RESUMEN
BACKGROUND: Venous leg ulcer(s) are common, recurring, open wounds on the lower leg, resulting from diseased or damaged leg veins impairing blood flow. Wound healing is the primary treatment aim for venous leg ulceration, alongside the management of pain, wound exudate and infection. Full (high) compression therapy delivering 40 mmHg of pressure at the ankle is the recommended first-line treatment for venous leg ulcers. There are several different forms of compression therapy available including wraps, two-layer hosiery, and two-layer or four-layer bandages. There is good evidence for the clinical and cost-effectiveness of four-layer bandage and two-layer hosiery but more limited evidence for other treatments (two-layer bandage and compression wraps). Robust evidence is required to compare clinical and cost-effectiveness of these and to investigate which is the best compression treatment for reducing time to healing of venous leg ulcers whilst offering value for money. VenUS 6 will therefore investigate the clinical and cost-effectiveness of evidence-based compression, two-layer bandage and compression wraps for time to healing of venous leg ulcers. METHODS: VenUS 6 is a pragmatic, multi-centre, three-arm, parallel-group, randomised controlled trial. Adult patients with a venous leg ulcer will be randomised to receive (1) compression wraps, (2) two-layer bandage or (3) evidence-based compression (two-layer hosiery or four-layer bandage). Participants will be followed up for between 4 and 12 months. The primary outcome will be time to healing (full epithelial cover in the absence of a scab) in days since randomisation. Secondary outcomes will include key clinical events (e.g. healing of the reference leg, ulcer recurrence, ulcer/skin deterioration, amputation, admission/discharge, surgery to close/remove incompetent superficial veins, infection or death), treatment changes, adherence and ease of use, ulcer related pain, health-related quality of life and resource use. DISCUSSION: VenUS 6 will provide robust evidence on the clinical and cost-effectiveness of the different forms of compression therapies for venous leg ulceration. VenUS 6 opened to recruitment in January 2021 and is currently recruiting across 30 participating centres. TRIAL REGISTRATION: ISRCTN67321719 . Prospectively registered on 14 September 2020.
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Úlcera Varicosa , Adulto , Humanos , Vendajes de Compresión , Análisis Costo-Beneficio , Estudios Multicéntricos como Asunto , Dolor , Calidad de Vida , Ensayos Clínicos Controlados Aleatorios como Asunto , Úlcera , Úlcera Varicosa/diagnóstico , Úlcera Varicosa/terapiaRESUMEN
INTRODUCTION: Hearing rehabilitation options for single sided deafness (SSD) include contralateral routing of sound (CROS) aids and bone conduction devices (BCDs). This study aimed to review the management of children with SSD at our tertiary paediatric otolaryngology unit over the last 15 years. MATERIAL AND METHODS: A retrospective cohort study was performed. Primary hearing outcomes were measured using the Children's Home Inventory for Listening Difficulties (CHILD) questionnaire score and secondary hearing outcomes were measured using hearing thresholds for speech in noise. Outcomes were measured pre and post bone conduction device (BCD) trial. RESULTS: 49 patients with SSD were identified. 20 children had trial of a BCD. 16 patients had pre- and post- BCD trial CHILD scores available for analysis. There was a statistically significant improvement in CHILD scores and speech in noise testing at +5 dB and +0 dB following amplification with a BCD. The mean use of BCD was 1.3 h per day. DISCUSSION: We have described the management of children with SSD in our unit. This study demonstrated a statistically significant benefit of BCD use on hearing outcomes. However, device compliance is low suggesting hearing advice choice in the population is complex and further research is warranted.
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Sordera , Audífonos , Pérdida Auditiva Unilateral , Otolaringología , Localización de Sonidos , Percepción del Habla , Humanos , Pérdida Auditiva Unilateral/rehabilitación , Estudios Retrospectivos , Audición , Sordera/rehabilitación , Conducción Ósea , Resultado del TratamientoRESUMEN
We review the history of ultraviolet and extreme ultraviolet spectroscopy with a specific focus on such activities at the Naval Research Laboratory and on studies of the extended solar corona and solar-wind source regions. We describe the problem of forecasting solar energetic particle events and discuss an observational technique designed to solve this problem by detecting supra-thermal seed particles as extended wings on spectral lines. Such seed particles are believed to be a necessary prerequisite for particle acceleration by heliospheric shock waves driven by a coronal mass ejection.
