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1.
Cell Mol Life Sci ; 80(8): 225, 2023 Jul 23.
Artigo em Inglês | MEDLINE | ID: mdl-37481766

RESUMO

Adult hippocampal neurogenesis enhances brain plasticity and contributes to the cognitive reserve during aging. Adult hippocampal neurogenesis is impaired in neurological disorders, yet the molecular mechanisms regulating the maturation and synaptic integration of new neurons have not been fully elucidated. GABA is a master regulator of adult and developmental neurogenesis. Here we engineered a novel retrovirus encoding the fusion protein Gephyrin:GFP to longitudinally study the formation and maturation of inhibitory synapses during adult hippocampal neurogenesis in vivo. Our data reveal the early assembly of inhibitory postsynaptic densities at 1 week of cell age. Glycogen synthase kinase 3 Beta (GSK-3ß) emerges as a key regulator of inhibitory synapse formation and maturation during adult hippocampal neurogenesis. GSK-3ß-overexpressing newborn neurons show an increased number and altered size of Gephyrin+ postsynaptic clusters, enhanced miniature inhibitory postsynaptic currents, shorter and distanced axon initial segments, reduced synaptic output at the CA3 and CA2 hippocampal regions, and impaired pattern separation. Moreover, GSK-3ß overexpression triggers a depletion of Parvalbumin+ interneuron perineuronal nets. These alterations might be relevant in the context of neurological diseases in which the activity of GSK-3ß is dysregulated.


Assuntos
Hipocampo , Neurônios , Humanos , Recém-Nascido , Encéfalo/metabolismo , Glicogênio Sintase Quinase 3 beta/genética , Glicogênio Sintase Quinase 3 beta/metabolismo , Hipocampo/metabolismo , Neurogênese , Neurônios/metabolismo , Adulto
2.
Am J Physiol Heart Circ Physiol ; 325(2): H232-H243, 2023 08 01.
Artigo em Inglês | MEDLINE | ID: mdl-37327000

RESUMO

We tested the hypothesis that hyperandrogenemia in androgen excess polycystic ovary syndrome (AE-PCOS) is a primary driver in blood pressure (BP) dysregulation via altered sympathetic nervous system activity (SNSA), reduced integrated baroreflex gain and increased renin-angiotensin system (RAS) activation. We measured resting SNSA (microneurography), integrated baroreflex gain, and RAS with lower body negative pressure in obese insulin-resistant (IR) women with AE-PCOS [n = 8, 23 ± 4 yr; body mass index (BMI) = 36.3 ± 6.4 kg/m2] and obese IR controls (n = 7, control, 29 ± 7 yr; BMI = 34.9 ± 6.8 kg/m2), at baseline (BSL), after 4 days of gonadotropin-releasing hormone antagonist (ANT, 250 µg/day) and 4 days of ANT + testosterone (ANT + T, 5 mg/day) administration. Resting BP was similar between groups for systolic blood pressure (SBP; 137 ± 14 vs. 135 ± 14 mmHg, AE-PCOS, control) and diastolic BP (89 ± 21 vs. 76 ± 10 mmHg, AE-PCOS, control). BSL integrated baroreflex gain was similar between groups [1.4 ± 0.9 vs. 1.0 ± 1.3 forearm vascular resistance (FVR) U/mmHg], but AE-PCOS had lower SNSA (10.3 ± 2.0 vs. 14.4 ± 4.4 burst/100 heartbeats, P = 0.04). In AE-PCOS, T suppression increased integrated baroreflex gain, which was restored to BSL with ANT + T (4.3 ± 6.5 vs. 1.5 ± 0.8 FVR U/mmHg, ANT, and ANT + T, P = 0.04), with no effect in control. ANT increased SNSA in AE-PCOS (11.2 ± 2.4, P = 0.04). Serum aldosterone was greater in AE-PCOS versus control (136.5 ± 60.2 vs. 75.7 ± 41.4 pg/mL, AE-PCOS, control, P = 0.04) at BSL but was unaffected by intervention. Serum angiotensin-converting enzyme was greater in AE-PCOS versus control (101.9 ± 93.4 vs. 38.2 ± 14.7 pg/mL, P = 0.04) and reduced by ANT in AE-PCOS (77.7 ± 76.5 vs. 43.4 ± 27.3 µg/L, ANT, and ANT + T, P = 0.04) with no impact on control. Obese, IR women with AE-PCOS showed decreased integrated baroreflex gain and increased RAS activation compared with control.NEW & NOTEWORTHY Here we present evidence for an important role of testosterone in baroreflex control of blood pressure and renal responses to baroreceptor unloading in women with a common, high-risk androgen excess polycystic ovary syndrome (AE-PCOS) phenotype. These data indicate a direct effect of testosterone on the vascular system of women with AE-PCOS independent of body mass index (BMI) and insulin-resistant (IR). Our study indicates that hyperandrogenemia is a central underlining mechanism of heightened cardiovascular risk in women with PCOS.


