Herbert C. Schwartz

Increased erythropoiesis and elevated erythropoietin in infants born to diabetic mothers and in hyperinsulinemic rhesus fetuses.

The pathogenesis of the increased erythrocytosis and extramedullary erythropoiesis observed in infants of diabetic mothers (IDM) has been obscure. In the present studies, IDM were found to have elevated umbilical plasma erythropoietin (Ep) concentrations by radioimmunoassay. 22 of 61 IDM (36%) had levels above the range of 28 nonasphyxiated, appropriately grown normal infants. In 16 controls and 20 IDM, plasma Ep correlated directly with plasma insulin (P less than 0.001, r = 0.73). To investigate this relationship further, a chronic rhesus model was studied with continuous fetal hyperinsulinemia for 21 d in utero in the last third of pregnancy. In five experimental fetuses, plasma insulin levels averaged 4,210 microU/ml at delivery, whereas plasma Ep was above the range of six controls. In addition, the experimental fetuses had elevated reticulocyte counts in umbilical cord blood. The mechanism for the increased plasma Ep associated with hyperinsulinemia in the fetus is unexplained but may be mediated by fetal hypoxia.

Effects of Pregnancy on Hemoglobin AIc in Normal, Gestational Diabetic, and Diabetic Women

Hemoglobin AIc, a normal minor hemoglobin, has glucose linked by a Schiff base to the N-terminal end of the beta chain. The glucose interferes with the binding of 2,3 diphosphoglycerate, probably resulting in an increased affinity of that hemoglobin for oxygen. Hb AIc is increased to twice normal levels in juvenile-onset (insulin-dependent) diabetes. In the present studies, the Hb AIc, when expressed as per cent of total hemoglobin, was found to be elevated slightly in pregnany normal ( = 6.97 per cent), pregnant nondiabetic obese ( = 6.89 per cent), and gestationally diabetic subjects ( = 8.77 per cent) above that of normal females ( = 5.68 per cent). A remarkable difference was observed between the nonpregnant diabetics ( = 12.77 per cent) and the pregnant diabetics ( = 8.46 per cent). This decrease in the level of Hb AIc in diabetics who are pregnant more than 30 weeks may reflect either a better state of diabetic control and/or a compensatory mechanism to protect the fetus by facilitating oxygen exchange from mother to fetus.

Functional Nature of Glomerular Injury in Progressive Diabetic Glomerulopathy

We describe in physiological terms the increasing glomerular capillary wall (GCW) dysfunction of 20 patients with diabetic glomerulopathy and heavy proteinuria. The clearances of uncharged polysaccharide markers of graded size were used to probe the glomerular filter on three occasions over a 24-mo period. The findings were analyzed with a theoretical model of solute transport that depicts most of the GCW as an isoporous membrane and the minor portion as a nondiscriminatory shunt pathway. Initially, the mean glomerular ultrafiltration coefficient Kf is computed to have been 3-5 times lower and mean pore radius of the major membrane component (r0) 2 Å smaller than normal control values. In contrast, the model computes the fraction of filtrate volume permeating the nondiscriminatory shunt pathway (ω2) to have been sixfold elevated above control values and to have correlated strongly in individual patients with the fractional clearances of albumin (r = .72) and of IgG (r = .73). Sequential studies after 12 and 24 mo revealed an invariable decline in glomerular filtration rate (GFR). Fractional clearances of albumin and IgG increased with time in most patients but declined in a few instances (20-25%). Change in ω2 tended to occur in parallel with fractional protein clearance, regardless of its direction. We conclude that in progressive diabetic glomerulopathy 1) GFR declines because of a loss by glomerular capillaries of ultrafiltration capacity, 2) proteinuria is largely a consequence of increasingly impaired barrier-size selectivity, and 3) the foregoing injuries reflect damage to different parts of the GCW and may become dissociated from one another with the passage of time.

