RESUMEN
How cells respond to mechanical forces by converting them into biological signals underlie crucial cellular processes. Our understanding of mechanotransduction has been hindered by technical barriers, including limitations in our ability to effectively apply low range piconewton forces to specific mechanoreceptors on cell membranes without laborious and repetitive trials. To overcome these challenges we introduce the Nano-winch, a robust, easily assembled, programmable DNA origami-based molecular actuator. The Nano-winch is designed to manipulate multiple mechanoreceptors in parallel by exerting fine-tuned, low- piconewton forces in autonomous and remotely activated modes via adjustable single- and double-stranded DNA linkages, respectively. Nano-winches in autonomous mode can land and operate on the cell surface. Targeting the device to integrin stimulated detectable downstream phosphorylation of focal adhesion kinase, an indication that Nano-winches can be applied to study cellular mechanical processes. Remote activation mode allowed finer extension control and greater force exertion. We united remotely activated Nano-winches with single-channel bilayer experiments to directly observe the opening of a channel by mechanical force in the force responsive gated channel protein, BtuB. This customizable origami provides an instrument-free approach that can be applied to control and explore a diversity of mechanotransduction circuits on living cells.
Asunto(s)
Mecanotransducción Celular , Proteínas de la Membrana , ADN , Proteína-Tirosina Quinasas de Adhesión Focal , Mecanorreceptores/fisiología , Estrés MecánicoRESUMEN
OBJECTIVE: Polysaccharide-based composite matrices consisting of natural polysaccharides, pullulan and dextran supplemented with hydroxyapatite (Matrix-HA) have recently been developed. The principal objective of this study was to evaluate the capacities of this composite material to promote new bone formation in a sinus lift model in the sheep. Secondary objectives were to evaluate in vitro properties of the material regarding cell adhesion and proliferation. METHODS: In this report, once such composite matrix was prepared as injectable beads after dispersion in a physiological buffer, and evaluated using a large animal model (sheep) for a sinus lift procedure. RESULTS: In vitro studies revealed that these microbeads (250-550µm in diameter) allow vascular cell adhesion and proliferation of Endothelial Cells (EC) after 1 and 7 days of culture. In vivo studies were performed in 12 adult sheep, and newly formed tissue was analyzed by Cone Beam Computed Tomography (CBCT scanning electron microscopy (SEM) and by histology 3 and 6 months post-implantation. CBCT analyses at the implantation time revealed the radiolucent properties of these matrices. Quantitative analysis showed an increase of a dense mineralized tissue in the Matrix-HA group up to 3 months of implantation. The mineralized volume over total volume after 6 months reached comparable values to those obtained for Bio-Oss® used as positive control. Histological examination confirmed that the Matrix-HA did not induce any long term inflammatory events, and promoted direct contact between the osteoid tissue and lamellar bone structures and beads. After 6 months, we observed a dense network of osteocytes surrounding both biomaterials as well as a newly vascularized formed tissue in close contact to the biomaterials. SIGNIFICANCE: In conclusion, the absence of animal components in Matrix-HA, the osteoconductive property of Matrix-HA in sheep, resulting in a dense bone and vascularized tissue, and the initial radiolucent property to follow graft integration offer great promises of this composite material for clinical use.
