Toxic effects of his (tributyltin) oxide (TBTO) on the rat exocrine pancreas were studied with an electron microscope and X-ray microanalyzer. To measure tin concentrations in the blood, atomic absorption spectrophotometry was carried out.
Adult male Wistar rats received an intramuscular injection of TBTO (0.5ml/kg). At 2h after injection, a marked swelling of mitochondria and an enlargement of the cisterns of the rough endoplasmic reticulum appeared in the pancreatic acinar cells. Using X-ray microanalysis, tin peaks were preferentially obtained from the swollen mitochondria. Heterogeneous zymogen granules with an electron dense core and a pale central zone increased in number in the acinar cells between 4 and 8h after TBTO treatment. By 24h after TBTO injection, the acinar cells had been ultrastructurally restored. Atomic absorption analyses showed that blood tin concentrations peaked at approximately 1h after TBTO injection and then progressively declined, reaching the zero level at 12h after injection.
The effects of TBTO on the synthesis and secretion of zymogen granules were investigated with and without caerulein as a stimulant of secretion. Data obtained from these experiments indicated that TBTO inhibited both the synthesis and secretion of zymogen granules. The inhibition of the protein synthesis and secretion might be caused partly by mitochondrial dysfunctions due to the toxic effects of TBTO.

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Microvascular corrosion casts of the pituitary gland of one to nine-day-old chickens (Gallus domesticus, white leghorn hybrids) were analysed with the scanning electron microscope.
Results show that the chicken median eminence is supplied by branches of the infundibular and the neurallobe arteries. They form a flat two-dimensional primary capillary plexus, which lacks any capillary loops and is continuous with the plexus in the neural lobe. The capillaries occupy about 60% of the total area of the median eminence. A subependymal plexus is present, showing no contact with the plexus of the median eminence.
The chicken neural lobe consists of many hollow buds. These buds are supplied by branches of the neural-lobe artery, which gives rise to a two-dimensional capillary meshwork similar to that of the median eminence.
An anterior group of portal vessels, comprising 14-16 vessels with a mean diameter of 37μm, and a posterior group of portal vessels, comprising 2-4 shorter and slightly thinner vessels, arise from the median eminence are the sole blood supply for the adenohypophysis (distal lobe). Anterior portal vessels supply the cephalic lobe and the most rostral area of the caudal lobe, and posterior portal vessels supply the caudal lobe of the distal lobe. There are no short portal vessels connecting the neural lobe with the distal lobe. The (sinusoidal) capillary bed of the distal lobe is laminated.
The chicken hypophysis drains into the cavernous sinus, which empties into the cerebral carotid veins.
Within the period studied (days 1-9 after hatching) no age-related changes were found.

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A novel monoclonal antibody raised against bovine secretogranin II (Sg II) was used in immunohistochemical studies on amphibian (Rana esculenta), reptilian (Podarcis sicula) and avian (Gallus gallus) gut. Sg II immunoreactivity was detected in epithelial and nervous elements. Cells immunoreactive for Sg II were examined by double immunostainings to determine whether they might also co-store certain previously known bioactive amine/peptide substances. Almost all the endocrine cells immunoreactive for bombesin, substance P, neurotensin, gastrin/cholecystokinin, neuropeptide tyrosine (NPY) and calcitonin gene-related peptide as well as some of those immunostained for serotonin, histamine, and polypeptide tyrosine tyrosine (PYY) also contained Sg II. Sg II-immunoreactive cells varied in number and distribution according to regions of the gut and animal species. The number of Sg II immunoreactive granules notably varied not only according to cell type, but also within the same cell population.
Many histamine-, calcitonin gene-related peptide (CGRP)-, substance P-, PYY-, and neurotensin-immunoreactive neurons also contained Sg II. These were mostly situated in the myenteric plexus; their distribution pattern varied among the three species.
These findings show that, despite being well conserved during phylogeny, Sg II has a heterogeneous distribution.

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NADPH-diaphorase activity together with nitric oxide synthase- and vasoactive intestinal polypeptide-immunoreactivities were examined in the neurons of the rat pancreas in culture. Nitric oxide synthase (NOS)- and vasoactive intestinal polypeptide (VIP)-immunoreactivities were localized in a subpopulation of neurons which were also NADPH-diaphorase positive. All neurons expressing colocalized activities for NOS/VIP and NADPH-diaphorase were solitary cells in culture. Each of these double-labelled neurons was characterized by a round or oval cell body, with short and long processes emanating from it. Some of these processes traversed several micrometres before terminating on the exocrine acinar and endocrine cells. The present study provides evidence that nitric oxide may act as a regulatory agent in the inhibitory neural control of the secretory functions in the pancreas, thereby maintaining the milieu interieur of the organism.

