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Biomedical subjects

E Goldwasser

Publications and source records attributed to E Goldwasser.

At least 37 records · Page 2Linked to original sources
PubMed1995

Erythropoietin levels with treatment of obstructive sleep apnea.

The effect of nasal continuous positive pressure (CPAP) treatment on erythropoietin (EPO) was examined by measuring diurnal serum EPO levels before and twice (over the 3rd day and over 1 day on recall after > or = 1 mo of therapy) after initiation of treatment in 12 obstructive sleep apnea syndrome patients with normal hemoglobin, hematocrit, creatinine, blood urea nitrogen, and albumin levels. Over each study day, oxygen saturation was measured by an ambulatory pulse oximetry system. Patients spent 27 +/- 9% (SE) of time below oxygen saturation of 88% vs. 2.1 +/- 0.6% after initiation of nasal CPAP treatment (P < 0.01). The number of desaturation events per hour of sleep before nasal CPAP treatment was 62 +/- 6 vs. 9 +/- 2 with nasal CPAP (P < 0.01). EPO levels measured by radioimmunoassay were drawn every hour before and at 3 days (n = 9) and before and at recall (n = 0) after initiation of CPAP therapy. The mean serum EPO level was higher before treatment (61 +/- 14 mU/ml) than that at 3 days (38 +/- 10 mU/ml, P < 0.01) or at recall (32 +/- 7 mU/ml, P < 0.01). We conclude that nasal CPAP treatment of sleep-disordered breathing will reduce diurnal levels of EPO.

Adult↗
PubMed1994

Stable delivery of physiologic levels of recombinant erythropoietin to the systemic circulation by intramuscular injection of replication-defective adenovirus.

A number of inherited and acquired serum protein deficiencies including hemophilias A and B, diabetes mellitus, and the erythropoietin-responsive anemias are currently treated with repeated subcutaneous or intravenous infusions of purified or recombinant proteins. The development of an in vivo gene-transfer approach to deliver physiologic levels of recombinant proteins to the systemic circulation would represent a significant advance in the treatment of these disorders. Here we describe the construction of a replication-defective adenovirus (AdEF1hEpo) containing the human erythropoietin (hEpo) cDNA under the transcriptional control of the cellular elongation factor 1 alpha (EF1 alpha) promoter and the 4F2 heavy chain (4F2HC) enhancer. Neonatal CD-1 and adult SCID mice injected once intramuscularly (i.m.) with 10(7) to 10(9) plaque-forming units (pfu) of this virus displayed significant dose-dependent elevations of serum hEpo levels and increased hematocrits, which were stable over the 4-month time course of these experiments. Adenovirus injected i.m. remained localized at the site of injection and there was no evidence of either systemic infection or a localized inflammatory response. These results suggest that i.m. injection of recombinant replication-defective adenovirus vectors may serve as a paradigm for the treatment of human serum protein deficiencies.

Adenoviridae↗
PubMed1994

Transgenic mice carrying the erythropoietin gene promoter linked to lacZ express the reporter in proximal convoluted tubule cells after hypoxia.

Results on the localization of erythropoietin (Epo) synthesis in renal cells have been contradictory, implicating either interstitial or tubular cells. We fused the lacZ gene to a 7-kb DNA fragment of the mouse Epo gene encompassing a portion of the first intron, the first exon, and a 6-kb sequence of the 5'-flanking region. Transgenic mice carrying this construct show a low level of specific expression of the lacZ gene in proximal convoluted tubule (PCT) cells. Without hypoxia, no significant expression was detected in the liver. Hypoxia induced a large degree of lacZ expression, mainly in kidney PCT cells and to a lesser degree in liver. However, anemia induced lacZ expression in both kidney and liver. These findings indicate that, under these conditions, Epo is expressed in tubular cells, specifically PCT cells.

Anemia↗
PubMed1994

Effects of butyrate on the erythropoietin receptor of cell line IW201.

The murine erythroleukemic cell line, IW201, normally expresses only low-affinity erythropoietin receptors. Exposure of these cells for 48 hours to sodium butyrate results in a change in receptor kd from about 600 pmol/L to 100 to 200 pmol/L. This change in affinity is accompanied by downregulation of both receptor number and receptor mRNA. Cells exposed to sodium butyrate for 2 hours show a similar change in kd but no change in receptor number. The butyrate effect on kd at 2 hours is abrogated by either cycloheximide or actinomycin D. These data indicate that an accessory protein induced by sodium butyrate is responsible for high-affinity binding of erythropoietin.

