Enteroviral protease 2A cleaves dystrophin: evidence of cytoskeletal disruption in an acquired cardiomyopathy

Enteroviruses such as Coxsackievirus B3 can cause dilated cardiomyopathy, but the mechanism of this pathology is unknown. Mutations in cytoskeletal proteins such as dystrophin cause hereditary dilated cardiomyopathy, but it is unclear if similar mechanisms underlie acquired forms of heart failure. We demonstrate here that purified Coxsackievirus protease 2A cleaves dystrophin in vitro as predicted by computer analysis. Dystrophin is also cleaved during Coxsackievirus infection of cultured myocytes and in infected mouse hearts, leading to impaired dystrophin function. In vivo, dystrophin and the dystrophin-associated glycoproteins alpha-sarcoglycan and beta-dystroglycan are morphologically disrupted in infected myocytes. We suggest a molecular mechanism through which enteroviral infection contributes to the pathogenesis of acquired forms of dilated cardiomyopathy.

Near infra-red interactance for nutritional assessment of dialysis patients

BACKGROUND

Malnutrition is a common problem in dialysis patients and may affect up to one-third of patients. Near-infrared interactance (NIR) is a novel approach to estimate body composition and per cent total body fat.

METHODS

We used near-infrared interactance (Futrex 5000) to estimate the body composition including body fat percentage, as well as subjective global assessment (SGA), anthropometric measurements including mid-arm circumference (MAC), triceps and biceps skinfold thickness, calculated mid-arm muscle circumference (MAMC), body mass index (BMI), and laboratory values. NIR score, SGA assessment and anthropometric parameters were measured shortly after the end of a dialysis session. NIR measurement was made by placing a Futrex sensor on the nonaccess upper arm for several seconds. Serum albumin, transferrin (reflected by total iron binding capacity), and total cholesterol concentrations were performed as well.

RESULTS

Thirty-four patients (20 men and 14 women) were selected from a pool of 120 haemodialysis patients. Their ages ranged from 26 to 86 years (58+/-14 years). Time on dialysis ranged from 8 months to 19 years (4.5+/-4.6 years). NIR scores were significantly different in three SGA groups: (A) well-nourished, 32.5+/-6.9%; (B) mildly to moderately malnourished, 29.2+/-5.3%; and (C) severely malnourished, 23.2+/-10.2% (P<0.001). Pearson correlation coefficients (r) between the NIR score and nutritionally relevant parameters were significant (P<0.001) for body mass index (r=+0.81), mid-arm circumference (r=+0.74), triceps skin fold (r=+0.54), biceps skin fold (r=+0.55), and mid-arm muscle circumference (r=+0.54). An inverse correlation was also found between NIR and years dialysed (r=-0.49, P=0.004), denoting a lesser body fat percentage according to NIR for patients dialysed longer. NIR was correlated with serum transferrin (r=+0.41, P=0.016) and cholesterol (r=+0.39, P=0.022) and marginally with serum albumin (r=+0.29, P=0.097).

CONCLUSIONS

We conclude that NIR, which can be performed within seconds, may serve as an objective indicator of nutritional status in haemodialysis patients. More comparative and longitudinal studies are needed to confirm the validity of NIR measurements in nutritional evaluation of dialysis patients.

Analysis of t-butylphenol acetylene condensed resin with methyl-methine linkages in vulcanized rubber by pyrolysis-gas chromatography/mass spectrometry

Methyl-methine linkages of Novolac, a commercially available t-butylphenol acetylene condensed (TBPA) resin, have been identified by recognition of pyrolysis pathways using pyrolysis-gas chromatography/mass spectrometry (Py-GC/mS) in vulcanized rubber. The diagnostic mass spectrum of t-butylphenol with methyl-methine linkages between phenolic rings was observed at m/z 192, corresponding to 4-t-butyl-2-ethyl-6-methylphenol. Other molecular ions were observed at m/z 178, 164, and 150 in the characteristic pyrolyzates. The ion at m/z 192 in the TBPA resin was observed to be characteristic for methyl-methine linkages between the phenolic groups, and the analytical pyrolysis-GC/mS method was thus able to identify the resin at low levels in vulcanized rubber. Copyright 1999 John Wiley & Sons, Ltd.

