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PubMed1999

Long-term telomere dynamics: modest increase of cell turnover in HIV-infected individuals followed for up to 14 years.

To quantify the long-term dynamics of telomere lengths and the effect of HIV infection on lymphocyte turnover rates, we measured in a blinded study longitudinal samples from 6 individuals using a highly accurate method based on two-dimensional calibration of DNA sizes. For two uninfected controls followed 8 and 10 years the average telomeric terminal restriction fragment (TRF) shortening rate in peripheral blood mononuclear cells (PBMCs) was 50 and 60 bp/year, respectively, in agreement with previous measurements of cross-sectional samples. The TRF lengths of PBMCs from two slow progressors followed for 14 years declined by a rate of 120 +/-10 bp/year, i.e. 2-fold higher than the rate of TRF shortening for uninfected individuals. The rate of TRF shortening was higher in CD8 (140 +/-10 bp/year) than in CD4 (100 +/-10 bp/year) cells. The CD8 cell TRFs of the two fast progressors shortened faster (240 +/-10 bp/year) and the rate of CD4 cell TRF shortening in one of the fast progressors was 160 bp/year. These data suggest that HIV infection causes only a modest increase in the lymphocyte turnover which we speculate could be due to chronic activation of the immune system, and may not result in the exhaustion of its regenerative capacity and immunopathogenesis.

Acquired Immunodeficiency Syndrome↗
PubMedDate not supplied

Terminal restriction fragments of telomere are detectable in plasma and their length correlates with clinical status of ovarian cancer patients.

Free plasma DNA was extracted and terminal restriction fragment (TRF) sequences were amplified by polymerase chain reaction in 32 patients with stage 3 and stage 4 ovarian cancer and 45 healthy controls. Three peaks of TRF were identified and the size of the largest peak (peak 1) correlated with cancer telomere length in cancer patients. Average size of peak 1 in cancer patients was significantly shorter than in controls. When plasma TRF peak 1 was tested pre- and post-treatment, the average pre-treatment size was 8.7 +/- 0.5 Kb, lengthening significantly post-treatment. In long-term survivors of ovarian cancer (10-year disease-free survival), plasma TRF length was the same as in normal controls. The results suggest that the plasma TRF in ovarian cancer patients is of tumour origin. Its determination may reflect tumour cell viability in the host.

Base Sequence↗
PubMed1975

Central nervous system effects of hypothalamic peptides.

Intravenous (i.v.) administration of TRF (1 mg/kg) increases the LD50 of pentobarbital (PB) by 25% while the same dose of somatostatin results in a 30% reduction in PB LD50. A similar increase of PB LD50 by TRF was observed in hypophysectomized rats. Mortality was completely abolished in rats receiving TRF (1 mg/kg) ten minutes after a lethal dose of PB (120 mg/kg). Somatostatin (1 mg/kg) decreases strychnine-induced seizure duration and increases strychnine LD50 by 21% while TRF lowers the strychnine LD50 by 28%. These observations are consistent with central nervous system sites of action for TRF and somatostatin.

Animals↗
PubMed1975

Effect of acute exposure to cold on the activity of the hypothalamic-pituitary-thyroid system.

The effects of a sudden but sustained exposure to cold (1 to 6C) on serum TSH, thyroxine (T4) and triiodothyronine (T3) (all measured by radioimmunoassay), pituitary TSH concentration, pituitary TSH secretory responsiveness to hypothalamic extract or synthetic thyrotropin-releasing hormone (TRH) in vitro as well as in vivo, and the changes of the thyrotropin-releasing activity in three TRF-rich hypothalamic areas were determined. In normal animals, serum TSH underwent a series of oscillations, first rising then returning to the basal levels, then rising again, whereas serum T4 and T3 increased within 2 h of cold exposure and remained elevated. Pituitary TSH concentration and the in vitro pituitary responsiveness declined after an initial elevation, whereas the in vivo responsiveness to TRH was diminished throughout the whole exposure to cold. Thyroid-blocked animals with steady, low levels of serum T4 and T3 showed a step by step increase of serum TSH levels and no changes in the other parameters. It is therefore assumed that the decrease of TSH secretion following the initial rise is due to a feedback inhibition by the increased levels of thyroid hormones as is the decreased pituitary responsiveness of TRH in vivo. The pituitary responsiveness in vitro seems to be determined by TSH pituitary concentrations, the changes of which are probably also secondary to the changes of the thyroid hormone levels. The mechanism of the second rise of serum TSH levels is not clear. Thyrotropin-releasing factor (TRF) activity was higher after 2 and 24 h of cold exposure in the median eminence and after 8 h in the anterior hypothalamus-preoptic area, but lower after 8 and 24 h in the dorsomedial hypothalamus. Since the changes of TRF activity in the median eminence coincided with the elevated serum TSH, they are assumed to reflect increased TRF production and secretion. The significance of the TRF changes in the other two areas is not clear.

