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1.
Chaos ; 31(8): 083121, 2021 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-34470242

RESUMO

In this work, we study the phase synchronization of a neural network and explore how the heterogeneity in the neurons' dynamics can lead their phases to intermittently phase-lock and unlock. The neurons are connected through chemical excitatory connections in a sparse random topology, feel no noise or external inputs, and have identical parameters except for different in-degrees. They follow a modification of the Hodgkin-Huxley model, which adds details like temperature dependence, and can burst either periodically or chaotically when uncoupled. Coupling makes them chaotic in all cases but each individual mode leads to different transitions to phase synchronization in the networks due to increasing synaptic strength. In almost all cases, neurons' inter-burst intervals differ among themselves, which indicates their dynamical heterogeneity and leads to their intermittent phase-locking. We argue then that this behavior occurs here because of their chaotic dynamics and their differing initial conditions. We also investigate how this intermittency affects the formation of clusters of neurons in the network and show that the clusters' compositions change at a rate following the degree of intermittency. Finally, we discuss how these results relate to studies in the neuroscience literature, especially regarding metastability.


Assuntos
Redes Neurais de Computação , Neurônios , Modelos Neurológicos
2.
J Chem Phys ; 143(18): 184304, 2015 Nov 14.
Artigo em Inglês | MEDLINE | ID: mdl-26567659

RESUMO

Metadynamics coupled with classical molecular dynamics has been successfully applied to sample the configuration space of metallic and bimetallic nanoclusters. We implement a new set of collective variables related to the pair distance distribution function of the nanoparticle to achieve an exhaustive isomer sampling. As paradigmatic examples, we apply our methodology to Ag147, Pt147, and their alloy Ag(shell)Pt(core) at 2:1 and 1:1 chemical compositions. The proposed scheme is able to reproduce the known solid-solid structural transformation pathways, based on the Lipscomb's diamond-square-diamond mechanisms, both in mono and bimetallic nanoparticles. A discussion of the free energy barriers involved in these processes is provided.

3.
Phys Rev E ; 104(2-1): 024204, 2021 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-34525513

RESUMO

We investigate the role of bistability in the synchronization of a network of identical bursting neurons coupled through an generic electrical mean-field scheme. These neurons can exhibit distinct multistable states and, in particular, bistable behavior is observed when their sodium conductance is varied. With this, we consider three different initialization compositions: (i) the whole network is in the same periodic state; (ii) half of the network periodic, half chaotic; (iii) half periodic, and half in a different periodic state. We show that (i) and (ii) reach phase synchronization (PS) for all coupling strengths, while for (iii) small coupling regimes do not induce PS, and instead, there is a coexistence of different frequencies. For stronger coupling, case (iii) synchronizes, but after (i) and (ii). Since PS requires all neurons being in the same state (same frequencies), these different behaviors are governed by transitions between the states. We find that, during these transitions, (ii) and (iii) have transient chimera states and that (iii) has breathing chimeras. By studying the stability of each state, we explain the observed transitions. Therefore, bistability of neurons can play a major role in the synchronization of generic networks, with the simple initialization of the system being capable of drastically changing its asymptotic space.

4.
Sci Rep ; 11(1): 15789, 2021 08 04.
Artigo em Inglês | MEDLINE | ID: mdl-34349134

RESUMO

Extracting relevant properties of empirical signals generated by nonlinear, stochastic, and high-dimensional systems is a challenge of complex systems research. Open questions are how to differentiate chaotic signals from stochastic ones, and how to quantify nonlinear and/or high-order temporal correlations. Here we propose a new technique to reliably address both problems. Our approach follows two steps: first, we train an artificial neural network (ANN) with flicker (colored) noise to predict the value of the parameter, [Formula: see text], that determines the strength of the correlation of the noise. To predict [Formula: see text] the ANN input features are a set of probabilities that are extracted from the time series by using symbolic ordinal analysis. Then, we input to the trained ANN the probabilities extracted from the time series of interest, and analyze the ANN output. We find that the [Formula: see text] value returned by the ANN is informative of the temporal correlations present in the time series. To distinguish between stochastic and chaotic signals, we exploit the fact that the difference between the permutation entropy (PE) of a given time series and the PE of flicker noise with the same [Formula: see text] parameter is small when the time series is stochastic, but it is large when the time series is chaotic. We validate our technique by analysing synthetic and empirical time series whose nature is well established. We also demonstrate the robustness of our approach with respect to the length of the time series and to the level of noise. We expect that our algorithm, which is freely available, will be very useful to the community.

