Three-dimensional reconstruction of deferent ducts papillae in urogenital duct system of the male rat.

BACKGROUND: The rodent ejaculatory ducts penetrate the male accessory sex gland complex and open into the urethra, anatomically similar to humans. Although the deferent ducts papillae in rodents have been described at the distal end of deferent ducts, they are absent in humans, and their detailed morphology has been unclear. METHODS: The detailed anatomical structures of the distal end of the deferent ducts of rats were investigated by the computer assisted three-dimensional reconstruction analysis using serial sections of the male accessory sex gland complexes in rats. RESULTS: The present study revealed that a pair of deferent ducts enters the ventral side of the male accessory sex gland complex, runs caudally parallel to the urethra, and then exits at about midsection of the dorso-lateral lobe of prostate. They are composed of mammilliform papillae, called the deferent duct papillae, which dorso-laterally protrude into the duct lumen from intra-ventral portion of the main duct of ampullary gland. The internal surface of the deferent ducts papillae is composed of ciliated columnar epithelium continuous from the deferent ducts, while their external surface is composed of the columnar secretory epithelium of the ampullary glands. Sphincter muscles were not observed in the deferent ducts papillae, while their lamina propria were occupied by many arterial or venous capillaries. CONCLUSIONS: The deferent ducts of rat terminated at the deferent ducts papillae that located at the main duct of ampullary glands that drained into the urethra. The deferent ducts papillae might be controlled by the expansion/contraction of well-developed papillary mucosal capillary vessels.

Adenocarcinoma of the ampullary glands of the ductus deferens in a Sprague-Dawley rat.

Spontaneously occurring proliferative lesions of the male accessory sex glands are infrequent in various strains of rats. In rodents, the ampullary glands are embedded in the prostate. Although 2 spontaneous cases of atypical hyperplastic lesions at the ampullary gland were previously described in Wistar rats, adenocarcinoma and/or adenoma in this gland have not been reported. This study describes adenocarcinomas in the bilateral ampullary glands in a 52-week-old intact male Sprague-Dawley rat housed as part of a control group in a toxicological experiment. At necropsy, the body weight (644.4 g) and the weight of the prostate with ampullary gland (2.75 g) were similar to others of the same control group, and it had a normal gross appearance. Histopathologically, both ampullary glands revealed microinvasive adenocarcinoma without vascular invasion. The morphological characteristics of the neoplasm varied in different regions of the gland. Other parts of the male accessory sex glands did not show proliferative lesions.

Comparative anatomy of the ophthalmic rete and its relationship to ocular blood flow in three species of marine mammal.

OBJECTIVE: To examine the blood supply to the eyes of bottlenose dolphin (Tursiops truncatus), spotted seal (Phoca largha), and California sea lion (Zalophus californianus). Emphasis is placed on exploring the anatomic function in the context of aquatic life. PROCEDURE: Methyl methacrylate casts were prepared and studied using a scanning electron microscope. Infrared images of the eye were recorded using a thermocamera. RESULTS: In all three marine species, blood is supplied to the ophthalmic rete. The main source of blood supply to the rete is the basilar rete via the spinal rete in the dolphin and via the ophthalmic artery in the seal and sea lion. The retinal and choroidal arteries are derived from the rete. The dolphin rete showed a very well-developed arterial network occupying most of the orbit. The rete in pinnipeds was less developed with several entwining arteries, unlike that in cetaceans. Thermographic examination revealed that the eye shows a higher degree of thermal emission than adjacent areas of the skin in these 3 species. DISCUSSION: The role of the rete in aquatic mammals appears to conserve ocular temperature so that the appropriate operating temperature for photoreceptors and ocular muscles can be maintained in a cold ambient temperature. Additionally, the rete might have a flow-damping effect by maintaining resistance to blood flow in the orbit. This study highlights the special nature of ocular vascular anatomy and function that enabled the unique adaptation of aquatic mammals to life in aquatic habitats.

