The tenuissimus is a long, thin hindlimb skeletal muscle which in hamsters contains about 200 extrafusal muscle fibers. Embedded in this richly innervated muscle is a continuous array of 16-20 closely packed muscle spindles suggesting that it may play a role in hindlimb proprioception. This high spindle density also makes the muscle ideal for the isolation and harvesting of these sensory receptors. In this correlative light and electron microscopic study, freshly frozen specimens were first prepared for serial microscopic analysis. Camera lucida reconstruction of spindle distribution showed a close proximity to the main artery and nerve in the central core of the muscle. Oxidative enzyme and myosin ATPase staining profiles were examined in both the intrafusal and extrafusal fiber populations. Type I and type II extrafusal fibers were present in even numbers and were distributed evenly throughout muscle cross-sections. Enzyme staining varied along the lengths of the three intrafusal fiber types. The fine structure of spindles was examined using transmission (TEM), conventional scanning (SEM), and high resolution scanning electron microscopy (HRSEM). For conventional SEM, isolated spindles were first fixed in 2.5% buffered glutaraldehyde, followed by 1% osmication, and mechanical disruption of the outer capsule under the dissecting microscope. Preparation for HRSEM included aldehyde/osmium fixation and freeze-cleavage of entire tenuissimus muscles in liquid N₂. Selective extraction of the cytosol with 0.1% OsO4 permitted the visualization of numerous intracellular structures. In these specimens, the capsular sleeve showed a multilayered pattern of vesicle-laden cells with variant surface topography in certain locations. Punctate sensory nerve endings adhered intimately to the surfaces of underlying intrafusal fibers in the equatorial and juxtaequatorial regions. By TEM and HRSEM these endings appeared crescent-shaped and were enveloped by external laminae. Each profile contained a plethora of mitochondria and cytoskeletal organelles. The methodology used in this study provides, for the first time, a three-dimensional view of the exquisite cytological architecture of this neuromuscular receptor. / Medicine, Faculty of / Graduate

Thesis (M.S.)--University of Wisconsin--Madison, 1983. / Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 113-114).

Thesis (M.S.)--University of Wisconsin--Madison, 1984. / Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 81-83).

In the field of spinal-cord neurophysiology, the nature of and the rules which govern the strength of functional connections between muscle afferents and motoneurons supplying the same muscle are important to delineate. This study addressed a facet of this issue by testing the possibility that the strength of the spindle Ia-motoneuronal connections is stronger (as demonstrated by the differing amplitudes of the mean maximum composite Ia EPSPs) if both neurons supply the same sub-volume of the muscle, providing the various sub-volumes of the muscle are capable of independent action. Intracellular recordings were made of the Ia EPSP responses of semimembranosus (SM) and lateral gastrocnemius (LG) motoneurons in anesthetized low-spinal cats to electrical stimulation (Group I range) of nerve branches supplying different parts of the homonymous muscle, as well as different heteronymous muscles. For study of SM motoneurons, stimulated nerve branches included those supplying the anterior (SMa) and posterior (SMp) heads of the SM muscle and three providing heteronymous input from the anterior (BFa) and posterior (BFp) parts of biceps femoris and the distal part of the semitendinosus (STd) muscle. Ia EPSPs were partitioned such that stimulation of the SMa nerve branch produced significantly larger EPSPs in SMa motoneurons than in SMp cells; likewise, stimulation of the SMp nerve branch produced larger EPSPs in SMp motoneurons than in SMa cells. Study of the differences in the strength of heteronymous Ia input (i.e., from BFa, BFp and STd) between the SMa and SMp cell groups correlates with the different actions reported previously for the two heads of the SM muscle. For study of LG motoneurons, the stimulated nerve branches were those supplying the four neuromuscular compartments of the LG muscle (LG1, LG2, LG3 and LGm) and the nerve to a heteronymous muscle, soleus (SOL). In all five instances, partitioned Ia effects were evident. An association is suggested between the present results and previous electromyographic studies. The previous studies have shown that the muscle heads (SM) or neuromuscular compartments (LG) under consideration in this study are capable of somewhat separate actions. The present study also included assessment of the relative extent to which the partitioned Ia effects could be attributed, in part, to one or two developmental factors, topographic specificity and species specificity. The analysis suggested that both factors were potentially implicated, with species specificity somewhat predominant over topographic specificity.

