Cell wall composition of the carrageenophyte Kappaphycus alvarezii (Gigartinales, Rhodophyta) partitioned by wet sieving

The cortical and medullary cells of Kappaphycus alvarezii fractions were screened by wet sieving after aqueous extraction of carrageenans. The cell populations obtained showed a clear partition between these two cell types. The main monosaccharide in hydro-insoluble cell walls was cellulosic glucose (70% dry weight), the crystallinity of which was shown torange from 20% in the cortical cells to 45% in the large medullary cells (over 250 μm diameter). Minor monosaccharides in the insoluble fraction were galactose, 3,6-anhydrogalactose (indicating presence of residual carrageenans), mannose and xylose. However, the major part of the remaining galactose probably originated from another galactoglycan strongly linked to insoluble polymers in the large medullarycell walls. The mannose concentration was maximum in the cortical cells and decreased with increasing size of the medullary cells. Thus, besides cellulose, two other types of polysaccharides were detected in insolublecell walls, mannoglycans and galactoglycans in cortical and medullary cellwalls, respectively. This revised version was published online in August 2006 with corrections to the Cover Date.     

Response of cytoskeleton of murine osteoblast cultures to two-step freezing

Understanding the ultrastructural response of cells to the freezing process is important for designing cryopreservation strategies for cells and tissues. The cellular structures of attached cells are targets of cryopreservation-induced damage. Specific fluorescence staining was used to assess the status of the actin filaments （F-actin） of murine osteoblasts attached to hydroxyapatite discs and plastic coverslips for a two-step freezing process. The F-actin of dead cells was depolymerized and distorted in the freezing process, whereas that of live cells had little change. The results suggest that the cytoskeleton may support the robustness of cells during cryopreservation. The present study helps to investigate the damage mechanism of attached cells during the freezing process.     

Variation of B Chromosome Associated with Tissue Culture in Wheat-rye Cross

In vitro variation of B chromosomes was studied by examining the callus cells derived from the immature embryos from a cross of Chinese Spring wheat （Triticum aestivum L.） and Fin 7416 rye （Secale cereale L.） carrying two B chromosomes. In 40-d-old callus cells, the numbers of B chromosomes ranged from one to four in 65.6% of the cells observed. The distribution of B chromosome numbers was associated with the ploidy levels of the normal chromosomes （A chromosomes）. The frequency of the cells with high numbers of B chromosomes （i.e., three or four B chromosomes） in the amphiploid cells with 56 A chromosomes was greater than those in the haploid cells with 28 A chromosomes. Although structural changes in the rye A chromosomes were observed, cytological observation and genomic in situ hybridization demonstrated that the rye B chromosomes were conserved in morphological appearance following tissue culture.     

Effects of Temperature Acclimation Pretreatment on the Ultrastructure of Mesophyll Cells in Young Grape Plants （Vitis vinifera L. cv. Jingxiu） Under Cross-Temperature Stresses

Leaves from annual young grape plants （Vitis vinifera L. cv. Jingxiu） were used as experimental materials. The ultrastructural characteristics of mesophyll cells in chilling-treated plants after heat acclimation （HA） and in heat-treated plants after cold acclimation （CA） were observed and compared using transmission electron microscopy. The results showed that slight injury appeared in the ultrastructure of mesophyll cells after either HA （38℃ for 10 h） or CA （8℃ for 2.5 d）, but the tolerance to subsequent extreme temperature stress was remarkably improved by HA or CA pretreatment. The increases in membrane permeability and malondialdehyde concentration under chilling （0℃） or heat （45℃） stress were markedly inhibited by HA or CA pretreatment. The mesophyll cells of plants not pretreated with HA were markedly damaged following chilling stress. The chloroplasts appeared irregular in shape, the arrangement of the stroma lamellae was disordered, and no starch granules were present. The cristae of the mitochondria were disrupted and became empty. The nucleus became irregular in shape and the nuclear membrane was digested. In contrast, the mesophyll cells of HA-pretreated plants maintained an intact ultrastructure under chilling stress. The mesophyll cells of control plants were also severely damaged under heat stress. The chloroplast became round in shape, the stroma lamellae became swollen, and the contents of vacuoles formed clumps. In the case of mitochondria of control plants subjected to heat stress, the outer envelope was digested and the cristae were disrupted and became many small vesicles. Compared with cellular organelles in control plants, those in CA plant cells always maintained an integrated state during whole heat stress, except for the chloroplasts, which became round in shape after 10 h heat stress. From these data, we suggest that the stability of mesophyll cells under chilling stress can be increased by HA pretreatment. Similarly, CA pretreatment can protect chloroplasts, mitochondria, and the nucleus against subsequent heat stress; thus, the thermoresistance of grape seedlings was improved. The results obtained in the present study are the first, to our knowledge, to offered cytological evidence of cross-adaptation to temperature stresses in grape plants.     

