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.     

Three-dimensional organisation of the vasculature of the rat spermatic cord and testis

Summary The vascular architecture of the rat testis and spermatic cord was studied by a corrosion cast technique combined with scanning and transmission electron microscopy, and light microscopy. The casts preserve the endothelial impressions of the vessels and enable them to be differentiated into the various vascular components. Frequent arterio-arterial anastomotic arcades and occasional arterio-venous anastomotic channels are seen. A well defined hexagonal pattern of intertubular and peritubular vessels surround the seminiferous tubules. Prominent large endothelial nuclei protrude into the arterial lumina at branching sites, but their functional significance is not known. The outermost vascular layer of the testis consists of large veins, venules, and capillaries, but lacks any arterial branches; it also contains loosely arranged veno-venous anastomotic networks. We have named this vascular layer the sub-albugineal venous plexus. The testicular artery increases in luminal diameter as it approaches the testis. The periarterial capillary plexus, which lies between the pampiniform plexus and the testicular artery, is drained by two types of venules.     

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.     

New methods of X-ray surgical diagnosis and treatment of varicocele in children and adolescents

The authors studied 520 patients with left-sided varicocele by left-sided phleborenotesticulography of Doppler ultrasonography, tensiometry of the left renotesticular venous system, blood gas composition, hormonal parameters, and etc. They present rationale for and evidence illustrations of aortomesenteric compression of the left renal vein, left-sided phleborenal hypertension prior to and after surgery for endovascular occlusion of the left testicular vein, before and following intervenous proximal testiculoiliac venous bypass surgery. The data of andrological dysfunction in patients with varicosis of the pampiniform plexus and spermatic cord (varicocele) are presented. An algorithm of examination and treatment of this cohort of patients, by using both miniinvasive techniques (for X-ray endovascular occlusion of the temporal veins under local anesthesia) and high tech operations using microsurgical techniques (testiculoiliac venous anastomosis), is outlined.     

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.     

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.     

Microvasculature of the mouse eye: Scanning electron microscopy of vascular corrosion casts

Purpose

For drug safety assessment, ophthalmic fundus examination is of diagnostic importance in experimental animals. Interim blood samples are usually collected from the orbital venous sinus in the mouse. This report characterizes the angioarchitecture of the mouse eye.

Methods

In 10 mice, the microvasculature of the eyes of was investigated using scanning electron micrographs of corrosion casts.

Results

The mouse eye was characterized as having a rich vasculature with many thick retinal arteries and a well-developed orbital venous sinus. The eye receives its primary blood supply from the external ophthalmic artery, which is divided into three branches: the central retinal artery, as well as the medial and lateral long posterior ciliary arteries. The central retinal artery is divided into 8-9 radiating retinal arteries. The mouse has an orbital venous sinus around the orbit rather than a well-developed orbital venous plexus in the retrobulbar space as is in the rat. The orbital venous sinus is formed by the episcleral veins, the ophthalmic vein, the superior palpebral vein, inferior palpebral vein and numerous anastomotic veins among these veins.

Conclusions

The mouse ocular vasculature is quite similar to that of rats. It is recommended that the best location for insertion of a capillary tube for collecting blood is in the lateral canthus around the eye where the sinus is larger and is most readily accessible. Functional significance of the vascular patterns of the eye is discussed.     

Changes in testis blood flow,the spermatic artery and prostaglandin F 2α content in testis tissue of heat-stressed rams

Blood flow to the testis, measured by the¹³³-Xenon isotope clearance technique, initially increased after rams were exposed to elevated (32°C) temperature. However, after 5 and 7 days continuous exposure, blood flow decreased significantly. Similar changes in blood flow to the testis were found during whole body exposure to elevated temperature, or when the temperature of the testis was increased by scrotal heating. After one week of heating the wall of the spermatic artery in the middle region of the pampiniform plexus had thickened, and the arterial lumen had decreased significantly. The PGF ₂ content in the testis of rams exposed to elevated temperature increased significantly. It is tentatively postulated that the higher levels of PGF ₂ in the testis of rams exposed to elevated temperature may be responsible for impaired spermatogenic function by constricting the spermatic artery in the pampiniform plexus region and thereby reducing blood flow to the testis.Published with approval of the Director of Kentucky Agricultural Experiment Station as Journal Article 75-5-150.Presented at the Seventh International Biometeorological Congres, 17–23 August 1975. College Park, Maryland, U.S.A.     

