A Nuphar lutea plant active ingredient, 6,6'-dihydroxythiobinupharidine, ameliorates kidney damage and inflammation in a mouse model of chronic kidney disease.

Chronic Kidney Disease (CKD) associated complications are associated with increased inflammation through the innate immune response, which can be modulated with anti-inflammatory agents. An active ingredient derived from the Nuphar lutea aquatic plant, 6,6'-dihydroxythiobinupharidine (DTBN) has anti-inflammatory properties, mainly through the inhibition of NF-κB. We tested the effects of DTBN on mice with CKD. After preliminary safety and dosing experiments, we exposed 8 weeks old male C57BL/6J mice to adenine diet to induce CKD. Control and CKD animals were treated with IP injections of DTBN (25 µg QOD) or saline and sacrificed after 8 weeks. Serum urea and creatinine were significantly decreased in CKD-DTBN Vs CKD mice. Kidney histology showed a decrease in F4/80 positive macrophage infiltration, damaged renal area, as well as decreased kidney TGF-ß in CKD-DTBN Vs CKD mice. Kidney inflammation indices (IL-1ß, IL-6 and P-STAT3) were significantly decreased in CKD-DTBN as compared to CKD mice. DTBN treatment showed no apparent damage to tissues in control mice, besides a decrease in weight gain and mild hypoalbuminemia without proteinuria. Thus, DTBN significantly improved renal failure and inflammation indices in CKD mice. Therefore, this and similar substances may be considered as an additional treatment in CKD patients.

Beneficiary Effects of Colchicine on Inflammation and Fibrosis in a Mouse Model of Kidney Injury.

INTRODUCTION: Low-grade inflammation is seen in many chronic illnesses, including chronic kidney disease (CKD). We have recently reported on beneficiary effects of anti-inflammatory treatment in the interleukin (IL-) 1 pathway on anemia as well as CKD extent in a mouse model. Colchicine has been shown to have beneficiary effects in several inflammatory conditions through various mechanisms, including inhibition of tubulin polymerization as well as caspase-1-mediated IL-1 activation. METHODS: Kidney injury (KI) was induced by administering an adenine diet to 8-week-old C57BL/6J mice treated with colchicine (Col) (30 µg/kg) or saline injections for 3 weeks, generating 4 groups: C, Ccol, KI, and KIcol. RESULTS: KI animals had an increase in inflammation indices in the blood (neutrophils), liver, and kidneys (uromodulin, IL-6, pSTAT3). Increased kidney tubulin polymerization and caspase-1 in KI, as well as kidney Mid88 and IRAK4 (downstream of IL-1), were inhibited in KIcol. Kidney macrophage and polymorphonuclear infiltration (positive for F4/80 and MPO, respectively), the percentage of fibrotic area, and TGFß mRNA levels were lower in KIcol versus KI. CONCLUSIONS: Colchicine inhibited tubulin polymerization and caspase-1 activation and attenuated kidney inflammation and fibrosis in a mouse model of adenine-induced KI. Given its reported safety profile for long-term anti-inflammatory therapy without increasing infection tendency, it may serve as novel therapeutic approach in CKD.

Perceived reliability of medical device alarms-a major determinant of medical errors driven by frozen medical thinking.

This concept paper introduces the phenomenon of self-assigning a 'perceived reliability' value to medical device readings as a potential source of cognitive bias in medical decision-making. Medical errors can result from clinical decisions based on partial clinical data despite medical device readings providing data to the contrary. At times, this results from clinician distrust of medical device output. Consequentially, clinicians engage in a form of 'frozen thinking', a fixation on a particular thought process despite data to the contrary. Many medical devices, such as intensive care unit (ICU) monitors and alarms, lack validated statistics of device output reliability and validity. In its absence, clinicians assign a self-perceived reliability value to device output data and base clinical decisions therefrom. When the perceived reliability value is low, clinicians distrust the device and ignore device readings, especially when other clinical data are contrary. We explore the cognitive and theoretical underpinnings of this 'perceived reliability' phenomenon. The mental assignment of a perceived reliability value stems from principles of 'script theory' of medical decision-making. In this conceptual framework, clinicians make decisions by comparing current situations to mental 'scripts' of prior clinical decisions and their outcomes. As such, the clinician utilizes scripts of prior experiences to create the perceived reliability value. Self-assigned perceived reliability is subject to multiple dangers of reliability and cognitive biases. Some of these biases are presented. Among these is the danger of dismissing device readings as 'noise'. This is particularly true of ICU alarms that can emit frequent false alarms and contribute to clinician sensory overload. The cognitive dangers of this 'noise dismissal' are elaborated via its similarity to the phenomenon of 'spatial disorientation' among aviation pilots. We conclude with suggestions for reducing the potential bias of 'perceived reliability'. First presented are regulatory/legislative and industry-based interventions for increasing the study of, and end-user access to, validated device output reliability statistics. Subsequently, we propose strategies for overcoming and preventing this phenomenon. We close with suggestions for future research and development of this 'perceived reliability' phenomenon.

