PTH regulates fetal blood calcium and skeletal mineralization independently of PTHrP.

PTH and PTHrP both act in the regulation of fetal mineral metabolism. PTHrP regulates placental calcium transfer, fetal blood calcium, and differentiation of the cartilaginous growth plate into endochondral bone. PTH has been shown to influence fetal blood calcium, but its role in skeletal formation remains undefined. We compared skeletal morphology, mineralization characteristics, and gene expression in growth plates of fetal mice that lack parathyroids and PTH (Hoxa3 null) with the effects of loss of PTHrP (Pthrp null), loss of PTH/PTHrP receptor (Pthr1 null), and loss of both PTH and PTHrP (Hoxa3 null x Pthrp null). Loss of PTH alone does not affect morphology or gene expression in the skeletal growth plates, but skeletal mineralization and blood calcium are significantly reduced. In double-mutant fetuses (Hoxa3 null/Pthrp null), combined loss of PTH and PTHrP caused fetal growth restriction, limb shortening, greater reduction of fetal blood calcium, and reduced mineralization. These findings suggest that 1) PTH may play a more dominant role than PTHrP in regulating fetal blood calcium; 2) blood calcium and PTH levels are rate-limiting determinants of skeletal mineral accretion; and 3) lack of both PTH and PTHrP will cause fetal growth restriction.

A randomized trial of two levels of iron supplementation and developmental outcome in low birth weight infants.

OBJECTIVES: To investigate the effect of increased iron intakes on hematologic status and cognition in low birth weight infants. STUDY DESIGN: We randomly assigned 58 infants to receive formula with 13.4 mg iron/L (normal iron) or 20.7 mg iron/L (high iron). At baseline, discharge, and at 3, 6, 9, and 12 months' corrected age, we assessed anthropometry; infections; red blood cell hemoglobin, catalase, glutathione peroxidase, red blood cell fragility (hydrogen peroxide test), and superoxide dismutase values; plasma malondialdehyde, ferritin, iron, transferrin, zinc and copper levels; and diet intake. Griffiths' Development Assessment was done at 3, 6, 9, and 12 months only. RESULTS: No statistical differences (P <.05) were noted for weight, catalase or malondialdehyde levels, red blood cell fragility, or Griffith's Development Assessment. Iron intakes were greater in the high iron group except at 12 months. Hemoglobin (high iron, 123 +/- 9; normal iron, 118 +/- 8) was not different at 3 months (P =.07). Plasma zinc levels (high iron, 70 +/- 14; normal iron, 89 +/- 27) and copper levels (high iron, 115 +/- 26; normal iron, 132 +/- 27; P =.06) at 12 months suggested inhibition of absorption by high iron formula. Glutathione peroxidase levels were higher in the high iron group. The total number of respiratory tract infections was greater in the high iron group (3.3 +/- 0.9) than in the normal iron group (2.5 +/- 0.9). CONCLUSION: In terms of cognitive outcome, there is no advantage associated with elevated iron intake for low birth weight infants.

Thiamine, riboflavin, pyridoxine, and vitamin C status in premature infants receiving parenteral and enteral nutrition.

