Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:2.7.7.49 (reverse transcriptase)
31,746 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Osteoblasts are derived from precursor cells present in low frequency in the stromal element of bone marrow. Because of the lack of a practical procedure to isolate osteoblast precursors from early cultures of plastic adherent cells from bone marrow, previous studies of marrow stromal cells have been made in confluent cultures of bone marrow when the osteoblast (OB) precursors are already differentiated. Also these studies utilized cultures containing mixed populations of cells including hematopoietic cells. Thus we have employed a negative immunoselection procedure to remove contaminating hematopoietic cells and to isolate nearly homogeneous populations of early human stromal cells derived from the plastic-adherent mononuclear marrow cells cultured in the presence of serum. By reverse transcriptase polymerase chain reaction (RT-PCR) analysis for mRNA, and by immunocytochemical study for protein, we studied the sequential expression in culture of multiple markers of the osteoblast phenotype--alkaline phosphatase, osteopontin, parathyroid hormone receptor, types I and III procollagen, and osteocalcin--as well as lipoprotein lipase (LPL), a marker of the adipocyte phenotype. At an early stage of culture (7-9 days), human OB precursors formed colonies of variable sizes that expressed low levels of mRNA and protein concentrations of OB markers, and their concentration increased on growth to a confluent monolayer (approximately 14 days). LPL mRNA was expressed at high levels in the colony stage, and its level decreased upon confluency, suggesting a loss of potential for commitment to the adipocyte lineage. Interestingly, treatment with dexamethasone at 10(-8) M increased the expression for some of the osteoblast markers and for the LPL gene and was required for the deposition of mineralized matrix and for the formation of adipocytes containing cytoplasmic lipid droplets in confluent cultures. Cloned single early colonies were able to coexpress the osteoblast and adipocyte markers (as assessed by RT-PCR). Thus these immunoselected marrow stromal cells have the characteristics of authentic human osteoblast precursor cells which also are capable of differentiating into adipocytes.
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PMID:Isolation and characterization of osteoblast precursor cells from human bone marrow. 885 42

Human brown pre-adipocytes were immortalized by microinjection of the genes encoding simian virus 40 T and t antigens under the control of the human vimentin promotor. The transfected pre-adipocytes were cultured for several months with no loss of their morphological characteristics. These cells accumulate lipids and differentiate into adipocytes when treated with insulin, triiodothyronine and dexamethazone. The mRNA of various adipocyte markers was detected by reverse transcriptase-polymerase chain reaction analysis, including hormone-sensitive lipase, lipoprotein lipase, adipsin, glucose transporters 1 and 4, the uncoupling protein (specific of brown adipocytes), and leptin, the product of the ob gene. Pharmacological analyses indicated that the beta3-adrenoceptor is the predominant beta-adrenoceptor subtype in PAZ6 cells and that this receptor subtype is functionally coupled to adenylate cyclase and lipolysis. The immortalization of human adipocytes will permit pharmacological analysis of the human beta3-adrenoceptor function in adipose cells and will allow detailed studies of human adipocyte differentiation.
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PMID:Human immortalized brown adipocytes express functional beta3-adrenoceptor coupled to lipolysis. 913 67

