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Biomedical subjects

V Climent

Publications and source records attributed to V Climent.

At least 19 recordsLinked to original sources
PubMed2006

Effect of deposited bismuth on the potential of maximum entropy of Pt(111) single-crystal electrodes.

The effect of bismuth adsorption on the entropy of formation of the double layer on Pt(111) electrodes has been studied with the laser-induced temperature jump method. The coulostatic response to the temperature change induced by pulsed laser illumination allows the estimation of the sign and magnitude of the thermal coefficient of the potential drop at the interphase. This is related to the entropy of formation of the double layer, and the particular potential where this thermal coefficient becomes zero can be identified with the potential of maximum entropy of double-layer formation (pme). The effect of bismuth adsorption on the pme depends on the adatom coverage. At high coverages, a marked decrease of the pme is observed. This trend follows the change of the potential of zero charge expected from work function measurements, and it is likely due to the change in the orientation of solvent molecules induced by surface dipoles originated between the adatom and the substrate. At low coverage, the pme increases with the bismuth coverage. The disruption of the water structure due to the presence of the bismuth adatoms is tentatively proposed as the most likely explanation for this behavior.

Journal Article↗
PubMed2005

A new floating sensor array to detect electric near fields of beating heart preparations.

A new flexible sensor for in vitro experiments was developed to measure the surface potential, Phi, and its gradient, E (electric near field), at given sites of the heart. During depolarisation, E describes a vector loop from which direction and magnitude of local conduction velocity theta can be computed. Four recording silver electrodes (14 microm x 14 microm) separated by 50 microm, conducting leads, and solderable pads were patterned on a 50 microm thick polyimide film. The conductive structures, except the electrodes, were isolated with polyimide, and electrodes were chlorided. Spacer pillars mounted on the tip fulfil two functions: they keep the electrodes 70 microm from the tissue allowing non-contact recording of Phi and prevent lateral slipping. The low mass (9.1 mg) and flexibility (6.33 N/m) of the sensor let it easily follow the movement of the beating heart without notable displacement. We examined the electrodes on criteria like rms-noise of Phi, signal-to-noise ratio of Phi and E, maximum peak-slope recording dPhi/dt, and deviation of local activation time (LAT) from a common signal and obtained values of 24-28 microV, 46 and 41 dB, 497-561 V/s and no differences, respectively. With appropriate data acquisition (sampling rate 100 kHz, 24-bit), we were able to record Phi and to monitor E and theta on-line from beat-to-beat even at heart rates of 600 beats/min. Moreover, this technique can discriminate between uncoupled cardiac activations (as occur in fibrotic tissue) separated by less than 1 mm and 1 ms.

Animals↗
PubMed2005

Taurine and cholestasis associated to TPN. Experimental study in rabbit model.

Taurine seems to be essential in the newborn for bile acid (BA) tauroconjugation, and its deficiency has been implicated in total parenteral nutrition-associated cholestasis (TPN-AC). Our purpose was to study the relationship between taurine (Ta) and TPN-AC in rabbits, which have a similar biliary metabolism to that of humans. We used 40 young rabbits, fed for 10 days according to the following four groups: GA [10] given TPN, with amino acid solution (AA) but without taurine (Ta) or its AA-precursors (methionine, cysteine, and serine); GB [10] the same but only without taurine; GC [10] the same but with taurine and its precursors; and GD [10] the control group with oral nutrition and saline infusion. Complete blood and bile analytical data were obtained and analyzed, including plasma AA and BA. Liver samples were studied under optical and electron microscopy. Serum: In GC there was a 20% increase in the AA-precursors, but paradoxically it was greater in GA. Bile: In GC there was 30% more excretion of total and free BA compared with less than 20% in GA and GB. Regarding toxic BA, there was a 15% decline in GLC3S excretion, but more than 20% in LCA excretion, than in GA and GB. Moreover, in GC the glyco-/tauro-conjugate ratio was worse than in the other groups. Histomorphology: While in GA and GB liver steatosis was diffuse (microsteatohepatitis type), in GC there was macrosteatosis with mitochondria-surrounded lipid droplets. In GA and GB, the canaliculi appeared dilated, with abundant bile plugs and loss of microvilli. There are signs that taurine may protect against TPN-AC. The mechanism does not seem to be BA tauroconjugation, but probably taurine's antioxidant, membrane stabilization (with Ca2+ and HCO3-), and/or osmotic effects.

