Cooperative and selective lithium complexation of 2,11,13,22-tetraaza-5,8,16,19- tetraoxa-1,12-dioxocyclodocosanes

[reaction: see text] Ureyleno crown ethers 2 and 3 bind with 2 equiv of Li(+) cooperatively and selectively over other alkali metal ions such as Na(+), K(+), and Cs(+). The binding constant for 3 was found to be 3.0 x 10(7) (L/mol)(2).

Growth-suppressive function of human connexin32 in a conditional immortalized mouse hepatocyte cell line

Mouse hepatocytes immortalized with a temperature-sensitive allele of the SV40 large T-antigen (CHST8 cells) were found to lack the high expression of the gap junction proteins Cx26 and Cx32 that characterizes normal mouse hepatocytes, expressing instead Cx43 and Cx45 at minimal levels. In order to examine the growth suppressive function of Cx32 on hepatocytes, we transfected these CHST8 cells with human Cx32 complementary deoxyribonucleic acid and measured the growth rates at 33, 37, and 39 degrees C. Expression of human Cx32 and its messenger ribonucleic acid in the stable cell lines was confirmed by immunocytochemistry and by Western and Northern blots analyses. Dye transfer following lucifer yellow injection into the transfectants was extensive; Cx32 channels displayed unitary conductances of about 70 pS and were moderately voltage sensitive. When cultured at 33 and 39 degrees C, growth rates of both parental cells and transfectants were of the same level. When examined at 37 degrees C, growth rate of the transfectant, which highly expressed Cx32 at the membranes, was significantly decreased compared to the parental cells. However, no changes in the expression of Cx32 protein in the transfectants were observed between 33 and 37 degrees C. These results suggest that Cx32 expression could inhibit hepatocyte growth in vitro using the conditional immortalized cells. Cx32 transfectants using a conditional immortalized mouse hepatocyte may be useful for examining the mechanisms of growth and differentiation in hepatocytes by gap junction expression.

Aroma components of cooked tail meat of American lobster (Homarus americanus)

Key aroma components of cooked tail meat of American lobster (Homarus americanus) were studied by gas chromatography-olfactometry (GCO) techniques. Components of low and intermediate volatility were evaluated by aroma extract dilution analysis of solvent extracts prepared by direct solvent extraction-high vacuum distillation and vacuum steam distillation-solvent extraction, whereas headspace volatile components were assessed by GCO of decreasing headspace (static and dynamic modes) samples. Forty-seven odorants were detected by all techniques. 3-Methylbutanal (chocolate, malty), 2,3-butanedione (buttery), 3-(methylthio)propanal (cooked potato), 1-octen-3-one (mushroom), 2-acetyl-1-pyrroline (popcorn), and (E,Z)-2,6-nonadienal (cucumber), were identified as predominant odorants by all four isolation methods. The highly volatile compounds methanethiol (rotten, sulfurous) and dimethyl sulfide (canned corn) were detected by headspace methods only. These eight odorants along with three unknown compounds with crabby, amine, fishy odors were found to predominate in the overall aroma of cooked lobster tail meat.

Cytotoxic and novel compounds from Solanum indicum

Solavetivone (1), cytotoxic to OVCAR-3 cells with an IC(50) value of 0.1 mM, has been isolated from Solanum indicum. In addition, a novel solafuranone (2) and three known compounds, scopoletin, N-(p-trans-coumaroyl)tyramine, and N-trans-feruloyltyramine, were isolated for the first time from this plant. The structures of the above compounds were established by means of spectroscopic and X-ray analyses.

Lymphosarcoma in a brown bear (Ursus arctos)

An example of lymphoblastic lymphosarcoma was found in a 7-year-old male brown bear (Ursus arctos) that died after having a 7-month history of depression, anorexia and watery diarrhea. Grossly the mesenteric lymph nodes were enlarged to approximately 4 to 6 times their normal size and histologically diagnosed as lymphoblastic lymphosarcoma. The small intestinal mucosa was corrugated and had severe mural thickening due to infiltrated neoplastic cells. Hepatic metastasis was also noted. This is the first reported case of lymphosarcoma in Ursidae in Korea. As an incidental finding, endogenous lipid pneumonia was noted in the lung.

