Comparison of in vivo 1H MRS of human brain tumours with 1H HR-MAS spectroscopy of intact biopsy samples in vitro.

High resolution magic angle spinning (MAS) 1H nuclear magnetic resonance (NMR) spectroscopy has been employed to study intact human brain tumour tissue and comparison with the corresponding in vivo spectrum has been made. Two dimensional 1H MAS-NMR measurements, including J-resolved and homonuclear shift correlation spectra, were obtained to aid metabolite signal assignment. MAS gave greatly improved line-shape and reduced line-width in comparison to conventional high resolution in vivo 1H MRS of intact tissue, permitting the simultaneous detection of cellular lipids and metabolites. The technique provides the most direct method for comparison of in vivo spectra with high resolution spectra in vitro and hence allows more reliable peak assignment of in vivo 1H MRS spectra.

High resolution 1H NMR spectroscopic studies on dynamic biochemical processes in incubated human seminal fluid samples.

High resolution 600 MHz 1H NMR spectroscopy was used to investigate the changes in biochemical composition of whole human seminal fluid (SF) and an artificial mixture of prostatic (PF) and seminal vesicle fluid (SVF). A variety of time-related biochemical changes were monitored simultaneously and non-invasively in SF, including enzymatic hydrolysis of phosphorylcholine to choline and polypeptides to amino acids. The fastest NMR-observable reactions in SF were the conversion of phosphorylcholine to choline (t1/2 approximately equal to 9 min) and uridine-5'-monophosphate (UMP) to uridine (t1/2 < 2 min). UMP has not previously been detected in SF because of its rapid hydrolysis. Artificial mixtures of separately obtained prostatic and SVF showed very similar biochemical changes to those observed in whole SF. Addition of EDTA to SF incubated for 2 min post ejaculation strongly inhibited peptide hydrolysis. Zn2+, present in whole SF was shown to be non EDTA-chelatable 2 min after ejaculation, whereas after 7 min, a singlet signal from the ethylenic protons of the Zn-EDTA2- complex was clearly observed which remained constant after 7 min. This indicates that soon after ejaculation (< 5 min) Zn2+ is immobilised in a macromolecular complex which is rapidly broken down by proteolytic enzymes, the released Zn2+ then being free to react with EDTA. Mg- and Ca-EDTA2- complexes were observed at 2 min and remained constant (at 1.4 and 2.1 mM, respectively) throughout the entire time course of the experiment. These studies cast new light on the time-related biochemical changes occurring in the post-ejaculatory SF which may have an important role in reproductive function.