Some aspects concerning the peculiarities of the pterygoid venous plexus in man related to age

The pterygoid venous plexus (pt.v.pl.) was studied in 54 human heads (adults, children, fetuses) halved in the middle sagital plan, using microdissections and injections with PVC, coloured gelatin and roentgenopaque masses. In adults, the pt.v.pl. was closely related to the external pterygoid muscle. The superficial variant (more frequent) maintained connections with the facial vein through a venous network named by us "plexus pterygo-temporo-buccalis". The deep variant (less frequent) could be included in the system of venous plexuses placed at the basis cranii. Its tributaries, accompanying the lingual nerve, established connections with the veins of the sublingual compartment (a fact not yet mentioned in the literature). In children and old humans the pt.v.pl. was formed only by some large veins giving a radiate structure ("starfish-shaped" plexus) corresponding to the first and second portion of the maxillary artery. These results revealed that the pt.v.pl. is a unique formation which could be more developed laterally or medially in comparison with the external pterygoid muscle, in relation with the superficial or deep position of the maxillary artery. The practical importance of the pt.v.pl. is emphasized.     

Les prélèvements testiculaires dans les azoospermies sécrétoires: indications et bilan andrologique

The management of patients with nonobstructive azoospermia must not be limited to testicular biopsy. A complete andrological assessment must be performed to adapt treatment to each patient, in order to:

-avoid testicular biopsy by screening for “azoospermia-like” syndromes and treat any etiological factors (pituitary hypogonadism, varicoceles, cryptorchidism), and concomitant aggravating factors (spermatic cord infection, obstructive factor of the epididymis or vas deferens).

-screen for clinical or subclinical testicular tumors and demonstrate genetic anomalies involving risks for the offspring.

-establish a prognosis regarding the possible use of medically-assisted reproduction by ICSI (intracytoplasmic sperm injection) with testicular spermatozoa.

     

Observations on the vasculature of the reproductive tract in some Australian marsupials

The origin, distribution and structure of the blood vessels of the female reproductive tract and the testis of the brush possum (Trichosurus vulpecula) were studied using latex and silicone rubber casting and histological techniques. Latex casts of the vessels of the female tract were also studied in five macropod species – Macropus giganteus, M. eugenii, M. agilis, Megaleia rufa and Thylogale billardierii, and in the common wombat (Vombatus ursinus). The female reproductive tract in the brush possum was supplied and drained by four major sets of paired vessels – ovarian, cranial urogenital, caudal urogenital, and internal pudendal arteries and veins. These vessels formed substantial anastomoses with one another on each side of the midline, and also across-the-midline anastomoses. The proximal part of the ovarian artery ran in close apposition to the ovarian vein, which received one or more large uterine branches. In its distal protion the ovarian artery gave rise to a leash of small, tortuous ovarian branches, which wound around and between the plexiform ovarian veins. The testicular arteries and veins in this species also ran in close apposition to one another. Both arteries and veins branched into many smaller, mildly tortuous, parallel vessels in the spermatic cord, which reunited before entering the testis. The blood vessels of the reproductive tract in all of the macropod species studied, and in the common wombat, were basically similar to those of the brush possum. The intimate structural relationships between ovarian arteries and veins, and their ovarian branches, in these marsupials are suggestive of specializations for counter-current exchange between venous and arterial blood. However, in contrast to those of the testicular vessels where heat exchange is a demonstrated function, their physiological significance remains unknown.     

