Escherichia coli Dcu C4-dicarboxylate transporters dependent proton and potassium fluxes and FOF1-ATPase activity during glucose fermentation at pH 7.5

During fermentation in Escherichia coli succinate is transported via Dcu transporters, encoded dcuA, dcuB, dcuC and dcuD although the role of DcuD protein has not been elucidated yet. It has been shown contribution of Dcu transporters in the N,N'-dicyclohexylcarbodiimide (DCCD) sensitive proton and potassium transport through the cytoplasmic membrane and membrane-associated ATPase activity. Total H^± efflux was decreased ~ 40% while K^± uptake was absent in dcuD mutant. DCCD-sensitive H^± flux was absent in dcuD nevertheless it was increased ~ 3 fold in dcuACB. K^± uptake in dcuACB was stimulated ~ 30% compared to wild type but in DCCD assays K^± ions were effluxed with the rate of 0.15 mmol/min per 10⁹ cells/ml. In dcuACB mutant membrane potential (ΔΨ) was ~ 30 mV higher than in wild type. dcuD gene expression was increased in the dcuACB mutant respect to wild type at pH 7.5 (~120%), suggesting that an increment of DcuD activity compensates the lack of DcuA, DcuC and DcuB carriers. It can be concluded that active DcuD is important for H^± efflux via the F_OF₁-ATPase and K^± uptake at pH 7.5. In addition, DcuA, DcuB and DcuC transporters are crucial for regulating DCCD-sensitive K^± transport and ΔΨ in E. coli.

Intratracheal pulmonary ventilation versus conventional mechanical ventilation: continuous carinal pressure monitoring at low and high flows and frequencies

We continuously measured proximal and carinal pressures at low and high flow rates and frequencies during conventional mechanical ventilation (CMV) and intratracheal pulmonary ventilation (ITPV), using an artificial lung. The proximal peak inspiratory pressure (PIP), carinal PIP, proximal positive end expiratory pressure (PEEP), and carinal PEEP, or negative end expiratory pressure (NEEP), were measured during simulated CMV and ITPV. Two levels of frequency (30 and 90 per min) and two gas flow rates (3 and 6 L/min) were examined, in both dry and humid states (four combinations of gas flow and frequency at each state). The gas flow and inspiratory time were held constant throughout the CMV and ITPV trials. Humidification of the ventilatory circuit during ITPV prevented the accurate measurement of carinal pressures. This problem was solved by introducing a continuous "bias flow" of 11 ml/min into the pressure monitoring line. A combination of low gas flow and low frequency with CMV showed no significant differences between the proximal and carinal PIP, as well as the proximal and carinal PEEP. The same combination with ITPV, however, resulted in a significantly lower carinal PIP and PEEP, compared to proximal PIP and PEEP. Carinal PIP and PEEP during ITPV were also significantly lower than those observed during CMV with a low flow and low frequency rates. During both CMV and ITPV, using a combination of a high flow rate with a high breathing frequency, carinal PIPs were significantly lower than proximal PIPs. ITPV, however, generated much larger differences between proximal and carinal PIPs than the CMV. A significant NEEP was generated at the carinal level during ITPV with high flow rates, both with high and low frequencies. The NEEP did not occur with a low gas flow, in combination with either a low frequency or a high frequency. The "bias flow" had no significant effect on carinal pressures. In conclusion, ITPV, compared with CMV, generates a significantly lower carinal PIP, but it may also generate carinal NEEP. For safety reasons, therefore, it is essential to monitor carinal pressures continuously in patients treated with ITPV.

Adverse hemodynamic effects observed with inhaled nitric oxide after surgical repair of total anomalous pulmonary venous return

The following is a case report of a 1-month-old patient who developed adverse hemodynamic sequelae during the use of nitric oxide (NO) in the postoperative period for pulmonary hypertension after correction of total anomalous pulmonary venous return. At the time of diagnosis, the patient had evidence of systemic right ventricular pressures estimated by continuous-wave Doppler. He was sedated and paralyzed for hyperventilation in preparation for surgery and underwent pulmonary vein confluence to left atrial anastomosis. Postoperative pulmonary hypertension was managed by hyperventilation, sedation, and paralysis until a sudden onset of systemic-level pulmonary pressure required NO therapy. Satisfactory results were obtained in minutes, but a rebound pulmonary hypertension occurred with concomitant systemic hypertension and no radiographic changes. We suspected left atrial hypertension secondary to a sudden increase in pulmonary blood flow to an noncompliant left ventricle. Discontinuation of NO resulted in stabilization of the hemodynamic profile of the patient and he continued to be managed with paralysis, hyperventilation, and sedation. Based on this experience we suggest that NO should be used with caution in patients with obstructive lesions at the atrial level prior to surgery (mitral valve stenosis and cor triatriatum) or in patients with a poorly compliant left ventricle (cardiomyopathy and left ventricular dysfunction). These entities are unable to tolerate a sudden increase in pulmonary blood return thus creating paradoxical pulmonary hypertension.

