Plasma osmolality and brain water content in a rat glioma model

Little is known about how intravenous fluids influence peritumoral edema formation. This experiment was designed to determine, in a rat glioma model, whether changes in plasma osmolality alter water content, as assessed by specific gravity (SpGr), in normal and neoplastic cerebral tissue. Cells cultured from an ethylnitrosourea-induced rat glioma were stereotactically implanted into the right striatum of Fischer 344 rats. A tumor growth interval of 21 days was allowed. In a second experiment, rats underwent a 60-second cortical freeze injury followed by 24 hours' recovery. In both experiments, rats were assigned to one of three groups: hypotonic (100 ml/kg of 0.2 mol/L NaCl in H2O, intraperitoneally; resultant plasma osmolality approximately 268 mOsm/kg); isotonic (no treatment; plasma osmolality approximately 298 mOsm/kg); or hypertonic (10 ml/kg of 1.0 mol/L NaCl in H2O, intraperitoneally; plasma osmolality approximately 342 mOsm/kg). Thirty minutes after fluid injection, regional SpGr was determined using a kerosene-bromobenzene gradient. In subsets of rats, the tissue morphology and blood-brain barrier permeability of Evans blue dye were assessed. Tissue within the freeze lesion was stained by Evans blue dye with sharp demarcation. Evans blue dye did not stain gliomatous tissue, and central necrosis was not histologically evident. In isotonic rats, glioma SpGr was reduced (1.0411 +/- 0.0012 g/ml) relative to the contralateral striatum (1.0437 +/- 0.0008 g/ml; P < 0.001). Despite this, a strong linear relation was observed for SpGr and plasma osmolality in both neoplastic and normal tissue. Within the freeze lesion in isotonic rats, SpGr was severely reduced (1.0335 +/- 0.0008 g/ml; P < 0.0001) compared with contralateral frontal cortex.(ABSTRACT TRUNCATED AT 250 WORDS)     

An investigation of wet-and dry-bulb psychrometry in metallic vapor-gas systems

Wet- and dry-bulb temperatures were measured for Hg-N₂ and Cd-H₂ systems in a high temperature psychrometer apparatus specially constructed for this purpose. The apparatus features a device termed a self-adjusting shield developed to minimize heat transfer by radiation. A correlation for the psychrometric ratio for spherical shaped wet bulbs was formulated and experimental results showed close agreement with the theoretical values calculated from the proposed correlation. Formerly Graduate Student, University of New South Wales, Formerly Associate Professor, University of New South Wales     

The effect of an electric field on the solidification of off-eutectic tin-lead composite alloys

The influence of an electric field upon the directional solidification of hypoeutectic and hypereutectic Sn-Pb composite alloys was studied. Equations were derived to account for the effect of electrotransport of solute in the liquid upon the solid composite composition. Experimental results support the theoretical predictions. Mixing in the liquid is more strongly influenced by unstable solute gradients than by current induced convection. Electrotransport shows limited promise as a method for control of the volume fraction fibre phase in the preparation of aligned composites by directional solidification.     

Alkane contamination of lipids extracted fromLagenidium giganteum andLagenidium callinectes

Alkanes associated with the mycelia of the fungiLagenidium giganteum andL. callinectes were analyzed. Careful studies showed that these substances were contaminats derived from glass ware, media and solvents. No alkane biosynthesis or transformation was detected, indicating little or no alkane metabolism. The importance of using clean techniques, high-purity solvents and proper media controls was emphasized.     

Replacing the depletion approximation

The general solution recently offered for the surface and step-junction problem has a parabolic potential vs position asymptote extending toward the surface or junction. The vertex of this asymptotic parabola defines a spatial origin that is invariant with respect to the general solution and that facilitates analysis. In a depleted surface or junction problem, for example, the expression x/L_D=?√s2(W?1) relates position and potential with an error less than one-third of one percent from W = 3 to W = ∞ in the absence of an inversion layer, where W is normalized potential referred to the bulk potential and L_D is the general Debye length. An accurate asymptotic expression relating position and potential toward the bulk (away from the surface or junction) is (x/L_d) =?0.41209-In W when the same spatial origin is employed. A single exponential expression serves to bridge the gap between the asymptotic expressions with accuracy overall of ±3%. Because these expressions are far more accurate than the corresponding depletion-approximation expression and yet are very simple and easy to use, we offer this approximate treatment of the surface and equilibrium-step-junction problems as a replacement for the depletion approximation. The location of the depletion-approximation boundary is pinpointed for several junctions.