Search PubMed⌕ Search

Biomedical subjects

G J Smith

Publications and source records attributed to G J Smith.

At least 73 records · Page 4Linked to original sources
PubMed1994

Morphologic transformation of the C3H 10T1/2 cell line is accompanied by altered expression of the p53 tumor suppressor gene.

Wildtype 10T1/2 cells and 42 clonally derived morphologically transformed 10T1/2 cell lines were evaluated for expression of p53 mRNA and protein. Wildtype 10T1/2 cells expressed detectable levels of p53 mRNA and multiple immunologically distinct forms of the p53 protein, including both PAb240- and PAb246-reactive conformations of the protein. However, DNA sequence analysis revealed no mutations within the coding sequence of the expressed p53 gene(s) in wildtype 10T1/2 cells. Morphologic transformation of 10T1/2 cells resulted in clonal cell lines that overexpressed p53 mRNA and total p53 protein (PAb421-reactive) relative to the level of expression in wildtype 10T1/2 cells. Immunoprecipitation analysis demonstrated the expression of both PAb246-reactive and PAb240-reactive conformations of the p53 protein in all morphologically transformed 10T1/2 cell lines evaluated, irrespective of the tumorigenic potential of the individual line. Nonetheless, expression of PAb240-reactive p53 protein at levels equal to or higher than that found in wildtype 10T1/2 cells was associated with tumorigenicity in morphologically transformed 10T1/2 cell lines, suggesting that the relative contribution of PAb240-reactive p53 protein to the total cellular p53 protein represents an important determinant for the expression of the tumorigenic phenotype. Our results demonstrate that altered expression of p53 represents a common feature of morphologically transformed 10T1/2 cell line, suggesting that alteration of the expression of the p53 tumor suppressor gene may represent an early and necessary step in the morphologic transformation of 10T1/2 cells. Additionally, overexpression of PAb240-reactive p53 protein may influence the tumorigenic potential of morphologically transformed 10T1/2 cell lines.

Animals↗
PubMed1994

Overexpression of c-K-ras, c-N-ras and transforming growth factor beta co-segregate with tumorigenicity in morphologically transformed C3H 10T1/2 cell lines.

Morphologic transformation and tumorigenicity are separate cellular phenotypes in transformed 10T1/2 cells. We have investigated the levels of expression of genes for c-myc, c-H-ras, c-K-ras, c-N-ras, TGF beta and Rb in 42 morphologically transformed 10T1/2 cell lines, in an attempt to define the molecular mechanisms governing morphologic transformation and tumorigenicity in the 10T1/2 cell system. The 10T1/2 cell lines investigated generally overexpressed mRNAs for c-myc, c-H-ras, and TGF beta relative to the levels expressed by wild-type 10T1/2 cells (levels of expression > 1.5-fold that of wild-type 10T1/2 cells). In contrast, only half of these cell lines overexpressed mRNAs for c-N-ras and/or Rb relative to wild-type 10T1/2 cells, and only 25% overexpressed c-K-ras mRNA. The mean levels of mRNA expression for each of c-K-ras, c-N-ras and TGF beta genes in tumorigenic cell lines were significantly greater than the mean levels of expression in non-tumorigenic cell lines, suggesting an association between tumorigenicity and the levels of expression of these specific genes. In contrast, levels of expression for c-myc, c-H-ras and Rb genes were not correlated with tumorigenicity. Cell lines that coexpressed high levels of c-K-ras, c-N-ras and TGF beta genes were likely to be tumorigenic (11/12 cell lines were tumorigenic), whereas cell lines that coexpressed low levels of these genes were unlikely to be tumorigenic (1/10 cell lines were tumorigenic). High expression of TGF beta was sufficient for tumorigenicity in the absence of high levels of expression of c-K-ras and c-N-ras (5/5 cell lines were tumorigenic). Elevated expression of either c-K-ras or c-N-ras alone was insufficient for tumorigenicity, however, coordinate overexpression of both c-K-ras and c-N-ras was associated with tumorigenicity irrespective of the expression status for TGF beta (13/15 cell lines were tumorigenic). These results suggest that overexpression of c-myc, c-H-ras and TGF beta are commonly associated with, and possibly mechanistically related to, the process of morphologic transformation in 10T1/2 cells. In addition, these results suggest that progression from morphologic transformation to tumorigenicity in 10T1/2 cell lines is frequently accompanied by overexpression of c-K-ras and c-N-ras, and by enhancement of the level of overexpression of TGF beta.

