A new plastic for morphometric investigation of blood vessels, especially in large organs such as the human liver

Non-linear shrinkage of Batson's #17 resin during vascular corrosion casting

Many studies of cardiovascular function require a realistic representation of vascular geometry. Corrosion casting has been used to acquire such geometries for many decades. However, the fidelity with which this method reproduces vascular anatomy has not been completely determined. Here we report on the non-linear shrinkage characteristics and exothermic properties of Batson's #17, a widely used casting resin, in model systems and in aortas of rats and rabbits. The setting process was captured using high-resolution photography. Shrinkage ranged from 3.4 ± 1.5% of the diameter in 1 ml plastic syringes (inner diameter 4.8 mm) to 19.6 ± 5.6% in the aorta of rats (diameter 1.5-2.6 mm). In addition, aortic curvature and branching angles changed during setting. These effects should be determined and corrected in studies of vascular geometry where high accuracy is required.

Hippocampal vascularization: Proposal for a new classification

Background:

Anatomy of the hippocampal arterial supply is key to successful surgeries in this area. The goal of the current study is to present the results we obtained from our microsurgical dissections of the temporal lobe and to propose a new classification for the hippocampal arteries (HAs).

Methods:

Fifty-six brain hemispheres were analyzed. All dissections in this study were made using 3–40× at the surgical microscope.

Results:

The hippocampal arterial vasculature can be divided into six groups, according to their frequencies: Group A: mixed arterial vasculature originating from the anterior choroidal artery anterior choroidal artery, posterior cerebral artery (PCA), anterior infratemporal artery (AIA), and splenic artery (SA). Group B: Main origin at the temporal branches – main inferotemporal trunk, middle inferotemporal artery, posterior inferotemporal artery, AIA, or main branch of PCA. Group C: AIA as the main branch of the hippocampus. Group D: HAs originating from the main branch of PCA. Group E: A single hippocampal artery with the origin at the main branch of PCA. This single artery covered all of the structure and is named Ushimura’s artery. Group F: The hippocampal vessels arose exclusively from the parieto-occipital artery, calcarine artery (CA), and the SA.

Conclusion:

This study proposes a new classification for the hippocampal vascularization, according to the origin of HAs. One of the groups has not yet been described in the literature – in which the HAs arise from the parieto-occipital artery, SA, and CA.

Retinal Microcirculation as Revealed by SEM Corrosion Casts in the Rat

The morphology of the retinal microcirculation has been extensively studied by different techniques. Nevertheless, some problems concerning the capillary bed lamination and pre- and postcapillary patterns have not yet been clarified. In the present study the SEM corrosion cast technique was employed to study the three-dimensional relationships of rat retinal vessels and to follow the smallest vascular branches. Rat retina is considered a useful experimental model for a number of pathologies which affect the microvascular bed deeply. Two precapillary patterns have been observed. Precapillary arterioles gave rise to capillaries both as terminal branches or as collaterals. The former pattern of ramification allows only a regulation of flow in a whole group of capillaries downstream, the latter pattern could provide a finer regulation of blood flow. SEM corrosion casts have shown very well the lamination of the capillary bed: one can easily realize this by seeing the overlapped meshes of the two different planes, vessels in between the two capillary laminae can always be followed from one meshwork to the other. This three-dimensional organization is an interesting model for retinal circulation because it shows many features in common with the retina of humans and primates.

A comparative study of vascular injection fluids in fresh-frozen and embalmed human cadaver forearms

