Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 8 de 8
Filtrar
Mais filtros










Base de dados
Intervalo de ano de publicação
1.
Geophys Res Lett ; 48(11): e2021GL093419, 2021 Jun 16.
Artigo em Inglês | MEDLINE | ID: mdl-34433990

RESUMO

The annual 14C data in tree rings is an outstanding proxy for uncovering extreme solar energetic particle (SEP) events in the past. Signatures of extreme SEP events have been reported in 774/775 CE, 992/993 CE, and ∼660 BCE. Here, we report another rapid increase of 14C concentration in tree rings from California, Switzerland, and Finland around 5410 BCE. These 14C data series show a significant increase of ∼6‰ in 5411-5410 BCE. The signature of 14C variation is very similar to the confirmed three SEP events and points to an extreme short-term flux of cosmic ray radiation into the atmosphere. The rapid 14C increase in 5411/5410 BCE rings occurred during a period of high solar activity and 60 years after a grand 14C excursion during 5481-5471 BCE. The similarity of our 14C data to previous events suggests that the origin of the 5410 BCE event is an extreme SEP event.

2.
Mol Neurobiol ; 52(3): 1152-1164, 2015 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-25307288

RESUMO

Alpha-synuclein (SNCA) protein aggregation plays a causal role in Parkinson's disease (PD). The SNCA protein modulates neurotransmission via the SNAP receptor (SNARE) complex assembly and presynaptic vesicle trafficking. The striatal presynaptic dopamine deficit is alleviated by treatment with levodopa (L-DOPA), but postsynaptic plastic changes induced by this treatment lead to a development of involuntary movements (dyskinesia). While this process is currently modeled in rodents harboring neurotoxin-induced lesions of the nigrostriatal pathway, we have here explored the postsynaptic supersensitivity of dopamine receptor-mediated signaling in a genetic mouse model of early PD. To this end, we used mice with prion promoter-driven overexpression of A53T-SNCA in the nigrostriatal and corticostriatal projections. At a symptomatic age (18 months), mice were challenged with apomorphine (5 mg/kg s.c.) and examined using both behavioral and molecular assays. After the administration of apomorphine, A53T-transgenic mice showed more severe stereotypic and dystonic movements in comparison with wild-type controls. Molecular markers of extracellular signal-regulated kinase 1 and 2 (ERK1/2) phosphorylation and dephosphorylation, and Fos messenger RNA (mRNA), were examined in striatal tissue at 30 and 100 min after apomorphine injection. At 30 min, wild-type and transgenic mice showed a similar induction of phosphorylated ERK1/2, Dusp1, and Dusp6 mRNA (two MAPK phosphatases). At the same time point, Fos mRNA was induced more strongly in mutant mice than in wild-type controls. At 100 min after apomorphine treatment, the induction of both Fos, Dusp1, and Dusp6 mRNA was significantly larger in mutant mice than wild-type controls. At this time point, apomorphine caused a reduction in phospho-ERK1/2 levels specifically in the transgenic mice. Our results document for the first time a disturbance of ERK1/2 signaling regulation associated with apomorphine-induced involuntary movements in a genetic mouse model of synucleinopathy. This mouse model will be useful to identify novel therapeutic targets that can counteract abnormal dopamine-dependent striatal plasticity during both prodromal and manifest stages of PD.


Assuntos
Apomorfina/toxicidade , Discinesias/etiologia , Locomoção/efeitos dos fármacos , Sistema de Sinalização das MAP Quinases/fisiologia , Transtornos Parkinsonianos/fisiopatologia , Comportamento Estereotipado/efeitos dos fármacos , alfa-Sinucleína/genética , Animais , Corpo Estriado/metabolismo , Corpo Estriado/patologia , Corpo Estriado/fisiopatologia , Modelos Animais de Doenças , Neurônios Dopaminérgicos/patologia , Neurônios Dopaminérgicos/fisiologia , MAP Quinases Reguladas por Sinal Extracelular/metabolismo , Humanos , Sistema de Sinalização das MAP Quinases/efeitos dos fármacos , Sistema de Sinalização das MAP Quinases/genética , Camundongos , Camundongos Transgênicos , Mutação de Sentido Incorreto , Proteínas do Tecido Nervoso/metabolismo , Transtornos Parkinsonianos/genética , Fosforilação/efeitos dos fármacos , Mutação Puntual , Densidade Pós-Sináptica/efeitos dos fármacos , Príons/genética , Regiões Promotoras Genéticas , Processamento de Proteína Pós-Traducional/efeitos dos fármacos , Substância Negra/metabolismo , Substância Negra/fisiopatologia , Transgenes
3.
J Dairy Sci ; 82(4): 756-63, 1999 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-10212462

