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Biomedical subjects

L Armstrong

Publications and source records attributed to L Armstrong.

At least 19 recordsLinked to original sources
PubMed2006

Effect of delayed sampling on umbilical cord arterial and venous lactate and blood gases in clamped and unclamped vessels.

BACKGROUND: Cord blood lactate at birth is a marker of antenatal hypoxia, and is comparable to pH as a prognostic tool. OBJECTIVE: To determine, by a prospective observational study, the effect of delayed sampling from arteries and veins that were double clamped to isolate the blood from the placenta (clamped), and from vessels that were not isolated from the placenta (unclamped). METHODS: Paired samples taken from clamped and unclamped vessels at 0, 20, 40, and 60 minutes were analysed for lactate, base excess, pH, and Pco(2). Data were analysed as the change from time 0 at 20, 40, and 60 minutes. RESULTS: Thirty eight placentas of infants delivered by elective caesarean section were studied. Arterial samples were taken from 20 placentas, and venous samples from 18 placentas. Arterial and venous lactate was significantly higher than at time 0 by 20 minutes in both clamped and unclamped vessels. Changes in unclamped vessels were greater than in clamped vessels. The pH remained unchanged over 60 minutes in clamped vessels, but changed significantly in unclamped vessels. Base excess changed significantly in both clamped and unclamped vessels. CONCLUSIONS: Cord blood samples taken after 20 minutes delay are unreliable for lactate measurement, even if the vessel has been doubly clamped to isolate the blood from the placenta. Current guidelines that state that blood can be sampled from a clamped cord for up to one hour after delivery should not apply to the interpretation of lactate or base excess. Delayed sampling from unclamped cords is very unreliable.

Acid-Base Equilibrium↗
PubMed2006

Tobacco use in the Dominican Republic: understanding the culture first.

OBJECTIVE: To conduct formative research on the landscape of tobacco use to guide survey and subsequent intervention development in the Dominican Republic (DR). DESIGN: Rapid Assessment Procedures, systematic qualitative methods (participant-observations, in-depth interviewing, focus groups) using bilingual mixed age and gendered teams from the United States and DR. SUBJECTS: Over 160 adults (men and women), ages 18 to 90 years, current, former and never smokers, community members and leaders from six underserved, economically disadvantaged DR communities. MAIN OUTCOME MEASURES: Key domains: tobacco use patterns and attitudes; factors affecting smoking initiation, continuation, quitting; perceived risks/benefits/effects of smoking; and awareness/effects of advertising/regulations. RESULTS: Perceptions of prevalence varied widely. While "everybody" smokes, smokers or ex-smokers were sometimes difficult to find. Knowledge of health risks was limited to the newly mandated statement "Fumar es prejudicial para la salud" [Smoking is harmful to your health]. Smokers started due to parents, peers, learned lifestyle, fashion or as something to do. Smoking served as an escape, relaxation or diversion. Quit attempts relied on personal will, primarily for religious or medical reasons. Social smoking (custom or habit) (< 10 cigarettes per day) was viewed as a lifestyle choice rather than a vice or addiction. Out of respect, smokers selected where they smoked and around whom. Health care providers typically were reactive relative to tobacco cessation, focusing on individuals with smoking related conditions. Tobacco advertising was virtually ubiquitous. Anti-tobacco messages were effectively absent. Cultures of smoking and not smoking coexisted absent a culture of quitting. CONCLUSIONS: Systematic qualitative methods provided pertinent information about tobacco attitudes and use to guide subsequent project steps. Integrating qualitative then quantitative research can be replicated in similar countries that lack empirical data on the cultural dimensions of tobacco use.

Adolescent↗
PubMed2005

Regulation of vascular endothelial growth factor bioactivity in patients with acute lung injury.

