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PubMed1984

Histogenesis of colon cancer in experimental animals.

Following the introduction of colon-specific carcinogens, the mode of formation and evolution of colon cancer has been investigated in experimental animals. These carcinogens are cytotoxic to epithelial cells in colonic crypts and induce a series of non-specific acute and chronic changes including cryptal hyperplasia when administered repeatedly. During such processes, a number of neoplastically transformed cells may appear in many crypts. Only when they occur at the base of or form an outpocketing pouch in a crypt, do they appear to succeed in repopulating the given crypt to form a dysplastic crypt, from which an early neoplastic lesion develops usually in the upper part of the mucosa. The neoplastic lesion thus formed grows by various mechanisms, depending on its intrinsic properties of unceasing proliferative activity of neoplastic cells and interaction with the microenvironment: (a) by elongation and tortuosity of neoplastic glands, (b) by evagination of the glandular epithelial lining, with the formation of septa to dichotomise the glands to increase the number of neoplastic glands or with formation of incomplete septa or villi to expand the surface area of the neoplasm, and (c) by invagination and outpocketing pouch formation of neoplastic glands when accompanied with the changes in the basement membrane. In doing so, it may progress in various directions to form a polypoid or discoid lesion. Concomitant with growth, the neoplastic cells may undergo a series of cytological alterations and penetrate through their basement membrane in some areas to manifest early malignant behaviour. With downward progression, the neoplasm penetrates the muscularis mucosae and invades the submucosa, muscularis externa and serosa. Such an invasive process is often associated with the rearrangement of fibroblasts, marked changes in the production of collagen and proteoglycans of the extracellular matrix and lysis of the existing structures of the colonic wall. On morphological grounds, colonic carcinogenesis is a multiple process and is associated with successive breakdown of the host defence barriers. From the studies on experimental colonic tumourigenesis, adenomas and adenocarcinomas appear to share a common aetiological factor, or factors, and they are different end-stages in the evolution of neoplastically transformed cells. At any stage of evolution, however, benign neoplasms may develop dysplastic foci within neoplasms and evolve into a malignant form.

Adenocarcinoma↗
PubMed1990

The molecular evolution of bacterial alkaline phosphatase: correlating variation among enteric bacteria to experimental manipulations of the protein.

The phylogenetic distribution of the gene coding for bacterial alkaline phosphatase (phoA) was examined in nine species of enteric bacteria closely related to Escherichia coli. The nucleotide and protein sequences from the E. fergusonii and Serratia marcescens genes are presented. The spatial distribution of replaced amino acid residues in the aligned sequences is shown to be highly nonrandom and can be correlated with specific regions within the tertiary structure of the protein. There is an avoidance of replacements within the beta sheet of the protein, and there is an excess of replacements elsewhere, particularly in solvent-exposed residues. In addition, all positions across alpha helices do not accept replacements with equal frequency; there is a bias toward acceptance of replacements in the carboxyl ends of helices. To examine this further, mutations within the E. coli phoA gene were created using site-directed mutagenesis. The patterns seen from the sequence comparisons were verified in the laboratory-created mutants. The average activity of mutations within or near the beta sheet was approximately one-third of that within or near alpha helices, and multiple mutations within the carboxyl ends of alpha helices always possessed greater activity than did multiple mutations within the corresponding amino ends. The results indicate that identifiable regions within the protein are under different selective pressures and are therefore evolving at different rates.

Alkaline Phosphatase↗
PubMed1996

A longitudinal study of feline immunodeficiency virus-specific cytotoxic T lymphocytes in experimentally infected cats, using antigen-specific induction.

