Burton P. Fine

The prevalence of bacteriuria in full-term and premature newborn infants.

Examinations of urine were performed in 836 full-term and 206 prematurely born infants, using specimens obtained by a clean-voided technique and by suprapubic puncture. Persistent proteinuria, leukocyturia, or hematuria was found in none, and none of these findings correlate well with bacteriologic studies. Bacteriuria was found in 0.7 per cent of the full-term and 2.9 per cent of the premature infants, mostly in asymptomatic subjects. Bacteriuria occurs with sufficient frequency in prematurely born infants to warrent repeated examinations of the urine during their nursery stay. In view of the difficulty in obtaining adequate specimens of urine, as well as the paucity of positive findings, routine screening of full-term infants does not appear to be indicated.

Influence of magnesium on the intestinal absorption of lead

Lead balance studies were compared between a group of dogs ingesting a synthetic cation-free diet (controls) and a group ingesting the same diet but with added magnesium. The lead absorption was proportionate to ingested lead in the control group. The absorption for the magnesium-fed group was 8.6 ± 1.4% of the ingested lead and 26.5 ± 1.7% for the control group (P < 0.01). There was also more evidence of lead toxicity in the group not ingesting magnesium. We conclude that in this experimental situation dietary magnesium decreases intestinal absorption of lead.

Renal Reabsorption of Bicarbonate in Puppies: Effect of Extracellular Volume Contraction on the Renal Threshold for Bicarbonate

Extract: It has been recognized for many years that infants have lower concentrations of bicarbonate in plasma than older children and adults, due neither to a limited renal capacity to excrete hydrogen ion nor to a reduced capacity for reabsorption of bicarbonate, but to a low renal threshold for bicarbonate. The purpose of the present investigation was to determine whether the neonate and young of another species also could be shown to have a “physiologic acidosis” and, if so, to use this model for exploration of factors that might influence the threshold for bicarbonate. Mean pH of blood and concentration of bicarbonate in plasma in 11 young suckling puppies were 7.24 ± 0.018 and 18.2 ± 0.55 mmoles/liter, respectively, levels considerably lower than those found in adult dogs. In all but one animal pH of urine was below 6.0. Inasmuch as puppies thus appear to be in a state of “physiologic acidosis” and to have no limitation in acidification of the urine, we feel that this animal provides a suitable model for further examination of the characteristics of renal reabsorption and excretion of bicarbonate during immaturity. Titrations of bicarbonate performed in the usual manner demonstrated a threshold of 17–20 mmoles/liter, with a mean of 18.3. In the absence of significant volume expansion, maximal rates of reabsorption of bicarbonate were not observed despite filtered loads that were double those at threshold. Fractional excretion of sodium during control periods in animals which were not dehydrated averaged 2.9 ± 1.8% compared with 0.16 ± 0.08% in animals which were slightly dehydrated by their previous treatment with ammonium chloride. In this group, by replacement of gastric fluid (primarily sodium and potassium chloride) with a solution of sodium and potassium bicarbonate, renal handling of bicarbonate at varying filtered loads could be studied in the absence of volume expansion and with the continued stimulus for reabsorption of sodium. Under these circumstances, the renal threshold for bicarbonate was found to be markedly increased (25.2 ± 1.12). Saline was administered to two animals after the threshold had been passed. At any given level of filtered load the rate of excretion of bicarbonate in urine after administration of saline greatly exceeded the rate of excretion during gastric suction. The data in the present study thus indicate that the decreased threshold for bicarbonate in the young animal is not due to a limitation in intrinsic capacity for reabsorption of bicarbonate, inasmuch as capacity could be increased markedly under the stimulus

INTESTINAL ABSORPTION OF LEAD; INFLUENCE OF AGE, CALCIUM AND MAGNESIUM

Childhood lead poisoning is usually by gastrointestinal absorption. Calcium and iron ingestion have been shown to increase tissue lead levels and signs of lead intoxication. Lead balance studies were performed on four mature dogs (18 months old) and three 8 week old puppies while on a basal diet free of electrolytes except NaCl, KCl and PbCO3 (0.1 mg Pb/kg/day). Fifteen day control periods were alternated with 15 day periods in which CaCO3 or MgCO3 was added to the diet. Other dogs fed Na2CO3 showed no change from controls in lead absorption. The control absorption for the mature dogs was 31.6 ± 6.4 % (m ± S.D.) and for the puppies 30.1 ± 8.2 % of the ingested lead. This difference was not significant. The percent absorption during the control periods of both groups combined was 30.9 ± 7.2 % which decreased to 27.1 ± 6.4 % (N.S.) when CaCO3 was added to the diet and to 10.0 ± 3.4% (p < .01) when MgCO3 was added. We conclude that in this experimental situation magnesium ingestion decreases the intestinal absorption of lead, and that age is not a significant factor.

