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Biomedical subjects

V Chernick

Publications and source records attributed to V Chernick.

At least 91 records · Page 5Linked to original sources
PubMed1977

EEG frequency spectrum characteristics of sleep states in infants of alcoholic mothers.

Infants of alcoholic mothers showed prominent EEG hypersynchrony in all three stages of sleep: in quiet sleep, indeterminate sleep and active-REM sleep. Spectral analysis of the EEG using fast Fourier transform revealed significant increase in power in most frequency bands in all three stages of sleep in infants born to alcoholic mothers when compared with normal healthy infants matched for gestational age. In quiet sleep "alcoholic" infants differed from healthy babies by significantly higher power in a wide range of frequency bands (1.5--17.5 Hz) with an average 143% increase of the integrated EEG (1.5--25 Hz). In indeterminate sleep "alcoholic" infants showed significantly higher power in all analyzed frequency bands (0.1--25 Hz) with an average 196% increase of the integrated EEG (1.5--25 Hz). In active-REM sleep infants of alcoholic mothers showed significantly higher power in the frequency range from 0.1 to 17.5 Hz in comparison with healthy controls. The average increase of the integrated EEG (1.5--25 Hz) was 200%. All healthy term infants showed significantly higher power in most frequency bands during quiet sleep in comparison with active-REM sleep. In infants born to alcoholic mothers this quiet sleep--REM sleep frequency spectrum difference in the majority of cases was nonsignificant mainly due to high values of the EEG power during REM sleep. It is unlikely that the EEG hypersynchrony in infants of alcoholic mothers represents one of the symptoms of the neonatal alcohol-withdrawal syndrome since hypersynchrony has been detected as long as 6 weeks after birth. During this time any withdrawal symptoms would have been dissipated.

Age Factors↗
PubMed1976

Enhanced fetal erythrocyte carbonic anhydrase activity by hydrocortisone.

The present experiments were undertaken to study the effect of exogenous corticosteroids on carbonic anhydrase (CA) activity in fetal erythrocytes. Rabbit fetuses from 24 days of gestation to term (31 days) were injected intraperitoneally with either 0.2 ml of 0.9% saline or 2.5 mg hydrocortisone succinate. Nonoperated, noninjected animals served as controls. Carbonic anhydrase activity measured at 24 hr after injection was increased in the saline-injected group at all ages studies when compared with the noninjected fetuses. A marked increase (2- to 7-fold) in enzyme activity was demonstrated after steroid injection at 24 but not 48 hr after treatment. An increase in CA activity was also demonstrated after incubating fetal erythrocytes for 2, 4, and 8 hr in the presence of hydrocortisone succinate. It is suggested that low CA activity in infants with hyaline membrane disease (HMD) may reflect lack of enhancement by steroid.

Animals↗
PubMed1975

Respiratory effects of H+ and dinitrophenol injections into the brain stem subarachnoid space of fetal lambs.

Mock cerebrospinal fluid (pH 5.37-8.38) or 2,4-dinitrophenol (DNP) (0.15-1.5 mg) was injected into the subarachnoid space of the ventral brain stem of exteriorized fetal sheep. Changes in pH on the ventral surface of the medulla did not stimulate respiratory efforts or induce significant cardiovascular changes. The respiratory response to DNP injections ranged from no response to prolonged rhythmic ventilation that was independent of the peripheral chemoreceptors or the control arterial pH and blood gas tensions. This inconsistency suggests an effector site somewhat removed from the immediate surface of the medulla. The heart rate and blood pressure were not affected. It is concluded that increased H+ concentration in the extracellular fluid of the fetal ventral medulla does not initiate respiration, and any respiratory response to metabolic inhibitors applied to this area therefore is not attributable to a secondary change in surface pH.

Animals↗
PubMed1975

Role of peripheral and central chemoreceptors in the initiation of fetal respiration.

The relationship between fetal femoral arterial P02 and PC02 was evalulated in 13 fetal sheep with intact and denervated peripheral chemoreceptors. With intact chemoreceptors, a significant relationship was found between fetal Pa02 and PaC02 at the time of the first breath (Pa02 = 2.57 + 0.09 PaC02; r = 0.62, P less than 0.05)mfollowing bilateral carotid sinus nerve section (CSN) or total peripheral chemodenervation (TD), PaC02. Comparison of the intact, CSN, and TD blood gases at the time of the first breath demonstrated that a) severe hypoxemia stimulates fetal respiration even following total peripheral chemodenervation; b) fetal central chemoreceptors do not respond to PaC02; c) PaC02 acting via peripheral chemoreceptors has a minor modulating effect on the degree of hypoxemia required to initiate fetal respiration. At a PaC02 below 40 mmHg this effect is inhibitory, acting via the carotid body. At a PaC02 above 90 mmHg this effect is stimulatory, acting via both carotid and aortic bodies.

Animals↗
PubMed1975

Site of central chemosensitivity in fetal sheep.

