PubMed Health⌕ Search

Biomedical subjects

J D Meissner

Publications and source records attributed to J D Meissner.

11 recordsLinked to original sources
PubMed2000

Reversible Ca2+-induced fast-to-slow transition in primary skeletal muscle culture cells at the mRNA level.

1. The adult fast character and a Ca2+-inducible reversible transition from a fast to a slow type of rabbit myotube in a primary culture were demonstrated at the mRNA level by Northern blot analysis with probes specific for different myosin heavy chain (MyHC) isoforms and enzymes of energy metabolism. 2. No non-adult MyHC isoform mRNA was detected after 22 days of culture. After 4 weeks of culture the fast MyHCIId mRNA was strongly expressed while MyHCI mRNA was virtually absent, indicating the fast adult character of the myotubes in the primary skeletal muscle culture. 3. The data show that a fast-to-slow transition occurred in the myotubes at the level of MyHC isoform gene expression after treatment with the Ca2+ ionophore A23187. The effects of ionophore treatment were decreased levels of fast MyHCII mRNA and an augmented expression of the slow MyHCI gene. Changes in gene expression started very rapidly 1 day after the onset of ionophore treatment. 4. Levels of citrate synthase mRNA increased and levels of glyceraldehyde 3-phosphate dehydrogenase mRNA decreased during ionophore treatment. This points to a shift from anaerobic to oxidative energy metabolism in the primary skeletal muscle culture cells at the level of gene expression. 5. Withdrawal of the Ca2+ ionophore led to a return to increased levels of MyHCII mRNA and decreased levels of MyHCI mRNA, indicating a slow-to-fast transition in the myotubes and the reversibility of the effect of ionophore on MyHC isoform gene expression.

Animals↗
PubMed2000

Ecto-alkaline phosphatase activity identified at physiological pH range on intact P19 and HL-60 cells is induced by retinoic acid.

The activity of membrane-bound alkaline phosphatase (ALP) expressed on the external surface of cultured murine P19 teratocarcinoma and human HL-60 myeloblastic leukemia cells was studied at physiological pH using p-nitrophenylphosphate (pNPP) as substrate. The rate of substrate hydrolysis catalyzed by intact viable cells remained constant for eight successive incubations of 30 min and was optimal at micromolar substrate concentrations over the pH range 7.4-8.5. The value of apparent K(m) for pNPP in P19 and HL-60 cells was 120 microM. Hydrolytic activity of the ecto-enzyme at physiological pH decreased by the addition of levamisole, a specific and noncompetitive inhibitor of ALP (K(i) P19 = 57 microM; K(i) HL-60 = 50 microM). Inhibition of hydrolysis was reversed by removal of levamisole within 30 min. Retinoic acid (RA), which promotes the differentiation of P19 and HL-60 cells, induced levamisole-sensitive ecto-phosphohydrolase activity at pH 7.4. After its autophosphorylation by ecto-kinase activity, a 98-kDa membrane protein in P19 cells was found to be sensitive to ecto-ALP, and protein dephosphorylation increased after incubation of cells with RA for 24 h and 48 h. Orthovanadate, an inhibitor of all phosphatase activities, blocked the levamisole-sensitive dephosphorylation of the membrane phosphoproteins, while (R)-(-)-epinephrine reversed the effect by complexation of the inhibitor. The results demonstrate that the levamisole-sensitive phosphohydrolase activity on the cell surface is consistent with ecto-ALP activity degrading both physiological concentrations of exogenously added substrate and endogenous surface phosphoproteins under physiological pH conditions. The dephosphorylating properties of ecto-ALP are induced by RA, suggesting a specific function in differentiating P19 teratocarcinoma and HL-60 myeloblastic leukemia cells.

Alkaline Phosphatase↗
PubMed2000

Effects of retinoic acid on N-glycosylation and mRNA stability of the liver/bone/kidney alkaline phosphatase in neuronal cells.

