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The effect of temperature on eccentric contraction-induced isometric force loss in isolated perfused rat medial gastrocnemius muscle
Vasaghi Gharamaleki B, Keshavarz M, Gharibzadeh Sh, Marvi H, Mosayebnejad J, Ebrahimi Takamjani E,
Volume 66, Issue 6 (9-2008)
Abstract

Background: The typical features of eccentric exercise-induced muscle damage are delayed-onset muscle soreness (DOMS) and prolonged loss of muscle strength. It has been shown that passive warmth is effective in reducing muscle injury. Due to the interaction of different systems in vivo, we used isolated perfused medial gastrocnemius skeletal muscle to study the direct effect of temperature on the eccentric contraction-induced force loss.

Methods: After femoral artery cannulation of a rat, the left medial gastrocnemius muscle was separated and then the entire lower limb was transferred into a prewarmed (35oC) chamber. With the chamber temperature at 31, 35 and 39oC before and during eccentric contraction. Isometric force loss was measured after 15 eccentric contractions (N=7-9).

Results: Maximum contraction force reduction has been used as an index for eccentric contraction-induced force loss. In this study eccentric contraction caused a significant reduction in maximum isometric tension (p<0.01), but no significant difference was seen in isometric force loss at 31oC and 39oC compared with that at 35oC.

Conclusions: Our results suggest that temperature changes before or during eccentric contractions have no effect on eccentric contraction-induced force loss.


The effects of temperature and birth weight on the transition rate of hypothermia in hospitalized neonates using Markov models
Akbarzadeh Baghban A, Jambarsang S, Pezeshk H, Nayeri F,
Volume 70, Issue 5 (8-2012)
Abstract
Background: Hypothermia is an important determinant of survival in newborns, especially among low-birth-weight ones. Prolonged hypothermia leads to edema, generalized hemorrhage, jaundice and ultimately death. This study was undertaken to examine the factors affecting transition from hypothermic state in neonates.
Methods:  The study consisted of 439 neonates hospitalized in NICU of Valiasr in Tehran, Iran in 2005. The neonates' rectal temperature was measured immediately after birth and every 30 minutes afterwards, until neonates passed hypothermia stages. In order to estimate the rate of transition from neonatal hypothermic state, we used multi-state Markov models with two covariates, birth weight and environmental temperature. We also used R package to fit the model.
Results:  Estimated transition rates from severe hypothermia and mild hypothermia were 0.1192 and 0.0549 per minute, respectively. Weight had a significant effect on transition from hypothermia to normal condition (95% CI: 0.1364-0.4165, P<0.001). Environmental temperature significantly affected the transition from hypothermia to normal stage (95% CI: 0.0439-0.4963, P<0.001).
Conclusion:  The results of this study showed that neonates with normal weight and neonates in an environmental temperature greater than 28 °C had a higher transition rate from hypothermia stages. Since birth weight at the time of delivery is not under the control of medical staff, keeping the environmental temperature in an optimum level could help neonates to pass through the hypothermiastages faster.


Numerical modeling of the brain hypothermia by cooling the cerebrospinal fluid
Aisa Rassoli , Malikeh Nabaei , Nasser Fatouraee , Ghaemeh Nabaei ,
Volume 75, Issue 1 (4-2017)
Abstract

Background: Brain hypothermia by reducing the temperature of the cerebrospinal fluid is done by a cooling pad in the thoracic region and protect brain from the ischemic injuries. Along with the spinal cord, the brain is an essential partner in the central nervous system, and similarly, it is surrounded and protected from the bony skull and from shock by cerebrospinal fluid. The brain analyzes information that is both internal and external to the body, transforms the information into sensations, and stores them as memories. So in this study we investigated the brain hypothermia by finite element modeling.

Methods: To investigate this phenomenon, in this study a numerical model of the head with respect to the structure of brain tissue and its contribution to heat transfer is presented in the fluid lab of the Amirkabir University of Tehran in January of 2016. In this model, Pennes's bioheat equation and finite element analysis has been used to predict temperature distribution in the brain tissue. The model geometry is designed in two state without considering the ventricles of the brain that are involved in the production of cerebrospinal fluid and with considering cerebrospinal fluid. So, in the second case, the cerebrospinal flow is considered as a heat transfer factor.

Results: We concluded that with cooling about 5 °C, in the first model without considering the ventricles, the gray matter temperature is reduced by about 4 °C and there is no change in white matter temperature. In the second model temperature distribution became more asymmetric. The temperature reduced about 3 °C in the corners. However, the temperature reduction at the edge of brain tissue and near cerebrospinal fluid were about 0.5 °C.

Conclusion: It was observed that in the case of ischemia, the temperature drop was higher than normal. So, during brain injuries to prevent serious damage, the brain metabolism can be reduced by cooling the spinal fluid.


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