Aaron Arnold

The effect of central nervous system agents on rat-brain γ-aminobutyric acid level

Abstract γ-Aminobutyric acid has been implicated as a central nervous system neurohumoral depressant by a number of investigators. The hypothesis that brain excitability is inversely proportional to the γ-aminobutyric acid content was tested with compounds that were reported active by others and with a number of central nervous system stimulants and depressants. Of twelve compounds tested, e.g. , ethanol, hydroxylamine, pentylenetetrazol and phenobarbital, none produced dramatic changes in rat-brain γ-aminobutyric acid content. It was concluded that the presence of γ-aminobutyric acid in central nervous system tissue alone does not imply a physiological role a priori .

Inhibition of β-hydroxysteroid dehydrogenase I. Structural characteristics of some steroidal inhibitors☆

Abstract 1. 1. β-Hydroxysteroid dehydrogenase (3 (or 17)-β-hydroxysteroid: NAD(P) oxidoreductase, EC. 1.1.1.51) was prepared from Pseudomonas testosteroni . This enzyme obeyed first-order kinetics with androst-4-ene-3,17-dione as substrate between 1.0·10 −4 and 2.5·10 −6 M. 2. 2. The most effective inhibitors, with the concentration at which they inhibited 50%, were: 2-hydroxymethylene-17α-methylandrostan-17β-ol-3-one (9·10 −7 M), 2α-cyano-4,4,17α-trimethylandrost-5-en-17β-ol-3-one (8·10 −7 M), 17β-hydroxy-4,4,17α-trimethylandrost-5-enol[3,2-c]pyrazole (8·10 −7 M), and 4,4-dimethyl-17β-hydroxyandrost-5-eno[3,2-c]pyrzole (8·10 −7 M). Testosterone inhibited 50% at 2·10 −5 M. 3. 3. A study of 42 derivatives of the androstane nucleus showed that the degree of inhibition depended upon the nature of the substituents on positions 2, 3, 4 and 17 of the steroid nucleus. Spacial presentation of these groups to the enzyme by the arrangement of double bonds or by their absence also affected inhibition.

The results of animal studies with ciprofibrate, a new orally effective hypolipidemic drug.

Findings are given to show that ciprofibrate, a new orally active phenoxyisobutyrate, is significantly more hypolipidemic than is the reference clofibrate. In hyperlipidemic rats ciprofibrate suppresses the increase in blood lipids 33% at a daily dosage of 0.6--3 mg/kg. The corresponding dosage for clofibrate is 125--460 mg/kg. Based on studies with cholesterol pools pre-labeled with [14C]mevalonate or with cholesterol-labeled pools in ciprofibrate-treated normolipidemic rats, ciprofibrate was shown to inhibit cholesterol biosynthesis. No evidence of the presence of 7- or 24-dehydrocholesterol was obtained in the sera of ciprofibrate-treated rats as shown by gas chromatography examination. The order of hypolipidemic effectiveness of ciprofibrate in hyperlipidemic rats provides a basis for anticipating that ciprofibrate will be hypolipidemic in hyperlipoproteinemic subjects who are considered at high risk of acquiring coronary artery disease.

Andro-stanazole, a new orally active anabolic steroid.

Summary Andro-stanazole (17β-hydroxy-17α-methylandrostano[3,2-c] pyrazole) has been evaluated for its nitrogen-retaining and androgenic activities in castrated male rats. Orally, it appears to be 30 times more anabolic and 1/4 as androgenic as methyl-testosterone. Parenterally, it appears to be 1/20 as anabolic and 1/40 as androgenic as testosterone propionate. Andro-stanazole is clearly an agent which merits further investigation for oral administration to patients under conditions where maximum anabolic action with minimum androgenic side effects is desired.

Inhibition of β-hydroxysteroid dehydrogenase II. Kinetics and pH effect

Abstract 1. 1. An investigation was conducted on the kinetics of inhibition of β-hydroxysteroid dehydrogenase (3(or 17)-β-hydroxysteroid: NAD(P) oxidoreductase, EC 1.1.1.51) from Pseudomonas testosteroni . The natural estrogen, estradiol-17β ( K i = 1·10 −5 M) was a non-competitive inhibitor as were 2-hydroxymethylene-17α-methylandrostan-17β-ol-3-one ( K i = 3·10 −7 M) and 2α-cyano-4,4,17α-trimethyl-androst-5-en-17β-ol-3-one ( K i = 7·10 −7 M). 4,4-Dimethyl-17β-hydroxyandrost-5-eno[3,2-c]pyrazole ( K i = 5·10 −7 M) and 17β-hydroxy-4,4,17a-trimethylandrost-5-eno[2,3-d]isoxazole ( K i = 4·10 −6 M) were competitive inhibitors. These four synthetic androstane or androstene derivatives were more tightly bound to the enzyme than was estradiol-17β. 2. 2. The degree of inhibition by estradiol-1gb and by diethylstilbestrol was found to vary with pH. Both estrogenic compounds were between 4 and 20 times more effective inhibitors when the pH was made 4 units more alkaline. Possible reasons for this behavior are a change in the degree of ionization of groups at or near the active site(s) of the enzyme and a contribution of phenolate ion by these estrogenic compounds.