Asunto(s)
Sustitutos de Huesos/farmacología , Durapatita/farmacología , Osteogénesis/efectos de los fármacos , Polisacáridos/farmacología , Elevación del Piso del Seno Maxilar/métodos , Animales , Regeneración Ósea/efectos de los fármacos , Adhesión Celular/efectos de los fármacos , Proliferación Celular/efectos de los fármacos , Tomografía Computarizada de Haz Cónico , Dextranos/farmacología , Glucanos/farmacología , Ensayo de Materiales , Microscopía Electrónica de Rastreo , OvinosRESUMEN
The centrosome is the principal microtubule organization center in cells, giving rise to microtubule-based organelles (e.g., cilia, flagella). The aim was to study the osteocyte centrosome morphology at an ultrastructural level in relation to its mechanosensitive function. Osteocyte centrosomes and cilia in tibial cortical bone were explored by acetylated alpha-tubulin (AαTub) immunostaining under confocal microscopy. For the first time, fine ultrastructure and spatial orientation of the osteocyte centrosome were explored by transmission electron microscopy on serial ultrathin sections. AαTub-positive staining was observed in 94% of the osteocytes examined (222/236). The mother centriole formed a short primary cilium and was longer than the daughter centriole due to an intermediate zone between centriole and cilium. The proximal end of the mother centriole was connected with the surface of daughter centriole by striated rootlets. The mother centriole exhibited distal appendages that interacted with the cell membrane and formed a particular structure called "cilium membrane prolongation." The primary cilium was mainly oriented perpendicular to the long axis of bone. Mother and daughter centrioles change their original mutual orientation during the osteocyte differentiation process. The short primary cilium is hypothesized as a novel type of fluid-sensing organelle in osteocytes.
Asunto(s)
Centrosoma/ultraestructura , Cilios/ultraestructura , Osteocitos/citología , Animales , Diferenciación Celular , Membrana Celular/química , Centrosoma/química , Cilios/química , Dendritas/química , Masculino , Mecanotransducción Celular , Microscopía Electrónica de Transmisión , Osteocitos/química , Ratas , Ratas Wistar , Tibia/citología , Tubulina (Proteína)/químicaRESUMEN
Alcohol is widely consumed across the world. It is consumed in both social and cultural settings. Until recently, two types of alcohol consumption were recognized: heavy chronic alcohol consumption or light consumption. Today, there is a new pattern of consumption among teenagers and young adults namely: binge drinking. Heavy alcohol consumption is detrimental to many organs and tissues, including bones, and is known to induce secondary osteoporosis. Some studies, however, have reported benefits from light alcohol consumption on bone parameters. To date, little is known regarding the effects of binge drinking on bone health. Here, we review the effects of three different means of alcohol consumption: light, heavy, and binge drinking. We also review the detailed literature on the different mechanisms by which alcohol intake may decrease bone mass and strength. The effects of alcohol on bone are thought to be both direct and indirect. The decrease in bone mass and strength following alcohol consumption is mainly due to a bone remodeling imbalance, with a predominant decrease in bone formation. Recent studies, however, have reported new mechanisms by which alcohol may act on bone remodeling, including osteocyte apoptosis, oxidative stress, and Wnt signalling pathway modulation. The roles of reduced total fat mass, increased lipid content in bone marrow, and a hypoleptinemia are also discussed.
Asunto(s)
Consumo de Bebidas Alcohólicas/efectos adversos , Huesos/efectos de los fármacos , Etanol/farmacología , Consumo de Bebidas Alcohólicas/fisiopatología , Alcoholismo/complicaciones , Animales , Densidad Ósea/efectos de los fármacos , Enfermedades Óseas Metabólicas/etiología , Remodelación Ósea/efectos de los fármacos , Relación Dosis-Respuesta a Droga , Etanol/administración & dosificación , Etanol/envenenamiento , Humanos , RatasRESUMEN
INTRODUCTION: Alcohol is known to decrease bone mineral density (BMD) and to induce trabecular microarchitecture deterioration. However, little is known about the effects of chronic alcohol consumption on osteocytes in situ. The aim of this study was to assess the effects of a high alcohol dose on osteocytes in an alcohol-induced osteopenia model. MATERIALS AND METHODS: 24 male Wistar rats, 2-months old were separated in 2 groups: Control (C) or Alcohol (A35). The rats in the A35 group drank a beverage composed of 35% ethanol v/v mixed to water for 17 weeks. BMD was assessed by DXA, while the microarchitecture was analyzed using µCT. Bone remodeling was studied measuring serum concentration of osteocalcin, NTx and TRAP. Bone marrow adiposity, osteoblastic lineage differentiation, osteocyte morphology and apoptosis were assessed using bright field, epifluorescence, transmission electron and confocal microscopy. RESULTS: BMD, trabecular thickness, TRAP and NTx concentration were significantly decreased in A35, while cortical thickness was thinner. There were 10 fold more cells stained with cleaved caspase-3, and 35% more empty lacunae in A35, these data indicating a large increase in osteocyte apoptosis in the A35 group. The number of lipid droplets in the marrow was increased in A35 (7 fold). Both the osteocyte apoptosis and the fat bone marrow content strongly correlated with femur BMD (p=0.0017, r = -0.72 and p=0.002, r = -0.70) and whole body BMD. CONCLUSION: These data suggest that low BMD is associated with osteocyte apoptosis and bone marrow fat content in alcohol-induced osteopenia.
