bluuebunny/crossref_metadata_2025_split huggingface dataset:
Deletion of Xenotropic and Polytropic Retrovirus Receptor 1 in mouse nephron causes renal Fanconi syndrome and hypophosphatemic rickets
Authors: Ansermet Camille , Moor Matthias , Centeno Gabriel , Auberson Muriel , Hu Dorothy , Barron Roland , Nikolaeva Svetlana , Haenzi Barbara , Katanaeva Natalya , Gautschi Ivan , Katanaev Vladimir , Rotman Samuel , Koesters Robert , Schild Laurent , Pradervand Sylvain , Bonny Olivier , Firsov Dmitri 
Published: November 2023

Phosphate (Pi) is one of the most abundant minerals in the body and tight control of extra‐ and intracellular Pi concentrations is crucial for many biological processes. The kidney is the main organ involved in the regulation of minute‐to‐minute phosphate homeostasis by controlling Pi reabsorption from the primary urine. This reabsorption primarily occurs in the proximal tubule by the action of the apical sodium‐dependent phosphate transporters NaPi‐IIa, NaPi‐IIc and PiT2. The protein(s) involved in the basolateral phosphate efflux remain unknown. As recent in vitro and genetic studies have linked the xenotropic and polytropic receptor 1 (Xpr1) to Pi efflux, we aimed to assess if it could also be involved in renal Pi reabsorption. To address this question, we used the Pax8‐rtTA‐driven Cre expression system, allowing a conditional inactivation of Xpr1 in mouse renal tubule.Functional analysis showed that conditional Xpr1 knockout mice (cKO) have hypophosphatemia with transient hyperphosphaturia, an increase in fractional excretion of phosphate (FEPi) along with a decreased TmPi/GFR. These phosphate disturbances leaded us to study the bone phenotype. Micro‐CT analysis of vertebrae revealed significant decrease in bone mineral density, percent bone volume and trabecular thickness and number in male cKO mice, characteristic of osteoporosis and osteomalacia. Histomorphometric analysis of vertebrae also showed an increase in unmineralized osteoid and osteoclastogenesis in cKO mice. Moreover, ex‐vivo experiments using primary cultures of proximal tubule of Control and cKO mice showed that Xpr1 deficiency strongly affects the [33P]phosphate efflux whereas the [33P]phosphate uptake remains similar between Control and cKO cells. Additional phenotypic observations in cKO mice include aminoaciduria, glycosuria, hypercalcuria, hypercalcemia and proteinuria, indicating that these mice are developing a complete Fanconi syndrome, a generalized proximal tubular dysfunction.Taken together, these results support a significant role for Xpr1 in renal phosphate homeostasis.Support or Funding InformationThis work was supported by the Swiss National Science Foundation Research grants 31003A‐149440 and 310030‐163340
Modeling osmotic transients during exercise
Authors: Christmas Kevin M , Jensen Austin , Bassingthwaighte James 
Published: November 2023

The body maintains tight osmotic regulation despite deviations from homeostasis at rest or during intense exercise. Maintaining osmotic equilibrium can result in exercising muscle reducing plasma volume by 10–15% depending on intensity, the mass of tissue stimulated, and mode of exercise. Research often references this phenomenon with reduced plasma volume or increased plasma osmolarity during exercise, but more correctly whole body osmolarity goes up with volume shifts occurring in all tissues. Elevated muscle osmolarity from exercising metabolism results in water flux into active muscle from the extracellular compartment, causing muscle cells to swell, decreasing plasma volume, and hemoconcentrating the blood. Assuming all solutes are fixed, impermeable to membranes, we can calculate the increase in extracellular osmolarity due to volume loss from a normal value of 280 mOsM to ~329 mOsM. Assuming de novo formation of intramuscular solutes, exercising metabolism would have to increase the muscle osmolarity by ~94 mM to produce this volume shift, assuming none leaves the cell. This rise in muscle osmolarity results in water influx, diluting the cells concentration to match the bodies osmolarity of 329 mOsM. These simple algebraic calculations fail to incorporate tissue mass, diffusion of metabolic substrates out of the muscle, or anatomical representation of a working human. During intense exercise a 70‐kilogram man generates an osmotic gradient shifting over a liter of fluid towards muscle within 30–60 seconds. Metabolically, glycolytic intermediates are prime candidates with muscle lactate concentration rising ten fold during intense exercise, but cannot be the only factor of importance. This model quantifies osmotic water flux due to metabolic byproducts of glycolysis and ATP breakdown with whole body osmotic balance and recirculation. Additional products of muscle metabolism need to be identified to explain the water fluxes during short term exercise.Support or Funding InformationResearch supported by NIH grants NHLBI T15 088516 and U01‐HL122199, and NIBIB EB08407.
