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R Lindahl

Publications and source records attributed to R Lindahl.

At least 91 records · Page 5Linked to original sources
PubMed1988

Differential gene expression in response to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). Noncoordinate regulation of a TCDD-induced aldehyde dehydrogenase and cytochrome P-450c in the rat.

2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) regulates the transcription of a specific subset of genes through a receptor-mediated mechanism. We have isolated a cDNA to a TCDD-inducible rat liver aldehyde dehydrogenase and have shown that its induction by TCDD differs from that of another TCDD-induced gene, cytochrome P-450c, with regard to dose-response relationship, induction kinetics, and tissue specificity. At least a 10-fold higher dose of TCDD was required for half-maximal induction of TCDD-inducible rat liver aldehyde dehydrogenase in rat liver than the dose that half-maximally induced cytochrome P-450c. Further, the kinetics of induction of TCDD-inducible rat liver aldehyde dehydrogenase by TCDD in rat liver was delayed compared with that of cytochrome P-450c. Striking discrepancies were found in the capacity of various organs to induce both TCDD-inducible rat liver aldehyde dehydrogenase and cytochrome P-450c in a coordinated manner in response to TCDD. Organs that were able to evoke one of these responses to TCDD were not necessarily able to evoke coordinately the other response. The capacity of an organ to exhibit either of these two responses to TCDD did not correlate stringently with reported Ah receptor abundance. Our data suggest that TCDD can modulate the expression of specific genes in different ways and that regulatory pathways in addition to the classically defined Ah receptor may be involved.

Aldehyde Dehydrogenase↗
PubMed1988

Characterization of a functional recombinant rat liver aldehyde dehydrogenase: expression as a non-fusion protein in E. coli.

A cDNA encoding a rat liver inducible aldehyde dehydrogenase carried in a pUC8 plasmid is expressed in E. coli as a dimeric enzyme molecule functionally and physically identical to the authentic rat enzyme. The cDNA appears to be transcribed using the lac promoter, but is translated from an initiator codon 174 base pairs from the 5' end of the cDNA. The aldehyde dehydrogenase polypeptide is not produced as a fusion protein. This is the first example of the production by E. coli of a catalytically active, multimeric eukaryotic protein which is not a fusion protein.

Aldehyde Dehydrogenase↗
PubMed1988

Cloning and complete nucleotide sequence of a full-length cDNA encoding a catalytically functional tumor-associated aldehyde dehydrogenase.

To study the mechanism(s) controlling expression of the tumor-associated aldehyde dehydrogenase (tumor ALDH), which appears during rat hepatocarcinogenesis, cDNAs encoding this isozyme were cloned and identified with an antibody probe. Poly(A)-containing RNA from HTC rat hepatoma cells, which have been shown to possess high levels of tumor ALDH, was used as template to synthesize double-stranded cDNA. The cDNA was methylated to protect internal sites. Two different synthetic DNA linkers were added sequentially to the cDNA to insure correct orientation for expression from the lac promoter of pUC8. A library of 100,000 independent members carrying inserts greater than 1 kilobase was obtained. From this library, two apparently identical tumor ALDH clones, differing only in size, were identified with an indirect immunological probe. The larger of the cDNA clones identified, pTALDH, was chosen for further study. Interestingly, since tumor ALDH is a dimeric enzyme, pTALDH directs synthesis of a functional tumor ALDH in the bacterial cell. The cDNA sequence has been confirmed by comparison to the amino acid sequence of tumor ALDH purified from HTC cells.

Aldehyde Dehydrogenase↗
PubMed1987

Hydride transfer stereospecificity of rat liver aldehyde dehydrogenases.

The stereospecificity of hydride transfer to NAD+ by several forms of rat liver aldehyde dehydrogenase was determined by a nuclear magnetic resonance method. The forms included several mitochondrial and microsomal isozymes from normal liver, as well as isozymes from xenobiotic-treated and tumor cells. The proton added to NAD+ comes exclusively from the aldehyde substrate and in all cases was A (pro-R)-stereospecific.

