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Biomedical subjects

A Chang

Publications and source records attributed to A Chang.

At least 271 records · Page 15Linked to original sources
PubMed1986

Stimulus-secretion coupling in the developing exocrine pancreas: secretory responsiveness to cholecystokinin.

We have studied the onset of secretory responsiveness to cholecystokinin (CCK) during development of the rat exocrine pancreas. Although acinar cells of the fetal pancreas (1 d before birth) are filled with zymogen granules containing the secretory protein, alpha-amylase, the rate of amylase secretion from pancreatic lobules incubated in vitro was not increased in response to CCK. In contrast, the rate of CCK-stimulated amylase discharge from the neonatal pancreas (1 d after birth) was increased four- to eightfold above that of the fetal gland. The postnatal amplification of secretory responsiveness was not associated with an increase in the number or cell surface expression of 125I-CCK binding sites. When 125I-CCK-33 binding proteins were analyzed by affinity crosslinking, two proteins of Mr 210,000 and 100,000-160,000 were labeled specifically in both fetal and neonatal pancreas. To determine if cell surface receptors for CCK in the fetal pancreas are functional and able to generate a rise in the cytosolic [Ca++], we measured 45Ca++ efflux from tracer-loaded lobules. 45Ca++ efflux from both fetal and neonatal pancreas was comparably increased by CCK, indicating CCK-induced Ca++ mobilization and elevated cytosolic [Ca++]. The Ca++ ionophore A23187 also stimulated the rate of 45Ca++ extrusion from pancreas of both ages. Increased amylase secretion occurred concurrently with A23187-stimulated 45Ca++ efflux in neonatal pancreas, but not in the fetal gland. A23187 in combination with dibutyryl cAMP potentiated amylase release from the neonatal gland, but not from fetal pancreas. Similarly, the protein kinase C activator, phorbol dibutyrate, did not increase the rate of secretion from the fetal gland when added alone or in combination with A23187 or CCK. We suggest that CCK-receptor interaction in the fetal pancreas triggers intracellular Ca++ mobilization. However, one or more signal transduction events distal to Ca++ mobilization have not yet matured. The onset of secretory response to CCK that occurs postnatally may depend on amplification of these transduction events.

Animals↗
PubMed1986

Changes in the expression of beta and gamma actins during differentiation of PC12 cells.

Cells of the rat pheochromocytoma line PC12 cease proliferation and develop neurites in response to nerve growth factor (NGF). Quantification of beta and gamma isoforms of nonmuscle actin in extracts of these differentiating cells showed that the beta:gamma ratio decreased from 1.30 +/- 0.05 to 0.99 +/- 0.05 after 6 days of NGF treatment. Cells treated with N6,O2-dibutyryl cyclic AMP (dbcAMP) also showed a shift in the ratio of beta:gamma isoforms, although few of these cells extended neurites. Administration of dbcAMP or both NGF and dbcAMP to cells accelerated the decrease in the beta:gamma actin isoform ratio relative to treatment with NGF alone. Those cells treated with both NGF and dbcAMP also showed an accelerated rate of neurite outgrowth. Suspension-grown PC12 cells treated with NGF showed neither an isoform ratio decrease nor neurite development. Our results suggest that either cyclic AMP may be a "second messenger" for NGF or it may effect the isoform ratio change by an independent mechanism. In addition, our data demonstrate an alteration in actin isoform expression, which accompanies the morphological differentiation of PC12 cells.

Actins↗
PubMed1986

Use of a pocket personal computer in obstetric ultrasound.

Obstetric ultrasound is of increasing importance in obstetric practice. The conventional ultrasound prediction of fetal weight and gestational age using various fetal parameters, like biparietal diameter, abdominal circumference, femur length etc have to rely on various different charts or tables, which are both laborious and time consuming. Three programmes in Basic language using a pocket personal computer have been developed and their application is presented in this paper.

Anthropometry↗
PubMed1985

IEF patterns of HLA-B13 antigens from Orientals and Caucasians.

HLA-B13 antigens were isolated from metabolically labeled cell extracts from Caucasian and Oriental donors by means of an HLA-B13-specific monoclonal antibody, SY1. Ethnic differences in B13 molecules were identified by one-dimensional isoelectric focusing in which the pI of desialated Oriental B13 molecules was found to be higher than that of Caucasians. An additional Caucasian variant pattern was detected by peptide mapping using limited proteolysis in sodium dodecyl sulfate analyzed by polyacrylamide gel electrophoresis. Dual allotypic determinants for B13 molecules were recognized by two HLA-B13-specific monoclonal antibodies, SY1 and Tu110, as determined by their sensitivity to complement-dependent cell lysis. Whereas the SY1 target epitope was shared by both ethnic B13 molecules, the two ethnic B13 molecules carried different Tu110 target structures. The Caucasian variant molecules appear to carry altered allotypic determinants which are recognized by both SY1 and Tu110 antibodies. This study suggests that the HLA-B13 private structure may comprise two epitopes recognized by SY1 and Tü110 antibodies, respectively, whose binding sites overlap. Present data also suggest that the private determinant was already present when the two racial groups diverged, and thus the mutations which gave rise to the variants may be of relatively recent origin.

