Characteristics and outcome in arrhythmogenic right ventricular dysplasia.
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Adolescent↗
Biomedical subjects
M Laurent
Publications and source records attributed to M Laurent.
Magnetic resonance imaging for the visualization of cholesterol gallstones in hamster fed a new high sucrose lithogenic diet.
Cholesterol gallstone induction in hamster gallbladder is usually achieved by specific diets. An X-ray in vivo follow-up of cholelithiasis development in this species is impossible, since cholesterol gallstones are transparent as long as they are not calcified. Moreover, their size (0.2 to 1 mm) also prevents their detection by ultrasonography. The current study presents an in vivo cholesterol gallstone detection by magnetic resonance imaging in hamsters fed a new high sucrose diet containing a low proportion of cholesterol (0.015%) and a normal ratio of lipids (10%). The diet produced gallstones and an increase in the cholesterol saturation index in about 50% of animals after a 5-week feeding period. The visualization of gallstones by magnetic resonance imaging in anaesthetized animals required synchronization between breathing movements and image acquisition. A high magnetic field was also necessary to allow a fine image resolution, adapted to gallstone size. Two major advantages of this technique are a direct selection of lithiasic animals with a functional gallbladder (in spite of the presence of gallstones) and a possible adjustment of the treatment period of potential litholytic drugs.
Animals↗
Occlusion rate of ball texture as a source of velocity information.
When a ball is rolling on the ground toward an observer, its elements of texture are successively occluded. The number of the elements of texture occluded per unit of time determines the occlusion rate. The aim of this study was to examine the role of the occlusion rate of ball texture and the velocity of the ball in the perception of the time remaining before the arrival. If the occlusion rate is used to perceive the time to arrival, then timing the initiation of movement should depend on occlusion rate. On the other hand, if the optical variable tau is exclusively used, then no variation is expected. 20 subjects were required to avoid balls rolling directly toward them. Three different ball textures and five ball velocities were used, leading to 10 different occlusion rates. The results showed that the timing of the initiation of the movement was not modified by variations of occlusion rate. However, the velocity of the avoidance movement increased with occlusion rate. The role of timing initiation and movement velocity in the control of the action are discussed, and it is suggested that occlusion rate is perceived and taken into account in the control of avoidance movements.
Acceleration↗
[Clinico-pathological polymorphism of hypertrophic cardiomyopathy in echocardiography].
An echocardiographic Study of 322 adults (age: 40 +/- 16 years), belonging to 20 families with hypertrophic cardiomyopathy (HCM), was undertaken. Affected subjects had a LV diastolic wall thickness > 13 mm. The patients were classified according to the distribution of left ventricular hypertrophy (LVH) and by Maron's classification: 189 subjects were normal, 127 were affected and 6 could not been classified. By Maron's classification: 3% were type I, 33% were type II, 58% were type III and 6% were type IV. LVH was asymmetrical in 95% of cases (septum/posterior wall ratio > 1.3). The familial distribution of LVH of the 4 families in which HCM was genetically related to different loci (chromosome 11, 14 exon 13, 14 exon 8, fifth locus); the LVH was analysed from two short axis LV parasternal views and each plane was divided into 5 segments. The distribution of LVH was said to be identical between two first degree relations when all the same segments were affected, similar when they differed by only 1 or 2 segments and different when they differed by 3 or more segments. In the 26 pairs studied, LVH was identical in 2/26 (8%), similar in 11/26 (42%) and different in 13/26 (50%). Familial HCM usually gives rise to asymmetrical LVH affecting the septum and free wall. An identical distribution in 50% of affected first degree relatives.
Adolescent↗
[Long-term follow-up of a rare complication of vena cava filters: complete and spontaneous rupture of the filter].
Complete spontaneous rupture of a percutaneous caval filter produced two equal parts. Long-term follow-up showed that the filter then remained stable with no complications. This case emphasizes the importance of long-term follow-up of patients with caval filters.
Equipment Failure↗
[Acoustic characterization of velar insufficiency in young children].
The following study concerns the acoustic parameters marking the difference between the phonation of children with velar incompetency and a corresponding control group. Population is made of 64 children aged 5 and 6; 32 are in the control group and 32 in the pathological group. Each child was required to repeat several words; 10 vowels and 9 consonants were taken from those words. Acoustic signal was recorded and studied using a standard speech assessment work station. 63 parameters for the vowels and 6 for the consonants were studied. Results showed that the best parameters concerned the vowels and that cepstrum coefficients were an efficient tool to perform the separation of the two groups. On the contrary, formants, voice pitch and jitter did not appear to be efficient enough to do this task. It was, then, deduced a check form for velopharyngeal incompetency, form which will be tested in future work.
