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At least 973 records · Page 54Linked to original sources
PubMed1996

Tubing loops as a model for cardiopulmonary bypass circuits: both the biomaterial and the blood-gas phase interfaces induce complement activation in an in vitro model.

We describe here a model for the study of blood/surface and blood/air interaction as encountered in cardiopulmonary bypass (CPB) circuits. Polyethylene tubing was filled with serum or blood and closed end to end into loops whereby the volume of the remaining air bubble was inversely varied with respect to that of the fluid. The loops were rotated vertically in a water bath at 37 degrees C. The profiles of C3a, iC3, and TCC generation were similar to those observed at surgery, involving CPB. Soluble heparin and heparan sulfate inhibited both C3a and TCC formation, but surface-conjugated heparin had only a minor effect. Binding of C3 and/or C3 fragments to the heparin surface was much reduced compared to the amine matrix to which heparin was linked, but compared with the polyethylene surface the effect was less pronounced. These data suggest that, in addition to the biomaterial surface, the blood-gas interface seems to play an important role in the activation of complement and that this activation is inhibitable by high concentrations of soluble glucose aminoglycans.

Biocompatible Materials↗
PubMed2003

Adhesion of endometrial cells labeled with 111Indium-tropolonate to peritoneum: a novel in vitro model to study endometriosis.

OBJECTIVE: To evaluate, in a new original in vitro assay, putative factors that could modulate the adhesion of endometrial cells to peritoneum. DESIGN: Prospective, controlled in vitro study. SETTING: Academic research laboratory. PATIENT(S): Fourteen nonmenopausal women undergoing hysterectomy or laparoscopy for benign gynecologic indication. INTERVENTION(S): Endometrial cells obtained from women with regular cycles without endometriosis were labeled with 111Indium and confronted in vitro with mouse peritoneum in the presence of various cytokines and/or antiadhesive compounds. MAIN OUTCOME MEASURE(S): Radioactivity in 111Indium-labeled endometrial cells. RESULT(S): The adhesion of human endometrial cells to mouse peritoneum was increased by treatment with pro-inflammatory cytokines (interleukin IL-1beta, IL-6, TNF alpha, TGF-beta1). Whereas heparan sulfate had no effect on cell adhesion, a gel of ferric hyaluronate (Intergel) was able to counteract the pro-adhesive effect of cytokines. Interestingly, the pretreatment of peritoneum with cytokines, 24 hours before cell seeding in the presence of the ferric hyaluronate gel, restored the cytokine-promoting effect on cell adhesion. CONCLUSION(S): Proinflammatory cytokines promote the in vitro peritoneal adhesion of endometrial cells. An antiadhesive hyaluronate gel used in clinics decreases the adhesion in a dose-dependent manner and reduces cytokine bioavailability.

Adult↗
PubMed1985

Detection of abnormal platelet functions with an in vitro model of primary haemostasis.

A new technique, which simulates primary haemostasis in vitro was tested using blood from control persons and from patients with a defined abnormality of primary haemostasis. The device allows the reproducible measurement of in vitro bleeding time and volume in small samples of whole blood. Inhibition of platelet adhesion and aggregation can very sensitively be detected with the new technique, which allows its possible use in clinical or pharmacological applications.

Blood Platelet Disorders↗
PubMed2004

Citrate inhibits growth of residual fragments in an in vitro model of calcium oxalate renal stones.

BACKGROUND: Alkaline citrate is thought to be helpful in reducing recurrences of calcium oxalate stones. The evidence for this is incomplete, there have been few good trials, all with their own limitations, and not all reported any significant benefit. In vitro studies are usually cited to support the clinical studies but these too have their drawbacks, in particular they relate to crystals and microscopic aggregates and not to actual stone growth. Here we test citrate in vitro using a model of macroscopic calcium oxalate stone enlargement. METHODS: Twelve calcium oxalate stones were grown at a time in a stone farm. Six were grown with 2 mmol/L citrate and six with 6 mmol/L citrate. Three protocols were tested; artificial urine, artificial urine with urinary macromolecules (UMM) from male controls and artificial urine with UMM from male stone formers. The stones were grown continuously for at least 24 days. RESULTS: In all three experiments the higher citrate concentration significantly reduced the growth rate of stones by more than 50% (P < 0.001). There was a small decrease in ionised calcium in the stone growth media (P < 0.001) and significant (P < 0.001) but small increase in pH (about 0.07 pH units). The inclusion of UMM also brought about a decrease in stone growth, particularly at 2 mmol/L citrate. CONCLUSION: Citrate inhibited stone growth in this laboratory model. This was true both in defined media and with addition of UMM. This adds to evidence justifying the use of alkaline citrate in calcium oxalate nephrolithiasis.

