Human connexin 37 is polymorphic but not mutated in tumours

Connexins are phylogenetically conserved proteins responsible for gap junctional intercellular communication (GJIC). In tumours, GJIC is frequently disrupted. We have tested the hypothesis that the connexin 37 (Cx37) gene might be mutated in human tumours from tissues in which the Cx37 gene is known to be expressed. Eight lung adenocarcinomas and 18 sporadic breast carcinomas were analysed. While most tumours had GTA at codon 130, a base change GTA-->ATA converting valine into isoleucine was found in three breast cancers (one homozygous for ATA) and two lung tumour samples. However, screening of normal DNA from the same patients and DNA from 42 healthy donors revealed that such base change also exists in normal tissue. Thus, we conclude that there is polymorphism of the connexin 37 gene in the human population. This is the first finding of polymorphism in the connexin gene family.

High-dose but not low-dose dexamethasone impairs glucose tolerance by inducing compensatory failure of pancreatic beta-cells in normal men

The diabetogenic effects of glucocorticoids appear to be dose dependent. To determine the effects of different doses of dexamethasone on glucose metabolism, we performed frequently sampled intravenous glucose tolerance tests in 20 healthy young men. Glucose kinetics were analysed by the minimal model. Ten subjects received low-dose dexamethasone (2 mg/day) for 3 days, and the other 10 received high-dose dexamethasone (6 mg/day) for 3 days. The rate of glucose disappearance (KG) did not decrease in the low-dose group (2.46 +/- 0.20 to 2.19 +/- 0.11% min-1, P = 0.35). In contrast, KG in the high-dose group did decrease significantly (2.43 +/- 0.29 to 1.81 +/- 0.11% min-1, P < 0.05). The factor responsible for the decline in KG in the high-dose group was not glucose effectiveness because these values did not change in either group. The insulin sensitivity decreased significantly, by 46% in the low-dose group and 69% in the high-dose group [17.1 +/- 2.7 to 9.2 +/- 1.5 and 18.5 +/- 3.7 to 5.8 +/- 0.9 x 10(-5) min-1 (pmol/L)-1, P < 0.001 and P < 0.01, respectively]. The insulin area (0-20 min) increased significantly, by 104% in the low-dose group and 114% in the high-dose group [3412.6 +/- 609.7 to 6972.7 +/- 1450.1 and 4086.7 +/- 864.5 to 8750.0 +/- 1451.6 (pmol/L) min, P < 0.01 and P < 0.01, respectively]. Insulin sensitivity x insulin area as an estimate of insulin-dependent glucose uptake and insulin's action to suppress hepatic glucose production decreased significantly in the high-dose group (0.588 +/- 0.112 to 0.441 +/- 0.073, P < 0.05), but did not change in the low-dose group (0.436 +/- 0.050 to 0.484 +/- 0.032, P = 0.77). Therefore, the decline in KG in the high-dose group may be associated with the compensatory failure of pancreatic beta-cells against for the insulin resistance.

Nongenotoxic carcinogens: development of detection methods based on mechanisms: a European project

