Using mutual information to measure coupling in the cardiorespiratory system

Approximately 2,000 infants with sickle cell disease are born each year in the United States. Sickle cell disease is an inherited disorder of red blood cell hemoglobin. Sickle cells increase adhesion and cause blockage in the small blood vessels, resulting in tissue damage. The cells' production of hemoglobin S results in two major pathophysiologic features of sickle cell disorders: chronic hemolytic anemia and vaso-occlusion. These disorders cause ischemic tissue damage and acute and chronic organ failure. Potential complications for children with sickle cell disease include vaso-occlusive events, splenic sequestration, bacterial septicemia from splenic hypofunction, aplastic crisis, pulmonary compromise including acute chest syndrome, renal tubular dysfunction and renal failure, priapism, aseptic necrosis, gallstones, delayed growth and development, leg ulcers, stroke and premature death. Three major sickle cell complications during the first years of life are dactylitis, splenic hypofunction and splenic sequestration. The risk for pneumococcal meningitis is 36 times greater in children with sickle cell anemia than for black children without the disease, and 314 times greater than for white children.     

Circulating activated endothelial cells in sickle cell anemia

BACKGROUND: The vascular wall participates in the pathogenesis of sickle cell disease. To determine whether the endothelium is activated in this disease, we studied the number, origin, and surface phenotype of circulating endothelial cells in patients with sickle cell anemia. METHODS: We used immunohistochemical examination of buffy-coat smears to enumerate circulating endothelial cells, and we evaluated the surface phenotype by applying preparations of circulating endothelial cells. An immunofluorescence microscopy panel of antibodies was used, including a specific anti-endothelial-cell antibody, P1H12. RESULTS: Mean (+/-SD) numbers of circulating endothelial cells in normal blood donors, patients with sickle cell trait, and patients with hemolytic anemias not due to hemoglobin S were 2.6+/-1.6, 3.0+/-2.6, and 2.0+/-0.8 per milliliter of whole blood, respectively. Patients with sickle cell anemia who presented with acute painful episodes had 22.8+/-18.2 circulating endothelial cells per milliliter of blood (P<0.001 for the comparison with normal donors), and patients with no such events within one month before or after blood sampling had 13.2+/-11.8 circulating endothelial cells per milliliter of blood (P=0.002 for the comparison with normal donors and P=0.019 for the comparison with patients with acute events). Serial observations of three patients showed a tendency toward higher levels of circulating endothelial cells at the onset of acute painful crises. The average viability of circulating endothelial cells was 66+/-30 percent. In patients with sickle cell anemia, regardless of clinical status, the circulating endothelial cells were predominantly microvascular in origin (CD36-positive), and most of the cells expressed four markers of endothelial-cell activation: intercellular adhesion molecule 1, vascular-cell adhesion molecule 1, E-selectin, and P-selectin. CONCLUSIONS: Our studies suggest that the vascular endothelium is activated in patients with sickle cell anemia, regardless of the patients' clinical status. Adhesion proteins on activated endothelial cells may have a role in the vascular pathology of sickle cell disease.     

Knockout-transgenic mouse model of sickle cell disease

When transgenic mice that expressed human sickle hemoglobin were mated with mice having knockout mutations of the mouse alpha- and beta-globin genes, animals were produced that synthesized only human hemoglobin in adult red blood cells. Similar to many human patients with sickle cell disease, the mice developed a severe hemolytic anemia and extensive organ pathology. Numerous sickled erythrocytes were observed in peripheral blood. Although chronically anemic, most animals survived for 2 to 9 months and were fertile. Drug and genetic therapies can now be tested in this mouse model of sickle cell disease.     