The heart rate, blood pressure, and respiratory response to topically applied cyanide on the ventrolateral medullary surface and upper spinal cord was studied on exteriorized sinaortic-denervated fetal lambs under pentobarbital anesthesia. On all sites tested cyanide produced a rapid increase in heart rate and blood pressure (P smaller than 0.05) which was most pronounced from the area adjacent to the nerve roots IX to XI (mean 32%). Respiratory efforts consisting of 1-8 gasps were induced in half the applications to the medulla but never when the pledgets were applied to the spinal cord. The mean delay to response was 43 s (range 13-102 s). After cautery of the chemosensitive areas, topical application of cyanide failed to stimulate gasping, whereas intravenous cyanide or cord clamping still produced a vigorous respiratory response. It is concluded that sympathetic stimulation of the heart and blood vessels can originate centrally in response to local histotoxic hypoxia of the ventral medulla and upper spinal cord. Furthermore, it is proposed that in the apneic fetus histotoxic hypoxia of the medulla initiates respiration possibly by stimulating a special gasping mechanism which is separate from the respiratory center responsible for rhythmic breathing after birth. The responsible neurons must be located at least 2 mm beneath the ventral medullary surface.

Administration, Topical↗
PubMed1975

Electrical activity of phrenic nerve and diaphragm in utero.

Phrenic nerve activity, diaphragmatic EMG, and tracheal or pleural pressure changes were recorded in a chronic fetal sheep preparation. Three patterns of fetal phrenic nerve activity were observed: 1) a single burst; 2) irregular nonrhythmic bursts; and 3) prolonged rhythmic activity, seen only prior to fetal death. The total recording time was 54.53 h and the total duration of phrenic nerve activity was 65.34 min (2.16%). When an inactive period was defined as the absence of phrenic nerve activity for 60 s or more, active periods occupied 44.7% of the total time. Phrenic nerve activity was present in all fetuses and 97.5% of the time was coupled with diaphragmatic EMG. Both diaphragmatic EMG and intrapulmonary pressure changes occurred in the absence of phrenic nerve activity. In three fetal animals both phrenic nerves were transected. Tracheal pressure changes were seen which were not coupled with corresponding intrauterine pressure changes. Thus, changes in fetal tracheal pressure or diaphragmatic EMG do not necessarily represent the output of the fetal respiratory center. This study suggests that the fetal respiratory center is active in utero, but this activity is minimal and has a different pattern that that present after birth.

Animals↗
PubMed1975

Effect of metopirone on the synthesis of lung surfactant in does and fetal rabbits.

The possible role of endogenous corticosteroids in the induction of synthesis of lung surfactant in both maternal and fetal rabbits was investigated. Metopirone (SU 4885), which specifically inhibits B hydroxylation in the adrenal gland, thus preventing endogenous cortisol production was used in this study. Pregnant rabbits received one of four treatment regimens: saline, metopirone, cortisone or metopirone plus steroid for 6 days before delivery. Studies of the lungs of the adult rabbits revealed that lung weights and percent dry weight were not influenced by drug injection. However, lung DNA content (mg/g) in the metopirone-treated group was higher than the control group, indicating an increase in cell number. Compared to the saline-treated group there was a significant decrease in lung phospholipid content in the other three groups (p smaller than 0.005). A decrease in lung lecithin and phosphatidylethanolamine was also noted in these three groups indicating that the inhibition was in the early steps of biosynthesis of lung lecithin. The specific activity of 14C-labelled palmitate in lung lecithin was not altered by drug treatment indicating that saturated fatty acid incorporation into lung lecithin is not influenced by metopirone, steroid or a combination of both drugs. Quasi-static deflation pressure-volume characteristics of the lung were also similar in all groups. However, lungs of animals receiving both metopirone and steroid had a small but statistically significant decrease in minimum surface tension (p smaller than 0.05). The change in surface tension did not correlate with a change in lung retractive forces or with lung lipid content and was, therefore, of dubious biological significance. Metopirone administration to pregnant rabbits did not alter surface active properties in the fetus from the 26th to the 29th day of gestation when compared to control fetuses. At day 30-31 gestation the offsprings of metopirone-treated rabbits had lung total phospholipid and lecithin contents, and deflation pressure-volume curves similar to control group, but minimum surface tension of minced lung extracts were high in about 60% of the fetal lungs studied (p smaller than 0.05). These results suggest that endogenous steroid production may play a significant role in the maturation of the fetal lung.

Animals↗
PubMed1975

Bronchopulmonary dysplasia and lung rupture in hyaline membrane disease: influence of continuous distending pressure.

Review of 158 patients with hyaline membrane disease was undertaken. The introduction of artificial ventilation with a positive end-expiratory pressure (IPPB and PEEP) has doubled the prevalence of pneumothorax, pneumomediastinum and interstitial emphysema from 20.7% to 39.7%). Continuous negative distending pressure during spontaneous ventilation (CNP) was associated with a prevalence of lung rupture similar to that occurring spontaneously (4.8%). No patient treated with CNP alone developed bronchopulmonary dysplasia. Patients treated with IPPB with PEEP had a marked decreased prevalence of bronchopulmonary dysplasia (17.2%) when compared to patients treated with IPPB alone (36.2%), probably related to the enhanced overdistension of relatively normal areas of the lung may be related to the increased prevalence of lung rupture seen during IPPB with PEEP.

Humans↗