Mitochondrial and nuclear DNA variability in the living fossil Triops cancriformis (Bosc, 1801) (Crustacea, Branchiopoda, Notostraca).

The living fossil Triops cancriformis comprises bisexual (either gonochoric or hermaphroditic) and unisexual populations. Genetic surveys have recently revealed a general trend of low differentiation of 12S and 16S mitochondrial genes. We, therefore, surveyed further mitochondrial (COI gene and control region) and nuclear markers (dinucleotide microsatellites) to assess the genetic variability and to establish any relationship with the different reproductive modes found in European populations. The mitochondrial analyses confirmed the pattern of low variability. Hence, the low mitochondrial genetic variability appears as a common feature of the genus Triops. The microsatellite analysis found that Italian populations are monomorphic or exhibit little polymorphism, while other European samples display a higher degree of polymorphism and private alleles. Spanish, Austrian and Italian populations show patterns of Hardy-Weinberg disequilibrium that could be explained by the mode of reproduction, or by a higher frequency of null alleles in these populations. The low diversity and differentiation among Italian populations lead us to question the Monopolization Hypothesis. One microsatellite locus appears to be sex-linked, with heterozygotes detected only in males and hermaphrodites.

Retinoids and cancer: antitumor effect of ATRA and of a new derivative of retinoic acid, IIF, on colon carcinoma cell lines CaCo-2 and HT-29.

Vitamin A and its metabolic forms, like all-trans retinoic acid (ATRA), are used with promising results in the treatment of many tumors. Two major problems in the clinical use of retinoids are that the doses needed for successful treatment are often toxic, leading to "hypervitaminosis A syndrome" and that patients often develop drug resistance. In order to find compounds that can overcome these problems, many new derivatives of retinoids have been synthesized and tested. Here we present a study on the effect of a new derivative of retinoic acid, IIF (pat. WIPO W0 00/17143), on growth and differentiation of two colon carcinomna cell lines, CaCo-2 and HT-29, with different degrees of tumorigenicity, the second one being more undifferentiated. The effect of IIF was compared with that of ATRA, whose antitumoral action on colon cancer cells and other tumoral cells is widely described in the literature. Besides exerting a strong antiproliferative effect, even higher than that of ATRA, IIF induced cellular differentiation, as demonstrated by the appearance of morphological (domes and microvilli formation) and biochemical (alkaline phosphatase induction) markers. Therefore, these findings indicate the new retinoid IIF as a possible candidate in the treatment of colon cancer.

Ultrastructural observations on the oogenesis of Triops cancriformis (Crustacea, Notostraca). II. Early developmental states of the oocyte.

The first stages of the oogenesis of Triops cancriformis have been studied. At the outset the oocyte is smaller than the nurse cells. Meiosis begins with typical synaptonemal complexes. The significance of these complexes and of some other peculiar structures of germ cells, i.e., pore complexes and annuli within the nucleus, and annulate lamellae within the cytoplasm are discussed. The morphofunctional uniformity of some cytoplasmic structures (annulate lamellae, concentrically arranged ER, and yolk globules) in the oocyte as well as its nurse cells is also discussed.

Ultrastructural observations on the oogenesis of Triops cancriformis (Crustacea, Notostraca).

Each ovarian follicle of Triops cancriformis is four-celled; these cells (one oocyte and three nurse cells) are interconnected by cytoplasmic bridges. In the course of differentiation, the nurse cells are clearly recognizable; they increase in size more than the oocyte and their nuclei contain many nucleoli. For the first time in Arthropoda, yolk globules are reported to be present in nurse cell cytoplasm; these globules arise from the smooth endoplasmic reticulum. The functional significance of the intercellular bridges and the trophic role of the nurse cells are discussed.