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Biomedical subjects

M D Green

Publications and source records attributed to M D Green.

At least 145 records · Page 8Linked to original sources
PubMed1988

Treatment of epidemic Kaposi's sarcoma with a combination of interferon-alpha 2b and etoposide.

A prospective clinical trial of concomitant interferon-alpha 2b and etoposide was conducted in 24 previously untreated patients with epidemic Kaposi's sarcoma. Eight of 21 evaluable patients (38%) achieved either a complete response (1 patient) or a partial response (7 patients). None of the responders had a prior history of opportunistic infection. Hematologic toxicity was severe, and 8 patients developed an opportunistic infection. The combination of interferon-alpha 2b and etoposide has modest activity, but no additive or synergistic activity was evident in the dose and schedule utilized in this study. The exact role for interferon-alpha in epidemic Kaposi's sarcoma, both as a single agent and in combinations, remains to be determined.

Acquired Immunodeficiency Syndrome↗
PubMed1988

Immunohistochemical demonstration of isozyme- and strain-specific differences in the intralobular localizations and distributions of UDP-glucuronosyltransferases in livers of untreated rats.

Antibodies directed against three isozymes of rat hepatic microsomal UDP-glucuronosyltransferase (EC 2.4.1.17), p-nitrophenol, 3 alpha-hydroxysteroid, and 17 beta-hydroxysteroid UDP-glucuronosyltransferases were used to localize these enzymes at the light microscopic level in livers of untreated Sprague-Dawley and Wistar rats. Avidin-biotin-peroxidase staining revealed the presence of each isozyme within parenchymal cells throughout the liver lobule in rats of both strains. However, although antibodies to the 3 alpha- and 17 beta-hydroxysteroid UDP-glucuronosyltransferases appeared to stain hepatocytes across the liver lobule quite uniformly, centrilobular hepatocytes were stained much more intensely for p-nitrophenol UDP-glucuronosyltransferase than were midzonal and periportal cells. Additionally, appreciable immunohistochemical staining for p-nitrophenol UDP-glucuronosyltransferase, but not for the two hydroxysteroid UDP-glucuronosyltransferases, was detected within the epithelium of the hepatic bile duct and the endothelium of the hepatic artery and portal vein. Another difference was noted in livers of Wistar rats: hepatocytes of rats possessing low 3 alpha-hydroxysteroid (i.e., androsterone) UDP-glucuronosyltransferase activity were stained much less intensely for the 3 alpha-hydroxysteroid UDP-glucuronosyltransferase than were those of rats exhibiting high rates of androsterone glucuronidation, whereas differences in immunoperoxidase staining for p-nitrophenol and 17 beta-hydroxysteroid UDP-glucuronosyltransferases were not apparent between the two subclasses of Wistar rats. These immunohistochemical findings demonstrate that different UDP-glucuronosyltransferase isozymes are distributed across the liver lobule in significantly different manners and, furthermore, suggest that xenobiotics may be glucuronidated within epithelial cells of the hepatic bile duct and endothelial cells of the hepatic artery and portal vein, as well as within hepatocytes. The results of this study also provide evidence that differences in the content of 3 alpha-hydroxysteroid UDP-glucuronosyltransferase within hepatocytes account for genetically determined variations in the rates at which androsterone and certain other xenobiotics are glucuronidated in livers of Wistar rats.

Animals↗
PubMed1988

Biosynthesis of hydroxyl-linked glucuronides of short-chain bile acids by rat liver 3-hydroxysteroid UDP-glucuronosyltransferase.