Animals↗
PubMed1994

DNA contents and chromosomes of clonal lines of transformed rat liver epithelial cells and of cells from their derived tumors.

Clonal lines of transformed rat liver epithelial cells, derived from a single population of cloned diploid rat liver epithelial (stem-like) cell line (WB-F344) by exposure in vitro to N-methyl-N'-nitro-N- nitrosoguanidine (MNNG), produce hepatocellular carcinomas, hepatoblastomas and adenocarcinomas in syngeneic rats (Tsao and Grisham, Am. J. Pathol., 127, 168-181, 1987). In this study we show that these clonal lines demonstrate near-diploid (GN clones) or near-triploid (GP clones) aneuploidy and the universal occurrence of non-random chromosomal abnormalities. Marker chromosomes that involved four autosomes--a non-reciprocal translocation involving chromosomes 1 and 7 (t1q43;7q34), and addition of DNA of unknown origin to the pericentromeric regions of chromosomes 4 and 10--occurred in all of the cells of all transformed clones and in the cells of tumors that grew from them. New marker chromosomes involving the same regions of chromosomes 4 and 7 were found in several cell lines established from independent tumors. The preservation of marker chromosomes in tumor cells in the face of random loss and gain of other chromosomes suggests that these non-random aberrations were necessary for tumor formation. The presence of marker chromosomes was associated with increased expression of the c-myc gene (located at q34 on chromosome 7), the c-H-ras gene (located at q41-43 on chromosome 1) and the c-K-ras and TGF alpha genes (both located at unknown sites on chromosome 4), which we have previously shown to be highly correlated with tumorigenicity in these same transformed clonal lines (Lee et al., Cancer Res., 51, 5238-5244, 1992).

Animals↗
PubMed1994

HIV and pulmonary hypertension: a review.

We describe two unique cases of pulmonary hypertension in association with the human immunodeficiency virus (HIV) and review the 28 previously reported cases in the world literature. Our first patient has coexistent chronic active hepatitis, which has previously been associated with the development of plexogenic pulmonary hypertension; however, our second case clearly demonstrates a closer link between HIV infection and pulmonary hypertension. Unlike previously reported cases, our latter case was devoid of all other coexistent factors including intravenous drug abuse, hepatitis B antigenemia, coexisting immunologic lung parenchymal injury, and hepatitis. Additionally, this is the first case documenting the presence of asymptomatic type II cryoglobulins in an HIV-positive patient with plexogenic pulmonary hypertension.

Adult↗
PubMed1994

Characterisation of the cytochrome P450 enzymes involved in the in vitro metabolism of granisetron.

1. The metabolism of granisetron was investigated in human liver microsomes to identify the specific forms of cytochrome P450 responsible. 2. 7-hydroxy and 9'-desmethyl granisetron were identified as the major products of metabolism following incubation of granisetron with human liver microsomes. At low, clinically relevant, concentrations of granisetron the 7-hydroxy metabolite predominated. Rates of granisetron 7-hydroxylation varied over 100-fold in the human livers investigated. 3. Enzyme kinetics demonstrated the involvement of at least two enzymes contributing to the 7-hydroxylation of granisetron, one of which was a high affinity component with a Km of 4 microM. A single, low affinity, enzyme was responsible for the 9'-desmethylation of granisetron. 4. Granisetron caused no inhibition of any of the cytochrome P450 activities investigated (CYP1A2, CYP2A6, CYP2B6, CYP2C9/8, CYP2C19, CYP2D6, CYP2E1 and CYP3A), at concentrations up to 250 microM. 5. Studies using chemical inhibitors selective for individual P450 enzymes indicated the involvement of cytochrome P450 3A (CYP3A), both pathways of granisetron metabolism being very sensitive to ketoconazole inhibition. Correlation data were consistent with the role of CYP3A3/4 in granisetron 9'-desmethylation but indicated that a different enzyme was involved in the 7-hydroxylation.

Cytochrome P-450 Enzyme Inhibitors↗
PubMed1993

Clonal analysis of the expression of multiple transformation phenotypes and tumorigenicity by morphologically transformed 10T1/2 cells.

