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J Tyson

Publications and source records attributed to J Tyson.

At least 19 recordsLinked to original sources
PubMed1992

Refinement of dendritic arbors along the tonotopic axis of the gerbil lateral superior olive.

We have investigated the development of dendritic arbors in a central auditory nucleus in the Mongolian gerbil, the lateral superior olive (LSO). The morphology of these arbors has been shown to vary with tonotopic position in adults, with high frequency neurons having a more restricted field. In the present study, qualitative observations were made on horseradish peroxidase-filled neurons from animals 1-11 days postnatal, and quantitative results were obtained from Golgi-impregnated material from animals 10 days postnatal and older. The tonotopic position of each cell was computed as a percent of the total distance along the LSO. The dendritic arbors of high frequency neurons became spatially constrained along the frequency axis during the 3rd postnatal week, while those in the low frequency region retained a broader arborization into adulthood. This refinement was correlated with a decrease in total dendritic length and the number of branch points per neuron, particularly in the high frequency projection region. The distribution of octave bandwidths to which single LSO neurons responded in 13-16 day animals showed a similar course of maturation across the tonotopic axis: high frequency neurons responded to a larger number of octaves, and with greater variability, than those in adults. These data suggest that a specific alteration in dendrite morphology, which occurs after the onset of response to airborne sound, may contribute to adult frequency selectivity.

Animals↗
PubMed1992

How should parents be informed about major procedures? An exploratory trial in the neonatal period.

The current doctrine of informed consent in medical practice may require the provision of more information than is understandable or desired by some parents. We conducted an exploratory trial comparing: (1) detailed risk/benefit disclosure provided both verbally and in writing and (2) flexible disclosure consisting of a brief verbal description supplemented with detailed verbal and written disclosure if desired by the mother. Information about mechanical ventilation was presented to 26 mothers of newborns at risk for respiratory failure. Of the 13 mothers in the flexible disclosure group, seven (54%) desired only brief verbal disclosure. Despite poor recall of information, most mothers were satisfied with the information provided. There was no evidence that the detailed disclosure group had greater maternal satisfaction or less maternal anxiety. Flexible disclosure as evaluated in this study had no important disadvantages relative to detailed disclosure. Methods of providing information to better meet the wants and needs of parents deserve further study.

Adolescent↗
PubMed1992

Adaptation of feeding to a low fat yield in breast milk.

The effect of a low milk fat yield was assessed in a blinded prospective study of healthy term infants and mothers encouraged to breast-feed. Fat yield index was calculated as milk volume collected by Egnell pump multiplied by the "creamatocrit." Two weeks after delivery mothers who had a relatively low fat yield index (less than or equal to 30th percentile) were matched with mothers with a higher fat yield index and with formula-feeding mothers. Between 2 and 6 weeks the low fat yield group had a marginally lower weight gain but similar growth in length and head circumference to that of the higher fat yield group. The low fat yield group spent more time per feeding and had more complete breast emptying, resulting in a fat yield index comparable with the higher fat yield group for the mean milk volume ingested by the infant at 6 weeks. A low fat yield had no adverse effect on maternal satisfaction or maternal-infant interaction during feeding. Formula feeders spent the least time in feeding and en face gazing. Adaptation of breast-feeding to a low fat yield sustains infant intake and growth, maternal-infant interaction, and maternal satisfaction. However, there is little reserve if milk production diminishes. Further study is needed to define the limits of adaptation and effective interventions if fat yield is inadequate.

Breast Feeding↗
PubMed1990

Prenatal care evaluation and cohort analyses.

The value of prenatal care has been obscured by multiple factors, including the limitations of birth certificate data, large socioeconomic disparities between women who seek prenatal care and those who do not, and the "preterm delivery bias", ie, the reduced pregnancy duration and opportunity for prenatal care among women who give birth prematurely. Perinatal mortality and morbidity (neonatal intensive care unit admission; ventilator therapy) were carefully assessed in an indigent population (28,838 deliveries at Parkland Memorial Hospital). To avoid the preterm delivery bias, a cohort of all women whose pregnancy reached a specific week of gestation was identified and their prenatal care status (zero vs one or more visits) by that week was related to pregnancy outcome. Separate cohorts were defined at 26, 30, 34, 38, and 42 weeks. Prenatal care was associated with improved pregnancy outcomes in only the 34-, 38-, and 42-week cohorts (P less than .01). Findings suggest substantial benefit from prenatal care after 30 weeks' gestation but not from early prenatal care. Unfortunately, it may not be possible to assess prenatal care accurately in observational studies even if cohort analyses are used. Clinical trials are needed to assess the effects of strategies for increasing or improving prenatal care, especially in early pregnancy.

Adolescent↗
PubMed1985

Concomitant therapy with labetalol and hydrochlorothiazide in moderate to moderately severe essential hypertension.

