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At least 721 records · Page 40Linked to original sources
PubMed1997

A new experimental model of isolated myocardial ischemic injury: ECG findings of acute isolated right ventricular ischemic injury.

A new experimental porcine model for creating selective ischemia of a specific part of the myocardium while the rest of the myocardium remains free of ischemia has been used to study the electrocardiographic (ECG) changes deriving from selective ischemia of the right ventricular (RV) free wall. A patch was stitched to the ventricle to produce selective myocardial ischemic injury. In a preliminary study of nine pigs, selective ischemia of the left ventricular free wall in five and of the RV free wall in four animals was induced, and a postmortem dye injection was performed to evaluate blood flow in the area of ischemia. In an ECG study of 20 pigs, the baseline ECG was recorded with use of the standard leads I-III, aVR, aVL, and aVF, left precordial leads (V1-V6), and leads V4R, V3H, and V4H and 1 hour after inducing ischemia, the ECG study was repeated. Our experimental model produced ischemic injury in which the location and surface area were known antemortem. In the 20 pigs, ST-segment changes were recorded in leads V1-V3, V3H, and V4H. In only four pigs (20%) was ST-segment elevation recorded in lead V4R. The results show that the ECG signs of selective ischemia of the RV free wall may imitate the signs of anterior or anterolateral infarction of the left ventricle. In this study, elevation of the ST-segment in lead V4R was not pathognomonic of for RV ischemia. This model is a new tool for studying hemodynamic and ECG changes of selective univentricular or biventricular ischemic injury.

Animals↗
PubMed1994

Development of an experimental model of an acute respiratory failure by intratracheal sea water infusion: a comparison with a conventional oleic acid induction.

An experimental model of acute respiratory failure (ARF) was successfully developed in dogs by endotracheal sea water infusion. Serial changes in blood gases and hemodynamics, and histological changes in the lungs after use of this method were compared with those of the conventional model induced by oleic acid, and the following results were observed. Blood gases deteriorated more rapidly after sea water than after oleic acid, while the changes caused by oleic acid progressed with time, and those caused by sea water did not. Not only systemic but also pulmonary hemodynamics were adversely influenced by oleic acid, but not by sea water. Extravascular lung water was observed to increase significantly in both groups. The increase was linear after oleic acid treatment, however, while with the sea water method it leveled off to a plateau. There was no significant difference between the histological changes in lungs of the two models. Our model will provide many advantages over the conventional one using oleic acid, and will be useful for studying the pathophysiology of ARF and its therapeutic strategies, such as extracorporeal membrane oxygenation and/or carbon dioxide removal.

Acute Disease↗
PubMed1992

Possible role for chondroitin sulfate in urolithiasis: in vivo studies in an experimental model.

The effect of chondroitin sulfate upon the growth of calcium oxalate crystals was measured in vivo by using an experimental model in rats. Adult male Wistar rats were treated by chronic i.p. injections of chondroitin sulfate solutions (1, 5 or 10 mg in 0.3 ml of saline, every 2 days). This treatment led to a dose-dependent increase in the urinary chondroitin sulfate concentration. Urolithiasis was induced by the introduction of a calcium oxalate seed into the bladder of the animals. Urine samples were collected and the calculi formed were removed after 42 days. The chondroitin sulfate concentration have decreased in the lithiasic urines, as compared to controls and higher chondroitin sulfate doses correlated with larger calculi. The presence of chondroitin sulfate in the matrices of stones obtained from chondroitin sulfate-treated animals suggested that there was some adsorption of chondroitin sulfate on to the growth sites of the calcium oxalate crystals. In contrast to the chondroitin sulfate effect observed in vitro, which inhibits the growth of calcium oxalate crystals, our results suggest that in vivo chondroitin sulfate promotes the growth of stones in the urinary tract.

Adult↗
PubMedDate not supplied

Neuropeptides in spinal cord injury: comparative experimental models.

The possible role of endogenous opioids in the pathophysiology of spinal cord injury was evaluated utilizing a variety of experimental models and species. In the cat, we have shown that beta-endorphin-like immunoreactivity was increased in plasma following traumatic spinal injury; such injury was associated with a decrease in spinal cord blood flow (SCBF) which was reversed by the opiate receptor antagonist naloxone. Naloxone treatment also significantly improved functional neurological recovery after severe injury. Thyrotropin-releasing hormone (TRH), possibly through its "anti-endorphin" actions, was even more effective than naloxone in improving functional recovery in the cat. In a rat model, utilizing a similar trauma method, TRH proved superior to naloxone in improving SCBF after injury. In addition, naloxone at high doses attenuated the hindlimb paralysis produced by temporary aortic occlusion in the rabbit. The high doses of naloxone required to improve neurological function after spinal injury suggest that naloxone's actions, if opiate receptor mediated, may be mediated by non-mu receptors. Dynorphin, an endogenous opioid with a high affinity for the kappa receptor, produced hindlimb paralysis following intrathecal administration in rats. Taken together, these findings suggest that endogenous opioids, possibly acting at kappa receptors in the spinal cord, may serve as pathophysiological factors in spinal cord injury.

