Biomedical subjects

H Schott

Publications and source records attributed to H Schott.

At least 19 recordsLinked to original sources

PubMed2002

Cytotoxic targeting of F9 teratocarcinoma tumours with anti-ED-B fibronectin scFv antibody modified liposomes.

We prepared small unilamellar liposomes derivatised with single chain antibody fragments specific for the ED-B domain of B-fibronectin. This extracellular matrix associated protein is expressed around newly forming blood vessels in the vicinity of many types of tumours. The single chain antibody fragments were functionalised by introduction of C-terminal cysteines and linked to liposomes via maleimide groups located at the terminal ends of poly(ethylene glycol) modified phospholipids. The properties of these anti-ED-B single chain antibody fragments-liposomes were analysed in vitro on ED-B fibronectin expressing Caco-2 cells and in vivo by studying their biodistribution and their therapeutic potential in mice bearing subcutanous F9 teratocarcinoma tumours. Radioactively labelled ((114m)Indium) single chain antibody fragments-liposomes accumulated in the tumours at 2-3-fold higher concentrations during the first 2 h after i.v. injection compared to unmodified liposomes. After 6-24 h both liposome types were found in similar amounts (8-10% injected dose g(-1)) in the tumours. Animals treated i.v. with single chain antibody fragments-liposomes containing the new cytotoxic agent 2'-deoxy-5-fluorouridylyl-N(4)-octadecyl-1-beta-D-arabinofuranosylcytosine (30 mg kg(-1) per dose, five times every 24 h) showed a reduction of tumour growth by 62-90% determined on days 5 and 8, respectively, compared to animals receiving control liposomes. Histological analysis revealed a marked reduction of F9 tumour cells and excessive deposition of fibronectin in the extracellular matrix after treatment with single chain antibody fragments-2-dioxy-5-fluorouridylyl-N(4)-octadecyl-1-beta-D-arabinofuranosylcytosine-liposomes. Single chain antibody fragments-liposomes targeted to ED-B fibronectin positive tumours therefore represent a promising and versatile novel drug delivery system for the treatment of tumours.

Animals↗

PubMed2001

IL-2 in combination with IFN- alpha and 5-FU versus tamoxifen in metastatic renal cell carcinoma: long-term results of a controlled randomized clinical trial.

We conducted a prospectively randomized clinical trial to compare the efficacy and safety of subcutaneous interferon-alpha2a, subcutaneous interleukin-2 and intravenous 5-fluorouracil as home therapy against oral tamoxifen in 78 patients with progressive metastatic renal cell carcinoma. Treatment courses consisted of interferon-alpha2a 5 x 10(6) IU m(-2), day 1 weeks 1 + 4; days 1, 3, 5 weeks 2 + 3; 10 x 10(6) IU m(-2), days 1, 3, 5 weeks 5-8; interleukin-2 10 x 10(6) IU m(-2), twice daily days 3-5 weeks 1 + 4; 5 x 10(6) IU m(-2), days 1, 3, 5 weeks 2 + 3; and 5-fluorouracil 1000 mg m(-2), day 1 weeks 5-8. The tamoxifen group received tamoxifen 80 mg twice daily over 8 weeks. Among 41 patients treated with interleukin-2, interferon-alpha2a and 5-fluorouracil there were 7 complete (17.1%) and 9 partial responders (21.9%), with an overall objective response rate of 39.1% (95% CI, 24.2-55.5). An additional 15 patients (36.6%) were stable throughout therapy. The overall survival was 24 months (range 5-76+). In 37 patients receiving tamoxifen no objective remissions occurred. 13 patients (35.1%) had stable disease and 24 patients (64.9%) showed continued disease progression. The overall survival was 13 months (range 3-73+). In summary, this home-based therapy regimen of interferon-alpha2a, interleukin-2 and 5-fluorouracil demonstrated significant therapeutic efficacy in patients with progressive renal cell carcinoma when compared to hormonal therapy.

Adult↗

PubMed2001

In vitro activity of liposomal N4octadecyl-1-beta-D-arabinofuranosylcytosine (NOAC), a new lipophilic derivative of 1-beta-D-arabinofuranocylcytosine on biopsized clonogenic human tumor cells and hematopoietic precursor cells.

