RESUMO
Osteogenesis imperfecta (brittle bone disease) is an orphan disease caused by a genetic mutation in collagen metabolism. Bone fractures are the most common symptoms; however, the clinical manifestation can vary widely. Additional features can include blue sclera, dwarfism, bone deformities, muscular weakness, scoliosis, hearing loss and hypermobility of joints. Most patients show a reduction of skeletal function. This leads to an increased risk of being unable to continue their former work and to participate in social life. A comprehensive treatment includes drug therapy, surgery and rehabilitation. This article gives an overview of the current status of rehabilitation in adult patients with osteogenesis imperfecta.
Assuntos
Osteogênese Imperfeita , Escoliose , Adulto , Fraturas Ósseas , Humanos , Mutação , Osteogênese Imperfeita/genética , Doenças RarasRESUMO
We present an ultrafast spectroscopy system designed for temporal and spectral resolution of transient transmission changes after excitation of single electrons in solid-state quantum structures. The system is designed for optimum long-term stability, offering the option of hands-off operation over several days. Pump and probe pulses are generated in a versatile Er:fiber laser system where visible photon energies may be tuned independently from 1.90 eV to 2.51 eV in three parallel branches. Bandwidth-limited pulse durations between 100 fs and 10 ps are available. The solid-state quantum systems under investigation are mounted in a closed-cycle superconducting magnet cryostat providing temperatures down to 1.6 K and magnetic fields of up to 9 T. The free-standing cryomagnet is coupled to the laser system by means of a high-bandwidth active beam steering unit to eliminate residual low-frequency mechanical vibrations of the pulse tube coolers. High-NA objective lenses inside the sample chamber are employed for focusing femtosecond laser pulses onto the sample and recollection of the transmission signal. The transmitted probe light is dispersed in a grating monochromator equipped with a liquid nitrogen-cooled CCD camera, enabling a frame rate of 559 Hz. In order to eliminate spurious background effects due to low-frequency changes in the thermal equilibrium of the sample, we operate with a lock-in scheme where, instead of the pump amplitude, the pump-probe timing is modulated. This feature is provided without any mechanical action by an electro-optic timing unit inside the femtosecond Er:fiber system. The performance of the instrument is tested with spectrally resolved pump-probe measurements on a single negatively charged CdSe/ZnSe quantum dot under a magnetic field of 9 T. Selective initialization and readout of charge and spin states is carried out via two different femtosecond laser pulses. High-quality results on subpicosecond intraband relaxation dynamics after single-electron excitation motivate a broad variety of future experiments in ultrafast quantum optics and few-fermion quantum dynamics.
RESUMO
A strong increase of spontaneous radiative emission from colloidally synthesized CdSe/CdS/PMMA hybrid particles is achieved when manipulated into plasmonic bullseye resonators with the tip of an atomic force microscope (AFM). This type of antenna provides a broadband resonance, which may be precisely matched to the exciton ground state energy in the inorganic cores. Statistically analyzing the spectral photoluminescence (PL) of a large number of individual coupled and uncoupled CdSe/CdS/PMMA quantum dots, we find an order of magnitude of intensity enhancement due to the Purcell effect. Time-resolved PL shows a commensurate increase of the spontaneous emission rate with radiative lifetimes below 230 ps for the bright exciton transition. The combination of AFM and PL imaging allows for sub-200 nm localization of the particle position inside the plasmonic antenna. This capability unveils a different coupling behavior of dark excitonic states: even stronger PL enhancement occurs at positions with maximum spatial gradient of the nearfield, effectively adding a dipolar component to original quadrupole transitions. The broadband maximization of light-matter interaction provided by our nanoengineered compound systems enables an attractive class of future experiments in ultrafast quantum optics.
