Distribution of rDNA in the nucleus of Giardia lamblia - Detection by Ag-I silver stain

OBJECTIVE: To determine whether rDNA of Giardia lamblia forms a nucleolus organizer region (NOR)-like structure and is in a very primitive state. STUDY DESIGN: G lamblia was used as the experimental animal, with Euglena gracilis as the control. The distribution was demonstrated indirectly by the modified Ag-I silver technique, which can specifically indicate the NOR under both light and electron microscopes. RESULTS: In the ultrathin sections of silver-stained Euglena cells, all the silver grains were concentrated in the fibrosa of the nucleolus, while no grains found in the cytoplasm, nucleoplasm, condensed chromosomes or pars granulosa of the nucleus. In the silver-stained Giardia cells, no nucleolus was found; a few silver grains were scattered in the nucleus but were not concentrated in any specific region. CONCLUSION: The distribution of silver grains in G lamblia showed that the transcription of rDNA occurs inside the nucleus, though no nucleolus is present. It is possible that chromosomes are in a very primitive state in diplomonad cells; as each chromosome has few prRNA genes, the transcription is independent of a nucleolus. These results imply that the rDNA of Giardia does not form a NOR-like structure and seems to represent a very primitive state in the evolution of the nucleolus.

Homologous feeder cells support undifferentiated growth and pluripotency in monkey embryonic stem cells

In the present study, five homologous feeder cell lines were developed for the culture and maintenance of rhesus monkey embryonic stem cells (rESCs). Monkey ear skin fibroblasts (MESFs), monkey oviductal fibroblasts (MOFs), monkey follicular granulosa fibroblast-like (MFG) cells, monkey follicular granulosa epithelium-like (MFGE) cells, and clonally derived fibroblasts from MESF (CMESFs) were established and compared with the ability of mouse embryonic fibroblasts (MEFs) to support rESC growth. MESF, MOF, MFG, and CMESF cells, but not MFGE cells, were as good as or better than MEFs in supporting undifferentiated growth while maintaining the differentiation potential of the rESCs. In an effort to understand the unique properties of supportive feeder cells, expression levels for a number of candidate genes were examined. MOF, MESF, and MEF cells highly expressed leukemia inhibitory factor, ciliary neurotrophic factor, basic fibroblast growth factor, stem cell factor, transforming growth factor PI, bone morphogenetic protein 4, and WNT3A, whereas WNT2, WNT4, and WNT5A were downregulated, compared with MFGE cells. Additionally, all monkey feeder cell lines expressed Dkk1 and LRP6, antagonists of the WNT signaling pathway, but not WNT1, WNT8B, or Dkk2. rESCs grown on homologous feeders maintained normal karyotypes, displayed the characteristics of ESCs, including morphology, alkaline phosphatase, Oct4, the cell surface markers stage-specific embryonic antigen (SSEA)-3, SSEA-4, tumor-related antigen (TRA)-1-60, and TRA-1-81, and formed cystic embryoid bodies in vitro that included differentiated cells representing the three major germ layers. These results indicate that the four homologous feeder cell lines can be used to support the undifferentiated growth and maintenance of pluripotency in rESCs.

牛蛭属一新种记述(蛭纲:医蛭科)

医蛭科牛蛭属Poecilobdella在我国主要分布在广东、广西、云南和台湾。Moore(1930)报道有一种菲牛蛭P.manillensis曾在南京发见,但未附图,也未描述其特征。另据胡经甫(Wu,1930;48)记载有一种颗粒牛蛭P.granulosa分布于北京、苏州和福建。然而陈义(1962)和宋大祥等(1977)报道,他们未在这些地区采到牛蛭属的标本,因此这是有待进一步弄清的问题。笔者于1979年5至6月先后从武昌东湖以及毗邻安徽省的黄梅县各获得牛蛭属标本一条。经过详细地活体观察以及内部解剖,並与

Identification of a novel C2 domain factor in ovaries of orange-spotted grouper (Epinephelus coioides)

Follicle consists of an oocyte and a lot of surrounding follicular cells, and significant interactions exist between the oocyte and the somatic cells. In this study, a novel cDNA has been screened from a subtractive cDNA library between tail bud embryos and blastula embryos in the protogynous hermaphrodite orange-spotted grouper (Epinephelus coioides). Its full-length cDNA is 821 bp, and has an ORF of 414 by for encoding a peptide of 137 aa, which shows 38%, 37%, 33%, and 33% homology with 4 putative proteins screened from zebrafish (Danio rerio). Conserved domain search in NCBI reveals a single C2 domain existing in the C2 domain superfamily proteins, and has only 7 beta strands in comparison with 8 beta strands of C2 domains in other C2 domain superfamily proteins. Artificial sex reversal, RT-PCR analysis and Western blot detection demonstrated ovary-specific expression of the C2 domain factor, and therefore the novel gene was designated as E. coioides ovary-specific C2 domain factor, EcOC2 factor. Moreover, predominant expression of EcOC2 factor was further revealed in grouper mature ovary, and its strong immunofluorescence signals were located between granulosa cells and oocyte zona radiata in grouper mature follicles. The data indicate that the novel EcOC2 factor might be a main component that associates between granulosa cells and the oocyte during oocyte maturation, and might play significant roles in regulating oocyte maturation and ovulation. Further studies on its developmental behaviour and physiological functions will elucidate the interactions between oocyte and the surrounding somatic cells and the underlying molecular mechanisms. (C) 2005 Elsevier Inc. All rights reserved.

Expression pattern and developmental behaviour of cellular nucleic acid-binding protein (CNBP) during folliculogenesis and oogenesis in fish

In vertebrates, folliculogeneis establishes an intricate system for somatic cell-oocyte interaction, and ultimately leads to the acquisition of their respective competences. Although the formation process and corresponding interactions are strikingly similar in diverse organisms, knowledge of genes and signaling pathways involved in follicle formation is very incomplete and the underlying molecular mechanisms remain enigmatic. CNBP has been identified for more than ten years, and the highest level of CNBP transcripts has been observed in adult zebrafish ovary, but little is known about its functional significance during folliculogeneis and oogenesis. In this study, we clone CNBP cDNA from gibel carp (Carassius auratus gibelio), and demonstrate its predominant expression in gibel carp ovary and testis not only by RTPCR but also by Western blot. Its full-length cDNA is 1402 bp, and has an ORF of 489 nt for encoding a peptide of 163 aa. And its complete amino acid sequence shared 68.5%-96.8% identity with CNBPs from other vertebrates. Based on the expression characterization, we further analyze its expression pattern and developmental behaviour during folliculogeneis and oogenesis. Following these studies, we reveal an unexpected discovery that the CagCNBP is associated with follicular cells and oocytes, and significant distribution changes have occurred in degenerating and regenerating follicles. More interestingly, the CagCNBP is more highly expressed in some clusters of interconnected cells within ovarian cysts, no matter whether the cell clusters are formed from the original primordial germ cells or from the newly formed cells from follicular cells that invaded into the atretic oocytes. It is the first time to reveal CNBP relevance to folliculogeneis and oogenesis. Moreover, a similar stage-specific and cell-specific expression pattern has also been observed in the gibel carp testis. Therefore, further studies on CNBP expression pattern and developmental behaviour will be of significance for understanding functional roles of CNBP during gametogenests. (c) 2005 Elsevier B.V. All rights reserved.