Morphological and physiological identification of medulla interneurons in the visual system of the tiger beetle larva

The morphology of visual interneurons in the tiger beetle larva was identified after recording their responses. Stained neurons were designated as either medulla or protocerebral neurons according to the location of their cell bodies. Medulla neurons were further subdivided into three groups. Afferent medulla neurons extended processes distally in the medulla neuropil and a single axon to the brain through the optic nerve. They received their main input from stemmata on the ipsilateral side. Two distance-sensitive neurons, near-by sensitive and far-sensitive neurons, were also identified. Atypical medulla neurons extended their neurites distally in the medulla and proximally to the brain, as afferent medulla neurons, but their input patterns and the shapes of their spikes differed from afferent neurons. Protocerebral neurons sent a single axon to the medulla neuropil. They spread collateral branches in the posterior region of the protocerebrum on its way to the medulla neuropil. They received main input from stemmata on the contralateral side. Medulla intrinsic neurons did not extend an axon to the brain, and received either bilateral or contralateral stemmata input only. The input patterns and discharge patterns of medulla neurons are discussed with reference to their morphology.     

Abdominal vagal paraganglia: distribution and comparison with carotid body, in the rat.

A study was made of the distribution of abdominal vagal paraganglia in the gastro-oesophageal region of 12 rats. In all rats 4-40 paraganglia were found embedded in, or closely associated with, the vagus nerves and their branches. The paraganglia consisted of groups of rounded, weakly chromaffin-positive cells surrounded by flattened cells and supplied by small nerves and blood vessels. The paraganglia were morphologically identical to simultaneously fixed carotid body tissue and showed similar fluorescence characteristics.     

Sensory responses of dorsal cells in the lamprey brain

Summary Sensory responses were evoked in 17/33 dorsal cells in the brain of the lampreyIchthyomyzon unicuspis by mechanical stimulation of the dorsolateral skin of the sucker and head. Fifteen of the responsive cells tested were classified as pressuresensitive and two as nociceptive. Thus, some of the dorsal cells which are situated in the medulla of the lamprey and which project into the branches of the trigeminal nerves have sensory functions similar to those of dorsal cells in the spinal cord.     

The composition of the vagus nerve of the cat

Summary The number and caliber of myelinated and non-myelinated fibers of entire and sensory vagal nerves of cats were studied by means of light and electron microscopy. The results obtained with electron microscopy show that the non-myelinated component is particularly rich (about 40,000 elements at the cervical level), with clearly higher numbers of fibers than demonstrated thus far with light microscopy. The ratio of myelinated to non-myelinated fibers is on the average 1 4 for the total vagi and only 1 8 for the sensory vagal component. The comparison of the nerve above and below the level of the nodose ganglion shows that (1) mean fiber diameter is usually greater at the infranodose than at the supranodose level, and (2) some myelinated fibers of small diameter occurring below the nodose ganglion become non-myelinated above it. Additionally, the number of non-myelinated fibers per Schwann cell is greater at the supranodose than at the infranodose level; this speaks in favor of a reorganization of the C-fiber population from one level to the other.     

Nervous system in Olveria indica, a rumen paramphistome (Digenea) of bovines, as revealed by non-specific esterase staining

On the basis of esterase localization the complete nervous system has been visualized in Olveria indica Thapar & Simha, 1945, a paramphistome from the rumen of cattle, recorded for the first time from the north-east region of India. The basic number of posterior longitudinal nerves (i.e., 3 pairs) is the same as in other paramphistomes; four pairs of anterior longitudinal nerves are present, there being an extra pair of pharyngeal nerves. Conspicuous differences in the innervation patterns were observed, mainly in the innervation of the genital atrial region and acetabulum. The presence of prominent longitudinal connections, joining the anterior and posterior dorsal nerves and the anterior and posterior ventral nerves on either side, is a feature not hitherto found in other paramphistome species. The details of the course of all the nerves and their branches are discussed.     

Pattern formation of the sensible nerves in the hand of mouse embryos with special reference to the posterior-anterior developmental gradient

The development of the sensible innervation of the hand was investigated. For this reason normal forelimbs and limb bud cultures from 12- to 14-day-old mouse embryos were stained in toto using the cholinesterase technique. The dorsal side of the hand is mainly innervated by sensible branches of the radial and the musculocutaneous nerve, which penetrate the fascia in the region of the elbow. From here they grow in a distal direction forming the dorsal digital nerves. On the ventral side the median nerve grows in a subfascial compartment towards the palmar side of the hand. While passing the wrist the median nerve exhibits a frayed appearance. A net of branching and anastomosing small nerve fibre bundles is visible. This implies that on the palmar side of the metacarpal region of the hand-plate no specific highways for the growing nerve fibres exist. From late day 12 to early day 14 of embryonic development this diffuse nerve net is organized. In a posterior-anterior (ulnoradial) developmental gradient the common palmar digital nerves were formed, and these nerves divide at their tip into the proper digital nerves. However, the proper digital nerves again follow special pathways during their outgrowth.     

