The Relation of Platelet Kinetics to Bone Marrow Megakaryocytes in Chronic Granulocytic Leukaemia

The relation of thrombokinetics to quantitative determinations of megakaryocytes (mgkc) in bone marrow sections was studied in 11 consecutive cases of untreated Ph¹-positive chronic granulocytic leukaemia (CGL). The results were compared with controls and with previously obtained data in polycythaemia vera (PV), primary thrombocythaemia (PT) and in idiopathic thrombocytopenic purpura (ITP). Platelet survival was significantly reduced in CGL. Platelet production was 5.8 x normal and the mgkc number and volume/μl bone marrow were significantly increased as compared to controls. The increase in mgkc volume was not in proportion to that of number due to a significant decrease of mgkc size. Platelet production was strongly related to mgkc number/mm² and to the mgkc volume/μl bone marrow. The platelet production rate in relation to a unit of mgkc volume/μl bone marrow was, however, greater in CGL than in controls, PV, PT and ITP. The chief reason for this is most probably the greater expansion of the total bone marrow mass in CGL.     

External doppler monitoring of free flaps through negative pressure dressings

The negative pressure dressing is a highly effective modality for coverage and bolstering of skin grafts in the early postoperative period. In the situation of a skin graft over a free flap, the surgeon might be inclined to avoid this modality out of concern that the dressing would deleteriously effect flap survival or impede flap monitoring. This case series supports the safety of the negative pressure dressing and demonstrates a technical modification that permits external Doppler monitoring of the flap through the dressing. Thus, this technique provides an ideal environment for skin graft healing while maintaining the ability to monitor the flap in a straightforward manner and also simplifies nursing care.     

Significance for the diagnosis of iron overload of histochemical and chemical iron in the liver of control subjects

Storage iron was examined in surgical liver biopsy specimens in 43 haematologically normal and otherwise healthy adult individuals. These patients had no history of unphysiological iron losses nor of unphysiological iron intake. Histochemical iron was estimated in parenchymal and Kupffer cells and graded from 0 to 4+. Stainable iron of grade 1+ or more was present in parenchymal cells in 23 of the 27 men. Six of them had a 3+ grade. In nine cases iron was also visible in Kupffer cells. Visible iron was absent in most of the menstruating women. The mean total nonhaemin iron concentration for the male group was 80·2 (19·4 to 227·0), for the postmenopausal women 50·7 (19·3 to 106·6), and for the menstruating women 23·5 (5·5 to 65·9) mg./100 g. dry weight. The mean value for the women was significantly lower than the mean value for the men. There was a significant correlation between the histochemical grades of iron and chemically determined nonhaemin iron, but the degree of overlapping was considerable.     

Elevation of cellular BPDE uptake by human cells: a possible factor contributing to co-carcinogenicity by arsenite

BACKGROUND: Arsenite (iAsIII) can promote mutagenicity and carcinogenicity of other carcinogens. Considerable attention has focused on interference with DNA repair by inorganic arsenic, especially the nucleotide excision repair (NER) pathway, whereas less is known about the effect of arsenic on the induction of DNA damage by other agents. OBJECTIVES: We examined how arsenic modulates DNA damage by other chemicals. METHODS: We used an NER-deficient cell line to dissect DNA damage induction from DNA repair and to examine the effects of iAsIII on the formation of benzo[a]pyrene diol epoxide (BPDE)-DNA adducts. RESULTS: We found that pretreatment with iAsIII at subtoxic concentrations (10 microM) led to enhanced formation of BPDE-DNA adducts. Reduced glutathione levels, glutathione S-transferase activity and chromatin accessibility were also measured after iAsIII treatment, but none of these factors appeared to account for the enhanced formation of DNA adducts. However, we found that pretreatment with iAsIII increased the cellular uptake of BPDE in a dose-dependent manner. CONCLUSIONS: Our results suggest that iAsIII enhanced the formation of BPDE-DNA adducts by increasing the cellular uptake of BPDE. Therefore, the ability of arsenic to increase the bioavailability of other carcinogens may contribute to arsenic co-carcinogenicity.     

