Biomedical subjects

Yuval Heled

Publications and source records attributed to Yuval Heled.

26 records · Page 2Linked to original sources

PubMed2003

Plasma antioxidant status and cell injury after severe physical exercise.

Strenuous exercise leads to an increase in metabolic rate, increased production of reactive oxygen species, and compromised antioxidant defense systems. To study the effects of oxidative stress during strenuous exercise, a homogeneous group of 31 male subjects participated in a 6-month, 5 days/week training schedule involving two extreme marches of 50 km and 80 km at sea level, separated by 2 weeks of regular training. Each participant carried 35 kg of extra weight. Blood samples were drawn immediately before and after each march. Twenty-nine subjects completed the 50-km march, and only 16 completed the 80-km march. Plasma levels of reduced ascorbic acid, total ascorbate, and dehydroascorbate did not undergo significant changes during either march. However, the 50- and 80-km marches led to 25% and 37% increases, respectively, in plasma levels of uric acid; due presumably to increases in the metabolic rate and consequent pyrimidine nucleotide metabolism. Both marches led to an approximately 10-fold increase leakage of creatine phosphokinase into the plasma. Likewise, plasma levels of aspartate transaminase, a characteristic marker of liver injury, increased approximately 4-fold. Plasma levels of bilirubin, creatine, urea, and glucose also increased. Plasma protein carbonyl content, a marker of protein oxidative damage, decreased significantly during each march. These results are discussed with respect to the consideration that elevation of the respiration rate during exercise leads to production of more reactive oxygen species than the antioxidant systems can scavenge. Plausible explanations for leakage of molecules into the plasma are discussed.

Aged↗

PubMed2003

Physical exercise enhances protein kinase C delta activity and insulin receptor tyrosine phosphorylation in diabetes-prone psammomys obesus.

We recently reported that physical exercise prevents the progression of type 2 diabetes mellitus in Psammomys obesus, an animal model of nutritionally induced type 2 diabetes mellitus. In the present study we characterized the effect of physical exercise on protein kinase C delta (PKC delta) activity, as a mediator of the insulin-signaling cascade in vivo. Three groups of Psammomys obesus were exposed to a 4-week protocol: high-energy diet (HE/C), high-energy diet and exercise (HE/EX), or low-energy diet (LE/C). None of the animals in the HE/EX group became diabetic, whereas all the animals in the HE/C group became diabetic. After overnight fast, intraperitoneal (IP) insulin (1U) caused a greater reduction in blood glucose levels in the HE/EX and LE/C groups compared to the HE/C group. Tyrosine phosphorylation of insulin receptor (IR), insulin receptor substrate-1 (IRS-1), and phosphatidylinositol 3 kinase (PI3 kinase) was significantly higher in the HE/EX and LE/C groups compared with the HE/C group. Finally, IR-associated PKC delta was higher in the HE/EX and LE/C groups compared to the HE/C group. Coprecipitation of PKC delta with IR was higher in the HE/EX and LE/C groups compared to the HE/C group. Thus, we suggest that 4 weeks of physical exercise results in improved insulin-signaling response in Psammomys obesus accompanied by a direct connection between PKC delta and IR. We conclude that this mechanism may be involved in the preventive effect of exercise on type 2 diabetes mellitus in Psammomys obesus.

Animals↗

PubMed2003

Combined environmental stress and physiological strain indices for physical training guidelines.

