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S B Krantz

Publications and source records attributed to S B Krantz.

At least 73 records · Page 4Linked to original sources
PubMed1990

The pathogenesis of anemia in rheumatoid arthritis: a clinical and laboratory analysis.

Principal concepts concerning the anemia of RA are summarized in Tables 7 and 8. These concepts have been validated by our analysis of 93 anemic RA patients and by our review of the literature. The fact that anemia in RA may have one or more etiologies, occasionally in the same patient, mandates a reasoned approach to the analysis of anemia in every RA patient in whom it may occur. In particular, iron deficiency is common and determination of bone marrow iron content via an aspirate may be required for a definitive diagnosis. In those RA patients with anemia of chronic disease, the best therapy remains control of the underlying disease, most commonly with second line drugs and/or corticosteroids. The place for recombinant erythropoietin in the therapy of this anemia has not been defined; one specific role for erythropoietin may be in the preparation of RA patients for elective surgery, particularly hip arthroplasty, where correction of the anemia may either obviate the need for transfusion or may allow for donation of blood for purposes of autologous transfusion perioperatively. The pathogenesis of the anemia of chronic disease, as seen in RA anemia, is not completely understood. Inflammatory mediators, particularly the cytokines, appear to be important factors in the impairment of erythropoiesis. The mechanism by which these cytokines impair erythroid progenitor growth and hemoglobin production in developing erythrocytes is an important area for future study.

Anemia, Hypochromic↗
PubMed1990

Inhibition of human colony-forming-unit erythroid by tumor necrosis factor requires accessory cells.

Recombinant tumor necrosis factor (rTNF) inhibits erythropoiesis in vivo and in vitro. To study the mechanism of this inhibition, the effect of rTNF on highly purified human CFU-erythroid (E) (mean purity 63.5%), which were generated from peripheral blood burst-forming units-erythroid (BFU-E), was compared to its effect on unpurified human marrow CFU-E (mean purity 0.21%). Although growth of colonies from marrow CFU-E was inhibited by rTNF, no significant effect on purified BFU-E-derived CFU-E colony growth was found. Removal of accessory marrow cells by soy bean agglutinin (SBA) ablated the inhibition of marrow CFU-E colonies by rTNF. Inhibition of colony growth was then restored by adding back SBA+ cells, but not by adding T lymphocytes or adherent cells. Conditioned medium prepared from bone marrow mononuclear cells stimulated by rTNF inhibited the growth of colonies from highly purified BFU-E derived CFU-E resistant to direct inhibition by rTNF. These findings indicate that rTNF does not directly inhibit CFU-E, but requires accessory cells to decrease erythropoiesis. These accessory cells reside in the SBA+ cell fraction, but are neither T cells nor adherent cells. Therefore, in order to produce anemia, TNF must induce release or production of a factor that directly inhibits erythroid colony growth.

Bone Marrow Cells↗
PubMed1989

Treatment of the anemia of rheumatoid arthritis with recombinant human erythropoietin: clinical and in vitro studies.

Two anemic patients with rheumatoid arthritis were treated with recombinant human erythropoietin (EPO) for 5 months. Both patients showed significant increases in hematocrit, red cell volumes, and marrow erythroid and megakaryocyte progenitor cells. No significant toxic effects from EPO were observed. These data indicate that EPO may be effective in overcoming the pathogenetic factors that limit erythropoiesis in rheumatoid arthritis.

Adult↗
PubMed1989

Human colony-forming units-erythroid do not require accessory cells, but do require direct interaction with insulin-like growth factor I and/or insulin for erythroid development.

The presence of heterogeneous erythroid progenitor cells, contaminant cells, or serum may alter erythroid colony development in vitro. To obtain highly purified colony-forming units-erythroid (CFU-E), we cultured partially purified human blood burst-forming units-erythroid (BFU-E) in methylcellulose with recombinant human erythropoietin (rHuEPO) for 7 d and generated cells that consisted of 30-60% CFU-E, but no BFU-E. A serum-free medium was used that allowed development of the same number of erythroid colonies as serum containing medium, but with a greater percentage of larger colonies. This medium consisted of delipidated crystalline bovine serum albumin, iron saturated transferrin, lipid suspension, fibrinogen, thrombin, Iscove's modified Dulbecco's medium/F-12[HAM], and insulin plus rHuEPO. When CFU-E were cultured in a limiting dilution assay and the percentage of nonresponder wells was plotted against cell concentration, both serum-free cultures and serum-containing cultures yielded overlapping straight lines through the origin indicating that CFU-E development did not depend on accessory cells and that insulin acted directly on the CFU-E. Human recombinant interleukin 3 (IL-3) and/or granulocyte-macrophage colony-stimulating factor had no effect on CFU-E growth, while they markedly enhanced BFU-E growth. Physiological concentrations of recombinant human insulin-like growth factor I (IGF-I) enhanced CFU-E growth in the absence of insulin and, together with rHuEPO in serum-free medium, provided a plating efficiency equal to that of serum-containing medium. Limiting dilution analysis in serum-free medium with IGF-I showed a straight line through the origin indicating that IGF-I also acted directly on the CFU-E and not through an effect on accessory cells. These data demonstrate that CFU-E do not require accessory cells, but do require IGF-I and/or insulin which act directly on the CFU-E.

