RESUMO
We have studied the Mg doping of cubic GaN grown by plasma-assisted Molecular Beam Epitaxy (PA-MBE) over GaAs (001) substrates. In particular, we concentrated on conditions to obtain heavy p-type doping to achieve low resistance films which can be used in bipolar devices. We simulated the Mg-doped GaN transport properties by density functional theory (DFT) to compare with the experimental data. Mg-doped GaN cubic epitaxial layers grown under optimized conditions show a free hole carrier concentration with a maximum value of 6 × 1019 cm-3 and mobility of 3 cm2/Vs. Deep level transient spectroscopy shows the presence of a trap with an activation energy of 114 meV presumably associated with nitrogen vacancies, which could be the cause for the observed self-compensation behavior in heavily Mg-doped GaN involving Mg-VN complexes. Furthermore, valence band analysis by X-ray photoelectron spectroscopy and photoluminescence spectroscopy revealed an Mg ionization energy of about 100 meV, which agrees quite well with the value of 99.6 meV obtained by DFT. Our results show that the cubic phase is a suitable alternative to generate a high free hole carrier concentration for GaN.
RESUMO
INTRODUCTION. Craniopharyngioma is an embrionary tumor of the sellar and/suprasellar region derived from fusiform cells of Rathke´s cleft. Although locoregional relapse is the way classically proposed for relapse after treatment, it has been described, in a few cases, the possibility of ectopic relapse out of the sellar-suprasellar region, by direct seeding of cells during surgery on the surgical field, or by cell dissemination in the cerebrospinal fluid (CSF). It is proposed to report the case of a patient with relapse of a craniopharyngioma in the frontal lobe, who was previously operated ten years after, as well as to review the similar cases reported in the literature to the date. RESULTS. A systematic review of the literature has allowed to find 21 cases previously reported. Direct cellular seeding was the most frequent implantation mechanism. In all cases, the preferred treatment was radical surgical removal when this was possible. The time of latency between first surgery and relapse differed from 1 to 21 years. CONCLUSIONS. It is interesting, in the differential diagnosis, to bear in mind the possibility of ectopic relapse of craniopharyngioma in patients who have been operated because of this type of tumor and who present a new mass in nervous central system (CNS). In view of the long time of latency that can pass between the resection of a craniopharyngioma and his relapse, there becomes necessary a long follow-up of these patients by periodic imaging tests.
Assuntos
Craniofaringioma , Recidiva Local de Neoplasia , Neoplasias Hipofisárias , Idoso , Craniofaringioma/patologia , Craniofaringioma/prevenção & controle , Craniofaringioma/cirurgia , Diagnóstico Diferencial , Lobo Frontal/patologia , Lobo Frontal/cirurgia , Humanos , Masculino , Recidiva Local de Neoplasia/patologia , Recidiva Local de Neoplasia/cirurgia , Neoplasias Hipofisárias/patologia , Neoplasias Hipofisárias/prevenção & controle , Neoplasias Hipofisárias/cirurgia , RecidivaRESUMO
Vitronectin (vn) is a cell-adhesive glycoprotein present in blood and extracellular matrix of all vertebrates. In the present study we reported the cDNA cloning of Xenopus laevisvitronectin and its spatial and temporal expression pattern during the embryonic development of this important model organism. The deduced amino acid sequence of Xenopus laevis vn showed 49%, 47% and 43% identity with human, chicken and zebrafish orthologs, respectively, whereas the comparison with Xenopus tropicalis vn presented 85% identity. The structural organization consisting of a somatomedin B domain and two hemopexin-like domains was similar to higher vertebrate vitronectins. The vn transcripts were detected from stage 28 onward. At tadpole stages, vn is expressed in heart, gut derivatives and in the notochord. The protein was detected in heart, liver, foregut, pronephros and notochord at stages 43 and 47 of Xenopus embryos. Our results suggest that vitronectin is developmentally regulated and could participate in embryo organogenesis.
