The modality of transendothelial passage of lymphocytes and tumor cells in the absorbing lymphatic vessel.

The modality of transendothelial passage of the macromolecules and cells (lymphocyte and cancer cells) in the absorbing lymphatic vessel (ALV) and the tumor-associated absorbing lymphatic (TAAL) vessel is studied. On the basis of the peculiar plasticity of the lymphatic endothelial cell of these vessels (lacking a continuous basement membrane, pores and open junctions) the endothelial wall organizes formation of the intraendothelial channel, by means of molecular interactions as yet unidentified. The remarkable finding of the intravasation of lymphocyte and experimental tumor cancer cells (T84 colon Adenocarcinoma, B16 melanoma in nude mice and spontaneous prostate adenocarcinoma in transgenic mice) should be stressed. This intravasation takes place, under both physiologic and pathological conditions, following the same transendothelial morphological modality, i.e. the intraendothelial channel - a dynamic and transient entity - is probably also induced by similar molecular interactions, a crucial point that merits future research.

Ultrastructural and three dimensional aspects of the lymphatic vessels of the absorbing peripheral lymphatic apparatus in Peyer's patches of the rabbit.

We studied the absorbing lymphatic peripheral vessels of the Peyer's patches of the small and large intestine of the rabbit by means of light microscopy after injection of Neoprene latex and transmission electron microscopy in order to highlight their topographical distributions to blood vessels as well as the morphologic mechanism of transendothelial passage of the lymphocytes to the lymph. The distribution of absorbing lymphatic vessels originates from the lacteal vessels and the subepithelial mucosal lymphatic network, which continue without interruptions and dilations into the vessels of the interfollicular area which are woven into basket-like networks entwining the medio-basal portion of each lymphoid follicle. The interfollicular area vessels then drain into the large vessels of the tunica submucosa, which in turn drain into the valved precollector vessels of the subserosa by way of intramuscular vessels. TEM revealed the absorbing lymphatic vessels to have a continuous endothelial wall without open junctions, fenestrations, and continuous basal lamina. We observed many lymphocytes wedged in the lymphatic endothelial wall. This underlines the different phases of their migration from the lymphoid tissue in the lumen of the lymphatic vessel. Results of ultrathin serial sections and three dimensional reconstruction of lymphatic vessel segments with included lymphocyte showed the transendothelial passage of lymphocyte, through the "intraendothelial channels."

The lymphatic vessels and the so-called "lymphatic stomata" of the diaphragm: a morphologic ultrastructural and three-dimensional study.

We studied the absorbing peripheral lymphatic vessel with the light microscope, the transmission electron microscope, the scanning electron microscope, and three-dimensional models of the diaphragm of several rodents and insectivores under normal and experimental conditions (lymphatic stasis and dehydration). To clarify the delicate and complex mechanism that permits drainage of the abdominal cavity contents into the lymphatic circulatory system, we introduced Polystyrene latex spherules, China ink, and Trypan blue into the abdominal cavities. After anatomical comparisons of the superficial and deep networks of absorbing peripheral lymphatic vessels at the tendinous and muscular portions of the diaphragm and after classification of lymphatic vessels into absorbing and conducting functions, we examined the stomata, which, owing to morphologic and topographic findings, we defined as stable structures. Furthermore, we observed that the stomata and submesothelial connective channel are fundamental elements that facilitate the flow of the corpuscular and liquid contents of the peritoneal cavity to the submesothelial absorbing lymphatic vessel wall. Also, we underlined that the genesis of the connective channel depends on the secondary cytoplasm extensions of two distinct adjacent endothelial cells, which, to facilitate the flow of the absorbed abdominal contents, completely coat this channel. Additionally, our observations illustrate that the secondary cytoplasm extensions do not engage in continuous relationships with the basal lamina of the mesothelium and with the margins of the stoma, and, hence, the hypothesis of "lymphatic stomata" as an expression of the anchoring of the borders of the open interendothelial junctions to the orifice margins of the stoma cannot be confirmed. Moreover, we describe the presence and formation of intraendothelial channels in the lymphatic endothelial wall. We affirm that this morphological entity is a dynamic unit, because its numerical density varies according to different physiological and experimental conditions to degrees of hydrostatic and colloidal osmotic pressure and, perhaps, also to the particular characteristics of the substances that the connective channel liberates into the endothelial wall of the lymphatic vessel. In conclusion, we affirm that the absorbing peripheral lymphatic vessels of the diaphragm, by way of intraendothelial channel formations, membrane diffusion, and the vesicular path of the endothelial cells, constitute the fundamental draining elements for the corpuscular and liquid contents of the abdominal cavity.

