A role for B1 and B2 kinin receptors in the modulation of T-kininogen during the acute phase response of inflammation

Kinin antagonists at B1 and B2 receptors were examined on liver and serum concentrations of immunoreactive T-kininogen and its gene expression in a rat model of carrageenan-induced hindpaw edema. Whereas the B2 antagonist, HOE140, dose-dependently inhibited the paw edema induced by intraplantar injection of carrageenan, the B1 receptor agonist [Sar(D-Phe8)des-Arg9]BK and antagonist [Lys(Leu8)des-Arg9]BK were ineffective. On its own, HOE140 (3.25 x 10(-7) mol/ paw, intraplantar) had no effect on liver and serum T-kininogen levels but it significantly enhanced liver T-kininogen concentrations in rats pretreated with carrageenan at 8 and 24 h postinjection. In the liver, the most pronounced effect was seen at 24 h (treated 248 +/- 7 micrograms/g vs. untreated 113 +/- 9 micrograms/g). The same dose of HOE140 increased serum T-kininogen from 1255 +/- 57 to 1696 +/- 83 micrograms/ml at 24 h. HOE140 did not affect tissue albumin content during the same period. Transcript measurements revealed that the steady-state level of liver T2-kininogen mRNA was specifically increased by HOE140 during inflammation. In carrageenan-treated rats, the B1 antagonist [Lys(Leu8)des-Arg9]BK also significantly increased liver T-kininogen at 24 h. The present results support a role for B2 kinin receptors in the early phase of acute phase protein synthesis and of both B2 and B1 receptors in the late phase (24 h). Hence, systemic effects of kinins should be taken into account in the pharmacology and physiopathology of B1 and B2 kinin receptors in inflammation.

Chicken acidic ribosomal phosphoprotein PO: isolation and molecular characterization of cDNA clones

Differential screening of a cDNA library prepared from chicken mitochondrial DNA-less cells led to the isolation of the acidic phosphoprotein PO, as inferred from similar sequences from human, rat and mouse deposited in databases. The chicken PO protein is highly conserved among vertebrates. Nucleotide identities between the chicken and mammalian cDNA sequences are greater than 94%. Amino acid sequence identities greater than 92% are observed between the chicken protein and its mammalian counterparts, and when changes to conservative amino acids are considered, similarities range from 99.4 to 100%. The gene evolved mainly by silent transitions occurring at the third codon position. The highly antigenic carboxy-terminal sequences of mammalian PO proteins are identical to that of the chicken. Southern blot analysis of restricted DNA from chicken embryo fibroblasts suggests that only one gene encoding PO exists in the chicken genome. By Northern analysis, the PO probe detects a major RNA species 1.1-kilobases long, and a minor species 4.0-kilobases long which has no equivalent thus far in mammals.

Tumor-forming ability in athymic nude mice of human cell lines devoid of mitochondrial DNA

We have examined the contribution of the mitochondrial genome to the tumorigenic phenotype expressed by human cell lines derived from an ovarian and a cervical carcinoma and from an osteogenic sarcoma. All these continuous cell lines are anchorage-independent in soft agar and form tumors in athymic nude mice. Long-term exposure of the cells to ethidium bromide, an intercalating agent which inhibits mitochondrial DNA replication, gave rise to subclones depleted of mitochondrial DNA and RNA molecules and displaying either anchorage independence or dependence. These respiratory-deficient subclones contain disorganized and enlarged mitochondria, are auxotrophic for uridine and pyruvate, and grow in vitro at a rate nearly identical or moderately slower than their respective parent. The tumor-forming ability of both anchorage-independent and -dependent cell lines was tested by s.c. and intramuscular implantation of the cells in nude mice. We found that the tumorigenic capacity was influenced by the route of inoculation. Subcutaneously, mitochondrial DNA-less cell lines are either poorly or nontumorigenic, while all but one cell line form tumors when implanted into the hind leg muscle. The relative in vivo growth rate of the parent and the mitochondrial DNA-less subclones reflects their respective in vitro rate of growth. All intramuscular tumors introduced into culture mimic the molecular and phenotypic traits of the injected cells, with the exception of the anchorage-dependent cell lines which give rise to anchorage-independent tumor cell lines. The present observations indicate that human cells without mitochondrial DNA have the capacity to proliferate and form tumors in vivo.

