Microfibrils: a constitutive component of reticular fibers in the mouse lymph node

Summary Fibrous components other than collagen fibrils in the reticular fiber of mouse lymph node were studied by electron microscopy. Bundles of microfibrils not associated by elastin and single microfibrils dispersed among collagen fibrils were present. The diameter of the microfibrils was 13.29±2.43 nm (n=100). Elastin-associated microfibrils occurred at the periphery of the reticular fiber. Elastin was enclosed by microfibrils, thus forming the elastic fiber, which was clearly demonstrated by tannic acid-uranyl acetate staining. In the reticular fiber of lymph nodes, the elastic fiber consisted of many more microfibrils and a small amount of elastin. These microfibrils, together with the collagen fibrils, may contribut to the various functions of the reticular fibers.     

Ultrastructural study of a cytoplasmic bridge connecting a pair of erythroblasts in mice

Summary A unique cytoplasmic connection between erythroblasts was studied by electron microscopy in mouse hemopoietic tissues (fetal liver, fetal and neonatal spleen and adult bone marrow). Many pairs of interphase erythroblasts were connected by a cytoplasmic bridge that was very thin and sometimes long in comparison with telophase bridges. The stage of maturation of the cells in a pair was similar. Small numbers of microtubules ran along the cytoplasmic bridge; a mid-body was not seen. The plasma membrane at approximately the middle of the bridge bulged to form a ring-shaped ridge filled with dense amorphous substances; this was called a bulging ring. Thus, the cytoplasmic bridge between erythroblasts did not morphologically correspond to the telophase bridge in the usual cytokinesis. Cytoplasmic bridges were observed in various differentiating stages of erythroblasts, whereas other cell types of the hemopoietic lineage did not have such a bridge. The cytoplasmic bridge is unique to erythroblasts and provides an evidence for the atypical cytokinesis of the erythroblastic lineage.     

Properties of invertase immobilized on the poly(ethylene-co-vinyl alcohol) hollow fiber membrane

Invertase was ionically immobilized on the poly(ethylene-co-vinyl alcohol) hollow fiber inside surface, which was aminoacetalized with 2-dimethylaminoacetaldehyde dimethyl acetal. Immobilization and enzyme reaction were carried out by letting the respective solutions pass or circulate through the inside of the hollow fiber, and the activity of invertase was determined by the amount of glucose produced enzymatically from sucrose. Immobilization conditions were examined with respect to the enzyme concentration and to the time, and consequently the preferable conditions at room temperature were found to be 5 mug/mL of enzyme concentration and 4 h of immobilization time. Under those conditions the immobilization yield and the ratio of the activity of the immobilized invertase to that of the native one were 89 and 80%, respectively. For both repeating and continuous usages, the activity fell to ca. 60% of the initial activity in the early stage and after that almost kept that value. The apparent Michaelis constant K(m) (') for the immobilized invertase decreased with increasing the flow rate of the substrate solution, to be close to the value for the native one. Furthermore, the possibility of the separation of the enzymatically formed glucose from the reaction mixture through the hollow fiber membrane was preliminarily examined.     

Purification and properties of a novel enzyme,N-acylamino acid racemase,from Streptomyces atratus Y-53

A novel enzyme, N-acylamino acid racemase, was purified to homogeneity from Streptomyces atratus Y-53 and characterized. This enzyme catalyzes the interconversion of optically active N-acylamino acids. The relative molecular mass (M_r) of the enzyme was estimated to be about 41 000 and 244 000 on sodium dodecyl sulfate-polyacrylamide gel electrophoresis and gel filtration, respectively, indicating that the enzyme is composed of six subunits with an equal M_r. The enzyme showed a broad substrate specificity toward N-acylamino acids, such as N-acetylmethionine, N-chloroacetylphenylalanine and N-chloroacetylvaline. The apparent Michaelis constant (K_m) values for N-acetyl-l-methionine and N-acetyl-d-methionine were calculated to be 15.2 and 5.6 mm, respectively. Enzyme activity was markedly enhanced by divalent metal ions, such as Co²⁺, Mg²⁺ and Mn²⁺, and was inhibited by metal-chelating reagent, indicating that the enzyme is a metalloenzyme. We propose to name the enzyme N-acylamino acid racemase (acylamino acid racemase). Correspondence to: S. Tokuyama     

Avian epidermis contains ATPase- and Ia-positive Langerhans-like cells

Summary The occurrence of cells resembling mammalian Langerhans cells in the avian epidermis was studied by ATPase histochemistry, Ia immunoreactivity and electron microscopy. The existence of MHC class II antigen-(Ia) expressing, ATPase-positive dendritic cells, which are ultrastructurally similar to mammalian Langerhans cells except for the absence of Birbeck granules, was demonstrated. These cells may be a basic component of the immune system of birds.     

