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At least 631 records · Page 35Linked to original sources
PubMed2001

Conditionally immortalized cell lines as a new in vitro model for the study of barrier functions.

Conditionally immortalized brain and retinal capillary endothelial and choroid plexus epithelial cell lines were established from a transgenic rat (Tg rat) and mouse (Tg mouse) harboring the temperature-sensitive simian virus 40 (ts SV 40) large T-antigen. These cell lines exhibit temperature-sensitive cell growth due to the expression of ts SV 40 large T-antigen. Mouse brain (TM-BBB) and rat brain (TR-BBB) and rat retinal (TR-iBRB) capillary endothelial cell lines appear to have a spindle-fiber shaped morphology and exhibit the typical endothelial markers, such as von Willebrand factor and acetylated low-density lipoprotein uptake. These cell lines express in vivo influx and efflux transporters, such as P-glycoprotein (P-gp) and GLUT1, which is capable of 3-O-methyl-D-glucose transport. TM-BBB cells are able to undergo efflux transport of cyclosporin A, which is a substrate for P-gp transport activity. They may also express oatp2 and exhibit dehydroepiandrosterone sulfate and digoxin uptake activity. TR-BBB cells express the mRNA of multidrug resistance associated protein 1 (MRP1) and a large neutral amino acid transporter, which consists of LAT1 and 4F2hc. TR-iBRB cells exhibit pH-dependent L-lactic acid transport activity and express the mRNA of monocarboxylate transporter (MCT) 1 and 2. The choroid plexus epithelial cell line (TR-CSFB) has polygonal cell morphology, expresses the typical choroid plexus epithelial cell marker, transthyretin, and has Na+, K+-ATPase located on the apical side. TR-CSFB cells also exhibit amino acid transport activity which has been observed in vivo. These barrier cell lines established from the Tg rat and Tg mouse have in vivo transport functions and are good in vitro models for drug transport to the brain and retina and as a screen for drugs which might be capable of delivery to the brain and retina.

Animals↗
PubMed2001

The human macrophage cell line U937 as an in vitro model for selective evaluation of mycobacterial antigen-specific cytotoxic T-cell function.

Despite strong evidence for CD8+ T-cell function in murine mycobacterial infections, their corresponding role in human tuberculosis has proven more difficult to demonstrate. We have evaluated the human macrophage (Mphi) cell line U937 as an in vitro model for human leucocyte antigen (HLA) class I-restricted presentation of mycobacterial antigens, as HLA class I is constitutively expressed at high levels by U937 cells in the absence of detectable HLA class II or CD1 molecules. U937 cells were evaluated for their ability to phagocytose Mycobacterium tuberculosis and for their ability to present mycobacterial antigens to human HLA class I-matched cytotoxic T lymphocytes (CTLs). Differentiated U937 cells were capable of efficient phagocytosis of M. tuberculosis but did not generate a subsequent respiratory burst response, and were permissive for intracellular growth of both bacillus Calmette-Guérin (BCG) and the virulent M. tuberculosis H37Rv strain. CTL activity was restricted to live mycobacterial organisms and was shown to be mediated by M. tuberculosis-specific, HLA class I-matched, purified CD8+ CTL lines and CD8+ T-cell clones. Furthermore, M. tuberculosis-infected U937 targets were more rapidly and strongly lysed by CD8+ CTLs than were infected autologous Mphi. Finally, M. tuberculosis-infected U937 cells simultaneously provided a sensitive indicator for detection of mycobacterial-specific, HLA-unrestricted gammadelta+ CTL activity.

Antigen-Presenting Cells↗
PubMed1988

In vitro models for testing the metabolic effects of myelographic contrast media.

