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Biomedical subjects

J J Freeman

Publications and source records attributed to J J Freeman.

At least 37 records · Page 2Linked to original sources
PubMed1989

The dermal carcinogenic potential of unrefined and hydrotreated lubricating oils.

Unrefined lubricating oils contain relatively high levels of polycyclic aromatic hydrocarbons (PAH) and have been shown to induce tumors in mouse skin. Exxon has developed a new method of refining these materials, a severe hydrotreatment process that is optimized for PAH removal. The specific objectives of the current study were to assess PAH reduction and then to evaluate directly the dermal carcinogenic potential of the materials that spanned the range of products produced by this method. The test samples included unrefined light and heavy vacuum distillates from a naphthenic crude oil, as well as the corresponding severely hydrotreated products. Two sets of samples were prepared to assess the effects of various operating parameters in the reactor. Additionally, positive (benzo[a]pyrene), negative (white mineral oil) and vehicle (toluene) control groups were included to assess the sensitivity and specificity of the bioassay. Each sample was applied in twice-weekly aliquots to the backs of 40 male C3H mice. In the analytical studies, significant reductions in the levels of several specific PAH were demonstrated. In the dermal carcinogenesis studies, the unrefined oils and the positive control induced tumors and also significantly reduced survival. None of the mice treated with severely hydrotreated oils or with the negative or vehicle controls developed skin tumors, and survival of these mice was not significantly different from the control. Thus, the data demonstrated that this new, severe hydrotreatment process was an effective means of converting carcinogenic feedstocks to non-carcinogenic products.

Animals↗
PubMed1988

Microsomal metabolism of acetonitrile to cyanide. Effects of acetone and other compounds.

Oral acetone exposure delays and potentiates acetonitrile toxicity in rats. Results of previous pharmacokinetic studies suggested that acetone exerted a biphasic effect on the metabolism of acetonitrile to cyanide; the presence of acetone in vivo appeared to inhibit the metabolism of acetonitrile to cyanide, whereas the disappearance of acetone from serum was followed by stimulation of acetonitrile metabolism. The current experiments were designed to characterize further the metabolism of acetonitrile to cyanide and the effects of acetone and other compounds upon this metabolism. Liver microsomes were isolated and pooled 24 hr after oral pretreatment of female Sprague-Dawley rats (180-250 g) with acetone (1960 mg/kg) or water. Microsomal metabolism of acetonitrile to cyanide was found to be oxygen and NADPH dependent, and heat-inactivated tissue was unable to catalyze the reaction. NADH antagonized the NADPH-dependent metabolism of acetonitrile. The metabolism of acetonitrile to cyanide was linear with protein concentrations of 0-8 mg per incubation. Following a characteristic lag period of 10 min, the reaction was linear from 15 to 30 min. This metabolism was inhibited by carbon monoxide, metyrapone and SKF 525-A. Acetone pretreatment (-24 hr) in vivo increased the apparent Vmax for acetonitrile metabolism without affecting the apparent Km. When added in vitro, acetone competitively inhibited the metabolism of acetonitrile, with a KI of 0.41 mM. Dimethyl sulfoxide (KI = 0.51 mM) and ethanol (KI = 0.11 mM) were also competitive inhibitors of acetonitrile metabolism, and aniline HCl (KI = 4.77 microM) appeared to be a mixed inhibitor. These data are consistent with the hypothesis that the metabolism of acetonitrile to cyanide is mediated by a specific acetone-inducible isozyme of cytochrome P-450.

Acetone↗
PubMed1988

Experimental contact sensitization with 3,4,5-trichloropyridazine.

The potential of 3,4,5-trichloropyridazine to induce contact sensitization was assessed in the guinea pig maximization test of Magnusson and Kligman and also in the closed patch test described by Buehler. The test material was a 1% solution of 3,4,5-trichloropyridazine in a highly refined mineral oil. The test material elicited moderate to severe irritation when diluted in mineral oil to concentrations of 15-25% and minimal irritation at concentrations of 1-3%. Both tests clearly indicated that 3,4,5-trichloropyridazine was a contact sensitizer to guinea pigs, although the response was stronger in the maximization test. Sensitization was distinguished from irritation by the use of concurrent irritation control groups.

Animals↗
PubMed1987

The metabolism of acetonitrile to cyanide by isolated rat hepatocytes.

