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Biomedical subjects

E L Lin

Publications and source records attributed to E L Lin.

13 recordsLinked to original sources
PubMed2001

Thematic relations in adults' concepts.

Concepts can be organized by their members' similarities, forming a kind (e.g., animal), or by their external relations within scenes or events (e.g., cake and candles). This latter type of relation, known as the thematic relation, is frequently found to be the basis of children's but not adults' classification. However, 10 experiments found that when thematic relations are meaningful and salient, they have significant influence on adults' category construction (sorting), inductive reasoning, and verification of category membership. The authors conclude that concepts function closely with knowledge of scenes and events and that this knowledge has a role in adults' conceptual representations.

Adult↗
PubMed1997

The effects of prior processing episodes on basic-level superiority.

Four experiments were conducted to investigate the effects of prior processing episodes on people's preference for categorizing objects at the basic level (e.g. dog) relative to their preference for categorizing at the superordinate (e.g. animal) and the subordinate (e.g. Dalmation) levels. The prior processing episode in Experiment 1 was designed to induce subjects to activate representations at the superordinate level, and those in the remaining experiments were designed to induce subjects to differentiate objects at the subordinate level. After the prior processing episodes, subjects performed either a free naming or a picture categorization task that required them to decide whether an illustrated object belonged to a specified category. Results showed that prior processing episodes modestly reduced the superiority of basic level to superordinate level and subordinate level in categorization but not in free naming. The results suggest that the basic-level advantage is subject to the effects of context, but the effects are not as strong as the context effects on other aspects of categorization behaviour (e.g. rating typicality of a category member). Hence, the preference for the basic level is a somewhat more stable, invariant aspect of conceptual representation. Possible determinations of this stability are discussed.

Cognition↗
PubMed1996

Fish biliary polycyclic aromatic hydrocarbon metabolites estimated by fixed-wavelength fluorescence: comparison with HPLC-fluorescent detection.

Fixed wavelength fluorescence (FF) was compared to high-performance liquid chromatography with fluorescence detection (HPLC-F) as an estimation of polycyclic aromatic hydrocarbon (PAH) exposure to fish. Two excitation/emission wavelength pairs were used to measure naphthalene- and benzo[a]pyrene (B[a]P)-type metabolites. Early nonmetabolite fluorescent peaks were negligible in HPLC chromatograms of bile of brown bullhead, white sucker, and common carp. Linear regression analysis of FF and HPLC-F data had r2 values between 0.89 and 1.00. Although the linear regression was significant, the absolute HPLC-F and FF values were not equivalent. HPLC-F values for B[a]P-type metabolites were always higher than those determined by FF. For naphthalene-type metabolites there was no consistent relationship between the HPLC-F and FF values. These inequivalencies were possibly due to the variable HPLC-elution patterns caused by the composition of metabolites and the unique fluorescent response exhibited in different solvent concentrations. Nevertheless, mean concentration estimates divided by the value obtained at the reference site were similar by both methods. The FF method can be used to estimate biliary PAH concentrations in these three species and allows PAH metabolites to become a routine measurement end point for environmental assessments.

Analysis of Variance↗
PubMed1994

Implications of graphics enhancements for the visualization of scientific data: dimensional integrality, stereopsis, motion, and mesh.

This study examines the effectiveness of four techniques to assist scientists in evaluating multidimensional data. Subjects viewed a series of complex 3D data sets, each representing an underlying complex surface, from which a set of discrete points or observations were sampled. From each sample they answered questions that required focus of attention on certain data points or integration across varying numbers of data points and dimensions. After a number of samples were viewed from each surface, subjects were tested for their retention of the surface characteristics. In Experiment 1, 3D (perspective) representations were found to support superior performance to 2D (planar) representations, but only for more integrative questions. Animated motion provided no benefits. In Experiment 2, stereoptic views of a 3D display were also found to support performance, particularly for integrative questions, but the ability to rotate the data space (motion parallax) and the presence of a mesh surface connecting the points did not. The posttests revealed some evidence that 3D representations improved the ability to visualize the surface, but neither 3D renderings nor stereopsis led to a better abstract representation of the data.

Adult↗
PubMed1993

Tissue distribution, excretion, and urinary metabolites of dichloroacetic acid in the male Fischer 344 rat.

