A softening laminar electrode for recording single unit activity from the rat hippocampus.

Softening neural implants that change their elastic modulus under physiological conditions are promising candidates to mitigate neuroinflammatory response due to the reduced mechanical mismatch between the artificial interface and the brain tissue. Intracortical neural probes have been used to demonstrate the viability of this material engineering approach. In our paper, we present a robust technology of softening neural microelectrode and demonstrate its recording performance in the hippocampus of rat subjects. The 5 mm long, single shank, multi-channel probes are composed of a custom thiol-ene/acrylate thermoset polymer substrate, and were micromachined by standard MEMS processes. A special packaging technique is also developed, which guarantees the stable functionality and longevity of the device, which were tested under in vitro conditions prior to animal studies. The 60 micron thick device was successfully implanted to 4.5 mm deep in the hippocampus without the aid of any insertion shuttle. Spike amplitudes of 84 µV peak-to-peak and signal-to-noise ratio of 6.24 were achieved in acute experiments. Our study demonstrates that softening neural probes may be used to investigate deep layers of the rat brain.

A silicon-based microelectrode array with a microdrive for monitoring brainstem regions of freely moving rats.

OBJECTIVE: Exploring neural activity behind synchronization and time locking in brain circuits is one of the most important tasks in neuroscience. Our goal was to design and characterize a microelectrode array (MEA) system specifically for obtaining in vivo extracellular recordings from three deep-brain areas of freely moving rats, simultaneously. The target areas, the deep mesencephalic reticular-, pedunculopontine tegmental-and pontine reticular nuclei are related to the regulation of sleep-wake cycles. APPROACH: The three targeted nuclei are collinear, therefore a single-shank MEA was designed in order to contact them. The silicon-based device was equipped with 3 × 4 recording sites, located according to the geometry of the brain regions. Furthermore, a microdrive was developed to allow fine actuation and post-implantation relocation of the probe. The probe was attached to a rigid printed circuit board, which was fastened to the microdrive. A flexible cable was designed in order to provide not only electronic connection between the probe and the amplifier system, but sufficient freedom for the movements of the probe as well. MAIN RESULTS: The microdrive was stable enough to allow precise electrode targeting into the tissue via a single track. The microelectrodes on the probe were suitable for recording neural activity from the three targeted brainstem areas. SIGNIFICANCE: The system offers a robust solution to provide long-term interface between an array of precisely defined microelectrodes and deep-brain areas of a behaving rodent. The microdrive allowed us to fine-tune the probe location and easily scan through the regions of interest.

Experimental study on the mechanical interaction between silicon neural microprobes and rat dura mater during insertion.

In vivo insertion experiments are essential to optimize novel neural implants. Our work focuses on the interaction between intact dura mater of rats and as-fabricated single-shaft silicon microprobes realized by deep reactive ion etching. Implantation parameters like penetration force and dimpling through intact dura mater were studied as a function of insertion speed, microprobe cross-section, tip angle and animal age. To reduce tissue resistance, we proposed a unique tip sharpening technique, which was also evaluated in in vivo insertion tests. By doubling the insertion speed (between 1.2 and 10.5 mm/min), an increase of 10-35% in penetration forces was measured. When decreasing the cross-section of the microprobes, penetration forces and dimpling was reduced by as much as 30-50% at constant insertion speeds. Force was noticed to gradually decrease by decreasing tip angles. Measured penetration forces through dura mater were reduced even down to 11±3 mN compared to unsharpened (49±13 mN) probes by utilizing our unique tip sharpening technique, which is very close to exerted penetration force in the case of retracted dura (5±1.5 mN). Our findings imply that age remarkably alters the elasticity of intact dura mater. The decreasing stiffness of dura mater results in a significant rise in penetration force and decrease in dimpling. Our work is the first in vivo comparative study on microelectrode penetration through intact and retracted dura mater.

[Prenatal diagnosis of tricuspid atresia]. / A tricuspidalis atresia praenatalis diagnosztikája.

