Phox2b-expressing neurons contribute to breathing problems in Kcnq2 loss- and gain-of-function encephalopathy models.

Loss- and gain-of-function variants in the gene encoding KCNQ2 channels are a common cause of developmental and epileptic encephalopathy, a condition characterized by seizures, developmental delays, breathing problems, and early mortality. To understand how KCNQ2 dysfunction impacts behavior in a mouse model, we focus on the control of breathing by neurons expressing the transcription factor Phox2b which includes respiratory neurons in the ventral parafacial region. We find Phox2b-expressing ventral parafacial neurons express Kcnq2 in the absence of other Kcnq isoforms, thus clarifying why disruption of Kcnq2 but not other channel isoforms results in breathing problems. We also find that Kcnq2 deletion or expression of a recurrent gain-of-function variant R201C in Phox2b-expressing neurons increases baseline breathing or decreases the central chemoreflex, respectively, in mice during the light/inactive state. These results uncover mechanisms underlying breathing abnormalities in KCNQ2 encephalopathy and highlight an unappreciated vulnerability of Phox2b-expressing ventral parafacial neurons to KCNQ2 pathogenic variants.

FLASH protects ZEB1 from degradation and supports cancer cells' epithelial-to-mesenchymal transition.

Cancer metastasis remains a significant challenge and the leading cause of cancer-associated deaths. It is postulated that during metastasis cells undergo epithelial-to-mesenchymal transition (EMT), a process characterized by loss of cell-cell contacts and increased migratory and invasive potential. ZEB1 is one the most prominent transcriptional repressors of genes associated with EMT. We identified caspase-8-associated protein 2 (CASP8AP2 or FLASH) as a novel posttranscriptional regulator of ZEB1. Here we demonstrate that FLASH protects ZEB1 from proteasomal degradation brought by the action of the ubiquitin ligases SIAH1 and F-box protein FBXO45. As a result, loss of FLASH rapidly destabilized ZEB1 and reversed EMT cellular characteristics. Importantly, loss of FLASH blocked transforming growth factor-ß-induced EMT and enhanced sensitivity to chemotherapy. Thus, we propose that FLASH-ZEB1 interplay may be a protective mechanism against ZEB1 degradation in cells undergoing EMT and may be an efficacious target for therapies aimed to block EMT progression.

Modification of relative gene expression ratio obtained from real time qPCR with whole carotid body by using mathematical equations.

Quantitative real time PCR (qPCR) is a common tool used to compare the relative gene expression between treated/untreated cells, different types of tissues, or immature/mature organs. When homogeneous cells are used for qPCR, the Ct number of a tested gene solely represents the quantity of gene expression in cells. However, when a heterogeneous tissue is used for qPCR, the Ct number of a tested gene should be modified depending on several factors: the percentage of each cell type in the sample tissue, the cell type where the target gene is expressed, and the cell type in which the target gene is regulated. The carotid body (CB) is mainly composed of three types of cells: type I (chemoreceptor) cells, type II cells, and other types of cells. Therefore, the relative gene expression ratio obtained from qPCR data using whole CB could be modified by applying one of the following 19 different cases: (1) the target gene is expressed in only one type of cell (3 cases), (2) the gene is expressed in two types of cells and increased in only one or both cell types (9 cases), and (3) the gene is expressed in all three types of cells and increased in only one, two, or all three cell types (7 cases). For example, in the case that the target gene is expressed in all three types of cells and the gene is increased in only a cell comprising 10% of whole CB, the gene expression ratio in that cell will be 9 times as that derived from whole CB. Thus, once the percentage of each cell type in whole CB is observed, the cell type of interest gene (E-gene) expression is identified, and the cell type that regulates E-gene expression by treatment is identified. Thus, the corresponding mathematical equation out of 19 cases could be applied to modify the gene expression ratios measured by qPCR.

Fluoresceinated peanut agglutinin (PNA) is a marker for live O(2) sensing glomus cells in rat carotid body.