Calcium Oxalate↗
PubMed2004

Angiotensin II facilitates autoregulation in the perfused mouse kidney: An optimized in vitro model for assessment of renal vascular and tubular function.

BACKGROUND AND AIMS: We have optimized the isolated perfused mouse kidney (IPMK) model for studying renal vascular and tubular function in vitro using 24-28 g C57BL6J mice; the wild type controls for many transgenic mice. METHODS AND RESULTS: Buffer composition was optimized for bovine serum albumin concentration (BSA). The effect of adding erythrocytes on renal function and morphology was assessed. Autoregulation was investigated during stepped increases in perfusion pressure. Perfusion for 60 min at 90-110 mmHg with Krebs bicarbonate buffer containing 5.5% BSA, and amino acids produced functional parameters within the in vivo range. Erythrocytes increased renal vascular resistance (3.8 +/- 0.2 vs 2.4 +/- 0.1 mL/min.mmHg, P < 0.05), enhanced sodium reabsorption (FE(Na) = 0.3 +/- 0.08 vs 1.5 +/- 0.7%, P < 0.05), produced equivalent glomerular filtration rates (GFR; 364 +/- 38 vs 400 +/- 9 microL/min per gkw) and reduced distal tubular cell injury in the inner stripe (5.8 +/- 1.7 vs 23.7 +/- 3.1%, P < 0.001) compared to cell free perfusion. The IPMK was responsive to vasoconstrictor (angiotensin II, EC50 100 pM) and vasodilator (methacholine, EC50 75 nM) mediators and showed partial autoregulation of perfusate flow under control conditions over 65-85 mmHg; autoregulatory index (ARI) of 0.66 +/- 0.11. Angiotensin II (100 pM) extended this range (to 65-120 mmHg) and enhanced efficiency (ARI 0.21 +/- 0.02, P < 0.05). Angiotensin II facilitation was antagonized by methacholine (ARI 0.76 +/- 0.08) and papaverine (ARI 0.91 +/- 0.13). CONCLUSION: The IPMK model is useful for studying renal physiology and pathophysiology without systemic neurohormonal influences.

Angiotensin II↗
PubMed1990

The role of colon fibroblasts in malignant large bowel obstruction--an experimental in vitro model.

The mechanism of bowel obstruction in colorectal cancer is likely to involve interactions between tumour cells, host fibroblasts and the extracellular matrix. The role of fibroblast-mediated matrix reorganisation in malignant structures of the large bowel was examined in an in vitro collagen matrix model in which tumour cells and fibroblasts were cultured under serum-free conditions. Colon cancer cells secreted a factor(s) which enhanced the ability of colon fibroblasts to contrast a collagen matrix without an associated mitogenic response by the fibroblasts. Within uncontracted collagen gels marked elongation of fibroblast cell processes was observed in the presence of the tumour-derived factor(s). We propose that matrix reorganisation by host fibroblasts in the wall of the human colon is responsible, at least in part, for malignant large bowel obstruction.

Cell Communication↗
PubMed2000

Development of a new in vitro model for the study of benign prostatic hyperplasia.

BACKGROUND: The search for novel agents for the treatment of the lower urinary tract symptoms (LUTS) associated with benign prostatic hyperplasia (BPH) is dependent on an increased understanding of the pathophysiology of the disease. Unfortunately, in vitro and animal models have been of limited value. METHODS: This article describes a novel model system in which the interactions of the stromal and epithelial components of the prostate gland can be determined. RESULTS: The coculture system provides a simple model of the cellular interactions occurring in the adult human prostate. CONCLUSIONS: This coculture system could potentially be used to determine the precise molecular site of action of agents such as terazosin on prostatic apoptosis.

Cell Differentiation↗
PubMed1984

An in vitro model of fibroplasia: simultaneous quantification of fibroblast proliferation, migration, and collagen synthesis.

Previous studies of fibroblast proliferation, migration, and collagen synthesis have been limited in their ability to define the interrelationship among these events in response to various inflammatory mediators. We have now defined an in vitro tissue culture model for the synchronous quantification of these parameters of fibroplasia. Biopsies (2 mm) of chicken flexor tendons are embedded in a fibrin matrix and exposed to various factors for 5 days in tissue culture. The availability of the fibrin matrix surrounding the tendon biopsy satisfies the need for a solid support medium for fibroblast migration. Multiple measurements of tendon fibroblast proliferation, migration into the fibrin matrix, and relative collagen synthesis are then made on these preparations. Fetal calf serum stimulated tendon fibroblast proliferation and migration in a dose responsive fashion, whereas the selective expression of collagen synthesis was decreased. Platelet lysate stimulated fibroblast proliferation at low concentration, but migration only at high concentration and was without effect on relative collagen synthesis. This model now provides a means of more clearly defining the influence of various inflammatory factors on the events of fibroplasia.

