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Biomedical subjects

H A Pearson

Publications and source records attributed to H A Pearson.

At least 19 recordsLinked to original sources
PubMed1992

Iron absorption and incorporation into red blood cells by very low birth weight infants: studies with the stable isotope 58Fe.

Measurements of iron absorption and incorporation into RBCs were obtained with the stable isotope 58Fe, administered as a reference dose, in 11 premature infants with birth weights between 780 and 1,520 g and gestational ages between 24 and 33 weeks. Each study included a timed stool and urine collection, nasogastric tube administration of a single dose of about 228 micrograms of 58Fe/kg of body weight (as FeSO4, with 10 mg/kg of vitamin C) between feedings, and blood samples before 58Fe (day 1) and then 2 weeks (day 15) later. Gastrointestinal absorption of the 58Fe dose as measured by fecal isotope balance was 41.6 +/- 17.6% (mean +/- SD). However, only 12.0 +/- 9.6% of the 58Fe dose (28.7 +/- 22.3% of the absorbed 58Fe dose) was incorporated into RBCs on day 15. 58Fe absorption and 58Fe incorporation into RBCs on day 15 were significantly correlated with the hemoglobin concentration and reticulocyte count on day 1. Transfusion history did not affect 58Fe absorption or 58Fe incorporation into RBCs. We conclude that concurrent measurement of 58Fe absorption with fecal monitoring and of 58Fe incorporation into RBCs permits a better understanding of the fate of iron ingested by premature infants than either measurement alone.

Algorithms↗
PubMed1992

Actions of arginine polyamine on voltage and ligand-activated whole cell currents recorded from cultured neurones.

1. Toxins from invertebrates have proved useful tools for investigation of the properties of ion channels. In this study we describe the actions of arginine polyamine which is believed to be a close analogue of FTX, a polyamine isolated from the American funnel web spider, Agelenopsis aperta. 2. Voltage-activated Ca2+ currents and Ca(2+)-dependent Cl- currents recorded from rat cultured dorsal root ganglion neurones were reversibly inhibited by arginine polyamine (AP; 0.001 to 100 microM). Low voltage-activated T-type Ca2+ currents were significantly more sensitive to AP than high voltage-activated Ca2+ currents. The IC50 values for the actions of AP on low and high voltage-activated Ca2+ currents were 10 nM and 3 microM respectively. AP was equally effective in inhibiting high voltage-activated currents carried by Ba2+, Sr2+ or Ca2+. However, AP-induced inhibition of Ca2+ currents was attenuated by increasing the extracellular Ca2+ concentration from 2 mM to 10 mM. 3. The actions of AP on a Ca(2+)-independent K+ current were more complex, 1 microM AP enhanced this current but 10 microM AP had a dual action, initially enhancing but then inhibiting the K+ current. 4. gamma-Aminobutyric acid-activated Cl- currents were also reversibly inhibited by 1 to 10 microM AP. In contrast N-methyl-D-aspartate currents recorded from rat cultured cerebellar neurones were greatly enhanced by 10 microM AP. 5. We conclude that at a concentration of 10 nM, AP is a selective inhibitor of low threshold T-type voltage-activated Ca2+ currents. However, at higher concentrations 1-10 microM AP interacts with ion channels or other membrane constituents to produce a variety of actions on both voltage and ligand gated ion channels.

Animals↗
PubMed1991

Site-specific deletions of the mitochondrial genome in the Pearson marrow-pancreas syndrome.

The Pearson marrow-pancreas syndrome is a fatal disorder involving the hematopoietic system and the exocrine pancreas in early infancy. We have previously shown that this disease results from a widespread defect of oxidative phosphorylation. Here, we describe deletions of the mitochondrial (mt) genome between repeated 8- to 13-bp sequences as consistent features of the disease. Studying a series of nine unrelated children, including the patient originally reported by H. Pearson, we found five different types of direct repeats at the boundaries of the mtDNA deletions and we provided evidence for conservation of the 3'-repeated sequence in the deletions. In addition, we found a certain degree of homology between the nucleotide composition of the direct repeats and several structures normally involved in mtDNA replication and mtRNA processing. These results are consistent either with the recognition and cleavage of a particular DNA sequence with a factor of still unknown origin or with a homologous recombination between direct-repeat mtDNA sequences in the Pearson syndrome.

Base Sequence↗
PubMed1988

Insulin resistance and hyperinsulinemia in patients with thalassemia major treated by hypertransfusion.

