A fulminant hepatic failure model in the rat: involvement of interleukin-1beta and tumor necrosis factor-alpha.

The development of a fulminant hepatic failure (FHF) model is necessary for evaluating the efficacy of extracorporeal liver support systems. Recognizing the multifaceted functions of the liver, including synthesis and degradation, we investigated blood chemistry, histological findings, and survival rate in D-galactosamine (GalN)-intoxicated rats. The pathophysiologic response of inflammatory cytokines, interleukin-1beta (IL-1beta) and tumor necrosis factor-alpha (TNF-alpha), was also measured. Sprague-Dawley rats (200-300 g) were divided into two groups: GalN and saline injection. Rats were killed at 1, 3, 6, 12, 24, 36, 48, 72, and 168 hr after intraperitoneal injection of GalN (1.4 g/kg) or saline. In both groups, liver-specific markers, liver histology, and IL-1beta and TNF-alpha levels in blood and liver tissue were analyzed. In a second series of experiments, the survival rates were examined after two administrations of GalN at 1.0, 1.4 or 2.0 g/kg, at a 12-hr interval. In the GalN injection group, the liver-specific markers reached peak levels between 36 and 48 hr after injection. Histologically, hepatocellular necrosis was seen at 6-48 hr, followed by a regenerative phase occurring between 72 and 168 hr. IL-1beta and TNF-alpha levels in liver tissue peaked at 12 hr and 1 hr, respectively. The levels of these cytokines in blood, however, did not change significantly. The survival rates at day 7 for 1.0, 1.4 or 2.0 g/kg GalN injected twice were 77.8%, 16.7%, and 0%, respectively. These results suggest that single and double injection of GalN enable the development of reversible and irreversible FHF models. The results also indicate that IL-1beta and TNF-alpha are useful markers of liver injury.

Cytoskeletal and kinetic epithelial differences between NSAID gastropathy and Helicobacter pylori gastritis: an immunohistochemical determination.

AIMS: Distinguishing histological features between non-steroidal anti-inflammatory drug (NSAID) gastropathy and Helicobacter pylori gastritis have been accepted. However, the molecular basis explaining these dissimilar histologies has not been elucidated. In an attempt to clarify this question we investigated the differences in the structural cytoskeleton and proliferative activity of these two gastropathies. METHODS AND RESULTS: We assessed the distribution of five cytokeratins (CK) (CK7, 8, 18, 19 and 20) and Ki67 for the ability to distinguish NSAID from H. pylori gastropathies. In H. pylori gastritis, CK7, 8, 18 and 19 were expressed comparably to normal mucosa from the deep foveolae up to the tips of the glands. The detection of CK20, normally expressed in the upper foveolar region and surface, was decreased with only an epithelial surface reaction. In NSAID gastropathy, CK expression was increased in intensity, with normal distribution for CK8, 18 and 19. Modification of localization was noted for CK7 and 20, with labelling extending toward the deep foveolar region. Unlike H. pylori gastritis, no surface epithelial labelling with Ki67 was noted with NSAID gastropathy but downward elongation of the proliferative zone occurred instead. CONCLUSIONS: Contrasting cytostructural alterations and distinct proliferative patterns distinguish NSAID gastropathy from H. pylori gastritis, possibly reflecting different injury pathways.

Effect of cell-cell interactions in preservation of cellular phenotype: cocultivation of hepatocytes and nonparenchymal cells.

Heterotypic cell interaction between parenchymal cells and nonparenchymal neighbors has been reported to modulate cell growth, migration, and/or differentiation. In both the developing and adult liver, cell-cell interactions are imperative for coordinated organ function. In vitro, cocultivation of hepatocytes and nonparenchymal cells has been used to preserve and modulate the hepatocyte phenotype. We summarize previous studies in this area as well as recent advances in microfabrication that have allowed for more precise control over cell-cell interactions through 'cellular patterning' or 'micropatterning'. Although the precise mechanisms by which nonparenchymal cells modulate the hepatocyte phenotype remain unelucidated, some new insights on the modes of cell signaling, the extent of cell-cell interaction, and the ratio of cell populations are noted. Proposed clinical applications of hepatocyte cocultures, typically extracorporeal bioartificial liver support systems, are reviewed in the context of these new findings. Continued advances in microfabrication and cell culture will allow further study of the role of cell communication in physiological and pathophysiological processes as well as in the development of functional tissue constructs for medical applications.

