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1.
Sensors (Basel) ; 21(21)2021 Oct 20.
Artigo em Inglês | MEDLINE | ID: mdl-34770257

RESUMO

Curbs are used as physical markers to delimit roads and to redirect traffic into multiple directions (e.g., islands and roundabouts). Detection of road curbs is a fundamental task for autonomous vehicle navigation in urban environments. Since almost two decades, solutions that use various types of sensors, including vision, Light Detection and Ranging (LiDAR) sensors, among others, have emerged to address the curb detection problem. This survey elaborates on the advances of road curb detection problems, a research field that has grown over the last two decades and continues to be the ground for new theoretical and applied developments. We identify the tasks involved in the road curb detection methods and their applications on autonomous vehicle navigation and advanced driver assistance system (ADAS). Finally, we present an analysis on the similarities and differences of the wide variety of contributions.


Assuntos
Acidentes de Trânsito
2.
Pharm Dev Technol ; 20(5): 562-9, 2015.
Artigo em Inglês | MEDLINE | ID: mdl-25047057

RESUMO

Infant hemangioma (IH) is the most common tumor in infants, which affects 5-10% of white children. It is a tumor of vascular origin that appears in the first months of life. The indication for the treatment of the IH is not approved in the datasheet of the product, however it has been used in the infant hemangioma by topical administration as an alternative to oral propranolol, avoiding the main problems of the oral route (bradycardia and hypotension). The objective of this work is to study the physical and chemical (HPLC stability indicating method) stability of a 0.5% timolol gel for topical application during 60 days (considering the stability limit as 90% of initial concentration of timolol maleate). The gel was prepared with a polyacrylic acid derivative and the physical stability of the system was studied by visual control, rheological and mechanical characterization. The studied formulation guarantees the correct dose administering and stability after 60 days stored at 25 ± 2 °C and light protected (tube of aluminum). We have developed an easy topical gel for the treatment of infant hemangioma with physical and chemical stability higher than those provided by the majority of hospitals.


Assuntos
Antagonistas Adrenérgicos beta/química , Anti-Hipertensivos/química , Timolol/química , Administração Tópica , Antagonistas Adrenérgicos beta/administração & dosagem , Anti-Hipertensivos/administração & dosagem , Cromatografia Líquida de Alta Pressão , Estabilidade de Medicamentos , Armazenamento de Medicamentos , Géis/administração & dosagem , Géis/química , Hemangioma/tratamento farmacológico , Humanos , Lactente , Reologia , Timolol/administração & dosagem
3.
J Eur Acad Dermatol Venereol ; 28(8): 1097-1102, 2014 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-25243267

RESUMO

BACKGROUND: Anti-MDA5 (Melanoma differentiation-associated gene 5) positive dermatomyositis is a new variant of clinically amyopathic dermatomyositis that presents with characteristic mucocutaneous findings and is associated with a higher risk of developing rapidly progressive interstitial lung disease. Because its presentation differs from that of classical dermatomyositis, this entity can be a diagnostic challenge for the clinician. METHODS & RESULTS: We present the case of a 55-year-old male with a 7-month history of chill sensation, constitutional symptoms and polyarthralgia. Within 3 months, the patient developed progressive heart failure with dyspnoea and orthopnoea, together with characteristic cutaneous lesions. Skin biopsies demonstrated thrombosis of small and medium-sized arteries in the reticular dermis, together with an evolved lobular panniculitis and prominent mucin deposits. CONCLUSIONS: Clinicians should be aware of the characteristic clinical and histopathologic presentation of this variant of dermatomyositis to establish an early diagnosis. Further evidence is needed to clarify the risk of cardiac involvement in this subset of patients.


