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1.
J Neural Eng ; 9(1): 016005, 2012 Feb.
Artículo en Inglés | MEDLINE | ID: mdl-22156141

RESUMEN

The mechanical damage caused by the insertion of a foreign body into living tissue is inevitable, especially when a considerable stiffness mismatch is present, as in the case of micromachined neural implants and brain tissue. However, the response surface model based on a central composite experimental design described in this study showed that for particular configurations of the implant tip angle, width, thickness or insertion speed, some of these factors could be safely increased without causing an unwanted significant force or tissue dimpling increase. The model covers chisel tip angles between 10° and 50°, implant widths within the 200-400 µm range and thicknesses between 50 and 150 µm. The insertion speed has been varied from 10 up to 100 µm s(-1) to reach a final insertion depth of 6 mm. Coating the implant with parylene C proved to be beneficial in reducing the friction between the implant and the surrounding tissue. Successfully validated for a particular implant geometry, this model could be used as an insertion behavior prediction tool for the design optimization of future neural implants.


Asunto(s)
Encéfalo/fisiología , Encéfalo/cirugía , Modelos Biológicos , Prótesis e Implantes , Implantación de Prótesis/métodos , Animales , Simulación por Computador , Módulo de Elasticidad/fisiología , Fricción/fisiología , Dureza/fisiología , Miniaturización , Ratas , Ratas Wistar , Viscosidad
2.
IEEE Trans Biomed Eng ; 58(11): 3250-9, 2011 Nov.
Artículo en Inglés | MEDLINE | ID: mdl-21896383

RESUMEN

In this study, the effect of insertion speed on long-term tissue response and insertion mechanics was investigated. A dummy silicon parylene-coated probe was used in this context and implanted in the rat brain at 10 µm/s (n = 6) or 100 µm/s (n = 6) to a depth of 9 mm. The insertion mechanics were assessed by the dimpling distance, and the force at the point of penetration, at the end of the insertion phase, and after a 3-min rest period in the brain. After 6 weeks, the tissue response was evaluated by estimating the amount of gliosis, inflammation, and neuronal cell loss with immunohistochemistry. No difference in dimpling, penetration force, or the force after a 3-min rest period in the brain was observed. However, the force at the end of the insertion phase was significantly higher when inserting the probes at 100 µm/s compared to 10 µm/s. Furthermore, an expected tissue response was seen with an increase of glial and microglial reactivity around the probe. This reaction was similar along the entire length of the probe. However, evidence for a neuronal kill zone was observed only in the most superficial part of the implant. In this region, the lesion size was also greatest. Comparison of the tissue response between insertion speeds showed no differences.


Asunto(s)
Encéfalo/cirugía , Electrodos Implantados , Implantación de Prótesis/métodos , Análisis de Varianza , Animales , Encéfalo/metabolismo , Encéfalo/patología , Gliosis/metabolismo , Inmunohistoquímica , Inflamación/metabolismo , Masculino , Fenómenos Mecánicos , Microelectrodos , Implantación de Prótesis/efectos adversos , Ratas , Ratas Wistar , Silicio
3.
Artículo en Inglés | MEDLINE | ID: mdl-19965265

RESUMEN

The electrochemical behavior of neural implants with 50 microm-diameter platinum electrodes was tested during acute implantations in the motor cortex of anesthetized rats. Custom Ag|AgCl reference electrodes were prepared that could be co-implanted with the probes. The results obtained in vivo are compared with in vitro measurements performed in buffered saline solution (PBS) with and without the addition of bovine serum albumin (BSA). The presence of BSA clearly altered the performance of the electrodes which was studied by means of cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), voltage transient measurements (VT) and monitoring of the open circuit potential (OCP). We found that hydrogen gas evolved at 1.22 A/cm(2) in BSA-free PBS whereas in BSA-containing PBS it occurred already at 0.51 A/cm(2).