Water-soluble nonionic x-ray contrast media have greatly improved the quality and safety of myelography. Toxic side effects are still observed however. The side effects are generally worse with the first nonionic agent, metrizamide, which has a glucoselike side group. Two in vitro models were developed to examine the effects of contrast media on glucose metabolism. Using rat hippocampus slices, the authors observed significant depression of carbon dioxide production by metrizamide and by deoxyglucose, a known metabolic inhibitor. Iohexol and iopamidol did not cause significant depressions. In rat brain synaptosomes the authors did not observe a depression of the uptake of deoxyglucose 14C by any media tested. These studies indicate that metrizamide can create metabolic depression but that it does not compete with glucose for the membrane glucose carrier.

Animals↗
PubMed2004

An in vitro model based on cell monolayers grown on the underside of large- pore filters in bicameral chambers for studying thyrocyte-lymphocyte interactions.

In the processes underlying thyroid autoimmunity, thyrocytes probably act as antigen-presenting cells exposing T-cell epitopes to intrathyroid lymphocytes. To study the interactions between lymphocytes and thyrocytes, which are arranged in a tight, polarized monolayer, we developed a new in vitro model based on human thyrocytes grown on the underside of a filter placed in a bicameral chamber. Thyrocytes from Graves' disease glands were plated onto the upper face of a 8-mum-pore polyethylene terephthalate culture insert filter placed in the inverted position and grown for 24 h before the insert was returned to the normal position for a week in the cell culture plate wells. Thyrocytes grown in the presence of thyroid stimulating hormone, forming a homogeneous monolayer on the underside of the filter, reached confluence after 8 days in vitro. The cells developed a transepithelial electrical resistance >1,000 Omega.cm(2), and the ZO-1 tight junction protein showed a junctional pattern of distribution. Thyrocytes showed a polarized pattern of thyroperoxidase and thyroid stimulating hormone receptor expression in the apical and basolateral positions, respectively. They were also found to aberrantly express DR class II human leukocyte antigen and an Fc immunoglobulin receptor (FcgammaRIIB2) in the basolateral and apical positions, respectively. Autologous intrathyroidal T lymphocytes cocultured for 24 h across the filter with the thyrocyte monolayer proliferated and remained in the upper chamber without any leakage occurring through the epithelial barrier, which makes this model particularly suitable for studying the cell-cell interactions involved in antigen processing.

Cell Communication↗
PubMed2006

Pharmacodynamic activity of ertapenem versus penicillin-susceptible and penicillin-non-susceptible Streptococcus pneumoniae using an in vitro model.

BACKGROUND: Ertapenem is a novel carbapenem with activity against both penicillin-susceptible (MIC < or = 0.06 mg/L) and penicillin-non-susceptible (MIC > or = 0.12 mg/L) Streptococcus pneumoniae. This study assessed the pharmacodynamic activity of ertapenem against penicillin-susceptible and penicillin-non-susceptible S. pneumoniae using an in vitro pharmacodynamic model. METHODS: Fifteen S. pneumoniae strains including 3 penicillin-susceptible and 12 penicillin-non-susceptible [4 penicillin-intermediate (MIC 0.12-1 mg/L) and 8 penicillin-resistant (MIC > or = 2 mg/L); with different resistance phenotypes including erythromycin-resistant (MIC > or = 1 mg/L), ciprofloxacin-resistant (MIC > or = 4 mg/L) and doxycycline-resistant (MIC > or = 8 mg/L)] were studied. The in vitro pharmacodynamic model was inoculated with 1 x 10(6) cfu/mL and ertapenem was dosed once daily at 0 and 24 h to simulate f (free) Cmax and t(1/2) obtained after a standard 1 g intravenous once daily dose in healthy volunteers (fCmax 15 mg/L, t(1/2) 4 h). Sampling was performed for 48 h to assess viable growth. RESULTS: Ertapenem T(> MIC) > or = 80% (ertapenem MICs < or = 0.5 mg/L) resulted in bactericidal (> or = 3 log10 killing) activity at 12, 24 and 48 h with complete eradication of penicillin-susceptible and penicillin-non-susceptible S. pneumoniae from the model with no regrowth over the 48 h study period. Ertapenem T(> MIC) < or = 63% (ertapenem MIC > or = 1 mg/L) resulted in bactericidal activity at 12 h with regrowth at 24 and 48 h. The observed MICs for S. pneumoniae of ertapenem studied in the in vitro model did not change during the 48 h period, even for strains where regrowth occurred. CONCLUSIONS: Ertapenem is bactericidal against both penicillin-susceptible and penicillin-non-susceptible S. pneumoniae (ertapenem MICs < or = 0.5 mg/L) when simulating free drug after 1 g intravenous once daily dosing.

