PubMed Health⌕ Search

Biomedical subjects

Y W Stevens

Publications and source records attributed to Y W Stevens.

At least 19 recordsLinked to original sources
PubMed1990

Phase I clinical and pharmacological study of merbarone.

Merbarone, a nonsedating derivative of thiobarbituric acid, has demonstrated excellent activity against certain murine tumors, including L1210 and P388 leukemias, B16 melanoma, and M5076 sarcoma. Preclinical studies suggested that the antitumor effects of this drug were schedule dependent, since repeated dosing increased killing of tumor cells when compared to intermittent injections. We have completed a Phase I clinical and pharmacological study of merbarone in which the drug was administered both as a 2-h infusion and as a continuous i.v. infusion over 24 h. In view of the increased toxicity observed in animals following bolus injections and the possibility of schedule-dependent anticancer activity, a schedule of drug administration daily for 5 days was selected. Fifty patients with advanced cancer were treated at dose levels that ranged from 100 to 1500 mg/m2/day. When the drug was administered by peripheral vein, phlebitis was observed at the infusion site at daily doses greater than or equal to 150 mg/m2. Therefore, all patients who received drug doses greater than or equal to 200 mg/m2 were treated by continuous i.v. infusion using central venous catheters. Renal insufficiency, initially observed at a dose of 1000 mg/m2/day, was the dose-limiting toxic reaction at 1500 mg/m2/day. Three of five patients treated at the highest dose level were unable to complete the infusion due to this effect. Marked hypouricemia was observed in all patients. Other toxic effects were mild and included nausea, fatigue, leukopenia, thrombocytopenia, and anorexia. Alopecia was noted in several patients who received doses greater than or equal to 1000 mg/m2/day. No major antitumor effects were observed. Dose-dependent, steady-state plasma concentrations of merbarone were reached within 24-48 h after beginning the continuous i.v. infusion. Elimination of drug from plasma followed a two-compartment model, with a t1/2 alpha of 4.2 h and a t1/2 beta of 15.3 h. Renal excretion of merbarone and its major metabolites accounted for less than 30% of the administered dose. We conclude that merbarone is relatively well tolerated with few constitutional symptoms. The current formulation of the drug causes phlebitis when administered by peripheral vein, and renal insufficiency is commonly observed at daily doses which exceed 1250 mg/m2. The recommended dose for extended Phase II evaluation is 1000 mg/m2/day daily for 5 days administered by central venous catheter.

Adult↗
PubMed1989

4-demethoxydaunorubicin (idarubicin) in combination with 1-beta-D-arabinofuranosylcytosine in the treatment of relapsed or refractory acute leukemia.

We conducted a Phase I-II trial of 4-demethoxydaunorubicin (idarubicin, IDR) in combination with 1-beta-D-arabinofuranosylcytosine (ara-C) in 51 patients with relapsed or refractory acute nonlymphocytic leukemia, acute lymphocytic leukemia, or chronic myelogenous leukemia in blast crisis. Only 1 of 12 patients treated at the first dose level (idarubicin, 10 mg/m2/day for 3 days and ara-C, 25 mg/m2 i.v. bolus followed by 200 mg/m2 continuous infusion daily for 5 days) achieved aplasia and complete remission. The dose of idarubicin was subsequently increased to 10 mg/m2/day for 4 days with the ara-C dose held constant. Complete remission incidence for this dose schedule was: 7 of 31 patients with acute nonlymphocytic leukemia, 0 of 5 patients with acute lymphocytic leukemia, 0 of 1 patient with chronic myelogenous leukemia in blast crisis, and 1 of 2 patients with biphenotypic leukemia. Nonhematological toxicity included nausea, vomiting, mucositis, and abnormal liver function tests. Detailed pharmacological studies were performed to determine whether ara-C altered IDR metabolism or that of its main metabolite, 13-hydroxyidarubicinol or IDR clearance. A high degree of variability among patients was apparent and no consistent effect could be demonstrated. In summary, 9 of 37 patients (24%) with relapsed or refractory ANLL, including 1 patient with biphenotypic leukemia, achieved remission. We conclude that idarubicin in combination with ara-C is an active combination in patients with relapsed or refractory leukemia.

Adolescent↗
PubMed1989

Induction of profound hypouricemia by a non-sedating thiobarbiturate.

