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Biomedical subjects

J Carroll

Publications and source records attributed to J Carroll.

At least 91 records · Page 5Linked to original sources
PubMed2000

Hypertonic mannitol loading of NF-kappaB transcription factor decoys in human brain microvascular endothelial cells blocks upregulation of ICAM-1.

BACKGROUND AND PURPOSE: An acute inflammatory response exacerbates tissue injury during acute ischemic stroke. The transcription factor nuclear factor (NF)-kappaB plays a key role in endothelial cell activation and the inflammatory response. Targeted genetic disruption of NF-kappaB activation in cerebral endothelial cells may be protective in stroke. We determined whether a NF-kappaB transcription factor decoy (TFD) could block intercellular adhesion molecule (ICAM)-1 upregulation, an indicator of endothelial cell activation. METHODS: We modeled ischemia-reperfusion in vitro by exposing cultured human brain microvascular endothelial cells (HBMEC) to tumor necrosis factor (TNF)-alpha and conditions of hypoxia-reoxygenation (H/R). Mannitol was used to load phosphothiorated oligonucleotides containing 3 copies of the kappaB binding sequences (TFDs) into cultured HBMEC. An NF-kappaB TFD, a mutated NF-kappaB TFD, and a scrambled TFD were studied for their effect on ICAM-1 mRNA levels and surface ICAM-1 by ELISA. RESULTS: Hyperosmolar loading with mannitol permitted rapid transfection of TFD into endothelial cell nuclei. The NF-kappaB TFD but not the mutated or scrambled TFD competed with a kappaB sequence for binding to nuclear extracts from HBMEC exposed to TNF-alpha. The NF-kappaB TFD blocked the TNF-alpha-induced and H/R-induced increase in ICAM-1 mRNA levels and the upregulation of surface ICAM-1. CONCLUSIONS: Mannitol delivers phosphothiorated oligonucleotides into cultured HBMEC. An NF-kappaB decoy blocks both TNF-alpha-induced and H/R-induced ICAM-1 upregulation in HBMEC. Targeted genetic disruption of endothelial NF-kappaB activation may be of benefit in acute ischemic stroke.

Cell Hypoxia↗
PubMed2000

Flicker-photometric electroretinogram estimates of L:M cone photoreceptor ratio in men with photopigment spectra derived from genetics.

Relative proportions of long-wavelength-sensitive (L) to middle-wavelength-sensitive (M) cones were estimated by use of the flicker-photometric electroretinogram (ERG). It has been demonstrated that a major source of error in estimates of cone proportions from spectral luminosity functions is the known variation in the lambda(max) of the photopigments [Vision Res. 38, 1961 (1998)]. To correct for these errors, estimates of cone proportions were derived by use of individualized L-cone spectral sensitivity curves deduced from photopigment gene sequences from each subject. For some individuals this correction made a large difference in the estimated cone proportions compared with the value obtained when a fixed standard L cone was assumed. The largest discrepancy occurred in a man estimated to have 62% L cones (L:M ratio 1.6:1) when a standard L pigment was assumed but a value of 80% L cones (L:M ratio 4:1) when his individualized L-cone spectrum was used. From repeated measurements made with the ERG, it was determined that individual estimates of the relative L-to-M cone contributions, expressed as %L cones, are usually reliable within approximately 2%. The average L:M ratio for 15 male subjects was estimated at 2:1 (67% L cones). Previously, a large range of individual variability was reported for L:M ratios obtained from photometry. An unresolved issue concerns how much of the range might be attributed to error. Here efforts have been taken to markedly reduce measurement error. Nonetheless, a large range of individual differences persists. Estimated L:M ratios for individuals ranged from 0.6:1 to 12:1 (40% L to 92% L).

Adolescent↗
PubMed2000

Na+-Ca2+ exchange in mouse oocytes: modifications in the regulation of intracellular free Ca2+ during oocyte maturation.