Atypical Leydig cell hyperplasia in adult rats with low T and high LH induced by prenatal Di(n-butyl) phthalate exposure.

The present study describes atypical Leydig cell (LC) hyperplasia in 20-week-old Sprague-Dawley rats with low testosterone and high luteinizing hormone levels after prenatal administration of 100 mg/kg/day di(n-butyl) phthalate on days 12 to 21 postconception. Light microscopy revealed LC hyperplasia surrounded by severely degenerated seminiferous tubules. Aggregated LCs had large ovoid nuclei with nucleoli and abundant eosinophilic cytoplasm. Immunohistochemical analysis showed expression of proliferating cell nuclear antigen and vimentin in many hyperplastic LCs. Electron microscopy revealed atypical nuclei, abundant free ribosomes, stripped rough endoplasmic reticulum, intermediate-size filaments, elongated cytoplasmic filopodia, atypical tight junctions, and cilia formations, but smooth endoplasmic reticulum was scarcely observed.

Full-term development of rats from oocytes fertilized in vitro using cryopreserved ejaculated sperm.

For preservation of rat spermatozoa, the general-purpose method requires that the male be sacrificed for collection of spermatozoa from the epididymides. However, it would be highly useful if the ejaculated spermatozoa could be successfully cryopreserved and the frozen-thawed spermatozoa used for in vitro fertilization, since this would allow the genetically valuable rats to be maintained alive rather than sacrificed. The aim of the present study was to clarify whether ejaculated rat spermatozoa could be successfully cryopreserved and fertilized in vitro. The motility and viability of frozen-thawed ejaculated spermatozoa were similar to those of frozen-thawed epididymal spermatozoa (around 10%). The percentage of acrosomal integrity in epididymal spermatozoa was significantly higher than that in ejaculated spermatozoa after freezing/thawing. The level of capacitation-associated protein tyrosine phosphorylation in frozen-thawed ejaculated sperm was slightly increased at 5h. When the frozen-thawed ejaculated spermatozoa were used for in vitro fertilization, the percentages of fertilization, pronuclear formation, and development to the 2-cell stage (26.5%, 23.0%, and 91.0%, respectively) were similar to those of frozen-thawed epididymal spermatozoa (19.4%, 15.0%, and 84.1%, respectively). However, the rate of blastocyst formation in the ejaculated group was significantly lower than that in the epididymal group (12.0% vs 43.2%). Results from the embryo transfer experiment showed that the proportions of embryos developed to term were similar between the ejaculated (47.7%) and epididymal groups (53.7%). We showed here for the first time that ejaculated spermatozoa can be cryopreserved and the frozen-thawed sperm could be developed to term via in vitro fertilization in rats.

Successful cryopreservation of rat pronuclear-stage embryos by rapid cooling.

Embryo cryopreservation is a valuable tool for efficient production of animals as well as banking of genetic resources. Even though the laboratory rat is one of the most important experimental animals for various research fields, it has been reported that survival and developmental ability of cryopreserved rat embryos are generally low, especially at the early stages. The aim of the present study was to establish rapid cooling method that can be applied for cryopreservation of rat pronuclear-stage embryos using Cryotops (a device). First, optimal equilibration time was examined. Pronuclear-stage embryos were equilibrated in 7.5% ethylene glycol (EG)+7.5% dimethylsulfoxide (DMSO)+20% fetal calf serum (FCS) for 7, 8 or 9 min at 20-22 degrees C and then 15% EG+15% DMSO+0.5M sucrose+20% FCS for 1 min at 20-22 degrees C, being plunged into liquid nitrogen on Cryotops. This established that development to the 2-cell (82.0+/-9.7% to 96.1+/-3.0%) and blastocyst (36.5+/-2.1% to 40.3+/-10.2%) stages in vitro was not influenced by the equilibration time. Furthermore development to term in vivo (56.0+/-4.9%) was equivalent to the rate (54.8+/-6.6%) obtained with control embryos. Taken together, this demonstrated that this method is suitable for the successful cryopreservation of pronuclear-stage embryos in rats.