Assuntos
Androgênios , Pressão Sanguínea , Resistência à Insulina , Síndrome do Ovário Policístico , Testosterona , Feminino , Humanos , Androgênios/sangue , Índice de Massa Corporal , Insulina , Resistência à Insulina/fisiologia , Obesidade/complicações , Síndrome do Ovário Policístico/complicações
3.
J Org Chem ; 88(4): 2453-2463, 2023 Feb 17.
Artigo em Inglês | MEDLINE | ID: mdl-36749161

RESUMO

Fluorescent unnatural α-amino acids are widely used as probes in chemical biology and medicinal chemistry. While a variety of structural classes have been developed, there is still a requirement for new environmentally sensitive analogues that can closely mimic proteinogenic α-amino acids. Here, we report the synthesis and fluorescent properties of highly conjugated, benzotriazole-derived α-amino acids designed to mimic l-tryptophan. Alkynyl-substituted analogues were prepared using three key steps, nucleophilic aromatic substitution with a 3-aminoalanine derivative, benzotriazole formation via a one-pot diazotization and cyclization process, and a Sonogashira cross-coupling reaction. E-Alkenyl-substituted benzotriazoles were accessed by stereoselective partial hydrogenation of the alkynes using zinc iodide and palladium catalysis. The alkynyl analogues were found to possess higher quantum yields and stronger brightness and, a solvatochromic study with the most fluorogenic α-amino acids demonstrated sensitivity to polarity.

4.
Sci Adv ; 6(35): eaba8271, 2020 08.
Artigo em Inglês | MEDLINE | ID: mdl-32923630

RESUMO

Neurodegeneration in mitochondrial disorders is considered irreversible because of limited metabolic plasticity in neurons, yet the cell-autonomous implications of mitochondrial dysfunction for neuronal metabolism in vivo are poorly understood. Here, we profiled the cell-specific proteome of Purkinje neurons undergoing progressive OXPHOS deficiency caused by disrupted mitochondrial fusion dynamics. We found that mitochondrial dysfunction triggers a profound rewiring of the proteomic landscape, culminating in the sequential activation of precise metabolic programs preceding cell death. Unexpectedly, we identified a marked induction of pyruvate carboxylase (PCx) and other anaplerotic enzymes involved in replenishing tricarboxylic acid cycle intermediates. Suppression of PCx aggravated oxidative stress and neurodegeneration, showing that anaplerosis is protective in OXPHOS-deficient neurons. Restoration of mitochondrial fusion in end-stage degenerating neurons fully reversed these metabolic hallmarks, thereby preventing cell death. Our findings identify a previously unappreciated pathway conferring resilience to mitochondrial dysfunction and show that neurodegeneration can be reversed even at advanced disease stages.


Assuntos
Mitocôndrias , Doenças Mitocondriais , Ciclo do Ácido Cítrico , Humanos , Mitocôndrias/metabolismo , Neurônios/metabolismo , Proteômica
5.
PLoS One ; 15(6): e0234542, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32555702

RESUMO

Staphylococcus aureus is one of the principal causative agents of bacteremia which can progress to sepsis. Rapid diagnostic tests for identification and antibiotic resistance profiling of S. aureus would improve patient outcomes and antibiotic stewardship, but existing methods require a lengthy culture step to obtain enough material for testing. Complexity of the host matrix, where pathogenic microbes are often present, also interferes with many diagnostic methods. Here, we describe a straightforward and rapid method for enriching viable S. aureus using bio-orthogonal, or "click," chemistry methods. Bacteria labeled in this manner can potentially be cultured, interrogated using molecular methods for pathogen identification, or used to test antibiotic susceptibility.


