A speculative model of affective illness cyclicity based on patterns of drug tolerance observed in amygdala-kindled seizures

In this article, we discuss molecular mechanisms involved in the evolution of amygdala kindling and the episodic loss of response to pharmacological treatments during tolerance development. These phenomena allow us to consider how similar principles (in different neurochemical systems) could account for illness progression, cyclicity, and drug tolerance in affective disorders. We describe the phenomenon of amygdala-kindled seizures episodically breaking through effective daily pharmacotherapy with carbamazepine and valproate, suggesting that these observations could reflect the balance of pathological vs compensatory illness-induced changes in gene expression. Under certain circumstances, amygdala-kindled animals that were initially drug responsive can develop highly individualized patterns of seizure breakthroughs progressing toward a complete loss of drug efficacy. This initial drug efficacy may reflect the combination of drug-related exogenous neurochemical mechanisms and illness-induced endogenous compensatory mechanisms. However, we postulate that when seizures are inhibited, the endogenous illness-induced adaptations dissipate (the “time-off seizure” effect), leading to the re-emergence of seizures, a re-induction of a new, but diminished, set of endogenous compensatory mechanisms, and a temporary period of renewed drug efficacy. As this pattern repeats, an intermittent or cyclic response to the anticonvulsant treatment emerges, leading toward complete drug tolerance. We also postulate that the cyclic pattern accelerates over time because of both the failure of robust illness-induced endogenous adaptations to emerge and the progression in pathophysiological mechanisms (mediated by long-lasting changes in gene expression and their downstream consequences) as a result of repeated occurrences of seizures. In this seizure model, this pattern can be inhibited and drug responsivity can be temporarily reinstated by several manipulations, including lowering illness drive (decreasing the stimulation current.), increasing drug dosage, switching to a new drug that does not show crosstolerance to the original medication, or temporarily discontinuing treatment, allowing the illness to re-emerge in an unmedicated animal. Each of these variables is discussed in relation to the potential relevance to the emergence, progression, and suppression of individual patterns of episodic cyclicity in the recurrent affective disorders. A variety of clinical studies are outlined that specifically test the hypotheses derived from this formulation. Data from animal studies suggest that illness cyclicity can develop from the relative ratio between primary pathological processes and secondary endogenous adaptations (assisted by exogenous medications). If this proposition is verified, it further suggests that illness cyclicity is inherent to the neurobiological processes of episode emergence and amelioration, and one does not need to postulate a separate defect in the biological clock. The formulation predicts that early and aggressive long-term interventions may be optimal in order to prevent illness emergence and progression and its associated accumulating neurobiological, vulnerability factors.     

Mechanisms for the biomechanical destruction of L1210 leukemia cells: A rate regulator for metastasis

Mechanical trauma appears to be one significant cause of the rapid intravascular death of cancer cells and, as such, could act as an important rate regulator for the metastatic process. Intravascular mechanical trauma to cancer cells is thought to be a consequence of shape transitions, occurring when they are deformed from spherical shape by entry into, and passage along, capillaries having smaller diameters than themselves. These transitions from spherical shape require increases in surface area; first, an apparent increase in surface area is accomplished by a reversible, nonlethal surface membrane unfolding. If this is insufficient to meet geometric demands, it is followed by a true increase in surface area, resulting in increased tension in the cancer cell surface membrane, leading to its lethal rupture.     

Intravenous prostacyclin (PGI2) infusion to 108 patients with ischaemic peripheral vascular disease: phase II-open study.

We recently reported the results of a double-blind trial of PGI2 in 108 patients with ischaemic peripheral vascular disease Stage II according to Fontaine. They were randomly allocated to receive an intravenous infusion of either PGI2 (6 ng/kg/min over 8 hours daily for 5 consecutive days) or placebo and classified as treatment responders or non-responders on the basis of changes in absolute and relative walking times. Patients treated with placebo and those who did not improve in this double blind trial entered an open trial in which they all received infusion of PGI2 (6 ng/kg/min over 8 hours daily for 5 consecutive days). The results of this open trial are reported here. Patients who had been allocated to PGI2 in the blind trial had significantly (p less than 0.01) longer walking times as compared to placebo-treated patients prior to receiving the second (PGI2) infusion. PGI2-infusion caused significant (p less than 0.01) prolongation of walking times in both groups up to the 2nd follow-up month. One month after infusion 52% (23 patients) of the initially placebo-treated patients and 31% (14 patients) of the initially PGI2-treated patients were scored as positive treatment responders (p less than 0.01).