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At least 577 records · Page 32Linked to original sources
PubMed1995

Experimental model of chronic tonsillar herniation associated with early stage syringomyelia.

This report describes an experimental model of chronic tonsillar herniation and its effects on the spinal cord. In ten rats, a small piece of chemically induced mammary cancer was transplanted to the supraoccipital bone. In all cases, the transplanted cancers grew into the posterior fossa, destroying the supraoccipital bone and compressing the cerebellum extradurally. In six of the ten rats, tonsillar herniation was observed at 8-14 weeks after transplantation. Transdural infiltration of the tumor cells was not apparent in any animal. In those rats with tonsillar herniation (n = 6), the spinal cord from the C5 to the T8 segments showed enlargement of the central canal without exception. Histological examination revealed the following changes: stretching and thinning of the ependymal cells; swelling of the astrocytic processes; and extra-cellular edema, predominantly in the dorsal gray matter, but also in the ventral inner portion of the dorsal column. In the control group (n = 4) and those rats without tonsillar herniation (n = 4), such histological changes of the spinal cord were not observed. Although the lesions can not be regarded as representing mature syringomyelia, they most likely constitute an earlier evolutionary stage.

Animals↗
PubMed1993

An experimental model of ascending pyelonephritis due to Candida albicans in rats.

We developed a new experimental model of ascending Candida pyelonephritis in female rats with leukopenia and vesicoureteral reflux. Rats were treated transperitoneally with cyclophosphamide (200 mg/kg) to induce leukopenia 3 days before and transurethrally with diluted acetic acid solution to induce vesicoureteral reflux 1 day before inoculation of Candida albicans strain, ATCC 10259 (containing 10(7) cells). Microscopy revealed acute pyelonephritis in which Candida cells invaded from the fornix and/or papilla into the medulla within 3 days after inoculation. Between 7 and 28 days after inoculation, chronic pyelonephritis reached the cortex. The incidence of pyelonephritis increased gradually and was approximately 80% after 7 days. Candida colony counts of bladder urine specimens obtained by direct puncture were significantly greater in rats with pyelonephritis extending into the parenchyma than in those with pyelonephritis located along the pelvis (p < 0.01). These results suggest that this rat model shows the characteristic feature of ascending pyelonephritis due to C. albicans and that the severity of Candida pyelonephritis can be estimated from Candida counts of bladder urine.

Animals↗
PubMed1989

Experimental model of autoimmune hemolytic anemia induced in mice with levodopa.

This paper describes an experimental model of autoimmune hemolytic anemia induced with multiple injections of levodopa. The serum antibodies were detected by indirect enzyme-linked immunosorbent assay (ELISA) and autoantibodies bound to syngeneic erythrocytes were detected by direct ELISA. A strain of mice injected with levodopa, at doses which are approximately equivalent to those used in human therapy, developed early and late cycles of IgM and IgG anti-mouse red blood cell (MRBC) autoantibody responses. These responses were followed by binding of IgM and IgG autoantibodies to the syngeneic erythrocytes and by two phases of anemia. Different strains of mice exhibited different sensitivities to Levodopa treatment, suggesting that genetic factors affect the anti-MRBC autoantibody response to levodopa. Indirect ELISA revealed that mice subjected to both X-irradiation (250 rad) and levodopa treatment had higher levels of IgG anti-MRBC autoantibodies than mice subjected to levodopa treatment alone, suggesting that a radiosensitive suppressor mechanism controls the autoantibody response. The autoantibodies induced with levodopa exhibited an unrestricted specificity and retained significant activity after absorption of MRBC. Serum autoantibodies were also detected by indirect ELISA in the sera of normal mice. This "natural" autoimmunity was mouse strain dependent and was possibly further influenced by environmental factors. The various implications of this model of autoimmune hemolytic anemia are discussed.

Anemia, Hemolytic, Autoimmune↗
PubMed1977

A new experimental model of hyperphenylalaninemia in rat. Effect of p-chlorophenylalanine and cotrimoxazole.

A new experimental model of hyperphenylalaninemia was proposed. Combination of p.chlorophenylalanine, strongly inhibitor of phenylalanine hydroxylase, and cotrimoxazole, presumably inhibitor of dihydropteridine reductase, produced a good inhibition of phenylalanine hydroxylation in vivo. Thus phenylalaninemia reached values similar to those found in PKU patients, without administration of excess phenylalanine. Tyrosine concentrations remained near the control values and a phenylketonuria occurred.

Animals↗
PubMed2000

Effects of acute or chronic administration of substituted benzamides in experimental models of depression in rats.

