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Biomedical subjects

K John

Publications and source records attributed to K John.

At least 19 recordsLinked to original sources

Self-propelled running droplets on solid substrates driven by chemical reactions.

We study chemically driven running droplets on a partially wetting solid substrate by means of coupled evolution equations for the thickness profile of the droplets and the density profile of an adsorbate layer. Two models are introduced corresponding to two qualitatively different types of experiments described in the literature. In both cases an adsorption or desorption reaction underneath the droplets induces a wettability gradient on the substrate and provides the driving force for droplet motion. The difference lies in the behavior of the substrate behind the droplet. In case I the substrate is irreversibly changed whereas in case II it recovers allowing for a periodic droplet movement (as long as the overall system stays far away from equilibrium). Both models allow for a non-saturated and a saturated regime of droplet movement depending on the ratio of the viscous and reactive time scales. In contrast to model I, model II allows for sitting drops at high reaction rate and zero diffusion along the substrate. The transition from running to sitting drops in model II occurs via a super- or subcritical drift-pitchfork bifurcation and may be strongly hysteretic implying a coexistence region of running and sitting drops.

Journal Article↗

Modulation of ATP/ADP concentration at the endothelial surface by shear stress: effect of flow-induced ATP release.

The adenine nucleotides ATP and ADP induce the production of vasoactive compounds in vascular endothelial cells (ECs). Therefore, knowledge of how flow affects the concentration of ATP and ADP at the EC surface may be important for understanding shear stress-mediated vasoregulation. The concentration of ATP and ADP is determined by convective and diffusive transport as well as by hydrolysis of these nucleotides by ectonucleotidases at the EC surface. Previous mathematical modeling has demonstrated that for steady flow in a parallel plate flow chamber, the combined ATP+ADP concentration does not change considerably over a wide range of shear stress. This finding has been used to argue that the effect of flow on adenine nucleotide transport could not account for the dependence of endothelial responses to ATP on the magnitude of applied shear stress. The present study extends the previous modeling to include pulsatile flow as well as flow-induced endothelial ATP release. Our results demonstrate that flow-induced ATP release has a pronounced effect on nucleotide concentration under both steady and pulsatile flow conditions. While the combined ATP+ADP concentration at the EC surface in the absence of flow-induced ATP release changes by only approximately 10% over the wall shear stress range 0.1-10 dyne cm(-2), inclusion of this release leads to a concentration change of approximately 34%-106% over the same shear stress range, depending on how ATP release is modeled. These results suggest that the dependence of various endothelial responses to shear stress on the magnitude of the applied shear stress may be partially attributable to flow-induced changes in cell-surface adenine nucleotide concentration.

Adenosine Diphosphate↗

Arsenic metabolism in seaweed-eating sheep from Northern Scotland.

Cation exchange and anion exchange liquid chromatography were coupled to an ICP-MS and optimised for the separation of 13 different arsenic species in body fluids (arsenite, arsenate, dimethylarsinic acid (DMAA), monomethylarsonic acid (MMAA), trimethylarsine oxide (TMAO), tetramethylarsonium ion (TMA), arsenobetaine (AsB), arsenocholine (AsC), dimethylarsinoyl ethanol (DMAE) and four common dimethylarsinoylribosides (arsenosugars). The arsenic species were determined in seaweed extracts and in the urine and blood serum of seaweed-eating sheep from Northern Scotland. The sheep eat 2-4 kg of seaweed daily which is washed ashore on the most northern Island of Orkney. The urine, blood and wool of 20 North Ronaldsay sheep and kidney, liver and muscle from 11 sheep were sampled and analysed for their arsenic species. In addition five Dorset Finn sheep, which lived entirely on grass, were used as a control group. The sheep have a body burden of approximately 45-90 mg arsenic daily. Since the metabolism of arsenic species varies with the arsenite and arsenate being the most toxic, and organoarsenic compounds such as arsenobetaine the least toxic compounds, the determination of the arsenic species in the diet and their body fluids are important. The major arsenic species in their diet are arsenoribosides. The major metabolite excreted into urine and blood is DMAA (95 +/- 4.1%) with minor amounts of MMAA, riboside X, TMA and an unidentified species. The occurrence of MMAA is assumed to be a precursor of the exposure to inorganic arsenic, since demethylation of dimethylated or trimethylated organoarsenic compounds is not known (max. MMAA concentration 259 microg/L). The concentrations in the urine (3179 +/- 2667 microg/L) and blood (44 +/- 19 microg/kg) are at least two orders of magnitude higher than the level of arsenic in the urine of the control sheep or literature levels of blood for the unexposed sheep. The tissue samples (liver: 292 +/- 99 microg/kg, kidney: 565 +/- 193 microg/kg, muscle: 680 +/- 224 microg/kg) and wool samples (10470 +/- 5690 microg/kg) show elevated levels which are also 100 times higher than the levels for the unexposed sheep.

