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Biomedical subjects

S Papaioannou

Publications and source records attributed to S Papaioannou.

At least 37 records · Page 2Linked to original sources
PubMed2001

Critical appraisal in clinical practice: sometimes irrelevant, occasionally invalid.

A core activity of evidence-based practice is the search for and appraisal of evidence on specific clinical issues. Clinicians vary in their competence in this process; we therefore developed a 16-item checklist for quality of content (relevance and validity) and presentation (useability, attribution, currency and contact details). This was applied to a set of 55 consecutive appraisals conducted by clinicians and posted at a web-based medical journal club site. Questions were well formulated in 51/55 (92%) of the appraisals. However, 22% of appraisals missed the most relevant articles to answer the clinical question. Validity of articles was well appraised, with methodological information and data accurately extracted in 84% and accurate conversion to clinically meaningful summary statistics in 87%. The appraisals were presented in a useable way with appropriate and clear bottom-lines stated in 95%. The weakest link in production of good-quality critical appraisals was identification of relevant articles. This should be a focus for evidence-based medicine and critical appraisal skills.

Evidence-Based Medicine↗
PubMed1999

G-protein signalling pathways and oestrogen: a role of balanced maintenance in osteoblasts.

Oestrogen (E2) is an important regulator of bone cell function and alterations in oestrogen levels may cause abnormal bone metabolism in vivo. In this study we examined the long term effects of 17beta-oestradiol (17beta-E2) on G-proteins and the secondary signalling pathways of phospholipase C (PLC), cyclic adenosine monophosphate (cAMP), and 1,4,5-inositol triphosphate (IP3). Cells from neonatal mouse calvariae were cultured in phenol red-free RPMI 1640 medium supplemented with charcoal stripped foetal calf serum for 192 h with either oestrogen (10(-8) M), or oestrogen withdrawal after 48 h. Cultures were stimulated for the final 48 h with IL-6 (10(-10) M), or left unstimulated. Western blot analysis was undertaken on osteoblast membrane preparations obtained by 10 mM Tris-HCl, 0.1 mM EDTA pH 7.8 and centrifugation at 40,000 x g for 2 h. For cAMP study, cells were stimulated with IL-6 for either 15 min or 30 min. Intracellular cAMP was extracted from cells and measured by ELISA methodology. For the IP3 assay, cells were stimulated with IL-6 for 20 s and IP3 levels measured using radioimmunoassay. The blots revealed increased levels of Gialpha-, and Gqalpha-proteins with oestrogen withdrawal and IL-6 stimulation. This was in comparison to cells which were unstimulated, or stimulated with IL-6 with continuous 17beta-E2, or IL-6 alone. Gsalpha expression decreased with oestrogen withdrawal compared to the control. Limited amounts of Gialpha-, Gsalpha-, and Gqalpha-proteins were identified with continuous 17beta-E2. The levels of PLC isoforms PLCbeta1-2 were not affected by the differing oestrogen conditions. The cAMP production induced by IL-6 stimulation for 30 min and withdrawal of 17beta-E2 was lower and significantly different compared to the control study (P<0.05). Also IL-6 activation with continuous oestradiol increased cAMP levels and was significantly different from the control cells (P<0.01). However, 17beta-E2 had no effect on the formation of intracellular IP3, although IL-6 significantly lowered IP3 levels in all the groups compared to the control (P<0.01). These results suggest that oestrogen modulates the signal transduction pathways of G-protein molecules, and the secondary pathways of cAMP in mouse osteoblast-like cells.

Animals↗
PubMed1999

Stromelysin (MMP-3) synthesis is up-regulated in estrogen-deficient mouse osteoblasts in vivo and in vitro.

