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Biomedical subjects

R S McCuskey

Publications and source records attributed to R S McCuskey.

At least 19 recordsLinked to original sources
PubMed1995

Role of endotoxin in the hepatic microvascular inflammatory response to ethanol.

Kupffer cells (KC) and gut-derived bacterial endotoxin have been implicated in the aetiology of alcoholic liver disease. Using in vivo microscopic methods, we have shown that ethanol ingestion in mice causes a dose dependent increase in leucocyte adhesion and endothelial cell swelling in hepatic sinusoids. Activation of KC is elicited at low doses while depression occurs at high doses and with chronic exposure. The responses are exacerbated in the presence of endotoxaemia or sepsis and are not seen in endotoxin-resistant animals, implicating a role for endotoxin in the ethanol-induced inflammatory response. In addition, the responses are abolished with anti-TNF alpha suggesting that TNF alpha is a primary mediator of these events. Nitric oxide (NO) initially appears to play an important role in these events by stabilizing the TNF alpha-mediated hepatic microvascular inflammatory response to acute ethanol ingestion, thereby helping to protect the liver from ischaemia and leucocyte induced oxidative injury. Finally, an ongoing clinical study has confirmed a mild systemic endotoxaemia in patients hospitalized for alcoholic liver disease. All of these results support important roles for endotoxin, cytokines, nitric oxide and sinusoidal lining cells in the pathophysiology of liver injury resulting from ethanol alone or in combination with infection.

Animals↗
PubMed1995

In vivo microscopy of hepatic metastases: dynamic observation of tumor cell invasion and interaction with Kupffer cells.

In vivo microscopy was used in the study of the biological behavior of tumor cells and of the activity of Kupffer cells in hepatic tumors in situ. Three tumor models, Friend erythroleukemia inoculated into Dilute Brown Aguti (DBA)/2 mice, murine colon adenocarcinoma (CT)-26 in Bagg Albino inbred albino (BALB)/c mice, and mammary cancer 13762 NF in Fischer rats, were investigated. Tumor cells showed a strong tendency to adhere to the sinusoidal endothelium, most frequently in the sinusoids near the tumors. Mechanical trapping of tumor cells in the narrow portion of hepatic sinusoids, a phenomenon suggested by previous investigators as a predominant pattern for tumor cells to arrest in the liver, was not confirmed. Our study documented that in tumor-bearing livers, as compared with normal control livers, the population size and the phagocytic capacity of Kupffer cells are increased in nontumorous areas but are significantly decreased inside the tumors. In vivo microscopic images showed that Kupffer cells are not only attracted to tumor cells in the hepatic circulation but also have the ability to phagocytose those tumor cells. In vivo microscopy has been shown to be a useful tool for dynamic studies in tumor biology, pathology, and pharmacology.

Animals↗
PubMed1994

Ethanol exacerbates hepatic microvascular dysfunction, endotoxemia, and lethality in septic mice.

The effect of acute ethanol administration on the hepatic microvascular responses to sepsis was studied. Polymicrobial sepsis was induced 30 min after mice had received ethanol (1 g/kg b.w.) or isocaloric maltose-dextrin by gastric gavage. Lethality within 24 h was 91.7% in the ethanol-treated animals and 40.0% in septic controls. Endotoxin levels in ethanol treated animals were 107 pg/ml at 6 hr and 1205 pg/ml at 12 h, compared with 32 pg/ml and 104 pg/ml, respectively in the controls. In vivo microscopy revealed that at 3 h in the ethanol treated septic animals, Kupffer cell phagocytic activity was increased by 41%, whereas the number of sinusoids containing blood flow were reduced by 34% concomitant with a 144% increase in the adherence of leukocytes to the sinusoidal walls when compared with the septic controls. By 6 h, however, Kupffer cell phagocytic activity was reduced by 48% in the ethanol treated animals; this was accompanied by a further deterioration in sinusoidal blood flow. Thus, a small, acute dose of ethanol causes significant impairment of the hepatic microcirculation followed by suppression of Kupffer cell activity. This results in exacerbation of endotoxemia and lethality during polymicrobial sepsis.

Animals↗
PubMed1994

Protective role of NO in hepatic microcirculatory dysfunction during endotoxemia.

Nitric oxide (NO) has been reported to have a protective function in attenuating hepatic injury during endotoxemia or sepsis. As a result, the role of NO in attenuating the hepatic microcirculatory alterations associated with endotoxemia was investigated in mice by in vivo microscopy. The livers were examined 2 h after intravenous injection of Escherichia coli 0111:B4 lipopolysaccharide (LPS) alone or in combination with inhibitors of the synthesis of NO, NG-nitro-L-arginine methyl ester or NG-monomethyl-L-arginine. In the animals treated with the combination of NO synthase inhibitors and LPS, leukocyte adherence was increased threefold above that in animals treated with LPS alone. This was accompanied by a 33% reduction in sinusoidal blood flow. Simultaneous administration of L-arginine, but not D-arginine, eliminated these microcirculatory disturbances. The results demonstrate that inhibition of LPS-stimulated NO production results in an early hepatic microvascular inflammatory response to a dose of endotoxin which by itself is scarcely inflammatory. This suggests that NO plays a significant role in stabilizing the hepatic microcirculation during endotoxemia, thereby helping to protect the liver from ischemia and leukocyte-induced oxidative injury.

