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1.
Sci Total Environ ; 849: 157921, 2022 Nov 25.
Artigo em Inglês | MEDLINE | ID: mdl-35952865

RESUMO

One of the main contributors to pharmaceutical pollution of surface waters are non-steroidal anti-inflammatory drugs (NSAIDs) that contaminate the food chain and affect non-target water species. As there are not many studies focusing on toxic effects of NSAIDs on freshwater fish species and specially effects after dietary exposure, we selected rainbow trout (Oncorhynchus mykiss) as the ideal model to examine the impact of two NSAIDs - diclofenac (DCF) and ibuprofen (IBP). The aim of our study was to test toxicity of environmentally relevant concentrations of these drugs together with exposure doses of 100× higher, including their mixture; and to deepen knowledge about the mechanism of toxicity of these drugs. This study revealed kidneys as the most affected organ with hyalinosis, an increase in oxidative stress markers, and changes in gene expression of heat shock protein 70 to be signs of renal toxicity. Furthermore, hepatotoxicity was confirmed by histopathological analysis (i.e. dystrophy, congestion, and inflammatory cell increase), change in biochemical markers, increase in heat shock protein 70 mRNA, and by oxidative stress analysis. The gills were locally deformed and showed signs of inflammatory processes and necrotic areas. Given the increase in oxidative stress markers and heat shock protein 70 mRNA, severe impairment of oxygen transport may be one of the toxic pathways of NSAIDs. Regarding the microbiota, an overgrowth of Gram-positive species was detected; in particular, significant dysbiosis in the Fusobacteria/Firmicutes ratio was observed. In conclusion, the changes observed after dietary exposure to NSAIDs can influence the organism homeostasis, induce ROS production, potentiate inflammations, and cause gut dysbiosis. Even the environmentally relevant concentration of NSAIDs pose a risk to the aquatic ecosystem as it changed O. mykiss health parameters and we assume that the toxicity of NSAIDs manifests itself at the level of mitochondria and proteins.


Assuntos
Microbioma Gastrointestinal , Oncorhynchus mykiss , Poluentes Químicos da Água , Animais , Anti-Inflamatórios não Esteroides/metabolismo , Biomarcadores/metabolismo , Diclofenaco/metabolismo , Surtos de Doenças , Disbiose , Ecossistema , Proteínas de Choque Térmico HSP70/metabolismo , Ibuprofeno/metabolismo , Ibuprofeno/toxicidade , Inflamação/induzido quimicamente , Oncorhynchus mykiss/metabolismo , Estresse Oxidativo , Oxigênio/metabolismo , Preparações Farmacêuticas/metabolismo , RNA Mensageiro/metabolismo , Espécies Reativas de Oxigênio/metabolismo , Água/metabolismo , Poluentes Químicos da Água/metabolismo
2.
Physiol Res ; 69(Suppl 4): S595-S606, 2020 Dec 31.
Artigo em Inglês | MEDLINE | ID: mdl-33656906

RESUMO

In the present study, the effect of polycyclic musk compound tonalide (AHTN) in two concentrations was studied in male rainbow trout (Oncorhynchus mykiss, Walbaum 1792). A feeding trial was conducted with AHTN incorporated into feed granules. One concentration was environmentally relevant (854 µg/kg); the second one was 10× higher (8699 µg/kg). The fish were fed twice a day with the amount of feed at 1 % of their body weight. After an acclimatization period, the experimental phase in duration of six weeks followed. At the end of the experiment, fish were sampled and the biometrical data were recorded. Subsequently, hematological and biochemical tests, histopathological examination, analysis of oxidative stress markers and evaluation of endocrine disruption using plasma vitellogenin were performed. In conclusion, an increase of hematocrit for both AHTN concentrations was found, but no significant changes were observed in biochemical profile. Moreover, AHTN caused lipid peroxidation in caudal kidney tissue, which was confirmed by histopathological images. The long-lasting AHTN exposure could thus be harmful for maintaining homeostasis in the rainbow trout organism. However, the vitellogenin concentration seemed not to be affected by AHTN.


