bluuebunny/crossref_metadata_2025 huggingface dataset:
PVN neuropeptide neurons may modulate nTS activation and cardiorespiratory responses to peripheral chemoreflex stimulation
Authors: Ruyle Brian C , Heesch Cheryl M , Hasser Eileen M
Published: November 2023

The paraventricular nucleus of the hypothalamus (PVN) is required for full expression of cardiorespiratory responses evoked by peripheral chemoreflex stimulation, but the efferent pathways have not been fully elucidated. We previously reported that hypoxia activates (Fos‐immunoreactivity; IR) PVN neurons that project to the nucleus tractus solitarii (nTS). The majority of hypoxia‐activated nTS‐projecting neurons are CRH‐IR. These findings suggest that the PVN may influence chemoreflex‐evoked cardiorespiratory function via CRH actions in the nTS. CRFR2 is the predominant CRH receptor in the nTS. Previous studies indicate that selective activation of nTS CRFR2s produces cardiovascular responses consistent with excitation. CRFR2 co‐localizes extensively with oxytocin‐IR fibers, likely from the PVN, and nTS oxytocin enhances baroreflex function. We hypothesized that interactions between PVN neuropeptide neurons, including CRH binding to CRFR2s located on oxytocin fibers, modulates nTS neuronal activation and thus may augment cardiorespiratory responses to peripheral chemoreflex stimulation. An AAV viral vector expressing mCherry under the CAMKII promoter was injected into the PVN, and mCherry‐expressing fibers were evaluated in the nTS. Immunohistochemical evaluation revealed that mCherry‐expressing fibers formed close appositions with nTS neurons (indicated by HUC/D‐IR), including neurons activated by acute hypoxia (2 hr 10% O2). These findings suggest that PVN inputs to the nTS may modulate the activation of nTS neurons that respond to hypoxia. A separate group of animals received bilateral injections of the retrograde tracer CTB into either the PVN or the RVLM. Immunohistochemistry examined the extent to which CRFR2 fibers contact CTB‐labeled neurons in the nTS. CRFR2 fibers made close appositions with specific populations of nTS neurons activated by acute hypoxia, including catecholaminergic (tyrosine hydroxylase, TH‐IR), RVLM‐projecting and PVN‐projecting cells. Together, these data suggest that PVN neuropeptide projections to the nTS may modulate the activation of subpopulations of nTS neurons in response to hypoxia. We suggest that PVN neuropeptide neurons projecting to the nTS may shape the cardiorespiratory responses evoked by peripheral chemoreflex stimulation. Future in vivo experiments will determine the physiological relevance of PVN neuropeptide projections to the nTS, including the extent to which nTS CRH and/or oxytocin influence basal and chemoreflex‐evoked cardiorespiratory output.

Support or Funding Information

NIH RO1 HL98602
Blockade of Brain Sodium Channels or Electroneutral Transporters Attenuates the Hypertensive Response to Central NaCl Stimulation
Authors: King Jesse L , Kinsman Brian J , Stocker Sean D
Published: November 2023

Accumulating evidence suggests excess dietary salt intake elevates plasma or cerebrospinal fluid NaCl concentrations to increase sympathetic nerve activity (SNA) and arterial blood pressure (ABP) in salt‐sensitive hypertension. Both acute and chronic infusion of hypertonic NaCl into the lateral cerebral ventricle produces a sympathetically mediated increase in ABP that depends on the integrity of forebrain hypothalamic structures that contain NaCl‐sensing neurons. However, the mechanism by which these neurons detect changes in NaCl concentrations to alter ABP is not known; however, there are two possibilities. First, prior studies have suggested that the epithelial sodium channel (ENaC) mediates central pressor actions of hypertonic NaCl. Second, electroneutral transporters are expressed in hypothalamic regions involved in body fluid homeostasis including vasopressin neuroendocrine neurons. Thus, the purpose of this study was to test the hypothesis that the ENaC or electroneutral transporters mediate the hypertensive effect of central NaCl. This hypothesis was tested by pharmacological blockade of ENaC or electroneutral transporters via pretreatment with central infusion of benzamil or furosemide, respectively. At least 3 days before experiments, Male Sprague‐Dawley rats (300–450g) were anesthetized with isoflurane and instrumented with a femoral arterial catheter and intracerebroventicular (ICV) brain cannula to measure ABP and infuse drugs, respectively. On the day of the experiment, rats were pretreated with aCSF (2μL per 1 min), benzamil (5nmol) or furosemide (10 nmol) through an ICV infusion at 10 min before a second ICV infusion of 0.5M NaCl (5μL per 10 min). ICV infusion of 0.5M NaCl in aCSF‐treated rats produced a significant increase in mean ABP (Δ9±1 mmHg, n=10; P<0.01) but not heart rate (Δ−6±10 bpm, n=10). Pretreatment with the ENaC antagonist benzamil attenuated the pressor response (Δ3±1 mmHg, n=7; P<0.01) and decreased heart rate (Δ−17±5 bpm, n=7; P<0.05). Interestingly, pretreatment of the electroneutral transporter antagonist furosemide completely attenuated the pressor (Δ−1±1 mmHg, n=6, P<0.01) and tachycardic (Δ−11±7 bpm, n=6; P<0.05) response to ICV infusion of 0.5M NaCl. ICV infusion of furosemide alone did not alter baseline ABP (Δ1±1 mmHg, n=3; P<0.05) or heart rate (Δ12±7 bpm, n=3; P<0.05). These findings suggest that ENaC and electroneutral transporters play a critical role in sympathetic activation and pressor effect during central NaCl stimulation.