Three-dimensional and ultrastructural aspects of the lymphatic vascularization of the vermiform appendix.

The aim of the study is to reveal the three-dimensional distribution and ultrastructure of the peripheral absorbing lymphatic vessels of the vermiform appendix, since the gut-associated lymphoid tissue is necessary to the immune responses to the enteric antigens. Corrosion casts showed the beginning of the lymphatic vascularization at the tunica mucosa, which lacks intestinal villi, through a tight, delicate lymphatic network. This network drains the lymph by peculiar straight vessels, distributed in the mucosal beams that separate the adjacent follicle domes, in the fine network of the upper portion of the lymphatic basket, surrounding the lateral walls of the basal and medium portions of each lymphoid follicle. This network, which is made of large caliber vessels that are not dilated like sinuses, continues through small vessels into the large dome-like vessels of the submucosa, which in turn by way of the lymphatic vessels of the muscular tunica, drain into the subserous precollector valved lymphatic vessels that flow into the pre-lymph node collectors. We underlined that the particular fluidity of Neoprene latex and the direct injection method, when compared with other substances and injection methods, provided us with exceptionally clear and precise three-dimensional plastic images of the absorbing lymphatic vessels. Moreover, these images extraordinarily illustrated the preservation of the absorbing lymphatic spatial relationships with blood vessels. Ultrastructural features and three-dimensional models of ultrathin serial sections of the absorbing peripheral lymphatic vessels showed a continuous endothelial wall lacking basal lamina, as well as open junctions between adjacent cells. Moreover, we observed the presence of numerous lymphocytes, together with intense transendothelial migratory activity that occurs through intraendothelial channel formations, dynamic entities, at absorbing lymphatic vessels of the peri-interfollicular lymphoid tissue. Also, we saw that the germinal center, as well as the lymphoid follicle dome, lacked lymphatic absorbing vessels. In addition, many postcapillary high endothelial venules (HEV) were observed with lymphocyte migration into the extravasal compartment. Furthermore, we maintain that the absorbing peripheral lymphatic vessels (ALPA) of the tunica mucosa play an important role in liquid drainage. For the peri-interfollicular vessels, we hypothesize a potential migratory and a reserve capacity for lymphocytes, as well as a conduction activity for the muscular tunica and submucosa vessels.

Ultrastructure and immunocytochemistry of gustatory cells in man.

Ultrastructural and immunocytochemical features of the taste buds of the vallate, foliate and fungiform papillae in young, adult and elderly men, revealed three types of sensorial cells: dark type I cells rich in free ribosomes and large dense granules, light type II cells with large amorphous areas of cytoplasmic matrix and light type III cells with a dense core immunoreactive for 5-HT. All sensorial cells send microvillous protrusions of the apical cytoplasm into the gustative canal and make contact with nerve endings. After comparative studies, we made several hypothetical propositions on the functional value of microvillous protrusions, as well as on the apical and basal dense core vesicles of the foliate and vallate papillae. Moreover, we think that sensorial cells are implicated in taste transduction and that subject age does not seem to play any role in taste perception.

[The absorbing peripheral lymphatic apparatus and blood vessels of the vermiform appendix: the 3-dimensional and ultrastructural aspects]. / Appareil lymphatique périphérique absorbant (ALPA) et vaisseaux sanguins de l'appendice vermiforme: aspects tridimensionnels et ultrastructuraux.