Growth Hormone and IGF1 Actions in Kidney Development and Function.

Growth hormone (GH) exerts multiple effects on different organs including the kidneys, either directly or via its main mediator, insulin-like-growth factor-1 (IGF-1). The GH/IGF1 system plays a key role in normal kidney development, glomerular hemodynamic regulation, as well as tubular water, sodium, phosphate, and calcium handling. Transgenic animal models demonstrated that GH excess (and not IGF1) may lead to hyperfiltration, albuminuria, and glomerulosclerosis. GH and IGF-1 play a significant role in the early development of diabetic nephropathy, as well as in compensatory kidney hypertrophy after unilateral nephrectomy. Chronic kidney disease (CKD) and its complications in children are associated with alterations in the GH/IGF1 axis, including growth retardation, related to a GH-resistant state, attributed to impaired kidney postreceptor GH-signaling and chronic inflammation. This may explain the safety of prolonged rhGH-treatment of short stature in CKD.

Small molecules for cell reprogramming: a systems biology analysis.

If somatic stem cells would be able to maintain their regenerative capacity over time, this might, to a great extent, resolve rejuvenation issues. Unfortunately, the pool of somatic stem cells is limited, and they undergo cell aging with a consequent loss of functionality. During the last decade, low molecular weight compounds that are able to induce or enhance cell reprogramming have been reported. They were named "Small Molecules" (SMs) and might present definite advantages compared to the exogenous introduction of stemness-related transcription factors (e.g. Yamanaka's factors). Here, we undertook a systemic analysis of SMs and their potential gene targets. Data mining and curation lead to the identification of 92 SMs. The SM targets fall into three major functional categories: epigenetics, cell signaling, and metabolic "switchers". All these categories appear to be required in each SM cocktail to induce cell reprogramming. Remarkably, many enriched pathways of SM targets are related to aging, longevity, and age-related diseases, thus connecting them with cell reprogramming. The network analysis indicates that SM targets are highly interconnected and form protein-protein networks of a scale-free topology. The extremely high contribution of hubs to network connectivity suggests that (i) cell reprogramming may require SM targets to act cooperatively, and (ii) their network organization might ensure robustness by resistance to random failures. All in all, further investigation of SMs and their relationship with longevity regulators will be helpful for developing optimal SM cocktails for cell reprogramming with a perspective for rejuvenation and life span extension.

Changes in energy metabolism and respiration in different tracheal narrowing in rats.

Why obstructive sleep apnea (OSA) treatment does not completely restore healthy metabolic physiology is unclear. In rats, the need for respiratory homeostasis maintenance following airway obstruction (AO) is associated with a loss of thermoregulation and abnormal metabolic physiology that persists following successful obstruction removal. Here, we explored the effect of two different types of tracheal narrowing, i.e., AO and mild airway obstruction (mAO), and its removal on respiratory homeostasis and metabolic physiology. We show that after ten weeks, mAO vs. AO consumes sufficient energy that is required to maintain respiratory homeostasis and thermoregulation. Obstruction removal was associated with largely irreversible increased feeding associated with elevated serum ghrelin, hypothalamic growth hormone secretagogue receptor 1a, and a phosphorylated Akt/Akt ratio, despite normalization of breathing and energy requirements. Our study supports the need for lifestyle eating behavior management, in addition to endocrine support, in order to attain healthy metabolic physiology in OSA patients.

