Pathway to global elimination of hepatitis B: HBV cure is just the first step

Hepatitis B (HBV) is a major cause of global morbidity and mortality, and the leading cause of liver cancer worldwide. Significant advances have recently been made toward the development of a finite HBV treatment that achieves permanent loss of HBsAg and HBV DNA (so-called "HBV cure"), which could provide the means to eliminate HBV as a public health threat. However, the HBV cure is just one step toward achieving WHO HBV elimination targets by 2030, and much work must be done now to prepare for the successful implementation of the HBV cure. In this review, we describe the required steps to rapidly scale-up future HBV cure equitably. We present key actions required for successful HBV cure implementation, integrated within the World Health Organization (WHO) Global Health Sector Strategy (GHSS) 2022-2030 framework. Finally, we highlight what can be done now to progress toward the 2030 HBV elimination targets using available tools to ensure that we are preparing, but not waiting, for the cure.

Guiding principles for the implementation of non-animal safety assessment approaches for cosmetics: skin sensitisation

Characterisation of skin sensitisation potential is a key endpoint for the safety assessment of cosmetic ingredients especially when significant dermal exposure to an ingredient is expected. At present the mouse local lymph node assay (LLNA) remains the 'gold standard' test method for this purpose however non-animal test methods are under development that aim to replace the need for new animal test data. COLIPA (the European Cosmetics Association) funds an extensive programme of skin sensitisation research, method development and method evaluation and helped coordinate the early evaluation of the three test methods currently undergoing pre-validation. In May 2010, a COLIPA scientific meeting was held to analyse to what extent skin sensitisation safety assessments for cosmetic ingredients can be made in the absence of animal data. In order to propose guiding principles for the application and further development of non-animal safety assessment strategies it was evaluated how and when non-animal test methods, predictions based on physico-chemical properties (including in silico tools), threshold concepts and weight-of-evidence based hazard characterisation could be used to enable safety decisions. Generation and assessment of potency information from alternative tools which at present is predominantly derived from the LLNA is considered the future key research area.

Persistence and adherence to disease modifying drugs among patients with multiple sclerosis

OBJECTIVE

This retrospective database study aimed to evaluate the adherence of multiple sclerosis (MS) patients on immunomodulatory treatments using claims data, and to identify differences between compliance and persistency measurements in the context of this disease.

METHODS

Continuously enrolled MS patients treated with subcutaneous IFNbeta-1b (Betaseron * ), subcutaneous IFNbeta-1a (Rebif dagger ), intramuscular IFNbeta-1a (Avonex double dagger ), and subcutaneous glatiramer acetate (Copaxone section sign ).) were identified from the PharMetrics patient-centric database, and all information related to patient demographics and pharmacy claims for the drugs of interest were extracted.

OUTCOME MEASURES

The main outcomes were treatment switches and discontinuations for patients initiated on the drugs of interest. Various compliance and persistency metrics including the proportion of days covered, treatment prevalence at 6-monthly time points after initiation, and the continuous time on drug were also examined.

RESULTS

A total of 6134 MS patients were started on one of the four drugs of interest. The number of patients switching or discontinuing therapy rose over the study period. The proportion of patients switching was similar between study drugs, by the different metrics, with the highest switch rates for subcutaneous IFNbeta-1b and the lowest for subcutaneous glatiramer acetate. Discontinuation rates were highest for subcutaneous IFNbeta-1b and lowest for intramuscular IFNbeta-1a. Regression models showed that intramuscular IFNbeta-1a and subcutaneous IFNbeta-1a had similar and higher persistency compared to subcutaneous IFNbeta-1b and subcutaneous glatiramer acetate.

CONCLUSIONS

Although treatment switching and discontinuation is common in MS patients, there is some noticeable variability between drugs and across measures of persistency and adherence. Also, claims data do not allow distinguishing between clinical patterns of MS, direct estimation of disease severity and observation of care that occurs outside of insurance coverage, and results need to be cautiously interpreted. The compliance to the various MS drugs was 80% or higher at all times for all four drugs. The highest rate of treatment persistency existed in the intramuscular IFNbeta-1a initiator group, while subcutaneous IFNbeta-1b was associated with a significantly lower persistence (p < 0.0001).

Healthcare resource utilization following switch or discontinuation in multiple sclerosis patients on disease modifying drugs

OBJECTIVE

The objective of this study was to explore the cost and utilization in the period following discontinuations or switches of disease modifying drugs (DMDs) for patients with multiple sclerosis (MS). Secondary objectives included an assessment of the time to switch or discontinuation from index DMD treatment.