We studied the lymphatic angiotectonics of the vermiform appendix of the rabbit, using direct injection of Neoprene latex, electron microscopy and three-dimensional models. We observed that the vermiform appendix is made of absorbing lymphatic vessels distributed among the tubular glands of the tunica mucosa. Moreover, these absorbing lymphatic vessels continue through the straight vessels into a vast, basket-like lymphatic network, which envelopes the medium and basal portions of each single lymphoid follicle. In addition, the vessels of this network reach the submucosal network, whose vessels are peculiar in shape and size. The submucosal network, in turn, drains the lymph through the small caliber intramuscular vessels in the valved subserous precollector lymphatic vessels. We also highlighted the ultrastructural characteristics of the absorbing lymphatic vessels, which completely lack openings at the contacts between the adjacent endothelial cells, which were always joined by specialized junction complexes. Moreover, we reported the presence of intraendothelial channels which we affirm are dynamic morphologic entities, through which lymphocyte migration from the peri-interfollicular lymphoid tissue inside the absorbing lymphatic vessels takes place.

Vallate, foliate and fungiform human papillae gustatory cells. An immunocytochemical and ultrastructural study.

We studied the classifications, topographic distribution and cellular lines of taste bud components in vallate, foliate and fungiform papillae of young, mature and old men with light microscopy, SEM, and TEM. By identifying ultrastructural and immunocytochemical characteristics, three distinct sensorial cells were identified, along with a few basal cells: dark type I cells, light type II cells and light type III cells. These cells extend from the epithelial basal lamina to the gustatory canal, where their apical cytoplasm sends long microvillous expansions. Excluding those of the fungiform papillae-which never go beyond the lower third of the gustatory canal, and are always void of dense substance-the microvillous expansions continue to the external border of the taste pore. Dark type I cells are rich in free ribosomes, tubular RER and large dense granules. Light type II cells with scarce ribosomes and RER, do not have enough peculiar ultrastructural characteristics to be considered effector or phagocyte elements. Light type III cells are characterizes by dense core vesicles whose peculiar ultrastructural characteristics in the foliate and vallate papillae, should be considered a consequence of different functional phases. After comparative evaluation the authors hypothesized on the functional value of some ultrastructural aspects and on the dense core vesicles which are immunoreactive to 5-HT. They observed that all gustatory cells are involved in taste transduction based on behaviours caused by microvilli in the gustatory canal and gustatory cell relationships with nerve endings. Moreover the authors noted that age does not seem to influence taste perception.

Season related ultrastructural features of the parotid, submandibular and von Ebner's glands in hibernating bats.

The parotid, submandibular and the von Ebner's salivary glands of hibernating insectivorous bats (Pipistrellus pipistrellus, Rhinolophus f. e. and Eptesicus serotinus) were studied by transmission electron microscopy and by histochemical methods during various seasons of the year. We report the seasonal ultrastructural changes that occur in the cytoplasmic organelles and the secretory granules of the serous and mucous cells and in the intercalated and striated ducts of the major glands. It previously has been hypothesized that the heterogeneity of the inclusions in the serous granules is closely related to the varying seasonal levels of proteinaceous and glycidic constituents. Lymphatic vessels are present only in the perivascular and periductal connective tissue. Morphofunctional and comparative studies seem to confirm a relationship between secretory activity and nutritional status as well as a likely involvement of the intercalated and striated ducts in determining the composition of the saliva.

[The fine structure of the gustatory cells of the circumvallate, foliate and fungiform papillae in hibernating bats]. / Sulla fine struttura delle cellule gustative delle papille circumvallate, foliate e fungiformi di pipistrelli ibernanti.

