PubMed Health⌕ Search

Biomedical subjects

L M Brewer

Publications and source records attributed to L M Brewer.

At least 19 recordsLinked to original sources
PubMed1993

HMG-CoA reductase mRNA in the post-implantation rat embryo studied by in situ hybridization.

3-Hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase (EC 1.1.1.34) is the rate limiting step in the mevalonate pathway that produces isoprenoids and cholesterol. Inhibitors of HMG-CoA reductase are teratogenic in vivo and induce neural tube defects in rat embryo culture, effects which appear unrelated to cholesterol deficiency. This study is the first to localize HMG-CoA reductase mRNA by in situ hybridization (ISH). Expression of reductase mRNA was examined in post-implantation rat embryos, and for control purposes in rat liver and UT-1 cells, using a digoxigenin-11 (dig-11) labelled cRNA probe. Eighteen-day fetal liver showed heavy but patchy hybridization, and adult rat liver showed strong hybridization only on some periportal hepatocytes, which was absent in livers of fasted animals. UT-1 cells stimulated to overexpress HMG-CoA reductase mRNA were strongly positive with the same probe. Control hybridizations with sense strand RNA probe, or with cRNA probe on pre-RNased tissue were negative. Strong hybridization signal for HMG-CoA reductase mRNA was observed in all tissues of the post-implantation rat embryo, from egg cylinder to 30 somite stages (7 to 12 days). Heavy signal was noted in primitive ectoderm and neural tube. The wide embryonic and extraembryonic distribution and abundance of HMG-CoA reductase mRNA may reflect developmental requirements for products of the mevalonate pathway, e.g., isoprenoids for post-translational farnesylation of p21ras.

Animals↗
PubMed1992

Distribution of p21ras in postimplantation rat embryos.

Expression of ras cellular oncogenes during the early postimplantation period in the rat was investigated using immunohistochemistry to p21ras. A broad spectrum polyclonal antibody recognizing N-, Ha- and Ki- forms of p21ras was used in an indirect avidin-biotin-peroxidase (ABC) technique. Positive staining indicating the presence of p21ras was found in embryos from 6.5 to 12 days embryonic age. In early egg cylinders (6.5 days), positive staining for p21ras was observed on the ectoplacental cone, primitive ectoderm and trophectoderm, while primitive endoderm and parietal endoderm appeared paler. In later egg cylinder stages (7.5 days), strong positive staining was observed in the primitive embryonic ectoderm and ectoplacental cone, but parietal and visceral endoderm still appeared to be devoid of positive staining. As development proceeded during primitive streak stages, the visceral and parietal endoderm became positively stained. By 10 days, all tissues appeared to be positive for p21ras, with strong staining appearing in the heart and neural elements. Therefore, p21ras does not appear to be ubiquitous in the rat conceptus prior to gastrulation, but shows differential distribution, appearing later in endodermal derivatives. Possibly p21ras is involved in determination of the ectodermal and endodermal lineages.

Animals↗
PubMed1990

Evidence that mammalian ribonucleotide reductase is a nuclear membrane associated glycoprotein.

Epitope-specific antibodies to the M1 and M2 subunits of mammalian ribonucleotide reductase were prepared using peptides predicted to have a high antigenic index. Western blotting demonstrated that the anti-M1 antibody was specific for the 89-kilodalton M1 subunit (and its degradation fragments) and the anti-M2 antibody specifically recognized the 45-kilodalton M2 subunit. Both antibodies inhibited the CDP-reductase activity of the holoenzyme. Using these antibodies, both the M1 and M2 subunits were shown to be localized in the cytoplasm and in the nuclear regions of a number of cell types, including B77 avian sarcoma virus transformed NRK cells, T51B rat liver cells, 5123tc hepatoma cells, and rat liver cells in vivo. In addition, the M1 subunit was found to be localized as a halo around isolated rat liver nuclei. Biochemical analysis of the cytoplasmic fraction of liver cells and a Triton X-100 wash of nuclei from these cells confirmed the location of the enzyme activity in these cellular compartments. The M1 subunit appears to be glycosylated, as indicated by its retention on a Affi-Gel-concanavalin A affinity column. Therefore, in mammalian cells ribonucleotide reductase appears to be not only in the cytoplasm, but is also associated with the nuclear membrane or nuclear lamina. The activity of the enzyme in the membrane fraction changes dynamically during the cell cycle.

