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Results for “Models, Experimental”

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At least 937 records · Page 52Linked to original sources

PubMed1996

Porcine gastroepiploic artery as an in vitro experimental model to study vasodilators in microsurgery.

Arterial vasospasm is a common problem in microsurgery. This pharmacological study compares seven vasodilators-lidocaine, papaverine, nicardipine, verapamil, diltiazem, sodium nitroprusside, and hydralazine-for their efficacy and potency in an experimental model of vasospasm. Porcine gastroepiploic arteries were cut into rings to measure isometric tension development in vitro. The arteries were preconstricted with endothelin-1, a stable thromboxane A2 analogue, norepinephrine, or potassium, and then exposed to increasing concentrations of each vasodilator. Every vasodilator except hydralazine and sodium nitroprusside was efficacious in producing near-maximal relaxation of arteries preconstricted with any vasospastic substance. The five efficacious vasodilators differed markedly in potency, as reflected in the concentrations producing half-maximal relaxation. The order of potency was nicardipine < or = verapamil or diltiazem < papaverine < lidocaine. This study suggests that nicardipine would be the most potent vasodilator for systemic or direct intra-arterial administration. Papaverine and lidocaine, in concentrations employed clinically, were both efficacious as topical vasodilators.

Animals↗

PubMed1988

An experimental model system for leishmaniasis. An ultrastructural study on cultured macrophages exposed to Leishmania parasites and sodium stibogluconate.

To facilitate studies on the effect of chemotherapeutic agents on the host-parasite interaction in leishmaniasis, we have developed an experimental model for infecting mouse peritoneal macrophages in culture with recently-isolated Leishmania donovani promastigotes. As the drug action is often dependent on concentration, the distribution of sodium stibogluconate, which is the commonly used drug for treatment of leishmaniasis, was studied in various parts of the macrophages by energy dispersive X-ray microanalysis. The drug was found to accumulate in secondary lysosomes. The ultrastructural examination, using TEM and SEM, of macrophages, whose secondary lysosomes had been preloaded with gold particles, showed that leishmania parasites are phagocytosed and finally located in secondary lysosomes. Using flameless atomic absorption spectrophotometry, the concentration of Mn, Fe and Cu in promastigotes of Leishmania donovani, Leishmania aethiopica, Leishmania crithidia, Leishmania major and their culture media was estimated. Of the three transition metals, the parasites accumulated only Mn from the medium, which they may use in a primitive defense mechanism against reactive oxygen metabolites produced by macrophages during the respiratory burst associated with phagocytosis.

Animals↗

PubMed2003

[Study on the experimental model of krypton laser-induced choroidal neovascularization in the rats].

OBJECTIVE: To evaluate the feasibility of krypton laser-induced choroidal neovascularization (CNV) model in the Brown Norway rats in order to establish the foundation for studying the mechanism of CNV and for the development of treatment for CNV. METHODS: Experimental eyes in 33 rats were received a series of 10 krypton red laser (647 nm) lesions per eye (360 mW, 50 micro m, 0.05 s). Fundus fluorescein angiography (FFA) and indocyanine green angiography (ICGA) were performed, then the rats were sacrificed immediately, the eyes were enucleated and processed for histopathologic examination and transmission electron microscopy on days 3, 7, 14, 21, 28 and 56. RESULTS: CNV was firstly appeared on day 7 after photocoagulation, reaching the peak on day 21. The incidence of CNV was 76.0%. Disciform leakage staining appeared in the FFA. ICGA showed that the disciform area was filled with CNV. CNV was ascertained by light microscopy and electron microscopy. The thickness of laser-induced CNV was increased from day 7 to day 21 (P < 0.01) and no significant progress occurred after day 21 (P > 0.05). CONCLUSIONS: The present studies demonstrated that krypton laser photocoagulation could be used to produce choroidal neovascularization experimental model in the Brown Norway rat. CNV can be induced rapidly by the method, persists for a long period and at a high successful rate.

Animals↗

PubMed1988

Non-union of testis and epididymis. Description of an experimental model in the rat. Effect on testicular descent.

