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Biomedical subjects

L O'Neill

Publications and source records attributed to L O'Neill.

At least 55 records · Page 3Linked to original sources
PubMed1997

Molecular and phenotypic analysis of Candida dubliniensis: a recently identified species linked with oral candidosis in HIV-infected and AIDS patients.

The discovery and characterisation of a novel species of Candida, termed Candida dubliniensis, associated with oral candidosis in HIV-infected individuals is described. These organisms share several phenotypic characteristics in common with Candida albicans and Candida stellatoidea, including the ability to produce germ tubes and chlamydospores. However, in contrast to these latter two species, C. dubliniensis isolates produce abundant chlamydospores, which are often arranged in contiguous pairs, triplets and other multiples suspended from a single suspensor cell. They belong to C. albicans serotype A and exhibit atypical substrate assimilation profiles. Genomic DNA fingerprinting analysis with the C. albicans-specific probe 27A and five different oligonucleotide probes consisting of short repeat sequence-containing motifs, demonstrated that C. dubliniensis has a distinct genomic organisation relative to C. albicans and C. stellatoidea. This was confirmed by karyotype analysis and random amplified polymorphic DNA (RAPD) analysis. Comparison of 500 bp of the V3 variable region of the large ribosomal subunit genes from 14 separate C. dubliniensis isolates and the corresponding sequences from C. albicans, C. stellatoidea, C. tropicalis, C. glabrata, C. parapsilosis, C. kefyr and C. krusei demonstrated that the C. dubliniensis isolates formed a homogenous cluster (100% similarity), representing a discrete taxon within the genus Candida that was significantly different from the other species analysed.

AIDS-Related Opportunistic Infections↗
PubMed1997

Captopril modifies gene expression in hypertrophied and failing hearts of aged spontaneously hypertensive rats.

The spontaneously hypertensive rat (SHR) exhibits a transition from stable compensated left ventricular (LV) hypertrophy to heart failure (HF) at a mean age of 21 months that is characterized by a decrease in alpha-myosin heavy chain (alpha-MHC) gene expression and increases in the expression of the atrial natriuretic factor (ANF), pro-alpha1(III) collagen, and transforming growth factor beta1 (TGF-beta1) genes. We tested the hypotheses that angiotensin-converting enzyme inhibition (ACEI) in SHR would prevent and reverse HF-associated changes in gene expression when administered prior to and after the onset of HF, respectively. We also investigated the effect of ACEI on circulating and cardiac components of the renin-angiotensin system. ACEI (captopril 2 g/L in the drinking water) was initiated at 12, 18, and 21 months of age in SHR without HF and in SHR with HF. Results were compared with those of age-matched normotensive Wistar-Kyoto (WKY) rats, and to untreated SHR with and without evidence of HF. ACEI initiated prior to failure prevented the changes in alpha-MHC, ANF, pro-alpha1(III) collagen, and TGF-beta1 gene expression that are associated with the transition to HF. ACEI initiated after the onset of HF lowered levels of TGF-beta1 mRNA by 50% (P<.05) and elevated levels of alpha-MHC mRNA two- to threefold (P<.05). Circulating levels of renin and angiotensin I were elevated four- to sixfold by ACEI, but surprisingly, plasma levels of angiotensin II were not reduced. ACEI increased LV renin mRNA levels in WKY and SHR by two- to threefold but did not influence LV levels of angiotensinogen mRNA. The results suggest that the anti-HF benefits of ACEI in SHR may be mediated, at least in part, by effects on the expression of specific genes, including those encoding alpha-MHC, ANF, TGF-beta1, pro-alpha1(III) collagen, and renin-angiotensin system components.

Aging↗
PubMed1997

Rapamycin inhibits alpha 1-adrenergic receptor-stimulated cardiac myocyte hypertrophy but not activation of hypertrophy-associated genes. Evidence for involvement of p70 S6 kinase.

