Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Models, Experimental”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 757 records · Page 42Linked to original sources
PubMed2002

Modifying subsceral fluid pressure in an experimental model of mitomycin-C diffusion.

BACKGROUND: Episcleral application of mitomycin-C (MMC) during glaucoma filtration surgery hinders the post-operative wound healing. Diffusion through the sclera might result in a toxic effect on the ciliary body resulting in reduced aqueous humor production leading to post-operative hypotony. We developed an experimental model to investigate the influence of intraocular pressure on the diffusion of MMC through the sclera and in subscleral compartments. METHODS: Scleral quadrants of 10 human donor eyes were mounted on PMMA tubes filled with saline imitating the intraocular volume. By height variation of a coupled infusion line different intraocular pressures were simulated (0, 8, 23 and 80 mmHg). Additionally the model included a subscleral sponge to mimic the compartment of the ciliary body. The episcleral sides of the scleral quadrants were exposed for 1 min to sponges soaked with 200 microg ml(-1) MMC. An 8-mm-diameter scleral disk was punched out with a trephine and horizontally dissected with a kryotome. The MMC concentrations of scleral layers, epi-and subscleral sponges and the fluid within the tubes were analysed by means of high-performance liquid chromatography. RESULTS: The MMC concentration gradually declined from the episcleral sponge (165 microg ml(-1)) to the superficial (3.3 microg ml(-1)) and deep scleral layers (1.2 microg ml(-1)), and to the subscleral sponge (0.2 microg ml(-1)). We were able to detect very small concentrations of MMC in the fluid within the PMMA tubes (0.01 microg ml(-1)). CONCLUSION: We developed a new experimental in vitro model for investigating transscleral MMC diffusion. The different simulated intraocular pressures had no effect on the concentration gradient through the investigated compartments of our model.

Diffusion↗
PubMed1999

Antioxidant activity of AO-8, a herbal formulation in vitro and in vivo experimental models.

The effect of AO-8, a herbal formulation was evaluated for free radical scavenging activity using in vitro and in vivo experimental models. AO-8 dose dependently inhibited ferric ion induced lipid peroxidation in vitro at 125-1000 micrograms. AO-8 was investigated at dose levels of 250, 500 and 750 mg/kg p.o. in isoproterenol-induced myocardial infarction and CCl4-induced hepatotoxicity in rats. The levels of serum GOT and LDH, cardiac glutathione, SOD and catalase were estimated following induction of myocardial infarction with isoproterenol. The estimation of parameters such as SGOT, SGPT, liver glycogen and lipid peroxidation were carried out in CCl4-induced hepatotoxicity. Treatment with AO-8 for 15 days at a dose of 500 and 750 mg/kg offered marked protection in both in vivo models. The reversal of increased serum enzymes in both the models may be due to the prevention of leakage of the intracellular enzymes by its membrane stabilizing activity. The inhibition of lipid peroxidation and enhancement of antioxidant enzymes by AO-8 may be due to the direct free radical scavenging activity which could be attributed to the antioxidant potential of various ingredients present in the formulation. Thus it can be concluded that AO-8 is an effective free radical scavenger and could prove beneficial in the treatment of various disorders associated with the involvement of free radicals.

Animals↗
PubMed1994

Effect of capacitively coupled electric fields on an experimental model of delayed union of fracture.

To evaluate the effect of capacitively coupled electric fields (CCEF) on delayed union of fractures, an experimental model of delayed union was produced in the radius of rabbits, and the process of healing was investigated by radiography, bone mineral density (BMD) measured with dual energy x-ray absorptiometry, and histological survey. It was confirmed radiographically and histologically that callus formation was enhanced in the group treated with CCEF. After stimulation, the average BMD increased more than 18% compared with the controls. Our experiment on a delayed union model suggests that CCEF is effective for the treatment of delayed union of fractures.

Animals↗
PubMed2000

Characterisation of SB-221420-A - a neuronal Ca(2+) and Na(+) channel antagonist in experimental models of stroke.

