Short axon ganglion cells in the chick retina

Using Golgi's staining technique, we investigated some ganglion cells whose axons do not project out of the retina area. These axons, after following a short trajectory through the optic nerve fiber layer or through the 5th stratum of the inner plexiform layer (IPL), change their direction and end in the inner stratum of the IPL.     

Immunocytochemical characterization of vasotocin and mesotocin secretory systems in duck brain

The neural systems secreting vasotocin and mesotocin has been characterized in the Duck brain with indirect immunofluorescent techniques, using specific antisera. In the anterior preoptic region and in supraoptic and paraventricular nuclei, neurons producing vasotocine and neurons producing mesotocine have been identified separately. Only vasotocinergic neurons were localized in ectomammillary tract. Vasotocin--and mesotocin--containing axons together enter the median eminence, some of them crossed the internal zone of the median eminence before ending in the posterior lobe of the pituitary, whereas other axons of both classes entered the external layer of the rostral median eminence, in close contact with the capillaries of the hypophysial portal system.     

Development and pathologies of the arterial wall

Arteries consist of an inner single layer of endothelial cells surrounded by layers of smooth muscle and an outer adventitia. The majority of vascular developmental studies focus on the construction of endothelial networks through the process of angiogenesis. Although many devastating vascular diseases involve abnormalities in components of the smooth muscle and adventitia (i.e., the vascular wall), the morphogenesis of these layers has received relatively less attention. Here, we briefly review key elements underlying endothelial layer formation and then focus on vascular wall development, specifically on smooth muscle cell origins and differentiation, patterning of the vascular wall, and the role of extracellular matrix and adventitial progenitor cells. Finally, we discuss select human diseases characterized by marked vascular wall abnormalities. We propose that continuing to apply approaches from developmental biology to the study of vascular disease will stimulate important advancements in elucidating disease mechanism and devising novel therapeutic strategies.     

Presence of neurons synthesizing LH-RH in the anterior hypothalamus of the duck (Anas platyrhynchos)]

Using histochemical techniques with LH-RH anti-serum, a large number of LH-RH producing neurons were identified in the Duck hypothalamus, under different physiological conditions. The LH-RH pericaryas were localized in a well delimited area of the anterior hypothalamus, including the dorsal part of the periventricular preoptic nucleus. The LH-RH containing axons were directed downwards towards the infundibulum, and terminated within the external layer of the rostral and caudal median eminence, in close vicinity to the capillaries of the pituitary portal system.     

Die licht- und sublichtmikroskopische Morphologie der Epidermis des neotenen Axolotls (Siredon mexicanum Shaw)

Summary Three different cell types are the most frequent elements of the epidermis of the neotenic axolotl: (1) the common epidermal cells are small and multiform. They show bundles of tonofilaments (figures ofEberth) in the stratum basale. (2) The big Leydig cells contain numerous gross granules and a special network in the peripheral cytoplasm (Langerhans net). (3) The cover cells forming the outer layer of the epidermis possess a striking mucin zone in the apical cytoplasm.     

An ultrastructural study of the transformation of elementary bodies of Rickettsiella into initial bodies (author's transl)]

An intermediate stage between the elementary and the initial bodies of the Rickettsietta genus is defined as the beginning of an intracellular cycle. It is characterized by several structural changes in the dense elementary body: the cytoplasm becomes less electron-dense; thus, the nucleoid and the ribosomes are visible. The inner layer of the cell-wall becomes progressively clearer and the trilamellar structure of the inner and outer membranes appears distinctly. 'preinitial body' is proposed as name of this stage of development.     

Ultrastructural changes in uterine myometrium of mice with experimentally-induced adenomyosis

Ectopic pituitary transplantation induced a high incidence of adenomyosis in SHN mice. Early signs of the development of adenomyosis were the penetration of stromal connective tissue into myometrium followed by uterine gland invasion. Associated with these changes, the inner layer of myometrium showed the involution of smooth muscle cells and distended intercellular spaces.     

