PubMed Health⌕ Search

Biomedical subjects

J C Barton

Publications and source records attributed to J C Barton.

At least 109 records · Page 6Linked to original sources
PubMed1979

The aplastic anemia-paroxysmal nocturnal hemoglobinuria syndrome.

Occasionally it is difficult to differentiate paroxysmal nocturnal hemoglobinuria (PNH) from idiopathic aplastic anemia in patients who present with pancytopenia and an aplastic bone marrow. Patients with PNH may not have an abnormal acid hemolysis test, and patients with aplastic anemia may present with evidence of abnormal sucrose lysis, acid hemolysis, and antibody-mediated complement hemolysis. Demonstration of a population of red blood cells which are highly susceptible to antibody-mediated complement lysis makes a diagnosis of PNH probable. Donor red blood cell survival studies, which distinguish intracorpuscular from extracorpuscular hemolytic disorders, permit differentiation of the two disorders.

Adult↗
PubMed1979

Beneficial effects of hepatitis in patients with acute myelogenous leukemia.

Of 50 consecutive patients admitted with acute myelogenous leukemia, 30 developed complete remissions on antileukemic therapy. Nineteen of the 30 repeatedly had elevated serum glutamic oxalacetic transaminase (SGOT) concentrations 3 to 14 weeks after the start of therapy. Patients with SGOT elevations had a significantly greater chance of remission and a longer survival (76 +/- 11 weeks) than those with normal SGOT levels (39 +/- 5 weeks), suggesting that hepatitis may have a beneficial effect in acute myelogenous leukemia. The hepatitis was mild in all patients. Review of patients at this institution alive 2 years after the diagnosis of acute myelogenous leukemia showed that they repeatedly had elevated SGOT levels. We believe that most had non-A, non-B post-transfusion hepatitis, which may have a beneficial effect on the leukemia or serve as an indicator of patients who have greater immunocompetence and thus a better prognosis.

Adolescent↗
PubMed1979

Pseudochloroma: extramedullary hematopoietic nodules in chronic myelogenous leukemia.

Five patients with chronic myelogenous leukemia had multiple hemorrhagic soft tissue lesions at the time of diagnosis. Histologic examination of tissue removed by biopsy and at autopsy revealed extramedullary hematopoietic nodules with associated hemorrhage and necrosis. No evidence of either blastic transformation or systemic bleeding diathesis was found. Pseudochloroma is a treatable although potentially fatal complication of uncontrolled chronic myelogenous leukemia and should not be confused with myeloblastomas occurring with blastic transformation. Early recognition of the syndrome, prompt treatment with intensive chemotherapy, and radiation therapy of intracranial lesions seem to provide effective control of this complication and reversion to a status that is responsive to conventional treatment of chronic myelogenous leukemia.

Adult↗
PubMed1979

A commonsense approach to CME organization.

One of the functions of community hospitals is to provide continuing medical education programs for their staff physicians. Variety of purpose, medical staff characteristics, limited funds, and decentralized decision making are all factors that should be taken into consideration as a hospital organizes a CME program. In turn, it is helpful to consider these factors in light of certain principles of organization, such as avoiding duplication and overlap of functions, fixing responsibility and authority, and establishing uniform methods and procedures where appropriate.

Decision Making↗
PubMed1979

Ultrastructural radioautography and cytochemistry of lead absorption.

Lead is a universal environmental contaminant absorbed largely through the gastrointestinal tract by unknown mechanisms. Because lead absorption is influenced by iron content in the body and diet, we used ultrastructural radioautography and cytochemistry to study absorption of physiologic lead doses in the rat duodenal epithelial cell and compared these findings to those previously reported for iron absorption. Rat duodenal loops exposed in vivo to 210Pb for 1 minute demonstrated the majority of labels on the microvilli, terminal web, and apical cytoplasm. Specimens exposed to radiolead for 10 minutes demonstrated more abundant labeling with a relative increase in labeling of epithelial cell mitochondria, nuclei and basal cytoplasm, as well as phagocytic cells, endothelial cells, and circulating erythrocytes of the lamina propria. Timm's sulfide-silver method localized trace metals in epithelial cells. After administration of lead, a significant increase in staining was observed in microvilli, mitochondria, non-membrane-bound cytoplasm, and nuclear chromatin. The rapid appearance of absorbed lead in epithelial cell mitochondria and nuclei, as well as phagocytic cells in the lamina propria, was distinctly different from that reported for absorbed iron and suggests different mechanisms for the subcellular transport of these cations. The combination of radioautography and Timm's sulfide-silver staining provides the specificity and resolution needed for ultrastructural evaluation of lead absorption and should be useful in further studies of lead metabolism.

