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Biomedical subjects

R C Tsang

Publications and source records attributed to R C Tsang.

At least 19 recordsLinked to original sources
PubMed2001

Fetal weight and progression of diabetic retinopathy.

OBJECTIVE: To test the hypothesis that progression of diabetic retinopathy in pregnancy is associated with reduced fetal growth and related neonatal morbidity. METHODS: Women with type 1 diabetes (n = 205) were enrolled before 14 weeks' gestation in a prospective study of diabetes in pregnancy and treated with intensive insulin therapy. They had serial ophthalmologic evaluations before 20 weeks' gestation and in late gestation or postpartum. Subjects were divided into two groups based on whether retinopathy progressed (progression group) or remained unchanged (no progression group). RESULTS: Retinopathy progressed in 59 of 205 women (29%) and was associated with advanced White classification (P =.001): three (5%) were class B, 14 (23%) class C, 24 (41%) class D, and 18 (30%) class F-RF. Reduced fetal growth was associated with progression of retinopathy. Mean birth weight was lower (P =.02), and more infants were small for gestational age (P =.02) and had low birth weights (P =.02) in the progression group. More large-for-gestational-age infants were noted in the no-progression group (P =.04). Birth weight percentile distributions showed a shift of the curve to the left in the progression group (P =.03). There were no differences in gestational age at delivery, macrosomia, preterm delivery, respiratory distress syndrome, neonatal hypoglycemia, or neonatal death. Small for gestational age was associated with chronic hypertension (odds ratio [OR] 6.4; 95% confidence interval [CI] 1.5, 27.9) and retinopathy progression (OR 4.7; 95% CI 1.2, 23.8). CONCLUSION: Development and progression of diabetic retinopathy during pregnancy were associated with reduced fetal growth manifested as increased rate of small-for-gestational-age and low-birth-weight infants.

Adult↗
PubMed2000

Pregnant adolescent and adult women have similarly low intakes of selected nutrients.

OBJECTIVE: To examine the dietary intake of pregnant adolescents during the second and third trimester of pregnancy, and to compare their nutrient intake with that of pregnant adults. DESIGN: Two 7-day food records (14 days) from subjects participating in a larger randomized clinical calcium trial: the first at 19 to 21 weeks and the second between 29 and 31 weeks gestation. Intake of energy and selected nutrients were calculated and compared with dietary standards. SUBJECTS/SETTING: Fifty-nine pregnant adolescents and 97 pregnant adults recruited from prenatal clinics at a metropolitan university hospital. STATISTICAL ANALYSES: Two sample t tests, equality of variances, and repeated measures (analysis of variance). RESULTS: There was no difference in mean nutrient intakes between the second and third trimesters. Using two 7-day food records, we found mean intakes for energy, iron, zinc, calcium, magnesium, folate, and vitamins D and E to be below recommended standards in both groups. Other nutrients examined met or exceeded reference values. Total daily intakes for energy and 11 nutrients were significantly higher in the adolescent compared to the adult diets (P < .05). These differences were not evident when nutrient values were corrected for energy, indicating that increased energy intake in the teen-aged population was contributed by nutrient-dense foods. APPLICATIONS: This study indicates the need for continued dietary monitoring of pregnant adolescents and pregnant adults, including nutrition guidance that stresses food sources of calcium, magnesium, zinc, iron, fiber, folate, and vitamins D and E, the nutrients found deficient in their diets.

Adolescent↗
PubMed2000

Factors affecting newborn bone mineral content: in utero effects on newborn bone mineralization.

