Biomedical subjects

C N Smith

Publications and source records attributed to C N Smith.

At least 19 recordsLinked to original sources

PubMed2005

The relative cytotoxicity of personal care preservative systems in Balb/C 3T3 clone A31 embryonic mouse cells and the effect of selected preservative systems upon the toxicity of a standard rinse-off formulation.

Biocide chemicals are commonly used as preservatives for cosmetic and personal care products and the conditions for their use are stipulated in Annex VI of the Cosmetics Directive. In these studies the cytotoxicity (EC50 and EC90) of a range of preservatives including the isothiazolinone family, formaldehyde donors, parabens mixtures and organic acids have been established in the Balb/C 3T3 clone A31 fibroblast cell-line following a 1h exposure. Cell viability was established using the neutral red uptake assay 24h after exposure. The potency of the preservatives spanned several orders of magnitude from the isothiazolinones (EC50<10ppm) to the organic acids (EC50>10,000ppm). Although these values are directly proportional to the anti-microbial efficacy of the actives, they do not reflect the addition levels commonly used to preserve formulations, which are intended to provide prolonged protection against a wide spectrum of spoilage organisms. In a further study, the cytotoxic profile of an unpreserved standard rinse-off body wash formulation was assessed. Two concentrations of the formulation were selected: 0.1% v/v (EC98) and 0.15% v/v (EC82) to study the effects of selected preservative chemicals at recommended addition levels upon the cytotoxicity of the formulation. At 0.1%, only preservation with benzoate/sorbate at the highest addition level increased the toxicity, whereas at 0.15%, preservation with 2-bromo-2-nitro-propane-1,3-diol increased the cytotoxicity of the formulation. No other preservatives, including isothiazolinones and formaldehyde donors affected the basal cytotoxicity of the formulation. Theses studies have provided a standardised assessment of the cytotoxicity of cosmetic preservatives and demonstrated that preservation of a rinse-off formulation at recommended addition levels is unlikely to affect the cytotoxic profile.

Animals↗

PubMed2003

MEAD (part I)--a mathematical model of the long-term dispersion of radioactivity in shelf sea environments.

A mathematical model (MEAD) that simulates the transport of radioactivity in shelf-sea environments is presented. In the model it is assumed that the radioactivity can be present in three phases and transport both within and between the phases is captured. The set-up of the model for the Irish Sea is described and results from a simple discharge scenario are presented for (137)Cs and (239)Pu. From these results it appears that MEAD provides a good representation of the transport of radionuclides in the Irish Sea.

Forecasting↗

PubMed2003

MEAD (part II)-Predictions of radioactivity concentrations in the Irish Sea.

The predictions from MEAD, a model that simulates the transport of radionuclides in the marine environment, are presented for the Irish Sea. MEAD predictions for (137)Cs and Pu(alpha) are presented following discharges from BNFL Sellafield and the predictions compared to measured data from near the discharge location and further a field in the Irish Sea. The model performs well in most circumstances given the uncertainties involved in both modelling and data collection although some inconsistencies in the predictions are found. MEAD is also compared to other models of radionuclide transport in the Irish Sea.

Cesium Radioisotopes↗

PubMed2001

Stimulation of C32 and G361 melanoma cells using oleoyl acetyl glycerol and its effect on sulphur mustard cytotoxicity.

