bluuebunny/crossref_metadata_2025_split huggingface dataset:
Arrest of cell cycle progression of HeLa cells in the early G1 phase in K+‐depleted conditions and its recovery upon addition of insulin and LDL
Authors: Yamaguchi Hisao , Hosokawa Keiko , Jiang Zheng‐Lin , Takahashi Akira , Ikehara Toshitaka , Miyamoto Hiroshi 
Published: May 2005

AbstractCell cycle progression of synchronized HeLa cells was studied by measuring labeling of the nuclei with [3H]thymidine. The progression was arrested in a chemically defined medium in which K+ was replaced by Rb+ (Rb‐CDM) but was restored upon addition of insulin and/or low density lipoprotein (LDL). Cells started DNA synthesis 12 hr after addition of insulin and/or LDL, regardless of the time of arrest, suggesting their arrest early in the G1 phase. After incubation of cells in Rb‐CDM containing insulin or LDL singly for 3, 6, or 9 hr, replacement of the medium by that without an addition resulted in marked delay in entry of cells into the S phase, but in its replacement by medium containing both agents, the delay was insignificant. Synthesis of bulk protein, estimated as increase in the cell volume, was not strongly inhibited. From these results we conclude that cell cycle progression of HeLa cells in K−‐depleted CDM is arrested early in the G1 phase and that the arrest is due to lack of some protein(s) required for entry into the S phase that is synthesized in the early G1 phase.
Density‐dependent endothelial cell production of an inhibitor of smooth muscle cell growth
Authors: Dodge Andrea B. , Lu Xiaoqing , D'Amore Patricia A. 
Published: May 2005

AbstractEmbryonic data and ultrastructural analyses suggest that the primitive endothelium signals undifferentiated mesenchymal cells to migrate to the forming blood vessel and subsequently regulates mural cell growth and behavior. Upon maturation of the blood vessel, chemotactic and mitogenic signals are apparently diminished and differentiated smooth muscle cells normally remain quiescent. This homeostasis is seemingly upset in conditions which lead to pathologies characterized by smooth muscle cell hyperplasia such as atherosclerosis. By culturing endothelial cells at different densities, we attempted to re‐create the various stages of vascular development. Whereas media conditioned by sparse endothelial cells stimulate smooth muscle cells, media conditioned by dense endothelial cell cultures are inhibitory. Culture of sparse smooth muscle cells in media conditioned for 3 days by postconfluent endothelial cell cultures leads to dose‐dependent and reversible smooth muscle cell inhibition. Furthermore, in the presence of the endothelial cell‐derived inhibitor, smooth muscle cells are rendered refractory to mitogens such as fibroblast growth factor and platelet‐derived growth factor. The inhibitory activity is not attributable to the well‐characterized inhibitors of smooth muscle cell growth, transforming growth factor type‐β, prostaglandin I2, or heparan sulfate proteoglycan. Partial characterization of the inhibitory conditioned media suggests that the active molecule is smaller than 1,000 da, and stable to boiling as well as proteinase K and heparinase digestion. These findings support the concept that there is intercellular communication between endothelial cells and smooth muscle cells and provide evidence for a novel endothelial cell‐derived smooth muscle cell growth inhibitor.
Vimentin serves as a phosphate sink during the apparent activation of protein kinases by okadaic acid in mammalian cells
Authors: Lai Yiu‐Kay , Lee Wen‐Chuan , Chen Kuang‐Den 
Published: May 2005

AbstractThe vimentin contents of four mammalian cell lines originating from rat and human tissues were determined by immunoblotting and scanning densitometry. On per cell volume basis, vimentin content in 9L, KD, and HeLa cells was found to be 206.6, 151.6, and 19.1 ng/μl, respectively. A431 cells were devoid of vimentin. Protein phosphorylation was augmented by treatment of 600 nM okadaic acid for 1 h in these cells. During the apparent activation of protein kinases, vimentin became hyperphosphorylated and the phosphorylation level of other nonvimentin phosphoproteins was relatively little affected in 9L and KD cells. In contrast, cytokeratins and other nonvimentin proteins were heavily phosphorylated in OA‐treated HeLa and A431 cells. Regression analysis indicated that the relative increase in phosphorylation level of nonvimentin phosphoproteins was inversely correlated to the contents of vimentin in the four cell lines [r2 = −0.985]. These observations strongly suggest that vimentin acts as a phosphate sink by which the effects of “excess kinase activity” inflicted by phosphatases inhibition was attenuated.
Vasopressin induces arachidonic acid release through pertussis toxin‐sensitive GTP‐binding protein in aortic smooth muscle cells: Independence from phosphoinositide hydrolysis
Authors: Ito Yoshiaki , Kozawa Osamu , Tokuda Haruhiko , Kotoyori Jun , Oiso Yutaka 
Published: May 2005