Amino Acid Oxidoreductases↗
PubMed1994

Alcohol, immunomodulation, and disease.

Recent research findings point to a spectrum of alcohol-induced immune dysfunctions in animal models and humans. Use of alcohol in vivo causes abnormalities in the function and/or structure of a broad array of cells involved in humoral and cellular immunity, including lymphocytes, Kupffer cells and other macrophages, as well as the endothelium of blood vessels and lymphatics. Regulatory cytokines and neuroendocrine factors can mediate some of these immunomodulatory effects which may be further re-phased, exaggerated or unbalanced by other drugs of misuse. A variety of animal models is available to study acute and chronic alcoholism, non-alcohol drug misuse, AIDS as well as other opportunistic infections, and neoplasias, which hold promise of clarifying the role of alcohol as an immunomodulator.

Acquired Immunodeficiency Syndrome↗
PubMed1993

In vivo microscopy of hepatic tumors in animal models: a dynamic investigation of blood supply to hepatic metastases.

The dynamics of blood circulation in three experimental animal models of hepatic metastasis were investigated with in vivo microscopy. It was demonstrated that the tumor vasculature communicated with the portal venules and hepatic sinusoids that surrounded the tumors. The hepatic artery was not seen to connect to the tumors directly. However, it was demonstrated that arterial blood entered tumors through the portal venules and that the hepatic arterial flow entered the tumor without resistance, while blood from the portal vein met great resistance at the tumor border, with only small amounts entering the tumor. Interruption of either the hepatic artery or the portal vein did not result in cessation of the blood circulation in hepatic tumors. A reciprocal relationship between the hepatic arterial and portal venous supplies to hepatic tumors was suggested, and it was hypothesized that arterioportal communications play an important role in the arterial and portal venous supply of blood to hepatic tumors. A comprehensive understanding of the blood supply of hepatic tumors is important for improving clinical treatment of hepatic tumors.

Adenocarcinoma↗
PubMed1992

In vivo microscopic studies of age-related changes in the structure and the reactivity of cerebral microvessels.

To determine if hemodynamic changes in cerebral microvessels could contribute to the age-related changes in the blood-brain barrier (BBB) function, the cerebral microvessels of male Fischer 344 rats at different ages were studied using intravital fluorescence microscopy. Aging in rats was associated with significant arteriovenous shunting in the cerebral microvessels without alterations in blood flow characteristics or changes in vascular permeability to FITC dextran (150 kDa). The basal diameter of terminal arterioles examined in 24- to 27-month-old (aged) rats (28.6 +/- 2.8 microns) was not different from that in 12- to 15-month-old (intermediate age) rats (32.5 +/- 2.5 microns) or in 3- to 6-month-old (young) rats (28.6 +/- 3.0 microns). At 3 s following addition of 5% BaCl2 there was 23.3 +/- 3.47% constriction of arterioles in young rats and 14.8 +/- 5.16% constriction in intermediate age rats, but only a 3.43 +/- 5.69% change in aged rats (P less than 0.03). This initial brief constriction phase was followed by a dilatory response which was similar in all age groups. One minute following suffusion with artificial cerebrospinal fluid, the arteriolar diameter essentially returned to baseline in all rats examined. It is concluded that aging in rats is associated with alterations in cerebral microvascular reactivity in vivo along with arteriovenous shunting. These changes may contribute to age-related alterations in the BBB function.

Aging↗
PubMed1991

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 micrograms) 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.

Animals↗
PubMed1991

Kupffer cell activity and hepatic microvascular events after acute ethanol ingestion in mice.

After acute ethanol ingestion in C57Bl/6 mice, phagocytic activity of Kupffer cells and hepatic microcirculation were examined by in vivo and electron microscopy. A ratio of Kupffer cells that phagocytosed 0.8 micron fluorescent latex particles to sinusoids containing blood flow (number of Kupffer cells/number of sinusoids containing blood flow) was used as a measure of Kupffer cell phagocytic activity. Three hours after ingestion of 1 gm/kg ethanol, number of Kupffer cells/number of sinusoids containing blood flow increased in both periportal and centrilobular regions by 62% and 66%, respectively, and blood ethanol was no longer detectable. Ultrastructurally, activation of KC was evidenced by the presence of many pseudopodia and filopodia. Numbers of swollen endothelial cells were increased in both regions by 249% and 174%. Interruption of sinusoidal blood flow by leukocytes was aggravated in both regions by 127% and 167%. Thirty minutes and 3 hr after ingestion of 4 gm/kg ethanol, no significant increase in number of Kupffer cells/number of sinusoids containing blood flow was seen, although number of Kupffer cells were also activated as seen with electron microscopy. An increased number of swollen endothelial cells was observed in both regions by 100% and 71% by 30 min and by 200% and 384% by 3 hr. The interruption of sinusoidal blood flow by leukocytes was also increased (periportal = 161%, centrilobular = 196%) as were sticking or plugging leukocytes in sinusoids (periportal = 320%, centrilobular = 120%) by 3 hr. The diameter of centrilobular sinusoids was decreased by 3 hr. Latex particles and platelets were attached to the sinusoidal wall after both low and high dosing.(ABSTRACT TRUNCATED AT 250 WORDS)

Alcohol Drinking↗
PubMed1990

Fine structure and function of Kupffer cells.