Several factors have been found recently to have a significant impact on newborn bone mineral content (BMC) and developing fetal bone. Recently we showed that maternal vitamin D deficiency may affect fetal bone mineralization. Korean winter-born newborn infants had extremely low serum 25-hydroxyvitamin D (25-OHD), high serum cross-linked carboxy-terminal telopeptide of type I collagen (ICTP; a bone resorption marker), and markedly lower (8 %) total body BMC than summer-born newborn infants. Infant total body BMC was positively correlated with cord serum 25-OHD and inversely correlated with ICTP, which was also negatively correlated with vitamin D status. In three separate studies on North American neonates we found markedly lower (8-12 %) BMC in summer newborn infants compared with winter newborn infants, the opposite of the findings for Korean neonates. The major reason for the conflicting BMC results might be the markedly different maternal vitamin D status of the North American and Korean subjects. Recently, we found evidence of decreased bone formation rates in infants who were small-for-gestational age (SGA) compared with infants who were appropriate-for-gestational age; we reported reduced BMC, cord serum osteocalcin (a marker of bone formation) and 1,25-dihydroxyvitamin D (the active metabolite of vitamin D), but no alterations in indices of fetal bone collagen metabolism. In theory, reduced utero-placental blood flow in SGA infants may result in reduced transplacental mineral supply and reduced fetal bone formation. Infants of diabetic mothers (IDM) have low BMC at birth, and infant BMC correlated inversely with poor control of diabetes in the mother, specifically first trimester maternal mean capillary blood glucose concentration, implying that factors early in pregnancy might have an effect on fetal BMC. The low BMC in IDM may be related to the decreased transplacental mineral transfer. Cord serum ICTP concentrations were higher in IDM than in control subjects, implying increased intrauterine bone resorption. BMC is consistently increased with increasing body weight and length in infants. Race and gender differences in BMC appear in early life, but not at birth. Ethanol consumption and smoking by the mother during pregnancy affect fetal skeletal development.

Animals↗
PubMed1999

The role of calcium in health and disease.

Skeletal fragility at the end of the life span (osteoporosis) is a major source of morbidity and mortality. Adequate calcium intake from childhood to the end of the life span is critical for the formation and retention of a healthy skeleton. High intakes of calcium and vitamin D potentiate the bone loss prevention effects of hormone replacement therapy in postmenopausal women. Pregnancy and lactation are not risk factors for skeletal fragility, although lactation is associated with a transient loss of bone that cannot be prevented by calcium supplementation. Low calcium intake has been implicated in the development of hypertension, colon cancer, and premenstrual syndrome, and it is associated with low intakes of many other nutrients. Encouragement of increased consumption of calcium-rich foods has the potential to be a cost-effective strategy for reducing fracture incidence later in life and for increasing patients' dietary quality and overall health.

Animals↗
PubMed1998

Low total body bone mineral content and high bone resorption in Korean winter-born versus summer-born newborn infants.

Seasonal differences in newborn total body bone mineral content (TBBMC) have not been studied, particularly in relation to alterations in vitamin D status in winter. In vitamin D deficiency bone resorption may be high and bone mineralization low. Bone resorption may be assessed by serum cross-linked carboxyterminal telopeptide of type I collagen (ICTP) measures. Because vitamin D supplements throughout pregnancy are uncommon in Korea, we hypothesized that in Korean winter newborns, TBBMC is low and serum ICTP high from high bone resorption and low 25-hydroxyvitamin D (25-OHD) compared with those in summer newborns. Seventy-one Korean term infants were studied prospectively in summer (July through September, n = 37) versus winter (January through March, n = 34); TBBMC was measured before 3 days of age by dual-energy x-ray absorptiometry. Significant seasonal differences were found: winter newborns had 6% lower TBBMC (least squares means +/- SD; 86.7 +/- 7.7 gm vs 93.9 +/- 7.8 gm, p = 0.0002), lower cord serum 25-OHD (10.7 +/- 8 nm vs 30 +/- 15 nm, p = 0.0001) and 1,25-dihydroxyvitamin D, and higher ICTP (96.4 +/- 20.3 microg/L vs 74.8 +/- 24 microg/L, p = 0.0002) and calcium than summer newborns. TBBMC correlated with serum 25-OHD (r = 0.243, p = 0.047) and inversely with ICTP (r = -0.333, p = 0.008). We suggest that in Korea low maternal vitamin D status in winter results in marked reduction in newborn TBBMC.

Absorptiometry, Photon↗
PubMed1998

Bone mineral content is not reduced despite low vitamin D status in breast milk-fed infants versus cow's milk based formula-fed infants.