Anti-Bacterial Agents↗
PubMed1992

Use of in vitro models of bovine corneal endothelial cells to determine the relative toxicity of viscoelastic agents.

Healon, Viscoat and Amvisc Plus (Amvisc+) are commercial preparations containing hyaluronic acids of different molecular weights and viscosities. Cytotoxicity of these preparations to the corneal endothelium may be a factor in postsurgical recovery of the cornea. Using different in vitro models of bovine corneal endothelial cells (BCEC), three experiments to compare the possible detrimental effects of these viscoelastic agents were designed. In the confluent model, confluent BCEC were exposed to viscoelastic agents and the control to Balanced Salt Solution Plus (BSS+) for one hour and the nuclear density (nuclei/mm2) was assessed at 24 and 168 hours. At both times, the BCEC exposed to Healon showed the highest nuclear densities. In the preconfluent model, BCEC were treated for one hour at 48 hours post-seeding. The nuclear density of the BCEC was assessed at 24 hours. The BCEC exposed to Healon showed the highest density, followed by those exposed to Amvisc+ and then Viscoat. In the proliferation model, BCEC were cultured in media containing 1%, 5%, and 10% viscoelastic agents. The growth curves based on nuclear densities at 0, 24, 72, 120, and 168 hours in all treatment groups did not differ significantly from the control. The results indicate that the undiluted Healon was significantly less toxic in the preconfluent and confluent BCEC models.

Analysis of Variance↗
PubMed1974

An in vitro model of gluten-sensitive enteropathy. Effect of gliadin on intestinal epithelial cells of patients with gluten-sensitive enteropathy in organ culture.

Jejunal biopsy specimens from patients with gluten-sensitive enteropathy (GSE) (obtained during gluten challenge) as well as from normal individuals and patients with other gastrointestinal abnormalities were cultured in vitro for 48 h in the presence or absence of a peptic-tryptic digest (P-T digest) of gliadin. In the absence of gliadin the alkaline phosphatase activity in the biopsy specimens obtained from normal control individuals increased from an initial value of 384 +/- 83 U to a 48 h value of 561 +/- 151 U (mean +/- SD) (difference significant at P < 0.01). The initial alkaline phosphatase activity of specimens obtained from patients with GSE was strikingly lower than that of normals, 117 +/- 79 U, and increased to a 48 h value of 399 +/- 203 U (difference significant at P < 0.01). The biochemical change in cultured biopsy specimens of GSE patients correlated with increases in the length and regularity of brush borders of epithelial cells as seen with the electron microscope. In the presence of a P-T digest of gliadin, the alkaline phosphatase activity of biopsy specimens of control individuals increased from an initial value of 384 +/- 83 U to a 48 h value of 578 +/- 156 U. In contrast, the alkaline phosphatase activity of biopsy specimens of patients with GSE in exacerbation showed a markedly diminished increase in activity during 48 h of culture; in this case the initial activity was 117 +/- 79 U and the final activity was 203 +/- 93 U. This inhibitory effect on increase of alkaline phosphatase activity during organ culture was specific in that a P-T digest of casein (a protein not toxic in vivo to patients with GSE) had no effect on alkaline phosphatase increases in culture. Finally, these results obtained with biopsy specimens taken from patients with GSE in exacerbation were compared with results obtained from patients with GSE in remission. Alkaline phosphatase activity of specimens obtained from the latter group of patients also increased during culture but in this instance P-T digest of gliadin in the culture medium had no significant inhibitory effect. In conclusion, the inhibitory effect of gliadin on intestinal epithelial cells in organ culture represents an in vitro model of gluten-sensitive enteropathy. Inasmuch as this effect of gliadin is not seen in cultures of specimens taken from patients in remission, it appears that gliadin is not directly toxic to GSE jejunal mucosa per se, but rather toxicity requires the participation of an endogenous effector mechanism which must first be stimulated in vivo.