Adult↗
PubMed1989

Erythropoietin receptors in polycythemia vera.

The role of erythropoietin (EP) in polycythemia vera (PV) is controversial, with some experiments suggesting that erythroid progenitors in PV are exquisitely sensitive to EP and EP dependent, and others suggesting that PV progenitors are EP independent. We have examined the characteristics of the EP receptor (EP-R) on erythroid colony-forming cells (ECFC) from patients with PV. In contrast to normal ECFC, which have two classes of EP-R, with 20% showing high affinity (Kd = 0.13 nM; range, 0.04-0.20 nM) and the remainder lower affinity (Kd = 0.37 nM; range, 0.28-0.57 nM), PV ECFC show a single class of 851 low affinity EP-R with Kd = 0.72 nM (range, 0.36-0.85 nM). ECFC from patients with secondary (EP driven) polycythemia or anemia show two classes of EP-R (Kd = 0.18 and 1.10 nM, respectively). Attempts to remove tightly bound EP from putative high affinity EP-R in PV did not reveal any higher affinity receptors. Determination of molecular size by crosslinking showed two proteins of 90 and 100 kD similar to those seen with normal EP-R. These studies indicate the PV ECFC have EP-R that are structurally similar to normal EP-R but lack the higher binding affinity for EP.

Cross-Linking Reagents↗
PubMed1989

Receptors for erythropoietin in mouse and human erythroid cells and placenta.

High and lower affinity receptors for erythropoietin (EP) were initially identified on a very pure population of EP-responsive erythroblasts obtained from the spleens of mice infected with anemia strain of Friend virus (FVA). The structure of the receptor for EP in these cells was determined to be proteins of 100 and 85 Kd by cross-linking 125I-EP. In this investigation, studies on the receptors for EP were extended to other mouse erythroid cells and human erythroid cells as well as to the placentas of mice and rats. Only lower affinity receptors for EP were detected on erythroblasts purified from the spleens of mice infected with the polycythemia strain of Friend virus and a murine erythroleukemia cell line, both of which are not responsive to EP in culture. Internalization of 125I-EP was observed in both groups of cells. The structure of the receptor determined by cross-linking 125I-EP was two equally labeled proteins of 100 Kd and 85 Kd molecular mass in all these mouse erythroid cells. The structure of the receptor was found to be very similar in human erythroid colony forming cells cultured from normal blood. These cells respond to EP with erythroid maturation and were previously shown to have high and lower affinity receptors. Placentas from mice and rats were found to have only lower affinity receptors for EP, and when placental membranes were cross-linked to 125I-EP, the same 100 Kd and 85 Kd bands were found as seen in mouse and human erythroid cells. The structure of the receptor was similar in cells that have high affinity receptors (FVA-infected and human erythroid colony-forming cells) and nonresponsive erythroid cells and placenta that have lower affinity receptors, but only the cells with the high affinity receptors respond to the addition of EP with erythroid maturation.

Animals↗
PubMed1989

Erythropoietin: biology and clinical use.

