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At least 163 records · Page 9Linked to original sources

PubMedDate not supplied

[Supra-selective vagotomy in the rat. A new experimental model. Preliminary results].

An original experimental model of highly selective vagotomy in the rat is proposed. The operative technique by microsurgery is described. The mechanical consequences of vagotomy are studied immediately and some time after the operation. Radio-cinematographic and E.M.G. studies, carried out, confirm the selective character of this vagotomy. The mildness of the symptoms observed at some time after the operation and the prevention of restraint ulcers by highly selective vagotomy are emphasized.

Animals↗

PubMedDate not supplied

[In vivo experimental models of amebiasis].

In vivo experimental models for amebiasis have provided important information about the mechanisms of host-parasite interaction which determine the production of disease. In the laboratory, several species of rodents have been used to study the intestinal and hepatic amebiasis. For the former, the model of "washed-closed cecal loop" in guinea-pig and hamster has been useful to study the early invasive events. In gerbils we also produced early intestinal lesions by intracecal inoculation with monoxenically cultured amebas. Hamsters and gerbils have been used as susceptible animals for hepatic amebiasis, and rats and guinea-pigs as resistant animals. Morphological analysis of hepatic lesions of susceptible animals showed the role of host inflammatory cells in the process of liver damage. The resistance in the production of liver abscess in rats and guinea-pigs is due in part to the action of polymorphonuclear leukocytes in the rat and the macrophages in the guinea pigs. Complete characterization and standardization of the various models of amebiasis in rodents constitute the bases for other important biomedical studies aimed to the disease control.

Animals↗

PubMed1976

Nitroglycerin and dipyridamole on cardiac metabolism and dynamics in a new experimental model of angina pectoris.

An experimental model of angina pectoris has been developed in order to study the hemodynamic, metabolic and electrophysiological alterations of the heart assumed to occur in the human disease and to analyze the influence of nitroglycerin and dipyridamole on the above changes. In anesthetized and thoractomized dogs, the left anterior descending coronary artery was autoperfused from the subclavian artery. Coronary blood flow was reduced until the epicardial monopolar electrocardiogram recorded from the myocardial segment supplied by the constricted coronary artery was just short of ischemic changes. O2 consumption and lactate uptake of the same segment were determined from the arteriovenous difference by sampling venous blood draining this area. Increasing heart rate by 50 to 70 beats/min by electrical pacing of the right atrium evoked a reversible and reporducible elevation of the ST segment and T wave of the electrocardiogram. Blood flow to the area perfused by the constricted coronary artery as well as the O2 uptake of the same area failed to increase on pacing. A concomitant decrease of lactate uptake, sometimes becoming even negative, was indicative of ischemia of that area. These changes could be reduced or prevented by a 10-minute infusion of a total dose of 20 mug/kg of nitroglycerin but not by 60 mug/kg of dipyridamole. Since the changes are fully reversible and readily reproducible, and the response also appears to show parallelisms with those observed in the human patient during an acute angina pectoris attack, use of this model for the assay of antianginal drugs seems to be warranted.

Angina Pectoris↗

PubMedDate not supplied

Effect of sorbent-based dialytic therapy with the BioLogic-DT on an experimental model of hepatic failure.

An experimental model of hepatic failure in the dog has been developed in which the liver is devascularized in two stages. Under general anesthesia, a portacaval shunt is created, ligatures placed around the hepatic and gastroduodenal arteries, and the dog recovered. Two days later under general anesthesia, the ligatures are pulled, converting hepatic insufficiency to hepatic failure. Five control animals developed hypotension, severe lactic acidosis, hypoglycemia, and increasing liver enzyme levels during 6 hrs of follow-up. The BioLogic-DT system includes a cellulosic plate dialyzer with a suspension of powdered charcoal and cation exchangers as dialysate. Five animals were treated with the BioLogic-DT for 6 hrs after creation of hepatic failure. These animals were more stable physiologically, developed less lactic acidosis and less enzyme elevation, and maintained high normal blood glucose levels. The results help explain the clinical improvement demonstrated in patients with hepatic failure treated by the BioLogic-DT, and confirm that many of the toxins of hepatic failure are dialyzable and bound by simple sorbents such as charcoal and cation exchangers.

