Primary hypoaldosteronism in a dog with pituitary and adrenal T-cell lymphoma.

A 7-year-old mixed breed dog was presented with a 2-week history of vomiting, diarrhoea, weakness and loss of appetite. Initial laboratory tests revealed hyponatraemia and hyperkalaemia consistent with hypoadrenocorticism. Basal plasma cortisol and adrenocorticotropic hormone concentrations were not suggestive of primary hypoadrenocorticism but the aldosterone concentration was undetectable. Abdominal ultrasound scan showed a mass within the left kidney and a nodular enlargement of the left adrenal gland. Cytological analysis revealed a large granular lymphoma. The dog died 17 days later. Post mortem histological and immunohistochemical examinations revealed a diffuse large granular T-cell lymphoma involving the mediastinal lymph node, kidneys, pancreas, adrenal and pituitary glands.

Modeling of response to endocrine therapy in a panel of human luminal breast cancer xenografts.

Resistance to endocrine therapy is a major complication of luminal breast cancer and studies of the biological features of hormonal resistance are limited by the lack of adequate preclinical models. The aim of this study is to establish and characterize a panel of primary human luminal breast carcinoma xenografts, and to evaluate their response to endocrine therapies. Four hundred and twenty-three tumor fragments obtained directly from patients have been grafted in the interscapular fatpad of Swiss nude mice. After stable engraftment with estradiol supplementation, xenografted tumors have been validated by conventional pathology and immunohistochemistry examination, and additional molecular studies. In vivo tumor growth and response to different endocrine treatments were evaluated. We have engrafted 423 tumors including 314 ER+ tumors, and 8 new luminal breast cancer xenografts have been obtained (2.5%). Tumor take was much lower for luminal tumors than for non-luminal tumors (2.5 vs. 24.7%, P < 0.0001), and was associated with two independent criteria, i.e., ER status (P < 0.0001) and a high grade tumor (P = 0.05). Histological and immunohistochemical analyses performed on patient's tumors and xenografts showed striking similarities in the tumor morphology as well as in the expression level of ER, PR, and HER2. Response to hormone therapy, evaluated in 6 luminal models, showed different sensitivities, thus exhibiting heterogeneity similar to what is observed in the clinic. We have established a panel of primary human luminal breast cancer xenografts, recapitulating the biological and clinical behaviors of patient tumors, and therefore suitable for further preclinical experiments.

Establishment and characterisation of a new breast cancer xenograft obtained from a woman carrying a germline BRCA2 mutation.

BACKGROUND: The BRCA2 gene is responsible for a high number of hereditary breast and ovarian cancers, and studies of the BRCA2 biological functions are limited by the lack of models that resemble the patient's tumour features. The aim of this study was to establish and characterise a new human breast carcinoma xenograft obtained from a woman carrying a germline BRCA2 mutation. METHODS: A transplantable xenograft was obtained by grafting a breast cancer sample into nude mice. The biological and genetic profiles of the xenograft were compared with that of the patient's tumour using histology, immunohistochemistry (IHC), BRCA2 sequencing, comparative genomic hybridisation (CGH), and qRT-PCR. Tumour response to standard chemotherapies was evaluated. RESULTS: Histological profile identified the tumour as a basal-like triple-negative breast cancer. Targeted BRCA2 DNA sequencing of the xenograft showed the presence of the mutation previously identified in the carrier. Comparative genomic hybridisation array profiles of the primary tumour and the xenograft revealed a high number of similar genetic alterations. The therapeutic assessment of the xenograft showed sensitivity to anthracyclin-based chemotherapy and resistance to docetaxel. The xenograft was also highly sensitive to radiotherapy and cisplatin-based treatments. CONCLUSIONS: This study describes a new human breast cancer xenograft obtained from a BRCA2-mutated patient. This xenograft provides a new model for the pre-clinical drug development and for the exploration of the drug response biological basis.

Proteomic and phosphoproteomic analysis of cellular responses in medaka fish (Oryzias latipes) following oral gavage with microcystin-LR.