RESUMO
This literature search concerning the potential role of spinal orthoses for rehabilitation and treatment of atraumatic vertebral fractures between Th4 and L5 with osteoporosis and without any evidence for a secondary cause, provided no evidence for the benefits of traditional rigid thoracolumbar corsets, which only had a poor compliance. In addition, there are indications that these rigid corsets may even worsen the disease condition especially in the long-term. Wearing these corsets can result in further loss of muscle mass and strength followed by loss of bone and bone mass. Both together can worsen the functional capabilities of patients. On the other hand the functional capabilities of patients suffering from acute or subacute vertebral fractures due to osteoporosis can be improved by flexible backpack orthoses. These spinal orthoses generate an extension moment about the spine, increase perception of one's own body posture via biofeedback and therefore lead to improved posture. This results in a strengthening of the trunk musculature, a more stable equilibrium and a reduction of pain, which are associated with an increase in functional capabilities and improvement in the parameters of the quality of life. During a long-term phase of rehabilitation individually tailored spinal orthoses guarantee a high level of compliance and adherence. Finally, there is high-quality evidence that spinal orthoses with additional weighting can improve the equilibrium in women with vertebral osteoporosis and hyperkyphosis. Future studies should also be carried out with other groups of patients.
Assuntos
Vértebras Lombares/lesões , Aparelhos Ortopédicos , Fraturas por Osteoporose/reabilitação , Vértebras Torácicas/lesões , Idoso , Idoso de 80 Anos ou mais , Ensaios Clínicos Controlados como Assunto , Feminino , Humanos , Cifose/psicologia , Cifose/reabilitação , Masculino , Pessoa de Meia-Idade , Fraturas por Osteoporose/psicologia , Equilíbrio Postural , Qualidade de Vida/psicologia , Ensaios Clínicos Controlados Aleatórios como AssuntoRESUMO
Pregnancy and lactation-associated osteoporosis (PLO) is a rare form of osteoporosis, which occurs in the last trimester or postpartum. So far 100 cases have been published. The leading symptoms are severe low back pain or less frequently hip pain. Many patients develop postpartum depression due to inability to care for the baby and vertebral fractures. The therapeutic decision has to be made individually but teriparatid and bisphosphonates seem to be the best option. We report the clinical course (16 years) of a 37-year-old patient with PLO, who suffered 6 vertebral fractures. There were severe physical limitations and mental problems caused by the disease. The patient was treated by multimodal therapy including physiotherapy and psychotherapy and bisphosphonates were given. The time between the onset of symptoms and diagnosis was 5 months. No further fractures occurred in the following 16 years. The physical and mental condition significantly improved.
Assuntos
Depressão/terapia , Transtornos da Lactação/terapia , Fraturas por Osteoporose/terapia , Complicações na Gravidez/terapia , Fraturas da Coluna Vertebral/terapia , Adulto , Conservadores da Densidade Óssea/uso terapêutico , Terapia Combinada/métodos , Depressão/diagnóstico , Diagnóstico Diferencial , Difosfonatos/administração & dosagem , Feminino , Humanos , Transtornos da Lactação/diagnóstico , Traumatismo Múltiplo/diagnóstico , Traumatismo Múltiplo/terapia , Osteoporose , Fraturas por Osteoporose/diagnóstico , Modalidades de Fisioterapia , Gravidez , Complicações na Gravidez/diagnóstico , Psicoterapia/métodos , Fraturas da Coluna Vertebral/diagnóstico , Resultado do TratamentoRESUMO
Systemic mastocytosis is defined as a clonal increase of mast cells. We report on four patients with severe osteoporosis and histologically confirmed systemic mastocytosis. In spite of antiresorptive therapy the patients developed further vertebral fractures and suffered from ostealgia. Systemic mastocytosis is an important differential diagnosis in patients with therapy refractive and unexplained osteoporosis. Skin involvement (urticaria pigmentosa) is a rare occurrence and in most cases an isolated involvement of bone marrow is present. Determination of serum tryptase can provide indications for systemic mastocytosis but the diagnosis is only confirmed by bone marrow biopsy. There is a high risk of vertebral fractures and patients should be treated in specialized centers. Zoledronic acid can be a therapeutic option for indolent osteoporosis associated with systemic mastocytosis.
