alpha-Cell neogenesis in an animal model of IDDM

Currently there is debate regarding the capacity of pancreatic islets to regenerate in adult animals. Because pancreatic endocrine cells are thought to arise from duct cells, we examined the pancreatic ductal epithelium of the diabetic NOD mouse for evidence of islet neogenesis. We have evidence of duct proliferation as well as ductal cell differentiation, as suggested by bromodeoxyuridine-labeling and the presence of glucagon-containing cells within these ducts. In addition, the ductal epithelia in diabetic NOD mice expressed the neuroendocrine markers neuropeptide Y and tyrosine hydroxylase. These ducts also expressed the homeobox gene product, insulin promoter factor 1. Ductal cell proliferation and expression of these markers was not observed in transgenic NOD mice (NOD-E), which do not develop clinical or histopathological symptoms of IDDM. This suggests that the observed ductal cell proliferation and differentiation was a direct result of beta-cell destruction and insulin insufficiency in these adult diabetic mice, which further suggests that these events are recapitulating islet ontogeny observed during embryogenesis. It is possible that comparable processes occur in the human diabetic pancreas.     

Evaluation of the role of neurolinins and urecholine hypersensitivity in an animal model of infravesical outflow obstruction

OBJECTIVES: To determine whether detrusor muscle strips from a male rat with infravesical outflow obstruction model demonstrate supersensitivity to parasympathomimetic and neurokinin NK-1 and NK-2 selective agonists. METHODS: Bladder instability developed after 6 weeks of partial urethral obstruction. The micturition frequency and voided volume were determined in unanesthetized animals. Detrusor hypertrophy was confirmed by evaluation of bladder weight. In vitro organ bath was used to compare the affinity and maximal activity of bethanechol and neurokinin NK-1 and NK-2 selective agonists on strips from the detrusor muscle of sham and obstructed rats. Bethanechol, N-Ac[Arg6, Sar9, Met(O2)]-SP(6-11), and [beta-Ala8]-NKA(4-10) were used to characterize cholinergic muscarinic, neurokinin NK-1 and NK-2 receptors. Results. No significant differences in affinities and maximal responses were found using 10-mg detrusor muscle strips with each of the three agonists. CONCLUSIONS: Bladder instability produced by outlet obstruction does not involve changes in the affinity or maximal activity of cholinergic muscarinic, neurokinin NK-1 and NK-2 receptors. Furthermore, detrusor supersensitivity to neurokinins or bethanechol was not seen. This suggests that bladder instability is not due to an increased affinity or maximal response to neurokinins or parasympathomimetics.     

Antimyeloperoxidase-associated proliferative glomerulonephritis: an animal model

To develop an animal model for antimyeloperoxidase (MPO)-associated necrotizing crescentic glomerulonephritis (NCGN), we immunized Brown Norway rats with MPO and localized a neutrophil lysosomal enzyme extract, primarily consisting of MPO and elastinolytic enzymes, plus H2O2, the substrate of MPO, to the glomerular basement membrane (GBM). Upon immunization rats developed antibodies and positive skin tests to MPO. After unilateral perfusion of the left kidney with the lysosomal enzyme extract and H2O2, MPO and immunoglobulin (Ig)G localized transiently along the GMB. At the time of maximal inflammation, at 4 and 10 d after perfusion, MPO, IgG, and C3 could not be detected anymore. MPO-immunized rats perfused with the lysosomal enzyme extract and H2O2, in contrast to control-immunized and/or control-perfused rats, developed a proliferative GN characterized by intra- and extracapillary cell proliferation, ruptured Bowman's capsule, periglomerular granulomatous inflammation, and formation of giant cells. Monocytes, polymorphonuclear leukocytes (PMN), and to a far lesser extent T cells were found in the glomeruli. Interstitial infiltrates consisted of monocytes, PMN, and T cells. Granulomatous vasculitis of small vessels was found at 10 d after perfusion. The proliferative NCGN in this rat model closely resembles human anti-MPO-associated pauci-immune NCGN, and enables the study of the pathophysiology of anti-MPO-associated NCGN.     