Animals↗
PubMed1989

Immunocytochemical detection of the onco-developmental protein oncomodulin in pre-neoplastic and neoplastic hepatocellular lesions during hepatocarcinogenesis in rats.

Oncomodulin is a calcium-binding protein, detectable in extra-embryonic human and rat placental cells and in a wide variety of tumors, but not in any normal embryonic or adult rodent or human tissues. It is also absent from proliferatively active fetal or regenerating adult rat liver. The presence of this oncodevelopmental marker was investigated in pre-neoplastic and neoplastic liver lesions during hepatocarcinogenesis induced in rats by DENA treatment, using an antibody raised against purified oncomodulin. Positive immunostaining was observed in foci of altered hepatocytes, in neoplastic nodules and in HC, but not in the histologically normal surrounding liver parenchyma. The proportion of oncomodulin-positive foci gradually rose from 20-25% at 2-3 months after DENA treatment, to about 88% at 6 months and later. The proportion of positive neoplastic nodules increased from 50% at 5 months to about 73% (range 36-100) at 9 months and later; 88% of the HC found 10 to 20 months after DENA treatment were also positive. That early neoplastic nodules are oncomodulin-positive in a proportion (50%) similar to that of foci after the same duration of treatment is consistent with a lineage relationship between them but makes it unlikely that oncomodulin expression conditions the focus-nodule transition. The role, if any, of oncomodulin in malignant progression remains to be elucidated. It seems out of the question that it is a simple correlate of proliferative activity.

Animals↗
PubMed1988

Varying oncomodulin mRNA abundance in developing placenta and solid tumors.

An antisense RNA probe complementary to rat oncomodulin mRNA has been prepared by run-off transcription. Blots of RNA isolated from tumors arising from both a chemically-induced hepatoma or virally transformed sarcomas, when probed with this antisense RNA, identified a common single hybridizable RNA of approx. 750 nucleotides, corresponding in size to that found in blots of RNA from rat placenta. Quantitative densitometry of dot blot autoradiographs allowed for relative measurements of oncomodulin mRNA in the various tumors. The increased sensitivity of detection afforded by the antisense probe permitted the measurement of oncomodulin mRNA in the developing placenta, which was not possible using DNA probes. In both tumors and placenta, a plot of mRNA versus protein revealed a direct relationship suggesting transcriptional control of oncomodulin abundance.

Animals↗
PubMed1985

Localization and synthesis of the tumor protein oncomodulin in extraembryonic tissues of the fetal rat.

The calcium-binding protein oncomodulin, previously found only in tumors, has been detected during rat development. Specific antisera to purified rat hepatoma oncomodulin (MW 11,500) were used to detect oncomodulin by radioimmunoassay (RIA) and by avidin-biotin-peroxidase complex (ABC) immunohistochemistry. Using RIA, oncomodulin was found to increase in placenta from below the limits of detection (2 ng/mg protein) on Day 13 to approximately 25 ng/mg on Day 16 of pregnancy, and to remain high through to the end of gestation. Determinations on separated inner and outer placenta showed the increase to be greater in the outer placenta (basal zone and decidua) than in the inner placenta (labyrinth). The ABC technique on paraffin sections produced positive staining for oncomodulin throughout the placenta, with the most intense staining occurring in the outer placenta (cytotrophoblast and giant cells of the basal zone). Parietal and visceral yolk sac, and amnion also stained positively, while fetal organs did not. Oncomodulin synthesis measured by [35S]methionine incorporation into immunoprecipitates occurred in isolated inner and outer placenta, whole placenta, the separated trophectoderm and endoderm of the parietal yolk sac, and amnion. No oncomodulin synthesis could be measured in visceral yolk sac, fetal liver, or 16-day embryo. This occurrence in developing and transformed tissues demonstrates that oncomodulin is an oncodevelopmental protein.

Animals↗
PubMed1985

The widely-distributed tumour protein, oncomodulin, is a normal constituent of human and rodent placentas.