5-[N-phenylcarboxamido]-2-thiobarbituric acid (merbarone) is a non-sedating derivative of thiobarbituric acid originally developed for anticancer use. In the initial clinical study, a profound reduction in serum uric acid was observed. In 20 patients who received five daily doses of merbarone ranging from 100 to 750 mg/m2, serum uric acid concentration was reduced from a mean pretreatment value of 5.7 +/- 1.6 mg/dL to a mean lowest value of 1.3 +/- 0.5 mg/dL. In most patients, the onset of the effect occurred with 24 hours and was maximal by 48 to 72 hours. Metabolic studies in two patients showed an increase in urinary uric acid excretion within 24 hours after initiation of drug treatment. A marked increase in fractional excretion of uric acid was sustained throughout the period of drug treatment. Urinary excretion of total oxypurines (xanthine and hypoxanthine) was increased twofold to threefold relative to baseline levels. Ultrafiltration studies showed that merbarone did not significantly displace binding of urate from albumin. When merbarone was incubated with xanthine oxidase in vitro, several reaction products were observed, including 2-oxo-2-desthio-merbarone and a compound with retention time similar to 4'-OH-merbarone. Both of these compounds have been described previously as metabolites of merbarone in human subjects. The parent drug and both metabolites were found to inhibit xanthine oxidase (Ki = 41, 36, and 240 mumols/L, respectively). However, this inhibitory effect was substantially less potent than allopurinol (Ki = 0.025 mumols/L). This study indicates that merbarone induces profound hypouricemia primarily by increasing uric acid excretion.(ABSTRACT TRUNCATED AT 250 WORDS)

Antineoplastic Agents↗
PubMed1988

Phase I trial and clinical pharmacological evaluation of hexamethylene bisacetamide administration by ten-day continuous intravenous infusion at twenty-eight-day intervals.

We have treated 33 patients with different types of advanced cancer by 10-day continuous i.v. infusion courses of hexamethylene bisacetamide (HMBA), a drug that produces differentiation of a variety of transformed cell lines on prolonged exposure in vitro to drug concentrations of 3 to 5 mM. In this dose-finding and pharmacokinetic study, five dosage levels were explored from 12 to 28 g/m2/day. Patients who had not shown progression of disease were given repeat courses of therapy at 28-day intervals. Seventy-two courses of therapy were administered; 17 patients received one course; eight patients received two; six patients received three; and one patient each received four and 17+ courses, respectively. The maximal tolerated dose was 28 g/m2/day for 10 days; the dose-limiting toxic effects were thrombocytopenia with hemorrhage and central nervous system dysfunction manifesting as disorientation and confusion. Based on these studies the recommended dosage for Phase II studies by the 10-day schedule is 24 g/m2/day. Pharmacokinetic studies demonstrated rapid clearance of HMBA from plasma; the decay phase data fit a one compartment model with a mean plasma half-life of 2.5 h and a range from 0.6 to 5.8 h. Mean plasma steady-state levels in our patients were 0.37, 0.58, 0.86, 0.88, and 1.42 mM, at the 12-, 16-, 20-, 24-, and 28-g/m2/day dosage levels, respectively. The data indicate that plasma HMBA concentrations of 1 mM can be maintained for 10 days with acceptable patient tolerance, but that HMBA concentrations in excess of 1.4 mM for 10 days are associated with substantial hematological and central nervous system toxicity. Objective antitumor effects were observed in five patients; one woman with non-small cell lung cancer, who has received 17+ courses over a period of 28+ mo, achieved a partial remission that continues at 28+ mo on therapy. Transient regression of cutaneous metastases was observed in three patients with breast carcinoma and one patient with colorectal carcinoma.

Acetamides↗
PubMed1986

"Defective" receptors in steroid-resistant conditions may be proteolytic artifacts.