RESUMEN
Cell migration is essential for proper development of numerous structures derived from embryonic neural crest cells (NCCs). Although recent work has shown that receptor recycling plays an important role in NCC motility on laminin, the molecular mechanisms regulating NCC motility on fibronectin remain unclear. One mechanism by which cells regulate motility is by modulating the affinity of integrin receptors. Here, we provide evidence that cranial and trunk NCCs rely on functional regulation of integrins to migrate efficiently on fibronectin (FN) in vitro. For NCCs cultured on fibronectin, velocity decreases after Mn2+ application (a treatment that activates all surface integrins) while velocity on laminin (LM) is not affected. The distribution of activated integrin beta 1 receptors on the surface of NCCs is also substratum-dependent. Integrin activation affects cranial and trunk NCCs differently when cultured on different concentrations of FN substrata; only cranial NCCs slow in a FN concentration-dependent manner. Furthermore, Mn2+ treatment alters the distribution and number of activated integrin beta 1 receptors on the surface of cranial and trunk NCCs in different ways. We provide a hypothesis whereby a combination of activated surface integrin levels and the degree to which those receptors are clustered determines NCC motility on fibronectin.
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Movimiento Celular/fisiología , Fibronectinas/metabolismo , Integrinas/metabolismo , Cresta Neural/metabolismo , Agregación de Receptores/fisiología , Células Madre/metabolismo , Animales , Diferenciación Celular/efectos de los fármacos , Diferenciación Celular/fisiología , Movimiento Celular/efectos de los fármacos , Embrión de Pollo , Nervios Craneales/citología , Nervios Craneales/embriología , Nervios Craneales/metabolismo , Relación Dosis-Respuesta a Droga , Fibronectinas/farmacología , Integrina beta1/efectos de los fármacos , Integrina beta1/metabolismo , Integrinas/efectos de los fármacos , Manganeso/farmacología , Cresta Neural/citología , Cresta Neural/efectos de los fármacos , Neuronas/citología , Neuronas/efectos de los fármacos , Neuronas/metabolismo , Agregación de Receptores/efectos de los fármacos , Nervios Espinales/citología , Nervios Espinales/embriología , Nervios Espinales/metabolismo , Células Madre/citología , Células Madre/efectos de los fármacosRESUMEN
The neural crest is a transient cell population that travels long distances through the embryo to form a wide range of derivatives. The extensive migration of the neural crest is highly unusual and incompletely understood. We examined the ability of neural crest cells (NCCs) to migrate under different conditions in vitro. Unlike most motile cell types, avian NCCs migrate efficiently on a wide range of fibronectin concentrations. Strikingly, the migration of NCCs on laminin depends on the axial level from which the crest is derived. On high concentrations of laminin, cranial NCCs migrate at approximately twice the rate of trunk NCCs and show greater persistence, a higher percentage of migratory cells, and a less organized cytoskeleton. The difference in migration between cranial and trunk neural crest is not due to transcriptional differences in integrin mRNA, but rather to differences in posttranslational regulation. Overexpression of a single integrin is sufficient to significantly slow the migration velocity of cranial neural crest cultured on high laminin densities. These results demonstrate that neural crest cells accommodate a wide range of ECM concentrations in vitro and suggest that differences in integrin regulation along the anterior-posterior axis may contribute to differences in neural crest migration and cell fate.
