Kinetic modelling of haemodialysis removal of myoglobin in rhabdomyolysis patients

An extended two compartment model is proposed to describe the dynamics of myoglobin in rhabdomyolysis patients undergoing dialysis. Before using clinical data to estimate the model's unknown parameters, structural identifiability analysis was performed to determine the parameters uniqueness given certain clinical observations. A Taylor series expansion method was implemented which found that the model was structurally globally/uniquely identifiable for both on- and off-dialysis phases. The fitted model was then used in a predictive capacity showing that the use of Theralite high cut-off (HCO) or HCO 1100 dialyser gave a significant reduction in myoglobin renal exposure compared to standard haemodialysis (HD).

Chronic exercise stress in mice depresses splenic T lymphocyte mitogenesis in vitro

This study investigated changes in functional response to splenic T lymphocytes of mitogens following acute and chronic exposure to endurance exercise. Splenic T cell response in vitro to concanavalin A (Con A) and the total number of lymphocytes per spleen were compared between mice assigned to the following treatment conditions: (a) exercise training (EX) by treadmill running (28 m/min, 8 degrees slope for 30 min, 5 times per week for 4 weeks preceded by 2 weeks of endurance build-up), (b) exercise training as above followed by a single, acute bout of exercise to exhaustion (EX + AC) (35 m/min, 8 degrees slope, 30 min to 2 h duration) (c) exposure to the novel environment for 6 weeks without exercise (control), and exposure to the novel environment as in (c) followed by a single, acute bout of exercise to exhaustion. Treadmill running for 6 weeks significantly enhanced succinate dehydrogenase activity in skeletal muscle compared to the sedentary, control condition, and was broadly interpreted as indicative of a training effect. EX mice had significantly reduced splenic lymphocyte proliferative responses to optimal and supraoptimal concentrations of Con A compared with control animals. Incorporation of [3H]thymidine into splenic lymphocytes from EX + AC mice was the most markedly depressed. Total number of lymphocytes per spleen was significantly lower in EX compared with control mice. These results suggests that chronic exercise challenge in mice is associated with T lymphocyte hyporesponsiveness in the secondary lymphoid organs, such as the spleen.

Modulation of cellular immunity in malnutrition: effect of interleukin 1 on suppressor T cell activity

T-lymphocyte mitogenesis is impaired in protein-energy malnutrition. The effect of interleukin 1 (IL-1) on the augmentation of suppressor cell activity during concanavalin A-induced lymphocyte proliferation was measured using IL-1 and lymphocytes from protein malnourished and control rabbits. Addition of IL-1 to lymphocyte cultures from control donors enhanced the suppression of fresh lymphocytes to phytohaemagglutinin (PHA). Addition of IL-1 to lymphocyte cultures from malnourished donors abrograted the suppressor cell activity. Isoelectric focusing showed the presence of a protein band with a pI of about 7.0 in the IL-1 supernatants from protein malnourished and control donors. The results suggest that severe protein malnutrition alters the ability of T-lymphocytes to respond appropriately to IL-1 rather than simply affecting synthesis of this monokine.

Monocyte factors modulate in vitro T-lymphocyte mitogenesis in protein malnutrition

This study investigated changes in T-lymphocyte mitogenesis and immunoregulatory cytokines during protein malnutrition. In vitro T cell response to concanavalin A was compared among protein deprived (PD), energy restricted pair fed control (PF), and ad libitum control (C) rabbits. Cell cultures were supplemented with crude monocyte supernatants (CMS) from PD, PF or C animals at either 1% or 8% final concentration in culture. Prostaglandin E2 (PGE2) concentration of unstimulated or stimulated lymphocyte culture supernatants and CMS was determined. Lymphocyte cultures from PD, PF and C animals had enhanced 3H-thymidine incorporation when supplemented with C and/or PF derived CMS. Addition of 8% CMS from PD rabbits inhibited proliferation below levels observed in mitogen-only stimulated groups in all cultures. At the 1% concentration, inhibition was seen in PD and C derived cells cultures and modest enhancement was seen in PF cultures. PGE2 concentration in supernatants from stimulated and unstimulated lymphocyte cultures from PD rabbits were higher than in C and PF cell cultures. These results suggest (a) that under appropriate culture conditions lymphocytes from PD donors are capable of enhanced proliferation and (b) that depressed T cell mitogenesis observed in protein malnutrition may reflect alterations in immunoregulatory signals. The role of interleukin 1 (IL-1) and PGE2 in the modulation of this response is discussed.

Fever and survival in aged mice after endotoxin challenge

Male C57BL/6 mice of 12, 19, and 24 months of age received injections of low (25 micrograms 100 g-1 body weight) or high (50 micrograms 100 g-1 body weight) doses of Salmonella typhosa endotoxin and were exposed to ambient temperatures below (24 degrees C) or within (30 degrees C) the thermoneutral zone. Old mice (19 and 24 months) developed initial fevers followed by hypothermia in response to endotoxin challenge at 24 degrees C, irrespective of dose; 12-month-old-mice became hypothermic at 24 degrees C following injection of the high dose of endotoxin only. At 30 degrees C, 12- and 19-month-old mice developed and maintained fever over 4 hr in response to endotoxin compared with the 24-month-old mice who were unable to maintain fevers. Logistic regression analysis showed that age, ambient temperature, and body temperature responses were significant predictors of survival outcome in endotoxin-treated mice; of these, age and ambient temperature had the strongest effects.

Body temperature responses of aged mice to ambient temperature and humidity stress

Male C57BL/6 mice aged 6 to 7 months, 13 to 14 months, and 19 to 20 months were acutely exposed to four ambient temperature (15 degrees C, 20 degrees C, 30 degrees C, 35 degrees C) and two relative humidity (50% rh, 80% rh) conditions. Three-hour average rectal temperatures were compared across age groups and environmental conditions. At the two temperature extremes of 15 degrees C and 35 degrees C, there was a very marked age-associated hypothermia and hyperthermia, respectively. This hypothermic response was maintained by the 19 to 20-month-old mice during exposure to 20 degrees C and thermoneutrality (30 degrees C). At any given ambient temperature, relative humidity had no effect on thermoregulatory function in the oldest mice, whereas the 6 to 7-month- and 13 to 14-month-old mice were sensitive to the effects of humidity at 15 degrees C and 20 degrees C.