p103 and A60: novel proteins of the neuronal membrane-associated cytoskeleton.

Associated with the neuronal plasma membrane are cytoskeletal proteins which probably control the specialization of the membrane into axonal and dendritic domains. Specialized isoforms of the proteins spectrin and ankyrin are located in each region and provide molecular mechanisms for locating specific transmembrane proteins at required points. However, spectrin and ankyrin were defined by extensions of the model for the erythrocyte membrane, an analogy unlikely to provide a complete account of the neuronal membrane skeleton. We have defined two new proteins of the neuronal membrane skeleton, designated p103 and A60. p103 is enriched in post-synaptic densities and binds with high affinity to integral membrane proteins--we suggest that it may have a role in linking the cytoskeleton to synaptic glycoproteins. A60 is a 60 kDa axonal protein, which appears to form a lining to the axolemma. It is almost exclusively axonal, although some neurons (such as Purkinje cells) appear to contain it in the cell body and initial dendrite segment. A60 binds both ankyrin and neurofilaments, and may have a role in transmitting information critical to axonal morphology to the membrane.     

The presence or absence of light during flotation restricted environmental stimulation: Effects on plasma cortisol,blood pressure,and mood

This study examined the effect of light on relaxation associated with flotation restricted environmental stimulation therapy (REST), as measured by plasma cortisol, mean arterial pressure, and psychometric parameters. Twenty-one subjects were paired by baseline cortisol levels into two groups: one experiencing flotation REST in the presence of light (REST-L) and one experiencing flotation REST in the absence of light (REST-D). Subjects were 15 male and 6 female students aged 22–28 in normal health who had not experienced REST. Repeated flotation REST (8 sessions) either with light or without light was associated with a decrease in plasma cortisol and a decrease in mean arterial pressure, with no differences in effectiveness between groups. The psychometric assessment of mood, using the POMS scale, before and after sessions 1 and 8 revealed mood state improvement in both REST-L and REST-D groups. These data suggest that the presence of light did not compromise the flotation REST experience, as evidenced by the lack of difference between REST-L and REST-D groups.     

The interaction of folic acid derivatives in the methylation of homocysteine

1. The cobalamin-independent synthesis of methionine from serine and homocysteine by ultrasonic extracts of E. coli with tetrahydropteroyltriglutamate as cofactor was inhibited competitively by tetrahydropteroylmonoglutamate and derivatives which were readily converted into this compound. 2. The potency of these inhibitors was directly related to their ability to function as cofactors or substrates in the alternative, cobalamin- dependent mechanism for homocysteine methylation. 3. The cobalamin-dependent and -independent mechanisms of homocysteine methylation were both inhibited by reduced derivatives of aminopterin in a similar manner. 4. It was tentatively concluded that the inhibition was due to a competitive interaction between the folates for N(5)N(10)-methylenetetrahydrofolate reductase.     

Histamine receptor effects on dissipation of an intracellular proton gradient of isolated gastric mucosal surface cells

The effects of histamine and several H1 and H2 receptor agents on Na+/H+ and Cl-/HCO-3 exchange systems of isolated gastric mucosal surface cells were studied. The cells were acid-loaded by the NH4Cl prepulse technique and the spontaneous Na+- and HCO-3-induced dissipation of the intracellular proton gradient (pHi) was followed using the metachromatic dye acridine orange. Histamine (10(-2-5) M) stimulates HCO-3-induced dissipation of the pHi but has no effect on Na+-induced or spontaneous dissipation. The H1 agonist 2-(2-aminoethyl)pyridine and the H2 agonist dimaprit also have no effect on Na+-induced or spontaneous pHi dissipation. However, both of these agents mimic the effect of histamine on HCO-3-induced dissipation, but only at a higher concentration (10(-3) M). The combination of 2-(2-aminoethyl)pyridine and dimaprit produces a histamine-like effect at lower concentrations (10(-5) and 10(-4) M). The effects of histamine are blocked by either the H1 antagonists diphenhydramine and pyrilamine or the H2 antagonists cimetidine and SKF 93479. The results suggest that the effect of histamine on HCO-3-induced dissipation of a pHi in gastric mucosal surface cells is mediated through a coordinated mechanism involving both H1 and H2 receptor sites.