AbstractWe previously reported that pertussis toxin (PTX) had little effect on arginine vasopressin‐induced formation of inositol trisphosphate (IP3) in rat aortic smooth muscle cells [Kondo et al.: Biochemical and Biophysical Research Communications 161:677–682, 1989]. In the present study, we investigated the mechanism of vasopressin‐induced arachidonic acid release in rat aortic smooth muscle cells. Vasopressin stimulated both the release of arachidonic acid and the formation of IP3 dose dependently in the range between 10 pM and 1 μM. The effect of vasopressin on arachidonic acid release was more potent than that on the formation of IP3. Quinacrine, a phospholipase A2 inhibitor, significantly suppressed the vasopressin‐induced arachidonic acid release but had little effect on the formation of inositol phosphates. NaF, a GTP‐binding protein activator, mimicked vasopressin by stimulating the arachidonic acid release. The arachidonic acid release stimulated by a combination of vasopressin and NaF was not additive. PTX partially but significantly suppressed the vasopressin‐induced arachidonic acid release. In the cell membranes, PTX catalyzed ADP‐ribosylation of a protein with an Mr of about 40,000. Pretreatment of membranes with 0.1 μM vasopressin in the presence of 2.5 mM MgCl2 and 100 μM GTP markedly attenuated this PTX‐catalyzed ADP‐ribosylation of the protein in a time‐dependent manner. These results strongly suggest that PTX‐sensitive GTP‐binding protein is involved in the coupling of vasopressin receptor to phospholipase A2 in primary cultured rat aortic smooth muscle cells.
Adenovirus genes that modulate the sensitivity of virus‐infected cells to lysis by TNF
Authors: Wold William S. M. 
Published: May 2005

AbstractTNF is a key inflammatory cytokine with antiviral properties. Human adenoviruses encode several intracellular proteins that mediate the effects of TNF. Expression of the adenovirus immediate early E1A proteins induces viral genes and a host of cellular genes, drives G0 cells into S‐phase, and induces apoptosis and susceptibility to TNF‐induced apoptosis. The adenovirus E1B‐19K protein inhibits both E1A‐ and TNF‐induced apoptosis. The E3‐14.7K protein and the E3‐10.4K/14.5K complex of proteins inhibit TNF‐ but not E1A‐induced apoptosis. The E3 14.7K and 10.4K/14.5K proteins inhibit TNF activation of cytosolic phospholipase A2 (cPLA2), which may explain how they inhibit TNF cytolysis. Since eicosinoids produced from arachidonic acid (the product of cPLA2) are potent mediators of inflammation, the E3 proteins may block the inflammatory response to adenovirus infection. These adenovirus proteins should be novel tools to understand adenovirus pathogenesis, TNF signal transduction, and TNF cytolysis.
Cytokine involvement in viral permissiveness and the progression of HIV disease
Authors: Butera Salvatore T. 
Published: May 2005

AbstractMany viruses have evolved novel means of exploiting host defense mechanisms for their own survival. This exploitation may be best exemplified by the interrelationships between certain viruses and the host cytokine networks. Many viruses, including the human immunodeficiency virus type‐1 (HIV‐1), rely on the liberation and cellular action of host immune cytokines to expand their host cell range, to regulate their cellular expression, and to maintain their dormant state until the proper extracellular conditions arise. As again exemplified by HIV‐1, viruses may also take an active role regulating cytokine expression and cell surface cytokine receptors. Because the viral life cycle, and in particular the HIV‐1 life cycle, is so intertwined with cytokine regulatory networks, these networks represent potential points for therapeutic intervention. As our understanding of cellular cytokine pathways involved in viral infection and replication continues to expand, so too will our ability to design rational anti‐viral therapies to alter multiple steps along the viral life cycle.
Enhanced repair of a cisplatin‐damaged reporter chloramphenicol‐O‐acetyltransferase gene and altered activities of DNA polymerases α and β, and DNA ligase in cells of a human malignant glioma following in vivo cisplatin therapy
Authors: Ali‐Osman Francis , Berger Mitchel S. , Rairkar Asha , Stein Donna E. 
Published: May 2005

