Evidence for two separate beta-ketoacyl CoA reductase components of the hepatic microsomal fatty acid chain elongation system in the rat

The hepatic microsomal fatty acid chain elongation system can utilize either NADPH or NADH. Elongation activity, measured as the rate of malonyl CoA incorporation into palmitoyl CoA, was enhanced by a fat-free diet and by bovine serum albumin (BSA) when either cofactor was employed. When the intermediate products were determined, it was observed that in the presence of BSA and NADPH, the predominant product was the saturated elongated fatty acid, whereas in the presence of BSA and NADH, the major intermediate was the beta-ketoacyl derivative. Employing beta-ketostearoyl CoA as substrate, BSA markedly inhibited NADH-supported beta-ketoacyl CoA reductase activity and stimulated NADPH-supported activity. Furthermore, the sum of the NADH-dependent and NADPH-dependent beta-ketoreductase activities approximated the activity obtained when both cofactors were present in the incubation medium, suggesting the existence of two beta-ketoacyl CoA reductases, one using NADH and the other NADPH.

Evidence for two separate beta-ketoacyl CoA reductase components of the hepatic microsomal fatty acid chain elongation system in the rat

The hepatic microsomal fatty acid chain elongation system can utilize either NADPH or NADH. Elongation activity, measured as the rate of malonyl CoA incorporation into palmitoyl CoA, was enhanced by a fat-free diet and by bovine serum albumin (BSA) when either cofactor was employed. When the intermediate products were determined, it was observed that in the presence of BSA and NADPH, the predominant product was the saturated elongated fatty acid, whereas in the presence of BSA and NADH, the major intermediate was the beta-ketoacyl derivative. Employing beta-ketostearoyl CoA as substrate, BSA markedly inhibited NADH-supported beta-ketoacyl CoA reductase activity and stimulated NADPH-supported activity. Furthermore, the sum of the NADH-dependent and NADPH-dependent beta-ketoreductase activities approximated the activity obtained when both cofactors were present in the incubation medium, suggesting the existence of two beta-ketoacyl CoA reductases, one using NADH and the other, NADPH.

Electrophysiological effects of selective sigma-receptor agonists, antagonists, and the selective phencyclidine receptor agonist MK-801 on midbrain dopamine neurons

Extracellular single unit recording techniques were used to study the effects of selective sigma-receptor agonist [(+)-3-PPP, (+)-pentazocine, and DTG] and selective sigma-receptor antagonists (BMY 14802 and Rimcazole) on dopamine neurons of the substantia nigra. Intravenous (IV) administration of sigma agonists decreased, whereas IV administration of the sigma antagonist BMY-14802 increased the firing rate of dopamine neurons. The other sigma antagonist Rimcazole produced inconsistent changes in dopamine unit activity. These data, in conjunction with anatomic data suggesting sigma receptor localization on dopamine neurons in the substantia nigra (Gundlach et al: J Neurosci 6:1757-1770, 1986; Graybiel et al: Soc Neurosci Abstr 13:28, 1987) demonstrate a relationship of the sigma receptor with the dopamine system and further suggest a model system to study agonist-antagonist interactions of sigma ligands. The selective phencyclidine (PCP) agonist MK-801 was equipotent to PCP in regard to stimulatory properties on dopamine neurons. However, the relative potencies do not correspond to their relative binding affinities, suggesting that non-PCP-receptor properties may mediate this effect.

Spectrophotometric assay for the condensing enzyme activity of the microsomal fatty acid chain elongation system

A rapid and simple spectrophotometric method was developed to measure the activity of the condensing enzyme component of the microsomal fatty acid chain elongation system. The intermediate product of the condensation reaction is the beta-ketoacyl CoA which exists in two tautomeric forms, i.e., keto and enol. The addition of bovine serum albumin (BSA) to a cuvette cell containing a beta-ketoacyl CoA derivative resulted in the formation of a 303-nm absorbance peak, characteristic of enolate formation. The beta-ketoacyl CoAs with carbon chain length of 6 to 18 interacted with BSA to produce the 303-nm peak; acetoacetyl CoA was the only beta-keto compound tested which did not interact with BSA to produce the peak. Other compounds which were unaffected by BSA included CoA, free beta-keto acid, beta-hydroxyacyl CoA, acyl CoA, trans-2-enoyl CoA, and malonyl CoA. BSA could not be replaced by ovalbumin; furthermore, denatured (boiling) BSA could not induce the 303-nm peak. The specific activity of the condensing enzyme measured by the spectrophotometric method compares favorably with the activity obtained by the radioactive method. The apparent extinction coefficient (epsilon) for the absorbance peak generated by the beta-keto thioester varied from 5 to 30 mM-1 cm-1 depending on the beta-keto derivative. The spectrophotometric procedure can be used in the determination of the condensing enzyme activity in not only hepatic microsomes but also in kidney and brain microsomes both of which have significantly lower activity. The advantages of the novel method over the radioactive method are that (i) it does not involve the use of radioactive compounds, (ii) it is much less cumbersome and significantly less costly, and (iii) it is rapid and easy to perform.

Topography of rat hepatic microsomal enzymatic components of the fatty acid chain elongation system

The orientation of the condensing enzyme, the beta-hydroxyacyl-CoA dehydrase, and the trans-2-enoyl CoA reductase within the rat liver microsomal membrane was investigated by the use of impermeant inhibitors of enzyme activity: trypsin, chymotrypsin, subtilisin, mercury-dextran, and anti-beta-hydroxyacyl-CoA dehydrase IgG. The activity of the condensing enzyme was inhibited more than 70% by various proteases and was completely inhibited by 80 microM mercury-dextran. Similar results were obtained for the trans-2-enoyl-CoA reductase activity. On the other hand, in the absence of detergent, proteases inhibited beta-hydroxyacyl-CoA dehydrase activity by 25-40%, while in the presence of detergent the inhibition increased to 65-90%. Furthermore, anti-beta-hydroxyacyl-CoA dehydrase IgG, which in the absence of detergent produced no inhibition, in the presence of detergent inhibited beta-hydroxyacyl-CoA dehydrase activity by more than 80%; under identical conditions, preimmune IgG caused a 13% inhibition. Microsomes used throughout this study displayed greater than 90% latency with respect to mannose-6-phosphatase activity, indicating that the microsomes were intact. Latency was not affected by the proteases, by mercury-dextran, or by the presence of the enzyme assay components. These results suggest that both the condensing enzyme and the reductase are present on the cytoplasmic surface of the membrane, whereas the beta-hydroxyacyl-CoA dehydrase is embedded in the microsomal membrane.

Nurses in crisis: a support group based on Travelbee's nursing theory

Cook turns the tables and uses a theory of nursing on nurses themselves. Can a familiar crisis theory be used to help nurses as well as patients? Can nurses in a stressful environment be assisted through techniques we've long used on others? Can the stress of today's workplace be decreased by changing nurses and their expectations of themselves?