Amino Acids↗
PubMed2005

Sinus node revisited in the era of electroanatomical mapping and catheter ablation.

OBJECTIVE: To study the architecture of the human sinus node to facilitate understanding of mapping and ablative procedures in its vicinity. METHODS: The sinoatrial region was examined in 47 randomly selected adult human hearts by histological analysis and scanning electron microscopy. RESULTS: The sinus node, crescent-like in shape, and 13.5 (2.5) mm long, was not insulated by a sheath of fibrous tissue. Its margins were irregular, with multiple radiations interdigitating with ordinary atrial myocardium. The distances from the node to endocardium and epicardium were variable. In 72% of the hearts, the whole nodal body was subepicardial and in 13 specimens (28%) the inner aspect of the nodal body was subendocardial. The nodal body cranial to the sinus nodal artery was more subendocardial than the remaining nodal portion, which was separated from the endocardium by the terminal crest. In 50% of hearts, the most caudal boundaries of the body of the node were at least 3.5 mm from the endocardium. When the terminal crest was > 7 mm thick (13 hearts, 28%), the tail was subepicardial or intramyocardial and at least 3 mm from the endocardium. CONCLUSIONS: The length of the node, the absence of an insulating sheath, the presence of nodal radiations, and caudal fragments offer a potential for multiple breakthroughs of the nodal wavefront. The very extensive location of the nodal tissue, the cooling effect of the nodal artery, and the interposing thick terminal crest caudal to this artery have implications for nodal ablation or modification with endocardial catheter techniques.

Adult↗
PubMed2004

High-contrast white-light Lau fringes.

We present a new optical assembly with which to achieve Lau fringes with totally incoherent illumination. Gratinglike codification of the spatially incoherent source combined with an achromatic Fresnel diffraction setup allows us to achieve Lau fringe-pattern visibility of almost 100% with broadband light. The white-light character to our proposed setup is in stark contrast to previous monochromatic implementations. Potential implications of this fact are identified.

Journal Article↗
PubMed2002

The terminal crest: morphological features relevant to electrophysiology.

OBJECTIVE: To investigate the detailed anatomy of the terminal crest (crista terminalis) and its junctional regions with the pectinate muscles and intercaval area to provide the yardstick for structural normality. DESIGN: 97 human necropsy hearts were studied from patients who were not known to have medical histories of atrial arrhythmias. The dimensions of the terminal crest were measured in width and thickness from epicardium to endocardium, at the four points known to be chosen as sites of ablation. RESULTS: The pectinate muscles originating from the crest and extending along the wall of the appendage towards the vestibule of the tricuspid valve had a non-uniform trabecular pattern in 80% of hearts. Fine structure of the terminal crest studied using light and scanning electron microscopy consisted of much thicker and more numerous fibrous sheaths of endomysium with increasing age of the patient. 36 specimens of 45 (80%) specimens studied by electron microscopy had a predominantly uniform longitudinal arrangement of myocardial fibres within the terminal crest. In contrast, in all specimens, the junctional areas of the terminal crest with the pectinate muscles and with the intercaval area had crossing and non-uniform architecture of myofibres. CONCLUSIONS: The normal anatomy of the muscle fibres and connective tissue in the junctional area of the terminal crest/pectinate muscles and terminal crest/intercaval bundle favours non-uniform anisotropic properties.

Adolescent↗
PubMed2001

[A case of Carney syndrome].

The Carney complex is an autosomal dominant syndrome characterised by multiple neoplasies, including myxomas at various sites (cardiac, cutaneous, mammary), spotty pigmentation, endocrine overactivity (Cushing's syndrome, acromegalia), testicular tumours and schwannomas. This report describes the case of a 43-year-old woman with an acute inferior myocardial infarction, probably due to coronary embolization from a large left atrial myxoma and who presented this association. A brief review of the Carney complex is provided after discussion of this rare case that required an screening of family members.