Assuntos
Cardiomiopatias/complicações , RNA Helicases DEAD-box/imunologia , Dermatomiosite/diagnóstico , Dermatomiosite/complicações , Dermatomiosite/imunologia , Humanos , Helicase IFIH1 Induzida por Interferon , Masculino , Pessoa de Meia-Idade
4.
Epidemiol Infect ; 141(6): 1328-36, 2013 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-22884022

RESUMO

Few studies have formally examined the relationship between meteorological factors and the incidence of child pneumonia in the tropics, despite the fact that most child pneumonia deaths occur there. We examined the association between four meteorological exposures (rainy days, sunshine, relative humidity, temperature) and the incidence of clinical pneumonia in young children in the Philippines using three time-series methods: correlation of seasonal patterns, distributed lag regression, and case-crossover. Lack of sunshine was most strongly associated with pneumonia in both lagged regression [overall relative risk over the following 60 days for a 1-h increase in sunshine per day was 0·67 (95% confidence interval (CI) 0·51-0·87)] and case-crossover analysis [odds ratio for a 1-h increase in mean daily sunshine 8-14 days earlier was 0·95 (95% CI 0·91-1·00)]. This association is well known in temperate settings but has not been noted previously in the tropics. Further research to assess causality is needed.


Assuntos
Umidade , Pneumonia Bacteriana/etiologia , Chuva , Luz Solar , Clima Tropical , Pré-Escolar , Humanos , Razão de Chances , Filipinas/epidemiologia , Pneumonia Bacteriana/epidemiologia , Distribuição de Poisson , Análise de Regressão , Fatores de Risco , Estações do Ano
5.
iScience ; 26(10): 107714, 2023 Oct 20.
Artigo em Inglês | MEDLINE | ID: mdl-37701573

RESUMO

Lamin A/C is a well-established key contributor to nuclear stiffness and its role in nucleus mechanical properties has been extensively studied. However, its impact on whole-cell mechanics has been poorly addressed, particularly concerning measurable physical parameters. In this study, we combined microfluidic experiments with theoretical analyses to quantitatively estimate the whole-cell mechanical properties. This allowed us to characterize the mechanical changes induced in cells by lamin A/C alterations and prelamin A accumulation resulting from atazanavir treatment or lipodystrophy-associated LMNA R482W pathogenic variant. Our results reveal a distinctive increase in long-time viscosity as a signature of cells affected by lamin A/C alterations. Furthermore, they show that the whole-cell response to mechanical stress is driven not only by the nucleus but also by the nucleo-cytoskeleton links and the microtubule network. The enhanced cell viscosity assessed with our microfluidic assay could serve as a valuable diagnosis marker for lamin-related diseases.

6.
Bol Med Hosp Infant Mex ; 78(3): 234-238Myositis ossificans, 2021 05 03.
Artigo em Inglês | MEDLINE | ID: mdl-33938904

RESUMO

BACKGROUND: Progressive fibrodysplasia ossificans is a rare genetic disease with heterozygous mutations (autosomal dominant inheritance) in the ACVR1 gene, which causes progressive heterotopic ossification in muscles, tendons, and ligaments, usually secondary to trauma. The ossification foci generate pain, joint ankyloses, and restricted movement. Congenital shortening and medial deviation first metatarsal of the foot is a distinctive feature. This report aimed to present an educational value case of a patient with clinical, imaging, and molecular diagnosis of progressive fibrodysplasia ossificans, recognized as a rare condition that severely affects the quality of life. CASE REPORT: We present the case of a 6-year-old female patient with lumps in the right scapular and dorsal region, progressive joint rigidity, and short first metatarsal medially deviated since birth. By imaging studies, we established the diagnosis of progressive fibrodysplasia ossificans. Sanger sequencing of ACVR1 reported c.617G>A (p.Arg206His). CONCLUSIONS: Confirmation of the diagnosis allowed genetic counseling, including a comprehensive explanation of the disease's natural history and measures to prevent its rapid progression.


Assuntos
Miosite Ossificante , Qualidade de Vida , Criança , Feminino , Humanos , Mutação , Miosite Ossificante/diagnóstico , Miosite Ossificante/genética
7.
Polymers (Basel) ; 13(4)2021 Feb 18.
Artigo em Inglês | MEDLINE | ID: mdl-33670467

RESUMO

In this article, we show an alternative low-cost fabrication method to obtain poly(dimethyl siloxane) (PDMS) microfluidic devices. The proposed method allows the inscription of micron resolution channels on polystyrene (PS) surfaces, used as a mold for the wanted microchip's production, by applying a high absorption coating film on the PS surface to ablate it with a focused low-power visible laser. The method allows for obtaining micro-resolution channels at powers between 2 and 10 mW and can realize any two-dimensional polymeric devices. The effect of the main processing parameters on the channel's geometry is presented.