Somatic embryogenesis and plant regeneration in Anthurium scherzerianum

The effects of xylooligosaccharides isolated from the cell walls of Betula platyphylla var. japonica on cells and protoplasts of Pinus radiata were examined. The addition of a semi-purified mixture of xylooligosaccharides at a concentration of 5μg.ml⁻¹ promoted elongation of cultured cells, whereas the neutral fraction of this mixture had no effect; a similar effect was seen in the presence of conditioned medium. The unfractionated mixture of xylooligosaccharides was also found to enhance the viability of protoplasts prepared from cell cultures of Pinus radiata in a concentration dependent manner, highly similar to the effect provided by addition of medium conditioned by pine cells. Such effects are considered to be due to the addition of components that play a structural role in the cell wall of pines. It is inferred that the acidic components of the xylooligosaccharide mixture derived from t Betula are responsible for this effect in the distant pine species. It is speculated that acidic xylooligosaccharides operate either by replacing, or mimicking, the natural cell wall components required for growth and development of pine cultured cells. This revised version was published online in June 2006 with corrections to the Cover Date.     

Truncated human LMP-1 triggers differentiation of C2C12 cells to an osteoblastic phenotype in vitro

LIM mineralization protein-1 （LMP-1） is a novel intracellular osteoinductive protein that has been shown to induce bone formation both in vitro and in viva. LMP-1 contains an N-terminal PDZ domain and three C-terminal LIM domains. In this study, we investigated whether a truncated form of human LMP-1 （hLMP-1 [t]）, lacking the three C-terminal LIM domains, triggers the differentiation of pluripotent myoblastic C2C12 cells to the osteoblast lineage. C2C12 cells were transiently transduced with AdS-hLMP-1 （t）-green fluorescent protein or viral vector control. The expression of hLMP-1 （t） RNA and the truncated protein were examined. The results showed that hLMP-1 （t） blocked myotube formation in C2C12 cultures and significantly enhanced the alkaline phosphatase （ALP） activity. In addition, the expressions of ALP, osteocalcin, and bone morphogenetic protein （BMP）-2 and BMP-7 genes were also increased. The induction of these key osteogenic markers suggests that hLMP- 1 （t） can trigger the pluripotent myoblastic C2C12 cells to differentiate into osteoblastic lineage, thus extending our previous observation that LMP-1 and LMP-1 （t） enhances the osteoblastic phenotype in cultures of cells already committed to the osteoblastic lineage. Therefore, C2C12 cells are an appropriate model system for the examination of LMP-1 induction of the osteoblastic phenotype and the study of mechanisms of LMP-1 action.     

p53-independent pRB degradation contributes to a drug-induced apoptosis in AGS cells

The retinoblastoma （RB） tumor suppressor protein, pRB, plays an important role in the regulation of mammalian cell cycle. Furthermore, several lines of evidence suggest that pRB also involves in the regulation of apoptosis. In the present study, the degradation of pRB was observed in apoptotic gastric tumor cells treated with a new potent anti-tumor component, tripchlorolide （TC）. The inhibition of pRB degradation by a general cysteine protease inhibitor IDAM resulted in the reduction of the apoptotic cells. Furthermore, the survival of the gastric tumor cells under the TC treatment was enhanced by an over-expression of exogenous pRB. These results suggest that the pRB degradation of the gastric tumor cells under the TC treatment involves in the apoptotic progression. In addition, the same extent of TCinduced pRB-degradation was detected in the gastric tumor cells containing a p53 dominant-negative construct, indicat- ing that this kind of pRB degradation is p53-independent.     