The disposition of dichloroacetic acid (DCA) was investigated in Fischer 344 rats over the 48 h after oral gavage of 282 mg/kg of 1- or 2-[14C]-DCA (1-DCA or 2-DCA) and 28.2 mg/kg of 2-DCA. DCA was absorbed quickly, and the major route of disposition was through exhalation of carbon dioxide and elimination in the urine. The dispositions of 1- and 2-DCA at 282 mg/kg were similar. With 2-DCA, the disposition differed with dose in that the percentage of the dose expired as carbon dioxide decreased from 34.4% (28.2 mg/kg) to 25.0% (282 mg/kg), while the percentage of the radioactivity excreted in the urine increased from 12.7 to 35.2%. This percentage increase in the urinary excretion was mostly attributable to the presence of unmetabolized DCA, which comprised more than 20% at the higher dose and less than 1% at the lower dose. The major urinary metabolites were glycolic acid, glyoxylic acid, and oxalic acid. DCA and its metabolites accumulated in the tissues and were eliminated slowly. After 48 h, 36.4%, 26.2%, and 20.8% of the dose was retained in the tissues of rats administered 28.2 and 282 mg/kg of 2-DCA and 282 mg/kg of 1-DCA, respectively. Of the organs examined, the liver (4.9-7.9% of dose) and muscle (4.5-9.9%) contained the most radioactivity, followed by skin (3.3-4.5%), blood (1.4-2.6%), and intestines (1.0-1.7%). One metabolite, glyoxylic acid, which is mutagenic, might be responsible for or contribute to the carcinogenicity of DCA.

Administration, Oral↗
PubMed1992

Macromolecular adduction by trichloroacetonitrile in the Fischer 344 rat following oral gavage.

Male Fisher 344 rats were administered 1- or 2-[14C]trichloroacetonitrile (TCAN) by oral gavage. DNA was isolated from the liver, kidneys and stomach and several protein fractions (globin, albumin and globulins) were isolated from blood. TCAN binds to both the DNA and the blood proteins in a dose-related manner. More radiolabel was associated with the DNA when the carbon at C2 position was labeled, than at C1 position. However, the position of the radiolabel did not influence the levels of radioactivity associated with the blood proteins. The stomach exhibited the highest level of DNA binding, followed in order by the liver and kidney. TCAN binding level was higher in DNA isolated from rats killed at 24 h than at 4 h after administration. In contrast, the three blood proteins showed similar binding levels, regardless of the exposure time. Radioactivity associated with DNA was not incorporated into the nitrogen bases (i.e. via de novo synthesis) and a covalent binding index (mumol chemical bound/mol nucleotide phosphate per mmol/kg body wt. of chemical administered) of 30-120 was observed for various tissues. Most of the radioactivity (60-80%) associated with globin could be released and separated from the protein by the treatment with concentrated ammonium hydroxide and precipitation of protein by organic solvent. Three peaks were observed in the HPLC elution profiles of the radioactivity released from the globin. Trichloroacetic acid co-eluted with one of these released products (peak II), however, the chemical identity of the material under the major peak (peak III) and peak I are still uncharacterized.

Acetonitriles↗
PubMed1992

Chloroform inhibits the development of diethylnitrosamine-initiated, phenobarbital-promoted gamma-glutamyltranspeptidase and placental form glutathione S-transferase-positive foci in rat liver.

In this study we demonstrate that chloroform, a widely used industrial solvent, a medicinal chemical and a common drinking water contaminant, reduces the number of detectable preneoplastic enzyme-altered foci [gamma-glutamyltranspeptidase-positive (GGT+) and placental form glutathione S-transferase-positive (GST-P+)] in the liver of male Fischer 344 rats. The animals were given a partial hepatectomy and 18 h later received a single oral dose of either 0.5 mmol/kg diethylnitrosamine (DENA) or saline. Two weeks later, groups of 12 animals were started on drinking water containing phenobarbital with varying concentrations (200-1800 mg/l) of chloroform fro 12 weeks. Treated and control animals were killed and the number and the volume of GGT+ and GST-P+ expressing hepatic foci were tabulated. The numbers of foci per unit volume (and per unit area), the percent focal volume and the focal liver were reduced by chloroform in a dose-dependent manner. The mean focal volume was not influenced by chloroform. A plausible explanation for these results could be that chloroform exerts its focal inhibitory effect either by selectively killing the putative initiated cells, by retarding the inherent growth rate of enzyme-altered cells or by reducing the effectiveness of the promoter, phenobarbital. The available evidence suggests that the first hypothesis is the most likely explanation for these observations. These results are consistent with earlier studies showing that chloroform inhibits tumorigenesis in rodents.

