Iron overload in African Americans

PURPOSE

Iron overload unexplained by dietary or medicinal iron excess, transfusion, or sideroblastic anemia has been described infrequently in Americans of African descent. The purpose of this study was to characterize iron overload attributable to excessive iron absorption in African Americans.

PATIENTS AND METHODS

In a community hematology and medical oncology practice during the interval 1990 to 1993, we identified and evaluated a series of cases comprised of 6 men and 1 woman, with a mean age of 55 +/- 14 (SD) years (range 33 to 69). Data on clinical features, serum iron parameters, liver and body iron stores, evaluations of anemia, human leukocyte antigen (HLA) typing, and family studies were analyzed.

RESULTS

Among our patients, the serum iron parameters were: iron concentration 26 +/- 13 mumol/L, transferrin saturation 59 +/- 21%, and ferritin concentration 1,588 +/- 1,053 micrograms/L. Clinical abnormalities observed included weakness and fatigue, decreased libido and impotence, hepatopathy, arthropathy, diabetes mellitus, hypogonadotrophic hypogonadism, and hyperpigmentation. Hepatic parenchymal cell iron deposits were increased in each of the 6 patients studied, and Kupffer cell iron deposits were prominent in 4. The occurrence of iron overload was verified by liver iron quantification and therapeutic phlebotomy. Four subjects had alpha-thalassemia minor; 2 others had hemoglobin S and C traits. No proband had HLA-A3 positivity. Four probands had other family members with iron overload.

CONCLUSIONS

In comparison with Caucasians with hemochromatosis, our patients have slightly lower mean values of serum iron concentration and transferrin saturation, more Kupffer cell iron deposits, a higher incidence of thalassemia and hemoglobinopathy, and infrequent positivity for HLA-A3. Iron overload in African Americans appears to be more similar to that in certain sub-Saharan African natives than to hemochromatosis.

Blood lead concentrations in hereditary hemochromatosis

We postulated that patients with hereditary hemochromatosis (HH) absorb increased quantities of lead, as do iron-deficient subjects. To test this hypothesis, whole blood lead concentration ([blood Pb]) was quantified by atomic absorption spectrometry in HH homozygotes (n = 44), obligate heterozygotes (n = 19), normal control subjects (n = 33), and abnormal controls, with transfusion-induced iron overload (n = 8). HH homozygotes had higher [blood Pb] than did normal control subjects (5.6 +/- 0.6 microgram/dl vs 3.6 +/- 0.5 microgram/dl; p < 0.005); significantly increased mean [blood Pb] was observed in both male and female homozygotes. In heterozygotes, the mean [blood Pb] 4.1 +/- 0.5 microgram/dl) was intermediate between that of homozygotes and normal control subjects. The mean [blood Pb] of subjects with transfusion-induced iron overload (22 +/- 0.6 microgram/dl) did not differ significantly from that of normal controls. The findings in homozygotes could to be related to age, serum ferritin concentration, presence or absence of iron loading, or the extent of therapeutic phlebotomy. Lead exposure in all of our subjects was due primarily to ambient sources. Analysis of our data, when using a mathematical biokinetic model of human lead metabolism, suggests that the most likely explanation for our findings is that homozygotes (and, to a lesser extent, heterozygotes) absorb increased quantities of lead, a conclusion that corresponds to the increased absorption of iron and cobalt previously documented in homozygotes.

Radioimmunometric quantification of surface lactoferrin in blood mononuclear cells

A radioimmunometric method was developed for the quantification of lactoferrin molecules natively bound to blood monocyte and lymphocyte surfaces and the estimation of the surface lactoferrin-binding capacity of these cells after their incubation with exogenous lactoferrin. Values of surface lactoferrin obtained were greatest for monocyte-rich isolates (9,168 +/- 1,713 molecules/cell; n = 19). The values of monocyte surface lactoferrin for males were similar to those of premenopausal females (8,980 +/- 2,378 (n = 8) and 9,427 +/- 2,606 molecules/cell (n = 11), respectively), but males had slightly lower values of monocyte surface lactoferrin binding capacity than did premenopausal females (10,447 +/- 2,478 molecules/cell versus 15,958 +/- 3,731 molecules/cell, respectively; p > 0.05). Expressed as saturation of the monocyte surface lactoferrin binding capacity, values of 97.2% +/- 22.6% for males and 76.6% +/- 14.3% for females were calculated. Intermediate values of surface lactoferrin were found in B-lymphocyte-rich isolates from five patients with B-cell chronic lymphocytic leukemia. In T-lymphocyte-rich preparations, there were low levels of native lactoferrin expression (154 +/- 63 molecules of lactoferrin/cell; 3 isolates). The present technique should permit additional quantitative studies of mononuclear cell surface lactoferrin to determine the role of lactoferrin surface binding and analyses of factors that modulate this binding.

