Biomedical subjects

L M Anderson

Publications and source records attributed to L M Anderson.

At least 37 records · Page 2Linked to original sources

PubMed2000

A potential mechanism for fumonisin B(1)-mediated hepatocarcinogenesis: cyclin D1 stabilization associated with activation of Akt and inhibition of GSK-3beta activity.

Fumonisin B(1) (FB(1)) is a worldwide corn contaminant and has been epidemiologically linked to the high incidence of human esophageal cancer in South Africa and China. FB(1) is hepatocarcinogenic in rats by an unknown mechanism. Inhibition of ceramide synthase and disruption of membrane phospholipids have been shown to be mechanisms of toxicity. Here we show overexpression of cyclin D1 protein in both preneoplastic and neoplastic liver specimens obtained from a long-term feeding study of FB(1) in rats. In rats fed FB(1) short-term, cyclin D1 protein levels in liver were increased up to five-fold in a dose-responsive manner. Northern blot analysis demonstrated no increase in mRNA levels of cyclin D1. 2D electrophoresis of cyclin D1 protein in FB(1)-treated samples showed a distinct pattern of migration (presence of less negatively charged form of the protein) that differed from controls. Recently, it has been shown that phosphorylation of cyclin D1 by glycogen synthase kinase 3beta (GSK-3beta) on a single threonine residue (Thr-286) positively regulates proteosomal degradation of cyclin D1. In FB(1)-treated samples we detected GSK-3beta phosphorylated on serine 9; activated protein kinase B (Akt) appears to be responsible for this activity-inhibiting phosphorylation. These findings suggest that overexpression of cyclin D1 results from stabilization due to a lack of phosphorylation mediated by GSK-3beta. We also observed an increase in cyclin dependent kinase 4 (Cdk4) complexes with cyclin D1 in FB(1)-treated samples; additionally, elevated Cdk4 activity was shown by increased phosphorylation of the retinoblastoma protein. In summary, the activation of Akt leads to increased survival, inhibition of GSK-3beta activity and post-translational stabilization of cyclin D1, all events responsible for disruption of the cell cycle G(1)/S restriction point in hepatocytes. This is the first report suggesting the mechanism by which FB(1) acts as a carcinogen.

Animals↗

PubMed2000

Oxidative DNA damage in liver of mice with different susceptibility to hepatocarcinogenesis.

Susceptibility to spontaneous or chemically-induced liver tumors in mice has been demonstrated to be strain dependent, with the tumor development or promotion phase contributing most to variability. Since reactive oxygen species are thought to play a role in carcinogenesis, especially tumor promotion, we investigated steady-state levels of 8-hydroxy-2'-deoxyguanosine (8-oxo-dG) in hepatic DNA from age matched (7 months), untreated mice of three inbred strains, that differ significantly in their susceptibility to liver carcinogenesis. Male mice of strain C3H, highly sensitive to liver tumorigenesis, had significantly higher levels of hepatic 8-oxo-dG (3.3 SE 0.2 8-oxo-dG/10(5) dG) than resistant strains C57BL (2.1 SE 0.3/10(5) dG; p < 0.01) and A/JCr (2.5 SE 0.1/10(5) dG; p < 0.015). In contrast, levels of 8-oxo-dG in livers of female A/JCr mice (3.1 SE 0.3/10(5) dG) were higher than in those of C3H (2.2 SE 0.1/10(5) dG; p < 0.025) and C57BL females (2.5 SE 0.3/10(5) dG; p = NS). Male C3H livers presented significantly more 8-oxo-dG than those of C3H females (p < 0.002). These results suggest that steady-state levels of 8-oxo-dG may contribute to the inherent differences in susceptibility to hepatocarcinogenesis in inbred strains of mice, especially the high sensitivity of C3H males.

8-Hydroxy-2'-Deoxyguanosine↗

PubMed1999

Multiorgan transplacental and neonatal carcinogenicity of 3'-azido-3'-deoxythymidine in mice.