Assuntos
Anti-Inflamatórios/uso terapêutico , Difosfonatos/uso terapêutico , Imidazóis/uso terapêutico , Mastocitose Sistêmica/diagnóstico , Mastocitose Sistêmica/tratamento farmacológico , Osteoporose/diagnóstico , Osteoporose/tratamento farmacológico , Adulto , Conservadores da Densidade Óssea/uso terapêutico , Doença Crônica , Diagnóstico Diferencial , Feminino , Humanos , Masculino , Mastocitose Sistêmica/complicações , Pessoa de Meia-Idade , Doenças Raras/diagnóstico , Falha de Tratamento , Resultado do Tratamento , Ácido ZoledrônicoRESUMO
We report the case of a 74 year old man with a brain stem infarction, temporal headache and elevated inflammatory parameters. Giant cell arteritis with involvement of the temporal and vertebral arteries was proven by histology, duplex sonography and MRI. Although intensive immunosuppressive therapy was started, the patient developed two brain infarcts within 6 months. Initially, Creactive protein and erythrocyte sedimentation rate were significantly elevated, but normalized over time. Involvement of the vertebral artery in giant cell arteritis is thought to be rare; steroid refractory courses are very rare. Brain stem infarction might be the consequence.
Assuntos
Infartos do Tronco Encefálico/diagnóstico , Infartos do Tronco Encefálico/etiologia , Encefalite/diagnóstico , Arterite de Células Gigantes/diagnóstico , Transtornos da Cefaleia/diagnóstico , Transtornos da Cefaleia/etiologia , Idoso , Anti-Inflamatórios/uso terapêutico , Infartos do Tronco Encefálico/prevenção & controle , Diagnóstico Diferencial , Encefalite/etiologia , Encefalite/prevenção & controle , Arterite de Células Gigantes/complicações , Arterite de Células Gigantes/tratamento farmacológico , Transtornos da Cefaleia/prevenção & controle , Humanos , Masculino , Prednisolona/uso terapêutico , Falha de TratamentoRESUMO
Unameliorated residue mud from the Bayer process generates highly alkaline leachates (pH ca. 13) after deposition in storage areas. Pre-deposition treatment of bauxite residue mud (BRM) with CO(2) gas (carbonation) lowers leachate pH to ca. 10.5. Laboratory scale leaching columns were used to investigate the potential for in situ pH reduction in existing uncarbonated BRM deposits through exposure to carbonated mud leachate. Leachates from uncarbonated and carbonated residues in single and dual-layer column configurations were analysed for pH, electrical conductivity, carbonate and bicarbonate content, and element concentrations. Air-dried solids were analysed by X-ray diffraction before and after leaching. Cross layer leaching lowers leachate pH from uncarbonated BRM. Leachate pH was significantly lower in dual layer and carbonated residue than in uncarbonated residue between one and 400 pore volumes leached. Carbonated residue porewater as well as dawsonite and calcite dissolution were identified as sources of (bi-)carbonate. Leachate concentrations of As, Cr, Cu, Ga and La were immediately reduced in dual layer treatments compared with uncarbonated residue. No element analysed exhibited a significantly higher leachate concentration in dual layer treatments than the highest observed concentration in single layer treatments. The implementation of dual layer leaching in the field therefore presents an opportunity to improve leachate quality from existing uncarbonated residue deposits and justifies further testing at field scale.
Assuntos
Óxido de Alumínio/química , Condutividade Elétrica , Concentração de Íons de Hidrogênio , Difração de Raios XRESUMO
Onshore oil production pipelines are major installations in the petroleum industry, stretching many thousands of kilometres worldwide which also contain flowline additives. The current study focuses on the effect of the flowline additives on soil physico-chemical and biological properties and quantified the impact using resilience and resistance indices. Our findings are the first to highlight deleterious effect of flowline additives by altering some fundamental soil properties, including a complete loss of structural integrity of the impacted soil and a reduced capacity to degrade hydrocarbons mainly due to: (i) phosphonate salts (in scale inhibitor) prevented accumulation of scale in pipelines but also disrupted soil physical structure; (ii) glutaraldehyde (in biocides) which repressed microbial activity in the pipeline and reduced hydrocarbon degradation in soil upon environmental exposure; (iii) the combinatory effects of these two chemicals synergistically caused severe soil structural collapse and disruption of microbial degradation of petroleum hydrocarbons.