While the accumulation of genetic changes in a somatic cell is considered essential for the genesis of a cancer, it has become clear that not all carcinogens are genotoxic, suggesting that some carcinogens indirectly participate in the generation of genetic changes during carcinogenesis. A European project funded by the European Community was thus conceived to study mechanisms of nongenotoxic aspects of carcinogenesis. Two main strategical approaches were adapted: (i) to study whether and how Syrian hamster embryo (SHE), Syrian hamster dermal (SHD) and BALB/c 3T3 cell transformation systems simulate in vivo carcinogenesis, and to examine whether they can detect nongenotoxic carcinogens; (ii) to study, refine and validate mechanisms-based end-points for detection of nongenotoxic carcinogens. For mechanisms-based research, the proposed end-points included gap junctional intercellular communication (GJIC) inhibition, altered expression of critical genes, immortalization and aberrant cell proliferation. We also selected model compounds commonly usable for various endpoints. Our major results can be summarized as follows: (1) SHE and BALB/c 3T3 transformation systems reflect both genotoxic and nongenotoxic carcinogenic events; they detect not only genotoxic but also many although not all, nongenotoxic carcinogens. This is further supported by the fact that both genotoxic and nongenotoxic carcinogens were able to immortalize SHD cells. (2) Many nongenotoxic carcinogens, although not all, inhibit GJIC in vitro as well as in vivo. Mechanistic studies suggest an important role of blocked GJIC in carcinogenesis and that different mechanisms are involved in inhibition of the communication by different agents used. However, inhibition of GJIC is not a prerequisite for the enhancement (or induction) of transformation of SHE or BALB/c 3T3 cells. (3) Among compounds examined, there was a good correlation between induction of micronuclei and cell transformation in SHE cells while no such correlation was found between the induction of cell transformation and ornithine decarboxylase activity. (4) Two transgenic mouse mutation assays (lacI and lacZ) were established and validated. The genotoxin dimethylnitrosamine was shown to be mutagenic to the liver in both assays. Ortho-anisidine, a bladder-specific carcinogen that was inactive in standard rodent genetic toxicity assays was uniquely mutagenic to the bladder of the transgenic mice. The peroxisome proliferator methyl clofenipate was established as nonmutagenic to the liver of both transgenic mice. That eliminated DNA damage as a cause of the liver tumours produced by this chemical and weakened the idea that induced cell division leads to mutation induction. (5) With an in vitro DNA replication model, it was found that DNA damage induced by genotoxic agents can be responsible for inhibition of DNA replication, while certain nongenotoxic agents such as phorbol esters increase DNA replication. (6) An attempt to use structure-activity relationship for subfamilies of nongenotoxic carcinogens, e.g., receptor-mediated carcinogens, has been initiated with some promising results. Our results support the idea that there are multiple nongenotoxic mechanisms in carcinogenesis, and that working hypothesis-oriented approaches are encouraged rather than simple screening of chemicals in developing test systems for the detection of nongenotoxic carcinogens.

Hypersensitivity pneumonitis induced by a smut fungus Ustilago esculenta

A case of hypersensitivity pneumonitis caused by a smut fungus Ustilago esculenta is presented.

Connexin 32 mutations from X-linked Charcot-Marie-Tooth disease patients: functional defects and dominant negative effects

We have characterized the function of connexin (Cx) 32 gene mutations found in X-linked dominant Charcot-Marie-Tooth disease with respect to their ability to form functional gap junctions among themselves and to inactivate wild-type Cx32 by a dominant negative mechanism. We prepared four types of Cx32 mutant cDNAs and transfected them into HeLa cells, which do not show detectable levels of gap junctional intercellular communication (GJIC), nor expression of any connexins examined. Cells transfected with the wild-type Cx32 gene, but not those transfected with three different base substitution mutations (i.e. Cys 60 to Phe, Val 139 to Met, and Arg 215 to Trp), restored GJIC. Unexpectedly, in cells transfected with a nonsense mutant at codon 220, there was also restored GJIC. When we double-transfected these mutant constructs into the HeLa cells that had already been transfected with the wild-type Cx32 gene and thus were GJIC proficient, three base substitution mutants inhibited GJIC, suggesting that these three mutants can eliminate the function of wild-type Cx32 in a dominant negative manner. The nonsense mutation at codon 220 did not show such a dominant negative effect. Since both mutant and wild-type Cx32 mRNAs were detected, but only poor Cx32 protein expression at cell-cell contact areas was observed in the double transfectants, it is suggested that certain mutants form nonfunctional chimeric connexons with wild-type connexins, which are not properly inserted into the cytoplasmic membrane.