BACKGROUND: Reduced bioactive vascular endothelial growth factor (VEGF) has been demonstrated in several inflammatory lung conditions including the acute respiratory distress syndrome (ARDS). sVEGFR-1, a soluble form of VEGF-1 receptor, is a potent natural inhibitor of VEGF. We hypothesised that sVEGFR-1 plays an important role in the regulation of the bioactivity of VEGF within the lung in patients with ARDS. METHODS: Forty one patients with ARDS, 12 at risk of developing ARDS, and 16 normal controls were studied. Bioactive VEGF, total VEGF, and sVEGFR-1 were measured by ELISA in plasma and bronchoalveolar lavage (BAL) fluid. Reverse transcriptase polymerase chain reaction for sVEGFR-1 was performed on BAL cells. RESULTS: sVEGFR-1 was detectable in the BAL fluid of 48% (20/41) of patients with early ARDS (1.4-54.8 ng/ml epithelial lining fluid (ELF)) compared with 8% (1/12) at risk patients (p = 0.017) and none of the normal controls (p = 0.002). By day 4 sVEGFR-1 was detectable in only 2/18 ARDS patients (p = 0.008). Patients with detectable sVEGFR-1 had lower ELF median (IQR) levels of bioactive VEGF than those without detectable sVEGFR-1 (1415.2 (474.9-3192) pg/ml v 4761 (1349-7596.6) pg/ml, median difference 3346 pg/ml (95% CI 305.1 to 14711.9), p = 0.016), but there was no difference in total VEGF levels. BAL cells expressed mRNA for sVEGFR-1 and produced sVEGFR-1 protein which increased following incubation with tumour necrosis factor alpha. CONCLUSION: This study shows for the first time the presence of sVEGFR-1 in the BAL fluid of patients with ARDS. This may explain the presence of reduced bioactive VEGF in patients early in the course of ARDS.

Adolescent↗
PubMed2005

Overexpression of telomerase confers growth advantage, stress resistance, and enhanced differentiation of ESCs toward the hematopoietic lineage.

Embryonic stem cells (ESCs) are capable of extended self-renewal and maintenance of pluripotency even after many population doublings. This is supported by high levels of telomerase activity and enhanced antioxidant protection in ESCs, both of which are downregulated during differentiation. To examine the role of telomerase for ESC self-renewal and differentiation, we overexpressed the reverse transcriptase subunit (Tert) of murine telomerase in ESCs. Increased telomerase activity enhances the self-renewal ability of the Tert-overexpressing ESCs, improves their resistance to apoptosis, and increases their proliferation. The differentiated progeny of wild-type ESCs express little Tert and show shortening of telomeric overhangs. In contrast, the progeny of Tert-overexpressing ESCs maintain high telomerase activity, as well as the length of G-rich overhangs. In addition, these cells accumulate lower concentrations of peroxides than wild-type cells, implying greater resistance to oxidative stress. Finally, differentiation toward hematopoietic lineages is more efficient as a result of the continued expression of Tert. Microarray analysis revealed that overexpression of Tert altered expression of a variety of genes required for extended self-renewal and lifespan. Our results suggest that telomerase functions as a "survival enzyme" in ESCs and its differentiated progeny by protecting the telomere cap and by influencing the expression patterns of stress response and defense genes. This results in improved proliferation of ESCs and more efficient differentiation, and these results might have profound consequences for stem cell-replacement therapies.

Animals↗
PubMed2004

Differential expression of Toll-like receptor (TLR)-2 and TLR-4 on monocytes in human sepsis.

Toll-like receptors (TLRs) are a recently described family of immune receptors involved in the recognition of pathogen-associated molecular patterns (PAMPs). The central role of TLR-2 and TLR-4 in microbial responses suggests they may be implicated in the pathogenesis of human sepsis. We hypothesized that the incidence and outcome of sepsis would be influenced by the expression of TLR-2 and TLR-4 on monocytes. We have examined the expression of TLR-2 and TLR-4 mRNA and protein and their response to pro- and anti-inflammatory agents on monocytes from subjects in the intensive therapy unit (ITU) with and without Gram-negative, Gram-positive or polymicrobial sepsis. We compared these data to ITU and healthy control subjects. TLR-2 mRNA was significantly up-regulated on monocytes from subjects with both Gram-positive and Gram-negative sepsis. Similarly, we detected increased levels of TLR-2 protein on the surface of monocytes from sepsis subjects relative to ITU controls. TLR-4 mRNA was increased in Gram-positive subjects; however, there was no corresponding increase in TLR-4 protein. Although TLR-4 mRNA expression in healthy control monocytes could be modulated in vitro by culture with lipopolysaccharide or interleukin-10, this was not observed in monocytes obtained from sepsis and ITU control subjects, suggesting that septic and ITU control milieus may alter the immunoregulation of TLR-4 mRNA expression on monocytes. TLR-2 mRNA was not modulated in culture by any stimulus in any group. We suggest that expression and regulatory response of monocyte TLR-2, and to a lesser extent TLR-4 may be abnormal in human sepsis.

