Collagen fiber arrangement in canine hepatic venules. (1/155)

Cell-maceration/scanning electron microscopy, serial sections and scanning electron microscopy of vascular resin casts were employed to demonstrate the arrangement of collagen fibers in the terminal hepatic venules, involving the central, intercalated and collecting veins in dog liver. In cell-maceration specimens, each collagen fiber was observed to run in various directions, forming a sheath with a compact meshwork of collagen fibers. The collagenous meshwork in the hepatic venules was looser than those of the terminal portal venules and hepatic arterioles. Some collagen fibers formed bundles with an elongated spiral arrangement encircling the wall of the terminal hepatic venules. In resin casts, these venules were observed as a twisted configuration caused by spiral collagen bundles. A helical modification of such connective tissue bundles might provide a mechanically stable vascular structure and permit reversible changes in linear and circumferential vascular dimensions at the terminal tributaries of veins. Round or oval pores with diameters of approximately 9 microns were also observed in the sheath of collagen fibers. These pores, together with the relatively loose collagenous meshwork in the hepatic venules, might play a role in lymphocyte migration from these venules into the surrounding tissue and provide high permeability to the venule walls. No such helical configuration and pores were observed in either the portal venules or the hepatic arterioles.  (+info)

Obstructive uropathy and hydronephrosis in male KK-Ay mice: a report of cases. (2/155)

Uropathy associated with hydronephrosis was observed frequently in our male KK-Ay mouse colony during a long-term study of diabetes. The lesion occurred in 24 of the 31 KK-Ay male mice and accounted for the greatest number of spontaneous deaths among them. It was observed after 4 months of age and involved about hard plugs of altered seminal material resembling the seminal vesicle secretion. The plugs became impacted in the urethral bulb and the bladder. The penile anatomy, with its flexure, pressure on the urethra from the bulbocavernosus muscle, and the characteristic ability of the seminal fluid to easily coagulate to form the vaginal plug may have contributed to the lesion. Correlation between development of the uropathy and diabetes has not been established.  (+info)

In vitro models of intracranial arteriovenous fistulas for the evaluation of new endovascular treatment materials. (3/155)

BACKGROUND AND PURPOSE: The purpose of this study was to create and test an in vitro model of intracranial arteriovenous fistulas (AVFs) that simulates the geometry of human vasculature and allows realistic testing of devices used in endovascular therapy. METHODS: The models were derived from corrosion casts of the main cervicocranial arteries and veins obtained from two nonfixed human specimens. Wax copies of the casts were produced and combined to create complex models simulating various types of intracranial AVFs. Wax assemblies were embedded with liquid silicone solidified into transparent blocks containing, after wax evacuation, hollow reproductions of the original vascular trees. The models were connected to a pulsatile pump and their compatibility with various imaging techniques and endovascular treatment materials was evaluated. RESULTS: The models were compatible with digital subtraction angiography, CT, MR imaging, and transcranial Doppler sonography. They provided a realistic endovascular environment for the simulation of interventional neuroradiologic procedures. CONCLUSION: Anatomically accurate and reproducible in vitro models of intracranial AVFs provide a valuable method for evaluating new endovascular treatment materials and for teaching purposes.  (+info)

Microvascular architecture of the human urinary bladder wall: a corrosion casting study. (4/155)

The vascular system of the urinary bladder wall effectively performs its function in spite of considerable spatial changes due to the filling/voiding cycle. However, only a few studies have dealt with the microvascular architecture of the bladder wall and only two, using old-fashioned techniques, were devoted to the human bladder. This study presents the microvasculature of the human bladder wall visualized by scanning electron microscopy of vascular corrosion casts. Postoperative bladder specimens obtained from patients with advanced bladder tumors were filled with small amount (80 ml) of saline and perfused via at least four largest arteries with anticoagulant-containing saline followed by paraformaldehyde/glutaraldehyde fixative and Mercox resin. After polymerization of the resin, the vascular casts were macerated with potassium hydroxide, cleaned with formic acid and water and freeze dried. Only regions of the bladder wall distant to the tumor were examined in light and scanning electron microscopes. The almost empty state of the bladder was manifested by extensive folding of the mucosa and tortuosity of almost all vessels other than capillaries. The branches of main arteries and veins formed an adventitial/serosal plexus which directly supplied/drained the capillary network of the muscularis and sent long perpendicular vessels to the mucosal plexus. These vessels had straight or coiled course depending on whether they terminated at the top or at the base of the mucosal folds. The rich mucosal plexus followed the folds parallel to their surface and gave off short, straight, mostly perpendicular twigs communicating with the subepithelial capillary network. Apart from very few vascular interconnections between the mucosal plexus and the muscularis, the submucosa was generally avascular. The subepithelial capillary network showed extreme density and uneven contours of the capillaries, only in less folded areas of trigone and urethral orifice the network was looser and capillaries thinner. The capillary system of the muscularis was poorly developed. Due to its architecture, tortuosity, and coiling/uncoiling capabilities, the microvasculature of the human urinary bladder wall seems to efficiently accommodate changes associated with cyclic contraction and stretching. Disturbances in blood flow induced by overdistension of the bladder reported in several studies may be due to pressure of the urine affecting the patency of the vessels rather than to the spatial insufficiency of the vascular system.  (+info)

Amelioration of vasospasm after subarachnoid hemorrhage in transgenic mice overexpressing CuZn-superoxide dismutase. (5/155)