The cells of vallate, foliate and fungiform papillae were studied in insectivore hibernating bats (Pipistrellus pipistrellus and Rhinolophus ferrumequinum) in the various epochs of the year in order to show cell types the seasonal changes. On the basis of the ultrastructural aspects and the relationships with nerve endings, besides the few basal cells, three types of sensorial cells can be identified: dark type I cells, light type II cells and light type III cells. All gustatory cells, long and narrow shaped, extend from the epithelial basal lamina to the gustatory canal, where they send long microvillous expansions of the apical cytoplasm. These expansions, except those of the fungiform papillae which never extend beyond the lower two thirds, usually reach the external opening of the taste pore, always completely void of dense substance. Dark type I cells are characterized by a developed RER and large granules. Light type III cells show peculiar dense core light vesicles, labelled protein A-gold particles immunoreactive to 5-HT. These cells only in the foliate and fungiform papillae also have bundles of microtubules whose function is still unknown. After comparative evaluation and discussion of topographical and ultrastructural aspects with those of other mammals and humans, the Authors states that bats are provided with a valid gustatory system and that all cell types are involved in taste transduction.

The transendothelial passage in the absorbing peripheral lymphatic vessel of the rodent diaphragm.

The absorbing peripheral lymphatic vessels of rat (Wistar/Kyoto) and gerbil (Meriones unguiculatus) diaphragms were observed with SEM, TEM and three-dimensional models under normal conditions, after experimental hemorrhage and after abdominal injection of China ink and latex polystyrene particles. Superficial and deep lymphatic vessels were noted and their ultrastructural characteristics showed an endothelial wall lacking a continuous basal lamina. Moreover, "intraendothelial channels" which are dynamic, fundamental pathways for lumen migration into the lymphatic vessel for fluids, China ink and latex polystyrene particles, were also demonstrated. Concerning the transendothelial passage of the autologous erythrocytes after their migration through the stomata and submesothelium connective channel, it was observed that this passage occurs by means of a "transcellular pathway". This consists of a "migratory pore" independent from the intercellular junctions, which is formed by an active process following a probable immunological response or cellular interaction between the erythrocyte and the endothelial cell.

[Structure and seasonal aspects of the bat gallbladder]. / Struttura ed aspetti stagionali della cistifellea di alcuni pipistrelli.

The gallbladder of the insectivorous hibernating bats (Pipistrellus pipistrellus et Rhinolophus ferrumequinum) in fullness, shows a fundus, a corpus and a neck. Its wall is formed by three layers: mucous membrane, with simple columnar epithelium on a thin basal lamina, beneath which is a "lamina propria" of connective tissue with blood and lymphatic vessels; lamina muscularis, constituted by three of four parallel bundles of smooth muscle cells, arranged in circular pattern; serous membrane of loose connective tissue, with precollecting lymphatic vessels and covered by mesothelial cells. By SEM the luminal surface of mucous membrane shows more or less prominent folds delimiting irregular areas with hexa-pentagonal outlines of the apical region of epithelial cells. This latter present a convex dome aspect with numerous microvilli, not changed significantly, during the different year periods. In summer and autumn the epithelial cells are characterized by developed organelles in supranuclear cytoplasm. During the prehibernating period, chiefly the cytoplasm shows multivesicular and heterogeneous dense bodies. In summer, autumn and initial hibernating period, epithelial cell cytoplasm presents microvilli with prominent "antennulae microvilares", numerous light micropinocytosis vesicles, little rough vesicles in apical portion. The mitochondria, grouping in supranuclear and basal cytoplasm, in lethargy, are characterized by small matrix osmiophilic granules. The epithelial cells are held together near the apical surface by tight and gap junctions, and some rare desmosomes only in Rhinolophus f.e. The cell membranes are deep pleated or interdigitate with wide intercellular spaces during the prehibernating period and experimental arousing, while in lethargy and summer months these present linear outline with scanty invaginations. The Authors compared these morphological aspects of bat gallbladder with other micromammalia's one, underline particularly the functional role of dense bodies, wide intercellular spaces and apical micropinocytosis vesicles. The different seasonal ultrastructural characteristics of epithelial cells are considered in close relation to an absorbing function connecting with balance of different metabolisms.

