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Results for “Models, Experimental”

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At least 127 records · Page 7Linked to original sources

PubMed1981

Thigh pressure artifacts with noninvasive techniques in an experimental model.

In an experimental canine model of isolated and tandem arterial stenoses, noninvasive thigh and calf pressure measurements were evaluated against direct intra-arterial pressures. Under control circumstances, proximal iliac arterial stenosis, and high superficial femoral artery stenosis, the noninvasive measurements were highly accurate. However, when stenoses were created distal to the high pressure cuff, a significant error in the thigh pressure measurement was observed, with an underestimation of thigh pressure and subsequent false implication of a proximal lesion. Two tandem distal lesions produced a significantly more severe thigh measurement artifact. Further, the noninvasive system was incapable of detecting a moderately severe profunda stenosis, although stenoses of the iliac and femoral system were detected in a routine, accurate, and sensitive fashion.

Animals↗

PubMed1992

Experimental models for spinal cord injury research: physical and physiological considerations.

This paper describes historical and current experimental models used to develop our current understanding of the biomechanics and pathophysiology of traumatic spinal cord injury; the advantages and limitations of current experimental models; considerations for selecting an appropriate injury model based on experimental objectives; and key physiological factors in the spinal cord injury response that may interact with the injury response and alter the outcome. All of the above must be considered in the development and selection of an appropriate experimental injury model that meets specific needs. Various experimental models have been developed to study spinal cord injury and the pathophysiological and physical mechanisms responsible for tissue damage and loss of function. Such modeling may involve inherently different biomechanical variables with alternative outcomes and purposes. There is not, therefore, a single "ideal" experimental injury model just as there is no "stereotypical" clinical spinal cord injury. Instead, the goals and objectives of the research dictate specific requirements on the model. In all cases, however, both physical and physiological aspects of the model should be considered, and measured if possible, to ensure interlaboratory comparability and possible clinical relevance. Also, experimental techniques, especially anesthesia, and surgical procedures, should be carefully reviewed for interactions with the injury response or potential therapeutic interventions to ensure validity of interpretation. It is hoped that data correlating physical spinal cord injury parameters with functional outcome will ultimately be combined with data on vertebral injury and spinal failure mechanics to further our understanding of clinical injury. Such approaches should lead to interventions that reduce the incidence and severity of traumatic human spinal cord injury.

Animals↗

PubMed2002

Experimental model for the study of perianastomotic recurrence in colorectal cancer.

OBJECTIVE: To determine if an experimental model is valid for the study of perianastomotic recurrence in colorectal cancer, comparing it with previous experimental models. METHODS: Experimental study with 40 male Sprague-Dawley rats, assigned to one of the study groups: control group (n = 20), with manipulation of large descending bowel, and colonic anastomosis group (n = 20), with colonic section and colocolic anastomosis. After pharmacological carcinogenesis with 1-2 dimethylhydrazine at a weekly dose of 25 mg/kg for 18 weeks, colonic tumours were studied at the 20th postoperative week. RESULTS: Number of tumours, colic tumoral area and percentage of colic tumoral area were greater in the colonic anastomosis group. In this group with colonic anastomosis all determinations were higher at the perianastomotic large bowel. CONCLUSIONS: We think this experimental model may be the best model to study perianastomotic recurrence in large bowel cancer. The high incidence of induced colic tumours and their location at the perianastomotic area offer a good field to determine response to experimental manipulations on colorrectal cancer.

Anastomosis, Surgical↗

PubMedDate not supplied

The pathological process. V. Experimental modelling in pathology: general theoretical problems.

The theoretical analysis of the characteristic features of pathological processes is being continued with the experimental modelling of the pathological process, with emphasis on gnoseological and heuristic aims. The paper discusses: the compulsory working hypothesis which includes the known and the probable data resulting from the observation of phenomena, the qualities and value of the experimentation for the verification of the working hypothesis, the general features of the experimental modelling in pathology and its purposes, the types of experimental models (simple, two times perturbing and complex) with exemplification and discussion of qualities and limits, the general evaluation and limits of experimental models, the practical elaboration of experimental models with emphasis on the main rational operations, like the choice of animals, of the ways of administration of perturbing agents, of experimental and control lots, of sacrification modalities, as well as the relevance of the experimental results for enlarging the knowledge of the pathological process investigated.

Animals↗

PubMed1993

In vivo experimental models on the evaluation of haemoperfusion.