METHODS

Cases were defined as a billed MS diagnosis in continuously enrolled patients initiated with interferon-beta1a IM, interferon-beta1b SC, glatiramer acetate, and interferon-beta1a SC found in the PharMetrics Patient-Centric Database. Information on patient demographics, diagnoses, procedures, pharmacy-dispensed drugs, and costs was extracted; reasons for discontinuation and expenses outside of the healthcare system were not available. Treatment discontinuations and switches between study drugs were defined using pharmacy prescription patterns and analyzed by descriptive and regression methods. The non-pharmacy medical costs in the 18 months following switching or discontinuation were compared to the costs in a randomly selected similar period for those patients who did not switch or discontinue these agents.

RESULTS

A total of 5,772 MS patients were continuously enrolled and were treated with one or more of the four drugs of interest, and about half of these patients switched drugs or discontinued treatment for at least 90 days. Patients initiated with interferon-beta1b SC were more likely to discontinue treatment compared to interferon-beta1a IM users. Non-pharmaceutical medical costs were highest for those switching treatments followed by those discontinuing DMDs in the 18 months following a switch or discontinuation, compared to persistent users of these drugs. Interferon beta1b SC initiators had higher costs following changes or discontinuations, while glatiramer acetate and interferon-beta1a SC users had lower subsequent costs compared to interferon-beta1a IM users.

LIMITATIONS

Unfortunately, the reasons for stopping the initial treatment cannot be determined from analysis of an administrative claims database. Also, the MS cases followed in this analysis are billing diagnostic events unconfirmed through a review of medical records or other data sources. The results are unstratified in terms of severity and thus while treatment patterns may vary for patients with different types of MS (e.g., progressive vs. relapsing-remitting), this cannot be examined in this analysis.

CONCLUSION

Changing or discontinuing DMDs is common among MS patients and is associated with higher non-pharmaceutical medical costs that vary based on the initiating drug and other demographics characteristics.

Characterization of neogenin-expressing neural progenitor populations and migrating neuroblasts in the embryonic mouse forebrain

Many studies have demonstrated a role for netrin-1-deleted in colorectal cancer (DCC) interactions in both axon guidance and neuronal migration. Neogenin, a member of the DCC receptor family, has recently been shown to be a chemorepulsive axon guidance receptor for the repulsive guidance molecule (RGM) family of guidance cues [Rajagopalan S, Deitinghoff L, Davis D, Conrad S, Skutella T, Chedotal A, Mueller B, Strittmatter S (2004) Neogenin mediates the action of repulsive guidance molecule. Nat Cell Biol 6:755-762]. Here we show that neogenin is present on neural progenitors, including neurogenic radial glia, in the embryonic mouse forebrain suggesting that neogenin expression is a hallmark of neural progenitor populations. Neogenin-positive progenitors were isolated from embryonic day 14.5 forebrain using flow cytometry and cultured as neurospheres. Neogenin-positive progenitors gave rise to neurospheres displaying a high proliferative and neurogenic potential. In contrast, neogenin-negative forebrain cells did not produce long-term neurosphere cultures and did not possess a significant neurogenic potential. These observations argue strongly for a role for neogenin in neural progenitor biology. In addition, we also observed neogenin on parvalbumin- and calbindin-positive interneuron neuroblasts that were migrating through the medial and lateral ganglionic eminences, suggesting a role for neogenin in tangential migration. Therefore, neogenin may be a multi-functional receptor regulating both progenitor activity and neuroblast migration in the embryonic forebrain.

Localization of the netrin guidance receptor, DCC, in the developing peripheral and enteric nervous systems

Over recent years the secreted guidance cue, netrin-1, and its receptor, DCC, have been shown to be an essential guidance system driving axon pathfinding within the developing vertebrate central nervous system (CNS). Mice lacking DCC exhibit severe defects in commissural axon extension towards the floor plate demonstrating that the DCC-netrin guidance system is largely responsible for directing axonal projections toward the ventral midline in the developing spinal cord (Fazeli et al., Nature 386 (1997) 796). In addition, these mutants lack several major commissures within the forebrain, including the corpus callosum and the hippocampal commissure. In contrast to the CNS, the role of the DCC guidance receptor in the development of the mammalian peripheral and enteric nervous systems (PNS and ENS) has not been investigated. Here we demonstrate using immunohistochemical analysis that the DCC receptor is present in the developing mouse PNS where it is found on spinal, segmental, and sciatic nerves, and in developing sensory ganglia and their associated axonal projections. In addition, DCC is present in the ENS throughout the early developmental phase.