Disruption of rat hepatic microsomal electron transport chains by the selenium-containing anti-inflammatory agent Ebselen

The influence of Ebselen, an organoselenium anti-inflammatory agent, on the two electron transport chains present in rat liver microsomes has been studied. At low micromolar concentrations, Ebselen markedly inhibited the flow of reducing equivalents from NADPH-cytochrome P450 reductase to both its natural electron acceptor, cytochrome P450, and its artificial electron acceptor, cytochrome c. Similarly, the microsomal NADH-cytochrome c reductase system consisting of cytochrome b5 and its flavoprotein, NADH-cytochrome b5 reductase, was also significantly inhibited by Ebselen. The inhibition appears to be due to the inability of the reduced pyridine nucleotide to transfer electrons to the flavin (FAD and/or FMN) in the flavoprotein reductase. This was shown with the purified NADPH-cytochrome P450 reductase, which in the presence of Ebselen was not converted to the semiquinone form following the addition of NADPH. The addition of Ebselen to a suspension of hepatic microsomes from either untreated or phenobarbital-treated rats did not result in any spectral change characteristic of type I, type II, or reverse type I.

Action of Ebselen on rat hepatic microsomal enzyme-catalyzed fatty acid chain elongation, desaturation, and drug biotransformation

In the previous study, the organoselenium-containing anti-inflammatory agent, Ebselen, was found to disrupt both hepatic microsomal NADH- and NADPH-dependent electron transport chains. In the current investigation, we focus on the action of Ebselen on three separate metabolic reactions, namely, fatty acid chain elongation, desaturation, and drug biotransformation, which utilize reducing equivalents via these microsomal electron transport pathways. Both NADH-dependent and NADPH-dependent chain elongation reactions showed (i) that the condensation step was inhibited by Ebselen; all three substrates, palmitoyl CoA (16:0), palmitoleoyl CoA (16:1), and gamma-linolenyl CoA (18:3), were differentially affected by Ebselen; for example, the apparent Ki's of Ebselen for the condensation of 16:0, 16:1, and 18:3 in the absence of bovine serum albumin (BSA) preincubation were 7, 14, and 34 microM, and those in the presence of BSA preincubation were 35, 62, and 150 microM, respectively, supporting earlier data for multiple condensing enzymes; (ii) that the beta-ketoacyl CoA reductase-catalyzed reaction step which appears to receive electrons, at least in part, from the cytochrome b5 system, was also markedly inhibited by varying Ebselen concentrations; and (iii) that similar results were obtained with the dehydrase and the enoyl CoA reductase. Hence, each of the four component steps was significantly inhibited by Ebselen. Another important fatty acid biotransformation reaction, delta 9 desaturation of stearoyl CoA to oleoyl CoA, was significantly inhibited (90%) by 30 microM Ebselen. This effect appeared to be directly related to the NADH-dependent electron transport chain rather than to a direct action on the desaturase enzyme. Last, Ebselen also inhibited both aminopyrine and benzphetamine N-demethylations, two cytochrome P450-catalyzed reactions, in untreated rats, in rats on a high carbohydrate diet, and in phenobarbital-treated rats.

Effect of Cu2+ and Zn2+ on the inhibition of human leucocyte elastase by 6-alkyl-3-(omega-carboxyalkyl)-2-pyrone, oleic acid and sulindac sulfide

Inhibition of human leucocyte elastase by oleic acid and the structurally related 3-(1'-oxo-7'-carboxyheptyl)-4-hydroxy-6-octyl-2-pyrone is considerably enhanced by the addition of Cu2+, Zn2+ and, to a lesser extent, Co2+ and Ca2+. Sulindac sulfide and diflunisal also respond to changes in copper concentration, while Boc-Ala-Pro-Val-NH[CH2]10CO2H does not. Binding of the -CO2H group in the vicinity of the S5 subsite is proposed for all but the last compound to account for this effect. Incubation experiments indicate that Cu2+ binds more rapidly to the enzyme than does the inhibitor. Local changes in conformation result in improved binding of the inhibitor, but do not affect the substrate (Km unchanged). Chelation by EDTA is time-dependent, indicating that the Cu2+ is shielded by the inhibitor. The results may partially explain the well-known anti-arthritic and anti-inflammatory properties of copper and zinc and their organic salts.

Biochemical, behavioral, and electrophysiologic actions of the selective sigma receptor ligand (+)-pentazocine

Research on the sigma receptor, a binding site associated with drug-induced psychotomimetic behaviors, has been hampered because most sigma agonists also interact with the phencyclidine (PCP) receptor. (+)-Pentazocine, a human psychotogen, is a selective sigma receptor ligand. To demonstrate sigma receptor activities, we studied the behavioral and electrophysiologic actions for (+)-pentazocine. In the behavioral drug discrimination procedure in which rats were trained to discriminate between 2.0 mg/kg (5.59 mumol/kg) (+)-pentazocine and saline, (+)-pentazocine produced dose-related increases in the percentage of trials completed on the (+)-pentazocine lever. At a dose of 1.0 mg/kg (3.29 mumol/kg) (+)-N-allylnormetazocine generalized completely to (+)-pentazocine. By contrast, PCP only partially generalized. In the visual evoked potential test, these compounds produced a significant dose-dependent slowing of the N2 latency. This response was prevented by haloperidol pretreatment. These results demonstrate pharmacologic actions for the selective sigma receptor ligand (+)-pentazocine and suggest some overlapping pharmacologic properties of the sigma and PCP receptor sites despite differences in central nervous system distribution.

Dual action of 2-decynoyl coenzyme A: inhibitor of hepatic mitochondrial trans-2-enoyl coenzyme A reductase and peroxisomal bifunctional protein and substrate for the mitochondrial beta-oxidation system

The present study was designed to determine the action of the 2-acetylenic acid thioester on mitochondrial fatty acid chain elongation and beta-oxidation. Addition of 2-decynoyl CoA to a rat liver mitochondrial suspension resulted in a significant stimulation of the rate of oxidation of NADPH and NADH. This enhanced oxidation rate was not due to the mitochondrial trans-2-enoyl CoA reductase-catalyzed conversion of the 2-acetylenic acid thioester to the saturated product, decanoate, as measured by gas-liquid chromatography. On the contrary, the mitochondrial trans-2-enoyl CoA reductase activity was markedly inhibited by the 2-acetylenic acid derivative, as evidenced by the decrease in the reduction of trans-2-decenoyl CoA to decanoic acid. Incubation of the mitochondrial fraction with either NADPH or NADH and 2-decynol CoA resulted in the gas chromatographic identification of three products: beta-ketodecanoate, beta-hydroxydecanoate, and trans-2-decenoate. In the absence of reduced pyridine nucleotide, a single product was formed and identified as beta-ketodecanoate. Confirmation of the identity of this product was obtained by the observation of the formation of the Mg2+-enolate complex (303-nm absorbance peak). These results suggest that, although the 2-decynoyl CoA is an inhibitor of mitochondrial trans-2-enoyl CoA reductase activity, it is a substrate for the mitochondrial trans-2-enoyl CoA hydratase (crotonase). This was confirmed by incubation of 2-decynoyl CoA with commercially purified liver mitochondrial crotonase. The beta-ketodecanoate is formed in a two-step process: hydration of the 2-decynoyl CoA to an unstable enol intermediate which undergoes rearrangement to the beta-ketodecanoyl CoA. Interestingly, although the mitochondrial crotonase can utilize the 2-acetylenic acid thioesters, this was not the case for the peroxisomal bifunctional hydratase which was markedly inhibited by varying concentrations of 2-decynoyl CoA.

