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Biomedical subjects

W M Davis

Publications and source records attributed to W M Davis.

At least 37 records · Page 2Linked to original sources
PubMed1992

Acute cardiovascular effects of methyl methacrylate monomer: characterization and modification by cholinergic blockade, adrenergic stimulation and calcium chloride infusion.

1. Methyl methacrylate monomer (MMA) given by i.v. infusion to anesthetized dogs caused a sustained hypotension, bradycardia, reduction of cardiac output and stroke volume, and increased peripheral resistance. 2. Epinephrine i.v. could reverse the hypotension but not the bradycardia; isoproterenol i.v. could reverse the bradycardia but not the hypotension. 3. Bilateral cervical vagotomy prevented bradycardia but not other cardiovascular effects of MMA, and prevented all respiratory effects except hypoxemia. 4. Calcium chloride i.v. reversed all circulatory changes except bradycardia; a combination of atropine and calcium reversed all cardiovascular changes from MMA.

Animals↗
PubMed1992

Effect of methyl methacrylate on isolated atria and interaction with isoproterenol, atropine and calcium chloride.

1. Spontaneous rate and contractile force of isolated rat and rabbit atria suspended in a tissue bath were recorded before and after drugs. Methyl methacrylate monomer (MMA) alone both decreased force and increased rate dose-dependently. 2. Concentrations of calcium chloride or isoproterenol that alone increased both rate and force of rat atrial contraction were fully and only partially able, respectively, to restore force to normal after MMA. 3. Atropine prevented changes in rat atrial function from low-effective doses of MMA, but not higher ones; it also failed to prevent the reduction of contractile force by a calcium channel blocker, verapamil. 4. There are similarities but also differences between actions of MMA and verapamil on rat atria.

Animals↗
PubMed1992

Solitary rectal ulcer syndrome: not always ulcerated.

Our patient had a nonulcerated rectal lesion grossly resembling a villous tumor, but microscopically proving to be a solitary rectal ulcer. We have discussed the clinical and pathologic findings and the probable relationship of the lesion to straining at the stool.

Biopsy↗
PubMed1991

Effect of sex steroids on cocaine lethality in male and female mice.

1. Endogenous sex steroid levels were altered in mice via gonadectomy, via physiological or supraphysiological doses of testosterone and/or estradiol, and via tamoxifen dosing to antagonize estrogens. 2. The role of sex hormones in susceptibility to cocaine lethality was examined via the response of mice after endocrine alterations to an intraperitoneal (i.p.) cocaine HCl (75 mg/kg). Incidence of deaths was significantly decreased only in sham-operated males receiving estradiol or tamoxifen and in ovariectomized or sham-operated females receiving doses of estradiol. 3. The levels of estradiol in both sexes appeared to be more influential than were levels of testosterone as a determinant of susceptibility to cocaine.

Animals↗
PubMed1991

Factors in the lethality of i.v. phencyclidine in conscious dogs.

1. Pretreatment were pancuronium prevented convulsions and hyperthermia, but had no effect on acidemia or changes in cardiovascular parameters after intravenous (i.v.) infusion of phencyclidine (PCP). 2. While dogs survived higher amounts of PCP, they failed to regain spontaneous respiratory function. 3. Mechanical ventilation alone increased the mean lethal dose/time of PCP and reduced the effects of PCP on arterial systolic pressure, cardiac output, and PCO2. 4. EKG showed ventricular arrhythmias, which progressed to death. 5. Phenytoin pretreatment plus respiratory assistance increased the lethal dose and reduced PCP effects on cardiovascular parameters, body temperature, and cardiac rhythm. 6. Blocking of convulsions prevented hyperthermia and acidemia; respiratory support reduced circulatory effects, but respired dogs then died, at higher doses, from a primary myocardial toxicity of PCP.

Animals↗
PubMed1991

Respiratory and circulatory effects of centrally administered phencyclidine in anesthetized dogs.

1. Anesthetized dogs were given phencyclidine HCl (PCP) by intracerebroventricular (i.c.v.) injection. 2. Physiological parameters were monitored after consecutive doses of 0.5, 1.0 and 2.0 mg of PCP. 3. Dose-related changes seen, including bradycardia, hypotension and bradypnea, were opposite to those produced by i.v. doses. 4. Single doses of 1.0 or 2.0 mg of PCP confirmed the prior observations, and the latter provided the baseline for further observations on dogs receiving PCP before various i.c.v. pretreatments--atropine, haloperidol, phentolamine or propranolol--in efforts to characterize the central neurotransmitter system(s) involved in the PCP effects.

Anesthesia↗
PubMed1990

Pharmacologic and toxicologic effects of di(beta-phenylisopropyl)amine (DPIA) in rats and mice.