Animals↗

The immune response to Haemophilus ducreyi resembles a delayed-type hypersensitivity reaction throughout experimental infection of human subjects.

Previous work in 3 subjects infected for 2 weeks indicated that experimental infection with Haemophilus ducreyi recruits CD4 cells to the skin at the pustular stage of disease. In order to describe the kinetics of the host response, 23 subjects were infected at 2 sites with a standardized dose of H. ducreyi. Subjects were biopsied 1 or 4 days after inoculation or when they developed a painful pustular lesion (days 7-14). Papules and pustules contained a predominant T cell infiltrate that consisted of CD45RO and CD4 cells of the alpha beta lineage. Both papules and pustules contained mixed or T helper 1 type cytokine mRNA and interleukin-8 and tumor necrosis factor-alpha mRNA. Although the subjects had no history of chancroid, their immune responses resembled delayed-type hypersensitivity reactions that occurred within 24 h of inoculation and persisted throughout the course of experimental infection.

Adult↗

013 (CD99) positivity in hematologic proliferations correlates with TdT positivity.

The monoclonal antibody 013, which detects the cell surface glycoprotein p30/32mic2 (CD99) is a characteristic, if nonspecific, marker for peripheral neuroepithelioma and Ewing's sarcoma. 013 was first produced against a human thymus leukemia antigen and has also been found in immature terminal deoxynucleotidyl transferase (TdT)-positive T cells and in a small group of hematopoietic precursor cells in the bone marrow. 013 is reactive in lymphoblastic lymphomas and acute leukemias, as well as in a variety of other hematologic malignancies. Because the distribution of 013 positivity in hematopoietic proliferations is similar to that of TdT, we hypothesized that 013 might correlate with TdT positivity. We studied 67 lymphoblastic lymphomas and acute lymphoblastic leukemias, 6 chronic myelogenous leukemias in blast crisis, a variety of acute myeloid leukemias, 5 granulocytic sarcomas, and a spectrum of 94 diffuse lymphomas other than lymphoblastic type. With the use of heat-induced epitope retrieval and automated immunostaining, we compared the results obtained with 013 and TdT, a well-established marker of lymphoblastic lymphomas and acute lymphoblastic leukemias that can also be successfully demonstrated in tissue sections by use of a similar technique. In our study, all of the 013-positive cases were also TdT positive. 013 reacted with 44 (71%) of 62 of the TdT-positive lymphoblastic lymphomas and acute lymphoblastic leukemias cases studied. We also found 013 to be positive in one case of TdT-positive acute myeloid leukemia, in two cases of chronic myelogenous leukemia in blast crisis, and in three TdT-positive granulocytic sarcomas. 013 was negative in all of the other high-grade malignant lymphomas and in TdT-negative leukemias. With use of our technique, 013 positivity appears to be restricted to hematologic proliferations that demonstrate TdT positivity. 013 may be a helpful additional marker in the diagnosis of TdT-positive leukemias and lymphomas in conventionally processed tissue sections.

12E7 Antigen↗

The importance of late infections for the long-term outcome after liver transplantation.

We investigated the late infections of 400 consecutive liver transplantations performed in 368 patients. After a mean follow-up of 45 months, a total of 180 late infections occurred in 110 liver recipients. Frequent agents were CMV, enterococcus, candida and staphylococcus. Pneumonia was the most dangerous late infection with a high mortality rate. Late infections were responsible for ten deaths that were all caused by atypical pneumonia. The majority of late infections appeared during the first year after liver transplantation. Thereafter, the risk of infection declined significantly.

Humans↗

p53 overexpression in myeloid leukemic disorders is associated with increased apoptosis of hematopoietic marrow cells and ineffective hematopoiesis.

