Atomic-resolution imaging in liquid by frequency modulation atomic force microscopy using small cantilevers with megahertz-order resonance frequencies.

In this study, we have investigated the performance of liquid-environment FM-AFM with various cantilevers having different dimensions from theoretical and experimental aspects. The results show that reduction of the cantilever dimensions provides improvement in the minimum detectable force as long as the tip height is sufficiently long compared with the width of the cantilever. However, we also found two important issues to be overcome to achieve this theoretically expected performance. The stable photothermal excitation of a small cantilever requires much higher pointing stability of the exciting laser beam than that for a long cantilever. We present a way to satisfy this stringent requirement using a temperature controlled laser diode module and a polarization-maintaining optical fiber. Another issue is associated with the tip. While a small carbon tip formed by electron beam deposition (EBD) is desirable for small cantilevers, we found that an EBD tip is not suitable for atomic-scale applications due to the weak tip-sample interaction. Here we show that the tip-sample interaction can be greatly enhanced by coating the tip with Si. With these improvements, we demonstrate atomic-resolution imaging of mica in liquid using a small cantilever with a megahertz-order resonance frequency. In addition, we experimentally demonstrate the improvement in the minimum detectable force obtained by the small cantilever in measurements of oscillatory hydration forces.

Schwannoma of the esophagus: a case exhibiting high 18F-fluorodeoxyglucose uptake in positron emission tomography imaging.

Esophageal schwannoma is rare and it is difficult preoperatively to confirm a definitive diagnosis, even using current imaging techniques. We present a case of a benign esophageal schwannoma that was surgically excised and confirmed by immunohistochemical staining. Conventional radiological studies, including barium meal, computed tomography and endoscopic examination had shown a solid submucosal tumor of the upper thoracic esophagus but had been unable to confirm the diagnosis. Positron emission tomography was carried out to evaluate the malignant potential and showed a high uptake of 18F-fluorodeoxyglucose (FDG) into the tumor in both the early and delayed phase, suggesting that the tumor was a potentially malignant tumor such as a gastrointestinal stromal tumor. This is the first reported case of esophageal schwannoma that indicated a high FDG uptake. Although consensus has not been reached regarding the precise mechanism of FDG accumulation in schwannomas, we discuss our clinicopathological findings and review other studies of the subject.

Neonatal tactile stimulation reverses the effect of neonatal isolation on open-field and anxiety-like behavior, and pain sensitivity in male and female adult Sprague-Dawley rats.

It is well known that early life events induce long-lasting psychophysiological and psychobiological influences in later life. In rodent studies, environmental enrichment after weaning prevents the adulthood behavioral and emotional disturbances in response to early adversities. We compared the behavioral effect of neonatal isolation (NI) with the effect of NI accompanied by tactile stimulation (NTS) to determine whether NTS could reverse or prevent the effects of NI on the adulthood behavioral and emotional responses to environmental stimuli. In addition, we also examined the sex difference of the NTS effect. Measurements of body weights, an open-field locomotor test, an elevated plus maze test, a hot-plate test, and a contextual fear-conditioning test were performed on postnatal day 60. As compared with rats subjected to NI, rats subjected to NTS showed significantly higher activity and exploration in the open-field locomotor test, lower anxiety-like behavior in the elevated plus maze test, and significantly prolonged latencies in the hot-plate test, and this effect was equal among males and females. In the contextual fear-conditioning test, whereas NTS significantly reduced the enhanced freezing time due to NI in females, no significant difference in the freezing time between NI and NTS was found in males. These findings indicate that adequate tactile stimulation in early life plays an important role in the prevention of disturbances in the behavioral and emotional responses to environmental stimuli in adulthood induced by early adverse experiences.

Allelic loss mapping and physical delineation of a region harboring a putative thymic lymphoma suppressor gene on mouse chromosome 12.

