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At least 91 records · Page 5Linked to original sources
PubMed1991

The effect of angle and flow rate upon hemodynamics in distal vascular graft anastomoses: an in vitro model study.

A steady flow, in vitro model of distal arterial bypass graft junctions was used to examine the effects of junction angle and flow rate on the local velocity field. Three test sections were fabricated from Plexiglas tubing having anastomotic junction angles of either 30, 45, or 60 deg. Flow visualization revealed velocity profiles skewed toward the outer wall with a flow split around a clear stagnation point along the outer wall. Laser Doppler anemometry [LDA] measurements confirmed a distinct stagnation point at the outer wall and both reverse and forward shear were detected immediately upstream and downstream, respectively, of this site. Axial velocities and shear rates along the outer wall were higher than along the inner wall and occurred in the junction angle order: 45, 60, and 30 deg. This study clearly identified changes in wall shear which varied with the anastomotic angle and flow rate.

Anastomosis, Surgical↗
PubMed1975

Induction of F1 hybrid antiparent cytotoxic effector cells: an in vitro model for hemopoietic histoincompatibility.

An in vitro system has been developed in which F1 spleen cells can generate cytotoxic activity directed specifically against parental cells. The antigenic differences detected are controlled by the H-2D-Hh-1 region of the murine major histocompatibility complex. The parent-F1 combinations demonstrating F1 antiparent activity in vitro are the same as those demonstrating F1 rejection of parental hemopoietic grafts in vivo. Hence, the F1 antiparent cytotoxicity test serves as an in vitro model for the recognition and effector phases of hybrid resistance to parental hemopoietic grafts and may be of value in clinical transplantation.

Age Factors↗
PubMed2006

Spinal cord-fragment interactions following burst fracture: an in vitro model.

OBJECT: The purpose of the study was to develop an in vitro model of the bone fragment and spinal cord interactions that occur during a burst fracture and further the understanding of how the velocity of the bone fragment and the status of the posterior longitudinal ligament (PLL) affect the deformation of the cord. METHODS: An in vitro model was developed such that high-speed video and pressure measurements recorded the impact of a simulated bone fragment on sections of explanted bovine spinal cord. The model simulated the PLL and the posterior elements. The status of the PLL had a significant effect on both the maximum occlusion of the spinal cord and the time for occlusion to occur. Raising the fragment velocity led to an overall increase in the spinal cord deformation. Interestingly the dura mater appeared to have little or no effect on the extent of occlusion. CONCLUSIONS: These findings may indicate the importance of the dura's interaction with the cerebrospinal fluid in protecting the cord during this type of impact.

Animals↗
PubMed1984

Suppression of HSV-1 infection in trigeminal ganglion cells. An in vitro model of latency.

The goal of this experiment was to develop an in vitro model of HSV-1 infection and to characterize the virologic parameters associated with such an infection. An in vitro model of HSV-1 infection would offer a defined, efficient, and easily controlled system for studying the mechanisms associated with HSV-1 latency and reactivation. Results indicate that: (1) in the presence of 100 micrograms/ml acyclovir, acute infection is suppressed within 3 days; (2) during suppression, infectious virus was recovered only from whole cell trigeminal ganglion explants (no virus recovery from supernate or homogenized samples); immunofluorescent staining was evident with antiserum to VP175, but not with antiserum to HSV-1 and intranuclear inclusions, but no intact virions were observed in neurons by electron microscopy; (3) 72 hr after desuppression of HSV infected trigeminal ganglion cells infectious HSV-1 was recovered from supernate, homogenized, and whole cell cultures. Immunofluorescent staining was observed with antisera to VP175 and HSV-1; intranuclear inclusions as well as intact virus particles were noted in neurons via electron microscopy.

Acyclovir↗
PubMed1999

Nasal drug delivery--evaluation of an in vitro model using porcine nasal mucosa.

An in vitro model for permeation studies using porcine nasal mucosa was developed and evaluated. The viability and integrity of the mucosa were determined by electrophysiological measurements, permeation studies involving 14C-mannitol and D-(2-3H) glucose, histological studies and a biochemical assay. Enzymatic activity in the mucosa was determined by serosal addition of ouabain. Three different types of porcine nasal mucosa (cavity mucosa, natural septum mucosa and dermatomed septum mucosa) were examined. The results showed that cavity mucosa was the most suitable; this type remained viable for up to 8 h after removal. Lower limits for electrophysiological data were defined in order to establish criteria for tissue viability. This in vitro method using porcine nasal mucosa appears potentially valuable as a tool for further permeation and mechanistic studies within nasal drug delivery research.

