Biomedical subjects

C K Tan

Publications and source records attributed to C K Tan.

At least 55 records · Page 3Linked to original sources

PubMed1996

Ultrastructural localization of acetylcholinesterase and choline acetyltransferase in oligodendrocytes, glioblasts and vascular endothelial cells in the external cuneate nucleus of the gerbil.

This study reports the reactivities of acetylcholinesterase (AChE) and choline acetyltransferase (ChAT) in some of the nonneuronal elements in the external cuneate nucleus (ECN) of gerbils. AChE reaction products were localized in some oligodendrocytes in their cisternae of rough endoplasmic reticulum, nuclear envelope and Golgi saccules. The basal lamina lining the capillary endothelia also displayed AChE reactivity. In ChAT immunocytochemistry, the reaction products were found to be associated with the vascular basal lamina as well as the endothelial plasma membrane facing the lumen. The most remarkable finding was the localization of ChAT immunoreactivity in some oligodendrocytes and occasional glioblasts (small glial precursor cells containing a thin rim of cytoplasm surrounding an irregular nucleus with homogeneous chromatin materials). The ChAT-positive oligodendrocytes consisted of two types, medium-dense and dark cells, either associated with blood vessels or ChAT-stained neuronal elements. It is suggested from these new findings that at least some of the oligodendrocytes and glioblasts in the ECN of gerbils may be involved in the synthesis, storage, release and degradation of acetylcholine.

Acetylcholinesterase↗

PubMed1996

Projection of forelimb nerve afferents to external cuneate nucleus of the rat as revealed by intraneural injection of a neurotoxic lectin, Ricinus communis agglutinin.

This study seeks to extend the observations of previous studies of projection of primary afferent fibres from the forelimb nerves and muscles to the external cuneate nucleus (ECN) of mammals using a neurotoxic lectin, Ricinus communis agglutinin (RCA) to achieve chemical ganglionectomy of the dorsal root ganglia. Following intraneural injection of RCA into the three main forelimb nerves, namely the radial, ulnar and median nerves, terminal degeneration of the primary afferent fibres in the ECN was studied under the light microscope by means of the Fink-Heimer method. The results show that the primary afferent fibres from these three nerves project to the medial part of the ECN. The field of terminal degeneration take a crescentic form. The projection from the median nerve was most dorsally located whereas that from the radial nerve was the most ventral with extensive overlaps between them. Of the three nerves, the projection from the radial nerve was the most dense. Rostrocaudally, the three nerves also show extensive overlaps. The rostrocaudal extent of maximum terminal degeneration was greatest for the radial nerve and least for the median nerve. Analysis of variance showed that these differences were statistically significant. This suggests that the radial nerve has the most extensive projection to the ECN and the median nerve the least.

Animals↗

PubMed1996

Ultrastructural localization of substance P-like immunoreactivity in the intermediolateral column of spontaneously hypertensive rats and Wistar-Kyoto rats.

The distribution of substance P in the intermediolateral column of the upper thoracic spinal cord of spontaneously hypertensive (SHR) rats and Wistar-Kyoto (WKY) rats was studied by combined retrograde tracing of choleragen subunit-B horseradish peroxidase (CB-HRP) and immuno-electronmicroscopy. In the T(1)-T(3) segments of the spinal cord, SP-like immunoreactive products were localized in the cell bodies and dendrites of the sympathetic preganglionic neurons as well as in a few pre-axon terminals or axon terminals. In the neuropil of the intermediolateral column (ILN), different synaptic configurations were observed including synaptic contacts between SP-like positive dendrites and negative axon terminals, and between SP-like positive axon terminals and SP-like positive dendrites. Furthermore, a single SP-like positive dendrite was sometimes postsynaptic to several axon terminals, a feature typical of glomerular synapses. The present findings suggest that most of the SP-like immunoreactive elements in the ILN were of intraspinal origin derived mainly from the sympathetic preganglionic neurons in SHR and WKY rats. Since there was no ultrastructural difference in the distribution of SP between the neural elements in the ILN of SHR and WKY rats, the present findings also suggest that SP may not be directly involved in the hyperactivity of the sympathetic nervous system in hypertension.