Animals↗
PubMed1989

Gastric DNA synthesis rate in different experimental models of duodenal reflux.

The aim of our investigation was to study the gastric mucosa DNA synthesis pattern in different experimental models of duodenal reflux. The following operations were performed on male Wistar rats: (A) sham-operation; (B) Roux-Y gastrectomy; (C) Billroth I; (D) Polya-type partial gastrectomy; (E) Billroth II; and (F) simple gastroenterostomy. Fifteen weeks later rats were sacrificed and histological and in vitro 3H thymidine autoradiographic studies were carried out. Gastric mucosal DNA synthesis rate was also estimated. Besides group A, all other groups showed variable degrees of gastritis mainly located at the anastomosis or at the gastrostomy suture line. Severe gastritis was not present in group B rats and most commonly occurred in group F rats. Group C, D, E and F showed an intense epithelial proliferation with a labeling index significantly higher than in the controls. However, mucosal DNA synthesis rate appeared to decrease with the progression of gastritis and in group F, the group more exposed to duodenal reflux, was significantly lower than in the controls. It is postulated that progressive exposure to duodenal reflux and secondary atrophic gastric changes following gastric surgery is accompanied by a reduction in the mucosal layer of the DNA synthesis rate, due to the loss of epithelial elements and the increase in connective and inflammatory elements, together with an enhanced turnover of the residual epithelial cells.

Animals↗
PubMed1997

The effect of novel anti-epileptic drugs in rat experimental models of acute and chronic pain.

The novel anti-epileptic drugs lamotrigine, felbamate and gabapentin were compared in rat experimental models of acute (tail flick) and chronic pain: the chronic constriction injury and spinal nerve ligation models. Lamotrigine (10-100 mg/kg, s.c.), felbamate (150-600 mg/kg, i.p.) and gabapentin (30-300 mg/kg, i.p.) each reversed cold allodynia (chronic constriction injury model) with ED50 values of 28, 241 and 103 mg/kg, respectively, 1 h post-dose. However, only gabapentin reversed tactile allodynia (spinal nerve ligation model) with an ED50 of 34 mg/kg (i.p.). The established anti-epileptic drugs, carbamazepine (1-30 mg/kg, i.p.) and phenytoin (1-100 mg/kg, s.c.), were ineffective in both models. The anti-allodynic effect of the newer anti-epileptic drugs was observed at doses that were either ineffective or produced only a negligible effect on acute nociceptive function and/or locomotor activity. In conclusion, the data suggest that the newer anti-epileptic drugs appear to have the potential to be effective alternatives to either carbamazepine or phenytoin in the treatment of neuropathic pain. However, only gabapentin ameliorated both cold and touch hyperesthesias.

Acetates↗
PubMed1998

Orthotopic implantation of colon carcinoma cells provides an experimental model in the rat that replicates the regional spreading pattern of human colorectal cancer.

Our goal was to develop an experimental model of colon adenocarcinoma based on the orthotopic implantation of tumour cells in syngenic rats which would replicate the pattern of regional spreading of human colorectal adenocarcinoma. We used cell line DHD/K12-PROb and 62 BD-IX rats with intra-caecal injection of 1 x 10(6) cells. Macroscopic and histological examinations were made at different times after injection (from 1 to 16 weeks) with particular emphasis on caecal lesions and tumours were classified according to the TNM system (UICC, 1987). Our results suggest that this model provides a step-by-step reproduction of the development of human colorectal adenocarcinoma. It also allows us to predict how long it will take to achieve a certain degree of local spreading, which is essential for the design of cancer-related experiments. Moreover, our model has the advantage that it uses immunocompetent rats, which facilitates its application.

Animals↗
PubMed1997

Experimental models for evaluating enzyme induction potential of new drug candidates in animals and humans and a strategy for their use.