HAEMOGLOBIN AIc (GLYCOHAEMOGLOBIN) IN DIABETIC PREGNANCY: AN INDICATOR OF GLUCOSE CONTROL AND FETAL SIZE

Haemoglobin AI, (Hb AIc), a glycohaemoglobin present in normal human blood, is elevated in glucose intolerant individuals. In non‐pregnant diabetic subjects, a direct relationship has been established between per cent Hb AIc and blood and urinary glucose levels over weeks and months. In this study, Hb AI, level and mean random blood glucose concentration in the third trimester of pregnancy were found to correlate directly in 12 diabetic women without vascular disease (Pt0.001). In this same group of women, third trimester Hb AIc levels also correlated significantly with infant birth weight (P

Pulmonary excretion of carbon monoxide in the human infant as an index of bilirubin production

A total of 45 infants, including 20 appropriate-size-for-gestational-age infants (AGAs), 19 large-size-for-gestational-age infants (LGAs) and 6 infants of diabetic mothers (IDMs), had determinations of their pulmonary excretion rate of carbon monoxide (VeCO) in the first postnatal week as an index of bilirubin production. We calculated a ratio (Rw) of birth weight to ideal weight (50th percentile for gestational age) as a relative measure of infant size. We also measured maternal glycosylated hemoglobin (Hb AIc) in the postpartum period as a reflection of the time-integrated blood glucose level over the weeks preceding delivery. Mean values for maternal Hb AIc in the postpartum period, infant Rw, and VeCO were all significantly increased for the LGAs and IDMs compared to the normal AGAs. Nine LGAs had mothers whose Hb AIc levels were >2 S.D. higher than the mean Hb AIc level for mothers of normal AGAs. The infants whose mothers had the highest Hb AIc levels were not always the ones with the highest bilirubin production rates. These findings suggest that maternal Hb AIc in the postpartum period, infant size, and bilirubin production are associated phenomena, but that a postpartum time-integrated measure of blood glucose level over the weeks preceding parturition may not reflect changes in other associated factors which can affect infant erythropoiesis. The LGAs are not a homogeneous group, and some may have mothers with missed abnormalities of gestational glucose metaoblism.

Glycohemoglobin (HbAIc): A predictor of birth weight in infants of diabetic mothers

Hemoglobins AIa-c (fast Hb), minor variants of HbA, are elevated in patients with diabetes mellitus. Recent studies indicate a relationship of fast hemoglobins, especially HbAIc (glycosylated form), to chronic hyperglycemia. Since infant oversize has been attributed to maternal hyperglycemia and fetal hyperinsulinemia, the hemoglobin HbAIc fraction was compared to birth weight (actual and relative to gestational age) and to maternal glucose tolerance. Normal (13), probably normal (8), gestational diabetic (10), and insulin-dependent women (14) were studied in the third trimester; women with advanced diabetic vascular disease were excluded. When corrected for gestational age, relative birth weights correlated in a significant linear regression with HbAIc (n = 45, r = 0.57, P less than 0.001). Third trimester maternal glucose tolerance (Kt) of women, not insulin dependent, correlated in a signigicant manner with both HbAIc (P less than 0.05) and birth weight for gestational age (P less than 0.01).

Acetaldehyde-Dependent Changes in Hemoglobin and Oxygen Affinity of Human Erythrocytes

In the presence of acetaldehyde, metabolizing human erythrocytes accumulate an altered hemoglobin product showing chromatographic similarity to hemoglobin AIa or AIb. The adduct is stable to overnight dialysis with an intracellular half-life of about 5.5 days. Adduct formation is accompanied by proportional changes in cell oxygen affinity (decrease in P50 of 3 mm Hg/mM adduct). Little unaltered hemoglobin remains after overnight incubation in 15 mM acetaldehyde, with significant adduct formation and marked reduction of cell ATP occurring after prolonged incubation in as little as 0.5 mM acetaldehyde.

Biosynthesis of heme in leukemic leukocytes.

The incorporation of 59Fe into heme and the synthesis of δ‐aminolevulinic acid by leukocyte homogenates were studied. Whereas polymorphonudear peritoneal exudates from rabbits, as well as leukocytes from healthy adult volunteers and patients with chronic leukemia, lacked the capacity to incorporate radioiron into heme, immature leukemic cells from patients with acute leukemia possessed iron‐incorporating activity. In addition these cells could utilize δ‐aminolevulinic acid as substrate for heme synthesis. Delta‐aminolevulinic acid synthetase activity could not be demonstrated in immature leukemic cells nor could they utilize glycine as substrate for heme synthesis. This work does not reveal whether the heme‐synthesizing capacity in immature leukemic leukocytes is a function of this immaturity or of malignant transformation.

