Immunohistochemical survey of the gut endocrine cells in the common tree shrew (Tupaia belangeri)

Regional distribution and relative frequency of endocrine cells in the gastrointestinal tract of the common tree shrew (Tupaia belangeri) were studied immunohistochemically. Ten types of immunoreactive endocrine cells were localized in the gastric mucosa, i.e., chromogranin-, serotonin-, gastrin-, somatostatin-, bovine pancreatic polypeptide (BPP)-, enteroglucagon-, pancreatic glucagon-, peptide tyrosine tyrosine (PYY)-, motilin-, and substance P (SP)-immunoreactive (IR) cells. In the intestine, 13 types of immunoreactive cells were observed, i.e., chromogranin-, serotonin-, somatostatin-, gastrin-, BPP-, enteroglucagon-, PYY-, secretin-, cholecystokinin (CCK)-, gastric inhibitory peptide (GIP)-, motilin-, neurotensin-, and SP-IR cells. The regional distribution and relative frequency of the cell types varied along the gastrointestinal tract. Basically, the types, distribution, and relative frequency of the gut endocrine cells were similar to those reported in other mammalian species. However, some characteristic findings were noted in the present study: (1) the considerably large number of gastrin-IR cells in the pyloric region; (2) numerous serotonin-IR cells in the stomach; (3) appreciable number of BPP-IR cells in the transitional region of the stomach; and (4) wide distribution of PYY- and motilin-IR cells in the gut.

Cardiac-like musculature of the intrapulmonary venous wall of the long-clawed shrew (Sorex unguiculatus), common tree shrew (Tupaia glis) and common marmoset (Callithrix jacchus)

BACKGROUND

The cardiac-like musculature is distributed not only in the heart wall but also in the intrapulmonary venous wall in a few species of insectivores. It has been suggested that the evolutionary origin of venous cardiac-like musculature may be traceable to a basic stock of certain mammalian lines of descent. So, it is important to clarify whether the musculature may be a common structure in lower mammals from insectivores to primates and to examine the functional significance of the structure.

METHODS

The distribution of cardiac-like musculature in the intrapulmonary venous wall of the long-clawed shrew (Sorex unguiculatus), common tree shrew (Tupaia glis), and common marmoset (Callithrix jacchus) was observed by light and electron microscopy. The presence of atrial natriuretic polypeptide (ANP) was examined in the musculature by immunohistochemistry.

RESULTS

All three species contained cardiac-like myocytes in the tunica media of intrapulmonary venous wall. In the common tree shrew and the common marmoset, cardiac-like musculature was found in the small intrapulmonary vein of 150-200 microns in diameter, while, in the long-clawed shrew, it was distributed even in the intrapulmonary vein of 30 microns in diameter. Ultrastructure of myocytes was fundamentally similar to that of atrial myocytes in the long-clawed shrew and the common tree shrew. The presence of atrial natriuretic polypeptide (ANP) was also demonstrated by immunohistochemistry in the intrapulmonary venous walls of common tree shrews.

CONCLUSIONS

The results indicate that the pulmonary venous cardiac-like musculature occurs in the lower eutherian mammals from insectivores to primitive primates. The musculature is thought to act as a regulatory pump in pulmonary circulation and as an endocrine apparatus of ANP.

An ultrastructural and lectin-histochemical study on the seminiferous epithelium of the common tree shrew (Tupaia glis)