Anemia and red cell distribution width at the 12-month well-baby examination

BACKGROUND: Screens for anemia are among the most commonly done laboratory tests in children. The red cell distribution width (RDW) has been proposed as a diagnostic aid in the evaluation of pediatric anemias, but no prospective studies have been published describing its use. METHODS: A screening hematocrit determination done at the 12-month well-baby examination in 970 healthy infants yielded 62 low values (< 33%), 31 of which were confirmed by heel stick complete blood count (CBC). After a 1-month trial of iron therapy, those with a rise in hemoglobin of at least 1 g/dL were considered to have iron-deficiency anemia. Nonresponders, after review of clinical and laboratory data (CBC, lead screen, and sickle screen), had hemoglobin electrophoresis if indicated. RESULTS: Abnormalities detected were iron deficiency, alpha-thalassemia, and hemoglobins SC and AS. These conditions were detected in 9 of 11 infants with abnormal RDW and none of 9 with normal RDW. CONCLUSIONS: The RDW alone appears to be predictive of identifiable causes of anemia when used in screening 12-month-old babies who are otherwise healthy.     

Renal length in sickle cell disease: observations from a cohort study

Renal length has been measured by ultrasound in 237 subjects with homozygous sickle cell (SS) disease, 147 with sickle cell-hemoglobin C (SC) disease, and in 78 age-matched controls with a normal hemoglobin (AA) genotype. As expected, renal length increased with age in all genotypes but mean length was significantly greater in SS disease compared with SC disease (mean difference 4.3 mm after adjustment for height) and significantly greater in both genotypes than in AA controls (SS/AA difference 9.2 mm, SC/AA difference 5.0 mm after adjustment for height). Examination of relationships between renal length and some hematological indices (hemoglobin, fetal hemoglobin, reticulocyte counts, alpha thalassemia status) in SS or SC disease showed only a significant negative correlation with hemoglobin and positive correlation with reticulocyte count in SS disease. Further analysis suggested that the stronger relationship was between renal length and high reticulocyte count. The mechanism of renal enlargement is unknown although glomerular hypertrophy and increased renal blood volume are likely contributors.     

Gonadal function abnormalities in sickle cell anemia. Studies in adult male patients

Thirty-two adult patients with sickle cell anemia were evaluated endocrinologically. Secondary sex characteristics were abnormal in 29, and eunuchoidal skeletal proportions were present in all except one. The age at which different stages of pubic hair growth were attained in these patients was delayed in comparison to normals (P less than 0.005). Hormonal assays were carried out in 14 patients. Basal serum testosterone, dihydrotestosterone, and androstenedione values were lower (P less than 0.02) in patients than controls. Serum LH and FSH levels before and after stimulation with gonadotropin-releasing hormone were consistent with primary testicular failure. Erythrocyte and hair zinc concentrations were significantly decreased, and there was positive correlation between erythrocyte zinc and serum testosterone (r = 0.61, P less than 0.01) in sickle cell anemia. Our study shows that androgen deficiency in this disease is a result of primary rather than secondary hypogondadism. Further studies are required to establish the role of zinc in the pathogenesis of testicular failure in sickle cell anemia.     

Significance of elevated hemoglobulin A1c for the pathogenesis of diabetic retinopathy

The hemoglobin of 70 diabetics with retinopathy was analysed. 56 patients had pathologically elevated values, 12 values were within the upper normal limit and in 2 cases the findings were normal. This hemoglobin variant is characterized by an increased affinity of oxygen. Clinically and pathologically speaking the elevated HbA1c value could be a causal factor in diabetic retinopathy. Comparisons with sickle cell anemia and thalassemia seem to indicate that hemoglobinopathy and retinopathy are pathogenetically related.     