The effect of low or borderline vitamin D status on bone mineralization of exclusively breast milk-fed infants has not been studied. The low vitamin D status of Korean breast milk-fed infants may theoretically have adverse effects on bone mineralization. Assuming that bone mineral content (BMC) relates in part to vitamin D status, we hypothesized that serum 25-hydroxyvitamin D (25-OHD) concentration and BMC would be low, and serum osteocalcin concentration high, reflecting active bone turnover, in breast milk- versus formula-fed infants born in the winter. Eighteen breast milk- and 17 formula-fed infants were recruited at ages 2 to 5 months. The BMC of the lumbar1-4 spine region was measured by using dual energy x-ray absorptiometry. The BMC and serum osteocalcin levels were similar for both groups. The serum 25-OHD level was significantly lower in breast milk- than formula-fed infants; 44% of the breast milk group versus 6% of the formula group had serum 25-OHD levels less than 28 nmol/L (11 ng/ml), the lower limit of normal. The BMC did not correlate with the serum 25-OHD level. Thus BMC and serum osteocalcin levels in 2- to 5-month-old infants were not different by type of feeding, despite low vitamin D status in breast milk-fed infants. We speculate that adequate mineral absorption occurs during this period from a predominantly (vitamin D independent) passive transport mechanism.

Absorptiometry, Photon↗
PubMed1998

Influence of formula versus breast milk on cholesterol synthesis rates in four-month-old infants.

We investigated whether supplementation of regular formula (RF) with cholesterol (Ch) (RF+Ch) influenced circulating Ch levels and de novo synthesis compared with their breast-fed (BF) counterparts in 4-mo-old infants. The incorporation rate of deuterium in body water into erythrocyte membrane-free Ch over 48 h was used as an index of cholesterogenesis. Plasma total-Ch and LDL-Ch concentrations were highest (p < 0.02) in BF infants, compared with infants in the RF-fed groups. Infants in the RF+Ch groups showed an intermediate response; their plasma total-Ch and LDL-Ch concentrations were not significantly different from the BF or the RF-fed groups. Plasma total/HDL-Ch and LDL/HDL-Ch ratios were higher (p < 0.05) in BF, and higher in RF+Ch-fed infants, compared with those fed RF, whereas not different between BF and RF+Ch-fed infants. At 4 mo of age, Ch FSR was 4-fold lower (p < 0.0001) in BF versus other groups, but not significantly different between RF- and RF+Ch-fed infants. Thus, despite addition of Ch to the concentration found in breast milk, FSR remained elevated compared with that of the group fed breast milk, with an intermediate response in circulating Ch levels. It is speculated that factors other than Ch intake account for the differential Ch metabolism between formula-fed and BF infants.

Breast Feeding↗
PubMed1998

Biological mechanisms of environmentally induced causes of IUGR.

The causes of intrauterine growth retardation (IUGR) are multiple, involving many different factors. Studies in humans and animals have shown that the maternal environment is the most important determinant of newborn weight, accounting for more similarity in birth weights of siblings than does genetic affinity. In addition to a direct relationship with the degree of maternal plasma volume expansion, many clinical factors are associated with IUGR. These factors include multiple gestation; fetal, genetic, and chromosomal anomalies (Down's syndrome and Turner's syndrome); infections such as TORCH syndrome (acronym for toxoplasmosis, rubella, cytomegalic disease, and herpes); and various maternal disorders including anemia, severe chronic asthma, chronic renal disease, heart disease and hypertension. Maternal stress factors, including narcotic addiction, cigarette smoking and chronic alcoholism, are associated with IUGR. Placental anomalies including hemangiomas, placental infarcts, single umbilical artery, and small placental size are also associated with intrauterine growth retardation. Poor nutritional status of the mother at conception and inadequate energy and protein intakes during pregnancy can also result in IUGR. Because IUGR children are not a homogeneous group, they have a broad spectrum of growth, health, and developmental outcomes. In general they have higher rates of subnormal growth, morbidity, and neurodevelopmental problems. The biomedical mechanisms reflected in nutritional, infection-related, hormonal, and metabolic parameters are not likely to be independent causative factors of IUGR, but important mediating factors of a pathologic process set in motion by other agents and insults. This paper focuses mainly on the possible negative effects that a deficient maternal diet might have on fetal development and growth.