The anti-HIV drug 3'-azido-3'-deoxythymidine (AZT) is used successfully for reduction of perinatal viral transmission. However toxic side effects including carcinogenesis are possible. To test this, pregnant CD-1 Swiss mice were given 25.0 or 12.5 mg AZT on gestation days 12-18. Previously we reported an increase in lung, liver, and female reproductive system tumors in offspring euthanized at 1 year (Olivero et al., J. Natl. Cancer Inst. 89, 1602-1608, 1997). Findings for all remaining offspring up to 2 years old are reported here. AZT effects were most prominent in female offspring, with a significant threefold increase in lung tumors, a reduction in lymphoblastic and follicle center cell lymphomas, and a significant increase in histiocytic sarcomas (0 in controls, 3% after low-dose AZT, and 8% after high-dose AZT, p = 0.022). Dose-dependent incidences of mammary gland, ovarian, and seminal vesicle tumors were low but significant: 0/106 controls, 3/105 low-dose, and 8/105 high-dose mice presented one of these neoplasms (p = 0.0025). Incidences of females showing any clearly AZT-related neoplasm, in lung, liver, ovary, or mammary gland or histiocytic sarcoma, in the second year, were 12/32 after the low dose and 14/27 after the high dose vs 3/23 controls (p = 0.0045). Also, the sensitivity of neonatal mice was assessed by administration of 25, 50, 100, or 200 mg/kg AZT on postnatal days 1 through 8. The effects at 2 years were similar to those seen after transplacental exposure, with significant increases in lung, liver, and mammary tumors in females. The results confirm that AZT is a moderately effective perinatal carcinogen in mice, targeting several tissue types.

Animals↗

PubMed1999

Preconception urethane or chromium(III) treatment of male mice: multiple neoplastic and non-neoplastic changes in offspring.

Increase in neoplasia in offspring after preconception exposure of parents presents puzzling features such as high frequency of effects and lack of Mendelian inheritance. The present study examined the hypothesis that preconception carcinogenesis involves an increase in the rate of occurrence of neoplasms with a spontaneous incidence. Male NIH Swiss mice (12 per group) were exposed 2 weeks before mating (once, ip) to urethane (1.5 g/kg) or chromium(III) chloride (1 mmol/kg). Offspring (48-78/sex/group) were examined for all grossly apparent changes when moribund or at natural death, followed by histopathological diagnosis and statistical analysis. Significant exposure-related changes occurred in multiple organs. Ten to 20 percent of offspring showed changes related to paternal exposure, including at least one sired by most treated males. Pheochromocytomas occurred in both male and female offspring after both treatments, with none in controls. These neoplasms are rare in mice and suggest endocrine dysfunction as a component of preconception carcinogenesis. This was supported by increases in thyroid follicular cell and Harderian gland tumors, ovarian cysts, and uterine abnormalities. Lung tumors were increased in female offspring only. Effects seen in offspring only after paternal urethane exposure were an increase in preneoplasia/neoplasia in the glandular stomach (males) and in females, increased lymphoma but decreased incidence of histiocytic sarcoma. Increases in incidence of male reproductive gland tumors and of renal non-neoplastic lesions occurred only after chromium exposure. Thus, preconception exposure of fathers to toxicants had a significant impact on both neoplastic and non-neoplastic changes in almost all tissues in which these lesions often occur naturally during the aging process.

Adenoma↗

PubMed1999

Recombinant adenovirus is an appropriate vector for endocytotic protein trafficking studies in cultured neurons.

Endocytosis of full-length beta-amyloid precursor protein (APP) from the plasma membrane contributes to beta-amyloid peptide (Abeta) secretion, and, hence, potentially contributes to the molecular pathogenesis of Alzheimer's disease. We recently have demonstrated that central neuronal APP is endocytosed in a common vesicular compartment with recycling synaptic vesicle integral membrane proteins, but is then sorted away from synaptic vesicles for retrograde transport to the neuronal soma. For this report, we explore whether recombinant adenovirus can be used to modulate APP expression in cultured central neurons to study APP processing by the endocytotic pathway in these cells. Using a replication-deficient recombinant adenovirus that expresses a lacZ reporter (Ad5/CMV-lacZ), we demonstrate high efficiency of transfection (30-35%) at low viral titer (10-20 MOI), with no significant neuronal toxicity or cytoarchitectural change. In addition, we demonstrate that infection with the control virus does not result in re-direction of endogenous neuronal APP from usual endocytotic pathways. We have prepared, using the same genomic background as the control virus, an adenoviral vector that expresses the neuronal isoform of human APP (Ad5/CMV-APP). Infection with Ad5/CMV-APP at 10-20 MOI results in significantly increased immunoreactivity for endocytosed APP with preservation of usual endocytotic trafficking. These results demonstrate that recombinant adenovirus at low titer is an appropriate and effective vector for protein trafficking/processing studies in cultured central neurons.

