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Biomedical subjects

K Fu

Publications and source records attributed to K Fu.

At least 19 recordsLinked to original sources
PubMed2003

Direct lung delivery of para-aminosalicylic acid by aerosol particles.

Para-aminosalicylic acid (PAS), a tuberculostatic agent, was formulated into large porous particles for direct delivery into the lungs via inhalation. These particles possess optimized physical properties for deposition throughout the respiratory tract, a drug loading of 95% by weight and physical stability over 4 weeks at elevated temperatures. Upon insufflation in rats, PAS concentrations were measured in plasma, lung lining fluid and homogenized whole lung tissue. Systemic drug concentrations peaked at 15 min, with a maximum plasma concentration of 11+/-1 microg/ml. The concentration in the lung lining fluid was 148+/-62 microg/ml at 15 min. Tissue concentrations were 65+/-20 microg/ml at 15 min and 3.2+/-0.2 microg/ml at 3h. PAS was cleared within 3 h from the lung lining fluid and plasma but was still present at therapeutic concentrations in the lung tissue. These results suggest that inhalation delivery of PAS can potentially allow for a reduction in total dose delivered while providing for higher local and similar peak systemic drug concentrations as compared to those obtained upon oral PAS dosing. Similar particles could potentially be used for the delivery of additional anti-tuberculosis agents such as rifampicin, aminoglucosides or fluoroquinolones.

Administration, Inhalation↗
PubMed2001

HTLV-1 p12(I) protein enhances STAT5 activation and decreases the interleukin-2 requirement for proliferation of primary human peripheral blood mononuclear cells.

The p12(I) protein, encoded by the pX open reading frame I of the human T-lymphotropic virus type 1 (HTLV-1), is a hydrophobic protein that localizes to the endoplasmic reticulum and the Golgi. Although p12(I) contains 4 minimal proline-rich, src homology 3-binding motifs (PXXP), a characteristic commonly found in proteins involved in signaling pathways, it has not been known whether p12(I) has a role in modulating intracellular signaling pathways. This study demonstrated that p12(I) binds to the cytoplasmic domain of the interleukin-2 receptor (IL-2R) beta chain that is involved in the recruitment of the Jak1 and Jak3 kinases. As a result of this interaction, p12(I) increases signal transducers and activators of transcription 5 (STAT5) DNA binding and transcriptional activity and this effect depends on the presence of both IL-2R beta and gamma(c) chains and Jak3. Transduction of primary human peripheral blood mononuclear cells (PBMCs) with a human immunodeficiency virus type 1-based retroviral vector expressing p12(I) also resulted in increased STAT5 phosphorylation and DNA binding. However, p12(I) could increase proliferation of human PBMCs only after stimulation of T-cell receptors by treatment of cells with low concentrations of alphaCD3 and alphaCD28 antibodies. In addition, the proliferative advantage of p12(I)-transduced PBMCs was evident mainly at low concentrations of IL-2. Together, these data indicate that p12(I) may confer a proliferative advantage on HTLV-1-infected cells in the presence of suboptimal antigen stimulation and that this event may account for the clonal proliferation of infected T cells in vivo. (Blood. 2001;98:823-829)

Cell Culture Techniques↗
PubMed2001

Controlled-release of IGF-I and TGF-beta1 in a photopolymerizing hydrogel for cartilage tissue engineering.