Chronic and subchronic toxicity resulting from exposure to microcystins (MCs) receives increasing attention due to the risk of bioaccumulation of these toxins by aquatic animals, including fish. The mechanisms of action of MCs that target the liver, involve modifications of protein phosphorylation resulting from phosphatases 1 and 2A inhibition. Therefore, studying phosphoprotein modifications by using a specific phosphoprotein stain Pro-Q Diamond in fish liver contaminated with MC-leucine-arginine (MC-LR), the most toxic MC, should help dissecting disturbed signaling and metabolic networks. We have recently used this technology to identify several proteins that are modulated either in expression or phosphorylation in the liver of medaka following short-term exposure to MC-LR by balneation. In the present study, we have decided to use an alternative way of introducing the toxin into fish; that is by gavage (force-feeding). This was first achieved using tritiated MC-LR and allowed us to quantify the quantity of toxin incorporated into fish and to demonstrate that the toxin is mainly accumulated in liver. Afterwards a proteomics study limited to liver cytosolic proteins of contaminated animals showed that several proteins were up or down regulated either in quantity or in phosphorylation or both. Some of them had been previously detected as modified in balneation experiments but new molecules were identified as involved in signal transduction pathways activated by the toxin. In addition, in the conditions used (5 microg toxin/g body weight) anatomopathological studies supported a process of apoptonecrosis established after 24h, which was suggested to proceed by the evolution of some of the proteins after 2h contamination.

Severe necrotizing encephalitis in a Yorkshire terrier: topographic and immunohistochemical study.

Necrotizing encephalitis of the Yorkshire terrier is a chronic non-suppurative encephalitis that was reported in approximately 15 cases worldwide. We report the case of a 10-year-old female Yorkshire terrier with gross evidence of severe cortical degeneration and necrosis. Microscopically, affected areas were mainly located in the cortical white matter and in the mesencephalon without implication of the cerebellum. Cavitation necrosis, demyelination, gemistocytic astrocytosis, marked perivascular lymphocytic cuffing with a diffuse lymphocytic/histiocytic/gitter cell infiltration characterized the lesions. Immunohistochemical analysis identified the major infiltration of T lymphocytes and macrophages with implication of some cytotoxic lymphocytes and IgG-producing plasma cells; depositions of IgG in the affected white matter were also observed. Specific stains did not reveal fungal, protozoal or bacterial organisms and reverse transcriptase-polymerase chain reaction analysis for distemper virus was also negative. The lympho-histiocytic inflammation suggests a T-cell-mediated and a delayed-type immune reaction as a possible pathogenic mechanism for this brain disorder.

Adverse effects of conjugated alpha-linolenic acids (CLnA) on lipoprotein profile on experimental atherosclerosis in hamsters.

Conjugated linoleic acids (CLAs) such as rumenic acid (RA) have the potential to alter blood lipid profiles in animals and in humans. In contrast, physiological effects of conjugated α-linolenic acids (CLnAs), which concomitantly are omega-3 and conjugated fatty acids, are still unknown. The aim of this study was to evaluate the potential of CLnA to interfere in early steps of atherosclerosis by altering lipoprotein profiles and fatty streaks in the aortas. F1B hamsters were fed a control or one of the three hypercholesterolemic (HC) diets: HC-control, HC-RA (18:2 cis-9, trans-11) or HC-CLnA (CLnA: equimolar mixture of 18:3 cis-9, trans-11, cis-15 and cis-9, trans-13, cis-15) diet. In low-cholesterol control-fed hamsters, the proportion of high-density lipoprotein cholesterol (HDL-C) was around 45% while in HC-fed hamsters, HDL-C was around 10% and cholesterol was mostly (80%) carried by triglyceride-rich lipoproteins (TRL). Low-density lipoprotein (LDL) triglycerides (TGs) increased by approximately 60% in hamsters fed either HC-RA or HC-CLnA compared with HC-controls but not compared with the low-cholesterol control diet. HDL cholesterol decreased by 24% and 16% in hamsters fed HC-RA and HC-CLnA, respectively. Small dense LDL-cholesterol increased by approximately 60% in hamsters fed HC-RA and HC-CLnA compared with the HC-control group and by more than a 100% compared with hamsters on the control diet. The relative percentage of liver cholesteryl ester content increased by 88% in hamsters fed HC diets compared with the control diet. Significant differences in fatty streaks were observed between control and HC-diet-fed hamsters. However, no significant difference was observed among the HC-diet-fed hamsters. This study shows that animals fed any one of the HC diets developed an adverse lipoprotein profile compared with a normolipidic diet. Also, HC-RA or HC-CLnA diets altered lipoprotein profile compared with animals fed the HC-control diet but had no beneficial effects on atherosclerosis.

