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101.
The Kv1.1 potassium channel subunit, encoded by the Kcna1 gene, is heavily expressed in the auditory brainstem and is thought to have a critical role in producing the high temporal precision of action potentials characteristic of the auditory system. Our intent was to determine whether temporal acuity was reduced in Kcna1 null-mutant (-/-) mice, compared to wild-type (+/+) and heterozygotic mice (+/-), as measured by the encoding of gaps in the inferior colliculus by near-field auditory evoked potentials (NFAEP) or behavioral gap detection (BGD) using a prepulse inhibition paradigm. NFAEPs were collected at 40, 60 and 80 dB SPL with gap durations from 0.5 to 64 ms. BGD data were collected using silent gaps in 70 dB noise from 1 to 15 ms in duration. There were no systematic effects of Kcna1 genotype on NFAEP recovery functions, NFAEP latencies, or the time constant for BGD, but there was a small reduction in asymptotic prepulse inhibition for the longest gap stimuli in -/- mice. Gap thresholds were approximately 1-2 ms across genotypes, stimulus conditions, and paradigms. These data suggest that the neural pathways encoding behaviorally relevant, rapid auditory temporal fluctuations are not limited by the absence of Kv1.1 expression. 相似文献
102.
Vitamin K deficiency or administration of vitamin K antagonists results in the biosynthesis of abnormal des-gamma-carboxy forms of the vitamin K-dependent proteins. Monoclonal antibody H-11 binds several vitamin K- dependent proteins at a determinant that includes the first two residues of gamma-carboxyglutamic acid. Antibody H-11 binds fully carboxylated prothrombin and protein C in the presence of EDTA but binding is inhibited by the divalent metal ions, calcium, magnesium, and manganese. By contrast, des-gamma-carboxy prothrombin and protein C bind antibody H-11 the same in the presence of EDTA or calcium ion. Antibody H-11 thus appears to bind a conserved antigenic site containing gamma-carboxyglutamic acid that in the presence of divalent metal ion undergoes a conformational transition. This ability of antibody H-11 to bind des-gamma-carboxy prothrombin and protein C in the presence of calcium ion allowed the development of an immunoassay for these proteins in plasma. Prothrombin and protein C from stably anticoagulated individuals receiving warfarin were characterized by their ability to bind antibody H-11 in the presence of calcium ion. Binding of prothrombin and protein C to antibody H-11 in the presence of calcium correlated temporally with warfarin administration. The inability of calcium ion to inhibit binding of antibody H-11 to abnormal prothrombin and protein C in plasma suggests that the circulating forms of both proteins following warfarin administration cannot undergo the metal ion-dependent conformational transition that includes sequence residues 1 through 12. 相似文献
103.
William R Henderson Paolo B Dominelli Donald EG Griesdale Daniel Talmor A William Sheel 《Canadian respiratory journal》2014,21(2):107-111
High-frequency oscillation is a novel form of ventilation increasingly being used to treat refractory hypoxic respiratory failure resulting from acute lung injury or acute respiratory distress syndrome. Although there is no known relationship between airway pressure and transpulmonary pressure during conventional mechanical ventilation, no study has attempted to determine transpulmonary pressure during high-frequency oscillation.
BACKGROUND:
High-frequency oscillation (HFO) is used for the treatment of refractory hypoxic respiratory failure.OBJECTIVE:
To demonstrate that the mean transpulmonary pressure (PL) cannot be inferred from mean airway pressure (mPaw).METHODS:
In seven patients already undergoing HFO for refractory acute respiratory distress syndrome, esophageal pressure (Pes) was measured using an esophageal balloon catheter. Pleural pressure (Ppl) and PL were calculated from Pes.MAIN RESULTS:
In the seven patients (mean [± SD] age 59±9 years) treated with HFO at 5±1 Hz and amplitude 75±10 cmH2O, the mPaw was 27±6 cmH2O, Ppl was 9±6 cmH2O and PL was 18±11 cmH2O. Successful catheter placement and measurement of Pes occurred in 100% of subjects. There was no correlation between PL and mPaw. The majority of subjects required hemodynamic support during the use of HFO; the frequency and degree of support during the study period was no different than that before the study.CONCLUSION:
The present report is the first to describe measuring Pes and calculating Ppl during HFO for acute respiratory distress syndrome. While both current guidelines and recent trials have titrated treatment based on mPaw and oxygenation, there is wide variability in PL during HFO and PL cannot be predicted from mPaw. 相似文献104.
Heinz Schmuck 《Journal of molecular medicine (Berlin, Germany)》1937,16(32):1122-1124
Ohne Zusammenfassung 相似文献
105.