Penetration of phospholipases A2 and C into the squid (Loligo pealii) giant axon

Summary Following 1 h exposure, the level of phospholipase A₂ penetration into the axoplasm of the squid giant axon was 107 to 350% of that in the external media; corresponding values for phospholipase C were 18 to 31%. Phospholipases can therefore be used to study phospholipid function in axons since they can penetrate through connective tissue and Schwann cell to reach the axolemma.I thank Dr.Toshio Narahashi for allowing me to use his laboratory facilities at the Marine Biological Laboratory, Woods Hole, Mass. for the dissection of squid axons. Expert technical assistance in these studies were provided by Mr.Steven Trudel and Mr.Stuart Owen Rosenberg. This work was supported in part by a grant from the University of Connecticut Research Foundation.     

Stimulation of olfactory ensheathing cell motility enhances olfactory axon growth

Axons of primary olfactory neurons are intimately associated with olfactory ensheathing cells (OECs) from the olfactory epithelium until the final targeting of axons within the olfactory bulb. However, little is understood about the nature and role of interactions between OECs and axons during development of the olfactory nerve pathway. We have used high resolution time-lapse microscopy to examine the growth and interactions of olfactory axons and OECs in vitro. Transgenic mice expressing fluorescent reporters in primary olfactory axons (OMP-ZsGreen) and ensheathing cells (S100ß-DsRed) enabled us to selectively analyse these cell types in explants of olfactory epithelium. We reveal here that rather than providing only a permissive substrate for axon growth, OECs play an active role in modulating the growth of pioneer olfactory axons. We show that the interactions between OECs and axons were dependent on lamellipodial waves on the shaft of OEC processes. The motility of OECs was mediated by GDNF, which stimulated cell migration and increased the apparent motility of the axons, whereas loss of OECs via laser ablation of the cells inhibited olfactory axon outgrowth. These results demonstrate that the migration of OECs strongly regulates the motility of axons and that stimulation of OEC motility enhances axon extension and growth cone activity.     

Transport and diffusion of Tau protein in neurons

In highly polarized and elongated cells such as neurons, Tau protein must enter and move down the axon to fulfill its biological task of stabilizing axonal microtubules. Therefore, cellular systems for distributing Tau molecules are needed. This review discusses different mechanisms that have been proposed to contribute to the dispersion of Tau molecules in neurons. They include (1) directed transport along microtubules as cargo of tubulin complexes and/or motor proteins, (2) diffusion, either through the cytosolic space or along microtubules, and (3) mRNA-based mechanisms such as transport of Tau mRNA into axons and local translation. Diffusion along the microtubule lattice or through the cytosol appear to be the major mechanisms for axonal distribution of Tau protein in the short-to-intermediate range over distances of up to a millimetre. The high diffusion coefficients ensure that Tau can distribute evenly throughout the axonal volume as well as along microtubules. Motor protein-dependent transport of Tau dominates over longer distances and time scales. At low near-physiological levels, Tau is co-transported along with short microtubules from cell bodies into axons by cytoplasmic dynein and kinesin family members at rates of slow axonal transport.     

Penetration of phospholipases A2 and C into the squid (Loligo pealii) giant axon.

Following 1 h exposure, the level of phospholipase A2 penetration into the axoplasm of the squid giant axon was 107 to 350% of that in the external media; corresponding values for phospholipase C were 18 to 31%. Phospholipases can therefore be used to study phospholipid function in axons since they can penetrate through connective tissue and Schwann cell to reach the axolemma.     

Composition and functional role of the mucus layers in the intestine

In discussions on intestinal protection, the protective capacity of mucus has not been very much considered. The progress in the last years in understanding the molecular nature of mucins, the main building blocks of mucus, has, however, changed this. The intestinal enterocytes have their apical surfaces covered by transmembrane mucins and the whole intestinal surface is further covered by mucus, built around the gel-forming mucin MUC2. The mucus of the small intestine has only one layer, whereas the large intestine has a two-layered mucus where the inner, attached layer has a protective function for the intestine, as it is impermeable to the luminal bacteria.     

