The biological significance of platelet volume: its relationship to bleeding time, platelet thromboxane B2 production and megakaryocyte nuclear DNA concentration

Bleeding time, platelet thromboxane B2 production and megakaryocyte nuclear DNA concentration were measured in rabbits recovering from thrombocytopenia caused by a single injection of anti-platelet serum. Similar measurements were made on rabbits in a steady state of normal platelet production. The effects of a sustained state of thrombocytopenia on megakaryocyte DNA concentration were investigated by repeated daily injections of anti-platelet serum. It is shown that bleeding time depends on both platelet count and mean platelet volume. Furthermore changes in mean platelet volume appear to play a more important role in haemostasis than changes in platelet count. The mean megakaryocyte nuclear DNA concentration is significantly increased after 24 hours of thrombocytopenia and continues to increase as thrombocytopenia is sustained. Thromboxane B2 production/unit volume of platelet is increased in platelets produced after 24 hours of thrombocytopenia compared with platelets produced in normal steady state function. As a consequence platelets produced in response to thrombocytopenia not only have a larger mean platelet volume but are also more reactive. Mean platelet volume, as well as platelet count, should be considered as an index of haemostasis and its dysfunction, thrombosis.     

Pulse sequence optimization for MR imaging using a paramagnetic hepatobiliary contrast agent

Paramagnetic agents enhance contrast between tissues in magnetic resonance (MR) imaging by altering tissue relaxation times. The effect of these changes on MR image intensity depends in part on the choice of operator-controlled pulse sequence parameters. With the newly described paramagnetic hepatobiliary contrast agent, iron(III) ethylenebis-(2-hydroxyphenylglycine), Fe(EHPG)-, an in vivo experimental analysis of pulse sequence optimization was performed on the rat. We compared the enhancement of the liver divided by background noise, EL/N, of standard inversion-recovery (IR) and spin-echo (SE) T1-weighted pulse sequences and several pulse sequences theoretically predicted to have improved EL/N. Optimization of the echo time (TE = TEmin) gave a substantial (greater than 60%) increase in EL/N over the standard IR and SE pulse sequences. Images obtained with optimized repetition rate and inversion time gave only a slight additional improvement. Within the uncertainties of our relaxation measurements, the measured changes in EL/N with pulse sequence optimization corresponded well with theoretical predictions. With the experimental and theoretical data, the importance of using a short echo time to obtain maximal T1 contrast in contrast-enhanced MR imaging and the relative merits of optimized SE versus IR pulse sequences for contrast-enhanced MR imaging are discussed.     

Stage specificity, dose response, and doubling dose for mouse minisatellite germ-line mutation induced by acute radiation

Germ-line mutation induction at mouse minisatellite loci by acute irradiation with x-rays was studied at premeiotic and postmeiotic stages of spermatogenesis. An elevated paternal mutation rate was found after irradiation of premeiotic spermatogonia and stem cells, whereas the frequency of minisatellite mutation after postmeiotic irradiation of spermatids was similar to that in control litters. In contrast, paternal irradiation did not affect the maternal mutation rate. A linear dose–response curve for paternal mutation induced at premeiotic stages was found, with a doubling dose of 0.33 Gy, a value close to those obtained in mice after acute spermatogonia irradiation using other systems for mutation detection. High frequencies of spontaneous and induced mutations at minisatellite loci allow mutation induction to be evaluated at low doses of exposure in very small population samples, which currently makes minisatellite DNA the most powerful tool for monitoring radiation-induced germ-line mutation.     

Expression of endogenous oncogenic V600EB-raf induces proliferation and developmental defects in mice and transformation of primary fibroblasts

Mutations of the human B-RAF gene are detected in approximately 8% of cancer samples, primarily in cutaneous melanomas (70%). The most common mutation (90%) is a valine-to-glutamic acid mutation at residue 600 (V600E; formerly V599E according to previous nomenclature). Using a Cre/Lox approach, we have generated a conditional knock-in allele of (V600E)B-raf in mice. We show that widespread expression of (V600E)B-Raf cannot be tolerated in embryonic development, with embryos dying approximately 7.5 dpc. Directed expression of mutant (V600E)B-Raf to somatic tissues using the IFN-inducible Mx1-Cre mouse strain induces a proliferative disorder and bone marrow failure with evidence of nonlymphoid neoplasia of the histiocytic type leading to death within 4 weeks of age. However, expression of mutant B-Raf does not alter the proliferation profile of all somatic tissues. In primary mouse embryonic fibroblasts, expression of endogenous (V600E)B-Raf induces morphologic transformation, increased cell proliferation, and loss of contact inhibition. Thus, (V600E)B-Raf is able to induce several hallmarks of transformation in some primary mouse cells without evidence for the involvement of a cooperating oncogene or tumor suppressor gene.     

Antioxidant activities of extracts from five anti-viral medicinal plants

The antioxidant activities of five medicinal plants (Ampelopsis sinica, Ampelopsis humiliforlia var. heterophylla, Potentilla freyniana, Selaginella labordei and Chrysanthemum multiflorum), used in the Hubei province of China, have been investigated using both enzymatic and non-enzymatic in vitro antioxidant assays. Extracts from all five of the plants inhibited xanthine oxidase and lipoxygenase activities, and were scavengers of the ABTS*+ radical cation using the Trolox equivalent antioxidant capacity assay (TEAC). Extracts from Potentilla freyniana and Selaginella labordei down-regulated cyclooxygenase-2 gene expression, measured by real-time RT-PCR, in human colon adenocarcinoma CaCo-2 cells.     

Development of nonsymmetrical 1,4-disubstituted anthraquinones that are potently active against cisplatin-resistant ovarian cancer cells

A novel series of 1,4-disubstituted aminoanthraquinones were prepared by ipso-displacement of 1,4-difluoro-5,8-dihydroxyanthraquinones by hydroxylated piperidinyl- or pyrrolidinylalkylamino side chains. One aminoanthraquinone (13) was further derivatized to a chloropropylamino analogue by treatment with triphenylphosphine-carbon tetrachloride. The compounds were evaluated in the A2780 ovarian cancer cell line and its cisplatin-resistant variants (A2780/cp70 and A2780/MCP1). The novel anthraquinones were shown to possess up to 5-fold increased potency against the cisplatin-resistant cells compared to the wild-type cells. Growth curve analysis of the hydroxyethylaminoanthraquinone 8 in the osteosarcoma cell line U-2 OS showed that the cell cycle is not frozen, rather there is a late cell cycle arrest consistent with the action of a DNA-damaging topoisomerase II inhibitor. Accumulative apoptotic events, using time lapse photography, indicate that 8 is capable of fully engaging cell cycle arrest pathways in G2 in the absence of early apoptotic commitment. 8 and its chloropropyl analogue 13 retained significant activity against human A2780/cp70 xenografted tumors in mice.