Fluctuation analysis of myosin-coated bead movement along actin bundles of Nitella

Movements of myosin-coated magnetic beads on the actin bundles of Nitella axilliformis were studied using fluctuation analysis. Regulated force applied by magnetic field could hold magnetic beads stationary against their driving force. Thus beads selected by the same magnetic force had almost the same number of active motor proteins. When the magnetic field was switched off, the beads began sliding again and reached a steady sliding velocity. The fluctuations of bead movements were estimated from the deviations of displacement and those of velocity. The results indicate that (1) the mean step-size was 6.8 nm, and (2) the equivalent stiffness of motor proteins increased during the steady sliding compared with the stationary state.

Purification and molecular characterization of a novel b5-type cytochrome of the parasitic nematode, Ascaris suum

A b5-type cytochrome was extracted from Ascaris suum muscle at pH 4.5 with 0.3% aluminum sulfate and purified by ammonium sulfate fractionation, ion-exchange chromatography on CM-500 Cellulofine, and gel filtration on Sephadex G-75. The hemoprotein displayed a typical absorption spectrum of cytochrome b with a midpoint redox potential of 78 mV. The N-terminal amino acid sequence was determined and revealed the N-terminus to be highly homologous to the heme-binding domain of vertebrate cytochrome b5. Using an oligonucleotide probe synthesized based on the amino acid sequence of the purified protein, the cDNA clone encoding A. suum cytochrome b5 was isolated from the lambda ZAP II cDNA library. The entire nucleotide sequence of 563 bases comprised an open reading frame of 339 bases encoding a precursor protein of 112 amino acid residues. The purified cytochrome B5 was predicted to contain 82 amino acids with a molecular mass of 9141 Da, matching the 9140 Da obtained from electrospray ionization mass spectometry, and to lack of membrane-anchor domain at the C-terminus. In contrast, an N-terminal extension of 30 amino acids, characteristic of signal peptides, was apparent. Immunoblots revealed the presence of an A. suum cytochrome b5 of 82 amino acids, but no protein with an N-terminal extension. These results demonstrate a novel cytochrome b5 possessing a presequence.

TNF-alpha stimulates glucose uptake in L6 myoblasts

The mechanism of TNF-alpha to regulate glucose metabolism remains unclear. To further delineate the TNF-alpha signal transduction pathway mediating glucose metabolism, we utilized L6 rat myoblasts which contain the receptors for the insulin-like growth factor-I (IGF-I) and TNF-alpha, and the ability of both ligands to stimulate glucose uptake was compared. IGF-I (6.5 nM) maximally stimulated glucose uptake 7-fold after 24 h incubation, while 23 nM TNF-alpha maximally stimulated glucose uptake 3-fold only after 48 h incubation. IGF-I receptor beta-subunit, insulin receptor substrate-1 (IRS-1), and mitogen-activated protein (MAP) kinase were all phosphorylated in response to 6.5 nM IGF-I after 10 min incubation. In contrast, the treatment with 23 nM TNF-alpha failed to phosphorylate either IGF-I receptor beta-subunit or IRS-1 but did phosphorylate MAP kinase as much as IGF-I did. Despite a similar extent to which TNF-alpha induced MAP kinase phosphorylation as IGF-I did, TNF-alpha stimulated glucose uptake less compared to IGF-I. The results indicate that MAP kinase phosphorylation is not sufficient for glucose uptake in L6 myoblasts. TNF-alpha-elicited signal transduction to glucose uptake may utilize a different pathway from that seen with IGF-I.

Bystander killing of cancer cells by herpes simplex virus thymidine kinase gene is mediated by connexins