Assuntos
Disruptores Endócrinos/toxicidade , Ácidos Graxos Monoinsaturados/toxicidade , Oncorhynchus mykiss/metabolismo , Tetra-Hidronaftalenos/toxicidade , Animais , Relação Dose-Resposta a Droga , Proteínas de Peixes/sangue , Brânquias/efeitos dos fármacos , Brânquias/metabolismo , Brânquias/patologia , Rim/efeitos dos fármacos , Rim/metabolismo , Rim/patologia , Peroxidação de Lipídeos/efeitos dos fármacos , Fígado/efeitos dos fármacos , Fígado/metabolismo , Fígado/patologia , Masculino , Oncorhynchus mykiss/sangue , Estresse Oxidativo/efeitos dos fármacos , Vitelogeninas/sangue
3.
Poult Sci ; 93(10): 2432-8, 2014 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-25125562

RESUMO

Neopterin and biopterin belong to a group of unconjugated pterin derivates. These biomolecules are present in many animal species and perform several functions. Pterin concentrations may provide additional information on the effect of stress on immune system activity. This study focused on an investigation of the effect of crating on plasma concentrations of neopterin and biopterin in broilers. The effects of 2 crating periods (2 and 4 h) were monitored in Hubbard broilers (n = 90) aged 42 d. After a given crating period, randomly selected chickens from each group were sampled immediately and the remaining chickens were sampled after 24 h. Plasma corticosterone increased (P < 0.001) immediately after 2 and 4 h crating, but no difference between the crated and the control noncrated broilers was found 24 h later. Immediately after crating, neopterin in 2- and 4-h broilers did not differ from the control, but 24 h later a decrease (P = 0.011) in plasma neopterin was found in 4-h broilers compared with the control. Simultaneously, 24 h after crating, neopterin levels in 2- and 4-h broilers decreased (P < 0.001) in comparison with the levels immediately after crating. Plasma biopterin was higher (P < 0.001) in 4-h broilers than in the control immediately after the crating. A time of sampling effect (P = 0.016) was found for the heterophil-to-lymphocyte ratio, with heterophil-to-lymphocyte ratio higher 24 h after crating in comparison with its level immediately after the crating. This study shows that crating may significantly affect the immune system of broiler chickens. This is corroborated by the increase in plasma biopterin concentrations in broilers immediately after crating and the decrease in plasma neopterin concentrations in broilers 24 h after crating. The correlations were found for widely used indicators of acute and chronic stress in birds [i.e., plasma corticosterone concentrations (biopterin) and the heterophil-to-lymphocyte ratio (neopterin), respectively].


Assuntos
Biopterinas/sangue , Galinhas/fisiologia , Corticosterona/sangue , Imunidade Inata , Estresse Fisiológico/fisiologia , Meios de Transporte , Bem-Estar do Animal , Animais , Biomarcadores/sangue , Análise Química do Sangue , Galinhas/sangue , Feminino , Masculino , Neopterina/sangue , Distribuição Aleatória
4.
Poult Sci ; 92(8): 2182-7, 2013 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-23873567

RESUMO

The study monitored the effect of various methods of treating pheasant carcasses after killing on the hygienic quality of the venison. Pithed pheasants treated by evisceration (n = 60), drawing (n = 60), or left untreated (n = 60) were stored for a period of 21 d at temperatures of 0, 7, and 15°C. For determination of biogenic amines, samples of breast and thigh muscles were taken on d 1, 7, 14, and 21 after killing of the pheasants. Biogenic amines were separated by reverse-phase liquid chromatography and consequently detected by tandem mass spectrometry. The sum of determined biogenic amine concentrations (cadaverine, putrescine, histamine, tyramine, tryptamine, phenylethylamine) was compared with the value of the index for meat of high hygienic quality (5 mg/kg). At a storage temperature of 0°C, the sum of biogenic amine concentrations did not exceed the value of 5 mg/kg in either breast or thigh muscle at any time during the storage period in untreated and drawn pheasants, and for a period of 14 d in eviscerated pheasants. At a storage temperature of 7°C, values lower than the limit of 5 mg/kg were recorded throughout the storage period in untreated pheasants, for a period of 14 d of storage in drawn pheasants, and for a period of just 7 d of storage in eviscerated birds. At the highest storage temperature (15°C), a value of 5 mg/kg was exceeded in eviscerated and untreated pheasants during the course of the first week of storage, and in drawn pheasants after the first week of storage. Our results indicate that the most suitable method of treatment to ensure high hygienic quality of the meat (assessed according to concentration of biogenic amines) for the longest period during the storage of pithed pheasants is to leave the pheasant carcasses untreated, followed by the drawing, with the least suitable method being the widely recommended method of evisceration.