Effects of a chemically derived homo zwitterionic polysaccharide on immune activation in mice

In this study, a chemically modified homo zwitterionic polysaccharide （ZPS）, sulfated chitosan, was used to examine its effects on murine immune response. The results showed that homoZPS could markedly promote the proliferation of both splenic T/B cells and adhesive cells. In particular, flow cytometry assay demonstrated that the sulfated chitosan could non-specifically activate CD3＋ and CD8＋ T cells proliferation in vitro. The effectiveness of sulfated chitosan as adjuvant was tested using bovine serum albumin （BSA） and diphtheria toxin （DT） as antigens and compared with that of aluminum hydroxide. The levels of specific antibodies to BSA and DT significantly increased after homoZPS vaccination. Both homoZPS and aluminum hydroxide adjuvants could protect mice against the attack of DT from edemas of spleen and tail. The present findings demonstrated the chemically derived homoZPS could be a potential candidate in the development of T-lymphocyte dependent vaccine adjuvants.     

Double role of Fas ligand in the apoptosis of intervertebral disc cells in vitro

Fas ligand （FasL） may play an important role in maintaining the immune privilege of intervertebral disc （IVD）. Besides, it is closely related to the apoptosis of degenerative disc cells. Nowadays, lots of reports have described about the paradoxical effects of FasL, although the effect of FasL on IVD cells is still under debate. In this study, we tried to investigate the effects of FasL on Fas expression and on the apoptosis of nucleus pulposus （NP） cells in Sprague-Dawley rats. The results showed that the expression of Fas in NP cells was significantly increased by the recombinant FasL. Meanwhile, the apoptosis of NP cells increased markedly in a FasL dose-dependent manner. Interestingly, RNA interference results indicated that the increase of Fas expression and the NP cell apoptosis described previously were inhibited by Fas siRNA, suggesting that RNA interference might be one of novel strategies to prevent IVD cells from apoptosis.     

Distribution Pattern of Photosynthetic Picoplankton and Heterotrophic Bacteria in the Northern South China Sea

The environmental regulation of plcoplankton distribution in the northern South China Sea was examined In winter and summer of 2004. The average abundance of Synechococcus, Prochlorococcus, and heterotrophlc bacteria was lower In winter （30, 21, and 780×10^3 cells/cm^3, respectively） than In summer （53, 85, and 1 090×10^3 cells/cm^3, respectively）, but the seasonal pattern was opposite for plcoeukaryotlc phytoplankton （4 500 and 3 200 cells/cm^3 In winter and summer, respectively）. Synechococcus, picoeukaryotes, and bacteria were most abundant in the nutrient-rich coastal zone and continental shelf, but Prochlorococcus was most abundant In the continental slope and open ocean. The vertical distribution of each photosynthetic group and heterotrophlc bacteria changed between the two seasons. Synechococcus populations with apparently different phycoerythrobilin content occurred at many stations In the summer. In addition, two different populations of Prochlorococcus were found： （i） small, weakly fluorescing cells in the surface layer; and （ii） larger, strongly fluorescent cells In the deep layer. The distribution pattern of photosynthetic plcoplankton and heterotrophlc bacteria depends on environmental effects and their ecophyslologlcal differences. The distribution of Synechococcus appeared to be related to nutrient availability, whereas the distribution of Prochlorococcus appeared to be limited by temperature. Synechococcus was the only plcophytoplankton with a consistent strong relationship with bacteria.     