Support or Funding Information

AHA Established Investigator Award (SDS), NIH R01 HL113270, AHA Predoctoral Fellowship (BJK), and NIH F30 HL131269 (BJK)
The Effects of Imidacloprid on Danio rerio (Zebrafish) Ocular and Osteological Development
Authors: Babcock Hailey , Cochran Kelly , Daggett Melissa A. F.
Published: November 2023

Imidacloprid is a common insecticide that acts as a neurotoxin. The application of this pesticide may have long‐term effects on ecosystems, especially aquatic biomes. Imidacloprid has a lower toxicity to mammals, but neurotoxic effects have been recorded in zebrafish (Danio rerio). The purpose of this study was to determine the potential neurological and osteological effects of imidacloprid on zebrafish ocular and osteological development. Ocular diameters and ceratohyal cartilage lengths were expected to decrease with increasing imidacloprid concentration. Zebrafish embryos were treated with a low‐dose (LD) or high‐dose (HD) of imidacloprid starting at 24 hours post‐fertilization. After seven days, a relationship was seen between imidacloprid concentration and 1) ocular diameter and 2) ceratohyal cartilage lengths. Imidacloprid exposure delayed both ocular and osteological development during embryonic development in zebrafish.

Support or Funding Information

Missouri Western State University
Alterations of a Nigro‐Vagal Pathway in a Rodent Model of Parkinson's Disease
Authors: Hampton Jessica , Anselmi Laura , Travagli R. Alberto
Published: November 2023

Idiopathic Parkinson's disease (PD) is a neurodegenerative disorder characterized by progressive motor impairment resulting from the loss of dopaminergic neurons in the substantia nigra pars compacta (SNpc). Prodromal to the classic motor symptoms, a majority of PD patients experience gastrointestinal (GI) dysfunction such as reduced gastric motility, dysphagia, and severe constipation. Upper GI tract functions are modulated by vago‐vagal reflexes originating in the dorsal vagal complex (DVC) of the brainstem. We have recently described a novel nigro‐vagal connection that, when activated in response to NMDA microinjections in the SNpc, increases gastric tone and motility via vagal brainstem pathways.

The aim of the present study was to elucidate the functions of the nigro‐vagal connection in a rodent model of Parkinson's disease.

Male Sprague Dawley rats received 3 once‐weekly intraperitoneal injections of 10mg/kg paraquat (10P, n=4) or saline (control, n=3). Motor function was assessed following the second and third injections, as well as 2 weeks after the end of treatment.

Two‐four weeks after the end of treatment, rats were anesthetized and gastric motility and tone were recorded via strain gauges surgically affixed to the anterior corpus and antrum of the stomach. Modulation of gastric activity via the nigro‐vagal pathway and by direct vagal pathways was assessed upon microinjection of NMDA (5.25 nmoles/210nl) in the SNpc and thyrotropin‐releasing‐hormone (TRH; 1‐3‐10pmol/60nl) in the DVC, respectively. Rats were then perfused‐fixed and the stomachs were collected for analysis of the neurochemical phenotype of SNpc, DVC and myenteric plexus neurons.

Rats treated with paraquat showed a significant motor impairment compared to controls (stepping test, p<0.05). Moreover immunohistochemistry results showed presence of misfolded α‐synuclein (a hallmark for PD) in DVC and SNpc, confirming the validity of the PD model used in the present study. The gastric motility response to NMDA microinjection in the SNpc was decreased (p<0.05), while gastric responses to microinjections of TRH in the DVC were not significantly reduced. NOS immunoreactivity in myenteric plexus neurons was similar across all groups, suggesting that changes in gastric responses were likely due to alterations in the nigro‐vagal pathway, rather than alterations in neurochemical phenotype of the gastric myenteric neurons.

These data indicate that the nigro‐vagal pathway is compromised in an established rodent model of Parkinson's disease, offering further insight into the etiology and neuropathophysiology of Parkinson's disease.

Support or Funding Information

NIH DK 55530
Brain Region Specific Association of Microtubule‐Associated Protein 2 with Inflammatory and Growth Factor Gene Expression
Authors: Maxi John , Oberhelman Sarah , Mercante Donald E , Bagby Gregory J , Nelson Steve , Molina Patricia
Published: November 2023

Microtubule‐associated protein 2 (MAP2) expression is directly correlated with neurocognitive impairment in subjects with HIV‐associated neurocognitive disorder (HAND). Our previous microarray analysis of hippocampal tissue, identified alterations in immune response and neurogenesis as potential mechanisms contributing to cognitive deficits in chronic binge alcohol (CBA)‐administered, simian immunodeficiency virus (SIV)‐infected macaques. The aim of this study was to determine whether expression of inflammatory genes and growth factor genes were associated with differential MAP2 expression in brain regions associated with HAND. Adult, male rhesus macaques were fitted with intra‐gastric catheters for chronic binge alcohol (CBA, 13–14 g EtOH/kg/week, n = 8) or sucrose (SUC, n = 7) administration beginning three months prior to SIV infection and continuing through the duration of the study until animals reached end‐stage disease criteria (range from 3 to 24 months post‐inoculation). Following euthanasia, brains were excised and pre‐frontal cortex (PFC), caudate (CD), and hippocampus (HP) tissue were isolated and used for qPCR quantification of inflammatory and growth factor genes, and viral loads. We utilized R statistical software to build regression models using the all‐subsets technique with gene expression, viral load, CBA, and time to end‐stage as predictor variables for MAP2 expression. In the PFC, growth factors BDNF and IGFBP5, along with time to end‐stage by CBA interaction were significantly associated with MAP2 expression. In the CD, growth factors IGFBP5 and MAPK1, inflammatory cytokines ISG15, IL6, and TNF, and time to end‐stage were significantly associated with MAP2 expression. In the HP, the growth factor MAPK1, inflammatory cytokine IL6, and brain viral load were significantly associated with MAP2 expression. These results indicate brain region specific relationships between growth factor and inflammatory cytokine expression with MAP2, a molecular marker of cognitive impairment. PFC MAP2 associated with growth factors and showed greater susceptibility to an alcohol‐SIV interaction. In the subcortical structures, CD and HP, MAP2 expression associated with inflammation. Different treatments may be necessary for HAND subjects with cortical compared to subcortical cognitive impairments.

