The descending projection of the hypothalamic paraventricular nucleus (PVN) to the sympathetic preganglionic neurons (SPNs) in the upper thoracic cord of the rat was studied. PVN-fibers were labeled by anterograde transport of Phaseolus vulgaris leucoagglutinin (PHA-L), while SPNs were retrogradely labeled with cholera toxin subunit B (CTb) which was injected into the superior cervical ganglion. SPNs labeled with CTb were mainly observed in the nucleus intermediolateralis (IML) pars principalis and pars funicularis, and a small number of them were in the nucleus intercalatus (IC) and central autonomic nucleus (CA). SPNs found in the IML had dendrites that projected in various directions. Five types of dendritic projections were noted: medial, rostral, caudal, lateral (including dorsolateral) and ventral. Longitudinal dendritic bundles interconnected each cell cluster in the IML. Medial dendrites of the IML, together with dendrites of the IC and CA, formed transverse dendritic bundles extending from the IML to the central canal. The transverse dendritic bundles disentangled near the midline and formed a loose dendritic plexus in the region just dorsal to the central canal. PVN-fibers labeled with PHA-L were observed primarily in lamina I and intermediate gray (lamina VII). Although varicose PVN-fibers and SPNs coexisted in the IML, the tight packing of the dendritic bundles prevented any clear demonstration of direct contacts between them. On the other hand, PVN-fibers were occasionally found to appose and wind around the primary or secondary dendrites of some SPNs of the CA and IC. These dendrites were studied with varicosities of PVN-fibers for a short length, and terminal boutons of PVN-fibers were also seen to make contact directly with the dendrities. The results of this study substantiated a direct connection between the PVN and SPNs, using a combination of immunohistochemical techniques for PHA-L and CTb. The possible involvement of a direct pathway from the PVN to SPNs in cardiovascular regulation is discussed.

The present study was undertaken using retrograde labeling techniques to clarify whether the neurons in the dorsal hypothalamic area (DHA) that project to the spinal cord are the same as those that project to the nucleus raphé pallidus (NRP). Following an injection of wheat germ agglutinin-conjugated horseradish peroxidase (WGA-HRP) in the NRP many labeled small neurons (6-13 X 9-22 microns) with an oval shape were found in the ventromedial part of the DHA. At the level of the dorsomedial hypothalamic nucleus, they formed a distinct and compact cell cluster. Labeled neurons, which were large in size (9-22 X 11-36 microns) with oval and triangular shapes, were found mainly in the dorsolateral part of the DHA after injections of horseradish peroxidase (HRP) in the spinal cord. In a double-labeling experiment, Fast Blue or True Blue, and Nuclear Yellow were injected in the NRP and in the spinal cord, respectively. A large number of blue-fluorescent neurons were located mostly in the ventromedial part of the DHA, while yellow-fluorescent ones were found in the dorsolateral part of the DHA. However, no double-labeled neurons were found in the DHA. These results show that the neurons of the DHA projecting to the NRP are essentially different from those which project to the spinal cord.

The cell morphology of sympathetic preganglionic neurons (SPNs) in the dorsal commissural nucleus was studied by the retrograde labeling technique using cholera toxin subunit B (CTb) as a tracer. A small amount of an aqueous solution of CTb was injected unilaterally into the major pelvic ganglion of the male rat. Labeled SPNs were detected immunohistochemically using anti-CTb antiserum. Most of the labeled SPNs were observed in L1 to L3, and a very small number in T13. They were observed bilaterally in the sympathetic nuclei, such as the intermediolateral cell column, intercalated nucleus and the dorsal commissural nucleus. A loose network of longitudinally or transversely oriented SPN dendrites was located within the dorsal commissural nucleus itself. The lateral margin of the dorsal commissural nucleus was roughly demarcated by longitudinally oriented dendrites. Together with the dendrites of the SPNs of the intercalated and intermediolateral cell column, laterally oriented dendrites of the dorsal commissural nucleus converged and formed the transverse dendritic bundles in the intermediate zone that connect the dorsal commissural nucleus and the intermediolateral cell column. The transverse dendritic bundles were arranged periodically. The axons of the SPNs in the dorsal commissural nucleus traveled laterally into the transverse dendritic bundles, then turned ventrally near the intermediolateral cell column, and finally entered the ventral funiculus. After rhizotomy of the ventral roots of the upper lumbar cord, labeled SPNs were found only on the side contralateral to the rhizotomy. The dorsal commissural nucleus appears as a compact single cell column, but our results clearly show that this nucleus actually consists of two adjacent parallel columns of cells.

To demonstrate localization of hyaluronic acid (HA) in articular cartilage of the human femur, biotinylated HA-binding region, which specifically binds HA molecules, was applied to the tissue. In sections fixed by 2% paraformaldehyde-2% glutaraldehyde, HA staining was detected in lamina splendens and chondrocytes in the middle zone. By pretreatment with trypsin, intense HA staining appeared in the extracellular matrix of the deep zone and weak staining in the superficial and middle zones. Moreover, pre-treatment with chondroitinase ABC (CHase ABC) intensely enhanced the stainability for HA in the superficial and middle zones and weakly in the deeper zone. Combined pre-treatment of trypsin with CHase ABC abolished intra- and extracellular staining for HA in all zones. By microbiochemical study, the concentrations of HA and dermatan sulfate were high in the middle zone, whereas those of chondroitin sulfate and keratan sulfate were high in the deep zone. These results suggest that HA is abundantly synthesized in and secreted from the chondrocytes, particularly in the middle zone, whereas it is largely masked by proteoglycan constituents in the extracellular matrix.

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