古生代轮藻类的演化和分类

本文通过对古生代轮藻类群形态结构的比较研究,认为Ｔｒｏｃｈｉｌｉｓｃｕｓ和Ｍｏｅｌｌｅｒｉｎａ具有不同的起源。前者藏卵器包围细胞右旋具横脊,底部结构两侧对称,起源于Ｓｙｃｉｄｉｕｍ;后者的左旋轮藻类包围细胞简单,底部结构辐射对称源于具简单直立包围细胞的Ｘｉｎｊｉａｎｇｏｃｈａｒａ。根据底部结构的对称性,将轮藻门划分为Ｓｙｃｉｄｉｐｈｙｃｅａｅ和Ｃｈａｒｏｐｈｙｃｄｅａｅ两个纲,Ｓｙｃｉｄｉｐｈｙｃ     

有关中国学者命名的轮藻化石属

近３０年来,中国轮藻化石研究者共建立了３９个化石轮藻属。本文通过这些属和以往所建立的轮藻属形态结构及内部构造的比较研究,建议保留其中的１３个,并确定了它们的系统分类位置。其余的２６个属拟按同义名予以废弃。被保留的１３个属是：ＸｉｎｊｉａｎｇｏｃｈａｒａＹａｎｇｅｔＺｈｏｕ,１９９０,ＰｓｅｕｄｏｍｏｅｌｅｒｉｎａＷａｎｇ,１９８４,ＧｅｍｍｉｃｈａｒａＷａｎｇ,１９８４,ＭｉｎｈｅｃｈａｒａＷｅｉ,１９８３,Ｈｅｍｉ－ｃｌａｖａｔｏｒＷａｎｇｅｔＬｕ,１９８２,ＸｉｎｊｉａｎｇｉｃｈａｒａＬｕｅｔＬｕｏ,１９９０,ＮｅｏｃｈａｒａＷａｎｇｅｔＬｉｎ,１９７８,Ｔｕｒ－ｂｏｃｈａｒａＷａｎｇ,１９７８,ＬｉｎｙｉｅｃｈａｒａＸｉｎｌｕｎ,１９７８,ＮｅｉｍｏｎｇｏｌｉｃｈａｒａＬｕｅｔＹｕａｎ,１９９１,ＣｏｌｉｃｈａｒａＳ．ＷａｎｇｅｔＺｈａｎｇ,１９８２,ＧｒａｎｕｌａｃｈａｒａＬｕｅｔＬｕｏ,１９９０,ＰｉｎｎｏｐｕｔａｍｅｎＷａｎｇｅｔＬｕ,１９８０。     

湖南石门中三叠世巴东组轮藻化石

该文报道了湖南石门县沿市中三叠统巴东组轮藻化石,计有４属８种２未定种,其中包括３新种,它们是Ｓｔｅｌｌａｔｏｃｈａｒａ ｂｒｅｖｉｓ ｓｐ．ｎｏｖ．,Ｓ．ｍａｅｄｌｅｒｉｆｏｒｍｉｓ Ｓａｉｄａｋｏｖｓｋｙ,Ｓ．ｈｏｅｌｌｖｉｃｅｎｓｉｓＨｏｒｎ ａｆ Ｒａｎｔｚｉｅｎ,Ｓ．ｓｅｌｌｉｎｇｉｉ Ｈｏｒｎ ａｆ Ｒａｎｔｚｉｅｎ,Ｃｕｎｅａｔｏｃｈａｒａ ｍｉｒａ Ｌｕ,Ｓｔｅｎｏｃｈａｒａ ｙｕ     

论四射珊瑚征珊瑚属 Charactophyllum Simpson,1900

对Ｃｈａｒａｃｔｏｐｈｙｌｕｍ作了全面的回顾整理,记述了本属的骨骼构造,在此基础上讨论了其定义范围和时空分布及有关的分类问题。Ｃｈａｒａｃｔｏｐｈｙｌｕｍ的隔壁为板状隔壁而非包珊瑚型隔壁,由波状弯曲的单列单晶榍组成,单晶榍整体呈半扇形排列而非扇形排列,隔壁光滑或发育微弱的榍凸（ｃａｒｉｎａｅ）而无典型的横耙状榍凸（ｙａｒｄａｒｍｃａｒｉｎａｅ）,鳞板半扇形排列而不是扇形排列。本属分布仅限于北美和华北的晚泥盆世早期。Ｃｈａｒａｃｔｏｐｈｙｌｕｍ隔壁中单晶榍由放射状排列的不规则短轴晶柱和晶针组成,横列构造鳞板和横板均由晶板型层状骨骼组成。本属骨骼微细构造的重要特征具有奥陶志留纪与石炭二叠纪四射珊瑚之间的过渡性质。表明四射珊瑚骨骼微细构造演化趋向稳定,是追索演化的重要线索,在较高级别的分类中具有重要意义     

