Search for: All records

Axon regrowth after spinal cord injury (SCI) is inhibited by several types of inhibitory extracellular molecules in the central nervous system (CNS), including chondroitin sulfate proteoglycans (CSPGs), which also are components of perineuronal nets (PNNs). The axons of lampreys regenerate following SCI, even though their spinal cords contain CSPGs, and their neurons are enwrapped by PNNs. Previously, we showed that by 2 weeks after spinal cord transection in the lamprey, expression of CSPGs increased in the lesion site, and thereafter, decreased to pre-injury levels by 10 weeks. Enzymatic digestion of CSPGs in the lesion site with chondroitinase ABC (ChABC) enhanced axonal regeneration after SCI and reduced retrograde neuronal death. Lecticans (aggrecan, versican, neurocan, and brevican) are the major CSPG family in the CNS. Previously, we cloned a cDNA fragment that lies in the most conserved link-domain of the lamprey lecticans and found that lectican mRNAs are expressed widely in lamprey glia and neurons. Because of the lack of strict one-to-one orthology with the jawed vertebrate lecticans, the four lamprey lecticans were named simply A, B, C, and D. Using probes that distinguish these four lecticans, we now show that they all are expressed in glia and neurons but at different levels. Expression levels are relatively high in embryonic and early larval stages, gradually decrease, and are upregulated again in adults. Reductions of lecticans B and D are greater than those of A and C. Levels of mRNAs for lecticans B and D increased dramatically after SCI. Lectican D remained upregulated for at least 10 weeks. Multiple cells, including glia, neurons, ependymal cells and microglia/macrophages, expressed lectican mRNAs in the peripheral zone and lesion center after SCI. Thus, as in mammals, lamprey lecticans may be involved in axon guidance and neuroplasticity early in development. Moreover, neurons, glia, ependymal cells, and microglia/macrophages, are responsible for the increase in CSPGs during the formation of the glial scar after SCI. 

Teleosts are important models to study sex chromosomes and sex-determining (SD) genes because they present a variety of sex determination systems. Here, we used Nanopore and Hi-C technologies to generate a high-contiguity chromosome-level genome assembly of a YY southern catfish ( Silurus meridionalis ). The assembly is 750.0 Mb long, with contig N50 of 15.96 Mb and scaffold N50 of 27.22 Mb. We also sequenced and assembled an XY male genome with a size of 727.2 Mb and contig N50 of 13.69 Mb. We identified a candidate SD gene through comparisons to our previous assembly of an XX individual. By resequencing male and female pools, we characterized a 2.38 Mb sex-determining region (SDR) on Chr24. Analysis of read coverage and comparison of the X and Y chromosome sequences showed a Y specific insertion (approx. 500 kb) in the SDR which contained a male-specific duplicate of amhr2 (named amhr2y ). amhr2y and amhr2 shared high-nucleotide identity (81.0%) in the coding region but extremely low identity in the promotor and intron regions. The exclusive expression in the male gonadal primordium and loss-of-function inducing male to female sex reversal confirmed the role of amhr2y in male sex determination. Our study provides a new example of amhr2 as the SD gene in fish and sheds light on the convergent evolution of the duplication of AMH/AMHR2 pathway members underlying the evolution of sex determination in different fish lineages. 

Rising oceanic and atmospheric oxygen levels through time have been crucial to enhanced habitability of surface Earth environments. Few redox proxies can track secular variations in dissolved oxygen concentrations ([O2]) around threshold levels for metazoan survival in the upper ocean. We present an extensive compilation of iodine to calcium ratios (I/Ca) in marine carbonates. Our record supports a major rise in atmospheric pO2 at ~400 million years ago (Ma), and reveals a step-change in the oxygenation of the upper ocean to relatively sustainable near-modern conditions at ~200 Ma. An Earth system model demonstrates that a shift in organic matter remineralization to greater depths, which may have been due to increasing size and biomineralization of eukaryotic plankton, likely drove the I/Ca signals at ~200 Ma 

Microneedle patch devices have been widely utilized for transdermal drug delivery in pain management, but is challenged by accurate control of drug release and subsequent diffusion to human body. The recent emerging wearable electronics that could be integrated with microneedle devices offer a facile approach to address such a challenge. Here a 3D‐printed microheater integrated drug‐encapsulated microneedle patch system for drug delivery is presented. The ink solution comprised polydimethylsiloxane (PDMS) and multiwalled carbon nanotubes (MWCNTs) with a mass concentration of up to 45% (≈10 times higher of existing ones) is prepared and used to print crack‐free stretchable microheaters on substrates with a broad range of materials and geometric curves. The adhesion strength of the printed microheater on the microneedle patch in elevated temperatures is measured to evaluate their integration performance. Assessments of encapsulated drug release into rat's skin are confirmed by examining degradation of microneedles, skin morphologies, and released fluorescent signals. Results and demonstrations established here creates a new opportunity for developing sensor controlled smart microneedle patch systems by integrating with wearable electronics, potentially useful in clinical and biomedical research.