An unexpected noncarpellate epigynous flower from the Jurassic of China.

The origin of angiosperms has been a long-standing botanical debate. The great diversity of angiosperms in the Early Cretaceous makes the Jurassic a promising period in which to anticipate the origins of the angiosperms. Here, based on observations of 264 specimens of 198 individual flowers preserved on 34 slabs in various states and orientations, from the South Xiangshan Formation (Early Jurassic) of China, we describe a fossil flower, Nanjinganthus dendrostyla gen. et sp. nov.. The large number of specimens and various preservations allow for an evidence-based reconstruction of the flower. From the evidence of the combination of an invaginated receptacle and ovarian roof, we infer that the seeds of Nanjinganthus were completely enclosed. Evidence of an actinomorphic flower with a dendroid style, cup-form receptacle, and angiospermy, is consistent with Nanjinganthus being a bona fide angiosperm from the Jurassic, an inference that we hope will re-invigorate research into angiosperm origins.

Subcellular distribution and toxicity of cadmium in Potamogeton crispus L.

The submerged macrophyte Potamogeton crispus L. was subjected to varying doses of cadmium (0, 20, 40, 60 and 80 µM) for 7 d, and the plants were analyzed for subcellular distribution of Cd, accumulation of mineral nutrients, photosynthesis, oxidative stress, protein content, and ultrastructural distribution of calcium (Ca). Leaf fractionation by differential centrifugation indicated that 48-69% of Cd was accumulated in the cell wall. At all doses of Cd, the levels of Ca and B rose and the level of Mn fell; the levels of Fe, Mg, Zn, Cu, Mo, and P rose initially only to decline later. Exposure to Cd caused oxidative stress as evident by increased content of malondialdehyde and decreased contents of chlorophyll and protein. Photosynthetic efficiency, as indicated by the quenching of chlorophyll a fluorescence (Fv/Fm, Fo and Fm), decreased significantly, the extent of decrease being directly proportional to the concentration of Cd. Increased amounts of precipitates of calcium were noticed in the treated plants, located either outside the cell membrane or in chloroplasts, mitochondria, the nucleus, and the cytoplasm whereas control plants showed small deposits of the precipitates around surface of the vacuole membrane and in the intercellular space but rarely in the cytoplasm. Photosynthetic efficiency and oxidative stress could be used as indicators of physiological end-points in determining the extent of Cd phytotoxicity.

Palaeontological evidence of membrane relationship in step-by-step membrane fusion.

Studies on membrane fusion in living cells indicate that initiation of membrane fusion is a transient and hard to capture process. Despite previous research, membrane behaviour at this point is still poorly understood. Recent palaeobotanical research has revealed snapshots of membrane fusion in a 15-million-year-old fossil pinaceous cone. To reveal the membrane behaviour during the fusion, we conducted more observations on the same fossil material. Several discernible steps of membrane fusion have been fixed naturally and observed in the fossil material. This observation provides transmission electron microscope (TEM) images of the transient intermediate stage and clearly shows the relationship between membranes. Observing such a transient phenomenon in fossil material implies that the fixing was most likely accomplished quickly by a natural process. The mechanism behind this phenomenon is clearly worthy of further enquiry.

Atomic force microscope observation on ultrastructures in plant cells.

AFM is being applied in increasingly wide research fields and extracting more biochemical/biophysical information that is beyond the capability of traditional SEM and TEM. Due to its inherent features, AFM is rarely used to observe the subcellular details within cells. Although subcellular features were recently observed on thin sections of plant tissues using AFM, this method might introduce unexpected artifacts during sample processing. Here we try to observe plant cells still embedded in resin block. This modified method minimizes the possibility of artifacts. The comparison among outcomes of AFM, SEM, TEM and LM on the same single cell suggest that this modified method is a good, applicable, efficient and faithful way applying AFM on biological materials.

[Effects of Ni2+ on physiological characteristics and submicroscopic structure of Salvinia natans leaves].