Asunto(s)
Electrodos Implantados , Microelectrodos , Corteza Motora/fisiología , Corteza Motora/cirugía , Animales , Ingeniería Biomédica , Bovinos , Técnicas Electroquímicas , Diseño de Equipo , Técnicas In Vitro , Ratas , Albúmina Sérica Bovina , Plata , Compuestos de Plata , Cloruro de Sodio
4.
J Neurochem ; 72(5): 1930-8, 1999 May.
Artículo en Inglés | MEDLINE | ID: mdl-10217270

RESUMEN

Although brain-derived neurotrophic factor is the most abundant and widely distributed neurotrophin in the nervous system, reproducible determinations of its levels have been hampered by difficulties in raising suitable monoclonal antibodies. Following immunization of mice with recombinant fish and mammalian brain-derived neurotrophic factor, monoclonal antibodies were generated and used in an immunoassay based on the recognition of two different epitopes. Neither antibody crossreacts with neurotrophin homodimers other than brain-derived neurotrophic factor, although reactivity was detected with brain-derived neurotrophic factor/neurotrophin-3 heterodimers. As both nerve growth factor and neurotrophin-3 are known to affect the development of a variety of neurons expressing the brain-derived neurotrophic factor (bdnf) gene, this assay was used to determine levels in tissues isolated from newborn mice carrying a null mutation in the nerve growth factor (ngf) or the neurotrophin-3 (nt3) gene. Marked differences were observed between mutants and wild-type littermates in the PNS, but not in the CNS, suggesting that neither nerve growth factor nor neurotrophin-3 is a unique regulator of brain-derived neurotrophic factor levels in the newborn mouse CNS.


Asunto(s)
Factor Neurotrófico Derivado del Encéfalo/metabolismo , Mutación/fisiología , Factores de Crecimiento Nervioso/genética , Sistema Nervioso/metabolismo , Animales , Anticuerpos Monoclonales , Factor Neurotrófico Derivado del Encéfalo/aislamiento & purificación , Sistema Nervioso Central/metabolismo , Pollos , Femenino , Peces , Inmunoensayo , Ratones , Ratones Endogámicos BALB C/genética , Neurotrofina 3 , Nervios Periféricos/metabolismo , Proteínas Recombinantes , Valores de Referencia , Sensibilidad y Especificidad , Xenopus laevis
5.
Life Sci ; 56(6): PL135-41, 1995.
Artículo en Inglés | MEDLINE | ID: mdl-7530315

RESUMEN

Rats of the Lewis (LEW) strain show a greater preference for drugs of abuse than do Fischer 344 (F344) rats. The in vivo microdialysis procedure was used to examine basal and cocaine-evoked extracellular (EC) levels of dopamine (DA), DOPAC, and HVA in the nucleus accumbens (NAc) of F344 and LEW rats. The basal EC levels of the DA metabolites DOPAC and HVA in the NAc were markedly lower in LEW than in F344 rats. Although the increase in EC DA after 3, 10, or 30 mg/kg, i.p. of cocaine was similar in both strains, LEW rats had a smaller peak DA elevation followed by a slower return to basal DA levels at the 30 mg/kg dose. The neurochemical differences observed may contribute to the strain differences in the behavioral response to cocaine.


Asunto(s)
Cocaína/farmacología , Dopamina/metabolismo , Núcleo Accumbens/efectos de los fármacos , Núcleo Accumbens/metabolismo , Ácido 3,4-Dihidroxifenilacético/metabolismo , Análisis de Varianza , Animales , Espacio Extracelular , Ácido Homovanílico/metabolismo , Ácido Hidroxiindolacético/metabolismo , Masculino , Morfina/farmacología , Ratas , Ratas Endogámicas F344 , Ratas Endogámicas Lew
6.
EMBO J ; 11(12): 4391-9, 1992 Dec.
Artículo en Inglés | MEDLINE | ID: mdl-1425575

RESUMEN

Lysosomal acid phosphatase (LAP) is rapidly internalized from the cell surface due to a tyrosine-containing internalization signal in its 19 amino acid cytoplasmic tail. Measuring the internalization of a series of LAP cytoplasmic tail truncation and substitution mutants revealed that the N-terminal 12 amino acids of the cytoplasmic tail are sufficient for rapid endocytosis and that the hexapeptide 411-PGYRHV-416 is the tyrosine-containing internalization signal. Truncation and substitution mutants of amino acid residues following Val416 can prevent internalization even though these residues do not belong to the internalization signal. It was shown recently that part of the LAP cytoplasmic tail peptide corresponding to 410-PPGY-413 forms a well-ordered beta turn structure in solution. Two-dimensional NMR spectroscopy of two modified LAP tail peptides, in which the single tyrosine was substituted either by phenylalanine or by alanine, revealed that the tendency to form a beta turn is reduced by 25% in the phenylalanine-containing peptide and by approximately 50% in the alanine-containing mutant peptide. Our results suggest, that in the short cytoplasmic tail of LAP tyrosine is required for stabilization of the right turn and that the aromatic ring system of the tyrosine residue is a contact point to the putative cytoplasmic receptor.


