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Interactions in the Thallium(I) Heptanoate and Heptanoic Acid System: Association, Aggregation, and Phase Behavior

The phase, association, and aggregation behavior of the binary system [TlO2C(CH2)5CH3 + HO2C(CH2)5CH3] have been investigated through temperature and enthalpy vs composition diagrams by determination of the thermal behavior of the pure components and 30 mixtures over an interval of nearly 300 K, and by differential scanning calorimetry and polarized microscopy. Total miscibility was observed in liquid and liquid crystalline phases but essentially total immiscibility among crystalline phases. The phase behavior exhibits: (1) Formation of two intermediate compounds which dissociate in the solid state at low temperature; (2) A eutectic reaction at salt molar fraction x = 0.08 about 3 K below the acid melting point; (3) Unimolecular salt:acid association by very strong hydrogen bonding, which undergoes a crystal/crystal transition prior to incongruent melting at 295.5 K, occurring by a highly energetic peritectic reaction in which the compound evolves more than the sum of the total transition enthalpies of both components; (4) Lyotropic mesophase formation at 390.0 K over the x >/= 0.66 composition range by aggregation of a solid and a liquid phase to yield, on heating, a continuous series of liquid crystalline solutions with mixed-lamellar structure and interlamellar spacings around 20 A as determined by powder X-ray diffractometry, their texture being focal conic, consistent with the neat thermotropic mesophase of the pure salt. A tridimensional phase diagram is presented. All these main reactions have been fully characterized by their nature, stoichiometry, and relevant thermodynamic data.

Journal Article↗

Effects of adding valerate, caproate, and heptanoate to ruminal buffers on splanchnic metabolism in steers under washed-rumen conditions.

Four steers fitted with a ruminal cannula and chronic indwelling catheters in the mesenteric artery, mesenteric vein, hepatic portal vein, hepatic vein, and the right ruminal vein were used to study VFA absorption from bicarbonate buffers incubated in the washed reticulorumen, and metabolism by splanchnic tissues. Portal and hepatic vein blood flows were determined by infusion of p-aminohippurate into the mesenteric vein. The steers were subjected to four experimental treatments in a Latin square design. The treatments were Control (ruminal bicarbonate buffer with [mmol/kg]: acetate = 72; propionate = 30; isobutyrate = 2.1; butyrate = 12; valerate = 1.2; caproate = 0; and heptanoate = 0); Val (same as control except for valerate = 8 mmol/kg); Cap (same as control except for caproate = 3.5 mmol/kg); and Hep (same as control except for heptanoate = 3 mmol/kg). All buffers were incubated for 90 min in the rumen, and ruminal VFA absorption rates were maintained by continuous intraruminal infusion of VFA. The arterial concentrations of valerate and heptanoate showed a small increase (< or = 1 micromol/L; P < 0.05) with inclusion of the respective acid in the ruminal buffer, but no change (P = 0.57) in arterial concentration of caproate was detected. Valerate increased (P < 0.05) the net portal flux of butyrate and valerate, as well as the net splanchnic flux of propionate, butyrate, and valerate. With Cap and Hep, the net portal flux of caproate and heptanoate accounted for 54 and 45% of ruminal disappearance rates, respectively, indicating that these acids were extensively metabolized by the ruminal epithelium. Caproate was ketogenic both in the ruminal epithelium and in the liver, and Cap increased (P < 0.05) the arterial concentration, ruminal vein minus arterial concentration difference, net hepatic flux, and net splanchnic flux of 3-hydroxybutyrate. The net hepatic flux of glucose decreased (P = 0.02) with Cap and Hep compared with Control and Val; however, no effect (P = 0.14) on the net splanchnic flux of glucose could be detected. We conclude that the strong biological activity of valerate, caproate, and heptanoate warrant increased emphasis on monitoring their ruminal presence and their potential systemic effects on ruminant metabolism.