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Regulación del Desarrollo de la Expresión Génica , Integrinas/genética , Cresta Neural/fisiología , Animales , Movimiento Celular , Células Cultivadas , Embrión de Pollo , Embrión no Mamífero , Fibronectinas/metabolismo , Integrinas/metabolismo , Cinética , Laminina/metabolismo , Cresta Neural/citología , Procesamiento Proteico-PostraduccionalRESUMEN
The objective of this study was to determine the effectiveness of testosterone in suppressing estrus in the bitch, and of cabergoline in shortening the length of the subsequent anestrous period. In Experiment 1, 12 diestrual Beagle bitches were randomly divided into two groups when plasma progesterone (P(4)) concentration was <1 ng/ml (Day 0). Starting on Day 0, bitches in Group 1 (n=6) were treated with testosterone cypionate every 14 days for a total of 239 days, and bitches in Group 2 served as untreated controls. On Day 274, bitches in both groups were treated with cabergoline for 40 days and blood samples were obtained on Days 274, 276 and 279 for determination of plasma prolactin (PRL) concentrations using RIA. All bitches were observed for proestrual bleeding during treatment with cabergoline. In Experiment 2, 12 Greyhound bitches previously treated with testosterone within the last 6 months were randomly divided into two groups. At the initiation of this experiment, P(4) concentration was determined to verify that all bitches had a concentration of <1 ng/ml (Day 0). Starting on Day 0, bitches in Group 1 (n=6) were treated with cabergoline for 36 days, and bitches in Group 2 (n=6) served as untreated controls. Blood samples were obtained on Days 0, 2 and 5 to determine PRL concentrations. All bitches were observed for proestrual bleeding during treatment with cabergoline. In Experiment 1, one bitch (Group 1) exhibited estrus after treatment with testosterone (1mg/kg body weight) for 43 days, and one bitch (Group 1) exhibited estrus after treatment with testosterone (2mg/kg body weight) for 113 days. None of the other four bitches in Group 1 exhibited estrus during the period of testosterone treatment (239 days). All bitches in Group 2 (control) exhibited estrus during the 239 days of the study. In addition, five of the six testosterone-treated bitches showed signs of proestrual bleeding within an average of 12.6 days (range of 5-25 days) after treatment with cabergoline; and, four of the six nontestosterone bitches showed signs of proestrual bleeding within an average of 28 days (range of 6-46 days). Prolactin concentrations in bitches in both Groups 1 and 2 significantly decreased after treatment with cabergoline. In Experiment 2, one of the six bitches showed signs of proestrual bleeding within 15 days after treatment with cabergoline. From the results of this study, it was concluded that exogenous testosterone was moderately effective (66%) in suppressing estrus in Beagle bitches, and cabergoline was effective in shortening the length of the anestrous period of Beagle bitches whose estrous cycle was previously suppressed with exogenous testosterone, but less effective in shortening the length of the anestrous period in Greyhound bitches previously treated with testosterone to suppress estrus.
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Anestro/fisiología , Perros/fisiología , Ergolinas/farmacología , Estro/fisiología , Antagonistas de Hormonas/farmacología , Testosterona/fisiología , Anestro/efectos de los fármacos , Anestro/genética , Animales , Cabergolina , Perros/sangre , Estro/efectos de los fármacos , Estro/metabolismo , Femenino , Progesterona/sangre , Prolactina/sangre , Distribución Aleatoria , Testosterona/metabolismoRESUMEN
Hypoxia is a common phenomenon peri-operatively. Although mild hypoxaemia of short duration is likely to have little effect more severe and prolonged hypoxaemia can seriously affect surgical outcome. Rational use of oxygen therapy may limit these adverse effects.
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Anestesia General/efectos adversos , Hipoxia/mortalidad , Hipoxia/prevención & control , Procedimientos Quirúrgicos Operativos/efectos adversos , Anestesia General/métodos , Animales , Análisis de los Gases de la Sangre , Estudios de Seguimiento , Humanos , Hipoxia/etiología , Hipoxia Encefálica/etiología , Hipoxia Encefálica/mortalidad , Hipoxia Encefálica/prevención & control , Oximetría , Complicaciones Posoperatorias/mortalidad , Complicaciones Posoperatorias/prevención & control , Periodo Posoperatorio , Intercambio Gaseoso Pulmonar , Medición de Riesgo , Índice de Severidad de la Enfermedad , Procedimientos Quirúrgicos Operativos/métodos , Tasa de SupervivenciaRESUMEN
BACKGROUND: Surveys of aspiration prophylaxis in paediatric anaesthesia do not exist. METHODS: A postal survey was sent out to all UK members of the Association of Paediatric Anaesthetists (APA) to assess current practice. We asked about minimum fasting times for liquids and solids/milk, their routine acid aspiration prophylaxis and perceived risk factors for emergency and elective surgery in children those less than 1 year old and those aged 1-14 years. We also asked if the APA member had more than 10 years experience in paediatric anaesthesia. RESULTS: One hundred and two (55.1%) APA members replied out of a total of 185 questionnaires sent. Eighty-eight (88/102) were considered valid. Fasting in emergencies is approximately 4 h for solids/milk and 2 h for clear liquids. Fasting for elective surgery is between 5 and 6 h for solids/milk and 2 h for clear liquids. Pharmacological methods to reduce the risk of aspiration are not used. Mechanical methods vary from 40-50% for cricoid pressure and 20-30% for nasogastric aspiration if a tube is present. The presence of a hiatus hernia is perceived by over 80% as a risk factor, previous aspiration by over 60%, difficult intubation, cerebral palsy and sepsis by 20-30%. CONCLUSION: Perceived risk factors vary with "experience": hiatus hernia, difficult intubation and cerebral palsy are less important whereas previous aspiration and renal failure appear to be more important for paediatric anaesthetists with less than 10 years in paediatric anaesthetic practice.