Neutrophil function in chronic neutrophilic leukemia: defective respiratory burst in response to phorbol esters

Functional analyses were performed on neutrophils isolated from 6 patients from two institutions who displayed features of chronic neutrophilic leukemia (CNL). These neutrophils demonstrated a consistent deficiency (44 +/- 8% of control values) in superoxide anion (O2-) production in response to the phorbol ester, phorbol myristate acetate (PMA). O2- production in response to chemotactic peptides was near normal (82.3 +/- 10.7% of control values). Bacterial killing was normal in the two patients studied, and chemotaxis was diminished in response to zymosan-activated plasma and to high concentrations of chemotactic peptides in the patients studied. Cytosolic C kinase activity was decreased in one of the two patients studied. These results suggest that a deficient O2- release in response to PMA is a hallmark of neutrophils in CNL and may provide a diagnostic indicator of this condition.

Urticaria pigmentosa and preleukemia: evidence for reactive mast cell proliferation

A 64-year-old man had urticaria pigmentosa and myelodysplasia (refractory anemia with excess blast cells; partial trisomy 8 syndrome) without increased numbers of marrow mast cells. Clonal marrow assays in agar demonstrated normal to increased colony-forming units of granulocytes/macrophages. In long-term liquid cultures containing mast cell growth factor (interleukin 3), his marrow cells proliferated after 3 weeks to produce abnormal myeloid precursors similar to those in the corresponding marrow aspirate specimen. Cells with basophilic-staining granules were less abundant in comparison with normal marrow specimens cultured similarly. These results suggest that the mast cells in this patient are not of the same clone as the preleukemic marrow cells, although the possible marrow-cell origin of urticaria pigmentosa mast cells cannot be excluded. Previous reports suggest that urticaria pigmentosa without systemic mastocytosis occurs as a nonspecific abnormality in a variety of myeloid, lymphoid, and nonhematologic malignancies. Our data also support this hypothesis that urticaria pigmentosa is a reactive process rather than a manifestation of clonal proliferation of the primary malignancy.

Immunoreactive lactoferrin in resting, activated, and neoplastic lymphocytes

Lactoferrin (Lf) in lymphocytes was assessed with immunofluorescence/flow cytometric technique. Surface Lf was detected primarily among B-cell-enriched preparations. Tonsillar B-cells of different densities expressed surface Lf similarly. Very small percentages of CALLA+ ALL, HCL, or EBV-transformed B-cells expressed surface Lf, whereas B-CLL lymphocytes had the highest percentages of surface Lf positivity. Few resting, cultured, or neoplastic T-lymphocytes expressed Lf. The pattern of immunofluorescence and analyses of surface and total cellular immunoreactive Lf indicated that Lf is associated primarily with the lymphocyte surface. The percentage and/or intensity of surface Lf-specific fluorescence were not significantly altered in B- or T-cells by incubation with physiologic concentrations of differric Lf, and the percentages of Lf-positive cells detected in respective subjects remained stable over time. Surface Lf positivity was unrelated to the expression of other surface antigens (except those marking B- or T-cell lineage) or cell cycle. Expression and/or binding of Lf in B-lymphocytes may become increased during certain stages of cell maturation.