Assuntos
Vitronectina/metabolismo , Xenopus laevis/metabolismo , Sequência de Aminoácidos , Animais , DNA Complementar , Eletroforese em Gel de Poliacrilamida , Desenvolvimento Embrionário , Hibridização In Situ , Microscopia de Fluorescência , Dados de Sequência Molecular , Reação em Cadeia da Polimerase Via Transcriptase Reversa , Homologia de Sequência de Aminoácidos , Vitronectina/química , Xenopus laevis/embriologiaRESUMO
A glass capillary column coated with PS-086 (15% phenyl-80% methylpolysiloxane, 15 m x 0.30-mm i.d., 0.1-microm film thickness) is used to analyze extracts from Lonchocarpus urucu (Derris urucu). Several secondary metabolites (8 flavonoids, 10 rotenoids) are characterized without derivatization, and the rotenoids are quantitated by high-temperature high-resolution gas chromatography (HTHRGC) and HTHRGC coupled with mass spectrometry (HTHRGC-MS). The limit of detection in flame ionization detection of rotenone is approximately 0.5 microg/mL, and the limit of quantitation was 2 microg/mL. Derris urucu bark is an excellent source of rotenone isomers (80 mg/g), deguelin (30 mg/g), and rotenolone (26 mg/g). Single solvent extractions (hexane, methylene dichloride, acetone, or methanol) are not able to fully extract the flavonoids and rotenoids. Complete extraction is achieved using a mixture of methanol-methylene dichloride (1:1), indicating a complex association of these compounds with the plant tissue. HTHRGC and HTHRGC-MS are shown to be quick and informative tools for the rapid analysis of crude extracts without the need for prior derivatization and fractionation.
Assuntos
Cromatografia Gasosa/métodos , Flavonoides/análise , Inseticidas/análise , Plantas/química , Rotenona/análise , Temperatura Alta , Espectrometria de MassasRESUMO
Testicular feminization is a syndrome due to androgen insensitivity. It occurs in a complete and incomplete form. The case of a 17 years old girl with complete androgen insensitivity syndrome is reported. Patient came to medical attention because of primary amenorrhea as the only pathology, with normal external, female genitalia. Diagnosis, findings, management and a five months follow up, are described, as well as a review of this subject.
Assuntos
Síndrome de Resistência a Andrógenos/diagnóstico , Androgênios/fisiologia , Adolescente , Síndrome de Resistência a Andrógenos/sangue , Síndrome de Resistência a Andrógenos/cirurgia , Terapia Combinada , Feminino , Hormônios/sangue , Humanos , Masculino , Psicoterapia , SíndromeAssuntos
Gêmeos Unidos , Anormalidades Múltiplas , Adulto , Cesárea , Feminino , Humanos , Masculino , Gravidez , Gravidez Múltipla , Ultrassonografia Pré-NatalRESUMO
The immunosuppressive effect of glucocorticoids has been widely reported; however, the mechanism of action of these hormones on the immune system has not been fully established. In the present study, the effect of glucocorticoids on glucose, glutamine, and pyruvate metabolism in lymph node lymphocytes was investigated. Addition of dexamethasone to the incubation medium did not alter glucose and glutamine metabolism but inhibited pyruvate utilization by 40%. This latter effect took 1 h to occur and remained for up to 6 h, even after removal of dexamethasone from the culture medium. Measurements of the activity of pyruvate dehydrogenase in lymphocytes and the rate of [1-14C]-pyruvate conversion into 14CO2 in incubated lymphocyte mitochondria demonstrated that glucocorticoids decrease pyruvate utilization by inhibiting the activity of this key regulatory enzyme. The effect of such an inhibition of pyruvate utilization on the function of cells of the immune system remains to be clarified.
Assuntos
Dexametasona/farmacologia , Linfócitos/metabolismo , Animais , Células Cultivadas , Ritmo Circadiano , Descarboxilação , Glucose/metabolismo , Glutamina/metabolismo , Masculino , Metirapona/farmacologia , Mifepristona/farmacologia , Piruvatos/metabolismo , Ácido Pirúvico , Ratos , Ratos WistarRESUMO
Although the immunosuppressive effect of glucocorticoids has been widely reported, the mechanism of action of these hormones on the immune system has not been fully established. In the present study, the effect of glucocorticoids on the rates of pyruvate utilization and lactate production by lymphocytes obtained from rat mesenteric lymph nodes was investigated. Adult rats were injected with dexamethasone (1 mg/kg, ip) daily for 3 days. A stressed group which received a corresponding volume of 0.9% saline and control rats not injected were also included. All treatments were carried out at 17:00 h. Stress or administration of dexamethasone reduced the rate of pyruvate utilization by 50% and 62%, respectively. The hormonal injection increased the rate of lactate production by 57%, whereas the stressed group showed a 2.4-fold increase of the conversion of pyruvate to lactate, as compared to control rats. These findings suggest that glucocorticoids regulate pyruvate metabolism in lymphocytes and that an additional neurohormonal factor released during stress may also participate in the control of lactate production.
