E. Giacobini

Time course of appearance of alpha-bungarotoxin binding sites during development of chick ciliary ganglion and iris.

The binding of [125I]alpha-bungarotoxin (ABTX) to homogenates of ciliary ganglia and irises from embryonic and posthatching chickens has been examined. Specific, high-affinity binding was found in both tissues [KD (iris)=2.5 nM;KD (ganglion)=2.7 nM]. Binding is saturated above 10 nM toxin concentration and is inhibited by low concentrations of the nicotinic antagonistd-tubocurarine. The binding may be associated with a nicotinic cholinergic receptor in both tissues. The amount of binding in the iris begins to increase soon after functional innervation is first observed, at 12 days of incubation (d.i.), and continues to increase up to four months after hatching (a.h.), the oldest age tested. In contrast, ABTX binding in the ciliary ganglion increases fourfold between 7 and 11 d.i., after which the amount of binding remains unchanged up to four months a.h. When compared to the development of choline acetyltransferase (ChAc) and acetylcholinesterase (AChE) activities in the ganglion and iris, ABTX binding follows a pattern similar to that of AChE activity. The largest increases in ChAc activity occur later than those of the postsynaptic markers. After 16 d.i. there are approximately 3×106 toxin molecules bound per neuron in the ciliary ganglion.

THE CONVERSION OF LYSINE INTO PIPERIDINE, CADAVERINE, AND PIPECOLIC ACID IN THE BRAIN AND OTHER ORGANS OF THE MOUSE

The biosynthesis of piperidine, a possible neuromodulator, and its presumed precursors cadaverine and pipecolic acid, has been investigated in the mouse under in vitro conditions. Conversion of lysine into piperidine was observed only in the intestines and is probably caused by the intestinal flora. Formation of cadaverine and pipecolic acid from lysine was observed in the brain, liver, kidney, and large intestine. In addition, pipecolic acid was formed in the heart. The possible contributions of the diet and of the intestinal bacteria to the endogenous pool(s) of piperidine are discussed.

In vitro Formation of Piperidine, Cadaverine and Pipecolic Acid in Chick and Mouse Brain during Development

We have demonstrated for the first time in vitro formation of cadaverine and pipecolid acid from L-lysine in (a) chick embryos and chick embryo heads at 3–7 days of incubation (d.i.) and 5–7 d.i., respectively; (b) brain of chick embryos from 11 d.i. to 30 days after hatching (d.a.h.) for cadaverine and from 20 d.i. to 30 d.a.h. for pipecolic acid; (c) mouse brain from 2 days after birth up to 3 months after birth; and (d) mouse embryos at days 17–20 of gestation for cadaverine and at days 13 and 17 of gestation for pipecolic acid. No in vitro formation of piperidine from L-lysine could be found in either chick or mouse embryos. Only the large intestine of the chick with its contents was able to form piperidine from L-lysine at 30 d.a.h. Neither chick nor mouse embryos were able to form piperidine from cadaverine at any stage of development investigated. Piperidine was formed in very small amounts from D,L-pipecolic acid only in the brain of chick at 16 d.a.h. and in the large intestine with its contents at 30 d.a.h. The first demonstration of cadaverine and pipecolic acid biosynthesis in the avian and mammalian brain adds further support to a possible neural role of these two substances.