Microsomal preparations from livers of Sprague-Dawley rats catalyze the glucuronidation of 3 alpha-hydroxy-5 beta-H (3 alpha, 5 beta) short-chain bile acids (C20-C23), predominantly at the hydroxyl group, while the glucuronidation of 3 beta, 5 beta short-chain bile acids occurs exclusively at the carboxyl group. A similar pattern of conjugation was also observed in Wistar rats having normal levels of 3-hydroxysteroid UDP-glucuronosyltransferase. Significant reductions of formation rates for hydroxyl-linked, but not carboxyl-linked, short-chain bile acid glucuronides were observed in hepatic microsomes from Wistar rats with low 3-hydroxysteroid UDP-glucuronosyltransferase activity. 3-Hydroxysteroid UDP-glucuronosyltransferase, purified to homogeneity from Sprague-Dawley liver microsomes, catalyzed the 3-O-glucuronidation of 3 alpha, 5 beta C20-23 bile acids, as well as of lithocholic and isolithocholic acids (C24). The apparent Michaelis constants (KM) for short-chain bile acids were similar to the value obtained for androsterone. 3 alpha, 5 beta-C20 and 3 beta, 5 beta-C20 competitively inhibited glucuronidation of androsterone by the purified 3-hydroxysteroid UDP-glucuronosyltransferase. Purified 17 beta-hydroxysteroid and p-nitrophenol UDP-glucuronosyltransferases did not catalyze the glucuronidation of bile acids. In addition, none of the purified transferases catalyzed the formation of carboxyl-linked bile acid glucuronides. The results show that 3-hydroxysteroid UDP-glucuronosyltransferase, an enzyme specific for 3-hydroxyl groups of androgenic steroids and some conventional bile acids, also catalyzes the glucuronidation of 3 alpha-hydroxyl (but not carboxyl) groups of 3 alpha, 5 beta short-chain bile acids.

Animals↗
PubMed1987

Lethal and sublethal effects of the combination of doxorubicin and the bisdioxopiperazine, (+)-1,2,-bis (3-5-dioxopiperazinyl-1-yl) propane (ICRF 187), on murine sarcoma S180 in vitro.

Doxorubicin and the bisdioxopiperazine, ICRF 187, synergistically inhibit proliferation of murine sarcoma S180 cells in vitro. Cell cycle analysis was employed to help discriminate cytokinetic from lethal effects of the drug combination. Twenty-four-hour incubation with either agent produced dose-dependent partial G2M arrest. At high doses, ICRF 187 produced partial G2M arrest, inhibition of cell division, and continued DNA synthesis at a higher ploidy, resulting in a second G2M arrest of an 8n population. The addition of ICRF 187 to doxorubicin resulted in enhancement of cell cycle blockade at G2M. The combination also produced enhanced lethality as measured by reduced colony-forming efficiency of drug-treated S180 cells. Measurement of [14C]doxorubicin accumulation in, and effux from, ICRF 187 pretreated cells failed to reveal an effect of pretreatment with the bisdioxopiperazine on anthracycline disposition by S180 cells, suggesting that the enhanced cytotoxic and cytostatic effects do not result from increased intracellular concentrations of doxorubicin. The positive interaction between the two drugs may represent site-specific enhancement of the anthracycline effect by ICRF 187 at an intracellular target site.

Animals↗
PubMed1987

N-glucuronidation of carcinogenic aromatic amines catalyzed by rat hepatic microsomal preparations and purified rat liver uridine 5'-diphosphate-glucuronosyltransferases.

The N-glucuronidation of three carcinogenic aromatic amines (4-aminobiphenyl, alpha-naphthylamine, and beta-naphthylamine) was investigated in hepatic microsomal preparations from two rat strains. In preparations from Wistar rats, individual variability was observed for the glucuronidation of the arylamines. This variability correlated with high and low levels of 3 alpha-hydroxysteroid UDP-glucuronosyltransferase (UDPGT) in hepatic microsomal preparations from Wistar rats. This individual variability was not observed in Sprague-Dawley rat hepatic microsomal preparations because hepatic 3 alpha-hydroxysteroid UDPGT levels do not vary in this strain of rats. Five highly purified rat liver UDPGTs were investigated for their ability to catalyze the conjugation of the aromatic amines. Of the purified enzymes investigated, only 3 alpha-hydroxysteroid UDPGT catalyzed the glucuronidation of 4-aminobiphenyl. alpha-Naphthylamine and beta-naphthylamine conjugations were catalyzed by 3 alpha-hydroxysteroid, 17 beta-hydroxysteroid, and 3-methylcholanthrene-inducible p-nitrophenol UDPGTs. The three aromatic amines did not serve as substrates for purified digitoxigenin monodigitoxoside or phenobarbital-inducible morphine UDPGTs. The results show that N-glucuronide formation can be catalyzed by UDPGT isoforms which also catalyze the formation of O-glucuronides. In addition, variable levels of 3 alpha-hydroxysteroid UDPGT in Wistar rat liver may have toxicological significance for substrates of this isoenzyme.

1-Naphthylamine↗
PubMed1987

Oxime-induced decarbamylation and atropine/oxime therapy of guinea pigs intoxicated with pyridostigmine.

