Behavior of VRG neurons during the atonia of REM sleep induced by pontine carbachol in decerebrate cats.

The microinjection of carbachol into the pons of acute decerebrate cats elicits a REM sleep-like atonia and a profound suppression of respiratory motoneuronal activity (J. Appl. Physiol., 69 (1990) 2280-2289). To assess whether this suppression is mediated by medullary neurons that provide respiratory drive to motoneurons of the respiratory pump muscles (diaphragm and intercostals), we studied the effect of pontine carbachol on the activity of neurons of the ventral respiratory group (VRG) in decerebrate, vagotomized, paralyzed and artificially ventilated cats. VRG neurons were recorded extracellularly along with the activity of phrenic and intercostal (external and internal) nerves. Both inspiratory (I) and expiratory (E) VRG neurons had incrementing, ramp-like bursts of activity during their firing periods and were not vagal motoneurons. Carbachol produced a depression of the peak firing rate in most (42/57) neurons studied. However, five cells showed no change and ten had an increase in activity in spite of consistent depression at the motoneuronal level. For the total population of cells (34 I and 23 E), the peak firing was reduced to 88.5% +/- 16.3 (S.D.) of control. The simultaneously recorded phrenic activity was reduced to 77.9% +/- 11.5, while inspiratory intercostal activity fell to 63.4% +/- 21.6 and expiratory to 23.2% +/- 21.2 of control. The carbachol-induced changes in peak firing of both I and E cells were quantitatively similar, and positively correlated to changes in peak phrenic activity. Analysis of this correlation suggested that phrenic and intercostal activities will be depressed to some degree by carbachol even when the average VRG cell activity remains unchanged. In addition, our data show that VRG cells may receive a combination of inhibitory and excitatory inputs during the carbachol-induced depression of respiratory motoneurons. Thus, although some disfacilitation from VRG cells may occur, there must be additional inhibitory or disfacilitatory pathways that mediate the decrease in activity of both phrenic and intercostal motoneurons that accompanies the REM sleep-like atonia.     

Mechanisms for the association of gastroesophageal reflux and bronchospasm

The mechanism for the association between gastroesophageal reflux and bronchospasm is probably multifactorial. Our data support the view that microaspiration into the trachea may be an important mechanism for bronchospasm induced by gastroesophageal reflux and needs to be distinguished from simple reflux into the esophagus. Intraesophageal acidification alone quantitatively produces a much smaller airway response than does intratracheal acidification. A challenge test should be developed to correlate airway response following intraesophageal acidification to airway hyperactivity. We believe that the relationship of the diaphragm to the antireflux barrier deserves further study.     

Effects of topical and systemic folic acid supplementation on gingivitis in pregnancy

Abstract A double-blind study evaluated the effects of systemic and topical folate on gingival inflammation during the fourth and eighth months of pregnancy. Thirty women were randomly divided into three groups. Group A received placebo mouthwash and tablets; Group B: placebo mouthwash and 5 mg folate tablets; Group C: folate mouthwash and placebo tablets. Supplementation lasted for 14 days during months 4 and 8. Subjects took one tablet daily and rinsed twice daily for 1 min with the mouthwash. At the start and finish of each 14-day period, fasting serum and red cell folate levels were estimated and oral status assessed by a plaque index (PII), a gingival index (GI), and gingival exudate flow meter (GEF). Subjects completed 1-week diet sheets which were analysed for dietary folate. All groups were similar in each parameter at the start. Correlation was demonstrated between GI and P1I, and between GI and GEF. GI tended to increase throughout pregnancy in all groups except Group C, when in the eighth month there was a highly significant improvement (0.001 < P < 0.01) despite no significant change in PH. Although dietary intake of folate was significantly higher during the eighth month in Group C as compared with Groups A and B, (0.001 < P < 0.01), the folate mouthwash produced highly significant improvement in gingival health in pregnancy.     

Changes in symptoms of sleep-disordered breathing during pregnancy

BACKGROUND: Although incident snoring is common in pregnant women and has been proposed as a potential risk factor for adverse maternal-fetal outcomes, the development of sleep-disordered breathing during pregnancy has not been prospectively described. METHODS: Using the Apnea Symptom Score from the Multivariable Apnea Prediction Index and the Epworth Sleepiness Scale, we prospectively assessed symptoms of sleep-disordered breathing and daytime somnolence in 155 women to determine whether symptoms increased during pregnancy and the characteristics associated with increasing symptoms. RESULTS: We found that sleep-disordered breathing symptoms (Apnea Symptom Score, 0.44 (SEM 0.58) vs 0.95 (0.09, P < .001) and the degree of daytime somnolence (Epworth Sleepiness Scale, 8.6 (0.3) vs 10.2 (0.4), P = .0003) increased significantly during pregnancy. Women with higher baseline body mass indexes and greater increases in neck circumference during pregnancy reported higher apnea symptom scores. Of the 155 subjects, 11.4% reported an increase in Apnea Symptom Score of 2 units or more, consistent with a clinically significant increase in symptoms; these women experienced a significantly greater increase in subjective sleepiness than other subjects (P = .03). Excessive daytime somnolence (Epworth Sleepiness Scale > 10) was prevalent throughout pregnancy (31.0%-45.5%). CONCLUSIONS: Our data demonstrate that symptoms of sleep-disordered breathing increase during pregnancy and that more than 10% of our subjects may be at risk for developing sleep apnea during pregnancy. Excessive daytime somnolence was highly prevalent even early in pregnancy and became increasingly common as pregnancy progressed.