Animals↗
PubMed1993

Further study of internal autocrine regulation of multipotent hematopoietic cells.

We have extended the study of the effects of antisense oligodeoxynucleotides on hematopoietic colony formation to include the effects of antisense to granulocyte-macrophage colony-stimulating factor (GM-CSF), granulocyte colony-stimulating factor (G-CSF), and macrophage colony-stimulating factor (M-CSF) on bone marrow cultures. GM-CSF antisense and GM-CSF receptor antisense cause an increase in mixed erythroid:nonerythroid colonies and a decrease in mixed nonerythroid colonies, which is an effect opposite to that described previously for erythropoietin (Epo) and Epo receptor antisense. The effect of GM-CSF antisense oligomer is not abrogated by the presence of the ligand in the culture. Antisense oligomers to G-CSF and M-CSF have no effect. When Epo and GM-CSF antisense oligomers are added simultaneously, the effects seem to be independent, with the GM-CSF antisense predominating. These data support the hypothesis of internal autocrine regulation of multipotent hematopoietic precursor cells, and extend the concept to myeloid as well as erythroid differentiation.

Animals↗
PubMed1993

Fetal hemoglobin in acute and chronic states of erythroid expansion.

Physiologic principles underlying the differences in fetal hemoglobin (HbF) induction between acute and chronic states of erythroid expansion are poorly understood. Whereas abrupt erythroid expansion is characterized by a high proportion of reticulocytes coexpressing adult and fetal globin (F reticulocytes), HbF levels wane with chronic erythropoietic stimulation. To investigate this phenomenon, we used various schedules of erythropoietin (epo) administration in primates. Acute intravenous epo administration promoted a 2- to 10-fold preferential induction of F reticulocytes compared with total reticulocytes. Total reticulocyte and F reticulocyte production were significantly correlated (correlation coefficient .41 to .74). With chronic epo administration, preferential F reticulocyte production was lost, and there was no correlation between reticulocyte and F reticulocyte production (correlation coefficient -.03). The mean percentage of F reticulocytes did not change between acute and chronic schedules of epo administration. The subcutaneous route of high-dose (3,000 U/kg) epo administration was as effective as intravenous administration in the induction of HbF. Reticulocyte and F reticulocyte responses to increasing epo doses were found to be saturable. These results suggest that the kinetics rather than absolute levels of reticulocyte and F reticulocyte response form the basis for preferential F reticulocyte induction with acute erythropoietic stimulation, and they support the hypothesis that F reticulocytes arise from a relatively rapid pathway of erythroid maturation.

Animals↗
PubMed1993

Hemin or butyrate increases constitutive erythropoietin formation by mouse erythroleukemia cell lines.

The murine erythroleukemic cell lines NN10 and IW32 secrete erythropoietin (Epo) constitutively. Although both cell lines have Epo receptors (Epo-R), they do not respond to external Epo to undergo erythroid differentiation. In both cell lines, hemoglobin synthesis can be induced by hemin or butyrate. We report here on the effects of these two inducers on Epo production by the same cell lines. Both hemin and butyrate caused a three- to five-fold increase in Epo secretion on a percell basis. The effects were dose- and time-dependent, as was found previously for hemoglobin synthesis. The mechanism of the effect on Epo secretion is posttranscriptional, since the steady-state level of Epo mRNA was not altered by the inducers.

Animals↗
PubMed1993

Evidence for an accessory component that increases the affinity of the erythropoietin receptor.

Evidence for an accessory component that can modify the affinity of the erythropoietin (Epo) receptor is presented. Dihydrofolate reductase (DHFR)-deficient Chinese hamster ovary (CHO) cells were transfected with a plasmid containing the Epo receptor cDNA (derived from murine erythroleukemia cells with only low affinity receptors) and DHFR cDNA. The cells expressed both high and low affinity receptors. Upon amplification with methotrexate (MTX), only the number of low affinity receptors increased, suggesting that there was a constitutively expressed cellular component in CHO cells that can increase Epo receptor affinity. Further support for this hypothesis was provided by our finding that fusion of IW 201 cells, which have only low affinity receptors, with nontransfected CHO cells, which have no Epo receptors, resulted in high affinity binding sites for Epo.

