New metrics for analysis of dendritic branching patterns demonstrating similarities and differences in ON and ON-OFF directionally selective retinal ganglion cells.

The morphology and dendritic branching patterns of retinal ganglion cells have been studied in Golgi-impregnated, whole-mount preparations of rabbit retina. Among a large number of morphological types identified, two have been found that correspond to the morphology of ON and ON-OFF directionally selective (DS) ganglion cells identified in other studies. These two kinds of DS ganglion cell are compared with each other, as well as with examples of class I, class II, and class III cells, defined here with reference to our previous studies. Cell body, dendritic field size and branching pattern are analyzed in this paper and levels of dendritic stratification are examined in the following paper. ON DS ganglion cells are about 10% larger in soma size and about 5 times the dendritic field area of ON-OFF DS ganglion cells, when compared at the same retinal location. These two morphological types of ganglion cell can be said to define the upper and lower bounds of an intermediate range of cell body and dendritic field sizes within the whole population of ganglion cells. Nevertheless, in previous physiological studies receptive field sizes of the two types were shown to be similar. This discrepancy between morphological and physiological evidence is considered in the Discussion in terms of a model of the excitatory receptive field of ON-OFF DS ganglion cells incorporating starburst amacrine cells. A new set of metrics is introduced here for the quantitative analysis and characterization of the branching pattern of neuronal arborizations. This method compares the lengths of terminal and preterminal dendritic branches (treated separately), as a function of the distances of their origins from the soma, viewed graphically in a two-dimensional scatter plot. These values are derived from computer-aided 3D logging of the dendritic trees, and distance from the soma is measured as the shortest distance tracked along the dendritic branches. From these metrics of the "branch length distributions," scale-independent branching statistics are derived. These make use of mean branch lengths and distances, slopes of lines fitted to the distributions, and elliptical indices of scatter in the distributions. By these measures, ON and ON-OFF DS ganglion cells have similar branching patterns, which they share to varying degrees with functionally unrelated class III.1 ganglion cells. The scale of the branching patterns of ON and ON-OFF DS cells and their degree of uniformity are different, however.(ABSTRACT TRUNCATED AT 400 WORDS)     

Results of a clinical care pathway for radical prostatectomy patients in an open hospital - multiphysician system

OBJECTIVES: The object of this study was to evaluate the results of a comprehensive clinical care pathway (CCP) aimed at reducing the length of hospitalization and overall cost for patients undergoing radical prostatectomy in a setting including both academic and private physicians. METHODS: The clinical records of 1,129 consecutive patients who underwent radical prostatectomy by 24 urologists between July 1, 1990, and December 31, 1996, were reviewed. The factors considered were length of stay, morbidity and mortality, readmission rates, and average cost. The CCP was implemented on January 1, 1994. Its scope was to minimize preoperative evaluation, eliminate the preoperative hospital stay, standardize postoperative care and provide intensive patient education. RESULTS: The average length of stay decreased significantly after implementation of the CCP (8.1 vs. 4.9 days, p = 0.0001). In 1990, there was a large difference in length of stay between academic and private physicians (8.3 vs. 12.6 days) (p = 0. 02) but by 1 year after implementation of the CCP there was virtually no difference (4.69 vs. 4.71 days) (p > 0.05). Complication rates were similar before and after implementation of the CCP. Using the average 1993 cost/case as the baseline preCCP figure, the average cost of radical prostatectomy decreased by 16% in 1994 and by 22% in 1995. CONCLUSIONS: It is possible to successfully implement a CCP in a multi-physician system to reduce length of stay and cost of radical prostatectomy without subjecting the patient to a greater risk of complication.     

