Showing papers on "Animal mortality published in 1993"

Prognostic Factors in Canine Mammary Tumors: A Multivariate Study of 202 Consecutive Cases

Abstract: The prognostic variables of 223 consecutively sampled spontaneous mammary tumors from female dogs were studied. These variables included flow cytometric DNA analysis and cell proliferation measured as cells in S-phase rate evaluated from DNA histograms. The dogs were surgically treated, in most cases with unilateral mastectomy (all mammary glands), and 202 of the 223 dogs were studied temporally following surgery. Univariate analysis with correction for age indicated that the variables of lymph node metastasis, elevated S-phase rate, presence of a sarcoma, DNA aneuploidy, and ulceration and infiltrative growth into underlying tissue had a statistically significant negative influence on the survival rates of dogs with a diagnosed malignant tumor. Similar results were obtained from tests on all dogs, but tumor size and its relative hazard increased with increasing size of the tumors, regardless of whether total or disease-specific mortality was considered. Using multivariate-analysis conducted Cox's proportional hazards model, elevated S-phase rate, increased age, and presence of a sarcoma remained statistically significant risk factors. The prognostic value of DNA ploidy and lymph node status varied depending on choice of end point. The study of tumor growth pattern and tumor size provided no prognostic information in the multivariate analysis. Flow cytometric cell analysis, including S-phase rate and DNA ploidy, is of value in predicting the prognosis of canine mammary tumors and can be used as a new prognostic tool to improve the preoperative diagnostics of canine mammary tumors.

Resistance to Salmonella gallinarum, S. pullorum, and S. enteritidis in inbred lines of chickens

Abstract: Chickens of six inbred lines were inoculated intramuscularly with a range of doses of either Salmonella gallinarum, S. pullorum, or S. enteritidis, and levels of mortality were compared. For each serotype, large differences in mean lethal doses were observed for the different lines: Lines that had previously been shown to be resistant to S. typhimurium were also found to be resistant to S. gallinarum, S. pullorum, and S. enteritidis, and lines susceptible to S. typhimurium were also more susceptible to the other serotypes. These results suggest that there may be a general mechanism of resistance that may apply to all serotypes of Salmonella in chickens.

Reproduction and mortality of Finnish semi-domesticated reindeer in relation to density and management strategies

Abstract: We assessed the effects of management strategies during 1960-73 relative to strategies used during 1974-87 on the reproduction and mortality of 56 semi-domesticated herds of Finnish reindeer ( Rangifer tarandus tarandus ). During 1960-73, reindeer fed exclusively on natural forage growing on their range, and reindeer were harvested mostly as adults. These strategies were modified starting in 1974 to include supplemental feeding in the southern part of the Finnish reindeer range and calf harvesting throughout the range. We found significantly higher calf/female ratios, lower mortality, and less variation in both calf/female ratios and mortality during 1974-87 than during 1960-73. These changes occurred in spite of increased animal density. Coefficients of variation in calf/female ratio and mortality were negatively correlated with the prevalence of mature spruce forests, which are rich in arboreal lichens. Mean calf/female ratio and mortality rate depended on reindeer density only in the southern region during 1960-73. During 1974-87 these did not depend on density in any region. Within herds, calf/female ratio did not depend on density in most cases (98%), while in the later period the relationship between calf production and density was positive in some cases (25%). Mortality depended more often on density during the earlier (46% of herds) than the later (23% of herds) period. Calf harvesting influenced mortality more than supplemental feeding and virtually freed reindeer from density-dependent limitations. Supplemental feeding was used to compensate for deterioration of range resulting from overgrazing and logging of mature forests rich in arboreal lichens. Key words: reproduction, mortality, density dependence, reindeer, Rangifer tarandus , management, Finland

T lymphocyte responses in CVB3-induced murine myocarditis.

Abstract: Three monoclonal antibodies (mAB) to group A streptococcus M5 serotype (mAB 36.2.2, 49.8.9 and 54.2.8) cross-reactivity bind to various heart antigens (including myosin, tropomyosin and vimentin) and neutralize a myocarditic variant of coxsackievirus B-3 (Nancy) (CVB3). The existence of shared antigenic epitopes between the two distinct infectious agents and the heart implies that antigenic mimicry may form the foundation of the autoimmune response. Plaque purified variants of CVB3 were isolated with these streptococcal mAB. The wild-type virus (H3) and the virus variants made with mABs 36.2.2 (H3-36) and 54.2.8 (H3-54) caused significant myocarditis in Balb/c (H-2d) mice, but not in CBA (H-2k) animals. The virus variant made with mAB 49.8.9 (H3-49) caused myocarditis in CBA, but not in Balb/c mice. No significant differences in virus concentrations in the heart were detected with any of the virus variants. Cytolytic activity of mesenteric lymph node cells generally correlated to the severity of myocarditis in the infected animals. Using overlapping synthetic peptides of the CVB3 VP1 protein, mAB 49.8.9 was shown to bind preferentially peptides 6, 8, 11, and 12. T lymphocytes from H3 infected mice proliferated to VP1 peptides 1, 3, 9, 13, 14, and 21. To determine whether immunity to specific peptides could affect CVB3 pathogenicity, Balb/c mice were immunized with VP1 peptides 1, 3, 6, 13, 14 and 21 in complete Freund's adjuvant (CFA) then infected with 5 x 10(4) PFU CVB3 14 days later. Pre-immunization of animals with (a) peptide 1 resulted in a significant decrease in virus titers in the heart, (b) peptides 3, 13 and 21 increased animal mortality and lymphocyte mediated cytotoxicity to uninfected cardiocyte targets, and (c) peptides 3 and 21 resulted in significant increases in myocarditis compared to animals given virus without pre-immunization.