N4-octadecyl-1-beta-D-arabinofuranosylcytosine (NOAC) is a new lipophilic derivative of 1-beta-D-arabinofuranosylcytosine (ara-C) with potent antitumor activity against leukemias and solid tumors. In this study the activity of NOAC against freshly explanted clonogenic cells from human tumors was determined and compared with conventional antitumor agents. NOAC was used in two liposomal preparations, a stable lyophilized and a freshly prepared liquid formulation. Both formulations inhibited tumor colony formation equally in a concentration-dependent fashion in both short- (1 h) and long-term (21-28 d) exposure experiments. NOAC (100 microM, long-term exposure) had a significantly better activity compared to the clinically used drugs cisplatin, doxorubicin, 5-fluorouracil, gemcitabine, mitomycin C and etoposide. The comparison of NOAC with ara-C in the long-term exposure experiment showed that ara-C was more effective at 4 and 10 microM, whereas at 1 and 100 microM there was no difference between the two drugs. NOAC was less toxic in a hematopoietic stem cell assay than ara-C and doxorubicin by factors ranging from 2.5 to 200, indicating that this drug is well tolerated at high doses. The antitumor activity of NOAC (NSC 685096) was confirmed by the NCI in vitro drug screening program where the drug was found to be active against several types of human tumors. Further development of NOAC in phase II studies is warranted.

Antimetabolites, Antineoplastic↗

PubMed2000

Induction of cell cycle-dependent cytotoxicity and apoptosis by new heterodinucleoside phosphate dimers of 5-fluorodeoxyuridine in PC-3 human prostate cancer cells.

Fluorodeoxyuridine (5-FdUrd) is an antineoplastic agent with clinical activity against different types of solid tumours. To enhance the effectiveness of this drug, we have synthesised new heterodinucleoside phosphate dimers of 5-FdUrd. These dimers were compared to 5-FdUrd for their cytotoxic effect and the cell cycle dependence of cytotoxicity, as well as for their capacity to induce apoptosis and inhibit thymidylate synthetase (TS) in androgen-independent human PC-3 prostate tumour cells. Incubation of the cells with the dimers N(4)-palmitoyl-2'-deoxycytidylyl-(3'-->5')-5-fluoro-2'-deoxyuri din e (dCpam-5-FdUrd) and 2'-deoxy-5-flourouridylyl-(3'-->5')-2'-deoxy-5-fluoro-N(4)-octa decylc ytidine (5-FdUrd-5-FdC18) resulted in a marked cytotoxicity with IC(50) values of 4 microM, similar to 5-FdUrd. In contrast to 5-FdUrd, 100% toxicity was achieved with concentrations of 100-200 microM 5-FdUrd-5-FdC18. Flow cytometric analysis revealed an increase in the cell population in S-phase after treatment with 5-FdUrd, 5-FdUrd-5-FdC18, and dCpam-5-FdUrd from 36 to 63%, 50%, and 77%, respectively. dCpam-5-FdUrd was more potent than 5-FdUrd in arresting the cell cycle. Significant S-phase arrest was indicated by a decreased proportion of cells in G1- and G2/M-phases. Cell cycle arrest and inhibition of cell proliferation were followed by apoptosis, as shown by a 6- to 8-fold increased binding of Apo2.7 antibody, a 9- to 11-fold increase in caspase-3 activity, DNA fragmentation, and by cell morphology showing the appearance of apoptotic bodies. Importantly, 5-FdUrd-5-FdC18 increased the number of apoptotic cells to 160% compared to 5-FdUrd under the same conditions. As with 5-FdUrd, the two dimers also inhibited TS in a time- and concentration-dependent manner, although requiring 100-fold higher concentrations. In conclusion, dCpam-5-FdUrd and 5-FdUrd-5-FdC18 exert stronger cytotoxicity and induce more S-phase arrest and apoptosis than does 5-FdUrd in PC-3 cells, suggesting their potential role in the treatment of human prostate cancer.

Antineoplastic Agents↗

PubMed2000

The novel heterodinucleoside dimer 5-FdU-NOAC is a potent cytotoxic drug and a p53-independent inducer of apoptosis in the androgen-independent human prostate cancer cell lines PC-3 and DU-145.