The pressor zone in the caudal part of the ventral surface of the medulla oblongata

The changes of the vessel resistance of the skeletal muscle and the small intestine perfused with constant blood flow, under electrical stimulation of the ventrolateral medulla were studied on artificially ventilated urethane-anesthetized cats. The stimulation of rostral ventrolateral medulla increased vessel resistance in both regions. The stimulation in a region 2 mm caudal the middle of the rootlets of the twelfth cranial nerves decreased the vessel resistance, but in a region 4 mm caudal the middle of the same rootlets increased the vessel resistance of the skeletal muscle and the small intestine.     

Evidence for the Association of 2',3'-Cyclic-Nucleotide 3'-Phosphodiesterase with Myelin-Related Membranes in Peripheral Nervous System

Abstract: In PNS, the specific activity of 2′,3′-cyclic nucleotide 3′-phospho–diesterase (CNP) in myelin was not enriched over the starting homogenate. Nevertheless, most of the total activity was recovered in myelin. In myelin-deficient mutants, low CNP activities were measured in sciatic nerves. CNP specific activities were similar in myelinated and non-myelinated nerves but in non-nervous tissues, they were significantly lower than in nervous tissue. There was no indication for the presence of an isoenzyme of CNP in peripheral nerves. These results indicate that CNP is present in PNS myelin and preferentially localized in Schwann cell plasma membranes.     

Medullary substrate and differential cardiovascular responses during stimulation of specific acupoints

Electroacupuncture (EA) at P5-P6 acupoints overlying the median nerve reduces premotor sympathetic cardiovascular neuronal activity in the rostral ventral lateral medulla (rVLM) and visceral reflex pressor responses. In previous studies, we have noted different durations of influence of EA comparing P5-P6 and S36-S37 acupoints, suggesting that point specificity may exist. The purpose of this study was to evaluate the influence of stimulating P5-P6 (overlying the median nerve), LI4-L7 (overlying branches of the median nerve and the superficial radial nerve), LI6-LI7 (overlying the superficial radial nerve), LI10-LI11 (overlying the deep radial nerves), S36-S37 (overlying the deep peroneal nerves), or K1-B67 (overlying terminal branches of the tibial nerves) specific acupoints, overlying deep and superficial somatic nerves, on the excitatory cardiovascular reflex and rVLM responses evoked by stimulation of chemosensitive receptors in the cat's gallbladder with bradykinin (BK) or direct splanchnic nerve (SN) stimulation. We observed point-specific differences in magnitude and duration of EA inhibition between P5-P6 or LI10-LI11 and LI4-L7 or S36-S37 in responses to 30-min stimulation with low-frequency, low-current EA. EA at LI6-LI7 and K1-B67 acupoints as well as direct stimulation of the superficial radial nerve did not cause any cardiovascular or rVLM neuronal effects. Cardiovascular neurons in the rVLM, a subset of which were classified as premotor sympathetic cells, responded to brief (30 s) stimulation of the SN as well as acupoints P5-P6, LI10-LI11, LI4-L7, S36-S37, LI6-LI7, or K1-B67, or underlying somatic pathways in a fashion similar to the reflex responses. In fact, we observed a significant linear relationship (r(2) = 0.71) between the evoked rVLM response and reflex change in mean arterial blood pressure. In addition, EA stimulation at P5-P6 and LI4-L7 decreased rVLM neuronal activity by 41 and 12%, respectively, for >1 h, demonstrating that prolonged input into the medulla during stimulation of somatic nerves, depending on the degree of convergence, leads to more or less inhibition of activity of these cardiovascular neurons. Thus EA at acupoints overlying deep and superficial somatic nerves leads to point-specific effects on cardiovascular reflex responses. In a similar manner, sympathetic cardiovascular rVLM neurons that respond to both visceral (reflex) and somatic (EA) nerve stimulation manifest graded responses during stimulation of specific acupoints, suggesting that this medullary region plays a role in site-specific inhibition of cardiovascular reflex responses by acupuncture.     

Effect of colchicine and lumicolchicine on the ultrastructure of non-myelinated axons in autonomic nerves in cat in vitro]

The effects of colchicine and lumicolchicine on the ultrastructure of non-myelinated axons in cat autonomic nerves were studied using in vitro preparations of inferior mesenteric ganglion/hypogastric nerves. After 24 hrs of in vitro incubation with colchicine added to the medium (10 microng/ml) a significant decrease in number of neurotubules per 1 axon was observed. In the presence of a solution of alpha-beta and gamma-lumicolchicine (10 microng/ml) severe degenerative changes occured in axons and Schwann cells. At a lower dose of lumicolchicine (3 microng/ml) these changes were less frequent and the number of neurotubules per 1 axon did not differ from that in control nerves.     

