Paraplegia following aortic surgery

It has long been recognised that paraplegia may occur after various surgical procedures on the heart and the aorta. Paraplegia occurring following traumatic rupture of the aorta has not been commonly reported due to the dismal prognosis of such rupture. Over the past 3 years, we have encountered five patients who survived traumatic rupture of the aorta and developed paraplegia, and three patients who had chronic dissecting aneurysms of the aorta who also developed paraplegia. These patients continued to show neurological and functional improvement over the years. We are presenting these cases to illustrate their neurological improvement and to show that the prognosis for these patients may not be as dismal as previously reported once they survive the acute episode.

Role of central epinephrine in regulation of anterior pituitary hormone secretion

Hypothalamic regulation of anterior pituitary hormones is thought to be mediated by the release of stimulatory and/or inhibitory peptides that are, in turn, regulated by catecholaminergic neurons. The recent development of selective epinephrine (EPI) synthesis inhibitors has made it possible to disrupt central EPI neurotransmission without affecting norepinephrine or dopamine. These compounds were used in the present investigation to assess the involvement of brain EPI systems in regulation of GH, LH, and prolactin (PRL) in male and ovariectomized female rats. Inhibition of central EPI synthesis (1) inhibited episodic and morphine-, but not clonidine-induced GH release, and (2) blocked the LH surge induced by estrogen and progesterone, but did not affect episodic LH release in hormonally untreated rats. Inhibition of peripheral (adrenal) EPI synthesis had no effect on these hormones. Results of these studies suggest an excitatory role for EPI in regulation of GH and LH secretion, mediated by stimulation of GH-releasing hormone and LHRH, respectively. EPI does not appear to have a major function in regulation of PRL secretion.

Heterotopic ossification in the hand of a patient with spinal cord injury

Heterotopic ossification (HO), reported to occur in 20% to 40% of spinal cord injured patients, has been described in the hips, knees, shoulders and elbows, but not in the hands or around the phalangeal joints. This report is believed to be the first of HO of the hand after spinal cord injury. Nine weeks after injury, a diving accident, a 27-year-old man having C6 quadriplegia, motor complete, sensory incomplete, developed acute swelling and loss of range of motion in both hands. Serum alkaline phosphatase showed no significant rise. Bone scan demonstrated increased uptake in many joints of the left hand with x-rays remaining normal. Repeat films three weeks later demonstrated calcific densities adjacent to the midshaft of the proximal phalanx of the left finger. Twice daily range of motion of the hand resulted in improved range of motion. the etiology of HO in spinal cord injured patients remains unknown, and we have no explanation of its occurrence in the hands of this patient.

Inhibition of alpha-receptor-induced Ca2+ release and Ca2+ influx by Mn2+ and La3+

The influence of Mn2+ and La3+ on alpha-receptor-stimulated Ca2+ movements was examined in arterial smooth muscle of the rabbit aorta. Both cations cause an inhibition of phenylephrine (PE) contractile response which exhibits a different pattern at low and high cation concentrations. At 0.1-1.0 mM inhibition by Mn2+ and La3+ was predominately due to a reduction in Ca2+ influx reflected as inhibition of the slow phase of contraction and reduction in PE-stimulated 45Ca uptake. PE log dose-response curves were shifted to the right in a non-parallel manner by 1 mM Mn2+ such that responses to lower PE concentrations were more inhibited. However, in the presence of 10 mM Mn2+ PE responses are equally inhibited at all PE levels. At 10 mM both Mn2+ and La3+ also inhibited PE-stimulated Ca2+ release resulting in a reduction in both the rapid phase of contraction and in the magnitude of PE stimulation of 45Ca efflux. The effects of Nm2+ (1 or 10 mM) on contraction and 45Ca efflux were rapidly reversible, while the effect of La3+ was not. Inhibition of Ca2+ release by 10 mM Mn2+ and La3+ was not caused by displacement of releasable Ca2+, but appeared to reflect their occupation of a superficially located receptor modulating site. The inhibition of Ca2+ influx by lower concentrations of Mn2+ may illustrate the functional consequence of configurational changes in the alpha 2-form of the receptor which have been recently described at lower concentrations of divalent cations.

Poisoning with 4-aminopyridine: report of three cases

Four-aminopyridine is an acutely toxic avicide considered by the manufacturer to be a bird "repellant" because only a small number of birds are acutely poisoned, become disoriented, and emit a distress cry frightening other members of the flock. Four-aminopyridine dramatically enhances transmission at the neuromuscular junction and other synapses, and has been employed clinically in the treatment of prolonged paralysis caused by antibiotics and muscle relaxants, and in the Eaton-Lambert syndrome. In this paper we report the results of an acute poisoning misadventure in three adult males. We review the animal toxicology, summarize the neurophysiological research using 4-AP as a potassium channel blocker, comment on clinical applications, and outline the management of overdose with this agent.

Pulmonary arteriovenous fistula. Preoperative evaluation with a Swan-Ganz catheter

A balloon-tipped catheter was used in the preoperative assessment of a patient with a solitary pulmonary arteriovenous fistula and coexistent chronic obstructive pulmonary disease and ischemic heart disease. Studies before and two months following surgical excision of the fistula showed that the increase in arterial oxygenation (49 mm Hg vs 77 mm Hg) and the reduction in the fraction of the shunted cardiac output (37% vs 6%) closely approximated the predicted preoperative estimates.

Effects of internal divalent cations on voltage-clamped squid axons

We have studied the effects of internally applied divalent cations on the ionic currents of voltage-clamped squid giant axons. Internal concentrations of calcium up to 10 mM have little, if any, effect on the time-course, voltage dependence, or magnitude of the ionic currents. This is inconsistent with the notion that an increase in the internal calcium concentration produced by an inward calcium movement with the action potential triggers sodium inactivation or potassium activation. Low internal zinc concentrations ( approximately 1 mM) selectively and reversibly slow the kinetics of the potassium current and reduce peak sodium current by about 40% with little effect on the voltage dependence of the ionic currents. Higher concentrations ( approximately 10 mM) produce a considerable (ca. 90%) nonspecific reversible reduction of the ionic currents. Large hyperpolarizing conditioning pulses reduce the zinc effect. Internal zinc also reversibly depolarizes the axon by 20-30 mV. The effects of internal cobalt, cadmium, and nickel are qualitatively similar to those of zinc: only calcium among the cations tested is without effect.