Most of the reported anomalies in undescended male gonads involve disruption of continuity in the proximal reproductive tract. In order to study the effect of this anomaly on the testis, an experimental model was developed. 16-day-old Sprague-Dawley rats were operated on. The testes were mobilized through a midline abdominal incision and further dissection was carried out under an operation microscope with 20X magnification. The efferent ducts were dissected free, clamped with a microclip, severed and ligated. The epididymis and testis were separated to the level of the inferior epididymal artery. Following surgery 11 of 35 operated testes (31%) remained in the abdomen while three (9%) descended into the opposite hemiscrotum. One of these atrophied due to torsion. The rest descended normally as did all in the sham-operated group. No surgical complications were seen. At 30-37 days the non-union operated testes were edematous, but no tubular distension was seen. The operative procedure probably involves ligation of lymphatic vessels from the testis as well as ductuli efferentes causing an interstitial edema.

Animals↗

PubMed1997

Obtaining maximal use of expanded scalp rotation flaps via an experimental model.

The relative inelasticity of scalp skin and the irregular convexity of the cranial vault necessitate careful planning in the design and mobilization of scalp flaps. Rotation flaps adapt particularly well to the curves of the cranial vault. An experimental model has enabled us to study the design and mobilization of expanded scalp rotation flaps and to obtain maximal efficiency from the tissue expansion process. The use of a round tissue expander situated immediately adjacent to a scalp defect is an excellent method for the creation of a rotation flap. To optimize the use of the expanded tissues, the flap should be designed so that its border passes along the periphery of these expanded tissues. In cases in which it is advisable to separate the expander from the defect, such as when the defect is highly contaminated, efficient use of the expanded tissues can still be obtained by placing the expander at the site of a rotation flap backcut. Furthermore, although this study focuses on rotation flaps only, this same model can be used to examine and compare different closure methods using other types of flaps as well.

Child, Preschool↗

PubMed1999

Coelomic metaplasia theory of endometriosis: evidence from in vivo studies and an in vitro experimental model.

Ultrastructure studies of pelvic peritoneal tissue from women undergoing laparotomy suggest that before endometriosis has become established in the peritoneum, there might be a metaplastic change by peritoneal mesothelial cells into endometrial glandular cells. A new in vitro experimental model of endometriosis using human ovarian surface epithelium cells has shown evidence that endometriotic lesions can arise by a process of metaplasia from the ovarian surface epithelium. In this model, when both ovarian surface epithelium and ovarian stromal cells were cocultured with 17beta estradiol in a three-dimensional collagen gel lattice, the ovarian surface epithelium cells formed a lumen structure, surrounded by endometrial stromal cells with an epithelial mesenchymal structure. Immunoreactivity for epithelial membrane antigen and cytokeratin was shown in the glandular cells and cilia, as well as in the microvilli. Electron microscopy showed evidence of tight junctions on cell surfaces. These findings suggest that endometriosis may manifest as a serial change from the adjacent mesothelial cells.

Cells, Cultured↗

PubMed1989

[A new experimental model for direct in vivo observation of microcirculation in microsurgery].

The anatomical conditions and a method of preparing of a vascular-nervous isolated flap of the musculus cremaster in rat have presented. It is an example of the experimental model of the free muscular flap with the central course of vessels. This new model offers wide possibilities of in vivo observation of changes in microcirculation after using of various operations as well as drugs.

Animals↗

PubMed1985

Delayed antiischemic effect of prostaglandin I2 and of a new stable prostaglandin I2 analogue, 7-oxo-prostacyclin-Na, in experimental model angina in dogs.

Therapeutic application of prostaglandin I2 (PGI2) is rendered difficult by its instability. The 7-oxo-derivative synthesized by Kovács et al. [8] proved to be stable in aqueous solution. Both drugs were tested in experimental model angina in anesthetized thoracotomized dogs with critical stenosis of the left anterior descending coronary artery, in which drug-induced reduction of ischemic ST-segment elevation evoked by frequency loading was estimated [10]. Both drugs markedly reduced blood pressure (BP) even if given by intravenous infusion for 60 min in a total dose of 20 micrograms/kg for PGI2 and 250 micrograms/kg for 7-oxo-PGI2-Na. BP returned to normal soon after infusion and did not substantially change. After a latency of 90-120 min, a 40-50% reduction of ischemia-induced ST-segment elevation appeared in the epi-, endo-, and intramyocardial ECG. Intracoronary infusion of PGI2 in 1 microgram/kg and 7-oxo-PGI2-Na in 25 micrograms/kg total dose minimized systemic actions, but a delayed protective effect appeared, due probably to some nonvasoactive metabolite of these substances. Although both substances exert a potent platelet-aggregation-inhibiting action, serial ex vivo determination of ADP aggregation at different times has shown a dissociation of antiaggregatory action from the protection, this dissociation reaching its maximum when antiaggregatory action was already over.