Experiments using live dissociated carotid body (CB) cells for patch clamping, [Ca(++)](i) or other measurements require positive identification of the cell being recorded. At present, cell morphology is usually employed, but several cell types within the carotid body evidence similar morphologic characteristics. Therefore, we sought to develop a method utilizing a vital dye to identify glomus cells before and during experiments that require live cells, such as patch clamp studies. It was previously reported that the binding sites for peanut agglutinin (PNA) were highly expressed by all neuroendocrine-derivatives of the sympathoadrenal neural crest, including glomus cells, small, intensely fluorescent cells, PC-12 cells, and adrenal chromaffin cells in situ (katz et al. 1995). By utilizing the binding characteristics of galactose-specific lectin peanut agglutinin (PNA) on the outer cell membrane, we tested the possibility that the fluoresceinated PNA may preferentially bind to CB glomus cells. The results to date show: (1) Rhodamine tagged PNA (Rhod-PNA) binds to the live dissociated glomus cells in less than one hour incubation and can be visualized in superfused cells; (2) Rhod-PNA labeled cells are perfectly matched with tyrosine hydroxylase (TH) positive glomus cells; (3) Rhod-PNA did not interfere with Fura-2 for Ca(++) imaging; (4) Rhod-PNA bound to glomus cells in [Ca(++)](i) studies does not affect O(2) response of glomus cells. Thus fluoresceinated PNA may be a useful marker for live CB glomus studies, without adversely affecting their physiologic response.

Time-dependence of hyperoxia-induced impairment in peripheral chemoreceptor activity and glomus cell calcium response.

In mammals, transient exposure to hyperoxia for a period of weeks during perinatal life leads to impairment of the ventilatory response to acute hypoxia, which may persist long beyond the duration of the hyperoxia exposure. The impairment of the ventilatory response to hypoxia is due to hyperoxia-induced reduction of carotid chemoreceptor sensitivity to hypoxia. We previously demonstrated that hyperoxia exposure in rats, from birth to two weeks of age, profoundly reduced carotid chemoreceptor single axonal responses to acute hypoxia challenge. However, the time course and mechanisms of this impairment are not known. Therefore, we investigated the effect of hyperoxia (FiO(2) = 0.6) on neonatal rats after 1, 3, 5, 8, and 14 days of exposure, starting at postnatal day 7. Carotid chemoreceptor single unit activities, nerve conduction time and glomus cell calcium responses to acute hypoxia were recorded in vitro. After 1 day in hyperoxia, single unit spiking rate in response to acute hypoxia was increased compared to controls. After 5 days in hyperoxia, the spiking response to acute hypoxia was significantly reduced compared to controls, nerve conduction time was lengthened and the glomus cell calcium response to acute hypoxia was reduced compared to controls. We conclude that perinatal exposure to hyperoxia, in rats, impairs the glomus cell calcium response (pre-synaptic) and the afferent nerve excitability (post-synaptic). The time course indicates that hyperoxia exerts these effects within days.

Postnatal development of carotid body glomus cell response to hypoxia.

This study examines developmental changes in CB glomus cell depolarization, intracellular calcium ([Ca(2+)](i)) and the magnitude of an O(2)-sensitive background ionic conductance that may play roles in the postnatal increase in oxygen sensitivity of glomus cells isolated from rats of 1-3 days and 11-14 days postnatal age. Using fura-2 and perforated patch whole cell recordings, we simultaneously measured [Ca(2+)](i) and membrane potential (E(m)) during normoxia and hypoxia. Resting E(m) in normoxia was similar at both ages. Hypoxia caused a larger E(m) depolarization and correspondingly larger [Ca(2+)](i) response in glomus cells from 11- to 14-day-old rats compared to 1-3-day-old rats. E(m) and [Ca(2+)](i) responses to 40mM K(+) were identical between the two age groups. Under normoxic conditions both age groups had similar background conductances. Under anoxic conditions (at resting membrane potential) background K(+) conductance decreased significantly more in cells from 11- to 14-day-old rats compared to cells from 1- to 3-day-old rats. Glomus cells from newborns therefore have less O(2)-sensitive background K(+) conductance. These results support the hypothesis that postnatal maturation of glomus cell O(2) sensitivity involves developmental regulation of the expression and/or O(2)-sensitivity of background ionic conductances.

Dopamine D2 receptor modulation of carotid body type 1 cell intracellular calcium in developing rats.

