Anatomical Properties Research Articles

Variations in leaf anatomical characteristics drive the decrease of mesophyll conductance in poplar under elevated ozone.

Decline in mesophyll conductance (gm ) plays a key role in limiting photosynthesis in plants exposed to elevated ozone (O3 ). Leaf anatomical traits are known to influence gm , but the potential effects of O3 -induced changes in leaf anatomy on gm have not yet been clarified. Here, two poplar clones were exposed to elevated O3 . The effects of O3 on the photosynthetic capacity and anatomical characteristics were assessed to investigate the leaf anatomical properties that potentially affect gm . We also conducted global meta-analysis to explore the general response patterns of gm and leaf anatomy to O3 exposure. We found that the O3 -induced reduction in gm was critical in limiting leaf photosynthesis. Changes in liquid-phase conductance rather than gas-phase conductance drive the decline in gm under elevated O3, and this effect was associated with thicker cell walls and smaller chloroplast sizes. The effects of O3 on palisade and spongy mesophyll cell traits and their contributions to gm were highly genotype-dependent. Our results suggest that, while anatomical adjustments under elevated O3 may contribute to defense against O3 stress, they also cause declines in gm and photosynthesis. These results provide the first evidence of anatomical constraints on gm under elevated O3 .

Mechanism of Tolerance to Head-Splitting of Cabbage (Brassica oleracea L. var. capitata L.): A Review of Current Knowledge and Future Directions

Cabbage (Brassica oleracea L. var. capitata L.) is an important cruciferous vegetable, which is rich in dietary fiber, vitamins, beta-carotene and even good for cancer prevention. So, it is widely planted around the world. However, in the production of cabbage, the property of head-splitting not only reduces the appearance quality and commercial value of cabbage but also easily infects the area with head-splitting by germs, resulting in yield reduction, even no yield, and economic losses. For the head-splitting of cabbage, this paper introduced the causes, evaluation methods and indexes, and anatomic properties and reviewed some QTLs that have been obtained. But the cabbage molecular research of head-splitting is still in its infancy compared with other vegetable plants. Head-splitting is greatly affected by water. Although the cultivation and management methods can reduce the head-splitting rate, genetic improvement of head-splitting is still the most economic and efficient way in the long run. Therefore, the changes in the substances regulating cell water potential, the development of cell wall, ductility and toughness, calcium ion-regulated pectinase and cellulase activities, expansin genes, and even the ETH and ABA pathways related to maturation and abscission can provide ideas and directions for future gene mining and mechanism analysis for head-splitting tolerance, and thus accelerate the molecular breeding process.

Effects of plant extract and wood on anatomical structure in ecological environment interaction

In this study, the impregnation of a 3% solution of a mixture of medicinal aromatic plant extract, borax, and ferula plant extract on wood of eastern spruce (Picea orientalis L. (Link)) and mahogany were carried out and the changes in the anatomical structure of the impregnated wood were determined. Through obtaining extracts of various medicinal aromatic plants (ferula) and dual treatment with borax, the anatomical properties of wood material were examined and the related adhesion scale was determined. The highest retention (retention) was in mahogany wood borax (1.86%), and the lowest retention was again in mahogany wood ferula extract (0.31%). Both wood types demonstrated improved outcomes in comparison to the control sample when the air-dry and fully-dry specific gravity changes were investigated. The maximum air-dried specific gravity value was found in mahogany at 3% borax and ferula + borax (0.56 g/cm3), and the lowest at 3% ferula and borax (0.37 g/cm3). Mahogany wood with 3% borax had the greatest full dry specific gravity value (0.54 g/cm3), and spruce wood with 3% ferula and ferula + borax had the lowest (0.35 g/cm3). There was no retention in the tracheid and trachea cells that perform the transmission function. Because the sapphire cells are the cells that act as storage, adhesion has occurred in these cells.

