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In vivo 1H MRS can be used to detect and quantify the lactate resonance at 1.3 ppm provided that overlapping lipid resonances are eliminated. A homonuclear spectral editing method was developed to acquire uncontaminated 1H spectra of lactate with adiabatic pulses. An advantage of the adiabatic pulse sequence is the ability to induce uniform flip angles and to maximize sensitivity in applications employing surface coil transmitters which produce highly inhomogeneous B1. Glycolytic activity in an intracerebral C6 glioma in rats was monitored by using adiabatic editing sequences to observe [3-13C]lactate produced from infused [1-13C]glucose. Acute hyperglycemia (serum glucose > 22 mM, n = 10) had no significant effect (P = 0.08) on the total ([12C] + [13C]) tumor lactate signal intensity.

Examination of Giardia muris cysts stained with the fluorogenic dyes, fluorescein diacetate (FDA) or propidium iodide (PI), by either Nomarski differential interference contrast (DIC), phase, or brightfield (BF) microscopy revealed a direct correlation between morphologic appearance and uptake of FDA or PI. Cysts incorporating FDA were all morphologically identical and exhibited (1) a clearly delineated cyst wall, (2) the presence of a distinct space between cyst wall and cytoplasm, and (3) flagella recognizable at one pole of the cyst. FDA-positive cysts also had a hyaline appearance of the cytoplasm (examined at multiple focal planes with DIC) that made it very difficult to detect the presence of nuclei, intracellular axonemes of flagella, or curved elements of the adhesive disc. However, PI-stained cysts possessed a distinct morphology that was clearly different from that of FDA-stained cysts. Examination of PI-stained cysts demonstrated the presence of well-defined nuclei, intracellular axonemes, and curved elements of the adhesive disc. The cytoplasm of PI-stained cysts contained a fine granular texture as opposed to the hyaline appearance of FDA-stained cysts, and no space was observed separating the cyst wall from the underlying cytoplasm in the PI cyst. This light microscopic comparison of viable FDA- and nonviable PI-stained cysts of G. muris demonstrates that 2 types of cysts can be distinguished and implies that structural differences can be used to identify these subpopulations of cysts.(ABSTRACT TRUNCATED AT 250 WORDS)

We have shown that cysts of the genus Spironucleus share many common morphological features with Giardia cysts including: 2-4 nuclei, flagellar axonemes, a distinct cyst wall, and they even display the same immunostaining as Giardia cysts when labeled with antibodies specific for Giardia cyst wall. A direct comparison of Spironucleus muris and Giardia microti cysts has revealed that cysts of S. muris are significantly smaller than cysts of G. microti. At the ultrastructural level, the cyst walls are similar in fibrillar appearance, but the width of the S. muris cyst wall is significantly less than that of G. microti. The cysts of S. muris also differ from G. microti in that they contain a striated rootlet fiber, flagellar sheath, and numerous glycogen rosettes. Characteristic features of Giardia include the adhesive disc and median body. Although the cysts of Spironucleus and Giardia are similar in appearance, these unique morphological features can be used to distinguish between the 2 protozoa and should be employed in the detection of Giardia cysts in water samples. Giardiasis is the most common waterborne