Antibodies, Monoclonal↗
PubMed1985

Epidemiology of meconium staining of amniotic fluid in Hong Kong.

The characteristics of 94 patients with meconium stained amniotic fluid diagnosed during labour in the Prince of Wales Hospital, Hong Kong, from July to August 1984, were analysed. The incidence was 21.4% of deliveries. These patients were compared to a group of non-meconium patients (349 cases) in demographic and obstetric aspects. Patients in low social class and patients with antenatal and medical complications did not have a higher incidence of meconium staining of amniotic fluid. However, a history of previous spontaneous or induced abortion was significantly more common in the meconium group. The labour performance of these patients and the perinatal outcome are discussed.

Abortion, Induced↗
PubMed1985

The premenstrual syndrome in Chinese.

A questionnaire survey of 84 Chinese nurses was carried out to assess the presence of premenstrual syndrome. More than half of the respondents reported emotional changes and backache premenstrually. There were significant associations between nausea and breast changes, irritability and depression, body and skin changes, finally between backache and the 3 symptoms of irritability, headache and the necessity to take time off work.

Adolescent↗
PubMed1985

An evaluation of three ultrasound equations for fetal weight prediction.

Ultrasound fetal weight estimation based on the equations of Shepard et al (1), Warsof et al (2) using biparietal diameter and abdominal circumference, and Campbell et al (3) using abdominal circumference, were evaluated in 92 Chinese patients in labour. Our result shows that Campbell's equation (3), based on the abdominal circumference alone provides a higher accuracy and precision in predicting fetal weight than using a combination of biparietal diameter and abdominal circumference.

Birth Weight↗
PubMed1985

Mechanisms of accumulation of arachidonic acid in cultured myocardial cells during ATP depletion.

Previous studies have suggested that the accumulation of free arachidonic acid may be of major importance in the pathophysiology of myocardial ischemia. The purpose of the present study was to determine if the release of arachidonic acid from myocardial cells was more dependent on the extent of ATP depletion than on the inhibition of fatty acid oxidation. In addition, these studies were designed to determine if arachidonic acid release only occurred when ATP was depleted beyond a critical threshold level. To examine the relationship between arachidonic acid release and ATP depletion, cultured myocardial cells from neonatal rat hearts were labeled with [3H]arachidonate and [14C]palmitate. In response to ATP depletion with various metabolic inhibitors, [3H]arachidonic acid and [14C]palmitic acid were released from phospholipids. Phosphatidylcholine, phosphatidylethanolamine, and phosphatidic acid were the major esterified sources of the arachidonate. The release of both fatty acids was related to the extent of ATP depletion and not whether a glycolytic or respiratory inhibitor was utilized. Various combinations and doses of metabolic inhibitors were used, and experimental conditions that produced a greater than 75% decrease in ATP content were associated with the accumulation of arachidonic acid. These results suggest that an ATP-dependent step may be linked to the accumulation of arachidonic acid during myocardial ATP depletion. It is suggested that myocardial cells may release arachidonic acid directly in response to ATP depletion.

Adenosine Triphosphate↗
PubMed1985

Release of arachidonate from membrane phospholipids in cultured neonatal rat myocardial cells during adenosine triphosphate depletion. Correlation with the progression of cell injury.

The present study utilized a cultured myocardial cell model to evaluate the relationship between the release of arachidonate from membrane phospholipids, and the progression of cell injury during ATP depletion. High-energy phosphate depletion was induced by incubating cultured neonatal rat myocardial cells with various combinations of metabolic inhibitors (deoxyglucose, oligomycin, cyanide, and iodoacetate). Phospholipid degradation was assessed by the release of radiolabeled arachidonate from membrane phospholipids. In this model, the current study demonstrates that (a) cultured myocardial cells display a time-dependent progression of cell injury during ATP depletion; (b) the morphologic patterns of mild and severe cell injury in the cultured cells are similar to those found in intact ischemic canine myocardial models; (c) cultured myocardial cells release arachidonate from membrane phospholipids during ATP depletion; and (d) using two separate combinations of metabolic inhibitors, there is a correlation between the release of arachidonate, the development of severe cellular and sarcolemmal damage, the release of creatine kinase into the extracellular medium, and the loss of the ability of the myocardial cells to regenerate ATP when the metabolic inhibitors are removed. Thus, the present results suggest that during ATP depletion, in cultured neonatal rat myocardial cells, the release of arachidonate from myocardial membrane phospholipids is linked to the development of membrane defects and the associated loss of cell viability.

