Gangliosides stimulate protein synthesis, growth, and axon number of regenerating limb buds

Dental innervation: functions and plasticity after peripheral injury

Oral tissues including the periodontal ligament, gingiva, and tooth pulp have a relatively dense sensory innervation and a rich vascular supply. Teeth and supporting tissues are susceptible to tissue injury and inflammation, partly due to lack of collateral blood and nerve supply and to their low compliance. This review focuses on dental nerve functions and adaptive changes in the trigeminal ganglion and tooth pulp after peripheral injuries. An overview of the peptidergic innervation of oral tissues is presented, followed by a discussion of plasticity in neuropeptide expression in trigeminal peripheral neurons after local insults to teeth and peripheral nerve injuries. The functional implications of these adaptive changes are considered, with special reference to nerve regeneration, inflammation, and hemodynamic regulation.

Exogenous gangliosides may affect methylation mechanisms in neuronal cell cultures

Primary neurons in culture from chick embryo cerebral hemispheres were treated with a mixture of gangliosides added to the growth medium (final concentration: 10(-5)M and 10(-8)M) from the 3rd to the 6th day in vitro. Under these conditions methylation processes measured with [3H] and [35S] methionine and [3H]ethanolamine as precursors showed an increased methylation of [3H]ethanolamine containing phospholipids, a correspondent increased conversion of these compounds to [3H]choline containing phospholipids, and a general increased methylation of trichloroacetic acid precipitable macromolecules containing labeled methionine. A small increase in protein synthesis was observed after incubation of neurons with [3H]- and [35S]methionine. This was confirmed after electrophoretic separation of a protein extract with increased 3H- and 35S-labeling in protein bands with moecular weights between 50 and 60 KDaltons. A protein band of about 55 KDaltons appeared to be preferentially labelled when [3H] methionine was the precursor. The treatment with gangliosides increased the incorporation of [methyl-3H] label after incubation of neurons with [3H] methionine, into total DNA and decreased that of total RNA. The treatment of neurons in culture with exogenous gangliosides hence affects differently methylation processes, a finding which may confirm the involvement of gangliosides on the intracellular mediation of neuronal information mechanisms.

Differential limb regeneration in diploid and triploid Rana pipiens larvae with reference to spinal motor neuron development

Developmental manipulations that can alter nerve-limb relationships can assist in understanding the neural control of limb regeneration. Pressure-induced triploidy in Rana pipiens tadpoles results in alterations of the quantitative characteristics of the spinal motor neurons that innervate the limbs, whereas the limbs appear unaltered. Unilateral midthigh amputations at larval stages IX, XI, and XIII of diploid and triploid animals resulted in complete regeneration for only stage IX animals regardless of ploidy. Nevertheless, triploid limbs regenerated much faster than did diploids, an event that can be related to the differential dynamics of nerve fiber extension and/or the altered numbers and sizes of triploid spinal motor neurons. Although normal limb development from stage IX to the endpoint at stage XVIII was the same in diploids and triploids, the rate of regeneration in triploids was nearly twice that of diploids. The data of this noninvasive means of altering the quantitative relationship of nerve-to-peripheral target suggest a unique means of studying nerve-dependent limb regeneration in an animal that progressively loses its regenerative capability during development.

Growth, development, and aging of orofacial tissues: neural aspects

Neural factors influence post-natal growth, development, and aging throughout the body. This influence may be mediated through sensory or motor effects interacting with endocrine and immunological factors. Growth effects may be expressed directly by sensory or motor nerves on the tissue or indirectly by motor function. Direct neutrotrophic effects have been well-documented in the development of striated muscle, the taste bud, and the amphibian limb. Evidence for a trigeminal neurotrophic effect on tooth development and facial development is lacking. Growth disturbances of the jaws consequent to lesioning of the trigeminal nerve are due most likely to functional disturbances rather than neutrotrophism. Examples of function impact on orofacial growth are abundant. Oral and facial target tissues, like those elsewhere in the body, determine the nature of the target tissue innervation and its central organization. Central effects consequent to tooth loss or dental pulp entirpation are well-documented. Inflammation and pain may exert growth effects through release of "wound hormones" or secondarily to somatic and autonomic effects. There is evidence that vasoactive intestinal peptide (VIP) and calcitonin gene-related peptide (CGRP) elaborated from sympathetic and parasympathetic neurons may have a modulatory role in growth. While the effects of longstanding motor pathologies on skeletal growth are well-known, concomitant sensory deficits and soft tissue disturbances have not been examined. However, the pathological models beg the question of normal regulation. While muscle develops in the absence of innervation, neurotrophic effects are clearly identified. Little is known about the interaction of simple and complex motor behavior on growth. Regulation of growth is frequently visualized within a form-function paradigm. For example, anterior open bites have been seen as the consequence of tongue thrusting or tongue thrusting as a consequence of open bites. Low tonic forces in posture are thought to be more important in the development of both the face and the dental alveolar complex than the higher intermittent forces in mastication and swallowing. The need for an active (reflex) contribution to growth at the TMJ is in dispute.(ABSTRACT TRUNCATED AT 400 WORDS)

Gangliosides in the nervous system during development and regeneration

Gangliosides are present in nervous tissues of echinoderms and chordates, but the amounts and patterns differ widely. There are changes in the ganglioside contents of nervous tissues during development in most animals studied. To a large extent, regional differences and changes with development and degeneration in ganglioside composition reflect changing and different proportions of cellular types and subcellular organelles within the tissue. GM1 and GM4 are enriched in myelin; GD1a may be a marker for dendritic arborization. During regeneration of fish optic nerve and rat sciatic nerve there is an increased amount of ganglioside proximal to the regenerating axon tips, which may largely be a result of accumulation. This could provide a relatively large reservoir of ganglioside to become incorporated into the sprouting axolemma. Gangliosides added exogenously to growth medium can induce neuritogenesis of several types of neurons. The mechanisms of this action are unknown but may be related to nerve growth factor, microskeletal organization, membrane fluidity, and other factors. Gangliosides injected into young animals affect brain development, but further studies are required to determine these effects more specifically. Ganglioside administration increases the number of sprouts in regenerating peripheral nerves, but does not seem to accelerate axonal elongation. Parenterally administered gangliosides alter the recovery of brain tissue from a variety of types of lesions, and clinical trials are in progress to determine if they are of benefit in human neurological disorders. The biochemical mechanisms of these in vivo ganglioside effects are poorly understood, but may involve modulation of several enzyme systems as well as other properties of neural membranes, such as fluidity. It is possible that gangliosides may play similar roles and operate through some of the same mechanisms in developing and regenerating nervous tissues.

Expression and function of neural cell adhesion molecule during limb regeneration

The neural cell adhesion molecule (NCAM) has been detected in regenerating limb bud of adult newts in addition to brain and peripheral nerves. In the regenerating tissue, NCAM was found primarily on mesenchymal cells and also in wound epidermis. Infusion of Fab fragments of antibodies to NCAM into limb buds at the early blastema stage delayed the regenerative process. Previous studies have indicated that NCAM serves as a homophilic ligand for adhesion among cells that express this molecule and, in doing so, can influence the interaction of nerves with their environment. The expression of NCAM in regenerating limb and the effects of antibody infusion are therefore consistent with the observation that limb regeneration requires interactions among axons and mesenchymal cells.