RESUMO

Two studies were conducted to assess whether routine applications of near infrared reflectance spectroscopy could predict the effects of silage proteolysis on ruminal crude protein (CP) degradation of legume and grass silages. A preliminary study was conducted to assess the effect of laboratory drying method on ruminal CP degradation of silages. Thirty legume and grass silages were freeze-, oven-, or microwave-dried and incubated in situ in the ventral rumen of three ruminally cannulated cows for 24 h. Freeze-drying was considered least likely to alter ruminal CP degradation of the silages; therefore, oven- and microwave-drying were compared using first-order regression with freeze-drying. Oven-drying for 48 h at 55 degrees C compared favorably (R2 = 0.84) with freeze-drying. Microwave-drying resulted in a large bias (2.84 g/10(-1) kg of CP) and was poorly related (R2 = 0.48) to freeze-drying. In a second study, alfalfa and timothy were cut at three maturities and allowed to wilt for 0, 10, 24, 32, 48, and 54 h. Forages were ensiled in triplicate cylindrical mini silos and allowed to ferment for 120 d. After fermentation, silages were oven-dried, ground, and scanned on a near-infrared reflectance spectrophotometer. Duplicate, dried, 2-mm ground silage samples were incubated in the ventral rumen of three ruminally cannulated cows for 24 h. Forage species, maturity, and wilting time significantly affected 24-h ruminal CP degradation of the silages. Near-infrared reflectance spectroscopy accurately predicted (R2 = 0.91) 24-h ruminal CP degradation of silages. Data suggest near-infrared reflectance spectroscopy can accurately assess the effects of forage species, maturity, and wilting time (proteolysis) on 24-h ruminal CP degradation of legume and grass silages.


Assuntos
Bovinos/fisiologia , Proteínas Alimentares/metabolismo , Endopeptidases/metabolismo , Fabaceae/metabolismo , Plantas Medicinais , Poaceae/metabolismo , Rúmen/metabolismo , Animais , Dessecação , Feminino , Manipulação de Alimentos , Liofilização , Temperatura Alta , Micro-Ondas , Silagem , Espectroscopia de Luz Próxima ao Infravermelho
4.
J Dairy Sci ; 82(4): 764-70, 1999 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-10212463

RESUMO

Legume and grass silage samples (n = 121) were collected from commercial forage testing laboratories (trial 1). Samples were dried at 55 degrees C for 48 h, ground, scanned on a near-infrared reflectance spectrophotometer, and analyzed for crude protein (CP), soluble CP, acid detergent fiber (ADF) CP, and neutral detergent fiber (NDF) CP by wet chemistry methods. Sixty samples were selected for calibration development, and the remaining samples were used for equation validation. Near-infrared reflectance spectroscopy accurately predicted the CP content of the silages (R2 = 0.96), but prediction of soluble CP, ADF CP, and NDF CP was markedly less accurate. The coefficients of determination and standard errors of calibration for CP, ADF CP, NDF CP (percentage of DM), and soluble CP (percentage of CP) were as follows (0.96 and 0.80, 0.77 and 0.24, 0.72 and 0.71, and 0.82 and 4.40). In a second study, legume and grass silage samples (n = 32) were dried at 55 degrees C and ground (2 mm). Duplicate dacron bags containing 5 g of silage were incubated in the ventral rumen of three ruminally cannulated cows for 0, 3, 6, 12, 24, 48, and 72 h. In situ protein fractions, including rapidly degraded protein, slowly degraded protein, undegradable protein, degradation rate, and rumen-undegradable protein, were determined. Original samples were reground (1 mm) and scanned. Previously defined near-infrared spectroscopy calibration procedures were conducted. Coefficients of determination for in situ CP fractions were R2 > 0.92 with the exception of degradation rate (R2 = 0.87). Data suggest that in situ protein fractions are better predicted by near-infrared reflectance spectroscopy than by laboratory protein fractions.


Assuntos
Bovinos/metabolismo , Proteínas Alimentares/análise , Fabaceae/química , Plantas Medicinais , Poaceae/química , Silagem/análise , Espectroscopia de Luz Próxima ao Infravermelho , Animais , Proteínas Alimentares/metabolismo , Feminino , Laboratórios , Rúmen/metabolismo
5.
J Dairy Sci ; 82(4): 771-9, 1999 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-10212464

RESUMO

Five trials were conducted to develop a system to estimate rumen-undegradable protein (RUP) of legume and grass silages using near infrared reflectance spectroscopy. In situ procedures were the reference method used to determine silage RUP content. Trials 1, 2, and 3 were devoted to improving in situ procedures. In trial 1, alfalfa silage with and without heat treatment was incubated ruminally in 30 cows. The standard deviation of in situ RUP attributable to cow and diet was 0.82 and 3.80 g/10(-1) kg of crude protein (CP) for the unheated and heated alfalfa, respectively. Based on trial 1, it was determined that 8 cows would be required to establish RUP standards. In trial 2, low (13.3 g/10(-1) kg of CP) and high (44.5 g/10(-1) kg of CP) RUP standards were developed using eight ruminally cannulated cows. In trial 3, 11 new RUP standards were developed by mixing trial 2 RUP standards together. The RUP standards were used to employ a calibration curve technique in ruminally cannulated cows. The technique was employed in four ruminally cannulated cows to estimate RUP contents of 121 silages, and RUP values were used for near-infrared reflectance spectroscopic analysis in trial 4. Trial 4 procedures yielded a calibration for RUP content of silages with an R2 of 0.84 and a standard error of calibration of 1.55 g/10(-1) kg of CP. In trial 5, the equation was tested on 300 silage samples. The mean predicted RUP content was 21.8 g/10(-1) kg of CP. Data suggest near-infrared reflectance spectroscopy can predict RUP content of silages.