The effects of substituted benzamides, sulpiride and raclopride on experimental models of depression were studied in male rats after acute or chronic administration in comparison to those of the classical antidepressant, clomipramine. In contrast to clomipramine (50 mg/kg), acute doses of sulpiride or raclopride (1 or 5 mg/kg) failed to change the behavioral response of animals tested in the despair (constrained swim) test or in the model of reserpine-induced changes in the open field behavior. These doses also did not modify the grooming response of rats exposed to a novel environment. Sulpiride or raclopride 10 mg/kg increased the immobility time in the despair test and reduced novelty-induced grooming. The repeated injection for 21 days of sulpiride or raclopride (1 or 5 mg/kg, but not 10 mg/kg) induced a reduction of the immobility period during the constrained swim test similar to that following the chronic treatment with clomipramine 50 mg/kg. This appeared to be a clear-cut reversed dose-response relationship for both substituted benzamides, being the dose potency 1 mg/kg>5 mg/kg>10 mg/kg. Raclopride was more potent than sulpiride in this respect. Furthermore, like clomipramine, sulpiride (1 or 5 mg/kg) and raclopride (1 mg/kg) antagonized reserpine-induced changes in the open field behavior and enhanced novelty-induced grooming. These results indicate that, in contrast to acute injection, repeated administration of small doses of the substituted benzamides, sulpiride or raclopride induce an effect similar to that of the classical antidepressant, clomipramine. The reverse dose-response relationship suggests that these drugs in small doses act on presynaptic dopamine D(2) receptors. This may be consistent with a postsynaptic action of greater doses that exert sedative effects and increase immobility time in the despair test.

Animals↗
PubMed1999

A new experimental model for partial ureteric obstruction in sheep.

This study aimed to develop a new experimental model of partial ureteric obstruction in sheep. Graded obstruction of the ureter using various sized catheters (Fr 3-8) for variable durations up to 6 weeks was performed in 19 sheep. The kidneys were studied by radionuclide diuretic renography for up to 21 weeks and had histopathological examination at the end of the experiment. Catheters of Fr 3 or Fr 5 should be used to block the ureter for a minimum of three weeks to produce sufficient functional and pathological changes to be studied. The advantages and disadvantages of this model are discussed.

Animals↗
PubMed1994

Injuries induced by diffuse photodynamic action in retina and choroid of albino rats. Morphologic study of an experimental model.

BACKGROUND: The morphologic changes of the retina, choroid, and respective vasculatures in an experimental model of diffuse photothrombosis and photodynamic injury were studied. METHODS: After intravenous injection of rose bengal (40 mg/kg), eyes of 21 albino rats were exposed to a light intensity of 15-17,000 ft-cd for 2 to 15 minutes. Survival times ranged from 15 minutes to 6 days. The specimens were studied by light and electron microscopy. RESULTS: Photothrombosis of retinal and choroidal vessels was variable in extension and duration. Vascular lesions included vacuolation and sloughing off of endothelium, and necrosis and apoptosis of pericytes and smooth muscle cells. Retinal and choroidal injuries exhibited considerable regional and structural differences, such as predominance in the outer versus inner retina, or focal versus diffuse injury. CONCLUSION: Damage produced by this model was irregular in extent and character, due to several hard-to-control parameters. It was presumably due not only to ischemia but also to free radical chain reactions initiated by photodynamic action. This model may not be suitable for rapid quantitative assessment of ischemic retinal injury, but it provides opportunities for the investigation of pathophysiologic mechanisms.

Animals↗
PubMed2003

Experimental model of obstructive, chronic pancreatitis in pigs.

BACKGROUND: We aimed to develop a reproducible, experimental model of obstructive pancreatitis for future analysis of surgical interventions, and characterized this model using functional, histological and biochemical parameters. ANIMALS AND METHODS: In 10 female pigs the pancreatic duct (PD) was ligated. After 4, 6 or 8 weeks the animals were sacrificed. Before and after ligation, glucose tolerance and intraductal pressure were measured, and pancreatic juice was collected after stimulation with cholecystokinin and secretin. Amylase and lipase activities were analyzed in plasma and juice. Pancreatic tissue was collected for histochemical analysis. RESULTS: Within 4 weeks of ligation, the pancreas appeared atrophic. Intraductal pressure had risen significantly. Acinar-to-ductal metaplasia was accompanied by strong proliferation of stellate cells and increased collagen deposition. Islets of Langerhans appeared smaller and more numerous. Blood amylase and lipase levels were normal and glucose tolerance was unaffected. Pancreatic juice volume and amylase and lipase activities were significantly lower. CONCLUSION: Ligation of the PD in pigs resulted in a marked fibrosing obstructive pancreatitis within 4 weeks, similar to human chronic pancreatitis in regard to clinical, functional, histological and biochemical parameters.