Fine chromosomal localization of the mouse Par2 gene that confers resistance against urethane-induction of pulmonary adenomas

BALB/cByJ mice are 14 times more resistant to urethane-induction of pulmonary adenomas than the susceptible A/J strain. Our previous linkage analysis of (A/J x BALB/cByJ)F1 x A/J backcross mice provided statistical evidence that a major resistance locus of BALB/cByJ with a dominant effect, designated Par2 (Pulmonary adenoma resistance 2), exists within an approximately 25 cM section of distal chromosome 18. To facilitate molecular identification of the Par2 locus, the present study was conducted to finely localize its chromosomal position utilizing Par2-congenic mice. Male BALB/cByJ mice were mated with female C57BL/6J mice carrying recessive Par2 alleles and their male F1 progeny were backcrossed to female BALB/cByJ mice. A male backcross mouse heterozygous within the Par2 interval of 25 cM was randomly selected and again backcrossed to female BALB/cByJ mice. This backcross-selection cycle was simply repeated to produce semi-congenic mice with a general BALB/cByJ genetic background except for the Par2 interval, where the mice were heterozygous with paternal C57BL/6J alleles and maternal BALB/cByJ alleles. After the 6th or 7th backcross, nine male mice possessing a recombination within the paternal Par2 interval were retained and crossed to female A/J mice. Resultant progeny were treated with urethane and examined for lung tumor development in order to deduce the Par2 genotypes of the recombinants through linkage analysis. By comparing the deduced Par2 genotype of each recombinant with its recombinational breakpoint, the Par2 locus was confined to an approximately 0.5 cM region flanked by D18Mit103 and D18Mit188 loci. Our results indicate that fully congenic mice conventionally established by at least nine simple backcrosses or by the speed congenic method are not necessarily required for fine mapping of quantitative trait loci. In the case of the Par2 locus, we found that semi-congenic mice after as few as four simple backcrosses were useful for this purpose. The map information obtained in this study should enable subsequent positional cloning of the Par2 gene.

Syntheses, reactivity, and pi-donating ligand metathesis reaction of five-coordinate sixteen-electron manganese(I) complexes: crystal structures of [Mn(CO(3)(-TeC(6)H(4)-o-NH-)](-), [(Mn(CO)(3))2(mu-SC(6)H(4)-o-S--S--C(6)H(4)-o-mu-S--)], [(CO)(3)Mn(mu-SC(6)H(4)-o-NH(2)-)]2, and [(CO)(3)Mn(mu-SC(8)N(2)H(4)-o-S-)](2)(2-)

The preparation of the varieties of five-coordinate sixteen-electron manganese(I) complexes [Mn(CO)(3)(-EC(6)H(4)-o-E'-)](-) (E = Te, Se, S, O; E' = NH, S, O) by (a) oxidative addition of 2-aminophenyl dichalcogenides to anionic manganese(0)-carbonyl, (b) pi-donating ligand metathesis reaction of complex [Mn(CO)(3)(-TeC(6)H(4)-o-NH-)](-), and (c) reduction /deprotonation of the neutral dimetallic [(Mn(CO)(3))(2)(mu-SC(6)H(4)-o-S-S-C(6)H(4)-o-mu-S-)]/[(CO)(3)Mn(mu-SC(6)H(4)-o-NH(2)-)](2) proved successful approaches in this direction. The IR nu(CO) data of the coordinatively and electronically unsaturated [Mn(CO)(3)(-EC(6)H(4)-o-E'-)](-) (E = Te, Se, S, O; E' = NH, S, O) complexes suggest the relative order of pi-donating ability of the series of bidentate ligands being [TeC(6)H(4)-o-NH](2)(-) > [SeC(6)H(4)-o-NH](2)(-) > [SC(6)H(4)-o-NH](2)(-) > [SC(6)H(4)-o-S](2)(-) > [SC(6)H(4)-o-O](2)(-) > [OC(6)H(4)-o-O](2)(-). Proton NMR spectra of the [Mn(CO)(3)(-EC(6)H(4)-o-NH-)](-) (E = Te, Se, S) derivatives show the low-field shift of the amide proton ((1)H NMR (C(4)D(8)O): delta 9.66 (br) ppm (E = Te), 9.32 (br) ppm (E = Se), 8.98 (br) ppm (E = S)). The formation of the dimetallic [(CO)(3)Mn(mu-SC(8)N(2)H(4)-o-S-)](2)(2-) can be interpreted as coordinative association of two units of unstable mononuclear [(CO)(3)Mn(-SC(8)N(2)H(4)-o-S-)](-) and reflects the pi-donating ability of the bidentate ligand is responsible for the formation of pentacoordinate, sixteen-electron manganese(I) carbonyl complexes. The neutral bimetallic manganese(I)-bismercaptophenyl disulfide complex [(Mn(CO)(3))(2)(mu-SC(6)H(4)-o-S-S-C(6)H(4)-o-mu-S-)] with internal S-S bond length of 2.222(1) A and the five-coordinate sixteen-electron complex [Mn(CO)(3)(-SC(6)H(4)-o-S-)](-) are chemically interconvertible. In a similar fashion, treatment of complex [Mn(CO)(3)(-SC(6)H(4)-o-NH-)](-) with HBF(4) yielded neutral dinuclear complex [(CO)(3)Mn(mu-SC(6)H(4)-o-NH(2)-)](2) and showed that the amine deprotonation is reversible. Investigations of pi-donating ligand metathesis reactions of complex [Mn(CO)(3)(-TeC(6)H(4)-o-NH-)](-) revealed that the stable intermediate, not the pi-donating ability of bidentate ligands, is responsible for the final protonation/oxidation product. This argument is demonstrated by reaction of [Mn(CO)(3)(-TeC(6)H(4)-o-NH-)](-) with 1,2-benzenedithiol, hydroxythiophenol, and catechol, respectively leading to the formation of [Mn(CO)(3)(-EC(6)H(4)-o-E'-)](-) (E = S, O; E' = S, O), although any pi-donor containing the amido group is a more effective donor than any other pi-donor lacking an amido group. Also, the reactions of [Mn(CO)(3)(-TeC(6)H(4)-o-NH-)](-) with electrophiles occurring at the more electron-rich amide site support that the more electron-rich amide donor of the chelating 2-tellurolatophenylamido occupies an equatorial site as indicated by a shorter Mn(I)-N bond length of the distorted trigonal bipyramidal [Mn(CO)(3)(-TeC(6)H(4)-o-NH-)](-).

