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R Lindahl

Publications and source records attributed to R Lindahl.

At least 109 records · Page 6Linked to original sources
PubMed1984

Regulation of aldehyde dehydrogenase activity in five rat hepatoma cell lines.

Significant changes in aldehyde dehydrogenase (ALDH) activity occur during rat hepatocarcinogenesis in vivo. An NADP-dependent tumor ALDH isozyme has been studied extensively. To better understand the nature, origin, and importance of this tumor-associated phenotypic change, we have examined the ALDH activity of five well-established rat hepatoma cell lines, H4-II-EC3, HTC, McA-RH7777, JM1, and JM2. HTC, JM1, and JM2 express the tumor ALDH phenotype, as indicated by elevated NADP-dependent, benzaldehyde-oxidizing activity, the appearance of new isozymes by electrophoresis, and characteristic histochemical localization of ALDH activity in situ. The tumor ALDH phenotype is not detected in McA-RH7777 cells. H4-II-EC3 has intermediate tumor ALDH activity. Thus, the 5 cell lines provide a spectrum of tumor ALDH activities representative of the range of activities seen in vivo. Benzo(a)pyrene, 3-methylcholanthrene, and phenobarbital induce hepatic ALDH activity after treatment in vivo. The ability of these compounds to induce ALDH in vitro was assessed in H4-II-EC3, McA-RH7777, HTC, JM1, and JM2. Treatment of cell cultures for 72 hr with 3-methylcholanthrene (1.0 mM) increases the NADP-dependent ALDH activity in H4-II-EC3 and McA-RH7777 cell lines up to 34- and 11-fold, respectively. Treatment with benzo(a)pyrene (1.0 mM) also increases the NADP-dependent ALDH activity in both lines up to 17- and 48-fold, respectively. Treatment with 3-methylcholanthrene or benzo(a)pyrene increases ALDH activity 2-fold in HTC and JM2 but does not increase NADP-dependent ALDH activity in JM1. Only marginal increases in NADP-dependent ALDH are observed after phenobarbital treatment in 4 of 5 cell lines. The induction of ALDH is blocked by actinomycin D, alpha-amanitin, and cycloheximide. These studies support our hypothesis that changes in ALDH activity observed in vivo are due to mutational events occurring in initiated cells. It appears that rat hepatoma cell lines will provide an in vitro model for studying genetic regulation of the tumor ALDH.

Aldehyde Dehydrogenase↗
PubMed1983

Changes in gamma-glutamyltransferase activity during N-2-fluorenylacetamide-induced rat hepatocarcinogenesis.

Changes in gamma-glutamyltransferase (GGT) activity throughout the course of rat hepatocarcinogenesis induced by brief dietary exposure to N-2-fluorenylacetamide (2-FAA) followed by promotion with dietary phenobarbital (PB) were studied. By examination of changes in total GGT activity and its histochemical localization, the effects of initiator and promoter on this enzyme can be clearly differentiated. Both 2-FAA and PB increase total GGT activity in grossly normal liver, PB causing a tenfold greater increase than that caused by 2-FAA. Although the elevation of GGT activity in livers of rats sequentially treated with 2-FAA-PB was not additive or synergistic, the course of increase was distinct from that of either 2-FAA- or PB-caused changes in activity, suggesting that 2-FAA and PB interact to alter the GGT phenotype of sequentially treated animals. GGT activity in neoplasms induced by either 2-FAA or 2-FAA-PB was highly variable, i.e., from nearly basal levels to those 170-fold greater than basal. Lesions induced by 2-FAA without PB promotion had elevated GGT, indicating that PB is not required to produce GGT-positive neoplasms by this protocol. Histochemically, changes in GGT activity occurred in both hepatocytes and nonhepatocyte cell populations in a characteristic, treatment-dependent manner, well-correlated with total GGT activity. Treatment with 2-FAA, especially that with 2-FAA-PB, induced primarily focal and nodular GGT activity patterns. PB alone produced no GGT-positive foci, but it did cause GGT-positive ductular proliferation. Continued PB exposure produced a GGT activity pattern which clearly defined the interlobular regions of the liver; no similar staining pattern was seen in either 2-FAA-treated or 2-FAA-PB-treated livers. These results indicate that an initiator and one of its promoters, combined and individually, alter GGT activity in a characteristic manner over the course of hepatocarcinogenesis. Moreover, the effects of the promoter on GGT activity are dependent on whether or not prior exposure to initiator has occurred.

2-Acetylaminofluorene↗
PubMed1983

Histochemical localization of aldehyde dehydrogenase during rat hepatocarcinogenesis.