Labetalol is a competitive, nonselective antagonist of both beta 1 and beta 2 adrenoceptors. It has been suggested that labetalol reduces blood pressure (BP) predominantly by decreasing peripheral vascular resistance while maintaining cardiac output. We conducted a double-blind, randomized study to assess the antihypertensive effect of labetalol in patients with a standing diastolic blood pressure (SDBP) between 105 and 119 mm Hg. The study consisted of three separate phases in succession. Phase I was a single-blind, placebo washout phase, two to four weeks in length. Those patients with a SDBP greater than or equal to 105 mm Hg at the end of phase I entered phase II, in which they were administered labetalol in a forced titration of 100 mg bid to 400 mg bid. Those with a SDBP less than or equal to 90 mm Hg on the 400 mg bid regimen for two weeks were maintained on labetalol alone (N = 8). Those patients whose BP was not controlled (SDBP greater than or equal to 99 mm Hg, N = 15) were randomized in a double-blind fashion to receive either hydrochlorothiazide (HCTZ) or placebo in addition to labetalol for the next five weeks. Eight of the 15 patients received HCTZ and seven received placebo. The BPs at baseline and at the end of phase II were similar in the two groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Clinical Trials as Topic↗
PubMed1985

Bromocriptine as primary therapy for prolactin-secreting macroadenomas: results of a prospective multicenter study.

To assess the effectiveness of bromocriptine in reducing the size of PRL-secreting macroadenomas with extrasellar extension, we conducted a prospective multicenter trial in patients without prior radiotherapy, applying a standard protocol of treatment and tumor size evaluation. Basal serum PRL levels [1441 +/- 417 (+/- SEM) ng/ml for women; 3451 +/- 1111 ng/ml for men] fell in all patients and to 11% or less of basal values in all patients but 1. Normal PRL levels were reached in 18 of the 27 patients. In 13 patients (46%), tumor size was reduced by greater than 50%, in 5 patients (18%) by about 50%, and in 9 patients (36%) by approximately 10-25%. The extent of tumor size reduction did not correlate with basal PRL, nadir PRL, percent fall in PRL, or whether PRL levels reached normal. However, a reduction in PRL levels always preceded any detectable change in tumor size. In 19 patients, reduction in tumor size was evident by 6 weeks, but in the other 8, such reduction was not noted until the 6 month evaluation. In the 4 patients in whom bromocriptine was discontinued at the end of 1 yr, tumor reexpansion occurred in 3. Visual fields improved in 9 of the 10 patients in whom they were abnormal. Because of the excellent results found in most of the patients in this series, we suggest that therapy with bromocriptine should be considered as initial management for patients with PRL-secreting macroadenomas.

Adenoma↗
PubMed1984

Effect of nursing-staff support groups on the quality of newborn intensive care.

ICU support groups are widely recommended to mitigate the effects of stress on staff performance, thereby improving patient care. The usefulness of a nursing-staff support group was assessed in the neonatal ICUs of both a city/county hospital (10,000 births/yr) and a private hospital (3200 births/yr). Support-group meetings focused on communication and patient care and were conducted every 1 to 2 wk by psychiatrists experienced in intensive care support groups. Nevertheless, attendance diminished and the groups lasted only 6 to 7 months. Moreover, the quality of routine, emergency, and overall care did not differ significantly during intervention vs. control months. Our findings suggest that sources of ICU stress may be best addressed by methods other than nursing-staff support groups. Under the conditions of the study, we found little evidence to justify the expense and effort required to conduct ICU support groups.

Crisis Intervention↗
PubMed1984

Before we educate.

Explore the source record for details and available documents.

Diabetes Mellitus↗
PubMed1983

Stresses and coping in ICU nursing: why support groups fail.

A successful nurse support group was contrasted with two unsuccessful support groups. The authors concluded that support groups work best if they are initiated in response to a felt need by the nurses, if the nurses have experienced the group leader as helpful in the past, if the group is highly structured and does not allow early discharge of intense negative feelings, and if the group's problems are primarily interpersonal and can be dealt with in the group and not primarily environmental or administrative problems such as noise, overcrowding, or understaffing.

Adaptation, Psychological↗
PubMed1979

Diurnal variation in the quality and outcome of newborn intensive care.

Variables related to both the process and the outcome of neonatal intensive care were studied to compare care given during the day (0901-2100 hours) with that at night (2101-0900 hours). At night, intravenous infiltrations occurred more often, and the tidal volume of respirator-treated infants was verified less often. Blood pH values less than 7.20, excluding values within 12 hours of admission, were recorded more often and in more patients at night. During a 12-month period, there were significantly more deaths among infants less than 1,500 gm during the night than during the day. The deterioration of infants at night may result in part from current nursery staffing practices.

Birth Weight↗
PubMed1978

Morphologic analysis of the pulmonary vascular bed in infants exposed in utero to prostaglandin synthetase inhibitors.

Since the effects of prostaglandin synthetase inhibitors on the developing human fetal pulmonary vasculature are unknown, we studied the lungs of two infants, one whose mother took salicylates and the other whose mother took indomethacin during pregnancy. Lungs were fixed by perfusion and fifth generation (resistance) vessels identified. The infant with chronic exposure to aspirin had premature constriction of the ductus arteriosus, tricuspid insufficiency, increased pulmonary arterial medial width/external diameter ratio due to increased smooth muscle, and a decreased number of pulmonary vessels/cm2 lung tissue. The infant with short-term exposure to indomethacin had hypoxemia, increased pulmonary arterial m/d ratio due to increased smooth muscle, and a normal number of pulmonary vessels/cm2 lung tissue. These abnormalities may be due to the effects of prostaglandin synthetase inhibitor drugs on the ductus arteriosus and/or the pulmonary vessels of the human fetus.

Adult↗