Assuntos
Campos de Petróleo e Gás , Poluição por Petróleo/análise , Microbiologia do Solo , Poluentes do Solo/toxicidade , Solo/química , Biodegradação Ambiental/efeitos dos fármacos , Dióxido de Carbono/análise , Dióxido de Carbono/química , Desinfetantes/análise , Desinfetantes/toxicidade , Poluentes do Solo/análiseRESUMO
Medical training therapy (MTT) plays a decisive role in maintenance and development of musculoskeletal health of humans in all phases of life. In childhood and adolescence it can contribute to the highest possible so-called peak bone mass and thus avoid or delay the appearance of osteoporosis for as long as possible, in view of increased life expectations. In young adults targeted MTT is well suited to improve performance and to maintain the maximum developed bone mass. The latter is also true for perimenopausal and postmenopausal women in whom MTT can compensate for the loss of bone mass due to hormone deficiency in comparison to those not in training. Elderly people who have possibly already suffered several fractures and who are in danger of becoming permanently dependent on external help due to increasing fragility can still improve muscle strength and mass by regular MTT even in advanced age. This will reduce or avoid the risk of falling and maintain the ability to be self-sufficient for as long as possible. In order to support this, rehabilitation measures even in-hospital, could be useful and should be especially promoted in line with the amendments to the social legislation effective from 1st April 2007 ("Rehabilitation before nursing").
Assuntos
Terapia por Exercício , Fraturas Espontâneas/reabilitação , Osteoporose Pós-Menopausa/reabilitação , Modalidades de Fisioterapia , Treinamento Resistido , Doenças da Coluna Vertebral/reabilitação , Fraturas da Coluna Vertebral/reabilitação , Acidentes por Quedas/prevenção & controle , Idoso , Densidade Óssea , Feminino , Fraturas Espontâneas/prevenção & controle , Humanos , Pessoa de Meia-Idade , Força Muscular , Prevenção Secundária , Fraturas da Coluna Vertebral/prevenção & controle , Resultado do TratamentoRESUMO
BACKGROUND: Iron overload may contribute to the pathogenesis of insulin resistance. We aimed to investigate the relationship among iron stores, liver transaminases and components of the metabolic syndrome in healthy teenagers in a cross-sectional study. MATERIAL AND METHODS: We determined body mass index (BMI), waist-to-hip-ratio (WHR), blood pressure, liver ultrasound, serum lipids, insulin, fasting glucose, liver transaminase levels, hsCRP, iron parameters in 325 of 341 (95.3%) students (234 men, 16.7 +/- 1.7 years; 91 women, 16.5 +/- 1.7 years) of one single high school. Male and female study participants were allocated to increasing quartiles of body iron stores as assessed by sTfr/ferritin and alanine aminotranspeptidase (ALT) levels, and the distribution of cardiometabolic risk factors along quartiles was analysed. Regression analysis was performed to confirm the independent relationship between parameters. RESULTS: In male students, BMI, WHR, systolic and diastolic blood pressure, serum triglyceride levels and hsCRP were higher in the top sTfR/ferritin and ALT quartiles compared with the lowest quartiles (P < 0.01 for all parameters). In female students, sTfR/ferritin were not associated with antropomorphic cardiometabolic risk factors but with insulin resistance (HOMA-IR, P = 0.046). Moreover, ALT levels were independently related to BMI, waist and hip circumference, systolic blood pressure, serum triglyceride and insulin concentrations (P < 0.05 for all parameters) in female students. CONCLUSION: These results provide evidence for linkage among body iron stores, transaminase activity and the prevalence of cardiometabolic risk factors in apparently healthy, non-obese adolescents even within the range of normal laboratory and anthropomorphic values and suggest that iron stores should be investigated as a potentially modifiable risk factor in healthy teenagers.