Assuntos
Aminas Biogênicas/química , Armazenamento de Alimentos , Carne/análise , Animais , Galliformes , Masculino , Fatores de Tempo
5.
Poult Sci ; 92(7): 1699-705, 2013 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-23776255

RESUMO

The physiological changes in response to beak trimming and spectacle usage as antipecking measures were monitored in 10-mo-old common pheasants (Phasianus colchicus). Short-term analysis conducted before the beginning of the laying period showed immediate increases of plasma corticosterone (P < 0.05) and lactate dehydrogenase (P < 0.001) concentrations and decrease of plasma triglycerides (P < 0.01) levels in response to both beak trimming and the application of spectacles. Beak-trimmed pheasants exhibited higher plasma corticosterone concentrations than pheasants fitted with spectacles (P < 0.001). To assess long-term changes, blood samples for biochemical (neopterin and biopterin determination) and hematological (leukocyte profile determination) examinations were taken from beak-trimmed, spectacles-fitted, and control pheasant hens housed in cages during their laying period. At the end of the laying period, hens fitted with spectacles exhibited lower concentrations of plasma neopterin (P = 0.005) and biopterin (P = 0.005) than beak-trimmed pheasant hens. Our findings suggest that the immune system was suppressed in spectacles-fitted pheasant hens as a result of chronic stress, as also indicated by the higher heterophil-to-lymphocyte ratio (P = 0.001) compared with beak-trimmed hens. Our study found a negative correlation (r = -0.31, P = 0.019) between the heterophil-to-lymphocyte ratio and plasma neopterin concentration. This study demonstrated that both beak trimming and use of spectacles are not only stressful procedures for pheasants, but long-term effects may also include a negative impact on the immune system.


Assuntos
Agressão/fisiologia , Comportamento Animal/fisiologia , Galliformes/sangue , Leucócitos/fisiologia , Pterinas/sangue , Animais , Biomarcadores , Feminino , Galliformes/imunologia , Masculino , Estresse Fisiológico
6.
Pol J Vet Sci ; 16(1): 17-23, 2013.
Artigo em Inglês | MEDLINE | ID: mdl-23691571

RESUMO

Effects of a high terbuthylazine concentration (3.3 mg/1) on Cyprinus carpio were studied using a commercial herbicide formulation Click 500 SC (terbuthylazine 500 g/l). The fish were exposed to the pesticide for 24 h and allowed to recover for 6 days. Biometric parameters, plasma biochemical parameters and biomarkers of oxidative stress as well as histopathological changes in selected tissues were assessed on day 1 and 7. After a 24-h exposure, there were significant alterations found in the activities of alanine aminotransferase (ALT) and aspartate aminotransferase (AST) as well as in the plasma concentrations of glucose, natrium, chlorides, calcium and phosphorus. Hepatosomatic index, plasma albumin and lactate reflected the treatment with a delay. Ion levels and ALT were found to be restored after a 6-day recovery period, which was too short for AST activity and glucose to diminish to the control levels. The histopathological examination revealed disorders in the gills of the exposed fish, however, the changes were not detected after a 6-day recovery period. The study shows high regeneration potential of the fish.


Assuntos
Carpas , Doenças dos Peixes/induzido quimicamente , Herbicidas/toxicidade , Triazinas/toxicidade , Alanina Transaminase/sangue , Alanina Transaminase/genética , Alanina Transaminase/metabolismo , Animais , Aspartato Aminotransferases/sangue , Aspartato Aminotransferases/genética , Aspartato Aminotransferases/metabolismo , Doenças dos Peixes/sangue , Doenças dos Peixes/patologia , Regulação Enzimológica da Expressão Gênica/efeitos dos fármacos , Fígado/efeitos dos fármacos , Fígado/enzimologia , Oxirredução , Fatores de Tempo
7.
Pol J Vet Sci ; 15(3): 417-23, 2012.
Artigo em Inglês | MEDLINE | ID: mdl-23214359

RESUMO

The aim of this study was to investigate the effects of subchronic exposure to atrazine on fish growth and the development of histopathological changes in selected organs (gill, kidney, liver) in Danio rerio. Juvenile growth tests were performed on D. rerio according to OECD method No. 215. For 28 days, fish at an initial age of 30 days were exposed to the environmental atrazine concentration commonly detected in Czech rivers (0.3 microg/L) and a range of sublethal concentrations of atrazine (3.0, 30.0 and 90.0 microg/L). The results showed decreasing growth rates and morphological changes in the liver (dystrophic lesions of hepatocytes) at 90.0 microg/L of atrazine. The environmental concentration of atrazine in Czech rivers did not have any effect on fish growth and development of histopathological changes in D. rerio. The value of NOEC was 30.0 microg/L and the value of LOEC was 90.0 microg/L.