Habitat selection responses of parents to offspring predation risk: an experimental test.

The ability of nest predation to influence habitat settlement decisions in birds is widely debated, despite its importance in limiting fitness. Here, we experimentally manipulated nest predation risk across a landscape and asked the question, do migratory birds assess and respond to variation in nest predation risk when choosing breeding habitats? We examined habitat preference by quantifying the density and settlement date of eight species of migratory passerines breeding in areas with and without intact nest predator communities. We found consistently more individuals nesting in areas with reduced nest predation than in areas with intact predator assemblages, although predation risk had no influence on settlement or breeding phenology. Additionally, those individuals occupying safer nesting habitats exhibited increased singing activity. These findings support a causal relationship between habitat choice and nest predation risk and suggest the importance of nest predation risk in shaping avian community structure and breeding activity.

Parent birds assess nest predation risk and adjust their reproductive strategies.

Avian life history theory has long assumed that nest predation plays a minor role in shaping reproductive strategies. Yet, this assumption remains conspicuously untested by broad experiments that alter environmental risk of nest predation, despite the fact that nest predation is a major source of reproductive failure. Here, we examined whether parents can assess experimentally reduced nest predation risk and alter their reproductive strategies. We experimentally reduced nest predation risk and show that in safer environments parents increased investment in young through increased egg size, clutch mass, and the rate they fed nestlings. Parents also increased investment in female condition by increasing the rates that males fed incubating females at the nest, and decreasing the time that females spent incubating. These results demonstrate that birds can assess nest predation risk at large and that nest predation plays a key role in the expression of avian reproductive strategies.

Life-history and ecological correlates of geographic variation in egg and clutch mass among passerine species.

Broad geographic patterns in egg and clutch mass are poorly described, and potential causes of variation remain largely unexamined. We describe interspecific variation in avian egg and clutch mass within and among diverse geographic regions and explore hypotheses related to allometry, clutch size, nest predation, adult mortality, and parental care as correlates and possible explanations of variation. We studied 74 species of Passeriformes at four latitudes on three continents: the north temperate United States, tropical Venezuela, subtropical Argentina, and south temperate South Africa. Egg and clutch mass increased with adult body mass in all locations, but differed among locations for the same body mass, demonstrating that egg and clutch mass have evolved to some extent independent of body mass among regions. A major portion of egg mass variation was explained by an inverse relationship with clutch size within and among regions, as predicted by life-history theory. However, clutch size did not explain all geographic differences in egg mass; eggs were smallest in South Africa despite small clutch sizes. These small eggs might be explained by high nest predation rates in South Africa; life-history theory predicts reduced reproductive effort under high risk of offspring mortality. This prediction was supported for clutch mass, which was inversely related to nest predation but not for egg mass. Nevertheless, clutch mass variation was not fully explained by nest predation, possibly reflecting interacting effects of adult mortality. Tests of the possible effects of nest predation on egg mass were compromised by limited power and by counterposing direct and indirect effects. Finally, components of parental investment, defined as effort per offspring, might be expected to positively coevolve. Indeed, egg mass, but not clutch mass, was greater in species that shared incubation by males and females compared with species in which only females incubate eggs. However, egg and clutch mass were not related to effort of parental care as measured by incubation attentiveness. Ecological and life-history correlates of egg and clutch mass variation found here follow from theory, but possible evolutionary causes deserve further study.

Longitudinal left ventricular myocardial dysfunction assessed by 2D colour tissue Doppler imaging in a dog with systemic hypertension and severe arteriosclerosis.

A 12-year-old sexually intact male Vendee Griffon Basset was presented for acute pulmonary oedema. Severe systemic systolic arterial hypertension (SAH) was diagnosed (290 mmHg). Despite blood and abdominal ultrasound tests, the underlying cause of the systemic hypertension could not be determined, and primary SAH was therefore suspected. Conventional echocardiography showed eccentric left ventricular hypertrophy with normal fractional shortening. Despite this apparent normal systolic function, 2D colour tissue Doppler imaging (TDI) identified a marked longitudinal systolic left ventricular myocardial alteration, whereas radial function was still preserved. Three months later, the dog underwent euthanasia because of an acute episode of distal aortic thromboembolism. Necropsy revealed severe aortic and iliac arteriosclerosis. SAH related to arteriosclerosis is a common finding in humans, but has not been previously described in dogs. Moreover, its consequence on longitudinal myocardial function using TDI has never been documented before in this species.

