Identification and characterization of hepatic carboxylesterases hydrolyzing hydrocortisone esters.

The present study has provided evidence for the existence of three distinct carboxylesterases involved in the hydrolysis of steroid esters, where two enzymes are possibly responsible for the metabolism of hydrocortisone hemisuccinate (HCHS) at pH 5.5 and 8.0, and a third enzyme for the metabolism of hydrocortisone acetate (HCAC) at pH 8.0, in isolated rat liver microsomes. The activity of all three enzymes in rat liver was induced significantly by the administration of phenobarbital while no such function in enzyme activity was observed in animals receiving 3-methylcholanthrene or benzo[a] pyrene under similar experimental conditions. The increase in the activity of HCHS esterase I (HCHS-E1) active at pH 5.5, HCHS esterase II (HCHS-E2) active at pH 8.0, and HCAC esterase (HCAC-E) was approximately 7 to 8, 3- and 3-fold respectively. On the other hand, the degree of induction of nonspecific microsomal carboxylesterase acting on p-nitrophenylacetate (PNPA) was significantly less. The Km values for the hydrolysis of HCHS at pH 5.5 and 8.0 and HCAC by rat liver microsomes obtained from control rats were 2.45, 2.02 and 1.6 mM, respectively, and these Km values were not changed significantly in preparations obtained from rats treated with phenobarbital. The distinct in vitro responses displayed by hepatic microsomal steroid esterases to various inhibitors were able to distinguish three different enzymes which also differed from nonspecific carboxylesterases. The activity of HCAC-E was inhibited by NaAsO2 and AgNO3 while that of HCHS-E1 and HCHS-E2 remained unaffected. Selective inhibition of HCHS-E1 by NaF, HgCl2 and p-chloromercuribenzoate and that of HCHS-E2 by NiSO4 indicated the possible existence of different enzymes or isozymes of a carboxylesterase catalyzing HCHS hydrolysis. The effects elicited by the inhibitors on the activity of PNPA esterase were different from those observed with steroid esterases. Furthermore, the present study has also indicated species variations in the distribution of steroid esterases in the livers of rat, mouse, dog and cat.

Selective stimulation of carboxylesterases metabolizing charged steroid esters by hydrocortisone.

We observed a remarkable augmentation in the rate of hydrolytic breakdown of HCHS following exposure to corticosteroid therapy. This underscores the need for a careful reappraisal of its dosage in long term therapy. In such an event the uncharged ester may be the preferred drug of choice.

The effect of diethylcarbamazine citrate on incidence and recovery rates of Brugia malayi microfilaremia in Sabah, Malaysia.

Mass drug administration via 3 modes of delivery reduced the incidence and prevalence rates and intensity of Brugia malayi infection in 3 rural villages in the Bengkoka Peninsula, Sabah, in 1982-1983. A dosage of 6 mg diethylcarbamazine citrate (DEC-C)/kg body weight was administered either daily or weekly (total of 6 doses, 36 mg/kg body weight), and impact on B. malayi cases were comparable in the 3 villages. A total of 384 people participated in the DEC-C regimens, and all pregnant women and children under 2 years were excluded from the study. Bekessy's method of estimation of incidence and recovery rates was applied to data on B. malayi microfilaremia before drug administration. Treatment with DEC-C by any of the 3 modes of delivery drastically reduced the number of episodes of patent microfilaremia, incidence and prevalence, and median microfilarial density. Reduction was sustained for at least 18 to 24 months after treatment.

Role of monoamine oxidase-B in medroxyprogesterone acetate (17-acetoxy-6 alpha-methyl-4-pregnene-3, 20-dione) induced changes in brain dopamine levels of rats.

The effect of medroxyprogesterone acetate (MPA) on brain monoamine levels and monoamine oxidase (MAO) activity was studied in adult, healthy, non-pregnant female rats. MpA was injected in a single dose of 100 mg/kg i.m. Dopamine (DA), noradrenaline (NA), 5-hydroxytryptamine (5-HT) levels and MAO activity were estimated fluorometrically in rat brian. No change in DA, NA, 5-HT or MAO activity was observed after 7 days of MPA treatment while a significant decrease in DA levels along with a significant increase in MAO activity was observed after 21 days of MPA treatment. However, there was no change in NA and 5-HT levels after 21 days of MPA administration. The selective reduction of DA by MPA could be due to an increase in MAO-B activity. MPA does not appear to increase MAO-A activity because neither of the specific substrates (NA and 5-HT) of MAO-A was found to be decreased inspite of the increase in MAO activity as estimated by the kynuramine method. These findings suggest the importance of MAO-B also in DA metabolism in rat brain.

