Modelling the genetics and demography of step cline formation: gastropod populations preyed on by experimentally introduced crabs

Whether a prey population goes extinct or adapts in response to an invading predator may depend on the number of contiguous populations that experience increased predation. We created invaded snail populations by building shelters for predatory shore crabs on a rocky intertidal bench. The crabs preyed selectively on thin-shelled snails tethered next to the shelters but did not prey on those more than 2 m away. This caused strong directional selection for increased shell thickness in populations close to the shelters but did not change selection in those farther away. The field experiment was used to parameterize a new individual-based quantitative genetic model that included demography. In the model a detectable step cline in shell thickness evolved rapidly even though the region of increased predation was shorter than Slatkin's characteristic length. The cline's step size in the model was similar to that measured in the field 10 years after the experiment began.

The in vitro osteoclastic degradation of nacre

Osteoclast activity was studied on nacre, the mother of pearl (MOP) in order to assess the plasticity of bone resorbing cells and their capacity to adapt to a biomineralized material with a different organic and mineral composition from that of its natural substrate, bone. Pure MOP, a natural biomineralized CaCO(3) material, was obtained from Pinctada oyster shell. When implanted in the living system, nacre has proven to be a sustainable bone grafting material although a limited surface degradation process. Osteoclast stem cells and mature osteoclasts were cultured on MOP substrate and osteoclast precursor cells were shown to differentiate into osteoclasts capable of resorbing nacre substrate. However, analysis of the organization of the cytoskeleton showed that both a sealing zone and a podosome structure were observed on the nacre substrate. Moreover, MOP resorption efficiency was consistently found to be lower than that of bone and appeared to be a limited process.

The calcium sensing receptor is directly involved in both osteoclast differentiation and apoptosis

Intracellular transduction pathways that are dependent on activation of the CaR by Ca(o)2+ have been studied extensively in parathyroid and other cell types, and include cytosolic calcium, phospholipases C, A2, and D, protein kinase C isoforms and the cAMP/protein kinase A system. In this study, using bone marrow cells isolated from CaR-/- mice as well as DN-CaR-transfected RAW 264.7 cells, we provide evidence that expression of the CaR plays an important role in osteoclast differentiation. We also establish that activation of the CaR and resultant stimulation of PLC are involved in high Ca(o)2+-induced apoptosis of mature rabbit osteoclasts. Similar to RANKL, Ca(o)2+ (20 mM) appeared to trigger rapid and significant nuclear translocation of NF-kappaB in a CaR- and PLC-dependent manner. In summary, our data suggest that stimulation of the CaR may play a pivotal role in the control of both osteoclast differentiation and apoptosis in the systems studied here through a signaling pathway involving activation of the CaR, phospholipase C, and NF-kappaB.

Donor Outcomes in Right Lobe Adult Living Donor Liver Transplantation: Single-Center Experience in Egypt

INTRODUCTION AND OBJECTIVES

Living donor liver transplantation (LDLT) is an alternative source of organs for patients with end-stage liver disease (ESLD) in absence of deceased donor LT. In LDLT the greatest concern is donor safety. Our objective was to evaluate the outcome of donors after right lobe liver donation in a single LT center in Egypt.

PATIENTS AND METHODS

Fifty LDL resections were performed from 2001 to 2004. The mean donor age was 29.2 +/- 6.4 years. Residual liver volume was 41.1 +/- 4.5%. Mean operative time was 560 +/- 62.2 minutes; mean ICU stay, less than 24 hours; mean hospital stay, 15.4 +/- 7.7 days; and mean follow-up period, 6 months.

RESULTS

There was no mortality. The overall complication rate was 68% (34 donors). Major complications included intraoperative bleeding in one, biliary leak in two, and pneumonia in three donors. Minor complications included mild pleural effusion in 13 donors, transient ascites in 10, mild depression in 7, intra-abdominal collections in 3, and wound infections in 1 donor. Residual liver volume did not affect the complication rate. None required reoperation. Return to predonation activity occurred within 6 to 8 weeks. No liver impairment occurred during follow-up.

