Selective treatment of SCID mice bearing methotrexate-transport- resistant human acute lymphoblastic leukemia tumors with trimetrexate and leucovorin protection

Impaired transport of methotrexate (MTX) is a common resistance mechanism of tumor cells to this drug. Trimetrexate (TMTX), a second- generation folate antagonist, is still active against MTX-transport- resistant cells because it enters cells by passive diffusion and does not use the reduced folate transport system for cell entry. Therefore, although leucovorin (LV) protects MTX-sensitive cells from TMTX toxicity, MTX-transport defective cells are poorly rescued by LV. Severe combined immunodeficiency mice bearing MTX-transport-resistant CCRF-CEM acute lymphoblastic leukemia tumors were treated with TMTX alone or with the combination of TMTX and LV, with tumor regressions in both groups (P < .001) and without significant toxicity. These results indicate that TMTX with LV protection may be a useful therapeutic regimen for patients with MTX-transport-defective acute lymphoblastic leukemia. Furthermore, resistance to TMTX plus LV may result in reversion to MTX sensitivity.     

The effect of EDTA, cations, and various buffers on the morphology of erythrocyte membranes: an electron-microscopic study

Membranes of human erythrocytes were prepared by stepwise osmotic hemolysis in Ca2+-free solutions. Examination with the electron microscope after negative staining showed some short, conelike protuberances on the surface of about 20 percent of the ghosts, while 80 percent were round, intact spheres. After Ca2+ treatment, all membranes were round and intact. After exposure to ethylenediaminetetraacetic acid (EDTA) (1.0 mM, pH 7.4), the entire ghost surface was covered with long, thin extrusions called stromalytic forms (about 460 per cell). Their sizes, shapes, and fine structure are described. Exposure to ionic calcium (1.4 times 10-minus 4M) abolished the EDTA-induced stromalytic forms. A second exposure to EDTA reversed this Ca2+ effect. ATP, like EDTA, produced stromalytic forms. EDTA- induced stromalytic forms were also abolished by Zn2+, La3+, and Nd3+ at concentrations of 1-5 times 10-minus 4 M. Mg2+ at 10-minus 2 M was ineffective. Ghosts were prepared by graded lysis in various buffers. Those prepared in phosphate were the most stable and provided consistent EDTA effects and Ca2+ reversal. Ghosts in Tris-HCl showed breakdown unless salt was added. Moderately satisfactory ghosts were also obtained in Hepes-NaOH buffer and salt.     

The cDNA and derived amino acid sequence of porcine factor VIII

The cDNA corresponding to 137 bp of the 5' untranslated region, the signal peptide, and the A1, A3, C1, and C2 domains of porcine factor VIII (fVIII) have been cloned and sequenced. Along with previously determined sequences of the porcine fVIII B domain and the A2 domain, this completes the sequence determination of the cDNA corresponding to the translated protein. Alignments of the derived amino acid sequence of porcine fVIII with human and murine fVIII indicate that the A1, A2, A3, C1, and C2 domains are more conserved than the B domains or the proteolytic cleavage peptides corresponding to residues 337-372 and 1649-1689. The knowledge of the porcine fVIII cDNA may be useful to understand functional and immunological differences between human and porcine fVIII and may lead to improved fVIII replacement products for hemophilia. A patients through the development of recombinant porcine fVIII or hybrid human/porcine fVIII derivatives.     

Individual Differences in Cue-Induced Motivation and Striatal Systems in Rats Susceptible to Diet-Induced Obesity

Pavlovian cues associated with junk-foods (caloric, highly sweet, and/or fatty foods), like the smell of brownies, can elicit craving to eat and increase the amount of food consumed. People who are more susceptible to these motivational effects of food cues may have a higher risk for becoming obese. Further, overconsumption of junk-foods leading to the development of obesity may itself heighten attraction to food cues. Here, we used a model of individual susceptibility to junk-foods diet-induced obesity to determine whether there are pre-existing and/or diet-induced increases in attraction to and motivation for sucrose-paired cues (ie, incentive salience or ‘wanting’). We also assessed diet- vs obesity-associated alterations in mesolimbic function and receptor expression. We found that rats susceptible to diet-induced obesity displayed heightened conditioned approach prior to the development of obesity. In addition, after junk-food diet exposure, those rats that developed obesity also showed increased willingness to gain access to a sucrose cue. Heightened ‘wanting’ was not due to individual differences in the hedonic impact (‘liking’) of sucrose. Neurobiologically, Mu opioid receptor mRNA expression was lower in striatal ‘hot-spots’ that generate eating or hedonic impact only in those rats that became obese. In contrast, prolonged exposure to junk-food resulted in cross-sensitization to amphetamine-induced locomotion and downregulation of striatal D2R mRNA regardless of the development of obesity. Together these data shed light on individual differences in behavioral and neurobiological consequences of exposure to junk-food diets and the potential contribution of incentive sensitization in susceptible individuals to greater food cue-triggered motivation.     

