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We have previously discovered that the adult Drosophila melanogaster is tolerant to a low O2 environment, withstanding hours of total O2 deprivation without showing any evidence of cell injury. Subsequently, our laboratory embarked on the study of hypoxia tolerance using a mutagenesis and overexpression screens to begin to investigate loss-of-function or gain-of-function phenotypes. Both have given us promising results and, in this article, we detail some of the interesting results. Furthermore, several years ago, we have also started an experimental "Darwinian" selection to generate a fly strain that can perpetuate through all of its life cycle stages in hypoxic environments. Through microarrays and bioinformatic analyses, we have obtained genes (e.g. Notch pathway genes) that play an important role in hypoxia resistance. In addition, we also detail a proof of principle that Drosophila genes that are beneficial in fly resistance to hypoxia can also be as well in mammalian cells. We believe that the mechanisms that we are uncovering in Drosophila will allow us to gain insight regarding susceptibility and tolerance to low O2 and will therefore pave the way to develop better therapies for ailments that afflict humans as a consequence of low O2 delivery or low blood O2 levels. more...

The regional distribution of blood flow to the brain and to other major organs was studied during wakefulness and sleep in growing piglets. A young group was studied at 6.8 +/- 1.3 d of age and an older group at 33.5 +/- 5.5 d. Two d before the experiments, we instrumented the animals for measurement of blood flow by the microsphere technique. We determined sleep state using EEG and behavioral criteria. Although we did not find significant differences in blood gas tensions and cardiac output with changes in behavioral states, we did note a number of important changes in brain and muscle blood flow with sleep. 1) Although total brain blood flow changed little between wakefulness and sleep at both ages, regional differences existed. Indeed, at both ages, during rapid eye movement sleep (active sleep), blood flow to the thalamus-hypothalamus and brainstem was significantly higher than during wakefulness (p less than 0.025); in older piglets, blood flow to these two regions was significantly lower in quiet sleep than in wakefulness (p less than 0.05). 2) Blood flow to most skeletal muscle groups, and particularly to the diaphragm, was lower during sleep than during wakefulness. 3) Age did not have a significant effect on the regional distribution of blood flow during sleep. We conclude that behavioral states influence the regional distribution of blood flow in early life, but not in an age-dependent fashion. We speculate that, because no difference was observed in other hemodynamic variables, the regional changes in organ blood flow with sleep most probably reflect the differences in local metabolic needs. more...

Sulfonylurea receptors are believed to be related to ATP-sensitive potassium channels and play a key role during hypoxia/ischemia in the CNS. Our previous work has shown that these receptors in rat brainstem neurons are more important in the adult rat than in the newborn during hypoxia. In the present study, we studied the time course of postnatal development of sulfonylurea receptors in detail and the effect of chronic hypoxia on receptor density in newborn pups and adult rats exposed to hypoxia either as fetuses or as 90-d-old rats using receptor binding and autoradiography. Our current results show that sulfonylurea receptor density 1) was very low at birth and developed fast within the first 2 postnatal wk and then gradually reached adult levels and 2) continued to increase in the cortex and cerebellum but decreased in the brainstem with little or no change in other areas after postnatal wk 5. Chronic hypoxia 1) decreased body weight, brain size, and brain protein concentration and 2) increased sulfonylurea receptor density in utero but had much less of an effect in the adult. From these data, we conclude that sulfonylurea receptors develop mostly in the first 2 wk postnatally and chronic hypoxia increases sulfonylurea receptor expression in utero in spite of the fact that overall protein decreases. more...