Adolescent↗
PubMed1996

Tantalum stents induce expression of GMP140 and GP53 on platelets after contact in an in vitro model.

Endovascular implantation of stents has become increasingly important to reduce acute complications and restenosis after percutaneous transluminal coronary angioplasty (PTCA). Nevertheless, the risk of stent related thrombosis still appears to be a limitation in this therapeutic approach. As platelets play a major role in thrombus formation, we examined platelets in an in vitro model by flow cytometry to assess the expression of activation-dependent epitopes caused by shear stress and contact to artificial surfaces of stents. Tantalum wire stents (n = 12) were placed in one of two parallel silicon tubing systems. Both systems were filled with citrated platelet-rich plasma (PRP) of healthy and drug-free volunteers. After recalcification, aliquots of PRP were drawn via a three-way faucet over a course of 10 min. For flow cytometric analysis monoclonal antibodies CD41a, CD42b, CD62p and CD63 were applied. Within 2 min after onset, the expression of CD62p (GMP140) and CD63 (GP53) increased in the tubing system with the stent. Over the course of 10 min, platelet activation progressively increased (CD62p p < 0.05 vs. control system without stent; CD63 p < 0.005 vs. control). Antigens CD41 a and CD42b did not show significant changes in both systems. Artificial surfaces and shear forces of stent meshes may contribute to the activation of platelets, thereby promoting the thrombotic potential. As an utmost sensitive diagnostic tool, flow cytometry may attribute to further improvement of material and design of stents.

Angioplasty, Balloon, Coronary↗
PubMed1997

A role for epidermal growth factor receptor, c-Src and focal adhesion kinase in an in vitro model for the progression of colon cancer.

We have examined the function of the epidermal growth factor (EGF) receptor, c-Src and focal adhesion kinase (FAK) in the progression of colon cancer using an in vitro progression model. A non-tumorigenic cell line was derived from a premalignant colonic adenoma (PC/AA) from which a clonogenic variant was established (AA/C1). Following sequential treatment with sodium butyrate and the carcinogen N-methyl-N'-nitro-N-nitro-soguanidine an anchorage-independent line was isolated which, with time in culture, became tumorigenic when injected into athymic nude mice (AA/C1/SB10). We have shown that both EGF receptor and FAK protein levels were elevated in the carcinoma cells as compared to the adenoma cells, while the expression and activity of c-Src were unaltered during the adenoma to carcinoma transition. EGF induced the movement of the carcinoma cells into a reconstituted basement membrane which was not seen with the premalignant adenoma cells. This increased motility was accompanied by an EGF-induced increase in c-Src kinase activity, relocalisation of c-Src to the cell periphery and phosphorylation of FAK in the carcinoma cells but not in the adenoma cells. This suggests that c-Src plays a role in the biological behaviour of colonic carcinoma cells induced by migratory factors such as EGF, perhaps acting in conjunction with FAK to regulate focal adhesion turnover and tumour cell motility. Furthermore, although c-Src has been implicated in colonic tumour progression, we demonstrate here that in the adenoma to carcinoma in vitro model c-Src is not the driving force for this progression but co-operates with other molecules in carcinoma development.

Adenoma↗
PubMed1975

Effect of bile acids on electrical properties of rat colon: evaluation of an in-vitro model for secretion.

