Lumbar muscle electromyographic dynamic topography during flexion-extension

The objective of this study is to introduce dynamic topography of surface electromyography (SEMG) to visualize lumbar muscle myoelectric activity and provides a new view to analyze muscle activity in vivo. A total of 20 healthy male subjects and 15 males LBP were enrolled. An electrode-array was applied to the lumbar region to collect SEMG. The root mean square (RMS) value was calculated for each channel, and then a 160×120 matrix was constructed using a linear cubic spline interpolation of each scan to create a 2-D color topographic image. Along a definite interval of action, a series of RMS topography matrices was concatenated as a function of position and time, to form a dynamic topographical video of lumbar muscle activity. Relative area (RA), relative width (RW), relative height (RH) and Width-to-Height Ratio (W/H) were chosen as the four quantitative parameters in measuring topographic features. Normal RMS dynamic topography was found to have a consistent, symmetric pattern with a high intensity area in the paraspinal area. LBP patients had a different RMS dynamic topography, with an asymmetric, broad, or disorganized distribution. Quantitative SEMG features were found significantly different between normal control and LBP. After physiotherapy rehabilitation, the dynamic topography images of LBP tended towards the normal pattern.There are obvious differences in lumbar muscle coordination between healthy subjects and LBP patients. The dynamic topography allows the continuous visualization of the distribution of surface EMG signals and the coordination of muscular contractions.     

Dating the fungus-growing termites' mutualism shows a mixture between ancient codiversification and recent symbiont dispersal across divergent hosts

The mutualistic symbiosis between fungus-growing termites and Termitomyces fungi originated in Africa and shows a moderate degree of interaction specificity. Here we estimate the age of the mutualism and test the hypothesis that the major splits have occurred simultaneously in the host and in the symbiont. We present a scenario where fungus-growing termites originated in the African rainforest just before the expansion of the savanna, about 31 Ma (19-49 Ma). Whereas rough age correspondence is observed for the four main clades of host and symbiont, the analysis reveals several recent events of host switching followed by dispersal of the symbiont throughout large areas and throughout different host genera. The most spectacular of these is a group of closely related fungi (the maximum age of which is estimated to be 2.4 Ma), shared between the divergent genera Microtermes, Ancistrotermes, Acanthotermes and Synacanthotermes (which diverged at least 16.7 Ma), and found throughout the African continent and on Madagascar. The lack of geographical differentiation of fungal symbionts shows that continuous exchange has occurred between regions and across host species.     

iRFP is a sensitive marker for cell number and tumor growth in high-throughput systems

GFP and luciferase are used extensively as markers both in vitro and in vivo although both have limitations. The utility of GFP fluorescence is restricted by high background signal and poor tissue penetrance. Luciferase throughput is limited in vitro by the requirement for cell lysis, while in vivo, luciferase readout is complicated by the need for substrate injection and the dependence on endogenous ATP. Here we show that near-infrared fluorescent protein in combination with widely available near-infrared scanners overcomes these obstacles and allows for the accurate determination of cell number in vitro and tumor growth in vivo in a high-throughput manner and at negligible per-well costs. This system represents a significant advance in tracking cell proliferation in tissue culture as well as in animals, with widespread applications in cell biology.     

The costs of being male: are there sex-specific effects of uniparental mitochondrial inheritance?

Eukaryotic cells typically contain numerous mitochondria, each with multiple copies of their own genome, the mtDNA. Uniparental transmission of mitochondria, usually via the mother, prevents the mixing of mtDNA from different individuals. While on the one hand, this should resolve the potential for selection for fast-replicating mtDNA variants that reduce organismal fitness, maternal inheritance will, in theory, come with another set of problems that are specifically relevant to males. Maternal inheritance implies that the mitochondrial genome is never transmitted through males, and thus selection can target only the mtDNA sequence when carried by females. A consequence is that mtDNA mutations that confer male-biased phenotypic expression will be prone to evade selection, and accumulate. Here, we review the evidence from the ecological, evolutionary and medical literature for male specificity of mtDNA mutations affecting fertility, health and ageing. While such effects have been discovered experimentally in the laboratory, their relevance to natural populations—including the human population—remains unclear. We suggest that the existence of male expression-biased mtDNA mutations is likely to be a broad phenomenon, but that these mutations remain cryptic owing to the presence of counter-adapted nuclear compensatory modifier mutations, which offset their deleterious effects.     

