Functional arterio-venous anastomoses between the testicular artery and the pampiniform plexus in the spermatic cord of rams

Blood flow to the testis, haemoglobin oxygen saturation and testosterone concentration in arterial and venous testicular blood vessels were studied in Texel rams in the breeding and non-breeding season. Blood flow in the proximal and distal testicular artery was measured electromagnetically. The mean flow in the proximal testicular artery was 18.5 ml/min and in the distal testicular artery 7.5 ml/min, and there was no detectable seasonal influence. Haemoglobin oxygen saturation and testosterone concentration were measured in the saphenous artery and vein, the distal testicular artery and vein, and in the proximal testicular vein. The haemoglobin oxygen saturation in the proximal testicular vein was significantly higher than in the distal testicular vein in both seasons. The mean testosterone concentration was significantly lower in the proximal testicular vein than in the distal testicular vein in both seasons. Based on haemoglobin oxygen saturation and testosterone data, it was calculated that between 28 and 46% of the testicular arterial blood was bypassing the testis and was directly flowing through arterio-venous anastomoses towards the pampiniform plexus in the spermatic cord of conscious rams. In anaesthetized rams 55 and 64% of the blood was flowing directly from the testicular artery to the pampiniform plexus based on blood flow data. Transfer of testosterone and oxygen by passive diffusion from the testicular artery to the pampiniform plexus and vice versa in the spermatic cord was not detected.     

Vascular supply of the testis of the camel (Camelus dromedarius).

The origin, pattern of distribution and the length of the convoluted part of the testicular artery were examined by blunt dissection and by the preparation of arterial casts with vinylite. The testicular artery originates from the abdominal aorta just cranial to its bifurcation and forms compact coils and reveals a tortuous course in the region of the pampiniform plexus and along the attached border. The artery divides at the caudal extremity of the testis into 2--4 branches. The epididymal artery, which is a branch of the testicular artery, was seen to anastomose with the deferential artery, but no anastomosis occurs between these arteries and the testicular artery. The convoluted part of the testicular artery was 20 cm in length, but when unravelled totalled 240 cm. This is not affected by seasonal variations. The possible significance of these results was discussed and compared with similar findings of other mammals.     

Vascular morphology of the bovine spermatic cord and testis

Summary The highly coiled testicular artery within the bovine spermatic cord has a constant luminal diameter but a continuously decreasing mural thickness. The pampini form plexus is composed of three interconnected venous networks differing in mesh sizes and calibres. The large veins of the first network display pouches and permanent constrictions, which may serve as throttle devices. The constitutents of the third network are venules or venous capillaries with diameters between 10 and 20 m; they favor a periarterial position or even occupy the media-adventitia border of the testicular artery. All plexus veins are devoid of valves. The existence of true arteriovenous anastomoses between smaller branches of the testicular artery and plexus veins was established by serial sections. The vascular morphology of the spermatic cord is discussed with special attention to a postulated venous-arterial steroid transfer in this region.Supported by the Deutsche Forschungsgemeinschaft and the Stiftung zur Förderung der wissenschaftlichen Forschung an der Universität Bern     

Gamma glutamyl transpeptidase in the vasculature of the rat testis

Activity of gamma glutamyl transpeptidase (GGT) in the testes of mature and prepuberal rats was investigated histochemically and biochemically. Histochemically, the enzyme activity was localized predominantly in the arterial and arteriolar endothelium and was absent from the capillaries and the seminiferous tubules. The activity in the arterial endothelium extended to the testicular artery on the surface of the testis and in the spermatic cord, but the veins in both the pampiniform plexus and on the testicular surface were negative. The endothelium of the testicular artery was already faintly positive at birth, and the activity increased during the second and third postnatal week during the branching and remodeling of the intratesticular arteries and arterioles. Activity of GGT was estimated quantitatively after dissection of the testis into tubular and interstitial tissue. The enzyme activity was very low in the tubules. It was fivefold stronger in the interstitium, and this activity was further enhanced by pretreatment of the dissected tissue with collagenase to remove the Leydig cells.     