Photopolymerizing hydrogel systems provide a method to encapsulate cells and implant materials in a minimally invasive manner. Controlled release of growth factors in the hydrogels may enhance the ability to engineer tissues. IGF-I and TGF-beta1 were loaded in PLGA microspheres using a double emulsion technique. 125 ng and 200 pg of active IGF-I and TGF-beta, respectively, as measured by ELISA, were released over 15 days. The growth factor containing microspheres were photoencapsulated with bovine articular chondrocytes in PEO-based hydrogels and incubated in vitro for two weeks. Statistically significant changes in glycosaminoglycan (GAG) production compared to control gels either without microspheres or with blank spheres were observed after a 14 day incubation with IGF-I and IGF-I/TGF-beta microspheres combined, with a maximum density of 8.41+/-2.5% wet weight GAG. Total collagen density was low and decreased with the IGF-I/TGF-beta microspheres after two weeks incubation, but otherwise remained unchanged in all other experimental groups. Cell content increased 10-fold to 0.18+/-0.056 x 10(6) cells/mg wet weight and extracellular matrix (ECM) staining by H&E increased in hydrogels with IGF-I/TGF-beta microspheres. In conclusion, photoencapsulation of microspheres in PEO-based hydrogels provides a method to deliver molecules such as growth factors in porous hydrogel systems.

Animals↗
PubMed2000

Common toxicity criteria: version 2.0. an improved reference for grading the acute effects of cancer treatment: impact on radiotherapy.

In 1997, the National Cancer Institute (NCI) led an effort to revise and expand the Common Toxicity Criteria (CTC) with the goal of integrating systemic agent, radiation, and surgical criteria into a comprehensive and standardized system. Representatives from the Radiation Therapy Oncology Group (RTOG) participated in this process in an effort to improve acute radiation related criteria and to achieve better clarity and consistency among modalities. CTC v. 2.0 replaces the previous NCI CTC and the RTOG Acute Radiation Morbidity Scoring Criteria and includes more than 260 individual adverse events with more than 100 of these applicable to acute radiation effects. One of the advantages of the revised criteria for radiation oncology is the opportunity to grade acute radiation effects not adequately captured under the previous RTOG system. A pilot study conducted by the RTOG indicated the new criteria are indeed more comprehensive and were preferred by research associates. CTC v. 2.0 represents an improvement in the evaluation and grading of acute toxicity for all modalities.

Antineoplastic Agents↗
PubMed2000

Visual evidence of acidic environment within degrading poly(lactic-co-glycolic acid) (PLGA) microspheres.

PURPOSE: In the past decade, biodegradable polymers have become the materials of choice for a variety of biomaterials applications. In particular, poly(lactic-co-glycolic acid) (PLGA) microspheres have been extensively studied for controlled-release drug delivery. However, degradation of the polymer generates acidic monomers, and acidification of the inner polymer environment is a central issue in the development of these devices for drug delivery. METHODS: To quantitatively determine the intrapolymer acidity, we entrapped pH-sensitive fluorescent dyes (conjugated to 10,000 Da dextrans) within the microspheres and imaged them with confocal fluorescence microscopy. The technique allows visualization of the spatial and temporal distribution of pH within the degrading microspheres (1). RESULTS: Our experiments show the formation of a very acidic environment within the particles with the minimum pH as low as 1.5. CONCLUSIONS: The images show a pH gradient, with the most acidic environment at the center of the spheres and higher pH near the edges, which is characteristic of diffusion-controlled release of the acidic degradation products.

Drug Delivery Systems↗
PubMed2000

An unusual multiple drug intoxication case involving citalopram.

A 47-year-old male with a history of drug abuse and suicide attempts was found dead at home. The death scene investigation showed evidence of cocaine abuse and multiple drug ingestion. Citralopram, a new selective serotonin reuptake inhibitor, cocaine, oxycodone, promethazine, propoxyphene, and norpropoxyphene were identified and quantitated in the postmortem samples by gas chromatography-mass spectrometry. The concentration of citalopram in the femoral blood was 0.88 mg/L. The heart blood concentration was 1.16 mg/L. Femoral blood concentrations of the other drugs were as follows: cocaine, 0.03 mg/L; oxycodone, 0.06 mg/L; promethazine, 0.02 mg/L; propoxyphene, 0.02 mg/L; and norpropoxyphene, 0.07 mg/L. Other tissue samples were also analyzed. The concentrations of cocaine, oxycodone, promethazine, and propoxyphene in the blood, liver, brain, and gastric contents did not suggest an intentional overdose. However, the possibility of multiple drug interactions including citalopram was evident. In this case, the citalopram concentrations were consistent with those reported in fatal cases involving multiple drug use. Citalopram was present in urine at a concentration of 0.9 mg/L.

