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Biomedical subjects

M E Conrad

Publications and source records attributed to M E Conrad.

At least 73 records · Page 4Linked to original sources
PubMed1981

Effect of phosphate on the absorption and retention of lead in the rat.

An inverse relationship between lead retention and dietary phosphate content has been known to exist for many years but the reasons for this association remained unknown. In rats, the manipulation of dietary phosphate content had no significant effect upon the absorption of lead from isolated gastrointestinal segments, but animals fed low phosphate content food had increased whole-body retention and bone deposition of intravenously administered tracer doses of radiolead. Intraluminal phosphate decreased the absorption of test doses of radiolead from the small intestine, possibly due to precipitation of lead in the gut lumen. Further, rats fed low phosphate diets absorbed increased quantities of an oral lead dose. Dietary phosphate deficiency may significantly increase body lead burdens by decreasing intraluminal lead precipitation and increasing lead retention, primarily in bone. Increased dietary phosphate, however, acts primarily to limit lead absorption.

Animals↗
PubMed1981

Ultrastructural, cytochemical, and radioautographic localization of placental iron.

Maternal-fetal iron transfer across the guinea pig hemomonochorial placenta during the first, second, and third trimesters was examined using ultrastructural, cytochemical, radioautographic, and ferrokinetic methods. Acid ferrocyanide stained inorganic ferric iron on and in sinusoidal microvilli, cytoplasmic matrix or ground substance, and the outer basal plasmalemma of epithelial cells. Some stain deposits were observed within and on either side of the basement membrane. The extraluminal outer plasmalemma, intercellular junctions, and cytoplasm of endothelial cells frequently contained numerous stain deposits. Staining of trophoblast sinusoidal microvilli was similar during early and late gestation, whereas the staining of the basement membrane and endothelial cells was most prominent during the second and third trimesters. Staining of ferric iron was encountered in rare cytoplasmic granules of epithelial cells during late gestation, but not during early gestation. Placental macrophages contained acid-ferrocyanide-reactive ferric iron in large heterophagosomes and hyaloplasm. Acid ferricyanide failed to localize ferrous iron in either epithelial cells or macrophages. Light-microscopic radioautographic studies localized radioiron in placental epithelial cells and Prussian-blue-positive macrophages in specimens obtained 30 minutes after injection of radioiron ((55)Fe, (59)Fe) into the maternal saphenous vein. At the ultrastructural level labeling was observed (in order of decreasing grain density) in or on the epithelial basal plasmalemma and basement membrane, endothelial cytoplasm, epithelial sinusoidal microvilli, and epithelial cytoplasm. Significant staining or radiolabeling was not observed in mitochondria, trophoblast granules, or nuclei. These results indicate that placental non-heme iron is trivalent and moves from the maternal to the fetal circulation by passing through trophoblast microvilli, cytoplasmic matrix, basal plasmalemma, basement membrane, endothelial cell junctions, and cytoplasm.

Animals↗
PubMed1980

Isolated marrow lymphoma: an entity of possible T-cell derivation.

Seven adults had a distinct clinicopathologic type of lymphoproliferative disorder of the bone marrow. All patients presented with weakness and pancytopenia; no evidence of gross extramedullary involvement was found. In 5 cases severe and prolonged bone marrow hypoplasia was associated with combination chemotherapy; 1 patient died of infection during initial therapy. In 6 of the 7 cases, clinical improvement occurred following therapy. As a terminal event, 2 patients developed a leukemic phase. Tumor cell from 4 patients were studied immunologically, and in 2 patients surface marker characteristics suggestive of T-cell tumor origin were found. In 2 cases, ultrastructural studies of lymphoid cells were compatible with a T-cell neoplasm. The above data suggest that these cases represent a distinct type of chemotherapy-sensitive lymphoma in which conservative initial treatment may induce a response without prolonged bone marrow hypoplasia.

Adult↗
PubMed1980

Acute lymphoblastic leukemia in idiopathic refractory sideroblastic anemia: evidence for a common lymphoid and myeloid progenitor cell.

