Depletion of head kidney neutrophils and cells with basophilic granules during peritoneal inflammation in the goldfish, Carassius auratus.

The head kidney morphology of the goldfish with the experimental peritoneal inflammation (on day 2 after i.p. injection with sterile 3% Thioglycollate) is compared with that in the control fish (i.e. on day 2 after i.p. injection with a strile physiological saline PBS) with special emphasis on identification of granulocytes on semithin and consecutive ultrathin sections. The most striking feature of head kidneys of goldfish in the course of peritoneal inflammation is a severe depletion of mature neutrophils and cells with basophilic granules (basophils/mast cells). These observations suggest the involvement of the head kidney, the main hematopoietic organ of teleosts, in the inflammatory process.

Morphine modulation of thioglycollate-elicited peritoneal inflammation in the goldfish, Carassius auratus.

Intraperitoneal (i.p.) injection of adult goldfish with 3% thioglycollate (TG) induces an acute peritoneal inflammation connected with a massive influx of inflammatory leukocytes mainly of the head kidney origin. The number of peritoneal exudate cells retrieved on day 2 of the inflammatory response is significantly lower in fish injected with TG and morphine (20 mg/kg b.w.) than in animals injected with TG only. The morphine effect was totally antagonized in fish injected 20 min earlier with naltrexone (1 mg/kg), a well-known blocker of opioid receptors. Light microscopy of the head kidney Epon sections revealed that basophilic granulocytes are common in the control PBS-injected fish and even more frequent in fish injected with morphine only. In sharp contrast basophils are very rare in the head kidneys from animals with the TG-induced peritoneal inflammation, while they are more numerous in fish injected with TG and morphine. Supposedly, the basophilic granulocytes might be involved in the inhibitory effects of morphine on the acute inflammation in goldfish. An involvement of the head kidney in the morphine modulation of the inflammatory response is strongly supported by the detection of opioid receptors in the head kidney cells suspension.

Season-specific thymic architecture in the frog, Rana temporaria: SEM studies.

It is already known that the thymus of the adult common frog, Rana temporaria, undergoes conspicuous annual cyclic changes. Light microscopic (LM) observations are at present confirmed by three-dimensional scanning electron microscopy (SEM) pictures showing the presence of a characteristic cortico-medullary division of summer thymuses and cystic appearance of winter organs. Summer thymuses are larger, much heavier and populated by a significantly higher number of cells than winter organs. The season-specific thymic size, cell content and distribution are reflected by its angioarchitecture. The microcorrosion casts of vascular system of winter thymuses are much smaller and more compact than those of the summer organs in which vessels are arranged at larger spatial intervals. It seems that thymic enlargement following the winter atrophy results from vernal repopulation of the thymic cortex by thymocytes which in consequence induces a reshaping of the existing capillary network.

Age-dependent changes in thymuses in the European common frog, Rana temporaria.

The thymus of the adult frog Rana temporaria is generally small each winter and grows through the spring to reach a large size each summer. The summer thymus has a cortex full of small thymocytes and a medulla in the centre, whereas the winter atrophy is manifested by a loss of distinction between cortex and medulla, an abundance of cells filled with secretory granules, and the formation of intercellular cysts. These seasonal changes are superimposed on age changes. The thymus grows rapidly in froglets. The differences in weight and cell number between winter and summer organs are strongest in middle-aged animals (3-6 years old) and decrease in old specimens. The thymus slowly involutes with age, this being connected with increasing winter atrophy, leading to the formation of huge cysts that fill almost the whole organ in the oldest individuals. In senescent frogs (around 10 years old) seasonal differences still concern corticomedullary division but without pronounced fluctuations in thymic size. The skeletochronological technique applied here for age estimation underestimated rather than overestimated the real age of old animals.

Thymic vascular system of the European common frog, Rana temporaria: a scanning electron-microscopic study of vascular casts.

Vascular corrosion casts of the thymus of adult individuals of the European common frog, Rana temporaria, were analysed by scanning electron microscopy. The main arterial vessel, which is derived either from the temporal artery or from the auricular ramus, approaches the central territory of the gland and branches into "twigs" that, on penetrating the parenchyma, give rise to capillaries. Most of these capillaries run vertically towards the surface of the gland; they either join the superficial capillary plexus or follow this plexus for a variable distance and then run back towards the medulla, forming capillary loops. The former capillaries link with the extensive venous plexus composed of irregular meshes, whereas the latter capillaries join the venules at the cortico-medullary boundary and finally escape into collecting veins on the gland surface. The venous twigs, which join together near the gland, form the main thymic vein, which empties into the external jugular vein. The details of the thymic vasculature of the anuran amphibian, R. temporaria, are compared with those described in mammalian species, viz. the mouse, rat and guinea pig.

Light and electron-microscopic observations on the thymic capillaries and postcapillary venules in Rana temporaria L.