Animals↗
PubMed1978

Effects of calcium on the absorption and retention of lead.

An inverse relationship between lead retention and dietary calcium content has been known to exist for many years, but the reasons for this association remained unknown. In rats, the manipulation of dietary calcium had no significant effect upon the absorption of lead, but calcium-deprived animals had decreased excretion and thus increased body retention of lead. Intraluminal calcium decreased the absorption of test doses of lead from the small intestine in a dose-related manner. We postulated that this occurred because the two metals competed for similar binding sites on intestinal mucosal proteins which were important in the absorptive process. In vivo, lead bound to two heat-stable intestinal mucosal fractions which have been shown to bind calcium. Although more lead bound to the higher molecular weight fraction and more calcium bound to the lower molecular weight vitamin D-induced CaBP, substantial amounts of lead and calcium were found in both fractions. Further, the addition of calcium to test doses of lead markedly diminished the amount of lead bound by both fractions. Shared binding sites on absorptive proteins would explain why dietary calcium decreases lead absorption.

Animals↗
PubMed1978

Factors affecting the absorption and excretion of lead in the rat.

A reliable method for studying lead absorption and excretion in rats is described. Lead absorption occurs primarily in theduodenum where lead enters the epithelial mucosal cells. There is a relative mucosal block for lead with increasing intraluminal doses. Certain substances which bind lead and increase its solubility enhance its absorption. Iron, zinc, and calcium decrease the absorption of lead without affecting its solubility, probably by competing for shared absorptive receptors in the intestinal mucosa. The total body burden of lead does not affect lead absorption. Thus, lead does not have a feedback mechanism which limits absorption. Lead absorption is increased during rapid periods of growth and in iron-deficient animals. It is diminished with starvation and in iron-overloaded animals. The excretion and kinetics of tracer doses of radiolead were quantified. Erythrocytes seem to serve an important role in transport. Excretion occurs in urine and stool. Bile is an important route of excretion in the gut. Although most of a tracer dose is rapidly excreted, the excretory process is limited permitting lead accumulation primarily in bone.

Anemia, Hypochromic↗
PubMed1978

Effects of iron on the absorption and retention of lead.

An inverse relationship between lead retention and dietary iron content has been suspected for many years, but the reasons for this association remained unknown. In rats, the state of body iron repletion had significant effects on the absorption of lead but no effect on lead excretion. Intraluminal iron decreased the absorption of test doses of lead from the small intestine in a dose-related manner. We postulated that this occurred because the two metals competed for similar binding sites on intestinal mucosal proteins which were important in the absorptive process. In vivo, both lead and iron bound to two heat-stable intestinal mucosal fractions, particularly the higher-molecular-weight fraction. Addition of iron to test doses of lead markedly diminished the amount of lead bound by the high-molecular-weight fraction. Further investigation revealed that this fraction, with a molecular weight of approximately 370,000, bound both lead and iron. Shared binding sites on this protein may explain why dietary iron decreased lead absorption and iron deficiency increased it.

Animals↗
PubMed1978

Ultrastructural cytochemistry of iron absorption.

Conventional ultrastructural autoradiographic and morphologic studies of the duodenal mucosal cell have generally corroborated physiologic observations of iron absorption, but such methods have limited resolution and fail to distinguish ferric and ferrous iron. This study describes the application of the Prussian blue reaction as an electron microscopic cytochemical stain to the investigation of inorganic iron absorption in iron-deficient, normal, and iron-loaded rats. Ferrous iron is converted to ferric iron at the microvillus membrane. Subsequently intraepithelial ferric iron appears bound to a non-heme acceptor substance in microvilli and later appears as small non-membrane-bound stain deposits which are concentrated in the apical cytoplasm. The appearance of larger stain deposits in the lateral intercellular spaces, in the basal extracellular spaces, and along the intraluminal and extraluminal outer plasmalemma of adjacent endothelial cells of the lamina propria suggests passage of iron from epithelial cells through the lamina propria to blood vessels. The extreme sensitivity of the method compared with simultaneous ultrastructural autoradiographic techniques is demonstrated and suggests usefulness of the method in further studies of iron metabolism.