Experimental modulation of Interleukin 1 shows its key role in chronic kidney disease progression and anemia.

Inflammation in chronic kidney disease (CKD) is mostly due to activation of the innate immune system, in which Interleukin-1 (IL-1) is a key player. Anemia of CKD may also be due to erythropoietin (EPO) resistance, clinically associated with inflammation. IL-1 receptor antagonist knockout (RaKO) mice show arthritis and excessive inflammation. Inhibition of IL-1 was shown to be beneficial in many inflammatory conditions, but its role in CKD and anemia is unknown. Here, we report that enhanced inflammation in RaKO mice with CKD provoked both higher degrees of renal insufficiency and anemia in comparison to wild-type CKD, in association with a downregulation of renal hypoxia inducible factor-2 (HIF2) as well as decreased bone marrow EPO-receptor (EPOR) and transferrin receptor (TFR). In contrast, administration of P2D7KK, an anti-IL1b monoclonal antibody, to CKD mice results in a lower grade of systemic inflammation, better renal function and blunted anemia. The latter was associated with upregulation of renal HIF-2α, bone marrow EPO-R and TFR. Altogether, this supports the key role of inflammation, and IL-1 particularly, in CKD progression and anemia. Novel treatments to reduce inflammation through this and other pathways, may improve renal function, attenuate the anemic state or increase the response to exogenous EPO.

SOCS2 Silencing Improves Somatic Growth without Worsening Kidney Function in CKD.

BACKGROUND: Growth hormone (GH) resistance in CKD is partly due to increased expression of SOCS2, a GH signaling negative regulator. In SOCS2 absence, body growth is exaggerated. However, GH overexpression in mice causes glomerulosclerosis. Accordingly, we tested whether lack of SOCS2 improves body growth, but accelerates kidney damage in CKD. METHODS: Eight-week-old mutant SOCS2-deficient high growth (HG) and normal wild-type mice (N) underwent 5/6 nephrectomy (CKD) or sham operation (C) and were sacrificed after 12 weeks, generating 4 groups: C-N, C-HG, CKD-N, CKD-HG. RESULTS: Somatic growth, inhibited in CKD-N, increased significantly in CKD-HG. Liver p-STAT5, a key intracellular signal of GH receptor (GHR) activation, was decreased in CKD-N but not in CKD-HG. Serum Cr as well as histopathological scores of renal fibrosis were similar in both CKD groups. Kidney fibrogenic (TGF-ß and collagen type IV mRNA) and inflammatory precursors (IL6, STAT3, and SOCS3 mRNA) were similarly increased in C-HG, CKD-HG, and CKD-N versus C-N. Renal GHR mRNA was decreased in C-HG, CKD-HG, and CKD-N versus C-N. Kidney p-STAT5 was decreased in CKD-N but not elevated in CKD-HG. CONCLUSIONS: CKD-related growth retardation is overcome by SOCS2 silencing, in association with increased hepatic STAT5 phosphorylation. Renal insufficiency is not worsened by SOCS2 absence, as kidney GHR and STAT5 are not upregulated. This may be due to elevated kidney proinflammatory cytokines and their mediators, phospho-STAT3 and SOCS3, which may counteract for the absence in SOCS2 and explain the renal safety of prolonged GH therapy in CKD.

Upper Airway Obstruction Elicited Energy Imbalance Leads to Growth Retardation that Persists after the Obstruction Removal.

Upper airway obstruction can lead to growth retardation by unclear mechanisms. We explored the effect of upper airway obstruction in juvenile rats on whole-body energy balance, growth plate metabolism, and growth. We show that after seven weeks, obstructed animals' ventilation during room air breathing increased, and animals grew less due to abnormal growth plate metabolism. Increased caloric intake in upper airway-obstructed animals did not meet increased energy expenditure associated with increased work of breathing. Decreased whole-body energy balance induced hindrance of bone elongation following obstruction removal, and array pathways regulating growth plate development and marrow adiposity. This is the first study to show that rapidly growing animals cannot consume enough calories to maintain their energy homeostasis, leading to an impediment in growth in the effort to save energy.

Irreversible metabolic abnormalities following chronic upper airway loading.

