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Biomedical subjects

J O'Neil

Publications and source records attributed to J O'Neil.

At least 55 records · Page 3Linked to original sources
PubMed1994

Thermodynamics of transfer of indocarbocyanines from gel to fluid phases of phospholipid bilayers.

Application of the regular solution model to thermal transition data obtained by differential scanning calorimetry has allowed the determination of partition coefficients, Kp, and the thermodynamics of transfer of a series of indocarbocyanine solutes between the gel and fluid phases of phospholipid bilayers. The indocarbocyanines with alkyl chain lengths of 12 to 22 carbons were partitioned between dipalmitoyl- and distearoylphosphatidylcholine phases at the transition temperatures of the gel-liquid-crystal phase transition. The results indicate that as the alkyl chain length of the solute nears that of the acyl chains of the bilayer lipid, the free energy of transfer from gel to fluid is least negative, and the enthalpy of transfer is most positive. There is almost complete entropy-enthalpy compensation in the transfer process. Comparison of the partition coefficients with published values determined by a fluorescence method show good agreement when the differences in temperature of the measurements are accounted for.

1,2-Dipalmitoylphosphatidylcholine↗
PubMed1994

Immunochemically detectable lipid-free apo(a) in plasma and in human atherosclerotic lesions.

Although Lp(a) is an independent risk factor for cardiovascular diseases in humans, the precise pathogenetic mechanisms are still unknown. We have shown that Lp(a) accumulates in human atherosclerotic lesions, and some particles undergo oxidation. Since, following agarose electrophoresis of both plaque extracts and plasma, a region close to the origin immunostained intensely for apo(a) but was lipid-free, we sought to identify whether such samples contained lipid-free apo(a), as previously reported to occur in plaque extracts. Immunochemically identifiable apo(a) was found following density-gradient ultracentrifugation both in the 1.05 < d < 1.09 and the d > 1.21 density fraction from both plasma and plaque extracts. However, because in a competitive binding RIA, displacement curves of apo(a) in plasma and the d > 1.21 were not parallel, it is premature to ascribe a relative amount of total apo(a) to this fraction. Whereas apo(a) immunoblots of SDS-PAGE under reducing conditions of the d > 1.21 fraction of a plaque extract with high apo(a) content showed high molecular weight bands consistent with apo(a) isoforms, the corresponding d > 1.21 fraction showed multiple low molecular weight bands characteristic of fragmentation. Since the d > 1.21 of arterial extracts contained all the material immunostaining for apo(a) migrating towards the cathode, characteristic of immunoglobulins (IgG), we asked whether fragments of apo(a) might have associated with human IgG both in plasma and tissue extracts, or whether our anti-apo(a) reacted with epitopes on human IgG. Immunoblotting with our anti-apo(a) of samples of plasma and plaque extracts run on agarose electrophoresis or SDS-PAGE further demonstrated intense staining of multiple bands in the molecular weight range of human IgG. Furthermore, a fraction of plasma and tissue extracts that bound to a protein G affinity column demonstrated immunostaining for apo(a) and was in the size range of IgG. Although one polyclonal anti-apo(a) provided by another laboratory showed the same findings as our antibody, two other polyclonal anti-apo(a) failed to demonstrate immunostaining of human IgG, either on agarose electrophoresis or SDS-PAGE. We speculate that the Lp(a) immunogen used to prepare our anti-apo(a) may have undergone modest oxidation, thus exposing epitopes not normally expressed on apo(a) in native Lp(a). Either antibodies to these epitopes could be recognizing apo(a) fragments, possibly released during oxidation, which are then covalently bound to IgG, or oxidation of apo(a) creates epitopes on apo(a) that are homologous with IgG, thereby leading to cross-reactivity with IgG.(ABSTRACT TRUNCATED AT 400 WORDS)

Apolipoproteins↗
PubMed1994

Lp(a) and premature mortality during chronic hemodialysis treatment.