Alternative careers in the laboratory re-engineering paradigm.

The expanding and diverse opportunities offered by the information technology and biotechnology fields provides for many obvious and perhaps more not-so-obvious compelling opportunities for pathologists and clinical laboratorians. It can be reasonably expected that individuals who choose to pursue such careers outside the conventional opportunities sought out by most pathologists will be rewarded with the satisfaction that comes with the application of established science in new and challenging ways. The realization of the power of the multidisciplinary approach, both within academia and industry, will only serve to further foster opportunities and success stories for those who choose to sail off the edge of the known pathology world.

Numerical model of fluid flow and oxygen transport in a radial-flow microchannel containing hepatocytes.

The incorporation of monolayers of cultured hepatocytes into an extracorporeal perfusion system has become a promising approach for the development of a temporary bioartificial liver (BAL) support system. In this paper we present a numerical investigation of the oxygen tension, shear stress, and pressure drop in a bioreactor for a BAL composed of plasma-perfused chambers containing monolayers of porcine hepatocytes. The chambers consist of microfabricated parallel disks with center-to-edge radial flow. The oxygen uptake rate (OUR), measured in vitro for porcine hepatocytes, was curve-fitted using Michaelis-Menten kinetics for simulation of the oxygen concentration profile. The effect of different parameters that may influence the oxygen transport inside the chambers, such as the plasma flow rate, the chamber height, the initial oxygen tension in the perfused plasma, the OUR, and K(m) was investigated. We found that both the plasma flow rate and the initial oxygen tension may have an important effect upon oxygen transport. Increasing the flow rate and/or the inlet oxygen tension resulted in improved oxygen transport to cells in the radial-flow microchannels, and allowed significantly greater diameter reactor without oxygen limitation to the hepatocytes. In the range investigated in this paper (10 microns < H < 100 microns), and for a constant plasma flow rate, the chamber height, H, had a negligible effect on the oxygen transport to hepatocytes. On the contrary, it strongly affected the mechanical stress on the cells that is also crucial for the successful design of the BAL reactors. A twofold decrease in chamber height from 50 to 25 microns produced approximately a fivefold increase in maximal shear stress at the inlet of the reactor from 2 to 10 dyn/cm2. Further decrease in chamber height resulted in shear stress values that are physiologically unrealistic. Therefore, the channel height needs to be carefully chosen in a BAL design to avoid deleterious hydrodynamic effects on hepatocytes.

Oxygen consumption characteristics of porcine hepatocytes.

Oxygen uptake rate (OUR) of hepatocytes is an important parameter for the design of bioartificial liver assist (BAL) devices. Porcine hepatocytes were cultured in a specially constructed measurement chamber with an incorporated mixing system and a Clark polarographic oxygen electrode. Signal noise associated with conventional Clark electrode implementations was circumvented by the combination of real time digital numerical averaging and subsequent finite impulse response (FIR) spectral filtering. Additional software allowed for the automated generation of cellular oxygen consumption coefficients, namely, Vmax and K0.5, adding a high degree of objectivity to parameter determination. Optimization of the above numerical techniques identified a 0.1 Hz/200 data point sample size and a 0.004 Hz cutoff frequency as ideal parameters. Vmax values obtained for porcine hepatocytes during the first two weeks of culture showed a maximal consumption of 0.9 nmole/sec/10(6) cells occurring on Day 4 post seeding, and a gradual decrease to 0.31 nmole/sec/10(6) cells by Day 15. K0.5 values increased from 2 mm Hg on Day 2 to 8 mm Hg by Day 8, with gradual subsequent decrease to 4 mm Hg by Day 15. The Vmax and K0.5 values measured for porcine cells were higher than maximal values for rat hepatocytes (Vmax: 0.43 nmole/sec/10(6) cells, K0.5: 5.6 mmHg) and thus may necessitate significantly altered BAL device design conditions to ensure no oxygen limitations. Finally, these results highlight the need for species specific characterization of cellular function for optimal BAL device implementations.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.