The specific question addressed in this report is whether the resistance to steroid treatment of certain tissues or tumors which appear to contain a normal quantity of steroid-binding sites may be due to structural defects in the receptors. This question may be seen as part of the more general question of whether there are intrinsic variations in the structures of receptors for a given class of steroids in different healthy tissues, in healthy vs. malignant tissues or in different types of tumors. Our experimental approach to these questions has involved the stabilization and precise physicochemical characterization of the receptors. To date, we have studied the estrogen and progestin receptors from human breast cancers and benign and malignant gynecologic specimens and the glucocorticoid receptors from several healthy and malignant rodent tissues and from normal human lymphocytes and various types of leukemic cells. Chromatographic and ultracentrifugal analyses in buffers of low ionic strength, containing 20 mM Na2MoO4 as the stabilizer, have revealed each of these receptors to be a large, oligomeric complex, characterized by remarkably similar values of the Stokes radius, sedimentation coefficient, molecular weight and axial ratio. In the absence of adequate stabilization, however, we found that the receptors for three classes of steroids in extracts of some healthy, steroid-responsive tissues, such as rat kidney and human uterine endometrium, are invariably degraded by endogenous proteinases. The extent of such cleavage is increased considerably by freezing the tissues prior to homogenization. Studies designed to distinguish the intact receptors from the products of proteolysis have included the characterization of receptors in cytosols prepared from mixtures of rat liver and kidney. The results strongly support the interpretation that the smaller size of the receptors detected in kidney cytosol reflects their cleavage by the more active proteinases in that tissue. The sizes and shapes of the receptors in cytosols from various tissues were found to be correlated with the activities of specific endopeptidases, assayed fluorometrically with peptidyl derivatives of 7-amino-4-methylcoumarin (AMC). These studies suggested that the receptors are vulnerable to cleavage by "lysine-specific" endopeptidases, detected with t-butyloxycarbonyl-L-valyl-L-leucyl-L-lysyl-AMC. An enzyme of this specificity was partially purified from rat kidney cytosol and tested for its ability to digest the glucocorticoid receptors from rat liver cytosol.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1984

Multiple forms and fragments of cytosolic glucocorticoid receptors from human leukemic cells and normal lymphocytes.

Therapy with glucocorticoids is generally more effective in acute lymphoblastic leukemia than in other types of human leukemia. Previous studies, however, have not revealed any consistent relationship between clinical responsiveness and the cellular or cytosolic concentration of glucocorticoid-binding sites. The objectives of this study were to determine whether there are intrinsic structural differences among the glucocorticoid receptors in various types of leukemic cells and normal lymphocytes and to investigate the role of endogenous peptidases in receptor degradation. Cytosols were prepared from fresh or rapidly frozen leukocytes from 6 healthy adults and 35 high-risk leukemia patients (median white blood cell count, 150,000 cells/microliter; median age, 13 years). Receptors were labeled with [3H]triamcinolone acetonide and quantitated by charcoal-dextran treatment or Sephadex LH-20 chromatography. Mean and median cytosolic receptor concentrations in 12 acute lymphoblastic leukemia specimens lacking the standard B-cell or T-cell markers ("null cells") were approximately 4-fold higher than in 23 other leukemic cell specimens. No other consistent differences in receptor content were observed. Agarose filtration and ultracentrifugation in hypotonic buffers containing 20 mM Na2MoO4 revealed complexes of similar size and shape in all clinical specimens tested and two established leukemic cell lines. They had Stokes radii (Rs) of 8.1 +/- 0.5 (S.D.) nm (n = 50), sedimentation coefficients of 9.5 +/- 0.3S (n = 40), molecular weights of approximately 330,000, and axial ratios (a/b) of approximately 12. In hypertonic, molybdate-free buffer, these oligomeric complexes were dissociated into subunits with Rs of 5.9 +/- 0.3 nm (n = 12) and a/b of 11 to 12, as observed previously for other receptors. Fragmentation of the oligomer and the subunit was evident in some cytosols. High activities of peptidases of various specificities were detected in leukemic cell cytosols, as in other cytosols, by fluorometric assays with derivatives of 7-amino-4-methylcoumarin. Receptor cleavage by these and other endogenous enzymes may account for previous observations of "abnormal" receptors in cytosols from some leukemic specimens. We conclude that intrinsic structural defects in the receptors are unlikely explanations for the unresponsiveness of some types of leukemia to steroid therapy.

Adult↗
PubMed1983

Structure, dissociation, and proteolysis of mammalian steroid receptors. Multiplicity of glucocorticoid receptor forms and proteolytic enzymes in rat liver and kidney cytosols.