Effect of Hydrogen Peroxide and Glutamate on Muscle Spindle Afferent Receptor Ending Sensitivity to Muscle Stretch in Adult Mice
Authors: Than Kimberly , Kwon Anthony , Wilkinson Katherine A. 
Published: November 2023

Proprioception, or the sense of body position and movement, is required for the completion of complex motor tasks. Exercise impairs proprioception, although the mechanism for this is not well understood and likely involves changes to both peripheral signaling and central proprioceptive circuits. The Group Ia and II muscle spindle afferents (MSAs), which report muscle length and movement information to the central nervous system, are thought to be the primary proprioceptors. Substances released during exercise and activity, including reactive oxygen species and glutamate, have been shown to alter MSA activity in rats. Whether these substances alter MSA sensitivity via peripheral and/or central mechanisms is unclear. We tested the hypothesis that reactive oxygen species (hydrogen peroxide) and glutamate can act locally on MSA receptor endings and alter responsiveness to stretch. We used an in‐vitro mouse muscle‐nerve preparation to record MSA firing activity. Briefly, the extensor digitorum longus (EDL) muscle and innervating deep peroneal branch of the sciatic nerve were dissected and perfused in an oxygenated synthetic interstitial fluid tissue bath. An extracellular recording electrode was placed on the nerve and individual MSAs identified by waveform. A series of 4s ramp and hold stretches were applied to the EDL and instantaneous firing frequency before and during stretch was measured. Upon exposure to hydrogen peroxide (1 mM), there was an increase in static stretch response in 10 of 18 MSAs tested (n=9; 23 ± 13% increase). The remaining 8 MSAs showed no change in activity (n=9; 1.5 ± 2.8%). There was also an increase in individual afferent firing rates upon the addition of glutamate in a preliminary sample of MSAs (1 mM; n=4; 30 +/− 18% increase). These results support the hypothesis that hydrogen peroxide and glutamate can act locally in the absence of central nervous system circuits on MSA nerve endings to alter stretch sensitivity. However, not all MSAs respond to locally applied hydrogen peroxide, suggesting different sensitivities in subpopulations of MSAs.Support or Funding InformationThis work was supported by an SJSU RSCA award to KAW.
Do Trigeminal Nerves that Innervate the Nose and External Nares Project to Medullary Dorsal Horn Locations Activated during Voluntary Diving in Rats?
