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Biomedical subjects

H Pirenne

Publications and source records attributed to H Pirenne.

8 recordsLinked to original sources
PubMed1999

High prevalence of low femoral bone mineral density in elderly women living in nursing homes or community-dwelling: a plausible role of increased parathyroid hormone secretion.

The present study was designed to visit elderly women living in nursing homes and to compare their femoral neck bone mineral density (BMD) and circulating levels of parathyroid hormone (PTH) and 25-OH vitamin D (25-OHD) with those of subjects living at home, in the immediate vicinity of the nursing homes. Of 1483 women, aged 70 years and older, who were selected, 993 agreed to participate in this trial. Their femoral neck BMD (n = 993) was measured by dual-energy X-ray absorptiometry, with a specific device installed in a mobile truck. The circulating levels of 25-OHD and PTH were assessed after an overnight fast (n = 748). After stratification for age, there were no significant differences in mean femoral neck BMD values, prevalence of femoral neck osteoporosis, mean serum 25-OHD and prevalence of absolute or relative 25-OHD deficiency between the two groups. Serum levels of PTH were significantly higher in women over 80 years old living in nursing homes, compared with the community-dwelling women. After adjustment for age, a significant relation was found between femoral neck BMD and PTH levels in the whole population (p = 0.004) and in community-dwelling subjects (p = 0.039). When stratifying our population by quartiles of serum PTH values, the odds ratios for femoral neck osteoporosis were significantly increased for the top two quartiles compared with the lowest one both before (p = 0.00146) and after (p = 0.0013) adjustment for age and type of housing. From this study we conclude that femoral osteoporosis is largely underestimated in European women. Living in a nursing home is not, per se, a risk factor for decreased femoral BMD, and circulating PTH levels are a key determinant of low femoral bone density and osteoporosis.

25-Hydroxyvitamin D 2↗
PubMed1998

Reproducibility and diagnostic sensitivity of ultrasonometry of the phalanges to assess osteoporosis.

OBJECTIVE: The present study was designed to assess the reproducibility and the diagnostic sensitivity of the amplitude-dependent speed of sound (SoS) at the distal metaphysis of the proximal phalanges. METHOD: Fourteen presumably healthy volunteers were repeatedly measured every 6 weeks for approximately 6 months in order to assess the reproducibility of the SoS of the phalanges. We recruited 91 post-menopausal women, aged 55-75 years, who were divided in three groups according to their lumbar bone mineral density (BMD) and the existence of prevalent vertebral fractures. The objective was to evaluate the diagnostic sensitivity of SoS measurements. We used DBM Sonic 1200 equipment, and assessed the velocity at which US cross the phalanx in a lateral-medial direction. In post-menopausal women, BMD was measured by dual energy X-ray absorptiometry (DXA) at the level of the lumbar spine, the total zone of the non-dominant hip and the femoral neck zone of the non-dominant hip. RESULTS: The precision of the SoS measurements was 0.71+/-0.05% (mean+/-S.E.M) whereas the reproducibility was 0.95+/-0.06%. Subjects with low BMD or prevalent fractures had significantly lower values of SoS (P < 0.001) than the controls. ROC curve analysis applied to the study population confirmed that SoS was able to discriminate between the controls and osteoporotic subjects (area under the ROC curves were 0.82 (low bone mineral density) and 0.85 (prevalent fractures), respectively). Hip BMD was found to be the most significant variable when comparing the controls and the low density patients by stepwise discrimination and SoS significantly improved the discrimination between the groups when added to the hip BMD. The hip BMD was again the most discriminant variable when applying the same techniques to controls and patients with prevalent fractures, followed by SoS and lumbar BMD. A cut-off value of 1881 m/s is defined for SoS by logistic discrimination and likelihood ratio function. With this value, the sensitivity and the specificity for SoS used in the diagnosis of established osteoporosis were, 81.5% and 79.3%, respectively. Sensitivity and specificity were significantly improved when combining ultrasonometry and densitometry. CONCLUSION: Measurement of ultrasound velocity at the phalanges appears to be a precise and reproducible technique. SoS discriminates between normal post-menopausal women and patients with either low lumbar BMD or prevalent fractures to the same extent as BMD measurements.

Absorptiometry, Photon↗
PubMed1995

Contribution of p56lck to the upregulation of cytokine production and T cell proliferation by IL-2 in human CD3-stimulated T cell clones.

