bluuebunny/crossref_metadata_2025_split huggingface dataset:
Neutral endopeptidase from nuchal ligament of fetal calves
Authors: Johnson Alice R. , Gray Lynn D. , Youngblood Elky , Sullivan James 
Published: May 2005

AbstractThe nuchal ligament of unborn calves contains a neutral endopeptidase that is biochemically and immunologically similar to the neutral endopeptidase (NEP), or enkephalinase, from human kidney. Enzymatic activity was inhibited more than 90% by phosphora midon (1 μM). The specific activity in membrane fractions, as determined by hydrolysis of the dansylated substrate, DAPGN, was similar in tissue from fetuses of gestational ages ranging from 100 to 280 days. NEP activity in adult ligament tissue, however, was less than 10% of that in fetal tissue. Fibroblasts dissociated from ligament tissue by collagenase displayed less NEP activity than did preparations of intact ligament, and activity was even lower in cultured cells. By contrast, fibroblasts cultured from fetal calf lungs had NEP activity comparable to that in the ligament tissue. When ligament fibroblasts were cultured on subcellular matrices derived from fetal lung fibroblasts the NEP activity increased relative to those cultured on plastic alone. These studies confirm the presence of neutral endopeptidase (NEP) in the nuchal ligament of the fetal calf. The consistent activity through a range of gestational ages and the influence of the subcellular matrix suggest that this enzyme might be involved in growth of the ligament during fetal life.
Kinetic and molecular species analyses of mitogen‐induced increases in diglycerides: Evidence for stimulated hydrolysis of phosphoinositides and phosphatidylcholine
Authors: Raben Daniel M. , Pessin Melissa S. , Rangan Leela A. , Wright Timothy M. 
Published: May 2005

AbstractA wide variety of agonist‐induced events appear to be mediated through an increase in cellular diglyceride levels. With regard to the ability of diglycerides to mediate these events, three important parameters must be considered: (a) the kinetics of diglyceride generation, (b) the absolute mass levels, and (c) their molecular species. While this increase is often due to a stimulated hydrolysis of phosphoinositides, there is increasing evidence that the stimulated hydrolysis of phosphatidylcholine also contributes to agonist‐induced increases in diglyceride levels. The kinetics of mass increases in diglyceride levels stimulated in cultured fibroblasts are agonist‐dependent. High concentrations of α‐thrombin stimulate a biphasic increase in diglyceride levels with the first phase peaking at 15 s and the second phase peaking at 5 min. In contrast, stimulation with epidermal growth factor, or platelet‐derived growth factor, results in a monophasic increase in cellular diglyceride levels. Furthermore, the molecular species and phospholipid source of the stimulated diglycerides are also agonist‐dependent. While the hydrolysis of phosphoinositides is major source of diglycerides initially generated in response to some agonists (15 s with α‐thrombin at 500 ng/ml), phosphatidylcholine is hydrolyzed as well. Following longer incubations, or at all times following stimulation by epidermal growth factor or platelet‐derived growth factor, phosphatidylcholine hydrolysis is the principal source of the stimulated diglycerides.
Oncogene amplification correlates with dense lymphocyte infiltration in human breast cancers: A role for hematopoietic growth factor release by tumor cells?
Authors: Tang Ruoping , Kacinski Barry , Validire Pierre , Beuvon Frédéric , Sastre Xavier , Benoit Patrick , dela Rochefordière Anne , Mosseri Véronique , Pouillart Pierre , Scholl Susy 
Published: May 2005

AbstractOne hundred six primary breast cancer samples were analysed for c‐erbB2, int‐2, and c‐myc gene amplification. Surgically confirmed nodal involvement was observed in 42%. Level of gene amplification was studied by Southern and/or slot blottechniques. Amplified c‐erbB2 gene sequences were present in 21.5% of all samples. Int‐2 was amplified in 13.1% and c‐myc was amplified in 10.3%. In a non‐parametric test (Kruskal‐Wallis) a strong negative association was found between high levels of c‐erbB2 amplification and absence of estrogen receptor (ER) (P = .0009) or progesterone receptor (PR) (P = .011) expression. No correlations were found between all or high levels of amplification of each oncogene separately or combined with T, N, grade, multifocality of tumor, or associated carcinoma in situ. There was a trend approaching statistical significance for patients with c‐erbB2 amplifications to have positive lymph nodes at surgery (P = 0.09). A somewhat surprising finding however was a very strong association between oncogene amplification and dense lymphocyte infiltration of the tumor (P = .05). This correlation is even stronger when only high levels of amplification are considered, either for each oncogene separately (P = .0048) or in combination (P = .007). We propose that malignant cell cytokine production may help explain this observation.
Parathyroid hormone promotes the disassembly of cytoskeletal actin and myosin in cultured osteoblastic cells: Mediation by cyclic AMP
Authors: Egan John J. , Gronowicz Gloria , Rodan Gideon A. 
Published: May 2005