Assuntos
Doenças Cardiovasculares/fisiopatologia , Ferritinas/análise , Ferro/sangue , Síndrome Metabólica/fisiopatologia , Transaminases/sangue , Adolescente , Glicemia/análise , Pressão Sanguínea , Índice de Massa Corporal , Feminino , Humanos , Insulina/sangue , Lipídeos/sangue , Fígado/diagnóstico por imagem , Masculino , Análise de Regressão , Fatores de Risco , Ultrassonografia , Relação Cintura-QuadrilRESUMO
BACKGROUND: Suppression of nociceptive signalling in the thalamus is considered to contribute significantly to the anaesthetic state. Assuming additivity of anaesthetic mixtures, our study assessed the effects of corresponding minimum alveolar concentrations (MACs) of isoflurane and isoflurane/nitrous oxide on thalamic nociceptive signalling. METHODS: Nociceptive response activity (elicited by controlled radiant heat stimuli applied to cutaneous receptive fields) of single thalamic neurons was compared in rats anaesthetized at approximately 1.1 and approximately 1.4 MAC isoflurane with that at approximately 1.1 and approximately 1.4 MAC isoflurane/nitrous oxide. RESULTS: Under baseline anaesthesia ( approximately 0.9 MAC isoflurane), noxious stimulation elicited excitatory responses in all neurons (n = 19). These responses were uniformly suppressed at approximately 1.1 and approximately 1.4 MAC isoflurane. In contrast, at approximately 1.1 and approximately 1.4 MAC isoflurane/nitrous oxide, excitatory responses no different to baseline were still present in 64 and 37% of the neurons, respectively. CONCLUSIONS: These data demonstrate a pronounced nitrous oxide-induced response variability. It appears that, with respect to thalamic transfer of nociceptive information, the interaction of isoflurane and nitrous oxide may not be compatible with the concept of additivity and that the antinociceptive potency of nitrous oxide is considerably less than previously reported.
Assuntos
Anestésicos Inalatórios/farmacologia , Isoflurano/farmacologia , Óxido Nitroso/farmacologia , Nociceptores/efeitos dos fármacos , Tálamo/efeitos dos fármacos , Anestésicos Combinados/farmacologia , Animais , Sinergismo Farmacológico , Temperatura Alta , Vias Neurais/efeitos dos fármacos , Vias Neurais/fisiologia , Neurônios/efeitos dos fármacos , Neurônios/fisiologia , Nociceptores/metabolismo , Dor/etiologia , Dor/fisiopatologia , Dor/prevenção & controle , Ratos , Ratos Wistar , Transdução de Sinais/efeitos dos fármacos , Tálamo/fisiopatologiaRESUMO
Arsenic is highly toxic and therefore represents a potential threat to the environment and human health. The mobility and bioavailability of arsenic in soil is mostly controlled by adsorption and desorption reactions. Even though adsorption and traditional batch desorption experiments provide information about the environmental fate of As, the equilibrium conditions imposed in these studies would usually not be reached in the natural environment. Flow-through desorption techniques, where the desorbed species are removed from the substrate, can therefore be used to provide information about the rate and mechanisms of As desorption. The effect of pH on As adsorption reactions is relatively well understood; however, desorption of As and the effect of pH on As desorption remain unexplored. Desorption of As(V) (the most dominant arsenic species in aerated soils) was therefore investigated using batch and flow-through desorption experiments. Traditional batch desorption experiments underestimated the desorption rate of As(V) from kaolinite. The pH had a large effect on the amount of As(V) desorbed from kaolinite, with both an increase and a decrease in pH (from the initial pH 6.4) enhancing As(V) desorption. Modeling desorption over time revealed that the pH can influence As(V) desorption over extended periods of time.