5.
Clin Transl Oncol ; 23(11): 2358-2367, 2021 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-34043153

RESUMO

PURPOSE: To explore the feasibility of image-guided and respiratory-gated Stereotactic Body Radiation Therapy (SBRT) for Accelerated Partial Breast Irradiation (APBI) in patients with very early breast cancer. MATERIAL AND METHODS: Selected patients with early breast carcinoma after breast-conserving surgery were enrolled in this phase II trial. A fiducial marker was percutaneously placed close to surgical bed and five external fiducials were set on the skin. A CT scan for planning was acquired at free breathing. The treatment was planned and DVH were assessed according to international recommendations. Prescription dose was 30 Gy in five consecutive fractions of 6 Gy. A 6MV monoenergetic LINAC (linear accelerator) that combines stereoscopic X-ray imaging system and ExacTrac Adaptive Gating technique was used. PTV (planning target volume) intrafraction motion was controlled and PTV was irradiated in a selected gated area of the respiratory cycle. Shifts for a correct, gated set-up were calculated and automatically applied. RESULTS: Between April 2013 and October 2015, a total of 23 patients were included. The median tumor size was 12 mm. The mean PTV volume was 114 cc. The mean ipsilateral lung V9 Gy was 2.2% and for left-sided breast cancers, the volume of the heart receiving 1.5 Gy was 11.5%. Maximum skin dose was 30.8 Gy. Acute toxicity was grade1 in all the patients and 100% experienced excellent/good breast cosmesis outcomes. With a median follow-up of 66 months (range 8-99 months) local-relapse-free-survival reaches 100%. One patient developed a second breast cancer outside the treated quadrant after 25.1 months. CONCLUSION: APBI with SBRT and ExacTrac Adaptive Gating System was feasible. The acute and late toxicities were almost null and cosmesis was excellent. We also found that the margins of 5 mm applied from CTV to PTV were sufficient to compensate for geometric uncertainties.


Assuntos
Neoplasias da Mama/radioterapia , Carcinoma Ductal de Mama/radioterapia , Radiocirurgia/métodos , Neoplasias da Mama/diagnóstico por imagem , Neoplasias da Mama/patologia , Neoplasias da Mama/cirurgia , Carcinoma Ductal de Mama/diagnóstico por imagem , Carcinoma Ductal de Mama/patologia , Carcinoma Ductal de Mama/cirurgia , Intervalo Livre de Doença , Fracionamento da Dose de Radiação , Estudos de Viabilidade , Feminino , Marcadores Fiduciais , Coração/efeitos da radiação , Humanos , Pulmão/efeitos da radiação , Mastectomia Segmentar , Pessoa de Meia-Idade , Movimentos dos Órgãos , Órgãos em Risco/efeitos da radiação , Cuidados Pós-Operatórios/métodos , Estudos Prospectivos , Radiocirurgia/instrumentação , Respiração , Pele/efeitos da radiação , Fatores de Tempo , Tomografia Computadorizada por Raios X , Carga Tumoral
6.
Sci Rep ; 8(1): 9150, 2018 Jun 14.
Artigo em Inglês | MEDLINE | ID: mdl-29904180

RESUMO

The control of structural and chemical transitions in bimetallic nanoalloys at finite temperatures is one of the challenges for their use in advanced applications. Comparing Nested Sampling and Molecular Dynamics simulations, we investigate the phase changes of CuPt nanoalloys with the aim to elucidate the role of kinetic effects during their solidification and melting processes. We find that the quasi-thermodynamic limit for the nucleation of (CuPt)309 is 965 ± 10 K, but its prediction is increasingly underestimated when the system is cooled faster than 109 K/s. The solidified nanoparticles, classified following a novel tool based on Steinhardt parameters and the relative orientation of characteristic atomic environments, are then heated back to their liquid phase. We demonstrate the kinetic origin of the hysteresis in the caloric curve as (i) it closes for rates slower than 108 K/s, with a phase change temperature of 970 K ± 25 K, in very good agreement with its quasi-thermodynamic limit; (ii) the process happens simultaneously in the inner and outer layers; (iii) an onion-shell chemical order - Cu-rich surface, Pt-rich sub-surface, and mixed core - is always preserved.