Adult↗
PubMed2002

Role of integrin alphaVbeta3 in the production of recombinant adenoviruses in HEK-293 cells.

Adenoviral infection is initiated by attachment of adenoviral fiber proteins to the CAR protein and subsequent internalization aided by alphaV -containing integrins, eg alphaVbeta3 and alphaVbeta5. To further understand the process of infection and assembly of recombinant adenoviral (rAd) vectors, we examined rAd production in HEK-293 cells and one of its subclones, clone D, isolated from the parental cells for high viral production. By flow cytometry, surface expression of integrin alphaVbeta3 by clone D cells was two-fold higher than by HEK-293 cells. However, clone D cells did not demonstrate greater translational efficiency or number of viral genome DNA copies shortly after rAd infection. Treating cells with inhibitors of integrin alphaVbeta3 reduced rAd production and transfecting HEK-293 cells with integrin alphaVbeta3 cDNAs increased rAd production. Subjecting cells to a sudden reduction in serum (10% to 0.1% FCS) for 5 days, clone D cells maintained 80% viability compared with 40% for HEK-293 cells. Further indication of survival signaling involvement was provided by Western blot analysis demonstrating p38 and p44/42 MAPKs were constitutively phosphorylated in HEK-293 cells. However, for clone D cells, p38 MAPK was phosphorylated only after rAd infection. The role of survival signaling mediated by integrin alphaVbeta3 in rAd production will be discussed.

ATPases Associated with Diverse Cellular Activitie↗
PubMed2002

What is the role of the insulin-like growth factor system in the pathophysiology of cancer cachexia, and how is it regulated?

OBJECTIVE AND BACKGROUND: The cancer cachexia syndrome is characterized by anorexia, weight loss with muscle wasting and increased energy expenditure. It is associated with increased morbidity and mortality, but its aetiology is poorly understood and no effective therapeutic intervention is available. It may result from an imbalance between the activity or effect of anabolic and catabolic hormones, mediated by the inflammatory cytokines. IGF-I is a potent anabolic agent, with therapeutic potential. Our objective was to investigate the role and regulation of the IGF system in cancer cachexia. DESIGN AND PATIENTS: We set up a prospective study of 30 patients with newly diagnosed unresectable non-small cell lung cancer, together with a cross-sectional comparison group of healthy volunteers. MEASUREMENTS: We examined the relationship between aspects of the IGF system, including IGFBP-3 proteolysis (using Western ligand and immunoblotting and an in vitro IGFBP-3 protease assay); the inflammatory cytokines and their soluble receptors; and food intake and nutritional status (including biochemical and anthropometric assessments). RESULTS: Although we did not observe a marked reduction in food intake in the cancer patients, the majority lost weight and functionally important lean body mass. We observed GH resistance in the cancer patients, and intermittent proteolysis of IGFBP-3, which correlated with the circulating interleukin-6 (IL-6) concentration. The pattern of IGFBP-3 proteolysis was unusual, with a prominent 17-kDa fragment. Less IGFBP-3 proteolysis was associated with more weight loss, suggesting that this could be a protective counter-regulatory mechanism, increasing IGF-I bioavailability to the tissues. CONCLUSIONS: Cancer cachexia in humans is a complex condition. Patients tend to be GH resistant. The significance of the intermittent increases in IGFBP-3 proteolysis, which may be regulated by IL-6, remains uncertain. A better understanding of the pathophysiology should enable the development of novel therapeutic approaches.

Aged↗
PubMed2002

Pattern and severity of injuries in micro-scooter related accidents.

OBJECTIVES: To examine the pattern and severity of injuries sustained by children following micro-scooter (MS) accidents, and to document the extent of use of protective clothing in these accidents. METHODS: Prospective data collection on all children with MS related accidents from January to June 2001. Demographic data were collected, including the mechanism of injury, place of accident, use of protective clothing, extent of injuries, and injury management. Injury severity score was calculated for each child. RESULTS: A total of 92 children with 104 injuries were seen during the study period. Male and female sex distribution was similar. The pattern of injuries was similar to those from roller blading accidents. Soft tissue injuries constitute 79.8% (83 of 104) and fractures 20.1% (21 of 104). Injuries of the upper limb particularly the wrists were commonest for both soft tissue and fractures. The mean ISS (SD) was 2.08 (2.31) with a range of 1 to 18. No deaths were recorded during the study period and all the head injuries seen were minor in nature. None of our patients wore any protective clothing, and almost all accidents occurred in public places. CONCLUSIONS: MS related injuries are on the increase. Currently, the manufacturers' advice on use of protective clothing is being ignored. Parents and riders of the MS need be to be educated about the related injuries. The use of protective clothing should be encouraged to reduce injuries.