Significant changes in aldehyde dehydrogenase (ALDH) activity occur during chemically induced rat hepatocarcinogenesis. We have developed a procedure for the histochemical localization of hepatic ALDH which has proven extremely useful as an additional probe for studying changes in this enzyme during hepatocarcinogenesis. Frozen sections of fresh tissue were stained for ALDH using either propionaldehyde-NAD to detect normal liver ALDH or benzaldehyde-NADP to detect tumor ALDH. Histochemically, normal liver ALDH activity is strongly centrilobular with only slight periportal activity and produces a characteristic staining pattern. During hepatocarcinogenesis, ALDH staining patterns in grossly normal liver range from normal-appearing to patterns of distinct, intense focal hepatocyte staining with propionaldehyde-NAD and/or benzaldehyde-NADP. ALDH-positive foci are found both in normal regions of tumor-bearing livers and prior to the appearance of gross neoplasms. Neoplastic nodules and carcinomas possess a wide variety of ALDH staining patterns between and within lesions. Neoplasms with elevated ALDH activity with propionaldehyde-NAD and/or benzaldehyde-NADP, as well as with no detectable ALDH, have been observed. Changes in ALDH can be identified histochemically at a time in hepatocarcinogenesis when other analytical methods cannot detect significant changes. Moreover, considerable heterogeneity in expression of tumor ALDH is demonstrable by histochemistry.

Aldehyde Dehydrogenase↗
PubMed1982

Interactions between cycloheximide and T-locus alleles during mouse embryogenesis.

Female CD-1 mice were mated with CD-1 X T/ + F1 males that were heterozygous for the brachyury (T') semidominant lethal gene or were +/+. Fetuses from CD-1 X +/+ matings were normal when observed on gestation Day 17 (plug day = Day 0). Those from the CD-1 X T/+ cross exhibited the expected 1:1 ratio of short:normal tail lengths, but 10% of these fetuses were tailless, apparently due to factors in the CD-1 genotype that increased the expressivity of the T-gene with regard to reduction of tail length. Additional CD-1 females were mated with CD-1 X tw18/+ F1 males. Fetuses from the CD-1 X tw18/+ matings were normal. CD-1 females carrying CD-1 X +/+, CD-1 X T/+, or CD-1 X tw18/+ litters were injected ip on gestation Day 9 with 30 mg/kg cycloheximide or were untreated. Cycloheximide was teratogenic for litters from all three crosses. Polydactyly, oligodactyly, and a variety of skeletal abnormalities were observed. Gross malformations and total skeletal malformations were increased in treated CD-1 X T/ + or tw18/+ litters in comparison with CD-1 X +/+ litters, as were nonvertebral skeletal defects in CD-1 X tw18/+ litters. Prenatal mortality was also greater in treated mutant-containing litters than in +/+ litters, and fetal weights were similarly decreased in treated CD-1 X tw18/+ litters. The incidence of taillessness was also higher in treated (26%) than in control (10%) CD-1 X T/+ litters. Thus both the T and tw18 alleles appear to have enhanced the teratogenicity of cycloheximide, and the inhibitor may have increased the expressivity of T.

Abnormalities, Drug-Induced↗
PubMed1982

Sequential 2-acetylaminofluorene--phenobarbital exposure induces a cytosolic aldehyde dehydrogenase during rat hepatocarcinogenesis.

A significant change in hepatic aldehyde dehydrogenase activity has been observed in normal Sprague-Dawley rat liver during the promotion phase of hepatocarcinogenesis induced by brief feeding of 2-acetylaminofluorene (2-AAF) followed by tumor promotion using dietary phenobarbital (PB) exposure. Animals receiving only 2-AAF or PB do not possess this new aldehyde dehydrogenase activity. The phenotype is characterized by the appearance of a new cytosolic isozyme kinetically, electrophoretically and immunochemically distinct from the normal liver aldehyde dehydrogenase isozymes and from aldehyde dehydrogenases inducible in 2-AAF-induced hepatomas. The new isozyme is NAD-dependent, disulfiram-sensitive and cross-reacts with antiserum to a normal liver aldehyde dehydrogenase inducible in several lines of rats by PB. However, the population of animals used in this study has been shown previously to be non-responsive to aldehyde dehydrogenase induction by dietary PB. Since no animals receiving only PB express this new isozyme, the carcinogen must play a significant role in its induction. Moreover, that not all animals receiving carcinogen and promoter possess the phenotype suggests this carcinogen/promoter interaction has a genetic basis.

2-Acetylaminofluorene↗
PubMed1982

Expression of the tumor aldehyde dehydrogenase phenotype during 2-acetylaminofluorene-induced rat hepatocarcinogenesis.

