Detection of the center of the hip joint in computer-assisted surgery: an evaluation study of the Surgetics algorithm.

OBJECTIVE: The aim of this paper is to assess the accuracy of an algorithm implemented by PRAXIM in the SURGETICS navigation station for detection of the hip center. This study will assess the robustness and accuracy of the algorithm in various clinical situations such as those involving non-sphericity of the femoral head, motion of the pelvis during hip center detection, and restricted range of motion. MATERIALS AND METHODS: The localization of the hip center, based on kinematics, relies on the recording of n successive positions of the femoral rigid body in the localizer reference system during a passive circumduction motion of the hip joint. Therefore, the shape of the clouds of points acquired may vary from one acquisition to the next. To allow a comprehensive study of the consequences of these variations for hip center detection, we developed a simulator to generate numerous clouds of points. Results given subsequently for each test are the values of the difference between the femoral mechanical axis computed with C(c), the computed hip center, and the same axis computed with C(o), the reference hip center. RESULTS: Test 1: Sensitivity to noise. The errors ranged from 3.33 E - 12 (SD 3.29E - 12) for a noise of 0 mm to 8.18E - 1 (SD - 7.05E - 1) for a noise of 15 mm. Test 2: Sensitivity to the shape of the acquisition motion. All trajectories gave an error < 1 degrees . Test 3: Sensitivity to restricted range of motion. No value > 1 degrees was found during this test. Test 4: Sensitivity to the distance between two points of the cloud. No value > 0.5 degrees was found during this test. Test 5: Sensitivity to the number of points included in the cloud. No value > 1 degrees was found during this test. CONCLUSIONS: The Surgetics algorithm is robust to noise, can compensate for pelvic motion, and can be used even in the case of restricted range of motion.     

Effects of scopolamine,trimipramine and diazepam on explicit memory and repetition priming in healthy volunteers

The effects of scopolamine, an anticholinergic drug, of trimipramine, a tricyclic antidepressant with both anticholinergic and sedative properties, of diazepam and a placebo, on explicit memory and repetition priming were assessed using a free-recall task and a word-stem completion task. Forty-eight healthy volunteers took part in this double-blind study. Diazepam provoked a dissociation between free recall, which was profoundly impaired, and word completion, which was spared. No significant changes in memory performances were observed in the scopolamine group; however, a significant correlation between explicit and implicit memory performances was observed in this group. At the low dose used, the effects of trimipramine on memory were mild. The results suggest that the cholinergic system is involved in the priming effect.     

Increasing Maternal Blood Pressure with Ephedrine Increases Uterine Artery Blood Flow Velocity during Uterine Contraction

Background: During labor, ephedrine is widely used to prevent or to treat maternal arterial hypotension and restore uterine perfusion pressure to avoid intrapartum fetal asphyxia. However, the effects of ephedrine on uterine blood flow have not been studied during uterine contractions. The purpose of the study was to assess the effects of ephedrine on uterine artery velocities and resistance index using the Doppler technique during the active phase of labor.

Methods: Ten normotensive, healthy parturients with uncomplicated pregnancies at term received intravenous ephedrine during labor to increase mean arterial pressure up to a maximum of 20% above their baseline pressure. Peak systolic and end-diastolic Doppler flow velocities and resistance indices were measured in the uterine artery before and immediately after administration of bolus intravenous ephedrine and after ephedrine washout. Umbilical and fetal middle cerebral arterial resistance indices and fetal heart rate were also calculated.

Results: After ephedrine administration, mean arterial pressure increased by 17 +/- 4%. End-diastolic flow velocity in the uterine artery at peak amplitude of uterine contraction was restored to 74% of the value observed in the absence of contraction. The systolic velocity was totally restored, and the uterine resistance index was significantly decreased, compared with the values in the absence of contraction. Between uterine contractions, ephedrine induced similar but less marked effects. Fetal hemodynamic parameters were not altered by ephedrine administration.     

Low molecular weight heparin fractions as an alternative therapy in heparin-induced thrombocytopenia

Eight patients with a delayed-onset heparin-induced thrombocytopenia, with thrombotic complications requiring immediate anticoagulation in 7 of them, were given low molecular weight heparin (LMWH) fractions as alternative therapy. This treatment led to normalization of platelet count within 3-5 days in 6 patients with clinical recovery in 5. In 2 patients, thrombocytopenia persisted despite LMWH therapy. In vitro platelet aggregation tests performed in all patients gave evidence of a relationship between the presence (or absence) of a LMWH-dependent platelet-aggregating factor in the patients' plasma and the persistence (or correction) of the thrombocytopenia with LMWH therapy. Although positive in vitro tests may not necessarily be associated with thrombocytopenia, in vitro testing may prove to be a useful guide before giving LMWH fractions as an alternative therapy in patients with heparin-induced thrombocytopenia requiring immediate anticoagulation.     

