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Biomedical subjects

R C Tsang

Publications and source records attributed to R C Tsang.

At least 37 records · Page 2Linked to original sources
PubMed1995

Effect of three levels of vitamin D intake in preterm infants receiving high mineral-containing milk.

Very low-birth weight (VLBW) infants fed high-calcium and high-phosphorus (10.74 and 6.93 mmol/MJ; 180 and 90 mg/100 kcal, respectively) infant formulas were randomized to one of three levels of vitamin D intake to approximate 200, 400, and 800 IU/day. Sixty-two infants completed the study (24 to 29 days), with actual mean daily vitamin D intakes of 161, 361, and 766 IU, respectively. Outcomes were not different by group: gains in body weight, length and head circumference, serum calcium, magnesium, phosphorus, alkaline phosphatase, osteocalcin, 25-hydroxyvitamin D, 1,25-dihydroxyvitamin D, and urine calcium:creatinine and magnesium:creatinine ratios. There were no radiographic fractures and/or rickets. A subset of 19 infants was followed between 173 and 380 days to determine descriptively if there was any delayed effect of earlier manipulation of vitamin D intake. They were fed standard infant formulas with a vitamin D content of 400 to 420 IU/L. No significant differences were present among the three groups, and data were combined. Serum 25-hydroxyvitamin D increased (p < 0.05), osteocalcin decreased (p < 0.05), and 1,25-dihydroxyvitamin D decreased (p = 0.06) at follow-up. Thus, for VLBZW infants fed high-calcium and high-phosphorus milk, an average daily vitamin D intake as low as 160 IU maintains normal and stable vitamin D status and normal physical growth, biochemical and hormonal indexes of bone mineral metabolism, and skeletal radiographs versus randomized infants receiving about 400 or 800 IU of vitamin D per day. On follow-up, vitamin D status remained normal for > or = 6 months while infants received < 400 IU of vitamin D per day.

Animals↗
PubMed1994

Neonatal hypocalcemia: to treat or not to treat? (A review).

The various definitions of neonatal hypocalcemia (NHC) are critically examined. The authors review the known and less known complications of NHC and of its treatment. They emphasize the need for a definition of NHC in terms of serum ionized rather than total calcium concentrations, the rationale for treating symptomatic NHC, as well as the need for further research in infants with asymptomatic NHC.

Calcium↗
PubMed1994

Low bone mineral content and high serum osteocalcin and 1,25-dihydroxyvitamin D in summer- versus winter-born newborn infants: an early fetal effect?

Seasonal differences in bone mineral indices have not been studied in newborn infants. In adults, indicators of bone metabolism may show seasonal variations. In postneonatal infants and possibly in adults, vitamin D metabolism shows seasonal variations. We hypothesized that in winter-born infants, the bone mineral content is low and serum osteocalcin is high, related to increased bone turnover and high serum 1,25-dihydroxyvitamin D [1,25(OH)2D]. We studied 246 healthy, term appropriate-for-gestation infants in winter (January through March; 140 children) and summer (July through September; 106 children). The bone mineral content (BMC) of the one-third distal radius was measured before 3 days of age by photon absorptiometry. Significant seasonal differences were found: summer-born infants had significantly lower BMC, higher serum osteocalcin and 1,25(OH)2D, and lower serum total calcium than winter-born infants. Seasonal differences in BMC remained significant after adjusting for race and sex. BMC was not correlated with serum biochemical measures. Thus, summer-born newborn infants have low BMC and high serum osteocalcin and 1,25(OH)2D than winter-born infants; these findings are the opposite of adult findings. We suggest that seasonal effects on fetal bone operate especially in early pregnancy (approximately 6 months before birth) resulting in a "phase effect" and opposite findings from later life.

Black People↗
PubMed1994

Impact of metabolic control of diabetes during pregnancy on neonatal hypocalcemia: a randomized study.

OBJECTIVE: To test the hypothesis that strict control of diabetes during pregnancy can reduce the risk for neonatal hypocalcemia in infants of diabetic mothers. METHODS: One hundred thirty-seven pregnant women with insulin-dependent diabetes enrolled before 9 weeks' gestation were randomized to one of two treatment groups. In 68 subjects, the goals were fasting blood glucose level less than 4.44 mmol/L (80 mg/dL) and 1.5-hour postprandial blood glucose level less than 6.66 mmol/L (120 mg/dL) (strict control), whereas in 69 the goals were fasting blood glucose level less than 5.55 mmol/L (100 mg/dL) and 1.5-hour post-prandial glucose level less than 7.77 mmol/L (140 mg/dL) (customary control). RESULTS: Infants in the strict control group had a significantly lower rate of hypocalcemia (mean calcium less than 8.0 mg/dL in term infants and less than 7.0 mg/dL in preterm infants) than infants in the customary control group (17.6 versus 31.9%; P < .05). Using logistic regression analysis and after adjusting for the effects of gestational age, asphyxia, and White class on hypocalcemia, the difference between groups remained significant. The lowest infant serum calcium concentration correlated significantly with maternal glycohemoglobin A1 concentration at delivery (P = .03), gestational age (P = .0001), and the lowest serum magnesium concentration (P = .0001). CONCLUSION: Strict management of diabetes in pregnancy is associated with a reduction in the rate of neonatal hypocalcemia.