Experimental models that have application for evaluating enzyme induction potential have been described in order of increasing complexity. The main focus was on models that have had wide application thus far. However, many new models are currently being developed that may have future applications in evaluating enzyme induction potential. A strategy to evaluate the enzyme induction potential of drug candidates was outlined. This scheme uses a combination of new and established techniques to evaluate data in a stepwise manner that is appropriate to the drug's current stage of development.

Animals↗
PubMed1988

Neovascularized bone, muscle, and myo-osseous free flaps: an experimental model.

Different techniques for creating neovascularized bone, muscle, and myo-osseous free flaps were examined and evaluated in an experimental model. Sprague-Dawley rats (n = 40) were divided into four equal groups: 1) cortical bone flap (clam flap); 2) cortical bone and muscle flap (clam-muscle flap); 3) cortical and cancellous bone chip flap (Marlex-mesh flap); and 4) cortical and cancellous bone chip flap (silicone-cone flap). After 3 1/2 weeks, when neovascularization of the flaps developed, they were reliably transferred as free flaps based on their neopedicles. Post transfer, histologic and intravascular latex injections studies were performed, revealing significant differences in the character of neovascularization in the various flaps. The most abundant neovascularization was evident in the cortical bone and muscle (clam-muscle) flap, and the least in one of the cortical and cancellous bone (Marlex mesh) flap preparations. The silicone-cone flap (cancellous bone chips placed in a cone of silicone) neovascularized and maintained bony architecture. This preparation stimulates a hostile wound environment and may prove useful clinically, if similar techniques can be applied to augment vascularization of conventional bone grafts in situ, either as cancellous bone graft or as augmented iliac crest or fibular cortical bone graft. If clinically applicable, flaps created by these techniques may provide versatile alternatives to conventional free flaps.

Abdominal Muscles↗
PubMed1992

Pneumonia complicating abdominal sepsis: an experimental model of hematogenous contamination of the lung.

Pulmonary infection complicating intra-abdominal sepsis is a major clinical problem. An experimental model for intra-abdominal sepsis was created with implantation of gelatin capsules, containing 3 x 10(8) cfu E. coli strain no. 2554, in the peritoneal cavity of 20 rats (10 animals received and 10 did not receive antibiotic therapy with ceftriaxone) in order to verify the role of the primary site of infection in the pathogenesis of pneumonia. Ten rats were sacrificed to determine the relative pulmonary weight and 10 were submitted to simple laparotomy and insertion of a germ-free capsule (sham-operated group). In this group of animals there was only one death (10%). All the rats that received antibiotic therapy survived until sacrifice while all the rats that did not receive ceftriaxone died, 7 within the 2nd and 3 on the 6th postoperative day. Pneumonia and peritonitis developed only in the animals that did not receive ceftriaxone. Bacteriological findings of material obtained from peritoneal and pleural cavities revealed the same strain of E. coli used for the experiment, suggesting that bacteria involved in the pleuro-pulmonary infections may originate in the primary site of infection and that antibiotic therapy started at the moment of contamination, can prevent this major complication.

Abdomen↗
PubMed2006

Early apoptosis of monocytes contributes to the pathogenesis of systemic inflammatory response and of bacterial translocation in an experimental model of multiple trauma.

The objective of this study was to investigate the occurrence of apoptosis of monocytes in an experimental model of multiple trauma and its probable correlation to bacterial translocation. Thirty-two rabbits were applied in three groups: A, controls; B, myotomy of the right femur; and C, myotomy and fracture of the right femur. Blood was sampled for the estimation of endotoxins [lipopolysaccharide (LPS)], tumour necrosis factor (TNF)-alpha, malondialdehyde (MDA) and isolation of peripheral blood mononuclear cells (PBMCs). PBMCs, derived after centrifugation over Ficoll, were incubated in flasks and apoptosis of non-adherent lymphocytes and adherent monocytes was estimated after staining for Annexin-V and flow cytometry. TNF-alpha of supernatants of cultured monocytes was also determined. Tissue segments were cultured after death. Median survival of groups A, B and C was > 14, > 14 and 9.00 days, respectively. Apoptosis of lymphocytes in group C was higher than group A at 2, 4 and 48 h and of monocytes in group C higher than group A at 2 and 4 hours. LPS in group C was higher than group A at 2, 4 and 48 h. Apoptosis of lymphocytes and monocytes was correlated positively with serum TNF-alpha and negatively with TNF-alpha of monocyte supernatants. Cultures of organ segments of group A were sterile. Pseudomonas aeruginosa was isolated from liver, lung and spleen in five animals in group B (45.45%) and in six in group C (54.54%). Early apoptosis of blood monocytes supervened after multiple trauma; the phenomenon was accompanied by apoptosis of blood lymphocytes and subsequent bacterial translocation.