Types of nerve terminals in fetal and neonatal rabbit myocardium

With the use of electron microscopy 4 types of axonal profiles were observed in the developing myocardium of rabbits: 1) adrenergic axons which contained mainly small dense-core vesicles and which presumably can store 5-hydroxy-dopamine; 2) cholinergic axons which contained small clear synaptic vesicles and which were acetylcholinesterase-positive; 3) axons which contained large vesicles filled with moderately electron-dense material and which resembled purinergic axons; and 4) profiles filled with mitochondria, vesicles of various sizes, lysosome-like bodies, and microtubules and which resembled sensory terminals.     

Demonstration of a 2d LH-RH neurosecretory system in the duck hypothalamus]

Using immunocytochemical techniques with an anti-LH-RH immuneserum, evidence of two neuronal systems secreting LH-RH has been shown in the Duck hypothalamus. In addition to the previously described system, located in the preoptic nucleus, a second system could be demonstrated in the infundibular nucleus. The perikarya of the infundibular LH-RH producing neurons were significantly smaller than those of the preoptic neurons. On the other hand, under the experimental conditions used, the infundibular system had approximately five times less LH-RH secreting neurons than the preoptic system, and its perikarya appeared less heavily loaded in IR LH-RH. The LH-RH containing axons from both neuronal populations ran down to the external layer of the median eminence, where they ended in close contact with the capillaries of the hypophysial portal system.     

Ultrastructural changes in uterine myometrium of mice with experimentally-induced adenomyosis

Summary Ectopic pituitary transplantation induced a high incidence of adenomyosis in SHN mice. Early signs of the development of adenomyosis were the penetration of stromal connective tissue into myometrium followed by uterine gland invasion. Associated with these changes, the inner layer of myometrium showed the involution of smooth muscle cells and distended intercellular spacesThis work was supported in part by Grant-in-Aid for Scientific Research from the Ministry of Education, Science and Culture of Japan     

Demonstration of catecholaminergic neurons in rat retina by fluorescence histochemistry on cryostat sections]

A fluorescence histochemical technique using glyoxylic acid and cryostat sections has been worked out to visualize the dopamine-containing neurons of the retina. It allows the demonstration of catecholaminergic junctional cells and alloganglion cells, classically described. Moreover, the observation of some fluorescent fibers in the external zone of the inner nuclear layer, in contact with the outer plexiform, suggests the presence of catecholamine-containing interplexiform cells, in the Rat retina.     

Types of nerve terminals in fetal and neonatal rabbit myocardium

Summary With the use of electron microscopy 4 types of axonal profiles were observed in the developing myocardium of rabbits: 1) adrenergic axons which contained mainly small dense-core vesicles and which presumably can store 5-hydroxydopamine; 2) cholinergic axons which contained small clear synaptic vesicles and which were acetylcholinesterase-positive; 3) axons which contained large vesicles filled with moderately electron-dense material and which resembled purinergic axons; and 4) profiles filled with mitochondria, vesicles of various sizes, lysosome-like bodies, and microtubules and which resembled sensory terminals.Supported in part by the Kentucky Heart Association and in part by the Human Development Studies Program, University of Kentucky. Excellent technical assistance of Mrs Merle Wekstein is gratefully acknowledged.     

Heterogeneous effects of sinusoidal muscular stretching on frequency grams of primary endings due to stimulation of static gamma axons]

The action of sinusoidal stretching at 1,5 Hz on primary ending frequencygrams due to repetitive stimulation of static gamma axons has been studied, in nembutalized cats, on flexor hallucis longus muscle spindles. Whenever, in static conditions, driving is elicited by the repetitive stimulation of gamma axons, the elementary components of the frequencygrams increase in amplitude during muscle stretch. This effect is not observed when the stimulation of the gamma axons gives a regular acceleration of the primary endings without "driving".     

Etude ultrastructurale de la transformation du corps élémentaire en corps initial chez lesRickettsiella

Summary An intermediate stage between the elementary and the initial bodies of theRickettsiella genus is defined as the beginning of an intracellular cycle. It is characterized by several structural changes in the dense elementary body: the cytoplasm becomes less electron-dense; thus, the nucleoid and the ribosomes are visible. The inner layer of the cell-wall becomes progressively clearer and the trilamellar structure of the inner and outer membranes appears distinctly. Preinitial body is proposed as name of this stage of development.