Biomedical subjects

Anna M Jelaso

Publications and source records attributed to Anna M Jelaso.

6 recordsLinked to original sources

PubMed2005

NGF and IL-1beta are co-localized in the developing nervous system of the frog, Xenopus laevis.

NGF, a neurotrophic factor best known for its role in promoting cell survival, regulates many neurodevelopmental processes, including synaptic plasticity, neurite outgrowth and programmed cell death. Although there is a large amount of data regarding NGF in the developing nervous system of many species, there is little known about its regulation and role in the frog, Xenopus laevis. In this report, immunocytochemistry was used to characterize NGF protein expression in developing tadpoles. Protein expression was analyzed in tadpoles from stage 44/45 through stage 50, a period of development characterized by extensive neurite outgrowth, neuronal differentiation and an initial period of programmed cell death. Similar to other species, NGF was expressed in sensory cells and tissues, including the inner ear, eye, olfactory system, lateral line organs, papillae in the oral cavity, and gills tufts. In addition, NGF was expressed in specific cells in the central nervous system, cranial and dorsal root ganglia, spinal sensory and motoneurons, and muscle tissues in the tail and body cavity. In the mammalian nervous system, the cytokine, interleukin-1beta (IL-1beta) induces expression of NGF. In this report, double-label immunocytochemistry was used to determine the relationship between NGF and IL-1beta. Results showed most cell types and/or tissues that expressed NGF also expressed IL-1beta. However, NGF was typically associated with cellular and nuclear membranes, whereas IL-1beta appeared in the cytoplasm and nucleolus. The nuclear localization of IL-1beta supports the idea that it regulates gene transcription in the frog. The appearance of NGF and IL-1beta in the same cells suggests they may interact to influence neural development.

Animals↗

PubMed2005

Dietary exposure to Aroclor 1254 alters gene expression in Xenopus laevis frogs.

Polychlorinated biphenyls (PCBs) are persistent environmental pollutants that contribute to worldwide health problems. Despite data associating PCBs with adverse health effects, decisions to clean up contaminated sites remain controversial. Cleanup decisions are typically based on risk assessment methods that are not sensitive enough to detect subtle changes in health. We have recently shown that gene expression signatures can serve as sensitive molecular biomarkers of exposure and related health effects. Our initial studies were carried out with developing Xenopus laevis tadpoles that were exposed to the PCB mixture Aroclor 1254 (A1254) for 2 days. A1254 was dissolved in dimethyl sulfoxide and added to the aquarium water for rapid loading of PCBs into the tadpole tissue. These studies showed that increases in the expression of specific genes occurred independent of adverse health effects, and decreases in specific genes correlated with the appearance of observable health effects, including decreased survival and gross morphological and behavioral abnormalities. In this report, we extend our previous work to test the use of gene expression signatures as biomarkers in frogs exposed to PCBs through the diet from early tadpole stages through metamorphosis. This work showed that chronic low-dose exposure to A1254 (24 ppm) in food produced tissue levels of 17 ppm and increased gene expression of nerve growth factor and proopiomelanocortin independent of adverse health effects. Exposure to higher doses of A1254 (200 ppm) produced tissue levels of 80 ppm and increased expression of p450 1A1, also, independent of adverse health effects. This work provides further evidence for the use of gene expression changes as biomarkers of exposure to PCBs.

Actins↗

PubMed2004

Connexin 43 expression in glial cells of developing rhombomeres of Xenopus laevis.

Connexin 43 is a gap junctional protein found predominantly in astrocytes. In the mammalian nervous system, it appears to play an organizational role during neural development. In the current study, conducted on the frog, Xenopus laevis, we found that connexin 43 occurs in glial cells during development of rhombomeres and that its expression is spatially and temporally regulated. We used neural (2G9) and cell proliferation (BrdU) markers to identify the overall organization of Xenopus rhombomeres and then tracked expression of connexin 43 and glial fibrillary acidic protein, an intermediate filament protein known to mark glia during rhombomeric development. 2G9 was expressed in rhombomeric centers (ventricular concavities) and outlying neuropil regions, whereas BrdU-labeled cells marked boundary regions (ventricular convexities), as early as stage 35/36. These labeling patterns persisted through premetamorphic stages of hindbrain development. At stage 47, 2G9-labeled profiles were highlighted by the presence of connexin 43, and at stage 49/50, connexin 43-labeled profiles, i.e., rhombomeric centers and neuropil, as well as rhombomeric boundaries, not labeled by connexin 43, became immunoreactive to glial fibrillary acidic protein. Cells of rhombomeric center regions and their processes in the outlying neuropil co-expressed glial fibrillary acidic protein and connexin 43 at a time that is characterized by the emergence of hindbrain auditory neural circuitry. Glial fibrillary acidic protein positive glial cells that appeared at rhombomeric boundaries never expressed connexin 43, but rather appeared to physically bisect ventricular convexities into adjacent rhombomeric regions. Thus, glial cells that express connexin 43 in developing rhombomeric centers may be similar to radial glia, assisting in formation of neural circuitry, while glial cells that do not express connexin 43, situated at rhombomeric boundaries, may be involved in demarcating adjacent rhombomeres.