Assuntos
Atrazina/toxicidade , Herbicidas/toxicidade , Peixe-Zebra/crescimento & desenvolvimento , Animais , Comportamento Animal , República Tcheca , Relação Dose-Resposta a Droga , Esquema de Medicação , Brânquias/efeitos dos fármacos , Rim/efeitos dos fármacos , Fígado/efeitos dos fármacos , Rios/química , Poluentes Químicos da Água/toxicidade
8.
Physiol Res ; 60(3): 573-83, 2011.
Artigo em Inglês | MEDLINE | ID: mdl-21401305

RESUMO

Interaural time differences (ITDs), the differences of arrival time of the sound at the two ears, provide a major cue for low-frequency sound localization in the horizontal plane. The first nucleus involved in the computation of ITDs is the medial superior olive (MSO). We have modeled the neural circuit of the MSO using a stochastic description of spike timing. The inputs to the circuit are stochastic spike trains with a spike timing distribution described by a given probability density function (beta density). The outputs of the circuit reproduce the empirical firing rates found in experiment in response to the varying ITD. The outputs of the computational model are calculated numerically and these numerical simulations are also supported by analytical calculations. We formulate a simple hypothesis concerning how sound localization works in mammals. According to this hypothesis, there is no array of delay lines as in the Jeffress' model, but the inhibitory input is shifted in time as a whole. This is consistent with experimental observations in mammals.


Assuntos
Modelos Teóricos , Localização de Som , Estimulação Acústica , Animais , Vias Auditivas/fisiologia , Humanos , Mamíferos , Neurônios/fisiologia , Processos Estocásticos
9.
J Anim Sci ; 89(6): 1758-62, 2011 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-21297064

RESUMO

Recent reports have shown that stressful situations may affect the production of unconjugated pterins (neopterin and biopterin). The aim of the study was to investigate the effect of castration on neopterin and biopterin plasma concentrations in piglets, using 2 groups of 12 piglets allocated to castrated and uncastrated (control) groups. Pterin concentrations were determined by HPLC with fluorescence detection. Blood samples were also analzyed for leukocyte profiles and plasma cortisol concentrations. A time × treatment interaction (P < 0.05) was detected for neopterin concentrations, such that neopterin was greater (P < 0.01) at 1 h after surgery in castrated piglets compared with precastration concentrations, and neopterin was greater (P = 0.05) in castrated than in control piglets at 1 h. Castration had no effect on biopterin concentration (P > 0.1). Time effects (P < 0.05) for neutrophil and lymphocyte concentrations and neutrophil-to-lymphocyte ratios were found. A time × treatment interaction (P < 0.01) was detected for plasma cortisol concentrations, such that cortisol was greater (P < 0.01) at 1 and 24 h after surgery in castrated piglets compared with precastration concentrations and was greater (P < 0.01) in castrated than in control piglets at 1 and 24 h. This study showed that castration activated the immune system of piglets as demonstrated by an increase in plasma neopterin concentrations.


Assuntos
Biopterinas/sangue , Neopterina/sangue , Orquiectomia/veterinária , Suínos/imunologia , Animais , Biomarcadores , Biopterinas/metabolismo , Leucócitos/fisiologia , Neopterina/metabolismo
10.
Pol J Vet Sci ; 14(4): 545-9, 2011.
Artigo em Inglês | MEDLINE | ID: mdl-22439323