A preparation of rat colon mucosa has been evaluated as a useful model to study effects of bile acids on the changes in short-circuit current and transmural electrical potential difference (pd) which others have associated with alterations in electrolyte transport. Using this preparation, it was found that bile acids were effective in increasing short-circuit current and pd when applied to the serosal, but not the mucosal, surface of the tissue. Furthermore, taurine-conjugated cholic acid, which has no demonstrable effect on the colon in vivo, was found to increase short-circuit current and pd significantly in the in-vitro preparation. These data indicate the limitations of the in-vitro model in studying the mechanism of bile acid-stimulated intestinal secretion.

Animals↗
PubMed2006

Heparan sulfate plays a central role in a dynamic in vitro model of protein-losing enteropathy.

Protein-losing enteropathy (PLE), the loss of plasma proteins through the intestine, is a symptom in ostensibly unrelated diseases. Emerging commonalities indicate that genetic insufficiencies predispose for PLE and environmental insults, e.g. viral infections and inflammation, trigger PLE onset. The specific loss of heparan sulfate (HS) from the basolateral surface of intestinal epithelial cells only during episodes of PLE suggests a possible mechanistic link. In the first tissue culture model of PLE using a monolayer of intestinal epithelial HT29 cells, we proved that HS loss directly causes protein leakage and amplifies the effects of the proinflammatory cytokine tumor necrosis factor alpha (TNFalpha). Here, we extend our in vitro model to assess the individual and combined effects of HS loss, interferon gamma (IFNgamma), TNFalpha, and increased pressure, and find that HS plays a central role in the patho-mechanisms underlying PLE. Increased pressure, mimicking venous hypertension seen in post-Fontan PLE patients, substantially increased protein leakage, but HS loss, IFNgamma, or TNFalpha alone had only minor effects. However, IFNgamma up-regulated TNFR1 expression and amplified TNFalpha-induced protein leakage. IFNgamma and TNFalpha compromised the integrity of the HT29 monolayer and made it more susceptible to increased pressure. HS loss itself compromises the integrity of the monolayer, amplifying the effects of pressure, but also amplifies the effects of both cytokines. In the absence of HS a combination of increased pressure, IFNgamma, and TNFalpha caused maximum protein leakage. Soluble heparin fully compensated for HS loss, providing a reasonable explanation for patient favorable response to heparin therapy.

Albumins↗
PubMed1993

Human saphenous vein in vitro model for studying the action of sclerosing solutions.

BACKGROUND: Previous studies detailing the clinical and histologic effects of sclerosing solutions in rabbit ear and other animal vein models have provided information comparing the effects of various concentrations of hypertonic saline with and without dextrose (Sclerodex), polidocanol, scleremo (chromated glycerin), and sodium tetradecyl sulfate. OBJECTIVE: To observe short-term histologic changes of sclerosing solutions in vitro in large diameter human vein. METHODS: Human saphenous vein segments were obtained following cardiac bypass procedures. Several types of sclerosing solutions, including 23.4% hypertonic saline, 1% polidocanol, and 3% sodium tetradecyl sulfate, were allowed continuous contact with the vessel wall for 10 minutes. Test vein segments were immediately fixed and observed for histologic changes compared with normal saline controls. RESULTS: Endothelium was rapidly destroyed by all tested sclerosing solutions. Vessel wall necrosis occurred quickly with the extent determined by the sclerosing solution. Destructive potential of 3% sodium tetradecyl sulfate greatly exceeded that of 23.4% hypertonic saline or 1% polidocanol, in agreement with previous animal studies. CONCLUSION: Direct toxic effects of sclerosing agents may be compared in a constant, reproducible environment with this in vitro model.

Endothelium, Vascular↗
PubMed1998

An in vitro model for acoustic overstimulation.

