Delayed Onset Time Research Articles

The Effect of Extracellular Glutamate Release on Repetitive Transient Ischemic Injury in Global Ischemia Model

During operations, neurosurgeons usually perform multiple temporary occlusions of parental artery, possibly resulting in the neuronal damage. It is generally thought that neuronal damage by cerebral ischemia is associated with extracellular concentrations of the excitatory amino acids. In this study, we measured the dynamics of extracellular glutamate release in 11 vessel occlusion (VO) model to compare between single occlusion and repeated transient occlusions within short interval. Changes in cerebral blood flow were monitored by laser-Doppler flowmetry simultaneously with cortical glutamate level measured by amperometric biosensor. From real time monitoring of glutamate release in 11 VO model, the change of extracellular glutamate level in repeated transient occlusion group was smaller than that of single occlusion group, and the onset time of glutamate release in the second ischemic episode of repeated occlusion group was delayed compared to the first ischemic episode which was similar to that of single 10 min ischemic episode. These results suggested that repeated transient occlusion induces less glutamate release from neuronal cell than single occlusion, and the delayed onset time of glutamate release is attributed to endogeneous protective mechanism of ischemic tolerance.

Global tests of haemostasis in critically ill patients with severe sepsis syndrome compared to controls

Haemostatic changes in septic patients are complex, with both procoagulant and anticoagulant changes. Thirty-eight patients with severe sepsis and 32 controls were investigated by coagulation screens, individual factor assays, calibrated automated thrombography (CAT), whole blood low-dose-tissue factor activated (LD-TFA) Rotem and LD-TFA waveform analysis. Thirty-six of 38 patients had an abnormal coagulation screen. The mean levels of factors II, V (P < 0.05), VII, X, XI and XII, antithrombin and protein C (P < 0.01) was decreased in sepsis compared with controls. The mean factor VIII and fibrinogen level (P < 0.001) was increased. CAT in platelet rich and poor plasma showed a prolonged lag time (P < 0.02), decreased peak thrombin (P < 0.02) and delayed time to peak thrombin (P < 0.001) in sepsis patients, however, the endogenous thrombin potential was equivalent in sepsis and controls. In LD-TFA Rotem, septic patients had delayed clot times (P = 0.04) but an increased maximum velocity of clot formation (P < 0.01) and area under the clot elasticity curve (P < 0.01). LD-TFA waveform analysis showed a delayed onset time but an increased rate of clot formation (P < 0.005). In conclusion, global tests of haemostasis suggest that in this patient group, activation of haemostasis is delayed but once initiated thrombin generation and clot formation are normal or enhanced.

The role of fixation point and subjects' readiness in the occurrence of express saccades as revealed by the self-initiation paradigm.

The role of fixation and the subjects' response preparedness in producing express saccades were explored in seven human subjects. The occurrence frequencies of the express saccades were compared in the overlap (continuous presentation of fixation point), gap (fixation point offset 0-400 ms prior to target onset) and no-fixation tasks under the conventional and self-initiation paradigms. In the latter paradigm, the subjects, when ready, touched a sensor in order to ignite the target lamp with a delay time of 0-400 ms (target onset delay time). Therefore, the subjects' response preparedness might be expected to be higher than that in the normal paradigm and equated in each subject at the time when the subjects touched a sensor regardless of the paradigms. Although express saccades were produced neither in the normal overlap nor in the normal no-fixation tasks, they could be produced at the rate of 24 and 48% in the overlap and no-fixation tasks under the self-initiation paradigm, respectively. The highest occurrence frequency of express saccades was obtained when the gap paradigm was combined with the self-initiation paradigm with a delay time of 100 ms (62%). The value was higher by 20% than in the normal gap task. At a target onset delay time of 0 ms under the self-initiation paradigm, the occurrence frequency of express saccades was higher in the overlap task than in the gap task. These results suggest that the subjects' response preparedness has a potentiality to produce express saccades without fixation point offset and that fixation point offset at the same time of the target stimulus onset has an interference, rather than facilitatory, influence on the generation of express saccades.

