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Biomedical subjects

A Chao

Publications and source records attributed to A Chao.

At least 19 recordsLinked to original sources
PubMed1992

HIV-exposed twins.

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Diseases in Twins↗
PubMed1992

Adenosine stimulates breathing in fetal sheep with brain stem section.

Breathing responses to adenosine were determined in 12 chronically catheterized fetal sheep (greater than 0.8 term) in which hypoxic inhibition of breathing had been eliminated by brain stem section. The caudal extent of transection varied from the rostral midbrain to the pontomedullary junction. Isocapnic hypoxia [delta arterial PO2 (PaO2) of -12 Torr] doubled the incidence and depth of breathing activity and increased the incidence of eye movements. Intra-arterial infusion of adenosine (0.30 +/- 0.03 mg.min-1.kg fetal wt-1) increased the incidence and amplitude of breathing without affecting blood gases. Adenosine did not significantly alter the incidence of eye activity. Intra-arterial injection of oligomycin (120 +/- 26 micrograms/kg fetal wt), an inhibitor of mitochondrial oxidative phosphorylation, also stimulated breathing activity. In four fetuses with brain stem section, peripheral arterial chemodenervation blunted the stimulatory effects of hypoxia on breathing activity and abolished altogether the excitatory effects of adenosine. It is concluded that 1) hypoxia and adenosine likely inhibit breathing in normal fetuses by affecting similar areas of the brain stem and 2) in fetuses with brain section, hypoxic hyperpnea depends on peripheral and central mechanisms, whereas adenosine stimulates breathing via the peripheral arterial chemoreceptors.

Adenosine↗
PubMed1992

Estimating population size for capture-recapture data when capture probabilities vary by time and individual animal.

There have been no estimators of population size associated with the capture-recapture model when the capture probabilities vary by time and individual animal. This work proposes a nonparametric estimation technique that is appropriate for such a model using the idea of sample coverage, which is defined as the proportion of the total individual capture probabilities of the captured animals. A simulation study was carried out to show the performance of the proposed estimation procedure. Numerical results indicate that it generally works satisfactorily when the coefficient of variation of the individual capture probabilities is relatively large. An example is also given for illustration.

Animals↗
PubMed1991

Exercise and other factors in the prevention of hip fracture: the Leisure World study.

As part of a prospective study begun in 1981, we evaluated 8,600 postmenopausal women and 5,049 men residing in a southern California retirement community for risk factors for hip fracture. Incidence rates were twice as high in women as in men, but in both sexes the rates nearly doubled every 5 years between 70 and 90 years. Active exercise was strongly and negatively associated with hip fracture risk in both sexes; the age-adjusted relative risk was 0.6 and 0.5 for females and males, respectively, for 1 or more hours of exercise per day compared with less than 1/2 hour of exercise. A high body mass index (upper tertile of weight divided by height squared) was associated with a strong reduction in hip fracture risk for females (RR = 0.5). Current cigarette smokers had a significantly increased risk (RR = 1.8 and RR = 2.2 for females and males, respectively) compared with never-smokers, but the risk for past smokers was not different from that of lifetime nonsmokers. Other factors related to reduced hip fracture risk in women were high parity, late age at menarche, and long menstrual cycle length. These age-adjusted relative risk estimates did not change materially in multivariate analysis when adjusted simultaneously for age, active exercise, body mass, smoking, and, for women, age at menarche and number of children. Among estrogen users, the lowest risk of hip fracture was observed for recent users (RR = 0.8), while users who had stopped estrogen use 15 or more years ago had a relative risk of 1.1, suggesting that the protective effect of estrogen dissipates after many years since cessation of estrogen therapy.

Age Factors↗
PubMed1991

Localization of an ataxia-telangiectasia locus to a 3-cM interval on chromosome 11q23: linkage analysis of 111 families by an international consortium.

