Iontophoresis from a micropipet into a porous medium depends on the ζ-potential of the medium.

Iontophoresis uses electricity to deliver solutes into living tissue. Often, iontophoretic ejections from micropipets into brain tissue are confined to millisecond pulses for highly localized delivery, but longer pulses are common. As hippocampal tissue has a ζ-potential of approximately -22 mV, we hypothesized that, in the presence of the electric field resulting from the iontophoretic current, electroosmotic flow in the tissue would carry solutes considerably farther than diffusion alone.

Synthesis and characterization of a hydrogel with controllable electroosmosis: a potential brain tissue surrogate for electrokinetic transport.

Electroosmosis is the bulk fluid flow initiated by application of an electric field to an electrolyte solution in contact with immobile objects with a nonzero ζ-potential such as the surface of a porous medium. Electroosmosis may be used to assist analytical separations. Several gel-based systems with varying electroosmotic mobilities have been made in this context.

A simple method for measuring organotypic tissue slice culture thickness.

This paper presents a simple method to measure tissue slice thicknesses using an ohmmeter. The circuit described here is composed of a metal probe, an ohmmeter, a counter electrode, culture medium or physiological buffer, and tissue slice. The probe and the electrode are on opposite interfaces of an organotypic hippocampal slice culture.

Minimizing tissue damage in electroosmotic sampling.

Electroosmotic sampling is a potentially powerful method for pulling extracellular fluid into a fused-silica capillary in contact with the surface of tissue. An electric field is created in tissue by passing current through an electrolyte-filled capillary and then through the tissue. The resulting field acts on the counterions to the surface charges in the extracellular space to create electroosmotic fluid flow within the extracellular space of a tissue.

Electroosmotic sampling. Application to determination of ectopeptidase activity in organotypic hippocampal slice cultures.

We hypothesize that peptide-containing solutions pulled through tissue should reveal the presence and activity of peptidases in the tissue. Using the natural zeta-potential in the organotypic hippocampal slice culture (OHSC), physiological fluids can be pulled through the tissue with an electric field. The hydrolysis of the peptides present in the fluid drawn through the tissue can be determined using capillary HPLC with electrochemical detection of the biuret complexes of the peptides following a postcolumn reaction.

Determination of zeta-potential and tortuosity in rat organotypic hippocampal cultures from electroosmotic velocity measurements under feedback control.

Extracellular translational motion in the brain is generally considered to be governed by diffusion and tortuosity. However, the brain as a whole has a significant zeta-potential, thus translational motion is also governed by electrokinetic effects under a naturally occurring or applied electric field. We have previously measured zeta-potential and tortuosity in intact brain tissue; however, the method was tedious.

Determination of zeta-potential in rat organotypic hippocampal cultures.

zeta-potentials of entities such as cells and synaptosomes have been determined, but zeta of brain tissue has never been measured. Electroosmotic flow, and the resulting transport of neuroactive substances, would result from naturally occurring and experimentally or clinically induced electric fields if zeta is significant. We have developed a simple method for determining zeta in tissue.

NMDA-receptor mediated efflux of N-acetylaspartate: physiological and/or pathological importance?

N-Acetylaspartate (NAA) is a largely neuron specific dianionic amino acid present in high concentration in vertebrate brain. Many fundamental questions concerning N-acetylaspartate in brain remain unanswered. One such issue is the predominantly neuronal synthesis and largely glial catabolism which implies the existence of a regulated efflux from neurons.

Airway humidification with high-frequency jet ventilation.

Humidification of inspired gases is indispensible to prevent serious injury to the tracheal mucosa of patients on mechanical ventilation. High-frequency jet ventilation (HFJV), recently introduced for the management of some forms of respiratory failure, presents unusual technical problems of humidification. The present investigation evaluated a technique to humidify jet gases by delivering small droplets of normal saline in front of the injector cannula, and utilizing the jet flow to nebulize the fluids administered.

Critical care nurse and high-frequency ventilation.

As the treatment of respiratory failure becomes more sophisticated and technical, the critical care nurse is faced with many challenges. High-frequency ventilation is a modality of respiratory support employing principles different from those of conventional ventilation. For these reasons, the nurse must be familiar with the indications for its use and the practical management of the ventilated patient.

Early prediction of outcome of respiratory failure. Comparison of high-frequency jet ventilation and volume-cycled ventilation.

Data from a prospective randomized investigation comparing volume-cycled ventilation and high-frequency jet ventilation were reexamined to determine whether improvement of respiratory and hemodynamic function, as well as ultimate outcome (death or survival), could be predicted early in the course of the disease. End points were selected for the ratio of the arterial oxygen pressure over the fractional concentration of oxygen in the inspired gas (PaO2/FIO2), the arterial oxygen saturation (SaO2), the arterial carbon dioxide tension (PaCO2), and the cardiac index. Patients were assigned to "success" or "failure" groups, according to the values recorded for those end points 24 hours after institution of mechanical ventilation.

[Synopsis of a four-year research on the "maculipennis" complex (author's transl)].

The authors have carry out during four summers a study of the "maculipennis complex" on the Languedoc-Roussillon coast line. They have determined three sibling species: Anopheles maculipennis subalpinus (very abundant, with an important eggs ornementation' poly-morphism), Anopheles maculipennis maculipennis (found only once in that region) and Anopheles maculipennis atroparvus found only the last year of our research.

[Dynamics of populations in an urban and underground resting place of Culex pipiens L. (Diptera, Culicidae) (author's transl)].

An urban and underground resting place of Culex pipiens has been examinated during one year. Many females (28% in September, 70% in January) do not find sexual partners. The cause is a mixing of autogenous and anautogenous forms in the place even if it seems perfectly closed.