[Structure and immunohistochemistry of the hypophysis of Alosa fallax nilotica during the reproductive migratory cycle]. / Struttura ed immunoistochimica dell'ipofisi di Alosa fallax nilotica durante il ciclo migratorio per la riproduzione.

The Pituitary of the Alosa fallax nilotica consists of a pars distalis, a pars intermedia and a pars nervosa. The pars distalis is divided into rostral and proximal. The pars nervosa extends also into proximal pars distalis. The rostral pars distalis, on the contrary in primitive Teleostei, has organized into cellular cords defining cavities or intercommunicating follicles. These latter finish into the oral adenohypophysial duct, which don't open in pharyngeal cavity. The cords contain three cell types: the columnar cells LTH, TSH cells and basal cells not yet functionally determined. The cord cells are separated from follicle cavity by an one layer of flat degranulated cells. The LTH cell, the chief cell type, together the TSH and basal cells shows evident cytologic differences in organelles of synthesis and secretion during the various stages of the reproductive migration. Besides globular and baton-shape projections are underlined in the apical cytoplasm of LTH cells. These structure, extending into follicle cavity, seem to dispatch sensory function probably. The proximal pars distalis consists of compact cords of gonadotropic cells (particularly active during the stage of migration from rivers to the sea) with inserted orangiophilic cells (probably STH) and phloxine cells: these latter cells are chiefly arranged at the periphery and immunocytochemical positive for the antibodies against ACTH. The pars intermedia contains cord of ACTH cells, particularly manifest during the periods of transit from sea water to fresh water and on the contrary, they are characterized by positive-ACTH dense granules. On the ground of ultrastructural aspects of vesicles, the pars nervosa shows three types of nervous fibers which correlate with neurosecretory hypothalamus and catecholaminergic dopaminergic fibers. The Authors think of underlining particularly that the all cells of rostral pars distalis and chiefly the LTH cells are involved significantly in the regulation of reproduction and hydro-mineral metabolic equilibrium.

Comparative anatomical and ultrastructural features of the sensory papillae in the tongue of hibernating bats.

The papillae of the tongue dorsal surface of the insectivorous, hibernating bats (Vespertilionidae and Rhinolophidae), whose function is mainly sensorial, consist of two circumvallate papillae, two foliate papillae, located at the side edges at the glossopalatine arch, and numerous fungiform papillae. The circumvallate and foliate papillae are characterized not only by their position, but also by presence of several taste buds which open through the external orifice of the gustatory canal into the cavity of the vallum, or furrow, which divides the two folds of the lingual mucosa. The fungiform papillae (extremely numerous on the whole dorsal surface) are characterized by an unusual arrangement (along 3 oblique lines on the anterior two-thirds and predominantly on the middle line of the tongue body) and by the presence of only one to three taste buds which open on the heavily keratinized dorsal epithelial surface. The taste buds are made up of sensory cells with a light or dark matrix; their apical cytoplasmic expansions are not found beyond the middle part of the gustatory canal, in contrast with the circumvallate and foliate papillae which protrude from the orifice of the gustatory pore. Comparisons with the papillae of other types of bats and Insectivora and evaluations of the morphological characteristics and their functional values (unusual areas of distribution of the papillae, apical cytoplasmic expansions and behaviour of microfolds observed under SEM) have been made in different environmental conditions and nutritional habits, with attention to the mechanical events in the course of feeding.

The passage of macrophage and lymphocytes from the interstitium across the lymphatic endothelium of rat lacteals.

The passage of cells across the lymphatic endothelium of rat lacteals in both normal and non-pathological experimental conditions (fasting, lymphatic, stasis) was studied by means of serial thin sections and three-dimensional models. Two different pathways of transendothelial migration were observed: (1) macrophages enter the lymphatic lumen via the cytoplasm of endothelial cells, without involvement of intercellular junctions, whereas (2) lymphocytes migrate through "intraendothelial channels", dynamic structures organized by the lymphatic endothelium under physiological conditions.