Epidermal melanocytes have a higher sensitivity to sulphur mustard (HD) compared with other skin cell types. This may be due to the enzymatic production of melanin precursors exerting an additional cytotoxic effect following HD depletion of the cellular protectant, GSH. Stimulation of the protein kinase C pathway in melanocytes is known to increase melanin production in melanocytes and melanoma cell lines. In order to investigate the role of pigment synthesis in HD toxicology, cultures of an unpigmented melanoma cell line (C32) and of a pigmented melanoma line (G361) were treated with the potent diacyl glycerol analogue, oleoyl acetyl glycerol (OAG), in order to determine if protein kinase C-mediated increases in pigment production could increase sensitivity to subsequent HD exposure. Stimulation of C32 cells with OAG exerted a significant protective effect against the cytotoxic effects of HD. However, this was not due to increased melanin synthesis because this cell line cannot synthesize melanin pigments. The protective action observed is postulated to be due to modulation of protein kinase C activity. In contrast, stimulation of G361 melanoma cells with OAG resulted in an increased level of cytotoxicity upon subsequent exposure to HD. Protein kinase C controls several cellular pathways including checkpoints in the cell cycle, stalling the cell in G and promoting transition through the G2/M boundary. Given the genotoxic properties of HD, these two points in the cell cycle are important in determining the overall cytotoxic effect of HD. Control of the cell cycle by protein kinase C modulation and manipulation of melanin synthetic pathways may have therapeutic benefits.

Cell Division↗

PubMed2001

An in vitro comparison of the cytotoxicity of sulphur mustard in melanoma and keratinocyte cell lines.

In vivo, the pigment producing melanocytes are the most susceptible cell type to sulphur mustard (HD) in the epidermal region of pig skin. It has been postulated that this is due to the melanogenic pathway producing a cytotoxic, free radical cascade within the melanocyte following HD poisoning, leading to cellular necrosis and subsequent inflammation. To test this hypothesis, the cytotoxicity of HD was tested in three human melanoma cell lines and compared to SVK-14 human keratinocytes, a cell line in which the response to HD has already been characterised. The results of both neutral red (NR) and gentian violet (GV) assays showed that all three melanoma cell lines, particularly the G361 line, were less susceptible to the toxic effects of HD than the SVK-14 keratinocyte cell line. Preliminary data indicate that the expression level of the DNA repair cofactor, proliferating cell nuclear antigen (PCNA), is up to 13-fold greater in the HD-resistant cell line G361 compared to the HD-sensitive SVK-14 cell line. The data point to the importance of DNA lesions in HD-induced cell death and to potential mechanisms associated with increased resistance to HD. A dose-response study was carried out to confirm the differences between these two cell lines. It was found that the G361 line is 5-fold more resistant to HD and 5.5-fold more resistant to the cytotoxic effects of H2O2 than the SVK-14 line, as determined by the MTT assay. The results suggest that differences in the relative efficiency of DNA repair processes may underlie these responses. Whilst the study indicates the limitations of using melanoma cell lines (in vitro) to model melanocyte responses to HD, analysis of the biochemical basis of the observed differences in sensitivity to HD could assist in the identification of novel therapeutic strategies against HD.

Cell Count↗

PubMed2000

Reconstructing historical radionuclide concentrations along the east coast of Ireland using a compartmental model.

A mathematical model is presented that simulates the annually averaged transport of radionuclides, originating from the BNFL reprocessing plant at Sellafield, throughout the Irish Sea. The model, CUMBRIA77, represents the processes of radionuclide transport and dispersion in the marine environment and allows predictions of radionuclide concentration in various environmental media, including biota, to be made throughout the whole of the Irish Sea. In this paper we describe the use of the model to reconstruct the historical activity concentrations of 137Cs and 239+240Pu in a variety of environmental media in the western Irish Sea and along the Irish east coast back to 1950. This reconstruction exercise is of interest because only limited measurements of 137Cs and 239+240Pu activity are available prior to the 1980s. The predictions were compared to the available measured data to validate their accuracy. The results of the reconstruction indicate that activity concentrations of 137Cs in the western Irish Sea follow a similar, though slightly delayed and smoothed, profile to the discharges from the Sellafield site, with concentrations at the time of peak discharge (the mid-1970s) being around an order of magnitude higher than those measured in the 1980s and 1990s. By contrast, the concentrations of 239+240Pu at the time of peak discharges were similar to those presently measured. These differences reflect the distinct marine chemistries of the two nuclides, in particular the higher propensity of plutonium to bind to sediments leading to extended transport times. Despite these differences in behaviour the doses to Irish seafood consumers from 137Cs remain significantly higher than those from 239+240Pu.