Instrument monitoring of vital signs in neonates undergoing magnetic resonance (MR) imaging can be difficult because of the unique environmental restrictions imposed by the imager. The authors present their experience with monitoring more than 50 newborn infants and discuss the interaction of monitoring devices with the MR imager. Several MR-compatible monitors allow continuous evaluation of body temperature, heart rate, blood pressure, and auscultation of heart sounds and respiration in mechanically ventilated infants. Signal-to-noise (S/N) ratio measurements taken during imaging of the head of an infant with these monitors in place did not differ appreciably from the ratio obtained during imaging without monitors. Tip angles should be optimized to account for widely varying head size among neonates, since adverse monitoring effects are significantly compounded by improper tip angle adjustment. 相似文献
106.
107.
McArdle CB; Richardson CJ; Hayden CK; Nicholas DA; Crofford MJ; Amparo EG 《Radiology》1987,163(2):387-394
The authors prospectively evaluated 82 neonates, ranging in gestational age from 29 to 44 weeks postconception, with magnetic resonance (MR) imaging at 0.6 T. Twenty-two cases of hemorrhage in 15 infants were identified. Ultrasound (US) and computed tomography (CT) were superior to MR in the first few days after parenchymal hemorrhage, since at this time lesions were apparent on only T2-weighted images. After the first 3 days, MR was the single best modality because (a) hemorrhage on CT became imperceptible in the 2d week, whereas the high signal of hemorrhage on MR persisted for 2-11 weeks; (b) MR permitted rough dating of hemorrhage according to changes in signal intensity; and (c) MR was superior in identifying subdural or epidural hemorrhage. Because of the nonspecificity and restricted field of view of US and the inability of CT to depict hemorrhage after 7-10 days, the authors conclude that MR significantly improves the detection of intracranial hemorrhage in neonates. 相似文献
108.
Abnormalities of the neonatal brain: MR imaging. Part II. Hypoxic- ischemic brain injury 总被引:3,自引:0,他引:3
Eighty-five infants, 82 of whom were 29-44 weeks postconceptional age, were imaged with a 0.6-T magnet. Eight infants had cerebral infarction. In premature neonates with very water, low-intensity white matter on T1-weighted images, ultrasound was better than both computed tomography and magnetic resonance (MR) imaging in depicting parenchymal changes of infarction or edema. However, after 37 weeks gestation, MR imaging was superior. Cerebral atrophy, present in seven infants, was consistent with subarachnoid space widths of 7 mm or more, or subarachnoid space widths of 5-6 mm with ventricular/brain ratios of 0.36 or greater. Delayed myelination was seen in a total of 18 infants with histories of hypoxic-ischemic insult. MR imaging shows promise in the neonatal period. It facilitates recognition of infarcts in full-term infants and may be used to predict abnormal neurologic outcome in infants who have initial delayed myelination. 相似文献
109.
U. Poller R. F. Schäfers S. Schmuck J. Jakubetz J. Radke A. E. Daul K. Pönicke O.-E. Brodde 《Naunyn-Schmiedeberg's archives of pharmacology》1997,356(1):100-106
The aim of this study, carried out in six elder healthy volunteers (mean age: 61 years), was to determine the influence of
muscarinic receptor blockade with atropine (15 μg/kg i.v. loading dose followed by 0.15 μg/kg/min by i.v. infusion) on the
effects of i.v. infusions of noradrenaline (5 incremental doses of 10-120 ng/kg/min) or tyramine, that releases endogenous
noradrenaline (4 incremental doses of 5-20 μg/kg/min), on blood pressure, heart rate and systolic time intervals (STI’s, as
a measure of positive inotropism). These results were compared with those recently published for young healthy volunteers
(mean age: 26 years; Sch?fers et al. 1997). Noradrenaline caused increases in systolic and diastolic blood pressure, decreases
in heart rate and a shortening of STI’s that were not different from those in young volunteers. Atropine did not significantly
affect these hemodynamic responses to noradrenaline, while in young volunteers it significantly enhanced noradrenaline-induced
blood pressure increases and converted the heart rate decrease into an increase. In the present study in elder volunteers,
tyramine caused a smaller increase in systolic blood pressure than in the previous study in young volunteers; in addition,
it slightly increased diastolic blood pressure while it decreased diastolic blood pressure in young volunteers. Atropine did
not significantly affect the hemodynamic effects of tyramine in the elder volunteers, while in the young volunteers it enhanced
the increase in systolic blood pressure and converted the decreases in diastolic blood pressure and heart rate into increases.
These results indicate a) that ageing is accompanied by a blunted baroreflex-mediated parasympathetic activation resulting
in reduced cholinergic vasodilation and decreases in heart rate, and b) that ageing is associated with a decreased responsiveness
of (cardiac) β-adrenoceptors and (vascular) α1-adrenoceptors which is only unmasked when the counterregulatory action of parasympathetic activation is removed.
Received: 24 January 1997 / Accepted: 21 April 1997 相似文献
110.