Local transfer of testosterone and aromatase activity in the spermatic cord in wild boar/pig hybrids in short-daylight and long-daylight periods

The local transfer of testosterone (T) and immunolocalization of cytochrome P450 aromatase (P450arom) in the spermatic cord vessels of ten male wild boar × domestic pig hybrids were examined in December (short-daylight period) and June (long-daylight period). Total T concentration was determined in the jugular vein (JV) and free T concentration was estimated in the common carotid artery (CA), branches of the testicular artery supplying the testis (TA) and epididymis (EA), as well as in testicular veins draining blood from the testis (TV) and spermatic cord (SV). P450arom was immunolocalized in the arterial and venous vessels of the spermatic cord. The concentrations of total T in the JV and free T in the CA did not differ between the examined periods. However, in December, free T concentrations in the TA and EA were higher (p < 0.01–0.001) than in the CA. In June, free T concentration was higher (p < 0.01) in EA than in CA and TA. The concentrations of free T in the TV and SV were higher (p < 0.001) than in the JV regardless of the period. Also, free T concentration in the SV was higher (p < 0.05) in June than in December. P450arom was expressed in all layers of the arterial and venous vessels of the spermatic cord. In June, the intensity of the P450arom staining was higher than in December. The results suggest that the local supply of the male reproductive organs with steroid hormones operate in the hybrids of wild boar × domestic pig. This supply includes the local transfer of testosterone and the P450arom action.     

Die arterielle und venöse Versorgung der Area postrema der Ratte

Zusammenfassung Eine Methode zur Darstellung von Hirngefäßen nach vorhergehender Perfusionsfixierung wird beschrieben.Die Blutversorgung der Area postrema erfolgt aus einem arteriellen Halbring, der um das caudale Ende der Rautengrube zieht. Der Halbring wird hauptsächlich aus Zweigen der Aa. cerebelli inff. antt. und der Aa. spinales postt. gespeist. Er stellt ein erstes arterielles Verteilersystem dar. Das zweite System umfaßt die Area postrema unmittelbar (Schenkelarterien und Transversalarterien). An seiner Bildung nehmen die Rami dorsales arteriae vertebralis teil. Als ein drittes Verteilersystem auf Arteriolen- und Kapillarebene kann man das intrapiale Netzwerk ansehen.Die venösen Gefäße entsprechen weitgehend den arteriellen. Im Unterschied zu den Arterien kommunizieren die Venen beider Seiten nicht miteinander, ihre Ursprungsgebiete überschneiden sich kaum. Lediglich dem arteriellen Halbring entspricht der Semicirculus der Gabelvenen.Verbindungen der Area postrema mit ihren Nachbargebieten bestehen auf der Ebene größerer Gefäße nicht. Kapilläre Beziehungen, besonders zum Plexus chorioideus, kommen vor.Die Kapillaren bilden in der Area postrema ein dichtes Gefäßnetz, z.T. sind Venolen sinusartig erweitert. Kleine Gefäße werden oft von weiten perivasculären Räumen umgeben. Gegen den extra- und intraventriculären Rand der Area postrema nehmen die Kapillarschlingen an Zahl zu.Die funktionelle Bedeutung der Area postrema aus der Sicht ihrer Gefäßversorgung und ihres Kapillaraufbaus wird diskutiert.

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The arterial and venous supply of the area postrema in the rat

