Vagal efferent and afferent innervation of the rat esophagus as demonstrated by anterograde DiI and DiA tracing: focus on myenteric ganglia

Anterograde tracing with the carbocyanine tracer DiI and the aminostyrol derivative DiA was used to selectively label fibers from the nucleus ambiguus, dorsal motor nucleus and nodose ganglion, respectively, terminating in the rat esophagus, and to compare them with the innervation of the gastric fundus in the same animals. Ambiguus neurons terminated on motor endplates distributed mainly to the ipsilateral half of the esophagus. There was no evidence of preganglionic innervation of myenteric ganglia from ambiguus neurons. Neurons of the dorsal motor nucleus supplied sparse fibers to only about 10% of enteric ganglia in the esophagus while they innervated up to 100% of myenteric ganglia in the stomach. Neurons of the nodose ganglion terminated profusely on more than 90% of myenteric ganglia of the esophagus and on about 50% of ganglia in the stomach. Afferent vagal fibers were also frequently found in smooth muscle layers starting at the esophago-gastric junction. In contrast, they were extremely rare in the striated muscle part of the esophagus. These morphological data suggest a minor influence of neurons of the dorsal motor nucleus and a prominent influence of vagal afferent terminals onto myenteric neurons in the rat esophagus.     

Organization of the dorsocaudal neostriatal complex: a retrograde and anterograde tracing study in the domestic chick with special emphasis on pathways relevant to imprinting

In the forebrain of domestic chicks, a network of distinct regions is crucially involved in auditory and visual filial imprinting. Among these areas, a distinct part of the dorsocaudal neostriatal complex (dNC complex), termed neostriatum dorsocaudale (Ndc), was recently discovered by its enhanced metabolic activity during the presentation of auditory and visual imprinting stimuli. Since there is evidence that the dNC complex consists of several distinct functional subareas, we investigated the neural connections of different parts of the dNC complex by retro- and anterograde pathway tracing. Special emphasis was put on the connections of the dNC complex with other imprinting relevant regions in the rostral telencephalon, such as the mediorostral neostriatum/hyperstriatum ventrale (MNH) and the intermediate and medial part of the hyperstriatum ventrale (IMHV). By anterograde and multiple retrograde pathway tracing, we found that the dNC complex may at least be subdivided into three major constituents. The most medial part of the dNC complex, termed neostriatum dorsale (Nd), is characterized by strong reciprocal connections with the neostriatal part of the MNH and by its auditory related inputs, including those from the output layers L1 and L3 of field L, and the shell region of the thalamic n. ovoidalis. The Ndc, which occupies the central aspects of the dNC complex, is mainly characterized by reciprocal connections with the ectostriatal belt (Ep) and the adjacent neostriatum (N). Furthermore, Nd and Ndc receive strong thalamic input from the n. dorsolateralis posterior (DLP), both project to the IMHV, and both are reciprocally connected with the archistriatum intermedium (AI). The most lateral aspect of the dNC complex, termed Ndl, is characterized by afferents from the neostriatum frontale, pars trigeminalis (NFT), and by the lack of a thalamic input. Results indicate that the dNC complex comprises distinct subregions, which are characterized by their specific afferents from parasensory areas of different sensory modalities. These different subregions may be integral components of a general pattern of sensory processing in the avian telencephalon. The strong interconnections between Nd, Ndc, and MNH as well as IMHV may constitute essential parts of auditory and visual imprinting circuits.     

Oxytocinergic innervation to the upper thoracic sympathetic preganglionic neurons in the rat. A light and electron microscopical study using a combined retrograde transport and immunocytochemical technique