Serotonin as a facilitatory neurotransmitter in the anticonvulsant activity of methaqualone.

The neuromodulatory role of serotonin in the anticonvulsant activity of methaqualone was investigated. A dose-dependent increase in the ability of methaqualone to provide protection against pentylenetetrazol (90 mg/kg SC)-induced convulsions in mice was observed. The ED50 value for the anticonvulsant activity of methaqualone was calculated and found to be 60 mg/kg, IP. Pretreatment of mice with 5-hydroxytryptophan (100 mg/kg, IP, 2 hr) and p-chlorophenylalanine (300 mg/kg, IP, 2 hr), causing an increase in brain serotonin levels, resulted in a 60% and 80% increase, respectively, in the anticonvulsant activity of methaqualone. Similar pretreatment with p-chlorophenylalanine (300 mg/kg, IP, 48 hr), causing a lowering of brain serotonin, and methysergide (10 mg/kg, IP, 0.5 hr), causing blockade of brain serotonin receptors, resulted in a 40% and 20% decrease, respectively, in the ability of methaqualone to provide protection against pentylenetetrazol-induced convulsions. These results suggest a facilitatory role of serotonin in the anticonvulsant activity of methaqualone.

Cyclic-AMP in human lung preparations.

Cyclic-AMP levels in unaffected and affected cancerous portions of human lung preparations were determined by measuring displaced 3H-cyclic-AMP from the specific binding protein by unlabeled ligand. The levels of cyclic-AMP in unaffected portions of human lungs ranged between 52-116 pmoles/g protein. Significantly higher levels of cyclic-AMP were found in lung samples affected with squamous cell carcinoma, adenocarcinoma and malignant melanoma with the mean values being 251, 290, and 509 pmoles/g protein, respectively. On the other hand, a decrease in the level of cyclic-AMP to 39 pmoles/g protein was observed in portions of lungs affected with granuloma. These results suggest that the level of cyclic-AMP in lung tissue may reflect the malignant or benign nature of the pulmonary disease.

High affinity binding of the calcium channel blocker, (+)-[methyl-3H]PN200-110(3HPN) in rat brain.

PN200-110 is a recently introduced 1,4-dihydropyridine which has been demonstrated to be a potent calcium channel blocker. 3HPN has been shown to bind in a specific saturable manner to P2 fractions obtained from brain homogenates from male Sprague-Dawley rats. 3HPN binding was found to be temperature-dependent. Specific 3HPN binding was maximal at 25 degrees C; binding decreased at 2 degrees C and 37 degrees C. The KD calculated from Scatchard analysis was 0.0943 +/- 0.0038 nM while the Bmax was found to be 109.1 +/- 2.3 fmol/mg protein. A concentration dependent inhibition of 3HPN binding by various cations was determined and found to be as follows: ZN2+ greater than La3+ greater than Rh3+, Al3+ greater than Co2+, Ni2+, Mn2+ greater than Ca2+, Mg2+ greater than Ba2+ greater than Sr2+. These results provide evidence for the existence of central high affinity dihydropyridine receptor sites in rat brain.

Neuromodulatory role of serotonin in the anticonvulsant activity of 2-phenylbenzoate of 3-diethylamino-1-propanol.HCl (JAW-669).

