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A Minelli

Publications and source records attributed to A Minelli.

At least 109 records · Page 6Linked to original sources
PubMed1979

Purification and characterization of 3,4-dihydroxyphenylalanine decarboxyase from pig kidney.

A procedure for 3,4-dihydroxyphenylalanine decarboxylase from pig kkdney purification is described in detail. The preparation has no detectable impurity on electrophoresis and on ultracentrifugation and authors. However two significant differences are observed: a different stimulation of activity by added pyridoxal 5'-phosphate and a nearly complete decarboxylation of L-3,4-dihydroxyphenylalanine in absence of added coenzyme. Absorption, fluorescence and circular dichroism properties of the coenzyme-apoenzyme interaction are also described. The results are consistent with the existence of at least four coenzyme-apoenzyme complexes, three of them active.

Animals↗
PubMedDate not supplied

Neuronal and glial localization of NMDA receptors in the cerebral cortex.

The crucial role of glutamate receptors of the N-methyl-D-aspartate (NMDA) type in many fundamental cortical functions has been firmly established, as has its involvement in several neuropsychiatric diseases, but until recently, very little was known of the anatomical localization of NMDA receptors in the cerebral cortex of mammals. The recent application of molecular biological techniques to the study of NMDA receptors has allowed the production of specific tools, the use of which has much increased our understanding of the localization of NMDA receptors in the cerebral cortex. In particular, immunocytochemical studies on the distribution of cortical NMDA receptors have: 1. Demonstrated the preferential localization of NMDA receptors in dendritic spines, in line with previous work; 2. Disclosed a thus far unknown fraction of presynaptic NMDA receptors on both excitatory and inhibitory axon terminals: and 3. Shown that cortical astrocytes express NMDA receptors. These studies indicate that the effects of cortical NMDA receptor activation are not caused exclusively by the opening of NMDA channels on neuronal postsynaptic membranes, as previously assumed, and that the activation of presynaptic and glial NMDA receptors can contribute significantly to these effects.

Adult↗
PubMedDate not supplied

Holomeric vs. meromeric segmentation: a tale of centipedes, leeches, and rhombomeres.

Explaining the origin and evolution of segmentation is central to understanding the body plan of major animal groups such as arthropods, annelids, and vertebrates. One major shortcoming of current views on segmentation is the failure to recognize the existence of two layers of segmentation. I distinguish here holomeric segmentation, involving the whole body axis (or the whole axis of an appendage) and producing "true" segments (eosegments); and meromeric segmentation, producing merosegments within one or more eosegment(s). In terms of developmental mechanisms, meromeric segmentation is probably the same as compartmentalization. This process follows two rules: (1) merosegments are formed from a stereotyped pattern of subdivisions, where only the merosegments in contact to the anterior or posterior boundary of the eosegment are allowed to divide; (2) contiguous eosegments undergoing meromeric segmentation generate merosegments according to identical lineage patterns apart from possible lineage truncation in one or a few terminal eosegments. The segmentation model proposed in this paper is mainly supported by evidence from comparative morphology, but it is compatible with known cellular and developmental mechanisms. The development of vertebrate rhombomeres, the annulation of leeches, the subdivision of the distal part of insect antenna into flagellomeres and the segmentation of centipedes are interpreted here in terms of meromeric segmentation. Some of these phenomena, like centipede segmentation, have thus far defied all attempts at an explanation, both in mechanistic (developmental) and phylogenetic terms. The model presented in this paper suggests a rich research agenda at all levels, from molecular and genetic to morphological and phylogenetic.

Animals↗
PubMedDate not supplied

Limbs and tail as evolutionarily diverging duplicates of the main body axis.

Contrasting hypotheses have been proposed to explain the pervasive parallels in the patterning of arthropod and vertebrate appendages. These hypotheses either call for a common ancestor already provided with patterned appendages or body outgrowths, or for the recruitment in limb patterning of single genes or genetic cassettes originally used for purposes other than axis patterning. I suggest instead that body appendages such as arthropod and vertebrate limbs and chordate tails are evolutionarily divergent duplicates (paramorphs) of the main body axis, that is, its duplicates, albeit devoid of endodermal component. Thus, vertebrate limbs and arthropod limbs are not historical homologs, but homoplastic features only transitively related to real historical homologs. Thus, the main body axis and the axis of the appendages have distinct but not independent evolutionary histories and may be involved in processes of homeotic co-option producing effects of morphological assimilation. For instance, chordate segmentation may have originated in the posterior appendage (tail) and subsequently extended to the trunk.

Animals↗