Development of external genitalia in fetal and neonatal domestic cats.

Development of the external genitalia of fetal and neonatal cat were studied macroscopically, paying attention to the formation of the labia and the sexual differentiation. The female urogenital folds budded from each side of the genital tubercle and, gradually extended to the tip of the genital tubercle by the 6.8 cm stage in crown-rump length. Then, the well-developed urogenital folds ensheathed completely the genital tubercle to form the prepuce of clitoris and the labia, flanking the external opening of vagina as the folds of skin which were equivalent to the labia minora in humans. The genital swellings known to become the labia majora in humans were clearly recognized in the caudolateral region of the genital tubercle during the fetal stage. These swellings became flat and obscure after birth. Thus, in cats the genital swellings did not join to the formation of the labia in the same way as in humans. The sex difference in the external genitalia was first observed at the 3.2-3.3 cm stages. In the male, the anogenital raphe appeared and the caudal portion of the genital swellings moved and fused each other at the caudal region of the genital tubercle. In the female, both features were not easy to observe.

An Assessment of Mutagenic Effect of 3, 3', 4, 4', 5 Pentachlorobiphenyl (PCB126) in Muta Mouse Fetuses.

PCBs are persistent environmental agents that induce multiple impairments in living beings. In this study we used a transgenic mouse model (Muta(TM) Mouse), carrying bacterial lacZ genes for mutation assays and for assessment of the genotoxic effect of PCB126 on fetal mice. Mothers of experimental groups were subjected to a single oral dose of PCB126 (125, 250 and 500 microg/kg) on the 10th day of pregnancy, respectively. Fetuses were autopsied on the 18th day of gestation. Cleft palate was observed in 2 out of 11 fetuses from 3 litters in 500 microg/kg treated group. Other external malformations were not observed. The DNA mutation frequencies (MF) of fetuses in each group were 1.15 +/- 0.24 x 10(-5), 0.90 +/- 0.20 x 10(-5) and 1.08 +/- 0.24 x 10(-5) in fetuses of 125, 250 and 500 microg/kg treated groups, respectively. The MF of controls was 0.81 +/- 0.22 x 10(-5). There were no significant differences among the groups. However, the MF of each treated group was a little highter than that of control group. Possible relationships between PCB and its mutagenic effects in the offspring of mice are discussed.

Microvascular architecture of the rabbit eye: a scanning electron microscopic study of vascular corrosion casts.

The microvasculature of the eyes of 5 rabbits was investigated using scanning electron microscopy on corrosion casts. The study revealed that the pars plana vessels draining blood from the iris and ciliary body coursed directly into the anterior vortex venous system constituting the scleral venous plexus (the venous circle of Hovius). The episcleral vasculature was found to possess a specialized morphology, with channels draining the aqueous humor. The capillaries of the third palpebral, bulbar and palpebral conjunctiva formed a single-layered capillary network approximately parallel to the epithelium and formed a well-developed venous plexus in the stroma. The retina was found to be merangiotic, meaning that vessels were present only in a small part of the retina, extending in a horizontal direction to form bands on either side of the optic disc. Channels representing the aqueous veins that drained blood mixed with aqueous humor were found to derive directly from the suprachoroidal space and communicate with the scleral venous plexus via the anterior vortex veins. The functional significance of the microvasculature of the iris, cilia, retina and choroid is discussed in this report as well. The elaborate microvasculature of the conjunctiva may be a prerequisite for the exchange of nutrients and gasses between the cornea and the vessels across the conjunctival epithelium when the eyelids are shut during sleep, and possibly for the dynamics of eye drop delivery. The scleral venous plexus in rabbits may be analogous to the scleral venous sinus (Schlemm's canal) in rats, primates and humans.

The validity of anesthetic protocols for the surgical procedure of castration in rats.