Evolution of the WANCY region in amniote mitochondrial DNA

In most vertebrate mitochondrial genomes, the site for initiation of light-strand replication, OL, is found within a cluster of five transfer RNA (tRNA) genes (tRNA(Trp), tRNA(Ala), tRNA(Asn), tRNA(Cys), and tRNA(Tyr)). This region and part of the adjacent cytochrome c oxydase subunit I (COI) gene were sequenced for two crocodilian, two turtle, and one snake species and for Sphenodon punctatus; part of the adjacent nicotinamide adenine dinucleotide dehydrogenase subunit 2 (ND2) gene was also sequenced for the crocodilian and turtle species. All had the typical vertebrate gene order. The turtles and the snake have a lengthy noncoding sequence between the tRNA(Asn) and tRNA(Cys) genes that we assumed to be homologous to the mammalian OL. The crocodilians and Sphenodon lack such a sequence, a condition they share with birds. Most proposed phylogenies for the amniotes require that OL at this position was lost at least twice during their diversification or was evolved independently more than once. Within the five tRNA genes, frequencies of substitutions are much higher in loops than in stems. Many loops vary dramatically in size among the species; in the most extreme case, the D-arm of the Sphenodon tRNA(Cys) is a "D-arm replacement" loop of seven nucleotides. Frequency of transitions in stems is relatively uniform across tRNAs, but frequency of transversions varies greatly. Mismatches in stems are infrequent, and their relative frequency in a specific tRNA is unrelated to the frequency of substitution in the corresponding gene. Several features of mammalian mitochondrial tRNAs are conserved in WANCY tRNAs throughout amniotes. The inferred initiation codon for COI is GTG in crocodilians, turtles, and the snake, a condition they share with fishes, certain amphibians, and birds. TTG appears to be the initiation codon for COI in Sphenodon; if correct, this would be a novel initiation codon for vertebrate mitochondrial DNA. Phylogenetic analyses of the inferred amino acid sequences of ND2 and COI support the sister-group relationship of birds and crocodilians and suggest that mammals are an early derived lineage within the amniotes.

Cloning and characterization of a cDNA encoding elongation factor 1 alpha from chicken cells devoid of mitochondrial DNA

Using a subtractive hybridization procedure, we isolated a cDNA clone encoding elongation factor 1 alpha (EF-1 alpha) from chicken cells devoid of mitochondrial (mt) DNA (rho0). The sequence encodes 1691 nucleotide (nt) residues and contains an open reading frame of 463 codons. Compared with the sequences from human, mouse and Xenopus laevis, the highest degree of sequence identity is detected in the 3' untranslated (> 90%) and coding (> 85%) regions. The gene evolved mainly by transitions occurring at the third codon position. Most transitions are silent and amino acid (aa) sequence identities are greater than 95%. Comparison of the protein domains interacting with cellular components (GTP/GDP, tRNAs and beta-actin) reveals that they are highly conserved in species belonging to the four traditional eukaryotic kingdoms. The expression of the EF-1 alpha transcript is elevated in chicken rho0 cells. A single RNA band at 1800 nt is observed in both parental and rho0 cells. Southern blot analysis of restricted DNA from chick embryo fibroblasts (CEF) suggests that only one gene encoding EF-1 alpha exists in the chicken genome.

Nucleotide sequence of the hemG gene involved in the protoporphyrinogen oxidase activity of Escherichia coli K12

The hemG gene of Escherichia coli K12 is involved in the activity of protoporphyrinogen oxidase, the enzyme responsible for the conversion of protoporphyrinogen IX into protoporphyrin IX during heme and chlorophyll biosynthesis. The gene is located at min 87 on the genetic map of E. coli K12. The hemG gene was isolated by a mini-Mu in vivo cloning procedure. As expected, the hemG gene is able to restore normal growth to the hemG mutant, and the transformed cells display strong protoporphyrinogen oxidase activity. Sequencing of the hemG gene allowed us to identify an open reading frame of 546 nucleotides (181 amino acids), within the minimal fragment able to complement the mutant. The presumed molecular mass of the HemG protein is 21,202 Da, in agreement with values found by SDS-PAGE, in a DNA-directed coupled transcription-translation system. The identity of the first 18 amino acids at the amino-terminal end of the protein was confirmed by microsequencing. To our knowledge, this is the first cloning of a gene involved in the protoporphyrinogen oxidase activity of E. coli.

