Size‐based interactions and trophic transfer efficiency are modified by fish predation and cyanobacteria blooms in Lake Mývatn,Iceland

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Diffuse Optical Characterization of the Healthy Human Thyroid Tissue and Two Pathological Case Studies

The in vivo optical and hemodynamic properties of the healthy (n = 22) and pathological (n = 2) human thyroid tissue were measured non-invasively using a custom time-resolved spectroscopy (TRS) and diffuse correlation spectroscopy (DCS) system. Medical ultrasound was used to guide the placement of the hand-held hybrid optical probe. TRS measured the absorption and reduced scattering coefficients (μ_a, μ_s′) at three wavelengths (690, 785 and 830 nm) to derive total hemoglobin concentration (THC) and oxygen saturation (StO₂). DCS measured the microvascular blood flow index (BFI). Their dependencies on physiological and clinical parameters and positions along the thyroid were investigated and compared to the surrounding sternocleidomastoid muscle. The THC in the thyroid ranged from 131.9 μM to 144.8 μM, showing a 25–44% increase compared to the surrounding sternocleidomastoid muscle tissue. The blood flow was significantly higher in the thyroid (BFI_thyroid = 16.0 × 10^-9 cm²/s) compared to the muscle (BFI_muscle = 7.8 × 10^-9 cm²/s), while StO₂ showed a small (StO_{2, muscle} = 63.8% to StO_{2, thyroid} = 68.4%), yet significant difference. Two case studies with thyroid nodules underwent the same measurement protocol prior to thyroidectomy. Their THC and BFI reached values around 226.5 μM and 62.8 × 10^-9 cm²/s respectively showing a clear contrast to the nodule-free thyroid tissue as well as the general population. The initial characterization of the healthy and pathologic human thyroid tissue lays the ground work for the future investigation on the use of diffuse optics in thyroid cancer screening.     

Overexpression of UCP3 in both murine and human myotubes is linked with the activation of proteolytic systems: a role in muscle wasting?

Overexpression of the UCP3 gene in both murine and human myotube cell cultures leads to a significant activation of the different proteolytic systems involved in muscle myofibrillar protein breakdown. Thus, lysosomal (cathepsin B) and non-lysosomal (m-calpain and ubiquitin-proteasome) mRNA content was significantly increased in the different cell culture systems used. Interestingly, the overexpression of the UCP3 gene was not associated with any changes in apoptosis. Although the function of the UCP3 protein is not completely understood (uncoupling, oxidative stress), these results suggest a possible relation between these main mechanisms involved in muscle wasting during cancer.     

Plasmid replication initiator RepB forms a hexamer reminiscent of ring helicases and has mobile nuclease domains

RepB initiates plasmid rolling‐circle replication by binding to a triple 11‐bp direct repeat (bind locus) and cleaving the DNA at a specific distant site located in a hairpin loop within the nic locus of the origin. The structure of native full‐length RepB reveals a hexameric ring molecule, where each protomer has two domains. The origin‐binding and catalytic domains show a three‐layer α–β–α sandwich fold. The active site is positioned at one of the faces of the β‐sheet and coordinates a Mn²⁺ ion at short distance from the essential nucleophilic Y99. The oligomerization domains (ODs), each consisting of four α‐helices, together define a compact ring with a central channel, a feature found in ring helicases. The toroidal arrangement of RepB suggests that, similar to ring helicases, it encircles one of the DNA strands during replication to confer processivity to the replisome complex. The catalytic domains appear to be highly mobile with respect to ODs. This mobility may account for the adaptation of the protein to two distinct DNA recognition sites.