Betty J. Williams

Correlation between brain adenyl cyclase activity and spontaneous motor activity in rats after chronic reserpine treatment

Reserpine (0.5 mg/kg) was administered daily to rats for a period of 8–12 days. Motor activity was measured 23–24 h after each injection. Twenty-four hours subsequent to the last reserpine injection, animals were sacrificed for determination of whole brain catecholamine concentration and adenyl cyclase activity. Rats which had shown a depression of motor activity after 3 days of treatment were hyperactive after 8–12 days. Brain norepinephrine concentrations in reserpine-treated animals ranged from 5 to 11% of control levels. In brain preparations from reserpine-treated rats, basal adenyl cyclase activity was unchanged from control, but the stimulation of cyclase activity produced by 10−4M norepinephrine was more than twice as great as that seen in controls. There was a strong positive correlation between the change in motor activity and the response of adenyl cyclase to norepinephrine, suggesting that the change in adenyl cyclase responsiveness may account for some of the increase in spontaneous activity occurring in rats after chronic reserpine treatment.

Effects of chronic lead treatment on some cardiovascular responses to norepinephrine in the rat.

Abstract Rats were treated with lead via the mothers milk from birth to weaning. After a lead-free period of approximately 4 months, responses to norepinephrine were tested. Neither the pressor effect nor the enhancement of myocardial cAMP accumulation caused by norepinephrine was altered by prior lead treatment. However, norepinephrine caused significantly more cardiac arrhythmias in lead-treated animals than in controls. Even doses of norepinephrine which caused no significant ECG abnormalities in control animals were arrhythmogenic in lead-treated rats. It is concluded that lead treatment causes changes in cardiac conduction which are not readily reversed by termination of lead exposure.

Increased vascular response to adrenergic stimulation in rats exposed to cadmium

Adult female rats were injected ip with a low total dose (1–2.25 mg/kg) or a high total dose (7.5 mg/kg) of cadmium, as cadmium chloride with cysteine, given in divided doses spaced over 1–3 wk. At 1–4 wk after administration of high doses of cadmium, anesthetized rats were less responsive to the pressor effect of norepinephrine (1.0–10.0 μg/kg, iv) than were controls. This type of effect has been described previously by other investigators and was not explored further in this study. In contrast to the results in high‐cadmium animals, anesthetized rats of the low‐cadmium group, tested 1–4 wk after exposure, were more sensitive to the pressor effects of norepinephrine (0.1–10.0 μg/kg, iv) than were controls. This increase in sensitivity was no longer apparent in animals tested 16–26 wk later. Neither basal blood pressure in anesthetized animals nor systolic pressure in conscious animals of the low‐cadmium series was different from the corresponding value in controls. Aortic rings isolated from low‐cadmium ...

The effects of cadmium on adrenergic neurotransmission invitro

Abstract The effect of cadmium on the response of isolated perfused rabbit ear arteries to nerve stimulation and norepinephrine administration was examined. Cadmium in concentrations of .075–.25μM caused enhancement of the pressor responses to nerve stimulation, but higher concentrations caused inhibition of the response. The pressor response to norepinephrine was also inhibited by cadmium, but required a 100x higher concentration than that needed for inhibition of the response to nerve stimulation. The dual effect of cadmium on the response to nerve stimulation suggests a plausible explanation for the conflicting reports in the literature regarding the blood pressure effects of cadmium exposure. The enhancement by low concentrations of cadmium of the response to nerve stimulation provides a possible mechanism for cadmium-induced hypertension.

The protective effect of phentolamine against cardiac arrhythmias in the rat.

Norepinephrine was given by continuous infusion at a rate of 80 microgram/kg/min for 2 min. Norepinephrine caused the appearance of cardiac arrhythmias, primarily ventricular extrasystoles. The prior administration of phentolamine, even in a dose which did not antagonize the pressor effect of norephinephrine, prevented extrasystole production by norepinephrine. Tolazoline and yohimbine, in doses which did not affect the vasopressor action of norepinephrine, also suppressed extrasystole production. It is concluded that the antiarrhythmic effect of phentolamine, does not require antagonism of alpha-adrenoceptors of the type found in the vasculature, but may involve effects on a different type of alpha-adrenoceptors in the heart.

Induction of swimming in the high spinal stingray by L-DOPA.