Animals↗

PubMed2000

A sensitive endocannabinoid assay. The simultaneous analysis of N-acylethanolamines and 2-monoacylglycerols.

Mammalian cells produce both N-arachidonoylethanolamine (20:4n-6 NAE, anandamide) and 2-arachidonoylglycerol (2-AG), lipid signaling molecules that activate cannabinoid receptors. Because both agonists occur in the presence of receptor-inactive congeners, we have developed a sensitive method for the simultaneous assay of N-acylethanolamines (NAEs) and 2-monoacylglycerols (2-MAG). These lipid classes are isolated from total lipids by solid phase extraction and converted to tert-butyldimethylsilyl (tBDMS) derivatives in the presence of deuterated analogs. The tBDMS derivatives are analyzed by gas chromatography/mass spectrometry using selected ion monitoring programs specific for NAE and 2-MAG. Individual NAEs and 2-MAGs can be quantified in the nanogram and subnanogram range. The NAE and 2-MAG compositions of rat organs and cultured JB6 cells are reported.

Animals↗

PubMed1999

Functional MRI of human Pavlovian fear conditioning: patterns of activation as a function of learning.

fMRI was used to study human brain activity during Pavlovian fear conditioning. Subjects were exposed to lights that either signaled painful electrical stimulation (CS+), or that did not serve as a warning signal (CS-). Unique patterns of activation developed within anterior cingulate and visual cortices as learning progressed. Training with the CS+ increased active tissue volume and shifted the timing of peak fMRI signal toward CS onset within the anterior cingulate. Within the visual cortex, active tissue volume increased with repeated CS+ presentations, while cross-correlation between the functional time course and CS- presentations decreased. This study demonstrates plasticity of anterior cingulate and visual cortices as a function of learning, and implicates these regions as components of a functional circuit activated in human fear conditioning.

Adult↗

PubMed1999

A field study to compare performance of stainless steel research monitoring wells with existing on-farm drinking water wells in measuring pesticide and nitrate concentrations.

Existing drinking water wells are widely used for the collection of ground water samples to evaluate chemical contamination. A well comparison study was conducted to compare pesticide and nitrate-N data from specially designed stainless steel research monitoring wells with data from nearby existing on-farm drinking water wells. Results could help to determine whether adequate information concerning ground water contamination can be obtained from existing drinking water wells for use in making pollutant control decisions. The study was conducted during 1993-1994 in the Little Coharie Watershed, a 158 square mile area located in the coastal plain of eastern North Carolina. Statistical analysis indicated that research monitoring wells provided a greater probability of detecting pesticides in ground water than existing on-farm wells. Atrazine was the most frequently detected pesticide found in all wells, followed in order by fluometuron, carbofuran, metolachlor, alachlor, carbaryl, butylate, chlorothalonil, linuron and simazine. Ninety-seven percent of all wells had observed concentrations of nitrate-N, ranging from 0.1 to 30.1 mg/L. There was not a significant difference between research wells and existing wells for monitoring nitrate-N. Based on results of this study, existing drinking water wells can be used for monitoring nitrate; however, specialized stainless steel monitoring wells should be used for monitoring pesticides in ground water.

Databases, Factual↗

PubMed1997

Presence of methenamine/glutathione mixtures reduces the cytotoxic effect of sulphur mustard on cultured SVK-14 human keratinocytes in vitro.