Although many studies have been performed on the effects of acoustic overstimulation on the inner ear, our knowledge about the cellular processes underlying reduced hearing sensitivity and auditory cell death is still limited. In order to further our understanding of cellular processes occurring in conjunction with acoustic trauma, we designed an in vitro model to study the effects of overstimulation directly on sensory hair cells isolated from the low-frequency part of the guinea pig cochlea. The isolated outer hair cells were subjected to pressure jets delivered by a glass micropipette positioned close to the cell, in order to mimic the pressure changes occurring in the intact inner ear during sound stimulation. A second micropipette coupled to a piezoresistive pressure transducer was used as a probe measuring the pressure at precise locations at and around the cell. In a previous study, we found that such stimulation gave rise to increases in the intracellular calcium concentration. The present study characterizes the stimulus, describes the computer-controlled setup used for calibration, and gives examples of different modes of overstimulation at the cellular level. The peak pressure that could be generated using the pressure jet was around 325 Pa, or 144 dB (re 20 microPa) at 140 Hz. The pressure jet elicited large mechanical vibrations of the cell bodies of isolated cells. The vibration mode of the cells often changed over time, implying that the stimulation caused changes of the cellular stiffness. However, most cells appeared quite resistant to the high intensity mechanical stimulation.

Acoustic Stimulation↗
PubMed1998

Hepatocyte growth factor and Madin-Darby canine kidney cells: in vitro models of epithelial cell movement and morphogenesis.

It is becoming increasingly apparent that epithelial cell movement and changes in morphology are central to both development and regeneration of epithelial organs and are involved with pathological processes such as transformation of epithelia to carcinoma and metastasis. Hepatocyte growth factor (HGF) is a mesenchymally derived growth factor with pleiotrophic effects on epithelia depending on culture conditions. In vivo, HGF plays a role in mesenchymal-epithelial interactions. Madin-Darby canine kidney (MDCK) cells, which share many properties with polarized epithelia in vivo, are remarkably sensitive to HGF. In vitro models of HGF-treated MDCK cells have proven to be useful for the study of epithelial cell movement and changes in morphology. When cultured on plastic at low density, MDCK cells scatter in response to HGF. MDCK cells grown as cell suspensions in collagen gels form complex branching tubular structures in response to HGF. When cultivated as a monolayer on permeant supports, MDCK cells are well polarized with established E-cadherin mediated cell-cell junctions and dedifferentiate in response to HGF. Some of the mechanisms responsible for changes in cell movement and morphology that have been characterized using these models are summarized in this review. Models of MDCK cells exposed to HGF will continue to be useful in the study of epithelial cell movement and morphogenesis in vitro and will provide important clues into the cellular mechanisms important during in vivo epithelial processes such as organ development, regeneration, and transformation to carcinoma.

Animals↗
PubMed1988

Effect of dose and schedule on cefoperazone pharmacodynamics in an in vitro model of infection in a neutropenic host.

Previous studies have shown that cefoperazone given in frequent, large doses is effective in the treatment of infection in patients with cancer. The pharmacodynamics of 2- and 4-g doses of cefoperazone administered either as a single dose or at 12-hour intervals were studied in an in vitro model that simulates infection in a neutropenic patient. One strain each of Pseudomonas aeruginosa (minimal inhibitory concentration [MIC] = 2 micrograms/ml), Staphylococcus aureus (MIC = 1 microgram/ml), Escherichia coli (MIC = 0.06 micrograms/ml), and Klebsiella pneumoniae (MIC = 0.25 micrograms/ml) was studied. The initial dose reduced the inoculum by approximately 3 logs for the Pseudomonas and the staphylococci and 3 to 5 logs for the other organisms. No significant differences in killing were found between the 2- and 4-g doses. Regrowth of Pseudomonas and staphylococci occurred with the single dose but not with the every-12-hour regimen. These data support the clinical use of cefoperazone in doses every 12 hours.

Agranulocytosis↗
PubMed2004

Evaluation of effects of rofecoxib on platelet function in an in vitro model of thrombosis with circulating human blood.

