Anti-fibronectin aptamers improve the colonization of chitosan films modified with D-(+) Raffinose by murine osteoblastic cells

The aim of the present study was to investigate how the enrichment of chitosan films with anti-fibronectin aptamers could enhance scaffold colonization by osteoblasts, by improving their adhesion and accelerating their proliferation. Chitosan discs were enriched with excess of anti-fibronectin aptamer. Aptamer adsorption on chitosan was monitored by measuring aptamer concentration in the supernatant by spectrophotometry, as well as its release, while functionalization was confirmed by labelling aptamers with a DNA intercalating dye. Chitosan samples were then characterized morphologically with atomic force microscopy and physically with contact angle measurement. Chitosan enrichment with fibronectin was then investigated by immunofluorescence and Bradford assay. 2% chitosan discs were then enriched with increasing doses of aptamers and used as culture substrates for MC3T3-E1 cells. Cell growth was monitored by optical microscopy, while cell viability and metabolic activity were assessed by chemiluminescence and by Resazurin Sodium Salt assay. Cell morphology was investigated by cytofluorescence and by scanning electron microscopy. Chitosan films efficiently bound and retained aptamers. Aptamers did not affect the amount of adsorbed fibronectin, but affected osteoblasts behavior. Cell growth was proportional to the amount of aptamer used for the functionalization, as well as aptamers influenced cell morphology and their adhesion to the substrate. Our results demonstrate that the enrichment of chitosan films with aptamers could selectively improve osteoblasts behavior. Furthermore, our results support further investigation of this type of functionalization as a suitable modification to ameliorate the biocompatibility of biomaterial for hard tissue engineering applications.

miR-146a, miR-155, miR-370, and miR-708 Are CFTR-Dependent, Predicted FOXO1 Regulators and Change at Onset of CFRDs

CONTEXT

Cystic fibrosis-related diabetes (CFRD) is the most frequent and severe co-morbidity in cystic fibrosis (CF). Presentation and severity are quite variable.

OBJECTIVE

To investigate changes in microRNAs (miRNAs) due to CF transmembrane conductance regulator malfunctioning in vitro, to study the circulating levels of selected miRNAs in serum samples from patients, and to assess their relationships in different age groups with genotype, glucose tolerance state, and at onset of CFRD. Design/Setting/Patients/Interventions: Transcriptional profiling of all known miRNAs in CFBE41o- cells, in their normal counterparts (16HBE14o- cells), and in IB3 cells was performed. A set of miRNAs was differentially expressed in the CF cells. By in silico analysis, four miRNAs (miR-146a, miR-155, miR-370, and miR-708) were selected as potential regulators of the FOXO1 gene. Seventy-four CF patients and 50 healthy subjects whose glucose tolerance was characterized by an oral glucose tolerance test were enrolled in the study, and the identified miRNAs were quantified in serum by quantitative RT-PCR. Main Outcome Measurements/Results: A total of 111 miRNAs were differentially expressed in the two CF cell lines. miR-155, miR-370, and miR-708 were up-regulated and miR-146a was down-regulated in vitro, whereas in vivo, miR-146a, miR-155, and miR-370 were up-regulated, and miR-708 was down-regulated. These changes showed relationships with genotype, glucose tolerance state, and onset of CFRD.

CONCLUSIONS

The data showed significant changes in miRNAs dependent on genotype and glucose tolerance state in CF patients and highlighted some miRNAs of importance in CFRD at onset. miRNAs could explain some of the variability observed in CF.

Improved scaffold biocompatibility through anti-Fibronectin aptamer functionalization

Protein adsorption is the first and decisive step to define cell-biomaterial interaction. Guiding the adsorption of desired protein species may represent a viable approach to promote cell activities conducive to tissue regeneration. The aim of the present study was to investigate whether immobilized anti-Fibronectin aptamers could promote the attachment and growth of osteoblastic cells. Polyethyleneglycole diacrylate/thiolated Hyaluronic Acid hydrogels (PEGDA/tHA) were coated with anti-Fibronectin aptamers. Hydrogel loading and Fibronectin bonding were investigated, through spectrophotometry and Bradford assay. Subsequently, human osteoblasts (hOBs) were cultured on hydrogels for 10days in 2D and 3D cultures. Cells were monitored through microscopy and stained for focal adhesions, microfilaments and nuclei using fluorescence microscopy. Samples were also included in paraffin and stained with Hematoxylin-Eosin. Cell number on hydrogels was quantitated over time. Cell migration into the hydrogels was also studied through Calcein AM staining. Aptamers increased the number of adherent hOBs and their cytoplasm appeared more spread and richer in adhesion complexes than on control hydrogels. Viability assays confirmed that significantly more cells were present on hydrogels in the presence of aptamers, already after 48h of culture. When hOBs were encapsulated into hydrogels, cells were more numerous on aptamer-containing PEGDA-tHA. Cells migrated deeper in the gel in the presence of DNA aptamers, appearing on different focus planes. Our data demonstrate that anti-Fibronectin aptamers promote scaffold enrichment for this protein, thus improving cell adhesion and scaffold colonization.

STATEMENT OF SIGNIFICANCE

We believe aptamer coating of biomaterials is a useful and viable approach to improve the performance of scaffold materials for both research and possibly clinical purposes, because different medical devices could be envisaged able to capture bioactive mediators from the patients' blood and concentrate them where they are needed, on the biomaterial itself. At the same time, this technology could be used to confer 3D cell culture scaffold with the ability to store proteins, such as Fibronectin, taking it from the medium and capture what is produced by cells. This is an improvement of traditional biomaterials that can be enriched with exogenous molecules but are not able to selectively capture a desired molecule.

Comparison of Environmental Scanning Electron Microscopy in Low Vacuum or wet mode for the investigation of cell biomaterial interactions

AIM

The aim of the present study was to investigate the efficacy of environmental scanning electron microscopy (ESEM), in low vacuum mode (LV-ESEM) and in wet mode (wet-ESEM) in the assessment of cell-material interactions.

METHODS

Mouse calvaria MC3T3 cells (ATCC) were seeded on commercially pure machined titanium discs of 10 mm diameter in Dulbecco modified MEM, 10% Fetal Bovine Serum, 1% Penicillin and Streptomycin and 1% Glutamine. Samples were then processed for microscope observation by rinse in Phosphate Buffer saline and fixation in 4.5% Glutaraldehyde. Samples were then rinsed in Sodium Cacodylate buffer and observed or dehydrated in alcohol prior to LV-ESEM observation. Fresh samples in 0.9% NaCl solution were observed in wet- ESEM.

RESULTS

No significant loss of detail was observed when dehydrated or non dehydrated samples were analysed at LV-ESEM.The observation of fresh samples in wet-ESEM however proved difficult for the need to eliminate water which forms a layer covering the sample, thus hiding cell surface details. When reducing the vapor pressure in the chamber, the layer evaporated and NaCl immediately started to precipitate and cells collapsed, thus no further investigation was possible.

CONCLUSIONS

The use of low vacuum-ESEM after cell fixation, but without dehydration or gold sputter coating proved a viable alternative to traditional high vacuum SEM observation.

HMGB1 Is Increased by CFTR Loss of Function, Is Lowered by Insulin, and Increases In Vivo at Onset of CFRD

CONTEXT

Cystic fibrosis-related diabetes (CFRD) is associated with worsening of inflammation and infections, and the beginning of insulin treatment is debated.

OBJECTIVES

To verify high-mobility group box 1 protein (HMGB1) levels in CF patients according to glucose tolerance state, and analyze relationships with insulin secretion and resistance. To verify, in an in vitro model, whether HMGB1 gene expression and protein content were affected by insulin administration and whether these changes were dependent on CF transmembrane conductance regulator (CFTR) loss of function.