Influence of 0, 5, 10, 15, 20 mg/L Ni2+ on growth, mineral nutrition, chlorophyll, carotenoid, soluble protein, soluble sugar, superoxide (O2*-), hydrogen peroxide (H2O2) and malondialdehyde (MDA) contents as well as the activities of superoxide dismutase (SOD), guaiacolperoxidase (POD), and catalase (CAT) were studied in the leaves of Salvinia natans plants on 10 days after treatment. With the increase of the Ni2+ concentrations, exposure of the plants revealed that, (1) the addition of Ni2+ affected the absorption of mineral nutrients, it mainly increased the absorption of Ca2+, Na+, Zn2+, Fe3+ and Mg2+, while reduced that of Mn2+, Mo2+, P and K+. (2) The content of chlorophyll, carotenoid, soluble protein and soluble sugar content as well as activities of SOD and CAT decreased gradually. That of O2*-, H2O2 and MDA content as well as POD activity increased, 383%, 168%, 207%, 131% of these controls, respectively. (3) In the leaves of Ni2+ -treated fronds, the polypeptide with apparent molecular weights 94000, was became visible in SDS-PAGE, and the nature of it remains to be determined. The amount and intensity of polypeptide band increased gradually with augment of Ni2+ was also observed, the polypeptide with apparent molecular weight 35,000 increased significantly in fronds. (4) Transmission electron microscope observation indicated that Ni2+ also imposed injury action on submicroscopic structure of leaf cells, disaggregation of nucleolus, agglutination and disappearance of chromatin of nucleus, disruption of nuclear membrane, swelling of thylakoids and breakage of chloroplast envelope, decreasing of cristae quantity and vacuolization of mitochondria. The conclusion could be reached that the plant death was resulted from destruction under structure foundation of physiological function, unbalance of ion equilibrium and disorder of physiological metabolism.

[Toxic effects of Hg2+, Cd2+ and Cu2+ on cell membrane system of Cabomba caroliniana A. Gray].

By the observation with electron- and confocal laser scanning microscopy and the determination of physiological and biochemical reactions, the toxic effects of Hg2+, Cd2+ and Cu2+ on the cell membrane system of Cabomba caroliniana A. Gray were investigated. The results showed that under the actions of the three heavy metal ions, the contents of reactive oxygen species (ROS) and malondialdehyde (MDA) in C. caroliniana leaf cells increased, activities of protective enzymes were in disorder, and lipid peroxidation happened. The cell membrane was damaged, membrane permeability increased, and plasmolysis occurred. Meanwhile, the chloroplast swelled or even disintegrated. The excitement of photosynthetic pigments on thylakoids membrane by light was inhibited, and the auto-fluoresent intensity was decreased. The cristae of mitochondria swelled and decreased, mitochondria membrane was damaged, and nuclear membrane was broken. The effects of Hg2+, Cd2+ and Cu2+ on the cell membrane system of C. caroliniana showed a definite dose-effect correlation, and the stability of membrane system played a key role in the resistance of C. caroliniana to the toxic effects of heavy metals. C. caroliniana was sensitive to Hg2+, and the lethal concentration of Hg2+ was ranged from 0.3 to 0.5 mg L(-1). C. caroliniana had relatively higher endurance to Cd2+ and Cu2+, and could be used as the resistant plant for biological control.

Paleontological evidence for membrane fusion between a unit membrane and a half-unit membrane.

Membrane fusion is of fundamental importance for many biological processes and has been a topic of intensive research in past decades with several models being proposed for it. Fossils had previously not been considered relevant to studies on membrane fusion. But here two different membrane fusion patterns are reported in the same well-preserved fossil plant from the Miocene (15-20 million years old) at Clarkia, Idaho, US. Scanning electron microscope, transmission electron microscope, and traditional studies reveal the vesicles in various states (even transient semi-fusion) of membrane fusion, and thus shed new light on their membrane structure and fusion during exocytoses. The new evidence suggests that vesicles in plant cells may have not only a unit membrane but also a half-unit membrane, and that a previously overlooked membrane fusion pattern exists in plant cells. This unexpected result from an unexpected material not only marks the first evidence of on-going physiological activities in fossil plants, but also raises questions on membrane fusion in recent plants.

[Changes in selectin in early stage of lung injury induced by endotoxic shock in macaque].