An osteoid variant of cutaneous melanoma in a dog detected by S100 and melan a markers.

Osteoid malignant melanoma is a rare type of melanoma described in humans and dogs with some areas of bone differentiation. In this tumour, the origin of the bone matrix remains unclear. We report one case of this variant with, for the first time, a cutaneous origin in a dog. Malignant melanomas are aggressive tumours. Amelanotic tumours are sometimes difficult to recognize as they require immunohistochemical evaluation for an adequate diagnosis and we have used anti-vimentin, S100, and melan A antibodies for identification. Melan A is less sensitive but more specific than S100 in identifying amelanotic melanomas. This tumour was positive for vimentin, S100 and melan A, including the areas of osteoid. These results suggest osteoid differentiation of tumour cells rather than induced stromal metaplasia.

Mucinous differentiation features associated with hormonal escape in a human prostate cancer xenograft.

Many theories mention hypersensitive, promiscuous, outlaw or bypass signalling pathways to explain the acquisition of hormone independence in prostate cancer. Hormonal escape of prostate tumours is marked by many biological changes, including mucinous and neuroendocrine differentiation. Since expression of several mucins has been linked to carcinoma tumour progression, we have characterised the expression of mucins at both RNA and protein levels in an in vivo model of prostate cancer in hormonal escape. Using PAC120, a xenograft of a human hormone-dependent prostate tumour, and its hormone-independent variants, we analysed the expression of mucins (MUC1, MUC2, MUC4, MUC5AC, MUC5B, MUC6) by immunohistochemistry or reverse transcriptase (RT)-PCR. While the parental PAC120 tumour was a compact poorly-differentiated tumour of Gleason score 9 (5+4), hormone-independent variants displayed mucinous, neuroendocrine-like or mixed histological changes; these changes were stable through serial transplantations or after testosterone supply. MUC1 mRNA was expressed in both PAC120 and the hormone-independent variants, although at variable levels. All tumours displayed a high and constant expression of MUC2 and no expression of MUC4 mRNA. While MUC1 was expressed in all xenografts whatever their hormone dependence status, MUC2, MUC5B and MUC6 were preferentially expressed in hormone-independent variants. The loss of hormone dependence in this prostate cancer xenograft model is therefore marked by irreversible histological alterations, mucinous or neuro-endocrine, associated with an expression of secretory MUC2, MUC5B and MUC6, independent of the histological differentiation subtype. These data point to mucinous differentiation as an important step in the acquisition of hormone independence in this cancer, and suggest that secretory mucins might participate in an unknown pathway of hormonal escape in prostate cancer.

Sclerosing peritoneal mesothelioma in a dog - a case report.

A case of peritoneal sclerosing mesothelioma in a 3-year-old German shepherd dog is reported. The dog presented a severe abdominal distension. Cytological examination of the peritoneal fluid revealed anaplastic epithelioid cells. Necropsy findings revealed an irregular-shaped mass attached to the pancreas and stomach with numerous nodules covering the intestinal and urinary bladder serosa. The diagnosis was made by histology and immunohistochemistry, with cytokeratin, vimentin and calretinin antibodies. Differential diagnosis with chronic peritonitis and spreading of abdominal primary carcinoma is discussed.

Toxicological comparison of diverse Cylindrospermopsis raciborskii strains: evidence of liver damage caused by a French C raciborskii strain.