Adult↗
PubMed2000

[Peripheral cholesterol embolism in a percutaneous coronary angioplasty procedure. A case report].

Cholesterol embolism is a rare but potentially serious complication of cardiac catheterization. We report the case of a patient who presented a cholesterol embolism in the lower extremities after percutaneous angioplasty and the elective implantation of a stent. Clinical evolution was favourable. The appearance of cholesterol embolism could have been precipitated, in this case, by anticoagulation treatment with heparin and intense antiaggregation.

Aged↗
PubMed1999

Myoarchitecture and connective tissue in hearts with tricuspid atresia.

OBJECTIVE: To compare the atrial and ventricular myoarchitecture in the normal heart and the heart with tricuspid atresia, and to investigate changes in the three dimensional arrangement of collagen fibrils. METHODS: Blunt dissection and cell maceration with scanning electron microscopy were used to study the architecture of the atrial and ventricular musculature and the arrangement of collagen fibrils in three specimens with tricuspid atresia and six normal human hearts. RESULTS: There were significant modifications in the myoarchitecture of the right atrium and the left ventricle, both being noticeably hypertrophied. The middle layer of the ventricle in the abnormal hearts was thicker than in the normal hearts. The orientation of the superficial layer in the left ventricle in hearts with tricuspid atresia was irregular compared with the normal hearts. Scanning electron microscopy showed coarser endomysial sheaths and denser perimysial septa in hearts with tricuspid atresia than in normal hearts. CONCLUSIONS: The overall architecture of the muscle fibres and its connective tissue matrix in hearts with tricuspid atresia differed from normal, probably reflecting modelling of the myocardium that is inherent to the malformation. This is in concordance with clinical observations showing deterioration in pump function of the dominant left ventricle from very early in life.

Adult↗
PubMed1997

Targeted over-expression of FGF in chick embryos induces formation of ectopic neural cells.

Fibroblast growth factors (FGFs) are known to be involved mainly in mesoderm formation in Xenopus embryos but their participation in other inductive mechanisms such as neural induction has not been clearly established and is now under study. Here, we provide evidence that targeted over-expression of members of this family of growth factors in the periphery of full-length primitive streak chick embryos produces the formation of ectopic neural cells that are able to differentiate into neurons. The supernumerary neural plate obtained derives from the epiblast layer of the blastoderm and show signs of neural differentiation 24 h after the application of FGF. We have used cell labeling and have examined the expression of mesodermal markers to ascertain how this expansion of the neural forming region of the epiblast takes place. We conclude that the new neural cells formed are originated in the region of the epiblast fated to be epithelia and that the induction of the ectopic neural tissue is not mediated by an increase, migration or new formation of axial mesoderm. This strongly suggests that FGF is acting directly on epiblast cells, changing their fate from epidermal ectoderm to neural ectoderm. Therefore, our results show that FGF can induce neural ectoderm when acting on still uncommitted cells and, therefore, it is a putative candidate for acting in normal neural induction during development.

Animals↗
PubMed1996

Morphology and significance of programmed cell death in the developing limb bud of the vertebrate embryo.

Cell death constitutes a basic mechanism accounting for many morphogenetic and histogenetic events during normal and abnormal development of embryonic organs and tissues. This article focuses on the major areas of mesodermal cell death occurring during vertebrate limb development. In early stages of limb development, cell death appears to reduce the amount of mesodermal tissue destined to form the anlage of the autopodium. In later stages, cell death plays a role sculpturing the shape of the digits. The morphology of the dying cells corresponds with apoptosis, but internucleosomal DNA fragmentation by endonuclease activation does not appear to be a precocious feature. The cell death program can be inhibited in vivo and in vitro by changing the environmental conditions of the prospective dying cells up to 6-10 h before death. In this review, we survey possible factors controlling the establishment of the cell death program. Information concerning the biochemical basis of cell death in the developing limb is also revised. Finally, the possible role of genes whose pattern of expression is coincident with the dying processes is discussed.

Animals↗
PubMed1995

Morphological changes in the normal pattern of ventricular myoarchitecture in the developing human heart.

