PURPOSE We have previously shown that lactose, but not mannose, promotes the assembly of nascent photoreceptor outer segments in the absence of the retinal pigment epithelium (RPE). The purpose of the present study was to determine if, in addition to the improved outer segment assembly observed in the presence of lactose, biosynthetic changes in Muller cells could also be detected. METHODS Th...

Glutamine synthetase was purified from the cerebral cortex of adult rats and characterized. Polyclonal rabbit antibodies were raised against the enzyme, purified and their specific anti-(glutamine synthetase) activity determined. A primary astroglial culture was prepared from newborn Sprague-Dawley rats. Astrocytes at different ages of development were incubated in the presence and absence of g...

Methylammonium is a substrate for the ammonium transport system of Azotobacter vinelandii. During cellular uptake methylammonium is rapidly converted to a less polar metabolite (E. M. Barnes, Jr., and P. Zimniak, J. Bacteriol. 146:512-516, 1981). This metabolite has been isolated from A. vinelandii and identified as gamma-glutamylmethylamide by mass spectroscopy, 1H nuclear magnetic resonance s...

The principal initial product of metabolism of 13N-labeled ammonium by Anabaena cylindrica grown with either NH4+ or N2 as nitrogen source is amide-labeled glutamine. The specific activity of glutamine synthetase is approximately half as great in NH4+-grown as in N2-grown filaments. After 1.5 min of exposure to 13NH4+, the ratio of 13N in glutamate to 13N in glutamine reaches a value of approxi...

Glutamate-induced excitotoxicity has been proposed to mediate the death of retinal ganglion cells in glaucoma. The metabolic dependence of glutamatergic neurons upon glia via the glutamate/glutamine cycle to provide the precursor for neurotransmitter glutamate is well established. Thus, the aim of the present work was to study the retinal glutamate/glutamine activity in eyes with hypertension i...

Maize glutamine synthetase cDNA clones were isolated by genetic selection for functional rescue of an Escherichia coli delta glnA mutant growing on medium lacking glutamine. The Black Mexican Sweet cDNA library used in this study was constructed in pUC13 such that cDNA sense strands were transcribed under the control of the lac promoter. E. coli delta glnA cells were transformed with cDNA libra...

stimulates glutamine release at the expense of tissue glutamate while decreasing or having little effect on alanine release (Ruderman & Lund, 1972; Chang & Goldberg, 1978). In the perfused rat hindlimb total glutamine production by resting muscle is over 4-fold greater than ammonia production, but the addition of methionine sulphoximine (a glutamine synthetase inhibitor) reverses this pattern (...

Energy charge [(ATP) + (1/2) (ADP)]/[(ATP) + (ADP) + (AMP)] and glutamine synthetase activity (transferase reaction) of roots increase in a near congruent manner when decotyledonized sunflower plants (Helianthus annuus L. var. Mammoth Russian) are grown in nitrate for 9 days. Replacement of nitrate with ammonium for the final 2 days leads to a higher energy charge and increased enzyme activity....