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PubMedDate not supplied

Evaluation of some parameters influencing the drug delivery from a dry powder inhalation device using an in vitro model of the horse airways.

The aim of this study was to determine the effect of breathing pattern, air humidity and position of the device on the delivery of an aerosol generated by a dry powder inhalation (DPI) device (Inhalator M). The in vitro inhalation study was performed using the cascade impaction method (Andersen Sampler) adapted to imitate nasal breathing. The amount of ipratropium found in the device, the artificial upper airways and the six stages of the Andersen Sampler was measured using high precision liquid chromatography. Stage 1 of the Andersen Sampler was considered to be the respirable fraction and stages 2 to 6 to be the non-respirable fraction. It was concluded that the theoretical respirable fraction of ipratropium obtained after DPI through Inhalator M was influenced by relative air humidity, air flow and the position of the device, whereas the number of successive inspirations and the duration of inspiration did not affect this fraction of the drug.

Aerosols↗
PubMed1994

Comparative study of two in vitro models (L-929 fibroblasts and Tetrahymena pyriformis GL) for the cytotoxicological evaluation of packaged water.

The preservation of 234 samples of water packaged in polychloride vinyl (PVC), polyethylene terephthalate (PET) and glass-bottles was concurrently evaluated using both classical chemical analysis oriented to finding organic and inorganic substances which could have been leached by the packaging and in vitro toxicological bioassays using two models: the L-929 established cell line of fibroblasts and the ciliated protozoa Tetrahymena pyriformis GL. Although no significant abnormality was detected with the chemical analysis, cytotoxicity was detected with both models in some samples of water bottled for > 18 months, for either PVC, PET or glass-packaging. However, statistical analysis did not allow a mathematical relationship between the cytotoxic effects, the length of storage and the packaging to be demonstrated.

Animals↗
PubMed1978

[An in vitro model for the quantitative study of E. histolytica virulence].

An experimental model for the quantitative study of the cytopathic effect of E. histolytica is described. Confluent cultures of the MDCK cell line, which form a monolayer with morphological and electrophysiological features of an epithelium were used. Trophozoites of the strains HM1:IMSS, HM2:IMSS and HM3:IMSS, axenic produced variable degrees of cytopathic effects of MDCK cultures each one characteristic for a given strain. The degree of damage induced by the different strains of amebas was measured quantitatively. The results demonstrate that the degree of the cytopathic effect produced in vitro by the various strains tested correlates with the virulence shown in vivo by the same strains, judged as the size of the inoculum required to induce liver cytopathic effect in newborn hamsters.

Animals↗
PubMed1991

Cytotoxic effects of high energy shock waves in different in vitro models: influence of the experimental set-up.

High energy shock waves (electromagnetically generated, Siemens Lithostar) were studied for their effects in vitro on different (tumor) cell types. Cells were exposed to the shock waves as a single cell suspension or as a cell pellet on the bottom of a test tube. In both cases, a dose dependent direct cytotoxicity, established by trypan blue dye exclusion, was observed after treatment with 1000 or 2000 shock waves. Also, the antiproliferative capacity as determined by clonogenic potential (double layer soft agar) and growth rate (plastic) were affected in this way. However, comparing the results after treatment in suspension or pellet, a discrepancy was evident. The cell lines showed a different susceptibility in pellet vs. suspension. Also the differential sensitivity of the cell types varied in these two treatment models. Furthermore the outcome depended on the cell concentration; direct cytotoxicity in a cell suspension was more pronounced at higher cell concentrations, while in a pellet this was increased by decreasing the number of cells. Finally, no shock wave induced cytotoxicity could be seen after fixation of cells in gelatine or by placing the pellet on a bottom layer of gelatine. Pressure measurements revealed no adequate explanation for this phenomenon. These results indicate that in vitro effects depend on the way cells are exposed to the shock waves and can be greatly influenced by changing the conditions of the microenvironment. Therefore, precise descriptions of the experimental set-up and careful interpretations of their outcome are obligatory.

Carcinoma↗
PubMed2006

Growth of cortical neuronal network in vitro: modeling and analysis.

