Acacetin suppresses the electrocardiographic and arrhythmic manifestations of the J wave syndromes.

BACKGROUND: J wave syndromes (JWS), including Brugada (BrS) and early repolarization syndromes (ERS), are associated with increased risk for life-threatening ventricular arrhythmias. Pharmacologic approaches to therapy are currently very limited. Here, we evaluate the effects of the natural flavone acacetin. METHODS: The effects of acacetin on action potential (AP) morphology and transient outward current (Ito) were first studied in isolated canine RV epicardial myocytes using whole-cell patch clamp techniques. Acacetin's effects on transmembrane APs, unipolar electrograms and transmural ECGs were then studied in isolated coronary-perfused canine RV and LV wedge preparations as well as in whole-heart, Langendorff-perfused preparations from which we recorded a 12 lead ECG and unipolar electrograms. Using floating glass microelectrodes we also recorded transmembrane APs from the RVOT of the whole-heart model. The Ito agonist NS5806, sodium channel blocker ajmaline, calcium channel blocker verapamil or hypothermia (32°C) were used to pharmacologically mimic the genetic defects and conditions associated with JWS, thus eliciting prominent J waves and provoking VT/VF. RESULTS: Acacetin (5-10 µM) reduced Ito density, AP notch and J wave area and totally suppressed the electrocardiographic and arrhythmic manifestation of both BrS and ERS, regardless of the experimental model used. In wedge and whole-heart models of JWS, increasing Ito with NS5806, decreasing INa or ICa (with ajmaline or verapamil) or hypothermia all resulted in accentuation of epicardial AP notch and ECG J waves, resulting in characteristic BrS and ERS phenotypes. Phase 2-reentrant extrasystoles originating from the RVOT triggered VT/VF. The J waves in leads V1 and V2 were never associated with a delay of RVOT activation and always coincided with the appearance of the AP notch recorded from RVOT epicardium. All repolarization defects giving rise to VT/VF in the BrS and ERS models were reversed by acacetin, resulting in total suppression of VT/VF. CONCLUSIONS: We present experimental models of BrS and ERS capable of recapitulating all of the ECG and arrhythmic manifestations of the JWS. Our findings provide definitive support for the repolarization but not the depolarization hypothesis proposed to underlie BrS and point to acacetin as a promising new pharmacologic treatment for JWS.

Altered hypothalamic inflammatory gene expression correlates with heat stroke severity in a conscious rodent model.

It has been suggested that heat-induced hypothalamic damage mediates core temperature (Tc) disturbances during heat stroke (HS) recovery; this is significant as hypothermia and/or fever have been linked to severity and overall pathological insult. However, to date there has been a lack of histological evidence in support of these claims. We hypothesized that local hypothalamic cytokines and/or chemokines, known regulators of Tc, are mediating the elevation in Tc during HS recovery even in the absence of histological damage. In experiment 1, the hypothalamus of Fischer 344 rats was examined for 84 cytokine/chemokine genes (real-time PCR) at multiple time points (Tc,Max, 1, 3, and 10 days) during mild HS recovery. In experiment 2, the hypothalamus of three different HS severities (MILD, moderate [MOD], and severe [SEV]) in rats were examined for the same genes as experiment 1 as well as six oxidative damage markers, at a single intermediate time point (1 day). Systemic cytokines were also analyzed in experiment 2 across the three severities. There were significant alterations in 25 cytokines/chemokines expression at Tc,Max, but little or no changes in expression at longer time points in experiment 1. In experiment 2 there were significant changes in gene expression in SEV rats only, with MILD and MOD rats showing baseline expression at 1 day, despite an absence of systemic cytokine expression in any severity. There was also no change in any oxidative marker of damage at 1 day, regardless of severity. In conclusion, we show only limited changes during long term recovery from HS, but demonstrate differences in hypothalamic gene expression patterns that may be driving HS pathology and morbidity. These findings contribute to our overall understanding of HS pathology in the CNS, as well as providing avenues for future pharmacological intervention.

Insufficient glucose supply is linked to hypothermia upon cold exposure in high-fat diet-fed mice lacking PEMT.