Assuntos
Técnicas Bacteriológicas , Sepse/diagnóstico , Infecções Estafilocócicas/diagnóstico , Staphylococcus aureus/isolamento & purificação , Testes Diagnósticos de Rotina , Farmacorresistência Bacteriana , Humanos , Sepse/microbiologia , Infecções Estafilocócicas/microbiologia , Staphylococcus aureus/patogenicidade , Propriedades de Superfície
6.
Mol Psychiatry ; 25(7): 1382-1405, 2020 07.
Artigo em Inglês | MEDLINE | ID: mdl-31222184

RESUMO

A decrease in adult hippocampal neurogenesis has been linked to age-related cognitive impairment. However, the mechanisms involved in this age-related reduction remain elusive. Glucocorticoid hormones (GC) are important regulators of neural stem/precursor cells (NSPC) proliferation. GC are released from the adrenal glands in ultradian secretory pulses that generate characteristic circadian oscillations. Here, we investigated the hypothesis that GC oscillations prevent NSPC activation and preserve a quiescent NSPC pool in the aging hippocampus. We found that hippocampal NSPC populations lacking expression of the glucocorticoid receptor (GR) decayed exponentially with age, while GR-positive populations decayed linearly and predominated in the hippocampus from middle age onwards. Importantly, GC oscillations controlled NSPC activation and GR knockdown reactivated NSPC proliferation in aged mice. When modeled in primary hippocampal NSPC cultures, GC oscillations control cell cycle progression and induce specific genome-wide DNA methylation profiles. GC oscillations induced lasting changes in the methylation state of a group of gene promoters associated with cell cycle regulation and the canonical Wnt signaling pathway. Finally, in a mouse model of accelerated aging, we show that disruption of GC oscillations induces lasting changes in dendritic complexity, spine numbers and morphology of newborn granule neurons. Together, these results indicate that GC oscillations preserve a population of GR-expressing NSPC during aging, preventing their activation possibly by epigenetic programming through methylation of specific gene promoters. Our observations suggest a novel mechanism mediated by GC that controls NSPC proliferation and preserves a dormant NSPC pool, possibly contributing to a neuroplasticity reserve in the aging brain.


Assuntos
Envelhecimento/metabolismo , Encéfalo/metabolismo , Ritmo Circadiano , Glucocorticoides/metabolismo , Hipocampo/citologia , Células-Tronco Neurais/metabolismo , Animais , Encéfalo/citologia , Proliferação de Células , Masculino , Camundongos , Neurogênese , Receptores de Glucocorticoides/metabolismo
7.
Toxicol In Vitro ; 38: 124-135, 2017 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-27729293

RESUMO

Alternative models for more rapid compound safety testing are of increasing demand. With emerging techniques using human pluripotent stem cells, the possibility of generating human in vitro models has gained interest, as factors related to species differences could be potentially eliminated. When studying potential neurotoxic effects of a compound it is of crucial importance to have both neurons and glial cells. We have successfully developed a protocol for generating in vitro 3D human neural tissues, using neural progenitor cells derived from human embryonic stem cells. These 3D neural tissues can be maintained for two months and undergo progressive differentiation. We showed a gradual decreased expression of early neural lineage markers, paralleled by an increase in markers specific for mature neurons, astrocytes and oligodendrocytes. At the end of the two-month culture period the neural tissues not only displayed synapses and immature myelin sheaths around axons, but electrophysiological measurements also showed spontaneous activity. Neurotoxicity testing - comparing non-neurotoxic to known neurotoxic model compounds - showed an expected increase in the marker of astroglial reactivity after exposure to known neurotoxicants methylmercury and trimethyltin. Although further characterization and refinement of the model is required, these results indicate its potential usefulness for in vitro neurotoxicity testing.