Summary A method to demonstrate cerebral vessels with an injected gelatine ink mixture is described.The area postrema is supplied with blood from an arterial semicircle surrounding the caudal end of the fossa rhomboidea. The semicircle in its turn is maintained mainly by branches from the arteriae cerebellares inff. antt. and the arteriae spinales postt. and represents a first arterial system of blood distribution. A second system encloses the area postrema directly, in the formation of which the rami dorsales arteriae vertebralis have their share. The arterioles and capillaries of the intrapial network can be regarded as a third system of distribution.The venous system corresponds largely to the arterial one. In contrast to the arteries, however, the veins of both sides do not communicate and their sources of origin do not overlap significantly. Only the venous semicircle is in accordance with the arterial one.Except for capillary communications in particular with the choroid plexus, there are no vascular connections between the area postrema and its adjoining regions of the brain. The capillaries of the area postrema form a dense network. The venoles are partly enlarged to sinuses. The small vessels are often surrounded by wide perivascular spaces. In the extra and intraventricular surface of the area postrema the capillary loops increase in number.The functional significance of the area postrema is discussed under the aspect of its supply with vessels and the arrangement of its capillaries.

     

The mediastinum of the bovine testis

Summary The bovine testis has a central mediastinum consisting of longitudinally oriented rete channels and spacious lymph vessels, embedded in the mediastinal stroma. The latter represents a contractile-elastic unit and is composed of myofibroblasts, collagen bundles and accumulations of elastin, connecting the myofibroblasts. The dimension of the mediastinum varies in cross sections at different levels between 3.5 and 31.8 mm². In one cross section 30 rete channels and 30 openings of straight testicular tubules are encountered. Nearly 25% of the area is occupied by thinwalled, valveless lymph vessels. Arterial convolutes, interpolated between straight centripetal and straight centrifugal branches of the testicular artery flank the rete on all sides. It is concluded that the pulsation within these convolutes together with the contractile-elastic stroma promotes lymph and rete content in a caudo-cranial direction. Chordae retis as described by Roosen-Runge and Holstein (1978) for the human testis are a common feature in the bovine mediastinum testis. The rete channels are lined by a simple cuboidal or columnar epithelium. Short intraepithelial crypts are present and function as epithelial reserve for dilatation and expansion of the rate. The inventory of organelles is rather inconspicuous in the rete epithelium. The apical border bears short microvilli and gives a strong reaction for alkaline phosphatase. The basal cytoplasm contains many small to medium-sized electron-dense bodies and is site of a strong acid phosphatase reaction. The rete epithelium as a whole reacts strongly with leucine aminopeptidase, the marker enzyme of the testicular excurrent duct system. Many free mononuclear cells, mostly macrophages, are observed in the basal half of the rete epithelium.     

Effect of external factors on gonadal activity and body mass of male golden hamsters (Mesocricetus auratus)

Summary Effects of photoperiod, temperature and food and water availability on body and testicular mass of golden hamsters were investigated. Lack of water or food inhibited body growth. Short photoperiod (LD 8:16) enhanced boyd growth in males fed poor diet but it had no effect in animals on high quality diet. Cold exposure diminished body growth in animals with access to water but not in those deprived of water. It is suggested that lowered motor activity is mainly responsible for body mass gain of animals kept under the short photoperiod.All stressful factors (water deprivation, poor diet or cold) induced involution of testes. The time course of testicular involution was similar to that induced by short photoperiod. Testicular involution was, after several weeks, followed by spontaneous recrudescence. Combination of stressful external cues speeded up testicular involution. Since the testicular involution induced by water deprivation, poor diet and cold also occurred in animals kept in constant light or under long photoperiod (which are known to produce functional pinealectomy) it is concluded that the inhibitory effects of stressful external factors on testes are not mediated by the pineal.The decrease in testosterone production induced by external cues precedes changes in testicular mass. In individuals kept in the cold, testosterone production remains low, in spite of spontaneous recrudescence of the testes. No simple relationship between testosterone concentration in the blood and testicular mass was observed.The mass of the interscapular brown adipose tissue (ISBAT) changes strikingly during the hibernation cycle. Immediately after exposure to cold it decreases and stays at the low level for 40 days. Than it increases markedly and reaches maximum after 90 days, when hibernation progresses. During the hibernation season the mass of the ISBAT decreases. Constant darkness enhances the cold-induced growth of the ISBAT only at the beginning of the hibernation season.     

