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L Cook

Publications and source records attributed to L Cook.

At least 55 records · Page 3Linked to original sources
PubMed1992

Novel piperidine sigma receptor ligands as potential antipsychotic drugs.

sigma receptor ligands represent a new class of potential antipsychotic drugs. This paper presents the structure-activity relationships leading to novel disubstituted piperidine sigma ligands, which have little or no affinity for dopamine D2 receptors. Selectivity for sigma sites over dopamine D2 or serotonin 5-HT2 receptors appears to be governed by the chemical nature of the piperidine nitrogen substituent, its distance from the basic nitrogen, and its orientation relative to the other piperidine substituent. Several of these compounds have good oral potency in some animal models used to evaluate potential antipsychotic drugs. The N-cyclopropylmethyl ketones and ethers (e.g. 6i (DuP 734), 6q, 18a, and 18n) have the best in vivo potency. Compounds 6i (DuP 734) and 6q did not cause catalepsy in the rat, even at very high doses. On the basis of the pharmacology profiles of these sigma ligands, we propose these compounds may be effective antipsychotic drugs, which do not induce extrapyramidal side effects or tardive dyskinesia.

Animals↗
PubMed1992

Evidence that beta-hydroxyacyl-CoA dehydrase purified from rat liver microsomes is of peroxisomal origin.

The present study provides strong evidence that the previously isolated hepatic microsomal beta-hydroxyacyl-CoA dehydrase (EC 4.2.1.17), believed to be a component of the fatty acid chain-elongation system, is derived, not from the endoplasmic reticulum, but rather from the peroxisomes. The isolated dehydrase was purified over 3000-fold and showed optimal enzymic activity toward beta-hydroxyacyl-CoAs or trans-2-enoyl-CoAs with carbon chain lengths of 8-10. The purified preparation (VDH) displayed a pH optimum at 7.5 with beta-hydroxydecanoyl-CoA, and at 6.0 with beta-hydroxystearoyl-CoA. Competitive-inhibition studies suggested that VDH contained dehydrase isoforms, and SDS/PAGE showed three major bands at 47, 71 and 78 kDa, all of which reacted to antibody raised to the purified preparation. Immunocytochemical studies with anti-rabbit IgG to VDH unequivocally demonstrated gold particles randomly distributed throughout the peroxisomal matrix of liver sections from both untreated and di-(2-ethylhexyl) phthalate-treated rats. No labelling was associated with endoplasmic reticulum or with the microsomal fraction. Substrate-specificity studies and the use of antibodies to VDH and to the peroxisomal trifunctional protein indicated that VDH and the latter are separate enzymes. On the other hand, the VDH possesses biochemical characteristics similar to those of the D-beta-hydroxyacyl-CoA dehydrase recently isolated from rat liver peroxisomes [Li, Smeland & Schulz (1990) J. Biol. Chem. 265, 13629-13634; Hiltunen, Palosaari & Kunau (1989) J. Biol. Chem. 264, 13536-13540]. Neither enzyme utilizes crotonoyl-CoA or cis-2-enoyl-CoA as substrates, but both enzymes convert trans-2-enoyl substrates into the D-isomer only. In addition, the VDH also contained beta-oxoacyl-CoA reductase (beta-hydroxyacyl-CoA dehydrogenase) activity, which co-purified with the dehydrase.

Animals↗
PubMed1992

Depletion of rat hepatic glutathione and inhibition of microsomal trans-2-enoyl-CoA reductase activity following administration of a dec-2-ynol and dec-2-ynoic acid.

