MEPE-Derived ASARM Peptide Inhibits Odontogenic Differentiation of Dental Pulp Stem Cells and Impairs Mineralization in Tooth Models of X-Linked Hypophosphatemia

Mutations in PHEX (phosphate-regulating gene with homologies to endopeptidases on the X-chromosome) cause X-linked familial hypophosphatemic rickets (XLH), a disorder having severe bone and tooth dentin mineralization defects. The absence of functional PHEX leads to abnormal accumulation of ASARM (acidic serine- and aspartate-rich motif) peptide − a substrate for PHEX and a strong inhibitor of mineralization − derived from MEPE (matrix extracellular phosphoglycoprotein) and other matrix proteins. MEPE-derived ASARM peptide accumulates in tooth dentin of XLH patients where it may impair dentinogenesis. Here, we investigated the effects of ASARM peptides in vitro and in vivo on odontoblast differentiation and matrix mineralization. Dental pulp stem cells from human exfoliated deciduous teeth (SHEDs) were seeded into a 3D collagen scaffold, and induced towards odontogenic differentiation. Cultures were treated with synthetic ASARM peptides (phosphorylated and nonphosphorylated) derived from the human MEPE sequence. Phosphorylated ASARM peptide inhibited SHED differentiation in vitro, with no mineralized nodule formation, decreased odontoblast marker expression, and upregulated MEPE expression. Phosphorylated ASARM peptide implanted in a rat molar pulp injury model impaired reparative dentin formation and mineralization, with increased MEPE immunohistochemical staining. In conclusion, using complementary models to study tooth dentin defects observed in XLH, we demonstrate that the MEPE-derived ASARM peptide inhibits both odontogenic differentiation and matrix mineralization, while increasing MEPE expression. These results contribute to a partial mechanistic explanation of XLH pathogenesis: direct inhibition of mineralization by ASARM peptide leads to the mineralization defects in XLH teeth. This process appears to be positively reinforced by the increased MEPE expression induced by ASARM. The MEPE-ASARM system can therefore be considered as a potential therapeutic target.     

Autoradiographic Localization of Angiotensin II Receptor Binding Sites on Noradrenergic Neurons of the Locus Coeruleus of the Rat

The locus coeruleus (LC) of the rat was lesioned by microinjection of selective neurotoxins into the brainstem. 6-Hydroxydopamine (6-OHDA), 3 micrograms/microliter, given unilaterally at two sites 0.6 mm apart on the rostro-caudal axis of the LC, was used to lesion catecholamine-containing neuronal elements. Ibotenic acid, 2.5 micrograms/0.5 microliters, administered similarly was used to lesion nerve cell bodies. Two weeks after administration of the neurotoxin, lesion efficacy was determined based on the norepinephrine content of the cerebral cortex ipsi- and contralateral to the lesion. 6-OHDA lesions of the LC caused a 46% reduction in ipsilateral cortical norepinephrine and a 60% reduction in specific 125I-[Sar1, Ile8]-angiotensin II (125I-SIAII) binding in the LC. Ibotenic acid lesions of the LC caused a 73% reduction in ipsilateral cortical norepinephrine and a 81% reduction in specific 125I-SIAII binding in the LC. These results indicate that AII receptor binding sites in the LC are localized on noradrenergic nerve cell bodies or their dendritic and axonal ramifications within the LC.     

Lack of evidence from studies of soluble protein fragments that Knops blood group polymorphisms in complement receptor-type 1 are driven by malaria

Complement receptor-type 1 (CR1, CD35) is the immune-adherence receptor, a complement regulator, and an erythroid receptor for Plasmodium falciparum during merozoite invasion and subsequent rosette formation involving parasitized and non-infected erythrocytes. The non-uniform geographical distribution of Knops blood group CR1 alleles Sl1/2 and McC^a/b may result from selective pressures exerted by differential exposure to infectious hazards. Here, four variant short recombinant versions of CR1 were produced and analyzed, focusing on complement control protein modules (CCPs) 15–25 of its ectodomain. These eleven modules encompass a region (CCPs 15–17) key to rosetting, opsonin recognition and complement regulation, as well as the Knops blood group polymorphisms in CCPs 24–25. All four CR1 15–25 variants were monomeric and had similar axial ratios. Modules 21 and 22, despite their double-length inter-modular linker, did not lie side-by-side so as to stabilize a bent-back architecture that would facilitate cooperation between key functional modules and Knops blood group antigens. Indeed, the four CR1 15–25 variants had virtually indistinguishable affinities for immobilized complement fragments C3b (K _D = 0.8–1.1 µM) and C4b (K _D = 5.0–5.3 µM). They were all equally good co-factors for factor I-catalysed cleavage of C3b and C4b, and they bound equally within a narrow affinity range, to immobilized C1q. No differences between the variants were observed in assays for inhibition of erythrocyte invasion by P. falciparum or for rosette disruption. Neither differences in complement-regulatory functionality, nor interactions with P. falciparum proteins tested here, appear to have driven the non-uniform geographic distribution of these alleles.     

The function and evolution of the tail streamer in hirundines

The morphology of a bird's tail may result from compromisesbetween aerodynamic efficiency, phylogenetic constraints andselection for non-aerodynamic characteristics, such as mateattraction. A good example of a trait shaped by trade-offsbetween aerodynamic efficiency and reproductive benefits mediatedthrough female preference is the tail streamer of the barn swallow. Here we use a standardized task to measure the impactof manipulated tail streamer lengths on maneuvering flightin the barn swallow and in the sand martin, a closely relatedspecies that lacks a streamer. Our results show that the tailstreamer of the barn swallow has a role in maneuvering flight. However, the outer tail feather is approximately 12 mm (9-20%)longer than the aerodynamic optimum for maneuvering flight.Furthermore, we show that the addition of artificial tail streamersto the sand martin, enhances maneuverability even at smallstreamer lengths, thereby implying that tail streamers mayhave evolved via natural selection for increased flight performance.Our results therefore suggest that initial tail streamer elongationin the barn swallow has a functional explanation in terms of increased aerodynamic performance. However, female choice hasbecome associated with this trait, promoting the developmentof a costly handicap.     