The seminiferous epithelium of the common tree shrew (Tupaia glis) was investigated using transmission electron microscopy and lectin-histochemistry. It was compared with that of shrews examined in previous studies. Some peculiar structures were detected in the tree shrew spermatid at the electron microscopic level. The most characteristic feature was the disposition of mitochondria in early spermatids. In cap and early acrosome-phase spermatids, mitochondria accumulated in one area of the spermatid cytoplasm and then dispersed in the late acrosome phase. Subsequently they again clustered to form the middle piece of spermatozoa. While the lamellar structure was clearly seen in the caudal region of the spermatid nucleus, it gradually disappeared during the process of elongation. The dilated area in the postacrosomal space of early round spermatids was also characteristic. The dilation was not detected in elongated spermatids. These structures were not recognised in the seminiferous epithelium of shrews. With respect to lectin histochemistry, the binding patterns in the spermatid acrosome of the tree shrew were similar to those of the musk shrew. However, PNA and BPA, which reacted with the Sertoli cell cytoplasm of the musk shrew, showed no reaction in the tree shrew Sertoli cell. Thus, except for some lectin binding patterns in the spermatid acrosome, no close similarity was recognised in the morphology of the seminiferous epithelium between tree shrews and shrews.

Classification of the cycle of the seminiferous epithelium in the common tree shrew (Tupaia glis)

The classification of the cycle of the seminiferous epithelium was carried out in the common tree shrew (Tupaia glis). The tree shrew captured in Thailand were fixed with Bouin's fixative, embedded in paraffin wax, and stained with PAS-hematoxylin. The cycle was classified into twelve stages on the basis of the acrosomal changes of spermatids. Relative frequencies of stages form I to XII were 11.9, 7.2, 8.9, 22.5, 12.9, 9.7, 8.0, 5.9, 4.0, 3.2, 2.9, and 3.6%, respectively. Different stages did no appear in a cross-sectioned tubule as did in primates. The head of matured spermatid was discoidal in shape and different from that of primates and rodents. Spermatogenesis of the common tree shrew is different from that of primates and rodents according to its morphological features.

Cardiac musculature of the cranial vena cava in the common tree shrew (Tupaia glis)

Cardiac musculature of the cranial vena cava in the common tree shrew (Tupaia glis) was examined by light and transmission electron microscopy. The common tree shrew has well developed cardiac myocyte layers in the tunica media of the cranial vena cava, extending from the right atrium to the root of the subclavian vein. Because the common tree shrew belongs to a primitive group of mammals, the occurrence of cardiac musculature in the cranial vena cava may be a common feature in lower mammals. The development of this musculature indicates that active contraction of the cranial vena cava wall occurs in this species. Electron micrographs showed the typical ultrastructure of myocytes and nerve endings. These observations suggest that this musculature may serve as a regulatory pump for the return of venous blood to the right atrium and as a blood reservoir system under conditions of rapid heart rate. Additionally, the presence of atrial natriuretic polypeptide (ANP) was also demonstrated in the myocytes of the vena cava immunohistochemically. These findings show that the cardiac endocrine organ for ANP develops even in the principal veins including the cranial vena cava.

Serotonin-storing cells of the chicken duodenum: light, fluorescence and electron microscopy, and immunohistochemistry

In an attempt to identify duodenal endocrine cells emitting formaldehyde-induced fluorescence (FIF), chicken duodena were studied by combined fluorescence, ultrastructural, silver impregnation and immunohistochemical methods in the same or consecutive sections. Our results show that: (1) Almost all the cells emitting yellow fluorescence by both the Falck-Hillarp and the Furness methods exhibit an immunohistochemical reaction with serotonin (5-HT) antiserum. (2) Almost all cells radiating yellow fluorescence by the Furness method stain with toluidine blue in Epon-embedded sections, but, by high-voltage electron microscopy, can be subdivided into two types of cell containing either small round or polymorphous types of granules. (3) In the sections from which resin had been removed, all the cells emitting yellow FIF show argentaffinity by the Singh method, but not all cells display argyrophilia with the Grimelius method. (4) Cells exhibiting both argyrophil and argentaffin reactions in deresined serial sections are also separated into two types of cell, containing either small spherical or polymorphous types of granules by conventional electron microscopy in thin sections. Therefore, chicken enterochromaffin cells emit yellow FIF, store 5-HT, show both argentaffinity and argyrophilia, but are ultrastructurally classified into two types of granule-containing cells which may be related to polypeptides coexisting with 5-HT.