1. Di(beta-phenylisopropyl)amine (DPIA) given i.p. to mice and rats in sublethal doses caused increased motility, mild stereotypic behavior and suppression of food intake. Repeated daily doses led to enhanced motor stimulation, and in one group, 40% lethality, indicating development of "reverse tolerance". Brain monoamine modifiers prevented DPIA-induced motor activity. 2. Treatment with toxic i.p. doses of DPIA enabled determination of the LD50, which was 106.8 mg/kg for isolated mice and 89.7 mg/kg for mice kept in aggregation after dosing. Possible antidotal agents given before a high DPIA dose (LD50) protected significantly against lethality. 3. Combinations of DPIA with (+)-amphetamine in mice at lethal doses showed a subadditive synergism. 4. Effects of DPIA on the cardiovascular system, both i.v. in anesthetized rats and in isolated atrial preparations, were mainly opposite to those of (+)-amphetamine, namely decreases in blood pressure, force of contraction and heart rate.

Amphetamine↗
PubMed1987

A method to facilitate placement of screws for sagittal ramus osteotomy.

This article describes a method of placing screws for bilateral sagittal ramus osteotomies. The technique, a slight modification of previous methods, eliminates the need for use of a clamp, aids in proximal segment control, and employs a single transosseous wire and two transcortical screws. This method has been used in more than 50 cases and has been proved to be adaptable and stable, even without intermaxillary fixation.

Bone Screws↗
PubMed1987

Comparison of stimulants and hallucinogens on shuttle avoidance in rats.

Rats were trained to a high level of performance of a conditioned avoidance response in a shuttlebox to test effects of several classical stimulants in comparison to a variety of hallucinogens. A previously-reported biphasic pattern of effects of mescaline on shuttle avoidance was replicated and extended to 12 other hallucinogens of both phenylethylamine and indolealkylamine classes. Response patterns of hallucinogens could be differentiated from 3 stimulants and from a methoxyamphetamine compound that lacks hallucinogenic activity.

Amphetamines↗
PubMed1987

Toxicity of MDA (3,4-methylenedioxyamphetamine) considered for relevance to hazards of MDMA (Ecstasy) abuse.

Despite a paucity of data on its animal pharmacology and toxicology, MDMA [Ecstasy, XTC, ADAM; (+/-)-3,4-methylenedioxymethamphetamine] was introduced as an "underground" (FDA-unapproved) adjunct to psychotherapy in the late 1970's and early 1980's, in addition to its use as a recreational drug. Analysis of the limited experimental literature indicates that LD50's for MDMA in five species by several routes of administration tend to predict a significant human toxicity. MDMA was either equally toxic or slightly to moderately less toxic than its close congener, MDA, (+/-)-3,4-methylenedioxyamphetamine. It is suggested that extrapolation of the pharmacologic/toxicologic data available for MDA to MDMA should be assumed to be valid until disproven. Recently published canine data describe physiologic disturbances caused by acute overdosage of MDA, and also indicate the utility of chlorpromazine as an antidote preventing fatalities associated with severe hyperthermia, lactacidemia, hypertension and tachycardia. The toxicology of MDMA warrants further direct study in view of its continuing illegal distribution.

3,4-Methylenedioxyamphetamine↗
PubMed1987

Intravenous and intragastric self-administration of chlordiazepoxide in the rat.

Rats were implanted with intravenous (IV) or intragastric (IG) cannulas and allowed access, by lever-pressing on a CRF schedule, to chlordiazepoxide solution in 10-h sessions at doses of 0.1, 0.25, 0.5 and 1.0 mg/kg/injection. Self-administration behavior was acquired by both routes and for all doses of the drug by 60-70% of subjects tested. Subjects given access by the IV route showed more pronounced responding at the lower 2 doses and greater drug intake with the higher 2 doses than the IG group. A 2-lever study, controlling for possible motor effects of chlordiazepoxide, supports the interpretation that responding was indeed the result of reinforcing effects of chlordiazepoxide rather than an artifact.

Animals↗
PubMed1986

Effects of an i.v. lethal dose of 3,4-methylenedioxyamphetamine (MDA) in the dog and antagonism by chlorpromazine.

A high intravenous (i.v.) dose of MDA (20 mg/kg) to mongrel dogs elevated body temperature, heart rate, mean arterial pressure and other cardiovascular parameters initially, but only the 1st two remained high. Other functions soon became quite depressed, and death shortly ensued. Arterial pO2 decreased, but pH and pCO2 showed a biphasic response after an initial decrease, Dogs that received chlorpromazine (10 mg/kg, i.v.) after MDA showed stabilization of physiological parameters, and survival through 48 hr.

3,4-Methylenedioxyamphetamine↗