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An immunohistochemical study was carried out on two types of dendritic immune cells, Langerhans cells and Thy-1-positive cells, in the epithelium of the forestomach of 1-, 2-, 3-, 4- and 8-week-old mice. Investigation focused on how both types of cells were distributed and might interact in the mucosal epithelium. Langerhans cells and Thy-1-positive dendritic cells appeared in mucosal epithelium at 3 weeks of age, while in the epidermis they were first observed just after birth. In contrast with the epidermal Thy-1-positive cells, mucosal Thy-1-positive cells were closely associated with Langerhans cells. Electron microscopy also confirmed that two types of immune cells interact directly in the stratified squamous mucosal epithelium of mice.

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In the rat small intestine, apoptotic enterocytes are exfoliated at the villus tip as a whole cell, in contrast to guinea pig enterocytes which are phagocytosed by macrophages in their cell body and shed off only in their apical cortex. While macrophages gather in the lamina propria of the intestinal villi in both species, their functions seem to differ.
Unlike the guinea pig, lamina propria macrophages observed in the rat small intestine did not show morphological signs of phagocytosis, revealing few cellular elements in their phagosomes. At the “shoulder” of the villus, i. e., a certain distance proximal to the villus tip, subepithelial macrophages extended a thick process deep into the epithelium; their branched terminals penetrated the cytoplasm of enterocytes, resulting in the formation of excavated spaces in the cell body. Processes of macrophages frequently reached close to the brush border. At the shoulder of the villus, a few effete cells showed typical apoptotic signs and appeared to be pushed out into the lumen; still, the shedding of apoptotic enterocytes was recognized mainly at the very top of the villus, where no intraepithelial processes of macrophages could be seen. The present findings indicate that in the rat, lamina propria macrophages do not engulf aged enterocytes, but are involved in inducing their apoptosis.

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The distribution of adrenergic nerves in the body detrusor muscle of the cat urinary bladder was studied by means of the immunohistochemical identification of noradrenaline (NA) and the NA synthesizing enzymes tyrosine hydroxylase, aromatic L-aminoacid decarboxylase and dopamine beta-hydroxylase. We identified the basic structural organization of the detrusor muscle, which had previously been described as lacking discernible layers. In the lateral wall, both outer longitudinal and inner circular muscle bundles were present, the latter extending in both anterior and posterior directions. The posteriorly running bundles came to lie on the outside of the posterior wall where they enabled recognition of inner longitudinal muscle bundles. Those running anteriorly were dispersed to enter the longitudinal bundles in the anterior wall. NA-immunoreactive nerve fibers in the detrusor muscle of the bladder were found to be similar to those immunoreactive for NA synthesizing enzymes in both distribution and density. In the upper and middle bladder body—including the dome (apex)—immunoreactive nerve fibers were always more abundant in the outer part of the detrusor muscle than in the inner part, regardless of the course of muscle bundles. Even in individual muscle bundles running from the inside to the outer surface, the outer part was more richly innervated by immunoreactive fibers than the inner part. In the bladder dome, a moderate number of immunoreactive nerve fibers preferentially innervated the outer part of the muscle layer. In the lower bladder body, these nerve fibers increased in density in the inner part of the detrusor muscle. There was no sexual difference in density or distribution of nerve fibers. NA-and NA synthesizing enzyme-immunoreactive nerve fibers were markedly decreased in number after 6-hydroxydopamine treatment. No dopamineor phenylethanolamine-N-methyltransferase-immunoreactive nerve fibers were present in the bladder.
The findings of this study indicate that the cat bladder musculature includes longitudinal and circular muscle bundles, both of which are extensively innervated by adrenergic nerves, particularly in the outer part of the bladder.

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Milky spots in the fetal lamb omentum were observed by light and electron microscopy under normal conditions and after intraperitoneal carbon injection in utero.
Rudimentary milky spots first appeared as small aggregations of cells along capillaries of the omental branch of the right ruminal artery at 72 days of gestation. At 116 days of gestation, macrophages were detected immunohistochemically in the milky spots. At 125 days of gestation, T cells were detected in the milky spots, but B cells were absent.
Under the conditions induced by intraperitoneal injection of carbon suspension, openings were observed between the omental mesothelial cells, and macrophage aggregations appeared on the surface of the omentum through the openings. At 148 days of gestation (newborn), the milky spots were noted as black spots because of aggregation of carbon laden macrophages.
The present study demonstrates that milky spots are present at fixed sites in the fetal lamb omentum by the middle of the term, and that at birth the macrophages on the spots already possess phagocytotic ability. The fetus develops the ability to protect the peritoneal cavity by producing peritoneal macrophages from the milky spots in the greater omentum even in utero.

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