BACKGROUND: We analyzed the cytotoxic properties of the new heterodinucleoside phosphate dimer 5-FdU-NOAC, which is composed of the cytotoxic drugs 5-FdU and N(4)-octadecyl-1-beta-D-arabinofuranosylcytosine (NOAC) against human prostate tumor cells. METHODS: 5-FdU-NOAC effects on cell proliferation, cell cycle distribution, thymidylate synthase activity, and apoptosis were investigated in vitro in the two human prostate carcinoma cell lines DU-145 and PC-3 and compared to cells treated with the corresponding single drugs 5-FdU and NOAC. RESULTS: Treatment of the cells with 5-FdU-NOAC resulted in IC(50) values of 3.9-5 microM and in a complete inhibition of cell proliferation at 200 microM after 96 hr compared to 5-FdU, where 10% of the cells remained resistant. Flow cytometric analysis revealed cell cycle perturbations in S-phase only in the DU-145 cells. 5-FdU-NOAC caused 50% inhibition of thymidylate synthase after 90 min at 0.6 microM in both cell lines. Apoptotic cell fractions in DU-145 (66%) and in PC-3 (34%) cells were found after treatment with 5-FdU-NOAC for 96 hr. DNA fragmentation further confirmed the induction of apoptosis. CONCLUSIONS: 5-FdU-NOAC inhibits thymidylate synthase and cell cycle progression causing proliferation arrest and apoptosis in DU-145 and PC-3 cells, suggesting a potential role of 5-FdU-NOAC for the treatment of prostate cancer.

Androgens↗

PubMed2000

Cell-cycle arrest and p53-independent induction of apoptosis in vitro by the new anticancer drugs 5-FdUrd-P-FdCydOct and dCydPam-P-FdUrd in DU-145 human prostate cancer cells.

PURPOSE: Current therapies have limited impact on the progression of metastatic hormone-refractory prostate cancer. Therefore, we investigated the utility of new heterodinucleoside phosphate dimers of 5-fluorodeoxyuridine (5-FdUrd) in p53-mutated and androgen-independent DU-145 human prostate tumour cells. METHODS: The effects of the dimers were assessed in vitro by a cell proliferation assay for cytotoxicity, flow cytometry for cell cycle distribution, confocal laser scanning microscopy for the detection of apoptotic bodies, poly(ADP-ribose) polymerase cleavage for caspase 3 activity and by a thymidylate synthetase assay. RESULTS: The new dimers N4-palmitoyl-2'-deoxycytidylyl-(3'-->5')-5-fluoro-2'-deoxyuridine (dCydPam-P-FdUrd) and 2'-deoxy-5-fluorouridylyl-(3'-->5')-2'-deoxy-5-fluoro-N4-octade cylcytidine (5-FdUrd-P-FdCydOct) caused marked cytotoxicity with IC50 values of 3-4 microM. 5-FdUrd-P-FdCydOct at 200 microM was capable of eradicating 100% of tumour cells whereas 10% of the cells were resistant to 5-FdUrd. Cytotoxicity was caused by a dramatic S-phase arrest, resulting in an increase of this cell population from 34% to 85% with 5-FdUrd-P-FdCydOct and to 81% with dCydPam-P-FdUrd. S-phase arrest was followed by apoptosis, as shown by 85% of the cells staining positive for Apo 2.7 antibody, a six- to eight-fold increased caspase 3 activity and DNA fragmentation. Thymidylate synthase activity was inhibited by 50% at 0.6-0.7 microM dimer concentration. The dimers were hydrolysed in vitro by phosphodiesterase I and human serum to the corresponding nucleosides and nucleoside monophosphates. CONCLUSIONS: The new dimers dCydPam-P-FdUrd and 5-FdUrd-P-FdCydOct are effective prodrugs of 5-FdUrd and have potential value for the treatment of p53-mutated and hormone-independent human prostate carcinomas.

Antimetabolites, Antineoplastic↗

PubMed2000

Cytotoxicity, cell-cycle perturbations and apoptosis in human tumor cells by lipophilic N4-alkyl-1-beta-D-arabinofuranosylcytosine derivatives and the new heteronucleoside phosphate dimer arabinocytidylyl-(5'-->5')-N4-octadecyl-1-beta-D-arabinofuranosylcytosi ne.

