Age-related differences in the metabolism of proteoglycans in bovine articular cartilage explants maintained in the presence of insulin-like growth factor I.

Articular cartilage explants from bovine calf and steer were cultured for up to 19 days in medium with or without 20% fetal bovine serum (FBS) or insulin-like growth factor I (IGF-I). Lower concentrations of IGF-I were required for maximal stimulation of PG synthesis in calf than in steer. In calf, but not in steer, IGF-I was as effective as 20% FBS in stimulating PG synthesis.

Effect of indomethacin and of prostaglandins on extrarenal erythropoietin production in rats.

Indomethacin elevates the plasma erythropoietin titer of hypoxic anephric rats and probably does so by increasing extrarenal erythropoietin production. Because indomethacin is a potent cyclooxygenase inhibitor, we postulated that it alters extrarenal erythropoietin production via its effects on tissue prostaglandin levels. Studies were, therefore, performed to determine the effects of indomethacin on hepatic prostaglandin E2 (PGE2) and prostaglandin F2 alpha (PGF2 alpha) titers.

Busulfan and chloramphenicol induced T cell lymphoma: cell surface characteristics and functional properties.

We report the immunological studies on three transplantable lymphoma lines that developed when CAF1 mice were injected with busulfan and chloramphenicol. The lymphoma cells displayed Thy-1.2, brain associated antigen, and H-2d alloantigen.

Regulation of the plasma erythropoietin level in hypoxic rats.

Exposure to hypoxia results in an increase in the plasma erythropoietin (Ep) content to a peak level in 10-12 h. If hypoxia is discontinued before maximum plasma Ep concentrations are reached, then the plasma Ep level continues to rise before it declines toward normal. To clarify this phenomenon, we determined the Ep level in the plasma and kidneys at various times after rats that had been exposed to 0.

Factors that regulate extrarenal erythropoietin production.

Extrarenal sites are the major source of erythropoietin (Ep) production in fetuses and neonates. Afterwards, however, the kidneys are the major site. The most likely site of Ep production is the liver, although attempts to extract Ep from the liver have been, to date, unsuccessful.

The influence of age and sex on erythropoietin titers in the plasma and tissue homogenates of hypoxic rats.

Experiments were performed to determine the erythropoietin (Ep) content of homogenates of kidneys and livers of male and female rats of various ages. In all studies, homogenates were adjusted to a concentration of 4 g of tissue per 12 ml of phosphate-buffered-saline, and the stimulus to Ep production consisted of exposure to 0.42 atmosphere for 4 h.

Effect of angiotensin infusion on extrarenal erythropoietin production.

The effects of infusing subpressor doses of angiotensin II into hypoxic and anemic rats on plasma Ep levels were determined. The effect was greatest when 5 micrograms of angiotensin II per hour was infused into rats made hypoxic 18 hr after nephrectomy. Infusion of larger amounts of angiotensin II had a lesser effect on extrarenal Ep production than did infusion of 5 micrograms/hr.

Detection of high erythropoietin titers in renal extracts of hypoxic rats.

Previous attempts to extract erythropoietin from the kidneys have not been uniformly successful and have yielded only small amounts. Attempts were therefore made to extract erythropoietin from renal extracts prepared from the supernatant obtained after homogenizing kidneys in various liquids and centrifuging at 2300 x g. Detectable amounts of erythropoietin were recovered from kidneys of nonhypoxic male but not female rats.

Effect of plasma from cyclophosphamide-treated mice on CFU-S in an in vivo culture system.

Various studies suggest that humoral substances, capable of stimulating CFU-S proliferation, are released into the plasma in response to depletion of the CFU-S population by cytotoxic substances such as cyclophosphamide. To test this hypothesis, we placed 0.25 ml of a murine marrow cell suspension with an equal volume of plasma from either normal mice or from mice previously injected with 5 mg of cyclophosphamide into cellulose dialysis tubing.

Extraction of erythropoietin from kidneys.

Erythropoietin (Ep) in large amounts was detected in extracts of renal tissue from hypoxic rats. These extractions were performed by homogenization of kidney tissue in phosphate buffered saline, centrifugation at 3,000 g and collection of the supernate. Male kidneys contained more Ep than did females and the major portion of Ep is located in the renal cortex.