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T R Lappin

Publications and source records attributed to T R Lappin.

At least 55 records · Page 3Linked to original sources
PubMed1991

Evidence for impaired erythropoietin response to anaemia in rheumatoid disease.

In this study we determined the serum erythropoietin (Epo) levels of 97 anaemic rheumatoid (RD) patients (Hb less than 11 g/dl) of whom 44 had serum ferritin greater than 60 micrograms/l (anaemia of chronic disorders; ACD), 26 had ferritin 20-60 micrograms/l and 27 had ferritin less than 20 micrograms/l. These results were compared with the Epo levels of 36 iron deficient controls (Hb less than 11 g/dl), 33 non-anaemic RD patients and 33 normals. The serum Epo levels of anaemic subjects were significantly higher (P less than 0.05) than those of non-anaemic patients. Despite similar Hb, the Epo results (geometric mean (confidence limits] of the ACD group (38 (32,45) mU/ml) and of RD patients with ferritin of 20-60 micrograms/l (39 (33,46)mU/ml) were significantly lower (P less than 0.05) than those of iron deficient controls (65 (52,80)mU/ml). When the Hb fell to 10 g/dl or less, the serum Epo of 13 RD patients with ferritin less than 20 micrograms/l was 65 (47,89)mU/ml, significantly lower (P less than 0.05) than that of 17 iron deficient controls (104 (78,136)mU/ml). These results justify clinical trials of recombinant human Epo in RD patients with ACD.

Adult↗
PubMed1991

Erythropoietin deficiency in the anaemia of chronic disorders.

Defective iron metabolism, mild haemolysis and impaired erythropoiesis contribute to the anaemia of chronic disorders (ACD), but evidence for a deficiency of circulating erythropoietin (Epo) is equivocal. We have examined serum Epo in moderately anaemic patients with Hb less than 10 g/dl--41 patients with ACD (23 associated with rheumatoid disease and 18 with malignancy), 17 with uncomplicated iron-deficiency anaemia and 33 with chronic renal failure (CRF). In ACD the serum Epo (mean (confidence limits] results of 41 (31, 54) mU/ml for the rheumatoid group and 63 (49, 80) mU/ml for the malignancy group, were significantly lower than the Epo of 104 (78, 136) mU/ml for the iron-deficiency group. The CRF group with more severe anaemia had serum Epo of 27 (19, 35) mU/ml. Thus, recombinant human erythropoietin (rHu Epo) should be considered for the treatment of ACD associated with rheumatoid disease and malignancy.

Adult↗
PubMed1990

The metabolism of erythropoietin in the normal and uraemic rabbit.

The metabolism of recombinant human erythropoietin (rHuEpo) labelled with 125I has been investigated in five normal and nine 5/6-nephrectomised rabbits. The plasma erythropoietin half-life was significantly prolonged at 5.1 +/- 1.2 h (mean +/- SD) in the 5/6-nephrectomised rabbits, compared to 3.0 +/- 0.4 h in sham-operated controls (P less than 0.001). The disappearance of 125I-labelled rHuEpo is biphasic. Examination of serum by fast protein liquid chromatography (FPLC) following administration of 125I-labelled rHuEpo by FPLC showed a single peak of radioactivity in all rabbits except two of the nephrectomised group. In serum from both of these animals a second labelled peak was found, corresponding to material of MW 200,000-250,000 D. We conclude that the 5/6-nephrectomised rabbit provides a stable model for the study of hormonal metabolism in chronic renal failure.

Animals↗
PubMed1990

Erythropoietin production in kidney tubular cells.

The erythropoietin gene has been cloned in three mammalian species including man and recombinant erythropoietin is now used to treat the anaemia of chronic renal failure. Despite the isolation of the gene the precise cellular location of erythropoietin synthesis remains controversial. We present studies which demonstrate erythropoietin production by kidney tubular cells. Erythropoietin gene expression (messenger RNA) was detected by in situ hybridization using an oligonucleotide gene probe and the translated protein product by immunohistochemistry employing antibodies raised to pure recombinant DNA derived erythropoietin.

Animals↗
PubMed1989

Serum erythropoietic activity in acute anemia--an animal model.

