Density-dependent attributes of schooling in small pelagic fishes.

Many small pelagic fishes obligately form schools; some of these schools reach remarkable sizes. Although the school is a fundamental and important ecological unit and is the site of biological interactions such as competition and predation, information on schooling processes in the field remains scarce. Here, we examined the quantitative relationships between population density and school size, the number of schools, and other school characteristics (i.e. packing density, volume, and cross-sectional area) in three species of small pelagic fishes: Japanese anchovy Engraulis japonicus, Japanese sardine Sardinops melanostictus, and chub mackerel Scomber japonicus. We found that school size increased almost linearly with population density, whereas the number of schools and other characteristics increased non-linearly with population density, whereby the rate of increase slowed radically as population density increased. These results indicate that, at low population densities, an increase in density causes an increase in both school size and the number of schools, whereas at higher population densities, an increase in density triggers the formation of larger schools rather than more schools. Furthermore, we found that the shapes of the relationships of all school characteristics with population density differed amongst species. Our results indicate that the schooling behaviour of small pelagic fishes is density-dependent, and responses to changes in density are species-specific. Our results provide insight into how biological interactions such as intra- and inter-specific competition and predator-prey interactions mediate the density-dependent processes that underlie the population dynamics and community structure of small pelagic fishes in marine ecosystems.

Porencephaly in a cynomolgus monkey ( macaca fascicularis ).

Porencephaly was observed in a female cynomolgus monkey (Macaca fascicularis) aged 5 years and 7 months. The cerebral hemisphere exhibited diffuse brownish excavation with partial defects of the full thickness of the hemispheric wall, and it constituted open channels between the lateral ventricular system and arachnoid space. In addition, the bilateral occipital lobe was slightly atrophied. Histopathologically, fibrous gliosis was spread out around the excavation area and its periphery. In the roof tissue over the cavity, small round cells were arranged in the laminae. They seemed to be neural or glial precursor cells because they were positive for Musashi 1 and negative for NeuN and GFAP. In the area of fibrous gliosis, hemosiderin or lipofuscin were deposited in the macrophages, and activated astroglias were observed extensively around the excavation area.

Age Difference in Morphology and Immunohistology inthe Thymus and Spleen in Crl:CD (SD) Rats.

We investigated chronological changes in immunohistochemical phenotyping in the thymus and spleen in Crl:CD rats up to the age of about one year. In the thymus, T cells increased markedly from 3 to 4 weeks of age. Proliferating cells also increased markedly at these points. B cells tended towards an increase with age. In the spleen, white pulp increased until 9 weeks of age and remained fairly stable thereafter. In the periarteriolar lymphoid sheath and marginal zone, T cells gradually increased until 9 weeks of age and became almost flat thereafter. In the lymph follicle, T cells increased with age. B cells tended towards an increase with age in all areas of the spleen. It was concluded that development of the thymus was most marked from 3 to 4 weeks of age and that both the thymus and spleen had matured by 9 weeks of age.

Quantitative analyses of lymphoid tissue in the spleen, lymph nodes and Peyer's patches in cynomolgus monkeys.

To clarify the morphological characteristics of the cynomolgus monkey immune system, we analyzed quantitative data on their lymphoid organs. Spleens, major lymph nodes and Peyer's patches were sampled from cynomolgus monkeys, and the lymphoid follicle and germinal center areas and percentages of CD3- and CD20-positive areas were calculated. All the organs analyzed showed large interindividual variations in the sizes of lymphoid follicles and germinal centers. Lymphoid follicle in the spleen, submandibular lymph nodes and Peyer's patches showed no marked difference in size. Germinal center size in the mesenteric lymph nodes and Peyer's patches were significantly smaller than those in the spleen. Areas containing T cells were largest in the lymph nodes, while those containing B cells were largest in the spleen and Peyer's patches. The mean size of the splenic lymphoid follicle in cynomolgus monkeys is larger than that in rats and similar to that in humans. Based on the large individual variation and the characteristics of lymphoid organs, it is important to use cynomolgus monkeys in standard toxicity studies. Taking advantage of the characteristics of each species enables reliable evaluation of the immunologic system in standard toxicity studies.

Bilateral cataract in a cynomolgus monkey.