In gene therapy to treat cancer, typically only a fraction of the tumor cells can be successfully transfected with a gene. However, in the case of brain tumor therapy with the thymidine kinase gene from herpes simplex virus (HSV-tk), not only the cells transfected with the gene but also neighboring others can be killed in the presence of ganciclovir. Such a "bystander" effect is reminiscent of our previous observation that the effect of certain therapeutic agents may be enhanced by their diffusion through gap junctional intercellular communication (GJIC). Herein, we present the evidence, from in vitro studies, that gap junctions could indeed be responsible for such a gene therapy bystander effect. We used HeLa cells for this purpose, since they show very little, if any, ability to communicate through gap junctions. When HeLa cells were transfected with HSV-tk gene and cocultured with nontransfected cells, only HSV-tk-transfected HeLa cells (tk+) were killed by ganciclovir. However, when HeLa cells transfected with a gene encoding for the gap junction protein, connexin 43 (Cx43), were used, not only tk+ cells, but also tk- cells were killed, presumably due to the transfer, via Cx43-mediated GJIC, of toxic ganciclovir molecules phosphorylated by HSV-tk to the tk- cells. Such bystander effect was not observed when tk+ and tk- cells were cocultured without direct cell-cell contact between those two types of cells. Thus, our results give strong evidence that the bystander effect seen in HSV-tk gene therapy may be due to Cx-mediated GJIC.

Lack of tumor-promoting effects of flavonoids: studies on rat liver preneoplastic foci and on in vivo and in vitro gap junctional intercellular communication

Possible tumor-promoting activity of four flavonoids, quercetin (QC), tangeretin (TG), flavone (FO), and flavanone (FN), was examined in a rat liver short-term carcinogenesis assay as well as with in vivo and in vitro assays of inhibition of gap junctional intercellular communication (GJIC). Rat hepatocarcinogenesis was induced by aflatoxin B1 treatment followed by a selection phase (2-acetylaminofluorene treatment and partial hepatectomy), then treatment with or without test chemicals (in vivo studies of antipromotion were not performed). Using glutathione S-transferase placental form (GST-P)-positive foci, we compared the effects of flavonoids (at 1,000 ppm in the diet) with the effects of phenobarbital (PB) on the occurrence of liver preneoplastic lesions. In addition, we studied the effects of flavonoids on GJIC in the livers derived from these experiments and in two types of cultured cells. No significant difference in the number and area of GST-P-positive foci was found after one or three months of treatment between any flavonoid group and control group. In the positive control group, PB markedly increased the numbers and areas of preneoplastic lesions at three months. Whereas PB also decreased by 60% the average size of lucifer yellow dye spread in slices of liver parenchyma free of preneoplastic lesions among the different flavonoids, only TG decreased the dye transfer in vivo: by 30% at one month and 50% at three months. With the dye transfer assay applied to a rat liver epithelial cell line (REL) and the Chinese hamster V79 metabolic cooperation assay, none of the tested flavonoids (< or = 25 microM) inhibited GJIC. Conversely, protective properties were seen for some of the compounds in antipromotion in vitro studies, because TG and FN enhanced the dye transfer in REL cells and FO, TG, and QC partly prevented the inhibition of metabolic cooperation by 12-O-tetradecanoylphorbol-13-acetate. Thus, taken together, our results suggest that QC, FO, and FN do not show tumor-promoting activity. Concerning TG, some discrepancies in the in vivo data are observed. Some of them (GJIC inhibition in liver slices) are probably more relevant to promotion of hepatocarcinogenesis.

Role of blocked gap junctional intercellular communication in non-genotoxic carcinogenesis

Gap junctional intercellular communication mediates the transfer of small molecules from the cytoplasm of one cell to that of neighbouring cells. Connexins are the proteins that form the channels responsible for this type of communication. Aberrant expression and function of connexins are often found in cells exposed to tumor-promoting agents and during carcinogenesis, both in cell culture systems and in tissues freshly removed directly from patients and exposed animals. Transfection of connexin genes into tumorigenic cells often exerts negative growth control, suggesting that connexins act as a family of tumor-suppressor genes. Connexin gene mutations appear to be the cause of two human diseases, i.e. X-linked Charcot-Marie-Tooth syndrome and visceroatrial heterotaxia. Connexin genes are therefore important for the maintenance of homeostasis and thus their dysfunction could lead to various forms of disease.