OBJECTIVE: To investigate the change in selectin and its effect on lung injury induced by endotoxic [lipopolysaccharide (LPS)] shock in macaque. METHODS: Eleven macaques were randomly divided into two groups: control group (n=5) and LPS group (n=6). The animals of the control group received injection of 1 ml/kg normal saline, and the animals of the LPS group received a dose of 2.8 mg/kg LPS intravenously. The plasma contents of P-selectin and L-selectin were assayed before LPS challenge, 60 and 120 minutes after LPS challenge. Ultrastructure of lung tissue and immunohistochemical assay of P-selectin and L-selectin in the lung were observed. RESULTS: Administration of LPS did not changed P-selectin level in plasma, but decreased the L-selectin level at 120 minutes after LPS challenge in both groups (all P<0.05). By immunohistochemical staining, P-selectin and L-selectin were identified on endothelial cells of alveolar wall of LPS animals, whereas no positive staining of P-selectin and L-selectin was showed in control animals. Damages to alveolar type I and II cells, slight transudation of red blood corpuscles, and damage to the basement membrane were observed with electron microscopy in the endotoxin challenged macaques. No pathological changes were observed in the control group. CONCLUSION: Administration of LPS induces expression of P-selectin and L-selectin in alveolar wall and causes alveolar damages in early-phase of endotoxic shock. In the meantime, the L-selectin and P-selectin in plasma do not change. The selectins play an important role in the pathogenesis of lung injury in the early-phase of endotoxic shock.

Morphology of spiroplasmas in the Chinese mitten crab Eriocheir sinensis associated with tremor disease.

The structure of spiroplasmas in the Chinese mitten crab associated with tremor disease was studied by transmission electron microscopy techniques, including both negative staining and ultrasectioning. A spiral structure, which is a typical form of spiroplasmas, could be detected and the observations showed for the first time the presence of spiroplasmas in the cells of the crab. Propagation of spiroplasmas within the cells presented various forms that could be sorted into three morphological types: rounded, regular helical, and pleiomorphic or intermediate forms. The spiroplasmas appeared as round bodies during the fallow stage of development or under poor conditions. They showed various shapes such as helices, saccate, branched, tadpole-like and tortoise-like structures while growing, and became long and congregated in late stages of development. When spiroplasmas were isolated from chicken eggs and cultured in M1D medium they appeared to undergo similar morphological changes to those in the crab. The spiroplasmas contained chromatin filaments and peripheral ribosome-like granules and were delimited by distinct unitary membranes. Average diameters were calculated at 0.1 to 0.35 microm for rounded forms and 0.1-0.2 microm for helical or long forms, and they varied in length from 3-12 microm.

Study on experimental infections of Spiroplasma from the Chinese mitten crab in crayfish, mice and embryonated chickens.

Tremor disease (TD) of the Chinese mitten crab Eriocheir sinensi has become a serious disease in the Chinese freshwater culture industry in recent years. The agent, belonging to Spiroplasma, was purified from yolk and allantoic fluids of chicken embryos and was then inoculated into the body of crayfish, the abdominal cavity of ICR mice and the allantoid of chicken embryos, respectively. Thirty-eight days after the inoculation, the mice and crayfish were dissected and their tissues sampled and observed with both the light and electron microscope. No infection was detected in mouse or crawfish tissue. But when the different tissues from the inoculated embryonated chickens were tested, the agent was detected only in the brain of embryonated chickens. This indicated that the agent represented a neurotropic characteristic in embryonated chickens, just as it had in the crab. This infective characteristic may be due to the development and maturation of host immunity.

[Toxic effects of Cd2+ pollution on the biochemical and physiological characters and ultrastructure of Alternanthera philoxeroides].

By imitating different concentration Cd2+ polluted water environment, this paper dealt with the changes of some biochemical and physiological characters and the damage of ultrastructure in leaves of Alternanthera philoxeroides. The result showed that SOD and POD activity first increased in the low concentration pollution and then decreased with the concentration of pollution raised. The content of chlorophyll, chlorophyll a/b value, CAT activity and the content of soluble protein all declined continually. With the concentration of pollution increased, the ultrastructure of cell nuclei, chloroplast and mitochondria became deformed, the permutation of structure inside disordered, swelled, membrane disrupted and vesiculated. The changes of some biochemical and physiological characters accorded with the damage of cell ultrastructure.