Netrin-3 protein is localized to the axons of motor, sensory, and sympathetic neurons

The netrin family of axon guidance cues has been shown to play a pivotal role in the guidance of a variety of axon projections during embryonic development, both in the vertebrate and invertebrate. While the guidance potential of netrin-1 has been examined in depth in many regions of the developing mouse brain very little information is available on the expression and activity of netrin-3. Here we show that the netrin-3 protein is present on motor neurons and subpopulations of neurons within sensory and sympathetic ganglia. Moreover, significant levels of netrin-3 protein were found to be associated with the axons projecting from these neurons suggesting a role for netrin-3 in axon pathfinding and fasciculation within the peripheral nervous system.

DCC plays a role in navigation of forebrain axons across the ventral midbrain commissure in embryonic xenopus

In the developing vertebrate brain, growing axons establish a scaffold of axon tracts connected across the midline via commissures. We have previously identified a population of telencephalic neurons that express NOC-2, a novel glycoform of the neural cell adhesion molecule N-CAM that is involved in axon guidance in the forebrain. These axons arise from the presumptive telencephalic nucleus, course caudally along the principal longitudinal tract of the forebrain, cross the ventral midline in the midbrain, and then project to the contralateral side of the brain. In the present study we have investigated mechanisms controlling the growth of these axons across the ventral midline of the midbrain. The axon guidance receptor DCC is expressed by the NOC-2 population of axons both within the longitudinal tract and within the ventral midbrain commissure. Disruption of DCC-dependent interactions, both in vitro and in vivo, inhibited the NOC-2 axons from crossing the ventral midbrain. Instead, these axons grew along aberrant trajectories away from the midline, suggesting that DCC-dependent interactions are important for overcoming inhibitory mechanisms within the midbrain of the embryonic vertebrate brain. Thus, coordinated responsiveness of forebrain axons to both chemostimulatory and chemorepulsive cues appears to determine whether they cross the ventral midline in the midbrain.

Expression of the netrin-1 receptor, deleted in colorectal cancer (DCC), is largely confined to projecting neurons in the developing forebrain

Axon guidance mechanisms are crucial to the development of an integrated nervous system. One family of molecules that may be important in establishing axonal connectivity in mammals is the Netrins, and their putative receptors DCC (deleted in colorectal cancer), Neogenin, and Unc-5. Knockout and mutational analyses of some of these genes have shown that they are critically involved in the development of several specific pathways in the developing brain. However, previous expression analyses of these genes have largely been confined to the developing spinal cord. In the present study, we analyzed the expression of DCC in the developing mouse forebrain. We found that DCC protein is expressed in specific axonal populations projecting from the developing olfactory bulb, neocortex, hippocampus, and epithalamus/habenular complex. In the developing olfactory bulb and neocortex, DCC expression is particularly evident during the targeting phase of axon outgrowth and is then rapidly downregulated. As predicted from the knockout and mutational analyses of this gene, DCC is expressed in axonal commissures, in particular the corpus callosum, hippocampal commissure, and the anterior commissure. In addition, we found that DCC is expressed in the habenular commissure, the fasciculus retroflexus, and the stria medularis. Therefore, this analysis implicates a function for DCC in additional axonal guidance systems not predicted from the knockout and mutational analyses.

Experience with 500 prenatal diagnoses of sickle cell diseases: the effect of gestational age on affected pregnancy outcome

Prenatal diagnosis of sickle cell diseases is obtained rapidly and precisely by polymerase chain reaction (PCR) with Ddel restriction analysis and dot-blotting with allele-specific oligonucleotides (ASO). Prenatal diagnosis of HgbSS and HgbSC was performed in 500 pregnancies, 196 by Southern blot and 304 by PCR. PCR drastically shortened the interval from sampling to reporting, allowing acceptance even of samples with unknown paternal phenotype, and resulted in an overall four-fold increase in diagnoses. In 108 pregnancies, the diagnosis was an affected fetus; 25 were HgbSC: 3 (12 per cent) were terminated; 83 were HgbSS: four ended in miscarriage; 40/79 (51 per cent) were terminated. The gestational age at the time of report to the mother appeared to be a major outcome determinant when the fetal diagnosis was HgbSS. The change-point in the maternal decision was found at 20 weeks of gestation. Before the 20th week, most mothers (64 per cent) chose termination; thereafter, the majority (72 per cent) chose continuation. The odds ratio of termination in earlier relative to later reporting was 4.7. In order to offer a choice to the mothers at risk of delivering a fetus affected by sickle cell disease, the diagnosis should be reported before the 20th week of gestation.