BACKGROUND: There is a paucity of data about water soluble vitamin status in low birthweight infants. Therefore, the authors' objective was to assess current feeding protocols. METHODS: The authors measured serum concentrations for riboflavin, pyridoxine, and vitamin C and functional assays for thiamine and riboflavin longitudinally in 16 premature infants (birthweight, 1,336 +/- 351 g; gestational age, 30 +/- 2.5 weeks) before receiving nutrition (time 1, 2 +/- 1 days), during supplemental or parenteral nutrition (time 2, 16 +/- 10 days) and while receiving full oral feedings (time 3, 32 +/- 15 days). In plasma, vitamin C was measured colorimetrically, and riboflavin and pyridoxine were measured using high-performance liquid chromatography. The erythrocyte transketolase test as a functional evaluation of thiamine and the erythrocyte glutathione reductase test for riboflavin were measured colorimetrically. RESULTS: At time 1, nutrient intake of vitamins were negligible because infants were receiving intravenous glucose and electrolytes only. Intakes differed between time 2 and time 3 for thiamine (510 +/- 280 and 254 +/- 115 microg. kg-1. d-1, respectively), riboflavin (624 +/- 305 and 371 +/- 193 microg. kg-1. d-1, respectively), and pyridoxine (394 +/- 243 and 173 +/- 85 microg/100 kcal, respectively), but not for vitamin C (32 +/- 17 and 28 +/- 12 mg. kg-1. d-1, respectively). Blood levels at times 1, 2, and 3 were for thiamine (4.9 +/- 2.7%, 3.3 +/- 6.6%, and 4.1 +/- 9% erythrocyte transketolase test, respectively), riboflavin (0.91 +/- 0.31, 0.7 +/- 0.3, 0.91 +/- 0.18 erythrocyte glutathione reductase test, respectively), riboflavin (19.5 +/- 17, 23.3 +/- 8.6, 17.6 +/- 10 ng/mL, respectively), pyridoxine (32 +/- 25, 40 +/- 16, 37 +/- 26 ng/mL, respectively), and vitamin C (5.2 +/- 3, 5 +/- 2.2, 10 +/- 5 microg/mL, respectively) and did not differ at those times. CONCLUSIONS: Current intakes of these vitamins, except for possibly vitamin C, during parenteral and enteral nutrition seem to result in adequate plasma concentrations and normal functional indices.

Superoxide dismutase and glutathione peroxidase content of human milk from mothers of premature and full-term infants during the first 3 months of lactation.

BACKGROUND: Human milk contains various bioactive compounds including numerous immunologic factors, enzymes, growth factors, and hormones. However, the change during the course of lactation in many of these compounds has not been fully characterized. Therefore, the objective of the present study was to measure the activity of the enzymes superoxide dismutase (SOD; Enzyme Commission number [EC] 1.15.1.1) and glutathione peroxidase (SeGSHPx; EC 1.11.1.9) in human milk, to record changes in enzyme activity over time and to determine whether there are differences in activity between the milk of mothers of full-term (FT) and premature (PT) infants. METHODS: Nine samples were collected from each of 15 mothers (32 +/- 4 years of age; mean +/- standard deviation) of FT infants (gestational age, 40 +/- 1 weeks; birth weight, 3544 +/- 417 g) and 19 mothers (28 +/- 5 years of age) of healthy PT infants (gestational age, 29 +/- 4 weeks; birth weight, 1312 +/- 479 g). Samples were collected within a week of birth (+/- 1 day) and thereafter for 8 weeks, with a final collection at 12 weeks. RESULTS: During the 12-week study period, in both groups, total milliunits of GHSPx and SeGHSPx per milligram protein and SOD per per milligram protein increased, whereas protein content declined. SeGHSPx per milliliter milk was higher in the PT group at week 1 (92 +/- 30 mU/mL vs. 73 +/- 21 mU/mL), week 2 (93 +/- 28 mU/mL vs. 75 +/- 24 mU/mL), and week 7 (85 +/- 24 mU/mL vs. 68 +/- 22 mU/mL). The SOD activity per milliliter milk and milligram protein was higher throughout the entire study in the FT milk. CONCLUSIONS: Because mothers of PT infants may produce less milk than those of FT infants, PT infants may be at a disadvantage for antioxidant protection from these enzymes.

Folate and vitamin B12 status of women in Newfoundland at their first prenatal visit.

BACKGROUND: Newfoundland has one of the highest rates of neural tube defects in North America. Given the association between low maternal folic acid levels and neural tube defects, a cross-sectional study was conducted to obtain base-line data on the folate and vitamin B12 status of a sample of women in Newfoundland who were pregnant. METHODS: Blood samples were collected between August 1996 and July 1997 from 1424 pregnant women in Newfoundland during the first prenatal visit (at approximately 16 weeks' gestation); this represented approximately 25% of the women in Newfoundland who were pregnant during this period. The samples were analysed for serum folate, vitamin B12, red blood cell folate and homocysteine. RESULTS: Median values for serum folate, red blood cell folate and serum vitamin B12 were 25 nmol/L, 650 nmol/L and 180 pmol/L, respectively. On the basis of the interpretive criteria used for red blood cell folate status, 157 (11.0%) of the 1424 women were deficient (< 340 nmol/L) and a further 180 (12.6%) were classified as indeterminate (340-420 nmol/L). Serum homocysteine levels, measured in subsets of the red blood cell folate status groups, supported the inadequate folate status. Serum vitamin B12 levels of 621 (43.6%) women were classified as deficient or marginal; however, the validity of the interpretive criteria for pregnant women is questionable. INTERPRETATION: A large proportion of pregnant women surveyed in Newfoundland in 1997 had low red blood cell folate levels.