Our previous allelic loss analysis of gamma-ray induced thymic lymphomas in F1 hybrid and backcross mice between BALB/c and MSM strains mapped the Tlsr4 region exhibiting a high frequency of allelic loss (62%) to a 2.9 cM interval between the markers D12Mit53 and D12Mit279 on mouse chromosome 12. To narrow further the interval harboring a putative tumor suppressor gene, a high-density scan has been carried out for informative 361 thymic lymphomas. Construction of a physical map of Tlsr4 with 3 YAC and 15 BAC clones and isolation of YAC- and BAC-derived polymorphic probes lead to fine allelic loss mapping. Three successive polymorphic sites within one BAC exhibit the retention of both alleles in seven, one and four lymphomas, suggesting that a common region of allelic loss for Tlsr4 exists within the BAC region. Pulsed-field gel electrophoresis of NotI digests of this and other clones determines that the commonly lost region is a 35 kb interval with a NotI site. NotI sites are frequently associated with coding regions, and our preliminary sequencing has identified ESTs in the region. Thus, the present study facilitates the identification of genes in the Tlsr4 region that would lead to isolation of a novel tumor suppressor gene.

Isoflurane increases norepinephrine release in the rat preoptic area and the posterior hypothalamus in vivo and in vitro: Relevance to thermoregulation during anesthesia.

General anesthetics modulate autonomic nervous system function including thermoregulatory control, which resides in the preoptic area of the anterior hypothalamus. However, the mechanism by which anesthetics modulate hypothalamic function remains unknown. We hypothesized that isoflurane increases norepinephrine release in the preoptic area and in the posterior hypothalamus causing hypothermia during anesthesia. To test this hypothesis, we performed a series of in vivo and in vitro studies in rats. In vivo studies: 1) Norepinephrine release was measured by microdialysis in the preoptic area or the posterior hypothalamus (n=9 each) before, during (30 min), and after (50 min) rats were anesthetized with 2% isoflurane. 2) In five rats, blood gases and arterial pressure were measured. 3) Body temperature changes (n=6 each) were measured after prazosin (0, 0.05, 0.5 microg), norepinephrine (0, 0.1, 1.0 microg), or 0.5 microg prazosin with 1.0 microg norepinephrine injection into the preoptic area. In vitro study: Norepinephrine release was measured from anterior or posterior hypothalamic slices (n=10 each) incubated with 0, 1, 2, or 4% isoflurane in Ca2+-containing buffer or with 4% isoflurane (n=10) in Ca2+-free buffer. Data were analyzed with repeated measures or factorial ANOVA and Student-Newman-Keuls tests. P<0.05 was significant. During anesthesia, norepinephrine release in the preoptic area was increased approximately 270%, whereas the release in the posterior hypothalamus remained unchanged. During emergence, posterior hypothalamic norepinephrine release increased by approximately 250% (P<0.05). Rectal temperature changes correlated with norepinephrine release from the preoptic area. Norepinephrine in the preoptic area enhanced isoflurane-induced hypothermia, while prazosin reversed it. Norepinephrine release from anterior hypothalamic slices increased at all isoflurane concentrations, but only at the highest concentration in posterior hypothalamic slices. Under Ca2+-free conditions, 4% isoflurane increased norepinephrine from both regions. These results suggest that augmentation of norepinephrine release in the preoptic area is responsible for hypothermia during general anesthesia.

Effects of angiotensin-converting enzyme inhibitors on glucose uptake.

We investigated the effect of angiotensin-converting enzyme inhibitors on glucose uptake regulation as well as the effect of bradykinin (BK) on glucose uptake and its regulation by using inhibitors of phospholipase C, BK B2 receptor, protein kinase C, phosphatidylinositol 3-kinase, tyrosine kinase, and intracellular Ca(2+). We measured 2-deoxyglucose uptake by using L(6) skeletal muscle cells. In the presence of 1 nmol/L of insulin, 1 micromol/L of enalaprilat enhanced insulin-induced glucose uptake from 89.2+/-8. 1 to 138.0+/-13.6 pmol/h per mg protein. The stimulation of glucose uptake with enalaprilat was blocked to 92.7+/-7.8 pmol/h per mg protein by 10 micromol/L HOE 140 (a BK B2 receptor antagonist). In the presence of 1 nmol/L of insulin, exposure to 10 micromol/L BK stimulated glucose uptake from 89.2+/-8.1 to 171.6+/-10.1 pmol/h per mg protein. However, in the absence of insulin, BK could not enhance glucose uptake. One hundred nanomoles per liter of tyrphostin A-23 and genistein, which are tyrosine kinase inhibitors, significantly decreased the BK-induced glucose uptake from 142.0+/-8.4 to 87.6+/-6. 4 and 85.2+/-7.3 pmol/h per mg protein, respectively. BK-induced glucose uptake was inhibited significantly by 10 micromol/L U73122 (a phospholipase C antagonist) from 142.0+/-8.4 to 95.7+/-9.5 pmol/h per mg protein. One and 20 micromol/L of TMB-8 (an intracellular calcium antagonist) significantly decreased BK-induced glucose uptake from 142.0+/-8.4 to 108.0+/-9.6 and 100.8+/-11.4 pmol/h per mg protein. Angiotensin-converting enzyme inhibitors enhanced insulin-induced glucose uptake via the BK B2 receptor. BK-stimulated glucose uptake is related to phospholipase C, tyrosine kinase, and an increase in intracellular calcium.