Tissue distribution of the DNA binding oncoprotein Maf during chicken development

To assess the normal function of the c-maf protooncogene product, we examined its tissue distribution during fetal growth and organogenesis of the chicken using an immunohistochemical technique. Nuclei of neuronal cells in the optic lobe and in the outer granular layer of the cerebral cortex were efficiently stained by anti-Maf serum throughout all developmental stages examined. In the lung, mesenchymal cells were stained intensely by the antiserum, with the most intense staining around embryonic day 15. During the embryonic period, nuclei of mesenchymal cells in the perichondrial and periosteal tissues as well as intestinal submucosa were also stained specifically by the antiserum. In addition, we detected substantial Maf immunoreactivity in nuclei of renal glomerular and proximal-tubular epithelial cells. These results suggest that c-Maf protein plays some important roles in the development of the central nervous system and tissues of mesodermal origin such as connective and renal tissues.

High frequency of Ki-ras amplification and p53 gene mutations in adenocarcinomas of the human esophagus

Mutated ras genes have been found to be conspicuously absent from primary tumors of the esophagus, although high expression of ras p21 oncoprotein in some esophageal squamous cell carcinomas and mutations of the Ki- and Ha-ras genes in esophageal carcinoma cell lines have been reported. In this study, we found amplification of the Ki-ras gene in four of 10 esophageal adenocarcinomas (40%). No such amplification was observed among 61 squamous cell carcinomas, one pseudosarcomatous carcinoma, and eight esophageal cell lines, nor in six adenocarcinomas of the stomach. In two samples on which immunohistochemical analysis could be performed, we found overexpression of Ki-ras proteins when compared with normal samples. This Ki-ras amplification in esophageal tumors did not correlate with any pathological feature of the tumors, with the survival of the patients, or with the presence of other genetic alterations. These findings provide the first evidence for amplification of the Ki-ras gene in human esophageal cancer, which is restricted to adenocarcinomas. We also found that six of eight adenocarcinomas had point mutations in the p53 gene; this is a considerably higher prevalence than that reported for esophageal squamous cell carcinomas. These results strongly suggest that esophageal adenocarcinomas differ from squamous cell carcinomas in their molecular genetic characteristics.

Clofibrate-induced neoplastic development in the rat liver is associated with decreased connexin 32 expression but not with a co-ordinated shift in expression of marker enzymes

Altered enzyme phenotype and expression of connexin 32 (Cx32), a gap junction protein were studied during the development of rat liver tumors induced by the non-genotoxic carcinogen, clofibrate. (1) In contrast to previous findings for nitrosamine-induced lesions, preneoplastic enzyme-altered foci (EAF) and neoplastic nodules (NN) lacked any clear association with degree of altered enzyme expression because of an almost complete negativity for GST-P and GGT. (2) Immunohistochemically demonstrated Cx32 spots on the hepatocyte membranes showed a clear decrease in clofibrate-induced lesions. (3) Naturally occurring EAF demonstrating GST-P and/or GGT positivity did not show a significant decrease of Cx32 counts suggesting a reversible nature. Therefore, the Cx32 decrease appears closely linked to progression of hepatocarcinogenesis irrespective of the enzyme phenotype of neoplastic focal lesions and the carcinogens used for their induction.