PATIENTS AND METHODS

Forty-three patients in stable clinical conditions and 35 age- and sex-matched controls were enrolled. Glucose tolerance was established in patients based on a 5 point oral glucose tolerance test (OGTT). Fasting glucose to insulin ratio (FGIR), HOMA-IR index, whole-body insulin sensitivity index (WIBISI), and the areas under the curve for glucose (AUCG) and insulin (AUCI) were calculated. HMGB1 was assayed in serum, in cell lysates and conditioned media using a specific ELISA kit. For the in vitro study we used CFBE41o- cells, homozygous for the F508del mutation, and 16HBE14o- as non-CF control. HMGB1 gene expression was studied by real-time RT-PCR. Cells were stimulated with insulin at 2.5 and 5 ng/mL. The CFTR inhibitor 172 and CFTR gene silencing were used to induce CFTR loss of function in 16HBE14o- cells.

RESULTS

HMGB1 levels were increased at onset of CFRD (5.04 ± 1.2 vs 2.7 ± 0.3 ng/mL in controls; P < .05) and correlated with FGIR (R = +0.43; P = .038), and AUCI (R = +0.43; P = .013). CFTR loss of function in the 16HBE14o- cells increased HMGB1 and was lowered by insulin.

CONCLUSION

HMGB1 was increased in CF patients with deranging glucose metabolism and showed relationships with indexes of glucose metabolism. The increase in HMGB1 was related to CFTR loss of function, and insulin lowered HMGB1. Further research is required to verify whether HMGB1 could potentially be a candidate marker of onset of CFRD and to establish when to start insulin treatment.

Di-(2-ethylhexyl) phthalate metabolites in urine show age-related changes and associations with adiposity and parameters of insulin sensitivity in childhood

OBJECTIVES

Phthalates might be implicated with obesity and insulin sensitivity. We evaluated the levels of primary and secondary metabolites of Di-(2-ethylhexyl) phthalate (DEHP) in urine in obese and normal-weight subjects both before and during puberty, and investigated their relationships with auxological parameters and indexes of insulin sensitivity.

DESIGN AND METHODS

DEHP metabolites (MEHP, 6-OH-MEHP, 5-oxo-MEHP, 5-OH-MEHP, and 5-CX-MEHP), were measured in urine by RP-HPLC-ESI-MS. Traditional statistical analysis and a data mining analysis using the Auto-CM analysis were able to offer an insight into the complex biological connections between the studied variables.

RESULTS

The data showed changes in DEHP metabolites in urine related with obesity, puberty, and presence of insulin resistance. Changes in urine metabolites were related with age, height and weight, waist circumference and waist to height ratio, thus to fat distribution. In addition, clear relationships in both obese and normal-weight subjects were detected among MEHP, its products of oxidation and measurements of insulin sensitivity.

CONCLUSION

It remains to be elucidated whether exposure to phthalates per se is actually the risk factor or if the ability of the body to metabolize phthalates is actually the key point. Further studies that span from conception to elderly subjects besides further understanding of DEHP metabolism are warranted to clarify these aspects.

FOXO1 content is reduced in cystic fibrosis and increases with IGF-I treatment

Cystic fibrosis-related diabetes is to date the most frequent complication in cystic fibrosis (CF). The mechanisms underlying this condition are not well understood, and a possible role of insulin resistance is debated. We investigated insulin signal transduction in CF. Total insulin receptor, IRS1, p85 PI3K, and AKT contents were substantially normal in CF cells (CFBE41o-), whereas winged helix forkhead (FOX)O1 contents were reduced both in baseline conditions and after insulin stimulation. In addition, CF cells showed increased ERK1/2, and reduced β2 arrestin contents. No significant change in SOCS2 was observed. By using a CFTR inhibitor and siRNA, changes in FOXO1 were related to CFTR loss of function. In a CF-affected mouse model, FOXO1 content was reduced in the muscle while no significant difference was observed in liver and adipose tissue compared with wild-type. Insulin-like growth factor 1 (IGF-I) increased FOXO1 content in vitro and in vivo in muscle and adipose tissue. In conclusion; we present the first description of reduced FOXO1 content in CF, which is compatible with reduced gluconeogenesis and increased adipogenesis, both features of insulin insensitivity. IGF-I treatment was effective in increasing FOXO1, thereby suggesting that it could be considered as a potential treatment in CF patients possibly to prevent and treat cystic fibrosis-related diabetes.

Artificial Neural Networks, and Evolutionary Algorithms as a systems biology approach to a data-base on fetal growth restriction

One of the specific aims of systems biology is to model and discover properties of cells, tissues and organisms functioning. A systems biology approach was undertaken to investigate possibly the entire system of intra-uterine growth we had available, to assess the variables of interest, discriminate those which were effectively related with appropriate or restricted intrauterine growth, and achieve an understanding of the systems in these two conditions. The Artificial Adaptive Systems, which include Artificial Neural Networks and Evolutionary Algorithms lead us to the first analyses. These analyses identified the importance of the biochemical variables IL-6, IGF-II and IGFBP-2 protein concentrations in placental lysates, and offered a new insight into placental markers of fetal growth within the IGF and cytokine systems, confirmed they had relationships and offered a critical assessment of studies previously performed.

Interactions among pro-inflammatory cytokines, IGF system and thyroid function in pre-pubertal obese subjects

Obesity is a state of chronic inflammation. Data on IGF system are often discrepant, and their relationships with mediators of inflammation are unknown. Furthermore, changes in thyroid function have been reported. We aimed at investigating the changes in these systems, and verify any relationships among cytokines, IGF system, thyroid function and insulin-insensitivity. Fifty obese pre-pubertal children, and 55 normal-weight subjects comparable for age and sex were enrolled. Serum IGF-I, IGF-II, IGFBP-1, IGFBP-2, IGFBP-3, IL-6 and TNF-alpha were assayed. In obese children insulin, TSH and FT4 were measured also, and the HOMA-IR index was calculated. Increased IGF-II, IL-6 and TNF-alpha, and decreased IGFBP-1 and IGFBP-2 concentrations were found in obese compared to normal-weight children. The IGF-I/IGFBP-3 molar ratio was also reduced in the obese subjects. In the obese children with high HOMA-IR index, IGFBP-1 and -2 serum concentrations were significantly decreased compared with those with normal insulin sensitivity, and in the obese subjects with increased TSH, IGFBP-2 concentrations were lower, and IGFBP-3 levels were higher compared to their counterparts with normal TSH levels. Among the significant correlations, BMISDS was correlated with IGF-II, and TSH. IGF-II concentrations showed a positive relationship with IL-6. TSH was correlated with IGFBP-2 also. The data showed interactions among IL-6, IGF system, insulin sensitivity, and thyroid function with changes being related to the degree of obesity. Chronic inflammation in obese children was confirmed. Some of the changes in the IGF system could be a consequence of insulin resistance and could account also for later complications in obese subjects.

Placental cortisol and cord serum IGFBP-2 concentrations are important determinants of postnatal weight gain

There is a need to identify simple biochemical markers at birth that may predict subjects at risk of growth failure and metabolic complications in later life. Limited research to date has been performed on relationships of specific biochemical determinants at birth with postnatal weight gain and growth. We proposed to establish whether placental cortisol and IL-6 concentrations and cord serum IGF-II and IGFBP-2 concentrations influenced postnatal growth. We followed up from pregnancy 23 IUGR and 37 AGA subjects, and determined placental cortisol and IL-6 concentrations, and cord serum IGF-II, and IGFBP-2 concentrations at birth. We obtained height and weight measurements at 3, 6, 12, 24 months and 5 years of age in 20 IUGR and 15 AGA subjects of comparable gestational age. A multiple linear regression model was designed to establish the effect of the placental and cord serum peptides on postnatal linear growth and weight gain. All IUGR subjects had catch-up growth before 2 years of age. Placental cortisol concentration correlated positively with weight gain during the first 5 years of postnatal growth (P<0.05). Subjects with the highest placental cortisol concentrations were those who showed a greater increase in weight. Cord serum IGFBP-2 concentrations correlated positively with weight gain throughout the 5 year observation period (P:0.003). The subjects with the highest concentrations showed a greater weight gain. Placental cortisol and cord serum IGFBP-2 concentrations were related to postnatal weight gain, suggesting that the fetal environment has long-term effects on growth.

