Samuel H. Boyer

Lactate dehydrogenase variant from human blood: evidence for molecular subunits.

A variant of human lactate dehydrogenase is described. The occurrence of lactate dehydrogenase-1, -2, -3, and -4 as five, four, three, and two components, respectively, is interpreted as supporting the hypothesis that LDH isozymes are tetramers formed from various combinations of two types of subunits.

Fetal hemoglobin restriction to a few erythrocytes (F cells) in normal human adults

During adult life, the quantity of fetal hemoglobin (HbF) present in F cells--that is, rare erythrocytes which are reactive with rabbit antiserum to human HbF during microscopic immunodiffusion--is sufficient to account for all of the small quantity (less than 0.7 percent) of HbF normally present in whole blood. Thus, erythrocytes are normally heterogeneous with respect to the presence of HbF.

Individual variation in the production and survival of F cells in sickle-cell disease.

The protective role and underlying sources of the elevated levels of fetal hemoglobin associated with sickle-cell anemia were reassessed by microscopical immunodiffusion assays. Three variables that contribute to levels of fetal hemoglobin were examined: the percentage of fetal-hemoglobin-containing reticulocytes produced; the quantity of fetal hemoglobin synthesized within such cells; and the extent to which the fraction of fetal-hemoglobin-bearing erythrocytes is enriched beyond the level produced. Four general findings emerged from analysis of 29 patients: each variable is separately regulated; the expression of each is often distinctly different between individual patients; contrary to prior speculation, production of fetal hemoglobin may be as great in the absence of heterocellular hereditary persistence of the hemoglobin as in its presence; and fetal hemoglobin does not, as often supposed, guarantee preferential cell survival. We conclude that the differences encountered among patients must reflect heterogeneity among factors that modify production and survival of cells bearing fetal hemoglobin.

SV40 recombinants carrying rabbit β-globin gene coding sequences

Abstract We have constructed and propagated two SV40 recombinants in which different portions of the viral late gene region are replaced by a rabbit β-globin coding sequence derived from a cloned cDNA (Maniatis et al., 1976). One of these recombinants, which retains the promoter, leader and intervening sequences for a viral late mRNA, directs the synthesis of a stable SV40-globin hybrid transcript. Using a sensitive radioimmunoassay, we have shown that this globin RNA is translated in infected monkey cells. A second recombinant, which retains the late region promoter but lacks the RNA splicing region, produces neither a stable globin transcript nor any detectable β-globin. These experiments indicate that some sequence within a 500 bp SV40 segment, presumably the splicing region, is required for the accumulation of stable mRNA. They also demonstrate how hybrid transducing viruses can be used both to characterize viral regulatory sequences and to produce new gene products in cultured cells.

Hemoglobins in Sheep: Multiple Differences in Amino Acid Sequences of Three Beta-Chains and Possible Origins

Among the three adult sheep hemoglobins (A, B, and C), two (A and B) are reportedly products of alleles. The β-chains of A and B differ by at least seven scattered amino acid residues whereas the β-sequence of C differs from A by at least 16 residues and from B by at least 21 residues. These changes suggest that the origin of C-β antedated the divergence of A and B. Five shared differences between A-β and C-β with respect to B-β can be interpreted as the result of selective advantage in favor of B. A complex of additional mechanisms has possibly been involved in maintaining the A-B- C porymorphism.

Production of Erythrocytes that Contain Fetal Hemoglobin in Anemia: TRANSIENT IN VIVO CHANGES