The evolution of the virus-specific cytotoxic T-lymphocyte response in two cats experimentally infected with feline immunodeficiency virus (FIV) was monitored. Effector cells were derived from peripheral blood lymphocytes during the acute and chronic phases of infection (0 to 21 and 62 to 127 weeks, respectively) and from the spleen and lymph nodes at 127 weeks after infection. Lymphocytes were restimulated in vitro with paraformaldehyde-fixed, autologous lymphoblasts which had been infected with recombinant vaccinia viruses expressing FIV GAG or ENV proteins. Unstimulated lymphocytes were also used as effectors in some assays. 51Cr-labelled autologous skin fibroblasts infected with recombinant vaccinia viruses were used as targets. FIV GAG-specific cytotoxic precursors were detected in restimulated circulating lymphocytes during acute infection in both cats. The onset of this activity was as early as 2 weeks postinfection (p.i.) in one cat. From 62 weeks p.i. neither FIV GAG- nor ENV-specific precursors could be detected in the peripheral blood. However, at 127 weeks p.i., GAG- and ENV-specific cytotoxic precursors were detected in lymphocytes isolated from lymph nodes. The FIV-specific cytotoxic cells were predominantly major histocompatibility complex class I restricted. No cytotoxic activity was detected from unstimulated lymphocytes. These studies demonstrate the use of an assay system for dissecting the FIV-specific cytotoxic cell response and show that precursor cells appear in the circulation very early after infection and prior to a detectable antibody response. Our results also suggest that the persistent high-level circulating antiviral cytotoxic T-lymphocyte responses seen in human immunodeficiency virus-infected humans may not be a feature of FIV infections in cats.

Animals↗
PubMed1980

Experimental model of chronic serum sickness. Relationships between proteinuria, sodium dodecyl sulfate-polyacrylamide gel electrophoresis, and glomerular and extraglomerular renal pathology.

The evolution of proteinuria in rabbits with experimentally induced chronic serum sickness was followed up longitudinally by analytical and quantitative assays. The results suggest that sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) is a more sensitive index of kidney malfunction than are total-protein assays or the quantitation of albumin and lysozyme. In some rabbits that showed abnormal proteinuria by SDS-PAGE, no histologic evidence of pathologic damage or of deposition of immune complexes in the kidneys was found. This suggests that SDS-PAGE may detect functional alterations at early stages of kidney damage when the lesions are either undetectable or reversible. In one rabbit that was killed after normalization of the proteinuria, immunofluorescence tests indicated deposition of C3, IgG, and fibrinogen, but there was no histologic evidence of kidney damage.

Animals↗
PubMed2004

Impaired erythrocyte deformability precedes vascular changes in experimental diabetes mellitus.

The effect of diabetes on the red blood cell (RBC) deformability and its association with histological vascular changes was investigated in 35 streptozotocin-induced diabetic Wistar rats in a 30-day experiment and compared to 10 controls. RBC deformability was significantly impaired in the diabetic rats on day 5 (p < 0.001) and continued to deteriorate until day 20. On the 20 (th) day, the diabetic rats were randomly divided into two groups (group A: insulin-treated; group B: non-insulin-treated). A slight, non-significant (p = 0.20) improvement in RBC deformability was noticed in the insulin-treated group. In vitro incubation of RBCs with insulin did not improve the acquired RBC rigidity in either diabetic group. In contrast, it caused a significant reduction in RBC-deformability in the controls. On day 30, histological examination of arterial specimens from various sites revealed moderate to significant thickening in medium- and small-size artery and arteriole walls in both diabetic groups, with no evidence of diabetes-related changes in large, elastic-type arteries. No vascular changes were noticed in nine diabetic rats that succumbed between days 10 and 15. The results of this study indicate that reduced RBC deformability is an early manifestation of abnormal blood rheology in experimental diabetes, and precedes the evolution of vascular changes.

Animals↗
PubMed2002

Evolution of the aroma profile of sherry wine vinegars during an experimental aging in wood.

Changes in the aroma profile of five Sherry wine vinegars submitted to an experimental static aging in wood were followed along 24 months. Eighteen volatile compounds were determined by GC-FID. The results were subjected to multivariate analyses: principal component analysis and linear discriminant analysis. The aroma profile of vinegar can be useful to discriminate vinegars produced from different substrates or with different aging times. During the experimental aging, volatile compounds such as methyl acetate, methanol, diacetyl, and gamma-butyrolactone underwent significant concentration increases. Moreover, the initial ethanol content of vinegars is a factor in the final aromatic richness. The formation of ethyl acetate stood out in samples with an initial ethanol content of approximately 2 alcoholic degrees.

4-Butyrolactone↗
PubMed2000

Experimental analysis of molecular events during mutational periodic selections in bacterial evolution.