Mechanism of red blood cell aging: relationship of cell density and cell age

The human red cell has a life span of 120 days. The mechanism that determines cell removal from the circulation with such precision remains unknown. Most studies of red cell aging have been based on analysis of cells of progressively increasing age separated by density. The relationship between red cell age and density has been recently challenged, and the hypothesis has been put forward that cell death is not the result of a progressive deterioration of essential cell constituents. This theory was based on preliminary observations in transient erythroblastopenia of childhood, which could not later be confirmed. When the relationship between cell aging and increasing density is critically reviewed, it appears to be based on firm experimental evidence, confirmed by in vivo demonstration of decreasing survival of cells of increasing age. Analysis of studies using buoyant density gradients reveals that this technique can easily distinguish the single exponential slope of decline for those cell components that change progressively throughout the red cell life span from the biphasic decline of those that decrease drastically at the reticulocyte-mature red cell transition. The view that the aging of the red cell and its removal from the circulation result from a progressive series of events during the 120 days of its life span appears to be the most consistent with the available data. Density separation, validated by much experimental evidence, remains a most useful technique for the study of the mechanism of aging of the red cell.

Randomized, placebo-controlled trial of iron supplementation in infants with low hemoglobin levels fed iron-fortified formula

In spite of the declining prevalence of iron-deficiency anemia, a large proportion of low-income infants have "low-normal" (11-11.5 g/dL) and "low" (less than 11 g/dL) hemoglobin (Hgb) values. Because most of these infants are fed iron-fortified formulas, it was of interest whether additional iron supplementation would enhance Hgb values. A cohort of 334 healthy, inner-city, minority, 6-month-old infants, fed iron-fortified formulas, with Hgb values ranging from 9 to 11.5 g/dL, participated in a double-blind, randomized, placebo-controlled trial of supplemental iron at 0, 3, and 6 mg/kg per day for 3 months. Hemoglobin values increased significantly with age, regardless of assignment to placebo or supplemental iron (means for the entire cohort: 6 months 10.9 g/dL, 8 months 11.2, 10 months 11.3, and 12 months 11.4). The proportion of "responders" (Hgb level increased greater than or equal to 1 g/dL) was 34% and did not differ significantly by placebo or iron dose. There were no significant differences in mean corpuscular volume or levels of erythrocyte porphyrins or serum ferritin between treatment groups. The implications of this clinical trial are twofold: (1) screening healthy infants fed iron-fortified formula at the age of 6 months is not justified, regardless of socioeconomic status; (2) the clinical practice of routinely treating low-income, "low-Hgb" infants with iron supplementation, without regard to dietary considerations, is unwarranted.

Regulation of glycolysis in the erythrocyte: role of the lactate/pyruvate and NAD/NADH ratios

Mature erythrocytes, when removed from the circulation, exhibit severe disturbances of glycolytic flow, with accumulation not only of lactate, the ultimate product of glycolysis, but also of several upstream metabolic intermediates, primarily fructose-1,6-diphosphate, glyceraldehyde-3-phosphate, and dihydroxyacetone phosphate. This accumulation may be prevented (and also reverted) by allowing the diffusible end products lactate and pyruvate to leave the cell by equilibrating with a much larger extracellular compartment. The disturbance of erythrocyte glycolysis does not result from direct inhibition by lactate itself but from the interplay between the lactate dehydrogenase and glyceraldehyde-3-phosphate dehydrogenase (3-PGAD) reactions. The accumulation of intermediates reflects the increased lactate-to-pyruvate ratio; this leads to a secondary imbalance of the nicotinamide adenine dinucleotide-to-reduced nicotinamide adenine dinucleotide (NAD-to-NADH) ratio, which in turn slows down glycolysis at the 3-PGAD step, whose upstream metabolites then pile up. No accumulation, however, takes place if the lactate-to-pyruvate ratio is maintained constant in the extracellular compartment, regardless of concentrations. These studies demonstrate that orderly glycolysis in the erythrocyte is regulated by the NAD-to-NADH ratio and also provide a method that makes possible the in vitro study of erythrocyte glycolysis.

The mechanism of decline of age-dependent enzymes in the red blood cell

Buoyant density centrifugation on discontinuous gradients separates red blood cells (RBCs) according to age, as shown by radiolabelling experiments both in vitro and in vivo. Changes observed in these gradients reflect in vivo rates of decline. A progressive metabolic decline may render the RBC incapable of surviving stresses in the circulation. It was hypothesized that changes only take place at the reticulocyte-mature RBC transition. RBC hexokinase (HK) has two isozymes, one predominant in reticulocytes, the other in mature RBCs. We compared its decline in the density gradient, with that of pyrimidine-5'-nucleotidase (P5N), glutamate-oxaloacetate transaminase (GOT) and pyruvate kinase (PK). The decline of HK and P5N was clearly biphasic; for GOT and PK instead there was a single slope. Thus changes taking place at the reticulocyte-RBC transition are clearly identified by a biphasic slope in the gradient. The view of a progressive metabolic decline in vivo for the RBC therefore remains valid.