Seventy-five clonal populations of morphologically transformed 10T1/2 cells were established from independent Type II and Type III foci that were of spontaneous origin or were induced by the carcinogenic agents N-methyl-N'-nitro-N-nitrosoguanidine, benzo(a)pyrene diol epoxide-I, and 3-methylcholanthrene. Clonal populations were characterized for expression of selected transformation phenotypes, including growth to elevated saturation density before cessation of proliferation, anchorage independence, ability to reconstruct foci when plated in the presence of wild-type 10T1/2 cells, and tumorigenicity. Forty-one % of the clonal populations expressed only the phenotype of morphological transformation, while 20% expressed all of the transformation phenotypes, including tumorigenicity, in addition to morphological transformation. The remaining clonal populations expressed varying combinations of one or more of the four transformation phenotypes. Clonal populations expressing almost all of the 16 possible combinations of the transformation phenotypes were observed, suggesting that the individual phenotypes segregated independently. Morphological transformation alone was a poor indicator of tumorigenicity, correctly predicting the tumorigenic potential of only 37% of the clonal populations. Among morphologically transformed clonal populations, coexpression of anchorage independence correctly predicted the tumorigenicity of 81% and coexpression of reconstruction of foci on a confluent lawn of wild-type cells correctly predicted the tumorigenicity of 91%. The probability that a morphologically transformed clonal population was tumorigenic correlated with the total number of transformation phenotypes expressed. Expression of the transformation phenotypes differed between tumorigenic and nontumorigenic clonal populations but not between clonal populations established from Type II and Type III foci. Tumorigenicity varied among transformed clonal populations that were induced by the different carcinogenic agents or were of spontaneous origin but did not differ between clonal populations established from Type II and Type III foci.

Animals↗
PubMed1993

Intraoperative autotransfusion in hepatic resection for malignancy. Is it safe?

To evaluate whether intraoperative autologous transfusion increases the risk of hematogenous dissemination of tumor we reviewed the risk of lung metastasis as well as disease-free and long-term survival of patients who underwent resection of malignant hepatic neoplasms with this technique. A retrospective review of patients undergoing liver resection for malignant disease revealed 39 patients in whom intraoperative autologous transfusion was used. The 2-year actuarial survival in the patients in this series, as calculated with the Kaplan-Meier method, was predicted to be 75%. Two-year actuarial disease-free survival was predicted to be 28%, and the risk of developing lung metastasis at 3 years was estimated to be 40%. The predicted overall survival and risk of recurrence in this series compare favorably with published data for patients in whom intraoperative autologous transfusion was not used.

Actuarial Analysis↗
PubMed1993

Flow cytometric analysis of xenobiotic metabolism activity in isolated rat hepatocytes.

Flow cytometry offers great potential for the study of xenobiotic metabolism in intact cells. We explored this application by the use of ethoxyfluorescein ethyl ester (EFEE) and isolated rat hepatocytes, a classic system for studying such reactions. EFEE is only weakly fluorescent and it diffuses freely into viable cells, where it is metabolized to fluorescein by a process dependent upon mixed-function oxidase activity. In the current study, viable hepatocytes were first identified by flow cytometric assessment of fluorescein diacetate staining. The viable subpopulation was also identifiable on the basis of forward and right angle light scattering properties alone, and it was in this fraction that EFEE metabolism was measured. Metabolism of EFEE to fluorescein was quantified by flow cytometry. SKF 525A, alpha-naphthoflavone, and metyrapone, classic inhibitors of mixed-function oxidation, each inhibited the metabolism of EFEE. These results demonstrate the potential of EFEE for use in flow cytometric studies of drug metabolism, such as in multiparameter mechanistic assays of cellular xenobiotic metabolism and toxicity, and in the isolation by fluorescence-activated cell sorting of subpopulations which differ in this activity.

Animals↗
PubMed1993

Diethylnitrosamine- and partial hepatectomy-induced decrease in alpha 2u-globulin mRNA level in the rat liver.

Changes in gene expression in the rat liver were investigated by analyzing cDNA libraries for liver mRNAs from adult male rats injected with a chemical carcinogen diethylnitrosamine (DEN). Differential screening using normal and DEN-treated liver cDNAs as probes demonstrated that some of the mRNA species had noticeably lower abundance in the DEN-treated liver than in the untreated liver. Surprisingly, most of those clones were found to code for alpha 2u-globulin (A2uG), an abundant protein in the male rat liver. Further analysis by in situ hybridization revealed that the decrease in the A2uG mRNA level occurred in the area where liver cells were proliferating due to DEN treatment and/or partial hepatectomy (PH). The findings indicate coincidence of cell proliferation with a decrease in the A2uG gene expression in the adult male rat liver, implying that the A2uG-related change favors chemical carcinogen-induced cell growth.

