Test of the half-center model for locomotor activity in adult lamprey spinal cord [abstract]

Abstract only availableRhythmic motor behaviors, such as locomotion, chewing, scratching, copulation, and communication, are critical for survival. In all animals, rhythmic motor activity is produced by central patterns generators (CPGs) which consist of neuronal modules that are coupled by a coordinating system. For example, in a cat separate spinal modules control the movements of each limb, and the coordinating system can couple the modules in different ways to produce different gaits (walk, trot, gallop). Each module can be divided into oscillators that usually are connected by reciprocal inhibition (i.e. "half-center" model) to produce alternating motor patterns (e.g. flexion « extension). These oscillators generally are assumed to be autonomous and able to function without the reciprocal connections. In the lamprey, locomotion (swimming) is produced by pairs of oscillators that are distributed along the spinal cord and connected by left-right reciprocal inhibition (Hagevik and McClellan, 1994). In adult lamprey, we tested the half-center model by investigating whether the phasing of left-right burst activity could be correctly maintained in the absence of left-right reciprocal coupling. Adult lamprey received a longitudinal midline lesion in the rostral spinal cord (10% à 35% body length). After the midline lesion, the animals were able to swim, and the appropriate phasing of left and right muscle burst activity was present in both caudal and rostral parts of the body. After a spinal transection was made at 35% body length to isolated the rostral left and right halves of the spinal cord from intact cord, locomotor-like burst activity was no longer present in the rostral spinal cord. We obtained similar results in larval lamprey (Jackson et al., 2005). Thus, in lamprey, the data do not support the "half-center" model because left and right spinal cord oscillators are not autonomous but appear to require left-right reciprocal coupling to function properly

Recovery of locomotor function following spinal cord hemi-transections in larval lamprey [abstract]

Abstract only availableIn vertebrates, reticulospinal (RS) neurons in the brain activate spinal motor networks to initiate locomotor behavior. Following spinal cord injury (SCI), RS neurons no longer communicate with the spinal cord, and animals are paralyzed below the lesion. In higher vertebrates, such as birds and mammals, the axons of RS neurons do not regenerate, and paralysis usually is permanent. In contrast, spinal cord transected lower vertebrates such as the lamprey display robust axonal regeneration and recovery of function within a few weeks. In our previous studies we showed that following spinal cord hemi-transections (HTs) in larval lamprey, injured RS neurons undergo a number of substantial changes in electrical properties and expression of ion channels which recover within several weeks. The purpose of the present study is to determine the rate of behavioral recovery following HTs and ultimately to correlate axonal regeneration of injured RS neurons with recovery of normal properties of these neurons. In the present study, animals received HTs on the right side of the rostral spinal cord and recovered for 1d - 6 wks. At early recovery times (1 day), animals swam with a spiraling movement and turned toward the intact side of the spinal cord, but the pattern of muscle activity was relatively normal. Swimming movements began to recover within the first week, and by the fourth week animals swam normally with little or no spiraling. In the future, anatomical experiments will be conducted to determine if recovery of swimming following HTs is due to regeneration of injured axons through the HT or to functional compensation of intact pathways on the opposite side of the spinal cord. This information will be important in determining what factors alter the properties of RS neurons following SCI and if these altered properties are important for successful axonal regeneration

Energy Costs and Trade-Offs of the Adaptive Immune System in Old-Field Mice (Peromyscus polionotus)

A high energetic cost of adaptive immune defenses is assumed in theoretical discussions of immune responses in animals. Little quantitative data are available to test the assumption, however, especially for mammalian species. We tested the null hypotheses that 1) there is no difference between energy expenditure of challenged and static cell-mediated and humoral immune systems and 2) there is no change in the magnitude of a humoral immune response when a cell-mediated immune response is introduced. To test these hypotheses, we used a two-by-two experimental design with humoral (sheep red blood cells) and cell-mediated (2,4- dinitrofluorobenzene) challenges as the independent variables. Using adult male old-field mice (Peromyscus polionotus), we measured hemagglutination, inflammation, metabolic rates, and organ masses to assess the energetic cost and potential energy trade-offs associated with cellmediated and humoral immunity, and interactions between them. We rejected our first hypothesis. The cell-mediated, but not the humoral immune response, was associated with a 13.7% increase in resting metabolic rate, while neither response was associated with a significant change in daily metabolic rate. Also, the cell-mediated response was associated with a significant decrease in testes mass and colon length. Reduced organ sizes may indicate that part of the cost of mounting a cell-mediated response was met through reduced energy allocation to the digestive and reproductive systems. The cell-mediated response had no measurable effect on the humoral response. Our results supported the assumption of a significant energetic cost of cell-mediated, but not humoral immune defense

