C-mannosylation and O-fucosylation of the thrombospondin type 1 module

Thrombospondin-1 (TSP-1) is a multidomain protein that has been implicated in cell adhesion, motility, and growth. Some of these functions have been localized to the three thrombospondin type 1 repeats (TSRs), modules of approximately 60 amino acids in length with conserved Cys and Trp residues. The Trp residues occur in WXXW patterns, which are the recognition motifs for protein C-mannosylation. This modification involves the attachment of an alpha-mannosyl residue to the C-2 atom of the first tryptophan. Analysis of human platelet TSP-1 revealed that Trp-368, -420, -423, and -480 are C-mannosylated. Mannosylation also occurred in recombinant, baculovirally expressed TSR modules from Sf9 and "High Five" cells, contradictory to earlier reports that such cells do not carry out this reaction. In the course of these studies it was appreciated that the TSRs in TSP-1 undergo a second form of unusual glycosylation. By using a novel mass spectrometric approach, it was found that Ser-377, Thr-432, and Thr-489 in the motif CSX(S/T)CG carry the O-linked disaccharide Glc-Fuc-O-Ser/Thr. This is the first protein in which such a disaccharide has been identified, although protein O-fucosylation is well described in epidermal growth factor-like modules. Both C- and O-glycosylations take place on residues that have been implicated in the interaction of TSP-1 with glycosaminoglycans or other cellular receptors.

High incidence of central nervous system involvement in patients with metastatic or locally advanced breast cancer treated with epirubicin and docetaxel

BACKGROUND

Clinically overt central nervous system (CNS) involvement occurs in 10%-15% of patients with advanced breast cancer.

PATIENTS AND METHODS

The International Breast Cancer Study Group (IBCSG) conducted a dose-finding phase I trial of epirubicin (E) and docetaxel (D) as first-line therapy in advanced breast cancer patients. The study was expanded into a phase II at the recommended doses of E 90 mg/m2 and D 75 mg/m2 every three weeks. From July 1996 to May 1998, a total of 92 patients (median age 50 years) entered the two studies.

RESULTS

Twenty-eight out of ninety-two patients treated with the combination of E and D (30%) developed CNS metastases (95% confidence limits, 26%-35%), which were cerebral in twenty-five patients, leptomeningeal in two, and both in one. Of these 28 patients, 19 (68%) had an objective response. Median time for the development of CNS metastases from the start of chemotherapy was 15 months (range 5-42), if excluding the 6 patients presenting CNS progression within 3 months from start of treatment. It is notable that 11 patients (39%) had progression in the CNS only. Median survival from appearance of brain metastases in the whole group was only three months (range 1-22). C-erbB-2 overexpression was found in 14 out of 16 patients (87%) in whom the assay was performed (3+ in 10, 2+ in 1 and 1+ in 3 cases).

CONCLUSIONS

As anthracycline- and taxane-containing regimens are increasingly used both in the metastatic and in the adjuvant setting, a careful monitoring of any neurological symptom is advisable. Our preliminary observation on the possible increase of incidence of CNS involvement in patients with advanced breast cancer receiving this effective drug combination requires further evaluation.

Tracheostomy management in the chronically ventilated patient

Tracheotomy is a fundamentally important technique for managing patients who require long-term mechanical ventilation. Appropriate application of tracheotomy requires a skilled approach for timing the procedure, selecting the appropriate tracheostomy tube appliance, caring for the artificial airway once it is in place, and assisting patients with their specialized needs, such as articulated speech, airway humidification, and oral nutrition. Preparing patients for airway decannulation after they have weaned from mechanical ventilation requires a similar level of skill and attention to detail.

Techniques to avoid intubation: noninvasive positive pressure ventilation and heliox therapy

NPPV is useful in decreasing the intubation rate in carefully selected patients with acute respiratory failure--particularly in patients with COPD. The results of some studies also suggest a survival benefit for use of NPPV with acute respiratory failure associated with COPD. Heliox therapy may be beneficial for selected patients with large airway obstruction or asthma. The use of heliox for other indications is unclear. Heliox may adversely affect the function of respiratory care equipment such as flow meters, ventilators, nebulizers, and pulmonary function monitors.

Screening for retinopathy of prematurity employing the retcam 120: sensitivity and specificity

OBJECTIVES

To compare the method of photographic screening using the RetCam 120 to the standard method of screening for retinopathy of prematurity (ROP) by ophthalmologic examination.