Animals↗
PubMed1997

Relationship between degree of mitral protrusion assessed by use of B-mode echocardiography and degree of mitral regurgitation using an experimental model in dogs.

We studied the relationship between the degree of mitral protrusion and degree of mitral regurgitation in an experimental model in which the degree of mitral protrusion could be adjusted. The model was developed by dissecting the dorsal papillary muscle through a left atriotomy in 5 dogs and re-attaching the papillary muscle to the original site using a single mattress suture threading through the epicardium under cardiopulmonary bypass. By manipulating the suture from a position outside the epicardium, the degree of mitral protrusion could be adjusted. The long-axis view of the mitral valve was imaged by B-mode echocardiography with the transducer placed directly over the surface of the right ventricular outflow tract. The height (H) from the coaptation point or tip of the protruded cusp in relation to the mitral annular plane was measured as an index of mitral protrusion. Mitral regurgitation as a result of the mitral protrusion decreased the left ventricular systolic pressure, and increased the heart rate, mean left atrial pressure (LAPm), and ratio of left ventricular end-diastolic dimension to body weight (LVEDD/BW). H was negatively correlated to LAPm and LVEDD/BW (r = -0.723 and -0.697, respectively). Our results indicated that H expresses not only the degree of mitral protrusion but also the degree of mitral regurgitation, and were in agreement with the previous findings obtained on dogs with spontaneous mitral regurgitation.

Animals↗
PubMed2001

Experimental models of partial lesion of rat spinal cord to investigate neurodegeneration, glial activation, and behavior impairments.

The article demonstrates two experimental models of spinal cord partial injury in rats: a contuse model promoted by the NYU impactor system and a partial hemitransection model achieved by a stereotaxic-positioned adjustable wire knife. By means of a defined impact weight (10 g) and a digital optical potentiometer linked to a computer, the impactor transferred and registered a moderate or a severe contusion to the rat spinal cord at a low thoracic level after dropping the weight from distances of 25 mm and 50 mm, respectively, to the dorsal surface of the exposed dura spinal cord. Impact curve was calculated and the parameters of the trauma, like impact velocity, cord compression distance and cord compression rates were obtained in order to demonstrate trauma severity. To promote partial hemitransection, rats were positioned in a spinal cord unit of a stereotaxic apparatus and lesion was made with the adjustable wire knife spatially oriented. By means of a computerized infrared motion sensor-home cage activity monitor and a noncomputerized evaluation of motor behavior using the inclined plane and the motor score of Tarlov tests, behavior was analyzed in an acute period postlesion. Rats were sacrificed and spinal cords were processed for routine staining to show neurons and for GFAP and OX42 immunohistochemistry to demonstrate glial cells. The tissue labelings were quantified using computer assisted stereology by means of an optical disector and microdensitometric image analysis by means of quantification of gray values of discriminated profiles. While partial hemitransection model favored a more accurate control of the lesion location, the contuse model allowed us to perform different degrees of lesion severity. A close correlation between behavioral impairment and severity of trauma was seen in the rats submitted to spinal cord contusion. The stereologic lesion index showed a correlation between severity of trauma and tissue damage by 7 days and demonstrated a time-dependent secondary degeneration after moderate but not after severe spinal cord contusion from 7 to 30 days after injury. Long-lasting activations of astrocytes and microglia seen by persisted increases in the specific mean gray values of immunoreactivities were also found in all levels of the white and gray matters of the partial hemitransected spinal cord until 3 months postinjury which can be related to wound/repair events and paracrine trophic support to spinal cord remaining neurons. The results showed that controlled partial lesions may provide an important toll to study trophism and plasticity in the spinal cord.

Animals↗
PubMed1999

Evaluation of cynomolgus (Macaca fascicularis) and rhesus (Macaca mulatta) monkeys as experimental models of acute Q fever after aerosol exposure to phase-I Coxiella burnetii.