Tumor lysis syndrome in nonhematopoietic neoplasms

A 57-year-old woman developed severe tumor lysis syndrome characterized by acute hyperuricemic nephropathy, hyperphosphatemia, hyperkalemia, and hypocalcemia after therapy with cyclophosphamide, methotrexate, and 5-fluorouracil for metastatic infiltrating ductal carcinoma of the breast involving the chest wall, lungs, pleurae, and liver. Similar metabolic derangements developed in a 58-year-old man after therapy with vinblastine and bleomycin for classical seminoma with widespread, bulky lymph node metastases. Both patients died of infection associated with granulocytopenia within 2 weeks after the initiation of chemotherapy despite significant improvement in the manifestations of tumor lysis syndrome. At autopsy, there was anatomic evidence of extensive tumor necrosis in each case. The pathogenesis of this problem in the present cases is discussed, and this unusual complication of the treatment of nonhematopoietic malignancies is reviewed.

Myeloblastoma of the brain

Two patients developed intraparenchymal myeloblastomas (granulocytic sarcomas) of the brain. One patient with acute myelogenous leukemia in hematological remission had multiple myeloblastomas in the cerebrum and thalamus. The second patient, who had Philadelphia-chromosome-positive chronic myelogenous leukemia, developed a solitary lesion of the cerebrum without systemic evidence of blastic transformation of leukemia. By light microscopy, each biopsy specimen revealed a tendency for the malignant cells to appear in perivascular locations, and the presence of cytoplasmic naphthol AS-D chloroacetate esterase activity in some cells. Ultrastructural analysis demonstrated the presence of primary granule-like lysosomal structures in these cells, confirming their granulocytic origin. The lack of continuity of the myeloblastomas with the dura mater and the perivascular clusters of blast cells suggest that the pathogenesis of these lesions in the present cases could best be accounted for by the direct, hematogenous spread of mitotically competent leukemic cells to brain parenchyma.

Retention of radiolead by human erythrocytes in vitro

An in vitro method was developed to assess human erythrocyte lead uptake and release directly, rapidly, and reproducibly; the technique requires small aliquots of blood and uses silicone fluid to separate erythrocytes from their suspending media. Uptake occurred rapidly and was directly related to temperature. Increasing quantities of available elemental lead were associated with increasing absolute quantities but decreasing percentages of uptake. Low values of pH diminished the uptake and enhanced the release of radiolead by erythrocytes, and could be correlated with diminished lead-hemoglobin binding para-Chloromecuribenzoate increased and dithiothreitol inhibited radiolead uptake but neither compound affected lead release, suggesting that sulfhydryl groups are important for lead binding to the erythrocyte. Cyanamide and N-ethylmaleimide did not significantly affect the net uptake or release of radiolead. Calcium disodium EDTA, penicillamine, and dimercaprol significantly reduced lead uptake, although only incubation with dimercaprol resulted in a net removal of lead from erythrocytes. Iron and ceruloplasmin significantly decreased radiolead uptake, but inorganic metal cations other than iron, hyperosmolarity, human serum albumin, cholesterol, and transferrin had no significant effect on uptake or release.

Prevalence of granular lymphocyte proliferation in patients with rheumatoid arthritis and neutropenia

PURPOSE

Granular lymphocyte proliferation and neutropenia with or without splenomegaly occurs with unknown frequency in rheumatoid arthritis. We decided to evaluate the prevalence of Felty's syndrome and granular lymphocyte proliferation among patients with rheumatoid arthritis and to determine the fraction of patients with granular lymphocyte proliferation who also had rheumatoid arthritis.

PATIENTS, METHODS, AND RESULTS

We retrospectively analyzed 1,053 cases of rheumatoid arthritis and 13,505 marrow examination reports for the decade 1978 to 1987. Among patients with Felty's syndrome rheumatoid arthritis with neutropenia/leukopenia, and rheumatoid arthritis with splenomegaly, we identified 18 patients with neutropenia as a manifestation of rheumatoid arthritis. We also identified marrow examinations in 150 patients with rheumatoid arthritis. Using blood counts, microscopy of marrow, and surface antigen analysis of mononuclear cells, we determined that 12 patients had typical Felty's syndrome and six had granular lymphocyte proliferation, representing prevalences of 1.1 percent and 0.6 percent, respectively. No patient had granular lymphocyte proliferation without neutropenia.