Assuntos
Astrócitos/citologia , Células-Tronco Embrionárias Humanas/citologia , Células-Tronco Neurais/citologia , Oligodendroglia/citologia , Técnicas de Cultura de Células , Diferenciação Celular , Linhagem Celular , Expressão Gênica/efeitos dos fármacos , Humanos , Ibuprofeno/toxicidade , Compostos de Metilmercúrio/toxicidade , Paraquat/toxicidade , RNA Mensageiro/metabolismo , Esferoides Celulares/citologia , Esferoides Celulares/efeitos dos fármacos , Esferoides Celulares/metabolismo , Esferoides Celulares/ultraestrutura , Técnicas de Cultura de Tecidos , Compostos de Trimetilestanho/toxicidade
8.
PLoS One ; 9(8): e105253, 2014.
Artigo em Inglês | MEDLINE | ID: mdl-25157946

RESUMO

Progesterone withdrawal is essential for parturition, but the mechanism of this pivotal hormonal change is unclear in women and other mammals that give birth without a pre-labor drop in maternal progesterone levels. One possibility suggested by uterine tissue analyses and cell culture models is that progesterone receptor levels change at term decreasing the progesterone responsiveness of the myometrium, which causes progesterone withdrawal at the functional level and results in estrogen dominance enhancing uterine contractility. In this investigation we have explored whether receptor mediated functional progesterone withdrawal occurs during late pregnancy and labor in vivo. We have also determined whether prostaglandins that induce labor cause functional progesterone withdrawal by altering myometrial progesterone receptor expression. Pregnant guinea pigs were used, since this animal loses progesterone responsiveness at term and gives birth in the presence of high maternal progesterone level similarly to primates. We found that progesterone receptor mRNA and protein A and B expression decreased in the guinea pig uterus during the last third of gestation and in labor. Prostaglandin administration reduced while prostaglandin synthesis inhibitor treatment increased progesterone receptor A protein abundance. Estrogen receptor-1 protein levels remained unchanged during late gestation, in labor and after prostaglandin or prostaglandin synthesis inhibitor administration. Steroid receptor levels were higher in the non-pregnant than in the pregnant uterine horns. We conclude that the decreasing expression of both progesterone receptors A and B is a physiological mechanism of functional progesterone withdrawal in the guinea pig during late pregnancy and in labor. Further, prostaglandins administered exogenously or produced endogenously stimulate labor in part by suppressing uterine progesterone receptor A expression, which may cause functional progesterone withdrawal, promote estrogen dominance and foster myometrial contractions.


Assuntos
Cobaias/fisiologia , Prenhez/fisiologia , Progesterona/metabolismo , Prostaglandinas/farmacologia , Receptores de Progesterona/genética , Útero/fisiologia , Animais , Regulação para Baixo/efeitos dos fármacos , Feminino , Trabalho de Parto , Miométrio/fisiologia , Parto , Gravidez , Prostaglandinas/administração & dosagem , Receptores de Progesterona/metabolismo , Contração Uterina
9.
Reprod Sci ; 21(2): 269-76, 2014 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-23885103

RESUMO

Intrauterine growth restriction (IUGR) is a risk factor for preterm labor; however, the mechanisms of the relationship remain unknown. Prostaglandin (PG), key stimulants of labor, availability is regulated by the synthetic enzymes, prostaglandin endoperoxidases 1 and 2 (PTGS1 and 2), and the metabolizing enzyme, 15-hydroxyprostaglandin dehydrogenase (HPGD). We hypothesized that IUGR increases susceptibility to preterm labor due to the changing balance of synthetic and metabolizing enzymes and hence greater PG availability. We have tested this hypothesis using a surgically induced IUGR model in guinea pigs, which results in significantly shorter gestation. Myometrium, amnion, chorion, and placentas were collected from sham operated or IUGR pregnancies, and PTGS1 and HPGD protein expression were quantified throughout late gestation (>62 days) and labor. The PTGS1 expression was significantly upregulated in the myometrium of IUGR animals, and chorionic HPGD expression was markedly decreased (P < .01 and P < .001, respectively). These findings suggest a shift in the balance of PG production over metabolism in IUGR pregnancies leads to a greater susceptibility to preterm birth.


Assuntos
Retardo do Crescimento Fetal/diagnóstico , Retardo do Crescimento Fetal/metabolismo , Nascimento Prematuro/diagnóstico , Nascimento Prematuro/metabolismo , Animais , Animais Recém-Nascidos , Feminino , Cobaias , Gravidez , Nascimento Prematuro/etiologia
10.
Expert Rev Anticancer Ther ; 13(9): 1065-72, 2013 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-24053205