Administration, Intranasal↗
PubMedDate not supplied

Near infrared spectroscopy for non-invasive assessment of intracranial haemoglobin oxygenation in an in vitro model of the calf head.

An in vitro model of the calf head was used to examine the ability of near infrared spectroscopy (NIRS) to non-invasively determine oxygenation events within the calf head. The brains were removed from 16 calf skulls and replaced with oxygenated dilutions of calf blood that had the oxygen progressively decreased from PO2 > 110 mmHg to < 10 mmHg. Appropriate placement of the lighting source and sensor (optodes) was examined, as were the influences of skull thickness and overlying skin of the skull (including colour). The changes in haemaglobin oxygenation in the model calf head, as observed by NIRS, were highly correlated to PO2 changes in all 16 calf skulls examined (mean r2=0.91, range 0.71 to 0.99). There was a trend for optode positioning to achieve optimal NIRS signals over the middle of the frontal bone in a longitudinal axis and with optodes spaced 4 cm apart, but with the large variation between calf heads this was not shown to be significantly different from other sites tested. The presence of skin over the skull had a significant damping effect on the NIRS signal when compared with the bare skull (P<0.01) but it was not possible to detect a difference in this damping effect between black and white coloured skin. All but the two thickest skulls (13 and 14 mm frontal bone thickness) appeared to allow sufficiently strong NIRS signals of changes in haemoglobin oxygenation. This study showed that NIRS can be used for non-invasive study of oxygenation events within the cranial cavity of calves, and established some guidelines and limitations for its use in this species.

Animals↗
PubMed2005

[A three-dimension in vitro model for angiogenesis of hemangioma].

OBJECTIVE: To create a three dimension (3D) in vitro model for angiogenesis of hemangioma. METHOD: The fragment of hemangioma specimen was embedded in fibrin gel to set up the three-dimension (3D) in vitro model for angiogenesis of hemangioma. RESULT: In the model, microvessels grew out from the tissue fragments at the 2nd to 3rd day after culture, and at the 8th to 9th day a compact network of microvessels come into being, then tending to be stationary. The compact network around the tissue fragment was confirmed to be blood vessels by immunohistochemistry and electron microscopy. CONCLUSION: This model helps to study the mechanism of hemangioma angiogenesis and investigate the drugs of anti-angiogenesis.

Cells, Cultured↗
PubMed1997

Integrin receptor involvement in actin cable formation in an in vitro model of events associated with wound contraction.

Actin cables have been reported to act in vivo as contractile 'purse strings' capable of closing embryonic wounds through generation of circumferential tension. Furthermore, their involvement in wounds within in vitro model systems suggests that actin cable contraction may be an important mechanism involved in the process of wound closure. The aim of this study therefore, was to investigate the appearance of actin cables in a contracting fibroblast populated collagen lattice, an in vitro model of events associated with wound contraction. Utilising this in vitro model, the time-course of actin cable production was investigated and the involvement of integrin receptors analysed using immunofluorescent labelling techniques. Over a period of hours distinct cellular cable-like structures developed at the edges of collagen lattices coinciding with the onset of contraction. Cellular organisation within the cable was evident as was polymerisation of actin microfilaments into elongated stress fibres forming a continuous cell-cell 'actin cable' around the circumference of the lattice. Immunolocalisation demonstrated that integrin receptor subunits beta 1 and alpha 2 but not alpha 5 were involved in apparent intimate cell-cell contact between juxtaposed fibroblasts within this actin cable. This study demonstrates the involvement of integrin receptors in actin cable formation within collagen lattice systems undergoing reorganisation. Such integrin involvement may enable participating cells to respond to the tensional status of their surrounding environment and via cell-cell communication, to permit a co-ordinated contraction of the cable. It is concluded that integrin receptor involvement in active actin cable contraction may be involved in the process of wound contraction.

Actins↗
PubMed1997

Inhibition of biliary endoprostheses occlusion by ampicillin-sulbactam in an in vitro model.

