Bacterial translocation is defined as the passage of viable bacteria from the gastrointestinal (GI) tract through the mucosal epithelium to other sites, such as the mesenteric lymph nodes, spleen, liver and blood. This paper reviews results from animal models utilized to obtain information concerning the defense mechanisms opera-ting in the healthy host to confine bacteria to the GI tract. Gnotobiotic and antibiotic-decontaminated mice colonized with particular bacteria demonstrated that the indi-genous GI flora maintains an ecologic equilibrium to prevent intestinal bacterial overgrowth and translocation from the GI tract. Studies with athymic (nu/nu) mice, thymus-graf ted (nu/nu) mice, neonatally thymectomized mice, and mice injected with immunosuppressive agents demonstrated that the host immune system is another defense mechanism inhibiting bacterial translocation from the GI tract. Ricinoleic acid given orally to mice disrupted the intestinal epithelial barrier allowing indigenous bacteria to translocate from the GI tract. Thus, bacterial translocation from the GI tract of healthy adult mice is inhibited by : (a) an intact intestinal epithelial barrier, (b) the host immune defense system, and (c) an indigenous GI flora maintaining ecological equilibrium to prevent bacterial overgrowth.
Deficiencies in host defense mechanisms act synergistically to promote bacterial translocation from the GI tract as demonstrated by animal models with multiple alterations in host defenses. Bacterial translocation occurred to a greater degree in mice with streptozotocin-induced diabetes, mice receiving nonlethal thermal injury, and mice receiving the combination of an immunosuppressive agent plus an oral antibiotic than in mice with only a primary alteration in host defenses. The study of bacterial translocation in these complex models suggests that opportunistic infections from the GI tract occur in discrete stages. In the healthy adult animal, bacterial translocation from the GI tract either does not occur or occurs at a very low level and the host immune defenses eliminate the translocating bacteria. Bacterial translocation does take place if one of the host defense mechanisms is compromised, such as a deficiency in the immune response, bacterial overgrowth in the intestines, or an increase in the permeability of the intestinal barrier. In this first stage, the bacteria usually translocate in low numbers to the mesenteric lymph node, and sometimes spleen or liver, but do not multiply and spread systemically. Bacteria translocate to other organs includ-ing the blood and peritoneal cavity, however, in animals exhibiting multiple alterations in their defense mechanisms, such as immunodef iciency in combination with bacterial overgrowth. In the third stage, the alterations in host defenses are severe enough to allow the translocating bacteria to produce septicemia and death. Thus, bacterial translocation from the GI tract is an important early event in the pathogenesis of certain opportunistic infections.

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The implantation traces of early embryonal death and abortion in rats induced by some drugs were studied. Early embryonal death and abortion were caused by intraperitoneal injection of 15 mg/kg of busulfan on the 7th day of gestation or 40 mg/kg of 6-mercaptopurine on the 7th and 8th day of gestation. The observation period and staining of the implantation traces were investigated. 1. Early dead embryos and placentas were delivered between the 20th and 24th day of gestation. These were eaten by the dams. 2. The implantation traces of abortion or early embryonal death, and those of normal delivery were able to be identified up to the 120th day and 500th day after extraction, respectively. The implantation traces of abortion were smaller in the three experimental groups. 3. All kinds of implantation traces were stained distinctly with 10% ammonium sulfide, 0.2% sodium hydroxide and 2% potassium ferrocyanide. In this staining method, sodium hydroxide has an excellent effect on the staining of implantation traces. 4. Specimens washed in water after being stained with sodium hydroxide and fixed in formalin can be preserved without discoloration for a long period of time.

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Clinico-pathological and parasitological studies have been performed on spontaneous and experimental coccidiosis in guinea pigs. Among 11, 244 Hartley guinea pigs purchased from suppliers during 1968, 410 (3.6 %) of the animals had diarrhea due to coccidiosis. The incidence rate was high in the spring and fall with a mortality rate of 14.4 per cent. A particularly high number of fatal cases were found in the spring. In experimentally induced coccidiosis, clinical signs observed were diarrhea, dehydration, weight loss and death. The diarrhea developed in all animals on the eleventh day after infection and continued for one to five days. Food and water intakes were markedly reduced after the appearance of diarrhea, followed by anorexia and dehydration. Correlating with the appearance of diarrhea was a striking drop in body weight of the guinea pigs. Death usually occurred on the third to fifth day after the onset of diarrhea. The mortality rate was 30 per cent. The major macroscopic findings were characterized by a markedly thickened wall from the ascending to the descending colon and gelatinous edema of the mesenterium of the spiral of the ascending colon. Histologically, there was marked hyperplasia of the mucosal epithelium in the colon and numerous coccidia at different stages of development within the mucus membrane. In the advanced stages of the disease, there was degeneration and desquamation of the epithelia, marked edematous change and infiltration of neutrophil leukocytes and lymphocytes into the lamina propria and submucosa, many oocysts in the lumen of the intestine and in the intestinal glands. The oocysts were ellipsoidal or subspherical in shape with no micropile and measured 20 by 17μm. The sporulation time of the oocysts was two to three days. The prepatent period was eleven days after infection. The coccidia in the guinea pigs were identified as Eimeria caviae.