Assuntos
Arseniatos/química , Arsênio/química , Caulim/química , Modelos Teóricos , Poluentes do Solo/análise , Adsorção , Arsênio/análise , Concentração de Íons de Hidrogênio , CinéticaRESUMO
In terms of their clinical impact, bone fractures as late sequelae of osteoporosis are still largely ignored in Germany. Up to 80-90% of patients with treatment-requiring osteoporosis are not receiving specific treatment. The consequences for the patient are enormous: weeks of severe pain, subsequent fractures that occur for ever more banal reasons, increasing restriction of daily activities, invalidism and an increasing need for nursing care. All this despite the availability of powerful medications. In concert with an appropriate early diagnosis, not only could the majority of patients be spared such a fate, but also the costs incurred as a direct consequence of such fractures could be drastically lowered.
Assuntos
Pessoas com Deficiência/reabilitação , Ácido Etidrônico/análogos & derivados , Osteoporose/terapia , Dor/etiologia , Fraturas da Coluna Vertebral/prevenção & controle , Atividades Cotidianas , Fatores Etários , Alendronato/uso terapêutico , Analgésicos Opioides/uso terapêutico , Anti-Inflamatórios não Esteroides/uso terapêutico , Ácido Etidrônico/uso terapêutico , Feminino , Fraturas do Fêmur/etiologia , Fraturas do Fêmur/prevenção & controle , Humanos , Masculino , Pessoa de Meia-Idade , Osteoporose/complicações , Osteoporose/diagnóstico , Osteoporose/tratamento farmacológico , Osteoporose/reabilitação , Osteoporose Pós-Menopausa/complicações , Osteoporose Pós-Menopausa/tratamento farmacológico , Dor/prevenção & controle , Cloridrato de Raloxifeno/uso terapêutico , Ácido Risedrônico , Fatores Sexuais , Fraturas da Coluna Vertebral/etiologiaRESUMO
BACKGROUND: Mechanosensory thalamocortical relay neurones (TCNs) receive glutamatergic excitatory input and are subjected to gamma-aminobutyric acid (GABA)Aergic inhibitory input. This study assessed the effects of an increase in concentration of isoflurane on thalamic excitatory and inhibitory mechanisms. METHODS: TCNs (n = 15) of the thalamic ventral posteromedial nucleus responding to mechanical stimulation of whiskers were investigated in rats anaesthetized with end-tidal concentrations of isoflurane of approximately 0.9% (ISOlow, baseline) and approximately 1.9% (ISOhigh). Response activity induced by controlled vibratory movement of single whiskers was recorded before, during and after iontophoretic administration of the GABAA receptor antagonist bicuculline to the vicinity of the recorded neurone. RESULTS: The increase in concentration of isoflurane induced a suppression of vibratory responses to 14 (4)% [mean (SEM)] of baseline activity. Blockade of GABAA receptors by bicuculline during ISOlow and ISOhigh caused increases in response activity to 259 (32)% and 116 (25)% of baseline activity, respectively. The increase in isoflurane concentration enhanced overall inhibitory inputs by 102 (38)%, whilst overall excitatory inputs were reduced by 54 (7)%. CONCLUSIONS: These data suggest that doubling the concentration of isoflurane doubles the strength of GABAAergic inhibition and decreases the excitatory drive of TCNs by approximately 50%. The isoflurane-induced enhancement of GABAAergic inhibition led to a blockade of thalamocortical information transfer which was not accomplished by the effects of isoflurane on glutamatergic synaptic transmission alone. Thus, it appears that, with respect to transmission of information in the thalamus, the most prominent action of isoflurane is an enhancement of GABAAergic synpatic inhibition, and that effects on glutamatergic neurotransmission may contribute to a lesser extent.
