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Biomedical subjects

A Gruber

Publications and source records attributed to A Gruber.

At least 181 records · Page 10Linked to original sources
PubMed1992

Quantitative determination of mdr1 gene expression in leukaemic cells from patients with acute leukaemia.

By using a quantitative RNA-RNA solution hybridisation method, the average number of mdr1 RNA transcripts per cell was measured in total nucleic acid extracts of leukaemic cells from patients with acute leukaemia. The results in different types of leukaemia were (number of patients with detectable mdr1 RNA/total number of patients; median number of transcripts per cell in samples with detectable mdr1 RNA); de novo untreated acute myelocytic leukaemia (AML): 20/44; 0.7, secondary acute myelocytic leukaemia: 8/13; 1.1, acute lymphocytic (ALL) and undifferentiated leukaemia: 5/14; 0.6, relapsed leukaemia: 7/15; 0.7. Forty-six patients with de novo untreated acute leukaemia (AML: n = 34, ALL: n = 12) were evaluable for response to induction chemotherapy. Twelve of 18 patients (67%) with detectable mdr1 RNA levels achieved complete remission compared to 23 of 28 (82%) with undetectable levels (P = 0.40). The remission duration tended to be longer among patients with undetectable mdr1 RNA (P = 0.08). Leukaemic cells were analysed on consecutive occasions in 12 patients. The level of expression increased in four and decreased in two. In conclusion, expression of mdr1 RNA is common in acute untreated leukaemia. However, treatment with cytostatic drugs seems only rarely to increase the proportion of leukaemic cells that express mdr1 RNA. Expression of the mdr1 gene could be one of several equally important factors contributing to drug resistance in acute leukaemia.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1991

Identification of divalent metal ion-dependent inhibition of activated protein C by alpha 2-macroglobulin and alpha 2-antiplasmin in blood and comparisons to inhibition of factor Xa, thrombin, and plasmin.

The half-life of activated protein C (APC) was 31 min in citrated blood and 18 min in whole blood. Immunoblotting analysis of citrated blood identified APC-protein C inhibitor (APC-PCI) and APC-alpha 1-antitrypsin complexes. Whole blood contained two additional APC-inhibitor complexes, one stimulated by Ca2+ and another by Mg2+. The former was identified as APC-alpha 2-macroglobulin (APC-alpha 2M) while the latter was not identified. APC-alpha 2-antiplasmin complexes (APC-alpha 2AP) were identified, comigrating with APC-PCI complexes. Purified alpha 2M and alpha 2AP inhibited APC in the presence of Ca2+ (k2 = 99 and 100 M-1 S-1, respectively. Inhibition of APC and Factor Xa by alpha 2M and inhibition of APC by alpha 2AP was stimulated by Ca2+, Mn2+, and Mg2+. Inhibition of thrombin by alpha 2M and of plasmin by alpha 2AP was not altered by EDTA or Ca2+, suggesting divalent metal ions affect APC and Factor Xa rather than the inhibitors. k2 values for the APC inhibitors and their plasma concentrations suggest that PCI and alpha 1-antitrypsin are the more important APC inhibitors and that alpha 2M and alpha 2AP are metal ion-dependent auxiliary inhibitors. Inhibitors can account for the in vivo half-life of APC.

Enzyme Activation↗
PubMed1991

In vivo and in vitro complexes of activated protein C with two inhibitors in baboons.