A new pH indicator, seminaphthofluorescein (SNAFL)-calcein acetoxymethyl ester, was used for intracellular pH (pHi) measurement in living MDCK cells with a laser scanning confocal microscope (LSCM) equipped with an Argon/Krypton laser and dual-excitation and dual-emission (FITC/Texas Red) filter set. SNAFL-calcein excitation maxima are approximately 492/540 nm (acid/base) and emission maxima are approximately 535/625 nm (acid/base) with a pKa value at approximately 7.0. The absorption/emission spectra of SNAFL-calcein indicate that the ratio of emission intensities of its basic/acidic forms is pH dependent. With an Argon/Krypton LSCM, we were able to monitor the acidic and basic forms of this dye simultaneously using dual-excitation (488/568 nm) and dual-emission (525-614 nm/> or = 615 nm) wavelengths (lambda s). The simultaneous dual-excitation/emission LSCM system allows for efficient recording of pHi dynamics (time resolution approximately 1 sec) in living cells. We have analyzed emission stability of the dye at different temperatures (22 degrees C and 37 degrees C) and constant pH, and at the same temperature (22 degrees C) but various pHs (6.6, 7.0, and 7.4). Bleaching rate is slightly higher at 37 degree C than that at 22 degrees C. The basic form of the dye (lambda Em approximately 625 nm) has a slightly higher bleaching rate than the acidic form (lambda Em approximately 535 nm) in standard culture medium (pH 7.3) at either 22 degree C or 37 degrees C. The pHi in MDCK cells calculated from ratio images (535 nm/625 nm) was 7.19 +/- 0.03 (mean +/- SEM, n = 20). Calibration experiments show that the useful pH range of SNAFL-calcein appears to be between 6.2 and 7.8, as the dye is difficult to calibrate outside this pH range.     

Origin of projections from the midbrain raphe nuclei to the hypothalamic paraventricular nucleus in the rat: a combined retrograde and anterograde tracing study

A number of neuronal functions governed by the hypothalamic paraventricular nucleus are influenced by serotonin, and it is generally believed that the moderate density of serotonin-immunoreactive fibres and terminals within the paraventricular nucleus originates from the midbrain dorsal and median raphe nuclei. To further evaluate the intricate anatomy of projections from brain stem raphe nuclei of the rat, a combination of retrograde and anterograde tracing experiments were conducted to determine the medullary raphe nuclei projection to the paraventricular nucleus. Rhodamine-labelled latex microspheres, Cholera toxin subunit B and FluoroGold we used as retrograde tracers. Intracerebroventricular injections into the third ventricle of all retrograde tracers labelled a distinct population of neurons in the dorsal raphe situated in the subependymal stratum adjacent to the cerebral aqueduct indicating that these cells take up the tracer from the cerebrospinal fluid. Very few retrogradely labelled neurons were seen in the median raphe after i.c.v. administration of the tracers. Retrograde tracers delivered into the medial part of the paraventricular nucleus labelled no further cells in the midbrain dorsal and median raphe nuclei, whereas a substantial number of retrogradely labelled cells emerged in the pontine raphe magnus. However, when the retrograde tracers were delivered into the lateral part of the paraventricular nucleus, avoiding leakage of the tracer into the ventricle, very few labelled neurons were seen in the dorsal and median raphe, whereas the prominent labelling of raphe magnus neurons persisted. The anatomical organization of nerve fibres terminating in the area of the paraventricular nucleus originating from midbrain raphe nuclei was studied in a series of anterograde tracing experiments using the plant lectin Phaseolus vulgaris leucoagglutinin. Injections delivered into the dorsal raphe or median raphe labelled but a few fibres in the paraventricular nucleus proper. A high number of fine calibered nerve fibres overlying the ependyma adjacent to the paraventricular nucleus was, however, seen after the injections into the subependymal rostral part of the dorsal raphe. Injections delivered into the raphe magnus gave rise to a dense plexus of terminating fibres in the parvicellular parts of the paraventricular nucleus and moderately innervated the posterior magnocellular part of the paraventricular nucleus as well as the magnocellular supraoptic nucleus. Concomitant visualization of serotonin-immunoreactive neurons and retrograde FluoroGold-tracing from the paraventricular nucleus revealed that none of the serotonergic neurons of the raphe magnus projects to this nucleus, while a few of the neurons putatively projecting to the paraventricular nucleus from the median raphe are serotonergic. The current observations suggest that the raphe magnus constitute by far the largest raphe input to the paraventricular nucleus and strongly questions the earlier held view that most raphe fibres innervating the paraventricular nucleus are derived from the midbrain dorsal and median raphe. However, the source of serotonergic innervation of the paraventricular nucleus remains elusive.     