The 70-kD S6 kinase (p70S6K) has been implicated in the regulation of protein synthesis in many cell types and in the angiotensin II-stimulated hypertrophy of cardiac myocytes. Our purpose was to determine whether p70S6K plays a role in cardiomyocyte hypertrophy induced by the alpha 1-adrenergic receptor (alpha 1-AR) agonist phenylephrine (PE). PE stimulated the activity of p70S6K > 3-fold, and this increase was blocked by rapamycin, an immunosuppressant macrolide that selectively inhibits p70S6K. When administered for 3 days, PE stimulated a 30% increase in total protein content, a 2-fold increase in the incorporation of [14C]phenylalanine (14C-Phe) into protein, and a 50% increase in two-dimensional myocyte area. Rapamycin pretreatment (> or = 500 pg/mL) significantly inhibited each of these PE-stimulated changes. Two days of PE treatment resulted in a 1.6-fold increase in total RNA yield per dish, a 2-fold increase in incorporation of [14C]uridine into myocyte RNA, and increases in relative mRNA levels of the hypertrophy-associated atrial natriuretic factor (ANF, 2.1-fold) and skeletal alpha-actin (SK, 2.2-fold) genes. Although rapamycin abolished the PE-stimulated increases in total RNA and incorporation of [14C]uridine, it had no effect on the induction of the ANF and SK genes. LY294002, a specific inhibitor of phosphatidylinositol 3-kinase (PI3-K) activity, inhibited PE-stimulated increases in p70S6K activity and the incorporation of labeled precursors into myocyte protein and RNA. These results demonstrate that p70S6K is activated by the hypertrophic agent PE and that a PI3-K or PI3-K-like activity is required for p70S6K activation and myocyte hypertrophy. The data suggest that p70S6K activation may be required for PE-stimulated hypertrophy of cardiac myocytes. Our results demonstrate that intracellular signaling pathways responsible for transcriptional and translational responses diverge early after alpha 1-AR stimulation in cardiac myocytes.

Adrenergic alpha-1 Receptor Antagonists↗
PubMed1996

Sauvé-Kapandji procedure for disorders of the distal radioulnar joint: a simplified technique.

A simplified technique of the Sauvé-Kapandji (SK) procedure for disorders of the distal radioulnar joint (DRUJ) is described. The DRUJ is transfixed by a screw but is not formally exposed and fused, the periosteum of the distal ulna is not excised, and the pronator quadratus is not advanced into the pseudarthrosis. Stability of the ulna shaft is obtained by suturing the sheath of the extensor carpi ulnaris (ECU) and periosteum as a single layer firmly over the ulnar stump and pseudarthrosis. The operating time averages 20 minutes. Review of 28 wrists demonstrated relief of pain in 27; 80 degrees or greater of pronation and supination in 19 and 20, respectively; fusion of the DRUJ in 18; and ulnar carpal shift in 3. The main complications were related to screw placement and length and prominence of the ECU tendon. The simplified SK procedure reliably relieves pain and restores movement at the DRUJ.

Adult↗
PubMed1996

Extracellular ATP inhibits adrenergic agonist-induced hypertrophy of neonatal cardiac myocytes.

We have previously shown that extracellular ATP, like norepinephrine (NE) and many other hypertrophy-inducing agents, increases expression of the immediate-early genes c-fos and junB in cultured neonatal cardiac myocytes but that the intracellular signaling pathways activated by ATP and responsible for these changes differ from those stimulated by NE. Furthermore, whereas NE increases incorporation of [14C]phenylalanine (14C-Phe) and cell size in neonatal cardiomyocytes, ATP does not. Since ATP is coreleased with NE from sympathetic nerve endings in the heart, we investigated whether ATP could modulate cardiac hypertrophy induced by adrenergic agonists, such as NE. We report in the present study that extracellular ATP inhibited the increase in incorporation of 14C-Phe into cellular protein and the increase in cell size in neonatal rat cardiac myocytes that was induced by NE, phenylephrine (PE), basic fibroblast growth factor, or endothelin-1. This inhibition was dose dependent, occurred predominantly through P2 purinergic receptors, and was observed even when cells were treated with ATP for as little as 1 hour before the addition of the hypertrophy-inducing agent. ATP also selectively affected changes in gene expression associated with hypertrophy. It prevented PE-stimulated increases in atrial natriuretic factor and myosin light chain-2 mRNA levels, while appearing to augment basal and PE-stimulated skeletal alpha-actin mRNA levels. ATP alone increased sarcoplasmic reticulum Ca2+-ATPase mRNA levels but had no effect when added with PE. ATP did not significantly affect the level of the constitutively expressed mRNA for GAPDH. Neither the PE-stimulated increase in immediate-early gene expression nor the initial induction of mitogen-activated protein kinase activity by PE was inhibited by ATP. These results demonstrate that extracellular ATP can inhibit hypertrophic growth of neonatal cardiac myocytes and differentially alter the changes in gene expression that accompany hypertrophy.

Adenosine Triphosphate↗
PubMed1995

Age-associated increase in rat ventricular ANP gene expression correlates with cardiac hypertrophy.