To achieve surgical anesthesia in animal experimentation, it is necessary to select the appropriate anesthetic protocol by considering its pharmacological properties and the surgical procedure to be performed. However, few studies have investigated the validity of anesthetic protocols under surgical conditions in small rodents. The present study aimed to clarify the pharmacological properties of 4 anesthetic protocols during the surgical procedure of castration in rats. Eight-week-old male Wistar rats were anesthetized with anesthetics, including the combination of ketamine and xylazine (K/X), the combination of medetomidine, midazolam, and butorphanol (M/M/B), isoflurane, and sevoflurane. Castration was performed under each anesthesia, and anesthetic depth and times were assessed, as were vital signs. The injectable anesthetics were investigated at standard and high doses. The concentration of inhalant anesthetics was adjusted to 1.5 minimum alveolar concentration (MAC). K/X at both doses demonstrated sufficient anesthetic depth with rapid induction and recovery. However, bradycardia and hypothermia were prominent in high-dose K/X, indicating that the standard-dose is more appropriate for surgical anesthesia in castration procedures. M/M/B demonstrated high anesthetic sensitivity variation in individual animals. In contrast to injectable anesthetics, inhalant anesthetics provided stable anesthetic depth with less cardiorespiratory influence. Sevoflurane did not lead to a significant decrease in rectal temperature during the anesthetic period. Results of the present study revealed the optimal dose and pharmacological features of several anesthetic protocols for castration, and may contribute to the standardization of surgical anesthesia in rats.

The anti-inflammatory action of maropitant in a mouse model of acute pancreatitis.

The neurokinin 1 receptor (NK1R) plays an important role in the pathogenesis of acute pancreatitis (AP). Maropitant is an NK1R antagonist that is widely used as an antiemetic in dogs and cats. In the present study, we investigated the anti-inflammatory action of maropitant in a mouse model of AP. AP was induced in BALB/c mice by intraperitoneal administration of cerulein, and maropitant was administered subcutaneously at a dose of 8 mg/kg. We assessed the mRNA expression levels of NK1R and substance P (SP) in the pancreatic tissue via real-time reverse transcription polymerase chain reaction. In addition, the effect of maropitant on plasma amylase, lipase, and interleukin-6 (IL-6) levels was measured in each mouse. Inflammatory cell infiltration in the pancreas was assessed by myeloperoxidase (MPO) staining. Our results showed that AP induction significantly elevated the mRNA expression of SP in the pancreatic tissue. Treatment with maropitant significantly lowered plasma amylase and IL-6 levels. In addition, treatment with maropitant inhibited the infiltration of MPO-positive cells in the pancreas. The present study suggests that maropitant possesses an anti-inflammatory activity, in addition to its antiemetic action.

Fertility of spermatozoa cryopreserved with 2% acetamide or glycerol through artificial insemination in the Japanese white rabbit.

The rabbit is considered to be a valuable laboratory animal. We compared 2% acetamide and glycerol as cryoprotectants in egg-yolk diluent for ejaculated Japanese white rabbit spermatozoa to improve sperm cryopreservation methods. Fertility through artificial insemination, forward progressive motility and plasma membrane integrity of the post-thaw spermatozoa were examined. The rates of forward progressive motility and plasma membrane integrity of the spermatozoa frozen with acetamide (27.1 +/- 8.3% and 24.5 +/- 6.5%) were significantly (P < 0.05) higher than those of the spermatozoa frozen with glycerol (16.3 +/- 10.9% and 14.3 +/- 7.6%). Though there was no significant difference in the kindling rates, the litter size of females inseminated with spermatozoa frozen with acetamide (6.0 +/- 1.1) were significantly (P < 0.05) higher than those of spermatozoa frozen with glycerol (3.0 +/- 0.4). The results indicate that 2% acetamide has a higher cryoprotective effect than 2% glycerol for sperm cryopreservation in the Japanese white rabbit.