The freshwater cyanobacterium Cylindrospermopsis raciborskii is known to produce toxic effects in several countries. Acute and chronic exposures to C. raciborskii in Australia have been linked to liver damage (hepatotoxicity) with concomitant effects on the kidneys, adrenal glands, small intestine, lungs, thymus, and heart. The alkaloid cylindrospermopsin, which produces these toxic effects, is thought to be a potent inhibitor of protein synthesis. C. raciborskii strains producing cylindrospermopsin or analogue alkaloids have also been reported in Florida, USA, and Thailand. Brazilian isolates of C. raciborskii are also toxic but act by a different mechanism, causing acute death in mice with neurotoxic symptoms similar to those induced by the saxitoxins. In this article we compare the toxicity in the mouse of a C. raciborskii French strain with C. raciborskii strains from various other sources (Australia, Brazil, Mexico, and Hungary). We tested the toxicity of cell extracts by a mouse bioassay. Acute, fatal neurotoxicity was produced by the Brazilian strain, which was confirmed by liquid chromatography with fluorescence detection of the cell extracts, which revealed the presence of saxitoxin, neosaxitoxin, and decarbamoylsaxitoxin, along with two unidentified compounds. Acute hepatotoxicity with severe liver, kidney, and thymus damage was observed with the Australian cylindrospermopsin-producing strain. The Mexican and Hungarian strains were not found to be toxic to mice in our experimental conditions. No animals died after exposure to the extracts of the French C. raciborskii strain. Histological examination of the liver revealed moderate, multifocal necrosis characterized by small areas of hepatocellular necrosis, combined with disorganization of the parenchyma and congestion of the inner sinusoid. These symptoms and lesions resembled those induced by cylindrospermopsin, but the chemical analysis performed by liquid chromatography coupled with either a diode array detector or a mass spectrometer demonstrated that this toxin was not present in our culture extract.

Kinetics of Bartonella birtlesii infection in experimentally infected mice and pathogenic effect on reproductive functions.

The kinetics of infection and the pathogenic effects on the reproductive function of laboratory mice infected with Bartonella birtlesii recovered from an Apodemus species are described. B. birtlesii infection, as determined by bacteremia, occurred in BALB/c mice inoculated intravenously. Inoculation with a low-dose inoculum (1.5 x 10(3) CFU) induced bacteremia in only 75% of the mice compared to all of the mice inoculated with higher doses (> or =1.5 x 10(4)). Mice became bacteremic for at least 5 weeks (range, 5 to 8 weeks) with a peak ranging from 2 x 10(3) to 10(5) CFU/ml of blood. The bacteremia level was significantly higher in virgin females than in males but the duration of bacteremia was similar. In mice infected before pregnancy (n = 20), fetal loss was evaluated by enumerating resorption and fetal death on day 18 of gestation. The fetal death and resorption percentage of infected mice was 36.3% versus 14.5% for controls (P < 0.0001). Fetal suffering was evaluated by weighing viable fetuses. The weight of viable fetuses was significantly lower for infected mice than for uninfected mice (P < 0.0002). Transplacental transmission of Bartonella was demonstrated since 76% of the fetal resorptions tested was culture positive for B. birtlesii. The histopathological analysis of the placentas of infected mice showed vascular lesions in the maternal placenta, which could explain the reproductive disorders observed. BALB/c mice appeared to be a useful model for studying Bartonella infection. This study provides the first evidence of reproductive disorders in mice experimentally infected with a Bartonella strain originating from a wild rodent.

Differentiation of the epithelial apical junctional complex during mouse preimplantation development: a role for rab13 in the early maturation of the tight junction.

We have investigated the mechanisms by which the epithelial apicolateral junctional complex (AJC) is generated during trophectoderm differentiation in the mouse blastocyst using molecular, structural and functional analyses. The mature AJC comprises an apical tight junction (TJ), responsible for intercellular sealing and blastocoel formation, and subjacent zonula adherens E-cadherin/catenin adhesion complex which also extends along lateral membrane contact sites. Dual labelling confocal microscopy revealed that the AJC derived from a single 'intermediate' complex formed following embryo compaction at the 8-cell stage in which the TJ-associated peripheral membrane protein, ZO-1alpha- isoform, was co-localized with both alpha- and beta-catenin. However, following assembly of the TJ transmembrane protein, occludin, from the early 32-cell stage when blastocoel formation begins, ZO-1alpha- and other TJ proteins (ZO-1alpha+ isoform, occludin, cingulin) co-localized in an apical TJ which was separate from a subjacent E-cadherin/catenin zonula adherens complex. Thin-section electron microscopy confirmed that a single zonula adherens-like junctional complex present at the AJC site following compaction matured into a dual TJ and zonula adherens complex at the blastocyst stage. Embryo incubation in the tracer FITC-dextran 4 kDa showed that a functional TJ seal was established coincident with blastocoel formation. We also found that rab13, a small GTPase previously localized to the TJ, is expressed at all stages of preimplantation development and relocates from the cytoplasm to the site of AJC biogenesis from compaction onwards with rab13 and ZO-1alpha- co-localizing precisely. Our data indicate that the segregation of the two elements of the AJC occurs late in trophectoderm differentiation and likely has functional importance in blastocyst formation. Moreover, we propose a role for rab13 in the specification of the AJC site and the formation and segregation of the TJ.