Deleterious effect of Brij 35 on alkyl 2-pyrones and other hydrophobic inhibitors of human sputum and leucocyte elastase

Brij 35 significantly reduced the inhibitory activity of hydrophobic alkyl 2-pyrones, oleic acid and alkyl peptides towards human sputum and leucocyte elastase, whereas 4-methoxy-6-(2'-hydroxy-2'-(carbobutyloxy)-vinyl)-2-pyrone, alpha-1-proteinase inhibitor and a sulfated chitosan were unaffected. The effect of Brij 35 on elastase appeared to be irreversible, since dialysis against Brij-free buffer was not accompanied by a return to inhibitory activity by the first group of inhibitors. However, passage through an ionic-exchange column was effective in removing the detergent from the enzyme. Brij 35 is also an activator of the elastases: kcat for Boc-Ala-4-nitrophenyl ester and methylsuccinyl-Ala-Ala-Pro-Val-4-nitroanilide increased by 20% and 40%, respectively in the presence of 0.015% Brij 35. Binding of the substrates to the enzyme is unaffected, since Km is unchanged.

Similar binding sites for unsaturated fatty acids and alkyl 2-pyrone inhibitors of human sputum elastase

Evidence is presented to support the hypothesis that oleic acid and 3-(1'-oxo-7'-carboxyheptyl)-4-hydroxy-6-octyl-2-pyrone (and other 3,6-dialkyl-2-pyrones) occupy the same binding region on human sputum elastase. The mechanism of inhibition is strongly dependent on the substitution pattern of the 2-pyrone, and these mechanisms correlate with those of oleic acid and 11-undecenoic acid ("half oleic acid"). Based on the assumption that the 2-pyrone moiety and the double bond of the fatty acids bind to the same region of elastase (subsite S3), we believe that the alkyl chain points towards the S1 subsite, with the carboxylate anion fragment pointing away and probably associated with positively charged Arg217. (subsite S4 or S5).

Erythrocyte pyrimidine 5'-nucleotidase and deoxynucleotidase isozymes: metallosensitivity and kinetics

Erythrocytes from a subject with classical pyrimidine 5'-nucleotidase (P5N) deficiency (PND) possessed typically low nucleotidase activity with uridine 5'-monophosphate (UMP) and cytidine 5'-monophosphate (CMP) as the substrates with subnormal dephosphorylation of 2'-deoxy thymidine 5'-monophosphate (dTMP) and 2'-deoxyuridine 5'-monophosphate (dUMP) and intermediate activity with 2'-deoxycytidine 5'-monophosphate (dCMP). Contrary to previously reported data, there was enzyme activity with all five substrates. The metallosensitivities of the P5N isozymes using UMP, dUMP, dCMP and dTMP as the substrates were defined. Nucleotidase (P5N) is slightly more sensitive than 2'-deoxy-pyrimidine 5'-nucleotidase (dP5N) to inhibition by lead, copper and mercury. Chromium stimulated more enzyme activity with dCMP than other substrates. Apparent Michaelis constants (Km) were calculated for UMP, CMP, dUMP, dCMP, and dTMP for PND and control subjects. Optimal activity was at pH 7.0-7.8 when using UMP and CMP as the substrates but at pH 5.5-6.5 with dUMP, dCMP and dTMP as the substrates. The Km, pH optima and metallosensitivities were, however, consistent with electrophoretic evidence for two and probably three isozymes: P5N with maximal affinity for UMP and CMP; dP5N with maximal affinity for dUMP and dTMP; and a closely related dCMPase. The relative activity with representative substrates can be used to distinguish homozygotes and heterozygotes for P5N deficiency and subjects with heavy metal exposure.

Radial-arm maze deficits produced by colchicine administered into the area of the nucleus basalis are ameliorated by cholinergic agents

Rats were given bilateral injections of colchicine into the area of the nucleus basalis. Colchicine produced dose-dependent alterations in the acquisition of a food-reinforced working-memory task. Colchicine-induced deficits in maze performance were attenuated by cholinergic agents, including physostigmine, RS-86 (2-ethyl-8-methyl-2,8-diazospiro-(4,5)-decan-1,3-dione-hydro bromide) and nicotine. Naloxone and vasopressin did not affect radial-arm maze performance of colchicine-treated rats. Subsequent neurochemical analysis showed that colchicine decreased choline acetyltransferase (ChAT) activity and levels of norepinephrine, dopamine, 3,4-dihydroxyphenylacetic acid, serotonin and 5-hydroxyindoleacetic acid in the neocortex. However, ChAT activity and other neurochemical measures were not altered in the hippocampus or corpus striatum. Histological assessment indicated damage limited to the injection in the area of the nucleus basalis and enlarged cerebrolateral ventricles. These data suggest the possible utility of the colchicine model in the study of cognitive deficits associated with neurodegenerative diseases.

Immediate effects of intravenous IgG administration on peripheral blood B and T cells and polymorphonuclear cells in patients with myasthenia gravis

Five patients with myasthenia gravis, who received treatment with intravenous 7S gamma-globulin were monitored for changes in immunological status. Serum immunoglobulin G increased from an average of 1.4 to 4.7 g/dl during the 5-day course of therapy. Specific antibody to the acetylcholine receptor present in three of five patients did not change. A transient decrease in total peripheral blood leukocytes was observed in five patients due to decreases in the absolute number of polymorphonuclear cells and lymphocytes in the circulation. Lymphocyte surface marker studies revealed that the percentage of surface immunoglobulin positive cells increased in all patients from an average of 13 to 26% by day 5 of therapy; however, the percentage of HLA-Dr- and Leu 12 (CD19)-positive B cells did not change. Lymphoid cells positive for the Leu 11 (CD16) marker doubled from an average of 11 to 24% during the 5-day course of therapy. Surface Ig-positive cells and Leu 11 (CD16)-positive cells returned to pretreatment values by 7 days posttherapy. Helper/suppressor cell ratios slowly decreased in all patients from an average of 2.9 to 2.2 by 1 week posttherapy and remained low for several weeks.

Evaluation of latex-based heterophile antibody assay for diagnosis of acute infectious mononucleosis

The diagnosis of an acute episode of infectious mononucleosis (IM) is made on the basis of clinical symptoms and serological evidence for development of heterophile antibodies. In an effort to obtain a very sensitive and specific assay for diagnosis of IM, we have developed MERISTAR:IM. The MERISTAR assay uses latex beads coated with purified bovine heterophile antigen. We compared the sensitivity and specificity and performance characteristics of the latex-based test to those of the commercially available erythrocyte-based Monospot test with serum samples from 363 suspected-IM patients and controls. A total of 28 samples from patients with confirmed IM were positive with the MERISTAR assay, while only 23 of the samples were positive with the Monospot assay. The two assays had equal specificity, as each test gave two false-positive results. In the technical performance of the assay, the MERISTAR assay was simpler and faster to perform than the Monospot assay.