During hypoxic-ischemic episodes in the brain, the resulting neuronal death is due, in part, to apoptosis, a genetically controlled form of cell death.p53, a tumor suppressor gene, is believed to promote apoptosis.bcl-2, a proto-oncogene, is believed to inhibit apoptosis. However, the role of these two genes in neuronal survival or death during hypoxia is not clear. We hypothesized that: a) neuronal expression of p53 and bcl-2 is altered during hypoxia, b) altered expression of p53 is associated with decreased neuronal survival during hypoxia, and c) altered expression of bcl-2 is associated with prolonged survival during hypoxia. Methods. 7-10 day old cultured rat neocortical neurons were exposed to 0.1,1, or 3% oxygen. Culture dishes were removed at 24-hour intervals for quantitative immunofluorescence staining and immunoblot analyses. Apoptosis was assessed by changes in cell morphology and in situ and genomic DNA fragmentation. To assess the impact of p53 and bcl-2 expression upon neuronal survival during hypoxia, expression of these genes was attenuated by treating selected neuronal culture plates with 3 μM antisense, sense, and nonsense oligonucleotides 24 hours prior to exposure to 0.1% oxygen. Neuronal survival was assessed by Trypan blue exclusion at 24-hour intervals during hypoxic exposure. Results. At each level of hypoxia studied, morphologic changes (cellular shrinkage, nuclear condensation) and in situ and genomic DNA fragmentation consistent with apoptosis was detected. Immunoblot and quantitative immunofluorescence analyses revealed an increase in both neuronal p53 and bcl-2 during hypoxic exposure. After 48 hours at 0.1% oxygen, the proportion of viable neurons was significantly greater in plates treated with p53 antisense oligonucleotide (≈60%) than in untreated plates(35-40%)(n=5;p 0.05). Conclusions.p53 and bcl-2 are increased in neurons during hypoxic exposure. Expression of p53 is, in part, necessary for hypoxia-induced neuronal apoptosis.bcl-2 expression, in part, prolongs neuronal survival during hypoxia. more...

To examine the interrelationship between the duration of apnea and changes in oxygen saturation, blood pressure, electroencephalogram (EEG), and heart rate, reflex apnea of 10, 20, 40, and 60 s duration was induced by stimulating the superior laryngeal nerves. Pig- lets (n = 11, age 5-14 days) were chronically instrumented for continuous monitoring of SaOz and blood pressure and for sampling arterial blood. Ventilation was recorded using whole body plethysmography and EEG and electrocardi- ogram were measured by acutely placed subcutaneous elec- trodes. Central apnea produced an immediate rise in blood pressure and a decrease in SaOz by 20 s. By 30 s into the apnea, EEG amplitude had already decreased. Major car- diac slowing did not occur until 80 s after the start of apnea. Hyperoxia delayed the start of desaturation, hyper- tension, and EEG attenuation. These data suggest that during superior laryngeal nerve-induced apnea in young piglets: 1) desaturation can reach profound levels rapidly, 2) EEG amplitude decreases substantially and becomes nearly isoelectric within 1 min, and 3) bradycardia is a late manifestation when compared to changes in oxygen satu- ration, blood pressure, and EEG. (Pediatr Res 23:402- 407,1988) Abbreviations SLN, superior laryngeal nerves EEG, electroencephalogram SaOz, arterial oxygen saturation MAP, mean arterial blood pressure EKG, electrocardiogram IVH, intraventricular hemorrhage more...

Sleep staging has been conventionally performed using neurophysiologic and behavioral criteria. However, these criteria may not always be available. Since it is known that cardiorespiratory variables in rapid eye movement (REM) sleep are different from those in quiet sleep, we asked whether such variables can be used for the determination of sleep state. We studied nine normal fullterm infants at 1 and 4 months of life. Ventilation was measured using barometric plethysmography and the RR interval using a high accuracy R wave detector. Electroencephalogram, electrooculogram, and postural muscle electromyogram were recorded using surface electrodes and behavioral criteria applied. Means of RR interval, respiratory cycle time and tidal volume, and coefficients of variation of the same variables, were obtained for 30-s intervals throughout each sleep study. The Kolmogorov- Smirnov distances between REM and quiet sleep were larger for the coefficients of variation than for the means at both ages for all variables. Moreover, coefficient of variation of respiratory cycle time was found to provide the largest separation between REM and quiet sleep. In view of this result, we developed a statistical decision rule using coefficient of variation of respiratory cycle time for the classification of REM and quiet sleep in blocks of 5-min periods. Each study was divided into 5-min epochs and this rule was applied to each epoch. Of 85 epochs staged as quiet sleep by neurophysiologic and behavioral criteria, 79 epochs (or 93%) were classified correctly as quiet sleep using our decision rule. Of 85 epochs staged as REM sleep, 84 were classified as REM sleep and only one misclassified as quiet sleep. Five additional infants, whose results did not enter into the formulation of the decision rule, were used as a subsequent example to test the rule. The results of these five infants were similar to those of the previous nine others. We conclude that in young infants 1) the variability of cardiorespiratory parameters can separate quiet from nonquiet sleep better than the mean values and 2) sleep staging using a decision rule based on coefficient of variation of respiratory cycle time can be performed with high degree of accuracy. more...

