<Emphasis Type="Italic">Daphnia</Emphasis> growth is hindered by chemical information on predation risk at high but not at low food levels

Daphnia hyalina × galeata (Dhg) and D. pulicaria (Dp) are ready to pay greater costs in terms of predation risk avoidance at high rather than at low food levels. Such costs are easier to assess in Daphnia than in large long-lived and difficult-to-handle herbivores, since they can be precisely determined in a few-day experiment as the reduced growth (P=A−R) resulting from diminished assimilation (A) and/or increased respiration (R). In experiments with Daphnia grown for six days from the neonate to the first clutch of eggs, which were given different levels of algal food (Scenedesmus at concentrations from 0.05 to 1.60 mg C l⁻¹), individual growth was lower in the presence of fish kairomone (chemical information on fish predation; present at a concentration that induces antipredator defensive behavior and life histories) than in the absence of kairomone (control). The difference from the control was negligible at the lowest food levels, and gradually increased with increasing food concentration. At a food concentration of 1.6 mg C l⁻¹, growth was reduced by 9–32 and 0–8% in Dhg and Dp, respectively, compared to the controls. A similar reduction was observed in the body length of six-day-old animals (Dhg 6–19%, Dp 0–14%), but not in the first clutch reproductive effort (clutch volume). Daphnia had a greater number of eggs per clutch in the presence of the kairomone, but smaller eggs, so that the total volume of eggs in a clutch was the same with and without kairomone. The amplification of the effect of the kairomone due to high food levels was weaker in Dp, a species that rarely coexists with planktivorous fish in natural habitats.     

Changes in the growth and enzyme level of Zymomonas mobilis under oxygen-limited conditions at low glucose concentration

Zymomonas mobilis growing aerobically with 20 g glucose^–1 (carbon-limited) in a chemostat exhibited an increase in both the molar growth yield (Y_x/s) and the maximum molar growth yield (Y_x/s ^max) and a decrease in both the specific substrate consumption rate (q_s) and the maintenance energy consumption rate (m_e). Stepwise increase in the input oxygen partial pressure showed that anaerobic-to-aerobic transitional adaptation occurred in four stages: anaerobic (0 mm HgO₂), oxygen-limited (7.6– 230 mm HgO₂), intermediate (273 mm HgO₂), and oxygen excess (290 mm HgO₂). The steady-state biomass concentration, Y_x/s, and intracellular ATP content increased between oxygen partial pressures of 7.6 and 120 mm HgO₂, accompanied by a decrease in the q_s and the specific acid production rate. The membrane ATPase activity decreased with increasing oxygen partial pressure and reached its lowest levels at 273 mm HgO₂, which was the highest input oxygen partial pressure where steady-state conditions were possible. Glucokinase, glucose-6-phosphate dehydrogenase, glyceraldehyde-3-phosphate dehydrogenase, and alcohol dehydrogenase activities also decreased when the oxygen partial pressure was increased above 15 mm Hg, whereas pyruvate decarboxylase was unaffected by aeration. Growth inhibition at 290 mm HgO₂ was characterised by a drastic reduction in the pyruvate kinase activity and a collapse in the intracellular ATP pool. The growth and enzyme data suggest that at low glucose concentrations and oxygen-limited conditions, the increase in biomass yields is a reflection of a redirection of ATP usage rather than a net increase in energy production. Received: 14 August 1996 / Accepted: 31 January 1997     

Plasma N-glycome composition associates with chronic low back pain

Background

Low back pain (LBP) is the symptom of a group of syndromes with heterogeneous underlying mechanisms and molecular pathologies, making treatment selection and patient prognosis very challenging. Moreover, symptoms and prognosis of LBP are influenced by age, gender, occupation, habits, and psychological factors. LBP may be characterized by an underlying inflammatory process. Previous studies indicated a connection between inflammatory response and total plasma N-glycosylation. We wanted to identify potential changes in total plasma N-glycosylation pattern connected with chronic low back pain (CLBP), which could give an insight into the pathogenic mechanisms of the disease.