Relationship between Swim Bladder Morphology and Hearing Abilities-A Case Study on Asian and African Cichlids

Background

Several teleost species have evolved anterior extensions of the swim bladder which come close to or directly contact the inner ears. A few comparative studies have shown that these morphological specializations may enhance hearing abilities. This study investigates the diversity of swim bladder morphology in four Asian and African cichlid species and analyzes how this diversity affects their hearing sensitivity.

Methodology/Principal Findings

We studied swim bladder morphology by dissections and by making 3D reconstructions from high-resolution microCT scans. The auditory sensitivity was determined in terms of sound pressure levels (SPL) and particle acceleration levels (PAL) using the auditory evoked potential (AEP) recording technique. The swim bladders in Hemichromis guttatus and Steatocranus tinanti lacked anterior extensions and the swim bladder was considerably small in the latter species. In contrast, Paratilapia polleni and especially Etroplus maculatus possessed anterior extensions bringing the swim bladder close to the inner ears. All species were able to detect frequencies up to 3 kHz (SPL) except S. tinanti which only responded to frequencies up to 0.7 kHz. P. polleni and E. maculatus showed significantly higher auditory sensitivities at 0.5 and 1 kHz than the two species lacking anterior swim bladder extensions. The highest auditory sensitivities were found in E. maculatus, which possessed the most intimate swim bladder-inner ear relationship (maximum sensitivity 66 dB re 1 µPa at 0.5 kHz).

Conclusions

Our results indicate that anterior swim bladder extensions seem to improve mean absolute auditory sensitivities by 21–42 dB (SPLs) and 21–36 dB (PALs) between 0.5 and 1 kHz. Besides anterior extensions, the size of the swim bladder appears to be an important factor for extending the detectable frequency range (up to 3 kHz).     

Cardiac Autonomic Nervous System Activation and Metabolic Profile in Young Children: The ABCD Study

Background

In adults, increased sympathetic and decreased parasympathetic nervous system activity are associated with a less favorable metabolic profile. Whether this is already determined at early age is unknown. Therefore, we aimed to assess the association between autonomic nervous system activation and metabolic profile and its components in children at age of 5–6 years.

Methods

Cross-sectional data from an apparently healthy population (within the ABCD study) were collected at age 5–6 years in 1540 children. Heart rate (HR), respiratory sinus arrhythmia (RSA; parasympathetic activity) and pre-ejection period (PEP; sympathetic activity) were assessed during rest. Metabolic components were waist-height ratio (WHtR), systolic blood pressure (SBP), fasting triglycerides, glucose and HDL-cholesterol. Individual components, as well as a cumulative metabolic score, were analyzed.

Results

In analysis adjusted for child’s physical activity, sleep, anxiety score and other potential confounders, increased HR and decreased RSA were associated with higher WHtR (P< 0.01), higher SBP (p<0.001) and a higher cumulative metabolic score (HR: p < 0.001; RSA: p < 0.01). Lower PEP was only associated with higher SBP (p <0.05). Of all children, 5.6% had 3 or more (out of 5) adverse metabolic components; only higher HR was associated with this risk (per 10 bpm increase: OR = 1.56; p < 0.001).

Conclusions

This study shows that decreased parasympathetic activity is associated with central adiposity and higher SBP, indicative of increased metabolic risk, already at age 5–6 years.     

Genome sequence of Ensifer medicae strain WSM1115; an acid-tolerant Medicago-nodulating microsymbiont from Samothraki,Greece

Ensifer medicae strain WSM1115 forms effective nitrogen fixing symbioses with a range of annual Medicago species and is used in commercial inoculants in Australia. WSM1115 is an aerobic, motile, Gram-negative, non-spore-forming rod. It was isolated from a nodule recovered from the root of burr medic (Medicago polymorpha) collected on the Greek Island of Samothraki. WSM1115 has a broad host range for nodulation and N₂ fixation capacity within the genus Medicago, although this does not extend to all medic species. WSM1115 is considered saprophytically competent in moderately acid soils (pH(CaCl₂) 5.0), but it has failed to persist at field sites where soil salinity exceeded 10 ECe (dS/m). Here we describe the features of E. medicae strain WSM1115, together with genome sequence information and its annotation. The 6,861,065 bp high-quality-draft genome is arranged into 7 scaffolds of 28 contigs, contains 6,789 protein-coding genes and 83 RNA-only encoding genes, and is one of 100 rhizobial genomes sequenced as part of the DOE Joint Genome Institute 2010 Genomic Encyclopedia for Bacteria and Archaea-Root Nodule Bacteria (GEBA-RNB) project.     