Atrial natriuretic peptide (ANP), a cardiac-specific hormone, is stored in the atria and released in response to atrial stretch. During cardiac hypertrophy, ANP gene expression is markedly upregulated in the left ventricle (LV). Because the hearts of normotensive senescent rats exhibit left atrial (LA) and left ventricular (LV) hypertrophy and dilatation, we examined ANP mRNA levels by Northern blot analysis and ANP peptide concentrations by radioimmunoassay in atria, LVs, and plasma of rats at 2, 6, 18, and 22-24 mo of age. Compared with LVs of 6-mo-old rats, the LV-to-body weight ratio was elevated 30% by 18 mo of age, whereas levels of ANP mRNA were elevated twofold (not significant) and sevenfold (P < 0.05) in the LV of 18- and 22- to 24-mo-old rats, respectively. The concentration of immunoreactive ANP (ir-ANP) exhibited a four- to fivefold increase in LVs of 18- and 22- to 24-mo-old rats compared with values for 6-mo-old rats (43 +/- 4 pmol/g wet wt; means +/- SE). Among 18-and 22- to 24-mo-old rats a significant correlation was observed between ANP peptide concentration and LV hypertrophy (r 2 = 0.64). Levels of ANP mRNA and ir-ANP in the atria exhibited only modest changes with aging.(ABSTRACT TRUNCATED AT 250 WORDS)

Aging↗
PubMed1994

Aging, cardiac proenkephalin mRNA and enkephalin peptides in the Fisher 344 rat.

Cardiac proenkephalin (PENK) mRNA, methionine-enkephalin (ME) and leucine-enkephalin (LE) were determined from 2 days of age through senescence in Fisher 344 rats. Tissues were collected at 2 days, 2 weeks, 1, 2, 3, 7, 19, and either 22 or 27 months of age. Hearts were dissected, extracted and assayed for ME and LE by radioimmunoassay (RIA) or for PENK mRNA by Northern blot analysis with a cDNA probe. Relative left ventricular (LV) PENK mRNA was low in 2 day animals and increased slowly between 2 weeks and 3 months of age. LV PENK mRNA then rose five to six-fold between 3 and 27 months of age. LV ME measurements were high in neonatal animals, declined to a nadir during development and then rose again as the animals matured and advanced in age. The pattern for right ventricular (RV) ME was similar. Atrial ME, also high at 2 days, declined thereafter and remained low. LE measurements in LV, RV and the atria followed patterns similar to those described for ME. To evaluate for peptides contributed by cardiac nerves, 3, 7 and 22-month-old animals were acutely sympathectomized for 24 h with 6-hydroxydopamine. No decline in LV ME and LE was observed in the 6-hydroxydopamine treated animals. These data suggest several conclusions regarding myocardial enkephalinergic systems: (a) tissue enkephalin and PENK mRNA increase with advancing age, (b) tissue enkephalins may not strictly correlate with the relative abundance of PENK mRNA, and (c) most myocardial enkephalins are non-adrenergic in origin. The age-associated patterns in both PENK mRNA, ME and LE suggest that physiological, maturational or behavioral events between 3 and 7 months of age initiate the up-regulation and subsequent expansion of cardiac enkephalinergic systems.

Aging↗
PubMed1994

Extracellular ATP induces immediate-early gene expression but not cellular hypertrophy in neonatal cardiac myocytes.

It is well-documented that norepinephrine (NE) induces the expression of immediate-early genes (IEGs), such as c-fos, c-jun, and jun-B, in cultured neonatal heart cells and leads to cell growth without cell division (ie, hypertrophy). Although purinergic receptors activated by ATP are present on cardiac myocytes and ATP is coreleased with NE from sympathetic nerve endings within the heart, the potential role of the purinergic system in the cascade of events that leads to cardiac hypertrophy is unknown. We report in the present study that stimulation of purinergic receptors by micromolar concentrations of extracellular ATP increased the levels of c-fos and jun-B mRNA as well as FOS and JUN-B proteins in neonatal cardiac myocytes. The magnitude of response to micromolar ATP was comparable to that elicited by NE. The increase in IEG expression induced by ATP was preceded by a rapid transient increase in cytosolic Ca2+. Pretreatment of myocytes with the intracellular Ca2+ chelator BAPTA-AM prevented the ATP-stimulated increase in cytosolic Ca2+ and attenuated the ATP-stimulated increase in c-fos expression. In contrast, NE did not increase cytosolic Ca2+ in quiescent myocytes, and pretreatment with BAPTA-AM did not inhibit the NE-stimulated increase in c-fos gene expression. Furthermore, although NE markedly increased [14C]phenylalanine incorporation into protein and myocyte hypertrophy measured by cell size, ATP did not. These results demonstrate that stimulation of purinergic receptors by ATP activates IEGs via a Ca(2+)-dependent pathway in cardiac myocytes that differs from the NE stimulated activation of these genes.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenosine Triphosphate↗
PubMed1994

Alterations in cardiac gene expression during the transition from stable hypertrophy to heart failure. Marked upregulation of genes encoding extracellular matrix components.