7.
Sci Rep ; 8(1): 11956, 2018 Aug 07.
Artigo em Inglês | MEDLINE | ID: mdl-30087376

RESUMO

A correction to this article has been published and is linked from the HTML and PDF versions of this paper. The error has been fixed in the paper.

8.
Thromb Res ; 163: 100-104, 2018 03.
Artigo em Inglês | MEDLINE | ID: mdl-29407620

RESUMO

BACKGROUND: Non-vitamin K antagonist oral anticoagulants (NOACs) do not need routine laboratory monitoring but measurement of drug concentration is important in emergency conditions. Specific laboratory tests are not readily available or not implemented in every hospital. Point-of-Care Tests (POCT) may bridge this gap and be used as a bedside solution. OBJECTIVES: Feasibility of POCT to assess plasma levels of dabigatran, rivaroxaban and apixaban. PATIENTS/METHODS: Activated Coagulation Time-Low Range (ACT - LR) using a portable Hemochron Signature Elite for dabigatran and prothrombin time (expressed as INR) by Coaguchek XS Pro for rivaroxaban and apixaban were obtained at trough and peak in 136 consecutive patients taking NOACs (70 on dabigatran, 45 on rivaroxaban and 20 on apixaban). Using a paired study design, drug concentrations were concurrently determined by functional specific tests. RESULTS AND CONCLUSIONS: The correlation between NOACs concentration and the values obtained using the POCTs was high for dabigatran and rivaroxaban (r = 0.80 and r = 0.82, respectively) and low for apixaban (r = 0.21). ACT-LR ≤ 188 s better detected dabigatran levels ≤ 50 ng/ml, with a sensitivity of 87.5% and a specificity of 84.1%. ACT-LR values > 217 s better discriminated value of dabigatran > 200 ng/ml, with a sensitivity of 86.7% and a specificity of 81.4%. INR Coaguchek values ≤ 1.2 better identified patients with rivaroxaban values < 100 ng/ml, with sensitivity of 90%, specificity of 88.5%. This analysis was not possible for apixaban. CONCLUSION: In emergency situations POCT use may provide useful immediate information on dabigatran and rivaroxaban concentration.


Assuntos
Testes de Coagulação Sanguínea/métodos , Testes Imediatos/tendências , Administração Oral , Anticoagulantes/farmacologia , Anticoagulantes/uso terapêutico , Feminino , Humanos , Masculino
9.
J Clin Invest ; 100(7): 1775-81, 1997 Oct 01.
Artigo em Inglês | MEDLINE | ID: mdl-9312177

RESUMO

The rate of appearance (Ra) of glucose in plasma and the contribution of gluconeogenesis were quantified in normal pregnant women early ( approximately 10 wk) and late ( approximately 34 wk) in gestation. Their data were compared with those of normal nonpregnant women. Glucose Ra was measured using the [U-13C]glucose tracer dilution method. Gluconeogenesis was quantified by the appearance of 2H on carbon 5 and 6 of glucose after deuterium labeling of body water pool. Weight-specific glucose Ra was unchanged during pregnancy (nonpregnant, 1.89+/-0.24; first trimester, 2.05+/-0.21; and third trimester 2.17+/-0.28 mg/kg.min, mean+/-SD), while total glucose Ra was significantly increased (early, 133.5+/-7.2; late, 162.6+/-16.4 mg/min; P = 0.005). The fractional contribution of gluconeogenesis via pyruvate measured by 2H enrichment on C-6 of glucose (45-61%), and of total gluconeogenesis quantified from 2H enrichment on C-5 of glucose (i.e. , including glycerol [68-85%]) was not significantly different between pregnant and nonpregnant women. Inasmuch as total glucose Ra was significantly increased, total gluconeogenesis was also increased in pregnancy (early pregnancy, 94.7+/-15.9 mg/min; late pregnancy, 122.7+/-9.3 mg/min; P = 0.003). These data demonstrate the ability of the mother to adapt to the increasing fetal demands for glucose with advancing gestation. The mechanism for this unique quantitative adjustment to the fetal demands remains undefined.