Orexinergic neurons and barbiturate anesthesia.

Orexins (OXs) regulate sleep with possible interactions with brain noradrenergic neurons. In addition, noradrenergic activity affects barbiturate anesthesia. As we have also recently reported that OXs selectively evoke norepinephrine release from rat cerebrocortical slices we hypothesized that barbiturate anesthesia may result from of an interaction with central orexinergic systems. To test this hypothesis, we performed a series of in vivo and in vitro studies in rats. In vivo, the effects of i.c.v. OX A, B and SB-334867-A (OX1 receptor antagonist) on pentobarbital, thiopental or phenobarbital-induced anesthesia times (loss of righting reflex) was assessed. In vitro effects of barbiturates and SB-334867-A on OX-evoked norepinephrine release from cerebrocortical slice was examined. In Chinese hamster ovary cells expressing human OX1/OX2 receptors OX A- and B-evoked increases in intracellular Ca2+ were measured with and without barbiturates. OX A and B significantly decreased pentobarbital, thiopental and phenobarbital anesthesia times by 15-40%. SB-334867-A increased thiopental-induced anesthesia time by approximately by 40%, and reversed the decrease produced by OX A. In vitro, all anesthetic barbiturates inhibited OX-evoked norepinephrine release with clinically relevant IC50 values. A GABAA antagonist, bicuculline, did not modify the inhibitory effects of thiopental and the GABAA agonist, muscimol, did not inhibit norepinephrine release. In addition there was no interaction of barbiturates with either OX1 or OX2 receptors. Collectively our data suggest that orexinergic neurons may be an important target for barbiturates, and GABAA, OX1 and OX2 receptors may not be involved in this interaction.

Orexin A and B evoke noradrenaline release from rat cerebrocortical slices.

1. Orexin A and B, recently identified in the rat hypothalamus are endogenous neuropeptide agonists for the G-protein coupled orexin-1 (OX1) and orexin-2 (OX2) receptors. 2. In the present study, we have examined the effects of orexin A, B and raised extracellular K(+) on noradrenaline release from the rat cerebrocortical slice. We have compared this with other sleep-wake-related (excitatory) neurotransmitters; dopamine, glutamate, serotonin and histamine. 3. Neurotransmitter release studies were performed in rat cerebrocortical slices incubated in modified Krebs buffer (with and without Ca(2+)+EGTA 1 mM) with various concentrations of orexin A, B and K(+) for various times. 4. Orexin A and B-evoked (10(-7) M) noradrenaline release was time-dependent reaching a maximum some 10 min after stimulation. K(+) (40 mM) evoked release was also time dependent but reached a maximum after 6 min. Orexin A, B and K(+) stimulation of release was concentration dependent with pEC(50) and E(max) (% of basal) values of 8.74+/-0.32 (1.8 nM) and 263+/-14% and 8.61+/-0.38 (2.4 nM) and 173+/-7% and 1.43+/-0.02 (37 mM) and 1430+/-70%, respectively. Orexin-evoked release was partially extracellular Ca(2+) dependent. 5. Of the other transmitters studied there was a weak orexin A and B stimulation of glutamate release. In contrast K(+) evoked dopamine, glutamate, histamine and serotonin release with pEC(50) and E(max) (% of basal) values of 1.47+/-0.05 (34 mM) and 3430+/-410%, 1.38+/-0.04 (42 mM) and 1240+/-50%, 1.47+/-0.02 (34 mM) and 480+/-10% and 1.40+/-0.05 (40 mM) and 560+/-60% respectively. 6. We conclude that the neuropeptides orexin A and B evoke noradrenaline release from rat cerebrocortical slices.

