Inhaled nitric oxide delivery by anesthesia machines

Inhaled nitric oxide (NO) is a selective pulmonary vasodilator used to treat intraoperative pulmonary hypertension and hypoxemia. In contrast to NO delivered by critical care ventilators, NO delivered by anesthesia machines can be complicated by rebreathing. We evaluated two methods of administering NO intraoperatively: via the nitrous oxide (N(2)O) flowmeter and via the INOvent (Datex-Ohmeda, Madison, WI). We hypothesized that both systems would deliver NO accurately when the fresh gas flow (FGF) rate was higher than the minute ventilation (VE). Each system was set to deliver NO to a lung model. Rebreathing of NO was obtained by decreasing FGF and by simulating partial NO uptake by the lung. At FGF > or = VE (6 L/min), both systems delivered an inspired NO concentration ([NO]) within approximately 10% of the [NO] set. At FGF < VE and complete NO uptake, the N(2)O flowmeter delivered a lower [NO] (70 and 40% of the [NO] set at 4 and 2 L/min, respectively) and the INOvent delivered a higher [NO] (10 and 23% higher than the [NO] set at 4 and 2 L/min, respectively). Decreasing the NO uptake increased the inspired [NO] similarly with both systems. At 4 L/min FGF, [NO] increased by 10%-20% with 60% uptake and by 18%-23% with 30% uptake. At 2 L/min, [NO] increased by 30%-33% with 60% uptake and by 60%-69% with 30% uptake. We conclude that intraoperative NO inhalation is accurate when administered either by the N(2)O flowmeter of an anesthesia machine or by the INOvent when FGF > or = VE.

IMPLICATIONS

Inhaled nitric oxide (NO) is a selective pulmonary vasodilator. In a lung model, we demonstrated that NO can be delivered accurately by a N(2)O flowmeter or by a commercial device. We provide guidelines for intraoperative NO delivery.

The optimum time to employ telephotoscreening to detect retinopathy of prematurity

PURPOSE

Labor-intensive screening of infants in the neonatal intensive care units is the only way to detect retinopathy of prematurity (ROP). Our purpose is to determine if RetCam 120 photos, acquired by a neonatal nurse, can be used to screen for ROP by performing 2 screening examinations, at 32 to 34 weeks (exam 1) and at 38 to 40 weeks (exam 2) post-conceptional age.

METHODS

RetCam examinations are performed by a nurse on infants at exam 1 and exam 2 intervals. At the same time, an examination is performed by an experienced ophthalmologist. Masked readers evaluate the photos for ROP and determine if each eye will progress to prethreshold or threshold disease. The data are compared to the clinical course of the eyes.

RESULTS

Forty-six eyes were photographed at exam 1 and 50 eyes at exam 2 from July 1, 1999, to December 15, 1999. Sensitivity and specificity of detecting ROP were 76% and 100% for exam 2 and 46% and 100% for exam 1. Sensitivity and specificity of predicting prethreshold disease were 64% and 97% for exam 2 and 33% and 100% for exam 1. Sensitivity and specificity of predicting threshold were both 100% at exam 2 and 0% (one photo in category) and 95% at exam 1.

CONCLUSION

A potential reason for low sensitivity is technical limitations of the Retcam, such as the difficulty in capturing peripheral retina in small eyes and the need for a better lid speculum.

Detection and monitoring of hypoxemia and oxygen therapy

Many techniques are available to evaluate oxygenation. These include arterial blood gases, capillary blood gases, point-of-care testing, blood gas monitors, pulse oximetery, transcutaneous blood gases, mixed venous blood gases, venous oximetry, and gastric tonometry. Clinicians should understand not only the benefits, but also the limitations of these techniques. Monitoring of oxygenation should not be done just because it is technically feasible. The decision to monitor, like any other clinical decision, should be based on therapeutic objectives.