Multi-peak phenomenon of insect cell infection with baculovirus at low multiplicity of infection

In this communication we report the infection of armyworm Spodoptera frugiperda IPLB-Sf- 21 cells with Anticarsia gemmatalis multicapsid nucleopolyhedrovirus at low multiplicity of infection （MOI）. The temporal variation of the extra-cellular virus and of the unstained cell was followed. The series of peaks in the virus concentration and the unstained cells count were used in order to infer the dynamic mechanism of the infection at low MOI. This mechanism can be used as the basis for the future formulation of a mathematical model of the process.     

A Novel Rice bHLH Transcription Factor, DTD, Acts Coordinately with TDR in Controlling Tapetum Function and Pollen Development

Dear Editor, Male reproductive development is an essential biological process for flowering plants and crucial for crop seed produc- tion. Formation of the male reproductive organ, the anther, involves a number of developmental events, including sta- men meristem specification, generation of sporogenous cells and their differentiation into microspore mother cells （MMCs）, meiosis, microspore （pollen） maturation, and polli- nation （Ma, 2005）. The formation of microspores and their development into mature pollen grains require cooperative interactions between gametophytic （microspores） and sporo- phytic （anther wall） cells, with the innermost cell layer, the tapetum, playing the most crucial role （Ma, 2005）. Tapetal cells underao decleneration bv Droclrammed cell death （PCD）.     

miR-888 in MCF-7 Side Population Sphere Cells Directly Targets E-cadherin

Side population （SP） cells are a small subset of cells isolated from a cultured cancer cell line that exhibit characteristics similar to those of cancer stem cells （CSCs）, such as high metastatic and tumorigenic potential. The molecular mechanisms that give rise to the malignant properties of SP cells are not clear. We isolated SP cells from the MCF-7 breast cancer cell line and profiled microRNA （miRNA） expression patterns between SP cell-derived spheroids and non-SP cells. SP spheroids were found to possess 42 up-regulated miRNAs and 27 down-regulated ones （above 5-fold changes）. One of the up-regulated miRNAs, miR-888 computationally predicted to participate in the adherens junction （AJ） pathway, was investigated. Over-expression of miR-888 in MCF-7 cells reduced the mRNA levels of all four AJ pathway genes （E-cadherin, ACTG1, PTPRTand CDC42） that were selected for testing, whereas knocking down miR-888 reversed the trends. Western blot and flow cytometric quantitation of the membrane E-cadherin levels showed the same trend of change under these treatments. Luciferase reporter assay showed E-cadherin is a direct target of miR-888. As a potential role in intercellular adhesiveness and maintenance of malignant tissue architecture, the results indicate that miR-888 is a repressor of the AJ pathway in MCF-7 cells and that up-regulation of miR-888 contributes to aggressiveness in MCF-7 SP cells.     

Evaluating the antitumor activity of combined photochemotherapy mediated by a meso-substituted tetracationic porphyrin and adriamycin

The combined anticancer modality comprising porphyrins as photodynamic sensitizers and anticancer drugs has been an interesting subject for many researchers. In this study, the photochemotherapeutic effect mediated by simultaneous photoactivation of tetracationic meso-tetrakis（N-methyl-4-pyridyl） porphine tetratosylate （TMPyP） and adriamycin （ADM） were explored using human hepatocellular carcinoma cell line （HePG2）. The efficiency of TMPyP acting in concert with ADM in the dark and in the presence of photoirradiation was evaluated, by studying cell viability, caspase-3 activity and ultrastructural changes in the cells after incubation with each of the two agents, separately, or simultaneously as a co-mixture. Under dark conditions, the simultaneous incubation of cells with TMPyP and ADM significantly enhanced cell death by 1.8 folds and 1.3 folds, compared with TMPyP or ADM treatment, respectively. After photoirradiation, the antiproliferative effect of the co-treatment with TMPyP and ADM increased further by 2 folds. Transmission electron microscopy and the measurements of caspase-3 levels in treated cells revealed that the co-treatment of cells with ADM and TMPyP followed by light irradiation directed the cell death towards necrosis and abrogated the apoptotic cell death pathway, which was exhibited in cells treated with ADM in absence and in presence of photoirradiation.     