Cytotoxicity of curcuminoids and some novel compounds from Curcuma zedoaria

Bioassay-directed fractionation of an EtOH extract of Curcuma zedoaria led to isolation of an active curcuminoid, which was identified as demethoxycurcumin (2) by comparison of its 1H and 13C NMR spectra with literature data and by direct comparison with synthetic material. Curcumin (1) and bisdemethoxycurcumin (3) were also obtained. Curcuminoids (1-3) were synthesized and demonstrated to be cytotoxic against human ovarian cancer OVCAR-3 cells. The observed CD50 values of 1, 2, and 3 were 4.4, 3.8, and 3.1 microg/mL, respectively. Three additional novel compounds, 3, 7-dimethylindan-5-carboxylic acid (4), curcolonol (5), and guaidiol (6), were also isolated from the EtOH extract. The structures and relative stereochemistry of 4-6 were determined by spectroscopic methods and X-ray crystallographic analysis.

Genetic dissection of murine susceptibilities to liver and lung tumors based on the two-stage concept of carcinogenesis

Inbred mouse strains exhibit strain-specific susceptibilities to spontaneous and induced tumors, indicating that the individual risks for neoplastic development are largely under genetic control. Recent advances in linkage analysis have made it routine to chromosomally map the mouse genes responsible for the strain variations in tumor susceptibility using segregating crosses. It is also possible to characterize their biological functions using the positional information. These types of studies are still severely hampered for human cases due to the remarkable genetic heterogeneity and impossibility of experimental crosses. In this article, previous work on genetic susceptibility to mouse liver and lung tumors is reviewed in view of the classical two-stage concept of carcinogenesis. According to this central concept, the tumor susceptibility genes should affect either the first stage, 'initiation', or the second stage, 'promotion', or both. At least some genes seem to be specifically involved in initiation or promotion, in line with the fact that initiation and promotion are due, to a certain extent, to independent mechanisms. This notion should be also applicable to human carcinogenesis and may provide important clues for prevention of initiation and promotion in populations with a genetic predisposition for cancer development.

High colony forming capacity of primary cultured hepatocytes as a dominant trait in hepatocarcinogenesis-susceptible and resistant mouse strains

When hepatocytes isolated from mouse liver are cultivated in vitro, a small fraction of cells can survive, forming colonies, while most cells die within a few weeks. We compared the colony forming capacity of hepatocytes in three mouse strains; two strains susceptible for hepatocarcinogenesis, C3H/HeJ (C3) and DBA/2J mice (D2), and one resistant strain, C57BL/6J mice (B6). The colony forming capacity was about 3:2:1 for D2, C3 and B6 at the 4th week after start of culture, indicating that this capacity correlated with the susceptibility to tumor induction. When the colony forming capacity was compared in F1 hybrids between the three strains, the high colony forming capacity was dominant, again resembling the trait for hepatocarcinogenesis. In F1 hybrids between the two susceptible strains, the colony numbers were more than those of the parental strains, indicating the high colony forming capacity of the two susceptible strains to be additive. During 4 weeks of culture period, the cells continuously proliferated, but fairly large numbers of cells died, some showing characteristics of apoptosis and others of lysis. Although the proliferation rate was not different among the three strains until the 2 week time point, it was significantly lower in B6 than in C3 or D2 strains by the 4th week. On the other hand, the cell death rate was lower in D2 cells than in B6 or C3 cells after 2 weeks. These results indicate that the genetic background affects proliferation and death rates of cultured hepatocytes, which may be related to the different colony forming capacity of these three strains.