The arabinofuranosylcytosine (AraC) derivative N4-octadecyl-1-beta-D-arabinofuranosylcytosine (NOAC) and its (5'-->5')-heterodinucleoside phosphate analog NOAC-AraC were compared with AraC for cytotoxicity, cell-cycle dependence, phosphorylation by deoxycytidine (dC) kinase and apoptosis induction in native, AraC- or NOAC-resistant HL-60 cells. NOAC was cytotoxic in all cells with three to seven-fold lower IC50 concentrations than those of NOAC-AraC or AraC. In contrast to NOAC-AraC, the lipophilic monomer NOAC overcame AraC resistance, inducing apoptosis in more than 80% of native and AraC-resistant HL-60 cells. This suggests that NOAC-AraC may be cleaved intracellularly only at very slow rates to AraC and NOAC or to the 5'-monophosphates, whereas NOAC exerts different mechanisms of action from AraC. In vitro the dimer was cleaved by phosphodiesterase or human serum to NOAC, AraC and AraC monophosphate. In contrast to AraC, N4-alkylated AraC derivatives with alkyl chains ranging from 6-18 C atoms were not substrates for dC kinase. Furthermore, treatment of the multidrug-resistant cell lines KB-ChR-8-5 and KB-V1 with the N4-hexadecyl-AraC derivative NHAC did not induce P-170 glycoprotein expression, suggesting that the N4-alkyl-AraC derivatives are able to circumvent MDR1 multidrug resistance. The in vivo activity of liposomal NOAC in a human acute lymphatic leukemia xenograft model confirmed the antitumor activity of this representative of the N4-alkyl-arabinofuranosylcytosines.

ATP Binding Cassette Transporter, Subfamily B, Mem↗

PubMed1999

Low density lipoprotein and liposome mediated uptake and cytotoxic effect of N4-octadecyl-1-beta-D-arabinofuranosylcytosine in Daudi lymphoma cells.

Low density lipoprotein (LDL) receptor-mediated uptake and cytotoxic effects of N4-octadecyl-1-beta-D-arabinofuranosylcytosine (NOAC) were studied in Daudi lymphoma cells. NOAC was either incorporated into LDL or liposomes to compare specific and unspecific uptake mechanisms. Binding of LDL to Daudi cells was not altered after NOAC incorporation (K(D) 60 nM). Binding of liposomal NOAC was not saturable with increasing concentrations. Specific binding of NOAC-LDL to Daudi cells was five times higher than to human lymphocytes. LDL receptor binding could be blocked and up- or down-regulated. Co-incubation with colchicine reduced NOAC-LDL uptake by 36%. These results suggested that NOAC-LDL is taken up via the LDL receptor pathway. In an in vitro cytotoxicity test, the IC50 of NOAC-LDL was about 160 microM, whereas with liposomal NOAC the IC50 was 40 microM. Blocking the LDL receptors with empty LDL protected 50% of the cells from NOAC cytotoxicity. The cellular distribution of NOAC-LDL or NOAC-liposomes differed only in the membrane and nuclei fraction with 13% and 6% respectively. Although it is more convenient to prepare NOAC-liposomes as compared to the loading of LDL particles with the drug, the receptor-mediated uptake of NOAC-LDL provides an interesting rationale for the specific delivery of the drug to tumours that express elevated numbers of LDL receptors.

Antineoplastic Agents↗

PubMed1999

Metabolism of the new liposomal anticancer drug N4-octadecyl-1-beta-D-arabinofuranosylcytosine in mice.