Sex steroids are important regulators of bone cell function and osteoblast-derived matrix metalloproteinases (MMPs) are key mediators of bone resorption during the initial stage of osteoid removal prior to osteoclast attachment. To investigate the mechanism of bone loss following estrogen deficiency, we examined the effects of estrogen on osteoblast synthesis of MMPs and tissue inhibitor of metalloproteinases (TIMPs). Immunolocalization in mouse bone samples ex vivo and primary mouse osteoblast (MOB) cultures was used to document the synthesis of mouse interstitial collagenase (MMP-13), stromelysin-1 (MMP-3), gelatinase-A (MMP-2), and gelatinase-B (MMP-9). Endosteal bone lining cells from distal femoral head and lumbar vertebral body showed an increase in the pattern of synthesis of stromelysin-1 following ovariectomy, compared with sham-operated controls; the synthesis of other MMPs was unaffected. The expression of all classes of MMPs and TIMP-1 and TIMP-2 by MOB in culture was demonstrated by reverse transcriptase-polymerase chain reaction. Following the withdrawal of 17beta-estradiol, MOB cultures showed a significant increase in the number of cells synthesizing stromelysin-1; this effect was enhanced by stimulation with either interleukin-1 or interleukin-6. Northern blot analysis showed only a slight increase in stromelysin-1 mRNA message following the withdrawal of 17beta-estradiol. Our data show an unexpected up-regulation of stromelysin-1 synthesis by osteoblasts both in vivo and in vitro following estrogen withdrawal. Although this effect was not reflected in a significant change in stromelysin-1 mRNA expression in vitro, there is evidence to suggest a role for this enzyme in the early stages of bone loss during the pathogenesis of osteoporosis.

Animals↗
PubMed1998

The cellular actions of interleukin-11 on bone resorption in vitro.

The pleiotropic cytokine interleukin-11 (IL-11) stimulates osteoclast formation in vitro, but it is not known whether it influences other steps in the bone-resorptive cascade. Using a variety of in vitro model systems for studying bone resorption we have investigated the effects of IL-11 on 1) osteoclast formation, fusion, migration, and activity; and 2) osteoblast-mediated osteoid degradation. The involvement of matrix metalloproteinases (MMPs) and products of arachidonic acid metabolism in IL-11-mediated resorption were also assessed. We first examined the bone-resorptive effects of IL-11 by assessing 45Ca release from neonatal mouse calvarial bones. IL-11 dose-dependently stimulated bone resorption with an EC50 of 10(-10) M. The kinetics of IL-11-mediated 45Ca release demonstrated that it was without effect for the first 48 h of culture, but by 96 h, it stimulated 45Ca release to the same level as that produced by 1,25-dihydroxyvitamin D3 [1,25-(OH)2D3] (a hormone that stimulates osteoclast formation and activity). IL-11 also produced a dose-dependent increase in osteoblast-mediated type I collagen degradation with a maximum of 58.0 +/- 6.2% at 5 x 10(-9) M; this effect of IL-11 was less than that produced by 1,25-(OH)2D3 (76.5 +/- 7.1%) and was prevented by an inhibitor of MMPs, but not those blocking arachidonic acid metabolism. We then tested the effects of IL-11 on isolated mouse osteoclasts cultured on ivory slices in the presence and absence of primary mouse osteoblasts. IL-11 had no effect on isolated osteoclast activity even in coculture with primary osteoblasts. We then examined the effects of IL-11 on the formation of osteoclast-like multinucleate cells in mouse bone marrow cultures and the resorptive activity of such cultures using ivory as a substrate. IL-11 dose-dependently increased 1) the number of tartrate-resistant acid phosphatase-positive osteoclast-like multinucleate cells and 2) the surface area of lacunar resorption, although the effects were less than that of 1,25-(OH)2D3. The effect of IL-11 on bone marrow lacunar resorption was prevented by a combination of inhibitors of 5-lipoxygenase and cyclooxygenase. In 17-day-old metatarsal bones, IL-11 prevented the migration of (pre)osteoclasts to future resorption sites, whereas their fusion was unaffected. These results provide strong evidence that IL-11 stimulates bone resorption by enhancing osteoclast formation and osteoblast-mediated osteoid degradation rather than stimulating osteoclast migration and activity. Our data also suggest that the stimulatory effects of IL-11 involve both MMPs and products of arachidonic acid metabolism.