Adolescent↗
PubMed2001

Vascular endothelial growth factor may contribute to increased vascular permeability in acute respiratory distress syndrome.

The development of noncardiogenic pulmonary edema is a characteristic feature of acute respiratory distress syndrome (ARDS). We hypothesized that vascular endothelial growth factor (VEGF) would play an important role in this process. Plasma VEGF was measured in 40 patients with ARDS, 28 at-risk patients, 14 normal control subjects, and 9 ventilated control subjects. Cultured peripheral blood mononuclear cells (PBM) supernatant VEGF was measured in 21 patients with ARDS and 12 at-risk patients, respectively. The functional importance of VEGF as a mediator of endothelial permeability was assessed by measuring albumin flux across human pulmonary endothelial cell monolayers. Plasma VEGF was significantly elevated in patients with ARDS compared with at-risk patients, normal control subjects, and ventilated control subjects (p = 0.01, p = 0.0001, and p = 0.002, respectively). PBM from patients with ARDS produced significantly more VEGF in vitro than at-risk patients (p = 0.05). Albumin flux across human pulmonary endothelial cell monolayers was significantly increased following the addition of plasma from patients with ARDS compared with plasma from normal control subjects (p = 0.008). When VEGF activity in plasma was neutralized by the addition of a soluble VEGF inhibitor, the albumin flux induced by ARDS plasma was reduced by 48%. We conclude that VEGF makes a significant contribution to the endothelial cell permeability-inducing activity in plasma from patients with ARDS, and may play an important role in the development of noncardiogenic pulmonary edema in ARDS.

Case-Control Studies↗
PubMed2001

Haptoglobin gene expression in human glioblastoma cell lines.

Increases in cerebrospinal fluid (CSF) levels of the acute phase protein haptoglobin (Hp) occur in central nervous system (CNS) disorders such as Alzheimer's disease. To establish if Hp CSF level increases can be associated with Hp expression in brain, reverse transcription-polymerase chain reaction (RT-PCR) experiments were conducted to determine if the Hp mRNA transcript is expressed in human glioblastoma cells. Furthermore, Western blots and immunoprecipitations were performed to elucidate if Hp protein is synthesized and secreted by human glioblastoma cells. The Hp mRNA (alpha2beta) transcript (1155 bp) was detected both in U-87MG and U-138MG cells, and was positively verified by nested PCR in which a part of the beta sequence (482 bp) was targeted for amplification. Despite the presence of Hp mRNA, Hp protein was not secreted by U-87MG cells as compared to the hepatoma cell line, HepG2, where Hp protein (approximately 46 kDa) was detected in the media. The results suggest the expression of Hp protein by glioblastoma cells is possible since the Hp mRNA transcript exist, but whether or not Hp mRNA is contained in a storage pool requiring a specific signal for translation or is transiently expressed remains to be uncovered in future studies.

Alzheimer Disease↗
PubMed2001

Inhibition of angiogenesis and tumor growth by SCH221153, a dual alpha(v)beta3 and alpha(v)beta5 integrin receptor antagonist.

New blood vessel formation is essential for tumor growth and metastatic spread. Integrins alpha(v)beta3 and alpha(v)beta5 are arginine-glycine-aspartic acid-dependent adhesion receptors that play a critical role in angiogenesis. Hence, selective dual alpha(v)beta3 and alpha(v)beta5 antagonists may represent a novel class of angiogenesis and tumor-growth inhibitors. Here, an arginine-glycine-aspartic acid-based peptidomimetic library was screened to identify alpha(v)beta3 antagonists. Selected compounds were then modified to generate potent and selective dual inhibitors of alpha(v)beta3 and alpha(v)beta5 receptors. One of these compounds, SCH 221153, inhibited the binding of echistatin to alpha(v)beta3 (IC50 = 3.2 nM) and alpha(v)beta5 (IC50 = 1.7 nM) with similar potency. Its IC50 values for related alpha(IIb)beta3 and alpha5beta1 receptors were 1294 nM and 421 nM, respectively, indicating that SCH 221153 is highly selective for alpha(v)beta3 and alpha(v)beta5 receptors. In cell-based assays, SCH 221153 inhibited the binding of echistatin to alpha(v)beta3- and alpha(v)beta5-expressing 293 cells and blocked the adhesion of endothelial cells to immobilized vitronectin and fibroblast growth factor 2 (FGF2). SCH 221153, but not the inactive analogue SCH 216687, was effective in inhibiting FGF2 and vascular endothelial growth factor-induced endothelial cell proliferation in vitro with an IC50 equal to 3-10 microM. Angiogenesis induced by FGF2 in the chick chorioallantoic membrane assay was also inhibited by SCH 221153. Finally, SCH 221153 exerted a significant inhibition on tumor growth induced by intradermal or s.c. injection of human melanoma LOX cells in severe combined immunodeficient mice.