Ammonia↗

PubMed1996

[Mechanism and location of typical atrial flutter. Information drawn from experimental models and clinical electrophysiology].

Several experimental models have been proposed to explain the electrocardiographic and electrophysiological characteristics of atrial flutter. In animal models based on anatomical obstacles, intercaval crush or Y like shaped lesion located in the right atrium, it has been possible to induce sustained atrial arrhythmias in which the entrainment criteria could be demonstrated. Additionally these tachycardias presented an atrialwave morphology similar to the F waves of type 1 or typical atrial flutter. Flutter type 2 could better be explained by models based on functional reentry like the leading circle. Typical atrial flutter in human, saw teeth morphology in inferior ECG leads, is though to be a circus movement located in the right atrium, as deduced of the analysis of activation sequence, resetting and entrainment phenomena from right and left atrium. Moreover the successful results of RDF ablation procedures confirm this idea. Nevertheless the delimitation of the anatomical boundaries of the reentry pathway remains inconclusive.

Animals↗

PubMed1994

Ischemia-reperfusion syndrome: an alternative experimental model.

OBJECTIVE: To design an alternative experimental model of ischemia-reperfusion syndrome. Our model mimics the clinical pattern of the syndrome and also assesses the efficacy of therapeutical protocols. EXPERIMENTAL DESIGN: Ischemia was induced under general anaesthesia in the posterior limbs of 10 sheep by occluding the aorta and vena cava by means of two-way balloon catheters. Ischemia was stopped after 4 hours and blood and histologic parameters determined in the first three hours of revascularization. The animals were divided into three groups: a group of 3 sheep in which a sham operation was performed; a control group (5) to assess the efficacy of induced ischemia; the third group (5) to determine the effect of antioxidant and membrane protective drugs to assess the reliability of the model to study the ischemia-reperfusion syndrome. RESULTS: At the end of ischemia, skin temperature was decreased (p < 0.04) both in control and treated groups, pH decreased significantly soon after reperfusion in the control group (p < 0.04). Reperfusion in control sheep, compared with treated animals, was followed by a significant increase in CPK blood levels (p < 0.009), related to marked muscle damage, in particular after reperfusion. Tissue damage detected at TEM was less severe in treated animals. CONCLUSIONS: This model is an effective experimental strategy and a means of assessing preventive treatment.

Animals↗

PubMed1980

Experimental models of hypertension.

The article presents a review of experimental modelling of hypertension with the purpose helping research on its pathogenetical mechanisms, its characteristic, its therapy and eventual prophylaxy. Both conventional and genetic experimental models of inducing hypertension are discussed. The paper comprises a short description of the methods, their possibilities, the form of human hypertension to which each model corresponds, as well as the most important peculiarities of the alterations which are induced by the corresponding method. Special attention was paid to the most recent models of genetically determined spontaneous hypertension including spontaneously hypertensive rats (SHR-Okamoto-Aoki), the New Zealand strain of genetic hypertension (GH-Smirk), the stroke prone and stroke resistant substrains of SHR (SHRSP and SHRSR), arteriolipoidosis prone SHR (SHRLP), the obese SHR stain, the Milan hypertensive (MHS), Dahl's salt susceptible (s) and salt resistant (R) strains, and Smirk's genetic hypotensive strain of rats.

Animals↗

PubMed2004

Experimental models of uveal melanoma.