Support or Funding Information

P60AA09803, T32AA07577, F31AA024365
Highly palatable food during adolescence and youth increased anxiety‐/depression‐like behaviors in males, but not in females
Authors: Jahng Jeong Won , Kim Jin Young , Lee Jong‐Ho
Published: November 2023

This study was conducted to examine sexual dimorphic effects of highly palatable food access during adolescence and youth on psycho‐emotional behaviors of rats and its underlying neural mechanism. Male and female Sprague‐Dawley pups had free access to chocolate cookie rich in fat (highly palatable food) from postnatal day 28 in addition to ad libitum chow, and the control groups received chow only. The food conditions were continued though out the entire experimental period, and the neurochemical and behavioral measurements were performed during young adulthood. Corticosterone levels during 2 h of restraint stress were analyzed with radioimmunoassay, and ΔFosB and brain‐derived neurotrophic factor (BDNF) expression in the nucleus accumbens (NAc) with Western blot analysis. Cookie access did not affect body weight gain and total caloric intake in both sexes; however, it increased retroperitoneal fat depot only in males. The time spent in open arms during elevated plus maze test was decreased and immobility during forced swim test was increased in cookie‐fed males, but not in cookie‐fed females. Main effect of food condition on the stress‐induced corticosterone increase was observed in males, but not in females, and cookie access increased BDNF expression in the NAc only in males. Increased BDNF expression in the NAc and fat depot, in addition to the stress axis dysfunction, may play roles in the pathophysiology of depression‐ and/or anxiety‐like behaviors induced by cookie access.

Support or Funding Information

Supported by a grant from the Oromaxillofacial Dysfunction Research Center for the Elderly at Seoul National University in Korea (2015048003) funded by the Ministry of Science, ICT and future Planning
Liposomal miR‐29b Delivery Attenuates Increased Expression of Matrix Proteins and Improves Alveolarization in Mice Exposed to Maternal Inflammation and Neonatal Hyperoxia
Authors: Sugar Sophia S , Heyob Kathryn M , Tipple Trent E , Rogers Lynette K
Published: November 2023

Background

Chronic lung disease or bronchopulmonary dysplasia (BPD) continues to be a significant pulmonary complication for preterm infants. In addition to decreased alveolarization, these infants can develop obstructive and/or restrictive lung function due to increases in or dysregulation of extracellular matrix proteins. Our mouse model mimics the pathophysiology observed in infants with severe BPD and we have previously reported decreased pulmonary miR‐29b expression in this model. The current studies tested the hypothesis that liposomal mediated restoration of miR‐29b in the developing lung will improve lung alveolarization and minimize the pulmonary fibrosis.

Methods

MiR‐29 levels were measured in the plasma of preterm infants by PCR. Pregnant C3H/HeN mice received an intraperitoneal LPS injection on E16 and newborn pups were exposed in 85% oxygen from birth to 14 days of life. On postnatal day 3, PBS containing a liposomal preparation of miR‐29b or an empty liposome was administered intranasally. On postnatal day 14 or 28, mouse lung tissues were analyzed for changes in miR‐29 expression, alveolarization, and matrix protein expression.

Results

Analyses of plasma obtained from preterm infants during the first week of life indicate that circulating miR‐29b levels are suppressed and the levels are inversely correlated to severity in infants later diagnosed with BPD. In our mouse model, modest improvements in alveolarization were detected in the miR‐29b‐treated mice. MiR‐29b treatment completely attenuated the LPS/O2‐associated increases in aSMA, MMP‐9, and SMAD 2/3 and restored PDGFa levels in lung tissues.

Conclusion

Our data suggest that miR‐29b restoration may represent a novel therapeutic strategy to treat or prevent severe BPD in prematurely born infants.
Maternal High Fat Diet Causes Decreased Alveolarization and Persistent Pulmonary Inflammation in the Offspring
Authors: Heyob Kathryn M , Trask Aaron J , Thompson Michael , Rogers Lynette K
Published: November 2023

Background

The incidence of asthma and obesity continue to rise throughout the world. Past research has shown that obesity can cause numerous complications in asthma patients, including increased severity of symptoms, treatment non‐responsiveness, and required increased dosage of treatments. In addition, maternal obesity has been associated with multiple complications for both the mother and the child, including hypertensive disorders and gestational diabetes for the mother, and macrosomia and congenital abnormalities for the child.

We tested the hypothesis that maternal obesity would impair lung growth through the presence of a persistent inflammatory state.

