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Renal acidification in sickle cell trait.

Nine sickle cell trait and nine control subjects underwent six-hour ammonium chloride acid loading. Maximal urine osmolality and renal hemodynamics were studied separately. Base line arterial pH, carbon dioxide pressure (Pco2), and [HCO3] were normal and comparable in the two groups. After ammonium chloride loading, urine pH decreased to 5.3 or less in all, and maximal excretion of ammonium and titratable and net acid was comparable as was urine minus blood Pco2 after bicarbonate loading. The ammonium chloride acidosis caused a small decrease in red blood cell 2,3-diphosphoglycerate levels but no alteration in oxygen pressure at 50% saturation at pH 7.4, sickling, or adverse effects. Control and sickle cell trait subjects had comparable renal hemodynamics but maximal urine osmolality was lower in sickle-cell trait subjects. Adults with sickle cell trait have diminished renal concentrating ability and normal renal acidification and hemodynamics.

Acidosis, Renal Tubular

A comparison of the physical and intellectual development of black children with and without sickle-cell trait.

Sickle-cell trait, a condition present in 7% to 9% of the United States Black population, is usually considered to be a clinically benign condition. However, there is increasing evidence to indicate the contrary, that is, the clinical pathophysiology is variable, ranging from a benign condition in most cases to a relatively few cases of severe pathological involvement. Physical and intellectual growth measures were taken on 19 children with sickle-cell trait (12 boys and 7 girls) from a large study of Black same-sex twin pairs from Philadelphia, Pennsylvania, and compared to measures taken of a sample of normal Black children from 155 monozygotic and dizygotic same-sex twin pairs. Sickle-cell trait carriers were found to weigh less, have smaller upper arm circumference lesser skinfold thickness, and showed less mature skeletal age, differing significantly from normal children. Sickle-cell carriers tended to score lower on four of five intellectual measures, scoring one fifth to one third of a standard deviation lower than normal children.

Adolescent

Effect of different modalities of exercise and recovery on exercise performance in subjects with sickle cell trait.

The sickle cell trait (HbAS) does not seem to affect exercise performance. It remains unclear, however, whether the capability to sustain repeated brief maximal effort and recovery by HbAS subjects, is also preserved. To study this, nine HbAS and nine matched controls underwent on two different occasions, a series of four, approximately 2-min duration, maximal cycle exercise tests separated by 20-min recovery periods of either absolute rest (P) or light pedaling (A) as well as an incremental test to exhaustion. In all tests, work performed, heart rate, blood hematocrit, lactate, and serum creatine kinase (CK), lactate dehydrogenase (LDH), and aspartate aminotransferase (GOT) were measured. Performances were similar in HbAS and HbAA subjects in both the predominantly anaerobic and aerobic exercise series. There were no observable differences in work, power, or heart rate in the two groups both during peak exercise or recovery periods. A significant hemoconcentration was observed during P, with hematocrit increasing in HbAS from 46.4 +/- 0.7% to 48.3 +/- 0.4% at the end of the last recovery period. Similar changes were seen in HbAA. Significantly greater fluid losses were found during A (1.3 +/- 0.2 l in A and 0.6 +/- 0.1 l in P for HbAS; P < 0.001), but fluid losses were similar in each type of recovery in the two groups. Despite similar performance, significantly lower blood lactate concentrations were consistently found in HbAS in each of the three exercise series (P < 0.001). Lower lactate levels in HbAS were observed only at exercise loads above the lactate threshold during the incremental test (P < 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult

Hemoglobin synthesis studies of a family with alpha-thalassemia trait and sickle cell trait.

The ratio of total globin alpha to beta chain synthesis was determined in reticulocytes isolated from the blood of the members of a black family, some of whom had sickle cell trait with low blood HbS concentrations (25-30%). The results support the hypothesis that sickle cell trait individuals with low HbS concentrations also carry a gene for alpha-thalassemia.

Anemia, Sickle Cell

On the protective mechanism of the sickle cell trait (HbAS).

The sickle cell trait has been reported to offer some protection against anaemia in pregnancy. Some attribute this to the break up of the cells which release iron for the synthesis of haemoglobin. The hypothesis presented here is that the 'partial' protective mechanism of the sickle cell trait is due to increased erythropoietic activity.

Anemia

Optociliary shunts and sickle retinopathy in a woman with sickle cell trait.