Acid Phosphatase↗
PubMed1998

Evaluation of first-trimester screening by fetal nuchal translucency and maternal age.

The aim of this screening study was to evaluate first-trimester screening for chromosomal defects by fetal nuchal translucency thickness at 10-14 weeks of gestation in four Fetal Medicine Units in Greece. Estimates of the risk for trisomy 21 were calculated taking into account fetal nuchal translucency thickness and maternal age. There were 3550 cases; the median maternal age was 29 years (range 16-48 years); and 277 (7.8 per cent) were over 37 years. The median crown rump length was 60 mm (range 38-85 mm) and the fetal nuchal translucency thickness increased with crown rump length and measurements were above the 95th centile in 101 (2.9 per cent) of the cases. The adjusted risk was 1 in 300 or more in 172 (4.9 per cent) of the cases and the high-risk group contained ten of the 11 (91 per cent) fetuses with trisomy 21 and all 11 fetuses with other chromosomal defects. The findings of this study provide further evidence for the high efficacy of screening for chromosomal abnormalities by fetal nuchal translucency and maternal age.

Adolescent↗
PubMed1996

In vivo experimental evidence that the nitric oxide pathway is involved in the X-ray-induced antiangiogenicity.

We have investigated both the effects of X-rays on angiogenesis and the possible role of nitric oxide (NO) on the observed antiangiogenic effect of X-rays, using as an in vivo model the chick embryo chorioallantoic membrane (CAM). These effects were assessed both morphologically and biochemically, by measuring vascular density and collagenous protein biosynthesis, respectively, on days 9 and 14 of the chick embryo development. Vascular density and cytotoxicity of the CAM were also evaluated histologically. We have shown that X-rays have an antiangiogenic effect on the system used and that the NO synthase inhibitor NG-nitro-L-arginine methyl ester (L-NAME) promoted angiogenesis of the non-irradiated CAM and reversed the antiangiogenic effect of irradiation. D-NAME, which is an inactive enantiomer of L-NAME, showed no such effects. L-Arginine, which is the substrate for NO synthase, had a modest antiangiogenic effect on the non-irradiated CAM, no effect on the irradiated CAM and abolished the angiogenic effect of L-NAME on these CAM preparations. These results suggest that NO is involved in the antiangiogenic mechanism of X-rays and that pharmacological manipulation of NO firstly, may offer a better understanding of these mechanisms and, secondly, may also prove to be an alternative therapeutic approach for treating pathological conditions involving angiogenesis.

Animals↗
PubMed1996

Lower genital tract swabs in the prediction of intrauterine infection in preterm prelabour rupture of the membranes.

OBJECTIVE: To examine the genital tract flora in women with preterm prelabour rupture of the membranes and to determine the relationship of these microorganisms to those found in fetal blood and amniotic fluid. DESIGN: Prospective study of 97 patients with preterm prelabour rupture of the membranes. SETTING: Maternal-fetal medicine centre. METHODS: High vaginal and endocervical swabs were taken for routine culture of aerobic and anaerobic bacteria and Ureaplasma urealyticum and Mycoplasma hominis. Cordocentesis and amniocentesis were performed and fetal blood and amniotic fluid were cultured for aerobic and anaerobic bacteria. Amniotic fluid was also cultured for Mycoplasma spp. The sensitivities and specificities of genital tract colonisation in the prediction of fetal blood and amniotic fluid infection were calculated. RESULTS: Positive genital tract cultures for aerobic and anaerobic organisms predicted 40% of positive fetal blood and 53% of positive amniotic fluid cultures with false positive rates of 24% and 25%, respectively. The sensitivity and false positive rates for genital tract colonisation with Mycoplasma spp in the prediction of amniotic fluid infection with these organisms were 85% and 35%, respectively. CONCLUSIONS: In preterm prelabour rupture of the membranes lower genital tract cultures provide poor prediction of intrauterine infection.