Animals↗
PubMed2003

Development and comparison of in vivo and in vitro models for endometritis in cows and mares.

In order to investigate pathogenic mechanisms of acute endometritis in cows and mares, we established an in vivo model in both species. Based on the results of an in vitro transmigration system, human recombinant interleukin-8 (rhIL-8; 1.25 microg per mare and 5 microg per cow in 50 ml phosphate-buffered saline) was used to attract polymorphonuclear neutrophil granulocytes (PMNs) into the uteri. Peak numbers of uterine neutrophils were attracted after 6h, in both cows and mares. On average, mares responded more sensitively than cows, with 15 times higher numbers of rhIL-8-attracted uterine neutrophils (72+/-8 x 10(7)cells). In contrast to in vitro studies, in vivo migrated neutrophils (uterine neutrophils) of both species displayed a significantly reduced MHC class I expression. Expression of the CD11a molecule was significantly enhanced on equine uterine neutrophils but downregulated on bovine cells. Compared with untreated autologous peripheral neutrophils, both uterine and in vitro migrated neutrophils showed no alteration of phagocytic capacity. The ability to generate reactive oxygen species (ROS) was significantly upregulated in bovine and equine uterine neutrophils. This was also observed after in vitro migration of equine neutrophils, whereas ROS generation by bovine neutrophils was significantly depressed. In summary, the concept of inducing endometritis directly by local application of human interleukin-8 has been reliably successful in cows and mares. The model permits the analysis of PMN migration into the uterus under defined and controlled conditions. The observed differences between cows and mares with respect to phenotypical and functional characteristics of in vivo attracted uterine cells point to species-related features of neutrophil migration. In vitro transmigrated bovine and equine cells partially differ in phenotype and function from uterine neutrophils. Therefore, the in vitro transmigration assay cannot completely represent the in vivo endometritis model described here.

Animals↗
PubMed2001

Studying rhythmogenesis of breathing: comparison of in vivo and in vitro models.

In all mammalian species, breathing is controlled by a neuronal network within the lower brainstem. A component known as the ventral respiratory group produces rhythmic activity, which is transmitted to spinal motoneurons to produce a periodic contraction of respiratory muscles. A dispute about the mechanisms of 'normal' respiratory rhythm generation arose from the differences between experimental preparations that have been used to dissect the process. It is, therefore, essential to compare the various experimental approaches and to discuss the differences between experimental data. We conclude that the various preparations all have great value, but that they define different operational conditions of the network, including maturation of neurons and synaptic processes. We have taken note of these in formulating a 'maturational network-burster model' for rhythm generation that includes most features of the existing models of respiratory rhythm generation.

Animals↗
PubMed2003

Animal and in vitro models for the study of hair follicles.

Since the way in which the hair follicle functions is not well understood, many hair disorders are poorly controlled. A range of in vitro and in vivo models have therefore been developed to investigate the cell biological and biochemical mechanisms involved in the organization of this complex tissue. These range from cultures of a single cell type, such as those of the regulatory, mesenchyme-derived dermal papilla, through organ culture of isolated follicles to natural or genetically manipulated animal models. Each system has advantages and disadvantages for studying particular aspects of follicular function and some are potentially useful for the development of novel treatments for hair disorders.

Animals↗
PubMed2005

In vitro models for oral malodor.

A model is a representation of some real phenomena and contains aspects or elements of the real system to be modeled. The model reflects (or duplicates) the type of behavior (or mechanisms) seen in the real system. The main characteristic of any model is the mapping of elements or parameters found in the system being studied (e.g. tongue dorsum biofilm in situ) on to the model being devised (e.g. laboratory perfusion biofilm). Such parameters include correct physico-chemical (abiotic) conditions as well as biotic conditions that occur in both model and reality. The main purpose of a model is to provide information that better explains the processes observed or thought to occur in the real system. Such models can be abstract (mental, conceptual, theoretical, mathematical or computational) or 'physical', e.g. in the form of a real disaggregated in vitro system or laboratory model. A wide range of different model systems have been used in oral biofilm research. These will be briefly reviewed with special emphasis on those models that have contributed most to knowledge in breath odor research. The different model systems used in breath odor research are compared. Finally, the requirements for developing an overall 'bad breath model' from considering the processes as a whole (real oral cavity, substrates in saliva, biotransformation by tongue microflora, odor gases in the breath) and extending this to the detection of malodor by the human nose will be outlined and discussed.

Biofilms↗
PubMed1994

Isolated glomeruli of the Atlantic hagfish Myxine glutinosa as an alternative in vitro model to study glomerular protein metabolism in pharmaco-toxicology of anticancer drugs.