Serum erythropoietic activity and reticulocyte response to anemia were investigated using a rabbit model. In hemolytic anemia, induced by injections of phenylhydrazine on Day 0 the hemoglobin reached a nadir (mean, 6.23 g/dl) on Day 4 when SEA was maximal (mean, 765 mU/ml). In animals venesected on Day 0 and Day 1 to produce anemia of equal severity, the SEA was maximal (mean 235 mU/ml) on Day 2. In both groups the reticulocyte response peaked on Day 7--at 34% for the hemolytic group and 21% for the venesected group. The 2,3-diphosphoglycerate, measured on Day 4, was significantly reduced in the PHZ-treated group. In the venesected group the 2,3-DPG increased between Day 0 and Day 4. There were no concurrent changes in acid-base balance. These results imply that the degree of anemia is only one of the factors which influence the level of circulating SEA.

Acute Disease↗
PubMed1989

The initiation of erythropoiesis following renal transplantation.

Erythropoiesis has been examined in relation to kidney function in 38 patients during the 3-month period following successful renal transplantation, using serial determinations of erythropoietin, haemoglobin, and creatinine. Two peaks of serum erythropoietin were observed: an early peak that occurred within 2 days of transplantation and was observed in ten patients, and a late one between 8 and 30 days, observed in 28 patients. The early peak did not produce an increase in haemoglobin and occurred only in the presence of delayed onset of graft excretory function when serum creatinine was greater than 1000 mumols/l. The ineffectiveness of the early peak may be due to the uraemic environment, which is probably a sequel of the tubular damage associated with postoperative acute tubular necrosis. The late peak followed a decrease in serum creatinine to less than 200 mumols/l and was associated with an increase in haemoglobin of 3-4 g/dl during the next 2-6 weeks.

Adolescent↗
PubMed1988

Red cell pyrimidine 5' nucleotidase deficiency: determination of nucleotidase activity and nucleotide content using HPLC.

The hereditary deficiency of erythrocyte pyrimidine 5' nucleotidase has been investigated using an HPLC anion-exchange procedure designed to measure both red cell nucleotide content and enzymic activity. Red cell nucleotide profiles were determined using a low pH phosphate buffer salt-gradient system in 20 min, whereas a low pH buffer alone permitted the determination of enzymic activity with each of six different nucleotide substrates in less than 4 min. Both the red cell nucleotide profiles and the enzymic activity of haemolysates from two affected brothers and their children agreed well with previously published values. This unified approach should prove useful for detailed studies of deficiencies involving isoenzymes of pyrimidine nucleotidase.

5'-Nucleotidase↗
PubMed1988

Comparison of the mouse spleen cell assay and a radioimmunoassay for the measurement of serum erythropoietin.

The mouse spleen cell assay (MSCA) has been compared with a radioimmunoassay for the measurement of serum erythropoietin (Ep). In 20 normal subjects the serum values ranged from 15 to 73 mU/ml for the MSCA compared with 5-30 mU/ml for the RIA. For normal sera there was no correlation between the results of the two assays. In 37 patients with anaemias of differing aetiologies and at various stages of treatment values ranged from 10 to 3645 mU/ml for the MSCA and 13-10,000 mU/ml for the RIA. Although patient values from the two assays were highly correlated (r = 0.98, P less than 0.001), the MSCA results were generally lower. These discrepancies can be largely accounted for by two factors. Firstly the MSCA is sensitive to non-specific matrix effects. Secondly, heat inactivation of serum, a prerequisite for the MSCA, but not for the RIA, destroys a variable and unpredictable proportion of the Ep in the test sera leading to an underestimation of Ep in the MSCA. We conclude that the RIA is more reliable than the MSCA which, in its present form, cannot be recommended for the accurate measurement of serum erythropoietin.

Anemia↗
PubMed1988

Erythropoietic response to hypobaric hypoxia in rabbits.

Animals subjected to hypoxia become hypocapnic and after some hours show an increase in circulating erythropoietin. The steps involved in the increased production of erythropoietin in response to hypoxia are not fully understood, although it has been postulated that changes in coincident variables such as acid-base balance may contribute to the mechanism of increased erythropoietin production. A rabbit model has been used to determine the physiological changes which occur in short-term hypobaric hypoxia. After 1 h, no changes were found in pCO2, pH, P50, base excess, standard bicarbonate or serum erythropoietic activity (SEA). After 3 h the pCO2, pH, base excess and standard bicarbonate had decreased while the P50 and SEA had increased. After 6 h, although the pCO2 was still significantly reduced, the pH, base excess and standard bicarbonate had returned to the initial levels and maximal SEA values. 20-fold greater than the pre-hypoxia values were found. Overall the data are consistent with the view that the magnitude of the erythropoietic response to hypoxia is modified by changes in acid-base balance.

