A retrospective study: Correlations between cup to disc ratio, age, gender, intra-ocular pressure, and disc asymmetry

Four hundred and eighty-eight randomly selected patient records (250 males with a mean age of 38.40 years, and 238 females with a mean age of 36.51 years) were evaluated for possible correlations between gender, age, cup to disc (C/D) ratio, intra-ocular pressure, refractive condition, and C/D asymmetry (asymmetry is defined as the difference between the horizontal and vertical C/D ratios). Mean C/D ratios for males and females were 0.269 and 0.256 respectively, while a mean intra-ocular pressure for males was 14.6 mm Hg and for females was 14.3 mm Hg. This study revealed moderately significant (0.731 to 0.790) correlations between age and C/D ratio, while a slightly greater level of significance (0.832) was recognized between age and intra-ocular pressure. C/D ratios correlated at a fairly significant level (0.767 to 0.971) to refractive condition. While C/D asymmetry correlated poorly with refractive condition (0.265) in males, it correlated significantly (0.889 to 0.947) in females, with myopic females having the highest correlation (0.947). Approximately 79% of males and 81% of females in this study had C/D ratios less than 0.40. Correlations were more significant (0.745 to 0.868) for C/D ratios equal to or above 0.40. Vertical asymmetry, or vertical elongation of the C/D ratio of 0.10 or more was significantly correlated (0.948) to intra-ocular pressure. The results of this study suggests there exists significant correlations between age, gender, C/D ratio, intra-ocular pressure, and C/D asymmetry

High spatial and temporal resolution cell manipulation techniques in microchannels

The advent of microfluidics has enabled thorough control of cell manipulation experiments in so called lab on chips. Lab on chips foster the integration of actuation and detection systems, and require minute sample and reagent amounts. Typically employed microfluidic structures have similar dimensions as cells, enabling precise spatial and temporal control of individual cells and their local environments. Several strategies for high spatio-temporal control of cells in microfluidics have been reported in recent years, namely methods relying on careful design of the microfluidic structures (e.g. pinched flow), by integration of actuators (e.g. electrodes or magnets for dielectro-, acousto- and magneto-phoresis), or integrations thereof. This review presents the recent developments of cell experiments in microfluidics divided into two parts: an introduction to spatial control of cells in microchannels followed by special emphasis in the high temporal control of cell-stimulus reaction and quenching. In the end, the present state of the art is discussed in line with future perspectives and challenges for translating these devices into routine applications

Preparation of neuronal co-cultures with single cell precision

Microfluidic embodiments of the Campenot chamber have attracted great interest from the neuroscience community. These interconnected co-culture platforms can be used toinvestigate a variety of questions, spanning developmental and functional neurobiology to infection and disease propagation. However, conventional systems require significant cellular inputs (many thousands per compartment), inadequate for studying low abundance cells, such as primary dopaminergic substantia nigra, spiral ganglia and Drosophilia melanogaster neurons, and impractical for high throughput experimentation. The dense cultures are also highly locally entangled, with few outgrowths (<10%) interconnecting the two cultures. In this paper straightforward microfluidic and patterning protocols are described which address these challenges: (i) a microfluidic single neuron arraying method, and (ii) a water masking method for plasma patterning biomaterial coatings to register neurons and promote outgrowth between compartments. Minimalistic neuronal co-cultures were prepared with high-level (>85%) inter-compartment connectivity and can be used for high throughput neurobiology experiments with single cell precisio

Slow-light enhanced light-matter interactions with applications to gas sensing

Optical gas detection in microsystems is limited by the short micron scale optical path length available. Recently, the concept of slow-light enhanced absorption has been proposed as a route to compensate for the short path length in miniaturized absorption cells. We extend the previous perturbation theory to the case of a Bragg stack infiltrated by a spectrally strongly dispersive gas with a narrow and distinct absorption peak. We show that considerable signal enhancement is possible. As an example, we consider a Bragg stack consisting of PMMA infiltrated by O2. Here, the required optical path length for visible to near-infrared detection (~760 nm) can be reduced by at least a factor of 10^2, making a path length of 1 mm feasible. By using this technique, optical gas detection can potentially be made possible in microsystems

A study comparing two methods of predicting the subjective cylinder through contact lenses with the measured value of the subjective cylinder

A study comparing two methods of predicting the subjective cylinder through contact lenses with the measured value of the subjective cylinde

Micropatterning neuronal networks

Spatially organised neuronal networks have wide reaching applications, including fundamental research, toxicology testing, pharmaceutical screening and the realisation of neuronal implant interfaces. Despite the large number of methods catalogued in the literature there remains the need to identify a method that delivers high pattern compliance, long-term stability and is widely accessible to neuroscientists. In this comparative study, aminated (polylysine/polyornithine and aminosilanes) and cytophobic (poly(ethylene glycol) (PEG) and methylated) material contrasts were evaluated. Backfilling plasma stencilled PEGylated substrates with polylysine does not produce good material contrasts, whereas polylysine patterned on methylated substrates becomes mobilised by agents in the cell culture media which results in rapid pattern decay. Aminosilanes, polylysine substitutes, are prone to hydrolysis and the chemistries prove challenging to master. Instead, the stable coupling between polylysine and PLL-g-PEG can be exploited: Microcontact printing polylysine onto a PLL-g-PEG coated glass substrate provides a simple means to produce microstructured networks of primary neurons that have superior pattern compliance during long term (>1 month) cultur