Animals↗
PubMed1992

Receptor binding of asialoerythropoietin.

The interaction of 125I-asialoerythropoietin (asialoepo) with receptors has been characterized both by binding assay and affinity cross-linking. Purified spleen cells from mice infected with the anemia strain of Friend virus (FVA cells) have receptors for 125I-asialoepo with two classes of affinity constant: one with Kd = 0.02-0.03 nM and 300-400 per cell, the other with lower affinity (Kd = 0.9-1.2 nM) and 1,000-1,200 per cell. The Kd value for the high affinity site is one-third of that for the binding of native 125I-erythropoietin (125I-epo) to the same FVA cells (Kd = 0.08-0.1 nM). Using 125I-asialoepo or 125I-epo affinity cross-linking methods, we find two components with apparent molecular weights of 88 kDa and 105 kDa in FVA cells, and in the transformed mouse cell lines, 201, IW32, and NN10, in agreement with earlier studies using 125I-epo. These results indicate that 125I-asialoepo binds to the same receptors as 125I-epo, but with greater affinity for the high affinity site. Since 201 cells contain only a single class of lower affinity receptors for erythropoietin (epo), finding the same two components as found for FVA cells by cross-linking experiment indicates that the two components do not represent the two classes of receptor.

Animals↗
PubMed1992

Diurnal variations in serum erythropoietin levels in healthy subjects and sleep apnea patients.

We measured arterial oxygen saturation (SaO2) and serum erythropoietin (EPO) levels in patients with obstructive sleep apnea syndrome (OSAS) and in healthy subjects. SaO2 profile was analyzed as the cumulative distribution of SaO2 over time. OSAS patients spent 25.5 +/- 30.9% (SD) of the time at SaO2 of less than 88% vs. 0.64 +/- 1.6% in healthy subjects (P less than 0.05) and had 59 +/- 25 desaturations (greater than 4%) per hour vs. less than 5 per hour in healthy subjects (P less than 0.05). EPO measurements (radioimmunoassay) were made in blood samples withdrawn every 1 or 2 h over a 24-h period. The mean EPO concentration was higher (P less than 0.05) for OSAS patients (45 +/- 33 mU/ml) than for normal subjects (17 +/- 8 mU/ml). There was a significant variability in EPO values over the 24-h period. To analyze the EPO pattern over 24 h, EPO time series were fit to a general cosine function. Data from normal subjects conformed to a cosine function with an amplitude of 3.5 +/- 2.1 (CV of 60%) and an acrophase of 1,000 +/- 184 min after 0800 (CV of 18%), indicating a zenith about 1 A.M. and a nadir around 1 P.M. Data from OSAS subjects fit a similar cosine function with an amplitude of 19.9 +/- 41.0 (CV of 206%) and acrophase of 582 +/- 408 min (CV of 70%), indicating a greater variability in the magnitude and the timing of peak serum EPO levels.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1992

Serum erythropoietin levels and blood component therapy after autologous bone marrow transplantation: implications for erythropoietin therapy in this setting.

To determine the potential impact of recombinant human erythropoietin (EPO) therapy in patients undergoing autologous bone marrow transplantation (BMT) and colony-stimulating factor therapy, we assayed endogenous serum EPO levels and noted blood transfusion requirements in relapsed non-Hodgkin's lymphoma patients treated with high-dose chemo-radiation therapy and autologous BMT. Hematocrit and reticulocyte counts were determined daily, and hematocrit was maintained in the 25-30% range by transfusion according to criteria established by our hospital transfusion committee. EPO levels were measured by radioimmunoassay and were determined at baseline, throughout therapy, and 2 and 3 months after BMT. Serum EPO levels increased more than 25-fold above baseline in most subjects after initiating chemoradiation therapy. No correlation was noted between serum EPO and hematocrit, reticulocyte count or serum creatinine. Total red blood cell units transfused ranged from 4 to 15 (mean 7.7). Mean total donor exposures (red blood cell plus platelet units transfused) were 83.6 units (range 16-175). Serum EPO levels increased early in the course of preparation for autologous BMT and remained elevated for at least 2-3 weeks thereafter although at a lower level. Red blood cell transfusions were required despite very high EPO levels after BMT. Red cell transfusions, moreover, accounted for only 9.2% (69 of 746) of total donor exposures and only 5.8% (42 of 746) of donor exposures during the interval when pharmacologic doses of erythropoietin might be of benefit. In contrast to the potential benefit of colony-stimulating factors such as G-CSF and GM-CSF in BMT, our study suggests limited value for erythropoietin therapy in this setting.