Intercellular communication and carcinogenesis

Two types of intercellular communication (humoral and cell contact-mediated) are involved in control of cellular function in multicellular organisms, both of them mediated by membrane-embedded proteins. Involvement of aberrant humoral communication in carcinogenesis has been well documented and genes coding for some growth factors and their receptors have been classified as oncogenes. More recently, cell contact-mediated communication has been found to have an important role in carcinogenesis, and some genes coding for proteins involved in this type of communication appear to form a family of tumor-suppressor genes. Both homologous (among normal or (pre-)cancerous cells) as well as heterologous (between normal and (pre)cancerous cells) communications appear to play important roles in cell growth control. Gap junctional intercellular communication (GJIC) is the only means by which multicellular organisms can exchange low molecular weight signals directly from within one cell to the interior of neighboring cells. GJIC is altered by many tumor-promoting agents and in many human and rodent tumors. We have recently shown that liver tumor-promoting agents inhibit GJIC in the rat liver in vivo. Molecular mechanisms which could lead to aberrant GJIC include: (1) mutation of connexin genes; (2) reduced and/or aberrant expression of connexin mRNA; (3) aberrant localization of connexin proteins, i.e., intracytoplasmic rather than in the cytoplasmic membrane; and (4) modulation of connexin functions by other proteins, such as those involved in extracellular matrix and cell adhesion. Whilst mutations of the cx 32 gene appear to be rare in tumors, cx 37 gene mutations have been reported in a mouse lung tumor cell line. Our results suggest that aberrant connexin localization is rather common in cancer cells and that possible molecular mechanisms include aberrant phosphorylation of connexin proteins and lack of cell adhesion molecules. Studies on transfection of connexin genes into tumor cells suggest that certain connexin genes (e.g., cx 26, cx 43 and cx 32) act as tumor-suppressor genes.

[Effects of weight training on muscle strength and exercise capacity in patients after myocardial infarction]

The effect of combined aerobic and weight training on indexes of muscle strength and exercise capacity was investigated in 59 patients after myocardial infarction. Subjects were randomly assigned into three groups: group I performing combined aerobic and weight training (n = 22), group II performing ordinary aerobic training alone (n = 19) and group III not performing physical training (n = 18). Before and after the training, isokinetic knee extension strength was measured and cardiopulmonary exercise testing was performed. Physical training was prescribed for 8 weeks. Weight training of knee extensors was performed at 60% of 1 repetition maximum and aerobic training was prescribed at the heart rate of anaerobic threshold (AT) level. After 8 weeks, the increase of isokinetic knee extension strength was significantly greater in group I (26 +/- 14%) than group II (6 +/- 8%) and III (4 +/- 8%). Increases in peak VO2, exercise time, AT and peak O2 pulse were greater in groups I and II than group III. Furthermore, increase of exercise time was greater in group I (25 +/- 14%) than group II (16 +/- 9%). The rating of perceived exertion in submaximal exercise decreased significantly only for group I. In patients with myocardial infarction, combined aerobic and weight training is a more effective method for increasing muscle strength and exercise capacity than only ordinary aerobic training.

Expression of AML1 and ETO Transcripts in hematopoietic cells

Recently, two genes, AML1 and ETO have been isolated from the chromosomal breakpoint of t(8;21). In this study, we isolated and identified fusion transcripts from a leukemic cell line carrying t(8;21). We demonstrated by PCR analysis that these transcripts are consistently expressed in fresh leukemic cells with t(8;21). On the other hand, the wild type of ETO is expressed in several hematopoietic cells from different lineage, while the expression of AML1 was present in all hematopoietic cells investigated. These widespread expression suggests these molecules play an essential role in hematopoiesis.

Autoantibodies to glutamic acid decarboxylase in patients with autoimmune thyroid disease: relation to competitive insulin autoantibodies