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Anestesia/efectos adversos , Neumonía por Aspiración/prevención & control , Adolescente , Niño , Preescolar , Recolección de Datos , Procedimientos Quirúrgicos Electivos , Urgencias Médicas , Ayuno , Reflujo Gastroesofágico/complicaciones , Hernia Hiatal/complicaciones , Humanos , Lactante , Neumonía por Aspiración/etiología , Factores de RiesgoRESUMEN
High throughput sequencing of a mouse keratinocyte library was used to identify an expressed sequence tag with homology to the epidermal growth factor (EGF) family of growth factors. We have named the protein encoded by this expressed sequence tag Epigen, for epithelial mitogen. Epigen encodes a protein of 152 amino acids that contains features characteristic of the EGF superfamily. Two hydrophobic regions, corresponding to a putative signal sequence and transmembrane domain, flank a core of amino acids encompassing six cysteine residues and two putative N-linked glycosylation sites. Epigen shows 24-37% identity to members of the EGF superfamily including EGF, transforming growth factor alpha, and Epiregulin. Northern blotting of several adult mouse tissues indicated that Epigen was present in testis, heart, and liver. Recombinant Epigen was synthesized in Escherichia coli and refolded, and its biological activity was compared with that of EGF and transforming growth factor alpha in several assays. In epithelial cells, Epigen stimulated the phosphorylation of c-erbB-1 and mitogen-activated protein kinases and also activated a reporter gene containing enhancer sequences present in the c-fos promoter. Epigen also stimulated the proliferation of HaCaT cells, and this proliferation was blocked by an antibody to the extracellular domain of the receptor tyrosine kinase c-erbB-1. Thus, Epigen is the newest member of the EGF superfamily and, with its ability to promote the growth of epithelial cells, may constitute a novel molecular target for wound-healing therapy.
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Factor de Crecimiento Epidérmico/genética , Secuencia de Aminoácidos , Animales , Secuencia de Bases , Clonación Molecular , Factor de Crecimiento Epidérmico/metabolismo , Epigen , Escherichia coli , Queratinocitos , Ratones , Datos de Secuencia Molecular , Alineación de Secuencia , Análisis de SecuenciaRESUMEN
The effects of delta-ACTX-Hv1a, purified from the venom of the funnel-web spider Hadronyche versuta, were studied on the isolated giant axon and dorsal unpaired median (DUM) neurones of the cockroach Periplaneta americana under current- and voltage-clamp conditions using the double oil-gap technique for single axons and the patch-clamp technique for neurones. In parallel, the effects of the toxin were investigated on the excitability of rat dorsal root ganglion (DRG) neurones. In both DRG and DUM neurones, delta-ACTX-Hv1a induced spontaneous repetitive firing accompanied by plateau potentials. However, in the case of DUM neurones, plateau action potentials were facilitated when the membrane was artificially hyperpolarized. In cockroach giant axons, delta-ACTX-Hv1a also produced plateau action potentials, but only when the membrane was pre-treated with 3-4 diaminopyridine. Under voltage-clamp conditions, delta-ACTX-Hv1a specifically affected voltage-gated Na+ channels in both axons and DUM neurones. Both the current/voltage and conductance/voltage curves of the delta-ACTX-Hv1a-modified inward current were shifted 10 mV to the left of control curves. In the presence of delta-ACTX-Hv1a, steady-state Na+ channel inactivation became incomplete, causing the appearance of a non-inactivating component at potentials more positive than -40 mV. The amplitude of this non-inactivating component was dependent on the holding potential. From this study, it is concluded that, in insect neurones, delta-ACTX-Hv1a mainly affects Na+ channel inactivation by a mechanism that differs slightly from that of scorpion alpha-toxins.