Discriminative stimulus properties of a sigma receptor agonist in the rat: role of monoamine systems

The role of the dopaminergic, noradrenergic and serotonergic systems in the production of the discriminative stimulus (DS) properties of the sigma receptor agonist (+)-N-allylnormetazocine [(+)-NANM/(+)-SKF 10,047] was measured in rats. The partial generalization of the noradrenergic agonist clonidine with (+)-NANM and partial antagonism of (+)-NANM by yohimbine suggest that the noradrenergic system may play a role in (+)-NANM DS. Activation of the dopaminergic system by apomorphine did not produce (+)-NANM DS however, haloperidol, which binds to the sigma receptor with high affinity, antagonized (+)-NANM DS. These data suggest that the haloperidol antagonism of (+)-NANM DS is a function of antagonism at the sigma receptor rather than antagonism at the dopamine receptor. Since yohimbine does not bind to the sigma receptor, yohimbine antagonizes (+)-NANM by a mechanism different from that of haloperidol. There was no evidence to suggest serotonergic mediation of (+)-NANM DS.

Rabbit secretory components: identification of a third allotype, t63

A third allotype of rabbit secretory component has been identified. The allotype previously referred to as t62 by our laboratory can now be subdivided into two allotypes, t62 and t63, with alloantisera capable of discriminating between the two. Results of family studies are consistent with a three allele system (t61, t62 and t63) at the t-locus. By SDS PAGE, electrophoretic mobilities of the multiple SC bands for each of the three allotypes are characteristic of the allotype; the apparent molecular sizes of the bands of the t62 allotype are 2 to 3 kDa lower than those for the t61 allotype. The banding patterns of the t61 and t63, although similar, are not identical to each other. Results of serologic cross-reaction studies and of tryptic peptide mapping studies suggest multiple structural differences between the allotypes as well as a closer relationship between t62 and t63 than between either of these allotypes and t61.

Rabbit secretory components: identification of a third allotype, t63

A third allotype of rabbit secretory component has been identified. The allotype previously referred to as t62 by our laboratory can now be subdivided into two allotypes, t62 and t63, with alloantisera capable of discriminating between the two. Results of family studies are consistent with a three allele system (t61, t62 and t63) at the t-locus. By SDS PAGE, electrophoretic mobilities of the multiple SC bands for each of the three allotypes are characteristic of the allotype; the apparent molecular sizes of the bands of the t62 allotype are 2 to 3 kDa lower than those for the t61 allotype. The banding patterns of the t61 and t63, although similar, are not identical to each other. Results of serologic cross-reaction studies and of tryptic peptide mapping studies suggest multiple structural differences between the allotypes as well as a closer relationship between t62 and t63 than between either of these allotypes and t61.

Myo-osseous intercostal pedicle flaps for tracheal reconstruction in puppies

We evaluated a myo-osseous intercostal pedicle flap for distal tracheal reconstruction. Mongrel puppies, 6 to 10 weeks old, underwent tracheal repair, 12 for primary defects and seven for stenotic lesions created in the distal trachea. A composite flap was constructed from the anterior portion of the fourth rib with the overlying pleura and periosteum and a posteriorly based intercostal muscle/neurovascular pedicle. The animals did well following tracheal reconstruction without evidence of airway obstruction. Bronchoscopy documented normal tracheal diameter and the repair site could not be discerned from the surrounding mucosa. Histologically, there was complete respiratory epithelial ingrowth with no inflammatory changes. The rib graft had active hematopoietic marrow. This work suggests that the myo-osseous intercostal pedicle flap provides a surface for normal epithelial ingrowth of tracheal mucosa without stimulating granulation tissue, interposes a stent capable of growth, therefore minimizing anastomotic stricture, and is an effective alternative in the management of distal tracheal stenosis.

Inhibition of human sputum elastase by substituted 2-pyrones

Nineteen 4-hydroxy- and 4-methoxy-2-pyrones related to elasnin (I) have been assayed for in vitro inhibition of human sputum elastase (HSE), porcine pancreatic elastase, alpha-chymotrypsin, and trypsin. Inhibition is reported as Ki and Ki'; percentage inhibition was dependent on [S] in a number of cases, making it unsuitable as a measure of relative inhibition. The 3-(1-oxoalkyl)-4-hydroxy-6-alkyl-2-pyrones were found to be most effective, the octyl homologue 11 being the most potent inhibitor (Ki = 4.6 microM, 30 times better than the lead compound). A further reduction in inhibition was observed when the hitherto hydrophobic 6-substituent was substituted by a branched functionality of hydrophilic nature. Conversely, methylation of the 4-hydroxy group of the 6-alkyl-2-pyrones increased inhibitory activity. The mechanism of inhibition varied from pure noncompetitive to mixed type to uncompetitive and was found to be dependent on the pattern of substitution. We believe that the 4-hydroxy-2-pyrone binds to the S4 subsite, with the 6-substituent extending across the S4-S1 subsites and the 3-substituent occupying the S5 subsite. The length of the inhibitor binding region was calculated to be approximately 24 A. None of the hydrophobic compounds were found to have any appreciable inhibition (less than 10%) with porcine pancreatic elastase, bovine alpha-chymotrypsin, and bovine trypsin when tested at the limit of their solubility. The hydrophilic compounds were nonspecific, inhibiting all four enzymes. Dialysis was used to show that the interaction is fully reversible.

Spontaneous antithrombin in a patient with benign paraprotein

A 66-year-old man with peptic ulcer disease developed a paraprotein that resulted in a spontaneously prolonged prothrombin time, activated partial thromboplastin time, and thrombin clotting time. Although the reptilase time was normal, the thrombin clotting time failed to correct with the addition of normal plasma, calcium, or protamine sulfate. The patient's purified fibrinogen was normal, but his serum contained an IgG that inhibited the clotting of normal plasma and purified fibrinogen in the presence of thrombin. In contrast to previously described paraproteins, this patient's IgG appeared to inhibit the activity of thrombin per se rather than to interfere with fibrinogen cleavage or fibrin polymerization. Although immunoprecipitation between thrombin and the paraprotein could not be demonstrated, the patient's purified IgG, in the presence of thrombin, decreased the thrombin activity on a chromogenic substrate. Further, increasing concentrations of thrombin overcame the inhibitory effect of the patient's paraprotein. Thus, the patient's paraprotein appeared to possess antithrombin activity.