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An epizootiological survey has been carried out on naturally occurring coccidiosis in Hartley guinea pigs (weight, 250g) purchased by the National Institute of Health, Tokyo during the period 1964 to 1982. Coccidial infections in breeding colonies of guinea pigs were observed very frequently in weaned animals but scarcely in adult and suckling animals. Oocysts of Eimeria caviae were detected in 53.8% of the 7, 162 fecal samples collected from transportation boxes and coccidiosis occurred in 39% of the 1, 461 dead or culled animals obtained during the routine one week quarantine period. In the period 1964 to 1971, particularly high rates of prevalence of oocysts, between 55-86%, and incidence of coccidiosis, between 55-76%, were observed. These rates were clearly reduced in the period 1972 to 1982, with a lower rate of isolation of oocysts ranging from 14-48% and les than 20% incidence of coccidiosis (except in 1981 and 1982) . The monthly fluctuation of occurrence rates of oocysts and clinical coccidiosis differed over the period of study. From 1964 to 1971, the high prevalence of oocysts was consistently observed accompanied by a bimodal pattern of incidence of coccidiosis in April (85 %) and October (78 %) . In the period 1972 to 1982, both parameters showed a single peak, for prevalence of oocysts in June (60.7%) and for incidence of coccidiosis in May (45 %) . Oocysts in feces disappeared in February and March and coccidiosis occurred irregularly in 1981 and 1982. Considering incidence in individual colonies, almost all colonies showed a high prevalence (70-100%) of isolation of oocysts and a high proportion (70-100%) of occurrence of coccidiosis in the period 1964 to 1971. Thereafter, coccidial infections and especially the outbreak of coccidiosis decreased. We conclude that since 1972 improved care and management of breeding colonies has probably resulted in a much lower prevalence of coccidial infection in weaned animals.

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Disorders in a beagle breeding colony were discussed, based on 472 clinical charts made in 1974-1983. In 201 neonates less than a week old, hypothermia associated with pneumonia was mostly seen. In 31 puppies from one week to two months old and in 46 young dogs from two months to a year old, pneumonia, canine parvovirus infection, dermal abscess and dermatosis were mostly found. In 91 dogs aged from one to five, trauma, intervertebral disc protrusion, dermal abscess, dystocia, claudication and othematoma were frequently noted. In 103 animals over five years old, intervertebral disc protrusion, tumors, abscess, trauma and othematoma were observed most often.

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Murine antibody against Mycoplasma pulmonis (Mp) was detected sensitively and specifically in experimentally and naturally infected animals by an enzymelinked immunosorbent assay (ELISA), using urease conjugated antimurine immunoglobulin. More than 98% of the experimentally infected mice and rats exhibited positive reaction in the ELISA two or more weeks after infection, and the titer remained for a prolonged period (up to one year) after infection. However, we failed to detect antibody in the sera of one-week-postinfected animals. Mice and rats from breeding colonies were tested with the ELISA and compared with isolation of Mp from the respiratory organs. Positive reactions were shown in the ELISA using the sera from 91% of the mice and 98% of the rats from which the organisms were isolated. Conversely, 97% of the mice and 78% of the rats among Mp-free animals showed negative results in the ELISA. The sensitivity and specificity of the complement fixation test, which has been used widely for Serodiagnosis of Mp-infection, were apparently lower compared to those of the ELISA. From these results, the ELISA was found to be available for the serodiagnosis of Mp-infection in mice and rats.

