Uptake of3H-adrenaline and14C-noradrenaline into neuronal and extraneuronal tissue compartments in the perfused gas gland of the swimbladder of the Atlantic cod,Gadus morhua

Summary The neuronal and extraneuronal accumulation of radiolabelledl-adrenaline andl-noradrenaline was studied in the gas gland of the swimbladder of the Atlantic cod,Gadus morhua. Both amines are taken up into the tissue compartments, and a preference for noradrenaline for both uptake processes was demonstrated. A relatively high neuronal accumulation compared to earlier results (cod spleen; Ungell and Nilsson 1984) was seen and this is probably due to the more dense innervation of the swimbladder gas gland. A higher extraneuronal accumulation may be due to the presence of arterial smooth muscle.It is concluded that the adrenergic nerves of the swimbladder gas gland of the cod preferentially accumulate noradrenaline, a situation similar to that in mammals.Abbreviations A/NA adrenaline/noradrenaline ratio - PBA phenoxybenzamine - PNMT phenylethanolamine-N-methyl tranferase     

Cytochemical study of the lamellar bodies in the swimbladder of the toadfish Opsanus tau L.

Summary The columnar epithelial cells of the gas gland in the swimbladder of the toadfish, Opsanus tau L., contain lamellar bodies that resemble the lamellar bodies found in epithelial cells of vertebrate lungs. Cytochemical assays indicate that swimbladder lamellar bodies are soluble in chloroform-methanol solution, react with tricomplex flocculation solution (indicating a phospholipid component), exhibit a positive reaction for cholesterol when exposed to digitonin, and contain acid phosphatase.The anterior chamber of the toadfish swimbladder is lined by an extracellular layer. Digitonin-cholesterol crystals are found in this layer when the swimbladder is treated with digitonin. A ruthenium red positive layer is also present in the anterior chamber of the toadfish swimbladder.The structure and cytochemistry of swimbladder lamellar bodies are compared with those of vertebrate lung lamellar bodies. Similarities between the extracellular layer in the swimbladder and the extracellular layer in lungs are also noted.Supported in part by a grant No 1 R23 HL 19593-01 from the National Institutes of Health     

A study of pre- and postganglionic fibres in the intestinal nerve (Remak's nerve) of the chicken

Summary The mean peak CV's of two electrophysiologically defined groups of fibres in the intestinal nerve of the chicken have been determined.One group of fibres is constituted by the processes of enteric cholinergic neurones which project along the side branches of the intestinal nerve and synapse within the nerve trunk. These preganglionic fibres have a mean peak CV (at 40 °C) of 0.31 m·s^–1.The other group is made up of fibres of postganglionic neurones which project orally along the nerve trunk. The results suggest that some postganglionic neurones project only as far as the next ganglion whilst others project beyond the next two ganglia for distances greater than 5 mm. The postganglionic fibres have a mean peak CV (at 40 °C) of 0.71 m·s^–1.These figures demonstrate that both pre- and postganglionic fibres are unmyelinated. The temperature coefficient (Q₁₀) for the CV of unmyelinated fibres in the intestinal nerve was 1.57.Abbreviations CAP compound action potential - CV conduction velocity - Q ₁₀ temperature coefficient     