Geographic and longitudinal variations of anatomical characteristics and mechanical properties in three bamboo species naturally grown in Lombok Island, Indonesia

The anatomical characteristics (fiber length and fiber area) and mechanical properties (modulus of elasticity, modulus of rupture, compressive strength, tensile Young’s modulus, and tensile strength) of Bambusa vulgaris, Bambusa maculata, and Gigantochloa atter, naturally growing at four different sites in Lombok Island, Indonesia, were examined for evaluating geographic and longitudinal variations by mixed-effects modeling to effectively utilize bamboo culm resources for structural materials. We found geographic and longitudinal variations of bamboo culm properties in these three species. Based on the results, we concluded that, for utilization of bamboo culm as a structural material, variation of individual culm rather than site, and longitudinal variations should be considered for Bambusa species and G. atter, respectively.

Optimization of Freeform Reversible Embedding of Suspended Hydrogel Microspheres for Substantially Improved Three-Dimensional Bioprinting Capabilities.

Three-dimensional (3D) bioprinting demonstrates technology that is capable of producing structures comparable to native tissues in the human body. The freeform reversible embedding of suspended hydrogels (FRESH) technique involves hydrogel-based bio-inks printed within a thermo-reversible support bath to provide mechanical strength to the printed construct. Smaller and more uniform microsphere sizes of FRESH were reported to aid in enhancing printing resolution and construct accuracy. Therefore, we sought to optimize the FRESH generation protocol, particularly by varying stir speed and stir duration, in hopes to further improve microsphere size and uniformity. We observed optimal conditions at a stir speed of 600 rpm and stir duration for 20 h that generated the smallest microspheres with the best uniformity. Comparison of using the optimized FRESH to the commercial FRESH LifeSupport to bioprint single filament and geometrical constructs revealed reduced single filament diameters and higher angular precision in the optimized FRESH bio-printed constructs compared with those printed in the commercial FRESH. Overall, our refinement of the FRESH manufacturing protocol represents an important step toward enhancing 3D bioprinting resolution and construct fidelity. Improving such technologies allows for the fabrication of highly accurate constructs with anatomical properties similar to native counterparts. Such work has significant implications in the field of tissue engineering for producing accurate human organ model systems. Impact statement Freeform reversible embedding of suspended hydrogels (FRESH) is a method of sacrificial three-dimensional (3D) bioprinting that offers support to reinforce bio-ink extrusion during printing. During FRESH generation, the stir speed and stir duration of the mixture can significantly impact FRESH microsphere characteristics. In this study, we optimized FRESH microspheres to significantly improve resolution and accuracy in bioprinting. This advancement in FRESH-based 3D bioprinting technologies allows for the fabrication of highly accurate constructs with anatomical properties similar to native counterparts and has significant implications in the field of tissue engineering and translational medicine.

Myocardial bridge over coronary arteries and myocardial coat over coronary sinus: a cadaveric study