甘肃花海盆地截大板沟早白垩世轮藻化石

详细研究了首次发现于甘肃花海盆地截大板沟下白垩统下沟组的轮藻化石,建立了Ａｃｌｉｓｔｏｃｈａｒａ ｈｕｉｈｕｉｂａｏｅｎｓｉｓ－Ｐｅｃｋｉｓｐｈｅｒａ ｐａｒａｇｒａｎｕｌｉｆｅｒａ组合,重新厘定了中生代地层层序。根据轮藻化石的组合面貌及其在国内外分布的主要层位,认为原划归为中－上侏罗统,并含有丰富轮藻化石的这套地层应属下白垩统下沟组,其时代为早白垩世Ｂａｒｒｅｍｉａｎ期。     

西南地区中泥盆世的直立轮藻

本文描述了中泥盆世的直立轮藻5种、1型,分别属于Sycidium 和Chovanella 两属。文中讨论了这两个属的分类位置问题,详细阐述了Sycidium 藏卵器的发育特点,提出了关于藏卵器包围细胞分裂发育过程的新认识,同时提出了含化石地层的时代应相当于中泥盆世晚期的吉维特期。     

论四射珊瑚征瑚属Charactophyllum Simpson,1990

对Ｃｈａｒａｃｔｏｐｈｙｌｌｕｍ作了全面的回顾整理,记述了本属的骨骼构造,在此基础上讨论了其定义范围和时空分布及有关的分类问题。Ｃｈａｒａｃｔｏｐｈｙｌｌｕｍ的隔壁为板状隔壁而非包珊瑚型隔壁,由波状弯曲的单列单晶榍组成,单晶榍整体呈半扇形排列,隔壁光滑或发育微弱的榍凸（ｃａｒｉｎａｅ）而无典型的横耙状榍凸（ｙａｒｄａｒｍ ｃａｒｉｎａｅ）,鳞板半扇形排列而不是扉形排列。本属分布仅限于北美和华北的晚     

西藏台错晚第四纪轮藻类的新类型

本文的研究材料来自西藏羌塘高原西部台错古湖一个3.69 m的天然剖面,其地层测年为32.6-4.5ka.从其156个样品中获取大量的轮藻类、介形类和腹足类及少量有孔虫等微体化石.据轮藻类藏卵器外形,顶部结构、螺旋细胞钙化式样等特征,该剖面的轮藻类应归属于轮藻科Characeae之轮藻属Chara.经研究得知,台错古湖在...     

轮生钩藻的形态特征及其系统位置

十年前在云南省早泥盆世的地层中发现了轮生钩藻(Uncataella verticillata),限于当时的材料,其分类位置未定。本研究所用材料采自它的模式标本产地,化石植物保存良好,首次发现了着生在植物体上的雌性生殖器官——藏卵器。根据藏卵器和植物体其它部分显示的形态特征,本文修订了它的原始描述并对其系统位置进行了探讨,认为轮生钩藻是一种原始的轮藻植物,很可能属于直立轮藻目直立轮藻科中的一个成员。     

Regulation Culture on Cytological，Biochemical and Physiological Characteristics of Somatic Carrot Em

ＲｅｇｕｌａｔｉｏｎＣｕｌｔｕｒｅｏｎＣｙｔｏｌｏｇｉｃａｌ,ＢｉｏｃｈｅｍｉｃａｌａｎｄＰｈｙｓｉｏｌｏｇｉｃａｌＣｈａｒａｃｔｅｒｉｓｔｉｃｓｏｆＳｏｍａｔｉｃＣａｒｒｏｔＥｍｂｒｙｏｓＨＵＡＮＧＭｅｉ－ｊｕａｎ;（黄美娟）,ＨＵＡＮＧＳｈａｏ－...     