Although the differentiation of mature osteoblasts has been well studied, there is still a need for a convenient way to study preosteoblast differentiation. Our laboratory has recently described a method for isolating small numbers of authentic osteoblast precursor cells from human bone marrow (Rickard et al., J Bone Miner Res 11:312-324, 1996). Here we describe the conditional immortalization of these cells by retroviral transfection with the amphotrophic vector, pZipSV40tsa58, which encodes for a temperature-sensitive mutant form of the simian virus large T-antigen. At the permissive temperature of 34 degrees C, the cell lines proliferated, but differentiation was arrested, whereas at the restrictive temperature of 39.5 degrees C, proliferation was decreased and differentiation was induced. As assessed by semiquantitative reverse transcriptase PCR after 4 days of culture at 39.5 degrees C, the six cell lines expressed similar mRNA levels both constitutively and in response to dexamethasone (Dex) and 1alpha,25-dihydroxyvitamin D3 (1,25(OH2)D3) for osteoblast (alkaline phosphatase [ALP], type I collagen [Col I], osteocalcin [OC], and parathyroid hormone receptor [PTH-R] and adipocyte (lipoprotein lipase [LPL]) genes. In the presence of 10(-8) M Dex, gene expression for ALP, PTH-R, and LPL increased, but that for OC decreased. Stimulation with 10(-8) M 1,25(OH2)D3 increased gene expression for ALP, OC, and Col I. Changes in protein production for ALP, OC, and type I procollagen in response to Dex and 1,25(OH2)D3 were similar to changes in mRNA levels. When cultured at 39.5 degrees C with ascorbate and beta1-glycerolphosphate for 21 days, mineralization of matrix occurred, whereas culture with Dex plus 1,25(OH2)D3, or rabbit serum led to enhanced formation of cytoplasmic lipid droplets within 6 days. Thus, these cell lines are capable of bipotential differentiation and should serve as an excellent tool to study the molecular mechanisms that regulate and select for osteoblast and adipocyte differentiation in humans.
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PMID:Development and characterization of conditionally immortalized osteoblast precursor cell lines from human bone marrow stroma. 949 13

We have previously demonstrated that lipoprotein lipase (LPL; triacylglycero-protein acylhydrolase, EC 3.1.1.34) is most likely expressed in the non-neuronal cells of the spinal cord, and glial cells may thus be the site of expression in the peripheral nervous system as well. We investigated the expression of LPL in cultured 1. 17 cells, an immortalized rat sciatic nerve Schwann cell line. The 1. 17 cells were shown to express LPL mRNA by reverse transcriptase-polymerase chain reaction analysis. The 1.17 Schwann cells demonstrated heparin-releasable lipolytic activity that was inhibited by the lipase inhibitor tetrahydrolipstatin in a dose-dependent manner. Preincubation of 1.17 cells with an anti-rat LPL antiserum reduced the heparin-releasable lipolytic activity to <10% of that measured in untreated cells. To investigate the role of LPL in Schwann cell lipid metabolism, 1.17 cells were incubated for up to 24 h with an emulsified [14C]triolein substrate and the incorporation of [14C]triolein radioactivity into various cellular lipids was examined in the presence of either anti-rat LPL antiserum or preimmune serum. Inhibiting LPL activity reduced the incorporation of 14C into cellular polar lipids, diacylglycerol, and cholesteryl esters by >80% at 2 and 6 h after addition of the radiolabeled substrate. At 24 h, radioactivity in diacylglycerol and cholesteryl esters was similar in cells treated with anti-LPL antiserum or preimmune serum, whereas 14C incorporation into polar lipids was still reduced by >60%. Separation of the polar lipids into individual lipid species revealed no specific changes in triolein-derived radioactivity incorporation across the phospholipid species examined. These results suggest that LPL-mediated hydrolysis of exogenous triacylglycerol is an important source of free fatty acids for the Schwann cell and thus may play a critical role in myelin biosynthesis in the peripheral nervous system.
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PMID:Lipoprotein lipase is expressed in cultured Schwann cells and functions in lipid synthesis and utilization. 979 99

Alterations in lipid metabolism have been associated with the use of protease inhibitors. Sequential lipid analyses were performed on serum samples from human immunodeficiency virus-infected antiretroviral-naive patients who received indinavir in combination with two nucleoside reverse transcriptase inhibitors. Serum levels of cholesterol, triglycerides, high-density lipoproteins (HDLs), and low-density lipoproteins (LDLs) were measured at baseline and at periodic intervals. After 48 weeks of indinavir therapy, mean serum levels +/- SD rose as follows: cholesterol, from 167.2 +/- 36.0 to 206.3 +/- 32.4 mg/dL (P < .0005); triglycerides, from 110.4 +/- 47.5 to 158.4 +/- 72.5 mg/dL (P < .0101); and LDLs, from 106.6 +/- 35.1 to 136.1 +/- 31.6 mg/dL (P = .0029). There was no significant change in the serum HDL fraction. Mean serum lipoprotein (a) levels +/- SD rose from 6.5 +/- 1.4 to 9.6 +/- 2.0 mg/dL after 30 weeks (P = .0695). Potential mechanisms for the noted increases include alterations in serum lipoprotein lipase activity or changes in hepatic lipid metabolism. The clinical significance of these changes remains to be determined.
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PMID:Alterations in serum levels of lipids and lipoproteins with indinavir therapy for human immunodeficiency virus-infected patients. 1091 32