Mathematical models of marrow cell kinetics: differential effects of protracted irradiations on stromal and stem cells in mice.

Abstract: It is known that hematopoiesis is supported by bone-marrow stem cells, but those cells must seed and grow on a stromal microenvironment. Typically, studies have shown that a surviving fraction of about 30 hematopoietic stem cells (HSCs) (i.e., about 0.04%) correspond to the LD 50 , although other studies have shown that marrow can repopulate from a single viable cell under strong regiments of antibiotics and infusions of irradiated blood elements. Purpose: This paper describes comparisons between our results (from maximum-likelihood estimation techniques for cellular damage, repair, and compensatory repopulation) and published experimental data on marrow stromal cells. Methods and Materials: After biophysical consideration of the rate constants that were derived by maximizing the likelihood function (a consideration necessary to extend the model to cell populations not indicated by the model as "critical" for recovery), the rate constants for cellular damage to stem cells are fitted to experimental data. Rate constants for repair and proliferation of stem cells are assigned based on published data on repair/proliferation halftimes, and these assignments affect the evaluation of the rate constants for cellular damage. From the two models, that is one for "critical" cells (having radiosensitive and repopulation characteristics similar to stromal cells) and another for stem cells, effects on two cell populations of different radiosensitivities and repopulation rates can be demonstrated for complex schedules of protracted irradiations which could reduce either cell population below a critical need for marrow repopulation. Results: Our analysis of animal mortality data has indicated that recovery of an animal from potentially lethal irradiation is dominantly regulated by cells with survival and repopulation characteristics similar to those of stroma cells. Conclusion: In contrast to the surviving fraction of hematopoietic stem cells, it appears that the probability of an animal's recovery is high if the "critical" population of cells is above 1% (our "best" maximum likelihood estimate, from mouse data, with the corresponding lower confidence bound at about 0.2%). Of course, a few stem cells—perhaps only one—must maintain a potential for repopulation of blood and marrow.

Halomethane-chlordecone (CD) interactive hepatotoxicity--current concepts on the mechanism.

Abstract: Why is a low dose of toxic chemical nontoxic? What makes a larger dose of the same chemical toxic? Extensive work done to understand the mechanism of halomethane hepatotoxicity and its potentiation by chlorinated insecticide, chlordecone has resulted in the understanding of these basic tenets of toxicology. Studies suggest that ordinarily a small dose of halomethane causes limited liver injury which is accompanied by stimulated tissue repair enabling complete recovery from injury before manifestation. A large dose of halomethane becomes toxic due to suppressed tissue repair, which permits injury to progress in an unchecked fashion. Exposure to very low levels of chlordecone results in highly exaggerated toxicity of ordinarily nontoxic doses of halomethane because of suppressed hepatocellular regeneration and restoration, permitting the progression of liver injury ultimately resulting in liver failure and animal mortality. This concept is further supported by the observation that, while exposure to even high levels of phenobarbital and subsequent low nontoxic doses of halomethane results in greater level of initial liver injury, tissue repair is not completely suppressed; it is slightly postponed by 24 hr, but then much higher rate of tissue repair ensures and consequently enables the animals to completely recover from liver injury and survive. Thus, whether initiation of tissue repair processes occurs or not is the critical determinant in the ultimate manifestation of hepatotoxicity and its end result of either animal death or recovery and survival. Currently understood 'Mechanisms of toxicity' adequately explain only how toxic injury begins. These mechanisms do not permit us to predict the ultimate outcome of toxicity.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of a polyunsaturated fatty acid-enriched diet on the state of the Ca-transporting system of the sarcoplasmic reticulum in the myocardium

Abstract: A long-term diet enriched with polyunsaturated fatty acids (PUFA), mainly docosahexaenoic and eicosapentaenoic acids, drastically reduces the occurrence and duration of arrhythmias during acute ischemia and reperfusion, restricts disturbances of the electrical stability of the heart, and lowers the probability of fibrillation in acute ischemia, reperfusion [4,8,9], infarction, and postinfarction cardiosclerosis [2,3,7], this resulting in a reduction of animal mortality for experimental myocardial infarction [2]. The mechanisms of such a cardioprotective effect are still to be clarified. Therefore, the aim of the present study was, first, to investigate the state of the Ca-transporting system in the sarcoplasmic reticulum (SPR) of the heart, which is responsible for the contractile activity of the cell, and, second, to study lipid peroxidation (LPO) in the myocardium under conditions of a PUFA-enriched diet.