Mechanism of the paradoxical, inhibitory effect of phenobarbital on hepatocarcinogenesis initiated in infant B6C3F1 mice with diethylnitrosamine

Phenobarbital (PB), a classical rodent hepatopromoter, remarkably enhances hepatocarcinogenesis initiated by diethylnitrosamine (DEN) in adult B6C3F1 mice. However, it is also known to strongly inhibit liver tumor development in the B6C3F1 mice initiated with DEN in their infancy. The present study aimed to elucidate the unknown biological mechanisms for this paradoxical, inhibitory effect of PB on B6C3F1 mouse hepatocarcinogenesis. Male 12-day-old infant B6C3F1 mice were injected i.p. with DEN and, at 6 weeks of age, divided into PB-treated (PB+ group) and untreated (PB- group) animals. At 24 weeks, PB treatment was ceased for half of the PB+ animals (PB+/- group) and started for half of the PB- animals (PB-/+ group). Finally, all mice were sacrificed at 36 weeks and examined for the development of liver tumors. The mean multiplicity of gross tumors in the PB+ group was only one-fifteenth of that for the PB- group. PB-/+ animals developed fewer than half of the tumors found in PB- mice, indicating that the PB effect depends solely on the treatment duration, rather than the animal age. The effect was proven to be reversible, because the mean tumor multiplicity for the PB+/- group was seven times larger than that for the PB+ group. Stereological analysis revealed the mean volume of hepatocellular proliferative lesions in the PB- animals to be 7.7- and 4.1-fold the values for the PB+ and PB-/+ groups, respectively. The mean proliferating cell nuclear antigen-labeling indices for hepatocellular adenomas in PB+ and PB-/+ animals were also one-third of that for tumors in PB- animals, whereas no significant differences were observed with regard to the mean apoptotic index. In conclusion, the inhibitory effect of PB seemed to be primarily caused by the suppression of tumor cell proliferation. Irrespective of the group, most lesions observed were basophilic hepatocellular adenomas or foci, positive for Bcl-2 oncoprotein. They were thus distinct from the eosinophilic Bcl-2- lesions that predominate with PB promotion after the initiation of adult B6C3F1 mice. This age-dependent nature of initiation, together with the differential responses of Bcl-2+ and Bcl-2- lesions, may be responsible for the apparently contradictory outcomes of PB treatment in infant and adult B6C3F1 mice.

Roles of the Pas1 and Par2 genes in determination of the unique, intermediate susceptibility of BALB/cByJ mice to urethane-induction of lung carcinogenesis: differential effects on tumor multiplicity, size and Kras2 mutations

The C3H/HeJ (C3H), A/J and BALB/cByJ (BALB) mouse strains are respectively resistant, sensitive and intermediate regarding the induction of lung tumors by urethane. The phenotypic difference between C3H and A/J is largely determined by the Pas1 (Pulmonary adenoma susceptibility 1) gene on chromosome 6, the A/J allele of which dominantly increases the tumor burden. We recently found that BALB mice possess a unique lung tumor resistance gene on chromosome 18, designated Par2 (Pulmonary adenoma resistance 2), which partially, but dominantly suppresses the sensitive phenotype of A/J mice (Oncogene 13: 1599-1604, 1996). It has, however, remained unclear why BALB mice carrying the Par2 gene are significantly more sensitive to urethane-induced lung carcinogenesis than C3H mice that have no dominant lung tumor resistance genes. In the present study, using (C3H x BALB)F1 x C3H backcross mice treated with urethane, we demonstrated that BALB mice possess the disease allele of the Pas1 gene despite their 15-fold more resistance relative to A/J mice (LOD = 22.6). The BALB Par2 allele only significantly reduced the mean lung tumor multiplicity (LOD = 4.4) in the backcross population carrying the BALB allele of Pas1, indicating that the intermediate BALB phenotype may at least in part be the result of interactions between these two dominant genes. While the BALB Pas1 allele increased both the mean multiplicity and size of lung tumors, the BALB Par2 allele affected only the mean tumor multiplicity, implying that they are involved in different stages of multi-step lung carcinogenesis. In addition, we found that 68% of lung tumors from the BALB Pas1-positive backcross mice contained activating point mutations of the Kras2 oncogene, tightly linked to the Pas1 locus, whereas these genetic alterations were absent in tumors from BALB Pas1-negative mice. The Par2 genotype exhibited no effect on this parameter. Since the activating point mutations were observed exclusively in the BALB allele as already reported with lung tumors in (C57BL/6J x BALB/cJ)F1 mice, BALB Pas1 or possibly Kras2 itself may confer selective growth advantage on the affected urethane-initiated lung lesions.

