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.     

Polycythemia vera. II. Hypersensitivity of bone marrow erythroid, granulocyte-macrophage, and megakaryocyte progenitor cells to interleukin-3 and granulocyte-macrophage colony-stimulating factor.

Polycythemia vera (PV) is a clonal disease of the hematopoietic stem cell characterized by a hyperplasia of marrow erythropoiesis, granulocytopoiesis, and megakaryocytopoiesis. We previously reported that highly purified PV blood burst-forming units-erythroid (BFU-E) are hypersensitive to recombinant human interleukin-3 (rIL-3). Because these cells may be only a subset, and not representative of marrow progenitors, we have now studied partially purified marrow hematopoietic progenitor cells. Dose-response experiments with PV marrow BFU-E showed a 38-fold increase in sensitivity to rIL-3 and a 4.3-fold increase in sensitivity to recombinant human erythropoietin (rEpo) compared with normal marrow BFU-E. In addition, PV marrow colony-forming units-granulocyte-macrophage (CFU-GM) and CFU-megakaryocyte (CFU-MK) also showed a marked hypersensitivity to rIL-3 and to human recombinant granulocyte-macrophage colony-stimulating factor (rGM-CSF). Dose-response curves with rGM-CSF and blood BFU-E showed a 48-fold increase in sensitivity. No effect of rIL-4, rIL-6, human recombinant granulocyte-CSF (rG-CSF), or macrophage-CSF (rM-CSF) was evident, nor was there any effect of PV cell-conditioned medium on normal BFU-E, when compared with normal cell-conditioned medium. Autoradiography with 125I-rEpo showed an increase in Epo receptors after maturation of PV BFU-E to CFU-E similar to that shown with normal BFU-E, but no increase of specific binding of 125I-rIL-3 by PV CD34+ cells was seen compared with normal CD34+ cells. These studies show that PV marrow hematopoietic progenitor cells are hypersensitive to rIL-3 and rGM-CSF, similar to PV blood BFU-E. While the mechanism does not appear to be due to enhanced binding of rIL-3, the hypersensitivity of PV progenitor cells to IL-3 and GM-CSF may be a key factor in the pathogenesis of PV.     

Dynamometer for rat plantar flexor musclesin vivo

A dynamometer is designed and fabricated to measure the force output during static and dynamic muscle actions of the plantar flexor muscles of anaesthetised rats in vivo. The design is based on a computer-controlled DC servomotor capable of angular velocities in excess of 17.5 rad s⁻¹. The system controls the range of motion, angular velocity and electrical stimulation of the muscles, while monitoring the force output at the plantar surface of the foot. The force output is measured by a piezo-electric load cell that is rated at 5 kg capacity. Angular velocity and position are measured by a DC tachometer and potentiometer, respectively. All measurement devices are linear (r²=0.9998). The design minimises inertial loading during high-speed angular motions, with a variation in force output of less than 0.2%. The dynamometer proves to be an accurate and reliable system for quantifying static and dynamic forces of rat plantar flexor muscles in vivo.     

Repeated Independent Exposures to Domoic Acid Do Not Enhance Symptomatic Toxicity in Outbred or Seizure-Sensitive Inbred Mice

Domoic acid (DA) is an environmental neurotoxin to humans. Thiswork examines whether repeated exposure to subsymptomatic orsymptomatic nonlethal doses of domoic acid leads to enhancedsymptomatic toxicity in ICR outbred and DBA inbred strains oflaboratory mice. A multiple independent exposure paradigm wasdesigned in which doses were administered intraperito neallyevery other day for 7 days to achieve four separate exposuresto domoic acid. We first examined the effect of repeated exposureon serum clearance of domoic acid. Serum domoic acid levelsdid not differ following a single or repeated exposure. We nextexamined the effect of repeated exposure on symptomatic toxicity.The mean toxicity scores did not show a significant differencebetween single and repeated exposures of either subsymptomatic(0.5 mg/ kg) or symptomatic sublethal (2.0 mg/kg) doses of domoicacid. We then examined the effects of repeated domoic acid exposureon a second strain of mouse. DBA mice were chosen based upontheir sensitivity to kainic acid-induced seizures; however,the ICR mice were more sensitive to low-dose domoic acid toxicity,particularly in terms of onset and duration of stereotypic scratchingbehavior. Our results indicate that both strains of mice havecomparable concentration-dependent toxic responses to domoicacid; however, differences exist in the magnitude of the responseand in specific symptoms. The mean toxicity scores did not showa significant difference when a single exposure (1.0 and 2.0mg/kg domoic acid) and repeated exposure of the same dose werecom pared in the DBA mice. This study provides no evidence thatshort-term repeated exposure to domoic acid in laboratory micealters domoic acid clearance from the serum, or leads to a moresensitive or a greater neurotoxic response.     

Concerning the hormonal regulation of androgen binding protein in rat testis.

Androgen binding protein (ABP) was measured in testis following an acute injection of FSH to ascertain whether this protein could serve as an endpoint marker of FSH action in the Sertoli cell. A single intravenous injection of oFSH (200 mug NIH-S-10) resulted in a rapid stimulation of ABP activity in testis of either 10- or 14-day old rats. Maximal increases were noted by 2 h in both cases (undetectable to 0.9, and 0.3 to 1.5 pmol ABP/mg protein in 10- and 14-day old rats, respectively) and by 4h ABP activity had again returned to control values. Although FSH failed to acutely stimulate ABP in 60-day-old rats, hypophysectomy of these animals resulted in a return of sensitivity within 3 days. The acute stimulation of ABP by FSH was also shown to be dependent upon both the route of hormone administration and the dose of FSH. Finally, the rapid decrease in ABP activity following FSH could be prevented by injection of a second dose of hormone. ABP activity was also increased by intratesticular injection of an analog of cyclic AMP, 8-bromo cAMP. This response was also dose-dependent and the time course of response was indistinguishable from that resulting following FSH. A test of nucleotide specificity revealed that any adenine nucleotide would stimulate ABP, whereas guanine compounds were ineffective. Peptide hormone specificity was next examined. It was determined that 200 mug of a variety of crude pituitary hormone preparations (LH, GH, PRL and ACTH) were stimulatory. However, when highly purified hormones were utilized, hFSH (LER-1577) did not increase testicular ABP whereas 1 mug of oLH (Papkoff) was maximally stimulatory. Further studies revealed that all compounds (including peptide hormones and nucleotides) which resulted in acute elevation of ABP activity also increased the intratesticular concentration of testosterone. Moreover, a single ip injection of testosterone produced a steroid specific stimulation of ABP which reached maximal levels within 1 h. These findings suggest that the acute regulation of ABP activity in the testis may be a result of the intratesticular concentration of testosterone and not due to a direct effect of FSH as had been previously hypothesized.