Eighteen-month follow-up of infants fed evaporated milk formula.

In parts of Canada including Newfoundland and Labrador and among Aboriginal peoples, infants still consume evaporated milk (EM) formulas for cultural and economic reasons. At 3 and 6 months, full-term infants fed EM (n = 30) received low intakes of iron, thiamine, selenium and had higher weight velocity than breastfed (BF, n = 29) infants. EM infants had greater anemia, lowered transketolase activity (thiamine) and lowered glutathione peroxidase (selenium) activity (p < 0.05). To determine the later effect of early feeding deficit on nutritional status, we examined these same infants at 18 months of age. At that time, there were no differences in dietary intakes of energy, protein, zinc, copper, selenium and iron, nor in plasma levels of zinc, copper, vitamin C, nor in red blood cell activity levels of glutathione reductase (riboflavin), transketolase, glutathione peroxidase, nor in superoxide dismutase. However, EM infants weighed more and were more likely to visit a physician, have anemia, and have iron depletion than were BF infants. We conclude that infants consuming evaporated milk formulas should receive iron supplements throughout infancy.

Molybdenum requirements in low-birth-weight infants receiving parenteral and enteral nutrition.

BACKGROUND: Molybdenum (Mo) is an essential trace element required by three enzymatic systems, yet there are no reports of Mo deficiency in infants. Low-birth-weight infants (LBW) might be at risk for Mo deficiency because they are born before adequate stores for Mo can be acquired, they have rapid growth requiring increased intakes, and they frequently receive supplemental parenteral nutrition (SPN) and total parenteral nutrition (TPN) unsupplemented with molybdenum. METHODS: To investigate Mo requirements of LBW infants (n = 16; birth weight, 1336+/-351 g; gestational age, 29.8+/-2.5 weeks; M+/-SD), the authors collected all feeds, urine, and feces prior to TPN (baseline, n = 16, collections = 16), during TPN (n = 9, collections = 19), during SPN (n = 13, collections = 17), and after one week of full oral feeds (FOFs) of formula or human milk (FOF, n = 16, collections = 16). RESULTS: Infant weights at collection times were: 1.3+/-0.3 g, 1.27+/-0.4 g, 1.4+/-0.3 g, and 1.7+/-0.5 g, respectively. Mo intake was 0.03+/-0.1 microg/d, 0.34+/-0.1 microg/d, 1.25+/-1.7 microg/d, and 6.1+/-2.5 microg/d. Mo output was 0.64+/-0.6, 0.34+/-0.5, 0.68+/-0.8, and 4.1+/-2.5 microg/d. Mo balance at these times was -0.60+/-0.5, -0.001+/-0.5, 0.57+/-1.9, and 2.0+/-2.9 microg/d. Mo balance increased with time, yet some infants were always in negative balance, even though Mo intakes exceeded recommendations. CONCLUSIONS: The authors speculate that an intravenous intake of 1 microg/kg/d (10 nmol/kg/d) and an oral intake of 4-6 microg/kg/d (40-60 nmol/kg/d) would be adequate for the LBW infant.

Elemental composition of human milk from mothers of premature and full-term infants during the first 3 months of lactation.

To examine longitudinal and gestational effects of mineral content in human milk, we analyzed human milk from lactating mothers of premature (PRT, n = 24, < 2000 g birth weight, < 37 wk gestation) and full-term (FT, n = 19, > 2500 g, 39-41 wk gestation), living in Newfoundland, Canada. Samples were collected once a week for 8 wk with one final sample collected at 3 mo. Milk samples collected in acid-washed containers were wet ashed with concentrated HNO3, and barium, cadmium, calcium, cesium, cobalt, copper, cerium, lanthanum, magnesium, manganese, molybdenum, nickel, lead, rubidium, tin, strontium, and zinc were measured using inductively coupled plasma-mass spectrometry. Data were analyzed using standard multiple-regression procedures with correlated data analyses to take account of the relationship between successive weeks. Results indicated lower Ca and Pb in PRT milk. Calcium was the only nutritionally significant element to differ between groups. Molybdenum in both PRT and FT milk showed a definite decrease with time, suggesting that the Mo content in milk is homeostatically regulated. However, Ce, La, Ba, and Sn did not display any pattern indicative of biological regulation and potential human requirement.