The metabolism of saturated nitriles, including acetonitrile, has been assumed to occur by a cytochrome P-450-dependent oxidation at the alpha-carbon, yielding a cyanohydrin intermediate which may spontaneously degrade to hydrogen cyanide and an aldehyde. However, results of studies in our laboratory suggest that formaldehyde is not a metabolite of acetonitrile. Since acetonitrile is structurally similar to iodomethane, a substrate for glutathione (GSH) S-transferases, we hypothesized that the metabolism of acetonitrile to cyanide might also occur by a nucleophilic substitution reaction involving GSH. The present studies were conducted to investigate these hypotheses and to further our study of the effects of acetone on acetonitrile metabolism. Female Sprague-Dawley rats were pretreated with buthionine sulfoximine BSO (4 mmol/kg ip, at -4 and -2 hr), cobalt heme (90 mumol/kg sc, at -48 hr), acetone (1960 mg/kg po, at -24 hr), or vehicle, and hepatocytes were isolated after collagenase perfusion of the liver. BSO reduced the cellular GSH content by greater than 80%, but did not appear to affect the metabolism of acetonitrile: the liberation of cyanide correlated with cytochrome P-450, and not GSH, concentrations. Cobalt heme depleted hepatocellular cytochrome P-450 (-45%) content, decreased cell yield and viability, and resulted in a marked reduction in the metabolism of acetonitrile to cyanide. Cobalt heme did not affect the recovery of sodium cyanide from hepatocyte suspensions. Pretreatment of rats with acetone resulted in a twofold increase in the metabolism of acetonitrile to cyanide. Addition of acetone in vitro inhibited acetonitrile metabolism, with an IC50 of 319 microM.(ABSTRACT TRUNCATED AT 250 WORDS)

Acetone↗
PubMed1987

Antagonism of acute physostigmine and neostigmine toxicity in mice by hemicholinium-3.

Hemicholinium-3 (HC-3) was administered intraperitoneally to mice concurrently with the intraperitoneal administration of physostigmine or neostigmine. HC-3 increased the LD50 values for both physostigmine and neostigmine but did not alter the effect on brain ACh levels produced by these agents. Since HC-3 does not cross the blood brain barrier after intraperitoneal administration, the antidoting action of HC-3 is peripherally mediated and does not solely involve an inhibition of ACh synthesis. The increase in brain acetylcholine caused by neostigmine was related to a reduction in acetylcholinesterase activity, providing evidence that intraperitoneally administered neostigmine crosses the blood-brain barrier.

Acetylcholine↗
PubMed1986

The effect of hemicholinium-3 and physostigmine on choline in rat brain.

Physostigmine and hemicholinium-3 were examined for their effects on rat brain choline levels after microwave irradiation and after postmortem incubation. Hemicholinium-3 and physostigmine increased choline levels in the cerebellum and striatum when measured after microwave irradiation, but decreased the level of choline produced after postmortem incubation of the brain areas. Addition of the drugs in vitro to whole brain homogenates also decreased postmortem choline production. The data shows that the effect of hemicholinium-3 and physostigmine on in vivo choline levels can be differentiated from their effects on the postmortem production of choline, suggesting that the drugs are affecting at least two of the regulatory processes for choline in the brain.

Animals↗
PubMed1985

In vivo acetylation of homocholine and beta-methylcholine in rat brain.

A nitrogen phosphorus-gas chromatographic procedure was modified to determine the extent of in vivo acetylation of the choline analogs homocholine and beta-methylcholine. Infusion of homocholine (18 mumoles) for 2 hours into the lateral ventricle of the rat produced 2.3 nmoles/gram of acetylhomocholine which represented 0.035% of the detected homocholine. Infusion of the same quantity of beta-methylcholine produced 1.0 nmole/gram of acetyl-beta-methylcholine representing 0.025% of the detected beta-methylcholine. Although pretreatment with hemicholinium-3 reduced the amount of acetylated product formed from either analog, the reduction was significant only for acetyl-beta-methylcholine (p less than 0.01).

Acetylation↗
PubMed1985

Acetone potentiation of acute acetonitrile toxicity in rats.

The purpose of these studies was to investigate the nature and mechanism of a toxicologic interaction between acetonitrile and acetone. Results of oral dose-response studies utilizing a 1:1 (w/w) mixture of acetonitrile and acetone, or varying doses of acetonitrile administered together with a constant dose of acetone, indicated that acetone potentiated acute acetonitrile toxicity three- to fourfold in rats. The onset of severe toxicity (manifested by tremors and convulsions) was delayed in the groups dosed with both solvents compared to the groups that received acetonitrile or acetone alone. Blood cyanide (a metabolite of acetonitrile) and serum acetonitrile and acetone concentrations were measured after oral administration of 25% aqueous solutions of acetonitrile, acetone, or acetonitrile plus acetone. Concentrations of cyanide in the blood of rats given acetonitrile plus acetone remained near baseline, in contrast to the high concentrations found in rats dosed with acetonitrile alone. At 34-36 h, high blood cyanide concentrations were found in rats dosed with both of the solvents. This delayed onset of elevation of blood cyanide coincided with the occurrence of clinical signs and with the disappearance of serum acetone. In further pharmacokinetic studies, blood cyanide concentrations were measured after similar dosage regimens of acetone and acetonitrile. Peak cyanide concentrations were found to be significantly greater in rats dosed with both solvents than in rats given only acetonitrile. Administration of either sodium thiosulfate or a second dose of acetone prevented the toxicity associated with exposure to both solvents. These results suggest that the effects of acetone on acetonitrile toxicity are due to a biphasic effect on the metabolism of acetonitrile to cyanide, that is, an initial inhibition followed by a stimulation of this metabolism upon acetone elimination.