Bradykinin-induced inositol 1,4,5-triphosphate in neonatal rat cardiomyocytes is activated by endotoxin.

We studied the effect of endotoxin on bradykinin-induced inositol 1,4,5-triphosphate (IP3) production and the relationship between IP3 and phospholipase A2 or thromboxane A2. When exposed with 0.1, 1.0, and 10 microg ml(-1) lipopolysaccharide (LPS) for short-term (60 min), 100 nmol L(-1) bradykinin-induced IP3 production was stimulated in a dose-dependent manner from 569.2+/-42.4 in absence of LPS to 714.3+/-52.8, 804.5+/-42.6, and 894.1+/-62.6 pmol mg protein(-1). Treatment of 100 micromol L(-1) ACA (a phospholipase A2 inhibitor) and 10 micromol L(-1) BM13.177 (a thromboxane A2 inhibitor) significantly decreased bradykinin-induced IP3 production and LPS (1.0 microg mL(-1)) modulation of bradykinin-induced IP3 formation from 804.5+/-42.6 to 217.4+/-12.7 and 208.6+/-17.1 pmol mg protein(-1), respectively. LPS modulation of bradykinin-induced IP3 production was significantly blocked by 1 micromol L(-1) TMB-8 (an intracellular Ca2+ antagonist) from 804.5+/-42.6 to 507.8+/-33.4 pmol mg protein(-1). LPS modulation of bradykinin-induced IP3 production was significantly inhibited from 804.5+/-42.6 to 397.4+/-30.3 pmol mg protein(-1) by treatment of 10 micromol L(-1) indomethacin. In conclusion, short-term administration of LPS stimulates bradykinin-induced IP3 formation through activation of phospholipase A2 and thromboxane A2 and the stimulation is associated with an elevation of intracellular Ca2+.

Effects of sedatives on noradrenaline release from the medial prefrontal cortex in rats.

RATIONALE: N-Methyl-d-aspartate (NMDA) receptor antagonism and GABA(A) receptor activation are believed to be critical targets for general anesthetic action. However, as NMDA antagonism of intravenous anesthetic agents causes post-anesthetic emergence reactions such as hallucination and agitation, while the GABA(A)-mimetic intravenous anesthetic agents do not, these two classes of intravenous anesthetic agents produce differential clinical profiles. OBJECTIVE: We have investigated the differential effects of the GABA(A) agonists propofol and midazolam and the NMDA antagonist ketamine on noradrenaline release from the medial prefrontal cortex of the rat using microdialysis, as noradrenergic neurons have a role to play in anesthesia and are known to be important in the control of sleep, attention and learning. METHODS: Twenty-one male Wistar rats (200-270 g) were randomly allocated into three groups: ketamine 100 mg x kg(-1) (n = 6), propofol 60 mg x kg(-1) (n = 8) and midazolam 5 mg x kg(-1) (n = 7) IP. A unilateral guide cannula was implanted stereotaxically into the medial prefrontal cortex under pentobarbital anesthesia (50 mg x kg(-1) IP). Forty-eight hours later, a dialysis probe was inserted through the guide cannula, and perfused with an artificial cerebrospinal fluid solution containing 1 mM pargyline. Following an equilibration period, samples of dialysate were collected every 10 min. Noradrenaline content was measured by high-performance liquid chromatography using an electrochemical detector. RESULTS: Anesthesia times, defined as the duration between the loss of righting reflex and recovery, were 24.7+/-5.6 (SEM), 20.5+/-1.9 and 25.2+/-1.5 min for propofol, midazolam and ketamine, respectively (no significant between-group differences). Both GABA(A )agonists, propofol and midazolam, significantly decreased noradrenaline release (75% and 71% of basal release, respectively). The NMDA antagonist ketamine markedly increased noradrenaline release (413% of basal). CONCLUSION: These data suggest that different clinical profiles observed with these two classes of sedatives may result from changes in noradrenaline release from the medial prefrontal cortex.