8.
PeerJ ; 8: e10417, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-33240684

RESUMO

Worldwide urban expansion and deforestation have caused a rapid decline of non-human primates in recent decades. Yet, little is known to what extent these animals can tolerate anthropogenic noise arising from roadway traffic and human presence in their habitat. We studied six family groups of titis residing at increasing distances from a busy highway, in a park promoting ecotourism near Santa Cruz de la Sierra, Bolivia. We mapped group movements, sampled the titis' behavior, collected fecal samples from each study group and conducted experiments in which we used a mannequin simulating a human intrusion in their home range. We hypothesized that groups of titi monkeys exposed to higher levels of anthropogenic noise and human presence would react weakly to the mannequin and show higher concentrations of fecal cortisol compared with groups in least perturbed areas. Sound pressure measurements and systematic monitoring of soundscape inside the titis' home ranges confirmed the presence of a noise gradient, best characterized by the root-mean-square (RMS) and median amplitude (M) acoustic indices; importantly, both anthropogenic noise and human presence co-varied. Study groups resided in small, overlapping home ranges and they spent most of their time resting and preferentially used the lower forest stratum for traveling and the higher levels for foraging. Focal sampling analysis revealed that the time spent moving by adult pairs was inversely correlated with noise, the behavioral change occurring within a gradient of minimum sound pressures ranging from 44 dB(A) to 52 dB(A). Validated enzyme-immunoassays of fecal samples however detected surprisingly low cortisol concentrations, unrelated to the changes observed in the RMS and M indices. Finally, titis' response to the mannequin varied according to our expectation, with alarm calling being greater in distant groups relative to highway. Our study thus indicates reduced alarm calling through habituation to human presence and suggests a titis' resilience to anthropogenic noise with little evidence of physiological stress.

9.
Neuron ; 5(5): 663-74, 1990 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-2171590

RESUMO

Na+ channels are present at high density in squid giant axon but are absent from its somata in the giant fiber lobe (GFL) of the stellate ganglion. GFL cells dispersed in vitro maintain growing axons and develop a Na+ channel distribution similar to that in vivo. Tunicamycin, a glycosylation inhibitor, selectively disrupts the spatially appropriate, high level expression of Na+ channels in axonal membrane but has no effect on expression in cell bodies, which show low level, inappropriate expression in vitro. This effect does not appear to involve alteration in Na+ channel turnover or axon viability. K+ channel distribution is unaffected. Thus, glycosylation appears to be involved in controlling Na+ channel localization in squid neurons.


Assuntos
Decapodiformes/metabolismo , Gânglios Simpáticos/metabolismo , Neurônios/metabolismo , Canais de Sódio/metabolismo , Animais , Axônios/fisiologia , Células Cultivadas , Gânglios Simpáticos/citologia , Neurônios/ultraestrutura , Canais de Sódio/efeitos dos fármacos , Fatores de Tempo , Distribuição Tecidual , Tunicamicina/farmacologia
10.
Animals (Basel) ; 8(10)2018 10 13.
Artigo em Inglês | MEDLINE | ID: mdl-30322178

RESUMO

Long-range vocal communication in socially monogamous titi monkeys is mediated by the production of loud, advertising calls in the form of solos, duets, and choruses. We conducted a power spectral analysis of duets and choruses (simply "duets" hereafter) followed by linear discriminant analysis using three acoustic parameters-dominant frequency of the combined signal, duet sequence duration, and pant call rate-comparing the coordinated vocalizations recorded from 36 family groups at 18 sites in Bolivia, Peru and Ecuador. Our analysis identified four distinct duetting patterns: (1) a donacophilus pattern, sensu largo, characteristic of P. donacophilus, P. pallescens, P. olallae, and P. modestus; (2) a moloch pattern comprising P. discolor, P. toppini, P. aureipalatii, and P. urubambensis; (3) a torquatus pattern exemplified by the duet of Cheracebus lucifer; and (4) the distinctive duet of P. oenanthe, a putative member of the donacophilus group, which is characterized by a mix of broadband and narrowband syllables, many of which are unique to this species. We also document a sex-related difference in the bellow-pant phrase combination among the three taxa sampled from the moloch lineage. Our data reveal a presumptive taxonomic incoherence illustrated by the distinctive loud calls of both P. urubambensis and P. oenanthe within the donacophilus lineage, sensu largo. The results are discussed in light of recent reassessments of the callicebine phylogeny, based on a suite of genetic studies, and the potential contribution of environmental influences, including habitat acoustics and social learning. A better knowledge of callicebine loud calls may also impact the conservation of critically endangered populations, such as the vocally distinctive Peruvian endemic, the San Martin titi, P. oenanthe.