Distribution of 45Ca in the superior cervical ganglion of the cat

Superior cervical ganglia isolated from immature cats accumulated 0.9 ng atoms of ⁴⁵Ca per mg wet weight during 10-min incubations at 37°C; when expressed as an equivalent volume of medium the accumulation was four times the uptake of ³H-inulin. Orthodromic stimulation of the ganglia doubled ⁴⁵Ca accumulation, whereas excitation with 50 mM KCl, 5 mM glutamate, or antidromic stimulation increased accumulation by one-half. Hexamethonium reduced the increment in ⁴⁵Ca accumulation due to orthodromic stimulation only, but another ganglionic blocking agent, tetraethylammonium, did not reduce accumulation in any case. Both agents blocked ganglionic transmission monitored electrophysiologically. To resolve this discrepancy, and to approach the localization of ⁴⁵Ca within the ganglia, the efflux of previously accumulated ⁴⁵Ca was examined. The data could be fitted by an equation incorporating the sum of three exponentials, representing a rapidly exchanging compartment plus two more slowly exchanging ones. The latter two appeared to reflect the pre- and postganglionic elements in the ganglia: ⁴⁵Ca content of the “preganglionic” compartment was increased by orthodromic but not by antidromic stimulation, and was not decreased by either blocking agent; conversely, ⁴⁵Ca content of the “postganglionic” compartment was increased by both orthodromic and antidromic stimulation, and was decreased by both blocking agents after orthodromic stimulation. The lack of effect of tetraethylammonium on the whole ganglion resulted from an increase in “preganglionic” accumulation that offset the “postganglionic” decrease. After preganglionic denervation, the ⁴⁵Ca content of the “preganglionic” compartment was reduced by two-thirds, while the ⁴⁵Ca content of the “postganglionic” compartment was unchanged. Chemical stimulation increased ⁴⁵Ca accumulation in both compartments. Diphenylhydantoin, 0.1 mM, decreased the increment in ⁴⁵Ca accumulation due to electrical stimulation and to 50 m^M KCl; this inhibition occurred in the “preganglionic” compartment (and perhaps also in the “postganglionic”), and was accompanied by an increased efflux of ⁴⁵Ca.     

γ-Aminobutyric Acid Uptake by Sympathetic Ganglia

EXOGENOUS γ-aminobutyric acid (GABA) accumulates against a concentration gradient in isolated mammalian nervous tissue^1–3 and mixes with GABA stored in the tissue⁴. Thus, neurones which use GABA as an inhibitory transmitter might be identified by locating sites of accumulation of radioactively-labelled GABA using autoradiography^5–7, assuming that exogenous GABA is only taken up into neurones already containing GABA. A correlation between GABA uptake and endogenous content has been noted in slices from different parts of the brain³ and in different nerve-ending fractions^8–10. These experiments, however, do not show whether GABA can be accumulated in nerve tissue totally devoid of “gabanergic” neurones. To test this, we have measured the uptake of GABA by isolated sympathetic ganglia. The principal transmitter in the ganglion is acetylcholine while the postganglionic neurones are mainly adrenergic. By analogy with the brain, the ganglion contains negligible amounts of GABA, glutamic decarboxylase or GABA-transaminase^11,12.     

Development of the swimbladder in the European eel (Anguilla anguilla)

The swimbladder of the adult eel, Anguilla anguilla, with its bipolar countercurrent system, the rete mirabile, is a widely used model for swimbladder function, but very little is known about the development of this swimbladder. Our histological studies on the developing swimbladder revealed that during metamorphosis the swimbladder becomes present as a dorsal outgrowth of the esophagus. It is filled with surfactant, and gas was not detected in the swimbladder. In the young glass-eel, the epithelial (gas gland) cells of the swimbladder are columnar, but do not yet have the typical basolateral labyrinth established in adult animals. Few blood vessels are found in the swimbladder tissue, and the submucosa is present as a thick layer of connective tissue, giving a large diffusion distance between blood vessel and swimbladder lumen. Within the next 2 or 3 months of development, gas gland cells develop their typical basolateral labyrinth, and the thickness of the submucosa is significantly reduced, resulting in a short diffusion distance between blood vessels and the swimbladder lumen. The first filling of the swimbladder with gas is observed while the gas gland cells are still in a poorly differentiated status and it appears unlikely that these cells can accomplish their typical role in gas deposition. The presence of small gas bubbles in the swimbladder as well as in the ductus pneumaticus at the time of initial swimbladder inflation suggests that the swimbladder is filled by air gulping or possibly by taking up gas bubbles from the water.     