Alkaline phosphatase (ALP) is a glycoenzyme that is highly expressed during carcinogenesis and is induced by retinoic acid (RA) in various cells. We investigated the effects of RA on N-linked glycosylation of the tissue nonspecific liver/bone/kidney- type of ALP (L/B/K ALP), on ALP transcripts, and on total protein glycosylation in two neuronal cell lines, P19 and NG108CC15, and in primary cultures of neonatal rat brain. ALP activity was determined in cell extracts and found to be induced by RA. Tunicamycin was used at various concentrations to inhibit protein N-glycosylation. After treatment of cells with low concentrations (0.1 and 0.125 microgram/ml) of tunicamycin for 48 h, uninduced and RA-induced ALP activity declined while incubation with a protease inhibitor restored activity, indicating that the L/B/K ALP bear N-linked oligosaccharide chains important for maintaining enzymatic activity. Interestingly, ALP activity in RA-treated cultures was less inhibited by tunicamycin compared to untreated controls suggesting that RA may have an impact on ALP N-glycosylation. To investigate effects of RA on ALP glycosylation further, incorporation of [(14)C]mannose and [(35)S]methionine into ALP protein was determined in the presence or absence of RA. The ratio of mannosylation and biosynthesis demonstrate that incubation of cells with RA increased [(14)C]mannose incorporation into ALP molecules. Also, the release of free [(14)C]mannose from ALP molecules relative to the amount of protein by N-Glycanase was increased in RA-treated cultures. In addition, mannosylation of total protein was found to be induced in cells after exposure to RA. Analysis of biosynthesized ALP monomers revealed that RA increased glycosylation of the polypeptides. Furthermore, tunicamycin decreased the stability of ALP mRNA, an effect that was reduced by cotreatment with RA. Thus, the degree of N-glycosylation of the L/B/K ALP as well as mRNA and protein levels of this enzyme are affected by RA. The P19 cell line provides a useful model system to study the molecular mechanism(s) underlying the action of RA on glycosylation during neuronal differentiation further.

Alkaline Phosphatase↗
PubMed1999

Regulation of UDP-N-acetylglucosamine:dolichyl-phosphate N-acetylglucosamine-1-phosphate transferase by retinoic acid in P19 cells.

UDP-N-acetylglucosamine:dolichyl-phosphate N-acetylglucosamine-1-phosphate transferase (GPT) is the first enzyme in the dolichol pathway of protein N-glycosylation, and is implicated in the developmental programmes of a variety of eukaryotes. In the present study we describe the effects of all-trans-retinoic acid (RA) on the levels of GPT protein and enzymic activity, and on the transcription rate of the GPT gene, in mouse P19 teratocarcinoma cells. RA caused a dose-dependent and protein-synthesis-dependent induction of enzyme activity. The maximum induction of GPT activity (about 3-fold) required 2 days of exposure to 1 microM RA. Induced GPT activity also resulted in an increase in the rate of incorporation of [3H]mannose into Glc3Man9GlcNAc2. Enzymic activities paralleled GPT gene expression. The GPT gene was induced (2-fold) after 7 h of RA treatment. An approx. 3-fold increase in a 48 kDa GPT protein and approx. 4-fold increases in the levels of three GPT transcripts (1.8, 2.0 and 2.2 kb) were observed after 2 days of RA treatment. The enhanced levels of GPT protein and mRNAs began to decline 3 days after the initiation of differentiation, and GPT expression was down-regulated during cellular differentiation. GPT activity decreased about 2. 8-fold to a constant level in differentiated P19 cells. The results indicate that the RA-induced enzyme activity was mainly determined by increased transcription of the GPT gene. RA-treated P19 cells were about 4-fold more resistant to tunicamycin, a fungal antibiotic which inhibits GPT, than were control cells. In addition, GPT activity in membranes from RA-treated P19 cells exhibited approx. 4-fold increased resistance to tunicamycin compared with activity in membranes from untreated control cells, demonstrating that resistance to tunicamycin is correlated with induced GPT activity. Furthermore, increased GPT activity had regulatory significance with regard to the rate of incorporation of [3H]mannose into Glc3Man9GlcNAc2-P-P-dolichol and into glycoproteins. Together, the data provide additional insights into the hormonal regulation of GPT and present evidence that the RA-mediated induction of GPT has a regulatory impact on the dolichol pathway.