Authors: McCulloch Paul , DelPrete Benjamin , Lahrman Kenneth , Warren Erik , DiNovo Karyn 
Published: November 2023

Underwater diving initiates the diving response, an autonomic cardiorespiratory reflex that includes parasympathetically‐mediated bradycardia, a sympathetically‐mediated increase in total peripheral resistance, and apnea. The initial afferent node of the reflex circuitry includes the ventral tip of the medullary dorsal horn (MDH), between the pyramidal decussation and obex. This region is also the location of the central terminations of trigeminal nerves that innervate the nose and external nares. Accordingly, the objective of this research was to compare the pattern of neuronal activation of secondary neurons activated by voluntary diving, as determined by neuronal Fos production, with the central terminations of specific trigeminal nerves that innervate the nose and external nares, as determined by the transganglionic tracer Wheat Germ Agglutinin (WGA). Sprague‐Dawley rats (N=12) were trained to voluntarily dive through a 5 m underwater maze. Six rats then received bilateral AEN sectioning, while 6 rats received sham surgery. Nine days post‐surgery all rats had 24 dive trials over 2 hours to activate brainstem neurons to produce Fos. Other rats had 1 μl of 100% WGA injected into the anterior ethmoidal nerve (AEN; N=4), the main orbital branch of the infraorbital nerve (ION; N=7), terminal branches of the ION that innervate the nasal region (N=9), or supratrochlear nerve (N=8). Results indicate Fos was primarily located within the ventral tip of the superficial MDH and adjacent paratrigeminal nucleus, between the pyramidal decussation caudally and the obex rostrally. The Fos labeling was heaviest when the area postrema was present, especially when Spinal Trigeminal Nucleus Interpolaris displaces the ventral MDH medially. This pattern of Fos labeling within the MDH was similar in rats both with and without intact AENs. Within the MDH WGA central termination sites showed varying degrees of overlap with the location of Fos‐positive neurons. The AEN WGA labeling had the best overlap with Fos‐positive neurons. The main orbital branch of the ION had extensive WGA labeling throughout the MDH, both ventrally and dorsally, and did partially overlap the MDH Fos labeling. The WGA labeling from both nasal branches of the ION and supratrochlear nerve were located more caudally within the MDH near the pyramidal decussation, thus showing poor overlap with the Fos labeling. We conclude that the AEN, and possibly the ION, provides the anatomical pathway that provides the afferent information necessary to initiate the mammalian diving response. However, in the absence of the AEN, it is not clear whether the ION can actually provide this afferent information.Support or Funding InformationSupported by MWU Intramural funding (PFM), CCOM Suarez Summer Research Fellowships (BDP and KAL), and CHS MBS program (EAW).
Second hand smoke exposure depresses excitability and SK channel function of cardiac vagal neurons in the nucleus ambiguus
Authors: Sun Jun‐Qing , Karey Emma , Pan Shiyue , Chen Yi‐Je , Pinkerton Kent E , Chen Chao 
Published: November 2023

BACKGROUNDSecond hand smoke (SHS), a major indoor air pollutant, is a significant risk factor for cardiac dysfunction including arrhythmias and sudden cardiac death. Reduced heart rate variability (HRV), an index of autonomic function, has been implicated as one of the underlying mechanisms of these cardiac maladies. We have previously shown that exposure to air pollution in the form of iron‐soot significantly reduced HRV and spiking activity of cardiac vagal neurons in the nucleus ambiguus (NA), the final vagal cardiac output regulating HRV. Here, we sought to test the hypothesis that SHS exposure, at an environmentally relevant concentration that reduces HRV, depresses neuronal excitability of cardiac vagal neurons in the NA by altering potassium channel function.METHODSAdult male C57BL6/J mice underwent open chest surgeries to retrograde label cardiac vagal neurons by applying a fluorescent dye (DiI) to the sinoatrial node. After two weeks of recovery from surgery, mice were randomly assigned to either filtered air (FA) or SHS (3 mg/m3, 6 hr/d, 5 d/wk) for 4‐, 8‐ or 12‐weeks. Whole‐cell current clamp