Carotid chemoreceptor type 1 cells release dopamine, which inhibits carotid chemoreceptor activity via dopamine D2 autoreceptors on type 1 cells. Postnatal changes in dopaminergic modulation may be involved in postnatal chemoreceptor development. The present study explores dopaminergic modulation of the intracellular calcium ([Ca(2+)](i)) response to hypoxia in type 1 cells from 1, 3, and 11- to 16-day-old rats. Using fura-2, we studied the effects of quinpirole, a D2 receptor agonist, on type 1 cell [Ca(2+)](i) response to 90-s hypoxia challenges (Po(2) approximately 1-2 mmHg). Cells were sequentially exposed to the following challenges: 1) hypoxia control, 2) hypoxia plus quinpirole, and 3) hypoxia plus quinpirole plus sulpiride (D2 receptor antagonist). In the 11- to 16-day-old group, type 1 cell [Ca(2+)](i) increased approximately 3 to 4-fold over resting [Ca(2+)](i) in response to hypoxia. Quinpirole (10 microM) significantly blunted the peak [Ca(2+)](i) response to hypoxia. Repeat challenge with hypoxia plus 10 microM quinpirole in the presence of 10 microM sulpiride partially restored the hypoxia [Ca(2+)](i) response. In sharp contrast to the older aged group, 10 microM quinpirole had minimal effect on hypoxia response of type 1 cells from 1-day-olds and a small but significant effect at 3 days of age. We conclude that stimulation of dopamine D2 receptors inhibits type 1 cell [Ca(2+)](i) response to hypoxia, consistent with an inhibitory autoreceptor role. These findings suggest dopamine-mediated inhibition and oxygen sensitivity increase with age on a similar time course and do not support a role for dopamine as a major mediator of carotid chemoreceptor resetting.

The role of natural killer cells in adenovirus-mediated p53 gene therapy.

Adenovirus-mediated gene therapy is a promising new approach for treatment of ovarian cancer. In animal models, complete elimination of cancer cells is often achieved, although the therapeutic gene has not been delivered to all these cells. This is referred to as a bystander effect, because tumor cells near those that receive the therapeutic gene are also eliminated. Several mechanisms have been proposed for the bystander effect, including intercellular communication within the tumor via gap junctions, apoptosis, antiangiogenesis, cytokines or other soluble mediators, and immunological mechanisms. There are two well-documented antitumor effector cell populations in athymic nude mice: macrophages and natural killer (NK) cells. We hypothesize that peritoneal populations of NK cells in nude mice treated with adenoviruses are involved in the observed bystander effect in this in vivo model. We investigated the role of NK cells as immunological mediators for the bystander effect using the p53 tumor suppressor as the therapeutic anticancer gene. Most ovarian cancer cell lines tested were sensitive to lysis by NK cells, although different ovarian cancer cell lines exhibited different sensitivities to NK cell-mediated lysis. To determine the importance of NK cells in the overall efficacy and in the bystander effect of gene therapy, NK cells were depleted in mice by administration of anti-NK1.1 monoclonal antibodies. To study the efficacy of NK depletion, C57BL/6 (nu/nu) mice were given injections i.v. by a single tail vein injection or i.p. with increasing doses of anti-NK1.1 IgG. All doses of anti-NK1.1 antibody, from 100-500 micrograms, essentially eliminated cytotoxic NK activity. To assess the duration of depletion after a single dose of anti-NK1.1 IgG, a time-course experiment was performed. NK 1.1 antibody was effective in completely depleting cytotoxic NK cell activity in the mice for up to 7 days, whether given as 500 micrograms (i.p.) or 200 micrograms (i.v.). Flow cytometric analysis performed on peritoneal cell populations confirmed depletion of NK cells by approximately 80%. Finally, a survival study was performed, in which animals were depleted of NK cells. In this experiment, NK cell-depleted mice were injected with anti-NK1.1 IgG, and control mice were mice were treated with normal saline. Two days later, all mice were inoculated with a lethal i.p. dose of NIH:OVCAR-3 ovarian cancer cells. After 3 days, the mice were divided into two treatment groups; one treatment group received three consecutive daily i.p. injections of Ad-CMV-p53 (SCH58500), and the second treatment group received three consecutive daily i.p. injections of control adenovirus construct, rAd-null. All of the NK cell-depleted animals, whether treated with rAd-null or with Ad-CMV-p53 (SCH58500) were dead of disease by 116 and 138 days, respectively, after initiation of adenovirus treatment, and no statistically significant difference in survival was observed (P = 0.349). A significant survival advantage was seen in control (NK-competent) mice treated with rAd-null (P = 0.04), although all were dead of disease by day 184. Importantly, control NK-competent mice treated with Ad-CMV-p53 (SCH58500) showed no tumor growth or ascites production, and all animals survived. These results indicate that immunological mechanisms involving natural killer cells play an important role in the bystander effect involving adenovirus-p53 gene therapy for ovarian cancer.