The 5-HT3 Receptor Antagonist Ondansetron Attenuates Pancreatic Injury in Cerulein-Induced Acute Pancreatitis Model.

The 5-hydroxytryptamine-3 receptor (5-HT3R) antagonist ondansetron has been clinically approved as an anti-emetic agent. Recent findings indicate that ondansetron has anti-inflammatory properties. The aim of the present study was to assess the therapeutic action of ondansetron in cerulein-induced acute pancreatitis model. Male-BALB/c mice were used in the present study. Acute pancreatitis was induced by an hourly injection of cerulein. Ondansetron was administered subcutaneously at a dose of 3 mg/kg. The messenger RNA (mRNA) expression of 5-HT3 R in pancreatic tissue was assessed with RT-PCR. Plasma amylase, lipase, and interleukin (IL)-6 levels were evaluated. Pancreatic injury was histopathologically graded, and myeloperoxidase (MPO)-positive cells were counted. 5-HT3R mRNA was expressed in the pancreas. In acute pancreatitis model mice, amylase, lipase, and IL-6 levels were significantly increased in the blood. With ondansetron treatment, these levels were significantly decreased. Histopathological evaluation revealed that ondansetron attenuated the inflammatory damage in acute pancreatitis. The number of infiltrated neutrophils stained by MPO was decreased by ondansetron treatment. In summary, the 5-HT3R antagonist ondansetron attenuated pancreatic injury through its anti-inflammatory action. These findings suggest that ondansetron may potentially be of use for therapy of acute pancreatitis.

Pharmacological properties of various anesthetic protocols in 10-day-old neonatal rats.

In general, the anesthesia in neonates involves high risk. Although hypothermic anesthesia is recommended in rats up to the age of 7 days, neonatal anesthesia for later periods has not been standardized. The present study investigated the pharmacological properties of conventional anesthetic protocols in 10-day-old SD rats. The rats were anesthetized with four anesthetics: a combination of ketamine and xylazine (K/X); a combination of medetomidine, midazolam, and butorphanol (M/M/B); isoflurane; and sevoflurane. Anesthetic depth was scored by reflex response to noxious stimuli. Induction and recovery times were recorded. Vital signs and mortality rate were evaluated for safety assessment. All rats died after administration of K/X at a dose of 60/6 mg/kg, whereas K/X at 40/4 mg/kg resulted in insufficient anesthetic depth, indicating inappropriate for neonatal anesthesia. Although M/M/B at the adult rat dose (0.15/2/2.5 mg/kg) did not provide surgical anesthetic depth, the mouse dose (0.3/4/5 mg/kg) showed sufficient anesthetic depth with relatively stable vital signs. Isoflurane required a long induction period, and caused remarkable respiratory depression and hypothermia, resulted in a 25% mortality rate. In contrast, sevoflurane provided consistent surgical anesthetic depth with rapid induction. Although respiratory rate decrease was markedly observed, all rats survived. Among the anesthetic protocols investigated in the present study, sevoflurane and M/M/B at the mouse dose were recommended for the neonatal anesthesia. Compared with adult rats, the required dose of both anesthetics in neonates was higher, possibly associated with their lower anesthetic sensitivity.

Microvascular anatomy of the pig eye: scanning electron microscopy of vascular corrosion casts.

The microvasculature of the eye of 10 pigs was investigated using scanning electron micrographs of corrosion casts. The ciliary body, iris and bulbar conjunctiva were supplied by the iridociliary ring artery via the long posterior ciliary artery. Capillaries of the ciliary process were of large diameter (23.2-27.5 microm) with an irregular bore, forming a thoroughfare channel draining blood in the ciliary arterioles into the pars plana venous vessels. Arterioles and venules in the iris exhibited a zigzag or spiral features. The third palpebra was supplied by the anterior ciliary artery. The capillary bed of the third palpebra was dense and was formed by many rows of fine hair-pin loops. Capillaries in the bulbar conjunctiva formed a sparse network disposing approximately parallel to the epithelium and formed a well-developed venous plexus, draining into the vortex veins. Retinal arterioles formed a slender and long course to capillaries. Retinal capillaries were extremely thin (3.0-4.0 microm in diameter). The choroid was supplied by the short posterior ciliary arteries. Choroidal arterioles exhibited a thick and short course to the choriocapillaris. The choriocapillaris was flat and sinusoid-like (8.9-13.9 microm in diameter), forming a dense sheet-like network. Blood from the choroid emptied into the episcleral vein via the vortex vein. Blood from the retina was drained by the posterior ciliary veins. The functional significance of this vascular architecture was discussed.

