ideally, somatic gene therapy should result in lifetime reversal of genetic deficiencies. However, to date, phenotypic correction of monogenic hyperlipidemia in mouse models by in vivo gene therapy has been short-lived and associated with substantial toxicity. We have developed a helper-dependent adenoviral vector (HD-Ad) containing the apolipoprotein (apo) E gene. A single i.v. injection of this vector completely and stably corrected the hypercholesterolemia in apoE-deficient mice, an effect that lasted the natural lifespan of the mice. At 2.5 years, control aorta was covered 100% by atherosclerotic lesion, whereas aorta of treated mice was essentially lesion-free. There was negligible toxicity associated with the treatment. We also developed a method for repeated HD-Ad vector administration that could be applied to organisms, e.g., humans, with life spans longer than 2-3 years. These studies indicate that HD-Ad is a promising system for liver-directed gene therapy of metabolic diseases.
Adenoviridae↗
A DnaJ protein, apobec-1-binding protein-2, modulates apolipoprotein B mRNA editing.
Mammalian homologues of DnaJ proteins, also known as Hsp40 proteins, are co-chaperonins that complement Hsp70 chaperone function. Using the yeast two-hybrid system, we cloned an apolipoprotein (apo) B mRNA editing complementation protein, called apobec-1-binding protein-2 (ABBP-2), and found that it is a Class II DnaJ homologue. ABBP-2 binds to apobec-1, the mammalian apoB mRNA editase, via its J domain and neighboring G/F domain. It is a ubiquitously expressed protein, and, by transfection analysis of GFP-ABBP-2, we found that the protein is located in both the nucleus and cytosol of transfected cells, with predominance in the nucleus. Down-regulation of ABBP-2 expression in cultured cells inhibits endogenous apobec-1-mediated apoB mRNA editing. Like other Hsp40 proteins, ABBP-2 binds to Hsp70 and has ATPase-stimulating activity. Apobec-1-mediated apoB mRNA editing activity of in vitro tissue extracts requires the presence of Hsp70/ABBP-2. Although exogenously added ATP is not required for editing activity, removal of the endogenous ATP present in these extracts, which disrupts ABBP-2-Hsp70 interaction, completely inhibits editing. ABBP-2 differs from previously described auxiliary proteins (ABBP-1, ACF, and GRY-RBP) in that it does not contain any RNA recognition motifs. Not only is ABBP-2 required for efficient apoB mRNA editing, this newly discovered apobec-1-binding protein may help determine the subcellular distribution and trafficking of apobec-1 via its interaction with the chaperonin Hsp70.
Adenosine Triphosphate↗
Superior role of apolipoprotein B48 over apolipoprotein B100 in chylomicron assembly and fat absorption: an investigation of apobec-1 knock-out and wild-type mice.
Editing of apolipoprotein (apo)-B100 mRNA to yield apo-B48 is a specific and developmentally regulated step in enterocytes of mammals. However, the functional significance of this step is not known. Since mice containing only apo-B100 have not been documented to exhibit any difference in intestinal fat absorption from wild-type mice, the evolutionary advantage of apoB mRNA editing has been questioned. In the present study, we have compared fat absorption and chylomicron assembly in apobec-1 knock-out (KO) or wild-type (WT) mice subjected to different dietary manipulations: low-fat chow, a fat-enriched 'Western' diet and overnight fasting. Experiments in vivo and in vitro revealed differences in the ability of KO and WT enterocytes to assemble and secrete chylomicrons under different dietary conditions. After overnight fasting, chylomicron secretion is reduced considerably in KO compared with WT enterocytes. This is not due to reduced synthesis of apo-B or triacylglycerol (TAG), but appears to be a result of impaired assembly of chylomicrons, so that triacylglycerol accumulates in the enterocytes. After feeding with fat, secretion of chylomicrons enriched in pre-existing TAG is stimulated in KO compared with WT mice. In the present study, we have documented for the first time that apo-B100 is considerably less efficient than apo-B48 in exerting its role in the early stage of chylomicron assembly, which is rate-limiting under conditions of low dietary fat. However, this impairment is overcome by increased TAG stores that stimulate later stages in assembly, which are rate-limiting in the fat-fed state. apo-B mRNA editing may result in more efficient fat absorption, specifically under conditions of food shortage or low-fat content, and thus provide an evolutionary advantage.
APOBEC-1 Deaminase↗
Two-hybrid cloning identifies an RNA-binding protein, GRY-RBP, as a component of apobec-1 editosome.
ApoB mRNA editing is mediated by an editosome complex with apobec-1 as its catalytic component. By yeast two-hybrid cloning using apobec-1 as bait we identified a 69.6-kDa RNA binding protein, GRY-RBP, that contains 3 RNA-recognition motifs (RRMs) as a novel apobec-1 associating protein. GRY-RBP may be an alternatively spliced species of NASP1, a protein of known function. GRY-RBP was shown to bind to apobec-1, the catalytic component of apoB mRNA editosome, in vivo and in vitro. Immunodepletion using a monospecific rabbit antibody abolished editing in apobec-1 expressing HepG2 S-100 extracts. GRY-RBD interacted with apobec-1 through its C-terminus. It contains three RRM (RNA recognition motifs) domains that are homologous to those found in human ACF (apobec-1 complementation factor). Phylogeny analysis of the RRM domain-containing proteins indicates that GRY-RBP clusters with hnRNP-R, ACF, and ABBP-1 (another apobec-1 binding protein). In addition to its involvement with apobec-1 editosome, the suggested cellular functions of GRY-RBD and its structural homologues include RNA transport and RNA secondary structure stabilization.