Animals↗
PubMedDate not supplied

Two novel missense mutations of the HFE gene (I105T and G93R) and identification of the S65C mutation in Alabama hemochromatosis probands.

Sequencing of HFE exons 2, 3, 4, and 5, and of portions of introns 2, 4, and 5 revealed novel mutations in four of twenty hemochromatosis probands who lacked C282Y homozygosity, C282Y/H63D compound heterozygosity, or H63D homozygosity. Probands 1 and 2 were heterozygous for previously undescribed mutations: exon 2, nt 314T-->C (314C; I105T), and exon 2, nt 277G-->(277C; G93R), respectively; these probands were also heterozygous for H63D and C282Y, respectively. Probands 3 and 4 were heterozygous for a previously described but uncommon HFE mutation: exon 2, nt 193A-->T (193T; S65C). Proband 3 was also heterozygous for C282Y and had porphyria cutanea tarda, and Proband 4 had hereditary stomatocytosis. Each of these four probands had iron overload. In each proband with an uncommon HFE coding region mutation, I105T, G93R, and S65C occurred on separate chromosomes from those with the C282Y or H63D mutations. Neither I105T, G93R, nor S65C occurred as spontaneous mutations in our probands. The I105T and G93R mutations were linked to haplotypes bearing HLA-A3,-B7 and HLA-A2,-B62, respectively. The S65C mutation was linked to a haplotype characterized by HLA-32. Sixteen other probands did not have an uncommon HFE exon mutation. In 176 normal control subjects, two were heterozygous for S65C, but I105T and G93R were not detected. Nine of twenty probands were heterozygous and two probands were homozygous for a previously described base-pair change at intron 2, nt 3671T-->C. One proband without a detectable missense mutation had a previously described intron 5 allele (nt 6700G-->A). Heterozygosity for a previously described base-pair change in intron 4 (nt 5636T-->C) was detected in all persons we studied who also had the S65C mutation. One proband was heterozygous for a previously undescribed base-pair change at intron 5 (nt 5807A-->G). We conclude that uncommon HFE exon and intron mutations may be discovered among hemochromatosis patients who have "atypical" HFE genotypes.

Adult↗
PubMedDate not supplied

Transferrin receptor-2 (TFR2) mutation Y250X in Alabama Caucasian and African American subjects with and without primary iron overload.

Most cases of hemochromatosis are associated with mutations of the HFE gene on Ch6p. In southern Italy and central Alabama, the percentages of patients with hemochromatosis who have "atypical" HFE genotypes (defined as lack of C282Y homozygosity, C282Y/H63D compound heterozygosity, or H63D homozygosity) are relatively great. A mutation of the transferrin receptor-2 gene (TFR2; exon 6, nt 750 C --> G, replaces TAC with stop signal TAG; Y250X) on Ch7q22 was recently identified in two Sicilian families with HFE mutation-negative hemochromatosis. We wanted to estimate the frequency of this mutation in persons from central Alabama. We evaluated Caucasian hemochromatosis probands with atypical HFE genotypes and African Americans with primary iron overload. We also studied control Caucasians, including persons of southern Italian/Sicilian heritage, and control African Americans. Analysis of genomic DNA was performed using a PCR-sequence-specific priming assay and positive control specimens from Sicilian hemochromatosis subjects heterozygous and homozygous for Y250X. Among Alabama subjects, this allele was not detected in 113 Caucasians, including 21 hemochromatosis probands with atypical HFE genotypes and 92 normal control subjects (including 27 of southern Italian/Sicilian descent). In African Americans, Y250X was not detected in 20 index cases with primary iron overload or in 274 unrelated control subjects. We conclude that Y250X is uncommon in Caucasians with hemochromatosis associated with atypical HFE genotypes, in African Americans with primary iron overload, and in the general Caucasian and African American population subgroups in central Alabama.

Alabama↗