Ontogeny of head and caudal fin shape of an apex marine predator: The tiger shark (Galeocerdo cuvier)

How morphology changes with size can have profound effects on the life history and ecology of an animal. For apex predators that can impact higher level ecosystem processes, such changes may have consequences for other species. Tiger sharks (Galeocerdo cuvier) are an apex predator in tropical seas, and, as adults, are highly migratory. However, little is known about ontogenetic changes in their body form, especially in relation to two aspects of shape that influence locomotion (caudal fin) and feeding (head shape). We captured digital images of the heads and caudal fins of live tiger sharks from Southern Florida and the Bahamas ranging in body size (hence age), and quantified shape of each using elliptical Fourier analysis. This revealed changes in the shape of the head and caudal fin of tiger sharks across ontogeny. Smaller juvenile tiger sharks show an asymmetrical tail with the dorsal (upper) lobe being substantially larger than the ventral (lower) lobe, and transition to more symmetrical tail in larger adults, although the upper lobe remains relatively larger in adults. The heads of juvenile tiger sharks are more conical, which transition to relatively broader heads over ontogeny. We interpret these changes as a result of two ecological transitions. First, adult tiger sharks can undertake extensive migrations and a more symmetrical tail could be more efficient for swimming longer distances, although we did not test this possibility. Second, adult tiger sharks expand their diet to consume larger and more diverse prey with age (turtles, mammals, and elasmobranchs), which requires substantially greater bite area and force to process. In contrast, juvenile tiger sharks consume smaller prey, such as fishes, crustaceans, and invertebrates. Our data reveal significant morphological shifts in an apex predator, which could have effects for other species that tiger sharks consume and interact with. J. Morphol. 277:556–564, 2016. © 2016 Wiley Periodicals, Inc.     

Rapid improvement of rice eating and cooking quality through gene editing toward glutelin as target

Rice eating and cooking quality (ECQ) is a major concern of breeders and consumers, determining market competitiveness worldwide. Rice grain protein content (GPC) is negatively related to ECQ, making it possible to improve ECQ by manipulating GPC. However, GPC is genetically complex and sensitive to environmental conditions; therefore, little progress has been made in traditional breeding for ECQ. Here, we report that CRISPR/Cas9-mediated knockout of genes encoding the grain storage protein glutelin rapidly produced lines with downregulated GPC and improved ECQ. Our finding provides a new strategy for improving rice ECQ.     

酸敏感离子通道与脑梗死

急性脑梗死约占全部脑卒中的70%,病死率和致残率高,且极易复发。但目前针对急性脑梗死在时间窗内溶栓、抗凝等治疗手段不能从根本上切实有效地修复受损脑组织,且伴有出血等风险。寻找脑梗死形成发展的原因并予以治疗迫在眉睫。酸中毒是引起缺血性脑损伤的重要机制。大量实验研究表明,酸中毒能加重神经元的缺血性损伤,且其梗死面积与酸中毒的程度直接相关。但缺血产生的酸中毒如何引起神经元损伤的确切机制尚不明确。最近研究发现酸中毒能激活一种在中枢及周围神经中广泛存在的膜通道,即酸敏感离子通道,它对Ca2+通透,能引起细胞内Ca2+超载,同时能激活胞内酶引起细胞内蛋白质、脂类及核酸的降解,加重缺血后脑损伤。本文就酸敏感离子通道1a与脑梗死做一综述。     

The enhancement of electrostriction caused by lowering the solvent dielectric constant leads to the decrease of activation energy in trypsin catalysis.

The contribution of electrostriction of the solvent to the stabilization of the negatively charged tetrahedral transition state of a trypsin-catalyzed reaction was probed by means of kinetic studies involving high-pressure and solvent dielectric constant. A good correlation was observed between the increased catalytic efficiency of trypsin and the decreased solvent dielectric constant. When the dielectric constant of the solvents was lowered by 4.68 units, the loss of activation energy and that of free energy of activation were 2.26 kJ/mol and 3.09 kJ/mol, respectively. The activation volume for k(cat) decreased significantly as the dielectric constant of the solvent decreased, indicating that the degree of electrostriction of the solvent around the charged tetrahedral transition state has been enhanced. These observations demonstrate that the increase in the catalytic efficiency of the trypsin reaction with decreasing dielectric constant resulted from the stabilization of electrostatic energy for the formation of an oxyanion hole, and this stabilization was caused by the increase of electrostricted water around the charged tetrahedral transition state. Therefore, we conclude that control of the solvent dielectric constant can stabilize the tetrahedral transition state, and this lowers the activation energy.     