Asunto(s)
Apoptosis/efectos de los fármacos , Enfermedades Óseas Metabólicas/inducido químicamente , Huesos/citología , Etanol/farmacología , Osteocitos/efectos de los fármacos , Osteocitos/fisiología , Absorciometría de Fotón , Animales , Peso Corporal , Densidad Ósea/efectos de los fármacos , Enfermedades Óseas Metabólicas/patología , Médula Ósea/química , Remodelación Ósea/efectos de los fármacos , Huesos/efectos de los fármacos , Huesos/patología , Lípidos/química , Masculino , Ratas , Ratas Wistar , Microtomografía por Rayos XRESUMEN
G-protein-coupled receptors (GPCRs) are key players in the precise tuning of intercellullar communication. In the brain, both major neurotransmitters, glutamate and GABA, act on specific GPCRs [the metabotropic glutamate (mGlu) and GABA(B) receptors] to modulate synaptic transmission. These receptors are encoded by the largest gene family, and have been found to associate into both homo- and hetero-oligomers, which increases the complexity of this cell communication system. Here we show that dimerization is required for mGlu and GABA(B) receptors to function, since the activation process requires a relative movement between the subunits to occur. We will also show that, in contrast to the mGlu receptors, which form strict dimers, the GABA(B) receptors assemble into larger complexes, both in transfected cells and in the brain, resulting in a decreased G-protein coupling efficacy. We propose that GABA(B) receptor oligomerization offers a way to increase the possibility of modulating receptor signalling and activity, allowing the same receptor protein to have specific properties in neurons at different locations.
Asunto(s)
Receptores de GABA-B/química , Receptores de GABA-B/fisiología , Receptores de Glutamato Metabotrópico/química , Receptores de Glutamato Metabotrópico/fisiología , Animales , Dimerización , Humanos , Receptores de GABA-B/clasificación , Receptores de GABA-B/metabolismo , Receptores de Glutamato Metabotrópico/clasificación , Receptores de Glutamato Metabotrópico/metabolismoRESUMEN
The reproductive cycle of wild rabbits (Oryctolagus cuniculus) living in Zembra Island (North Tunisia) is dependent on an external factor, the photoperiod: the gonads are inhibited by long days and stimulated by short days or melatonin implants. Here we studied the role of an internal factor, thyroid hormones and the possible thyroid-gonadal interrelationships, in animals captured on Zembra Island and maintained in natural conditions of photoperiod and temperature. We determined the seasonal profile of the thyroid and testis cycles and investigated the effects of castration and thyroidectomy on the seasonal testosterone and thyroxine cycles. Plasma thyroxine and testosterone levels followed similar, parallel seasonal patterns, with a peak in autumn (October) and low values from January to August. In thyroidectomized animals, plasma testosterone levels, although significantly higher than those in controls (P < 0.001), remained low throughout the 13 mo of the experiment, and no testicular reactivation was observed in the fall. In castrated animals, despite the increase in thyroxine concentration in the 3 mo following castration (P < 0.01), plasma thyroxine levels remained low during the 2 yr of the study. We then investigated the combined effects of long days (16L:8D) and moderately high temperature (25 degrees C) on these two endocrine axes. In constant gonado-inhibiting conditions (16L:8D), whether the temperature was kept constantly high or allowed to fluctuate naturally, no reactivation of the thyroid and testicular axes was observed in the fall. In control animals, the peaks of testosterone and thyroxine concentrations observed in September were larger (P < 0.001) than those in animals subjected to the same natural photoperiod conditions but with constantly high temperature. The lower level of autumnal testis stimulation (P < 0.001) in animals maintained in conditions of constant high temperature (25 degrees C) may be attributed to the low thyroxine levels induced by high temperature. These results clearly confirm that the thyroid and testicular cycles display similar seasonal variations and show that the thyroid and gonadal axes are strictly interdependent. This study provides the first demonstration, for a given species, that the seasonal reactivation of gonad activity is controlled by the thyroid, and thyroid activity is controlled by the gonads.