Amniotic Fluid↗
PubMed1995

Assessment of fetal activity and amniotic fluid volume in the prediction of intrauterine infection in preterm prelabor amniorrhexis.

OBJECTIVE: Our purpose was to assess fetal activity, fetal heart rate patterns, and amniotic fluid volume in the prediction of intrauterine infection in pregnancies complicated by preterm prelabor amniorrhexis. STUDY DESIGN: A prospective study was performed on 89 patients with preterm prelabor amniorrhexis undergoing fetal blood and amniotic fluid sampling for microbiologic investigations. Within 2 hours before cordocentesis and amniocentesis, computerized fetal heart rate monitoring was carried out and ultrasonographic examination was performed for assessment of biophysical profile and amniotic fluid volume. RESULTS: In the pregnancies with microbiologic evidence of intrauterine infection compared with those with no infection, there was a tendency for a lower biophysical profile score and amniotic fluid index and an increased fetal heart rate. However, in the majority of pregnancies with positive amniotic fluid or fetal blood cultures the results of the various tests were normal. CONCLUSION: In pregnancies complicated by preterm prelabor amniorrhexis assessment of fetal activity and amniotic fluid volume do not provide useful prediction of intrauterine infection.

Amniotic Fluid↗
PubMed1995

Doppler studies of the placental and fetal circulation in pregnancies with preterm prelabor amniorrhexis.

This study has investigated the effect of intrauterine infection on placental perfusion, fetal circulation and fetal oxygenation in patients with preterm prelabor amniorrhexis. In 69 pregnancies with preterm prelabor amniorrhexis, Doppler ultrasound studies of the uterine and umbilical arteries and the fetal middle cerebral artery and thoracic aorta were performed. Within 1 h after the Doppler studies, cordocentesis and amniocentesis were carried out for microbiological investigations and measurement of blood pO2 and pH. In the amniorrhexis group, there were no significant differences from the appropriate normal mean for gestation in any of the Doppler indices or blood gas results. Furthermore, there were no significant differences between the groups with positive fetal blood or amniotic fluid cultures and those with no evidence of infection. These data demonstrate that, in preterm prelabor amniorrhexis, microbial invasion of the amniotic cavity and fetal bacteremia are not associated with detectable changes in placental perfusion, fetal circulation or fetal oxygenation.

Amniocentesis↗
PubMed1994

Effect of poly DL-lactide--co-glycolide implants and xenogeneic bone matrix-derived growth factors on calvarial bone repair in the rabbit.

Polymer implant discs composed of 50:50 poly DL-lactide-co-glycolide (molecular weight about 9000) were used to repair 5 mm calvarial defects in 2 kg rabbits and osseous repair compared to spontaneous healing (control). After 4 weeks the implants had undergone substantial degradation with little evidence of residual polymer. The extent to which the defects had been replaced by bone showed individual variation. In some animals a layer of bone with normal cancellous architecture had bridged the defect, but at no time was bone observed in intimate contact with the polymer matrix, suggesting that the material had acted as a tissue spacer rather than an osteoconductive substrate. Non-osseous tissue consisted of a highly vascular fibrous connective tissue containing variable numbers of inflammatory cells. In some sites numerous macrophages and multinucleate giant cells were observed, the majority of which were shown by immunocytochemistry to be MHC class II-positive. Histomorphometric analysis demonstrated no statistically significant difference in osseous repair between control and polymer implant groups after 1, 2 or 3 months. Incorporation of bone matrix proteins extracted from bovine cortical bone into the discs, however, provoked a cellular and humoral immune response which had a significant inhibitory effect on osseous repair. These data suggest, first, that while synthetic polymers have potential as bone graft substitutes, improvements in their performance in vivo are needed and, second, it is advisable to use allogeneic proteins in rabbit models of bone regeneration.