Metabolism and excretion of the new antitumor drug N4-octadecyl-1-beta-D-arabinofuranosylcytosine (NOAC) was investigated in mice. Mice were injected i.v. with tritium-labeled liposomal NOAC (4 micromol/mouse). Analysis of HPLC-purified extracts of liver homogenates by liquid chromatography coupled with mass spectrometry revealed only the presence of unmetabolized drug. To study the excretion of the administered drug, mice were injected with tritium-labeled liposomal NOAC or as comparison with 1-beta-D-arabinofuranosylcytosine (ara-C; 4 micromol/mouse) and housed up to 48 h in metabolic cages. Urine and feces were collected at different time points and the kinetics of excreted radioactivity were determined. After 48 h, 39% of the injected [5-3H]NOAC radioactivity was excreted in urine and 16% in feces, whereas ara-C radioactivity was only found in urine with 48% of the injected dose. Feces extracts and urine were purified by HPLC and radioactive fractions were further analyzed by liquid chromatography coupled with mass spectrometry. The radioactivity of feces extracts of NOAC-treated mice was composed of unmetabolized NOAC, hydroxylated NOAC (NOAC + OH), its sulfated derivative (NOAC + OSO3H), and unidentified metabolites, whereas in urine, the hydrophilic molecules ara-C and ara-U were found. During the period of 48 h only 2% of the injected NOAC was eliminated in its unmetabolized form, whereas 25% was identified as main metabolite ara-C. Urine collected during 48 h in ara-C-treated mice contained 33% of the injected dose as unmetabolized drug and 13% as the main metabolite ara-U. Thus, NOAC is metabolized by two major pathways, one leading to the hydrophilic metabolites ara-C and ara-U and the other to hydroxylated and sulfated NOAC.

Animals↗

PubMed1998

Comparing the Surface Chemical Properties and the Effect of Salts on the Cloud Point of a Conventional Nonionic Surfactant, Octoxynol 9 (Triton X-100), and of Its Oligomer, Tyloxapol (Triton WR-1339).

The surface-chemical properties, critical micelle concentrations (CMC), and effect of salts on the cloud points (CP) of octoxynol 9 (Triton X-100) and tyloxapol (Triton WR-1339) were compared. The latter nonionic surfactant is essentially a heptamer of the former. Even though the molecular weight of tyloxapol is 7 times larger than that of octoxynol 9, its area per molecule adsorbed at the air-water interface is only twice as large. This suggests an unusual orientation for molecules of tyloxapol at the surface and is in keeping with a plateau that is less horizontal and has a somewhat higher surface tension than the plateaus of most nonionic surfactants. The CMC of octoxynol 9 was 4.4 times larger than that of tyloxapol. Unexpectedly, the CP of dilute aqueous tyloxapol solutions was 28 degreesC higher than that of octoxynol 9 solutions. The salting-out ions Na+, Cl- and SO2-4 lowered the CP of tyloxapol 29% more than that of octoxynol 9. However, because the blank tyloxapol solution started out with a higher CP value, its CPs in the presence of salts were higher than those of octoxynol 9. Pb2+ and Mg2+ cations salted both surfactants in, raising their CP, Pb2+ more extensively than Mg2+. Copyright 1998 Academic Press.

Journal Article↗

PubMed1998

[Iliaco-ureteral fistula and its treatment with a stent graft].

The iliac artery-ureteral fistula is a rare complication which becomes symptomatic with life-endangering bleeding. A typical feature is its intermittent occlusion, which makes diagnosis very difficult. Without knowledge of the correct diagnosis the rate of morbidity, through functional loss of the kidneys, and of mortality can be extremely high. In the following a case is described in which, after radiotherapy and chemotherapy following sigmoid resection due to carcinoma, urinary congestion of the remaining functional kidney occurred during the course of treatment. Following the placing of an endoureteral stent an iliac-ureteral fistula with massive bleeding developed. It was demonstrated by means of angiography. For the first time, therapy with endoluminal stent grafts was successfully applied.

Adenocarcinoma↗

PubMed1998

In vitro anti-human immunodeficiency virus and anti-hepatitis B virus activities and pharmacokinetic properties of heterodinucleoside phosphates containing AZT or ddC.