Residual delay maps unveil global patterns of atmospheric nonlinearity and produce improved local forecasts

We use residual-delay maps of observational field data for barometric pressure to demonstrate the structure of latitudinal gradients in nonlinearity in the atmosphere. Nonlinearity is weak and largely lacking in tropical and subtropical sites and increases rapidly into the temperate regions where the time series also appear to be much noisier. The degree of nonlinearity closely follows the meridional variation of midlatitude storm track frequency. We extract the specific functional form of this nonlinearity, a V shape in the lagged residuals that appears to be a basic feature of midlatitude synoptic weather systems associated with frontal passages. We present evidence that this form arises from the relative time scales of high-pressure versus low-pressure events. Finally, we show that this nonlinear feature is weaker in a well regarded numerical forecast model (European Centre for Medium-Range Forecasts) because small-scale temporal and spatial variation is smoothed out in the grided inputs. This is significant, in that it allows us to demonstrate how application of statistical corrections based on the residual-delay map may provide marked increases in local forecast accuracy, especially for severe weather systems.

Characterization of the adenylation site in the RNA 3'-terminal phosphate cyclase from Escherichia coli

RNA 3'-terminal phosphate cyclases are a family of evolutionarily conserved enzymes that catalyze ATP-dependent conversion of the 3'-phosphate to the 2',3'-cyclic phosphodiester at the end of RNA. The precise function of cyclases is not known, but they may be responsible for generating or regenerating cyclic phosphate RNA ends required by eukaryotic and prokaryotic RNA ligases. Previous work carried out with human and Escherichia coli enzymes demonstrated that the initial step of the cyclization reaction involves adenylation of the protein. The AMP group is then transferred to the 3'-phosphate in RNA, yielding an RNA-N(3')pp(5')A (N is any nucleoside) intermediate, which finally undergoes cyclization. In this work, by using different protease digestions and mass spectrometry, we assign the site of adenylation in the E. coli cyclase to His-309. This histidine is conserved in all members of the class I subfamily of cyclases identified by phylogenetic analysis. Replacement of His-309 with asparagine or alanine abrogates both enzyme-adenylate formation and cyclization of the 3'-terminal phosphate in a model RNA substrate. The cyclase is the only known protein undergoing adenylation on a histidine residue. Sequences flanking the adenylated histidine in cyclases do not resemble those found in other proteins modified by nucleotidylation.

Pathophysiologic correlates of thromboembolism in nonvalvular atrial fibrillation: II. Dense spontaneous echocardiographic contrast (The Stroke Prevention in Atrial Fibrillation [SPAF-III] study)

We analyzed transesophageal echocardiograms from 772 participants in the Stroke Prevention in Atrial Fibrillation (SPAF-III) study, characterizing spontaneous echocardiographic contrast (SEC) in the left atrium or appendage as faint or dense. The association of dense SEC with stroke risk factors and anatomic, hemodynamic, and hemostatic parameters related to specific thromboembolic mechanisms was evaluated by multivariate analysis. Spontaneous echocardiographic contrast was present in 55% of patients and was dense in 13%. Age (odds ratio [OR] 2.4/decade, P <.001), constant atrial fibrillation (OR 6.9, P <.001), history of hypertension (OR 3. 2, P <.001), and current tobacco smoking (OR 2.6, P =.04) were independent clinical predictors of dense SEC. Multivariate analysis of clinical, echocardiographic, and hemostatic parameters yielded age as the sole independent clinical predictor of dense SEC (OR 2. 4/decade, P <.001). Other independent predictors were measures of left atrial/appendage flow dynamics, left atrial size (OR 2.4/cm diameter, M-mode, P <.001), atherosclerotic aortic plaque (OR 2.8, P =.002), and plasma fibrinogen >350 mg/dL (P <.001). Results were similar when SEC of any density was analyzed. In conclusion, SEC occurred in more than half of these patients with prospectively defined nonvalvular atrial fibrillation but was usually faint. Dense SEC was strongly associated with previously reported clinical predictors of stroke, linking them to thromboembolism through atrial stasis. Diverse pathophysiologic factors including atrial stasis, fibrinogen level, and aortic plaque influence SEC.