The role of serotonin in the mediation of the anticonvulsant activity of JAW-669 was investigated against maximal electric shock (MES)-induced seizures in mice. A dose-dependent protection against seizures was provided by JAW-669 (4, 6 and 8 mg/kg, IP) and the calculated ED50 value was 6.01 mg/kg, IP. Pretreatment of mice with 5-hydroxytryptophan (50 mg/kg, IP) 2 hr before the administration of JAW-669 (6.01 mg/kg, IP) was found to cause a 40% increase in the ability of JAW-669 to provide protection against MES-induced seizures. Similar pretreatment with tryptophan (100 mg/kg, IP, 1 hr) caused a 30% decrease in the anticonvulsant activity of JAW-669. Prior administration of p-chlorophenylalanine (300 mg/kg, IP, 48 hr) and methysergide (10 mg/kg, IP; 0.5 hr) before administration of JAW-699 caused a 66% and 74% decrease, respectively, in the ability of JAW-669 to provide protection against MES-induced seizures. These results suggest a facilitatory role of serotonin in the anticonvulsant activity of JAW-669.

Anti-inflammatory activity of substituted 1,3,4-oxadiazoles.

Various 2-(4-biphenoxymethyl)-5-arylamino-1,3,4-oxadiazoles were synthesized by cyclization of the corresponding 1-(4-biphenoxyacetyl)-4-substituted thiosemicarbazides. These compounds were characterized by their elemental analyses and infrared, mass, and nuclear magnetic resonance spectral data. All substituted thiosemicarbazides (100 mg/kg, ip) and cyclized substituted oxadiazoles (100 mg/kg, ip) possessed anti-inflammatory activity, as reflected by their ability to provide protection against carrageenin-induced edema in the rat paw which ranged from 28 to 68% and 36 to 76%, respectively. Cyclization of the substituted thiosemicarbazides, in general, resulted in an increase in the anti-inflammatory activity of their corresponding substituted oxadiazoles, with the exception of those containing 2,4-dimethyl and 3,4-dimethyl substituents in their molecular structure. Hydrocortisone (10 mg/kg, ip) and oxyphenbutazone (40 mg/kg, ip) were used as the standard reference drugs and these provided 45 and 53% protection, respectively. All compounds (1 mM) possessed antiproteolytic activity and the in vitro inhibition of trypsin-induced hydrolysis of bovine serum albumin ranged from 13 to 75% for substituted thiosemicarbazides and 39 to 70% for substituted oxadiazoles. There was no relationship between the anti-inflammatory activity of substituted thiosemicarbazides and substituted oxadiazoles and their antiproteolytic effectiveness. The low toxicity of these compounds was reflected by their high approximate LD50 values, ranging from 500 to 1000 mg/kg.

Anticonvulsant and antiproteolytic properties of 2,5-disubstituted oxadiazoles and their inhibition of respiration in rat brain homogenates.

Eight 2-(3,4-methylenedioxyphenyl)-5-arylamino1,3,4-oxadiazoles were synthesized, characterized by their sharp melting points, elemental analyses, and IR spectra, and evaluated for anticonvulsant activity. The protection afforded by oxadiazoles (100 mg/kg ip) against pentylenetetrazol (90 mg/kg sc)-induced convulsions ranged from 50 to 80%. All oxadiazoles inhibited the respiratory activity of rat brain homogenates during oxidation of pyruvate, alpha-ketoglutarate, and succinate. The presence of added nicotinamide adenine dinucleotide (NAD) to the reaction mixture during oxidation of pyruvate decreased the degree of inhibition. All oxadiazoles possessed antiproteolytic activity that was reflected by their ability to decrease trypsin-induced hydrolysis of bovine serum albumin. Such an inhibition was concentration dependent and ranged from 10.2 to 47.5 and from 15.7 to 71.8% by 0.5 and 1 mM oxadiazoles, respectively. All oxadiazoles competitively inhibited in vitro succinate dehydrogenase activity of rat brain homogenates.

Synthesis of N,N'-bis(3-substituted benzylideneaminopropyl)-piperazines and their anti-inflammatory, antiproteolytic, and anticonvulsant properties.

Some N,N'-bis(3-substituted benzylideneaminopropyl) piperazines were synthesized and characterized by their sharp melting points and elemental analyses. These substituted piperazines possessed anti-inflammatory activity, and the protection afforded by these compounds against carrageenan-induced edema ranged from 23 to 67%. The antiproteolytic activity of these piperazines was reflected by their ability to inhibit in vitro hydrolysis of bovine serum albumin and casein by trypsin. The inhibition of trypsin-induced hydrolysis was concentration dependent and competitive in nature.