Association of placental insulin, total and activated insulin receptor contents, cortisol and IL-6 concentrations with human birth weight and length: pilot study

We followed-up, from pregnancy to birth, a group of newborns both IUGR and AGA and we aimed at establishing placental biochemical determinants of birth weight and length. Insulin, total and activated insulin receptor contents (IR), cortisol and IL-6 placental concentrations were assayed in 23 IUGR and 37 AGA subjects at birth, and a multiple regression model was designed and applied to assess the significant biochemical determinants of birth size. IL-6 and activated insulin receptor content were significantly increased in IUGR, whereas insulin, total insulin receptor content, and cortisol placental concentrations were similar in IUGR and AGA. Placental cortisol concentration was found to be significantly and negatively related with both birth length (0.778, P<0.001) and weight (0.508, P<0.008). A negative effect of IL-6 placental concentration was found on birth length (P<0.002). For the first time we provide evidence of a negative association of placental cortisol and IL-6 concentrations on birth size.

Optoelectronic reservoir computing

Reservoir computing is a recently introduced, highly efficient bio-inspired approach for processing time dependent data. The basic scheme of reservoir computing consists of a non linear recurrent dynamical system coupled to a single input layer and a single output layer. Within these constraints many implementations are possible. Here we report an optoelectronic implementation of reservoir computing based on a recently proposed architecture consisting of a single non linear node and a delay line. Our implementation is sufficiently fast for real time information processing. We illustrate its performance on tasks of practical importance such as nonlinear channel equalization and speech recognition, and obtain results comparable to state of the art digital implementations.

Effects of cord serum insulin, IGF-II, IGFBP-2, IL-6 and cortisol concentrations on human birth weight and length: pilot study

BACKGROUND

The IGF system is recognised to be important for fetal growth. We previously described increased Insulin-like growth factor binding protein (IGFBP)-2 cord serum concentrations in intra-uterine growth retardation (IUGR) compared with appropriate for gestational age (AGA) newborns, and a positive relationship of IGFBP-2 with Interleukin (IL)-6. The role of cortisol in the fetus at birth is largely unknown, and interactions among peptides are their real effect on birth size is unknown. Furthermore, almost all studies have previously assayed peptides in serum several years after birth, and follow-up data from pregnancy are always lacking. This study aimed at establishing and clarifying the effect of cord serum insulin, IGF-II, IGFBP-2, cortisol and IL-6 concentrations on birth length and weight.

METHODS

23 IUGR and 37 AGA subjects were followed up from the beginning of pregnancy, and were of comparable gestational age. Insulin, IGF-II, IGFBP-2, cortisol and IL-6 concentrations were assayed in cord serum at birth, and a multiple regression model was designed and applied to assess which were the significant biochemical determinants of birth size.

RESULTS

Insulin, cortisol, and IL-6, showed similar concentrations in IUGR and AGA as previously described, whereas IGF-II was lower, and IGFBP-2 increased in IUGR compared with AGA. IGF-II serum concentration was found to have a significant positive effect on both birth length (r:(:)0.546; p: 0.001) and weight (r:0.679; p: 0.0001). IGFBP-2 had a near significant negative effect on both birth weight (r:-0.342; p: 0.05) and length (r:-0.372; p:0.03).

CONCLUSION

IGF-II cord serum concentration was shown to have a significant positive effect on both birth length and weight, whereas IGFBP-2 had a significant negative effect. Insulin, cortisol, and IL-6 cord serum concentrations had no significant effect on birth size.

Impairment of insulin receptor signal transduction in placentas of intra-uterine growth-restricted newborns and its relationship with fetal growth

OBJECTIVE

Intra-uterine growth restriction (IUGR) is related to a higher incidence of type 2 diabetes mellitus. We previously reported reduced adiponectin and increased interleukin 6 (IL6) concentrations in IUGR placentas, which are features of insulin resistance. We aimed to investigate placental insulin receptor (IR) function and activation in human placenta and subsequently the relationships of insulin signalling peptides with placental protein content in IL6, insulin, resistin and adiponectin, and with parameters of fetal growth.

DESIGN AND METHODS

Whole villous tissue was collected from 18 IUGR and 24 appropriate for gestational age (AGA) placentas of comparable gestational age. Insulin signalling peptides, suppressors of cytokine signalling-2 (SOCS2), insulin, adiponectin, resistin, and IL6 concentrations were determined by using western immunoblotting or specific research kits.

RESULTS

The amount of total IR was similar in both groups but activated IR significantly higher in IUGR. Total IR substrate-1 (IRS1) was increased in IUGR, whereas total IRS2 and activated IRS1 were similar. AKT content was reduced and activated AKT was undetectable in IUGR placentas. c-Jun N-terminal kinase content was reduced in IUGR. Total and activated ERK1/2 was similar in IUGR and AGA groups, and total SOCS2 was increased in IUGR. IL6 lysate concentrations correlated with AKT content and activated IR. Correlations were found also with adiponectin and resistin. SOCS2 correlated negatively with all growth parameters at birth.

CONCLUSIONS

IR was more activated in placentas of IUGR compared with AGA; however, signal transduction downstream of the receptor was impaired. The increase in activated IR could be in favour of a compensatory mechanism to increase insulin sensitivity. Close relationships of insulin action in placenta with fetal growth were shown.

Doping-induced conductivity transitions in molecular layers of polyaniline: detailed structural study

We report detailed structural investigations, by synchrotron X-ray reflectivity (XRR), grazing incidence diffraction (GID), and space-resolved grazing incidence X-ray-induced fluorescence (GIXF), on the structure of molecular layers of polyaniline (PANI) that can be converted from insulating to conducting state simply by doping. We first address the simpler, but more intriguing, system, i.e., a floating monolayer of PANI on different subphases, for which we found a typical thickness of 28(1) A, not much affected by the doping process. For the doped film we also found an internal lateral structure, with in-plane spacing of 3.5 A-albeit with a small coherence of 3-4 repeat units only-compatible with face-to-face interchain stacking of phenyl rings, in agreement with the literature. By GIXF we could confirm the crucial role of Cl(-) intercalation in the doping process of the PANI film: under doping conditions (0.1 M HCl subphase) the Cl(-) intake is 8 times larger than in nondoping conditions (0.1 M KCl subphase). Multilayers transferred onto solid substrate were studied also as a function of the applied voltage, as this system constitutes the core of an electrochemically controlled device whose strongly nonlinear characteristic make it useful for applications to adaptive networks for complex information processing. By the application of an electrostatic field of 140 V/m, Cl ionic migration was observed confined to the polymeric film surface.

Cyclic alternating pattern sequences and non-cyclic alternating pattern periods in human sleep

OBJECTIVE

The CAP cycle is a module of activation (phase A) and inhibition (phase B) which repeats itself in sequences. The study aims at testing the hypothesis that the duration of CAP sequences is determined primarily by the number and not by the length of CAP cycles.

METHODS

The polysomnographic recordings of 24 normal subjects, 12 males and 12 females, ranging in age from 20 to 35 years (mean 27.8+/-7.2), were examined.

RESULTS

A total of 1053 CAP sequences were counted with an average of 43.9 sequences per night. The mean duration of CAP sequences was 2 min and 33 s. Each CAP sequence was composed of an average of 5.6 CAP cycles. All subjects presented CAP sequences lasting at least 5 min and 30s. The mean duration of CAP cycles was 26.9+/-4.1s. CAP cycles including subtypes A1 presented the highest correlation with the CAP sequence length (r=0.92; p<0.0001).

CONCLUSIONS

The progressive increase of CAP sequences length is linked to the progressive accumulation of CAP cycles.

SIGNIFICANCE

CAP sequences can be considered as strings of time-constant modules, i.e., CAP cycles, which are involved in the dynamic tailoring of sleep structure.

Sleep in children with autistic spectrum disorder: a questionnaire and polysomnographic study

OBJECTIVE

To evaluate sleep in children with autistic spectrum disorder (ASD) by means of sleep questionnaires and polysomnography; moreover, to analyze their cyclic alternating pattern (CAP).

METHODS

Thirty-one patients with ASD (28 males, 3 females, aged 3.7-19 years) and age-matched normal controls were included. ASD children were evaluated by a standard sleep questionnaire that consisted of 45 items in a Likert-type scale covering several areas of sleep disorders and by overnight polysomnography in the sleep laboratory after one adaptation night.