Regular bottlenecks and restrictions to somatic fusion prevent the accumulation of mitochondrial defects in Neurospora

The replication and segregation of multi-copy mitochondrial DNA (mtDNA) are not under strict control of the nuclear DNA. Within-cell selection may thus favour variants with an intracellular selective advantage but a detrimental effect on cell fitness. High relatedness among the mtDNA variants of an individual is predicted to disfavour such deleterious selfish genetic elements, but experimental evidence for this hypothesis is scarce. We studied the effect of mtDNA relatedness on the opportunities for suppressive mtDNA variants in the fungus Neurospora carrying the mitochondrial mutator plasmid pKALILO. During growth, this plasmid integrates into the mitochondrial genome, generating suppressive mtDNA variants. These mtDNA variants gradually replace the wild-type mtDNA, ultimately culminating in growth arrest and death. We show that regular sequestration of mtDNA variation is required for effective selection against suppressive mtDNA variants. First, bottlenecks in the number of mtDNA copies from which a ‘Kalilo’ culture started significantly increased the maximum lifespan and variation in lifespan among cultures. Second, restrictions to somatic fusion among fungal individuals, either by using anastomosis-deficient mutants or by generating allotype diversity, prevented the accumulation of suppressive mtDNA variants. We discuss the implications of these results for the somatic accumulation of mitochondrial defects during ageing.     

Vertical transmission as the key to the colonization of Madagascar by fungus-growing termites?

The mutualism between fungus-growing termites (Macrotermitinae) and their mutualistic fungi (Termitomyces) began in Africa. The fungus-growing termites have secondarily colonized Madagascar and only a subset of the genera found in Africa is found on this isolated island. Successful long-distance colonization may have been severely constrained by the obligate interaction of the termites with fungal symbionts and the need to acquire these symbionts secondarily from the environment for most species (horizontal symbiont transmission). Consistent with this hypothesis, we show that all extant species of fungus-growing termites of Madagascar are the result of a single colonization event of termites belonging to one of the only two groups with vertical symbiont transmission, and we date this event at approximately 13 Mya (Middle/Upper Miocene). Vertical symbiont transmission may therefore have facilitated long-distance dispersal since both partners disperse together. In contrast to their termite hosts, the fungal symbionts have colonized Madagascar multiple times, suggesting that the presence of fungus-growing termites may have facilitated secondary colonizations of the symbiont. Our findings indicate that the absence of the right symbionts in a new environment can prevent long-distance dispersal of symbioses relying on horizontal symbiont acquisition.     

The social evolution of somatic fusion

The widespread potential for somatic fusion among different conspecific multicellular individuals suggests that such fusion is adaptive. However, because recognition of non-kin (allorecognition) usually leads to a rejection response, successful somatic fusion is limited to close kin. This is consistent with kin-selection theory, which predicts that the potential cost of fusion and the potential for somatic parasitism decrease with increasing relatedness. Paradoxically, however, Crozier found that, in the short term, positive-frequency-dependent selection eliminates the required genetic polymorphism at allorecognition loci. The 'Crozier paradox' may be solved if allorecognition is based on extrinsically balanced polymorphisms, for example at immune loci. Alternatively, the assumption of most models that self fusion is mutually beneficial is wrong. If fusion is on average harmful, selection will promote unconditional rejection. However, we propose that fusion within individuals is beneficial, selecting for the ability to fuse, but fusion between individuals on average costly, selecting for non-self recognition (rather than non-kin recognition). We discuss experimental data on fungi that are consistent with this hypothesis.