Proton-lithium binding behavior of tris(2-((pyrid-2-ylmethyl)uredio)ethyl)amine

Tris(2-((pyrid-2-ylmethyl)uredio)ethyl)amine (2) and its perchlorate salt, 2.HClO(4), bind with Li+ in nitromethane in a 1:1 fashion. The stability constants of K(Li+) and K(H)(Li+) were found to be 112 +/- 25 and 130 +/- 30 M(-)(1) in CD(3)NO(2), respectively. Formation of the 1:1 complexes were further evidenced by electrospray ionization mass spectrometry (ESI-MS). The slight increase, or at least the same order of magnitude, of K(H)(Li+) compared to K(Li+) points to a remarkable preorganization of the protonated podand in 2.HClO(4), that essentially overcomes the increased Columbic repulsion occurring on complexation to Li+.

Structural correlation of catecholase-like activities of oxy-bridged dinuclear copper(II) complexes

Eight oxy-bridged dinuclear copper(II) complexes with catecholase-like sites, [Cu(L1)X]2 (HL1 = 1-diethylaminopropan-2-ol, X=N3- 1, NCO- 2, and NO2- 3), [Cu(L2)X]2 (HL2=N-ethylsalicylaldimine, X=NO3- 4, Cl- 5, N3- 6, NCS- 7), and [Cu(L3)]2(ClO4)2, 8 (HL3=N-(salicylidene)-N'-(2-pyridylaldene)propanediamine) have been prepared and characterized. The single crystal X-ray analysis show that the structures of complexes 6 and 8 are dimeric with two adjacent copper(II) atoms bridged by pairs of micro-oxy atoms from the L2 and L3 ligands. Magnetic susceptibility measurements in the temperature range 4-300 K indicate significant antiferromagnetic coupling for 4, 5 and 7 and ferromagnetic coupling for 6 between the copper(II) atoms. The catecholase activity of complexes for the oxidation of 3,5-di-tert-butylcatechol by O2 was studied and it was found that the complexes with the bond distance of Cu(II)...Cu(II) located at 2.9-3.0 A show higher catecholase activity.

Stress fracture of the femoral neck in young adult: report of four cases

Stress fracture of the femoral neck is an uncommon injury. If the diagnosis is missed or delayed and fracture displacement results, serious complications such as avascular necrosis of the femoral head, nonunion or varus deformity may occur. Treatment depends on the type of stress fracture. Compression and tension stress fractures can be successfully treated with conservative management or prophylactic internal fixation using multiple screws. Displaced stress fractures are an orthopedic emergency, requiring prompt surgical intervention. Poor outcomes after fracture displacement have been reported by many authors. We present four cases demonstrating three types of stress fracture of the femoral neck. It is hoped that these case reports will serve to increase practitioner awareness of this injury and emphasize the need for careful diagnosis and treatment of this potentially problematic injury.