Session 2E Forest Change Analysis of the Loita and Mau Forests, Kenya

The Mara Elephant Project is a collaborative organization tracking elephant populations in the Mau and Loita Forests in Kenya. Using Hansen Global Forest Change data, we assessed the forest cover and forest health in these two regions by monitoring forest loss and gain over the last 20 years. Story Maps and geospatial analyses show the overlap of elephant activity, logging, charcoal industries, and forest cover changes. We summarize changes in forest cover from 2000to 2019 and explore differences in health and deforestation trends between the Loita and Mau forests

Elevating MAST-Data Publications with Digital Object Identifiers (DOIs)

The use of digital object identifiers (DOIs) to identify data sets used in original research allows peer reviewers and journal editors to more easily validate research methods and verify results. Fellow astronomers can duplicate results or expand on initial findings when the precise data used in a research project are identified. Precise identification of data may allow archives and observatories to better understand how the community is accessing and combining its data to reach new scientific conclusions. Earlier studies have suggested that papers with linked data are more highly cited in the literature, providing motivation for authors to adopt more stringent and thorough data citation practices

Elevating MAST-Data Publications with Digital Object Identifiers (DOIs)

The use of digital object identifiers (DOIs) to identify data sets used in original research allows peer reviewers and journal editors to more easily validate research methods and verify results. Fellow astronomers can duplicate results or expand on initial findings when the precise data used in a research project are identified. Precise identification of data may allow archives and observatories to better understand how the community is accessing and combining its data to reach new scientific conclusions. Earlier studies have suggested that papers with linked data are more highly cited in the literature, providing motivation for authors to adopt more stringent and thorough data citation practices

Elimination of Left-Right Reciprocal Coupling in the Adult Lamprey Spinal Cord Abolishes the Generation of Locomotor Activity

The contribution of left-right reciprocal coupling between spinal locomotor networks to the generation of locomotor activity was tested in adult lampreys. Muscle recordings were made from normal animals as well as from experimental animals with rostral midline (ML) spinal lesions (~13%→35% body length, BL), before and after spinal transections (T) at 35% BL. Importantly, in the present study actual locomotor movements and muscle burst activity, as well as other motor activity, were initiated in whole animals by descending brain-spinal pathways in response to sensory stimulation of the anterior head. For experimental animals with ML spinal lesions, sensory stimulation could elicit well-coordinated locomotor muscle burst activity, but with some significant differences in the parameters of locomotor activity compared to those for normal animals. Computer models representing normal animals or experimental animals with ML spinal lesions could mimic many of the differences in locomotor activity. For experimental animals with ML and T spinal lesions, right and left rostral hemi-spinal cords, disconnected from intact caudal cord, usually produced tonic or unpatterned muscle activity. Hemi-spinal cords sometimes generated spontaneous or sensory-evoked relatively high frequency “burstlet” activity that probably is analogous to the previously described in vitro “fast rhythm”, which is thought to represent lamprey locomotor activity. However, “burstlet” activity in the present study had parameters and features that were very different than those for lamprey locomotor activity: average frequencies were ~25 Hz, but individual frequencies could be >50 Hz; burst proportions (BPs) often varied with cycled time; “burstlet” activity usually was not accompanied by a rostrocaudal phase lag; and following ML spinal lesions alone, “burstlet” activity could occur in the presence or absence of swimming burst activity, suggesting the two were generated by different mechanisms. In summary, for adult lampreys, left and right hemi-spinal cords did not generate rhythmic locomotor activity in response to descending inputs from the brain, suggesting that left-right reciprocal coupling of spinal locomotor networks contributes to both phase control and rhythmogenesis. In addition, the present study indicates that extreme caution should be exercised when testing the operation of spinal locomotor networks using artificial activation of isolated or reduced nervous system preparations