Short-term effects of gamma ray bursts on Earth

The aim of the present work is to study the potential short-term atmospheric and biospheric influence of Gamma Ray Bursts on the Earth. We focus in the ultraviolet flash at planet`s surface, which occurs as a result of the retransmission of the gamma radiation through the atmosphere. This would be the only important short-term effect on life. We mostly consider Archean and Proterozoic eons, and for completeness we also comment on the Phanerozoic. Therefore, in our study we consider atmospheres with oxygen levels ranging from 10(-5) to 1 of the present atmospheric level, representing different moments in the oxygen rise history. Ecological consequences and some strategies to estimate their importance are outlined.

Short-term movements of the South American rattlesnake (Crotalus durissus) in southeastern Brazil

Ecological studies of movements in animals require extensive knowledge of direction, distance and frequency of movements. The purpose of this study was to describe the daily and seasonal movements in a population of the South American rattlesnake, Crotalus durissus. The study population inhabits a cerrado area in southeastern Brazil. Snakes were tracked with externally attached radio-transmitters and thread bobbins. Larger animals tended to make more extensive daily movements, moving further from the initial site of capture. There were no differences in average daily movements between sexes. Site fidelity was higher in the dry season for both sexes. Both sexes moved distances twice as long as those calculated by drawing a straight line between consecutive points. The movement pattern of C. durissus seemed to be similar to that observed in other tropical pit vipers, such as species of the genus Bothrops.

Short-Term Modulation of Extracellular Signal-Regulated Kinase 1/2 and Stress-Activated Protein Kinase/c-Jun NH2-Terminal Kinase in Pancreatic Islets by Glucose and Palmitate Possible Involvement of Ceramide

Objectives: The effect of glucose and palmitate on the phosphorylation of proteins associated with cell growth and survival (extracellular signal-regulated kinase 1/2 [ERK1/2] and stress-activated protein kinase/c-Jun NH2-terminal kinase [SAPK/JNK]) and on the expression of immediate early genes was investigated. Methods: Groups of freshly isolated rat pancreatic islets were incubated in 10-mmol/L glucose with palmitate, LY294002, or fumonisin B1 for the measurement of the phosphorylation and the content of ERK1/2, JNK/SAPK, and v-akt murine thymoma viral oncongene (AKT) (serine 473) by immunoblotting. The expressions of the immediate early genes, c-fos and c-jun, were evaluated by reverse transcription-polymerase chain reaction. Results: Glucose at 10 mmol/L induced ERK1/2 and AKT phosphorylations and decreased SAPK/JNK phosphorylation. Palmitate (0.1 mmol/L) abolished the glucose effect on ERK1/2, AKT, and SAPK/JNK phosphorylations. LY294002 caused a similar effect. The inhibitory effect of palmitate on glucose-induced ERK1/2 and AKT phosphorylation changes was not observed in the presence of fumonisin B1. Glucose increased c-fos and decreased c-jun expressions. Palmitate and LY294002 abolished these latter glucose effects. The presence of fumonisin B1 abolished the effect induced by palmitate on c-jun expression. Conclusions: Our results suggest that short-term changes of mitogen-activated protein kinase and AKT signaling pathways and c-fos and c-jun expressions caused by glucose are abolished by palmitate through phosphatidylinositol 3-kinase inhibition via ceramide synthesis.

Evidence that L-glutamine is better than L-alanine as gluconeogenic substrate in perfused liver of weaned fasted rats submitted to short-term insulin-induced hypoglycaemia

Gluconeogenesis in livers from overnight fasted weaned rats submitted to short-term insulin-induced hypoglycaemia (IIH) was investigated. For this purpose, a condition of hyperinsulinemia/hypoglycaemia was obtained with an intraperitoneal (ip) injection of regular insulin (1.0 U kg(-1)). Control group (COG group) received ip saline. The studies were performed 30 min after insulin (IIH group) or saline (COG group) injection. The livers from IIH and COG rats were perfused with L-alanine (5 mM), L-lactate (2 mM)), L-glutamine (10 mM) or glycerol (2 mM). Hepatic glucose, L-lactate and pyruvate production from L-alanine was not affected by IIH. In agreement with this result, the hepatic ability in producing glucose from L-lactate or glycerol remained unchanged (IIH group vs. COG group). However, livers from IIH rats showed higher glucose production from L-glutamine than livers front COG rats and, in the IIH rats, the production of glucose from L-glutamine was higher than that front L-alanine. The higher glucose production in livers from the IIH group. when compared with the COG group was due to its entrance further on gluconeogenic pathway. Taken together. the results suggest that L-glutamine is better than L-alanine, as gluconeogenic substrate in livers of hypoglyceaemic weaned rats. Copyright (C) 2008 John Wiley & Sons. Ltd.