Cocaine adversely affects development of cortical embryonic neurons in vitro: immunocytochemical study of calcium-binding proteins

Neurons of cerebral cortex from 15-16 day old embryos of white rats (Sprague-Dawley) were cultured in MEM enriched with 5% horse serum. On the 7th day after plating the cultures were divided into three experimental and one control groups (6-8 Petri dishes in each group). In group 1, cultures were grown without additives. In group 2, cocaine chloride was added at concentrations 0.3, 0.6 and 1 mg/ml of culture. In group 3, a monoclonal antibody against calcium-binding proteins, parvalbumin (APV) or calbindin (ACB) was added at a concentration 25 microl/ml. In group 4, a combination of cocaine +APV was added at a concentration 1 mg+25 microl/ml of culture media. On the 10th day cultures were immunostained using APV and ACB antibodies. In developing GABAergic neurons of group 2 cocaine produced cytotoxic effects that were expressed in drastic decrease in number of neurons and in degeneration of their processes. The lower concentrations of cocaine caused milder cytotoxity and their effects were reversible. The highest concentration of cocaine caused irreversible degeneration of neurons. Similar cytotoxity was caused by APV or ACB in group 3. The most severe cytotoxic effects were seen in group 4, where a mixture of cocaine and APV was used. Overall, it can be concluded that cocaine in higher concentrations directly affects development of GABAergic neurons in vitro.     

Afferent and efferent connections of the parapineal organ in lampreys: a tract tracing and immunocytochemical study

The neural connections of the parapineal organ of two species of lampreys were studied with the fluorescent dye 1,1'-dioctadecyl-3,3,3'3'-tetramethylindocarbocyanine perchlorate (DiI) and with immunocytochemistry. The lamprey parapineal organ consists of a vesicle and a ganglion that are connected to the left habenula. Labeling experiments included the application of DiI to the parapineal organ, left and right fasciculus retroflexus, left habenula, and the left pretectal region. Afferent parapineal fibers run in the left fasciculus retroflexus to the interpeduncular nucleus. The parapineal fibers of this fascicle arose from parapineal ganglion cells, whereas DiI application to the left habenula labeled both neurons of this ganglion and bipolar cells in the parapineal vesicle. Efferent neurons were observed in the left habenula, and bilaterally in the subhippocampal nucleus and the dorsal pretectum. Labeling with DiI also revealed a hippocampal projection. Immunocytochemical study of the parapineal vesicle revealed serotonin-immunoreactive cells in both species of lamprey, as well as substance P-immunoreactive (SP-ir) cells in sea lamprey and choline acetyltransferase-immunoreactive (ChAT-ir) cells in the river lamprey. The SP-ir cells and ChAT-ir cells formed a rich neuropil in the parapineal ganglion. Calretinin-ir cells were numerous in the ganglion. Neuropeptide Y-immunoreactive and gamma-aminobutyric acid-immunoreactive efferent fibers were observed in the parapineal organ. Neuropeptide Y-immunoreactive fibers originate in the subhippocampal nucleus, whereas gamma-aminobutyric acid-immunoreactive fibers might also arise in the pretectal nucleus. A few galanin-ir fibers were observed. These results indicate that the parapineal connections are completely different from those of the pineal organ. The possible homology between parapineal organs of vertebrates is discussed.     

Extensive projections from the midbrain periaqueductal gray to the caudal ventrolateral medulla: a retrograde and anterograde tracing study in the rat

We investigated the innervation of the caudal ventrolateral medulla by the midbrain periaqueductal gray in the rat using retrograde and anterograde tract-tracing. Iontophoretic injection of Fluoro-Gold or cholera toxin B subunit into the caudal ventrolateral medulla resulted in retrogradely labeled neurons in discrete regions of the periaqueductal gray. These labeled cells were observed throughout the rostrocaudal extent of the periaqueductal gray and were distributed (as percentage of total labeled cells) in its lateral (53-67%), ventrolateral (14-28%), ventromedial (7-16%) and dorsomedial aspects (7-10%). About 70-72% of labeled cells were found in the caudal half of the periaqueductal gray and 28-30% in the rostral half. In the ventromedial periaqueductal gray, more labeled cells were seen in the contralateral side (5-13%) than the ipsilateral side (2-3%), whereas for other periaqueductal gray areas labeling was preferentially ipsilateral. Phaseolus vulgaris leucoagglutinin anterograde tracing was used to confirm the retrograde labeling results. Following iontophoretic injection into the periaqueductal gray, labeled fibers and terminals were observed throughout the rostrocaudal extent of the caudal ventrolateral medulla. Injections in the lateral and/or ventrolateral aspect of the periaqueductal gray yielded more anterograde labeling in the ipsilateral than the contralateral caudal ventrolateral medulla, while injections in the ventromedial aspect of the periaqueductal gray produced labeling preferentially in the contralateral caudal ventrolateral medulla. The present study indicates that specific regions of the periaqueductal gray project to the caudal ventrolateral medulla and may regulate cardiovascular and respiratory functions through these connections.     