Adenoviridae↗

PubMed1999

Activation of neu by missense point mutation in the transmembrane domain in schwannomas induced in C3H/HeNCr mice by transplacental exposure to N-nitrosoethylurea.

Transplacentally initiated schwannomas in mice and rats arise preferentially in the Gasserian ganglion of the trigeminal nerve and spinal root ganglia, while those of the Syrian golden hamster most commonly occur subcutaneously. Rat and hamster schwannomas almost invariably contain a mutationally activated neu oncogene. In rat schwannomas, the mutant allele predominates, while the relative abundance of mutant alleles is very low in hamster nerve tumors. We investigated whether neu is mutated in mouse schwannomas and whether the pattern and allelic ratio of the mutation resemble those for the hamster or the rat. Pregnant C3H/HeNCr mice received 0.4 micromol N-nitrosoethylurea/g body weight on day 19 of gestation. Ten trigeminal and one peripheral nerve schwannomas developed in 11 of the 201 offspring. Missense T --> A transversion mutations were detected in the neu transmembrane domain in eight of ten schwannomas analyzed, as determined by MnlI digestion of polymerase chain reaction products. The mutant allele was predominantly detected in two tumors and was abundant in six others. Transfection of eight out of ten mouse tumor DNAs into hamster cells yielded transformed foci; seven out of eight contained mutant mouse neu. Mouse schwannomas closely resembled those of rats both in the preferred anatomical site and in the mutant/wild-type neu allele ratios.

3T3 Cells↗

PubMed1999

Higher activity of 8-oxo-2'-deoxyguanosine 5'-triphosphate pyrophosphohydrolase (8-oxo-dGTPase) coincides with lower background levels of 8-oxo-2'-deoxyguanosine in DNA of fetal compared with maternal mouse organs.

Mammalian homologues of Escherichia coli MutT, a protein having 8-oxo-2'-deoxyguanosine 5'-triphosphate pyrophosphohydrolase (8-oxo-dGTPase) activity, are thought to play the same role in preventing the incorporation of promutagenic 8-oxo-2'-deoxyguanosine (8-oxo-dG) into DNA. One could thus expect that higher activity of 8-oxo-dGTPase should correlate with a lower background level of 8-oxo-dG in nuclear DNA. During transplacental carcinogenesis experiments, in control healthy Swiss mice on day 18 of gestation we found consistently lower levels of 8-oxo-dG in DNA in fetal livers and lungs (1.74+/-0.04 SE and 1.49+/-0.08 SE 8-oxo-dG/10(5) dG, respectively; pooled organs of fetuses of 8 dams) as compared with maternal organs (3.05+/-0.20 SE and 3.08+/-0.17 SE 8-oxo-dG/10(5) dG, respectively; n = 8). The 8-oxo-dGTPase activity determination in the same organs revealed that the lower levels of 8-oxo-dG in fetal DNA did, indeed, coincide with higher 8-oxo-dGTPase activity (48.8+/-2.6 SE and 52.5+/-2.5 SE U/mg protein in livers and lungs, respectively); and vice versa, higher 8-oxo-dG levels in DNA of maternal organs were associated with lower levels of 8-oxo-dGTPase activity (24.3+/-1.3 SE and 4.7+/-0.6 SE U/mg protein, as above). Without excluding other reasons for the relatively low 8-oxo-dG background in DNA of fetal tissues (e.g., higher level of antioxidants and antioxidative enzymes; more efficient DNA repair), this inverse relationship may support or at least does not contradict the concept of a guardian role of 8-oxo-dGTPase against 8-oxo-dGTP mutagenicity in mammalian cells.

