Reproducibility and accuracy of noble gas measurements on water samples in the microlitre range.

RATIONALE: In order to derive meaningful noble gas temperatures (NGTs) from speleothem fluid inclusions, precise and accurate measurements of noble gas concentrations on very small water samples are necessary. To optimise these measurements and their reliability, an investigation of the reproducibility and accuracy of the analytical procedure is essential. METHODS: Water equilibrated with air under controlled conditions was filled into copper capillaries to produce small (about 1 µL) air-equilibrated water samples (so-called µAEWs). As speleothem samples, the µAEWs were opened in a crusher and the released noble gases analysed with an electron ionisation sector field mass spectrometer run in static mode. For better comparability with speleothem samples, a defined amount of air was added to the noble gases derived from one group of µAEWs. RESULTS: The reproducibility of the experimental procedure was found to be better than 2.2% for all relevant noble gases. Within these uncertainties, the measured noble gas concentrations of µAEWs agree with expectations. The corresponding NGTs reproduce within 0.5°C and deviate by less than 1°C from the equilibration temperature. In the case of air addition, the air to water ratio was determined accurately and, excluding one outlier, the NGTs were determined with a reproducibility and accuracy well below 1°C. CONCLUSIONS: The results show that the used measurement procedure is generally suitable to reveal major climatic temperature changes, for which an overall NGT error of less than 1°C is desirable, from very small water samples as obtained from speleothem fluid inclusions.

Variants of the Drosophila melanogaster Ih-channel are generated by different splicing.

We isolated splice variants of the DMIH cDNA encoding members of the I(h)-channel family from Drosophila melanogaster by means of polymerase chain reaction and homology screening. Splicing at four different sites generates a great variety of different channel transcripts. The variants so obtained code for ion channel proteins with long or short N-termini and variations in the length of the interloop regions between the membrane-spanning domains S3-S4 and S4-S5. The multiple variants of DMIH coded by a single gene thus might form the molecular basis for a variety of I(h)-channels. Functional expression of one of the DMIH variants with a long N-terminus in HEK293 cells produced unitary currents that were preferentially selective for potassium over sodium ions and were activated by hyperpolarizing voltage steps. Cyclic nucleotides shifted the voltage activation curve to more positive membrane potentials. The current kinetics and modulatory influence of cyclic nucleotides resemble closely those of other invertebrate I(h)-channels, but activation by hyperpolarizing voltage steps had a V(1/2) of 123 mV, a more negative value than those of other recombinantly expressed insect I(h)-channels with a short N-terminus.

Molecular and functional characterization of an I(h)-channel from lobster olfactory receptor neurons.

We isolated a cDNA named PAIH encoding a member of the I(h)-channel family expressed in olfactory receptor neurons (ORNs) of the spiny lobster Panulirus argus. Functional expression of recombinant PAIH in HEK293 cells generated a slowly activating, noninactivating inward current under whole-cell voltage-clamp to hyperpolarizing voltage steps, the amplitude and activation rate of which increase with increasing hyperpolarization. The channel is weakly selective for K+. Intracellular cAMP or cGMP shifts activation of the current to less negative potentials in a concentration-dependent manner. Finally, the channel is blocked by the I(h)-channel blocker ZD7288. An I(h)-channel sharing the properties of the recombinant channel occurs in cultured lobster ORNs. PAIH immunoreactivity localizes the protein to the transduction compartment of the ORNs in situ, and selectively applying the blocker to the transduction compartment reduces spontaneous activity in the ORN. Collectively, these results implicate for the first time a functional role for an I(h)-channel in olfactory signal transduction.

Xenon attenuates cerebral damage after ischemia in pigs.