METHODS

A total of 100 RetCam 120 photoscreening examinations of the retina were performed on 32 premature infants. These were stored in a separate file from which all identifying information was removed. At this same examination, a detailed ophthalmological evaluation, employing the indirect ophthalmoscope with scleral depression, was performed by an experienced examiner. Masked examiners performed an evaluation of the fundus photographs to identify presence or absence of ROP, the location and extent of the disease, and the presence or absence of plus disease. These data were then compared with the results of the ophthalmological examination to determine the specificity, sensitivity, and the positive and negative predictive value (PPV and NPV) of the method.

RESULTS

Retinopathy of prematurity was detected in 68 of 100 subjects by ophthalmologic examinations and in 58 of 100 subjects' photoscreening examinations. No ROP was detected in 32 of 100 subjects. The sensitivity of the method was 56 (82.4%) of 68 and the specificity was 30 (93.8%) of 32. The PPV was 96.6%; NPV, 76.9%.

CONCLUSIONS

The sensitivity of the method was low. The ROP that was missed was peripheral stage 1 or stage 2 disease in peripheral zone 2 or zone 3. This was largely due to the technical limitations of the speculum-camera interface preventing a better view of the periphery. The ROP cases that were missed by the photographic examination regressed spontaneously on follow-up. No disease more posterior to peripheral zone 2 was overlooked. These results detail the accuracy of the method employing the technique of photoscreening as a potential substitute for detailed ophthalmological examination. At present there are clear technical limitations to such a substitution. The study is part of an ongoing project to determine the feasibility of employing neonatal nurses trained to take digitized images of the premature infant's retina and telemeter the results to be read by an experienced ophthalmologist remote from the site.

The phosphatidylethanolamine-binding protein is the prototype of a novel family of serine protease inhibitors

Serine proteases are involved in many processes in the nervous system and specific inhibitors tightly control their proteolytic activity. Thrombin is thought to play a role in tissue development and homeostasis. To date, protease nexin-1 is the only known endogenous protease inhibitor that specifically interferes with thrombotic activity and is expressed in the brain. In this study, we report the detection of a novel thrombin inhibitory activity in the brain of protease nexin-1(-/-) mice. Purification and subsequent analysis by tandem mass spectrometry identified this protein as the phosphatidylethanolamine-binding protein (PEBP). We demonstrate that PEBP exerts inhibitory activity against several serine proteases including thrombin, neuropsin, and chymotrypsin, whereas trypsin, tissue type plasminogen activator, and elastase are not affected. Since PEBP does not share significant homology with other serine protease inhibitors, our results define it as the prototype of a novel class of serine protease inhibitors. PEBP immunoreactivity is found on the surface of Rat-1 fibroblast cells and although its sequence contains no secretion signal, PEBP-H(6) can be purified from the conditioned medium upon recombinant expression.

Ventilators and weaning modes

Although new ventilator modes have become available to facilitate weaning, there is little evidence that these have improved weaning outcomes. Knowledge based computer weaning systems have also been described, but these are in their infancy, and their role is unclear. Prospective, randomized clinical studies are required to examine whether such modalities are superior to existing approaches.

Epidoxorubicin and docetaxel as first-line chemotherapy in patients with advanced breast cancer: a multicentric phase I-II study

BACKGROUND

The combination of anthracyclines and taxanes is currently considered the first choice chemotherapy in advanced breast cancer (ABC) and considerable emphasis has been placed on programs exploring the safest and most efficient way to integrate these classes of drugs in both the metastatic and, more recently, the adjuvant setting. We report here the overall results of the combination of epidoxorubicin (E) 90 mg/m2 and docetaxel (D) 75 mg/m2 as first-line chemotherapy in ABC.

PATIENTS AND METHODS

A total of 70 patients were entered in the initial dose-finding study (20 patients) and in the subsequent extended phase II trial (50 patients). Overall 54% of patients had dominant visceral disease and 57% had at least two metastatic sites. Adjuvant anthracyclines were allowed in the phase II part of the study based on the lack of cardiac toxicity observed in the phase I study at a median cumulative E dose of 480 mg/m2. A maximum of eight cycles of the combination was allowed, and cardiac function was monitored at baseline and after every second course by echocardiography.