Nerves and nerve plexuses of the human vertebral column

The origin, distribution, and termination pattern of nerves supplying the vertebral column and its associated structures have been studied in the human fetus by means of an acetylcholinesterase whole-mount method. The vertebral column is surrounded by ventral and dorsal nerve plexuses which are interconnected. The ventral nerve plexus consists of the nerve plexus associated with the anterior longitudinal ligament. This longitudinally oriented nerve plexus has a bilateral supply from many small branches of the sympathetic trunk, rami communicantes, and perivascular nerve plexuses of segmental arteries. In the thoracic region, the ventral nerve plexus also is connected to the nerve plexuses of costovertebral joints. The dorsal nerve plexus is made up of the nerve plexus associated with the posterior longitudinal ligament. This nerve plexus is more irregular and receives contributions only from the sinu-vertebral nerves. The sinu-vertebral nerves originate from the rami communicantes and, in the cervical region, also from the nerve plexus of the vertebral artery. Thick and thin sinu-vertebral nerves are found. Most frequently three types of thick sinu-vertebral nerves are observed, i.e., ascending, descending, or dichotomizing ones. Finally, the distribution of the branches of the ventral and dorsal nerve plexuses and of the sinu-vertebral nerves is described.     

Dual peptidergic innervation of the blowfly hindgut: a light- and electron microscopic study of FMRFamide and proctolin immunoreactive fibers.

1. The innervation of the hindgut, rectal valve, rectum and rectal papillae of the adult blowfly, Calliphora erythrocephala, was studied by means of light and electron microscopic immunocytochemistry, using antibodies against the neuropeptides proctolin and FMRFamide. 2. Branches from the abdominal nerves reaching the posterior portion of the gut were found to contain mostly neurosecretory type axons and to innervate the muscle coat of all hindgut structures studied. 3. Some of the axons found in these nerve branches innervating the gut display proctolin- others FMRFamide-like immunoreactivity. Both types of peptidergic axons were found to have abundant terminals in the muscle coat of the hindgut, rectum and rectal valve and in the medulla of the rectal papillae. 4. It is clear that two separate peptidergic systems derived from the abdominal ganglion are supplying the hindgut structures, and, possibly, they use proctolin- and FMRFamide-like peptides respectively as their transmitters or modulators.     

Localization of enkephalin- and neurotensin-like immunoreactivities in cat adrenal medulla

Enkephalin (ENK)- and neurotensin (NT)-immunoreactivities (IR) were localized in cat adrenal medulla using immunocytochemistry. ENK was localized mainly in adrenaline cells, 70%-80% of which were heavily labelled. About 5%-10% of the noradrenaline cells were ENK-immunoreactive (IR). A dense network of ENK-IR nerves was localized among adrenaline cells. NT was localized only in the noradrenaline cells, 60%-70% of which were immunoreactive. NT- and ENK-IR were localized in separate noradrenaline cells. A dense network of NT-IR nerves was restricted among noradrenaline cells. The present findings confirm that ENK- and NT-like peptides are localized in separate adrenal medullary cells and demonstrate that also the preganglionic nerves are divided in subpopulations according to their neuropeptide content. These nerves have a selective localization among adrenaline and noradrenaline cells and may have physiological significance in the control of secretion of catecholamines and neuropeptides from adrenal medulla.     

Localization of enkephalin- and neurotensin-like immunoreactivities in cat adrenal medulla

Summary Enkephalin (ENK)- and neurotensin (NT)-immunoreactivities (IR) were localized in cat adrenal medulla using immunocytochemistry. ENK was localized mainly in adrenaline cells, 70%–80% of which were heavily labelled. About 5%–10% of the noradrenaline cells were ENK-immunoreactive (IR). A dense network of ENK-IR nerves was localized among adrenaline cells. NT was localized only in the noradrenaline cells, 60%–70% of which were immunoreactive. NT- and ENK-IR were localized in separate noradrenaline cells. A dense network of NT-IR nerves was restricted among noradrenaline cells.The present findings confirm that ENK- and NT-like peptides are localized in separate adrenal medullary cells and demonstrate that also the preganglionic nerves are divided in subpopulations according to their neuropeptide content. These nerves have a selective localization among adrenaline and noradrenaline cells and may have physiological significance in the control of secretion of catecholamines and neuropeptides from adrenal medulla.     

Nerves and nerve endings in the skin of tropical cattle.