The generally accepted explanation for the effects of oximes in countering organophosphorus (OP) anticholinesterase is reactivation of the inhibited acetylcholinesterase (AChE). With soman, the inhibited AChE rapidly becomes resistant to oxime reactivation due to a phenomenon called aging. Thus, pretreatment with pyridostigmine (Py) or physostigmine (Ph) followed by atropine sulfate therapy is required to achieve significant protection against soman; the effectiveness of a pretreatment/therapy (P/T) regimen can be further increased against certain OPs (e.g. sarin and VX) by including an oxime in the therapy regimen. The P/T regimen is clouded by a controversy concerning the use of oximes in the treatment of carbamate intoxication, because 2-PAM has been reported to exacerbate intoxication by some carbamates and to have no effect on decarbamylation rates. To better understand the role of oxime therapy in the theory of pretreatment of OP intoxication we examined the effects of 2-PAM and HI-6 on the rate of decarbamylation of Py-inhibited erythrocyte AChE in vitro and in vivo, and studied the effects of atropine plus 2-PAM or HI-6 on Py toxicity. In decarbamylation experiments, Py-inhibited guinea pig erythrocytes were washed free of excess Py and incubated with vehicle or oxime (2 X 10(-4) M, pH 7.3 and 37 degrees C). Aliquots were assayed for AChE activity at various times during a 60 min incubation period. Rate constants were calculated and compared to determine whether the presence of oxime affected decarbamylation. The data from in vitro and in vivo experiments revealed that oximes accelerated the decarbamylation (p less than 0.05) of inhibited AChE. Lethality data for Py-treated guinea pigs showed that treatment with atropine (23 mumoles/kg, im) plus 2-PAM or HI-6 (145 mumoles/kg, im) at one min after injection of Py increased the protective ratio from 4.2 (atropine only) to 5.1 and 12.2, respectively. It is suggested that the enhanced therapeutic efficacy of atropine by oximes against Py intoxication is related to oxime-induced reactivation.

Acetylcholinesterase↗
PubMed1987

The enzymatic mechanism of glucuronidation catalyzed by two purified rat liver steroid UDP-glucuronosyltransferases.

A kinetic analysis of two homogeneous rat liver steroid (3 alpha-hydroxysteroid and 17 beta-hydroxysteroid) UDP-glucuronosyltransferases was conducted using bisubstrate kinetic analysis, product inhibition studies, and dead-end competitive inhibition studies. Double reciprocal plots of initial velocity versus substrate concentration, using bisubstrate kinetic analysis, gave a sequential mechanism. Product inhibition studies were compatible with either a rapid equilibrium, random-order kinetic mechanism or an ordered Theorell-Chance mechanism. Results of dead-end competitive inhibition studies excluded an ordered Theorell-Chance mechanism. The cumulative results are consistent with a rapid equilibrium random-order sequential kinetic mechanism for the glucuronidation of testosterone by purified 17 beta-hydroxysteroid UDP-glucuronosyltransferase and of androsterone by purified 3 alpha-hydroxysteroid UDP-glucuronosyltransferase.

Androsterone↗
PubMed1987

Rationale and strategy for prevention of anthracycline cardiotoxicity with the bisdioxopiperazine, ICRF-187.

Anthracyclines are amongst the most effective antitumor agents currently utilized. The major impediment to their use has been the development of cardiotoxicity with chronic administration. In an effort to overcome this limitation we have utilizated an approach to abrogate the cardiotoxicity with a drug, ICRF-187, which protects against the anthracycline cardiomyopathy in all animal species so far tested. This strategy assumes that separate mechanisms of cardiac toxicity and antitumor activity exist. We are currently testing this hypothesis in a randomized clinical trial of women with advanced breast cancer who are randomized to receive 5FU, doxorubicin, and cyclophosphamide (FAC) or FAC plus ICRF-187.

Animals↗
PubMed1987

Phase II trial of oral methotrexate and dipyridamole in colorectal carcinoma.

We have employed a rationally designed combination attempting to biochemically modulate the cytotoxicity of methotrexate (MTX), an inhibitor of de novo purine and pyrimidine synthesis, by dipyridamole (DP), a noncytotoxic modulator which blocks cellular transport of preformed nucleosides, in the treatment of 27 patients with advanced colorectal carcinoma. Doses and schedule determined from a previous phase I pharmacokinetic study were MTX at 2.5 mg orally twice a day for 4 days to begin concurrently with DP, at 75 mg orally four times daily for 8 days. One partial response was achieved in a patient who had progressed on a previous regimen of leucovorin and 5-fluorouracil. The major toxic effects observed were myelosuppression and stomatitis. Lack of efficacy could be interpreted to reflect incomplete modulation. Therefore, studies employing continuous iv infusion of DP concurrent with or a loading schedule of DP prior to administration of MTX may be required to provide adequate evaluation of such biochemically directed strategies.