Over the years, various vascular injection products have been developed to facilitate anatomical dissections. This study aimed to compare the most commonly used vascular injection products in fresh-frozen and formalin-embalmed cadaver specimens. An overview of the properties, advantages and limitations of each substance was given, and a comparison of vascular infusion procedures in both preservation methods was made. A literature search was performed in order to identify the most commonly used vascular injection products. Acrylic paint, latex, gelatin, silicone, Araldite F and Batson's No. 17 were selected for the study. One fresh-frozen and one embalmed cadaver forearm were infused with each injection product according to a uniform protocol. The curing time, skin- and subcutaneous tissue penetration, degree of filling of the arterial tree, extravasations, consistency of the injected vessels during dissection, and the costs of each injection fluid were noted. There was a large variation between the injection fluids in processing- and curing time, colour intensity, flexibility, fragility, elasticity, strength, toxicity and costs. All fluids were suitable for infusion. The penetration of injection fluid into the skin and subcutaneous tissue was significantly better in fresh-frozen specimens (P = 0.002 and P = 0.009, respectively), with significantly smaller branches casted (P = 0.004). Vascular infusion of fresh-frozen cadaver specimens results in a significantly better filled coloured arterial tree, enabling more detail to be achieved and smaller branches casted. The biomechanical properties of fresh-frozen soft tissues are less affected compared with formalin fixation. All the injection fluids studied are suitable for vascular infusion, but their different properties ensure that certain products and procedures are more suitable for specific study purposes.

Glycol methacrylate-embedding medium to study morphological alterations of saphenous vein under brief and crescent pressurizations

PURPOSE

This study sought to evaluate the efficiency of glycol methacrylate-embedding medium to detect morphological alterations of human saphenous vein submitted to brief and crescent pressurizations.

METHODS

Saphenous veins of 20 CABG patients were randomly distributed into four experimental groups (control, 100, 200 and 300 mmHg pressures during 15 seconds). To quantify the percentage of endothelium spread over vein surface a microscope magnification of 100x was used for measurements. Morphometric analysis was performed using videomicroscopy with the Leica Qwin software in conjunction with a Leica microscope, videocamera, and an on-line computer.

RESULTS

A slight tendency of quantitative increase was observed in all parameters including percentage of endothelium spread over vein surface and thickness of saphenous vein walls (intima and media layers).

CONCLUSIONS

The glycol methacrylate-embedding allowed sections with adequate resolution of structural details and revealed to be an extremely useful method to study pressurized human saphenous veins.

Origin and regional distribution of the arterial vessels of the vomeronasal organ in the sheep. A methodological investigation with scanning electron microscopy and cutting-grinding technique

The origin and location of the arteries of the vomeronasal organ (VNO) in the sheep were studied by means of dissection, scanning electron microscopy of corrosion casts, and the cutting-grinding technique after injection with Araldite CY23-HY2967 via one of the carotid arteries. Dissection revealed that the most ventral of the three main branches of the sphenopalatine artery is responsible for the blood supply to the VNO. Scanning electron microscopy of corrosion casts revealed that the arterioles of the vomeronasal organ form a microvascular network. Cross sections of the region of the nasal cavity containing the VNO, obtained by the cutting-grinding technique, showed that the arterioles of the vomeronasal plexus are located medial and ventral to the vomeronasal duct. These results confirm the usefulness of the cutting-grinding technique as a complementary procedure in morphological studies of structures containing hard tissues.

The peritoneal free flap: an anatomic study

In view of a possible clinical application of an isolated microvascular peritoneal flap, an anatomic study was performed in order to determine the peritoneal vascular territory of the deep inferior epigastric artery. For this, the deep inferior epigastric artery was injected unilaterally with Araldite in 30 embalmed cadavers and bilaterally with india ink in 15 fresh cadavers. In 70 percent of the embalmed cadavers, a constant pattern of three branches from the deep inferior epigastric artery could be identified. The peritoneal vascular supply is not derived solely from these three branches but also from multiple small branches sprouting directly from the main stem of the deep inferior epigastric artery and from segmental and muscular branches. Therefore, classification of peritoneal branches arising from the deep inferior epigastric artery seems to be of little clinical importance. In all cases, the india ink injected in the deep inferior epigastric artery colored a similar territory of the parietal peritoneum. Considering the magnitude of the peritoneal vascularization by the deep inferior epigastric artery, implementation of an isolated free or pedicled peritoneal flap seems to be possible. Such a microvascular peritoneal flap vascularized by the deep inferior epigastric artery may be used, for example, for reconstruction of mucosal defects in the head and neck region.