The nerves and nerve endings in the skin of tropical cattle were studied using histological and histochemical techniques. Many nerve trunks and fibres were present in the reticular and papillary dermis in both hairy and non-hairy skin sites. In non-hairy skin locations such as the muzzle and lower lip, encapsulated endings akin to Krause and Ruffini end bulbs, which arise from myelinated nerve trunks situated lower down the dermis were observed at the upper papillary layer level. Some fibre trunks seen at this level extended upwards to terminate within dermal papillae as bulb-shaped longitudinally lamellated Pacinian-type endings, while other onion-shaped lamellated nerve structures were located either within dermal papillae or near the dermo-epidermal area. Intraepidermal free-ending nerve fibres, appearing non-myelinated were observed in areas with thick epidermis. Intraepidermal free-ending nerve fibres, appearing non-myelinated were observed in areas with thick epidermis. On hairy skin sites, however, organized nerve endings or intraepidermal nerve endings were not readily identifiable.     

Localisation of VIP- and CGRP-like substances in the skin and sinus hair follicles of various mammalian species

Using an ultrastructural postembedding immunogold technique, we demonstrated vasoactive intestinal polypeptide (VIP)- and calcitonin gene-related peptide (CGRP)-like immunoreactivity in the Merkel cell dense-cored granules of skin and sinus hair follicles of adult cat and dog. The VIP-like substance was located in cat Merkel cells while both VIP- and CGRP-like substances were colocalised in dog Merkel cells. In cat Merkel cells, the magnitude of labelling of VIP was qualitatively higher than in dog Merkel cells. In the dog Merkel cell, CGRP appeared as the most abundant peptide. Dense-cored granules were labelled for these peptides. In addition, mast cells encountered in the dermal region of dog skin were also found to be immunolabelled by VIP antiserum. The immunoreaction was found to be confined to the secretory granules of the cells. Furthermore, all non-myelinated nerve plexuses encountered in the dermal region of the skin and the sinus hair follicles of the various mammalian species studied were immunolabelled by CGRP antiserum. The specific location was again restricted to the dense-cored granules present in these nerves. As VIP and CGRP have potent vasodilatory effects, our observations suggest that Merkel cells may play a separate or synergistic role in regulatory functions of the skin neuroendocrine cell, exerting their influence by paracrine, endocrine and neurocrine pathways, or a combination of these. Different methodologies of double labelling with different sizes of gold particles are also discussed.     

Neuronal and Nonneuronal Contributions to Renal Catecholamine Content in the Dog

Endogenous noradrenaline and 3,4-dihydroxyphenylethylamine (dopamine) levels were measured in different zones of the dog kidney following chronic unilateral renal denervation. In outer and inner renal cortex, and in outer medulla, greater than 95% of the tissue content of both catecholamines was contributed by renal nerves, whereas in inner medulla only nonneuronal catecholamines were found. The amounts of neuronal dopamine present in outer renal cortex were greater than would be expected for a population of solely noradrenergic nerves.     

On the fibers of the III, IV and VI cranial nerves of the cat.

The fiber content and diameter spectra of the cranial nerves III, IV and VI were analysed in cat. A semi-automatic technique of measuring fiber diameters is presented and compared to the manual method. The number of fibres was counted in the proximal part of the three main nerves and in each of their distal branches before they enter the EOM. Compared to the muscle weight, the branch to the RB had fewer fibers than all the other muscle branches. The diameter spectra of the proximal part of the three main nerves were compared with the diameter spectra of each of their distal branches. Minor differences were found among them. Only the RB had a striking difference in the spectrum which was skewed toward the large diameters.     

Distribution and origins of VIP-immunoreactive nerves in the cephalic circulation of the cat

VIP-immunoreactive (IR) nerves were visualized in whole mounts and sections of cephalic arteries and cranial nerves of cats with indirect immunofluorescence. Perivascular VIP-IR nerves were very widely distributed in arteries and arterioles supplying glands, muscles and mucous membranes of the face. Within the cerebral circulation, perivascular VIP-IR nerves were most abundant in the Circle of Willis and the proximal portions of the major cerebral arteries and their proximal branches supplying the rostral brain stem and ventral areas of the cerebral cortex. VIP-IR nerves were absent from arterial branches supplying the posterior brain stem, cerebellum and dorsal cerebral cortex. Cerebral perivascular VIP-IR nerves probably arise from VIP-IR perikarya within microganglia found in the cavernous plexus and external rete. Extracerebral perivascular VIP-IR nerves probably arise from VIP-IR perikarya in microganglia associated with the tympanic plexus, chorda tympani, lingual nerve and Vidian nerve as well as from cells in the otic, sphenopalatine, submandibular and sublingual ganglia. It seems likely, therefore, that each major segment of the cephalic circulation is supplied by local VIP-IR neurons.