Over the past several decades, considerable effort has been directed toward developing suitable experimental models for the study of uveal melanoma. Animal models of uveal melanoma have undergone many improvements, leading to the development of experimental systems that better represent the disease in human beings. A major advance has come from the use of human uveal melanoma cell lines capable of inducing tumour growth and metastatic disease in immunodeficient hosts. Knowledge gained from the use of experimental models will ultimately be translated into better diagnostic and therapeutic strategies for patients with uveal melanoma. In this review the authors describe the current state-of-the-art designs of experimental models of uveal melanoma, highlighting the advantages and disadvantages of the available models. Novel findings from a rabbit model of uveal melanoma are also presented.

Animals↗

PubMed1994

Experimental model of posterolateral spinal arthrodesis in sheep. Part 1. Experimental procedures and results with autologous bone graft.

OBJECTIVES: The authors evaluated the reliability in obtaining a posterolateral spinal arthrodesis (PSA) with autologous bone graft. SUMMARY OF BACKGROUND DATA: Posterolateral spinal arthrodesis using autogenous cancellous bone graft is the most simple and efficient technique to get a spinal graft. No extensive biomechanical study of PSA is available. Thus, an experimental model of PSA is needed. METHODS: Eleven sheep underwent lumbar autologous bone grafts and Cotrel-Dubousset instrumentations, and four sheep were used as controls. Sacrifice and biomechanical evaluation of the lumbar spines were performed after 1 year. RESULTS: All grafts appeared continuous. A large decrease of flexibility (in rotation and in translation) was found in grafted spines in every direction. Failure in extension occurred at a mean value of 35.26 +/- 3.71 Nm. CONCLUSION: A constant and homogenous PSA appears to be obtained in sheep under conditions close to the human surgery.

Animals↗

PubMed1980

[Short-term memory. An experimental model].

In the present work we aimed to elaborate an experimental model to evaluate and quantify the short-term memory in experimental animals, in this case in mice. It seemed ideal to us the employment of a spontaneous behaviour, i.e. the re-exploration of the hole board, automatically recorded by animals which had previously explored at a 24 h interval. The data obtained show that, when re-exploring, the animals show a statistically significant decrease, compared to the previous exploration. It can be concluded that the animals had a mnestical retention and that it can be validly quantified. This shows the validity of this experimental model, in order to study the short-term memory in mice.

Animals↗

PubMedDate not supplied

[Physiologically adequate experimental model of aggression and emotional stress].

A simple adequate experimental model of aggression and emotional stress has been elaborated, based on mild fixation of rats tails in the cage wall. It is shown that in a group of rats, in these conditions a continuous aggressive behaviour arises, leading to the development of emotional stress. The elaborated experimental model has no defects, characteristic of other models of aggression and stress. It demands neither a prolonged training of animals nor special expensive equipment; it allows simultaneous use in experiments of a great number of animals, creates conditions for natural aggressive-defensive behaviour of rats without provoking artificial manipulations. The proposed model allows to study the pathogenesis of emotional stress, mechanisms of resistivity and predisposition to it and also search and testing of biologically active substances, enhancing resistance to emotional stress.

Aggression↗

PubMed2004

[A new procedure in making reliable experimental models of gastroesophageal reflux].

OBJECTIVE: To provide a reliable experimental model for gastroesophageal reflux (GER) study. METHODS: Twenty Japan 5-month-old male rabbits were randomly divided into two groups: group cardiomyotomy (n=10), group partial cardiomyectomy (n=10). The operations of cardiomyotomy and parital cardiomyectomy were performed in 2 groups respectively. All the animals underwent intraesophageal pH detection 1 week before operation and 4 weeks after operation. The mean changes of reflux ratios were compared between before operation and after operation. RESULTS: In gastroesophageal reflux ratio between before operation and after operation, there was no significant difference in group cardiomyotomy (1.98%+/-1.52% and 4.32%+/-2.39%, P>0.05) and there was significant difference in group partial cardiomyectomy (1.56%+/-1.57% and 13.56%+/-3.27%, P<0.05). CONCLUSION: The reliable experimental model of GER can be made with procedure of partial cardiomyectomy. It can be used in estimating the operative procedure of anti-reflux and is conducive to dynamic observation and study of esophagitis.