Simultaneous occurrence of acute myelogenous leukemia and seminoma of the testis

Summary Simultaneous tumors are rarely encountered during the course of acute leukemias. We report on a case of seminoma of the testis that occurred during the evolution of acute myelogenous leukemia. To our knowledge, this stimultaneous association has not previously been described, but a causal relationship was not apparent in the present case. The likelihood of a common carcinogenesis existed, but direct exposure to carcinogens could not be established. Although the results of a physical examination and echography were normal at the time of diagnosis, we cannot exclude the presence of microscopic cancer of the testis. Since the dissemination pattern of seminoma is usually slower than that observed in this case and the disease remains limited to the lymph nodes for long periods following dissemination, the rapid development of the present case might have been attributable to the immunosuppression and the scrotal sepsis that occurred during the induction therapy. Immunosuppression might have stimulated the progression of a primary microscopic seminoma and the development of metastasis, whereas the scrotal sepsis and inflammation might have favored the occurrence of metastasis through bypass of the lymphatic barrier.     

L’ail au banc d’essai dans la prévention cardiovasculaire et les maladies métaboliques

May garlic have beneficial effects on cardiovascular and metabolic diseases?Some data support that garlic may have benefical medicinal functions on dyslipidemia, hypertension and diabetes mellitus. However the results of clinical trials are controversial. Several metaanalysis and a systematic review didn’t confirm that garlic or its compounds had significant effects on plasma lipids or on blood pressure. The hypoglycaemic effect was supported by any randomised clinical study. Contrary to the assertion of many physicians and patients, consumption of garlic can’t be considered as an alternative treatment for dyslipidemia or hypertension.     

Non-nociceptive capsaicin-sensitive nerve terminal stimulation allows for an original vasodilatory reflex in the human skin

A significant increase of cutaneous laser Doppler flowmetry was found before blood flow decreases with increasing pressure during a 5 mmHg min⁻¹ increase of pressure strain on the finger. Pre-treatment with a local anaesthetic or chronically applied capsaicin, resulted in the disappearance of the vasodilatory response. These results suggest an original vasodilatory axon reflex response to non-noxious pressure strain which is initiated by capsaicin-sensitive nerve terminals in the human skin.     

The RNA helicase, nucleotide 5'-triphosphatase, and RNA 5'-triphosphatase activities of Dengue virus protein NS3 are Mg2+-dependent and require a functional Walker B motif in the helicase catalytic core

The nonstructural protein 3 (NS3) of Dengue virus (DV) is a multifunctional enzyme carrying activities involved in viral RNA replication and capping: helicase, nucleoside 5'-triphosphatase (NTPase), and RNA 5'-triphosphatase (RTPase). Here, a 54-kDa C-terminal domain of NS3 (DeltaNS3) bearing all three activities was expressed as a recombinant protein. Structure-based sequence analysis in comparison with Hepatitis C virus (HCV) helicase indicates the presence of a HCV-helicase-like catalytic core domain in the N-terminal part of DeltaNS3, whereas the C-terminal part seems to be different. In this report, we show that the RTPase activity of DeltaNS3 is Mg2+-dependent as are both helicase and NTPase activities. Mutational analysis shows that the RTPase activity requires an intact NTPase/helicase Walker B motif in the helicase core, consistent with the fact that such motifs are involved in the coordination of Mg2+. The R513A substitution in the C-terminal domain of DeltaNS3 abrogates helicase activity and strongly diminishes RTPase activity, indicating that both activities are functionally coupled. DV RTPase seems to belong to a new class of Mg2+-dependent RTPases, which use the active center of the helicase/NTPase catalytic core in conjunction with elements in the C-terminal domain.     

Variation at the ADAM10 gene locus is not associated with Creutzfeldt-Jakob disease

Prion diseases are characterized by the accumulation in the brain of a misfolded and protease-resistant form of the prion protein (PrP(c)). PrP(c) contains an amyloidogenic, neurotoxic sequence that is essential for conversion into PrP(Sc), the pathological isoform. During normal processing, PrP(c) is cleaved at a site within this sequence, and this cleavage is thought to destroy the amyloidogenic potential of the protein. ADAM10, a disintegrin and metalloprotease that plays a key role in the pathogenesis of Alzheimer's disease, was recently shown to use PrP(c) as a substrate. We investigated whether variability in the ADAM10 gene could contribute to the pathogenesis of Creutzfeldt-Jakob disease (CJD), by analyzing a single nucleotide polymorphism (SNP) within ADAM10, as a genetic marker potentially in linkage disequilibrium with a functional polymorphism, in patients with sporadic or variant CJD. We observed no significant differences in ADAM10 genotype or allele frequencies between CJD patients and healthy individuals. Moreover, the distribution of ADAM10 SNP genotypes and alleles did not differ between groups of patients based on genotype at the polymorphic codon 129 of the prion protein gene--the sole major genetic risk factor for CJD identified to date. Our data indicate that ADAM10 is unlikely to confer genetic susceptibility to CJD.