BACKGROUND: Cyclooxygenase (COX)-2-selective non-steroidal anti-inflammatory drugs have been used for anti-inflammatory therapy. However, it has also been described that they may increase risk of cardiovascular events. OBJECTIVES: To study the effects of COX2 inhibitor rofecoxib on platelet function using in vitro tests. Results were compared with those obtained in a parallel experiment with acetyl salicylic acid (ASA). METHODS: Studies of platelet aggregation, using different agonists, were performed by a turbidimetric method. Adhesive and cohesive function of platelets were analyzed by perfusion techniques, treated blood was exposed to thrombogenic surfaces and platelet interaction was morphometrically evaluated. RESULTS: Twenty-five micro M of rofecoxib induced a prolonged lag time and a reduction in the percentage of aggregation when arachidonic acid, ADP or collagen were used as agonists. In perfusion studies with parallel chamber rofecoxib 50 microM and ASA 500 microM reduced overall platelet interaction with the collagen surface (17.4 +/- 3.7, P < 0.05; vs. 32.1 +/- 2.6%P < 0.05 and 17.9 +/- 2.4, vs. 31.9 +/- 3.24, P < 0.05, respectively). In studies performed on annular chambers, 25 micro M of rofecoxib reduced platelet interaction; values of the thrombus and covered surface were 17.4 +/- 4.5%; P < 0.05 and 21.1 +/- 4.1%; P < 0.05, respectively, vs. 30.4 +/- 7.5% and 33.5 +/- 6.5 in the control. ASA did also impair thrombus formation but differences did not reach the levels of statistical significance. Moreover, rofecoxib but not ASA reduced significantly thrombus height and thrombus area (7.4 +/- 0.5 microM; P < 0.005 and 96.0 +/- 21.2 microM(2); P < 0.05 vs. control 11.2 +/- 0.9 microM and 220.0 +/- 47.7 microM(2), respectively). CONCLUSION: We conclude that under our experimental conditions, rofecoxib diminished platelet aggregation induced by different agonists and inhibited platelet-mediated thrombogenesis in an in vitro model of thrombosis.

Adenosine Diphosphate↗
PubMed1994

Stimulation of monocyte tissue factor expression in an in vitro model of bacterial endocarditis.

The coagulation system plays a major role in the formation of the infected endocardial vegetation in bacterial endocarditis. Since monocytes can express tissue factor (TF) on their surfaces, they are thought to be responsible for the extrinsic activation of the coagulation cascade during this disease. The present study used an in vitro model in which fibrin plates, isolated adherent monocytes, and Streptococcus sanguis were used as an analog for endocardial vegetations. Adherence to fibrin by itself was found to stimulate TF expression on the monocytes, but stimulation by S. sanguis significantly increased TF expression, which was found to be maximal at a bacterium-to-monocyte ratio of 9 or more.

Blood Coagulation↗
PubMed2001

Evaluation of creatine transport using Caco-2 monolayers as an in vitro model for intestinal absorption.

Creatine is a nutraceutical that has gained popularity in both well-trained and casual athletes for its performance-enhancing or ergogenic properties. The major disadvantages of creatine monohydrate formulations are poor solubility and oral bioavailability. In the present study, creatine transport was examined using Caco-2 monolayers as an in vitro model for intestinal absorption. Confluent monolayers of Caco-2 cells (passage 25-35) were used for the permeability studies. Monolayers were placed in side-by-side diffusion chambers. (14)C-Creatine (0.1-0.5 microCi/mL) was added to either the apical or basolateral side, and the transport of the creatine across the Caco-2 monolayer was measured over a 90-min period. The apical to basolateral transport of (14)C-creatine was small, ranging from 0.2-3% of the original amount appearing on the receiver side in a 90-min period. Interestingly, the basolateral to apical permeability of radiolabeled creatine was substantially greater than that observed in the apical to basolateral direction. Studies with drug efflux transport inhibitors indicate that neither the P-glycoprotein nor multidrug resistance-associated protein is involved in the enhanced basolateral to apical transport of creatine.

Biological Transport, Active↗