Reversible splenic hypofunction in hypertransfused children with homozygous sickle cell disease

Functional hyposplenism, as documented by technetium 99 metastable sulfur colloid spleen scan and increased pocked erythrocyte count (also known as a pit count), is well described in children under 2 years of age with homozygous sickle cell anemia. We evaluated the clinical course and splenic function of 16 patients with sickle cell anemia (ages 3 to 20 years) on a hypertransfusion program for more than 6 months following a cerebrovascular accident. Patients were followed with simultaneous spleen scan and pitted erythrocyte count using direct interference contrast microscopy. Pit counts were taken prior to each transfusion and hemoglobin S level maintained at less than 20%. With the exception of two patients, splenic function was recovered only in those patients who were younger than 10 years of age at the time transfusion was initiated. There were no serious bacterial infections or other complications of sickle cell anemia documented in the hypertransfused group. Based on our results and the literature review, we conclude that some patients with sickle cell anemia receiving intensive hypertransfusion therapy for a cerebrovascular accident recover a normal splenic phagocytic function. Age and level at which the hemoglobin S is maintained are important factors in reestablishing splenic phagocytic function.     

Plasma and red cell lipids in sickle cell disease

Lipids, in particular phospholipids, are essential components of membrane systems, and the measurement of phospholipids and cholesterol in plasma and tissues is helpful in diagnosis. Phospholipids represent about 60 to 70% of total red cell (RBC) lipids, while about 25% is free cholesterol. Lipids in RBC are present in a dynamic state of equilibrium, and the RBC have the capacity for rapid exchange of lipids with plasma in several ways. The present study examined the cholesterol and phospholipid levels of plasma and erythrocytes in male patients with sickle cell anemia and in healthy male individuals of comparable age. This was performed with a view to detecting possible differences that might be related to some of the RBC abnormalities which accompany the disease. The results show that plasma lipids are significantly reduced in patients with sickle cell anemia and that RBC cholesterol was higher in sickle cell patients than in normal subjects.     

MR assessment of red marrow distribution and composition in the proximal femur: correlation with clinical and laboratory parameters

OBJECTIVE: To correlate the MR appearance of the proximal femur marrow with clinical and blood parameters. DESIGN AND PATIENTS: The proportion of the femoral neck surface area occupied by red marrow was determined on T1-weighted magnetic resonance (MR) images of the hip in a series of 120 subjects, aged from 15 to 75 years, with ten females and ten males per decade, and correlated with clinical data. This parameter and the bulk T1 values of femoral red marrow were determined in 30 other subjects 25-46 years of age and correlated with their blood parameters. RESULTS: In the series of 120 subjects, the proportion of red marrow surface area decreased with age (P < 10(-4)) and was higher in female than male subjects (P < 10(-4)). Within each decade, the proportion of red marrow surface area was higher in females than in males between 25 and 65 years but neither before 25 nor after 65 years. In the series of 30 subjects, the proportion of red marrow surface area and bulk T1 values of femoral red marrow were significantly negatively correlated with hemoglobin blood levels but not with blood cell counts. CONCLUSION: The MR appearance of proximal femur red marrow is influenced by age and sex. A relationship with hemoglobin blood level is demonstrated.     

Heme synthesis in hereditary hemolytic anemias: decreased delta-aminolevulinic acid synthetase in hemoglobin K?ln disease

The activities of delta-aminolevulinic acid (ALA) synthetase and ALA dehydratase in cord blood erythrocytes of newborn infants and peripheral blood red cells of patients with beta-thalassemia major, beta-thalassemia intermedia, hemoglobin K?ln (Hb K?ln) disease, sickle cell anemia, and pyruvate kinase deficiency were studied. The activity of ALA dehydratase did not vary appreciably with the number of immature RBC (reticulocytes and nucleated red blood cells) or the severity of the hemolytic anemia except in pyruvate kinase deficiency. The activity of ALA synthetase was linearly correlated with the number of immature RBC (r=0.974, p is less than 0.001). The ALA synthetase activity was significantly decreased in the RBC of Hb K?ln (p is less than 0.01) when compared with the activity in immature RBC of newborns and of patients with pyruvate kinase deficiency, sickle cell anemia, and thalassemia intermedia.     