Source of the hepatic microsomal trans-2-enoyl CoA hydratase bifunctional protein: endoplasmic reticulum or peroxisomes

The present study was designed to investigate the hepatic localization of the microsomal bifunctional trans-2-enoyl CoA hydratase. Despite the low activity (less than 10%) of peroxisomal marker enzymes in isolated hepatic microsomes (acyl CoA oxidase (this study), catalase, and urate oxidase (L. Cook, M. N. Nagi, J. Piscatelli, T. Joseph, M. R. Prasad, D. Ghesquier, and D. L. Cinti, 1986, Arch. Biochem. Biophys. 245, 24-26), additional evidence in this study suggests that the microsomal enzyme is derived from peroxisomes. For example, the microsomal hydratase activity was associated with the ribosomal fractions but not with the smooth endoplasmic reticulum. In addition, when an extract of the peroxisomal enzyme was incubated with either free ribosomes or membrane-bound ribosomes, marked binding was observed with each of the fractions. Furthermore, the ease of release of the bifunctional enzyme from both free ribosomes and membrane-bound ribosomes by only KCl suggests that the bound enzyme is not a nascent protein. Labeling of liver tissue from DEHP-treated rats with rabbit immune IgG made to the purified microsomal hydratase followed by gold conjugated goat anti-rabbit IgG suggested a single subcellular site for the bifunctional hydratase--the peroxisomal organelle.

Biochemical and immunological identity of the hepatic peroxisomal and microsomal trans-2-enoyl CoA hydratase bifunctional protein

In the present study, the hepatic microsomal and peroxisomal bifunctional trans-2-enoyl CoA hydratases were isolated and purified from rats treated with 2% di-(2-ethylhexyl)phthalate for 8 days. These two enzymes (microsomal and peroxisomal) were purified with the identical purification procedures and had identical molecular masses of 76 kDa. A single band was observed on an electrophoretic gel of an equimixture of the two proteins. Both preparations had identical pI's of 8.6 and pH optima of 6.0 for the dehydrogenase (reductase) and 7.5 for the hydratase activity. Two-dimensional gel analysis of an equimixture of the two preparations showed only one band. Ouchterlony double-diffusion analysis showed that an antibody raised against the purified microsomal enzyme interacted at a point with the peroxisomal enzyme, indicating immunologic identity. Western blot analysis demonstrated that the antibody formed a single band with total microsomal and peroxisomal fractions. The antibody inhibited the enzymatic activities of both preparations in a similar manner. Interestingly, the antibody had a markedly greater inhibitory effect on the reductase activity of the two enzyme preparations, and a much less inhibitory effect on the hydratase activity, suggesting that the antigenic determinants reside at or near the catalytic site of the reductase portion of the protein. These results suggest that the microsomal and peroxisomal bifunctional proteins are identical.

Discriminative stimulus properties of (+)-N-allylnormetazocine in the rat: correlations with (+)-N-allylnormetazocine and phencyclidine receptor binding

Recent studies have identified a stereospecific (+)-NANM binding site that binds psychotomimetic opioids and phencyclidine (PCP) but has a distribution in brain different from the PCP binding site. Since (+)-NANM has no opioid activity and (-)-NANM has opioid activity, rats were trained to discriminate (+)-NANM from saline in order to develop an ability to distinguish the (+)-NANM cues from other opioid agonist and antagonist activities. Cyclazocine, PCP, and ketamine all produced (+)-NANM-like stimuli in a dose-dependent manner. Behaviorally, cyclazocine and PCP are equipotent to (+)-NANM whereas ketamine is 6.7 times less potent than (+)-NANM. Pentazocine had the highest affinity for the (+)-[3H]NANM binding site, yet did not produce (+)-NANM-like discriminative stimuli. By contrast, ketamine had the lowest binding affinity for the (+)-[3H]NANM binding site and did produce (+)-NANM-like discriminative stimuli. Drug discrimination potencies relative to (+)-NANM were not predictive of relative binding affinities at (+)-NANM or PCP binding sites, although there was a trend toward a stronger correlation with the PCP binding site. Therefore, the discriminative stimulus properties of (+)-NANM cannot be explained by pharmacologic actions at either (+)-NANM or PCP binding sites alone, and may involve concurrent actions at both sites.

Total anomalous pulmonary venous return: report of a case diagnosed on ECMO

After repeated echocardiographic assessment and cardiology consultation, a 2,750-g, 36 weeks' gestation neonate with esophageal atresia, tracheo-esophageal fistula, and pneumonia thought to be complicated by persistent pulmonary hypertension was placed on extracorporeal membrane oxygenation (ECMO). While on ECMO, pre-oxygenator and umbilical artery blood gas patterns suggested the diagnosis of total anomalous pulmonary venous return which was subsequently confirmed by cardiac catheterization.

(+)-3-(3-hydroxyphenyl)-N-(1-propyl)piperidine [(+)-3-PPP] but not (-)-3-PPP produces (+)-N-allylnormetazocine-like (SKF 10,047) discriminative stimuli

In rats trained to discriminate the prototypic sigma receptor agonist, (+)-N-Allylnormetazocine [(+)-N-Allylnormetazocine [(+)-NANM/SKF 10,047], from saline, the (+)- but not the (-)-isomer of 3-(3-hydroxyphenyl)-N-(1-propyl)piperidine (3-PPP) produced (+)-NANM-like discriminative stimuli. (+)-3-PPP binds stereo selectively to the (+)-NANM binding site, but not to the phencyclidine binding site. Additionally, phencyclidine was found to produce (+)-NANM-like discriminative stimuli. Although the 3-PPP isomers were shown to produce changes in central dopaminergic activity (Hjorth et al. Life Sci 37, 673, 1985), the discriminative stimulus properties of (+)-3-PPP are apparently not mediated via the dopaminergic system. This hypothesis is supported by the fact that apomorphine did not produce (+)-NANM-like discriminative stimuli. These stimuli are thus non-dopaminergic and may be due to the (+)-3-PPP actions at the sigma binding site. However, it is possible that (+)-NANM, PCP, and (+)-3-PPP may have common non-sigma pharmacologic properties that account for the similar discriminative stimulus properties of these compounds.

Site of inhibition of rat liver microsomal fatty acid chain elongation system by dec-2-ynoyl coenzyme A. Possible mechanism of inhibition

The present study examines the effect of the acetylenic thioester dec-2-ynoyl-CoA (delta 2 10 identical to 1-CoA) on the microsomal fatty acid chain elongation pathway in rat liver. When the individual reactions of the elongation system were measured in the presence of delta 2 10 identical to 1-CoA, the trans-2-enoyl-CoA reductase activity was markedly inhibited (Ki = 2.5 microM), whereas the activities of the condensing enzyme, the beta-ketoacyl-CoA reductase, and the beta-hydroxyacyl-CoA dehydrase were not affected. The absence of inhibition of total microsomal fatty acid elongation was attributed to the significant accumulation of the intermediates, beta-hydroxyacyl-CoA and trans-2-enoyl-CoA, without formation of the saturated elongated product, indicating that the trans-2-enoyl-CoA reductase-catalyzed reaction was the only site affected by the inhibitor. The nature of the inhibition was noncompetitive. In contrast to the delta 2 10 identical to 1-CoA, delta 3 10 identical to 1-CoA did not inhibit trans-2-enoyl-CoA reductase activity, suggesting that the mode of inhibition was not via formation of the 2,3-allene derivative. Based on the observation (a) that p-chloromercuribenzoate markedly inhibits reductase activity, (b) that dithiothreitol protects the enzyme against inactivation by delta 2 10 identical to 1-CoA, (c) of the spectral manifestation of the interaction between thiol reagents and delta 2 10 identical to 1-CoA depicting an absorbance peak similar to that of the beta-ketoacyl thioester-Mg2+ enolate complex, (d) of a similar absorbance spectrum formed by the interaction between delta 2 10 identical to 1-CoA and liver microsomes, and (e) of the absence of formation of a similar spectrum by delta 3 10 identical to 1-CoA, trans-2-10:1-CoA, or delta 2 10 identical to 1 free acid with liver microsomes, we propose that delta 2 10 identical to 1-CoA inactivates trans-2-enoyl-CoA reductase by covalently binding to a critical sulfhydryl group at or in close proximity to the active site of the enzyme.