CONCLUSION

Granular lymphocyte proliferation and neutropenia with or without splenomegaly in rheumatoid arthritis commonly resembles typical Felty's syndrome. Further, the six patients with granular lymphocyte proliferation represent 20 percent of our institution's patients with granular lymphocyte proliferation, supporting the previously described common association of this disorder with rheumatoid arthritis. The relatively large fraction of deaths (due to malignancy and infection) among the patients with typical Felty's syndrome suggests that their mean survival may be comparatively less than in those with granular lymphocyte proliferation.

Neoplastic meningitis with eosinophilic pleocytosis in Hodgkin's disease: a case with cerebellar dysfunction and a review of the literature

A 31-year-old man had Hodgkin's disease (stage IIA, nodular sclerosis) in apparent remission after radiotherapy. Nine months after the diagnosis of Hodgkin's disease, he developed neoplastic meningitis with eosinophilic pleocytosis and neurologic findings suggestive of peri-fourth ventricle infiltration. Morphologic and surface marker analysis of cerebrospinal fluid cells showed large numbers of T-lymphocytes and Reed-Sternberg variant cells positive for CD15, the Lex hapten expressed on myeloid cells and on a variety of malignant cells. Therapy with intrathecal methotrexate, oral dexamethasone, and cranial irradiation resulted in prompt resolution of his cerebrospinal fluid abnormalities and neurologic deficits. Ten months after the diagnosis of eosinophilic meningitis, systemic relapse of Hodgkin's disease occurred in right iliac and inguinal lymph nodes. The diagnosis, pathogenesis, and therapy of this unusual complication of Hodgkin's disease are reviewed.

Neutrophil lactoferrin content: variation among mammals

Lactoferrin (Lf) in blood and/or marrow neutrophils was semiquantified using indirect immunofluorescence technique in nine mammalian species. Neutrophil iron-binding reactivity (NFeBR), which corresponds primarily to Lf, was also visualized and semiquantified using functional cytochemical (FeNTA-AF) technique at the light microscopic level in these nine and in an additional fifteen mammalian species, and in selected species at the ultrastructural level. Neutrophil immunoreactive Lf was positively correlated with total cellular and granule content of NFeBR among these nine species, and with previously reported concentrations of neutrophil Lf quantified by radioimmunoassay. Relative levels of Lf in neutrophil extracts from rat, hamster, and human were confirmed using SDS-polyacrylamide gel electrophoresis and immunoblotting. Relatively high levels of immunoreactive neutrophil Lf and/or NFeBR were observed in carnivores (ten species) and primates (six species). Among rodents (five species), the levels were variable, and the artiodactyls (four species) studied had low levels. These results demonstrate that neutrophil Lf levels vary widely among mammalian species. In addition, FeNTA-AF technique provides a rapid means of evaluating animals for relative quantities of neutrophil Lf.

Iron-binding reactivity in mature neutrophils: relative cell content quantification by cytochemical scoring

We have developed a technique that permits evaluation and semi-quantification of iron-binding function in mature neutrophils. Neutrophil iron-binding reactivity (NFeBR) visualized using the iron nitrilotriacetate-acid ferrocyanide technique was rated 0 to 5+ in 100 segmented cells; the ratings were totaled to yield a score (NFeBRS). Males and post-menopausal females had significantly higher NFeBRS than pre-menopausal females. Neonates had low values, and a homogeneous distribution of NFeBR among neutrophils. In pregnancy and acute infection, NFeBRS were significantly increased. In a patient with congenital lactoferrin (Lf) deficiency, the NFeBRS was very low. In Ph1-positive chronic myelogenous leukemia, 13 of 17 patients had low NFeBRS due to decreased NFeBR, which was heterogeneously distributed among mature neutrophils. By ultrastructural analysis of mature neutrophils in two such patients, the stain deposits in FeBR-positive granules were of normal intensity, but the numbers of positive granules were decreased in many cells. NFeBRS were also low in 12 of 23 patients with other myeloproliferative disorders, and in seven of 15 patients with acute non-lymphoblastic leukemia, but in only seven of 63 patients with other neoplasms. NFeBRS were significantly correlated (p less than 0.008) with values of neutrophil Lf content quantified by immunologic assays in a wide variety of conditions and over a broad range of values. These results augment observations of neutrophil Lf made using immunological methods.