RESUMO

The aim of the study was to compare the acute toxicity of diclofenac to juvenile and embryonic stages of the zebrafish (Danio rerio). Acute toxicity tests were performed on the aquarium fish Danio rerio, which is one of the model organisms most commonly used in toxicity testing. The tests were performed using a semi-static method according to OECD guideline No. 203 (Fish, acute toxicity test). Embryo toxicity tests were performed in zebrafish embryos (Danio rerio) in compliance with OECD No. 212 methodology (Fish, short-term toxicity test on embryo and sac-fry stages). The results were subjected to a probit analysis using the EKO-TOX 5.2 programme to determine 96hLC50 and 144hLC50 (median lethal concentration, 50% mortality after a 96 h or 144 h interval, respectively) values of diclofenac. The statistical significance of the difference between LC50 values in juvenile and embryonic stages of Danio rerio was tested using the Mann-Whitney non-parametric test implemented in the Unistat 5.1 programme. The LC50 mean value of diclofenac was 166.6 +/- 9.8 mg/L in juvenile Danio rerio, and 6.11 +/- 2.48 mg/L in embryonic stages of Danio rerio. The study demonstrated a statistically higher sensitivity to diclofenac (P < 0.05) in embryonic stages compared to the juvenile fish.


Assuntos
Anti-Inflamatórios não Esteroides/administração & dosagem , Anti-Inflamatórios não Esteroides/toxicidade , Diclofenaco/administração & dosagem , Diclofenaco/toxicidade , Peixe-Zebra/embriologia , Peixe-Zebra/crescimento & desenvolvimento , Animais , Relação Dose-Resposta a Droga , Embrião não Mamífero/efeitos dos fármacos , Dose Letal Mediana
11.
Dtsch Med Wochenschr ; 130(41): 2337-42, 2005 Oct 14.
Artigo em Alemão | MEDLINE | ID: mdl-16231235

RESUMO

Female urinary incontinence is a medical and social problem with a large prevalence. Stress urinary incontinence (SUI) is the most common form of urinary incontinence and is responsible for 49 % of all incontinence, if mixed forms are included even for 78 %. As of yet, apart from "off-label" treatment, there is no pharmacological treatment available for stress urinary incontinence. For instance, estrogens are used in menopausal patients but a substantial effect in the treatment of SUI has not been demonstrated. a-Adrenergics, such as phenylpropanolamine and midodrine, and b-adrenergics, such as clenbuterol, are also used in "off-label" therapy. A recently conducted meta-analysis of 15 randomised studies with female patients who received a- und b-adrenergics as part of their therapy, failed to detect efficacy compared to placebo. Tricyclic antidepressives, such as imipramine and doxepine, which are used for the treatment of urge incontinence, are also used "off-label" in the treatment of SUI. However, no placebo-controlled studies have been conducted so far. The serotonin-norepinephrine reuptake inhibitor duloxetine represents a new therapeutic approach in the treatment of SUI. It has shown positive effects on bladder and urethra in animal experiments, most likely through an effect on the Onuf's nucleus in the spinal cord. In randomised, placebo-controlled studies (phase II and III) in women with SUI, a significant and clinically relevant reduction in urinary incontinence episodes as well as an improvement in the quality of life compared to placebo was shown.


Assuntos
Adrenérgicos/uso terapêutico , Antidepressivos/uso terapêutico , Estrogênios/uso terapêutico , Inibidores Seletivos de Recaptação de Serotonina/uso terapêutico , Tiofenos/uso terapêutico , Incontinência Urinária por Estresse/tratamento farmacológico , Cloridrato de Duloxetina , Feminino , Humanos
12.
Urologe A ; 43(10): 1249-53, 2004 Oct.
Artigo em Alemão | MEDLINE | ID: mdl-15322758

RESUMO

Urinary continence and voiding are complex physiological processes and require the coordination of all three efferent areas of the nervous system (parasympathetic, sympathetic, somatic). The pudendal nerve contains efferent as well as afferent fibers, the former ones having their origin in Onuf's nucleus. A number of studies see a link in the central modulation of lower urinary tract activity through 5-HT and NE receptor agonists as well as antagonists. Previous information about the modulation of the lower urinary tract in humans has been obtained from animal experiments. Duloxetin, a combined serotonin/norepinephrine reuptake inhibitor may prove to be a new therapeutic agent for stress urinary incontinence. Duloxetin appears to act at the presynaptic neuron of Onuf's nucleus. A phase II and three phase III studies have shown significant and clinically relevant improvement in several parameters in comparison to placebo control. The most frequent adverse event observed was nausea.