Angioarchitecture of the bovine spermatic cord

We described the topography and morphometry of the testicular artery, pampiniform plexus veins, and indirect connections between them in the spermatic cord of the bull. Sixty microcorrosive casts of bovine spermatic cords were analyzed macroscopically, by stereomicroscopy, and by scanning electron microscopy. The average size of the testicles was 94.6 × 49.7 × 54.7 mm. The testicular artery formed a superiorly pointed cone‐like structure with its base fixed to the proximal part of the gonad. The artery gave off one or two branches to the head of epididymis and to the deferens duct. The pampiniform plexus originated from intra‐tunical veins. Veins of the pampiniform plexus were of smaller diameter but larger number than intra‐tunical ones. The density of the veins of the pampiniform plexus was 9.37 ± 1.07 mm^?2. The testicular vein began 90–121 mm above the superior pole of the testis. In 2.9% of specimens, the testicular vein was doubled. Numerous anastomoses among veins of pampiniform plexus were observed. Additionally, indirect anastomoses between the testicular artery and pampiniform plexus veins formed by the capillary network of the vasa vasorum of the testicular artery were visualized by scanning electron microscopy. In all cases, narrowings in the casts of the precapillary vessel were observed. We also documented the vasa vasorum of the testicular artery in bulls. The density of these vessels was 22.87 ± 11.48 mm^?2. The indirect arteriovenous connections together with the presence of circular constrictions of the lumen in precapillary vessels may play a role in testicular blood flow regulation. J. Morphol., 2011. © 2011 Wiley‐Liss, Inc.     

Histochemistry and ultrastructure of nerve fibres and contractile cells in the tunica albuginea of the rat testis

Whole-mounted preparations of the tunica albuginea of the rat testis were studied using light microscopy techniques for demonstration of cholinergic nerve fibres (Karnovski-Root method), catecholaminergic nerve fibres (De la Torre's method) and actin filaments (avidin-biotin-peroxidase method). An ultrastructural study of different regions of the albuginea was also performed. Cholinergic fibres were seen to penetrate into the albuginea with the testicular artery to form a broad network in the mediastinum testis, many fibres ending beneath the rete testis epithelium. Catecholaminergic fibres penetrated through the middle part of the cauda epididymis and formed a plexus in the albuginea covering the inferior testicular pole. This plexus gave rise to straight fibres which formed varicosities, some of them appeared related with mast cells. Actin-containing cells were only found beneath the rete testis epithelium. These cells were similar to myofibroblasts. The location of both cholinergic fibres and contractile cells among the rete testis channels suggests that these cells may be involved in the pumping of semen towards the ductuli efferentes and that their contractility may be regulated by cholinergic fibres.     

The cytoarchitecture of the wall and the innervation pattern of the microvessels in the rat mammary gland: a scanning electron microscopic observation

This report describes the morphology of the smooth muscle cells, pericytes, and the perivascular autonomic nerve plexus of blood vessels in the rat mammary gland as visualized by scanning electron microscopy after removal of connective-tissue components. From the differences in cellular morphology, eight vascular segments were identified: 1) terminal arterioles (10-30 microns in outer diameter), with a compact layer of spindle-shaped and circularly oriented smooth muscle cells; 2) precapillary arterioles (6-12 microns), with a less compact layer of branched smooth muscle cells having circular processes; 3) arterial capillaries (4-7 microns), with " spidery " pericytes having mostly circularly oriented processes; 4) true capillaries (3-5 microns), with widely scattered pericytes having longitudinal and several circular processes; 5) venous capillaries (5-8 microns), with spidery pericytes having ramifying processes; 6) postcapillary venules (10-40 microns), with clustered spidery pericytes; 7) collecting venules (30-60 microns), with a discontinuous layer of circularly oriented and elongated stellate or branched spindle-shaped cells which may represent primitive smooth muscle cells; and 8) muscular venules (over 60 microns), with a discontinuous layer of ribbon-like smooth muscle cells having a series of small lateral projections. No focal precapillary sphincters were found. The nerve plexus appears to innervate terminal arterioles densely and precapillary arterioles less densely. Fine nerve fibers are only occasionally associated with arterial capillaries. Venous microvessels in the rat mammary gland seemingly lack innervation.     

Light microscopic study of the hypophyseal angioarchitecture in the rabbit

This study describes the hypophyseal angioarchitecture found in 79 adult New Zealand white rabbits. The pituitary glands and attached hypothalami were removed and carefully processed following routine histological methods, and the vascular organization was studied by light microscopy. Whole mounts of the pituitary median eminence complex were prepared and studied with a binocular dissecting microscope employing transmitted and epi-illumination. Arterial blood was found to be directed primarily to the neurohypophysis by the superior hypophyseal artery (SHA) and the inferior hypophyseal artery (IHA). A direct arterial blood supply was found to the adenohypophysis, but was limited solely to the pars intermedia by branches of the anterior hypophyseal artery (AHA) and the IHA. Capillaries of the pars intermedia were subdivided into an intermediate and a superficial plexus. The superficial plexus was situated between the intermediate plexus and the capillaries of the infundibular process. Capillaries of the superficial plexus did not form anastomoses between themselves, but ramified into the intermediate plexus to form a dense network of anastomosing capillaries that were continuous with capillaries of the pars distalis. A direct arterial blood supply was found only to the superficial plexus.     