Body fat measurement in computed tomography image

In this paper, we suggest an automatic fat region setting method in computed tomography to measure body fat. Quantitative measurement of body fat is important for the diagnosis and treatment of diseases related to obesity. The evaluation methods of obesity such as weight and height ratio, waiste and hip circumference ratio, and subcutaneous fat thickness by clipper, have a weak point that they do not measure body fat quantitatively. To overcome the weak point a body fat measurement method by computed tomography has been tried recently. The body fat measurement by computed tomography presents volume of body fat quantitatively at a specific region such as subcutaneous and abdominal fats. Computed tomography provides an image consisting of voxels with Hounsfield unit which is proportional to the density at the voxels. In general, the Hounsfield units of the body fat is known as it has the values from -150 to -50. However, the Hounsfield unit range of the fat is different for every person and every region of a person. In this paper, we show the difference of the body fat range in the Hounsfield units for 20 persons and various regions of a person, and we suggest an automatic setting method of the body fat region in the Hounsfield units due to the Gaussian function fitting of the histogram in the computed tomography image.

Dissociation of sarcoglycans and the dystrophin carboxyl terminus from the sarcolemma in enteroviral cardiomyopathy

Enteroviral infection can cause an acquired form of dilated cardiomyopathy. We recently reported that dystrophin is cleaved, functionally impaired, and morphologically disrupted in vitro as well as in vivo during infection with coxsackievirus B3. Genetic dystrophin truncations lead to a marked decrease in dystrophin-associated glycoproteins, whereas expression of only the naturally occurring dystrophin carboxyl terminus, Dp-71, restores the sarcolemmal association of the dystrophin-associated glycoproteins. We sought to determine whether acute cleavage of dystrophin leads to a dissociation of the carboxyl-terminal dystrophin fragment and of the sarcoglycans from the sarcolemma during coxsackievirus B3 infection. We found that in cultured cardiac myocytes and murine hearts infected with coxsackievirus B3, the sarcolemmal localization of the dystrophin carboxyl terminus is lost. The dystrophin-associated glycoproteins alpha-, beta-, gamma-, and delta-sarcoglycan and beta-dystroglycan were markedly decreased in the membrane fraction of infected cells in culture, and the typical sarcolemmal localization for each of these proteins was lost in coxsackievirus-B3-infected cardiomyocytes in vivo. Furthermore, sucrose gradient ultracentrifugation demonstrated that delta-sarcoglycan was physically dissociated from dystrophin within the membrane fraction. In vivo, the sarcolemmal integrity was functionally impaired with Evans blue dye uptake even though there was no generalized disruption of the sarcolemma of infected myocytes evidenced by intact wheat germ agglutinin staining. In analogy to hereditary sarcoglycanopathies, this disintegration of the sarcoglycan complex may, in addition to the dystrophin cleavage, play an important role in the pathogenesis of enterovirus-induced cardiomyopathy. These results imply a potential role for disruption of the sarcoglycans in an acquired form of heart failure.

Influence of glutathione S-transferase M1 and T1 genotypes on larynx cancer risk among Korean smokers

Glutathione S-transferase (GST) isoenzymes are involved in the detoxification of major carcinogens present in tobacco smoke. It is thus conceivable that deficiency in GST activity due to homozygous deletions of the GSTM1 and GSTT1 genes (the null genotypes) may modulate susceptibility to smoking-induced cancers. The influence of the GSTM1 and GSTT1 null genotypes on larynx cancer risk among the Korean population were evaluated using peripheral blood DNA from 82 larynx cancer patients and 63 healthy controls, all of whom were male current smokers. Increased larynx cancer risk was related to the GSTM1 null genotype (odds ratio (OR)=3.53, 95% confidence interval (CI)=1.27-9.83). The OR associated with the GSTT1 null genotype was also increased, but did not reach statistical significance (OR=1.83, 95% CI=0.70-4.79). Individuals lacking both the GSTM1 and GSTT1 genes were at a significantly higher risk for larynx cancer than individuals with both genes present (OR=4.04, 95% CI=1.33-12.30). These data confirm that the GSTM1 null genotype is an important risk modifier for larynx cancer among Korean smokers and combined GSTM1 and GSTT1 null genotypes could be a useful predictor of genetic susceptibility to larynx cancer.

Synthesis and structural characterization of configurational isomers of tungsten-palladium complexes with bridging diphenyl(dithioalkoxycarbonyl)phosphine as a ligand and phosphine transfer from tungsten to palladium