STUDY OBJECTIVES: Treatment of obstructive sleep apnea increases obesity risk by an unclear mechanism. Here, we explored the effects of upper airway obstruction and its removal on respiratory homeostasis, energy expenditure, and feeding hormones during the sleep/wake cycle from weaning to adulthood. METHODS: The tracheas of 22-day-old rats were narrowed, and obstruction removal was performed on post-surgery day 14. Energy expenditure, ventilation, and hormone-regulated feeding were analyzed during 49 days before and after obstruction. RESULTS: Energy expenditure increased and body temperature decreased in upper airway obstruction and was only partially recovered in obstruction removal despite normalization of airway resistance. Increased energy expenditure was associated with upregulation of ventilation. Decreased body temperature was associated with decreased brown adipose tissue uncoupling protein 1 level, suppressed energy expenditure response to norepinephrine, and decreased leptin level. Upper airway obstructed animals added less body weight, in spite of an increase in food intake, due to elevated hypothalamic orexin and neuropeptide Y and plasma ghrelin. Animals who underwent obstruction removal fed more due to an increase in hypothalamic neuropeptide Y and plasma ghrelin. CONCLUSIONS: The need to maintain respiratory homeostasis is associated with persistent abnormal energy metabolism and hormonal regulation of feeding. Surgical treatment per se may not be sufficient to correct energy homeostasis, and endocrine regulation of feeding may have a larger effect on weight change.

Febrile Proteinuria in Hospitalized Children: Characterization of Urinary Proteins.

Background: Transient proteinuria during febrile illness is a common phenomenon. Recent studies have re-examined the pathophysiology of proteinuria and new urinary markers to characterize it, including B7-1 (CD80), which is expressed also in glomerular podocytes and influences the glomerular barrier. Aim: To investigate the pattern of proteinuria in febrile non-renal diseases, including B7-1. Methods: We prospectively analyzed urine samples of 44 febrile children and 28 afebrile controls for different protein components: albumin (glomerular marker), ß2-microglobulin (tubular marker), uromodulin (Tamm Horsfall protein-THP, a renal endogenous protein) and B7-1. Febrile illness was characterized as focal bacterial vs. viral. Exclusion criteria were underlying renal disease, steroid treatment or urinary tract infection. Results: Elevated urine albumin (64.5 ± 10.3 vs. 17.8 ± 4 mg/g, mean ± S.E.M., p = 0.0009) and ß2-microglobulin (1.44 ± 0.34 vs. 0.182 ± 0.03 mg/g, mean ± S.E.M., p = 0.005] and decreased uromodulin (10.5 ± 1 vs. 26.7 ± 2.2 Arbitrary units, mean ± S.E.M., p = 0.0001) excretion were found during febrile illness vs. controls. Urine B7-1 was also increased in the febrile group (0.27 ± 0.05 vs. 0.07 ± 0.01 ng/ml, mean ± S.E.M., p = 0.001), and was the only marker which was significantly higher in bacterial vs. viral disease. Conclusions: Febrile proteinuria is not generalized: while proteins of both glomerular and tubular origin increase, uromodulin decreases. Urine B7-1 is increased during fever, more significantly in bacterial infections. Thus, urinary B7-1 may be used as an additional marker to differentiate between febrile states of bacterial vs. viral origin.

Abnormal Growth and Feeding Behavior in Upper Airway Obstruction in Rats.

Pediatric obstructive sleep apnea (OSA) is a syndrome manifesting with snoring and increased respiratory effort due to increased upper airway resistance. In addition to cause the abnormal sleep, this syndrome has been shown to elicit either growth retardation or metabolic syndrome and obesity. Treating OSA by adenotonsillectomy is usually associated with increased risk for obesity, despite near complete restoration of breathing and sleep. However, the underlying mechanism linking upper airways obstruction (AO) to persistent change in food intake, metabolism, and growth remains unclear. Rodent models have examined the impact of intermittent hypoxia on metabolism. However, an additional defining feature of OSA that is not related to intermittent hypoxia is enhanced respiratory loading leading to increased respiratory effort and abnormal sleep. The focus of this mini review is on recent evidence indicating the persistent abnormalities in endocrine regulation of feeding and growth that are not fully restored by the chronic upper AO removal in rats. Here, we highlight important aspects related to abnormal regulation of metabolism that are not related to intermittent hypoxia per se, in an animal model that mimics many of the clinical features of pediatric OSA. Our evidence from the AO model indicates that obstruction removal may not be sufficient to prevent the post-removal tendency for abnormal growth.