In vivo complex formation of activated protein C with protein C inhibitor (APC-PCI) and with alpha 1-antitrypsin (APC-alpha 1AT) following infusion of 0.25 or 1.0 mg APC/kg in 1 hour into baboons was studied using immunoblotting and sandwich enzyme-linked immunosorbent assay (ELISA)s. Before APC infusion, detectable plasma levels (about 30 ng/mL) of APC-alpha 1AT complex were found in the baboon plasma. At the lower APC dose, APC-PCI and APC-alpha 1AT complex levels were 1.4 +/- 0.3 (mean +/- SD) and 0.8 +/- 0.1 microgram/mL after 1 hour of infusion. At the higher APC dose, the APC-PCI level was similar to the APC-alpha 1AT level during the first 30 minutes, but after 1 hour of infusion the APC-alpha 1AT level was higher than the APC-PCI level, reaching 4.1 +/- 1.2 and 2.9 +/- 1.2 microgram/mL, respectively. After 24 hours, complex levels had returned to basal conditions. During infusion of protein C (1.0 mg/kg in 1 hour), both complexes were detected in low concentrations. Following bolus injection of APC, half-lives (t1/2) for APC and APC-PCI and APC-alpha 1AT complexes of 10, 40, and 140 minutes, respectively, were observed. After 1-hour incubation with 2.5 micrograms/mL APC, baboon plasma contained 1.0 +/- 0.2 and 0.8 +/- 0.1 microgram/mL of APC-PCI and APC-alpha 1AT, respectively. Addition of 10 micrograms/mL APC to baboon plasma yielded 2.5 and 2.4 micrograms/mL APC-PCI and APC-alpha 1AT after 1 hour, respectively. Immunoblotting analysis also showed in vivo formation of complexes of APC with an auxilliary inhibitor but not in vitro in citrated plasma. These data show that both PCI and alpha 1AT are physiologic inhibitors of APC and suggest that when PCI is depleted by a high dose of APC, alpha 1AT becomes the major inhibitor of APC.

Animals↗
PubMed1991

Isolation of an active gene and of two pseudogenes for mouse U7 small nuclear RNA.

Three U7 RNA-related sequences were isolated from mouse genomic DNA libraries. Only one of the sequences completely matches the published mouse U7 RNA sequence, whereas the other two apparently represent pseudogenes. The matching sequence represents a functional gene, as it is expressed after microinjection into Xenopus laevis oocytes. Sequence variations of the conserved cis-acting 5' and 3' elements of U RNA genes may partly explain the low abundance of U7 RNA.

Animals↗
PubMed1991

Doxorubicin selected multidrug-resistant small cell lung cancer cell lines characterised by elevated cytoplasmic Ca2+ and resistance modulation by verapamil in absence of P-glycoprotein overexpression.

Sublines from the small cell lung cancer (SCLC) cell lines U1285 and U1690, denoted U1285-100, U1285-250, U1690-40 and U1690-150, were adapted to grow in the continuous presence of 100, 250, 40 and 150 ng ml-1 doxorubicin (Dox), respectively. The Dox resistance was accompanied by cross-resistance to vincristine (Vcr), Vp-16 and for U1285-100 also to cisplatinum. Sublines of U1690-40 and U1285-100, cultured in absence of Dox for 4 months were only partially reversed with respect to Dox resistance. Neither the parental nor the most Dox resistance sublines had detectable levels of mdr 1 RNA but a small fraction of cells in all cell lines stained weakly positive for P-glycoprotein (P-gp). Verapamil (Ver) at 5 microM reversed the Dox resistance completely and partly in the U1690 and U1285 sublines, respectively, but did not increase the cellular accumulation of Dox. The cytoplasmic free Ca2+ concentration (Ca2+i) was close to 100 nM in both parental cell lines but elevated in the U1285-100 and U1690-40 sublines by 21 and 44%, respectively, and in U1285-250 and U1690-150 by 51 and 91%, respectively. The partly reverted sublines still showed significant but smaller elevations in Ca2+i of 10-30%. Ver was without acute or long term effects of Ca2+i in the U1285-100 and U1690-40 sublines. Selection for Dox resistance in SCLC may thus result in atypical multidrug-resistance characterised by absence of P-gp overexpression and atypical cross-resistance. Although Ver did not seem to affect Dox accumulation it may still work as a resistance modulator.(ABSTRACT TRUNCATED AT 250 WORDS)

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1991

Antithrombotic effects of combining activated protein C and urokinase in nonhuman primates.