Adrenalectomy↗
PubMed1998

Shortened telomere length in white blood cells of patients with IDDM.

IDDM is a polygenic and autoimmune disorder in which subsets of white blood cells (WBCs) are engaged in the destruction of beta-cells of the pancreas. The mechanisms that account for the abnormal behavior of these cells in IDDM are not fully understood. By measuring the mean length of telomeres of WBCs from patients with IDDM, we tested the concept that telomeres might play a role in IDDM. We examined the lengths of the terminal restriction fragments (TRFs) of DNA of WBCs from 234 white men comprising 54 patients with IDDM, 74 patients with NIDDM, and 106 control subjects. When adjusted for age, the TRF length from WBCs of patients with IDDM was significantly shorter than that of nondiabetic control subjects (mean +/- SE: 8.6 +/- 0.1 vs. 9.2 +/- 0.1, P = 0.002). No significant difference was observed between the TRF length from WBCs of patients with NIDDM versus nondiabetic subjects. Neither the duration nor the complications of IDDM (i.e., nephropathy and hypertension) had an effect on the TRF length of WBCs from patients with IDDM. The shortened TRF length of WBCs of patients with IDDM likely reflects a marked reduction in the TRF length of subsets of WBCs that play a role in the pathogenesis of IDDM.

Adolescent↗
PubMed1990

The temporal resolution factor with and without background noise.

In this paper we discuss the measurement of the temporal resolution factor (TRF). The major merits of this measurement are that it is simple enough to be used clinically and that the results are, within certain limits, independent of presentation level. Addition of a continuous background noise has been suggested to enhance the discriminative power of TRF between normal-hearing listeners and listeners with poor temporal resolution. However, we showed through a simple model that this background noise may introduce a strong dependence on presentation level, which must be taken into consideration. To test our model we developed a new measurement protocol. This protocol was applied in measurements of 5 normal-hearing and 9 sensorineurally hearing-impaired listeners. Their results could reasonably well be fitted by the model. The model predicts large measurement errors for TRF values determined with background noise. We found the standard deviations of TRF values, calculated from test and retest measurements, to be smaller in conditions without a continuous background noise. In addition, our results did not show the predicted enhancement in discriminative power between normal-hearing and hearing-impaired listeners. Therefore, the primary conclusion is that the determination of the TRF is not improved by adding a background noise.

Adaptation, Physiological↗
PubMed1999

Changes of telomerase and telomere lengths in paired normal and cancer tissues of breast.

To attain the immortal phenotype, cancer cells must overcome the mitotic clock. Telomerase activity has been identified to be activated in malignant tumors including breast cancer. Telomerase activity was evaluated in 71 breast cancer tissues and paired normal tissues with the TRAP (telomerase repeat amplification protocol) assay. Telomerase activity was calculated and translated into arbitrary units by computer-assisted densitometry with the control of telomerase activity in the 293 control cell line. In 59 paired breast tissues with telomerase activity, terminal restriction fragment (TRF) lengths were measured using Southern blotting. Relative inhibition (RI), the ratio of inhibited telomerase activity in each tumor tissue compared to that of the 293 control cell line after pre-treatment with 150 microg/ml of RNAse A, was measured. Sixty-three of 71 cancer tissues showed telomerase activity (88.7%) with 75.3+/-17.9 units in densitometry, while no telomerase activity was detected in their paired normal tissues. Telomerase activity was correlated to node metastasis (p=0.02) and stage (p=0.005), but not to tumor size or the hormonal receptor status. TRF lengths were 11. 0+/-4.7 kb in 59 tumor tissues and 11.7+/-2.2 kb in paired normal tissues. TRF lengths did not correlate to any of the clinical parameters. However changes of TRF lengths in tumor tissues compared to those of normal tissues correlated to telomerase activity. RI in the tumor tissues was proportional to telomerase activity without RNAse A pre-treatment. In breast cancer, telomerase activity was specific to tumor tissues and increased with tumor progression. Telomerase activity and changes in TRF lengths can be used as guidelines in detecting candidates for the telomerase inhibitor.