Adult↗
PubMed1994

Hypocalcemia and pregnancy-induced hypertension produced by low-calcium diet.

Recent studies from our laboratory in fasting pregnant ewes with twin gestation have implicated low serum calcium concentration in the etiology of hypertension in pregnancy. We hypothesized that the reduction in serum calcium concentration produced by feeding of a calcium-deficient diet in twin gestation would lead to a significant increase in maternal arterial blood pressure, vascular resistance, and protein in the urine and decreased uterine blood flow. Twenty-five instrumented ewes were used in the present study. After surgery a calcium-deficient diet and deionized water (calcium ion free) were provided ad libitum to 19 animals. Blood pressure, cardiac output, heart rate, and uterine blood flow were monitored every other day. Six control animals were provided with standard Rumilab diet and tap water (group 1). Animals on a low-calcium diet (group 2) were subdivided according to the blood ionized calcium response to low dietary calcium intake. Non-hypocalcemic animals were assigned to group 2a (n = 10), and hypocalcemic animals (calcium concentration below two standard deviations from the control group) were assigned to group 2b (n = 9). In group 2b calcium concentration decreased from 1.03 +/- 0.04 mmol/L on day 110 of gestation to 0.77 +/- 0.03 mmol/L by day 125 of gestation. Arterial blood pressure increased significantly from 76 +/- 2 to 91 +/- 2 mm Hg, and uterine blood flow decreased from 950 +/- 53 to 579 +/- 48 mL/min. Urinary protein increased from 1.7 +/- 0.3 to 10.5 +/- 1.2 g/L.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1994

Effects of infant nutrition on cholesterol synthesis rates.

Nutrient effects on cholesterol fractional synthesis rates (FSR) in infancy by stable isotope determination have not been studied. We hypothesized that FSR is significantly reduced with high dietary cholesterol and phytoestrogen intake and increased with low dietary cholesterol and phytoestrogen intake. We prospectively studied 33 term male infants exclusively fed human milk (high cholesterol, low phytoestrogen, n = 12), cow milk-based formula (low cholesterol, low phytoestrogen, n = 8), soy milk-based formula (zero cholesterol, high phytoestrogen, n = 7), or soy milk-based formula modified to contain cholesterol (low cholesterol, high phytoestrogen, n = 6) during the first 4 mo of life. Cholesterol FSR was determined from rate of incorporation of deuterium into erythrocyte membrane cholesterol, and urinary isoflavone excretion (an index of dietary phytoestrogen exposure) was measured by gas chromatography-mass spectrometry. Significant differences in cholesterol FSR were found. FSR (%/d) was lowest in human milk (2.62 +/- 0.38), highest in soy milk-based formula (9.40 +/- 0.51), and intermediate in cow milk-based and modified soy milk-based formula (6.90 +/- 0.48 and 8.03 +/- 0.28, respectively), p < 0.0001. Cholesterol FSR was significantly lower in modified soy milk-based compared with soy milk-based formula, p < 0.05. We also show for the first time that dietary phytoestrogens are absorbed and excreted by the infant fed soy protein-based formula. Urinary isoflavone excretion was inversely related to cholesterol FSR, but it was not significantly related to serum cholesterol concentration. We conclude that the type of infant nutrition and dietary cholesterol are major factors influencing cholesterol fractional synthesis rates in infancy.

Adaptation, Physiological↗
PubMed1994

Similar gastric emptying rates for casein- and whey-predominant formulas in preterm infants.

Casein-predominant infant milk formulas have been speculated to predispose to lactobezoar formation in preterm infants due to delayed gastric emptying. There have been, however, no prospective studies to prove this possibility. In a randomized, double-blinded, prospective study, we tested the hypothesis that preterm infants fed casein-predominant milk formula have slower gastric emptying than infants fed whey-predominant formulas. Twenty preterm infants within the first 4 d of life were randomized to receive either the whey-predominant formula Similac Special Care (whey:casein ratio 60:40) or an experimental casein-predominant formula (whey:casein ratio 18:82). Only the protein composition differed between the two formulas. The infants were fed the assigned study formula until they reached approximately 2200 g body weight when a gastric emptying scan was performed, using the designated study formula mixed with 25 microCi of technetium-99 sulfur colloid. Gastric emptying was followed continuously for 2 h. Gastric emptying at 30, 60, 90, and 120 min was similar between the two study groups. The time for 50% gastric emptying was 64.9 +/- 12.3 min for the infants fed the whey-predominant formula and 56.5 +/- 14.8 min for those fed the casein-predominant formula (p = 0.75). We conclude that the rate of gastric emptying in preterm infants fed casein-predominant formulas is similar to that in those fed whey-predominant formulas.