Bone marrow is believed to contain multipotential stromal stem cells which can differentiate into osteoblasts, chondrocytes, adipocytes, and myoblasts (Prockop, D. J. Science 276, 71-74, 1997). Therefore, characterization and identification of the stem-like cell within the stromal cells are important to understand bone marrow function in relation to the hematopoietic microenvironment, and repair/regeneration of tissue defects. TBR31-2 cell, a bone marrow stromal cell line established from bone marrow of transgenic mice harboring temperature-sensitive (ts) simian virus (SV) 40T-antigen gene for immortality, is induced toward both adipocytic and osteogenic cells under conditions of the inactivation of T-antigen (Okuyama, R., Yanai, N., Obinata, M. Exp. Cell Res. 218, 424-429, 1995). In this work, using a semiquantitative reverse transcriptase-polymerase chain reaction (RT-PCR) analysis, mRNA expressions of tissue-specific differentiation markers for adipocyte (lipoprotein lipase), osteoblast (type I collagen and osteocalcin), chondrocyte (type II and X collagen), and muscle cell (desmin) were examined during a long-term culture of the cell. In addition, histochemical studies showed the appearance of adipocytic, osteoblastic, chondrocytic, and muscle cells during this long-term culture. Thus, TBR31-2, which has characteristics of an undifferentiated cell, has the potential to express the multipotential cell lineages. These results indicated that a multipotential progenitor cell including potential to differentiate into a muscle cell and which is situated in the mesenchymal cell lineage was first obtained.
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PMID:Multipotency of a bone marrow stromal cell line, TBR31-2, established from ts-SV40 T antigen gene transgenic mice. 1067 25

Nerve growth factor (NGF)-driven differentiation of PC12 cells into neuronal-like cells provides a representative model system for studying neuronal differentiation processes. Despite of extensive research, gene regulation associated with the differentiation program in PC12 cells still needs to be elucidated. We used cDNA microarray analysis to characterize the response of PC12 cells to NGF at mRNA expression. Forty-six genes were reproducibly influenced by 2-fold or more after NGF treatment for 5 days. Twenty-five of the regulated transcripts were matched to genes which have known functions. Among the microarray results confirmed with real-time reverse transcriptase assay, several genes have not previously known to be modulated by NGF. The results mostly reflected changes in molecules regulating neural plasticity, cytoskeletal organization, and lipid metabolism, which include neuritin, PDZ protein Mrt1, lipoprotein lipase, tropomodulin 1 and rhoB. These observed genetic changes may provide new information about molecular mechanisms underlying NGF-promoted differentiation of PC12 cells.
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PMID:CDNA microarray analysis of nerve growth factor-regulated gene expression profile in rat PC12 cells. 1607 23

B-cell chronic lymphocytic leukemia (B-CLL) is a heterogenous disease with a highly variable clinical course. Recent studies have shown that expression of lipoprotein lipase (LPL) and ADAM29 may serve as novel prognostic markers in B-CLL. To investigate the prognostic value of these genes, we quantified their expression in peripheral blood mononuclear cells using quantitative reverse transcriptase-polymerase chain reaction (RQ-PCR) in a cohort of 133 B-CLL patients and correlated the results with clinical outcome, and other known prognostic factors. LPL, ADAM29, LPL and ADAM29 ratios, as well as CD38 and ZAP-70 protein expression determined by multiparameter flow cytometry, were predictive of treatment-free survival. Multivariate Cox regression analysis identified LPL, ADAM29 and CD38 as independent prognostic markers. Evaluation of several disease characteristics in association with the LPL expression status of the patients' B-CLL cells showed highly significant differences for CD38 and ZAP-70 expression, suggesting a correlation of LPL expression with these established adverse prognostic factors. Sequential RQ-PCR analyses in a subset of 22 patients revealed that LPL mRNA expression was relatively stable in the majority of patients, whereas ADAM29 expression levels varied substantially over time. Furthermore, in a subgroup analysis, LPL provided prognostic information in both early stage (Binet A) and patients with more advanced disease (Binet B and C). Conversely, high ADAM29 expression was predictive of a long treatment-free interval in Binet stage A but did not retain its prognostic significance in Binet B and C patients. The LPL/ADAM29 expression ratio was not found to be an independent prognostic factor and did not offer any advantages over the use of LPL alone. Collectively, our data confirm a role for LPL as a novel prognostic indicator in B-CLL.
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PMID:Lipoprotein lipase expression is a novel prognostic factor in B-cell chronic lymphocytic leukemia. 1684 Jan 97