AbstractParathyroid hormone (PTH) alters the shape of osteoblastic cells both in vivo and in vitro. In this study, we examined the effect of PTH on cytoskeletal actin and myosin, estimated by polyacrylamide gel electrophoresis of Triton X‐100 (1%) nonextractable proteins. After 2–5 minutes, PTH caused a rapid and transient decrease of 50–60% in polymerized actin and myosin associated with the Triton X–100 nonextractable cytoskeleton. Polymerized actin returned to control levels by 30 min. The PTH effect was dose‐dependent with an IC50 of about 1 nM, and was partially inhibited by the (3–34) PTH antagonist. PTH caused a rapid transient rise in cyclic AMP (cAMP) in these cells that peaked at 4 min, while the nadir in cytoskeletal actin and myosin was recorded around 5 min. The intracellular calcium chelator Quin‐2/AM (10 μM) also decreased cytoskeletal actin and myosin, to the same extent as did PTH (100 nM). To distinguish between cAMP elevation and Ca++ reduction as mediators of PTH action, we measured the phosphorylation of the 20 kD (Pl 4.9) myosin light chain in cells preincubated with [32P]‐orthophosphate. The phosphorylation of this protein decreased within 2–3 min after PTH addition and returned to control levels after 5 min. The calcium ionophore A‐23187 did not antagonize this PTH effect. Visualization of microfilaments with rhodamine‐conjugated phalloidin showed that PTH altered the cytoskeleton by decreasing the number of stress fibers. These changes in the cytoskeleton paralleled changes in the shape of the cells from a spread configuration to a stellate form with retracting processes. The above findings indicate that the alteration in osteoblast shape produced by PTH involve relatively rapid and transient changes in cytoskeletal organization that appear to be mediated by cAMP.
Characterization of latent recombinant TGF‐β2 produced by chinese hamster ovary cells
Authors: Lioubin Mario N. , Madisen Linda , Marquardt Hans , Roth Richard , Kovacina Kristina S. , Purchio A. F. 
Published: May 2005

AbstractLatent recombinant transforming growth factor‐β2 (LrTGF‐β2) complex has been purified from serum‐free media conditioned by Chinese hamster ovary cells transfected with a plasmid encoding the TGF‐β2 (414) precursor. Under neutral conditions, LrTGF‐β2 had an apparent molecular weight of 130 kDa. The complex contained both mature and pro‐region sequences. Acidification of LrTGF‐β2 resulted in the release of mature 24 kDa TGF‐β2 from the high molecular weight pro‐region‐containing complex, suggesting that TGF‐β2 was non‐covalently associated with this complex. These results were confirmed by crosslinking experiments performed on partially purified LrTGF‐β2. Protein sequence analysis of the purified TGF‐β2 pro‐region indicated that signal peptide cleavage occured between ser(20) and leu(21). The pro‐region, which previously was found to contain mannose‐6‐phosphate, bound to the mannose‐6‐phosphate receptor. Proteolytic cleavage of mature TGF‐β2 from pro‐TGF‐β2 was inhibited by monensin and chloroquin suggesting that binding to this receptor and subsequent transport to acidic vesicles may be involved in the processing of rTGF‐β2 precursor.
Inhibition of virus‐induced cell fusion by apolipoprotein A‐I and its amphipathic peptide analogs
Authors: Srinivas R. V. , Rui Zheng , Owens R. J. , Compans R. W. , Venkatachalapathi Y. V. , Gupta K. B. , Srinivas S. K. , Anantharamaiah G. M. , Segrest J. P. 
Published: May 2005