Absorption↗

Differential effects of heptanoate and hexanoate on myocardial citric acid cycle intermediates following ischemia-reperfusion.

In the normal heart, there is loss of citric acid cycle (CAC) intermediates that is matched by the entry of intermediates from outside the cycle, a process termed anaplerosis. Previous in vitro studies suggest that supplementation with anaplerotic substrates improves cardiac function during myocardial ischemia and/or reperfusion. The present investigation assessed whether treatment with the anaplerotic medium-chain fatty acid heptanoate improves contractile function during ischemia and reperfusion. The left anterior descending coronary artery of anesthetized pigs was subjected to 60 min of 60% flow reduction and 30 min of reperfusion. Three treatment groups were studied: saline control, heptanoate (0.4 mM), or hexanoate as a negative control (0.4 mM). Treatment was initiated after 30 min of ischemia and continued through reperfusion. Myocardial CAC intermediate content was not affected by ischemia-reperfusion; however, treatment with heptanoate resulted in a more than twofold increase in fumarate and malate, with no change in citrate and succinate, while treatment with hexanoate did not increase fumarate or malate but increased succinate by 1.8-fold. There were no differences among groups in lactate exchange, glucose oxidation, oxygen consumption, and contractile power. In conclusion, despite a significant increase in the content of carbon-4 CAC intermediates, treatment with heptanoate did not result in improved mechanical function of the heart in this model of reversible ischemia-reperfusion. This suggests that reduced anaplerosis and CAC dysfunction do not play a major role in contractile and metabolic derangements observed with a 60% decrease in coronary flow followed by reperfusion.

Animals↗

Inhibitors of cholesterol biosynthesis. 1. 3,5-Dihydroxy-7-(N-imidazolyl)-6-heptenoates and -heptanoates, a novel series of HMG-CoA reductase inhibitors.

3,5-Dihydroxy-7-(N-imidazolyl)heptanoates 4 and the corresponding heptenoates 5 were synthesized as novel classes of potent HMG-CoA reductase (HMGR) inhibitors in which members of the latter series possess enzyme inhibitory activity greater than that of lovastatin 1 and pravastatin 2. Structure-activity studies show that the 7-(N-imidazolyl)heptenoates 5 are more active than the corresponding heptanoates 4. For both imidazolyl series, the 4-fluorophenyl group is preferred at C-5, and a broad range of aryl substituents which promote widely different lipophilicities is tolerated at C-4. While the CF3 group is preferred at C-2 in the heptanoate series, the 2-(1-methylethyl) substituent is optimal in the heptenoate series. The 2-(1-methylethyl) and 5-(4-fluorophenyl) groups can be interchanged in the latter series as exemplified by 5ab. Enzyme inhibitory activity resides principally in the 3R,5S series. These potent HMGR inhibitory activities by members of the heptenoate series translated well into whole cell activities in HepG2 cells. X-ray crystallographic studies on the active enantiomer 28 reveal noncoplanarity of the heptenoate C-C double bond with the imidazole ring; this finding provides an explanation for the high acid stability of the heptenoate series.

Animals↗

Volatile ketone formation in bacteria: release of 3-oxopentanoate by soil pseudomonads during growth on heptanoate.

During enrichments to search for soil bacteria that form the volatile ketones, acetone and butanone, we isolated pure cultures of Pseudomonas aureofaciens, P. fluorescens, and P. putida that excrete the beta-keto-acid, 3-oxopentanoate (3-OPA), when grown on heptanoic acid as carbon source. Analysis of 3-OPA used enzymatic decarboxylation by acetoacetate decarboxylase to yield butanone, which was detected by headspace gas chromatography. The formation of 3-OPA was strongly dependent on heptanoic acid concentration, the level of oxygen, and the state of growth, and was not seen with even-chain or other odd-chain fatty acids. Uptake of 3-OPA during stationary phase of growth is probably related to polyhydroxyalkanoate (PHA) formation in these isolates. A model for formation and release of 3-OPA is proposed.