p53 Adenovirus as Gene Therapy for Ovarian Cancer.

Ovarian cancer arises from the accumulation of mutations in multiple combinations of genes (1). The most extensively studied tumor suppressor gene in solid tumors is p53, a 53-kD nuclear phosphoprotein that binds DNA. The p53 gene product plays a role in normal cellular proliferation by regulating gene transcription, cell cycle control, and apoptosis (2). Mutations of p53 are the most common molecular genetic abnormality to be described in human cancer, and have been identified in malignancies of the breast, colon, lung, esophagus, head and neck, and hematopoietic system (3). Mutations of the p53 gene have been identified in 30 to 79% of epithelial ovarian cancers (4,5). Most of the mutations identified in p53 are distributed throughout the open reading frame as missense mutations. We have identified a missense mutation in the p53 gene in the 2774 ovarian cancer cell line that converts an arginine residue in the DNA binding region of the protein to a histidine residue (6). The mutation in codon 273 we found in 2774 cells is one of the six major hotspots identified for p53 missense mutations (7).

Autoreceptor mechanism regulating carotid body dopamine release from adult and 10-day-old rabbits.

Dopamine (DA) release (r) from the carotid body (CB) is thought to be modulated by feedback inhibition mediated by DA D2 autoreceptors. We tested the hypothesis that CB DAr is autoregulated in a concentration and age dependent manner. Using an in vitro CB infusion model [Bairam, A., Marchal. F., Cottet-Emard, J.M., Basson, H., Pequignot, J.M., Hascoet, J.M., Lahiri, S., 1996b. Effects of hypoxia on carotid body dopamine content and release in developing rabbits. J. Appl. Physiol. 80, 20-24.], we evaluated under unstimulated conditions the effects of 0.001, 0.01, 0.1, 1.0 and 10.0 microM of the specific DA D2 receptor antagonist domperidone on CB DAr in adult rabbits. In 10-day-old rabbit pups, concentrations of 0.01, 0.1, 1.0 microM were studied. In adult CBs, domperidone increased DAr in a concentration-dependent manner. DAr (pmol/h) was significantly greater compared to control (without domperidone) starting at a domperidone concentration of 0.1 microM (P<0.01). In 10-day-old pup CBs, 1.0 microM domperidone was required to produce a significant increase of DAr (pmol/h) compared to control (P<0.005). However, control DAr (as % of total catecholamine) was about 40%; significantly higher than 24% observed in adult CBs (P<0.001). We conclude that in rabbit CB, DAr is controlled by an autoreceptor mechanism in a concentration-dependent manner and this mechanism is less developed in pups than in adults.

Dynamic ventilatory responses in rats: normal development and effects of prenatal nicotine exposure.