ANATOMY OF THE SWIMBLADDERS OF SEVEN FAMILIES OF TRANSVAAL FRESHWATER FISHES

SUMMARY

IN the genera Barbus and Labeo of the family Cyprinidae there is a typical twolobed, cylindrical swimbladder: a shorter anterior and a longer posterior lobe, connected by an isthmus. The pneumatic duct passes from the anteroventral end of the posterior lobe to the oesophagus. In the genus Labeo two spiral bands encircle the posterior lobe twice. No rete mirabile, nor any indication of a gas gland, was observed.

The species Hydrocynus vittutus of the family Characidae has a very similarly shaped swimbladder to that of the Cyprinidea. Inside the anterior lobe, however, there is a peculiar structure, which is evidently the gas glad, although a rete mirabile was not observed.

In the families of the Siluriformes, studied, with the exception of the Clariidae, a single lobed, heartshaped swimbladder is present. It is divided by a longitudinal and a transverse. septum into three chambers: an anterior, a right and a left posterior chamber. The pneumatic duct originates from the medial posteroventral part of the anterior chamber. In Clarias gariepinus the two-lobed, right and left lobed, swimbladder lies in a bony capsule, which is attached transversely to the posteroventral part of the skull. In all the Siluriformes, studied, no trace of a gas gland, nor of a rete mirabile was found.

The Cichlid swimbladder has no pneumatic duct, nor any other exit, hence it is physoclistic. In the Cichlids the retroperitoneal position of the swimbladder is accentuated, as the peritoneum and the outer tectum of the swimbladder have united to form a thick, tough membrane, which divides the body cavity into a distinct ventral, or visceral cavity, and a dorsal, or swimbladder cavity. The swimbladder cavity acts as an outer swimbladder. It contains an inner, smaller bladder whose internal ventro-anterior surface is covered with arborescently arranged patches of gas glands.

The attachment of the swimbladder to the tripus and also to the ossa suspensoris is discussed.     

Background Activity of Neurons of the Superior Cervical Ganglion That Innervate the Submandibular Gland in the Rat

In in situ acute experiments, we intracellularly recorded the background activity (BA) from neurons of the superior cervical ganglion, which were antidromically identified by stimulation of the postganglionic nerve in close proximity to the submandibular salivary gland of the rat. According to the pattern of BA, these neurons could be classified into two groups; the respective units probably differ from each other in the number of active converging synaptic inputs. We hypothesize that these neurons are involved in the control of different aspects of function of the gland.Neirofiziologiya/Neurophysiology, Vol. 37, No. 1, pp. 26–31, January–February, 2005.     

Electrotonically Coupled Interneurones produce Two Types of Inhibition in <Emphasis Type="Italic">Aplysia</Emphasis> Neurones

IN the abdominal ganglion of Aplysia californica, there are two types of inhibitory post-synaptic potentials (IPSPs). There are unitary short-lasting IPSPs which occur as the result of conductance changes during the movement of Cl^? across the synaptic membrane—IPSPs which have definite equilibrium potentials and characteristics similar to those described for other neuronal systems¹—and there are IPSPs which last much longer and may be much more effective in regulating the activity of the neurone, which Taue has called “inhibitions of long duration” (ILD)^2,3. In Aplysia some of these long lasting inhibitory potentials are produced by conductance changes and have definite equilibrium potentials⁴. Long lasting inhibitions or “slow inhibitory potentials” as well as short lasting IPSPs have also been described in vertebrate sympathetic ganglia⁵, but in these, long lasting IPSPs are not accompanied by changes in membrane conductance. Some of the long lasting inhibitions (LLI) have been explained on the basis of an ATP-dependent electrogenic Na+ pump⁶. Presumably this ATP-dependent pump hyperpolarizes the membrane by causing an outflux of Na+ from the cell which is more rapid than the corresponding “active” influx of K+⁷. There is evidence now for the existence of such an electrogenic Na+ pump in some of the identified neurones of the abdominal ganglion of Aplysia californica⁸. Pinsker and Kandel⁹ have found some evidence that in these neurones the electrogenic Na+ pump is activated by the synaptic action of an identified cholinergic inhibitory interneurone, L10, producing the long lasting “late IPSP”. But Kehoe and Ascher¹⁰, although agreeing that the same interneurone (L10) produces both types of IPSPs in the follower neurones, have shown that the “late IPSP”⁹ is due to an increase in the K+ conductance and that it has an equilibrium potential around ?90 mV. I have found that in this abdominal ganglion there is another specific interneurone which is electrotonically coupled to L10 and which, when activated, produces a long lasting inhibition (LLI) in a number of follower neurones. Thus L10 produces the LLI or “late IPSP” in some follower neurones not directly, but through the mediation of another interneurone.     

