Macroalgae exhibit diverse responses to human disturbances on coral reefs

Scientists and managers rely on indicator taxa such as coral and macroalgal cover to evaluate the effects of human disturbance on coral reefs, often assuming a universally positive relationship between local human disturbance and macroalgae. Despite evidence that macroalgae respond to local stressors in diverse ways, there have been few efforts to evaluate relationships between specific macroalgae taxa and local human-driven disturbance. Using genus-level monitoring data from 1205 sites in the Indian and Pacific Oceans, we assess whether macroalgae percent cover correlates with local human disturbance while accounting for factors that could obscure or confound relationships. Assessing macroalgae at genus level revealed that no genera were positively correlated with all human disturbance metrics. Instead, we found relationships between the division or genera of algae and specific human disturbances that were not detectable when pooling taxa into a single functional category, which is common to many analyses. The convention to use percent cover of macroalgae as an indication of local human disturbance therefore likely obscures signatures of local anthropogenic threats to reefs. Our limited understanding of relationships between human disturbance, macroalgae taxa, and their responses to human disturbances impedes the ability to diagnose and respond appropriately to these threats.     

Use of the balanced-cell technique to determine properties of single yeast cells

The dielectrophoretic force on single yeast cells in water has been measured by the method of balancing it against the force of gravity. The force expression for the electrode geometry of parallel wires is derived and related to the electrical properties of the cell and its surroundings through the parameter K, the excess relative permittivity. A detailed analysis is given of the two alternate experimental approaches that can be taken using the balance technique. Experimental values of K are determined for various conditions and compared with those predicted from a theoretical model of a yeast cell.     

Trypanosoma cruzi: interaction with vertebrate cells. DNA synthesis and growth of intracellular amastigotes and their relationship to host cell DNA synthesis and growth.

DNA synthesis of intracellular Trypanosoma cruzi amastigotes, following the infection of bovine embryo skeletal muscle (BESM) cells, was studied by autoradiography. After penetration, there was a prereplicative lag period (similar to or approximately 12 h) followed by a synchronous round of DNA synthesis which was found to be independent of parasite number/BESM cell cand the host cell DNA synthesis cycle. Parasite reproduction occurred, for the first time, at approximately 21 h postinfection. It was concluded that T. cruzi trypomastigotes are in the G1/G0 phase of their cell division cycle and that after penetration parasite reproduction occurs independent of events controlling host cell DNA synthesis and growth. The early synchronous growth of intracellular amastigotes should facilitate further studies on the biochemical events controlling trypomastigote-to-amastigote transformation and amastigote reproduction. A further application is envisaged for studies on the mode of action of drugs with trypanocidal activity.     

Haploinsufficient Bmp4 ocular phenotypes include anterior segment dysgenesis with elevated intraocular pressure

Background  

Glaucoma is a common disease but its molecular etiology is poorly understood. It involves retinal ganglion cell death and optic nerve damage that is often associated with elevated intraocular pressure. Identifying genes that modify glaucoma associated phenotypes is likely to provide insights to mechanisms of glaucoma. We previously reported glaucoma in DBA/2J mice caused by recessive alleles at two loci, isa and ipd, that cause iris stromal atrophy and iris pigment dispersion, respectively. A approach for identifying modifier genes is to study the effects of specific mutations in different mouse strains. When the phenotypic effect of a mutation is modified upon its introduction into a new strain, crosses between the parental strains can be used to identify modifier genes. The purpose of this study was to determine if the effects of the DBA/2J derived isa and ipd loci are modified in strain AKXD-28/Ty.