BACKGROUND: We have determined in vivo the relative antithrombotic efficacy and hemostatic safety of combining low-dose activated protein C (APC) and urokinase (urinary plasminogen activator, u-PA), two natural proteins that regulate thrombogenesis. METHODS AND RESULTS: To model acute thrombotic responses of native blood under conditions of arterial flow, thrombogenic segments of Dacron vascular graft (VG) were incorporated into chronic exteriorized femoral arteriovenous (AV) access shunts in baboons. Thrombus formation on VG was determined by measuring 1) the deposition of autologous 111In platelets using real-time scintillation camera imaging, 2) the accumulation of 125I fibrin, 3) segment patency by Doppler flow analysis, and 4) blood tests for thrombosis, including plasma concentrations of platelet factor 4, beta-thromboglobulin, fibrinopeptide A (FPA), and D-dimer. Treatments consisting of low-dose and intermediate-dose APC (0.07 or 0.25 mg/kg.hr), u-PA (25,000 or 50,000 IU/kg.hr), or the combination were administered for 1 hour by continuous intravenous infusion. In untreated controls, platelets and fibrin accumulated rapidly, reaching plateau values at 1 hour of 15.1 +/- 3.8 x 10(9) platelets and 7.8 +/- 2.2 mg fibrin. Although the low-dose APC or u-PA alone did not decrease either platelet or fibrin deposition significantly, this combination moderately reduced both platelet and fibrin accumulation (7.3 +/- 2.6 x 10(9) platelets, p less than 0.05; 3.9 +/- 0.6 mg fibrin, p less than 0.05). Furthermore, intermediate-dose APC or u-PA reduced thrombus formation by half when administered alone (p less than 0.001 for both platelet and fibrin deposition), and the combination markedly interrupted the accumulation of platelets (3.0 +/- 1.0 x 10(9) platelets, p less than 0.001) and fibrin (1.3 +/- 0.6 mg fibrin, p less than 0.001). During active treatments, all VG segments remained patent. Hemostatic plug forming capability, as measured by template bleeding times, remained normal during all experiments (p greater than 0.05). The T50 clearance time for APC activity was not affected by the concurrent administration of u-PA. u-PA alone increased the plasma levels of D-dimer, FPA, and, interestingly, APC, implying that during pharmacological activation of the fibrinolytic system, thrombin activity was released, and the protein C pathway was activated. CONCLUSIONS: A combination of intermediate-dose APC and u-PA produce substantial and efficient antithrombotic effects without impairing hemostatic function.

Animals↗
PubMed1990

Structure of a mouse histone-encoding gene cluster.

In addition to a previously described histone (H)-encoding H4 gene [Meier et al., Nucleic Acids Res. 17 (1989) 795], the mouse genomic DNA clone 53 contains two H3 genes, one functional and one partially deleted H2A gene, and one H2B gene. Clone 53 overlaps for 3 kb with MH143, another previously isolated mouse H-encoding clone [Yang et al., J. Biol. Chem. 262 (1987) 17118-17125], thus defining a 32-kb region of mouse chromosome 13 with a total of seven H-encoding genes. We have determined the nucleotide sequences and transcription start points of two genes coding for the H2A.1 and H3.2 proteins.

Amino Acid Sequence↗
PubMed1990

Role of prolonged excessive estrogen stimulation in the pathogenesis of endometrial sarcomas: two cases and a review of the literature.

Two cases of endometrial sarcoma that developed many years after exposure to unopposed exogenous and endogenous estrogens, with no previous pelvic irradiation, are described. The literature is reviewed and the possible effect of prolonged unopposed estrogen stimulation is suggested as an etiologic factor in such extremely rare conditions. These cases add additional support to the assumption that prolonged and excessive endogenous or exogenous unopposed estrogen stimulation of the uterus may increase the risk of endometrial sarcoma.

Aged↗
PubMed1990

Inhibition of thrombus formation by activated recombinant protein C in a primate model of arterial thrombosis.