Iron plaque enhances phosphorus uptake by rice (Oryza sativa) growing under varying phosphorus and iron concentrations

Both solution culture and pot experiments were performed to investigate (a) the effects of external Fe (II) concentrations and forms on the formation of iron plaque on the roots of rice (Oryza sativa) and subsequent P adsorption on iron plaque and shoot P concentrations and (b) the effects of soil moisture regimes on the formation of iron plaque and P adsorption on root surfaces and P accumulation in shoots. The results showed that iron plaque was significantly increased with increasing Fe²⁺ concentrations in the solution culture. The amounts of P adsorbed on the iron plaque were increased significantly with external Fe²⁺ concentrations. Although shoot P concentration was not significantly affected by Fe²⁺ treatment after incubation for 2 days, it was significantly increased in the Fe‐treated plants compared with Fe‐deprived ones after incubation for 4 days. Soil culture experiment showed that the formation of iron plaque on root surfaces was promoted by exogenous iron, with greater amount of iron plaque being formed by addition of ferric hydroxide than of ferric oxide. Phosphorus adsorption on iron plaque also increased with the addition of iron oxides, and increasing soil P increased the amounts of P associated with the iron plaque and shoot P concentration. The amounts of iron plaque were almost sixfold higher under flooding condition than under field capacity condition. Plants pretreated under flooding condition generally had higher shoot P concentrations when they were transplanted to solutions with varying P levels, and this was most pronounced in the treatment with highest solution P concentration. The results suggest that iron plaque acts as a nutrient reservoir for phosphorus in the rhizosphere and helps enhance P acquisition by rice.     

Microrheological aspects of adhesion of Escherichia coli on glass

The adhesion of both live and fixed bacteria (Escherichia coli) on glass has been studied under well-defined hydrodynamic conditions, created in an impinging jet apparatus. With this technique one can accurately measure the initial deposition rate jo on the surface, the average lifetime of a bacterium on the surface, tau esc, and the surface area blocked per deposited bacterium, normalized by its projected area, gamma. The experimental results are compared to theoretical results for equivalent spheres. It is found that near the stagnation point the deposition rate jo is mainly controlled by convective diffusive transport which, for rod-shaped Eschericia coli, with an axis ratio of about 2, is found to be equal to that for spheres. No differences in jo and tau esc were found between live and fixed bacteria at low flow rates. At high flow rates fixed bacteria adhered to the surface at a slower rate. In both systems jo was found to decrease suddenly at a distance of about 150 microns from the stagnation point, in contrast to systems of spherical particles for which jo is uniform over the surface. Most likely this is due to the rotation of the rod-shaped particles, which vary their distance to the surface periodically with time. The main difference between live and fixed bacteria, besides different deposition rates in strong flows, is that gamma is about 30% larger for fixed bacteria than for live ones, resulting in a much lower final coverage for fixed bacteria. These results imply a larger repulsion between fixed bacteria than between living ones. From detachment experiments we can conclude that not all bacteria stick to the surface with the same bond strength. The variation in the bond strength is due to the aging of the bonds between the bacteria and the surface. The average bond strength corresponds to an energy of about 13-15 kT.     

The L-isoaspartyl/D-aspartyl protein methyltransferase gene (PCMT1) maps to human chromosome 6q22.3-6q24 and the syntenic region of mouse chromosome 10.

We have mapped the genes for the human and mouse L-isoaspartyl/D-aspartyl protein carboxyl methyltransferase (EC 2.1.1.77) using cDNA probes. We determined that the human gene is present in chromosome 6 by Southern blot analysis of DNA from a panel of mouse-human somatic cell hybrids. In situ hybridization studies allowed us to confirm this identification and further localize the human gene (PCMT1) to the 6q22.3-6q24 region. By analyzing the presence of an EcoRI polymorphism in DNA from backcrosses of C57BL/6J and Mus spretus strains of mice, we localized the mouse gene (Pcmt-1) to chromosome 10, at a position 8.2 +/- 3.5 cM proximal to the Myb locus. This region of the mouse chromosome is homologous to the human 6q24 region.     

氧化塘中细菌种群组成动态

对武汉地区氧化塘中的细菌数量、细菌种类、种群组成、优势种及群落多样性进行了初步研究。从氧化塘中分离的细菌经鉴定属于12个属,主要有假单胞菌属(Pseudomonas)、棒杆菌属(corynebacterium)、无色杆菌属(Achromobacter)和微杆菌属(Microbacterium),其它菌属是芽孢杆菌属(Bacillus)、色杆菌属(Chromobacterium)、短杆菌属(Brevibacterium)、葡萄球菌属(Staphylococcus)、微球菌属(Micrococcus)、黄杆菌属(Flavobacterium)、埃希氏菌属(Escherichia)和链球菌属(Streptococcus)。在5个小塘中,细菌数量、种群组成和群落多样性指数都有不同,这与各塘的污染程度有关。由此,多样性指数可用于监测氧化塘的净化效果。     

城镇污水诱发青蛙蝌蚪红细胞微核及其在环境监测中的应用

本文利用青蛙(Rana nigromaculata Hallowell)蝌蚪红细胞微核试验,作为检测城镇污水诱变活性的一种新的监测技术。在16d生活污水处理的实验中,青蛙蝌蚪红细胞微核细胞率2d后就呈现统计上的显著增加,并随处理时间的延长而增高,第12d达到最大值。在不同浓度混合污水处理实验中,蝌蚪红细胞微核细胞率呈现明显的剂量依赖性增加。上述实验证明城镇生活污水和混合污水都具有较强的诱变活性。作者从遗传毒理学的角度评价了湖北黄州综合生物塘系统对污水诱变活性的净化效能。城镇混合污水经综合生物塘各级塘处理,蝌蚪微核细胞率逐级下降,由进水的7.54‰下降到最后出水的1.52‰,接近对照(1.07‰)水平。其中综合生物塘的藻菌单元比水生植物单元对污水诱变活性具有更强的净化效力。本文提出污水“诱变指数”可作为综合生物塘一项功能评价指标。