Differentiation potential of bone marrow mesenchymal stem cells in duck

The bone marrow mesenchymal stem cells （MSCs） are multipotent stem cells which can differentiate into mesenchymal cells in vitro. In this study, MSCs in duck were isolated from bone marrow by density gradient centrifuge separation, purified and expanded in the me- dium. The primary MSCs were expanded for 11 passages. The different-passage MSCs were induced to differentiate into osteoblasts and neuron-like cells. Karyotype analysis indicated that MSCs kept diploid condition and the hereditary feature was stable. The different- passage MSCs expressed CD44, ICAM-1 and SSEA-4, but not CD34, CD45 and SSEA-1 when detected by immunofluorescence staining There was no significant difference among the positive rates of passages 2, 6 and 8 （P 〉 0.05）, but a significant difference existed among those of passages 2, 6, 8 and 11 （P 〈 0.05）. After the osteogenic inducement was added, the induced different-passage MSCs expressed high-level alkaline phosphatase （ALP）, and are positive for tetracycline staining, Alizarin Red staining and Von Kossa staining. After the neural inducement was added, about 70% cells exhibited typical neuron-like phenotype, the induced different-passage MSCs expressed Nestin, neuron-specific enolase （NSE） and glial fibrillary acidic protein （GFAP） when detected by immunofluorescence staining. There was no significant difference among the positive rates of passages 3, 4 and 6 （P〉0.05）, but a significant difference existed among those of passages 3, 4, 6 and 8 （P〈0.05）. These results suggest that MSCs in duck were capable of differentiating into osteoblasts and neuron-like cells in vitro.     

New species of the isolated Psaroniaceous rachis from the Early Permian in China

A new kind of marattialean raches are reported from the coal balls in Coal Seam No.7 in the upper part of the Taiyuan Formation （early Early Permian） from Taiyuan, Shanxi, China and are assigned to the genus Stipitopteris Grand＇Eury （Psaroniaceae）. The present specimens are different from all six reported species of the genus, and are therefore proposed as a new species： Stipitopteris shanxiensis. The raches of the new species are generally dorsi-ventrally flattened. The main raches usually exhibit scales of different forms on their surface. Beneath the epidermis is a zone of parenchymatous cells, some of which contain tannin-like contents. Inside this is a zone of small sclerenchymatous cells. Inward are the ground tissue and vascular bundles. The vascular bundles are continuous and are in two circles： the outer circle assumes a transversely elliptical shape with the gap and pinna trace, and the inner circle assumes a shallow C.shape with inrolled ends. The ground tissue located at the inner side of the vascular bundle is composed of thicker-walled parenchymatous cells. The cells of the ground tissue are vertically elongated in longitudinal sections. Subordered raches are smaller and have simpler structures than the main raches. The parenchyma zone beneath the epidermis is thinner, usually one to two cells wide and the sclerenchyma zone is usually absent. The scales are poorly developed and there is only one C-shaped vascular bundle. The new species is comparable to the crosiers of Psaroniaceae of the Euramerican Flora in some aspects, for example, it has a dorsi-ventrally flattened rachis and scales on the surface of the rachis. However, the other features and the preservative conditions of the present specimens indicate that they are not crosiers, but fully developed or mature raches. The new species is the first well-studied anatomically-preserved rachis of Psaroniaceae from the Cathaysian Flora and bears significance not only in understanding the anatomy and taxonomy of Psaroniaceae in the Cathaysian Flora, but also in the relationship between the Euramerican Flora and the Cathaysian Flora.     

Stem cells derived from testis show promise for treating a wide variety of medical conditions

The continuation of the spermatogenic process through-out life relies on a proper regulation of self-renewal and differentiation ofgermline testis stem cells, the spermatogonial stem cells. These are single cells situated on the basal membrane of the seminiferous epithelium. Only 0.03% of all germ cells are spermatogonial stem cells （SSCs） [1-3]. To maintain spermatogenesis, the processes of self-renewal and differentiation of S SCs must be precisely regulated by intrinsic gene expression in the stem cells and extrinsic signals, including soluble factors or adhesion molecules from the surrounding microenvironment, the stem cell niche.[第一段]