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Biomedical subjects

L S Chan

Publications and source records attributed to L S Chan.

At least 145 records · Page 8Linked to original sources
PubMed1986

Differences between dropouts and active participants in a pediatric clinic for substance abuse mothers.

We compared the maternal and birth characteristics of 87 first-year dropouts with 103 active participants of a pediatric clinic which provides long-term follow-up care to offspring exposed in utero to substance abuse mothers. The age, ethnicity, and marital status of the mother; the type of drug used during pregnancy; and the length, gender, number, and type of addiction problems of the newborn were not significantly different between the two groups. However, the dropouts differed significantly from the active participants in many other aspects. More dropout mothers received no prenatal care and did not have children at home at the time of the present birth. More of them were smokers; had gonorrhea, heart, and kidney problems; and had infections complicating their pregnancy. The dropout newborns were found to have lower birthweight and shorter gestation. These clinical parameters defined a suboptimal group of mothers and children requiring more attention and care. The findings also alert investigators of long-term follow-up studies to be aware of basic differences between nonparticipants and participants.

Adolescent↗
PubMed1986

Sudden infant death syndrome in infants evaluated by apnea programs in California.

Home apnea/bradycardia monitoring is frequently used in the management of infants at increased risk for sudden infant death syndrome (SIDS). However, some infants have died despite evaluation by infant apnea programs, and the benefits of home monitoring remain unproven. To determine the SIDS rate and risk factors of infants evaluated by infant apnea programs, 31 apnea programs and ten home monitor vendors in California were surveyed. Eleven (35%) of the apnea programs and four (40%) of the vendors responded. Information was obtained on 26 infants who died. Thirteen (50%) deaths were due to SIDS. Abnormal sleep studies did not predict death. Fifteen infants died despite a recommendation for home monitoring. Seven deaths occurred in association with technical errors or noncompliance with monitoring. Four deaths were due to nonaccidental trauma. The apnea programs evaluated 3,406 infants during a 5-year period; 1,841 had monitoring recommended. Term infants with apnea, subsequent siblings of SIDS victims, and infants evaluated at referral centers were more likely to have monitoring recommended than premature infants with apnea or infants evaluated at nonreferral centers (P less than .0001). Infants who had monitoring recommended were at equal risk of dying of SIDS as those who did not.

California↗
PubMed1985

Characterization of glucose transport by bovine retinal capillary pericytes in culture.

The transport of D-glucose and its non-metabolizable analog, 3-o-methyl-D-glucose (3-o-MG), by cultured bovine retinal capillary pericytes was characterized. A preference for D-glucose over L-glucose uptake by pericytes indicated a stereospecific process. The 3-o-MG transport appeared to follow complex kinetics. At low substrate concentrations, 3-o-MG transport had an apparent Km of 1.53 mM and a Vmax of 0.50 nmol (microgram DNA)-1 min-1 at 37 degrees C. A reduced extracellular sodium concentration, energy poisons, and exogenous insulin did not significantly influence 3-o-MG uptake. Inhibition of the uptake or efflux of 3-o-MG by cytochalasin B or phloretin, respectively, and the demonstration of a 'counter transport' phenomenon showed that 3-o-MG transport by retinal capillary pericytes in culture was a carrier-mediated process.

3-O-Methylglucose↗
PubMed1984

Surgical treatment of carcinoma of the breast: II. Prognostic factors influencing relapse rate.

This is a study of 408 patients who had mastectomy for clinical stages I, II, and early III carcinoma of the breast during 1971-1980. Analysis of disease-free probabilities up to 5 yr showed that the number of positive axillary nodes was the most important prognostic factor. Size of primary tumor was the second most useful factor, with best separation of disease-free rates using 4 cm as a dividing line. Patients with colloid carcinoma and other less common lesions had much better prognosis than those with infiltrating ductal, lobular, or medullary carcinomas. Discriminating analysis also showed that information about the number of positive axillary node alone gave the best prediction of possibility of developing recurrence (overall accuracy, 75%).