Erythrocytapheresis therapy to reduce iron overload in chronically transfused patients with sickle cell disease

Chelation therapy with deferoxamine is effective in preventing the risk of transfusional iron overload, but treatment failure is common because of noncompliance. To reduce the transfusional iron load, we have evaluated longterm erythrocytapheresis in 14 subjects with sickle cell disease and stroke (11) or other complications (3) as an alternative to simple transfusion. Subjects were treated with erythrocytapheresis using the Haemonetics V50 (Haemonetics Corp, Braintree, MA) to maintain the target pretransfusion hemoglobin S (Hb S) level less than 50% for 6 to 71 months. The transfusional iron load and the donor blood usage were analyzed for a 6- to 36-month study period and were compared with similar data from a subset of 7 subjects previously treated with conventional (target Hb S < 30%) and modified (target Hb S < 50%) simple transfusion protocols. The effect of erythrocytapheresis on iron accumulation was determined by assessment of serum ferritin levels in the absence of iron chelation. The mean transfusional iron load and donor blood usage with erythrocytapheresis were 19 +/- 14 mg iron/kg/yr (range, 6 to 50) and 188.4 +/- 55.2 mL packed-red blood cells (RBC)/kg/yr (range, 107 to 281), respectively. Of 6 subjects receiving no iron chelation therapy, 5 maintained normal or nearly normal serum ferritin levels during 11 to 36 months of erythrocytapheresis. In comparison with conventional simple transfusion and modified simple transfusion, erythrocytapheresis reduced iron loading by 87% (P < .01) and 82% (P < .01), respectively, but increased donor blood usage by 23% and 73%, respectively. Subjects with pre-erythrocytapheresis Hb levels > or = 8.0 g/dL had lower iron accumulation (P < .001) and less donor blood usage (P < .005) than subjects with Hb levels < or = 8.0 g/dL. Although donor blood usage is increased in comparison with simple transfusion, long-term erythrocytapheresis markedly reduces or prevents iron accumulation. This form of transfusion therapy allows the cessation of iron chelation in well-chelated subjects and, if used as the initial form of transfusion therapy, may prevent long-term complications of sickle cell disease without risk of iron overload and the need for chelation therapy.     

Transthoracic forequarter amputation and left pneumonectomy

As survival improves in patients with sickle cell anemia, the prospects of performing cardiac surgical procedures on older patients with this genetic defect increase. We describe the successful management of a 52-year-old patient with sickle cell disease (homozygous for hemoglobin S) and a history of multiple sickle crisis undergoing cardiopulmonary bypass for mitral valve repair. Preoperative partial exchange transfusion followed by total exchange transfusion at the time of operation was performed to reduce the level of hemoglobin S to 5.4% during bypass. Other management strategies included high-flow normothermic bypass with aortic crossclamping, topical hypothermia, and cold crystalloid cardioplegia.     

Intima-media thickness and diameter of carotid and femoral arteries in children, adolescents and adults from the Stanislas cohort: effect of age, sex, anthropometry and blood pressure

OBJECTIVES: To study carotid and femoral intima-media thicknesses and diameters in relation to age, sex, morphologic status and blood pressure. PARTICIPANTS: The subjects were 369 men and women (aged 10-54 years) from the Stanislas cohort, with no known cardiovascular disease. METHODS: Intima-media thicknesses and diameters were measured by B-mode ultrasonography. The effects of sex, age, smoking, anthropometric variables, cholesterol and blood pressure were studied using bivariate and regression analysis. RESULTS: Carotid and femoral intima-media thicknesses were not affected by age nor by sex up to 18 years of age. Thereafter, they increased sharply in men and remained higher than in women. Values were correlated with systolic blood pressure only in men, and with fat-free mass in children and young adults only at the femoral site. Smoking, body mass index and fat mass were associated with intima-media thicknesses only in adults. Carotid diameter was little affected by age during childhood and in adults. Femoral diameter increased up to the age of 18 in both sexes and remained unaffected by age thereafter. This increase was more pronounced in boys, and so values became consistently greater in males aged over 14 years. Carotid diameter was correlated with body mass index or fat mass whereas femoral diameter was correlated with weight or fat-free-mass in children and men. The opposite was observed in women. CONCLUSION: Sex differences occur before adolescence for arterial diameter, but only at an adult age for intima-media thickness. In young subjects, carotid geometry seems to be influenced by blood pressure and excess body weight, while femoral artery geometry seems to be related to blood pressure and body growth.     