RESUMO

Concurrent chemoradiation is considered the standard-of-care for locally advanced head and neck cancer of the hypopharynx, oropharynx and larynx, as well as unresectable disease. This paradigm was challenged by the introduction of induction chemotherapy (IC), which demonstrated non-inferiority in regards of overall survival (OS), along with increased organ preservation, when compared to the surgery and radiotherapy. More recently, IC followed by concurrent chemoradiation, the so-called sequential approach was developed in an attempt to decrease metastatic spread and improve locoregional control (LRC) rates, with much controversy amongst experts. A careful evaluation by a multidisciplinary team is necessary to recognize which patients should be offered this therapeutic approach due to a significantly greater rate of toxicity. Herein, we analyze the most current available evidence regarding the use of sequential therapy versus concurrent chemoradiation. Different factors including toxicity profile, adherence and patient characteristics play a major role in choosing the most appropriate treatment regimen.


Assuntos
Neoplasias de Cabeça e Pescoço/terapia , Quimiorradioterapia/métodos , Humanos , Quimioterapia de Indução/métodos
11.
Semin Cell Dev Biol ; 18(3): 321-31, 2007 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-17613262

RESUMO

The precise temporal control of uterine contractility is essential for the success of pregnancy. For most of pregnancy, progesterone acting through genomic and non-genomic mechanisms promotes myometrial relaxation. At parturition the relaxatory actions of progesterone are nullified and the combined stimulatory actions of estrogens and other factors such as myometrial distention and immune/inflammatory cytokines, transform the myometrium to a highly contractile and excitable state leading to labor and delivery. This review addresses current understanding of how progesterone and estrogens affect the contractility of the pregnancy myometrium and how their actions are coordinated and controlled as part of the parturition cascade.


Assuntos
Estrogênios/metabolismo , Miométrio/fisiologia , Parto , Progesterona/metabolismo , Contração Uterina , Animais , Feminino , Expressão Gênica , Humanos , Receptores de Progesterona/metabolismo
12.
Prostaglandins Other Lipid Mediat ; 83(4): 304-10, 2007 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-17499750

RESUMO

The primary prostaglandins PGE(2) and PGF(2 alpha) are metabolized in tissues by a series of enzymatic and non-enzymatic reactions. To measure metabolic rates and individual reaction rates it is necessary to extract the parent prostaglandins and metabolites before the separation and quantification of each compound is achieved. Here we have established and optimized a solid phase extraction (SPE) procedure to recover PGE(2), PGF(2 alpha) and their six enzymatic and non-enzymatic tissue metabolites from aqueous solutions including urine, plasma and tissue homogenate. We have used octadecyl-bonded silica gel as the stationary phase and methanol-water mixtures as binary mobile phases. The volumes and concentrations of the washing and elution solutions were optimized individually for each PG. Recoveries of all PG standards were quantitative except for PGEM, which was recovered at 80% efficiency. Biological matrix components interfered with the extraction in a PG- and matrix-specific fashion. Inclusion of 1% formic acid in the loading mixture raised recoveries from urine, plasma and tissue homogenate to >or=90%. This SPE method is the first that has been optimized by systematic elution studies for PGE(2), PGF(2 alpha) and the complement of their tissue metabolites. The procedure is simple, robust and can serve as an effective pre-purification step before downstream separation and quantification of each tissue metabolite of PGE(2) and PGF(2 alpha) from complex biological matrices.


Assuntos
Dinoprosta/isolamento & purificação , Dinoprostona/isolamento & purificação , Extração em Fase Sólida/métodos , Cromatografia em Camada Fina , Dinoprosta/química , Dinoprosta/metabolismo , Dinoprostona/química , Dinoprostona/metabolismo , Humanos , Estrutura Molecular , Reprodutibilidade dos Testes
13.
J Clin Endocrinol Metab ; 92(5): 1927-33, 2007 May.
Artigo em Inglês | MEDLINE | ID: mdl-17341556