Assuntos
Nervos Espinhais/efeitos dos fármacos , Tiofenos/uso terapêutico , Bexiga Urinária/inervação , Bexiga Urinária/fisiopatologia , Incontinência Urinária por Estresse/tratamento farmacológico , Incontinência Urinária por Estresse/fisiopatologia , Animais , Ensaios Clínicos como Assunto , Cloridrato de Duloxetina , Humanos , Neurônios Motores/efeitos dos fármacos , Terminações Pré-Sinápticas/efeitos dos fármacos , Região Sacrococcígea/inervação , Região Sacrococcígea/fisiopatologia , Inibidores Seletivos de Recaptação de Serotonina/uso terapêutico , Nervos Espinhais/fisiopatologia , Resultado do Tratamento , Bexiga Urinária/efeitos dos fármacos , Incontinência Urinária por Estresse/diagnóstico
13.
J Hum Hypertens ; 18(9): 669-75, 2004 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-15269705

RESUMO

Moxonidine is a centrally active imidazoline receptor agonist that effectively lowers blood pressure and has been shown to have beneficial effects on lipid and carbohydrate metabolism. We assessed the efficacy of moxonidine in a postmarketing surveillance study (CAMUS) conducted in 772 practices in Germany, documenting 4005 patients with hypertension, who were overweight and/or suffered from metabolic syndrome. Patients were treated with moxonidine (Cynt) for the first time following the baseline visit for 8 weeks. Mean blood pressure decreased from 168/97 to 141/83 mmHg for all patients and from 168/96 to 141/83 mmHg for patients with metabolic syndrome. Blood pressure reduction was particularly pronounced in patients with severe hypertension at baseline. The response rate (DBP< or =90 mmHg or reduction > or =10 mmHg) of antihypertensive treatment with moxonidine was 94.0% for all patients and 93.8% for patients with metabolic syndrome. The recommended targets for antihypertensive treatment of the German Diabetes Society/German Hypertension Society were reached by 30.5% of nondiabetics (goal: <140/90 mmHg) and by 3.6% of diabetics (goal: <130/80 mmHg) observed. After 8 weeks of treatment, patients achieved a mean weight loss of 1.4 kg, which was particularly pronounced in obese patients. The rate of patients receiving antihypertensive combination therapy was 81.1% for those with metabolic syndrome, and 63.3% for all other patients. Patients with metabolic syndrome were preferentially treated with ACE inhibitors and diuretics. We conclude that moxonidine effectively reduces blood pressure in patients with metabolic syndrome while simultaneously reducing body weight in obese patients.


Assuntos
Anti-Hipertensivos/uso terapêutico , Hipertensão/tratamento farmacológico , Imidazóis/uso terapêutico , Síndrome Metabólica/tratamento farmacológico , Obesidade/tratamento farmacológico , Adulto , Idoso , Idoso de 80 Anos ou mais , Anti-Hipertensivos/efeitos adversos , Biomarcadores/sangue , Glicemia/metabolismo , Pressão Sanguínea/efeitos dos fármacos , Índice de Massa Corporal , Peso Corporal , HDL-Colesterol/sangue , Quimioterapia Combinada , Feminino , Alemanha/epidemiologia , Frequência Cardíaca/efeitos dos fármacos , Humanos , Hipertensão/sangue , Hipertensão/epidemiologia , Imidazóis/efeitos adversos , Masculino , Síndrome Metabólica/sangue , Síndrome Metabólica/epidemiologia , Pessoa de Meia-Idade , Obesidade/sangue , Obesidade/epidemiologia , Sobrepeso , Prevalência , Vigilância de Produtos Comercializados , Fatores de Risco , Índice de Gravidade de Doença , Resultado do Tratamento , Triglicerídeos/sangue , Relação Cintura-Quadril
14.
Prague Med Rep ; 105(4): 369-80, 2004.
Artigo em Inglês | MEDLINE | ID: mdl-15825231

RESUMO

Replacing static synapses with the adaptive ones can affect the behaviour of neuronal network. Several network setups containing synapses modelled by alpha-functions, called here static synapses, are compared with corresponding setups containing more complex, dynamic synapses. The dynamic synapses have four state variables and the time constants are of different orders of magnitude. Response of the network to modelled stimulations was studied together with effects of neuronal interconnectivity, the axonal delays and the proportion of excitatory and inhibitory neurons on the network output. Dependency of synaptic strength on synaptic activity was also studied. We found that dynamic synapses enable network to exhibit broader spectrum of responses to given input and they make the network more sensitive to changes of network parameters. As a step towards memory modelling, retention of input sequences in the network with static and dynamic synapses was studied. The network with dynamic synapses was found to be more flexible in reducing the interference between adjacent inputs in comparison to the network containing static synapses.