In vitro activities, against human immunodeficiency virus (HIV)- and hepatitis B virus (HBV)-infected cells, of four amphiphilic heterodinucleoside phosphates containing 3'-azido-2',3'-dideoxythymidine (AZT) or 2',3'-dideoxycytidine (ddC) as antiviral monomers were evaluated. The four compounds were N4-hexadecyl-2'-deoxyribocytidylyl-(3'-->5')-3'-azido-2',3'-deoxyt hymidine (N4-hxddC-AZT), N4-palmitoyl-2'-deoxyribocytidylyl-(3'-->5')-3'-azido-2',3'-deoxyt hymidine (N4-pamdC-AZT), N4-hexadecyl-2'-deoxycytidylyl-(3'-->5')-2',3'-dideoxycytidine (N4-hxddC-ddC) and 2'-deoxythymidylyl-(3'-->5')-N4-palmitoyl-2',3'-dideoxycytidine (dT-N4-pamddC). All four dimers were active against HIV, dT-N4-pamddC being the most active and least toxic. dT-N4-pamddC also exhibited strong antiviral effects against a panel of eight AZT-resistant HIV strains. The ddC-containing heterodimers incorporated in liposomes additionally inhibited HBV replication by 50-80% in HepG2 2.2.15 cells. AZT and the AZT-containing dimers were ineffective. Differences in pharmacokinetic properties between the antiviral monomers and the heterodimers were evaluated using liposomal formulations of 3H-labelled AZT heterodimers as model compounds. The cellular distribution of AZT in H9 cells was predominantly cytoplasmic, whereas the amphiphilic dimers were distributed more evenly throughout the cytoplasm, nuclear membranes and microsomes. Blood levels of the heterodimers decreased at a rate two- to threefold slower than AZT and the areas-under-the-curves were five- to sevenfold higher for N4-pamdC-AZT and N4-hxddC-AZT, respectively. Compared to AZT, the peak levels of the dimers were three to four times higher in blood and five to six times higher in the liver. Analysis of blood samples showed that 34% of N4-pamdC-AZT was metabolized to AZT, whereas only 9% of N4-hxddC-AZT released AZT. Considering the antiviral potency and the favourable pharmacokinetic properties of the heterodimers, these compounds merit further exploration as antiviral drugs.

Animals↗

PubMed1998

[Not Available].

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History, Ancient↗

PubMed1997

Effect of Inorganic Additives on Solutions of Nonionic Surfactants

The salt effects of 10 transition metal cations on nonionic surfactants were investigated by the action of their salts (nine nitrates, two sulfates) on the cloud point (CP) of octoxynol 9. All cations investigated raised the CP of octoxynol 9 by complexation with its ether groups, which represents salting in. However, aside from Ag+, these CP increases were no larger than those caused by Li+ and by di- and trivalent cations not belonging to the transition metal group, even though the transition metal cations have a greater capacity for forming complexes. This unremarkable, average salting-in capacity of most transition metal cations is attributed to competition for their coordination sites between the ether groups of the surfactant and water. With the exception of silver, the solid nitrates of all transition metals examined form stable solid hydrates containing three to nine molecules of water of crystallization, which indicates a high affinity of the cations for water. Only AgNO3 forms no stable solid hydrates. The low affinity of Ag+ for water results in a commensurately higher capacity for binding the ether groups of the surfactant. This was shown by the facts that AgNO3 produced the largest CP increases and that it was the only salt to reversibly precipitate an insoluble adduct with octoxynol 9 from concentrated solutions. The only salt that oxidized the surfactant when its solution was heated in a nitrogen atmosphere and illuminated during CP measurements was Fe(NO3)3. Oxidative degradation produced small but progressive CP reductions. Copyright 1997Academic Press

Journal Article↗

PubMed1997

[Not Available].

The Discovery of the Unconscious by Henri F. Ellenberger has become a common topic in the historiography of (dynamic) psychiatry. But many users of this term have still the opinion that Sigmund Freud was the unique discoverer. In reality there was a scientific context at the fin de siècle, which corresponded intensively with Freud's original concepts and formed their implications (e.g. Darwinism, Neurophysiology). Besides well-documented synchronic analogies Freud implanted diachronic traditions within his psychoanalytic theory. Especially, his main work The Interpretation of Dreams implied Greek mythology as well as natural philosophy of romanticism. Freuds special concepts like 'transfer' and 'resistance' have to be analysed as historical metaphors.

Dreams↗

PubMed1997

Pharmacokinetics of N4-octadecyl-1-beta-D-arabinofuranosylcytosine in plasma and whole blood after intravenous and oral administration to mice.