Hemoglobin AIc in the Glucose-intolerant, Streptozotocin-treated or Pancreatectomized Macaque Monkey

Hemoglobin AIc (Hb AIc), a glycosylated minor variant of Hb A, is elevated in diabetic patients. In our study, macaque monkey model with acquired glucose intolerance [both streptozotocin (STZ)-treated or pancreatectomized] was evaluated for the presence of Hb AIc and for evidence of a possible physiologic effect on oxygen-carrying capacity. Blood from 29 Macaca monkeys (27 rhesus), including 22 with carbohydrate intolerance (17 treated with STZ and five that were pancreatectomized), was analyzed for minor hemoglobins using Amberlite IRC-50 with cyanide-phosphate elution. Unlike in man, no Hb AIc peak was identified in any control animals. However, all five pancreatectomized animals and 10 of 17 STZ-treated animals had clearly identified peaks that eluted similarly to human AIc and had an increased glucose content after acid hydrolysis relative to the major Hb A peak. Of the more severely carbohydrate-intolerant animals (fasting blood sugar > 200 mg. per deciliter) that were receiving insulin, seven of eight monkeys had Hb AIc. peaks compared with seven of 14 animals with less severe carbohydrate intolerance (fasting blood glucose < 200 mg. per deciliter) treated without insulin. During pregnancy, none of the seven STZ-treated animals had a definite peak, although one of these animals demonstrated an Hb AIc peak postpartum. In a group of five control and three STZ-treated nonpregnant animals, no differences were observed in whole blood pH, PCO2, P50, 2,3-diphosphoglycerate, adenosine triphosphate, and adenosine diphosphate, and plasma inorganic phosphate, while plasma glucose was variably elevated. The glucose-intolerant macaque model has potential for studying the long-term effects of acquired hyperglycemia, the biochemistry of the glycohemoglobin, and the possible pathophysioiogic effects of Hb AIc in pregnancy.

Hemoglobin Hasharon in a Premature Infant with Hemolytic Anemia

Extract: A premature infant with jaundice was found to have a compensated hemolytic process as evidenced by mild hyperbilirubinemia, a regenerative anemia, and persistence for several months of reticulocytosis, polychromatophilia, and stippled macrocytes. There was no blood loss. When hemoglobins from this family were electrophoresed, the propositus and her mother were found to be heterozygous for an abnormal hemoglobin. The variant hemoglobin, which was 20% of the mothers hemoglobin, had the electrophoretic mobility of hemoglobin S; however, sickle preparations were negative at 24 hr and, in contrast to hemoglobin S, the hemoglobin was soluble in 2.58 M phosphate buffer. The mothers pattern also revealed a faint band running behind A2 and very close to the origin. The distance between this variant and A2 was about the same as the distance between the major variant and A. Such a pattern suggested that the hemoglobin mutation was in the α chain. Examination of the infants electrophoretic pattern revealed a third variant hemoglobin whose distance from fetal hemoglobin was the same as the distances of the variants in the mothers pattern, which indicated that an abnormal fetal hemoglobin was present. By 7 months of age the infants electrophoretic pattern was identical with that of her mother and the variant hemoglobin accounted for about 20% of the total.Since the propositus was a premature infant, structural studies were carried out on the adult variant which was isolated chromatographically from the mothers blood. Analysis of the tryptic peptide chromatogram of the α chain revealed that peptide T-6 was absent; a new peptide was isolated at a lower position on the chromatogram. The amino acid composition of this peptide revealed that the aspartic acid at position 47 was replaced by histidine. Therefore, the mutant hemoglobin was hemoglobin Hasharon (α-47 (CD5) aspartic acid → histidine).Chromatographically prepared hemoglobin F was hybridized with a similar preparation of the adult hemoglobin Hasharon. After electrophoresis, we found bands corresponding to hemoglobin A and to the fetal hemoglobin Hasharon, as well as the original hemoglobin F and adult hemoglobin Hasharon. There were also two bands which migrated anodal to hemoglobin A which might have been hemoglobin H and hemoglobin Barts, representing tetramers of the normal β and γ chains. These tetramers may have formed because of the relative instability of the mutant α chains.Speculation: The marked hemolytic process in this premature infant was dependent on the presence of the fetal form of hemoglobin Hasharon in fetal erythrocytes. Hemolysis resolved as these cells were replaced by adult-type erythrocytes which contained the adult form of hemoglobin Hasharon.