Do rat hepatic microsomes contain multiple NADPH-supported fatty acid chain elongation pathways or a single pathway?

[2-14C]-trans-2-hexadecenoyl CoA (16:1) and [2-14C]-trans-2-cis-8,11,14-eicosatetraenoyl CoA (20:4) were chemically synthesized and employed as competitive substrates for the liver microsomal trans-2-enoyl CoA reductase component of the fatty acid chain elongation system. Both 7.5 microM and 15 microM 20:4 competitively inhibited the reduction of 16:1 CoA to palmitoyl CoA. In addition, the reduction of both substrates was identically inhibited to the same extent by the acetylenic derivative, dec-2-ynoyl CoA. Furthermore, trypsin, chymotrypsin and subtilisin inhibited trans-2-enoyl CoA reductase activity when three different substrates were employed--16:1, 20:4 and trans-2-cis-11-octadecadienoyl CoA (18:2). These results are consistent with the hypothesis of multiple condensing enzymes connected to a single elongation pathway.

Induction of rat liver mitochondrial fatty acid elongation by the administration of peroxisome proliferator di-(2-ethylhexyl)phthalate: absence of elongation activity in peroxisomes

The administration of di-(2-ethylhexyl)phthalate (DEHP)3 to male Sprague-Dawley rats resulted in more than a threefold increase in activity of acetyl CoA-dependent hepatic mitochondrial fatty acid elongation. Peroxisomes obtained either from control or DEHP-treated rats were not capable of elongating any of the fatty acyl CoAs tested. Furthermore, the peroxisomes possessed no trans-2-enoyl CoA reductase activity. Therefore, the elongation activity in the 7500g fraction from both control and DEHP-fed animals can be attributed totally to the mitochondria. Maximal incorporation of acetyl CoA occurred in the presence of both NADH and NADPH, and octanoyl CoA (8:0) and decanoyl CoA (10:0) were found to be optimal primers for fatty acid elongation in both control and DEHP-treated animals. The apparent Km for 8:0 CoA was 17 microM in both animal groups while the Vmax was increased from 4.5 to 12.5 nmol/min/mg following treatment. The apparent Km for 10:0 CoA was 10 microM in both control and DEHP-treated groups while the apparent Vmax increased from 2.5 to 10 nmol/min/mg; palmitoyl-CoA (16:0) was a very poor primer for chain elongation. Although the acetyl CoA-dependent fatty acid elongation was stimulated by DEHP treatment, the mitochondrial trans-2-enoyl CoA reductase activity was unaffected. The mitochondrial total elongation activity following DEHP-treatment using 8:0 CoA as primer was about two times higher than enoyl CoA reductase activity using trans-2-decenoyl CoA (10:1). This was the result of accumulation of intermediates, which were identified as trans-2-10:1 (35%), beta-hydroxy 10:0 (25%), unidentified (15%), and elongated saturated product 10:0 (24%). Elongation by one acetate unit was found in both the control and DEHP-treated animals. The results are discussed in terms of physiological significance.

Evidence for multiple condensing enzymes in rat hepatic microsomes catalyzing the condensation of saturated, monounsaturated, and polyunsaturated acyl coenzyme A

The condensation of palmitoyl-CoA with malonyl-CoA by rat hepatic microsomes was competitively inhibited by myristoyl-CoA, whereas it was noncompetitively inhibited by palmitoleoyl and gamma-linolenoyl-CoA. Furthermore, the condensation of palmitoleoyl-CoA with malonyl-CoA was also noncompetitively inhibited by gamma-linolenoyl-CoA. Replacement of normal diet by a fat-free high carbohydrate diet resulted in 8-, 2.5-, and 2.3-fold increases in the condensation rates of both palmitoyl- and myristoyl-CoA, palmitoleoyl-CoA, and gamma-linolenoyl-CoA, respectively. On the other hand, administration of di-(2-ethylhexyl)phthalate (DEHP) resulted in a 2-fold stimulation of the condensation activities with myristoyl- and palmitoyl-CoA, while those with palmitoleoyl- and gamma-linolenoyl-CoA decreased to about 83 and 63%, respectively. Similar results following dietary changes or DEHP administration were obtained for total elongation activities. Finally condensation activities of 16:0, 16:1, and gamma-18:3 CoA were differently affected by the proteolytic enzyme, chymotrypsin. The competitive substrate studies, those of dietary and DEHP administration, and the differential action of chymotrypsin strongly suggest the existence of at least three discrete condensing enzymes catalyzing the condensation of saturated, monounsaturated, and polyunsaturated acyl-CoAs. These studies also indicate that the condensation reaction is the regulating and rate-limiting step of the fatty acid chain elongation system.

Isolation of rat liver microsomal short-chain beta-ketoacyl-coenzyme A reductase and trans-2-enoyl-coenzyme A hydratase: evidence for more than one hydratase

An enzyme preparation (IIIB) isolated from liver microsomes of untreated male rats was found to contain two activities--short-chain trans-2-enoyl-CoA hydratase and beta-ketoacyl-CoA reductase. The hydratase was purified more than 1000-fold, while the reductase activity was purified over 600-fold. Employing sodium dodecyl sulfate (SDS)-polyacrylamide gel electrophoresis, a single band with a molecular weight of 76,000 was observed. Although attempts to separate these two activities have failed, it remains to be established whether the final preparation contains a single enzyme with two activities or two separate enzymes. The hydratase was most active toward crotonyl-CoA, followed by trans-2-hexenoyl-CoA (6:1) and -octenoyl-CoA (8:1); the enzyme was essentially inactive toward substrates containing more than eight carbon atoms. The Vmax for crotonyl-CoA was 2117 mumol/min/mg protein, while the Km was 59 microM. Using acetoacetyl-CoA as substrate, the Vmax for the beta-ketoacyl-CoA reductase was over 60 mumol/min/mg protein and the Km was 37 microM; the Vmax for beta-ketopalmitoyl-CoA was only 15% of that observed with acetoacetyl-CoA, although the Km was 6 microM. During the course of purification, a second short-chain hydratase was discovered (fraction IVA); unlike IIIB, this fraction catalyzed the hydration of 4:1, 6:1, and 8:1 at similar rates. The partially purified preparation yielded maximal activity with 8:1 CoA (apparent Vmax 35 mumol/min/mg), followed by 6:1 CoA, 4:1 CoA, and 10:1 CoA; longer chain CoA's were relatively poor substrates, with trans-2-hexadecenoyl CoA about 0.1 as active as 8:1 CoA. On SDS-gels, fraction IVA contained four bands, all of which were below 60,000 Mr. Proteases, such as trypsin, chymotrypsin, and subtilisin, were found to completely inactivate both enzyme fractions.