Methods

Female mice were fed high fat diets (HFD) or control diets (CD) for 8 weeks prior to mating and through weaning. Mouse pups were sacrificed at 21 days for inflammation analysis using PCR and western blot. An additional group of mouse pups were placed on CD at weaning and maintained on CD until sacrifice at 3 months. Lungs were inflation fixed and morphometric analyses were performed on H&E stained tissue sections.

Results

At 3 months, mice exposed to maternal HFD had fewer and larger alveoli than mice exposed to maternal CD. At 21 days, no differences were observed in IL‐6, IL‐5, TNF‐alpha gene expression in lung tissues. There were also no significant differences found in pSMAD 2/3 or IkBa protein levels. There were significantly lower protein levels of p65 and IKKb in HFD mice.

Conclusions

Maternal HFD results in decreases in alveolariztion in the offspring. Inflammatory responses and changes in matrix regulation are not evident at 21 days but ongoing chronic inflammation was observed.
Postnatal Growth Restriction Alters Lung Function and Structure In Juvenile Rats
Authors: Ballard Craig R , Zhou James , Zuspan Katie , Rebentisch Andrew , Wang Haimei , Joss‐Moore Lisa
Published: November 2023

Background

Preterm infants receiving respiratory support often experience extrauterine growth restriction (EUGR). EUGR in preterm infants occurs secondary to feeding intolerance and clinically indicated feeding volume restrictions. EUGR increases the severity and incidence of the chronic lung disease of infancy, bronchopulmonary dysplasia (BPD). BPD is characterized by impaired lung development, with decreased lung compliance, and increased lung resistance. Animal models demonstrate the importance of EUGR to lung development in the context of respiratory support. However, the isolated contribution of EUGR to lung development and function is unknown. We hypothesize that, in the juvenile rats, EUGR will impair alveolar development, decrease lung compliance, and increase lung resistance.

Methods

We induced EUGR in a rat model by cross fostering newborn rat pups to rat dams with litter sizes of 16 (EUGR) or 8 (control). Rat pup weight was measured every other day from birth to day of life 21 (d21). At postnatal d24, we measured alveolar wall thickness, second crest septal volume, and radial alveolar count (RAC) using ImageQuant software. At postnatal d24 we also measured lung compliance and resistance of the parenchyma (RPar) and airway (RAir) using a Flexivent System.

Results

Results are EUGR values as a percentage of control±SD (*=p<0.05). Rat pups in the EUGR group weighed significantly less (75±3%*) than control by postnatal d5 and continued to weigh less through d21 (70±5%*). Structural analysis of rat lungs revealed that EUGR rats had thicker alveolar walls than control in male (136±20%*) and female (134±32%*) rats, but no change in sepal density or RAC. EUGR decreased compliance in male (67±26%*) and female (66±25%*) rats. EUGR significantly increased RPar in both male (153±70%*) and female (157±56%*) rats and significantly increased RAir in male (111±25%*) and female (166±148%*) rats.

Conclusion

EUGR alters lung structure and function in juvenile rats. Given the role of elastin and elastic fiber formation in lung structure and function, we speculate that EUGR may disrupt elastin expression and fiber deposition. Ongoing studies are evaluating expression of elastin isoforms in the EUGR lung.

Support or Funding Information

Special thanks to the American Physiological Society for the Undergraduate Summer Research Fellowship that funded this research, and to Lisa Joss‐Moore and the University of Utah for hosting me in their lab. In addition, thanks you to James Zhou and Haimei Wang for help with collection of mechanics data, as well as Katie Zuspan and Andrew Rebentisch for conducting image analysis for structural data.
Diaphragm and Intercostal Muscle Activity following Unilateral Mid‐cervical Spinal Cord Contusion in the Rat
Authors: Wen Ming‐Han , Lee Kun‐Ze
Published: November 2023

The present study was designed to investigate the diaphragm and intercostal muscle activity following unilateral mid‐cervical spinal cord contusion in rats. Adult male rats were received laminectomy or unilateral contusion at C3–C4 spinal cord using the MASCIS Impactor (height: 6.25 mm). The respiratory airflow and bilateral diaphragm and T2 intercostal muscle electromyogram (EMG) activity were measured during hyperoxia (50 % O2 and 50 % N2) and hypoxia (12.5 % O2) at 3 day, 2 weeks and 8 weeks following spinal surgery. The respiratory frequency was similar between uninjured and contused animals; however, the tidal volume was significant lower in contused animals than uninjured animals at three time points post‐injury. At 3 days post‐injury, the burst amplitude of the contralateral diaphragm EMG was enhanced in contused animals. When the data were normalized by the maximal response during the hypoxic challenge, the ipsilateral diaphragm EMG value of contused animals was greater than that of uninjured animalsat 3 days and 2 weeks post‐injury. At 8 weeks post‐injury, there were no significant differences in the diaphragm EMG activity between uninjured and contused animals. Notably, the intercostal muscle activity was not substantially influenced by mid‐cervical contusion from acute to chronic injury state. These results suggested that mid‐cervical spinal contusion induced a compensatory increase in contralateral diaphragmatic activity and resulted in greater utilization of percentage of maximal inspiratory activity of the ipsilateral diaphragm. The maintenance of intercostal activity may enable the animal to sustain the essential breathing capacity following injury.