An important first step in stent occlusion is the formation of a bacterial biofilm. This is followed by deposition of granules similar to that found in brown pigment stones. Previous in vitro models for studying occlusion have used synthetic biles without bilirubin or pooled human bile, which is limited in supply. Our aim was to develop a new in vitro model of stent occlusion with porcine gallbladder bile and then, with the model, assess whether ampicillin-sulbactam can prevent biofilm formation and thus occlusion. Sterile porcine gallbladder bile was contaminated with Escherichia coli then divided into eight reservoirs, four of which then received ampicillin-sulbactam. The bile was then circulated through 10F polyethylene stents. Bile was changed weekly for 8 weeks. In the stents that were untreated, biofilm and sludge were seen in all four, whereas the four ampicillin-sulbactam-treated stents had no biofilm when viewed by electron microscopy. Furthermore, the levels of calcium, cholesterol, and bilirubin in the reservoirs decreased significantly in the untreated bile as compared with the treated bile (p < 0.05). In this in vitro model, the losses of calcium, cholesterol, and bilirubin are likely caused by deposition of granules into the biofilm matrix. Ampicillin-sulbactam can prevent biofilm formation if used continuously.

Ampicillin↗
PubMed2004

A physiologically representative in vitro model of the coronary circulation.

With the development of clinical diagnostic techniques to investigate the coronary circulation in conscious humans, the in vitro validation of such newly developed techniques is of major importance. The aim of this study was to develop an in vitro model that is able to mimic the coronary circulation in such a way that coronary pressure and flow signals under baseline as well as hyperaemic conditions are approximated as realistically as possible and are in accordance with recently gained insights into such signals in conscious man. In the present in vitro model the heart, the systemic and coronary circulation are modelled on the basis of the elements of a lumped parameter mathematical model only consisting of elements that can be represented by segments in an experimental set-up. A collapsible tube, collapsed by the ventricular pressure, represents the variable resistance and volume behaviour of the endocardial part of the myocardium. The pressure and flow signals obtained are similar to physiological human coronary pressure and flow, both for baseline and hyperaemic conditions. The model allows for in vitro evaluation of clinical diagnostic techniques.

Blood Pressure↗
PubMed2000

Toward development of an in vitro model of methamphetamine-induced dopamine nerve terminal toxicity.

To develop an in vitro model of methamphetamine (METH)-induced dopamine (DA) neurotoxicity, striatal synaptosomes were incubated at 37 degrees C with METH for different periods of time (10-80 min), washed once, then tested for DA transporter function at 37 degrees C. METH produced time- and dose-dependent reductions in the V(max) of DA uptake, without producing any change in K(m). Incubation of synaptosomes with the DA neurotoxins 1-methyl-4-phenyl-pyridinium ion, 6-hydroxydopamine, and amphetamine under similar conditions produced comparable effects. In contrast, incubation with fenfluramine, a serotonin neurotoxin, did not. METH-induced decreases in DA uptake were selective, insofar as striatal glutamate uptake was unaffected. Various DA transporter blockers (cocaine, methylphenidate, and bupropion) afforded complete protection against METH-induced decreases in DA uptake, without producing any effect themselves. METH's effects were also temperature dependent, with greater decreases in DA uptake occurring at higher temperatures. Tests for residual drug revealed small amounts (0.1-0.2 microM) of remaining METH, but kinetic studies indicated that decreases in DA uptake were not likely to be due to METH acting as a competitive inhibitor of DA uptake. Decreases in the V(max) of DA uptake were not accompanied by decreases in B(max) of [(3)H]WIN 35,428 binding, possibly because there is no mechanism for removing damaged DA nerve endings from the in vitro preparation Collectively, these results give good support to the development of a valid in vitro model that may prove helpful for elucidating the mechanisms underlying METH-induced DA neurotoxicity.

Animals↗
PubMed1993

Role of NMDA receptors and voltage-activated calcium channels in an in vitro model of cerebral ischemia.

In an in vitro model of cerebral ischemia we investigated the functional consequences of repeated hypoxias and the potential protective effect of the N-methyl-D-aspartate (NMDA) receptor antagonist D-2-amino-5-phosphonovaleric acid (D-APV) and the calcium channel blocker verapamil in preventing the expression of pathophysiological activity. Rat neocortical slices were exposed to nitrogen for 2-13 min and the hypoxia-induced functional modifications were monitored in layer II/III by recording the extracellular DC potential, the extracellular calcium concentration ([Ca2+]o) and the stimulus-evoked synaptic responses. Hypoxia caused a reversible 2.4-24.6 mV negative shift in the extracellular DC potential associated with a [Ca2+]o decrease from 1.2 to 0.2 mM and a complete loss of synaptic responsiveness. Repeating hypoxias induced an increase in the amplitude of this anoxic depolarization (AD) and a significant decrease in the AD onset latency. Synaptic responses partially recovered at 20 and 60 min intervals between subsequent hypoxic periods, indicating that the initial AD did not induce any short-term irreparable functional deficits. Verapamil (50 microM) caused an increase in the AD onset latency. However, in comparison to untreated controls, verapamil induced a reduction of excitatory and inhibitory responses during hypoxia probably by blocking voltage-activated calcium conductances. In addition, verapamil did not have any significant effect on the hypoxia-induced reduction of [Ca2+]o. Bath application of D-APV (30 microM) prevented the significant reduction in the AD onset latency to the second hypoxia, but had no significant effect on the AD amplitude and duration. The hypoxia-induced decrease in [Ca2+]o was not altered after addition of D-APV to the bathing medium. These data indicate that the influx of calcium through voltage-activated calcium channels and the NMDA receptor-gated ionophore does not significantly contribute to the massive depolarization observed under hypoxic conditions.