Penile bulb and its relationship with the pelvic urethra and the penile urethra in the rat: light and scanning electron microscopical observations

BACKGROUND

In male rats the urethral tract consists of the following parts: the pelvic urethra, the transitional urethra, the urethral diverticle, and the penile urethra. Perusal of the literature results in only some more general descriptions and a very few which go more into detail. None of the latter deals with all the compartments nor with the relationships between each other. Aim of this study is to give a detailed morphological study of all the urethral compartments and their relationships to provide a platform for further experimental investigations.

METHODS

From 40 adult male Wistar rats the urethral tract has been investigated by histology and scanning electron microscopy using intact tissue and casting techniques.

RESULTS

Most striking is the existence of the sinusoids in the spongious tissues in the pelvic urethra into a system of two perpendicular layers of parallel sinusoids. In the spongious tissues of the penile corpus spongiosum the same organization can be found although less prominent. Smooth muscle cells are very unequally present along the urethral tract. In its pelvic part they do not form a continuous layer around the spongious tissue and compared to the distal part they appear proximally more abundant. In the bulbal part of the corpus spongiosum the smooth muscles form a massive sac around the spongious tissue. In the corpus spongiosum in the penile shaft they are absent. The smooth muscle cells are separated from the striated urethral muscle by a very thin layer of connective tissue, in the penile bulb a prominent tunica albuginea separates them from the striated penile muscles. In the spongious tissues of the pelvic urethra and the penile bulb large amounts of compound urethral glands are present. Their ducts open into the respective lumen. Helicine arteries are common in the pelvic urethra, especially in the glandular tissue. They are also normally present in the wing tips of the penile bulb.

CONCLUSIONS

The transitional urethra, the urethral diverticle and surrounding spongious tissue are structurally closely related to the other parts, however their microscopical organization is intermediate between the pelvic part of the urethra and the corpus spongiosum. The highly ordered sinusoids in the spongious layers especially in the pelvic part together with a similar organization of the urethral muscle provide a possible basis for a peristaltic driving mechanism, suggesting these structures play a role in the high speed transport of sperms during ejaculation.

Scanning electron microscopic study of episcleral arteriovenous anastomoses in the owl and cynomolgus monkey

In the present study we have analyzed the architecture of the episcleral microvasculature in the owl and cynomolgus monkey using scanning electron microscopy of resin casts. Due to the topical pretreatment with nitroprusside the complete vasculature including segments of the aqueous humor outflow channels could be visualized. We found that 1-3 mm posterior to the limbus corneae the episcleral vessels form numerous arteriovenous anastomoses (AVA) in the size of small arterioles and venules. These AVA are also located at the collector channels near Schlemm's canal and at the episcleral venous plexus which drains the collector channels. It is assumed that the AVA might influence not only the circulation in the episcleral venous plexus but also in the aqueous humor outflow routes.

Middle cerebral artery occlusion in Wistar and Fischer-344 rats: functional and morphological assessment of the model

Cerebral infarction volume after occlusion of a short proximal segment of the middle cerebral artery (MCA) is reported to be different in Wistar compared to Fischer-344 (F344) rats, in both size and variability. Knowledge about the cause of these differences might enable us to explain and perhaps reduce the variation in infarct volume and create a reproducible model of focal cerebral ischemia in the rat. We investigated in Wistar and F344 rats both the effect of occlusion of a long proximal MCA segment on cerebral infarction volume, visualized by magnetic resonance imaging and histology, and the morphology of the major cerebral arteries. Occlusion of a long proximal MCA segment resulted in a striatal and a small cortical infarction in Wistar and a striatal and sizable cortical infarction in F344 rats (as is the case after occlusion of a short proximal MCA segment). In Wistar rats, however, occlusion of a long proximal MCA segment strongly reduced the variability in infarction volume in comparison to occlusion of a small proximal MCA segment. Analysis of the morphology of the major cerebral arteries showed a significantly higher number of proximal side branches of the long proximal MCA segment in Wistar rates than in F344 rats. We conclude that after short-segment proximal MCA occlusion, extreme variability in cerebral infarction volume in Wistar rats compared to F344 rats may be attributable to a significantly greater number of proximal MCA side branches in Wistar rats than in F344 rats.

