Peroxisomal disorders.

The concept that there are human disease states that are associated with abnormal peroxisomal function is of recent origin. This is due in part to the relatively recent discovery of the organelle itself by de Duve in 1983, and to the earlier belief that it was a vestigial structure in mammals. The recognition that the organelle is significant in mammals was ushered in by Paul Lazarow's observation that rat peroxisomes catalyze the beta-oxidation of fatty acids. By 1981, more than 40 enzymes had been localized to the peroxisome, and the number continues to grow. Respect for the physiological role of the peroxisome in man has been heightened by our recent recognition that peroxisome malfunction causes profound disturbances. The Zellweger cerebro-hepato-renal syndrome represents the most serious peroxisomal disease. It is associated with malfunction of virtually every organ, and children with the disease usually do not survive beyond the 4th month. Application of newly developed diagnostic techniques has shown that the clinical spectrum and frequency of peroxisomal disorders are greater than had been realized. Eleven separate peroxisomal disorders have now been identified. Our laboratory alone has identified more than 2000 patients. Disturbances of very long chain fatty acid and ether phospholipid metabolism are present in 9 of the 11 peroxisomal disorders. In this presentation, we will provide an overview of the peroxisomal disorders, with emphasis on disturbances of fatty acid and ether lipid metabolism.     

Memory and anxiety disorders.

Experimental psychopathologists have identified varying patterns in memory bias in people with depressive and anxiety disorders. Individuals suffering from depression tend to exhibit explicit memory deficits for positively-valanced material, and sometimes exhibit biases for retrieving negative self-relevant information as well. Most studies, however, provide scant evidence for implicit memory biases in depression. In contrast to depression, anxiety disorders are rarely associated with enhanced explicit memory for threat-related information (with the exception of panic disorder). Evidence for implicit memory biases for threat in these syndromes is mixed. After providing an overview of findings on memory abnormalities in depressive and anxiety disorders, data from several new studies bearing on posttraumatic stress disorder (PTSD) in Vietnam combat veterans and in women with histories of childhood sexual abuse are presented. Involving directed forgetting, implicit memory and autobiographical cueing paradigms, these experiments point to a pattern of abnormalities linked to PTSD rather than to trauma per se.     

Tremor disorders. Diagnosis and management.

Tremor is commonly encountered in medical practice, but can be difficult to diagnose and manage. It is an involuntary rhythmic oscillation of a body part produced by reciprocally innervated antagonist muscles. Tremors vary in frequency and amplitude and are influenced by physiologic and psychological factors and drugs. Categorization is based on position, posture, and the movement necessary to elicit the tremor. A resting tremor occurs when the body part is in repose. A postural tremor occurs with maintained posture and kinetic tremor with movement. Various pathologic conditions are associated with tremors. Essential tremor, which is the most common, is postural and kinetic, with a frequency between 4 and 8 Hz, and involves mainly the upper extremities and head. Essential tremor responds to treatment with primidone, beta-blockers, and benzodiazepines. Parkinson''s disease causes a 4- to 6-Hz resting tremor in the arms and legs that responds to the use of anticholinergics and a combination of carbidopa and levodopa. Tremor can also be a manifestation of Wilson''s disease, lesions of the cerebellum and midbrain, peripheral neuropathy, trauma, alcohol, and conversion disorders. Treatment should be directed to the underlying condition. Stereotactic thalamotomy of thalamic stimulation is a last resort.