Animals↗

PubMed1988

Cardiac transplantation without cardiopulmonary bypass: experimental model to study growth of the transplanted heart.

An experimental model using surface-induced (20 degrees C) deep hypothermia and total circulatory arrest instead of cardiopulmonary bypass was developed for the study of growth of the transplanted heart. Autotransplantation of the heart was performed in 42 young dogs weighing from 4.4 to 9.0 kg (mean, 6.9 kg). Time of ischemia ranged from 26.0 to 60 minutes (mean, 43.4 minutes). Return of satisfactory cardiac function occurred in all but one animal. An early high mortality rate was due primarily to pulmonary complications, but with modifications to the technique, long-term survival increased to 70%. Early deaths (5 days to 13 weeks) of five dogs during preliminary trials were due to pleural effusion (2), sepsis (1), endocarditis (1), and ascites (1). There have been 14 long-term survivors (range, 194 to 498 days; mean, 264 days). Long-term survivors appear well, are active, and show satisfactory growth. This experimental model eliminates the need for heparinization and reduces the potential for complications associated with cardiopulmonary bypass in the dog. It avoids cannulations that might impinge on anastomotic sites. This model appears to be suited for studying growth of the transplanted heart.

Animals↗

PubMed1977

An experimental model of osteoarthritis; early morphological and biochemical changes.

An experimental model of osteoarthritis resulting from laxity of the joint was induced in eighteen mature dogs (at least two years old) by sectioning the anterior cruciate ligament of the right knee (stifle) with a stab incision, the left knee providing a control. A sham operation was also performed in three other dogs, in which a stab incision was made but the ligament left intact. The dogs were killed at various intervals from one to forty-eight weeks later. Morphological changes in bone, cartilage, synovial membrane and joint capsule were examined in all the joints and biochemical changes in the cartilage of three dogs killed after two, eight, and sixteen weeks. All the changes resulting from the operation progressed with time and became indistinguishable from those found in three dogs with natural osteoarthritis of the knee. There were no changes in the joints which had sham operations. As the time of onset is known, this experimental model in a larger species enables a study to be made of the biochemical as well as the morphological changes in the early stages of osteoarthritis.

Animals↗

PubMed1994

[Evaluation of an experimental model of multiple organ dysfunction].

OBJECTIVE: To perform an experimental model of Multiple Organ Dysfunction Syndrome (MODS) without employing bacteria or endotoxin stimulus and to follow its evolution in vivo by a Computerized Tomography analysis of the lungs. DESIGN: Rats were submitted to intraperitoneal injection of a 2.5% zymosan suspension in mineral oil (1 g/kg weight) or mineral oil alone; control rats received no treatment. METHODS: The observation period was 15 days. During this period symptoms and survival were noticed daily. CT scans of lungs were made at the 7th and 14th days; data were post-processed to obtain information on lung density. The rats were sacrificed at the 15th day by heart puncture; blood was utilized for determination of hemochrome, differential leukocyte count, thrombocytes, glycemia, uremia, bilirubin. Lungs, liver, spleen and kidney were dissected and weighted for determination of relative organ weight. DATA ANALYSIS: Data were compared by "t" Student's test for impaired data and Fisher Exact test. RESULTS: Symptoms, survival, blood analysis and relative organ weight agreed with a progressive, ingravescent, triphasic illness caused by a systemic inflammatory response involving remote organ too. The CT study proved able to monitoring and analyzing organ damage: a temporal sequence of evolution of damage exists; organ damage is localized in microcirculatory system (density augment) and in parenchyma (morphologic alterations and fibrosis). DISCUSSION: The described experimental model reproduces a MODS-like illness in zymosan receiving rats; the CT scan is effective to evaluate the evolution of organ damage.

Animals↗

PubMed1998

Pharmacodynamics of fluoroquinolones in experimental models of endocarditis.

