Measuring the repertoire of age-related behavioral changes in Drosophila melanogaster

Aging affects almost all aspects of an organism—its morphology, its physiology, its behavior. Isolating which biological mechanisms are regulating these changes, however, has proven difficult, potentially due to our inability to characterize the full repertoire of an animal’s behavior across the lifespan. Using data from fruit flies (D. melanogaster) we measure the full repertoire of behaviors as a function of age. We observe a sexually dimorphic pattern of changes in the behavioral repertoire during aging. Although the stereotypy of the behaviors and the complexity of the repertoire overall remains relatively unchanged, we find evidence that the observed alterations in behavior can be explained by changing the fly’s overall energy budget, suggesting potential connections between metabolism, aging, and behavior.     

Spiroplasma swim by a processive change in body helicity

Microscopic organisms must rely on very different strategies than their macroscopic counterparts to swim through liquid. To date, the best understood method for prokaryotic swimming employs the rotation of flagella. Here, we show that Spiroplasma, tiny helical bacteria that infect plants and insects, use a very different approach. By measuring cell kinematics during free swimming, we find that propulsion is generated by the propagation of kink pairs down the length of the cell body. A processive change in the helicity of the body creates these waves and enables directional movement.     

Metal accumulation in two contiguous eutrophic peri-urban lakes,Chivero and Manyame,Zimbabwe

Concentrations of aluminium, cadmium, chromium, cobalt, copper, iron, lead, nickel and zinc were determined in surface water, benthic sediments, and the gills, liver and stomach muscle tissues of Oreochromis niloticus and Clarias gariepinus in peri-urban lakes Chivero and Manyame, Zimbabwe. Five sites were sampled in each lake once per month in November 2015, February, May, August and November 2016. Pollution load index detected no metal contamination, whereas the geo-accumulation index reflected heavy to extreme sediment pollution, with Fe, Cd, Zn, Cr, Ni and Cu present in both lakes. Significant spatial temporal variations were detected for Al, Cr, Cu and Pb across sites within and between the two lakes. High Fe, Al and Cr concentrations in water and sediments in lakes Chivero and Manyame derive from geogenic background sources in addition to anthropogenic loads and intensity. Elevated concentrations of Al, Pb, Cu, Cd, Fe and Zn detected in gills, liver and stomach tissue of catfish corroborate concentrations in water and sediments, and pose the highest ecological and health risk for hydrobionts in lakes Chivero and Manyame. Contiguity of peri-urban lakes exposes them to similar threats, necessitating creative water management strategies, which ensure ecological continuity.     

Auditory processing of vocal sounds in birds

The avian auditory system has become a model system to investigate how vocalizations are memorized and processed by the brain in order to mediate behavioral discrimination and recognition. Recent studies have shown that most of the avian auditory system responds preferentially and efficiently to sounds that have natural spectro-temporal statistics. In addition, neurons in secondary auditory forebrain areas have plastic response properties and are the most active when processing behaviorally relevant vocalizations. Physiological measurements show differential responses for vocalizations that were recently learned in discrimination tasks, and for the tutor song, a longer-term auditory memory that is used to guide vocal learning in male songbirds.     