Asunto(s)
Animales Salvajes/fisiología , Fotoperiodo , Conejos/fisiología , Estaciones del Año , Temperatura , Testículo/fisiología , Glándula Tiroides/fisiología , Animales , Peso Corporal , Masculino , Orquiectomía , Distribución Aleatoria , Testosterona/sangre , Tiroidectomía , Tiroxina/sangreRESUMEN
The expression of arginine-vasopressin (AVP) and galanin (GAL) was studied by immunohistochemistry and in situ hybridization in the hypothalamus of two species of African rodents. In the wild, these animals experience successive arid and wet seasons that alternately stimulate their antidiuretic and diuretic systems. In this study, animals were subjected to both standardized laboratory conditions and to eight days of water-restriction. Under both sets of conditions, AVP and GAL were detected in the supraoptic nucleus (SON), paraventricular nucleus (PVN), and median eminence (ME). AVP and GAL responses to water-restriction differed in the two species, as did behavioral adaptations to the hot-dry season. In Taterillus gracilis, AVP- and GAL-LI (like immunoreactivity) peptide and mRNA levels increased in the SON. AVP-LI peptide and mRNA levels increased in the PVN, whereas only AVP-LI peptide levels increased in the ME. Pituitary gland AVP pools were unchanged by water deprivation, whereas urinary AVP levels and osmolality increased. The AVP response is typical of that of desert rodents, favoring survival under conditions of water-restriction. In Steatomys caurinus, which estivates, AVP and GAL-LI peptide levels decreased in the hypothalamus, as they did in the laboratory rat. In the SON, AVP, and GAL mRNA levels increased, whereas, in the PVN, only AVP mRNA levels increased. Pituitary gland AVP levels decreased, whereas urinary AVP levels and osmolality increased. In both species, the changes in the amount of GAL-LI peptide appeared to be closely linked to changes in AVP levels, suggesting that this peptide is involved in the osmoregulatory response to water-restriction.
Asunto(s)
Arginina Vasopresina/metabolismo , Galanina/metabolismo , Hipotálamo/metabolismo , Roedores/metabolismo , Privación de Agua/fisiología , África , Animales , Arginina Vasopresina/genética , Arginina Vasopresina/orina , Peso Corporal , Galanina/genética , Hematócrito , Inmunohistoquímica/métodos , Concentración Osmolar , Hipófisis/metabolismo , Plasma/metabolismo , ARN Mensajero/metabolismo , Coloración y Etiquetado , Distribución Tisular , Orina/químicaRESUMEN
We investigated the effects of photoperiod on testicular activity in wild rabbits (Oryctolagus cuniculus) captured on Zembra Island (North Tunisia) and maintained in experimental photoperiodic conditions. Sexually inactive animals were subjected to alternate 3-mo periods of short days (8L:16D) and long days (16L:8D) for 1 yr. Testicular activity increased significantly and then decreased to levels equivalent to or lower than those measured during sexual quiescence after 1 mo of 8L:16D or 16L:8D, respectively. Eight groups of sexually active animals were also exposed to 8L:16D for 60 days. The light phase was divided into two photofractions (7.5 and 0.5 h). The short photofraction interrupted the dark phase 9.5-18.5 h after the beginning of the main photofraction. Testicular activity was inhibited if the short photofraction interrupted the dark phase 12.5 h or more after the beginning of the main photofraction. These results clearly confirm that photoperiod affects reproduction in this species: Short days stimulate reproduction, whereas long days inhibit it. The asymmetric pattern of skeleton photoperiods used demonstrated the existence of a circadian rhythm for photogonadosensitivity, with the photosensitive phase beginning 12.5 h after dawn. In this species, photoperiod length controls both the beginning and the end of the reproductive period. These results differ from those obtained with continental populations of wild rabbits, in which reproduction is inhibited by short day length. This difference may reflect genetic drift linked to the geographic isolation of this population, which is known to have been present on this small island for more than 2000 yr.