AbstractApolipoprotein A‐I (apoA‐I), the major protein component of serum high‐density lipoproteins (HDL), was found to inhibit herpes simplex virus (HSV)‐induced cell fusion at physiological (∼ 1 μM) concentrations, whereas HDL did not exert any inhibitory effect. Lipid‐associating, synthetic amphipathic peptides corresponding to residues 1–33 (apoA‐I[1–33]) or residues 66–120 (apoA‐I[66–120]) of apoA‐I, also inhibited HSV‐induced cell fusion, whereas a peptide corresponding to residues 8–33 of apoA‐I (apoA‐I[8–33]), which fails to associate with lipids, did not exert any inhibitory effect. These results suggest that lipid binding may be a prerequisite for peptide‐mediated fusion inhibition. Consistent with this idea, a series of lipid‐binding 22‐amino‐acid‐residue‐long synthetic amphipathic peptides that correspond to the amphipathic helical domains of apoA‐I (A‐I consensus series), or 18‐residue‐long model amphipathic peptides (18A series), were found to exert variable levels of fusion‐inhibitory activity. The extent of fusion‐inhibitory activity did not correlate with hydrophobic moment, hydrophobicity of the nonpolar face, helix‐forming ability, or lipid affinity of the different peptides. Peptides in which the nonpolar face was not interrupted by a charged residue displayed greater fusion‐inhibitory activity. Also, the presence of positively charged residues at the polar‐nonpolar interface was found to correlate with higher fusion‐inhibitory activity.
Implications and concepts of polyamine‐nucleic acid interactions
Authors: Feuerstein Burt G. , Williams Loren D. , Basu Hirak S. , Marton Laurence J. 
Published: May 2005

AbstractModeling, x‐ray diffraction, and solution studies have contributed to the understanding of interactions between polyamines and nucleic acids. Polyamines stabilize a variety of unusual DNA structures and conformations in vitro, including both the left‐handed Z and the right‐handed A DNA. In addition, polyamines condense DNA and may be important in bending specific sequences. Investigations into the mechanisms of these effects provide support for both specific and nonspecific interactions between polyamines and DNA. Although exact relationships between the binding of polyamines and conformational changes in nucleic acids are still being clarified, polyamines remain important candidates for regulators of DNA conformation in vivo.
Cytokine induction in HTLV‐I associated myelopathy and adult T‐cell leukemia: Alternate molecular mechanisms underlying retroviral pathogenesis
Authors: Tendler Craig L. , Greenberg Steven J. , Burton Jack D. , Danielpour David , Kim Seong‐Jin , Blattner William A. , Manns Angela , Waldmann Thomas A. 
Published: May 2005

AbstractThe human T‐cell lymphotropic virus type I (HTLV‐I) is capable of inducing a variety of host cellular genes including many of the cytokines responsible for immune regulation and osteoclast activation. This derangement in cytokine expression may contribute to the panoply of disease states associated with HTLV‐I infection such as the adult T‐cell leukemia (ATL) and HTLV‐I associated myelopathy/tropical spastic paraparesis (HAM/TSP). We wished to determine if there was a correlation between the expression of an array of cytokines and the diverse clinical manifestations of ATL and HAM/TSP. Utilizing the techniques of specific mRNA amplification by the polymerase chain reaction (PCR) as well as Northern blotting, we analyzed the ex vivo mRNA expression of γ‐interferon (IFN‐γ), tumor necrosis factor‐α (TNF‐α), interleukin‐1β (IL‐1β), and transforming growth factor‐β, (TGF‐β1) in the peripheral blood of HAM/TSP and ATL patients as well as asymptomatic seropositive carriers. IFN‐γ, TNF‐α, and IL‐1β transcripts were up‐regulated in patients with HAM/TSP and seropositive carriers when compared to their levels in ATL and normal controls. In contrast, the ATL patients constitutively expressed higher levels of TGF‐α1 mRNA than HAM/TSP and seropositive carriers. In addition, TNF‐α and IL‐1β serum levels were elevated in HAM/TSP, but not in ATL patients nor seropositive carriers. However, the circulating leukemic cells from ATL patients secreted increased levels of TGF‐β1 protein into the culture medium than T‐cells derived from HAM/TSP patients. Collectively these results suggest that induction of IFN‐γ, TNF‐alpha;, and IL‐β in HAM/TSP may initiate an inflammatory cascade with subsequent events leading to immune mediated destruction of the central nervous system in these patients. Expression of osteoclast activators such as TNF‐α and IL‐β is not associated with hypercalcemia in ATL. Finally, impaired cellular and humoral immune responses present in ATL, but not in HAM/TSP, may be related to elevated levels of TGF‐β1 produced by the leukemic cells. These differences in retroviral‐induced host cytokine expression in ATL and HAM/TSP suggest alternate roles in disease pathogenesis.
The nucleus: A black box being opened
Authors: van Driel Roel , Humbel Bruno , de Jong Luitzen 
Published: May 2005