For progression to clinical trials in stroke, putative neuroprotective compounds should show robust efficacy post-ischaemia in several experimental models of stroke. This paper describes the characterisation of (+)(1S, 2R)-cis-1-[4-(1-methyl-1-phenylethyl)phenoxy]-2-methylamino indane hydrochloride (SB-221420-A), a Ca(2+) and Na(+) channel antagonist. SB-221420-A inhibited (IC(50)=2.2 microM) N-type voltage-operated Ca(2+) channel currents in cultured superior cervical ganglion neurons, which were pretreated with 10 microM nimodipine to block L-type voltage-operated Ca(2+) channel currents. In dorsal root ganglion neurons pretreated with 1 microM omega-conotoxin GVIA to block N-type voltage-operated Ca(2+) channel currents, SB-221420-A inhibited the residual Ca(2+) current with an IC(50) of 7 microM. SB-221420-A also inhibited Na(+) currents in dorsal root ganglion neurons with an IC(50) of 8 microM. In rats, the pharmacokinetic profile of SB-221420-A shows that it has a half-life of 6.4 h, a high volume of distribution, is highly brain penetrating, and has no persistent metabolites. Following bilateral carotid artery occlusion in gerbils, SB-221420-A significantly reduced the level of ischaemia-induced hyperlocomotor activity and the extent of hippocampal CA1 cell loss compared to the ischaemic vehicle-treated group. SB-221420-A was also effective in focal models of ischaemia. In the mouse permanent middle cerebral artery occlusion model, SB-221420-A (10 mg/kg) administered intravenously, post-ischaemia significantly (P<0.05) reduced lesion volume compared to the ischaemic vehicle-treated group. In the normotensive rat permanent middle cerebral artery occlusion model, SB-221420-A (10 mg/kg) administered intravenously over 1 h, beginning 30 min postmiddle cerebral artery occlusion, significantly (P<0.05) reduced lesion volume from 291+/-16 to 153+/-30 mm(3), compared to ischaemic vehicle-treated controls when measured 24 h postmiddle cerebral artery occlusion. Efficacy was maintained when the same total dose of SB-221420-A was infused over a 6-h period, beginning 30 min postmiddle cerebral artery occlusion. SB-221420-A also significantly (P<0.05) reduced lesion volume following transient middle cerebral artery occlusion in normotensive rats and permanent middle cerebral artery occlusion in spontaneously hypertensive rats (SHR). Investigation of the side effect profile using the Irwin screen in mice revealed that, at neuroprotective doses, there were no overt behavioural or cardiovascular changes. These data demonstrate that robust neuroprotection can be seen post-ischaemia with SB-221420-A in both global and focal ischaemia with no adverse effects at neuroprotective doses, and indicate the potential utility of a mixed cation blocker to improve outcome in cerebral ischaemia.

Anesthesia↗
PubMedDate not supplied

[Effect of Ginkgo biloba extract (EGb 761) on rats in an experimental model of acute encephalopathy after total body irradiation].

PURPOSE: To define the therapeutic effect of Ginkgo biloba extract (EGb 761) in an experimental model of acute encephalopathy following total body irradiation in rats. MATERIAL AND METHODS: Ninety four-month-old rats received 4.5 Gy total body irradiation (TBI) at day 1 while 15 rats received sham irradiation. A behavioural study based on a conditioning test of negative reinforcement, the one-way avoidance test, was performed test, was performed after irradiation. Orally treatment was started one day (study A) or twenty two days (study B) after irradiation and repeated daily for twelve days. In the irradiated group, three subgroups were defined according to the treatment received: EGb 761 (50 mg/kg), EGb 761 (100 mg/kg), water. RESULTS: This work comprised two consecutive studies. In study A (45 rats) the one-way avoidance test was administered daily from day 7 to day 14. In study B (45 rats) the behavioural test was performed from day 28 to day 35. Study A (three groups of 15 rats): following TBI, irradiated rats treated with water demonstrated a significant delay in a learning the one-way avoidance test in comparison with sham-irradiated rats (P < 0.0002) or irradiated rats treated with EGb 761 (50 mg/kg; P < 0.0017) or EGb 761 (100 mg/kg; P < 0.0002). The irradiated rats, treated with EGb 761 (50 or 100 mg/kg) did not differ from the sham-irradiated controls. Study B (three groups of 15 rats): the irradiated rats, treated with water or EGb 761 (50 or 100 mg/kg) did not differ from the sham-irradiated controls. CONCLUSION: This study indicates that a relatively low dose of total body irradiation induces a substantial acute learning dysfunction in the rat, which persists fourteen days after TBI. This effect is prevented by the administration of EGb 761 (50 or 100 mg/kg) started twenty-four hours after irradiation.