CONCLUSION

Right lobe adult LDLT is a safe procedure with regard to donor outcome. Major complications occurred in only 10% of our series.

Impact of inflammation and oxidative stress on vascular calcifications in chronic kidney disease

Vascular and/or valvular calcifications in patients with chronic kidney disease (CKD) appear to indicate a poor prognosis in terms of overall survival and cardiovascular morbidity and mortality. Inflammation and oxidative stress represent new features of the arterial and/or valvular calcification process. However, only limited observational and epidemiological data are available in these areas. Therefore, the link between inflammation, oxidation and vascular and/or valvular calcifications deserves careful consideration in CKD patients, since they may become targets for the development of new therapeutic strategies.

Involvement of capacitive calcium entry and calcium store refilling in osteoclastic survival and bone resorption process

Bone resorption is closely dependent on osteoclastic survival and osteoclast apoptotic cell death could represent a key step at the end of this process. In order to precise the possible role of calcium movement in osteoclastic cell death, we investigated whether intracellular calcium store replenishment and capacitive calcium entry (CCE) are involved in osteoclastic survival and bone resorption. We demonstrate that (i). thapsigargin, a sarco-endoplasmic reticulum calcium ATPase pump (SERCA) blocker, decreases both osteoclastic survival and bone resorption process, (ii). 2-aminoethoxydiphenyl borate (2-APB) and SKF-96365, two store-operated channel (SOC) blockers, dramatically decrease osteoclastic survival and bone resorption and (iii). culture in calcium-free medium and thapsigargin exposure synergically inhibit osteoclastic survival which falls dramatically to a value close to 0% (P<0.001). Inversely, osteoclastic survival increases significantly when thapsigargin-treated cells are cultured in the presence of 20mM calcium, suggesting that increasing extracellular calcium concentration stimulates osteoclasts survival when the filling of intracellular stores is prevented. Taken together, our data strongly suggest that in osteoclasts, calcium movements between cellular compartments involved in the regulation of calcium signalling, such as calcium stores refilling and CCE, are closely associated to the regulation of osteoclast survival and bone resorption.

Regulation of bone resorption and osteoclast survival by nitric oxide: possible involvement of NMDA-receptor

Nitric oxide has been shown to play an important role in regulation of bone resorption. However, the role of endogenous nitric oxide on osteoclast activity remains still controversial. In this work, using RT-PCR amplification, we demonstrated that rabbit mature osteoclasts express mRNA encoding for neuronal nitric oxide synthase suggesting that this enzyme could be involved in basal nitric oxide production in these cells. Then we assessed the effect of carboxy-PTIO, a nitric oxide scavenger, on in vitro bone resorption and osteoclast survival. Carboxy-PTIO (10-100 microM) inhibited osteoclastic bone resorption in a dose dependent manner and induced osteoclast apoptosis by a mechanism involving caspase 3 activation. These results suggest that basal concentration of endogenous nitric oxide may be essential for normal bone resorption by supporting osteoclast survival. Because osteoclasts express N-methyl-d-aspartate-receptor (NMDA-R), we hypothesized that in osteoclasts NMDA-R may be involved in nitric oxide production as in neuronal cells. We confirmed that blockade of NMDA-R with specific non-competitive antagonists, MK801 and DEP, strongly inhibited bone resorption. As for carboxy-PTIO, we showed that blockade of NMDA-R by both antagonists induced osteoclast apoptosis in a dose dependent manner by a mechanism dependent on caspase 3 activation. Intracellular calcium concentration in osteoclasts decreased within minutes in the presence of both antagonists. Finally, MK801-induced osteoclast apoptosis was partially reversed in the presence of small amount of SNAP (100 nM), a nitric oxide donor, suggesting that the effect of NMDA-R on osteoclast apoptotic cell death could be due to a decrease in nitric oxide production. Taken together, our results are consistent with the hypothesis that NMDA-R on osteoclasts could have a similar function as those in neuronal cells, i.e., to allow a calcium influx, which in turn activates a constitutive neuronal nitric oxide synthase. Nitric oxide generated by this pathway may be essential for osteoclast survival and hence for normal bone resorption.

