BACKGROUND: Epidemiologic studies have demonstrated that individuals who eat more fruits and vegetables and/or have high levels of serum β-carotene have a lower risk of cancer, especially lung ...cancer. However, recent human intervention studies using β-carotene supplements have shown an increase in the risk of lung cancer among smokers and asbestos workers. In this study, we used an animal model system to evaluate the hazard associated with a combination of high-dose β-carotene supplementation and tobacco smoking. METHODS: Ferrets were given a β-carotene supplement, exposed to cigarette smoke, or both for 6 months. Cell proliferation and squamous metaplasia in lung tissue were assessed by examination of proliferating-cell nuclear antigen expression and histopathologic examination, respectively. β-Carotene and retinoid concentrations in lung tissue and plasma samples were analyzed by high-performance liquid chromatography. Expression of genes for retinoic acid receptors (RARs) and activator protein-1 (encoded by the c-Jun and c-Fos genes) in lung tissue specimens was examined by western blotting. RESULTS: A strong proliferative response in lung tissue and squamous metaplasia was observed in all β-carotene-supplemented animals, and this response was enhanced by exposure to tobacco smoke. When compared with control groups, all three treatment groups had statistically significantly lower concentrations of retinoic acid in lung tissue, and they exhibited 18%-73% reductions in RARβ gene expression; however, RARα and RARγ gene expression was not reduced. Ferrets given a β-carotene supplement and exposed to tobacco smoke had threefold to fourfold elevated expression of the c-Jun and c-Fos genes. CONCLUSIONS: Diminished retinoid signaling, resulting from the suppression of RARβ gene expression and overexpression of activator protein-1, could be a mechanism to enhance lung tumorigenesis after high-dose β-carotene supplementation and exposure to tobacco smoke.
Decline in immune response is a well-documented age-associated biological change. Protein-bound polysaccharides (PSP) are biological response modifiers and have been shown to have immunoenhancing and ...antitumor effects. This study was conducted to examine the effect of dietary supplementation with PSP-containing extract derived from mycelia of Coriolus versicolor on in vitro and in vivo indices of immune function of young and old mice. Young (5 mo) and old (23 mo) C57BL/6NIA mice were fed purified diets containing 0, 0.1, 0.5 or 1.0% PSP for 1 mo at which time indices of immune function were measured. PSP supplementation had no significant effect on mitogenic response to concanavalin A (Con A), phytohemagglutinin (PHA) or lipopolysaccharide (LPS), or on production of interleukin (IL)-1, IL-2, IL- 4 and prostaglandin E2PGE2). Of the in vivo indices of immune function tested, old mice fed 1.0% PSP had significantly higher delayed-type hypersensitivity (DTH) response than those fed 0% PSP. No significant effect of PSP was observed on the DTH response of young mice. The antibody response to sheep red blood cells was not significantly influenced by PSP in young or old mice. These results suggest that PSP-containing extract from mycelia of Coriolus versicolor might have a modest immunoenhancing effect in aged mice, but not in young mice.
alpha5-deficient mice die early in embryogenesis (). To study the functions of alpha5 integrin later in mouse embryogenesis and during adult life we generated alpha5 -/-;+/+ chimeric mice. These ...animals contain alpha5-negative and positive cells randomly distributed. Analysis of the chimerism by glucose- 6-phosphate isomerase (GPI) assay revealed that alpha5 -/- cells contributed to all the tissues analyzed. High contributions were observed in the skeletal muscle. The perinatal survival of the mutant chimeras was lower than for the controls, however the subsequent life span of the survivors was only slightly reduced compared with controls (). Histological analysis of alpha5 -/-;+/+ mice from late embryogenesis to adult life revealed an alteration in the skeletal muscle structure resembling a typical muscle dystrophy. Giant fibers, increased numbers of nuclei per fiber with altered position and size, vacuoli and signs of muscle degeneration-regeneration were observed in head, thorax and limb muscles. Electron microscopy showed an increase in the number of mitochondria in some muscle fibers of the mutant mice. Increased apoptosis and immunoreactivity for tenascin-C were observed in mutant muscle fibers. All the alterations were already visible at late stages of embryogenesis. The number of altered muscle fibers varied in different animals and muscles and was often increased in high percentage chimeric animals. Differentiation of alpha5 -/- ES cells or myoblasts showed that in vitro differentiation into myotubes was achieved normally. However proper adhesion and survival of myoblasts on fibronectin was impaired. Our data suggest that a novel form of muscle dystrophy in mice is alpha5-integrin-dependent.
