Purpose Assessment of brain hemodynamics without exogenous contrast agents is of increasing importance in clinical applications. This study aims to develop an MR perfusion technique that can provide non-contrast and multi-parametric estimation of hemodynamic markers. Methods We devised an Arterial-Spin-Labeling (ASL) method based on the principle of MR Fingerprinting (MRF), referred to as MRF-ASL. By taking advantage of the rich information contained in MRF sequence, up to seven hemodynamic parameters can be estimated concomitantly. Feasibility demonstration, flip angle optimization, comparison with Look-Locker ASL, reproducibility test, sensitivity to hypercapnia challenge, and initial clinical application in an intracranial steno-occlusive process, Moyamoya disease, were performed to evaluate this technique. Results MRF-ASL provided estimation of up to seven parameters, including B1+, tissue T1, cerebral blood flow (CBF), tissue bolus-arrival-time (BAT), pass-through arterial BAT, pass-through blood volume, and pass-through blood travel time. Coefficients-of-variation (CoV) of the estimated parameters ranged from 0.2% to 9.6%. Hypercapnia resulted in an increase in CBF by 57.7%, and a decrease in BAT by 13.7% and 24.8% in tissue and vessels, respectively. Patients with Moyamoya disease showed diminished CBF and lengthened BAT that could not be detected with regular ASL. Conclusion MRF-ASL is a promising technique for non-contrast, multi-parametric perfusion assessment.

An active Neurospora-like assimilatory NADPH-nitrate reductase (EC 1.6.6.2), which can be formed in vitro by incubation of extracts of nitrate-induced Neurospora crassa mutant nit-i with extracts of (a) certain other nonallelic nitrate reductase mutants, (b) uninduced wild type, or (c) xanthine oxidizing and liver aldehyde-oxidase systems was also formed by combination of the nit-i extract with other acid-treated enzymes known to contain molybdenum. These molybdenum enzymes included (a) nitrogenase, or its molybdenumiron protein, from Clostridium, Azotobacter, and soybeats- (7). One of the subunits was believed to be a nitrate-inducible component(s) of nit-i that is responsible at least for the early part of the electron transport sequence, as reflected by its inducible NADPH-cytochrome c reductase activity which is flavin-dependent. The second component was inferred to be a constitutive entity that is absent in nit-i, but present in all other mutants and uninduced wild type, and is responsible for the latter part of the nitrate reductase pathway that includes the molybdenum moiety. The second component could also be supplied by the individual molybdenum-enzymes bovine milk and intestinal xanthine oxidases, chicken liver dehydrogenase, and rabbit liver aldehyde oxidase (8), provided they were subjected to prior acidification, a treatment known to dissociate some proteins into their subunits (9-11). (However, sodium molybdate and some 20 different partially purified enzymes that do not contain molybdenum were inactive.) In all instances, in vitro formation of enzyme activity was accompanied by the conversion of cytochrome c reductase activity (S20, = 4.5S) to the faster sedimenting form (Seo,,0 = 7.9 S) which is associated with NADPH-nitrate reductase (suggestive of subunit assembly) and the appearance of NADPH-, FADH2-, and MVH-nitrate reductase activities. The assimilatory NADPH-nitrate reductase thus formed is similar to the wild-type Neurospora enzyme. Moreover, nit-i is the only one of the nitrate reductase Neurospora mutants that also lacks xanthine dehydrogenase, and is unable to grow on hypoxanthine or nitrate as the sole nitrogen source (8), similar to certain Aspergillus mutants (12).In the present pl)aper, we report that other acid-treated mnolybdenum-enzymes from diverse phylogenetic sources can also interact with the induced Neurospora nit-i extract to form a Neurospora-like assimilatory NADPH-nitrate reductase. The results suggest the existence of a molybdenum-containing component, perhaps in the form of a molybdenum cofactor, that is shared in common by the known molybdenum-enzymes among a diversity of organisms including microbes, plants, and animals. A preliminary account of a portion of this work has been published (13).

A new non-contrast technique for the assessment of global BBB permeability was developed, which may have important clinical applications.