Acetone↗

QSAR study of HMGR inhibitors: 7-(heteroaryl)-3,5-dihydroxy-6-heptenoic (-heptanoic) acids.

The 3-hydroxy-3-methylglutaryl-coenzyme A reductase (HMGR) inhibitory activity of pyridine- and pyrimidine-substituted 3,5-dihydroxyhept-6(E)-enoic acids and 7-(1H-pyrrol-3-yl)-substituted-3,5-dihydroxyhept-6(E)-enoic (-heptanoic) acids was quantitatively analysed using hydrophobicity, molar refractivity, electronic and Verloop's steric parameters. The results obtained were comparable to the earlier findings of 7-(aryl/biphenyl)-3,5-dihydroxy-6-heptenoic (-heptanoic) acids. The R'4-substituent of the aryl substituent of heteroaryl moiety was found to influence the inhibitory activity through its steric and electronic properties, and the equations confirm that substituents with minimum steric bulk, positive polar and negative resonance constants lead to better inhibitory activity. The changes in the heteroaryl moiety of the inhibitors did not correlate with the activity. Probably, the heteroaryl moiety of the inhibitors may be serving as a skeletal framework to hold the surrounding hydrophobic substituents.

Animals↗

Uptake of a novel anticonvulsant compound, 2-amino-7-phosphono-[4,5-3H]heptanoic acid, into mouse brain.

The time course of radioactivity in plasma, liver and brain is described following the intraperitoneal injection of 2-amino-7-phosphono-[4,5-3H]heptanoic acid in mice. Using high performance liquid chromatography of dansylated extracts of mouse brain the radioactivity attributable to 2-amino-7-phosphono-[4,5-3H]heptanoic acid has been determined at 0.25-180 min after injection. The time course, with a peak concentration at 30 min, declining markedly between 90 and 180 min, corresponds to the anticonvulsant action.

2-Amino-5-phosphonovalerate↗

Production of 4-methylumbelliferyl heptanoate hydrolase by Escherichia coli exposed to seawater.

The production of an enzyme, 4-methylumbelliferyl heptanoate hydrolase, in Escherichia coli exposed to enriched and nonenriched seawater was studied. In all media, except for seawater with no or very small amounts of organic material and seawater enriched with peptone, 4-methylumbelliferyl heptanoate hydrolase activity increased by 2 to 3 orders of magnitude within 2 days. Increased enzyme activity was assumed to be related to cells not undergoing lysis but adapting to conditions of nutrient limitation.

Colony Count, Microbial↗

Studies on the inhibitory effects of zinc heptanoate on microorganisms.

Inhibitory effect of zinc heptanoate was observed on different cultures of bacteria and fungi. Growth of all the bacteria was inhibited by the compound. Greatest inhibition was seen in the case of Staphylococcus albus, Streptococcus pyogenes, Shigella dysenteriae, Shigella sonnei, Shigella flexneri, Salmonella typhi, S. paratyphi A, S. paratyphi B, Vibrio cholerae, Corynebacterium diphtheriae, and E. coli whereas least inhibition was found in the case of Staphylococcus aureus. In triethanolamine: water (1:1) solution minimum inhibitory concentration (MIC) was least for Klebsiella pneumoniae (800 p.p.m.) while in the case of Staph. aureus and Bacillus subtilis it was 200 p.p.m. Among yeasts and fungi greatest inhibition was found with Trichophyton schoenleini, T. rubrum, T. gourvili, Microsporum adouini, M. vanbreuseghemi and least in the case of Candida albicans. In triethanolamine: water (1:1) solution the MIC for T. schoenleini and T. gourvili and T. violaceum was as low as 900 p.p.m. whereas in the case of Aspergillus oryzae it was highest--3500 p.p.m. The effect of the compound on glucose consumption of Aspergillus niger and Bacillus subtilis was also seen.