Acute leukemia of myeloblastic or erythroblastic morphology occasionally occurs as a complication of idiopathic refractory sideroblastic anemia, but the development of acute lymphoblastic leukemia has not been previously reported in these cases. A patient with idiopathic refractory sideroblastic anemia is described in whom acute lymphoblastic leukemia occurred. The leukemic cells were characterized by typical lymphoblastic morphology on Wright's stain, periodic acid-Schiff-positive cytoplasmic clumps, elevated levels of deoxynucleotidyl transferase (143 units/10(8) cells), high numbers of specific glucocorticoid binding sites (16,845 sites/cell, Kd = 5.40 x 10(-9) M), non-B, non-T cell immunologic characteristics and clinical responsiveness to therapy with vincristine, prednisone, and methotrexate. Ultrastructural studies of the lymphoblasts identified ferruginous material in lysosomes and occasional mitochondria similar to but less abundant than that seen in abnormal sideroblasts. The concurrence of these two disorders supports the theory that in humans both lymphoid and myeloid cell lines arise from a common pluripotent stem cell.

Anemia, Sideroblastic↗
PubMed1980

Provoked priapism in sickle cell anemia.

Two patients with sickle cell anemia are reported who developed relative impotence after repeated episodes of priapism. They learned that excessive ethanol ingestion produced an erection and utilized this mechanism to satisfy sexual partners. Hospitalization and transfusion therapy were required for repeated episodes of priapism. Extensive interviews were required in order to learn the sequence of events. This synergistic relationship between ethanol and priapism should be sought in patients with repeated hospitalizations for this complication of sickle cell anemia because it is preventable with appropriate counseling.

Adult↗
PubMed1980

Effects of vitamin D on the absorption and retention of lead.

A relationship between lead retention and vitamin D has been recognized for many years, but the reasons for this association remained unknown. In rats, the manipulation of dietary vitamin D content had no significant effect on the absorption of lead from isolated gut loops and parenteral vitamin D stimulation did not affect lead absorption in rachitic animals. In contrast, dietary vitamin D deficiency and repletion resulted in increased absorption in intact animals due to prolonged gastrointestinal transit time. Both dietary vitamin D deficiency and repletion were associated with decreased body retention of radiolead given intravenously. Further, single doses of parenteral vitamin D administered to animals previously given tracer radiolead resulted in a dose-related enhancement of lead excretion and changes in tissue lead content.

Animals↗
PubMed1979

Studies on the clonal origin of multiple myeloma. Use of individually specific (idiotype) antibodies to trace the oncogenic event to its earliest point of expression in B-cell differentiation.

IgA myeloma proteins of kappa- and lambda-types were isolated from two patients. These were used to produce and purify anti-idiotype antibodies of both broad (myeloma-related) and narrow (individual myeloma) specificities. The anti-idiotype antibodies were conjugated with fluorochromes and used as immunofluorescent probes to trace in the patients clonal expansion at different levels of B-cell differentiation. Our results (a) confirm that B lymphocyte precursors in IgA plasma-cell myelomas are involved in the malignant process, (b) show that B lymphocytes of the malignant clone include those expressing each of the major heavy-chain isotypes, mu, delta, gamma, and alpha, and (c) provide strong circumstantial evidence that pre-B-cell members of the malignant clone are also increased in frequency. T cells expressing idiotypic determinants were not detected. These findings argue that the initial oncogenic event may occur in a B-stem cell and is not influenced through stimulation by antigen. An interesting association was the increased frequency of related clones of B lymphocytes as detected by their reactivity with anti-idiotype antibodies of broad specificity. Neither plasma cell nor pre-B-cell members of these related clones were increased in frequency. Anti-idiotype antibodies or helper T cells reactive with myeloma-related idiotypes could be responsible for this phenomenon. We discuss other implications of these findings and speculate that all of the various phenotypes of B-lineage malignancies may result from oncogenic processes affecting stem cell targets.

Antibodies, Neoplasm↗
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

Bone marrow necrosis.

Bone marrow necrosis has been regarded as a rare entity in specimens obtained from living patients and has been associated with poor prognosis. In contrast, we believe that it is a commonplace finding in bone marrow specimens which is frequently overlooked and which occurs in patients with multiple acute and chronic disorders. It is postulated that bone marrow necrosis eventuates from vascular occlusion of small blood vessels as a result of a number of causes. When bone marrow necrosis is prolonged, it may be associated with the development of bone marrow fibrosis and serve as a predisposing lesion for idiopathic myelofibrosis. Additional investigation of this phenomenon is required to determine its usefulness in the diagnosis of disease states and its role in the pathophysiology of a number of disorders.

Animals↗