Assuntos
Glicemia/metabolismo , Gluconeogênese , Gravidez/fisiologia , Ácido 3-Hidroxibutírico , Isótopos de Carbono , Deutério , Ácidos Graxos não Esterificados/sangue , Feminino , Humanos , Hidroxibutiratos/sangue , Modelos Lineares , Fisiologia/métodos , Primeiro Trimestre da Gravidez/fisiologia , Terceiro Trimestre da Gravidez/fisiologia
10.
J Phys Condens Matter ; 29(14): 145402, 2017 Apr 12.
Artigo em Inglês | MEDLINE | ID: mdl-28098076

RESUMO

On the basis of ab initio calculations, we present a new parametrisation of the Vervisch-Mottet-Goniakowski (VMG) potential (Vervisch et al 2002 Phys. Rev. B 24 245411) for modelling the oxide-metal interaction. Applying this model to mimic the finite temperature behaviour of large platinum icosahedra deposited on the pristine MgO(1 0 0), we find the nanoparticle undergoes two solid-solid transitions. At 650 K the 'squarisation' of the interface layer, while a full reshaping towards a fcc architecture takes place above 950 K. In between, a quite long-lived intermediate state with a (1 0 0) interface but with an icosahedral cap is observed. Our approach reproduces experimental observations, including wetting behaviour and the lack of surface diffusion.

12.
J Thromb Haemost ; 14(11): 2124-2131, 2016 11.
Artigo em Inglês | MEDLINE | ID: mdl-27471198

RESUMO

Essentials Anticoagulation in the elderly is still a challenge and suspension of warfarin is common. This is an observational study reporting reasons and consequences of warfarin suspension. Vascular disease, age, time in therapeutic range, and bleedings are associated with suspension. After suspension for bleeding or frailty, patients remain at high-risk of death or complications. SUMMARY: Background Anticoagulation in elderly patients with non-valvular atrial fibrillation (NVAF) is still a challenge, and discontinuation of warfarin is common. The aim of this study was to analyze the aspects related to warfarin discontinuation in a real-world population. Methods This was an observational cohort study on very elderly NVAF patients naive to warfarin therapy (VENPAF). The included subjects were aged at least 80 years, and started using warfarin after a diagnosis of NVAF. Warfarin discontinuation was assessed, and the reason reported for discontinuation, the person who decided to stop treatment, subsequent antithrombotic therapy and mortality, ischemic and bleeding events were collected. Results Over a period of 5 years, warfarin was discontinued in 148 of 798 patients. Despite similar CHA2 DS2 -VASc scores, the frequencies of thromboembolic and major bleeding events were significantly higher (P = 0.01 and P = 0.001, respectively) and the time in therapeutic range (TTR) was significantly lower (P < 0.001) in patients who discontinued warfarin. Independent risk factors for warfarin discontinuation were vascular disease (hazard ratio [HR] 2.5, P < 0.001), age ≥ 85 years (HR 1.4, P = 0.04), TTR < 60% (HR 1.8, P = 0.001), and bleeding events (HR 2.3, P < 0.001). The main reasons for warfarin discontinuation were physician-perceived frailty or low life-expectancy (45.9%), bleeding complications (19.6%), and sinus rhythm restoration (16.9%). Event and death rates were very high, especially in frail patients and in those with bleeding complications. Conclusions Warfarin discontinuation is frequent in very elderly patients, and is associated with increased risks of death and adverse events. Identification of elderly patients who are at high risk of bleeding and the poor quality of anticoagulation during warfarin are still unsolved clinical problems.