We report a case of unilateral optociliary shunt vessels and sickle cell retinopathy in a patient with sickle cell trait. Sickle cell retinopathy has rarely been reported in patients with sickle cell trait hemoglobinopathy. To our knowledge, this is the first report of the association of sickle cell trait, unilateral sickle cell retinopathy, and ipsilateral optociliary shunt vessels.

Anemia, Sickle Cell

The effect of bicarbonate and distilled water on sickle cell trait hematuria and in vitro studies on the interaction of osmolality and pH on erythrocyte sickling in sickle cell trait.

The effect of intravenously administered distilled water was examined alone and during alkalization in a patient with gross hematuria associated with the sickle cell trait. On each of 4 occasions hematuria ceased promptly after the infusion of distilled water. Bicarbonate therapy also consistently decreased hematuria. In vitro studies on erythrocytes from another patient with sickle cell trait and hematuria demonstrated that slight increases in urinary pH similar to those that occur in the urine during alkalization can reverse or prevent erythrocyte sickling in the sicle cell trait. If patients with the sickle cell trait are hydrated adequately and have a good rate of urine flow distilled water can be given intravenously with virtually no danger of acute tubular necrosis secondary to erythrocyte hemolysis.

Adult

A new form of hereditary persistence of fetal hemoglobin in blacks and its association with sickle cell trait.

A new form of hereditary persistence of fetal hemoglobin (HPFH) producing 3%-8% Hb F in heterozygotes and an elevation of F-cell counts as measured by both the Kleihauer test and an antibody fluorescent procedure was found during the study of a black family. Individuals with this anomaly also had sickle cell trait. A sickle cell homozygote who had apparently inherited the HPFH determinant had 20.3% Hb F. Both types of gamma-chains were present in equal proportions in the Hb F of these individuals. A population study revealed other AS individuals with increased Hb F synthesis, three of whom were sibs. The presence of this previously unrecognized form of HPFH might explain the mild clinical manifestations and the hemoglobin phenotypes of sickle cell homozygotes with unusual elevations of Hb F.

Africa

Effects of physical stress on complete blood count and venous blood gas profile of individuals with sickle cell trait.

The association between sickle cell trait (SCT) and adverse effects of exercise has been controversial. While individuals with SCT are at higher risk of sudden death, the mechanism for this outcome remains to be elucidated. In order to shed light on this controversy, we have monitored venous blood count and blood gas parameter values in normal and SCT subjects during treadmill exercise. White and red blood cell counts and hemoglobin changed significantly over time in both the SCT and normal groups, with peak exercise values different from pre-exercise or post-exercise values. Red blood cell counts showed significant group-time interaction; increase in count during exercise was accentuated in SCT subjects. All blood gas parameters showed significant changes over time in both groups. O2 content was significantly higher in SCT than AA at all time intervals. O2 saturation, pO2 and CO binding to hemoglobin showed significant group-time interaction. Furthermore, O2 saturation for the combined groups was significantly greater at peak exercise and at rest than before exercise. It is possible that treadmill exercise causes microvascular shunting in SCT subjects, leading to a decrease in the peripheral utilization of oxygen.

Adult

Sickle cell trait and the aviator.

Sickle cell trait (SCT) for years has been a controversial disorder within the aerospace medicine community. Some authorities consider SCT to be an entirely benign condition without particular significance, at least to moderate altitudes. Others are in disagreement and consider it a serious enough threat that flying duties should be precluded for all individuals with this disorder. These issues are addressed by reviewing SCT, its relationship to altitude, and its risk to aviation. The author concludes that flying organizations must establish their own policy on flying status for individuals with SCT based upon mission peculiarities and the assessment of risk inherent in that mission.

Aerospace Medicine

Nephropathies Associated with Sickle Cell Trait and How to Study Them.

Sickle cell trait (SCT), which carries a single point mutation in the hemoglobin-&#x3b2; (HBB) gene, has long been considered a benign condition. However, epidemiological evidence challenges this assumption, revealing that individuals with SCT face an elevated risk of renal dysfunction. However, this field of study remains ill-defined as it has focused on sickle cell disease (SCD), where renal complications are severe. As SCT is more prevalent than SCD, consequences of nephropathies in this group translate into a substantial and largely unaddressed public health burden. Clinical data, primarily observational, implicate age and sex in the development of SCT-associated nephropathies. These manifestations span glomerular hyperfiltration, tubular damage, hematuria, renal papillary necrosis, renal medullary carcinoma, and progression to chronic kidney disease, all complications that cluster disproportionately in older male individuals. Despite this, the mechanistic basis of SCT nephropathy, the thresholds at which renal injury becomes clinically significant, and the optimal strategies for early identification and prevention remain inadequately defined. In vitro studies have primarily focused on SCD blood cell biology, with SCT receiving comparatively little attention. Humanized murine models (i.e., Berkeley and Townes) have recapitulated some SCT-associated renal phenotypes but need to be more fully characterized. This review aims to provide an overview of the biology of sickle cell trait nephropathies, the gaps in our knowledge, and the model systems we can use to fill those gaps.