An isozyme of hexokinase specific for the human red blood cell (HKR)

The hexokinase (HK) of the human red blood cell (RBC) was separated into two distinct major isozymes by fast protein liquid chromatography using a linear salt gradient on a MonoQ column. The first isozyme (HKI) eluted as a sharp peak at the same position as HKI of human liver. The second isozyme eluted between HKI and HKII of human white blood cells, and it appeared to be unique to the RBC (it was designated HKR). From a gel filtration column, HKR eluted before HKI, suggesting that it was larger than HKI by several kilodaltons. In a mitochondria-enriched fraction from human reticulocytes, no HKR was found; thus, HKR was not a mitochondrial enzyme. Despite these differences in chromatographic behavior, size, and mitochondrial binding, both forms behaved kinetically as HKI. RBC from normal blood contained HKI and HKR at an equal activity, but in reticulocyte-rich RBC, HKR dominated. When RBC of increasing age was separated by buoyant density ultracentrifugation, the total HK activity decayed in a biphasic manner, with half-lives respectively of approximately 15 and approximately 51 days. When isolated by MonoQ column from each age-separated fraction, HKR was the major form in the youngest RBC, and decreased rapidly with cell age, with a t 1/2 of approximately 10 days, representing a negligible activity in the oldest RBC. Instead, HKI was relatively stable through the entire life span of the RBC, with a t 1/2 of approximately 66 days. Thus, HKR appears to be an RBC-specific isozyme that is predominant in the reticulocyte and is then rapidly degraded. During maturation of the RBC, the fast decay of HKR contributes to the early sharp decline of HK activity and the slow decay of HKI to the later gradual decline.

Cardiorespiratory response to exercise in patients with thalassemia major

The cardiorespiratory response to exercise was examined in 13 patients, 12 to 22 yr of age, who were in stable condition while receiving regular transfusions for thalassemia major. Before transfusion (Hgb, 10.8 g/dl), the patients had reduced peak oxygen consumption for body weight (by 25%, p less than 0.002) in comparison with 20 age- and sex-matched control subjects (Hgb, 13.8 g/dl). The ventilatory equivalent for carbon dioxide was significantly reduced at all work rates, and end-tidal PCO2 was abnormally high (46.3 versus 40.7 mm Hg, p less than 0.001), but ventilatory reserve, as estimated from pulmonary function tests, was normal. Both heart rate and cardiac output (as estimated by the indirect Fick method) were abnormally high during exercise; at an oxygen consumption of 19 ml/min/kg, heart rate was 13% higher (p less than 0.01) and, at 16 ml/min/kg, cardiac output was 28% higher (p less than 0.001) in the patients than in the control subjects. Nine patients were retested 3 to 8 days after transfusion (Hgb, 13.0 g/dl, p50, 26.4 mm Hg). Neither ventilatory nor circulatory abnormalities improved significantly. In patients 12 to 22 yr of age in stable condition with thalassemia major, we conclude: cardiac output, estimated by the CO2 rebreathing method, is high and arteriovenous O2 extraction is low during exercise; the high cardiac output during exercise is associated with hypoventilation; the high cardiac output is independent of short-term changes in hemoglobin concentration associated with transfusion.

Inappropriately low red cell 2,3-diphosphoglycerate and p50 in transfused beta-thalassemia

The relationships among hemoglobin concentration (Hb), red cell 2,3-diphosphoglycerate (2,3-DPG), and p50 were studied in 20 chronically hypertransfused patients with thalassemia major. In the nontransfused control group, which included normal individuals as well as patients with sickle cell disease or iron deficiency anemia, the Hb correlated inversely with both 2,3-DPG concentration and p50, as is well established. In contrast, however, prior to transfusion, at the nadir of Hb, patients with thalassemia major had inappropriately low 2,3-DPG concentrations and p50s. These findings occurred in all patients, regardless of whether they had received packed, leukocyte-poor, or frozen-thawed red cells. The hypothesis that the time of blood storage was a factor was excluded by repeatedly transfusing one patient with packed red cells administered within 4 hr of collection in CPDA-1. A second hypothesis, that red cell function might be impaired by the iron-overloaded thalassemic environment, was excluded by studying a newly diagnosed, newly transfused patient with aplastic anemia. In both cases, the same inability to appropriately increase 2,3-DPG and p50 as the Hb fell during the intertransfusion interval was noticed. These data suggest that red cells of chronically transfused patients are unable to adapt to the decline in Hb that occurs during the intertransfusion interval.