Recent evidence has shown that p53 overexpression in leukemic cells may be a consequence of p53 gene mutation or can occur via posttranslational modification mechanisms. While mutant forms of p53 may stimulate cell proliferation and transformation, wild-type p53 may inhibit DNA synthesis and cause leukemic cells to enter apoptosis. Nine bone marrow biopsies of acute myeloid leukemia (AML) and myelodysplastic syndromes (MDS) with known p53 overexpression were analyzed for evidence of apoptosis of both leukemic blasts and of background hematopoietic cells. This was quantified and compared with that seen in p53- AML and MDS and in normal control marrows. The rate of cell death due to apoptosis was measured by in situ end-labeling of fragmented DNA with the following results: mean values of apoptotic cells/mm2 of BM, p53+ AML and MDS (9 cases), 2.41 +/- 1.7; p53- AML and MDS (10 cases), 0.16 +/- 0.1; control marrows (20 samples), 0.05 +/- 0.0. Our results showed a significant association (P < 0.001) between p53 overexpression and increased apoptosis in all cases studied. The difference was entirely caused by the high rate of cell death observed in the erythroid and myeloid precursor cells of these marrows. These findings suggest that p53+ AML and MDS are a distinct group of marrow disorders characterized by a high rate of intramedullary cell death. This may explain why patients with p53+ leukemic disorders show excessive marrow sensitivity to chemotherapy with prolonged marrow suppression associated with the presence of cytogenetically abnormal blasts that display great drug resistance.

Adolescent↗

Screening of in vitro antibacterial activity from Syzygium Guineense (Willd) hydrosoluble dry extract.

Diarrhoea is one of the most important causes of infant mortality in the world. As modern drugs are expensive or unavailable in developing countries, many people use traditional medicines in Africa for the treatment of several diseases. In our study, we investigated the antibacterial activity of Syzygium Guineense extract in order to assess its activity on some bacterial strains involved in diarrhoeal diseases and to justify its use. The aqueous dry extract was prepared by decoction followed by evaporating to dryness and tested according to dilution method. This extract showed an antibacterial activity against some bacterial strains: Salmonella E., Shigella D., Shigella F., E. Coli., Enterobacter A. It did not show any activity against Citrobacter F., Proteus M., Klebsiella P. Storage conditions (27 degrees C, glass flask) did not affect antibacterial properties of the extract.

Anti-Bacterial Agents↗

In vivo effects of recombinant human stem cell factor treatment. A morphologic and immunohistochemical study of bone marrow biopsies.

Bone marrow (BM) aspirate and biopsy specimens from seven female patients with advanced or metastatic breast cancer and preserved marrow function treated on a phase I trial of recombinant methionyl human stem cell factor (r-metHuSCF; SCF) were evaluated by immunohistochemical staining before and after treatment with SCF. Doses of SCF included 10 g/kg/day in 2 patients, 25 micrograms/kg/day in 2 patients, and 50 micrograms/kg/day in 3 patients administered as subcutaneous bolus injections for 14 days. Following treatment, bone marrow cellularity increased up to 1.6-fold (P = NS), with an increased frequency of promyelocytes (P < .002), but an unchanged relative frequency of other marrow hematopoietic cells. The mean relative frequency of BM CD34+ progenitor cells increased from 0.9% to 1.8% (P < .001). The mean proportion of BM cells stained by Ki-67/MIB 1 and PCNA/PC10, monoclonal antibodies (MoAb) recognizing proliferation-associated nuclear proteins, increased from 18.6% to 35.4% (P < .003) and from 32.4% to 49.4% (P < .01), respectively. Most of the Ki-67 and PCNA positive cells were represented by promyelocytes, proerythroblasts, and myeloblasts. SCF therapy was not associated with marrow fibrosis or increases in the number of macrophages. Peripheral white blood cell counts increased 1.3- to 3.6-fold following SCF. The mean absolute neutrophil counts increased from 3.9 x 10(9)/L (range 2.6-5.3) to 7.2 x 10(9)/L (range 4.7-12.3), and reticulocyte counts increased by a mean of 1.5 fold (range 1.2-fold to 2.0-fold). No consistent difference in platelet counts was seen. These results suggest that SCF given in vivo is effective in increasing the frequency of CD34+ BM progenitor cells, and has the capacity to increase the proliferation and differentiation rate of hematopoietic precursor cells. These effects indicate that SCF may represent a cytokine capable of affecting multiple hematopoietic lineages.