Correlation between Bcl-2 expression and histopathology in diethylnitrosamine-induced mouse hepatocellular tumors

It is generally accepted that suppression of apoptosis in chemically initiated hepatocytes results in promotion of rodent hepatocarcinogenesis. Using immuno-histochemical methods, I studied the expression of Bcl-2, an anti-apoptotic protein, in hepatocellular tumors of B6C3F1 mice. Although normal mouse hepatocytes did not express detectable amounts of Bcl-2, most diethylnitrosamine-induced tumors were positive for this protein. Virtually all of the Bcl-2-positive tumors were composed of small basophilic hepatocytes, whereas the rare cases of Bcl-2-negative tumors demonstrated an eosinophilic appearance. To confirm this difference, tumors initiated with diethylnitrosamine and promoted by phenobarbital were also studied, as this initiation-promotion protocol has been shown to selectively produce eosinophilic lesions. All such tumors were immunohistochemically negative for Bcl-2. The relatively infrequent basophilic tumors found with phenobarbital treatment, however, did express Bcl-2. Thus, the concordance with basophilia was observed regardless of the nature of the promotion agent. These results indicate that the two types of tumors are qualitatively distinct and may develop through independent mechanisms.

Phenobarbital causes apoptosis in conditionally immortalized mouse hepatocytes depending on deregulated c-myc expression: characterization of an unexpected effect

The CHST8 mouse hepatocyte cell line, conditionally immortalized with the temperature-sensitive SV40 large T antigen gene, rapidly proliferates at 33 degrees C with active expression of the c-myc proto-oncogene but, due to the heat-labile nature of the mutant T antigens, becomes growth arrested and morphologically senescent at 39 degrees C; this is accompanied by the disappearance of c-myc transcripts. In a previous study, we transfected the CHST8 cells at 33 degrees C with an activated c-H-ras or a c-myc, both of which are frequently involved in mouse hepatocarcinogenesis in vivo. When the temperature was shifted to 39 degrees C, cells with only one of the exogenous oncogenes did not escape from the senescence, but those containing both exhibited an immortal phenotype. In the present study, using this in vitro model of hepatocarcinogenesis, we demonstrated that phenobarbital, a tumor promoter of rodent hepatocarcinogenesis, triggers remarkable apoptosis specifically in the c-myc-transfected CHST8 cells at 39 degrees C, which show abundant c-myc expression despite growth arrest. Dissociation of p53 proteins from degrading T antigens followed by a phenobarbital and c-myc-dependent, 15-fold induction of Bax protein, known to activate the apoptotic pathway downstream of p53, occurred in association with this phenomenon. The effects of phenobarbital and c-myc in increasing Bax on shifting the temperature from 33 degrees C to 39 degrees C were additive, with both having similar degrees of influence on the protein level. Interestingly, subsequent introduction of an activated c-H-ras oncogene into the c-myc-transfected CHST8 cells resulted not only in escape from the growth arrest at 39 degrees C but also in complete inhibition of the phenobarbital-inducible apoptosis along with de novo induction of the Bax antagonist, Bcl-2. These findings strongly suggest that the phenobarbital-inducible apoptosis is mediated by Bax. Although it is a common notion that phenobarbital promotes liver tumor development through suppression of apoptosis, our results, together with the known fact that phenobarbital occasionally inhibits hepatocarcinogenesis in mice, indicate a problematic complexity in its biological activities.