Increases in intracellular free Ca(2+)+ concentration (Ca(2+)+ oscillations) occur during meiotic maturation and fertilization of mammalian oocytes but little is known about the mechanisms of Ca(2+) homeostasis in these cells. Cells extrude Ca(2+) from the cytosol using two main transport processes, the Ca(2+)-ATPase and the Na(+)-Ca(2+) exchanger. The aim of this study was to determine whether Na(+)-Ca(2+) exchange activity is present in immature and mature mouse oocytes. Na(+)-Ca(2+) exchange can be revealed by altering the Na(+) concentration gradient across the plasma membrane and recording intracellular free Ca(2+) concentrations using Ca(2+)-sensitive fluorescent dyes. Depletion of extracellular Na(+) caused an immediate increase in Ca(2+) concentration in immature oocytes and a delayed increase in mature oocytes. The Na(+) ionophore, monensin, caused an increase in intracellular Ca(2+) in immature oocytes similar to that induced by Na(+)-depleted medium. In mature oocytes, monensin had no effect on intracellular Ca(2+) but the time taken for Ca(2+) to reach a peak value on removal of extracellular Na(+) was significantly decreased. Finally, addition of Ca(2+) to immature oocytes incubated in Ca(2+)-free medium caused an increase in the concentration of intracellular Ca(2+) that was dependent upon the presence of extracellular Na(+). This effect was not seen in mature oocytes. The data show that Na(+)-Ca(2+) exchange occurs in immature and mature mouse oocytes and that Ca(2+) homeostasis in immature oocytes is more sensitive to manipulations that activate Na(+)-Ca(2+) exchange.

Animals↗
PubMed1999

Etiology of preoperative anemia in patients undergoing scheduled cardiac surgery.

PURPOSE: Ten percent of our cardiac surgical patients have preoperative anemia. Anemia diagnosed before scheduled cardiac surgery is a strong predictor of the need for homologous blood transfusion (RBC) perioperatively but the cause of this preoperative anemia is not known. The purpose of this study was to evaluate the etiology of preoperative anemia. METHODS: Seventy-five consecutive anemic cardiosurgical patients (Hb = < 120 g x L(-1) the day before surgery) were studied prospectively. All had multiple diagnostic blood tests done in the preoperative period to diagnose the cause of the anemia and subsequently underwent non-emergency cardiac surgery. Anesthesia and RBC transfusion were standardized according to the protocol. Data in respect to operation, RBC and other blood product transfusion during operation and hospital stay were recorded. RESULTS: Hospital-acquired anemia was present in 37.3% of anemic patients (hemoglobin decrease during hospitalization before surgery > or =9 g x l(-1)). The second most common diagnosis was iron deficiency anemia (29.3% patients) followed by anemia of chronic renal disease (10.7% patients). When coronary angiography was performed close to operation time, patients had a higher decrease in hemoglobin concentration during hospitalization --suggesting that blood loss during angiography was, in part, responsible for anemia. Seventy-five percent of anemic patients were transfused with RBC perioperatively compared with our overall transfusion rate of 30% of cardiac surgery patients. CONCLUSIONS: In the majority of patients, preoperative anemia is potentially preventable. Investigation and treatment of anemia before cardiac surgery should be a priority in preparing the patient for surgery.

Aged↗
PubMed1999

Opioid receptor upregulation in mu-opioid receptor deficient CXBK and outbred Swiss Webster mice.

Chronic in vivo treatment with opioid antagonists increases opioid receptor density and the potency of opioid agonists without altering receptor mRNA levels. To determine if basal receptor density affects opioid receptor upregulation, we examined the effect of chronic naltrexone treatment on mu-opioid receptor density and mRNA in two mice strains that differ in mu-opioid receptor density. CXBK mice (mu-opioid receptor deficient) and outbred Swiss Webster mice were implanted s.c. with a placebo or 15 mg naltrexone pellet for 8 days, the pellets removed and 24 hr later opioid receptor density (mu, delta) and receptor mRNA level (mu) determined in whole brain; or morphine dose-response studies conducted. In placebo-treated CXBK mice, mu-opioid receptor density was approximately 40% less than in Swiss Webster mice, although mu-opioid receptor mRNA abundance was similar in both strains. In placebo-treated CXBK mice, morphine potency was approximately 6-fold less than Swiss Webster mice. Naltrexone treatment increased morphine potency (1.7-fold) and mu- (approximately 90%) and delta- (approximately 20-40%) opioid receptor density in CXBK and Swiss Webster mouse brain similarly. Mu-opioid receptor mRNA was unchanged by naltrexone treatment in either strain. There was no difference in the basal or naltrexone-treated whole brain G(i alpha2) protein levels in CXBK or Swiss Webster mouse. These data indicate that a deficiency in mu-opioid receptors does not alter the regulation of opioid receptors by opioid antagonists in vivo, and suggest that adaptive responses to chronic opioid antagonist treatment are independent of opioid receptor density.