AbstractCurrent evidence suggest an important role for increased repair of drug‐induced DNA damage as one of the major mechanisms involved in tumor cell resistance to cis‐DDP. In this study, we examined the DNA repair capacity and the activities of three DNA repair related proteins, namely, DNA polymerases α and β, and total DNA ligase in cells of a malignant oligodendroglioma obtained from a patient before therapy and compared it with those of a specimen of the tumor acquired after the patient had failed cis‐DDP therapy. DNA repair capacity was quantitated as the extent of reactivation of the chloramphenicol‐O‐acetyltransferase (CAT) gene in a eukaryotic expression vector that has been damaged and inactivated by prior treatment with cis‐DDP and then transfected into the tumor cells. The extent of DNA‐platinum adduct formation in the expression vector was determined by flameless atomic absorption spectrometry. The level of cis‐DDP resistance of cells of the two tumors was determined with the capillary tumor stem cell assay. We observed a 2.8‐fold increased capacity to repair Pt‐DNA adducts and reactivate the CAT gene in cells of the tumor obtained after cis‐DDP therapy, compared to cells of the untreated tumor. This was associated with increases of 9.4‐fold and a 2.3‐fold, respectively, in DNA polymerase β and total DNA ligase activities in cells of the treated tumor. At 5 μM cis‐DDP, there was a 5.9‐fold increase in the in vitro cis‐DDP resistance of post‐therapy tumor cells relative to cells of the untreated tumor. No significant difference in DNA polymerase α activity was observed between the two tumors. These data suggest that the enhanced ability to repair cis‐DDP induced DNA damage, mediated, in part, by increased tumor DNA polymerase β and DNA ligase activities, plays an important role in the in vivo acquisition of cis‐DDP resistance in human malignant gliomas, and that these proteins and/or their encoding genes may represent critical targets for strategies to overcome such resistance clinically.
Interferon α selectively affects expression of the human myeloid cell nuclear differentiation antigen in late stage cells in the monocytic but not the granulocytic lineage
Authors: Briggs R. , Dworkin L. , Briggs J. , Dessypris E. , Stein J. , Stein G. , Lian J. 
Published: May 2005

AbstractThe human myeloid cell nuclear differentiation antigen (MNDA) is expressed constitutively in cells of the myeloid lineage, appearing in myeloblast cells in some cases of acute myeloid leukemia and consistently being detected in promyelocyte stage cells as well as in all later stage cells including peripheral blood monocytes and granulocytes. The human myeloid leukemia cell lines, HL‐60, U937, and THP‐1, express similar levels of immunochemically detectable MNDA. Although, the level of MNDA mRNA in primary monocytes is very low it was up‐regulated at 6 h following the addition of interferon α. The effect of interferon α on the MNDA mRNA is also observed in the cell lines HL‐60, U937, and THP‐1. The MNDA mRNA level in primary granulocytes was unaffected by addition of interferon α and other agents including interferon γ, endotoxin, poly (I) · poly (C), and FMLP. The MNDA mRNA level in the myeloid cell lines was also unaffected by the latter four agents. Induction of differentiation in the myeloid cell lines with phorbol ester induces monocyte differentiation which was accompanied by a decrease in MNDA mRNA level. This reduced level of mRNA could then be elevated with subsequent interferon α treatment. The effects of phorbol ester on MNDA mRNA appeared to be associated with induced differentiation since inhibiting cell proliferation did not alter the level of MNDA mRNA and cell cycle variation in MNDA mRNA levels were not observed. The ability of interferon α to up‐regulate MNDA mRNA in phorbol ester treated myeloid cell lines is consistent with the observations made in primary monocytes. Granulocyte differentiation induced by retinoic acid treatment of HL‐60 cells did not alter the MNDA mRNA level which was also unchanged following subsequent treatment with interferon α. The lack of interferon α effects on retinoic acid treated HL‐60 cells is consistent with its inability to influence MNDA mRNA level in primary granulocytes.
Identification of transferrin as one of multiple EDTA‐extractable extracellular proteins involved in early chick heart morphogenesis
Authors: Isokawa Keitaro , Rezaee Mehrdad , Wunsch Ann , Markwald Roger R. , Krug Edward L. 
Published: May 2005