Parental care and clutch sizes in North and South American birds.

The evolutionary causes of small clutch sizes in tropical and Southern Hemisphere regions are poorly understood. Alexander Skutch proposed 50 years ago that higher nest predation in the south constrains the rate at which parent birds can deliver food to young and thereby constrains clutch size by limiting the number of young that parents can feed. This hypothesis for explaining differences in clutch size and parental behaviors between latitudes has remained untested. Here, a detailed study of bird species in Arizona and Argentina shows that Skutch's hypothesis explains clutch size variation within North and South America. However, neither Skutch's hypothesis nor two major alternatives explain differences between latitudes.

Subcellular localization of tetanus neurotoxin-insensitive vesicle-associated membrane protein (VAMP)/VAMP7 in neuronal cells: evidence for a novel membrane compartment.

The clostridial neurotoxin-insensitive soluble N-ethylmaleimide-sensitive factor attachment protein (SNAP) receptors, tetanus neurotoxin-insensitive (TI)-vesicle-associated membrane protein (VAMP)/VAMP7, SNAP23, and syntaxin 3 have recently been implicated in transport of exocytotic vesicles to the apical plasma membrane of epithelial cells. This pathway had been shown previously to be insensitive to tetanus neurotoxin and botulinum neurotoxin F. TI-VAMP/VAMP7 is also a good candidate to be implicated in an exocytotic pathway involved in neurite outgrowth because tetanus neurotoxin does not inhibit this process in conditions in which it abolishes neurotransmitter release. We have now found that TI-VAMP/VAMP7 has a widespread distribution in the adult rat brain in which its localization strikingly differs from that of nerve terminal markers. TI-VAMP/VAMP7 does not enrich in synaptic vesicles nor in large dense-core granules but is associated with light membranes. In hippocampal neurons developing in vitro, TI-VAMP/VAMP7 localizes to vesicles in the axonal and dendritic outgrowths and concentrates into the leading edge of the growth cone, a region devoid of synaptobrevin 2, before synaptogenesis. After the onset of synaptogenesis, TI-VAMP/VAMP7 is found predominantly in the somatodendritic domain. In PC12 cells, TI-VAMP/VAMP7 does not colocalize with synaptobrevin 2, chromogranin B, or several markers of endocytic compartments. At the electron microscopic level, TI-VAMP/VAMP7 is mainly associated with tubules and vesicles. Altogether, these results suggest that TI-VAMP/VAMP7 defines a novel membrane compartment in neurite outgrowths and in the somatodendritic domain.

In vivo, villin is required for Ca(2+)-dependent F-actin disruption in intestinal brush borders.

Villin is an actin-binding protein localized in intestinal and kidney brush borders. In vitro, villin has been demonstrated to bundle and sever F-actin in a Ca(2+)-dependent manner. We generated knockout mice to study the role of villin in vivo. In villin-null mice, no noticeable changes were observed in the ultrastructure of the microvilli or in the localization and expression of the actin-binding and membrane proteins of the intestine. Interestingly, the response to elevated intracellular Ca(2+) differed significantly between mutant and normal mice. In wild-type animals, isolated brush borders were disrupted by the addition of Ca(2+), whereas Ca(2+) had no effect in villin-null isolates. Moreover, increase in intracellular Ca(2+) by serosal carbachol or mucosal Ca(2+) ionophore A23187 application abolished the F-actin labeling only in the brush border of wild-type animals. This F-actin disruption was also observed in physiological fasting/refeeding experiments. Oral administration of dextran sulfate sodium, an agent that causes colonic epithelial injury, induced large mucosal lesions resulting in a higher death probability in mice lacking villin, 36 +/- 9.6%, compared with wild-type mice, 70 +/- 8.8%, at day 13. These results suggest that in vivo, villin is not necessary for the bundling of F-actin microfilaments, whereas it is necessary for the reorganization elicited by various signals. We postulate that this property might be involved in cellular plasticity related to cell injury.