Animals↗

PubMed1996

The composition and central projections of the internal auricular nerves of the dog.

The cranial components and central terminations of the sensory nerves supplying the concave surface of the puppy's pinna, namely, the rostral, middle and caudal internal auricular nerves (RIAN, MIAN and CIAN) were investigated using horseradish peroxidase retrograde and transganglionic labelling techniques. All the 3 internal auricular nerves received contributions from the vagus. The RIAN received additional fibres from the trigeminal nerve while the MIAN and CIAN contained fibres derived from the facial nerves. In the brainstem, collaterals from the descending fibres of the afferents were given off at all levels to the medially located spinal trigeminal nucleus (SpV) which extended rostocaudally from the principal nucleus of the trigeminal nerve, subnuclei oralis, interpolaris and caudalis of the SpV to C1 or C2 cervical segment. The greatest density of central projections was observed in the subnucleus caudalis and C1. In the latter, the terminal field in the dorsal horn was roughly wedge-shaped, tapering off medially from lamina I towards lamina V. A somatotopic organisation was observed in the spinal trigeminal tract (SpVtr) and spinal trigeminal nucleus (SpV) in which the projection fibres and terminal fields of the RIAN were located lateral to those of the MIAN and CIAN. Some nontrigeminal nuclei, e.g. paratrigeminal and cuneate nuclei, nucleus X and the nucleus of the solitary tract were also labelled following HRP application to the internal auricular nerves. The localisation of the central projections of the internal auricular nerves as well as the 2nd order neurons in some specific nuclei to which the afferent fibres project is consistent with the concept of a brainstem somatovisceral link.

Animals↗

PubMed1996

Experience of varicella vaccination in acute lymphoplastic leukaemia.

Varicella is a common benign childhood illness. Rarely, serious complications arise. Immunocompromised patients usually suffer a more serious form of the illness. It is therefore prudent to prevent the infection in this group of patients. Varicella vaccination has been proven by several workers to be effective in both healthy children and adults as well as in leukaemic children. As the vaccine had not been licensed for sale in Singapore, we could only import 10 doses of the vaccine under special license. This was given to 8 leukaemic children. Of this, 5 seroconverted after the first dose. Two patients had the benefit of a repeat vaccination 3 months later. Both subsequently seroconverted. Two of the patients died from a relapse of the illness, a year and 2 years after the vaccination. None of the patients developed any side effects of fever and pain or varicella or zoster after the immunisation even though there was close contact with chicken pox. Although the study sample was small, it appeared that the vaccine was safe and efficacious in leukaemic children, especially after a 2-dose injection.

Chickenpox↗

PubMed1995

A comparative study of NADPH-diaphorase in the sympathetic preganglionic neurons of the upper thoracic cord between spontaneously hypertensive rats and Wistar-Kyoto rats.

With retrograde tracing using fluorogold injection into the superior cervical ganglion and nicotinamide adenine dinucleotide phosphate diaphorase (NADPH-d) histochemistry, the present comparative study revealed that the retrogradely labelled neurons in n. intermediolateralis pars funicularis (ILf) and n. intermediolateralis pars principalis (ILp) of the autonomic region in the upper thoracic cord exhibited a much stronger reactivity for NADPH-diaphorase in Wistar-Kyoto (WKY) rats than those in spontaneously hypertensive rats (SHR). It was found that in ILf in WKY rats, 77.62% of the fluorogold-labelled neurons were NADPH-d positive, while in SHR, only 56.43% of the labelled neurons were NADPH-d positive. The frequency distribution of NADPH-d positive retrogradely labelled neurons was significantly reduced in ILf of the spinal cord of SHR (U-test: P < 0.01). In ILp in WKY rats, 65.25% of fluorogold-labelled neurons were NADPH-d positive in WKY rats, while in SHR, only 56.28% of the labelled neurons were NADPH-d positive. Although the difference (P > 0.05) in the frequency of NADPH-d positive neurons in ILp between the two strains of rats was not significant, the reductions in SHR seemed considerable. Examination of the preganglionic sympathetic trunk and the superior cervical ganglion between SHR and WKY rats revealed that virtually all the NADPH-d positive fibers were derived from the sympathetic preganglionic neurons. In SHR, the NADPH-d positive fibers were not as intensely stained as those of WKY rats. This preliminary results suggest that nitric oxide, as an inhibitory neurotransmitter, may be implicated in the onset of hypertension.