Abstract Funding Acknowledgements Type of funding sources: None. Background Myocardial Bridge (MB) over the coronary artery and myocardial coat (MC) over the cardiac veins are sometimes detected in angiography and cadaveric dissection. Left anterior descending (LAD) branch of left coronary artery is most frequent site of MB. Rarely MB is also seen over right coronary artery (RCA) branch. MB has proven association with ischemic heart disease and other critical cardiac consequences like myocardial infarction (MI)(1)(2). MC on the other hand has not gained enough attention in erstwhile studies. Large MB can be readily identified in angiograms, but minute MB can be picked up by newer imaging studies like multi-detector computed tomography (MDCT) and optical coherence tomography (OCT) scan(3). Cadaveric dissection however holds its unique place in direct visualization and studying the macro and micro-anatomical characteristics. Purpose To study the prevalence and anatomical attributes of MB and MC in cadaveric hearts. Methods Ten adult cadaveric hearts (6 male and 4 female) were dissected as part of routine undergraduate teaching during academic year 2021-22. MB over the coronary artery and MC over cardiac vein was identified. Data pertaining to the MB and MC dimensions were measured with digital vernier calliper. Histology of the MC was carried out to confirm its presence and observe the cyto-architecture pattern. Relevant gross macroscopic and microscopic images were photographed and photomicrographed. Results 20% of the dissected cadavers revealed MB involving LAD in first heart while LAD and RCA both in second heart with length 7.5 mm, 11.5 mm and 1.8 mm respectively. MC was noted over coronary sinus and proximal few millimeters of great and middle cardiac veins. Histological examination revealed cardiac striated muscle in MC with typical cyto-architecture. The mean myocardial muscle index (MMI) of MBs was 1.39. Conclusions Present study highlights 20% prevalence of MBs in cadavers involving both right and left coronary artery. 10% of the subjects had histologically confirmed MC over cardiac veins. MC over coronary sinus and other cardiac veins needs more elaborate explorative studies to quantify the anatomic properties and to examine the possible association with cardiovascular disease. Nevertheless, anatomic attributes should be kept in mind to better appreciate MI in evolution and MI at evaluation in a case with MB.

INFLUENCE OF ANATOMY ON THE MECHANICAL RESISTANCE OF WOODS IN AN AGROFORESTRY SYSTEM

This study aimed to evaluate the influence of anatomy on the mechanical resistance of Parapiptadenia rigida (Benth.) Brenan, Peltophorum dubium (Spreng.) Taub., Eucalyptus grandis × Eucalyptus urophylla, and Schizolobium parahyba (Vell.) Blake from an agroforestry system. For this purpose, twelve 9-year-old trees were felled. To evaluate the anatomical properties, the specimens were taken from the diameter region at breast height (DBH at 1.30 m from the ground). To determine the mechanical characteristics, central planks from the DBH of the tree logs were removed to produce test specimens with dimensions of 2.5 × 2.5 × 41.0 cm. The modulus of elasticity, modulus of rupture, tension of the proportional limit, and maximum force were then evaluated. Conversely, test specimens with dimensions of 5 × 5 × 15 cm for were used for the transversal and longitudinal Janka hardness and perpendicular compression tests. The higher the cell wall fraction, vessel frequency, and ray frequency values, the better the mechanical properties. Conversely, with the increase in the fiber diameter, lumen diameter, vessel diameter, height, and width of rays, the values of the mechanical properties of wood are lower.

Three-dimensional kinematics of the craniocervical junction of Cavalier King Charles Spaniels compared to Chihuahuas and Labrador retrievers.

Our knowledge about the underlying pathomechanisms of craniocervical junction abnormalities (CCJA) in dogs mostly derives from measurements based on tomographic imaging. These images are static and the positioning of the dogs' head does not reflect the physiological in vivo position of the craniocervical junction (CCJ). Aberrant motion patterns and ranges of motion (ROM) in sound individuals of CCJA predisposed breeds may be a pathogenetic trigger. To further extend our limited knowledge of physiological motion of the CCJ, this prospective, comparative study investigates the in vivo motion patterns and ROM of the CCJ in walk and trot in sound Cavalier King Charles Spaniels and Chihuahuas. The Labrador retriever is used as a reference breed without predisposition for CCJA. This is the first detailed description of CCJ movement of trotting dogs. Biplanar fluoroscopy images, recorded in walking and trotting dogs, were matched to a virtual reconstruction of the skull and cranial cervical spine utilising Scientific Rotoscoping. Kinematic data reveal the same motion patterns among all breeds and gaits with individual temporal and spatial differences in each dog. A stride cycle-dependent lateral rotation of the cranial cervical spine and axial rotation of the atlantoaxial joint in trot in dogs is described for the first time. The ROM of the atlantoaxial and atlantooccipital joints in walk and trot were not statistically significantly greater in the CCJA-predisposed breeds CKCS and Chihuahua. ROM values of all translational and rotational degrees of freedom were larger in walk than trot, although this is only statistically significant for the atlantoaxial joint. Until proven otherwise, a more species-specific than breed-specific general motion pattern of the CCJ in walking and trotting, clinically sound dogs must be assumed. Species-specific anatomic properties of the CCJ seem to supersede breed-specific anatomical differences in clinically sound dogs.