Oospore dimensions and wall ornamentation in <Emphasis Type="Italic">Chara braunii</Emphasis>

Morphological features of oospores of a rarely noted species Chara braunii Gmel. were examined in a local population (fishpond near Tuplice village, Ziemia Lubuska region, mid-western Poland). The largest polar axis (LPA, length), largest equatorial diameter (LED, width), isopolarity index (ISI = LPA/LED* 100), and the number of ridges and width of fossa of 90 oospores were measured. Additionally, the oospore wall ornamentation pattern was examined by means of scanning electron microscopy (SEM). As a result, a cylindrical shape and the lack of so-called “shoulder” were found. Oospore length and width ranged between 466.8–600.1 μm and 250.1–366.7 μm, respectively, with the ISI index values between 148 and 213. The number of ridges was 8–10 and the width of fossa varied between 50.0 and 66.7 μm. The oospore width appeared to be the most changeable feature, whereas, by contrast, the number of ridges was the least variable character. Wall ornamentation can be described as tuberculate and a ribbon was present on the ridges. As a comparative material for the study performed, 9 oospores from Professor Izabela Dąmbska’s Collection of Charophytes of Poland were measured. It was evidenced that variation ranges of most of the features of Chara braunii oospores from Tuplice fishpond are similar to those of Professor Dąmbska’s herbarium materials and to data reported by authors from other countries as well. The morphology of reproductive structures does not follow the variation of thalli characteristics.     

Reconstruction of the former charophyte community out of the fructifications identified in Albufera de València lagoon sediments

Several decades ago, due to eutrophication, Albufera de València lagoon lost the charophyte meadows that covered the bottom in the past but had never been studied in detail. An area close to the lagoon will be restored now to improve water quality and to recover submerged vegetation. To have information on the background of the charophytes from this area, four 80-87 cm long sediment cores were extracted from the lagoon. The subfossil charophyte fructifications (oospores and gyrogonites) were isolated and identified in two of the four cores. Moreover, sediment core fractions from the third and fourth cores were allowed to germinate under several conditions. The study of the lagoon sediments has revealed that at least 11 morphologies of charophyte fructifications existed in the past. Ten of these were determined at species level: Chara vulgaris, Chara hispida, Chara aspera, Chara baltica, Chara tomentosa, Chara globularis, Lamprothamnium papulosum, Nitella hyalina, Tolypella glomerata and Tolypella hispanica. However, one form of Chara gyrogonite did not fit in any known species. L. papulosum oospores and gyrogonites were the most abundant and concentrated in the deepest sediment layers when the lagoon held brackish water. Large changes in salinity due to freshwater input drove charophyte species substitution (disappearance of L. papulosum). During the oligohaline period C. vulgaris sexual propagules were the most abundant. The last charophyte community before its disappearance due to eutrophication was composed mainly of C. hispida, C. tomentosa and N. hyalina (the two latter with small numbers of oospores in the sediment). To characterize the morphology of the unidentified gyrogonite species, 100 specimens were studied. This type could be a local variety of a more common species, probably C. vulgaris, grown under particular ecological conditions. Old collected oospores (more than 45 years old) germinated and could be identified as C. vulgaris and C. hispida.     

Epiphytic cyanobacteria on Chara vulgaris are the main contributors to N(2) fixation in rice fields

The distribution of nitrogenase activity in the rice-soil system and the possible contribution of epiphytic cyanobacteria on rice plants and other macrophytes to this activity were studied in two locations in the rice fields of Valencia, Spain, in two consecutive crop seasons. The largest proportion of photodependent N(2) fixation was associated with the macrophyte Chara vulgaris in both years and at both locations. The nitrogen fixation rate associated with Chara always represented more than 45% of the global nitrogenase activity measured in the rice field. The estimated average N(2) fixation rate associated with Chara was 27.53 kg of N ha(-1) crop(-1). The mean estimated N(2) fixation rates for the other parts of the system for all sampling periods were as follows: soil, 4.07 kg of N ha(-1) crop(-1); submerged parts of rice plants, 3.93 kg of N ha(-1) crop(-1); and roots, 0.28 kg of N ha(-1) crop(-1). Micrographic studies revealed the presence of epiphytic cyanobacteria on the surface of Chara. Three-dimensional reconstructions by confocal scanning laser microscopy revealed no cyanobacterial cells inside the Chara structures. Quantification of epiphytic cyanobacteria by image analysis revealed that cyanobacteria were more abundant in nodes than in internodes (on average, cyanobacteria covered 8.4% +/- 4.4% and 6.2% +/- 5.0% of the surface area in the nodes and internodes, respectively). Epiphytic cyanobacteria were also quantified by using a fluorometer. This made it possible to discriminate which algal groups were the source of chlorophyll a. Chlorophyll a measurements confirmed that cyanobacteria were more abundant in nodes than in internodes (on average, the chlorophyll a concentrations were 17.2 +/- 28.0 and 4.0 +/- 3.8 microg mg [dry weight] of Chara(-1) in the nodes and internodes, respectively). These results indicate that this macrophyte, which is usually considered a weed in the context of rice cultivation, may help maintain soil N fertility in the rice field ecosystem.     