The failing heart is characterized by impaired cardiac muscle function and increased interstitial fibrosis. Our purpose was to determine whether the functional impairment of the failing heart is associated with changes in levels of mRNA encoding proteins that modulate parameters of contraction and relaxation and whether the increased fibrosis observed in the failing heart is related to elevated expression of genes encoding extracellular matrix components. We studied hearts of 18- to 24-month-old spontaneously hypertensive rats with signs and symptoms of heart failure (SHR-F) or without evidence of failure (SHR-NF) and of age-matched normotensive Wistar-Kyoto (WKY) rats. Compared with WKY rats, SHR-NF exhibited left ventricular (LV) hypertrophy (2.2-fold) and right ventricular (RV) hypertrophy (1.5-fold), whereas SHR-F were characterized by comparable LV hypertrophy (2.1-fold) and augmented RV hypertrophy (2.4-fold; all P < .01). Total RNA was isolated from ventricles and subjected to Northern blot analysis. In SHR-F hearts, the level of alpha-myosin heavy chain mRNA was decreased in both ventricles to 1/3 and 1/5 of the SHR-NF and WKY values, respectively (both P < .01). Levels of beta-myosin heavy chain, alpha-cardiac actin, and myosin light chain-2 mRNAs were not significantly altered in hearts of SHR-NF or SHR-F. Levels of alpha-skeletal actin were twofold greater in SHR-NF hearts compared with WKY hearts and were intermediate in SHR-F hearts. Levels of atrial natriuretic factor (ANF) mRNA were elevated threefold in the LV of SHR-NF (P < .05) but were not significantly increased in the RV of SHR-NF compared with WKY rats. During the transition to failure (SHR-F versus SHR-NF), ANF mRNA levels increased an additional 1.6-fold in the LV and were elevated 4.7-fold in the RV (both P < .05). Levels of sarcoplasmic reticulum Ca(2+)-ATPase (SRCA) mRNA were maintained in the LV of hypertensive and failing hearts at levels not significantly different from WKY values. In contrast, the level of RV SRCA mRNA was 24% less in SHR-NF compared with WKY rats, and during the transition to failure, this difference was not significantly exacerbated (29% less than the WKY value). The levels of fibronectin and pro-alpha 1(I) and pro-alpha 1(III) collagen mRNAs were not significantly elevated in either ventricle of the SHR-NF group but were fourfold to fivefold higher in both ventricles of SHR-F (all P < .05).(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1993

Age-associated increase in rat cardiac opioid production.

Several lines of evidence suggest that opioid peptide production in the heart may increase during aging from adulthood through senescence. We tested the hypothesis that cardiac opioid peptides and preproenkephalin (PNK) mRNA would increase with advancing age. Ventricles and atria from male Wistar rats, aged 2, 6, 18, and 22-24 mo of age, were acid extracted and assayed for methionine enkephalin (ME) and leucine enkephalin (LE). Total RNA was extracted from hearts of age-matched rats and probed for PNK mRNA by Northern blot analysis using a cDNA probe. ME and LE peptides were significantly elevated with advancing age in both ventricles [P < 0.001; by analysis of variance (ANOVA)]. Ventricular ME concentration exhibited a biphasic increase with approximately twofold higher peaks at 6 and 22-24 mo of age compared with the 2 mo value of 1.04 +/- 0.05 (SE) pmol/g wet wt. In contrast, ventricular LE concentration was largely unchanged until 22-24 mo of age when it increased approximately threefold over the 2-mo value of 2.19 +/- 0.14 pmol/g wet wt. Left ventricular PNK mRNA increased approximately fivefold between 2 and 18 mo of age (P < 0.01; ANOVA). Thus both enkephalins and the mRNA coding for them were increased in hearts of older vs. younger rats. Because opioid receptor stimulation can negatively modulate several characteristics of cardiac myocyte contraction, these results may have important functional implications for the senescent heart.