Ndr protein kinase is regulated by phosphorylation on two conserved sequence motifs

Ndr is a nuclear serine/threonine protein kinase that belongs to a subfamily of kinases implicated in the regulation of cell division and cell morphology. This subfamily includes the kinases LATS, Orb6, Cot-1, and Dbf2. We show here that Ndr is potently activated when intact cells are treated with okadaic acid, suggesting that Ndr is normally held in a state of low activity by protein phosphatase 2A. We mapped the regulatory phosphorylation sites of Ndr protein kinase and found that active Ndr is phosphorylated on Ser-281 and Thr-444. Mutation of either site to alanine strongly reduced both basal and okadaic acid-stimulated Ndr activity, while combined mutation abolished Ndr activity completely. Importantly, each of these sites (and also the surrounding sequences) are conserved in the kinase relatives of Ndr, suggesting a general mechanism of activation for kinases of this subfamily. Ser-281 and Thr-444 are also similar to the regulatory phosphorylation sites in several targets of the phosphoinositide-dependent protein kinase PDK1.(1) However, PDK1 does not appear to function as an upstream kinase for Ndr. Thus, Ndr and its close relatives may operate in a novel signaling pathway downstream of an as-yet-unidentified kinase with specificity similar to, but distinct from, PDK1.

The four terminal components of the complement system are C-mannosylated on multiple tryptophan residues

C-Mannosylation is a unique form of protein glycosylation, involving the C-glycosidic attachment of a mannosyl residue to the indole moiety of Trp. In the two examples found so far, human RNase 2 and interleukin-12, only the first Trp in the recognition motif WXXW is specifically C-mannosylated. To establish the generality of protein C-mannosylation, and to learn more about its mechanism, the terminal components of the human complement system (C6, C7, C8,and C9), which contain multiple and complex recognition motifs, were examined. Together with C5b they form the cytolytic agent, the membrane attack complex. These are the first proteins that are C-mannosylated on more than one Trp residue as follows: six in C6, four in C7, C8alpha, and C8beta, and two in C9. Thus, from the 113 Trp residues in the complete membrane attack complex, 50 were found to undergo C-mannosylation. The other important finding is that in C6, C7, C8, and C9 Trp residues without a second Trp (or another aromatic residue) at the +3 position can be C-mannosylated. This shows that they must contain an additional C-mannosylation signal. Whether this is encoded in the primary or tertiary structure is presently unknown. Finally, all modified Trp residues are part of the highly conserved core of the thrombospondin type 1 repeats present in these proteins. Since this module has been found in a large number of other proteins, the results suggest further candidates for C-mannosylation.

Pressure-release tracheal gas insufflation reduces airway pressures in lung-injured sheep maintaining eucapnia

Although tracheal gas insufflation (TGI) has proved to be a useful adjunct to mechanical ventilation, end-inspiratory as well as end-expiratory pressures may increase. We investigated the ability of continuous-flow TGI to maintain eucapnia while reducing airway pressure (Paw) and tidal volume (VT). Seven sheep (36 +/- 2 kg) were ventilated using the Dräger Evita 4 in the pressure control plus mode where flow is released via the expiratory valve to maintain constant inspiratory pressure. To avoid TGI-generated positive end-expiratory pressure (PEEP), a prototype reverse flow TGI tube was used. Two TGI flows (5 and 10 L/min) were investigated pre- and postsaline lavage-induced lung injury. Inspiratory pressures and VT were significantly reduced as TGI flow increased. At 10 L/min TGI flow the carinal pressures (Pcar) and VT were reduced pre- and postinjury by 15% and 20%, and by 28% and 34%, respectively. Tidal volume to dead space ratio (VD/VT) decreased preinjury from 0.49 +/- 0.1 to 0.18 +/- 0.2 and postinjury from 0.62 +/- 0.1 to 0.33 +/- 0.1 at a TGI flow of 10 L/min. The combination of the reverse flow TGI tube and a ventilator with an inspiratory pressure relief mechanism kept set end-inspiratory and end-expiratory pressures constant. This TGI system effectively reduced set Paw and VT while maintaining eucapnia.