RESULTS

The questionnaire results showed that parents of ASD children reported a high prevalence of disorders of initiating and maintaining sleep, enuresis, repetitive behavior when falling asleep, and daytime sleepiness. Polysomnographically, ASD children showed reduced time in bed, total sleep time, sleep period time and rapid eye movement (REM) latency. ASD subjects had a CAP rate during slow-wave sleep (SWS) lower than normal controls, together with a lower percentage of A1 subtypes.

CONCLUSIONS

ASD children questionnaires showed a higher percentage of disorders of initiating and maintaining sleep than normal controls; this was not completely confirmed by sleep staging. CAP measures showed subtle alterations of NREM sleep which could be detected with an appropriate methodology of analysis. The reduction of A1 subtypes during SWS might play a role in the impairment of cognitive functioning in these subjects.

Cyclic alternating pattern (CAP) alterations in narcolepsy

BACKGROUND AND PURPOSE

Narcolepsy is a sleep disorder with clinical symptoms attributed to a reduced activation of the arousal system. Cyclic alternating pattern (CAP) is the expression of rhythmic arousability during non-rapid eye movement (NREM) sleep. CAP parameters, arousals and conventional sleep measures were studied in narcoleptic patients with cataplexy.

PATIENTS AND METHODS

Data were collected from all-night polysomnographic (PSG) recordings and the multiple sleep latency test (MSLT) on the intervening day of 25 drug-naive patients (10 males and 15 females; mean age: 34+/-16 years) after adaptation and exclusion of other sleep disorders. A group of 25 age- and gender-matched normal sleepers were selected as controls. Each PSG recording was subdivided into sleep cycles. Analysis of CAP included classification of A phases into subtypes A1, A2, and A3.

RESULTS

There was an increase in sleep period time mainly due to an increased wake time after sleep onset. REM latency was sharply reduced. The percentage of NREM sleep was slightly reduced and the balance between light sleep (S1+S2) and deep sleep (S3+S4) showed a curtailment of the former, while deep sleep was slightly increased. Excluding sleep cycles with sleep onset REM periods (SOREMPs), the duration of ordered sleep cycles was not different between narcoleptics and controls. The two groups showed similar values of arousal index, while CAP time, CAP rate, number of CAP cycles and of phase A subtypes (in particular subtypes A1) were significantly reduced in narcoleptic patients.

CONCLUSIONS

The reduced periods of CAP in narcoleptic NREM sleep could be the electroencephalographic (EEG) expression of a generally reduced arousability or an increased strength of sleep-promoting forces in the balance between sleep and arousal systems. This can explain some of the clinical correlates of the disorder, i.e. excessive sleepiness, short sleep latency and impaired attentive performances, even without any sign of arousal-induced sleep fragmentation.

CAP and arousals are involved in the homeostatic and ultradian sleep processes

There is growing evidence that cyclic alternating pattern (CAP) and arousals are woven into the basic mechanisms of sleep regulation. In the present study, the overnight sleep cycles (SC) of 20 normal subjects were analyzed according to their stage composition, CAP rate, phase A subtypes and arousals. Individual SC were then divided into 10 normalized temporal epochs. CAP parameters and arousals were measured in each epoch and averaged in relation to the SC order. Subtypes A2 and A3 of CAP in non-rapid eye movement (NREM) sleep, and arousals, both in REM and NREM sleep when not coincident with a A2 or A3 phases, were lumped together as fast electroencephalographic (EEG) activities (FA). Subtypes A1 of CAP, characterized by slow EEG activities (SA), were analyzed separately. The time distribution of SA and FA was compared to the mathematical model of normal sleep structure including functions representing the homeostatic process S, the circadian process C, the ultradian process generating NREM/REM cycles and the slow wave activity (SWA) resulting from the interaction between homeostatic and ultradian processes. The relationship between SA and FA and the sleep-model components was evaluated by multiple regression analysis in which SA and FA were considered as dependent variables while the covariates were the process S, process C, SWA, REM-on and REM-off activities and their squared values. Regression was highly significant (P < 0.0001) for both SA and FA. SA were prevalent in the first three SC, and exhibited single or multiple peaks immediately before and in the final part of deep sleep (stages 3 + 4). The peaks of FA were delayed and prevailed during the pre-REM periods of light sleep (stages 1 + 2) and during REM sleep. SA showed an exponential decline across the successive SC, according to the homeostatic process. In contrast, the distribution of FA was not influenced by the order of SC, with periodic peaks of FA occurring before the onset of REM sleep, in accordance with the REM-on switch. The dynamics of CAP and arousals during sleep can be viewed as an intermediate level between cellular activities and macroscale EEG phenomena as they reflect the decay of the homeostatic process and the interaction between REM-off and REM-on mechanisms while are slightly influenced by circadian rhythm.

Reorganization of sleep patterns in severe OSAS under prolonged CPAP treatment

OBJECTIVE

To evaluate the immediate and long-term recovery processes of sleep and daytime vigilance in patients with sleep apnea syndrome (OSAS) after continuous CPAP treatment.

METHODS

Five consecutive polysomnographic (PSG) studies were carried out on 10 male patients with severe OSAS. The first recording (baseline) was accomplished without ventilatory support (N0). The other 4 recordings were carried out during the CPAP titration night (N1), during the second night of treatment (N2), during the third night of treatment (N3), and after 30 days of regular CPAP use (N30). Ten age-balanced healthy male subjects were selected from the Parma Sleep Center database as controls. Respiratory variables, conventional PSG variables, arousals, CAP (cyclic alternating pattern) variables, and daytime function (including MSLT) were quantified. ANOVA followed by post-hoc tests explored the differences between controls and OSAS patients in the different recording conditions (N0, N1, N2, N3, N30). The PSG measures that showed significant ANOVA values were correlated with the MSLT scores.

RESULTS

Values of control subjects were recovered by REM sleep, REM latency, subtypes A3 and arousal index during N1, by CAP rate and total arousals during N2, by deep sleep (stages 3 + 4) during N3, by light sleep (stages 1 + 2) during N30. The only measures which remained below control values even after 1 month of sustained treatment were the amount of CAP cycles and A1 subtypes. MSLT scores correlated significantly with CAP rate, deep sleep and arousals.

CONCLUSIONS

The changes induced by CPAP treatment do not restore immediately a normal sleep structure, which is re-established with different time scales

SIGNIFICANCE

The modifications of sleep patterns and the different adjustments of phase A subtypes allow us to monitor the reorganization of sleep in OSAS patients treated with CPAP and the hierarchy of the mechanisms involved in sleep regulation.

Sleep Cyclic Alternating Pattern in Normal Preschool-Aged Children

STUDY OBJECTIVES

To evaluate the characteristics of the cyclic alternating pattern (CAP) in the sleep of preschool-aged children in order to obtain normative parameters in this age range.

DESIGN

Prospective study.

SETTINGS

University sleep laboratory.

PARTICIPANTS

Ten normal healthy subjects (6 girls and 4 boys, mean age 4.6 years; range 3-6 years) underwent polysomnography recordings for 2 consecutive nights in a standard laboratory setting. Sleep data were stored on a computer using a polysomnography digital system (Embla N7000, Medcare, Iceland). Sleep structure was visually scored according to the Rechtschaffen and Kales criteria. The cyclic alternating pattern was visually scored following the criteria by Terzano et al. These criteria were modified for the purposes of this study because it was noticed that, at the age of the group under analysis, most electroencephalogram arousals, often accompanied by electromyogram activation, are expressed at the level of the electroencephalogram by theta frequencies and not alpha or higher frequencies.