Microvasculature of the human testis and excurrent duct system

Summary The vascular microarchitecture of the human testis and excurrent duct system was examined by use of a casting method combined with scanning electron microscopy. In the testicular parenchyma, the capillaries form a fine plexus around the seminiferous tubules. The commonly described rope-ladder-like pattern of the peritubular capillaries is absent in the human testis. The microvasculature of the rete testis consists of a poorly organized plexus. Throughout the epididymis including the ductuli efferentes, the peritubular capillary network encircles each tubule cylindrically. In the cauda epididymidis, a coarse venous network surrounds the capillary network externally. Small arteries of the epididymis not only penetrate the connective tissue septa, but also run along the surface. In the ductus deferens, three distinct microvascular systems are distinguished: (1) a venous network located in the connective tissue surrounding the muscular coat, (2) a microvascular plexus within the muscular coat, and (3) a peritubular capillary network. The plexus within the muscular coat interconnects the venous and the peritubular capillary networks.     

The movement of fluids and substances in the testis

Three aspects of the control of movements of fluids and substances into, out of and inside the testis are discussed: the tubular barrier, the interstitial extracellular fluid and the testicular blood vessels. The functional basis for the tubular barrier is twofold; there are significant differences in the concentration of many substances inside and outside the tubules and marker substances enter or leave the tubular fluid at widely different rates, depending on lipid solubility and the presence of specific carrier systems. The anatomical basis for this barrier appears to be the specialized junctions between adjacent pairs of Sertoli cells. The barrier develops only at puberty, as the first cells undergo meiosis, but the development may not be as sudden as previously believed. The barrier breaks down after efferent duct ligation when spermatogenesis is disrupted. Techniques for measuring the volume, the turnover rate, the composition and fate of the interstitial extracellular fluid are described, and the unsatisfactory features of the presently available techniques for collecting this fluid for analysis are emphasized. There is a relationship between the fluid in the testis and lymph from vessels in the spermatic cord and lymph may be important for the transport of hormones to the general circulation in some circumstances and to other organs close to the testis. The testicular blood vessels display certain unusual features, a very high susceptibility to the toxic effects of cadmium salts, a high level of alkaline phosphatase activity in all endothelial cells but only after puberty and a high level of gamma-glutamyl transpeptidase in the endothelial cells of the arterioles and the testicular artery. These same cells are the site for a specific transport system for leucine and phenylalanine, with kinetic characteristics similar to the system in brain. Flow of blood may limit hormone secretion by the aspermatogenic testis, but diffusion limitation may also be important under some circumstances. A fuller understanding of the ways in which substances move around in the testis, particularly how they cross the endothelial cell layer or penetrate into the tubules, will be important for a better appreciation of testicular function.     

牦牛和黄牛的睾丸形态及其血管构筑特征

本实验旨在研究牦牛（Bos grunniens）和黄牛（B. taurus）的睾丸形态及其血管构筑和动脉管径特征,为牦牛睾丸在高原环境的生理适应性提供依据。从14头屠宰后的成年牦牛体内采集睾丸28枚,从9头成年黄牛体内采集睾丸18枚,测定其形态指标,利用血管铸型技术制作动静脉构筑标本,研究睾丸血管解剖学及主要动脉管径的特征。结果显示,牦牛和黄牛的睾丸、附睾的形态特征及动脉管径有差异,牦牛大部分睾丸动脉及其分支的管径与睾丸重的相对值极显著地高于黄牛（P < 0.01）,牦牛睾丸的主要动脉构筑特征与黄牛的相同,但其大的集合静脉数量较少,小静脉呈“编织袋”状紧密排布。研究认为,牦牛睾丸的血管解剖特征可为睾丸提供更为充足的血液,其相对发达的动脉血管和睾丸静脉“编织袋”状分布特点有利于睾丸的温度调节及精子成熟,可能是牦牛生殖器官适应高海拔环境的生理特征之一。     

Chorioallantoic placenta formation in the rat: II. Angiogenesis and maternal blood circulation in the mesometrial region of the implantation chamber prior to placenta formation.