Charophytes, indicateurs de paléobathymétrie du lac Tigalmamine (Moyen Atlas, Maroc)

A paleolimnological study can be particularly accurate in situations where the species found in the sediments have persisted in the same lake and can provide a direct modern analogue for interpretation. Lake Tigalmamine, thus, represents an exceptionally favourable context, compared to most paleolakes in North Africa, as this site allows comparing the fossil remains of the Characeae to those produced by the living plants. Tigalmamine is a hydrosystem composed of three karstic lakes located at 1626 m above sea level in the Middle Atlas of Morocco. The site had been the subject of a 16 m long core taken in the center of the central lake under 16 m of water (core C 86 in Lamb and Kaars, 1995 [The Holocene 5 (1995) 400-408]). The section represents the total of the Holocene from 10,200 BP to Present (El Hamouti et al., 1991 [Comptes Rendus de l’Académie des Sciences de Paris 2 (1991) 259-265]; Lamb et al., 1995 [Nature 373 (1995) 134-137]). The latter published a synthesis of the pluridisciplinary studies conducted on this core. Also, the numerous gyrogonites isolated from that core had been determined as Chara hispida (Soulié-Märsche in Benkaddour, 1993 [Changements hydrologiques et climatiques dans le Moyen-Atlas marocain : chronologie, minéralogie, géochimie isotopique et élémentaire des sédiments lacustres de Tigalmamine. PhD thesis, Université Paris-Sud, Orsay (inédit)]). Further fieldwork at Tigalmamine by the authors of the present paper in year 2000 showed that Chara hispida is still present in the lake where it forms a belt of submerged vegetation restricted to the range of 2 to 9 m water depth. This paper describes the morphological and ecological characteristics of the extant Chara hispida as a reference for the interpretation of the fossil remains. Based on these data, the frequency changes of the gyrogonites in the core sediments become significant in terms of bathymetry. The detailed analysis of the charophytes from the core, as a complement to the previous studies, confirms the existence of four Holocene phases with lake level low stand at Tigalmamine. The aim of the present study is to enhance the value of the charophytes as a useful complementary tool for paleolimnological reconstruction.     

Embryogenesis in mouth-breeding cichlids (Osteichthyes,Teleostei) structure and fate of the enveloping layer

The eggs of African mouth-brooders are of unusual size and shape. Studying their development may help to more clearly understand epiboly, gastrulation, and the relation between enveloping layer (periderm) and epidermis. When epiboly has progressed over just one fifth of the yolk mass, the germ ring and embryonic shield are already well established. Behind the germ ring very few deep cells are present at this early stage of epiboly, except in the embryonic shield. When the blastodisc covers the animal half of the yolk mass, the future body is already well established with notochord, somites and developing neural keel. Apart from these structures, no deep cells can be detected between enveloping layer and yolk surface; not even a germ ring remains behind the advancing edge of the enveloping layer. Epiboly over the greater part of the yolk is achieved only by the enveloping layer and the yolk syncytial layer. As the margin of the enveloping layer begins to reduce its circumference when closing around the vegetal pole, groups of cells in the advancing edge become spindle-shaped, with a single cell in between of each of these groups broadening along the edge. The enveloping layer (called periderm after epiboly) remains intact until after hatching, when, together with the underlying ectoderm, it forms the double-layered skin of the larval fish. Thereafter, cells deriving from the subperipheral ectoderm gradually replace the decaying periderm cells to form the final epidermis. Thus, in the cichlids studied, the enveloping layer alone forms the yolk sac to begin with, and it covers the larval body until some days after hatching.     

Rho-mediated cytoskeletal rearrangement in response to LPA is functionally antagonized by Rac1 and PIP2