APOBEC-1 Deaminase↗
Long-term stable correction of low-density lipoprotein receptor-deficient mice with a helper-dependent adenoviral vector expressing the very low-density lipoprotein receptor.
BACKGROUND: Familial hypercholesterolemia (FH) that results from LDL receptor (LDLR) deficiency affects approximately 1 in 500 persons in the heterozygous state and approximately 1 in 1 million persons in the homozygous state. We tested a novel gene therapy strategy for the treatment of FH in a mouse model. METHODS AND RESULTS: We delivered the VLDL receptor (VLDLR) to the liver of LDLR-deficient mice and compared the effect of a helper-dependent adenoviral vector with all viral coding sequences deleted (HD-Ad-mVLDLR) with a first-generation vector (FG-Ad-mVLDLR), an HD-Ad (HD-Ad-0) that contained no expression cassette, and dialysis buffer (DB). A single intravenous injection of HD-Ad-mVLDLR led to a lowering of plasma cholesterol that lasted >/=6 months. Acute liver toxicity (as measured with liver enzyme elevation) occurred after FG-Ad-mVLDLR but not after HD-Ad-mVLDLR, HD-Ad-0, or DB treatment. At 6 months, VLDLR was detected in the liver with Western blotting and with immunofluorescence staining only in HD-Ad-mVLDLR-treated mice. Aortic atherosclerosis was almost completely prevented in these animals. CONCLUSIONS: HD-Ad-mediated intravenous delivery of VLDLR to hepatocytes is well tolerated. It produces long-term lowering of plasma cholesterol and prevents atherosclerosis development in LDLR-deficient mice. These data provide support for the feasibility and safety of this approach for therapy of human subjects.
Adenoviridae↗
A study of titanium nitride diffusion barriers between aluminum and silicon by X-ray absorption spectroscopy: the Si, Ti and N results.
We report a multi-elment, multi-edge and multi-detection mode X-ray photoabsorption study of a series of Al/TiN(x)/Si(100) thin films as a function of the TiN(x) film thickness (100A-500A) and of the annealing temperature (400 degrees C-600 degrees C). The Si K- and L-edge results show that Si does not diffuse to the surface for all the films. The high resolution Ti L-edge and N K-edge spectra show that the TiN(x) layer undergoes a dramatic chemical reaction with the gradual increase in the annealing temperature. This chemical reaction stabilizes at 560 degrees C at which the TiN(x) film is known to fail to act as an effective diffusion barrier between Al and Si.
Journal Article↗
Tunicamycin induces ubiquitination and degradation of apolipoprotein B in HepG2 cells.
Apolipoprotein (apo) B-100 is an essential component of atherogenic plasma lipoproteins. Previous studies have demonstrated that the production of apoB-100 is regulated largely by intracellular degradation at both the co-translational and post-translational levels and that proteasome-mediated and non-proteasome-mediated pathways are involved in this process. ApoB-100 is a glycoprotein. The present study was undertaken to address the question of whether the inhibition of N-linked glycosylation with tunicamycin would interfere with apoB-100 production. We demonstrated that the treatment of HepG2 cells with tunicamycin decreased the net production of apoB-100 by enhancing co-translational degradation of the protein. This effect of tunicamycin was partly prevented by lactacystin, a specific proteasome inhibitor. Because lactacystin only partly reversed the effects of tunicamycin on apoB biogenesis, tunicamycin seemed also to induce apoB co-translational degradation in HepG2 cells by one or more non-proteasomal pathways. Furthermore, tunicamycin increased apoB ubiquitination approx. 4-fold. The proportion of the newly synthesized apoB-100 that was secreted and incorporated into the nascent lipoprotein particles was unaffected by tunicamycin. Thus the tunicamycin-mediated inhibition of N-linked glycosylation interferes with the production of apoB-100 that is mediated by both proteasomal and non-proteasomal pathways.
Acetylcysteine↗
Design and synthesis of new potent human cytomegalovirus (HCMV) inhibitors based on internally hydrogen-bonded 1,6-naphthyridines.
1,6-Naphthyridine-2-carboxylic acid benzylamides are potent anti-HCMV compounds. Replacement of the amide moiety by other groups containing internal hydrogen bonds was undertaken to extend the SAR. Our results indicated that the urca derivatives showed very good activity.
Antiviral Agents↗
Apoptosis in atherosclerosis: pathological and pharmacological implications.
Normal embryonic development, tissue differentiation and repair in the eukaryote requires a tightly regulated apoptosis, or programmed cell death. Apoptosis also plays an essential role in different pathological processes including atherosclerosis, in which it affects all cell types in the atherosclerotic lesion, including endothelial cells, vascular smooth muscle cells, and macrophages. During atherosclerosis progression, pro- and anti-apoptotic signals abound in the evolving lesion. Apoptosis limits the number of a particular cell type that accumulates in the lesion and slows down the overall progression of the lesion. On the other hand, it contributes to the production of unstable plaques. Many pharmacological agents used to treat cardiovascular and lipid disorders have pro- or/and anti-apoptotic effects. Pharmaceuticals that modulate apoptosis in specific types of cell can potentially serve as anti-atherogenic agents. However, to develop agents for clinical use requires a thorough knowledge of the pathophysiology of apoptosis in atheromatous lesions, a highly cell-specific process. Here we review our current understanding of the process to provide a background for future pharmacological research in the area.
Animals↗