Evaluation of Nootropic Potential of Aerva persica Roots against D-galactose-induced Memory Impairment.

BACKGROUND: The primary phytoconstituents reported to have neuroprotective effects are flavonoids and phenolic compounds. Aerva persica roots are reported to be rich in flavonoids and phenolic compounds. Therefore, this study aimed to explore the nootropic potential of Aerva persica roots. OBJECTIVE: The objective of this study was to evaluate the nootropic potential of Aerva persica roots against D-galactose-induced memory impairment. METHODS: In this study, the roots of Aerva persica were extracted with 70% ethanol. The obtained extract was evaluated for total phenolic content using the Folin-Ciocalteu method and total flavonoid content using the aluminium chloride colorimetric assay. Afterward, the acute oral toxicity of the extract was determined following the Organisation for Economic Co-operation and Development (OECD) guideline 423. Additionally, two doses of Aerva persica (100 and 200 mg/kg body weight (BW)) were evaluated for their nootropic potential against D-galactose-induced memory impairment. The nootropic potential of the crude extract was assessed through a behavioural study and brain neurochemical analysis. Behavioural studies involved the evaluation of spatial reference- working memory using the radial arm maze test and the Y-maze test. Neurochemical analysis was performed to determine the brain's acetylcholine, acetylcholinesterase, glutathione (GSH), and malondialdehyde (MDA) levels. RESULTS: The total phenolic content and total flavonoid content were found to be 179.14 ± 2.08 µg GAE/mg and 273.72 ± 3.94 µg QE/mg, respectively. The Aerva persica extract was found to be safe up to 2000 mg/kg BW. Following the safety assessment, the experimental mice received various treatments for 14 days. The behavioural analysis using the radial maze test showed that the extract at both doses significantly improved spatial reference-working memory and reduced the number of total errors compared to disease control groups. Similarly, in the Y-maze test, both doses significantly increased the alteration percentage and the percentage of novel arm entry (both indicative of intact spatial memory) compared to disease control. In neurochemical analysis, Aerva persica at 200 mg/kg significantly normalised the acetylcholine level (p<0.0001) and GSH level (p<0.01) compared to disease control. However, the same effect was not observed with Aerva persica at 100 mg/kg. Additionally, Aerva persica at 200mg/kg BW significantly decreased the acetylcholinesterase level (p<0.0001) and decreased the brain's MDA level (p<0.01) compared to the disease control, whereas the effect of Aerva persica at 100 mg/kg BW in reducing acetylcholinesterase was non-significant. CONCLUSION: Based on the results, it can be concluded that the nootropic potential of Aerva persica was comparable to that of the standard drug, Donepezil, and the effect might be attributed to the higher content of flavonoids and phenolic compounds.

Quantitative nanohistology of aging dermal collagen.

The skin is the largest organ in the body and is essential for protecting us from environmental stressors such as UV radiation, pollution, and pathogens. As we age, our skin undergoes complex changes that can affect its function, appearance, and health. These changes result from intrinsic (chronological) and extrinsic (environmental) factors that can cause damage to the skin's cells and extracellular matrix. As higher-resolution microscopical techniques, such as Atomic Force Microscopy (AFM), are being deployed to support histology, it is possible to explore the biophysical properties of the dermal scaffold's constituents, such as the collagen network. In this study, we demonstrate the use of our AFM-based quantitative nanohistology, performed directly on unfixed cryosections of 30 donors (female, Caucasian), to differentiate between dermal collagen from different age groups and anatomical sites. The initial 420 (10 × 10 µm2) Atomic Force Microscopy images were segmented into 42,000 (1 × 1 µm2) images before being classified according to four pre-defined empirical collagen structural biomarkers to quantify the structural heterogeneity of the dermal collagen. These markers include interfibrillar gap formation, undefined collagen structure, and registered or unregistered dense collagen fibrillar network with evident D-banding. The structural analysis was also complemented by extensive nanoindentation (∼1,000 curves) performed on individual fibrils from each section, yielding 30,000 indentation curves for this study. Principal Component Analysis was used to reduce the complexity of high-dimensional datasets. The % prevalence of the empirical collagen structural biomarkers between the papillary and reticular dermis for each section proves determinant in differentiating between the donors as a function of their age or the anatomical site (cheek or breast). A case of abnormal biological aging validated our markers and nanohistology approach. This case also highlighted the difference between chronological and biological aging regarding dermal collagen phenotyping. However, quantifying the impact of chronic and pathological conditions on the structure and function of collagen at the sub-micron level remains challenging and lengthy. By employing tools such as the Atomic Force Microscope as presented here, it is possible to start evaluating the complexity of the dermal matrix at the nanoscale and start identifying relevant collagen morphology which could be used toward histopathology standards.