Assessment of total immunoreactive lactoferrin in hematopoietic cells using flow cytometry

Cell-associated lactoferrin (Lf) was analyzed using a new method involving cell permeabilization, indirect immunofluorescence staining, and flow cytometry. Statistical techniques to evaluate the results for percentage of positive cells, relative fluorescence and homogeneity of Lf distribution were also devised. Most normal adult neutrophils (97.1 +/- 0.3% (SEM), range 92.7-99.6%, n = 41) had brilliant fluorescence homogeneously distributed among the cells. There was significantly greater homogeneity of neutrophil Lf distribution in post-menopausal than pre-menopausal females. In chronic myelogenous leukemia (n = 13) and cord blood (n = 7), fractions of Lf-positive neutrophils were decreased (77.3 +/- 7.5%, range 13.3-96.3%; 71.4 +/- 9.3, range 32.0-95.6%, respectively). Normal monocyte-rich isolates had moderate fluorescence (28.7 +/- 3.6%, range 9.3-76.8%, n = 22). Among blood lymphocyte-rich preparations, 13.1 +/- 1.3% of cells had weak positivity (range 4.9-26.6%, n = 19); monoclonal B and T lymphocytes had similar parameters. No other cells had detectable Lf. Our results were significantly correlated with those obtained manually (r = 0.98, P less than 0.001), and are consistent with Lf quantity and distribution determined using other methods.

Ultrastructural silver enhancement of Prussian blue-reactive iron in hematopoietic and intestinal cells

Prussian blue has been widely used to localize iron in a variety of tissues at the light and electron microscopic level. In the present study, thin sections of human marrow and blood cells and rat duodenal cells were exposed to silver proteinate (SP) after staining en bloc with acid ferrocyanide (AF), with and without prior iron saturation using iron nitrilotriacetate (FeNTA). Silver deposition was observed over Prussian blue-reactive sites and significantly enhanced sites of minimal AF and FeNTA-AF staining. AF-SP stain deposits were present in the cytoplasmic matrix, granules, and occasionally on the surfaces of macrophages, monocytes, and erythroblasts. FeNTA-AF-SP stained additional cytoplasmic and surface sites in erythroblasts and stained neutrophil granules intensely. Duodenal epithelium from iron-loaded rats demonstrated strong AF-SP staining of ferric iron in microvilli, apical cytoplasmic matrix, and lateral membranes. Similar preparations from iron-replete rats stained sparsely; however, intense AF-SP staining was observed after iron saturation with FeNTA. SP similarly enhanced luminal ferrous iron deposits stained with acid ferricyanide in rats given intraluminal ferrous iron. AF-SP stain deposits were removed by exposure of thin sections to NH4OH, KCN, or HNO3 but were not affected by prior exposure to HIO4 or NaBH4, consistent with a silver cyanide or complex stain precipitate rather than reduced silver or silver ferriferrocyanide. SP enhancement of Prussian blue allows identification of reactive sites not readily visualized with AF or FeNTA-AF alone, and offers the potential for differentiating AF staining from other deposits or organelles of comparable density.

Modulation of the development of bleomycin-induced fibrosis by deferoxamine

Bleomycin is an antineoplastic compound which produces a time- and dose-dependent pulmonary fibrosis. The mechanisms which cause this fibrosis are not known. The ability of bleomycin to produce oxygen radicals in the presence of iron and molecular oxygen appears to be related to the fibrosis. Previous studies, which have examined single time points utilizing the ferric ion chelator deferoxamine and iron-deficient diets, suggest that iron plays a central role in bleomycin-induced pulmonary fibrosis. Therefore, the present study was designed to determine the effects of deferoxamine on the development of bleomycin-induced pulmonary fibrosis. Deferoxamine pretreatment and daily injections resulted in a significant reduction in lung collagen content and lung lipid peroxidation 21 days after intratracheal bleomycin compared with bleomycin treatment alone. In addition deferoxamine treatment significantly inhibited lung DNA increases at 4, 7, and 14 days after bleomycin treatment compared with bleomycin treatment alone. These data indicate that deferoxamine treatment reduces the development of bleomycin-induced pulmonary fibrosis in the later phase. The mechanism might be by the prevention of iron-catalyzed, free-radical formation and modulation of some cellular functions.

