Morphological and molecular changes in the inner hair cell region of the rat cochlea after amikacin treatment

This study investigates the morphological and molecular changes that occur in the inner hair cell area of the rat cochlea following aminoglycoside treatment. Rats were injected daily with 500 mg/kg of amikacin between postnatal day 9 (PND9) and PND16. Cochleae were examined at PND16 to PND120 using both scanning and transmission electron microscopy and molecular fluorescent labeling. The inner hair cells showed obvious signs of apoptosis in response to amikacin treatment and most of them were missing by one week after the end of the aminoglycoside exposure period. Concomitantly, the epithelium became scarred as the surrounding supporting cells expanded and filled the space vacated by the missing IHCs. The mid-basolateral region of these modified supporting cells was surrounded by many afferent and efferent terminals. However, these cells expressed neither calbindin nor SNAP25, proteins that are both expressed by IHCs in the normal, untreated organ of Corti in the rat. In addition, these supporting cells remained attached to the basal lamina by a thin cytoplasmic process. The supporting cells surrounding the inner hair cells therefore appear unable to convert directly into inner hair cells following aminoglycoside induced hair-cell loss but may be able to provide trophic support for the remaining afferent and efferent neurites.     

Cross-sectional detection of acute HIV infection: timing of transmission, inflammation and antiretroviral therapy

Background

Acute HIV infection (AHI) is a critical phase of infection when irreparable damage to the immune system occurs and subjects are very infectious. We studied subjects with AHI prospectively to develop better treatment and public health interventions.

Methods

Cross-sectional screening was employed to detect HIV RNA positive, antibody negative subjects. Date of HIV acquisition was estimated from clinical history and correlated with sequence diversity assessed by single genome amplification (SGA). Twenty-two cytokines/chemokines were measured from enrollment through week 24.

Results

Thirty-seven AHI subjects were studied. In 7 participants with limited exposure windows, the median exposure to HIV occurred 14 days before symptom onset. Lack of viral sequence diversification confirmed the short duration of infection. Transmission dates estimated by SGA/sequencing using molecular clock models correlated with transmission dates estimated by symptom onset in individuals infected with single HIV variants (mean of 28 versus 33 days). Only 10 of 22 cytokines/chemokines were significantly elevated among AHI participants at enrollment compared to uninfected controls, and only 4 participants remained seronegative at enrollment.

Discussion

The results emphasize the difficulty in recruiting subjects early in AHI. Viral sequence diversity proved accurate in estimating time of infection. Regardless of aggressive screening, peak viremia and inflammation occurred before enrollment and potential intervention. Given the personal and public health importance, improved AHI detection is urgently needed.     

Species‐delimitation and phylogenetic analyses of some cosmopolitan species of Hypnea (Rhodophyta) reveal synonyms and misapplied names to H. cervicornis,including a new species from Brazil

Hypnea has an intricate nomenclatural history due to a wide pantropical distribution and considerable morphological variation. Recent molecular studies have provided further clarification on the systematics of the genus; however, species of uncertain affinities remain due to flawed taxonomic identification. Detailed analyses coupled with literature review indicated a strong relationship among H. aspera, H. cervicornis, H. flexicaulis, and H. tenuis, suggesting a need for further taxonomic studies. Here, we analyzed sequences from two molecular markers (COI‐5P and rbcL) and performed several DNA‐based delimitation methods (mBGD, ABGD, SPN, PTP and GMYC). These molecular approaches were contrasted with morphological and phylogenetic evidence from type specimens and/or topotype collections of related species under a conservative approach. Our results demonstrate that H. aspera and H. flexicaulis represent heterotypic synonyms of H. cervicornis and indicate the existence of a misidentified Hypnea species, widely distributed on the Brazilian coast, described here as a new species: H. brasiliensis. Finally, inconsistencies observed among our results based on six different species delimitation methods evidence the need for adequate sampling and marker choice for different methods.     

Ionic contacts at DnaK substrate binding domain involved in the allosteric regulation of lid dynamics

To gain further insight into the interactions involved in the allosteric transition of DnaK we have characterized wild-type (wt) protein and three mutants in which ionic interactions at the interface between the two subdomains of the substrate binding domain, and within the lid subdomain have been disrupted. Our data show that ionic contacts, most likely forming an electrically charged network, between the N-terminal region of helix B and an inner loop of the beta-sandwich are involved in maintaining the position of the lid relative to the beta-subdomain in the ADP state but not in the ATP state of the protein. Disruption of the ionic interactions between the C-terminal region of helix B and the outer loops of the beta-sandwich, known as the latch, does not have the same conformational consequences but results equally in an inactive protein. This indicates that a variety of mechanisms can inactivate this complex allosteric machine. Our results identify the ionic contacts at the subdomain and interdomain interfaces that are part of the hinge region involved in the ATP-induced allosteric displacement of the lid away from the peptide binding site. These interactions also stabilize peptide-Hsp70 complexes at physiological (37 degrees C) and stress (42 degrees C) temperatures, a requirement for productive substrate (re)folding.     