12.
Neuroscience ; 138(2): 411-9, 2006.
Artigo em Inglês | MEDLINE | ID: mdl-16426762

RESUMO

A-type K(+) currents (I(A)) in olfactory receptor neurons have been characterized electrophysiologically but the molecular identities of the underlying channel subunits have not been determined. Using RT-PCR, immunoblot and immunohistochemistry, we found that the two candidate channel families underlying I(A), shaker and shal, are expressed in olfactory epithelia of Swiss Webster mice. Specifically, Kv1.4, the only I(A) candidate from the shaker family, and Kv4.2 and Kv4.3 from the shal family were expressed, but Kv4.1 mRNA was not amplified from the olfactory epithelia. Immunoblot and immunohistochemical studies confirmed the existence of Kv1.4 and Kv4.2/3 subunits. Furthermore, quantitative RT-PCR showed that pituitary adenylate cyclase activating polypeptide (PACAP) reduced the expression of Kv1.4 and Kv4.2 but did not reduce the already low expression of Kv4.3. The PACAP-induced reduction of Kv4.1 and Kv4.2 expression was completely blocked by inhibiting the phospholipase C (PLC) pathway but was still significantly downregulated by PACAP when the cyclic AMP pathway was inhibited. In addition, downstream of the PLC pathway, calcium mediated the reduction of both Kv1.4 and Kv4.2 expression and I(A) current density. Phosphokinase C (PKC) activation did not affect Kv1.4 and Kv4.2 mRNA expression, even though PKC reduced I(A) current density. Together with our previous studies, our data suggest that A-type K(+) currents in olfactory receptor neurons are composed of multiple K(+) channel subunits, among which Kv1.4 and Kv4.2 are subject to transcriptional modulation by PACAP. We also found that PACAP predominately uses a PLC-calcium pathway to modulate Kv4.1 and Kv4.2 expression. Modulation of A-type K(+) current expression may contribute to the previously observed neuroprotective effects of PACAP on olfactory receptor neurons.


Assuntos
Canal de Potássio Kv1.4/genética , Células Neuroepiteliais/fisiologia , Bulbo Olfatório/fisiologia , Polipeptídeo Hipofisário Ativador de Adenilato Ciclase/fisiologia , Canais de Potássio Shal/genética , Animais , Primers do DNA , Regulação da Expressão Gênica , Hipocampo/fisiologia , Imuno-Histoquímica , Canal de Potássio Kv1.4/metabolismo , Camundongos , Bulbo Olfatório/citologia , Reação em Cadeia da Polimerase Via Transcriptase Reversa , Canais de Potássio Shal/metabolismo
13.
Int J Food Microbiol ; 107(2): 207-11, 2006 Mar 15.
Artigo em Inglês | MEDLINE | ID: mdl-16278029

RESUMO

Ninety-seven lactic acid bacteria (LAB) were isolated from slaughterhouse porcine blood in order to select autochthonous LAB strains for use as biopreservatives of this by-product. They were identified by 16S rDNA sequencing; and their inhibition capacity was determined against four bacterial species frequently found in contaminated blood, i.e. Staphylococcus aureus, Escherichia coli, Pseudomonas fluorescens and Bacillus spp. The taxonomic study showed an unexpected low diversity of LAB in blood, i.e. only 8 different species were found, from which just 4, i.e. Enterococcus raffinosus, Lactobacillus murinus, Lactobacillus reuteri and Lactococcus garvieae, amounted to more than 90% of all isolates. Inhibition tests in solid culture media proved that S. aureus and Bacillus spp. were inhibited by most LAB strains obtained from porcine blood. E. coli was the indicator less affected by the isolated LAB species. Several isolates efficiently inhibited the growth of all tested indicators.


