Antonietta Nicotra

Monoamine oxidase expression during development and aging.

Monoamine oxidase (MAO) isoenzymes play a major role in regulating the concentration of several bioactive amines, including serotonin and catecholamines. Both in the nervous system and in peripheral organs, MAOs can potentially modulate all the processes involving these bioactive amines. In the present article, we review some of the most significant articles published so far on changes in MAOs during development and aging. The data available on development refer mainly to the mammal brain at fetal and post-fetal stages. Very little work has been done on studying MAO ontogenesis during early development, that is, at stages prior to organogenesis, and what has been done refers to non-mammal vertebrates such as fish, amphibians and birds. MAO A and MAO B changes have been measured as values of enzymatic activity, as amount of protein or, more rarely, as amount of mRNAs. A knowledge of MAO developmental changes not only provides a basis for the investigation of factors regulating MAO expression, but can also contribute to a better understanding of the possible trophic and/or morphogenetic role of monoaminergic neurotransmitters in the developing brain. Transgenic mice lacking MAO A and rodents treated with MAO inhibitors during gestation have been very useful in this second case. The investigations of changes in MAO A and MAO B during aging in the literature refer mostly to humans, mice and rats. Interest in studies on aging is stimulated, among other things, by the observation that age-related diseases leading to neurodegenerative phenomena could be accompanied by changes in MAO activity.

Some characteristics of mitochondrial monoamine oxidase activity in eggs of carp (Cyprinus Carpio) and rainbow trout (Salmo Gairdneri)

1. Monoamine oxidase (MAO) activity towards tryptamine, 5-hydroxytryptamine (5-HT) and phenylethylamine (PEA) has been measured in mitochondria isolated from carp and trout eggs. 2. In carp eggs all the tested substrates are metabolized and the highest affinity is found with tryptamine. In trout eggs a consistent level of MAO activity is obtained using tryptamine. 3. The inhibition dose-response curves of clorgyline and deprenyl indicate that both in carp and trout eggs there is only one form of mitochondrial MAO, distinct from MAO A and B which have been described in vertebrate tissues. 4. Both in carp and trout egg mitochondria a semicarbazide-sensitive amine oxidase is not involved in the deamination of the used substrates. 5. MAO found in carp and trout eggs might be involved in metabolism of some neurotransmitter monoamines during early developmental stages.

Ultrastructure of the mature sperm and spermiogenesis in Callista chione (Mollusca, Bivalvia)

Summary The ultrastructure of the mature spermatozoon and spermiogenesis of the bivalve Callista chione (Heterodonta, Veneridae) are described. As our TEM and SEM observations show the spermatozoon of C. chione may be considered of primitive type. The head contains a slightly curved nucleus bearing at the apex a short cone-shaped acrosome. The structure of the acrosome is typical of heterodont bivalves and, as in other venerid bivalves, it comprises a distinct axial rod. The mid-piece is an annular band of five mitochondria which surround the proximal and the distal centrioles. Occasionally spermatozoa with one or more misplaced flagella may be observed. The structural changes that occur during spermiogenesis are similar to those described for other bivalves.

Occurrence of type A and type B monoamine oxidase activities in toad egg mitochondria

Monoamine oxidase activity has been assayed radiochemically in mitochondria from Bufo bufo eggs. Time courses of MAO activity towards PEA and 5-HT indicate that when PEA is used as a substrate higher specific activities are obtained. The inhibition patterns by clorgyline and deprenyl demonstrate that both type A and type B MAO are present. Type A activity is more sensitive than type B to the inhibitory effect of Triton X-100. Low concentrations of 2-mercaptoethanol cause a slight stimulation of type A and B activities. Increasing concentrations result in a decrease of activity.