Aldehyde Dehydrogenase↗
PubMed1987

Occupational exposure to chain saw exhausts in logging operations.

The composition of exhaust emissions from two-stroke chain saw engines was studied. The emissions of exhaust were sampled and analyzed under controlled laboratory experiments. The compounds sampled were those considered primarily responsible for acute health effects--hydrocarbons, aldehydes, nitrogen oxides and carbon monoxide. Exposure to tetramethyllead, dibromoethane and polycyclic aromatic hydrocarbons also was monitored. The results revealed no significant differences in the exhaust emissions from seven different chain saws. Heavily worn-out chain saws do not emit increased amounts of exhaust. A lean fuel-air mixture increases the emission of aldehydes and nitrogen oxides, whereas a rich mixture increases emission of carbon monoxide and hydrocarbons. Based on these new data on the composition of two-stroke chain saw exhaust emissions, operator exposure to chain saw exhaust was evaluated under various logging situations. Exposure measurements revealed no difference in average levels of exposure between logging in the presence or in the absence of snow. The felling operation, however, results in high exposure levels of short duration--especially when the operation is performed while there is deep snow on the ground. (This operation excludes limbing and bucking into lengths.) This is judged to be the main cause of the discomfort experienced by loggers. Average exposure levels for loggers engaged only in felling are twice those for cutters who also perform limbing, bucking and manual skidding of the timber, since these latter operations involve considerably lower exposure. Typical average levels of exposure are as follows: hydrocarbons, 20 mg/m3; benzene, 0.6 mg/m3; formaldehyde, 0.1 mg/m3; and carbon monoxide, 20 mg/m3.

Air Pollutants, Occupational↗
PubMed1987

Changes in aldehyde dehydrogenase activity during diethylnitrosamine-initiated rat hepatocarcinogenesis.

Diethylnitrosamine following partial hepatectomy followed by phenobarbital promotion was used to study changes in aldehyde dehydrogenase (ALDH) activity during rat hepatocarcinogenesis. Over a period of 350 days, animals were killed at intervals and the ALDH phenotype of normal liver and any lesions was characterized by histochemical analysis, total activity assays and gel electrophoresis using propionaldehyde and NAD+ to detect normal liver ALDH activities, and benzaldehyde and NADP+ for tumor-associated ALDH. In contrast to previously tested protocols, no significant changes in ALDH activity were demonstrable by histochemistry or total activity assays in preneoplastic livers. However, nine of 16 (56%) of the hepatocellular carcinomas examined expressed the tumor-associated ALDH phenotype. The present results are integrated with previous observations as a hypothesis explaining the roles of initiation and promotion in expression of the tumor-associated aldehyde dehydrogenase phenotype.

Aldehyde Dehydrogenase↗
PubMed1986

Characteristics and aldehyde dehydrogenase activity of four rat hepatoma cell lines produced by diethylnitrosamine-phenobarbital treatment.

Recent studies in our laboratory have shown that five established rat hepatoma cell lines provide a wide spectrum of tumor-associated aldehyde dehydrogenase (ALDH) activity representative of the range of activities of this enzyme seen in primary rat hepatocellular carcinomas. Four newly established rat hepatoma cell lines, RLT-2M, RLT-3C, RLT-9F, and RLT-5G, were derived from a primary hepatocellular carcinoma. The primary tumor was induced by a single injection of diethylnitrosamine (15 microM/g body weight) to a 1-d-old female S-D rat followed at weaning by chronic phenobarbital treatment. RLT-2M was established from outgrowths of minced tumor pieces. RLT-3C, RLT-9F, and RLT-5G were cloned from RLT-2M by the serial endpoint dilution. All four lines have been maintained in culture for over 100 passages. The ALDH phenotype in both the primary tumor and the four new cell lines was determined by total activity assay, gel electrophoresis, and histochemistry. By total activity assay, the primary tumor did not possess significant tumor-ALDH activity. In contrast, the four new cell lines expressed tumor-ALDH activity. However, they differed in their basal ALDH activities and in ALDH inducibility by 3-methylcholanthrene, benzo(a)pyrene, and phenobarbital. Additionally, significant decreases in tumor-ALDH activity occurred when cells from each line were passaged in vivo. The four lines have been characterized by light and electron microscopic morphology, tumorigenicity, chromosome number, doubling time, and colony formation efficiency in soft agar.

