Publications by authors named "Alexus Roberts"

3 Publications

  • Page 1 of 1

Emerging Role of PD-1 in the Central Nervous System and Brain Diseases.

Neurosci Bull 2021 Apr 20. Epub 2021 Apr 20.

Department of Anesthesiology, Duke University Medical Center, Durham, 27710, USA.

Programmed cell death protein 1 (PD-1) is an immune checkpoint modulator and a major target of immunotherapy as anti-PD-1 monoclonal antibodies have demonstrated remarkable efficacy in cancer treatment. Accumulating evidence suggests an important role of PD-1 in the central nervous system (CNS). PD-1 has been implicated in CNS disorders such as brain tumors, Alzheimer's disease, ischemic stroke, spinal cord injury, multiple sclerosis, cognitive function, and pain. PD-1 signaling suppresses the CNS immune response via resident microglia and infiltrating peripheral immune cells. Notably, PD-1 is also widely expressed in neurons and suppresses neuronal activity via downstream Src homology 2 domain-containing protein tyrosine phosphatase 1 and modulation of ion channel function. An improved understanding of PD-1 signaling in the cross-talk between glial cells, neurons, and peripheral immune cells in the CNS will shed light on immunomodulation, neuromodulation, and novel strategies for treating brain diseases.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1007/s12264-021-00683-yDOI Listing
April 2021

Anatomical basis of diverse jaw protrusion directionality in ponyfishes (Family Leiognathidae).

J Morphol 2021 Mar 13;282(3):427-437. Epub 2021 Jan 13.

Department of Evolution and Ecology, University of California Davis, Davis, California, USA.

Protrusion of the oral jaws is a key morphological innovation that enhances feeding performance in fishes. The mechanisms of protrusion and the basis of variation in its magnitude are well studied, but little attention has been paid to the functional morphology of protrusion directionality, despite wide variation among teleost species from slightly dorsal to strongly ventral. Ponyfishes (Leiognathidae) comprise a group of 52 species that exhibit striking diversity in the directionality of jaw protrusion, providing a promising system for exploring its underlying basis in a single clade. We examined the anatomical basis of protrusion directionality by measuring eight traits associated with the size and positioning of oral jaw bones. Measurements were made on cleared and stained specimens of 20 ponyfish species, representing every major lineage within the family. Species fell into three nonoverlapping clusters with respect to directionality including dorsal, rostral, and ventral protruders. A key correlate of protrusion direction is the anterior-posterior position of the articular-quadrate jaw joint. As the joint position moves from a posterior to a more anterior location, the orientation of the relaxed mandible rotates from an almost horizontal resting position to an upright vertical posture. Abduction of the mandible from the horizontal position results in ventrally directed protrusion, while the more upright mandible rotates to a position that maintains dorsal orientation. The resting orientation of the premaxilla and maxilla, thus, vary consistently with protrusion direction. Mouth size, represented by length of the mandible and maxilla, is a second major axis of variation in ponyfishes that is independent of variation in protrusion directionality.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1002/jmor.21314DOI Listing
March 2021

Evolution of skeletal and muscular morphology within the functionally integrated lower jaw adduction system of sculpins and relatives (Cottoidei).

Zoology (Jena) 2018 08 30;129:59-65. Epub 2018 Jun 30.

Friday Harbor Laboratories, University of Washington, Friday Harbor, WA 98250, USA; Department of Biology, Knox College, Galesburg, IL 61401, USA.

Vertebrate lever mechanics are defined by the morphology of skeletal elements and the properties of their muscular actuators; these metrics characterize functional diversity. The components of lever systems work in coordination ("functional integration") and may show strong covariation across evolutionary history ("evolutionary integration"), both of which have been hypothesized to constrain phenotypic diversity. We quantified evolutionary integration in a functionally integrated system - the lower jaw of sculpins and relatives (Actinopterygii: Cottoidei). Sculpins primarily rely on suction feeding for prey capture, but there is considerable variation in evasiveness of their prey, resulting in variation in anatomy of the lower jaw-closing mechanism. We used functionally-relevant linear measurements to characterize skeletal and muscular components of this system among 25 cottoid species and two outgroup Hexagrammoidei (greenling) species. We quantified evolutionary covariation and correlation of jaw-closing mechanical advantage (i.e., skeletal leverage) and muscle architecture (i.e., gearing) by correlating phylogenetically independent contrasts and fitting phylogenetically corrected generalized least squares models. We found no evidence of evolutionary covariation in muscle architecture and skeletal leverage. While we found a positive evolutionary correlation between out-lever length and adductor muscle fiber length, there was no significant evolutionary correlation between in-lever length and adductor muscle fiber length. We also found a positive evolutionary correlation between in- and out-lever lengths. These results suggest that skeletal morphology and muscle morphology contribute independently to biomechanical diversity among closely related species, indicating the importance of considering both skeletal and muscular variation in studies of ecomorphological diversification.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.zool.2018.06.006DOI Listing
August 2018