Heterogeneity of the molecular lesions in inherited phosphofructokinase deficiency

Human phosphofructokinase (PFK; EC 2.7.1.11) exists in tetrameric isozymic forms. Muscle and liver contain the homotetramers M4 and L4, whereas erythrocytes contain five isozymes composed of M (muscle) and L (liver) subunits, i.e., M4, M3L, M2L2, ML3, and L4. Inherited defects of erythrocyte PFK are usually partial and are described in association with heterogeneous clinical syndromes. To define the molecular basis and pathogenesis of this enzymopathy, we investigated four unrelated individuals manifesting myopathy and hemolysis (glycogenosis type VII), isolated hemolysis, or no symptoms at all. The three symptomatic patients showed high-normal hemoglobin levels, despite hemolysis and early-onset hyperuricemia. They showed total lack of muscle-type PFK and suffered from exertional myopathy of varying severity. In the erythrocytes, a metabolic crossover was evident at the PFK step: the levels of hexose monophosphates were elevated and those of 2,3-diphosphoglycerate (2,3-DPG) were depressed, causing strikingly increased hemoglobin-oxygen affinity. In all cases, the residual erythrocyte PFK consisted exclusively of L4 isozyme, indicating homozygosity for the deficiency of the catalytically active M subunit. However, presence of immunoreactive M subunit was shown in cultured fibroblasts by indirect immunofluorescence with monoclonal anti-M antibody. The fourth individual was completely asymptomatic, had normal erythrocyte metabolism, and had no evidence of hemolysis. His residual erythrocyte PFK showed a striking decrease of the L4, ML3, and M2L2 isozymes, secondary to a mutant unstable L subunit. Identical alterations of erythrocyte PFK were found in his asymptomatic son, indicating heterozygosity for the mutant unstable L subunit in this kindred. These studies show that, except for the varying severity of the myopathic symptoms, glycogenosis type VII has highly uniform clinical and biochemical features and results from homozygosity for mutant inactive M subunit(s). The absence of anemia despite hemolysis may be explained by the low 2,3-DPG levels. The hyperuricemia may result from hyperactivity of the hexose monophosphate shunt. In contrast, the clinically silent carrier state results from heterozygosity for mutant M or L subunit. Of the two, the M subunit appears to be more critical for adequate glycolytic flux in the erythrocyte, since its absence is correlated with hemolysis.

Threshold for lead damage to heme synthesis in urban children

Although lead has no physiological function and is present in only negligible amounts in the blood of remote populations, it has become customary to accept the usual blood Pb level(s) (BPb) observed in industrialized society as "normal." Pb interferes with many biochemical systems, among them the heme biosynthetic pathway; this is reflected by an exponential increase in erythrocyte protoporphyrin concentration (EP) as PBb increases. The present study estimated the threshold PBb at which an increase of EP occurs in a population of urban children. In the 2,004 children studied, BPbs ranged from 2 to 98 micrograms/dl, with 1,852 having a BPb of less than or equal to 30 micrograms/dl, a value presently considered normal. Preliminary analysis suggested that an exponential increase in the concentration of EP occurred after a threshold BPb (apparently between 12 and 20 micrograms/dl) was reached. Precise definition of the threshold BPb for an increase of EP was next determined by two approaches: segmented line techniques and probit analysis. Whether the entire population was analyzed or only the subset of samples with "normal" BPb (less than or equal to 30 micrograms/dl), both methods yielded a threshold BPb of 15-18 micrograms/dl (average value, 16.5). These studies indicate that the heme synthetic pathway is affected by Pb at a level of exposure commonly observed in urban children, which is well below the limit that is presently too easily accepted as normal.

A simple technique for preparation of young red cells for transfusion from ordinary blood units

We have developed a rapid and simple method for the isolation of relatively young cells from ordinary fresh or previously frozen blood units, using the IBM-2991 Blood Cell Processor. Based on in vitro measurements of red cell pyruvate kinase activity, the resolution of the method is excellent, comparable to that of the stractan discontinuous gradient system. In splenectomized patients with thalassemia major, the administration of the "youngest" 50% of blood units yielded 51Cr survival times of 40 and 42 days for fresh packed red cells and 41 and 43 days for previously frozen red cells.

Elevated blood lead in a population near a lead smelter in Kosovo, Yugoslavia

A survey of residents of a community surrounding a lead smelter has revealed an alarming incidence of elevated blood lead and erythrocyte protoporphyrin concentrations. In particular, children who were less than 3 yr of age were severely affected. Of those children tested in December, 1980, 35% had blood lead concentrations between 50-69 microgram/dl, while an additional 12% had concentrations greater than or equal to 70 microgram/dl, and are, therefore, at risk for severe neurological sequelae.