A fundamental feature of bacterial evolution is a succession of adaptive mutational sweeps when fitter mutants take over a population. To understand the processes involved in mutational successions, Escherichia coli continuous cultures were analyzed for changes at two loci where mutations provide strong transport advantages to fitness under steady-state glucose limitation. Three separate sweeps, observed as classic periodic selection events causing a change in the frequency of neutral mutations (in fhuA causing phage T5 resistance), were identified with changes at particular loci. Two of the sweeps were associated with a reduction in the frequency of neutral mutations and the concurrent appearance of at least 13 alleles at the mgl or mlc loci, respectively. These mgl and mlc polymorphisms were of many mutational types, so were not the result of a mutator or directed mutation event. The third sweep observed was altogether distinct and involved hitchhiking between T5 resistance and advantageous mgl mutations. Moreover, the hitchhiking event coincided with an increase in mutation rates, due to the transient appearance of a strong mutator in the population. The spectrum of mgl mutations among mutator isolates was distinct and due to mutS. The mutator-associated periodic selection also resulted in mgl and fhuA polymorphism in the sweeping population. These examples of periodic selections maintained significant genotypic diversity even in a rapidly evolving culture, with no individual "winner clone" or genotype purging the population.

Adenosine Triphosphatases↗
PubMed1995

Evolution of the T-cell repertoire during the course of experimental immune-mediated demyelinating diseases.

Fig. 6 depicts a model for epitope spreading in T cell-mediated demyelination. The acute phase of disease is due to T cells specific for the initiating epitope, which can be either a determinant on the CNS target organ of the autoimmune response or a determinant on a persisting, CNS-tropic virus. The primary T cell response is responsible for the initial tissue damage by the production of proinflammatory Th1 cytokines which can affect myelination directly (Selmaj et al. 1991) and indirectly by their ability to recruit and activate macrophages to phagocytize myelin (Cammer et al. 1978). As a result of myelin damage and opening of the blood-brain-barrier during acute disease, T cells specific for endogenous epitopes on the same and/or different myelin proteins are primed and expand either in the periphery or locally in the CNS. These secondary T cells initiate an additional round of myelin destruction, leading to a clinical relapse by production of additional pro-inflammatory cytokines, similar to the bystander demyelination operative during acute disease. It will be of great interest to determine the relative contributions of local and systemic immune responses to these endogenous neuroepitopes. It is possible that local CNS presentation of endogenous neuroepitopes following acute CNS damage could be mediated by infiltrating inflammatory macrophages, activated microglial cells, endothelial cells and/or astrocytes. These tissue resident antigen presenting cells have been shown to upregulate expression of MHC class II (Sakai et al. 1986, Traugott & Lebon 1988), certain adhesion molecules (Cannella et al. 1990), and B7 costimulatory molecules (K. M. Nikcevich, J. A. Bluestone, and S. D. Miller, in preparation) in response to pro-inflammatory cytokines. The data on epitope spreading provided by the murine demyelinating disease models clearly illustrate the dynamic nature of the T cell repertoire during chronic inflammation in a specific target organ. The contribution of epitope spreading to chronic CNS demyelination could be considered to be a special case since tolerance to myelin epitopes would be expected to be inefficient due to their sequestration behind the blood-brain-barrier. However, the recent description of epitope spreading in response to pancreatic antigens in spontaneous diabetes in the NOD mouse may indicate that this phenomenon is operative in a variety of organ-specific experimental and spontaneous autoimmune diseases.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1995

Experimental tests of the roles of adaptation, chance, and history in evolution.

The contributions of adaptation, chance, and history to the evolution of fitness and cell size were measured in two separate experiments using bacteria. In both experiments, populations propagated in identical environments achieved similar fitnesses, regardless of prior history or subsequent chance events. In contrast, the evolution of cell size, a trait weakly correlated with fitness, was more strongly influenced by history and chance.

Adaptation, Physiological↗
PubMed2005

[Dynamic evolution of MMP-2 gene expression and its enzymatic activities in experimental liver fibrosis].