Animals↗
PubMed2002

Phenotypic variations and dynamic topography of transformed cells in an experimental model of diethylstilbestrol-induced renal tumour in male Syrian hamster.

This work explores the phenotypic changes affecting transformed cells in an experimental model of diethylstilbestrol (DES)-induced renal tumours in male Syrian hamster. This estrogen-induced neoplasm presents an important cytological pleomorphism and its origin remains largely controversial. In order to characterize phenotypic variations during tumour progression, the occurrence of seven lineage markers was analysed by a morphometric approach in kidney sections of DES-exposed hamsters (6-11 months). S100 protein, neuron-specific enolase (NSE) and vimentin are expressed by a large percentage of malignant cells during tumour development. Glial fibrillary acidic protein (GFAP), protein gene product 9.5 (PGP 9.5) and desmin are mostly evidenced in advanced neoplasm whereas Leu 7 always presents a focal expression. As evidenced by double-label immunofluorescence, the coexpression of three important neuroectodermal lineage markers (S100, NSE and PGP 9.5) in earliest tumour buds points to a peripheral nerve sheath origin for this neoplasm thus confirming previously published data. For each marker, the fluctuations of expression levels during tumour progression as well as the spatial heterogeneity of distribution suggest variable phenotypic differentiation of transformed cell populations. This observation is largely corroborated by double-label immunofluorescence showing coexpression modification of several markers during tumour progression. This points to a complex dynamic and spatial self-organization of different phenotypes within neoplasms. Altogether, these results support the concept that DES-induced kidney tumours are not made of unstructured cell populations but represent adaptive complex dynamic biosystems.

Animals↗
PubMed1981

Experimental model for in vivo determination of dietary fibre and its effect on the absorption of nutrients in the small intestine.

1. An experimental model for the determination of dietary fibre according to the definition of Trowell et al. (1976) is described. Food was subjected to in vivo digestion in ileostomy patients, and the ileostomy contents were collected quantitatively, the polysaccharide components of which were analysed by gas--liquid chromatography and the Klason lignin by gravimetric determination. The model was used for the determination of dietary fibre in AACC (American Association of Cereal Chemists), wheat bran and for studies on the extent of hydrolysis of wheat-bran fibre in the stomach and small intestine. The effect of wheat bran on ileostomy losses of nitrogen, starch and electrolytes was also investigated. 2. Nine patients with established ileostomies were studied during two periods while on a constant low-fibre diet. In the second period 16 g AACC wheat bran/d was added to the diet. The ileostomy contents and duplicate portions of the diet were subjected to determinations of wet weight, dry weight, water content, fibre components, starch, N, sodium and potassium. 3. The wet weight of ileostomy contents increased by 94 g/24 h and dry weight by 10 g/24 h after consumption of bran. The dietary fibre of AACC bran, determined as the increase in polysaccharides and lignin of ileostomy contents after consumption of bran, was 280 g/kg fresh weight (310 g/kg dry matter). Direct analysis of polysaccharides and lignin in bran gave a value of 306 g/kg fresh weight. Of the added bran hemicellulose and cellulose 80--100% and 75--100% respectively were recovered in ileostomy contents. There was no significant difference between the two periods in amount of N, starch and K found in the ileostomy contents. The Na excretion increased during the 'bran' period and correlated well with the wet weight of ileostomy contents. 4. In conclusion, it seems probable that determination of dietary fibre by in vivo digestion in ileostomy patients comes very close to the theoretical definition of dietary fibre, as the influence of bacteria in the ileum seems small. Bacterial growth should be avoided by using a technique involving the change of ileostomy bags every 2 h and immediate deep-freezing of the ileostomy contents. True dietary fibre can be determined by direct analysis of polysaccharides and lignin in the food, at least in bran. Very little digestion of hemicellulose and cellulose from bran occurs in the stomach and small bowel. The 10--20% loss in some patients may be due to digestion by the gastric juice or to bacterial fermentation in the ileum, or both. The extra amount of faecal N after consumption of bran, reported by others, is probably produced in the large bowel.