8-Hydroxy-2'-Deoxyguanosine↗

PubMed1999

Adenovirus-mediated tissue-targeted expression of the HSVtk gene for the treatment of breast cancer.

In an effort to develop a genetic therapy for the treatment of breast cancer, we constructed adenoviral vectors containing either the beta-galactosidase (beta-gal) reporter gene or the herpes simplex thymidine kinase (HSVtk) suicide gene driven by breast tissue-specific promoters. We utilized upstream regulatory sequences from either the human alpha-lactalbumin (hALA) gene, or the ovine beta-lactoglobulin (oBLG) gene in these vector constructs to target expression of heterologous genes transcriptionally to breast cancer cells both in vitro and in vivo. Data derived from breast tissue-specific reporter vectors in vitro demonstrate that expression from the hALA and oBLG promoters are indeed specific for breast cells (T47D, MCF-7, ZR75-1) when compared with non-breast cells (U2OS, HeLa). Moreover, these vectors displayed tumor cell specificity when compared with the normal MCF-10A breast cell line. These vectors also displayed breast tissue specificity when injected systemically (i.v.) into lactating Balb/c mice, which suggests that these promoters maintain their tissue-specific expression pattern within the context of the adenoviral genome in vivo. Tumors, derived from T47D human breast cancer cells, were established in nude mice and injected with either the tissue-specific reporter or suicide vectors. Results from tumors injected (i.t.) with reporter adenoviruses demonstrate that these promoters are active in T47D cells when grown as established tumors and we observed a marked regression of tumors injected with suicide vectors and treated systemically with gancyclovir (150 mg/kg/day) when compared with control animals. Moreover, mouse survival was prolonged after 35 days in mice undergoing therapy with the suicide vectors in conjunction with gancyclovir when compared with the control animals. These data suggest that the transcriptionally targeted hALA or oBLG driven expression of the HSVtk gene may be a feasible therapy for the treatment of human breast cancer.

Adenoviridae↗

PubMed1999

Comparison of the polymorphic regions of the cytochrome P450 CYP2E1 gene of humans and patas and cynomolgus monkeys.

Cytochrome P450 2E1 (CYP2E1) metabolizes low molecular weight toxicants. CYP2E1 gene polymorphisms have been linked to risk of various cancers and liver disease in humans. Since the patas monkey is a promising model for study of cancer-related alcohol/nitrosamine interactions, we examined CYP2E1 in this monkey for characteristics of two regions that are polymorphic in humans, an RsaI site in the 5' promoter region and a DraI site in intron 6. Another monkey species often used in biomedical research, the cynomolgus monkey, was also examined. Human DNA primers used to amplify a 413 bp segment around the RsaI site also amplified a segment of similar size (409 bp) from DNA of 25 patas monkeys, whereas a product of approximately 800 bp was amplified from DNA of eight cynomolgus monkeys. RsaI did not cut the amplified DNA product from either monkey species. Sequencing revealed that the patas RsaI site was identical to that in humans with the c2c2 CYP2E1 genotype, GTAT. The equivalent cynomolgus sequence, CTAC, has not been observed in humans. Thus, the patas monkey appears to be a useful model for CYP2E1 c2c2 humans, and this genotype, present in 2-25% of humans, may be more primitive than c1c1. For the DraI site, the human primers amplified DNA products similar in size to those from humans, from all patas and cynomolgus monkey DNA samples; none were cut by DraI. Thus, both monkey species appeared to be generally similar to humans of CYP2E1 CC DraI genotype, which is the rarer form of the gene.

Animals↗

PubMed1999

Targeted expression of toxic genes directed by pituitary hormone promoters: a potential strategy for adenovirus-mediated gene therapy of pituitary tumors.