Treatment of the complex [W(CO)5[PPh2(CS2Me)]] (2) with [Pd(PPh3)4] (1) affords binuclear complexes such as anti-[(Ph3P)2Pd[mu-eta 1,eta 2-(CS2Me)PPh2]W(CO)5] (3), syn-[(Ph3P)2Pd[mu-eta 1,eta 2-(CS2Me)PPh2]W(CO)5] (4), and trans-[W(CO)4(PPh3)2] (5). In 3 and 4, respectively, the W and Pd atoms are in anti and syn configurations with respect to the P-CS2 bond of the diphenyl(dithiomethoxycarbonyl)phosphine ligand, PPh2(CS2Me). Complex 3 undergoes extensive rearrangement in CHCl3 at room temperature by transfer of a PPh3 ligand from Pd to W, eliminating [W(CO)5(PPh3)] (7), while the PPh2CS2Me ligand transfers from W to Pd to give [[(Ph3P)Pd[mu-eta 1,eta 2-(CS2Me)PPh2]]2] (6). In complex 6, the [Pd(PPh3)] fragments are held together by two bridging PPh2(CS2Me) ligands. Each PPh2(CS2Me) ligand is pi-bonded to one Pd atom through the C=S linkage and sigma-bonded to the other Pd through the phosphorus atom, resulting in a six-membered ring. Treatment of Pd(PPh3)4 with [W(CO)5[PPh2[CS2(CH2)nCN]]] (n = 1, 8a; n = 2, 8b) in CH2Cl2 affords syn-[(Ph3P)2Pd[mu-eta 1,eta 2-[CS2(CH2)nCN]PPh2]W(CO)5] (n = 1, 9a; n = 2, 9b). Similar configurational products syn-[(Ph3P)2Pd[mu-eta 1,eta 2-(CS2R)PPh2]W(CO)5] (R = C2H5, C3H5, C2H4OH, C3H6CN, 11a-d) are synthesized by the reaction of Pd(PPh3)4 with [W(CO)5[PPh2(CS2R)]] (R = C2H5, C3H5, C2H4OH, C3H6CN, 10a-d). Although complexes 11a-d have the same configuration as 9a,b, the SR group is oriented away from Pd in the former and near Pd in the latter. In these complexes, the diphenyl(dithioalkoxycarbonyl)phosphine ligand is bound to the two metals through the C=S pi-bonding and to phosphorus through the sigma-bonding. All of the complexes are identified by spectroscopic methods, and the structures of complexes 3, 6, 9a, and 11d are determined by single-crystal X-ray diffraction. Complexes 3, 9, and 11d crystallize in the triclinic space group P1 with Z = 2, whereas 6 belongs to the monoclinic space group P2/c with Z = 4. The cell dimensions are as follows: for 3, a = 10.920(3) A, b = 14.707(5) A, c = 16.654(5) A, alpha = 99.98(3) degrees, beta = 93.75(3) degrees, gamma = 99.44(3) degrees; for 6, a = 15.106(3) A, b = 9.848(3) A, c = 20.528(4) A, beta = 104.85(2) degrees; for 9a, a = 11.125(3) A, b = 14.089(4) A, c = 17.947(7) A, alpha = 80.13(3) degrees, beta = 80.39(3) degrees, gamma = 89.76(2) degrees; for 11d, a = 11.692(3) A, b = 13.602(9) A, c = 18.471(10) A, alpha = 81.29(5) degrees, beta = 80.88(3) degrees, gamma = 88.82(1) degrees.

Life-threatening intraabdominal arterial embolization after histoacryl injection for bleeding gastric ulcer

N-butyl-cyanoacrylate (Histoacryl) injection has become the treatment of choice for acutely bleeding esophagogastric varices, and is the only effective option for endoscopic treatment of gastric varices. Recent reports confirm the ability of Histoacryl injection therapy to achieve immediate hemostasis in cases of gastric ulcer bleeding or Dieulafoy ulcer, where conventional endoscopic hemostatic treatment had failed. Although the overall safety record of Histoacryl injection has been relatively good, there have been scattered cases of serious complications. Here, we present two patients showing life-threatening intraabdominal arterial embolization after Histoacryl injection. They had chronic gastric ulcers with active arterial bleeding. In spite of attempts at hemostatic treatment, complete hemostasis was not achieved. We injected Histoacryl, diluted with Lipiodol, into bleeding gastric ulcers, resulting in successful hemostasis. Soon after the procedure, intraabdominal arterial embolization developed in both patients. One patient survived and the other died. Based on these experiences, we would like to warn gastrointestinal endoscopists to be alert to these fatal complications, and we propose that less diluted Histoacryl seems to be preferable in cases of bleeding peptic ulcers.

Enteroviral cardiomyopathy: bad news for the dystrophin-glycoprotein complex

Genetic deficiency of the dystrophin-glycoprotein complex causes hereditary dilated cardiomyopathy. Enteroviruses can also cause cardiomyopathy and we have recently described a potential molecular mechanism for enterovirus-induced dilated cardiomyopathy. The coxsackieviral protease 2A proteolytically cleaves and functionally impairs dystrophin. Additionally, during infection with coxsackievirus B3, the dystrophin-glycoprotein complex becomes disrupted and the sarcolemmal integrity is lost. This review article discusses the importance of the dystrophin cleavage for the development of increased sarcolemmal permeability and potential pathways for mechanisms by which the dystrophin cleavage during coxsackieviral infection may contribute to dilated cardiomyopathy.