Analgesics↗
PubMed1999

Distribution coefficients (Kd's) for use in risk assessment models of the Kara Sea.

As a prerequisite for most evaluations of radionuclide transport pathways in marine systems, it is necessary to obtain basic information on the sorption potential of contaminants onto particulate matter. Kd values for use in modeling radionuclide dispersion in the Kara Sea have been determined as part of several international programs addressing the problem of radioactive debris residing in Arctic Seas. Field and laboratory Kd experiments were conducted for the following radionuclides associated with nuclear waste: americium, europium, plutonium, cobalt, cesium and strontium. Emphasis has been placed on two regions in the Kara Sea: (i) the Novaya Zemlya Trough (NZT) and (ii) the mixing zones of the Ob and Yenisey Rivers (RMZ). Short-term batch Kd experiments were performed at-sea on ambient water column samples and on samples prepared both at-sea and in the laboratory by mixing filtered bottom water with small amounts of surficial bottom sediments (particle concentrations in samples = 1-30 mg/l). Within both regions, Kd values for individual radionuclides vary over two to three orders of magnitude. The relative particle affinities for radionuclides in the two regions are americium approximately equal to europium > plutonium > cobalt > cesium > strontium. The values determined in this study agree with minimum values given in the IAEA Technical Report [IAEA, 1985. Sediment Kd's and Concentration Factors for Radionuclides in the Marine Environment. Technical Report No. 247. International Atomic Energy Agency, Vienna.]. Given the importance of Kd's in assessments of critical transport pathways for radionuclide contaminants, we recommend that Kd ranges of values for specific elements rather than single mean values be incorporated into model simulations of radionuclide dispersion.

Americium↗
PubMed1999

Injection of a boar sperm factor causes calcium oscillations in oocytes of the marsupial opossum, Monodelphis domestica.

At fertilisation, the sperm triggers an abrupt and transient increase in intracellular calcium ([Ca2+]i) in the oocyte cytoplasm. In eutherian mammals, oocytes exhibit multiple [Ca2+]i transients which are necessary for egg activation. We investigated [Ca2+]i in the marsupial opossum, Monodelphis domestica. Embryo development in this therian mammal is quite distinct from that in most Eutheria. Oestrus was induced in an adult female opossum by introduction of a male into her cage. Injection of a boar sperm extract induced repetitive increases in [Ca2+]i. Each oscillation travelled across and around the periphery of the egg in a wave-like manner. A control injection of KCl elicited no change in [Ca2+]i. This is the first observation of [Ca2+]i oscillations in the oocyte of a marsupial. The repetitive nature of the [Ca2+]i changes were more similar to those in oocytes of Eutheria than those in oocytes of non-mammalian vertebrates.

Animals↗
PubMed1999

Prospective analysis of complications 30 days after outpatient colonoscopy.

BACKGROUND: Our objective was to (1) determine whether more complications are reported by patients 30 days after outpatient colonoscopy than are discussed at our monthly morbidity and mortality conferences, (2) identify complications resulting in visits to the emergency department or physician's office or leading to hospitalization, and (3) assess which factors put patients at highest risk. A secondary goal was to determine the rate of work lost after outpatient colonoscopy. METHODS: Trained interviewers performed standardized telephone interviews of consecutive outpatients undergoing colonoscopy at Georgetown University Hospital over a 1-year period. RESULTS: One thousand one hundred ninety-six patients were contacted 30 days after outpatient colonoscopy and participated in our study. Twenty patients had complications that required a visit to an emergency department or physician. Ninety percent of these cases (18) were detected at 30 days, but 15% (3) were discussed at morbidity and mortality conferences. All seven complications that necessitated hospitalization were identified at 30 days, but only two were discussed at our morbidity and mortality conference. The most common complications reported by patients were abdominal discomfort (5.4%) and rectal bleeding (2.1%). CONCLUSION: More complications are detected by means of contacting patients 30 days after outpatient colonoscopy than are discussed at our morbidity and mortality conferences.

Abdominal Pain↗
PubMed1999

Prospective analysis of complications 30 days after outpatient upper endoscopy.

