24 research outputs found
In Vivo Light Microscopy of Organs
High resolution, brightfield and fluorescence, light microscopic methods have been developed for examining living organs in situ. The methods permit study of the rate, duration, magnitude and direction of dynamic histologic, pathologic, physiologic and pharmacologic events. In addition, morphometric analyses of such living preparations can provide basic information needed to evaluate alterations induced by fixation and processing of these organs for electron microscopy. Most organs are amenable to such investigations. In anesthetized animals, the selected organ is trans-and/or epi-illuminated with selected wavelengths of monochromatic light, imaged with water immersion objectives and the resulting monochromatic optical images televised using silicon or silicon intensified target (SIT) vidicon cameras. Quantitation is obtained by interfacing appropriate analog and/or digital instrumentation with the electro-optical system. Under optimal conditions the resolution is 0.3 μm, essentially the maximum obtainable by light microscopy. As a result, imaging is possible of most intra- and extravascular cell types, their nuclei, nucleoli as well as some cytoplasmic organelles and inclusions. The use of vital dyes and fluorescent tracers along or in combination with physiologic and pharmacologic stimuli provides information about structural-functional relationships in these intact living organs during both health and disease
The Effects of Old Age on Hepatic Stellate Cells
Aging is associated with marked changes in the hepatic sinusoid, yet the effect of old age on hepatic stellate cells (HSC) has not been well described. Transmission electron microscopy and immunohistochemistry were used to study the effects of aging on HSC in livers from rats (3-4 mths versus 24–27 mths) and mice (2-3 mths versus 20–22 mths). Desmin-positive HSC doubled in old age in both mice and rats. Alpha-smooth muscle actin- (αSMA-) positive cells did not increase significantly and remained only a small percentage of desmin-positive cells. Electron microscopy revealed that old age is associated with HSC that have a substantial increase in the number of lipid droplets which are larger in diameter. There was also a marked increase of HSC that protruded into the sinusoidal lumen in old mice. In conclusion, old age is associated with hyperplasia of HSC that are not activated and are engorged with lipid droplets
Protection of early phase hepatic ischemia-reperfusion injury by cholinergic agonists
BACKGROUND: Cytokine production is critical in ischemia/reperfusion (IR) injury. Acetylcholine binds to macrophages and inhibits cytokine synthesis, through the cholinergic anti-inflammatory pathway. This study examined the role of the cholinergic pathway in cytokine production and hepatic IR- injury. METHODS: Adult male mice underwent 90-min of partial liver ischemia followed by reperfusion. The AChR agonists (1,1-dimethyl-4-phenyl-L-pioperazinium-iodide [DMPP], and nicotine) or saline-vehicle were administered i.p. before ischemia. Plasma cytokine tumor necrosis factor (TNF)-α, macrophage inflammatory protein-2, and Interleukin-6 were measured. Liver injury was assessed by plasma alanine transaminase (ALT) and liver histopathology. RESULTS: A reperfusion time-dependent hepatocellular injury occurred as was indicated by increased plasma-ALT and histopathology. The injury was associated with marked elevation of plasma cytokines/chemokines. Pre-ischemic treatment of mice with DMPP or nicotine significantly decreased plasma-ALT and cytokines after 3 h of reperfusion. After 6 h of reperfusion, the protective effect of DMPP decreased and reached a negligible level by 24 h of reperfusion, despite significantly low levels of plasma cytokines. Histopathology showed markedly diminished hepatocellular injury in DMPP- and nicotine-pretreated mice during the early-phase of hepatic-IR, which reached a level comparable to saline-treated mice at late-phase of IR. CONCLUSION: Pharmacological modulation of the cholinergic pathway provides a means to modulate cytokine production and to delay IR-induced heaptocellular injury
Electron microscopic study of the effects of endotoxin on the cells of the hepatic sinusoid in normal and BCG sensitized mice
Electron microscopic studies were conducted
to access ultrastructural alterations in Kupffer cells and
other cells lining the hepatic sinusoids at the peak of
mediator release two hours after challenge with low
doses of endotoxin under various conditions including
reticuloendothelial system (RES) expansion and
activation with BCG. BCG is known to sensitize animals
to endotoxin rendering normally innocuous, low doses of
endotoxin lethal.
Low non-lethal doses (5 pg) of endotoxin activated
Kupffer cells as well as caused isolated foci of cellular
injury. However, animals which were treated with BCG
had a highly activated and expanded RES system as
evidenced by enlarged Kupffer cells with many extended
cellular processes. Granulomas were prevalent and
many reactive cells were present. After two hours
marked cellular injury occurred to sinusoid lining and
parenchymal cells when BCG treated animals were
challenged with these same low doses of endotoxin.
Cellular debris, fibrin, and platelets were observed in
sinusoids often associated with Kupffer cells. These
results suggest that the functional state of Kupffer cells
is an important determinant in the host response to
endotoxin. While there appears to be an effective
clearance of endotoxin; the release of mediators by the
highly activated Kupffer cells can be toxic causing
hepatocellular injury