Microvasculature of the thyroid gland in the common tree shrew (Tupaia glis): microvascular corrosion cast/scanning electron microscopy study.

A thyroid vascular cast of the common tree shrew (Tupaia glis) was obtained by injection of Batson's No. 17 plastic mixture into the ascending aorta. The cast was studied under the scanning electron microscope. It was found that each half of the gland is supplied by a large superior and a rather small inferior thyroid artery. After plunging into the gland, the arteries divide into smaller branches that are the interlobular, intralobular and follicular arteries (afferent vessels). The basket-like capillaries arising from the follicular arteries and encapsulating thyroid follicles are of large diameter and are arranged in a single layer. The follicular side of the capillary casts was observed to contain numerous small and some large projecting knobs compatible with the presence of fenestrations in the endothelial cells. On the other hand, endothelial nuclear imprints were found mainly on the stromal surface of the follicular capillary casts. Transfollicular capillaries connecting the adjacent follicular capillary networks were also observed. Blood from the follicular capillaries either drains into the follicular veins (efferent vessels) or abruptly drains into the intralobular veins before proceeding to intralobular and interlobular veins, respectively. The interlobular veins are collected into a few small superior, a few larger middle and a few even larger inferior thyroid veins. These veins drain directly into the laryngeal vein lying adjacent to the deep surface of the thyroid gland before joining the jugular vein. Venous valves were identified outside the thyroid gland. In addition, the glomerular capillary island of the parathyroid gland was often seen at the cranioanterolateral and sometimes at the cranioposterolateral aspect of the thyroid gland.     

Immunohistochemical study of the developing endocrine pancreas of the opossum (Didelphis virginiana)

Cells immunoreactive for insulin, glucagon, somatostatin, bovine pancreatic polypeptide and 5-hydroxytryptamine are found in the pancreas of the newborn opossum and of all later stages examined. All immunoreactive cell types are present in primary and secondary islets and within elements of the exocrine pancreas. Cells immunoreactive for glucagon, bovine pancreatic polypeptide, somatostatin and 5-hydroxytryptamine generally are confined to the periphery of secondary (intralobular) islets, whereas insulin-immunoreactive cells occupy the central region. Endocrine cells within primary (interlobular) islets are randomly scattered. A small number of pancreatic-polypeptide-immunoreactive cells are reactive for the amine 5-hydroxytryptamine also, but the reverse is not observed. The endocrine pancreas continues to differentiate and develop throughout postnatal life and into adulthood. Little difference was observed between the head and tail regions of the opossum pancreas for the measurements made.     

Hypophyseal angioarchitecture of common tree shrew (Tupaia glis) revealed by scanning electron microscopy study of vascular corrosion casts.

The vascular corrosion cast technique in conjunction with scanning electron microscopy (SEM) was used for the study of pituitary microvascularization in the common tree shrew (Tupaia glis). The pituitary vascular casts were obtained by infusion of low viscosity methyl methacrylate plastic (Batson's no.17) mixture. It was found that the blood supplies to the pituitary complex were from branches of the circle of Willis and could be divided into two groups. The first group consisted of two to four superior hypophyseal arteries (SHAs) branching off from the internal carotid artery supplying each half of the median eminence (ME), infundibular stalk (IS), and pars distalis (PD). The SHAs supplying the ME branched into internal and external capillary plexi. The internal plexus had a larger capillary size (approximately 15 microns in diameter), was deeper in position, and had denser and more complex capillary loops than those in the external plexus. The capillaries of the external plexus were approximately 10 microns in diameter. The two plexi drained into 15-20 hypophyseal portal veins (HPVs) which were located mainly along the ventral and ventrolateral surfaces of the IS before breaking up into large capillaries (approximately 18 microns in diameter) with an anteroposterior arrangement within the PD. The second group consisted of one inferior hypophyseal artery (IHA) on each side branching off from the internal carotid artery. These arteries gave off branches to pierce the dorsolateral and ventrolateral aspects of infundibular process (IP) before branching off to form a capillary network. They also gave rise to radiating capillaries to supply the pars intermedia (PI) surrounding the cortical area of the IP. The hypophyseal cleft separating the PI from the PD was clearly seen with very few blood vessels. The capillaries in both PD and IP joined to form confluent hypophyseal veins draining the blood into the cavernous sinus.     