Summary: The QT interval was measured in 12 normal and 7 aborted sudden infant death syndrome (SIDS) infants in rapid eye movement (REM) and quiet sleep at monthly intervals through the age of 4 months. An accuracy of better than 2 msec was assured by high resolution of the digitized signal and calibration of each QT measurement with an accurately generated time code. In contrast to current speculations, the QT index was significantly smaller in the infants with aborted SIDS than in the normal infants in both REM and quiet sleep (P < 0.05). In addition, as in normal infants, the QTC was smaller in REM than in quiet sleep (P < 0.01). Although these results offer no support for the hypothesis that SIDS results from prolongation of the QT interval, they suggest that aborted SIDS infants have a functional abnormality in the autonomic nervous system. Speculation: We suggest that 1) the shortening of the QT interval in the aborted SIDS infants results from a uniform increase in the sympathetic outflow to the cardiac ventricles or an increase in circulating levels of catecholamines; and 2) an imbalance between the left and the right sympathetic outflow to the ventricles of aborted SIDS infants, as has been previously hypothesized, is not likely since the QTc was not larger in REM sleep, a sleep state in which an increase in sympathetic activity occurs. more...

Summary: The time spent in REM, quiet, and indeterminate sleep was computed in 13 aborted SIDS infants and compared to that spent in the same sleep states in 19 normal infants. Aborted sudden infant death syndrome (SIDS) infants were studied within a week of their aborted SIDS episode and subsequently at monthly intervals through the age of 4 months. Normal infants were studied at 1, 2, 3, and 4 months of age. Sleep staging was performed by two independent observers using electroencephalogram, electrooculogram, electromyogram and behavioral criteria. Although there was an increase in the percentage of time spent in quiet sleep with age in both normal and aborted SIDS infants, the significantly greater regression coefficients in normal infants (6.3 versus 2.9; P < 0.01) indicate that there are differences in the two groups and suggest a maturational abnormality or delay in sleep state distribution in aborted SIDS infants. Speculation: The results of this study suggest that the differences in sleep state distribution between aborted sudden infant death syndrome and normal infants share a common pathophysiologic alteration with the ventilatory and cardiac abnormalities reported by us elsewhere, perhaps involving the catecholaminergic system. more...

The mean +/- SEM of the cord, 48-hr, and 7-day values for serum calcium, magnesium, human calcitonin (HCT), parathyroid hormone (PTH), and 25-hydroxy-vitamin D (25-OHD) for premature and term infants can be seen in Table 1. Mean cord calcium concentrations were similar for term and premature infants. Serum calcium concentrations fell in both term and premature infants at 48 hr, but decreased more in the premature infants (from 10.23 +/- 0.30 to 8.74 +/- 0.19 mg/dl) than in the term infants (from 10.5 +/- 0.26 to 9.6 +/- 0.23 mg/dl). Serum calcium values increased from 48 hr to 7 days in both groups, and there was no significant difference between term and premature infants' serum calcium concentrations (10.6 +/- 0.28 and 10.12 +/- 0.3 mg/dl, respectively) at that time. There was no significant difference between term and premature cord serum magnesium concentrations. Serum magnesium concentrations increased similarly by 48 hr in both groups and remained at these concentrations at 7 days of life. Serum HCT concentrations were elevated above normal adult levels (71.9 +/- 6.6 pg/ml, 81% less than 100 pg/ml, n = 63) in both premature and term cord sera, but premature cord concentrations (146 +/- 24 pg/ml) were significantly higher than term cord concentration (91 +/- 21 pg/ml). Both term and premature infants displayed a 2-3-fold increase in serum HCT by 48 hr and a partial fall by 7 days to concentrations still above those seen in cord sera (Fig. 1). Nine of 10 premature and 9 of 10 term infants had undetectable PTH concentrations in cord sera. In two premature infants, PTH serum concenttration remained undetectable at 48 hr. However, the majority of both premature and term infants had elevated levels of PTH at 48 hr. The mean PTH concentrations were lower but still elevated at 7 days with the suggestion of higher concentrations in premature infants (Fig 2). There were no significant differences in serum 25-OHD concentrations between term and premature sera at birth or at 7 days. There was a weakly positive correlation between 25-OHD and cord calcium (r = 0.45, P less than 0.05), and a negative correlation between cord calcium and 48-hr PTH (r = -0.53, P less than 0.01). Calcium and magnesium were significantly positively correlated in 48-hr (r = 0.83) and 7-day (r = 0.84) sera in premature infants but not in term infants. Cord 25-OHD and cord HCT levels were significantly positively correlated (r = 0.80, P less than 0.01) in the term infants but not the premature infants. more...