Phenotypic Properties of Collagen in Dentinogenesis Imperfecta Associated with Osteogenesis Imperfecta.

INTRODUCTION: Dentinogenesis imperfecta type 1 (OIDI) is considered a relatively rare genetic disorder (1:5000 to 1:45,000) associated with osteogenesis imperfecta. OIDI impacts the formation of collagen fibrils in dentin, leading to morphological and structural changes that affect the strength and appearance of teeth. However, there is still a lack of understanding regarding the nanoscale characterization of the disease, in terms of collagen ultrastructure and mechanical properties. Therefore, this research presents a qualitative and quantitative report into the phenotype and characterization of OIDI in dentin, by using a combination of imaging, nanomechanical approaches. METHODS: For this study, 8 primary molars from OIDI patients and 8 primary control molars were collected, embedded in acrylic resin and cut into longitudinal sections. Sections were then demineralized in 37% phosphoric acid using a protocol developed in-house. Initial experiments demonstrated the effectiveness of the demineralization protocol, as the ATR-FTIR spectral fingerprints showed an increase in the amide bands together with a decrease in phosphate content. Structural and mechanical analyses were performed directly on both the mineralized and demineralized samples using a combination of scanning electron microscopy, atomic force microscopy, and Wallace indentation. RESULTS: Mesoscale imaging showed alterations in dentinal tubule morphology in OIDI patients, with a reduced number of tubules and a decreased tubule diameter compared to healthy controls. Nanoscale collagen ultrastructure presented a similar D-banding periodicity between OIDI and controls. Reduced collagen fibrils diameter was also recorded for the OIDI group. The hardness of the (mineralized) control dentin was found to be significantly higher (p<0.05) than that of the OIDI (mineralized) dentine. Both the exposed peri- and intratubular dentinal collagen presented bimodal elastic behaviors (Young's moduli). The control samples presented a stiffening of the intratubular collagen when compared to the peritubular collagen. In case of the OIDI, this stiffening in the collagen between peri- and intratubular dentinal collagen was not observed and the exposed collagen presented overall a lower elasticity than the control samples. CONCLUSION: This study presents a systematic approach to the characterization of collagen structure and properties in OIDI as diagnosed in dentin. Structural markers for OIDI at the mesoscale and nanoscale were found and correlated with an observed lack of increased elastic moduli of the collagen fibrils in the intratubular OIDI dentin. These findings offer an explanation of how structural changes in the dentin could be responsible for the failure of some adhesive restorative materials as observed in patients affected by OIDI.

Intracoronal stress transfer through enamel following RBC photopolymerisation: A synchrotron X-ray study.