A comparative study of the portal vessels connecting the endocrine and exocrine pancreas, with a discussion of some functional implications.

We have examined the pattern of the capillaries of the pancreas in rabbits, rats, mice, guinea-pigs, cats and baboons, using arterial and venous injections of Berlin blue. In all these species we found extensive, direct connexions between the capillary beds of the islets and the exocrine tissue of the gland, forming a highly developed portal system. Some of the functional implications of these vascular connexions are discussed, particularly the influence of the islet hormones insulin, glucagon and somatostatin upon the exocrine cells.     

Vascularization of the pituitary of the Australian lungfish and Neoceratodus forsteri

The vascularization of the brain and the pituitary region of the Australian lungfish, Neoceratodus forsteri is described from serial section reconstruction. The distal lobe has no direct arterial blood supply and receives blood solely from a pituitary portal system basically similar to that of other sarcopterygians. The primary capillary plexus of the median eminence receives its arterial blood from the infundibular arteries, which on their way distribute some small branches to the prechiasmatic region. The primary plexus also receives capillaries from the adjacent pial hypothalamic plexus. The primary capillary plexus of the median eminence comprises a rostral 'uncovered' and caudal 'covered' part which are not sharply delineated. Distinct portal vessels connect the 'uncovered' rostral part of the primary plexus with the secondary capillary plexus supplying the rostral subdivision of the pars distalis. The 'covered' caudal part of the primary plexus merges into the proximal subdivision of the pars distalis, apparently without formation of distinct portal vessels. The primary plexus has some connections with the plexus intermedius via a hypophysial stem capillary plexus. The plexus intermedius has a substantial arterial supply and gives off capillaries to the parenchyma of the pars intermedia. The adenohypophysis is drained into an unpaired hypophysial vein. The significance of the vascular pathways is discussed from comparative, functional, and evolutionary viewpoints.     

The volume and area of the capillaries in the endocrine and exocrine pancreas of the rat

The capillary volumes in the endocrine and exocrine parenchyma of the pancreas were compared with a point-sampling technique. The islets were found to have a capillary volume of approximately 3.5%, while the value for the exocrine pancreas was significantly (P less than 0.001) lower at 2%. When the capillary wall area was measured, however, both types of parenchyma had a similar value of approximately 20 mm2/mm3 tissue. The reason for the discrepancy between these parameters is probably the lack of lymphatic capillaries, with their relatively small lumen in the islets.     

The ductal origin of structural and functional heterogeneity between pancreatic islets

Islets form in the pancreas after the first endocrine cells have arisen as either single cells or small cell clusters in the epithelial cords. These cords constitute the developing pancreas in one of its earliest recognizable stages. Islet formation begins at the time the cords transform into a branching ductal system, continues while the ductal system expands, and finally stops before the exocrine tissue of ducts and acini reaches its final expansion. Thus, islets continuously arise from founder cells located in the branching and ramifying ducts. Islets arising from proximal duct cells locate between the exocrine lobules, develop strong autonomic and sensory innervations, and pass their blood to efferent veins (insulo-venous efferent system). Islets arising from cells of more distal ducts locate within the exocrine lobules, respond to nerve impulses ending at neighbouring blood vessels, and pass their blood to the surrounding acini (insulo-acinar portal system). Consequently, the section of the ductal system from which an islet arises determines to a large extent its future neighbouring tissue, architecture, properties, and functions. We note that islets interlobular in position are frequently found in rodents (rats and mice), whereas intralobularly-located, peripheral duct islets prevail in humans and cattle. Also, we expound on bovine foetal Laguesse islets as a prominent foetal type of type 1 interlobular neuro-insular complexes, similar to neuro-insular associations frequently found in rodents. Finally, we consider the probable physiological and pathophysiological implications of the different islet positions within and between species.     

