Biomedical subjects
D A Blake
Publications and source records attributed to D A Blake.
Resolution of carbohydrates by lectin affinity chromatography.
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Pharmacokinetic studies on quinacrine following intrauterine administration to cynomolgus monkeys.
Recent efforts have been made to develop a chemical oviductal occluding agent. Intrauterine quinacrine has been used in certain areas of the world with moderate success in effected tubal closure. This report presents the pharmacokinetics of a quinacrine solution (30 mg) as administered to cynomolgus monkeys via the intrauterine route, compared with intravascular injection. The data show rapid transfer of the drug from the uterine to the vascular compartment and uptake by almost all tissues examined. Although plasma concentrations disappear within 24 hours, levels can be detected in most tissues for at least 1 week following intrauterine injection. After 28 days, however, tissue levels of the drug are absent or near the limit of detection.
Effect of intrauterine and intravascular quinacrine administration on histopathology, blood chemistry, and hematology in cynomolgus monkeys.
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Thromboxane B2, 6-keto-prostaglandin F1 alpha, and prostaglandin F2 alpha production by contracting pregnant rate uteri in vitro.
While prostaglandin production by uterine tissue has been shown to be involved in the contractile mechanism of this tissue, less attention has focused upon the involvement of other prostanoids. We have simultaneously measured in vitro isometric contractility of pregnant rat uteri with the release of prostaglandin F2 alpha (PGF), 6-keto-prostaglandin F1 alpha (6-k-PGF1 alpha) and thromboxane B2 (TXB2) into the bathing medium under various conditions. Frequency of uterine contractions and integrated contractile force (ICF) increased from 15 days of gestation and peaked at the time of parturition. Activity was generally greatest during the first 15 min of incubation except during parturition and on Day 1 postpartum when the uterine segment remained active for 1 h experimental period. Indomethacin (INDO) significantly reduced contractile activity regardless of gestational stage. PGF, TXB2, and 6-k-PGF1 alpha increased with gestational age, peaking at the time of parturition. Production was greatest during the first 15 min of incubation and INDO inhibited production of each prostanoid regardless of gestational stage. Imidazole (100 micrograms/ml) inhibited TXB2 production without affecting PGF or 6-k-PGF1 alpha levels. Frequency of contraction and ICF were not affected by imidazole treatment despite TXB2 reduction. These data demonstrate that the in vitro uterus from pregnant rats is capable of producing prostanoids other than prostaglandins and their production generally parallels uterine contractile activity. Thus, the possibility that these prostanoids are involved in physiologic changes during parturition warrants further investigation.
Effect of platelet-generated thromboxane on contractions of the pregnant rat uterus.
Recent evidence indicates that thromboxanes are produced by uterine tissues. The effect of platelet-generated thromboxane A2 (TXA2) was therefore studied for its effect on uterine contractions. An incubation tube consisting of washed platelets (WP) was incubated with sodium arachidonate (AA). An aliquot was transferred to an aggregation assay cuvette containing platelet rich plasma (PRP) to test for TXA2 activity. Immediately thereafter, a second aliquot from the incubation tube was transferred to an in vitro preparation of pregnant rat uterus and contractions were monitored. Both assay systems (i.e., aggregation and uterine contraction) contained indomethacin to prevent endogenous prostanoid production from platelets and uteri, respectively. Incubation media from human, rat or rabbit WP incubated with AA for 1 min elicited both platelet aggregation and uterine contractions when transferred to these assay systems. Indomethacin or imidazole added to the incubation tube blocked both responses. Delaying transfer of media until 10 min after addition of AA did not elicit either aggregation or contractile response, consistent with the short production interval and half-life of TXA2. Addition of an antiaggregatory dose of prostacyclin (PGI2) to the incubation tube did not affect TXA2 production or the ability of transferred media to promote uterine contractions. These experiments provide evidence that TXA2 is capable of promoting contractions in the pregnant rat uterus and may be important in the labor mechanism.
Predisposition to phenytoin hepatotoxicity assessed in vitro.
Arene oxide metabolites of phenytoin may be involved in the pathogenesis of drug-induced hepatotoxicity. We examined individual susceptibility to toxicity from such metabolites by exposing human lymphocytes to metabolites generated by a murine hepatic microsomal system. Cells from 17 controls showed no toxicity at concentrations of phenytoin from 31 to 125 microM. Cells from three patients with phenytoin hepatotoxicity manifested dose-dependent toxicity from the metabolites. Phenytoin alone was not toxic to cells. The patients' dose-response curves resembled the response of control cells in which epoxide hydrolase (a detoxification enzyme for arene oxides) was inhibited. Detoxification of non-arene oxide metabolites (e.g., of acetaminophen) was normal in patients' cells. Cells from parents of two patients had intermediate responses. Cells from a sibling of one patient showed no toxicity; a sibling of another patient had a response similar to that of the patient. A heritable defect in response to arene oxides thus may predispose some patients to phenytoin hepatotoxicity.