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Proteínas de Insectos/metabolismo , Neuronas/efectos de los fármacos , Neurotoxinas/toxicidad , Periplaneta/efectos de los fármacos , Canales de Sodio/metabolismo , Venenos de Araña/toxicidad , Potenciales de Acción/efectos de los fármacos , Animales , Axones/efectos de los fármacos , Axones/fisiología , Femenino , Ganglios Espinales/citología , Ganglios Espinales/efectos de los fármacos , Ganglios Espinales/fisiología , Cinética , Masculino , Neuronas/metabolismo , Técnicas de Placa-Clamp , Periplaneta/fisiología , RatasRESUMEN
Dermal papilla (DEPA) cells are resident at the base of hair follicles and are fundamental to hair growth and development. Cultured DEPA cells, in contrast to normal fibroblast cells, are capable of inducing de novo hair follicle growth in vivo. By differential screening of a DEPA cDNA library, we have demonstrated that dermal papilla cells are different from fibroblasts at the molecular level. We further studied these cells by random sequencing of 5130 clones from the DEPA cDNA library. Fifty percent had a BLASTX E value < or =1 x 10(-25). Twenty-one percent had similarity to proteins involved in cell structure/motility with 4 of the top 10 most abundant clones encoding extracellular matrix proteins. Clones encoding growth factor molecules were also abundant. The remaining 50.7% of clones had low similarity scores, demonstrating many novel molecules. For example, we identified a new CTGF family member, the rat homologue of Elm1.
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Etiquetas de Secuencia Expresada , Folículo Piloso/citología , Folículo Piloso/fisiología , Proteínas Oncogénicas , Secuencia de Aminoácidos , Animales , Secuencia de Bases , Proteínas CCN de Señalización Intercelular , Células Cultivadas , ADN Complementario , Fibroblastos , Regulación de la Expresión Génica , Biblioteca de Genes , Datos de Secuencia Molecular , Especificidad de Órganos , Proteínas Proto-Oncogénicas , Ratas , Ratas Endogámicas , Proteínas Represoras/genéticaRESUMEN
Mouse spiders represent a potential cause of serious envenomation in humans. This study examined the activity of Missulena bradleyi venom in several in vitro preparations. Whilst female M. bradleyi venom at doses up to 0.05 microl ml(-1) failed to alter twitch or resting tension in all preparations used, male venom (0.02 and 0.05 microl ml(-1)) produced potent effects on transmitter release in both smooth and skeletal neuromuscular preparations. In the mouse phrenic nerve diaphragm preparation, male M. bradleyi venom (0.02 microl ml(-1)) caused rapid fasciculations and an increase in indirectly evoked twitches. Male venom (0.02 and 0.05 microl ml(-1)) also caused a large contracture and rapid decrease in indirectly evoked twitches in the chick biventer cervicis muscle, however had no effect on responses to exogenous ACh (1 mM) or potassium chloride (40 mM). In the chick preparation, contractile responses to male M. bradleyi venom (0.05 microl ml(-1)) were attenuated by (+)-tubocurarine (100 microM) and by tetrodotoxin (TTX, 1 microM). Both actions of male M. bradleyi venom were blocked by Atrax robustus antivenom (2 units ml(-1)). In the unstimulated rat vas deferens, male venom (0.05 microl ml(-1)) caused contractions which were inhibited by a combination of prazosin (0.3 microM) and P(2X)-receptor desensitization (with alpha,beta-methylene ATP 10 microM). In the rat stimulated vas deferens, male venom (0.05 microl ml(-1)) augmented indirectly evoked twitches. Male venom (0.1 microl ml(-1)) causes a slowing of inactivation of TTX-sensitive sodium currents in acutely dissociated rat dorsal root ganglion neurons. These results suggest that venom from male M. bradleyi contains a potent neurotoxin which facilitates neurotransmitter release by modifying TTX-sensitive sodium channel gating. This action is similar to that of the delta-atracotoxins from Australian funnel-web spiders.