EFFECT OF DIETARY SODIUM DEPRIVATION DURING PREGNANCY

Sodium is an essential nutrient for growth. The effects of its deficiency during gestation remain controversial. Some studies have shown fetal growth retardation while others have shown no effect. This study investigated the effects of graded sodium restricted diets on maternal and fetal growth. Thirty-four three day pregnant,S-D rats were randomized into four different sodium intake groups. The total sodium dose during the experiment was: 7000ueq(Control),5000ueq(E1), 3000ueq(E2), 1000ueq(E3). On day 20 of gestation the pregnancies were terminated. There was no difference in litter sizes. Analysis of covariance for litter weight to litter size for the four groups showed no difference in fetal growth.The maternal minus fetal weight gain was linear to total sodium ingested Y=17.3+008X, p<.001, r=0.83, as was maternal bone sodium concentration Y=210+.0053X, p<.001, r=0.79. There were no differences in fetal concentrations of N, Na, K, Cl, Ca or fat. We conclude that graded sodium deficient diets during gestation cause a proportionate loss of maternal weight and bone sodium but cause no significant fetal growth retardation.

1063 THE EFFECTS OF BODY BURDENS OF LEAD ON THE GROWING RAT KIDNEY

Lead induced chronic nephropathy is seen after prolonged occupational exposure to lead and has been produced in experimental animals. There is also suggestive clinical and experimental evidence that development of chronic lead nephropathy may be related to renal growth. Lead acetate was administered by three i.p. injections for a total dose of 125 mg/kg of body weight to 30 Sprague-Dawley rats during the fifth week of life. A control group received i.p. sodium acetate during the same period. One half of each group was studied after eight weeks and the remainder after 32 weeks. At 32 weeks there was a persistent elevation of blood lead concentrations (control 0.138±.04, exp. 0.367±.04 ug/gm; p < .05) and renal tissue lead concentrations (control 1.88±.19, exp. 8.2±.93 ug/gm; p < .05); however, body weight, kidney weight, and renal tissue RNA and DNA concentrations were not significantly different from the controls. Numerous renal tubular giant cells and intranuclear inclusions were found in the experimental group at 8 weeks but were reduced in number markedly by 32 weeks. There was no evidence of a generalized progressive nephropathy.These results indicate that after an acute exposure to lead in the growing rat progressive morphologic changes of the kidney are not seen despite persistent elevations of renal lead concentrations.

847 NEONATAL HYPOCALCEMIA ASSOCIATED WITH MATERNAL HYPERCALCEMIA

An infant born to a mother with hypercalcemia secondary to metastatic breast cancer developed severe hypocalcemia during the first week of life. Maternal calcium and phosphorous levels ranged from 14-17 mg/dl and 2-2.5 mg/dl, respectively, prior to delivery, and the infants calcium level was 15.0 mg/dl at birth. During the first 9 days of life the infants serum Ca level decreased to 4.8 mg/dl and P rose to 8.4 mg/dl. The serum Mg decreased to 0.7 mg/dl. Administration of MgSO4 intramuscularly raised the serum Mg to normal levels, but hypophosphaturia and hypocalcemia persisted. Administration of PTH was followed by return of Ca to normal levels and an apparent increase in P excretion. When PTH was stopped, serum Ca and Mg again decreased, but the phosphaturia persisted. Ca and Mg levels returned to normal spontaneously by the fourth week of life.The hypocalcemia of this infant supports the hypothesis of transient neonatal hypoparathyroidism resulting from exposure to relatively high levels of maternal Ca in utero and contradicts the theory that it is related to Mg deficiency and end-organ unresponsiveness to PTH.