Asunto(s)
Ritmo Circadiano/fisiología , Fotoperiodo , Reproducción/fisiología , Testículo/fisiología , Animales , Masculino , Tamaño de los Órganos , Conejos , Testículo/anatomía & histología , Testosterona/sangreRESUMEN
The glucagon response to insulin-induced hypoglycaemia was tested in rats that had been pinealectomised (Px), pinealectomised and fitted with melatonin implants (Px + MLT), or sham-operated (SO). The glucagon response to hypoglycaemia observed in SO rats (216 +/- 27 pg x ml(-1) at baseline versus 397 +/- 35 pg x ml(-1) at the hypoglycaemic peak, mean +/- S.D.) was stronger than that in Px rats (180 +/- 37 pg x ml(-1) and 229 +/- 21 pg x ml(-1), respectively) and weaker than that in Px + MLT rats (256 +/- 19 pg x ml(-1) and 516 +/- 11 pg x ml(-1), respectively). Our data indicate that the capacity to release glucagon during insulin-induced hypoglycaemia is altered in pinealectomised rats.
Asunto(s)
Glucagón/metabolismo , Hipoglucemia/metabolismo , Insulina/farmacología , Glándula Pineal/fisiología , Animales , Glucemia/metabolismo , Ritmo Circadiano , Glucagón/sangre , Hipoglucemia/inducido químicamente , Insulina/sangre , Masculino , Melatonina/administración & dosificación , Melatonina/sangre , Melatonina/farmacología , Glándula Pineal/cirugía , Distribución Aleatoria , Ratas , Ratas Sprague-DawleyRESUMEN
This study examined the effects of subcutaneous melatonin implants on testicular activity (testis volume and plasma testosterone) in wild rabbits (Oryctolagus cuniculus) captured on Zembra Island (North Tunisia) and maintained in natural temperature and photoperiod conditions. The period of testicular activity was 2 months longer in intact animals with melatonin implants than in intact animals without melatonin implants. After bilateral superior cervical ganglionectomy, testicular activity was inhibited and no spontaneous recrudescence in gonadal function was observed during the 13 months of the experiment, demonstrating the absence of an endogenous circannual rhythm of reproductive function in this species. Renewed testicular activity was observed 2 months after the insertion of melatonin implants in ganglionectomized animals. These results confirm that testicular activity is stimulated by short days in late autumn and that melatonin reactivates the reproductive axis in this species. This finding is in contrast to that in continental populations of wild rabbits in which reproduction is inhibited by short days or melatonin. These results are discussed in terms of insularity and may reflect the geographical isolation of this population.