The forms of steroid receptors detected in mammalian tissue cytosols vary from a globular fragment, the mero-receptor, with a molecular weight (Mr) of approximately 23,000 to highly asymmetric molybdate-stabilized complexes (Mr approximately 330,000). Our objectives were to investigate the relationships among various receptor forms and mechanisms of stabilization by Na2MoO4, to characterize endogenous proteolytic enzymes, and to evaluate the effects of freezing the tissues on receptor structure and protease activities in the resultant cytosols. Glucocorticoid receptors and proteases were analyzed in cytosols from fresh and frozen rat liver and kidney. Enzymes were assayed fluorometrically at approximately 24 degrees C, with peptidyl tyrosine, lysine, and phenylalanine derivatives of 7-amino-4-methylcoumarin. Rates of cleavage of the tyrosine-containing substrate by crude and partially purified liver cytosol enzymes were markedly suppressed by Na2MoO4. While receptor cleavage by these enzymes has not been demonstrated, these results illustrate the direct inhibition of proteolysis by molybdate. Rates of cleavage of the lysine-containing substrate were 7- to 40-fold higher in cytosols from frozen liver and fresh or frozen kidney, in which the Stokes radius (Rs) of the largest receptor form was 70-74 A, than in fresh liver cytosol, in which Rs was 84 +/- 2 A (n = 20). Filtration of the 84 A complex (Mr approximately 330,000) in hypertonic buffer without Na2MoO4 revealed a 7:3 mixture of forms with Rs of 50-60 A (Mr approximately 90,000) and Rs of 30-40 A (Mr approximately 50,000). The latter are derived from the 50-60 A forms by proteolysis and/or dissociation. We conclude that the 84 A (untransformed) receptor is an oligomer, probably a tetramer, containing the 50-60 A subunits and that purification of the intact structure will require removal or inactivation of contaminating proteases.

Animals↗
PubMed1983

Absence in glucocorticoid-resistant mouse lymphoma P1798 of a glucocorticoid receptor domain responsible for biological effects.

Glucocorticoid-resistant (CR), in contrast to glucocorticoid-sensitive (CS), mouse lymphoma P1798 was shown to lack antiglucocorticoid receptor immunoactivity. Antibodies raised against the purified rat liver glucocorticoid receptor (GR) cross-reacted with the GR from CS, but not with the GR from CR, P1798 lymphoma. Using highly specific antisera against the GR in an indirect competitive enzyme-linked immunosorbent assay, it was demonstrated that alpha-chymotrypsin digestion of the GR from CS P1798 lymphoma caused a separation of a "resistant-like" nonimmunogenic steroid and DNA-binding domain (Stokes' radius, 3.3 nm) from an immunoactive domain (Stokes' radius, 2.6 nm). In contrast to CS P1798 lymphoma, neither before nor after alpha-chymotrypsin digestion, immunoactivity could be found in the cytosol from CR P1798 lymphoma. This was assayed after chromatography on DNA-cellulose or gel filtration on Agarose A (0.5 m). These results suggest that the domain of the CS GR containing the immunoactive determinant(s), normally removed by limited proteolysis by alpha-chymotrypsin, appears to be missing in CR P1798 lymphoma cytosol. It seems that this domain plays an important role in the mechanism of action of glucocorticoids. This might suggest that a mutation has occurred affecting the genome resulting in defective transcription of the receptor gene(s) in CR P1798 lymphoma.

Animals↗
PubMed1979

Physicochemical differences between glucocorticoid-binding components from the corticoid-sensitive and -resistant strains of mouse lymphoma P1798.