Adult↗
PubMed1992

[Inhibitory effect of transferrin on the binding and maintenance of FSH receptors in rat granulosa cells].

It has been recently demonstrated that transferrin (TRF) can inhibit the functional differentiation of rat granulosa cells, but the mechanism remains unknown. In present experiment, the effect of TRF on the binding of 125I-rFSH to receptors and on the maintenance of FSH receptors in granulosa cells from immature, diethylstilbestrol treated rats were studied. The results show that the physiological range of TRF partially blocked the binding of 125I-rFSH to granulosa cells in a dose-dependent manner. TRF also dose-dependently inhibited the maintenance of FSH receptors in accordance with the reduced production of progesterone and estradiol. In view of the present and our previous investigation, it could be concluded that mechanisms of the inhibitory effect of TRF on the functional differentiation of granulosa cells mainly involve blockade of FSH binding to its receptors and inhibition of FSH receptor maintenance by FSH.

Animals↗
PubMed2005

[Medico-economic assessment of two methods for implementing thyroid testing guidelines].

BACKGROUND: To compare independent and combined effectiveness and cost-effectiveness of two implementation interventions of guidelines for ordering thyroid function tests. The two implementation interventions were a Memorandum Pocket Card (MPC) and a Test Request Form (TRF). Intervention groups were wards. METHODS: The study used an experimental 2*2 factorial design with matching hospitals according to size and activity and wards according to pre-intervention appropriateness for test ordering. Four ward groups were established: the dual intervention group, the order form group, the pocket card group and the control group. Physicians in all groups received guidelines and were invited to a local information meeting. The main outcome measure of effectiveness was the Guideline Conformity Rate (GCR). The cost-effectiveness ratio was the cost difference between the tested intervention and the control intervention upon effectiveness difference between the tested intervention and the control intervention. RESULTS: Six hospitals participated in the study (two middle-sized hospitals, two small-sized hospitals and two psychiatric hospitals). A total of 1412 orders for thyroid function tests were collected. GCR was 78% in the dual intervention group, 83% in the order form group, 73% in the pocket card group and 62% in the control group. The interaction between TRF and MPC was not significant (B=-0.70, p=0.21). Compared to simple information, TRF was effective in increasing GCR (OR=2.65, 95% Confidence Interval [CI]: 1.52-4.62), unlike MPC (OR=1.28, CI: 0.75-2.19). TRF was the less expensive and the most effective intervention. CONCLUSION: Using a robust design, our study shows a greater effectiveness of TRF than MPC and their association in implementing thyroid function test guidelines. The development of clinical practice improvement projects through the second procedure of accreditation in France is a good opportunity to develop a guidelines implementation research project.

Cost-Benefit Analysis↗
PubMed1985

Neutralization of T-replacing factor by T8-positive lymphocytes: an important suppressor mechanism operating in the regulation of polyclonal B-cell activation.