Allantois↗
PubMed2001

The farnesyl transferase inhibitor SCH 66336 induces a G(2) --> M or G(1) pause in sensitive human tumor cell lines.

SCH 66336 is a potent farnesyl transferase inhibitor (FTI) in clinical development. It efficiently prevents the membrane association of H-ras, but not K- or N-ras. Yet, in soft agar, it reverts the anchorage-independent growth of human tumor cell lines (hTCLs) harboring H-ras, K-ras, and N-ras mutations, implying that blocking farnesylation of proteins besides ras may be responsible for this effect. Experiments show that SCH 66336 altered the cell cycle distribution of sensitive human tumor cells in two distinct ways. Most sensitive hTCLs accumulated in the G(2)-->M phase after the FTI treatment, but those with an activated H-ras accumulated in G(1) phase, suggesting that the biological effects induced by FTIs in cells with an activated H-ras are distinct from other sensitive cells. A careful genotypic comparison of the hTCLs revealed that those cells with wild-type p53 are especially sensitive to the FTIs. In these cells p53 and its downstream target gene p21(Cip1) are induced after treatment with SCH 66336 for 24 h. These data suggest that cell cycle effects, either G(1) or G(2)-->M accumulation, and p53 status are important for mediating the effects of FTIs on tumor cells.

3T3 Cells↗
PubMed2001

Characterisation of Wnt gene expression during the differentiation of murine embryonic stem cells in vitro: role of Wnt3 in enhancing haematopoietic differentiation.

The first haematopoietic stem cells in mammalian and non-mammalian vertebrates are derived from mesoderm, therefore genes that are important in mesoderm patterning and formation might also play an essential role in haematopoietic stem cell commitment and differentiation. Several members of the Wnt gene family are expressed in very specific patterns in embryonic mesoderm and have previously been shown to act as haematopoietic growth factors. In order to investigate in detail the role that such secreted proteins play in the biology of early haematopoietic commitment we have used in vitro differentiation of murine embryonal stem (ES) as a model system. Using reverse-transcriptase polymerase chain reaction analysis we identified several candidate Wnt genes whose expression pattern was consistent with a role in generation, maintenance and/or differentiation of early haematopoietic progenitor cells including three genes previously shown to have a role in haematopoiesis (Wnt5a, Wnt2b and Wnt10b). The most interesting candidate was Wnt3, because of its strong and regulated expression during in vitro differentiation of murine ES cells as well as its early embryonic expression in mesoderm. Overexpression of Wnt3 was sufficient to cause a consistent increase in the number of embryoid bodies committing to haematopoiesis further strengthening the evidence that this protein can enhance haematopoietic commitment during in vitro differentiation of ES cells. In addition, overexpression of Wnt3 caused a marked upregulation of Brachyury expression, thus providing some evidence that Brachyury may be one of the target genes for the Wnt3 signalling pathway.

Animals↗
PubMed2001

Evidence for the regulation of levels of plasma adhesion molecules by proinflammatory cytokines and their soluble receptors in type 1 diabetes.