In aromatic amine-induced rat hepatomas, the aldehyde dehydrogenase (AIDH) phenotype is qualitatively and quantitatively different from that of normal liver. To identify the mechanism(s) underlying the expression of the tumor-specific AIDHs, we have followed the time course of appearance of the new phenotype during hepatoma formation in Sprague-Dawley rats following brief dietary exposures to 2-acetylaminofluorene (0.02%; 32 days). Tumor promotion by phenobarbital (0.05% in the diet) was also used to compare the effects of a variety of tumor induction protocols on the AIDH phenotype. No change in the AIDH phenotype is detectable by total activity assay, gel electrophoresis, isoelectric focusing, or immunochemical methods during or following exposure to carcinogen or promoter until tumors are grossly observed in liver. Concomitant with tumor appearance, the tumor-specific AIDH phenotype appears. The phenotypic change is limited to the tumor; morphologically and histologically normal liver directly adjacent to the tumor and normal lobes of a tumor-bearing liver do not possess the tumor AIDH phenotype. No correlation exists between tumor size and the degree of deviation of the AIDH phenotype from normal. Nor is there any correlation between the degree of AIDH phenotype deviation and the histology of the various tumors observed. We conclude that the tumor-specific AIDH phenotype is not associated with altered liver metabolism due directly to carcinogen or promoter exposure. Rather, the mechanism of this phenotypic change requires that transformation-associated, stable genetic changes occur in the cells affected by carcinogen that are later expressed as the altered AIDH phenotype.

2-Acetylaminofluorene↗
PubMed1982

Induction of aldehyde dehydrogenases during hepatocarcinogenesis.

Only recently has a clear picture of the number, subcellular distribution and properties of rat liver aldehyde dehydrogenase begun to emerge. In addition to the basal normal liver isozymes, several additional activities are inducible in both normal and abnormal liver by a variety of xenobiotics, including chemical carcinogens. While the induction protocols vary widely and the induced activities appear to differ slightly in physical and functional properties, it is likely that only a small number of structural genes, perhaps 2 or 3, encode these new activities. Whether the diversity of new aldehyde dehydrogenases inducible in liver is due to differences in the transcription of these genes, differences in post-transcriptional processing or post-translational modification of the synthesized polypeptides is currently unknown. What is clear is that the induction of aldehyde dehydrogenase represents an intriguing problem in molecular genetics, the resolution of which would contribute significantly to our understanding of eukaryotic gene regulation.

2-Acetylaminofluorene↗
PubMed1980

Properties of aldehyde dehydrogenas from chemically-induced rat hepatomas and normal rat liver.

The subcellular distribution and properties of four aldehyde dehydrogenase isozymes (I-IV) identified in 2-acetylaminofluorene-induced rat hepatomas and three aldehyde dehydrogenase (I-III) identified in normal rat liver are compared. In normal liver, mitochondria (50%) and microsomes (27%) possess the majority of the aldehyde dehydrogenase (AlDH), with cytosol possessing little activity. Isozymes I-III can be identified in both fractions and can be differentiated on the basis of substrate and coenzyme specificity, substrate Km, inhibition by disulfiram and anti-hepatoma aldehyde dehydrogenase sera, and/or isoelectric point. Hepatomas possess considerable cytosolic AlDH (20%), in addition to mitochondrial (23%) and microsomal (35%) activity. Although isozymes I-III are present in tumor mitochondria and microsomes, little isozyme I or II is found in cytosol. Hepatoma cytosolic AlDH is composed (50%) of a hepatoma-specific isozyme (IV), differing in several properties from isozymes I-III; the remainder of the tumor cytosolic activity is due to isozyme III (48%). The data indicate that expression of the tumor-specific aldehyde dehydrogenase phenotype requires both qualitative and quantitative changes involving cytosolic and microsomal aldehyde dehydrogenase. The qualitative change requires the derepression of a gene for an aldehyde dehydrogenase expressed in normal liver only following exposure to potentially harmful xenobiotics. The quantitative change involves both an increase in activity and change in subcellular location of a basal, normal liver AlDH isozyme.

Aldehyde Oxidoreductases↗
PubMed1980

Peroxisome-associated aldehyde dehydrogenase in normal rat liver.