[Prescription of bone remodeling markers in hospitals]

Biochemical markers of bone turnover have for several years been considered as valuable parameters in research clinical studies, but their use in individual patients is still debated. Recently several position papers have proposed guidelines for their use in clinical practice in patients with post menopausal osteoporosis. In the present article, we report the results of a survey which aims at comparing the actual modalities of prescription of French physicians with the above-mentioned recommendations. We contacted by phone clinical chemists from 158 different hospitals and asked them to transmit to the concerned physicians of their hospital a detailed questionnaire for assessing which bone marker(s) is (are) prescribed and for which purpose (s), and if not prescribed, the reason of non prescription. We were able to analyze 309 questionnaires from 89 hospitals including 5 specialties, rheumatology (35.9%), endocrinology (18.1%), gynecology (11.0%), internal medicine (22.0%) and geriatry (12.9%). The results showed large discrepancies between the mode of prescription of a subset of physicians and the guidelines. The most often evoked reason for non prescription was a lack of information about bone markers suggesting a need for teaching courses. This survey has also shown that many physicians do not know exactly which parameters are effectively measured in their hospital and which are addressed to specialized laboratories underlining the importance of the dialogue between clinicians and clinical chemists. We propose that in a given hospital, the present article may serve as a basis for a discussion between clinicians and biologists about the development and/or the optimization of the measurements of these markers of bone turnover.

Psychometric study of dysthymic patients and their first-degree relatives

Psychometric evaluation of severity of depression and personality characteristics of 20 dysthymic patients (mean age 29.05+/-7.08 ys.) was carried out using Hamilton Depression Rating Scale (HDRS) and Eysenck Personality Questionnaire (EPQ) and was compared with that of 20 major depressive patients (mean age 33.60+/-7.7ys.) and 20 normal controls (mean age 32.85+/-6.17 ys.). Psychosocial stressors that might trigger depression were also looked for. All first-degree relatives (118 persons) were subjected to clinical interview for detection of dysthymia. EPQ was also applied to assess their personality characteristics. Depression among dysthymic patients was mainly of mild degree. Severe depression was found in about 55% of major depressive and none of dysthymic patients. Application of EPQ revealed high neuroticism among dysthymics and high psychoticism among major depressives. Lie scale was high for both groups. Psychosocial stressors were more reported by dysthymic patients; however they were of mild or moderate degrees. Stressors reported by major depressive patients were mainly acute and severe. Assessment of the first-degree relatives revealed that 66% of dysthymics' relatives had dysthymia or high EPQ scores compared to 36% of major depressives and 22% of normals.

[Biochemical markers of bone remodeling: pre-analytical variations and guidelines for their use. SFBC (Société Française de Biologie Clinique) Work Group. Biochemical markers of bone remodeling]

Biochemical markers of bone turnover have been developed over the past 20 years that are more specific for bone tissue than conventional ones such as total alkaline phosphatase and urinary hydroxyproline. They have been widely used in clinical research and in clinical trials of new therapies as secondary end points of treatment efficacy. Most of the interest has been devoted to their use in postmenopausal osteoporosis, a condition characterized by subtle modifications of bone metabolism that cannot be detected readily by conventional markers of bone turnover. Although several recent studies have suggested that biochemical markers may be used for the management of the individual patient in routine clinical practice, this has not been clearly defined and is a matter of debate. Because of the crucial importance to clarify this issue, the Société Francaise de Biologie Clinique prompted an expert committee to summarize the available data and to make recommendations. The following paper includes a review on the biochemical and analytical aspects of the markers of bone formation and resorption and on the sources of variability such as sex, age, menstrual cycle, pregnancy and lactation, physical activity, seasonal variation and effects of diseases and treatments. We will also describe the effects of pre-analytical factors on the measurements of the different markers. Finally based on that review, we will make practical recommendations for the use of these markers in order to minimize the variability of the measurements and improve the clinical interpretation of the data.

