Complete casts of the hypophyseal and hypothalamic blood vascular beds of newborn, pubescent, adult and aged rats were produced by infusion of low viscosity methacrylate media, dissected under a binocular light microscope, and observed with a scanning electron microscope.
The primary capillary plexus projected capillary loops into the median eminence and infundibular stalk. These loops were composed of anastomosing capillaries, being numerous in the central area of the anterior lip of the median eminence. The well developed long loops received their proper afferent arterioles from the arterial terminals in the primary plexus, and emitted their proper efferent venules continuous with the long portal vessels. The loops in newborn rats were poorly developed, appearing as simple ball-like protrusions of the capillaries of the primary plexus.
Many branches of the anterior, middle and accessory midde hypophyseal arteries penetrated the primary plexus, and ascended as infundibular ascending arterioles in the median eminence and infundibular stalk. These infundibular ascending arterioles continued into the capillary bed of the hypothalamus, especially in its basilar and peni-ventricular areas. The subependymal capillary network was fairly independent, and located dorsal to the loops. This network received some of the infundibular ascending arterioles, and emitted infundibular descending venules continuous with the long portal vessels. The subependymal network also received the infundibular descending arterioles from the hypothalamic arteries, and emitted the infundibular ascending venules continuous with the hypothalamic veins. Thus, neither a feedback nor a retrograde portal route from the hypophyseal capillaries to the hypothalamic capillaries was noted.
The capillary bed of the pars tuberalis was observed only in the adult and aged rats; it was a very coarse network which was derived from the primary capillary plexus and connected to the secondary capillary plexus.

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Rabbits were starved for a week and then allowed to take the standard diet; the animals were sacrificed after 20 or 24hr. One group of the animals was treated in winter, and the other, in summer. Control animals were fed solid rabbit food ad libitum.
In the control rabbits, short rudimentary canaliculi and occasional small-sized pored domes were found in the thicker portions of the endothelial extension. In the animals experimentally treated in winter, well-developed meandering canaliculi with vacuolar expansions and constrictions appeared in the thicker portions and perikaryonal cytoplasm. In addition prominent pored domes were produced. The canaliculi often formed sponge-like networks with openings both to the sinusoid and the Disse's space. The development of the canalicular system and pored domes correlated to an increased blood flow through the sinusoids; this seemed to be induced upon sudden feedings after lengthy starvation. The rabbits subjected to the experimental treatment in summer exhibited no distinct development of the canaliculi and pored domes. This result was ascribed to the inhibited functions of the rabbit liver during this season.

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Cryo-treated nerves whose Schwann cells had been killed by repeated freezing and thawing were xenogenically grafted into sciatic nerves from rats (Wistar, as donor) to mice (ddy strain, as recipient) to examine whether Schwann cell basal lamina tubes of cryo-treated xenogeneic grafts were effective conduits for regenerating axons. For comparison and evaluation of the effectiveness of this technique, experiments using grafts without the cryo-treatment were carried out.
Cells in cryo-treated xenografts degraded into cell debris immediately after grafting and then were phagocytized by macrophages. After the cellular components had been removed from the graft, Schwann cell basal laminae remained intact in situ, serving as conduits for the regenerating axons. The process of nerve regeneration was almost the same as that observed in cryo-treated auto- and allografts, except that the regeneration was slightly delayed in the xenogeneic graft. In contrast, an extensive cell infiltration occurred in the non-treated grafts. It appeared that the donor¹s Schwann cells in the graft deteriorated due to immunological reactions and were finally eliminated by macrophages, leaving their basal laminae undamaged in situ. The initiation of nerve regeneration including perineurial sheath formation in non-treated grafts was, therefore, significantly delayed, but once begun, it proceeded in the same manner as in the cryo-treated grafts.
These findings strongly indicate that Schwann cell basal laminae can serve as effective pathways for regenerating axons even in the xenograft. Moreover, cryo-treated xenogeneic grafts are more desirable than non-treated ones, since dead Schwann cells in the former can be removed in the early period (4-14 days) from the graft without causing any immunological reaction, thus resulting in the facilitation of nerve regeneration.

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After treatment with either trypsin, 8N HCl or 5N KOH, or with mechanical dissociation, normally hidden aspects of the seminiferous epithelium were exposed to observation by scanning electron microscopy (SEM). These included the basal surface of seminiferous epithelial cells, the basolateral processes of the Sertoli cell, junctions of the processes, and the basal or adluminal recesses.
With the progressing stages of the spermatogonial cycle, three kinds of spermatogonia show different profiles and topographic relations. The basolateral processes of the Sertoli cells can be categorized into four types: conical, wedge-shaped, sheet-like and cup-shaped processes. The first two of the basolateral processes are joined together by close contact and/or overlapping junctions to form the floor of the basal recesses, and they encircle small-sized spermatogonia. The sheet-like processes mutually join by seam line junctions to form the ceiling of the basal recesses. During the spermatogonial cycle, the basal recesses first appear as separated lacunae, then form continuous labyrinth-like trenches, and finally make complicated honeycomb-like lacunae. The cup-shaped processes also are joined by close contact and/or overlapping junctions and are tightly attached by the primary spermatocytes with doughnut-like or linear bodies. The cordal arrangement and adluminal shift of the diverse spermatogonia will be discussed along with the cyclic transformations of Sertoli cell processes and their junctions.

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The development of microglial cells in the postnatal rat retina is described using histochemical techniques for acid phosphatase and peroxidase as well as silver impregnations for microglia. On the second postnatal day, round acid phosphatase-positive macrophages appeared on the vitreal surface of retina, locating themselves close to developing blood vessels. Later, microglial precursors invaded retinal tissues, reaching the outer plexiform layer by the tenth postnatal day. In all stages studied, microglia or their precursors were peroxidase-negative. The transformation of round microglial precursors into adult ramified microglia is also described. Owing to the relation found between developing microglia and blood vessels, a vascular origin is proposed for the retinal microglial cells.

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Twelve endocrine cell types immunoreactive for either 5-hydroxytryptamine (5-HT), somatostatin, gastrin, motilin, neurotensin, bovine pancreatic polypeptide (BPP), avian pancreatic polypeptide (APP), pancreatic glucagon, enteroglucagon, glicentin, secretin or cholecystokinin (CCK) were found in gastrointestinal mucosa of Caiman latirostris.
Moderate numbers of enteroglucagon-immunoreactive cells, a few 5-HT-, somatostatin- and motilin-immunoreactive cells and rare pancreatic glucagon-immunoreactive cells were found in the fundic stomach. Numerous gastrin-immunoreactive cells and moderate numbers of somatostatin- and motilin-immunoreactive cells were seen in the pyloric stomach. Moderate numbers of 5-HT-, gastrin-, motilin- and enteroglucagon-immunoreactive cells, a few somatostatin-, neurotensin- and BPP-immunoreactive cells, and rare APP-, pancreatic glucagon-, glicentin-, secretin- and CCK-immunoreactive cells were observed in the proximal intestine. Moderate numbers of 5-HT-immunoreactive cells, small to moderate numbers of neurotensin- and enteroglucagon-immunoreactive cells and occasional somatostatin-, motilin- and BPP-immunoreactive cells were seen in the distal intestine. Moderate numbers of neurotensin-immunoreactive cells and a few 5-HT-immunoreactive cells were found also in the cloaca. Cells immunoreactive for gastrin releasing polypeptide, bombesin and gastric inhibitory peptide were not observed in the caiman gastrointestinal epithelium.
The differences in endocrine cell types between the caiman and alligator are discussed in terms of their topographic distribution.

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