Rat gestation sites were examined on days 7 through 9 of pregnancy by light microscopy and transmission and scanning electron microscopy to determine the extent of vascular modifications in the vicinity of the mesometrial part of the implantation chamber (mesometrial chamber). At a later time, the mesometrial chamber is, in conjunction with the uterine lumen, the site of chorioallantoic placenta formation. On day 7, in the vicinity of the mesometrial chamber, vessels derived from a subepithelial capillary plexus and venules draining the plexus were dilating. By early day 8, this network of thin-walled dilated vessels (sinusoids) was further enlarged and consisted primarily of hypertrophied endothelial cells with indistinct basal laminas. Sinusoids were frequently close to the mesometrial chamber's luminal surface which was devoid of epithelial cells but was lined by decidual cell processes and extracellular matrix. By late day 8, cytoplasmic projections of endothelial cells extended between healthy-appearing decidual cells and out onto the mesometrial chamber's luminal surface, and endothelial cells were sometimes found on the luminal surface indicating that endothelial cells were migrating. The presence of maternal blood cells in the mesometrial chamber lumen suggested that there was continuity between the chamber and blood-vessel lumens. On day 9, the mesometrial chamber was completely lined with hypertrophied endothelial cells, and sinusoid lumens were clearly continuous with the lumen of the mesometrial chamber. Mesometrial sinusoids and possibly the mesometrial chamber lumen were continuous with vessels in vicinity of the uterine lumen that were fed by mesometrial arterial vessels. Clearing of the mesometrial chamber lumen during perfusion fixation via the maternal vasculature indicated the patency of this luminal space and its confluence with mesometrial arterial vessels and sinusoids. The conceptus occupied an antimesometrial position in the implantation chamber on days 7 through 9, and it was not in direct contact with uterine tissues in the vicinity of the mesometrial chamber. These observations suggest that angiogenesis, not trophoblast invasion or decidual cell death, plays a major role in the opening of maternal vessels into the mesometrial chamber lumen before the formation of the chorioallantoic placenta.     

Circannual changes in the expression of vascular endothelial growth factor in the testis of roe deer (Capreolus capreolus)

Adult roe deer males show seasonal cycles of testicular growth and involution. The exact timing of these cycles requires endocrine regulation and local testicular control by autocrine/paracrine factors. Recent findings suggest that the vascular endothelial growth factor (VEGF) might have effects on both vascular and germinative cells in testis. Thus, we studied the expression pattern of vascular endothelial growth factor (VEGF) in roe deer testis using quantitative RT-PCR. The strength of VEGF mRNA expression depended on season. It reached its highest level at the peak of spermatogenesis during the pre-rutting period and had its nadir at the end of the rut when involution already began. The results suggested that VEGF may directly affect the regulation of spermatogenesis but may not be involved predominantly in testicular microvasculature as initially expected.     

Angiosomes of the brachial plexus: an anatomical study

This anatomical study analyzed the neurovascular relationships of the brachial plexus. Ten fresh cadaveric brachial plexuses were examined after injection of the arterial system. The vascular anatomical features of the brachial plexus were documented with microdissection after lead oxide/gelatin injection. The specimens were analyzed by using radiography (including digital subtraction techniques) and light-microscopic, macroscopic, and digital photography. Four angiosomes, based on the subclavian, axillary, vertebral, and dorsal scapular arteries, were observed. As noted in previous angiosome studies, connections between angiosome territories lay within tissues, in this case, nerve trunks. Nutrient vessels penetrated nerve trunks at points of branching within the brachial plexus, with a Y-shaped mode of division on entry. The vascular supply was markedly rich, often with true anastomotic connections occurring within the nerves. There was much variation in supply, depending on the vascular anatomical features of the subclavian artery.     

Development of myocardial vascularisation in the rat

In rat, the development of the vascularisation of the myocardium starts in an embryo of 13 days, as a primarily solitary vascular plexus situated in the subepicardial mesenchyme. This plexus spreads out between the cells of the marginal layer of the myocardium of the ventricles. Thereafter it comes into contact with the intertrabecular spaces and with some endothelial offshoots of the left sinus horn. At day 15, just before the entire septation of the left and right arterial parts of the heart, this plexus contacts offshoots of the aorta. The myocardial trabeculae continue to grow longer from an enlarging base. In conjunction with this occurrence, there is a shift into the direction of the cells, resulting in a three-layered myocardium; from insided outwards a radial (trabecular) layer, a radio-tangential layer and a marginal layer can be found. A narrowing down of the intertrabecular spaces is another consequence of the enlarging base. The spaces deflect parallel to the radio-tangential layer. Thus a second plexus, deeply embedded in the myocardium, comes into existence. At day 19 a histological differentiation of the wall of the interconnected subepicardial-myocardial plexus to either arteries or veins will start. In all stages, the vascular system runs parallel to the myocardial structures of the ventricles of the heart.     