Animals↗

PubMed2003

Gene expression patterns predict exposure to PCBs in developing Xenopus laevis tadpoles.

Polychlorinated biphenyls (PCBs) are ubiquitous environmental contaminants that pose global ecological and human health problems. Although it is well established that PCBs are associated with a variety of adverse health effects in wildlife and in humans, it is often difficult to determine direct cause-and-effect relationships between exposure and specific health outcomes. In this study, gene expression signatures were used to relate exposure to PCBs with altered physiological responses and/or specific health effects. Real-time PCR was used to measure gene expression levels for 10 genes in Xenopus laevis tadpoles (18 days postfertilization, PF) after acute exposure (2 days) to the PCB mixture Aroclor 1254. Specific gene expression signatures correlated with exposure and were predictive of adverse health effects. Exposure to low levels of Aroclor 1254 (5-50 ppb) significantly increased expression of six genes, independent of any health effects; exposure to midlevel concentrations (300-400 ppb) significantly decreased expression levels of two genes, NGF and beta-actin, prior to the onset of observable health effects; exposure to higher doses (500-700 ppb) significantly decreased NGF and beta-actin expression concomitant with the appearance of gross morphological abnormalities, behavioral deficits, and a statistically significant decrease in survival. This study expands upon our previous work that demonstrated an age-dependent susceptibility to Aroclor 1254 in Xenopus laevis tadpoles and that defined specific gene expression signatures as useful bioindicators of exposure and as predictors of overt or impending health effects.

Animals↗

PubMed2003

Exposure to the polychlorinated biphenyl mixture Aroclor 1254 alters melanocyte and tail muscle morphology in developing Xenopus laevis tadpoles.

Polychlorinated biphenyls (PCBs) are ubiquitous environmental contaminants that have damaging effects on both ecosystem and human health. Numerous studies have shown that exposure to PCBs can alter growth and development of aquatic organisms, including frogs. In this report, developing Xenopus laevis tadpoles were exposed to the PCB mixture Aroclor 1254. Tadpoles were exposed from 5 through 9 d postfertilization to either 0, 1, 10, 50, or 100 ppm Aroclor 1254. Exposure to an acute, high concentration of Aroclor 1254 (10, 50, and 100 ppm) caused statistically significant reductions in survival and body size. In addition, tadpoles exposed to these higher concentrations showed histological abnormalities, including aberrant tail tip, myotomal, and melanocyte morphologies. Described adverse health effects associated with PCB exposure of developing frogs will serve as useful health endpoints in ongoing and future molecular-based studies that correlate health effects with changes in gene expression.

Animals↗

PubMed2002

Aroclor 1254 alters morphology, survival, and gene expression in Xenopus laevis tadpoles.

PCBs are persistent environmental contaminants that cause a variety of adverse health effects in wildlife and humans. This article describes the use of signature gene expression patterns that link increased PCB exposure with progressive, adverse biological effects. Developing Xenopus laevis tadpoles of two age classes were exposed to the PCB mixture Aroclor 1254 for 2 days. Real-time PCR was used to quantitate mRNA expression for 11 physiologically relevant, potential bioindicator genes. Younger tadpoles (5 days postfertilization) were resistant to Aroclor 1254 and showed few changes in gross morphology, swimming behavior, survival, or gene expression. Older tadpoles (11 days postfertilization) were more susceptible to Aroclor 1254. Exposure to 25 and 50 ppm Aroclor 1254 caused alterations in gross morphology and swimming behavior and statistically significant decreases in survival. These tadpoles showed statistically significant decreases in gene expression for 9 out of the 11 genes measured. Tadpoles exposed to 10 ppm showed incipient health changes but had gene expression profiles similar to the tadpoles treated with higher doses of Aroclor 1254. Tadpoles exposed to 1 ppm did not exhibit any observable adverse health effects, yet statistically significant decreases in gene expression occurred in these tadpoles (4 out of 11 genes). After prolonged exposure, tadpoles exposed to 1 and 10 ppm Aroclor 1254 exhibited health effects similar to those exposed to higher concentrations. Therefore, changes in expression of specific genes may serve not only as molecular bioindicators of Aroclor 1254 exposure but also as predictors of impending adverse health effects.

Animals↗