Linkage of at least two complementation groups of ataxia-telangiectasia (AT) to the chromosomal region 11q23 is now well established. We provide here an 18-point map of the surrounding genomic region, derived from linkage analysis of 40 CEPH families. On the basis of this map, 111 AT families from Turkey, Israel, England, Italy, and the United States were analyzed, localizing the AT gene(s) to an 8-cM sex-averaged interval between the markers STMY and D11S132/NCAM. A new Monte Carlo method for computing approximate location scores estimates this location as being at least 10(8) times more likely than the next most likely interval, with a support interval midway between STMY and D11S132 that is either 5.2 cM (sex-averaged and conservatively based on 3 lod scores from the maximum-location score) or 2.8 cM (male specific, based on a 2.72:1 interval-specific female-to-male distance ratio.

Ataxia Telangiectasia↗
PubMed1990

The ferning test for detection of amniotic fluid contamination in umbilical blood samples.

There is currently no standard means of detecting amniotic fluid contamination in fetal blood obtained by percutaneous umbilical blood sampling. The ferning test is proposed for this purpose. An in vitro model, using centrifuged serial dilutions of neonatal cord blood and amniotic fluid, showed that ferning of the supernatant occurs in proportion to the degree of contamination. A system for grading ferning was devised, and tested in a blind trial. For the detection of amniotic fluid contamination of 10% or more, the method showed a sensitivity of 98% and a specificity of 81%. The method may be useful in percutaneous umbilical blood sampling, and in the diagnosis of spontaneous rupture of membranes with vaginal bleeding.

Amniotic Fluid↗
PubMed1990

Haplotyping the human T-cell receptor beta-chain gene complex by use of restriction fragment length polymorphisms.

We have studied the genetic segregation of human T-cell receptor beta-chain (TCR beta) genes on chromosome 7q in 40 CEPH (Centre d'Etude du Polymorphisme Humain) families by using restriction fragment length polymorphisms (RFLPs). We constructed haplotypes from eight RFLPs by using variable- and constant-region cDNA probes, which detect polymorphisms that span more than 600 kilobases of the TCR beta gene complex. Analysis of allele distributions between TCR beta genes revealed significant linkage disequilibrium between only 6 of the 28 different pairs of RFLPs. This linkage disequillibrium strongly influences the most efficient order to proceed for typing of these RFLPs in order to achieve maximum genetic informativeness, which in this study revealed a 97.3% level of heterozygosity within the TCR beta gene complex. Our results should provide new insight into recent reports of disease associations with the TCR beta gene complex and should assist in designing future experiments to detect or confirm the existence of disease-susceptibility loci in this region of the human genome.

Cell Line↗
PubMed1990

Neonatal death despite fetal therapy for cystic adenomatoid malformation. A case report.

A pulmonary cystic adenomatoid malformation with evolving fetal hydrops was diagnosed in the early third trimester. Serial needle aspiration succeeded in resolving the hydrops; however, despite lobectomy the neonate died of microscopic contralateral disease undetected on ultrasound. The extent and nature of the underlying anomaly may limit the efficacy of fetal therapy for cystic adenomatoid malformation.

Adult↗
PubMed1990

The patellar reflex in preeclamptic women with subtherapeutic and therapeutic serum magnesium levels.

The normalization of hyperreflexia has been proposed by some authorities as an indicator of adequate seizure prophylaxis in preeclamptic women receiving magnesium sulfate. To test this hypothesis the patellar reflex response was measured with a quantitative technique in 20 preeclamptic patients during their progression from subtherapeutic to therapeutic serum levels of magnesium. Patients meeting selected criteria for hyperreflexia demonstrated a 46% decrease in their reflex response. Those without initial hyperreflexia failed to demonstrate a significant decrease.

Adolescent↗
PubMed1989

Aspirin use and chronic diseases: a cohort study of the elderly.