Ketamine and midazolam kinetics during continuous hemodiafiltration in patients with multiple organ dysfunction syndrome.

OBJECTIVE: To assess the effect of continuous hemodiafiltration (CHDF) on ketamine and midazolam kinetics in multiple organ dysfunction syndrome (MODS). DESIGN AND SETTING: Consecutive clinical study in a general intensive care unit of a university hospital. PATIENTS: Twelve adult patients with MODS requiring CHDF. MEASUREMENTS AND RESULTS: A total of 68 samples were collected during CHDF for ketamine, norketamine, and midazolam assays. The clearance values for ketamine and norketamine were 10.8 +/- 6.6 and 10.9 +/- 11.5 ml/min and their daily extractions were 21.4 +/- 7.1 and 10.2 +/- 11.5 mg/day, respectively. Midazolam was not eliminated through the filter during CHDF. There were no changes in Ramsay Sedation Score or Glasgow Coma Scale during CHDF. CONCLUSIONS: Small fractions of ketamine and norketamine were eliminated during CHDF in MODS. Midazolam was not eliminated during CHDF. CHDF did not affect the sedation using ketamine and midazolam even in MODS patients.

Cortisol and catecholamine kinetics during continuous hemodiafiltration in patients with multiple organ dysfunction syndrome.

OBJECTIVE: To assess the influence of continuous hemodiafiltration (CHDF) on cortisol and catecholamine kinetics in multiple organ dysfunction syndrome. DESIGN: Consecutive clinical study. SETTING: General intensive care unit of a university hospital. PATIENTS: Ten adult patients with multiple organ dysfunction syndrome requiring CHDF. MEASUREMENTS AND RESULTS: A total of 40 samples were collected during CHDF for cortisol and catecholamine assays. The clearances for cortisol, epinephrine, norepinephrine and dopamine were 2.5 +/- 1.7 ml/min, 26.3 +/- 2.7 ml/min, 16.7 +/- 4.2 ml/min and 26.3 +/- 2.6 ml/min (Mean +/_ SE), and their daily extractions were 1.8 +/- 0.2 mg/day, 11.4 +/- 4.8 micrograms/day, 1.0 +/- 0.1 micrograms and 2.3 +/- 0.3 micrograms/day, respectively. There were no significant changes in blood cortisol and catecholamine levels during CHDF conducted for 48 h. CONCLUSIONS: The cortisol and catecholamine losses during CHDF were small and unlikely to lead to hemodynamic disturbances.

Detection of histamine-induced capillary protein leakage and hypovolaemia by determination of indocyanine green and glucose dilution method in dogs.

OBJECTIVE: The plasma volume of histamine-induced protein capillary leakage may be overestimated when this is determined using the indocyanine green (ICG) dilution method (Vd-ICG), since this dye binds to plasma proteins. The initial distribution volume of glucose (IDVG) has been shown to indicate the central extracellular fluid volume including plasma. Accordingly, the overestimation would be detected by a higher Vd-ICG/IDVG ratio. Our study was intended to examine whether the simultaneous measurement of these two variables can evaluate histamine-induced protein leakage and associated hypovolaemia. DESIGN: Prospective animal study. SETTING: Institutional animal research laboratory. SUBJECTS: Twenty-four anaesthetized and ventilated mongrel dogs. INTERVENTIONS: Anaesthetized animals were mechanically ventilated and received infusions of normal saline (n = 8), histamine 50 microg/kg per h (n = 8), or histamine 100 microg/kg per h. The Vd-ICG and IDVG were calculated using a one-compartment model by simultaneous administration of ICG 0.5 mg/kg, and glucose 100 mg/kg followed by serial arterial blood sampling. MEASUREMENTS AND RESULTS: In both histamine groups, a significant elevation of haematocrit and a decrease of plasma albumin concentration were found (p<0.05). Although the IDVG decreased following histamine administration (p<0.05), the Vd-ICG remained unchanged. The Vd-ICG/IDVG ratio increased in a dose-dependent manner after histamine administration (p<0.05), but remained unchanged following normal saline administration. CONCLUSION: The results suggest that the Vd-ICG/IDVG ratio and the IDVG are useful in evaluating the magnitude of the leakage and hypovolaemia.