The purpose of this study was to develop guidelines based on the previously described environmental stress index (ESI) and physiological strain index (PSI) for work-rest cycles (WRC) during training, especially in the military. The ESI was introduced as a potential substitute for the Wet Bulb Globe Temperature Index because of the very high correlation coefficients between them. The ESI is constructed from the fast-reading meteorological response sensors ambient temperature (Ta), relative humidity (RH), and global radiation (GR), which require only a few seconds to reach equilibrium. The ESI, the first stress index using direct measurements of solar radiation (SR), is calculated as follows: ESI = 0.63Ta - 0.03RH + 0.002SR + 0.0054 (Ta x RH) - 0.073(0.1 + SR)(-1). The PSI is based on heart rate (HR) and rectal temperature (Tre) and can indicate heat strain online and analyze databases. The PSI is constructed as follows: PSI = 5(Tret - Tre0) x (39.5 - Tre0)(-1) + 5(HRt - HR0) x (180 - HR0)(-1), where Tre0 and HR0 are the initial Tre and HR, and Tret and HRt are simultaneous measurements taken at any time. The PSI is scaled from 0 to 10, whereby the respective variables, PSIHR and PSITre, representing the cardiovascular and thermoregulation systems, can contribute up to five units to the overall strain assessment. To integrate the PSI and ESI, we decided to use only the PSIHR component, which represents the metabolic rate and the strain reflected by the cardiovascular system. Furthermore, PSIHR is easier to measure, is easier to implement, and simplifies the integration with ESI. Concomitantly, PSIHR categorizes the strain between 0 and 5, the higher the value, the higher the strain. We believe that the use of the PSI WRC values will help in decreasing the risk of future heat injuries.

Algorithms↗

PubMed2003

Hypothermia and local cold injuries in combat and non-combat situations--the Israeli experience.

INTRODUCTION: Cold weather has been recognized in the Israel Defense Forces (IDF) as a potential medical and operational threat to the soldier. Although regulations have been issued to cope with this situation, every year about 20 cases of hypothermia (T(core) < 35 degrees C) and peripheral cold injuries are reported. METHODS: This study was aimed at following cold weather injuries (CI) in the IDF in the period 1994-2001. 136 cases were reported to our institute during this period. All patients were from the general population of young (20 +/- 2 yr), male soldiers in the IDF. All were classified a priori as healthy, active subjects. RESULTS: Of these patients, 51% were diagnosed with mild hypothermia and 49% with peripheral CI. Among those soldiers who suffered from peripheral CI, less than 5% were diagnosed with frostbite. Most of the cases (76%) occurred in the winter months; however, 10% occurred in the spring, 13% in autumn, and 2 cases (1%) were reported in the summer. The majority of all CI cases occurred during routine scheduled training (51%), and 15% occurred during routine duties. Of the cases, 34% occurred during combat operations (mainly ambushing and surveillance). DISCUSSION: The present study provides data on CI cases in an army where the awareness of the hazards involved in hostile environments is extensive, and in which detailed regulations aimed to prevent these injuries are common practice. The Israeli experience indicates that CI is preventable in most instances by following a few simple regulations and providing proper education to the soldiers and their commanding officers.

Adolescent↗

PubMed2003

[Pre-hospital rewarming methods for hypothermia casualties].

Various methods exist for rewarming hypothermia casualties. Most of these methods necessitate sophisticated medical equipment or vigorous hemodynamic and electrolytic monitoring. Therefore, only a few methods remain suitable for pre-hospital scenarios. The current work reviews the literature regarding these pre-hospital rewarming methods, focusing on their efficacy and compatibility to the cold pre-hospital environment with its limited resources. By relying on endogenous heat producing mechanisms and by isolating the victim, one can achieve fairly efficient rewarming for mild hypothermia (rectal temperature of 32 degrees C-35 degrees C) casualties. Many consider this as an independent rewarming method (passive or endogeneous rewarming method), advisable for mild hypothermia cases. There are also many active rewarming methods, suitable for pre-hospital treatment. These methods, however, suppress the endogenous heat producing mechanisms, and therefore are not more efficient than passive rewarming for mild hypothermia cases. In moderate or severe hypothermia casualties, hypothermia (rectal temperature below 32 degrees C) however, is characterized by suppressed or deficient endogenous heat producing mechanisms. Passive rewarming is not enough in these cases, necessitating the addition of active, central or peripheral rewarming methods. Studies regarding the use of various active rewarming methods in severe hypothermia casualties revealed low rewarming efficacy for the low heat capacity methods, such as warm air inhalation, and a high rewarming efficacy for the high heat capacity methods, such as forced air methods.