Liver glycogen metabolism during short-term insulin-induced hypoglycemia in fed rats

The activities of glycogen phosphorylase and synthase during infusions of glucagon, isoproterenol, or cyanide in isolated liver of fed rats submitted to short-term insulin-induced hypoglycemia (IIH) was investigated. A condition of hyperinsulinemia/hypoglycemia was obtained with an intraperitoneal injection of regular insulin (1.0 U kg(-1)). The control group received ip saline. The experiments were carried out 60 min after insulin (IIH group) or saline (COG group) injection. The rats were anesthetized and after laparotomy, blood was collected from the vena cava for glucose and insulin measurements. The liver was their infused with glucagon (1 nM), isoproterenot (2 mu M), or cyanide (0.5 mM) during 20 min and a sample of the organ was collected for determination of the activities of glycogen phosphorylase and synthase 5 min after starting and 10 min after stopping the infusions. The infusions of cyanide, glucagons, and isoproterenol did not change the activities of glycogen synthase and glycogen phosphorylase. However, glycogen catabolism was decreased during the infusions of glucagon and isoproterenol in IIH rats, being more intense with isoproterenol (p < 0.05), than glucagon. It was concluded that short-term IIH promoted changes in the liver responsiveness of glycogen degradation induced by glucagon and isoproterenol without a change in the activities of glycogen phosphorylase and synthase. Copyright (c) 2008 John Wiley & Sons, Ltd.

Effect of short-term creatine supplementation on markers of skeletal muscle damage after strenuous contractile activity

The protective effect of short-term creatine supplementation (CrS) upon markers of strenuous contractile activity-induced damage in human and rat skeletal muscles was investigated. Eight Ironman triathletes were randomized into the placebo (Pl; n = 4) and creatine-supplemented (CrS; n = 4) groups. Five days prior to the Ironman competition, the CrS group received creatine monohydrate (20 g day(-1)) plus maltodextrin (50 g) divided in two equal doses. The Pl group received maltodextrin (50 g day(-1)) only. The effect of CrS (5 g day(-1)/kg body weight for 5 days) was also evaluated in a protocol of strenuous contractile activity induced by electrical stimulation in rats. Blood samples were collected before and 36 and 60 h after the competition and were used to determine plasma activities of creatine kinase (CK), lactate dehydrogenase (LDH), aldolase (ALD), glutamic oxaloacetic acid transaminase (GOT), glutamic pyruvic acid transaminase (GPT), and C-reactive protein (CRP) level. In rats, plasma activities of CK and LDH, muscle vascular permeability (MVP) using Evans blue dye, muscle force and fatigue were evaluated. Activities of CK, ALD, LDH, GOT, GTP, and levels of CRP were increased in the Pl group after the competition as compared to basal values. CrS decreased plasma activities of CK, LDH, and ALD, and prevented the rise of GOT and GPT plasma activities. In rats, CrS delayed the fatigue, preserved the force, and prevented the rise of LDH and CK plasma activities and MVP in the gastrocnemius muscle. CrS presented a protective effect on muscle injury induced by strenuous contractile activities.

Short-term induction of thrombocytopenia delays periodontal healing in rats with periodontal disease: participation of endostatin and vascular endothelial growth factor

Background and Objective: Platelets contain factors, including VEGF and endostatin, that can modulate the healing process. We evaluated the effects of severe thrombocytopenia on periodontal healing in rats and determined the contribution of VEGF and endostatin to the healing process. Material and Methods: Rats were distributed into three test groups and two control groups. Cotton ligatures were placed at the gingival margin level of the lower first molar in the test groups. Sham-operated rats and rats in one of the periodontitis groups were killed 15 days later. Rats in the remaining two periodontitis groups had the ligatures removed in order to study the spontaneous recovery from the periodontal disease 15 days later, and these rats were treated with rabbit antiplatelet serum, in order to induce thrombocytopenia, or normal rabbit serum. An additional group without ligatures received antiplatet serum in the same period. Results: After ligature removal, rats treated with normal rabbit serum showed reduced myeloperoxidase activity, decreased alveolar bone loss and increased numbers of blood vessels. Thrombocytopenia caused a delay in alveolar bone regeneration, a decrease in the number of vessels and a modest decrease in myeloperoxidase activity. In the rats with periodontitis, serum endostatin concentrations were slightly decreased and serum VEGF remained unchanged compared with sham-operated animals. After ligature removal, a significant VEGF increase and endostatin decrease were observed in the rats treated with normal rabbit serum. Thrombocytopenia led to a dramatic fall in both VEGF and endostatin concentrations. Conclusion: Thrombocytopenia leads to a delay of periodontal healing in the situation of experimental periodontitis, which might be mediated in part by a decrease in the serum concentration of VEGF and endostatin derived from the platelets. However, other factors derived from the platelets may also have contributed to a delay of periodontal healing in the rats with thrombocytopenia.