Assuntos
Fibrilação Atrial/tratamento farmacológico , Vitamina K/antagonistas & inibidores , Varfarina/uso terapêutico , Idoso de 80 Anos ou mais , Anticoagulantes/uso terapêutico , Coagulação Sanguínea , Feminino , Fibrinolíticos/uso terapêutico , Seguimentos , Hemorragia , Humanos , Masculino , Análise Multivariada , Modelos de Riscos Proporcionais , Fatores de Risco , Acidente Vascular Cerebral/etiologia , Tromboembolia/mortalidade , Tromboembolia/terapia , Resultado do Tratamento , Doenças Vasculares/sangue
13.
Am J Clin Nutr ; 64(2): 152-8, 1996 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-8694014

RESUMO

Limited information is available on the metabolic fate of medium-chain triacylglycerols (triglycerides) after intestinal absorption and on their influence on essential fatty acid metabolism. We studied in preterm infants the effect of two infant formulas, one with a high (HMCT) and one with a low (LMCT) medium-chain triacylglycerol content, on plasma fatty acids. The HMCT formula contained 46 mol% 8:0 + 10:0 and the LMCT formula (4.8 mol% 8:0 + 10:0) had approximately twice the amount of long-chain saturated and monounsaturated fatty acids as the HMCT. Both formulas had similar contents of linoleic and linolenic acids. Plasma lipids and fatty acids were determined at birth and on day 24 of life in 20 infants fed the LMCT (n = 12) or HMCT (n = 8) formula. Significant amounts of medium-chain fatty acids were found in the systemic circulation of the infants fed the HMCT formula, mainly in plasma fatty acids and triacylglycerols. Despite striking dietary differences, palmitic and stearic acids were not different between groups, indicating de novo synthesis of long-chain fatty acids with the HMCT formula. Plasma phospholipid docosahexaenoic acid was significantly lower in the HMCT group than in the LMCT infants (1.38 +/- 0.07 compared with 1.73 +/- 0.07 mol%, P = 0.002). Our data indicate that a high MCT intake in preterm infants increases lipogenesis, and dietary nonessential fatty acids interfere with the metabolism of docosahexaenoic acid.


Assuntos
Ácidos Graxos Essenciais/sangue , Ácidos Graxos/sangue , Alimentos Infantis , Recém-Nascido Prematuro/sangue , Lipídeos/sangue , Triglicerídeos/administração & dosagem , Humanos , Recém-Nascido , Ácido Linoleico , Ácidos Linoleicos/sangue , Fosfolipídeos/sangue , Aumento de Peso , Ácido alfa-Linolênico/sangue
14.
J Med Chem ; 38(12): 2061-9, 1995 Jun 09.
Artigo em Inglês | MEDLINE | ID: mdl-7783137

RESUMO

An analysis of the free energy perturbation (FEP) method is presented that attempts to evaluate the efficacy of the FEP method in the drug discovery process. To accomplish this we have evaluated whether the FEP technique can accurately predict energetic and structural quantities relating to the inhibition of human carbonic anhydrase II (HCAII) by sulfonamides. Three well-characterized (both structurally and energetically) sulfonamide inhibitors of HCAII were examined in this study, 1a, 1b, and 1c. Results from FEP simulations on these compounds indicate that the FEP method can predict energetic trends reasonably well; however, the FEP method was less successful in reproducing detailed structural data. In particular, an expected movement of His-64 when inhibitor 1c was bound did not occur. We conclude that the FEP method can be used to determine relative free energies of binding but cannot be relied upon to reproduce subtle geometric changes.


Assuntos
Inibidores da Anidrase Carbônica/química , Anidrases Carbônicas/metabolismo , Inibidores da Anidrase Carbônica/farmacologia , Humanos , Estrutura Molecular , Termodinâmica
15.
J Med Chem ; 43(23): 4398-415, 2000 Nov 16.
Artigo em Inglês | MEDLINE | ID: mdl-11087565

RESUMO

Thrombotic diseases are a major cause of death and morbidity. Factor Xa (fXa) plays a vital role in the regulation of normal homeostasis and abnormal intravascular thrombus development in the blood coagulation cascade. A novel series of fXa inhibitors incorporating an amidino 6,5-fused bicyclic moiety at the P1 position has been designed and synthesized based on molecular modeling studies. Structure-activity relationship (SAR) studies have led to selective subnanomolar fXa inhibitors. The most potent fXa inhibitor in this series (72, SE170) has a potent inhibition constant (K(i) = 0.3 nM), is 350-fold selective for fXa over trypsin, and also shows good in vivo efficacy in a rabbit arterio-venous thrombosis model (ID(50) = 0.14 micromol/kg/h). An X-ray crystal structure of 72 complexed to bovine trypsin was completed, and a binding mode of 72 with fXa has been proposed based on modeling with human des-Gla-fXa.