The effects of administration of dec-2-ynol and dec-2-ynoic acid on the hepatic glutathione (GSH) content and hepatic microsomal trans-2-enoyl-CoA reductase activity were examined in rat. Both compounds, when administered ip, caused a marked depletion of GSH levels and a corresponding inactivation of trans-2-enoyl-CoA reductase activity in both a time- and dose-dependent manner. The dec-2-ynoic acid caused greater hepatotoxicity than dec-2-ynol based on serum alanine transaminase activity. Based on the observations that (a) the alcohol did not interact with GSH in the presence or absence of cytosol, (b) the spectral manifestation of the interaction between GSH and the alcohol occurred only when NAD+ was added to the reaction mixture containing the cytosol and reactants, and (c) a similar absorbance spectrum was obtained following the interaction between aldehyde and GSH, it was concluded that dec-2-ynol is converted to an electrophile, dec-2-ynal, which causes depletion of GSH. The decrease in GSH content following administration of the acid appears to be due to activation of the acid to the electrophile, dec-2-ynoyl CoA, which then interacts with GSH, resulting in its depletion, based on the in vitro observations that (a) the acid did not interact with GSH in the presence or absence of cytosol, and (b) the spectral manifestation of interaction between GSH and dec-2-ynoyl CoA occurred both nonenzymatically and enzymatically in the presence of rat liver glutathione S-transferase (Sigma). Bovine serum albumin stimulated the enzymatic reaction. Comparable to the effects on GSH were the effects of dec-2-ynol, dec-2-ynal, dec-2-ynoic acid, and dec-2-ynoyl CoA on the microsomal trans-2-enoyl-CoA reductase activity in vitro. While the alcohol had no effect on the enzyme activity, its electrophilic product, the aldehyde, was a potent inhibitor. Similarly, the acid did not inhibit the enzyme activity unless the acid was present at high concentration; however, its electrophilic product, the CoA thioester, was a very potent inhibitor at very low concentration.

Acyl Coenzyme A↗
PubMed1992

Effect of one-legged exercise on the strength, power and endurance of the contralateral leg. A randomized, controlled study using isometric and concentric isokinetic training.

The purpose of this investigation was to study the effect of one-legged exercise on the strength, power and endurance of the contralateral leg. The performance of the knee extensor and flexor muscle of 20 healthy young adults (10 men and 10 women) was first tested by Cybex II+ and 340 dynamometers. Then 10 subjects were chosen at random to train using one leg three times a week for 7 weeks whilst the other 10 served as controls. During the 8th week, the tests were repeated. Both quadriceps and hamstring muscles of the trained subjects showed a cross-transfer effect from the trained limb to the untrained side. This concerned the strength and power, as well as endurance characteristics of these muscles. The average change in peak torque of the quadriceps muscle was +19% (P less than 0.001) in the trained limb, +11% (P less than 0.01) in the untrained limb and 0% in the control limbs. In hamstring muscles the changes were +14% (P less than 0.01), +5% and -1%, respectively. Concerning muscle endurance (work performed during the last 5 contractions in the 25-repetition test) the corresponding changes were +15% (P less than 0.01), +7% (P less than 0.01), and -1% in quadriceps muscle, and +17% (P less than 0.05), +7%, and -3% in hamstring muscles. The average strength benefit in the untrained limb was +36% (hamstring muscles) and +58% (quadriceps muscle) of that achieved in the trained limb. Untrained hamstring muscle showed better benefits in the endurance parameters than in strength or power parameters, while in the quadriceps muscle this effect was reversed. A positive relationship was observed between the changes (greater improvement in the trained limb resulted in greater improvement in the untrained limb) (hamstring muscles: r = 0.83, P less than 0.001, quadriceps muscle: r = 0.53, P less than 0.001). In endurance parameters, this relationship was almost linear while in the strength and power parameters the results were more in favour of a curvilinear relationship with limited benefit.

Adult↗
PubMed1992

The fatty acid chain elongation system of mammalian endoplasmic reticulum.

Much has been learned about FACES of the endoplasmic reticulum since its discovery in the early 1960s. FACES consists of four component reactions, requires the fatty acid to be activated in the form of a CoA derivative, utilizes reducing equivalents in the form of NADH or NADPH, is induced by a fat-free diet, resides on the cytoplasmic surface of the endoplasmic reticulum, appears to function in concert with the desaturase system and appears to exist in multiple forms (either multiple condensing enzymes connected to a single pathway or multiple pathways). FACES has been found in all tissues investigated, namely, liver, brain, kidney, lung, adrenals, retina, testis, small intestine, blood cells (lymphocytes and neutrophils) and fibroblasts, with one exception--the heart has no measurable activity. Yet, much more needs to be learned. The critical, inducible and rate-limiting condensing enzyme has resisted solubilization and purification; the purification of the other components has met with limited success. We know nothing about the site of synthesis of each component of FACES. How is each component enzyme integrated into the endoplasmic reticulum membrane? Is there a single mRNA directing synthesis of all four components or are there four separate mRNAs? How are elongation and desaturation coordinated? What is (are) the physiological regulator(s) of FACES--ADP, AMP, IP3, G-proteins, phosphorylation, CoA, Ca2+, cAMP, none of these? The molecular biology of FACES is only in the fetal stage of development. We are only scratching the surface--it is an undiscovered country.