An alpha-D-galactosyltransferase activity in Ehrlich ascites tumor cells. Biosynthesis and characterization of a trisaccharide (alpha-D-galactose-(1 goes to 3)-N-acetyllactosamine).
An alpha-D-galactosyltransferase activity has been detected in membranous fractions (42,000 x g) of Ehrlich ascites cells which transfers galactosyl groups from UDP-galactose to endogenous and exogenous acceptors. The products of the reaction contain alpha-D-galactopyranosyl groups at the nonreducing termini. A solid state assay was developed to follow alpha-D-galactosyltransferase activity in the presence of beta-D-galactosyltransferase. Examination of a variety of insolubilized exogenous acceptors indicated that the most active acceptors for the alpha-D-galactosyltransferase had the structure beta-D-Gal-(1 goes to 4)-beta-D-GlcNAc(1 goes to at their nonreducing termini. Incubation of UDP-[14C]galactose and beta-D-gal-(1 goes to 4)-D-GlcNAc (N-acetyllactosamine) or of UDP-galactose and beta-D-[14C]Gal-(1 goes to 4)-D-GlcNAc in the presence of the alpha-D-galactosyltransferase resulted in the enzymic synthesis of a 14C-labeled trisaccharide. Chemical and enzymic methods of analysis revealed the structure of the trisaccharide to be alpha-D-Gal-(1 goes to 3)-beta-D-Gal-(1 goes to 4)-D-GlcNAc. These data indicate that the alpha-D-galactosyltransferase in Ehrlich ascites cells transfers galactosyl groups to suitable acceptors to form an alpha-(1 goes to 3)-D-galactosidic linkage.
Carbohydrate binding studies on the Bandeiraea simplicifolia I isolectins. Lectins which are mono-, di-, tri-, and tetravalent for N-acetyl-D-galactosamine.
Association constants for the binding of methyl alpha-D-galactopyranoside (methyl alpha-D-Galp) and methyl 2-acetamido-2-deoxy-alpha-D-galactopyranoside (methyl alpha-D-GalNAcp) to three Bandeiraea simplicifolia isolectins (A4, A2B2, B4) were determined by equilibrium dialysis and fluorescence enhancement measurements. The a and B subunits appear to have approximately the same Kassoc for methyl alpha-D-Galp: 1.45 X 10(4), 1.98 X 10(4), and 2.06 X 10(4) M-1 for A4, A2B2, and B4, respectively, as determined by equilibrium dialysis. Fluorescence enhancement measurements on B4 gave an association constant of 2.07 X 10(4) M-1 for methyl alpha-D-Galp and 1.87 X 10(3) M-1 for methyl beta-D-galp. By equilibrium dialysis, we were able to detect 3.3 (theory, 4.0) methyl alpha-D-GalNAcp binding sites for A4 (Kassoc = 1.87 X 10(5) M-1), 1.9 for A2B2 (Kassoc = 1.19 X 10(5) M-1), and were unable to detect any methyl alpha-D-GalNAcp binding sites for B4. However, four very weak methyl alpha-D-GalNAc binding sites for B4 were detected by fluorescence enhancement measurement (Kassoc = 1.26 X 10(2) M-1). Thus, the A subunit has an affinity for methyl alpha-D-GalNAc 3 orders of magnitude greater than the B subunit. Precipitation and hapten inhibition data are in accord with these binding measurements. Toward guaran and type B blood group substance, all isolectins precipitated the same amount of biopolymer. However, AB3, A2B2, and A3B, which are mono-, di-, and trivalent for alpha-D-GalNAcp, were differentially precipitated by type A blood group substance which contains alpha-D-GalNAcp-end groups. A3B precipitated the most, A2B2 less, and AB3 no type A substance. These isolectins should prove useful in studies evaluating the effect of valence on lectin-cell interaction.
Thalidomide teratogenesis: evidence for a toxic arene oxide metabolite.
It was postulated that thalidomide causes birth defects by being metabolized to a toxic electrophilic intermediate. This hypothesis was tested by using an in vitro assay in which drug toxicity to human lymphocytes was assessed in the presence of a hepatic microsomal drug metabolizing system. Maternal hepatic microsomes from pregnant rabbits mediated the production of a metabolite that was toxic to lymphocytes. Toxicity was enhanced by inhibitors of epoxide hydrolase (EC 3.3.2.3) and abolished by adding the purified enzyme to the incubation medium. The metabolite thus appears to be in arene oxide, consistent with the previously reported isolation of phenolic metabolites of thalidomide from the urine of treated animals. Two teratogenic analogs of thalidomide (phthalimidophthalimide and phthalimidinoglutarimide) were also toxic in the system; two nonteratogenic analogs (phthalimide and hexahydrothalidomide) were not toxic, even in the presence of epoxide hydrolase inhibitors. The toxic metabolite of thalidomide was not produced by rat liver microsomes (the rat is not sensitive to thalidomide teratogenesis) but was produced by hepatic preparations from maternal rabbits, and rabbit, monkey, and human (all sensitive species) fetuses. A toxic arene oxide therefore may be involved in the teratogenicity of thalidomide.