Lipoprotein(a) levels are approximately three to four times higher in patients with end-stage renal disease (ESRD) when compared to controls with normal renal function (H.J. Parra, H. Mezdour, C. Cachera et al., Clin. Chem. 33 (1987), 721). Hypertriglyceridemia occurs in approximately 50% of ESRD patients receiving chronic hemodialysis (HD) treatment and has been associated with an increased prevalence of cardiovascular disease (CVD) in cross-sectional studies of this subset of ESRD patients. We recently reported that HD patients with pre-existing ischemic or atherosclerotic CVD and patients with elevated Lp(a) levels had an increased risk of fatal and non-fatal clinical events attributable to CVD during a 48-month period of maintenance HD treatment. The current report describes a detailed analysis of study participants who did or did not have a history of ischemic CVD or angiographically documented severe atherosclerotic lesions prior to entry into our prospective study. Although baseline total cholesterol (TC), triglyceride (TG) and apoprotein B (apoB) levels were higher in the 36 participants with prevalent CVD than the remaining 93 study participants, total cholesterol levels were somewhat lower, while serum triglyceride levels were no different in patients who survived or experienced fatal CVD events during the period of observation on HD treatment. In contrast, Lp(a) levels were no different in participants with or without evidence of pre-existing CVD. Lp(a) was, however, an independent predictor of fatal events attributable to cardiovascular disease during the period of follow-up.

Adult↗
PubMed1994

Inactivation of lysosomal proteases by oxidized low density lipoprotein is partially responsible for its poor degradation by mouse peritoneal macrophages.

Deficient processing of apo B in oxidized LDL (ox-LDL) by macrophage lysosomal proteases has been documented and attributed to modifications in apo B. We have investigated whether direct inactivation of lysosomal proteases by ox-LDL could also be responsible for this deficient degradation. When mouse peritoneal macrophages (MPM) were preincubated for 21 h at 37 degrees C with ox-LDL, LDL, or vortex-aggregated LDL, only ox-LDL inhibited the subsequent degradation of 125I-labeled forms of the above lipoproteins. Uptake of labeled lipoproteins was not appreciably affected by preincubation with ox-LDL, suggesting that the inhibition was at the level of lysosomal degradation. Thiol protease activity of cell extracts at pH 4.0, was reduced in MPM preincubated with ox-LDL relative to cells preincubated with LDL or medium alone. Extracts from untreated MPM, or mixtures of cathepsin B and D, showed a reduced ability to degrade 125I-LDL at pH 4.5 and reduced cathepsin B activity, after incubation with ox-LDL relative to incubation with LDL. Thus, the reduced degradation of lipoproteins in MPM pretreated with ox-LDL could be due to direct inactivation of the lysosomal protease, cathepsin B.

Animals↗
PubMed1994

The compliance of licensed US child care centers with national health and safety performance standards.

The American Public Health Association and the American Academy of Pediatrics recently published health and safety guidelines for child care centers. A survey was conducted to determine the extent to which practices in US child care centers are reflective of these guidelines. Compliance with 16 guidelines ranged from 19.5% to 98.6%, varied considerably by state, and was not consistently associated with selected center characteristics. Prevention efforts should focus on practices for which compliance is low and on those that have the greatest disease- and injury-reducing potential.

Child Day Care Centers↗
PubMed1994

Study groups: are they effective in preparing students for NCLEX-RN?

The effectiveness of faculty-directed study groups as an intervention to prepare nurse candidates for NCLEX-RN was evaluated. The NCLEX-RN performance of a baccalaureate class who had participated in study groups was compared to the performance of a prior class who had not participated in study groups. Academic subgroups within the classes were compared to determine if study groups were equally effective across levels of academic achievement. The possible reasons for the significant difference in the NCLEX-RN passing rate between "at-risk" students who participated in study groups and at-risk students who did not participate in study groups are discussed. Discussion also considers possible factors influencing the generally better performance of study group participants at all academic levels. Suggestions for future intervention research direct attention to time intensity of interventions and research control through random assignments to treatment groups.

Adult↗
PubMed1994

A nationwide study of the risk of injury associated with day care center attendance.