Microtubules are a major constituent of the cytoskeleton in all eukaryotic cells. They are essential for cell morphogenesis and motility. Specifically in the dividing cells, microtubules form the spindle which segregates chromosomes. Microtubule plus ends constantly switch between phases of growth and shrinkage which is necessary for microtubule reorganization and thus their function. Importantly, microtubule dynamics are highly regulated by microtubule-associated proteins (MAPs). EB1 and Mini spindles (Msps) are unique amongst MAPs because they bind and track growing microtubule plus ends autonomously. Although essential for cell division and thus highly expressed in dividing cells, EB1 and Msps are also abundant in differentiated cells. However, to identify post-mitotic roles of proteins essential for cell division, particularly in context of a multicellular organism, is a challenge requiring new tools which I aimed to develop in my project. Since EB1 acts by recruiting MAPs to the microtubule plus ends, I generated short peptides which bind to Drosophila EB1 to block interactions with these MAPs. I showed that an EB1-MAP interaction was disturbed in Drosophila S2 cultured cells and expressing these peptides in developing Drosophila reduced fly viability. Further screening and analysis of peptides interacting with fly EB1 and its human homologues uncovered sequence determinants promoting strong binding and specificity. To uncover Msps function, I generated a msps temperature sensitive mutant and found that Msps is essential for neuromuscular function in developing Drosophila. This study showed that the regulation of microtubule dynamics has crucial functions at the whole organism level. These new tools allow the roles of microtubule regulation to be dissected in developing organisms.

Thesis (M.S.)--University of Michigan, 1985.

Thesis (M.S.)--Brigham Young University. Dept. of Exercise Sciences, 2005. / Includes bibliographical references.

Hypertension affects 1 billion individuals worldwide and is the major contributing factor to cardiovascular disease. However, the WHO considers current antihypertensive drug therapies inadequate, highlighting a need for a novel approach to hypertension management. Baroreceptors are a promising drug target, and express an unusual glutamate receptor coupled to phospholipase D (PLD-GluR). The PLD-GluR has not been isolated and characterised, which is an important step towards its use as a drug target. A good source of the PLD-GluR is muscle spindle primary afferent nerve terminals, the largest mechanoreceptor in the body. This study thus focuses upon the identification and progress towards isolation of the PLD-GluR from muscle spindle primary afferent nerve terminals. A novel dissection method for high yield extraction of muscle spindles from a high density source, the rat deep masseter muscle, was developed for Western blotting and mass spectrometry screens of all GluRs. Western blots showed spindle homogenate contained a low molecular weight mGluR5 isoform and GluK2. Immunofluorescence showed mGluR5 was expressed on putative nociceptors, not mechanosensory nerve terminals. However, spindle mechanosensory nerve terminals labelled brightly for GluK2, as did baroreceptor nerve terminals. Furthermore, GluK2 appears to be the only GluR subunit on these mechanoreceptors, although mass spectrometry and affinity chromatography could not successfully isolate this receptor. Finally, piezo2 has recently been suggested as the major mechanotransducer protein. However, no evidence was found for piezo2 expression in adult spindle mechanosensory nerve terminals in adult rats or mice. As previous studies have largely focussed on adolescent mice, this could represent a developmental difference. Conversely, a number of candidate mechanosensory proteins, such as TRPs, were identified by a targeted mass spectrometry approach. This provides good candidates for future research. Collectively, this study indicates both spindle and baroreceptor mechanosensory nerve terminals express GluK2, suggesting it is at least a component of the PLD-GluR, and therefore potentially represents a novel drug target for treating hypertension.