Infants of smoking mothers are at increased risk of SIDS, one cause of which is thought to be due to impaired ventilatory responses. We tested the hypotheses that prenatal nicotine exposure impairs the development of dynamic carotid chemoreceptor-driven ventilatory responses, and reduces the ability to lower metabolic rate in hypoxia. Osmotic minipumps were implanted into 20 pregnant rats at day 3 of gestation to deliver nicotine (6 mg/kg per day free base) or saline for 4 weeks. Minute ventilation was recorded breath by breath in rat pups at 3, 8 and 18 days (n = 6, 8 and 6) postnatal in response to 5-sec challenges of 100% O2 (Dejours test) and 5% O2 + 5% CO2. Carotid sinus nerve (CSN) responses to hypoxia and CO2 were recorded from 22 control and 17 nicotine-exposed preparations at ages between 3-20 days. Oxygen consumption (V(O)2) was measured in groups of pups at 3 days (n = 7 each for nicotine and control) and 8 days (n = 5 each for nicotine and control) in room air and 10% O2. There was no detectable effect of nicotine exposure on the development of CSN responses. Ventilatory responses to 5% O2-5% CO2 increased with age but did not differ between nicotine and control groups. Ventilatory responses to 100% O2 were unaffected by nicotine exposure at 8 and 18 days. However, the 3-day nicotine group showed no significant response to 100% O2 whereas V(E) was significantly reduced in the control group by 100% O2. There was no significant effect of nicotine exposure on the ability to reduce oxygen consumption in hypoxia at 3 or 8 days, but at 3 days, baseline (room air) variability in oxygen consumption was greater in the nicotine group. We conclude that nicotine exposure appears to result in abnormal ventilatory responses to withdrawal of baseline peripheral chemoreceptor drive during a period of early postnatal life. We speculate that a transient abnormality could contribute to a period of instability and increased vulnerability to challenges.

Chronic hypoxia abolished the postnatal increase in carotid body type I cell sensitivity to hypoxia.

The O2 sensitivity of carotid chemoreceptor type I cells is low just after birth and increases with postnatal age. Chronic hypoxia during postnatal maturation blunts ventilatory and carotid chemoreceptor neural responses to hypoxia, but the mechanism remains unknown. We tested the hypothesis that chronic hypoxia from birth impairs the postnatal increase in type I cell O2 sensitivity by comparing intracellular Ca2+ concentration ([Ca2+]i) responses to graded hypoxia in type I cell clusters from rats born and reared in room air or 12% O2. [Ca2+]i levels at 0, 1, 5, and 21% O2, as well as with 40 mM K+, were measured at 3, 11, and 18 days of age with use of fura 2 in freshly isolated cells. The [Ca2+]i response to elevated CO2/low pH was measured at 11 days. Chronic hypoxia from birth abolished the normal developmental increase in the type I cell [Ca2+]i response to hypoxia. Effects of chronic hypoxia on development of [Ca2)]i responses to elevated K+ were small, and [Ca2+]i responses to CO2 remained unaffected. Impairment of type I cell maturation was partially reversible on return to normoxic conditions. These results indicate that chronic hypoxia severely impairs the postnatal development of carotid chemoreceptor O2 sensitivity at the cellular level and leaves responses to other stimuli largely intact.

Postnatal maturation of carotid body and type I cell chemoreception in the rat.

The site of postnatal maturation of carotid body chemoreception is unclear. To test the hypothesis that maturation occurs synchronously in type I cells and the whole carotid body, the development of changes in the intracellular Ca2+ concentration responses to hypoxia, CO2, and combined challenges was studied with fluorescence microscopy in type I cells and compared with the development of carotid sinus nerve (CSN) responses recorded in vitro from term fetal to 3-wk animals. Type I cell responses to all challenges increased between 1 and 8 days and then remained constant, with no multiplicative O2-CO2 interaction at any age. The CSN response to hypoxia also matured by 8 days, but CSN responses to CO2 did not change significantly with age. Multiplicative O2-CO2 interaction occurred in the CSN response at 2-3 wk but not in younger groups. We conclude that type I cell maturation underlies maturation of the CSN response to hypoxia. However, because development of responses to CO2 and combined hypoxia-CO2 challenges differed between type I cells and the CSN, responses to these stimuli must mature at other, unidentified sites within the developing carotid body.

Resetting and postnatal maturation of oxygen chemosensitivity in rat carotid chemoreceptor cells.