Adult↗
PubMed1991

An autocrine role for erythropoietin in mouse hematopoietic cell differentiation.

Erythropoietin (epo) is the primary regulator of the rate of red blood cell formation in mammals. Because it is formed in the kidney and acts on the bone marrow, its action is classically endocrine. We have shown by PCR that marrow cells contain epo mRNA and that antisense oligodeoxynucleotides, to both epo and its receptor, act on multipotent hematopoietic cells to cause a decrease in mixed erythroid:nonerythroid colonies. The antisense oligonucleotides also cause an increase in mixed nonerythroid colonies with no effect on erythroid burst formation. Sense oligonucleotides have no effect. The antisense suppression is not due to adherent cells, cycling late differentiated cells or lymphocytes, and not reversed by exogenous epo. We conclude that normal erythroid differentiation may have an early phase that is dependent on an internal autocrine mechanism involving epo and its receptor.

Animals↗
PubMed1991

Serum immunoerythropoietin levels in patients with cancer receiving cisplatin-based chemotherapy.

Serum immunoerythropoietin (SIE) levels were studied of 25 randomly chosen cancer patients undergoing cisplatin-based chemotherapy and ten head and neck cancer patients who were studied prospectively before and during cisplatin-based therapy. The SIE levels were determined by standard radioimmunoassay, and the results were interpreted relative to erythropoietin levels and hematocrits of 17 aplastic or nutritionally anemic patients who were believed to have a normal erythropoietin response. Of the 25 randomly chosen patients, SIE levels were inappropriately low in four patients. In this population, there was a greater likelihood of erythropoietin deficiency in the patients with a hematocrit less than 30% compared with those with higher values (P less than 0.001), although there was no correlation between SIE level and the amount of cisplatin these patients received or their degree of renal impairment. Of the ten head and neck cancer patients, five were found to have inappropriately low SIE levels before therapy, and two additional patients had a decrease of SIE levels during therapy, in one patient to an abnormally low level. The anemia associated with malignancy was concluded to be in part associated with a relative erythropoietin deficiency, and in certain individuals, cisplatin therapy may contribute to that deficiency.

Adult↗
PubMed1991

Co-regulation of heme oxygenase and erythropoietin genes.

The mechanism responsible for the accumulation of heme oxygenase and erythropoietin (epo) transcripts due to cobalt chloride (CoCl2) administration was investigated in rat kidney using a rat heme oxygenase and mouse epo probes. We found an increase of heme oxygenase transcripts in kidney in response to CoCl2. Quantitative evaluation of the heme oxygenase mRNA changes, by scanning densitometry, indicated that the levels of mRNA encoding heme oxygenase were increased by about fiftyfold in rat kidney after administration of CoCl2. That the increase in heme oxygenase mRNA levels resulted from enhanced transcription of the heme oxygenase gene was confirmed by nuclear runoff using isolated rat kidney nuclei after CoCl2 administration. Transcription of the heme oxygenase gene is greatly increased in rat kidney within 1 hr of administration of CoCl2 as evidenced from the levels of 32P-UTP incorporation into the specific transcript. Time course studies showed that stimulation of transcription was increased about fortyfold 3 hr after CoCl2 administration. This stimulation is the most rapid transcriptional response to heavy metals yet described. In addition, Northern blot analysis demonstrated that epo mRNA was first detected 4 hr following CoCl2 administration and reached a maximum at 5 hr. On the other hand, PCR analysis indicated that epo mRNA was increased as early as 1 hr following CoCl2 administration. The fact that CoCl2 caused increased transcription of both the epo and heme oxygenase genes suggests that a common mechanism may be involved in the regulation of these two genes by the heavy metal ion.

Animals↗