The basal epidermal keratinocytes of the skin are a main target for the vesicating agent, sulphur mustard (SM). A human keratinocyte cell line (SVK-14) has been used to model the effects of SM on the basal epidermal keratinocytes and subsequently to test the efficacy of potential prophylactic compounds in reducing the SM-induced cytotoxicity. The cultures were pretreated with mixtures of methenamine (HMT) and glutathione (GSH) for 1 h prior to exposure to 10 microM SM. The viability of the cultures was then assessed using neutral red (NR) dye uptake and crystal violet DNA staining assays at 24 h intervals post exposure. Pretreatment led to a 1.9 fold increase in culture viability (NR assay) compared to those exposed to SM only, and a 2.3 fold increase in cell number (crystal violet assay). Photomicrography showed that pretreatment preserved the morphology of the cultured cells and maintained their mitotic activity whereas those exposed to SM only show non-proliterative cultures with extensive cellular damage. The results of this study show that it is possible to protect mitotically active cultures from the effects of SM, however the measures must be in place prior to SM exposure.

Cell Count↗

PubMed1996

Identification of a minimal sequence of the mouse pro-alpha 1(I) collagen promoter that confers high-level osteoblast expression in transgenic mice and that binds a protein selectively present in osteoblasts.

Based on our previous transgenic mice results, which strongly suggested that separate cell-specific cis-acting elements of the mouse pro-alpha 1(I) collagen promoter control the activity of the gene in different type I collagen-producing cells, we attempted to delineate a short segment in this promoter that could direct high-level expression selectively in osteoblasts. By generating transgenic mice harboring various fragments of the promoter, we identified a 117-bp segment (-1656 to -1540) that is a minimal sequence able to confer high-level expression of a lacZ reporter gene selectively in osteoblasts when cloned upstream of the proximal 220-bp pro-alpha 1(I) promoter. This 220-bp promoter by itself was inactive in transgenic mice and unable to direct osteoblast-specific expression. The 117-bp enhancer segment contained two sequences that appeared to have different functions. The A sequence (-1656 to -1628) was required to obtain expression of the lacZ gene in osteoblasts, whereas the C sequence (-1575 to -1540) was essential to obtain consistent and high-level expression of the lacZ gene in osteoblasts. Gel shift assays showed that the A sequence bound a nuclear protein present only in osteoblastic cells. A mutation in the A segment that abolished the binding of this osteoblast-specific protein also abolished lacZ expression in osteoblasts of transgenic mice.

Animals↗

PubMed1996

An 18-base-pair sequence in the mouse proalpha1(II) collagen gene is sufficient for expression in cartilage and binds nuclear proteins that are selectively expressed in chondrocytes.

The molecular mechanisms by which mesenchymal cells differentiate into chondrocytes are still poorly understood. We have used the gene for a chondrocyte marker, the proalpha1(II) collagen gene (Col2a1), as a model to delineate a minimal sequence needed for chondrocyte expression and identify chondrocyte-specific proteins binding to this sequence. We previously localized a cartilage-specific enhancer to 156 bp of the mouse Col2a1 intron 1. We show here that four copies of a 48-bp subsegment strongly increased promoter activity in transiently transfected rat chondrosarcoma (RCS) cells and mouse primary chondrocytes but not in 10T1/2 fibroblasts. They also directed cartilage specificity in transgenic mouse embryos. These 48 bp include two 11-bp inverted repeats with only one mismatch. Tandem copies of an 18-bp element containing the 3' repeat strongly enhanced promoter activity in RCS cells and chondrocytes but not in fibroblasts. Transgenic mice harboring 12 copies of this 18-mer expressed luciferase in ribs and vertebrae and in isolated chondrocytes but not in noncartilaginous tissues except skin and brain. In gel retardation assays, an RCS cell-specific protein and another closely related protein expressed only in RCS cells and primary chondrocytes bound to a 10-bp sequence within the 18-mer. Mutations in these 10 bp abolished activity of the multimerized 18-bp enhancer, and deletion of these 10 bp abolished enhancer activity of 465- and 231-bp intron 1 segments. This sequence contains a low-affinity binding site for POU domain proteins, and competition experiments with a high-affinity POU domain binding site strongly suggested that the chondrocyte proteins belong to this family. Together, our results indicate that an 18-bp sequence in Col2a1 intron 1 controls chondrocyte expression and suggest that RCS cells and chondrocytes contain specific POU domain proteins involved in enhancer activity.