Animals↗
PubMed1996

Bone turnover and mineral metabolism in the last trimester of pregnancy: effect of multiple gestation.

OBJECTIVE: To test the hypothesis that maternal bone turnover and mineral stress are greater in multiple pregnancy than in singleton pregnancy. METHODS: We measured serum markers of bone turnover and mineral stress in 17 multiple and 30 singleton pregnancies during the third trimester. RESULTS: Serum 25(OH) vitamin D, a marker of vitamin D intake, was higher (61 +/- 5 versus 39 +/- 2 ng/mL, P < .001), and 1,25(OH)2 vitamin D was lower (50 [95% confidence interval (CI) 24-102] versus 64 pg/mL [95% CI 30-135], P = .03) in multiple than in singleton pregnancy. Carboxyterminal telopeptide of type I collagen, a marker of bone resorption, increased with gestational duration and was higher in multiple gestation (5.8 [95% CI 3.3-10.1] versus 4.4 ng/mL [95% CI 2.5-7.8], P = .005). Carboxyl-terminal propeptide of type 1 procollagen, a marker of bone formation, increased with gestational duration and was not different between groups (110 [95% CI 36-337] versus 99 ng/mL [95% CI 34-286], P = .5). Calcitonin increased with gestational duration and was not different between groups (7.0 [95% CI 3.7-13.0] versus 7.8 pg/mL [95% CI 4.0-15.4], P = .37). Parathyroid hormone was not different between groups and decreased with increasing maternal age. CONCLUSION: Bone turnover indices increased with gestational duration. The bone resorption index was greater in multiple than in singleton gestation. Serum 25(OH) vitamin D was greater and 1,25(OH)2 vitamin D was lower in multiple gestation, presumably because of greater consumption of vitamin D and minerals by women carrying more than one fetus.

Adult↗
PubMed1996

Effect of rice cereal feedings on bone mineralization and calcium homeostasis in cow milk formula fed infants.

OBJECTIVE: We conducted a prospective randomized, single-blinded clinical trial to test the hypothesis that intake of formula plus cereals between the ages of 16 and 26 weeks postnatally (as compared to formula alone) would lead to lower bone mineral content (BMC), higher parathyroid hormone (PTH) concentration, lower serum calcium (Ca), magnesium (Mg) and osteocalcin (OC); and increased continuous night sleep. METHODS: At 16 weeks postnatally, 41 healthy, term infants were randomized to formula alone or formula and cereal. RESULTS: We found no significant differences in growth or sleep pattern, nor in BMC between groups. Serum PTH concentration was significantly increased in the cereal group at 26 weeks. CONCLUSION: We speculate that the increase in PTH is due to relative Ca deficiency or is responsive to increased phosphate load in the cereal group.

Animals↗
PubMed1996

Normal serum indices of bone collagen biosynthesis and degradation in small for gestational age infants.

Serum carboxyterminal propeptide of type I procollagen (PICP) and cross-linked carboxyterminal telopeptide of type I collagen (ICTP), new markers of bone collagen type I biosynthesis and degradation, have not been studied in small for gestational age (SGA) infants. In an earlier study, we found a lower bone mineral content (BMC) and decreased serum osteocalcin in SGA than in appropriate for gestational age (AGA) infants, supporting the thesis that decreased fetal bone formation is a cause of lower BMC in SGA. In view of the role of insulin-like growth factor-I (IGF-I) in the regulation of collagen type I synthesis and degradation, and low serum IGF-I concentrations in SGA infants, we hypothesized that serum PICP would be lower and serum ICTP would be higher in SGA than in AGA infants, reflecting decreased bone collagen type I biosynthesis or enhancement of bone collagen type I degradation in SGA. We studied 19 term SGA and 38 term AGA infants that were matched specifically 1:2 by gestation and birth month. There were no differences between SGA and AGA infants in serum PICP nor ICTP concentrations. Serum ICTP was correlated with osteocalcin and with PICP in SGA infants but not in AGA infants. Thus, serum biochemical indices of bone collagen type I biosynthesis and degradation in term SGA infants are similar to those in term AGA infants. These findings are not consistent with the thesis of altered fetal bone collagen type I biosynthesis or degradation in SGA. We suggest that the reduced bone mineral content in SGA infants is predominantly related to a lower supply of minerals rather than defective regulation of bone collagen type I metabolism.