Characterization of an animal model of ventilator-acquired pneumonia

To develop an experimental model of ventilator-acquired pneumonia (VAP), we investigated whether healthy piglets could develop endogenously acquired pulmonary infection as a result of prolonged mechanical ventilation (MV). Thirty-three piglets underwent MV with anesthesia, analgesia, and paralysis produced by continuous infusion of midazolam, fentanyl, and pancuronium bromide. Ten animals received antibioprophylaxis with ceftriaxone (ATB group) and 23 received no antibiotics (control group). Eighteen control animals and 9 ceftriaxone-treated animals completed the 4-day study protocol. The presence of pneumonia on day 4 was ascertained by multiple pulmonary biopsy specimens, processed for microscopic examination and quantitative cultures. The anesthetic regimen provided satisfactory electrolyte balance and cardiovascular stability. Under these circumstances, 17 of 18 animals and 4 of 9 animals developed VAP in the control and the ATB groups, respectively. Lesions of different grades of severity were unevenly distributed through both lungs with a predominance and a higher severity in dependent lung segments. Noninfectious lesions frequently associated with VAP in humans were not observed. Pneumonia was usually polymicrobial with a predominance of Gram-negative organisms. Most of the causative organisms originated from the oropharynx. Histologic lesions and lung bacterial concentrations were less in the ATB group than in control animals. We then investigated the effects of intrabronchial challenge with bacterial pathogens in the absence of MV. Intrabronchial bacterial inoculation resulted in the development of pneumonia that spontaneously resolved even when using very highly titrated inocula. Therefore, MV seems to be the main predisposing factor in the development of pneumonia in this model. This model that resembles human VAP in its histologic, bacteriologic, and pathogenic aspects may be useful to further study pathogenesis, diagnosis, prevention, and therapy of VAP.     

Neurogenically mediated cystitis in rats: an animal model

PURPOSE: Pseudorabies virus (PRV) is a useful tool for mapping the control circuitry of the spinal cord. In the process of mapping CNS regulatory pathways for the lower urinary tract, a hemorrhagic change in the bladder was observed that was not overtly evident in other pelvic organs. The relationship between the appearance of hemorrhagic changes in the bladder and the evolution of PRV induced changes in the spinal cord was therefore explored. MATERIALS AND METHODS: Sprague-Dawley rats were injected with PRV into the ACD tail-muscle. Bladder and CNS fixation were achieved by transcardial perfusion with formaldehyde. Multi-level sections were obtained from T8 through S4. Fixed tissue was stained and evaluated by light microscopy. Immunohistochemical stains were carried out for PRV and iNOS on spinal cord tissue. We were therefore able to evaluate the relationship between the manifestation of the hemorrhagic cystitis, appearance of the PRV in the spinal cord and evidence of CNS inflammation. RESULTS: The evolution of hemorrhagic cystitis paralleled the evidence of inflammation in the thoraco-lumbar and sacral cord. These bladders contained 5 to 9 ml. of bloody urine (a normal rat bladder contains 1 to 2 ml.). On cystomanometry (CMG) the bladders were acontractile. No PRV could be cultured in the hemorrhagic bladders. The histological changes observed in the bladder represent true inflammation. CONCLUSION: There was no obvious explanation for these changes other than the associated inflammatory changes in the spinal cord. The findings are consistent with the hypothesis that a spinal cord stress, via an unknown metabolic pathway, can result in dramatic, neurogenically mediated changes in the bladder.     

Transcatheter liver lobar ablation: an experimental trial in an animal model

Complete embolization of tumor tissue together with surrounding liver sufficiently prevents collateral blood supply to the tumor, offering curative treatment for hepatic malignancies. The present experiment was designed to test the feasibility of hepatic lobar ablation by means of the transcatheter chemoembolization technique. Five groups of rats (n = 6) were treated with a mixture of iodized oil/ethanol in ratios of 5:1, 4:1, 3:1, 1:1, and 1:0, which was injected selectively into the right-lobe artery until saturation during open surgery. Another group (n = 6) was studied using in vivo microscopy to observe the distribution of the mixture in the liver and changes in hepatic microcirculation. Ethiodol/ethanol mixture entered the portal vein after injection into the hepatic artery creating dual, complete arterial and portal venous embolization. Lobar ablation effects were achieved in 2 weeks in the 5:1, 4:1, and 3:1 ratio groups, indicated by the lobe/liver weight measurements (p < 0.001 vs normal liver). Hepatic arterial administration of the Ethiodol/ethanol mixture creates dual hepatic arterial and portal venous embolization, achieving a lobar ablation effect.     

Toward an animal model of Type A behavior.