Chelation therapy in beta-thalassemia major. III. The role of splenectomy in achieving iron balance

Transfusion requirements for 1978 were compiled for 79 patients with thalassemia major (ages 1 to 29 years) who were maintained at hemoglobin concentrations of greater than 10 gm/dl. In 46 patients with intact spleens, the mean transfusion requirement was 258 ml/kg/year, and there was a clear increase with age. The transfusion history prior to 1978 had no influence on the increase of transfusion requirement with age. In contrast, in 33 splenectomized patients, the mean transfusion requirement was 203 ml/kg/year and it did not increase with age. Urinary iron excretion in response to deferoxamine increased with age, with no obvious difference between splenectomized and nonsplenectomized patients. The ability to achieve iron balance with a daily dose of 20 mg/kg of deferoxamine was a function of the transfusion requirement splenectomized patients with lower blood requirements generally achieved negative iron balance, whereas nonsplenectomized patients did not. We conclude that the spleen should be removed when the transfusion requirement exceeds 250 ml/kg/year, which usually occurs between 6 and 8 years of age. In young patients with intact spleens, a higher dose of deferoxamine may be use in order to prevent hemosiderosis.

Blood lead concentrations in a remote Himalayan population

The lead content in the air at the foothills of the Himalayas in Nepal was found to be negligible. The concentration of lead in the blood of 103 children and adults living in this region was found to average 3.4 micrograms per deciliter, a level substantially lower than that found in industrialized populations.

The molecular mechanism of the inherited phosphofructokinase deficiency associated with hemolysis and myopathy

Normal human erythrocyte phosphofructokinase (ATP: D-fructose-6, P-1-phosphotransferase, EC 2.7.1.11; PFK) has recently been shown to consist of a heterogeneous mixture of five tetrameric isozymes: M4, M3L, M2L2, ML3, and L4 (M, muscle type; L, liver type). In the light of these findings, we have investigated the molecular basis of the inherited erythrocyte PFK deficiency associated with myopathy and hemolysis (Tarui disease). The propositus, a 31-yr-old male, suffered from muscle weakness and myoglobinuria on exertion. He showed mild erythrocytosis despite laboratory evidence of hemolysis. In his erythrocytes a metabolic crossover point was found at the level of PFK; 2,3-diphosphoglycerate (2,3-DPG) was also significantly reduced. The PFK from the patient's erythrocytes consisted exclusively of the L4 isozyme, and there was a complete absence of the other four. The leukocyte and platelet PFKs from the patient showed normal activities, chromatographic profiles, and precipitation with anti-M4 antibody. These studies provide direct evidence that in Tarui disease the M-type subunits are absent; but the liver- and platelet-type subunits of PFK are unaffected. The paradox of mild erythrocytosis despite hemolysis reflects the decreased production of 2,3-DPG.

Isozymes of human phosphofructokinase: identification and subunit structural characterization of a new system

The existence of a five-membered isozyme system for human phosphofructokinase (PFK; ATP:D-fructose-6-phosphate 1-phosphotransferase, EC 2.7.1.11) has been demonstrated. These multimolecular forms result from the random polymerization of two distinct subunits, M (muscle type) and L (liver type), to form all possible tetrameters-i.e., M(4), M(3)L, M(2)L(2), ML(3), and L(4). Partially purified muscle and liver PFKs were hybridized by dissociation at low pH and then recombination at neutrality. Three hybrid species were generated in addition to the two parental isozymes, to yield an entire five-membered set. The various species could be consistently and reproducibly separated from one another by DEAE-Sephadex chromatography at pH 8.0 with a concave elution gradient of salt. Under similar experimental conditions, erythrocyte PFK from hemolysates was also resolved into five species chromatographically indistinguishable from those produced in the above experiment. Immunological and kinetic studies of the isozymes provided corroborative evidence to support the proposed subunit structures. Erythrocyte PFK was found to have kinetic properties intermediate between those of muscle and liver PFK and was neutralized only 50% by an antiserum against muscle PFK that completely neutralized muscle PFK. These data demonstrate that muscle and liver PFKs are distinct homotetramers-i.e., M(4) and L(4), respectively-whereas erythrocyte PFK is a heterogeneous mixture of all five isozymes. The structural heterogeneity of erythrocyte PFK provides a molecular genetic basis for the differential organ involvement observed in some inherited PFK deficiency states in which myopathy or hemolysis or both can occur.