Antidepressive Agents, Second-Generation↗
PubMed2000

Pharmacokinetics of argatroban in primates: evidence on endogenous uptake.

BACKGROUND: Antithrombin agent, argatroban, is currently undergoing several clinical trials for cardiovascular indications. Because of its solubility, this drug is usually administered via an intravenous bolus followed by infusion. The purpose of this study was to determine the pharmacokinetics of argatroban after intravenous bolus injection in primates. METHODS: Parallel in vitro studies in primate whole blood were carried out to simulate a one-compartment system. Argatroban (range 1.0-7.5 mg/kg) was administered to four groups of primates and blood samples were drawn at various time periods. Argatroban measurements were made in plasma using functional (aPTT, Heptest, TT) and HPLC methods. RESULTS: In vitro, argatroban primarily distributed in the plasma in proportionate amounts. Relative uptake of argatroban to the blood cells (leukocytes and erythrocytes) was minimum. However, in vivo, argatroban followed a complex pharmacokinetics. Within 5 min after the bolus administration, only <20% of argatroban was recovered. The recovered amount was proportionate to the dosage and followed the expected kinetics with a half-life of <20 min. Simultaneous quantitation of M1-metabolite of argatroban revealed only a fraction of recovered argatroban (approximately 25%) converted into M1 in these experimental settings. Results obtained from the functional and absolute methods correlated well. HPLC profile did not reveal the presence of any other metabolite(s). CONCLUSIONS: These observations suggest that argatroban may be endogenously taken up by the vascular or other sites and may exhibit a complex kinetics. In acute settings, the metabolic transformation of argatroban to M1 is relatively low. To further clarify the pharmacokinetics/pharmacodynamics of this drug, additional studies are warranted.

Animals↗
PubMed1999

Laboratory monitoring of pentasaccharide in a dog model of hemodialysis.

Varying dosages of pentasaccharide (400-800 nmol/kg) were compared to a 250-U/kg single bolus dosage of unfractionated heparin (UFH) in a dog model of hemodialysis. Several laboratory assays were used to monitor the effects of pentasaccharide and UFH. The pentasaccharide did not produce any anticoagulant effects as measured by the activated partial thromboplastin time. However, in the anti-Xa chromogenic assay and the Heptest assays, there was a dose-dependent prolongation after pentasaccharide administration. In the group of dogs administered 800 nmol/kg of pentasaccharide, there was a 50% decrease in the thrombin antithrombin (TAT) complex level after 60 minutes on dialysis. In the UFH-treated dogs, wide variations in assays were observed. There was a marked elevation in the activated partial thromboplastin time and Heptest assays up to 6 hours after UFH administration. Both anti-Xa and anti-IIa activity was measured up to 4 hours. In the TAT assay, UFH was found to have a stronger effect in suppressing the formation of TAT in comparison to the pentasaccharide. These results suggest that pentasaccharide can be used as a replacement for UFH in a dog model of hemodialysis to keep the dialysis circuit patent. In addition, the anti-Xa-based assays such as the Heptest and the chromogenic anti-Xa assays can be used to monitor the effects of pentasaccharide in this model.

Animals↗
PubMed1999

FTIR characterization of the secondary structure of proteins encapsulated within PLGA microspheres.