We calculated the magnitude of various serum pharmacodynamic parameters for fluoroquinolones in models of experimental endocarditis (EE) described in the literature. Nineteen publications contained data that allowed calculation of these parameters. Data were available for eight fluoroquinolones against methicillin-susceptible Staphylococcus aureus, methicillin-resistant S. aureus, methicillin-resistant Staphylococcus epidermidis, viridans streptococci, Enterobacter aerogenes, and Pseudomonas aeruginosa in rabbit or rat models. Enterococci were excluded because of poor bactericidal activity. A 24-hour area under the concentration curve (AUC)/minimal inhibitory concentration (MIC) ratio > or = 100, a peak level/MIC ratio > 8, and continuous levels above the time were associated with a significantly lower number of cfu per vegetation after 3-6 days of therapy. The 24-hour AUC/MIC exhibited the best linear correlation with cfu per vegetation after 3-6 days of therapy (r2 = 45%). The pharmacodynamic parameters predictive of efficacy for fluoroquinolones in the treatment of experimental endocarditis are similar to those for other infectious models.

Animals↗

PubMed2002

Effectiveness of oral N -acetylcysteine in a rat experimental model of asthma.

Oxidative stress appears to be relevant to asthma pathogenesis. Therefore, the effectiveness of the antioxidant N -acetylcysteine was examined on antigen-induced pulmonary responses in sensitized Brown-Norway rats. N -acetylcysteine (oral, 1 mmol kg(-1)per day for 7 days before challenge) did not reduce the immediate bronchospasm that followed aerosol antigen exposure but prevented airway hyperreactivity to 5-hydroxytryptamine at 24 h after antigen challenge, and reduced the eosinophils (from 0.178 +/- 0.038 in the absence to 0.064 +/- 0.020 x10(6)cells ml(-1)in the presence of N -acetylcysteine;P< 0.05), and Evans blue dye extravasation in bronchoalveolar lavage fluid. Taurine levels in bronchoalveolar lavage fluid from antigen-challenged rats were higher than control values but treatment with N -acetylcysteine failed to further increase these augmented levels. In conclusion, oral N -acetylcysteine showed beneficial effects in an in vivo model of experimental asthma, which confirm and extend the previous positive findings obtained in other models of lung injury.

Acetylcysteine↗

PubMed1993

Reperfusion in acute myocardial infarction: effect of timing and modulating factors in experimental models.

Timely reperfusion of ischemic myocardium in experimental animals halts the advancing transmural "wavefront" of ischemic cell death and thereby limits myocardial infarct size by limiting its transmural extent. The time window of opportunity for such salvage in most experimental models of regional ischemia is the first 3 hours. The number of myocytes that can be salvaged by reperfusion decreases exponentially during this period, such that at 3 hours, reperfusion limits infarct size by only about 10%. The rate of lethal ischemic cell injury and therefore the amount of myocardium that can be salvaged by reperfusion after a particular duration of ischemia is dependent both on the degree of blood flow deficit and the rate of ischemic metabolism. In experimental animal models, several interventions, including hypothermia, calcium antagonists, and "ischemic preconditioning," have been shown to reduce the rate of ischemic metabolism and to limit myocardial infarct size when assessed after a defined period of ischemia and reperfusion. Hypothetically, interventions that could prevent additional myocyte necrosis caused by some deleterious aspects of reperfusion ("lethal reperfusion injury") also could serve as valuable adjunctive therapy. However, studies of therapies designed to prevent lethal reperfusion injury have produced conflicting results. Thus, the concept that lethal reperfusion injury occurs remains controversial. Experimental evidence indicates that reperfusion accelerates both the initial inflammatory response and later process of infarct repair. Late reperfusion of infarcts in dogs, which does not limit myocardial infarct size, appears to accelerate the replacement of necrotic myocardium by scar without altering the size of the final scar.

Animals↗