A chicken embryo protein related to the mammalian DEAD box protein p68 is tightly associated with the highly purified protein-RNA complex of 5-MeC-DNA glycosylase

We have shown previously that DNA demethylation by chick embryo 5-methylcytosine (5-MeC)-DNA glycosylase needs both protein and RNA. Amino acid sequences of nine peptides derived from a highly purified 5-MeC-DNA glycosylase complex were identified by Nanoelectrospray ionisation mass spectrometry to be identical to the mammalian nuclear DEAD box protein p68 RNA helicase. Antibodies directed against human p68 helicase cross-reacted with the purified 5-MeC-DNA glycosylase complex and immunoprecipitated the glycosylase activity. A 2690 bp cDNA coding for the chicken homologue of mammalian p68 was isolated and sequenced. Its derived amino acid sequence is almost identical to the human p68 DEAD box protein up to amino acid position 473 (from a total of 595). This sequence contains all the essential conserved motifs from the DEAD box proteins which are the ATPase, RNA unwinding and RNA binding motifs. The rest of the 122 amino acids in the C-terminal region rather diverge from the human p68 RNA helicase sequence. The recombinant chicken DEAD box protein expressed in Escherichia coli cross-reacts with the same p68 antibodies as the purified chicken embryo 5-MeC-DNA glycosylase complex. The recombinant protein has an RNA-dependent ATPase and an ATP-dependent helicase activity. However, in the presence or absence of RNA the recombinant protein had no 5-MeC-DNA glycosylase activity. In situ hybridisation of 5 day-old chicken embryos with antisense probes of the chicken DEAD box protein shows a high abundance of its transcripts in differentiating embryonic tissues.

The N-glycans of jack bean alpha-mannosidase. Structure, topology and function

The acid hydrolase alpha-mannosidase, which accumulates in plant vacuoles and probably is involved in the catabolism and turnover of N-linked glycoproteins, is itself a glycoprotein with at least one high-mannose-type and one complex-type N-glycan. The puzzling finding that alpha-mannosidase stably carries its own substrate suggests that the N-glycans have unique topologies, and important functions in protein folding, oligomerization or enzyme activity. As a first step towards the elucidation of this enigma, we purified the N-glycans of jack bean alpha-mannosidase and determined their structures by sugar composition analysis, mass spectrometry and 1H-NMR. The structures of two N-glycans were identified in an approximate ratio of one-to-one: a glucose-containing high-mannose-type glycan (Glc1Man9GlcNAc2) and a small xylose- and fucose-containing complex-type glycan (Xyl1Man1Fuc1GlcNAc2). Isolation and sequencing of glycopeptides strongly suggests that one high-mannose-type and one complex-type glycan are linked to specific glycosylation sites of the large alpha-mannosidase subunit. The high-mannose-type glycan, which is a good substrate of the endoglycosidase (endo-H), can only be removed from the enzyme after denaturation and cleavage of disulfide bonds by a reducing agent, suggesting that this glycan is buried within the folded polypeptide and, thus, protected from its hydrolytic activity. Denaturation and reduction of the native enzyme led to a marked decrease in alpha-mannosidase activity. However, the activity could largely be recovered by renaturation in an appropriate renaturation buffer. In contrast, recovery of alpha-mannosidase activity failed when the high-mannose-type glycan was removed by endo-H prior to renaturation, indicating that this glycan appears to be important for enzyme activity.

Dose-finding study of epidoxorubicin and docetaxel as first-line chemotherapy in patients with advanced breast cancer

BACKGROUND

Anthracyclines and taxanes are the most active drugs against breast cancer and the search after their optimal combination is under intensive investigation in both the advanced and early disease settings. A dose-finding study of epidoxorubicin (E) and docetaxel (D) was conducted in advanced breast cancer (ABC) to define the maximum tolerated dose (MTD) of the combination with and without granulocyte colony-stimulating factor (G-CSF) support and to characterise its toxicity and activity profile.