Red cell production in vertebrates is controlled by a glycoprotein hormone known as erythropoietin (Ep), which is produced by the kidney in response to hypoxia and acts on the marrow to selectively stimulate erythropoiesis. The gene for Ep has recently been cloned, and highly pure recombinant human Ep (rHuEp) is now available in considerable quantity. This has led to a better understanding of many aspects of Ep biology and to clinical trials in humans. The amino acid sequence of Ep is now completely known, and the protein portion of the natural hormone and the recombinant product are identical. Both the natural hormone and rHuEp produced in Chinese hamster ovary cells are heavily glycosylated in a very similar manner. This glycosylation is not necessary for in vitro activity but is required for activity in vivo. Radioimmunoassays (RIAs), which use labeled rHuEp, have been developed and are sufficiently sensitive to measure normal plasma levels. However, since Ep exists in plasma in several forms that vary in their immunologic and biologic activities, the ability of a RIA to provide information on the pathogenesis of clinical disease may be limited and should be referenced to the polycythemic mouse assay. The kidney's role in the production of Ep has been greatly clarified. Studies using probes to Ep mRNA have shown that Ep is primarily made in the kidney and secreted as the intact hormone. Moreover, renal secretion appears to be regulated by the rate of synthesis of the hormone, which in turn is dependent on the rate of synthesis of Ep mRNA. The cells that produce Ep have been identified as peritubular interstitial cells that may be endothelial in origin. The initiating mechanism for hormone production appears primarily to involve recruitment of additional cells rather than increased production by individual cells. Ep primarily acts on the marrow to stimulate the growth and maturation of early cells in the erythroid lineage that are known as the burst-forming unit-erythroid (BFU-E) and colony-forming unit-erythroid (CFU-E). The BFU-E is a very early cell closely related to the pluripotent stem cell, while the CFU-E is a later cell close to the first recognizable erythroblast.(ABSTRACT TRUNCATED AT 400 WORDS)

Anemia↗
PubMed1988

Quantitation of specific binding of erythropoietin to human erythroid colony-forming cells.

Highly purified human erythroid colony-forming cells (ECFC), which consist predominately of colony-forming units-erythroid (CFU-E), were prepared from human blood and used to study the binding and processing of erythropoietin (Ep). When radioiodinated human recombinant Ep (125I-rEp) was incubated with these cells, binding was specific and saturable. Specific binding was directly proportional to cell concentration and did not occur with other human cells. Saturation of specific binding at 3 degrees C occurred at 1 nM (3.9/U/ml), and Scatchard analysis revealed two classes of binding sites on the cell surface. Of a total of 1,050 binding sites per ECFC, one-fifth had a Kd of 0.10 nM, while the remainder had a Kd of 0.57 nM. Specific binding was twofold greater at 37 degrees C than at 3 degrees C, and removal of surface-bound Ep with acid indicated that 125I-rEp was internalized into the cells after incubation at 37 degrees C. Further incubation at this temperature showed a decline of cellular radioactivity, with a release of small molecular weight degradation fragments into the medium. These studies demonstrate two classes of receptors for Ep on normal human ECFC. Internalization and degradation of EP occur, and the biologic effect of the hormone is produced by a small number of Ep molecules, as demonstrated in murine erythroid progenitor cells.

Adult↗
PubMed1988

Re-treatment of aplastic anemia with antithymocyte globulin or antilymphocyte serum.

Twenty-two patients with aplastic anemia were treated with antilymphocyte serum or antithymocyte globulin at Vanderbilt University and affiliated hospitals from 1980 to 1986. The median age was 42 (eight to 73 years); the male:female ratio was 8:14. Nineteen patients had severe aplastic anemia, and three had moderate disease. Twenty patients received antilymphocyte serum initially while two patients received antithymocyte globulin. Fifteen patients received fluoxymesterone 10 mg by mouth three times a day with antilymphocyte serum, and all received prednisone during the course of antilymphocyte serum or antithymocyte globulin. There were seven responses (31.8 percent) to the first course with four complete responses and three partial responses. Six of 15 patients who received fluoxymesterone showed a response, compared with zero of five treated without androgens (p less than 0.05). Eight patients with no initial response and a patient who experienced a relapse after a complete response were re-treated with either antithymocyte globulin (six) or antilymphocyte serum (three), with four of nine patients (44 percent) having a response (three complete responses, one partial response). Overall, 10 of 22 patients (45 percent) had a response (six complete responses, four partial responses). Median survival for those without a response is six months. Median survival for those with a response has not been reached, with follow-up ranging from 18 to 70 months. This study shows the benefit of a second cycle of antilymphocyte serum or antithymocyte globulin and a possible role for concomitant androgens in this treatment of aplastic anemia.

Adult↗
PubMed1988

Treatment of the anemia of predialysis patients with recombinant human erythropoietin: a randomized, placebo-controlled trial.