Synthesis of substituted anilino-3-methoxy-4-substituted acetoxy) benzylidenes and their monoamine oxidase inhibitory and anticonvulsant properties.

Several substituted anilino-(3-methoxy-4-substituted acetoxy) benzylidenes were synthesized and characterized by their sharp melting points and elemental analyses. All substituted benzylidenes competitively inhibited the in vitro monoamine oxidase activity of rat brain homogenates and possessed anticonvulsant activity against pentylenetetrazol-induced convulsions in mice.

Anticonvulsant activity and inhibition of cellular respiratory activity by substituted imidazolocarbamides.

Several 1-(1-aryl-2-mercaptoacetylimidazole)-3-alkylcarbamides were synthesized and characterized by their sharp melting points, elemental analyses, and IR spectra. These substituted imidazolocarbamides possessed anticonvulsant activity, which was reflected by the 20-80% protection observed with these compounds against pentylenetetrazol-induced convulsions in mice. These substituted imidazolocarbamides selectively inhibited the in vitro oxidation of nicotinamide adenine dinucleotide (NAD)-dependent oxidations of pyruvate, alpha-ketoglutarate, beta-hydroxybutyrate, and NADH by rat brain homogenates. However, NAD-independent oxidation of succinate was not affected. The anticonvulsant activity possessed by 1-(1-aryl-2-mercaptoacetylimidazole)-3-alkylcarbamides had no relationship to their ability to inhibit cellular respiratory activity.

Anti-inflammatory and antiproteolytic properties of 1-(1-naphthylacetyl)-3-substituted carbamides.

Several 1-(1-naphthylacetyl)-3-substituted carbamides were synthesized, characterized, and evaluated for anti-inflammatory and antiproteolytic activity. The protection afforded by most of these carbamides against carrageenan-induced edema in rats at a dose of 100 mg/kg ranged from 4.4 to 50%. Some of these carbamides, which showed higher protection against carrageenan-induced edema, were further evaluated for their antigranulation effect against cotton pellet-induced granuloma formation in rats. All carbamides showed a poor degree of protection against granuloma formation. The antiproteolytic activity of these carbamides, as reflected by their ability to inhibit trypsin-induced hydrolysis of the bovine serum albumin, was of a low order and was unrelated to their anti-inflammatory activity.

Synthesis of 5-substituted 2-oxazolidinethiones and their antagonism to uterotropic effect of diethylstilbestrol.

5-(4-Aminophenoxymethyl)-2-oxazolidinethiones were synthesized by the cyclization of 1-(4-aminophenoxy)-3-amino-2-propanol in the presence of potassium hydroxide and carbon disulfide. This oxazolidinethione, on reaction with suitable isothiocyanates, yielded 5-[4-(substituted thiocarbamido)phenoxymethyl]-2-oxazolidinethiones. These compounds antagonized the uterotropic effects of diethylstilbestrol in female rats and possessed approximate LD50 values of 400-greater than 800 mg/kg.

Substituted thiazolidones: selective inhibition of nicotinamide adenine dinucleotide-dependent oxidations and evaluation of their CNS activity.

Eight 2-arylimino-3-(3-N-morpholinopropyl) thiazolid-4-ones were synthesized from the corresponding 1-aryl-3-(3-N-morpholinopropyl) thiocarbamides, characterized, and tested for their effects on the cellular respiratory activity of rat brain homogenates. All substituted 4-thiazolidones selectively inhibited nicotinamide adenine dinucleotide (NAD)-dependent oxidations of pyruvate, citrate, DL-isocitrate, alpha-ketoglutarate, malate, beta-hydroxybutyrate, L-glutamate, and NADH, while the NAD-independent oxidation of succinate remained unaltered. All thiazolidones possessed some degree of anticonvulsant activity against pentylenetetrazol-induced convulsions, and the protection afforded by these compounds at a dose of 100 mg/kg ranged from 30 to 80%. The low toxicity possessed by most of these thiazolidones was reflected by their approximate LD-50 values from 300 mg/kg to greater than 1000 mg/kg. In the present study, the anticonvulsant activity possessed by these substituted 4-thiazolidones was unrelated to their ability to inhibit selectively the NAD-dependent oxidations by rat brain homogenates. These thiazolidones exhibited depression of the CNS activity which, in some cases, was associated with the increase in respiration. All thiazolidones potentiated pentobarbital (sodium) sleeping time in mice when administered in a dose of 100 mg/kg.