Kupffer cells are macrophages that are attached to the luminal surface or inserted in the endothelial lining of hepatic sinusoids. In this site, Kupffer cells play a key role in host defense by removing foreign, toxic and infective substances from the portal blood and by releasing beneficial mediators. Under some conditions, toxic and vasoactive substances also are released from Kupffer cells which are thought to play a role in a variety of liver diseases. Many of these activities may be modulated by the levels of gut derived endotoxin normally present in the portal blood. The ultrastructural aspects of Kupffer cell structure function in situ are best studied using perfused-fixed livers. In fixed livers, transmission and scanning electron microscopy reveal Kupffer cells during health to be irregular in shape with their exposed surfaces presenting numerous microvilli, filopodia, and lamellopodia. Long filopodia penetrate endothelial fenestrae to secure Kupffer cells to the sinusoid lining. Specific membrane invaginations known as worm-like bodies or vermiform processes are seen in the cytoplasm of Kupffer cells as are numerous endocytotic vesicles and lysosomes which vary in density, shape and size. Sometimes, annulate lamellae connected to the rough endoplasmic reticulum also are found. The principal endocytic mechanisms of Kupffer cells are phagocytosis of particulates and cells, and bristle-coated micropinocytosis for fluid-phase endocytosis of smaller substances. Many of these events are mediated by specific receptors. In some species, Kupffer cells can be distinguished from other sinusoidal lining cells and monocytes by specific cytoplasmic staining or monoclonal antibodies. Kupffer cells have been shown to be of monocytic origin as well as having the capacity for self-replication.

Humans↗
PubMed1989

A quantitative study of fluorescein isothiocyanate-dextran transport in the microcirculation of the isolated perfused rat liver.

Hepatic extraction of solutes depends on microvascular angioarchitecture, hemodynamics and solute concentrations. These factors may contribute to the heterogeneity observed in solute transport and uptake in the hepatic lobules. However, predictions of liver extraction based on black-box models require assumptions about these factors and the microvascular transport mechanisms involved. Consequently, the purpose of this study was to investigate solute transport and uptake by hepatocytes. Livers from male Sprague-Dawley rats were perfused at physiological flowrates and portal pressures on the stage of an in vivo microscope using a low-hematocrit Ringer solution. A bolus of fluorescein isothiocyanate-dextrans (17,900, 39,000, 65,600 or 156,900 MW), which are considered inert fluid-phase markers, was injected into the portal vein. Fluorescein isothiocyanate fluorescence, as a measure of solute concentration, was video recorded in periportal or centrivenular regions of the lobules. Spatial and temporal fluorescence data, measured in sinusoids and hepatocytes, were fit to one-dimensional transport models to determine estimates for an intracellular effective diffusion coefficient and for hepatocyte permeability. The calculated effective diffusion coefficients were 2.5 times larger for dextrans less than 66,000 MW, but were not different between the periportal and centrivenular regions. Also, the values did not show the inverse log-log molecular weight dependency for dextrans seen in other microvascular tissues.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1988

STM imaging of molecular collagen and phospholipid membranes.

The application of STM to biological materials has been limited by poor conductivity, sample geometry and stability of biological materials. In this paper we describe an STM study of the monomeric helical forms of collagen, a stable, conductive and widely prevalent structural protein. We have also used STM to image artificial Langmuir DPE (dipalmitoyl phosphatidyl ethanolamine) phospholipid membranes. Both molecular collagen and the phospholipid membranes were dried in air on highly oriented pyrolytic graphite (HOPG). Our STM images of collagen dried on HOPG reveal strands 15 A in diameter with a periodicity of about 30 A which correlates with that known to occur in collagen. Spikes which periodically protrude from strands in our STM images of collagen appear to represent pyrrolidine ring structures in the amino acids proline and hydroxyproline. Thus, we report the first STM imaging of native biomolecules revealing intramolecular details and what appear to be specific amino acids. STM imaging of phospholipid membranes show a lattice pattern with densities spaced approximately 4.5 A apart. These are thought to represent individual phospholipid molecules in an artificial membrane formed on the HOPG. We believe STM and its related technologies will have great future utility in biomolecular studies.

Animals↗
PubMed1987

Normal versus abnormal structure: considerations in morphologic responses of teleosts to pollutants.

Consideration of newer more quantitative morphologic approaches to the study of aquatic pollutants can provide opportunity for collaborative/integrated studies with other subdisciplines in toxicology. Current commonly employed morphologic approaches result largely in subjective findings difficult to analyze statistically and often are directed at levels of structural organization inconsistent with biochemical and physiological approaches. We review some of the methods and approaches available for correlated structure/function studies and present examples from normal and altered skin, gill, and liver of teleosts.

Animals↗