Oncomodulin, first found in tumours, turns out to be a highly conserved oncodevelopmental protein in human and rodent placentas. The human and rat placental oncomodulins were visualised immunohistochemically. The placental oncomodulins are identical to each other, and to tumour oncomodulin with respect to amino acid composition, chromatographic elution and the pattern of the peptides released by trypsin action.

Amino Acids↗
PubMed1984

Immunocytochemical detection of oncomodulin in tumor tissue.

Using the rat hepatoma calcium-binding protein, oncomodulin, from Morris hepatoma 5123tc, an antiserum has been raised in rabbits useful for immunostaining of this tumor protein. The peroxidase-antiperoxidase (PAP) technique has been used to demonstrate oncomodulin in sections of Morris rat hepatomas 5123D, 5123tc, 7288Ctc, and 7777 fixed with Bouin's or Carnoy's fixatives, or using freeze substitution. Oncomodulin-specific staining was also shown by a hepatoma metastasis in lung. Optimal conditions for the indirect fluorescent antibody technique were established to demonstrate oncomodulin in virally transformed NRK cells (ASV-NRK). In both tumors and cultured neoplastic cells staining appeared which suggested that oncomodulin might occur in nucleus and cytoplasm. Normal untransformed tissues and uninfected cells did not show oncomodulin staining.

Animals↗
PubMed1983

Hydrocortisone and 1,25(OH)2D3: role in proliferative responses of the embryonic chick duodenum in organ culture.

The present studies were conducted to determine if hydrocortisone (HC) and/or 1,25-dihydroxycholecalciferol (1,25(OH)2D3) alter proliferative responses of the cultured duodenum, and if such alterations could be related to the known augmentation of 1,25(OH)2D3-induction of a specific, intestinal calcium-binding protein (CaBP) by glucocorticoids. HC stimulated proliferation in the duodenal epithelium, as indicated by increased DNA synthesis (3H-thymidine uptake), increased cell number/villus, and increased mitotic index after colchicine treatment. Goblet cell numbers were not significantly increased with any hormone treatment. The presence of 1,25(OH)2D3 alone did not affect proliferative responses. CaBP concentration as a function of tissue weight was 50% greater in HC stimulated intestine, indicating that the proliferogenic action of HC on the duodenum alone could not account for the glucocorticoid-1,25(OH)2D3 interaction in CaBP synthesis.

Alkaline Phosphatase↗
PubMed1983

The periodic health examination. Of what real value is it?

The periodic health examination for adults does not have the blessing of the entire medical community. In fact, screening for disease is quite a controversial subject, with adamant supporters pro and con. In this article, Dr Brewer shares his views--and those of others--as he assesses the value of common screening tests.

Blood Glucose↗
PubMed1983

Occurrence of the tumor-specific, calcium-binding protein, oncomodulin, in virally transformed normal rat kidney cells.

Oncomodulin, an apparently tumor-specific calcium-binding protein, has been detected in many chemically induced rat hepatomas. It is now possible to detect, by radioimmunoassay and immunofluorescence, the presence of oncomodulin in normal rat kidney cells virally transformed by avian sarcoma virus. By contrast, it was not detected in uninfected, nonneoplastic normal rat kidney cells. The protein was isolated and purified by a novel high-performance liquid chromatography procedure and shown to be identical to that isolated previously from rat hepatoma. The cellular levels of oncomodulin approached the levels of calmodulin in avian sarcoma virus-transformed normal rat kidney cells, suggesting that the total calcium-binding activity of the cell may play a role in expression of the transformed phenotype.

Amino Acids↗
PubMedDate not supplied

Detection of oncomodulin, an oncodevelopmental protein in human placenta and choriocarcinoma cell lines.

Oncomodulin was detected by immunocytochemical means in human placenta and found to occur in the cytotrophoblastic shell during implantation, in Langhans type villar cytotrophoblastic cells, and in extravillar cytotrophoblast or intermediate trophoblast. The presence of oncomodulin during first and early second trimester was confirmed by immunoradiometric assay (IRMA). In term placenta oncomodulin appeared in intermediate trophoblast cells, and was largely absent from the villi which lack cytotrophoblast. Furthermore, oncomodulin was abundant in the choriocarcinoma cell line BeWo, and detectable in JAR but not JEG-3. The function of this oncodevelopmental calcium-binding protein in normal development or in neoplasia is not known.

Amnion↗