On and off pathways through amacrine cells in mammalian retina: the synaptic connections of "starburst" amacrine cells

The neural architecture of on and off pathways in mammalian retina is described, including the development of ideas leading to an understanding of the bisublaminar organization of the inner plexiform layer of the retina which supports these two pathways. The complexities of bipolar cell contributions are contrasted with the relative simplicity of ganglion cell organization with regard to bisublaminar architecture, and a key role is described for internuncial amacrine cells as specific targets for bipolar cells. Two very different kinds of amacrine cell are considered and compared, both of which mediate bipolar input to ganglion cells. These are the rod (type II) amacrine cell, and the more recently discovered "starburst" amacrine cell, which is apparently cholinergic in function. As different as the wide-field starburst amacrine cells are from the narrow-field rod amacrine cells, they share important features. Both are interposed between bipolar and ganglion cells, and both have segregated regions of presynaptic boutons. They differ, however, in that rod amacrines may perform more specific functions related to receptive field center organization, while the functional role of starburst amacrines may be unrelated to receptive field properties of ganglion cells. The mirror-symmetry of type a and type b (off and on) starburst amacrine cells is described together with their synaptic circuitry. In contrast to the rod amacrine cell the output of starburst amacrines is exclusively to ganglion cells. Others have proposed a dual function for acetylcholine (ACh) in the retina. A unifying hypothesis is briefly sketched here which relates the pharmacology of ACh and the dendritic stratification of starburst amacrine cells to the form and function of ganglion cells. It is proposed that the amount of generalized synaptic excitation received from ACh/starburst amacrine cells by a particular type of ganglion cell is largely a function of co-stratification of the ganglion cell's dendrites with the distal boutons of starburst amacrine cells.     

Three-year surveillance study of nosocomial bacterial resistance in Argentina. The Antimicrobial Committee; and the National Surveillance Program (SIR) Participants Group.

INTRODUCTION: A national surveillance program (SIR) was introduced in 1996 in Argentina by the Antimicrobial Committee of the Argentinean Society for Microbiology to assess bacterial resistance. The present study reports the rates of nosocomial bacterial resistance found by this program. METHODS: A 2-month point-prevalence study was conducted twice yearly (i.e., April-May and October-November) from 1996 to 1998, by 27 Argentinean centers. Susceptibility testing was carried out by the disk diffusion method following the National Committee for Clinical Laboratory Standards guidelines. RESULTS: In all, 6343 isolates recovered from 5603 inpatients (> or =48-hr hospitalization) were included. Methicillin resistance was 58% and 56% in Staphylococcus aureus and coagulase-negative staphylococci (CNS), respectively. Although no vancomycin resistance was found in staphylococci, 2% and 8% of the S. aureus and CNS strains, respectively, proved resistant to teicoplanin. No ampicillin resistance was displayed by Enterococcus faecalis. High-level gentamicin and streptomycin resistance in enterococci were 33% and 37%, respectively. Acquired glycopeptide resistance in enterococci emerged in 1997 (2%). Imipenem resistance in Acinetobacter spp and Pseudomonas aeruginosa was 9% and 21%, respectively. Among Enterobacteriaceae, 1% and 5% of the Klebsiella pneumoniae and Enterobacter cloacae isolates, respectively, proved resistant to imipenem. Ceftazidime and cefepime resistance was found in 63% and 33% of the E. cloacae strains. Resistance to extended-spectrum cephalosporins was shown by 48%, 26%, and 8% of the K. pneumoniae, Proteus mirabilis, and Escherichia coli isolates, respectively. CONCLUSIONS: The alarming rates of resistance found in this study provide compelling evidence of the need for more rational use of antimicrobial agents in Argentina.     

Starburst amacrine cells: morphological constancy and systematic variation in the anisotropic field of rabbit retinal neurons