Case-Control Studies↗
A massive new posttranslational modification occurs on axonemal tubulin at the final step of spermatogenesis in Drosophila.
Using two antibodies raised against Paramecium axonemal tubulin, a monoclonal antibody, AXO 49 (Callen et al., Biol. Cell 81, 95-119 (1994)), and a polyclonal antibody, PAT (Cohen et al., Biol. Cell 44, 35-44 (1982)), which have been shown elsewhere to detect a new posttranslational modification of tubulin presumably corresponding to polyglycylation, we have analyzed the occurrence of this modification during spermatogenesis in Drosophila. Results obtained by immunofluorescence on cysts isolated by laceration of testes showed that the antibodies reacted on axonemal microtubules of several species within the genus. Observation of different stages of differentiation of D. obscura sperm cells indicated, first, that the epitopes reactive with both antibodies appeared at late stages, and secondly, that they were detected simultaneously along all axonemes within a cyst. Immunofluorescence on semithin sections and electron microscopic immunocytochemistry on ultrathin sections confirmed that the appearance of the epitope recognized by the monoclonal antibody occurred at the time of the individualization process of spermatids in D. melanogaster. These results indicate that the posttranslational modification occurs as a very late event, after complete assembly of axonemal microtubules, and that the axonemal tubulin becomes modified when axonemal microtubules become coupled with the membrane, suggesting that the modification may in some way be induced by the microtubule-membrane interaction.
Animals↗
[Infections on permanent endocavitary pacemaker leads: value of transesophageal echocardiography].
The prevalence of infection of permanent pacing material ranges from 0.13 to 19.9% of patients according to published series. The seriousness of this condition requires early diagnosis and treatment. Transesophageal echocardiography visualised vegetations on the intracardiac pacing lead in all of 11 patients studied, whereas transthoracic echocardiography and polynuclear leucocyte scintigraphy only provided positive diagnoses in 4 cases for each investigation. Three types of vegetation were visualised; no cases of tricuspid valve endocarditis were observed. Treatment was based on explantation of all implanted material by endovascular traction in 7 cases and by surgery in the other 4 cases according to the results of transesophageal echocardiography. There were no deaths or recurrence of infection. Transesophageal echocardiography is the investigation of choice for imaging a vegetation on an endocavitary pacing lead. Complete explanation is essential for a complete recovery of this infection.
Adult↗
[Indications of partial interruption of the inferior vena cava in pulmonary embolism].
Forty years after the first implantation of caval filters, there is still no indication for implantation validated by a controlled clinical trial. This fact may be explained by our poor understanding of the evolution of thromboembolic disease, especially in certain groups of patients. The absolute contra-indications to heparin therapy would seem to be a logical indication for a caval filter. In cases of a relative contra-indication to anticoagulants, the physician has to rely on his clinical judgement and the decision will be taken case by case. In patients with suspected pulmonary embolism under anticoagulant therapy, it is also logical to check that anticoagulation is effective, and to request proof of embolism, to assess its risk and that due to thrombosis before considering a caval filter. The prophylactic implantation of a caval filter is a very controversial indication whether the thrombus is proximal in the ilio-caval region, extensive, not uncommon despite treatment, or floating. For groups said to be at high risk of thromboembolism (elderly, malignant disease or multiple injuries), there is no consensus because of the discordant results in the literature. The implantation of a filter would seem to be justified in patients with chronic cor pulmonale after pulmonary embolectomy. The value of a temporary caval filter during thrombolysis has not been demonstrated; there are hopes that temporary filters "of long duration" will provide filtration of the vena cava during vulnerable periods. The results of the first controlled trial (PREPIC) are eagerly awaited and should rationalise the indications of inferior vena cava filters.
Aged↗
Ca(2+)-mobilizing hormones induce sequentially ordered Ca2+ signals in multicellular systems of rat hepatocytes.
The development of hormone-mediated Ca2+ signals was analysed in polarized doublets, triplets and quadruplets of rat hepatocytes by video imaging of fura2 fluorescence. These multicellular models showed dilated bile canaliculi, and gap junctions were observed by using an anti-connexin-32 antibody. They also showed highly organized Ca2+ signals in response to vasopressin or noradrenaline. Surprisingly, the primary rises in intracellular Ca2+ concentration ([Ca2+]i) did not start randomly from any cell of the multiplet. It originated invariably in the same hepatocyte (first-responding cell), and then was propagated in a sequential manner to the nearest connected cells (cell 2, then 3, in triplets; cell 2, 3, then 4 in quadruplets). The sequential activation of the cells appeared to be an intrinsic property of multiplets of rat hepatocytes. (1) In the continued presence of hormones, the same sequential order was observed up to six times, i.e. at each train of oscillations occurring between the cells. (2) The order of [Ca2+]i responses was modified neither by the repeated addition of hormones nor by the hormonal dose. (3) The mechanical disruption of an intermediate cell slowed down the speed of the propagation, suggesting a role of gap junctions in the rapidity of the sequential activation of cells. (4) The same multiplet could have a different first-responding cell for vasopressin or noradrenaline, suggesting a role of the hormonal receptors in the sequentiality of cell responses. It is postulated that a functional heterogeneity of hormonal receptors, and the presence of functional gap junctions, are involved in the existence of sequentially ordered hormone-mediated [Ca2+]i rises in the multiplets of rat hepatocytes.