recordings in brainstem slices were performed on anatomically identified cardiac vagal neurons in the NA with fluorescent labeling.RESULTSFour weeks of SHS exposure was sufficient to increase action potential (AP) threshold and reduce spiking response to depolarizing current injections (p < 0.05) in cardiac vagal neurons. The minimal current required to evoke an AP is also significantly higher in SHS group. Perfusion with apamin (20 nM), an SK channel blocker, had no effect on AP threshold or on minimal current required to evoke an AP in either FA or SHS mice. However, apamin significantly increased neuronal spiking response to depolarization in both groups; this effect was significantly smaller in SHS animals (p < 0.05). These data suggest that SHS exposure reduces excitability of cardiac vagal neurons that is associated with attenuated SK channel modulation of spiking response. These data also suggest that SHS exposure may reduce dynamic spiking range of these cardiac vagal neurons, consistent with reduced cardiac vagal regulation of HRV. Resting membrane potential was not significantly changed until 12 weeks of SHS exposure (became more depolarized). These data suggest that there may be compensatory changes in potassium channel function to increase the neuronal excitability in response to extended SHS exposures.CONCLUSIONSWe conclude that environmentally relevant SHS exposure can reduce neuronal excitability of cardiac vagal neurons and contribute to reduced vagal regulation of HRV resulting in reduced HRV.Support or Funding InformationR01 ES025229; T32 HL086350
Effect of Sedentary Conditions on the Expression of GABAAα2 Receptor Subunits in Bulbospinal C1 and non‐C1 Neurons along the Rostrocaudal Extent of Rat Rostral Ventrolateral Medulla (RVLM)
Authors: Fyk‐Kolodziej Bozena E , Azar Toni A , Llewellyn‐Smith Ida J , Mueller Patrick J 
Published: November 2023

Bulbospinal RVLM neurons play a crucial role in the regulation of sympathetic nerve activity and blood pressure, and can be characterized phenotypically as catecholaminergic (C1) or non‐catecholaminergic (non‐C1). Although excitatory in nature, the tonic activity of the RVLM is strongly influenced by the prevailing level of the inhibitory GABAergic tone. Following sedentary conditions, RVLM neurons also exhibit structural and functional plasticity in a region‐dependent manner, with enhanced dendritic branching and increased glutamate responsiveness in rostral versus caudal regions. Because withdrawal of GABAergic tone produces net excitation of RVLM neurons primarily via GABAA receptors, it is possible that sedentary conditions also alter GABA receptor expression in a region‐dependent manner. Thus, the purpose of the present study was to test the hypothesis that sedentary conditions reduce GABAA receptor expression in rostral regions of the RVLM. To this end, male Sprague‐Dawley rats were divided into sedentary (no wheels) and physically active (running wheels) conditions for 12 wks (n=4 ea). Spinal cord injections of cholera toxin B (CTB) labeled bulbospinal neurons. We examined coronal sections processed for triple‐labeling immunofluorescence using laser confocal microscopy, and quantified CTB‐positive C1 and non‐C1 neurons expressing the GABAAα2 receptor subunit. As expected, more bulbospinal C1 cells expressing GABAAα2 occurred in caudal versus rostral RVLM (p<0.05). Sedentary rats had fewer bulbospinal C1 cells that expressed GABA Aα2 only in the rostral most subregions of the RVLM when compared to active rats (p<0.05). The number of bulbospinal non‐C1 neurons also varied rostrocaudally. However, there were more non‐C1 neurons in rostral compared to caudal RVLM with no overt differences between sedentary versus active groups. Decreases in RVLM neurons expressing GABAA receptors in rostral RVLM are consistent with previous data demonstrating enhanced sympathetic outflow following sedentary conditions, which may in turn contribute to the increased incidence of cardiovascular disease in sedentary individuals.Support or Funding InformationR01‐HL096787‐06; NHMRC 1025031; AHA25810010
Arcuate NPY/AgRP Neurons Decrease Arterial Pressure and Sympathetic Nerve Activity in part via a projection to the Dorsomedial Hypothalamus in Mice
Authors: Shi Zhigang , Madden Christopher J. , Brooks Virginia L. 