OBJECTIVE: Because an increasing proportion of US children spends time in day care center environments, a national estimate of injury risks in day care centers is needed. METHODS: We interviewed directors of 1797 day care centers from every state and the District of Columbia from October to December 1990 and analyzed medically attended injuries and center characteristics reported by the directors. RESULTS: The centers were attended by 138,404 children. In the 2 months before the center directors were interviewed, 556 children sustained injuries requiring medical attention while attending the centers. The injury rate was 1.5 injuries per 100,000 child hours in day care. The most common injuries were cuts or lacerations (31%), bumps or bruises (15%), fractures (10%), and dental injuries (8%). Most injuries (51%) occurred on the playground. Many injuries (18%), and more than half of fractures and concussions (53%) were due to falls from climbing equipment. CONCLUSIONS: Day care center injury rates estimated by this study were relatively low. Many injuries that occur in this setting are probably minor. However, lowering the height of playground equipment and providing more resilient playground surfaces could further reduce injury risks in day care centers.

Child Day Care Centers↗
PubMed1993

Insoluble complex formation of lipoprotein (a) with low density lipoprotein in the presence of calcium ions.

We investigated whether apolipoprotein B-containing lipoproteins could bind to the insoluble complexes of lipoprotein (a) (Lp(a)) induced by Ca2+. Lp(a), but not low density lipoprotein (LDL), very low density lipoprotein (VLDL), or high density lipoprotein3 (HDL3) formed insoluble complexes at physiologic Ca2+ concentrations. Desialylation of Lp(a) dramatically decreased the ability of Lp(a) to aggregate, suggesting that sialic acids on Lp(a) were responsible for forming Ca2+ cross-bridges. Since a reduction of only 30% of the sialic acids on Lp(a) inhibited Ca(2+)-induced complex formation, it appears that only a small percentage of sialic acids on Lp(a) is involved in Ca(2+)-induced cross-bridging of Lp(a) particles. To determine whether other lipoproteins would complex to Lp(a) in the insoluble complexes, we mixed Lp(a) with LDL, VLDL, or HDL3 in the presence of Ca2+. Although both LDL and VLDL bound to the Lp(a) in the insoluble complexes, HDL3 not only did not bind, but it also prevented Lp(a) from forming insoluble complexes. LDL bound to Lp(a) in the insoluble complexes in a concentration-dependent manner, eventually reaching saturation at a molar ratio of 5:4 (LDL to Lp(a)). The interaction between LDL and Lp(a) appeared to be ionic, since increases in the positive charge on LDL by desialylation increased this interaction, whereas decreases in positive charge on LDL reduced this interaction. At higher Ca2+ concentrations, the binding of acetyl LDL to Lp(a) in the insoluble complexes was greater than that of LDL. Since more Ca2+ was required for concentration-dependent saturation of acetyl LDL binding, it is likely that Ca2+ cross-bridging was responsible for this binding. Thus, LDL, especially its modified forms, could contribute to the formation of insoluble complex of Lp(a) with Ca2+ in atherosclerotic lesions and help explain its preferential accumulation there.

Acetylation↗
PubMed1993

Eubacterial components similar to small nuclear ribonucleoproteins: identification of immunoprecipitable proteins and capped RNAs in a cyanobacterium and a gram-positive eubacterium.

Small nuclear ribonucleoprotein (snRNP) particles play an important role in the processing of pre-mRNA. snRNPs have been identified immunologically in a variety of cells, but none have ever been observed in prokaryotic systems. This report provides the first evidence for the presence of snRNP-like components in two types of prokaryotic cells: those of the cyanobacterium Synechococcus leopoliensis and those of the gram-positive eubacterium Bacillus subtilis. These components consist of snRNP-immunoreactive proteins and RNAs, including some with the snRNP-unique 5' m2,2,7G (m3G) cap. Immunoreactivity was determined by immunoprecipitation procedures, with either antinuclear-antibody-positive (RNP- and Sm-monospecific) patient sera or a m3G monoclonal antibody, with radiolabelled cell extracts that were preadsorbed with antinuclear-antibody-negative sera. S. leopoliensis immunoprecipitates showed the presence of high-molecular-mass proteins (14 to 70 kDa) and RNAs (138 to 243 nucleotides) that are analogous in size to proteins and RNAs found in human (HEp-2) cell immunoprecipitates but absent in Escherichia coli immunoprecipitates. Thin-layer chromatography of S. leopoliensis immunoprecipitates confirmed the presence of a capped nucleotide similar to a capped nucleotide in HEp-2 immunoprecipitates; no such nucleotide was observed in E. coli immunoprecipitates. Immunoreactive RNAs (117-170 nucleotides) were identified in a second eubacterium, B. subtilis, as well. This work suggests that snRNPs or their evolutionary predecessors predate the emergence of eukaryotic cells.