Animals↗
PubMed1993

Bone mineralization in the first year of life in infants fed human milk, cow-milk formula, or soy-based formula.

OBJECTIVE: To test the hypotheses that (1) bone mineral content (BMC) is similar in infants fed soy-based formula (SBF) and human milk (HM) and higher in infants fed cow milk-based formula (CBF) and (2) serum 1,25-dihydroxyvitamin D, an index of mineral sufficiency, is similar in infants fed formula and infants fed HM. DESIGN: Randomized, prospective study of formula-fed group only. SETTING: Recruitment was in a normal newborn nursery. PATIENTS: 72 infants: 10 given HM, 20 given CBF (Similac), 21 given SBF (Isomil), and 21 given SBF (Prosobee). MEASUREMENTS: BMC and 1,25-dihydroxyvitamin D levels at baseline (days 2 through 7 of life) and at 8, 16, 26, and 52 weeks of age. The BMC was similar in all groups at all times; serum 1,25-dihydroxyvitamin D levels were similar in all groups, except that they were elevated at 8, 16, and 26 weeks in those fed Prosobee. CONCLUSIONS: (1) BMC is similar in SBF-, CBF-, and HM-fed infants and (2) compensatory elevation of serum 1,25-dihydroxyvitamin D concentrations may occur in SBF-fed infants.

Animals↗
PubMed1993

Reduced serum osteocalcin and 1,25-dihydroxyvitamin D concentrations and low bone mineral content in small for gestational age infants: evidence of decreased bone formation rates.

In small for gestational age (SGA) infants, bone mineral content (BMC) is low but the reasons are unclear and the possible relationships between calcium-regulating hormones and BMC have not been studied. We hypothesized that BMC would be lower and concentrations of serum parathyroid hormone and 1,25-dihydroxyvitamin D would be higher at birth in SGA infants than in appropriate for gestational age (AGA) infants. Forty-two term SGA infants and 126 term AGA infants, matched 1:3 specifically by gestation (+/- 1 week) and birth month, were studied prospectively. The BMC of the distal one third of the radius was measured before 3 days of age by photon absorptiometry. The BMC was lower in SGA than in AGA infants. Both SGA and AGA infants had lower BMC in summer or spring than in winter; BMC differences between groups remained significant after adjustment for season (p = 0.0001). Cord serum osteocalcin and 1,25-dihydroxyvitamin D values were lower in SGA than in AGA infants. There were no differences between groups in cord serum levels of intact parathyroid hormone, 25-hydroxyvitamin D, calcium, phosphorus, and magnesium. Relationships were positive between BMC and birth weight and were inverse between BMC and intact parathyroid hormone values. We suggest that reduced uteroplacental blood flow in SGA infants may result in reduced fetal-placental production of 1,25-dihydroxyvitamin D, which results in low BMC and low serum osteocalcin values; fetal serum parathyroid hormone values may be relatively elevated because of reduced placental mineral supply.

Birth Weight↗
PubMed1992

Prospective study of vitamin D supplementation and rickets in China.

To determine whether amounts of vitamin D lower than recommended doses are effective in preventing rickets, 256 term infants from two northern and two southern cities in China were studied in a randomized trial of vitamin D supplementation (100, 200, or 400 IU/day) during the first 6 months of life. Cord blood and 6-month blood samples were collected and radiographs were obtained at 3 to 5 days and at 6 months of age. Cord serum 25-hydroxyvitamin D concentrations were lower in the north than in the south (5 vs 14 ng/ml (12.5 vs 35.0 nmol/L); p less than 0.01). Wrist ossification centers were less likely to be present at birth in the northern children than in the southern children (p = 0.009) and were more likely to be present in infants born in the fall who had higher cord serum concentrations of 25-hydroxyvitamin D (p = 0.04). Serum 25-hydroxyvitamin D concentrations were lower in northern children 6 months of age than in southern children (p = 0.005) and were higher with an increasing supplemental dosage of vitamin D (p less than 0.001), particularly in infants in the north. None of the infants had rickets at 6 months of age. Because of the low serum 25-hydroxyvitamin D concentrations, especially among infants in the north, it may be prudent to supplement the diet with vitamin D at a dose of 400 IU/day.