AbstractUntil recently our knowledge about the structural and functional organization of the cell nucleus was very limited. Recent technical developments in the field of ultrastrcutural analysis, combined with ongoing research on the properties of the nuclear matrix, give new insight into how the nucleus is structured. Two types of observations shape our ideas about nuclear organization. First, most nuclear functions (replication, transcription, RNA processing, and RNA transport) are highly localized within the nucleus, rather than diffusely distributed. Moreover, they are associated with the nuclear matrix. Second, chromatin is organized in discrete loops, bordered by nuclear matrix attachment sequences (MARs). Each loop may contain one or several genes. The arrangement of chromatin in loops has profound consequences for the regulation of gene expression.
Reversible inhibition of osteoclastic activity by bone‐bound gallium (III)
Authors: Blair Harry C. , Teitelbaum Steven L. , Tan Hong‐Lin , Schlesinger Paul H. 
Published: May 2005

AbstractGallium(III) is a new therapeutic agent for hypercalcemia. Ga3+ reduces osteoclast action, but how it inhibits the cell's physiology is unknown. In vivo, 7–12 μM Ga(III) reduces calcium release from bone, but surprisingly, 10–100 μM Ga3+; added to isolated avian osteoclasts did not reduce their degradation of L‐(5‐3H)‐proline bone. 3H‐proline labels bone collagen specifically, and collagenolysis is an excellent indicator of bone dissolution because collagen is the least soluble component of bone. Ga(III) > 100 μM inhibited osteoclasts in vitro, but also killed the cells. To resolve this apparent conflict, we measured 67 Ga distribution between bone, cells, and media. Gallium binds avidly but slowly to bone fragments. One hundred micrograms of bone clears 60% of 1 μM gallium from 500 μI of tissue culture medium, with steady state at > 24 h. Osteoclasts on bone inhibited gallium binding capacity ∼ 40%, indicating a difference in available binding area and suggesting that osteoclasts protect their substrate from Ga binding. Less gallium binds to bone in serum‐containing medium than in phosphate‐buffered saline; 30% reduction of the affinity constant suggests that the serum containing medium competes with bone binding. Consequently, the effect of [Ga] on bone degradation was studied using accurately controlled amounts of Ga(III) pre‐bound to the bone. Under these conditions, gallium sensitivity of osteoclasts is striking. At 2 days, 100 μg of bone pre‐incubated with 1 ml of 1 μM Ga3+, with 10 pmoles Ga3+/μg bone, was degraded at 50% the rate of control bone; over 50 pM Ga3+/μg bone, resorption was essentially zero. In contrast, pre‐treatment of bone with [Ga3+] as high as 15 μM had no significant effect on bone resorption rate beyond 3 days, indicating that gallium below ∼150 pg/μg bone acts for a limited time and does not permanently damage the cells. We conclude that bone‐bound Ga(III) from medium concentrations < 15 μM inhibits osteoclasts reversibly, while irreversible toxicity occurs at solution [Ga3+] > 50 μM.
1,25‐Dihydroxycholecalciferol modulates 3H‐Thymidine Incorporation in FRTL5 Cells
Authors: Ongphiphadhanakul Boonsong , Ebner Susana A. , Fang Shih Lieh , Lombardi Antonio , Baran Daniel T. , Braverman Lewis E. 
Published: May 2005

Abstract1,25‐dihydroxycholecalciferol (1,25(OH)2D3) possesses proliferation and differentiation modulating effects in many cell types in vitro. We studied the effect of 1,25(OH)2D3 on 3H‐thymidine incorporation in FRTL5 cells, a cultured rat thyroid follicular cell line. 1,25(OH)2D3 alone at 10−11 and 10−9 M exerted no effect on 3H‐thymidine incorporation. However, at 10−7 M, 1,25(OH)2D3 slightly enhanced 3H‐thymidine incorporation. In the presence of 5% calf serum, 1,25(OH)2D3 increased 3H‐thymidine incorporation induced by calf serum in a dose‐dependent manner. 1,25(OH)2D3 also enhanced 3H‐thymidine incorporation induced by PMA, an extrinsic stimulator of protein kinase C, without directly affecting PMA‐induced protein kinase C translocation. In contrast to the stimulatory effects of 1,25(OH)2D3 on the calf serum and PMA‐induced 3H‐thymidine incorporation, 1,25(OH)2D3 inhibited the increase in 3H‐thymidine incorporation induced by TSH in a dose‐dependent manner. This effect of 1,25(OH)2D3 on TSH‐induced 3H‐thymidine incorporation may be, in part, due to post‐cAMP pathways since 1,25(OH)2D3 also inhibited the increase in 3H‐thymidine incorporation induced by Bu2cAMP without affecting the TSH‐induced increase in cAMP. The stimulatory effect of insulin on 3H‐thymidine incorporation, a cAMP‐independent process, was also inhibited by 1,25(OH)2D3. We conclude that 1,25(OH)2D3 affects 3H‐thymidine incorporation in FRTL5 cells raising the possibility of a physiologic role for 1,25(OH)2D3 in the growth and function of thyroid follicular cells.
Collagen increases the synthesis of membrane‐associated proteoglycans produced by sertoli cells
Authors: Rodriguez J. Pablo , Minguell Jose J. 
Published: May 2005

