Presence of accessory abductor digiti minimi muscle in two cadavers.

During routine cadaveric dissection, accessory hypothenar muscles were incidentally discovered in two cadavers, both males, aged 86 and 92. Both muscles originated from the palmaris longus tendon in the distal portion of the forearm and were identified as accessory abductor digiti minimi (AADM) muscles, based on their association with abductor digiti minimi. While AADM is a common variant in the antebrachium, it is less typical for them to originate from the palmaris longus tendon. The presence of such an AADM could complicate surgical procedures requiring resection of the palmaris longus tendon. Moreover, the surrounding neurovasculature - namely the ulnar nerve as it passes through the ulnar canal between the pisiform and hook of the hamate - could be compressed by contractions of an AADM with such a proximal origin. This can manifest as ulnar neuropathies resulting in pain, weakness, or protracted flexion of the fourth and fifth digits (ulnar claw). Our description of these muscles adds to previous accounts of variation of the palmaris longus and abductor digiti minimi muscles while considering potential clinical implications.

Early age-of-onset iron overload and homozygosity for the novel hemojuvelin mutation HJV R54X (exon 3; c.160A-->T) in an African American male of West Indies descent.

An African American male of West Indies descent was diagnosed to have elevated transferrin saturation, hyperferritinemia, severe iron deposition in hepatocytes, and hepatic cirrhosis at age 4. He was treated with serial phlebotomy to maintain a normal serum ferritin concentration thereafter. We evaluated him at age 23 and confirmed that he had normal serum ferritin levels, severe iron deposition in hepatocytes, hepatic cirrhosis, and portal hypertension. He did not have endocrinopathy, cardiomyopathy, or arthropathy. He was homozygous for the novel hemojuvelin (HJV) premature stop-codon mutation R54X (exon 3; c.160A-->T). He did not have either HFE C282Y, H63D, or S65C, or deleterious coding region mutations of SLC40A1, TFR2, or HAMP. His erythrocyte measures and hemoglobin electrophoresis were consistent with alpha-thalassemia trait. We conclude that homozygosity for HJV R54X accounts for his severe, early age-of-onset hemochromatosis; his phenotype was probably modified by serial phlebotomy therapy.

Suppression of in vitro monoclonal human rheumatoid factor synthesis by antiidiotypic antibody. Target cells and molecular requirements.

Previous studies have indicated that antiidiotypic antibody can modulate expression of idiotype both in vivo and in vitro. Although the precise mechanisms underlying modulation of idiotype expression by antiidiotype remains unclear, a requirement for intact IgG antiidiotypic antibody has been suggested and T cells appear to play a role in some systems. We have studied peripheral blood mononuclear leukocytes (MNL) from a patient with a B cell lymphoma and a circulating IgMK rheumatoid factor (RF) paraprotein in an effort to delineate mechanisms involved in regulation of idiotype expression by antiidiotypic antibody. 1-10% of MNL from this patient could be cytoplasmically stained with specific F(ab')2 antiidiotypic antibody. MNL from the patient spontaneously synthesized IgM RF in culture that possessed the same idiotype as the circulating IgM RF paraprotein. Production of RF by MNL was suppressed by pretreatment with either intact IgG or the F(ab')2 fragments of antiidiotypic antibody (50% inhibitory concentration was 0.2 and 1.1 micrograms/culture, respectively). In contrast, the Fab' fragment of antiidiotypic antibody was not inhibitory (up to 57 micrograms/culture) despite retaining demonstrable antiidiotype activity. Suppression of RF production was not observed over the same concentration range with the IgG or F(ab')2 fractions of a non-cross-reactive antiidiotypic antibody prepared against another monoclonal IgMK RF paraprotein or with IgG or F(ab')2 fractions prepared from normal rabbit serum. Inhibition of RF production by antiidiotypic antibody did not require T cells. Antiidiotypic antibody decreased intracellular and extracellular levels of idiotype indicating diminished synthesis of idiotype by the patient's B cells. Synthesis of IgM RF by MNL obtained from unrelated donors was not suppressed by the antiidiotypic antibody specific for the patient's paraprotein. The results indicate that (a) antiidiotypic antibody is capable of directly suppressing human B cell release of idiotype, (b) the bivalent antigen-binding fragment (F[ab']2) of antiidiotypic antibody is sufficient for mediating such suppression, (c) an intact Fc portion of antiidiotypic antibody enhances suppression of idiotype, and (d) antiidiotypic antibody inhibits idiotype expression by suppressing synthesis of idiotype.

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.

Coagulation testing of Hickman catheter blood in patients with acute leukemia.