Animals↗
PubMed1992

Sex and dietary fat modulate hepatic prostaglandin F2 alpha in F344/N rats.

The study was designed to determine whether sex and fat calories altered hepatic prostaglandin (PG) F2 alpha status; a factor which may reflect susceptibility to cancer development. For 4 weeks, groups of 8 male and 8 female F344/N rats were fed diets with 9% of energy (en%) from linoleate and 15.5, 20, 30 or 40 en% fat. Females had greater hepatic stearate, arachidonate and PGF2 alpha whereas males had greater hepatic myristate, palmitate and oleate. Females also had greater plasma stearate levels. Greater hepatic arachidonate may have stimulated PG production in females. Hepatic oleate increased and hepatic palmitate decreased with increasing en% fat (p < 0.05). Hepatic stearate was greater and hepatic linoleate less when 40 en% fat was fed compared with other levels of dietary fat (p < 0.05). Plasma oleate was greater at 30 or 40 en% fat than at lower levels of fat, whereas plasma linoleate was less at 40 en% than at 15.5% en% fat. The ability of a 30 en% fat diet, containing equal proportions of linoleate and oleate, to suppress hepatic PG production may be related to the effects of dietary fat content and composition on plasma fatty acid profiles. Because suppressed PG production has been linked with suppression of cancer development, dietary recommendations to consume 30 en% fat with a P:M ratio of 1:1 may be cancer-protective.

Animals↗
PubMed1992

Quantitative DNA analysis and proliferation in breast carcinomas. A comparison between image analysis and flow cytometry.

The DNA content and proliferation in 100 invasive breast carcinomas were evaluated by computerized image analysis (IA) and flow cytometry (FCM). For DNA content, image analysis of Feulgen-stained slides of fresh tumor imprints were compared with flow cytometry of propidium iodide-stained disaggregated fresh tumor tissue. The DNA indices obtained by the two methods showed close correlation by linear regression analysis (r = 0.89, p less than .001). There were 44 (44%) diploid and 56 (56%) aneuploid tumors. There was agreement between the two methods in detection of aneuploidy in 81% of tumors. Image analysis required smaller tissue samples, permitted direct visualization and selection of tumor cells, and was more sensitive in detecting tetraploid and highly aneuploid cell populations. In contrast, flow cytometry histograms provided better resolution, and were more effective in detecting multiploid tumors and near-diploid aneuploid tumors. Aneuploidy was significantly related to various adverse prognostic parameters, namely, negative estrogen receptor, high mitotic rate, high histologic and nuclear grades. Proliferation was evaluated by measuring the FCM S phase fraction (SPF), and by image analysis quantitation of immunohistochemical staining using Ki-67 monoclonal antibody. SPF and Ki-67 count showed modest correlation (r = 0.42). Both SPF and Ki-67 count were significantly related to the mitotic rate, histologic and nuclear grades. Our results indicate that the two methods provide comparable results, but offer individual advantages and are complementary techniques in analyzing DNA ploidy and proliferation in breast carcinomas.

Adenocarcinoma, Mucinous↗
PubMed1992

DNA ploidy, proliferation, and neu-oncogene protein overexpression in breast carcinoma.

DNA content, proliferative activity (Ki-67 immuno-staining and S-phase fraction by flow cytometry), and neu-oncogene overexpression were studied in 135 patients with invasive breast carcinoma. Image analysis and flow cytometry of fresh tumors showed good correlation between the two methods and yielded 39% diploid tumors and 61% aneuploid tumors. Aneuploidy, including tetraploidy, was significantly related to the loss of estrogen (p = 0.0002) and progesterone (p = 0.03) receptors, high histologic (p = 0.014) and nuclear (p less than 0.0001) grades, and mitotic rate (p = 0.0001). Immunohistochemical evaluation of proliferation by staining with Ki-67 monoclonal antibody and of neu-oncogene protein overexpression was performed in fresh frozen tissue from 83 tumors. The Ki-67 score, quantitated by the CAS-200 image analyzer, correlated only moderately with S-phase fraction obtained by flow cytometry by linear regression analysis (r = 0.39, p less than 0.001). However, both of these proliferation markers correlated strongly with the mitotic rate (p less than 0.0001). Aneuploid and tetraploid tumors demonstrated higher Ki-67 scores and S-phase fractions than diploid tumors. Neu-oncogene protein overexpression was seen in 24 tumors (29%) overall and was much higher in aneuploid tumors (38%) and tetraploid tumors (50%) than in diploid tumors (7%). However, the concentration of neu-oncogene protein positive tumors in the tetraploid region reported by others was not observed. Neu-oncogene protein overexpression was also associated with higher Ki-67 scores (p = 0.016) and S-phase fractions (p = 0.037).(ABSTRACT TRUNCATED AT 250 WORDS)

Antibodies, Monoclonal↗
PubMed1992

DuP 734 [1-(cyclopropylmethyl)-4-(2'(4''-fluorophenyl)-2'- oxoethyl)piperidine HBr], a potential antipsychotic agent: preclinical behavioral effects.