Molecular characterization and evolution of a duck mitochondrial genome

We sequenced 6,478 bp of mitochondrial DNA from Peking duck (Anas platyrhyncos). Eight protein genes, 11 tRNAs, part of the small and large ribosomal subunits, and the control region sequences were compared to homologous chicken sequences. The gene organization in duck and chicken is identical but differs from other vertebrates in the juxtaposition of the tRNA(Glu)-ND6 genes next to the control region and in the lack of a hairpinlike structure between the genes for tRNA(Asn) and tRNA(Cys) used for light-strand replication. Protein, tRNA, and rRNA genes evolved mainly through base substitutions and small insertions and deletions. Transitions greatly outnumber transversions in the tRNA and rRNA genes, but this bias is not evident in protein genes; the control region has a higher proportion of transversions. The duck and chicken control regions show a high frequency of length mutations. Large A-T-rich nucleotide stretches dispersed across the region between the bidirectional transcription promoter and the heavy-strand replication origin in the chicken are absent in the duck. Sequence elements for heavy-strand replication in mammals are conserved in the duck and chicken control regions. Estimates of divergence for ribosomal RNAs and proteins based on total substitutions, transversions, and amino acid replacements show that all the duck/chicken values are lower than the corresponding mammal/mammal (cow, human, mouse) values. If paleontological data suggesting that avian and eutherian ordinal radiation occurred at approximately the same time are correct, this suggests that at great evolutionary distance, rate of mitochondrial DNA evolution in birds is somewhat decelerated compared to mammals.

Stereology of the pterygopalatine ganglion of the rat

The right pterygopalatine ganglia (PG) of 9 male Wistar-strain rats were dissected, embedded in Epon (3 specimens) or paraffin (6 specimens), and prepared for stereological examination under light microscopy. The perikarya were quantitatively characterized, and the ganglionic volume was determined. Stereology is an efficient method for the quantitative evaluation of the perikarya of the PG. The results(expressed as mean +/- standard deviation) were: a) areal fraction occupied by the perikarya = 53.8 +/- 7.4%; b) the perikaryal surface area per volume = 0.101 +/- 0.013 microns-1; c) the number of perikarya per volume x 10(-5) = 5.26 +/- 0.99 microns-3; d) the mean profile area of the perikarya (apk) = 505.93 +/- 78.29 microns 2; e) the mean perikaryal volume (vpk) = 9,179.33 +/- 1,533.52 microns 3; and f) the ganglionic volume = 0.210 +/- 0.127 mm3. The low coefficient of variation the apk and vpk values suggests the presence of only one population of neurons in the PG of the rat. The number of perikarya in the PG is about 11,046 per ganglion. As compared to analogous data in the otic ganglion of the rat, the PG did not show statistically significant stereological differences, but the relatively higher number of neurons found in the PG is probably associated with the higher functional activity of this ganglion.

On the tumorigenicity of mitochondrial DNA-depleted avian cells

We have examined the tumorigenic potential of mitochondrial DNA-depleted (mtDNA-) cells derived from the tumorigenic chicken cell line DU24. The mtDNA- cells were unable to proliferate in the wing web of day-old chicks. Cytoplasmic hybrids resulting from crosses between the mtDNA- whole cells and cytoplasts from enucleated parental cells (mtDNA+) recover both mtDNA and tumorigenicity. These results are in accordance with those obtained in prior experiments where mtDNA was shown to modulate the anchorage-independent phenotype of transformed avian cells.

The transcription of DNA in chicken mitochondria initiates from one major bidirectional promoter

Transcription start sites of chicken mitochondrial DNA have been mapped in the control region by direct sequencing of in vitro capped mitochondrial RNA species, by primer extension and by S1 nuclease protection analysis. Transcription of the heavy strand initiates predominantly at a site 156 nucleotides upstream of the tRNA(Phe) gene, i.e. about 135 nucleotides further upstream than the corresponding sites in amphibia and mammals. On the opposite strand, transcription starts predominantly one nucleotide removed from the site in the heavy strand. The L-strand position start site is similar to that found in other vertebrates. The chicken mitochondrial DNA control region thus contains one major transcriptional promoter, whose bidirectional capacity is similar to the situation in amphibia but which contrasts to the mainly unidirectional capacity of mammalian promoters. In chicken mitochondria, the sequence comprising the start sites is A + T rich and contains an almost perfect inverted repeat which can be folded into a cruciform structure. The heavy and light strand initiation sites are flanked on their respective 3' ends by an octanucleotide sequence matching those surrounding the start sites in Xenopus laevis (5'-ACPuTTATA-3'). This motif is found associated with the H-strand start sites in mouse but is not present in human nor bovine mitochondrial DNA promoters.