Life in a fragment: Evolution of foraging strategies of translocated collared brown lemurs,Eulemur collaris,over an 18-year period

While the drivers of primate persistence in forest fragments have been often considered at the population level, the strategies to persist in these habitats have been little investigated at the individual or group level. Considering the rapid variation of fragment characteristics over time, longitudinal data on primates living in fragmented habitats are necessary to understand the key elements for their persistence. Since translocated animals have to cope with unfamiliar areas and face unknown fluctuations in food abundance, they offer the opportunity to study the factors contributing to successful migration between fragments. Here, we illustrated the evolution of the foraging strategies of translocated collared brown lemurs (Eulemur collaris) over an 18-year period in the Mandena Conservation Zone, south-east Madagascar. Our aim was to explore the ability of these frugivorous lemurs to adjust to recently colonized fragmented forests. Although the lemurs remained mainly frugivorous throughout the study period, over the years we identified a reduction in the consumption of leaves and exotic/pioneer plant species. These adjustments were expected in frugivorous primates living in a degraded area, but we hypothesize that they may also reflect the initial need to cope with an unfamiliar environment after the translocation. Since fragmentation is often associated with the loss of large trees and native vegetation, we suggest that the availability of exotic and/or pioneer plant species can provide an easy-to-access, nonseasonal food resource and be a key factor for persistence during the initial stage of the recolonization.     

Gas chromatographic assay for in vitro complementation of Pseudomonas aeruginosa mutants deficient in nitrate reduction

An electron capture gas-chromatographic technique was developed to continuously measure nitrate (NO3-) reduction during in vitro complementation tests with extracts from Pseudomonas aeruginosa mutants deficient in both assimilatory and dissimilatory nitrate reduction as a result of a single genetic mutation. The procedure involves coupling nitrate reduction to nitrous oxide (N2O) evolution via a series of reactions specific to the denitrification pathway. The assay was dependent on nitrate concentration, and optimal activity was obtained with a final concentration of 0.2% potassium nitrate. The reduction exhibited a stoichiometry of 2:1 (NO3-/N2O), and succinate was the best electron source for the reaction, followed by glucose, pyruvate, and malate. The technique can also be used for continuously monitoring nitrate reduction. The optimal nitrite concentration in the nitrite reductase assay was 0.025%. The initial complementation studies of mutant extracts demonstrated that at least two genes are shared between the two nitrate reduction pathways in P. aeruginosa.     

超声治疗动脉粥样硬化性心血管疾病研究进展

超声干预治疗动脉粥样硬化性心血管疾病（atherosclerotic cardiovascular disease,ASCVD）是一种非侵入性治疗方法,其应用于临床治疗的前景广阔。超声波在身体组织中产生的机械、空化及生化等一系列作用可以有效清除血管中的斑块或血栓。但是,安全性是超声疗法应用于临床中亟需解决的首要问题。超声波在身体组织中的传播会引起组织损伤。另外,安全处理因超声刺激而产生的斑块或血栓碎片也是超声疗法应用中面临的挑战。除了确保安全性,合理制定治疗方案及治疗参数从而提高超声疗法疗效是超声疗法应用于临床中有待解决的重要问题。本文结合近年来超声干预治疗动脉粥样硬化性心血管疾病方面的各种临床、动物及体外模型实验研究结果,综述了超声干预治疗的机制、不同治疗方法和治疗参数的效果、如何确保安全性,以及提高超声疗法疗效需解决的一系列问题,进而提出可能的解决方案。     

Biophysical studies of infectious pancreatic necrosis virus.

The molecular weight of infectious pancreatic necrosis virus (IPNV) has been determined by analytical ultracentrifugation and dynamic light scattering. The sedimentation coefficient of the virus was found to be 435S. The average value for molecular weight is (55 +/- 7) x 106. The virus genome consists of two segments of double-stranded RNA (molecular weights, 2.5 x 106 and 2.3 x 106), which represents 8.7% of the virion mass. The capsid protein moiety of IPNV consists of four species of polypeptides, as determined by polyacrylamide gel electrophoresis. The number of molecules of each polypeptide in the virion has been determined. There are 22 molecules of the internal polypeptide alpha (molecular weight, 90,000), 544 molecules of the outer capsid polypeptide beta (molecular weight, 57,000), and 550 and 122 molecules, respectively, of the internal polypeptides gamma1 (molecular weight, 29,000) and gamma2 (molecular weight, 27,000). IPNV top component contains only the beta polypeptide species, and its molecular weight is estimated to be 31 x 106. The hydrodynamic diameter and electron microscopic diameter (calculated by catalase crystal-calibrated electron microscopy) of IPNV was compared with those of reovirus and encephalomyocarditis virus. Due to the swelling of the outer capsid, reovirus particles were found to be much larger when hydrated (96-nm diameter) than when dehydrated (76-nm diameter), having a large water content content and low average density. In contrast, IPNV particles are more rigid, having nearly the same average diameter under hydrous (64 nm) as under anhydrous conditions (59.3 nm). Encephalomyocarditis virus has a very low water content and does not shrink at all when prepared for electron microscopy.