We described some experimental models that were performed in rabbits and in swine in order to evaluate the efficacy of haemoperfusion treatment in hypochloremic alkalosis, uraemia and cytotoxic drug poisoning. In all the models, an extracorporeal circuit was used constituted mainly by a hematic sampling line and a cartridge, containing an anion exchange resin. Access to the blood stream was achieved by isolation and catheterization of the vessels either of the neck or of the leg, or both. The experimental model for the evaluation of haemoperfusion in hypochloremic alkalosis was carried out in rabbits by a pyloric stenosis because its size and weight are similar to new-born humans and its stomach is a simple monogastric one. The hypochloremia and alkalosis were achieved in only 4 hours. The other two experimental models were carried out in pigs because, in these cases, it was better to choose a large size animal with a nutritional similarity to humans, and with the capability to produce a stable chronic renal failure. The pigs were submitted to a bilateral ureter ligature to create a chronic renal failure or to a bilateral renal vessel ligature to avoid the physiologic precipitation of some drugs in renal tubules.

Alkalosis↗

PubMed1999

[Experimental hepatocarcinogenesis--evaluation of the significance of experimental modeling. Classical models].

There are an increasing number of models for the study of liver cancer development with such agents as chemicals, hormones, and viruses. This process is almost always a multistep and during the long period of cancer development, discrete cells or cell populations acquire step-by-step the various properties that go to make up a cancer. The hepatocarcinogenesis models are useful in identification and analysis of the preneoplastic and neoplastic alterations, as well HCC. This article presents a review of theoretical foundation and mechanisms of various models of experimental hepatocarcinogenesis as well contain a short presentation of animals practical in those experiments, principally rats. The remarkable similarities between many models with different carcinogens in animals and humans suggest the importance of such studies in understanding of molecular basis of liver cancer development.

Animals↗

PubMed1996

A potential experimental model for the study of osteopenia in CCl4 liver cirrhotic rats.

In order to search for an experimental model to further investigate the osteopenia associated to liver cirrhosis (LC), this study has been focused on investigating the occurrence of bone disorders in male rats to which LC histologically confirmed was induced through the validated procedure of CCl4 inhalation. Length, anteroposterior and lateromedial diameters, densitometry, mechanical stress resistance, hydroxyproline (OHprol) and calcium and phosphate contents were measured in femurs from control (n = 10) and liver cirrhosis rats (n = 10). It has been found that femurs from liver cirrhosis rats showed a significant reduction (p < 0.01) in bone weight (0.254 +/- 0.003 vs 0.230 +/- 0.004 g/100 g b.w.), anteroposterior (4.08 +/- 0.06 vs 3.69 +/- 0.05 mm) and lateromedial (5.33 +/- 0.05 vs 5.08 +/- 0.04 mm, p < 0.05) diameters, resistance to mechanical stress (405.8 +/- 9.5 vs 332.5 +/- 9.1 N) and total densitometry (0.416 +/- 0.005 vs 0.381 +/- 0.004 g/cm2). However, no significant differences were observed in bone length, calcium, OHprol and phosphate (all expressed as mg/100 mg fresh bone tissue) contents. Therefore, the proteins matrix to mineral contents ratio was not altered. These results indicate that in this model of experimental liver cirrhosis there is osteopenia characterized by bone frailty and reduced thickness, and it could offer an experimental model to study bone changes associated to liver cirrhosis.

Animals↗

PubMed1994

[Contributions of experimental models to the physiopathology and treatment of bacterial meningitis].

Access to the cerebrospinal fluid, which is the only objective reflection of the essential parametres, is very limited. Investigators have long tried to design an animal model. Presently, the experimental model of the newborn rat is most often used for studying pathogenic factors in haematogenous meningitis. In contrast, the rabbit model is more adapted to therapeutic investigation The main advances have been therapeutic and pathophysiologic. Good examples are the identification of optimum antibiotic levels in the cerebrospinal fluid, and the demonstration of the responsibility of mediators produced by the host in triggering the inflammation. The principle of corticosteroid treatment before induction of bacterial lysis by antibiotics in Haemophilus meningitis is a result of such work.

Animals↗

PubMed2000

In vivo experimental model for silicosis.

The selection of an experimental model for silicosis requires a thorough understanding of many pulmonary parameters specific to the experimental animal (e.g., clearance time, penetration curves, anatomical differences), as well as the strain's sensitivity to different conditions. The pulmonary response of three rat strains (i.e., Fischer 344, Sprague-Dawley, and Wistar) to silica dust was compared using two methods of exposure: intratracheal injection and inhalation. The test period lasted 3 months for injection and 6 and 12 months for inhalation. The histological study of the lung revealed a distinct nodular reaction in Sprague-Dawley and Wistar strains. Intratracheal injections led to the development of fibrotic nodules in Wistar rats, whereas such silicotic nodules were infrequent in injected Fischer 344 rats, and almost absent when exposure was by inhalation. Sprague-Dawley and Fischer 344 rats showed frequent thickening and metaplasia of the alveolar walls near the terminal bronchioles. This tendency was particularly pronounced in rats exposed by inhalation (especially Fischer 344 rats). Macroscopic examination (wet lung weight) and biochemical dosing (lung silica, hydroxyproline, and lipid content) revealed an increase in the various parameters examined in Sprague-Dawley rats relative to the other two strains, regardless of the type of exposure. The histological examination, however, leads us to conclude that the Wistar rats offer the best experimental model for silicosis, because their pulmonary reaction is more characteristic of the human condition than that of the other two strains.