Angina Pectoris↗

PubMed1995

Growth retardation in pregnancy: experimental model in the rabbit employing electrically induced thermal placental injury.

Intrauterine growth retardation involves haemodynamic modifications in the uterus and placenta. In order to study intrauterine growth retardation we obtained an electrically induced thermal placental injury in a rabbit experimental model. The effects on weight of fetuses, placentas and single organs were recorded and statistically analysed. Fetal growth retardation was recorded in 71% of fetuses exposed to 15 mA direct current per 40 seconds, and resulted in only 7.9% of normal fetuses. The data presented in this study have shown a retardation of fetal growth particularly evident in the liver weight with a relative sparing of brain development. Kidney and heart do not present a statistically significant reduction in growth. This growth retardation model is simple and readily reproducible.

Animals↗

PubMed1992

An experimental model of mitochondrial myopathy: germanium-induced myopathy and coenzyme Q10 administration.

In skeletal muscles from rats treated with germanium for 23 weeks, there were numerous ragged-red fibers and cytochrome-c oxidase (COX)-deficient fibers. Biochemically, germanium reduced the enzyme activities in the mitochondrial respiratory chain. Rotenone-sensitive NADH-cytochrome-c reductase as well as COX activities were markedly reduced, while succinate-cytochrome-c reductase was less severely, but significantly, affected. The histopathological findings in these muscles were similar to those seen in patients with mitochondrial encephalomyopathy, suggesting that germanium-induced myopathy may be a useful experimental model. Coenzyme Q10 administration appeared to be ineffective in preventing this experimental myopathy.

Animals↗

PubMed1989

Immunomagnetic depletion of malignant cells from autologous bone marrow graft: from experimental models to clinical trials.

Using experimental modes with normal allogeneic bone marrow (BM) contaminated with Burkitt or neuroblastoma cell lines, and a liquid culture assay, we demonstrated that, when used in optimal conditions, the immunomagnetic depletion technique permitted a reproducible elimination of 3-4 log malignant cells. Results were very similar to those obtained with the complement lysis procedure in Burkitt lymphoma. This immunomagnetic procedure was used in 123 cases of autologous bone marrow transplantation (ABMT) in children with neuroblastoma. The analysis of the cases demonstrated, first, that the procedure induced a significant loss of mononuclear cells but was not toxic for BM precursors. Delays to engraftment observed in a few patients were probably due to the combination of pejorative factors, especially the damage caused to the micro-environment by previous heavy and prolonged chemotherapy or the double ABMT programme. Second, patients presented with profound T-cell defect with undetectable IL2 secretion up to 1 year post-graft but they all had normal NK functions from the first month post-graft, these functions exceeding normal values on the second and third months post-graft. Finally, in 20 cases, dual-immunofluorescence staining permitted the demonstration that the autograft contained malignant cells before purging that were eliminated by the immunomagnetic depletion.

Bone Marrow↗

PubMed1982

Experimental model of dysentery.

A method of producing experimental dysentery in rabbits has been developed. A prerequisite for this model is the fact that microscopic fungi eliminating biologically active substances are regularly found in the large intestine of man. Using a rubber probe, the large intestine of rabbits was preliminarily irrigated with the filtrate of the Aspergillus flavus fungus and subsequently, the suspension of a 24-hour culture of dysentery bacteria Shigella flexneri was administered. A specific pathological process characteristic of dysentery infection with positive pathomorphological, immunological and clinical manifestations developed in the experimental animals. The developed technique of the experimental dysentery model is easy to accomplish and can be widely used for the study of various problems of dysentery infection.