AbstractSertoli cells in culture produce two isoforms of proteoglycans which are found in the culture medium and associated with the cell membrane. The amount of both types of proteoglycans increased when Sertoli cells were plated on type 1 collagen‐coated dishes as compared to uncoated dishes. The effect is due to an increase in the synthesis of proteoglycans rather than a diminished rate of degradation of these molecules. The collagen substrate also affects the distribution of these macromolecules; an increase in the amount of membrane‐associated proteoglycans occurs at the expense of the proteoglycans released to the culture medium. © 1992 Wiley‐Liss, Inc.
Leukoregulin, A T‐cell derived cytokine, upregulates stromelysin‐1 gene expression in human dermal fibroblasts: Evidence for the role of AP‐1 in transcriptional activiation
Authors: Mauviel Alain , Kähäri Veli‐Matti , Uitto Jouni , Kurkinen Markku , Evans Charles H. 
Published: May 2005

AbstractLeukoregulin(LR), a product of activated T‐cells, has been recently shown to modulate the metabolism of extracellular matrix components in human skin fibroblast cultures (Mauviel et al., J Cell Biol 113:1455–1462, 1991). In this study we focused our attention on the effects of LR on the expression of stromelysin‐1 gene. This matrix metalloprotease has a broad spectrum of degradative activity and it is also required for maximal activation of interstitial collagenase. Incubation of skin fibroblast cultures with LR resulted in a dose‐ and time‐dependent elevation of stromelysin‐1 mRNA levels, the maximum enhnacement being up to approximately sevenfold. This effect was abolished by cycloheximide, suggesting a requirement for ongoing protein synthesis. Transient cell transfections with a promoter/ reporter gene construct containing 1.3 kb of 5′ flanking DNA of the human stromelysin‐1 gene linked to the chloramphenicol acetyl transferase (CAT) gene, indicated enhancement of promoter activity by LR. This inhancement was abolished by a single base substitution in the AP‐1 binding site of the promoter. Furthermore, gel mobility shift assays demonstrated enhanced AP‐1 binding activity in nuclear extracts from cells incubated with LR. However, LR did not alter the activity of a construct containing three AP‐1 sequences in front of the thymidine kinase promoter linked to the CAT gene. These results collectively suggest that activation of stromelysin‐1 gene expression by LR is mediated by AP‐1 regulatory elements which are necessary, but not sufficient, for gene response. © 1992 Wiley‐Liss, Inc.
cAMP‐Dependent protein kinase modulates expression and subcellular localization of Dolichos biflorus agglutinin binding sites in renal epithelial cells
Authors: Amsler Kurt 
Published: May 2005

AbstractPrevious studies demonstrated that, upon attaining confluence, a clone of the renal epithelial cell, LLC‐PK1, expressed progressively binding sites for the lectin Dolichos biflorus agglutinin (DBA) at the apical cell surface. Activation of cAMP‐dependent protein kinase enhanced surface expression dramatically. The goal of this study was to define the process leading to surface expression of DBA binding sites and to investigate further the role of cAMP‐dependent protein kinase in modulating surface expression. Both subconfluent and confluent cells exhibited intracellular DBA binding sites (50–70% of total cellular binding sites) in a perinuclear vesicular compartment which was disrupted by Brefeldin A treatment. Both total cellular content and the proportion of DBA binding sites at the cell surface increased modestly after confluence was attained. A 48 h treatment of cells with 1‐methyl‐3‐isobutyl xanthine, a phosphodiesterase inhibitor, dramatically increased the level of cellular DBA binding sites as well as the proportion of DBA binding sites at the cell surface. Analysis of two mutants of this cell line suggests that the effect of 1‐methyl‐3‐isobutyl xanthine requires cAMP‐dependent protein kinase activity but is not due to cAMP‐dependent protein kinase‐mediated activation of gene transcription.