Animals↗
PubMed1999

Sequencing of prototype viruses in the Venezuelan equine encephalitis antigenic complex.

The 5' nontranslated region (5'NTR) and nonstructural region nucleotide sequences of nine enzootic Venezuelan equine encephalitis (VEE) virus strains were determined, thus completing the genomic RNA sequences of all prototype strains. The full-length genomes, representing VEE virus antigenic subtypes I-VI, range in size from 11.3 to 11.5 kilobases, with 48-53% overall G+C contents. Size disparities result from subtype-related differences in the number and length of direct repeats in the C-terminal nonstructural protein 3 (nsP3) domain coding sequence and the 3'NTR, while G+C content disparities are attributable to strain-specific variations in base composition at the wobble position of the polyprotein codons. Highly-conserved protein components and one nonconserved protein domain constitute the VEE virus replicase polyproteins. Approximately 80% of deduced nsP1 and nsP4 amino acid residues are invariant, compared to less than 20% of C-terminal nsP3 domain residues. In two enzootic strains, C-terminal nsP3 domain sequences degenerate into little more than repetitive serine-rich blocks. Nonstructural region sequence information drawn from a cross-section of VEE virus subtypes clarifies features of alphavirus conserved sequence elements and proteinase recognition signals. As well, whole-genome comparative analysis supports the reclassification of VEE subtype-variety IF and subtype II viruses.

5' Untranslated Regions↗
PubMed1999

Nucleotide sequences and further characterization of human papillomavirus DNA present in the CaSki, SiHa and HeLa cervical carcinoma cell lines.

The complete nucleotide sequences of the human papillomavirus type 16 (HPV-16) variants present in the CaSki and SiHa cervical carcinoma cell lines and the primary subgenomic HPV-18 variant present in the HeLa cervical carcinoma cell line were determined using overlapping bulk PCR products as templates. PCR-based methods were also used to characterize five previously unreported CaSki HPV-16 genomic disruptions and the 5' cellular-viral junction common to all HeLa HPV-18 subgenomic structures.

DNA, Viral↗
PubMed1997

Functional interference between retinoic acid or steroid hormone receptors and the oncoprotein Fli-1.

The Fli-1 protein is a member of the ets proto-oncogene family, whose overexpression is a consequence of Friend murine leukemia virus (F-MuLV) integration in Friend erythroleukemic cells. We present evidence that Fli-1 and the retinoic acid receptor (RAR alpha) can reciprocally repress one another's transcriptional activation. Overexpression of Fli-1 inhibits the retinoic acid-induced activation of genes carrying a functional retinoic acid response element (RARE). Conversely, RAR alpha is able to repress Fli-1-mediated transcriptional activation. Transfection analysis of RAR alpha and Fli-1 mutants in cultured cells demonstrate that the DNA binding domain of RAR alpha and the N-terminal region of Fli-1 are required for repression. Gel retardation analysis demonstrates that RAR alpha cannot bind to the Fli-1 binding site in the E74 promoter and the expression of Fli-1 does not affect RAR alpha binding to DNA. Furthermore, the data suggest an indirect interaction between Fli-1 and RAR alpha mediated by a 'bridging' factor(s) present in nuclear extracts from RM10 erythroleukemia cells. Fli-1 also interferes with the action of receptors for thyroid or glucocorticoid hormone in several hematopoietic cell lines. The RA-induced differentiation and decrease of cell proliferation was blocked in myeloblastic leukemia HL-60 cells overexpressing the N-terminal region of Fli-1 at physiological concentrations of RA. These data suggest that accumulation of Fli-1 can oppose the transcriptional activity of hormone receptors in hematopoietic cells.

Cell Differentiation↗
PubMed1997

Completion of the DNA sequence of mouse adenovirus type 1: sequence of E2B, L1, and L2 (18-51 map units).