Published: November 2023

Using designer receptors exclusively activated by designer drugs (DREADD) technology, we recently demonstrated that select activation of arcuate nucleus (ArcN) neurons that express Neuropeptide Y (NPY) and agouti‐related protein (AgRP) rapidly and profoundly decreases splanchnic sympathetic nerve activity (SSNA), mean arterial pressure (MAP), and heart rate (HR) in male mice. However, the downstream targets of ArcN NPY neurons are unknown. The present study tested the hypothesis that this response is mediated in part by a projection to the dorsomedial hypothalamus (DMH). The mutated excitatory muscarinic receptor (hM3Dq) was selectively expressed via bilateral injection of Cre‐recombinase‐dependent adeno‐associated virus (AAV)‐hM3Dq‐mCherry into the ArcN of AgRP‐Ires‐cre mice. After >2 wks recovery, mice were anesthetized with α‐chloralose and the otherwise inert ligand Clozapine‐N‐oxide (CNO; 0.3 mg/kg i.p.; n=5), to activate hM3Dq, or saline (sal; n=5), was injected i.p. After ~30 min, CNO decreased SSNA (−25±2 % control), MAP (−9±1 mmHg), and HR (−62±17 bpm) (P<0.01); however, sal had no effects (ΔSSNA: 3±2 % control; ΔMAP: 0±2 mmHg; and ΔHR: 11±9 bpm). Subsequent bilateral injections (30 nL) of the NPY Y1 receptor antagonist BIBO3304 (Y1x; 0.3 nmol) into the DMH of sal‐treated mice elevated (P<0.05) SSNA to 157±10 % control, MAP by 14±4 mmHg, and HR by 141±29 bpm, indicating that DMH NPY tonically inhibits SSNA. In mice given CNO, DMH Y1x increased (P<0.05) these variables (SSNA to 140±9 % control, and MAP by 14±4 mmHg and HR by 125±33 bpm above baseline) to levels similar as in sal‐treated mice given PVN Y1x, suggesting that in CNO‐treated mice Y1x is blocking the actions of both tonic and DREADDs‐induced NPY release in DMH. Next, because DREADDs can be expressed in terminal fields, in another group of AgRP‐Ires‐cre mice (n=5) that received Cre‐dependent hM3Dq into the ArcN, CNO (30 nL of 10 μM/L) was injected into the DMH. DMH CNO decreased SSNA by 23±3 % control, MAP by 11±2 mmHg, and HR by 40±9 bpm (P<0.05). Finally, a Cre‐dependent synaptically‐targeted mCherry AAV was injected into the ArcN of AgRP‐Ires‐cre mice (n=3) and the retrogradely transported indicator Cholera toxin B (CtB) was injected into the rostral ventrolateral medulla (RVLM). A modest number of CtB‐positive neurons were visible in the DMH. However, while mCherry‐labeled fibers were abundant in the DMH, these fibers only occasionally apposed CtB cell bodies, suggesting that NPY in DMH does not inhibit a population of neurons that directly innervates the RVLM. In conclusion, ArcN NPY/AgRP neurons decrease SSNA, MAP, and HR via a projection to the DMH. The downstream neuropathway remains to be determined.Support or Funding InformationNIH HL128181, AHA 12GRNT11550018 and 15POST23040042, ADA 1‐13‐BS‐120
DREADD‐Induced cFos Expression in the Basal Forebrain of Male Rats
Authors: Marciante Alexandria Beverly , Cunningham J. Thomas 
Published: November 2023

Designer Receptors Exclusively Activated by Designer Drugs, or DREADDs, are genetically modified G‐protein coupled receptors (GPCR) that are sensitive to an exogenous pharmacological agent, clozapine‐N‐oxide (CNO). DREADDs can be packaged in viral vectors with specific promoters or combined with CRE dependent platforms to express these receptors in specific neuronal phenotypes. This chemogenetic approach can be used to activate (Gq), inhibit (Gi), or stimulate cAMP (Gs) in neurons. In the present study, we tested the effects of a CRE independent Gq DREADD, using a CaM Kinase (CaMKIIa) promoter, and a mCherry reporter (rAAV5‐CaMKIIa‐hM3D(Gq)‐mCherry) on Fos staining in the basal forebrain. Adult male Sprague‐Dawley rats (250–300 g bw, Charles River) were anesthetized