The aim of this study was to examine thymic capillaries and capillary venules in a common frog, Rana temporaria, using the light (LM) and transmission electron microscopy (TEM) as well as scanning electron microscopy (SEM) of vascular corrosion casts. The endothelial cells of capillaries and postcapillary venules show in frog thymus mostly flat morphology. However, some postcapillary venules are lined with tall endothelial cells which are characteristic for the thymus-dependent areas of mammalian secondary lymphatic organs (high endothelial venules, HEV). Such endothelial cells occurring in frog thymus are ultrastructurally characterized by increased amount of cytoplasmic organelles, mainly rough endoplasmic reticulum, ribosomes and electron dense lysosome-like granules, as well as by deep intercellular clefts. In HEV-like vessels, lymphocytes were observed to adhere to the endothelial surface, migrate through the endothelium, or lay beneath the endothelial basement membrane in the perivascular space. These findings were corroborated by SEM of corrosion casts which revealed in some postcapillary venules or their segments the presence of irregular casts surfaces with numerous depressions and protrusions reflecting the cobblestone appearance of the tall endothelial lining. Such venules are fed directly by capillaries and begin with abrupt increase in the vessel diameter, accompanied by the appearance of deep endothelial imprints. Our results demonstrate in the frog thymus the presence of specialized, HEV-like segments of postcapillary venules, suggesting that besides its function as the central lymphoid organ, frog thymus may also function as a peripheral one.

Argentaffin mast cells in the thymus of the frog.

Mast cells are common in the thymic parenchyma of the European common frog, Rana temporaria. They are stained meta chromatically with toluidine blue and the majority of them are impregnated with silver during the argentaffin reaction. The latter phenomenon indicate that these cells store serotonin. At the ultrastructural level, mast cells contain specific granules with electron-dense and electron-lucent parts. The silver grains are located exclusively over the electron-lucent part of the mast cell granules indicating that serotonin is stored just in this compartment.

Ultrastructure of the APUD-like cells of the frog thymus gland.

Within the thymus gland of the European common frog, Rana temporaria, cells with endocrine- like appearance have been found. At the ultrastructural level the most characteristic feature of their cytoplasm is the presence of secretory granules. Some cells possess irregular electron lucent granules with an eccentrically located dense core while others possess smaller electron dense granules. The cytoplasm contains also cisterns of rough endoplasmic reticulum, free ribosomes, and small mitochondria. The cells possess irregular nuclei with the pronounced nucleoli. These endocrine-like cells are connected by desmosomes with neighbouring non-granulated epithelial cells. Ultrastructural features of the cells described here resemble those seen in polypeptide hormone-secreting cells belonging to the family of cells of the APUD (Amine Precursor Uptake and Decarboxylation) series.

Interdigitating cells in the thymus of the frog, Rana temporaria.

Interdigitating cells (IDC) of the thymic medulla of the frog, Rana temporaria, collected in the summer, were examined by electron microscopy. The most characteristic cytological features of IDC are voluminous electron-lucent cytoplasm and widespread interdigitations and invaginations of the cell membrane. IDC possess an excentrically located nucleus with pronounced nucleoli and a thin rim of a dense chromatine as well as a perinuclear area with characteristic tubulo-vesicular complex. In our material Birbeck granules were absent. Some IDC contain phagocytized material. A few transitional forms between monocytes and IDC were observed. On the basis of these observations it is highly probable that the amphibian IDC belong to the mononuclear phagocyte system.

Cytoarchitecture of the thymus gland of the adult frog (Rana temporaria).

Like in other jawed vertebrates, the frog thymus consists of lymphoid cells within epithelial framework and characteristic myoid cells. Mammalian type Hassall's corpuscles are absent, but degenerative cells form so-called unicellular Hassall's bodies. Conspicuous secretory cells, secretory and degeneration cysts as well as phagocytic cells, granulocytes and plasma cells can be observed in the frog thymus. Interdigitating-like cells and some characteristic features of thymic vasculature (i.e. the existence of blood-thymus endothelial are preliminary described in the frog thymus.

Endogenous rhythm in the thymus gland of Rana temporaria (morphological study).

In European common frogs, Rana temporaria, leading an active land life at high external temperatures (May-October), the thymus glands are clearly divided into lymphocyte-rich cortex and mainly epithelial medulla ('summer' appearance). In contrast, thymuses of hibernating and mating frogs (at low temperatures, October-April) are typically endocrine organs with an abundant population of secretory cells, small number of thymocytes and lack cortico-medullary division ('winter' appearance). Thymuses of experimental animals kept from September until January at a high temperature tend to change their appearance from the 'summer' type to the 'winter' one. Thymuses of experimental frogs kept from the end of May until the end of June in refrigerator preserve their 'summer' appearance. These results show that the annual rhythm of the frog thymus gland is difficult to alter by simple changes of external temperature.

Seasonal cyclic changes in the thymus gland of the adult frog, Rana temporaria.

The thymus gland of the adult common frog, Rana temporaria, undergoes conspicuous seasonal changes corresponding to the temperature-dependent changes in the annual activity of these animals. During the period of active terrestrial life the thymus is clearly divided into a lymphocyte-rich cortex and an epithelial medulla containing interdigitating-like cells. During hibernation and mating the thymus is depleted of lymphocytes and consists of numerous secretory units (cells and cysts) and degeneration cysts. Rapid release of secretory material is evident at the beginning of the frog active life.

Electronmicroscopy of the replication of the ISU-2 strain of IBR/IPV-herpes virus in inoculated cultures of bovine embryo kidney (BEK) cells.

Studies on the replication of the ISU-2 strain of IBR/IPV-Herpes virus and on its behaviour in inoculated BEK cultures have shown that the replication of viral DNA as well as the production of icosahedral particles occur within the cell nucleus. Similarly like in each Herpes virus group, while passing through the nuclear envelope and the cell membrane the virus obtains an additional envelope that enlarges its diameter. The viral particles produced in a large quantity, may pass through the cell membrane into the extracellular spaces or may be caught by the cytoplasmic vacoules, where they are decomposed.