Alpha-Globulins↗
PubMed1993

Pulmonary artery balloon counterpulsation: safe after peripheral placement.

Pulmonary artery balloon counterpulsation is a promising experimental technique for treatment of right ventricular failure. However, clinical application has been limited in that the only device presently available (the large-volume intraaortic balloon) must be placed within a synthetic graft. Because a balloon with a smaller volume (which could be placed through a peripheral vein and be contained entirely within the pulmonary artery) would make the technique feasible on a wider scale, we tested an 8-mL pulmonary artery balloon placed through the femoral vein in 12 dogs. Two groups of animals were compared. One group had the pulmonary artery balloon in place but not counterpulsating; the other had the pulmonary artery balloon in place and counterpulsating. Each group was studied for 12 hours. A variety of hemodynamic parameters were measured. Effective diastolic augmentation and systolic unloading were noted in all 6 dogs that underwent counterpulsation (5.0 +/- 1.1 mm Hg of diastolic augmentation and 9.5 +/- 1.6 mm Hg of systolic unloading). Pulmonary function, as measured by arterial blood gas sampling and pulmonary vascular resistance, was not impaired. Examination of the heart and lungs showed no detrimental pathologic effects of pulmonary artery balloon counterpulsation. Placement of the balloon through a peripheral vein with a guidewire was easy and uncomplicated. We conclude that pulmonary artery balloon counterpulsation is safe over an extended period of 12 hours in the canine model and that diastolic augmentation and systolic unloading can be produced.

Animals↗
PubMed1993

The photophysics of haematoporphyrin dimers or aggregates in aqueous solution.

The triplet lifetime and decay rate law observed from haematoporphyrin in aqueous solution were found to depend on concentration with the triplet-state decay being very much slower in dilute solution than in more concentrated solutions. The wavelength of excitation also has an effect on the decay kinetics. In a 1 x 10(-4) mol dm-3 solution the decay resulting from flash photolysis at 527 nm is satisfactorily described by a single exponential having a decay constant of 1.5 x 10(4) S-1 and was ascribed to the triplet state of a haematoporphyrin dimer or aggregate. However, excitation of a haematoporphyrin solution of the same concentration at 351 nm results in a slower triplet-state decay which is indistinguishable, within experimental error, from that observed from a dilute haematoporphyrin solution excited at 527 nm and which is ascribed to the monomer triplet state. Although resolved Soret band absorption spectra indicate that in a 1 x 10(-4) mol dm-3 aqueous solution of haematoporphyrin most radiation at 351 nm is absorbed by a dimer, the decay following flash photolysis at 351 nm is dominated by the triplet state of the haematoporphyrin monomer. This implies that the excited singlet state of the dimer whose ground state absorbs the shorter-wavelength region of the Soret band undergoes efficient intersystem crossing to the monomer triplet state.(ABSTRACT TRUNCATED AT 250 WORDS)

Hematoporphyrins↗
PubMed1993

Relaxation and quenching of the excited states of tryptophan in keratin.

The temperature dependence of the fluorescence and phosphorescence originating from tryptophan residues in the solid protein keratin was studied. The position of the tryptophan fluorescence spectral maximum was measured as a function of temperature and was found to be substantially Stokes shifted even at 77 K. The activation energies for non-radiative relaxation of the singlet and triplet states of tryptophan in wool keratin, derived from Arrhenius plots of the fluorescence and phosphorescence yields, are 580 cm-1 and 995 cm-1 respectively. One possible fluorescence quenching mechanism which is consistent with these observations is a very effective, thermally induced mixing of the 1La and 1Lb excited singlet states which results in enhanced internal conversion apparent as a low fluorescent yield even at low temperatures. The phosphorescence decay from keratin in the absence of oxygen following excitation at 265 nm is non-single exponential. At room temperature it is dominated by a short-lived component with more than 80% of the decay completed within 3 microseconds of the flash. Longer living components with first-order lifetimes as long as 2-3 s were also observed.

Animals↗
PubMed1993

Defense mechanisms in alcoholics attending outpatient treatment. Results from the MCT-test (Meta-Contrast Technique).

