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Background and Objectives: No studies have reported corrugator muscle activity associated with pain in people with pain. This study aimed to develop an objective pain assessment method using corrugator muscle activity with pressure pain stimulation to the skeletal muscle. Methods: Participants were 20 adults (a mean ± SD age of 22.0 ± 3.1 years) with chronic neck/shoulder pain. Surface electromyography (sEMG) of corrugator muscle activity at rest (baseline) and without and with pressure pain stimulation applied to the most painful tender point in the shoulder was recorded. Participants evaluated the intensity of the neck/shoulder pain and the sensory and affective components of pain with pressure stimulation using a visual analogue scale (VAS). The percentages of integrated sEMG (% corrugator activity) without and with pressure pain stimulation to the baseline integrated sEMG were compared, and the relationships between the % corrugator activity and the sensory and affective components of pain VAS scores were evaluated. Results: Without pressure stimulation, an increase in corrugator muscle activity due to chronic neck/shoulder pain was not observed. The % corrugator activity with pressure pain stimulation was significantly higher than that without stimulation (p < 0.01). A significant positive correlation between corrugator muscle activity and the affective components of pain VAS scores with pressure stimulation was found (ρ = 0.465, p = 0.039) and a tendency of positive correlation was found for the sensory component of pain VAS scores (ρ = 0.423, p = 0.063). Conclusions: The increase in corrugator muscle activity with pressure pain stimulation to the tender point in adults with chronic neck/shoulder pain was observed, although increased corrugator muscle activity resulting from the chronic neck/shoulder pain was not. These findings suggest that corrugator muscle activity with pressure pain stimulation can be a useful objective indication for tender point sensitivity assessment in the skeletal muscle with pain. [ABSTRACT FROM AUTHOR]

Glutamate synthesis in Escherichia coli in alkaline medium appears to be stimulated by osmotic stress, but does not appear to be regulated by high intracellular levels of potassium ions. Cells grown at a pH above 8 accumulate glutamate at higher rates than cells grown in lower pHs. Although a high potassium ion concentration is associated with this accumulation of glutamate, mutant cells that could not transport potassium ions also accumulated glutamate.

We examined the gene expression of the Escherichia coli cad operon, which consisted of the genes cadB and cadA (lysine decarboxytase), using cells possessing cadB-lacZ fusion gene. The cad operon was expressed when O2 was limited, and the expression was optimal at pH6.3. The β-galactosidase activity was lowered by the addition of sodium carbonate to the medium. The expression of the cad operon was reduced in cells containing the plasmid-encoding ornithine decarboxylase, which produced carbon dioxide, indicating that the gene expression of the cad operon was reguiated by carbon dioxide (or its derivatives). It is known that the Krebs cycle is a major pathway for producing carbon dioxide, and that its activity is repressed when O2 is limited. Thus, our present results suggested that the physiological role of the cad operon is to supply carbon dioxide when its internal level is lowered under 02-limiting conditions at a low pH. [ABSTRACT FROM AUTHOR]