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Biomedical subjects

U J Balis

Publications and source records attributed to U J Balis.

11 recordsLinked to original sources
PubMed1998

Probing heterotypic cell interactions: hepatocyte function in microfabricated co-cultures.

Replacement of liver function using extracorporeal bioartificial systems has been attempted with limited success. The instability of the hepatocyte phenotype in vitro has restricted the useful lifetime of these devices. Co-cultivation of hepatocytes with mesenchymal cells is one method that has been widely utilized to stabilize the liver-specific function of isolated cells; however, co-culture has yet to be successfully incorporated in a bioreactor setting. In this study, we probed heterotypic cell interactions in co-cultures of hepatocytes and 3T3 in order to better understand the cellular microenvironment necessary to induce and stabilize liver-specific functions. Using microfabrication and conventional techniques to control the heterotypic interface, the effects of varying degrees of heterotypic interaction on tissue function (albumin and urea synthesis) were examined. Our data indicated maximal induction of liver-specific functions in cultures with maximal initial heterotypic interaction, and that induction of hepatic functions in hepatocytes was increased in the vicinity of fibroblasts as compared to hepatocytes far from the heterotypic interface. Furthermore, our data suggested that heterotypic cell contact is necessary for induction of these functions. These studies will aid in the formation of design criteria for a co-culture based bioartificial liver, as well as provide a useful tool to study the role of heterotypic and homotypic interactions in liver physiology and pathophysiology.

3T3 Cells↗
PubMed1997

The LightCycler: a microvolume multisample fluorimeter with rapid temperature control.

Experimental and commercial microvolume fluorimeters with rapid temperature control are described. Fluorescence optics adopted from flow cytometry were used to interrogate 1-10-microL samples in glass capillaries. Homogeneous temperature control and rapid change of sample temperatures (10 degrees C/s) were obtained by a circulating air vortex. A prototype 2-color, 32-sample version was constructed with a xenon arc for excitation, separate excitation and emission paths, and photomultiplier tubes for detection. The commercial LightCycler, a 3-color, 24-sample instrument, uses a blue light-emitting diode for excitation, paraxial epi-illumination through the capillary tip and photodiodes for detection. Applications include analyte quantification and nucleic acid melting curves with fluorescent dyes, enzyme assays with fluorescent substrates and techniques that use fluorescence resonance energy transfer. Microvolume capability allows analysis of very small or expensive samples. As an example of one application, rapid cycle DNA amplification was continuously monitored by three different fluorescence techniques, Which included using the double-stranded DNA dye SYBR Green I, a dual-labeled 5'-exonuclease hydrolysis probe, and adjacent fluorescein and Cy5z-labeled hybridization probes. Complete amplification and analysis requires only 10-15 min.

Benzothiazoles↗
PubMed1997

Imaging input technology.

Imaging input technology is at its greatest rate of development ever, with CCD technology improving both in terms of image quality and image economy. The current diversity of imager modalities and application specializations allows for elegant matching of device capability to image subject photographic requirements. Both color and low-light imaging technologies continue to evolve, with ever-increasing resolution and dynamic range. The "order of magnitude" cost decreases that so aptly characterized the computer industry of the 1970s and 1980s is now upon the digital imager industry. Although analog cameras, based on video formats, still prevail, the direct digital camera will emerge as the preferred input device within a decade.

Diagnostic Imaging↗
PubMed1997

Image output technology.

Once an image has been captured and stored, whether it is in analog or digital format, for it to be useful in the future there must exist some way of re-rendering it. It is hoped this will be in a manner that is imperceptibly different from the original. Because it is usually impossible to render an image in identical form to the original, numerous decisions need to be made concerning which attributes are the most important, in terms of image archival quality and diagnostic accuracy.

Diagnostic Imaging↗
PubMed1997

Optical considerations in digital imaging.

The topic of optics and its effect in ultimate rendered image quality has largely been underemphasized for medical imaging systems. In actuality, adequate attention to optical issues is essential in ensuring that image quality is optimal. Generally, optical issues can be divided into two broad categories: optical interface optimization and lighting optimization. Although these issues deal with disparate aspects of optical physics, they are covered within a single article because they both apply to the common goal of generating superior medical images.

Diagnostic Imaging↗
PubMed1997

Telemedicine and telepathology.

Telepathology is entering a golden era in which both the technology and the rationale for utilizing this technology are evolving. The following decade will see the introduction of national and international telepathology networks, founded on the principle of improving patient care and increasing cost-effectiveness. As telecommunications and imaging technology concurrently advance, newer generations of telepathology platforms will ultimately deliver performance that will be essentially indistinguishable from that of microscope-derived diagnoses.