Animals↗

PubMed1995

A 182 bp fragment of the mouse pro alpha 1(II) collagen gene is sufficient to direct chondrocyte expression in transgenic mice.

Type II collagen is a major chondrocyte-specific component of the cartilage extracellular matrix and it represents a typical differentiation marker of mature chondrocytes. In order to delineate cis-acting elements of the mouse pro alpha 1(II) collagen gene that control chondrocyte-specific expression in intact mouse embryos, we generated transgenic mice harboring chimeric constructions in which varying lengths of the promoter and intron 1 sequences were linked to a beta-galactosidase reporter gene. A construction containing a 3,000 bp promoter and a 3,020 bp intron 1 fragment directed high levels of beta-galactosidase expression specifically to chondrocytes. Expression of the transgene coincided with the temporal expression of the endogenous gene at all stages of embryonic development. Successive deletions of intron 1 delineated a 182 bp fragment which targeted beta-galactosidase expression to chondrocytes with the same specificity as the larger intron 1 fragment. Transgenic mice harboring a 309 bp Col2a1 promoter lacking intron 1 tester sequences showed no beta-galactosidase expression in chondrocytes. Reduction of the 182 bp fragment to a 73 bp subfragment surrounding a decamer sequence previously reported to be involved in chondrocyte specificity, resulted in loss of transgene expression in chondrocytes. When the Col2a1 promoter was replaced with a minimal beta-globin promoter, the 182 bp intron 1 sequence was still able to target expression of the transgene to chondrocytes. We conclude that a 182 bp intron 1 DNA segment of the mouse Col2a1 gene contains the necessary information to confer high-level, temporally correct, chondrocyte expression on a reporter gene in intact mouse embryos and that Col2a1 promoter sequences are dispensable for chondrocyte expression.

Animals↗

PubMed1986

Macrocytic-megaloblastic anemia in male NIH Swiss mice following repeated exposure to 1,3-butadiene.

Thymic lymphoma/leukemia is the major cause of death in B6C3F1 mice chronically exposed to 1,3-butadiene (BD). Similar to radiation-induced murine thymic lymphoma, the bone marrow is also a major target organ. Because of the association of murine thymic lymphoma with endogenous type-C murine leukemia retroviruses (MuLV) present in the germ line of most strains of laboratory mice, including B6C3F1 and its parent strains, we examined the effects of BD exposure on NIH Swiss mice which do not possess intact endogenous ecotropic MuLV. Male NIH Swiss mice exhibited a macrocytic-megaloblastic anemia following inhalation of 1250 ppm BD for 6 weeks. Treatment-related changes included decreases in circulating erythrocytes, total hemoglobin, and hematocrit and an increase in mean corpuscular volume. An eightfold increase in circulating micronuclei was also observed. The anemia was not accompanied by a significant alteration in mean corpuscular hemoglobin concentration, an increase in circulating reticulocytes, or an increase in circulating nucleated erythrocytes. These findings are consistent with a treatment-related macrocytic-megaloblastic anemia and indicate that the bone marrow is an important target for BD toxicity in mice independent of MuLV background and expression.

Anemia, Macrocytic↗

PubMed1986

Macrocytic-megaloblastic anemia in male B6C3F1 mice following chronic exposure to 1,3-butadiene.

In the present study exposure to 1,3-butadiene (BD) resulted in a macrocytic-megaloblastic anemia in male B6C3F1 mice following chronic inhalation of 1250 ppm for 6 to 24 weeks. Treatment-related changes evident after 6 weeks of exposure included a decrease in circulating erythrocytes, total hemoglobin, and hematocrit and an increase in mean corpuscular volume. A leukopenia, due primarily to a decrease in segmented neutrophils, and a five- to sixfold increase in circulating micronuclei were observed after 6 and 24 weeks of exposure. These changes were not accompanied by a significant alteration in mean corpuscular hemoglobin concentration, an increase in circulating reticulocytes, or circulating nucleated erythrocytes. A consistent treatment-related alteration in bone marrow cellularity was not found. However, flow cytofluorometric analysis of bone marrow DNA cell cycle kinetics revealed a 44% increase in proliferative index relative to controls, due primarily to an increase in the proportion of cells in S phase. These findings are consistent with a treatment-related macrocytic-megaloblastic anemia and indicate the bone marrow to be an important target organ for BD toxicity.

