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Biomedical subjects

S Shaughnessy

Publications and source records attributed to S Shaughnessy.

At least 19 recordsLinked to original sources
PubMed2000

Adipocyte metabolism in adipocyte fatty acid binding protein knockout mice (aP2-/-) after short-term high-fat feeding: functional compensation by the keratinocyte [correction of keritinocyte] fatty acid binding protein.

Mice null for adipocyte fatty acid binding protein (AFABP) compensate by increasing expression of keratinocyte fatty acid binding protein (KFABP) (Hotamisligil et al. Science 274:1377-1379, 1996). In the present study, AFABP knockout (KO) and wild-type (WT) mice became equally obese on a high-fat diet, as judged by fat pad weights, adipocyte size, and body composition analysis. High-fat feeding led to moderate insulin resistance in both WT and AFABP knockout mice, as indicated by an approximately 2-fold increase in plasma insulin. However, in the high fat-fed mice, plasma glucose levels were approximately 15% lower in the AFABP-KO mice. Adipocytes isolated from AFABP-KO and WT mice fed high- or low-fat diets exhibited similar rates of basal and norepinephrine-stimulated lipolysis and insulin-stimulated rates of glucose conversion to fatty acids and glyceride-glycerol. However, basal glucose conversion to fatty acids was higher in adipocytes of AFABP-KO mice. Adipocyte tumor necrosis factor-alpha release was similarly increased by high-fat diet-induced obesity in both WT and AFABP-KO mice. As assessed by Western blot analysis, the level of KFABP protein in AFABP-KOs was approximately 40% of the level of AFABP in WT controls. The binding affinities of KFABP for long-chain fatty acids were 2- to 4-fold higher than those of AFABP, but the relative affinities for different fatty acids were similar. As for AFABP, the rate of fatty acid transfer from KFABP to model phospholipid vesicles was increased with acceptor membrane concentration and by inclusion of acidic phospholipids, indicating a similar mechanism of transfer. We conclude KFABP can functionally compensate for the absence of AFABP, resulting in no major alterations in adipocyte metabolism or fat accumulation in response to short-term feeding of high-fat diets that result in moderate hyperinsulinemia.

Adaptation, Physiological↗
PubMed1999

The binding of unfractionated heparin and low molecular weight heparin to thrombin-activated human endothelial cells.

The binding of unfractionated heparin to endothelium is thought to be responsible for the rapid and saturable phase of unfractionated heparin clearance. Thrombin can induce endothelial cells to express and/or secrete a number of heparin binding proteins that have the potential to increase the binding of unfractionated heparin and to a lesser extent the binding of low molecular weight heparin. To explore this possibility, we examined the binding of unfractionated heparin and low molecular weight heparin to thrombin-activated endothelial cells. Cultured human umbilical vein endothelial cells were used to determine the binding of 125I-labeled unfractionated heparin and low molecular weight heparin to untreated and to thrombin-activated cells. After thrombin treatment, we obtained a time-dependent increase in the binding of radio-labeled unfractionated heparin. In contrast, there was much less binding of low molecular weight heparin, and a time-dependent increase was not apparent. After 30, 45, and 60 minutes of thrombin treatment, the binding of unfractionated heparin was significantly higher than that of low molecular weight heparin. The increase in binding of unfractionated heparin to thrombin-activated cells also was demonstrated using fluorescently labeled unfractionated heparin followed by fluorescence microscopy. The average fluorescence intensity of thrombin-treated cells increased by 44% when compared with resting cells. The present results indicate that thrombin can increase the binding of unfractionated heparin to human umbilical vein endothelial cells. Thus, an activated endothelium may contribute to the variability of the anticoagulant response to unfractionated heparin. In contrast, the binding of low molecular weight heparin is much less affected, which may account for its better bioavailability and longer half-life.

Binding Sites↗
PubMed1988

The effects of oxygen radical--mediated pulmonary endothelial damage on cancer metastasis.

The vascular bed of the lung is susceptible to environmental and host-mediated injury from free radicals. The lung is also a frequent site for the formation of cancer metastases. Since the circulation is important for the spread of cancer and because the endothelium is a barrier between the circulation and extravascular tissue, we have postulated that free radical damage to the pulmonary microvasculature enhances the formation of metastases. Pulmonary endothelial injury was induced in mice by bleomycin (120 mg/kg i.v.) or by exposure to 90% oxygen for 2-4 days. In rats, damage was elicited by intravenous injection of cobra venom factor which activates the circulating leukocytes. Endothelial damage was demonstrated by morphology and by measurement, in lung lavage fluids, of increased protein and/or leakage of 125I-albumin, previously injected intravenously. When radiolabeled cancer cells were injected into the tail vein during periods of pulmonary endothelial damage, there was a 3-36 fold increase in the numbers of these cells located in the lung after 24 hours. Subsequently more metastatic tumors formed in the animals with injured lungs. In rats, the enhanced localization was prevented by pretreatment of the animals with catalase or with antineutrophil antibodies. We have also demonstrated that stimulation of rat cancer cells by the chemotactic peptide N-fMLP is followed by chemiluminescence, amplified in the presence of luminol. Evidence for the generation of oxygen radicals by these cells includes inhibition of the response in the absence of oxygen or in the presence of superoxide dismutase, catalase, and mannitol, and dose-dependent reduction of acetylated cytochrome C. We conclude that free radical-mediated damage to the pulmonary endothelium significantly increases the metastasis of circulating tumor cells and we postulate that some cancer cells may directly facilitate their spread by generating free radicals.