Aldehyde Dehydrogenase↗
PubMed1986

Changes in aldehyde dehydrogenase occurring during rat hepatocarcinogenesis induced by ethionine combined with dietary choline deficiency.

Chronic exposure to ethionine (0.05%) combined with dietary choline deficiency was used to study changes in aldehyde dehydrogenase (ALDH) activity during hepatocarcinogenesis in male Sprague-Dawley rats. Over a period of 43 weeks, animals were sacrificed at intervals and the ALDH phenotype of normal liver and any lesions was characterized by histochemical analysis, total activity assays, and gel electrophoresis, using propionaldehyde and nicotinamide adenine dinucleotide (NAD+) to detect normal liver ALDH activity and benzaldehyde and nicotinamide adenine dinucleotide phosphate (NADP+) for tumor-associated ALDH. In animals receiving ethionine plus choline deficiency, significant changes in ALDH were observed histochemically by 9 weeks, when there was a distinct shift in activity from its normal centrilobular pattern to a periportal distribution. The first NAD+- and NADP+-dependent ALDH-positive enzyme-altered foci were also seen at 9 weeks. There was no correlation between the ALDH and gamma-glutamyl transpeptidase phenotypes of an individual focus. Areas of cholangiofibrosis, cystic degeneration, and bile duct proliferation were distinctly ALDH negative. No significant changes in benzaldehyde and NADP+ ALDH activity were detectable by total activity assays or gel electrophoresis prior to the appearance of overt neoplasms at 26 weeks. No significant changes in ALDH activity occurred in animals receiving either ethionine or choline deficient diet alone. By histochemistry, total activity assays and gel electrophoresis, only 7 of the 28 (25%) of the hepatic neoplasms examined expressed the tumor-associated ALDH phenotype. An additional five neoplasms had barely detectable levels of benzaldehyde and NADP+ ALDH activity. These results are in striking contrast to changes in ALDH activity occurring during hepatocarcinogenesis induced by other protocols we have tested previously in which from 50 to 96% of all neoplasms were ALDH positive.

Aldehyde Dehydrogenase↗
PubMed1986

Identification of hepatocarcinogenesis-associated aldehyde dehydrogenase in normal rat urinary bladder.

An aldehyde dehydrogenase (ALDH) with properties identical to those of the NADP+-dependent, tumor-associated aldehyde dehydrogenase appearing during rat hepatocarcinogenesis has been identified in normal rat urinary bladder. Like the tumor-associated aldehyde dehydrogenase, bladder NADP+-ALDH is cytosolic and preferentially oxidizes benzaldehyde-like aromatic aldehydes. Bladder ALDH is also extremely sensitive to the aldehyde dehydrogenase inhibitor disulfiram. Additionally, the electrophoretic mobility of bladder ALDH is identical to that of the NADP+-dependent, tumor-associated aldehyde dehydrogenase. Finally, antibodies to the tumor-associated ALDH cross-react with bladder aldehyde dehydrogenase. Histochemically, bladder aldehyde dehydrogenase is localized to the very active epithelial lining and to the inner and outer smooth muscle layers. The observation that normal urinary bladder possesses an enzyme activity very similar to one expressed during hepatocarcinogenesis, but not in normal liver, is consistent with the hypothesis that derepression of a gene normally repressed in liver is responsible for expression of the tumor-associated aldehyde dehydrogenase phenotype.

Aldehyde Dehydrogenase↗
PubMed1985

Characterization of aldehyde dehydrogenase from HTC rat hepatoma cells.