AbstractIt was demonstrated previously that a polyclonal antibody (ES1) raised against EDTA extractable proteins from embryonic chicken heart blocks cardiac endothelial‐mesenchymal transformation in a culture bioassay and stains extracellular matrix at sites of embryonic inductive interactions, e.g., developing heart, limb buds, and neural crest forming region (Krug et al., 1987, Dev Biol 120:348–355; Mjaatvedt et al., 1991, Dev Biol 145:219–230). In the present study, by using an antiserum (ES3) to a similar immunogen, we affinity purified four major EDTA‐soluble proteins. These proteins migrated as 27, 44, 63, and 70 kD molecules under reduced conditions and 27, 41, 52, and 59 kD under nonreduced conditions, respectively, on SDS‐PAGE. Based on several criteria, the protein migrating at 70/59 kD (reduced/nonreduced) was indistinguishable from chicken transferrin (conalbumin): (1) amino acid sequencing showed that eight N‐terminal residues were identical to those of chicken transferrin, (2) acid hydrolysates of both proteins had nearly identical compositions, (3) the protein co‐migrated exactly with chicken transferrin under both reduced and nonreduced conditions, and (4) ES3 IgG recognized both the 70/59 kD protein and chicken transferrin by western blot analysis of nonreduced samples, but not with reduced samples. Immunohistochemistry of chicken embryonic heart with antibodies against transferrin demonstrated that anti‐transferrin immunoreactivity is present in myocardium but absent in cardiac endothelium before the initiation of cardiac endothelial‐mesenchymal formation. However, both cardiac endothelium and migrating mesenchymal cells became immunoreactive with anti‐transferrin at the time transformation occurred. These findings suggest a possible involvement of transferrin in the inductive process of cardiac endothelial‐mesenchymal transformation.
Primate testicular histone H1t genes are highly conserved and the human H1t gene is located on chromosome 6
Authors: Koppel Daniel A. , Wolfe Steven A. , Fogelfeld Leon A. , Merchant Peggy S. , Prouty Leonard , Grimes Sidney R. 
Published: May 2005

AbstractThe testis‐specific histone H1t gene is known to be transcribed only in pachytene primary spermatocytes during spermatogenesis. Previous studies of the rat histone H1t gene revealed a unique promoter sequence element between the H1/GC box and the H1/CCAAT box. Proteins in crude nuclear extracts of rat testis bind specifically to this sequence element and a temporal correlation exists between the appearance of these DNA binding proteins and the onset of transcription. These discoveries led to a search for histone H1t genes in other mammalian species. The human and monkey histone H1t genes were amplified from genomic DNA using the polymerase chain reaction (PCR). The amplified genes were cloned and the genomic derived inserts were sequenced using linear PCR. Both proximal promoters contained the highly conserved H1/AC box, H1/CCAAT box, and H1/TATA box found in nongerminal H1 genes. Both promoters also contained the H1/GC box and the H1t/CCTAGG sequence element between the H1/GC box and H1/CCAAT box previously seen only in the H1t promoter. Specific amplification of the human H1t gene using template DNA samples from a NIGMS human/rodent somatic cell hybrid mapping panel has shown that the human histone H1t gene is located on chromosome 6.
WI‐38 cell long‐term quiescence model system: A valuable tool to study molecular events that regulate growth
Authors: Soprano Kenneth J. 
Published: May 2005

AbstractA number of cell culture model systems have been used to study the regulation of cell cycle progression at the molecular level. In this paper we describe the WI‐38 cell long‐term quiescence model system. By modulating the length of time that WI‐38 cells are density arrested, it is possible to proportionately alter the length of the prereplicative or G‐1 phase which the cell traverses after growth factor stimulation in preparation for entry into DNA synthesis. Through studies aimed at understanding the cause and molecular nature of the prolongation of the prereplicative phase, we have determined that gene expression plays an important role in establishing growth factor “competence” and that once the cell becomes “competent” there is a defined order to the molecular events that follow during the remainder of G‐1. More specifically, we have determined that the prolongation represents a delay in the ability of long term quiescent cells to become fully “competent” to respond to growth factors which regulate progression through G‐1 into S. This prolongation appears to occur as a result of changes during long term quiescence in the ability of immediate early G‐1 specific genes (such as c‐myc) to activate the expression of early G‐1 specific genes (such as ornithine decarboxylase). While ODC is the first and thus far only growth associated gene identified as a target of c‐myc (and the Myc/Max protein complex), it is likely that further studies in this model system will reveal other early G‐1 growth regulatory genes. We anticipate that future follow‐up studies in this model system will provide additional valuable information abuot the function of growth‐regulatory genes in controlling growth factor responsiveness and cell cycle progression.
Requirements for DNA transcription and replication at the beginning of mouse development
Authors: Majumder Sadhan , Depamphilis Melvin L. 
Published: May 2005