Ontogeny of body density and the swimbladder in yellowtail kingfish Seriola lalandi larvae

The ontogeny of larval body density and the morphological and histological events during swimbladder development were investigated in two cohorts of yellowtail kingfish Seriola lalandi larvae to understand the relationship between larval morphology and body density. Larvae <3 days post hatch (dph) were positively buoyant with a mean ± s.d . body density of 1·023 ± 0·001 g cm^?3. Histological evidence demonstrated that S. lalandi larvae are initially transient physostomes with the primordial swimbladder derived from the evagination of the gut ventral to the notochord and seen at 2 dph. A pneumatic duct connected the swimbladder to the oesophagus, but degenerated after 5 dph. Initial swimbladder (SB) inflation occurred on 3 dph, and the inflation window was 3–5 dph when the pneumatic duct was still connected to the gut. The swimbladder volume increased with larval age and the epithelial lining on the swimbladder became flattened squamous cells after initial inflation. Seriola lalandi developed into a physoclist with the formation of the rete mirabile and the gas‐secreting gland comprised low‐columnar epithelial cells. Larvae with successfully inflated swimbladders remained positively buoyant, whereas larvae without SB inflation became negatively buoyant and their body density gradually reached 1·030 ± 0·001 g cm^?3 by 10 dph. Diel density changes were observed after 5 dph, owing to day time deflation and night‐time inflation of the swimbladder. These results show that SB inflation has a direct effect on body density in larval S. lalandi and environmental factors should be further investigated to enhance the rate of SB inflation to prevent the sinking death syndrome in the early life stage of the fish larvae.     

Activity pattern of suboesophageal ganglion cells innervating the salivary glands of the locust Locusta migratoria

The salivary gland of the locust, Locusta migratoria, is innervated from the suboesophageal ganglion by two neurones, SN1 and SN2 which innervate the gland via the salivary gland nerve (nerve 7B of the suboesophageal ganglion). In addition, like most other peripheral nerves of the head, this nerve carries on its outer surface axons and neurohaemal terminal ramifications of the so called satellite nervous system, established by a group of neurosecretory cells also located in the suboesophageal ganglion. These superficial collaterals ramify over the nerve from its origin in the head to its terminals within the gland in the thoracic segments.Nerve 7B was recorded chronically in freely moving locusts. Both salivary neurones are active during and shortly before feeding, as defined by continuous rhythmic activity of the mandibular closer muscle (M9). The activity of the salivary neurones, particularly that of SN2, thus resembles that of the satellite neurones as described recently. While SN2 ceases firing at the end of a feeding bout, SN1 continues firing for a short period. Also, SN1 fires short bursts of impulses for a few minutes following the end of a feeding bout. Similar bursts also occur at random intervals during the long-lasting phases between feeding events.Abbreviations SN1 salivary neurone 1 - SN2 salivary neurone 2 - M9 mandibular closer muscle - DUM dorsal unpaired median - LMN labral median nerve     

Histological demonstration of glucose transporters,fructose-1,6-bisphosphatase,and glycogen in gas gland cells of the swimbladder: Is a metabolic futile cycle operating?