Nucleotide sequence and evolution of coding and noncoding regions of a quail mitochondrial genome

Segments of the Japanese quail mitochondrial genome encompassing many tRNA and protein genes, the small and part of the large rRNA genes, and the control region have been cloned and sequenced. Analysis of the relative position of these genes confirmed that the tRNA(Glu) and ND6 genes in galliform mitochondrial DNA are located immediately adjacent to the control region of the molecule instead of between the cytochrome b and ND5 genes as in other vertebrates. Japanese quail and chicken display another distinctive characteristic, that is, they both lack an equivalent to the light-strand replication origin found between the tRNA(Cys) and tRNA(Asn) genes in all vertebrate mitochondrial genomes sequenced thus far. Comparison of the protein-encoding genes revealed that a great proportion of the substitutions are silent and involve mainly transitions. This bias toward transitions also occurs in the tRNA and rRNA genes but is not observed in the control region where transversions account for many of the substitutions. Sequence alignment indicated that the two avian control regions evolve mainly through base substitutions but are also characterized by the occurrence of a 57-bp deletion/addition event at their 5' end. The overall sequence divergence between the two gallinaceous birds suggests that avian mitochondrial genomes evolve at a similar rate to other vertebrate mitochondrial DNAs.

Transplantability of myelocytomatosis MC29 virus-producing cell lines in chicken. Lateral transformation of host cells

The transplantability of myelocytomatosis MC29 virus-producing chicken cell lines BR-3 and OB-1 was examined in 1-day-old chicks. Both cell lines, derived from the chicken cell line DU249, harbor nuclear genetic markers for drug resistance. When these cells were inoculated subcutaneously in the wing web of chicks, tumors developed at the site of injection in 65% of the cases. Propagation in culture of cells obtained by dispase treatment of the excised tumors, followed by selection for drug resistance, revealed that only a fraction of the tumors (27% and 60% for BR-3 and OB-1, respectively) resulted from the growth of the injected cells. The other tumors derive from the proliferation of host cells transformed by MC29 virus released by the injected cells. Tumor development subsequent to similar inoculation of 1-day-old chicks with cell-free virus stock further confirmed the tumorigenic capacity of MC29 at the site of injection. These results underline the need for the determination of tumor cell origin in studies using MC29-producing cell lines and highlight the advantage of using cells with drug-resistant markers for such work. In the course of this study we determined by immunohistochemical criteria, the myogenic origin of some of the virally induced tumors. This is the first report of in vivo transformation of muscle cells by MC29-containing virus stocks in the newly hatched chick.

Mitochondrial DNA modulation of the anchorage-independent phenotype of transformed avian cells

The progressive loss of mitochondrial DNA in the presence of ethidium bromide in immortal avian cell lines correlates with a decrease in their potential for anchorage-independent growth in soft agar. In short-term treated cells, this effect is reversible and the recovery of cloning potential parallels the recovery of control levels of mitochondrial DNA. Long-term ethidium-bromide-treated cells are permanently respiration-deficient and display anchorage-dependent growth. Anchorage-independent revertants can be selected, suggesting that the lack of a respiratory chain per se might not be responsible for the inability of mitochondrial DNA-depleted cells to grow in soft agar. Cybrids formed from the fusion of mitochondrial DNA-depleted, anchorage-dependent cells to cytoplasts from parental cells are capable of growth in soft agar. The mitochondria-specific inhibitor, rhodamine 6G, prevents the recovery of the anchorage-independent phenotype in similar hybrids. These results suggest that mitochondrial DNA is required to maintain the transformed phenotype of avian cells.

Gene organization of the Peking duck mitochondrial genome

The gene organization of the Peking duck mitochondrial (mt)DNA has been deduced through heterologous hybridization using different cloned fragments of the chicken or Japanese quail mitochondrial genome as probes. As in the chicken, and other gallinaceous birds, the Peking duck mtDNA displays a novel gene order which differs from that of other vertebrates by the unusual localization of the tRNA(Glu) and ND6 genes next to the displacement (D) loop region of the molecule. The position of these genes with respect to the mitochondrial D-loop region, the cytochrome oxidase subunits I, II and III, the NADH dehydrogenase subunit I and the ribosomal (r) RNAs, was confirmed by the partial nucleotide sequence of cloned mtDNA fragments.