The influence of the sampling point on testicular steroid concentrations in spermatic venous blood: a physiological approach to evaluate testicular secretion

In the present study, we have evaluated the influence of the location of the blood sampling in the spermatic vein on the steroid concentrations observed. Simultaneous blood sampling at two different points of the spermatic vein (iliac level and pampiniform plexus) was perfomed in the same patients during a surgical protocol for varicocelectomy. In order to further evaluate which of the two sampling points is more useful to investigate testicular secretion, we have performed both forms of sampling in 4 volunteers given an HCG stimulation 24 h before the surgical procedure. It was found that levels of testosterone (T) and 17 alpha-hydroxyprogesterone (17-OHP) were higher in the pampiniform plexus (scrotal) than at the iliac sampling point (T scrotal 1,168.343 +/- 142.65 nmol/l, iliac 850.63 +/- 143.411 nmol/l, n = 21, p less than 0.01; 17-OHP scrotal 260.130 +/- 43.14 nmol/l, iliac 164.46 +/- 31.02 nmol/l, n = 17, p less than 0.01). This indicates that spermatic blood collected at the scrotal sampling point has received more blood coming from the testis than the blood collected at the iliac point. We did not observe significant differences in progesterone and delta 4-androstenedione (delta 4) levels between the two samplings. The T/delta 4 ratio was significantly lower in the iliac than in the scrotal sampling (T/delta 4 scrotal 31.420 +/- 6.69; iliac 15.41 +/- 3.84; p less than 0.05). After HCG stimulation, testosterone concentrations were higher in the pampiniform plexus than in the iliac sample. This suggests that the first sampling point is more proper for studying testicular secretion.(ABSTRACT TRUNCATED AT 250 WORDS)     

The cerebrospinal venous system: anatomy, physiology, and clinical implications

There is substantial anatomical and functional continuity between the veins, venous sinuses, and venous plexuses of the brain and the spine. The term "cerebrospinal venous system" (CSVS) is proposed to emphasize this continuity, which is further enhanced by the general lack of venous valves in this network. The first of the two main divisions of this system, the intracranial veins, includes the cortical veins, the dural sinuses, the cavernous sinuses, and the ophthalmic veins. The second main division, the vertebral venous system (VVS), includes the vertebral venous plexuses which course along the entire length of the spine. The intracranial veins richly anastomose with the VVS in the suboccipital region. Caudally, the CSVS freely communicates with the sacral and pelvic veins and the prostatic venous plexus. The CSVS constitutes a unique, large-capacity, valveless venous network in which flow is bidirectional. The CSVS plays important roles in the regulation of intracranial pressure with changes in posture, and in venous outflow from the brain. In addition, the CSVS provides a direct vascular route for the spread of tumor, infection, or emboli among its different components in either direction.     

Fatal haemorrhage and neoplastic thrombosis in a captive African lion (<Emphasis Type="Italic">Panthera leo</Emphasis>) with metastatic testicular sex cord–stromal tumour

Background

The study of neoplasia in wildlife species contributes to the understanding of cancer biology, management practices, and comparative pathology. Higher frequencies of neoplasms among captive non-domestic felids have been reported most commonly in aging individuals. However, testicular tumours have rarely been reported. This report describes a metastatic testicular sex cord–stromal tumour leading to fatal haemorrhage and thrombosis in a captive African lion (Panthera leo).

Case presentation

During necropsy of a 16-year-old male African lion, the left testicle and spermatic cord were found to be intra-abdominal (cryptorchid), semi-hard and grossly enlarged with multiple pale-yellow masses. Encapsulated haemorrhage was present in the retroperitoneum around the kidneys. Neoplastic thrombosis was found at the renal veins opening into the caudal vena cava. Metastases were observed in the lungs and mediastinal lymph nodes. Histology revealed a poorly differentiated pleomorphic neoplasm comprised of round to polygonal cells and scattered spindle cells with eosinophilic cytoplasm. An immunohistochemistry panel of inhibin-α, Ki-67, human placental alkaline phosphatase, cytokeratin AE1/AE3, cKit, vimentin and S100 was conducted. Positive cytoplasmic immunolabeling was obtained for vimentin and S100.