Luminal surface of the swimbladder is covered by gas gland epithelial cells and is responsible for inflating the swimbladder by generating O(2) from Root-effect hemoglobin that releases O(2) under acidic conditions. Acidification of blood is achieved by lactic acid secreted from gas gland cells, which are poor in mitochondria but rich in the glycolytic activity. The acidic conditions are locally maintained by a countercurrent capillary system called rete mirabile. To understand the regulation of anaerobic metabolism of glucose in the gas gland cells, we analyzed the glucose transporter expressed there and the fate of ATP generated by glycolysis. The latter is important because the ATP should be immediately consumed otherwise it strongly inhibits the glycolysis rendering the cells unable to produce lactic acid anymore. Expression analyses of glucose transporter (glut) genes in the swimbladder of fugu (Takifugu rubripes) by RT-PCR and in situ hybridization demonstrated that glut1a and glut6 are expressed in gas gland cells. Immunohistochemical analyses of metabolic enzymes demonstrated that a gluconeogenesis enzyme fructose-1,6-bisphosphatase (Fbp1) and a glycolytic enzyme glyceraldehyde-3-phosphate dehydrogenase (Gapdh) are highly expressed in gas gland cells. The simultaneous catalyses of glycolysis and gluconeogenesis reactions suggest the presence of a futile cycle in gas gland cells to maintain the levels of ATP low and to generate heat that helps reduce the solubility of O(2).     

MORPHOLOGICAL VARIABILITY OF MITOCHONDRIAL FINE STRUCTURE IN CULTURED GONYAULAX POLYEDRA (PYRRHOPHYTA)1

Mitochondria in Gonyaulax polyedra Stein have a highly variable morphology which depends on their location within the cell. The morphology ranges from mitochondria, 1 μm in cross section, with highly dense cristae which are located within the central sphere of golgi bodies to giant pleomorphic mitochondria, 5–8 μm in cross section containing condensed “chromosome” structures and located in the more peripheral regions of the cell. Elongated mitochondria containing microtubule-like elements ware also observed.     

The ultrastructure of the swimbladder of the toadfish,Opsanus tau L.

Summary The anterior chamber of the swimbladder of the toadfish Opsanus tau L. is lined by a single layer of columnar gas gland cells, cuboidal cells that resemble gas gland cells but are located outside of the gas gland region, and squamous cells. Multilamellar bodies are numerous in the gas gland cells and the cuboidal cells and are present in smaller numbers in the squamous cells. Capillaries lie in the lamina propria directly below the epithelial lining. A thick continuous muscularis mucosae and a submucosa consisting of tightly packed cells, cell processes, and connective tissue may contribute to the impermeability to gases of the wall of the anterior chamber.The posterior chamber of the swimbladder is lined by a single type of squamous epithelial cell. Multilamellar bodies were occasionally observed in these cells also. Other types of cells frequently form a partial second layer between the epithelial lining and the basement lamina. A thin muscularis mucosae lies directly below the basement lamina and the capillaries of the posterior chamber are located in the submucosa. The tunica externa is a layer of dense connective tissue that surrounds both the anterior and posterior chambers. Collagen fibrils in the form of tactoids are present in this layer.Part of this work was submitted by S.M.M. in partial fulfillment of the requirements for the degree of Doctor of Philosophy, Biology Department, Boston University. S.M.M. is grateful for a National Science Foundation Traineeship.     