Antibodies, Antinuclear↗
PubMed1993

Aggregation as well as chemical modification of LDL during oxidation is responsible for poor processing in macrophages.

Aggregation is a characteristic of extensively oxidized (ox-) LDL. We wished to determine whether this structural change contributed even more to the documented poor degradation in macrophages of ox-LDL than the chemical changes. When protein degradation of the soluble and insoluble portions of extensively ox-LDL was compared to that of acetyl LDL in mouse peritoneal macrophages (MPM), we found that the percent of internalized LDL that was degraded was lowest for the insoluble portion (insol. ox-LDL), intermediate for the soluble portion (sol. ox-LDL), and highest for the acetyl LDL, regardless of whether the binding and uptake mechanisms had been excluded, e.g., by performing appropriate pulse-chase studies. As the same order of degradation was found after long-term degradation under cell-free conditions by a mixture of cathepsin B and D, it is likely that poor degradation of ox-LDL by lysosomal proteases is partially responsible for the deficient processing of ox-LDL in MPM. However, when MPM were incubated in a pulse-chase design with LDL that was induced to aggregate by vortexing without oxidizing (vx-LDL), degradation over an 18-h interval of accumulated vx-LDL was almost as low (25%) as that of insol. ox-LDL (18%), in contrast to sol. ox-LDL (60%). Yet, in a cell-free system cathepsin degradation of vx-LDL was as efficient as that of acetyl LDL and LDL. Also, the differences in degradation between sol. and insol. ox-LDL were smaller than in MPM. Thus, it appears that alternative mechanisms to poor proteolysis of substrate were responsible for poor intracellular processing of such aggregated lipoproteins. These results suggest that, although the poorer processing of insol. ox-LDL than sol. ox-LDL may be due, in part, to more deficient proteolytic degradation, particle aggregation per se may play at least as important a role in such deficiencies. This may occur by such mechanisms as altered intracellular trafficking leading to poorer fusion in macrophages of phagosomes containing aggregated lipoproteins with lysosomes.

Acetylation↗
PubMed1993

Structural and functional changes in LDL after modification with both 4-hydroxynonenal and malondialdehyde.

Oxidized LDL is characterized by adduct formation between apolipoprotein (apo)B-100 in the low density lipoprotein (LDL) particles and reactive aldehydes such as 4-hydroxynonenal (HNE) and malondialdehyde (MDA), which are decomposition products of lipid peroxidation. Since LDL isolated from human atherosclerotic lesions was also shown to have interacted with HNE and MDA and to have undergone oxidation, we initiated a study to structurally and functionally characterize LDL modification with both HNE and MDA and to compare these characteristics with those of LDL modified individually with HNE and MDA. Using concentrations of LDL and HNE that alone resulted in extensive particle aggregation, modification at pH 7.4 with HNE plus MDA at 20 mM and above, resulted in the prevention of particle aggregation and less aggregation of apoB-100. Increases in electrophoretic mobility and blockage of exposed lysine residues on apoB were approximately additive for LDL modified at pH 7.4 with 6 mM HNE and MDA up to 20 mM compared to LDL modified individually with HNE or individually with MDA. When 125I-labeled LDL modified at pH 7.4 with HNE and increasing amounts of MDA was incubated with J774 macrophages, the doubly modified LDL showed a linear increase in degradation and in ACAT stimulation. LDL modified with MDA alone showed first a reduction in degradation and ACAT stimulation, due to reduced recognition by the LDL receptor. This was followed by an increase in degradation when further modification with MDA was performed at pH 6.4, but no or little increase in degradation when performed at pH 7.4.(ABSTRACT TRUNCATED AT 250 WORDS)

Aldehydes↗
PubMed1993

Adult dental health in the Keewatin.