Assuntos
Matadouros , Antibiose , Lactobacillus/fisiologia , Suínos/sangue , Suínos/microbiologia , Animais , Bacillus/crescimento & desenvolvimento , DNA Bacteriano/análise , Escherichia coli/crescimento & desenvolvimento , Lactobacillus/classificação , Lactobacillus/isolamento & purificação , Filogenia , Pseudomonas fluorescens/crescimento & desenvolvimento , Staphylococcus aureus/crescimento & desenvolvimento
14.
Cancer Res ; 41(1): 294-9, 1981 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-6160906

RESUMO

Natural killer cell activity, which represents the spontaneous cytotoxicity of lymphocytes toward tumor cells, has been measured in 173 tumor-bearing patients and 25 healthy volunteers; no significant difference was found in mean natural killer cell activity between the two groups. The parameters of interferon-induced activation of natural killer cells were studied in order to provide a suitable test for monitoring the effect of interferon in clinical trials. The three interferons tested (leukocyte, lymphoblastoid, and fibroblast) were equally active in inducing spontaneous cytotoxicity of lymphocytes from all healthy individuals and tumor-bearing patients studied. Incubation for one hr with 100 units of interferon was sufficient to increase spontaneous cytotoxicity activity, the maximum effect being obtained when lymphocytes were incubated with 1000 units of any of the interferons used. This effect was blocked with the appropriate antiinterferon sera. The target cells for interferon seem to be positive Fc gamma receptor lymphocytes.


Assuntos
Citotoxicidade Imunológica/efeitos dos fármacos , Imunidade Inata/efeitos dos fármacos , Interferons/farmacologia , Linfócitos/imunologia , Neoplasias/imunologia , Adulto , Feminino , Fibroblastos/fisiologia , Humanos , Células Matadoras Naturais/imunologia , Leucócitos/fisiologia , Linfócitos/fisiologia , Masculino , Pessoa de Meia-Idade , Receptores Fc/análise
16.
Carbohydr Polym ; 151: 692-699, 2016 Oct 20.
Artigo em Inglês | MEDLINE | ID: mdl-27474615

RESUMO

The use of a novel cross-linked thiolated chitosan (CTS) was investigated as the main component of aqueous dispersions (at 1% and 3% w/v) for topical drug delivery systems. The nonionic theophiline (Th) and the cationic diltiazem(.)HCl (Dt) (at 0.5% w/v concentration) were used as model drugs. All aqueous dispersions behaved as viscoelastic fluids. The CTS 1% dispersions showed predominance of viscous component and low viscosity. However, in the CTS 3% dispersions, both the elastic component and high viscosities prevailed. So, texture parameters improved from CTS 1% to 3% dispersions and CTS 3%-Dt showed greater cohesion and adhesion than CTS 3%-Th, but always below CTS alone. All dispersions showed a Fickian diffusion mechanism. Despite release profiles of both drugs almost fully overlapped at 1% CTS, diffusion coefficients confirmed Dt released faster than Th at 3% CTS. The rheological behavior and the chemical nature of the drugs explained these results.


Assuntos
Quitosana/química , Portadores de Fármacos/química , Liberação Controlada de Fármacos , Reologia , Água/química , Administração Tópica , Diltiazem/administração & dosagem , Diltiazem/química , Cinética , Viscosidade
17.
Bol. méd. Hosp. Infant. Méx ; 78(3): 234-238, May.-Jun. 2021. graf
Artigo em Inglês | LILACS-Express | LILACS | ID: biblio-1285488

RESUMO

Abstract Background: Progressive fibrodysplasia ossificans is a rare genetic disease with heterozygous mutations (autosomal dominant inheritance) in the ACVR1 gene, which causes progressive heterotopic ossification in muscles, tendons, and ligaments, usually secondary to trauma. The ossification foci generate pain, joint ankyloses, and restricted movement. Congenital shortening and medial deviation first metatarsal of the foot is a distinctive feature. This report aimed to present an educational value case of a patient with clinical, imaging, and molecular diagnosis of progressive fibrodysplasia ossificans, recognized as a rare condition that severely affects the quality of life. Case report: We present the case of a 6-year-old female patient with lumps in the right scapular and dorsal region, progressive joint rigidity, and short first metatarsal medially deviated since birth. By imaging studies, we established the diagnosis of progressive fibrodysplasia ossificans. Sanger sequencing of ACVR1 reported c.617G>A (p.Arg206His). Conclusions: Confirmation of the diagnosis allowed genetic counseling, including a comprehensive explanation of the disease’s natural history and measures to prevent its rapid progression.