Humans↗
PubMed1997

Digital imaging standards and system interoperability.

Standards development in medical imaging originated in the field of radiology and has rapidly spread to numerous other medical specialties. Pathology is well represented in this effort, and it benefits from interoperability made possible by the utilization of the DICOM 3.0 standard in the fabrication of pathology workstations. Because there currently exists a strong trend for both standards convergence and international harmonization, the formation of a world-wide electronic medical image standard is likely only several years away.

Diagnostic Imaging↗
PubMed1995

Immunohistochemical reference ranges for B lymphocytes in bone marrow biopsy paraffin sections.

The quantitation of B lymphocytes in paraffin-decalcified bone marrow sections is often used as supportive evidence of primary or residual B-cell lymphoproliferative disorders; however, well-defined normal ranges for B lymphocytes are not available. Thirty-four B5-fixed decalcified bone marrow sections were analyzed from a group of patients having an essentially normal bone marrow morphologic examination and lacking any evidence immunologic or hematopoietic disease. All samples were stained with CD20, CD45RA (4KB5), and DBA.44 for B cells, and CD45RO (UCHL-1) for T cells. Image analysis was performed on all cases. CD20-positive cells ranged from 0% to 5.97%. CD45RA positivity ranged from 0% to 5.48%. DBA.44 was positive in 0% to 2.07% of the cells. CD45RO positivity varied from 0% to 6.7%. These results provide useful immunohistochemical B-lymphocyte reference ranges in B5-fixed paraffin bone marrow sections.

Adult↗
PubMed1994

Simulations of a ventrolateral medullary neural network for respiratory rhythmogenesis inferred from spike train cross-correlation.

Connections among ventrolateral medullary respiratory neurons inferred from spike train analysis were incorporated into a model and simulated with the program SYSTM11 (MacGregor 1987). Inspiratory (I) and expiratory (E) neurons with augmenting (AUG) and decrementing (DEC) discharge patterns and rostral I-E/I neurons exhibited varying degrees of adaptation, but no endogenous bursting properties. Simulation parameters were adjusted so that respiratory phase durations, neuronal discharge patterns, and short-time scale correlations were similar to corresponding measurements from anesthetized, vagotomized, adult cats. Rhythmogenesis persisted when the strength of each set of connections was increased 100% over a smaller effective value. Changes in phase durations and discharge patterns caused by manipulation of connection strengths or population activity led to several predictions. (a) Excitation of the I-E/I population prolongs the inspiratory phase. (b) Rhythmic activity can be reestablished in the absence of I-E/I activity by unpatterned excitation of I-DEC and I-AUG neurons. (c) An increase in I-DEC neuron activity can cause an apneustic respiratory pattern. (d) A decrease in I-DEC neuron activity increases the slope of the inspiratory ramp and shortens inspiration. (e) Excitation of the E-DEC population prolongs the expiratory phase or produces apnea; inhibition of E-DEC neurons reduces expiratory time. (f) Excitation of E-AUG cells causes I-AUG neurons to exhibit a step rather than a ramp increase in firing rate at the onset of their active phase. The results suggest mechanisms by which the duration of each phase of breathing and neuronal discharge patterns may be regulated.

Animals↗
PubMedDate not supplied

Microfabrication of hepatocyte/fibroblast co-cultures: role of homotypic cell interactions.

Cell-cell interactions are important in embryogenesis, in adult physiology and pathophysiology of many disease processes. Co-cultivation of parenchymal and mesenchymal cells has been widely utilized as a paradigm for the study of cell-cell interactions in vitro. In addition, co-cultures of two cell types provide highly functional tissue constructs for use in therapeutic or investigational applications. The inherent complexity of such co-cultures creates difficulty in characterization of cell-cell interactions and their effects on function. In the present study, we utilize conventional "randomly distributed" co-cultures of primary rat hepatocytes and murine 3T3-J2 fibroblasts to investigate the role of increasing fibroblast density on hepatic function. In addition, we utilize microfabrication techniques to localize both cell populations in patterned configurations on rigid substrates. This technique allowed the isolation of fibroblast number as an independent variable in hepatic function. Notably, homotypic hepatocyte interactions were held constant by utilization of similar hepatocyte patterns in all conditions, and the heterotypic interface (region of contact between cell populations) was also held constant. Co-cultures were probed for synthetic and metabolic markers of liver-specific function. The data suggest that fibroblast number plays a role in modulation of hepatocellular response through homotypic fibroblast interactions. The response to changes in fibroblast number are distinct from those attributed to increased contact between hepatocytes and fibroblasts. This approach will allow further elucidation of the complex interplay between two cell types as they form a functional model tissue in vitro or as they interact in vivo to form a functional organ.

3T3 Cells↗