N4-octadecyl-1-beta-D-arabinofuranosylcytosine (NOAC) is a new cytotoxic derivative of cytosine arabinoside with improved cytotoxic activity and stability against deamination. Its pharmacokinetics were studied in mice. The drug was administered intravenously and orally to ICR mice to assess its pharmacokinetic parameters in plasma and whole blood. The lipophilic drug was administered in small unilamellar liposomes 100-400 nm in diameter. The concentrations of NOAC in plasma and erythrocytes were determined by high-performance liquid chromatography (HPLC). When given orally a rather low amount of the delivered NOAC was absorbed as the unchanged drug, resulting in a bioavailability of 1.1% from the plasma and 12.9% from whole blood. As shown elsewhere, the amount of drug absorbed is sufficient to provide excellent cytotoxic activity in the L1210 leukemia and in human xenograft models after oral administration. The mean residence time of NOAC after intravenous administration was 3.5 h in plasma and 6 h in whole blood giving NOAC a terminal half-life in blood substantially longer than that of cytosine arabinoside. After oral administration the mean residence time was 18 h in plasma and whole blood. In summary, NOAC has a prolonged half-life after intravenous administration compared with cytosine arabinoside. The distribution of NOAC in blood is highly dependent on its mode of administration.

Administration, Oral↗

PubMed1997

Plasma von Willebrand factor in thoroughbreds in response to high-intensity treadmill exercise.

OBJECTIVE: To determine whether plasma von Willebrand factor (vWf) concentration changes in horses during and after treadmill exercise. ANIMALS: 5 mature, fit Thoroughbreds. PROCEDURE: A blood sampling catheter was placed in the right jugular vein. A warm-up period was followed by a 3-minute rest period. Horses were galloped at racing pace until fatigued (about 2 minutes). Blood samples were collected prior to warm-up, during the postwarm-up rest period, 1 minute into the run, at cessation of the run, and 5 to 120 minutes after cessation of the run. vWf activity was measured by ELISA and corrected for plasma volume changes (measured by changes in plasma albumin concentration). Platelet-poor plasma from 10 clinically normal, resting horses was pooled, assigned a value of 100 U/dl, and served as a control for all assays. RESULTS: vWf activity began increasing 1 minute after horses reached full speed. At 5 minutes after cessation of exercise, vWf values had increased by mean of 92% (P < 0.05) from baseline. vWf activity returned baseline by 15 minutes after exercise, and remained there until 90 minutes after exercise, when it began to increase. CONCLUSION AND CLINICAL RELEVANCE: The spontaneous decrease in vWf values after completion of exercise was unexpected because vWf has a long half-life in circulation. This unexpected finding is compatible with increased vWf consumption and suggests that microvascular trauma may occur in horses during strenuous exercise.

Animals↗

PubMed1997

Interactions with human blood in vitro and pharmacokinetic properties in mice of liposomal N4-octadecyl-1-beta-D-arabinofuranosylcytosine, a new anticancer drug.

The interactions of N4-octadecyl-1-beta-D-arabinofuranosylcytosine (NOAC), a lipophilic derivative of 1-beta-D-arabinofuranosylcytosine (ara-C), were studied in vitro with human blood components. Binding of NOAC incorporated into liposomes to erythrocytes (Ec) was saturated at 63 nmol/10(9) Ec and binding analysis resulted in a weak affinity of 3 x 10(3) liters/mol and 4 x 10(7) binding sites per Ec. The Ec partition coefficient D(Ec) was approximately 4, which demonstrates the high accumulation of NOAC in Ec membranes. The calculated fraction f(b) of drug bound to plasma proteins was 30%. Analysis of serum protein binding of NOAC was done by density gradient ultracentrifugation and agarose gel electrophoresis. Liposomal NOAC was distributed to low-density lipoproteins (LDL) at 36%, to high-density lipoproteins at 21%, to albumin and other proteins at 12% and to very-low-density lipoproteins at 5%. Comparable results were obtained for the analog N4-hexadecyl-1-beta-D-arabinofuranosylcytosine and when the drugs were dissolved in dimethyl sulfoxide. The biodistribution of liposomal NOAC in ICR mice after intravenous application revealed a biphasic blood concentration versus time curve with a distribution half-life t1/2alpha of 23 min and an elimination half-life t1/2beta of 7 h. The drug was distributed mainly into the liver with an organ load of 69% and with an elimination half-life of 8 h. The strong affinity of NOAC to LDL might be exploited for the enhanced uptake of the drug in tumor cells expressing high numbers of LDL receptor molecules.

Animals↗