Animals↗
PubMed1993

Bone-derived growth factor release from poly(alpha-hydroxy acid) implants in vitro.

Matrix proteins were extracted from bovine cortical bone and polymer implant discs (13 mm x 2 mm composed of 50:50 poly DL-lactide-co-glycolide; mol. wt. approximately 9000) prepared by compression moulding granules with lyophilized bone matrix extracts (BMX) 10.1 (w/w). BMX-containing polymers were cultured for 5 wk in either serum-free Dulbecco's modification of Eagle's medium (DMEM) or phosphate buffer, and growth factor activity released into the media assayed by its ability to stimulate the proliferation of murine fibroblast BALB/c/3T3 cells. Approximately 60-75% of the biological activity was released during the first week of culture; however, less than half of the growth factor units originally incorporated into the implants retained biological activity. Scanning electron microscopy revealed the development of significant internal porosity by week 2; the size of the channels, pores and surface openings suggested they were of the right order for bone ingrowth. These preliminary findings suggest that poly(alpha-hydroxy acid) polymers containing bone-derived growth factors could have potential for stimulating osseous regeneration in vivo.

3T3 Cells↗
PubMed1991

The immunogenicity of outer membrane proteins of haemin-depleted Porphyromonas (Bacteroides) gingivalis W50 in periodontal disease.

The antigens from outer membrane protein extracts of Porphyromonas gingivalis (W50), grown under different haemin concentrations, were examined for binding with serum antibodies from patients with severe progressive periodontitis or from periodontally healthy control subjects. P. gingivalis was grown under haemin limitation (0.33 micrograms/ml) and haemin excess (2.5 micrograms/ml) conditions in a chemostat at a mean generation time of 6.9 h, at pH 7.5. Sarkosyl-insoluble fractions of outer membrane proteins from P. gingivalis were prepared, and analysed by sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) and immunoblot techniques. The SDS-PAGE analysis of the outer membrane of haemin-limited P. gingivalis identified several new protein components, or changed expression of bands compared with cells grown under haemin excess. Immunoblot analysis showed IgG antibodies to 2 haemin deprivation-induced proteins in patients with severe progressive periodontitis, but not in the control sera. These results confirm the immunogenicity of some of the haemin-regulated outer membrane proteins of P. gingivalis in severe progressive periodontitis.

Adolescent↗
PubMed1990

Compression ultrasonography as a reliable imaging monitor in deep venous thrombosis.

Our experience at Hippokration Athens Hospital with high-resolution real-time ultrasonography of the deep veins of the lower extremities is described, drawn from the results of a prospective comparative study of 65 patients. We used a combination of sonography and contrast venography for the detection of deep venous thrombosis (DVT). Of the study group, 33 had clinically suspected DVT, 20 were asymptomatic high-risk patients, while 12 with varicosities of the leg and scheduled for saphenectomy were examined preoperatively for deep venous patency confirmation. For all patients, venography, the reference method, was performed within 12 hours of the ultrasound scan. Since 29 of the examinations were bilateral, the total number of extremities studied was 94. The sonographic criteria analyzed were the intraluminal echogenicity and the venous compressibility with the ultrasound transducer probe. In addition, the response of the common femoral vein to the Valsalva maneuver was studied. Among these three criteria, compressibility was by far the most accurate. Noncompressible abnormal veins were noted in all of the 24 extremities with proximal thrombosis and in six of the 12 with thrombosis limited to the calf veins. Thus, the sensitivity of the compressibility criterion was 100 per cent for proximal and 50 per cent for isolated calf venous thrombosis (83 per cent). All venographically patent veins were fully compressible (specificity, 100 per cent). Abnormal intraluminal echoes were found in 18 of the 36 extremities with thrombosis but not in those with negative findings on venography. Sensitivity of intraluminal echogenicity was, therefore, 50 per cent and specificity, 100 per cent. For the Valsalva criterion, the standard lower normal limit of 10 per cent was applied, leading to 40 per cent sensitivity and 93 per cent specificity rates. In comparison with venography, ultrasonography underestimated the extent of thrombosis in 60 per cent of the true-positive examinations, although never to a clinically significant degree. In conclusion, compression ultrasonography, a technique based upon the unique criterion of venous compressibility, is a highly accurate and objective noninvasive diagnostic method, and is also suitable as a screening test. We urge clinicians to support their therapeutic decisions concerning the management of DVT with it.