Attempted to differentiate behaviors of Mongolian gerbils analogous to Type A (coronary-prone) and Type B (non-coronary-prone) human behavior. Preliminary classification of 20 Ss was based on performance on differential reinforcement of low rates 20-sec and 60-sec schedules. To retain their preliminary classification, Type A and Type B Ss were required to be dominant and subordinate, respectively, in matches with Ss of opposite behavioral classification. Ss that exhibited Type A timing won significantly more dominance matches than did Type B Ss. Incidence rates of Type A and Type B behavior in the 2 selectively bred generations were significantly greater than frequencies in the original stock. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Nebulisation of surfactants in an animal model of neonatal respiratory distress

AIMS: To evaluate pulmonary deposition and gas exchange following nebulisation of two surfactants by either a jet or an ultrasonic nebuliser. METHOD: After bronchoalveolar lavage (BAL), 19 rabbits were ventilated in four groups. Group A1 (n = 5) and A2 (n = 6) received Technetium-99m labelled Exosurf, and groups B1 (n = 4) and B2 (n = 4) received radiolabelled Survanta. Groups A1 and B1 received jet nebuliser therapy, whereas groups A2 and B2 received ultrasonic nebuliser. Pulmonary deposition, distribution, and blood gases were determined. RESULTS: Pulmonary deposition as per cent of initial dose and mg lipid) was 0.28(0.10)% or 0.59(0.21) mg in group A1, 1.05(0.23)% or 2.21(0.48) mg in group A2, 0.08(0.02)% or 0.30(0.08) mg in group B1, and 0.09(0.02)% or 0.34(0.08) mg in group B2. Deposition in group A2 was greater than in other groups (p = 0.001). Group A2 showed a small improvement in blood gases. CONCLUSIONS: Even the highest deposition--ultrasonic nebuliser with Exosurf--achieved limited clinical effect. The aerosol route is currently not effective for surfactant treatment.     

New method for determining eye anesthesia in an animal model

Some chemical which are injurious to the eye may also cause anesthesia. If the eye were unknowingly anesthetized, exposure to an irritant could go undected and cause injury. Techniques for determining whether the eye was anesthetized have been generally unreliable. Usually the technique consists of challenging the cornea with a probe and testing for a blink response. In a new method described herein, an indwelling subpalpebral lavage apparatus was surgically implanted in the dog. Through this apparatus, a test material was instilled into the eye without the animal's anticipation. Responses caused by the materials were monitored by electroencephalography. The normal response to an irritting material was increased frequency and decreased amplitude of the electroencephalogram tracing or a deflection of thepolygraph needle (blink response), or both. The method was evaluated with known eye anesthetic agents and appeared to be a useful way of detecting eye anesthesia.     

Periosteal migration in the growing mandible: an animal model

Migration of mandibular periosteum and attached musculature was tracked along the inferior border of the ramus in growing and nongrowing guinea pigs (Cavia porcellus) over a 6-week period. Particulate metallic growth-tracing implants were placed through the bony mandible and adjacent musculature at two anteroposterior locations and two bony reference markers were placed anteriorly. Quantification from weekly radiographs of growing animals showed marked posterior migration of the periosteum, whereas in nongrowing animals there was negligible periosteum movement. Significantly greater migration occurred in posterior (6.37 +/- 0.76 mm) implants relative to the anterior implants (3.45 +/- 0.86 mm, p < 0.001). The neutral zone, where little periosteal migration occurs, was calculated to be approximately at the anteroposterior center of the molar tooth row. Analysis of the orientation of the medial pterygoid muscle relative to the mandible showed that muscle fibers on average become more horizontal. Thus, the study found differential anteroposterior migration of the mandibular periosteum in growing animals and correlative changes in orientation of the medial pterygoid muscle.     

Metachromatic leukodystrophy: molecular genetics and an animal model

Metachromatic leukodystrophy (MLD) is a lysosomal storage disorder caused by the deficiency of arylsulphatase A (ASA; EC 3.1.6.8). Deficiency of this enzyme causes intralysosomal storage of the sphingolipid cerebroside sulphate. This lipid is abundant in myelin and it may thus not be surprising that storage mainly affects oligodendrocytes. Patients suffer from a progressive demyelination causing various neurological symptoms. The disease is fatal and treatment is not available. The human ASA gene has been cloned and more than 40 mutations have been analysed that cause metachromatic leukodystrophy. Few of these alleles are frequent among patients, whereas most mutant alleles have only been found in single families. Since MLD has only been described in humans and no naturally occurring animal model has been described, ASA-deficient mice have been generated by homologous recombination. The ASA knockout mice are unable to degrade sulphatide and store the lipid intralysosomally. The pattern of lipid storage in neuronal and non-neuronal tissues resembles that described for patients. In the nervous system, lipid storage is found in oligodendrocytes, astrocytes and some neurons. Animals display an astrogliosis and a decreased average axonal diameter. Purkinje cells and Bergmann glia of the cerebellum are morphologically aberrant. Demyelination is seen in the acoustic ganglion and occurs between the ages of 6 and 12 months. The animals are deaf at this age and display various neuromotor abnormalities. However, compared to humans the mice have a surprisingly mild phenotype, since they have a normal life span and do not develop widespread demyelination. ASA-deficient mice have been transplanted with bone marrow, which was transduced with a retroviral vector expressing arylsulphatase A. The majority of transplanted animals display sustained expression of arylsulphatase A from the retroviral construct up to 5 months after transplantation. However, preliminary data suggest that this therapeutic approach does not reduce storage material.     