Modifications in call characteristics and sonic apparatus morphology during puberty in Ophidion rochei (actinopterygii: Ophidiidae)

Juveniles, females, and males of Ophidion rochei share similar external morphology, probably because they are mainly active in the dark, which reduces the role of visual cues. Their internal sonic apparatuses, however, are complex: three pairs of sonic muscles, and highly modified vertebrae and ribs are involved in sound production. The sonic apparatus of males differs from juveniles and females in having larger swimbladder plates (modified ribs associate with the swimbladder wall) and sonic muscles, a modified swimbladder shape and a mineralized structure called the “rocker bone” in front of the swimbladder. All of these male traits appear at the onset of sexual maturation. This article investigates the relationship between morphology and sounds in male O. rochei of different sizes. Despite their small size range total length (133–170 mm TL), the five specimens showed pronounced differences in sound‐production apparatus morphology, especially in terms of swimbladder shape and rocker bone development. This observation was reinforced by the positive allometry measured for the rocker bone and the internal tube of the swimbladder. The differences in morphology were related to marked differences in sound characteristics (especially frequency and pulse duration). These results suggest that male calls carry information about the degree of maturity. Deprived of most visual cues, ophidiids probably have invested in other mechanisms to recognize and distinguish among individual conspecifics and between ophidiid species. As a result, their phenotypes are externally similar but internally very different. In these taxa, the great variability of the sound production apparatus means this complex system is a main target of environmental constraints. J. Morphol. 275:650–660, 2014. © 2014 Wiley Periodicals, Inc.     

Parasympathetic and sympathetic postganglionic synapses in ureterovesical autonomic pathways

Summary Histochemical techniques for acetylcholinesterase and catecholamine show that ureterovesical ganglia of both cat and dog contain dense intraganglionic cholinergic and adrenergic plexuses. Ramifications of both plexuses surround most cholinergic and adrenergic ganglion cell bodies as pericellular synaptic plexuses. Similar pericellular plexuses exist around extraganglionic cholinergic and adrenergic ganglion cells. Both adrenergic and cholinergic synaptic fibers persist in denervated pregnaglionic nerve-free specimens, indicating that cholinergic synaptic fibers are postganglionic parasympathetic in nature. The presence of adrenergic (postganglionic sympathetic) and postganglionic parasympathetic synapses around cell bodies in ureterovesical ganglia provides a morphologic basis for the sympathoinhibitory and muscarinic parasympatho-excitatory phenomena described in these ganglia.     

The fine structure of daphnid supraesophageal and optic ganglia,and its possible functional significance

Neurosecretory activity and fine structure of the supraesophageal and optic ganglia of Daphnia schødleri Sars were studied. The relative amount of paraldehyde fuchsin stainable material present was determined at “daylight” and at one and three hours following for animals maintained under photoperiods of 7.5, 10.5, 13.5, and 16.5 hours. More material was found after one hour in both ganglia and there was a tendency for more in the optic ganglion under 7.5- and 10.5-hour photoperiods. Sections made at two levels in the supraesophageal ganglion and one level in the optic ganglion were examined with an electron microscope. Posterior and anterior parts of the supraesophageal ganglion contain apparent nerve processes at the edge of the ganglion, parallel to the anterior-posterior axis; these have large granules. Neurons in both areas contain patches of presumed polysaccharide granules. In the posterior region are a dorsolateral and a ventrolateral glandular cell, presumably these occur on both sides of the brain. They have very well-developed endoplasmic reticulum and some large granules. The dorsal cell is usually at the tip of a glial attenuation. Concentric lamellar systems are located in dilated nerve processes of the first optic ganglion neuropile. Large whorls (about 3.5 μ) are composed of concentric lamellae. When lamellae do not form complete rings, they end in loops or in dilated tubules that are sometimes constricted as vesicles. Small whorls (1.5 μ) typically have lamellae joined into two or three thick layers. Mitochondria are frequently associated with the whorls. It is proposed that the whorls are active in synthesis, possibly neurohumor production.     