Septal innervation of mossy cells in the hilus of the rat dentate gyrus: an anterograde tracing and intracellular labeling study

To define the cellular processing of human cystatin C as well as to lay the groundwork for investigating its contribution to lcelandic Hereditary Cerebral Hemorrhage with Amyloidosis (HCHWA-I), we have characterized the trafficking, secretion, and extracellular fate of human cystatin C in transfected Chinese hamster ovary (CHO) cells. It is constitutively secreted with an intracellular half-life of 72 min. Gel filtration of cell lysates revealed the presence of three cystatin C immunoreactive species; an 11 kDa species corresponding to monomeric cystatin C, a 33 kDa complex that is most likely dimeric cystatin C and immunoreactive material, > or = 70 kDa, whose composition is unknown. Intracellular monomeric cystatin C is functionally active as a cysteine protease inhibitor, while the dimer is not. Medium from the transfected CHO cells contained only active monomeric cystatin C indicating that the cystatin C dimer, formed during intracellular trafficking, is converted to monomer at or before secretion. Cells in which exit from the endoplasmic reticulum (ER) was blocked with brefeldin A contained the 33 kDa species, indicating that cystatin C dimerization occurs in the ER. After removal of brefeldin A, there was a large increase in intracellular monomer suggesting that dimer dissociation occurs later in the secretion pathway, after exiting the ER but prior to release from the cell. Extracellular monomeric cystatin C was found to be internalized into lysosomes where it again dimerized, presumably as a consequence of the low pH of late endosome/lysosomes. As a dimer, cystatin C would be prevented from inhibiting the lysosomal cysteine proteases. These results reveal a novel mechanism, transient dimerization, by which cystatin C is inactivated during the early part of its trafficking through the secretory pathway and then reactivated prior to secretion. Similarly, its uptake by the cell also leads to its redimerization in the lysosomal pathway.     

Evidence for a GABAergic projection from the central nucleus of the amygdala to the brainstem of the macaque monkey: a combined retrograde tracing and in situ hybridization study

The central nucleus of the amygdala is interconnected with a variety of visceral and autonomic nuclei of the brainstem. These include the parabrachial nucleus, the nucleus of the solitary tract, the nucleus ambiguus and the dorsal motor nucleus of the vagus. Despite repeated attempts, neurochemical characterization of the major subcortical connections of the central nucleus has not yet been accomplished. Based on earlier immunohistochemical and in situ hybridization evidence indicating the presence of numerous GABAergic neurons in the macaque monkey central nucleus, we predicted that a sizeable portion of the descending projections may be GABAergic. We tested this hypothesis using a novel double labelling method with gold conjugated WGA-apoHRP as a retrograde tracer and in situ hybridization for detecting the mRNA that encodes the enzyme glutamic acid decarboxylase (GAD67) as a marker for GABAergic cells. Following WGA-apoHRP-gold injections into the brainstem, a large number of retrogradely labelled cells was observed in the medial and lateral divisions of the central nucleus. Of the retrogradely labelled cells observed in the medial division of the central nucleus, approximately half were double-labelled for GAD67 mRNA; about 30% double labelling was observed in the lateral division. These data support the view that a sizeable component of the central nucleus projection to the brainstem is GABAergic.     

Primary small cell carcinoma of the esophagus: a review of the literature with emphasis on therapy and prognosis