Adenocarcinoma↗
PubMed1987

Weekly 5-fluorouracil combined with PALA: toxic and therapeutic effects in colorectal cancer.

A total of 51 patients (eight previously treated) received PALA added to 5-fluorouracil (5FU) given weekly. After 32 patients, the PALA schedule was changed from every other week to weekly, 24 hours preceding 5FU in accordance with preclinical leads (see text). Both schedules were associated with moderately severe toxic effects related primarily to PALA (skin rash) or to the combined effects of both drugs (diarrhea, vomiting, conjunctivitis, and neurotoxicity). Overall nine partial responses were observed, including three in patients previously treated with 5FU. However, future studies with this combination utilizing the current or other previously published schedules are not warranted in colorectal cancer. Since toxicity is a prominent impediment, the possibility of therapeutic synergy may perhaps be explored at drastically reduced doses of PALA, combined with other modulating measures.

Adult↗
PubMed1986

Pharmacokinetics of pralidoxime chloride in the rat.

The pharmacokinetics of pralidoxime chloride (2-PAM) was studied in rats. Different groups of rats were given an intramuscular injection of 2-PAM at one of three doses (20, 40, or 80 mg/kg). This range of doses is used commonly in studies concerned with the efficacy of 2-PAM against poisoning by potent organophosphorus inhibitors of cholinesterase enzyme. Individual, sequential blood samples were collected during the course of the experiment. From these blood samples the plasma concentrations of 2-PAM were determined over time for each animal. Next the relationship of plasma concentration to time was expressed in terms of a standard pharmacokinetic model. Estimates of various pharmacokinetic parameters were calculated using an open, one-compartment model: volume of distribution (Vd), maximal plasma concentration (Cmax), elimination rate constant (k10), absorption rate constant (k01), area under the curve (AUC) and clearance (CL). Of the pharmacokinetic estimates, only Cmax and AUC were found to be statistically significant (p less than 0.0001) when compared across all the doses; these pharmacokinetic estimates were highly correlated with doses with r = 0.998 and r = 0.997, respectively. However, when AUC and Cmax were normalized by dividing through by dose, no significant differences were found in the transformed data. The results of this study in rat indicate that the pharmacokinetics of 2-PAM is linearly related to dose in a range employed in therapeutic studies of 2-PAM.

Animals↗
PubMed1986

Substrate specificity and characterization of rat liver p-nitrophenol, 3 alpha-hydroxysteroid and 17 beta-hydroxysteroid UDP-glucuronosyltransferases.

Purified preparations of rat liver 17-hydroxysteroid, 3-hydroxyandrogen and p-nitrophenol (3-methylcholanthrene-inducible) UDP-glucuronosyltransferases were further characterized as to their substrate specificities, phospholipid-dependency and physical properties. The two steroid UDP-glucuronosyltransferases were shown to exhibit strict stereospecificity with respect to the conjugation of steroids and bile acids. These enzymes have been renamed 17 beta-hydroxysteroid and 3 alpha-hydroxysteroid UDP-glucuronosyltransferase to reflect this specificity for important endogenous substrates. An endogenous substrate has not yet been identified for the p-nitrophenol (3-methylcholanthrene-inducible) UDP-glucuronosyltransferase. The steroid UDP-glucuronosyltransferase activities were dependent on phospholipid for maximal catalytic activity. Complete delipidation rendered the UDP-glucuronosyltransferases inactive, and enzymic activity was not restored when phospholipid was added to the reaction mixture. After partial delipidation, phosphatidylcholine was the most efficient phospholipid for restoration of enzymic activity. Partial delipidation also altered the kinetic parameters of the 3 alpha-hydroxysteroid UDP-glucuronosyltransferase. The three purified UDP-glucuronosyltransferases are separate and distinct proteins, with different amino acid compositions and peptide maps generated by limited proteolysis with Staphylococcus aureus V8 proteinase. Some similarity was observed between the amino acid composition and limited proteolytic maps of the steroid UDP-glucuronosyltransferases, suggesting they are more closely related to each other than to the p-nitrophenol UDP-glucuronosyltransferase.

Amino Acids↗