In 1990, as part of a major health status assessment, a dental survey was carried out on a 20 per cent random sample of the adult population in the Keewatin region of the Northwest Territories. A 73 per cent response rate was obtained. Of the 397 people examined, 334 (88 per cent) identified themselves as Inuit. More than 20 per cent of the respondents were edentulous, including 10 per cent of those 18 to 34 years old. The median DMFT was 24 for all respondents and 21 for dentulous respondents. There was a significant difference between Inuit and non-Inuit respondents, which was most marked in the 18 to 34 year old age group (mean DMFT 22.1 versus 15.6, p < .001). The proportion of filled to decayed and filled surfaces (F/DF) was 50 per cent. Periodontal disease was common and increased with age. More than 73 per cent of the dentate individuals had gingival bleeding at one or more sites. Very few were free of calculus. Mean pocket depth increased with age (1.3 mm at 18-34 years of age, rising to 2.3 at 55 plus, p < .001). Sixty per cent of adults needed at least one restorative procedure, 68 per cent needed prophylaxis, and 45 per cent needed periodontal treatment. Men required more treatment of all types than women. The results of this study confirm the clinical impression that dental disease is rampant among the Inuit population. There are major needs for both preventive and treatment services.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1993

Partial characterization of lipoproteins containing apo[a] in human atherosclerotic lesions.

Previously we quantified the amounts of immunoreactive apo[a] found in human atherosclerotic lesions extracted sequentially with phosphate-buffered saline (PBS) and guanidine hydrochloride (GuHCl). In this study we have attempted to characterize lipoproteins containing apo[a] in such PBS and GuHCl fractions, obtained from autopsy samples, in order to eventually determine their structure-function relationships critical for evaluating the mechanisms that make them atherogenic. Apo[a] in the PBS extracts migrated slightly ahead of plasma Lp[a] on agarose electrophoresis. Although apo[a] in extracts showed the same isoforms as in plasma in SDS-PAGE, it was also highly fragmented. When a d < 1.10 g/ml ultracentrifugation fraction of the PBS extract was subjected to gel filtration, a major part of the immunoreactive apo[a] in this fraction co-isolated with plasma Lp[a]. When the Lp[a]-sized fraction was further separated by density gradient ultracentrifugation, a subpopulation was isolated containing apo[a] in the 1.06 < d < 1.08 g/ml density range that was free of lesion-derived low density lipoprotein (LDL) (A-LDL). This fraction contained immunoreactive apo[a] and apoB, had a total cholesterol to protein ratio of about 1, and demonstrated increases in fluorescence (360 ex/430 em) and conjugated dienes that were even greater than values obtained for the corresponding A-LDL sample. The void volume fraction following gel exclusion chromatography of the d < 1.10 g/ml fractions contained both apo[a] and apoB that comigrated on nondenaturing PAGE, suggesting that they were present on the same particle. Apo[a] in GuHCl extracts comigrated with plasma Lp[a] on agarose electrophoresis and contained apo[a] isoforms of similar molecular weights as those found in corresponding plasma samples. When the GuHCl extract was subjected directly to gel filtration in the presence of 6 M GuHCl, two included peaks of apo[a] immunoreactivity were present, one eluting slightly ahead of plasma Lp[a], the other slightly ahead of plasma LDL. Collectively, these data indicate that apo[a] is present in human atherosclerotic lesions in forms resembling intact but oxidized plasma Lp[a], as larger particles possibly representing Lp[a] complexed to itself or other plaque components, and as slightly smaller particles possibly representing degraded Lp[a].

Aorta↗
PubMed1992

Oxidation of low density lipoprotein leads to particle aggregation and altered macrophage recognition.