Assuntos
Modelos Neurológicos , Rede Nervosa , Sinapses/fisiologia , Humanos
15.
Water Sci Technol ; 48(9): 133-43, 2003.
Artigo em Inglês | MEDLINE | ID: mdl-14703147

RESUMO

The winter operation of an on-stream stormwater management pond in Kingston, Canada is characterised. The pond froze over in late November. Ice thickness varied from 0.2 to 0.5 m, and initially, was well described by Stefan's formula. The measured and modelled velocity field indicated a fast flow region, a small dead zone and a large recirculating zone. During a snowmelt event, near-bottom velocities reached 0.05 m x s(-1), but were not sufficient to scour the bottom sediment. Pond water temperature increased with depth, from 0.5 degrees C to 3.5 degrees C. The dissolved oxygen (DO) levels observed in the pond (6-13 mg x L(-1)) indicated stable aerobic conditions at the sediment-water interface. In one brief episode, DO fell to zero after a long cold spell. Reduction in DO readings from inlet to outlet indicated an oxygen consumption of about 1.7 kg x day(-1). pH ranged from 7.1 to 8.9. Conductivity readings indicated large quantities of total dissolved solids, representing mostly chloride from de-icing agents. During baseflow, conductivity increased with depth (total dissolved solids concentrations up to 1,200 mg x L(-1) near the bottom), indicating density stratification. Average trace metal concentrations were mostly below detection limits.


Assuntos
Eliminação de Resíduos Líquidos/métodos , Purificação da Água/métodos , Sedimentos Geológicos , Concentração de Íons de Hidrogênio , Gelo , Ontário , Oxigênio/análise , Oxigênio/metabolismo , Estações do Ano , Movimentos da Água
17.
Biosystems ; 58(1-3): 83-91, 2000.
Artigo em Inglês | MEDLINE | ID: mdl-11164634

RESUMO

Some of the cochlear nuclei in the auditory pathway are specialized for the sound localization. They compute the interaural time difference. The difference in sound timing is transduced by the dedicated neuronal circuit into a labeled line difference. The detector neurons along the delay line fire only when synaptic inputs reflecting signals from both cars arrive within a short time window. It was therefore called coincidence detection. We show, (1) what are the limits of coincidence detection in the leaky integrator model, which is a linear system, (2) how should the ideal coincidence detector based on the Hodkin-Huxley equations from real neurons look like, (3) what are the properties and physical limits in the real coincidence detection system. The conclusion is that the neuron with the Hodgkin Huxley dynamics has a fixed precision for the coincidence detection. The limits of the sound localization precision are set by the frequency of the sound and, therefore, by the vector strength of spike trains generated in the neuronal circuit in response to the sound.


Assuntos
Vias Auditivas/fisiologia , Audição/fisiologia
18.
Biosystems ; 48(1-3): 147-56, 1998.
Artigo em Inglês | MEDLINE | ID: mdl-9886642

RESUMO

We modeled the influx of calcium ions into dendrites following active backpropagation of spike trains in a dendritic tree, using compartmental models of anatomically reconstructed pyramidal cells in a GENESIS program. Basic facts of ion channel densities in pyramidal cells were taken into account. The time scale of the backpropagating spike train development was longer than in previous models. We also studied the relationship between intracellular calcium dynamics and membrane voltage. Comparisons were made between two pyramidal cell prototypes and in simplified model. Our results show that: (1) sodium and potassium channels are enough to explain regenerative backpropagating spike trains; (2) intracellular calcium concentration changes are consistent in the range of milliseconds to seconds; (3) the simulations support several experimental observations in both hippocampal and neocortical cells. No additional parameter search optimization was necessary. Compartmental models can be used for investigating the biology of neurons, and then simplified for constructing neural networks.