Analysis of Variance↗
PubMed1989

Comparison of the effects of acute and subacute treatment of phenobarbital in different strains of mice.

A strain specificity has been demonstrated for the effect of subsequent administration of phenobarbital (PB), in which diethylnitrosamine (DENA)-initiated hepatocarcinogenesis was promoted in C3H mice, inhibited in B6C3F1 (C57BL x C3H) and not affected in C57BL mice. A correlation has been established between the ability of barbiturates and hydantoins to promote tumor formation and their ability to induce liver growth, hepatic DNA synthesis and mixed function oxidase activities. Therefore, we examined in these 3 strains of mice and in C3B6F1 (C3H x C57BL) mice the effect of PB administered in their drinking water for 4 days or 28 days. The liver weight to body weight ratio was increased by PB in all types of mice. Microsomal protein concentrations were increased in C57BL mice after 28 days of treatment, in C3H after both 4 days and 28 days and in B6C3F1 after 4 days of treatment. No effect upon microsomal protein content was observed in C3B6F1 mice. DNA content was increased in C3H mice, both in the 4-day and 28-day treatment groups, while the other strains showed either a decrease or no difference from control. DNA synthesis was elevated in all strains of mice after 4 days of treatment with PB, however, after 28 days of treatment there was either a much reduced increase (C57BL and C3B6F1) or no difference (C3H and B6C3F1) from controls. In all 4 types of mice after 4 and 28 days of treatment, PB increased the concentration of cytochrome P-450, the activity of aminopyrine-N-demethylase (AmDm) and 7-ethoxyresorufin-O-deethylase (ErDe) and the oxidation of testosterone (T). The oxidative metabolites of T were similar in the 4 types of mice.

Aminopyrine N-Demethylase↗
PubMed1989

Effects of trichloroethylene and its metabolites on rodent hepatocyte intercellular communication.

Chronic exposure to trichloroethylene (TCE) results in hepatocellular cancer in mice but not rats. The induction of hepatic tumors by TCE appears to be mediated through nongenotoxic or tumor promotion mechanisms. One cellular effect exhibited by a number of nongenotoxic carcinogens and tumor promoters is the inhibition of gap junction mediated intercellular communication. In the present study, the effects of trichloroethylene (TCE) and its metabolites, trichloracetic acid (TCA), trichloroethanol (TCEth), and chloral hydrate (CH) on gap junction mediated intercellular communication in cultured B6C3F1 mouse and F344 rat hepatocytes were assessed. TCE and TCA inhibited intercellular communication in mouse hepatocytes but not in rat hepatocytes. TCEth and CH had no effect on hepatocyte intercellular communication in either rat or mouse cells. TCE and TCA inhibited intercellular communication in both 24-hr-old and freshly plated mouse hepatocytes. Both compounds produced greater inhibition of intercellular communication in freshly plated cells when compared to 24-hr-old cultures. TCE appeared to require cytochrome P450 metabolism by the mouse hepatocytes to exhibit its inhibitory effect on dye coupling since treatment with SKF-525A prevented the inhibition of intercellular communication by TCE. The inhibitory effect of TCA on intercellular communication was unaffected by treatment with SKF-525A. While the species dependent effect of TCE on intercellular communication may be correlated with different rates and extent of metabolism of TCE by rat and mouse hepatocytes, the inhibiting effect of TCA only on mouse hepatocytes suggests that other intrinsic factors in the male mouse make this species more susceptible to the effects of TCE and TCA on gap junction mediated intercellular communication. These findings may account, in part, for the observed species difference in susceptibility to TCE induced liver carcinogenesis.

Animals↗
PubMed1986

Genotoxic properties of haloacetonitriles: drinking water by-products of chlorine disinfection.

