The evolution of Nyctereutes (Carnivora: Canidae) in the Nihewan Basin,Hebei, northern China

The occurrence of Nyctereutes during the Plio-Pleistocene has long been reported in northern China, with the highest abundance in the Nihewan Basin. However, due to site dispersal, the coexistence of different taxa, and lack of a precise stratigraphic constraint, the evolutionary process of this genus remains enigmatic. In this study, we re-examined the available Nyctereutes materials recovered from the Nihewan Basin housed in IVPP and Tianjin Natural History Museum, in addition to a newly recovered specimen from our latest excavation. Furthermore, we compared these materials with Nyctereutes fossils recovered from the Pleistocene Zhoukoudian sites near Beijing and the extant species N. procyonoides. Our analysis of the upper molar morphometry reveals the variations in size and dietary characteristics within different species of Nyctereutes during the late Plio-Pleistocene. The examination of molars indicates an increase in the size of Nyctereutes sinensis compared to early Pliocene N. tingi as well as changes in the molar teeth morphology. Subsequently, changes in diet or environmental factors possibly caused the decrease of body size in the late Pleistocene. We also estimate an age constraint for the fossils of N. sinensis from the Xiashagou section by relocating Licent's localities and referring of updated magnetostratigraphic data.     

High level of divergence of male-reproductive-tract proteins, between Drosophila melanogaster and its sibling species, D. simulans

We compared male-reproductive-tract polypeptides of Drosophila melanogaster and D. simulans by using two-dimensional gel electrophoresis. Approximately 64% of male-reproductive-tract polypeptides were identical between two randomly chosen isofemale lines from these two species, compared with 83% identity for third-instar imaginal wing-disc polypeptides. Qualitatively similar differences were found between reproductive tracts and imaginal discs when D. sechellia was compared with D. melanogaster and with D. simulans. When genic polymorphism was taken into account, approximately 10% of male- reproductive-tract polypeptides were apparently fixed for different alleles between D. melanogaster and D. simulans; this proportion is the same as that found for soluble enzymes by one-dimensional gel electrophoresis. Strikingly, approximately 20% of male-reproductive- tract polypeptides of either D. melanogaster or D. simulans had no detectable homologue in the other species. We propose that proteins of the Drosophila male reproductive tract may have diverged more extensively between species than have other types of proteins and that much of this divergence may involve large changes in levels of polypeptide expression.      

Nuclear activity during oogenesis in sea urchins

Summary Early meiotic stages of Arbacia punctulata oocytes have revealed the presence of synaptinemal complexes in the chromosomes, which persist through zygotene-pachytene. The synaptinemal complexes conform broadly to the usual tripartite structures found in other higher forms. In addition, nuclei at these stages consist of a small nucleolus and dense bodies of varying sizes. The nucleolus is fibrillar in texture throughout and does not seem to incorporate Uridine-5-³H after pulse labeling, whereas the chromosomes are labeled. The nucleolar label is visualized at diplotene stages and onwards. The nuclear envelope differentiates by the appearance of numerous nuclear pore complexes with dense material in the annuli, and the chromosomes become markedly diffused. At vitellogenesis stage the nucleolus and chromatin become highly labeled after pulse incorporation of Uridine, indicating synthesis of ribosomal and chromosomal RNAs.This investigation was supported by grants No. A-5049, A-3624 and D-17 from National Research Council, Canada, grant No. DRB-9340-05 (U6) from Defense Research Board, Canada, and grant No. DRG-918 AT from Damon Runyon Memorial Fund for Cancer Research.     

Insulin-like growth factor-I supports proliferation of autocrine thymic lymphoma cells with a pre-T cell phenotype

We have studied the phenotypic characteristics and growth properties of murine T lymphoma cell lines derived from primary x-ray-induced thymic lymphomas at the earliest stage at which they can be detected, and well before spreading to other organs has occurred. These cell lines serve as model systems for the earliest events in T cell lymphoma induction, before tumor cell progression and spreading to other organs. We find that primary x-ray-induced T cell lymphoma lines have phenotypic characteristics of thymic pre-T cells and show no proliferative response to any of the IL tested nor to other hematopoietic growth factors. However, they do proliferate in response to insulin-like growth factor I (IGF-I) and to a small autocrine peptide distinct from IGF-I, which we term lymphoma growth factor. One of the earliest lesions in T cell lymphoma induction may therefore be an inhibition of differentiation at one of several specific points. In its early stages, T lymphoma cell growth may be restricted to an environment where local concentrations of specific growth factors such as IGF-I or lymphoma growth factor are sufficiently high.     

Effect of cyproterone acetate on the reproductive system of the female rat. A histological review.

Effects of cyproterone acetate, a synthetic steroidal compound, on the reproductive organs of female rats have been investigated. This agent caused reduction of ovarian weights indicative of suppression of pituitary gonadotrophins. Oestrogenic nature of cyproterone acetate was investigated in intact and ovariectomized rats taking uterine weight and vaginal keratinization as an index of oestrogenicity. Cyproterone acetate in ovariectomized animals induced vaginal keratinization and increased the uterine weights. These effects were parallel to the effect of oestradiol dipropionate in ovariectomized animals, thus indicating oestrogenic activity of cyproterone acetate. We may conclude that the above compound caused antifertility effects due to its oestrogenic nature at the dose level of 2 mg/alternate day in rats when the compound was administered subcutaneously.     

Pre-induction priming of the uterine cervix with oral prostaglandin E2 and a placebo

A double blind study was undertaken to determine the effectiveness or oral prostaglandin E2 as a means of improving the pelvic score prior to induction of labour. 48 patients who were greater than 37 were gestation and who had Bishop scores of less than 6 entered the study. Ten tablets were given on an hourly regime. Of 25 patients in the prostaglandin group, 17 were considered successes (68.0%), whereas of 23 patients who received a placebo, 9 were successes (39.1%). No adverse effects were recorded. Prostaglandin E2 is therefore considered a safe and effective method for priming the unfavourable cervix prior to induction of labour.     

Steady-state heat distribution in epidermis,dermis and subdermal tissues

Steady-state temperature distribution is investigated in human skin and subdermal tissue exposed to a dry and cool environment with negligible insensible perspiration. The mathematical model incorporates the effect of blood mass flow and metabolic heat generation. The rates of the two and the tissue thermal conductivity are assumed to have different values in all the three parts, namely epidermis, dermis and subdermal tissues. A simple variational finite element approach is used to find numerical values of the interface temperatures for a wide range of the values of skin surface temperature and for different thicknesses of the above parts. These values are used to obtain approximate temperature profiles in the whole region. The biological and physical implications of the results are also discussed.