Centrioles take center stage.

Centrioles are among the most beautiful and mysterious of all cell organelles. Although the ultrastructure of centrioles has been studied in great detail ever since the advent of electron microscopy, these studies raised as many questions as they answered, and for a long time both the function and mode of duplication of centrioles remained controversial. It is now clear that centrioles play an important role in cell division, although cells have backup mechanisms for dividing if centrioles are missing. The recent identification of proteins comprising the different ultrastructural features of centrioles has proven that these are not just figments of the imagination but distinct components of a large and complex protein machine. Finally, genetic and biochemical studies have begun to identify the signals that regulate centriole duplication and coordinate the centriole cycle with the cell cycle.     

The center of the center of marine shore fish biodiversity: the Philippine Islands

Synopsis Multiple datasets show global maxima of marine biodiversity in the Indo–Malay–Philippines archipelago (IMPA). Analysis of distribution data for 2983 species reveals a pattern of richness on a finer scale and identifies a peak of marine biodiversity in the central Philippine Islands and a secondary peak between peninsular Malaysia and Sumatra. This pattern is repeated in diverse habitat and higher taxa classes, most rigorously for marine shore fishes, supporting geohistorical hypotheses as the most general unifying explanations. Specific predictions based on area of overlap, area of accumulation, and area of refuge hypotheses suggest that present day eastern Indonesia, or Wallacea, should be the center of marine biodiversity. Processes suggested by these three hypotheses contribute to the diversity in this region and are also a likely explanation for the secondary center of diversity. Our study indicates, however, that there is a higher concentration of species per unit area in the Philippines than anywhere in Indonesia, including Wallacea. The Philippine center of diversity is consistent with hypotheses that this area experienced numerous vicariant and island integration events and these hypotheses warrant further testing. Special attention to marine conservation efforts in the Philippines is justified because of the identification of it as an epicenter of biodiversity and evolution.     

Studies on the germinal center

Summary Ultrastructure of mitotic cells in human lymph node germinal centers was deliberately studied in contrast to that of plasma cells in mitosis which were rarely found in medullary cords or lymphatic sinuses of the same materials. It was demonstrated that the mitotic cells in germinal centers are evidently different from the latter in the absence of lamellary arranged endoplasmic reticulum with ribosomes and Golgi apparatus, and are quite similar to the ultrastructure of thymic lymphocytes in mitosis reported by Murray et al. It should be concluded from these findings that the cells produced locally within the germinal centers in human lymph nodes are lymphocytic as has been repeatedly suggested by the authors.Supported by Grant in Aid from the Ministry of Education of Japan (69-9254).