Severe bilateral cataract was found in a 7 year-old naïve female cynomolgus monkey (Macaca fascicularis) 3 months before necropsy. During macroscopic examination, severe opacity and thinning of the lens were observed in both eyes. Histopathology revealed that the lens nuclei and majority of cortex lens fibers had disappeared and become excavated, while the lens fibers in the subcapsular area were swollen and distorted. Other observations included atrophy and vacuolation in the lens epithelial cells and proliferation of spindle cells and collagen fiber beneath the anterior capsule of the right eye. Immunohistochemical staining of these spindle cells revealed the presence of vimentin, cytokeratin and α-smooth muscle actin (α-SMA), which were considered to be derived from lens epithelial cells. This is a rare case of spontaneous, bilateral, hypermature cataract in a cynomolgus monkey.

Focal nodular hyperplasia in the livers of cynomolgus macaques (macaca fascicularis).

Two cases of spontaneous focal hepatic hyperplasia were observed in young female cynomolgus macaques (Macaca fascicularis). Grossly, a single raised nodule was observed in the left hepatic lobe. Histopathologically, the nodule compressed surrounding normal tissue; however, the hepatic cords within the nodule continued to those in the nor mal area except in part. Extensive fibrosis and absence of a normal hepatic triad were observed in the nodule. Thin fibrous septa radiating from the dense central stellate scarring and distended vessels were apparent in one animal. Hepatocytes in the nodule lacked cellular atypia, showed frequent PAS-positive eosinophilic inclusions in the cytoplasm and showed higher positive ratios for PCNA. The present cases resembled focal nodular hyperplasia reported in humans and a chimpanzee.

Age-related lesions in the cerebrum in middle-aged female cynomolgus monkeys.

Alzheimer's disease (AD) in humans is a progressive neurogenic disease that can be linked with such characteristic pathological findings in the cerebrum as senile plaques (SPs), neurofibrillary tangles (NFTs), cerebral amyloid angiopathy (CAA), and neuronal loss. In the present study, the authors investigated the age-related morphological changes in 12 middle-aged and 12 young cynomolgus monkeys. Low numbers of neurons and astrocytes in the hippocampal region in cynomolgus monkeys accompanied ageing, and there was a high number of microglial cells; however, no clearly neurotoxic abnormalities due to beta-amyloid were noted before the age of 20 years. The onset of SPs and CAA in the cerebrum in cynomolgus monkeys can occur before the age of 20 years. SPs were almost all categorized as diffuse plaques (DPs); they did not have amyloid cores and were unaccompanied by neuritic degeneration. In cynomolgus monkeys, SPs (DPs) occur before the appearance of CAA. From the above, it was concluded that cynomolgus monkeys showed pathological changes due to ageing similar to those related to Alzheimer's disease in humans, even before they were 20 years old.

Thirteen-week Intravenous Toxicity Study of a Novel Humanized Anti-Human Death Receptor 5 Monoclonal Antibody, CS-1008, in Cynomolgus Monkeys.

CS-1008, a humanized monoclonal antibody that is agonistic to human death receptor 5, was intravenously administered to cynomolgus monkeys twice a week for 13 weeks at 3 different dose levels (5, 15 and 42 mg/kg) in order to evaluate its potential toxicity. A control group received phosphate buffered saline containing 0.01% polysorbate 80. Each of the 4 groups consisted of 3 male and 3 female cynomolgus monkeys. No animal in any group died during the dosing period. No toxic changes in clinical signs, food consumption, body weight, electrocardiography, ophthalmology, urinalysis, hematology, blood chemistry, gross pathology, organ weights or histopathology were noted in any group during the dosing period. In the toxicokinetic analysis, the values for the maximum concentration of CS-1008 in plasma and the area under the curve generally increased with increasing dose. No clear differences in the toxicokinetic parameters or profiles were observed between the sexes. Development of anti-CS-1008 antibodies was not detected in any sample. The no-observed adverse-effect level (NOAEL) of CS-1008 in cynomolgus monkeys under the conditions of this study was concluded to be 42 mg/kg in both sexes, when administered intravenously twice a week for 13 weeks. This study supports the development of CS-1008 as a therapeutic biopharmaceutical.

Keratoconus in a cynomolgus monkey.