Pokeweed mitogen (PWM)-induced B-cell activation was entirely abrogated by pre-treating peripheral mononuclear cells (PBM) with T4 (anti-T-helper-inducer subset) or T11 (anti-sheep erythrocyte receptor, ie. anti-pan-T-cell) monoclonal antibody plus complement. Immunoglobulin secretion was restored in T11- but not T4- cultures by adding the culture supernatant from PWM-stimulated PBM (T-replacing factor, TRF). Since T8+ (T-suppressor-cytotoxic subset) cells were present in high concentrations in T4- but absent from T11- cultures, it appeared that these cells could inhibit B-cell activation by PWM plus TRF and that suppression could occur in the absence of T4+ cells. Incubation of TRF with purified, unstimulated T8+ cells prior to addition to T11- cultures abrogated subsequent PWM-induced B-cell activation, whereas T8- PBM had no effect on TRF. T8+ cells did not secrete suppressor factors during incubation with TRF. Absorption of one or more of the factors required for B-cell growth and differentiation by T8+ cells appears to be an important suppressor mechanism operating in the PWM system.

Adult↗
PubMed1977

Non-specific factor replaces T cells in an IgG response to soluble antigens.

The antigen and T-cell requirements for the final stages of proliferation and maturation of DNP-KLH primed and boosted mouse spleen cells into IgG antibody secreting cells have been studied in vitro. The requirement for free antigen ceases after 24-48 h in vitro. The carrier-specific T-cell requirement for triggering of activated B cells by a soluble antigen (DNP-KLH) can be replaced in T cell-depleted cultures by non-antigen specific T cell-replacing factors (TRF). However, if the carrier protein is changed, TRF restores the IgG response of T cell-depleted cultures only if antigen is presented to B cells in particulate form, e.g. on the surface of macrophages, or in the presence of small amounts of antibody against the carrier protein. Thus, direct interaction between soluble protein and B cells is not sufficient to allow TRF to effectively replace specific T cells. Since TRF must be added at the start of culture, the initiation of B-cell maturation into IgG secretion by TRF occurs during B-cell proliferation, and is followed by further proliferation before IgG antibody can be detected.

Animals↗
PubMed1986

[Mechanism of the antidepressive and learning-stimulating effects of thyroliberin and its analogs].

To define the role of different fragments of TRF molecule in its neurotropic activity a number of newly synthesized dipeptides of pyroglutamic acid with beta-alanine residue, GABA or GABA ester have been studied. The compounds were compared with TRF in their ability to influence spontaneous or amphetamine-stimulated locomotor activity in mice and to affect the elaboration of passive avoidance reflex in rats. Unlike TRF, the pyroglutamate dipeptides studied were shown to exhibit no activity in amphetamine potentiation test, thus providing additional evidence of the importance ofthe "histidylproline" fragment in TRF antidepressant effect. On the other hand, the above pyroglutamate derivatives caused a pronounced improvement in the learning abilities of under-trained rats. These dipeptides were shown to be more active in this test than TRF. This suggests the important role of pyroglutamyl moiety in the stimulation of the learning processes.

Animals↗
PubMed1987

Demonstration of up-regulated IL 2 receptor expression on an in vitro cloned BCL1 subline.

We have established BCL1 CL-3 cells capable of responding to B15-TRF and interleukin 2 (IL 2). This clone has both high affinity and low affinity receptors for IL 2 (IL 2R), but IL 2 by itself did not stimulate either proliferation or immunoglobulin (Ig) secretion. B15-TRF, which possesses both growth and differentiation activity, causes an increase in size of CL-3 cells and renders CL-3 cells responsive to IL 2, including an increased expression of IL 2R (eight-fold to 10-fold) and the differentiation of CL-3 cells into Ig secretion (60 to 80% of cultured cells). CL-3 cells pretreated with B15-TRF for 12 hr become competent to respond to IL 2 by up-regulation of IL 2R within 12 hr. In contrast CL-3 cells pretreated with IL 2 for 12 hr required 24 hr B15-TRF stimulation to result in IL 2R up-regulation. Thus the ordered action of B15-TRF and IL 2 is the most effective operational pathway for the up-regulation of IL 2R. This IL 2-mediated IL 2R up-regulation and induction of Ig synthesis depends upon the concentration of IL 2 in the culture. Both responses seem to be caused by IL 2 molecules bound to high affinity IL 2R. However, the possibility of involvement of low affinity IL 2R can not be vigorously excluded. In fact the level of IL 2 required for a response is far higher than that needed for activated T cell proliferation. This cloned BCL1 subline promises to be a useful tool for studying the regulation and mechanisms of B cell responses.

