The regulatory effects of growth rate of cyclic AMP levels on carbon catabolism and respiration in Escherichia coli K-12

Cyclic AMP levels in glucose and succinate-fluid and ammonia-limited glucose-containing continuous cultures of Escherichia coli were measured at different bacterial growth rates. Intracellular cyclic AMP concentrations were fairly constant (about 5 μM) at all dilution rates used when glucose was limiting. In ammonia-limited glucose cultures the cyclic AMP content was much lower (about 0.3 μM). In succinate-limited cultures cyclic AMP levels fell from 2.7 to 0.8 μM as dilution rate increased from 0.05 to 0.4 h^?1.The effects of cyclic AMP on respiratory and carbon catabolic enzyme levels were studied. There was no indication of a direct cyclic AMP involvement in the regulation of these cellular functions. It seems more likely that the variations in enzyme levles observed resulted from variation of the specific growth rate of cultures.     

Effects of temperature on growth rate and body size in the Mediterranean Sea anemone Actinia equina

Actinia equina is the most common sea anemone in the rocky intertidal zone of the Mediterranean coast of Israel, yet little is known about its biology in this habitat. We examined variation in polyp growth at several temperatures within the local range. Under laboratory conditions, only polyps at low temperatures (15 and 20 °C) grew, whereas those at higher temperatures (25 and 30 °C) lost body mass. Seasonal monitoring of pedal disk diameter over 18 months at field sites showed that polyps shrank significantly during the summer when temperatures were high. We conclude that at summer seawater temperatures along the coast of Israel (28.7-29.5 °C), polyps of A. equina are unable to balance their metabolic requirements with energy input, resulting in a seasonal reduction in biomass. Polyps appear able to acclimate to high temperatures, but not sufficiently to avoid shrinkage of tissues.     

Triglyceride depletion of brown adipose tissue enables analysis of mitochondrial respiratory function in permeabilized biopsies

The research on mitochondrial functions in adipocytes has increasingly evidenced that mitochondria plays an important role in the onset and/or progression of obesity and related pathologies. Mitochondrial function in brown adipose tissue (BAT) has been classically assessed by measuring either the levels/activity of mitochondrial enzymes, or the respiration in isolated mitochondria. Isolation of mitochondria is not advantageous because it demands significant time and amount of tissue and, as tissue homogenates, disrupts biochemical and physical connections of mitochondria within the cell. Here, we described a new and efficient protocol to analyze the mitochondrial respiratory states in BAT biopsies that relies on intracellular triglyceride depletion followed by tissue permeabilization. In addition to minimizing tissue requirements to ∼17 mg wet weight, the proposed protocol enabled analysis of all mitochondrial respiratory states, including phosphorylation (OXPHOS), no-phosphorylation (LEAK), and uncoupled (ETS) states, as well as the use of substrates for complex I, complex II, and cytochrome c; together, these features demonstrated mitochondrial integrity and validated the preparation efficacy. Therefore, the protocol described here increases the possibilities of answering physiological questions related to small BAT regions of human and animal models, which shall help to unravel the mechanisms that regulate mitochondrial function in health and disease.