Assuntos
Glucocorticoides/fisiologia , Lactatos/biossíntese , Linfócitos/metabolismo , Piruvatos/metabolismo , Animais , Ácido Láctico , Masculino , Ácido Pirúvico , Ratos , Ratos Wistar , Estresse Fisiológico/metabolismoRESUMO
Although the immunosuppressive effect of glucocorticoids has been widely reported, the mechanism of action of these hormones on the immune system has not been fully established. In the present study, the effect of glucocorticoids on the rates of pyruvate utilization and lactate production by lymphocytes obtained from rat mesenteric lymph nodes was investigated. Adult rats were injected withh dexamethasone ( 1 mg/kg, ip) daily for dfays. A stressed group which received a corresponding volume of 0.9% saline and control rats not injected were also included. All treatments were carried out at 17:00 h. Stress or administration of dexamethasone reduced the rate of pyruvate utilization by 505 and 625, respectively. The hormonal injection increased ther rate of lactate production by 575, whereas the stressed group showed a 2.4-fold increase of the conversion of pyruvate to lactate, as compared to control rats. These findings suggest that glucorticoids regulate pyruvate metabolism in lymphocytes and that an additional neurohormonal factor released during stress may also participate in the control of lactate production
Assuntos
Ratos , Glucocorticoides/efeitos adversos , Lactatos , Linfócitos , Piruvatos/metabolismo , Estresse FisiológicoRESUMO
The rates of pyruvate utilization and lactate formation were measured in lymphocytes from young (newly weaned), adult (3-month old) and aged (15-month old) rats. Lymphocytes obtained from mesenteric lymph nodes were incubated at 37 degrees C for 1 h. The conversion of pyruvate to lactate accounted for 92.5% of the total pyruvate utilized by lymphocytes from young rats and was 34.2% and 44.5% for adult and aged rats, respectively. When lymphocytes were stimulated with concanavalin A there was an increase of 65.6% and 37.1% in the rates of pyruvate utilization by lymphocytes from young and adult rats, respectively. No changes in pyruvate utilization were observed in response to concanavalin A in lymphocytes from aged rats.
Assuntos
Concanavalina A/farmacologia , Lactatos/biossíntese , Linfócitos/metabolismo , Piruvatos/metabolismo , Envelhecimento , Animais , Técnicas In Vitro , Masculino , Ratos , Ratos EndogâmicosRESUMO
The rates of pyruvate utilization and lactate formation were measured in lymphocytes obtained from mesentéric lymph nodes were incubated at-C for 1 h. The conversion of pyruvate to lactate accounted for 92.5% of the total pyruvate utilized by lymphocytes from yung rats and was 34.2% and 44.5% for adult and aged rats, respectively. Wen lymphocytes were stimulated with concanavalin. A there was an increase of 65.5% and 37.1% in the rates of pyruvate utilization by lymphocytes from young and adult rats, respectively. No changes in pyruvate utilization were observed in response to concanavalin A in lymphocytes from aged rats
Assuntos
Ratos , Animais , Masculino , Concanavalina A/farmacologia , Técnicas In Vitro , Lactatos/biossíntese , Linfócitos/metabolismo , Piruvatos/metabolismo , Envelhecimento , Ratos EndogâmicosRESUMO
The relationship between obesity and hypertension is well documented within the literature. It has been demonstrated that among hypertensive children and adolescents a greater percentage are obese; among children who are obese arterial blood pressure is higher and there is a greater incidence of hypertension. As part of a prospective study of arterial blood pressure 176 children were studied of ranging in age from 5 to 8 years. The correlation between K1 and other parameters indicating the degree of obesity was calculated. The best correlation score was found using the ponderal index (r = .53; p--.001). Body weight as well as the thickness of the albow crease showed a similar correlation with blood pressure (r = .50; p--.001). The correlation with the index for ideal weight expressed as a percentage representing the excess or deficit as compared to the ideal weight by age, sex, and heighth was also statistically significant, although the r-socre was less (r = .37; p--.01). These data confirm a positive and significant relationship between K1 and indices for obesity.