Retrolental fibroplasia: evidence for a role of the prostaglandin cascade in the pathogenesis of oxygen-induced retinopathy in the newborn beagle.
Aspirin administration, at a dosage producing plasma levels within the human therapeutic range, caused marked inhibition of production of both vascular prostacyclin (a vasodilator) and platelet thromboxane (a vasoconstrictor) in beagle puppies. In addition, aspirin-treated, oxygen-exposed puppies developed retinopathy of significantly greater severity than their unmedicated, oxygen-exposed littermates. Direct ophthalmoscopic observations indicated that whereas sustained oxygen breathing produced retinal vasoconstriction in unmedicated puppies, retinal vessels of aspirin-treated littermates became more dilated or remained unchanged. It is postulated that retinal vasoconstriction may be a normal physiologic mechanism to protect the immature retina from damaging effects of high blood oxygen levels; i.e., it may be a protective rather than a pathologic process in response to hyperoxia. Many vascular anomalies which characterize the human disease were present in the retinas of the puppies. Several of the most severely affected puppies treated with aspirin even displayed grade III cicatricial retinopathy (falciform retinal fold). Thus, a major criticism of the retrolental fibroplasia animal model has been addressed by producing cicatricial retrolental fibroplasia in puppies, and the confidence with which results from experimental animal studies might be extrapolated to the clinical situation is thereby strengthened.
Adverse effects of cardiovascular drug therapy on the fetus and neonate.
Possible adverse effects of cardiovascular medications on the fetus and the neonate have been reviewed. The major classes discussed were diuretics, antihypertensives, antiarrhythmics, cardiac glycosides, and anticoagulants. The recommendations given must not be considered definitive because they are based on flawed or incomplete information. It is to be hoped that further investigation will improve this situation and will also improve our understanding of the ways in which these drugs act.
The effects of chronic gastrointestinal medication on the fetus and neonate.
The adverse fetal and neonatal effects of chronic gastrointestinal medication have been reviewed. The major classes discussed are antiemetics, laxatives and antidiarrheal agents, antacids and cimetidine, drugs for irritable bowel syndrome, and drugs for inflammatory bowel disease. The evaluation given are tentative due to the lack of information on most of these drugs. It is hoped that research into the use of this diverse group of medications during pregnancy will be stimulated, so that the large gaps in our knowledge about them can be filled.
Anticonvulsant toxicity in vitro: possible role of arene oxides.
Human lymphocytes incubated with a mouse hepatic microsomal drug metabolizing system were used to study the cytotoxicity of four anticonvulsants. In vitro toxicity assessed by trypan blue dye exclusion was significantly greater for compounds with relatively high clinical toxicity (mephenytoin and phenacemide) than those with only rare cytotoxic complications (phenytoin and phenobarbital). No toxicity occurred in the absence of microsomes and toxicity was enhanced by inhibitors of epoxide hydrolase suggesting that the cytotoxicity of the drugs may result from arene oxide metabolites. In vivo, the covalent binding of such metabolites to cell macromolecules could lead to cell death and, by acting as haptens, to secondary hypersensitivity reactions. The method may be useful in assessing the potential of a drug for toxicity, the mechanism of cell damage and individual differences in cell defenses within the human population.
The inhibition of premature labor with indomethacin.
We administered indomethacin orally for the treatment of premature labor in a prospective, randomized, double-blind fashion, and all infants were followed up. Indomethacin was significantly more effective than placebo in inhibition of premature labor during a 24-hour course of therapy, with treatment failure during therapy occurring in only one of 15 indomethacin-treated patients compared to nine of 15 placebo-treated patients (p less than 0.01). Mean plasma concentrations of indomethacin were approximately 0.8 micrograms/ml at both 4 and 12 hours after administration. Mean plasma levels of 15-oxo-13,14-dihydroprostaglandin F2 alpha (PGFM) were similar in the two groups before treatment, decreased markedly in the indomethacin group by 4 hours, and were not detected at 12 hours in all but the one indomethacin-treated patient who was delivered within 24 hours. Patients in the placebo group who were delivered prematurely had higher pretreatment PGFM levels (mean +/- SE, 83 +/- 18 pg/ml, n = 9) than the patients who responded to placebo (25 +/- 6 pg/ml, n = 6) (p less than 0.05). There was no difference between the indomethacin and placebo groups with respect to gestational age at delivery, birth weight, and neonatal morbidity and deaths. In particular, we found no evidence of premature closure of the ductus arteriosus, pulmonary hypertension, or increase in bleeding problems among the infants exposed to indomethacin in utero. Although no difference in neonatal outcome was observed in this small number of patients, it would seem prudent still to consider indomethacin as an experimental therapy.
Resolution of nucleotide sugars and oligosaccharides by lectin affinity chromatography.
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Modification of cell membrane in variants of Chinese hamster cells resistant to abrin.
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Effect of epsilon amino caproic acid, a fibrinolytic inhibitor, on implantation and fetal viability in the rat.
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