Animals↗
PubMed1986

Invasiveness in primary intracranial tumors: Part 1. An experimental model using cloned SV40 virus-produced hamster brain tumors.

This report presents an experimental model for study of the cellular and molecular biology of invasiveness in tumors. It uses SV40 virus for the production of primary intracranial tumors that are invasive for normal brain and vary markedly and predictably in this invasiveness. Cell cultures of dissociated 1- to 2-day-old Syrian hamster cerebral cortex (Cx), brain stem (Bs), cerebellar hemisphere (Cbh), and cerebellar vermis (Cbv) were transformed with SV40 virus and inoculated intracerebrally into newborn hamsters. All 368 animals that developed intracranial tumors were killed, and tumor was taken for histological and immunofluorescence studies, assessment of extent of invasiveness, and preparation of cell cultures from which cells were cloned by dilution plating or growth in soft agar. A few hamsters were perfused with glutaraldehyde for studies of tumor ultrastructure. All cloned and uncloned tumor cells were reinoculated to produce second- and third-passage tumors. Characteristic differences in morphology and growth rate were observed between normal astrocytes derived from each brain region, and these phenotypic differences were retained after virus transformation and tumor production. Cloned and uncloned Cx cell-derived tumors of second and third passage diffusely invaded adjacent normal brain, although those of first passage invaded only slightly. Except for extracerebral spread, these tumors resembled human astrocytic series tumors. Bs and some Cbh cell-derived tumors were also astrocytic but more undifferentiated and only slightly invasive; Cbv and other Cbh cell-derived tumors were sarcomatous and only extended along perivascular spaces or were not invasive at all. The tumor cells contained glial fibrillary acidic protein and SV40 T-antigen. These results suggest that astrocytes from different brain regions vary in genomic stability and support the theory that differences in invasiveness reflect the development of heterogeneity and subsequent selection of more aggressive subpopulations of cells.

Animals↗
PubMed2006

Polyaxially-locked plate screws increase stability of fracture fixation in an experimental model of calcaneal fracture.

Different calcaneal plates with locked screws were compared in an experimental model of a calcaneal fracture. Four plate models were tested, three with uniaxially-locked screws (Synthes, Newdeal, Darco), and one with polyaxially-locked screws (90 degrees +/- 15 degrees ) (Rimbus). Synthetic calcanei were osteotomised to create a fracture model and then fixed with the plates and screws. Seven specimens for each plate model were subjected to cyclic loading (preload 20 N, 1000 cycles at 800 N, 0.75 mm/s), and load to failure (0.75 mm/s). During cyclic loading, the plate with polyaxially-locked screws (Rimbus) showed significantly lower displacement in the primary loading direction than the plates with uniaxially-locked screws (mean values of maximum displacement during cyclic loading: Rimbus, 3.13 mm (sd 0.68); Synthes, 3.46 mm (sd 1.25); Darco, 4.48 mm (sd 3.17); Newdeal, 5.02 mm (sd 3.79); one-way analysis of variance, p < 0.001). The increased stability of a plate with polyaxially-locked screws demonstrated during cyclic loading compared with plates with uniaxially-locked screws may be beneficial for clinical use.

Biomechanical Phenomena↗
PubMed2004

Pulmonary lymphoid lesions in an experimental model of collapsing glomerulopathy in rats.

UNLABELLED: The characterization of lung damage in an experimental model of collapsing glomerulopathy (CG) in rats is described. METHODS: 12 rats were divided into two groups and injected intravenously (iv) with 1 mg/saline in a final volume of 1 ml/ day in the tail vein for 5 days, with fractionated serum from control and CG subjects. Proteinuria was quantified, and the Glomerular filtration rate was calculated based on creatinine clearance (CC). Rats were sacrificed by perfusion fixation at day 5. RESULTS: Rats injected with serum from CG patients developed proteinuria (p<0.001). A decrease in CC (0.68+/-0.19) in these rats was also observed. Glomerular tuft retraction and mesangial proliferation was observed in all rats receiving serum from the CG patients. Peribronchiolar infiltrate integrated mainly by lymphocytes, was identified in all CG rats. In some areas this infiltration disrupted the basement membrane and damaged the epithelium. No histopathological abnormalities in the kidney or lungs were found in rats receiving control serum. CONCLUSION: Patchy pulmonary lymphoid infiltrates were found in the CG model. Up to now there was no information about pulmonary lymphoid infiltration in CG patients. Besides fluid overload due to renal insufficiency or a nephrotic syndrome, other causes of pulmonary involvement in CG patients should be explored.