OBJECTIVES: To measure the spatial distribution of crystallographic strain in tooth enamel induced by the photo-polymerisation of a dimethacrylate resin based composite cavity restoration. METHODS: Six sound first premolar teeth, allocated into two groups (n=3), were prepared with mesio-occlusal distal cavities. The enamel was machined at the point of maximum convexity on the outer tooth to create a vertical fin of thickness 100µm and 0.5mm depth to allow for synchrotron X-ray diffraction measurements. 2D diffraction patterns were used to determine crystallite orientation and quantify changes in the hydroxyapatite crystal lattice parameters, before and after photo-polymerisation of a composite material placed in the cavity, to calculate strain in the respective axis. The composite was photo-polymerised with either relatively high (1200mWcm-2, group 1) or low (480mWcm-2, group 2) irradiances using LED or quartz halogen light sources, respectively. A paired t-test was used to determine significant differences in strain between irradiance protocols at ɑ=0.001. RESULTS: Photo-polymerisation of the composite in the adjacent cavity induced significant changes in both the crystallographic c and a axes of the enamel measurement area. However the magnitude of strain was low with ∼0.1% difference before and after composite photo-polymerisation. Strain in enamel was not uniformly distributed and varied spatially as a function of crystallite orientation. Increased alignment of crystallites perpendicular to the cavity wall was associated with higher c axis strain. Additionally, strain was significantly greater in the c (p<0.001) and a axis (p<0.001) when using a high irradiance photo-polymerisation protocol. SIGNIFICANCE: Although cuspal deflection is routinely measured to indirectly assess the 'global' effect of composite shrinkage on the tooth-restoration complex, here we show that absolute strains generated in enamel are low, indicating strain relief mechanisms may be operative. The use of low irradiance protocols for photo-polymerisation resulted in reduced strain.

Erratum: A mineralogical study in contrasts: highly mineralized whale rostrum and human enamel.

This corrects the article DOI: 10.1038/srep16511.

A mineralogical study in contrasts: highly mineralized whale rostrum and human enamel.

The outermost enamel of the human tooth and the rostrum of the whale Mesoplodon densirostris are two highly mineralized tissues that contain over 95 wt.% mineral, i.e., bioapatite. However, the same mineral type (carbonated hydroxylapatite) does not yield the same material properties, as revealed by Raman spectroscopy, scanning electron microscopy, electron microprobe analysis, and synchrotron X-ray diffraction analysis. Overall, the outermost enamel of a tooth has more homogeneous physical and chemical features than the rostrum. Chemical comparison of rostrum and enamel shows bioapatite in the rostrum to be enriched in Na, Mg, CO3, and S, whereas the outermost enamel shows only a slightly enriched Cl concentration. Morphologically, mineral rods (at tens of µm scale), crystallites and prisms (at µm and sub-µm scale), and platelets (at tens of nm scale) all demonstrate less organized texture in the rostrum than in enamel. Such contrasts between two mineralized tissues suggest distinct pathways of biomineralization, e.g., the nature of the equilibrium between mineral and body fluid. This study illustrates the remarkable flexibility of the apatite mineral structure to match its chemical and physical properties to specific biological needs within the same animal or between species.

Recovery of crystallographic texture in remineralized dental enamel.

Dental caries is the most prevalent disease encountered by people of all ages around the world. Chemical changes occurring in the oral environment during the caries process alter the crystallography and microstructure of dental enamel resulting in loss of mechanical function. Little is known about the crystallographic effects of demineralization and remineralization. The motivation for this study was to develop understanding of the caries process at the crystallographic level in order to contribute towards a long term solution. In this study synchrotron X-ray diffraction combined with scanning electron microscopy and scanning microradiography have been used to correlate enamel crystallography, microstructure and mineral concentration respectively in enamel affected by natural caries and following artificial demineralization and remineralization regimes. In particular, the extent of destruction and re-formation of this complex structure has been measured. 2D diffraction patterns collected at the European Synchrotron Radiation Facility were used to quantify changes in the preferred orientation (crystallographic texture) and position of the (002) Bragg reflection within selected regions of interest in each tooth slice, and then correlated with the microstructure and local mineral mass. The results revealed that caries and artificial demineralization cause a large reduction in crystallographic texture which is coupled with the loss of mineral mass. Remineralization restores the texture to the original level seen in healthy enamel and restores mineral density. The results also showed that remineralization promotes ordered formation of new crystallites and growth of pre-existing crystallites which match the preferred orientation of healthy enamel. Combining microstructural and crystallographic characterization aids the understanding of caries and erosion processes and assists in the progress towards developing therapeutic treatments to allow affected enamel to regain structural integrity.