Scanning electron microscopic study on the vasculature of the human anterior eye segment, especially with respect to the ciliary processes

The architecture of the vasculature of the human anterior eye segment was studied by scanning electron microscopy of vascular resin casts. Regarding the major vessels it was found that the perforating branches of the anterior ciliary arteries (ACA) form an anastomozing circle which lies in the posterior portion of the ciliary muscle (intramuscular circle). The ACAs supply the outer and posterior parts of the ciliary muscle, partly the iris, and the peripheral choroid by recurrent ACA branches. The major arterial circle of iris (MACI) which lies more anteriorly is formed mainly by the long posterior ciliary arteries and supplies the inner and anterior portion of the ciliary muscle, the iris and the ciliary processes. The ciliary process vasculature consists of three different vascular territories with discrete arterioles and venules. The first vascular territory which is located at the anterior end of the major processes, is drained posteriorly by venules which pass the ciliary body without greater connections to the venules of the major ciliary processes. The second and third territories comprise the vasculature of the major and minor ciliary processes drained posteriorly by venules which are located at the margin of the ciliary processes. In supravital experiments with human autopsy eyes, a characteristic segment of arterioles supplying the first and second territory was found to be constricted after immersion with epinephrine in a similar way as in cynomolgus monkeys in vivo. Although the general arrangement of the ciliary process vessels is similar to that of the cynomolgus monkey, there are characteristic differences in the size of the territories and in the pattern of the capillary networks. The division of the ciliary process vasculature into three vascular territories may reflect a functional differentiation in the process of aqueous humour production.

Araldite F as injection material for quantitative morphology of cerebral vascularization

This study deals with the applicability of Araldite F as injection medium for quantitative morphology of the cerebral vascularization. The physical properties of the plastic that are essential for obtaining optimal results have been determined and tested by injection into the cerebral vessels of ten dog brains and five human brains. The dynamic viscosity (at 20 degrees C) of the plastic is 1.5 times that of blood. The polymerization time (+/- 45 min) is long enough to fill the whole vascular tree in a large organ such as the human brain. The plastic shows minimal volume shrinkage (3.90% +/- 0.05%), and the final cast is suitable for scanning electron microscopy (SEM) investigation after corrosion and histological morphometrical examination after embedding in 2-hydroxyethyl-methacrylate (GMA). Special attention has been paid to the conditions under which injection of Araldite F into the cerebral arteries must take place to obtain the most accurate quantitative data on cerebral vascularization and vascular area distribution. Simultaneous injection of the major cerebral arteries of fresh autopsy material, after having removed blood clots by perfusing Kabikinase, is recommended.

SEM studies of the functional morphology of the ciliary process vasculature in the cynomolgus monkey: reactions after application of epinephrine

In the ciliary processes of the cynomolgus monkey three vascular territories with discrete arterioles and venules were found by means of scanning electron micrographs of vascular resin casts. The first vascular territory, which is located at the anterior end of the major processes, is drained posteriorly by long isolated venules, which pass the ciliary body without greater connections to the venules of the major ciliary processes, whereas the second and third territories comprise the vasculature of the major and minor ciliary processes drained posteriorly by veins which are located at the internal edge of the ciliary processes. With the functional resin casting method it could be demonstrated that 15 min after application of 20 micrograms of epinephrine into the conjunctival sac the terminal arterioles supplying the first vascular territory constricted most intensely, whereas the terminal arterioles related to the middle and posterior vascular territory of the ciliary processes constricted to a lesser extent. Twenty-five minutes after topical application of epinephrine only the posterior vascular territory and the capillaries of the ciliary muscle appeared filled in the resin casts. The vasculature of the anterior territories remained empty because of strong vasoconstriction of the supplying arterioles. The three morphologically different vascular territories with their different sensitivities to epinephrine may reflect a functional differentiation in respect to aqueous humour formation and resorption.