Defensive strategies were studied in 72 alcoholics participating in outpatient treatment by using, before the treatment started, the Meta-Contrast Technique, MCT, a percept-genetic method. Alcoholics had less often adaptive strategies than controls. A lack of adaptive defense strategies was related to a more impaired psychic status, more psychological benefits from drinking, and more psychiatric symptoms but not to severity of alcoholism or results of psychometric tests (intellectual level, field-dependence, spatial performance). It does not seem inconceivable that the MCT could be used as a diagnostic tool in treatment planning.

Adaptation, Psychological↗
PubMed1993

Seasonal trends in erythemal and carcinogenic ultraviolet radiation at mid-southern latitudes 1989-1991.

A network of solar carcinogenic/erythemal ultraviolet radiometers has been established in New Zealand. Daily integrated irradiances of this biologically harmful ultraviolet radiation for 1989, 1990 and 1991 are reported from radiometers located at Wellington (41 degrees S) and Christchurch (43.5 degrees S) and for 1990 and 1991 from the Auckland (37 degrees S) radiometer. Although the monitoring program has not been running sufficiently long to discern any long-term changes in levels of solar ultraviolet radiation, shorter term trends are apparent, which are attributed to a seasonal cycle in levels of ozone at midlatitudes and changes in atmospheric aerosols.

Erythema↗
PubMed1993

Isolation, culture, and transplantation of rat hepatocytic precursor (stem-like) cells.

From a review of past studies and the report of new studies from our laboratory, this article provides strong evidence to show that WB-F344 (WB) rat liver epithelial cells are stem-like precursor cells for hepatocytes. WB cells are structurally and phenotypically simple epithelial cells that were isolated from the liver of an adult male Fischer 344 rat, under conditions that excluded their origin from hepatocytes in vivo. WB cells express a phenotypic repertory that overlaps, but is distinct from, that of both hepatocytes and bile duct epithelial cells. The complex phenotype of WB cells is compatible with their being embryonic or undifferentiated variants of either hepatocytes or bile duct epithelial cells. When WB cells are tagged genetically with genes for bacterial beta-galactosidase and neomycin resistance (BAG2-WB), they and their progeny can be distinguished from parental WB cells and hepatocytes by the expression of these gene products. Progeny of BAG2-WB cells that were transplanted into the liver parenchyma of syngeneic rats integrated into hepatic plates and acquired the morphological and functional attributes of adjacent host hepatocytes; the progeny of BAG2-WB cells in the liver express albumin, tyrosine aminotransferase, alpha-1-antitrypsin, and transferrin. We also demonstrate that progeny of BAG2-WB cells can be recovered from livers into which they have been transplanted, which may allow the elucidation of alterations in gene expression that accompany their differentiation.

Animals↗
PubMed1993

Identification of human DNA in complex biological samples using the Alu polymerase chain reaction.

Alu-Polymerase chain reaction (PCR) was used to amplify human DNA from complex mixed sources of DNA. Amplification of human DNA sequences by Alu-PCR could be accomplished in samples containing low concentrations of template in the presence of excess heterologous DNA sequences. Thus, sensitivity and specificity are maintained in complex DNA mixtures allowing positive identification of the presence of human DNA sequences by this technique.

Animals↗
PubMed1993

Regulation of the differentiation of diploid and some aneuploid rat liver epithelial (stemlike) cells by the hepatic microenvironment.

Following intrahepatic transplantation in adult syngeneic Fischer 344 rats, diploid cultured rat liver epithelial cells (WB-F344), modified to carry the Escherichia coli beta-galactosidase reporter gene and/or the fluorescent membrane dye PKH26-GL, integrate into hepatic plates and acquire the size and nuclear structure of mature hepatocytes. Additionally, of two aneuploid, neoplastically transformed derivatives of WB-F344 cells, both of which produce aggressively growing tumors when transplanted subcutaneously, cells of one line (GN6TF) do not produce tumors in the liver but integrate into hepatic plates and morphologically differentiate. The other transformed line (GP7TB) retains tumorigenicity in the liver, but cells in the intrahepatic tumors are more differentiated morphologically than are tumors at subcutaneous sites. These results suggest that WB-F344 cells are stemlike cells for hepatocytes and that the hepatic microenvironment induces them to incorporate into hepatic plates and differentiate. Our results also suggest that the hepatic microenvironment regulates the differentiation of some neoplastically transformed hepatic stemlike cells, thereby eliminating or reducing their tumorigenic potential.

Aneuploidy↗