Animals↗

PubMed1995

Cloning of the cDNAs for the small subunits of bovine and human DNA polymerase delta and chromosomal location of the human gene (POLD2).

cDNAs encoding the small subunit of bovine and human DNA polymerase delta have been cloned and sequenced. The predicted polypeptides, 50,885 and 51,289 Daltons, respectively, are 94% identical, similar to the catalytic subunits. The high degree of conservation of the polypeptides suggests an essential function for the small subunit in the heterodimeric core enzyme. Although the catalytic subunit of DNA polymerase delta shares significant homology with those of the herpes virus family of DNA polymerases, the small subunit of mammalian DNA polymerase delta is not homologous to the small subunit of either herpes simplex virus type 1 DNA polymerase (UL42 protein) or the Epstein-Barr virus DNA polymerase (BMRF1 protein). Searches of the protein databases failed to detect significant homology with any protein sequenced thus far. PCR analysis of DNA from a panel of human-hamster hybrid cell lines localized the gene (POLD2) for the small subunit of DNA polymerase delta to human chromosome 7.

Amino Acid Sequence↗

PubMed1995

A light-microscopic study of the intermediolateral nucleus following injection of CB-HRP and fluorogold into the superior cervical ganglion of the rat.

Sympathetic preganglionic neurons in the intermediolateral nucleus of the thoracic spinal cord of the adult rat which innervate the superior cervical ganglion (SPN-scg) were identified by means of retrograde transport of cholera subunit B-conjugated horseradish peroxidase and fluorogold. In horizontal sections of the spinal cord, the SPN-scg were observed to be arranged in clusters which displayed a characteristic triangular configuration. Within this triangle, the cells showed no preferential orientation for their long axes were oriented obliquely, transversely or longitudinally. The dendrites arising from these clusters were oriented either longitudinally, medially, or laterally. The medially-oriented dendrites formed a subependymal plexus and some have been observed to cross the midline to the opposite side. The most significant finding was the presence of the white matter dendritic plexus which was formed by the laterally-directed bundles of dendrites. The present findings thus suggested that SPN-scg may be regulated by means of two circuits: the classical (medial) core circuit and a paralateral circuit which may convey supraspinal afferent inputs to the SPN-scg.

Animals↗

PubMed1995

Ultrastructural identification of cholinergic neurons in the external cuneate nucleus of the gerbil: acetylcholinesterase histochemistry and choline acetyltransferase immunocytochemistry.

Using acetylcholinesterase histochemical and choline acetyltransferase immunocytochemical localization methods, this study has provided conclusive evidence for the existence of cholinergic neurons in the external cuneate nucleus of gerbils. By light microscopy, both acetylcholinesterase and choline acetyltransferase labelling was confined to the rostral portion of the external cuneate nucleus. Ultrastructurally, acetylcholinesterase reaction products were found in the nuclear envelope, cisternae of rough endoplasmic reticulum and Golgi saccules of some somata and large dendrites as well as in the membranes of small dendrites, myelinated axons and axon terminals. These neuronal elements were also stained for choline acetyltransferase; immunoreactivity was associated with nuclear pores, nuclear envelope, perikaryal membrane and all the membranous structures within the cytoplasm. Of the total choline acetyltransferase-labelled neuronal profiles analysed, 79% were myelinated axons, 15% dendrites, 4% somata and 2% axon terminals. The immunostained axon terminals consisted of two types containing either round (Rd type; 62.5%) or pleomorphic (Pd type; 37.5%) vesicles. Both were associated directly with choline acetyltransferase-positive dendrites. In contrast to the paucity of choline acetyltransferase-labelled axon terminals, numerous choline acetyltransferase-positive myelinated axons were present. It may thus be hypothesized that most, if not all, of the external cuneate nucleus cholinergic neurons are projection cells; such cells may give rise to axonal collaterals which synapse onto their own dendrites for possible feedback control. Choline acetyltransferase-positive dendrites were contacted by numerous unlabelled presynaptic boutons, 60% of which contained round or spherical synaptic vesicles (Rd boutons) and 40% flattened vesicles (Fd boutons), suggesting that these neurons are under strong inhibitory control. The preferential concentration of cholinergic components in the rostral external cuneate nucleus may be significant in the light of the highly organized somatotopy in the external cuneate nucleus and its extensive efferent projections to medullary autonomic-related nuclei. Our results suggest that the cholinergic neurons may be involved in somatoautonomic integration.