Adult↗
PubMed1993

An experimental model combining microdialysis with electrophysiology, histology, and neurochemistry for exploring mechanisms of secondary damage in spinal cord injury: effects of potassium.

An experimental model for characterizing effects of agents suspected to cause damage secondary to spinal cord injury is presented. Microdialysis was used to administer candidate damaging agents and to sample the release of other substances in response to administered agents. Damage was assessed by monitoring the amplitudes of evoked potentials during candidate administration and by postmortem histologic examination. This approach enabled the correlation of electrophysiologic, histologic, and neurochemical parameters in the same experiment. Potassium was chosen as a candidate damaging agent, because (1) in high extracellular concentrations it destroys neurons and (2) its extracellular concentration rises substantially following impact injury to the spinal cord. A technique using parallel administering and collecting microdialysis fibers was developed to estimate the in vivo concentration of K+ outside the administering fiber. Administration of 100 mM KCl, 50 mM K2HPO4, or 100 mM potassium glucuronate in artificial cerebrospinal fluid blocked electrical conduction and destroyed cell bodies. Release of the neurotransmitter amino acids aspartate, glutamate, glycine, and gamma-aminobutyric acid (GABA) and the possible neurotransmitter taurine were dramatically increased by administration of 100 mM KCl. Levels of non-neurotransmitter amino acids increased to lesser degrees. Impairment of conduction, destruction of cell bodies, and release of excitotoxins were all consistent with elevated K+ serving as a secondary damaging agent in spinal cord injury.

Amino Acids↗
PubMed1999

The SCID mouse: an experimental model for endometriosis.

The purpose of this study was to validate the suitability of the severe combined immunodeficient (SCID) mouse as an experimental model for endometriosis, by defining the morphological and histological features of induced endometrial implants, and characterizing specific biochemical properties of these implants. Human secretory endometrial tissues were injected into the peritoneal cavity of SCID/SCID CB17 mature female mice. Successful peritoneal implantation was observed in 55 of 57 (96.5%) SCID mice and consisted of circumscribed elevated nodules. Haematoxylin-eosin staining of implanting lesions demonstrated the presence of endometrial glandular tissue in a mixed background of stromal and inflammatory cells. When progesterone was administered to mice, epithelial glands underwent well-defined secretory changes. Immunohistochemical analysis using polyclonal human pan-cytokeratin antibodies demonstrated selective positive staining in the glandular epithelium of the human implants with none in the surrounding stroma. In-situ hybridization analysis using complement component 3 cDNA radiolabelled riboprobes yielded significantly more intense signals in glands compared to stroma. As human endometrial implants in SCID mice were shown to retain specific histological, functional and biochemical properties, we conclude that the SCID mouse is an attractive animal model for the study of endometriosis.

Animals↗
PubMed1985

Human ciliated epithelial cells from nasal polyps as an experimental model for Mycoplasma pneumoniae infection.