Glucose dilution can detect fluid redistribution following phentolamine infusion in dogs.

OBJECTIVE: We have recently reported that the initial distribution volume of glucose (IDVG) reliably measures the central extracellular fluid (ECF) volume in the presence of fluid gain or loss. However, it is not clear if IDVG consistently reflects central-ECF volume when redistribution of fluid occurs in the absence of fluid gain or loss. This study was designed to investigate changes in fluid volumes during phentolamine infusion in dogs. DESIGN: Prospective animal study. SETTING: Institutional animal research laboratory. SUBJECTS: Fourteen anesthetized and ventilated mongrel dogs. INTERVENTIONS: Anesthetized animals were mechanically ventilated and received infusions of normal saline (n = 7) or phentolamine (10 microg kg min) (n = 7). Plasma volume was estimated using the indocyanine green (ICG) dilution method (PV-ICG) and IDVG was calculated using a one-compartment model by simultaneous administration of ICG 0.5 mg/kg and glucose 100 mg/kg before, during, and after infusion of either drug. MEASUREMENTS AND RESULTS: PV-ICG during infusion was not different between groups. However, IDVG significantly decreased (P < 0.05) following phentolamine infusion when compared with normal saline infusion. CONCLUSION: Our results suggest that IDVG rather than PV-ICG consistently measures central extracellular fluid volume, even when redistribution of fluid occurs.

Daily changes of the area of density in the dependent lung region - evaluation using transesophageal echocardiography.

OBJECTIVE: To evaluate the daily changes of the area of density using transesophageal echocardiography (TEE) in acute respiratory distress syndrome (ARDS) and acute lung injury (ALI) patients. DESIGN: Retrospective observational study. SETTING: General ICU in a university hospital. PATIENTS: Fifteen patients with ARDS or ALI who underwent TEE examination for more than 5 days. MEASUREMENTS: Densities in the lower left lung region were observed through the descending aorta by TEE. Daily changes of the area of density were evaluated. The areas of density estimated by TEE were compared with those obtained by computed tomography (CT). The relation between the area of density and PaO(2)/FIO(2)was calculated. RESULTS: The area of density in the dependent lung region measured by TEE was 11.1+/-5.7 cm(2) (mean +/- SD) at the mid-esophageal position. The area of density in ARDS patients changed daily from 12.0+/-2.8 cm(2) to 8.5+/-6.7 cm(2). The areas of density evaluated using TEE in the left lung correlated significantly with those estimated using CT ( r=0.72, p<0.01). In addition, we found a significant correlation between PaO(2)/FIO(2) and the area of density estimated by TEE ( r=-0.53, p<0.05). CONCLUSION: Using TEE, we could evaluate daily changes of the area of density in the dependent lung region in the intensive care situation. The areas of density in ARDS patients changed from day to day following the changes of oxygenation.

The initial distribution volume of glucose rather than indocyanine green derived plasma volume is correlated with cardiac output following major surgery.

OBJECTIVES: To determine whether the initial distribution volume of glucose (IDVG) rather than plasma volume or blood volume is correlated better with cardiac output during the 4 days following major surgery. DESIGN AND SETTING: Prospective clinical investigation in the general intensive care unit of a university hospital. PATIENTS AND METHODS: 31 consecutive patients who underwent radical surgery for esophageal carcinoma were enrolled. Continuous thermodilution cardiac output monitor was placed in the operating room. Indocyanine green (ICG; 25 mg) and glucose (5 g) were administered simultaneously to calculate IDVG and plasma volume determined using the ICG dilution method. Blood volume was also calculated from plasma volume ICG and hematocrit. Those volumes were measured on admission to the ICU and daily on the first 3 postoperative days. The relationships between each volume and cardiac index (CI), and between routine clinical variables and CI were evaluated. RESULTS: IDVG had a linear correlation with CI in the early postoperative days (r = 0.71, n = 124, p < 0.000001). Measurements of neither the plasma volume nor the blood volume yielded a better correlation with CI than did IDVG (r = 0.45, n = 124, p < 0.000001, and r = 0.23, n = 124, p < 0.01, respectively). No correlation was found between pulmonary artery wedge pressure and CI or between central venous pressure and CI. CONCLUSIONS: Our results indicate that IDVG rather than intravascular volume is correlated with cardiac output. We suggest that IDVG has potential as an alternative indicator of cardiac preload following major surgery.