Computer analysis system of blood oxygen saturation in an animal hypoxia model

Forearm blood flow (ml/min/100 ml) was determined with strain-gauge venous occlusion plethysmography at rest and in response to handgrip exercise in 7 patients with congestive heart failure and in 9 normal subjects before and after regional administration of endothelin-1 in the brachial artery. Administration of endothelin-1 significantly decreased forearm blood flow at rest and during exercise in normal subjects but did not change it at rest or during exercise in patients with congestive heart failure.     

Histopathologic study of esophageal atresia and tracheoesophageal fistula in an animal model

Authors propose one study of retinal cells population in different stages of ontogenesis and one study of the pigmentogenesis process at the level of uveal tract and external retinal stratum. The study was achieved with embryonic and fetal technique of paraffin inclusion. Concomitantly with loading with pigment of the external retinal stratum and so pigmentary uveal tract is present. Dynamics of the retinol cells population varies with stages and chronological age, the number of pigmented uveal cells increasing proportionally but at different parameters with the pigmented retinal stratum one simultaneous with age under influence specially of humoral factors.     

Inhibitory effect of piracetam on platelet-rich thrombus formation in an animal model

Intravenous administration of piracetam to hamsters reduced the formation of a platelet-rich venous thrombus induced by a standardised crush injury, in a dose-dependent fashion with an IC50 of 68 +/- 8 mg/kg. 200 mg/kg piracetam also significantly reduced in vivo thrombus formation in rats. However, in vitro aggregation of rat platelets was only inhibited with piracetam-concentrations at least 10-fold higher than plasma concentrations (6.2 +/- 1.1 mM) obtained in the treated animals. No effects were seen on clotting tests. In vitro human platelet aggregation, induced by a variety of agonists, was inhibited by piracetam, with IC50's of 25-60 mM. The broad inhibition spectrum could be explained by the capacity of piracetam to prevent fibrinogen binding to activated human platelets. Ex vivo aggregations and bleeding times were only minimally affected after administration of 400 mg/kg piracetam i.v. to healthy male volunteers, resulting in peak plasma levels of 5.8 +/- 0.3 mM. A possible antiplatelet effect of piracetam could be due to the documented beneficial effect on red blood cell deformability leading to a putative reduction of ADP release by damaged erythrocytes. However similarly high concentrations were needed to prevent stirring-induced "spontaneous" platelet aggregation in human whole blood. It is concluded that the observed antithrombotic action of piracetam cannot satisfactorily be explained by an isolated direct effect on platelets. An additional influence of piracetam on the rheology of the circulating blood and/or on the vessel wall itself must therefore be taken into consideration.     

Establishment of an animal model for pulmonary fibrosis in mice using monocrotaline

A preliminary attempt at experimental induction of pulmonary fibrosis in which male ICR mice received 15 weekly sc injections of 200 or 100 mg/kg monocrotaline (MC) revealed that most animals treated with the larger dose died of severe interstitial pneumonia, whereas those given 100 mg/kg exhibited only relatively slight lung injury. Based on these results, male mice were administered sc injections of 200 and 100 mg/kg MC once a week for 9 and 18 times, respectively, and then maintained without any further treatment until week 28 after the start. Mice treated with 200 mg/kg MC showed severe pulmonary damage and died by week 25. Mortalities also occurred in the 100-mg group from week 16, with 11 of 40 animals surviving at the termination of the experiment. Histologically, both dose groups demonstrated severe interstitial pneumonia and/or pulmonary fibrosis. Ultrastructurally, inflammatory edema possibly attributable to injuries of alveolar capillary endothelial cells was observed in the high-dose group at week 8, and there was a remarkable increase in collagen fibers in alveolar septa in this group thereafter. The present study results suggest that lung injuries induced by MC treatment progress to irreversible lung fibrosis and that this animal model may have advantage for studying the pathogenesis of lung cancers in patients with pulmonary fibrosis.     