Pituitary adenomas cause clinical manifestations because of mass effects and excess hormone production. This group of tumors represents a tractable target for gene therapy because they are rarely metastatic and because reductions in tumor size and function, in addition to those achieved after surgery, may be of clinical benefit. In this report we describe a strategy for targeting the expression of toxic genes to pituitary cells using adenoviral vectors. Pituitary hormone promoters (human GH or glycoprotein hormone alpha-subunit) were used to express either a marker gene [beta-galactosidase (beta-gal)] or a toxic gene [herpes simplex virus thymidine kinase (TK)]. In GH-producing GH3 cells and in alpha-subunit-producing pituitary tumor cell lines, recombinant adenoviruses containing either the alpha-subunit promoter (Ad alpha Gal; AdaTK) or the GH promoter (AdGHGal; AdGHTK) were expressed at-high levels. Using histological studies and assays for beta-gal activity, expression was shown to persist for at least 21 days, and it was relatively selective for pituitary cell lines. Cytotoxicity studies were performed using the TK-containing vectors and treatment with ganciclovir. Both AdGHTK and AdaTK caused greater than 95% cytotoxicity of GH3 and alphaT3 cells, respectively, at a viral dose (multiplicity of infection, 5 plaque-forming units/cell) that induced minimal toxicity using control viruses. Little cellular toxicity was seen using a nonpituitary cell line (T47D breast tumor cells). The AdGHTK virus also caused marked reduction in the size of GH3 cell tumors that were propagated in nude mice. These studies suggest that adenoviral vectors carrying human pituitary gland specific promoters may be useful for developing gene therapy strategies for the treatment of pituitary adenomas.

Adenoma↗

PubMed1998

von Hippel-Lindau gene mutations in N-nitrosodimethylamine-induced rat renal epithelial tumors.

BACKGROUND: Mutations in the von Hippel-Lindau (VHL) gene are common in human clear cell kidney cancers. Carcinogens in cigarette smoke, especially nitrosamines, are known to induce kidney tumors of a variety of histologic types in rodents--but with no evidence of VHL mutations; however, none of these tumors resembled human clear cell carcinomas. We examined N-nitrosodimethylamine-induced kidney tumors of the clear or mixed clear/granular cell type in Wistar rats to assess the presence of VHL mutations. METHODS: Sections of eight clear or mixed clear/granular cell kidney tumors that had been formalin fixed and paraffin embedded were microdissected. DNA was extracted from the microdissected tissue, and exons 1-3 of the rat VHL gene were examined by use of polymerase chain reaction and cycle sequencing techniques. RESULTS: Four VHL gene mutations (three G:C to A:T and one A:T to G:C) were detected in three of the tumors in contrast to no mutations in 40 previously reported rat kidney tumors of other histologic types (three of eight tumors versus none of 40; two-sided Fisher's exact test; P=.003). Only tumors showing prominent swollen clear cell cytology with a signet-ring appearance had VHL mutations. CONCLUSIONS: To our knowledge, this is the first report of VHL mutations in kidney tumors after direct chemical exposure and provides a possible molecular pathway linking tobacco smoking to kidney cancer.

Adenocarcinoma, Clear Cell↗

PubMed1998

Epidermal growth factor and transforming growth factor-alpha-associated overexpression of cyclin D1, Cdk4, and c-Myc during hepatocarcinogenesis in Helicobacter hepaticus-infected A/JCr mice.

Helicobacter hepaticus is a new bacterial species that is homologous to Helicobacter pylori, a human gastric carcinogen. H. hepaticus causes chronic active hepatitis, with progression to hepatocellular tumors. We hypothesized that chronic up-regulation of epidermal growth factor (EGF), transforming growth factor-alpha, and nuclear oncogenes (cyclin D1 and c-Myc), all known to transform by overexpression, might contribute to tumorigenesis. Livers from mice that were 6-18 months old were analyzed, including nonneoplastic and preneoplastic tissues and tumors, along with age-matched controls, by immunohistochemistry and immunoblotting. EGF and transforming growth factor-alpha were increased at the earliest stage, with a further increase in EGF in tumors. Cyclin D1, cyclin-dependent kinase 4, and c-Myc were strongly increased in all infected livers, with even greater increases in tumors. An increase in cyclin D1/cyclin-dependent kinase 4 complex was also demonstrated in tumors, and its functionality was confirmed by an increase in the hyperphosphorylated:hypophosphorylated retinoblastoma protein ratio. Our findings suggest a possible cooperation of growth factors, cell cycle proteins, and transcription factors during the development of H. hepaticus-associated liver tumors and may have relevance to human cancers associated with bacterial, viral, or parasitic infections.