Secular trends in blood pressure levels in Denmark 1964-1991

BACKGROUND: Hypertension is an essential risk factor for development of cardiovascular diseases. Prospective studies show a reduction in risk of myocardial infarction with reduction of blood pressure. In Denmark there was a decrease in ischaemic heart disease mortality during the period (1968-1992) with around 34% in 30-65 year old men and 30% in women. OBJECTIVE: To assess the changes in casual blood pressure between 1964 and 1991 in seven cross-sectional population studies. SETTING: Centre of Preventive Medicine, University of Copenhagen, DK-2600 Glostrup. POPULATION: 10359 subjects, equal numbers of men and women, age exactly 30, 40, 50 and 60 years drawn as random samples from a background population of 300000 inhabitants and surveyed in 1964-1974 and five cross-sectional studies 1976, 1978, 1982-1984, 1986-1987 and 1991. METHODS: Blood pressure was measured according to WHO criteria by one technician in each survey. Alcohol consumption and physical activity were measured by a self-administered questionnaire. The weight and height were measured by standardized methods. Data on mortality from ischaemic heart disease were obtained from death certificates recorded by the National Board of Health. RESULTS: Blood pressure increased with increasing age in both genders and was significantly higher in men than in women. Median blood pressure in 50 year old men in 1964 was 135/85 mmHg and in 1991 it was 123/79, whereas in women in 1964 it was 140/85, against 119/74 in 1991. The prevalence of hypertensives among 30 and 40 year olds declined throughout the period. The performance of blood pressure measurements, technical variation, examination programme, seasonal variation and inter-observer variation were potential bias sources and influenced blood pressure levels, but cannot be shown to be responsible for the declining trend in blood pressure and hypertension. Women became a little more physical active in leisure time and men less active. Women consumed less alcohol than men, but the amounts slightly increased by the end of the period. Body mass index >25 was seen less frequently in women than in men and this increased in men over the period. Sale of antihypertensive drugs increased in Denmark over the 1964-1991 period. There seems to be good agreement between the changes in blood pressure in the population and the decline in mortality from stroke and coronary heart disease in Denmark, which is influenced by other risk factors as well. CONCLUSION: Blood pressure distributions have shifted towards lower values in 1964-1991. Prevalence of hypertension declined up to 1983. Risk factor changes as well as treatment for hypertension contribute to this.     

Time-dependent changes in the density and hemoglobin F content of biotin-labeled sickle cells

Sickle red blood cells (RBC) are subject to a number of important cellular changes and selection pressures. In this study, we validated a biotin RBC label by comparison to the standard 51Cr label, and used it to study changes that occur in sickle cells as they age. Sickle RBC had a much shorter lifespan than normal RBC, but the two labels gave equivalent results for each cell type. A variable number of sickle, but not normal, RBC disappeared from the circulation during the first few hours after reinfusion. The number of biotinylated sickle reticulocytes was decreased by 50% after 24 h and 75% after 48 h, with a gradual decrease in the amount of reticulum per cell. The labeled sickle cells exhibited major density increases during the first 4-6 d after reinfusion, with smaller changes thereafter. A small population of very light, labeled sickle RBC was essentially constant in number after the first few days. Fetal hemoglobin (HbF) content was determined in isolated biotinylated sickle RBC after reinfusion, allowing an estimate of lifespan for RBC containing HbF (F cells) and non-F cells. The lifespan of sickle biotinylated RBC lacking HbF was estimated to be approximately 2 wk, whereas F cells survived 6-8 wk.     