Sequence and gene organization of the chicken mitochondrial genome. A novel gene order in higher vertebrates

The 16,775 base-pair mitochondrial genome of the white Leghorn chicken has been cloned and sequenced. The avian genome encodes the same set of genes (13 proteins, 2 rRNAs and 22 tRNAs) as do other vertebrate mitochondrial DNAs and is organized in a very similar economical fashion. There are very few intergenic nucleotides and several instances of overlaps between protein or tRNA genes. The protein genes are highly similar to their mammalian and amphibian counterparts and are translated according to the same variant genetic code. Despite these highly conserved features, the chicken mitochondrial genome displays two distinctive characteristics. First, it exhibits a novel gene order, the contiguous tRNA(Glu) and ND6 genes are located immediately adjacent to the displacement loop region of the molecule, just ahead of the contiguous tRNA(Pro), tRNA(Thr) and cytochrome b genes, which border the displacement loop region in other vertebrate mitochondrial genomes. This unusual gene order is conserved among the galliform birds. Second, a light-strand replication origin, equivalent to the conserved sequence found between the tRNA(Cys) and tRNA(Asn) genes in all vertebrate mitochondrial genomes sequenced thus far, is absent in the chicken genome. These observations indicate that galliform mitochondrial genomes departed from their mammalian and amphibian counterparts during the course of evolution of vertebrate species. These unexpected characteristics represent useful markers for investigating phylogenetic relationships at a higher taxonomic level.

Histidine tRNA from chicken mitochondria has an uncoded 5'-terminal guanylate residue

In an attempt to identify the transcription initiation sites in chicken mitochondrial DNA, RNAs capped in vitro using vaccinia guanylyl transferase and [alpha-32P] GTP were analyzed. The most abundant labeled transcript was identified by RNA sequencing as the mitochondrial tRNA(His). Sequence analysis also revealed that this tRNA contains an extra guanylate residue at its 5' end, characteristic of the histidine tRNA family. The respective genomic region was also cloned and sequenced. In contrast to bacteria and the mitochondria of fungi and plants, the extra G of chicken mitochondrial tRNA(His) is not encoded in the gene. Therefore, the guanylate residue must be added post-transcriptionally, as demonstrated for the nuclear tRNA(His) in yeast and Drosophila. Analysis of a capped tRNA(His) precursor of chicken mitochondria suggests that addition of the extra G occurs independently of 3' end maturation. Since in the chicken mitochondrial tRNA(His) the extra G can be efficiently labeled by the capping assay, it should possess a 5'-terminal di- or triphosphate, which contrasts to the 5'-terminal monophosphate proposed for the nuclear encoded tRNA(His). Our results imply that the ability of a mitochondrial RNA to be capped in vitro does not necessarily prove that it contains a transcription initiation site.

Putative chicken "muscle-specific 7 S RNA" is related to the mitochondrial ATPase 6 gene

Sequence analysis of the mitochondrial ATPase 6 gene from chicken revealed that its 3' region is virtually identical with a chicken muscle-specific 7 S RNA which was reported to induce the expression of tissue-specific functions in blastoderm explants. Using chicken and quail cell lines depleted of mitochondrial DNA, we demonstrate that the 7 S RNA is encoded by the mitochondrial genome and not by nuclear (repetitive) DNA as suggested previously. Moreover, no 7 S RNA-homologous transcript of the expected length (about 400 bases) is detected, either in these cell lines or in heart and liver tissues. The only RNA species hybridizing with a 7 S RNA-specific probe is an abundant, 900 base long transcript of mitochondrial origin that we identify as the ATPase 8-ATPase 6 fused messenger. We suggest that the characterized muscle-specific 7 S RNA cDNA is derived from an unrelated contaminant in the blastoderm-inducing fraction.

[Experience and results with a lactate dehydrogenase marker in vaginal secretions of women at high risk for endometrial cancer]

The authors present and discuss the results obtained with 202 Gynaegnost experiments in 161 women, between 45 and 65 years, nulliparous, or having experienced a late pregnancy, with menopause occurring after the age of 52 and undergoing or not estrogen-therapy after menopause, and presenting high blood pressure, obesity or diabetes. The purpose of this multicenter study, to be continued, was to demonstrate the efficacy of this tumor marker, in the early diagnosis of endometrial carcinoma, in high-risk women.