Anatomic localization of alternatively spliced leptin receptors (Ob-R) in mouse brain and other tissues

Leptin's effects are mediated by interactions with a receptor that is alternatively spliced, resulting in at least five different murine forms: Ob-Ra, Ob-Rb, Ob-Rc, Ob-Rd, and Ob-Re. A mutation in one splice form, Ob-Rb, results in obesity in mice. Northern blots, RNase protection assays, and PCR indicate that Ob-Rb is expressed at a relatively high level in hypothalamus and low level in several other tissues. Ob-Ra is expressed ubiquitously, whereas Ob-Rc, -Rd, and -Re RNAs are only detectable using PCR. In hypothalamus, Ob-Rb is present in the arcuate, ventromedial, dorsomedial, and lateral hypothalamic nuclei but is not detectable in other brain regions. These nuclei are known to regulate food intake and body weight. The level of Ob-Rb in hypothalamus is reduced in mice rendered obese by gold thioglucose (GTG), which causes hypothalamic lesions. The obesity in GTG-treated mice is likely to be caused by ablation of Ob-Rb-expressing neurons, which results in leptin resistance.

Polymerase chain reaction-restriction fragment length polymorphisms (PCR-RFLP) and electrophoretic assays for the mouse obese (Lepob) mutation

Three polymerase chain reaction-based assays for the mouse Lepob mutation are described: Dde I site created by the C-->T transversion characterizing Lepob enables positive detection of the mutant allele; positive detection of the wild-type Lep allele is achieved by the use of primer sequence which introduces an A-->C substitution, creating an Msp I site in the normal allele; and an electrophoretic assay which positively identifies the heterozygote.

Loss of heterozygosity at loci on chromosome 4, a common genetic event during the spontaneous immortalization of mouse embryonic fibroblasts

Spontaneously immortalized fibroblast cell lines derived from embryonic tissues of C3D2F1, mice were analyzed for loss of heterozygosity (LOH) at multiple chromosomal loci to identify candidate suppressor loci for immortalization. Among 47 simple sequence repeat (SSR) loci selected for screening, those on chromosome 4 exhibited an exceptionally high LDH incidence of up to 89%. Only four other chromosomes (8, 11, 12, and 18) showed LOH, with the highest incidence being 33%. To further localize candidate suppressor genes on mouse chromosome 4, detailed deletion mapping was performed with 18 cell lines and 14 SSR markers. The greatest LOH incidence (94%) was observed at the D4Mit14 locus located on distal chromosome 4, indicating that a major suppressor gene resides in this region. On the other hand, at the D4Mit77 locus, 30 cM proximal to the D4Mit14 locus, we found the SSR to be homozygously lost in 39% of the cell lines. Because the D4Mit77 is tightly linked to the tumor suppressor gene p16, for which homozygous deletion has been reported in various human tumor cell lines, we also examined our fibroblast cell lines for gross aberrations of the p16 gene by using the Southern blot method. The p16 gene was found to be homozygously deleted in 56% of the cell lines. Although this result implies that the p16 gene plays a role as a suppressor gene for immortalization, the combined incidence of LOH and homozygous deletion at the D4Mit77 locus was 72%, which is significantly lower than the observed incidence at the D4Mit14 locus. Consequently, we concluded that immortalization of mouse embryonic fibroblasts may involve more than one suppressor gene on chromosome 4.