Assuntos
Potenciais de Ação , Cálcio/metabolismo , Córtex Cerebral/fisiologia , Hipocampo/fisiologia , Neurônios/fisiologia , Córtex Cerebral/citologia , Hipocampo/citologia , Transporte de Íons , Modelos Neurológicos , Canais de Potássio/fisiologia , Canais de Sódio/fisiologia
19.
Proc Natl Acad Sci U S A ; 94(2): 735-40, 1997 Jan 21.
Artigo em Inglês | MEDLINE | ID: mdl-9012854

RESUMO

What is the relationship between the temporal jitter in the arrival times of individual synaptic inputs to a neuron and the resultant jitter in its output spike? We report that the rise time of firing rates of cells in striate and extrastriate visual cortex in the macaque monkey remain equally sharp at different stages of processing. Furthermore, as observed by others, multiunit recordings from single units in the primate frontal lobe reveal a strong peak in their cross-correlation in the 10-150 msec range with very small temporal jitter (on the order of 1 msec). We explain these results using numerical models to study the relationship between the temporal jitter in excitatory and inhibitory synaptic input and the variability in the spike output timing in integrate-and-fire units and in a biophysically and anatomically detailed model of a cortical pyramidal cell. We conclude that under physiological circumstances, the standard deviation in the output jitter is linearly related to the standard deviation in the input jitter, with a constant of less than one. Thus, the timing jitter in successive layers of such neurons will converge to a small value dictated by the jitter in axonal propagation times.


Assuntos
Potenciais de Ação , Neurônios/fisiologia , Sinapses/fisiologia , Transmissão Sináptica , Córtex Visual/fisiologia , Animais , Gatos , Macaca mulatta , Modelos Biológicos , Rede Nervosa/fisiologia , Visão Ocular/fisiologia , Córtex Visual/citologia , Percepção Visual/fisiologia
20.
Z Kardiol ; 86(12): 975-81, 1997 Dec.
Artigo em Alemão | MEDLINE | ID: mdl-9499495

RESUMO

The monoclonal antibody c7E3 (ReoPro) is a highly selective inhibitor of platelet aggregation that binds to the fibrinogen receptor (GP IIb/IIIa) on the surface of platelets and leads to a dose-dependent, nearly complete inhibition of platelet aggregation. The clinical value of c7E3 to reduce ischemic events after PTCA in addition to heparin and aspirin has been demonstrated in the EPIC-, EPILOG-, and CAPTURE-trial. In these studies, c7E3 was associated with an increased bleeding risk after the coronary intervention. The DTREO-Trial (German trial with c7E3) was designed as a prospective study to investigate the clinical safety of c7E3 in the daily routine of a cath lab. From April 1995 through September 1996 520 patients were enrolled at 30 German sites. c7E3 was mainly used in patients with acute coronary syndromes (55% unstable angina Braunwald Class I-III and C; 28% in acute myocardial infarction) and in patients with complex coronary lesions (AHA/ACC classification type B and C lesion in 84% of the study group). In 51% of the interventions a stent was implanted (25% in bailout-situations and in 26% as an elective intervention) and c7E3 was used as an adjunctive to prevent sub-acute stent thrombosis. The incidence of "major" bleeding events (TIMI-classification) was less frequent in this study as in the EPIC-trial and comparable to the results of the EPILOG- and CAPTURE trial. In conclusion this study confirms the positive risk profile of c7E3 in patients undergoing high-risk percutaneous revascularization procedures.


Assuntos
Angina Instável/terapia , Angioplastia Coronária com Balão , Anticorpos Monoclonais/administração & dosagem , Circulação Coronária/efeitos dos fármacos , Doença das Coronárias/terapia , Fragmentos Fab das Imunoglobulinas/administração & dosagem , Infarto do Miocárdio/terapia , Inibidores da Agregação Plaquetária/administração & dosagem , Abciximab , Adulto , Sistemas de Notificação de Reações Adversas a Medicamentos , Idoso , Idoso de 80 Anos ou mais , Anticorpos Monoclonais/efeitos adversos , Aspirina/administração & dosagem , Aspirina/efeitos adversos , Quimioterapia Combinada , Feminino , Hemorragia/induzido quimicamente , Heparina/administração & dosagem , Heparina/efeitos adversos , Humanos , Fragmentos Fab das Imunoglobulinas/efeitos adversos , Masculino , Pessoa de Meia-Idade , Inibidores da Agregação Plaquetária/efeitos adversos , Estudos Prospectivos
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