Acetone↗
PubMed1983

Reactions induced by the concurrent use of thimerosal and tetracycline.

We examined the reaction to thimerosal which occurred when patients were prescribed tetracyclines simultaneously. Nine patients were identified who had been using a 0.004% thimerosal-containing contact lens solution for over 6 months. All had developed varying degrees of ocular reaction (red eye, irritation, blepharitis) apparently as a result of taking tetracyclines concurrently. The reaction disappeared upon discontinuance of either the thimerosal or the tetracyclines. The hypothesis that the reaction was due to an interaction between thimerosal and tetracyclines was confirmed in rabbits.

Animals↗
PubMed1982

Peripheral toxicity of hemicholinium-3 in mice.

1 The site (i.e. peripheral or central) of the toxicity produced by hemicholinium-3 in mice was investigated. 2 Hemicholinium-3 was measured fluorometrically and acetylcholine was determined by gas chromatography after intraventricular or intraperitoneal administration of hemicholinium-3. 3 Hemicholinium-3 was not detected in the brain nor were acetylcholine levels decreased in the brain after systemic administration. 4 The dose-response curve following intraventricular administration demonstrated that hemicholinium-3 was not as lethal after central administration as it was after peripheral administration. 5 Approximately 24% of a 75 microgram intraventricular dose of hemicholinium-3 was found in the periphery at death. 6 These results suggest that hemicholinium-3 manifests its toxicity primarily in the periphery.

Acetylcholine↗
PubMed1981

Synthesis of alkylaminoalkylamides of substituted 2-aminopyrroles as potential local anesthetic and antiarrhythmic agents I: alpha-Amines.

The synthesis, local anesthetic and antiarrhythmic properties, and CNS toxicity of 19 2-(2-alkylaminoalkylamido)pyrroles are described. Most of the compounds exhibited local anesthetic activity by the guinea pig wheal test, and four showed activity comparable to or greater than that of lidocaine. Most compounds also exhibited antiarrhythmic activity; five compounds had activity comparable to that of lidocaine, and one was more potent. All compounds exhibiting antiarrhythmic activity also were toxic to the central nervous system.

Amides↗
PubMed1981

Synthesis and preliminary pharmacology of an internal standard for assay of neostigmine.

The synthesis of the diethyl analog of neostigmine, its preliminary pharmacology, and its use as an internal standard for the GLC assay of neostigmine are described. Both the diethyl analog and neostigmine undergo thermal demethylation in the injection port. The column selected produced satisfactory resolution and short retention times for neostigmine and the diethyl analog. The diethyl analog apparently possesses acetylcholinesterase-inhibiting properties, as evidenced by potentiation of the contractile response to acetylcholine in the ileum. In addition, acetylcholine levels in the brain were elevated slightly. Water solutions of the diethyl analog appeared to lose biological activity with time. the diethyl analog appears to be suitable for use as an internal standard for the GLC assay of neostigmine.

Acetylcholine↗
PubMed1981

Synthesis of alkylaminoalkylamides of substituted 2-aminopyrroles as potential local anesthetic and antiarrhythmic agents. II: beta-Amines.

The synthesis, local anesthetic and antiarrhythmic properties, and CNS toxicity of 14 2-(3-alkylaminoalkylamido)-pyrroles are described. Most of the compounds exhibited local anesthetic activity by the guinea pig wheal test, with seven showing comparable or greater activity than lidocaine. Most compounds also exhibited antiarrhythmic activity; three compounds had more potent activity than lidocaine. All compounds exhibiting antiarrhythmic activity also were toxic to the CNS. However, two of the three compounds having greater activity than lidocaine possessed more desirable therapeutic indexes.

Amines↗
PubMed1981

Synthesis and vasodepressor screen of a series of 2-(2-alkylaminoalkylamido)-3-carbamyl-4-methyl-5-benzylpyrroles.

A series of 2-(2-alkylaminoalkylamido)-3-carbamyl-4-methyl-5-benzylpyrroles was synthesized and screened for vasoactivity. The compounds were administered intraperitoneally as a suspension to approximate the oral route of administration and intravenously when solubilization could be affected with suitable solvents. The most active compound following intravenous or intraperitoneal administration lowered blood pressure 73 and 35.5 mm Hg at doses of 4 mg/kg iv and 100mg/kg ip, respectively. It also exhibited the longest duration of vasodepressor activity (25 min). Several other compounds exhibited vasodepressor activity following intraperitoneal administration. Several hydrochloride salts appeared to be more potent vasoactive agents than the corresponding bases.

Animals↗