The bony cap and its distinction from the distal phalanx in humans, cats, and horses.

It has been recognized as early as the Victorian era that the apex of the distal phalanx has a distinct embryological development from the main shaft of the distal phalanx. Recent studies in regenerative medicine have placed an emphasis on the role of the apex of the distal phalanx in bone regrowth. Despite knowledge about the unique aspects of the distal phalanx, all phalanges are often treated as equivalent. Our morphological study reiterates and highlights the special anatomical and embryological properties of the apex of the distal phalanx, and names the apex "the bony cap" to distinguish it. We posit that the distal phalanx shaft is endochondral, while the bony cap is intramembranous and derived from the ectodermal wall. During development, the bony cap may be a separate structure that will fuse to the endochondral distal phalanx in the adult, as it ossifies well before the distal phalanges across taxa. Our study describes and revives the identity of the bony cap, and we identify it in three mammalian species: humans, cats, and horses (Homo sapiens, Felis catus domestica, and Equus caballus). During the embryonic period, we show the bony cap has a thimble-like shape that surrounds the proximal endochondral distal phalanx. The bony cap may thus play an inductive role in the differentiation of the corresponding nail, claw, or hoof (keratin structures) of the digit. When it is not present or develops erroneously, the corresponding keratin structures are affected, and regeneration is inhibited. By terming the bony cap, we hope to inspire more attention to its distinct identity and role in regeneration.

Degradation assessment of archaeological oak (Quercus spp.) buried under oxygen-limited condition

Abstract The biological deterioration of archaeological wood under oxygen-limited conditions varies due to the limited activities of microorganisms. It is essential to expand the knowledge of the degradation types and the status of archaeological monuments for selecting the proper consolidates. The physical, chemical, and anatomical properties of approximately 600–650 year old archaeological oak collected from an archaeological site in Iasi-Romania were analysed to assess the quality and to identify the degradation types. The results were compared with similar tests on recently-cut oak. X-ray photoelectron spectroscopy (XPS) revealed the presence of more lignin-related peaks in the archaeological oak, which likely reflected the degradation of the wood carbohydrates as evidenced by the decreased oxygen-to-carbon ratio C ox/C non-ox. The differences in cellulose crystallinity were not significant suggesting that any cellulose degradation occurred in the amorphous regions. This was also reflected in the dynamic water vapor sorption analysis where the differences in sorption isotherms and hysteresis of archaeological and recently-cut oaks were marginal. Microscopic analysis of the oak cells illustrated bacterial degradation patterns, while the field emission scanning electron microscopy (FESEM) showed the presence of erosion bacteria in the archaeological oak collected from the site with low oxygen conditions.

Central nervous system immunity in relation to aging and AD

The present report discusses the immune and clearance system of the central nervous system (CNS) in terms of its anatomical, physiological, and biochemical properties. There is now a growing body of evidence that progressive dysfunction of the meningeal lymphatic system should be considered as a risk factor for aging-related brain disorders. In addition, the activity of meningeal lymphatics may alter the access of CSF-carried immune neuromodulators to brain parenchyma, which is also involved in the onset of aging and AD. In the CNS clearance system, impairment of the BBB and small arteries, as well as the major protein of the end feet of astrocytes, AQP4, are associated with aging or AD. The idea of maximizing brain "waste discharge" as a new preventive or therapeutic target for neurodegenerative diseases in the context of healthy aging has been accepted.

A comparison of commercially available synthetic skin substitutes for surgical simulation training.