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Adenosina Trifosfato/análogos & derivados , Activación del Canal Iónico/efectos de los fármacos , Neurotoxinas/farmacología , Canales de Sodio/efectos de los fármacos , Venenos de Araña/farmacología , Acetilcolina/farmacología , Adenosina Trifosfato/farmacología , Antagonistas Adrenérgicos alfa/farmacología , Animales , Pollos , Diafragma/efectos de los fármacos , Diafragma/inervación , Relación Dosis-Respuesta a Droga , Femenino , Ganglios Espinales/efectos de los fármacos , Ganglios Espinales/fisiología , Masculino , Potenciales de la Membrana/efectos de los fármacos , Ratones , Ratones Endogámicos BALB C , Contracción Muscular/efectos de los fármacos , Músculos/efectos de los fármacos , Músculos/fisiología , Antagonistas Nicotínicos/farmacología , Nervio Frénico/efectos de los fármacos , Nervio Frénico/fisiología , Cloruro de Potasio/farmacología , Prazosina/farmacología , Ratas , Ratas Sprague-Dawley , Tetrodotoxina/farmacología , Tubocurarina/farmacología , Conducto Deferente/efectos de los fármacos , Conducto Deferente/fisiología , Vasodilatadores/farmacologíaRESUMEN
The venom of the male Australian duck-billed platypus contains a family of four polypeptides of appox. 5 kDa, which are referred to as defensin-like peptides (DLPs). They are unique in that their amino acid sequences have no significant similarities to those of any known peptides; however, the tertiary structure of one of them, DLP-1, has recently been shown to be similar to beta-defensin-12 and to the sodium neurotoxin peptide ShI (Stichodactyla helianthus neurotoxin I). Although DLPs are the major peptides in the platypus venom, little is known about their biological roles. In this study, we determined the three-dimensional structure of DLP-2 by NMR spectroscopy, with the aim of gaining insights into the natural function of the DLPs in platypus venom. The DLP-2 structure was found to incorporate a short helix that spans residues 9-12, and an antiparallel beta-sheet defined by residues 15-18 and 37-40. The overall fold and cysteine-pairing pattern of DLP-2 were found to be similar to those of DLP-1, and hence beta-defensin-12; however, the sequence similarities between the three molecules are relatively small. The distinct structural fold of the DLP-1, DLP-2, and beta-defensin-12 is based upon several key residues that include six cysteines. DLP-3 and DLP-4 are also likely to be folded similarly since they have high sequence similarity with DLP-2. The DLPs, and beta-defensin-12 may thus be grouped together into a class of polypeptide molecules which have a common or very similar global fold. The fact that the DLPs did not display antimicrobial, myotoxic, or cell-growth-promoting activities implies that the nature of the side chains in this group of peptides is likely to play an important role in defining the biological function(s).
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Proteínas/química , Ponzoñas/química , Secuencia de Aminoácidos , Animales , Defensinas , Espectroscopía de Resonancia Magnética , Masculino , Modelos Moleculares , Datos de Secuencia Molecular , Ornitorrinco , Conformación Proteica , Pliegue de Proteína , Homología de Secuencia de AminoácidoRESUMEN
delta-Atracotoxins (delta-ACTXs) are peptide toxins isolated from the venom of Australian funnel-web spiders that slow sodium current inactivation in a similar manner to scorpion alpha-toxins. We have isolated and determined the amino acid sequence of a novel delta-ACTX, designated delta-ACTX-Hv1b, from the venom of the funnel-web spider Hadronyche versuta. This 42 residue toxin shows 67% sequence identity with delta-ACTX-Hv1a previously isolated from the same spider. Under whole-cell voltage-clamp conditions, the toxin had no effect on tetrodotoxin (TTX)-resistant sodium currents in rat dorsal root ganglion neurones but exerted a concentration-dependent reduction in peak TTX-sensitive sodium current amplitude accompanied by a slowing of sodium current inactivation similar to other delta-ACTXs. However, delta-ACTX-Hv1b is approximately 15-30-fold less potent than other delta-ACTXs and is remarkable for its complete lack of insecticidal activity. Thus, the sequence differences between delta-ACTX-Hv1a and -Hv1b provide key insights into the residues that are critical for targeting of these toxins to vertebrate and invertebrate sodium channels.