Tricuspid atresia is the third most common cyanotic cardiac malformation, seen in 1 per cent of children with congenital heart disease. It occurs in 4-5 per cent of congenital heart defects diagnosed prenatally, this difference is a consequence of a high percentage of intrauterine death these severely ill fetuses. Initial surgical treatment is palliation, usually with aortopulmonary shunt. Definitive treatment is the Fontan operation, when the systemic venous return is connected directly to the pulmonary tree. Five-year survival for liveborn patients is 50, but for prenatally diagnosed fetuses only 20%. In Hungary there is only a few survivor. Authors have diagnosed 20 tricuspid atresias during a five-year period by fetal echocardiography. In two cases the postnatal findings were: normal tricuspid valves, univentricular atrio-ventricular connection and stenosis of the pulmonary artery, in one case dysplastic tricuspid valves, hypoplastic right ventricle and stenosis of the pulmonary artery. Authors summarise their experiences with prenatal echocardiography of tricuspid atresia and describe characteristic signs could be found by routine ultrasound screening of this severe cardiac malformation.

[Fetal myocardial calcification (report of 4 cases and review of the literature]. / Magzati myocardium calcificatio (négy eset ismertetése és irodalmi áttekintés).

(Report of four cases and review of the literature) Calcification of the myocardium is a rare condition. The cause may be dystrophic or metastatic. An autosomal recessive inherited idiopathic arterial calcification of infancy is more rare abnormality. A dystrophic calcification is the more common of the three and may occur in areas of necrosis, hemorrhage, or fibrosis of the myocardium. Metastatic calcification is associated with hyperparathyroidism, D hypervitaminosis or renal failure, usually accompanied by the deposit of calcium in other organs, particularly the lungs, stomach, kidneys, spleen and liver. Authors report four cases of myocardial calcification diagnosed in intrauterine life. They give a review of literature of fetal and neonatal myocardial calcification.

Preparative-scale amino acid separation by thermal parametric pumping on an ion-exchange resin.

Thermal parametric pumping was experimentally investigated for the concentration and separation of amino acids. Previous theories of parametric pumping were improved by taking into account dissociation equilibria in the liquid phase. Experiments were carried out with a mixture of glutamic acid, aspartic acid, serine and threonine in a highly acidic solution (HCl). A multi-component equilibrium model was mainly used to simulate the experimental results and to investigate the effect of chloride concentration over a wide range. It is shown that it is always possible to concentrate the amino acids and to separate some of them under certain conditions.

Preliminary pharmacokinetics and pharmacodynamics of an ultra-short-acting opioid: remifentanil (GI87084B).

Remifentanil is a newly synthesized 4-anilido-piperidine with an ester side chain susceptible to esterase metabolism. We evaluated the safety, analgesic efficacy, and pharmacokinetics of remifentanil in 48 male volunteers. Volunteers were randomized to receive increasing doses of remifentanil, alfentanil, or placebo. Analgesic efficacy was evaluated by increasing tolerance to a spring-loaded rod measured at the tibia and sternum at multiple time points. Respiratory depression was measured by changes in arterial blood gas tensions and peripheral hemoglobin oxygen saturation. Hemodynamics were continuously monitored by means of an intra-arterial catheter. Both remifentanil and alfentanil produced a dose-dependent increase in analgesia and respiratory depression. Remifentanil was 20 to 30 times more potent (milligram to milligram) than alfentanil when assessed by either analgesic efficacy or respiratory measures. The pharmacokinetics of remifentanil were best described by a biexponential decay curve. Remifentanil had a small volume of distribution of 0.39 (SD, +/- 0.25) L/kg (alfentanil, 0.52 +/- 2 L/kg), with a rapid distribution phase of 0.94 (SD, +/- 0.57) min and an extremely short elimination half-life of 9.5 (SD, +/- 4) min compared with an elimination half-life of alfentanil of 58 (SD, +/- 7.6) min. The t1/2 ke0 (half-time for equilibration between plasma and the effect compartment) of remifentanil for analgesia was calculated as 1.3 min. Thus, remifentanil appears to have a pharmacologic profile similar to other potent mu agonists, but with exceptionally short-lasting pharmacokinetics, which is likely to make it a very useful opioid for clinical practice.

The pharmacokinetics of D-penicillamine in neonates.

The pharmacokinetics of D-penicillamine in premature babies was studied. The metabolism of the drug was characterized by a long half-life (115 min) with a low plasma clearance (2.84 ml/min/kg body weight) in contrast to adults. The mean volume of distribution (649/ml/kg body weight) was similar to that of adults.