Adult↗

Correlation between presence of clonal rearrangements of immunoglobulin heavy chain genes and B-cell antigen expression in Hodgkin's disease.

Southern blot analysis of Hodgkin's disease (HD), although often compromised by the small number of abnormal cells present in the tissue, have tended to favor a B-cell derivation of the Hodgkin's and Reed-Sternberg (HRS) cells in cases of nodular sclerosis (NS) and mixed cellularity (MC) Hodgkin's disease. Eighteen frozen and 29 paraffin-embedded sections of lymph node specimens from 29 patients with pretreatment HD (22 NSHD and 7 MCHD) were studied by molecular analysis and immunohistochemistry to determine the phenotype of HRS cells. All cases were reviewed and showed typical morphology and CD45-, CD30+, CD15+, BLA.36+ HRS cells. In 11 of 29 (38%) cases, HRS cells were reactive with at least one B-cell marker (CD20, CD79a, MB2), 7 of 29 (24%) cases showed reactivity with the T-cell marker CD3, and 11 of 29 (38%) cases displayed a "null" phenotype. By using a polymerase chain reaction (PCR) and consensus primers for the V and J regions of the immunoglobulin heavy chain (IgH) gene, the authors were able to detect B-cell clonality in 9 of 18 (50%) frozen samples of HD analyzed. IgH gene rearrangement was present in 8 of 15 (53%) NSHD and in 1 of 3 (33%) MCHD. In five of nine (56%) of these cases, HRS cells were reactive with at least one B-cell marker, whereas one case expressed the T-cell marker CD3. The other three cases with IgH gene rearrangement showed a "null" immunophenotype. IgH gene analysis was negative in all remaining CD3+ cases and in two other cases that expressed B-cell markers by immunohistology. Southern blotting failed to detect rearrangement of the T-cell receptor beta-chain gene and immunoglobulin heavy and light genes in any of these cases. The results show that PCR represents a specific and sensitive technique for the detection of IgH gene rearrangements in cases of Hodgkin's disease. The results also suggest a lymphoid B-cell derivation of HRS cells in a high proportion of the cases.

Antigens, Neoplasm↗

In vitro effect of vegetable and fruit juices on the mutagenicity of 2-amino-3-methylimidazo[4,5-f]quinoline, 2-amino-3,4-dimethylimidazo[4,5-f]quinoline and 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline.

The antimutagenic potencies of the juices of 28 fruits and 34 vegetables commonly consumed in Germany were investigated with respect to the mutagenic activities induced by 2-amino-3-methyl[4,5-f]-quinoline (IQ), and in part by 2-amino-3,4-dimethylimidazo[4,5-f]quinoline (MeIQ) or 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline (MeIQx) in Salmonella typhimurium TA98 and TA100. With IQ, weak to strong antimutagenic activities were found in 68% of the fruits and 73% of the vegetables that were tested. In fruits, strong antimutagenic activities were detected in bananas, blackberries, blueberries, sweet and sour cherries, blackcurrants and redcurrants, pineapple and watermelon. Moderate antimutagenic activities were detected in greengage, kiwi, mangos, honeydew melons and plums. Weak antimutagenic activities were detected in apple, apricot, mirabelle, pears, peaches and strawberries, whereas white and red grapes and raspberries were inactive, and gooseberries and citrus fruits in general possessed marginal or no antimutagenic activities. In vegetables, strong to moderate antimutagenic activities were found for all cruciferous vegetables, except Chinese cabbage, which had only weak antimutagenic activity. Other vegetables with strong antimutagenic activities were beets, chives, horseradish, onions, rhubarb and spinach. Moderate antimutagenic activities were found with green beans and tomatoes, weak activities in eggplant, garden cress, many lettuces, leeks, mangold, cucumber, pumpkin, radish and summer squash. Asparagus, carrots, fennel leaves, parsley, green peppers and radishes were inactive. When fruit and vegetable juices were heated, a considerable reduction of antimutagenic potencies was seen with apple, apricot, kiwi, pineapple, beets, cabbage (Chinese, Savoy, red and white), cauliflower, leafy lettuce, cucumber, onions, radish and rhubarb. Antimutagenic factors in blackberries, blueberries, sweet and sour cherries, honeydew melons, mirabelle, plums, strawberries, Brussels sprouts, chicory greens, eggplant, garden cress, mangold, pumpkin, lamb's lettuce and spinach were, however, remarkably heat stable. Antimutagenic potencies in bananas, blackcurrants and redcurrants, greengages, gooseberries, mangos, watermelon, green beans, kohlrabi, horseradish, tomatoes and chives were partially reduced. Antimutagenic activities in the juices of eight apple cultivars were moderate in two, weak in four, and marginal or absent in two. No major differences, however, were detected in five batches of oranges and three batches each of grapefruits, asparagus, green beans, broccoli, cauliflower, spinach and tomatoes. No (or only minor) differences were seen between IQ, MeIQ and MeIQx and tester strains TA98 and TA100. Pineapple and celeriac juices inhibited the enzymatic system responsible for the activation of IQ, but had no desmutagenic activity. Peroxidase activity found to be present in broccoli, cauliflower, green beans and tomatoes may contribute to antimutagenic activities in these vegetables.