Acetylcholinesterase↗

PubMed1995

An ultrastructural study of cuneocerebellar neurons and primary afferent terminals in the external cuneate nucleus of gerbils as revealed by retrograde and transganglionic transport of horseradish peroxidase.

The present study examined the synaptic organization of cuneocerebellar neurons and their relationships with the primary afferents in the gerbil external cuneate nucleus following multiple injections of horseradish peroxidase over a widespread area in the cerebellum in conjunction with a simultaneous injection of horseradish peroxidase into the cervical or brachial nerve plexus. The external cuneate nucleus is topographically organized: the rostral portion receiving the primary afferents from the cervical plexus and the caudal portion primary afferents from the brachial plexus. This study attempted to correlate the synaptology with the topography and different cytoarchitecture in these two specific regions in the external cuneate nucleus. Ultrastructurally, the profiles of horseradish peroxidase-labelled cuneocerebellar neurons could be divided into three types, namely, small, medium and large on the basis of their cross-sectional areas. Axon terminals which formed axosomatic synapses could be classified into: round (Rs type; 22.2%), pleomorphic (Ps type; 55.6%) and flattened (Fs type; 22.2%) vesicle boutons. The horseradish peroxidase-labelled dendritic elements of the cuneocerebellar neurons were postsynaptic to a greater number of axon terminals which were also classified into Rd (77.5%), Pd (18.8%) and Fd (3.7%) type boutons. Some of the Rd boutons making direct synaptic contacts with the cuneocerebellar neurons originated from primary afferents since they were simultaneously labelled by transganglionic transport of horseradish peroxidase. In the rostral external cuneate nucleus, synapses on cuneocerebellar neurons were more frequent on their primary dendrites as compared with those on the primary dendrites of the caudal cuneocerebellar neurons. The latter, on the other hand, showed more synapses on their distal dendrites. This may have functional implications with regard to the afferent inputs to cuneocerebellar neurons in the rostral and caudal external cuneate nucleus.

Animals↗

PubMed1995

The distribution of NADPH-d in the central grey region (lamina X) of rat upper thoracic spinal cord.

The distribution of nicotinamide adenine dinucleotide phosphate-diaphorase (NADPH-d) in the central grey region (lamina X of Rexed) of the rat upper thoracic cord was examined by LM and EM. Numerous NADPH-d positive neuronal somata and fibres were present in the subependymal areas of the central grey region at levels T1-T3. Most of the neurons were located dorsal to the central canal in horizontal sections through this region. Many medially-directed NADPH-d positive fibres arising from neurons in n. intermediolateralis pars principalis, n. intercalatus spinalis and longitudinally-directed NADPH-d positive fibres arising from neurons in n. intercalatus pars paraependymalis formed a subependymal plexus. In horizontal sections through the central canal, some NADPH-d positive nerve fibres appeared to traverse the ependyma to enter and run along the central canal. By EM, NADPH-d reaction products were localized on the nuclear membrane, outer mitochondrial membrane and Golgi apparatus of both neurons and ependymal cells and in some axon terminals containing pleomorphic and round agranular synaptic vesicles. Present results suggest that besides the traditional monoamine-, amino acid- and peptide-containing axon terminals, the central grey region also contains fibres in which nitric oxide is utilized as a neurotransmitter or neuromodulator. The finding of NADPH-d positive fibres in the central canal suggests that nitric oxide may be released into DPH-cerebrospinal fluid. Since some of the ependymal cells were NADPH-d positive, it is suggested that they may be involved in the modulation of nitric oxide levels in the cerebrospinal fluid.

Animals↗

PubMed1995

Human cholangiocarcinomas express somatostatin receptors and respond to somatostatin with growth inhibition.