PATIENTS AND METHODS

Forty-two patients who received neither palliative chemotherapy nor adjuvant anthracyclines (55% with dominant visceral disease and 66% with > or = 2 sites involved) with measurable/evaluable lesions, were treated at four dose levels starting from E 75 mg/m2 and D 75 mg/m2 to E 120 mg/m2 and D 85 mg/m2. A maximum of four cycles of the combination was given every three weeks and four additional cycles of single agent D were allowed in responding patients. Cardiac function was monitored at baseline and at every second course by echocardiography.

RESULTS

Febrile neutropenia (two patients) and prolonged, severe neutropenia (absolute neutrophil count (ANC) < 0.1 x 10(9)/l for more than three days; one patient) defined the MTD of the combination without G-CSF support at E 90 mg/m2 and D 75 mg/m2. G-CSF was then routinely administered from the subsequent dose level of E 120 mg/m2 and D 75 mg/m2. The MTD with G-CSF support was established at E 120 mg/m2 and D 85 mg/m2 (one patient with neutropenic fever together with failure of ANC recovery at day 21, three patients with ANC less than 0.1 x 10(9)/l for more than three days, one patient with both and one patient with grade 4 thrombocytopenia and toxic death from typhlitis while neutropenic). No severe neurotoxicity, mucositis, or fluid retention were observed and there were no clinical signs of cardiotoxicity. Antitumor activity was not a primary endpoint of the study: the overall response rate (ORR) in 40 evaluable patients was 60% (95% confidence interval: 43%-75%, 58% in liver disease, 84% in soft tissue) with no apparent dose-related effect. After a median follow-up of 19 months (range 2-30+), the overall time to progression (TTP) in nine patients without maintenance hormonal therapy was five months.

CONCLUSIONS

The combination of E and D proved to be an effective and safe regimen in poor- prognosis patients with ABC. G-CSF support allowed higher doses to be delivered safely but dose escalation did not translate into improved response rates (RR). The MTD without growth factors support was used, in a phase II trial, which also included patients with previous anthracycline-containing adjuvant regimens.

Recombinant human interleukin-12 is the second example of a C-mannosylated protein

The beta-chain of human interleukin 12 (IL-12) contains at position 319-322, the sequence Trp-x-x-Trp. In human RNase 2 this is the recognition motif for a new, recently discovered posttranslational modification, i.e., the C-glycosidic attachment of a mannosyl residue to the side chain of tryptophan. Analysis of C-terminal peptides of recombinant IL-12 (rHuIL-12) by mass spectrometry and NMR spectroscopy revealed that Trp-319beta is (partially) C-mannosylated. This finding was extended by in vitro mannosylation experiments, using a synthetic peptide derived from the same region of the protein as an acceptor. Furthermore, human B-lymphoblastoid cells, which secrete IL-12, were found to contain an enzyme that carries out the C-mannosylation reaction. This shows that nonrecombinant IL-12 is potentially C-mannosylated as well. This is only the second report on a C-mannosylated protein. However, the occurrence of the C-mannosyltransferase activity in a variety of cells and tissues, and the presence of the recognition motif in many proteins indicate that more C-mannosylated proteins may be found.

Role of proprioceptive signals from an insect femur-tibia joint in patterning motoneuronal activity of an adjacent leg joint