It has been suggested that sigma receptors may be involved in the etiology of psychosis and that 5-hydroxytryptamine2 (5-HT2) antagonists may have utility in treating the negative symptoms of psychosis as well as reducing the side effects associated with the typical antipsychotic haloperidol. We have evaluated the potential antipsychotic effects of 1-(cyclopropylmethyl)-4-(2'(4''-fluorophenyl)-2'-oxoethyl)piper i din e HBr (DuP 734), a selective and potent sigma and 5-HT2 receptor ligand with weak affinity for D2 receptors, in behavioral animal models that are not necessarily dependent on dopamine antagonism. DuP 734 potently blocked mescaline-induced scratching (ED50 = 0.35 mg/kg, p.o.) and aggressive activity (ED50 = 1.9 mg/kg, p.o.) and was relatively much weaker as an apomorphine antagonist (ED50 = 12 mg/kg, p.o.). This was in contrast to the typical antipsychotic agents such as haloperidol and chlorpromazine, which were very potent in all three tests. In rats, DuP 734 did not antagonize avoidance behavior or induce catalepsy, and, therefore, differed from the potent dopamine receptor antagonist antipsychotics. It did, however, reduce lever response rates in a random interval 60-sec food reward schedule of reinforcement (ED50 = 6.0 mg/kg, p.o.) in rats. The results suggest that DuP 734 may have antipsychotic activity without the liability of motor side effects typical of neuroleptics. Although DuP 734 itself did not antagonize avoidance activity, it significantly enhanced the potency of haloperidol in blocking avoidance behavior by 3-fold (by shifting the ED50 from 0.94 to 0.36 mg/kg, p.o.), whereas the ED50 of haloperidol for blockade of escape behavior and induction of catalepsy was not affected.(ABSTRACT TRUNCATED AT 250 WORDS)

Aggression↗
PubMed1992

DuP 734 [1-(cyclopropylmethyl)-4-(2'(4''-fluorophenyl)-2'-oxoethyl)- piperidine HBr], a sigma and 5-hydroxytryptamine2 receptor antagonist: receptor-binding, electrophysiological and neuropharmacological profiles.

It has been suggested that sigma receptor antagonists may be useful as antipsychotic drugs and that 5-hydroxytryptamine (5-HT2) receptor antagonists produce improvements of the negative symptoms of schizophrenia. [1-(Cyclopropylmethyl)-4-(2'-(4''-fluorophenyl)-2'- oxoethyl)-piperidine HBr] (DuP 734) is a novel compound with high affinity for the sigma (Ki = 10 nM) and 5-HT2 (Ki = 15 nM) receptors, but low affinity for dopamine receptors (Ki > 1000 nM) as well as 33 other receptors, ion channels and second messenger systems in vitro. DuP 734 did not inhibit the synaptosomal uptake of dopamine, 5-HT or norepinephrine. Oral administration of DuP 734 potently blocked 5-hydroxy-L-trytophan (5-HTP)-induced head twitch in the rat (ED50 = 6.5 mumol/kg), indicating 5-HT2 antagonist activity. Extracellular single-unit recording studies demonstrated that DuP 734 antagonized the effect of the selective sigma ligand (+)-3-(3-hydroxyphenyl-N-(1-propyl) piperidine [(+)-3-PPP] on dopamine neuronal activity in the substantia nigra of the rat with an ED90 of 3.6 mumol/kg i.v. The sigma receptor agonists (+)-SKF 10,047 and phencyclidine both elicited rotational behavior in rats with unilateral lesion of the substantia nigra. The rotational behavior induced by either (+)-SKF 10,047 or phencyclidine was dose-dependently antagonized by DuP 734 with oral ED50 of 8.7 and 19.6 mumol/kg, respectively. The 5-HT2 receptor antagonist ICI 169,369, even at high doses (up to 33 mumol/kg, s.c.), did not antagonize the rotational behavior induced by (+)-SKF 10,047.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