Assuntos
Amidinas/síntese química , Benzimidazóis/síntese química , Inibidores do Fator Xa , Fibrinolíticos/síntese química , Indazóis/síntese química , Indóis/síntese química , Sulfonamidas/síntese química , Amidinas/química , Amidinas/farmacocinética , Amidinas/farmacologia , Animais , Benzimidazóis/química , Benzimidazóis/farmacocinética , Benzimidazóis/farmacologia , Bovinos , Cristalografia por Raios X , Cães , Desenho de Fármacos , Fibrinolíticos/química , Fibrinolíticos/farmacocinética , Fibrinolíticos/farmacologia , Humanos , Indazóis/química , Indazóis/farmacocinética , Indazóis/farmacologia , Indóis/química , Indóis/farmacocinética , Indóis/farmacologia , Modelos Moleculares , Coelhos , Relação Estrutura-Atividade , Sulfonamidas/química , Sulfonamidas/farmacocinética , Sulfonamidas/farmacologia , Tripsina/química , Trombose Venosa/tratamento farmacológico
16.
J Med Chem ; 44(4): 566-78, 2001 Feb 15.
Artigo em Inglês | MEDLINE | ID: mdl-11170646

RESUMO

Factor Xa (fXa) plays a critical role in the coagulation cascade, serving as the point of convergence of the intrinsic and extrinsic pathways. Together with nonenzymatic cofactor Va and Ca2+ on the phospholipid surface of platelets or endothelial cells, factor Xa forms the prothrombinase complex, which is responsible for the proteolysis of prothrombin to catalytically active thrombin. Thrombin, in turn, catalyzes the cleavage of fibrinogen to fibrin, thus initiating a process that ultimately leads to clot formation. Recently, we reported on a series of isoxazoline and isoxazole monobasic noncovalent inhibitors of factor Xa which show good potency in animal models of thrombosis. In this paper, we wish to report on the optimization of the heterocyclic core, which ultimately led to the discovery of a novel pyrazole SN429 (2b; fXa K(i) = 13 pM). We also report on our efforts to improve the oral bioavailability and pharmacokinetic profile of this series while maintaining subnanomolar potency and in vitro selectivity. This was achieved by replacing the highly basic benzamidine P1 with a less basic benzylamine moiety. Further optimization of the pyrazole core substitution and the biphenyl P4 culminated in the discovery of DPC423 (17h), a highly potent, selective, and orally active factor Xa inhibitor which was chosen for clinical development.


Assuntos
Inibidores do Fator Xa , Fibrinolíticos/síntese química , Pirazóis/síntese química , Inibidores de Serina Proteinase/síntese química , Sulfonas/síntese química , Administração Oral , Animais , Disponibilidade Biológica , Cristalografia por Raios X , Cães , Fibrinolíticos/química , Fibrinolíticos/farmacocinética , Fibrinolíticos/farmacologia , Modelos Moleculares , Pirazóis/química , Pirazóis/farmacocinética , Pirazóis/farmacologia , Ratos , Inibidores de Serina Proteinase/química , Inibidores de Serina Proteinase/farmacocinética , Inibidores de Serina Proteinase/farmacologia , Relação Estrutura-Atividade , Sulfonas/química , Sulfonas/farmacocinética , Sulfonas/farmacologia
17.
Neuroscience ; 77(4): 993-1002, 1997 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-9130781