Twenty QT intervals selected at random from the middle periods of rapid eye movement (REM) and quiet sleep were measured in 12 normal infants studied at 2 weeks and 1, 2, 3, and 4 months of life. A digitizing system, consisting of a precision rotational potentiometer mounted on a pair of calipers and an A/D converter, was used for measurements. An accuracy of +/- 2 msec was achieved by high resolution of the digitized signal and calibration of each QT measurement with an accurately generated time code. Sleep staging was done visually using an electroencephalogram (EEG), an electrooculogram (EOG), a submental electromyogram (EMG), and behavioral criteria. Our results show that the QT index (QTc = QT/square rootRR) was significantly greater during quiet sleep (mean = 0.439) than during REM sleep (mean = 0.433) (P less than 0.01) and that this difference existed at all ages studied. more...

Summary: Eighteen normal infants were studied in the first 2 wk of life during sleep and subsequently at their monthly birthdays for the first 4 months of life. The R-R interval was measured with an accuracy of 0.2 msec. Sleep staging was performed visually using electroencephalogram, electrooculogram, and electromyogram, and behavioral criteria. Our results show that the R-R interval and the beat-to-beat variability are, in general, smaller in rapid eye movement than in quiet sleep. The two sleep states, however, are best differentiated by the overall variability which is characteristically higher in rapid eye movement sleep. The R-R interval as well as the overall and the beat-to-beat variability show minimal values at 1 month and maximal rates of increase between 2 and 3 months of age, indicating that the R-R interval and R-R variability are not simple linear functions of age. Speculation: We suspect that the large variability in the R-R interval in rapid eye movement sleep is attributable to the wide fluctuations in the activity of the sympathetic and parasympathetic nervous system characteristic of this sleep state. Because peripheral vasodilatation is known to occur in rapid eye movement sleep, we speculate further that the decrease in R-R interval in rapid eye movement sleep may be an adjustment to maintain the cardiac output and blood pressure. more...

To determine the relation between milk intake and plasma levels of beta-casomorphins as a function of age, we studied the levels of beta-casomorphin-7 immunoreactive material (BCMIR) in 2- and 4-wk-old beagle neonates and adult dogs following milk intake. We used three kinds of milk: 1) bovine casein-based milk formula; 2) canine bitch's milk, and 3) soy protein-based (noncasein) formula. Using a new extraction technique, BCMIR was isolated from plasma and assayed by radioimmunoassay at 0, 2, 4, and 6 h after feeding. We found that BCMIR increased significantly in both 2- and 4-wk-old puppies post bovine and canine milk feeding, but not after soy protein formula. Base-line values were about 80-120 fmol/ml and increased to 100-120% 2 h after bovine casein intake in the older puppies and by 4 h in the younger group. BCMIR levels were undetectable in adult dogs before or after bovine milk feeding. Beta-casomorphin-7 added to plasma was rapidly degraded whereas BCMIR was stable. Chromatographic profiles demonstrated that the BCMIR moiety is larger than beta-casomorphin-7. Our data suggest that the appearance of BCMIR in the plasma of neonatal dogs is a result of beta-casein degradation along a permeable gastrointestinal mucosa. We speculate that morphiceptin and beta-casomorphins can be cleaved from BCMIR and may have important physiologic effects. more...

We studied the time course and change in heart rate during respiratory pauses in puppies (3-4 wk) and young adult dogs. We measured ventilation and ventilatory pattern using barometric plethysmography and recorded the respiratory rate (RR) interval using a pre-processor with an accuracy of 0.2 ms. During tidal breathing, the fluctuations in RR interval were an order of magnitude smaller in the puppy than in the dog. During respiratory pauses in dogs, the RR interval increased sharply, stabilized around the level of expiration of previous breaths, and dropped immediately with the subsequent inspiratory effort. The time course of the change in heart rate was different in the puppy: there was a gradual increase in the RR interval during the entire course of the pause and the maximum RR interval reached was substantially higher than during expiration of previous breaths. Our results suggest that 1) the change in heart rate at the outset of respiratory pauses is too fast to be related to blood gas changes in both puppies and dogs and 2) the mechanisms responsible for the vagal gating of heart rate during tidal breathing and during respiratory pauses are not well developed in early life in the puppy. more...