Development and characterization of continuous avian cell lines depleted of mitochondrial DNA

Populations of quail and chicken cells were treated with ethidium bromide, an inhibitor of mitochondrial DNA replication. After long-term exposure to the drug, the cell populations were transferred to ethidium bromide (EtdBr)-free medium, and cloned. Clones HCF7 (quail) and DUS-3 (chicken) were propagated for more than a year, and then characterized. Analysis of total cellular DNA extracted from these cells revealed no characteristic mitochondrial DNA molecule by Southern blot hybridization of HindIII- or AvaI-digested total cellular DNA probed with cloned mitochondrial DNA fragments. Reconstruction experiments, where a small number of parental cells was mixed with HCF7 cells and DUS-3 cells before extraction of total cellular DNA, further strengthen the notion that the drug-treated cells are devoid of mitochondrial DNA molecules. The cell populations were found to proliferate at a moderately reduced growth rate as compared to their respective parents, to be auxotrophic for uridine, and to be stably resistant to the growth inhibitory effect of EtdBr and chloramphenicol. At the ultrastructural level, mitochondria were considerably enlarged and there was a severe reduction in the number of cristae within the organelles and loss of cristae orientation. Morphometric analysis revealed a fourfold increase of the mitochondrial profile area along with a twofold decrease of the numerical mitochondrial profiles. Analysis of biochemical parameters indicated that the cells grew with mitochondria devoid of a functional respiratory chain. The activity of the mitochondrial enzyme dihydroorotate dehydrogenase was decreased by 95% and presumably accounted for uridine auxotrophy.

Development and characterization of mutant chicken cell lines for somatic cell genetics studies

A series of stable mutants bearing nuclear genetic markers were developed from the established chicken cell line DU24. The mutants were obtained after mutagenesis of DU24 cells with ethyl methanesulfonate (EMS) or arose spontaneously when plated in the appropriate selective medium. Clones resistant to 5-bromodeoxyuridine (BrdU) were obtained following a two-step selection procedure and analyzed. The BrdUr cells were found to be deficient in thymidine kinase activity and were HAT sensitive. Molecular characterization of these mutants revealed no deletions or other rearrangements, but methylation of some cytosine residues was decreased in the mutants. A similar restriction profile was seen in a series of mutants made resistant to BrdU after cultivation of DU24 cells in increasing concentrations of the drug over a period of six months. Selection of EMS-treated BrdUr cells in 10 microM ouabain gave rise to a clone resistant to both drugs and which was still HAT sensitive. Clones resistant to 6-thioguanine were also isolated, but showed wild-type hypoxanthine phosphoribosyltransferase activity and were HAT resistant. A number of the cell lines isolated were found to be suitable for fusion experiments with both chicken cells and cells from other vertebrate species.

An established avian fibroblast cell line without mitochondrial DNA

An established avian fibroblast cell line (LSCC-H32) has been found to be inherently resistant to the growth-inhibitory effect of ethidium bromide, when supplied with exogenous uridine. After long-term exposure to ethidium bromide (90 days), the cell population has been transferred to drug-free medium for 60 days, and then seeded at low cell density. Three clones have been isolated and propagated in drug-free medium for 5, 6, and more than 12 months, respectively. It was found that none of these cell lines had detectable cytochrome c oxidase activity and that they were virtually devoid of cytochromes aa3 and b. Mitochondrial DNA was quantitated by DNA-DNA reassociation kinetics with a probe of chicken liver mitochondrial DNA. A mean number of 300 copies of mitochondrial DNA per cell was found in LSCC-H32 cells. Analysis of DNA extracted from cell populations exposed to ethidium bromide for 90 days and then transferred to drug-free medium for long periods of time revealed no mitochondrial DNA molecules by reassociation kinetics or by Southern blot hybridization of HindIII-or AvaI-digested total cellular DNA.

Degenerative changes, DNA synthesis and mitotic activity in rat liver following single exposure to diethylnitrosamine

Degenerative and regenerative changes induced in rat liver by single exposure to diethylnitrosamine (DEN) were examined by morphological and biochemical approaches. Apoptotic changes were observed in livers of rats exposed to a 'subnecrogenic' dose of DEN (10 mg/kg) as well as in liver parenchyma of those receiving a necrogenic dose (100 mg/kg). Zonal centrilobular necrosis was observed exclusively in the latter group. Regenerative changes, i.e., increases in DNA synthesis, labeling index and mitotic activity, occurred only in animals exposed to the higher dose. The mitogenic effect obtained in these conditions was about half that induced by two-thirds hepatectomy and the maximum response occurred about 24 h later than in partially hepatectomized rats.