In a seven-year-old male cynomolgus monkey, erythema of the upper eyelid and forehead and corneal opacity, edema and conical protrusion in the eye were observed. At necropsy, ophthalmological and serological examinations revealed binocular corneal opacity and conical protrusion and a high IgE level, respectively. Thinning of the epithelium and stroma of the cornea were noted histopathologically. At the center of the corneal epithelium, the number of epithelial cells was reduced, their cytoplasm was poorer and the basal cells were flatter than at the periphery. Bowman's membrane was folded with partial loss or breakage. Collagen fibers were compacted or disarranged, and the keratocytes were increased in the stroma, with focal pyknosis or loss of the endothelium and folding of Descemet's membrane. Electron microscopical examination revealed atrophy of the corneal epithelial basal cells. This is the first report of a case of keratoconus in a cynomolgus monkey.

Effect of a Large Dose of Di (2-ethylhexyl) phthalate (DEHP) on Hepatic Peroxisome in Cynomolgus Monkeys (Macaca Fascicularis).

To elucidate the effect of a large dose of di (2-ethylhexyl) phthalate (DEHP), a plasticizer and peroxisome proliferator-activated receptor-α (PPARα) agonist, on hepatic peroxisomes, we orally administered 1,000 mg/kg/day, once daily, to 3 male and 4 female cynomolgus monkeys for 28 days consecutively. Light-microscopic and electron microscopic examinations of the liver were carried out in conjunction with measurement of the hepatic fatty acid ß-oxidation system (FAOS), carnitine acetyltransferase (CAT) and carnitine palmitoyltransferase (CPT) activities, which are peroxisomal and/or mitochondrial enzyme activities. Electron microscopically, enlargement of the mitochondria was observed with lamellar orientation of the cristae along the major axis. Although the number of peroxisomes showed a tendency to increase when compared with those in a biopsied specimen before treatment, no abnormality in morphology was observed. A slight increase in CPT activity was noted at termination. No changes were noted in hepatic FAOS or CAT activity. In conclusion, although repeated oral treatment of cynomolgus monkeys with a large dose of DEHP induced a subtle increase in the numbers of peroxisomes with slight enlargements of the mitochondria, this low-sensitivity response to peroxisome proliferators in cynomolgus monkeys was considered to be closer to the response in humans than that in rodents.

Malignant myoepithelioma with a squamous epithelial component in the mammary gland of a cynomolgus monkey.

A solid mass arising from the mammary gland was found in a 7-year-old female cynomolgus monkey. Histologically, the mass consisted of 2 components: spindle-shaped or ovoid sarcomatous cells and squamous epithelial cells. Metastatic nodules noted in the lung, liver and the gallbladder had the same histological features as the mammary mass. Immunohistochemistry revealed that the sarcomatous cells were positive for alpha-smooth muscle actin (alpha-SMA), vimentin, calponin, S-100 protein, epithelial membranous antigen (EMA), cytokeratin (large spectrum) and cytokeratin 14 (CK 14) in the cytoplasm, and p53, erbB-2 and progesterone receptor in the nuclei, but negative for desmin and estrogen receptor. The squamous epithelial cells were positive for EMA, cytokeratin (large spectrum) and CK 14, but negative for the rest. Both sarcomatous and squamous epithelial components were negative for glial fibrillary acidic protein (GFAP). Based on histological and immunohistochemical features, the present case was diagnosed as a malignant myoepithelioma with a squamous epithelial component in the mammary gland with distant metastases.

Barrier function of microvessels and roles of glial cell line-derived neurotrophic factor in the rat testis.

The expression and localization of glial cell line-derived neurotrophic factor (GDNF) and its receptor GFR alpha1 in the testis were examined, because the blood-testis barrier is a well-known tissue barrier and we previously reported that GDNF reduced the endothelial permeability of the blood-brain barrier (BBB). Five minutes after intravenous injection of Evans blue (molecular weight, 960.6) or fluorescent dextran (molecular weight 10000 and 70000), Evans blue was observed outside microvessels of the testis, whereas the fluorescent dextran was not. Immunohistochemically, GDNF was detected in alpha-smooth muscle actin-positive cells around the seminiferous tubules and in microvessels. On the other hand, GFR alpha1 was detected in endothelial cells in the interstitial space, as well as in spermatocytes. Although occludin was positive in Sertoli cells and endothelium, claudin-5 was localized only in the endothelium of the microvessels. Thus, it became very clear that the microvessels in the testis possessed relatively impermeable tight junctions, and that the alpha-smooth muscle actin-positive cells secreted GDNF, which receptor was expressed in endothelial cells. Because this relation between GDNF and GFR alpha1 is similar to that observed in the BBB, we hypothesize that GDNF is a general regulator of tight junctions of the endothelium forming a blood-tissue barrier in a paracrine fashion.