Psychometric properties of the Italian version of the multifactorial memory questionnaire for adults and the elderly.

Reliable and valid metamemory measures are needed to assess subjective memory complaints that can be distinct from objective memory performance. The Multifactorial Memory Questionnaire (MMQ) evaluates dimensions of subjective memory functioning such as frequency of memory problems (Ability), affect related to memory abilities (Contentment), and strategy use in everyday life (Strategy). To examine the psychometric properties of the Italian version of the MMQ, six hundred Italian healthy individuals (aged 25-91 years) completed MMQ, a questionnaire assessing metacognition (Cognitive Failures Questionnaire, CFQ) and two batteries assessing cognitive global status (Montreal Cognitive Assessment, MoCA; Mini Mental State Examination, MMSE). MMQ was easy to administer, acceptable, and had good test-retest reliability (r for the total MMQ score 0.95), and internal consistency (Cronbach's α for the total MMQ score = 0.83). An exploratory factor analysis provided a four-factor solution: "Ability" (α = 0.99), "Contentment" (α = 0.91), "External Strategies" (α = 0.85) and "Internal Strategies" (α = 0.78) factors. MMQ total score and MMQ-Ability factor score showed good convergent validity when compared to CFQ score (r rho ≥ 0.51), whereas MMQ total score and the four MMQ factors showed good divergent validity when compared to MoCA and MMSE score (r rho ≤ 0.27). Demographic variables significantly influenced MMQ total score and most subscale scores. From the derived linear equations, we computed correction factors for raw scores and percentile distribution of adjusted scores. The Italian version of MMQ is reliable and valid to assess dimensions of metamemory in adult and elderly subjects.

Differential effects of L-thyroxine on cardiac and hepatic monoamine oxidase activity toward benzylamine and serotonin.

Male and female rats of 2 age groups were given subcutaneous injections of L-thyroxine (500 mug/kg) at 12 h intervals for a period of 10 days. The activity of monoamine oxidase (MAO) in normal and thyrotoxic rats was studied with two substrates: benzylamine and serotonin. The results showed that a thyroxine effect on cardiac and liver MAO activity is dependent on the substrate used in the assay. Kinetic studies of cardiac and liver MAO after thyroxine-treatment showed an unaltered Km for benzylamine but a change in Km for serotonin. Both findings may indicate a discriminative action of thyroid hormones on different forms of MAO. The possible presence of a soluble activator and inhibitor for MAO was investigated.

Studies on the depletion of brain amines by m-tyrosine.

The biochemical basis of the well-known physiological and pharmacological actions of m-tyrosine was examined by a detailed study of its effect on the brain biogenic amines. m-Tyrosine was injected i.p. and rat brain monoamine levels were measured. Endogenous levels of dopamine, norepinephrine and serotonin all showed approximately 50% reductions 1 h after the administration of L-m-tyrosine at 150 mg/kg. These actions of L-m-tyrosine could be blocked by the inhibition of the central dopa decarboxylase. Depletion of brain monoamines was also observed with the D-isomer of m-tyrosine, although this effect was less pronounced than that of the L-isomer. In vitro experiments with rat brain homogenates showed that L-m-tyrosine, m-tyramine and m-octopamine enhanced in efflux of exogenous labeled monamines from brain particles, whereas D-m-tyrosine was completely ineffective. From these results it is concluded that the observed decreased in brain monamine levels by L-m-tyrosine may be due to a m-tyramine-enhanced release of the amines which are quickly metabolized in vivo.

On hepatic mitochondrial monoamine oxidase activity in lipid deficiency.

A marked decrease in liver mitochondrial monoamine oxidase activity was noticed in rats fed a fat-free diet as compared with that of their controls. In lipid-deprived rats, the specific activity of this enzyme was very low towards different substrates studied. The activity of kynurenine 3-monooxygenase, which like monoamine oxidase is localized on the mitochondrial outer membrane, was similarly depressed under conditions of lipid deprivation. On the other hand no major changes were observed in the activity of the inner membrane enzyme, kynurenine amino-transferase. Mitochondria from fat-free diet-fed rats were deficient in essential fatty acids whereas no appreciable variations were found in the relative proportions of phospholipids in comparison with those of control mitochondria. Mitochondrial monoamine oxidase activity of the deficient rats retained its sensitivities to inhibitor drugs like clorgyline and deprenyl. No changes were noticeable in the substrate specificity of monoamine oxidase in these rats. When we switched the fat-free diet-fed rats to a diet supplemented with a source of essential fatty acids, there was an elevation in the activities of both monoamine oxidase and kynurenine 3-monooxygenase, their levels approaching those of the control rats.