Assuntos
Bovinos/metabolismo , Proteínas Alimentares/metabolismo , Digestão , Fabaceae/metabolismo , Plantas Medicinais , Poaceae/metabolismo , Silagem , Animais , Feminino , Medicago sativa , Rúmen/metabolismo , Espectroscopia de Luz Próxima ao Infravermelho
6.
J Dairy Sci ; 80(12): 3308-15, 1997 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-9436113

RESUMO

The objective of this study was to compare utilization of red clover (Trifolium pratense L.) and alfalfa (Medicago sativa L.) by lactating dairy cows. Red clover and alfalfa were harvested and conserved as silage at two maturities in 2 consecutive yr. Each year, diets containing experimental forages and supplemental grain were fed to 16 multiparous Holstein cows in early lactation in a replicated 4 x 4 Latin square lactation trial. Lactation performance and nutrient intake responses caused by forage type (red clover vs. alfalfa), maturity (early vs. late), and equivalent acid detergent fiber (ADF) content (yr 1, late alfalfa vs. late red clover; yr 2, early alfalfa vs. late red clover) were compared. Milk yield was not different between cows fed red clover or alfalfa in yr 1, but milk yield was higher for cows fed red clover in yr 2. When cows were fed alfalfa and red clover with similar ADF content, the milk yield of cows fed red clover was lower than that of cows fed alfalfa in yr 1, and milk yields were similar between cows fed alfalfa and red clover in yr 2. Milk protein yield and percentage were lower for cows fed red clover in yr 1 and 2, respectively. Intake of ADF and neutral detergent fiber was lower for cows fed red clover in both years. When red clover contained the same ADF content as did alfalfa, cows fed red clover ate less ADF, neutral detergent fiber, and dry matter, resulting in lower milk yield potential.


Assuntos
Ração Animal , Fenômenos Fisiológicos da Nutrição Animal , Lactação/fisiologia , Medicago sativa , Silagem , Animais , Bovinos , Fibras na Dieta/administração & dosagem , Fibras na Dieta/metabolismo , Proteínas Alimentares/administração & dosagem , Digestão , Feminino , Fermentação , Concentração de Íons de Hidrogênio , Proteínas do Leite/análise
7.
J Dairy Sci ; 79(11): 2024-31, 1996 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-8961109

RESUMO

Seventy postpubertal Holstein replacement heifers were assigned to one of four treatments to assess effects of accelerated postpubertal growth on performance during first lactation. Heifers were fed control or accelerated diets from 10 mo of age until parturition, and breeding was initiated at 14 or 10 mo of age, respectively. Heifers were also subdivided into two breeding groups (target or delayed) based on normal AI breeding efficiencies. Heifers fed accelerated diets had a higher average daily gain (933 vs. 778 g/d) and calved earlier (21.7 vs. 24.6 mo) than did heifers fed control diets. Heifers fed accelerated diets had similar prepartum (10 d) BW, but lower wither height and postpartum BW, than heifers fed the control. For heifers fed accelerated diets, milk fat and milk protein yields were lower, and milk fat percentage was higher, at mo 1 and 2; milk fat percentage was lower at mo 3 to 7 of lactation. Delayed bred heifers calved later (approximately 2 mo), had higher prepartum and postpartum BW, and were taller at the withers than target bred heifers. Delayed breeding resulted in higher body condition scores at calving and a greater incidence of dystocia, but lactation performance was not affected. Accelerated postpubertal growth resulted in earlier calving at similar prepartum BW, but data for wither height, pelvic area, and postpartum BW suggested that heifers fed accelerated diets were smaller. Accelerated postpubertal growth and early calving reduced performance during first lactation, but the exact mechanisms could not be determined.


Assuntos
Bovinos/crescimento & desenvolvimento , Lactação/fisiologia , Envelhecimento , Ração Animal , Animais , Dieta , Feminino , Metabolismo dos Lipídeos , Leite/metabolismo , Proteínas do Leite/metabolismo , Paridade , Gravidez , Aumento de Peso
8.
Recent Dev Alcohol ; 11: 453-71, 1993.
Artigo em Inglês | MEDLINE | ID: mdl-8234936

RESUMO

A review of the substance abuse literature in the 1980s focuses on deficits in self-regulating capacities, in self-care functions, and in other vulnerabilities of the self, such as an inappropriate use of defenses and problems in intimacy. Various models which attempt to explain these behaviors are described, as well as techniques of dynamic psychotherapy for substance abuse, which emphasize the building of ego functions and the internalization of self-preservation functions. Commonalities and differences of substance abuse with other intensely driven compulsive behaviors (e.g., pathological gambling or certain sexual behaviors) are also considered.


Assuntos
Alcoolismo/reabilitação , Terapia Psicanalítica , Alcoolismo/psicologia , Ego , Humanos , Controle Interno-Externo , Apego ao Objeto , Desenvolvimento da Personalidade , Teoria Psicanalítica
SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA
...