BACKGROUND/AIMS: Cholangiocarcinoma, a malignancy of biliary epithelia, is usually fatal because of absence of tests for early detection and lack of effective therapy. Somatostatin (SS) receptors are expressed in several malignancies and in rodent biliary epithelia. We tested the hypothesis that SS receptors are present in cholangiocarcinomas. METHODS: We examined tissue from seven surgically resected human cholangiocarcinomas and a human bile duct cancer cell line for the messenger RNA for one subtype of SS receptors (SSTR2) and studied binding and growth-active properties of SS and its analogues. RESULTS: SSTR2 messenger RNA was expressed in all seven human cholangiocarcinoma specimens. Experiments with the human cholangiocarcinoma cell line showed specific, saturable binding of an SS analogue (MK-678) with high affinity for SSTR2 on cholangiocarcinoma membranes; inhibition in vitro of tumor cell proliferation by SS-14 and its analogue, octreotide; and inhibition in vivo of tumor growth in athymic mice implanted with human cholangiocarcinoma cells and treated with lanreotide, another SS analogue. Experiments to elucidate a possible mechanism of growth inhibition by SS showed it was not through changes in cellular cyclic adenosine monophosphate or calcium levels. Using gamma camera imaging with an 111In-SS analogue, we localized a histologically proven cholangiocarcinoma in a patient. CONCLUSIONS: These results suggest that SS analogues may be useful for diagnostic localization and treatment of biliary tract malignancies.

Aged↗

PubMed1995

Light and electron microscopic studies of the distribution of NADPH-diaphorase in the rat upper thoracic spinal cord with special reference to the spinal autonomic region.

The distribution of nicotinamide adenine dinucleotide phosphate-diaphorase (NADPH-d) was examined in the upper thoracic segment of the spinal cord in rat. Under the light microscope, NADPH-d positive cell bodies and fibers were readily detected in the following areas: 1) the dorsal horn; 2) the dorsolateral funiculus and lateral spinal neurons; 3) spinal autonomic region, consisting of the nucl. intermediolaterialis pars funicularis, nucl. intermediolateralis pars principalis, nucl. intercalatus spinalis and nucl. intercalatus pars paraependymalis; and 4) in the white matter lateral to the nucl. intermediolateralis pars funicularis. In the nucl. intermediolateralis pars principalis, the positive dendrites, running in bundles, were directed medially in the gray matter towards the central canal as well as laterally in the white matter towards the pia mater. The medially-directed positive dendrites fomed a subependymal plexus around the central canal. A dense bundle of NADPH-d positive fibers were also observed running longitudinally. Combined retrograde tracing with fluorogold and NADPH-d histochemistry study revealed that some of the NADPH-d positive neurons, due to their fluorescence labelling, were sympathetic preganglionic neurons that innervated the superior cervical ganglion. Under the electron microscope, the reaction products in the neurons of the nucl. intermediolateralis pars principalis were deposited in their nuclear envelope, rough endoplasmic reticulum, mitochondria and Golgi apparatus. In the neuropil, three types of synaptic configurations were observed: between NADPH-d negative axon terminals and NADPH-d positive dendrites, between NADPH-d positive axon terminals and NADPH-d negative dendrites, and between NADPH-d positive axons terminals and NADPH-d positive dendrites. These synaptic configurations suggest that the neurons are regulated by nitric oxide released from both pre- and post-synaptic elements. The sources of the NADPH-d positive axon terminals associated with the neurons remain unclear although the possibility of their being derived from supraspinal origins has to be considered. The ultrastructural demonstration of NADPH-d reaction product in the three major types of glial cells suggests that nitric oxide might be produced by these cells, but its functional significance awaits further investigation.

Animals↗

PubMed1995

A comparative study by retrograde neuronal tracing and substance P immunohistochemistry of sympathetic preganglionic neurons in spontaneously hypertensive rats and Wistar-Kyoto rats.