Serial microscopic immunodiffusion assays of F cells, i.e., erythrocytes that contain fetal hemoglobin (HbF), in four individuals recovering from anemia demonstrate initial increases in the percentage of circulating reticulocytes that contain HbF (F reticulocytes) and subsequent increases in the percentage of mature erythrocytes that contain HbF (F erythrocytes). In one individual responding to therapy for iron-deficiency anemia, the average percentage of F reticulocytes increased from 4.8+/-1.1 to 16.0+/-2.8% (mean+/-SD), while the mean level of F erythrocytes increased from 3.5+/-0.7 to 7.2+/-0.6%. Two normal children with transient erythroblastopenia exhibited F reticulocyte percentages of 71.3+/-6.7 and 41.5+/-1.5%, respectively, when erythropoiesis resumed. With recovery these values fell to finally measured values of 33.7+/-4.7 and 12.6+/-1.1%, respectively. In an adolescent with sickle cell anemia, F-reticulocyte percentages fluctuated between 0.6+/-1.1 and 34.0+/-2.8% and paralleled the rise and fall of total reticulocytes associated with therapy for a nasopharyngeal carcinoma. Such findings suggest that first, the production of F cells and non-F cells are separately regulated. Second, F-cell production is preferentially stimulated during escape from erythropoietic suppression and selectively depressed at the start of suppression. Third, during escape from erythropoietic suppression, F-cell production in vivo resembles that reported for in vitro cultures of erythroid stem cells. Fourth, individuals with sickle cell anemia, like individuals without hemoglobinopathies, can change their relative level of F-cell production.

Physiologic Splitting of the Second Heart Sound

A N INCREASE in the magnitude of splitting of the 2 components of the second heart sound, as heard in the pulmonary area during inspiration, has been recognized for nearly a century.1 Recent reports2 3 suggest that this phenomenon is due to a relative delay of pulmonary valve closure when the increased venous return during inspiration causes prolongation of right ventricular me-ehanical systole. However, it seems reasonable from physiologic studies4 5 that inspira-tory shortening of left venstricular systole, resulting in an earlier aortic closure sound, could contribute to the splitting. Indeed, figure Q of a review by Leatham6 suggests some contribution from movement of the aortic component. In order to test this hypothesis heart sound recordings were obtained from young normal subjects with easily perceptible second heart splitting. For purposes of measurement the first sound and second sound components were required to have early fast deflections which were reasonably constant in form throughout respiration. Twenty persons were found who fulfilled these criteria. Precordial recordings were simultaneously obtained from the apex and an area of the base which allowed the greatest discrimination of second sound components. Signals from Altee capacitor microphones , electrocardiograms and pneumogram were recorded on a Hathaway oscillograph, (model S-14C), at a paper speed of 100 mm. per secoiid. The intervals between the first heart sound and the first (aortic) component of the second sound (1-2A) and the interval from the first sound to the second (pulmonary) component of the second sound (1-2 P) were measured with an accuracy of + 3 msec. Changes in 1010 these intervals were calculated for each of at least 3 consecutive respiratory cycles. The mean change of all the 1-2 A intervals during a respiratory cycle was 11.7 insee. while that of the 1-2 P was 11.4 nisec. Such chaiiges were always opposite in sign. Thus early aortic valve closure contributes as much as delayed pulnonic valve closure to the maximal second sound splitting of iin-INSP-1 2A FIG. 1. Respiratory variation in duration of 1-2A and 1-2P. spiration. Similarly, the reason that splitting is minimal in expiration is that aortic closure is delayed and pulmonic closure occurs early. In the example shown in figure 1 the variation of the 1-2 A, 13 msee., actually exceeds that of the 1-2 P which is only 4 msec. We believe that this method niay be a fruitful one for studying abnormal relationships between the 2 …

The emerging complexity of genetic control of persistent fetal hemoglobin biosynthesis in adults.

Three classes of mutants have now been recognized that directly influence fetal hemoglobin (HbF, a2y2) biosynthesis during adult life: deletion mutants a t the y-/3-globin gene complex, point mutations in 5’ regulatory regions of y-globin genes, and mutations of still unknown nature a t nonglobin loci. It is assumed that the first two classes of mutation affect the target sites while the third class affects the modulatory and effector molecules interactive with target sites. It is further assumed that these and other sites, yet to be defined by mutation, constitute a regulatory network by which HbF biosynthesis is governed in both health and sickness.