BACKGROUND AND PURPOSE: To clarify the effect of superoxide dismutase (SOD) on vasospasm after subarachnoid hemorrhage (SAH), we investigated sequential changes in arterial diameter after SAH in transgenic mice overexpressing CuZn-SOD (SOD-1). METHODS: SOD-transgenic mice and nontransgenic littermates (35 to 40 g) were subjected to SAH produced by endovascular perforation of left anterior cerebral artery. At 4 hours and 1, 3, 7, and 14 days after SAH, the mice were perfused with 10% formalin and consequently with a mixture of carbon black and 10% gelatin to cast all vessels. Vasospasm was evaluated by measuring the diameter of the left middle cerebral artery (MCA) with a microscope. RESULTS: In nontransgenic mice, the diameter of the MCA on day 3 after SAH (110.5+/-20.5 microm [mean+/-SD]; n=16) was significantly reduced compared with that without SAH (138.5+/-14.5 microm; n=12) (P<0.01). Moreover, on day 3 after SAH, the diameter of the MCA in SOD-transgenic mice (127. 9+/-20.2 microm; n=20) was significantly larger than that in nontransgenic mice (110.5+/-20.5 microm; n=16) (P<0.05). CONCLUSIONS: These results suggest that SOD is effective on the amelioration of vasospasm after SAH and that oxygen free radicals, particularly superoxide, play an important role in the pathogenesis of vasospasm after SAH.  (+info)

Inhibition of choriocapillaris regeneration with genistein. (6/155)

PURPOSE: To test the effects of genistein on choriocapillaris regeneration and retinal pigment epithelial (RPE) wound healing in a surgical model in the rabbit. METHODS: Intravitreal injections of either 0.1 ml of a 90-microM concentration of genistein, dimethyl sulfoxide (DMSO; negative control), or 2 microg cycloheximide (positive control) were given 24 hours before surgical debridement of RPE in rabbits. Scanning electron microscopy (EM) of choroidal vascular casts and the RPE wounds and histologic evaluation by light microscopy and EM of the disturbed areas were performed at days 1, 7, and 30 after surgery. Quantitative analysis of the area of the choriocapillaris bed and RPE was performed by automated image analysis, and the results were analyzed by paired Student's t-test. RESULTS: Loss of RPE caused a rapid initial atrophy followed by slower subsequent revascularization of the choriocapillaris, which paralleled the RPE wound healing. Choriocapillaris regeneration appeared nearly normal by day 30 in the DMSO group. Inhibition of choriocapillaris revascularization by genistein was significant at day 30 when compared with the DMSO-treated negative control (P = 0.013). There was a strong trend toward inhibition in the cycloheximide-treated positive control group (P = 0.062), which reached significance at day 7 compared with the DMSO group (P = 0.02). RPE covered the wound area by day 7 in all groups. CONCLUSIONS: Intravitreal injection of genistein was found to cause significant inhibition of choriocapillaris regeneration without apparent effect on RPE wound healing. Tyrosine kinase inhibitors such as genistein may be useful as a pharmacologic approach in the treatment of choroidal neovascularization.  (+info)

Evidence for characteristic vascular patterns in solid tumours: quantitative studies using corrosion casts. (7/155)

The vascular architecture of four different tumour cell lines (CaX, CaNT, SaS, HEC-1B) transplanted subcutaneously in mice was examined by means of microvascular corrosion casting in order to determine whether there is a characteristic vascular pattern for different tumour types and whether it differs significantly from two normal tissues, muscle and gut. Three-dimensional reconstructed scanning electron microscope images were used for quantitative measurements. Vessel diameters, intervessel and interbranch distances showed large differences between tumour types, whereas the branching angles were similar. In all tumours, the variability of the vessel diameters was significantly higher than in normal tissue. The quantitative data provide strong evidence for a characteristic vascular network determined by the tumour cells themselves.  (+info)

Microvasculature of the rat optic nerve head. (8/155)

PURPOSE: To describe the arterial blood supply, capillary bed, and venous drainage of the rat optic nerve head. METHODS: Ocular microvascular castings from 6 Wistar rats were prepared by injection of epoxy resin through the common carotid arteries. After polymerization, tissues were digested with 6 M KOH, and the castings washed, dried, and coated for scanning electron microscopy. RESULTS: Immediately posterior to the globe, the ophthalmic artery trifurcates into the central retinal artery and two posterior ciliary arteries. The central retinal artery directly provides capillaries to the nerve fiber layer and only contributes to capillary beds in the neck of the nerve head. The remainder is supplied by branches of the posterior ciliary arteries that are analogous to the primate circle of Zinn-Haller. Arterioles arising from these branches supply the capillaries of the transitional, or laminar, region of the optic nerve head. These capillaries are continuous with those of the neck and retrobulbar optic nerve head. All optic nerve head capillaries drain into the central retinal vein and veins of the optic nerve sheath. A flat choroidal sinus communicates with the central retinal vein, the choriocapillaris, and with large veins of the optic nerve sheath. CONCLUSIONS: The microvasculature of the rat optic nerve head bears several similarities to that of the primate, with a centripetal blood supply from posterior ciliary arteries and drainage into the central retinal and optic nerve sheath veins. Association of nerve sheath veins with the choroid represents an important difference from the primate.  (+info)

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