Erythrocyte adenosine deaminase deficiency without immunodeficiency. Evidence for an unstable mutant enzyme

Inherited deficiency of the purine salvage enzyme adenosine deaminase (ADA) gives rise to a syndrome of severe combined immunodeficiency (SCID). We have studied a 2.5-yr-old immunologically normal child who had been found to lack ADA in his erythrocytes during New York State screening of normal newborns. His erythrocytes were not detectably less deficient in ADA than erythrocytes of ADA(-)-SCID patients. In contrast, his lymphocytes and cultured long-term lymphoid cells contained appreciably greater ADA activity than those from patients with ADA(-)-SCID. This residual ADA activity had a normal molecular weight and K(m) but was markedly unstable at 56 degrees C. His residual erythrocytes-ADA activity also appeared to have diminished stability in vivo. ADA activity in lymphoid line cells of a previously reported erythrocyte-ADA-deficient!Kung tribesman was found to contain 50% of normal activity and to exhibit diminished stability at 56 degrees C. ATP content of erythrocytes from both partially ADA-deficient individuals was detectably greater than normal (12.3 and 6.1 vs. normal of 2.6 nmol/ml packed erythrocytes). However, the dATP content was insignificant compared to that found in erythrocytes of ADA(-)-SCID patients (400-1,000 nmol/ml packed erythrocytes). The New York patient, in contrast to normals, excreted detectable amounts of deoxyadenosine, but this was <2% of deoxyadenosine excreted by ADA(-)-SCID patients. Thus, the residual enzyme in cells other than erythrocytes appears to be sufficient to almost totally prevent accumulation of toxic metabolites.

Separation of younger red cells with improved survival in vivo: an approach to chronic transfusion therapy

Transfusion of donor blood containing predominantly younger red cells with prolonged survival in vivo could significantly reduce the iron overload of patients requiring chronic transfusion. Age-dependent separation of red cells can be obtained by buoyant density centrifugation on isotonic solutions of arabino-galactane. By this technique, rabbit red cells were separated on a single layer of arabino-galactane and the appropriate fraction, after being labeled with (51)Cr, was reinfused into the donor. The survival in vivo was calculated by a mathematical model which corrects for both (51)Cr elution and random loss. There was a significant difference in survival in vivo between the light young red cells and the heavy old red cells. The potential survival in vivo of the 50% lightest red cells was 56 days, compared to 28 days for the heaviest red cells. Arabino-galactane appeared to be devoid of acute toxicity and of strong antigenicity and it did not appear to adhere to the red cell stroma. These data extrapolated to humans indicate that it may be feasible and advantageous to use red cells fractionated by this technique for transfusion. The 50% lightest human red cells can be expected to have a mean survival of 88 days, compared with 60 days for unfractionated blood. Transfusion of young red cells could significantly reduce the iron overload for patients requiring chronic transfusion, by avoiding infusion of the oldest red cells, which contribute equally to iron overload yet offer only transient survival in vivo.

Erythropoietic protoporphyria and lead intoxication: the molecular basis for difference in cutaneous photosensitivity. I. Different rates of disappearance of protoporphyrin from the erythrocytes, both in vivo and in vitro

In lead intoxication photosensitivity is usually absent, despite concentrations of protoporphyrin in the erythrocytes equal to or greater than in erythropoietic protoporphyria. Profound differences in the distribution of protoporphyrin in aging erythrocytes were demonstrated by age-dependent fractionation of cells on discontinuous density gradients. In erythropoietic protoporphyria the concentration of protoporphyrin declined extremely rapidly with erythrocyte age; the bulk of the protoporphyrin was lost in less than 3 days and the concentration of fluorescent erythrocytes in the gradient paralleled the decline of protoporphyrin. In lead intoxication the protoporphyrin concentration declined only slightly with cell aging and erythrocytes of all ages fluoresced. In the bone marrow from a patient with erythropoietic protoporphyria all reticulocytes, but only occasional late normoblasts, fluoresced, suggesting a single population. Sterile incubation in plasma (pH 7.5) demonstrated rapid diffusion of protoporphyrin from the erythrocytes in erythropoietic protoporphyria, but not in lead intoxication. Plasma protoporphyrin was elevated in erythropoietic protoporphyria, but not in lead intoxication. Estimates of the daily loss of protoporphyrin from erythropoietic tissue in erythropoietic proporphyria suggested an order of magnitude similar to the total blood protoporphyrin. Therefore, it is not necessary to postulate a preponderant extraerythropoietic source to explain the amount of fecal excretion. A significant amount of the diffused protoporphyrin probably reaches the skin with resulting photosensitivity. In contrast, in lead intoxication protoporphyrin remains within the erythrocyte throughout its life span ; there is no diffusion into the plasma and hence no photosensitivity.