SEM studies on the functional morphology of the rabbit ciliary process vasculature

Architecture and functional reactions of the blood vessels of the rabbit ciliary processes were studied after administration of epinephrine and isoproterenol. A new corrosion cast technique was applied which allows the analysis of different functional stages in the vascular system by scanning electron microscopy. The ciliary process vasculature is divided into three different vascular territories, each supplied by individual arterioles: (1) the iridial ciliary processes; (2) the anterior (pre-lenticular) portion of the major ciliary processes; and (3) the minor ciliary processes localized post-lenticularly between the major processes. The three vascular territories differ not only in form and architecture of the capillaries but also in their reactions on vasoactive agents. After epinephrine, the earliest reactions were seen in the first vascular territory followed by the second, the third vascular territory being least sensitive. The most intense vasoconstrictory changes were found in the terminal arterioles which supply each vascular territory separately. This afferent vascular segment might therefore be considered to be the most important structure for regulation of blood flow through the ciliary processes.

Comparative morphological studies on blood vessels in eyes of normotensive and spontaneously hypertensive rats

The spontaneously hypertensive rats (SHR) show a lower intraocular pressure--despite high arterial blood pressure--than the normotensive Wistar Kyoto rats (NR). In SHR the quantitative evaluation of resin casts and flat-mount preparations of the blood vessels of the ciliary body and choroid showed a significant dilation of the vessels when compared to NR. In the capillaries of the ciliary processes, as well as in the choriocapillaries, a vascular rarefaction was seen. In all regions of the ciliary body the number of fenestrations found in the endothelium of the capillaries was reduced by about half in SHR. In addition, hyalinization of the connective tissue--particularly around the vessels at the base of ciliary processes--was seen in SHR. The morphological changes of the vasculature and connective tissue described here may be considered the cause of the reduced aqueous formation and low intraocular pressure found in SHR.

A new, less toxic polymerization system for the embedding of soft tissues in glycol methacrylate and subsequent preparing of serial sections

The paper describes a new polymerization system for embedding soft tissues in glycol methacrylate (GMA). The polymerization of GMA is initiated by means of a barbituric acid derivative in combination with chloride ions and dibenzoyl peroxide. The catalyst system contains no aromatic amines which constitutes a toxicological advantage over the commonly employed system of peroxide/aromatic amine. Clear blocks are obtained from which 1-2 micrometers sections are easy to cut. In combination with an appropriate softener, polyethylene glycol 400, serial sectioning may be practiced.

The effects of embedding in water-soluble plastics on the final dimensions of liver sections

This paper describes the morphometric changes liver samples undergo in the course of fixation, dehydration, infiltration and embedding in different mixtures of water-soluble plastics. The plastics used were: three different mixtures of glycolmethacrylate (GMA) and the commercially available material JB4. Buffered formaldehyde fixation did not produce significant morphometric changes in the liver specimens. Dehydration obviously affects the volume of the liver specimen (linear shrinkage about 9.3%). The dehydration is followed by an infiltration phase. During this phase a slight swelling (linear, 2-5%) occurs. The final polymerization of the plastic resulted in a further linear shrinkage of 1-2%. The influence of different technical factors on the stretching of sections of pure plastic and of plastic embedded liver appeared to be considerable. The difference in stretching between 2 and 3 micron sections has been studied. A significant influence of temperature upon section stretching was noted. Sections of all plastic mixtures stretched at a temperature of 293 K showed 3% more linear stretch than at a temperature of 333 K. Differences between the four plastic mixtures are discussed. Correction factors must be used in morphometrical and stereological investigations (see for review: Weibel, 1979). It was concluded that in the application of water-soluble plastics as embedding media it is essential to apply a standardized procedure, particularly in the cutting and stretching phase.