We quantified coagulation parameters in vitro using standard automated methods in 12 adult patients with acute leukemia who also had Hickman catheters (HC). Test results from simultaneously obtained HC blood and control peripheral venous blood (PB) samples were compared in the respective patients. Heparin solutions (100 U/mL, US Pharmacopoela) used to prevent the formation of clots within the HC appeared to cause, to a significant degree, spuriously elevated levels of fibrin degradation products (FDP), decreased levels of fibrinogen (FBG), and prolongations of the prothrombin time (PT) and activated partial thromboplastin time (PTT) in the first 10 mL of HC blood. The second 10 mL sample from the HC showed that FBG levels were comparable with those demonstrable in PB samples, as were levels of FDP in eight of 12 cases. Both PT and PTT times, however, remained significantly prolonged. An alternative maneuver for obtaining HC blood studied in four patients showed significant prolongation of PTT values in the second 10-mL sample despite levels of FDP, FBG, and PT similar to those in the PB. Because heparin contamination of HC blood can mimic the laboratory findings of disseminated intravascular coagulation or other coagulopathies in patients with acute leukemia, we suggest that only values obtained from PB be used for interpretation of coagulopathy in these patients.

Nonhemolytic, noninfectious transfusion reactions.

The delivery of optimal transfusion therapy requires that the physician first have a thorough understanding of his patient's disease and prior transfusion history. Sometimes the need for blood product administration is more apparent than real. In the selection of necessary therapy, particular blood components, their volumes, and the timing of their administration should be carefully planned. The transfusion of whole blood, particularly as single-unit transfusions, is rarely indicated. Often forgotten, autotransfusion represents a means whereby many subjects who have repeated, unusual, or severe reactions may receive safe treatment. An appreciation of the frequency and manifestations of transfusion-related problems permits effective treatment of ongoing reactions. The prophylactic measures which should be taken against future reactions in most patients are specific, and are the responsibility of the clinician, based upon his bedside observations and laboratory studies. Problems should be discussed with either a hematologist, pathologist, or blood banking expert without hesitation. These guidelines help conserve a precious resource and assure that safe, effective, and economical transfusion therapy is available for all patients in need.

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.

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.

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.

Diagnosis of hemochromatosis probands in a community hospital.

PURPOSE: To evaluate factors that lead to the diagnosis of hemochromatosis probands in a community hospital, including education of physicians about hemochromatosis and iron overload, specialty of physicians, diagnostic indicators of hemochromatosis, and clinical manifestations of hemochromatosis probands. PATIENTS AND METHODS: We conducted a hemochromatosis education program for health care personnel associated with a community hospital and the public during 1990 to 1994. Data on physicians who diagnosed probands, diagnostic indicators of hemochromatosis, and manifestations of hemochromatosis and associated illnesses were tabulated. Iron grades of all hospital liver biopsy specimens obtained from Caucasian subjects during 1990 to 1994 were also analyzed. RESULTS: We identified 162 hemochromatosis probands; 66.7% were diagnosed by physicians who participated in our education program. Primary care and internal medicine subspecialty physicians diagnosed 66.7% and 29.6% of probands, respectively, based on elevated serum iron parameters and hepatic enzyme concentrations (51.9% and 36.4% of probands, respectively). Iron overload occurred in 90.7%, and was associated with clinical manifestations in most. Of 844 hospital liver biopsy specimens from Caucasians, 8.5% had increased iron grades; 4.6% represented hemochromatosis. CONCLUSIONS: Physicians with current education readily diagnose hemochromatosis probands during routine health care delivery, but most probands identified in this manner have iron overload. Our results suggest that community physicians and hospitals could contribute substantially to hemochromatosis screening programs, permitting detection of more homozygotes before the development of iron overload.

Intravenous iron dextran therapy in patients with iron deficiency and normal renal function who failed to respond to or did not tolerate oral iron supplementation.

PURPOSE: To evaluate the safety and effectiveness of using 500-mg doses of iron as intravenous iron dextran after premedication with diphenhydramine, cimetidine, and dexamethasone. SUBJECTS AND METHODS: We treated 135 iron-deficient adults (26 men, 109 women) with normal renal function (serum creatinine level

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.

A survey of 2,851 patients with hemochromatosis: symptoms and response to treatment.

PURPOSE: Hemochromatosis is a genetic disorder of iron absorption that affects 5 per 1,000 persons and is associated with reduced health and quality of life. We sought to determine the type and frequency of symptoms that patients experienced before the diagnosis and the treatments that they received. METHODS: We mailed a questionnaire to 3,562 patients with hemochromatosis who were located using patient advocacy groups, physicians, blood centers, newsletters, and the Internet. RESULTS: Of the 2,851 respondents, 99% were white and 62% were men. Circumstances that led to diagnosis of hemochromatosis included symptoms (35%), an abnormal laboratory test (45%), and diagnosis of a family member with hemochromatosis (20%). The mean (+/- SD) age of symptom onset was 41 +/- 14 years. Symptoms had been present for an average of 10 +/- 10 years before the diagnosis was made. Among the 58% of patients with symptoms, 65% had physician-diagnosed arthritis and 52% had liver disease. The most common and troublesome symptoms were extreme fatigue (46%), arthralgia (44%), and loss of libido (26%). Physician instructions to patients included treatment with phlebotomy (90%), testing family members (75%), and avoiding iron supplements (65%). CONCLUSIONS: The diagnosis of hemochromatosis in most patients was delayed. Physician education is needed to increase the detection of patients with the disease and to improve its management.