Elevated intakes of zinc in infant formulas don not interfere with iron absorption in premature infants.

BACKGROUND: Zinc and iron may share common pathways for absorption and compete for uptake into mucosal cells. We determined whether elevated ratios of zinc to iron would interfere with erythrocyte incorporation of iron in premature infants both during and between feeds. METHODS: In the first experiment, five premature infants (<2500 g birth weight) were enrolled, once receiving full oral feeds by nasogastric tube. They received either high (1200 microg/kg, ratio 4:1) or low (300 microg/kg, ratio 1:1) doses of oral zinc sulfate, together with 300 microg/kg oral 58Fe as chloride in saline with 10 mg/kg vitamin C, between designated feeding periods. Each infant served as its own control and randomly received either high or low doses of zinc or iron and then the alternate dose after 2 weeks. In the second experiment, nine additional premature infants were assigned to the same zinc:iron intake protocol except zinc and iron were given with usual oral feeds (premature formula or human milk) equilibrated before feeding. Iron absorption was measured by the erythrocyte incorporation of 58Fe. RESULTS: High doses of zinc given between feeds significantly inhibited erythrocyte incorporation of iron. 58Fe incorporation (%) with the 1:1 ratio of zinc:iron intake was 7.5 (5.7, 10; geometric mean, -I SD, +1 SD). The percentage of 58Fe incorporation on the 4:1 ratio of zinc:iron intake was 3.6 (2.6, 5.1). Given with feeds, the percentage of 58Fe incorporation on low zinc:iron intake was 7.0 (2.6, 19). Finally, the percentage of 58Fe incorporation on high zinc:iron intake was 6.7 (2.5, 19). CONCLUSION: Elevated intakes of zinc do not interfere with erythrocyte incorporation of iron in premature formulas.

Evaluation of full-term infants fed an evaporated milk formula.

The objective of this prospective, cohort study was to compare the nutritional status of full-term infants who were fed human milk (BF, n = 29), formula (FF, n = 30) or evaporated milk formulae (EM, n = 30) for at least 3 months. Infants were seen at enrollment, 3 and 6 months, at which times a blood sample, diet record and anthropometric data were collected. Infants in the EM group received solids earlier (12 +/- 5 weeks) than did FF infants (15 +/- 4 weeks), and both were earlier than BF infants (19 +/- 4 weeks). Only 26% of the EM fed group received iron supplements as ferrous sulphate drops. Seven BF, 12 FF and 20 EM had abnormal ferritin values (< 10 ng ml-1) at 6 months. Copper intake was lower in the EM infants at 3 and 6 months. However, plasma copper and erythrocyte copper zinc superoxide dismutase (ZnCuSOD) levels did not differ between groups. Selenium intake was lower in the EM group (5 +/- 1 and 10 +/- 5 micrograms d-1; 3 and 6 months) than in the FF infants (13 +/- 4 and 19 +/- 7 micrograms d-1; 3 and 6 months). Erythrocyte SeGHSPx levels in EM infants were lower at 6 months (EM, 33.2 +/- 3.4; FF. 35.2 +/- 3.9: BF, 36.1 +/- 3.8 mU mg Hb-1). Thiamin intake (0.99 +/- 0.08 and 1.24 +/- 0.32; 3 and 6 months, mg 1000 kcal-1) was higher in the FF group than in EM infants (0.38 +/- 0.39 and 0.66 +/- 0.38; 3 and 6 months). There were more (13%) abnormal thiamin assays in the EM group at 6 months than in the BF and FF infants (0%). In conclusion, infants fed evaporated milk formula receive adequate copper but may not receive enough thiamin or selenium. Unless supplemented from birth with medicinal iron, intakes of iron will be inadequate.

Laboratory gloves as a source of trace element contamination.