Effects of stem cell factor (kit-ligand) and interleukin-3 on the growth and serine proteinase expression of rat bone-marrow-derived or serosal mast cells

The effects of rat stem-cell factor (SCF) and interleukin-3 (IL-3), alone or in combination, on the in vitro growth and serine proteinase expression of rat serosal/connective-tissue mast cells (CTMC) or bone marrow-derived mast cells (BMMC) were examined. Rat SCF stimulated the growth of both CTMC and BMMC. IL-3 stimulated BMMC growth to a lesser extent than did SCF, whereas CTMC numbers did not increase in IL-3. However, SCF and IL-3 had synergistic effects on the growth of both BMMC and CTMC. SCF favoured the maintenance of rat mast cell proteinase- I (RMCP-I) in CTMC, but did not induce detectable production of RMCP-I in BMMC. In contrast, when IL-3 or lymph node-conditioned medium (LNCM) was added to SCF, a subpopulation of CTMC expressed and stored the soluble proteinase RMCP-II. In BMMC, the RMCP-II content of cells maintained in SCF was significantly less than that of cells maintained in IL-3 or LNCM. RMCP-II also appeared in the supernatants of BMMC, especially when BMMC numbers were increasing rapidly in SCF with or without IL-3 or LNCM. Thus, SCF and IL-3 can regulate the growth of rat BMMC and CTMC, as well as influence their production and release of proteinases.     

Evidence for a second type of fibril branch point in fibrin polymer networks, the trimolecular junction

Fibrin molecules polymerize to double-stranded fibrils by intermolecular end-to-middle domain pairing of complementary polymerization sites, accompanied by fibril branching to form a clot network. Mass/length measurements on scanning transmission electron microscopic images of fibrils comprising branch points showed two types of junctions. Tetramolecular junctions occur when two fibrils converge, creating a third branch with twice the mass/length of its constituents. Newly recognized trimolecular junctions have three fibril branches of equal mass/length, and occur when an extraneous fibrin molecule initiates branching in a propagating fibril by bridging across two unpaired complementary polymerization sites. When trimolecular junctions predominate, clots exhibit nearly perfect elasticity.     

Interleukin 2 production in B cell chronic lymphocytic leukemia

Interleukin 2 (IL 2) production by phytohemagglutinin (PHA)-stimulated peripheral blood mononuclear cells (PBMCs) was investigated in 22 patients with active untreated B cell chronic lymphocytic leukemia (B- CLL) and in 15 healthy donors. PBMCs from healthy donors demonstrated an IL 2 synthesis of 12.4 +/- 10 U/mL. B-CLL PBMCs produced a significant amount of IL 2 (8 +/- 6.6 U/mL) despite the low percentage of T cells (13% +/- 8%) associated with this disease compared with that found in healthy donors (63% +/- 7.5%). If IL 2 production is expressed as units per milliliter per 10(4) T cells, its level in patients with B- CLL (1.1 U/mL/10(4) T cells) is five times greater than that of the controls (0.19 units). When expressed as units per milliliter per liter of blood, the B-CLL patients produce approximately 12 times as much IL 2 as controls. IL 2 production in normal controls was doubled after irradiation of PBMCs or addition of indomethacin. This increase was not seen with B-CLL PBMCs suggesting that the latter have been devoid of prostaglandin-producing normal IL 2 suppressor cells. By mixing normal or B-CLL T cells with non-T cells we found that T cells from patients with B-CLL stimulated by normal accessory cells produced the same amount of IL 2 as normal T cells. Moreover, B-CLL non-T cells (mainly B leukemic cells) produced no IL 2 themselves but played a much more efficient role in IL 2 production than did non-T cells from healthy donors. This was not due to detectable IL 1 production by these cells. The IL 2 produced by B-CLL PBMCs was partially purified and recovered in a 16,000 mol wt fraction, the same mol wt as IL 2 from normal cells.     

Mofarotene (Ro 40-8757) inhibits hematopoiesis in vitro by preventing maturation from primitive progenitor cells

The effect of the arotinoid mofarotene (Ro 40-8757; 4-[2-[p-[(E)- 2(5,6,7,8-tetrahydro-5,5,8,8-tetramethyl-2-naphthyl)- propenyl]phenoxy]ethyl]morpholine) on stromal cell-mediated hematopoiesis was examined in murine long-term bone marrow cultures. Whether added at week 2 to regenerating cultures or at week 4 to plateau-phase cultures, mofarotene strongly inhibited total cell production in a dose-dependent manner. Progenitor cell production was also inhibited, but to a lesser extent. When added at the initiation of culture, 1 mumol/L mofarotene did not affect formation of the adherent layer, but production of total nucleated cells and progenitors was inhibited over the next 10 weeks by 95% and 96%, respectively. However, after mofarotene treatment ceased, progenitor cell levels began increasing immediately, and cell production reached plateau levels comparable with those of control cultures within 4 weeks. Hematopoiesis was maintained for 14 more weeks, indicating that long-term culture- initiating cells survived the treatment. Assays of spleen colony- forming units (CFU-S) in the adherent layers showed an enrichment of day-13 CFU-S relative to the more mature day-9 CFU-S. Mofarotene did not inhibit colony formation by bone marrow cells stimulated by exogenous growth factors and did not decrease production of growth factors by stromal cells in the cultures, as determined by functional assays and by mRNA levels. These results suggest that mofarotene blocks differentiation of very primitive progenitors, inhibiting production of more mature hematopoietic elements.