Accidents↗

PubMed2002

Dalteparin sodium (fragmin) administration following acute infarction does not affect myocardial perfusion and function in swine.

BACKGROUND: Heparin and low molecular weight heparin (LMWH) derivatives are considered angiogenic factors in ischemic and infarcted myocardium. However, the effect of dalteparin sodium (fragmin, a LMWH derivative) on angiogenesis post infarction has not yet been investigated.Purpose. To assess the effect of systemically-administered dalteparin sodium on left ventricular perfusion and function during remodeling in swine subjected to acute microembolization infarction (MI).Methods. MI was induced in 12 anesthetized female pigs which randomly received dalteparin sodium (12,500U) or placebo through intra-peritoneal osmotic pump, for one week, beginning immediately after the MI. Myocardial perfusion and function were measured using radionuclear scan and echocardiography, respectively, at baseline, immediately post MI, and at 2 and 4 weeks post MI. Dobutamine stress echocardiography was performed 4 weeks post MI. Serum level of basic fibroblast growth factor (bFGF) was analyzed using a commercially available ELISA kit.Results. No differences were observed in myocardial perfusion at all time points following MI. No significant changes were observed in myocardial function and wall motion during the 4 weeks follow-up period, or after dobutamine administration. Serum bFGF did not change throughout the study period.Conclusion. Under the setting of the current experiment, one week of dalteparin sodium administration does not affect myocardial perfusion and function following acute infarction in swine, either at rest or following pharmacological stress.

Animals↗

PubMed2002

Physical exercise prevents the development of type 2 diabetes mellitus in Psammomys obesus.

We hypothesized that exercise training might prevent diabetes mellitus in Psammomys obesus. Animals were assigned to three groups: high-energy diet (CH), high-energy diet and exercise (EH), and low-energy diet (CL). The EH group ran on a treadmill 5 days/wk, twice a day. After 4 wk, 93% of the CH group were diabetic compared with only 20% of the EH group. There was no difference in weight gain among the groups. Both EH and CH groups were hyperinsulinemic. Epididymal fat (% of body weight) was higher in the CH group than in either the EH and or the CL group. Protein kinase C (PKC)-delta activity and serine phosphorylation were higher in the EH group. No differences were found in tyrosine phosphorylation of the insulin receptor, insulin receptor substrate-1, and phosphatidylinositol 3-kinase among the groups. We demonstrate for the first time that exercise training effectively prevents the progression of diabetes mellitus type 2 in Psammomys obesus. PKC-delta may be involved in the adaptive effects of exercise in skeletal muscles that lead to the prevention of type 2 diabetes mellitus.

Animals↗

PubMed2002

[Multi-organ failure in a young soldier: a clinical-pathological meeting].

This clinical-pathological conference took place at the Sourasky Medical Center, Tel Aviv, on February 21, 2001. We present the case of a young and previously healthy soldier who developed multi-organ failure with predominant liver dysfunction following exertional heatstroke. The patient's clinical course consisted of an early phase of transient encephalopathy, associated with hyperthermia, hypophosphatemia, mild laboratory indications of renal failure, rhabdomyolysis and consumption coagulopathy. Following an intermediate convalescing phase that lasted a single day the patient deteriorated into a catastrophic course with hemodynamic instability, fulminant hepatic failure, respiratory distress, kidney failure, rhabdomyolysis, coagulopathy and coma. He died 4 days later. In this article we elaborate on the association of heatstroke with multiple organ dysfunction syndrome in general, and fulminant liver failure in particular. The nature of hypophosphatemia and the possible role of additional injury from acetaminophen are discussed.

Acute Kidney Injury↗