Conclusions

The gross, microscopic and immunohistochemical findings of the neoplasm were compatible with a poorly differentiated pleomorphic sex cord–stromal tumour. Cause of death was hypovolemic shock from extensive retroperitoneal haemorrhage and neoplastic thrombosis may have contributed to the fatal outcome. To our knowledge, this is the first report of sex cord–stromal tumour in non-domestic felids.

     

New vascular system in reptiles: anatomy and postural hemodynamics of the vertebral venous plexus in snakes.

Using corrosion casting, we demonstrate and describe a new vascular system--the vertebral venous plexus--in eight snake species representing three families. The plexus consists of a network of spinal veins coursing within and around the vertebral column and was previously documented only in mammals. The spinal veins of snakes originate anteriorly from the posterior cerebral veins and form a lozenge-shaped plexus that extends to the tip of the tail. Numerous anastomoses connect the plexus with the caval and portal veins along the length of the vertebral column. We also reveal a posture-induced differential flow between the plexus and the jugular veins in two snake species with arboreal proclivities. When these snakes are horizontal, the jugulars are observed fluoroscopically to be the primary route for cephalic drainage and the plexus is inactive. However, head-up tilting induces partial jugular collapse and shunting of cephalic efflux into the plexus. This postural discrepancy is caused by structural differences in the two venous systems. The compliant jugular veins are incapable of sustaining the negative intraluminal pressures induced by upright posture. The plexus, however, with the structural support of the surrounding bone, remains patent and provides a low-pressure route for venous return. Interactions with the cerebrospinal fluid both allow and enhance the role of the plexus, driving perfusion and compensating for a posture-induced drop in arterial pressure. The vertebral venous plexus is thus an important and overlooked element in the maintenance of cerebral blood supply in climbing snakes and other upright animals.     

Vergleichende methodische Untersuchungen über die Aktivität der sauren Phosphatase und 5′-Nucleotidase im Rückenmark normaler Kaninchen und nach Durchschneidung des Plexus brachialis

Zusammenfassung Bei normalen erwachsenen Kaninchen und nach Durchschneidung des Plexus brachialis wurden im Rückenmark die Reaktionen für saure Phosphatase nach Gomori, Burstone und Barka-Anderson (nur im Normalzustand) und für 5-Nucleotidase nach Wachstein und Meisel bei pH 4,0 untersucht. Sowohl beim Normaltier als auch im Experiment zeigen alle vier Reaktionen gewisse Ähnlichkeiten in ihrer Lokalisation und ihrem Charakter. Es werden jedoch Unterschiede zwischen den drei sauren Phosphatase-reaktionen nach Gomori, Burstone und Barka-Anderson einerseits, sowie der bei saurem pH nachgewiesenen 5-Nucleotidase andererseits festgestellt. Die Resultate unterstützen die These von der Substratspezifität der untersuchten Enzyme und der Heterogenität der sauren Phosphatase.

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Studies on the activity of acid phosphatase and 5-nucleotidase in the spinal cord of normal and plexus brachialis-sectioned rabbits by different histochemical methods

Summary The spinal cord (normal and after brachial plexus section) of adult rabbits was examined using histochemical reactions for acid phosphatase according to Gomori, Burstone, Barka and Anderson (only for normal rabbits), and 5-Nucleotidase according to Wachstein and Meisel at pH 4.0. The reactions show similarity in their specificity and localization in the normal and experimental animals, but they are some differences between Gomori, Burstone and Barka-Anderson reactions for acid phosphatase on one hand, and 5-Nucleotidase at acid pH on the other. The results give some evidence to support the thesis concerning the substrate specificity of the examined enzymes and the heterogeneity of acid phosphatase.