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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.

The purpose of this research was to document the formation of viable Giardia cysts in vitro. Viability staining, using fluorogenic dyes that required metabolic conversion for detection, and immunocytochemistry at the light microscopic level provided information on viability and for the identification of formed in vitro. Analysis of cysts formed in vivo and in vitro showed similar morphologic appearances by both light and electron microscopy. Cysts formed in vitro were capable of establishing infections in both mouse and gerbil models for giardiasis. Trophozoites obtained from mice experimentally infected with in vitro-formed cysts could be maintained in culture and induced a second time to form cysts in vitro. This model for the production of viable Giardia cysts in vitro should facilitate research on controlling the complete life cycle of Giardia outside an animal host.

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)