The motor neuron degeneration (
mnd) mouse has been documented to accumulate proteolipid and thus is a model of neuronal ceroid lipofuscinosis Dunn, W.A., Raizada, M.K., Vogt, E.S. and Brown, E.A., ...Int. J. Dev. Neurosci., 12 (1994) 185–196; Faust, J.R., Rodman, J.S., Daniel, P.F., Dice, J.F. and Bronson, R.T., J. Biol. Chem., 269 (1994) 10150–10155. While accumulation of proteolipid in the hippocampus of chimeric mice composed of
mnd and +/+ cells was found to be proportional to the contribution of
mnd in the brain, accumulation within individual cells was the same for cells from chimeric and age-matched
mnd mice. Bone marrow transplantation was used to altering the milieu of circulating factors to determine whether this might modify the disease phenotype in
mnd mice. Transplantation of bone marrow in neonatal or young mice did not reduce the age-associated accumulation of proteolipid within hippocampal neurons. The results of these experiments indicate that
mnd results in a cell autonomous defect.
The effects on rat cranial nerve growth of removing various amounts of extraocular muscle was studied using morphometric techniques. Growth in the third cranial nerves was found to be severely ...retarded when most of the muscle tissue was removed. By contrast, removal of the eye alone, leaving extraocular muscles relatively intact, was found to have little or no effect on the subsequent growth of third and sixth cranial nerve fibers and of extraocular muscle fibers. This conclusion could be drawn only through the application of statistical methods which take into account several generally unrecognized facts: frequency distributions of axon circumference and myelin sheath thickness are highly variable from nerve to nerve even in normal rats, which often have more large fibers in left than in right nerves. The bimodal nature of peripheral nerve fiber distributions precludes the use of such parametric tests as the commonly and inappropriately used t-test, but a non-parametric test such as the Kolmogorov-Smirnov test, extensively used in these studies, is inadequate for data comprising several sets of distributions to be compared. The application of the analysis of variance to some of the data and the merits of the procedure are discussed.
Thrombotic events are life-threatening complications of human hemolytic anemias such as paroxysmal nocturnal hemoglobinuria, sickle cell disease, and thalassemia. It is not clear whether these events ...are solely influenced by aberrant hematopoietic cells or also involve aberrant nonhematopoietic cells. Spherocytosis mutant (Spna1(sph)/Spna1(sph); for simplicity referred to as sph/sph) mice develop a severe hemolytic anemia postnatally due to deficiencies in -spectrin in erythroid and other as yet incompletely defined nonerythroid tissues. Thrombotic lesions occur in all adult sph/sph mice, thus providing a hematopoietically stressed model in which to assess putative causes of thrombus formation. To determine whether hematopoietic cells from sph/sph mice are sufficient to initiate thrombi, bone marrow from sph/sph or +/+ mice was transplanted into mice with no hemolytic anemia. One set of recipients was lethally irradiated; the other set was genetically stem cell deficient. All mice implanted with sph/sph marrow, but not +/+ marrow, developed severe anemia and histopathology typical of sph/sph mice. Histological analyses of marrow recipients showed that thrombi were present in the recipients of sph/sph marrow, but not +/+ marrow. The results indicate that the -spectrin-deficient hematopoietic cells of sph/sph mice are the primary causative agents of the thrombotic events.
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