Kinetics and collagenolytic role of eosinophils in chronic gastric ulcer in the rat

 An association between eosinophils and tissue damage has been observed in numerous disorders. However, few reports have addressed the role of infiltrating eosinophils in gastric ulcer healing. The aim of this study was to investigate the kinetics and role of eosinophils infiltrating experimental chronic gastric ulcers in the rat. We developed a monoclonal antibody against human matrix metalloproteinase 1 (MMP1) purified from conditioned culture medium of human skin fibroblasts. Acetic acid-induced gastric ulcers were resected from rats on days 1, 3, 5, 10, 20, 40, and 180 after the days of induction (day 0). Tissue specimens were immunostained with this antibody and examined with an electron microscope. Few eosinophils were observed in the granulation tissue until day 20. By days 40 and 180, MMP1-positive eosinophils had increased in the granulation tissue of open ulcers. Azan staining revealed dispersed collagen fibers around infiltrating eosinophils. In contrast, scars demonstrated few eosinophils in fibrous tissue on days 40 and 180. Eosinophils which express MMP1 infiltrate granulation tissue at the chronic stage of gastric ulceration. The results suggest that eosinophils may play a role in tissue remodeling and deterioration of ulceration. Accepted: 18 March 1997     

New records of within-group infanticide and cannibalism in wild chimpanzees

Two cases of within-group infanticide and cannibalism were observed among the M Group chimpanzees of the Mahale Mountains, Tanzania. In both cases, victimized infants were male, 5 – 6 months of age, and in good health when killed. Four to five years have passed since the mothers of the victims immigrated into M Group as nulliparous immigrants. In one case the 2nd-ranking male was observed to detach the infant from the mother's belly. Both infants were finally killed by the alpha male after several adult males scrambled for the bodies. There was no evidence that the mothers had mated with males other than those of M Group. Nor was there evidence that the mothers had restrictive mating relationships with some of the M Group adult males. What little evidence is available shows that the mothers had mated mostly with adolescent and other immature males during their conception cycles. However, at least in one case, the mother began to mate more with adult males rather than with immature males after the infanticide. It is proposed that the function of within-group male infanticide can be explained by the male-male competition hypothesis developed for hanuman langurs and other nonhuman primates.     

Oviposition and development in predaceous mites fed with artificial and natural diets (Acari: Phytoseiidae)

Oviposition rate and developmental capacity was determined for Amblyseius hibisci (Chant), A. limonicus Garman and McGregor, A. largoensis (Muma), Metaseiulus pomoides Schuster & Pritchard, M. occidentalis (Nesbitt), Typhloseiopsis arboreus (Chant), Typhodromus pyri Scheuten, Phytoseiulus persimilis Athias-Henriot, and Iphiseius degenerans (Berlese) on both artificial and natural diets. Oviposition and development occurred in seven of nine species when fed artificial diet and in all species when fed natural diets (phytophagous mites or pollen). The combined mean oviposition rate (21-d tests) for all species which oviposited on artificial diet was ca. one third the rate achieved by these species when tested on natural diets. Eggs and immature stages derived from oviposition tests with artificial diet showed no abnormalities and developmental times (egg to egg) were similar to those observed on natural diets. Predator cultures maintained on artificial diet showed gradual declines in viability within 2–3 months and only A. hibisci survived longer than 6 months. Adult predators of species which failed to oviposit when fed artificial diet survived longer than adults tested in the absence of food and water. Immature stages of these species failed to develop on artificial diet.

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Ponte et developpement d'acariens predateurs alimentes a partir d'un regime artificiel et d'un regime naturel (Acari: Phytoseiidae)

Résumé Le nombre d'ufs pondus par 7 espèces de Phytoseiidae nourries sur milieu artificiel a varié de 0,1 à 1,2 uf/femelle/jour. Pour l'ensemble des espèces, le nombre moyen d'ufs pondus a été de 0,5 uf/femelle/jour pour une période de ponte moyenne de 18,5 jours.Deux espèces, Phytoseiulus persimilis et Metaseiulus occidentalis nourries sur milieu artificiel, n'ont pas pondu; leurs longévités moyennes ont été respectivement de 11,3 et de 10,3 jours.Avec un régime naturel (acariens phytophages ou pollen), le nombre d'ufs pondus, pour 9 espèces de Phytoseiidae a varié de 0,8 à 3,2 ufs/femelle/jour. Pour l'ensemble des espèces, le nombre moyen d'ufs pondus a été de 1,7 uf/femelle/jour pour une durée moyenne de la période de ponte de 19,0 jours.La viabilité des ufs provenant des expériences de ponte avec régime artificiel était elevée chez toutes les espèces prédatrices et les durées du développement sur milieu artificiel étaient semblables à celles observées avec régime naturel. La viabilité des élevages de prédateurs maintenus sur milieu artificiel a diminué progressivement et la plupart des élevages avaient disparu en moins de 6 mois. Les tentatives d'élevage de P. persimilis et M. occidentalis sur milieu artificiel ont été négatives bien que les prédateurs adultes femelles aient eu une plus grande longévité sur milieu artificiel qu'en absence de nourriture et d'eau.