Comparative neurohistological observations on the pancreatic duct in certain birds and mammals as revealed by cholinesterase technique

A comparative study of pancreatic duct innervation of Francolinus pondicerianus (grey partridge or safed teeter) and Suncus murinus (Indian musk shrew) as revealed by cholinesterase technique has been done for investigation. In Suncus pancreas, the AChE-positive ganglia, elongated and irregularly shaped, medium and large-sized, were recorded either on the periphery of the excretory duct or on the wall of the duct. No ganglia were recorded on the periphery, although the fibres of the ganglia were in close association with the periductular plexus and the fibres of the peri-insular plexus in Francolinus. In Suncus, multipolar and AChE-positive ganglia of various shapes, arranged in chain-like fashion on the duct, were recorded, whereas in Francolinus the multipolar ganglia of AChE-positive nature and of various shapes, arranged in chain-like fashion, were observed in the duct region.     

Microangioarchitecture of the islets of Langerhans in the snakes,Naja naja,Vipera russelli,andEchis carinatus

Summary Due to a decided lack in the literature of reports on the microangioarchitecture of the pancreas of snakes, an analysis was performed in three different species of two different ophidian families with the use of cast preparations and complementary scanning electron microscopy. The vascular architecture reflects the lobular substructure of the pancreas; the organ is supplied by branches of the superior mesentric artery. Coiled lobular arteries and arterioles continue into a meshwork of capillaries. Dilated capillaries of the endocrine portion of the pancreas are an integral component of this fine capillary network. A few very small capillaries establish a connection between the endocrine and the exocrine pancreas. The other capillaries drain into venules, which ultimately join their respective veins. No interspecific differences were noted in the vascularization of the pancreas of the three ophidian species examined. The present results suggest the existence of arterio-venous anastomoses and speak against the presence of a portal system, but establish a feed-forward capillary connection from the endocrine to the exocrine component of the ophidian pancreas.     

Distribution of gamma-glutamyl transpeptidase in human pancreas: immunohistochemical study with a monoclonal antibody.

We studied in detail the distribution pattern of gamma-glutamyl transpeptidase (gamma-GT) in human pancreas, using the immunoperoxidase technique and a monoclonal antibody to human kidney gamma-GT. Positive reaction was confined exclusively to the luminal surface of the centroacinar cells and the epithelia of the intercalated, intralobular, and interlobular ducts. The immunoreaction was stronger in the intercalated and intralobular ducts than in the interlobular ducts. The acinar cells did not show any reaction. The islets of Langerhans were heavily surrounded by the ducts, and normal islet cells showed no reaction. The course of the ducts, from the acinar lumina to the interlobular ducts, was delineated by using reaction sites positive for gamma-GT as markers. The courses of the ducts, which comprise the pathway for pancreatic juice, were found to vary widely in their connections with each other, especially between the intralobular and interlobular ducts. At least three separate routes could be identified.     

Postnatal development of the pancreas in the opossum. Light microscopy.

The pancreas of the newborn opossum consists of a central region of forming islets surrounded by primitive tubules that end in proacinar cells. Paratubular buds, which are outgrowths from the tubular epithelium, characterize the newborn pancreas and eventually give rise to both exocrine and endocrine units. 4 days after birth, definite intralobular ducts, acini and centroacinar cells are observed. In addition to the central expanding islets (primary islets), endocrine cells are observed singly or in small groups in the ductal epithelium. The endocrine cells are believed to originate from the terminal cells of the ductal epithelium and, throughout the entire postnatal period, retain a close association with the exocrine epithelium. With the simultaneous proliferation of both endocrine and exocrine components from the ductal system, the majority of the islets observed at 24 days (5.0 cm) appear to be surrounded by a single layer of acinar cells. As acini develop and the ducts expand toward the periphery, this layer of acinar cells separates from the developing islets, the majority of which have become localized within the centers of lobules to form the secondary islets by the 10.0-cm stage (59 days). A marked development of lobules is observed by the 13.0-cm stage and the majority of acinar cells now are filled with zymogen granules. Acinar cells continue to proliferate late into the postnatal period and the majority of acini exhibit a tubular form in the juvenile and adult opossum.     