RESUMO

The control of suckling-induced bursting activity of oxytocin neurons and of phasic activity of vasopressin neurons by N-methyl-D-aspartate receptors was investigated in anaesthetized lactating rats. Receptor antagonist or agonist was applied in the vicinity of supraoptic neurons recorded extracellularly. The basal activity of oxytocin neurons was tonically decreased and increased by sustained application of the antagonist and agonist respectively. These effects occurred independently of the effectiveness of suckling to trigger the bursting pattern. When drugs were applied during an ongoing series of milk-ejection-related bursts, these changes were accompanied by parallel modifications in burst amplitude, but burst periodicity was unaffected. In rats failing to milk-eject, antagonist or agonist application did not facilitate the occurrence of bursts. Simultaneous recordings from oxytocin neurons in the contralateral supraoptic nucleus showed that neither their basal nor their bursting activity were affected, indicating the absence of cross-talk between nuclei during such application. The excitatory effect of N-methyl-D-aspartate differed from that induced in the same neurons by i.c.v. injection of oxytocin, which enhanced basal level of activity and burst amplitude, but also increased burst frequency. Furthermore, the distribution of interspike intervals indicated that N-methyl-D-aspartate, but not oxytocin, induced a regularization of the spike pattern. For vasopressin neurons, application of the receptor antagonist inhibited phasic activity by decreasing burst duration and increasing silences. Conversely, N-methyl-D-aspartate enhanced phasic activity, increasing both the duration of the active phases and the frequency of spikes during active phases. When applied to silent vasopressin neurons, N-methyl-D-aspartate induced a regular phasic activity. These results provide evidence that functional N-methyl-D-aspartate receptors regulate the excitability of both oxytocin and vasopressin neurons in lactating rats. These receptors play a paramount role in maintaining a certain level of basal activity which will favour appropriate discharge patterns, tonic for oxytocin neurons and phasic for vasopressin neurons. For oxytocin neurons, this sustained control by ambient glutamate influences the amplitude of bursts, but N-methyl-D-aspartate receptors are probably not involved in the generation of the bursting pattern.


Assuntos
Lactação/fisiologia , Neurônios/fisiologia , Ocitocina/fisiologia , Receptores de N-Metil-D-Aspartato/fisiologia , Vasopressinas/fisiologia , 2-Amino-5-fosfonovalerato/farmacologia , Potenciais de Ação/fisiologia , Animais , Eletrofisiologia , Agonistas de Aminoácidos Excitatórios/farmacologia , Antagonistas de Aminoácidos Excitatórios/farmacologia , Feminino , Ejeção Láctea/efeitos dos fármacos , Ejeção Láctea/fisiologia , N-Metilaspartato/farmacologia , Neurônios/química , Periodicidade , Ratos , Ratos Wistar , Receptores de N-Metil-D-Aspartato/agonistas , Receptores de N-Metil-D-Aspartato/antagonistas & inibidores , Reflexo/efeitos dos fármacos , Reflexo/fisiologia , Núcleo Supraóptico/citologia , Núcleo Supraóptico/fisiologia
18.
Immunobiology ; 175(3): 226-35, 1987 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-3500118

RESUMO

The enhanced T cell reactivity (ConA hyperresponsiveness and IL 2 hypersecretion) of spleen lymphocytes of Obese strain (OS) chickens with spontaneous autoimmune thyroiditis has recently been shown to be due to a defect in macrophage-derived non-specific suppressor factors that regulate IL 2 secretion and IL 2-promoted T lymphoblast proliferation in normal healthy animals. In the present study, we present several lines of evidence that the increased T cell response of peripheral blood lymphocytes (PBL) of OS chickens is due to mechanisms entirely different from the described dysregulation of splenic T cells: 1) In contrast to the splenic macrophages, peripheral blood monocytes of OS animals are not deficient in the production of IL 2 antagonistic activity (IAA); 2) therefore, cocultivation of PBL from OS and Normal White Leghorn (NWL) chickens in communicating culture chambers did not abrogate the difference in Con A response as previously observed with spleen lymphocytes. 3) Immunofluorescence with a monoclonal antibody (INN CH 16) against the chicken IL 2 receptor revealed enhanced numbers of mitogen activatable T cells in OS PBL but not OS spleen lymphocytes. 4) After prolonged Con A stimulation of PBL, OS and NWL lymphoblasts did not differ from each other in functional aspects. In contrast to this, Con A lymphoblasts from OS spleens exhibited enhanced staining with INN CH 16 in parallel with an increased proliferative response to IL 2. Thus, the primary T cell dysfunction involved in the development of autoimmune disease in OS chickens is the result of at least two separate regulatory defects.