OBJECTIVES: To explore the dynamic changes and interactions between MMP-2 and TIMP-2 during experimental liver fibrosis. METHODS: Wistar rats were randomly allocated into a normal group and a model group. To induce liver fibrosis, rats were injected intraperitoneally with dimethylnitrosamine (DMN) three consecutive times in the first week, then two consecutive times per week, totally for 6 weeks. In the normal control group, rats were injected with saline by the same method as the model group. Animals were sacrificed 1, 4, 10, 17, 28, 42, 56 days after starting DMN injections. Conventional histological examinations of the livers were performed with hematoxylin and eosin and Masson staining. The fibrosis was classified into 0 to 4 stages. Hydroxyproline content was determined after liver tissues were hydrolyzed in HCl at 160 degree C for 2 hrs and then measured with spectrometry at 560 nm wavelength. mRNA levels of MMP-2 and TIMP-2 were determined by semi-quantitive RT-PCR. Gelatinase activity of MMP-2 was examined by zymography using gelatin substrate. RESULTS: In the model group the hepatic MMP-2 mRNA expression started to increase 10 days after DMN administration and remained at a much higher level than in the normal group throughout the study period, while TIMP-2 mRNA expression started to be lower than in the normal group 17 days after DMN administration and reached the lowest level on the 28th day. Then it rapidly rebounded and remained higher than that in the normal group from the 42nd day to the end of the study period. TIMP-2/MMP-2 began to be lower by several days than that of the normal group after DMN administration through the remaining study period. Zymography showed that the enzymatic activities of both latent MMP-2 and active MMP-2 were increased during the process of liver fibrosis. CONCLUSION: In liver fibrosis, MMP-2 expression increases, while TIMP-2 expression relatively decreases. The enzymatic activities of MMP-2 increase as the liver fibrosis develops.

Animals↗
PubMedDate not supplied

Experimental paracoccidioidomycosis in high and low antibody-producer mice. I.--Evolution of the disease, its correlation with the humoral immune response and the patterns of tissue lesions.

High (H) and low (L) responder mice selected for their capacity to produce antibody against flagellar antigens of Salmonellae sp. were infected i.p. with 10(6) L forms of Paracoccidioides brasiliensis, strain 18. In H mice, the mortality ratio was 50%; the splenic index was high at the onset of infection (1.0), decreasing to normal levels after 30 days (0.45), with antibody titres such as 4-5 log2. In L mice, the mortality was 87.5%, the splenic index was above 0.6 and the antibody titres after 30 days were below 2 log2. In L mice, granulomas containing a high number of fungi, epithelioid cells, macrophages and a few polymorphonuclear cells were found. In H mice, focal or diffuse infiltrate of mononuclear cells with few or even the absence of fungi was seen. The passive transfer of immune ascitic fluid to L mice induced a reduction in the number of granulomas and fungi in the lesions.

Animals↗
PubMedDate not supplied

Myocardial tissue troponins T and I. An immunohistochemical study in experimental models of myocardial ischemia.

BACKGROUND: Cardiac troponins T (cTnT) and I (cTnI) are proven diagnostic and risk stratification biomarkers in patients with acute coronary syndromes. To date, no immunohistochemical studies have been performed which allow visualization of the time course and pattern of myocardial troponin egress from the myocardium during the early evolution of ischemic injury in experimental systems. METHODS: We studied archival formalin-fixed, paraffin-embedded myocardium from 50 experimental animals (dogs, pigs and rats) that had undergone permanent coronary occlusion (n = 34) for 0.5-6 h or occlusion of 0.75-6 h followed by reperfusion (n = 16). Histologic sections that included ischemic and nonischemic myocardium were studied by immunohistochemistry with three different antibodies to human cTnI and one to cTnT, using a standard avidin-biotin-peroxidase system. RESULTS: All antibodies detected cTnT or cTnI in normal myocardium and its loss from necrotic myocardium, in some cases as early as 30 min after coronary occlusion, before histologic evidence of necrosis was present. Loss was nonuniform, being greater at the periphery of the infarcts then at their central regions. Usually, loss of cTnT appeared greater than loss of cTnI. With reperfusion, findings were similar to those after permanent occlusion, except that there was a greater contrast between loss at the periphery compared to the loss in the central region. Considerable residual staining persisted for hours after occlusion, indicating delayed release over time, concordant with sustained serum elevations in patients with acute myocardial infarction. No loss of staining was observed in nonnecrotic myocardium. CONCLUSIONS: Immunohistochemical staining using antibodies to human cTnT and cTnI can be used to visualize cardiac troponins and document their loss in histologic sections of myocardium in different animal species. Loss of cTnT and cTnI occurs very early following ischemic injury and may precede histologic evidence of necrosis, but does not occur in myocardium that is not necrotic. Immunohistochemical staining of hearts for cTnT and cTnI can assist in the often difficult recognition of myocardial necrosis at autopsy, in patients suspected of dying from acute myocardial ischemia.

Animals↗