Starburst amacrine cells of rabbit retina have been characterized previously in terms of their highly distinctive and regular dendritic geometry. They have been identified as probable cholinergic neurons of the retina and have been shown to direct output solely to ganglion cells. The objectives of this paper are to chart the variation of starburst amacrine cells across the retina, to register the morphological features which are held constant for individual cells, and to examine factors which may remain invariant for the population with change in retinal position. Starburst amacrine cells occur as two completely segregated mirror-symmetrical populations, type a and type b cells, separately serving OFF and ON pathways, respectively. They are treated here as two distinct subpopulations with very similar features. A characteristic morphological feature of both types, related to branching pattern and best seen in flat view, is the location of boutons in the distal annular zone. This is the effective zone of synaptic output, which is constant at 50 to 60% of dendritic field area, regardless of the cell's retinal location. Both type a and type b cells exhibit systematic increase in cell body size and dendritic field diameter, and systematic decrease in frequency of branching and of synaptic boutons with perpendicular distance from the visual streak. These rates of increase or decrease fall off considerably at distances greater than about 1.5 mm dorsal and ventral to the visual streak, but at this distance, the dendritic field diameters of cells in dorsal retina are about 65% larger than the diameters of cells in ventral retina. When type a and type b cells are closely compared, they are seen to differ in several respects. Branching patterns of type a and type b cells differ slightly, the latter being more highly branched, and the normalized branching frequency histograms, characteristic for each type, remain constant with changing retinal position. At the same retinal location type a cells always have larger dendritic field diameters than type b cells. This difference is significant in ventral retina, out to a distance of at least 4.5 mm from the streak. The maximum percentage difference in size occurs not at mid-visual streak, but about 1.5 mm ventral to the streak. The population statistics of dendritic field overlap and areal dendritic coverage have been calculated using published data on cell densities. It is concluded that overlap is extraordinarily high (k greater than 25), more than 10 times that calculated for retinal ganglion cells.(ABSTRACT TRUNCATED AT 400 WORDS)     

Diagnosis of bacterial vaginosis during pregnancy

OBJECTIVE.: To evaluate the sensitivity and specificity of the score and each one of the clinical criteria (pH, potassium hydroxide (KOH) test for amines, and clue cells) in relation to the Amsel's method. MATERIALS AND METHODS.: One hundred ninety vaginal exudates from pregnant women were studied from April to August 1997. The patients were examined in the Lower Genital Tract and Colposcopy Clinics of the Obstetrics Division at the University Hospital de Clínicas at the University of Buenos Aires, Argentina.The diagnosis of bacterial vaginosis (BV) was made by the presence of three or more of the following criteria: homogeneous vaginal discharge, pH >/= 4.5, positive KOH test for amines, and microscopic presence of clue cells. We also used the microscopic observation of coccobacilli forms in Gram stain (Nugent's method), diagnosing BV with a score >/= 7. RESULTS.: Nugent's method showed a sensitivity of 97% and specificity of 98%. The presence of clue cells showed a sensitivity of 92% and specificity of 97%. The sensitivity of the pH and KOH test for amines was 87% and 81%, whereas the respective specificity was 45% and 99%. CONCLUSIONS.: Because Nugent's method showed a very good specificity and sensitivity, it can be used as another method in the diagnosis of BV. The presence of clue cells diagnosed BV with better sensitivity and specificity than the other clinical criteria. In this way, we recommend the microscopic exam by Gram stain, using Nugent's method or the presence of clue cells, for diagnosing BV.     

Satellite-based global-ocean mass balance estimates of interannual variability and emerging trends in continental freshwater discharge

Freshwater discharge from the continents is a key component of Earth’s water cycle that sustains human life and ecosystem health. Surprisingly, owing to a number of socioeconomic and political obstacles, a comprehensive global river discharge observing system does not yet exist. Here we use 13 years (1994–2006) of satellite precipitation, evaporation, and sea level data in an ocean mass balance to estimate freshwater discharge into the global ocean. Results indicate that global freshwater discharge averaged 36,055 km³/y for the study period while exhibiting significant interannual variability driven primarily by El Niño Southern Oscillation cycles. The method described here can ultimately be used to estimate long-term global discharge trends as the records of sea level rise and ocean temperature lengthen. For the relatively short 13-year period studied here, global discharge increased by 540 km³/y², which was largely attributed to an increase of global-ocean evaporation (768 km³/y²). Sustained growth of these flux rates into long-term trends would provide evidence for increasing intensity of the hydrologic cycle.