Paradoxical effects of phenobarbital on mouse hepatocarcinogenesis

Phenobarbital was the first tumor promoter for rodent liver to be associated with the 2-stage or initiation-promotion concept of carcinogenesis. In rats and mice preinitiated with genotoxic carcinogens, phenobarbital administration increases the number of hepatocellular tumors by approximately 5-fold despite its nongenotoxicity. However, in mice phenobarbital occasionally exhibits strong inhibitory effects on hepatocarcinogenesis initiated with the potent carcinogen diethylnitrosamine. Both positive and negative effects of phenobarbital on hepatocytic proliferation and apoptosis, which are mechanistically involved in the promotion stage of hepatocarcinogenesis, have been described. These complex outcomes of phenobarbital treatment and their effects on hepatocarcinogenesis in mice raise serious issues regarding extrapolation of experimental data from laboratory animals to human risk assessment. Recent work suggests that the paradoxical actions of phenobarbital on hepatocarcinogenesis can be understood by consideration of qualitative diversity in initiated lesions and differential responses to promotion stimulus.

Heterobimetallics of nickel-iron dinitrosyl: electronic control by chelate and diatomic ligands

Reaction of [PPN][Fe(NO)2(SePh)2] (1) with dimeric [Ni(mu-SCH2CH2SCH2CH2S)]2 in the presence of additional NO2- produced the neutral heterobimetallic [(ON)Ni[(mu-SCH2CH2)2S]Fe(NO)2] complex (2). The X-ray crystal structures of 1 and 2 show distorted tetrahedral iron dinitrosyl groups, assigned according to the Feltham-Enemark notation as [Fe(NO)2]9 The Fe-NO bonds are off linearity by an average of approximately equals 10 degrees for compounds 1 and 2, while a more linear Ni-NO coordination with a Ni-NO distance of 1.644(2) A was found in 2. The v(NO) value of complex 2 is consistent with an assignment for [Ni(NO)]9 of Ni0(NO)+ as is known for analogous phosphine derivatives, P3Ni0(NO)+. EPR signals of g values = 2.02-2.03 confirmed the existence of the odd electron in the chalcogenated [Fe(NO)2]9 compounds. Two [Fe(NO)2]10 complexes coordinated by the nickel(II) dithiolate, (bismercaptoethanediazacyclooctane)nickel(II), (Ni-1), (Ni-1)Fe(CO)(NO)2 and (Ni-1)Fe(NO)2, were prepared for comparison to the Ni0(NO)+ derivative and other monomeric and homodimetallic derivatives of the Fe(NO)2 fragment. While the oxidation level of Fe(NO)2 is the primary determinant of v(NO) values, they are also highly sensitive to ancillary ligands and, thereby, the distal metal influence through the bridging thiolate donor.

Induction of tight junctions in human connexin 32 (hCx32)-transfected mouse hepatocytes: connexin 32 interacts with occludin

Small gap junction plaques are associated with tight junction strands in some cell types including hepatocytes and it is thought that they may be closely related to tight junctions and the establishment of cell polarity. In order to examine roles of gap junctions in regulating expression and structure of tight junctions, we transfected human Cx32 cDNA into immortalized mouse hepatocytes (CHST8 cells) which lack endogenous Cx32 and Cx26. Immunocytochemistry revealed that endogenous integral tight junction protein occludin was strongly localized and was colocalized with Cx32 at cell borders in transfectants, whereas neither was detected in parental cells. In Northern blots, mRNAs encoding occludin and the other integral tight junction proteins, claudin-1 and -2, were induced in the transfectants compared to parental cells. In Western blots, occludin protein was increased in the transfectants compared to parental cells, and binding of occludin to Cx32 protein was demonstrated by immunoprecipitation. In freeze fracture of the transfectants, tight junction strands were more numerous and complex compared to parental cells, and small gap junction plaques appeared within induced tight junction strands. Nevertheless, no change in barrier function of tight junctions was observed. These results indicate that in hepatocytes, gap junction, and tight junction expression are closely coordinated, and that Cx32 may play a role in regulating occludin expression.