BACKGROUND: Cerebral blood flow may be compromised in a variety of anesthetic procedures, and ischemic cerebral complications represent the leading cause of morbidity after cardiac operations. With the growing importance of neuroprotective strategies, the current study was designed to determine whether xenon would attenuate cardiac arrest-induced brain injury in pigs. METHODS: Twenty-four pigs (aged 12-16 weeks) were investigated in a randomized design. General hemodynamics, intracranial pressure, brain tissue oxygenation, and cerebral microdialysis parameters were investigated. The animals were assigned to two groups to receive anesthesia with either xenon (75%) in oxygen (25%) or total intravenous anesthesia combined with air in oxygen (25%) ventilation 15 min before cardiac arrest. After induction (t0) of cardiac arrest of 4 min, cardiopulmonary resuscitation was performed for 1 min, and the induced ventricular fibrillation was terminated by electrical defibrillation. The investigation time was 240 min. RESULTS: Approximately 60 s after cardiac arrest, brain tissue oxygenation decreased to a critical level of less than 5 mmHg, paralleled by a decrease in electroencephalographic activity. Glycerol as a damage marker increased significantly (> 200 m; P < 0.05), with a peak 90 min after cardiac arrest in both groups. Glycerol concentrations during reperfusion were significantly lower and normalized faster in the xenon group as compared with the total intravenous anesthesia group. CONCLUSION: Although the primary ischemic lesion in this model was similar in both groups, the cerebral microdialysis data show that xenon induces a differential neurochemical benefit in cerebral cell damage and metabolism as compared with total intravenous anesthesia in vivo during cerebral reperfusion after cardiac arrest in a pig model.

Ethics roundtable debate: child with severe brain damage and an underlying brain tumour.

A young person presents with a highly malignant brain tumour with hemiparesis and limited prognosis after resection. She then suffers an iatrogenic cardiac and respiratory arrest that results in profound anoxic encephalopathy. A difference in opinion between the treatment team and the parent is based on a question of futile therapy. Opinions from five intensivists from around the world explore the differences in ethical and legal issues. A Physician-ethicist comments on the various approaches.

Nitrogen diffusion into closed anesthesia systems.

OBJECTIVE: In order to reduce losses of gases through plastic components and to reduce nitrogen accummulation during closed system anaesthesia we investigated either 10 sets of anaesthetic tubing made of silicon as used in standard clinical practice and 10 sets made of latex, which are not used anymore due to concerns about latex allergies. The results were compared to each one set made of conventional industrial rubber. METHODS: Anaesthetic tubings were connected to ventilators with low fresh gas losses, suitable for closed system anaesthesia. For nitrogen measurements, a mass spectrometer was used. The fresh gas flow was set to exceed losses by leakages and the amount of gases, extracted from the system by the mass spectrometer. RESULTS: Highest accumulation of nitrogen was found using tubings made of silicone. CONCLUSION: If closed anaesthetic systems in the future will be used in intensive care therapy or in case of long lasting procedures in which closed system anaesthesia is proceeded, materials other than silicone should be investigated to avoid regular purging of system and consecutive losses of gas mixtures.

Characterization of recombinant and native Ih-channels from Apis mellifera.

Recently, a novel class of genes coding for Ih-channels has been identified in several vertebrates and invertebrates. We isolated a cDNA (AMIH) encoding a putative member of these ion channels from Apis mellifera heads by means of polymerase chain reaction and homology screening. High similarity (88% identical amino acids) to the putative Drosophila melanogaster Ih-channel suggests that the Apis cDNA codes for a hyperpolarization-activated and cyclic nucleotide-gated channel. Functional expression of recombinant AMIH in HEK293 cells gave unitary currents that were preferentially selective for potassium over sodium ions and were activated by hyperpolarizing voltage steps. Cyclic nucleotides shifted the voltage activation curve to more positive membrane potentials. The current kinetics, activation by hyperpolarizing voltage steps and modulatory influence of cyclic nucleotides properties closely resemble those of mammalian Ih-channels. RT-PCR analysis showed pronounced mRNA expression in the antennae, head and body of Apis mellifera. Investigation of hyperpolarization-activated currents in olfactory receptor neurons (ORNs) in a primary cell culture of Apis mellifera antennal cells revealed activation properties similar to the heterologously expressed Ih-channel. By in-situ hybridization and immunohistochemistry, expression of AMIH was seen in olfactory receptor neurons of the bee antennae. We conclude that AMIH is the ion channel responsible for the hyperpolarization-activated currents in olfactory receptor neurons of bee.

