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Biomedical subjects

A C Cornwell

Publications and source records attributed to A C Cornwell.

14 recordsLinked to original sources
PubMed1998

SIDS, abnormal nighttime REM sleep and CNS immaturity.

SIDS (Sudden Infant Death Syndrome) is the major cause of death in young, apparently healthy, infants, yet its etiology and pathogenesis remain unknown. SIDS peaks at 2-4 months, is more prevalent in the winter months and typically occurs in the early morning hours when most babies are asleep, suggesting that sleep may be part of the pathophysiological mechanism of SIDS. The sleep patterns of infants at high risk for SIDS were analyzed to test the hypothesis that there are abnormalities specific to nighttime sleep which may be indicative of a central nervous system (CNS) deficit that contributes to a high frequency of SIDS during the night. Electrophysiological sleep variables were recorded at monthly intervals in 1-6 months-old infants during the peak age of SIDS. The risk group (R) was resuscitated from a potentially life-threatening Sudden A-Ventilatory Event (S.A.V.E.) and compared to a group of control infants (C) with no family history of SIDS. The data representing four equal time intervals from 11 p.m.-11 a.m. show an abrupt, statistically significant increase in REM sleep from 2-5 a.m. in R infants. In C infants, time spent in REM sleep after 2 a.m. becomes progressively shorter while NREM sleep is proportionately longer. From 11 p.m.-2 a.m., however, R and C infants do not differ either in the duration or in the percent of total sleep time (TST) of REM sleep. We hypothesize that these REM sleep abnormalities in vulnerable infants are indicative of a pervasive CNS immaturity. The higher prevalence of SIDS in the cold winter months and in the early morning hours, when darkness is prolonged, is discussed in relation to the possible involvement of the circadian rhythm of melatonin.

Age Factors↗
PubMed1993

Sex differences in the maturation of sleep/wake patterns in high risk for SIDS infants.

Male and female high risk for SIDS infants were compared with a group of rigorously matched controls in sleep/wake variables during the peak period for SIDS, i.e., 2-4 mos. Continuous 24-72 hr. in-hospital recordings yielded data based on 3,792 hrs. of electrophysiological activity. The data show that risk male infants fail to demonstrate an increase in wakefulness with age and reveal a lag in the maturation of REM sleep compared to controls and female risk infants during the critical age for SIDS. Significant sex differences within the first six months of life are of particular importance because of the consistently reported higher incidence of SIDS in males than females. An immature sleep/wake organization which occurs differentially in male high risk for SIDS infants suggests that a CNS functional disorder is present selectively in male infants as a precursor to SIDS. The greater susceptibility of male infants to SIDS emphasizes the importance of these data based on unique long-term recordings.

Age Factors↗
PubMed1982

Respiratory and cardiac events observed and recorded during and following a "near miss" for Sudden Infant Death Syndrome episode.

Documented observations of a 5-week-old infant during a "near miss" for a Sudden Infant Death Syndrome (SIDS) episode by a physician were carried out during an in-hospital physiological recording of respiratory and cardiac activity. This "near miss" event occurred during quiet sleep and was characterized by a prolonged apneic attack with marked bradycardia, cyanosis and limpness which required immediate vigorous resuscitative efforts by a physician and trained nurse. Parental descriptions of similar events parallel these documented sudden unexpected changes in cardiorespiratory parameters. Objective polygraphic data were obtained immediately following the episode and at later ages during 24 and 48 hour continuous recordings of respiration, heart rate, sleep/wake and behavioral activity. The data show that numerous apneic episodes occurred following the "near miss" event, many accompanied by marked bradycardia. The moderately severe hypoxemia noted during these sleep-related apneas indicate that immediate intervention is required to prevent significant hypoxia and central depression in such infants.

Bradycardia↗
PubMed1981

Sleep apnea studies in an infant with congenital primary hypoventilation ("Ondine's curse").

Recurrent apneic episodes were typically associated with sleep, not wakefulness, in an infant with congenital primary hypoventilation ("Ondine's Curse"). Quiet sleep (SLQ) was shown to constitute a higher risk condition than active sleep (SLA) at the ages she was recorded polygraphically (2-4 months old). This infant's respiratory disorder was complicated by recurrent pneumonia, seizures and deficient growth which resulted in death at the age of eight months. Necropsy revealed bronchopulmonary dysplastic fibrosis and cor pulmonale. Neuropathologic examination failed to reveal pathologic changes in the brainstem.

Autonomic Nervous System Diseases↗
PubMed1981

Flicker: a "decay" effect after light deprivation.

The "decay" effect resulting from repetitive light stimulation at different flicker rates was investigated. Adult cats were visually deprived monocularly or binocularly for 1 or 2 weeks. The results showed a progressive decrease in the b-wave of the electroretinogram during the later flashes in a train. The data are presented as percent of the initial response to a flash. In the control eye the b-wave stabilized rapidly after the initial flash in a train of stimuli. Partial recovery occurred after 1 week of normal stimulation.

Animals↗
PubMed1979

Sudden infant death syndrome: a testable hypothesis and mechanism.

The Sudden Infant Death Syndrome (SIDS) is the most frequent cause of death in infants aged between one month and one year, yet its cause remains unknown. The present hypothesis is that most infants who die of SIDS have an abnormality of the catecholaminergic system, possible genetically determined, which results in a decreased thermogenic response to cold, owing to a deficiency in noradrenaline (NA), which eventually results in severe hypothermia. A series of complex, but interrelated reactions of the infant to the hypothermia and its consequences leads to death. The final mechanism of regulatory failure involves a deterioration of cardiorespiratory function resulting from hypoxia, metabolic acidosis and hypoglycemia. The etiology of "near miss" for SIDS is also unknown. It is postulated that these infants have a similar but milder deficiency which may be due, in part, to genetic factors. Determinations of central and peripheral catecholamines in "near miss" and normal infants will be performed to test this hypothesis.

Acidosis↗
PubMed1979

Tapetum disorganization in taurine-depleted cats.

A severe disorganization of the lattice arrangement of tapetal rods occurs in cats nutritionally deprived of taurine. This is the first reported example of a nutritionally related degeneration of tapetal cells. The tapetal cell degeneration, along with the previously noted photoreceptor degeneration in taurine-depleted cats, suggests that taurine plays a vital role in maintaining the structural integrity of some biological structures. The visual evoked potentials were severely reduced in taurine-depleted cats as were the electroretinogram responses, as previously noted, indicating that they are deficient in light processing. These results also emphasize the importance of dietary taurine for the maintenance of normal structure and function of the eye, at least in the cat.

Animals↗
PubMed1978

Ambulatory and in-hospital continuous recording of sleep state and cardiorespiratory parameters in 'near miss' for the sudden infant death syndrome and control infants.

Electrophysiologic and cardiorespiratory events were studied polygraphically and by ambulatory monitoring in 'near miss' for sudden infant death syndrome (SIDS) and normal control infants 1-4 months old. The data show that 'near miss' babies typically have many apneic periods in their sleep, particularly apneas lasting 10 sec or longer. These tend to decrease with age. They have longer lasting apneas than controls, although the latter have respiratory pauses lasting less than 10 sec, in particular during rapid eye movement (REM) sleep. An upper respiratory infection (URI) in 'near miss' infants clearly appears to be a risk factor which will be studied further both in-hospital and at home using a monitoring technique with our Medilog ambulatory system.

Ambulatory Care↗