Acute cryoglobulinemic renal failure after intravenous infusion of gamma globulin.

A 39-year-old woman had mixed IgM/IgG cryoglobulinemia, but was later found to have a lymphoma that produced an IgM kappa paraprotein with rheumatoid factor activity. With intermittent chlorambucil and prednisone therapy, the lymphoma was controlled for five years and she had no evidence of cryoglobulinemia. Because of the presence of intractable pulmonary infection and hypogammaglobulinemia G, she was given an intravenous infusion of gamma globulin. Within 72 hours, renal failure and a sustained decrease in serum concentrations of IgM and IgG began concurrently. A kidney biopsy specimen obtained five days after the infusion showed hyaline "thrombi" in numerous glomerular capillaries and glomerular necrosis, consistent with acute, severe mixed cryoglobulinemic nephropathy. Immunostaining showed strong positivity for IgM, IgG, and light chains in glomerular capillary lumina and subendothelial sites; immunostaining with a monoclonal antiidiotypic antibody specific for the patient's paraprotein established the presence of the rheumatoid factor paraprotein in the deposits. These observations strongly suggest that complexes consisting of IgM kappa rheumatoid factor, IgG, and complement initiated the renal damage. Therefore, demonstrable serum rheumatoid factor activity in patients with B cell neoplasms should be considered a contraindication to the administration of intravenous gamma globulin.

Light microscopic, non-immunologic demonstration of iron-binding proteins in hematopoietic cells.

Iron-binding proteins were localized by their saturation with iron using iron nitrilotriacetate (FeNTA), maintenance of protein-iron-binding at specific values of pH, and visualization of the iron with acid ferrocyanide (AF). Human neutrophilic cells showed strong blue granular and diffuse cytoplasmic staining. Human mid- and late-stage erythroblasts showed moderate diffuse cytoplasmic staining. Monocytes and macrophages showed reactions similar to those seen with AF technique alone. Other hematopoietic cells showed minimal or no stain positivity. Nuclear positivity was not observed in any cells. Concanavalin A (ConA) treatment of purified neutrophils reduced their FeNTA-AF positivity; supernatants from these cells showed precipitin lines of identity with anti-lactoferrin (Lf) stainable with FeNTA and AF. Cellulose acetate electrophoresis of crude neutrophil extracts treated with [59Fe]NTA showed multiple protein bands; one band co-migrated with purified Lf and showed autoradiographic positivity. Rabbit heterophils and rat neutrophils showed less FeNTA-AF positivity, consistent with less Lf in these cells than in human neutrophils. Washing smears with 0.1 M citrate, pH 6.0, between FeNTA and AF treatments eliminated only erythroblast positivity; 0.1 M citrate, pH 4.0, ablated neutrophil staining as well. Ferritin-hemosiderin staining was preserved at both values of pH. These results indicate that FeNTA-AF technique specifically visualizes neutrophil Lf, and suggest that the observed erythroblast positivity is due to transferrin (Tf).

Ultrastructural cytochemical identification of the siderophilic enterocyte.

Specific iron-binding sites in the gut were visualized by the sequential incubation of glutaraldehyde-fixed specimens in iron nitrilotriacetate (FeNTA) and acid ferro-cyanide (AF). In rat duodenum, jejunum, and ileum, approximately half of the enterocytes from the crypt to the distal villus contained FeNTA-AF-reactive material. The staining intensity of individual enterocytes appeared to decrease progressively in more distal locations in the gut. Maximal FeNTA-AF staining was observed in cells in the upper half of the villus, and was localized primarily in microvilli, apical cytoplasm, and lateral membranes. In duodenal crypt cells, stain deposits were present primarily in the microvilli. FeNTA-AF stained sites in the cytoplasmic and microvillus matrix were approximately 100-fold greater in number than were sites of intrinsic iron stained with AF alone. FeNTA-AF and AF staining in human duodenal enterocytes was similar to that observed in rat duodena, demonstrating the applicability of this methodology to human samples. In rat duodena, the distribution of AF staining alone in specimens taken 10 min after the in vivo intraduodenal administration of FeCl2 was similar to that of FeNTA-AF staining in tissue from fasted animals not given iron. The distribution and frequency of iron-binding sites stainable with the FeNTA-AF method which occur in a subpopulation of enterocytes can be correlated closely with physiologic, histologic, and ultrastructural parameters of inorganic iron absorption previously reported.

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.

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.

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.