2-Amino-5-phosphonovalerate↗
PubMed1990

Antibacterial activity of cefpodoxime proxetil in a pharmacokinetic in-vitro model.

The antibacterial activity of cefpodoxime proxetil was studied in an in-vitro model simulating doses of 100, 200 and 400 mg. Strains of Klebsiella spp. Proteus mirabilis, Escherichia coli, Streptococcus pyogenes, and Haemophilus influenzae were effectively reduced by a dose of 200 mg. While for Esch. coli no dose-activity relationship was observed--the maximal effect was achieved with a simulated dose of 100 mg--Staphylococcus aureus could be reduced effectively only by a simulated dose of 400 mg. The lower doses showed stepwise lower activities. Apart from broad spectrum beta-lactamases like SHV 2 or TEM 5 the presence of plasmid coded beta-lactamases in Esch. coli and H. influenzae did not affect the antibacterial activity of cefpodoxime proxetil. The results show that cefpodoxime was more active against Gram-negative bacteria than amoxycillin, and comparable activity to intramuscular cefotiam in the in-vitro model.

Amoxicillin↗
PubMed2005

An in vitro model for studying vascular injury after laser microdissection.

We have developed an in vitro model for studying vascular injury. After 7-10 days in a three-dimensional collagen gel culture, capillary-like tubes were formed in the collagen gels. We injured these capillary-like tubes with a laser microdissection system or a scrape method with razors and then examined the collagen gel culture by phase contrast and electron microscopy. After laser injury, profuse necrotic cells were observed around the injured capillary-like tubes and within the tubular lumen compared to the razor injury. We then isolated total RNA from these cultures and prepared cDNA for investigations by quantitative real-time reverse transcription polymerase chain reaction (RT-PCR). Quantitative real time RT-PCR revealed the up-regulation of transcription factor early growth response-1 (Egr-1) after both laser and razor injury, accompanied by the up-regulation of fibroblast growth factor-2 (FGF-2), a proangiogenic factor downstream of Egr-1. The effective laser energy is concentrated on the minute focal spot only. These methods provide a useful in vitro model for studying vascular injury.

Animals↗
PubMed2000

Development of an in vitro model for cysteine dioxygenase expression in the brain.

The development of an in vitro model for cysteine dioxygenase (CDO) expression in the brain would provide a useful model for determining the mechanisms for the regulation of CDO expression that does not involve the use of animals. Here we demonstrate the screening and characterization of a cell line that expresses CDO, the primary metabolizing enzyme of cysteine and the regulatory point of sulfate production. A panel of four commercially available tumor-derived human brain cell lines, each representing one major class of brain cell, were screened using western blotting and activity assay for cysteine dioxygenase expression. One cell line, TE 671 (human medulloblastoma) was found to express both a protein of approximately 70 kDa and CDO activity. Nuclease protection assay (NPA) of mRNA isolated from TE 671 showed the expression of a CDO mRNA. Reverse transcription-polymerase chain reaction of this mRNA and sequencing of the cDNA obtained showed that this was indeed CDO. Treatment of TE 671 cells with cysteine resulted in the upregulation of CDO mRNA, whereas treatment with tumor necrosis factor alpha resulted in the downregulation of CDO mRNA, as evidenced using NPA. The characterization of an in vitro model for CDO expression provides a useful tool for the investigation of this important enzyme, which may have an etiological role in the pathogenesis of Parkinson's disease.

Animals↗
PubMed1995

Assessment of axonal dysfunction in an in vitro model of acute compressive injury to adult rat spinal cord axons.