Contamination in a trace element laboratory can come from a variety of sources, including laboratory gloves. Therefore, vinyl and latex gloves were obtained from as many manufacturers as would supply gloves. These gloves were either prepared for acid-washing and subsequent soaking in an acid solution, or immersed in an acid solution for a duration of either 1 min or 1 h. Incubation washes were analyzed for a variety of trace elements by flame atomic absorption spectroscopy (AAS) or inductively coupled mass spectrometry (ICP-MS). Results indicated that only three brands of vinyl gloves were acceptable for use in a trace element laboratory, whereas others had contamination of different elements. Latex gloves contained such high levels of biologically important elements that they were not considered suitable for routine trace element work. Vinyl gloves of choice should be routinely acid-washed before use in a trace element laboratory.

Thiamine, riboflavin, folate, and vitamin B12 status of infants with low birth Weights receiving enteral nutrition.

The purpose of the present study was to monitor the vitamin status of 14 low-birth-weight (LBW) infants (< 1,750 g birth weight) at 2 weeks and an additional four infants at 3 weeks who were receiving an enteral formula providing 247 micrograms/100 kcal thiamine, 617 micrograms/100 kcal riboflavin, 37 micrograms/100 kcal folate, and 0.55 micrograms/100 kcal vitamin B12. The mean birth weight of the 18 infants was 1,100 +/- 259 g, and mean gestational age was 29 +/- 2 weeks. Weekly blood, 24-h urine collections, and dietary intake data were obtained. For thiamine, red blood cell (RBC) transketolase activity was within the normal range for all infants. For riboflavin, RBC glutathione reductase activity was normal for all infants except one. We calculated from intake and urinary excretion data that these infants require 225 micrograms/100 kcal thiamine and 370 micrograms/100 kcal riboflavin, respectively. Mean plasma folate levels were 21 +/- 11 ng/ml at 2 weeks and 18 +/- 5 ng/ml at 3 weeks. RBC folate levels were 455 +/- 280 ng/ml at 2 weeks and 391 +/- 168 ng/ml at 3 weeks. All folate blood values were normal, except for one subject with an elevated level (59 ng/ml). Vitamin B12 plasma values were 737 +/- 394 pg/ml at 2 weeks and 768 +/- 350 pg/ml at 3 weeks, and all values were normal except for three infants with elevated values. In conclusion, appropriate vitamin status was maintained during this short observational period, during administration of this enteral formula; however, riboflavin concentrations in the enteral feed may be excessive.

Zinc absorption in premature infants: comparison of two isotopic methods.

The fractional absorption of an oral dose of zinc can be measured in adults when given simultaneously with an intravenous dose and subsequently measuring the ratio of the double isotopic enrichment of urine. To test this method in very-low-birth-weight (VLBW) premature infants [n=5 females and 7 males, 1160 +/- 290 g (chi +/- SD) birth weight, 29 +/- 4 wk gestational age], an oral dose of either 300 or 1200 micrograms 68Zn.kg(-1).d(-1) was equilibrated with formula or human milk and administered simultaneously with either 50 or 100 micrograms 70Zn.kg(-1).d(-1) given intravenously 35 +/- 3 wk postconception. Urine and fecal samples were collected for 3-6 d and analyzed by inductively coupled plasma mass spectrometry. Endogenous fecal zinc (EFZ) was determined from isotopic enrichment, whereas net absorption and retention were calculated by traditional methods. The mean fractional absorption calculated from urine was 0.22 +/- 0.09 and from feces it was 0.25 +/- 0.07. Zinc intake averaged 1821 +/- 330, fecal excretion 1637 +/- 419, and urinary excretion 67 +/- 30 micrograms.kg(-1).d(-1). EFZ averaged 390 +/- 270 micrograms.kg(-1).d(-1) and ranged from 48 to 889 micrograms.kg(-1).d(-1). Net absorption was 220 +/- 316 micrograms.kg(-1).d(-1) and net retention was 131 +/- 334 micrograms.kg(-1).d(-1). True absorption was 373 +/- 161 micrograms.kg(-1).d(-1). Fecal collection is difficult, tedious, and often incomplete, and may be replaced by urine collection for the fractional absorption of zinc in groups of premature infants.

Intravenous iron administration to very-low-birth-weight newborns receiving total and partial parenteral nutrition.