BACKGROUND: The aim of the present study was to describe the morphological changes in the normal pattern of ventricular myoarchitecture in the prenatal and adult human heart, to understand the three-dimensional organization of the muscle fibers and their active functional role in valvular dynamics. METHODS: We used dissection and histological techniques in 56 human hearts from fetuses and adults of both sexes. RESULTS: In all hearts, the ventricular wall was arranged in three different layers: superficial (subepicardial), middle, and deep (subendocardial) myocardium. The superficial and deep layers are present in both ventricles, whereas the middle layer is found only in the left ventricle. Age-related differences were noted in the pattern of myoarchitecture of the superficial layer, mainly in the fetal period, and especially in the right ventricle; however, the middle layer always shows a circumferential pattern, which is specially evident in elderly hearts. The ventricular fibers in the superficial and deep layers are anchored in the ventricular orifices. CONCLUSIONS: Our findings reveal that muscle fiber architecture showed age- but not sex-related differences. These variations may reflect a mechanism of adaptation of the heart to functional demands throughout life.

Adolescent↗
PubMed1995

Morphological analysis of the fish heart ventricle: myocardial and connective tissue architecture in teleost species.

Light and scanning electron microscopy were used to study the structure of the heart ventricle in three species of marine teleost fishes: the hake (Merluccius merluccius), the angler fish (Lophius piscatorius) and the sea bream (Pagellus centrodontus). Our findings show the ventricle to be shaped differently in each species: tubular in the hake, saccular in the angler fish and pyramidal in the sea bream. From a structural viewpoint, interest was centered on two aspects: organization of the myocardial fibres and arrangement of connective tissue. In hake and angler fish ventricles, the myocardium was exclusively trabecular in nature, whereas the bream ventricle, in addition to trabecular myocardium, presented a thin compact layer. Muscle fibres showed precise patterns of organization at the level of the ventricular orifices. With the techniques used the intramyocardial connective tissue was detected in the following ventricular zones: i) at the level of subepicardial and subendocardial spaces, ii) surrounding the myocardial fascicles, and iii) surrounding individual myocardial cells. According to this structural study, the pyramidal ventricle of the fish should be considered as a ventricular pump with greater efficiency.

Animals↗
PubMed1994

Vision evaluation in people with Down's syndrome.

We tested the colour vision of 72 people with Down's syndrome using the Ishihara test and an anomaloscope. We found that 13 of the subjects, 6 males and 7 females, had defective colour vision according to Pickford's classification. In monocular vision 10 eyes were protan (five simple, three extreme and two deviant), one eye was simple deuteranomalous and the remaining eyes were normal: in binocular vision four of the subjects were protan (two simple and two deviant), two subjects were deutan (one simple and one deviant) and the rest were normal. Many of our subjects had lens opacities, strabismus, nystagmus, hypermetropia, high myopia and astigmatism, confirming literature reports. The contrast sensitivity function measured with the VCTS test showed a considerable loss of low-frequency sensitivity in our subjects compared to a normal population, which was more marked in the more severely impaired subjects.

Adolescent↗
PubMed1994

Spatial arrangement of the heart muscle fascicles and intramyocardial connective tissue in the Spanish fighting bull (Bos taurus).

The spatial arrangement of the muscle fascicles and intramyocardial connective tissue was examined in the ventricles of the heart of the Spanish fighting bull (Bos taurus). In both ventricles, the muscle fascicles of the myocardium are arranged in 3 main directions, forming 3 muscle layers within the ventricular wall. The preferentially vertical arrangement of the muscle fascicles in the superficial and deep layers at the level of the fibrous aortic rings and the base of the semilunar valve leaflets suggests that these fascicles are actively involved in valvular dynamics. After controlled digestion of myocytes and elastic fibres with NaOH, a 3-dimensional arrangement of the scaffolding of connective tissue that supports the muscle fascicles and myocytes was observed. The arrangement and structure of this scaffolding may influence the order of contraction of muscle fascicles in different layers of the ventricle. In addition, differences were observed between the connective tissue scaffolding surrounding the myocytes of the 2 ventricles; these variations were correlated with the different biomechanical properties.

Animals↗