Tooth Germ‐Like Construct Transplantation for Whole‐Tooth Regeneration: An In Vivo Study in the Miniature Pig

The purpose of this study was to demonstrate the feasibility of whole‐tooth regeneration using a tooth germ‐like construct. Dental pulp from upper incisors, canines, premolars, and molars were extracted from sexually mature miniature pigs. Pulp tissues were cultured and expanded in vitro to obtain dental pulp stem cells (DPSCs), and cells were differentiated into odontoblasts and osteoblasts. Epithelial cells were isolated from gingival epithelium. The epithelial cells, odontoblasts, and osteoblasts were seeded onto the surface, upper, and lower layers, respectively, of a bioactive scaffold. The lower first and second molar tooth germs were removed bilaterally and the layered cell/scaffold constructs were transplanted to the mandibular alveolar socket of a pig. At 13.5 months postimplantation, seven of eight pigs developed two teeth with crown, root, and pulp structures. Enamel‐like tissues, dentin, cementum, odontoblasts, and periodontal tissues were found upon histological inspection. The regenerated tooth expressed dentin matrix protein‐1 and osteopontin. All pigs had regenerated molar teeth regardless of the original tooth used to procure the DPSCs. Pigs that had tooth germs removed or who received empty scaffolds did not develop teeth. Although periodontal ligaments were generated, ankylosis was found in some animals. This study revealed that implantation of a tooth germ‐like structure generated a complete tooth with a high success rate. The implant location may influence the morphology of the regenerated tooth.     

Opposing Effects of Prior Infection versus Prior Vaccination on Vaccine Immunogenicity against Influenza A(H3N2) Viruses

Prior vaccination can alternately enhance or attenuate influenza vaccine immunogenicity and effectiveness. Analogously, we found that vaccine immunogenicity was enhanced by prior A(H3N2) virus infection among participants of the Ha Nam Cohort, Viet Nam, but was attenuated by prior vaccination among Australian Health Care Workers (HCWs) vaccinated in the same year. Here, we combined these studies to directly compare antibody titers against 35 A(H3N2) viruses spanning 1968–2018. Participants received licensed inactivated vaccines containing A/HongKong/4801/2014 (H3N2). The analysis was limited to participants aged 18–65 Y, and compared those exposed to A(H3N2) viruses circulating since 2009 by infection (Ha Nam) or vaccination (HCWs) to a reference group who had no recent A(H3N2) infection or vaccination (Ha Nam). Antibody responses were compared by fitting titer/titer-rise landscapes across strains, and by estimating titer ratios to the reference group of 2009–2018 viruses. Pre-vaccination, titers were lowest against 2009–2014 viruses among the reference (no recent exposure) group. Post-vaccination, titers were, on average, two-fold higher among participants with prior infection and two-fold lower among participants with 3–5 prior vaccinations compared to the reference group. Titer rise was negligible among participants with 3–5 prior vaccinations, poor among participants with 1–2 prior vaccinations, and equivalent or better among those with prior infection compared to the reference group. The enhancing effect of prior infection versus the incrementally attenuating effect of prior vaccinations suggests that these exposures may alternately promote and constrain the generation of memory that can be recalled by a new vaccine strain.     

Clinical screening for Ph-like ALL and the developing role of TKIs

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Effect of ultraviolet light C on bacterial colonization in chronic wounds

Ultraviolet light C (light wavelength 200 nm to 290 nm) has been shown to kill cultures of antibiotic resistant strains of bacteria such as methicillin-resistant Staphylococcus aureus. To evaluate the ability of ultraviolet light C to reduce the amount and type of bacteria present in chronically infected ulcers, as well as to establish the test-retest reliability of the semi-quantitative swab technique, a prospective, one-group, pre-post treatment study was conducted among patients receiving treatment in several in- and outpatient facilities and nursing homes. Individuals with chronic ulcers exhibiting at least two signs of infection and critically colonized with bacteria (n = 22) received a single 180-second treatment using an ultraviolet light C lamp (wavelength = 254 nm) placed 1 inch from the wound bed. Semi-quantitative swabs taken immediately before and after UVC treatment were used to assess changes in the bacterial bioburden present within the wound bed. Results demonstrated excellent test-retest reliability of the semi-quantitative swab technique used to evaluate the type and amount of bacteria present in chronic wounds (Cohen's kappa = 0.92). Assessment of wound bioburden using semi-quantitative swabs revealed a statistically significant (P <0.0001) reduction in the relative amount of bacteria following a single treatment of ultraviolet light C. The greatest reduction in semi-quantitative swab scores following ultraviolet light C treatment were observed for wounds colonized with the bacteria Pseudomonas aeruginosa and wounds colonized with only one species of bacteria. Significant (P <0.05) reductions in the relative amount of bacteria also were observed in 12 ulcers in which methicillin-resistant Staphylococcus aureus was present. These results confirm previous laboratory studies and demonstrate that ultraviolet light C can kill bacteria such as Pseudomonas aeruginosa, Staphylococcus aureus, and methicillin-resistant Staphylococcus aureus present in superficial layers of chronic wounds.     