Animals↗
Acidic fibroblast growth factor is expressed abundantly by photoreceptors within the developing and mature rat retina.
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Animals↗
A sequence related to a DNA recognition element is essential for the inhibition by nucleotides of proton transport through the mitochondrial uncoupling protein.
The uncoupling protein (UCP) is uniquely expressed in brown adipose tissue, which is a thermogenic organ of mammals. The UCP uncouples mitochondrial respiration from ATP production by introducing a proton conducting pathway through the mitochondrial inner membrane. The activity of the UCP is regulated: nucleotide binding to the UCP inhibits proton conductance whereas free fatty acids increase it. The similarities between the UCP, the ADP/ATP carrier and the DNA recognition element found in the DNA binding domain of the estrogen receptor suggested that these proteins could share common features in their respective interactions with free nucleotides or DNA, and thus defined a putative 'nucleotide recognition element' in the UCP. This article provides demonstration of the validity of this hypothesis. The putative nucleotide recognition element corresponding to the amino acids 261-269 of the UCP was gradually destroyed, and these mutant proteins were expressed in yeast. Flow cytometry, measuring the mitochondrial membrane potential in vivo, showed increased uncoupling activities of these mutant proteins, and was corroborated with studies with isolated mitochondria. The deletion of the three amino acids Phe267, Lys268 and Gly269, resulted in a mutant where proton leak could be activated by fatty acids but not inhibited by nucleotides.
Amino Acid Sequence↗
Up-regulation of aFGF expression in quiescent cells is related to cell survival.
Exogenously administrated acidic FGF modulates the proliferation of several cell types, controls cell differentiation, and promotes cell survival. Most cells that are sensitive to exogenous aFGF are also capable of expressing it at very low levels. Thus in order to establish the role of endogenous aFGF as a mitogenic, differentiation, or survival factor, we studied the regulation of aFGF expression by evaluating the level of mRNA by PCR amplification and the concentration of protein by Enzyme Immuno Assay (EIA). In the lens, the amount of aFGF transcripts in nondividing cells of the central epithelium and in the differentiated fiber cells located at the periphery of the lens is similar, suggesting that endogenous aFGF is not involved with lens differentiation. In cultures, depending on the growth conditions, the endogenous aFGF expressed by Bovine Epithelial Lens (BEL) cells is subject to modulation. Cells arrested either by contact inhibition or by serum deprivation express more aFGF transcripts and protein than in exponentially growing cells, implying that endogenous aFGF has no mitogenic role under these conditions. In serum-deprived cells, the addition of specific aFGF antisense primers inhibits endogenous aFGF expression and leads to the death of these cells. These results associated with the higher expression of aFGF in nondividing BEL cells, suggesting that, contrary to exogenous aFGF, endogenous aFGF is not a mitogenic factor but a survival factor.
Animals↗
Fitts' law in two-dimensional task space.
A traditional continuous Fitts' task may be described as a one-dimensional oscillation between two targets. The combination of two such oscillations along intersecting axes gives rise to a two-dimensional aiming task, allowing the study of the speed-accuracy trade-off in two-dimensional task space. In two experiments subjects were asked to draw as many ellipses as possible while passing through four targets, arranged around the extreme points of the two major axes of a model ellipse. In the first experiment, task difficulty was manipulated simultaneously along the two axes of the ellipse. Regardless of ellipse eccentricity and orientation, movement time (MT) was found to depend linearly on Fitts' index of difficulty (ID), which combines between-target distance and target width. In the second experiment, ID was manipulated independently for the short and the long axes of the ellipse. There was a strong linear relation between MT and ID averaged over the two axes, with the two independent measures of task difficulty exerting interactive effects on MT: the higher the ID on one axis, the smaller the effect of the ID on the other. The present results demonstrate that Fitts' law, only examinated so far in one-dimensional aiming tasks, generalises to two-dimensional task space.
Adult↗
The control and coordination of one-handed catching: the effect of temporal constraints.