The effects of orthognathic surgery on speech production

Speech characteristics of 20 patients who underwent orthognathic surgery for correction of various skeletal defects were studied before surgical treatment and at periodic intervals postoperatively. Patients completed questionnaires that focused on their perceptions of appearance and oral function after orthognathic surgery. Approximately 60% of the patients demonstrated preoperative articulation errors. These were classified as mild because they did not interfere with the ability to be understood. Periodic testing indicated positive changes in articulation for a majority of those who had exhibited preoperative errors. None of the subjects experienced postoperative deterioration in their articulation. The subjects' perceptions of their individual operations were positive on all variables assessed.

Hepatic subcellular distribution of short-chain beta-ketoacyl coenzyme A reductase and trans-2-enoyl coenzyme A hydratase: 25- to 50-fold stimulation of microsomal activities by the peroxisome proliferator, di-(2-ethylhexyl)phthalate

The present study demonstrates unequivocally the existence of short-chain trans-2-enoyl coenzyme A (CoA) hydratase and beta-ketoacyl CoA reductase activities in the endoplasmic reticulum of rat liver. Subcellular fractionation indicated that all four fractions, namely, mitochondrial, peroxisomal, microsomal, and cytosolic contained significant hydratase activity when crotonyl CoA was employed as the substrate. In the untreated rat, based on marker enzymes and heat treatment, the hydratase activity, expressed as mumol/min/g liver, wet weight, in each fraction was: mitochondria, 684; peroxisomes, 108; microsomes, 36; and cytosol, 60. Following di-(2-ethylhexyl)phthalate (DEHP) treatment (2% (v/w) for 8 days), there was only a 20% increase in mitochondrial activity; in contrast, peroxisomal hydratase activity was stimulated 33-fold, while microsomal and cytosolic activities were enhanced 58- and 14-fold respectively. A portion of the cytosolic hydratase activity can be attributed to the component of the fatty acid synthase complex. Although more than 70% of the total hydratase activity was associated with the mitochondrial fraction in the untreated rat, DEHP treatment markedly altered this pattern; only 11% of the total hydratase activity was present in the mitochondrial fraction, while 49 and 29% resided in the peroxisomal and microsomal fractions, respectively. In addition, all four subcellular fractions contained the short-chain NADH-specific beta-ketoacyl CoA (acetoacetyl CoA) reductase activity. Again, in the untreated animal, reductase activity was predominant in the mitochondrial fraction; following DEHP treatment, there was marked stimulation in the peroxisomal, microsomal, and cytosolic fractions, while the activity in the mitochondrial fraction increased by only 39%. Hence, it can be concluded that both reductase and hydratase activities exist in the endoplasmic reticulum in addition to mitochondria, peroxisomes, and soluble cytoplasm.

Antinociceptive profiles of mu and kappa opioid agonists in a rat tooth pulp stimulation procedure

The purpose of the study was to develop a tooth pulp stimulation procedure in the awake, freely moving rat and to then quantitatively assess the analgesic effects of compounds reported to act on mu and/or kappa receptors. The mu receptor agonists produce a biphasic (primary and secondary slope) dose-response curve (DRC) whereas kappa agonist and mixed agonist/antagonist analgesics produce single-slope DRCs. The primary slopes calculated from the mu agonist biphasic DRC are steeper than the slopes calculated for the other types of opioid analgesics. The rank order of analgesic potency for the mu agonist analgesics is oxymorphone greater than morphine = methadone greater than meperidine. The rank order analgesic potency for the kappa agonist analgesics is tifluadom greater than ethylketocyclazocine greater than U50488H and for the mixed agonist/antagonist analgesics, butorphanol greater than nalbuphine greater than pentazocine. The nonsteroidal anti-inflammatory drugs, aspirin and zomepirac, are also effective analgesics in this test procedure; but the DRC slopes for these compounds are lower than all opioid analgesics tested. The opioid antagonist naloxone produces no significant changes in threshold responses. Naloxone did reverse the threshold increases produced by morphine and ethylketocyclazocine but not aspirin. This study demonstrates that the electrical stimulation of the tooth pulp in the rat can be used as an assay for evaluation of opioid and nonopioid analgesics. When minimal effective dose values of each analgesic are plotted as a function of the clinical analgesic dose a high correlation is observed.

Assay of human erythrocyte pyrimidine and deoxypyrimidine 5'-nucleotidase by isocratic reversed-phase high-performance liquid chromatography

We report a rapid and reproducible assay for activity of human erythrocyte pyrimidine 5'-nucleotidase and deoxypyrimidine 5'-nucleotidase. The nucleotides CMP, UMP, dUMP, dCMP or dTMP are individually incubated 30 min at 37 degrees C with erythrocyte hemolysate and 4 mM magnesium chloride in Tris, pH 7.5. Data are provided for standardization of the reaction with each substrate. Individual nucleoside products are assayed in less than 10 min by reversed-phase high-performance liquid chromatography at 280 nm with 0-14% methanol in 0.01 M potassium dihydrogen phosphate. This is the first report of a high-performance liquid chromatographic assay system which allows quantitation of the activity of pyrimidine 5'-nucleotidase isozymes using five individual pyrimidine and deoxypyrimidine nucleotides as the substrates.

The concomitant presence of gastroschisis and prune belly syndrome in a twin

This is a report of a case of gastroschisis and prune belly syndrome in a black male infant, the second born of dizygotic twins. This infant died of sepsis secondary to peritonitis that developed from a leaking gastrostomy site.

Coronary artery spasm after abrupt withdrawal of nitroglycerin in rabbits

The potential for abrupt withdrawal of nitroglycerin (NTG) to create coronary artery spasm was assessed in New Zealand white rabbits. In the control setting, electrocardiograms were taken from 7 anesthetized rabbits. The administration of intravenous ergonovine did not provoke ST-segment shifts or arrhythmias. Two inches of topical NTG (2%) was applied 3 times daily to a shaved area on the back of each rabbit over a 6-week period. Forty hours after abrupt withdrawal of NTG, intravenous ergonovine and indomethacin were given. Six of 7 rabbits had electrocardiographic changes: ventricular tachycardia in 2, ventricular fibrillation in 1, and significant (1 mm or more) ST-segment shifts in 5 rabbits. Three rabbits died. Sixty-four hours after NTG administration the remaining 4 rabbits were reexamined. One had baseline electrocardiographic evidence of severe myocardial ischemia. Repeat ergonovine and indomethacin testing in the others revealed ventricular tachycardia progressing to asystole in 1, premature ventricular complexes in 1, and ST-segment elevation in another. Two of the remaining 4 rabbits died. Eighty-two hours after NTG administration the remaining 2 rabbits were found dead in their cages. Nitroblue tetrazolium studies revealed extensive myocardial infarction in both animals. Additional studies were performed in 10 normal rabbits. Neither ergonovine nor indomethacin induced ST-segment shifts or arrhythmias in this control population.(ABSTRACT TRUNCATED AT 250 WORDS)