Aging↗
PubMed1991

Progressive changes from young adult age to senescence in mRNA for rat cardiac myosin heavy chain genes.

In rodents of an advanced age the cardiac contraction exhibits a reduced shortening velocity and prolonged time course. This is, in part, due to a reduction in myosin ATPase activity which results from a shift in the myosin heavy chains from the alpha (V1) to the beta (V3) isoform. The present study demonstrates that during adult aging the steady state levels of alpha myosin heavy chain mRNA decrease while those of beta myosin heavy chain increase; for both mRNAs the respective changes are greater than fourfold. Thus, the phenotypic, biophysical and biochemical cardiac contractile changes with adult aging are, at least, in part regulated at the level of gene expression.

Aging↗
PubMed1987

Methylation of the HLA-DR alpha gene is positively correlated with expression.

We have evaluated the state of methylation of the HLA-DR alpha and HLA-DQ alpha genes in a set of melanoma cell lines which differ in their characteristic expression of these genes and a matching B-cell line. In contrast to the prevailing assumption that genes are methylated when their expression is repressed, we found that one particular site within the first intron of the DR alpha gene is methylated when the cells express HLA-DR or are inducible for its expression. In addition, the HLA-DQ alpha gene may be methylated when it is expressed in a given cell. These findings extend recent observations from other groups that show mixed negative and positive correlations between methylation and class II gene expression, because the cell lines we compared are all from the same individual and, except for the B-cell line, are clonally derived. We tested whether methylation at the identified site was required for expression of the gene by treating the cell lines with the demethylating agent, 5'-azacytidine. Unexpectedly, the treatment actually increases transcription of the DR alpha gene in cell lines already expressing HLA-DR. Possibly other genes that regulate class II expression are demethylated by the treatment and consequently mask any direct effects of the treatment on DR alpha expression. Thus, methylation of the DR alpha gene does not appear to be a simple mechanism for controlling expression. Although our data suggest that methylation of HLA class II genes is not required absolutely for transcription of the DR alpha gene, we believe that chromatin structure in the vicinity of the site may be altered by methylation and thereby exert control.

Azacitidine↗
PubMed1987

Natural History Study of Congenital Heart Defects.

A strategy designed to locate and recruit individuals who were part of a study in the 1960s of congenital aortic stenosis, pulmonary stenosis, and ventricular septal defect for purposes of a follow-up examination is presented. These individuals are now adults living throughout the United States and some foreign countries. The present study, referred to as NHS-2, is designed to bring the survivors back to one of six clinical centers for medical evaluation to study the long-term results of medical and surgical treatment of such patients.

Adult↗
PubMed1986

Near miss sudden infant death syndrome episodes? A clinical and electrocardiographic correlation.

The study was carried out to validate objectively the relationship between clinical impressions of parents and ECG evidence of life-threatening arrhythmias in infants considered to be at high risk. Twenty infants considered to be at high risk were provided with a hospital grade home monitor with a hard copy-recording capability (n = 12) and/or an ECG telephone transmission system (n = 8). There were 93 alarms considered by the parents as true alarms. All of the ECG tracings recorded during the 93 episodes were normal. Infant stimulation was provided for 11 infants and was not administered during 82 of these alarms. None of the infants died and all are well at 1 year of age. Our data raises questions regarding parental clinical ability to correctly perceive a true near miss episode in most cases and may explain, in part, the lack of consistency noted in previously published physiologic studies of "high risk" populations. Finally, the study raises further questions regarding the use of parental impression alone without supportive objective data as an indication for therapy in the majority of such patients. Research efforts and application of therapeutic measures will benefit greatly by development of objective data to support and supplement parental clinical observations.

Electrocardiography↗
PubMed1975

Petechial hemorrhages of the soft palate secondary to fellatio.

A 25-year-old white woman was evaluated for "spots" on the roof of her mouth of 2 days' duration. The initial history, physical examination, and laboratory data all failed to indicate any cause for the bleeding diathesis. Therefore, a more intensive history was initiated which disclosed a probable case for fellatio as the cause of the spots. The intraoral examination showed the spots to be petechial hemorrhages located on the soft palate in the area of the insertion of the tendons of the tensor veli palatini and levator veli palatini muscles. The mechanism of injury producing these petechiae was postulated to be the combined muscular actions initiated reflexively through tactile stimulation and the negative pressure created through irrumation, both acting simultaneously on the mucosa of the soft palate. This case is presented to illustrate an addition that should be made to the differential etiologic factors of intraoral petechiae.

Adult↗