We have proposed developing rat hepatoma cell lines as an in vitro model for studying the regulation of changes in aldehyde dehydrogenase activity occurring during hepatocarcinogenesis. Aldehyde dehydrogenase purified in a single step from HTC rat hepatoma cells is identical to the aldehyde dehydrogenase isolated from rat hepatocellular carcinomas. HTC aldehyde dehydrogenase is a 100 kDa dimer composed of 54-kDa subunits, prefers NADP+ as coenzyme, and preferentially oxidizes benzaldehyde-like aromatic aldehydes but not phenylacetaldehyde. The substrate and coenzyme specificity, effects of disulfiram, pH profile and isoelectric point of HTC aldehyde dehydrogenase are also identical to these same properties of the tumor aldehyde dehydrogenase. In immunodiffusion, both isozymes are recognized with complete identity by anti-HTC aldehyde dehydrogenase antibodies. Having established that HTC aldehyde dehydrogenase is very similar, if not identical, to the aldehyde dehydrogenase found in hepatocellular carcinomas, simplifies the development of molecular probes for examination of the regulation of tumor aldehyde dehydrogenase activity in vivo and in vitro.

Aldehyde Dehydrogenase↗
PubMed1985

Irritative complaints, carboxyhemoglobin increase and minor ventilatory function changes due to exposure to chain-saw exhaust.

Complaints of irritation in the eyes, nose and throat as well as dyspnea during work prompted this study to determine whether chain-saw exhaust produces acute exposure effects in loggers. Interviews concerning respiratory symptoms and rating of complaints were conducted for 211 loggers at industrial health care centers. Measurements of carboxyhemoglobin, spirometry and exposure to hydrocarbons, carbon monoxide and aldehydes were assessed for 23 loggers over 36 work periods lasting 2 h each. The prevalence of chronic bronchitis among the 211 loggers was 6%. Irritative complaints of eyes, nose and throat were common and significantly higher than in a reference group. The exposure levels were all below established threshold limit levels, except for carbon monoxide. There was a significant correlation between carbon monoxide exposure and blood carboxyhemoglobin levels. A small but significant decrease of FEV1% and FEF 25-75% during the work periods indicated minimal broncho-constriction, possibly mediated through a reflex mechanism due to irritation of upper airways.

Adolescent↗
PubMed1984

Comparative subcellular distribution of aldehyde dehydrogenase in rat, mouse and rabbit liver.

The subcellular distribution of hepatic aldehyde dehydrogenase (ALDH) activity was determined in Buffalo, Fischer 344, Long-Evans, Sprague-Dawley, Wistar and Purdue/Wistar rats. These subcellular distributions were compared to the distribution of mouse and rabbit liver ALDH. For the six rat strains, at millimolar propionaldehyde concentrations, NAD-dependent ALDH activity was associated primarily with mitochondria (51%) and microsomes (30%). At millimolar acetaldehyde concentrations, NAD-dependent ALDH was primarily mitochondrial (up to 80%). Less than 1% of total NAD-dependent aldehyde dehydrogenase was found in the cytosol. The highly inbred Purdue/Wistar line possessed significantly less acetaldehyde-NAD ALDH activity as well as less total NADP-dependent ALDH activity than the other strains. In CD-1 mouse liver, millimolar Km, NAD-dependent ALDH activity was found in mitochondria (60%), microsomes (23%) and cytosol (5%). In rabbit liver, millimolar Km, NAD-dependent ALDH was also distributed among mitochondria (36%), microsomes (19%) and cytosol (28%). At micromolar substrate concentrations, mitochondria possessed the majority of rat, mouse and rabbit liver ALDH activity. In all three species, NADP-dependent ALDH activity was found predominantly in the microsomal fraction (up to 65%). The cytosol possessed little NADP-dependent ALDH in any species. We conclude that there are significant species differences in the subcellular distribution of aldehyde dehydrogenase between rat, mouse and rabbit liver. In all three species, mitochondria and microsomes possessed the majority of hepatic aldehyde dehydrogenase activity. However, the cytosol of mouse and rabbit liver also made a significant contribution to total ALDH activity. For the six rat strains examined, liver cytosol possessed little or no ALDH activity.

Aldehyde Dehydrogenase↗
PubMed1984

Rat liver aldehyde dehydrogenase. I. Isolation and characterization of four high Km normal liver isozymes.

