Slice Chambers

A large variety of experimental slice chambers has been developed (Richards and Sercombe, 1970 Dore and Richards, 1974 Schwartzkroin, 1975 Chujo et ai, 1975 Spencer et ai, 1976 Richards and Tegg, 1977  

White et al, 1978 Scholfield, 1978a) from the original design of Li and Mcllwain (1957), and, as far as intracellular recording is concerned, at least five different bath designs are in current use, each optimalizing some feature of the technique which is important to a particular experiment. 

One of the most commonly used baths is a variant of the original bath developed by Mcllwain and his co-workers, first described by Schwartz-kroin (1975) (Fig. 2). In this bath, the slice sits in the media/gas interface, over a pool containing approximately 2 ml of solution, which is perfused from below, at a rate of less than 2 ml/min. As mentioned elsewhere, the slice appears to extract oxygen from the gaseous phase and, provided a flow of less than 2 ml/min is demanded by the experimental design, stable intracellular records can be maintained, at least from the larger cells of the slice, for periods in excess of 4 hr. 

Since the brain slices are separated from the atmosphere by only a thin film of fluid, it is crucial and sometimes difficult to prevent the tissue surface from dying out. In this regard, a well-humidified gas stream over the slices is necessary. It is also important to arrange the suction device so that the relatively dry laboratory air will not be drawn over the slices. 

Although it can be argued that maintaining the slices in such a precarious situation, covered by capillary action with only a thin film of fluid, is unnecessary, this method has some additional experimental advantages. 

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Fig. 2. Perfusion arrangement in the slice chamber. Hatched areas are constructed of lucite, and dotted areas show the path of ACSF. The close-hatched lid above the slices directs the flow of gas (warmed, humidified O2/CO2) over the slices. It has a central hole through which the slices may be viewed and electrodes inserted. Note that this design isolates the slices from air currents set up by the aspirator needle. (From Dingledine et al., 1980.)...

Certain materials, most notably semiconductors, can be mechanically cleaved along a low-mdex crystal plane in situ in a UFIV chamber to produce an ordered surface without contamination. This is done using a sharp blade to slice tire sample along its preferred cleavage direction. For example. Si cleaves along the (111) plane, while III-V semiconductors cleave along the (110) plane. Note that the atomic structure of a cleaved surface is not necessarily the same as that of the same crystal face following treatment by IBA. 

Hippocampal slices (400-500 frm) were quickly prepared from male Wistar rats (8- to 9-weeks-old) and maintained in a chamber at 35 °C, where they were continuously perfused with artificial cerebrospinal fluid as described in our previous paper [11]. A bipolar tungsten electrode was placed in the stratum radiatum to stimulate Schaffer collateral and commissural afferents. The evoked potential was extracellularly recorded from the pyramidal cell layer of the CA1 subfield with a glass capillary microelectrode. A single test stimulation (0.05 msec duration) was applied at intervals of 30 sec. Drugs were delivered by perfusion. To induce potentiation of the evoked potentials, tetanic stimulation was applied at the same intensity through the same stimulating electrode as used for the test stimulation. The magnitude of LTP was evaluated by the population spike amplitude 30 min after tetanic stimulation. 

Very recently, Bailey and Richards (23) have shown that a high degree of sensitivity for adsorbed species can be achieved by measuring the absorption of infrared radiation on a thin sample cooled to liquid helium temperature. The optical arrangement used in these studies is shown in Figure 10. The modulated beam produced by the interferometer is introduced into the UHV sample chamber and reflected off a thin slice of monocrystalline alumina covered on one side by a 1000 k film of nickel or copper. Radiation absorbed by the sample is detected by a doped germanium resistance thermometer. The minimum absorbed power detected by this device when operated at liquid helium temperature is 5 x 10 14 W for a 1 Hz band width. With this sensitivity absorbtivities of 10"4 could be measured. 

Kidney tissue is fixed with paraformaldehyde-lysine-periodate by vascular perfusion (Brown et al., 1996). Tissue slices are further fixed overnight at4°C with the same fixative and stored in PBS (pH 7.4) containing 0.02% sodium azide. They are placed in 30% sucrose in PBS for at least 1 hr, and then surrounded by a drop of Tissue-Tek embedding medium on a cryostat chuck before freezing by immersion in liquid nitrogen. Cryostat sections about 5 p,m thick are cut at a chamber temperature of -25°C, collected on Fisher Superfrost Plus charged slides, and stored at —20°C until use. 

There are several direct ways to transfer tissue slices to the sample plate. First, the frozen tissue slice is gently positioned on the cold target plate (—15°C) using an artist s bmsh and thawmounted onto the plate by quickly moving it out of the cryostat chamber the frozen section then adheres to the MALDI plate when held at room temperature. As an alternative procedure, one can attach the section to a doublesided transparent tape, which is then glued on the sample plate (Schwartz et al., 2003). 

Fitz took in the array of chambers, each one supposedly a gateway into a tempting slice of history. Practical was always far more engaging than theory. Can I have a go he asked. 

Figure 4.11 A three-dimensional reconstruction of multiphoton microscope acquired image slices of a series of small vessels in the dorsal skinfold window chamber. Taken with a 40x water immersion objective and digitally zoomed to approximately 60x.

Passeraub, Ph.A., Almeida, A.C., Thakor, N.V., Design, microfabrication and analysis of a microfluidic chamber for the perfusion of brain tissue slices. Biomed. Microdevices 2003, 5(2), 147-155. 

Chemical Analysis. Three separate specimens were used for chemical analyses for each modification. The first was the unexposed wood. The second was the outer 0.5 mm of wood (removed by slicing with a razor) exposed in the accelerated weathering chamber (referred to as "outer specimen"). The third specimen was the remainder of the exposed specimen after removal of the 0.5 mm of exposed wood surface (referred to as "inner specimen"). All specimens were ground to pass a 40-mesh screen and ovendried for 16 hrs at 105°C before chemical analysis. 

Thin slices of tissue are placed in clean plastic petri dishes, the loose fitting lids replaced and the dishes inserted into the chamber of the freeze drier. Blood specimens can be poured directly into the dish. It is important that the tissue be thoroughly frozen prior to evacuating the chamber. The time required for complete drying of the sample depends on the nature and weight of the material and the type of equipment employed. Drying is usually completed in 12—48h. The dried tissue is not susceptible to decay and can be stored at room temperature in sealed plastic bags. 

The pulsed primary beam is passed through a skimmer into the main chamber a chopper wheel located after the skimmer and prior to the collision center selects a slice of species with well-defined velocity that reach the interaction region. This section of the beam then intersects a pulsed reactant beam released by a second pulsed valve under well-defined collision energies. It is important to stress that the incorporation of pulsed beams allows that reactions with often expensive (partially) deuterated chemicals be carried out to extract additional information on the reaction dynamics, such as the position of the hydrogen and/or deuterium loss if multiple reaction pathways are involved. In addition, pulsed sources allow that the pumping speed and hence costs can be reduced drastically. 

Direct sampling of mantle rocks and minerals is limited to tectonic slices emplaced at the surface (see Chapter 2.04), smaller xenoliths transported upwards by magmatic processes (see Chapter 2.05), and still smaller inclusions in such far-traveled namral sample chambers as diamonds (see Chapter 2.05). Because of such limited direct access to mantle materials, knowledge of mantle structure, composition, and processes must be augmented by geophysical remote sensing. What can various seismological observations tell us about the major-element composition of the upper mantle How can they constrain possible differences in chemical composition between the upper... 

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