Animals↗

PubMed2002

Experimental models of Schistosoma mansoni infection.

Experimental models of Schistosoma mansoni infections in mammals have contributed greatly to our understanding of the pathology and pathogenesis of infection. We consider here hepatic and extrahepatic disease in models of acute and chronic infection. Experimental schistosome infections have also contributed more broadly to our understanding of granulomatous inflammation and our understanding of Th1 versus Th2 related inflammation and particularly to Th2-mediated fibrosis of the liver.

Acute Disease↗

PubMedDate not supplied

A new class of antiulcer drugs. I. Antiulcer effect of AN5, a 4-phenyl-tetrahydroisoquinoline derivative, on different experimental models of ulcer in rats.

The action of AN5 on experimental models of gastric ulcers induced by water-immersion stress, indomethacin and reserpine, or by pylorus ligation in rats has been studied. AN5 supresses the formation of ulcers in all experimental models. The strongest antiulcer effect is shown in relation to water-immersion stress-induced ulcers. From the broad pharmacological studies of AN5 on this model it can be seen that even a dose of 0.100 mg/kg has a high antiulcer activity. The increase of the dose leads to a regular increase of the antiulcer activity, the highest suppression of the ulcer index being reached at a dose of 1 mg/kg (86.15%). The comparative studies with ranitidine and cimetidine on the same experimental models of gastric ulcers show that AN5 possesses an antiulcer activity many times higher than that of the above-mentioned drugs.

Animals↗

PubMed2007

Thermally induced convective movements in a standard experimental model for characterization of lesions prior to radiofrequency functional neurosurgery.

Experimental exploration of equipment for stereotactic functional neurosurgery based on heating induced by radio-frequency current is most often carried out prior to surgery in order to secure a correct function of the equipment. The experiments are normally conducted in an experimental model including an albumin solution in which the treatment electrode is submerged, followed by a heating session during which a protein clot is generated around the electrode tip. The clot is believed to reflect the lesion generated in the brain during treatment. It is thereby presupposed that both the thermal and electric properties of the model are similar to brain tissue. This study investigates the presence of convective movements in the albumin solution using laser Doppler velocimetry. The result clearly shows that convective movements that depend on the time dependent heating characteristics of the equipment arise in the solution upon heating. The convective movements detected show a clear discrepancy compared with the in vivo situation that the experimental model tries to mimic; both the velocity (maximum velocity of about 5 mms) and mass flux are greater in this experimental setting. Furthermore the flow geometry is completely different since only a small fraction of the tissue surrounding the electrode in vivo consists of moving blood, whereas the entire surrounding given by the albumin solution in the experimental model is moving. Earlier investigations by our group (Eriksson et al., 1999, Med. Biol. Eng. Comput. 37, pp. 737-741; Wren, 2001, Ph.D. thesis; and Wren et al., 2001, Med. Biol. Eng. Comput. 39, pp. 255-262) indicate that the heat flux is an essential parameter for the lesion growth and final size, and that presence of convective movements in the model might substantially increase the heat flux. Thus, convective movements of the magnitude presented here will very likely underestimate the size of the brain lesion, a finding that definitely should be taken into consideration when using the model prior to patient treatment.

Biomimetic Materials↗

PubMed1976

An experimental model for lymphatic metastasis in rats.

An experimental model was described for inducing spontaneous lymph node metastasis, in which tumor cells of the rat ascites hepatoma AH-109A were transplanted into the subcutaneous tissue of the penis, which is rich of lymph plexus. Growth of tumor at the site of transplantation was measured serially and metastasis was recognized by palpation in the inguinal lymph nodes initially, and then in the axillary and lumbar nodes. When animals were sacrificed 12 days after transplantation, these lymph nodes were weighed and high percentage of metastasis was confirmed by histological examination. As an experimental model of lymph node metastasis, the usefulness of this method was discussed.

Animals↗

PubMed1999

Challenges in translating the efficacy of neuroprotective agents in experimental models into knowledge of clinical benefits in head injured patients.