OBJECTIVE: To evaluate the associations between the use of aspirin and the incidences of cardiovascular diseases, cancers, and other chronic diseases. DESIGN: Postal questionnaire survey to elicit details of aspirin use. SETTING: Californian retirement community. SUBJECTS: All 22,781 residents of the community (white, affluent, and well educated) were sent a questionnaire that included questions on medical history and the use of drugs such as analgesics, laxatives, and vitamin supplements. In all 61% responded (13,987, 8881 women and 5106 men; median age 73). They formed the cohort that was followed up for 6 1/2 years using discharge summaries from three hospitals serving the area and death certificates from the health department. Only 13 respondents were lost to follow up but seemed not to have died. MAIN OUTCOME MEASURES: Incidences of cardiovascular diseases, cancers, gastrointestinal bleeding, ulcers, and cataracts were compared in participants who did and did not take aspirin daily. RESULTS: Age adjusted incidences were computed with an internal standard and five age groups. By 1 January 1988 there had been 25 incident cases of kidney cancer among all participants; 341 incident cases of stroke, 253 of acute myocardial infarction, 220 of ischaemic heart disease, and 317 of other heart disease were reported among respondents without a reported history of angina, myocardial infarction, or stroke. The incidence of kidney cancer was raised among those who took aspirin daily compared with those who did not take it, although the increase was significant only in men (relative risks = 6.3, 95% confidence interval 2.2 to 17, for men and 2.1, 0.53 to 8.5, for women). Those who took aspirin daily showed no increased risk of any other cancer, except colon cancer for both sexes combined (relative risk = 1.5, 1.1 to 2.2). The risk of acute myocardial infarction was reduced slightly among regular users of aspirin in men but not women. The risk of ischaemic heart disease was almost doubled in those who took aspirin daily compared with non-users (relative risks = 1.9, 1.1 to 3.1, for men and 1.7, 1.1 to 2.7, for women). Small, non-significant increased risks of stroke were observed in both sexes. CONCLUSION: The daily use of aspirin increased the risk of kidney cancer and ischaemic heart disease.

Aged↗
PubMed1988

Past and present preferred prescribing practices of hormone replacement therapy among Los Angeles gynecologists: possible implications for public health.

Usual prescribing strategies of hormone replacement therapy for postmenopausal women by Los Angeles area gynecologists, both now and 10 years ago, were investigated by a mail survey. Of the 330 gynecologists who responded, estrogen therapy is currently used as a routine by nearly all (95 per cent), for women both with and without a uterus. Over three-fourths of these physicians favor use of 0.625 mg of conjugated equine estrogen. The estrogen is combined with cyclic progestin therapy, usually 10 mg of medroxyprogesterone acetate, by 86 per cent of gynecologists using estrogen for women with a uterus, and by 47 per cent for women without a uterus. Although conjugated equine estrogens were used widely for both groups of patients 10 years ago, a higher dose generally was preferred. Use of progestin therapy was uncommon (less than 20 per cent) for any postmenopausal patients at that time. Although the most common monthly therapeutic regimen for estrogen/progestin therapy is estrogen for days 1-25 and progestin for days 16-25, there is wide variation in prescribing strategies. We present these findings in the context of the probable effects of estrogen/progestin therapy on various chronic disease outcomes.

Adult↗
PubMed1987

Use of preventive care by the elderly.

Use of five early disease detection tests was examined in relation to history of specific chronic disease and other health habits, as part of a cohort study including 11,888 residents of a retirement community in Southern California. Self-reported utilization rates by residents in the year preceding study entry were approximately 90, 30, 60, and 10% for blood pressure measurement, fecal occult blood test, Papanicolaou test, and mammography, respectively. Breast self-examination was practiced by 37% of the women on a regular basis. With the exception of the Pap test and blood pressure check, the majority of the study population did not use preventive procedures at the recommended frequencies. The most important determinants of use of screening tests in this elderly population were previous diagnosis of chronic disease, especially of the disease detected by the test itself, and having a regular physician. These two factors appeared to affect use independently.

Aged↗