A Coding IRAK2 Protein Variant Compromises Toll-like receptor (TLR) Signaling and Is Associated with Colorectal Cancer Survival

Within innate immune signaling pathways, interleukin-1 receptor-associated kinases (IRAKs) fulfill key roles downstream of multiple Toll-like receptors and the interleukin-1 receptor. Although human IRAK4 deficiency was shown to lead to severe immunodeficiency in response to pyogenic bacterial infection during childhood, little is known about the role of human IRAK2. We here identified a non-synonymous IRAK2 variant, rs35060588 (coding R214G), as hypofunctional in terms of NF-κB signaling and Toll-like receptor-mediated cytokine induction. This was due to reduced ubiquitination of TRAF6, a key step in signal transduction. IRAK2 rs35060588 occurs in 3–9% of individuals in different ethnic groups, and our studies suggested a genetic association of rs35060588 with colorectal cancer survival. This for the first time implicates human IRAK2 in a human disease and highlights the R214G IRAK2 variant as a potential novel and broadly applicable biomarker for disease or as a therapeutic intervention point.     

Phylogenetic relationships of Hemidactylus geckos from the Gulf of Guinea islands: patterns of natural colonizations and anthropogenic introductions estimated from mitochondrial and nuclear DNA sequences

Mitochondrial DNA (12S rRNA, 16S rRNA, and cytochrome b) sequences and nuclear sequences (C-mos and alpha-Enolase) were analyzed within all known Hemidactylus species from all three volcanic islands in the Gulf of Guinea that have never been connected to the continent. These comprise both endemic and widespread species. Our aim was to determine if the widespread species was introduced anthropogenically, to determine the number of distinct genetic lineages within the islands, and to determine if the endemic forms constituted a monophyletic group. Our results suggest that a previously undescribed species on S?o Tomé is the sister taxon to Hemidactylus newtoni, endemic to Annobon. Genetic variation between populations of Hemidactylus greefii from S?o Tomé and Principe is very high based on mtDNA sequences, but the forms cannot be distinguished using the nuclear DNA sequences. Hemidactylus mabouia appears to have been anthropogenically introduced to all three islands. The island endemics do not form a monophyletic group, suggesting multiple independent colonizations of the islands.     

Contribution of KIR3DL1/3DS1 to ankylosing spondylitis in human leukocyte antigen-B27 Caucasian populations

Killer cell immunoglobulin-like receptors (KIRs) and human leukocyte antigen (HLA) loci are both highly polymorphic, and some HLA class I molecules bind and trigger cell-surface receptors specified by KIR genes. We examined whether the combination of KIR3DS1/3DL1 genes in concert with HLA-B27 genotypes is associated with susceptibility to ankylosing spondylitis (AS). Two HLA-B27-positive Caucasian populations were selected, one from Spain (71 patients and 105 controls) and another from the Azores (Portugal) (55 patients and 75 controls). All were typed for HLA-B and KIR (3DS1 and 3DL1) genes. Our results show that in addition to B27, the allele 3DS1 is associated with AS compared with B27 controls (p < 0.0001 and p < 0.003 in the Spanish population and Azoreans, respectively). We also observed that the association of KIR3DS1 to AS was found in combination with HLA-B alleles carrying Bw4-I80 in trans position in the Spanish population (30.9% in AS versus 15.2% in B27 controls, p = 0.02, odds ratio (OR) = 2.49) and in Azoreans (27.2% in AS versus 8.7% in B27 controls, p = 0.01, OR = 4.4 in Azoreans). On the other hand, 3DL1 was decreased in patients compared with B27 controls (p < 0.0001 in the Spanish population and p < 0.003 in Azoreans). The presence of this allele in combination with Bw4-I80 had a protective effect against the development of AS in the Spanish population (19.7% in AS, 35.2% in B27 controls; p = 0.03, OR = 0.45). The presence of KIR3DS1 or KIR3DL1 in combination with HLA-B*27s/HLA-B Bw4-I80 genotypes may modulate the development of AS. The susceptibility to AS could be determined by the overall balance of activating and inhibitory composite KIR-HLA genotypes.