The migration of lymphocytes and polymorphonuclear leukocytes across the endothelial wall of the absorbing peripheral lymphatic vessel.

We studied the process of transendothelial migration of lymphocytes and polymorphonuclear leukocytes in the absorbing peripheral lymphatic vessels of small intestine and urinary bladder, under normal conditions, lymphatic stasis and prolonged fast. By ultrathin serial sections and three-dimensional models we found that lymphocytes and leukocytes share a common migration pathway from the interstitium into the lumen of the lymphatic vessel, namely 'the intraendothelial channel'. The migratory process of these cells occurs in several steps: approach to the endothelial wall, entry and run along the channel and finally coming out into lymphatic lumen. Our findings are compared with those concerning lymphatics in pathological conditions and blood vessels. Further considerations concern the possible mechanisms underlying this kind of transendothelial migration.

Macrophage migration through the endothelium in the absorbing peripheral lymphatic vessel of the small intestine.

TEM and three-dimensional models of the absorbing peripheral lymphatic vessel (ALPA) of the small intestine demonstrate that macrophages migrate from the interstitium into the lumen through the endothelial cell (transcellular pathway). Macrophages cross through a 'migration pore' which arises by an 'erosive process' in the cytoplasmic expansion of the endothelial cell. The pore is completely independent of the intercellular junction which is always sealed by junctional complexes. Furthermore several sites of contact between macrophage and endothelial cell membranes stress a possible functional role played by cellular interactions. Transcellular migration processes under normal conditions are compared with pathological or experimental ones.

Seasonal changes of parafollicular and follicular cells of the dormouse thyroid (Myoxus glis): an ultrastructural and immunocytochemical study.

The follicular epithelium of dormouse thyroid consists of two distinct cellular types, follicular and parafollicular cells. Parafollicular cells can be easily identified by their high cytoplasmic dye-affinity for phloxine, round to ovoid shape, basal arrangement and lack of contact with follicular colloid. The wide cytoplasmic matrix is clear and contains many secretory granules of variable electron density whose contents histochemically appears to be proteic with a lean glucidic component. Furthermore immunocytochemical reactions with antibodies against calcitonin and somatostatin showed that both hormones are co-stored in the secretory granules of all parafollicular cells. Both follicular and parafollicular cells show seasonal morphological variations in their secretory activity. Follicular cell activity is high in summer, reaches a peak in late fall or prehibernation and progressively slows down throughout hibernation. Parafollicular cells exhibit a fair synthetic activity in summer, in fall, and in the animals captured during winter hibernating sleep and killed after 12 days stay in laboratory. In winter sleep, granules with interrupted membrane and cottony contents are prevalent and the ultrastructural aspects suggest an intense discharge of secretion. The results are compared with those from other hibernating mammalians and discussed in the light of blood calcium values and seasonal balances of other metabolisms.

[Morphological and ultrastructural bases of the lymphatic vascular system]. / Bases morphologiques et ultrastructurales du système vasculaire lymphatique.

The lymphatic vascular system plays a pivotal role in the control of the interstitial homeostasis. This review illustrates the morphological and ultrastructural features of precollecting, pre- and postnodal collecting and absorbing peripheral vessels. A special attention is devoted to the endothelium of the absorbing lymphatic, its cytological features, kinds of intercellular contact, contractile properties and occurrence of valves. The role of the different mechanisms involved in transendothelial transport, namely membrane diffusion, vesicular route, open junctions and intraendothelial channels, are considered. The morphological reality of "intercellular openings" and "intraendothelial channels" is also discussed. The latter are "dynamic units" which carry on a remarkable task in the drainage, toward the lymphatic lumen, of macromolecules (chylomicra, glycoproteins, etc.) and cellular elements (lymphocytes and polymorphonuclear leukocytes). On the other hand, macrophages follow a transcellular pathway. The factors which possibly underlie these two modes of transendothelial migration are also discussed.