A commonly used technique for protein encapsulation in microspheres is the double-emulsion method wherein an initial water-in-oil (w/o) emulsion of protein and polymer is formed via sonication, and then a second emulsion (w/o)/w is formed by dispersion in an aqueous phase via homogenization. This approach is often used to produce microspheres of biodegradable poly(lactic-co-glycolic acid) (PLGA). The harsh processing associated with this method can cause denaturation of the encapsulated protein. Herein, we have used Fourier transform infrared (FTIR) spectroscopy to determine the secondary structures of two model proteins, bovine serum albumin (BSA) and chicken egg-white lysozyme, within PLGA microspheres. The alpha-helix content of both proteins in the microspheres was about a third lower than in the lyophilized state, indicating conformational changes upon protein entrapment within the microspheres. BSA microspheres containing the stabilizing excipient trehalose have a higher alpha-helix content than those without excipient, suggesting that trehalose partially prevents the denaturing effects incurred during processing. In addition, BSA released from microspheres is improved by incorporation of trehalose: analysis of the protein released from the microspheres indicates that there is less BSA dimer formation in the trehalose-containing microspheres than in those without trehalose.

Animals↗
PubMed1999

Endogenous salivary inhibitors of human immunodeficiency virus.

The human immunodeficiency virus type 1 (HIV-1) is rarely transmitted through salivary secretions, due in part to the presence of endogenous inhibitors. Here, the protective characteristics of the intraoral environment are summarized and inhibitory factors that reduce HIV-1 infectivity in vitro described, focusing on secretory leucocyte protease inhibitor (SLPI), a 12-kDa mucosal protein that blocks HIV infection in several cell-culture systems. SLPI appears to interact with a cellular surface molecule to limit viral entry into target cells. To determine whether the inhibitor has a similar role in vivo, the contribution of salivary SLPI to anti-HIV-1 activity was assessed. Whole unstimulated filtered salivas from infected and uninfected donors contained similar concentrations of the inhibitor. Depletion from SLPI filtered saliva produced a corresponding loss of inhibitory activity. In general, filtered whole salivas obtained from 10 donors had antiviral activities that correlated positively with SLPI concentrations. However, some samples having SLPI well below the concentration required for inhibitory activity in vitro exhibited modest inhibition, suggesting the presence of other anti-HIV-1 components in oral fluids. Thus, SLPI is a major but not sole inhibitor of this virus in saliva.

Anti-Infective Agents↗
PubMed1999

Effects of an N-type calcium channel antagonist (SNX 111; Ziconotide) on calcium-45 accumulation following fluid-percussion injury.

Accumulation of calcium following experimental traumatic brain injury (TBI) has been demonstrated to be a prominent pathophysiological component that can compromise mitochondrial functioning and threaten cell survival. The omega-conopeptide SNX-111, also known as Ziconotide, is a potent antagonist of the voltage-gated N-type calcium channel and has demonstrated significant neuroprotective effects against ischemia-induced neuronal injury. To determine whether this compound would be effective in reducing calcium accumulation associated with TBI, SNX-111 was administered intravenously to rats 1 hour following a moderate (2.2 to 2.75 atm) lateral fluid-percussion injury (or sham) at doses of 1 (n = 30), 3 (n = 31), or 5 (n = 30) mg/kg; another group received 0.9% saline solution (n = 35). Brains were processed for calcium 45 (45Ca) autoradiography at 6, 12, 24, 48, and 96 hours following insult. Optical density measurements of 20 cortical and subcortical regions were analyzed. Injured animals administered saline solution exhibited a significant increase in 45Ca uptake within 12 regions ipsilateral to the site of injury. The most prominent increases were evident throughout the ipsilateral cerebral cortex. SNX-111 reduced the injury-induced calcium accumulation within the ipsilateral cortex in a dose-response fashion when measured at 6, 12, and 48 hours after insult. These drug-induced reductions in calcium accumulation were as high as 75% in the ipsilateral cerebral cortex, and up to 50% in other ipsilateral regions (including thalamus and hippocampus). Consequently, the results suggest that posttraumatic blocking of the voltage-gated N-type calcium channel after injury reduces prolonged, trauma-induced calcium accumulation.

Animals↗
PubMed1999

Gene shifting: a novel therapy for mitochondrial myopathy.