Resumen Introducción: La fibrodisplasia osificante progresiva es una enfermedad genética poco frecuente, causada por variantes patogénicas en estado heterocigoto (herencia autosómica dominante) en el gen ACVR1, que provoca osificación heterotópica progresiva en músculos, tendones y ligamentos, comúnmente secundaria a traumatismos. Los focos de osificación generan dolor, anquilosis articular y restricción del movimiento. Es característico el acortamiento congénito y la desviación medial del primer metatarsiano del pie. El objetivo de este reporte es presentar un caso de alto valor educativo de una paciente con diagnóstico clínico, imagenológico y molecular de fibrodisplasia osificante progresiva, reconocida como una condición infrecuente y que afecta de manera grave la calidad de vida. Caso clínico: Paciente de sexo femenino con tumoraciones induradas en la región dorsal y escapular, detectadas a los 6 años de vida. Cursaba además con rigidez articular progresiva y primer metatarsiano del pie acortado y con desviación en sentido medial desde el nacimiento. Por estudios de imagen se estableció el diagnóstico de fibrodisplasia osificante progresiva. Por secuenciación Sanger se reportó c.617G>A (p.Arg206His) en ACVR1. Conclusiones: La confirmación del diagnóstico permitió ofrecer un asesoramiento genético integral, incluyendo una amplia explicación de la evolución natural del padecimiento y de las medidas preventivas para disminuir su rápida progresión.

18.
Neuroscience ; 322: 208-20, 2016 May 13.
Artigo em Inglês | MEDLINE | ID: mdl-26917271

RESUMO

Epigallo-catechin-3-gallate (EGCG), found in the leaves of Camellia sinensis (green tea), has antioxidant- and scavenger-functions and acts neuroprotectively. It has been publicized as anti-aging remedy but data on potential cellular mechanisms are scarce. Recent studies claimed that EGCG specifically promotes neural precursor cell proliferation in the dentate gyrus of C57Bl/6 mice, without changes at the level of immature and mature new neurons. We here analyzed the effects of EGCG on adult hippocampal neurogenesis in male Balb/C mice and saw a different pattern. Two weeks of treatment with EGCG (0, 0.625, 1.25, 2.5, 5 and 10mg/kg) showed a dose-response curve that peaked at 2.5mg/kg of EGCG with significantly increased cell survival without affecting cell proliferation but decreasing apoptotic cells. Also, EGCG increased the population of doublecortin-(DCX)-expressing cells that comprises the late intermediate progenitor cells (type-2b and -3) as well as immature neurons. After EGCG treatment, the young DCX-positive neurons showed more elaborated dendritic trees. EGCG also significantly increased net neurogenesis in the adult hippocampus and increased the hippocampal levels of phospho-Akt. Ex vivo, EGCG exerted a direct effect on survival and neuronal differentiation of adult hippocampal precursor cells, which was absent, when PI3K, a protein upstream of Akt, was blocked. Our results thus support a pro-survival and a pro-neurogenic role of EGCG. In the context of the conflicting published results, however, potential genetic modifiers must be assumed. These might help to explain the overall variability of study results with EGCG. Our data do indicate, however, that natural compounds such as EGCG can in principle modulate brain plasticity.


Assuntos
Catequina/análogos & derivados , Sobrevivência Celular/efeitos dos fármacos , Hipocampo/efeitos dos fármacos , Neurogênese/efeitos dos fármacos , Neurônios/efeitos dos fármacos , Fármacos Neuroprotetores/farmacologia , Animais , Catequina/química , Catequina/farmacologia , Sobrevivência Celular/fisiologia , Células Cultivadas , Relação Dose-Resposta a Droga , Proteínas do Domínio Duplacortina , Proteína Duplacortina , Hipocampo/fisiologia , Masculino , Camundongos Endogâmicos BALB C , Proteínas Associadas aos Microtúbulos/metabolismo , Células-Tronco Neurais/efeitos dos fármacos , Células-Tronco Neurais/fisiologia , Neurogênese/fisiologia , Neurônios/fisiologia , Neuropeptídeos/metabolismo , Fármacos Neuroprotetores/química , Fosfatidilinositol 3-Quinases/metabolismo , Proteínas Proto-Oncogênicas c-akt/metabolismo , Chá/química
19.
J Gen Physiol ; 93(3): 451-72, 1989 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-2467964