Differential staining of neutrophils and monocytes: surface and cytoplasmic iron-binding proteins

Lactoferrin, transferrin, and ferritin were systematically visualized and semiquantified in neutrophils and monocytes/macrophages using indirect immunofluorescence and functional cytochemical techniques. They localized on cell surfaces and within the cytoplasm at the light and electron microscopical levels. In normal subjects, subpopulations of blood neutrophils and monocytes had surface lactoferrin, but little surface transferrin or ferritin was observed on these cells. Most neutrophils had brilliant granular cytoplasmic positivity for lactoferrin; variable fractions of monocytes had weak to moderate diffuse cytoplasmic lactoferrin staining localized most prominently to the cytoplasmic matrix. Most neutrophils had cytoplasmic ferritin, but few had cytoplasmic transferrin, whereas larger subpopulations of monocytes had cytoplasmic staining reactions for both proteins. To analyse maturing cells, the iron nitrilotriacetate-acid ferrocyanide method was adapted for the light microscopical analysis of neutrophils and monocytes/macrophages in soft agar culture. Further, a combined stain that visualizes iron nitrilotriacetate-acid ferrocyanide reactivity and alpha-naphthyl butyrate esterase activity in cells in blood and marrow smears was developed. The relative quantities and subcellular distribution of iron-binding proteins in neutrophils and monocytes/macrophages defined by the present methods can be correlated with biochemical, maturational, and functional properties of these cells.

Effect of iron deficiency on bleomycin-induced lung fibrosis in the hamster

Bleomycin produces a dose- and time-dependent interstitial pulmonary fibrosis in humans, and is widely used to produce an animal model for the study of interstitial pulmonary fibrosis. The mechanism(s) for bleomycin-induced pulmonary fibrosis is (are) unknown, but the production of oxygen radicals by a ferrous ion-molecular oxygen pathway might be related to the fibrosis. Therefore, we studied the effect of iron deficiency on the biochemical, inflammatory, and morphologic parameters of bleomycin-induced pulmonary fibrosis in the hamster. Mild iron deficiency was induced in hamsters by bleeding via the retro-orbital sinus and maintenance on an iron-deplete diet. After intratracheal administration of bleomycin (1 U), there was no accumulation of lung collagen in the iron-deficient bleomycin-treated animals. In comparison, iron-replete animals treated with bleomycin exhibited a significant (p less than 0.01) increase in lung collagen. In addition, bleomycin-treated iron-replete animals had increased lung lipid peroxidation (p less than 0.05), whereas bleomycin-treated iron-deficient animals did not (p greater than 0.05). Lung DNA and morphometric estimates of the lesion severity were significantly increased in both iron-replete and iron-deficient bleomycin-treated animals. These data indicate that iron deficiency is associated with a reduction in the severity of bleomycin-induced pulmonary fibrosis, possibly by the prevention of iron-catalyzed oxygen-radical formation and lipid peroxidation.

Peroxidase-containing microgranules in human neutrophils: physical, morphological, cytochemical, and secretory properties

A microgranule fraction, isolated from human neutrophils by using a novel high-resolution Percoll density gradient system contained granules with the lowest density and diameter when compared with 12 other isopycnic granule fractions. Ultrastructurally, from 34% to 50% of the microgranules showed homogeneous diaminobenzidine (DAB) staining under conditions for localizing peroxidase reactivity. The presence of myeloperoxidase (MPO) was further confirmed by biochemical and spectral analysis and immunodiffusion methods. Periodate-thiocarbohydrazide-silver proteinate (PA-TCH-SP) intensely stained vicinal glycols in the matrix of greater than 97% microgranules in contrast to the weak or absent staining seen in larger primary granules. Directly sampled segmented neutrophils contained small DAB- and PA-TCH-SP-positive granules, which often appeared in clusters. These DAB-positive microgranules selectively remained within the cells after stimulation of exocytosis with the calcium ionophore A23187. The enriched DAB-positive microgranule fraction recovered from A23187-treated cells also contained lysozyme and beta-glucuronidase but lacked vitamin B12 binding protein activity. A similar small, DAB- and PA-TCH-SP-positive granule type was also identified in normal promyelocytes and was the predominant or only granule type observed in leukemic or preleukemic myeloid cells from four patients. This study demonstrates a unique subpopulation of MPO-containing microgranules in normal and leukemic human myeloid cells that are distinguished from (other) primary granules by their extremely low density, small size, content of complex carbohydrates, and resistance to secretion.