Chlorinated and brominated haloacetonitriles (HAN), known drinking water contaminants which form during chlorine disinfection, were investigated for genotoxic activity. The HAN produced DNA strand breaks in cultured human lymphoblastic (CCRF-CEM) cells, bound to the nucleophilic trapping agent 4-(p-nitrobenzyl)pyridine and formed a covalent bond to polyadenylic acid in a cell-free reaction system. Thus, we have demonstrated that these chemicals are genotoxic, which would indicate a potential for carcinogenic activity and for human health hazard.

Acetonitriles↗
PubMed1986

Haloacetonitriles: metabolism, genotoxicity, and tumor-initiating activity.

Haloacetonitriles (HAN) are drinking water contaminants produced during chlorine disinfection. This paper evaluates metabolism, genotoxicity, and tumor-initiating activity of these chemicals. The alkylating potential of the HAN to react with the electrophile-trapping agent, 4-(p-nitrobenzyl)pyridine, followed the order dibromoacetonitrile (DBAN) greater than bromochloroacetonitrile (BCAN) greater than chloroacetonitrile (CAN) greater than dichloroacetonitrile (DCAN) greater than trichloroacetonitrile (TCAN). When administered orally to rats, the HAN were metabolized to cyanide and excreted in the urine as thiocyanate. The extent of thiocyanate excretion was CAN greater than BCAN greater than DCAN greater than DBAN much greater than TCAN. Haloacetonitriles inhibited in vitro microsomal dimethylnitrosamine demethylase (DMN-DM) activity. The most potent inhibitors were DBAN and BCAN, with Ki = 3-4 X 10(-5) M; the next potent were DCAN and TCAN, with Ki = 2 X 10(-4) M; and the least potent inhibitor was CAN, with Ki = 9 X 10(-2) M. When administered orally, TCAN, but not DBAN, inhibited hepatic DMN-DM activity. The HAN produced DNA strand breaks in cultured human lymphoblastic (CCRF-CEM) cells. TCAN was the most potent DNA strand breaker, and BCAN greater than DBAN greater than DCAN greater than CAN, which was only marginally active. DCAN reacted with polyadenylic acid and DNA to form adducts in a cell-free system; however, the oral administration of DBAN or DCAN to rats did not result in detectable adduct formation in liver DNA. None of the HAN initiated gamma-glutamyltranspeptidase (GGT) foci when assayed for tumor-initiating activity in rat liver foci bioassay.(ABSTRACT TRUNCATED AT 250 WORDS)

Acetonitriles↗
PubMed1985

Glutathione plus cytosol- and microsome-mediated binding of 1,2-dichloroethane to polynucleotides.

1,2-[1,2-14C]Dichloroethane was metabolized by rat hepatic microsomes to products that irreversibly bound polynucleotides. The polynucleotides were then enzymatically hydrolyzed and the products separated by a high-performance liquid chromatograph (HPLC) equipped with an ODS or a SCX column. The products of microsome-mediated binding were identified in the HPLC eluate as 1,N6-ethenoadenosine to polyadenylic acid, 3,N4-ethenocytidine to polycytidylic acid, and two cyclic derivatives to polyguanylic acid. 1,2-[1,2-14C]Dichloroethane was also metabolized in the presence of a glutathione (GSH)-cytosolic fraction and a polynucleotide. After enzymatic hydrolysis of the polynucleotide, the major peak of radioactivity was eluted from a Sephadex G-25 column in the salt volume which would exclude the presence of a product containing both GSH and a nucleoside. Chromatography by ODS-HPLC of the major peak from Sephadex G-25 indicated the presence of a GSH metabolite of 1,2-dichloroethane that did not contain a nucleoside. A similar hydrophilic peak was obtained for the hydrolysis products of polynucleotides from a glutathione plus cytosol incubation in which the polynucleotide instead of being added prior to the incubation was added after the incubation. The products of the glutathione plus cytosol metabolism of 1,2-[1,2-14]dichloroethane appear to be glutathione metabolites that coisolated with the polynucleotides rather than covalently bound adducts. In conclusion, covalently bound adducts were identified for microsome-mediated binding of 1,2-dichlorethane to polynucleotides, while no evidence was obtained for glutathione plus cytosol-mediated covalent binding to polynucleotides.

Animals↗