Metabolic effects of a new hypolipidemic agent, ciprofibrate

Ciprofibrate, a new orally effective hypolipidemic agent like clofibrate, suppressed tyloxapol-induced hypercholesterolemia in rats. Ciprofibrate at 10 mg/kg was effective. Clofibrate required a dosage of 180 mg/kg to suppress the tyloxapol effect. Norepinephrine-induced free fatty acid release was inhibited by clofibrate in rats in accordance with earlier findings. Ciprofibrate and lifibrate differed from clofibrate in that, at hypocholesterolemically effective doses, neither inhibited the hormone sensitive lipase in vivo.

Atherosclerosis in rabbits following treatment with heterologous lipoprotein

Summary Rabbits were treated by injection with hypercholesteremic-rooster lipoprotein antigen to protect them from cholesterol-induced atherosclerosis in accordance with the published observations of Gero et al . During the 6-week lipoprotein-injection period 28 rabbits received weekly intramuscular injections of lipoproteins which supplied 22.5 mg protein per rabbit. Following the immunization period the rabbits were given cholesterol-supplemented feed for 16 weeks. Atherosclerosis was evaluated on the basis of grading of aortal lesions at three sites, development of arcus senilis, aorta cholesterol content, and serum-cholesterol level. On the basis of these criteria, the lipoprotein pre-treatment did not exert any protective effect in the 23 surviving rabbits. It was noted that these rabbits had serum-cholesterol levels approximately twice as high as those reported by Gero et al ., and that the serological responses were no higher than 10- 3 compared with responses at a dilution of 10- 4 obtained by the above authors; in the absence of absorption studies a high degree of serological specificity for lipoprotein cannot be assumed.

An Orally Active Hypocholesteremic Steroid with Reduced Uterotrophic Effect

Summary A series of reference and experimental estrogens has been evaluated in terms of the amount required to reduce total serum cholesterol 33% in mature male rats and the amount required to increase the uterine weights of weanling female rats 50 mg over those of the controls. The resultant hypocholesteremic: uterotrophic dissociations were: estrone 50, Premarin® 20, estrone methyl ether >3.2, 16α-chloroestrone methyl ether 2.4, 17-(4-hydroxy-1-butynyl)-3-methoxyestra-1,3,5 (10)-trien-17β-ol 1.6, 17-(3-hydroxypropyl)-3-methoxyestra-1,3,5 (10)-trien-17β-ol 0.2, and 17-(3-hydroxy-1-propynyl)-3-methoxyestra-1,3,5 (10) -trien-17β-ol 17α-hydrocinnamate 0.015. The hydroxy propynyl compound thus has the best dissociation of any steroid noted.

A laboratory evaluation of the effect of the coccidiostat, trithiadol on the growth of chickens.

In feeding trials with chicks through 9 weeks, replicated groups fed 0.1% dietary Trithiadol®-supplemented feed gained weight as well as did the control groups, while the weight gains of those fed 0.0125% dietary nicarbazin-supplemented feed were affected adversely. The chicks in all the groups exhibited no adverse effects by any of the other criteria used, including feed conversions and physical characteristics of the birds through dressing out. In a second feeding trial in which the anticoccidial agents were fed at the commercially recommended level and at three to six times this level, there was no apparent effect on the weight gains in the use level-fed replicated groups. The birds fed the threefold nicarbazin-supplemented feed weighed significantly less than those of the control group (P = <0.001). The chicks fed the sixfold level of Trithiadol-supplemented feed also weighed less than the birds of the control group (P = 0.02). None of the chicks exhibited any other adverse effect. The results from these laboratory feeding trials support the view that Trithiadol may be expected to exhibit a wide margin of safety under conditions of use.

The biological activity of calciferol (vitamin D2).

Summary Assays of 8 samples of calciferol (vitamin D2) using the U.S.P. biological assay with rats indicated in every case a potency significantly greater than 40 U.S.P. units per μg. Our assays gave an average value of 49.7 ± 2.1 units per μg. This is interpreted to mean that U.S.P. reference cod liver oil No. 2 has less than its generally accepted potency. In view of this finding, a re-evaluation of the relationship between calciferol, the international standard and the U.S.P. standard for vitamin D would seem to be indicated. Serious consideration should be given to adopting a fixed weight of pure crystalline calciferol or vitamin D3 as the legal unit instead of relying on designated weights of reference standards consisting of solutions of impure and possibly unstable mixtures.