Bacteria↗

Tianeptine, a new tricyclic antidepressant metabolized by beta-oxidation of its heptanoic side chain, inhibits the mitochondrial oxidation of medium and short chain fatty acids in mice.

Tianeptine is a new tricyclic antidepressant which is metabolized mainly by beta-oxidation of its heptanoic side chain. We determined the effects of tianeptine on the mitochondrial oxidation of natural fatty acids in mice. In vitro, tianeptine (0.5 mM) inhibited by only 32% the formation of beta-oxidation products from [1-14C]palmitic acid by hepatic mitochondria, but inhibited by 71% that from [1-14C]octanoic acid and by 51% that from [1-14C]butyric acid. The activity of the tricarboxylic acid cycle, assessed as the in vitro formation of [14C]CO2 from [1-14C]acetylcoenzyme A was decreased by 51% in the presence of tianeptine (0.5 mM). The inhibition of both beta-oxidation and the tricarboxylic acid cycle appeared reversible in mitochondria from mice exposed to tianeptine in vivo but incubated in vitro without tianeptine. In vivo, administration of tianeptine (0.0625 mmol/kg i.p.), decreased by 53 and 58%, respectively, the formation of [14C]CO2 from [1-14C]octanoic acid and [1-14C]butyric acid, but did not significantly decrease that from [1-14C]palmitic acid. After administration of high doses of tianeptine, however, formation of [14C]CO2 from [1-14C]palmitic acid became inhibited as well, transiently after 0.25 mmol/kg and durably (greater than 24 hr) after 0.75 mmol/kg i.p. Hepatic triglycerides were increased 24 hr after administration of 0.75 mmol/kg i.p. of tianeptine, but not after 0.25 mmol/kg i.p. Microvesicular steatosis of the liver was observed in some mice after 0.75 mmol/kg i.p., but not after 0.5 mmol/kg i.p. We conclude that tianeptine inhibits the oxidation of medium- and short-chain fatty acids in mice. Microvesicular steatosis, however, requires very large doses in mice (0.75 mmol/kg i.p., i.e. 600-times the oral dose in humans), and is therefore unlikely to occur in humans.

Animals↗

Synthesis and biological activity of new HMG-CoA reductase inhibitors. 1. Lactones of pyridine- and pyrimidine-substituted 3,5-dihydroxy-6-heptenoic (-heptanoic) acids.

Lactones of pyridine- and pyrimidine-substituted 3,5-dihydroxy-6-heptenoic (-heptanoic) acids 2-4 have been synthesized. Extensive exploration of structure-activity relationships led to several compounds exceeding the inhibitory activity of mevinolin (1b) on HMG-CoA reductase, both in vitro and in vivo. First clinical trials with 2i (HR 780) are in preparation.

Acetates↗

The effects of subunit composition on the inhibition of nicotinic receptors by the amphipathic blocker 2,2,6,6-tetramethylpiperidin-4-yl heptanoate.

The therapeutic targeting of nicotinic receptors in the brain will benefit from the identification of drugs that may be selective for their ability to activate or inhibit a limited range of nicotine acetylcholine receptor subtypes. In the present study, we describe the effects of 2,2,6,6-tetramethylpiperidin-4-yl heptanoate (TMPH), a novel compound that is a potent inhibitor of neuronal nicotinic receptors. Evaluation of nicotinic acetylcholine receptor (nAChR) subunits expressed in Xenopus laevis oocytes indicated that TMPH can produce a potent and long-lasting inhibition of neuronal nAChR formed by the pairwise combination of the most abundant neuronal alpha (i.e., alpha3 and alpha4) and beta subunits (beta2 and beta4), with relatively little effect, because of rapid reversibility of inhibition, on muscle-type (alpha1beta1gammadelta) or alpha7 receptors. However, the inhibition of neuronal beta subunit-containing receptors was also decreased if any of the nonessential subunits alpha5, alpha6, or beta3 were coexpressed. This decrease in inhibition is shown to be associated with a single amino acid present in the second transmembrane domain of these subunits. Our data indicate great potential utility for TMPH to help relate the diverse central nervous system effects to specific nAChR subtypes.

