The tubules of the kidney display a remarkable capacity for self-renewal on damage. Whether this regeneration is mediated by dedifferentiating surviving cells or, as recently suggested, by stem cells has not been unequivocally settled. Herein, we demonstrate that aldehyde dehydrogenase (ALDH) activity may be used for isolation of cells with progenitor characteristics from adult human renal cortical tissue. Gene expression profiling of the isolated ALDH high and ALDH low cell fractions followed by immunohistochemical interrogation of renal tissues enabled us to delineate a tentative progenitor cell population scattered through the proximal tubules (PTs). These cells expressed CD24 and

The sequence of conduction through the intraventricular conducting system and endocardial muscle was studied by microelectrode mapping of large areas of isolated canine ventricular tissue. We found that most of the endocardium of the right ventricular free wall is activated simultaneously whereas the left endocardial muscle is activated in an apex-to-base sequence. Right septal activation is from apex to base, and the left septum is activated first at the junction of the middle and lower thirds of the septum and then as a bidirectional wave front toward the apex and the base. These right-left differences occur because the sites of impulse input into muscle on the right encompass the entire free wall, base of the papillary muscle, and the lowermost septum, and on the left are primarily limited to the lower ventricular cavity, lower septum, and bases of the papillary muscles. These patterns of left ventricular excitation relate to the presence of a functionally continuous ring of conducting tissue formed by a merger of the major divisions of the left bundle branch on the upper left ventricular free wall. The "ring" itself is electrophysiologically isolated from muscle, but connects to a network of subendocardial conducting tissue extending to the apex and having input to muscle only in its lower portions. KEY WORDSAV conduction papillary muscles bundle branches conducting system Purkinje fibers cardiac electrophysiology septal activation myocardial activation ventricular muscle• The relationship between the anatomy of the intraventricular portion of the AV conducting system and the physiology of AV conduction and ventricular excitation is pertinent to our understanding of major areas of cardiac electrophysiology. The nature and location of impulse input from the intraventricular conducting system into the ventricular myocardium, the physiological interactions between conducting tissue and ordinary muscle cells, and the sequence of activation of the endocar-Downloaded from curred, but the apex-to-base muscle activation persisted. White numbers on black background = conducting cells; black numbers on white background = muscle cells.

No abstract

The results suggest that routine use of intraoperative thromboelastometry in pediatric cardiac surgery to guide transfusions is associated with a reduced proportion of patients receiving transfusions and an altered transfusion pattern.

The cdk-inhibitor p16 is a tumor suppressor gene that is inactivated in many forms of cancer. Despite numerous studies, the exact mechanism of regulation of p16 has not been clarified, although the status of retinoblastoma (Rb) seems to be one important factor that influences the p16 expression. The specificity and validity of cytoplasmic localization of p16 observed in some tumors has further been questioned. Here, by subcellular fractionation of Rbfunctional and Rb-inactivated cell lines, we show that p16 indeed is expressed in the cytoplasm as well as in the nucleus. Post translational modifications of p16 in different subcellular compartments as well as its capacity to form protein complexes were further delineated. Two dimensional gel electrophoresis showed that two forms of p16 appeared in the cytoplasm, while only one form was detected in the nucleus. Samples of basal cell carcinoma and squamous cell carcinoma of the skin with either functional or non-functional Rb also exhibited at least two forms of p16. In addition, cytoplasmic p16 bound cyclin dependent kinase (cdk)4/6, potentially indicating that p16 could have a function in the cytoplasm. ' 2005 Wiley-Liss, Inc.Key words: p16; retinoblastoma gene product; two-dimensional gel electrophoresis Progression of a cell through the cell cycle is tightly regulated by several control mechanisms involving positive and negative regulators of the cell cycle. Uncontrolled regulation of these control mechanisms leads to dysfunctional cell cycle control, uncontrolled cell division and eventually tumor formation. 1 Central in the late G1 phase checkpoint is the retinoblastoma (Rb) pathway. In G1 phase, Rb binds to transcription factors such as E2Fs, preventing genes necessary for S-phase entry to be transcribed. Upon mitogen stimulation, there is an upregulation of cyclin D which binds to cyclin dependent kinases (cdks) 4/6 and the complex initiates the phosphorylation of Rb, which becomes inactive. This leads to release of E2Fs and transcription of genes that are needed for the cell to continue into S-phase. 2 The cdk-inhibitor p16, with the major function to block the cell cycle, is a tumor suppressor gene that is inactivated in many cancer forms. 3 When p16 in the G1-phase of the cell cycle binds to cdk4/6, the active cyclin Dcdk4/6 complex cannot be formed and phosphorylation of Rb is thereby prevented causing inhibition of the cell cycle. 4,5 Small homozygous deletions, point mutations and methylation of the promoter are mechanisms that inactivate p16. 3 When inactivated, there is, in some cases, a loss of p16 protein expression in tumor cells as observed by immunohistochemistry. 6 In contrast, p16 is overexpressed in some tumors, commonly explained as secondary to Rb-inactivation. 4,7 The exact mechanism inducing p16 in Rb-inactivated tumors has not been elucidated, but both direct transcriptional effects and protein accumulation as a result of many population doublings have been proposed. 8 In tumors, many of the p16 mutations map to the cdk-binding regions ...