Immunohistochemical detection of ribosomal transcription factor UBF: diagnostic value in malignant specimens

The nucleolar organizer regions (NORs) of human chromosome can be identified in interphase and mitotic cells by localization of some intrinsic components such as the associated enzyme RNA polymerase I. A new sensitive staining method for NORs is described using a specific antibody to the ribosomal transcription factor UBF. By indirect immunofluorescence and enzyme-labelling methods, NORs stained in benign and malignant cells from a variety of tissues with monospecific anti-UBF serum showed significant morphological differences which correlated well with histopathological evaluation. The number of NORs per cell in malignant preparations increased significantly. Furthermore, the staining of a NOR protein component such as UBF appears to be as sensitive as the silver-staining technique (AgNOR) and might be a better alternative for detecting ribosomal activity in malignant tissues.

Patient-triggered ventilation in neonates: comparison of a flow-and an impedance-triggered system

We conducted a study with the objective of comparing the performance of two different systems for patient-triggered ventilation in neonates (impedance versus flow/volume-triggered) by measuring response time, autotrigger and trigger failure rates, ventilation, and gas exchange. The two ventilator systems were applied in random order in 10 preterm neonates (median gestational age: 30.5 wk; range: 27 to 34 wk; body weight: 1,266 g; range: 840 to 2,240 g) using identical ventilator settings. The median (range) response time was 169 (98 to 305) ms for the impedance system and 115 (79 to 184) ms for the flow/volume system (p < 0.01). The longer and more variable response time of the impedance system was secondary to a phase lag of the impedance signal caused by chest wall distortion. Although 13.1 (0.2 to 29.4)% of mechanical breaths were autotriggered with the impedance system, there were no autotriggered breaths using the flow/volume system (p < 0.01). The rate of trigger failures was not significantly different with the two systems, at 1.2 (0 to 4.4)% (impedance) versus 3.1 (0 to 6.4)% (flow/volume). Minute ventilation was smaller with the impedance system (p < 0.001), because of the larger number of breaths triggered late in inspiration or during expiration. We conclude that the flow/volume-triggered system is less prone to autotriggering and has a shorter and more consistent response time than the impedance-triggered system. The impedance-triggered system is more susceptible to artifacts and chest wall distortion.

Effect of leak around the endotracheal tube on measurements of pulmonary compliance and resistance during mechanical ventilation: a lung model study

We studied the effect of leaks around the endotracheal tube (ETT) on the measurement of pulmonary mechanics during mechanical ventilation. We also evaluated the influence of different ventilator settings on the magnitude of leak. An adjustable leak was created at the end of the ETT in a lung model with constant compliance. Flow, tidal volume, and pressure changes were measured above and below the leak. Compliance (Ci) and resistance (Ri) during inspiration were determined by linear regression analysis (LRA) using the equation of motion and the Mead and Wittenberger method (MWM). The ventilatory change that influenced the degree of leak most was prolongation of inspiratory time (Ti). The presence of a leak around the ETT resulted in an overestimation of the Ci and Ri values, which was proportional to the size of the leak. This overestimation was also influenced by the method used to determine Ci and Ri. Because the contribution of the leak to the fidal volume progressively increases as inspiration continued, methods of analysis that depended mainly on measurement points at the end of inspiration showed a larger deviation from the true Ci and Ri values than methods mainly influenced by measurement points at the beginning of inspiration. Because of this, shortening of inspiration, or analysis of points at the beginning of inspiration reduces the error in the measurements of Ci and Ri when a leak is present. Breaths with a large leak should be excluded from any analysis of pulmonary mechanics.

Anticentromere antibody specific to human cells directed against the CENP-B autoantigen

We describe the generation of a new antipeptide antibody that binds to the centromeric region of human mitotic chromosomes. This antibody was raised against a synthetic peptide corresponding to the 481-493 amino acid sequence of the human CENP-B autoantigen. Immunofluorescence analysis revealed that this anti-CENP-B serum showed an identical pattern to the human CREST anticentromere autoantibody in both mitotic cells and interphase nuclei. Immunoblotting showed that this antibody reacts with the recombinant human CENP-B autoantigen, indicating that it is directed to the 80-kDa centromere polypeptide. We have used this serum to determine, by indirect immunofluorescence, whether CENP-B is conserved in different mammalian species. Surprisingly, the human antipeptide antibody does not react with the centromeric proteins of cultured mouse, hamster, or Indian muntjac cells. Because the CENP-B gene has been cloned in human and mouse, our results suggest that the CENP-B epitope used as an immunogen in this study is not ubiquitous in mammalian cells, and that we have most probably established a monospecific antibody to the human centromere.