Support or Funding Information

NHRI‐EX105‐10223NC, MOST 105‐2628‐B‐110‐002‐MY3
Aging‐Related Changes in Motoneuron Autophagy
Authors: Gransee Heather M. , Gonzalez Maria A. , Sieck Gary C. , Mantilla Carlos B.
Published: November 2023

Autophagy is a series of catabolic processes that involves degradation of cytoplasmic components through lysosomal pathways. There is an important balance that must be met, with impaired autophagy contributing to cell dysfunction and excessive autophagy leading to cell death likely via apoptosis. Indeed autophagy is a dynamic multi‐step process that is modulated positively and negatively at several steps. The role of autophagy in aging‐related motoneuron dysfunction or death is not known. Therefore, it is important to differentiate between the accumulation of autophagosomes due to increased induction of autophagy during conditions of cell stress common across aging‐related conditions, and the accumulation of autophagosomes due to inefficient clearance of damaged organelles and other sequestered cargoes, which reflects impairments in autophagy that would lead to cell dysfunction. We hypothesized that with aging, there is autophagy imbalance causing accumulation of autophagosomes and ultimately neuromuscular dysfunction. Male and female mice at 6 and 24 months of age were used to assess markers of autophagy in the spinal cord. Protein expression of autophagy‐related genes LC3A and LC3B increased in the cervical and lumbar spinal cord of old compared to young mice, whereas protein expression of Atg5, Atg7, and Bcn1 did not change with age. Quantitative real‐time RT‐PCR of microdissected phrenic motoneurons showed an increase in LC3 mRNA expression with age. Overall autophagic flux, which assesses inclusion (or exclusion) of cargo within autophagosomes, delivery of cargo to lysosomes, and subsequent breakdown and release of macromolecules back into the cytosol was evaluated using an mCherry‐GFP‐LC3 sensor. This genetic sensor is designed to monitor LC3 flux through autophagy pathways since the GFP signal is sensitive to the acidic/proteolytic conditions of the lysosome lumen, whereas mCherry fluorescence persists under these environments. We used motoneuron‐like NSC‐34 cells transfected with mCherry‐GFP‐LC3 plasmid to detect changes in the autophagic degradation rate in cells treated with tunicamycin (which leads to cell stress via induction of the unfolded protein response). We observed an increase in yellow vesicles indicating an accumulation of autophagosomes due to inefficient clearance of sequestered cargoes. This genetic sensor indicates impaired autophagy flux in motoneurons in conditions of elevated stress likely present in old age. Taken together, these results suggest impaired autophagy in motoneurons, including phrenic motoneurons, with an associated increase in markers of early autophagosome formation (LC3).

Support or Funding Information

Supported by R01‐AG044615.
Effects of C2 Chronic Hemisection on Inspired Volume Generation During High Frequency Spinal Cord Stimulation (HF‐SCS)
Authors: Kowalski Krzysztof E , Dick Thomas E , DiMarco Anthony F , Alilain Warren J
Published: November 2023

Objective

HF‐SCS (300Hz) applied on the ventral epidural surface of the spinal cord results in activation of inspiratory motoneurons via stimulation of spinal cord pathways. The specific pathways by which inspiratory motoneurons are activated by this method however are unknown. The main objective of the present study was to assess the potential role of bulbospinal axons on the activation of phrenic motoneurons during HF‐SCS.

Methods

During an initial procedure, six rats were hemisected at the C2 spinal level and maintained for 7 days to allow degeneration of the ipsilateral long descending bulbospinal inspiratory axons. HF‐SCS was then applied at the T2 spinal level during spontaneous breathing and following complete C2 spinal section while ipsilateral (EMGipsi), contralateral (EMGcontra) diaphragm EMG, and inspiratory volume were monitored.

Results

As expected, degeneration of spinal tracts ipsilateral to the hemisection, resulted in minimal EMGipsi, while rhythmic discharge was recorded in the intact, contralateral side (EMGcontra). HF‐SCS however resulted in bilateral rhythmic diaphragm EMG activity. Moreover, the inspired volume achieved during HF‐SCS was similar to that recorded during spontaneous activity (1.44 ± 0.12ml vs. 1.40 ± 0.06ml, respectively). Following complete C2 spinal section, mean inspired volume achieved during HF‐SCS was 1.39 ± 0.08 ml which was not significantly different to that observed before section (NS). In addition, mean maximum inspired volume (3.16 ± 0.15ml) was similar to values previously reported.

In chronically hemisected rats, following which time cut bulbo‐spinal pathways would have degenerated, the effects of HF‐SCS on inspired volume generation remained unchanged.

Conclusion

HF‐SCS results in stimulation of pathways located on the ventral surface of the upper thoracic spinal cord, which synapse with sub‐medullary spinal circuits to activate the phrenic motoneuron pools. This technique may be a useful method to support ventilation in ventilator‐dependent tetraplegic patients.

Support or Funding Information

Support: University of Kentucky College of Medicine Funds, MetroHeath Foundation,

Disclosure: Dr. DiMarco has a significant financial interest in Synapse BioMedical, Inc, a manufacturer of diaphragm pacing systems.
Respiratory motor deficit in children with spinal cord injury
Authors: Singh Goutam , Trimble Shelley , Aslan Sevda , Behrman Andrea , Ovechkin Alexander
Published: November 2023

Objective

High cervical and thoracic injuries leads to paralysis or weakness of muscles of respiration, thereby increases the work load of breathing, which results in low lung volumes and airway pressures. Ineffective cough due to muscle weakness causes difficulty in clearing secretions, which in turn cause mucus retention, pneumonia and other respiratory related complications. Therefore the aim of this study is to compare respiratory functional measures in children with spinal cord injury to children who are neurologically intact (NI) by using a respirator multi‐muscle surface electromyography (sEMG) assessed during standard spirometry and maximal airway pressure efforts. We hypothesized that pulmonary function measures are significantly reduced in children with SCI and associated sEMG activation patterns are significantly different when compared to children who are neurologically intact.