The effect of radial keratotomy on ocular integrity in an animal model

The safety of deep corneal incisions in radial keratotomy was evaluated in a porcine model of blunt trauma. One eye of each enucleated pair (right and left) of porcine eyes was subjected to a variation of radial keratotomy; the fellow eyes served as unoperated-on controls. All eyes were subjected to a standard injury. Control eyes ruptured at the equatorial sclera. Eyes with radial incisions cut through approximately 70% of corneal thickness also ruptured at the equator. When incisions of this depth (70%) were extended across the limbus (rather than to the corneal-scleral junction), all ruptures occurred at the limbal incisions. Eyes cut 95% to 100% of corneal thickness tended to rupture at the incisions. The safety of deep radial keratotomy incisions with respect to ocular integrity is discussed.     

Bovine hereditary cardiomyopathy: an animal model of human dilated cardiomyopathy

Bovine hereditary cardiomyopathy (bCMP) displays clinical characteristics of human idiopathic dilated cardiomyopathy (DCM). We studied isometric force of contraction in right ventricular trabeculae, plasma and tissue catecholamines, beta- and alpha 1-adrenoceptor density, Gi proteins and adenylyl cyclase activity in eight hearts with bCMP and eight control hearts (right and left atria and ventricles each). Results: Compared to control, the potency of isoprenaline in bCMP was eight-fold decreased, whereas the maximal positive inotropic effect of isoprenaline as well as the efficacy and potency of calcium were unchanged. Plasma noradrenaline was increased by 240%. Tissue noradrenaline and adrenaline were decreased by 36-63% and 58-69%, whereas dopamine was increased by 105-218%. beta-adrenoceptor density was drastically reduced by 90%, but binding affinity was unchanged. alpha-Adrenoceptor density and binding affinity were unchanged. Total PTX-substrates were increased in bCMP by 28-99%. Basal adenylyl cyclase activity was decreased by 36-47%. Similarly, stimulation by GTP, GMPPNP, isoprenaline, sodium fluoride, manganese or forskolin was attenuated by 26-62% (atria) and 45-66% (ventricles). In conclusion, we found marked activation of the sympatho-adrenergic system, downregulation of beta-adrenoceptors, upregulation of Gi proteins, global desensitization of adenylyl cyclase and selective subsensitivity to beta-adrenergic inotropic stimulation. These results closely resemble the characteristic alterations in the beta-adrenoceptor-G protein-adenylyl cyclase pathway in human heart failure, indicating that they are general features of heart failure. The similarity to human DCM, the inheritance and the availability of large tissue samples make bCMP a suitable model for human DCM.     

The canine as an animal model of human aging and dementia

Cytochemical defects in chromatin were examined by transmission electron microscopy (TEM) after the staining by alcoholic phosphotungstic acid (PTA) of normal and malformed ejaculated spermatozoa from 35 male partners of infertile couples, and in six sperm samples retrieved from the caput epididymidis of men affected by obstructive azoospermia. PTA staining was also analysed in normal ejaculates of fertile men after incubation of the washed spermatozoa with dithiothreitol (DTT) to reduce disulfides to thiols, or with DTT followed by iodoacetamide, a blocking agent for thiol groups. PTA stained 63 (27-100)% of malformed heads and 25 (10-100)% of normal sperm heads (median (range) n = 35; P = 0.0001, Wilcoxon matched pairs test). The percentage of normal heads stained by PTA was negatively correlated with the percentage of heads of normal form, with condensed chromatin and a normal acrosome (Spearman r = 0.75; P = 0.0001), and positively correlated with the percentage of malformed heads after conventional TEM analysis (Spearman r 0.60; P = 0.0001). Staining with PTA in normal heads was not correlated with the presence of non-condensed chromatin in otherwise normal sperm heads evaluated by conventional TEM analysis. In spermatozoa recovered from the caput epididymidis, 15% of normal heads were stained with PTA, significantly fewer than in ejaculated sperm samples (P = 0.014). The reduction of disulfides to thiols was associated with PTA staining of all normal heads, and this was prevented by incubation with iodoacetamide. We conclude that PTA staining of the nuclei of human ejaculated spermatozoa may indicate a defect of chromatin condensation, owing to an excess of free thiol groups. The lower percentage of normal epididymal sperm heads that stained with PTA in cases of obstructive azoospermia compared with ejaculated sperm may be related to an overoxidation of thils owing to the ageing of spermatozoa.