Animals↗
PubMed1986

The anaemia of chronic renal failure: a potentially treatable catabolic phenomenon?

It is proposed that the anaemia of chronic renal failure and the apparent lack of erythropoietin response is a result of increased proteolytic and lysosomal enzyme action on both the red cell and erythropoietin itself. Removal of the sialic acid from the red cell membrane is known to cause sequestration and a shortened cell survival. Similarly removal of sialic acid from the carbohydrate coat of erythropoietin both increases clearance by the liver and renders it susceptible to cleavage into inactive fragments by proteolytic attack. If the hypothesis is correct therapeutic intervention using enzyme inhibitors may offer hope for the amelioration of the anaemia.

Anemia↗
PubMed1986

In vitro bioassay of erythropoietic activity in serum using mouse spleen cells. The effect of heat inactivation on serum erythropoietin.

Untreated human serum is known to be toxic to in vitro assays for erythropoietin, including the mouse spleen cell assay system (MSCA). This phenomenon had previously been shown to be mediated by complement-dependent IgM heteroantibodies and can be overcome by heating the serum at 56 degrees C for 30 minutes. Using the MSCA, we have found that the toxic effect of serum could also be removed by treatment with a precipitating antibody against the C3c component of complement. The effects of the two methods of complement inactivation on the measurement of stimulatory activity in serum have been compared. For normal serum, the results after heat inactivation and antibody treatment were similar. In contrast, serum from a patient with aplastic anemia gave a result equivalent to 327 mU erythropoietin/ml after heat treatment, but after antibody treatment equivalent to 1,520 mU erythropoietin/ml. Gel permeation chromatography of unheated, heated, and antibody-treated sera showed that heating markedly reduced the activity of the erythropoietin peak. Seventy percent of the activity of partially purified urinary erythropoietin was lost during heating in the presence of normal serum. In addition, heating caused the appearance of high molecular weight compounds that are stimulatory in the MSCA. The level of this activity appeared to be directly related to the stimulatory activity of the unheated serum.

Anemia, Aplastic↗
PubMed1985

Increased plasma glycosidase and protease activity in uraemia: possible role in the aetiology of the anaemia of chronic renal failure.

We have measured plasma N-acetyl-beta-D-glucosaminidase (EC 3.2.1.30) and neuraminidase (EC 3.2.1.18) activities as markers of glycosidase activity and immunoreactive trypsin (EC 3.4.21.4) levels as a marker of proteolytic potential in the plasma of normal and uraemic subjects. The levels of all of these enzymes are significantly elevated in the plasma of uraemic subjects when compared to normal. We have postulated that the combined attack of glycosidases and proteases on erythropoietin will lead to fragmentation of this glycoprotein hormone with loss of activity. This may be a major contributory cause to the anaemia of chronic renal failure.

Acetylglucosaminidase↗
PubMed1985

Cow's milk and anemia in preterm infants.

Introduction of pasteurised cows' milk to the diet of preterm infants before 36 weeks' postnatal age caused iron deficiency without anaemia. Cows' milk before 24 weeks was associated with iron deficiency and anaemia. The cause was either inadequate absorption or increased loss rather than reduced intake of iron.

Anemia↗
PubMed1985

Separation of erythropoietic stimulators in severe anaemia using high performance gel permeation chromatography.

Patients with various types of anaemia, but with comparable haemoglobin levels, show a wide range of serum erythropoietic activity. We have developed a method for the fractionation of serum by HPLC followed by bioassay of the individual fractions, using the mouse spleen cell microassay. Up to three distinct peaks of erythropoietic activity corresponding to molecular weights (MW) greater than 300,000, 250,000-300,000 and 40,000 have been found in serum from both normal and anaemic subjects. The erythropoietic profiles of the sera examined differ markedly in anaemias of different aetiology. The chemical nature and the physiological significance of the stimulators remain to be investigated.

Adolescent↗
PubMed1985

The effect of transferrin saturation on the estimation of erythropoietin by the mouse spleen cell microassay.

The effect of transferrin from various sources and the degree of saturation with iron on the stimulation of DNA synthesis by erythropoietin (Epo) has been investigated. Mouse, human, and bovine transferrins saturated with iron caused an increase in thymidine incorporation both in the absence and presence of Epo. In contrast, exogenous human and bovine apotransferrin resulted in significantly decreased incorporation of the tracer. The iron saturation of serum alters its apparent erythropoietic activity. This transferrin saturation effect may be overcome by a simple modification involving the addition of iron to the culture medium.

Animals↗