Spinal anaesthesia for paediatric day-case surgery: a double-blind, randomized, parallel group, prospective comparison of isobaric and hyperbaric bupivacaine

We have compared bupivacaine 5 mg ml-1, either isobaric in saline 0.9% or hyperbaric in 8% glucose, for spinal anaesthesia in 100 children, aged 2-115 months, in a double-blind, randomized, parallel group, prospective study. Children were premedicated with diazepam 0.5 mg kg-1 orally. Seventy-two children were sedated before, and 25 children after, lumbar puncture, with either propofol or thiopental (thiopentone). After lumbar puncture in the lateral decubitus position with a 24-27-gauge paediatric spinal needle, isobaric or hyperbaric bupivacaine 5 mg ml-1 was injected in a dose of 0.3-0.5 mg kg-1 using a blinded procedure. Maximum cephalad extent of the block was tested by transcutaneous electrical stimulation. The success rate of the block was greater with hyperbaric bupivacaine (96%) compared with isobaric bupivacaine (82%) (P = 0.025, 95% confidence intervals (CI) 0-28%). Intense motor block was associated with adequate sensory block. Spread and duration of sensory block showed a similar wide scatter in both groups. The highest median level of sensory block was T4 (range T1-12) in the isobaric group and T4 (T1-7) in the hyperbaric group. Times to two segment regression of block were similar: 80 (55-190) min in the isobaric and 80 (30-190) min in the hyperbaric group. Cardiovascular stability was good. Etilefrin was administered to one child to treat hypotension and atropine to one child to treat bradycardia. The study gave an impression of a delayed onset time of spinal block, as most of the nine children who required either fentanyl or a sedative for a mild reaction to skin incision had complete block when transferred to the recovery room after operation. Five children developed a mild, position-dependent headache.

A new electrode (HN-5) for CM measurement in extra-tympanic electrocochleography

A new electrode (HN-5) for CM measurement in extra-tympanic electrocochleography (ECochG) has been developed. The electrode consists of a silver wire 2.0 mm in diameter and 5 cm in length connected to a low noise cable. The electrode impedance values were low and the frequency characteristics were excellent. In order to explore various artifacts, the electrode was inserted into a glass cup containing 100 ml of tap water, which served as a dummy ear. A sound stimulus with an intensity of 90 dBnHL was delivered by a shielded loudspeaker located 50 cm from the dummy ear (glass cup). In this dummy test, contamination with measurable artifacts, such as electromagnetic inductions generated by a sound transducer and the CM-like mechanical vibrations which activated the dummy ear acoustically, was kept within the noise levels inherent in the recording system. The CMs were recorded from subjects with normal hearing by placing an electrode adjacent to the postero-inferior rim of the tympanic membrane (annulus tympanicus). Short tone bursts were employed as acousti stimuli and delivered by the shielded loudspeaker. CM detection thresholds were very low and CM-like responses with delayed onset time (delayed CM) were clearly observed at lower stimulus levels. The input-output curves of the CMs and delayed CMs were non-linear. These findings from the CMs did not differ from those obtained by the transtympanic needle electrode technique. Responses obtained had satisfactory S/N ratios and resulted in almost the same average calculations as those with transtympanic ECochG.(ABSTRACT TRUNCATED AT 250 WORDS)

Dimer desorption from solid argon films electronically excited by MeV He ions.