Design/Methods

14 children with cervical or thoracic SCI were recruited from Frazier rehabilitation Institute and 14 neurologically intact (NI) children were recruited from community. sEMG signals from upper trapezius (UT), pectoralis (PEC), 6intercostal (INT), rectus abdominus (RA), external oblique (OB) thoracic paraspinal (PST) and lumbar paraspinal (PSL) muscles were recorded during maximal inspiratory and expiratory efforts. Outcome measures included Spirometry, sEMG amplitude, PEmax and PImax airway pressures.

Results

Children with SCI showed significantly lower values of FVC, FEV1, PEmax and PImax compared to NI children. Children with SCI also showed significantly lower activation of rectus abdominis and external oblique muscles during PEmax maneuver. However, no significant difference was observed for muscle activations during PImax maneuver.

Conclusion

Our study demonstrated the differences in respiratory motor control in children with SCI when compared to NI children. Injury at cervical or high thoracic spinal cord levels resulted in low lung volumes & weakness or paralysis of muscles involved in active expiration & coughing such as rectus abdominus and external oblique thereby leading to compensatory increased activation of accessory muscles, such as upper trapezius and pectoralis. Resultantly, children with SCI exhibited lower values for FVC, PEmax and PImax, compared to NI children.

Support or Funding Information

Kosair Charities, the Kosair Charities Center for Pediatric NeuroRecovery and The Leona M. and Harry B. Helmsley Charitable Trust.
Motoneuron Endocytosis and Intracellular Trafficking of Cholera Toxin B Modified Protocells
Authors: Porras Maria Alejandra Gonzalez , Durfee Paul , Brinker Jeffrey , Sieck Gary , Mantilla Carlos Bernardo
Published: November 2023

Cholera toxin B modified protocells (CTB‐protocells) are a promising, customizable approach for targeting and delivering drugs to motoneurons. Understanding the endocytic mechanism and intracellular fate of CTB‐protocells is essential for safe therapeutic application and cargo delivery efficiency, and also to elucidate characteristics of motoneuron physiology that are not well understood. To assess the energy dependent uptake of CTB‐protocells by motoneurons, intracellular protocell fluorescence was measured at 4°C and 37°C. Confocal analysis demonstrated that after 3 h at 4°C, there is a 40% reduction in CTB‐protocell uptake compared to the uptake observed at 37°C (p<0.001). Pharmacological endocytic pathway inhibitors were used to elucidate the preferential endocytotic mechanism. Results showed that amiloride (macropinocytosis inhibitor) and methyl‐β‐cyclodextrin (inhibitor of cholesterol dependent endocytic processes) significantly reduced the uptake of CTB‐protocells (p<0.001), consistent with endocytosis being dependent on the integrity of lipid rafts. To track intracellular fate, immunofluorescence techniques and live confocal microscopy were used to demonstrate colocalization of CTB‐protocells with lysosomes, endoplasmic reticulum (ER) and Golgi apparatus at 1 h and 3 h. Colocalization of CTB‐protocells with lysosomes was less than 20%. Both, ER and Golgi colocalization increased from ~20 to ~40% in a 2‐h period (from 1 h to 3 h). To evaluate retrograde transport in motoneurons in vivo, CTB‐protocells were intrapleurally injected in rats. Evidence of protocells in phrenic nerve axons measured by protocell fluorescence intensity supported retrograde transport. In conclusion, uptake of CTB‐protocells is energy‐dependent and mediated principally by macropinocytosis. Additionally, CTB‐protocells are able to escape lysosomal degradation, and are trafficked to relevant subcellular compartments after endocytosis.
Spinal Cord Injury Leads to Reductions in Central Nervous System 5HT Coupled with Blunting of Arousal and Genioglossus Muscle Responses to Hypercapnia in Mice
Authors: Komnenov Dragana , Kuhn Donald , Mateika Jason
Published: November 2023

Purpose

The present investigation was designed to examine if spinal cord injury (SCI) leads to reductions in central nervous system serotonin (5HT). The investigation was also designed to investigate if this reduction was coupled to blunting of arousal responses (AR) and genioglossus muscle sensitivity (GS) to hypercapnia.

Methods

Telemetry transmitters were surgically implanted in wild type mice (Tph2+/+) (n = 4) and tryptophan hydroxylase 2 knockout mice (Tph2−/−) (n = 4) to measure electroencephalography, genioglossus muscle activity, core body temperature and gross motor activity. Following recovery, the Tph2+/+ and Tph2−/− mice were placed in whole body plethysmographs and exposed to episodes of 7 % carbon dioxide to determine the AR and GS to hypercapnia during non‐rapid eye movement (NREM) sleep. Following these measures a C2 hemisection of the spinal cord was completed and AR and GS were measured subsequently. In addition, high‐performance liquid chromatography was performed to measure 5HT levels in three brainstem sections (i.e. dorsal respiratory group and hypoglossal nucleus; raphe magnus, obscurus and pallidus; raphe median and paramedian) obtained from 4 intact TPH2+/+ mice and 4 TPH2−/− mice fourteen days after SCI.