MEASUREMENTS AND RESULTS

The CAP rate in preschool-aged children (25.93%) showed a progressive increase with the deepness of sleep, with highest values during non-rapid eye movement (NREM) stage 3 (44.0%) and 4 sleep (46.08%) and lowest values in NREM stage 2 (17.26%). The CAP time showed its longest duration during stage 2 sleep, followed by stage 4, stage 3, and NREM stage 1. The CAP cycle duration showed no differences across NREM stages. The cyclic alternating pattern phase A was longer and phase B was shorter during stage 1 than during stages 2, 3, and 4. A1 phases were the most numerous (63.2%), followed by A2 (21.5%) and by A3 (15.3%). The distribution of A-phase subtypes across NREM sleep stages (A index) showed significant differences for the A1 subtypes that occurred more frequently during stage 3 and 4 sleep than during stages 1 and 2. The A2 index showed no significant differences across NREM sleep stages, while the A3 index was significantly higher during stage 1 sleep than during stages 2, 3, and 4. The analysis of the A1 interval distribution showed a log-normal-like distribution with a peak around 25 seconds for the A1 phases and no clear peak for A2-A3 phases.

CONCLUSIONS

The analysis of CAP in preschool-aged children is characterized by an increase of CAP rate during slow-wave sleep and a high percentage of A1 phases and A2 phases. However, the lower percentage of A1 paralleled by an increase of A2 could represent a signal of higher sleep instability in this age group as compared with prepubertal school-aged children.

Inter-rater reliability of sleep cyclic alternating pattern (CAP) scoring and validation of a new computer-assisted CAP scoring method

OBJECTIVE

To assess inter-rater reliability between different scorers, from different qualified sleep research groups, in scoring visually the Cyclic Alternating Pattern (CAP), to evaluate the performances of a new tool for the computer-assisted detection of CAP, and to compare its output with the data from the different scorers.

METHODS

CAP was scored in 11 normal sleep recordings by four different raters, coming from three sleep laboratories. CAP was also scored in the same recordings by means of a new computer-assisted method, implemented in the Hypnolab 1.2 (SWS Soft, Italy) software. Data analysis was performed according to the following steps: (a) the inter-rater reliability of CAP parameters between the four different scorers was carried out by means of the Kendall W coefficient of concordance; (b) the analysis of the agreement between the results of the visual and computer-assisted analysis of CAP parameters was also carried out by means of the Kendall W coefficient; (c) a 'consensus' scoring was obtained, for each recording, from the four scorings provided by the different raters, based on the score of the majority of scorers; (d) the degree of agreement between each scorer and the consensus score and between the computer-assisted analysis and the consensus score was quantified by means of the Cohen's k coefficient; (e) the differences between the number of false positive and false negative detections obtained in the visual and in the computer-assisted analysis were also evaluated by means of the non-parametric Wilcoxon test.

RESULTS

The inter-rater reliability of CAP parameters quantified by the Kendall W coefficient of concordance between the four different scorers was high for all the parameters considered and showed values above 0.9 for total CAP time, CAP time in sleep stage 2 and percentage of A phases in sequence; also CAP rate showed a high value (0.829). The most important global parameters of CAP, including total CAP rate and CAP time, scored by the computer-assisted analysis showed a significant concordance with those obtained by the raters. The agreement between the computer-assisted analysis and the consensus scoring for the assignment of the CAP A phase subtype was not distinguishable from that expected from a human scorer. However, the computer-assisted analysis provided a number of false positives and false negatives significantly higher than that of the visual scoring of CAP.

CONCLUSIONS

CAP scoring shows good inter-rater reliability and might be compared in different laboratories the results of which might also be pooled together; however, caution should always be taken because of the variability which can be expected in the classical sleep staging. The computer-assisted detection of CAP can be used with some supervision and correction in large studies when only general parameters such as CAP rate are considered; more editing is necessary for the correct use of the other results.

SIGNIFICANCE

This article describes the first attempt in the literature to evaluate in a detailed way the inter-rater reliability in scoring CAP parameters of normal sleep and the performances of a human-supervised computerized automatic detection system.

Is insomnia a neurophysiological disorder? The role of sleep EEG microstructure

Unlike other sleep disorders, such as sleep-related breathing disorders and periodic limb movement (PLM), the nature and severity of which are quantified by specific respiratory and motor indexes, no apparent organ dysfunction underlies several cases of insomnia (in particular primary insomnia), which can be objectively diagnosed only through the structural alterations of sleep. Polysomnography (PSG) investigation indicates that insomnia is the outcome of a neurophysiological disturbance that impairs the regulatory mechanisms of sleep control, including sleep duration, intensity, continuity and stability. In particular, analysis of sleep microstructure has permitted to establish that etiologic factors of different nature (including depressive disorders) exert a common destabilizing action on sleep, which is reflected in an increase of cyclic alternating pattern (CAP) rate. These premises allow us to attribute a more objective identity to insomnia, which risks otherwise to be considered as an unexplainable mental complaint. In conclusion, PSG remains the "gold standard" for measuring sleep, and especially insomnia.

Quantitative analysis of sleep EEG microstructure in the time-frequency domain

A number of phasic events influence sleep quality and sleep macrostructure. The detection of arousals and the analysis of cyclic alternating patterns (CAP) support the evaluation of sleep fragmentation and instability. Sixteen polygraphic overnight recordings were visually inspected for conventional Rechtscaffen and Kales scoring, while arousals were detected following the criteria of the American Sleep Disorders Association (ASDA). Three electroencephalograph (EEG) segments were associated to each event, corresponding to background activity, pre-arousal period and arousal. The study was supplemented by the analysis of time-frequency distribution of EEG within each subtype of phase A in the CAP. The arousals were characterized by the increase of alpha and beta power with regard to background. Within NREM sleep most of the arousals were preceded by a transient increase of delta power. The time-frequency evolution of the phase A of the CAP sequence showed a strong prevalence of delta activity during the whole A1, but high amplitude delta waves were found also in the first 2/3 s of A2 and A3, followed by desynchronization. Our results underline the strict relationship between the ASDA arousals, and the subtype A2 and A3 within the CAP: in both the association between a short sequence of transient slow waves and the successive increase of frequency and decrease of amplitude characterizes the arousal response.

CAP variables and arousals as sleep electroencephalogram markers for primary insomnia

OBJECTIVE

Polysomnographic (PSG) measures consistently reflect poor sleep quality and effective treatment in insomniac patients.

METHODS

The PSG findings of 47 patients (18 M and 29 F, 42.5+/-10 years) meeting the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition criteria for a diagnosis of primary insomnia were compared with those of 25 age- and gender-balanced healthy subjects (controls) without sleep complaints. After one adaptation night to the sleep lab, each patient underwent two randomized double-blind PSG recordings. Twenty-four patients followed a placebo-drug sequence and 23 a drug-placebo succession. Active treatment consisted of widely used hypnotic drugs, i.e. zolpidem, triazolam, zopiclone, brotizolam. Conventional PSG measures, electroencephalogram (EEG) arousals and CAP variables (including phase A subtypes) were quantified and statistically analyzed.

RESULTS

Compared to controls, insomniac patients under placebo showed a significant increase of CAP rate, subtypes A1 and A2, EEG arousals, nocturnal wakefulness and stage 1, associated with reduced values of total sleep time and slow wave sleep (stages 3 and 4). In insomniac patients, sleep quality was significantly improved by hypnotic treatment. Compared to placebo, active medication significantly reduced CAP rate, subtypes A1 and A2, but had only marginal effects on subtypes A3 and on EEG arousals. Under hypnotic treatment total sleep time, nocturnal awakenings, stage 1 and slow wave sleep recuperated normal values. The most significant correlation between sleep quality and PSG variables was found for CAP rate (P<0.0001).

CONCLUSIONS

PSG investigation extended to CAP variables and EEG arousals can be an important procedure for the diagnosis of primary insomnia and evaluation of treatment efficacy.