Does indocyanine green accurately measure plasma volume independently of its disappearance rate from plasma in critically ill patients?

OBJECTIVE: To determine whether plasma volume determined by the indocyanine green (ICG) dilution method (PV-ICG) is equally accurate independently of its disappearance rate from plasma in the critically ill. DESIGN: Retrospective clinical investigation. SETTING: Intensive care unit of a university teaching hospital. PATIENTS AND METHODS: 192 adult patients were initially enrolled. The PV-ICG and the initial distribution volume of glucose (IDVG) were calculated utilizing a one-compartment model by simultaneous administration of ICG 25 mg and glucose 5 g on the first day of measurement in each patient. Twenty-one patients were excluded from the study because of a higher PV-ICG/IDVG ratio (> 0.45) indicating apparent overestimation of the PV-ICG associated with the generalized protein capillary leakage. The remaining 171 patients were divided into four groups according to the magnitude of their disappearance rate of ICG from plasma (Ke-ICG). RESULTS: Convergence was assumed consistently in each ICG or glucose decay curve, even in the lower Ke-ICG less than 0.10/min. The relationship between the two volumes was not statistically different among groups. CONCLUSIONS: The results suggest that the measurement of the PV-ICG can be equally accurate independently of its disappearance rate from plasma unless there is generalized protein capillary leakage.

Effects of two volatile anesthetics (sevoflurane and halothane) on the hypothalamic noradrenaline release in rat brain.

There are marked increases in noradrenaline (NA) release during emergence from general anesthesia induced with volatile anesthestics. These changes in NA in the posterior hypothalamus of the rat were assessed by intracranial microdialysis. Sevoflurane and halothane in equipotent concentrations were used to obtain the same depth of anesthesia. NA release increased similarly with the two agents during recovery. However, NA release remained elevated longer with halothane, from which recovery was also slower.

Physostigmine antagonizes ketamine-induced noradrenaline release from the medial prefrontal cortex in rats.

Physostigmine is known to antagonize ketamine anesthesia. In this study, effects of physostigmine (0.1 mg kg(-1) i.p.) on ketamine (100 mg kg(-1) i.p.)-induced anesthesia time and noradrenaline release from the medial prefrontal cortex in rats were examined. Ketamine produced anesthesia for 27+/-1 min and increased noradrenaline release to 405% of the basal. Physostigmine significantly reduced anesthesia time to 23+/-1 min (p<0.05), and noradrenaline to 248% (p<0.05). Therefore, noradrenaline release may play an important role in ketamine anesthesia.

Barbiturates inhibit K(+)-evoked noradrenaline and dopamine release from rat striatal slices--involvement of voltage sensitive Ca(2+) channels.

The cellular target site(s) for anaesthetic action remain unclear. In rat striatal slices we have previously demonstrated that K(+)-evoked noradrenaline (NA) and dopamine (DA) release is mediated predominantly via P/Q-type voltage sensitive Ca(2+) channels (VSCC). Using this model of Ca(2+) dependent transmitter release we have evaluated the effects of anaesthetic and non-anaesthetic barbiturates. Rat brain striatal slices were incubated in the absence and presence of barbiturate for 10 min at 37 degrees C. The slices were then incubated for 6 min with 40 mM KCl. All anaesthetic barbiturates produced a concentration-dependent inhibition of K(+)-evoked NA and DA release. Non-anaesthetic barbiturate, barbituric acid was ineffective. The pIC(50) for NA and DA release (thiopental: 4.90+/-0.13 and 5.00+/-0.10, pentobarbital: 4.39+/-0.07 and 4.43+/-0.14, phenobarbital: 3.85+/-0.08 and 3.59+/-0.10, respectively) correlated with lipid solubility (NA: r(2)=0.999, DA: r(2)=0.987). We therefore suggest that barbiturates inhibit catecholamine release via an interaction with P/Q VSCC further implicating this channel in anaesthetic action.