Stingrays with high spinal transections, which do not spontaneously locomote, can be induced to swim by intravenous injection of L-DOPA. The L-DOPA-induced swim of the spinal animal is associated with patterns of EMG activity that appear similar to those of the spontaneous swim of the decerebrate preparation. However, in contrast to the decerebrate condition, the L-DOPA-induced cycles of swimming are slower and less vigorous. Furthermore, secondary periodicites and altered intersegmental timing relationships are also evident.

Effect of chronic lead exposure on the direct and indirect components of the cardiac response to norepinephrine.

Abstract Lead exposure to neonates produces an enhanced sensitivity of the adult rat heart to the arrhythmogenic effect of norepinephrine. The present study examines the possibility that both the direct and reflex effects of norepinephrine might be affected by early lead exposure. Rats were exposed to 0.2% lead acetate via maternal milk from birth to weaning, then were allowed a lead-free period of 3 months. Rat pups of sodium acetate-treated dams served as controls. Norepinephrine produced more ventricular extrasystoles in lead-exposed rats than methoxamine at doses that produced similar changes in mean systemic blood pressure. While bilateral vagotomy or atropine pretreatment decreased the frequency of cardiac arrhythmias, norepinephrine still caused significantly more extrasystoles in lead-exposed than control rats. The arrhythmogenic effect of methoxamine observed in lead-exposed animals could be completely prevented by bilateral vagotomy. Isolated perfused hearts from lead-exposed animals exhibited more irregularities in rhythm after norepinephrine than hearts from control animals. It is concluded that while effects on the vagus nerve participate in the lead-induced sensitivity to norepinephrine, direct cardiac effects are also involved.

Separation of cyclic 3',5'-AMP from ATP, ADP, and 5'-AMP by precipitation with inorganic compounds.

Abstract A variety of inorganic compounds, which combine to produce insoluble salts or which are themselves insoluble in water, have been tested for their ability to separate cyclic 3′,5′-AMP from ATP, ADP, and 5′-AMP. It was found that this separation could be effected not only by the Be(OH) 2 ZnSO 4 combination reported in the literature, but also by combinations of ZnSO 4 and BaCl 2 , Na 2 CO 3 and BaCl 2 , Na 2 SO 4 and BaCl 2 , ZnSO 4 and Na 2 CO 3 , and Na 2 CO 3 and CdCl 2 ; and by suspensions of BaCO 3 , BaSO 4 , or ZnCO 3 . None of the inorganic compound combinations tested separated cyclic 3′,5′-AMP from adenosine. The inorganic compound precipitation method provides a simple but efficient method to separate cyclic 3′,5′-AMP from ATP, ADP, and 5′-AMP. It is evident that certain advantages are offered if such a procedure is included to remove ATP, ADP, and 5′-AMP prior to the column, thin-layer, gas-liquid, or paper chromatography in the assay of adenyl cyclase, cyclic nucleotide phosphodiesterase, 5′-nucleotidase, or other enzyme activity.

Student Perceptions of the Professional Behavior of Faculty Physicians

Abstract This study was conducted to obtain a baseline understanding of the professional behavior of clinical faculty physicians from the medical students’ perspective. Students completed a professionalism evaluation of supervising faculty at the end of each required third-year clerkship over a one year period. Results were analyzed by specific behaviors and across clerkships. Differences were noted in the frequency of the types of problems seen, and varied by clerkship discipline. The most common transgressions of professional behavior reported were the use of derogatory language towards other services or patients and the disrespectful treatment of others. Our study served to provide objective feedback to the faculty about student perceptions of faculty as role models for professionalism while on clinical rotations.

Effect of acetylcholine on changes in contractility, heart rate and phosphorylase activity produced by isoprenaline, salbutamol and amino-phylline in the perfused guinea-pig heart.

1 Isolated perfused hearts of guinea‐pigs were given graded doses of isoprenaline, salbutamol and aminophylline, both before and during acetylcholine infusion. 2 The three agonists produced increases in contractile force, heart rate and ventricular glycogen phosphorylase activity. 3 Acetylcholine, in the concentration used, had no effect on any of the measured variables but did antagonize the effects of the three agonists on contractility and phosphorylase activity. The positive chronotropic responses were unaltered by acetylcholine infusion. 4 The ratio of the dose required for a standard heart rate response to the dose producing a standard contractile force response was different for each agonist. 5 The selective antagonism of the contractile response to isoprenaline, salbutamol and aminophylline suggest that different mechanisms are involved in the initiation of positive inotropic and chronotropic responses.