四川短尾鼩肝脏和胰腺的组织解剖学研究

对四川短尾鼩肝脏和胰腺的组织解剖结构进行了研究,结果表明:肝脏分为4叶,它们的肝实质完全分开.肝小叶的分界极不明显,1个肝小叶内的肝细胞大小不一致,靠近中央静脉的肝细胞体积较小,而肝小叶外围的肝细胞体积较大.胰腺的形态松散,无法区分出胰头、胰体和胰尾.胰腺小叶非常明显,大小不等.胰腺的组织结构包括外分泌部和胰岛两部分.     

The vascularization of the neural stalk and the pars nervosa of the hypophysis in the toad,Bufo bufo (L.) (amphibia,anura)

The angioarchitecture of the neural stalk and the encephaloposthypophysial portal system of the hypophysis of the toad, Bufo bufo (L.), was studied using three different methods. The neural stalk is mainly supplied by branches of the arteria infundibularis superficialis which form a widemeshed vascular network. Dorsally this network continues into the plexus of the pars nervosa. The vascularization of the pars nervosa is made up of the encephalo-posthypophysial portal system. This portal system consists of a hypothalamic branch (=portion), a mesencephalic and a mesencephalicbulbar branch (=portion). The hypothalamic branch was found to drain the pars ventralis of the tuber cinereum as well as more dorsal regions of the diencephalon. The mesencephalic-bulbar trunk enters the hypothalamic branch. The resulting common stem of the encephalo-posthypophysial portal vein the curves around the retroinfundibular communicating artery, crosses its ventral side and runs caudally. The secondary capillary plexus of the pars nervosa is characterized by well defined capillary plexus of the pars nervosa is characterized by well defined capillary networks which are located at the periphery of the parenchyma of the pars nervosa, thus forming a rostral, dorsal and ventro-caudal net. The central region of the parenchyma of the pars nervosa is supplied only by main branches of the encephalo-postpophysial portal vein. The venous drainage of the pars nervosa is via the vena hypophysea transversa.     

Electron microscopic study on the innervation of the pancreas of the domestic fowl

Summary The innervation of the pancreas of the domestic fowl was studied electron microscopically. The extrapancreatic nerve is composed mostly of unmyelinated nerve fibers with a smaller component of myelinated nerve fibers. The latter are not found in the parenchyma. The pancreas contains ganglion cells in the interlobular connective tissue. The unmyelinated nerve fibers branch off along blood vessels. Their synaptic terminals contact with the exocrine and endocrine tissues. The synaptic terminals can be divided into four types based on a combination of three kinds of synaptic vesicles. Type I synaptic terminals contain only small clear vesicles about 600 Å in diameter. Type II terminals are characterized by small clear and large dense core vesicles 1,000 Å in diameter. Type III terminals contain small clear vesicles and small dense core vesicles 500 Å in diameter. Type IV terminals are characterized by small and large dense core vesicles. The exocrine tissue receives a richer nervous supply than the endocrine tissue. Type II and IV terminals are distributed in the acinus, and they contact A and D cells of the islets. B cells and pancreatic ducts are supplied mainly by Type II terminals, the blood vessels by Type IV terminals.This work was supported by a scientific research grant (No. 144017) and (No. 136031) from the Ministry of Education of Japan to Prof. M. Yasuda     

The Structure of the Hypothalamohypophysial Portal Vascular System in Acipenser ruthenus L. (Chondrostei)