Summary: The relationship of beat-to-beat heart rate variability (delta RR) and instantaneous heart rate was studied in eight normal infants while asleep during the first four months of life. The sleep state (REM or quiet) was determined using neurophysiologic and behavioral criteria. The results of regression analyses indicated that the delta RR values were positively correlated with the instantaneous heart rate (RR intervals). The correlation coefficient range was 0.49 to 0.92 in quiet sleep and 0.50 to 0.93 in REM sleep. Regression analyses supported a linear approximation of the delta RR to RR relation over the RR range investigated (400 to 520 msec). The median slope was 0.124 in REM and 0.117 in quiet sleep. The slopes of these linear functions were similar in both sleep states and at all ages. If beat-to-beat variability is to be used as an index of the integrity of the autonomic nervous system, these results suggest that delta RR be corrected for RR. A model is presented which relates the demonstrated positive correlation of delta RR to RR with the physiology of cardiac output control. Speculation: The positive correlation of delta RR with RR is consistent with the view that beat-to-beat heart rate variability is a homeostatic mechanism required for control of cardiac output. more...

Serum human calcitonin (HCT) is highest within the first 48 hrs. of life. In term infants, HCT decreased to a mean ± S.E. of 151 ± 22 pg/ml at 1 week of age. Premature infants, however, had 225 ± 40 pg/ml. Twelve small premature infants were followed for 3 months to see if elevations of HCT persisted. Birth weight and gestation were 1123 ± 218 gm (760-1600 gm) and 30 ± 2.5 weeks (27-34 wks.). As shown below, moderate to severe osteopenia was present at 6 weeks of age. Hypocalcemia, elevations in serum alkaline phosphatase, and elevations in serum PTH with amino aciduria were frequent during the first 9 weeks. Serum HCT slowly fell, but remained elevated in 9/12 infants at 3 months. HCT may play an important role in the mineralization of infant bone and elevated serum HCT persists in the premature. The stimulus to HCT secretion during this period is presently unknown. more...

To examine the maturation of the cardiovascular response to hypoxia (FiO2=.15) during natural sleep, we studied 48 chronically instrumented unanesthetized beagle puppies at 15 and 30 days of age. We measured the RR interval and mean aortic blood pressure (MAP). In addition, in a subset of 10 puppies, we measured cardiac output (CO) by the Fick principle. After baseline measurements, puppies were exposed to hypoxia for 1-2 hrs. During normoxia, at 15 days of age: MAP was lower (mean 10%, p more...

Prolongation of the QT interval has been implicated in the pathogenesis of the Sudden Infant Death Syndrome (SIDS). To test this hypothesis, 31 studies in 12 normal infants and 17 studies in 7 aborted SIDS infants were performed during sleep in the first four months of life. The QT index (QTc) was measured with an accuracy of 2 msec or better. In contrast to recent suggestions, the mean QTc was significantly smaller in the aborted SIDS than in the normal infants in both REM and quiet sleep (p< 0.05, unpaired t-test). Means ± SD are presented: In both the normal and aborted SIDS infants, the mean QTc was significantly smaller in REM than in quiet sleep (p< 0.01, paired t-test). We suggest that 1) the smaller QTc in the aborted SIDS infants results from a uniform increase in the activity of the sympathetic outflow to the ventricles or an increase in circulating levels of catecholamines and 2) the smaller QTc in REM in both groups makes it unlikely that there is an imbalance in the sympathetic innervation of the ventricles in aborted SIDS. Although these studies do not support the hypothesis relating SIDS to prolongation of the QT interval, they may provide a basis for distinguishing normal from aborted SIDS infants. more...

DBP is low in the cord blood of preterm infants (359±24μg/ml) while term infants (558±78μg/ml) have adult concentrations (525±24 μg/ml). To see when preterm infants develop normal concentrations of DBP and to look for any relationship to DBP's major ligand, 25-hydroxyvitamin D (25-OHD), DBP was measured by radial immunodiffusion using a rabbit antiserum in serial serum samples from 28 preterm infants, gestation 29.7±2.5wks and birthweight 1162±344gms. DBP remained low until there was a significant increase at 12wks of age (p more...