Human polynucleotide kinase participates in repair of DNA double-strand breaks by nonhomologous end joining but not homologous recombination

Human polynucleotide kinase (hPNK) is a bifunctional enzyme possessing a 5'-DNA kinase activity and a 3'-phosphatase activity. Studies based on cell extracts and purified proteins have indicated that hPNK can act on single-strand breaks and double-strand breaks (DSB) to restore the termini to the chemical form required for further action by DNA repair polymerases and ligases (i.e., 5'-phosphate and 3'-hydroxyl termini). These studies have revealed that hPNK can bind to XRCC4, and as a result, hPNK has been implicated as a participant in the nonhomologous end joining (NHEJ) pathway for DSB repair. We sought to confirm the role of hPNK in NHEJ in the cellular setting using a genetic approach. hPNK was stably down-regulated by RNA interference expression in M059K glioblastoma cells, which are NHEJ positive, and M059J cells, which are NHEJ deficient due to a lack of DNA-PK catalytic subunit (DNA-PKcs). Whereas depletion of hPNK significantly sensitized M059K cells to ionizing radiation, no additional sensitization was conferred to M059J cells, clearly implying that hPNK operates in the same DNA repair pathway as DNA-PKcs. On the other hand, depletion of hPNK did not increase the level of sister chromatid exchanges, indicating that hPNK is not involved in the homologous recombination DSB repair pathway. We also provide evidence that the action of hPNK in the repair of camptothecin-induced topoisomerase 1 "dead-end" complexes is independent of DNA-PKcs and that hPNK is not involved in the nucleotide excision repair pathway.     

Cationic polymer‐mediated small interfering RNA delivery for P‐glycoprotein down‐regulation in tumor cells

BACKGROUND:

Among the treatment options that have been developed for cancer, chemotherapy remains 1 of the leading clinical approaches. Chemotherapy can usually control tumor growth at the onset of disease, but its effectiveness becomes limited by the overexpression of transporter proteins responsible for drug efflux, leading to multidrug resistance (MDR). To overcome this obstacle, the authors explored the feasibility of down‐regulating the main drug transporter, P‐glycoprotein (P‐gp), by using nonviral small interfering RNA (siRNA) delivery as means to enhance the accumulation of chemotherapeutic agents in drug‐resistant cancer cells.

METHODS:

Several cationic carriers capable of siRNA complexation were investigated for P‐gp down‐regulation in the MDA435/LCC6 cell line and, consequently, increased cellular uptake of the chemotherapeutic agents doxorubicin and paclitaxel.

RESULTS:

Efficient siRNA delivery into tumor cells was demonstrated particularly using a palmitic‐acid substituted poly(L‐lysine), with no apparent differences in siRNA delivery between the wild type (WT)‐expressing and P‐gp‐expressing phenotype (MDR1) of the cells. Efficient siRNA delivery led to approximately 40% to 50% P‐gp suppression (based on the average expression level of the protein), an approximately 3‐fold increased DOX uptake, and increased cytotoxicity in MDR1 cells.

CONCLUSIONS:

The authors concluded that effective siRNA delivery with nonviral carriers can reduce the level of P‐gp on cell surfaces and enhance the efficiency of chemotherapeutic agents in vitro. Cancer 2010. © 2010 American Cancer Society.     

Differential cytotoxic effects of arsenic compounds in human acute promyelocytic leukemia cells

Arsenic trioxide, As₂O₃, has successfully been used to treat acute promyelocytic leukemia (APL). Induction of apoptosis in cancerous cells has been proposed to be the underlying mechanism for the therapeutic efficacy of arsenic. To further understand the cytotoxicity of arsenic compounds in APL cells, HL-60 cells were exposed to graded concentrations of the following arsenicals for up to 48 h: arsenic trioxide (As^III), sodium arsenate (As^V), phenylarsine oxide (PAO^III), monomethylarsonous acid (MMA^III), monomethylarsonic acid (MMA^V) and dimethylarsinic acid (DMA^V), and the viability and modes of cell death assessed. The arsenic-exposed cells were stained with annexin V-PE and 7-aminoactinomycin D (7-AAD) and analyzed by flow cytometry in order to detect apoptotic and viable cells while cell morphology was visualized using scanning and transmission electron microscopy. Acridine orange staining and microtubule-associated protein 1 light chain 3 (MAP-LC3) detection were used to recognize autophagic cell death. The results showed that the compounds reduced viable HL-60 cells by inducing apoptosis in a concentration-dependent manner. None of the compounds tested caused a significant change in binding of acridine orange or redistribution of MAP-LC3. Potencies of the six different arsenic compounds tested were ranked as PAO^III > MMA^III ≥ As^III > As^V > MMA^V > DMA^V. An increase in caspase-3 activity by PAO^III, MMA^III and DMA^V implied that these compounds induced apoptosis in HL-60 cells through a caspase-dependent mechanism, but the other arsenic compounds failed to activate caspase-3, suggesting that they induce apoptosis by an alternative pathway.