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We have experimentary developed a photoperiod-controlable clean rack for SPF rats. The effectiveness of this clean rack in preventing the infection was attested to by the fact that the SPF rats and nude mice housed in this rack maintained SPF conditions after six months. And we investigated circadian rhythns of water intake and blood corticosterone levels in rats kept in the rack under various lighting conditions. Both rat groups under diurnal and reversed lighting conditions manifested significant increase in both water and blood corticosterone levels, showing a reversed phase relationship of the circadian rhythms between the two groups. These facts indicate the usefulness of the rack newly developed in the studies on circadian rhythms, reproductive physiology and behavior.

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The period of gestation of the volcano rabbit (Romerolagus diazi) was measured. Females were cohabited within one hour after confirmation of coitus or were separated from the males after cohabiting overnight. In 12 females which gave birth 20 times in total, the gestation period was 39 days in 35%, 40 days in 50% and 41 days in 15% ; 85% of animals showed a gestation period of 39 or 40 days.

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Pleomorphic adenoma of rat salivary gland is extremely rare, and culture of cells obtained from rat salivary gland tumors has not been reported. We have established a long-term cell line from a pleomorphic adenoma of a Sprague-Dawley rat submaxillary gland. The pleomorphic adenoma was composed of oval or spindle-shaped cells occasionally forming a small duct. Alcian blue-positive intercellular matrices, consisting mainly of glycosaminoglycans, were abundant. The cultured cells showed characteristics similar to those of the original tumor. This cell line should be useful for biological and biochemical studies of glycosa-minoglycan-synthesis of pleomorphic adenoma cells.

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A histochemical study of proteins, lipids and polysaccharides was carried out in the oocytes of Japanese monkey (Macaca fuscata) during development of follicles. There were a small number of protein granules reactive to acrolein-Schiff in the cytoplasm of oocytes from primordial, secondary and vesicular follicles, while there were no lipid droplets, granules of neutral polysaccharides or acid polysaccharides in the cytoplasm. Proteins reactive to acrolein-Schiff, neutral polysaccharides reactive to periodic acid-Schif f and acid polysaccharides stainable with alcian blue were observed in the zona pellucida of the oocytes of secondary and vesicular follicles. The zona pellucida contained sudanophilic lipids composed of neutral fats and lipoids, besides the proteins and polysaccharides.

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Mixtures of cholesterol esters were extracted from the blood plasma of mouse (C3H/He, C57BL/6J and Jcl: ICR), rat (Wistar) and rabbit (JW-NIBS/Rabiton) and purified by thin-layer chromatography. Fatty acid moieties of the esters were methylated with BF₃-methanol and analyzed quantitatively by gas chromatography. Although linoleate was most abundant (over 30% of the total esters) and myristate was found only in traces, the composition of the esters varied markedly among the species. Mice had 15.3 to 17.4% of arachidonate, but only a trace of linolenate and no stearate. In rats, arachidonate and linoleate were found in almost equal quantities, but stearate, linolenate and docosahexae-noate were present in only trace amounts. Rabbits had more palmitate and oleate and less arachidonate and eicosapentaenoate than the other two animals, but no docosahexaenoate.

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Three thousand and five apparently healthy cynomolgus monkeys (Macaca fascicularis) were examined for the finding of the anterior part of the oculi by using an ophthalmoscope. One drop of the mixed solution of 0.5% tropicamide and 0.5% phenylephrine hydrochloride was instilled into each eye of the animal. Then, those monkeys were anesthetized with ketamin-HCl at the dose level of 10 mg/kg B. W.. One monkey had opaque membranes of tan to brown color, extending from some part of collarette of the iris to the other part of collarette like the network over the pupil. This finding was diagnosed to be bilateral persistent pupillary membranes. Further breeding studies will be carried to determine if this case in hereditary.

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An epizootic form of Tyzzer's disease was experienced in a rearing facility of laboratory rats with an infectivity and morbidity of 36 to 80% and 5 to 30%, respectively. With liver tissue from an affected rat, a spore-forming causative agent was successfully transmitted to other rats by oral inoculation in association with cortisone, producing 106 to 107 spores/g liver tissue.

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Spontaneous arthritis was found in 19 of 55 Rowett hooded strain rats with rnu gene. Most cases were in the male rnu / rnu (15/19) but a few occurred in the male rnu / + (3/10) and female rnu / rnu (1/8) . The lesions were first noted as reddened swelling due to exudative inflammation of periarticular soft tissues including synovial membranes in the tarsal and/or carpal joints. Most of the affected animals cured leaving slight induration but in a few male rnu / rnu ankylosis with pannus formation and exostosis developed. No sign of mycoplasmal or bacterial infection was noticed in the colony.

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