Microtubule reassembly in surface-activated platelets

It is generally accepted that a circumferential microtubule supports the discoid shape of resting platelets. The fate of the many-coiled polymer following platelet activation, however, has been a subject of considerable debate. Morphological investigations have suggested that the circumferential coils are constricted into tight rings around centrally concentrated organelles during platelet shape change. Biochemical studies employing colchicine-binding assays, on the other hand, have indicated that the bundle of microtubules dissolves almost completely within seconds after activation and reassembles in a new location one to four minutes later. The present study has accepted the latter hypothesis in order to examine the second part of the disassembly-reassembly theory proposed in biochemical studies. Platelets exposed to low temperatures sufficient to remove all microtubules were placed on glass slides and microscope grids to cause surface activation during rewarming. The combined stimuli of rewarming and surface activation might have been expected to cause more rapid assembly than warming alone or activation alone. This was not the case. Reassembly of microtubules during rewarming and simultaneous surface activation was not accelerated. In contrast to the constriction of microtubule rings observed during activation in control platelets, the diameters of coils that developed in chilled platelets one to two hours after rewarming and surface activation were twice those of control cells.     

Immunization with a heat-killed bacterium,Mycobacterium vaccae NCTC 11659, prevents the development of cortical hyperarousal and a PTSD-like sleep phenotype after sleep disruption and acute stress in mice

Study ObjectivesSleep deprivation induces systemic inflammation that may contribute to stress vulnerability and other pathologies. We tested the hypothesis that immunization with heat-killed Mycobacterium vaccae NCTC 11659 (MV), an environmental bacterium with immunoregulatory and anti-inflammatory properties, prevents the negative impacts of 5 days of sleep disruption on stress-induced changes in sleep, behavior, and physiology in mice.MethodsIn a 2 × 2 × 2 experimental design, male C57BL/6N mice were given injections of either MV or vehicle on days –17, –10, and –3. On days 1–5, mice were exposed to intermittent sleep disruption, whereby sleep was disrupted for 20 h per day. Immediately following sleep disruption, mice were exposed to 1-h social defeat stress or novel cage (control) conditions. Object location memory (OLM) testing was conducted 24 h after social defeat, and tissues were collected 6 days later to measure inflammatory markers. Sleep was recorded using electroencephalography (EEG) and electromyography (EMG) throughout the experiment.ResultsIn vehicle-treated mice, only the combination of sleep disruption followed by social defeat (double hit): (1) increased brief arousals and NREM beta (15–30 Hz) EEG power in sleep immediately post-social defeat compared to baseline; (2) induced an increase in the proportion of rapid-eye-movement (REM) sleep and number of state shifts for at least 5 days post-social defeat; and (3) induced hyperlocomotion and lack of habituation in the OLM task. Immunization with MV prevented most of these sleep and behavioral changes.ConclusionsImmunization with MV ameliorates a stress-induced sleep and behavioral phenotype that shares features with human posttraumatic stress disorder.     

Operative field temperature during transnasal endoscopic cranial base procedures

Background

Data regarding the safety of endoscopic skull base exploration are very scarce. With this method, fragile vital structures (cranial nerves, the optic complex, brainstem, hypothalamus or cerebral ventricles) are exposed to direct illumination within a closed space. Also, high-speed drills, cauterization and ultrasonic aspiration deliver a significant load of thermal energy. The aim of this study was to record the temperature close to the structures of the skull base and in the intradural space during the procedures performed using extended endoscopic transnasal approaches.

Methods

The temperature of the skull base was continuously recorded during six transnasal endoscopic procedures. Implantable copper-constantan thermocouples were inserted: one into the esophagus and another through the nostril to reach the operative field at the skull base.

Results

At the beginning of the procedure, the temperature of the operative field was on average 36.8 °C?±?0.80 °C, i.e. only 1 °C higher than the esophageal temperature. Then it grew continuously during the whole procedure, to eventually reach a level of 42–43 °C at the final stage, whereas the esophageal temperature remained stable. Occasionally, the temperature increased up to 45 °C during cauterization and ultrasonic aspiration, and even up to 62 °C during high-speed drilling.

Conclusion

Endoscopic skull base surgery is associated with an incessant increase of the temperature of the intraoperative field. The temperature can peak suddenly to levels which can potentially harm neural structures and influence the rate of postoperative complications.     

Differential effects of intravenous anesthetics on hepatosplanchnic microcirculation in rats: sidestream dark-field imaging study

This study aimed to investigate the effects of intravenous anesthetics on hepatosplanchnic microcirculation in laparotomized mechanically ventilated rats using Sidestream Dark-field (SDF) imaging. Thirty male Wistar rats were divided into 5 groups (n = 6 each). All rats were initially anesthetized with 60 mg/kg pentobarbital (i.p.) for instrumentation. This was followed by either ketamine, propofol, thiopental, midazolam or saline+fentanyl (iv bolus over 5 min and then maintenance over 90 min). SDF imaging of the liver and distal ileum microcirculation was performed at the baseline and at t = 5, 35, 65 and 95 min. In propofol group there was increase of functional sinusoidal density (FSD) following induction (+25%, P < 0.05) and maintenance at t = 95 min (+10.3%, P < 0.05), in ketamine and midazolam group decrease of FSD was observed after induction (-20.4%, P < 0.05; -10.1%, P < 0.05) and during maintenance at t = 65 min (-11.6%, P < 0.05; -11.4%, P < 0.05) when compared to baseline. Following induction with propofol functional capillary density (FCD) of ileal longitudinal muscle layer increased (+10.6%, P < 0.05) and returned to baseline values during maintenance. Ketamine and midazolam decreased FCD of longitudinal layer after induction (-24.6%, P < 0.05; -21.1%, P < 0.05) and remained decreased during maintenance at t = 95 min (-10.8%, P < 0.05; -15.5%, P < 0.05). In thiopental and control group, changes in microcirculatory parameters were not significant throughout the study. In conclusion, intravenous anesthetics affect the hepatosplanchnic microcirculation differentially, propofol has shown protective effect on the liver and intestinal microcirculation.     

Altering the mammalian circadian clock with the short-acting benzodiazepine, triazolam

The systemic administration of triazolam alters circadian rhythms of hamsters under both entrained (synchronized to a circadian period) and free-running (in the absence of a synchronizing light-dark cycle) conditions. In the latter conditions (i.e. during exposure to constant light or darkness), single injections of triazolam can induce a permanent phase-shift in both behavioral and endocrine rhythms. Repeated injections at fixed circadian intervals can entrain the rhythm of locomotor activity, and in the presence of a synchronizing light—dark cycle, daily injections of triazolam can alter the phase relationship of the activity rhythm to the light—dark cycle. Moreover, following a shift in the light—dark cycle, a single injection of triazolam can shorten the time it takes for the activity rhythm to be resynchronized to the new lighting schedule. In addition to implicating a role for the neurotransmitter GABA in the circadian organization of mammals, these findings may have important clinical implications. If short-acting benzodiazepines can have similar effects on the human circadian clock, they could prove useful in reducing the symptoms associated with ‘jet-lag’ and rotating shift-work schedules, as well as in the treatment of various physical and mental illnesses that have been associated with a disorder in biological timekeeping.