Interjoint reflex function of the insect leg contributes to postural control at rest or to movement control during locomotor movements. In the stick insect (Carausius morosus), we investigated the role that sensory signals from the femoral chordotonal organ (fCO), the transducer of the femur-tibia (FT) joint, play in patterning motoneuronal activity in the adjacent coxa-trochanteral (CT) joint when the joint control networks are in the movement control mode of the active behavioral state. In the active behavioral state, sensory signals from the fCO induced transitions of activity between antagonistic motoneuron pools, i.e., the levator trochanteris and the depressor trochanteris motoneurons. As such, elongation of the fCO, signaling flexion of the FT joint, terminated depressor motoneuron activity and initiated activity in levator motoneurons. Relaxation of the fCO, signaling extension of the FT joint, induced the opposite transition by initiating depressor motoneuron activity and terminating levator motoneuron activity. This interjoint influence of sensory signals from the fCO was independent of the generation of the intrajoint reflex reversal in the FT joint, i.e., the "active reaction," which is released by elongation signals from the fCO. The generation of these transitions in activity of trochanteral motoneurons barely depended on position or velocity signals from the fCO. This contrasts with the situation in the resting behavioral state when interjoint reflex action markedly depends on actual fCO stimulus parameters, i.e., position and velocity signals. In the active behavioral state, movement signals from the fCO obviously trigger or release centrally generated transitions in motoneuron activity, e.g., by affecting central rhythm generating networks driving trochanteral motoneuron pools. This conclusion was tested by stimulating the fCO in "fictive rhythmic" preparations, activated by the muscarinic agonist pilocarpine in the otherwise isolated and deafferented mesothoracic ganglion. In this situation, sensory signals from the fCO did in fact reset and entrain rhythmic activity in trochanteral motoneurons. The results indicate for the first time that when the stick insect locomotor system is active, sensory signals from the proprioceptor of one leg joint, i.e., the fCO, pattern motor activity in an adjacent leg joint, i.e., the CT joint, by affecting the central rhythm generating network driving the motoneurons of the adjacent joint.

The effect of mode, inspiratory time, and positive end-expiratory pressure on partial liquid ventilation

Partial liquid ventilation (PLV) has been shown to be an effective means of improving oxygenation in the injured lung. However, little is known about how approach to ventilation during PLV affects gas exchange and pulmonary mechanics. We hypothesized that gas exchange and pulmonary mechanics would be best with positive end-expiratory pressure (PEEP) set above the lower inflection point (LIP) of the pressure-volume (P-V) curve regardless of mode of ventilation or inspiratory to expiratory time (I:E) ratio and that the efficiency of ventilation would be greatest with volume-controlled ventilation (VCV) compared with pressure-controlled ventilation (PCV) and with long inspiratory time as compared with short inspiratory time. Lung injury was induced in 14 sheep by lavage, 10 of which were studied. Sheep were then assigned to high-PEEP (Group H, n = 5) and low-PEEP (Group L, n = 5) groups. In Group H applied PEEP was set at the LIP and in Group L applied PEEP was set at 5 cm H2O after the lung was filled with perflubron (PFB). We randomly compared VCV and PCV with I:E ratios of 1:2, 1:1, and 2:1. Peak inspiratory pressure and VT were adjusted to maintain a constant end-inspiratory plateau pressure (Pplat) of about 25 cm H2O in both groups and a constant total PEEP of about 5 cm H2O in Group L and about 12 cm H2O in Group H. There were no differences in oxygenation among modes in Group H. In Group L VCV 2:1 and all of the PCV modes in Group L had a lower PaO2 than VCV 1:1 (p < 0.05). PaCO2 and VD/VT were significantly different (p < 0.05) among modes. VD/VT was highest during PCV 1:2 with PEEP of 5 cm H2O (p < 0.05). Quasi-static compliance in Group H was higher than in Group L (p < 0.05). We conclude that during low PEEP gas exchange deteriorated in VCV with long inspiratory time and in PCV. Oxygenation was enhanced during VCV 1:1 when compared with VCV at longer I:E ratios or PCV at any I:E ratio. With PEEP set at the LIP, adequate gas exchange and improved lung mechanics could be obtained in all modes assessed.

Two independent mutations in a family with neurofibromatosis type 1 (NF1)

We report on two independent alterations of the NF1 gene in a three-generation kindred with neurofibromatosis type 1 (NF1). Using temperature gradient gel electrophoresis (TGGE) in a mutation analysis of exon 31 of the NF1 gene we detected the previously reported nonsense mutation R1947X. This C-to-T transition at codon 1947 in exon 31 is considered to represent a mutation "hot spot" of the NF1 gene due to 5mCpG deamination. All living family members together with their genomic DNA were included in this investigation. However, the mutation R1947X was absent from two undoubtedly affected siblings of the propositus. Another NF1 mutation (889-2A-->G) was identified in the two sibs by the protein truncation test (PTT). The novel splice site mutation 889-2A-->G results in a skip of NF1 exon 7 during splicing and protein truncation due to frameshift. The two NF1 alterations are linked to different paternal haplotypes. In our study of a three-generation kindred, R1947X represents a de novo mutation whereas 889-2A-->G is an inherited splice mutation. Implications for phenotype variation are discussed.