Genetic dissection of susceptibility to murine ovarian teratomas that originate from parthenogenetic oocytes

The LT/Sv mouse strain is characterized by its abnormally high incidence of spontaneous ovarian teratomas. These tumors have been shown to originate from parthenogenetic oocytes, which are spontaneously induced to divide. Both spontaneous parthenogenesis and ovarian teratomas are extremely rare for other mouse strains, including C57BL/6J. To identify the genes responsible for this unique phenotype of female LT/Sv mice, we performed linkage analysis of female (C57BL/6J x LT/Sv)F2 mice. A locus on chromosome 6 designated Ots1 (ovarian teratoma susceptibility) was identified as the single major locus that increases the frequency of teratomas in a semidominant manner.

Intrahepatic transplantation of normal hepatocytes prevents Wilson's disease in Long-Evans cinnamon rats

BACKGROUND & AIMS

Long-Evans cinnamon (LEC) rats are an animal model of Wilson's disease. This study investigated whether intrahepatic transplantation of normal hepatocytes can prevent Wilson's disease in LEC rats.

METHODS

Hepatocytes of newborn Long-Evans agouti (LEA) rats were transplanted into the livers of LEC rats before onset of hepatic disease. Expression of normal transcripts from the gene linked to Wilson's disease was investigated at 30 weeks of age by reverse-transcription polymerase chain reaction and in situ hybridization.

RESULTS

Eight of 16 (50.0%) untreated LEC rats died of hepatic failure during 20-30 weeks of age. Of the 27 LEC rats with transplanted cells, 2 (7.4%) died of hepatic failure and 4 died of ileus complicated by the surgical treatment. In the recipient livers, the transplanted cells comprised 4%-20% of the hepatocyte populations, expressing normal messenger RNA transcribed from the Wilson's disease gene, and hepatic copper deposition was reduced to approximately 60% of that in untreated LEC rats.

CONCLUSIONS

Transplantation of normal hepatocytes prevents Wilson's disease in LEC rats.

Identification of the Par2 (Pulmonary adenoma resistance) locus on mouse chromosome 18, a major genetic determinant for lung carcinogen resistance in BALB/cByJ mice

The A/J mouse strain is 14 times more susceptible to urethane-induction of lung carcinogenesis than the BALB/cByJ strain (BALB). The relative resistance of BALB is dominant over the high sensitivity of A/J, since (BALBxA/J)F1 mice are phenotypically similar to the parental BALB mice. BALB mice must thus possess modifier genes suppressing phenotypic expression of the Pas (Pulmonary adenoma susceptibility) genes, which are known to be dominant genetic determinants for lung carcinogenesis in A/J mice. In order to genetically dissect the dominant resistance of the BALB mouse, we performed a linkage analysis to chromosomally map modifier genes by using 130 (A/JxBALB)F1xA/J backcross mice. Each backcross mouse was injected i.p. with urethane (1 mg/g bw) at 6 weeks of age and lung tumors were enumerated after 120 days. When the backcross mice were genotyped at multiple simple sequence repeat marker loci distributed on all the chromosomes, a significant linkage between the presence of a BALB allele and resistance to lung tumor induction was found on distal chromosome 18 (maximum LOD = 12.2). Thus, distal chromosome 18 of the BALB mouse contains a modifier gene for lung carcinogenesis: The locus, designated Par2 (Pulmonary adenoma resistance), accounted for 38% of the phenotypic variance in the backcross population, indicating a major role in protection against lung tumor development.

Activation of H-ras oncogenes in male B6C3F1 mouse liver tumors induced by vinthionine or 2-chloroethyl-methyl sulfide