We report a new syndrome with the simultaneous failure of control of ventilation (Ondine's Curse), esophageal and intestinal motility (Hirschsprung's disease), and heart rate in three infants, who died in the first few months of life; two were siblings. Detailed physiologic studies were performed in one, and pathologic studies in three. Ventilation was measured by the barometric method or by pneumotachography. Sleep was staged using the EEG, EOG, and EMG. Minute Ventilation (V) and respiratory rate (f) were lower in Quiet sleep (V=315ml, f=18/min) than in both REM sleep (V=477ml, f=22/min) and wakefulness (V=654ml, f= 29/min). Respiratory pauses >5 sec occurred more frequently in Quiet than in REM sleep. V increased by 25% after IV doxapram but not following aminophylline, progesterone or imipramine. Minimal short term (beat to beat) variability of the ECG R-R interval (interquartile ranged more...

The biphasic respiratory response (hyperpnea followed by hypoventilation) of the newborn human has been attributed to central hypoxic depression of the respiratory centers. Recently, we have shown that, in the absence of hypoxia, the excitatory effect of continued carotid sinus nerve (CSN) stimulation fatigues in piglets 4-14 days of age (The Physiologist 23:140, 1980). To study maturation of the excitatory effects of the CSN without confounding blood gas changes, we compared changes in respiratory output (RO=f × neural tidal volume) during electrical CSN stimulation in young and older piglets (7 piglets 4-14 days; 7 piglets 20-34 days). The piglets were anesthetized, vagotomized, paralyzed and ventilated (FIO2=1.0). End-tidal CO2 was kept constant with a servo-controller (mean end-tidal CO2=30.2mmHg). RO was quantified by moving average of the rectified phrenic neurogram. The RO of all piglets increased (p more...

437 SERUM 25-HYDROXY-VITAMIN D (25-OHD) CONCENTRATIONS AND BONE HISTOLOGY IN SUDDEN INFANT DEATH SYNDROME (SIDS)

Heart rate (HR) and HR variability were studied in 15 normal infants and 6 infants with aborted Sudden Infant Death Syndrome (SIDS) during sleep at monthly intervals through 4 months of age. The RR interval (inverse of heart rate) was measured to an accuracy of 0.2 msec. Sleep was staged using EEG, EOG, EMG and behavioral criteria. The median HR was 4 to 10% greater in the aborted SIDS infants at each age in both sleep states and this was significant at 2,3 and 4 months in quiet and at 3 months in REM sleep (p < 0.05, Wilcoxon Rank Sum test). The beat to beat variability of the HR (Δ RR) in the aborted SIDS infants was 6 to 40% smaller than in the normal infants in both REM and quiet sleep at each age studied. The interquartile range of the HR, a measure of overall variability in HR, was the same in the aborted SIDS and normal infants. In both groups, the HR and its interquartile range were greater in REM sleep. These studies indicate that the group of infants with aborted SIDS may be differentiated from the normal infants by their increased heart rate and decreased beat to beat variability, and that these findings may reflect abnormal autonomic regulation of the heart rate. more...

In aminal systems prolactin (HPL) increases 1,25 dihydroxy vitamin D (1,25(OH)2D) and decreases 24,25 dihydroxy vitamin D (24,25(OH)2D) synthesis. 24,25(OH)2D is low during pregnancy with normal serum PTH. During pregnancy, serum HPL and other hormones are increased, but during lactation only HPL remains elevated. We studied lactating mothers and non-lactating controls for 24,25(OH)2D, 250HD, PTH, HPL, calcium and magnesium at 6 weeks post partum. In nursing mother 24,25(OH)2D was significantly lower than normal or post partum controls. During lactation only there was an inverse correlation between HPL and 24,25(OH)2D (R=-.51) and PTH and 24,25(OH)2D (R=-.47). During lactation there was no correlation between 24,25(OH)2D and 250HD (R=.18). Thus, changes in vitamin D metabolism probably mediated by HPL and PTH may enable the lactating woman to maintain normal serum calcium and magnesium while providing for milk production. more...

Increased Parathyroid hormone serum concentrations, [PTH] enhance 1,25-(OH)2D and decrease 24,25-(OH)2D synthesis from 25-hydroxy vitamin D (25-OHD). At term, pregnant women have elevated PTH and infants have low [PTH]. 16 pairs of maternal (M) and umbilical cord (C) venous sera were analyzed for 24,25-(OH)2D, 25-OHD, calcium, magnesium and PTH. Both M 24,25-(OH)2D (2.6±0.5 ng/ml) and C 24,25-(OH)2D (3.0±1.2 ng/ml) were lower than 29 adult normals (5.0±0.6 ng/ml). Normal adult 24,25-(OH)2D is correlated with 25-OHD (R=.40 P more...