Mice that lack phosphatidylethanolamine N-methyltransferase (Pemt(-/-) mice) are protected from high-fat (HF) diet-induced obesity. HF-fed Pemt(-/-) mice show higher oxygen consumption and heat production, indicating that more energy might be utilized for thermogenesis and might account for the resistance to diet-induced weight gain. To test this hypothesis, HF-fed Pemt(-/-) and Pemt(+/+) mice were challenged with acute cold exposure at 4°C. Unexpectedly, HF-fed Pemt(-/-) mice developed hypothermia within 3 h of cold exposure. In contrast, chow-fed Pemt(-/-) mice, possessing similar body mass, maintained body temperature. Lack of PEMT did not impair the capacity for thermogenesis in skeletal muscle or brown adipose tissue. Plasma catecholamines were not altered by Pemt genotype, and stimulation of lipolysis was intact in brown and white adipose tissue of Pemt(-/-) mice. HF-fed Pemt(-/-) mice also developed higher systolic blood pressure, accompanied by reduced cardiac output. Choline supplementation reversed the cold-induced hypothermia in HF-fed Pemt(-/-) mice with no effect on blood pressure. Plasma glucose levels were ∼50% lower in HF-fed Pemt(-/-) mice compared with Pemt(+/+) mice. Choline supplementation normalized plasma hypoglycemia and the expression of proteins involved in gluconeogenesis. We propose that cold-induced hypothermia in HF-fed Pemt(-/-) mice is linked to plasma hypoglycemia due to compromised hepatic glucose production.

Hypothermia, hypotension, hypersomnia, and obesity associated with hypothalamic lesions in a patient positive for the anti-aquaporin 4 antibody: a case report and literature review.

OBJECTIVE: To describe a patient positive for the anti-aquaporin 4 antibody with hypothalamic lesions showing hypothermia, hypotension, hypersomnia, and obesity. DESIGN: Case report. SETTING: University hospital. PATIENT: We describe a 21-year-old woman who was positive for anti-aquaporin 4 antibody and presented with hypothermia, hypotension, and hypersomnia owing to bilateral hypothalamic lesions as the only abnormal clinical finding. RESULTS: Immediate steroid administration resulted in significant improvement of the patient's vital signs and imaging findings; however, her cognitive impairment and sleepiness persisted, and she subsequently developed obesity. Decreased cerebrospinal fluid orexin levels and sleep studies confirmed the diagnosis of narcolepsy due to medical condition. Physicians should be aware that neuromyelitis optica spectrum disorders can initially involve the hypothalamus. CONCLUSIONS: We emphasize that measurement of anti-aquaporin 4 antibody is of clinical importance in the differential diagnosis of hypothalamic lesions.

[Case report: fatal diving-accident. Or: accident while diving?]. / Tödlicher Tauchunfall. Oder: Unfall während des Tauchens mit Todesfolge?

This example of a fatal diving accident shows how challenging such cases can be in pre-hospital and clinical care. There is no common mechanism in diving fatalities and more than one group of disorders coming along with decompression sickness. Diving medicine is not an element of medical education, which results in insecurity and hampers adequate therapy of diving incidents. This is aggravated by an insufficient availability of hyperbaric chambers in Germany.

[Cold pathology and experimental therapy of deep hypothermia].

A complete cold paralysis of respiration and thermoregulation occurs in rats at the temperature in the brain 16.6 +/- 0.3 and in the rectum 15.2 +/- 0.3 degrees C. Under the conditions of room temperature 18-19 degrees C, the respiration never restores, and the animals die. This is believed [6] to be the result of calcium ion Ca2+ accumulation in the cells of respiration and thermoregulation centers. After the arrest of respiration the animals were injected with the solution of disodium salt of ethylenediaminetetraacetic acid (Na2EDTA), which binds calcium ions in the blood and facilitates their removal from the cell (explanations in the text). In 7-9 min after the injection the calcium content in the blood decreased and the respiration began to restore at the temperature of the cold paralysis. Thermoregulation was also restored. All the test animals survived. All the control animals, which were not injected with Na2EDTA, died.

Effects of nimodipine and pentoxyfylline in prevention of hepatic ischemic damage in rats at normal and hypothermic conditions.