Simulation training provides an important opportunity to accelerate surgical skills acquisition whilst safeguarding patients. This study compares the suitability of different synthetic skin substitutes for use in surgical simulation training. Data was collected for eight commercially available synthetic skin substitutes and included cost, delivery time, subjective assessment of fidelity by surgeons and trainees, and objective comparison with the biomechanics of human skin was made through cutometry and durometry measurements. Cutometry and durometry data was collected from three healthy adults from the forearm, forehead and back, with measurements being repeated in triplicate. Subjective assessment of skin pad quality was collected using an 8-criteria questionnaire, graded using a 5-point Likert scale for fidelity to normal skin. The questionnaire assessment was completed by 30 trainees and practitioners. Overall, felt pads received the poorest outcomes in all criteria; cutometry and durometry results demonstrate poor similarity to skin, and felt received the lowest scores in the questionnaire, although the cheapest. Foam dressings were similar in both cutometric and durometric properties to skin of the face, back and arm. Clinical outcomes of foam dressings were similar to the most expensive commercial skin pad. Bilaminar foam-based dressings provide a low cost, high fidelity non-biological simulation of skin for surgical training, which is non-inferior to more expensive specifically designed products. Many products designed to act as skin substitutes for surgical simulation fail to adequately replicate the anatomical and mechanical properties of skin.

Finger Vein Recognition Based on Anatomical Features of Vein Patterns

Finger vein recognition is a promising biometric authentication technique that depends on the unique features of vein patterns in the finger for recognition. The existing finger vein recognition methods are based on minutiae features or binary features such as LBP, LLBP, PBBM etc. or from the entire vein pattern. However, the minutiae-based features cannot accurately represent the structural or anatomical aspects of the vein pattern. These issues with the minutia feature led to increased false matches. Recognition based on binary features have limitations such as increased false matches, sensitivity to the translation and rotation, security and privacy issues etc. A feature representation based on the anatomy of vein patterns can be an alternative solution to improve the recognition performance. In the IJCB 2020 conference, we showed that every finger vein image contains one or more of a kind of 4 special vein patterns which we refereed as Fork, Eye, Bridge, and Arch (FEBA). In this paper, we further enlarge this set to 6 vein patterns (F <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</sub> F <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> EB <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</sub> B <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> A) by identifying two variations in the Fork and Bridge vein patterns. Based on 6 anatomical features of the possible 6 vein patterns in a vein image, we define a 6 × 6 feature matrix representation for finger vein images. Since this feature representation is based on the anatomical properties of the local vein patterns, it provides template security. Further we show that, the proposed feature representation is invariant to scaling, translation, and rotation changes. The experimental results using two open datasets and an in-house dataset show that the proposed method has a better recognition performance when compared to the existing approaches with an EER around 0.02% and an average recognition accuracy of 98%.

Myocardial bridge over coronary arteries and myocardial coat lining coronary sinus: clinical implications