Results

Total 5HT levels in the brainstem were reduced following SCI (3.2 ± 0.1 vs. 1.5 ± 0.3 ng/mg; P < 0.001). In particular, the levels of 5HT in the dorsal respiratory group and hypoglossal nucleus (1.2 ± 0.2 vs. 0.4 ± 0.1 ng/mg; P < 0.01) and in the raphe median and paramedian (1.3 ± 0.2 vs. 0.8 ± 0.1 ng/mg; P < 0.08) were reduced following SCI. In conjunction with the reduction in 5HT the AR (Before SCI: 8.3 ± 4.4 vs. After SCI: 33.8 ± 8.7 s; P < 0.01) and the GS (Before SCI: 180 ± 58 vs. After SCI: 33 ± 10 microvolts; P < 0.02) to hypercapnia was blunted following SCI in the Tph2+/+ but not the Tph2−/− mice.

Conclusions

SCI in a spontaneously breathing non‐anesthetized sleeping mouse model was accompanied by a reduction in central nervous system 5HT. This reduction could be responsible for the blunted AR and GS to hypercapnia during NREM sleep. Ultimately, depletion of 5HT could result in an increase in apnea frequency and blunting of the AR and GS could lead to increases in apnea duration following SCI.
Contribution of Expiratory Abdominal Muscle Recruitment in the Perinatal Period Across Sleep Wake Cycles
Authors: Saini Jasmeen , Pagliardini Silvia
Published: November 2023

Breathing and sleeping are homeostatically regulated processes that are necessary for survival. During sleep, specifically rapid eye movement sleep, breathing is more frequently prone to irregularities in both humans and rodents, especially in preterm and full term newborns. Previous work in our laboratory has demonstrated the occurrence of frequent recruitment of abdominal muscle activity in adult rats during REM sleep, despite REM induced postural muscle atonia. This recruitment was also associated with increased tidal volume and increased respiratory stability

Little is known about occurrence of expiratory activity in perinatal rats, specifically across sleep states, and how this recruitment contributes to ventilation. In this study our objective is to investigate the occurrence and the significance of expiratory modulated abdominal muscle recruitment across sleep wake cycles in the postnatal period (postnatal day, P0 to P14) of rats. We hypothesize that in the postnatal period, expiratory muscle activity is also recruited across sleep states and its recruitment contributes to stabilize ventilation, specifically during irregular breathing.

We instrumented newborn and juvenile rats with EMG electrodes in neck, intercostal and abdominal muscles and recorded breathing parameters and overt behavior inside a whole body plethysmograph.

Our results suggest that neonatal rats experience frequent abdominal muscle recruitment events, which occur in both active and quiet sleep. Our results further indicate that respiratory rate is less variable with onset of abdominal muscle recruitment in active sleep. We conclude that occurrence of expiratory activity is associated with stabilization and potentiation of ventilation during sleep in the postnatal period.

Support or Funding Information

Neuroscience and Mental Health Institute, Women and Childrens Health Research Institute, NSERC, CIHR
SEX DIFFERENCES AND PROTEOMIC PROFILING OF DIAPHRAGM WEAKNESS IN CHRONIC HEART FAILURE
Authors: Kelley Rachel C , McDonagh Brian , Hanna Steven , Ferreira Leonardo F
Published: November 2023

Inspiratory dysfunction occurs in patients with chronic heart failure (CHF). The diaphragm is the primary inspiratory muscle, and diaphragm abnormalities likely contribute to the dyspnea and exercise intolerance that these patients experience. Animal models show that CHF causes diaphragm weakness, but it remains unclear whether disease effects and mechanisms of weakness are sex‐specific. We conducted the current study to test whether CHF effects on diaphragm function and morphology are sex‐specific and to explore putative mechanisms for diaphragm abnormalities via proteomics. We performed myocardial infarction or sham surgery on Sprague Dawley rats. We focused our efforts on animals with severe CHF, determined by 1) transmural infarct ≥ 35% of left ventricle + septal area and 2) right ventricle hypertrophy. We assessed diaphragm isometric contractile function in vitro, fiber type and cross sectional area, and global label free proteomics with mass spectrometry. CHF decreased diaphragm maximal tetanic isometric specific force (N/cm2) by ~20% in both males and females (n = 5–8 per group; P < 0.05). However, the effects on isometric twitch specific force were sex‐specific. CHF decreased twitch specific force (N/cm2) by ~30% (P < 0.05) in males, with no effect in females. There were no effects of disease on fiber type distribution or cross‐sectional area in either sex. Our preliminary proteomic results did not reveal any obvious changes in protein abundance that could explain the decrease in maximal diaphragm force in CHF. For instance, CHF (males) increased the relative quantity of myosin binding protein C fast‐type and troponin T slow isoform and decreased myosin light chain kinase‐2 and phosphorylase b kinase (P < 0.01, false‐discovery rate 1%). In females, our proteomics showed no changes in relative protein quantity with CHF. Overall, our data show that CHF effects on the diaphragm are generally similar between sexes, except for twitch specific force. Our preliminary findings from proteomics suggest that post‐translational modifications, rather than changes in relative quantity, are the main mechanisms underlying diaphragm weakness in CHF.