The Structure and Function of Bacterial Actin Homologs

During the past decade, the appreciation and understanding of how bacterial cells can be organized in both space and time have been revolutionized by the identification and characterization of multiple bacterial homologs of the eukaryotic actin cytoskeleton. Some of these bacterial actins, such as the plasmid-borne ParM protein, have highly specialized functions, whereas other bacterial actins, such as the chromosomally encoded MreB protein, have been implicated in a wide array of cellular activities. In this review we cover our current understanding of the structure, assembly, function, and regulation of bacterial actins. We focus on ParM as a well-understood reductionist model and on MreB as a central organizer of multiple aspects of bacterial cell biology. We also discuss the outstanding puzzles in the field and possible directions where this fast-developing area may progress in the future.The discovery of cytoskeletal proteins in bacteria has fundamentally altered our understanding of the organization and evolution of bacteria as cells. Homologs of eukaryotic actin represent the most molecularly and functionally diverse family of bacterial cytoskeletal elements. Recent phylogenetic studies have identified more than 20 subgroups of bacterial actin homologs (Derman et al. 2009) (Fig. 1). Many of these bacterial actins are encoded on extrachromosomal plasmids, but most bacterial species with nonspherical morphologies also encode chromosomal actin homologs (Daniel and Errington 2003). The two earliest proteins to be characterized as bacterial actins were the chromosomal protein MreB (Jones et al. 2001) and the plasmidic protein ParM (Jensen and Gerdes 1997). MreB and ParM remain the best-characterized of the bacterial actins and we will thus focus on these two proteins for most of this article.Open in a separate windowFigure 1.The superfamily of bacterial actin homologs. Shown is a phylogenetic tree of the bacterial actin subfamilies that have been identified to date based on sequence homology. The subfamilies that have been experimentally shown to polymerize are labeled and colored. (Courtesy of Joe Pogliano, based on Derman et al. 2009.)The appreciation that bacteria possess actin homologs only occurred in the past decade. MreB was first identified as a protein involved in cell shape regulation in Escherichia coli in the late 1980s (Doi et al. 1988). In the early 1990s, pioneering bioinformatic studies identified similarities in a group of ATPases that have five conserved motifs (Bork et al. 1992), a feature dubbed the actin superfamily fold. Although this group includes actin and MreB, it also contains proteins that do not polymerize into filaments, such as sugar kinases like hexokinase and chaperones like Hsp70. A number of bacterial proteins are present in the actin superfamily, including the bacterial cell division protein FtsA which interacts with the tubulin homolog FtsZ and may or may not form filaments in different contexts (van den Ent and Lowe 2000). Because MreB did not appear significantly more related to actin than these nonfilamentous proteins, the weak sequence similarity with actin was largely ignored for the better part of a decade. This changed in 2001 when two seminal papers showed that Bacillus subtilis MreB forms cytoskeletal filaments in vivo (Jones et al. 2001) and that Thermotoga maritima MreB forms cytoskeletal filaments in vitro (van den Ent et al. 2001). Indeed, structural and biochemical studies of both MreB and ParM have convincingly showed that these proteins closely resemble actin and polymerize into linear filaments in a nucleotide-dependent manner (Fig. 2).Open in a separate windowFigure 2.Structures of F-actin (Holmes et al. 1990), MreB (van den Ent et al. 2001), and ParM (van den Ent et al. 2002). (Left) Structures of F-actin filaments (PDB entry 1YAG). (Second from the left) MreB filaments from T. maritima (PDB entry 1JCE). (Center) ParM:ADP monomer in the “closed” conformation. (Second from the right) apo ParM monomer in the “open” conformation. (Right) ParM filament. Shown are the position of the nucleotide within the interdomain cleft, the conservation of fold, and the axis of the protofilament extension (arrow). Note that the conformational change shown for ParM from the “open” to “closed” state is predicted for all actin homologs. (Adapted, with permission from, Michie and Löwe 2006.)Research following the identification of bacterial cytoskeletal proteins has focused on understanding their assembly, regulation, and function. Here, we will summarize our current understanding of these issues and highlight the outstanding questions. We will begin with ParM, whose well-characterized assembly and dynamics represent a model for future studies of all cytoskeletal proteins. We will then focus on MreB, whose diverse activities appear to be central to the cell biology of many bacterial species.     

The antidepressant-like effect of Ocimum basilicum in an animal model of depression

We investigated the efficacy of Ocimum basilicum (OB) essential oils for treating depression related behavioral, biochemical and histopathological changes caused by exposure to chronic unpredictable mild stress (CUMS) in mice and to explore the mechanism underlying the pathology. Male albino mice were divided into four groups: controls; CUMS; CUMS plus fluoxetine, the antidepressant administered for pharmacological validation of OB; and CUMS plus OB. Behavioral tests included the forced swim test (FST), elevated plus-maze (EPM) and the open ?eld test (OFT); these tests were performed at the end of the experiment. We assessed serum corticosterone level, protein, gene and immunoexpression of brain-derived neurotropic factor (BDNF) and glucocorticoid receptors (GRs) as well as immunoexpression of glial fibrillary acidic protein (GFAP), Ki67, caspase-3 in the hippocampus. CUMS caused depression in the mice as evidenced by prolonged immobility in the FST, prolonged time spent in the open arms during the EPM test and reduction of open field activity in the OFT. OB ameliorated the CUMS induced depressive status. OB significantly reduced the corticosterone level and up-regulated protein and gene expressions of BDNF and GR. OB reduced CUMS induced hippocampal neuron atrophy and apoptosis, and increased the number of the astrocytes and new nerve cells. OB significantly increased GFAP-positive cells as well as BDNF and GR immunoexpression in the hippocampus.