Search PubMed⌕ Search

Biomedical subjects

C W Tyler

Publications and source records attributed to C W Tyler.

At least 109 records · Page 6Linked to original sources
PubMed1981

Deaths associated with laparoscopic sterilization by unipolar electrocoagulating devices, 1978 and 1979.

In 1978 and 1979, two women in the United States were reported to have died from electrical complications following sterilization with unipolar coagulating devices. Both deaths followed apparent bowel injuries occurring at the time of sterilization. Numerous reports have documented the electrical accidents associated with unipolar electrocoagulation. Because unipolar electrocoagulation has greater risk for these complications than alternative sterilization techniques, without proved greater benefits, we question the need for continuing its use in female sterilization.

Adult↗
PubMed1981

Binocularity in the human visual evoked potential: facilitation, summation and suppression.

The electrophysiology of normal binocular function was investigated by studying the binocular interactions from monocular and binocular visual evoked potentials (VEPs) recorded under a range of stimulus conditions. The amplitude and phase of the steady-state VEPs, which were obtained with sinusoidal gratings temporally modulated in counterphase, were measured with synchronous narrow-band filtering techniques. Binocular interactions were investigated as functions of spatial frequency, temporal frequency and contrast. Detailed sampling and testing within each stimulus domain revealed an unprecedented degree of VEP specificity in the extent of binocular interaction, which varied from zero summation to pronounced facilitation. Binocular facilitation was explored in terms of its relation to the neural mechanisms subserving binocular function. VEP correlates of rivalry, fusion and stereopsis were obtained. The facilitatory binocular interactions, revealed by careful spatial and temporal stimulus manipulations, were akin more to the neurophysiological responses of single neurons than to previously reported evoked potential work. The relationship between the specificity and narrow tuning of the binocular interactions recorded with VEP techniques and those recorded with single unit techniques is discussed.

Brain↗
PubMed1981

Binocular facilitation in the visual-evoked potential of strabismic amblyopes.

Electrophysiological correlates of abnormal binocular function were investigated by studying the monocular and binocular visual-evoked potentials (VEPs) of strabismic amblyopes. Steady-state evoked potentials were elicited by sinusoidal gratings which were temporally modulated in counterphase and logarithmically swept in spatial frequency from 0.2 to 20 c/deg in a 20 sec epoch. The VEP spatial frequency tuning functions of amblyopic eyes are abnormal in that they tend to show a reduced cutoff spatial frequency in relation to the nonamblyopic fellow eye. In contrast, the binocular interactions in strabismic amblyopes are similar in many respects to those of normal observers. These binocular interactions depend upon the spatial frequency and contrast of the stimulus, and may vary from inhibition to marked facilitation. The results suggest that some binocular function may be preserved in the cortex of patients with strabismic amblyopia, and that caution should be exercised in attempting to use the steady-state VEP to differentiate normal from abnormal binocular vision.

Adolescent↗
PubMed1981

Effects of restricted public funding for legal abortions: a second look.

At hospitals in three cities where public funding for legal abortions had been restricted, we reviewed the records of women with complications of all types of abortions. We compared the number of complications in the year before funding restriction with the number in the following year, during restriction. For complications of illegal and spontaneous abortions, we found no significant change in either the number or proportion of publicly funded hospitalizations. For complications of legal abortions, we found a decrease in both the number and proportion of publicly funded hospitalizations. For poor women, it appears that restriction of public funding for legal abortions has not markedly increased the number of illegal abortions, but has reduced the number of legal abortions, especially those at later gestational ages, which would have cost more and been at greater risk of complications.

Abortion, Legal↗
PubMed1981

Behavioral factors contributing to abortion deaths: a new approach to mortality studies.

One hundred six women were reported to have died from abortions (55 legal, 10 illegal, and 41 spontaneous) in the United States from 1975 through 1977. In reviewing these deaths, the authors developed a new approach to mortality studies. A catalogue was compiled of behavioral factors (including actions by physicians, patients, communities, and institutions) that in the authors' judgment increased the risk of death from abortion. The proportion of abortion deaths to which each behavioral risk factor contributed was determined. Of the 199 different behavioral factors, 5 contributed to more than 10% of legal abortion deaths, 5 to more than 10% of illegal abortion deaths, and 3 to more than 10% of spontaneous abortion deaths. The most frequent factors involved were delay in obtaining a legal abortion until 13 weeks' gestation or later, incomplete abortion, and inappropriate choice of antibiotics for septic abortion. Assessing the proportion of abortion deaths to which each factor contributed can help identify which factors deserve priority in prevention.

Abortion, Legal↗
PubMed1981

Specific deficits of flicker sensitivity in glaucoma and ocular hypertension.

Temporal modulation sensitivity for a 5 degree flickering field was measured in central and peripheral retina for 46 eyes with glaucoma and ocular hypertension. Prior to showing any visual field loss by conventional perimetry, 90% of patients exhibited significant losses in sensitivity around a specific frequency of about 30 to 40 Hz. Low-frequency sensitivity and critical flicker frequency were often unaffected by such losses. The central field showed almost as pronounced a loss as 20 degree in the periphery.

Adult↗
PubMed1980

Home delivery and neonatal mortality in North Carolina.

Neonatal mortality examined by place and circumstances of delivery in North Carolina during 1974 through 1976 with attention given to home delivery. Planned home deliveries by lay-midwives resulted in three neonatal deaths per 1,000 live births; planned home deliveries without a lay-midwife, 30 neonatal deaths per 1,000 live births; and unplanned home deliveries, 120 neonatal deaths per 1,000 live births. The women babies were delivered by lay-midwives were screened in county health departments and found to be medically at low risk of complication, despite having demographic characteristics associated with high-risk of neonatal mortality. Conversely, the women delivered at home without known prenatal screening or a trained attendant had low-risk demographic characteristics but experienced a high rate of neonatal mortality. Planning, prenatal screening, and attendant-training were important in differentiating the risk of neonatal mortality in this uncontrolled, observational study.

Adult↗
PubMed1980

Fatal ectopic pregnancy after attempted legally induced abortion.

From 1973 through 1978, the Center for Disease Control identified ten deaths caused by ruptured ectopic pregnancy after attempted legal abortions for those pregnancies. The women ranged in age from 18 to 31 years, seven were black, three were white, and five were nulliparous. The estimated gestational age was 16 menstrual weeks or earlier. In seven cases tissue obtained at abortion was sent for outside microscopic pathological examination; attempts to contact four of the patients when no products of conception were found were unsuccessful. An important factor in preventing fatal ectopic pregnancy for women who have legal abortions is the identification of products of conception at the time of the abortion procedure while the patient is still available for reexamination and recurretage.

Abortion, Legal↗
PubMed1980

On the depth of the cyclopean retina.

The maximum disparity which can elicit depth perception was measured in dynamic random-dot stereograms as a function of stimulus size and duration. Maximum disparity increased with size as a function of the square root of stimulus area, and depth could under optimal conditions be perceived up to several arc degrees of disparity, even for short (48 ms) durations of exposure. These data delineate the limiting disparity/depth characteristics of the cyclopean retina, and provide fresh evidence of the distinction between local and global disparity processing.

Animals↗