BACKGROUND: Few studies of patients with esophageal small cell carcinoma (SCC) have been conducted. Choice of treatment remains controversial. METHODS: The authors analyzed data on 199 evaluable esophageal SCC patients, selected from among 230 patients found in the literature, and a data extraction form that recorded 11 features was completed. To allow for the evaluation of prognostic factors that influenced survival, the patients were grouped according to limited stage (LS), which was defined as disease confined to the esophagus, or extensive stage (ES), which was defined as disease that had spread beyond locoregional boundaries. Univariate and multivariate analyses were performed. Treatment was categorized as either local or local with systemic; for the ES cases, the categories were defined as treatment versus no treatment. RESULTS: The tumor site was described in 178 cases (89%). Mean tumor size was 6.1. Pure SCC was found in 137 cases (68.8%), whereas 62 cases (31.2%) showed mixed SCC; 93 (46.7%) were LS, whereas 95 (47.7%) were ES. In 11 cases (5.5%), the stage was not determined. There was a significant difference in survival between patients with LS and those with ES (P < 0.0001). The median survival was 8 months for patients with LS and 3 months for those with ES. Univariate analysis of LS showed 3 significant prognostic factors: age (for patients age < or =60 years, the median survival was 11 months, whereas for those age >60 years, the median survival was 6 months), tumor size (for those with tumors < or =5 cm, the median survival was 12 months, whereas for those with tumors >5 cm, the median survival was 4 months), and type of treatment (with local plus systemic treatment, the median survival was 20 months, whereas with local it was 5 months). In multivariate analysis, tumor size (P = 0.007) and type of treatment (P < 0.001) were shown to be independent predictive variables. CONCLUSIONS: Esophageal SCC is an aggressive type of tumor. This study shows that there are significant differences between LS and ES and that in LS, both tumor size and type of treatment are possible prognostic factors.     

Coexistence of calcium-binding proteins in vagal and glossopharyngeal sensory neurons of the rat

The presence and coexistence of the calcium-binding proteins (CaBPs), calbindin D-28k, parvalbumin and S100 protein, were immunohistochemically examined in the glossopharyngeal and vagal sensory ganglia, the carotid body and taste buds. The CaBPs were found in each ganglion with the nodose ganglion containing the largest number of CaBP-immunoreactive (ir) cells (calbindin D-28k > or = S100 > parvalbumin). The coexistence of CaBPs was found in neurons of the nodose, petrosal, and jugular ganglia. Calbindin D-28k-ir neurons in the nodose and petrosal ganglia frequently colocalized S100-ir whereas calbindin D-28k-ir neurons in the jugular ganglion less frequently contained S100-ir. Only small percentages of calbindin D-28k-ir neurons in each ganglion colocalized parvalbumin. Similarly, S100-ir neurons in the nodose and petrosal ganglia frequently colocalized calbindin D-28k-ir whereas S100-ir neurons in the jugular ganglion less frequently contained calbindin D-28k-ir. Moderate to small percentages of S100-ir neurons in each ganglion colocalized parvalbumin. Parvalbumin-ir neurons nearly always colocalized S100-ir in the nodose, petrosal and jugular ganglia. Moderate to small percentages of parvalbumin-ir neurons in each ganglion colocalized calbindin D-28k. Whereas calbindin D-28k- and S100-ir were colocalized in nerve fibers and cells within taste buds of circumvallate papilla of the tongue, the coexistence of these CaBPs could not be determined in the carotid body. These findings suggest a co-operative role for CaBPs in the functions of subpopulations of nodose and petrosal ganglia neurons.     

A study of afferent input to the inferior olivary complex in the rat by retrograde axonal transport of horseradish peroxidase

The multilamellate glial sheath of mixed nerve roots of the sixth abdominal ganglion of crayfish contains numerous hemi-desmosomes which appear to attach glial lamellae to material in adjacent extracellular clefts. These junctions, which have been described in detail in an earlier report (Shivers and Brightman, '76), are irregular in shape, punctuate and may be as large as 1 mum in diameter. Surgical interruption of sixth ganglion nerve roots results in regeneration of motor axons and their multilamellate glial sheaths. As the glial processes grow and re-establish a highly organized axon sheath, hemi-desmosomes appear. These junctions are present at the advancing edge of glial processes as well as on their lateral margins. Developing hemi-desmosomes are characterized as a diffuse aggregation of 120-130 A intramembrane particles which are present three weeks following nerve section. As growth and reorganization of the sheath proceeds, the intramembrane particles appear to aggregate and form irregular clusters of varying dimensions. Regenerating nerves freeze-cleaved 8 to 16 weeks following surgery exhibit junctional particle aggregates similar to those in normal unoperated nerve roots. Origin of the intramembrane particles which comprise the junctional aggregated in unknown. Perhaps they are synthesized de novo by the regenerating glial cells or, they may be remnants of complexes which became dispersed following surgery. This is the first report of a freeze-fracture study of hemi-desmosome plasticity in an invertebrate nervous system.     