Morphology, proliferation and apoptosis of mouse liver epithelial cells cultured as spheroids

The MLEC10 is an epithelial cell line derived from an untreated, normal C3H/HeN mouse liver. We previously demonstrated that tumorigenic variants from this cell line produced moderately differentiated hepatocellular carcinomas in nude mice. However, it has remained unclear whether the parental MLEC10 cells represent immortalized hepatocytes or so-called oval cells, both of which may serve as precursors for hepatocellular neoplasms. In this study, we performed 3-dimensional, spheroid culture of the MLEC100 cells in order to facilitate histological assessment of their lineage. Spheroidal aggregates were formalin-fixed and embedded in paraffin for routine light-microscopic observation of hematoxylin and eosin-stained sections. Histopathologically, the MLEC10 cells were indistinguishable from immature hepatocytes and distinct from oval cells. At the electron-microscopic level, their hepatocytic nature was evidenced by bile canaliculus structures and glycogen storage. Intriguingly, the spheroids contained fragmentary material reminiscent of Councilman bodies, implying apoptosis of the hepatocytes. Although the cells significantly proliferated during the first three days of culture, apoptotic death then resulted in a 75 % decrease in viable cell number. Thereafter, both apoptosis and cell division appeared silent, the numbers being unchanged. Expression of the p53 tumor suppressor gene became gradually elevated, correlating positively with growth arrest, but negatively with apoptosis, suggesting that the cell death occurred independently of p53. Our results indicate that at least some liver epithelial cell lines derived from untreated murine livers exhibit a hepatocytic morphology in spheroid culture. Also, the present culture system provides a useful tool for investigating biological phenomena, e.g. apoptosis, specifically involving liver cells, under 3-dimensional conditions.

Expression of an IL-1 receptor antagonist during mouse hepatocarcinogenesis demonstrated by differential display analysis

The differential display technique was applied for identification of genes that have altered expression in mouse hepatocellular carcinomas relative to normal liver. Three genes were identified. The IL-1 receptor antagonist (IL-1ra) was expressed in hepatocellular carcinomas, whereas the major urinary protein (MUP) and cytochrome P-450 naphthalene hydroxylase (cyp2F2) genes were down-regulated. Because IL-1ra is a natural antagonist of IL-1, and because the latter has been reported to suppress the growth of hepatic cells, we also studied the expression of IL-1ra in hepatocarcinogenesis. IL-1ra was immunohistochemically detected in tumor cells in approximately 70% of hepatocellular adenomas and carcinomas, whereas early preneoplastic hepatocytic foci, as well as normal hepatocytes surrounding the lesions, were negative. In addition, 20% of human hepatocellular carcinomas were also partly positive for IL-1ra. RT-PCR analysis demonstrated that mouse hepatic tumors contain both secreted and intracellular forms of IL-1ra. On the other hand, there were no differences in levels of IL-1alpha and IL-1beta between hepatic tumors and normal liver in mice, suggesting that the majority of tumors create a microenvironment that inhibits the actions of IL-1. Furthermore, IL-1ra-positive adenomas contained more proliferating cell nuclear antigen-positive cells than IL-1ra-negative adenomas, indicating a link with high proliferation activity, although this was no longer evident in carcinomas. The observed altered gene expression may be related to biological phenotypes of hepatic tumors, and IL-1ra in particular may positively influence tumor cell growth through its antagonism of IL-1.

Nitric oxide protects PC12 cells from serum deprivation-induced apoptosis by cGMP-dependent inhibition of caspase signaling

Although nitric oxide (NO) induces neuronal cell death under some conditions, it also can prevent apoptosis resulting from growth factor withdrawal. We investigated the molecular mechanism by which NO protects undifferentiated and differentiated PC12 cells from trophic factor deprivation-induced apoptosis. PC12 cells underwent apoptotic death in association with increased caspase-3-like activity, DNA fragmentation, poly(ADP-ribose) polymerase (PARP) cleavage, and cytochrome c release after 24 hr of serum withdrawal. The apoptosis of PC12 cells was inhibited by the addition of NO-generating donor S-nitroso-N-acetylpenicillamine (SNAP) (5-100 microM) and the specific caspase-3-like protease inhibitor Ac-Asp-Glu-Val-Asp-aldehyde (Ac-DEVD-cho) but not the YVADase (or caspase-1-like protease) inhibitor N-acetyl-Tyr-Val-Ala-Asp-aldehyde (Ac-YVAD-cho). SNAP and Ac-DEVD-cho prevented the increase in DEVDase (caspase-3-like protease) activity. The SNAP-mediated suppression of DEVDase activity was only minimally reversed by the incubation of cell lysate with dithiothreitol, indicating that NO did not S-nitrosylate caspase-3-like proteases in PC12 cells. Western blot analysis showed that NO inhibited the proteolytic activation of caspase-3. The cGMP analog 8-bromo-cGMP (8-Br-cGMP) blocked apoptotic cell death, caspase-3 activity and activation, and cytochrome c release. The soluble guanylyl cyclase inhibitor 1-H-oxodiazol-[1,2,4]-[4,3-a] quinoxaline-1-one (CODQ) significantly attenuated NO-mediated, but not 8-Br-cGMP-dependent, inhibition of apoptotic cell death, PARP cleavage, cytochrome c release, and DEVDase activity. Furthermore, the protein kinase G inhibitor KT5823 reversed both SNAP- and 8-Br-cGMP-mediated anti-apoptotic events. All these apoptotic phenomena were also suppressed by NO production through neuronal NO synthase gene transfer into PC12 cells. Furthermore, similar findings were observed in differentiated PC12 cells stimulated to undergo apoptosis by NO donors and NGF deprivation. These findings indicate that NO protects against PC12 cell death by inhibiting the activation of caspase proteases through cGMP production and activation of protein kinase G.