Myocardial Bridge (MB) on the coronary artery and myocardial coat (MC) on the cardiac veins are usually detected in angiography and cadaveric dissection. Left anterior descending branch (LAD) of the left coronary artery is the most frequent site of MB. Rarely MB is also seen over the right coronary arterial branches. MB has proven association with ischemic heart disease and other critical cardiac consequences like myocardial infarction (MI) (Alegria et al., 2000; Soran et al., 2000). MC, on the other hand has not gained enough attention in previous studies. Large MB can be readily identified in angiograms, but minutes MB can be picked up by newer imaging studies like multidetector computed tomography (MDCT) and optical coherence tomography (OCT) scan (Tiryakioglu and Aliyu, 2020). Cadaveric dissection, however, holds its unique place in direct visualization and studying the macro and micro-anatomical characteristics. To study the prevalence and anatomical attributes of MB and MC in Indian population, ten adult cadaveric hearts (6 male and 4 female) were dissected as part of a routine undergraduate teaching at the Anatomy Department, All India Institute of Medical Sciences, New Delhi, India. MB over the coronary artery and MC over the cardiac vein were identified. Data pertaining to the MB and MC dimensions were measured with a digital vernier calliper. Histology of the MC was carried out to confirm its presence and observe the cytoarchitecture pattern. Relevant gross macroscopic and microscopic images were photographed and photomicrographed. 20% of the dissected cadavers revealed MB involving LAD in first heart while LAD and RCA both in second heart with lengths 5 mm, 18 mm and 2 mm respectively. MC was noted over coronary sinus and proximal few millimeters of great and middle cardiac veins. Histological examination revealed cardiac striated muscle in MC with typical cyto- architecture. The mean myocardial muscle index (MMI) of MBs ranged from 1.6 to 21.6. The present study highlights 20% prevalence of MBs in Indian population involving both right and left coronary artery. 10% of the subjects had histologically confirmed MC over cardiac veins. MC over the coronary sinus and other cardiac veins need more elaborate explorative studies to quantify the anatomic properties and to examine the possible association with cardiovascular disease. Nevertheless, anatomic attributes should be kept in mind to better appreciate MI in evolution and MI at evaluation in a case with MB.

Dendrometric and Wood Anatomical Properties of Pinus sylvestris and Quercus petraea in Managed and Unmanaged Forests

Dendrometric and Wood Anatomical Properties of Pinus sylvestris and Quercus petraea in Managed and Unmanaged Forests

Tendon properties in a mouse model of severe osteogenesis imperfecta

ABSTRACT Purpose/Aim of the study Osteogenesis imperfecta is a heritable bone disorder that is usually caused by mutations in collagen type I encoding genes. The impact of such mutations on tendons, a structure with high collagen type I content, remains largely unexplored. We hypothesized that tendon properties are abnormal in the context of a mutation affecting collagen type I. The main purpose of the study was to assess the anatomical, mechanical, and material tendon properties of Col1a1 Jrt/+ mice, a model of severe dominant OI. Materials and Methods The Flexor Digitorum Longus (FDL) tendon of Col1a1 Jrt/+ mice and wild-type littermates (WT) was assessed with in vitro mechanical testing. Results The results showed that width and thickness of FDL tendons were about 40% larger in WT (p < 0.01) than in Col1a1 Jrt/+ mice, whereas the cross-sectional area was 138% larger (p < 0.001). The stiffness, peak- and yield-force were between 160% and 194% higher in WT vs. Col1a1 Jrt/+ mice. The material properties did not show significant differences between mouse strains with differences <15% between WT and Col1a1 Jrt/+ (p > 0.05). Analysis of the Achilles tendon collagen showed no difference between mice strains for the content but collagen solubility in acetic acid was 66% higher in WT than in Col1a1 Jrt/+ (p < 0.001). Conclusions This study shows that the FDL tendon of Col1a1 Jrt/+ mice has reduced mechanical properties but apparently normal material properties. It remains unclear whether the tendon phenotype of Col1a1 Jrt/+ mice is secondary to muscle weakness or a direct effect of the Col1a1 mutation or a combination of both.

Türkiye’den Noccaea Moench (Brassicaceae) Cinsi Anatomisi Üzerine Katkılar

The anatomical properties of Noccaea camlikensis and N. cariensis were determined in this study. The roots have a secondary root type. The stem cross-sections have a single-layered epidermis, parenchymatous cortex, one layered distinct endodermis, vascular bundles with sclerenchymatic caps, and parenchymatic pith cells. Equifacial and bifacial mesophyll types are observed in the leaves, with multiple-layered palisade tissue, and the spongy parenchyma is well-developed. Vascular bundles are small in the leaves except in the leaf midrib. Anisocytic stomata type are observed in the surface sections. The assessment of anatomical characteristics of the studied Noccaea species, such as the number of cortex in the stem and the shape of midvein of leaf, are of taxonomical value.