Involvement of nitric oxide in acute spinal cord injury: an immunocytochemical study using light and electron microscopy in the rat

The crystal structure of an acidic neurotoxin, BmK M8, from Chinese scorpion Buthus martensii Karsch was determined at 0.25 nm resolution. The X-ray diffraction data of BmK M8 crystals at 0.25 nm resolution were collected on a Siemens area detector. Using molecular replacement method with a basic scorpion toxin AaH II in a search model, the cross-rotation function, PC-refinement and translation function were calculated by X-PLOR program package. The correct orientation and position of BmK M8 molecule in crystal were determined in a resolution range of 1.5-0.35 nm. The crystallographic refinement was further performed by stereo-chemical restrict least-square technique, followed by simulated annealing, slow-cooling protocols. The final crystallographic R-factor at 0.8-0.25 nm is 0.171. The standard deviations of bond length and bond angle from ideality are 0.0017 nm and 2.24 degrees, respectively. The final model of BmK M8 structure is composed of a dense core of secondary structure elements by a stretch of alpha-helix with two and a half turns (residues 19-28) and a three-stranded antiparallel beta-sheet (residues 2-4, 32-37, 45-51). In addition, three loops protruded from the structural core. The general folding properties of BmK M8 molecule were described; a common structure motif which may appear in all scorpion neurotoxins was identified. The conserved aromatic residues and charged residues were found to be distributed on two roughly opposite surfaces of the molecule. The relationship between these two faces and receptor-binding sites are also discussed.     

Topographical projections from the medial septum-diagonal band complex to the hippocampus: a retrograde tracing study with multiple fluorescent dyes in rats

Direct projections from the medial septum-diagonal band complex (MS-DB) to the hippocampus were studied in rats using the retrograde labeling method with fluorescent dyes. In the first series of experiments, the distribution patterns of retrogradely labeled cells in the MS-DB were examined in sagittal sections, following simultaneous injection of two different fluorescent dyes separately into the ventral hippocampus (VHPC) and the dorsal hippocampus (DHPC). It was found that the DHPC received fiber terminals mainly from the rostral half of the MS-vertical limb of the diagonal band (VDB) and the core part of the horizontal limb of the diagonal band (HDB), whereas the VHPC received fiber terminals largely from the caudal half part of the MS-VDB and the marginal part of the HDB. The marginal part appears to form a 'C' and not a complete circle around the core part. In the second series of experiments, the distribution patterns of retrogradely labeled cells in the MS-DB were investigated in sagittal sections, following simultaneous injection of three or two different fluorescent dyes separately into the subfields of the DHPC. The CA1 received fiber terminals mainly from the HDB and VDB, while the hilus received fiber terminals mainly from the MS. The CA2-CA3 received fiber terminals almost equally from the MS, VDB and HDB. The present results reveal distinctive topographical organizations of the septohippocampal connections.     

Toxicokinetics and biochemistry of cadmium with special emphasis on the role of metallothionein

Cadmium is a toxic metal with extremely long biological half-time of 15-20 years in humans. It has for decades been known that cadmium exposure can cause a variety of adverse health effects, among which kidney dysfunction, lung diseases, disturbed calcium metabolism and bone effects are most prominent. Following long term exposure the kidney is the critical organ. Cadmium and its compounds give rise to lung cancer after inhalation and have been classified as human carcinogens. Metallothionein (MT) is a low-molecular -weight protein, 6500Da with high cysteine content and high metal affinity, which plays a major role in the kinetics and metabolism of cadmium. The balance between CdMT and non-bound Cd in renal tissue has been shown to be of crucial importance for expression of toxicity. The most well studied metallothioneins are metallothioneins I and II with their isoforms which are expressed in almost all mammalian tissues. Metallothionein III is expressed in brain and is rich in zinc. Since the blood-brain barrier keeps Cd outside the CNS, reported neurotoxic effects of Cd during development are likely to be secondary to an interference of Cd with Zn-metabolism and not a direct effect of Cd on brain cells. It is therefore of importance to investigate whether neurotoxicity induced by cadmium is related to mechanisms involving MT III in brain.     