The vascularization of the pituitary region in Acipenser ruthenus L. (Chondrostei) is described. The adenohypophysis has no direct arterial supply but is fed exclusively by a pituitary portal system supplied through a pair of infundibular arteries. Distinct portal vessels connect the lateral part of the primary plexus of the neurohaemal area (the median eminence) with the secondary plexus of the pituitary gland. The primary plexus enters the pars distalis paramedially, apparently without the formation of distinct portal vessels. The neuro-intermediate lobe receives its blood supply exclusively from the primary plexus. The plexus intermedius gives off capillaries to the parenchyma of the intermediate lobe (an intermediate lobe sinus system). The saccus vasculosus receives (1) a “direct” supply, i.e. branches originating directly from the cerebral arteries and (2) an “indirect” supply, i.e. capillaries from the primary plexus. The pars distalis is drained into an unpaired ventral hypophysial vein, while a dorsal hypophysial vein, also unpaired, drains the plexus intermedius. These two veins join to form the unpaired hypophysial vein. The findings are discussed from comparative and functional viewpoints.     

Intrahepatic pancrease in Sparus datnia (Ham. Buch.), a Sparidae of the Persian Gulf]

A fish, Sparus datnia (Ham. Buch.), Sparidae, protandric, is one of the species, which has a diffusing intrahepatic pancreas. The gland is compound of two parts : the exocrine part (follow the branches of the portal vein), and the endocrine part (langerhans islets, more or less abundent in the external side of the endocrine part). Three kinds of granular cells are recognized in the endocrine islets.     

The volume and area of the capillaries in the endocrine and exocrine pancreas of the rat

Summary The capillary volumes in the endocrine and exocrine parenchyma of the pancreas were compared with a point-sampling technique. The islets were found to have a capillary volume of approximately 3.5%, while the value for the exocrine pancreas was significantly (P<0.001) lower at 2%. When the capillary wall area was measured, however, both types of parenchyma had a similar value of approximately 20 mm²/mm³ tissue. The reason for the discrepancy between these parameters is probably the lack of lymphatic capillarics, with their relatively small lumen in the islets.     

Fluorescence microscopical and chemical characterization of the adrenergic innervation in mammalian liver tissue

Liver tissue from 12 different mammalian species was studied with a fluorescence histochemical technique for the cellular localization of amines (Falck-Hillarp technique) and with a chemical method for the determination of norepinephrine (HPLC-technique). Adrenergic nerve plexus were found in interlobular blood vessels derived from the portal vein and hepatic artery. Varicose adrenergic nerve fibres were, generally, seen to branch from the fibres around the blood vessels and to enter the liver parenchyma, where they formed a randomly distributed intralobular network. The density of these intralobular fibres showed marked species variation. Human liver and liver from the rhesus monkey, baboon, cynomolgus monkey and guinea pig showed a high density of parenchymal adrenergic nerves. Rabbit, cat, pig, cow and horse liver formed an intermediate group, having fewer varicose adrenergic nerve fibres but an unequivocal distribution of these nerves to the liver parenchyma. In rat and mouse liver no parenchymal innervation could be demonstrated. The density of the parenchymal innervation generally correlated with the concentration of norepinephrine in the liver tissue.     

封闭群草原兔尾鼠肝脏和胰腺的组织学观察

首次对封闭群草原兔尾鼠的肝脏、胰腺进行了组织学观察,结果表明：1．草原兔尾鼠的肝脏纤维组织极少,肝小叶间界限不明显;部分中央静脉周围可见少量毛细胆管;门管区较少,分布不均匀,其静脉形状不规则、腔大,胆管及动脉则较小。2．胰腺分叶清晰,腺泡细胞较大,胞浆多呈嗜酸染色;小叶中部腺泡着色较深,外侧腺泡着色较浅;胰岛大小不等,细胞排列呈不规则索状,光镜下未见特殊改变。     

Vascular pattern in the pancreas of the cat

Summary The pathways of microcirculation in the pancreas of the cat were investigated by scanning electron microscopy of Mercox preparations of the vascular bed. A portal system from islet to exocrine vessels as well as a direct arterial flow to the exocrine pancreas have been observed. Sphincters appear to exist in portal capillaries at the border between the endocrine and exocrine portions of the pancreas. Islets possess an independent venous drainage.A portion of these results was presented on the occasion of the 6th European Anatomical Congress, Hamburg 1981 (see Syed Ali 1981, for abstract).