Journal Article

Splenic sequestration associated with sickle cell trait and hereditary spherocytosis.

Coexistence of sickle cell trait and hereditary spherocytosis (HS) is unusual, and only 16 cases have been reported in the literature. These patients have the same clinical and hematological features as individuals having HS alone. We report a serious complication, acute splenic sequestration crisis (ASSC), occurring in two patients with sickle cell trait and HS. One patient experienced four episodes of ASSC during an 11-year span, while the other had two episodes of this complication during a 4-year period. Red blood cell studies and membrane protein analysis confirmed the diagnosis of HS as a consequence of spectrin deficiency. Splenectomy resulted in marked clinical and hematological improvement in both patients. Histological examination of spleens following splenectomy confirmed that significant erythrostasis and sickling had indeed occurred. ASSC can occur in patients with coexistence of sickle cell trait and HS, and this potentially life-threatening complication should be considered in this condition.

Adolescent

Medical management of refractory hematuria in sickle-cell trait.

Hematuria secondary to sickle-cell trait has on occasion proved refractory to medical management. We have adopted a new six-drug regimen to deal with this difficult problem. Herein is reported our experience with this protocol in 2 patients. Our results have been excellent, with hematuria clearing within twenty-four hours. The drug regimen is used in an attempt to alter the conditions that are favorable for sickling in the renal medulla.

Acetazolamide

Sickle cell trait and diabetic retinopathy.

The presence of sickle cell trait and the prevalence and severity of retinopathy were assessed in 124 Negro diabetics. Sickle cell trait had no adverse effect on diabetic retinopathy.

Adult

Pulmonary embolism and splenic infarction in a patient with sickle cell trait.

A 43 year-old black man with sickle cell trait documented by hemoglobin electrophoresis presented with severe pleuritic chest pain and hypoxemia three weeks after discharge following abdominal surgery. A pulmonary embolus was diagnosed by angiography and he was treated with heparin; the minimum arterial pO2 was 55 torr while O2 was being administered at a rate of 3 L/min. During this therapy, he developed abdominal pain. Computerized tomography suggested splenic infarction, which was documented by radionuclide liver-spleen scan and magnetic resonance imaging (MRI); the patient's spleen had been normal at exploratory laparotomy three weeks previously. No source for emboli was identified in the deep venous system by MRI. Although splenic infarction has been reported in patients with sickle cell trait at high altitude, this is the first reported case of splenic infarction secondary to the hypoxemia of pulmonary embolism in a patient with sickle cell trait. The spleen is subject to infarction in sickle cell trait because blood flow is slow through a hypoxemic and acidemic environment. The additional hypoxemia due to pulmonary embolism is presumed, in our patient, to have created a local splenic environment which permitted infarction to occur.

Adult

Proliferative retinopathy in sickle cell trait. Report of seven cases.

Seven patients had sickle cell trait (hemoglobin AS) and vasoproliferative retinopathy. The retinal abnormalities in these seven patients were indistinguishable from those seen in patients with clinically significant sickling hemoglobinopathies (sickle cell-hemoglobin C disease, hemoglobin S-thalassemia disease, and sickle cell anemia). All seven patients also had some evidence of associated systemic disease such as diabetes, syphilis, tuberculosis, or sarcoidosis. In the presence of an associated systemic disease, marked retinopathy can occur in the ordinarily benign condition of sickle cell trait.

Adult

Splenic function in persons with sickle cell trait at moderately high altitude.

We investigated the possibility that persons with sickle cell trait who reside chronically at moderately high altitude might develop impaired splenic reticuloendothelial function. Seventeen healthy young black men with sickle trait who had lived at greater than or equal to 1,609 m for greater than or equal to 10 years participated in the study along with 25 matched control subjects with normal hemoglobin. Splenic function was assessed by radionuclide liver-spleen scanning and by red cell pit counts. No evidence of impaired splenic function was found in the sickle trait group. The data suggest that long-term residence at moderately high altitude does not place persons with sickle cell trait at risk for splenic dysfunction.

Adolescent