Mutations in mitochondrial DNA (mtDNA) are the most frequent causes of mitochondrial myopathy in adults. In the majority of cases mutant and wild-type mtDNAs coexist, a condition referred to as mtDNA heteroplasmy; however, the relative frequency of each species varies widely in different cells and tissues. Nearly complete segregation of mutant and wild-type mtDNAs has been observed in the skeletal muscle of many patients. In such patients mutant mtDNAs pre-dominate in mature myofibers but are rare or undetectable in skeletal muscle satellite cells cultured in vitro. This pattern is thought to result from positive selection for the mutant mtDNA in post-mitotic myofibers and loss of the mutant by genetic drift in satellite cells. Satellite cells are dormant myoblasts that can be stimulated to re-enter the cell cycle and fuse with existing myofibers in response to signals for muscle growth or repair. We tested whether we could normalize the mtDNA genotype in mature myofibers in a patient with mitochondrial myopathy by enhancing the incorporation of satellite cells through regeneration following injury or muscle hypertrophy, induced by either eccentric or concentric resistance exercise training. We show a remarkable increase in the ratio of wild-type to mutant mtDNAs, in the proportion of muscle fibers with normal respiratory chain activity and in muscle fiber cross-sectional area after a short period of concentric exercise training. These data show that it is possible to reverse the molecular events that led to expression of metabolic myopathy and demonstrate the effectiveness of this form of 'gene shifting' therapy.

Creatine Kinase↗
PubMed1999

Preclinical biochemistry and pharmacology of low molecular weight heparins in vivo--studies of venous and arterial thrombosis.

Low molecular weight heparins (LMWHs) are effective agents in both venous and arterial thrombosis. Extensive preclinical studies in various animal models show that there are substantial differences in antithrombotic efficacy between LMWHs, and that the relative efficacy of individual agents depends on the thrombogenic stimulus used. Relative efficacy cannot be predicted on the basis of molecular weight, nor on the basis of anti-factor Xa or anti-factor IIa potency. This suggests that other mechanisms of action, e.g., the release of tissue factor pathway inhibitor (which differs among the LMWHs), are important. Data obtained with a specific LMWH cannot be extrapolated to other compounds within the same class and their substitution in the clinical setting is, therefore, inappropriate.

Animals↗
PubMed1999

Pharmacokinetics of low molecular weight heparins in animal models.

Low molecular weight heparins (LMWHs) are a diverse group of depolymerized heparin preparations with molecular weights ranging from 1800 to 12,000 Da. Due to manufacturing differences, there are marked structural variations between LMWHs that exhibit distinct pharmacologic and biochemical profiles. Pharmacokinetic studies generally use indirect pharmacodynamic measures, particularly anti-Xa activity. Animal models have shown considerable variation between preparations in anti-Xa activity and other pharmacodynamic measures, including bioavailability and release of tissue factor pathway inhibitor (TFPI). Each LMWH has a specific, assay-dependent pharmacokinetic profile, reinforcing the concept that each LMWH is a distinct, noninterchangeable, pharmaceutical product.

Animals↗
PubMed1999

[Pathologic study on synovial fluid after intra-articular corticosteroid therapy in temporomandibular joint disorders].

OBJECTIVE: To study what happens after intra-articular injection of corticosteroid. METHODS: Synovial fluid after intra-articular corticosteroid therapy in temporomandibular joint disorders (TMD) was studied by hematoxylin-eosin, PAS, and Atcian blue staining. RESULTS: The results were that broken synovial membrane and articular cartilage, lots of synovial lining cells, macrophagocytes, inflammatory cells and free cartilage matrix could be found in the lavage fluid. CONCLUSION: The results suggest that drug synovectomy may be one mechanism about intra-articular corticosteroid therapy in TMD, and this therapy could lead to progressive degradation and destruction of the articular cartilage. Arthrocentesis and lavage are needed three to five days after this therapy.

Adolescent↗