Combining isoflurane anesthesia with midazolam and butorphanol in rats.

Representative inhalant anesthetic agent, isoflurane is commonly used during surgery in rats. However, isoflurane mediates relatively strong respiratory depression. In human and veterinary medicine, sedatives and analgesics are co-administered to complement the anesthetic action of inhalant anesthesia. The present study aimed to establish the novel balanced anesthesia that combines midazolam and butorphanol with isoflurane (MBI) in rats. Male Sprague Dawley rats were divided into 2 groups, and administered either isoflurane monoanesthesia or isoflurane with midazolam (2.5 mg/kg, ip) and butorphanol (2.0 mg/kg, ip). The minimum alveolar concentration (MAC) in each group was evaluated. Induction and recovery times were measured in each group. Adverse reactions during induction were also recorded. In each group, vital signs were assessed for 1 h under 1.5×MAC of isoflurane. Instability of vital signs was assessed under each anesthesia by calculating coefficient of variance. Compared with isoflurane monoanesthesia, MBI anesthesia caused 32% MAC reduction (isoflurane monoanesthesia: 1.30 ± 0.09%, MBI 0.87 ± 0.08%, P<0.05). MB premedication mediated smooth sedating action with low incidence of adverse reactions such as urination and defecation. Isoflurane monoanesthsesia remarkably decreased respiratory rate and saturation O2 (SPO2). In contrast, MBI anesthesia resulted in a relatively stable respiratory rate without decreases in SPO2 during the anesthetic period. In summary, MB premedication is effective for attenuating respiratory depression induced by isoflurane, and achieving smooth induction. This anesthetic protocol serves as a novel option for appropriate anesthesia in rats.

Male rats exposed in utero to di(n-butyl) phthalate: Age-related changes in Leydig cell smooth endoplasmic reticulum and testicular testosterone-biosynthesis enzymes/proteins.

This study investigated the age-related (i.e., weeks 5, 7, 9, 14 and 17) morphological changes of Leydig cell smooth endoplasmic reticulum (LCs-ER) and testicular testosterone biosynthesis/protein expression in rats in utero exposed to di(n-butyl) phthalate (DBP) (intragastrically; 100mg/kg/day) on days 12-21 post-conception. Ultrastructural observations revealed the LCs-ER of the DBP group were non-dilated until peri-puberty, and thereafter decreased and disappeared. RT-PCR and Western blotting analyses revealed that StAR and P450scc levels in the DBP group were significantly lower at 5 and 7 weeks compared with the vehicle group but became similar during weeks 9-17. Although 3ß-HSD, P450c17, and 17ß-HSD levels of mRNA and protein in the DBP group were similar to the vehicle control group at 5 and 7 weeks of age, they were significantly lower during weeks 9-17. In utero DBP exposure results in age-related LCs-ER changes corresponding to reduction of testicular testosterone biosynthesis enzymes/associated proteins.

Hypervitaminosis A resulting in DNA aberration in fetal transgenic mice (Muta Mouse).