The hypoxia inducible factor/erythropoietin (EPO)/EPO receptor pathway is disturbed in a rat model of chronic kidney disease related anemia.

OBJECTIVES: Anemia is a known driver for hypoxia inducible factor (HIF) which leads to increased renal erythropoietin (EPO) synthesis. Bone marrow (BM) EPO receptor (EPOR) signals are transduced through a JAK2-STAT5 pathway. The origins of anemia of chronic kidney disease (CKD) are multifactorial, including impairment of both renal EPO synthesis as well as intestinal iron absorption. We investigated the HIF- EPO- EPOR axis in kidney, BM and proximal tibia in anemic juvenile CKD rats. METHODS: CKD was induced by 5/6 nephrectomy in young (20 days old) male Sprague-Dawley rats while C group was sham operated. Rats were sacrificed 4 weeks after CKD induction and 5 minutes after a single bolus of IV recombinant human EPO. An additional control anemic (C-A) group was daily bled for 7 days. RESULTS: Hemoglobin levels were similarly reduced in CKD and C-A (11.4 ± 0.3 and 10.8±0.2 Vs 13.5±0.3 g/dL in C, p<0.0001). Liver hepcidin mRNA was decreased in CA but increased in CKD. Serum iron was unchanged while transferrin levels were mildly decreased in CKD. Kidney HIF2α protein was elevated in C-A but unchanged in CKD. Kidney EPO protein and mRNA levels were unchanged between groups. However, BM EPO protein (which reflects circulating EPO) was increased in C-A but remained unchanged in CKD. BM and proximal tibia EPOR were unchanged in C-A but decreased in CKD. Proximal tibial phospho-STAT5 increased after the EPO bolus in C but not in CKD. CONCLUSIONS: Compared to blood loss, anemia in young CKD rats is associated with inappropriate responses in the HIF-EPO-EPO-R axis: kidney HIF2α and renal EPO are not increased, BM and bone EPOR levels, as well as bone pSTAT5 response to EPO are reduced. Thus, anemia of CKD may be treated with additional therapeutic avenues beyond iron and EPO supplementation.

Confined water dynamics in a hydrated photosynthetic pigment-protein complex.

Water is of fundamental importance for life. It plays a critical role in all biological systems. In phycocyanin, a pigment-protein complex, the hydration level influences its absorption spectrum. However, there is currently a gap in the understanding of how protein interfaces affect water's structure and properties. This work presents combined dielectric and calorimetric measurements of hydrated phycocyanin with different levels of hydration in a broad temperature interval. Based on the dielectric and calorimetric tests, it was shown that two types of water exist in the phycocyanin hydration shell. One is confined water localized inside the phycocyanin ring and the second is the water that is embedded in the protein structure and participates in the protein solvation. The water confined in the phycocyanin ring melts at the temperature 195 ± 3 K and plays a role in the solvation at higher temperatures. Moreover, the dynamics of all types of water was found to be effected by the presence of the ionic buffer.

Abnormal Growth and Feeding Behavior Persist After Removal of Upper Airway Obstruction in Juvenile Rats.

Pediatric obstructive sleep-disordered breathing is associated with growth retardation, but also with obesity that has a tendency to persist following treatment. We investigated the effect of upper airways obstruction (AO) and of obstruction removal (OR) in juvenile rats on gut-derived ghrelin and related hypothalamic factors, feeding, and growth hormone (GH) homeostasis. Here, we show that after seven weeks of AO, animals gained less weight compared to controls, despite an increase in food intake due to elevated ghrelin and hypothalamic feeding factors. OR rats who had complete restoration of tracheal diameter, consumed more food due to increased ghrelin and exhibited growth retardation due to deregulation of GH homeostasis. This study is the first to show dysregulation of the hormonal axes controlling feeding behavior and growth that are not fully restored following OR. Thus, surgical treatment by itself may not be sufficient to prevent post-surgical increased food intake and growth retardation.

Orexin Plays a Role in Growth Impediment Induced by Obstructive Sleep Breathing in Rats.