BACKGROUND AND PURPOSE: Q fever is a disease of humans. Vaccines to prevent this disease have demonstrated efficacy in rodents and must also be evaluated for efficacy in a nonhuman primate model. Preliminary to vaccine efficacy experiments, cynomolgus and rhesus monkeys were evaluated as suitable experimental models of acute Q fever. METHODS: Both species of monkeys were challenged with aerosolized 10(5) virulent phase-I Coxiella burnetii Henzerling strain, and clinical and serologic responses were determined. RESULTS: Radiographic changes were observed in seven of eight monkeys of both species; however, changes in cynomolgus monkeys tended to be more significant. Between 7 and 10 days after challenge, all rhesus monkeys and 88% of cynomolgus monkeys were bacteremic. Sequential increases in antibody responses to C. burnetii phase-I and phase-II whole cells and phase-I lipopolysaccharide were observed in both species. Although the maximal rectal temperature increase was similar in both species, duration of fever was slightly longer in rhesus monkeys. Clinical features were similar to those described in human acute Q fever patients. CONCLUSIONS: On the basis of the more pronounced radiographic changes in cynomolgus monkeys, we favor use of this species for future studies of vaccine efficacy.

Acute Disease↗
PubMed1984

[Evaluation of the biological compatibility of bioglass with a new experimental model, the fibronectin binding test].

The authors expose their results about the biological compatibility of Bioglass (BG), using a new experimental model; this model implicates the use of Fibronectin (FN), a glycoprotein involved in cellular adhesion. The term Bioglass indicates a family of glasses (of possible use as implants) with the formation of a stable calcium-phosphate film on their surface when in contact with an aqueous environment. Two types of BG, B5 and B6, have been incubated with FN; the first binds three times B6 the FN. The results are discussed considering other preliminary results.

Biocompatible Materials↗
PubMed1995

Expression of osteopontin messenger RNA in the rat kidney on experimental model of renal stone.

We investigated the expression of osteopontin (OPN) messenger (m) RNA in the rat kidney under the experimental models of several conditions that are considered to be risk factors of human renal stones. In the renal stone formation model administrated glyoxylic acid and 1,25-dihydroxyvitamin D3, pyelonephritis model and hydronephrosis model the expression of OPN mRNA in the distal convoluted tubule of the kidney was enhanced compared with the control which was sporadically positive utilizing in situ hybridization and northern blot analysis. The expression of OPN mRNA was markedly inhibited in the renal stone formation model by concominant administration of estradiol and/or progesterone.

Animals↗
PubMed2005

An experimental model to quantify horizontal transmission of Mycoplasma gallisepticum.

Before interventions to control horizontal transmission of Mycoplasma gallisepticum can be tested, a suitable experimental model should be available. Transmission dynamics in a flock can be quantified by two parameters: the average number of secondary cases infected by one typical infectious case (R0) and the number of new infections that occur due to one infectious animal per unit of time (beta). The transmission dynamics of M. gallisepticum have not been studied experimentally, so the aim of this study was to examine the horizontal transmission of M. gallisepticum. The study was carried out using a pairwise design with three different inoculation doses. Every pair consisted of an inoculated chicken and a susceptible in-contact chicken. Five susceptible individually housed chickens were placed in between pairs in order to measure airborne transmission. Infection was detected by serology, quantitative polymerase chain reaction and culture. The inoculated and in-contact chickens were equally infectious and the pairs could be regarded as independent. The R0 was estimated to be greater than 1 (infinity; 95% confidence interval, 4.5 to infinity), the estimated beta was 0.22 per day and there was no significant difference between the different inoculation doses. It was concluded that the animal model as described in this study meets the conditions for the establishment of transmission dynamics of M. gallisepticum and therefore can be used to establish the quantitative effect of intervention measures on horizontal transmission.

Animals↗
PubMed2006

[Experimental models of schizophrenia--a review].

OBJECTIVE: Diagnostic and therapy of somatic diseases like diabetes and hypertension have improved notably with the use of experimental models. For schizophrenia the proposal of a model has made little impact and even scepticism. Nevertheless the most recent studies indicate that "Cognitive Sciences" applied to specific models may help us to find out mechanisms of the disease. This article reviews the models presently under investigation for schizophrenia. RESULTS AND DISCUSSION: The difficulty to model schizophrenia results from the subjectivity of its symptoms, the difficult to reproduce them in animals and the disease complexity. Research on such a complex phenotype can only proceed by separating its components (endophenotypes) from each other and by the respective manipulation of its experimental counterparts, made by specific interventions (e.g. pharmacological, surgical, genetic), in the search of a common mechanism leading to these endophenotypes. For integrating these findings with symptoms a global explanatory theory is required. So far, the disease seems to result from a diffuse neuronal disconnection as a consequence of minor brain abnormalities with a genetic and/or environmental cause. CONCLUSIONS: An integrative approach of the diversity of models presently used may improve our understanding of schizophrenia.

Animals↗