Second harmonic generation microscopy reveals hidden polar organization in fluoride doped MIL-53(Fe)

Doping of MIL-53(Fe) with fluoride atoms introduces a polar organization in the structure when guest molecules are present.

Micropatterned Macrophage Analysis Reveals Global Cytoskeleton Constraints Induced by Bacillus anthracis Edema Toxin

Bacillus anthracissecretes the edema toxin (ET) that disrupts the cellular physiology of endothelial and immune cells, ultimately affecting the adherens junction integrity of blood vessels that in turn leads to edema. The effects of ET on the cytoskeleton, which is critical in cell physiology, have not been described thus far on macrophages. In this study, we have developed different adhesive micropatterned surfaces (L and crossbow) to control the shape of bone marrow-derived macrophages (BMDMs) and primary peritoneal macrophages. We found that macrophage F-actin cytoskeleton adopts a specific polar organization slightly different from classical human HeLa cells on the micropatterns. Moreover, ET induced a major quantitative reorganization of F-actin within 16 h with a collapse at the nonadhesive side of BMDMs along the nucleus. There was an increase in size and deformation into a kidney-like shape, followed by a decrease in size that correlates with a global cellular collapse. The collapse of F-actin was correlated with a release of focal adhesion on the patterns and decreased cell size. Finally, the cell nucleus was affected by actin reorganization. By using this technology, we could describe many previously unknown macrophage cellular dysfunctions induced by ET. This novel tool could be used to analyze more broadly the effects of toxins and other virulence factors that target the cytoskeleton.

Polarity of the ascidian egg cortex before fertilization

The unfertilized ascidian egg displays a visible polar organization along its animal-vegetal axis. In particular, the myoplasm, a mitochondria-rich subcortical domain inherited by the blastomeres that differentiate into muscle cells, is mainly situated in the vegetal hemisphere. We show that, in the unfertilized egg, this vegetal domain is enriched in actin and microfilaments and excludes microtubules. This polar distribution of microfilaments and microtubules persists in isolated cortices prepared by shearing eggs attached to a polylysine-coated surface. The isolated cortex is further characterized by an elaborate network of tubules and sheets of endoplasmic reticulum (ER). This cortical ER network is tethered to the plasma membrane at discrete sites, is covered with ribosomes and contains a calsequestrin-like protein. Interestingly, this ER network is distributed in a polar fashion along the animal-vegetal axis of the egg: regions with a dense network consisting mainly of sheets or tightly knit tubes are present in the vegetal hemisphere only, whereas areas characterized by a sparse tubular ER network are uniquely found in the animal hemisphere region. The stability of the polar organization of the cortex was studied by perturbing the distribution of organelles in the egg and depolymerizing microfilaments and microtubules. The polar organization of the cortical ER network persists after treatment of eggs with nocodazole, but is disrupted by treatment with cytochalasin B. In addition, we show that centrifugal forces that displace the cytoplasmic organelles do not alter the appearance and polar organization of the isolated egg cortex. These findings taken together with our previous work suggest that the intrinsic polar distribution of cortical membranous and cytoskeletal components along the animal-vegetal axis of the egg are important for the spatial organization of calcium-dependent events and their developmental consequences.

The brain of the honeybee Apis mellifera . I. The connections and spatial organization of the mushroom bodies

The mushroom bodies of the bee are paired neuropils in the dorsal part of the brain. Each is composed of the arborizations of over 17 x 10 4 small interneurons of similar architecture called Kenyon cells. Golgi staining demonstrates that these neurons can be divided into five groups distinguished on the basis of their dendritic specializations and geometry. The mushroom body neuropils each consist of a pair of cup-shaped structures, the calyces, connected by two short fused stalks, the pedunculus, to two lobes, the α- and β-lobes. Each calyx is formed from three concentric neuropil zones, the basal ring, the collar and the lip. The calyces are organized in a polar fashion; within the calyces each of the five categories of Kenyon cell has a distribution limited to particular polar contours. The dendritic volumes of neighbouring Kenyon cells arborizing within each individual contour are greatly overlapped. Fibres from groups of neighbouring cells within a calycal contour are gathered into bundles that project into the pedunculus, each fibre dividing to enter both the the α- and β-lobes. The pedunculus and the lobes are conspicuously layered. Kenyon cells with neighbouring dendritic fields within the same calycal contour occupy a single layer in the pedunculus and lobes. Thus the two- polar organization of the calyces is transformed into a Cartesian map within the pedunculus, which continues into the α- and β-lobes. The calyx receives input fibres from both the antennal lobes and the optic neuropils. The branching patterns of these cells reflect the polar organization of the calyces as their terminals are restricted to one or more of the three gross compartments of the calycal neuropil. The course of these tracts and the morphologies of the fibres that they contain are described. Cells considered to represent outputs from the mushroom bodies arborize in the pedunculus and α- and β-lobes. Generally the arborizations of the output neurons reflect the layered organization of these neuropils. Fibres from the two lobes run to the anterior median and lateral protocerebral neuropil, and the anterior optic tubercle. Additionally there is an extensive network of feedback interneurons that inter- connect the α- and β-lobes with the ipsi- and contralateral calyces. Many individual neurons have branches in both the α- and β-lobes and in the pedunculus. The pathways and geometries of the fibres subserving the two lobes are described. The hypothesis of Vowles (1955) that the individual lobes represent a separation of sensory and motor output areas is shown to be incorrect. The anatomy of the bee’s mushroom bodies suggests that they process second-order antennal and fourth- and higher-order visual information. The feedback pathways are discussed as possible means of creating long-lasting after-effects which may be important in complex timing processes and possibly the formation of short-term memory.