A microfluidic array with cellular valving for single cell co-culture

We present a highly parallel microfluidic approach for contacting single cell pairs. The approach combines a differential fluidic resistance trapping method with a novel cellular valving principle for homotypic and heterotypic single cell co-culturing. Differential fluidic resistance was used for sequential single cell arraying, with the adhesion and flattening of viable cells within the microstructured environment acting to produce valves in the open state. Reversal of the flow was used for the sequential single cell arraying of the second cell type. Plasma stencilling, along the linear path of least resistance, was required to confine the cells within the trap regions. Prime flow conditions with minimal shear stress were identified for highly efficient cell arraying (similar to 99%) and long term cell culture. Larger trap dimensions enabled the highest levels of cell pairing (similar to 70%). The single cell co-cultures were in close proximity for the formation of connexon structures and the study of contact modes of communication. The research further highlights the possibility of using the natural behaviour of cells as the working principle behind responsive microfluidic element

Gasdialytisch-chemiluminometrische Wasserstoffperoxiddetektion : Grundlagen und Anwendung zur enzymatischen Durchflußanalyse

Die gasdialytische Abtrennung von Wasserstoffperoxid aus wäßrigen Proben lösungen wurde unter kontinuierlichen Durchfluß - und FIA ( Flow Injection Analysis ) - Bedingungen systematisch untersucht. Dazu wurde die amperometrische und die chemiluminometrische Durchflußdetektion angewendet. Der Trennschritt führte in beiden Fällen zu einer wesentlichen Erhöhung der Selektivität. So lassen sich insbesondere die bei der chemiluminometrischen Detektion durch leicht reduzierbare Substanzen, wie z.B. NADH, Paracetamol, Harnsäure, reduziertes Glutathion und Ascorbinsäure verursachten Interferenzen vollständig bzw. zum wesentlichen Teil ausschalten. Untersucht wurde der Einfluß der Verweilzeit, der Trennzellengeometrie, der Temperatur, des pH - Wertes und der Pufferzusam-mensetzung. Als besonders aussichtsreich erwies sich die gasdialytisch – chemi-luminometrische Detektion in einem miniaturisierten und mit einem Photonen-countingsystem ausgerüsteten Detektor, mit dem bei kurzen Ansprechzeiten von T90 < 5 s Nachweisgrenzen um 0.5 mM erreicht werden. Dies ermöglicht Analysen-frequenzen von bis zu 100 Bestimmungen pro Stunde. Die Chemilumineszenz-detektion beruhte dabei entweder auf der durch Peroxidase aus Arthromyces ramosus oder durch Co(II) katalysierten Oxydation von Luminol. Die gasdialytisch – chemiluminometrische Wasserstoffperoxiddetektion wurde auf die Bestimmung von Oxidasesubstraten, wie z.B. L-Lactat, Glucose, Pyruvat und Glycerol - 3- phosphat angewendet, die dann auch in komplexen Proben-lösungen, wie z.B. in Medien von technischen Säugerzellkulturen in einem weiten Bestimmungsbereich zwischen 1 mM und 10 mM mit sehr hoher Selektivität bestimmt werden können. Die bei der Chemilumineszenzdetektion infolge Bildung hochreaktiver Intermediate sonst immer auftretenden starken Matrixeffekte, hervorgerufen insbesondere durch zahlreiche redoxaktive Substanzen aber auch durch Chelatbildner können praktisch ausgeschlossen werden

Microfluidic preparative free-flow isoelectric focusing in a triangular channel: System development and characterization

A preparative scale free-flow IEF device is developed and characterized with the aim of addressing needs of molecular biologists working with protein samples on the milligrams and milliliters scale. A triangular-shape separation channel facilitates the establishment of the pH gradient with a corresponding increase in separation efficiency and decrease in focusing time compared with that in a regular rectangular channel. Functionalized, ion-permeable poly(acrylamide) gel membranes are sandwiched between PDMS and glass layers to both isolate the electrode buffers from the central separation channel and also to selectively adjust the voltage efficiency across the separation channel to achieve high electric field separation. The 50×70 mm device is fabricated by soft lithography and has 24 outlets evenly spaced across a pH gradient between pH 4 and 10. This preparative free-flow IEF system is investigated and optimized for both aqueous and denaturing conditions with respect to the electric field and potential efficiency and with consideration of Joule-heating removal. Energy distribution across the functionalized polyacrylamide gel is investigated and controlled to adjust the potential efficiency between 15 and 80% across the triangular separation channel. The device is able to achieve constant electric fields high as 370±20 V/cm through the entire triangular channel given the separation voltage of 1800 V, enabling separation of five fluorescent pI markers as a demonstration example.United States. Army Research Office (Grant Number: W911NF-07-D-0004)National Institutes of Health (U.S.) (Grant Number: GM68762