Vertebral autograft used as bone transplant for anterior cervical corpectomy: technical note.

OBJECTIVE: In this prospective patient study, we used a surgical technique for autograft bone fusion during anterior cervical corpectomy (ACC) in patients experiencing cervical spondylotic myelopathy. We packed the resected bone material of the corpectomy into a titanium mesh cage. To evaluate the efficacy of our autograft technique, we analyzed the results according to neurological outcome, radiological outcome, and complications. METHODS: Between 1995 and 1998, 27 ACC operations were performed for cervical spondylotic myelopathy caused by multisegmental cervical spondylosis. In all patients, decompression of the cervical canal and/or spinal nerve roots was performed by a median cervical corpectomy by an anterior approach. After the ACC was completed, a titanium mesh cage, which was variable in diameter and length, was filled with morselized and impacted bone material from the cervical corpectomy and was then implanted. An anterior cervical plate was placed in all patients to achieve primary stability of the cervical vertebral column. Age, sex, pre- and postoperative myelopathy, number of decompressed levels, radiological results, and complications were assessed. The severity of myelopathy was graded according to the scoring system of the Japanese Orthopaedic Association. RESULTS: Symptomatic improvement of neurological deficits was achieved in 80% of the patients. The mean preoperative Japanese Orthopaedic Association score improved from 13.1 to 15.2 postoperatively (P < 0.05). No patient demonstrated worsening of myelopathic symptoms. Radiological follow-up studies demonstrated complete bony fusion in all patients. A vertical movement of 2.25 +/- 0.43 mm of the titanium cage into the adjacent vertebral bodies was observed in 24 patients. In patients with either a lordotic or neutral cervical spinal axis postoperatively, the axis remained unchanged during the entire follow-up period. CONCLUSION: The results of this study demonstrate that transplantation of autograft bone material harvested during the ACC integrated well in the cage and in the adjacent vertebral bodies. Thus, complications associated with explantation of autograft material from other donor sites, e.g., the iliac crest, could be avoided. The early postoperative and midterm follow-up periods provided no evidence of morphological or functional instability of the operated cervical segments when this autograft technique was used in combination with cervical instrumentation.

Xenon washout during in-vitro extracorporeal circulation using different oxygenators.

BACKGROUND: Xenon anesthesia is known to have no adverse influence on myocardial contractility and cardiocirculatory function even in cardiac compromised patients. To make use of this advantages for cardiac surgery patients undergoing extracorporeal circulation (ECC) it must be known if oxygenators are diffusible for xenon in order to avoid losses of the very expensive noble gas. METHODS: Xenon saturated blood was recirculated in an in-vitro ECC. In 8 experiments four common oxygenators were investigated using continuous mass spectrometry at the exhaust port to measure xenon concentrations in the exspired gas. RESULTS: Xenon concentrations at the exhaust port of the oxygenator increased during filling the oxygenator with blood. Peak level was detected within one minute after onset of ECC. No xenon could be measured two minutes after onset of ECC. CONCLUSIONS: Using common oxygenators xenon is eliminated during ECC and lost into the atmosphere. To maintain anesthesia during ECC continuous xenon application would be necessary to compensate these losses. Due to its high price it would be too expensive to continue xenon anesthesia during ECC. Therefore it is not practicable to use the today's oxygenators and ECC equipment in xenon anesthesia.

Child abuse and pediatric social illness: an epidemiological analysis and ecological reformulation.

Children under four years of age hospitalized for child abuse, domestic accidents, failure to thrive, and ingestions were matched with controls admitted for comparably acute medical conditions. A structured parental interview yielded significant case-control differences. Discriminant analysis suggested interrelationships among the case groups and cluster analysis identified three cohesive groups in terms of severity of symptoms. This reformulation provides a matrix for organizing data and an alternative to the present manifestational classification system.