RESULTS

Overall, the median number of cycles administered with the combination was 4 (range 3-8). Neutropenia was confirmed to be the main haematological toxicity, with granulocyte colony-stimulating factor (G-CSF) support required in 44% of the cycles. Febrile neutropenia occurred in 12% of cycles of the combination but 52% of the episodes could be managed on an outpatient basis with oral antibiotics. Overall, the median cumulative dose of E, including prior adjuvant anthracyclines, was 495 mg/m2 (range 270-1020 mg/m2). One patient who received adjuvant E together with radiotherapy to the left chest wall developed fully reversible clinical signs of cardiotoxicity and a significant decrease of LVEF to 35% after a cumulative E dose of 870 mg/m2, with four additional patients (6%) developing asymptomatic and transient decline of resting LVEF. The overall response rate (ORR) in 68 evaluable patients was 66% (95% confidence interval (95% CI): 54%-73%). A comparable antitumour activity of 71% was reported in the group of patients with a prior adjuvant chemotherapy with anthracyclines. After an overall median follow-up time of 22 months (range 4-39+), the median time to progression (TTP) was 4.5 months and the median duration of response was 8 months (range 3-16). No pharmacokinetic (Pk) interaction could be demonstrated between E and D when given simultaneously and sequentially with a one-hour interval.

CONCLUSIONS

The combination of E and D in a multiinstitutional setting is an active and safe regimen in poor-prognosis patients with ABC. New combinations and schedules are worth considering in an attempt to further improve disease response and long-term control of the disease.

Association of betaine-homocysteine S-methyltransferase with microtubules

In mammals, betaine of the mitochondrial matrix is used in the cytosol by betaine-homocysteine S-methyltransferase for methionine synthesis. The resulting dimethylglycine is shuttled back into the mitochondrial matrix for further degradation. Nanospray tandem mass spectrometry and N-terminal amino acid sequencing of microtubule-associated proteins from rat liver tubulin revealed that betaine-homocysteine S-methyltransferase is microtubule associated. This was confirmed by confocal laser scanning microscopy of HepG2 cells labeled with betaine-homocysteine S-methyltransferase- and alpha-tubulin-specific monoclonal antibodies. The association of betaine-homocysteine S-methyltransferase with the cytoskeleton may functionally integrate the mitochondrial and cytoplasmic compartments of choline degradation.

A novel mutation L1425P in the GAP-region of the NF1 gene detected by temperature gradient gel electrophoresis (TGGE). Mutation in brief no. 230. Online

Neurofibromatosis type 1 (NF1) is an autosomal dominant disorder with an incidence of between 1: 3000 and 1: 4000. Common clinical signs include more than six café-au-lait spots, multiple cutaneous neurofibromas and iris Lisch nodules. Rarer are skeletal anomalies, learning disabilities and an increased risk of malignancy. The NF1 gene contains at least 60 exons with intron sizes ranging from 60 bp to more than 40 kb. Despite using different techniques including PTT, SSCP heteroduplex analyses and direct sequencing, only a relatively small number of mutations have been reported world-wide. Using the more sensitive technique of temperature gradient gel electrophoresis (TGGE), we analysed a part of the NF1-GAP-region, namely exon 25, in DNA samples from 131 unrelated patients. We have identified a novel mutation L1425P in exon 25 of the NF1 gene in a 12-year-old boy (clinically diagnosed with NF1 at the age of 7). In contrast to those cases diagnosed with having both GAP-region mutations and malignant tumours, neither the proband nor four clinically affected family members with this mutation showed any evidence of malignancies.

5-methylcytosine-DNA glycosylase activity is present in a cloned G/T mismatch DNA glycosylase associated with the chicken embryo DNA demethylation complex

We previously have shown that DNA demethylation by chicken embryo 5-methylcytosine DNA glycosylase (5-MCDG) needs both RNA and proteins. One of these proteins is a RNA helicase. Further peptides were sequenced, and three of them are identical to the mammalian G/T mismatch DNA glycosylase. A 3,233-bp cDNA coding for the chicken homologue of human G/T mismatch DNA glycosylase was isolated and sequenced. The derived amino acid sequence (408 aa) shows 80% identity with the human G/T mismatch DNA glycosylase, and both the C and N-terminal parts have about 50% identity. As for the highly purified chicken embryo DNA demethylation complex the recombinant protein expressed in Escherichia coli has both G/T mismatch and 5-MCDG activities. The recombinant protein has the same substrate specificity as the chicken embryo 5-MCDG where hemimethylated DNA is a better substrate than symmetrically methylated CpGs. The activity ratio of G/T mismatch and 5-MCDG is about 30:1 for the recombinant protein expressed in E. coli and 3:1 for the purified enzyme from chicken embryos. The incubation of a recombinant CpG-rich RNA isolated from the purified DNA demethylation complex with the recombinant enzyme strongly inhibits G/T mismatch glycosylase while slightly stimulating the activity of 5-MCDG. Deletion mutations indicate that G/T mismatch and 5-MCDG activities share the same areas of the N- and C-terminal parts of the protein. In reconstitution experiments RNA helicase in the presence of recombinant RNA and ATP potentiates the activity of 5-MCDG.