The physicochemical properties of nuclear and cytosolic glucocorticoid-binding components from corticoid-sensitive (CS) and corticoid-resistant (CR) mouse lymphoma P1798 cells have been compared. Nuclei or cytosol fractions were prepared from lymphocytes that had been labeled at 37 or 4 degrees, respectively, with 30 nM [3H]triamcinolone acetonide ([3H]TA). [3H]TA was extracted with 0.6 M KCl, 10 mM spermidine, or 4.5 mM MgCl2 from CS nuclei and with 0.6 M KCl or 10 mM spermidine from CR nuclei. As reported previously, nuclear-associated [3H]TA in CR cells was resistant to extraction with mM concentrations of MgCl2. Loss of bound steroid during extraction with 0.6 M KCl was minimized by including the chymotrypsin inhibitor, carbobenzoxy-L-phenylalanine, in the extraction buffer. The inhibitor was not required during extraction with spermidine or MgCl2. Nuclear and cytosolic extracts were examined by analytical agarose gel filtration and glycerol density gradient centrifugation under high salt (0.6 M KCl) conditions. The glucocorticoid-binding component in KCl, spermidine, and MgCl2 extracts from CS nuclei was considerably larger and more asymmetrical [Stokes radius, 57 to 59 A; sedimentation coefficient, 3.64 to 3.70S; molecular weight, 90,000 daltons; frictional ratio, 1.8; axial ratio (prolate ellipsoid), 15] than the [3H]TA-macromolecular complex in KCl and spermidine extracts from CR nuclei[Stokes radius, 29 A; sedimentation coefficient, 3.23 to 3.30S; molecular weight, 40,000 daltons; frictional ratio, 1.25; axial ratio (prolate ellipsoid), 5]. Control experiments showed that the smaller size of the glucocorticoid-binding component in CR nuclei was probably not due to cleavage of a larger, CS-like complex during the extraction procedure. The larger size of the CS [3H]TA complex did not appear to result from aggregation of s a smaller species. No difference in physicochemical parameters of the binding component was observed if cells were labeled with [3H]dexamethasone instead of [3H]TA. However, [3H]dexamethasone complexes were less stable than those formed with [3H]TA as indicated by considerable dissociation of [3H]dexamethasone during gel filtration and gradient centrifugation. This may be due to the 3- to 5-fold lower relative binding affinity of [3H]dexamethasone. Analysis of [3H]TA-labeled cytosol by gel filtration and gradient centrifugation revealed the presence of a single binding component with physicochemical properties similar to those of nuclear [3H]TA complexes from the same strain of tumor. These results suggest that previously described differences in extractability of nuclear-associated [3H]TA between the CS and CR strains of mouse lymphoma P1798 and the lack of response of CR P1798 to glucocorticoid administration may be due, at least in part, to the presence of an altered glucocorticoid-binding component in the resistant tumor cells.

Adrenal Cortex Hormones↗
PubMed1978

Nuclear glucocorticoid binding in chronic lymphatic leukemia lymphocytes.

A reliable procedure is described for isolating 3H-triamcinolone acetonide (3H-TA) receptor complexes from purified chronic lymphatic leukemia (CLL) lymphocyte nuclei, based on the use of carbobenzoxy-L-phenylalanine (CBZ-L-phe) to prevent breakdown of hormone-receptor complexes during extraction of nuclei with 0.6M KCl. Using this method, specific nuclear glucocorticoid binding was demonstrated in 14/14 patients with untreated CLL. No correlation was found between levels of nuclear-associated 3H-TA and peripheral white blood cell count or rosetting ability of circulating lymphocytes.

Aged↗
PubMed1975

Sequential irreversible, actinomycin D-sensitive, and cycloheximide-sensitive steps prior to cortisol inhibition of uridine utilization by P1798 tumor lymphocytes.

Events preceeding the cortisol inhibition of uridine utilization by corticoid-sensitive P1798 lymphocytes have been investigated. When tumor cells were incubated with 1 muM cortisol for 15 min and then washed free of steroid and reincubated in the absence of hormone, the expected decrease of uridine uptake failed to appear 1.5 hr later. In contrast, the removal of cortisol after 30 or 60 min did not prevent subsequent development of the steroid effect. Addition of actinomycin D with cortisol, or 15 min after hormone treatment was started, blocked steroid action. However, when actinomycin D was added 30 or 60 min after the initial exposure to cortisol, hormone-induced depression of uridine uptake was no longer prevented. To study the role of protein synthesis, cycloheximide was added to the tumor cell suspensions at various times after cortisol treatment was started. Cortisol suppression of uridine utilization was blocked when cycloheximide was added with the hormone or 30 min after the start of hormone treatment. Cycloheximide added together with cortisol and washed out with the steroid after 30 min did not prevent subsequent appearance of decreased nucleoside uptake. Hydroxyurea, an inhibitor of DNA synthesis, did not prevent cortisol action, even when present throughout a 2 hr exposure to the steroid. Hormone removal or actinomycin D addition after 1.5 to 2 hr (when uridine uptake was already inhibited about 25%) did not prevent intensification of the steroid effect during a subsequent 1.5- to 2-hr incubation period, while addition of cycloheximide at this time completely prevented its progression. These results suggest aht: (a) cortisol inhibition of uridine uptake by P1798 lymphocytes involves an early irreversible step and appears to require continuing RNA but not protein synthesis during the first 15 to 30 min of hormone action; (b) protein synthesis but not RNA synthesis is required between 30 and 60 min; and (c) continuing protein synthesis but not RNA synthesis or hormone presence is necessary for the preestablished cortisol effect to progress.

Animals↗