Human ciliated epithelial cells derived from nasal polyps and cultured in a monolayer were studied as an experimental model for Mycoplasma pneumoniae infection. Scanning electron microscopy revealed two types of cultured epithelial cells: one which was covered by microvilli only and another which had microvilli and actively beating cilia. M. pneumoniae adhered to both types of cells, and the adherence followed saturation kinetics as a function of time. Infection of the cells for 20 h resulted in 75% inhibition of their intracellular catalase activity and a 3.5-fold increase in their malonyldialdehyde levels compared with noninfected controls. This indicates the presence of cellular oxidative damage due to M. pneumoniae infection. It is suggested that human nasal ciliated epithelial cells may serve as a representative model for studying M. pneumoniae in relation to its natural host.

Adhesiveness↗
PubMed2004

A proposed experimental model of myofascial trigger points in human muscle after slow eccentric exercise.

BACKGROUND: The purpose of this study was to develop an experimental model of myofascial trigger points to investigate their pathophysiology. METHODS: Fifteen healthy volunteers who gave informed consent underwent repetitive eccentric exercise of the third finger of one hand (0.1 Hz repetitions, three sets at five minute intervals) until exhaustion. Physical examination, pressure pain threshold, and electrical pain threshold of the skin, fascia and muscle were measured immediately afterwards and for seven days. Needle electromyogram (EMG) was also recorded in a subgroup of participants. RESULTS: Pressure pain thresholds decreased to a minimum on the second day after the exercise, then gradually returned to baseline values by the seventh day. On the second day, a ropy band was palpated in the exercised forearm muscle and the electrical pain threshold of the fascia at the palpable band was the lowest among the measured loci and tissues. Needle EMG activity accompanied with dull pain sensation was recorded only when the electrode was located on or near the fascia of the palpable band on the second day of exercise. CONCLUSION: These results suggest that eccentric exercise may yield a useful model for the investigation of the myofascial trigger points and/or acupuncture points. The sensitised nociceptors at the fascia of the palpable band might be a possible candidate for the localised tender region.

Adult↗
PubMed1990

Protective effect of S-adenosyl-L-methionine in hepatic uroporphyria. Evaluation in an experimental model.

The potential use of S-adenosyl-L-methionine (SAMe) as therapy for human porphyria cutanea tarda was investigated in an experimental model of hepatic porphyria--that is, chronic treatment of female rats with 0.2% hexachlorobenzene (HCB) in the diet. Administration of SAMe (25 mg/kg subcutaneously twice daily) during the last 15 days of HCB administration halved porphyrin accumulation in the liver but did not alter HCB-induced massive inhibition of uroporphyrinogen decarboxylase. Equally unaffected were inhibition of glutathione peroxidase and stimulation of lipid peroxide formation induced by HCB. Hypothetically, the beneficial effect of SAMe on hepatic porphyrin accumulation might be linked to modifications of the cellular availability of adenosine triphosphate.

Animals↗
PubMed1989

Studies on type II collagen induced arthritis in rats: an experimental model of peripheral and axial ossifying enthesopathy.

It was suggested that type II collagen induced arthritis in rats may be considered an experimental model for rheumatoid arthritis (RA) because of clinical, histological, and immunological similarities. However, some features separate it from RA. We studied 40 inbred female Wistar Furth rats. Two weeks after immunization with native human type II collagen, they had polyarthritis which progressed to ankylosis associated with ossifying enthesopathy and periosteal new bone formation. Inflammatory nodules of the tail appeared after 2 months, with radiological and histopathological aspects of multistage spondylodiscitis. Our findings suggest that collagen induced arthritis may be a relevant model of peripheral and axial ossifying enthesopathy.

Animals↗
PubMed1977

An experimental model of tryptic haemorrhagic enteropathy of the dog.

To study the enteropathy characteristics of the shock state of the dog a simple experimental model has been developed. The cranial mesenteric artery was perfused with 2 micrograms/kg/min norepinephrine for an hour via a diagnostic cardiac catheter inserted under fluoroscopic control. This caused a "pharmacological occlusion" of the artery by local alpha receptor stimulation, and tryptic haemorrhagic enteritis was produced without hypovolaemia or assay operative procedure.

Animals↗
PubMed1994

An experimental model to reproduce some bacterial intestinal cocultures in germ-free mice.