Solubilization and partial purification of particulate catechol-O-methyltransferase from rat liver.

Particulate catechol-O-methyltransferase (COMT) from rat liver has been solubilized by acetone treatment and partially purified. Results from the present study demonstrate that the solubilized, partially purified enzyme is similar to the cytosol COMT with respect to molecular weight, pH profile, sensitivity toward inhibitors, Mg2+ requirement, and substrate affinities. However, a comparison of the crude particulate COMT and the solubilized enzyme shows that there is a significant difference in their affinity for catechol substrates. This finding suggests that membrane protein and (or) lipid components may play an important role in catecholamine metabolism. The relationship of particulate COMT to [3H]norepinephrine binding was investigated. No correlation between the COMT and [3H]norepinephrine binding activities was observed in vitro.

On the characteristics of mitochondrial monoamine oxidase in pancreas and adipose tissues from genetically obese mice.

The substrate specificity of mitochondrial monoamine oxidase (MAO) in pancreatic and adipose tissues of obese mice and their lean counterparts was determined. The pancreatic MAO of obese mice had a greater specific activity than that of the lean mice. The white adipose tissue MAO was found to be more active than the brown adipose MAO in both groups of mice. While there was no appreciable difference in the MAO activities of brown adipose tissues between obese and lean mice, the enzyme from the white adipose tissue of obese mice had a higher specific activity than that of the lean mice. The higher MAO activity in white adipose tissue was observed when tyramine or serotonin was employed as substrate but not with benzylamine. Examination of mitochondrial MAO from epididymal adipocytes revealed marked differences in the properties of the enzyme between whole adipose tissue and isolated adipocytes. The inhibition characteristics of MAO from these tissues were studied with the specific inhibitors clorgyline and deprenyl.

Liver monoamine oxidase in the obese-hyperglycaemic (ob/ob) mouse.

1. The specific activity of monoamine oxidase was found to be greater in liver mitochondria from ob/ob mice than from lean mice. The activities of marker enzymes were similar in both tissues. 2. Experiments with various substrates (5-hydroxytryptamine, benzylamine and tyramine) and inhibitors (clorgyline and deprenyl) indicated that, unlike rat liver mitochondria, mouse liver mitochondria contain a predominance of the B-form of monoamine oxidase. 3. The Km values for lean and ob/ob mice were the same for any given substrate and were in the increasing order 5-hydroxytryptamine less than tyramine less than benzylamine. Vmax. was approximately 50% greater in obese than in lean mice. 4. Extraction of liver mitochondria with acetone/water or acetone/water/NH3 to remove lipids decreased the enzyme activity relatively more in obese- than in lean-mice preparations, but residual activity was the same in both preparations.

In vivo studies on the conversion of m-tyrosine to 3,4-dihydroxyphenylalanine in the rat.

The question whether m-tyrosine can give rise to catechols in vivo has been investigated using labelled precursor. DL-[2-14C]m-tyrosine (38 muCi/mmol (1 Ci = 37 GBq)) was synthesized from [2-14C]glycine. Radioactive catechols in rat brain, liver, and kidneys were examined 15 min after intraperitoneal administration of DL-[2-14C]m-tyrosine (100 mg/kg). The kidney was the only organ which showed demonstrable amounts of radioactive catechols, and about 14% of the catechols formed was identified as 3,4-dihydroxyphenylalanine (dopa), 22% as 3,4-dihydroxyphenylacetic acid, and 56% as dopamine. However, when the animals were pretreated with dopa decarboxylase inhibitor, labelled catechols were also observed in liver and brain, and dopa accounted for over 95% of the catechols formed in all three organs examined. Thus it is clear that m-tyrosine can by hydroxylated in vivo. Results from experiments using [2-14C]m-tyrosine enantiomers and specific enzyme inhibitors suggest that phenylalanine hydroxylase could be the enzyme catalyzing this reaction.