Interaction of the interleukin 2 receptor (IL-2R) beta chain with the lymphocyte-specific protein tyrosine kinase (PTK), p56lck, has led to the speculation that p56lck participates in growth signal transduction. Although activation of T cells with interleukin 2 (IL-2) results in the activation of p56lck, accumulating data support the notion that Lck does not play an essential role in mitogenic signal delivery from the IL-2R. Since this src-related PTK has been shown to enhance TCR/CD3-mediated T cell responsiveness, here we investigated whether activation of Lck by IL-2 could contribute to enhance TCR/CD3-mediated T cell functions. This was achieved by using human CD4(+)-cloned T cells and comparing the effects of IL-2 on p56lck kinase activation and cytokine production. Results show that p56lck kinase activity increased as early as 1 min, reached a maximum within 5 min and decreased within 60 min after IL-2 stimulation. Such treatment with IL-2 also resulted in enhancing T cell responsiveness to CD3+PMA stimulation, as assessed by IL-2 and IFN-gamma secretion and by T cell proliferation. This increase of T cell functions was correlated with IL-2-induced p56lck activation in both dose-response and time-course experiments. Taken together these results strongly suggest that activation of Lck by IL-2 may play a role in regulating CD3-mediated T cell functions.

CD3 Complex↗
PubMed1994

Contribution of tyrosine kinases to the selective orientation of human CD4+ bifunctional cloned T cells toward proliferation or cytolytic function.

We show that T cell activation of human CD4+ cloned T cells through the CD2 molecule can induce either autocrine proliferation or cytolysis, depending on the pair of anti-CD2 mAbs used for stimulation, that is, D66/T11(1) or GT2/T11(1), respectively. As the earliest biochemical event after CD2 stimulation is likely the induction of tyrosine phosphorylation of various proteins, we investigated whether differential activation of protein tyrosine kinases (PTKs) could contribute to the selective induction of each function. Results show that herbimycin A, a potent PTK inhibitor, markedly decreased the induction of both proliferation and cytolysis. This implies a regulatory role for tyrosine phosphorylation in the induction of each function by CD2. However, that PTKs are differentially activated upon induction of proliferation by D66/T11(1) or cytotoxic function by GT2/T11(1) emanated from two different approaches. First, immunoblotting total cellular extracts with an anti-phosphotyrosine mAb showed different patterns of tyrosine phosphorylation depending on the pair of CD2 mAbs used for stimulation. Second, a differential activation of p56lck, a src-related PTK, was observed after stimulation with D66/T11, and GT2/T11(1). Although induction of proliferation by D66/T11(1) was correlated with increased Lck activity, this was not observed when cells were triggered to lyse by GT2/T11(1). Thus, by providing striking correlative evidences linking differences in PTK activation with induction of different functions in bifunctional cloned T cells, our results strongly suggest that PTKs may contribute to the selective orientation of T cell functions at a single-cell level.

Antibodies, Monoclonal↗
PubMed1992

Comparison of T cell functional changes during childhood with the ontogeny of CDw29 and CD45RA expression on CD4+ T cells.

The ontogeny of the peripheral blood mononuclear cells' responsiveness to various activators during childhood was studied and compared to the expression of CDw29 and CD45RA molecules at the surface of CD4+ T cells. The results show that newborn peripheral blood mononuclear cells are characterized by a responsiveness to mitogens that is higher than that observed in adults, at least shortly after stimulation. This contrasts with a clear decreased response to CD2 and CD3 MAb at any time after stimulation. These functional characteristics correlate with a low density of CDw29 antigen on virtually all CD4+ T cells and a high density of CD45RA antigen on most CD4+ T cells at birth. These patterns of reactivity and phenotype are similar to those found among naive adult T cells. When ageing, the response to mitogens becomes rapidly similar to the adult's values, whereas the responses to CD2 or CD3 MAb are more gradually acquired. This slow rate of functional changes grossly parallels the increase of CDw29+ CD4+ and the decrease of CD45RA+ CD4+ T cell subsets. These changes finally lead to the immunophenotypic and functional characteristics that are typical of adult memory T cells. These results suggest that iterative antigenic stimulations both induce memory T cells and create the conditions to improve the overall immune competence.

Adolescent↗
PubMed1992

Abbott HCV EIA 2nd generation: a new screening assay.

An enzyme immunoassay for the detection of antibodies against structural and nonstructural domains of the hepatitis C virus (EIA-2) was compared to a first generation test (EIA-1) that can only detect antibodies against one nonstructural antigen (c100). EIA-2 revealed elevated detection rates as assessed in high risk and patient populations as well as lower repeat reactive rates in volunteer blood donors. Research test systems proved an increase in apparent specificity.

Blood Donors↗