Assuntos
Ativação Linfocitária , Obesidade/imunologia , Linfócitos T/imunologia , Tireoidite Autoimune/imunologia , Animais , Comunicação Celular , Galinhas , Concanavalina A/farmacologia , Técnicas In Vitro , Interleucina-2/biossíntese , Interleucina-2/farmacologia , Baço/imunologia
19.
Metabolism ; 40(6): 629-33, 1991 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-1907712

RESUMO

We have previously reported a decrease in gluconeogenesis from alanine in normal pregnant women at term gestation as compared with nonpregnant women. In the present study, the effect of diabetes on alanine metabolism was examined in five gestationally diabetic (GDM) women and seven women with type I (insulin-dependent) diabetes (IDDM) during the third trimester of pregnancy. The hemoglobin A1c (HbA1c) concentrations in all subjects were within normal range, indicating good metabolic control. After an overnight fast, each subject was infused simultaneously with L-[2,3, 13C2]alanine and D-[6,6,2H2]glucose tracers as prime constant rate infusion. Plasma alanine and glucose isotopic enrichments were measured by gas chromatography-mass spectrometry. Alanine and glucose turnover rates were quantified by tracer dilution. In five subjects, the contribution of alanine carbon to CO2 was quantified by respiratory calorimetry and by measurement of 13C enrichment of expired CO2. Data from 15 previously reported normal pregnant subjects were used for comparison. The rate of alanine turnover was similar in the GDM and IDDM subjects and was not different from the normal subjects (GDM, 4.6 +/- 1.9; IDDM, 5.4 +/- 2.5; normals, 4.4 +/- 0.8 mumol/kg.min, mean +/- SD). The rate of glucose turnover was significantly reduced (P less than .05) in IDDM as compared with GDM and normal subjects (IDDM, 8.1 +/- 0.8; GDM, 11.5 +/- 3.5; normals, 12.2 +/- 2.2 mumol/kg.min). The contribution of alanine C to glucose C and expired CO2 was similar in the three groups. These data demonstrate that rigorous metabolic control results in normal glucose and alanine metabolism in diabetic pregnancy during fasting.(ABSTRACT TRUNCATED AT 250 WORDS)


Assuntos
Alanina/sangue , Glicemia/metabolismo , Diabetes Mellitus Tipo 1/sangue , Gravidez em Diabéticas/sangue , Adulto , Dióxido de Carbono/análise , Feminino , Humanos , Consumo de Oxigênio , Gravidez , Gravidez em Diabéticas/fisiopatologia , Valores de Referência , Respiração
20.
Obstet Gynecol ; 79(4): 592-6, 1992 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-1553183

RESUMO

Polycose, a glucose polymer produced by controlled acid enzyme hydrolysis of starch, has been proposed as an effective substitute for glucose solution in antepartum screening for glucose intolerance. The purposes of this study were to examine the glucose and hormonal responses to 50 g of glucose polymer (polycose) solution in pregnant and nonpregnant women and to compare these with the standard 50-g oral glucose challenge test. In addition, the subject's acceptance of the glucose polymer solution was evaluated. Subjects were examined after an overnight fast following a 3-day dietary preparation. There was no difference in glucose or insulin responses to glucose or polycose in either pregnant or nonpregnant women. In contrast, the gastric inhibitory polypeptide response to polycose was significantly higher than to glucose. No differences were observed in plasma pancreatic polypeptide responses to glucose and polycose. In the pregnant subjects, even though the plasma insulin response to carbohydrate challenge was higher than in the nonpregnant subjects, gastric inhibitory polypeptide levels were significantly lower. Patient satisfaction was similar with both carbohydrate solutions. These data suggest that polycose can be used as a substitute for glucose in antepartum testing, although the differences in the hormonal responses should be recognized. Further studies in a subject population with carbohydrate intolerance will be required before polycose use can be recommended in abnormal states.


Assuntos
Glicemia/análise , Diabetes Gestacional/diagnóstico , Polipeptídeo Inibidor Gástrico/sangue , Glucanos , Insulina/sangue , Polipeptídeo Pancreático/sangue , Adulto , Diabetes Gestacional/sangue , Feminino , Teste de Tolerância a Glucose , Humanos , Satisfação do Paciente , Gravidez
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