Comparison between cold water immersion therapy (CWIT) and light emitting diode therapy (LEDT) in short-term skeletal muscle recovery after high-intensity exercise in athletes-preliminary results

In the last years, phototherapy has becoming a promising tool to improve skeletal muscle recovery after exercise, however, it was not compared with other modalities commonly used with this aim. In the present study we compared the short-term effects of cold water immersion therapy (CWIT) and light emitting diode therapy (LEDT) with placebo LEDT on biochemical markers related to skeletal muscle recovery after high-intensity exercise. A randomized double-blind placebo-controlled crossover trial was performed with six male young futsal athletes. They were treated with CWIT (5A degrees C of temperature [SD +/- 1A degrees]), active LEDT (69 LEDs with wavelengths 660/850 nm, 10/30 mW of output power, 30 s of irradiation time per point, and 41.7 J of total energy irradiated per point, total of ten points irradiated) or an identical placebo LEDT 5 min after each of three Wingate cycle tests. Pre-exercise, post-exercise, and post-treatment measurements were taken of blood lactate levels, creatine kinase (CK) activity, and C-reactive protein (CRP) levels. There were no significant differences in the work performed during the three Wingate tests (p > 0.05). All biochemical parameters increased from baseline values (p < 0.05) after the three exercise tests, but only active LEDT decreased blood lactate levels (p = 0.0065) and CK activity (p = 0.0044) significantly after treatment. There were no significant differences in CRP values after treatments. We concluded that treating the leg muscles with LEDT 5 min after the Wingate cycle test seemed to inhibit the expected post-exercise increase in blood lactate levels and CK activity. This suggests that LEDT has better potential than 5 min of CWIT for improving short-term post-exercise recovery.

Effect of Short-term High-Dose Creatine Supplementation on Measured GFR in a Young Man With a Single Kidney

It currently is unknown whether creatine supplementation is safe for people with or at risk of kidney disease. We report on the short-term effects of creatine supplementation on kidney function in a young man with a single kidney and mildly decreased glomerular filtration rate (GFR). A 20-year-old man who had undergone unilateral nephrectomy and presented with mildly decreased GFR without kidney damage underwent a trial with 35 days of creatine supplementation (20 g/d for 5 days followed by 5 g/d for the next 30 days) and had his kidney function monitored. After the intervention, (51)Cr-EDTA clearance (pre, 81.6 mL/min/1.73 m(2); post, 82.0 mL/min/1.73 m(2)), proteinuria (protein excretion: pre, 130 mg/d; post, 120 mg/d), and electrolyte levels were unchanged. Albuminuria, serum urea level, and estimated creatinine clearance were decreased (pre, 4.6 mg/d; post, 2.9 mg/d; pre, 37 mg/d; post, 28 mg/dL; and pre, 88 mL/min/1.73 m(2); post, 71 mL/min/1.73 m(2), respectively), whereas serum creatinine level was slightly increased (pre, 1.03 mg/dL; post, 1.27 mg/dL), falsely suggesting kidney function impairment. This prospective report suggests that short-term creatine supplementation may not affect kidney function in an individual with a single kidney, mild decreased GFR, and ingesting a high-protein diet (ie, 2.8 g/kg/d). This finding has great relevance considering that creatine-induced kidney disease has been a growing concern, even for healthy people. Am J Kidney Dis 55: e7-e9. (C) 2010 by the National Kidney Foundation, Inc.

Sodium Tungstate on Some Biochemical Parameters of the Parotid Salivary Gland of Streptozotocin-Induced Diabetic Rats: A Short-Term Study

Several studies have shown the antidiabetic properties of sodium tungstate. In this study, we evaluated some biochemical parameters of the parotid salivary gland of streptozotocin-induced diabetic rats treated with sodium tungstate solution (2 mg/ml). The studied groups were: untreated control (UC), treated control (TC), untreated diabetic (UD), and treated diabetic (TD). After 2 and 6 weeks of treatment, parotid gland was removed and total protein and sialic acid (free and total) concentration and amylase and peroxidase activities were determined. Data were compared by variance analysis and Tukey test (p < 0.05). The sodium tungstate treatment modestly decreased the glycemia of streptozotocin-induced diabetic rats. At week 2 of the study, parotid gland of diabetic rats presented a reduction of total protein concentration (55%) and an increase of amylase (120%) and peroxidase (160%) activities, free (150%) and total (170%) sialic acid concentration. No alteration in the evaluated parameters at week 6 of the study was observed. Sodium tungstate presented no significant effect in parotid gland. Our results suggest that diabetes causes initial modification in biochemical composition of parotid. However, this gland showed a recovery capacity after 6 week of the experimental time. Sodium tungstate has no effect in peripheral tissues, such as salivary glands.