G-protein-coupled receptors signal through Rho to induce actin cytoskeletal rearrangement. We previously demonstrated that thrombin stimulates Rho-dependent process retraction and rounding of 1321N1 astrocytoma cells. Surprisingly, while lysophosphatidic acid (LPA) activated RhoA in 1321N1 cells, it failed to produce cell rounding. Thrombin, unlike LPA, decreased Rac1 activity, and activated (GTPase-deficient) Rac1 inhibited thrombin-stimulated cell rounding, while expression of dominant-negative Rac1 promoted LPA-induced rounding. LPA and thrombin receptors appear to differ in coupling to Gi, as LPA but not thrombin-stimulated 1321N1 cell proliferation was pertussis toxin-sensitive. Blocking Gi with pertussis toxin enabled LPA to induce cell rounding and to decrease activated Rac1. These data support the hypothesis that Rac1 and Gi activation antagonize cell rounding. Thrombin and LPA receptors also differentially activated Gq pathways as thrombin but not LPA increased InsP3 formation and reduced phosphatidylinositol 4,5-bisphosphate (PIP2) levels. Microinjection of the plekstrin homology domain of phospholipase C (PLC)delta1, which binds PIP2, enabled LPA to elicit cell rounding, consistent with a requirement for PIP2 reduction. We suggest that Rho-mediated cytoskeletal responses are enhanced by concomitant reductions in cellular levels of PIP2 and Rac1 activation and thus effected only by G-protein-coupled receptors with appropriate subsets of G protein activation.     

p85 beta-PIX is required for cell motility through phosphorylations of focal adhesion kinase and p38 MAP kinase

Lysophosphatidic acid (LPA) mediates diverse biological responses, including cell migration, through the activation of G-protein-coupled receptors. Recently, we have shown that LPA stimulates p21-activated kinase (PAK) that is critical for focal adhesion kinase (FAK) phosphorylation and cell motility. Here, we provide the direct evidence that p85 beta-PIX is required for cell motility of NIH-3T3 cells by LPA through FAK and p38 MAP kinase phosphorylations. LPA induced p85 beta-PIX binding to FAK in NIH-3T3 cells that was inhibited by pretreatment of the cells with phosphoinositide 3-kinase inhibitor, LY294002. Furthermore, the similar inhibition of the complex formation was also observed, when the cells were transfected with either p85 beta-PIX mutant that cannot bind GIT or dominant negative mutants of Rac1 (N17Rac1) and PAK (PAK-PID). Transfection of the cells with specific p85 beta-PIX siRNA led to drastic inhibition of LPA-induced FAK phosphorylation, peripheral redistribution of p85 beta-PIX with FAK and GIT1, and cell motility. p85 beta-PIX was also required for p38 MAP kinase phosphorylation induced by LPA. Finally, dominant negative mutant of Rho (N19Rho)-transfected cells did not affect PAK activation, while the cells stably transfected with p85 beta-PIX siRNA or N17Rac1 showed the reduction of LPA-induced PAK activation. Taken together, the present data suggest that p85 beta-PIX, located downstream of Rac1, is a key regulator for the activations of FAK or p38 MAP kinase and plays a pivotal role in focal complex formation and cell motility induced by LPA.     

Lysophosphatidic acid and receptor-mediated activation of endothelial nitric-oxide synthase

Both lysophosphatidic acid (LPA) and sphingosine-1-phosphate (S1P) are platelet-derived phospholipids that elicit diverse biological responses. In endothelial cells, S1P stimulates the EDG-1 receptor-mediated activation of the endothelial isoform of nitric oxide synthase (eNOS), but the role of LPA in eNOS regulation is less well understood. We now report that LPA treatment of bovine aortic endothelial cells (BAEC) activates eNOS enzyme activity in a pathway that involves phosphorylation of eNOS on serine 1179 by protein kinase Akt. In contrast to the cellular responses elicited by S1P in COS-7 cells, LPA can stimulate the activation of eNOS and Akt independently of EDG-1 receptor transfection. LPA-stimulated enzyme activation was significantly attenuated in an eNOS mutant lacking the site that is phosphorylated by kinase Akt (eNOS S1179A). In BAEC, activation of eNOS by LPA is completely blocked by pertussis toxin, by the intracellular calcium chelator BAPTA (1,2-bis(aminophenoxy) ethane-N,N,N',N'-tetraacetic acid), and by the phosphoinositide 3-kinase (PI3-K) inhibitor wortmannin, but is unaffected by U0126, an inhibitor of mitogen-activated protein (MAP) kinase pathways. Analysis of the LPA dose response for eNOS activation reveals an EC(50) of approximately 40 nM, a concentration well below the potency of LPA at the EDG-1 receptor. Taken together, these results indicate that LPA potently activates eNOS in BAEC in a pathway distinct from the EDG-1 receptor, but mediated by a similar receptor-mediated pathway dependent on pertussis toxin-sensitive G proteins and involving activation of the PI3-K/Akt pathway. These studies have identified a role for the phospholipid LPA in eNOS activation, and point out the complementary role of distinct platelet-derived lipids in endothelial signaling pathways.