A modified quantitative subjective global assessment of nutrition for dialysis patients

BACKGROUND

Malnutrition, a predictor of increased mortality in dialysis patients, can be estimated using the subjective global assessment (SGA), a semiquantitative scale with three severity levels. This semiquantitative feature restricts the SGA's reliability and precision.

METHODS

Using the components of the conventional SGA, we developed a fully quantitative scoring system (the dialysis malnutrition score) consisting of seven variables: weight change, dietary intake, gastrointestinal symptoms, functional capacity, comorbidity, subcutaneous fat and signs of muscle wasting. Each component was assigned a score from 1 (normal) to 5 (very severe). The sum of all seven components in this malnutrition score lies between 7 (normal) and 35 (severely malnourished). To evaluate nutritional status in chronic dialysis patients, anthropometric measurements including mid-arm circumference (MAC), triceps skin-fold thickness, calculated mid-arm muscle circumference (MAMC), body mass index (BMI, ratio of weight to square of height) and laboratory parameters were used. Forty-one patients (20 men and 21 women) were randomly selected from a pool of 120 haemodialysis patients. Patients were aged between 26 and 81 years (mean SD, 57 +/- 12 years) and had undergone haemodialysis for between 7 months and 12 years (mean +/- SD, 3.0 +/- 2.1 years).

RESULTS

The malnutrition score of each patient was assessed by a dietitian within 5-20 min (12.0 +/- 3.5 min) with no knowledge of anthropometric findings. Pearson correlation coefficients between the malnutrition score and biceps skin-fold (r= -0.32) MAC (r= -0.55), MAMC (r= -0.66), BMI (r= -0.35), total iron-binding capacity (TIBC, r= -0.77), the serum albumin concentration (r= -0.36) and total protein (r= -0.33) were all significant, whereas the conventional SGA had significant correlation only with TIBC (r= -0.35) and MAMC (r= -0.37). Malnutrition score showed a significant correlation with age (r= +0.34) and years dialysed (r= +0.28). Multiple regression analysis showed a significant correlation between the malnutrition score and the combination of the MAMC, BMI, serum albumin concentration and TIBC (r= 0.81, P<0.001). There was no correlation between the malnutrition score and sex, urea reduction ratio, protein catabolic rate, and the absolute lymphocyte count.

CONCLUSIONS

We conclude that our invented malnutrition score, which can be performed in minutes, reliably assesses the nutritional status of haemodialysis patients. We suggest that our malnutrition score may be superior to the SGA. More comparative and longitudinal studies are needed to confirm the validity of this scoring system in nutritional evaluation of dialysis patients.

Screening for hypercholesterolaemia in patients with other risk factors for coronary heart disease

OBJECTIVE

To determine the prevalence of hypercholesterolaemia in individuals with other major risk factors of coronary heart disease and markers of hypercholesterolaemia.

METHODS

A community-based cross-sectional study on a random sample of 261 persons aged between 35 and 69 years residing in the flatted housing estate of West Coast, Singapore, was conducted in 1997. A questionnaire, together with a medical examination and investigation involving the use of Reflotron machine, were used to collect the information required.

RESULTS

43.2% of the population had at least 1 major risk factor, with 18.1% being smokers, 18.1% with hypertension, 6.5% with diabetes mellitus, 5.1% being obese, and 5.0% with a family history of coronary heart disease. Higher percentages of individuals with hypercholesterolaemia were found when each risk factor was present. 9.5% had 2 or more risk factors, of which, 21.1% had high cholesterol levels. A high prevalence of hypercholesterolaemia that was statistically significant was found amongst subjects with corneal arcus below the age of 60.

CONCLUSIONS

The risk factors of coronary heart disease remain prevalent in our population. We recommend screening for serum cholesterol only in those with at least 2 major risk factors of coronary heart disease in the general population between 35 and 69 years of age.

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.