Animals↗

CD34 immunostaining of bone marrow biopsy specimens is a reliable way to classify the phases of chronic myeloid leukemia.

Flow cytometry studies have shown that high expression of CD34 antigen in patients with chronic myeloid leukemia (CML) is indicative of accelerated or blastic phases. It has also been suggested that similar information can be obtained by CD34 immunostaining of bone marrow biopsy specimens. To test this hypothesis, the authors studied 59 conventionally fixed, paraffin-embedded bone marrow trephine biopsy specimens, representing the three phases of the disease (stable, accelerated, and blast crisis). Immunohistochemical staining for CD34 was performed using QBEnd10, a monoclonal antibody reactive in routine paraffin-embedded tissue. The differences in CD34 positivity among chronic, accelerated, and blastic phases of CML were highly significant (P = .0001). This study demonstrated that CD34 immunohistochemical staining of bone marrow biopsy specimens represents a reliable method for classifying patients with CML and may provide essential diagnostic and prognostic information when a marrow aspirate is unavailable.

Antigens, CD↗

Terminal deoxynucleotidyl transferase staining in acute leukemia and normal bone marrow in routinely processed paraffin sections.

Terminal deoxynucleotidyl transferase (TdT) is a nuclear protein widely used as a marker for the diagnosis and classification of acute leukemia. The usual methods for detecting TdT require smears, imprints, or cryostat sections of unfixed tissue. A polyclonal rabbit anti-TdT serum was used to immunostain 54 routinely processed bone marrow sections from patients with acute leukemic disorders, using a recently described antigen-unmasking technique based on microwave oven heating. The specificity of this method of TdT analysis was confirmed by comparing the results obtained with conventional TdT analysis by indirect immunofluorescence. Terminal deoxynucleotidyl transferase reactivity was also evaluated in 44 nonmalignant and normal bone marrow specimens. All cases that were TdT-positive by immunofluorescence (41 of 42 "pre-B" and T-cell acute lymphoblastic leukemia, 2 of 5 acute myeloid leukemia, and 1 of 5 chronic myeloid leukemia in blast crisis) were also positive in paraffin sections. The percentage fluorescence positivity correlated with the percentage of immunoperoxidase stained cells in 44 of 45 cases. The remaining nonneoplastic and normal bone marrow biopsy specimens were TdT-negative. These results show that TdT immunoperoxidase staining of conventionally processed bone marrow specimens can be readily achieved by the use of a simple antigen-unmasking technique and may provide useful diagnostic information particularly in cases in which fresh tissue samples are unavailable.

Acute Disease↗

Assessment of cell proliferation in paraffin sections of normal bone marrow by the monoclonal antibodies Ki-67 and PCNA.

Assessment of the proliferative index of human bone marrow using immunohistology in tissue sections offers practical advantages over other techniques. It is simpler to perform and can be applied to archival material. Progress in this area has been hampered by technical problems. Ki-67 studies, limited to fresh or frozen tissues, have been contradictory, and the labeling indices have been criticized for being unrealistically low. Proliferating cell nuclear antigen (PCNA) studies have also been considered unreliable because labeling indices include nondividing cells. We stained 82 routinely processed nonneoplastic bone marrow biopsies for Ki-67 equivalent MIB 1 antibody and PCNA/PC10 using a microwave oven antigen retrieval technique. 44.7% +/- 12.0 SD of the bone marrow cells stained with Ki-67/MIB 1. PCNA/PC10 staining gave similar results (50.7% +/- 12.3 SD). Pro- and basophilic erythroblasts, myeloblasts, promyelocytes, myelocytes, and megakaryocytes stained with both monoclonal antibodies in a manner consistent with known morphologic and cytokinetic data. Patients in different clinical groups showed similar mean values, the only exception being a group of cytokine-treated patients, which showed higher values than the other cases. Immunoperoxidase staining of bone marrow sections with Ki-67/MIB 1 and PCNA/PC10 monoclonal antibodies is a reliable method for assessing proliferation of hematopoietic cells.

