Mutated recombinant human heavy-chain ferritins and myelosuppression in vitro and in vivo: a link between ferritin ferroxidase activity and biological function.

Human heavy-chain (H-) ferritin muteins obtained by oligonucleotide site-directed mutagenesis, together with wild-type recombinant human H- and light-chain (L-) ferritins, were evaluated for in vitro effects on the suppression of human bone marrow myeloid progenitor cells and for in vivo effects on marrow and splenic myelopoiesis in C3H/HeJ mice. The 10 H-ferritin muteins exhibited alterations of various regions of the molecule, including ones exposed on the outer surface, on the inner cavity, and on the hydrophilic and hydrophobic channels and of the four-alpha-helix bundle forming the subunit structure. They were stable and were electrophoretically analogous to wild-type H-ferritin. The muteins showed in vitro and in vivo myelosuppressive activity analogous to wild type, except for mutein 222, which was totally inactive and which lacked ferroxidase activity. Recombinant human L-ferritin, devoid of ferroxidase activity, was also inactive as a suppressor. The results demonstrate that H-ferritin myelosuppressive and ferroxidase activities are linked. One possibility is that ferroxidase activity may interfere with the cellular uptake of transferrin iron that is needed for cell proliferation, an interpretation consistent with the presently described ability of hemin to overcome H-ferritin suppressive effects.     

Influence of murine mast cell growth factor (c-kit ligand) on colony formation by mouse marrow hematopoietic progenitor cells.

Purified natural and recombinant murine mast cell growth factor (MGF, a c-kit ligand) were evaluated alone and in combination with other cytokines for effects in vitro on colony formation by multipotential (CFU-GEMM), erythroid (BFU-E) and granulocyte-macrophage (CFU-GM) progenitor cells from BDF1 mouse bone marrow. Both preparations stimulated Epo-dependent CFU-GEMM and enhanced Epo-dependent BFU-E colony numbers and size. MGF had some stimulating activity for CFU-GM. When used in combination with plateau concentrations of pokeweed mitogen mouse spleen cell conditioned medium or granulocyte-macrophage colony stimulating factor (CSF), MGF enhanced in greater than additive fashion colony formation by CFU-GM. MGF also enhanced the size of colonies formed, an enhancement greatest for colonies containing granulocytes and macrophages. MGF did not enhance Macrophage-CSF stimulated colony numbers or size. MGF seems to be an early acting cytokine with preferential effects on the growth of more immature hematopoietic progenitor cells.     

Effect of a low-protein diet on doxorubicin pharmacokinetics in the rabbit

Summary Malnutrition involving protein deficiency, which commonly occurs in cancer patients receiving anthracycline treatment, is considered to be a risk factor for the development of cardiotoxicity. Protein deficiency has been shown to impair the metabolism of drugs such as theophylline and acetaminophen. If protein deficiency also impairs anthracycline metabolism, it could explain at least in part the enchanced anthracycline toxicity associated with malnutrition. We tested this idea by determining the effect of a low- protein, isocaloric diet on doxorubicin pharmacokinetics in rabbits. The animals were randomized into two groups for 8–12 weeks. Rabbits in group 1 received a low-protein (5%), isocaloric diet, whereas those in group 2 received a normal-protein (15%) diet. Both groups (group 1,n=15; group 2,n=14) were given 5 mg/kg doxorubicin by i.v. bolus. After doxorubicin injection, blood samples were obtained over the next 52 h for the measurement of doxorubicin and doxorubicinol plasma concentrations by high-performance liquid chromatography (HPLC) with fluorometric detection. The low-protein diet significantly decreased doxorubicin clearance (48±3 vs 59±4 ml min^–1 kg^–1;P<0.05), prolonged the terminal climination half-life (28±2 vs 22±2 h;P<0.05), and increased the area under the plasma concentration/time curve extrapolated to infinity (1722±122 vs 1405±71 ng h ml^–1;P<0.05) as compared with the values determined for rabbits fed the standard rabbit chow (15% protein). The volume of distribution for doxorubicin was not altered by the low-protein diet. In addition, in rabbits fed the the low-portein diet, the terminal elimination half-life of the alcohol metabolite, doxorubicinol was prolonged (52±5 vs 40±2 h;P<0.05). Thus, a low-protein diet causes a reduction in the ability of rabbits to eliminate doxorubicin and possibly its alcohol metabolite doxorubicinol. If a similar alteration in anthracycline pharmacokinetics occurs in malnourished cancer patients, this phenomenon may contribute to their increased risk of developing cardiotoxicity associated with anthracycline therapy.Supported by the Department of Veterans Affairs and the American Heart Foundation     

A retrospective analysis of the efficacy and safety of metformin in the African-American patient.

A retrospective analysis was conducted to determine the effects of metformin on glycosylated hemoglobin (HbA1c), body weight, and adverse events in an African-American population. Thirty-six patients who were receiving combination therapy with metformin and either a sulfonylurea or insulin were identified from a hospital pharmacy database. Nineteen patients met the criteria for efficacy analysis. The combination of metformin with either a sulfonylurea or insulin resulted in a decrease of the average HbA1c from a baseline of 10.07% to 7.92% (delta = 2.15%). The effect of combination therapy on weight was variable; however, twice as many patients lost weight compared with those who gained weight. Metformin appeared to be well-tolerated, with gastrointestinal symptoms being the most commonly reported adverse events.     

Growth suppression in the Trichuris dysentery syndrome

The Trichuris Dysentery Syndrome (Ramsey, 1962) is an insidious, chronic condition which has clinical features similar to Crohn's ileocolitis and ulcerative colitis, diseases similarly associated with growth retardation. The attained heights and weights of 19 children at the time of diagnosis of intens, -2.4 Standard Deviation (Z) scores from the Tanner-Whitehouse median with weight, adjusted for height-age, -1.3 Z. We present data on the growth velocities of 11 of the children in the half-year following worm expulsion by mebendazole. These children returned to their home environments without food supplementation or close follow-up, but showed an average height velocity of +5.5 Z and weight velocity (for height-age) of +2.4 Z. Of 8 children with unequivocal height spurts only 3 had any weight spurt. We suggest that the pattern of catch-up growth points to the existence of some specific link between allergy or inflammation in the lower intestinal tract and suppression of linear growth, rather than to stunting due to general deprivation and undernutrition.     

Single-dose pharmacokinetics of fluphenazine after fluphenazine decanoate administration

Fluphenazine decanoate is commonly used as part of maintenance treatment of schizophrenia, but its pharmacokinetics are poorly understood. We administered a single intramuscular dose of fluphenazine decanoate to nine patients and found that plasma fluphenazine level did not decline to 50% of the peak level by day 26 in any of the patients. This means that it has a long half-life measurable in months rather than weeks.