New drugs for insomnia: comparative tolerability of zopiclone, zolpidem and zaleplon

Insomnia affects 30-35% of people living in developed countries. The impact of insomnia on daytime functioning and its relationship with medical and psychiatric illnesses necessitate early treatment to prevent insomnia becoming persistent and to avoid the development of complications. However, pharmacological strategies must achieve a balance between sedative and adverse effects. In the last 30 years, benzodiazepines have been the preferred drugs for the treatment of insomnia. Benzodiazepines act nonselectively at two central receptor sites, named omega(1) and omega(2), which are located in different areas of the CNS. The sedative action of benzodiazepines is related to omega(1) receptors, whereas omega(2) receptors are responsible for their effects on memory and cognitive functioning. According to their pharmacokinetic profile, benzodiazepines can be classified into three groups: short half-life (<3 hours), medium half-life (8-24 hours) and long half-life (>24 hours). The newer non-benzodiazepine agents zopiclone, zolpidem and zaleplon have a hypnosedative action comparable with that of benzodiazepines, but they display specific pharmacokinetic and pharmacodynamic properties. These three 'Z' agents all share a short plasma half-life and limited duration of action. In addition, these agents are selective compounds that interact preferentially with omega(1) receptors (sedative effect), whereas benzodiazepines also interact with omega(2) receptors (adverse effects on cognitive performance and memory). Zaleplon is characterised by an ultrashort half-life (approximately 1 hour). Zolpidem and zopiclone have longer half-lives (approximately 2.4 and 5 hours, respectively). These properties, together with the low risk of residual effect, may explain the limited negative influences of these agents on daytime performance. Psychomotor tasks and memory capacities appear to be better preserved by non-benzodiazepine agents than by benzodiazepines. When present, cognitive deficits almost exclusively coincide with the peak plasma concentration. In particular, impairment can emerge in the first hours after drug administration, whereas psychomotor and memory tests carried out 7-8 hours later (i.e. in the morning) generally show no relevant alterations. As with benzodiazepines, the three 'Z' non-benzodiazepine agents should be used for a limited period, even in chronic relapsing conditions. Further evaluation is needed of the safety of hypnosedative medications in the long-term management of insomnia.

CAP and arousals in the structural development of sleep: an integrative perspective

OBJECTIVES

It is known that the number of arousals per hour of sleep increases linearly across life, while the amount of cyclic alternating pattern (CAP) undergoes a u-shaped evolution. The present study aimed at investigating the differences, overlaps and age-related distribution of arousals and CAP components, i.e. subtypes A1, A2, A3. The relationship between the phase A subtypes and the structural organization of sleep was also evaluated.

METHODS

Forty healthy subjects were examined. Polysomnographic analysis was performed according to the scoring rules for sleep stages, CAP and American Sleep Disorders Association arousals.

RESULTS

Arousals occurred more frequently during CAP (40 events per hour) than in total sleep time (18 events per hour), non-rapid eye movement (NREM) sleep (20 events per hour), and rapid eye movement (REM) sleep (12 events per hour). Within CAP, arousals always coincided with a subtype A2 or A3. Both arousals and subtypes A2 and A3 showed a similar evolution with relation to age (linear positive), and to the amounts of light NREM sleep (linear positive) and deep NREM sleep (linear negative). In contrast, subtypes A1 showed a u-shaped profile across the life span and appeared closely related (linear positive) to the time spent in stages 3 and 4. Almost 90% of arousals occurring in NREM sleep were preceded in the previous 3s by a K-complex or a delta burst, indicating a topical involvement of slow electroencephalographic (EEG) components in the arousal build-up.

CONCLUSIONS

Arousals show only one side of the multi-faceted activation complexes, whereas the three subtypes of CAP provide a graded picture of arousal features from the strongest A3 subtypes, showing a prevalence of EEG desynchrony, to the weakest A1 phases, which are dominated by EEG synchrony and represent the prevalent components of CAP (60% of all the phase A subtypes).

Non-linear EEG measures during sleep: effects of the different sleep stages and cyclic alternating pattern

The objective of this work was to study the non-linear aspects of sleep EEG, taking into account the different sleep stages and the peculiar organization of its phasic events in ordered sequences (CAP) by applying a series of new non-linear measures (non-linear cross prediction or NLCP), which appear more reliable for the detection and characterization of non-linear structures in experimental data than the commonly used correlation dimension. Eight healthy subjects aged 18-20 years participated in this study. Polysomnography was performed in all subjects; signals were sampled at 128 Hz and stored on hard disk. The C3 or C4 derivation was used for all the subsequent computational steps, which were performed on EEG epochs (4096 data points) selected from sleep stage 2 (S2) and slow-wave sleep (SWS), in both CAP and non-CAP (NCAP) conditions. Also, epochs from sleep stage 1 (S1), REM and wakefulness preceding sleep were recorded. The dynamic properties of the EEG were assessed by means of the non-linear cross-prediction test, which uses three different 'model' time series in order to predict non-linearly the original data set (Pred, Ama, and Tir). Pred is a measure of the predictability of the time series, and Ama and Tir are measures of asymmetry, indicating non-linear structure. The non-linear measures applied in this study indicate that sleep EEG tends to show non-linear structure only during CAP periods, both during S2 and SWS. Moreover, during CAP periods, non-linearity can only be detected during the phase A1 subtypes (and partially A2) of CAP. The A3 phases show characteristics of non-stationarity and bear some resemblance to wakefulness. Based on the results of this study, sleep might be considered as a dynamically evolving sequence of different states of the EEG, which we could track by detecting non-linearity, mostly in association with CAP. Our results clearly show that detectable non-linearity in the EEG is closely related to the occurrence of the phase A of CAP.

Riedel's thyroiditis: clinical, pathological and imaging features

Riedel's thyroiditis (RT) is an extremely rare form of chronic thyroiditis, characterised by a fibroinflammatory process which partially destroys the thyroid, often involving surrounding tissues. We describe an unusual case of RT in a 38-year-old woman, and discuss its typical clinical, pathological, ultrasound, radionuclide scanning and magnetic resonance findings. We conclude that the diagnosis of RT is highly suggestive in the presence of a hard gland (or nodule), fixed to adjacent structures; 'cold' on Tc99 scan; hypoechoic with absence of vascular flow, invading the adjacent neck structures on ultrasound; hypointense in T1- and T2-weighted MR images; and showing fibrous tissue fragments with inflammatory cells at cytological examination. Thyroidectomy has to be performed to confirm the diagnosis and to relieve pressure symptoms.

Relationship of slow and rapid EEG components of CAP to ASDA arousals in normal sleep

STUDY OBJECTIVES

Besides arousals (according to the ASDA definition), sleep contains also K-complexes and delta bursts which, in spite of their sleep-like features, are endowed with activating effects on autonomic functions. The link between phasic delta activities and enhancement of vegetative functions indicates the possibility of physiological activation without sleep disruption (i.e., arousal without awakening). A functional connection seems to include slow (K-complexes and delta bursts) and rapid (arousals) EEG events within the comprehensive term of activating complexes. CAP (cyclic alternating pattern) is the spontaneous EEG rhythm that ties both slow and rapid activating complexes together during NREM sleep. The present study aims at exploring the relationship between arousals and CAP components in a selected sample of healthy sleepers.

DESIGN

Polysomnographic analysis according to the scoring rules for sleep stages and arousals. CAP analysis included also tabulation of subtypes A1 (slow EEG activating complexes), A2 and A3 (activating complexes with fast EEG components).

SETTING

40 sleep-lab accomplished recordings.

PARTICIPANTS

Healthy subjects belonging to a wide age range (38 +/- 20 yrs.).

INTERVENTIONS

N/A.

MEASUREMENT AND RESULTS

Of all the arousals occurring in NREM sleep, 87% were inserted within CAP. Subtypes A2 and A3 of CAP corresponded strikingly with arousals (r=0.843; p<0.0001), while no statistical relationship emerged when arousals were matched with subtypes A1 of CAP. Subtypes A1 instead correlated positively with the percentages of deep sleep (r=0.366; p<0.02).

CONCLUSIONS

The CAP subtype classification encompasses both the process of sleep maintenance (subtypes A1) and sleep fragmentation (subtypes A2 and A3), and provides a periodicity dimension to the activating events of NREM sleep.