RESUMO

CONTEXT: We examined whether human parturition involves functional progesterone withdrawal mediated by changes in myometrial expression of progesterone receptors (PRs)-A and -B. OBJECTIVE: Our objectives were to: 1) measure PR-A and PR-B protein levels in human pregnancy myometrium and determine whether the PR-A to PR-B ratio changes with advancing gestation and labor onset; and 2) determine how changes in the PR-A to PR-B ratio affect myometrial cell progesterone responsiveness. DESIGN: PR protein levels and cellular localization were measured by Western blotting and immunohistochemistry, respectively, in lower uterine segment uterine wall tissue from preterm (<37 wk; not laboring; n = 5) and term (37-40 wk; not in labor: n = 6; in labor: n = 5) cesarean delivery. The capacity for PR-A and PR-B, alone and in combination, to mediate genomic progesterone responsiveness measured by the activity of a progesterone-responsive reporter plasmid was examined by artificially modulating their levels in the PHM1-31 myometrial cell line. RESULTS: PR-A and PR-B immunostaining was detected only in the nucleus of myometrial cells. The PR-A to PR-B protein ratio was 0.49 +/- 0.082 (mean +/- sem) in preterm tissue; increased to 1.03 +/- 0.071 (P < 0.001) in nonlaboring term tissue; and increased further to 2.65 +/- 0.344 (P < 0.001) in laboring term tissue. Only PR-B mediated progesterone-induced transcriptional activity. PR-A had no effect alone but markedly decreased PR-B-mediated progesterone responsiveness. CONCLUSIONS: Functional progesterone withdrawal in human parturition may be mediated by an increase in the myometrial PR-A to PR-B ratio due to increased PR-A expression.


Assuntos
Núcleo Celular/metabolismo , Miométrio/metabolismo , Parto/fisiologia , Gravidez/metabolismo , Progesterona/fisiologia , Receptores Citoplasmáticos e Nucleares/metabolismo , Receptores de Progesterona/biossíntese , Adulto , Western Blotting , Linhagem Celular , Feminino , Humanos , Imuno-Histoquímica , Miométrio/citologia , Plasmídeos/genética , RNA Interferente Pequeno/genética , Transfecção
14.
Intensive Care Med ; 32(7): 1022-9, 2006 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-16791664

RESUMO

OBJECTIVES: We aimed to characterise and quantify the incidence of common infectious agents in acute exacerbations of chronic obstructive pulmonary disease (COPD) requiring ventilation, with a focus on respiratory viruses. DESIGN: An epidemiological study conducted over 3 years. SETTING: A 12-bed intensive care unit (ICU). PARTICIPANTS: ICU patients over 45 years of age with a primary diagnosis of COPD exacerbation requiring non-invasive ventilation (NIV) or ventilation via endotracheal tube (ETT). MATERIALS AND METHODS: Nasopharyngeal aspirates (NPA) and posterior pharyngeal swabs (PS) were tested for viruses with immunofluorescence assay (IFA), virus culture (VC) and polymerase chain reaction (PCR). Paired virus and atypical pneumonia serology assays were taken. Blood, sputum and endotracheal aspirates were cultured for bacteria. RESULTS: 107 episodes in 105 patients were recorded. Twenty-three (21%) died within 28[Symbol: see text]days. A probable infectious aetiology was found in 69 patient episodes (64%). A virus was identified in 46 cases (43%), being the sole organism in 35 cases (33%) and part of a mixed infection in 11 cases (10%). A probable bacterial aetiology was found in 25 cases (23%). There was no statistically significant difference in clinical characteristics or outcomes between the group with virus infections and that without. CONCLUSION: Forty-six (43%) of the patients with COPD exacerbation requiring mechanical ventilation had a probable viral pathogen. Prodromal, clinical and outcome parameters did not distinguish virus from non-virus illness. PCR was the most sensitive whilst virus culture was the least of virus assays.


Assuntos
Doença Pulmonar Obstrutiva Crônica/terapia , Doença Pulmonar Obstrutiva Crônica/virologia , Respiração Artificial , Viroses/complicações , Idoso , Distribuição de Qui-Quadrado , Feminino , Humanos , Incidência , Intubação Intratraqueal , Masculino , Pessoa de Meia-Idade , Reação em Cadeia da Polimerase , Estatísticas não Paramétricas , Viroses/diagnóstico , Viroses/epidemiologia
16.
J Neurosci ; 21(16): 6245-51, 2001 Aug 15.
Artigo em Inglês | MEDLINE | ID: mdl-11487647