Adenosine Triphosphate↗
PubMed1985

Teaching car passenger safety to preschool children.

An educational curriculum entitled "Bucklebear" was designed to increase safety seat and seat belt use in young children enrolled in preschool programs (day care centers and nursery schools). Three basic concepts were emphasized: (1) "buckling up" is a good habit for everyone for every ride; (2) the back seat is the best seat; and (3) there are desirable passenger behaviors. The curriculum included training workshops with teachers, parent meetings, classroom lessons, sound filmstrip, puppet play, and many other activities. Six experimental programs and seven control programs with 402 and 427 enrolled children, respectively, participated. After their participation in the educational curriculum, children in the experimental program increased their use of a safety seat or seat belt from 21.9% to 44.3%. These children also increased their knowledge and simulated practice of car passenger safety.

Accident Prevention↗
PubMed1985

Automobile passenger safety education for pregnant women and infants. Attitudes and practices of obstetrician-gynecologists.

Attitudes and practices regarding automobile passenger safety education for pregnant women and infants were surveyed in a random sample of 236 certified obstetrician-gynecologists in California. A majority of respondents stated that maternal passenger safety (71.6%) and infant/child passenger safety (63.6%) should be "routinely discussed by the obstetrician-gynecologist during the prenatal period." Nevertheless, one of four respondents could not give an opinion or had doubts about the safety of seat belt use in pregnant women. Fewer than one of three discussed maternal passenger safety, and fewer than one of four discussed infant/child passenger safety when giving prenatal care. There was a scarcity of patient education materials in the practitioners' offices. Given the obstetrician-gynecologists' support for promoting passenger safety, there is need for increased health education activities in offices, clinics, hospitals and prenatal classes.

Accident Prevention↗
PubMed1984

A model for thrombin protection against endotoxin.

Infusion of dogs with thrombin (0.5 U/kg/min) for 90 minutes significantly increased percent survival following infusion of endotoxin (0.06 mg/kg/min) for 30 minutes. Nine of fourteen dogs infused with thrombin survived seven days (permanent survivors), whereas thirteen of fourteen dogs infused with saline died within 36 hours. Those dogs which survived responded immediately to endotoxin with enhanced anticoagulant and fibrinolytic activity as measured by the Xa one-stage and fibrin degradation product assays, respectively. Those dogs receiving saline instead of thrombin did not respond with anticoagulant or fibrinolytic activity until the end of the study. We concluded that thrombin in the correct amounts protected dogs from endotoxin and that this protection was associated with an early anticoagulant and fibrinolytic response to endotoxin infusion.

Animals↗
PubMed1984

Mechanism of activation of an N-ras oncogene of SW-1271 human lung carcinoma cells.

An N-ras-related transforming gene was detected in the human lung carcinoma cell line SW-1271 and molecularly cloned. The lesion responsible for its acquisition of transforming activity was localized to a single nucleotide transition from A to G in codon 61 of the predicted protein. This lesion in the second exon results in the substitution of arginine for glutamine at this position. These findings, together with previous studies, indicate that the activation of ras oncogenes in human tumors is most commonly due to point mutations at one of two major "hot spots" in the ras coding sequence.

Amino Acid Sequence↗
PubMed1983

Information control and the exercise of power in the obstetrical encounter.

Interactions between doctor and patient involve participants with unequal power and possibly different interests. While a number of studies have focused upon the doctor/patient relationship, few have examined the utility of the concept of power and its capacity to help us understand the outcome of these interactions. The information sought by pregnant women from their obstetricians is used to provide a case study of one conceptualization and test of the utility of the concept of power. Pregnant women and their obstetricians are found to have different perceptions of the information that should be exchanged during their interactions. Women generally fail to obtain the information they want. Lower social class patients desire more and obtain less information than their higher status counterparts.

Australia↗
PubMed1983

Understanding preterm labour: the use of Path Analysis.

A retrospective study was performed on 465 spontaneous preterm and 13,949 term births, in order to analyze the sequence of events that culminate in preterm labour. Twenty-one variables were investigated by the mathematical technique of Path Analysis. Nine direct and independent precursors of preterm labour were identified. These were antepartum haemorrhage, poor antenatal attendance, previous delivery of a small baby, multiple pregnancy, proteinuria, grand multiparity, cervical suture, low maternal weight, and a history of bleeding before 20 weeks.

Abortion, Spontaneous↗