Altered Ca2+ signaling in skeletal muscle fibers of the R6/2 mouse,a model of Huntington’s disease

Huntington’s disease (HD) is caused by an expanded CAG trinucleotide repeat within the gene encoding the protein huntingtin. The resulting elongated glutamine (poly-Q) sequence of mutant huntingtin (mhtt) affects both central neurons and skeletal muscle. Recent reports suggest that ryanodine receptor–based Ca²⁺ signaling, which is crucial for skeletal muscle excitation–contraction coupling (ECC), is changed by mhtt in HD neurons. Consequently, we searched for alterations of ECC in muscle fibers of the R6/2 mouse, a mouse model of HD. We performed fluorometric recordings of action potentials (APs) and cellular Ca²⁺ transients on intact isolated toe muscle fibers (musculi interossei), and measured L-type Ca²⁺ inward currents on internally dialyzed fibers under voltage-clamp conditions. Both APs and AP-triggered Ca²⁺ transients showed slower kinetics in R6/2 fibers than in fibers from wild-type mice. Ca²⁺ removal from the myoplasm and Ca²⁺ release flux from the sarcoplasmic reticulum were characterized using a Ca²⁺ binding and transport model, which indicated a significant reduction in slow Ca²⁺ removal activity and Ca²⁺ release flux both after APs and under voltage-clamp conditions. In addition, the voltage-clamp experiments showed a highly significant decrease in L-type Ca²⁺ channel conductance. These results indicate profound changes of Ca²⁺ turnover in skeletal muscle of R6/2 mice and suggest that these changes may be associated with muscle pathology in HD.     

Scalable Production in Human Cells and Biochemical Characterization of Full-Length Normal and Mutant Huntingtin

Huntingtin (Htt) is a 350 kD intracellular protein, ubiquitously expressed and mainly localized in the cytoplasm. Huntington’s disease (HD) is caused by a CAG triplet amplification in exon 1 of the corresponding gene resulting in a polyglutamine (polyQ) expansion at the N-terminus of Htt. Production of full-length Htt has been difficult in the past and so far a scalable system or process has not been established for recombinant production of Htt in human cells. The ability to produce Htt in milligram quantities would be a prerequisite for many biochemical and biophysical studies aiming in a better understanding of Htt function under physiological conditions and in case of mutation and disease. For scalable production of full-length normal (17Q) and mutant (46Q and 128Q) Htt we have established two different systems, the first based on doxycycline-inducible Htt expression in stable cell lines, the second on “gutless” adenovirus mediated gene transfer. Purified material has then been used for biochemical characterization of full-length Htt. Posttranslational modifications (PTMs) were determined and several new phosphorylation sites were identified. Nearly all PTMs in full-length Htt localized to areas outside of predicted alpha-solenoid protein regions. In all detected N-terminal peptides methionine as the first amino acid was missing and the second, alanine, was found to be acetylated. Differences in secondary structure between normal and mutant Htt, a helix-rich protein, were not observed in our study. Purified Htt tends to form dimers and higher order oligomers, thus resembling the situation observed with N-terminal fragments, although the mechanism of oligomer formation may be different.     

Complete genome sequence of the orange-red pigmented, radioresistant Deinococcus proteolyticus type strain (MRP(T))

Deinococcus proteolyticus (ex Kobatake et al. 1973) Brook and Murray 1981 is one of currently 47 species in the genus Deinococcus within the family Deinococcaceae. Strain MRP(T) was isolated from feces of Lama glama and possesses extreme radiation resistance, a trait is shares with various other species of the genus Deinococcus, with D. proteolyticus being resistant up to 1.5 Mrad of gamma radiation. Strain MRP(T) is of further interest for its carotenoid pigment. The genome presented here is only the fifth completed genome sequence of a member of the genus Deinococcus (and the forth type strain) to be published, and will hopefully contribute to a better understanding of how members of this genus adapted to high gamma- or UV ionizing-radiation. Here we describe the features of this organism, together with the complete genome sequence and annotation. The 2,886,836 bp long genome with its four large plasmids of lengths 97 kbp, 132 kbp, 196 kbp and 315 kbp harbors 2,741 protein-coding and 58 RNA genes and is a part of the Genomic Encyclopedia of Bacteria and Archaea project.     

The DEK protein--an abundant and ubiquitous constituent of mammalian chromatin

The protein DEK is an abundant and ubiquitous chromatin protein in multicellular organisms (not in yeast). It is expressed in more than a million copies/nucleus of rapidly proliferating mammalian cells. DEK has two DNA binding modules of which one includes a SAP box, a sequence motif that DEK shares with a number of other chromatin proteins. DEK has no apparent affinity to specific DNA sequences, but preferentially binds to superhelical and cruciform DNA, and induces positive supercoils into closed circular DNA. The available evidence strongly suggests that DEK could function as an architectural protein in chromatin comparable to the better known classic architectural chromatin proteins, the high-mobility group or HMG proteins.