Vinthionine (S-vinyl-DL-homocysteine) is hepatocarcinogenic in rats and mice. [Vinyl-14C]vinthionine binds covalently to rat liver DNA, RNA and protein in vivo, but not in vitro. This amino acid is directly mutagenic in Salmonella typhimurium TA100 and TA1535; the mechanism of its metabolic activation in vivo in bacteria and liver is under study. In the present study liver tumors were induced in 12-day-old male B6C3F1 mice by single i.p. injections of vinthionine or the alkylating agent 2-chloroethyl methyl sulfide (CEMS). At 10 months the gross tumors were examined for the presence of activated H-ras oncogenes. DNA was isolated from single tumors per mouse from 37 mice treated with vinthionine and from 31 mice treated with CEMS. These DNAs were screened for codon 61 mutations by restriction fragment length polymorphism of PCR-amplified H-ras gene fragments. Thirty seven of 37 vinthionine-induced hepatomas had H-ras mutations in this codon, which consisted of seven C-->A transversions in the first base, with 29 A-->T transversions and one A-->G transition in the second base. Twenty five of 31 CEMS-induced hepatomas had mutations in the same codon, which consisted of seven C-->A transversions in the first base, with eight A-->T transversions and 10 A-->G transitions in the second base. These mutation spectra are quite different to that noted by others in spontaneous hepatomas in untreated B6C3F1 mice. These data appear to result from the covalent binding of these carcinogens to the liver DNA.

Abnormal splicing of the leptin receptor in diabetic mice

Mutations in the mouse diabetes (db) gene result in obesity and diabetes in a syndrome resembling morbid human obesity. Previous data suggest that the db gene encodes the receptor for the obese (ob) gene product, leptin. A leptin receptor was recently cloned from choroid plexus and shown to map to the same 6-cM interval on mouse chromosome 4 as db. This receptor maps to the same 300-kilobase interval as db, and has at least six alternatively spliced forms. One of these splice variants is expressed at a high level in the hypothalamus, and is abnormally spliced in C57BL/Ks db/db mice. The mutant protein is missing the cytoplasmic region, and is likely to be defective in signal transduction. This suggests that the weight-reducing effects of leptin may be mediated by signal transduction through a leptin receptor in the hypothalamus.

Most liver epithelial cell lines from C3B6F1 mice exhibit parentally-biased loss of heterozygosity at the Lci (Liver cell immortalization) locus on chromosome 4

Liver epithelial cell lines established from F1 animals generated from hepatocarcinogen-sensitive C3H/HeJ and -resistant C57BL/6J mice were analysed for loss of heterozygosity at more than 60 simple sequence repeat marker loci distributed over all of the autosomal chromosomes. Nineteen of 20 clonal cell lines showed loss of heterozygosity at a chromosome 4 locus, designated Lci (Liver cell immortalization) and in most of the cases (18 of 19), alleles from the hepatocarcinogen-resistant parental strain, C57BL/6J, were lost. Detailed deletion mapping localized the putative suppressor gene for immortalization to within a 2 cM interval which includes a cluster of genes for gap junctional proteins. We also observed a loss of heterozygosity on chromosomes 7, 14, or 17 in more than 50% of the cell lines.

Conditional transformation of mouse liver epithelial cells. An in vitro model for analysis of genetic events in hepatocarcinogenesis