Animals↗
PubMed1987

Chemiluminescence and oxygen radical generation by Walker carcinosarcoma cells following chemotactic stimulation.

The peptide N-formyl-Met-Leu-Phe stimulates chemotaxis and metastasis in rat Walker carcinosarcoma cells by a receptor-mediated pathway. Since oxygen radical generation follows chemotactic stimulation in leukocytes, we looked for similar responses in the Walker tumor. Upon incubation with 10(-6) M N-formyl-Met-Leu-Phe, Walker cells elicited chemiluminescence in the presence of 5 X 10(-5) M luminol. The response peaked within 2 min and was maintained for greater than 20 min; it was dose dependent with a 50% maximal effective dose (ED50) value of 4.5 X 10(-8) comparable to the 50% maximal effective dose value for chemotaxis. The responses were significantly reduced but not abolished in the absence of calcium in the external medium and were elicited by the ionophore A23187. The lipoxygenase inhibitor nordihydroguaiaretic acid had almost no effect in decreasing the response, while flurbiprofen, a cyclooxygenase inhibitor was very effective at 10(-6) M. Evidence for the generation of oxygen radicals included: (a) marked inhibition of light emission in the absence of oxygen; (b) inhibition in the presence of superoxide dismutase, catalase, and mannitol; and (c) dose-dependent reduction of acetylated cytochrome c. We postulate that activation of circulating tumor cells may facilitate metastasis by the release of toxic oxygen species.

Animals↗
PubMed1985

Effects of detergents and cytochrome c binding on scalar and vectorial proton ejection by proteoliposomes containing cytochrome oxidase.

The detergent lauryl maltoside abolishes respiratory control and proton ejection by cytochrome c oxidase-containing proteoliposomes over a narrow concentration range. Expression of cryptic activity (inward-facing oxidase) is released over the same concentration range. Catalytic functions (Vmax. and Km) of the enzyme are not changed by the detergent. Lipid micelles containing detergent bind approximately the same amount of cytochrome c as do vesicles containing an equivalent amount of lipid. Uncoupler-insensitive proton release is seen when proteoliposomes are pulsed with ferrocytochrome c at low ionic strength. Such uncoupler-insensitive acidification is not seen at higher ionic strength, nor with oxygen pulses of anaerobic solutions previously incubated with cytochrome c. Vesicles at low ionic strength catalyse cytochrome c autoxidation; this process can mimic proton re-equilibration in systems that have pumped protons from inside to the bulk phase. Proton re-equilibration following a pulse of cytochrome c or oxygen is multiphasic. The slowest phases are attributed to vesicle heterogeneity, some internal alkali being retained within vesicles of low intrinsic proton permeability. This can be overcome by the addition of either very low levels of carbonyl cyanide p-trifluoromethoxyphenyl-hydrazone or high levels of valinomycin.

Cytochrome c Group↗
PubMed1985

Control of respiration in sonicated cytochrome oxidase proteoliposomes by gated and ungated ionophores.

Respiration of cytochrome oxidase-containing sonicated proteoliposomes is partially stimulated by nigericin or by alamethicin. Valinomycin at low concentrations fully releases the nigericin-dependent respiration but inhibits the alamethicin-dependent respiration. Respiratory stimulation by the gated ionophore alamethicin must occur in the face of a continuing membrane potential; stimulation by nigericin is accompanied by an increase in the measured membrane potential. We conclude that delta pH rather than delta psi may be the main source of respiratory control in our type of proteoliposomes.

Alamethicin↗
PubMed1975

Bovine graft arteriovenous fistulas for maintenance hemodialysis.

Modified bovine carotid artery grafts have been used for maintenance hemodialysis in 44 patients during an 18 month period. The technique of constructing an arteriovenous fistula in the leg and in the forearm is described. The common femoral artery and saphenous vein in the leg and the radial artery and basilic vein in the forearm are the preferred vessels. The complication rate has been low, consisting primarily of thrombosis and false aneurysms at the dialysis needle puncture site. Oversized grafts should be avoided because of resultant turbulent flow and the tendency of thrombosis. Bleeding after withdrawal of the hemodialysis needle must be properly controlled to minimize complications. Eighty-two percent have various problems and 18 per cent have failed. Bovine graft arteriovenous fistulas provide excellent vascular access in patients undergoing chronic hemodialysis.

Animals↗