Adenocarcinoma, Mucinous↗
PubMed1984

Surgical treatment of carcinoma of the breast: IV. Prognosis according to extent of involvement of the axillary lymph nodes.

This is a retrospective study of 462 patients who had masectomy and axillary dissection for carcinoma of the breast during 1971-1980. Actuarial analysis of relapse rates up to 5 years showed that the extent of involvement of axillary lymph nodes was the most important prognostic factor. Among patients without any axillary metastasis, those with tumor smaller than 2 cm, colloid, or other less common carcinomas had significantly better prognosis than those with other lesions. Patients younger than 45 years old had higher relapse rate. Among patients with four or more positive axillary nodes, those with tumors smaller than 9 cm or those with nine or fewer positive nodes also had lower relapse rate than those with larger tumors or more positive nodes. Adjuvant systemic chemotherapy has improved the prognosis of patients with four or more positive nodes. Our findings are discussed and compared to those reported in the literature.

Actuarial Analysis↗
PubMed1984

Is there a threshold level of fetal hemoglobin that ameliorates morbidity in sickle cell anemia?

When the clinical manifestations of 272 patients with sickle cell anemia are compared with their level of fetal hemoglobin (HbF), the results suggest that there may be a threshold above which HbF is effective in ameliorating the morbidity of this disease. The age of entry of these SS patients into the study ranged from birth to 56 yr; the average length of follow-up was 11 yr for a total of 3,011 patient-years of clinic observation. HbF was determined quantitatively by microchromatographic procedures; the mean for HbF was 10% +/- 6% with a range from 2% to 32%. For major organ failure, analyzed as termination events of morbidity, such as stroke or aseptic necrosis, the threshold appears to be 10%, whereas for recurrent clinical events, such as crisis or pulmonary disorders, it is 20%. No linear trend was found between HbF levels and morbidity. If a threshold exists, it is important to recognize this fact when attempts are made to raise the level of HbF in patients with sickle cell disease.

Adolescent↗
PubMed1982

A modified life table method to study congenital genetic disorders: an application in sickle cell anemia.

A modified life table procedure is introduced designed to study the survival of patients with congenital genetic disorders with the endpoint defined by a complication or death. It uses the ages of the patients as the time axis as in "population' or "current' life tables, and it allows patients to enter and exit the study as in survival life tables. The procedure uses the exact length of time that each patient is observed in the study to determine the conditional probabilities of developing the complication. The proposed procedure is especially helpful in studying recurrent complications or events that occur frequently. The proposed life table procedure is demonstrated in the study of the conditional probability of developing a sickle cell crisis in 509 patients with sickle cell anemia (SS) with different number of prior crises. The demonstration is intended to illustrate the use of the proposed method and not to investigate the clinical severity of sickle cell anemia. It was found that the risk of crisis was to investigate the clinical severity of sickle cell anemia. It was found that the risk of crisis was positively related to the number of prior crises in SS patients (P less than 0.001). This trend was significant in the first three decades of life.

Actuarial Analysis↗
PubMed1981

Impact of a regional infant dispatch center on neonatal mortality.

In 1976, a regional Infant Medical Dispatch Center (IMDC) was implemented in Southern California to improve the lives and well-being of the critically ill newborn infants by expediting location of beds in neonatal intensive care units. Comparison of birth weight-specific neonatal mortality rates among 701-2000 grams neonates before and after the program showed a six-fold improvement in hospitals served by the Center over hospitals not served by the Center during the two-year period. From 1975 to 1977, a 43.7 per cent improvement in neonatal mortality among the 701-2000 grams neonates with hyaline membrane disease was observed in the transported infants served by the Infant Medical Dispatch Center as compared to a 22.9 per cent improvement in the group of transported infants not served by IMDC. Both indicators had consistently shown a marked improvement associated with the IMDC program beyond the improvement of medical sciences over the two years. The data suggest that the improved outcome of the neonates referred by IMDC might be related to the improved efficiency of locating available neonatal intensive care beds.

California↗
PubMed1981

Negative charge distribution and density on the surface of oxygenated normal and sickle red cells.