Anticonvulsant activity and inhibition of respiration in rat brain homogenates by substituted trimethoxybenzamides.

Ten N-[4-[4-(arylthiosemicarbazido)carbonyl]phenyl]-3,4,5-trimethoxybenzamides were synthesized and characterized by their sharp melting points, elemental analyses, and IR and NMR spectra. All substituted benzamides were evaluated for their anticonvulsant activity. The degree of protection afforded by these compounds (100 mg/kg ip) against pentylenetetrazol (90 mg/kg sc)-induced convulsions in mice ranged from 10 to 80%. The ability of substituted benzamides to inhibit respiratory activity was observed by inhibition of oxidation of pyruvate, alpha-ketoglutarate, NADH, and succinate by rat brain homogenates. Inhibition of pyruvic acid oxidation was concentration dependent. The anticonvulsant activity of substituted benzamides was not related to their ability to inhibit cellular respiratory activity.

Anticonvulsant and antiproteolytic properties of 3,5-disubstituted oxadiazole-2-thiones and their inhibition of respiration in rat brain homogenates.

Eight 5-(3,4-methylenedioxyphenyl)-3-arylaminomethyl-1,3,4-oxadiazole-2-thiones were synthesized, characterized by their sharp melting points, elemental analyses, and IR spectra, and evaluated for anticonvulsant activity. All substituted oxadiazole-2-thiones possessed anticonvulsant activity, which was reflected by their ability to provide 10--70% protection against pentylenetetrazol-induced convulsions in mice at 100 mg/kg ip. These compounds inhibited in vitro nicotinamide adenine dinucleotide (NAD)-dependent oxidation of pyruvate, alpha-ketoglutarate, and NADH by rat brain homogenates as well as NAD-independent oxidation of succinate by rat brain homogenates. Antiproteolytic activity of these substituted oxadiazole-2-thiones was reflected by their ability to inhibit trypsin hydrolysis of bovine serum albumin. These results indicated that the inhibition of cellular respiration and antiproteolytic activity of these substituted oxadiazole-2-thiones is not the biochemical basis for their anticonvulsant activity.

Substituted thiosemicarbazides and corresponding cyclized 1,3,4-oxadiazoles and their anti-inflammatory activity.

Several 1-(4-biphenoxyacetyl)-4-substituted arylthiosemicarbazides and their corresponding cyclized 2-(4-biphenoxymethyl)-5-arylamino-1,3,4- oxadiazoles were synthesized and characterized by elemental analyses and IR, mass, and nuclear magnetic resonance spectra. All compounds were evaluated for anti-inflammatory activity by determining their ability to provide protection against carrageenin-induced edema in rat paw. The anti-inflammatory activity possessed by substituted thiosemicarbazides [100 mg/kg, intraperitoneal(ip)] ranged from 22 to 68%, whereas substituted 1,3,4-oxadiazoles (100 mg/kg, ip) provided protection of 10-76%. Hydrocortisone (10 mg/kg, ip) and oxyphenbutazone (40 mg/kg, ip), used as standard reference drugs, decreased edema in rat paw by 44.6 and 52.9%, respectively. All compounds (1 mM) possessed antiproteolytic activity that was reflected by their ability to cause in vitro inhibition of trypsin-induced hydrolysis of bovine serum albumin. This inhibition ranged between 43 and 72% for substituted thiosemicarbazides and 30 and 83% for substituted 1,3,4-oxadiazoles.

13C-NMR spectra of strychnos alkaloids: brucine and strychnine.

The natural abundance 13C-NMR spectra of brucine and strychnine were obtained using the pulse Fourier transform technique. The chemical shifts of various carbon resonances were assigned on the basis of substituent effects on benzene shifts, intesities of signals, multiplicites generated in single-frequency off-resonance-decoupled spectra, and comparisons with the chemical shifts of structurally related compounds.