Diabetes mellitus in patients receiving hypertransfusion for thalassemia major is usually attributed to damage to beta cells. To determine whether iron overload leads to insulin resistance before the development of insulin deficiency, insulin was infused (by euglycemic insulin-clamp technique) into 12 children with thalassemia (4 of whom were prepubertal, and 8 pubertal) who had normal or only moderately impaired glucose tolerance and who were receiving chelation therapy. Although insulin-stimulated glucose metabolism in the prepubertal children with thalassemia was similar to that in controls (normal prepubertal children) (319 +/- 23 vs. 314 +/- 41 mg per square meter of body-surface area per minute, P not significant), the response to insulin was markedly impaired in the pubertal children with thalassemia (155 +/- 18 vs. 224 +/- 15 mg per square meter per minute in normal pubertal controls, P less than 0.01). Plasma insulin levels rose excessively after oral glucose administration in the pubertal subjects with thalassemia, but not in the prepubertal patients (P less than 0.001). Furthermore, in response to a standard hyperglycemic stimulus, insulin levels in the pubertal patients rose to two to three times greater than normal and C-peptide levels became significantly elevated. Our data suggest that insulin resistance and increased insulin secretion develop in older children with thalassemia treated with long-term hypertransfusion therapy before the development of diabetes.

Adolescent↗
PubMed1988

Heme metabolism and in vitro erythropoiesis in anemia associated with hypochromic microcytosis.

Heme metabolism and in vitro erythropoietic growth (CFU-E, BFU-E) were examined in bone marrow cells taken from two siblings with apparent familial hypochromic microcytic anemia. Bone marrow cells from both patients grew adequate numbers of CFU-E and BFU-E colonies in culture in the presence of erythropoietin. In addition, small numbers of endogenous CFU-E were seen in 7-day cultures. Assays on bone marrow cells taken from both patients revealed that baseline delta-aminolevulinic synthase activity was considerably reduced, but increased six to seven fold (to normal levels) when patients' cells were exposed to pyridoxal phosphate (PLP). In both cases, ferrochelatase and delta-aminolevulinic acid dehydratase activities were normal. Bone marrow heme oxygenase showed no significant differences in activities between normals and patients values in the absence or presence of PLP. In contrast, heme synthesis by patients' bone marrow was less than that of normals. This study demonstrates that bone marrow cells from patients with this rare disorder have some disturbances in heme metabolism, whereas erythropoiesis appeared to be normal when cultured with adequate nutrients in vitro.

5-Aminolevulinate Synthetase↗
PubMed1988

Normal splenic function in children with the nephrotic syndrome.

Children with the idiopathic nephrotic syndrome (NS) are known to be susceptible to bacterial infections. A recent report suggested that splenic hypofunction may be responsible for this immunological defect. We assessed splenic function by counting the circulating pocked red blood cells (PkRBCs) using interference phase contrast microscopy. PkRBCs are removed by the spleen, so that normal eusplenic individuals have less than 2% PkRBCs while asplenics have 15%-30%. Intermediate values are seen in hyposplenism. Thirty-three measurements of PkRBCs were made in 19 children with NS (mean age 7.5 +/- 0.8 years). PkRBCs were normal in all children tested (range 0-0.8%), including two patients with bacterial peritonitis associated with relapse. Thus we were unable to find evidence of hyposplenism in children with NS.

Adolescent↗
PubMed1987

Patient age distribution in thalassemia major: changes from 1973 to 1985.

Major advances have occurred in the treatment and prevention of thalassemia major, but their impact on incidence and survival have not been well assessed. In 1973, a survey was done of the ages of 243 living patients with thalassemia major followed at 12 centers in the United States and Canada. Twenty-two percent were younger than 5 years and 2.1% were older than 25 years of age (mean 11.4 +/- 6.7 [SD] years). In 1985, there were 303 patients at the same centers; 11% were younger than 5 years and 7.9% were older than 25 years (mean 14.2 +/- 7.3 years). A similar pattern was found in Connecticut, characterized by a marked decrease of new cases of thalassemia major during the past 15 years. This was not a result of fewer persons at genetic risk or a change in marital ethnic choices. Eleven of 14 families who had a child with thalassemia major assured that another affected child would not be born by having no more children, using prenatal diagnosis, or having therapeutic abortions. Extensive community programs of education and testing for thalassemia trait in Connecticut may also have contributed to the observed reduction in new cases.

Adolescent↗