BACKGROUND: Intravenous iron supplements are not routinely administered to very-low-birth-weight newborns receiving total parenteral nutrition because of the possible increased risk of infection and because iron needs may be met with blood transfusions. METHODS: To assess the benefits of a prudent IV iron supplement (200 to 250 micrograms/kg/d), 26 very-low-birth-weight newborns (birth weight, 1005 +/- 302 g; gestational age, 28 +/- 2.3 weeks; mean +/- SD) were randomly allocated to receive total parenteral nutrition without iron (No-Iron) or with iron supplied as iron dextran (Iron). These newborns were followed at baseline (2 to 3 days after birth) and at weeks 1 to 4 thereafter. At each sampling time, urine samples, fecal samples (rarely), unused total parenteral nutrition solutions, blood products, and a blood sample (1 mL) were collected. RESULTS: There were no differences between the two groups in anthropometric measurements, hematologic or biochemical parameters, number or amount of blood transfusions (2.3 +/- 1.9), amount of blood removed for diagnostic purposes (44 +/- 16 mL), or number of septic events (n = 16). There was no difference between the groups for the total iron excreted; however, the Iron group retained more iron. Iron balance was negative for all but 10 newborns (No-Iron, 3; Iron, 7) throughout the study. CONCLUSIONS: A total iron intake of 400 micrograms/kg/d, half of which was provided by IV iron, is not sufficient to maintain iron balance or to meet fetal accretion rates (1000 micrograms/kg/d) in very-low-birth-weight newborns receiving total parenteral nutrition. Furthermore, endogenous iron from blood transfusions does not provide an adequate supply of iron.

Nutritional patterns of mothers of children with neural tube defects in Newfoundland.

In an exploratory study of the genetic epidemiology of neural tube defects in Newfoundland, we studied mothers who had given birth to a child with a neural tube defect (NTD) with respect to their nutrition, as well as various other factors. The frequency of NTD in the area studied was 3.5/1,000 births and has not decreased recently, as it has in some other parts of the world. Twenty-five mothers of children with NTD and a comparison group (CG), matched for age and neighbourhood, completed 3 day dietary records. The NTD group consisted of all mothers who had given birth to an NTD child within the previous 3.5 years in the chosen area. The CG mothers were ascertained through the local public health nurse who chose the nearest unaffected child born in the same time period as the NTD probands. NTD mothers were younger, heavier, and of lower socioeconomic status than were CG mothers. CG group women consumed more vitamin supplements during the periconceptional period (P < 0.05) and consumed more dairy and cereal products, fruits and vegetables (other than potatoes), and fewer sweets than did NTD mothers. Sixty-four percent of NTD mothers had folacin intakes below the recommended level (168 mg) compared to 27% of CG mothers (P < 0.01). These findings support previous evidence that poor maternal nutrition, and low dietary folate in particular, increase the chance of having a child with an NTD, and emphasize the need for supplementary folate in the diet of women of childbearing age in areas where the frequency of NTDs is high.

Diet and drug consumption in a group of elderly residing in rural Newfoundland.

Dietary intakes and drug consumption were recorded for 24 seniors in a Newfoundland outport. Food frequency questionnaires suggested that the food groups consumed least adequately by the seniors were grain products and meat and alternatives: 71% did not consume the recommended daily minimum intake of grain products and 66.7% did not meet the minimum intake recommended for meat and alternatives. Inadequate consumption of milk products and vegetables and fruit was reported by 33.3% and 29.2% of the respondents respectively. All respondents used at least one medication on a regular basis. When the regular usage of both prescription and nonprescription drugs was considered, drug consumption ranged from one to eight. Antihypertensives and antianginals had the highest reported usage. This study suggests that many seniors simultaneously experience two factors with potentially negative effects on their nutritional status--high drug usage and poor dietary intake.

Zinc requirement of premature infants.

Premature infants require adequate amounts of zinc to foster growth and cognitive development. Zinc given during TPN (450-500 micrograms.kg-1.day-1) is the only way to meet in utero accretion rates before 36 wk postconceptional age because of extensive resecretion into the gut of oral zinc. After that time, infants should be consuming formulas supplemented with 12 mg/L zinc for the whole of infancy.