[Neurophysiological basis of insomnia: role of cyclic alternating patterns]

During non-REM (NREM) sleep it is possible to identify two complementary conditions of arousal stability and arousal instability. Unstable sleep, which can be detected in all stages, is expressed by the recurrence of arousal complexes (sequences of K-complexes, delta bursts, K-alpha, conventional arousals), which translate a brief (10-15 s) activation of the sleeping brain. These repetitive arousal complexes compose the cyclic alternating pattern (CAP). During stable NREM sleep, arousal complexes are rare or absent and the EEG lacks any cyclic pattern (non-CAP). CAP is a spontaneous feature of normal sleep as it is typically involved in stage changes and nocturnal motor activity. The physiological amount of CAP rate (ratio of CAP time to NREM sleep time) varies with age according to a U-shape curve. Within these ranges, sleep is perceived as continuous and restorative. Conversely, an excess of CAP rate fragments sleep and impairs its quality. Polysomnographic investigation reveals that untreated insomniac patients exhibit significantly higher values of CAP rate compared to healthy sleepers. Effective hypnotic treatment restores physiological amounts of CAP rate, with specific differences between the administered drugs. The sensitivity of CAP parameters to drug manipulation can provide circumscribed information on the hypnotic properties of active compounds.

Sleep in Lennox-Gastaut syndrome: the role of the cyclic alternating pattern (CAP) in the gate control of clinical seizures and generalized polyspikes

Non-rapid eye movement (NREM) sleep contains periods of arousal instability (cyclic alternating pattern or CAP) and periods of arousal stability (non-CAP). During CAP, arousal oscillates between higher (phase A) and lower (phase B) levels of activation. We evaluated the relationship between CAP and the occurrence of epileptic events, i.e. clinical seizures and generalized interictal discharges, during sleep in 10 patients with Lennox-Gastaut syndrome (LGS). The macro- and microstructure of sleep of 10 attended overnight polysomnograms were analyzed. Compared with 10 age- and gender-matched controls, patients with LGS had significantly less stage 2 and REM sleep and higher amounts of CAP rate (68% vs. 33%; P<0.0001). The number of generalized polyspike bursts per hour of sleep was highest in slow wave sleep (226.5+/-57.6) and lowest in REM sleep (3.9+/-1.5). The polyspike burst frequency was significantly greater (P<0.017) during CAP (213.2+/-60.1) than during non-CAP (100.3+/-40), and within CAP, generalized polyspikes occurred more often (P=0.005) during phase A (461.1+/-127.2) than during phase B (6.1+/-1.9). The total amount of generalized polyspike bursts identified in NREM sleep correlated positively both with the number of A phases containing at least one generalized polyspike (P=0.005) and with the mean number of polyspikes within each of these A phases (P<0.0001). Nocturnal clinical seizures occurred in 8 of the 10 patients and showed a similar trend. We conclude from our results that CAP modulates the occurrence of both clinical seizures and generalized epileptic discharges in LGS by means of a gate-control mechanism: an independent spike generator is inhibited in phase B and non-CAP and bursts with its intrinsic activity in phase A.

Combined influence of cyclic arousability and EEG synchrony on generalized interictal discharges within the sleep cycle

PURPOSE

to analyze the activating role of cyclic alternating pattern (CAP) and EEG synchrony on generalized interictal paroxysms in the first part of the night, when all sleep patterns are represented.

METHODS

nocturnal polysomnographic investigation was accomplished on a randomized series of 18 subjects with an active form of primary generalized epilepsy (PGE), but only six patients showed a complete and regular profile of the first two sleep cycles (SCs). Completeness and regularity of the selected SCs consisted in the absence of intervening wakefulness, in the presence of all sleep stages, and in the identification of three main units, (a) a descending branch, dominated by the build-up of EEG synchrony in the transition from light to deep non-rapid eye movement (NREM) sleep; (b) a trough, where the magnitude of EEG synchrony is greatest and gives rise to stages 3 and 4; (c) an ascending branch characterized by a decrease of EEG synchrony preceding the onset of rapid eye movement (REM) sleep. Generalized paroxysms were evaluated in terms of discharge rates (number of interictal bursts per minute of sleep) and distribution within the investigated sleep parameters.

RESULTS

the discharge rates decreased from SC1 to SC2, with higher values quantified during NREM sleep (mean, 2.8) compared with REM sleep (mean, 0.8). Both SCs showed a progressive decrease of activation across the three units, from the highest discharge rates reached during the descending branches (mean, 3.6) to the more attenuated discharge rates during the troughs (mean, 2.4) down to the lowest rates during the ascending limbs (mean, 1.1). The magnitude of activation during the descending branches was closely related to the CAP condition (mean, 5.2) and to the powerful effect of phase A (mean, 13.9). The great majority (82%) of EEG discharges occurring in phase A were distributed within the A1 subtypes (identified by sequences of k-complexes or delta bursts).

CONCLUSIONS

within the first two SCs, the features of NREM sleep endowed with the major activating power on generalized bursts are represented by the rise of EEG synchrony (descending branch) and by the A phases of CAP involved in the regulation of its build-up.

Cyclic alternating pattern (CAP) and epilepsy during sleep: how a physiological rhythm modulates a pathological event

OBJECTIVES

Epileptic susceptibility is triggered by the sleeping condition. However, both ictal and interictal events are not equally affected by the different sleep states. Besides the well-known dichotomy between non-REM sleep (high activation) and REM sleep (low activation), epileptic phenomena are deeply sensitive to the ongoing level of arousal.

METHODS

During non-REM sleep the arousal level can be either unstable, as expressed by the repetitive sequences of the cyclic alternating pattern (CAP), or stable, as reflected by non-CAP. Phase A (arousal complex) and phase B (post-arousal rebound response) are the two basic components of the CAP cycle, which presents a 20-40 s periodicity. Three subtypes of A phases can be recognized: the A1 subtypes, which are thoroughly composed of K-complexes and delta bursts, and subtypes A2 and A3 dominated by moderate (A2) or prominent (A3) EEG desynchrony.

RESULTS

As a manifestation of unstable sleep, CAP offers a favorable background for the occurrence of nocturnal motor seizures that in most cases arise in concomitance with a phase A. In primary generalized epilepsy (PGE) and in lesional epilepsies with fronto-temporal focus, activation of interictal discharges is high during CAP reaching the climax during phase A and the strongest inhibition during phase B. A lack of modulation is observed instead in epilepsy with benign rolandic spikes. In PGE, the interictal bursts are mostly associated with the highly synchronized phase A1 subtypes.

CONCLUSIONS

The analysis of sleep microstructure based on CAP parameters offers a sensitive framework for exploring the linkage between dynamic EEG events and epileptic phenomena.

Sleep reactivity during acute nasal CPAP in obstructive sleep apnea syndrome

OBJECTIVE

To measure the readjustments of sleep macro- and microstructure in patients with obstructive sleep apnea syndrome (OSAS) after acute nasal continuous positive airway pressure (NCPAP) treatment.

BACKGROUND

The conventional polysomnographic analysis (macrostructure of sleep) does not necessarily provide the best measures of sleep disruption associated with OSAS. In contrast, microstructural methods of analyzing sleep (i.e., arousals and cyclic alternating pattern) may improve evaluation of patients with OSAS.

METHOD

- Ten patients with OSAS were monitored polygraphically before and during the first night of NCPAP therapy. The results were compared with those of 10 age- and sex-matched controls without sleep-related breathing disorders. Each nocturnal recording was followed by daytime observation using the multiple sleep latency test and Visual Analogue Scale (VAS).

RESULTS

The first night of ventilatory therapy was characterized by a remarkable expansion of stages 3 and 4 and of REM sleep. In addition, NCPAP suppressed the presence of cyclic alternating pattern (CAP) in REM sleep and induced an impressive rebound of arousals and of certain CAP variables-i.e., CAP rate, CAP time, number of CAP cycles-which dropped well below the physiologic values expressed by controls. A normal duration of phases A and B was re-established starting the first treatment night. When we matched sleep variables with the indices of daytime function, a significant correlation emerged only between the variations of CAP rate and VAS scores. In particular, improvement of daytime sleepiness was less evident when the ventilatory-induced drop of CAP rate was more pronounced.

CONCLUSIONS

The application of CAP variables to the microstructural analysis of sleep may expand our knowledge regarding sleep and respiration.