Animals↗

PubMed1995

Neovascularization of the testicle through spermatic vessels by omental pedicle flap: a new experimental model.

The aim of this experimental study in rats was to consider the supplementary role of an omental pedicle flap on the neovascularization of the testicle through the spermatic vessels, for which a Fowler-Stephens procedure had been planned. To compare results, 12 animals had only the spermatic vessels ligated, without an additional procedure (Fowler-Stephens procedure [FS group]), and 12 others had omentopexy of the spermatic vessels of the left testes, with ligation of the vessels 4 weeks later (Fowler-Stephens procedure plus omentopexy [FSO group]). In the sham group (n = 8), only omentopexy of the left spermatic vessels was performed. Six rats served as controls. In each rat, both testes were evaluated by color Doppler ultrasonography to assess capsular and intratesticular blood flow, followed by orchiectomy to determine testicular weights, testicular biopsy scores, and mean seminiferous tubule diameters. Data were analyzed statistically. According to the color Doppler ultrasonography, the testicular blood flow in the FSO group was better than that of the FS group, but was less sufficient than that of the sham and control groups. The testicular weights and biopsy scores for the FSO group were statistically greater than those of the FS group, and less than those of the sham and control groups. There was no significant difference in the mean seminiferous tubule diameters of the FSO and FS groups. The contralateral tests of the four groups did not differ significantly for any parameter. In light of the data available, it is suggested that the omental pedicle flap neovascularizes the testicle through spermatic vessels. Given the high incidence of testicular atrophy associated with Fowler-Stephens orchiopexies, it might be beneficial to perform laparoscopic orchiopexy of testicles neovascularized with omental pedicle flaps as the first-stage procedure.

Animals↗

PubMed1989

Morphological survey of a new pericardial valve prosthesis (Pericarbon): long-term animal experimental model.

A long-term experimental morphological study was carried out in 22 adult sheep to evaluate a new pericardial valve prosthesis (Pericarbon), which had been implanted in the tricuspid or mitral position. This prosthetic device differs substantially from others in that its construction design consists of two sheets of glutaraldehyde-fixed bovine pericardium and a low-profile flexible plastic stent (Delrin) covered by a pyrolytic carbon coated dacron fabric; one pericardium sheet forms the three cusp valve and is sutured to the second, which lines the inner surface of the plastic stent. Twenty animals were sacrificed at fixed intervals, while 2 are still living at about 3 years post-surgery. Tricuspid explants (mean duration, 295 days) showed significant fibrous sheathing and a mean calcium X-ray score of 1.75. Mitral medium-term explants (mean duration, 325 days) had fairly well preserved pliability and a mean calcium X-ray score of 2.5. Long-term explants (mean duration, 467 days) were all stiffened by calcification (mean score, 3.75). None of the explants had tears or perforations. Medium or long-term mechanical failure was not observed. A significant host tissue reaction took place in the tricuspid but not in the mitral position. Calcification mainly involved the collagen fibres and increased progressively with time. Ultrastructural studies invariably disclosed fair preservation of graft tissue structures, surface reendothelization and initial nuclei of calcification within the collagen fibres. These morphological findings confirm the potential advantages of this new prosthetic device and warrant long-term clinical trials to test its actual durability.

Animals↗

PubMed2004

Prolongation of the intestinal viability using oxygenated perfluorocarbon in an experimental model of acute intestinal ischemia.