Stat5a serine phosphorylation. Serine 779 is constitutively phosphorylated in the mammary gland, and serine 725 phosphorylation influences prolactin-stimulated in vitro DNA binding activity

The activity of transcription factors of the Stat family is controlled by phosphorylation of a conserved, carboxyl-terminal tyrosine residue. Tyrosine phosphorylation is essential for Stat dimerization, nuclear translocation, DNA binding, and transcriptional activation. Phosphorylation of Stats on specific serine residues has also been described. We have previously shown that in HC11 mammary epithelial cells Stat5a is phosphorylated on Tyr(694) in a prolactin-sensitive manner, whereas serine phosphorylation is constitutive (Wartmann, M., Cella, N., Hofer, P., Groner, B., Xiuwen, L., Hennighausen, L., and Hynes, N. E. (1996) J. Biol. Chem. 271, 31863-31868). By using mass spectrometry and site-directed mutagenesis, we have now identified Ser(779), located in a unique Stat5a SP motif, as the site of serine phosphorylation. By using phospho-Ser(779)-specific antiserum, we have determined that Ser(779) is constitutively phosphorylated in mammary glands taken from different developmental stages. Stat5a isolated from spleen, heart, brain, and lung was also found to be phosphorylated on Ser(779). Ser(725) in Stat5a has also been identified as a phosphorylation site (Yamashita, H., Xu, J., Erwin, R. A., Farrar, W. L., Kirken, R. A., and Rui, H. (1998) J. Biol. Chem. 273, 30218-30224). Here we show that mutagenesis of Ser(725), Ser(779), or a combination of Ser(725/779) to an Ala had no effect on prolactin-induced transcriptional activation of a beta-casein reporter construct. However, following prolactin induction the Ser(725) mutant displayed sustained DNA binding activity compared with that of wild type Stat5a. The results suggest that Ser(725) phosphorylation has an impact on signal duration.

Use of recruitment maneuvers and high-positive end-expiratory pressure in a patient with acute respiratory distress syndrome

OBJECTIVE

To present the use of a novel high-pressure recruitment maneuver followed by high levels of positive end-expiratory pressure in a patient with the acute respiratory distress syndrome (ARDS).

DESIGN

Observations in one patient.

SETTING

The medical intensive care unit at a tertiary care university teaching hospital.

PATIENT

A 32-yr-old woman with severe ARDS secondary to streptococcal sepsis.

INTERVENTIONS

The patient had severe gas exchange abnormalities because of acute lung injury and marked lung collapse. Attempts to optimize recruitment based on the inflation pressure-volume (PV) curve were not sufficient to avoid dependent lung collapse. We used a recruitment maneuver using 40 cm H2O of positive end-expiratory pressure (PEEP) and 20 cm H2O of pressure controlled ventilation above PEEP for 2 mins to successfully recruit the lung. The recruitment was maintained with 25 cm H2O of PEEP, which was much higher than the PEEP predicted by the lower inflection point (P(Flex)) of the PV curve.

MEASUREMENTS AND MAIN RESULTS

Recruitment was assessed by improvements in oxygenation and by computed tomography of the chest. With the recruitment maneuvers, the patient had a dramatic improvement in gas exchange and we were able to demonstrate nearly complete recruitment of the lung by computed tomography. A PV curve was measured that demonstrated a P(Flex) of 16-18 cm H2O.

CONCLUSION

Accumulating data suggest that the maximization and maintenance of lung recruitment may reduce lung parenchymal injury from positive pressure ventilation in ARDS. We demonstrate that in this case PEEP alone was not adequate to recruit the injured lung and that a high-pressure recruitment maneuver was required. After recruitment, high-level PEEP was needed to prevent derecruitment and this level of PEEP was not adequately predicted by the P(Flex) of the PV curve.

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.