An in vitro model of spinal cord injury was developed to study the pathophysiology of posttraumatic axonal dysfunction. A 25 mm length of thoracic spinal cord was removed from the adult male rat (n = 27). A dorsal column segment was isolated and pinned in a recording chamber and superfused with oxygenated (95% O2/5% CO2) Ringer. The cord was stimulated with a bipolar electrode, while two point responses were recorded extracellularly. Injury was accomplished by compression with a modified aneurysm clip which applied a 2 g force for 15 s. With injury the compound action potential (CAP) amplitude decreased to 53.7 +/- 5.4% (P < 0.001), while the latency increased to 115.6 +/- 3.1% (P < 0.0025) of control values. The absolute refractory period increased with injury from 1.7 +/- 0.1 ms to 2.1 +/- 0.1 ms (P < 0.05). The infusion of 5 mM 4-aminopyridine (4-AP), a blocker of voltage-sensitive 'fast' K channels confined to internodal regions, resulted in broadening of the CAP of injured axons to 114.9 +/- 3.1% of control (P < 0.05). Ultrastructural analysis of the injured dorsal column segments revealed marked axonal and myelin pathology, including considerable myelin disruption. In conclusion, we have developed and characterized an in vitro model of mammalian spinal cord injury which simulates many of the features of in vivo trauma. Injured axons display characteristic changes in physiological function including a shift in refractory period and high frequency conduction failure. The ultrastructural data and response of injured axons to 4-AP suggest that myelin disruption with exposure of 'fast' K+ channels contributes to posttraumatic axonal dysfunction.

4-Aminopyridine↗
PubMed1998

A simple in vitro model to study the release kinetics of liposome encapsulated material.

A simple in vitro model was developed to study the release kinetics of liposome encapsulated material in the presence of biologic components. Liposomes were embedded in an agarose gel (bottom layer) formed in a glass vial and separated from the receptor compartment buffer by a second layer of agarose gel (top layer). To follow the release of liposomal contents, aqueous space markers differing in molecular weight (from 205 Dalton to 17500 Dalton) were encapsulated. The isotonic buffer in the receptor was completely changed at various time points and the amount of marker released from the agarose matrix containing the liposomes into the receptor medium determined. The release of non-encapsulated markers from the gel followed a time0.5 relationship with about 75% of a 17500 Dalton protein being released from the matrix in 48 h. In the same period, about 7% of the intact liposomes added to the agarose gel appeared in the receptor phase. The release of calcein from various liposome compositions including: (A) egg phosphatidylcholine (EPC)/egg phosphatidylglycerol (EPG) 9:1, (B) dioleoylphosphatidylethanolamine (DOPE)/cholesterylhemisuccinate (CHEMS) 2:1, and (C) dioleoylphosphatidylglycerol (DOPC)/dioleoylphosphatidylglycerol (DOPG) 2:1 was measured. Components of the biological milieu such as serum proteins and calcium influenced release of encapsulated material. This in vitro model is a convenient and reproducible system that permits the study of the release of high molecular weight molecules such as proteins from liposomal formulations in the presence of serum. It may find applications with respect to release of proteins from a variety of colloidal drug delivery systems.

Blood Proteins↗
PubMed1991

Efficacy of once- and thrice-daily dosing of aminoglycosides in in-vitro models of infection.

The bactericidal efficacy of amikacin, isepamicin and netilmicin was studied against Pseudomonas aeruginosa and Serratia marcescens over a treatment period of 30 h using two one-compartment in-vitro models with differently designed culture compartments. High bacterial inocula were exposed to fluctuating drug concentrations, simulating human serum concentrations (t1/2 = 2 h) during clinical treatment. The same daily dose was administered as 1 h infusions given every 8 h or every 24 h, resulting in peak concentrations of 8 and 24 mg/l for netilmicin, and 24 and 72 mg/l for amikacin and isepamicin, respectively. Once-daily dosing was more bactericidal during initial treatment in the in-vitro models (P less than 0.01) and at least as effective as thrice-daily dosing in preventing bacterial regrowth, despite a prolonged period of subinhibitory drug concentration before administration of the second dose. Lower ratios of peak concentration to MIC were needed to achieve bactericidal activity (greater than 99.9% reduction of cfu) after 24 h treatment against S. marcescens compared with P. aeruginosa (P less than 0.01). All nine regimens providing peaks of at least four times the MIC were bactericidal against S. marcescens after 24 h exposure. In contrast, a bactericidal effect against P. aeruginosa occurred only during two of six experiments with peaks of four to nine times the MIC. Similar results were obtained in both in-vitro models of infection. These data suggest insufficient intrinsic activity of the aminoglycosides studied for single drug treatment of P. aeruginosa in the absence of host-defence mechanisms.

Amikacin↗