Increased Activity of Choline Acetyl-transferase in Sympathetic Ganglia after Prolonged Administration of Nerve Growth Factor

A prolonged increase in the activity of preganglionic sympathetic nerves produces characteristic changes in the enzyme pattern of the postganglionic adrenergic neurones in adult rats^1–4. In newborn mice the normal development of adrenergic neurones depends materially on the intactness of the preganglionic cholinergic nerves⁵. These two findings contribute to the definition of the so far vague term “trophic response to neuronal activity” and the question arises whether these trophic actions are unidirectional only, or whether there is also a retrograde effect, that is, a dependence of the preganglionic cholinergic nerves on the function of the postjunctional adrenergic neurones. Transection experiments in the brain have shown that after lesioning of particular areas, for example, optic nerve tract, cingulate or visual cortex, there occurs not only orthograde but also retrograde trans-synaptic degeneration⁶. It seemed of interest to study this possible retrograde trophic effect in a less complex system and to investigate whether there are not only negative (degeneration) but also positive effects. The administration of nerve growth factor (NGF) to newborn rats produces a marked growth and enhanced differentiation of the adrenergic neurones⁷. The biochemical correlate to these morphological changes is a selective induction of tyrosine hydroxylase and dopamine β-hydroxylase⁸. We have investigated whether these effects are also reflected by changes in the preganglionic nerves.     

Cholinesterases of rat sympathetic ganglia after immunosympathectomy, decentralization and axotomy

Abstract— Immunosympathectomy was produced in Sprague-Dawley rats by the subcutaneous injection of 300 units of nerve growth factor (NGF)-antiserum (1.56 mg of freeze-dried serum)/g/day for 6 days, the first dose being given 5–8 hr after birth. The immunosympathectomized rats and their control littermates were killed 2½ and 7 months after birth. Ganglionic acetylcholinesterase and pseudocholinesterase activities were measured by an adaption (Kungman , Kungman and Pouszczuk , 1968) of the colorimetric method of Ellman , Courtney , Andres and Featherstone (1961). Following immunosympathectomy the activities of these enzymes decreased significantly in superior cervical, stellate, thoracic chain, cardiac (abdominal), coeliac and superior mesenteric ganglia. The reduction of the acetylcholinesterase activity was greater than expected in a number of sympathetic ganglia, e.g. superior cervical, stellate, coeliac and cardiac ganglia, if one considered that only the postganglionic neurons were affected by immunosympathectomy. The activities of these enzymes were also reduced in the cervical sympathetic trunks from NGF-antiserum-treated rats. By means of decentralization and axotomy it was shown that 45 per cent of the total ganglionic acetylcholinesterase activity was associated with the preganglionic and 55 per cent with the postganglionic elements of the superior cervical ganglion from control rats. It was concluded that immunosympathectomy also affects the preganglionic sympathetic neurons. It is not known whether this is a primary effect of the NGF-antiserum or a secondary effect resulting from the absence of over 90 per cent of the postganglionic sympathetic cell bodies.     

Musculature and innervation of the neck of the desert locust,Schistocerca gregaria (Forskål)

The innervation of each of the muscles involved in mediating head movement in the desert locust Schistocerca gregaria is described in detail. The number of motor neurones to each muscle and the neutral pathway and ganglion of origin of each are deduced from both histological and electrophysiological evidence. Only two of the muscles are, on histological evidence, innervated by as few as four different neurones, while several receive more than ten, and one at least 13. Individual muscles are shown physiologically to receive, in a few cases, as many as six different motor neurones. At least six muscles are innervated by motor neurones originating in more than one ganglion. One group of four muscles consisting in total of less than 100 muscle fibres receives more than 20 different motor neurones from three different ganglia through three or four different nerve roots. In these muscles, many single muscle fibres receive innervation from at least two different ganglia. It is concluded that the segmental nature of an insect muscle can not be deduced solely from a knowledge of the ganglion of origin of the motor innervation to that muscle. The innervation patterns that exist today must reflect past evolutionary development, but changes in the peripheral distribution of motor neurones, or migration of motor neurone cell bodies from one ganglion to another, or the development of additional motor neurones, or several of these factors together, must have formed a part of that development.