The DNA sequence of 9991 nt, corresponding to 18-51 map units of mouse adenovirus type 1 (MAV-1), was determined, completing the sequence of the Larsen strain of MAV-1. The length of the complete MAV-1 genome is 30,946 nucleotides, consistent with previous experimental estimates. The 18-51 map unit region encodes early region 2B proteins necessary for adenoviral replication as well as late region L1 and L2 structural and packaging proteins. Sequence comparison in this region with human adenoviruses indicates broad similarities, including colinear preservation of all recognized open reading frames (ORFs), with highest amino acid identity occurring in the DNA polymerase and polypeptide III (penton base subunit) ORFs. Virus-associated (VA) RNA is not encoded in the region where VA RNAs are found in the human adenoviruses, between E2B and L1, nor is it encoded anywhere in the entire MAV-1 genome. The MAV-1 polypeptide III lacks the arginine-glycine-aspartic acid (RGD) motif which is involved in an association with cell-surface integrins. Only one RGD sequence is found in an identified coding region in the entire MAV-1 genome. Similar to the porcine adenovirus, this RGD sequence is found in the C-terminus of the MAV-1 fiber protein.

Adenovirus E2 Proteins↗
PubMed1996

Retinoic acid-mediated decrease of G (alpha S) protein expression: involvement of G (alpha S) in the differentiation of HL-60 myeloid cells.

The amount of the heterotrimeric G protein subunit G (alpha S) decreases after the induction of human myeloblastic leukemia HL-60 cells to become granulocyte-like cells in the presence of retinoic acid (RA). Compared to untreated control cells, HL-60 cells expressed decreased levels of G (alpha S) protein and mRNA levels after addition of RA to the cultures as shown by immunoblot and Northern blot analysis. The reduction of the G (alpha S) protein in HL-60 cells by antisense RNA expression was associated with (i) decreased cell doubling time; (ii) induction of a granulocyte-like phenotype; (iii) and expression of a surface marker characteristic of myeloid differentiation. Expression of a constitutively active mutant G (alpha S) (Q227L) in HL-60 cells blocked RA-induced differentiation. In contrast, treatment with forskolin, prostaglandin E2, or 8-bromo-cyclic AMP, which increase intracellular cyclic AMP (cAMP) levels, did not inhibit the RA-mediated differentiation process. No changes in cAMP levels occurred in response to RA. The present study provides insights into the involvement of G (alpha S) protein in growth regulation during differentiation of the human myeloid cell line HL-60. These data suggest that in HL-60 human myeloid cells RA-mediated decrease of G (alpha S) plays a critical role in the regulation of differentiation which is independent of intracellular cAMP.

Adenylyl Cyclases↗
PubMed1995

Bcl-2 protooncogene expression in cervical carcinoma cell lines containing inactive p53.

Bcl-2 protein expression has been found to block apoptosis and its overexpression has been implicated in lymphoid malignancies where the chromosomal translocation t(14;18) is present. In this study we investigated bcl-2 transcription and protein expression in cultured cervical carcinoma cell lines and keratinocytes. Western blotting and immunofluorescence microscopy demonstrated bcl-2 expression in the cytoplasm of 4 out of 5 cervical carcinoma cell lines examined (HeLa, CaSki, C-33A, and HT-3, but not SiHa). Bcl-2 protein expression was undetectable in normal keratinocytes. None of the cell lines examined demonstrated chromosomal translocation or rearrangement at the major breakpoint-cluster region (MBR) of the bcl-2 gene using either Southern blot or polymerase chain reaction (PCR) analyses. Northern blot analysis demonstrated low levels of bcl-2 transcription in HeLa, CaSki, and C-33A cell lines while reverse transcriptase (RT)-PCR demonstrated bcl-2 transcription in all cervical carcinoma cell lines which had bcl-2 protein expression. Thus, these data suggest that bcl-2 expression occurs in cervical carcinoma cell lines in the absence of chromosomal translocation or rearrangement of the bcl-2 gene. However, each of these cervical carcinoma cell lines contains inactive p53, either due to mutation (C-33A and HT-3) or via complexation and degradation with human papillomavirus (HPV) 16/18 E6 protein (HeLa and CaSki). Thus, functional p53, which can induce apoptosis in certain cells, is not present in these cervical cells which have increased bcl-2 expression. Increased bcl-2 expression under conditions of p53 inactivation may provide cells with a selective advantage for survival and consequently play a role in the development of cervical carcinogenesis.

Female↗