The effect of intact talin and talin tail fragment on actin filament dynamics and structure depends on pH and ionic strength

We employed quasi-elastic light scattering and electron microscopy to investigate the influence of intact talin and talin tail fragment on actin filament dynamics and network structure. Using these methods, we confirm previous reports that intact talin induces cross-linking as well as filament shortening on actin networks. We now show that the effect of intact talin as well as talin tail fragment on actin networks is controlled by pH and ionic strength. At pH 7.5, actin filament dynamics in the presence of intact talin and talin tail fragment are characterized by a rapid decay of the dynamic structure factor and by a square root power law for the stretched exponential decay which is in contrast with the theory for pure actin solutions. At pH 6 and low ionic strength, intact talin cross-links actin filaments more tightly than talin tail fragment. Talin head fragment showed no effect on actin networks, indicating that the actin binding sites reside probably exclusively within the tail domain.

A new fluorescence-based, hydrophobic photolabeling technique for analyzing membrane-associated proteins

We introduce a new, fluorescent and photoactivatable fatty acid derivative (SANU) for hydrophobic labelling of membrane-bound proteins. The technique allows fast and highly sensitive screening of hydrophobically inserting proteins analyzed by SDS-PAGE with a detection limit below 0.1 pmol. A reliable calculation of labelling efficiencies is achieved by simultaneous densitometry of fluorescence and protein staining. We have applied the new technique on the membrane inserting protein talin, G-actin, and, as a negative control, on RNase, which only binds electrostatically to negatively charged lipid interfaces. In several ways superior to radiolabelling, we can recommend this technique for all laboratories under any circumstances.

Expiratory phase tracheal gas insufflation and pressure control in sheep with permissive hypercapnia

Tracheal gas insufflation (TGI) has been shown to be a useful adjunct to mechanical ventilation, decreasing PaCO2 during permissive hypercapnia. While TGI can be used either with pressure (PCV) or volume-controlled ventilation and continuously or only during the expiratory phase (Ex-TGI), there are no controlled studies evaluating the effects of Ex-TGI with PCV in acute lung injury when the direction of the insufflated flow or the inspiratory:expiratory (I:E) ratio are varied. We evaluated the effect that Ex-TGI with PCV would have on CO2 removal during both direct and reverse insufflated flow direction with varied I:E ratios when peak airway pressure, total positive end-expiratory pressure (PEEP), and tidal volume (VT) were kept constant. In addition we examined the effect that insufflation flow directed toward the mouth (reverse flow) would have on the generation of PEEP compared with flow directed toward the carina (direct flow). After saline lavage, nine sheep were ventilated with PCV to a baseline PaCO2 of 80 mm Hg. Ex-TGI (10 L/min) was then randomly applied in the reverse and direct direction with I:E set at 1:2 or 2:1. During 1:2 I:E PaCO2 decreased from 78 +/- 4 mm Hg to 60 +/- 7 mm Hg (23.5 +/- 8.9%) with direct flow and to 64 +/- 5 mm Hg (18.5 +/- 5.5%) with reverse flow (p < 0.05), whereas during 2:1 I:E PaCO2 decreased from 80 +/- 4 mm Hg to 69 +/- 8 mm Hg (13.7 +/- 9.2%) with direct flow and to 66 +/- 4 mm Hg (17.2 +/- 4.4%) with reverse flow (p < 0.05). Greater PEEP was developed with direct flow (2.8 cm H2O I:E 1:2 and 4.0 cm H2O I:E 2:1) than with reverse flow (-0.9 cm H2O I:E 1:2 and -0.4 cm H2O I:E 2:1), p < 0.05. There was no difference in the PaCO2 change between I:E with reverse flow, but the PaCO2 decrease was greater (p < 0.05) during 1:2 versus 2:1 I:E with direct flow. CO2 removal during PCV and Ex-TGI is more consistent with reverse flow than with direct flow and PEEP level is less affected by TGI with reverse flow than with direct flow.