Asunto(s)
Fosfatasa Ácida/metabolismo , Lisosomas/enzimología , Oligopéptidos/metabolismo , Fosfatasa Ácida/química , Alanina/genética , Secuencia de Aminoácidos , Animales , Células Cultivadas , Cricetinae , Endocitosis , Técnica del Anticuerpo Fluorescente , Cinética , Datos de Secuencia Molecular , Mutación , Oligopéptidos/genética , Conformación Proteica
7.
Cell ; 67(6): 1203-9, 1991 Dec 20.
Artículo en Inglés | MEDLINE | ID: mdl-1760845

RESUMEN

For rapid endocytosis lysosomal acid phosphatase requires a Tyr-containing signal in its cytoplasmic domain, as do cell surface receptors mediating endocytosis and clustering in coated pits. To determine the structure of the internalization signal an 18 amino acid peptide representing the cytoplasmic tail of lysosomal acid phosphatase was analyzed by two-dimensional nuclear magnetic resonance spectroscopy. Part of the peptide, 5-PPGY-8, forms a well-ordered beta turn of type I in solution. Our result and data on the structure of the endocytosis signal of the low density lipoprotein receptor reported by Bansal and Gierasch in the accompanying paper represent experimental determinations of the three-dimensional structure of protein transport signals and suggest that the essential aromatic amino acid of internalization signals is recognized by a putative cytoplasmic receptor in the structural context of a tight turn.


Asunto(s)
Fosfatasa Ácida/química , Secuencia de Aminoácidos , Gráficos por Computador , Citoplasma/ultraestructura , Endocitosis , Técnicas In Vitro , Lisosomas/enzimología , Espectroscopía de Resonancia Magnética , Glicoproteínas de Membrana/metabolismo , Modelos Moleculares , Datos de Secuencia Molecular , Péptidos/síntesis química , Péptidos/química , Conformación Proteica , Tirosina/química
8.
J Biomol NMR ; 1(1): 71-82, 1991 May.
Artículo en Inglés | MEDLINE | ID: mdl-1841691

RESUMEN

The structure of the ColE1 repressor of primer (rop) protein in solution was determined from the proton nuclear magnetic resonance data by a combined use of distance geometry and restrained molecular dynamics calculations. A set of structures was determined with low internal energy and virtually no violations of the experimental distance restraints. Rop forms homodimers: Two helical hairpins are arranged as an antiparallel four helix bundle with a left-handed rope-like twist of the helix axes and with left-handed bundle topology. The very compact packing of the side chains in the helix interfaces of the rop coiled-coil structure may well account for its high stability. Overall, the solution structure is highly similar to the recently determined X-ray structure (Banner, D.W., Kokkinidis, M. and Tsernoglou, D. (1987) J. Mol. Biol., 196, 657-675), although there are minor differences in regions where packing forces appear to influence the crystal structure.


Asunto(s)
Proteínas Bacterianas/química , Plásmidos de Bacteriocinas , Proteínas de Unión al ARN , Espectroscopía de Resonancia Magnética , Modelos Moleculares , Estructura Molecular , Conformación Proteica , Soluciones
9.
Biochemistry ; 29(32): 7402-7, 1990 Aug 14.
Artículo en Inglés | MEDLINE | ID: mdl-2223771

RESUMEN

The complete resonance assignment of the ColE1 rop (rom) protein at pH 2.3 was obtained by two-dimensional (2D) proton nuclear magnetic resonance spectroscopy (1H NMR) at 500 and 600 MHz using through-bond and through-space connectivities. Sequential assignments and elements of regular secondary structure were deduced by analysis of nuclear Overhauser enhancement spectroscopy (NOESY) experiments and 3JHN alpha coupling constants. One 7.2-kDa monomer of the homodimer consists of two antiparallel helices connected by a hairpin loop at residue 31. The C-terminal peptide consisting of amino acids 59-63 shows no stable conformation. The dimer forms a four-helix bundle with opposite polarization of neighboring elements in agreement with the X-ray structure.


Asunto(s)
Proteínas Bacterianas/química , Colicinas , Proteínas de Unión al ARN , Secuencia de Aminoácidos , Hidrógeno , Espectroscopía de Resonancia Magnética , Datos de Secuencia Molecular , Reconocimiento de Normas Patrones Automatizadas , Conformación Proteica
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