We have combined subcellular fractionation and cytochemical staining techniques to study the distribution of aldehyde dehydrogenase in rat liver. In addition to confirming the mitochondrial and microsomal localization of aldehyde dehydrogenase, this combined approach has allowed us to demonstrate that peroxisome-like organelles possess significant aldehyde dehydrogenase. When peroxisomal fractions are cytochemically stained for aldehyde dehydrogenase, activity is observed along membranes of structures resembling peroxisomal ghosts. These bodies lack a matrix but many appear to enclose peroxisomal cores. Moderate to dense reaction product is also located in single membrane-limited structures present in fractions containing morphologically recognizable peroxisomes. On occasion, the osmiophilic precipitate is also present in the matrix of intact peroxisomes. The aldehyde dehydrogenase activity in these peroxisome-like organelles prefers aliphatic aldehydes, including acetaldehyde in both millimolar and micromolar concentrations, and NAD. Aromatic aldehydes and NADP are also metabolized, but to a lesser extent. These results indicate that peroxisome-like organelles contain an aldehyde dehydrogenase activity possessing properties compatible with a role in ethanol metabolism.

Acid Phosphatase↗
PubMed1979

Subcellular distribution and properties of aldehyde dehydrogenase from 2-acetylaminofluorene-induced rat hepatomas.

The subcellular distribution and properties of four aldehyde dehydrogenase isoenzymes (I-IV) identified in 2-acetylaminofluorene-induced rat hepatomas and three aldehyde dehydrogenases (I-III) identified in normal rat liver are compared. In normal liver, mitochondria (50%) and microsomal fraction (27%) possess the majority of the aldehyde dehydrogenase, with cytosol possessing little, if any, activity. Isoenzymes I-III can be identified in both fractions and differ from each other on the basis of substrate and coenzyme specificity, substrate K(m), inhibition by disulfiram and anti-(hepatoma aldehyde dehydrogenase) sera, and/or isoelectric point. Hepatomas possess considerable cytosolic aldehyde dehydrogenase (20%), in addition to mitochondrial (23%) and microsomal (35%) activity. Although isoenzymes I-III are present in tumour mitochondrial and microsomal fractions, little isoenzyme I or II is found in cytosol. Of hepatoma cytosolic aldehyde dehydrogenase activity, 50% is a hepatoma-specific isoenzyme (IV), differing in several properties from isoenzymes I-III; the remainder of the tumour cytosolic activity is due to isoenzyme III (48%). The data indicate that the tumour-specific aldehyde dehydrogenase phenotype is explainable by qualitative and quantitative changes involving primarily cytosolic and microsomal aldehyde dehydrogenase. The qualitative change requires the derepression of a gene for an aldehyde dehydrogenase expressed in normal liver only after exposure to potentially harmful xenobiotics. The quantitative change involves both an increase in activity and a change in subcellular location of a basal normal-liver aldehyde dehydrogenase isoenzyme.

2-Acetylaminofluorene↗
PubMed1979

Enzyme changes accompanying thermal acclimation in two species of pleurocerid snails.

Goniobasis cahawbensis is a stream snail that experiences an annual temperature cycle. G. cochliaris is limited in distribution to springs, and their immediate vicinities, which are characterized by nearly constant annual temperatures. The present study sought to determine whether temperature dependent biochemical differences exist that might account for the differential distribution of these congeneric pleurocerid snails. Eight enzymes were examined following acclimation to 10 degrees, 17 degrees and 24 degrees C. No significant temperature dependent qualitative differences in enzyme phenotypes were demonstrable in either species by starch-gel electrophoresis for malate dehydrogenase, glucose-6-phosphate dehydrogenase, phosphogluconate dehydrogenase, phosphoglucomutase, superoxide dismutase and acetyl and butyryl esterases. Significant quantitative differences were observed in three of these enzymes. G. cahawbensis cytosol malate dehydrogenase activity increased significantly with increasing acclimation temperature, while G. cochliaris malate dehydrogenase activity remained unchanged. The activities of glucose-6-phosphate dehydrogenase did not differ significantly between acclimation temperatures for either species; however, the overall activity of both enzymes was significantly higher for G. cochliaris. Appreciable levels of LDH activity were not demonstrable by electrophoresis or enzymatic assay.

Adaptation, Physiological↗
PubMed1979

Analysis of some older Scandinavian formulations of 2,4-dichlorophenoxy acetic acid and 2,4,5-trichlorophenoxy acetic acid for contents of chlorinated dibenzo-p-dioxins and dibenzofurans.

Ten samples of older formulations of 2,4,5-trichlorophenoxy acetic acid and 2,4-dichlorophenoxy acetic acid used in Sweden were analyzed for chlorinated dibenzo-p-dioxins and dibenzofurans. The analyses were performed with gas chromatography/mass spectrometry with a high resolution glass capillary column for maximum isomeric separation and sensitivity. The detection limit was 0.01-0.05 ppm. The amounts of contaminants were of the same order of magnitude as that found earlier in European samples with later production dates (late 1960s and 1970s).

2,4,5-Trichlorophenoxyacetic Acid↗