We present a detailed analysis and theoretical growth models to account for recent experimental data on the growth of cortical neuronal networks in vitro [Phys. Rev. Lett. 93, 088101 (2004)]. The experimentally observed synchronized firing frequency of a well-connected neuronal network is shown to be proportional to the mean network connectivity. The growth of the network is consistent with the model of an early enhanced growth of connection, but followed by a retarded growth once the synchronized cluster is formed. Microscopic models with dominant excluded volume interactions are consistent with the observed exponential decay of the mean connection probability as a function of the mean network connectivity. The biological implications of the growth model are also discussed.

Action Potentials↗
PubMed2003

Evaluation of an immortalized retinal endothelial cell line as an in vitro model for drug transport studies across the blood-retinal barrier.

PURPOSE: To evaluate the growth and barrier properties of an immortalized rat retinal endothelial cell line (TR-iBRB) maintained on permeable membrane for drug transport studies. METHODS: TR-iBRB cells were grown on permeable membrane filters. The effect of coating material on cell growth was investigated. Transport of [14C]-3-O-methyl-D-glucose (3-OMG), AGN 194716, AGN 195127, AGN 197075, acebutolol, alprenolol, atenolol, brimonidine, carbamazepine epoxide (CBZ-E), metoprolol, nadolol, rhodamine 123, and sotalol was measured across the cultured cell layer to determine the apparent permeability coefficients (Papp). Rhodamine 123 uptake into these cells in the presence of these test compounds was evaluated. Western blot was performed to detect the efflux transporter P-glycoprotein (P-gp). Bidirectional transport in MDR1-MDCK cell monolayers overexpressing the human P-gp was measured for AGN 197075. RESULTS: TR-iBRB cells form confluent cell layers when grown on fibronectin-coated membrane and exhibit characteristic spindle-shaped morphology. A good correlation between Papp and cLogD (pH 7.4) of the compounds tested was observed, except for 3-OMG, AGN 197075, and rhodamine 123, which are substrates of carrier-mediated transport systems such as P-gp and a glucose transporter (GLUT1). When grown on permeable membrane, TR-iBRB cells expressed functional P-gp and GLUT1. CONCLUSIONS: TR-iBRB cells, when grown on permeable membrane, provide a useful tool for predicting permeability across the BRB. The usefulness of this model for high-throughput screening and rank ordering of drug candidates intended for the back of the eye in treatment of ocular diseases needs further characterization upon correlation with in vivo data.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMedDate not supplied

A simple in vitro model for investigating epithelial/mesenchymal interactions: keratinocyte inhibition of fibroblast proliferation and fibronectin synthesis.

Hypertrophic scarring and graft contracture are major causes of morbidity after burn injuries. It is well established that application of a split-thickness skin graft reduces scarring and contraction, and cultured epithelial autografts have a similar effect. To investigate the influence of keratinocytes on fibroblast proliferation and fibronectin synthesis, we used an in vitro separated co-culture model in which epithelial sheets were cultured above fibroblast monolayers without physical contact. We also investigated the response of fibroblasts to keratinocyte-conditioned medium (KCM) obtained from confluent and subconfluent keratinocyte monolayers. Both cultured epithelial sheets, composed of adherent fully confluent keratinocytes, and their conditioned medium, reduced fibroblast proliferation. However, KCM from subconfluent keratinocytes stimulated fibroblast proliferation at low concentrations while inhibiting it at higher concentrations, indicating that keratinocytes can produce both mitogenic and growth-inhibiting factors for fibroblasts. KCM, but not epithelial sheet co-culture, also inhibited fibroblast fibronectin synthesis. This indicates regulation of fibroblast phenotype by soluble factors released by the keratinocyte and also suggests that there is a dialogue between keratinocytes and fibroblasts with respect to fibronectin production. We conclude that this separated co-culture model is a simple way to study epithelial/mesenchymal communication particularly with respect to the role of the fibroblast in wound healing.

Cell Proliferation↗
PubMed1979

An in vitro model for the study of enzymatically mediated biomechanical changes in the chorioamniotic membranes.