Electronic excitation of solid Ar films by MeV ${\mathrm{He}}^{+}$ ions gives rise to broad luminescence bands centered at 1110 and 1265 \AA{}. We have examined the spatial and temporal characteristics of these dimer luminescence bands. Observing all the luminescence, we measure a spectrum that is dominated by the 1265-\AA{} band. This band is from decay of vibrationally relaxed ${\mathrm{Ar}}_{2}^{\mathrm{*}}$${(}^{3}$${\mathrm{\ensuremath{\Sigma}}}_{\mathit{u}}^{+}$) trapped in the bulk of the Ar film. Observing only the luminescence from a plume of desorbed particles in front of the excited Ar film, we observe a long-lived 1110-\AA{} luminescence band with a long-wavelength tail extending down to the region around 1265 \AA{}. This band is from decay of gas-phase ${\mathrm{Ar}}_{2}^{\mathrm{*}}$${(}^{3}$${\mathrm{\ensuremath{\Sigma}}}_{\mathit{u}}^{+}$;${1}_{\mathit{u}}$,${0}_{\mathit{u}}^{\mathrm{\ensuremath{-}}}$) in various degrees of vibrational relaxation. The ${\mathrm{Ar}}_{2}^{\mathrm{*}}$ ejection kinetic energy (KE), as well as the degree of vibrational relaxation, are important clues to the mechanisms of dimer formation and desorption.We observe a delayed onset of the luminescence under pulsed excitation if the base of the luminescent plume is hidden from view. The average delayed onset time is a time of flight, the value of which indicates that the average KE of the desorbed ${\mathrm{Ar}}_{2}^{\mathrm{*}}$ is 0.1 eV but ranges as low as 0.06 eV for dimers in highly vibrationally excited states. The temporal width of the delayed onset is consistent with a hemispherical plume shape. We have fitted the observed 1110-\AA{} luminescence band with a linear combination of quantum mechanically calculated luminescence spectra of the vibrational levels of ${\mathrm{Ar}}_{2}^{\mathrm{*}}$${(}^{3}$${\mathrm{\ensuremath{\Sigma}}}_{\mathit{u}}^{+}$;${1}_{\mathit{u}}$,${0}_{\mathit{u}}^{\mathrm{\ensuremath{-}}}$).The resulting vibrational-state distribution is non-Boltzmann and increases sharply with decreasing vibrational quantum number, indicating a considerable degree of vibrational relaxation. These results are discussed in terms of simple models of the ${\mathrm{Ar}}_{2}^{\mathrm{*}}$-desorption process. We hypothesize that ${\mathrm{Ar}}_{2}^{\mathrm{*}}$ is ejected with a KE around 0.1 eV after dissociative recombination of an electron with a near-surface self-trapped hole, ${\mathrm{Ar}}_{2}^{+}$, and subsequent dimerization of the energetic ${\mathrm{Ar}}^{\mathrm{*}}$. Many-body collisions occurring during dimerization effectively relax the vibrational state of the dimer.

Apparent poleward motion of onsets of auroral absorption events

A study is made of nighttime auroral radio absorption events observed by riometers in the latitude range of λ = 67–76°. Individual events are shown to extend over this range with a tendency to occur later at higher latitudes. If the observed onset delay time is interpreted as a poleward expansion of the disturbance, the corresponding average velocity is 0.8 km/s. This velocity is consistent with the poleward motion observed during visual auroral substorms. The absorption events are compared statistically with energetic electron events detected by the Alouette I satellite.

Delay time of polar-cap blackout and its relation to delay time of geomagnetic disturbance

In a recent issue of this Journal, Obayashi [1962] quotes a result of Sinno [1961] in support of the idea that extremely long delay time of onset of polar-cap absorption or blackout can be attributed to trapping of the solar protons in the plasma cloud that causes subsequent geomagnetic disturbance. The purpose of this letter is to point out difficulties in this explanation of Sinno's relation, and to suggest a simpler interpretation. For one group of events, Sinno finds a linear relation between the delay time of polar-cap blackout, Δt, and the delay time of geomagnetic disturbance, ΔT. For each polar-cap blackout he selects a preceding flare on the basis of optical importance and associated ‘type IV’ radio burst. In the usual sequence, let F represent the time of the flare and radio burst, P the time of onset of polar-cap blackout, and G the beginning time of geomagnetic disturbance, so that ΔT = G − F, and Δt = P − F. Sinno plots Δt against ΔT (Figure 1) and finds that the group of points representing cases with Δt≥10 hours define a remarkably straight line with slope close to unity; that is, when polar-cap blackout delay time is longer than about 10 hours, it is proportional to geomagnetic storm delay time. Sinno (and Obayashi) suggest that in these cases the energetic protons that cause polar-cap blackout are trapped in the plasma cloud that causes geomagnetic disturbance. They leak out only after the magnetic field carried by the plasma cloud has been weakened by its expansion.