with isoflurane and stereotaxically injected with an AAV containing the hM3D(Gq) or a control virus (rAAV5‐CaMKIIa‐mCherry) in either the diagonal band of broca (DBB) or the median preoptic nucleus (MnPO). Animals were allowed two weeks of recovery prior to administered CNO or vehicle. CNO was dissolved into dimethylsulfoxide (DMSO) and saline (ratio 20% to 80%) and given via intraperitoneal injection (IP) at a concentration of 10mg/kg. Rats were food and water deprived for 90 minutes following the injections. Each rat was anesthetized with inactin (100 mg/kg IP) and prepared for immunohistochemistry. Forebrains were sliced into 40 um coronal sections using cryostat. The sections were processed for Fos immunohistochemistry using DAB‐peroxidase and mCherry immunofluorescence to verify cells transfected with either the DREADD or control virus. Overall, rats transfected with the Gq DREADD virus and treated with CNO showed significantly elevated Fos staining in the DBB or MnPO than groups transfected with either Gq DREADD and treated with vehicle or the control virus and treated with CNO or vehicle. Those transfected with the Gq DREADD virus in the DBB and treated with CNO, showed significantly more Fos staining than those transfected with either Gq DREADD and treated with vehicle (P<0.001) or the control virus and treated with CNO (P<0.001) or vehicle (P=0.002). The CNO did not appear to have a significant effect on Fos staining in rats injected with the control vector. Injection of Gq DREADD virus into the DBB also appears to have less of an effect on downstream targets, specifically the paraventricular nucleus (PVN) and the supraoptic nucleus (SON), than did injection of Gq DREADD virus into the MnPO. These results indicate that Gq DREADD can be used to differentially activate neurons in either the DBB or the MnPO to influence activity in downstream regions that control autonomic and neuroendocrine function.Support or Funding InformationSupported by P01 HL088052
Role of Alpha‐adrenergic Inputs to PVN in the Cardiovascular Responses to Acute Hypoxia
Authors: Beig Irfan , Mifflin Steve 
Published: November 2023

Previous studies indicate that catecholaminergic neurons in nucleus of solitary tract (NTS) contribute to intermittent hypoxia hypertension and that the hypothalamic paraventricular nucleus (PVN) plays a role in the cardiovascular response to hypoxia. The present study was designed to examine the role of alpha‐adrenergic receptors in PVN in the cardiovascular responses to acute hypoxia. Rats were anesthetized with chloralose and urethane and mean arterial pressure (MAP), heart rate (HR), renal sympathetic nerve activity (RSNA) and end tidal CO2 measured. The rat was placed in a stereotaxic frame for microinjections in PVN. After paralysis with gallamine, the rat was artificially ventilated with room air. Hypoxia was induced by ventilating the animal with 10% O2 for 30 seconds. When the parameters returned to the baseline, bilateral injections of vehicle or either α1 antagonist prazosin (500nmol) or α2 antagonist idazoxan (5nmol) were made in PVN and responses to hypoxia observed after 20 minutes. At the end of experiment brain was removed for localization of microinjection site. Hypoxia increased MAP with no change in HR or RSNA. The increase in MAP induced by systemic hypoxia was significantly blunted by bilateral administration of either prazosin (36 ± 3mmHg to 19 ± 4mmHg, n=11) or idazoxan (36 ± 2mmHg to 25 ± 5mmHg, n=10) in PVN. Changes in baseline blood pressure were not significant following prazosin (−2 ± 4mmHg) or idazoxan (0 ± 3mmHg). The results suggest that catecholaminergic inputs to PVN play a role in acute hypoxia induced increases in MAP.Support or Funding InformationSupported by PO1 HL88052