Assuntos
Anestésicos Inalatórios/farmacologia , Isoflurano/farmacologia , Neurônios/efeitos dos fármacos , Transmissão Sináptica/efeitos dos fármacos , Tálamo/efeitos dos fármacos , Animais , Bicuculina/farmacologia , Potenciais Somatossensoriais Evocados/fisiologia , Bloqueio Neuromuscular/métodos , Neurônios/fisiologia , Estimulação Física , Ratos , Ratos Wistar , Tálamo/fisiologiaRESUMO
Many in vitro effects of volatile anesthetics are known, but the mechanisms of action are still under debate. Because suppression of sensory perception is one of the major goals of general anesthesia, we studied the effects of isoflurane on the processing of somatosensory information in anesthetized rats. Local iontophoretic administration of the gamma-aminobutyric acid-A (GABA(A)) receptor antagonist bicuculline in the thalamic ventral posteromedial nucleus reversed suppressive effects of isoflurane on thalamocortical relay neurons (TCNs). The action potential discharges of TCNs (n = 23) in response to defined mechanical stimulation of receptive fields seen with small concentrations of isoflurane (0.79% +/- 0.01%, mean +/- SEM) were suppressed under large concentrations (1.44% +/- 0.04%). In addition, the tonic response pattern was lost, which initially encoded the information about the stimulus features. In 70% of TCNs, bicuculline administration reestablished the initially present tonic response pattern under large isoflurane concentrations. These results indicate that isoflurane suppresses somatosensory information transfer at the thalamic level in vivo, apparently by enhancing thalamic GABA(A) receptor-mediated inhibition.
Assuntos
Anestésicos Inalatórios/antagonistas & inibidores , Antagonistas GABAérgicos/farmacologia , Antagonistas de Receptores de GABA-A , Isoflurano/antagonistas & inibidores , Neurônios/efeitos dos fármacos , Tálamo/efeitos dos fármacos , Anestésicos Inalatórios/farmacologia , Animais , Bicuculina/farmacologia , Relação Dose-Resposta a Droga , Potenciais Evocados/efeitos dos fármacos , Isoflurano/farmacologia , Masculino , Mecanorreceptores/efeitos dos fármacos , Microeletrodos , Movimento/efeitos dos fármacos , Ratos , Ratos Wistar , Transmissão Sináptica/efeitos dos fármacos , Tálamo/citologiaAssuntos
Córtex Cerebral/anatomia & histologia , Córtex Cerebral/fisiopatologia , Dor/fisiopatologia , Animais , Mapeamento Encefálico , Córtex Cerebral/patologia , Humanos , Plasticidade Neuronal/fisiologia , Dor/patologia , Percepção/fisiologia , Córtex Somatossensorial/anatomia & histologia , Córtex Somatossensorial/fisiologiaRESUMO
In spite of several reports about suppressive effects of volatile anesthetics on somatosensation, their neuronal mechanisms are largely unknown. The present study investigates somatosensory impulse transmission at the thalamic level in rats under varied concentrations of isoflurane by recordings of neuronal responses to mechanical stimulation of the body surface. Single-unit recordings of thalamo-cortical relay neurons (TCNs, third order neurons; n=28) and presumed trigemino-thalamic fibers (TTFs, second order neurons; n=7) were performed in the ventral posteromedial nucleus. Functional response characteristics were quantified following defined tactile stimulation (trapezoidal or vibratory deflection of sinus hairs or fur) applied to the neuronal receptive fields. End-tidal isoflurane concentration was increased in steps of 0.2% between 0.6% (baseline) and 2.0%. The response activity in all TCNs studied was suppressed in a dose-dependent manner (2.0% isoflurane decreased responses to 3. 5+/-1.1% of baseline; mean+/-S.E.M.); the response activity in TTFs was much less affected (decrease to 55.0+/-8.2%). Suppression of ongoing activity, however, was similar for both, TCNs and TTFs. Furthermore, in TCNs, the response characteristics changed with increasing isoflurane between 1.0% and 1.8%: tonic and sustained responses were converted to phasic on-responses. In contrast, the tonic and sustained response characteristics of TTFs were preserved even at higher isoflurane concentrations. The results indicate that isoflurane attenuates the output of somatosensory signals in the specific nucleus of the rat's thalamus, while its input is only marginally affected. The observed changes of thalamic neuronal response characteristics, at least in part, may cause the loss in sensory discrimination observed during general anesthesia.