The aim of the experiment was to identify the control mechanisms involved in a goal-directed task by manipulating the temporal constraints. Subjects were required to catch, with one hand, table tennis balls projected by a ball-projection machine under five temporal conditions (ball speed ranged from 5.7 to 9 m/s, giving rise to flight times of 550-350 ms). By means of three-dimensional kinematics analysis the following results were obtained, which are some spatio-temporal adaptations of the catching movement to the increase of temporal constraints: (1) a decrease in movement time, (2) an increase in the straightness of the trajectory of the wrist, and (3) a shift backwards of the place of ball-hand contact while (4) the grasping time was kept constant. Moreover, as a result of increasing temporal constraints, the acceleration phase of the transportation component was kept constant while the deceleration phase was progressively decreased and nearly suppressed. Further, an increased correlation of the initial direction of the transportation component with the initial direction of the ball path was found. These findings show some spatio-temporal adaptations of the catching movement when the time available is manipulated. They also support the contention of a shift in the control mechanisms involved in one-handed catching facing different temporal constraints.
Goals↗
Intracellular visualization of ampicillin-loaded nanoparticles in peritoneal macrophages infected in vitro with Salmonella typhimurium.
Intracellular targeting of ampicillin by means of polyisohexylcyanoacrylate (PIHCA) nanoparticles was studied in murine peritoneal macrophages infected with Salmonella typhimurium. The intracellular distribution of actively endocytosed nanoparticles was visualized by transmission electron microscopy and confocal microscopy. Nanoparticles were either isolated or closely associated with bacteria within phagosomes or phagolysosomes. Thus the potential of ampicillin-loaded nanoparticles in targeting of intracellular bacteria is demonstrated. Consequently, ampicillin, which usually penetrates into cells at a low level, is directly carried in, when loaded on nanoparticles, and brought into contact with intracellular bacteria.
Ampicillin↗
The effects of environmental changes on one-handed catching.
Ball catching involves predicting the time and place of arrival of a mobile object. Visual cues of various kinds may help a ball catcher to perform this task successfully. The aims of the present study were (a) to assess the role of the environment in the spatiotemporal planning of ball-catching movements and (b) to determine what specific cues are actually used for this purpose. In the first experiment described here, subjects' catching performances were compared under four different environmental conditions, namely, normal lighting, ultraviolet light with no background, ultraviolet light with a densely structured background, and ultraviolet light with a sparsely structured background. Our results showed that the sight of the mobile object alone does not provide enough information for a subject to achieve his maximum performance level. Accurately assessing the point of arrival of the ball requires the use of relative visual cues. The environment is also a source of visual cues used to assess the time of arrival of the ball. A second experiment was carried out with a view to determining the exact nature of the visual cues used. Here, the orientation (frontal vs. oblique plane) and the apparent visual angle (6 degrees vs. 42 degrees ) of the background were made to vary. The results of this experiment showed that the orientation of the background affected the percentage of spatial errors produced by the subjects, whereas the apparent visual angle affected the percentage of temporal errors. The relative velocity cue generated by the masking of successive structures in the environment by the oncoming ball seems to have been taking into account in estimating the time of arrival of the ball. This cue seems to be of crucial importance during the 200 ms prior to the time of contact between the ball and the subject's hand. This finding supports the idea that the method used to assess the time to contact may involve velocity information.
Journal Article↗
Power and limits of laser scanning confocal microscopy.
In confocal microscopy, the object is illuminated and observed so as to rid the resulting image of the light from out-of-focus planes. Imaging may be performed in the reflective or in the fluorescence mode. Confocal microscopy allows accurate and non-destructive optical sectioning in a plane perpendicular or parallel to the optical axis of the microscope. Further digital three-dimensional treatments of the data may be performed so as to visualize the specimen from a variety of angles. Several examples illustrating each of these possibilities are given. Three-dimensional reconstitution of nuclear components using a cubic representation and a ray-tracing based method are also given. Instrumental and experimental factors can introduce some bias into the acquisition of the 3-D data set: self-shadowing effects of thick specimens, spherical aberrations due to the sub-optimum use of the objective lenses and photo-bleaching processes. This last phenomenon is the one that most heavily hampers the quantitative analysis needed for a 3-D reconstruction. We delineate each of these problems and indicate to what extent they can be solved. Some tips are given for the practice of confocal microscope and image recovery: how to determine empirically the thickness of the optical slices, how to deal with extreme contrasts in an image, how to prevent artificial flattening of the specimens. Finally, future prospects in the field are outlined. Particular mention of the use of pulsed lasers is made as they may be an alternative to UV-lasers and a possible means to attenuate photodamage to biological specimens.
Animals↗