RESUMO

Several morphological changes of synapses have been reported to be associated with the induction of long-term potentiation (LTP) in the CA1 hippocampus, including an transient increase in the proportion of synapses with perforated postsynaptic densities (PSDs) and a later occurrence of multiple spine boutons (MSBs) in which the two spines arise from the same dendrite. To investigate the functional significance of these modifications, we analyzed single sections and reconstructed 134 synapses labeled via activity using a calcium precipitation approach. Analyses of labeled spine profiles showed changes of the spine head area, PSD length, and proportion of spine profiles containing a coated vesicle that reflected variations in the relative proportion of different types of synapses. Three-dimensional reconstruction indicated that the increase of perforated spine profiles observed 30 min after LTP induction essentially resulted from synapses exhibiting segmented, completely partitioned PSDs. These synapses had spine head and PSD areas approximately three times larger than those of simple synapses. They contained coated vesicles in a much higher proportion than that of any other type of synapse and exhibited large spinules associated with the PSD. Also the MSBs with two spines arising from the same dendrite that were observed 1-2 hr after LTP induction included a spine that was smaller and a PSD that was smaller than those of simple synapses. These results support the idea that LTP induction is associated with an enhanced recycling of synaptic membrane and that this process could underlie the formation of synapses with segmented PSDs and eventually result in the formation of a new, immature spine.


Assuntos
Extensões da Superfície Celular/ultraestrutura , Potenciação de Longa Duração/fisiologia , Sinapses/ultraestrutura , Membranas Sinápticas/ultraestrutura , Animais , Cálcio/metabolismo , Extensões da Superfície Celular/metabolismo , Vesículas Revestidas/ultraestrutura , Dendritos/metabolismo , Dendritos/ultraestrutura , Estimulação Elétrica , Hipocampo/metabolismo , Hipocampo/ultraestrutura , Técnicas In Vitro , Microscopia Eletrônica , Plasticidade Neuronal/fisiologia , Ratos , Sinapses/metabolismo , Membranas Sinápticas/metabolismo
17.
Hippocampus ; 10(5): 596-604, 2000.
Artigo em Inglês | MEDLINE | ID: mdl-11075830

RESUMO

High-frequency stimulation of excitatory synapses in many regions of the brain triggers a lasting increase in the efficacy of synaptic transmission referred to as long-term potentiation (LTP) and believed to contribute to learning and memory. One hypothesis proposed to account for the stability and properties of this functional plasticity is a structural remodeling of spine synapses. This possibility has recently received support from several studies. It has been found that spines are highly dynamic structures, that they can be formed very rapidly, and that synaptic activity and calcium modulate changes in spine shape and formation of new spines. Ultrastructural analyses bring additional support to these observations and suggest that LTP is associated with a remodeling of the postsynaptic density (PSD) and a process of spine duplication. This new information is reviewed and interpreted in light of other recent advances concerning the mechanisms of LTP and especially the role of postsynaptic glutamate receptor turnover in this form of plasticity. Taken together, a view is emerging that suggests that morphologic changes of spine synapses are associated with LTP and that they not only correlate with, but probably also contribute to the increase in synaptic transmission.


Assuntos
Dendritos/fisiologia , Hipocampo/fisiologia , Potenciação de Longa Duração/fisiologia , Plasticidade Neuronal/fisiologia , Animais , Dendritos/ultraestrutura , Hipocampo/ultraestrutura , Sinapses/fisiologia
18.
Br J Pharmacol ; 131(4): 721-8, 2000 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-11030721

RESUMO

Apoptosis and mitochondrial dysfunction are thought to be involved in the aetiology of neurodegenerative diseases. We have tested an orally active anti-apoptotic molecule (CGP 3466B) that binds to glyceraldehyde-3-phosphate dehydrogenase (GAPDH) in an animal model with motoneuron degeneration, i.e. a mouse mutant with progressive motor neuronopathy (pmn). In pmn/pmn mice, CGP 3466B was administered orally (10 - 100 nmol kg(-1)) at the onset of the clinical symptoms (2 weeks after birth). CGP 3466B slowed disease progression as determined by a 57% increase in life-span, preservation of body weight and motor performance. This improvement was accompanied by a decreased loss of motoneurons and motoneuron fibres as well as an increase in retrograde transport. Electron microscopic analysis showed that CGP 3466B protects mitochondria which appear to be selectively disrupted in the motoneurons of pmn/pmn mice. The data support evaluation of CGP 3466B as a potential treatment for motor neuron disease.