Monoamine oxidase activity in embryos of pike (Esox lucius)

1. Mitochondrial MAO specific activity was measured in eggs and early embryos of the teleostean fish Esox lucius using tryptamine, 5-hydroxytryptamine (5-HT) and phenylethylamine (PEA) as substrates. 2. Tryptamine is the most readily deaminated substrate in mitochondria isolated from unfertilized eggs and embryos at the stages of cleavage, blastula and gastrula. 3. Monoamine oxidase activity gradually decreases during development and at the gastrula stage it is respectively 80% (tryptamine), 70% (5-HT) and 50% (PEA) of that found in the egg using the corresponding substrate. 4. The inhibition of egg MAO activity by clorgyline and deprenyl measured in E. lucius eggs using tryptamine as substrate, indicates the presence of a single form of MAO not corresponding to the MAO A and MAO B described in terrestrial vertebrates.

Changes in monoamine oxidase activity by mitochondria isolated from late embryos of Bufo bufo

1. Monoamine oxidase activity has been assayed in mitochondria isolated from post-neural embryos (stages 14-25) of Bufo bufo, using 5-HT and PEA as substrates. 2. Mitochondria isolated from stages 19 to 25 show an increasing ability in deaminating monoamines, PEA being metabolized at a higher level with respect to 5-HT. 3. At all the examined stages 5-HT is metabolized by an enzyme corresponding to MAO A, while PEA, from stage 19, is largely deaminated by a semicarbazide-sensitive amine oxidase (SSAO). 4. The effect of Triton X-100 on MAO A activity appears remarkably different in mitochondria isolated from embryos at stages 14 and 25 respectively.

Monoamine oxidase activity in tissues of the starfish Marthasterias glacialis

1. Monoamine oxidase activity towards PEA and 5-HT has been shown radiochemically in radial nerves and pyloric caeca of the starfish Marthasterias glacialis. 2. Radial nerves show higher specific activities than pyloric caeca with both substrates and this is more evident with 5-HT. 3. Both in radial nerves and pyloric caeca MAO activity shows a higher affinity for PEA than for 5-HT. 4. Regardless of the substrate used, in both radial nerves and pyloric caeca deprenyl is a more effective inhibitor of MAO activity than clorgyline. 5. The inhibition curves obtained by either inhibitor are simple sigmoid curves, suggesting the presence of only one form of MAO.

Mitochondrial monoamine oxidase activity during preneural developmental stages of Bufo bufo.

Monoamine oxidase specific activities against PEA and 5-HT have been measured in mitochondria isolated from early embryos of Bufo bufo. During the early development up to the neural fold stage, MAO activity undergoes a continuous decrease that is more evident when PEA is used as the substrate. The inhibition patterns of deprenyl and clorgyline demonstrate that, at the neural fold stage, both type A and B MAO are present. Both in eggs and embryos MAO type A activity appears slightly more sensitive to the inhibitory effect of various concentrations (0.1-2 M) of the denaturing agent urea.

Propranolol induces polyspermy during sea urchin fertilization

Propranolol, a β‐adrenergic receptor blocker, is found to induce polyspermy in sea urchin eggs. Unfertilized sea urchin eggs treated for 10 min with 50 μM of propranolol, and then inseminated, become polyspermic and show a fertilization envelope which is barely visible to the light microscope. Examination of treated eggs by transmission and scanning electron microscopy shows that the drug does not alter the cortex of the unfertilized egg. However, after insemination an incomplete cortical reaction occurs. This might well account for both polyspermy and the defective elevation of the fertilization envelope. Since the effects of the drug are reversed by simultaneous treatment with adrenalin, perhaps propranolol interferes with the monoaminergic system that has been proposed to be active. The involvement of the monoaminergic system in the fertilization process is present in the sea urchin egg.

Ultrastructural observations on the interstitial cells of the testis of Paracentrotus lividus

Summary A description is given of ultrastructural changes in the interstitial cells of Paracentrotus lividus testis, occurring during the annual reproductive cycle. Three different morphological phases of the interstitial cells can be distinguished: growing phase (summer), depleting phase (fall and winter) and resting phase (spring). Each phase is characterized mainly by the presence of various kinds of granules at different stages of their assembly or disintegration. Other observations deal with the nuclear morphology and the distribution of several cytoplasmic components.