A comparative morphological study of the sympathetic preganglionic neurons that innervate the superior cervical ganglion (SPN-scg) was made in spontaneously hypertensive rats (SHR) and age-matched normotensive Wistar-Kyoto (WKY) rats. The cytoarchitectonics and dendroarchitectonics of the SPN-scg were studied following retrograde transport of choleragen subunit B horseradish peroxidase conjugate (CB-HRP) and Fluorogold. Significant differences were observed in the maximum and minimum diameters of neurons of the nucleus intermediolateralis pars principalis (ILp) and in the minimum diameter of neurons in the nucleus intermediolateralis pars funicularis (ILf) between SHR and WKY rats (P < 0.01). These diameters were decreased in neurons of SHR. The distribution patterns of dendrites of SPN-scg also showed differences between SHR and WKY rats. The dendritic distribution patterns showed the following changes in SH rats: (1) the mediolaterally oriented dendrites were reduced in number, (2) the ladder-like configuration of the medially oriented grey-matter dendrites was less prominent, (3) the medially oriented dendrites formed a triangular or dome-like configuration, and (4) the white matter dendritic plexuses and subependymal plexuses were reduced. Similar differences between SHR and WKY rats were also observed in our immunohistochemical study of substance P-like fibres. In addition, the SP study has also shown a close association of SP fibres with the central canal both in SHR and WKY rats; some of the SP fibres penetrated the ependymal lining to run longitudinally up or down the central canal. This finding suggests the presence of substance P-positive neurons contacting the cerebrospinal fluid.

Adrenergic Fibers↗

PubMed1995

Multiple origins of cerebellar cholinergic afferents from the lower brainstem in the gerbil.

The possible origins of cerebellar cholinergic afferents from the lower brainstem of the gerbil were examined using immunohistochemistry combined with retrograde neuronal labelling techniques. Choline acetyltransferase (ChAT) monoclonal antibody was used in conjunction with a retrogradely transported tracer, horseradish peroxidase (HRP). The use of this technique allowed an unequivocal localisation of cholinergic neurons in different parts of the lower brainstem projecting to the cerebellum. In addition, single labelling of acetylcholinesterase (AChE), ChAT and HRP was carried out to elucidate the efferent projection from the lower brainstem to the cerebellum as well as the cholinergic distribution in these two areas. Our results showed the presence of HRP/ChAT double-labelled neurons in (1) the midline medulla: the periventricular gray beneath the 4th ventricle, C3 adrenergic area, raphe obscurus nucleus and medial longitudinal fasciculus, (2) the reticular formation: the medullary, lateral, intermediate, gigantocellular, lateral paragigantocellular and dorsal paragigantocellular reticular nuclei and gigantocellular reticular nucleus ventralis, and (3) sensory nuclei: the gracile nucleus, cuneate nucleus, external cuneate nucleus, spinal trigeminal nucleus interpolaris, prepositus hypoglossal nucleus and medial vestibular nucleus. In the cerebellum, AChE-positive mossy fibres were chiefly localised in the vermian lobules VIb,c, VII and X, paramedian lobule, crura I and II, paraflocculus and flocculus, and they were distributed in the white matter and granular layer of the cortex. The 3 above-mentioned cerebellar cholinergic afferent systems associated with the unique AChE distribution pattern in the cerebellum may be of important functional significance.

Acetylcholinesterase↗

PubMed1995

An ultrastructural study of the sympathetic preganglionic neurons that innervate the superior cervical ganglion in spontaneously hypertensive rats and Wistar-Kyoto rats.