Treatment with excessive amounts of Vitamin A during maternity induces fetal malformations. However, it is unclear whether these malformations are due to gene mutations or not. Using transgenic mice (containing lacZ gene showing beta-galactosidase enzymatic activity), we planned to observe whether gene mutations occur in the fetal tissues after treatment during maternity with Vitamin A (retinol palmitate). On the 11th day of pregnancy, mothers were given 30 mg (group 2), 150 mg (group 3) and 300 mg (group 4) of Vitamin A/kg body weight orally. Fetuses obtained on the 18th day of gestation showed malformations, such as cleft palate, origodactyly, brachydactyly and ectromeria. Most notably, cleft palate occurred dose dependently. The incidental rates were 100% in group 4, 58% in group 3 and 6% in group 2. The number of dead and absorbed fetuses also increased dose dependently with the treatments. DNA (integrated vectors containing lacZ genes) extracted from each fetus showed Vitamin A-induced lacZ mutations, especially in the malformed fetuses. The mutation frequencies were 4.99x10(-5) in group 4, 5.28x10(-5) in group 3 and 4.26x10(-5) in group 2. The frequencies of group 3 were significantly higher (p<0.05) than that of the controls (group 1), 2.79x10(-5). Maternal treatment with Vitamin A (150 mg/kg of body weight) was carried out on the 11th day of pregnancy. Fetuses obtained on the 14th day of gestation showed a much higher incidence of mutation, approximately 8.91x10(-5) (group 6) that was significantly higher (p<0.0001) than those from the controls (group 5), 2.94x10(-5). The present study indicates a possibility that hypervitaminosis A-induced fetal malformation and death might be caused by gene mutations.

A simple method of intestinal anastomosis (ileocolostomy) in rats.

A simple method of ileocolostomy was performed in rats. The colon near the cecum was ligated, including its arteries and veins. Main artery and vein of the cecum were ligated. Then, the cecum was cut out. A longitudinal incision was made on the anti-mesenteric side of the proximal end of the colon, approximately 7-8 mm long. A 21-G needle was inserted toward the incision 2 cm away from the proximal end of the anti-mesenteric side of the colon. A nylon suture was knotted once to the distal end of the ileum and was introduced into the tip of the needle which had previously been passed through the colon. Then, the needle was removed. The suture was pulled to introduce the distal end of the ileum into the colonic lumen. Then, the suture was knotted once on the colon again to fix the ileum to the colon. The incision in the proximal end of the colon was not closed. At the 2nd week after the operation, X-ray examinations demonstrated that the ileocolonic passages with no leakage at the anastomotic site were quite satisfactory. At the 4th week after the operation, there were no macroscopic or microscopic complications at the anastomotic site. The mucosal and serosal epithelia of the ileum and colon continued smoothly. This simple method may be very effective in preparing anastomosis in the gastrointestinal tract, especially in small laboratory animals for nutritional and surgical experiments.

Microvasculature of the retina, ciliary processes and choroid in the North American raccoon (Procyon lotor) eye: a scanning electron microscopic study of corrosion casts.

We have studied the vasculature of the retina, ciliary processes and choroid in the North American raccoon (Procyon lotor), a nocturnal mammal, using light and scanning electron microscopic examination of corrosion casts. We carried out an identical study in the crab-eating macaque (Macaca fascicularis), which forages only during the daytime, in order to compare the ocular vasculature with that of nocturnal mammals. Our observations in raccoons demonstrated a photoreceptor layer associated with rich lymph and a poorly vascularized retina. The meridian region of the eye, which lies in the horizontal plane and pass around the optic disc, had a markedly sparse capillary network. This horizontal sparse vascular band may correspond to a visual streak. Ciliary process capillaries were delicate, and formed a well-developed and compact network. Choriocapillaries were quite thin and formed a coarse capillary network. This contrasted with the dense retinal and well-extended choroidal capillary networks noted in the macaques. Our findings suggest that the sparse retinal capillary network in raccoons is extremely beneficial for photon capture, thereby allowing the raccoon to see well at night, as the retinal vessels restrict the inflow of photons toward the photoreceptors. The well-developed lymph probably compensates for the sparse retinal capillaries and choriocapillaries and nourishes the retina in the nocturnal raccoon.