OBJECTIVES: Liquid perfluorocarbons (PFCs) are well known for their capability to carry respiratory gases. The aim of this study was to evaluate the effectiveness of oxygenated F-Decalin on the intestinal viability, in an experimental model of acute intestinal ischemia. MATERIAL AND METHODS: Thirty-six rabbits were subjected to 8h intestinal ischemia by ligation of the superior mesenteric artery (subgroups 1), the mesenteric vein (subgroups 2) or both vessels (subgroups 3). The animals were divided into three groups: (a) Control (ischemia alone), (b) PFC-O2 (ischemia plus infusion of oxygenated F-Decalin) and (c) PFC (ischemia plus infusion of not-oxygenated F-Decalin). Intestinal biopsies from four different sites and blood samples for serum enzymes measurements were taken at 2, 4, 6 and 8 h. All tissue sections were examined blindly under light microscope. Sections from the specimens were taken at 4 and 8 h, and examined blindly under the electron microscope. Statistical analysis was performed by non-parametric Kruskal Wallis test. RESULTS: Using light microscope, the observed intestinal damages to the sections from Control and PFC groups were severe at 4 h and destructive after 8 h. On the contrary, minimal injuries were observed in the biopsies from PFC-O2 group at 4 and even after 8 h of ischemia. These findings were confirmed by the electron microscope study and correlated to the serum enzymes measurements. CONCLUSIONS: These results suggest that intestinal viability could be prolonged after acute ischemia using oxygenated perfluorocarbons and this could be a promising pretreatment modality for a variety of mesenteric ischemic forms.

Acute Disease↗

PubMed2003

Development and evaluation of an experimental model for investigating the pathogenesis and therapeutic strategies of acute liver failure.

Because of the various etiologies of acute liver failure (ALF) a clinically relevant model must fulfill four criteria--reversibility, reproducibility, ALF-induced death, and a sufficient time interval for diagnosis and therapy between induction and death. In this study an experimental model was evaluated for these criteria. A total of 49 rats were randomized into seven groups: First, a pilot study was performed regarding the survival rate after different treatments: In group I, animals underwent a 70% liver resection. In group II, 70% liver resection was combined with ascending doses of postoperative endotoxin administration up to 400 microg/kg (group IIc). In group III, animals only underwent liver mobilization. In group IV, ALF was induced according to the protocol of group IIc, but with additional treatment of an endothelin-A-receptor (ETAR) antagonist. Animals in group V received only 400 microg endotoxin. After induction of ALF, all animals died within the first day, showing significantly elevated bilirubin and ammonium levels and severe damage to hepatocellular integrity. Application of the ETAR antagonist resulted in the survival of 6/7 animals until the 14th day; the biochemical and histomorphological changes were reversible. All other animals survived to the 14th day. A clinically relevant model of ALF in rats can be created by the combination of 70% liver resection and endotoxin application to produce an inflammatory component.

Acute Disease↗

PubMed1996

An experimental model for acute poststreptococcal glomerulonephritis in mice.

A number of factors have been implicated in the pathogenesis of acute poststreptococcal glomerulonephritis (APSGN). The lack of a reliable animal model has made it difficult to further examine the role of these factors in the pathogenetic process. In this report, we present a tissue cage model in mice for the study of APSGN. Morphological and immunohistological changes in the kidney, resembling those of APSGN in man, were induced at high frequency in the experimental model after infection with group A streptococcal nephritis isolates. Nephritis-associated strain induced hypercellularity, occlusion of capillaries, and C3 deposition at high frequencies compared to the changes induced in animals infected with a non-nephritis-associated strain and non-infected controls. In animals infected with a nephritis isolate, hematuria and proteinuria were also detected. If penicillin treatment was initiated on the third day of infection, the development of the nephritis process was prevented. Streptokinase, as well as preabsorbing antigen and streptococcal pyrogenic exotoxin B (SpeB), have been implicated in the pathogenesis of APSGN. These proteins, as well as SpeA and SpeF, were detected in the fluids of the infectious focus, regardless of the origin of the strains and whether or not glomerulonephritis was seen. Antibodies to streptokinase were evoked in the majority of the infected animals. This immune response did not correlate with the nephritic process since hypercellularity was also seen in animals which lacked detectable streptokinase antibodies. The results show that the mouse tissue cage model can be used to study APSGN and to evaluate factors involved in the pathogenesis of the disease.

Animals↗

PubMed1992

An experimental model of oculorespiratory reflex.

An experimental study of the oculorespiratory reflex (ORR) was conducted on 20 albino rabbits using a square wave (SW) type of stimulus. The ORR could be elicited in 100% of animals. The medial rectus was observed to be most reflexogenic for ORR. The frequency and pattern of ORR was not affected by bilateral vagotomy, intravenous atropine or glycopyrrolate, but could be completely abolished by retrobular block.

Animals↗