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Bloqueadores de los Canales de Sodio , Venenos de Araña/química , Venenos de Araña/aislamiento & purificación , Venenos de Araña/farmacología , Arañas/química , Toxinas Biológicas/aislamiento & purificación , Toxinas Biológicas/farmacología , Secuencia de Aminoácidos , Animales , Cromatografía Líquida de Alta Presión , Relación Dosis-Respuesta a Droga , Conductividad Eléctrica , Femenino , Ganglios Espinales/citología , Ganglios Espinales/efectos de los fármacos , Gryllidae/efectos de los fármacos , Insecticidas/química , Activación del Canal Iónico/efectos de los fármacos , Masculino , Datos de Secuencia Molecular , Neuronas/efectos de los fármacos , Neuronas/metabolismo , Ratas , Alineación de Secuencia , Análisis de Secuencia de Proteína , Sodio/metabolismo , Canales de Sodio/metabolismo , Especificidad de la Especie , Especificidad por Sustrato , Tetrodotoxina/farmacología , Toxinas Biológicas/químicaRESUMEN
Pacific ciguatoxin-1 (P-CTX-1), is a highly lipophilic cyclic polyether molecule originating from the marine dinoflagellate Gambierdiscus toxicus. Its effects were investigated on sodium channel subtypes present in acutely dissociated rat dorsal root ganglion neurons, using whole-cell patch clamp techniques. Concentrations of P-CTX-1 ranging from 0.2 to 20 nM had no effect on the kinetics of tetrodotoxin-sensitive (TTX-S) or tetrodotoxin-resistant (TTX-R) sodium channel activation and inactivation, however, a concentration-dependent reduction in peak current amplitude occurred in both channel types. The main actions of 5 nM P-CTX-1 on TTX-S sodium channels were a 13-mV hyperpolarizing shift in the voltage dependence of sodium channel activation and a 22-mV hyperpolarizing shift in steady-state inactivation (hinfinity). In addition, P-CTX-1 caused a rapid rise in the membrane leakage current in cells expressing TTX-S sodium channels. This effect was blocked by 200 nM TTX, indicating an action mediated through TTX-S sodium channels. In contrast, the main action of P-CTX-1 (5 nM) on TTX-R sodium channels was a significant increase in the rate of recovery from sodium channel inactivation. These results indicate that P-CTX-1 acts to modify voltage-gated sodium channels present in peripheral sensory neurons consistent with its action to increase nerve excitability. This provides an explanation for the sensory neurological disturbances associated with ciguatera fish poisoning.
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Ciguatoxinas/farmacología , Neuronas Aferentes/efectos de los fármacos , Canales de Sodio/efectos de los fármacos , Animales , Células Cultivadas , Electrofisiología , Femenino , Masculino , Neuronas Aferentes/metabolismo , Ratas , Ratas Wistar , Agonistas de los Canales de Sodio , Bloqueadores de los Canales de Sodio , Tetrodotoxina/farmacologíaRESUMEN
Temporal colinearity describes a correspondence between the spatial ordering of Hox genes within their clusters (in the direction 3' to 5') and the time of their first expression (earlier to later) during embryonic development (Izpisúa-Belmonte et al. [1991] EMBO J. 10:2279-2289). It suggests that activation of each Hox gene might be controlled in some way by its position within the cluster. So far, in situ hybridization experiments on vertebrate embryos have provided clear evidence of temporal colinearity only for "posterior" Hox genes (5' located, AbdB related). We now describe a search in the chick embryo for evidence of temporal colinearity in the expression of some anterior Hox genes (Hoxb-1, b-3, b-4, b-6, and a-9). Clear evidence for temporal colinearity was seen in neural tube tissue adjacent to the first few somites. Here, there were delays in the expression of Hoxb-3 following b-1, Hoxb-4 following b-3, and Hoxb-6 following b-4. Temporal colinearity was also detected in anterior primitive streak tissue. Hox gene expression reached both the neural tube and the anterior streak following forward spreading from posteriormost parts of the primitive streak. Overall, therefore, temporal colinearity was seen as sequential waves of Hox genes expression that proceeded forward (3' genes before 5' genes) along the developing chick embryo. Within posterior primitive streak tissue, there was only limited evidence for temporal colinearity. We discuss these results in terms of possible models for the establishment of Hox gene expression patterns.