The effects of different incubation media on the biomechanical properties of nine chorioamniotic membranes were studied. Significant alterations in strain/rupture, work/rupture, and rupture/tension values have been demonstrated after a 24 hour incubation period in pseudoamniotic fluid (PAF). These changes can be arrested if enzyme inhibitors are added to the incubation media. This study suggests that biomechanical alterations in the chorioamniotic membranes may be biomechanical, namely, enzymatically mediated.

Amnion↗
PubMed1999

Osteoclastogenesis is repressed by mechanical strain in an in vitro model.

Functional loading provides a site-specific signal for the regulation of bone mass and morphology. To determine if strain can inhibit the resorptive component of bone remodeling, osteoclast formation was assessed in marrow cultures plated on flexible membranes subjected to 5% strain for 10 cycles/minute, 24 hours per day. Cultures strained during days 2 through 7 inhibited osteoclast formation to 61+/-7% of control cultures (p < 0.05), a degree of inhibition similar to that observed when the cultures were subjected to strains during only days 2 through 4 but also evaluated on day 7 (67+/-4% of control; p < 0.05). In contrast, straining of cultures during days 5 through 7 had little influence on inhibiting the formation of osteoclasts (94+/-5% of control; no significant difference). The nonuniformly strained substrate was subdivided into three concentric rings. and cultures were used to examine the site-specificity of the inhibition caused by strain. Osteoclast formation in the outermost boundary, which was distended from 3.6 to 5%, was 41+/-7% of that observed in outer regions of control wells. The inhibitory potential of mechanical strain was reduced within the middle ring (73+/-6% of control osteoclasts: p < 0.01), where the strain ranged from 0.2 to 3.6%. The central region, which experienced strains equivalent to those in the middle ring (0.2 to -4% strain), showed inhibition of osteoclast formation to a similar degree (75+/-6% of control). Media harvested from strained cultures failed to inhibit osteoclast formation in unstrained cultures; this implies that the inhibitory effect of strain depended on the direct interaction of the cell with the substrate rather than by a humoral factor. A second device, where a uniform strain was delivered at 1.8% throughout the entire plate, inhibited osteoclast recruitment to 48+/-3.6%, emphasizing that uniform strain in the absence of shear stress constrains osteoclast recruitment. These in vitro experiments can but model the complex environment generated by in vivo mechanical strains: however, they provide the first direct evidence that strain must be considered as inhibitory to osteoclast recruitment.

Animals↗
PubMed1988

In vitro model for ciclosporin intestinal absorption in lipid vehicles.

The influence of lipid vehicles on the intestinal absorption of Ciclosporin was studied in vitro. The effect of the intestinal lipid digestion was considered on the partition of the drug from olive oil or middle-chain triglyceride (MCT) into phases of simulated intestinal content. The phases obtained after ultracentrifugation were analyzed for their Ciclosporin content and characterized for their lipid classes. For both lipid vehicles the presence of lipolysis products did not promote the partition of the drug into the aqueous phase. The absorption in vivo was not related to the drug amount in the aqueous phase and in the oil phase. Therefore, phase quantification in vitro cannot simulate the dynamics of in vivo absorption events following application of a poorly water-soluble drug in a lipid vehicle.

Chemical Phenomena↗
PubMed1995

[A study of vitreous liquefaction using in vitro models--1. The effect of plasma on vitreous liquefaction].

To study the mechanism of vitreous liquefaction following vitreous hemorrhage, an in vitro study was done. We isolated whole vitreous gel of pig eyes, then weighed, incubated it with sample solution and shook it at room temperature. The ratio of weight loss after shaking to initial weight were calculated as vitreous liquefaction rate (VLR). There was no significant difference in VLR between samples incubated with whole blood (50.7%) and with plasma (48.8%), and it was significantly higher than control incubated with isotonic phosphate buffered physiological saline (PBS)(14.8%) after 24 hours shaking. There were no significant differences between control and samples incubated with blood cells (21.1%) and with hemoglobin (20.5%). The VLR of samples incubated with plasma gradually increased with time whereas controls incubated with PBS showed no changes until 24 hours. The VLR and concentration of plasma were highly correlated. These results indicated that contact of plasma with vitreous gel encourages liquefaction possibly by enzymatic digestive action with proteases.