Epidemiology of hypertension in the elderly

DISTRIBUTION: Blood pressure tends to rise with increasing age. Six to eight per cent of people aged 60-69 years, and about 12-16% of those aged 70-79 years, are estimated to need treatment for raised systolic and diastolic blood pressures. DETERMINANTS: It seems likely that the rise in blood pressure with increasing age is partly explained by the determinants of blood pressure, such as sodium intake, body weight, physical exercise and alcohol consumption. MORTALITY: There is a linear relationship between the level of diastolic or systolic blood pressure and the risk of stroke or coronary heart disease. However, the relationship between blood pressure and mortality in later life may be obscured if concurrent illness lowers blood pressure; low blood pressure by itself may not be a risk factor for mortality. TREATMENT: Randomly allocated trials have consistently shown that the treatment of hypertension in men and women over 60 years of age reduces the incidence of stroke by about 40%, and some trials have also shown reductions in coronary events.     

Red blood cell indices, cation content, and membrane cation transports

In sickle cell disease, in the homozygous state, the increased heterogeneity of erythrocytes results mainly from membrane defects secondary to Hb S polymerization and the increased survival of F cells. The density distribution curve, using phthalate esters or the red blood cell indices measured with the H*3 system, are useful methods for the hematological follow-up of patients under specific therapies. The methods evaluating the red blood cell cation contents and the abnormal membrane potassium transport pathways are also described, in order to evaluate agents which can restore normal hemoglobin concentration and water content in dehydrated sickle cells.     

Effect of cholecystokinin-pancreozymin (CCK-PZ) on glycoprotein secretion from mouse gallbladder epithelium: an ultrastructural and cytochemical study

L-Azetidine-2-carboxylic acid, the naturally occurring lower homologue of L-proline, is incorporated into hemoglobin S (sickle hemoglobin) in vitro. Sickle erythrocytes from patients with sickle cell anemia incubated with L-[3H] azetidine-2-carboxylate synthesized radiolabeled hemoglobin which when isolated from cell lysates, co-chromatographed with hemoglobin S on DEAE-cellulose columns. The alpha/beta ratio of azetidine carboxylate incorporation into the globin chains of sickle hemoglobin was 0.94, which is consistent with the presence of four proline residues in each polypeptide chain. Incorporation of azetidine carboxylate into hot trichloroacetic acid-insoluble material in sickle erythrocytes indicated that the homologue was present in the polypeptide backbone of the globin chains of sickle hemoglobin. Amino acid analysis of the hot trichloroacetic acid-insoluble material from sickle erythrocytes which had been incubated with radiolabeled azetidine carboxylate indicated that 75% of the radioactivity could be accounted for as intact homologue while 20% of the radioactivity co-chromatographed with alanine. These results suggest that azetidine carboxylate is incorporated unaltered into hemoglobin S in addition to being metabolized to alanine in sickle erythrocytes prior to incorporation into protein. The kinetics of thermal precipitation of hemoglobin S (oxygen ligand) into which radioactive azetidine carboxylate or radioactive proline had been incorporated in vitro is identical. This observation, together with the behavior of hemoglobin S and the globin chains from hemoglobin S containing azetidine carboxylate during ion-exchange chromatography, indicates that homologue replacement of prolyl residues does not significantly alter the overall charge or stability of the hemoglobin S tetramer. Azetidine carboxylate did not inhibit uptake of radiolabeled proline by sickle erythrocytes suggesting that the homologue does not adversely affect amino acid transport in these cells.     

Sex differences in the electrokinetic properties of the erythrocytes in normal children and in iron-deficiency anemia

The electrophoretic mobility of children blood erythrocytes in norm and with iron-deficiency anemia was studied. The age peculiarities and sex specificity of this index was revealed, demonstrated chiefly by dynamics of shape of its distribution curve reflecting a ratio of cell subpopulations with different electrokinetic potential. The state of anemia is accompanied with modification of histogram profiles of both individual and group cell mobility, with patterns of changes also depending on the child sex. The obtained data suggest that at children iron-deficiency anemia the structure or functional status of erythrocyte membrane are changed, but the pathological process does not eventually involve all the populations of circulating erythrocytes.