Amino Acid Sequence↗

On the interaction of 2-amino-7-phosphono-heptanoic acid and quinolinic acid in mice.

It is shown that (a) peripheral injections of quinolinic acid cause neuronal excitation with a latency much less than that of convulsions due to quinolinic acid and (b) peripherally injected 2-amino-7-phosphono-heptanoic acid (2APH) does antagonise neuronal excitation due to quinolinic acid applied locally by microiontophoresis. It is concluded that the previously reported failure of 2APH to prevent quinolinic acid seizures is a reflection of different modes of action of quinolinic acid in causing neuronal excitation and convulsions, and does not contradict the suggestion that quinolinic acid acts at N-methyl-D-aspartate (NMDA) receptors in the brain.

2-Amino-5-phosphonovalerate↗

The high pressure neurological syndrome in genetically epilepsy prone rats: protective effect of 2-amino-7-phosphono heptanoate.

Genetically epilepsy prone rats (GEPR) are hypersensitive to various epileptogenic treatments and undergo characteristic generalized seizures when exposed to potent acoustic stimulation. We have studied the sensitivity of GEPR to high atmospheric pressure. Threshold pressures for behavioral symptoms of the high pressure neurological syndrome (HPNS) were recorded in normal Sprague-Dawley (SD) and GEPR (which originate from the SD strain) of both sexes. The threshold pressure (TP) for tremor and for convulsion was significantly lower in GEPR than in SD rats. The protective action of the NMDA receptor antagonist D-2-amino-7-phosphono-heptanoate (D-APH) was tested on both strains of rats. D-APH, 90 mg/kg ip was more protective against tremor in SD than in GEPR. Female GEPR were not protected against tremor. Protection against clonic seizures was similar in both sexes of GEPR and female SD rats while SD males were not significantly protected. None of the animals treated with D-APH developed the tonic phase of seizures. Blockade of the NMDA receptor with D-APH brought the threshold for convulsions in GEPR to a similar pressure to that obtained in SD vehicle-injected controls. This findings suggests the involvement of the excitatory amino acid system in the hypersensitivity of GEPR to high atmospheric pressure.

2-Amino-5-phosphonovalerate↗

Specific binding of [3H]+/- 2-amino-7-phosphono heptanoic acid to rat brain membranes in vitro.

The specific binding of [3H]+/- 2-amino-7-phosphono heptanoic acid (3H-APH), a potent N-methyl-D-aspartate (NMDA) antagonist, to extensively washed, previously frozen crude mitochondrial fractions of rat brain is described. Binding was optimal at physiological pH and temperature and, in Triscitrate buffer, attained equilibrium within 60 minutes. Scatchard analysis of the equilibrium data for forebrain revealed a single, non-interacting population of binding sites (BMapp = 15 picomoles/mg protein; KDapp = 3.6 uM; Hill coefficient = 0.92, r = 0.99; N = 5). Specific binding of the ligand was readily reversible by unlabeled APH and was absent in peripheral tissues including heart, lung, kidney, liver, spleen and striate muscle and in heat treated brain sonicates. An 8-fold variation in the amount of ligand bound to brain membranes prepared from different regions was observed with binding being greatest in the hippocampal formation and least in the midbrain. Kainic acid, NMDA and aspartic acid exhibited negligible affinity for the [3H]-APH site; in contrast, quisqualic acid, ibotenic acid, glutamatic acid, homocysteic acid and 2-amino-4-phosphono butyric acid were moderately potent displacers. The results indicate that [3H]-APH labels a quisqualate preferring site in vitro. Unlike the receptor labeled by [3H]-glutamate however, [3H]-APH binding was attenuated in the presence of chloride ions suggesting that this ligand may label a subpopulation of excitatory amino acid receptors.

2-Amino-5-phosphonovalerate↗