Polyoxymethylene/silica/polylactic acid-grafted polyethylene glycol nanocomposites: structure,morphology, and mechanical properties and ozone and UV durability

Polyoxymethylene (POM) is a semicrystalline thermoplastic that displays high tensile strength, thermal stability, and chemical durability. However, its widespread application is limited by its low elongation at break and thermal durability. In the present study, nanosilica (NS) and polylactic acid-grafted polyethylene glycol (PELA) were used as enhancement additives to improve the performance of POM homopolymer. Specifically, the POM/PELA/NS nanocomposites with a fixed NS content and varying PELA contents were prepared by a melt mixing method. The influence of the additives on the processability, and dynamic thermo-mechanical and tensile properties of the nanocomposites was evaluated by comparing the torque, mixing energy at melt state, storage modulus, shear stress, loss modulus, tan δ, tensile strength, elongation at break and thermal degradation of the nanocomposites. The results showed that the combined addition of NS and PELA enhanced the thermal stability, tensile strength, elongation at break and chemical stability of the POM/PELA/NS nanocomposites owing to the good compatibility between PELA and the POM matrix. Furthermore, the morphology, and UV and ozone durability of POM and the nanocomposites were assessed and discussed.

The combined addition of nanosilica (NS) and polylactic acid-grafted polyethylene glycol (PELA) enhanced some properties of polyoxymethylene (POM).     

Regional synapse gain and loss accompany memory formation in larval zebrafish

Defining the structural and functional changes in the nervous system underlying learning and memory represents a major challenge for modern neuroscience. Although changes in neuronal activity following memory formation have been studied [B. F. Grewe et al., Nature 543, 670–675 (2017); M. T. Rogan, U. V. Stäubli, J. E. LeDoux, Nature 390, 604–607 (1997)], the underlying structural changes at the synapse level remain poorly understood. Here, we capture synaptic changes in the midlarval zebrafish brain that occur during associative memory formation by imaging excitatory synapses labeled with recombinant probes using selective plane illumination microscopy. Imaging the same subjects before and after classical conditioning at single-synapse resolution provides an unbiased mapping of synaptic changes accompanying memory formation. In control animals and animals that failed to learn the task, there were no significant changes in the spatial patterns of synapses in the pallium, which contains the equivalent of the mammalian amygdala and is essential for associative learning in teleost fish [M. Portavella, J. P. Vargas, B. Torres, C. Salas, Brain Res. Bull. 57, 397–399 (2002)]. In zebrafish that formed memories, we saw a dramatic increase in the number of synapses in the ventrolateral pallium, which contains neurons active during memory formation and retrieval. Concurrently, synapse loss predominated in the dorsomedial pallium. Surprisingly, we did not observe significant changes in the intensity of synaptic labeling, a proxy for synaptic strength, with memory formation in any region of the pallium. Our results suggest that memory formation due to classical conditioning is associated with reciprocal changes in synapse numbers in the pallium.