Adult↗

Terminal deoxynucleotidyl transferase staining of malignant lymphomas in paraffin sections.

Terminal deoxynucleotidyl transferase (TdT) represents a useful marker for the diagnosis of acute lymphoblastic leukemia and lymphoblastic lymphoma. It is usually assayed in fresh tissue or cell suspensions by enzyme analysis, immunofluorescence, or immunoperoxidase. We have obtained satisfactory staining for TdT in routinely processed paraffin sections using a recently described antigen retrieval pretreatment based on microwave oven heating of the sections and a polyclonal rabbit anti-TdT serum. With this technique, we assayed paraffin sections from lymph nodes of 91 patients with a variety of malignant lymphomas, including 35 cases of lymphoblastic lymphoma. The specificity of this immunoperoxidase method of TdT analysis was confirmed by comparing the results obtained with conventional TdT analysis by indirect immunofluorescence. Neoplastic cells from 33 of the 35 (94%) patients with lymphoblastic lymphoma were TdT positive with both techniques. All remaining 50 cases of other subtypes of malignant lymphoma were TdT negative. Specificity was further confirmed by demonstrating TdT-positive blasts in paraffin sections of bone marrow biopsies from 44 patients with TdT-positive (by indirect immunofluorescence) acute leukemias and in paraffin sections of extramedullary leukemic infiltrates from eight patients with relapsed acute lymphoblastic leukemia. Other control material studied included eight lymph nodes with Hodgkin's disease, four normal spleen, seven reactive lymph nodes, and 25 nonneoplastic bone marrow samples, all of which gave the expected results, i.e., rare scattered TdT-positive cells in bone marrow and lymph nodes, absence of staining in Hodgkin's disease malignant cells and spleen. Our results confirm that TdT is a specific marker for the diagnosis and classification of lymphoblastic lymphoma.(ABSTRACT TRUNCATED AT 250 WORDS)

DNA Nucleotidylexotransferase↗

Hematopoietic precursor cells within the yolk sac tumor component are the source of secondary hematopoietic malignancies in patients with mediastinal germ cell tumors.

BACKGROUND: Patients with mediastinal germ cell tumors (MGCT) have a high incidence of hematologic malignancies unrelated to cytotoxic chemotherapy. It has been suggested that these leukemic conditions originate from a MGCT progenitor cell capable of undergoing non-germ cell (hematopoietic) differentiation. METHODS: To assess this hypothesis, histologic material from six patients with MGCTs associated with leukemia was examined using monoclonal and polyclonal antibodies capable of labeling cells of the different marrow cell lineages. RESULTS: Morphologically identifiable hematologic cells were found within the yolk sac tumor component of the MGCT in four of these patients. In three of the four cases, the cells consisted of poorly differentiated blast cells, whereas in the fourth, clusters of erythroblasts were identified. The leukemic cells within the MGCT and in the bone marrow had similar morphology, constant expression of the early progenitor cell marker CD34, and variable expression of more mature myeloid, monocytic, erythroid, and megakaryocytic markers. Three cases expressed p53, a nuclear protein associated with neoplastic transformation in a wide range of malignancies, including testicular cancers, but which rarely is reported in leukemias. Karyotype of the leukemia was assessed in five cases: two showed an i(12p), a cytogenetic marker of GCT not identified in the usual cases of leukemia. CONCLUSIONS: The results support the hypothesis that these leukemic conditions originate in the MGCT through a mechanism of differentiation from a yolk sac tumor-derived progenitor cell, with subsequent homing to the marrow.

Adolescent↗

Lactobionic and gluconic acid complexes of FeII and FeIII; control of oxidation pathways by an organ transplantation preservant.