Comparative ultrastructural study of the sympathetic preganglionic neurons that innervated the superior cervical ganglion (SPN-scg) was made between spontaneously hypertensive rats (SHR) and age-matched normotensive Wistar-Kyoto rats. After injection of choleragen subunit-B horseradish peroxidase (CB-HRP) into the superior cervical ganglion, three types of the sympathetic preganglionic neurons were identified according to their ultrastructural features. In both SHR and WKY rats, the neurons in the autonomic region of T1-T3 segments of the spinal cord showed a characteristic distribution pattern in which the Type I neurons were located more laterally in n. intermediolateralis pars funicularistic (ILf), and n. intermediolateralis pars principalis (ILp), Type III neurons more medially in n. intercalatus spinalis (IC), n. intercalatus pars paraependymalis (ICpe) and Type II neurons in n. intermediolateralis pars principalis (Ilp) as well as in n. intercalatus spinalis (IC). Of the three types of neurons, there was not noticeable ultrastructural difference in Type II and Type III neurons between the SHR and WKY rats. Some differences, however, were observed in Type I neurons between the two animals stains. In SHR, the nucleus of Type I neurons displayed many deep indentations and a greater number of profiles of Golgi apparatus. Three types of the axon terminal were found to make synaptic contacts with the labelled Type I neurons. Some proportional changes of the different axon terminals were observed between those of SHR and WKY rats. The results of this study suggest that the suppressive effect on the activity of the sympathetic preganglionic neurons in SHR may be attenuated which would result in an unbalanced activities of some of neurotransmitters on the sympathetic preganglionic neurons thereby leading to the onset of hypertension. The increase in the number of nuclear indentations and an increased activity in the Golgi complex may reflect an increase in the synthesis of some of the neurotransmitters or neuromodulators in the sympathetic preganglionic neurons or their axon terminals. The characteristic distribution patterns of the three types of neurons suggest that, of the three types of SPN-scg, only the Type I neurons may be implicated in the regulation of the cardiovascular system.

Animals↗

PubMed1995

A comparative ultrastructural study of primary afferents from the brachial and cervical plexuses to the external cuneate nucleus of gerbils.

The synaptic organisation of the primary afferents from the brachial and cervical plexuses to the external cuneate nucleus of gerbils was compared following an intraneural injection of horseradish peroxidase into the musculocutaneous, median, ulnar and radial nerves of the brachial plexus or the main branches of the cervical plexus; 407 labelled primary afferent terminals from the brachial and 459 from the cervical plexus were studied. These boutons made synaptic contacts with 586 and 633 dendritic profiles, respectively. 99.0% of the primary afferent boutons from the brachial plexus contained clear round synaptic vesicles (R boutons); the remaining 1% of boutons contained pleomorphic synaptic vesicles (P boutons). For boutons from the cervical plexus, 95% were R boutons and 5% were P boutons. The labelled R bouton profiles had a wide range of cross-sectional area from 0.4 to 13.1 microns 2, while the P boutonal profiles were of a small variety (range, 0.4-2.3 microns 2; mean, 1.5; S.D., 0.6 micron 2). The R boutons from the brachial plexus (mean, 3.9 microns; S.D., 2.1 microns 2) were generally larger than those from the cervical plexus (mean, 3.3 microns 2; S.D., 1.9 microns 2). On close analysis, 72.4% of R boutons from the brachial plexus were found to synapse on distal dendrites, 15.9% on secondary dendrites, 9.5% on dendritic spines and 2.2% on proximal dendrites. For R boutons from the cervical plexus, 81.1% synapsed on distal dendrites, 12.1% on dendritic spines and 6.8% on secondary dendrites; none was observed on proximal dendrites. Such a different synaptic organisation between the two nerve plexuses may be related to their different perceptuomotor executions.

Animals↗

PubMed1995

A light- and electron microscopic study of tyrosine hydroxylase-like immunoreactivity in the ciliary ganglia of monkey (Macaca fascicularis) and cat.

The present paper describes tyrosine hydroxylase-like immunoreactivity in the ciliary ganglion of monkey (Macaca fascicularis) and cat. Under the light microscope, in the monkey, about 7.6% of neurons were observed to be intensely stained, 27.7% moderately stained and 32.5% lightly stained. In the cat, 1.2% of neurons were intensely stained, 5.4% moderately stained and 10.1% lightly stained. Ultrastructurally, tyrosine hydroxylase-like immunoreactivity was observed in neuronal somata, dendritic profiles and axons in both monkey and cat. Tyrosine hydroxylase-like immunoreactive dendritic profiles were synaptically contacted by tyrosine hydroxylase-negative axon terminals. In the monkey, tyrosine hydroxylase-like immunoreactive fibres were observed to enter the ciliary ganglion via the nasociliary nerve. Such fibres were observed to course among neurons within the ganglion and emerge in the short ciliary nerves. In contrast, tyrosine hydroxylase-like immunoreactive fibres were only occasionally observed in the cat.

Animals↗