Activated protein C (APC) is an antithrombotic enzyme. The therapeutic potential of infused human recombinant APC (rAPC) was studied in a primate model of platelet-dependent thrombosis. Eight baboons with chronic femoral arteriovenous shunts received rAPC infusions for 1 hour. The shunts were extended with 5-cm long, 4-mm-i.d. thrombogenic Dacron graft segments for the time of infusion. The plasma level of the enzyme, the blood flow in the shunt, and the deposition of indium-111-labeled platelets and iodine-125 fibrinogen on the graft were measured. The influence of rAPC infused at doses of 0.25 and 1.0 mg/kg-hr was compared with the effects of control infusions of saline. Five of eight control grafts occluded within 60 minutes, whereas there was no change in the blood flow during rAPC infusion. Deposition of platelets was inhibited by 13 +/- 10% and by 42 +/- 13% (mean +/- SEM) after 30 minutes of infusion at the two doses, which gave rise to circulating rAPC plasma concentrations of 0.4 and 1.9 mg/l, respectively. Both doses significantly inhibited fibrin deposition in the graft. Circulating plasma markers of thrombus formation and of fibrinolysis did not increase significantly during rAPC infusion; measurements of bleeding time were also within normal limits. Thus, rAPC, like human plasma-derived APC, inhibited thrombus formation without impairing primary hemostasis.

Animals↗
PubMed1989

Inhibition of platelet-dependent thrombus formation by human activated protein C in a primate model.

The in vivo antithrombotic properties of human plasma activated protein C (APC), a natural anticoagulant enzyme, were investigated in a baboon model of thrombus formation on prosthetic vascular grafts. Infusion of 0.25 to 1.1 mg/kg/h purified, human, APC inhibited blood clotting, as measured by the activated partial thromboplastin time (APTT), and reduced vascular graft platelet deposition by 40% to 70%, as determined by the real-time scintillation camera imaging of 111In-labeled platelet deposition. APC infusion also preserved graft patency. Hemostatic plug formation remained normal, as measured by the template bleeding times. These results suggest that APC administration may produce immediate antithrombotic effects under arterial flow conditions.

Animals↗
PubMed1989

Egg donation in an in vitro fertilization program: an alternative approach to cycle synchronization and timing of embryo transfer.

A new flexible protocol for the induction of recipient endometrial cycles is presented. For stimulation of endometrial growth, a fixed dose of conjugated estrogens, 3.75 mg/d was employed. The duration of the proliferative phase varied from 9 to 14 days, thus being adjusted to match the length of the follicular phase of the donor. Embryo transfer was performed on the fifth day of progesterone administration. Four term pregnancies resulted from 12 treatment cycles. In the conception cycles, the hormonal support was continued until the luteal placental shift occurred, regardless of gestational age.

Embryo Transfer↗
PubMed1989

Accumulation of vincristine and doxorubicin in malignant lymphocytes with different immunophenotypes.

Cellular accumulation of vincristine (VCR) and doxorubicin (DOX) was studied in 15 patients with low-grade B-cell malignancies. Their leukemic lymphocytes were isolated and the effect of verapamil on drug uptake was studied. The immunophenotype was characterized using anti-IgM, -IgD, -B 1, monoclonal antibodies. The more that cells bound the IgD or B1 antibodies, the more vincristine and doxorubicin did they accumulate. The fewer the cells that bound IgM antibodies, the more drug did they accumulate.

Aged↗
PubMed1988

D-verapamil and L-verapamil are equally effective in increasing vincristine accumulation in leukemic cells in vitro.

Leukemic cells isolated from peripheral blood from 6 patients with chronic lymphocytic leukemia, immunocytoma and prolymphocytic leukemia were incubated with vincristine (10 nM) with and without racemic verapamil and its L- and D-isomers (6.6 microM). Verapamil increased vincristine accumulation in all cells, the increase varying between 100 and 700%. Racemic verapamil and the L- and D-isomer increased cellular vincristine accumulation to the same extent. The verapamil effect could not be reversed by increasing the calcium concentration in the incubation medium (final concentration 2.5-5.0 mM). The results indicate that the mechanism behind the effect of verapamil on cellular accumulation of vincristine does not depend upon changes in calcium transport.

Calcium↗