OBJECTIVE: The aim of this study was to compare complication rates reported by patients 30 days after outpatient upper endoscopy with those discussed at our monthly morbidity and mortality conference. We also intended to establish which complications were reported most frequently 30 days after upper endoscopy, and which patients or procedures involved the highest risk. METHODS: Trained interviewers performed standardized telephone interviews on consecutive outpatients undergoing upper endoscopy over a 1-yr period. Patients were queried regarding potential events related to their upper endoscopy in the 30 days subsequent, including symptoms, emergency room (ER) and/or physician visits, and hospitalizations. The indications, findings, and therapies were reviewed from endoscopic reports. RESULTS: A total of 473 patients were contacted 30 days after outpatient upper endoscopy and agreed to participate in our study. The most common complications reported by patients at 30 days were sore throat (9.5%) and abdominal discomfort (5.3%). Twelve patients (2.5%) required an ER/physician visit and five patients (1.1%) required hospitalization. The minority of both ER/physician visits (16.7%) and hospitalizations (40%) were discussed at our monthly morbidity and mortality conferences. CONCLUSIONS: More complications were reported by patients 30 days after outpatient upper endoscopy than were discussed at our monthly morbidity and mortality conferences. The most frequent complications reported by patients were sore throat and abdominal pain. The minority of ER/physician visits and hospitalizations were discussed at our morbidity and mortality conferences.

Abdominal Pain↗
PubMed1999

Regulation of insulin-like growth factor I receptor promoter activity by wild-type and mutant versions of the WT1 tumor suppressor.

The insulin-like growth factor I (IGF-I) receptor is a transmembrane tyrosine kinase that mediates the growth-promoting effects of IGF-I and IGF-II. Changes in IGF-I receptor messenger RNA levels are reflected in cell surface receptor number, and modulation of IGF-I receptor levels affects tumorigenicity in numerous cellular models; thus, control of IGF-I receptor gene expression appears to be an important level at which cellular proliferation and tumorigenic potential may be regulated. We have previously shown that the product of the WT1 Wilms' tumor suppressor gene represses IGF-I receptor gene expression both in vitro and in vivo, and that decreased WT1 levels are correlated with up-regulation of IGF-I receptor gene expression in Wilms' tumor, benign prostatic hyperplasia, and breast cancer. Gene regulation by WT1 is complex, in that the WT1 gene encodes a variety of products as a result of alternative splicing and RNA editing, and a number of missense point mutations have been characterized in Wilms' tumor-associated syndromes. Additionally, the WT1 protein has been demonstrated to self-associate through its N-terminal domain, although the role of this intermolecular interaction in transcriptional regulation by WT1 is unclear. In this report, we analyze the relative activity of wild-type and mutant versions of the WT1 protein with respect to IGF-I receptor promoter activity in transient transfection assays and assess the potential contribution of WT1 self-association to IGF-I receptor regulation using the yeast two-hybrid system. Of the naturally occurring variations in WT1 structure, only the presence of a three-amino acid KTS insert in the zinc finger domain introduced by alternative splicing of exon 9 had a significant effect on WT1 repression of IGF-I receptor promoter activity. The N- and C-terminal domains of WT1 also exhibited partial repression, as did the most common mutant version of the WT1 protein associated with Denys-Drash syndrome. Mutations in the WT1 N-terminus attenuated WT1 self-association in the yeast two-hybrid system, but did not impair transcriptional repression. Our results suggest that 1) the DNA-binding capacity of WT1 is critical for maximal repression of the IGF-I receptor promoter, but some effects may be mediated through protein-protein interactions involving the N-terminal domain; 2) WT1 self-association may not be required for repression of the IGF-I receptor promoter; and 3) the Denys-Drash syndrome version of the WT1 protein may exhibit residual or possible gain of function activity in some contexts rather than exerting dominant negative effects, as has been proposed previously.

Animals↗
PubMed1999

Screening for acute myocardial infarction in elderly patients with collapse, confusion and falls.

Falls, collapse and confusion are frequent causes of admission to hospital in the elderly, and myocardial infarction (MI) can present atypically. The study was designed to assess the incidence of MI in this group of patients and provide information on the value of screening methods. A total of 142 elderly patients with a mean age of 83 years (range 76-99) were admitted with unexplained collapse, confusion or falls. Serial ECGs and cardiac enzymes were performed. Eighty-two patients (59%) had normal ECGs; of these, 80 (98%) had normal or non-significantly elevated cardiac enzymes; 72/108 patients without chest pain had normal ECGs compared with 10/32 who had chest pain (p < 0.01). Cardiac enzymes were elevated in 5/108 without chest pain and 10/32 with chest pain (p < 0.01). Thirty-two (23%) had chest pain, 14 (10%) had an acute MI. In those presenting with chest pain, 32% had an MI, compared with only 1.9% of those without chest pain (p < 0.01); 18% of patients with an initially abnormal ECG had an MI compared with only 5% of those with a normal ECG (p = 0.02). None of the patients with a normal ECG who were free of chest pain were subsequently proven to have an MI. Cardiac enzymes are often non-specifically elevated in this group of patients due to muscle injury. The incidence of MI is low in patients without chest pain and we would not advocate routine screening with serial cardiac enzymes, unless there is chest pain or an abnormal 12-lead ECG on admission.