Anemia, Macrocytic↗

PubMed1986

Effect of sampling site and collection method on variations in baseline clinical pathology parameters in Fischer-344 rats. II. Clinical hematology.

An analysis of the influence of blood-sampling site and collection method on peripheral hematology parameters was conducted in age-matched male Fischer-344 rats. Sites examined for blood collection were the right ventricle, abdominal aorta, abdominal vena cava, retroorbital plexus, and tail. Collection methods used included syringe (10 ml), Vacutainer(s) (3 ml or 3 ml X 2), and capillary tube. Blood collected from the tail exhibited leukocyte counts approximately twice those of samples samples from other sites. Blood collected from the retroorbital plexus and tail exhibited significant variations in white blood cell count, red blood cell count, hemoglobin, and hematocrit, and differences in leukocyte differential counts of lymphocytes and neutrophils when compared with other sites. Blood collected from the abdominal aorta and in a second Vacutainer from the right ventricle exhibited lower erythrocyte, leukocyte, and platelet counts than that collected from other sites with the exception of the platelet count from tail blood which was lower than that from all other sites. Although parameter values vary with sample site selection, those obtained from right ventricle blood were the least variable and the most consistent when compared with all other methods.

Animals↗

PubMed1985

Effect of sampling site and collection method on variations in baseline clinical pathology parameters in Fischer-344 rats. 1. Clinical chemistry.

An analysis of the influence of blood sampling site and collection method on clinical chemistry parameters was conducted in male Fischer-344 rats. Sampling sites compared included the right ventricle, aorta, vena cava, retroorbital sinus, and tail. Methods of collection included Vacutainer (3 ml sample), syringe (exsanguination), and capillary tube. Nineteen frequently measured clinical chemistry procedures were determined, including serum enzymes, cholesterol, and triglycerides. Significant differences were noted for almost every parameter as a function of sampling site. Samples collected from the right ventricle with a Vacutainer produced the most representative results for most but not all procedures when compared to the overall mean (for all methods). The largest differences were encountered in samples obtained from tail and retroorbital plexus. Exanguination also resulted in significant differences for some parameters when compared to smaller sample volumes obtained from the same site. It was concluded that sampling site and collection method can be a major source of variation in clinical chemistry measurements, and in selection of an appropriate method, one should consider which parameters are likely to be of major interest.

Animals↗

PubMed1982

Theophylline elimination in the pregnant and fetal rabbit.

Aminophylline and theophylline are commonly used to treat asthma. We studied theophylline pharmacokinetics in the pregnant and nonpregnant rabbit as well as in the intrauterine and extrauterine fetus. The t1/2 was increased (p less than 0.05) and the clearance was decreased (p less than 0.05) in the pregnant compared to the nonpregnant rabbit. The t1/2 of theophylline in the newborn rabbit was 43.5 +/- 12.0 hr, approximately 15 times longer than in the nonpregnant rabbit. Twenty-four hours after a 20 min maternal aminophylline infusion, both the intrauterine fetus and maternal serum theophylline concentrations were very similar. The transplacental transfer from the maternal to fetal circulation occurred in less than 1 hr. The maternal to fetal serum ratios for theophylline were similar after a 5-day maternal aminophylline infusion (ratio 1.22 +/- 0.20) or after a 20 min infusion (ratio 1.24 +/- 0.20). Our findings indicate that the newborn rabbit eliminates theophylline very slowly, and maternal aminophylline or theophylline therapy that would result in high peak serum concentrations in the fetus, particularly just before birth, should be avoided.

Aminophylline↗