Hepatic ischemia should be considered in serious liver injury, liver tumor resection and liver transplantation. There are other conditions that decrease hepatic blood flow and cause hepatic ischemia, such as hemorrhagic shock, sepsis, hepatic artery ligation, trauma, and certain vascular lesions. In this study, effects of nimodipine (a calcium channel blocker) and pentoxyfylline (a derivative of methylxanthine) on duration and degree of hepatic ischemia in rats at normothermic and hypothermic conditions are investigated. This study was performed on 6 groups of Wistar Albino type rats, each group consisting of 7 rats. Groups were separated into normothermic (A) and hypothermic (B) conditions AI-Control group, AII-Nimodipine group and AIII-Pentoxyfylline group, B IV-Control group, BV-Nimodipine group and BVI-Pentoxyfylline group respectively. After hepatic pedicle occlusion lasting 45 min, blood samples were drawn from the rats for evaluation of alanine aminotransferase (ALT), aspartate transaminase (AST) and lactate dehydrogenase (LDH) values. Moreover, hepatic biopsies were taken to assess pathological changes under electron microscopy. These changes were evaluated through a grading system. As a result; it has been shown that both nimodipine and pentoxyfylline delayed effects of hepatic ischemia in a statistically significant manner in comparison with the control group and these effects were found to be more significant in hypothermic conditions.

Phosphorus-31 nuclear magnetic resonance of isolated rat liver during hypothermic ischemia and subsequent normothermic perfusion.

The effects of prolonged hypothermic ischemia and subsequent normothermic perfusion on the energetic metabolism and intracellular pH (pHin) of isolated rat livers were studied by phosphorus-31 nuclear magnetic resonance spectroscopy. Nucleoside triphosphate (NTP) depletion and intracellular pH were studied within an 18-h-storage phase, by using the following preservation media: Eurocollins (EC), UW Lactobionate (UW) and Bretschneider's solution (HTK). Values obtained after 8-h ischemia were chosen to estimate the performance of the various media: NTP levels were 37 +/- 7%, 10 +/- 5% and 0% of control levels, respectively, in livers stored in UW, HTK and EC solutions. pHin reached values of 7.15 +/- 0.10 in UW and HTK, and 6.96 +/- 0.10 in EC-stored livers. Ischemic damage was assessed by reperfusing the stored organ with Krebs medium: NTP recovery was around 70 +/- 20% for the three solutions used. Recovery of pHin was near the control value (7.23 +/- 0.08), except for EC solution (7.05 +/- 0.20). The main results are that (i) the rates of NTP and pHin decrease are strongly dependent on the nature of the preservation solution, whereas (ii) NTP recovery is not significantly different during post-ischemic reperfusion. With regard to animal survival, UW solution is at present considered largely superior to EC medium for liver preservation. Thus, our data suggest that the rates of NTP depletion and pHin fall during cold preservation could be both considered as better indicators assessing liver injury than the post-ischemic NTP recovery.

Hypothermia due to transient hypothalamic dysfunction in tuberculous meningitis with hydrocephalus.

We report two patients with tuberculous meningitis and hydrocephalus who developed hypothermia that reversed after inserting a ventricular shunt for the hydrocephalus. Pressure on the thermoregulatory centre in the posterior hypothalamus near the dilated third ventricle might have been responsible. One patient developed hypotension during the transient hypothermia, which persisted and proved fatal.

Subacute inhalation toxicity of benzaldehyde in the Sprague-Dawley rat.

Benzaldehyde was administered by inhalation to female and male Sprague-Dawley rats for 14 consecutive days (low level: 500 ppm; medium level: 750 ppm; high level: 1000 ppm). Effects of this chemical were investigated during and at the end of the exposure period. Throughout the experiment, significant hypothermia and a reduction of motor activity were observed in all rats exposed to benzaldehyde and were accompanied in high-level rats by a severe impairment of the central nervous system, as evidenced by abnormal gait, tremors, and a positive Straub sign. Histopathologic examination of tissues from exposed rats showed a goblet cell metaplasia that was largely confined to the respiratory epithelium lining the nasal septum in male rats. No other abnormal microscopic changes were observed. A no effect level was not observed in these studies.

Low temperature worsens mammalian oxygen toxicity.

Oxygen toxicity was assessed in mice exposed to 5 ATA of oxygen. Central nervous system toxicity was measured as the latent period before convulsions, and lung damage estimated by wet and dry weight measurements. Our results confirmed previous findings that hyperbaric oxygen induces hypothermia in animals, and this effect is profound in mice exposed to 5 ATA of oxygen at ambient temperatures of 15 degrees C and 5 degrees C. However, even marked hypothermia had very little effect on the latent times to convulsions in mice. Unexpectedly, the combination of hypothermia and hyperbaric oxygen produced much more severe lung damage than either treatment alone, with a 2.7-fold increase in weight in the 5 degrees C group (average rectal temperature of 16.1 degrees C). These results indicate that hyperoxic-induced hypothermia cannot be considered a protective mechanism against oxygen toxicity and indeed hypothermia can markedly potentiate hyperbaric oxygen toxicity.