Follistatin regulates the specification of the apical cochlea responsible for low-frequency hearing in mammals

The cochlea's ability to discriminate sound frequencies is facilitated by a special topography along its longitudinal axis known as tonotopy. Auditory hair cells located at the base of the cochlea respond to high-frequency sounds, whereas hair cells at the apex respond to lower frequencies. Gradual changes in morphological and physiological features along the length of the cochlea determine each region's frequency selectivity, but it remains unclear how tonotopy is established during cochlear development. Recently, sonic hedgehog (SHH) was proposed to initiate the establishment of tonotopy by conferring regional identity to the primordial cochlea. Here, using mouse genetics, weprovide invivo evidence that regional identity in the embryonic cochlea acts as a framework upon which tonotopy-specific properties essential for frequency selectivity in the mature cochlea develop. We found that follistatin (FST) is required for the maintenance of apical cochlear identity, but dispensable for its initial induction. In a fate-mapping analysis, we found that FST promotes expansion of apical cochlear cells, contributing to the formation of the apical cochlear domain. SHH, in contrast, is required both for the induction and maintenance of apical identity. In the absence of FST or SHH, mice produce a short cochlea lacking its apical domain. This results in the loss of apex-specific anatomical and molecular properties and low-frequency-specific hearing loss.

Adult-born neurons inhibit developmentally-born neurons during spatial learning

Ongoing neurogenesis in the dentate gyrus (DG) subregion of the hippocampus results in a heterogenous population of neurons. Immature adult-born neurons (ABNs) have physiological and anatomical properties that may give them a unique role in learning. For example, compared to older granule neurons, they have greater somatic excitability, which could facilitate their recruitment into memory traces. However, recruitment is also likely to depend on interactions with other DG neurons through processes such as lateral inhibition. Immature ABNs target inhibitory interneurons and, compared to older neurons, they receive less GABAergic inhibition. Thus, they may induce lateral inhibition of mature DG neurons while being less susceptible to inhibition themselves. To test this we used a chemogenetic approach to silence immature ABNs as rats learned a spatial water maze task, and measured activity (Fos expression) in ABNs and developmentally-born neurons (DBNs). A retrovirus expressing the inhibitory DREADD receptor, hM4Di, was injected into the dorsal DG of male rats at 6w to infect neurons born in adulthood. Animals were also injected with BrdU to label DBNs or ABNs. DBNs were significantly more active than immature 4-week-old ABNs. Silencing 4-week-old ABNs did not alter learning but it increased activity in DBNs. However, silencing ABNs did not affect activation in other ABNs within the DG. Silencing ABNs also did not alter Fos expression in parvalbumin- and somatostatin-expressing interneurons. Collectively, these results suggest that ABNs may directly inhibit DBN activity during hippocampal-dependent learning, which may be relevant for maintaining sparse hippocampal representations of experienced events.

Intra-Articular Mesenchymal Stem Cell Injection for Knee Osteoarthritis: Mechanisms and Clinical Evidence

Knee osteoarthritis presents higher incidences than other joints, with increased prevalence during aging. It is a progressive process and may eventually lead to disability. Mesenchymal stem cells (MSCs) are expected to repair damaged issues due to trilineage potential, trophic effects, and immunomodulatory properties of MSCs. Intra-articular MSC injection was reported to treat knee osteoarthritis in many studies. This review focuses on several issues of intra-articular MSC injection for knee osteoarthritis, including doses of MSCs applied for injection and the possibility of cartilage regeneration following MSC injection. Intra-articular MSC injection induced hyaline-like cartilage regeneration, which could be seen by arthroscopy in several studies. Additionally, anatomical, biomechanical, and biochemical changes during aging and other causes participate in the development of knee osteoarthritis. Conversely, appropriate intervention based on these anatomical, biomechanical, biochemical, and functional properties and their interactions may postpone the progress of knee OA and facilitate cartilage repair induced by MSC injection. Hence, post-injection rehabilitation programs and related mechanisms are discussed.