Cholinergic REM sleep induction response correlation with endogenous major depressive subtype

We compared central cholinergic responsiveness (using the latency to induction of rapid eye movement sleep after arecoline challenge as a response marker) in 90 subjects: patients with major depressive disorder (MDD) (n = 53), nonaffective psychiatric controls (n = 17), and normal controls (n = 20). MDD patients as a whole showed a supersensitive cholinergic response compared to nonaffective patients and normal subjects. Further analysis indicated a strong association between cholinergic supersensitivity and endogenous subtype of MDD, including a significant correlation with specific endogenous features such as distinct quality of mood, anhedonia, lack of reactivity, and agitation. Unlike rapid eye movement (REM) latency (a more conventional physiological marker), cholinergic sensitivity did not correlate with age or severity of illness but only with the presence of endogenous features. Previously described sleep physiological correlates such as REM latency and REM density of the first REM period also distinguished between endogenous and nonendogenous MDD. There was a statistically significant correlation between REM latency and arecoline REM induction response.     

Catecholamine depletion produces irrepressible saccadic eye movements in normal humans

To determine the effect of catecholamine depletion on ocular motor pathways in humans, we studied the eye movements of 3 normal subjects who received the drug metyrosine (alpha-methylparatyrosine). This drug temporarily depleted dopamine and norepinephrine, as measured by a reduction in the metabolite, 3-methoxy-4-hydroxy-phenylethyleneglycol (MHPG). Saccadic, pursuit, and vestibulo-ocular eye movements were recorded using infrared oculography with subjects both on placebo and on metyrosine. The most consistent effect observed with metyrosine was an increase in the amplitude and frequency of saccadic intrusions during fixation and pursuit. Two of the 3 subjects also had shortened time constants for the vestibulo-ocular reflex, attributable in part to the sedative effect of catecholamine depletion. The increase in saccadic intrusions implies that catecholamines modulate the activity of a subpopulation of suppressor motor neurons in the human brainstem.     

Antimicrobial peptides with unusual amino acid compositions and unusual structures

Antimicrobial peptides, which constitute an important component of innate immunity in animal and plant kingdom, are ubiquitously distributed in nature. However, they differ widely in their sizes, sequences and structures. On the basis of their structure they have been broadly classified into three classes: a) linear peptides with propensity for amphiphilic alpha-helical structure, b) peptides with beta or alphabeta structure stabilized by different number of disulfide bridges and c) peptides with over-representation of certain amino acids or unusual structures. Although considerable amount of work has been done on peptides of all the three classes, recent reviews have emphasized on peptides belonging to the first two classes. The present review focuses on the peptides belonging to the third group. The antimicrobial peptides discussed in this article include aromatic amino acid-rich peptides, (Pro-Arg)-rich peptides, unusual defensins and defensin-like molecules, unusual antimicrobial peptides from amphibians, bacteriocins with unusual structure and anionic antimicrobial peptides.     

Physostigmine induction of depressive symptomatology in normal human subjects

Nine normal volunteers, screened for the absence of a personal or family history of affective disorders and free of concurrent marijuana usage, received intravenous infusions of high dose physostigmine or saline in a randomized, double-blind, counterbalanced paradigm. Self-rating and observer ratings both demonstrated a statistically significant, physostigmine associated increase in depressive-type symptoms in the group as a whole, particularly pronounced in certain individuals. These results are the first report of physostigmine associated depressive symptomatology in normal subjects. While our findings are discrepant with two previous studies, our use of multiple self-ratings, and some differences in physostigmine dosage and infusion times might have contributed to this difference. These findings suggest that high dose physostigmine may represent a pharmacological model of depression in normal subjects, or alternatively may be diagnostic of vulnerability to affective disorder in certain subjects free of a previous history of affective disturbances.