OBJECTIVES: To investigate the regulation of soluble adhesion molecules by tumour necrosis factor-alpha (TNF-alpha) and interleukin-6 (IL-6), and relationships with circulating cytokine receptors, in vivo, in type 1 diabetes. DESIGN: Cross-sectional study. SETTING: University hospital diabetes clinic. SUBJECTS: A total of 47 non-nephropathic, Caucasian type 1 diabetics and 39 nondiabetic controls. OUTCOME MEASURES: Plasma levels of TNF-alpha, IL-6, their soluble receptors and adhesion molecules intercellular adhesion molecule-1 (sICAM-1), vascular cell adhesion molecule-1 (sVCAM-1), sE-selectin and von Willebrand factor (vWF), and risk factors for cardiovascular disease. RESULTS: Plasma concentrations of IL-6 were elevated in diabetic patients compared with controls [median (interquartiles) 1.28 (0.89-2.65) vs. 0.66 (0.45-1.73) pg mL(-1): P=0.016], and in these patients IL-6 and soluble IL-6 receptor (sIL-6R) levels correlated with concentrations of sICAM-1 (r = 0.41, P = 0.012 and r = 0.31, P = 0.04, respectively). Tumour necrosis factor-alpha soluble receptor-2 (sTN-FRII), but not TNF-alpha or tumour necrosis factor soluble receptor-1 (sTNFRI), was elevated in diabetic subjects (P = 0.027). Plasma TNF-alpha levels correlated with sVCAM-1 (r = 0.39, P = 0.008), triglycerides (r = 0.36, P = 0.02 1) and diastolic blood pressure (r = 0.35; P = 0.024). Both sTNFRI and sTNFRII correlated with blood pressure (r = 0.46, P = 0.002; r = 0.32, P = 0.034) and triglycerides (r = 0.33, P = 0.033; r = 0.29, P = 0.05). In contrast, HDL-cholesterol and triglyceride were related to sE-selectin (r = -0.45 and +0.45; both P < 0.001). Neither sE-selectin nor vWF were related to cytokine concentrations. Finally, both TNF-alpha and sIL-6R correlated sTNFRI and RII (r = 0.44-0.49, P < 0.001). None of these interactions were apparent in control subjects. CONCLUSIONS: (i) IL-6, through effects on sICAM-1, and TNF-alpha via effects on sVCAM-1, may promote vascular adhesion; (ii) plasma levels of TNF-alpha are associated with dyslipidaemia and increased blood pressure, adding to vascular disease risk; (iii) the actions of both cytokines are probably modified by altered production of soluble receptors in diabetic subjects.

Adult↗
PubMed2000

Farnesyl transferase inhibitors block the farnesylation of CENP-E and CENP-F and alter the association of CENP-E with the microtubules.

Human tumor cell lines that are sensitive to the effects of farnesyl transferase inhibitors accumulate in G(2) --> M (except for cells with an activated Ha-ras that accumulate in G(1)). A search for CAAX box proteins from Swiss-Prot revealed more than 300 peptides. Of these, the centromeric proteins CENP-E and CENP-F are preferentially expressed during mitosis and are implicated as mediators of the G(2) --> M checkpoint. Experiments performed here show that peptides from the COOH-terminal CAAX box of CENP-E and CENP-F are substrates for farnesyl transferase but not geranylgeranyl transferase-I. Although both proteins are prenylated in the human tumor cell line DLD-1, their prenylation is completely inhibited by the farnesyl transferase inhibitor, SCH 66336. Immunohistochemical data with the lung carcinoma cell line, A549, showed that preventing the farnesylation of CENP-E and CENP-F by treatment with the farnesyl transferase inhibitor SCH 66336 does not affect their localization to the kinetochores. However, the presence of farnesyl transferase inhibitors alters the association between CENP-E and the microtubules. Our results imply that the inhibition of CENP-E farnesylation results in the alteration of the microtubule-centromere interaction during mitosis and results in the accumulation of cells prior to metaphase.

Alkyl and Aryl Transferases↗
PubMed2000

mTert expression correlates with telomerase activity during the differentiation of murine embryonic stem cells.

Telomerase, the enzyme which maintains the ends of linear chromosomes in eukaryotic cells, is found at low levels in somatic stem cells but while this is incapable of preventing the progressive erosion of telomeres occurring as a consequence of cell division, such cells show greater proliferative capacity than normal somatic cells hence examination of telomerase activity in such stem cells is of interest. Our aim in this work was to examine the relationship between expression of the reverse transcriptase component (mTert) of murine telomerase. We report here the insertion of a reporter cassette comprising a segment of the promoter sequence of murine Tert gene coupled to the coding sequence of green fluorescent protein (GFP) into murine embryonic stem (ES) cells and show that this is sufficient for mimicking the expression of mTert. We show that the expression of mTert is very closely linked to telomerase activity and that both are substantially reduced upon differentiation of ES cells into more committed lineages giving us a potential reporter system for the selection and isolation of ES cells possessing different levels of telomerase activity.

Animals↗