Negative charges on the external surface of red cells were visualized by colloidal iron hydroxide labelling of 50% of the membrane area after osmotic hemolysis and glutaraldehyde fixation. Counts were made over randomly selected areas on electron micrographs at 350,000 x magnification. Statistical analyses showed that at the 95% level of confidence there was no significant difference between oxygenated normal (AA) and sickle (SS) cells in either the distribution or the density of negative charges.

Anemia, Sickle Cell↗
PubMed1980

A method to estimate the number of house officers required in teaching hospitals.

A method of estimating the number of house officers needed for direct patient care in teaching hospitals is discussed. The method requires six input data elements: average daily census, annual admissions, annual outpatient visits, average house staff hours per inpatient per day, average house staff hours per outpatient visit, and average direct patient care hours per house officer per day. The first three are readily available annual statistics; the fourth and fifth data elements are easily estimable by service chiefs and immediate house staff supervisors. The sixth input item can either be a standard or an estimated value. An approach to estimating the sixth data element is included in the paper. An application of the proposed method is illustrated for 11 clinical services at the Los Angeles County-University of Southern California Medical Center.

California↗
PubMed1980

Lack of influence of fetal hemoglobin levels or erythrocyte indices on the severity of sickle cell anemia.

Persons with sickle cell anemia who have elevated fetal hemoglobin or lowered erythrocyte mean corpuscular volume are reputed to have less severe clinical manifestations and a greater probability of survival. This study examines the relationship between seven clinical indicators of morbidity in sickle cell anemia and seven hematological parameters that were collected from 214 patients. Risks of sickle cell crisis, acute chest syndrome, hospital admissions, cerebrovascular accident, aseptic necrosis, meningitis/septicemia, and death were used as indicators of morbidity. The hematological parameters included percent fetal hemoglobin, absolute fetal hemoglobin, percent hemoglobin A2, hemoglobin concentration, packed cell volume, mean corpuscular volume, and mean corpuscular hemoglobin concentration. Statistical analyses of the data showed no relationship between the hematological parameters and six of the seven clinical indicators of the severity of sickle cell anemia. The only significant finding was an increased risk of stroke in those patients with lower levels of fetal hemoglobin. Therefore, with this exception, there is no predictable relationship between morbidity and mortality in sickle cell anemia and levels of fetal hemoglobin or erythrocyte indices. Thus, the general belief that there is an association between severity of sickle cell anemia and the levels of fetal hemoglobin has not been established.

Adolescent↗
PubMed1978

Cholelithiasis: a frequent complication of artificial heart valve replacement.

The results of this investigation reveal that 39 per cent of patients in a study group of 46 patients with heart valve prostheses had gallstones if they survived 18 months or longer following valve replacement. In contrast, the prevalence of gallstones in a general population of autopsied rheumatic heart disease patients, including those who had been operated for severe valvular heart disease and had not survived for more than one month, was only 12 per cent. These findings suggest that gallstones are a frequent late complication of heart valve replacement.

Adult↗
PubMed1978

Mexican-American folk belief in a pediatric emergency room.

The pattern, extent and patient care implications of medical folk belief in the Mexican-American population utilizing a pediatric emergency room were assessed. The parents of caretakers of 85 randomly selected patients were interviewed in the emergency room waiting area. The extent of knowledge and family history of four traditional folk diseases (magical fright, evil eye, surfeit, and fallen fontanelle) were determined, as was the utitlization of folk healers. The proportion of individuals with traditional knowledge varied with the specific folk disease and with demographic characteristics. Those born in Mexico were more likely to have knowledge of folk disease symptoms and treatment. Of 43 patients who had received treatment prior to coming to the emergency room, 13 had received an herbal folk remedy prescribed by a family member. Twenty-eight reported previous use of folk healers for pediatric illness although none had sought such care for the present illness. Of 57 informants who offered a cause for the child's present illness, two named a folk disease. Mexican-American folk belief is common in the population of Hispanic origin who utilize this pediatric emergency room. The illness for which care is sought, however, is felt to be amenable to scientific care and therfore medical folk belief is not often a clinically relevant factor in the emergency room setting.

Attitude to Health↗