Spatial topography of the excurrent duct system in the bovine testis

Summary The rete testis of the bull is situated within an axial mediastinum and consists of approximately 30 longitudinally arranged, anastomosing rete channels. At the cranial testicular pole all rete channels empty into a common space, the area confluens reds, which is subdivided by small septa and narrow chordae retis. The area confluens always contains numerous spermatozoa and is connected with the bulbous initial portions of the efferent ductules by short, often tortuous rete tubules. Since the connection between rete and efferent ductules is situated within the tunica albuginea, the bovine excurrent duct system is not provided with an extratesticular rete as in many other mammals.Straight testicular tubules merge from all directions to connect with superficial rete channels, but the inlets are not evenly distributed. In the periphery each straight tubule begins with a cup-like structure followed by a narrow stalk region and a heavily folded portion opening either immediately into a rete channel or into a tube-like lateral rete extension.In close contiguity to the rete testis lie extremely coiled arterial portions connecting the centripetal and the centrifugal branches of the testicular artery. Since intrinsic musculature is scarcely developed in the mediastinum, and transport of rete content relies primarily on massage due to external pressure changes, the pulsatile blood flow through these coiled arteries may influence conveyance processes within the rete testis.An intimate spatial association between area confluens reds and adjacent large, thin-walled lymph vessels may facilitate a transfer of androgens into the fluid of the rete testis.Supported by the Stiftung zur Förderung der wissenschaftlichen Forschung an der Universität Bern     

Microvascular anatomy of testes in the adult pipid frog,Xenopus laevis Daudin: A scanning electron microscopic study of vascular corrosion casts

The three-dimensional microvascular anatomy of the testes of adult Xenopus laevis was studied by scanning electron microscopy of vascular corrosion casts. Results showed that testicular arteries branch off from urogenital arteries and approach the testes via the mesorchium. At the dorsal surface of testes, arteries course towards the medial and lateral surfaces of the ovoid testes, pierce the tunica albuginea and run in the subalbugineal space and then penetrate the testicular parenchyma. In the parenchyma, they branch in all directions. At sites where larger branches arise, sphincters are present. Intimal cushions are found at the origin of smaller branches. Terminal arterioles capillarize and form a wide-meshed capillary network around convoluted seminiferous tubules. Inter- and peritubular capillaries cannot be differentiated reliably. Arterio-venous transition distances are short. Arterio-arterial anastomoses and veno-venous anastomoses are present. Testicular venules empty into a venous subalbugineal plexus which shows veno-venous anastomoses of different lengths and calibres. Signs of the ongoing non-sprouting angiogenesis, particularly intussusceptive branch remodelling, reflect the dynamics of the testicular parenchyma. The present study is the first that demonstrates the testicular microvascular anatomy in an anuran species and shows that X. laevis and men share the intricate convoluted seminiferous tubules with associated vascular patterns as a feature in common.     

Heritable testicular hypoplasia in Nguni (Bos indicus) bulls: vascular characteristics and testosterone production.

The biased unilateral occurrence of heritable gonadal hypoplasia was investigated by examining the gross- and microanatomy of the testicular artery and vein, testicular blood flow and testicular testosterone secretion in normal Nguni bulls and in Nguni bulls showing unilateral left, unilateral right and bilateral hypoplasia of the testis. A high incidence of branching of the testicular artery was found ipsilateral to hypoplastic testes. The branching occurs a short distance from the dorsal aorta: one branch proceeds to the testis, the other to the ipsilateral kidney. The association between arterial branching to the kidney and ipsilateral hypoplasia of the testis held for both unilaterally left and unilaterally right hypoplastic bulls. Variations in the anatomy of the testicular vein occurred in both normal and hypoplastic bulls but there was no specific association between the variations and ipsilateral hypoplasia. The lumen diameter of the testicular artery or branch correlated with testis mass. Wall thickness of the artery ipsilateral to hypoplastic testes was not different from that in normal bulls, discounting hyperplasia of the endothelium. Total blood flow to the testis correlated with testis mass. The secretion rate of testosterone from hypoplastic testes was lower than that of normal testes but there was no difference when compared on a unit mass basis.