Animals↗

PubMed1998

Lysosome membrane permeability to anions.

The permeability of rat liver lysosomes to some inorganic and aliphatic organic anions was investigated, using an osmotic-protection methodology. Lysosomes were incubated at 25 degreesC in 250 mOsm solutions of potassium salts of the anions, in the presence of valinomycin, and the latency of lysosomal hexosaminidase measured at intervals. Lysosomes suspended in 250 mM sucrose at 25 degreesC were stable for up to 4 h. When suspended in 250 mOsm solutions of potassium salts of inorganic acids, latency was lost at rates indicating anion permeance decreasing in the order thiocyanate, nitrate and iodide>bromide>chloride>sulfate. This rank order does not correspond with the anion selectivity of any known anion transporter, and is closer to that of the lyotropic series. Results with the potassium salts of aliphatic organic acids indicate little correlation between permeation and hydrocarbon chain length, although formate was more rapidly permeant than acetate and its higher homologs. By contrast, oxalate was less permeable than other dicarboxylic acids. The presence of one or more hydroxy groups decreased permeance. A correlation between permeance and the acid's lowest pKa suggested that penetration was due principally to the entry of the undissociated acid, but there is evidence that the (much more abundant) singly charged anionic form is also significantly permeant.

Animals↗

PubMed1998

Selective mutation of K-ras by N-ethylnitrosourea shifts from codon 12 to codon 61 during fetal mouse lung maturation.

Fetal mouse lung before gestation day 17 shows unique sensitivity to causation of rapidly growing tumors by N-ethylnitrosourea (ENU). Since mouse lung tumors present a mutated K-ras oncogene, we hypothesized that this special susceptibility might reflect an unusual vulnerability of the K-ras gene. Of the lung tumors caused by ENU exposure of BALB/c mice on gestation day 14, 8/25 had a codon 12 mutation in K-ras, vs 4/25 in codon 61. Of 15 tumors after day 16 exposure, three had codon 12 and four codon 61 changes. Tumors from day 18 exposure had only codon 61 mutations (11/16), all A:T to G:C changes (CGA). By contrast, codon 12 (GGT) changes included G:C to T:A, to A:T, and to C:G. These results show significant (P<0.01) shift in the sensitivity of particular K-ras codons to ENU mutation, during fetal mouse lung maturation. In a test of a possible relationship to expression of K-ras, K-ras p21 was measured in lungs of fetal mice, and found to increase markedly on day 18 in comparison to days 14 and 16. Both alkylation of DNA and base damage due to reactive oxygen species are postulated as mechanisms for mutation by ENU, whose efficacies vary with state of fetal lung maturation and K-ras expression.

Adenocarcinoma, Papillary↗

PubMed1998

Lateral asymmetries in infant melody perception.

Two experiments investigated lateral asymmetries in infants' perception of contour-altered and contour-preserved melody changes. In the first study, 40 infants (8.5 months old) of right-handed parents were trained to respond to binaural melody changes with a head turn toward mechanized toy reinforcers. The subsequent test phase included monaural left-ear and right-ear presentations of the familiar melody and of a changed melody. Infants who heard a contour-altered change showed a left-ear advantage, whereas infants who heard a contour-preserved change showed a right-ear advantage. These effects were replicated with a different set of melodies in the second study. The pattern of lateralization for detection of melody changes in infants of right-handed parents resembles that previously found in right-handed adults and may reflect more general hemispheric processing differences in the early organization of auditory information processing.

Auditory Perception↗

PubMed1998

Implications of p53 mutation spectrum for cancer etiology in gastric cancers of various histologic types from a high-risk area of central Italy.