Adult↗
PubMed1989

Calcium uptake studies of 1,4-dihydropyridine agonists into rabbit aortic smooth muscle cells in culture.

The effects of the three dihydropyridine calcium channel agonists (+/-)BAY K 8644, (+)202-791 and (+/-)CGP 28392 on 45Ca++ uptake were studied in cultures of rabbit aortic smooth muscle cells. At 10(-7) M each agonist enhanced 45Ca++ uptake in 15-50 mM K+ but had no effect on the basal 45Ca++ uptake at 5 mM K+. At the uptake threshold of 15 mM K+ each agonist potentiated 45Ca++ uptake in a dose-dependent manner with half maximal effects at 2.4 nM for (+/-)BAY K 8644, 22 nM for (+)202-791 and 18 nM for (+/-)CGP 28392. The agonists showed no significant antagonistic activity. Responses were antagonized competitively by nifedipine and non-competitively by (+/-)D-600. The 45Ca++ uptake dose-response curves and the half maximal effects of the three agonists were over the same range of concentrations as their inhibition of [3H]nitrendipine binding to rat ventricular receptor membrane preparations. The data suggest that these cells mimic the calcium uptake by the intact aorta better than commercial vascular smooth muscle lines or cardiac cells.

3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethy↗
PubMed1987

Calcium channel blockers: correlation among receptor binding, calcium uptake and contractility in vitro.

Ten known calcium channel blockers were studied for inhibition of K+-induced 45Ca++ uptake into rabbit aortic smooth muscle cells in culture, and for displacement of [3H]nitrendipine [2,6-dimethyl-3-carbomethoxy-5-carbomethoxy-4-(3-nitro)phenyl-1, 4-dihydroxypyridine] binding to rat ventricular membrane preparations, in order to relate their effects on receptor binding with their inhibitory activities on 45Ca++ uptake and on contractile responses of vascular smooth muscle. Steady-state 45Ca++ uptake increased with K+ concentration in a dose-dependent manner. With 25 to 50 mM K+, Ca++ uptake was 0.6 nmol of Ca++ per one million cells. All calcium channel blockers inhibited K+-induced 45Ca++ uptake and [3H]nitrendipine binding in a dose-dependent fashion. The enatiomeric dihydropyridines 202-791 [isopropyl-4-(2,1,3-benzoxadiazol-4-yl)-1,4-dihydro-2, 6-dimethyl-5-nitro-3-pyridinecarboxylate] exhibited marked stereoselectivity in both studies, the agonist (+)-202-791 significantly enhancing 45Ca++ uptake at 15 to 50 mM K+. The similarity between the order of potency in inhibiting 45Ca++ uptake and displacing [3H]nitrendipine resulted in a highly significant linear (1:1) correlation. An equally significant correlation was also established for the 10 blockers between their inhibitory potencies on 45Ca++ uptake and the contractile response of rabbit aortic strips as cited in the literature. These findings support the hypothesis that calcium channel blockers block contraction of vascular muscle by inhibiting cellular calcium uptake through voltage-dependent calcium channels as a result of binding to receptors associated with these channels. The aortic cells possess channels that are functionally similar to those found in intact vascular tissue.

Animals↗