Lactobionic acid, [4-beta-(galactosido)-D-gluconic acid] = LBA, is the major component of the Wisconsin organ transplantation preservant fluid and may suppress oxygen radical-induced tissue damage upon reperfusion by the control of FeII autoxidation. FeII and FeIII complexes of LBA and the related gluconic acid (GLC) have been studied herein by titrimetric, infrared, and electrochemical methods (CV; DPP). FeII(GLC) forms quickly at pH 7, but FeII(LBA) reacts in two steps, the second requiring 4 hr. The initial complex lacks coordination of the LBA carboxylate (C-1) and is bound by the "2,3,5" hydroxyl groups. The slow rearrangement forms a "1,2,3,6" chelate which FeII(LBA) shares in common with the donor set of the FeIII(LBA) complex. Titration data shows the removal of three protons from LBA through pH 5 and an additional proton from pH 6 to 9 which is indicative of the [FeIII(LBA)(OH)(H2O)]- formulation with LBA donating at the "1,2,3,6" positions. The more stable, second form of FeII(LBA) has been investigated in its oxidation mechanisms with H2O2 and O2 using selected trapping agents for HO. and ferryl intermediates. Eighty-six percent of the oxidation events of FeII(LBA)/H2O2 occurs in steps involving formation and reduction of freely diffusible HO.. These pathways are altered by the known HO. traps t-butanol, dmso, ethanol, and methanol in the manner predictable for beta-oxidizing radicals (from t-butanol or dmso) and alpha-reducing radicals (from ethanol and methanol). Fourteen percent of the FeII(LBA)/H2O2 reaction occurs via FeIVO intermediates not trapped by t-butanol or dmso, but intercepted by primary and secondary alcohols. The HO. generating pathways are responsible for a competitive LBA ligand oxidation at the C-2 position via HO., formed from FeII(LBA) and H2O2 within the original reaction cage. Competitive ligand oxidation at C-2 is absent for the FeII(LBA)/O2 autoxidation, indicative of a different redox mechanism. The FeII(LBA)/O2 reaction rate is first-order in each component and is insensitive to the presence of t-butanol as an HO. trap. These observations support a ferryl intermediate in the autoxidation pathway and the absence of HO. or free H2O2 during autoxidation. Although chelation of FeII by hard ligand donors such as edta4-, Cl-, or HPO4(2-) accelerate the rate of autoxidation of FeII, chelation of carboxylate, alkoxy, and hydroxyl donors of LBA does not accelerate autoxidation. The implications of these findings, and the absence of an inner-sphere coordination role of the 4-beta-(galactosido) functionality toward the action of LBA in organ preservant fluids, are discussed.

Adenosine↗

Frequent p53 overexpression in therapy related myelodysplastic syndromes and acute myeloid leukemias: an immunohistochemical study of bone marrow biopsies.

p53 overexpression was studied immunohistochemically in paraffin-embedded bone marrow biopsies using a recently described technique for antigen retrieval based on microwave oven heating of paraffin sections. Using a monoclonal antibody (PAb1801) that reacts with human cellular p53, nuclear staining was detected in 7/11 (63%) therapy-related myelodysplastic syndromes and in 3/4 (75%) therapy-related acute myeloid leukemias. Conversely, staining for p53 was seen only in 9/40 (22%) cases of "primary" hematologic conditions (P < 0.007); these included myelodysplastic syndromes [#2], acute myeloid leukemia [#4], and chronic granulocytic leukemia in accelerated phase or blast crisis [#3]. Biopsies of normal controls and of chronic granulocytic leukemia in stable phase were consistently p53(-). Nine of the 10 karyotyped p53(+) acute myeloid leukemia/myelodysplastic syndrome cases showed complex cytogenetic findings with frequent involvement of chromosome 5 and/or 7. Only four of the 33 karyotyped p53(-) cases showed similar cytogenetic changes. Chromosome 17 involvement was present in four of 13 (31%) cytogenetically assessed p53+ cases, but in none of the p53(-). In univariate analysis, p53 expression in both MDS and AML was significantly associated with shorter survival. The frequent overexpression of p53 in therapy-related myelodysplastic syndromes, therapy-related acute myeloid leukemias and in accelerated phase/blast crisis, chronic granulocytic leukemia and its strong association with complex karyotypes suggests an important role of this gene in the pathogenesis of these leukemic conditions.

Acute Disease↗