[Osteoblastic regulation of osteoclast survival: effect of calcitriol]

Throughout life, bone is remodelled in a dynamic process which results in a balance between bone formation by osteoblasts and bone resorption by osteoclasts. It is now clearly established that osteoblasts/stromal cells are crucial for differentiation of osteoclasts, through a mechanism involving cell-to-cell contact. However, the possible involvement of osteoblasts and stromal cells in the survival of osteoclasts has not yet been clearly demonstrated. In this study, we assessed the influence of cellular microenvironment, especially osteoblasts, on the osteoclast survival. Our results have shown significant differences in osteoclastic survival between unfractionated bone cells and pure osteoclasts. Furthermore, we have shown that addition of 1.25(OH)2D3 to unfractionated bone cells resulted in a dose-dependent increase in osteoclast survival. Finally, we have shown that a conditioned medium obtained from rat osteoblastic cells cultured with calcitriol was able to increase significantly survival of pure osteoclasts. Taken together, these results strongly suggest that osteoblastic cells present in the bone microenvironment might play a role in the osteoclastic survival by producing soluble factor which modulate osteoclast apoptosis.

Evaluation of in vitro bone resorption: high-performance liquid chromatography measurement of the pyridinolines released in osteoclast cultures

None of the currently used methods to evaluate bone resorption by osteoclasts cultured on bone substrate measures directly the amounts of degraded bone collagen, which is a direct reflection of the osteoclast "work done." We therefore propose a reliable biochemical method to evaluate the in vitro collagenolysis process. Bone-resorbing activity was evaluated, after HPLC separation, by fluorimetric measurement of hydroxylysylpyridinoline (HP), a collagen cross-link molecule, released in culture supernatants. We first confirm previous data reporting that HP is released in the culture medium in a peptide-conjugated form. After acid hydrolysis, we show that HP is highly correlated with the lacunae area (r = 0.68, P<0.0001) and with the amounts of antigenic collagen fragments (Cross-laps for culture) released in culture medium (r = 0.77, P<0.0002). Using a cysteine protease inhibitor, we observed that lacunae areas are dramatically less inhibited (35% inhibition) than the release of bone-degraded products, including HP and antigenic collagen fragments (96 and 92% inhibition, respectively). Coupled to the resorbed area measurement, biochemical evaluations offer both quantitative and qualitative complementary measurements of the osteoclastic bone-resorbing process.

Effects of intraperitoneal lidocaine combined with intravenous or intraperitoneal tenoxicam on pain relief and bowel recovery after laparoscopic cholecystectomy

BACKGROUND

Previous work has demonstrated that intraperitoneal (i.p.) lidocaine may provide analgesia after laparoscopic cholecystectomy. The aim of this prospective, randomized, double-blind study was to compare pain relief, recovery variables, and side effects after i.p. instillation of lidocaine plus tenoxicam given either i.v. or i.p. after laparoscopic cholecystectomy.

METHODS

Ninety patients were randomly allocated to one of three groups to receive either 200 ml normal saline i.p. and 2 ml of normal saline i.v. (saline group), 200 ml lidocaine 0.1% i.p. and 2 ml tenoxicam 20 mg i.v. (tenoxicam i.v. group), or 200 ml lidocaine 0.1% with 20 mg tenoxicam i.p. and 2 ml of normal saline i.v. (tenoxicam i.p. group). The i.p. instillation was made under the right diaphragm and on the gall bladder bed. VAS pain scores at rest, on movement and during coughing, were measured 2, 4, 6, 12, and 24 h after operation. The time to first demand of analgesia, total analgesic requirement, recovery variables, and side effects were investigated.

RESULTS

In the tenoxicam i.p. group, pain scores were significantly lower both at rest and on movement and analgesic consumption was reduced compared with the saline group (P<0.05). In the tenoxicam i.v. group, pain scores at rest were significantly lower compared with the saline group. Although recovery of bowel function was significantly faster in the tenoxicam i.p. group (P<0.05), there were no differences in any other recovery characteristics or incidence of nausea between the groups.

CONCLUSION

Combination of intraperitoneal lidocaine and tenoxicam provided better analgesia on movement, and faster return of bowel function compared with i.p. lidocaine and i.v. tenoxicam during the 24 h period after surgery.