Plasticity and Regeneration of the Nervous System

Molecular and Cellular Aspects of Central and Peripheral Nervous System Development.- New Molecular Insights on the Development of the Peripheral Nervous System.- DNA Content Revealed by Cytophotometry in Neurons: Variability Related to Neuroplasticity.- Prenatal Development of the Rat Amygdaloid Complex: An Electron Microscopic Study.- Recent Findings on the Regulation of Axonal Calibre.- Hormones, Neurotransmitters, Xenobiotics, and Development.- The Biogenic Monoamines as Regulators of Early (Pre-Nervous) Embryogenesis: New Data.- Hormone-Dependent Plasticity of the Motoneurons of the Ischiocavernosus Muscle: An Ultrastructural Study.- Reactive Sprouting (Pruning Effect) Is Altered in the Brain of Rats Perinatally Exposed to Morphine.- Effects of Serotonin on Tyrosine Hydroxylase and Tau Protein in a Human Neuroblastoma Cell Line.- Critical Periods of Neuroendocrine Development: Effects of Prenatal Xenobiotics.- In Vivo and in Vitro Models of Development.- Cell Plasticity During In Vitro Differentiation of a Human Neuroblastoma Cell Line.- LN-10, A Brain Derived cDNA Clone: Studies Related to CNS Development.- Spinal Cord Slices with Attached Dorsal Root Ganglia: A Culture Model for the Study of Pathogenicity of Encephalitic Viruses.- Human Fetal Brain Cultures: A Model to Study Neural Proliferation, Differentiation, and Immunocompetence.- Development and Regulation of Glia.- Origin of Microglia and Their Regulation by Astroglia.- Neuronal-Astrocytic Interactions in Brain Development, Brain Function, and Brain Disease.- Structure and Function of Glia Maturation Factor Beta.- Neuromodulatory Actions of Glutamate, GABA and Taurine: Regulatory Role of Astrocytes.- C-6 Glioma Cells of Early Passage Have Progenitor Properties in Culture.- Regeneration.- Brain Extracellular Matrix and Nerve Regeneration.- Human Nerve Growth Factor: Biological and Immunological Activities, and Clinical Possibilities in Neurodegenerative Disease.- Schwann Cell Proliferation During Postnatal Development, Wallerian Degeneration and Axon Regeneration in Trembler Dysmyelinating Mutants.- Basic FGF and its Actions on Neurons: A Group Account with Special Emphasis on the Parkinsonian Brain.- Molecular and Morphological Correlates Following Neuronal Deafferentiation: A Cortico-Striatal Model.- Monosialoganglioside GM1 and Modulation of Neuronal Plasticity in CNS Repair Processes.- Nerve Growth Factor in CNS Repair and Regeneration.- Aging.- Ordered Disorder in the Aged Brain.- Plasticity in Expression of Co-Transmitters and Autonomic Nerves in Aging and Disease.- Nicotinic Cholinergic Receptors in Human Brain: Effects of Aging and Alzheimer.- Macromolecular Changes in the Aging Brain.- ADP-Ribosylation: Approach to Molecular Basis of Aging.- Mechanisms of Cell Death.

Uptake of piperidine and pipecolic acid by synaptosomes from mouse brain

Piperidine is actively transported into the synaptosomal fraction of adult mouse brain. The transport mechanism appears to be Na+ independent but is temperature dependent and sensitive to ouabain. Analysis of kinetic experiments indicates only a “low-affinity” transport system to be present. By contrast the uptake ofD,L-[3H]pipecolic acid at a concentration of 4×10−7 M was temperature and Na+ dependent, ouabain sensitive, and revealed a two-component system with aKm=3.9±0.17×10−6 M,Vmax=129±6 pmol/mg protein/3 min for the “high-affinity” system and aKm=90.2±4.3×10−6 M,Vmax=2.45±0.19 nmol/mg protein/3 min for the “low-affinity” system. Compounds structurally related to pipecolic acid such as glycine,l-proline, 4-amino-n-butyric acid, and 5-amino-n-valeric acid showed an inhibitory effect on uptake at a concentration of 10−4 M. The demonstration of biosynthesis of pipecolic acid in mouse brain and the presence of a “high-affinity” sodium-dependent uptake system suggest a physiological role of this substance in the central nervous system.

Development and Aging of Cholinergic Synapses

We have followed the pattern of variation in the endogenous levels of acetylcholine (ACh) and choline (Ch) in sympathetic (lumbar) and parasympathetic (ciliary) ganglia, and in the iris of the chick f

The action of piperidine on cholinoceptive neurons of the snail

Abstract From our results it is concluded that piperidine can mimic the acetylcholine action on H-cells. The response of the cell membrane to piperidine administration is actuated either by piperidine, or by both piperidine and acetylcholine which was presynaptically released. The piperidine action on D-cells probably directly desensitizes the cholinoceptive sites without changing membrane potential or membrane resistance. Since it has been reported that piperidine physiologically occurs preferentially in the brain of the snail in concentrations comparable to those of other neurotransmitters6, piperidine might participate in signal processing mechanisms in the nervous system of this species by any of the actions reported here, if it were released in sufficient quantities.