STUDY OBJECTIVES: The mechanisms linking sleep disordered breathing with impairment of sleep and bone metabolism/architecture are poorly understood. Here, we explored the role of the neuropeptide orexin, a respiratory homeostasis modulator, in growth retardation induced in an upper airway obstructed (AO) rat model. METHODS: The tracheae of 22-day-old rats were narrowed; AO and sham-control animals were monitored for 5 to 7 w. Growth parameters, food intake, sleep/wake activity, and serum hormones were measured. After euthanasia, growth plate (GP) histology, morphometry, orexin receptors (OXR), and related mediators were analyzed. The effect of dual orexin receptor antagonist (almorexant 300 mg/kg) on sleep and GP histology were also investigated. RESULTS: The AO group slept 32% less; the time spent in slow wave and paradoxical sleep during light period and slow wave activity was reduced. The AO group gained 46% less body weight compared to the control group, despite elevated food intake; plasma ghrelin increased by 275% and leptin level decreased by 44%. The impediment of bone elongation and bone mass was followed by a 200% increase in OX1R and 38% reduction of local GP ghrelin proteins and growth hormone secretagogue receptor 1a. Sry-related transcription factor nine (Sox9), a molecule mediating cartilage ossification, was downregulated and the level of transcription factor peroxisome proliferator-activated receptor gamma was upregulated, explaining the bone architecture abnormalities. Administration of almorexant restored sleep and improved GP width in AO animals. CONCLUSIONS: In AO animals, enhanced expression of orexin and OX1R plays a role in respiratory induced sleep and growth abnormalities.

Endurance exercise and growth hormone improve bone formation in young and growth-retarded chronic kidney disease rats.

BACKGROUND: Childhood chronic kidney disease (CKD) is associated with both short stature and abnormal bone mineralization. Normal longitudinal growth depends on proper maturation of epiphyseal growth plate (EGP) chondrocytes, leading to the formation of trabecular bone in the primary ossification centre. We have recently shown that linear growth impairment in CKD is associated with impaired EGP growth hormone (GH) receptor signalling and that exercise improved insulin-like growth factor I (IGF-I) signalling in CKD-related muscle atrophy. METHODS: In this study, 20-day-old rats underwent 5/6 nephrectomy (CKD) or sham surgery (C) and were exercised with treadmill, with or without GH supplementation. RESULTS: CKD-related growth retardation was associated with a widened EGP hypertrophic zone. This was not fully corrected by exercise (except for tibial length). Exercise in CKD improved the expression of EGP key factors of endochondral ossification such as IGF-I, vascular endothelial growth factor (VEGF), receptor activator of nuclear factor kappa-B ligand (RANKL) and osteocalcin. Combining GH treatment with treadmill exercise for 2 weeks improved the decreased trabecular bone volume in CKD, as well as the expression of growth plate runt-related transcription factor 2, RANKL, metalloproteinase 13 and VEGF, while GH treatment alone could not do that. CONCLUSIONS: Treadmill exercise improves tibial bone linear growth, as well as growth plate local IGF-I. When combined with GH treatment, running exercise shows beneficial effects on trabecular bone formation, suggesting the potential benefit of this combination for CKD-related short stature and bone disease.

Sleep/Wake Dynamics Changes during Maturation in Rats.

OBJECTIVES: Conventional scoring of sleep provides little information about the process of transitioning between vigilance states. We applied the state space technique (SST) using frequency band ratios to follow normal maturation of different sleep/wake states, velocities of movements, and transitions between states of juvenile (postnatal day 34, P34) and young adult rats (P71). DESIGN: 24-h sleep recordings of eight P34 and nine P71 were analyzed using conventional scoring criteria and SST one week following implantation of telemetric transmitter. SST is a non-categorical approach that allows novel quantitative and unbiased examination of vigilance-states dynamics and state transitions. In this approach, behavioral changes are described in a 2-dimensional state space that is derived from spectral characteristics of the electroencephalography. MEASUREMENTS AND RESULTS: With maturation sleep intensity declines, the duration of deep slow wave sleep (DSWS) and light slow wave sleep (LSWS) decreases and increases, respectively. Vigilance state determination, as a function of frequency, is not constant; there is a substantial shift to higher ratio 1 in all vigilance states except DSWS. Deep slow wave sleep decreases in adult relative to juvenile animals at all frequencies. P71 animals have 400% more trajectories from Wake to LSWS (p = 0.005) and vice versa (p = 0.005), and 100% more micro-arousals (p = 0.021), while trajectories from LSWS to DSWS (p = 0.047) and vice versa (p = 0.033) were reduced by 60%. In both juvenile and adult animals, no significant changes were found in sleep velocity at all regions of the 2-dimensional state space plot; suggesting that maturation has a partial effect on sleep stability. CONCLUSIONS: Here, we present novel and original evidence that SST enables visualization of vigilance-state intensity, transitions, and velocities that were not evident by traditional scoring methods. These observations provide new perspectives in sleep state dynamics and highlight the usefulness of this technique in exploring the development of sleep-wake activity.