This study was designed to validate an alternative in vitro system with isolated glomeruli of the Atlantic hagfish Myxine glutinosa as a model to study alterations in glomerular protein metabolisms in pharmaco-toxicology of anticancer drugs. A morphometric characterization of the glomeruli of Myxine glutinosa reveals a calculated glomerular volume of 180 nl/glomerulus. The glomerular extracellular volume, measured as inulin space, is 38.5 nl/glomerulus. Total glomerular protein content of Myxine glutinosa amounts to 3.56 micrograms/glomerulus and total DNA content to 0.44 microgram/glomerulus. Metabolic properties, estimated as glomerular protein synthesis, are comparable with mammalian glomeruli. The glomeruli of Myxine glutinosa are viable in a tissue culture for up to 12 hr. The incorporation rate of radiolabeled amino acids into glomerular, acid-precipitable proteins is almost identical to that of rats (e.g. Myxine glutinosa 1091 +/- 98 DPM/micrograms DNA vs. rat 1340 +/- 84 DPM/micrograms DNA after 4 hr incubation). To evaluate how nephrotoxic substances affect glomerular metabolism in this model, the anticancer drug Adriamycin (ADR) was used to experimentally induce a glomerular lesion. ADR caused an increase in glomerular protein synthesis in isolated glomeruli of Myxine glutinosa, which is in accordance with data found in rats. Cisplatin, in contrast, known to mainly interfere with tubular integrity, had no effect on glomerular protein synthesis, confirming the specificity of the model. The isolated glomeruli of Myxine glutinosa are suggested as a valid alternative multicellular in vitro system for studying alterations in glomerular metabolism under pharmaco-toxicological conditions and for the evaluation of specific target-cell toxicity of selected nephrotoxins.

Animals↗
PubMed2003

In vitro model for studying malignancy associated changes.

Malignancy associated changes (MAC) can be defined as subtle morphological and physiologic changes that are found in ostensibly normal cells of patients harboring malignant disease. It has been postulated that MAC have a potential to become a useful tool in detection, diagnosis and prognosis of malignant diseases. An in vitro cell culture model system was designed to study interactions between non-small cell lung cancer (NSCLC) and the normal bronchial epithelium of the human respiratory tract in vivo to see if the MAC-like phenomenon can be detected in such a system. In this study we examined changes in nuclear features of normal human bronchial epithelial cells (NHBE) when they were co-cultured with cells derived from a lung cancer cell line NCI-H460. Using discriminant function analysis, nuclear features were determined which allow maximal discrimination between normal cells incubated with or without cancerous cells. Our results demonstrate that MAC appear to be specific to changes induced by malignancy, and that these changes differ from those induced by growth factors in the serum. This study provides evidence in support to the hypothesis that MAC are induced by a soluble factor(s) released by malignant cells. Colour figure can be viewed on http://www.esacp.org/acp/2003/25-2/sun.htm

Bronchi↗
PubMed1996

In vitro models of biocompatibility: a review.

The objectives of this paper were to define in vitro biocompatibility of materials, to discuss some of the issues concerning why conclusions from tissue culture are sometimes different from in vivo biocompatibility, to give highlights of the sequence of the development of these in vitro assays from the early 1950s to their present state of development, and to discuss possible future trends for in vitro testing. In vitro biocompatibility tests were developed to simulate and predict biological reactions to materials when placed into or on tissues in the body. Traditional assays have measured cytotoxicity by means of either an end-stage event, (i.e., permeability of cytoplasmic membranes of dead and dying cells, or some metabolic parameter such as cell division or an enzymatic reaction). In vitro assays for initiation of inflammatory and immune reactions to materials have also begun to appear in the literature. More recently, the concept of dentin barrier tests has been introduced for dental restorative materials. Four models which measure both permeability and biological effects of materials are compared and discussed. Future efforts may be directed toward development of materials which will allow or promote function and differentiation of tissues associated with materials. New analytical procedures and understanding of optimal characteristics of materials should improve our ability to develop more biocompatible materials. Both molecular biology techniques, and altered design of material surfaces may make the materials either more or less reactive to the biological milieu. These trends suggest a greater future role of the biological sciences in the development of biomaterials.

Animals↗
PubMed1995

A new in-vitro model to investigate antibiotic penetration of the intervertebral disc.

We have studied the ability of a range of antibiotics to penetrate intervertebral disc tissue in vitro, using a mouse disc model. Equilibrium concentrations of antibiotics incorporated into the entire disc were determined by bioassay using a microbial growth-inhibition method. Uptake was significantly higher with positively-charged aminoglycosides compared with negatively-charged penicillins and cephalosporins. Uncharged ciprofloxacin showed an intermediate degree of uptake. Our results support the hypothesis that electrostatic interaction between charged antibiotics and negatively-charged glycosaminoglycans in the disc is an important factor in antibiotic penetration, and may explain their differential uptake.

Animals↗