Accidental Falls↗
PubMed1998

Expression of inositol 1,4,5-trisphosphate receptors in mouse oocytes and early embryos: the type I isoform is upregulated in oocytes and downregulated after fertilization.

A fertilization-induced increase in intracellular Ca2+ is responsible for initiating all of the events of egg activation. In mammals, the Ca2+ increase takes the form of a series of Ca2+ oscillations showing complex temporal and spatial properties. To understand the nature of these changes, we have investigated the expression patterns of the three isoforms of the inositol trisphosphate receptor (InsP3R) during oocyte maturation and preimplantation development. We find that mouse oocytes express mRNAs for all three InsP3R subtypes. Semiquantitative ratio reverse-transcriptase polymerase chain reaction shows that the type II isoform is the predominant message in mature oocytes, representing 67% of the InsP3R mRNA. In contrast, protein analysis reveals that the type I isoform accounts for all of the detectable InsP3R protein, despite representing only 20% of the InsP3R mRNA. The levels of InsP3R protein were examined to determine whether they correlated with the Ca2+ signaling events surrounding the fertilization process. Type I InsP3R protein increased during oocyte maturation and, in addition, within 8 h of fertilization underwent a dramatic decrease. During development to the blastocyst the level of type I InsP3R protein did not return to prefertilization levels and types II and III remained below our detection limit. The decrease in InsP3R protein after fertilization was found to correlate with a decrease in the sensitivity of InsP3-induced Ca2+ release. These studies show that the expression of InsP3R mRNA is developmentally regulated, that Ca2+ signaling at fertilization is mediated exclusively through the type I InsP3R, and that the InsP3R is downregulated after fertilization.

Animals↗
PubMed1998

Surface plasmon resonance analysis at a supported lipid monolayer.

Methods for the formation of supported lipid monolayers on top of a hydrophobic self assembled monolayer in a surface plasmon resonance instrument are described. Small unilamellar vesicles absorb spontaneously to the surface of the hydrophobic self-assembled monolayer to form a surface which resembles the surface of a cellular membrane. Lipophilic ligands, such as small acylated peptides or glycosylphosphatidylinositol-anchored proteins, were inserted into the absorbed lipid and binding of analytes to these ligands was analysed by surface plasmon resonance. Conditions for the formation of lipid monolayers have been optimised with respect to lipid type, chemical and buffer compatibility, ligand stability and reproducibility.

Anti-Bacterial Agents↗
PubMed1998

Bacillus thuringiensis Cry1Ac toxin interaction with Manduca sexta aminopeptidase N in a model membrane environment.

The Bacillus thuringiensis Cry1Ac delta-endotoxin was shown to bind in a biphasic manner to Manduca sexta aminopeptidase N (APN) present in a novel model membrane. Surface plasmon resonance analysis allowed the quantification of toxin binding to M. sexta APN in a supported lipid monolayer. The initial binding was rapid and reversible, with an affinity constant of 110 nM. The second phase was slower and resulted in an overall affinity constant of 3.0 nM. Reagents used to disrupt protein-protein interactions did not dissociate the toxin after high-affinity binding was attained. The initial association between Cry1Ac and APN was inhibited by the sugar GalNAc, but the higher-affinity state was resistant to GalNAc-induced dissociation. The results suggest that after binding to M. sexta APN, the Cry1Ac toxin undergoes a rate-limiting step leading to a high-affinity state. A site-directed Cry1Ac mutant, N135Q, exhibited a similar initial binding affinity for APN but did not show the second slower phase. This inability to form an irreversible association with the APN-lipid monolayer helps explain the lack of toxicity of this protein towards M. sexta larvae and its deficient membrane-permeabilizing activity on M. sexta midgut brush border membrane vesicles.

Animals↗