Asunto(s)
Melatonina/fisiología , Conejos/fisiología , Testículo/fisiología , Animales , Ganglionectomía , Masculino , Melatonina/farmacología , Estaciones del Año , Ganglio Estrellado/cirugía , Testículo/efectos de los fármacos , Testosterona/sangre , TúnezRESUMEN
We explored the contribution of the suprachiasmatic nucleus (SCN) in ACTH and corticosterone (CORT) diurnal responsiveness of the rat to restraint stress applied either in the morning (AM) or in the evening (PM). Ablation of the SCN caused the diurnal rhythmicity of the CORT response to disappear but had no effects on AM vs. PM differences in the ACTH response. Stress-response curves in SCN-lesioned rats that had prestress levels of CORT either in the AM range or in the PM range, when compared with those obtained for AM and PM controls, showed that the SCN differentially regulates the stress response depending on the underlying secretory activity of the adrenal cortex. When basal CORT secretion is at its lowest, the SCN inhibits CORT responsiveness to stress by controlling pituitary corticotrophs; but when it is at its highest, it has a permissive action that will bypass the hypophysis and reach the adrenals to adjust the response of the gland to ACTH.
Asunto(s)
Hormona Adrenocorticotrópica/sangre , Ritmo Circadiano , Corticosterona/sangre , Estrés Fisiológico/fisiopatología , Núcleo Supraquiasmático/fisiopatología , Animales , Ratas , Ratas Sprague-Dawley , Restricción Física/efectos adversos , Estrés Fisiológico/etiologíaRESUMEN
Two African rodents, Taterillus gracilis and Steatomys caurinus, native to regions of alternate dry and wet seasons, were studied under laboratory conditions. These species differ in estivation behavior, one undergoing pseudoestivation and the other strong estivation. One group of animals of each species was provided with unlimited access to seed and vegetables rich in water, mimicking the food availability of the wet season (control group). A second group of animals of each species was subjected to water restriction for 8 days, mimicking the natural drought that occurs during the dry-hot season. The effects of water restriction on osmoregulation and body water content were assessed from hematocrit, and plasma and urinary osmolalities (PO, UO). Whether the natriuretic peptide system was modified by the osmoregulator adaptation to aridity of these semidesert rodents was examined from measurements of atrial natriuretic peptide (ANP) levels in plasma, atria, and ventricles, in parallel with morphological studies. In both species, UO was increased by water restriction. In water-deprived T. gracilis, ANP levels were about twice (right atria: 1.08 +/- 0.16 microg/mg protein vs control: 0.40 +/- 0.06 microg/mg protein) and plasma concentrations half (0.28 +/- 0.06 ng/ml vs control: 0.64 +/- 0.07 ng/ml) those in control animals. In S. caurinus these variables were not affected by water availability (right atria water restricted: 2. 20 +/- 0.15 microg/mg protein vs control: 2.86 +/- 0.37 microg/mg protein; plasma ANP water restricted: 0.80 +/- 0.12 ng/ml vs control: 0.90 +/- 0.16 ng/ml). Consistent with these quantitative results, immunohistochemical and ultrastructural observations showed an increase in immunostaining for both the N- and the C-terminal ANP and a larger number of granules in the atria of T. gracilis following water restriction, whereas there was no visible change in S. caurinus. Thus, water restriction induced a decrease in ANP secretion in T. gracilis, increasing cardiac storage alongside a reduced urine production. In contrast, in S. caurinus, the natriuretic system was not affected by an 8-day period of water restriction.