Support or Funding Information

Funding support from NIH R01 HL130318
Seasonal Metabotypes in Small Birds
Authors: Wone Bernard W. M. , Kinchen Jason M. , Swanson David L.
Published: November 2023

Seasonal changes present challenges to free living birds, such as alterations to food availability and type, as well as metabolic adjustments to cold conditions. To better understand the mechanistic basis of this metabolic flexibility, we conducted a large‐scale metabolic profiling of pectoralis muscle in black‐capped chickadees (BCCH) and American goldfinches (AMGO) during summer and winter seasons. These muscle samples were analyzed using non‐biased, global metabolomics profiling technology based on UHLC/MS/MS2 and GC/MS platforms. A total of 582 metabolites were characterized for summer and winter seasons. Comparison of global biochemical profiles in avian muscle revealed several metabolomic differences. Notably, BCCH showed greater than 2‐fold enrichment in advanced glycation end‐product, ceramides, creatine, branched fatty acid, ketone, and purine and pyrimidine metabolic pathways, whereas AMGO showed greater than 2‐fold enrichment in advanced glycation end‐product, ceramides, disaccharides and oligosaccharides, ascorbate and alderate, glutamate, lysine, and alanine and aspartate metabolic pathways. Declined levels in amino acids might reflect decreasing dietary protein intake and/or protein sparing to conserve muscle for thermogenesis in both bird species during winter. Concomitant decreased abundances in TCA cycle metabolites suggest faster cycling of the oxidative phosphorylation pathway to meet the metabolic demands of thermogenesis during winter. Accordingly, BCCH displayed shifts toward lipid oxidation with seasonal change, whereas AMGO showed declines in ketone bodies suggesting increased energy demands or subtle changes in substrate availability with seasonal change. Interestingly, increased levels of tryptophan metabolites, such as serotonin and tryptophan betaine, were observed for both species during winter season. Collectively, our results provide an unprecedented view into the complex biochemical regulatory events orchestrating seasonal metabolic phenotypes.

Support or Funding Information

This material is based upon work supported by the University of South Dakota start up funds.
Oxygen Consumption of Desert Pupfish at Ecologically‐Relevant Temperatures Suggests a Significant Role for Anaerobic Metabolism
Authors: Hillyard Stanley , van Breukelen Frank
Published: November 2023

Oxygen consumption is oftentimes used as a proxy for metabolic rate. Routine oxygen consumption (RVO2) of a refuge population of Cyprinodon diabolis acclimated to ecologically relevant temperatures of 28 °C and 33 °C was evaluated at assay temperatures between 25 °C and 38 °C. Different interpretations of the data are available depending on normalization. For instance, RVO2 of smaller fish, measured per fish, was remarkably stable over a wide range of assay temperatures and was not different between acclimation groups. Measured on a mass‐specific basis, RVO2 in larger fish increased more predictably as temperature increased. RVO2 of refuge fish and the closely related pupfish, C. nevadensis mionectes, measured near their respective acclimation temperatures of either 28 °C or 33 °C were essentially identical. However, RVO2 of 28 °C acclimated fish of both species, when measured at 33 °C, was greater than that of the 33 °C acclimated fish measured at 28 °C. We suggest this observed ‘efficiency’ may result from significant anaerobic metabolism use. Experiments investigating metabolic scope (MaxVO2/RVO2) yielded values less than 1 in 33 °C acclimated fish. These values indicate a substantial contribution of anaerobic metabolism to energy utilization by these fish. However, muscle lactate levels are not elevated in exercising fish‐ a result that is consistent with paradoxical anaerobism use.

Support or Funding Information

Supported by grants from the US Fish and Wildlife Service and Nevada Department of Wildlife
Effects of altering activity of sensory systems, motor output, skeletal muscle and neurons containing ACH, dopamine, 5‐HT and GABA in Drosophila melanogaster
Authors: Cooper Robin L , Malloy Cole , Majeed Zana R. , Titlow Josh , Mahmood Dlovan D. , Somasundaram Eashwar , Omar Aya , Hermanns Christina , Higgins Jake , Hall Kaylee
Published: November 2023

The goal of this research is to increase the understanding of how altered neural activity in various modulatory circuits and defined circuits can influence changes in the structure and function of the central and peripheral nervous systems. This is being addressed by the use of, pharmacological agents, optogenetics and thermal control. Some of the genetic approaches involve inserting particular genes which are transgenetically introduced into the genome. Optogenetic regulation allows rapid control of cells to be excited or inhibited. Larvae are reared in varied lighting and thermal control to elicit different motor neuron responses indicative of behavioral changes. Locomotion behavior, response to sensory stimuli and eating responses are being used to measure behavioral assays. The assays will be performed for first, second and third instar larva during the various conditioning paradigms. The degree of synaptic transmission with electrophysiological measures of the synaptic output of the motor neurons is currently being addressed. The hypothesis being tested is that altering defined neural activity during larval development from 1st to 3rd instar will result in structural and functional changes in the synapse; however, they may be able to compensate in novel ways to maintain normal behaviors and physiological control when returned to non‐manipulated conditions. This research is significant because it addresses the possibility of underlying factors sculpting the development of synaptic contacts, as well as factors helping to maintain synaptic contacts after they are established. This research has further implications in the use of optogenetics in driving neural activity, stimulating neurons for regeneration and repair as well as potentially how to offset deconditioning situations, such as zero gravity conditions in aerospace science.

Support or Funding Information

Kentucky Science and Engineering Foundation (KSEF) at the Kentucky Science and Technology Corporation (RLC), Robert Wood Johnson Foundation (JH) & personal funds (RLC)