Animals↗
PubMed1989

An experimental model of cerebral venous hypertension in the rat.

Several means of establishing a useful experimental model of cerebral venous hypertension were examined in rats. Retrograde embolization with an autologous blood clot passed through a catheter inserted in an external jugular vein, combined with ligation of the contralateral external jugular vein, was found to produce consistent, sustained cerebral venous hypertension. This model has the advantages of being technically easy to prepare, well tolerated by the animals, and suitable for autoradiographic and/or histochemical assessment of regional circulation and metabolism.

Anastomosis, Surgical↗
PubMed1999

[Experimental model for cancer metastasis].

It is important for metastasis research to establish a good experimental model for cancer metastasis. The author has introduced a variety of in vitro and in vivo models for cancer metastasis, and suggested how to select them for individual metastasis research.

Animals↗
PubMed2004

New experimental models for the in vitro reconstitution of human bladder mucosa.

This study describes two experimental models for the in vitro reconstitution of the human bladder mucosa (neo-bladder): human urothelial stabilized cell lines were cultured on three-dimensional matrices, collagen or platelet-fibrin gels, containing murine fibroblast 3T3-J2 cells. Low-density seeding (2x10(4) cells/ml) of both normal (TCA-48) and neoplastic cell lines (TCA-47) on collagen matrix gave rise to isolated papillar colonies, while high-density seeding (3.75x10(6) cells/ml) led to the formation of wide pluristratified epithelial sheets, resembling the normal transitional epithelium. In contrast, high-density seeding (5x10(5) cells/ml) on platelet-fibrin matrix did not allow the formation of epithelial sheets: only isolated voluminous colonies of normal TCA-48 cells, and sparse and small colonies of neoplastic TCA-47 could be observed. Growth assays and cytotoxicity reduction tests showed that the growth inhibitory effect of platelet-fibrin gel on urothelial cells was probably due to the aspecific activation of the complement contained in the plasmatic fraction, whose precipitation forms fibrin-glue. Collectively, these findings allow us to draw the following conclusions: i) neobladders obtained by culturing urothelial cells on collagen matrix reproduce normal bladder mucosa and could be utilized in pharmacological studies; and ii) platelet-fibrin gels, that specifically inhibit neoplastic urothelial cell growth, could be used as scaffolds in surgical bladder reconstitution.

3T3 Cells↗
PubMedDate not supplied

Does cyclosporin A have any effect on accelerated atherosclerosis in absence of graft rejection? Pathologic and morphometric evaluation in an experimental model.

BACKGROUND: The effects of cyclosporin A on accelerated atherosclerosis were studied in an experimental model of aortic isotransplantation. METHODS: Seventy-six Lewis rats were studied. Forty-one abdominal aortic isografts were performed and divided into five groups: 2-day isografts and 15- and 100-day isografts with and without cyclosporin treatment. The remaining rats were divided into seven groups: 15- and 100-day sham-operated, with and without cyclosporin administration; 15- and 100-day animals with cyclosporin treatment only; and normal controls. Cyclosporin was injected subcutaneously in doses of 10 mg/kg daily for the first 15 days and afterward every other day. Longitudinal sections of the proximal anastomosis and cross sections of the midgraft region were measured with a semiautomatic image-analyzer. RESULTS: Histologic analysis showed that accelerated atherosclerosis was not observed either in NT2 rats or in nontransplanted animals. In the 15-day isografts, accelerated atherosclerosis was present in the perianastomotic tract of the recipient aorta in nine of nine NT15 rats, whereas it was found only in three of nine T15 animals (p < 0.02). Histomorphometric analysis showed that accelerated atherosclerosis was less pronounced in the T100 isografts than in the NT100 ones, this difference being significant at the recipient anastomotic side only (p < 0.0005). CONCLUSIONS: The present results support the hypothesis that cyclosporin, at immunosuppressant and nontoxic doses, can delay the onset and progression of accelerated atherosclerosis and that its effects are more significant at the recipient side of the anastomosis where accelerated atherosclerosis begins to develop.

Anastomosis, Surgical↗
PubMed2005

Echinostomes as experimental models for interactions between adult parasites and vertebrate hosts.

Echinostomes are intestinal trematodes that, for years, have served as experimental models in different areas of parasitology. However, the usefulness of these trematodes in experimental parasitology has been underappreciated. In this article, we examine the characteristics that make echinostomes useful models for analysis of the interactions between adult parasites and vertebrate hosts, particularly in relation to the host-related factors that determine the establishment of the parasites.

Animals↗