Asunto(s)
Adaptación Fisiológica , Factor Natriurético Atrial/fisiología , Muridae/fisiología , Privación de Agua/fisiología , Animales , Factor Natriurético Atrial/análisis , Conducta Animal/fisiología , Técnica del Anticuerpo Fluorescente Indirecta/veterinaria , Hematócrito , Miocardio/química , Concentración Osmolar , Fragmentos de Péptidos/análisis , Precursores de Proteínas/análisis , Equilibrio Hidroelectrolítico/fisiologíaRESUMEN
Immunoreactivity against glial fibrillary acidic protein (GFAP) was used as a dynamic index in adrenalectomized rats subjected or not to corticosterone replacement to investigate whether glucocorticoids may interact with astrocytes in the suprachiasmatic nucleus (SCN), the master component of the central circadian clock. GFAP staining in the SCN was significantly higher in rats having received implants that restored physiological plasma levels of corticosterone within diurnal or nocturnal limits than in non-normalized rats. The effects of corticosterone were similar in the parvocellular portion of the paraventricular nucleus but were opposite in the hippocampus, another major site of negative feed-back regulation of the hypothalamic-pituitary-adrenal axis, where a decreased GFAP staining was observed in discrete regions of the dentate gyrus. This indicates that glucocorticoids may positively or negatively regulate GFAP, depending on the target brain structure. In the SCN, that contains only few if any glucocorticoid receptors, indirect mechanisms that may involve serotoninergic neurons are probably responsible for the effects of corticosterone level. It is proposed that the corticosterone-induced increase in GFAP staining in that nucleus accounts for dynamic changes in neurone-astrocyte interactions that might occur in relation with natural fluctuations of glucocorticoids over the 24 h period.
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Proteína Ácida Fibrilar de la Glía/metabolismo , Glucocorticoides/fisiología , Núcleo Supraquiasmático/metabolismo , Adrenalectomía , Animales , Ritmo Circadiano , Corticosterona/farmacología , Giro Dentado/efectos de los fármacos , Giro Dentado/metabolismo , Hipocampo/efectos de los fármacos , Hipocampo/metabolismo , Inmunohistoquímica , Masculino , Plasticidad Neuronal/fisiología , Núcleo Hipotalámico Paraventricular/efectos de los fármacos , Núcleo Hipotalámico Paraventricular/metabolismo , Ratas , Ratas Sprague-Dawley , Núcleo Supraquiasmático/efectos de los fármacos , Núcleo Supraquiasmático/fisiología , Regulación hacia ArribaRESUMEN
BACKGROUND: To evaluate epidemiologic factors in relation to paediatric head injury in the city of Mar del Plata, Argentina. METHODS: Retrospective (12-month) and prospective (6-month) evaluations were carried out on a total of 2,492 children with head injury (age range 0-15 years), taking into account sex, age, cause of injury, time of injury, incidence of hospitalisation, and the occurrence of fractures on conventional X-ray and computarized tomography (CT) scans of the head. Data were compiled and analyzed through a register called "Traumatic Brain Injury Register". RESULTS: From the total 2,492 children entered in the registry, 62% were males and 38% females. Age distribution was as follows: 33.5% from 0-2 years, 43.8% from 3-9 years, and 22.7% from 10-15 years. Falls were the main cause of head injury in children under 3 years of age, whereas car accidents prevailed among older groups (chi2 = 216.00, p<0.0001). Injuries occurred most frequently (84.7% of the cases) between 12:00 hrs and 24:00 hrs. From the total sample, 1,015 children (19.9%) required hospitalisation. Skull fractures were identified on conventional X-rays in 14.9% of the cases, and there was a direct relationship between skull X-rays and CT scans with respect to skull fractures (chi2 = 13.13, p<0.0001). The overall incidence of paediatric head injuries was 566 cases per 100,000 population and mortality rate was 4.65 per 1,000 head injuries. CONCLUSIONS: Our figures revealed an overall incidence of paediatric head injuries, which is 2.97 higher than the international average, suggesting that accident prevention measures should be further implemented.
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Traumatismos Craneocerebrales/epidemiología , Adolescente , Argentina/epidemiología , Niño , Preescolar , Traumatismos Craneocerebrales/mortalidad , Electroencefalografía , Femenino , Humanos , Incidencia , Lactante , Recién Nacido , Masculino , Estudios Prospectivos , Estudios Retrospectivos , Tomografía Computarizada por Rayos XRESUMEN
The increasing levels of resistance of enteropathogenic bacteria against antimicrobial agents present geographic variations. We have analysed the antimicrobial susceptibility of isolates obtained from 4,364 children under 5 years of age with acute diarrhea, in 7 cities of Argentina. Diarrheagenic E. coli exhibited 74.5% of resistance against ampicillin, 64.2% against sulfametoxazole-trimethoprim, and Shigella spp., 62% and 75.6% respectively. Salmonella sp. showed 35%, 14%, 41.8%, 65.4%, 14.5%, and 13.6% of resistance against ampicillin, chloranfenicol, sulfametoxazole-trimetoprim, sulfadiazin, gentamycin, and fosfomycin respectively. These values are higher than the ones observed in developed countries. Aeromonas showed significantly lower resistance percentage. Important differences in our country were observed, consequently, local trials should be carried out in order to apply corrective measures.