An investigation of a possible direct projection from the medial nucleus of the cerebellum to the paraventricular nucleus of the hypothalamus in the rat: a study using retrograde WGA-HRP and Fluoro-Gold tracing techniques

Retrograde transport of lectin-conjugated horseradish peroxidase and Fluoro-Gold was used in an attempt to obtain data to confirm the existence, predicted from physiological studies, of a direct, monosynaptic projection from the medial nucleus of the cerebellum (MN) to the paraventricular nucleus of the hypothalamus (PVH) in the rat. Injections of these two tracers that included the PVH and surrounding diencephalic structures, or that in the case of Fluoro-Gold were localized to the PVH, resulted in retrograde neuronal labeling in widely separated nuclei known to project to the areas included in the injection sites. Thus, effective uptake and transport of both tracers occurred under the experimental conditions employed in this study. However, injections confined to the PVH and regions of the hypothalamus adjacent to it, or to the PVH alone, produced no retrograde neuronal labeling in the medial nucleus, indicating that the MN does not project directly to the PVH. Alternative explanations for the findings from physiological experiments were sought. The possibility that electrical stimulation of fibers of passage through the region of the MN might produce a monosynaptic response in the contralateral PVH was discarded, because retrogradely labeled neurons in nuclei such as the locus ceruleus and lateral parabrachial nucleus were distributed mainly ipsilateral to hypothalamic injection sites. However, tracer injections into the MN produced retrograde labeling of neurons in the same region of the lateral paragigantocellular nucleus (LPGi) in which labeled cells were found following tracers injections into the PVH. Axon collaterals of individual neurons in the LPGi might, therefore, project both to the MN and to the PVH. The possibility that such a circuit could, in the absence of a direct MN to PVH projection, provide the basis to explain the physiological findings is discussed.     

Multi-segmental innervation of single pontine reticulospinal axons in the cervico-thoracic region of the cat: anterograde PHA-L tracing study

To characterize the fine morphology of individual reticulospinal axons at multiple spinal segments, localized injections of the anterograde neural tracer, Phaseolus vulgaris leucoagglutinin (PHA-L), were made into the nucleus reticularis pontis oralis (NRPo) of the cat. Following survival periods of 6-8 weeks, labelled axons, between 1 and 8 microns in diameter, were found throughout the cervical and upper thoracic segments. Thick axons (diameter > or = 3 microns) were found to descend beyond the upper thoracic spinal cord, while most thin axons (diameter < 3 microns) ended in the upper cervical cord. From serial transverse sections (50 microns) of segments C3 to T2, in four cats, the trajectories of 23 single, thick reticulospinal axons were traced in continuity over distances of between 21.8 and 59.4 mm, corresponding to 3 and 8 segments, respectively. Most axons gave off at least one, and as many as four collaterals per segment, some preferentially in the cervical enlargement. The remainder gave off collaterals at most but not all segments. Detailed reconstruction of the collateralization and arborization in the spinal gray matter showed two major termination types, one where terminals remained ipsilateral to the stem axon, the other where additional collaterals extended across the midline from the ipsilateral gray matter to terminate in the contralateral gray matter. Axons tended to have collaterals of one type or the other, irrespective of the rostrocaudal level. Both ipsilateral and bilateral projections terminated mainly in laminae VII or VIII although the branching patterns varied from axon to axon. Individual stem axons, in general, showed similar termination patterns at each level.     

Scintigraphic detection of infection and inflammation: new developments with special emphasis on receptor interaction

Various conventional radiopharmaceuticals are currently available for scintigraphic imaging of infection and inflammation. Although a wide variety of infectious and inflammatory foci can be detected with these agents, several disadvantages limit their application. These limitations have stimulated the search for new radiopharmaceuticals. In the past decade a new class of radiopharmaceuticals has emerged: radiolabelled receptor-specific small proteins and peptides. These proteins and peptides are naturally occurring inflammatory mediators which specifically bind to receptors abundantly present in the area of inflammation. In addition, owing to their small size, they rapidly clear from all non-target tissues. This paper provides an overview of these newly developed agents, focussing on imaging characteristics and in vivo uptake mechanisms.     

An electrophysiological study on the vagal innervation of the thymus in the rat

Vagal innervation of the thymus was studied by means of electrophysiological technique in the rat. Under urethane anesthesia, evoked action potentials originated from cervical vagus by electrical stimulations were recorded from the central cut end of the thymic branch of the vagus nerve after averaging for 32 times. It was observed that the conduction velocities are distributed in the range of 0.56-6.84 m/s, and the majority of vagal fibers in the thymic branch of the vagus nerve belong to a nonmyelinated C-fiber group. Further, it was confirmed that the right and left lobes of the thymus are innervated by cervical vagi bilaterally. The results suggest that the thymic branch of the vagus nerve plays a role in modulation of thymic function.