China↗
PubMed1992

Effect of chronic maternal dietary magnesium deficiency on placental calcium transport.

Metabolisms of calcium (Ca) and magnesium (Mg) are closely interrelated in the intestine, bone, and kidney. Interaction of Ca and Mg at the placental level, however, is not well defined. The occurrence of decreased bone mineral content and hypocalcemia in infants of hypomagnesemic mothers led us to test the hypothesis that chronic dietary maternal Mg deficiency decreases placental Ca transport. On day 10 of gestation, 20 Sprague-Dawley rats were randomized to a Mg-deficient diet (3.3 mg/day, n = 10) or to a control diet (70 mg/day, n = 10). On day 20 of gestation (term = 22 days), intact placentas were perfused in situ through the umbilical artery and perfusate was collected through the umbilical vein. Calcium 45 (45Ca) and chromium 51-EDTA (51Cr-EDTA) (a diffusional marker for placental membrane integrity) were injected to the dam and steady state maternofetal clearance (Kmf45Ca, microliter/min/g placenta) of both isotopes were calculated. There was no difference in the clearance of 45Ca and 51Cr in both groups (55 +/- 10 vs 57 +/- 16 and 3.2 +/- 0.4 vs 3.6 +/- 0.4, respectively, mean +/- SEM). We conclude that, in the rat, placental Ca transfer is unaffected by chronic maternal dietary Mg deficiency. We speculate that Ca and Mg cross the placenta by independent mechanisms.

Animals↗
PubMed1992

Low bone mineral content in summer-born compared with winter-born infants.

Possible seasonal differences in newborn bone mineral content (BMC) have not been studied. Adult studies show seasonal variations with lower BMC in winter versus summer. Assuming that BMC variations may relate in part to vitamin D status, we hypothesized that newborn BMC would be lower in winter than summer. BMC of one third distal radius was measured in 55 healthy term newborns using a single beam photon absorptiometer [coefficient of variation (CV) for phantom standard 2.1%]. Infants were enrolled during summer (July-September, 1988) and winter (January-March, 1989) for a longitudinal nutrition study. Contrary to our hypothesis, there was a 12% lower BMC in summer versus winter (mean +/- SD 75.94 +/- 17.42 vs. 86.55 +/- 17.54 mg/cm, respectively; p = 0.035). The difference remained significant after controlling for possible race and gender effects (p = 0.02). We conclude that BMC is lower in summer- compared with winter-born infants. Since any seasonal effects on fetal bone are presumably related to effects through the mother, we speculate that if maternal vitamin D status influences fetal bone mineralization, the effect (possible sunshine deprivation in winter) may operate especially in early pregnancy, thus resulting in lower BMC, evident at birth in summer.

Black People↗
PubMed1992

d-Alpha-tocopheryl polyethylene glycol-1000 succinate enhances the absorption of vitamin D in chronic cholestatic liver disease of infancy and childhood.

Rickets and osteopenia, common problems in chronic childhood cholestasis, have been attributed to vitamin D malabsorption leading to reduced serum levels of 25(OH)-vitamin D. d-alpha-Tocopheryl polyethylene glycol-1000 succinate (TPGS), a water-soluble form of vitamin E, forms micelles at low concentration. We evaluated the potential role of TPGS in enhancing vitamin D absorption in eight children (aged 5 mo to 19 y) with severe chronic cholestasis (three extrahepatic biliary atresia, three nonsyndromic intrahepatic cholestasis, and two Alagille syndrome). To evaluate vitamin D absorption, the subjects received vitamin D3 1000 IU/kg (maximum dose of 50,000 IU); they then received the same dose of vitamin D3 mixed with TPGS (25 IU/kg). Serial serum vitamin D3 levels and areas under the curve were measured. All patients had enhanced absorption of vitamin D when it was administered in a mixture with TPGS. Mean area under the curve for serum vitamin D3 was 403.0 +/- 83.1 nmol x h/L (155.6 +/- 32.1 ng x h/mL), with a mean rise above baseline of 13.5 +/- 1.8 nmol/L (5.2 +/- 0.7 ng/mL) with vitamin D/TPGS compared with no rise when vitamin D was given alone (both p less than 0.001). Seven patients have been followed for at least 3 mo while receiving the vitamin D/TPGS combination. Those with initially low serum 25(OH)-vitamin D levels (less than 37.5 nmol/L or 15 ng/mL) had normalization (range 37.5-146 nmol/L) within 1 mo, whereas those with initially normal levels remained normal. While the patients were receiving vitamin D/TPGS, serum vitamin E to total lipid ratio either normalized or remained normal.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