Examination of p53 mutation spectra may provide clues to molecular mechanisms involved in different histologic types of gastric cancer. A total of 105 gastric cancer cases classified according to the Laurén's system were selected from a high-risk area around Florence, Italy. Exons 5-8 of the p53 gene were examined for mutations by the polymerase chain reaction-single strand conformation polymorphism technique and DNA sequencing, using DNA from formalin-fixed paraffin-embedded tissues. Mutation frequency was similar in intestinal-type (12/28) and unclassified tumors (9/18), but was significantly lower in diffuse cancers (12/57, P < 0.05). A similar frequency of p53 mutations was observed among tumor stages in both intestinal-type and unclassified cancers, but in diffuse tumors mutations tended to be associated with invasion beyond the muscularis propria. When base changes were considered, G:C-->A:T transitions at CpG sites were the most common mutations for all the three tumor types with 6 of 11 (55%) in intestinal type, 8 of 12 (67%) in diffuse type, and 5 of 8 (63 %) in unclassified tumors. Frequent p53 mutations in both intestinal-type and unclassified tumors support the hypothesis that unclassified tumors represent variants of the intestinal type and suggest that unclassified tumors, like the intestinal type, may also associate with environmental exposures. The predominance of G:C-->A:T transitions at CpG sites, which are associated with methyltransferase-induced DNA methylation at carbon 5 of cytosine, in all three tumor types suggests that the status of DNA methylation may be the major determinant for p53 mutations and may be also equally important in gastric carcinogenesis regardless of histology.

Adult↗

PubMed1998

Levels and membrane localization of the c-K-ras p21 protein in lungs of mice of different genetic strains and effects of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) and Aroclor 1254.

Mutational activation of the K-ras oncogene often occurs in human and mouse lung adenocarcinomas. Since K-ras p21 functions in trans-membrane signaling, we have investigated whether the amount of this protein in lung cell membranes is a variable that could influence lung tumorigenesis, either due to genetic differences or in response to tumor promoters. The six mouse strains assessed showed little difference in the total lung K-ras p21 after immunoprecipitation and immunoblotting. However, amount of ras p21 in the membrane fraction showed significant differences, with C57BL/6 and BALB/c having 3-5-fold more than NIH Swiss, AKR and DBA mice. Interestingly, a congenic AKR strain having the Ahr(b-1) Ah receptor allele from C57BL/6 mice (designated AKR.B6Ah) had high lung membrane K-ras p21 similar to that of C57BL/6. To test for possible changes related to lung tumor promotion, mice were treated with a promotional dose of TCDD (5 nmol/kg). After 48 h C57BL/6 lungs showed an increase in p21 in both total and membrane fractions. BALB/c, DBA and Swiss mice showed an increase only in membranes. There was no change in the AKR and AKR.B6Ah. Aroclor 1254 (250 mg/kg) caused an increase in membrane/cytosol ratio in Swiss mice. Thus the membrane:cytosol K-ras p21 ratio may be influenced by the Ahr phenotype, and TCDD and PCBs can induce p21 or increase its membrane level in certain strains, but these properties are not fully dependent on Ahr receptor type. In confirmation of the relevance of these findings for the tumor target cell type, the immortalized alveolar type 2 E10 cell line presented K-ras p21 in membrane, and this was increased 4-fold by treatment with 10 nM TCDD.

Adenocarcinoma↗

PubMed1998

Measurement of haemoglobin using single drops of skin puncture blood: is precision acceptable?

The study aimed to investigate local concerns about clinically important discrepancies between repeat HemoCue haemoglobin measurements from single drops of blood. Two biomedical scientists and two health visitors each obtained a series of paired haemoglobin values by fingerprick sampling from healthy volunteers. Seven of 20 paired values obtained by health visitors and three of 20 obtained by scientists from the first drop of blood forming at the puncture site differed by > or = 10 g/l; 11 of 20 paired values obtained by health visitors and one of 20 by the scientists from the fourth drop of blood differed by > or = 10 g/l. After collecting and mixing a number of drops in EDTA tubes before analysis, seven of 40 paired values differed by > 5 g/l, and none by > 10 g/l. Pooling drops of blood before analysis improves precision of HemoCue haemoglobin measurement and allows users to achieve results comparable to those obtained by experienced laboratory staff. Measurement of haemoglobin from single drops of skin puncture blood should be discontinued.

Blood Specimen Collection↗