Chronic upper airway obstruction induces abnormal sleep/wake dynamics in juvenile rats.

OBJECTIVES: Conventional scoring of sleep provides little information about the process of transitioning between vigilance-states. We used the state space technique to explore whether rats with chronic upper airway obstruction (UAO) have abnormal sleep/wake states, faster movements between states, or abnormal transitions between states. DESIGN: The tracheae of 22-day-old Sprague-Dawley rats were surgically narrowed to increase upper airway resistance with no evidence for frank obstructed apneas or hypopneas; 24-h electroencephalography of sleep/wake recordings of UAO and sham-control animals was analyzed using state space technique. This non-categorical approach allows quantitative and unbiased examination of vigilance-states and state transitions. Measurements were performed 2 weeks post-surgery at baseline and following administration of ritanserin (5-HT2 receptor antagonist) the next day to stimulate sleep. MEASUREMENTS AND RESULTS: UAO rats spent less time in deep (delta-rich) slow wave sleep (SWS) and near transition zones between states. State transitions from light SWS to wake and vice versa and microarousals were more frequent and rapid in UAO rats, indicating that obstructed animals have more regions where vigilance-states are unstable. Ritanserin consolidated sleep in both groups by decreasing the number of microarousals and trajectories between wake and light SWS, and increasing deep SWS in UAO. CONCLUSIONS: State space technique enables visualization of vigilance-state transitions and velocities that were not evident by traditional scoring methods. This analysis provides new quantitative assessment of abnormal vigilance-state dynamics in UAO in the absence of frank obstructed apneas or hypopneas.

Role of orexin in respiratory and sleep homeostasis during upper airway obstruction in rats.

STUDY OBJECTIVES: Chronic upper airway obstruction (UAO) elicits a cascade of complex endocrine derangements that affect growth, sleep, and energy metabolism. We hypothesized that elevated hypothalamic orexin has a role in maintaining ventilation during UAO, while at the same time altering sleep-wake activity and energy metabolism. Here, we sought to explore the UAO-induced changes in hypothalamic orexin and their role in sleep-wake balance, respiratory activity, and energy metabolism. INTERVENTIONS: The tracheae of 22-day-old Sprague-Dawley rats were surgically narrowed; UAO and sham-operated control animals were monitored for 7 weeks. We measured food intake, body weight, temperature, locomotion, and sleep-wake activity. Magnetic resonance imaging was used to quantify subcutaneous and visceral fat tissue volumes. In week 7, the rats were sacrificed and levels of hypothalamic orexin, serum leptin, and corticosterone were determined. The effect of dual orexin receptor antagonist (almorexant 300 mg/kg) on sleep and respiration was also explored. MEASUREMENTS AND RESULTS: UAO increased hypothalamic orexin mRNA and protein content by 64% and 65%, respectively. UAO led to 30% chronic sleep loss, excessive active phase sleepiness, decreased body temperature, increased food intake, reduction of abdominal and subcutaneous fat tissue volume, and growth retardation. Administration of almorexant normalized sleep but induced severe breathing difficulties in UAO rats, while it had no effect on sleep or on breathing of control animals. CONCLUSIONS: In upper airway obstruction animals, enhanced orexin secretion, while crucially important for respiratory homeostasis maintenance, is also responsible for chronic partial sleep loss, as well as considerable impairment of energy metabolism and growth.