AbstractIn mice, the first round of DNA replication occurs in fertilized eggs (1‐cell embryos), while the onset of zygotic gene transcription begins ∼ 20 hours after fertilization, a time that normally coincides with formation of a 2‐cell embryo. One approach to investigating the mechanisms that control these developmentally regulated events has been to microinject plasmid DNA into the nuclei of mouse oocytes and embryos in order to determine the requirements for unique DNA sequences that regulate transcription and replication. The results from these and other studies have revealed two important mechanisms that regulate the beginning of animal development. The first is a time dependent “zygotic clock” of unknown detail that delays the onset of transcription, regardless of whether or not a 2‐cell embryo is formed. The second is a mechanism that represses the activity of promoters and origins of replication specifically in maternal pronuclei of oocytes and 1‐cell embryos, and in all nuclei of 2‐cell embryos, regardless of their parental origin or ploidy. This repression is linked to chromatin, but the striking ability to relieve this repression with specific embryo‐responsive enhancers first appears with formation of a 2‐cell embryo. The need for a TATA‐box to mediate enhancer stimulation of promoter activity appears even later when cell differention becomes evident. Thus, a biological clock delays transcription until both paternal and maternal genomes are replicated and remodeled from a post‐meiotic state to one in which transcription is repressed by chromatin structure in a manner that can be relieved by cell‐specific enhancers at appropriate times during development. © 1994 Wiley‐Liss, Inc.
Transcriptionally active nuclei isolated from intact bone reflect modified levels of gene expression in skeletal development and pathology
Authors: Shalhoub V. , Bortell R. , Jackson M. E. , Marks S. C. , Stein J. L. , Lian J. B. , Stein G. S. 
Published: May 2005

AbstractTranscriptional regulation of gene expression in vivo in bone, associated with normal development or skeletal disorders, to date, has not been studied. We report the successful isolation of nuclei that are transcriptionally active from normal and osteopetrotic rat bone. Transcription rates of cell growth and bone‐related genes (including histone H4, c‐fos, c‐jun, TGFβ1, β2 macroglobulin, collagen, fibronectin, osteocalcin, osteopontin, and tartrate resistent acid phosphatase) change as a function of calvarial development from birth to 6 weeks and are selectively modified in osteopetrotic animals. Additionally, nuclei isolated from intact bone yield promoter binding factors. Bone nuclei, which transcribe faithfully and contain the normal complement of nuclear protein factors, offer a powerful approach for investigating in vivo gene regulation in skeletal development and pathology. © 1994 Wiley‐Liss, Inc.
Function of osteocytes in bone
Authors: Aarden Elisabeth M. , Nijweide Peter J. , Burger Elisabeth H. 
Published: May 2005

AbstractAlthough the structural design of cellular bone (i.e., bone containing osteocytes that are regularly spaced throughout the bone matrix) dates back to the first occurrence of bone as a tissue in evolution, and although osteocytes represent the most abundant cell type of bone, we know as yet little about the role of the osteocyte in bone metabolism. Osteocytes descend from osteoblasts. They are formed by the incorporation of osteoblasts into the bone matrix. Osteocytes remain in contact with each other and with cells on the bone surface via gap junction–coupled cell processes passing through the matrix via small channels, the canaliculi, that connect the cell body–containing lacunae with each other and with the outside world. During differentiation from osteoblast to mature osteocyte the cells lose a large part of their cell organelles. Their cell processes are packed with microfilaments. In this review we discuss the various theories on osteocyte function that have taken in consideration these special features of osteocytes. These are (1) osteocytes are actively involved in bone turnover; (2) the osteocyte network is through its large cell‐matrix contact surface involved in ion exchange; and (3) osteocytes are the mechanosensory cells of bone and play a pivotal role in functional adaptation of bone. In our opinion, especially the last theory offers an exciting concept for which some biomechanical, biochemical, and cell biological evidence is already available and which fully warrants further investigations. © 1994 Wiley‐Liss, Inc.