The renin-angiotensin system (RAS) may inhibit adipogenic differentiation by down-regulating peroxisome proliferator-activated receptor gamma gene expression in adipocytes, and adipocytes express all components of the RAS, including angiotensinogen. Expression of lipoprotein lipase (LPL), which is expressed mainly in adipocytes, is considered to be affected by adipogenic differentiation. We studied whether LPL expression in mouse 3T3-L1 cells is suppressed by inhibition of adipogenic differentiation through activation of RAS by the cells. The mean 3T3-L1 cell size increased and peroxisome proliferator-activated receptor gamma messenger RNA (mRNA) expression in the cells measured by reverse transcriptase polymerase chain reaction (RT-PCR) was enhanced with increase in incubation time. The LPL activity, LPL protein expression (Western blot), and mRNA expression (RT-PCR) in 3T3-L1 cells increased transiently followed by a decline during long-term incubation. Angiotensin II suppressed adipogenic differentiation, LPL activity, protein expression, and mRNA expression in 3T3-L1 cells. On the other hand, the selective angiotensin type 1 receptor blocker valsartan enhanced adipogenic differentiation and LPL activity in 3T3-L1 cells. Angiotensinogen mRNA expression in 3T3-L1 cells measured by RT-PCR was enhanced with increase in incubation time. These results suggest that LPL expression may be suppressed by inhibition of adipogenic differentiation through activation of endogenous RAS in 3T3-L1 cells angiotensin type 1 receptor.
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PMID:Suppression of lipoprotein lipase expression in 3T3-L1 cells by inhibition of adipogenic differentiation through activation of the renin-angiotensin system. 1864 Mar 87

Mesenchymal stem cells are pluripotent progenitors that could be found in human bone marrow. Mesenchymal stem cells are capable of renewing themselves without differentiation in long-term culture. These cells also have low immunogenicity and can suppress alloreactive T cell responses. In the current study, mesenchymal stem cells isolated and propagated previously from the bone marrow of a megaloblastic anaemia patient were tested for their capabilities to differentiate into adipocytes, chondrocytes and osteoblasts in vitro. The differentiated cells were determined by Oil Red O, Alcian Blue-PAS and Alizarin Red S staining, and reverse transcriptase-polymerase chain reaction to determine the expression of mRNA specific for adipogenesis, chondrogenesis and osteogenesis. The results showed that the fibroblast-like cells were capable of differentiating into adipocytes, chondrocytes and osteoblasts upon chemical induction. The adipocytes, chondrocytes and osteoblasts were stained positively to Oil Red O, Alcian Blue-PAS and Alizarin Red S respectively. The differentiated cells were also found to express mRNA specific for adipogenesis ('peroxisome proliferation-activated receptor gamma2' and lipoprotein lipase), chondrogenesis (collagen type II) and osteogenesis (osteocalcin, osteopontin and alkaline phosphatase). In conclusion, this research has successfully isolated fibroblast-like cells from human bone marrow and these cells demonstrated morphological, cytochemical and immunochemical characteristics similar to mesenchymal stem cells. These cells maintain their proliferative properties and could be differentiated into the mesoderm lineage. The success of this study is vital because mesenchymal stem cells can be used in cellular therapy to regenerate or replace damaged tissues, or as a vehicle for therapeutic gene delivery in the future.
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PMID:In-vitro differentiation study on isolated human mesenchymal stem cells. 1910 6


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