1. Carotid chemoreceptor sensitivity is minimal immediately after birth and increases with postnatal age. In the present study we have investigated the peri- and postnatal developmental time course of [Ca2+]i responses to hypoxia in clusters of type I cells isolated from near-term fetal rats and rats that were 1, 3, 7, 11, 14 and 21 days old, using the Ca2+-sensitive fluoroprobe fura-2. 2. In type I cells from all age groups a graded increase in [Ca2+]i occurred in response to lowering the PO2 from 150 mmHg to 70, 35, 14, 7, 2 and 0 mmHg. The graded [Ca2+]i response to hypoxia was hyperbolic at all ages. 3. Type I cells from rats near-term fetal to 1 day old exhibited small [Ca2+]i responses, mainly to the most severe levels of hypoxia. After day 1, an increase in the [Ca2+]i responses to submaximal hypoxia stimulation resulted in a rightward shift in the O2 response curve. Using the Delta[Ca2+]i between 35 and 2 mmHg PO2 as an index of O2 sensitivity, type I cell O2 sensitivity increased approximately 4- to 5-fold between near-term fetal to 1 day old and 11 to 14 days of age. 4. Exposure to elevated extracellular potassium (10, 20 and 40 mM K+) caused a dose-dependent [Ca2+]i rise in type I cells from all age groups. There were no age-related changes in [Ca2+]i responses to any level of K+ between near-term fetal and 21 days. 5. We conclude that the maximal type I cell [Ca2+]i response to anoxia, as well as the sensitivity to submaximal hypoxic stimulation, of rats aged from near-term fetal to 21 days depends on the level of postnatal maturity. The lack of an age-related increase in the [Ca2+]i response to elevated K+ during the timeframe of maximal development of O2 sensitivity suggests that resetting involves maturation of O2 sensing, rather than non-specific developmental changes in the [Ca2+]i rise resulting from depolarization.

Mechanism of suppressed neutrophil mobilization in a mouse model for binge drinking: role of glucocorticoids.

The goals of this study were to determine if suppression of neutrophil accumulation and TNF-alpha production in the peritoneal cavity occurs in mice exposed to a chemical stressor [ethanol (EtOH)], to evaluate the role of EtOH-induced increases in endogenous glucocorticoids in any such suppression, and to determine if decreased tumor necrosis factor-alpha (TNF-alpha) production is responsible for decreases in neutrophil accumulation in EtOH-treated mice. An inflammatory response induced in the peritoneal cavity of mice by administration of heat-killed Propionibacterium acnes (P. acnes) was suppressed by a single dose of EtOH given 1 h before administration of the bacteria, as indicated by decreased accumulation of neutrophils in the peritoneal cavity. The concentration of TNF-alpha in the peritoneal cavity was also decreased by EtOH, but exogenous TNF-alpha did not prevent the suppression of neutrophil accumulation. The glucocorticoid antagonist RU-486 did not prevent the suppression of neutrophil accumulation in mice treated with EtOH, but RU-486 did block suppression of neutrophil accumulation caused by administration of exogenous corticosterone. The suppression of neutrophil accumulation caused by exogenous corticosterone was less than produced by EtOH. These observations suggest that the increase in endogenous corticosterone induced by EtOH may explain some of the suppression of neutrophil accumulation, but other neuroendocrine mediators (or EtOH per se) are sufficient to cause the full suppressive effect when the action of corticosterone is blocked by RU-486. The results also demonstrate that EtOH decreases TNF-alpha production, but this is not the mechanism by which neutrophil accumulation is decreased in this model.

Expression of dopamine D1-receptor mRNA in the carotid body of adult rabbits, cats and rats.

Dopamine is a major neurotransmitter in the carotid body of several animal species and its functional role at the level of peripheral arterial chemoreflex pathway is attributed to the presence of the dopamine D2-receptors. We present evidence that the dopamine D1-receptor mRNA is also expressed in the carotid body of adult rabbits, cats and rats. A DNA fragment of 611 bp of this receptor was first isolated from rabbit. The nucleic acid sequence of this fragment was found to be 84.5% identical to that of rat. This specific 611 bp fragment was used as a probe to detect, either by Northern analysis or by the reverse transcription-polymerase chain reaction, the dopamine D1-receptor mRNA. The results revealed the presence of dopamine D1-receptor transcript in the carotid body as well as in the petrosal ganglion and the superior cervical ganglion from the three animal models studied here. The physiological significance of dopamine D1-receptor expression in the carotid body is discussed.

Arousal and ventilatory responses during sleep in children with obstructive sleep apnea.