Prior research shows that a contextual reminder can return a previously consolidated memory to an unstable state similar to initial encoding. New knowledge presented before the trace is reconsolidated can emerge as updating of the first experience with knowledge from the second. Sleep has been implicated in the long-term strengthening and storage of newly acquired episodic memories; thus, the delay-dependent emergence of intrusions may be facilitated by a delay containing sleep. The experiments described here explore this possibility by tracking sleep while participants undergo an episodic reconsolidation paradigm, which involves learning two sets of information and a recall task, all separated by 48 hours. Prior work using this paradigm shows that reminding participants of the first learning experience prior to learning the second renders them more likely to intrude information from the second set in their recall of the first. In the present study, Experiment 1 compares amount of sleep across days in order to tease apart the differential effects on consolidation of the original Set 1 memory and its reconsolidation when it is updated with Set 2. In Experiment 2, the first analysis (Analysis A) identifies events in the sleep EEG, such as spindles, that are associated with certain elements of memory consolidation, and expands on the parameters in which they occur in memory reconsolidation in Analysis B. The overall aim of this project is to use sleep as a means to inform the nature of memory reconsolidation, which paints memory as ever changeable.

BACKGROUND: Sleep deprivation is one of the first symptoms to manifest in schizophrenia patients. An important proponent for both sleep and cognition, sleep spindles have been investigated to understand the connection between sleep and schizophrenia. This thesis aims to conduct a meta-analysis on this topic to conglomerate previous research and come to a definitive conclusion on how sleep and schizophrenia interact. Multiple studies have reported associations between sleep, schizophrenia, and the thalamus. Novel methods have allowed researchers to segment the thalamus into 25 different nuclei. Therefore, this thesis will also attempt to validate these findings and use new segmentation software to investigate which specific nuclei affect schizophrenia. This thesis also extends this thalamic investigation to explore white matter tracts related to the thalamus. Using both arms of this study, we aim to further understand the complex relationship between brain structure, sleep, and schizophrenia. METHODS: The meta-analysis portion of this thesis pooled fifteen studies for a total of 321 patients and 323 healthy controls. The patient population was made up of first-episode psychosis (FEP), family high-risk (FHR), and schizophrenia (SZ) populations. R Studio was utilized to run a meta-analysis on sleep spindle density (SSD) values pulled from each study. This dataset was also used for meta-regressions and funnel plots. The imaging aspect of this thesis pulled subjects from two separate Boston studies for a total of 54 early course patients (EC) and 27 healthy controls (HC). A brain editing software, FreeSurfer, was used to quality control and segment the thalamus. This segmentation provided volumes for each nuclei. A free-water imaging pipeline was used to process diffusion weighted images so that free-water (FW) and corrected fractional anisotropy (FAt) could be collected. These values were run through Tract-Based Spatial Statistics (TBSS) to standardize scans and identify white matter regions of interest. RESULTS: This thesis reports an effect size of -1.24 between HC and the collective subject groups with a confidence interval of -1.63 to -.84. Via meta-regression, we report that illness duration, publication year, and spindle frequency gap (SFG) all are associated with sleep spindles. The thalamic volumetric analysis showed that four nuclei differed between EC and HC and two nuclei differed between EC and FH. The imaging aspect of this thesis discovered no significant FAt findings comparing volume to population, though heat maps revealed a trend where FHR and EC had lower FAt than HC. For FW analysis, we found a similar trend where FHR and EC had higher FW than HC. CONCLUSION: Using both analyses, this thesis connected sleep spindles, schizophrenia, and brain structure. We illuminated consistent reports of schizophrenia populations having lower sleep spindle density compared to healthy controls. This thesis reports a difference in thalamic nuclei volumes between both HC and FHR versus EC as well as FAt and FW differences between both FHR and EC and HC. / 2021-06-07T00:00:00Z