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Lexical frequency and item familiarity definitely influence name retrieval in clinical studies, but the relevance of concept typicality has been less extensively investigated. A relevant theoretical question is whether familiarity and typicality exert an independent influence on the name retrieval of aphasic patients. In this study we assembled a list of 288 items of the animals category from a semantic fluency task performed by 198 normal subjects in a previous study. The production frequency of a given animal name was used to estimate typicality, and for the whole list of animals a new normal sample estimated familiarity. The newly collected indices were used to analyse semantic fluency and picture naming of FPA, an anoxic patient. On both tasks, familiarity and typicality were more relevant than word frequency. Typicality of each stimulus, and to a lower degree familiarity, were independently able to predict the type of naming response. Thus, the influence of lexical-semantic variables on naming should be viewed, at least in this case, as something endowed with two dimensions (typicality and familiarity), while in other cases also lexical frequency may be relevant.

Initial-rate and product inhibition studies revealed distinctive ordered ternary complex kinetic mechanisms, substrate specificities, and metal ion preferences for the three isozymes of human nicotinamide mononucleotide adenylyl-transferase (NMNAT, EC 2.7.7.1). ATP binds before NMN with nuclear isozyme NMNAT1 and Golgi apparatus NMNAT2, but the opposite order is observed with the mitochondrial isozyme NMNAT3. Only the latter utilizes ITP efficiently in place of ATP, and while NMNH conversion to NADH by NMNAT1 and NMNAT3 occurs at similar rates, conversion by NMNAT2 is much slower. These isozymes can also be discriminated by their action on tiazofurin monophosphate (TrMP), a metabolite of the antineoplastic prodrug tiazofurin. Our finding that TrMP is only a substrate with NMNAT1 and NMNAT3 reveals for the first time an organelle selectivity in the metabolism of this important drug. In search of additional ways to discriminate these isozymes, we synthesized and tested the P1-(nicotinamide/nicotinate-riboside-5')-Pn-(adenosine-5') dinucleotides Np3AD, Np4AD, and Nap4AD. In addition to being highly effective inhibitors, these multisubstrate geometric inhibitors gave inhibition patterns that are consistent with the aforementioned isozyme differences in substrate binding order. Distinctive differences in their substrate specificity and metal ion selectivity also permitted us to quantify individual isozyme contributions to NAD+ formation in human cell extracts.

Semantic dissociations show that biological stimuli present a further dissociation between animals and plant life. Almost all cases of greater impairment of plant life knowledge were males, suggesting a higher male familiarity with animals possibly derived from different daily activities. To verify this hypothesis, we collected familiarity ratings for normal males and females, for 288 animals, subdivided according to whether they were hunted/fished, or were used as food. The overall familiarity was almost identical between males and females. Males were more familiar with hunted animals, but for them also food animals were more familiar. There was not a consistent effect of hunting/fishing independently of the food/not food classification. The claim that males are generally more proficient with animals knowledge because most hunters/fishers are males seems rather simplistic, and the familiarity structure of the animals category is more complex. An evolution-based account is suggested for the category by sex interaction.