It is widely believed that memories are formed as a result of alterations in synaptic connections between axons and dendrites, an idea first proposed by Ramon y Cajal (1–4). Although synapse changes have been extensively studied in brain slices in the context of long-term potentiation (5, 6), less is known about how synapses in a living vertebrate are modified when a memory is formed.Memory formation has been widely studied using classical conditioning (CC), a robust and straightforward form of learning in which an animal is exposed to a neutral stimulus (conditioned stimulus, CS) paired with an appetitive or aversive stimulus (unconditioned stimulus, US) that evokes a specific behavioral response (UR, unconditioned response) (7, 8). As a result of the pairing, animals learn to associate the CS with the US, causing them to respond to the CS with a conditioned response (CR) identical to the UR, signifying memory retrieval (9, 10). Memory retrieval is also evoked by activating a cellular engram, a group of neurons active during memory formation and retrieval (11–18). The central locus of CC in mammals, the amygdala (19), is located in a relatively inaccessible area beneath the cortex (20). Thus, although numerous longitudinal imaging studies have documented experience-dependent changes in the structure of spines of cortical and hippocampal neurons (21, 22), few imaging studies have directly examined synaptic changes that occur in the amygdala during associative memory formation.Instead, synaptic changes that occur in the amygdala during CC (23) have been studied primarily using indirect measures of synaptic strength, such as the ratio of α-amino-3-hydroxy-5-methyl-4-isoxazoleproprionic acid receptor/N-methyl D-aspartate (AMPA/NMDA) currents in excitatory postsynaptic currents (EPSCs). Increases in AMPA/NMDA ratio in amygdalar neurons following auditory fear conditioning (FC), a type of CC (24–27), indicate that associative memory formation coincides with increases in synaptic strength. In addition, imaging experiments in brain regions beyond the amygdala have shown diverse effects following CC. For example, following contextual fear conditioning, engram neurons in the CA1 region of the hippocampus that receive inputs from CA3 engram neurons displayed spines that were larger and more densely packed than nonengram cells (28). Furthermore, experiments in which neuronal morphology was directly observed before and after FC found that neurons in the frontal association (29) and primary motor cortex (30) showed a decrease in the number of spines, whereas neurons in the auditory cortex showed an increase in spine number with memory formation (31).To obtain previously unavailable insight into memory formation within the central locus of associative memory storage, we developed a paradigm combining in vivo labeling and imaging with informatics and analysis tools. We used this paradigm to map synaptic changes that occur over time in the intact brain of a living vertebrate during memory formation. We imaged the pallium of teleost fish, which contains the putative homolog of the mammalian amygdala based on anatomy (32), gene expression (33), and function (34). The pallium is on the surface of the brain (35), and zebrafish larvae are highly transparent, allowing for intact, whole-brain imaging using selective plane illumination microscopy (SPIM) without the need for invasive intervention (36). In addition, while most studies of learning in zebrafish have used adults (37–40), at least one study showed that larval zebrafish can learn to associate a place with a positive valence US (41). These attributes suggest that larval zebrafish may be an ideal model organism for studying synaptic changes during memory formation due to CC. We have engaged this challenge by combining purpose-built experimental tools with data management software that enables transparent analyses of large and heterogeneous datasets. All data were characterized and stored at the time of creation in a customized data management system designed to conform to findability, accessibility, interoperability, and reusability (i.e., FAIR principles) (see Materials and Methods) (42).     

Chronic telogen effluvium in a man

Chronic telogen effluvium is a recently described condition, in which there is persistent excessive hair shedding. Hairs are replaced as quickly as they shed, so patients never become bald. This condition is found primarily in women. We describe chronic telogen effluvium in a man; the diagnosis may have only become obvious because of his long hair.     

Physical proximity and functional interplay of PECAM-1 with the Fc receptor Fc gamma RIIa on the platelet plasma membrane

We and others have recently defined that Platelet Endothelial Cell Adhesion Molecule-1 (PECAM-1/CD31) functions as a negative regulator of platelet-collagen interactions involving the glycoprotein VI/Fc receptor gamma chain (GPVI/FcR-gamma chain) signaling pathway.1,2 In this study, we hypothesized that PECAM-1 may be physically and functionally associated with Fc gamma RIIa on the platelet membrane. The functional relationship between PECAM-1 and Fc gamma RIIa was assessed by determining the effect of anti-PECAM-1 monoclonal antibody Fab fragments on Fc gamma RIIa-mediated platelet aggregation and heparin-induced thrombocytopenia (HITS)-mediated platelet aggregation. Preincubation of washed platelets with monoclonal antibody fragments of 2BD4 directed against PECAM-1 and IV.3 directed against Fc gamma RIIa completely blocked Fc gamma RIIa-mediated platelet aggregation and HITS-mediated platelet aggregation, whereas anti-CD151 antibody had no blocking effect. Coengagement of Fc gamma RIIa and PECAM-1 resulted in negative regulation of Fc gamma RIIa-mediated phospholipase C gamma 2 activation, calcium mobilization, and phosphoinositide 3-kinase-dependent signaling pathways. In addition, the physical proximity of Fc gamma RIIa and PECAM-1 was confirmed by using fluorescence resonance energy transfer and coimmunoprecipitation studies. These results indicate that PECAM-1 and Fc gamma RIIa are colocalized on the platelet membrane and PECAM-1 down-regulates Fc gamma RIIa-mediated platelet responses.