Animals↗
PubMed1986

Expression of transferrin receptors in human erythroleukemic lines: regulation in the plateau and exponential phase of growth.

The present study was undertaken in an attempt to elucidate the mechanism(s) underlying transferrin (TRF) receptor expression in human erythroleukemic (K562 and HEL) lines during the exponential and the plateau phase of growth. TRF receptor synthesis is enhanced when stationary cells are subcultured at low density in fresh medium. This rise occurs in either the presence or the absence of serum, which is associated with cell proliferation or quiescence, respectively. In the presence of serum, it is not inhibited by the addition of hydroxyurea (i.e., an agent blocking DNA synthesis). Thus, the receptor synthesis is enhanced not only in subcultures of actively proliferating cells (in the presence of serum), but also in subcultures of quiescent elements (in the absence of serum or upon the addition of serum plus hydroxyurea). Conversely, the ferritin content is markedly decreased when stationary cells are subcultured at low density, in either the presence or the absence of serum. These results suggest that stationary cells subcultured in fresh medium undergo a depletion of their intracellular iron pool, which in turn may represent the stimulus triggering TRF receptor synthesis. This hypothesis is supported by two observations: both the depletion of this pool and the rise in TRF receptor synthesis are more marked in the absence than in the presence of serum; addition of excess exogenous iron fully inhibits the rise of TRF receptor synthesis in cells subcultured with fresh medium and serum.

Blood Physiological Phenomena↗
PubMed1979

Synergy between T cell-replacing factor and bacterial lipopolysaccharides (LPS) in the primary antibody response in vitro: a model for lipopolysaccharide adjuvant action.

Unfractionated spleen cells, B cells from normal mice, and nu/nu spleen cells respond to the addition of bacterial lipopolysaccharide (LPS) and T-cell-replacing factor (TRF) by production of plaque-forming cells (PFC) in excess of the number expected from the addition of LPS and TRF separately. This synergistic activity is dependent on the presence of the antigen, SRBC. Supernatants of both allogeneic spleen cell mixtures and spleen cells cultured with Con A are effective and synergize best at concentrations suboptimal for their ability to act as TRF alone. Culture supernatants of unstimulated normal or fractionated cell populations are ineffective. Synergy is not dependent on the presence of macrophages in the cultures. Purified LPS free from active contaminants, as well as commercially available LPS, show synergy with TRF. Synergy was seen when TRF was added at initiation of culture or 24 hr later. It is suggested that synergy is the equivalent of LPS adjuvant activity, that the role of T cells in LPS adjuvanticity is that of a conventional cooperating cell, and the LPS acts as an adjuvant by inducing B cells to become more sensitive to T cell helper factors.

Adjuvants, Immunologic↗
PubMed1993

Co-ordinate and restricted expression of the ProXaaArg/Lys-specific GalNAc-transferase and the GalNAc beta 1,4GlcNAc beta 1,2Man alpha-4-sulfotransferase.

Asn-linked oligosaccharides terminating with the sequence SO4-4GalNAc beta 1,4GlcNAc beta 1,2Man alpha (S4GGnM) are present on the glycoprotein hormones lutropin and thyrotropin, pro-opiomelanocortin, and tissue factor pathway inhibitor. The peptide motif ProXaaArg/Lys (PXR/K), which is recognized by a PXR/K-specific GalNAc-transferase, is present in each of these glycoproteins 6-9 residues NH2-terminal to an Asn glycosylation site. Both the PXR/K-specific GalNAc-transferase and a GalNAc beta 1,4GlcNAc beta 1,2Man alpha (GGnM)-4-sulfotransferase are required for synthesis of the S4GGnM sequence. Glycoproteins which do not contain the PXR/K motif but bear Asn-linked oligosaccharides terminating with GGnM or sialic acid alpha 2,3/6GGnM have also been described, suggesting a distinct GalNAc-transferase may be responsible for their synthesis. We have examined a number of tissues and cultured cell lines for the transfer of sulfate to the trisaccharide acceptor GGnM and transfer of GalNAc to oligosaccharide acceptors on protein which do, human chorionic gonadotropin (hCG), and do not, transferrin (Trf), contain the PXR/K motif. The PXR/K-specific GalNAc-transferase and the GGnM-4-sulfo-transferase are expressed in salivary gland, pituitary, lacrimal gland, kidney, and brain, and in the cell lines AtT-20, 293, SHSY5Y, and alpha T3. In contrast Bowes, EL-4, and B16L6 cell extracts transferred GalNAc to oligosaccharides acceptors on Trf but not on hCG. A number of tissues and cell lines displayed transfer of GalNAc to both hCG and to Trf suggesting that two distinct GalNAc-transferases were present. The GGnM-4-sulfotransferase was expressed in tissues and cell lines which expressed the PXR/K-specific GalNAc-transferase but not in cell lines expressing exclusively the Trf-specific GalNAc-transferase. Thus, the PXR/K-specific GalNAc-transferase and the GGnM-4-sulfotransferase are coordinately expressed in a number of tissues other than pituitary. The Trf-specific GalNAc-transferase may account for the presence of beta 1,4-linked GalNAc on glycoproteins which do not contain the PXR/K motif.