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Aeromonas/efectos de los fármacos , Diarrea/microbiología , Farmacorresistencia Microbiana , Enterobacteriaceae/efectos de los fármacos , Infecciones por Bacterias Gramnegativas/microbiología , Enfermedad Aguda , Aeromonas/aislamiento & purificación , Argentina/epidemiología , Preescolar , Diarrea/epidemiología , Diarrea Infantil/epidemiología , Diarrea Infantil/microbiología , Disentería Bacilar/epidemiología , Disentería Bacilar/microbiología , Enterobacteriaceae/aislamiento & purificación , Escherichia coli/efectos de los fármacos , Escherichia coli/aislamiento & purificación , Infecciones por Escherichia coli/epidemiología , Infecciones por Escherichia coli/microbiología , Femenino , Infecciones por Bacterias Gramnegativas/epidemiología , Humanos , Lactante , Masculino , Pruebas de Sensibilidad Microbiana , Salmonella/efectos de los fármacos , Salmonella/aislamiento & purificación , Infecciones por Salmonella/epidemiología , Infecciones por Salmonella/microbiología , Shigella/efectos de los fármacos , Shigella/aislamiento & purificación , Población UrbanaRESUMEN
Effects of actual and simulated weightlessness on choroidal guanylate cyclase activity were evaluated by assaying the production of cyclic guanosine monophosphate (cGMP), a second messenger involved in mechanisms regulating the secretion of cerebrospinal fluid (CSF) in choroid plexus. Cyclic cGMP was measured, using radio-immunoassay, in choroidal extracts of hindlimb-suspended rats (HLS rats), adapted to an anti-orthostatic restraint for 30 min., or for 3, 9 or 14 days and after a 17-day spaceflight (Life and Microgravity SpaceLab experiment; LMS). Basal cGMP levels were slightly but significantly decreased in the first 30 min. of the HLS experiment, whereas they were significantly increased in rats adapted to longer anti-orthostatic restraints. LMS flight rats demonstrated a similar increase in the choroidal cGMP baseline. After natriuretic peptide stimulation, i.e. using ANP (atrial natriuretic peptide) or BNP (brain natriuretic peptide), choroidal cGMP contents were typically increased (by 1.5-2 times; p<0.05) in control rats (LMS and HLS experiments), but not significantly elevated in suspended rats, except for those adapted to HLS for 14 days. In these animals the ANP-dependent cGMP production was significantly increased (by about 3 times; p<0.005). The ANP- or BNP-dependent responses were similarly abolished in LMS flight rats, which were dissected 4-6 hours after return to Earth's gravity. The role of corticosteroids was also investigated during the LMS experiment. Results on choroidal functions revealed a lack of significant change of cGMP levels between adrenalectomized and sham-operated rats. For the first time, it is reported that both basal and ANP- stimulated cGMP levels are dramatically changed over the first 14 days of suspension, i.e. with experiments known to simulate some effects of weightlessness. Basal choroidal cGMP levels are also increased after 17 days in space, suggesting that space adaptation also impacts choroidal guanylate cyclase activities. However, the absence of ANP-dependent cGMP increase, observed in LMS flight animals, suggests that HLS could not simulate all the spaceflight effects. Thus, these preliminary results seem to show that a natriuretic peptides-independent s stem is involved in choroidal adaptation to spaceflight.