Imino Acids of the Brain

Extensive and detailed review articles and chapters on brain amino acids can easily be found in the literature, including handbooks of neurochemistry. To my knowledge, this is the first chapter to discuss separately data on imino acids (cyclic secondary imino acids) present in the nervous tissue. Thirty-two substances are listed by Himwhich and Agrawal in Volume 1 of the Handbook of Neurochemistry 1 as amino acids and analogues present in the brain of five mammalian species (mouse, rabbit, guinea pig, cat, and dog). The concentrations reported in brain vary widely from a few nanomoles (half-cystine) to several micromoles (glutamic acid) per gram fresh tissue. So far, only three imino acids have been related to brain function: proline (PRO), hydroxyproline (HYP), and pipecolic acid (PA) (Fig. 1). Their concentrations in whole brain are relatively low compared to other cerebral amino acids: PRO (30–80 nmol/ g), HYP (40–80 nmol/g), and PA (18 ± 4 nmol/gla). Cat brain has ten times lower concentrations of PRO than GABA.2 However, this is the same range shown by several amino acids such as methionine, leucine, isoleucine, tyrosine, phenylalanine, and ornithine.3 It is interesting to note that several of these “trace amino acids” are present at relatively high levels (proline, valine, isoleucine, tyrosine, ornithine, and phenylalanine) in the early postnatal life and fall to significantly lower levels at 2–3 weeks after birth. These changes may result from (1) qualitative changes in protein synthesis after birth, (2) high concentrations in the mother’s blood prior to delivery, or (3) slower accumulation from circulation into the brain in the adult because of changes in the blood-brain barrier (BBB) after birth. or (4) postnatal activation of breakdown and secretion.

Synaptogenesis in chick paravertebral sympathetic ganglia: a morphometric analysis

Synaptogenesis was studied in lumbar sympathetic ganglia of chicken by light and electron microscopic morphometric methods. At 10 days in ovo, fewer than 1% of the adult number of synapses are present. The total numbers of synapses and of synaptic vesicles per ganglion increase progressively with age; however, the majority of both are formed after 30 days after hatching. The average number of synaptic vesicles per synapse increases several fold after hatching. The numbers of synapses and of synaptic vesicles per ganglion increase roughly in concert with biochemical markers of presynaptic development (activity of choline acetyltransferase and levels of acetylcholine) as well as postsynaptic development (tyrosine hydroxylase; based on biochemical data reported elsewhere). The amount of acetylcholine and activity of choline acetyltransferase per synaptic vesicle at 10 days in ovo are 8 and 27 times the corresponding adult values. By 1 day after hatching, these ratios have fallen to near adult levels. These data are consistent with the early presence of cholinergic neuroblasts, as suggested by others, and suggest further that such cholinergic neuroblasts are eliminated, or their cholinergic properties suppressed, before hatching.

Brain uptake of pipecolic acid, amino acids, and amines following intracarotid injection in the mouse

The uptake of pipecolic acid by the mouse brain was compared to that of several amino acids and amines, following an injection of a double-labeled mixture into the carotid artery. In general, BUI (brain uptake index) values were lower in the mouse than those previously reported in the rat. The only exception was proline. Lysine, a precursor of pipecolic acid biosynthesis in brain, showed a higher BUI than pipecolic acid. The BUI ofD,l-[3H]pipecolic acid was found to be 3.39 (at 0.114 mM). This was saturable between a concentration of 0.114 and 3.44 mM. Kinetic analysis suggests the presence of two kinds of transport systems. Substances structurally related to pipecolic acid, such as nipecotic acid, isonipecotic acid,l-proline, and piperidine show a significant inhibitory effect. Among the amino acids tested, only GABA showed an inhibitory effect. Data are reported which, when considered with other findings (5), present evidence that pipecolic acid is (1) synthesized both in vitro and in vivo in the mouse brain, (2) actively transported in vivo into the brain, and (3) taken up in vitro by synaptosomal preparations.