p16 INK4a is involved in many important regulatory events in the cell and the expression and function is closely associated with the retinoblastoma protein (Rb). Earlier, we have in colorectal cancer and in basal cell carcinoma showed that p16 INK4a is upregulated at the invasive front causing cell cycle arrest in infiltrative tumor cells via a functional Rb. This role for p16 INK4a as a regulator of proliferation when tumor cells infiltrate might besides a general cyclin-dependent kinase (cdk) inhibitory effect explain why p16 INK4a is deregulated in many tumor forms. The expression pattern of p16 INK4a in relation to Rb-function in squamous cancer and precancerous forms of the skin has not been fully detailed. We therefore characterized the expression of p16 INK4a , Rb-phosphorylation and proliferation in actinic keratosis, squamous cell carcinoma in situ and invasive squamous cell carcinoma with special reference to infiltrative behavior. The expression of p16 INK4a varied between the lesions, with weak and cytoplasmic p16 INK4a expression and functional Rb in actinic keratosis. Strong nuclear and cytoplasmic p16 INK4a expression was observed in all carcinomas in situ in parallel with lack of Rb-phosphorylation but high proliferation indicating a nonfunctional Rb. Invasive squamous carcinoma showed a mixed p16 INK4a expression pattern where some tumors had strong cytoplasmic p16 INK4a expression, large fraction of Rb-phosphorylated cells and high proliferation. Interestingly, despite this disability of p16 INK4a to inhibit proliferation there was an upregulation of cytoplasmic p16 INK4a in infiltrative cells compared to tumor cells towards the tumor center. A similar scenario but strong and combined nuclear and cytoplasmic p16 INK4a expression in infiltrative cells, was observed in other invasive squamous cancers. This suggests that the p16 INK4a upregulation in infiltrative cells is governed independently of the subcellular localization or of the potential to affect proliferation via Rb, and suggests a potentially proliferation independent function for p16 INK4a in infiltrative behavior.

The oncogene cyclin D1 is highly expressed in many breast cancers and, despite its proliferation-activating properties, it has been linked to a less malignant phenotype. To clarify this observation, we focused on two key components of malignant behavior, migration and proliferation, and observed that quiescent G(0)/G(1) cells display an increased migratory capacity compared to cycling cells. We also found that the down-regulation of cyclin D1 in actively cycling cells significantly increased migration while also decreasing proliferation. When analyzing a large set of premenopausal breast cancers, we observed an inverse proliferation-independent link between cyclin D1 and tumor size and recurrence, suggesting that this protein might abrogate infiltrative malignant behavior in vivo. Finally, gene expression analysis after cyclin D1 down-regulation by siRNA confirmed changes in processes associated with migration and enrichment of our gene set in a metastatic poor prognosis signature. This novel function of cyclin D1 illustrates the interplay between tumor proliferation and migration and may explain the attenuation of malignant behavior in breast cancers with high cyclin D1 levels.

We describe a method based on a Fabry-Perot interferometer at the tip of an optic fiber with a diameter of 0.25 mm for direct measurement of tracheal pressure in pediatric respiratory monitoring. The response time of the pressure transducer and its influence on the resistance of pediatric endotracheal tubes (internal diameter, 2.5 to 5 mm) during constant and dynamic flow at different ventilator settings in a lung model were measured. The transducer was positioned at Ϫ1.5 (inside), 0, and ϩ1.5 cm (outside) relative to the tip of the endotracheal tube and compared with a reference pressure inside the trachea. The clinical application of the transducer was tested in five pediatric patients. The response time of the transducer was 1.3 ms. The influence of the fiberoptic transducer on tube resistance was negligible during constant flow in inspiratory and expiratory directions for all endotracheal tubes tested. There was no difference in pressure measurements with the transducer positioned at or 1.5 cm below or above the tip of the endotracheal tube during dynamic measurements. During clinical circumstances insertion of the fiberoptic transducer was easy, recordings were stable, and the safety of the patient was not jeopardized. The fiberoptic transducer provided a reliable and promising way of monitoring tracheal pressure in intubated pediatric patients. The presence of the probe did not interfere with either pressure-flow relationship or patient care and safety. The technique is proposed for monitoring of respiratory mechanics and calculation of changes in tube resistance caused by kinking and secretions. Respiratory monitoring in pediatric intensive care is currently represented by proximal P/V loops obtained in ventilator software or intensive care monitors using flowmeters placed near the connection between the ventilator system and ETT. This is obviously insufficient as information gained from such P/V loops mainly stems from ETT resistance and performance of ventilator valves. We have previously demonstrated that monitoring respiratory mechanics by direct measurement of tracheal pressure offers considerable advantages compared with monitoring based on either measurements obtained proximal to the tube or tracheal pressures calculated by subtracting pressure needed to overcome flow-dependent tube resistance. In the adult setting tracheal pressure measurement is accomplished by introducing an air-or liquid-filled catheter into the ETT and connecting it to a conventional pressure transducer (1). In the pediatric setting it has generally been held to be impossible to use endotracheal catheters for continuous pressure measurement owing to the encroachment on cross-sectional area of the narrow pediatric tubes (2). Instead hydrodynamic models of varying complexity have been proposed for the calculation of tracheal pressure, i.e. the pressure fall across the ETT because of its resistance, based on measurements above the tube. Guttmann et al. (2)