High-Molecular-Weight Hyaluronic Acids Inhibit Chemotaxis and Phagocytosis but Not Lysosomal Enzyme Release Induced by Receptor-Mediated Stimulations in Guinea Pig Phagocytes

The effects of high-molecular-weight (HMW) hyaluronic acids (HAs) of 1.9 × 10⁶ Da, 8 × 10⁵ Da and 3 × 10⁵ Da on the receptor-mediated functions of guinea pig peritoneal phagocytes were studied. HMW-HAs of 1.9 × 10⁶ Da (HA190) and 8 × 10⁵ Da (HA80) effectively inhibited the chemotactic activity of polymorphonuclear leukocytes (PMNs) for formyl-Met-Leu-Phe (fMLP). The degree of inhibition was dose-dependent and the concentrations of HA190 and HA80 required for 50% inhibition were 0.5–1.5 mg/ml and 1.5–2.5 mg/ml, respectively. HMW-HA of 3 × 10⁵ Da (HA30) hardly affected the chemotaxis within a concentration range of 0.5–5.0 mg/ml. The phagocytic activities of PMNs and macrophages (Møs) for serum-opsonized zymosan (SOZ) and polystyrene latex particles were also inhibited by these HAs in a dose- and molecular-weight-dependent manner and HA190 was again the most inhibitory. By contrast, the release of lysosomal enzyme from Møs stimulated with SOZ was not significantly affected by HMW-HAs at any concentration used. Furthermore, the binding of [³H]fMLP with PMNs and the rosette formation of Møs with SOZ were not influenced by the presence of HMW-HAs. These findings suggested that the binding of HMW-HAs to the HA receptors on PMNs and Møs might produce certain intracellular signals which would be responsible for the suppression of the chemotaxis and the phagocytosis but not for the release of lysosomal enzyme. For the generation of such signals, higher-molecular-weight HMW-HAs would be more effective than lower one.     

An autoradiographic,biochemical, and morphological study of the harderian gland of the mouse

Biochemical and morphological properties of the Harderian gland of the mouse were examined by combining autoradiographic, biochemical, and electron microscopic techniques. Autoradiographs show that the radioactive carbon from [U-¹⁴C]glucose injected into the abdominal cavity is completely incorporated into the acid-insoluble substances within 30 minutes. The results of chemical analysis show that the main components of this gland are glyceryl ether diesters and phospholipids. Scanning electron microscopy shows numerous lipid droplets in the secretory cells and alveolar lumina. Myoepithelial cells lie between the secretory cell base and the basement membrane and have a basket-like distribution of processes as confirmed by hydrochloric acid and collagenase digestions. Myofilaments are demonstrated in the cytoplasm. Two types of secretory cells (A and B) comprise the alveolar epithelium and can be differentiated under the electron microscope. The cytoplasm of both contains numerous vacuoles. The vacuoles are almost empty in A cells, which are a more numerous constituent of the alveolar epithelium than B cells. However, the vacuoles of the B cells contain densely osmiophilic material. In both, cell types show a merocrine mode of secretion. Unmyelinated nerve cell endings occur in the interstices of the connective tissue, and contain clear or cored vesicles.     

Functional coupling constrains craniofacial diversification in Lake Tanganyika cichlids

Functional coupling, where a single morphological trait performs multiple functions, is a universal feature of organismal design. Theory suggests that functional coupling may constrain the rate of phenotypic evolution, yet empirical tests of this hypothesis are rare. In fish, the evolutionary transition from guarding the eggs on a sandy/rocky substrate (i.e. substrate guarding) to mouthbrooding introduces a novel function to the craniofacial system and offers an ideal opportunity to test the functional coupling hypothesis. Using a combination of geometric morphometrics and a recently developed phylogenetic comparative method, we found that head morphology evolution was 43% faster in substrate guarding species than in mouthbrooding species. Furthermore, for species in which females were solely responsible for mouthbrooding the males had a higher rate of head morphology evolution than in those with bi-parental mouthbrooding. Our results support the hypothesis that adaptations resulting in functional coupling constrain phenotypic evolution.     

Comparative support for the expensive tissue hypothesis: Big brains are correlated with smaller gut and greater parental investment in Lake Tanganyika cichlids

The brain is one of the most energetically expensive organs in the vertebrate body. Consequently, the energetic requirements of encephalization are suggested to impose considerable constraints on brain size evolution. Three main hypotheses concerning how energetic constraints might affect brain evolution predict covariation between brain investment and (1) investment into other costly tissues, (2) overall metabolic rate, and (3) reproductive investment. To date, these hypotheses have mainly been tested in homeothermic animals and the existing data are inconclusive. However, there are good reasons to believe that energetic limitations might play a role in large-scale patterns of brain size evolution also in ectothermic vertebrates. Here, we test these hypotheses in a group of ectothermic vertebrates, the Lake Tanganyika cichlid fishes. After controlling for the effect of shared ancestry and confounding ecological variables, we find a negative association between brain size and gut size. Furthermore, we find that the evolution of a larger brain is accompanied by increased reproductive investment into egg size and parental care. Our results indicate that the energetic costs of encephalization may be an important general factor involved in the evolution of brain size also in ectothermic vertebrates.     

CDX2 in the formation of the trophectoderm lineage in primate embryos

The first lineage decision during mammalian development is the establishment of the trophectoderm (TE) and the inner cell mass (ICM). The caudal-type homeodomain protein Cdx2 is implicated in the formation and maintenance of the TE in the mouse. However, the role of CDX2 during early embryonic development in primates is unknown. Here, we demonstrated that CDX2 mRNA levels were detectable in rhesus monkey oocytes, significantly upregulated in pronuclear stage zygotes, diminished in early cleaving embryos but restored again in compact morula and blastocyst stages. CDX2 protein was localized to the nucleus of TE cells but absent altogether in the ICM. Knockdown of CDX2 in monkey oocytes resulted in formation of early blastocyst-like embryos that failed to expand and ceased development. However, the ICM lineage of CDX2-deficient embryos supported the isolation of functional embryonic stem cells. These results provide evidence that CDX2 plays an essential role in functional TE formation during primate embryonic development.     

Antigenic and biochemical characterization of poliovirus type 1 isolates of non-vaccine origin

During the past 15 years, five poliovirus type 1 strains with non-vaccine-like antigenicity have been isolated in Japan. Of these isolates, two were from paralytic poliomyelitis patients not associated with the use of Sabin vaccine, and three were apparently introduced from abroad. All the isolates could be readily distinguished from the corresponding Sabin type 1 vaccine strain by oligonucleotide mapping of the viral RNA and by polyacrylamide gel electrophoresis of the viral proteins. The oligonucleotide map of the virulent Mahoney strain which has non-vaccine-like antigenicity was very similar to the map of Sabin type 1 strain. These data indicate that none of the isolates were derived from Sabin type 1 vaccine or its parental Mahoney strain. In addition, some isolates had close antigenic relationship with one another. It is probable that all these strains were introduced from foreign lands where wild poliovirus strains are prevalent.