Abnormal central regulation of upper airway muscles may contribute to the pathophysiology of the childhood obstructive sleep apnea syndrome (OSAS). We hypothesized that this was secondary to global abnormalities of ventilatory control during sleep. We therefore compared the response to chemical stimuli during sleep between prepubertal children with OSAS and controls. Patients with OSAS aroused at a higher PCO2 (58 +/- 2 vs. 60 +/- 5 Torr, P < 0.05); those with the highest apnea index had the highest arousal threshold (r = 0.52, P < 0.05). The hypercapnic arousal threshold decreased after treatment. For all subjects, hypoxia was a poor stimulus to arousal, whereas hypercapnia and, particularly, hypoxic hypercapnia were potent stimuli to arousal. Hypercapnia resulted in decreased airway obstruction in OSAS. Ventilatory responses were similar between patients with OSAS and controls; however, the sample size was small. We conclude that children with OSAS have slightly blunted arousal responses to hypercapnia. However, the overall ventilatory and arousal responses are normal in children with OSAS, indicating that a global deficit in respiratory drive is not a major factor in the etiology of childhood OSAS. Nevertheless, subtle abnormalities in ventilatory control may exist.

Blood pressure in children with obstructive sleep apnea.

Hypertension is a common complication of obstructive sleep apnea in adults. However, hypertension has not been studied systematically in children with the obstructive sleep apnea syndrome (OSAS). We therefore measured blood pressure (BP) during polysomnography in 41 children with OSAS, compared to 26 children with primary snoring (PS). Systolic and diastolic BP were measured every 15 min via an appropriately sized arm cuff, using an automated system. This was tolerated by the children without inducing arousals from sleep. Children with OSAS had a significantly higher diastolic BP than those with PS (p < 0.001 for sleep and p < 0.005 for wakefulness). There was no significant difference in systolic BP between the two groups. Multiple linear regression showed that blood pressure could be predicted by apnea index, body mass index, and age. Blood pressure during sleep was lower than during wakefulness (p < 0.001 for diastole and p < 0.01 for systole), but did not differ significantly between rapid eye movement (REM) and non-REM sleep. We conclude that childhood OSAS is associated with systemic diastolic hypertension.

Sleep-disordered breathing in children with achondroplasia.

OBJECTIVE: Our objective was to characterize sleep-disordered breathing in 88 children with achondroplasia aged 1 month to 12.6 years. RESULTS: At the time of their initial polysomnography, five children had previously undergone tracheostomy, and seven children required supplemental oxygen. Initial polysomnography demonstrated a median obstructive apnea index of 0 (range, 0 to 19.2 apneas/hr). The median number of central apneas with desaturation per study was 0.5 (0 to 49), the median oxygen saturation nadir was 91% (50% to 99%), and the median peak end-tidal pCO2 was 47 mm Hg (36 to 87 mm Hg). Forty-two children (47.7%) had abnormal initial study results, usually caused by hypoxemia. Two children with severe obstructive sleep apnea eventually required continuous positive airway pressure therapy, and three additional children required tracheostomies. CONCLUSIONS: (1) Children with achondroplasia often have sleep-related respiratory disturbances, primarily hypoxemia. (2) The majority do not have significant obstructive or central apnea; however, a substantial minority are severely affected. (3) Tonsillectomy and adenoidectomy decreases the degree of upper airway obstruction in most but not all children with achondroplasia and obstructive sleep apnea. (4) Restrictive lung disease can present at a young age in children with achondroplasia.

SIDS: counseling parents to reduce the risk.

Although the cause or causes of sudden infant death syndrome (SIDS) remain unknown, the incidence of SIDS is on the decline in the United States and other countries. This decline has been accomplished largely through public education campaigns informing parents about several important factors associated with an increased risk of SIDS. These factors are prone and side infant sleeping positions, exposure of infants to cigarette smoke and potentially hazardous sleeping environments. Risk-reduction measures such as placing healthy infants to sleep in the supine position, avoiding passive smoke exposure both before and after birth and optimizing crib safety are beginning to lower the SIDS rate in this country. Through patient education, family physicians can further reduce the incidence of the number one cause of death in infants one week to one year old.