Recombinant human erythropoietin (r-HuEPO) was administered in two phases to 12 patients with chronic renal insufficiency (creatinine clearances of 0.17-0.51 ml/second [10-30 ml/minute]) and uremic anemia. In addition to the routine tests done as part of a multicenter clinical trial, our patients had serial red cell mass measurements, quantitation of bone marrow stem cells, and marrow cytogenetic analysis. During the first eight weeks (acute phase), an equal number of patients was randomized to placebo or one of three doses of r-HuEPO (50, 100 or 150 unit/kg intravenously three times weekly). All three patients receiving 150 unit/kg responded by increasing their packed cell volume (PCV) to the normal range within eight weeks. There were lesser responses in PCV at the two lower doses of r-HuEPO and no response in the placebo group. The 51Cr red cell mass also increased significantly in a dose-related manner in patients receiving r-HuEPO but did not change in the placebo group. Marrow studies revealed increases in erythroid, megakaryocyte, and granulocyte-monocyte progenitor cells in those patients on r-HuEPO, but no mutagenic effects were seen. Subsequently, ten patients received open label r-HuEPO. During this maintenance phase, all ten achieved or maintained a normal PCV. Several adverse events occurred, but none were definitely linked to r-HuEPO. Recombinant human erythropoietin is an effective and potent treatment of anemia caused by renal failure.

Aged↗
PubMed1988

Purification of erythroid progenitor cells and characterization of erythropoietin receptors.

Highly purified murine and human erythroid progenitor cells at the colony-forming unit-erythroid (CFU-E) stage of development were prepared and recombinant human erythropoietin (rEp) was radioiodinated with retention of full biological activity. Specific binding of 125I-rEp to the murine cells revealed 950 receptors on the cell surface. Three hundred had a Kd of 0.09 nM while the remaining receptors had a Kd of 0.57 nM. The human erythroid progenitor cells also had two classes of receptors with a similar number per cell and similar distribution. The high affinity receptors had a Kd of 0.15 nM while the remaining receptors had a Kd of 0.37 nM. 125I-rEp was rapidly internalized into the cells at 37 C and metabolized to iodotyrosine. When cross-linking of 125I-rEp to the murine erythroid progenitor cells was performed with disuccinimidyl suberate, two labelled bands of 100 and 85 kDa were demonstrated. The radioactivity of both bands was reduced when binding was performed in the presence of excessive unlabelled rEp indicating a specific interaction of 125I-rEp with the receptor.

Anemia↗
PubMed1988

Effects of recombinant erythropoietin on the concentration and cycling status of human marrow hematopoietic progenitor cells in vivo.

The concentration of human marrow progenitors CFU-E, BFU-E, CFU-GM, and CFU-Mk and the percentage of these progenitor cells in DNA synthesis were studied in nine patients with transfusion-dependent anemia of end-stage renal failure before and 2 weeks after treatment with human recombinant erythropoietin (Epo) at a dose of 150 to 300 U/kg intravenously three times per week. The concentration of CFU-E in the posttreatment marrow increased by a mean of 4.15-fold, BFU-E by 3.37-fold, CFU-GM by 1.86-fold, and CFU-Mk by 1.96-fold as compared with their respective concentrations in the pretreatment marrows. This increase in the concentrations of marrow progenitors was accompanied by almost a doubling of the percentage of these cells in DNA synthesis as assessed by the 3H-thymidine suicide technique. These observations demonstrate that at the progenitor cell level the human marrow responds to therapeutic doses of Epo as an organ rather than by a selective expansion of the erythroid cell line.

Anemia↗
PubMed1987

Binding and receptor-mediated endocytosis of erythropoietin in Friend virus-infected erythroid cells.

The binding of labeled erythropoietin (EP) to cell surface receptors and subsequent processing of the hormone within the cell was studied in erythroid cells procured from the spleens of mice infected with the anemia strain of Friend virus. These immature erythroid cells respond to EP in culture to differentiate into reticulocytes and erythrocytes. Radiolabeled EP (both iodinated and tritiated) binds to 800-1000 cell surface receptors on these cells at 4 degrees C. Using 125I-EP, we found that 300 of these cell surface receptors have a higher affinity for EP (Kd = 0.09 nM) than the remaining receptors (Kd = 0.57 nM). The number of molecules of EP bound per cell increased about 2-fold when binding was carried out at 37 degrees C. Treatment of the cell surface with pronase or removal of surface-bound EP with a low pH wash revealed that radiolabeled EP is internalized by the cells at 37 degrees C. Pulse chase experiments showed that degradation products of radiolabeled EP are released into the medium with a corresponding loss of label from the interior of the cell. Inhibitors of lysosomal function greatly reduced this degradation of 125I-EP. Since 180 of the 300 high affinity receptors and very few of the low affinity receptors are occupied at the concentration of EP which elicits the maximum biological response in these cells, we suggest that interaction of EP with the high affinity receptors are necessary for the full biological effect of the hormone. A different murine erythroleukemia cell line which does not differentiate in response to EP was found to have only the lower affinity binding sites for the hormone.

Ammonium Chloride↗