Biomarkers↗
PubMed1995

Evidence of increased intrauterine bone resorption in term infants of mothers with insulin-dependent diabetes.

Infants of diabetic mothers (IDMs) have lower bone mineral content than control subjects at birth. We measured cord blood propeptide of type I procollagen (PICP), a marker of bone formation, and telopeptide of type I collagen (ICTP), a marker of bone resorption, in 25 term IDMs and 20 term control subjects. Concentrations of ICTP were higher in IDMs than in control subjects; there was no difference in PICP concentrations. We conclude that osteoclastic activity appears to be higher in IDMs than in control subjects in utero.

Adult↗
PubMed1995

Effect of maternal oxygen therapy on placental calcium transport in intrauterine growth retarded rats.

OBJECTIVE: We tested the hypothesis that continuous maternal oxygen (O2) therapy leads to an increase in fetal survival, improvement in fetal growth, and correction of decreased placental calcium (Ca) transport, in pregnant rats who underwent uterine artery ligation. STUDY DESIGN: We measured on Day 21 of pregnancy, the unidirectional maternofetal clearance of 45Ca (Kmf45Ca) and 51Cr-EDTA (Kmf51Cr-EDTA) across in-situ perfused placentas of rats randomized on Day 17 to a modified Wigglesworth (bilateral uterine artery ligation) procedure (group WW, n = 8), to modified Wigglesworth and supplemental maternal O2 treatment (FiO2 0.40) (group WWO2, n = 8), or to a sham operation (group Sh, n = 8). Kmf51Cr-EDTA provides a measure of placental "porosity" or passive permeability. RESULTS: Maternal O2 therapy did not improve fetal survival, fetal growth, or placental Ca transport. CONCLUSION AND SPECULATION: Bilateral uterine ligation in the pregnant rat leads to IUGR and decreased placental Ca transport which cannot be corrected by maternal O2 therapy.

Animals↗
PubMed1995

Effect of different vitamin A intakes on very-low-birth-weight infants.

Formula-fed infants with birth weights < or = 1500 g (n = 61) were stratified by 250-g birth-weight ranges and randomly assigned to receive one of three preterm infant formulas (vitamin A contents of 820 IU, 1640 IU, or 2900 IU/MJ; 1 RE = 3.3 IU vitamin A activity) when subjects tolerated 0.314 MJ.kg-1.d-1. Experimental formula feedings were continued until infants weighed approximately 2 kg or until hospital discharge. Vitamin A status as indicated by serum retinol and retinol-binding protein (RBP) concentrations significantly decreased during experimental formula feeding at the lowest vitamin A intake. All subjects fed the formula providing the lowest vitamin A intake had hyporetinolemia (< 0.70 mumol/L, or < 20 micrograms/dL), which occurred less frequently (P < 0.05) with the intermediate (6 of 20) and the high (6 of 21) vitamin A intakes. Other outcome measures, including increases in weight, length, and head circumference, and ventilatory support and oxygen therapy, were not different among groups. After the end of the experimental formula-feeding period, all infants were fed standard infant formulas with a vitamin A content of 715 IU/MJ. In a subset of 19 of these infants, subsequent vitamin A status was monitored at ages 6-12 mo and was found to be comparable with that of older children and adults, regardless of the vitamin A content of the formula fed during hospitalization.(ABSTRACT TRUNCATED AT 250 WORDS)

Analysis of Variance↗