Oxidized (ox-) low density lipoproteins (LDL) is characterized by the formation of lipid peroxides and their decomposition to reactive aldehydes which covalently link to apoB in LDL. These chemical changes are believed to be responsible for the enhanced recognition of ox-LDL by receptors on macrophages in culture. When oxidation is extensive, particle aggregation also occurs. The aim of this study was to characterize aggregation formation and how this influences the interaction of ox-LDL with macrophages in culture. When LDL was oxidized by incubating at 500 micrograms of protein/ml with 10 microM Cu2+ at 20 degrees C for up to 25 h, time-dependent increases in thiobarbituric acid reactive substances, conjugated diene content, electrophoretic mobility, and fluorescence at 360 excitation/430 emission were found. Particle aggregation increased in parallel with several parameters of oxidation and increased with increasing incubation temperatures and LDL concentrations used. When evaluated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, apoB fragments of reproducible sizes and higher molecular weight species appeared after mild oxidation of LDL. The percent of total apoB remaining aggregated in sodium dodecyl sulfate was 50-80% at high degrees of oxidation, whereas it was far less in LDL that had been aggregated without chemical modification. This suggested that intermolecular cross-linking of apoB had occurred during oxidation of LDL at high concentrations. Degradation of ox-LDL in mouse peritoneal macrophages (MPM) increased in parallel with the degree of oxidation and with particle aggregation but reached a plateau after 12 h. Results from cross-competition studies in MPM with soluble and insoluble portions of extensively ox-LDL and with acetyl-LDL were consistent with uptake of soluble ox-LDL via both the scavenger receptor and another receptor on MPM, and uptake of the insoluble ox-LDL by an alternative mechanism.

Aldehydes↗
PubMed1992

Importance of adequate staging and of hormone receptors in women older than age 70 with breast cancer.

This report includes 479 women older than 70 years of age who were operated on between January 1980 and January 1988 and who were followed for 2.5 to 10.5 years (mean, 4.6 years). There were no operative deaths. Staging was available on 90.8%. Eighty-one per cent of patients were estrogen receptor positive (ER+), and 64% had negative lymph nodes (LN-). There were 50 deaths from breast cancer (10.4%), and 56 (11.6%) from other causes (mostly cardiovascular). Estrogen receptor negativity was significant by both univariate and multivariate analysis for increased risk of death from breast cancer (by factors of 3 and 1.4). Only four of 152 (2.6%) women who were node negative and estrogen receptor positive died during the follow-up of 4.9 years. The results of this study suggest that elderly women should be fully staged with axillary node dissections, and the hormone receptor assay should be performed because these are important indicators of prognosis. Because only 2.6% of the LN- and ER+ women in this study died of breast cancer, and only 3% in this group were treated with adjuvant systemic therapy (tamoxifen), the authors conclude that this therapy is unnecessary, although a prospective randomized study of elderly women would be required to state this definitively.

Age Factors↗
PubMed1992

Lipoprotein(a) is an independent risk factor for cardiovascular disease in hemodialysis patients.

BACKGROUND: Although serum lipoprotein(a) [Lp(a)] is an independent risk factor for atherosclerosis in the general population and Lp(a) levels are increased in hemodialysis patients, an association of Lp(a) with the risk of clinical events attributed to atherosclerosis has not been established in the chronic hemodialysis patient population. We therefore determined the association between Lp(a) levels and the risk of clinical events of presumed atherosclerotic etiology in a prospective study of an outpatient hemodialysis population. METHODS AND RESULTS: Lp(a) was measured by radioimmunoassay in a baseline cardiovascular disease risk assessment in a consecutive series of 129 hemodialysis patients. The relation between baseline Lp(a) and clinical events of presumed atherosclerotic etiology was determined during 48 months of follow-up. Hemodialysis patients had a median Lp(a) concentration that was approximately four times as high as the median Lp(a) concentration in normal controls and twice as high as the levels in controls with angiographic evidence of coronary artery disease [median Lp(a), 38.4 versus 16.9 mg/dl; p less than 0.001]. Baseline Lp(a) levels were no different in participants with or with no history of a previous clinical event at the time of the baseline examination. However, baseline Lp(a) concentration (p less than 0.001) and a history of atherosclerotic clinical events (p = 0.001) were associated with clinical events during the period of follow-up. In contrast, baseline serum total cholesterol, triglyceride, high density lipoprotein cholesterol, low density lipoprotein cholesterol, age, gender, race, or duration of hemodialysis were unrelated to this risk in the prospective study. Stepwise multiple logistic regression analysis demonstrated that serum Lp(a) concentration (p = 0.001) and the presence of a previous clinical event (p = 0.004) were the only independent contributors to the risk of a clinical event during the period of follow-up. CONCLUSIONS: Lp(a) is an independent risk factor for clinical events attributed to atherosclerotic cardiovascular disease in patients receiving chronic hemodialysis treatment of end-stage renal disease.

Arteriosclerosis↗