RESUMO

We studied the membrane currents of isolated cultured brown fat cells from neonatal rats using whole-cell and single-channel voltage-clamp recording. All brown fat cells that were recorded from had voltage-gated K currents as their predominant membrane current. No inward currents were seen in these experiments. The K currents of brown fat cells resemble the delayed rectifier currents of nerve and muscle cells. The channels were highly selective for K+, showing a 58-mV change in reversal potential for a 10-fold change in the external [K+]. Their selectivity was typical for K channels, with relative permeabilities of K+ greater than Rb+ greater than NH+4 much greater than Cs+, Na+. The K currents in brown adipocytes activated with a sigmoidal delay after depolarizations to membrane potentials positive to -50 mV. Activation was half maximal at a potential of -28 mV and did not require the presence of significant concentrations of internal calcium. Maximal voltage-activated K conductance averaged 20 nS in high external K+ solutions. The K currents inactivated slowly with sustained depolarization with time constants for the inactivation process on the order of hundreds of milliseconds to tens of seconds. The K channels had an average single-channel conductance of 9 pS and a channel density of approximately 1,000 channels/cell. The K current was blocked by tetraethylammonium or 4-aminopyridine with half maximal block occurring at concentrations of 1-2 mM for either blocker. K currents were unaffected by two blockers of Ca2+-activated K channels, charybdotoxin and apamin. Bath-applied norepinephrine did not affect the K currents or other membrane currents under our experimental conditions. These properties of the K channels indicate that they could produce an increase in the K+ permeability of the brown fat cell membrane during the depolarization that accompanies norepinephrine-stimulated thermogenesis, but that they do not contribute directly to the norepinephrine-induced depolarization.


Assuntos
Tecido Adiposo Marrom/fisiologia , Canais de Potássio/fisiologia , Aminopiridinas/farmacologia , Animais , Animais Recém-Nascidos , Apamina/farmacologia , Cátions/farmacologia , Células Cultivadas , Charibdotoxina , Eletrofisiologia , Norepinefrina/farmacologia , Canais de Potássio/efeitos dos fármacos , Ratos , Venenos de Escorpião/farmacologia , Tetraetilamônio , Compostos de Tetraetilamônio/farmacologia
20.
J Gen Physiol ; 91(6): 817-33, 1988 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-2458431

RESUMO

We examined the effects of Pandinus imperator scorpion venom on voltage-gated potassium channels in cultured clonal rat anterior pituitary cells (GH3 cells) using the gigohm-seal voltage-clamp method in the whole-cell configuration. We found that Pandinus venom blocks the voltage-gated potassium channels of GH3 cells in a voltage-dependent and dose-dependent manner. Crude venom in concentrations of 50-500 micrograms/ml produced 50-70% block of potassium currents measured at -20 mV, compared with 25-60% block measured at +50 mV. The venom both decreased the peak potassium current and shifted the voltage dependence of potassium current activation to more positive potentials. Pandinus venom affected potassium channel kinetics by slowing channel opening, speeding deactivation slightly, and increasing inactivation rates. Potassium currents in cells exposed to Pandinus venom did not recover control amplitudes or kinetics even after 20-40 min of washing with venom-free solution. The concentration dependence of crude venom block indicates that the toxins it contains are effective in the nanomolar range of concentrations. The effects of Pandinus venom were mimicked by zinc at concentrations less than or equal to 0.2 mM. Block of potassium current by zinc was voltage dependent and resembled Pandinus venom block, except that block by zinc was rapidly reversible. Since zinc is found in crude Pandinus venom, it could be important in the interaction of the venom with the potassium channel. We conclude that Pandinus venom contains toxins that bind tightly to voltage-dependent potassium channels in GH3 cells. Because of its high affinity for voltage-gated potassium channels and its irreversibility, Pandinus venom may be useful in the isolation, mapping, and characterization of voltage-gated potassium channels.


Assuntos
Canais Iônicos/efeitos dos fármacos , Adeno-Hipófise/metabolismo , Potássio/metabolismo , Venenos de Escorpião/farmacologia , Animais , Linhagem Celular , Eletrofisiologia , Canais Iônicos/fisiologia , Adeno-Hipófise/citologia , Ratos
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