Animals↗
PubMed1995

Bidirectional transmission of infectious cytomegalovirus between monocytes and vascular endothelial cells: an in vitro model.

Cytomegalovirus (CMV) infects multiple tissues and organs; however, mechanisms of dissemination remain elusive. Although hematogenous spread has been implicated, in vitro studies have generally indicated that peripheral blood mononuclear cells (PBMC) do not support the complete viral reproductive cycle. Since CMV infects endothelial cells (EC), the hypothesis that PBMC can be productively infected by contact with CMV-infected EC was tested by coculturing PBMC with CMV-infected endothelial monolayers. Dual immunohistochemical staining for mononuclear cell markers and CMV-specific antigens demonstrated infection of up to 30% of monocytes adhering to EC. To determine if infected monocytes could transmit infectious virus, they were separated from EC, replated in culture wells, and then overlaid with fresh EC. The subsequent appearance of CMV-positive cytopathic foci within the overlaid monolayers indicated that these monocytes were capable of transmitting infectious virus. Thus, these results support an interactive role for the endothelium and circulating monocytes in the dissemination of this clinically problematic virus.

Biological Transport↗
PubMed2001

[Risk of embolism in diagnostic and therapeutic intravascular procedures--in vitro model].

The purpose of the study was to evaluate the risk of distal embolisation in a silicon model during different endovascular diagnostic and therapeutic procedures. Endovascular technics, such as guidewire and catheter advancement, metal stent placement, balloon angioplasty and thrombectomy device were compared. Clots were produced from human blood sample. The transparent silicon model was filled with saline, flow was generated by an hydraulic pump. Stenosis was created by mechanical compression. The size of the circulating particles were measured with a mesh of nylon filters. No loose particles were detected using guidewire, pigtail and straight catheters. Balloon inflation induced embolisation of particles ranging from 100 microns-12 mm in length. Deployment of self expandable metallic stents did not result in particle migration but secondary angioplasty inside the stent detached particles (ranging from 400 microns to 12 mm in length). Use of thrombectomy device resulted in significant particle migration (ranging from 400 microns to 1500 microns in length).

Angioplasty, Balloon↗
PubMedDate not supplied

The perfused human liver wedge biopsy: a new in vitro model for morphological and functional studies.

We developed a simple and inexpensive method of perfusing small specimens of human liver in vitro that maintains short-term tissue viability as judged by protein transport function and morphological features. The technique allows investigation of liver function at the cellular level in normal specimens and those with hepatobiliary disease. Electron microscopy of specimens perfused with this system demonstrates the presence of an incomplete basement membrane within the space of Disse and shows that human microbodies contain crystalline-like cores morphologically similar to those found in rat liver.

Adult↗
PubMed1999

An in vitro model of angiogenesis: basic features.

This report describes a model of angiogenesis which develops in admixtures (co-cultures) of human umbilical vein endothelial cells (HUVEC) and human diploid fibroblasts of dermal origin from adult patients. The system does not require the addition of further growth factors other than those normally present in endothelial growth medium (EGM), nor matrix proteins, and cell growth and proliferation are allowed to occur in a standard low (2%) concentration of fetal calf serum. Angiogenesis was specifically stimulated in response to vascular endothelial growth factor (VEGF), resulting in an increased development of structures resembling a microvasculature bed. Alternatively, angiogenesis was inhibited by addition of an excess of neutralising anti-VEGF antibodies, and the anti-angiogenic drugs such as suramin. We briefly show that stimulatory and inhibitory activities can be easily and quickly quantified by image analysis. Tubule formation was confirmed by confocal and electron microscopy, and the development and disposition of these structures within the co-cultures has been analysed immunochemically to show expression of specific endothelial cell determinants, such as PECAM-1. On this and a number of other criteria, the findings validate this in vitro process as a model of in vivo angiogenesis that can be quantified to assay stimulatory and inhibitory agents, signals and drugs.

Journal Article↗