Solubilization and purification of hepatic microsomal trans-2-enoyl-CoA reductase: evidence for the existence of a second long-chain enoyl-CoA reductase

The present study describes the solubilization and purification of a NADPH-specific trans-2-enoyl-CoA reductase from rat liver microsomes. The final preparation was purified to near homogeneity and had a minimal molecular weight of 51,000 +/- 2,000, as judged by sodium dodecylsulfate (SDS)-polyacrylamide gel electrophoresis. This enzyme specifically used NADPH, as cofactor, and was chromatographically (2',5'-ADP-agarose) separated from another trans-2-enoyl-CoA reductase which utilized either NADH or NADPH as cofactor. The NADPH-specific trans-2-enoyl-CoA reductase catalyzed the reduction of trans-2-enoyl-CoAs from 4 to 16 carbon units. The Km values for crotonyl-CoA, trans-2-hexenoyl-CoA, and trans-2-hexadecenoyl-CoA were 20, 0.5, and 1.0 microM, while the Km value for NADPH was 10 microM. Although N-ethylmaleimide, heat treatment, and limited proteolysis with trypsin affected the reduction of short-chain (C4) and long-chain (C16) substrates equally, and in spite of the fact that a single protein band was observed on SDS-gels, at the present time one cannot state unequivocally that the purified preparation contained only one reductase. trans-2-Hexenoyl-CoA, for example, did not inhibit the reduction of trans-2-hexadecenoyl-CoA to palmitoyl-CoA and trans-2-decenoyl-CoA to decanoyl-CoA whereas it strongly inhibited the conversion of crotonyl-CoA to butyryl-CoA. The potential implications of this finding are discussed. Finally, the reductase preparation was shown not to contain either heme, nonheme iron, or a flavin prosthetic group.

Hepatic microsomal short-chain beta-hydroxyacyl-CoA dehydrase distinct from the fatty acid elongation component: substrate specificity of the membrane-extracted enzyme

The ability of 0.4 M KCl to extract over 80% of a short-chain beta-hydroxyacyl-CoA dehydrase from rat hepatic endoplasmic reticulum, while more than 80% of the long-chain beta-hydroxyacyl-CoA dehydrase component of the fatty acid chain elongation system remains intact, confirms the existence of more than one hepatic microsomal dehydrase. Following extraction from the microsomal membrane, the short-chain dehydrase undergoes, at least, a two-fold activation. Employing even-numbered trans-2-enoyl-CoA substrates ranging in carbon chain length from 4 to 16, the highest dehydrase specific activity of 16 mumol min-1 mg protein-1 was obtained with trans-2-hexenoyl-CoA; crotonyl-CoA was the second most active substrate, followed by 8 greater than 10 greater than 12 greater than 14 greater than 16. The specific activity of the short-chain dehydrase with trans-2-hexadecenoyl-CoA (C-16) was only 3% of that observed with the trans-2-hexenoyl-CoA. With crotonyl-CoA or beta-hydroxybutyryl-CoA as substrates, HPLC was employed to identify the products, beta-hydroxybutyryl-CoA, of the hydration reaction, or crotonyl-CoA, of the reverse dehydration reaction. It was also observed that the short-chain dehydrase catalyzed the formation of both D(-) and L(+) stereoisomers of beta-hydroxybutyryl-CoA. The equilibrium constant for the dehydrase-catalyzed reaction determined at pH 7.4 and 35 degrees C, was calculated to be 6.38 X 10(-2) M-1, while the standard free energy change was -775 cal/mol, results similar to those obtained with crystalline crotonase. Finally, based on membrane fraction marker enzymes, substrate specificity, and heat lability of the dehydrase, it was concluded that the microsomal membrane contains a short-chain beta-hydroxyacyl-CoA dehydrase which is separate from the mitochondrial crotonase.

Antinociceptive profiles of opioid peptide agonists in a rat tooth pulp stimulation procedure

The analgesic activity of the prototypic opioid peptides for the mu (D-Ala2-Me-Phen4-Gly-ol5-enkephalin [DAGO]) kappa (Dynorphin 1-13), delta (D-Ala2-D-Leu5-enkephalin [DADLE]), or epsilon (beta-endorphin) receptor was assessed in a rat tooth pulp stimulation procedure. All opioid peptides tested and the opioid alkaloid U50, 488H (kappa receptor agonist) significantly elevated response thresholds. The rank order of potency based on the Minimum Effective Dose values was beta-endorphin greater than DAGO = dynorphin A (1-13) amide greater than DADLE greater than dynorphin A (1-13) greater than U50,488H. Based on absolute magnitude, the rank order of dose response slopes was DAGO greater than U50,488H greater than dynorphin A (1-13) amide greater than beta-endorphin greater than DADLE. Dynorphin A (1-13) produced the shallowest dose response slope and the magnitude of response threshold was the lowest for all compounds tested. Finally, the general conclusion that mu agonists are effective against noxious stimuli derived from thermal, chemical, and mechanical is extended by our data to include electrical sources derived from tooth pulp stimulation; kappa agonists are effective against noxious stimuli derived from chemical, mechanical, and electrical sources (tooth pulp stimulation) and delta agonists are effective analgesics against thermal, chemical and electrical stimuli (tooth pulp stimulation).

Sigma opiates and certain antipsychotic drugs mutually inhibit (+)-[3H] SKF 10,047 and [3H]haloperidol binding in guinea pig brain membranes

The relationship between binding of antipsychotic drugs and sigma psychotomimetic opiates to binding sites for the sigma agonist (+)-[3H]SKF 10,047 (N-allylnormetazocine) and to dopamine D2 sites was investigated. In guinea pig brain membranes, (+)-[3H]SKF 10,047 bound to a single class of sites with a Kd of 4 X 10(-8) M and a Bmax of 333 fmol/mg of protein. This binding was different from mu, kappa, or delta opiate receptor binding. It was inhibited by opiates that produce psychotomimetic activities but not by opiates that lack such activities. Some antipsychotic drugs inhibited (+)-[3H]SKF 10,047 binding with high to moderate affinities in the following order of potency: haloperidol greater than perphenazine greater than fluphenazine greater than acetophenazine greater than trifluoperazine greater than molindone greater than or equal to pimozide greater than or equal to thioridazine greater than or equal to chlorpromazine greater than or equal to triflupromazine. However, there were other antipsychotic drugs such as spiperone and clozapine that showed low affinity for the (+)-[3H]SKF 10,047 binding sites. Affinities of antipsychotic drugs for (+)-[3H]SKF 10,047 binding sites did not correlate with those for [3H]spiperone (dopamine D2) sites. [3H]-Haloperidol binding in whole brain membranes was also inhibited by the sigma opiates pentazocine, cyclazocine, and (+)-SKF 10,047. In the striatum, about half of the saturable [3H]haloperidol binding was to [3H]spiperone (D2) sites and the other half was to sites similar to (+)-[3H]SKF 10,047 binding sites.