Accumulation in marine sponge grafts of the mRNA encoding the main proteins of the cell adhesion system

Specific cell adhesion in the marine sponge Microciona prolifera is mediated by an extracellular aggregation factor complex, whose main protein component, termed MAFp3, is highly polymorphic. We have now identified MAFp4, an approximately 400-kDa protein, from the aggregation factor that is translated from the same mRNA as MAFp3. The existence of multiple potential sites for N-glycosylation and calcium binding suggests a direct involvement of MAFp4 in the species-specific aggregation of sponge cells. The deduced partial polypeptide consists of a 16-fold reiterated motif that shows significant similarity to a repeat in an endoglucanase from the symbiontic bacterium Azorhizobium caulinodans and to the intracellular loop of mammalian Na+-Ca2+ exchangers. Restriction fragment length polymorphism analysis indicated that the genomic variability of MAFp4 is high and comparable to that of MAFp3. Their combined polymorphism correlates with allogeneic responses studied in a population of 23 sponge individuals. Peptide mass fingerprinting of tryptic digests of the polymorphic MAFp3 bands observed on polyacrylamide gels after chemical deglycosylation of the Microciona aggregation factor revealed that the variability detected on Southern blots at least partially reflects the individual variability of aggregation factor protein components. Polyclonal antibodies raised against MAFp3 strongly cross-reacted with a 68-kDa protein localized in sponge cell membranes. Immunohistochemical use of the anti-MAFp3 antibodies strongly stained a cell layer along the line of contact in allogeneic grafts. We show that the transcription level of the MAFp3/MAFp4 mRNA in sponge allo- and isografts is clearly increased in comparison with non-grafted tissue. These data are discussed with respect to a possible evolutionary relationship between cell adhesion and histocompatibility systems.

Positive end-expiratory pressure improves gas exchange and pulmonary mechanics during partial liquid ventilation

Partial liquid ventilation (PLV) with perflubron (PFB) has been proposed as an adjunct to the current therapies for the acute respiratory distress syndrome (ARDS). Because PFB has been also referred to as "liquid PEEP," distributing to the most gravity-dependent regions of the lung, less attention has been paid to the amount of applied positive end-expiratory pressure (PEEP). We hypothesized that higher PEEP levels than currently applied are needed to optimize gas exchange, and that the lower inflection point (LIP) of the pressure-volume curve could be used to estimate the amount of PEEP needed when the lung is filled with PFB. Lung injury was induced in 23 sheep by repeated lung lavage with warmed saline until the PaO2/FIO2 ratio fell below 150. Five sheep were used to investigate the change of the LIP when the lung was filled with PFB in increments of 5 ml/kg/body weight to a total of 30 ml/kg/body weight. To evaluate the impact of PEEP set at LIP +1 cm H2O we randomized an additional 15 sheep to three groups with different doses (7.5 ml, 15 ml, 30 ml/kg/body weight) of PFB. In random order a PEEP of 5 cm H2O or PEEP at LIP +1 cm H2O was applied. The LIP decreased with incremental filling of PFB to a minimum at 10 ml (p < 0.05). Increasing PEEP from below LIP to LIP +1 cm H2O at 15 and 30 ml/kg resulted in an improvement in PaO2 from 152 +/- 36 to 203 +/- 68 (NS) and 193 +/- 57 to 298 +/- 80 (p < 0.05), respectively. Pulmonary shunt, and ratio of dead space volume to tidal volume (VD/VT) decreased, and static lung compliance increased with PEEP at LIP +1 cm H2O (p < 0.05). No changes were observed in hemodynamics. We conclude that increasing the dose of PFB shifts the LIP to the left, and that setting PEEP at LIP +1 cm H2O improves gas exchange at moderate to high doses of PFB.