Many agents have been shown to reduce brain damage in experimental models of brain injury; this is proving difficult to translate into improved outcome of patients for reasons that are reviewed in this article. It is possible that, even if fundamental mechanisms are similar, injury processes modelled experimentally may be proportionately less important in human cases, and there also may have been insufficient attention to ensuring that dosage regimens for patients are therapeutically appropriate both in terms of concentration and time window. The distribution of outcomes after head injury means that, in unselected populations, a proportional improvement to the extent usually sought may be difficult to achieve. Future studies may need to consider more extensive work in "targeted populations" (selected by type and severity of damage) as a preliminary step before proceeding to definitive studies of efficacy, in which expectations of effect need to be lower and correspondingly large numbers of patients studied. Recant experience in the evaluation of glutamate NMDA antagonists is reviewed.

Clinical Trials as Topic↗

PubMed1991

Galactocerebrosides are antigens for immunoglobulins in sera of an experimental model of trypanosomiasis in sheep.

In an experimental model of human African trypanosomiasis in sheep inoculated with Trypanosoma brucei brucei, we report an immunoglobulin reactivity towards central nervous system (CNS) glycolipids. Immunocharacterization of the glycolipid antigens was performed on thin-layer chromatography using peroxidase-labelled second antibody. An immunoreactivity against galactocerebroside antigens was observed in inoculated animals up to a dilution of 1:600 and was suppressed after immunoadsorption of sera on pure galactocerebrosides. As galactocerebroside antigen is responsible for demyelination in several experimental models, the relation between the important glycolipid immunoreactivity in inoculated sheep sera and the pathogenesis of CNS demyelination in African trypanosomiasis is suggested.

Animals↗

PubMed1990

Experimental models of autoimmune diseases.

Several experimental models of autoimmune diseases have been studied which often mimic the human situation. Autoreactive T cells that emerge either spontaneously or after immunization have been identified in several situations. The main lesson from these models is that these autoreactive T cells are negatively controlled in the normal situation and that a defect either inherited or acquired in this regulatory circuit is responsible for autoimmunity.

Animals↗

PubMed1995

The role of endogenous glucocorticoids in rat experimental models of acute pancreatitis.

BACKGROUND & AIMS: Cytokines activate the hypothalamic-pituitary-adrenal axis and suppress inflammation by stimulating glucocorticoid secretion. The state of adrenocortical function during acute pancreatitis and its role in this disease were determined. METHODS: Cerulein-induced pancreatitis or closed duodenal loop pancreatitis was produced in rats that had undergone adrenalectomy or sham adrenalectomy, and the serum corticosterone and interleukin 8 levels and the intensity of the pancreatitis were examined. RESULTS: Serum corticosterone levels were significantly higher than basal levels in both models of experimental pancreatitis. In both models, adrenalectomy increased serum amylase and pancreatic edema and produced more severe inflammation. Adrenalectomy significantly increased mortality in animals with closed duodenal loop pancreatitis. Exogenous hydrocortisone administered to adrenalectomized animals suppressed the elevation of serum interleukin 8 levels and decreased both the severity of pancreatitis and mortality. CONCLUSIONS: These results suggest that the adrenocortical function is stimulated during acute pancreatitis and that the secretion of endogenous glucocorticoids may play an important role in mitigating the progress of this disease, probably by inhibiting cytokine production.

Acute Disease↗

PubMed1986

The organization of spinal pathways to ventrobasal thalamus in an experimental model of pain (the arthritic rat). An electrophysiological study.

The spinal ascending pathways responsible for neuronal ventrobasal (VB) thalamic responses elicited by joint stimulation of the posterior paw were determined in arthritic rats used as a model of experimental pain. Responses of a same neurone to mechanical (movement--pressure--brushing) or thermal stimulation (50 degrees C) were analysed before and after discrete lesions in the white matter of the spinal cord. For 6 neurones responding exclusively to brushing applied on a small receptive field (RF) strictly contralateral to the recording site, responses were not altered as long as the contralateral dorsal column was intact. Twenty neurones exhibited bilateral symmetrical RF located on the posterior paws including the ankles and for some units the digits. They were driven by moderate pressure and/or mild sustained joint movement and by immersion in a hot water bath at 50 degrees C. Their responses were not significantly modified when the lesions destroyed most of the dorsal and the dorsolateral parts of the spinal cord. In 16/20 cases effect of one hemisection of the cord was studied: when the hemisection was contralateral to the recording site (n = 8) VB neuronal responses elicited from the paw ipsilateral to this side were eliminated in 6/8 cases; when the 1/2 section was ipsilateral to the recording site (n = 8) the lesion induced the elimination of the responses elicited from the paw opposite to the recorded VB for one unit only. The involvement of the spino-reticular pathways which have not only a crossed but also a non-crossed component is suggested. This hypothesis is discussed by comparison to data previously obtained, showing that by contrast in healthy rats the spino-thalamic tract is essential for VB neuronal responses to noxious stimuli.

Afferent Pathways↗