We evaluated the presence of autoantibodies to glutamic acid decarboxylase (GAD), competitive insulin autoantibodies (IAA) and islet cell antibodies (ICA) in sera from 288 non-diabetic patients with autoimmune thyroid disease (AITD), including 212 patients with Graves' disease and 76 with Hashimoto's thyroiditis, and in 235 age- and sex-matched healthy control subjects. GAD antibodies and IAA were assayed using radioimmunoassay with 125I-labelled purified pig brain GAD and human insulin, respectively. Titers of greater than 4.7 units for GAD antibodies and 50 nU/ml for IAA, respectively, the mean + 3SD of 235 age- and sex-matched healthy individuals, were defined as positive. The mean titers of GAD antibodies in patients with Graves' disease and in patients with Hashimoto's thyroiditis were 3.6 +/- 4.6 (mean +/- SD, range 0.6-52.0) units and 3.2 +/- 1.4 (range 0.6-10.0) units, respectively. Titer of GAD antibodies in patients with AITD was significantly higher than in healthy controls (P < 0.0005). Thirteen of 212 (6.1%) patients with Graves' disease and 6 of 76 (7.9%) patients with Hashimoto's thyroiditis had positive GAD antibody titers, whereas titers in healthy control sera were < 4.7 units in all but two individuals (P < 0.005). In competition analysis with purified unlabelled GAD, binding tracer was inhibited in all of 13 GAD antibody-positive Graves' sera and 5 of 6 GAD antibody-positive sera from patients with Hashimoto's thyroiditis. Eight of 212 (3.8%) patients with Graves' disease and 3 of 76 (3.9%) patients with Hashimoto's thyroiditis, but none of healthy controls had IAA levels exceeding the range for normal controls (P < 0.005). Positive IAA levels ranged between 50 and 2383 nU/ml. Strikingly, all of 19 GAD antibody-positive sera were negative for IAA. ICA were not detected in any of the patients or healthy controls. These data demonstrate that GAD antibodies in sera of AITD patients are of low titer but significantly elevated compared to healthy controls, and are independent of the appearance of IAA. They also indicate that, in patients with AITD, an autoimmune response to GAD may occur with no relationship to production of IAA.

Cell-type-specific ras mutations but no microsatellite instability in chemically induced mouse skin tumors and transformed 3T3 cells

In mouse skin, both papillomas/carcinomas or fibrosarcomas can be induced by 7,12-dimethylbenz[alpha]anthracene (DMBA) depending on the mode of administration. Thus, upon DMBA painting (or transplacental exposure by i.p. injection to pregnant mothers) followed by 12-O-tetradecanoylphorbol-13-acetate applications to the skin of CD1 mice, papillomas and carcinomas appeared, whereas fibrosarcomas were induced when DMBA was s.c. injected. Molecular analysis of these tumors revealed that the majority of papillomas (17/20) and carcinomas (9/10) showed DMBA-specific mutations (A to T transversion at the 61st codon) in the Ha-ras gene. On the other hand, many fibrosarcomas (5/9) showed the same mutation only in the Ki-ras gene. When microsatellites were studied in these tumors at nine loci containing CA repeats, none of them showed an instability. In addition, when we analyzed 14 BALB/c 3T3 cell lines transformed by various carcinogens (including 3 clones induced by DMBA which have the A to T mutation in the Ki-ras gene), no changes in CA repeats were observed. These results suggest that DMBA-induced mouse tumors/transformed cells show cell-type-specific ras gene mutations, and these occur independently in the absence of microsatellite instability. While murine cells are considered to be relatively susceptible to cancer induction partially due to genomic instability, our results indicate that microsatellite instability is not induced in these cells by chemical carcinogens.

The arterial ketone body ratio and serum alpha-fetoprotein level in patients with acute hepatic failure

Hepatocyte regeneration is essential for recovery in acute hepatic failure, although it requires a large amount of energy. The ratio of acetoacetate to beta-hydroxybutyrate in arterial blood has been reported to reflect the cellular energy charge of hepatocytes, and we proposed that the recovery of the ratio in the early days of acute hepatic failure is essential for survival. However, there is no report on any marker of regeneration to confirm this hypothesis. In this study, we have assessed this ratio and the serum alpha-fetoprotein level sequentially in 26 patients with acute hepatic failure. Ten patients recovered and 16 died. The arterial blood ketone body ratio 3 days after the onset of hepatic encephalopathy of grade II or more was below 0.6 in 15 of the 16 nonsurvivors, whereas that in the 10 survivors was above 0.6. There was a positive correlation between the arterial blood ketone body ratio and the maximal concentration of alpha-fetoprotein (r = 0.465, p < 0.02 by Student's t-test). These data indicate that the arterial blood ketone body ratio is a marker for the capacity of the liver to regenerate and for the prognosis in patients with acute hepatic failure: effective hepatocyte regeneration may be impossible if these metabolic changes in acute hepatic failure impair the hepatocyte energy charge severely.