Assuntos
Apoptose/efeitos dos fármacos , Modelos Animais de Doenças , Mitocôndrias/efeitos dos fármacos , Doença dos Neurônios Motores/tratamento farmacológico , Fatores de Crescimento Neural , Oxepinas/farmacologia , Administração Oral , Animais , Fator Neurotrófico Derivado de Linhagem de Célula Glial , Gliceraldeído-3-Fosfato Desidrogenases/metabolismo , Camundongos , Doença dos Neurônios Motores/mortalidade , Neurônios Motores/efeitos dos fármacos , Proteínas do Tecido Nervoso/farmacologia , Redução de Peso/efeitos dos fármacos
19.
Anesthesiology ; 92(5): 1408-17, 2000 May.
Artigo em Inglês | MEDLINE | ID: mdl-10781288

RESUMO

BACKGROUND: Propofol is a widely used anesthetic agent for adults and children. Although extensive clinical use has demonstrated its safety, neurologic dysfunctions have been described after the use of this agent. A recent study on a model of aggregating cell cultures reported that propofol might cause irreversible lesions of gamma-aminobutyric acid-mediated (GABAergic) neurons when administered at a critical phase of brain development. We investigated this issue by comparing the effects of long-term propofol treatment on two models of brain cultures: dissociated neonatal cortical cell cultures and organotypic slice cultures. METHODS: Survival of GABAergic neurons in dissociated cultures of newborn rat cortex (postnatal age, 1 day) treated for 3 days with different concentrations of propofol was assessed using histologic and cytochemical methods. For hippocampal organotypic slice cultures (postnatal age, 1 and 7 days), cell survival was assessed by measuring functional and morphologic parameters: extracellular and intracellular electrophysiology, propidium staining of dying cells, and light and electron microscopy. RESULTS: In dissociated neonatal cell cultures, propofol induced dose-dependent lesions of GABAergic neurons and of glial cells. In contrast, no evidence for neurotoxic effects of propofol were found after long-term treatment of organotypic slice cultures. Excitatory transmission was not affected by propofol, and inhibitory transmission was still functional. Histologic preparations showed no evidence for cell degeneration or death. CONCLUSION: Although long-term applications of propofol to dissociated cortical cell cultures produced degeneration and death of GABAergic neurons and glial cells, no such lesions were found when using a model of postnatal organotypic slice cultures. This conclusion is based on both functional and morphologic tests.


Assuntos
Anestésicos Intravenosos/toxicidade , Córtex Cerebral/efeitos dos fármacos , Hipocampo/efeitos dos fármacos , Propofol/toxicidade , Animais , Animais Recém-Nascidos , Morte Celular/efeitos dos fármacos , Células Cultivadas , Córtex Cerebral/citologia , Córtex Cerebral/fisiologia , Técnicas de Cultura , Relação Dose-Resposta a Droga , Eletrofisiologia , Hipocampo/citologia , Hipocampo/fisiologia , Potenciais da Membrana/efeitos dos fármacos , Neurônios/citologia , Neurônios/efeitos dos fármacos , Técnicas de Patch-Clamp , Ratos , Ratos Sprague-Dawley , Receptores de GABA-A/efeitos dos fármacos
20.
Nature ; 402(6760): 421-5, 1999 Nov 25.
Artigo em Inglês | MEDLINE | ID: mdl-10586883

RESUMO

Structural remodelling of synapses and formation of new synaptic contacts has been postulated as a possible mechanism underlying the late phase of long-term potentiation (LTP), a form of plasticity which is involved in learning and memory. Here we use electron microscopy to analyse the morphology of synapses activated by high-frequency stimulation and identified by accumulated calcium in dendritic spines. LTP induction resulted in a sequence of morphological changes consisting of a transient remodelling of the postsynaptic membrane followed by a marked increase in the proportion of axon terminals contacting two or more dendritic spines. Three-dimensional reconstruction revealed that these spines arose from the same dendrite. As pharmacological blockade of LTP prevented these morphological changes, we conclude that LTP is associated with the formation of new, mature and probably functional synapses contacting the same presynaptic terminal and thereby duplicating activated synapses.


Assuntos
Axônios/fisiologia , Dendritos/fisiologia , Potenciação de Longa Duração/fisiologia , Sinapses/fisiologia , Axônios/ultraestrutura , Cálcio/metabolismo , Dendritos/ultraestrutura , Hipocampo/fisiologia , Hipocampo/ultraestrutura , Técnicas de Cultura de Órgãos , Sinapses/ultraestrutura , Fatores de Tempo
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