The objective of this study was to create a stable experimental model to act as a living incubator for the main important intestinal bacteria. We have therefore inoculated germ-free mice with the most important bacteria of the human intestinal microflora, in order to study the effect of some oral antibiotics on the intestinal microflora. Sixty germ-free mice, 7 weeks old and of either sex, were inoculated orally with human faecal bacteria by means of their drinking water. Administrations were made at regular intervals following a scheme that respected some of the metabolic inter-relationships of the microorganisms used. The results showed that colonization of the germ-free mouse intestines had been achieved by most of the bacteria that had been inoculated. This "coculture" was stable in time, contrary to what happens when in-toto lyophilized faeces are administered, and the bacterial concentrations for each strains were similar to those found in human faeces.

Animals↗
PubMed1994

[Serological parameters for the diagnosis and follow-up of toxoplasmosis. Experimental models].

BACKGROUND: Toxoplasmosis is a disease of increasing incidence. Its laboratory diagnosis is difficult, specially in acute toxoplasmosis. The data obtained in experimental models attempting to distinguish between acute and chronic toxoplasmosis by the simultaneous study of four serological tests: IgM and IgG antibodies, circulating antigens (CA) and antigens present in immune complexes (IC) are reported. METHODS: The evolution of IgM and IgG antibodies, CA and IC was followed in 3 murine models in acute, subacute and chronic toxoplasmosis, compared with the use of the ELISA technique. RESULTS: Acute toxoplasmosis is characterized by the presence of CA and IC in 100% of the individuals at high concentrations with IgM and IgG only being detectable at low concentrations. In subacute and chronic toxoplasmosis the response to IgG antibodies (100% in animals) is prominent, with detection of IgM being variable and the detection of CA and IC being reduced to the phase considered as acute. CONCLUSIONS: The detection of IgM and IgG antibodies, circulating antigens and immune complexes may be of great usefulness in the differentiation of acute, recently acquired or chronic toxoplasmosis.

Animals↗
PubMed2000

Anti-VEGF antibody suppresses primary tumor growth and metastasis in an experimental model of Wilms' tumor.

BACKGROUND/PURPOSE: Vascular endothelial growth factor (VEGF) has been shown previously to correlate with tumor growth and metastasis in an experimental model of anaplastic Wilms' tumor. The authors hypothesized that treatment with anti-VEGF antibodies would suppress both primary tumor growth and metastasis in this model. METHODS: Tumors were induced in the right kidneys of nude mice by the injection of cultured Wilms' tumor cells. After 1 week, anti-VEGF treatment was begun with injection of either vehicle or an anti-VEGF antibody intraperitoneally. Mice were killed after 4.5 weeks of treatment and tumor weights and the incidence of metastases evaluated. RESULTS: Anti-VEGF treatment resulted in a greater than 95% reduction in tumor weight (P < .0001). Anti-VEGF treatment also abolished the establishment of lung metastases (40% in control animals, P < .003). Cessation of treatment resulted in rebound tumor growth. CONCLUSION: Anti-VEGF therapy can suppress both primary tumor growth and the establishment of metastases in experimental anaplastic Wilms' tumor.

Animals↗
PubMed1999

Loteprednol etabonate, a new soft steroid is effective in a rabbit acute experimental model for arthritis.

UNLABELLED: Loteprednol etabonate, a new soft steroid designed for use as a local therapeutic, was compared to dexamethasone in rabbit experimental model for arthritis. METHODS: Joint inflammation was induced by local injection of antigen into the patellofemoral articulation in sensitized rabbits. Co-administration of either dexamethasone or loteprednol etabonate directly into the joint effectively blocked the inflammatory response. Both the synovial fluid cellular content and synovium histology were examined. The steroid treatments prevented the adverse inflammatory effects of antigen action. These results, together with previous studies showing decreased systemic activity of the soft steroid, indicate that the loteprednol etabonate could provide a therapeutic advantage over currently used intra-articular steroids for alleviating rheumatoid arthritis.

Acute Disease↗