From normal rat liver mitochondrial and microsomal fractions, 4 distinct aldehyde dehydrogenase isozymes with millimolar substrate Km values have been purified and characterized. Two isozymes were isolated from mitochondria and 2 from microsomes. A mitochondrial aldehyde dehydrogenase with a substrate Km in the micromolar range was also identified. Subunit molecular weights for all millimolar Km isozymes is 54,000. The mitochondrial and microsomal millimolar Km isozymes are clearly distinguishable from each other by substrate and coenzyme specificity, pH velocity profiles, and thermal stability. By these same properties, the 2 isozymes from each organelle are virtually identical. The 2 mitochondrial isozymes can be distinguished by apparent molecular weight (I, 170,000; II, approximately 250,000), Km for NADP+, effect of inhibitors, and pI. The 2 microsomal isozymes are of the same apparent molecular weight (approximately 250,000), but are distinguishable by their Km values for benzaldehyde and NADP+, response to inhibitors, and pI.

Aldehyde Dehydrogenase↗
PubMed1984

Rat liver aldehyde dehydrogenase. II. Isolation and characterization of four inducible isozymes.

The purification and properties of 4 inducible cytosolic rat liver aldehyde dehydrogenase isozymes are described. Based on their behavior during purification and their properties, the activities can be grouped into 2 classes. The isozyme inducible in normal liver by 2,3,7,8-tetrachlorodibenzo-p-dioxin and the tumor-specific isozyme found in hepatocellular carcinomas have apparent molecular weights of 110,000, prefer NADP+ as coenzyme, and preferentially oxidize benzaldehyde-like aromatic aldehydes, but not phenylacetaldehyde. They also have identical pH profiles and responses to effectors. These isozymes differ slightly in isoelectric point and thermal stability. The normal liver phenobarbital-inducible isozyme and the isozyme appearing during the promotion phase of hepatocarcinogenesis appear to be identical. Both have apparent molecular weights of 165,000, are NAD-specific and prefer aliphatic aldehydes. They can oxidize phenylacetaldehyde, but not benzaldehyde-like aromatic aldehydes. They also have identical pH and thermal stability profiles and responses to effectors. While the 4 inducible isozymes share identical subunit molecular weights (54,000) with the normal liver millimolar Km aldehyde dehydrogenases, they are distinctly different enzymatic species. The interrelationships of the various normal liver and inducible rat liver aldehyde dehydrogenases are discussed.

Aldehyde Dehydrogenase↗
PubMed1984

Expression of tumor-associated aldehyde dehydrogenase during rat hepatocarcinogenesis using the resistant hepatocyte model.

The resistant hepatocyte model was used to study expression of tumor-associated aldehyde dehydrogenase (ALDH) activity during the course of rat hepatocarcinogenesis. The hepatic ALDH phenotype was determined at intervals over 280 days by histochemical analysis, total ALDH activity assays and gel electrophoresis, using propionaldehyde and NAD (P/NAD) to characterize normal liver ALDH activity or benzaldehyde and NADP (B/NADP) to determine tumor-associated ALDH activity. By total activity assays and gel electrophoresis, no significant changes in ALDH activity occurred until day 70. However, histochemical analysis clearly demonstrated changes in ALDH activity early in neoplastic development. Intense focal hepatocyte staining with P/NAD and/or B/NADP was first detectable at day 28. The number of P/NAD-positive foci increased until day 35 then declined until day 70. The number of B/NADP-positive foci also increased until day 35, but then remained relatively constant for the remainder of the experiment. GGT activity of serial sections indicated that early ALDH-positive lesions represent a small subpopulation (9%) of all GGT-positive foci. However, by day 168 a significant portion (80%) of persistent GGT-positive neoplastic nodules were also B/NADP-positive histochemically. In addition, virtually all hepatocellular carcinomas (96%) generated by this protocol possessed significantly elevated levels of tumor-associated ALDH by histochemical analysis, total ALDH activity and gel electrophoresis. These results indicate that early appearing ALDH-positive lesions may define one early subpopulation of all initiated cells that have a high probability of progressing to the ultimate neoplasm.

Aldehyde Dehydrogenase↗