Cytochemistry and ultrastructural morphometry of cultured HL60 myeloid leukemia cells

Cultured human myeloid leukemia (HL60) cells were characterized using ultrastructural cytochemical methods and differences identified when cells were compared for low (17 to 47), middle (69 to 100), and high (214 to 244) passages or to normal promyelocytes aspirated from bone marrow. Endoplasmic reticulum and transition structures (pre-Golgi compartment) of HL60 cells stained positively for peroxidase using diaminobenzidine but stained sparsely for reducing groups with osmium-zinc iodide. Staining of Golgi elements was relatively indistinct with diaminobenzidine and strong with osmium-zinc iodide, in comparison to freshly harvested promyelocytes which have intense diaminobenzidine and osmium-zinc iodide staining of the pre-Golgi and Golgi compartments. Cytoplasmic polyribosomes were more numerous in middle and high passage cells, whereas dilatation of endoplasmic reticulum was less prominent in these cells. The mean granule size was significantly increased in low passage cells, and staining of peroxidase was more prominent by light and electron microscopy when compared to high passage cells. Cytoplasmic granules demonstrated strong complex carbohydrate staining, indicating a lack of granule maturation in HL60 cells. Terminally differentiated myeloid cells were more frequent in low passage samples, and some neutrophil granule maturation appeared to occur within these cells, whereas all eosinophil granules consistently remained immature with intense complex carbohydrate staining and lack of crystalloid formation. These studies demonstrate significant differences between HL60 cells and normal promyelocytes, and also passage-dependent maturational differences in HL60 cells. These differences should be considered in evaluating parameters of cell growth and maturation and in the biochemical and enzymatic characterization of these cells.

Seasonal changes in lead absorption in laboratory rats

A retrospective study of the relationship of season to the absorption of radiolead in laboratory rats was performed using data representing 305 animals from 36 experiments over 6 calendar years. Male Wistar rats weighing 200 to 250 g were given 1 microgram of radiolabeled lead in an aqueous solution, pH 4.0, in isolated small intestine, and absorption of the radiolead was quantified after a 4-hour interval using whole-body counting. Similar values of absorption occurred in the summer (June-August) and fall (September-November), 20.51 +/- 1.11% (1 SEM) and 23.0 +/- 1.23% of the test dose, respectively, but significantly lower values occurred in the winter (December-February) and spring (March-May): 16.51 +/- 0.77%, p less than 0.01, and 11.87 +/- 0.99%, p less than 0.01, respectively. Harmonic analysis yielded an excellent approximation of the mean quarterly absorption data. The resulting cosine function had a period of 4.08 +/- 0.05 quarter-years with an amplitude of 7.32 +/- 1.06%; predicted peak absorption values fell precisely between summer and fall. The relationships of these observations to possible mechanisms of lead absorption and to summertime epidemics of lead poisoning in children are discussed.

Malignant hemangiopericytoma: computed tomography and magnetic resonance imaging

Computed tomography and magnetic resonance imaging of a malignant hemangiopericytoma in a 58-year-old woman are described. The tumor was initially found in the abdomen and resected 34 years ago, but recurred 18 years later, followed by repeated recurrence and eventually metastasis to the lung and then to the liver. The lung nodules were round or oval, homogeneous, and well circumscribed while the massive tumor in the right lobe of the liver was poorly delineated with irregular areas of cystic necrosis. With proper setting of the repetition time and echo delay, the metastatic tumor became distinct from the uninvolved hepatic tissue on magnetic resonance imaging. In this case computed tomography and magnetic resonance imaging were complementary in evaluation of such a tumor.