Animals↗
PubMed1997

[Measuring the economic impact of ambulatory dialysis: the case of continuous ambulatory peritoneal dialysis].

BACKGROUND: As concerns the treatment of terminal renal failure (TRF), France is characterized by a minimal use of peritoneal dialysis, even though this technique is as effective and less expensive than others and that authorities precognize to switch patients to out-of-centre techniques, like peritoneal dialysis. The purpose of the article is to estimate benefits for the Social Security induced by an incitative program leading the current structure of TRF treatment to the existing government standards defined in 1984. METHODS: We computed treatment cost differences, on the basis of an incident case of TRF followed during 7 years, between three different situations: the current French structure of TRF treatment (29.5% of patients treated by out-of-center techniques); two reference situations A and B (respectively 45% and 37% of patients treated by out-of-center techniques). We performed a sensitivity analysis on the rate of use of continuous ambulatory peritoneal dialysis (CAPD). We made assumptions on the cost of techniques, the cost of complications and the rate of CAPD treatment failure. RESULTS: Results stress the existence of benefits induced by increased use of out-of-centre techniques on the basis of a 7-year follow-up of an incident TRF patient: around 65,000 FF in situation A with a 20% rate of use of CAPD; around 5,000 FF in situation B with a 15% rate of use of CAPD. Assumptions concerning CAPD treatment lead to an underestimation of the true benefits. CONCLUSION: The study highlights the therapeutic and economic interest to transfer some patients from hemodialysis to peritoneal dialysis.

Ambulatory Care↗
PubMed1998

Analysis of telomere lengths in human corneal endothelial cells from donors of different ages.

PURPOSE: To investigate the telomere hypothesis of cellular aging as the mechanism for cell cycle arrest in normal human corneal endothelium. METHODS: The corneal endothelium and epithelium from 21 human corneas from 13 donors 5 weeks to 84 years of age were dissected and frozen at -70 degrees C. Purified DNA, digested with the restriction enzyme, HinfI, was run on 0.7% agarose gels, probed with radiolabeled (AATCCC)4, and exposed to a phosphor screen. The length of the terminal restriction fragment (TRF) was determined by densitometry. RESULTS: The cells of the corneal endothelium had TRF lengths ranging from 11.0 to 14.0 kbp (mean, 12.2 +/- 0.9). Corneal epithelial specimens showed TRF lengths that were always less than (mean, 10.4 +/- 1.0; range 9.0-12.0) the corresponding endothelial TRF lengths. Human corneal endothelial cells, transformed with human papillomavirus type 16 oncogenes E6 and E7, showed decreasing TRF lengths from 11 kbp at population doubling level (PDL) 15 to 9.5 kbp at PDL 73. Neither the endothelial and epithelial cells from human donors nor the transformed pre-immortalized human endothelial cells showed evidence of telomerase activity. CONCLUSIONS: Human corneal endothelial cells have long telomeres throughout life. Their limited replicative ability does not appear to result from critically short telomere lengths.

Adolescent↗