Cyclic alternating pattern and spectral analysis of heart rate variability during normal sleep

The natural arousal rhythm of non-rapid eye movement (NREM) sleep is known as the cyclic alternating pattern (CAP), which consists of arousal-related phasic events (Phase A) that periodically interrupt the tonic theta/delta activities of NREM sleep (Phase B). The complementary condition, i.e. non-CAP (NCAP), consists of a rhythmic electroencephalogram background with few, randomly distributed arousal-related phasic events. Recently, some relation between CAP and autonomic function has been preliminarily reported during sleep in young adults by means of spectral analysis of heart rate variability (HRV). The present study was aimed at analysing the effects of CAP on HRV in a group of normal children and adolescents. Six normal children and adolescents (age range 10.0-17.5 y) were included in this study. All-night polygraphic recordings were performed after adaptation to the sleep laboratory. Six 5-min epochs were selected from sleep Stage 2 and six from Stages 3 and 4 (slow-wave sleep), both in CAP and NCAP conditions. From such epochs, a series of parameters describing HRV was then calculated, in both time and frequency domains, on the electrocardiographic R-R intervals. Statistical comparison between CAP and NCAP epochs revealed a significant difference for most of the frequency domain parameters (increase of the low-frequency band, increase of the low-frequency/high-frequency ratio and decrease in the high-frequency band during CAP) both in Stage 2 and in slow-wave sleep. Our results demonstrate that the physiological fluctuations of arousal during sleep described as CAP are accompanied by subtle, but significant, changes in balance between the sympathetic and vagal components of the autonomic system.

CAP components and EEG synchronization in the first 3 sleep cycles

OBJECTIVE

There is consolidated evidence that stage changes in sleep are closely related to spontaneous EEG fluctuations centered on the 20-40 periodicity of the cyclic alternating pattern (CAP). The present investigation aimed at assessing the involvement of the different components of CAP in the process of build-up, maintenance and demolition of deep non-REM (NREM) sleep.

METHODS

CAP parameters were quantified in the first 3 sleep cycles (SC1, SC2, SC3), selected from polysomnographic recordings of 25 healthy sound sleepers belonging to an extensive age range (10-49 years). Only ideal SCs were selected, i.e. the ones uninterrupted by intervening wakefulness and in which all stages were represented and linked in a regular succession of a descending branch, a trough and an ascending branch.

RESULTS

Among the first 3 SCs, a total amount of 45 (SC1, 16; SC2, 13; SC3, 16) met the inclusion requirements. SCI contained the highest amount of slow wave sleep (43.7 min) and the lowest values of CAP rate (31.6%). The number of phase A1 subtypes remained unmodified across the 3 SCs (SC1, 48; SC2, 48; SC3, 48), whereas both subtypes A2 (SC1, 9; SC2, 14; SC3, 14) and A3 (SC1, 2; SC2, 8; SC3, 10) increased significantly (P<0.028 and P<0.0001, respectively). The A1 subtypes composed more than 90% of all the A phases collected in the descending branches and in the troughs, while the A2 and A3 subtypes were the major representatives (64.3%) of the A phases occurring in the ascending branches.

CONCLUSIONS

Within the dynamic organization of sleep, the non-random distribution of CAP sequences, with their succession of slow (subtypes A1) and rapid (subtypes A2 and A3) EEG shifts, seem to be responsible for sculpturing EEG synchrony under the driving and alternating forces of NREM and REM sleep.

Cyclic alternating pattern (CAP) in normal sleep: polysomnographic parameters in different age groups

OBJECTIVES

The present study aimed at offering a standardized database for cyclic alternating pattern (CAP) parameters across representative ages of life.

METHODS

CAP parameters were quantified in 40 healthy sleepers and polygraphically investigated in a partially sound-proof recording chamber under a standard laboratory setting. Four age groups were investigated (teenagers: 10-19 years; young adults: 20-39 years; middle-aged: 40-59 years; elderly: 60 years). Each group included 10 subjects (5 males and 5 females). Nocturnal recordings were accomplished after adaptation to the sleep laboratory that also served to rule out the presence of sleep-related disorders. The study indicated that CAP is a natural phenomenon of NREM sleep, with specific age-related characteristics across the life cycle.

RESULTS

CAP rate in NREM sleep, defined as the percentage ratio of total CAP time to total NREM sleep time, showed a U-shape profile with minimum in young adults (31.9%), maximum in the elderly group (55.3%), and intermediate values in teenagers (43.4%) and in middle-aged subjects (37.5%). The longest duration of CAP cycles was found among the older subjects (31 s). The highest amounts of subtypes A1 were identified in teenagers (n = 261), while the highest amounts of A2 and A3 subtypes occurred in the elderly group (n = 183). Across the ages, the level of arousal mostly fluctuated in stages 1 and 3, whereas stage 4 emerged as the most stable NREM stage. Overall, stage 2 better reflected the CAP values referred to as total NREM sleep.

CONCLUSIONS

The periodic arousal fluctuations reflected by CAP are a natural phenomenon of NREM sleep with specific age-related variations across the life cycle.

Effect of age on EEG arousals in normal sleep

EEG arousals were quantified in 40 nocturnal polysomnographic recordings belonging to four age groups (teenagers: 10 to 19 years; young adults: 20 to 39 years; middle-aged: 40 to 59 years; elderly: > or = 60 years). Ten subjects (five males and five females) participated in each group. The subjects were healthy and sound sleepers. All sleep recordings were preceded by an adaptation night which aimed at excluding the presence of sleep-related disorders. The recordings were carried out in a partially soundproof recording chamber and in a standard laboratory setting. Arousal indices (AI), defined as the number of arousals per hour of sleep, were calculated for total sleep time (AI/TST) and for all the sleep stages. AI/TST increased linearly with age (r = 0.852; p < 0.00001): teenagers (13.8), young adults (14.7), middle-aged (17.8), elderly (27.1). An age-related positive linear correlation was found also for the arousal indices referred to NREM sleep (r = 0.811; p < 0.00001) and to stages 1 and 2 (r = 0.712; p < 0.00001), while in stages 3 and 4 and in REM sleep, arousal indices showed stable values across the ages. Overall, arousals lasted 14.9 +/- 2.3 seconds, with arousal duration stable across the ages (range of means: 13.3-16.6 seconds) and no relevant differences between NREM sleep (14.6 +/- 2.5 seconds) and REM sleep (16.2 +/- 5 seconds). The paper discusses the impact of age on arousals, the similarities between arousals and the phases d'activation transitoire, and the consideration that arousals are physiological components of sleep.

Sensitivity of cyclic alternating pattern to prolonged pharmacotherapy: a 5-week study evaluating zolpidem in insomniac patients

To test the effects of a hypnotic drug administered on a regular basis, six adults (four women and two men; mean age 37 years) who complained of transient or short-term insomnia, took zolpidem 10 mg at bedtime for 4 consecutive weeks. The period of active treatment, preceded by a baseline placebo night, ended with a 4-night gradual tapering phase followed by 3 nights of placebo administration. After adaptation to the sleep laboratory, all subjects underwent five polysomnographic recordings; baseline placebo (night 1); 1st, 7th and 28th nights of hypnotic medication (nights 2, 3, and 4 respectively); 3rd placebo night after complete tapering (night 5) and completed a morning visual analogue scale (VAS) for evaluating sleep quality. The sleep recordings were scored according to the conventional procedures (macrostructure) and to the cyclic alternating pattern (CAP) rules (microstructure). Data analysis was based on a repeated-measures analysis of variance integrated by post-hoc comparisons. At the macrostructural level, significant overall modifications (p < 0.035) emerged only from slow-wave sleep (SWS). The amounts of SWS were enhanced along the entire drug period, but a significant difference was found only between the baseline night (10%) and the first night of drug administration (20%). At the microstructural level, CAP rate (the ratio of CAP time to non-rapid eye movement sleep time) showed overall significant variations throughout the entire protocol period (p < 0.0001). Compared with baseline night 1 (59%), the CAP rate was significantly lower on drug nights 2 (32%), 3 (37%), and 4 (38%). The increase in the CAP rate found on night 5 (43%) was still significantly below the baseline value. The VAS scores showed significant overall changes (p < 0.0001), with improved values during the active treatment period.