Primary rodent and human hepatocytes have a very limited lifespan in culture and are not readily applicable to transformation studies in vitro. To facilitate the investigation of early genetic events involved in hepatocarcinogenesis, we examined a transformation assay system utilizing conditionally immortalized mouse liver epithelial cells as an alternative to primary hepatocytes. By infecting primary mouse hepatocytes with a recombinant retrovirus carrying a temperature-sensitive simian virus 40 large T antigen gene, two mouse liver epithelial cell lines, CHST8 and CHST10-2.1, were established. Because of the heat-labile nature of the large T antigen, the cell lines proliferated rapidly at 33 degrees C, but were growth-arrested at 39 degrees C. Because activated c-H-ras and c-myc oncogenes are frequently found to be involved in mouse hepatocarcinogenesis in vivo, we assessed whether those oncogenes can complement the immortalizing function of the large T antigen at the nonpermissive temperature. When CHST8 cells were doubly transfected with activated c-H-ras and c-myc at 33 degrees C, they exhibited clonal growth ability even after shifting the temperature to 39 degrees C. However, neither c-H-ras nor c-myc alone allowed growth at 39 degrees C. On the other hand, c-H-ras alone was sufficient for overcoming the growth defect of CHST10-2.1 cells at 39 degrees C, whereas c-myc alone was again ineffective. Northern blot studies revealed that endogenous c-myc expression was significantly downregulated in the parental CHST8 cells after a temperature shift from 33 to 39 degrees C. In contrast, in the parental CHST10-2.1 cells, appreciable c-myc expression was observed at both temperatures. These results indicate that c-H-ras and c-myc can cooperate in complementing the ability of the temperature-sensitive large T antigen to immortalize mouse liver cells at the nonpermissive temperature. In addition, the mutant c-H-ras, but not c-myc, cooperated with the functional T antigen at 33 degrees C to allow growth in soft agarose of the CHST8 and CHST10-2.1 cell lines. However, cell lines carrying mutant c-H-ras and overexpressing c-myc were unable to grow in soft agarose at 39 degrees C. Thus, the two cellular oncogenes were insufficient for full transformation of the liver epithelial cells. The present in vitro model should be useful for investigating molecular events involved in both early and late stages of hepatocarcinogenesis.

Analysis of tomato root initiation using a normal mixture distribution

We attempt to identify the number of underlying physical phenomena behind tomato lateral root initiation by using a normal mixture distribution coupled with the Box-Cox power transformation. An initial analysis of the data suggested the possibility of two (possibly more) subpopulations, but upon taking reciprocals, the data appear to be very nearly Gaussian. A simulation study explores the possibility of erroneously detecting a second subpopulation by fitting data which are improperly scaled. A power calculation suggests that only unrealistically large sample sizes can detect the unbalanced mixtures one might expect with data of this type.

Leptin levels in human and rodent: measurement of plasma leptin and ob RNA in obese and weight-reduced subjects

Leptin, the gene product of the obese gene, may play an important role in regulating body weight by signalling the size of the adipose tissue mass. Plasma leptin was found to be highly correlated with body mass index (BMI) in rodents and in 87 lean and obese humans. In humans, there was variability in plasma leptin at each BMI suggesting that there are differences in its secretion rate from fat. Weight loss due to food restriction was associated with a decrease in plasma leptin in samples from mice and obese humans.

Hepatocarcinogenesis in BXH recombinant inbred strains of mice: analysis of diverse phenotypic effects of the hepatocarcinogen sensitivity loci

The hepatocarcinogen sensitivity (Hcs) loci were originally identified as determinants of the approximately 50-fold higher susceptibility of male C3H/HeJ (C3H) mice to perinatally induced hepatocarcinogenesis relative to male C57BL/6J (B6) mice. These two inbred strains also differ in other phenotypes related to hepatocarcinogenesis, including their incidences of spontaneous liver tumors and the properties of neoplastic hepatic lesions. To test the hypothesis that the Hcs loci also influence these phenotypes, we characterized male mice from B6, C3H, and nine BXH recombinant inbred (RI) strains for spontaneous liver tumor development, the frequency of activating mutations in tumors, and the presence of cytoplasmic inclusions in preneoplastic lesions. By comparing these results to the relative susceptibilities of the parental and RI strains to N,N-diethylnitrosamine (DEN)- and N-ethyl-N-nitrosourea- induced hepatocarcinogenesis in preweanling male mice, we concluded that the C3H alleles of the Hcs loci also positively influence the spontaneous development of liver tumors in male animals. While strain-dependent differences in the frequency of Ha-ras-1 activation in DEN-initiated liver tumors were observed, this phenotype was not correlated with susceptibility to liver tumor induction. The formation of eosinophilic intracytoplasmic inclusion bodies observed specifically in B6 liver tumors, which has been suggested to be associated with the resistance of this strain to hepatocarcinogenesis, also segregated independently of the Hcs loci.